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Sample records for resonance relaxation studies

  1. A numerical study of vector resonant relaxation

    NASA Astrophysics Data System (ADS)

    Kocsis, Bence; Tremaine, Scott

    2015-04-01

    Stars bound to a supermassive black hole interact gravitationally. Persistent torques acting between stellar orbits lead to a rapid resonant relaxation of the orbital orientation vectors (`vector' resonant relaxation) and slower relaxation of the eccentricities (`scalar' resonant relaxation), both at rates much faster than two-body or non-resonant relaxation. We describe a new parallel symplectic integrator, N-RING, which follows the dynamical evolution of a cluster of N stars through vector resonant relaxation, by averaging the pairwise interactions over the orbital period and periapsis precession time-scale. We use N-RING to follow the evolution of clusters containing over 104 stars for tens of relaxation times. Among other results, we find that the evolution is dominated by torques among stars with radially overlapping orbits, and that resonant relaxation can be modelled as a random walk of the orbit normals on the sphere, with angular step size ranging from ˜0.5-1 rad. The relaxation rate in a cluster with a fixed number of stars is proportional to the root mean square (rms) mass of the stars. The rms torque generated by the cluster stars is reduced below the torque between Kepler orbits due to apsidal precession and declines weakly with the eccentricity of the perturbed orbit. However, since the angular momentum of an orbit also decreases with eccentricity, the relaxation rate is approximately eccentricity-independent for e ≲ 0.7 and grows rapidly with eccentricity for e ≳ 0.8. We quantify the relaxation using the autocorrelation function of the spherical multipole moments; this decays exponentially and the e-folding time may be identified with the vector resonant relaxation time-scale.

  2. Electron spin resonance and muon spin relaxation studies of single molecule magnets

    NASA Astrophysics Data System (ADS)

    Blundell, Stephen

    2005-03-01

    We use a combination of electron spin resonance, muon-spin relaxation and SQUID magnetometry to study polycrystalline and single crystal samples of various novel single molecule magnets (SMMs). We also describe a theoretical framework which can be used to analyse the results from each technique. Electron spin resonance measurements are performed using a millimetre vector network analyser and data are presented on several SMM systems using microwave frequencies from 40-300 GHz. Muon-spin relaxation measurements have been performed on several SMM systems in applied longitudinal magnetic field and in temperatures down to 20 mK. The results suggest that dynamic local magnetic field fluctuations are responsible for the relaxation of the muon spin ensemble. We discuss what can be learned from these experiments concerning SMMs and suggest experiments which can probe the quantum nature of SMMs. (Work in collaboration with S Sharmin, T Lancaster, A Ardavan, F L Pratt, E J L McInnes and R E P Winpenny) References: S. J. Blundell and F. L. Pratt, J. Phys.: Condens. Matter 16, R771 (2004); T. Lancaster et al., J. Phys.: Condens. Matter 16, S4563 (2004); S. Sharmin et al., Appl. Phys. Lett. in press.

  3. Resonant dipolar relaxation in poly ( ɛ -caprolactone)—A thermally stimulated depolarization current study

    NASA Astrophysics Data System (ADS)

    Patidar, M. M.; Jain, D.; Nath, R.; Ganesan, V.

    2016-07-01

    Resonant dipolar relaxation in poly( ɛ-caprolactone) (PCL) is reported using thermally stimulated discharge current spectroscopy. PCL is a bio-medically known shape memory polymer having a well defined γ, β, α, and α ' relaxations, respectively, centered around 125 K, 170 K, 220 K, and 270 K as seen by the measurements. By employing a new protocol variable poling temperature at constant freezing temperature, resonant dipolar relaxation in PCL could be induced, especially in the vicinity of α relaxation. Such a protocol is useful in de-convoluting the features in a more meaningful fashion. By an analysis of activation process, we could show a clear contrast enhancement of the dynamics of the participating dipoles by means of a minimum in the activation energies situated around the glass transition region. The relevant parameters of interest such as activation energies and relaxation times are estimated and discussed.

  4. Chemical relaxation of H bonds in formic acid vapor studied by resonant photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Winkler, A.; Mehl, J. B.; Hess, P.

    1994-02-01

    The chemical relaxation of hydrogen bonds in dimeric formic acid (methanoic acid) was studied in the gas phase by means of precise measurement of the speed of sound and the sound absorption as functions of the pressure and the temperature by exciting standing acoustic waves. The first radial acoustic resonance of a cylindrical cavity was excited by a modulated CO2 laser beam. Resonance profiles were measured and recorded by a computer-controlled system. Due to the high information content of this method, a consistent set of thermodynamic and kinetic parameters can be obtained. The equilibrium constants of the dimer/monomer and the cis-/trans-monomer equilibrium, the dissociation rate constant of (HCOOH)2 and the mean relaxation time of the vibrational states of the monomer-dimer mixture were determined by fitting a detailed theoretical model of the resonator to the measured values for the resonance frequency and the resonance broadening for total pressures in the range from 0.3 to 50 mbar and temperatures from 290 to 325 K. We obtained 159±2 J/(mol K) for the entropy and 61.8±0.5 kJ/mol for the enthalpy of dissociation at 300 K. We inferred a value for the enthalpy of isomerization of 10±5 kJ/mol. For the first time the pressure dependence of the dissociation rate constant was determined. It was found that the unimolecular decay is in the second-order regime at these low pressures as expected. The mean collision efficiency for the dissociation process relative to the dimer was obtained for HCOOH, He, and Ar to be 0.5±0.2, 0.05±0.02, and 0.08±0.02, respectively, independent of the temperature. We measured an average (pτ) value of 10±2 ns bar for the relaxation of the vibrational degrees of freedom. The activation energy of the dissociation of dimeric formic acid was determined to be 33±1 kJ/mol.

  5. Impurities and electron spin relaxations in nanodiamonds studied by multi-frequency electron spin resonance

    NASA Astrophysics Data System (ADS)

    Cho, Franklin; Takahashi, Susumu

    2014-03-01

    Nano-sized diamond or nanodiamond is a fascinating material for potential applications of fluorescence imaging and magnetic sensing of biological systems via nitrogen-vacancy defect centers in diamonds. Sensitivity of the magnetic sensing strongly depends on coupling to surrounding environmental noises, thus understanding of the environment is critical to realize the application. In the present study, we employ multi-frequency (X-band, 115 GHz and 230 GHz) continuous-wave (cw) and pulsed electron spin resonance (ESR) spectroscopy to investigate impurity contents and spin relaxation properties in various sizes of nanodiamonds. Spectra taken with our home-built 230/115 GHz cw/pulsed ESR spectrometer shows presence of two major impurity contents; single substitutional nitrogen impurities (P1) also common in bulk diamonds and paramagnetic impurities (denoted as X) unique to nanodiamonds. The ESR measurement also shows a strong dependence of the population ratio between P1 and X on particle size. Furthermore, we will discuss the nature of spin-lattice relaxation time T1 of nanodiamonds studied by pulsed ESR measurements at X-band, 115 GHz and 230 GHz.

  6. Probing α-relaxation with nuclear magnetic resonance echo decay and relaxation: a study on nitrile butadiene rubber.

    PubMed

    Sturniolo, Simone; Pieruccini, Marco; Corti, Maurizio; Rigamonti, Attilio

    2013-01-01

    One dimensional (1)H NMR measurements have been performed to probe slow molecular motions in nitrile butadiene rubber (NBR) around its calorimetric glass transition temperature Tg. The purpose is to show how software aided data analysis can extract meaningful dynamical data from these measurements. Spin-lattice relaxation time, free induction decay (FID) and magic sandwich echo (MSE) measurements have been carried out at different values of the static field, as a function of temperature. It has been evidenced how the efficiency of the MSE signal in reconstructing the original FID exhibits a sudden minimum at a given temperature, with a slight dependence from the measuring frequency. Computer simulations performed with the software SPINEVOLUTION have shown that the minimum in the efficiency reconstruction of the MSE signal corresponds to the average motional frequency taking a value around the inter-proton coupling. The FID signals have been fitted with a truncated form of a newly derived exact correlation function for the transverse magnetization of a dipolar interacting spin pair, which allows one to avoid the restriction of the stationary and Gaussian approximations. A direct estimate of the conformational dynamics on approaching the Tg is obtained, and the results are in agreement with the analysis performed via the MSE reconstruction efficiency. The occurrence of a wide distribution of correlation frequencies for the chains motion, with a Vogel-Fulcher type temperature dependence, is addressed. A route for a fruitful study of the dynamics accompanying the glass transition by a variety of NMR measurements is thus proposed.

  7. Study of anisotropy in nuclear magnetic resonance relaxation times of water protons in skeletal muscle.

    PubMed Central

    Kasturi, S R; Chang, D C; Hazlewood, C F

    1980-01-01

    The anisotropy of the spin-lattice relaxation time (T1) and the spin-spin relaxation times (T2) of water protons in skeletal muscle tissue have been studied by the spin-echo technique. Both T1 and T2 have been measured for the water protons of the tibialis anterior muscle of mature male rats for theta = 0, 55, and 90 degrees, where theta is the orientation of the muscle fiber with respect to the static field. The anisotropy in T1 and T2 has been measured at temperatures of 28, -5 and -10 degrees C. No significant anisotropy was observed in the T1 of the tissue water, while an average anisotropy of approximately 5% was observed in T2 at room temperature. The average anisotropy of T2 at -5 and -10 degrees C was found to be approximately 2 and 1.3%, respectively. PMID:6266530

  8. Mechanisms of Tissue–Iron Relaxivity: Nuclear Magnetic Resonance Studies of Human Liver Biopsy Specimens

    PubMed Central

    Ghugre, Nilesh R.; Coates, Thomas D.; Nelson, Marvin D.; Wood, John C.

    2010-01-01

    MRI is becoming an increasingly important tool to assess iron overload disorders, but the complex nature of proton–iron interactions has troubled noninvasive iron quantification. Intersite and intersequence variability as well as methodological inaccuracies have been limiting factors to its widespread clinical use. It is important to understand the underlying proton relaxation mechanisms within the (human) tissue environment to address these differences. In this respect, NMR relaxometry was performed on 10 fresh human liver biopsy specimens taken from patients with transfusion-dependent anemia. T1 (1/R1) inversion recovery, T2 (1/R2) single echo, and multiecho T2 CPMG measurements were performed on a 60-MHz Bruker Minispectrometer. NMR parameters were compared to quantitative iron levels and tissue histology. Relaxivities R1 and R2 both increased linearly with hepatic iron content, with R2 being more sensitive to iron. CPMG data were well described by a chemical-exchange model and predicted effective iron center dimensions consistent with hemosiderin-filled lysosomes. Nonexponential relaxation was evident at short refocusing intervals with R2 and amplitude behavior suggestive of magnetic susceptibility-based compartmentalization rather than anatomic subdivisions. NMR relaxometry of human liver biopsy specimens yields unique insights into the mechanisms of tissue–iron relaxivity. PMID:16215963

  9. Diffusion, relaxation, and chemical exchange in casein gels: A nuclear magnetic resonance study

    NASA Astrophysics Data System (ADS)

    Gottwald, Antje; Creamer, Lawrence K.; Hubbard, Penny L.; Callaghan, Paul T.

    2005-01-01

    Water in protein/water mixtures can be described in terms of bound water and free water, by exchange between these two states, and by its exchange with appropriate sites on the protein. 1H-NMR diffusion and relaxation measurements provide insights into the mobility of these states. T2 relaxation-time dispersions (i.e., T2 relaxation times at different echo pulse spacings) reveal additional information about exchange. We present a comprehensive set of diffusion and T2 dispersion measurements on casein gels for which the protein/water ratio ranges from 0.25 to 0.5. The combination of these methods, taken in conjunction with concentration dependence, allows a good estimate of the parameters required to fit the data with Luz/Meiboom and Carver/Richards models for relaxation and chemical exchange. We compare the exchange (a) between water and protein and (b) between free water and bound water. Further, we attempt to distinguish chemical site exchange and diffusion/susceptibility exchange.

  10. Off-resonance rotating frame spin-lattice NMR relaxation studies of phosphorus metabolite rotational diffusion in bovine lens homogenates

    SciTech Connect

    Caines, G.H.; Schleich, T.; Morgan, C.F. ); Farnsworth, P.N. )

    1990-08-21

    The rotational diffusion behavior of phosphorus metabolites present in calf lens cortical and nuclear homogenates was investigated by the NMR technique of {sup 31}P off-resonance rotating frame spin-lattice relaxation as a means of assessing the occurrence and extent of phosphorus metabolite-lens protein interactions. {sup 31}P NMR spectra of calf lens homogenates were obtained at 10 and 18{degree}C at 7.05 T. Effective rotational correlation times ({tau}{sub 0,eff}) for the major phosphorus metabolites present in cortical and nuclear bovine calf lens homogenates were derived from nonlinear least-squares analysis of R vs {omega}{sub e} data with the assumption of isotropic reorientational motion. Intramolecular dipole-dipole ({sup 1}H-{sup 31}P, {sup 31}P-{sup 31}P), chemical shift anisotropy (CSA), and solvent (water) translational intermolecular dipole-dipole ({sup 1}H-{sup 31}P) relaxation contributions were assumed in the analyses. A fast-exchange model between free and bound forms, was employed in the analysis of the metabolite R vs {omega}{sub e} curves to yield the fraction of free (unbound) metabolite ({Theta}{sub free}). The results of this study establish the occurrence of significant temperature-dependent (above and below the cold cataract phase transition temperature) binding of ATP (cortex) and PME (nucleus) and p{sub i} (nucleus) in calf lens.

  11. Laser double-resonance studies of electronic spectroscopy and state-resolved collisional relaxation in highly vibrationally excited acetylene

    SciTech Connect

    Tobiason, J.D.

    1992-01-01

    Vibrational overtone excitation combined with laser-induced fluorescence detection of acetylene molecules permits rotation-selected spectroscopy of the ([tilde A][sup 1]A[sub u]) electronic state and direct, state-resolved measurements of collisional energy transfer in the highly vibrationally excited ground electronic state. The author assigns energies of 1,045 transitions to previously unobserved ungerade vibrational states 2800-4500 cm[sup [minus]1] above the [tilde A] state origin. An analysis yields frequencies of 2856.4 and 3894.3 cm[sup [minus]1] for [nu][sub v][prime] and [nu][sub 3][prime] + [nu][sub 5][prime]. The author performs the first normal coordinate analysis of [tilde A] state acetylene based only on directly observed fundamentals. The spectroscopy measurements enable double-resonance experiments on the collisional dynamics of highly vibrationally excited acetylene. The quenching rate for single rotational states is twice the Lennard-Jones gas kinetic rate and fairly independent of vibrational energy level. Collision-induced detection of vibrational overtone excitation under single collision conditions allows direct measurements of state-of-state rotational and vibrational energy transfer. A collision-induced spectrum obtained by this new technique immediately identifies transfer channels and the [Delta]J and [Delta]E dependence of the transfer rates. The author observes changes of [vert bar][Delta]J[vert bar] and [Delta]E [approx] 3kT in a single collision. Directly measured rates for one set of vibrational relaxation pathways account for [approximately]3% of the total relaxation rate. The author also observes other vibrational relaxation pathways. The available pathways suggest that vibrational relaxation accounts for the rest of the total relaxation. Changes of [vert bar]J[vert bar] = 18 and [vert bar][Delta]E[vert bar] [approximately] 500 cm[sup [minus]1] in a single collision are observed.

  12. A brief overview of some physical studies on the relaxation dynamics and Förster resonance energy transfer of semiconductor quantum dots.

    PubMed

    Sadhu, Suparna; Patra, Amitava

    2013-08-26

    This article highlights some physical studies on the relaxation dynamics and Förster resonance energy transfer (FRET) of semiconductor quantum dots (QDs) and the way these phenomena change with size, shape, and composition of the QDs. The understanding of the excited-state dynamics of photoexcited QDs is essential for technological applications such as efficient solar energy conversion, light-emitting diodes, and photovoltaic cells. Here, our emphasis is directed at describing the influence of size, shape, and composition of the QDs on their different relaxation processes, that is, radiative relaxation rate, nonradiative relaxation rate, and number of trap states. A stochastic model of carrier relaxation dynamics in semiconductor QDs was proposed to correlate with the experimental results. Many recent studies reveal that the energy transfer between the QDs and a dye is a FRET process, as established from 1/d(6) distance dependence. QD-based energy-transfer processes have been used in applications such as luminescence tagging, imaging, sensors, and light harvesting. Thus, the understanding of the interaction between the excited state of the QD and the dye molecule and quantitative estimation of the number of dye molecules attached to the surface of the QD by using a kinetic model is important. Here, we highlight the influence of size, shape, and composition of QDs on the kinetics of energy transfer. Interesting findings reveal that QD-based energy-transfer processes offer exciting opportunities for future applications. Finally, a tentative outlook on future developments in this research field is given.

  13. High precision study of chemical relaxation in the system N2O4=2NO2 by photoacoustic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Fiedler, M.; Hess, P.

    1990-12-01

    The chemical relaxation of the N2O4 dissociation was studied using Ar+ laser excited acoustic resonances of a cylindrical cavity. The resonance profiles of the first radial mode were measured as a function of pressure and temperature by a computer controlled setup. The N2O4 dissociation rate constant and the mean rotational and vibrational relaxation time of the N2O4-NO2 mixture were obtained for temperatures between 273 and 317 K by fitting a detailed theoretical model of the resonator to the measured values for frequency dispersion, resonance broadening, and strength of the photoacoustic signal. Excellent agreement between theory and experiment was obtained for the frequency dispersion and the photoacoustic signal. An empirical correction function had to be introduced to account for discrepancies between the theoretically predicted and measured values of the resonance broadening which was in the percent region. A value of 6.1×10-15 cm3/molecule s was determined for the rate constant of N2O4 dissociation in the low pressure limit at 298 K. The activation energy of the N2O4 dissociation for 20 mbar pressure was determined to be EA=36 kJ/mol. A comparison of the measured low-pressure limit of the unimolecular rate constant with theoretical predictions of RRKM theory yielded values for the mean collision efficiency of N2O4 and NO2 between 0.95 and 0.5 in the temperature range 273-317 K.

  14. Relaxation and resonances in fluctuating dielectric systems

    NASA Astrophysics Data System (ADS)

    Garcia-Colin, L. S.; del Castillo, L. F.

    1989-09-01

    In this paper we show how the ideas behind extended irreversible thermodynamics are used to generate a systematic treatment of the relaxation and resonance phenomena in the propagation and absorption of electromagnetic energy in dielectric materials in a nonequilibrium state. Two cases are discussed: the first, in which the forced oscillations arising from the correlation between the fluctuations of the polarization vector and the electric field are neglected, and the second, in which this term is taken into account. In both cases we show how the main equations serve to make a connection between the macroscopic approach followed here and a number of results obtained for both, gases and polar liquids using molecular models. The results obtained here are compared with previous work on this problem, and new effects arising from the second case are pointed out.

  15. PREFACE: Muon spin rotation, relaxation or resonance

    NASA Astrophysics Data System (ADS)

    Heffner, Robert H.; Nagamine, Kanetada

    2004-10-01

    To a particle physicist a muon is a member of the lepton family, a heavy electron possessing a mass of about 1/9 that of a proton and a spin of 1/2, which interacts with surrounding atoms and molecules electromagnetically. Since its discovery in 1937, the muon has been put to many uses, from tests of special relativity to deep inelastic scattering, from studies of nuclei to tests of weak interactions and quantum electrodynamics, and most recently, as a radiographic tool to see inside heavy objects and volcanoes. In 1957 Richard Garwin and collaborators, while conducting experiments at the Columbia University cyclotron to search for parity violation, discovered that spin-polarized muons injected into materials might be useful to probe internal magnetic fields. This eventually gave birth to the modern field of muSR, which stands for muon spin rotation, relaxation or resonance, and is the subject of this special issue of Journal of Physics: Condensed Matter. Muons are produced in accelerators when high energy protons (generally >500 MeV) strike a target like graphite, producing pions which subsequently decay into muons. Most experiments carried out today use relatively low-energy (~4 MeV), positively-charged muons coming from pions decaying at rest in the skin of the production target. These muons have 100% spin polarization, a range in typical materials of about 180 mg cm-2, and are ideal for experiments in condensed matter physics and chemistry. Negatively-charged muons are also occasionally used to study such things as muonic atoms and muon-catalysed fusion. The muSR technique provides a local probe of internal magnetic fields and is highly complementary to inelastic neutron scattering and nuclear magnetic resonance, for example. There are four primary muSR facilities in the world today: ISIS (Didcot, UK), KEK (Tsukuba, Japan), PSI (Villigen, Switzerland) and TRIUMF (Vancouver, Canada), serving about 500 researchers world-wide. A new facility, JPARC (Tokai, Japan

  16. PREFACE: Muon spin rotation, relaxation or resonance

    NASA Astrophysics Data System (ADS)

    Heffner, Robert H.; Nagamine, Kanetada

    2004-10-01

    To a particle physicist a muon is a member of the lepton family, a heavy electron possessing a mass of about 1/9 that of a proton and a spin of 1/2, which interacts with surrounding atoms and molecules electromagnetically. Since its discovery in 1937, the muon has been put to many uses, from tests of special relativity to deep inelastic scattering, from studies of nuclei to tests of weak interactions and quantum electrodynamics, and most recently, as a radiographic tool to see inside heavy objects and volcanoes. In 1957 Richard Garwin and collaborators, while conducting experiments at the Columbia University cyclotron to search for parity violation, discovered that spin-polarized muons injected into materials might be useful to probe internal magnetic fields. This eventually gave birth to the modern field of muSR, which stands for muon spin rotation, relaxation or resonance, and is the subject of this special issue of Journal of Physics: Condensed Matter. Muons are produced in accelerators when high energy protons (generally >500 MeV) strike a target like graphite, producing pions which subsequently decay into muons. Most experiments carried out today use relatively low-energy (~4 MeV), positively-charged muons coming from pions decaying at rest in the skin of the production target. These muons have 100% spin polarization, a range in typical materials of about 180 mg cm-2, and are ideal for experiments in condensed matter physics and chemistry. Negatively-charged muons are also occasionally used to study such things as muonic atoms and muon-catalysed fusion. The muSR technique provides a local probe of internal magnetic fields and is highly complementary to inelastic neutron scattering and nuclear magnetic resonance, for example. There are four primary muSR facilities in the world today: ISIS (Didcot, UK), KEK (Tsukuba, Japan), PSI (Villigen, Switzerland) and TRIUMF (Vancouver, Canada), serving about 500 researchers world-wide. A new facility, JPARC (Tokai, Japan

  17. High-pressure nuclear-magnetic-resonance study of carbon-13 relaxation in 2-ethylhexyl benzoate and 2-ethylhexyl cyclohexanecarboxylate

    NASA Astrophysics Data System (ADS)

    Adamy, S. T.; Grandinetti, P. J.; Masuda, Y.; Campbell, D.; Jonas, J.

    1991-03-01

    Natural abundance carbon-13 spin-lattice relaxation times and 13G-1H nuclear Overhauser enhancement (NOE) times of 2-ethyl hexylbenzoate (EHB) and 2-ethyl hexylcyclohexanecarboxylate (EHC) have been measured along isotherms of -20, 0, 20, 40, and 80 °C at pressures of 1-5000 bars using high-pressure, high-resolution NMR techniques. The ability to use pressure as an experimental variable has allowed us to study a wide range of molecular motions from extreme narrowing into the slow motional regime. In addition, the high-resolution capability even at high pressure permits the measurement of 13C and NOE for each individual carbon in the molecules studied. Relaxation in both molecules is successfully analyzed in terms of a model assuming a Cole-Davidson distribution of correlation times. The comparison of parameters used in the model demonstrates the increased flexibility of the EHC ring over the EHB ring and also shows how the presence of the flexible ring contributes to the increased over-all mobility of the EHC molecule. The analysis of molecular reorientations in terms of activation volumes also indicates that EHB motion is highly restricted at low temperature.

  18. A theoretical study of rotational diffusion models for rod-shaped viruses. The influence of motion on 31P nuclear magnetic resonance lineshapes and transversal relaxation.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1993-01-01

    Information about the interaction between nucleic acids and coat proteins in intact virus particles may be obtained by studying the restricted backbone dynamics of the incapsulated nucleic acids using 31P nuclear magnetic resonance (NMR) spectroscopy. In this article, simulations are carried out to investigate how reorientation of a rod-shaped virus particle as a whole and isolated nucleic acid motions within the virion influence the 31P NMR lineshape and transversal relaxation dominated by the phosphorus chemical shift anisotropy. Two opposite cases are considered on a theoretical level. First, isotropic rotational diffusion is used as a model for mobile nucleic acids that are loosely or partially bound to the protein coat. The effect of this type of diffusion on lineshape and transversal relaxation is calculated by solving the stochastic Liouville equation by an expansion in spherical functions. Next, uniaxial rotational diffusion is assumed to represent the mobility of phosphorus in a virion that rotates as a rigid rod about its length axis. This type of diffusion is approximated by an exchange process among discrete sites. As turns out from these simulations, the amplitude and the frequency of the motion can only be unequivocally determined from experimental data by a combined analysis of the lineshape and the transversal relaxation. In the fast motional region both the isotropic and the uniaxial diffusion model predict the same transversal relaxation as the Redfield theory. For very slow motion, transversal relaxation resembles the nonexponential relaxation as observed for water molecules undergoing translational diffusion in a magnetic field gradient. In this frequency region T2e is inversely proportional to the cube root of the diffusion coefficient. In addition to the isotropic and uniaxial diffusion models, a third model is presented, in which fast restricted nucleic acid backbone motions dominating the lineshape are superimposed on a slow rotation of the

  19. Control of Transport-Barrier Relaxations by Resonant Magnetic Perturbations

    SciTech Connect

    Leconte, M.; Beyer, P.; Benkadda, S.

    2009-01-30

    Transport-barrier relaxation oscillations in the presence of resonant magnetic perturbations are investigated using three-dimensional global fluid turbulence simulations from first principles at the edge of a tokamak. It is shown that resonant magnetic perturbations have a stabilizing effect on these relaxation oscillations and that this effect is due mainly to a modification of the pressure profile linked to the presence of both residual magnetic island chains and a stochastic layer.

  20. Identification of chloride-binding sites in hemoglobin by nuclear-magnetic-resonance quadrupole-relaxation studies of hemoglobin digests.

    PubMed

    Chiancone, E; Norne, J E; Forsén, S; Bonaventura, J; Brunori, M; Antonini, E; Wyman, J

    1975-07-01

    35Cl minus-nuclear magnetic resonance (NMR) studies indicate that various digests of human hemoglobin with carboxypeptidase A and B, or a combination of the two, may be used for the identification of chloride binding sites. All the digestion products contain, like hemoglobin itself, at least two classes of binding sites, one of high, the others of low affinity. The pH dependence of the excess linewidth of the 35Cl minus NMR signal indicates that in the simple digests with either carboxypeptidase A or B, chloride is bound with high affinity at or near His-beta146-Asp-beta94 and at or near Val-alpha1-Arg-alpha141. The high-affinity sites show, in the case of the simple digests, a strong oxygen linkage which is lost in the forms digested with both carboxypeptidase A and B; this linkage may thus be correlated to the presence of conformational changes. Organic phosphates, like inositol hexaphosphate, show competition for some of the high-affinity chloride binding sites in hemoglobin and in the simple digests. This competition is likewise lost in the doubly digested hemoglobins. PMID:236

  1. Pharmaceutical Applications of Relaxation Filter-Selective Signal Excitation Methods for ¹⁹F Solid-State Nuclear Magnetic Resonance: Case Study With Atorvastatin in Dosage Formulation.

    PubMed

    Asada, Mamiko Nasu; Nemoto, Takayuki; Mimura, Hisashi

    2016-03-01

    We recently developed several new relaxation filter-selective signal excitation (RFS) methods for (13)C solid-state nuclear magnetic resonance (NMR) that allow (13)C signal extraction of the target components from pharmaceuticals. These methods were successful in not only qualification but also quantitation over the wide range of 5% to 100%. Here, we aimed to improve the sensitivity of these methods and initially applied them to (19)F solid-state NMR, on the basis that the fluorine atom is one of the most sensitive NMR-active nuclei. For testing, we selected atorvastatin calcium (ATC), an antilipid BCS class II drug that inhibits 3-hydroxy-3-methylglutaryl-coenzyme A reductase and is marketed in crystalline and amorphous forms. Tablets were obtained from 2 generic drug suppliers, and the ATC content occurred mainly as an amorphous form. Using the RFS method with (19)F solid-state NMR, we succeeded in qualifying trace amounts (less than 0.5% w/w level) of crystalline phase (Form I) of ATC in the tablets. RFS methods with (19)F solid-state NMR are practical and time efficient and can contribute not only to the study of pharmaceutical drugs, including those with small amounts of a highly potent active ingredient within a formulated product, but also to the study of fluoropolymers in material sciences.

  2. Resonant Perturbation Theory of Decoherence and Relaxation of Quantum Bits

    DOE PAGES

    Merkli, M.; Berman, G. P.; Sigal, I. M.

    2010-01-01

    We describe our recenmore » t results on the resonant perturbation theory of decoherence and relaxation for quantum systems with many qubits. The approach represents a rigorous analysis of the phenomenon of decoherence and relaxation for general N -level systems coupled to reservoirs of bosonic fields. We derive a representation of the reduced dynamics valid for all times t ≥ 0 and for small but fixed interaction strength. Our approach does not involve master equation approximations and applies to a wide variety of systems which are not explicitly solvable.« less

  3. Gd3+ spin-lattice relaxation via multi-band conduction electrons in Y(1-x)Gd(x)In3: an electron spin resonance study.

    PubMed

    Cabrera-Baez, M; Iwamoto, W; Magnavita, E T; Osorio-Guillén, J M; Ribeiro, R A; Avila, M A; Rettori, C

    2014-04-30

    Interest in the electronic structure of the intermetallic compound YIn3 has been renewed with the recent discovery of superconductivity at T ∼ 1 K, which may be filamentary in nature. In this work we perform electron spin resonance (ESR) experiments on Gd(3+) doped YIn3 (Y1-xGdxIn3; 0.001 ⪅ x ⩽̸ 0.08), showing that the spin-lattice relaxation of the Gd(3+) ions, due to the exchange interaction between the Gd(3+) localized magnetic moment and the conduction electrons (ce), is processed via the presence of s-, p- and d-type ce at the YIn3 Fermi level. These findings are revealed by the Gd(3+) concentration dependence of the Korringa-like relaxation rate d(ΔH)/dT and g-shift (Δg = g - 1.993), that display bottleneck relaxation behavior for the s-electrons and unbottleneck behavior for the p- and d-electrons. The Korringa-like relaxation rates vary from 22(2) Oe/K for x ⪅ 0.001 to 8(2) Oe/K for x = 0.08 and the g-shift values change, respectively, from a positive Δg = +0.047(10) to a negative Δg = -0.008(4). Analysis in terms of a three-band ce model allows the extraction of the corresponding exchange interaction parameters Jfs, Jfp and Jfd.

  4. Nuclear Magnetic resonance quadrupole relaxation studies of chloride binding to the isolated hemoglobins from trout (Salmo irideus).

    PubMed

    Chiancone, E; Norne, J E; Forsén, S; Brunori, M; Antonini, E

    1975-02-01

    NMR studies of chloride binding to the main components of trout blood, Hb Trout I and Hb Trout IV, indicate that although the affinity of chloride is high for both hemoglobins, the characteristics of the binding process are markedly differnet. In Hb Trout IV chemical exchange at the chloride binding site(s) is fast and quadrupole effects determine the linewidth; chloride binding has a definite pH dependence, but there is no significant oxygen linkage. In contrast Hb Trout I represents a unique case of slow chemical exchange, which may depend on unusual stereoche mical characteristics of the chloride binding site; chloride binding is pH independent, but shows a significant oxygen linkage, which may be attributed to changes of the lifetime of chloride at the binding site. The chloride binding properties displayed by Hb Trout I and IV have been compared with those of normal and modified human hemoglobins and discussed in terms of the structural differences in the C- and N-terminal regions of the alpha- and beta-chains. PMID:236050

  5. 13C-NMR off-resonance rotating frame spin-lattice relaxation studies of bovine lens gamma-crystallin self association: effect of 'macromolecular crowding'.

    PubMed

    Stevens, A; Wang, S X; Caines, G H; Schleich, T

    1995-01-01

    The NMR technique of 13C off-resonance rotating frame spin-lattice relaxation, which provides an accurate assessment of the effective rotational correlation time (tau 0, eff) for macromolecular rotational diffusion, was applied to the study of gamma-crystallin association as a function of protein concentration and temperature. Values of the effective rotational correlation time for gamma-crystallin rotational diffusion were obtained at moderate to high protein concentrations (80-350 mg/ml) and at temperatures above, and below, the cold cataract phase transition temperature. With increasing concentration gamma-crystallin was observed to increasingly associate as reflected by larger values of tau 0, eff Decreasing temperature in the range of 35 to 22 degrees C was found to result in no change in the temperature corrected value of tau 0, eff at a gamma-crystallin concentration of 80 mg/ml, whereas at temperatures of 18 degrees C or below, this parameter was approx. twofold larger, suggesting the occurrence of a well defined phase transition, which correlated well with the cold cataract phase transition temperature. At higher protein concentrations, by contrast, tau 0, eff (temperature corrected) was found to increase by approx. 1.6- to 2-times in the temperature interval 35 degrees C to 22 degrees C, a result consistent with the dependence of the cold cataract phase transition temperature on gamma-crystallin concentration. Analysis of intensity ratio dispersion curves, using an assumed model of isodesmic association, permitted the estimation of the association constant characterizing the aggregation under particular conditions of concentration and temperature. The significant increase in the value of the association constant with moderate increases in protein concentration was rationalized by invoking the effect of 'macromolecular crowding'. The results obtained in this study suggest that in the intact lens, where high protein concentrations prevail, gamma

  6. Direct Simulation of Magnetic Resonance Relaxation Rates and Line Shapes from Molecular Trajectories

    PubMed Central

    Rangel, David P.; Baveye, Philippe C.; Robinson, Bruce H.

    2012-01-01

    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. PMID:22540276

  7. A 15N CPMG relaxation dispersion experiment more resistant to resonance offset and pulse imperfection

    NASA Astrophysics Data System (ADS)

    Jiang, Bin; Yu, Binhan; Zhang, Xu; Liu, Maili; Yang, Daiwen

    2015-08-01

    Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion is a powerful NMR method to study protein dynamics on the microsecond-millisecond time scale. J-coupling, resonance offset, radio frequency field inhomogeneity, and pulse imperfection often introduce systematic errors into the measured transverse relaxation rates. Here we proposed a modified continuous wave decoupling CPMG experiment, which is more unaffected by resonance offset and pulse imperfection. We found that it is unnecessary to match the decoupling field strength with the delay between CPMG refocusing pulses, provided that decoupling field is strong enough. The performance of the scheme proposed here was shown by simulations and further demonstrated experimentally on a fatty acid binding protein.

  8. Suppression of Spin-Exchange Relaxation Using Pulsed Parametric Resonance

    NASA Astrophysics Data System (ADS)

    Korver, A.; Wyllie, R.; Lancor, B.; Walker, T. G.

    2013-07-01

    We demonstrate that spin-exchange dephasing of Larmor precession at near-Earth-scale fields is effectively eliminated by dressing the alkali-metal atom spins in a sequence of ac-coupled 2π pulses, repeated at the Larmor precession frequency. The contribution of spin-exchange collisions to the spectroscopic linewidth is reduced by a factor of the duty cycle of the pulses. We experimentally demonstrate resonant transverse pumping in magnetic fields as high as 0.1 G, present experimental measurements of the suppressed spin-exchange relaxation, and show enhanced magnetometer response relative to a light-narrowed scalar magnetometer.

  9. Evaluation of brain edema using magnetic resonance proton relaxation times

    SciTech Connect

    Fu, Y.; Tanaka, K.; Nishimura, S. )

    1990-01-01

    Experimental and clinical studies on the evaluation of water content in cases of brain edema were performed in vivo, using MR proton relaxation times (longitudinal relaxation time, T1; transverse relaxation time, T2). Brain edema was produced in the white matter of cats by the direct infusion method. The correlations between proton relaxation times obtained from MR images and the water content of white matter were studied both in autoserum-infused cats and in saline-infused cats. The correlations between T1 as well as T2 and the water content in human vasogenic brain edema were also examined and compared with the data obtained from the serum group. T1 and T2 showed good correlations with the water content of white matter not only in the experimental animals but also in the clinical cases. The quality of the edema fluid did not influence relaxation time and T1 seemed to represent almost solely the water content of the tissue. T2, however, was affected by the nature of existence of water and was more sensitive than T1 in detecting extravasated edema fluid. It seems feasible therefore to evaluate the water content of brain edema on the basis of T1 values.

  10. Deuterium off-resonance rotating frame spin-lattice relaxation of macromolecular bound ligands.

    PubMed Central

    Rydzewski, J M; Schleich, T

    1996-01-01

    Deuterated 3-trimethylsilylpropionic acid binding to bovine serum albumin was used as a model system to examine the feasibility and limitations of using the deuterium off-resonance rotating frame spin-lattice relaxation experiment for the study of equilibrium ligand-binding behavior to proteins. The results of this study demonstrate that the rotational-diffusion behavior of the bound species can be monitored directly, i.e., the observed correlation time of the ligand in the presence of a protein is approximately equal to the correlation time of the ligand in the bound state, provided that the fraction of bound ligand is at least 0.20. The presence of local ligand motion and/or chemical exchange contributions to relaxation in the bound state was inferred from the observation that the correlation time of the bound ligand was somewhat smaller than the correlation time characterizing the overall tumbling of the protein. An approximate value for the fraction of bound ligand was obtained from off-resonance relaxation experiments when supplemental spin-lattice or transverse relaxation times were employed in the analysis. Incorporation of local motion effects for the bound species into the theoretical relaxation formalism enabled the evaluation of an order parameter and an effective correlation time, which in conjunction with a wobbling in a cone model, provided additional information about ligand motion in the bound state. PMID:8785304

  11. Stellar dynamics around a massive black hole - II. Resonant relaxation

    NASA Astrophysics Data System (ADS)

    Sridhar, S.; Touma, Jihad R.

    2016-06-01

    We present a first-principles theory of resonant relaxation (RR) of a low-mass stellar system orbiting a more massive black hole (MBH). We first extend the kinetic theory of Gilbert to include the Keplerian field of a black hole of mass M•. Specializing to a Keplerian stellar system of mass M ≪ M•, we use the orbit-averaging method of Sridhar & Touma to derive a kinetic equation for RR. This describes the collisional evolution of a system of N ≫ 1 Gaussian rings in a reduced 5-dim space, under the combined actions of self-gravity, 1 post-Newtonian (PN) and 1.5 PN relativistic effects of the MBH and an arbitrary external potential. In general geometries, RR is driven by both apsidal and nodal resonances, so the distinction between scalar RR and vector RR disappears. The system passes through a sequence of quasi-steady secular collisionless equilibria, driven by irreversible two-ring correlations that accrue through gravitational interactions, both direct and collective. This correlation function is related to a `wake function', which is the linear response of the system to the perturbation of a chosen ring. The wake function is easier to appreciate, and satisfies a simpler equation, than the correlation function. We discuss general implications for the interplay of secular dynamics and non-equilibrium statistical mechanics in the evolution of Keplerian stellar systems towards secular thermodynamic equilibria, and set the stage for applications to the RR of axisymmetric discs in Paper III.

  12. The Effects of Resonant Relaxation and Relativistic Precession on the Rate of Extreme Mass Ratio Inspirals

    NASA Astrophysics Data System (ADS)

    Gill, Michael; Miller, M.; Richardson, D.; Trenti, M.

    2010-01-01

    Extreme Mass Ratio Inspirals (EMRIs), during which a stellar-mass compact object in close orbit around a supermassive black hole gradually loses energy and angular momentum through the emission of gravitational radiation, are likely to be key sources of long-wavelength gravitational waves. Because the expected wavelengths fall in the band to which the Laser Interferometer Space Antenna will be most sensitive, these events should be detectable and thus provide a probe of the strong-field limit of gravity. Despite many years of study of EMRIs, there exist key uncertainties in relevant processes such as resonant relaxation. We present preliminary simulations of the center of a typical galaxy using a tree N-body code, and discuss the implications of our results for resonant relaxation in relativistic gravity. This work was funded in part by NASA grant NNX08AH29G.

  13. A (15)N CPMG relaxation dispersion experiment more resistant to resonance offset and pulse imperfection.

    PubMed

    Jiang, Bin; Yu, Binhan; Zhang, Xu; Liu, Maili; Yang, Daiwen

    2015-08-01

    Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion is a powerful NMR method to study protein dynamics on the microsecond-millisecond time scale. J-coupling, resonance offset, radio frequency field inhomogeneity, and pulse imperfection often introduce systematic errors into the measured transverse relaxation rates. Here we proposed a modified continuous wave decoupling CPMG experiment, which is more unaffected by resonance offset and pulse imperfection. We found that it is unnecessary to match the decoupling field strength with the delay between CPMG refocusing pulses, provided that decoupling field is strong enough. The performance of the scheme proposed here was shown by simulations and further demonstrated experimentally on a fatty acid binding protein. PMID:26037134

  14. Effects of pulmonary inhalation on hyperpolarized krypton-83 magnetic resonance T1 relaxation.

    PubMed

    Stupic, K F; Elkins, N D; Pavlovskaya, G E; Repine, J E; Meersmann, T

    2011-07-01

    The (83)Kr magnetic resonance (MR) relaxation time T(1) of krypton gas in contact with model surfaces was previously found to be highly sensitive to surface composition, surface-to-volume ratio, and surface temperature. The work presented here explored aspects of pulmonary (83)Kr T(1) relaxation measurements in excised lungs from healthy rats using hyperpolarized (hp) (83)Kr with approximately 4.4% spin polarization. MR spectroscopy without spatial resolution was applied to the ex vivo lungs that actively inhale hp (83)Kr through a custom designed ventilation system. Various inhalation schemes were devised to study the influence of anatomical dead space upon the measured (83)Kr T(1) relaxation times. The longitudinal (83)Kr relaxation times in the distal airways and the respiratory zones were independent of the lung inhalation volume, with T(1) = 1.3 s and T(1) = 1.0 s, depending only on the applied inhalation scheme. The obtained data were highly reproducible between different specimens. Further, the (83)Kr T(1) relaxation times in excised lungs were unaffected by the presence of up to 40% oxygen in the hp gas mixture. The results support the possible importance of (83)Kr as a biomarker for evaluating lung function.

  15. Effects of pulmonary inhalation on hyperpolarized krypton-83 magnetic resonance T1 relaxation

    NASA Astrophysics Data System (ADS)

    Stupic, K. F.; Elkins, N. D.; Pavlovskaya, G. E.; Repine, J. E.; Meersmann, T.

    2011-07-01

    The 83Kr magnetic resonance (MR) relaxation time T1 of krypton gas in contact with model surfaces was previously found to be highly sensitive to surface composition, surface-to-volume ratio, and surface temperature. The work presented here explored aspects of pulmonary 83Kr T1 relaxation measurements in excised lungs from healthy rats using hyperpolarized (hp) 83Kr with approximately 4.4% spin polarization. MR spectroscopy without spatial resolution was applied to the ex vivo lungs that actively inhale hp 83Kr through a custom designed ventilation system. Various inhalation schemes were devised to study the influence of anatomical dead space upon the measured 83Kr T1 relaxation times. The longitudinal 83Kr relaxation times in the distal airways and the respiratory zones were independent of the lung inhalation volume, with T1 = 1.3 s and T1 = 1.0 s, depending only on the applied inhalation scheme. The obtained data were highly reproducible between different specimens. Further, the 83Kr T1 relaxation times in excised lungs were unaffected by the presence of up to 40% oxygen in the hp gas mixture. The results support the possible importance of 83Kr as a biomarker for evaluating lung function.

  16. Measurement of cyclotron resonance relaxation time in the two-dimensional electron system

    SciTech Connect

    Andreev, I. V. Muravev, V. M.; Kukushkin, I. V.; Belyanin, V. N.

    2014-11-17

    Dependence of cyclotron magneto-plasma mode relaxation time on electron concentration and temperature in the two-dimensional electron system in GaAs/AlGaAs quantum wells has been studied. Comparative analysis of cyclotron and transport relaxation time has been carried out. It was demonstrated that with the temperature increase transport relaxation time tends to cyclotron relaxation time. It was also shown that cyclotron relaxation time, as opposed to transport relaxation time, has a weak electron density dependence. The cyclotron time can exceed transport relaxation time by an order of magnitude in a low-density range.

  17. Gadolinium oxide nanoplates with high longitudinal relaxivity for magnetic resonance imaging.

    PubMed

    Cho, Minjung; Sethi, Richa; Narayanan, Jeyarama Subramanian Ananta; Lee, Seung Soo; Benoit, Denise N; Taheri, Nasim; Decuzzi, Paolo; Colvin, Vicki L

    2014-11-21

    Molecular-based contrast agents for magnetic resonance imaging (MRI) are often characterized by insufficient relaxivity, thus requiring the systemic injection of high doses to induce sufficient contrast enhancement at the target site. In this work, gadolinium oxide (Gd2O3) nanoplates are produced via a thermal decomposition method. The nanoplates have a core diameter varying from 2 to 22 nm, a thickness of 1 to 2 nm and are coated with either an oleic acid bilayer or an octylamine modified poly(acrylic acid) (PAA-OA) polymer layer. For the smaller nanoplates, longitudinal relaxivities (r1) of 7.96 and 47.2 (mM s)(-1) were measured at 1.41 T for the oleic acid bilayer and PAA-OA coating, respectively. These values moderately reduce as the size of the Gd2O3 nanoplates increases, and are always larger for the PAA-OA coating. Cytotoxicity studies on human dermal fibroblast cells documented no significant toxicity, with 100% cell viability preserved up to 250 μM for the PAA-OA coated Gd2O3 nanoplates. Given the 10 times increase in longitudinal relaxivity over the commercially available Gd-based molecular agents and the favorable toxicity profile, the 2 nm PAA-OA coated Gd2O3 nanoplates could represent a new class of highly effective T1 MRI contrast agents.

  18. Giant thermo-optical relaxation oscillations in millimeter-size whispering gallery mode disk resonators.

    PubMed

    Diallo, Souleymane; Lin, Guoping; Chembo, Yanne K

    2015-08-15

    In this Letter, we show that giant thermo-optical oscillations can be triggered in millimeter (mm)-size whispering gallery mode (WGM) disk resonators when they are pumped by a resonant continuous-wave laser. Our resonator is an ultrahigh-Q barium fluoride cavity that features a positive thermo-optic coefficient and a negative thermo-elastic coefficient. We demonstrate for the first time, to our knowledge, that the complex interplay between these two thermic coefficients and the intrinsic Kerr nonlinearity yields very sharp slow-fast relaxation oscillations with a slow timescale that can be exceptionally large, typically of the order of 1 s. We use a time-domain model to gain understanding into this instability, and we find that both the experimental and theoretical results are in excellent agreement. The understanding of these thermal effects is an essential requirement for every WGM-related application and our study demonstrates that even in the case of mm-size resonators, such effects can still be accurately analyzed using nonlinear time-domain models.

  19. Semimicroscopic description of basic modes of relaxation of the Gamow-Teller resonance

    SciTech Connect

    Safonov, I. V. Urin, M. H.

    2012-12-15

    Semimicroscopic approach based on the continuum version of the random-phase approximation and on a phenomenological method for taking into account the fragmentation effect is used to describe quantitatively basic relaxation parameters of the Gamow-Teller resonance in magic and nearmagic nuclei. For the {sup 208}Bi nucleus, the results obtained by calculating the resonance parameters in question are compared with respective experimental data.

  20. Robust determination of surface relaxivity from nuclear magnetic resonance DT(2) measurements.

    PubMed

    Luo, Zhi-Xiang; Paulsen, Jeffrey; Song, Yi-Qiao

    2015-10-01

    Nuclear magnetic resonance (NMR) is a powerful tool to probe into geological materials such as hydrocarbon reservoir rocks and groundwater aquifers. It is unique in its ability to obtain in situ the fluid type and the pore size distributions (PSD). The T1 and T2 relaxation times are closely related to the pore geometry through the parameter called surface relaxivity. This parameter is critical for converting the relaxation time distribution into the PSD and so is key to accurately predicting permeability. The conventional way to determine the surface relaxivity ρ2 had required independent laboratory measurements of the pore size. Recently Zielinski et al. proposed a restricted diffusion model to extract the surface relaxivity from the NMR diffusion-T2 relaxation (DT2) measurement. Although this method significantly improved the ability to directly extract surface relaxivity from a pure NMR measurement, there are inconsistencies with their model and it relies on a number of preset parameters. Here we propose an improved signal model to incorporate a scalable LT and extend their method to extract the surface relaxivity based on analyzing multiple DT2 maps with varied diffusion observation time. With multiple diffusion observation times, the apparent diffusion coefficient correctly describes the restricted diffusion behavior in samples with wide PSDs, and the new method does not require predetermined parameters, such as the bulk diffusion coefficient and tortuosity. Laboratory experiments on glass beads packs with the beads diameter ranging from 50 μm to 500 μm are used to validate the new method. The extracted diffusion parameters are consistent with their known values and the determined surface relaxivity ρ2 agrees with the expected value within ±7%. This method is further successfully applied on a Berea sandstone core and yields surface relaxivity ρ2 consistent with the literature.

  1. Robust determination of surface relaxivity from nuclear magnetic resonance DT2 measurements

    NASA Astrophysics Data System (ADS)

    Luo, Zhi-Xiang; Paulsen, Jeffrey; Song, Yi-Qiao

    2015-10-01

    Nuclear magnetic resonance (NMR) is a powerful tool to probe into geological materials such as hydrocarbon reservoir rocks and groundwater aquifers. It is unique in its ability to obtain in situ the fluid type and the pore size distributions (PSD). The T1 and T2 relaxation times are closely related to the pore geometry through the parameter called surface relaxivity. This parameter is critical for converting the relaxation time distribution into the PSD and so is key to accurately predicting permeability. The conventional way to determine the surface relaxivity ρ2 had required independent laboratory measurements of the pore size. Recently Zielinski et al. proposed a restricted diffusion model to extract the surface relaxivity from the NMR diffusion-T2 relaxation (DT2) measurement. Although this method significantly improved the ability to directly extract surface relaxivity from a pure NMR measurement, there are inconsistencies with their model and it relies on a number of preset parameters. Here we propose an improved signal model to incorporate a scalable LT and extend their method to extract the surface relaxivity based on analyzing multiple DT2 maps with varied diffusion observation time. With multiple diffusion observation times, the apparent diffusion coefficient correctly describes the restricted diffusion behavior in samples with wide PSDs, and the new method does not require predetermined parameters, such as the bulk diffusion coefficient and tortuosity. Laboratory experiments on glass beads packs with the beads diameter ranging from 50 μm to 500 μm are used to validate the new method. The extracted diffusion parameters are consistent with their known values and the determined surface relaxivity ρ2 agrees with the expected value within ±7%. This method is further successfully applied on a Berea sandstone core and yields surface relaxivity ρ2 consistent with the literature.

  2. Robust determination of surface relaxivity from nuclear magnetic resonance DT(2) measurements.

    PubMed

    Luo, Zhi-Xiang; Paulsen, Jeffrey; Song, Yi-Qiao

    2015-10-01

    Nuclear magnetic resonance (NMR) is a powerful tool to probe into geological materials such as hydrocarbon reservoir rocks and groundwater aquifers. It is unique in its ability to obtain in situ the fluid type and the pore size distributions (PSD). The T1 and T2 relaxation times are closely related to the pore geometry through the parameter called surface relaxivity. This parameter is critical for converting the relaxation time distribution into the PSD and so is key to accurately predicting permeability. The conventional way to determine the surface relaxivity ρ2 had required independent laboratory measurements of the pore size. Recently Zielinski et al. proposed a restricted diffusion model to extract the surface relaxivity from the NMR diffusion-T2 relaxation (DT2) measurement. Although this method significantly improved the ability to directly extract surface relaxivity from a pure NMR measurement, there are inconsistencies with their model and it relies on a number of preset parameters. Here we propose an improved signal model to incorporate a scalable LT and extend their method to extract the surface relaxivity based on analyzing multiple DT2 maps with varied diffusion observation time. With multiple diffusion observation times, the apparent diffusion coefficient correctly describes the restricted diffusion behavior in samples with wide PSDs, and the new method does not require predetermined parameters, such as the bulk diffusion coefficient and tortuosity. Laboratory experiments on glass beads packs with the beads diameter ranging from 50 μm to 500 μm are used to validate the new method. The extracted diffusion parameters are consistent with their known values and the determined surface relaxivity ρ2 agrees with the expected value within ±7%. This method is further successfully applied on a Berea sandstone core and yields surface relaxivity ρ2 consistent with the literature. PMID:26340435

  3. Gadolinium oxide nanoplates with high longitudinal relaxivity for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Cho, Minjung; Sethi, Richa; Ananta Narayanan, Jeyarama Subramanian; Lee, Seung Soo; Benoit, Denise N.; Taheri, Nasim; Decuzzi, Paolo; Colvin, Vicki L.

    2014-10-01

    Molecular-based contrast agents for magnetic resonance imaging (MRI) are often characterized by insufficient relaxivity, thus requiring the systemic injection of high doses to induce sufficient contrast enhancement at the target site. In this work, gadolinium oxide (Gd2O3) nanoplates are produced via a thermal decomposition method. The nanoplates have a core diameter varying from 2 to 22 nm, a thickness of 1 to 2 nm and are coated with either an oleic acid bilayer or an octylamine modified poly(acrylic acid) (PAA-OA) polymer layer. For the smaller nanoplates, longitudinal relaxivities (r1) of 7.96 and 47.2 (mM s)-1 were measured at 1.41 T for the oleic acid bilayer and PAA-OA coating, respectively. These values moderately reduce as the size of the Gd2O3 nanoplates increases, and are always larger for the PAA-OA coating. Cytotoxicity studies on human dermal fibroblast cells documented no significant toxicity, with 100% cell viability preserved up to 250 μM for the PAA-OA coated Gd2O3 nanoplates. Given the 10 times increase in longitudinal relaxivity over the commercially available Gd-based molecular agents and the favorable toxicity profile, the 2 nm PAA-OA coated Gd2O3 nanoplates could represent a new class of highly effective T1 MRI contrast agents.Molecular-based contrast agents for magnetic resonance imaging (MRI) are often characterized by insufficient relaxivity, thus requiring the systemic injection of high doses to induce sufficient contrast enhancement at the target site. In this work, gadolinium oxide (Gd2O3) nanoplates are produced via a thermal decomposition method. The nanoplates have a core diameter varying from 2 to 22 nm, a thickness of 1 to 2 nm and are coated with either an oleic acid bilayer or an octylamine modified poly(acrylic acid) (PAA-OA) polymer layer. For the smaller nanoplates, longitudinal relaxivities (r1) of 7.96 and 47.2 (mM s)-1 were measured at 1.41 T for the oleic acid bilayer and PAA-OA coating, respectively. These values

  4. Relaxation nuclear magnetic resonance imaging (R-NMRI) of desiccation in M9787 silicone pads.

    SciTech Connect

    Alam, Todd M; Cherry, Brian Ray; Alam, Mary Kathleen

    2004-06-01

    The production and aging of silicone materials remains an important issue in the weapons stockpile due to their utilization in a wide variety of components and systems within the stockpile. Changes in the physical characteristics of silicone materials due to long term desiccation has been identified as one of the major aging effects observed in silicone pad components. Here we report relaxation nuclear magnetic resonance imaging (R-NMRI) spectroscopy characterization of the silica-filled and unfilled polydimethylsiloxane (PDMS) and polydiphenylsiloxane (PDPS) copolymer (M9787) silicone pads within desiccating environments. These studies were directed at providing additional details about the heterogeneity of the desiccation process. Uniform NMR spin-spin relaxation time (T2) images were observed across the pad thickness indicating that the drying process is approximately uniform, and that the desiccation of the M9787 silicone pad is not a H2O diffusion limited process. In a P2O5 desiccation environment, significant reduction of T2 was observed for the silica-filled and unfilled M9787 silicone pad for desiccation up to 225 days. A very small reduction in T2 was observed for the unfilled copolymer between 225 and 487 days. The increase in relative stiffness with desiccation was found to be higher for the unfilled copolymer. These R-NMRI results are correlated to local changes in the modulus of the material

  5. Nuclear magnetic resonance transverse relaxation in muscle water.

    PubMed Central

    Fung, B M; Puon, P S

    1981-01-01

    The origin of the nonexponentiality of proton spin echoes of skeletal muscle has been carefully examined. It is shown that the slowly decaying part of the proton spin echoes is not due to extracellular water. First, for muscle from mice with in vivo deuteration, the deuteron spin echoes were also nonexponential, but the slowly decaying part had a larger weighing factor. Second, for glycerinated muscle in which cell membranes were disrupted, the proton spin echoes were similar to those in intact muscle. Third, the nonexponentiality of the proton spin echoes in intact muscle increased when postmortem rigor set in. Finally, when the lifetimes of extracellular water and intracellular water were taken into account in the exchange, it was found that the two types of water would not give two resolvable exponentials with the observed decay constants. It is suggested that the unusually short T2's and the nonexponential character of the spin echoes of proton and deuteron in muscle water are mainly due to hydrogen exchange between water and functional groups in the protein filaments. These groups have large dipolar or quadrupolar splittings, and undergo hydrogen exchange with water at intermediate rates. The exchange processes and their effects on the spin echoes are pH-dependent. The dependence of transverse relaxation of pH was observed in glycerinated rabbit psoas muscle fibers. PMID:7272437

  6. Resonant Scattering off Magnetic Impurities in Graphene: Mechanism for Ultrafast Spin Relaxation

    NASA Astrophysics Data System (ADS)

    Kochan, D.; Gmitra, M.; Fabian, J.

    We give a tutorial account of our recently proposed mechanism for spin relaxation based on spin-flip resonant scattering off local magnetic moments. The mechanism is rather general, working in any material with a resonant local moment, but we believe that its particular niche is graphene, whose measured spin relaxation time is 100-1000 ps. Conventional spin-orbit coupling based mechanisms (Elliott-Yafet or Dyakonov-Perel) would require large concentrations (1000 ppm) of impurities to explain this. Our mechanism needs only 1 ppm of resonant local moments, as these act as local spin hot spots: the resonant scatterers do not appear to substantially affect graphene's measured resistivity, but are dominating spin relaxation. In principle, the local moments can come from a variety of sources. Most likely would be organic molecule adsorbants or metallic adatoms. As the representative model, particularly suited for a tutorial, we consider hydrogen adatoms which are theoretically and experimentally demonstrated to yield local magnetic moments when chemisorbed on graphene. We introduce the scattering formalism and apply it to graphene, to obtain the T-matrix and spin-flip scattering rates using the generalized Fermi golden rule.

  7. A study of molecular dynamics and freezing phase transition in tissues by proton spin relaxation.

    PubMed Central

    Rustgi, S N; Peemoeller, H; Thompson, R T; Kydon, D W; Pintar, M M

    1978-01-01

    Muscle, spleen, and kidney tissues from 4-wk-old C57 black mice were studied by proton magnetic resonance. Spin-lattice relaxation times at high fields and in the rotating frame, as well as the spin-spin relaxation times, are reported as a function of temperature in the liquid and frozen phase. Motions of large molecules and of water molecules and their changes at the freezing phase transition are studied. The shortcomings of the two-state fast-exchange relaxation model are discussed. PMID:667294

  8. Mineralogical controls on NMR rock surface relaxivity: A case study of the Fontainebleau Sandstone

    NASA Astrophysics Data System (ADS)

    Livo, Kurt

    Pore size distribution is derived from nuclear magnetic resonance, but is scaled by surface relaxivity. While nuclear magnetic resonance studies generally focus on the difficulty of determining pore size distribution in unconventional shale reservoirs, there is a lack of discussion concerning pure quartz sandstones. Long surface relaxivity causes complications analyzing nuclear magnetic resonance data for pore size distribution determination. Currently, I am unaware of research that addresses the complicated pore size distribution determination in long relaxing, pure sandstone formations, which is essential to accurate downhole petrophysical modeling. The Fontainebleau sandstone is well known for its homogenous mineralogical makeup and wide range of porosity and permeability. The Hibernia sandstone exhibits a similar mineralogy and is characterized by a similar and porosity-permeability range to the Fontainebleau sandstones, but with a significantly higher portion of clay minerals (1-6%). I present systematic petrophysical properties such as porosity, pore size distribution from nuclear magnetic resonance transverse relaxation times, permeability, and volumetric magnetic susceptibility to aide in characterization of the Fontainebleau sandstone. Analysis of collected nuclear magnetic resonance data is then compared to other petrophysical studies from literature such as helium porosity and permeability, magnetic susceptibility, and electrical conductivity. I find that the lack of impurities on the grain surfaces of pure quartz samples imparts a lower surface relaxivity as compared to clay containing sandstones and makes nuclear magnetic resonance analysis more complex. Thus, inverted nuclear magnetic resonance data from cleaner outcrop samples incorrectly models pore size distribution without accounting for wider surface relaxivity variation and is improperly used when characterizing the Fontainebleau sandstone. This is further supported by evidence from less

  9. Resonantly enhanced spin-lattice relaxation of Mn2 + ions in diluted magnetic (Zn,Mn)Se/(Zn,Be)Se quantum wells

    NASA Astrophysics Data System (ADS)

    Debus, J.; Ivanov, V. Yu.; Ryabchenko, S. M.; Yakovlev, D. R.; Maksimov, A. A.; Semenov, Yu. G.; Braukmann, D.; Rautert, J.; Löw, U.; Godlewski, M.; Waag, A.; Bayer, M.

    2016-05-01

    The dynamics of spin-lattice relaxation in the magnetic Mn2 + ion system of (Zn,Mn)Se/(Zn,Be)Se quantum-well structures are studied using optical methods. Pronounced cusps are found in the giant Zeeman shift of the quantum-well exciton photoluminescence at specific magnetic fields below 10 T, when the Mn spin system is heated by photogenerated carriers. The spin-lattice relaxation time of the Mn ions is resonantly accelerated at the cusp magnetic fields. Our theoretical analysis demonstrates that a cusp occurs at a spin-level mixing of single Mn2 + ions and a quick-relaxing cluster of nearest-neighbor Mn ions, which can be described as intrinsic cross-relaxation resonance within the Mn spin system.

  10. Coaxial probe for nuclear magnetic resonance diffusion and relaxation correlation experiments

    NASA Astrophysics Data System (ADS)

    Tang, Yiqiao; Hürlimann, Martin; Mandal, Soumyajit; Paulsen, Jeffrey; Song, Yi-Qiao

    2014-02-01

    A coaxial nuclear magnetic resonance (NMR) probe is built to measure diffusion and relaxation properties of liquid samples. In particular, we demonstrate the acquisition of two-dimensional (2D) distribution functions (T1-T2 and diffusion-T2), essential for fluids characterization. The compact design holds promise for miniaturization, thus enabling the measurement of molecular diffusion that is inaccessible to conventional micro-NMR setups. Potential applications range from crude oil characterization to biomolecular screening and detections.

  11. Effects of Off-Resonance Irradiation, Cross-Relaxation, and Chemical Exchange on Steady-State Magnetization and Effective Spin-Lattice Relaxation Times

    NASA Astrophysics Data System (ADS)

    Kingsley, Peter B.; Monahan, W. Gordon

    2000-04-01

    In the presence of an off-resonance radiofrequency field, recovery of longitudinal magnetization to a steady state is not purely monoexponential. Under reasonable conditions with zero initial magnetization, recovery is nearly exponential and an effective relaxation rate constant R1eff = 1/T1eff can be obtained. Exact and approximate formulas for R1eff and steady-state magnetization are derived from the Bloch equations for spins undergoing cross-relaxation and chemical exchange between two sites in the presence of an off-resonance radiofrequency field. The relaxation formulas require that the magnetization of one spin is constant, but not necessarily zero, while the other spin relaxes. Extension to three sites with one radiofrequency field is explained. The special cases of off-resonance effects alone and with cross-relaxation or chemical exchange, cross-relaxation alone, and chemical exchange alone are compared. The inaccuracy in saturation transfer measurements of exchange rate constants by published formulas is discussed for the creatine kinase reaction.

  12. Nuclear magnetic resonance proton dipolar order relaxation in thermotropic liquid crystals: A quantum theoretical approach

    NASA Astrophysics Data System (ADS)

    Zamar, R. C.; Mensio, O.

    2004-12-01

    By means of the Jeener-Broekaert nuclear magnetic resonance pulse sequence, the proton spin system of a liquid crystal can be prepared in quasiequilibrium states of high dipolar order, which relax to thermal equilibrium with the molecular environment with a characteristic time (T1D). Previous studies of the Larmor frequency and temperature dependence of T1D in thermotropic liquid crystals, that included field cycling and conventional high-field experiments, showed that the slow hydrodynamic modes dominate the behavior of T1D, even at high Larmor frequencies. This noticeable predominance of the cooperative fluctuations (known as order fluctuations of the director, OFD) could not be explained by standard models based on the spin-lattice relaxation theory in the limit of high temperature (weak order). This fact points out the necessity of investigating the role of the quantum terms neglected in the usual high temperature theory of dipolar order relaxation. In this work, we present a generalization of the proton dipolar order relaxation theory for highly correlated systems, which considers all the spins belonging to correlated domains as an open quantum system interacting with quantum bath. As starting point, we deduce a formulation of the Markovian master equation of relaxation for the statistical spin operator, valid for all temperatures, which is suitable for introducing a dipolar spin temperature in the quantum regime, without further assumptions about the form of the spin-lattice Hamiltonian. In order to reflect the slow dynamics occurring in correlated systems, we lift the usual short-correlation-time assumption by including the average over the motion of the dipolar Hamiltonian together with the Zeeman Hamiltonian into the time evolution operator. In this way, we calculate the time dependence of the spin operators in the interaction picture in a closed form, valid for high magnetic fields, bringing into play the spin-spin interactions within the microscopic time

  13. Exceeding natural resonance frequency limit of monodisperse Fe3O4 nanoparticles via superparamagnetic relaxation

    PubMed Central

    Song, Ning-Ning; Yang, Hai-Tao; Liu, Hao-Liang; Ren, Xiao; Ding, Hao-Feng; Zhang, Xiang-Qun; Cheng, Zhao-Hua

    2013-01-01

    Magnetic nanoparticles have attracted much research interest in the past decades due to their potential applications in microwave devices. Here, we adopted a novel technique to tune cut-off frequency exceeding the natural resonance frequency limit of monodisperse Fe3O4 nanoparticles via superparamagnetic relaxation. We observed that the cut-off frequency can be enhanced from 5.3 GHz for Fe3O4 to 6.9 GHz forFe3O4@SiO2 core-shell structure superparamagnetic nanoparticles, which are much higher than the natural resonance frequency of 1.3 GHz for Fe3O4 bulk material. This finding not only provides us a new approach to enhance the resonance frequency beyond the Snoek's limit, but also extend the application for superparamagnetic nanoparticles to microwave devices. PMID:24196377

  14. 'Coulomb' description of basic relaxation parameters of isobar analog and charge-exchange giant monopole resonances

    SciTech Connect

    Gorelik, M. L.; Rykovanov, V. S.; Urin, M. G.

    2010-12-15

    Within a semimicroscopic approach, basic relaxation parameters of the isobaric analog resonance and of the charge-exchange giant monopole resonance, which is an overtone of the isobaric analog resonance, are interpreted in terms of the mean Coulomb field of a nucleus. The continuum version of the random-phase approximation, allowance for an approximate isospin conservation in nuclei in an explicit form, and a phenomenological description of the fragmentation effect are basic ingredients of the approach used. The aforementioned parameters were calculated for a number of magic and near-magic nuclei by using a partly self-consistent phenomenological nuclear mean field and the isovector part of the Landau-Migdal interaction in the particle-hole channel. The results of the calculations are compared with corresponding experimental data.

  15. Dielectric relaxation, resonance and scaling behaviors in Sr3Co2Fe24O41 hexaferrite.

    PubMed

    Tang, Rujun; Jiang, Chen; Qian, Wenhu; Jian, Jie; Zhang, Xin; Wang, Haiyan; Yang, Hao

    2015-08-28

    The dielectric properties of Z-type hexaferrite Sr3Co2Fe24O41 (SCFO) have been investigated as a function of temperature from 153 to 503 K between 1 and 2 GHz. The dielectric responses of SCFO are found to be frequency dependent and thermally activated. The relaxation-type dielectric behavior is observed to be dominating in the low frequency region and resonance-type dielectric behavior is found to be dominating above 10(8) Hz. This frequency dependence of dielectric behavior is explained by the damped harmonic oscillator model with temperature dependent coefficients. The imaginary part of impedance (Z″) and modulus (M″) spectra show that there is a distribution of relaxation times. The scaling behaviors of Z″ and M″ spectra further suggest that the distribution of relaxation times is temperature independent at low frequencies. The dielectric loss spectra at different temperatures have not shown a scaling behavior above 10(8) Hz. A comparison between the Z″ and the M″ spectra indicates that the short-range charges motion dominates at low temperatures and the long-range charges motion dominates at high temperatures. The above results indicate that the dielectric dispersion mechanism in SCFO is temperature independent at low frequencies and temperature dependent at high frequencies due to the domination of resonance behavior.

  16. High homogeneity B(1) 30.2 MHz Nuclear Magnetic Resonance Probe for off-resonance relaxation times measurements.

    PubMed

    Baranowski, M; Woźniak-Braszak, A; Jurga, K

    2011-01-01

    This paper reports on design and construction of a double coil high-homogeneity ensuring Nuclear Magnetic Resonance Probe for off-resonance relaxation time measurements. NMR off-resonance experiments pose unique technical problems. Long irradiation can overheat the sample, dephase the spins because of B(1) field inhomogeneity and degrade the signal received by requiring the receiver bandwidth to be broader than that needed for normal experiment. The probe proposed solves these problems by introducing a separate off-resonance irradiation coil which is larger than the receiver coil and is wound up on the dewar tube that separates it from the receiver coil thus also thermally protects the sample from overheating. Large size of the irradiation coil also improves the field homogeneity because as a ratio of the sample diameter to the magnet (coil) diameter increases, the field inhomogeneity also increases (Blümich et al., 2008) [1]. The small receiver coil offers maximization of the filling factor and a high signal to the noise ratio.

  17. Coaxial probe for nuclear magnetic resonance diffusion and relaxation correlation experiments

    SciTech Connect

    Tang, Yiqiao; Hürlimann, Martin; Mandal, Soumyajit; Paulsen, Jeffrey; Song, Yi-Qiao

    2014-02-21

    A coaxial nuclear magnetic resonance (NMR) probe is built to measure diffusion and relaxation properties of liquid samples. In particular, we demonstrate the acquisition of two-dimensional (2D) distribution functions (T{sub 1}-T{sub 2} and diffusion–T{sub 2}), essential for fluids characterization. The compact design holds promise for miniaturization, thus enabling the measurement of molecular diffusion that is inaccessible to conventional micro-NMR setups. Potential applications range from crude oil characterization to biomolecular screening and detections.

  18. Soil and litter phosphorus-31 nuclear magnetic resonance spectroscopy: extractants, metals, and phosphorus relaxation times.

    PubMed

    Cade-Menun, B J; Liu, C W; Nunlist, R; McColl, J G

    2002-01-01

    Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy is an excellent tool with which to study soil organic P, allowing quantitative, comparative analysis of P forms. However, for 31P NMR to be tative, all peaks must be completely visible, and in their correct relative proportions. There must be no line broadening, and adequate delay times must be used to avoid saturation of peaks. The objective of this study was to examine the effects of extractants on delay times and peak saturation. Two samples (a forest litter and a mineral soil sample) and three extractants (0.25 M NaOH, NaOH plus Chelex (Bio-Rad Laboratories, Hercules, CA), and NaOH plus EDTA) were used to determine the differences in the concentration of P and cations solubilized by each extractant, and to measure spin-lattice (T1) relaxation times of P peaks in each extract. For both soil and litter, NaOH-Chelex extracted the lowest concentrations of P. For the litter sample, T1 values were short for all extractants due to the high Fe concentration remaining after extraction. For the soil sample, there were noticeable differences among the extractants. The NaOH-Chelex sample had less Fe and Mn remaining in solution after extraction than the other extractants, and the longest delay times used in the study, 6.4 s, were not long enough for quantitative analysis. Delay times of 1.5 to 2 s for the NaOH and NaOH-EDTA were adequate. Line broadening was highest in the NaOH extracts, which had the highest concentration of Fe. On the basis of these results, recommendations for future analyses of soil and litter samples by solution 31P NMR spectroscopy include: careful selection of an extractant; measurement of paramagnetic ions extracted with P; use of appropriate delay times and the minimum number of scans; and measurement of T1 values whenever possible.

  19. Metabolic properties in stroked rats revealed by relaxation-enhanced magnetic resonance spectroscopy at ultrahigh fields.

    PubMed

    Shemesh, Noam; Rosenberg, Jens T; Dumez, Jean-Nicolas; Muniz, Jose A; Grant, Samuel C; Frydman, Lucio

    2014-01-01

    (1)H magnetic resonance spectroscopy (MRS) yields site-specific signatures that directly report metabolic concentrations, biochemistry and kinetics-provided spectral sensitivity and quality are sufficient. Here, an enabling relaxation-enhanced (RE) MRS approach is demonstrated that by combining highly selective spectral excitations with operation at very high magnetic fields, delivers spectra exhibiting signal-to-noise ratios >50:1 in under 6 s for ~5 × 5 × 5 (mm)(3) voxels, with flat baselines and no interference from water. With this spectral quality, MRS was used to interrogate a number of metabolic properties in stroked rat models. Metabolic confinements imposed by randomly oriented micro-architectures were detected and found to change upon ischaemia; intensities of downfield resonances were found to be selectively altered in stroked hemispheres; and longitudinal relaxation time of lactic acid was found to increase by over 50% its control value as early as 3-h post ischaemia, paralleling the onset of cytotoxic oedema. These results demonstrate potential of (1)H MRS at ultrahigh fields. PMID:25229942

  20. Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions

    PubMed Central

    Costabel, Stephan; Yaramanci, Ugur

    2013-01-01

    [1] For characterizing water flow in the vadose zone, the water retention curve (WRC) of the soil must be known. Because conventional WRC measurements demand much time and effort in the laboratory, alternative methods with shortened measurement duration are desired. The WRC can be estimated, for instance, from the cumulative pore size distribution (PSD) of the investigated material. Geophysical applications of nuclear magnetic resonance (NMR) relaxometry have successfully been applied to recover PSDs of sandstones and limestones. It is therefore expected that the multiexponential analysis of the NMR signal from water-saturated loose sediments leads to a reliable estimation of the WRC. We propose an approach to estimate the WRC using the cumulative NMR relaxation time distribution and approximate it with the well-known van-Genuchten (VG) model. Thereby, the VG parameter n, which controls the curvature of the WRC, is of particular interest, because it is the essential parameter to predict the relative hydraulic conductivity. The NMR curves are calibrated with only two conventional WRC measurements, first, to determine the residual water content and, second, to define a fixed point that relates the relaxation time to a corresponding capillary pressure. We test our approach with natural and artificial soil samples and compare the NMR-based results to WRC measurements using a pressure plate apparatus and to WRC predictions from the software ROSETTA. We found that for sandy soils n can reliably be estimated with NMR, whereas for samples with clay and silt contents higher than 10% the estimation fails. This is the case when the hydraulic properties of the soil are mainly controlled by the pore constrictions. For such samples, the sensitivity of the NMR method for the pore bodies hampers a plausible WRC estimation. Citation: Costabel, S., and U. Yaramanci (2013), Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions, Water

  1. Alterations in Magnetic Resonance Imaging T2 Relaxation Times of the Ovine Intervertebral Disc Due to Non-enzymatic Glycation

    PubMed Central

    Jazini, Ehsan; Sharan, Alok D; Morse, Lee Jae; Dyke, Jonathon P; Aronowitz, Eric A; Chen, Louis KH; Tang, Simon Y

    2011-01-01

    Study Design An in vitro study using ovine intervertebral discs to correlate the effects of advanced glycation end-products (AGEs) with disc hydration evaluated by magnetic resonance imaging (MRI). Objective To determine the relationship between the level of AGEs and tissue water content in intervertebral discs using T2 relaxation MRI. Summary of Background Data AGEs result from nonenzymatic glycation, and AGEs have been shown to accumulate in the IVD tissue with aging and degeneration. AGEs can alter biochemical properties, including the hydrophobicity of the extracellular matrix. Since one of the degenerative signs of the IVD is the reduced hydration, it was hypothesized that increased levels of tissue AGEs may contribute to disc hydration. T2 relaxation MRI has been shown to be sensitive to the hydration status of the disc, and may be valuable in detecting the changes in the IVD mediated by the increase of AGEs. Methods Thirty-eight IVDs were obtained from 4 ovine spines, and the annulus fibrosis (AF) and nucleus pulposus (NP) tissues were isolated from these discs. The tissues were incubated in either a ribosylation or control solution for up to 8 days to induce the formation of AGEs. These tissues were subsequently analyzed for tissue water content and concentration of AGEs. T2 relaxation times were obtained from these tissues after ribosylation. Results Ribosylation led to the increased accumulation of AGEs and reduced water content in both the AF and NP in a dose-dependent manner. When analyzed by MRI, ribosylation significantly altered the mean T2 relaxation times in the NP (p=0.001), but not in the AF (p=0.912). Furthermore, the mean T2 values in the NP significantly decreased with increasing periods of incubation time (p<0.001). Conclusion This study demonstrates that levels of AGEs in the IVD may affect the tissue water content. Moreover, these ribosylation-mediated changes in tissue hydration were detectable using T2 relaxation MRI. T2 relaxation MRI

  2. In vivo proton magnetic resonance spectroscopy of liver metabolites in non-alcoholic fatty liver disease in rats: T2 relaxation times in methylene protons.

    PubMed

    Song, Kyu-Ho; Baek, Hyeon-Man; Lee, Do-Wan; Choe, Bo-Young

    2015-10-01

    The aim of this study was to evaluate the transverse relaxation time of methylene resonance as compared to other lipid resonances. The examinations were performed using a 3.0 T scanner with a point-resolved spectroscopy (PRESS) sequence. Lipid relaxation time in a lipid phantom filled with canola oil was estimated with a repetition time (TR) of 6000ms and echo time (TE) of 40-550ms. For in vivo proton magnetic resonance spectroscopy ((1)H-MRS), eight male Sprague-Dawley rats were given free access to a normal-chow (NC) and another eight male Sprague-Dawley rats were given free access to a high-fat (HF) diet. Both groups drank water ad libitum. T2 measurements in the rats' livers were conducted at a fixed TR of 6000ms and TE of 40-220ms. Exponential curve fitting quality was calculated through the coefficients of determination (R(2)). Chemical analyses of the phantom and livers were not performed, but T2 decay curves were acquired. The T2 relaxation time of methylene resonance was estimated as follows: NC rats, 37.1±4.3ms; HF rats, 31.4±1.8ms (p<0.05). The extrapolated M0 values were higher in HF rats than in NC rats (p<0.005). This study of (1)H MRS led to sufficient spectral resolution and signal-to-noise ratio differences to characterize the T2 relaxation times of methylene resonance. (1)H MRS relaxation times may be useful for quantitative characterization of various liver diseases, including fatty liver disease.

  3. Phospholipid bilayer relaxation dynamics as revealed by the pulsed electron-electron double resonance of spin labels

    NASA Astrophysics Data System (ADS)

    Syryamina, V. N.; Dzuba, S. A.

    2012-10-01

    Electron paramagnetic resonance (EPR) spectroscopy in the form of pulsed electron-electron double resonance (ELDOR) was applied to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid bilayers containing lipids that were spin-labeled at different carbon positions along the lipid acyl chain. Pulsed ELDOR detects motionally induced spin flips of nitrogen nuclei in the nitroxide spin labels, which manifests itself as magnetization transfer (MT) in the nitroxide EPR spectrum. The MT effect was observed over a wide temperature range (100-225 K) on a microsecond time scale. In line with a previous study on molecular glasses [N. P. Isaev and S. A. Dzuba, J. Chem. Phys. 135, 094508 (2011), 10.1063/1.3633241], the motions that induce MT effect were suggested to have the same nature as those in dielectric secondary (β) Johari-Goldstein fast relaxation. The results were compared with literature dielectric relaxation data for POPC bilayers, revealing some common features. Molecular motions resulting in MT are faster for deeper spin labels in the membrane interior. The addition of cholesterol to the bilayer suppresses the lipid motions near the steroid nucleus and accelerates the lipid motions beyond the steroid nucleus, in the bilayer interior. This finding was attributed to the lipid acyl chains being more ordered near the steroid nucleus and less ordered in the bilayer interior. The motions are absent in dry lipids, indicating that the motions are determined by intermolecular interactions in the bilayer.

  4. High resolution NMR study of T{sub 1} magnetic relaxation dispersion. IV. Proton relaxation in amino acids and Met-enkephalin pentapeptide

    SciTech Connect

    Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L.; Vieth, Hans-Martin

    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.

  5. Wide-band nanoscale magnetic resonance spectroscopy using quantum relaxation of a single spin in diamond

    NASA Astrophysics Data System (ADS)

    Wood, James D. A.; Broadway, David A.; Hall, Liam T.; Stacey, Alastair; Simpson, David A.; Tetienne, Jean-Philippe; Hollenberg, Lloyd C. L.

    2016-10-01

    We demonstrate an all-optical approach of nanoscale magnetic resonance (MR) spectroscopy whereby quantum relaxation (T1) of a single probe spin in diamond is monitored during a precise static magnetic field sweep to construct a spectrum of the surrounding spin environment. The method is inherently noninvasive as it involves no driving fields, and instead relies on the natural resonance between the quantum probe and target spins. As a proof of concept, we measure the T1-MR spectra across a wide band [megahertz (MHz) to gigahertz (GHz)] of a small ensemble of 14N impurities surrounding a single probe spin, providing information on both electron spin transitions (in the GHz range) and nuclear spin transitions (in the MHz range) of the 14N spin targets. Analysis of the T1-MR spectrum reveals that the electron spin transitions are probed via dipole interactions with the probe, while the relatively weak nuclear spin resonances are dramatically enhanced by hyperfine coupling in an electron-mediated process. With a projected sensitivity to external single-proton spins, this work establishes T1-MR as a powerful noninvasive wide-band technique for nanoscale MR spectroscopy.

  6. PREFACE: 13th International Conference on Muon Spin Rotation, Relaxation and Resonance

    NASA Astrophysics Data System (ADS)

    2014-12-01

    The 13th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2014) organized by the Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute in collaboration with the University of Zurich and the University of Fribourg, was held in Grindelwald, Switzerland from 1st to 6th June 2014. The conference provided a forum for researchers from around the world with interests in the applications of μSR to study a wide range of topics including condensed matter physics, materials and molecular sciences, chemistry and biology. Polarized muons provide a unique and versatile probe of matter, enabling studies at the atomic level of electronic structure and dynamics in a wide range of systems. The conference was the thirteenth in a series, which began in Rorschach in 1978 and it took place for the third time in Switzerland. The previous conferences were held in Cancun, Mexico (2011), Tsukuba, Japan (2008), Oxford, UK (2005), Williamsburg, USA (2002), Les Diablerets, Switzerland (1999), Nikko, Japan (1996), Maui, USA (1993), Oxford, UK (1990), Uppsala, Sweden (1986), Shimoda, Japan (1983), Vancouver, Canada (1980), and Rorschach, Switzerland (1978). These conference proceedings contain 67 refereed publications from presentations covering magnetism, superconductivity, chemistry, semiconductors, biophysics and techniques. The conference logo, displayed in the front pages of these proceedings, represents both the location of μSR2014 in the Alps and the muon-spin rotation technique. The silhouette represents the famous local mountains Eiger, Mönch and Jungfrau as drawn by the Swiss painter Ferdinand Hodler and the apple with arrow is at the same time a citation of the Wilhelm Tell legend and a remembrance of the key role played by the muon spin and the asymmetric muon decay (which for the highest positron energy has an apple like shape). More than 160 participants (including 32 registered as students and 13 as accompanying persons) from 19 countries

  7. Proton capture resonance studies

    SciTech Connect

    Mitchell, G.E. |; Bilpuch, E.G. |; Bybee, C.R. |; Cox, J.M.; Fittje, L.M. |; Labonte, M.A.; Moore, E.F.; Shriner, J.D. |; Shriner, J.F. Jr. |; Vavrina, G.A. |; Wallace, P.M. |

    1997-02-01

    The fluctuation properties of quantum systems now are used as a signature of quantum chaos. The analyses require data of extremely high quality. The {sup 29}Si(p,{gamma}) reaction is being used to establish a complete level scheme of {sup 30}P to study chaos and isospin breaking in this nuclide. Determination of the angular momentum J, the parity {pi}, and the isospin T from resonance capture data is considered. Special emphasis is placed on the capture angular distributions and on a geometric description of these angular distributions. {copyright} {ital 1997 American Institute of Physics.}

  8. Measuring relative acetylcholine receptor agonist binding by selective proton nuclear magnetic resonance relaxation experiments.

    PubMed Central

    Behling, R W; Yamane, T; Navon, G; Sammon, M J; Jelinski, L W

    1988-01-01

    A method is presented that uses selective proton Nuclear Magnetic Resonance (NMR) relaxation measurements of nicotine in the presence of the acetylcholine receptor to obtain relative binding constants for acetylcholine, carbamylcholine, and muscarine. For receptors from Torpedo californica the results show that (a) the binding constants are in the order acetylcholine greater than nicotine greater than carbamylcholine greater than muscarine; (b) selective NMR measurements provide a rapid and direct method for monitoring both the specific and nonspecific binding of agonists to these receptors and to the lipid; (c) alpha-bungarotoxin can be used to distinguish between specific and nonspecific binding to the receptor; (d) the receptor--substrate interaction causes a large change in the selective relaxation time of the agonists even at concentrations 100x greater than that of the receptor. This last observation means that these measurements provide a rapid method to monitor drug binding when only small amounts of receptor are available. Furthermore, the binding strategies presented here may be useful for the NMR determination of the conformation of the ligand in its bound state. Images FIGURE 1 PMID:3395661

  9. Understanding the effects of diffusion and relaxation in magnetic resonance imaging using computational modeling

    NASA Astrophysics Data System (ADS)

    Russell, Greg

    The work described in this dissertation was motivated by a desire to better understand the cellular pathology of ischemic stroke. Two of the three bodies of research presented herein address and issue directly related to the investigation of ischemic stroke through the use of diffusion weighted magnetic resonance imaging (DWMRI) methods. The first topic concerns the development of a computationally efficient finite difference method, designed to evaluate the impact of microscopic tissue properties on the formation of DWMRI signal. For the second body of work, the effect of changing the intrinsic diffusion coefficient of a restricted sample on clinical DWMRI experiments is explored. The final body of work, while motivated by the desire to understand stroke, addresses the issue of acquiring large amounts of MRI data well suited for quantitative analysis in reduced scan time. In theory, the method could be used to generate quantitative parametric maps, including those depicting information gleaned through the use of DWMRI methods. Chapter 1 provides an introduction to several topics. A description of the use of DWMRI methods in the study of ischemic stroke is covered. An introduction to the fundamental physical principles at work in MRI is also provided. In this section the means by which magnetization is created in MRI experiments, how MRI signal is induced, as well as the influence of spin-spin and spin-lattice relaxation are discussed. Attention is also given to describing how MRI measurements can be sensitized to diffusion through the use of qualitative and quantitative descriptions of the process. Finally, the reader is given a brief introduction to the use of numerical methods for solving partial differential equations. In Chapters 2, 3 and 4, three related bodies of research are presented in terms of research papers. In Chapter 2, a novel computational method is described. The method reduces the computation resources required to simulate DWMRI experiments. In

  10. Relaxation mechanism of β-carotene from S2 (1Bu(+)) state to S1 (2Ag(-)) state: femtosecond time-resolved near-IR absorption and stimulated resonance Raman studies in 900-1550 nm region.

    PubMed

    Takaya, Tomohisa; Iwata, Koichi

    2014-06-12

    Carotenoids have two major low-lying excited states, the second lowest (S2 (1Bu(+))) and the lowest (S1 (2Ag(-))) excited singlet states, both of which are suggested to be involved in the energy transfer processes in light-harvesting complexes. Studying vibrational dynamics of S2 carotenoids requires ultrafast time-resolved near-IR Raman spectroscopy, although it has much less sensitivity than visible Raman spectroscopy. In this study, the relaxation mechanism of β-carotene from the S2 state to the S1 state is investigated by femtosecond time-resolved multiplex near-IR absorption and stimulated Raman spectroscopy. The energy gap between the S2 and S1 states is estimated to be 6780 cm(-1) from near-IR transient absorption spectra. The near-IR stimulated Raman spectrum of S2 β-carotene show three bands at 1580, 1240, and 1050 cm(-1). When excess energy of 4000 cm(-1) is added, the S1 C═C stretch band shows a large upshift with a time constant of 0.2 ps. The fast upshift is explained by a model that excess energy generated by internal conversion from the S2 state to the S1 state is selectively accepted by one of the vibronic levels of the S1 state and is redistributed among all the vibrational modes.

  11. Effect of tissue fat and water content on nuclear magnetic resonance relaxation times of cardiac and skeletal muscle.

    PubMed

    Scholz, T D; Fleagle, S R; Parrish, F C; Breon, T; Skorton, D J

    1990-01-01

    Understanding tissue determinants that affect the nuclear magnetic resonance (NMR) properties of myocardium would improve noninvasive characterization of myocardial tissue. To determine if NMR relaxation times would reflect changes in tissue fat content, two experimental models were investigated. First, an idealized model using mixtures of beef skeletal muscle and beef fat was studied to investigate the effects of a wide range of tissue fat content. Second, myocardium with varying fat content from hogs raised to have varying degrees of ponderosity was analyzed. Tissue fat and water contents and spin-lattice (T1) and spin-spin (T2) relaxation times at 20 MHz were measured. The skeletal muscle/fat mixtures ranged in fat content from 35% to 95% with water content variations from 50% to 75%. Water content decreased as fat content increased. A significant inverse linear relationship was found between T1 and sample fat content (r = -0.997). Spin-spin relaxation times showed a significant positive curvilinear relationship with fat content (r2 = 0.96). In the animal experiments, 18 hogs were studied with samples obtained from both right and left ventricular (LV) free walls, with care taken to avoid epicardial fat. Myocardial fat content ranged from 3% to 25%. A significant correlation was found between LV fat content and corrected LV mass (r = 0.62), which suggested that the increase in LV mass could be explained, at least in part, by changes in myocardial fat content. Similar to the muscle/fat mixture model, a significant positive curvilinear relationship was found between myocardial T2 and tissue fat content (r2 = 0.67) for all the myocardial samples.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Femtosecond UV studies of the electronic relaxation processes in Cytochrome c.

    PubMed

    Bräm, Olivier; Consani, Cristina; Cannizzo, Andrea; Chergui, Majed

    2011-11-24

    We report on an experimental study with UV and visible ultrafast time-gated emission and transient absorption of the early photodynamics of horse heart Cytochrome c in both ferric and ferrous redox states. A clear separation in time and energy of tryptophan and haem emission is observed. Excitation of the haem via resonant energy transfer from the tryptophan residue is observed in the subsequent haem electronic relaxation. Different Trp-haem energy transfer time constants of the ferrous and ferric forms are obtained. An almost instantaneous relaxation to the lowest singlet excited state (corresponding to the so-called Q band) characterizes the earliest electronic dynamics of the haem, independent of excitation energy, while dark intermediate states govern the ground-state recovery. The information gathered in these two experiments and in the literature allows us to propose a simple scheme for the electronic relaxation leading to ligand dissociation.

  13. Studies of MRI relaxivities of gadolinium-labeled dendrons

    NASA Astrophysics Data System (ADS)

    Pan, Hongmu; Daniel, Marie-Christine

    2011-05-01

    In cancer detection, imaging techniques have a great importance in early diagnosis. The more sensitive the imaging technique and the earlier the tumor can be detected. Contrast agents have the capability to increase the sensitivity in imaging techniques such as magnetic resonance imaging (MRI). Until now, gadolinium-based contrast agents are mainly used for MRI, and show good enhancement. But improvement is needed for detection of smaller tumors at the earliest stage possible. The dendrons complexed with Gd(DOTA) were synthesized and evaluated as a new MRI contrast agent. The longitudinal and transverse relaxation effects were tested and compared with commercial drug Magnevist, Gd(DTPA).

  14. NMR relaxation study of water dynamics in superparamagnetic iron-oxide-loaded vesicles

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Wen; Hsieh, Chu-Jung; Lin, Chao-Min; Hwang, Dennis W.

    2013-02-01

    Superparamagnetic iron oxide (SPIO) nanoparticles have been introduced as contrast agents for clinical applications in magnetic resonance imaging. Recently, SPIO has been also used for tracking cells. However, NMR relaxation of water molecules behaves differently in a SPIO solution and SPIO-loaded cells. In this study, we used water-in-oil-in-water double emulsions to mimic cellular environments. The MR relaxation induced by the SPIO-loaded vesicles and SPIO solution indicates that T2* is sensitive to the iron concentration alone, and the behavior was very similar in both SPIO-loaded vesicles and SPIO solution. However, T2 relaxation of water in SPIO-loaded vesicles was faster than that in a SPIO solution. In addition, the contribution of water inside and outside the vesicles was clarified by replacing H2O with D2O, and water inside the vesicles was found to cause a nonlinear iron concentration dependency. The studied dilution revealed that vesicle aggregation undergoes a structural transition upon dilution by a certain amount of water. R2* relaxation is sensitive to this structural change and shows an obvious nonlinear iron concentration dependency when the SPIO loading is sufficiently high. Random walk simulations demonstrated that in the assumed model, the vesicles aggregate structures causing the differences between R2* and R2 relaxation of water in vesicles in the presence of SPIO particles.

  15. Electronic Relaxation after Resonant Laser Excitation of Cr in Superfluid Helium Nanodroplets

    PubMed Central

    2013-01-01

    Chromium (Cr) atoms embedded into helium nanodroplets (HeN) are ejected from the droplets upon photoexcitation. During ejection they undergo electronic relaxation resulting in bare Cr atoms in various excited states. In a study of the relaxation process we present absorption spectra observed via laser induced fluorescence and beam depletion as well as dispersed fluorescence spectra and time-resolved fluorescence measurements. Broad and shifted absorption structures were found for the strong z7P° ← a7S3 and y7P° ← a7S3 excitations from the ground state. Emission lines are, in contrast, very narrow, which indicates that fluorescence is obtained from bare excited Cr atoms after ejection. Upon excitation into the y7P2,3,4° states we observed fluorescence from y7P2°, z5P1,2,3°, and z7P2,3,4°, indicating that these states are populated by electronic relaxation during the ejection processes. Relative population ratios are obtained from the intensities of individual spectral lines. Excitation into the z7P2,3,4° states resulted in fluorescence only from z7P2°. Estimates of the time duration of the ejection process are obtained from time-resolved measurements. PMID:23410146

  16. Understanding generalized inversions of nuclear magnetic resonance transverse relaxation time in porous media.

    PubMed

    Mitchell, J; Chandrasekera, T C

    2014-12-14

    The nuclear magnetic resonance transverse relaxation time T2, measured using the Carr-Purcell-Meiboom-Gill (CPMG) experiment, is a powerful method for obtaining unique information on liquids confined in porous media. Furthermore, T2 provides structural information on the porous material itself and has many applications in petrophysics, biophysics, and chemical engineering. Robust interpretation of T2 distributions demands appropriate processing of the measured data since T2 is influenced by diffusion through magnetic field inhomogeneities occurring at the pore scale, caused by the liquid/solid susceptibility contrast. Previously, we introduced a generic model for the diffusion exponent of the form -ante(k) (where n is the number and te the temporal separation of spin echoes, and a is a composite diffusion parameter) in order to distinguish the influence of relaxation and diffusion in CPMG data. Here, we improve the analysis by introducing an automatic search for the optimum power k that best describes the diffusion behavior. This automated method is more efficient than the manual trial-and-error grid search adopted previously, and avoids variability through subjective judgments of experimentalists. Although our method does not avoid the inherent assumption that the diffusion exponent depends on a single k value, we show through simulation and experiment that it is robust in measurements of heterogeneous systems that violate this assumption. In this way, we obtain quantitative T2 distributions from complicated porous structures and demonstrate the analysis with examples of ceramics used for filtration and catalysis, and limestone of relevance to the construction and petroleum industries. PMID:25494741

  17. Understanding generalized inversions of nuclear magnetic resonance transverse relaxation time in porous media.

    PubMed

    Mitchell, J; Chandrasekera, T C

    2014-12-14

    The nuclear magnetic resonance transverse relaxation time T2, measured using the Carr-Purcell-Meiboom-Gill (CPMG) experiment, is a powerful method for obtaining unique information on liquids confined in porous media. Furthermore, T2 provides structural information on the porous material itself and has many applications in petrophysics, biophysics, and chemical engineering. Robust interpretation of T2 distributions demands appropriate processing of the measured data since T2 is influenced by diffusion through magnetic field inhomogeneities occurring at the pore scale, caused by the liquid/solid susceptibility contrast. Previously, we introduced a generic model for the diffusion exponent of the form -ante(k) (where n is the number and te the temporal separation of spin echoes, and a is a composite diffusion parameter) in order to distinguish the influence of relaxation and diffusion in CPMG data. Here, we improve the analysis by introducing an automatic search for the optimum power k that best describes the diffusion behavior. This automated method is more efficient than the manual trial-and-error grid search adopted previously, and avoids variability through subjective judgments of experimentalists. Although our method does not avoid the inherent assumption that the diffusion exponent depends on a single k value, we show through simulation and experiment that it is robust in measurements of heterogeneous systems that violate this assumption. In this way, we obtain quantitative T2 distributions from complicated porous structures and demonstrate the analysis with examples of ceramics used for filtration and catalysis, and limestone of relevance to the construction and petroleum industries.

  18. Understanding generalized inversions of nuclear magnetic resonance transverse relaxation time in porous media

    NASA Astrophysics Data System (ADS)

    Mitchell, J.; Chandrasekera, T. C.

    2014-12-01

    The nuclear magnetic resonance transverse relaxation time T2, measured using the Carr-Purcell-Meiboom-Gill (CPMG) experiment, is a powerful method for obtaining unique information on liquids confined in porous media. Furthermore, T2 provides structural information on the porous material itself and has many applications in petrophysics, biophysics, and chemical engineering. Robust interpretation of T2 distributions demands appropriate processing of the measured data since T2 is influenced by diffusion through magnetic field inhomogeneities occurring at the pore scale, caused by the liquid/solid susceptibility contrast. Previously, we introduced a generic model for the diffusion exponent of the form -ant_e^k (where n is the number and te the temporal separation of spin echoes, and a is a composite diffusion parameter) in order to distinguish the influence of relaxation and diffusion in CPMG data. Here, we improve the analysis by introducing an automatic search for the optimum power k that best describes the diffusion behavior. This automated method is more efficient than the manual trial-and-error grid search adopted previously, and avoids variability through subjective judgments of experimentalists. Although our method does not avoid the inherent assumption that the diffusion exponent depends on a single k value, we show through simulation and experiment that it is robust in measurements of heterogeneous systems that violate this assumption. In this way, we obtain quantitative T2 distributions from complicated porous structures and demonstrate the analysis with examples of ceramics used for filtration and catalysis, and limestone of relevance to the construction and petroleum industries.

  19. Understanding generalized inversions of nuclear magnetic resonance transverse relaxation time in porous media

    SciTech Connect

    Mitchell, J.; Chandrasekera, T. C.

    2014-12-14

    The nuclear magnetic resonance transverse relaxation time T{sub 2}, measured using the Carr-Purcell-Meiboom-Gill (CPMG) experiment, is a powerful method for obtaining unique information on liquids confined in porous media. Furthermore, T{sub 2} provides structural information on the porous material itself and has many applications in petrophysics, biophysics, and chemical engineering. Robust interpretation of T{sub 2} distributions demands appropriate processing of the measured data since T{sub 2} is influenced by diffusion through magnetic field inhomogeneities occurring at the pore scale, caused by the liquid/solid susceptibility contrast. Previously, we introduced a generic model for the diffusion exponent of the form −ant{sub e}{sup k} (where n is the number and t{sub e} the temporal separation of spin echoes, and a is a composite diffusion parameter) in order to distinguish the influence of relaxation and diffusion in CPMG data. Here, we improve the analysis by introducing an automatic search for the optimum power k that best describes the diffusion behavior. This automated method is more efficient than the manual trial-and-error grid search adopted previously, and avoids variability through subjective judgments of experimentalists. Although our method does not avoid the inherent assumption that the diffusion exponent depends on a single k value, we show through simulation and experiment that it is robust in measurements of heterogeneous systems that violate this assumption. In this way, we obtain quantitative T{sub 2} distributions from complicated porous structures and demonstrate the analysis with examples of ceramics used for filtration and catalysis, and limestone of relevance to the construction and petroleum industries.

  20. Dynamics of phosphate head groups in biomembranes. Comprehensive analysis using phosphorus-31 nuclear magnetic resonance lineshape and relaxation time measurements.

    PubMed Central

    Dufourc, E J; Mayer, C; Stohrer, J; Althoff, G; Kothe, G

    1992-01-01

    Phospholipid head group dynamics have been studied by pulsed phosphorus-31 nuclear magnetic resonance (31P-NMR) of unoriented and macroscopically aligned dimyristoylphosphatidylcholine model membranes in the temperature range, 203-343 K. Lineshapes and echo intensities have been recorded as a function of interpulse delay times, temperature and macroscopic orientation of the bilayer normal with respect to the magnetic field. The dipolar proton-phosphorus (1H-31P) contribution to the transverse relaxation time, T2E, and to lineshapes was eliminated by means of a proton spin-lock sequence. In case of longitudinal spin relaxation, T1Z, the amount of dipolar coupling was evaluated by measuring the maximum nuclear Overhauser enhancement. Hence, the results could be analyzed by considering chemical shift anisotropy as the only relaxation mechanism. The presence of various minima both in T1Z and T2E temperature plots as well as the angular dependence of these relaxation times allowed description of the dynamics of the phosphate head group in the 31P-NMR time window, by three different motional classes, i.e., intramolecular, intermolecular and collective motions. The intramolecular motions consist of two hindered rotations and one free rotation around the bonds linking the phosphate head group to the glycerol backbone. These motions are the fastest in the hierarchy of time with correlation times varying from less than 10(-12) to 10(-6) s in the temperature range investigated. The intermolecular motions are assigned to phospholipid long axis rotation and fluctuation. They have correlation times ranging from 10(-11) s at high temperatures to 10(-3) s at low temperatures. The slowest motion affecting the 31P-NMR observables is assigned to viscoelastic modes, i.e., so called order director fluctuations and is only detected at high temperatures, above the main transition in pulse frequency dependent T2ECP experiments. Comprehensive analysis of the phosphate head group dynamics

  1. Host spin-lattice relaxation narrowing and the electron paramagnetic resonance of Mn(II) in single crystals of hexakis(pyridine N-oxide)cobalt(II) complexes

    NASA Astrophysics Data System (ADS)

    Murugesan, R.; Thamaraichelvan, A.; Milton Franklin, A.; Ramakrishnan, V.

    The electron paramagnetic resonance spectra of Mn(C5H5NO)6. X2 (X ≡ ClO-4, BF-4 and NO-3) doped in single crystals of isomorphous paramagnetic Co(C5H5NO)6. X2 are studied at various temperatures. Zero-field splitting in all three crystals is axially symmetric and the magnitude of D is unusually large for an octahedral coordination polyhedron with all ligands identical. The sharp resonance of Mn(II) in the paramagnetic host observed at high temperatures is interpreted in terms of random modulation of the dipolar interaction between the guest Mn(II) and host Co(II) ions by the rapid spin-lattice relaxation of Co(II). The spin-lattice relaxation times of Co(II) ions at 300 K, estimated from the temperature dependent linewidth of the Mn(II) resonance, are 24 × 10-12, 28 × 10-12 and 23 × 10-12 s in perchlorate, fluoborate and nitrate crystals respectively. The temperature dependence of the relaxation is of the form 1/(at + bt5) and below 270 K the direct process dominates.

  2. Iodine-xenon studies and the relax mass spectrometer

    NASA Astrophysics Data System (ADS)

    Gilmour, J. D.; Ash, R. D.; Lyon, I. C.; Johnston, W. A.; Hutchison, R.; Bridges, J. C.; Turner, G.

    1994-07-01

    RELAX combines a resonance ionization ion source with a cryogenic sample concentrator to achieve ultrasensitivity. Gas is extracted from samples using either a continuous wave laser microprobe based on an argon-ion laser or a filament microfurnace. Recent refinements in the operating procedure have resulted in optimum sensitivities such that detection rates of 1 cps are achieved from fewer than 500 atoms. A Xe-128 spike reservoir has also been added and characterized, allowing accurate determinations of absolute amounts of gas. We have completed a preliminary study of the iodine-xenon system in samples from the Bjurbole and Parnallee meteorites. Bjurbole chondrules ranging in mass from 5.45 mg to 260 micrograms were analyzed by laser microprobe. The results from these samples are consistent with an effectively uniform formation age, suggesting that the use of Bjurbole chondrules for calibration of this chronometer can be extended to samples in this size range. Samples from two chondrules from the Parnallee meteorite have been analyzed to date. An alpha-cristobalite-bearing chondrule (designated CB1) was found to have a formation age 4.62 +/- 0.44 Ma after Bjurboele, while a porphyritic olivine macrochondrule appears to have been reset after the decay of I-129(t1/2 17 Ma). Consideration of these results alongside Ar-Ar data from the macrochondrule and whole rock samples suggests that Parnallee has a complex history: The macrochondrule underwent an early postcrystallization degassing event but appears to have been essentially unaffected by the later (1.9 Ga) partial resetting of the bulk meteorite.

  3. PREFACE: 13th International Conference on Muon Spin Rotation, Relaxation and Resonance

    NASA Astrophysics Data System (ADS)

    2014-12-01

    The 13th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2014) organized by the Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute in collaboration with the University of Zurich and the University of Fribourg, was held in Grindelwald, Switzerland from 1st to 6th June 2014. The conference provided a forum for researchers from around the world with interests in the applications of μSR to study a wide range of topics including condensed matter physics, materials and molecular sciences, chemistry and biology. Polarized muons provide a unique and versatile probe of matter, enabling studies at the atomic level of electronic structure and dynamics in a wide range of systems. The conference was the thirteenth in a series, which began in Rorschach in 1978 and it took place for the third time in Switzerland. The previous conferences were held in Cancun, Mexico (2011), Tsukuba, Japan (2008), Oxford, UK (2005), Williamsburg, USA (2002), Les Diablerets, Switzerland (1999), Nikko, Japan (1996), Maui, USA (1993), Oxford, UK (1990), Uppsala, Sweden (1986), Shimoda, Japan (1983), Vancouver, Canada (1980), and Rorschach, Switzerland (1978). These conference proceedings contain 67 refereed publications from presentations covering magnetism, superconductivity, chemistry, semiconductors, biophysics and techniques. The conference logo, displayed in the front pages of these proceedings, represents both the location of μSR2014 in the Alps and the muon-spin rotation technique. The silhouette represents the famous local mountains Eiger, Mönch and Jungfrau as drawn by the Swiss painter Ferdinand Hodler and the apple with arrow is at the same time a citation of the Wilhelm Tell legend and a remembrance of the key role played by the muon spin and the asymmetric muon decay (which for the highest positron energy has an apple like shape). More than 160 participants (including 32 registered as students and 13 as accompanying persons) from 19 countries

  4. Ultrafast studies of photodissociation in solution: Dissociation, recombination and relaxation

    SciTech Connect

    King, J.C.

    1995-05-01

    Photodissociation of M(CO){sub 6} (M=Cr,Mo,W) and the formation of solvated M(CO){sub 5}{center_dot}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{sub 2}{sup -} and IBr{sup {minus}} 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{sub 3}{sup {minus}} and IBr{sub 2}{sup {minus}} 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 {ge}5.5 kcal/mol. The more complex photochemistry of M{sub 3}(CO){sub 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.

  5. NMR relaxation studies in doped poly-3-methylthiophene

    NASA Astrophysics Data System (ADS)

    Singh, K. Jugeshwar; Clark, W. G.; Gaidos, G.; Reyes, A. P.; Kuhns, P.; Thompson, J. D.; Menon, R.; Ramesh, K. P.

    2015-05-01

    NMR relaxation rates (1 /T1 ), magnetic susceptibility, and electrical conductivity studies in doped poly-3-methylthiophene are reported in this paper. The magnetic susceptibility data show the contributions from both Pauli and Curie spins, with the size of the Pauli term depending strongly on the doping level. Proton and fluorine NMR relaxation rates have been studied as a function of temperature (3-300 K) and field (for protons at 0.9, 9.0, 16.4, and 23.4 T, and for fluorine at 9.0 T). The temperature dependence of T1 is classified into three regimes: (a) For T <(g μBB /2 kB ) , the relaxation mechanism follows a modified Korringa relation due to electron-electron interactions and disorder. 1H - T1 is due to the electron-nuclear dipolar interaction in addition to the contact term. (b) For the intermediate temperature range (g μBB /2 kB ) relaxation mechanism is via spin diffusion to the paramagnetic centers. (c) In the high-temperature regime and at low Larmor frequency the relaxation follows the modified Bloembergen, Purcell, and Pound model. T1 data analysis has been carried out in light of these models depending upon the temperature and frequency range of study. Fluorine relaxation data have been analyzed and attributed to the P F6 reorientation. The cross relaxation among the 1H and 19F nuclei has been observed in the entire temperature range suggesting the role of magnetic dipolar interaction modulated by the reorientation of the symmetric molecular subgroups. The data analysis shows that the enhancement in the Korringa ratio is greater in a less conducting sample. Intra- and interchain hopping of charge carriers is found to be a dominant relaxation mechanism at low temperature. Frequency dependence of T1-1 on temperature shows that at low temperature [T <(g μBB /2 kB ) ] the system shows three dimensions and changes to quasi one dimension at

  6. Rotational Mobility in a Crystal Studied by Dielectric Relaxation Spectroscopy

    ERIC Educational Resources Information Center

    Dionisio, Madalena S. C.; Diogo, Herminio P.; Farinha, J. P. S.; Ramos, Joaquim J. Moura

    2005-01-01

    A laboratory experiment for undergraduate physical chemistry courses that uses the experimental technique of dielectric relaxation spectroscopy to study molecular mobility in a crystal is proposed. An experiment provides an excellent opportunity for dealing with a wide diversity of important basic concepts in physical chemistry.

  7. On resonance phase alternated CWFP sequences for rapid and simultaneous measurement of relaxation times.

    PubMed

    Monaretto, Tatiana; Andrade, Fabiana Diuk; Moraes, Tiago Bueno; Souza, Andre Alves; deAzevedo, Eduardo Ribeiro; Colnago, Luiz Alberto

    2015-10-01

    T1 and T2 relaxation times have been frequently used as probes for physical-chemical properties in several time-domain NMR applications (TD-NMR) such as food, polymers and petroleum industries. T2 measurements are usually achieved using the traditional Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence because it is a fast and robust method. On the other hand, the traditional methods for determining T1, i.e., inversion and saturation recovery, are time-consuming, driving several authors to develop rapid 1D and 2D methods to obtain T1 and T2 or T1/T2 ratio. However, these methods usually require sophisticated processing and/or high signal to noise ratio (SNR). This led us to develop simple methods for rapid and simultaneous determination of T1 and T2 using Continuous Wave Free Precession (CWFP) and Carr-Purcell Continuous Wave Free Precession (CP-CWFP) pulse sequences. Nevertheless, a drawback of these sequences is that they require specific adjustment of the frequency offset or the time interval between pulses (Tp). In this paper we present an alternative form of these sequences, named CWFPx-x, CP-CWFPx-x, where a train of π/2 pulses with phases alternated by π enable performing the experiments on-resonance and independently of Tp, when Tprelaxation times are determined using the magnitude of the signals after the first pulse |M0| and in the steady-state |Mss|, as well as the exponential time constant T(∗) to reach the steady-state regime, as in conventional CWFP. CP-CWFPx-x shows the highest dynamic range to measure T(∗) among CWFP sequences and, therefore, is the best technique to measure T1 and T2 since it is less susceptible to SNR and can be performed for any T1/T2 ratio. PMID:26363504

  8. On resonance phase alternated CWFP sequences for rapid and simultaneous measurement of relaxation times

    NASA Astrophysics Data System (ADS)

    Monaretto, Tatiana; Andrade, Fabiana Diuk; Moraes, Tiago Bueno; Souza, Andre Alves; deAzevedo, Eduardo Ribeiro; Colnago, Luiz Alberto

    2015-10-01

    T1 and T2 relaxation times have been frequently used as probes for physical-chemical properties in several time-domain NMR applications (TD-NMR) such as food, polymers and petroleum industries. T2 measurements are usually achieved using the traditional Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence because it is a fast and robust method. On the other hand, the traditional methods for determining T1, i.e., inversion and saturation recovery, are time-consuming, driving several authors to develop rapid 1D and 2D methods to obtain T1 and T2 or T1/T2 ratio. However, these methods usually require sophisticated processing and/or high signal to noise ratio (SNR). This led us to develop simple methods for rapid and simultaneous determination of T1 and T2 using Continuous Wave Free Precession (CWFP) and Carr-Purcell Continuous Wave Free Precession (CP-CWFP) pulse sequences. Nevertheless, a drawback of these sequences is that they require specific adjustment of the frequency offset or the time interval between pulses (Tp). In this paper we present an alternative form of these sequences, named CWFPx-x, CP-CWFPx-x, where a train of π/2 pulses with phases alternated by π enable performing the experiments on-resonance and independently of Tp, when Tp < T2∗. Moreover, a CPMG type sequence with π/2 refocusing pulses shows similar results to CP-CWFP when the pulses are alternated between y and -y axis, CPMG90y-y. In these approaches, the relaxation times are determined using the magnitude of the signals after the first pulse |M0| and in the steady-state |Mss|, as well as the exponential time constant T∗ to reach the steady-state regime, as in conventional CWFP. CP-CWFPx-x shows the highest dynamic range to measure T∗ among CWFP sequences and, therefore, is the best technique to measure T1 and T2 since it is less susceptible to SNR and can be performed for any T1/T2 ratio.

  9. Casein-Coated Fe5C2 Nanoparticles with Superior r2 Relaxivity for Liver-Specific Magnetic Resonance Imaging

    PubMed Central

    Cowger, Taku A.; Tang, Wei; Zhen, Zipeng; Hu, Kai; Rink, David E.; Todd, Trever J.; Wang, Geoffrey D.; Zhang, Weizhong; Chen, Hongmin; Xie, Jin

    2015-01-01

    Iron oxide nanoparticles have been extensively used as T2 contrast agents for liver-specific magnetic resonance imaging (MRI). The applications, however, have been limited by their mediocre magnetism and r2 relaxivity. Recent studies show that Fe5C2 nanoparticles can be prepared by high temperature thermal decomposition. The resulting nanoparticles possess strong and air stable magnetism, suggesting their potential as a novel type of T2 contrast agent. To this end, we improve the synthetic and surface modification methods of Fe5C2 nanoparticles, and investigated the impact of size and coating on their performances for liver MRI. Specifically, we prepared 5, 14, and 22 nm Fe5C2 nanoparticles and engineered their surface by: 1) ligand addition with phospholipids, 2) ligand exchange with zwitterion-dopamine-sulfonate (ZDS), and 3) protein adsorption with casein. It was found that the size and surface coating have varied levels of impact on the particles' hydrodynamic size, viability, uptake by macrophages, and r2 relaxivity. Interestingly, while phospholipid- and ZDS-coated Fe5C2 nanoparticles showed comparable r2, the casein coating led to an r2 enhancement by more than 2 fold. In particular, casein coated 22 nm Fe5C2 nanoparticle show a striking r2 of 973 mM-1s-1, which is one of the highest among all of the T2 contrast agents reported to date. Small animal studies confirmed the advantage of Fe5C2 nanoparticles over iron oxide nanoparticles in inducing hypointensities on T2-weighted MR images, and the particles caused little toxicity to the host. The improvements are important for transforming Fe5C2 nanoparticles into a new class of MRI contrast agents. The observations also shed light on protein-based surface modification as a means to modulate contrast ability of magnetic nanoparticles. PMID:26379788

  10. Casein-Coated Fe5C2 Nanoparticles with Superior r2 Relaxivity for Liver-Specific Magnetic Resonance Imaging.

    PubMed

    Cowger, Taku A; Tang, Wei; Zhen, Zipeng; Hu, Kai; Rink, David E; Todd, Trever J; Wang, Geoffrey D; Zhang, Weizhong; Chen, Hongmin; Xie, Jin

    2015-01-01

    Iron oxide nanoparticles have been extensively used as T2 contrast agents for liver-specific magnetic resonance imaging (MRI). The applications, however, have been limited by their mediocre magnetism and r2 relaxivity. Recent studies show that Fe5C2 nanoparticles can be prepared by high temperature thermal decomposition. The resulting nanoparticles possess strong and air stable magnetism, suggesting their potential as a novel type of T2 contrast agent. To this end, we improve the synthetic and surface modification methods of Fe5C2 nanoparticles, and investigated the impact of size and coating on their performances for liver MRI. Specifically, we prepared 5, 14, and 22 nm Fe5C2 nanoparticles and engineered their surface by: 1) ligand addition with phospholipids, 2) ligand exchange with zwitterion-dopamine-sulfonate (ZDS), and 3) protein adsorption with casein. It was found that the size and surface coating have varied levels of impact on the particles' hydrodynamic size, viability, uptake by macrophages, and r2 relaxivity. Interestingly, while phospholipid- and ZDS-coated Fe5C2 nanoparticles showed comparable r2, the casein coating led to an r2 enhancement by more than 2 fold. In particular, casein coated 22 nm Fe5C2 nanoparticle show a striking r2 of 973 mM(-1)s(-1), which is one of the highest among all of the T2 contrast agents reported to date. Small animal studies confirmed the advantage of Fe5C2 nanoparticles over iron oxide nanoparticles in inducing hypointensities on T2-weighted MR images, and the particles caused little toxicity to the host. The improvements are important for transforming Fe5C2 nanoparticles into a new class of MRI contrast agents. The observations also shed light on protein-based surface modification as a means to modulate contrast ability of magnetic nanoparticles.

  11. Muon spin relaxation studies of interstitial and molecular motion.

    PubMed

    Cox, S F

    1998-03-01

    The unusual methods of preparation and analysis of spin polarization in muSR spectroscopy, which exploit the unique properties of the positive muon, are introduced in this article. Following a summary overview of applications, particular attention is paid to the problem of spin-lattice relaxation for a muon experiencing a hyperfine interaction with a single unpaired electron. The specific cases considered are the interstitial diffusion of muonium--the 1-electron atom which may be considered as a light isotope of hydrogen-and the molecular dynamics of organic radicals labelled by muonium. Rate equations for the evolution of population in the hyperfine-coupled spin states are solved numerically for various relaxation mechanisms. The formalism is equally valid for conventional ESR studies of paramagnetic states but is pursued specifically to simulate T1-relaxation in muSR. The simulations are compared with literature data. Also treated is the case of intermittent hyperfine coupling, appropriate to electron capture and loss in semiconductors or soliton motion in polymers; for this, a Monte Carlo approach is used to simulate the muon response. (For low-dimensional motion, the relaxation function is not exponential, so that a unique value of T1 cannot be defined.) Finally, a proposal is made to implement muon-T1 measurements in the rotating frame; this is designed for the selective study of electronically diamagnetic muonium states (i.e., those without hyperfine coupling) in the presence of a paramagnetic muonium or radical fraction.

  12. Muon spin relaxation studies of interstitial and molecular motion.

    PubMed

    Cox, S F

    1998-03-01

    The unusual methods of preparation and analysis of spin polarization in muSR spectroscopy, which exploit the unique properties of the positive muon, are introduced in this article. Following a summary overview of applications, particular attention is paid to the problem of spin-lattice relaxation for a muon experiencing a hyperfine interaction with a single unpaired electron. The specific cases considered are the interstitial diffusion of muonium--the 1-electron atom which may be considered as a light isotope of hydrogen-and the molecular dynamics of organic radicals labelled by muonium. Rate equations for the evolution of population in the hyperfine-coupled spin states are solved numerically for various relaxation mechanisms. The formalism is equally valid for conventional ESR studies of paramagnetic states but is pursued specifically to simulate T1-relaxation in muSR. The simulations are compared with literature data. Also treated is the case of intermittent hyperfine coupling, appropriate to electron capture and loss in semiconductors or soliton motion in polymers; for this, a Monte Carlo approach is used to simulate the muon response. (For low-dimensional motion, the relaxation function is not exponential, so that a unique value of T1 cannot be defined.) Finally, a proposal is made to implement muon-T1 measurements in the rotating frame; this is designed for the selective study of electronically diamagnetic muonium states (i.e., those without hyperfine coupling) in the presence of a paramagnetic muonium or radical fraction. PMID:9650794

  13. Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Haar, Peter J.; Broaddus, William C.; Chen, Zhi-jian; Fatouros, Panos P.; Gillies, George T.; Corwin, Frank D.

    2010-06-01

    A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s)-1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

  14. Multiple relaxation and inhomogeneous broadening in resonance enhanced Raman scattering - Application to tunable infrared generation

    NASA Technical Reports Server (NTRS)

    Ryan, J. C.; Lawandy, N. M.

    1989-01-01

    The solutions for the imaginary susceptibility of the Raman field transition with arbitrary relaxation rates and field strengths are examined for differing sets of relaxation rates with emphasis on alkali metal vapors which have spontaneous emission dominated relaxation. The model is further expanded to include Doppler broadening and used to predict the peak gain as a function of detuning for a frequency doubled alexandrite laser-pumped cesium vapor gain cell.

  15. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    SciTech Connect

    Sachleben, J. R.

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and {sup 13}C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution {sup 1}H and {sup 13}C liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 {angstrom}. Internal motion is estimated to be slow with a correlation time > 10{sup {minus}8} s{sup {minus}1}. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O{sub 2} and ultraviolet. A method for measuring {sup 14}N-{sup 1}H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T{sub 1} and T{sub 2} experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in {sup 13}C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  16. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    NASA Astrophysics Data System (ADS)

    Sachleben, J. R.

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and C-13 enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution H-1 and C-13 liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 angstrom. Internal motion is estimated to be slow with a correlation time greater than 10(exp -8) s(exp -1). The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O2 and ultraviolet. A method for measuring (N-14)-(H-1) J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T(sub 1) and T(sub 2) experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in C-13 enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  17. Backbone dynamics of barstar: a (15)N NMR relaxation study.

    PubMed

    Sahu, S C; Bhuyan, A K; Majumdar, A; Udgaonkar, J B

    2000-12-01

    Backbone dynamics of uniformly (15)N-labeled barstar have been studied at 32 degrees C, pH 6.7, by using (15)N relaxation data obtained from proton-detected 2D (1)H-(15)N NMR spectroscopy. (15)N spin-lattice relaxation rate constants (R(1)), spin-spin relaxation rate constants (R(2)), and steady-state heteronuclear (1)H-(15)N NOEs have been determined for 69 of the 86 (excluding two prolines and the N-terminal residue) backbone amide (15)N at a magnetic field strength of 14.1 Tesla. The primary relaxation data have been analyzed by using the model-free formalism of molecular dynamics, using both isotropic and axially symmetric diffusion of the molecule, to determine the overall rotational correlation time (tau(m)), the generalized order parameter (S(2)), the effective correlation time for internal motions (tau(e)), and NH exchange broadening contributions (R(ex)) for each residue. As per the axially symmetric diffusion, the ratio of diffusion rates about the unique and perpendicular axes (D( parallel)/D( perpendicular)) is 0.82 +/- 0.03. The two results have only marginal differences. The relaxation data have also been used to map reduced spectral densities for the NH vectors of these residues at three frequencies: 0, omega(H), and omega(N), where omega(H),(N) are proton and nitrogen Larmor frequencies. The value of tau(m) obtained from model-free analysis of the relaxation data is 5.2 ns. The reduced spectral density analysis, however, yields a value of 5.7 ns. The tau(m) determined here is different from that calculated previously from time-resolved fluorescence data (4.1 ns). The order parameter ranges from 0.68 to 0.98, with an average value of 0.85 +/- 0.02. A comparison of the order parameters with the X-ray B-factors for the backbone nitrogens of wild-type barstar does not show any considerable correlation. Model-free analysis of the relaxation data for seven residues required the inclusion of an exchange broadening term, the magnitude of which ranges from 2

  18. Use of a high-Tc SQUID-based nuclear magnetic resonance spectrometer in magnetically unshielded environments to discriminate tumors in rats, by characterizing the longitudinal relaxation rate

    NASA Astrophysics Data System (ADS)

    Huang, K.-W.; Chen, H.-H.; Yang, H.-C.; Horng, H.-E.; Liao, S.-H.; Chieh, J.-J.; Yang, S. Y.

    2012-06-01

    This study uses a sensitive, high-Tc SQUID-detected nuclear magnetic resonance spectrometer in magnetically unshielded environments to discriminate liver tumors in rats, by characterizing the longitudinal relaxation rate, T1-1. The high-Tc SQUID-based spectrometer has a spectral line width of 0.9Hz in low magnetic fields. It was found that relaxation rate for tumor tissues is (3.6 ± 0.02) s-1 and the relaxation rate for normal tissues is (7.7 ± 0.02) s-1. The difference in the longitudinal relaxation rates suggests that water structures around the DNA of cancer cells are different from those of normal tissues. The optimized detection sensitivity for the established system is 0.21 g at the present stage. It is concluded that T1-1 can be used to distinguish cancerous tissues from normal tissues. The high-Tc, SQUID-detected NMR and MRI in magnetically unshielded environments may also be useful for discriminating other tumors.

  19. Assessment of tissue repair in full thickness chondral defects in the rabbit using magnetic resonance imaging transverse relaxation measurements.

    PubMed

    Ramaswamy, Sharan; Gurkan, Ilksen; Sharma, Blanka; Cascio, Brett; Fishbein, Kenneth W; Spencer, Richard G

    2008-08-01

    The purpose of this study was to determine if the noninvasive and nondestructive technique of magnetic resonance imaging could be used to quantify the amount of repair tissue that fills surgically-induced chondral defects in the rabbit. Sixteen 4-mm diameter full-thickness chondral defects were created. A photopolymerizable hydrogel was used to seal the defects as a treatment modality. At 5 weeks, the animals were sacrificed and the distal femur was subjected to MRI analyses at high field (9.4 T). The transverse relaxation time (T(2)) in each defect was measured. Histology and histomorphometric analysis were used to quantify the amount of repair tissue that filled each defect. The relationship between T(2) and percent tissue fill was found to fit well to a negatively sloped, linear model. The linear (Pearson's product-moment) correlation coefficient was found to be r = -0.82 and the associated coefficient of determination was r(2) = 0.67. This correlation suggests that the MRI parameter T(2) can be used to track changes in the amount of repair tissue that fills cartilage defects. This would be especially useful in in vivo cartilage tissue engineering studies that attempt to determine optimal biomaterials for scaffold design.

  20. Spatial analysis of magnetic resonance T1ρ and T2 relaxation times improves classification between subjects with and without osteoarthritis

    PubMed Central

    Carballido-Gamio, Julio; Stahl, Robert; Blumenkrantz, Gabrielle; Romero, Adan; Majumdar, Sharmila; Link, Thomas M.

    2009-01-01

    Purpose: Studies have shown that functional analysis of knee cartilage based on magnetic resonance (MR) relaxation times is a valuable tool in the understanding of osteoarthritis (OA). In this work, the regional spatial distribution of knee cartilage T1ρ and T2 relaxation times based on texture and laminar analyses was studied to investigate if they provide additional insight compared to global mean values in the study of OA. Methods: Knee cartilage of 36 subjects, 19 healthy controls and 17 with mild OA, was divided into 16 compartments. T1ρ and T2 relaxation times were studied with first order statistics, eight texture parameters with four different orientations using gray-level co-occurrence matrices and by subdividing each compartment into two different layers: Deep and superficial. Receiver operating characteristic curve analysis was performed to evaluate the potential of each technique to correctly classify the populations. Results: Although the deep and superficial cartilage layers had in general significantly different T1ρ and T2 relaxation times, they performed similarly in terms of subject discrimination. The subdivision of lateral and medial femoral compartments into weight-bearing and non-weight-bearing regions did not improve discrimination. Also it was found that the most sensitive region was the patella and that T1ρ discriminated better than T2. The most important finding was that with respect to global mean values, laminar and texture analyses improved subject discrimination. Conclusions: Results of this study suggest that spatially assessing MR images of the knee cartilage relaxation times using laminar and texture analyses could lead to better and probably earlier identification of cartilage matrix abnormalities in subjects with OA. PMID:19810478

  1. Long-Lasting and Efficient Tumor Imaging Using a High Relaxivity Polysaccharide Nanogel Magnetic Resonance Imaging Contrast Agent.

    PubMed

    Chan, Minnie; Lux, Jacques; Nishimura, Tomoki; Akiyoshi, Kazunari; Almutairi, Adah

    2015-09-14

    Clinically approved small-molecule magnetic resonance imaging (MRI) contrast agents are all rapidly cleared from the body and offer weak signal enhancement. To avoid repeated administration of contrast agent and improve signal-to-noise ratios, agents with stronger signal enhancement and better retention in tumors are needed. Therefore, we focused on hydrogels because of their excellent water accessibility and biodegradability. Gadolinium (Gd)-chelating cross-linkers were incorporated into self-assembled pullulan nanogels to both impart magnetic properties and to stabilize this material that has been extensively studied for medical applications. We show that these Gd-chelating pullulan nanogels (Gd-CHPOA) have the highest reported relaxivity for any hydrogel-based particles and accumulate in the 4T1 tumors in mice at high levels 4 h after injection. This combination offers high signal enhancement and lasts up to 7 days to delineate the tumor clearly for longer imaging time scales. Importantly, this long-term accumulation does not cause any damage or toxicity in major organs up to three months after injection. Our work highlights the clinical potential of Gd-CHPOA as a tumor-imaging MRI contrast agent, permitting tumor identification and assessment with a high signal-to-background ratio.

  2. Nuclear Magnetic Resonance Technology for Medical Studies.

    ERIC Educational Resources Information Center

    Budinger, Thomas F.; Lauterbur, Paul C.

    1984-01-01

    Reports on the status of nuclear magnetic resonance (NMR) from theoretical and clinical perspectives, reviewing NMR theory and relaxation parameters relevant to NMR imaging. Also reviews literature related to modern imaging strategies, signal-to-noise ratio, contrast agents, in vivo spectroscopy, spectroscopic imaging, clinical applications, and…

  3. Relaxation Nuclear Magnetic Resonance Imaging Investigation of Heterogeneous Aging in a Hydroxy-Terminated Polybutadiene-Based Elastomer

    SciTech Connect

    Alam, Todd M.; Cherry, Brian R.; Minard, Kevin R.; Celina, Mat C.

    2005-12-27

    Relaxation nuclear magnetic resonance imaging (R-NMRI) was employed to investigate the effects of thermo-oxidative aging in a hydroxy-terminated polybutadiene (HTPB) based elastomer. A series of three-dimensional (3D) Hahn-echo weighted single point images (SPI) of the elastomer were utilized to generate a 3D parameter map of the aged material. NMR spin-spin relaxation times (T2) were measured for each voxel producing a 3D NMR parameter (T2) map of the aged polymer. These T2 maps reveal a dramatic reduction of local polymer mobility near the aging surface with the degree of T2 heterogeneity varying as a function of aging. Using correlations between NMR T2 and material modulus, the impact of this heterogeneous thermo-oxidative aging on the material properties is discussed.

  4. Dielectric relaxation in dimethyl sulfoxide/water mixtures studied by microwave dielectric relaxation spectroscopy.

    PubMed

    Lu, Zijie; Manias, Evangelos; Macdonald, Digby D; Lanagan, Michael

    2009-11-01

    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 (g(K) = 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.

  5. Resonant excited state absorption and relaxation mechanisms in Tb3+-doped calcium aluminosilicate glasses: an investigation by thermal mirror spectroscopy.

    PubMed

    Bianchi, G S; Zanuto, V S; Astrath, F B G; Malacarne, L C; Terra, I A A; Catunda, T; Nunes, L A O; Jacinto, C; Andrade, L H C; Lima, S M; Baesso, M L; Astrath, N G C

    2013-11-15

    Resonant excited state absorption (ESA) and relaxation processes in Tb(3+)-doped aluminosilicate glasses are quantitatively evaluated. A model describing the excitation steps and upconversion emission is developed and applied to interpret the results from laser-induced surface deformation using thermal mirror spectroscopy. The fluorescence quantum efficiency of level (5)D(4) was found to be close to unity and concentration independent while, for the level (5)D(3), it decreases with Tb(3+) concentration. Emission spectroscopy measurements supported these results. ESA cross sections are found to be more than three orders of magnitude higher than the ground state absorption cross section. PMID:24322101

  6. HRXRD studies of strain relaxation in ion-implanted strained Si on relaxed Si 1- xGe x

    NASA Astrophysics Data System (ADS)

    Phen, M. S.; Craciun, V.; Jones, K. S.; Hansen, J. L.; Larsen, A. N.

    2006-12-01

    The relaxation process of ion-implanted strained silicon films grown on silicon-rich relaxed Si 1- xGe x alloys was studied to determine the critical strain regime necessary for the breakdown of solid phase epitaxial recrystallization. Experimental structures were grown via molecular beam epitaxy (MBE) and contained a 50 nm strained silicon capping layer on relaxed Si 1- xGe x. The relaxed Si 1- xGe x alloy compositions range from 0 to 30 at.% germanium. A 12 keV Si + implant at a fluence of 1 × 10 15 atoms/cm 2 was used to generate an amorphous layer ˜30 nm thick, confining it to the strained silicon cap. The degree of relaxation of the silicon cap layer was quantified by high-resolution X-ray diffraction (HRXRD) omega-2theta rocking curves and reciprocal space maps. Maps were acquired for the (0 0 4) and (1 1 3) reflections to obtain the in and out-of-plane lattice parameter of the layers. Upon annealing, the solid phase regrowth (SPER) process broke down for the highest level of strain. Additionally, regrowth related defects were observed in these samples using cross-sectional transmission electron microscopy (XTEM). These results indicate a reduction of strain in the Si 0.7Ge 0.3 samples occur as a result of SPER breakdown that generated dislocations and stacking faults throughout the silicon capping layer.

  7. Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating.

    PubMed

    Tretiak, O Yu; Blanchard, J W; Budker, D; Olshin, P K; Smirnov, S N; Balabas, M V

    2016-03-01

    The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements compared to a bare glass surface by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene. PMID:26957176

  8. Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating

    NASA Astrophysics Data System (ADS)

    Tretiak, O. Yu.; Blanchard, J. W.; Budker, D.; Olshin, P. K.; Smirnov, S. N.; Balabas, M. V.

    2016-03-01

    The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements compared to a bare glass surface by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene.

  9. Nuclear magnetic resonance relaxation and diffusion in the presence of internal gradients: the effect of magnetic field strength.

    PubMed

    Mitchell, J; Chandrasekera, T C; Johns, M L; Gladden, L F; Fordham, E J

    2010-02-01

    It is known that internal magnetic field gradients in porous materials, caused by susceptibility differences at the solid-fluid interfaces, alter the observed effective Nuclear Magnetic Resonance transverse relaxation times T2,eff. The internal gradients scale with the strength of the static background magnetic field B0. Here, we acquire data at various magnitudes of B0 to observe the influence of internal gradients on T2-T2 exchange measurements; the theory discussed and observations made are applicable to any T2-T2 analysis of heterogeneous materials. At high magnetic field strengths, it is possible to observe diffusive exchange between regions of local internal gradient extrema within individual pores. Therefore, the observed exchange pathways are not associated with pore-to-pore exchange. Understanding the significance of internal gradients in transverse relaxation measurements is critical to interpreting these results. We present the example of water in porous sandstone rock and offer a guideline to determine whether an observed T2,eff relaxation time distribution reflects the pore size distribution for a given susceptibility contrast (magnetic field strength) and spin echo separation. More generally, we confirm that for porous materials T1 provides a better indication of the pore size distribution than T2,eff at high magnetic field strengths (B0>1 T), and demonstrate the data analysis necessary to validate pore size interpretations of T2,eff measurements.

  10. Relaxation dynamics of the Fe₈ molecular nanomagnet as probed by nuclear magnetic resonance.

    PubMed

    Carretta, S; Bianchi, A; Santini, P; Amoretti, G

    2010-05-28

    The relaxation dynamics in molecular nanomagnets can be probed by measurements of NMR 1/T(1). By modelling magnetoelastic interactions, we theoretically investigate the behaviour of the prototype Fe(8) nanomagnet. The results of our model are in agreement with AC susceptibility and recent NMR measurements.

  11. Interfacial membrane docking of cytosolic phospholipase A2 C2 domain using electrostatic potential-modulated spin relaxation magnetic resonance

    PubMed Central

    Ball, Andy; Nielsen, Robert; Gelb, Michael H.; Robinson, Bruce H.

    1999-01-01

    The C2 domain of cytosolic phospholipase A2 (C2cPLA2) plays an important role in calcium-dependent transfer of the protein from the cytosol to internal cellular membranes as a prelude for arachidonate release from membrane phospholipids. By using a recently developed electron paramagnetic resonance approach together with 13 site-specifically nitroxide spin labeled C2cPLA2s and membrane-permeant and -impermeant spin relaxants, we have determined the orientation of C2cPLA2 with respect to the surface of vesicles of the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphomethanol. The structure reveals that the two calcium-binding regions on C2cPLA2 that display hydrophobic residues, CBR1 and CBR3, are partially inserted into the core of the membrane. CBR2 that contains predominantly hydrophilic residues is close to the membrane but not inserted. The long axis of the cylindrical C2cPLA2 molecule is tilted with respect to the bilayer normal, which brings a cluster of basic protein residues close to the phospholipid headgroups. Such an orientation places the two bound calcium ions close to the membrane surface. All together, the results provide structural support for previous proposals that binding of C2cPLA2 to the membrane interface is driven in part by insertion of hydrophobic surface loops into the membrane core. The results are contrasted with previous studies of the interfacial binding of the first C2 domain of synaptotagmin I, which has shorter surface loops that display basic residues for electrostatic interaction with the bilayer surface. PMID:10359764

  12. Tacrine derivatives-acetylcholinesterase interaction: 1H NMR relaxation study.

    PubMed

    Delfini, Maurizio; Di Cocco, Maria Enrica; Piccioni, Fabiana; Porcelli, Fernando; Borioni, Anna; Rodomonte, Andrea; Del Giudice, Maria Rosaria

    2007-06-01

    Two acetylcholinesterase (AChE) inhibitors structurally related to Tacrine, 6-methoxytacrine (1a) and 9-heptylamino-6-methoxytacrine (1b), and their interaction with Electrophorus Electricus AChE were investigated. The complete assignment of the 1H and 13C NMR spectra of 1a and 1b was performed by mono-dimensional and homo- and hetero-correlated two-dimensional NMR experiments. This study was undertaken to elucidate the interaction modes between AChE and 1a and 1b in solution, using NMR. The interaction between the two inhibitors and AChE was studied by the analysis of the motional parameters non-selective and selective spin-lattice relaxation times, thereby allowing the motional state of 1a and 1b, both free and bound with AChE, to be defined. The relaxation data pointed out the ligands molecular moiety most involved in the binding with AChE. The relevant ligand/enzyme interaction constants were also evaluated for both compounds and resulted to be 859 and 5412M(-1) for 1a and1b, respectively.

  13. Vitamin E and related ether-phenols: A low-temperature dielectric relaxation study

    NASA Astrophysics Data System (ADS)

    Gilchrist, John le G.; Burton, Graham W.; Ingold, Keith U.

    1985-05-01

    Within a classs of phenols comprising durenols and methylated chromenols, chromanols and coumaranols, hydrogen-abstraction rate constants, and therefore radical-scavenging and antioxidant effectiveness are closely paralleled by low-temperature relaxation rates, and are apparently influenced in similar proportions by the inductive and resonance effects of para-alkoxy groups. Relaxation rates of 2,3,5,6-tetrachlorophenol and 2,6-di-tertiary-butyl phenol with and without 4-methoxy substituents are also reported and discussed.

  14. Mesenteric artery contraction and relaxation studies using automated wire myography.

    PubMed

    Bridges, Lakeesha E; Williams, Cicely L; Pointer, Mildred A; Awumey, Emmanuel M

    2011-09-22

    Proximal resistance vessels, such as the mesenteric arteries, contribute substantially to the peripheral resistance. These small vessels of between 100-400 μm in diameter function primarily in directing blood flow to various organs according to the overall requirements of the body. The rat mesenteric artery has a diameter greater than 100 μm. The myography technique, first described by Mulvay and Halpern(1), was based on the method proposed by Bevan and Osher(2). The technique provides information about small vessels under isometric conditions, where substantial shortening of the muscle preparation is prevented. Since force production and sensitivity of vessels to different agonists is dependent on the extent of stretch, according to active tension-length relation, it is essential to conduct contraction studies under isometric conditions to prevent compliance of the mounting wires. Stainless steel wires are preferred to tungsten wires because of oxidation of the latter, which affects recorded responses(3).The technique allows for the comparison of agonist-induced contractions of mounted vessels to obtain evidence for normal function of vascular smooth muscle cell receptors. We have shown in several studies that isolated mesenteric arteries that are contracted with phenylyephrine relax upon addition of cumulative concentrations of extracellular calcium (Ca(2+)(e;)). The findings led us to conclude that perivascular sensory nerves, which express the G protein-coupled Ca(2+)-sensing receptor (CaR), mediate this vasorelaxation response. Using an automated wire myography method, we show here that mesenteric arteries from Wistar, Dahl salt-sensitive(DS) and Dahl salt-resistant (DR) rats respond differently to Ca(2+)(e;). Tissues from Wistar rats showed higher Ca(2+)-sensitivity compared to those from DR and DS. Reduced CaR expression in mesenteric arteries from DS rats correlates with reduced Ca(2+)(e;)-induced relaxation of isolated, pre-contracted arteries. The data

  15. Changes of the local pore space structure quantified in heterogeneous porous media by 1H magnetic resonance relaxation tomography

    NASA Astrophysics Data System (ADS)

    Borgia, G. C.; Bortolotti, V.; Fantazzini, P.

    2001-08-01

    Magnetic resonance imaging and relaxation analysis are combined in a spatially resolved technique (relaxation tomography), which is able to quantify the parameters connected to the local structure in the internal regions of a porous material saturated by water, giving information on the pore space structure beyond the nominal instrumental resolution. Voxel-by-voxel longitudinal (T1) and transverse (T2) relaxation curves are acquired in order to obtain T1, T2 and S(0) maps, where S(0) is the extrapolation to zero time of the total equilibrium magnetization corrected for T2 decay. The proposed method permits evaluation of the porosity (ratio of pore space to total volume), at different length scales, from the sample to the voxel, not all achievable by traditional methods. More striking is its ability to describe how porosity is shared among different classes of surface-to-volume ratios of diffusion cells (the regions that the individual water molecules, starting at their particular positions, can experience by diffusion before relaxing). This is a consequence of the fact that relaxation times of water confined in a porous material can, under favorable circumstances, distinguish regions with the same local porosity but with different pore sizes and connections. So, parameters can be introduced, such as the microporosity fraction, defined as the fraction of the "micropore" volume with respect to the total pore volume, and several voxel average porosities, defined as the average porosities of the voxels characterized by particular classes of diffusion cells. Moreover, the imaging methods enable us to get all this information in a user-defined region of interest. The method has been applied to quantify changes in the structure of carbonate cores with wide distributions of pore sizes induced by repeated cycles of freezing and heating of the sample. With freezing, the microporosity fraction decreases significantly; the voxel average porosity of voxels with T1 shorter than

  16. Dielectric relaxation and birefringence study of 7.O5O.7 dimeric liquid crystal compound

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Debanjan; Paul-Choudhury, Sandip; Alapati, Parameswara Rao; Bhattacharjee, Ayon

    2016-05-01

    Measurement of dielectric relaxation and birefringence phenomenon of dimeric liquid crystal compound with the dependence of temperature was reported in this paper. Homogeneous (HG) and homeotropic (HT) alignment of the cell are introduced to investigate the dielectric relaxation, activation energy and birefringence. Cole-Cole plots analyzed the dielectric relaxation of the dimeric compound. The observed Cole-Cole plots were semi-circular, and the relaxation mechanism obeys the non-Debye type of relaxation behaviour. Slater's perturbation equations have been used to analysis the activation energy of the compound. The birefringence of the compound has positively anisotropy and thin prism mechanism was used to study the anisotropy of the compound.

  17. Hydrogen bond fluctuations and dispersive interactions of alcohol/alkane mixtures. An ultrasonic relaxation study

    NASA Astrophysics Data System (ADS)

    Kaatze, Udo; Behrends, Ralph

    2011-06-01

    The relaxation behaviour of 1-hexanol/n-heptane and 1-dodecanol/n-tetradecane mixtures has been studied at some compositions using ultrasonic attenuation spectrometry in the frequency range 0.4-3000 MHz. All mixtures reveal a relaxation term due to hydrogen network fluctuations. It is discussed in conjunction with the principle dielectric relaxation of alcohol/alkane mixtures, indicating a dynamically micro-heterogeneous liquid structure. The spectra of the long-chain alcohol system display an additional relaxation due to the structural isomerisation of the hydrocarbon chains. In terms of a torsional oscillator model this relaxation reveals the effect of molecular ordering on the enthalpy of activation.

  18. Wide frequency range capacitive detection of loss in a metallic cantilever using resonance and relaxation modes.

    PubMed

    Richert, Ranko

    2007-05-01

    The impedance of a capacitor which embraces a charged cantilever is used to measure the mechanical properties of the cantilever material. The technique has been tested with an amorphous metallic specimen, but is applicable for many other solids. The material damping can be measured at the resonance frequency of the cantilever via the width of the resonance curve or by recording the ring-down behavior. Additionally, several decades in frequency are accessible below the resonance frequency, where values as low as nu=0.03 Hz are achieved easily. The data are analyzed with a single equation that captures the damping at all frequencies in terms of the material specific Young's modulus E and its loss angle tan delta=E"/E'.

  19. ACCRETION DISK WARPING BY RESONANT RELAXATION: THE CASE OF MASER DISK NGC 4258

    SciTech Connect

    Bregman, Michal; Alexander, Tal

    2009-08-01

    The maser disk around the massive black hole (MBH) in active galaxy NGC 4258 exhibits an O(10 deg.) warp on the O(0.1 pc) scale. The physics driving the warp is still debated. Suggested mechanisms include torquing by relativistic frame dragging or by radiation pressure. We propose here a new warping mechanism: resonant torquing of the disk by stars in the dense cusp around the MBH. We show that resonant torquing can induce such a warp over a wide range of observed and deduced physical parameters of the maser disk.

  20. NOTE: Detection limits for ferrimagnetic particle concentrations using magnetic resonance imaging based proton transverse relaxation rate measurements

    NASA Astrophysics Data System (ADS)

    Pardoe, H.; Chua-anusorn, W.; St. Pierre, T. G.; Dobson, J.

    2003-03-01

    A clinical magnetic resonance imaging (MRI) system was used to measure proton transverse relaxation rates (R2) in agar gels with varying concentrations of ferrimagnetic iron oxide nanoparticles in a field strength of 1.5 T. The nanoparticles were prepared by coprecipitation of ferric and ferrous ions in the presence of either dextran or polyvinyl alcohol. The method of preparation resulted in loosely packed clusters (dextran) or branched chains (polyvinyl alcohol) of particles containing of the order of 600 and 400 particles, respectively. For both methods of particle preparation, concentrations of ferrimagnetic iron in agar gel less than 0.01 mg ml-1 had no measurable effect on the value of R2 for the gel. The results indicate that MRI-based R2 measurements using 1.5 T clinical scanners are not quite sensitive enough to detect the very low concentrations of nanoparticulate biogenic magnetite reported in human brain tissue.

  1. Spectroscopic Studies of the Super Relaxed State of Skeletal Muscle.

    PubMed

    Nogara, Leonardo; Naber, Nariman; Pate, Edward; Canton, Marcella; Reggiani, Carlo; Cooke, Roger

    2016-01-01

    In the super-relaxed state of myosin, ATPase activity is strongly inhibited by binding of the myosin heads to the core of the thick filament in a structure known as the interacting-heads motif. In the disordered relaxed state myosin heads are not bound to the core of the thick filament and have an ATPase rate that is 10 fold greater. In the interacting-heads motif the two regulatory light chains appear to bind to each other. We have made single cysteine mutants of the regulatory light chain, placed both paramagnetic and fluorescent probes on them, and exchanged them into skinned skeletal muscle fibers. Many of the labeled light chains tended to disrupt the stability of the super-relaxed state, and showed spectral changes in the transition from the disordered relaxed state to the super-relaxed state. These data support the putative interface between the two regulatory light chains identified by cryo electron microscopy and show that both the divalent cation bound to the regulatory light chain and the N-terminus of the regulatory light chain play a role in the stability of the super-relaxed state. One probe showed a shift to shorter wavelengths in the super-relaxed state such that a ratio of intensities at 440nm to that at 520nm provided a measure of the population of the super-relaxed state amenable for high throughput screens for finding potential pharmaceuticals. The results provide a proof of concept that small molecules that bind to this region can destabilize the super-relaxed state and provide a method to search for small molecules that do so leading to a potentially effective treatment for Type 2 diabetes and obesity. PMID:27479128

  2. Spectroscopic Studies of the Super Relaxed State of Skeletal Muscle

    PubMed Central

    Naber, Nariman; Pate, Edward; Canton, Marcella; Reggiani, Carlo; Cooke, Roger

    2016-01-01

    In the super-relaxed state of myosin, ATPase activity is strongly inhibited by binding of the myosin heads to the core of the thick filament in a structure known as the interacting-heads motif. In the disordered relaxed state myosin heads are not bound to the core of the thick filament and have an ATPase rate that is 10 fold greater. In the interacting-heads motif the two regulatory light chains appear to bind to each other. We have made single cysteine mutants of the regulatory light chain, placed both paramagnetic and fluorescent probes on them, and exchanged them into skinned skeletal muscle fibers. Many of the labeled light chains tended to disrupt the stability of the super-relaxed state, and showed spectral changes in the transition from the disordered relaxed state to the super-relaxed state. These data support the putative interface between the two regulatory light chains identified by cryo electron microscopy and show that both the divalent cation bound to the regulatory light chain and the N-terminus of the regulatory light chain play a role in the stability of the super-relaxed state. One probe showed a shift to shorter wavelengths in the super-relaxed state such that a ratio of intensities at 440nm to that at 520nm provided a measure of the population of the super-relaxed state amenable for high throughput screens for finding potential pharmaceuticals. The results provide a proof of concept that small molecules that bind to this region can destabilize the super-relaxed state and provide a method to search for small molecules that do so leading to a potentially effective treatment for Type 2 diabetes and obesity. PMID:27479128

  3. Synchronisation of self-oscillations in a solid-state ring laser with pump modulation in the region of parametric resonance between self-modulation and relaxation oscillations

    SciTech Connect

    Dudetskiy, V Yu; Lariontsev, E G; Chekina, S N

    2014-01-31

    The synchronisation of the self-modulation oscillation frequency in a Nd : YAG ring laser by an external periodic signal modulating the pump power in the region of parametric resonance between self-modulation and relaxation oscillations is studied theoretically and experimentally. The characteristic features of synchronisation processes in lasers operating in the self-modulation regime of the first kind and in the regime with a doubled self-modulation period are considered. Two bistable branches of synchronisation of self-modulation oscillations are found by numerical calculation. The experimental data agree well with the numerical simulation results for one of these branches, but the other branch of bistable self-modulation oscillations was not observed experimentally. (control of laser radiation parameters)

  4. SNAKE DEPLORIZING RESONANCE STUDY IN RHIC

    SciTech Connect

    BAI,M.; CAMERON, P.; LUCCIO, A.; HUANG, H.; PITISYN, V.; ET AL.

    2007-06-25

    Snake depolarizing resonances due to the imperfect cancellation of the accumulated perturbations on the spin precession between snakes were observed at the Relativistic Heavy Ion Collider (RHIC). During the RHIC 2005 and 2006 polarized proton runs, we mapped out the spectrum of odd order snake resonance at Q{sub y} = 7/10. Here, Q, is the beam vertical betatron tune. We also studied the beam polarization after crossing the 7/10th resonance as a function of resonance crossing rate. This paper reports the measured resonance spectrum as well as the results of resonance crossing.

  5. Study of stomach motility using the relaxation of magnetic tracers.

    PubMed

    Carneiro, A A; Baffa, O; Oliveira, R B

    1999-07-01

    Magnetic tracers can be observed in the interior of the human body to give information about their quantity, position and state of order. With the aim of detecting and studying the degree of disorder of these tracers after they have been previously magnetized inside the stomach, a system composed of magnetization coils and magnetic detectors was developed. Helmholtz coils of diameter 84 cm were used to magnetize the sample and the remanent magnetization (RM) was detected with two first-order gradiometric fluxgate arrays each with a 15 cm base line, sensitivity of 0.5 nT and common mode rejection (CMR) of at least 10. The system allows simultaneous measurement in the anterior and posterior projections of the stomach. Measurements of the time evolution of the RM were performed in vitro and in normal subjects after the ingestion of a test meal labelled with magnetic particles. The data were fitted with an exponential curve and the relaxation time tau was obtained. Initial studies were performed to ascertain the action of a drug that is known to affect the gastric motility, showing that the decay of the remanent magnetization was indeed due to stomach contractions. PMID:10442706

  6. On a ghost artefact in ultra low field magnetic resonance relaxation imaging

    NASA Astrophysics Data System (ADS)

    Volegov, P.; Schultz, L.; Espy, M.

    2014-06-01

    Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are widely used techniques across numerous disciplines. While typically implemented at fields >1 T, there has been continuous interest in the methods at much lower fields for reasons of cost, material contrast, or application. There have been numerous demonstrations of MR at much lower fields (from 1 μT to 1 mT), the so-called ultra-low field (ULF) regime. Approaches to ULF MR have included superconducting quantum interference device (SQUID) sensor technology for ultra-sensitive detection and the use of pulsed pre-polarizing fields to enhance the signal strength. There are many advantages to working in the ULF regime. However, due to the low strength of the measurement field, acquisition of MRI at ULF is more susceptible to ambient fields that cause image distortions. Imaging artifacts can be caused by transients associated with non-ideal field switching and from remnant fields in magnetic shielding, among other causes. In this paper, we introduce a general theoretical framework that describes effects of non-ideal measurement field inversion/rotation due to presence of these transient fields. We illustrate imaging artifacts via simulated and experimental examples.

  7. Laboratory Studies of Vibrational Relaxation: Important Insights for Mesospheric OH

    NASA Astrophysics Data System (ADS)

    Kalogerakis, Konstantinos S.; Matsiev, Daniel

    2016-04-01

    The hydroxyl radical has a key role in the chemistry and energetics of the Earth's middle atmosphere. A detailed knowledge of the rate constants and relevant pathways for OH(high v) vibrational relaxation by atomic and molecular oxygen and their temperature dependence is absolutely critical for understanding mesospheric OH and extracting reliable chemical heating rates from atmospheric observations. We have developed laser-based experimental approaches to study the complex collisional energy transfer processes involving the OH radical and other relevant atmospheric species. Previous work in our laboratory indicated that the total removal rate constant for OH(v = 9) + O at room temperature is more than one order of magnitude larger than that for removal by O2. Thus, O atoms are expected to significantly influence the intensity and vibrational distribution extracted from the Meinel OH(v) emissions. We will report our most recent laboratory experiments that corroborate the aforementioned result for OH(v = 9) + O and provide important new insights on the mechanistic pathways involved. We will also highlight relevant atmospheric implications, including warranted revisions of current mesospheric OH models. Research supported by SRI International Internal R&D and NSF Aeronomy grant AGS-1441896. Previously supported by NASA Geospace Science grant NNX12AD09G.

  8. Quasi crystals: Studies of stability and phason relaxation

    SciTech Connect

    Gronlund, L.D.

    1989-01-01

    This dissertation is in two distinct parts. In chapter I the author considers a simple model of solidification based on Landau theory and investigates whether this model can have stable or metastable quasicrystalline solutions. The model is that proposed by Kalugin, Kitaev, and Levitov with an additional local quartic term in the free energy. In this case, the body-centered cubic (bcc) crystal is the global minimum. He assesses the stability of the quasicrystalline solutions and shows that they are not even metastable, being unstable against a collapse to the bcc crystal. In chapter II he proposes a simple model for phason dynamics in quasicrystals. Phason shifts in the Penrose tiling model of quasicrystals appear as flips of rows of tiles, known as worms. When worms cross one another a hierarchy is established in which some of the worms cannot flip until others have. A complex set of constraints on worm flips is thereby introduced by the intricate pattern of worm crossings in quasicrystalline tilings. He introduces a simple model of interacting sets of one-dimensional Ising chains that mimics this set of constraints and study the possible consequences of these constraints for phason dynamics and the relaxation of phason strain in quasicrystals.

  9. NMR relaxation study of crosslinked cis-1,4-polybutadiene

    SciTech Connect

    Munie, G.C.; Jonas, J.; Rowland, T.J.

    1980-01-01

    Proton relaxation measurements have been used to investigate the effects of crosslinking on the segmental motion in cis-1,4-polybutadiene samples. The temperature dependence of proton spin-lattice relaxation time T/sub 1/ and spin-spin relaxation time T/sub 2/ at 60 and 24.3 MHz is reported in cis-1,4-polybutadiene (PB) samples with different crosslink density including uncrosslinked PB and samples with 140, 40, and 14 repeat units between crosslinks. In addition, spin-lattice relaxation times in rotating coordinate frame, T/sub 1p/, have also been determined. The relaxation data are interpreted in terms of the effects of crosslinks on segmental chain motions. Because of their sensitivity to low-frequency motion, T/sub 2/ data are of major interest. At temperatures well above the T/sub 1/ minimum the small T/sub 2/ temperature dependence resembles solidlike behavior reflecting the nonzero averaging of dipolar interactions due to anisotropic motion of the chain segments between crosslinks. The magnitude of T/sub 2/ at 60/sup 0/C is found to be proportional to the average mass between crosslinks.

  10. One-Shot Measurement of Spin-Lattice Relaxation Times in the Off-Resonance Rotating Frame of Reference with Applications to Breast

    NASA Astrophysics Data System (ADS)

    Fairbanks, Ethan Jefferson

    1994-01-01

    Off-resonance spin locking makes use of the novel relaxation time T_{1rho} ^{rm off}, which may be useful in characterizing breast disease. Knowledge of T _{rm 1rho}^{rm off} is essential for optimization of spin -locking imaging methods. The purpose of this work was to develop an optimal imaging technique for in vivo measurement of T_{rm 1rho}^ {rm off}. Measurement of T _{1rho}^{rm off } using conventional methods requires long exam times which are not suitable for patients. Exam time may be shortened by utilizing a one-shot method developed by Look and Locker, making in vivo measurements possible. The imaging method consisted of a 180^circ inversion pulse followed by a series of small-angle alpha pulses to tip a portion of the longitudinal magnetization into the transverse plane for readout. During each relaxation interval (between alpha pulses), a spin-locking pulse was applied off-resonance to achieve T_ {1rho}^{rm off} relaxation. The value of T_{rm 1rho}^{rm off} was then determined using a three-parameter non-linear least-squares fitting procedure. Values of T_ {1rho}^{rm off} were measured for normal and pathologic breast tissues at several resonant offsets. These measurements revealed that image contrast can be manipulated by altering the resonant offset of the spin-locking pulse. Whereas T _1 relaxation times were nearly identical for normal and cancerous tissues, T_{1 rho}^{rm off} relaxation times differed significantly. These results may be useful in improving image contrast in magnetic resonance imaging.

  11. Relaxation Kinetic Study of Eudragit® NM30D Film Based on Complex Modulus Formalism.

    PubMed

    Penumetcha, Sai Sumana; Byrn, Stephen R; Morris, Kenneth R

    2015-10-01

    This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (T g) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to T g and the β relaxations occurring below T g were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film was elucidated using the complex modulus of the dielectric response employing loss modulus and permittivity data. Activation energies of these relaxations and the fundamental frequency so determined support the assignment of the relaxation pattern in the Eudragit® NM30D film. DEA methodology of the complex modulus formalism is a useful tool for differentiating the α and β relaxation kinetics in Eudragits® not easily studied using traditional thermal methods such as DSC. The kinetics associated with α and β relaxations so determined will provide formulation design support for solid orals that incorporate Eudragit® polymers. As mobility changes can affect stability and diffusion, the dipolar α and β relaxations revealed through DEA analysis may enable a better correlation to functionality of Eudragit® based pharmaceutical dosage forms.

  12. Prognostic Significance of Transverse Relaxation Rate (R2*) in Blood Oxygenation Level-Dependent Magnetic Resonance Imaging in Patients with Invasive Breast Cancer

    PubMed Central

    Choi, Hye Young; Ko, Eun Sook; Han, Boo-Kyung; Kim, Eun Ju; Kim, Sun Mi; Lim, Yaeji; Kim, Rock Bum

    2016-01-01

    Objective To examine the relationship between magnetic resonance transverse relaxation rate (R2*) and prognostic factors. Materials and Methods A total of 159 women with invasive ductal carcinomas (IDCs) underwent breast magnetic resonance imaging (MRI) including blood oxygenation level-dependent (BOLD) sequence at 3 T. The distribution of the measured R2* values were analyzed, and the correlation between R2* and various prognostic factors (age, tumor size, histologic grade, lymphovascular invasion, and axillary lymph node status, as well as expression of estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, p53, and Ki-67) were retrospectively assessed using patient medical records. Results The baseline R2* values of the IDCs were very heterogeneous with wide range among the patients. The mean R2* value was (32.8 ± 14.0) Hz with a median of 29.3 Hz (range 13.5–109.4 Hz). In multivariate analysis, older age was associated with decreased R2* value (P = 0.011) and IDCs with p53-overexpression showed higher R2* values than those without p53-overexpression group (P = 0.031). Other prognostic factors were not significantly correlated with R2* value. Conclusion In this study, R2* values were significantly correlated with age and expression of p53. Further studies are necessary to determine the prognostic value of BOLD-MRI. PMID:27384310

  13. Relaxation transition in glass-forming polybutadiene as revealed by nuclear resonance X-ray scattering.

    PubMed

    Kanaya, Toshiji; Inoue, Rintaro; Saito, Makina; Seto, Makoto; Yoda, Yoshitaka

    2014-04-14

    We investigated the arrest mechanism of molecular motions in a glass forming polybutadiene near the glass transition using a new nuclear resonance synchrotron X-ray scattering technique to cover a wide time range (10(-9) to 10(-5) s) and a scattering vector Q range (9.6-40 nm(-1)), which have never been accessed by other methods. Owing to the wide time and Q ranges it was found for the first time that a transition of the α-process to the slow β-process (or the Johari-Goldstein process) was observed in a Q range higher than the first peak in the structure factor S(Q) at the critical temperature T(c) in the mode coupling theory. The results suggest the important roles of hopping motions below T(c), which was predicted by the recent extended mode coupling theory and the cooperative motions due to the strong correlation at the first peak in S(Q) in the arrest mechanism. PMID:24735317

  14. Relaxation transition in glass-forming polybutadiene as revealed by nuclear resonance X-ray scattering

    NASA Astrophysics Data System (ADS)

    Kanaya, Toshiji; Inoue, Rintaro; Saito, Makina; Seto, Makoto; Yoda, Yoshitaka

    2014-04-01

    We investigated the arrest mechanism of molecular motions in a glass forming polybutadiene near the glass transition using a new nuclear resonance synchrotron X-ray scattering technique to cover a wide time range (10-9 to 10-5 s) and a scattering vector Q range (9.6-40 nm-1), which have never been accessed by other methods. Owing to the wide time and Q ranges it was found for the first time that a transition of the α-process to the slow β-process (or the Johari-Goldstein process) was observed in a Q range higher than the first peak in the structure factor S(Q) at the critical temperature Tc in the mode coupling theory. The results suggest the important roles of hopping motions below Tc, which was predicted by the recent extended mode coupling theory and the cooperative motions due to the strong correlation at the first peak in S(Q) in the arrest mechanism.

  15. Relaxation transition in glass-forming polybutadiene as revealed by nuclear resonance X-ray scattering

    SciTech Connect

    Kanaya, Toshiji; Inoue, Rintaro; Saito, Makina; Seto, Makoto; Yoda, Yoshitaka

    2014-04-14

    We investigated the arrest mechanism of molecular motions in a glass forming polybutadiene near the glass transition using a new nuclear resonance synchrotron X-ray scattering technique to cover a wide time range (10{sup −9} to 10{sup −5} s) and a scattering vector Q range (9.6–40 nm{sup −1}), which have never been accessed by other methods. Owing to the wide time and Q ranges it was found for the first time that a transition of the α-process to the slow β-process (or the Johari-Goldstein process) was observed in a Q range higher than the first peak in the structure factor S(Q) at the critical temperature T{sub c} in the mode coupling theory. The results suggest the important roles of hopping motions below T{sub c}, which was predicted by the recent extended mode coupling theory and the cooperative motions due to the strong correlation at the first peak in S(Q) in the arrest mechanism.

  16. NMR Relaxation in Systems with Magnetic Nanoparticles: A Temperature Study

    PubMed Central

    Issa, Bashar; Obaidat, Ihab M.; Hejasee, Rola H.; Qadri, Shahnaz; Haik, Yousef

    2013-01-01

    Purpose To measure and model NMR relaxation enhancement due to the presence of Gd substituted Zn-Mn ferrite magnetic nanoparticles at different temperatures. Materials and Methods Relaxation rates were measured at 1.5 T using FSE sequences in samples of agarose gel doped with uncoated and polyethylene glycol (PEG) coated Mn0.5Zn0.5Gd0.02Fe1.98O4 nanoparticles over the temperature range 8 to 58°C. Physical characterization of the magnetic nanoparticles synthesized using chemical co-precipitation included scanning (SEM) and transmission (TEM) electron microscopy, inductively coupled plasma (ICP), dynamic light scattering (DLS), and magnetometry. Results Relaxivity (in s−1 mM−1 Fe) for the uncoated and coated particles, respectively, increased as follows: from 2.5 to 3.2 and 0.4 to 0.7 for T1, while for T2 it increased from 162.3 to 253.7 and 59.7 to 82.2 over the temperature range 8 to 58°C. T2 data was fitted to the echo limited motional regime using one fitting parameter that reflects the degree of agglomeration of particles into a cluster. This parameter was found to increase linearly with temperature and was larger for the PEG coated particles than the uncoated ones. Conclusion The increase of 1/T2 with temperature is modeled successfully using echo limited motional regime where both diffusion of the protons and nanoparticle cluster size increase with temperature. Both transverse and longitudinal relaxation efficiencies are reduced by PEG coating at all temperatures. If prediction of relaxation rates under different particle concentrations and operating temperatures is possible then the use of MNP in temperature monitoring and hyperthermia applications may be achieved. PMID:23720101

  17. Cutting stems before relaxing xylem tension induces artefacts in Vitis coignetiae, as evidenced by magnetic resonance imaging.

    PubMed

    Ogasa, Mayumi Y; Utsumi, Yasuhiro; Miki, Naoko H; Yazaki, Kenichi; Fukuda, Kenji

    2016-02-01

    It was recently reported that cutting artefacts occur in some species when branches under tension are cut, even under water. We used non-destructive magnetic resonance imaging (MRI) to investigate the change in xylem water distribution at the cellular level in Vitis coignetiae standing stems before and after relaxing tension. Less than 3% of vessels were cavitated when stems under tension were cut under water at a position shorter than the maximum vessel length (MVL) from the MRI point, in three of four plants. The vessel contents remained at their original status, and cutting artefact vessel cavitation declined to <1% when stems were cut at a position farther than the MVL from the MRI point. Water infiltration into the originally cavitated vessels after cutting the stem, i.e. vessel refilling, was found in <1% of vessels independent of cutting position on three of nine plants. The results indicate that both vessel cavitation and refilling occur in xylem tissue under tension following stem cutting, but its frequency is quite small, and artefacts can be minimized altogether if the distance between the monitoring position and the cutting point is longer than the MVL.

  18. Secondary and primary relaxations in hyperbranched polyglycerol: a comparative study in the frequency and time domains.

    PubMed

    Garcia-Bernabé, Abel; Dominguez-Espinosa, Gustavo; Diaz-Calleja, Ricardo; Riande, Evaristo; Haag, Rainer

    2007-09-28

    The non-Debye relaxation behavior of hyperbranched polyglycerol was investigated by broadband dielectric spectroscopy. A thorough study of the relaxations was carried out paying special attention to truncation effects on deconvolutions of overlapping processes. Hyperbranched polyglycerol exhibits two relaxations in the glassy state named in increasing order of frequency beta and gamma processes. The study of the evolution of these two fast processes with temperature in the time retardation spectra shows that the beta absorption is swallowed by the alpha in the glass-liquid transition, the gamma absorption being the only relaxation that remains operative in the liquid state. In heating, a temperature is reached at which the alpha absorption vanishes appearing the alphagamma relaxation. Two characteristics of alpha absorptions, decrease of the dielectric strength with increasing temperature and rather high activation energy, are displayed by the alphagamma process. Williams' ansatz seems to hold for these topologically complex macromolecules. PMID:17902934

  19. Secondary and primary relaxations in hyperbranched polyglycerol: a comparative study in the frequency and time domains.

    PubMed

    Garcia-Bernabé, Abel; Dominguez-Espinosa, Gustavo; Diaz-Calleja, Ricardo; Riande, Evaristo; Haag, Rainer

    2007-09-28

    The non-Debye relaxation behavior of hyperbranched polyglycerol was investigated by broadband dielectric spectroscopy. A thorough study of the relaxations was carried out paying special attention to truncation effects on deconvolutions of overlapping processes. Hyperbranched polyglycerol exhibits two relaxations in the glassy state named in increasing order of frequency beta and gamma processes. The study of the evolution of these two fast processes with temperature in the time retardation spectra shows that the beta absorption is swallowed by the alpha in the glass-liquid transition, the gamma absorption being the only relaxation that remains operative in the liquid state. In heating, a temperature is reached at which the alpha absorption vanishes appearing the alphagamma relaxation. Two characteristics of alpha absorptions, decrease of the dielectric strength with increasing temperature and rather high activation energy, are displayed by the alphagamma process. Williams' ansatz seems to hold for these topologically complex macromolecules.

  20. Experimental and Numerical Study on Stress Relaxation of Sandstones Disturbed by Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Zhu, Wancheng; Li, Shuai; Niu, Leilei; Liu, Kai; Xu, Tao

    2016-10-01

    Time-dependent rheological deformation of rocks affects the stability of underground stopes or constructions. It may also be altered by dynamic disturbances, such as rock blasting. To study such effects, a new stress relaxation-disturbance testing machine was invented, capable of loading conditions for stress relaxation and dynamic disturbance. Effects of testing machine stiffness on rock deformation behavior were examined to confirm that rocks had undergone stress relaxation. Stress relaxation tests on specimens under uniaxial compression were carried out over 6 or more days. Under single-stage stress relaxation, axial stress relaxed within 5-7 days, stabilizing at constant strain. During two-stage stress relaxation, larger stress decay was observed under the higher strain level. A dynamic disturbance from a pendulum hammer was applied to specimens under stress relaxation to evaluate their response. In these tests, stress decline and strain increase were related to residual strain induced by the dynamic disturbance. The strain variation in specimens was found to be within 1.5 % of values before the disturbance. Finally, a damage-based constitutive model for rocks subjected to stress relaxation and dynamic disturbance is proposed. It reproduces the stress relaxation behavior of rock observed in our experiments. The model was used to quantify stress relaxation of rocks and the effects of dynamic disturbance on this process. The larger stress decay of rocks under higher strain is likely related to damage in the rock. Clearly, increases in strain and decreases in stress induced by dynamic loading, coupled with rock damage, are over-estimated in our numerical simulations.

  1. Ferromagnetic Resonance Studies of Magnetic Recording Media

    NASA Astrophysics Data System (ADS)

    Yu, Yuwu

    1995-01-01

    Angular dependence of maximum remanence (ADMR) and/or x-ray diffraction (XRD) techniques have been used to determine particle orientation distributions for various recording media, including gamma -rm Fe_2O_3, Co- gamma-rm Fe_2O_3, CrO_2, Ba-ferrite, and MP tapes. A distribution of column directions for metal evaporated (ME) tape has been determined from transmission electron microscopy (TEM) pictures. However, the ferromagnetic resonance (FMR) results suggest a much more narrow distribution of magnetic anisotropy directions. For Ba-ferrite tapes, the distribution functions measured by ADMR are consistent with those by XRD if interparticle interactions are accounted for. The predetermined distribution function has been used to fit FMR spectra for the above tapes. Landau-Lifshitz damping constants have been measured with high accuracy for particulate recording media. An excellent correlation has been found between the damping constants and the switching constants for these media. The results suggest that the FMR technique may be useful in predicting the switching speed of particulate recording media. The FMR technique is also useful in looking for methods of increasing the damping constant of recording media. Possible methods of increasing the switching speed of Ba-ferrite media have been studied. The reduction of Ba-ferrite particles in a hydrogen atmosphere increases the damping constant significantly. It is predicted that reduced Ba-ferrite probably switches faster than ordinary Ba-ferrite. Qualitative discussions on the origin of damping for various recording media have been presented within the framework of magnon relaxation theory. The dependence of the damping constant on magnetic properties, such as particle orientation, media coercivity, and particle interactions are also discussed.

  2. Relaxation processes and glass transition in confined 1,4-polybutadiene films: A Molecular Dynamics study

    NASA Astrophysics Data System (ADS)

    Paul, Wolfgang; Solar, Mathieu

    We will present results from Molecular Dynamics simulations of a chemically realistic model of 1,4-polybutadiene (PB) chains confined by graphite walls. Relaxation processes in this system are heterogeneous and anisotropic. We will present evidence for a slow additional relaxation process related to chain desorption from the walls. We also study the structural relaxation resolved with respect to the distance from the graphite walls and show the influence of structural changes on the relaxation behavior. The temperature dependence of the dielectric relaxation in layers of different thickness near the walls shows no indication of a shift of Tg as a function of thickness when analyzed with a Vogel-Fulcher fit. We explain this by the importance of intramolecular dihedral barriers for the glass transition in PB which dominate over the density changes next to a wall except for a 1 nm thick layer directly at the wall.

  3. Proton nuclear magnetic resonance studies on brain edema

    SciTech Connect

    Naruse, S.; Horikawa, Y.; Tanaka, C.; Hirakawa, K.; Nishikawa, H.; Yoshizaki, K.

    1982-06-01

    The water in normal and edematous brain tissues of rats was studied by the pulse nuclear magnetic resonance (NMR) technique, measuring the longitudinal relaxation time (T1) and the transverse relaxation time (T2). In the normal brain, T1 and T2 were single components, both shorter than in pure water. Prolongation and separation of T2 into two components, one fast and one slow, were the characteristic findings in brain edema induced by both cold injury and triethyl tin (TET), although some differences between the two types of edema existed in the content of the lesion and in the degree of changes in T1 and T2 values. Quantitative analysis of T1 and T2 values in their time course relating to water content demonstrated that prolongation of T1 referred to the volume of increased water in tissues examined, and that two phases of T2 reflected the distribution and the content of the edema fluid. From the analysis of the slow component of T2 versus water content during edema formation, it was demonstrated that the increase in edema fluid was steady, and its content was constant during formation of TET-induced edema. On the contrary, during the formation of cold-injury edema, water-rich edema fluid increased during the initial few hours, and protein-rich edema fluid increased thereafter. It was concluded that proton NMR relaxation time measurements may provide new understanding in the field of brain edema research.

  4. Discrete dislocation dynamics study of strained-layer relaxation.

    PubMed

    Schwarz, K W

    2003-10-01

    Numerical simulations are performed to follow the evolution of an initial density of dislocation loops in an infinite strained layer to the point where the dislocations have stopped moving. Several unexpected results are obtained. First, many of the threading arms are either annihilated or prematurely immobilized by hardening interactions such as jogging and junction formation. Second, the remaining dislocation arms are eventually trapped by stress fluctuations that arise more from local overrelaxation than from the blocking mechanisms usually considered. Third, the degree of relaxation that can be attained depends strongly on the initial density of threading arms. PMID:14611535

  5. Discrete Dislocation Dynamics Study of Strained-Layer Relaxation

    NASA Astrophysics Data System (ADS)

    Schwarz, K. W.

    2003-10-01

    Numerical simulations are performed to follow the evolution of an initial density of dislocation loops in an infinite strained layer to the point where the dislocations have stopped moving. Several unexpected results are obtained. First, many of the threading arms are either annihilated or prematurely immobilized by hardening interactions such as jogging and junction formation. Second, the remaining dislocation arms are eventually trapped by stress fluctuations that arise more from local overrelaxation than from the blocking mechanisms usually considered. Third, the degree of relaxation that can be attained depends strongly on the initial density of threading arms.

  6. Cut and paste RNA for nuclear magnetic resonance, paramagnetic resonance enhancement, and electron paramagnetic resonance structural studies.

    PubMed

    Duss, Olivier; Diarra Dit Konté, Nana; Allain, Frédéric H-T

    2015-01-01

    RNA is a crucial regulator involved in most molecular processes of life. Understanding its function at the molecular level requires high-resolution structural information. However, the dynamic nature of RNA complicates structure determination because crystallization is often not possible or can result in crystal-packing artifacts resulting in nonnative structures. To study RNA and its complexes in solution, we described an approach in which large multi-domain RNA or protein-RNA complex structures can be determined at high resolution from isolated domains determined by nuclear magnetic resonance (NMR) spectroscopy, and then constructing the entire macromolecular structure using electron paramagnetic resonance (EPR) long-range distance constraints. Every step in this structure determination approach requires different types of isotope or spin-labeled RNAs. Here, we present a simple modular RNA cut and paste approach including protocols to generate (1) small isotopically labeled RNAs (<10 nucleotides) for NMR structural studies, which cannot be obtained by standard protocols, (2) large segmentally isotope and/or spin-labeled RNAs for diamagnetic NMR and paramagnetic relaxation enhancement NMR, and (3) large spin-labeled RNAs for pulse EPR spectroscopy.

  7. Alpha resonant scattering for astrophysical reaction studies

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-01

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of 7Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the 7Be(α,γ) reaction, and proposed a new cluster band in 11C.

  8. Alpha resonant scattering for astrophysical reaction studies

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-02

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

  9. Nuclear magnetic resonance relaxation characterisation of water status of developing grains of maize (Zea mays L.) grown at different nitrogen levels.

    PubMed

    Krishnan, Prameela; Chopra, Usha Kiran; Verma, Ajay Pal Singh; Joshi, Devendra Kumar; Chand, Ishwar

    2014-04-01

    Changes in water status of developing grains of maize (Zea mays L.) grown under different nitrogen levels were characterized by nuclear magnetic resonance (NMR) spectroscopy. There were distinct changes in water status of grains due to the application of different levels of nitrogen (0, 120 and 180 kg N ha(-1)). A comparison of the grain developmental characteristics, composition and physical properties indicated that, not only the developmental characteristics like grain weight, grain number/ear, and rate of grain filling increased, but also bound water characterized by the T2 component of NMR relaxation increased with nitrogen application (50-70%) and developmental stages leading to maturation (10-60%). The consistency in the patterns of responses to free water and intermediate water to increasing levels of nitrogen application and grain maturity suggested that nitrogen application resulted in more proportion of water to both bound- and intermediate states and less in free state. These changes are further corroborated by the concomitant increases in protein and starch contents in grains from higher nitrogen treatments as macromolecules like protein and starch retain more amount of water in the bound state. The results of the changes in T2 showed that water status during grain development was not only affected by developmental processes but also by nitrogen supply to plants. This study strongly indicated a clear nutrient and developmental stage dependence of grain tissue water status in maize.

  10. Two 1H-nuclear magnetic resonance methods to measure internal porosity of bone trabeculae: By solid-liquid signal separation and by longitudinal relaxation

    NASA Astrophysics Data System (ADS)

    Fantazzini, Paola; Bortolotti, Villiam; Brown, Robert J. S.; Camaiti, Mara; Garavaglia, Carla; Viola, Rossella; Giavaresi, Gianluca

    2004-01-01

    Parameters related to pore-space structure of the trabeculae in cancellous bone are difficult to determine quantitatively, but they can be important to characterize changes induced in bone by diseases such as osteoporosis. We present two nuclear magnetic resonance (NMR) methods to measure the internal porosity φtrab of the trabeculae, based on two different measurements of the fraction of intratrabecular and intertrabecular pore-space in animal femur samples. These procedures have been developed within the more general framework of the NMR studies for fluids in porous media. In the first method we use the ratio between the amount of collagen (solid-like) 1H and that of the fluids in the samples. In the second, which can be applied only on defatted and water saturated samples, we use the distributions of longitudinal relaxation times. The φtrab values obtained are constant for porosity φ of the samples over the range 40%-70%, with each method giving φtrab=(29±4)%, which is consistent with the only data available, the porosity of related cortical bone. The traditional parameter bone volume fraction is simply given by (1-φ)/(1-φtrab).

  11. Theoretical Studies of the Relaxation Matrix for Molecular Systems

    NASA Astrophysics Data System (ADS)

    Ma, Qiancheng; Boulet, C.

    2016-06-01

    The phenomenon of collisional transfer of intensity due to line mixing has an increasing importance for atmospheric monitoring. From a theoretical point of view, all relevant information about the collisional processes is contained in the relaxation matrix where the diagonal elements give half-widths and shifts, and the off-diagonal elements correspond to line interferences. For simple systems such as those consisting of diatom-atom or diatom-diatom, accurate fully quantum calculations based on interaction potentials are feasible. However, fully quantum calculations become unrealistic for more complex systems. On the other hand, the semi-classical Robert-Bonamy formalism, which has been widely used to calculate half-widths and shifts for decades, fails in calculating the off-diagonal matrix elements resulting from applying the isolated line approximation. As a result, in order to simulate atmospheric spectra where the effects from line mixing are important, semi-empirical fitting or scaling laws such as the energy corrected sudden (ECS) and the infinite order sudden (IOS) models are commonly used. Recently, we have found that in developing this semi-classical line shape theory, to rely on the isolated line approximation is not necessary. By eliminating this unjustified assumption, and accurately evaluating matrix elements of the exponential operators, we have developed a more capable formalism that enables one not only to reduce uncertainties for calculated half-widths and shifts, but also to calculate the whole relaxation matrix. This implies that we can address the line mixing with the semi-classical theory based on interaction potentials between molecular absorber and molecular perturber. We have applied this formalism for Raman and infrared spectra of linear and asymmetric-top molecules. Recently, the method has been extended into symmetric-tops with inverse symmetry such as the NH3 molecule. Our calculated half-widths of NH3 lines in the νb{1} and the pure

  12. Strain relaxation in He implanted UO2 polycrystals under thermal treatment: An in situ XRD study

    NASA Astrophysics Data System (ADS)

    Palancher, H.; Kachnaoui, R.; Martin, G.; Richard, A.; Richaud, J.-C.; Onofri, C.; Belin, R.; Boulle, A.; Rouquette, H.; Sabathier, C.; Carlot, G.; Desgardin, P.; Sauvage, T.; Rieutord, F.; Raynal, J.; Goudeau, Ph.; Ambard, A.

    2016-08-01

    Within the frame of the long-term evolution of spent nuclear fuel in dry disposal, the behavior of He in UO2 polycrystals has to be studied. Here, strain relaxation in He implanted samples has been characterized using in situ X-ray diffraction during thermal annealing. The influence of a wide range of experimental parameters (annealing atmosphere, He ion energy, orientation of the UO2 grains probed by X-rays) has been evaluated. If each of them contributes to the strain relaxation kinetics in the implanted layer, strain relaxation is not completed for temperatures below 900 °C which is equivalent to what has been found on He implanted UO2 single crystals, or aged UO2 pellets doped with α-emitters. In the case of implantation with 500 keV He ions, we clearly show that strain relaxation and He release are not correlated for temperatures below 750 °C.

  13. Time-resolved positron annihilation spectroscopy study of relaxation dynamics of ion damage in fused quartz

    NASA Astrophysics Data System (ADS)

    Tsuchida, Hidetsugu; Mizuno, Shohei; Tsutsumi, Hironori; Kinomura, Atsushi; Suzuki, Ryoichi; Itoh, Akio

    2016-05-01

    Relaxation dynamics of ion damage in fused quartz is investigated by our newly developed pump–probe technique combining energetic ions (pump) with slow positrons (probe). This method enables determination of time-resolved positron lifetime. We study the time-dependent relaxation of ion damage, by analyzing the intensity variation in the ortho-positronium lifetime component associated with irradiation damage. For irradiation with 160 keV He ions in the temperature range of 300–573 K, the positron annihilation lifetime spectra are obtained as a function of time after ion irradiation. We observe that the relaxation time of ion damage is strongly influenced by specimen temperatures; the relaxation time constant is approximately 400 ms at room temperature (300 K) and becomes smaller with an increasing temperature. Analysis for the effect of temperature on damage accumulation reveals that the activation energy for thermal annealing of the observed damage is approximately 0.1 eV.

  14. Transient absorption microscopy studies of energy relaxation in graphene oxide thin film

    NASA Astrophysics Data System (ADS)

    Murphy, Sean; Huang, Libai

    2013-04-01

    Spatial mapping of energy relaxation in graphene oxide (GO) thin films has been imaged using transient absorption microscopy (TAM). Correlated AFM images allow us to accurately determine the thickness of the GO films. In contrast to previous studies, correlated TAM-AFM allows determination of the effect of interactions of GO with the substrate and between stacked GO layers on the relaxation dynamics. Our results show that energy relaxation in GO flakes has little dependence on the substrate, number of stacked layers, and excitation intensity. This is in direct contrast to pristine graphene, where these factors have great consequences in energy relaxation. This suggests intrinsic factors rather than extrinsic ones dominate the excited state dynamics of GO films.

  15. Merging of the α and β relaxations in polybutadiene: A neutron spin echo and dielectric study

    NASA Astrophysics Data System (ADS)

    Arbe, A.; Richter, D.; Colmenero, J.; Farago, B.

    1996-10-01

    The local dynamics of 1,4 polybutadiene below and above the merging of the α and β relaxations have been investigated by combining neutron spin echo (NSE) and dielectric spectroscopy. The study of the dynamic structure factor measured by NSE over a wide momentum transfer range allows us to characterize the α relaxation as an interchain process while the β relaxation originates from mainly intrachain motions. At temperatures below the merging, the dynamic structure factor can be described by a superposition of elemental processes for the β relaxation as obtained from dielectric spectroscopy. The elemental motions behind this process can be related to rotational jumps of the chain building blocks around their center of mass. Furthermore, we have been able to consistently describe the dynamic structure factor above the merging of the α and β relaxations by assuming that both processes are statistically independent. In the framework of this scenario a procedure for analyzing the dielectric response in the α-β merging region has been developed. Its application to the dielectric data allows us to describe the dielectric response in this region on the basis of the low temperature behavior of the α and β processes and without considering any particular change in the relaxation mechanism of these processes. The temperature dependence found for the relaxation time of the α process follows now the viscosity, a masked feature in the experimental data due to the merging process. In this way, we have been able to consistently describe the relaxation of both, the polarization and the density fluctuations, by using the same scenario, i.e., independent α and β processes, and considering the same functional forms and temperature dependences of the characteristic times of the two processes.

  16. Spectral density mapping at multiple magnetic fields suitable for 13C NMR relaxation studies

    NASA Astrophysics Data System (ADS)

    Kadeřávek, Pavel; Zapletal, Vojtěch; Fiala, Radovan; Srb, Pavel; Padrta, Petr; Přecechtělová, Jana Pavlíková; Šoltésová, Mária; Kowalewski, Jozef; Widmalm, Göran; Chmelík, Josef; Sklenář, Vladimír; Žídek, Lukáš

    2016-05-01

    Standard spectral density mapping protocols, well suited for the analysis of 15N relaxation rates, introduce significant systematic errors when applied to 13C relaxation data, especially if the dynamics is dominated by motions with short correlation times (small molecules, dynamic residues of macromolecules). A possibility to improve the accuracy by employing cross-correlated relaxation rates and on measurements taken at several magnetic fields has been examined. A suite of protocols for analyzing such data has been developed and their performance tested. Applicability of the proposed protocols is documented in two case studies, spectral density mapping of a uniformly labeled RNA hairpin and of a selectively labeled disaccharide exhibiting highly anisotropic tumbling. Combination of auto- and cross-correlated relaxation data acquired at three magnetic fields was applied in the former case in order to separate effects of fast motions and conformational or chemical exchange. An approach using auto-correlated relaxation rates acquired at five magnetic fields, applicable to anisotropically moving molecules, was used in the latter case. The results were compared with a more advanced analysis of data obtained by interpolation of auto-correlated relaxation rates measured at seven magnetic fields, and with the spectral density mapping of cross-correlated relaxation rates. The results showed that sufficiently accurate values of auto- and cross-correlated spectral density functions at zero and 13C frequencies can be obtained from data acquired at three magnetic fields for uniformly 13C -labeled molecules with a moderate anisotropy of the rotational diffusion tensor. Analysis of auto-correlated relaxation rates at five magnetic fields represents an alternative for molecules undergoing highly anisotropic motions.

  17. {sup 1}H nuclear magnetic resonance study of hydrated water dynamics in perfluorosulfonic acid ionomer Nafion

    SciTech Connect

    Han, Jun Hee; Lee, Kyu Won; Jeon, G. W.; Lee, Cheol Eui; Park, W. K.; Choi, E. H.

    2015-01-12

    We have studied the dynamics of hydrated water molecules in the proton exchange membrane of Nafion by means of high-resolution {sup 1}H nuclear magnetic resonance (NMR) measurements. “Bound” and “free” states of hydrated water clusters as well as the exchange protons were identified from the NMR chemical shift measurements, and their activation energies were obtained from the temperature-dependent laboratory- and rotating-frame spin-lattice relaxation measurements. Besides, a peculiar motional transition in the ultralow frequency region was observed at 373 K for the “free” hydrated water from the rotating-frame NMR spin-lattice relaxation time measurements.

  18. Nuclear quadrupole resonance studies of the SORC sequence and nuclear magnetic resonance studies of polymers

    SciTech Connect

    Jayakody, J.R.P.

    1993-12-31

    The behavior of induction signals during steady-state pulse irradiation in {sup 14}N NQR was investigated experimentally. Because Strong Off-resonance Comb (SORC) signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these steady-state SORC signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method. Also as part of the NQR work, cocaine base has been detected using conventional NQR techniques. The experimental results show that SORC detection can be of sufficient sensitivity to form the basis of narcotics screening devices for both mail and airline baggage. A new NMR technique, to obtain the correlation time of the random thermal motion of a polymer at temperatures near the glass transition has been introduced. The temperature dependence is a result of thermal motion. For slow-motion of a polymer chain near the glass transition, the CSA parameter begins to decrease. This motional narrowing can be interpreted to yield the correlation time of the thermal motion. In this work nitrocellulose isotopically highly enriched with {sup 15}N was studied at four different temperatures between 27{degrees} and 120{degrees} Celsius and the correlation times for polymer backbone motions were obtained. Naflon films containing water (D{sub 2}O and H{sub 2} {sup 17}O) and methanol (CH{sub 3}OD, CH{sub 3} {sup 17}OH), have been studied using deuteron and oxygen-17 NMR spectroscopy. Glassy behavior of the water domains at low temperature is evidenced by the specific nature of the {sup 2}H NMR lineshapes. Activation energies extracted from {sup 2}H spin-lattice relaxation data on the high temperature side of the T{sub 1} minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra of both unstretched and stretched samples reflect considerable anisotrophy of the host polymer.

  19. Studies of narrow autoionizing resonances in gadolinium

    SciTech Connect

    Bushaw, Bruce A.; Nortershauser, W.; Blaum, K.; Wendt, Klaus

    2003-06-30

    The autoionization (AI) spectrum of gadolinium between the first and second limits has been investigated by triple-resonance excitation with high-resolution cw lasers. A large number of narrow AI resonances have been observed and assigned total angular momentum J values. The resonances are further divided into members of AI Rydberg series converging to the second limit or other ''interloping'' levels. Fine structure in the Rydberg series has been identified and interpreted in terms of Jc j coupling. A number of detailed studies have been performed on the interloping resonances: These include lifetime determination by lineshape analysis, isotope shifts, hyperfine structure, and photoionization saturation parameters. The electronic structure of the interloping levels is discussed in terms of these studies. Linewidths generally decrease with increasing total angular momentum and the J = 7 resonances are extremely narrow with Lorentzian widths ranging from < 1 MHz up to 157 MHz. The strongest resonances are found to have cross-sections of {approx}10-12 cm{sup 2} and photoionization can be saturated with powers available from cw diode lasers.

  20. In Vitro Longitudinal Relaxivity Profile of Gd(ABE-DTTA), an Investigational Magnetic Resonance Imaging Contrast Agent

    PubMed Central

    Varga-Szemes, Akos; Kiss, Pal; Rab, Andras; Suranyi, Pal; Lenkey, Zsofia; Simor, Tamas; Bryant, Robert G.; Elgavish, Gabriel A.

    2016-01-01

    Purpose MRI contrast agents (CA) whose contrast enhancement remains relatively high even at the higher end of the magnetic field strength range would be desirable. The purpose of this work was to demonstrate such a desired magnetic field dependency of the longitudinal relaxivity for an experimental MRI CA, Gd(ABE-DTTA). Materials and Methods The relaxivity of 0.5mM and 1mM Gd(ABE-DTTA) was measured by Nuclear Magnetic Relaxation Dispersion (NMRD) in the range of 0.0002 to 1T. Two MRI and five NMR instruments were used to cover the range between 1.5 to 20T. Parallel measurement of a Gd-DTPA sample was performed throughout as reference. All measurements were carried out at 37°C and pH 7.4. Results The relaxivity values of 0.5mM and 1mM Gd(ABE-DTTA) measured at 1.5, 3, and 7T, within the presently clinically relevant magnetic field range, were 15.3, 11.8, 12.4 s-1mM-1 and 18.1, 16.7, and 13.5 s-1mM-1, respectively. The control 4 mM Gd-DTPA relaxivities at the same magnetic fields were 3.6, 3.3, and 3.0 s-1mM-1, respectively. Conclusions The longitudinal relaxivity of Gd(ABE-DTTA) measured within the presently clinically relevant field range is three to five times higher than that of most commercially available agents. Thus, Gd(ABE-DTTA) could be a practical choice at any field strength currently used in clinical imaging including those at the higher end. PMID:26872055

  1. A dynamical study of Galactic globular clusters under different relaxation conditions

    NASA Astrophysics Data System (ADS)

    Zocchi, A.; Bertin, G.; Varri, A. L.

    2012-03-01

    Aims: We perform a systematic combined photometric and kinematic analysis of a sample of globular clusters under different relaxation conditions, based on their core relaxation time (as listed in available catalogs), by means of two well-known families of spherical stellar dynamical models. Systems characterized by shorter relaxation time scales are expected to be better described by isotropic King models, while less relaxed systems might be interpreted by means of non-truncated, radially-biased anisotropic f(ν) models, originally designed to represent stellar systems produced by a violent relaxation formation process and applied here for the first time to the study of globular clusters. Methods: The comparison between dynamical models and observations is performed by fitting simultaneously surface brightness and velocity dispersion profiles. For each globular cluster, the best-fit model in each family is identified, along with a full error analysis on the relevant parameters. Detailed structural properties and mass-to-light ratios are also explicitly derived. Results: We find that King models usually offer a good representation of the observed photometric profiles, but often lead to less satisfactory fits to the kinematic profiles, independently of the relaxation condition of the systems. For some less relaxed clusters, f(ν) models provide a good description of both observed profiles. Some derived structural characteristics, such as the total mass or the half-mass radius, turn out to be significantly model-dependent. The analysis confirms that, to answer some important dynamical questions that bear on the formation and evolution of globular clusters, it would be highly desirable to acquire larger numbers of accurate kinematic data-points, well distributed over the cluster field. Appendices are available in electronic form at http://www.aanda.org

  2. Experimental study of laser-detected magnetic resonance based on atomic alignment

    SciTech Connect

    Di Domenico, Gianni; Bison, Georg; Groeger, Stephan; Knowles, Paul; Pazgalev, Anatoly S.; Rebetez, Martin; Saudan, Herve; Weis, Antoine

    2006-12-15

    We present an experimental study of the spectra produced by optical-radio-frequency double resonance in which resonant linearly polarized laser light is used in the optical pumping and detection processes. We show that the experimental spectra obtained for cesium are in excellent agreement with a very general theoretical model developed in our group [Weis, Bison, and Pazgalev, Phys. Rev. A 74, 033401 (2006)] and we investigate the limitations of this model. Finally, the results are discussed in view of their use in the study of relaxation processes in aligned alkali-metal vapors.

  3. What can we learn from relaxation measurements of a laser-perturbed atmosphere? A modeling study

    NASA Technical Reports Server (NTRS)

    Clericetti, Agostino; Vandenbergh, Hubert; Rossi, Michel J.

    1994-01-01

    The chemical kinetic aspects of a transient increase in OH and HO2 by several orders of magnitude are explored in three model tropospheres. This chemical kinetic modeling effort was undertaken to support the operation of a pump-and-probe LIDAR instrument. A powerful excimer laser pulse perturbs the troposphere after which its relaxation back to steady state is examined by remote sensing, for example by DIAL or LIF. Instead of probing ambient levels of key free radicals, a study of the relaxation kinetics in real time enables chemical mechanistic studies in situ.

  4. Graphene oxide-Fe{sub 3}O{sub 4} nanoparticle composite with high transverse proton relaxivity value for magnetic resonance imaging

    SciTech Connect

    Venkatesha, N.; Srivastava, Chandan; Poojar, Pavan; Geethanath, Sairam; Qurishi, Yasrib

    2015-04-21

    The potential of graphene oxide–Fe{sub 3}O{sub 4} nanoparticle (GO-Fe{sub 3}O{sub 4}) composite as an image contrast enhancing material in magnetic resonance imaging has been investigated. Proton relaxivity values were obtained in three different homogeneous dispersions of GO-Fe{sub 3}O{sub 4} composites synthesized by precipitating Fe{sub 3}O{sub 4} nanoparticles in three different reaction mixtures containing 0.01 g, 0.1 g, and 0.2 g of graphene oxide. A noticeable difference in proton relaxivity values was observed between the three cases. A comprehensive structural and magnetic characterization revealed discrete differences in the extent of reduction of the graphene oxide and spacing between the graphene oxide sheets in the three composites. The GO-Fe{sub 3}O{sub 4} composite framework that contained graphene oxide with least extent of reduction of the carboxyl groups and largest spacing between the graphene oxide sheets provided the optimum structure for yielding a very high transverse proton relaxivity value. It was found that the GO-Fe{sub 3}O{sub 4} composites possessed good biocompatibility with normal cell lines, whereas they exhibited considerable toxicity towards breast cancer cells.

  5. Microstructure of Wet Cement Pastes: a Nuclear Magnetic Resonance Study

    NASA Astrophysics Data System (ADS)

    Jehng, Jyh-Yuar

    1995-01-01

    Nuclear magnetic resonance relaxation analysis has been applied to interpret the evolution of microstructure in a cement paste during hydration. The work in this thesis has yielded a better understanding of the geometric and physical characterization of porous materials, and specifically cement pastes. A basic understanding of the wet-dry and freeze-thaw processes of cement pastes has been developed. The pore structure evolution has been studied by the suppression of the freezing temperature of water and compared with relaxation analysis performed at room temperature. Both methods consistently show that hydrating cement pastes have two principal components in their size distribution. Firstly, in situ measurements have been made of the water consumption, the total specific surface area, and pore water size distribution as a function of hydration time. The amount of evaporable water in the pore space can be determined from the magnitude of the NMR signal, and the NMR relaxation times provide a measure of the characteristic pore sizes. Drying studies have been performed to determine the surface spin-spin relaxation time. The NMR results on evolution of cement pore structure with hydration clearly show five different stages. The water consumption was determined to be a linear function of the logarithm of hydration time over a wide range during which the total surface area of the wet gel remains constant. These experiments support a model of capillary and gel pores in the cement paste and provide strong evidence of a stable dense-gel structure. Secondly, supercooling and thawing point depression of confined water has been studied systematically. The depression of the freezing point of liquid water confined within a pore was found to be dependent on the pore size with capillary pore water freezing at 240 K and the remaining gel pore water freezing over a temperature range extending to as low as 160 K. Finally, an important application of NMR has been developed to monitor

  6. Collisionless Relaxation in Non-Neutral Plasmas

    SciTech Connect

    Levin, Yan; Pakter, Renato; Teles, Tarcisio N.

    2008-02-01

    A theoretical framework is presented which allows us to quantitatively predict the final stationary state achieved by a non-neutral plasma during a process of collisionless relaxation. As a specific application, the theory is used to study relaxation of charged-particle beams. It is shown that a fully matched beam relaxes to the Lynden-Bell distribution. However, when a mismatch is present and the beam oscillates, parametric resonances lead to a core-halo phase separation. The approach developed accounts for both the density and the velocity distributions in the final stationary state.

  7. Electrodynamic study of YIG filters and resonators

    NASA Astrophysics Data System (ADS)

    Krupka, Jerzy; Salski, Bartlomiej; Kopyt, Pawel; Gwarek, Wojciech

    2016-10-01

    Numerical solutions of coupled Maxwell and Landau-Lifshitz-Gilbert equations for a magnetized yttrium iron garnet (YIG) sphere acting as a one-stage filter are presented. The filter is analysed using finite-difference time-domain technique. Contrary to the state of the art, the study shows that the maximum electromagnetic power transmission through the YIG filter occurs at the frequency of the magnetic plasmon resonance with the effective permeability of the gyromagnetic medium μr ≈ ‑2, and not at a ferromagnetic resonance frequency. Such a new understanding of the YIG filter operation, makes it one of the most commonly used single-negative plasmonic metamaterials. The frequency of maximum transmission is also found to weakly depend on the size of the YIG sphere. An analytic electromagnetic analysis of resonances in a YIG sphere is performed for circularly polarized electromagnetic fields. The YIG sphere is situated in a free space and in a large spherical cavity. The study demonstrates that both volume resonances and magnetic plasmon resonances can be solutions of the same transcendental equations.

  8. Electrodynamic study of YIG filters and resonators

    PubMed Central

    Krupka, Jerzy; Salski, Bartlomiej; Kopyt, Pawel; Gwarek, Wojciech

    2016-01-01

    Numerical solutions of coupled Maxwell and Landau-Lifshitz-Gilbert equations for a magnetized yttrium iron garnet (YIG) sphere acting as a one-stage filter are presented. The filter is analysed using finite-difference time-domain technique. Contrary to the state of the art, the study shows that the maximum electromagnetic power transmission through the YIG filter occurs at the frequency of the magnetic plasmon resonance with the effective permeability of the gyromagnetic medium μr ≈ −2, and not at a ferromagnetic resonance frequency. Such a new understanding of the YIG filter operation, makes it one of the most commonly used single-negative plasmonic metamaterials. The frequency of maximum transmission is also found to weakly depend on the size of the YIG sphere. An analytic electromagnetic analysis of resonances in a YIG sphere is performed for circularly polarized electromagnetic fields. The YIG sphere is situated in a free space and in a large spherical cavity. The study demonstrates that both volume resonances and magnetic plasmon resonances can be solutions of the same transcendental equations. PMID:27698467

  9. A study on oscillating second-kind boundary condition for Pennes equation considering thermal relaxation

    NASA Astrophysics Data System (ADS)

    Zhu, Weiping; Xu, Peng; Xu, Dong; Zhang, Meimei; Liu, Huiming; Gong, Linghui; Lu, Junfeng

    2014-05-01

    To study the effects of the thermal relaxation, the blood perfusion and the oscillating of ambient heat flux on the living tissue temperature in detail, we analytically investigated the one-dimensional CV model, a thermal wave model presented by Cattaneo and Vernott, for Pennes' bio-heat transfer equation under oscillating second-kind boundary condition. The results showed that the blood perfusion has the effect of maintaining the tissue's temperature. The heat propagation velocity decreases with the thermal relaxation time, while the absolute value of tissue's mean excess temperature at steady state increases with the thermal relaxation time. When the ambient heat flux oscillates, the tissue's temperature oscillates in the same period with a lag time. The results obtained in this paper are valuable for the research reference on the topic of tumor hyperthermia, heat injury, etc.

  10. NMR and dielectric studies of hydrated collagen and elastin: Evidence for a delocalized secondary relaxation

    NASA Astrophysics Data System (ADS)

    Lusceac, Sorin A.; Rosenstihl, Markus; Vogel, Michael; Gainaru, Catalin; Fillmer, Ariane; Böhmer, Roland

    2011-01-01

    Using a combination of dielectric spectroscopy and solid-state deuteron NMR, the hydration water dynamics of connective tissue proteins is studied at sub-ambient temperatures. In this range, the water dynamics follows an Arrhenius law. A scaling analysis of dielectric losses, 'two-phase' NMR spectra, and spin-lattice relaxation times consistently yield evidence for a Gaussian distribution of energy barriers. With the dielectric data as input, random-walk simulations of a large-angle, quasi-isotropic water reorientation provide an approximate description of stimulated-echo data on hydrated elastin. This secondary process takes place in an essentially rigid energy landscape, but in contrast to typical {\\beta}-relaxations it is quasi-isotropic and delocalized. The delocalization is inferred from previous NMR diffusometry experiments. To emphasize the distinction from conventional {\\beta}-processes, for aqueous systems such a matrix-decoupled relaxation was termed a {\

  11. Fetal imaging by nuclear magnetic resonance: a study in goats: work in progress

    SciTech Connect

    Foster, M.A.; Knight, C.H.; Rimmington, J.E.; Mallard, J.R.

    1983-10-01

    Nuclear magnetic resonance proton imaging was used to obtain images of goat fetuses in utero. The long T1 relaxation time of amniotic fluid makes it appear black on proton density images when examined using the Aberdeen imager, and so allows very good discrimination of the position and structure of the fetus. Some fetal internal tissues can be seen on T1 images. These findings suggest that NMR imaging has great potential in pregnancy studies.

  12. Positron annihilation and relaxation dynamics from dielectric spectroscopy and nuclear magnetic resonance: Cis-trans-1,4-poly(butadiene)

    NASA Astrophysics Data System (ADS)

    Bartoš, J.; Šauša, O.; Schwartz, G. A.; Alegría, A.; Alberdi, J. M.; Arbe, A.; Krištiak, J.; Colmenero, J.

    2011-04-01

    We report a joint analysis of positron annihilation lifetime spectroscopy (PALS), dielectric spectroscopy (BDS), and nuclear magnetic resonance (NMR) on cis-trans-1,4-poly(butadiene) (c-t-1,4-PBD). Phenomenological analysis of the orthopositronium lifetime τ3 - T dependence by linear fitting reveals four characteristic PALS temperatures: T_{b1} ^G = 0{.63}T_g^{PALS}, T_g^{PALS}, T_{b1} ^L = 1.22T_g^{PALS}, and T_{b2} ^L = 1.52T_g^{PALS}. Slight bend effects in the glassy and supercooled liquid states are related to the fast or slow secondary β process, from neutron scattering, respectively, the latter being connected with the trans-isomers. In addition, the first bend effect in the supercooled liquid coincides with a deviation of the slow effective secondary βeff relaxation related to the cis-isomers from low-T Arrhenius behavior to non-Arrhenius one and correlates with the onset of the primary α process from BDS. The second plateau effect in the liquid state occurs when τ3 becomes commensurable with the structural relaxation time τα(Tb2). It is also approximately related to its crossover from non-Arrhenius to Arrhenius regime in the combined BDS and NMR data. Finally, the combined BDS and NMR structural relaxation data, when analyzed in terms of the two-order parameter (TOP) model, suggest the influence of solidlike domains on both the annihilation behavior and the local and segmental chain mobility in the supercooled liquid. All these findings indicate the influence of the dynamic heterogeneity in both the primary and secondary relaxations due to the cis-trans isomerism in c-t-1,4-PBD and their impact into the PALS response.

  13. A Resonant Damping Study Using Piezoelectric Materials

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

    2008-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

  14. Instructional Set, Deep Relaxation and Growth Enhancement: A Pilot Study

    ERIC Educational Resources Information Center

    Leeb, Charles; And Others

    1976-01-01

    This study provides experimental evidence that instructional set can influence access to altered states of consciousness. Fifteen male subjects were randomly assigned to three groups, each of which received the same autogenic biofeedback training in hand temperature control, but each group received a different attitudinal set. (Editor)

  15. Local Ordering at Mobile Sites in Proteins from Nuclear Magnetic Resonance Relaxation: The Role of Site Symmetry.

    PubMed

    Tchaicheeyan, Oren; Freed, Jack H; Meirovitch, Eva

    2016-03-24

    Restricted motions in proteins (e.g., N-H bond dynamics) are studied effectively with NMR. By analogy with restricted motions in liquid crystals (LC), the local ordering has in the past been primarily represented by potentials comprising the L = 2, |K| = 0, 2 spherical harmonics. However, probes dissolved in LCs experience nonpolar ordering, often referred to as alignment, while protein-anchored probes experience polar ordering, often referred to as orientation. In this study we investigate the role of local (site) symmetry in the context of the polarity of the local ordering. We find that potentials comprising the L = 1, |K| = 0, 1 spherical harmonics represent adequately polar ordering. It is useful to characterize potential symmetry in terms of the irreducible representations of D2h point group, which is already implicit in the definition of the rotational diffusion tensor. Thus, the relevant rhombic L = 1 potentials have B1u and B3u symmetry whereas the relevant rhombic L = 2 potentials have Ag symmetry. A comprehensive scheme where local potentials and corresponding probability density functions (PDFs) are represented in Cartesian and spherical coordinates clarifies how they are affected by polar and nonpolar ordering. The Cartesian coordinates are chosen so that the principal axis of polar axial PDF is pointing along the z-axis, whereas the principal axis of the nonpolar axial PDF is pointing along ±z. Two-term axial potentials with 1 ≤ L ≤ 3 exhibit substantial diversity; they are expected to be useful in NMR-relaxation-data-fitting. It is shown how potential coefficients are reflected in the experimental order parameters. The comprehensive scheme representing local potentials and PDFs is exemplified for the L = 2 case using experimental data from (15)N-labeled plexin-B1 and thioredoxin, (2)H-, and (13)C-labeled benzenehexa-n-alkanoates, and nitroxide-labeled T4 lysozyme. Future prospects for improved ordering analysis based on combined atomistic and

  16. Investigation of the applicability of dielectric relaxation properties of amino acid solutions within the resonant recognition model.

    PubMed

    Pirogova, Elena; Simon, George P; Cosic, Irena

    2003-06-01

    The resonant recognition model (RRM) is a physicomathematical approach used to analyze the interactions of a protein and its target, using digital signal processing methods. The RRM is based on the finding that there is a significant correlation between the spectra of numerical presentation of protein sequences and their biological activities. Initially, the electron-ion interaction potential was used to represent each amino acid in the protein sequences. In this paper, the dielectric constant (epsilon') and dielectric loss tangent (tan delta) parameters have been determined for their possible use in the RRM. These parameters are based on the values of capacitance and conductance obtained experimentally for 20 amino acid solutions using dielectric spectroscopy for the case of the real component of dielectric permittivity; the parameter used is the dielectric increment (deltaepsilon'), the difference between dielectric constant of the amino acid solution and that of the solvent alone. The results of multiple cross-spectral analyses have shown that parameters analyzed generate in the consensus spectrum one dominant peak corresponding to the common biological activity of proteins studied, allowing the conclusion that these new parameters are suitable for use in the RRM approach.

  17. Composition Dependent Analysis of Raman Spectra in the Modified Boroaluminosilicate System: Implications for Coupling Between Structural Resonance and Relaxation in the Glass Network

    SciTech Connect

    S. V. Raman; R. S. Czernuszewicz; A. A. Zareba

    2004-04-01

    The boroaluminosilicate system was systematically modified by addition of magnesium, sodium and zirconium oxides. Strong bridging silicate bands and narrow and intense nonbridging silicate bands compose the Raman spectra of glasses. The fundamental nonbridging molecular species bands are related to the bridged network bands by the first overtone and signify anharmonic oscillation. At a constant degree of depolymerisation, the nonbridging band intensity depends on the silica content. With decrease in silica content, the bridged network band frequency shifts to a higher value and simultaneously the nonbridging bands intensify. The sharp rise in intensity for the nonbridging bands is attributed to resonant oscillations between the bridged lattice network and nonbridging molecular species. The resonance between the two structural entities possibly occurs in response to relaxation of the bridged network with decrease in silica content. Contributions to enhancement of intensity also presumably arise from resonance in valency bonds and oscillations in the oxygen edge shared polyhedral (ESP) structure for the nonbridging molecular species. The force constant of the ESP species varies as a function of zirconium, sodium and magnesium coordination to apex nonbridging oxygens. The single ESP band transforms to Fermi doublet upon crystallisation to orthosilicate structures of zircon and forsterite. 32 refs.

  18. Magnetic resonance diffusion and relaxation characterization of water in the unfrozen vein network in polycrystalline ice and its response to microbial metabolic products

    NASA Astrophysics Data System (ADS)

    Brown, Jennifer R.; Brox, Timothy I.; Vogt, Sarah J.; Seymour, Joseph D.; Skidmore, Mark L.; Codd, Sarah L.

    2012-12-01

    Polycrystalline ice, as found in glaciers and the ice sheets of Antarctica, is a low porosity porous media consisting of a complicated and dynamic pore structure of liquid-filled intercrystalline veins within a solid ice matrix. In this work, Nuclear Magnetic Resonance measurements of relaxation rates and molecular diffusion, useful for probing pore structure and transport dynamics in porous systems, were used to physically characterize the unfrozen vein network structure in ice and its response to the presence of metabolic products produced by V3519-10, a cold tolerant microorganism isolated from the Vostok ice core. Recent research has found microorganisms that can remain viable and even metabolically active within icy environments at sub-zero temperatures. One potential mechanism of survival for V3519-10 is secretion of an extracellular ice binding protein that binds to the prism face of ice crystals and inhibits ice recrystallization, a coarsening process resulting in crystal growth with ice aging. Understanding the impact of ice binding activity on the bulk vein network structure in ice is important to modeling of frozen geophysical systems and in development of ice interacting proteins for biotechnology applications, such as cryopreservation of cell lines, and manufacturing processes in food sciences. Here, we present the first observations of recrystallization inhibition in low porosity ice containing V3519-10 extracellular protein extract as measured with Nuclear Magnetic Resonance and Magnetic Resonance Imaging.

  19. Polymer relaxation and stretching dynamics in semi-dilute DNA solutions: a single molecule study

    NASA Astrophysics Data System (ADS)

    Hsiao, Kai-Wen; Brockman, Christopher; Schroeder, Charles

    2015-03-01

    In this work, we study polymer relaxation and stretching dynamics in semi-dilute DNA solutions using single molecule techniques. Using this approach, we uncover a unique scaling relation for longest polymer relaxation time that falls in the crossover regime described by semi-flexible polymer solutions, which is distinct from truly flexible polymer chains. In addition, we performed a series of step-strain experiments on single polymers in semi-dilute solutions in planar extensional flow using an automated microfluidic trap. In this way, we are able to precisely control the flow strength and the amount of strain applied to single polymer chains, thereby enabling direct observation of the full stretching and relaxation process in semi-dilute solutions during transient start-up and flow cessation. Interestingly, we observe polymer individualism in the conformation of single chains in semi-dilute solutions, which to our knowledge has not yet been observed. In addition, we observe the relaxation data can be explained by a multi-exponential decay process after flow cessation in semi-dilute solutions. Overall, our work reports key advance in non-dilute polymer systems from a molecular perspective via direct observation of dynamics in strong flows. DOW fellowship.

  20. Defect-related internal dissipation in mechanical resonators and the study of coupled mechanical systems.

    SciTech Connect

    Friedmann, Thomas Aquinas; Czaplewski, David A.; Sullivan, John Patrick; Modine, Normand Arthur; Wendt, Joel Robert; Aslam, Dean (Michigan State University, Lansing, MI); Sepulveda-Alancastro, Nelson (University of Puerto Rico, Mayaguez, PR)

    2007-01-01

    Understanding internal dissipation in resonant mechanical systems at the micro- and nanoscale is of great technological and fundamental interest. Resonant mechanical systems are central to many sensor technologies, and microscale resonators form the basis of a variety of scanning probe microscopies. Furthermore, coupled resonant mechanical systems are of great utility for the study of complex dynamics in systems ranging from biology to electronics to photonics. In this work, we report the detailed experimental study of internal dissipation in micro- and nanomechanical oscillators fabricated from amorphous and crystalline diamond materials, atomistic modeling of dissipation in amorphous, defect-free, and defect-containing crystalline silicon, and experimental work on the properties of one-dimensional and two-dimensional coupled mechanical oscillator arrays. We have identified that internal dissipation in most micro- and nanoscale oscillators is limited by defect relaxation processes, with large differences in the nature of the defects as the local order of the material ranges from amorphous to crystalline. Atomistic simulations also showed a dominant role of defect relaxation processes in controlling internal dissipation. Our studies of one-dimensional and two-dimensional coupled oscillator arrays revealed that it is possible to create mechanical systems that should be ideal for the study of non-linear dynamics and localization.

  1. A study of xenon isotopes in a martian meteorite using the RELAX ultrasensitive mass spectrometer

    SciTech Connect

    Whitby, J A; Gilmour, J D; Turner, G

    1997-01-15

    The Refrigerator Enhanced Analyser for Xenon (RELAX), an ultrasensitive resonance ionization time-of-flight mass spectrometer, has been used with a laser microprobe to investigate the isotopic composition of xenon trapped in the martian meteorite ALH84001. The laser microprobe has a spatial resolution of the order of 100{mu}m thus allowing the in situ analysis of individual mineral grains in a polished section when combined with ultrasensitive, low blank sample analysis. We present results showing that the mineral orthopyroxene in ALH84001 contains a trapped xenon component consistent with a martian origin. Additionally, a cosmic ray exposure age of 15Ma for ALH84001 is obtained from spallation derived xenon trapped within an apatite grain.

  2. Study of relaxation and transport processes by means of AFM based dielectric spectroscopy

    SciTech Connect

    Miccio, Luis A.

    2014-05-15

    Since its birth a few years ago, dielectric spectroscopy studies based on atomic force microscopy (AFM) have gained a growing interest. Not only the frequency and temperature ranges have become broader since then but also the kind of processes that can be studied by means of this approach. In this work we analyze the most adequate experimental setup for the study of several dielectric processes with a spatial resolution of a few nanometers by using force mode AFM based dielectric spectroscopy. Proof of concept experiments were performed on PS/PVAc blends and PMMA homopolymer films, for temperatures ranging from 300 to 400 K. Charge transport processes were also studied by this approach. The obtained results were analyzed in terms of cantilever stray contribution, film thickness and relaxation strength. We found that the method sensitivity is strongly coupled with the film thickness and the relaxation strength, and that it is possible to control it by using an adequate experimental setup.

  3. A magnetic resonance (MR) compatible selective brain temperature manipulation system for preclinical study

    PubMed Central

    Liu, Qingwei; Cai, Yu; Lin, Weili; Turner, Gregory H; An, Hongyu

    2012-01-01

    There is overwhelming evidence that hypothermia can improve the outcome of an ischemic stroke. However, the most widely used systemic cooling method could lead to multiple side effects, while the incompatibility with magnetic resonance imaging of the present selective cooling methods highly limit their application in preclinical studies. In this study, we developed a magnetic resonance compatible selective brain temperature manipulation system for small animals, which can regulate brain temperature quickly and accurately for a desired period of time, while maintaining the normal body physiological conditions. This device was utilized to examine the relationship between T1 relaxation, cerebral blood flow, and temperature in brain tissue during magnetic resonance imaging of ischemic stroke. The results showed that this device can be an efficient brain temperature manipulation tool for preclinical studies needing local hypothermic or hyperthermic conditions. PMID:23166453

  4. A comparative study of potassium-induced relaxation in vascular smooth muscle of tiger salamanders and rats.

    PubMed

    Malvin, G M; Webb, R C

    1984-07-01

    This study compares potassium-induced relaxation in vascular tissue of an amphibian (Ambystoma tigrinum) and a mammal (rat). Aortas (salamanders) and tail arteries (rats) were cut into helical strips for isometric force recording. After norepinephrine-induced contraction in potassium-free solution, arteries relaxed in response to added potassium (1-20 mmol/l). Potassium-induced relaxation was greater in rat tail arteries than in salamander aortas. Half-maximal relaxation occurred at a potassium concentration of approximately 3 mmol/l in both species. Ouabain inhibited potassium-induced relaxation; salamanders were more sensitive to the glycoside than rats. Potassium-induced relaxation decreased as the temperature of the bathing medium was lowered; half-maximal inhibition occurred at 19 and 29 degrees C for salamander aortas and rat tail arteries, respectively. Potassium-induced relaxation also varied with the interval in potassium-free solution, the hydrogen ion concentration (rats only), and the magnitude of norepinephrine-induced contraction. It appears that the cellular mechanism causing potassium-induced relaxation is similar in blood vessels of salamanders and rats. The observations are consistent with the hypothesis that stimulated electrogenic sodium transport produced membrane hyperpolarization and relaxation in vascular smooth muscle.

  5. A study of the stack relaxation in thermal batteries on activation

    SciTech Connect

    GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; THOMAS,EDWARD V.

    2000-04-17

    The stack-relaxation processes occurring in a thermal-battery upon activation and discharge were studied dynamically with a special test fixture that incorporated an internal load cell. The factors which were screened initially included stack diameter and height (number of cells), thickness and binder content of the separator, temperature, and closing pressure. A second series of more-detailed experiments included only those factors that were identified by the screening study as being important (as closing force, number of cells, and separator thickness). The resulting experimental data from this second series of experiments were used to generate a surface-response model based on these three factors. This model accounted for 94% of the variation in the response (final stack-relaxation pressure) over the range of conditions studied.

  6. A nuclear magnetic resonance study of water in aggrecan solutions

    PubMed Central

    Foster, Richard J.; Damion, Robin A.; Baboolal, Thomas G.; Smye, Stephen W.; Ries, Michael E.

    2016-01-01

    Aggrecan, a highly charged macromolecule found in articular cartilage, was investigated in aqueous salt solutions with proton nuclear magnetic resonance. The longitudinal and transverse relaxation rates were determined at two different field strengths, 9.4 T and 0.5 T, for a range of temperatures and aggrecan concentrations. The diffusion coefficients of the water molecules were also measured as a function of temperature and aggrecan concentration, using a pulsed field gradient technique at 9.4 T. Assuming an Arrhenius relationship, the activation energies for the various relaxation processes and the translational motion of the water molecules were determined from temperature dependencies as a function of aggrecan concentration in the range 0–5.3% w/w. The longitudinal relaxation rate and inverse diffusion coefficient were approximately equally dependent on concentration and only increased by upto 20% from that of the salt solution. The transverse relaxation rate at high field demonstrated greatest concentration dependence, changing by an order of magnitude across the concentration range examined. We attribute this primarily to chemical exchange. Activation energies appeared to be approximately independent of aggrecan concentration, except for that of the low-field transverse relaxation rate, which decreased with concentration. PMID:27069663

  7. Quadrupole resonance spectroscopic study of narcotic materials

    NASA Astrophysics Data System (ADS)

    Rayner, Timothy J.; West, Rebecca; Garroway, Allen N.; Lyndquist, R.; Yesinowski, James P.

    1997-02-01

    Bulk narcotic detection systems based upon Quadrupole Resonance Analysis (QRA) technology have a major advantage over imaging technologies, in that QRA is chemical-specific and consequently has a lower rate of false alarms. QRA is a magnetic resonance technology which occurs as a result of the inherent molecular properties of the atomic nuclei in crystalline and amorphous solids. The QRA response is characterized by 1) the precessional frequency of the nucleus, and 2) the nature of the electric field gradient experienced by the nucleus,due to its molecular environment. Another important detection parameter is linewidth, resonant quality. All of these parameters depend on sample purity and manufacturing process. Quantum Magnetics recently carried out a study on the QRA signatures of various narcotic materials with the support of the US Army, US Customs, and the Office of National Drug Control Policy. The aim of the study was to fully characterize the variation in QRA spectroscopic parameters of different samples of cocaine base and cocaine hydrochloride. The results from this study ar discussed here.

  8. Determining Stroke Onset Time Using Quantitative MRI: High Accuracy, Sensitivity and Specificity Obtained from Magnetic Resonance Relaxation Times

    PubMed Central

    McGarry, Bryony L.; Rogers, Harriet J.; Knight, Michael J.; Jokivarsi, Kimmo T.; Gröhn, Olli H.J.; Kauppinen, Risto A.

    2016-01-01

    Many ischaemic stroke patients are ineligible for thrombolytic therapy due to unknown onset time. Quantitative MRI (qMRI) is a potential surrogate for stroke timing. Rats were subjected to permanent middle cerebral artery occlusion and qMRI parameters including hemispheric differences in apparent diffusion coefficient, T2-weighted signal intensities, T1 and T2 relaxation times (qT1, qT2) and f1, f2 and Voverlap were measured at hourly intervals at 4.7 or 9.4 T. Accuracy and sensitivity for identifying strokes scanned within and beyond 3 h of onset was determined. Accuracy for Voverlap, f2 and qT2 (>90%) was significantly higher than other parameters. At a specificity of 1, sensitivity was highest for Voverlap (0.90) and f2 (0.80), indicating promise of these qMRI indices in the clinical assessment of stroke onset time.

  9. A new substance to relax polychaete worms (Annelida) prior to morphological study

    PubMed Central

    Bonyadi-Naeini, Alieh; Rahimian, Hassan; Glasby, Christopher J.

    2016-01-01

    Abstract A variety of chemical substances have been used to relax and/or immobilize polychaete worms, and other invertebrates, prior to specimen preparation for morphological examination. To solve difficulties encountered during the study of nereidid polychaetes (Annelida: Phyllodocida), an experiment was designed and carried out to investigate a new relaxing agent to immobilize nereidid specimens and stimulate pharynx eversion. The new substance, Dentol® (Khoraman laboratory, Iran), a dental anesthetic and antiseptic medicine containing 10% Carvacrol as the effective ingredient, was used for the first time and compared with other substances that have been used traditionally in polychaete studies. Crosstab analysis showed significant differences between different treatment groups, with Dentol® providing much better results for all considered criteria. PMID:27408556

  10. A new substance to relax polychaete worms (Annelida) prior to morphological study.

    PubMed

    Bonyadi-Naeini, Alieh; Rahimian, Hassan; Glasby, Christopher J

    2016-01-01

    A variety of chemical substances have been used to relax and/or immobilize polychaete worms, and other invertebrates, prior to specimen preparation for morphological examination. To solve difficulties encountered during the study of nereidid polychaetes (Annelida: Phyllodocida), an experiment was designed and carried out to investigate a new relaxing agent to immobilize nereidid specimens and stimulate pharynx eversion. The new substance, Dentol® (Khoraman laboratory, Iran), a dental anesthetic and antiseptic medicine containing 10% Carvacrol as the effective ingredient, was used for the first time and compared with other substances that have been used traditionally in polychaete studies. Crosstab analysis showed significant differences between different treatment groups, with Dentol® providing much better results for all considered criteria.

  11. Relaxation and guided imagery in Hispanic persons diagnosed with fibromyalgia: a pilot study.

    PubMed

    Menzies, Victoria; Kim, Sunny

    2008-01-01

    Fibromyalgia (FM) is a chronic pain disorder affecting 2% of the population in the United States. Another 16 million Hispanics suffer from generically identified rheumatic diseases that likely include FM. Because there are few reported studies of Hispanics with FM, a pilot study using a repeated-measures pretest-posttest design investigated the effects of a 10-week mind-body intervention (visual imagery with relaxation) on symptom management. The change in means from baseline to week 10 demonstrated improvement in self-efficacy for managing pain and other symptoms and functional status. Visual imagery with relaxation is a mind-body intervention that may be used for symptom management in this population. PMID:18552601

  12. A new substance to relax polychaete worms (Annelida) prior to morphological study.

    PubMed

    Bonyadi-Naeini, Alieh; Rahimian, Hassan; Glasby, Christopher J

    2016-01-01

    A variety of chemical substances have been used to relax and/or immobilize polychaete worms, and other invertebrates, prior to specimen preparation for morphological examination. To solve difficulties encountered during the study of nereidid polychaetes (Annelida: Phyllodocida), an experiment was designed and carried out to investigate a new relaxing agent to immobilize nereidid specimens and stimulate pharynx eversion. The new substance, Dentol® (Khoraman laboratory, Iran), a dental anesthetic and antiseptic medicine containing 10% Carvacrol as the effective ingredient, was used for the first time and compared with other substances that have been used traditionally in polychaete studies. Crosstab analysis showed significant differences between different treatment groups, with Dentol® providing much better results for all considered criteria. PMID:27408556

  13. Structural relaxation mechanisms in liquid Eugenol. A depolarized light scattering study

    NASA Astrophysics Data System (ADS)

    Bezot, P.; Hesse-Bezot, C.; Roynard, D.; Jeanneaux, F.

    1988-07-01

    A depolarized light scattering study of liquid Eugenol, over a large temperature range including the supercooled region, is proposed. Comparisons with shear mechanical impedance measurements, obtained at lower frequencies, lead to more precise information on the viscoelastic parameters in the supercooled region. The structural relaxation process measurements by means of the photon correlation technique are compared to the dielectric and mechanical measurements. Molecular mechanisms are proposed.

  14. The impedance spectroscopic study and dielectric relaxation in A(Ni1/3Ta2/3)O3 [A=Ba, Ca and Sr

    NASA Astrophysics Data System (ADS)

    Hoque, Md M.; Dutta, A.; Kumar, S.; Sinha, T. P.

    2012-09-01

    We present the results of impedance spectroscopic study with its analytical interpretations in the framework of electric modulus formalism for Barium Nickel Tantalate Ba(Ni1/3Ta2/3)O3 (BNT), Calcium Nickel Tantalate Ca(Ni1/3Ta2/3)O3 (CNT) and Strontium Nickel Tantalate Sr(Ni1/3Ta2/3)O3 (SNT) synthesized by the solid-state reaction technique. The results of powder X-ray diffraction study reveal that BNT and SNT crystallize in cubic structure with lattice parameter a=4.07 Å and 3.98 Å respectively, whereas CNT crystallizes in monoclinic structure having lattice parameters, a=5.71 Å, b=13.45 Å and c=5.47 Å with β=118.3°. The logarithmic angular frequency dependence of the real part of complex dielectric permittivity and loss tangent as a function of temperature indicate significant dielectric relaxation in the samples, which have been explained by the Debye theory. The frequency dependence of the loss peak and the imaginary part of electrical modulus are found to obey the Arrhenius law. The relaxation mechanism of these samples is modeled by the Cole-Cole equation. This confirms that the polarization mechanism in BNT, CNT and SNT is due to the bulk effect arising in semiconductive grains. The scaling behavior of imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures but relaxation frequency is strongly temperature dependent. The normalized peak positions of tan δ/tan δm and M″/M″m versus log ω for BNT, CNT and SNT do not overlap completely and are very close to each other. These indicate the presence of both long-range and localized relaxation. Due to their high dielectric constant and low loss tangent, these materials may find several technological applications such as in capacitors, resonators, filters and integrated circuits.

  15. Ultrasonic relaxation studies of mixed micelles formed from alcohol-decyltrimethylammonium bromide-water

    SciTech Connect

    Jobe, D.J.; Verrall, R.E.; Skalski, B.

    1992-08-06

    This paper discusses how ultrasonic relaxation and conductance studies of alcohol (1-pentanol or 1-butanol)-DTAB-water mixed micelles reveal two relaxation frequencies related to the exchange of monomer surfactant and of alcohol between the micelles and the bulk phase. Conductance and time-resolved fluorescence measurements were used to obtain the alcohol distribution coefficients, micelle ionization, critical micellar concentration, and the alcohol and surfactant mean aggregation numbers. Using two models (Aniansson and Hall & Wyn-Jones), information about the forward and backward rate constants, polydispersity of the mixed micelles and the change in volumes of the two exchange processes are obtained and compared with 1-propanol-DTAB-water. Alcohol chain length influence on thermodynamics and kinetics is also discussed. 16 refs., 12 figs., 6 tabs.

  16. Comparative study of acoustic relaxation time of cholesteric liquid crystal and mixtures

    NASA Astrophysics Data System (ADS)

    Bhave, Manisha G.; Gharde, Rita; Radha, S.

    2016-09-01

    The present study focuses on the relaxation processes in Cholesteric Liquid Crystal and mixtures. We have dispersed two different monomers in CLC to form Polymer dispersed liquid crystals (PDCLCs). PDLC films have a remarkable electro-optical behavior since they can be switched from highly light scattering state (OFF) to transparent state (ON) simply by application of an electric field. We have also doped ferroelectric nano - powder (NP) in CLC. The phase transitions occurred at temperatures lower than those exhibited by the mesogenic component before doping. The viscosity, ultrasonic velocity and density show variation with change in the material as well as temperature. The acoustic relaxation time and ultrasonic attenuation decrease with increase in temperature for CLC and CLC+NP. The parameters of PDCLC2 in comparison with PDCLC1 are more linear in isotropic and anisotropic regions. For PDCLC2 the values reach maximum value at the Cholesteric-isotropic transition.

  17. Combined off-resonance imaging and T2 relaxation in the rotating frame for positive contrast MR imaging of infection in a murine burn model

    PubMed Central

    Andronesi, Ovidiu C.; Mintzopoulos, Dionyssios; Righi, Valeria; Psychogios, Nikolaos; Kesarwani, Meenu; He, Jianxin; Yasuhara, Shingo; Dai, George; Rahme, Laurence G.; Tzika, Aria A.

    2010-01-01

    Purpose To develop novel magnetic resonance (MR) imaging methods to monitor accumulation of macrophages in inflammation and infection. Positive-contrast MR imaging provides an alternative to negative-contrast MRI, exploiting the chemical shift induced by ultra-small superparamagnetic iron-oxide (USPIO) nanoparticles to nearby water molecules. We introduce a novel combination of off-resonance (ORI) positive-contrast MRI and T2ρ relaxation in the rotating frame (ORI-T2ρ) for positive-contrast MR imaging of USPIO. Materials and Methods We tested ORI-T2ρ in phantoms and imaged in vivo the accumulation of USPIO-labeled macrophages at the infection site in a mouse model of burn trauma and infection with Pseudomonas aeruginosa (PA). PA infection is clinically important. The USPIO nanoparticles were injected directly in the animals in solution, and macrophage labeling occurred in vivo in the animal model. Results We observed a significant difference between ORI-T2ρ and ORI, which leads us to suggest that ORI-T2ρ is more sensitive in detecting USPIO signal. To this end, the ORI-T2ρ positive contrast method may prove to be of higher utility in future research. Conclusion Our results may have direct implications in the longitudinal monitoring of infection, and open perspectives for testing novel anti-infective compounds. PMID:21031524

  18. Structural relaxation in the hydrogen-bonding liquids N-methylacetamide and water studied by optical Kerr effect spectroscopy.

    PubMed

    Turton, David A; Wynne, Klaas

    2008-04-21

    Structural relaxation in the peptide model N-methylacetamide (NMA) is studied experimentally by ultrafast optical Kerr effect spectroscopy over the normal-liquid temperature range and compared to the relaxation measured in water at room temperature. It is seen that in both hydrogen-bonding liquids, beta relaxation is present, and in each case, it is found that this can be described by the Cole-Cole function. For NMA in this temperature range, the alpha and beta relaxations are each found to have an Arrhenius temperature dependence with indistinguishable activation energies. It is known that the variations on the Debye function, including the Cole-Cole function, are unphysical, and we introduce two general modifications: One allows for the initial rise of the function, determined by the librational frequencies, and the second allows the function to be terminated in the alpha relaxation.

  19. Development of qualitative and quantitative analysis methods in pharmaceutical application with new selective signal excitation methods for 13 C solid-state nuclear magnetic resonance using 1 H T1rho relaxation time.

    PubMed

    Nasu, Mamiko; Nemoto, Takayuki; Mimura, Hisashi; Sako, Kazuhiro

    2013-01-01

    Most pharmaceutical drug substances and excipients in formulations exist in a crystalline or amorphous form, and an understanding of their state during manufacture and storage is critically important, particularly in formulated products. Carbon 13 solid-state nuclear magnetic resonance (NMR) spectroscopy is useful for studying the chemical and physical state of pharmaceutical solids in a formulated product. We developed two new selective signal excitation methods in (13) C solid-state NMR to extract the spectrum of a target component from such a mixture. These methods were based on equalization of the proton relaxation time in a single domain via rapid intraproton spin diffusion and the difference in proton spin-lattice relaxation time in the rotating frame ((1) H T1rho) of individual components in the mixture. Introduction of simple pulse sequences to one-dimensional experiments reduced data acquisition time and increased flexibility. We then demonstrated these methods in a commercially available drug and in a mixture of two saccharides, in which the (13) C signals of the target components were selectively excited, and showed them to be applicable to the quantitative analysis of individual components in solid mixtures, such as formulated products, polymorphic mixtures, or mixtures of crystalline and amorphous phases. PMID:23147444

  20. Silica-F127 nanohybrid-encapsulated manganese oxide nanoparticles for optimized T1 magnetic resonance relaxivity.

    PubMed

    Wei Hsu, Benedict You; Wang, Miao; Zhang, Yu; Vijayaragavan, Vimalan; Wong, Siew Yee; Yuang-Chi Chang, Alex; Bhakoo, Kishore Kumar; Li, Xu; Wang, John

    2014-01-01

    To properly engineer MnO nanoparticles (MONPs) of high r1 relaxivity, a nanohybrid coating consisting of silica and F127 (PEO106PPO70PEO106) is designed to encapsulate MONPs. Achieved by an interfacial templating scheme, the nanohybrid encapsulating layer is highly permeable and hydrophilic to allow for an optimal access of water molecules to the encapsulated manganese oxide core. Hence, the efficacy of MONPs as MRI contrast agents is significantly improved, as demonstrated by an enhancement of the MR signal measured with a pre-clinical 7.0 T MRI scanner. The nanohybrid encapsulation strategy also confers high colloidal stability to the hydrophobic MONPs by the surface decoration of PEO chains and a small overall diameter (<100 nm) of the PEO-SiO2 nanohybrid-encapsulated MONPs (PEOMSNs). The PEOMSNs are not susceptible to Mn-ion leaching, and their biocompatibility is affirmed by a low toxicity profile. Moreover, these hybrid nanocapsules exhibit a nano-rattle structure, which would favor the facile loading of various therapeutic reagents for theranostic applications.

  1. Strain relaxation of CdTe on Ge studied by medium energy ion scattering

    NASA Astrophysics Data System (ADS)

    Pillet, J. C.; Pierre, F.; Jalabert, D.

    2016-10-01

    We have used the medium energy ion scattering (MEIS) technique to assess the strain relaxation in molecular-beam epitaxial (MBE) grown CdTe (2 1 1)/Ge (2 1 1) system. A previous X-ray diffraction study, on 10 samples of the same heterostructure having thicknesses ranging from 25 nm to 10 μm has allowed the measurement of the strain relaxation on a large scale. However, the X-ray diffraction measurements cannot achieve a stress measurement in close proximity to the CdTe/Ge interface at the nanometer scale. Due to the huge lattice misfit between the CdTe and Ge, a high degree of disorder is expected at the interface. The MEIS in channeling mode is a good alternative in order to profile defects with a high depth resolution. For a 21 nm thick CdTe layer, we observed, at the interface, a high density of Cd and/or Te atoms moved from their expected crystallographic positions followed by a rapid recombination of defects. Strain relaxation mechanisms in the vicinity of the interface are discussed

  2. Study of the effects of hydroxyapatite nanocrystal codoping by pulsed electron paramagnetic resonance methods

    NASA Astrophysics Data System (ADS)

    Gafurov, M. R.; Biktagirov, T. B.; Mamin, G. V.; Shurtakova, D. V.; Klimashina, E. S.; Putlyaev, V. I.; Orlinskii, S. B.

    2016-03-01

    The effect of codoping of hydroxyapatite (HAP) nanocrystals with average sizes of 35 ± 15 nm during "wet" synthesis by CO 3 2- carbonate anions and Mn2+ cations on relaxation characteristics (for the times of electron spin-spin relaxation) of the NO 3 2- nitrate radical anion has been studied. By the example of HAP, it has been demonstrated that the electron paramagnetic resonance (EPR) is an efficient method for studying anion-cation (co)doping of nanoscale particles. It has been shown experimentally and by quantummechanical calculations that simultaneous introduction of several ions can be energetically more favorable than their separate inclusion. Possible codoping models have been proposed, and their energy parameters have been calculated.

  3. Relaxation phenomena in supercooled liquid and glassy acetaminophen studied by dielectric, photon correlation and Brillouin light scattering spectroscopies

    NASA Astrophysics Data System (ADS)

    Kwon, Hyun-Joung; Kim, Tae Hyun; Ko, Jae-Hyeon; Hwang, Yoon-Hwae

    2013-01-01

    Relaxation phenomena and acoustic properties of acetaminophen in the glassy and supercooled liquid phase were studied by dielectric, photon correlation and Brillouin spectroscopies. Dielectric and photon correlation studies revealed the structural relaxation process while a new relaxation process was found by dielectric measurement in a much lower frequency range. The acoustic anomalies clearly indicated a glass transition at 293 K and some remnant localized motions in the glassy phase that contributed to the acoustic damping. Partial crystallization in the supercooled liquid phase was signified at temperatures above 318 K by drastic changes in the Brillouin spectrum and decrease in the dielectric strength.

  4. The slow relaxation dynamics in active pharmaceutical ingredients studied by DSC and TSDC: Voriconazole, miconazole and itraconazole.

    PubMed

    Ramos, Joaquim J Moura; Diogo, Hermínio P

    2016-03-30

    The slow molecular mobility of three active pharmaceutical drugs (voriconazole, miconazole and itraconazole) has been studied by differential scanning calorimetry (DSC) and thermally stimulated depolarization currents (TSDC). This study yielded the main kinetic features of the secondary relaxations and of the main (glass transition) relaxation, in particular their distribution of relaxation times. The dynamic fragility of the three glass formers was determined from DSC data (using two different procedures) and from TSDC data. According to our results voriconazole behaves as a relatively strong liquid, while miconazole is moderately fragile and itraconazole is a very fragile liquid. There are no studies in this area published in the literature relating to voriconazole. Also not available in the literature is a slow mobility study by dielectric relaxation spectroscopy in the amorphous miconazole. Apart from that, the results obtained are in reasonable agreement with published works using different experimental techniques.

  5. 2H nuclear magnetic resonance study of deuterated water dynamics in perfluorosulfonic acid ionomer Nafion

    NASA Astrophysics Data System (ADS)

    Han, Jun Hee; Lee, Kyu Won; Lee, Cheol Eui

    2016-11-01

    We have employed deuteron nuclear magnetic resonance (NMR) spectroscopy in order to study the dynamics of the deuterated water (D2O) molecules introduced into a perfluorosulfonic acid ionomer Nafion (NR-211) film. According to the 2H NMR spectral analysis, the deuterated water molecules at low temperatures occupied either relatively rigid or mobile sites up to the temperature TM=240 K where all the deuterated water molecules became mobile. The temperature-dependent NMR linewidths sensitively reflected the motional narrowing of the rigid and mobile sites, and the NMR chemical shift reflected significant changes in the hydrogen bonds of the deuterated water. While a slow- to fast-limit motional transition was manifested at TM in the laboratory-frame NMR spin-lattice relaxation, the rotating-frame spin-lattice relaxation indicated no bulk liquid water state down to 200 K.

  6. Relaxation of NH(a(1)Delta, v = 1) in collisions with H((2)S): an experimental and theoretical study.

    PubMed

    Defazio, P; Petrongolo, C; McBane, G C; Adam, L; Hack, W; Akpinar, S; Schinke, R

    2009-12-31

    Collisions of electronically and vibrationally excited NH(a(1)Delta, v = 1) with H atoms were investigated by experimental, quantum mechanical (QM) wavepacket, and quasiclassical trajectory (QCT) methods. The NH(a(1)Delta, v = 1) total loss rate constant, corresponding to the sum of the NH vibrational relaxation, N((2)D)+H(2) formation, and electronic quenching to NH(X(3)Sigma(-)), was measured at room temperature. Most of the calculations were performed within the Born-Oppenheimer approximation, neglecting electronic quenching due to Renner-Teller coupling because QCT calculations showed that for the loss of NH(a(1)Delta, v = 1) the contribution of quenching is negligible. The QM study included Coriolis couplings, and the QCT study counted only trajectories ending close to a vibrational quantum level of the product diatom. The collisions are dominated by long-lived intermediate complexes, and QM probabilities and cross sections thus exhibit pronounced resonances. QM and QCT cross sections and rate coefficients of the various processes are in very good agreement. The measured rate constant is (9.1 +/- 3.3) x 10(-11) cm(3) s(-1), compared with (14.4 +/- 0.5) x 10(-11) and (15.6 +/- 1.6) x 10(-11) cm(3) s(-1), as obtained from QM and QCT calculations, respectively. The reason for the theoretical overestimation is unknown.

  7. Structure and dynamics in protic ionic liquids: a combined optical Kerr-effect and dielectric relaxation spectroscopy study.

    PubMed

    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.

  8. Study on load relaxation based on hot bending and sizing of Ti6Al4V alloy sheet

    NASA Astrophysics Data System (ADS)

    Po, Liu; Yingying, Zong; Debin, Shan; Bin, Guo

    2013-05-01

    The mechanism of hot sizing following sheet thermal forming of titanium alloy is considered as stress relaxation based on creep flow. A certain amount of internal stress in sheet metal parts can be relaxed during hot-sizing stage and hence the springback can be markedly reduced. Hot v-bending of Ti6Al4V sheet were carried out to study the behavior of load relaxation and springback in specimens after hot sizing, also known as shape retention. Experimental results reveal that load relaxation occurs during hot sizing following sheet v-bending. Reduction of springback angle obtained using hot sizing is obviously larger than that obtained without hot sizing under the same thermal environment. During hot sizing, springback angle decreases with increase in temperature and time, respectively. Load relaxation behavior is affected by loading method, namely constant velocity and two step loading. The linear relation between creep rate and load relaxation rate was deduced in hot-sizing stage. The calculated ratio shows good agreement with experimental data obtained by two-step loading. V-bending and sizing together with appropriate loading method are demonstrated as a good approach for stress relaxation analysis.

  9. [Gastric magnetic resonance study (methods, semiotics)].

    PubMed

    Stashuk, G A

    2003-01-01

    The paper shows the potentialities of gastric study by magnetic resonance imaging (MRI). The methodic aspects of gastric study have been worked out. The MRI-semiotics of the unchanged and tumor-affected wall of the stomach and techniques in examining patients with gastric cancer of various sites are described. Using the developed procedure, MRI was performed in 199 patients, including 154 patients with gastric pathology and 45 control individuals who had no altered gastric wall. Great emphasis is placed on the role of MRI in the diagnosis of endophytic (diffuse) gastric cancer that is of priority value in its morphological structure. MRI was found to play a role in the diagnosis of the spread of a tumorous process both along the walls of the stomach and to its adjacent anatomic structures.

  10. Normal variation of magnetic resonance T1 relaxation times in the human population at 1.5 T using ShMOLLI

    PubMed Central

    2013-01-01

    Background Quantitative T1-mapping is rapidly becoming a clinical tool in cardiovascular magnetic resonance (CMR) to objectively distinguish normal from diseased myocardium. The usefulness of any quantitative technique to identify disease lies in its ability to detect significant differences from an established range of normal values. We aimed to assess the variability of myocardial T1 relaxation times in the normal human population estimated with recently proposed Shortened Modified Look-Locker Inversion recovery (ShMOLLI) T1 mapping technique. Methods A large cohort of healthy volunteers (n = 342, 50% females, age 11–69 years) from 3 clinical centres across two countries underwent CMR at 1.5T. Each examination provided a single average myocardial ShMOLLI T1 estimate using manually drawn myocardial contours on typically 3 short axis slices (average 3.4 ± 1.4), taking care not to include any blood pool in the myocardial contours. We established the normal reference range of myocardial and blood T1 values, and assessed the effect of potential confounding factors, including artefacts, partial volume, repeated measurements, age, gender, body size, hematocrit and heart rate. Results Native myocardial ShMOLLI T1 was 962 ± 25 ms. We identify the partial volume as primary source of potential error in the analysis of respective T1 maps and use 1 pixel erosion to represent “midwall myocardial” T1, resulting in a 0.9% decrease to 953 ± 23 ms. Midwall myocardial ShMOLLI T1 was reproducible with an intra-individual, intra- and inter-scanner variability of ≤2%. The principle biological parameter influencing myocardial ShMOLLI T1 was the female gender, with female T1 longer by 24 ms up to the age of 45 years, after which there was no significant difference from males. After correction for age and gender dependencies, heart rate was the only other physiologic factor with a small effect on myocardial ShMOLLI T1 (6ms/10bpm). Left and right ventricular

  11. Study of Relaxation Dynamics in Mixed Iodide Doped Silver-Vanado-Borate Superionic Glass System

    NASA Astrophysics Data System (ADS)

    Sharma, Poonam; Kanchan, D. K.; Pant, Meenakshi; Gondaliya, Nirali; Jayswal, Manish S.

    2011-07-01

    Electrical conductivity and impedance measurements were carried out for a new mixed metal iodide salt doped silver vanado-borate i.e., [(PbI2-CuI)-Ag2O-V2O5-B2O3] super-ionic glass system. The impedance plots (Z″ vs. Z') for all the prepared glass samples were recorded and found to exhibit depressed semi circles over the studied temperature range. Frequency dependence of the imaginary part of impedance Z″ and the imaginary part of modulus M″ at different temperatures were also investigated. Also, relaxation dynamics in framework of modulus formalism has been discussed.

  12. Solution deuterium NMR quadrupolar relaxation study of heme mobility in myoglobin

    SciTech Connect

    Johnson, R.D.; La Mar, G.N.; Smith, K.M.; Parish, D.W.; Langry, K.C. )

    1989-01-18

    NMR spectroscopy has been used to monitor the quadrupolar relaxation and motional dynamics of {sup 2}H selectively incorporated into skeletal and side chain positions of the heme in sperm whale myoglobin. The hyperfine shifts of the heme resonances in paramagnetic states of myoglobin allow resolution of the signals of interest, and paramagnetic contributions to the observed line widths are shown to be insignificant. The {sup 2}H line widths for the skeletal positions of deuterohemin-reconstituted myoglobin yield a correlation time identical with that of overall protein tumbling (9 ns at 30{degree}C) and hence reflect an immobile heme group. The {sup 2}H NMR line widths of heme methyl groups exhibit motional narrowing indicative of very rapid internal rotation. Hence the methyl rotation is effectively decoupled from the overall protein tumbling, and the residual quadrupolar line width can be used directly to determine the protein tumbling rate. The {sup 2}H NMR lines from heme vinyl groups were found narrower than those from the heme skeleton. However, the range of quadrupolar coupling constants for sp{sup 2} hybridized C-{sup 2}H bonds does not permit an unequivocal interpretation in terms of mobility. 48 refs., 4 figs.

  13. Novel nuclear magnetic resonance techniques for studying biological molecules

    SciTech Connect

    Laws, David D.

    2000-06-01

    Over the fifty-five year history of Nuclear Magnetic Resonance (NMR), considerable progress has been made in the development of techniques for studying the structure, function, and dynamics of biological molecules. The majority of this research has involved the development of multi-dimensional NMR experiments for studying molecules in solution, although in recent years a number of groups have begun to explore NMR methods for studying biological systems in the solid-state. Despite this new effort, a need still exists for the development of techniques that improve sensitivity, maximize information, and take advantage of all the NMR interactions available in biological molecules. In this dissertation, a variety of novel NMR techniques for studying biomolecules are discussed. A method for determining backbone ({phi}/{psi}) dihedral angles by comparing experimentally determined {sup 13}C{sub a}, chemical-shift anisotropies with theoretical calculations is presented, along with a brief description of the theory behind chemical-shift computation in proteins and peptides. The utility of the Spin-Polarization Induced Nuclear Overhauser Effect (SPINOE) to selectively enhance NMR signals in solution is examined in a variety of systems, as are methods for extracting structural information from cross-relaxation rates that can be measured in SPINOE experiments. Techniques for the production of supercritical and liquid laser-polarized xenon are discussed, as well as the prospects for using optically pumped xenon as a polarizing solvent. In addition, a detailed study of the structure of PrP 89-143 is presented. PrP 89-143 is a 54 residue fragment of the prion proteins which, upon mutation and aggregation, can induce prion diseases in transgenic mice. Whereas the structure of the wild-type PrP 89-143 is a generally unstructured mixture of {alpha}-helical and {beta}-sheet conformers in the solid state, the aggregates formed from the PrP 89-143 mutants appear to be mostly {beta}-sheet.

  14. [Muscle relaxants in the morphometric study of the respiratory muscles in human beings].

    PubMed

    Aguar, M C; Gea, J; Orozco-Levi, M; Corominas, J; Pastó, M; Broquetas, J M

    1995-10-01

    The morphological examination of respiratory muscle can be affected by muscular contraction following biopsy. Most morphometric studies of respiratory muscles, however, have been carried out without taking into account this factor, the effect of which can be reduced by using relaxants when taking samples. Objective. To examine the effect of using a relaxant in the morphometric analysis of muscle fibers. We examined 31 muscle samples from 7 patients. Immediately after removal, each pipe was divided in half. One was placed in an isotonic physiological solution and the other in a solution of curare 0.02%. Later, both samples were processed for morphometric study with ATP-ase, NADTH and PAS tincture. Morphological data recorded for the different types of fibers included measurement of minimum diameter (Dmin), atrophy and hypertrophy indices (AI and HI) and heterogeneity of distribution (SDDmin). The Dmin was smaller in fibers transported in a curare solution than in those transported in physiological solution (67 +/- 2 microns vs. 71 +/- microns, p < 0.05). The same was true of SDDmin (13 +/- 3 vs. 12 +/- 3, p < 0.05), HI (300 +/- 88 vs. 457 +/- 107, p < 0.05). Likewise, we found a similar direct correlation between size of fibers processed with physiological solution and those processed in curare (Dmin, r = 0.731, p < 0.001; HI, r = 0.827, p < 0.001; SDDmin, r = 0.636, p < 0.0001). The use of relaxants in processing muscle samples prevents contraction and should be used systematically in the morphological analysis of muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7582429

  15. Observation of structural relaxation during exciton self-trapping via excited-state resonant impulsive stimulated Raman spectroscopy

    SciTech Connect

    Mance, J. G.; Felver, J. J.; Dexheimer, S. L.

    2015-02-28

    We detect the change in vibrational frequency associated with the transition from a delocalized to a localized electronic state using femtosecond vibrational wavepacket techniques. The experiments are carried out in the mixed-valence linear chain material [Pt(en){sub 2}][Pt(en){sub 2}Cl{sub 2}]⋅(ClO{sub 4}){sub 4} (en = ethylenediamine, C{sub 2}H{sub 8}N{sub 2}), a quasi-one-dimensional system with strong electron-phonon coupling. Vibrational spectroscopy of the equilibrated self-trapped exciton is carried out using a multiple pulse excitation technique: an initial pump pulse creates a population of delocalized excitons that self-trap and equilibrate, and a time-delayed second pump pulse tuned to the red-shifted absorption band of the self-trapped exciton impulsively excites vibrational wavepacket oscillations at the characteristic vibrational frequencies of the equilibrated self-trapped exciton state by the resonant impulsive stimulated Raman mechanism, acting on the excited state. The measurements yield oscillations at a frequency of 160 cm{sup −1} corresponding to a Raman-active mode of the equilibrated self-trapped exciton with Pt-Cl stretching character. The 160 cm{sup −1} frequency is shifted from the previously observed wavepacket frequency of 185 cm{sup −1} associated with the initially generated exciton and from the 312 cm{sup −1} Raman-active symmetric stretching mode of the ground electronic state. We relate the frequency shifts to the changes in charge distribution and local structure that create the potential that stabilizes the self-trapped state.

  16. Magnetic Resonance Studies of Energy Storage Materials

    NASA Astrophysics Data System (ADS)

    Vazquez Reina, Rafael

    In today's society there is high demand to have access to energy for portable devices in different forms. Capacitors with high performance in small package to achieve high charge/discharge rates, and batteries with their ability to store electricity and make energy mobile are part of this demand. The types of internal dielectric material strongly affect the characteristics of a capacitor, and its applications. In a battery, the choice of the electrolyte plays an important role in the Solid Electrolyte Interphase (SEI) formation, and the cathode material for high output voltage. Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) spectroscopy are research techniques that exploit the magnetic properties of the electron and certain atomic nuclei to determine physical and chemical properties of the atoms or molecules in which they are contained. Both EPR and NMR spectroscopy technique can yield meaningful structural and dynamic information. Three different projects are discussed in this dissertation. First, High energy density capacitors where EPR measurements described herein provide an insight into structural and chemical differences in the dielectric material of a capacitor. Next, as the second project, Electrolyte solutions where an oxygen-17 NMR study has been employed to assess the degree of preferential solvation of Li+ ions in binary mixtures of EC (ethylene carbonate) and DMC (dimethyl carbonate) containing LiPF6 (lithium hexafluo-rophosphate) which may be ultimately related to the SEI formation mechanism. The third project was to study Bismuth fluoride as cathode material for rechargeable batteries. The objective was to study 19F and 7Li MAS NMR of some nanocomposite cathode materials as a conversion reaction occurring during lithiation and delithation of the BiF3/C nanocomposite.

  17. Functional magnetic resonance imaging studies of language.

    PubMed

    Small, Steven L; Burton, Martha W

    2002-11-01

    Functional neuroimaging of language builds on almost 150 years of study in neurology, psychology, linguistics, anatomy, and physiology. In recent years, there has been an explosion of research using functional imaging technology, especially positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), to understand the relationship between brain mechanisms and language processing. These methods combine high-resolution anatomic images with measures of language-specific brain activity to reveal neural correlates of language processing. This article reviews some of what has been learned about the neuroanatomy of language from these imaging techniques. We first discuss the normal case, organizing the presentation according to the levels of language, encompassing words (lexicon), sound structure (phonemes), and sentences (syntax and semantics). Next, we delve into some unusual language processing circumstances, including second languages and sign languages. Finally, we discuss abnormal language processing, including developmental and acquired dyslexia and aphasia.

  18. Studies of structural, optical, dielectric relaxation and ac conductivity of different alkylbenzenesulfonic acids doped polypyrrole nanofibers

    NASA Astrophysics Data System (ADS)

    Hazarika, J.; Kumar, A.

    2016-01-01

    Polypyrrole (PPy) nanofibers doped with alkylbenzenesulfonic acids (ABSA) have been synthesized using interfacial polymerization method. HRTEM studies confirm the formation of PPy nanofibers with average diameter ranging from 13 nm to 25 nm. Broad X-ray diffraction peak in 2 θ range 20-23.46° reveals amorphous structure of PPy nanofibers. The ordering or crystallinity of polymer chains increases, while their interplanar spacing (d) and interchain separation (R) decreases for short alkyl chain ABSA doped PPy nanofibers. FTIR studies reveal that short alkyl chain ABSA doped PPy nanofibers show higher value of "effective conjugation length". PPy nanofibers doped with short alkyl chain ABSA dopant exhibit smaller optical band gap. TGA studies show enhanced thermal stability of short alkyl chain ABSA doped PPy nanofibers. Decrease in dielectric permittivity ε ‧ (ω) with increasing frequency suggests presence of electrode polarization effects. Linear decrease in dielectric loss ε ″ (ω) with increasing frequency suggests dominant effect of dc conductivity process. Low value of non-exponential exponent β (<1) reveals non-Debye relaxation of charge carriers. Scaling of imaginary modulus (M ″) reveals that the charge carriers follow the same relaxation mechanism. Moreover, the charge carriers in PPy nanofibers follow the correlated barrier hopping (CBH) transport mechanism.

  19. Nuclear magnetic resonance studies of liquids morphology inside partially saturated porous media

    NASA Astrophysics Data System (ADS)

    Nechifor, Ruben; Badea, Codruta; Ardelean, Ioan

    2009-08-01

    In the present contribution we are investigating the relationship between liquid morphology and relaxation time distribution in partially saturated pores. The filling fluids are acetone (polar) and tetradecane (nonpolar). The porous sample is a silica glass (Vitrapor#5) with the nominal mean pore size is d = 1 μm (± 0.6 μm). All nuclear magnetic resonance relaxation experiments are performed at 20C using a NMR instrument operable at 20 MHz proton resonance frequency. The experimental results are compared with a two phase exchange model providing us information on the strength of surface relaxation.

  20. Methyl quantum tunneling and nitrogen-14 NQR NMR studies using a SQUID magnetic resonance spectrometer

    SciTech Connect

    Black, B.E. |

    1993-07-01

    Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) techniques have been very successful in obtaining molecular conformation and dynamics information. Unfortunately, standard NMR and NQR spectrometers are unable to adequately detect resonances below a few megahertz due to the frequency dependent sensitivity of their Faraday coil detectors. For this reason a new spectrometer with a dc SQUID (Superconducting Quantum Interference Device) detector, which has no such frequency dependence, has been developed. Previously, this spectrometer was used to observe {sup 11}B and {sup 27}Al NQR resonances. The scope of this study was increased to include {sup 23}Na, {sup 51}V, and {sup 55}Mn NQR transitions. Also, a technique was presented to observe {sup 14}N NQR resonances through cross relaxation of the nitrogen polarization to adjacent proton spins. When the proton Zeeman splitting matches one nitrogen quadrupoler transition the remaining two {sup 14}N transitions can be detected by sweeping a saturating rf field through resonance. Additionally, simultaneous excitation of two nitrogen resonances provides signal enhancement which helps to connect transitions from the same site. In this way, nitrogen-14 resonances were observed in several amino acids and polypeptides. This spectrometer has also been useful in the direct detection of methyl quantum tunneling splittings at 4.2 K. Tunneling, frequencies of a homologous series of carboxylic acids were measured and for solids with equivalent crystal structures, an exponential correlation between the tunneling frequency and the enthalpy of fusion is observed. This correlation provides information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

  1. Phosphorus magnetic resonance spectroscopy studies in schizophrenia.

    PubMed

    Yuksel, Cagri; Tegin, Cuneyt; O'Connor, Lauren; Du, Fei; Ahat, Ezgi; Cohen, Bruce M; Ongur, Dost

    2015-09-01

    Phosphorus magnetic resonance spectroscopy ((31)P MRS) allows in vivo quantification of phosphorus metabolites that are considered to be related to membrane turnover and energy metabolism. In schizophrenia (SZ), (31)P MRS studies found several abnormalities in different brain regions suggesting that alterations in these pathways may be contributing to the pathophysiology. In this paper, we systematically reviewed the (31)P MRS studies in SZ published to date by taking patient characteristics, medication status and brain regions into account. Publications written in English were searched on http://www.ncbi.nlm.nih.gov/pubmed/, by using the keywords 'phosphomonoester', 'phosphodiester', 'ATP', 'phosphocreatine', 'phosphocholine', 'phosphoethanolamine','glycerophosphocholine', 'glycerophosphoethanolamine', 'pH', 'schizophrenia', and 'MRS'. Studies that measured (31)P metabolites in SZ patients were included. This search identified 52 studies. Reduced PME and elevated PDE reported in earlier studies were not replicated in several subsequent studies. One relatively consistent pattern was a decrease in PDE in chronic patients in the subcortical structures. There were no consistent patterns for the comparison of energy related phosphorus metabolites between patients and controls. Also, no consistent pattern emerged in studies seeking relationship between (31)P metabolites and antipsychotic use and other clinical variables. Despite emerging patterns, methodological heterogeneities and shortcomings in this literature likely obscure consistent patterns among studies. We conclude with recommendations to improve study designs and (31)P MRS methods in future studies. We also stress the significance of probing into the dynamic changes in energy metabolism, as this approach reveals abnormalities that are not visible to steady-state measurements. PMID:26228415

  2. Dielectric relaxation studies of ion diffusion into low-k dielectrics

    NASA Astrophysics Data System (ADS)

    Raja, Archana; Shaw, Thomas; Liniger, Eric; Chen, Fen; Grill, Alfred; Borja, Juan; Bonilla, Griselda; Plawsky, Joel; Heinz, Tony; Laibowitz, Robert

    2014-03-01

    High speed interconnects in advanced integrated circuits require ultra-low-k dielectrics to reduce the RC time constant. Reduction of the dielectric constant in these films is typically achieved via incorporation of nanopores in materials containing silicon, carbon, oxygen and hydrogen (SiCOH). Trap states build-up as dielectric breakdown is approached and increased leakage is observed. To understand the mechanism of breakdown we study nanoporous SiCOH films of k=2.4 to 2.7 primarily using dielectric relaxation. Dielectric films, in the thickness range of 40 nm, are incorporated into interwoven capacitor structures. To quantify dielectric relaxation in the pre-breakdown regime, capacitance and dielectric losses are determined as a function of frequency and temperature. Through these dielectric measurements, we have obtained activation energies in the range of 0.1-0.2 eV for humidified and annealed capacitors; and 0.9-1.2 eV for copper ion incursion into the dielectric. We also deduce a charge center density of 1015/cm3. Our measurements provide an estimate of the impurity content and changes in activation energy with annealing and other fabrication parameters.

  3. Direct 13C-detection for carbonyl relaxation studies of protein dynamics.

    PubMed

    Pasat, Gabriela; Zintsmaster, John S; Peng, Jeffrey W

    2008-08-01

    We describe a method that uses direct 13C-detection for measuring rotating-frame carbonyl (13CO) relaxation rates to describe protein functional dynamics. Key advantages of method include the following: (i) unique access to 13CO groups that lack a scalar-coupled 15N-1H group; (ii) insensitivity to 15N/1H exchange-broadening that can derail 1H-detected 15N and HNCO methods; (iii) avoidance of artifacts caused by incomplete water suppression. We demonstrate the approach for both backbone and side-chain 13CO groups. Accuracy of the 13C-detected results is supported by their agreement with those obtained from established HNCO-based approaches. Critically, we show that the 13C-detection approach provides access to the 13CO groups of functionally important residues that are invisible via 1H-detected HNCO methods because of exchange-broadening. Hence, the 13C-based method fills gaps inherent in canonical 1H-detected relaxation experiments, and thus provides a novel complementary tool for NMR studies of biomolecular flexibility. PMID:18514001

  4. Changes in Porcine Muscle Water Characteristics during Growth—An in Vitro Low-Field NMR Relaxation Study

    NASA Astrophysics Data System (ADS)

    Bertram, Hanne Christine; Rasmussen, Marianne; Busk, Hans; Oksbjerg, Niels; Karlsson, Anders Hans; Andersen, Henrik Jørgen

    2002-08-01

    This study investigates the effects of developmental stage and muscle type on the mobility and distribution of water within skeletal muscles, using low-field 1H-NMR transverse relaxation measurements in vitro on four different porcine muscles ( M. longissimus dorsi, M. semitendinosus, M. biceps femoris, M. vastus intermedius) from a total of 48 pigs slaughtered at various weight classes between 25 kg and 150 kg. Principal component analysis (PCA) revealed effects of both slaughter weight and muscle type on the transverse relaxation decay. Independent of developmental stage and muscle type, distributed exponential analysis of the NMR T 2 relaxation data imparted the existence of three distinct water populations, T 2b, T 21, and T 22, with relaxation times of approximately 1-10, 45-120, and 200-500 ms, respectively. The most profound change during muscle growth was a shift toward faster relaxation in the intermediate time constant, T 21. It decreased by approx. 24% in all four muscle types during the period from 25 to 150 kg live weight. Determination of dry matter, fat, and protein content in the muscles showed that the changes in relaxation time of the intermediate time constant, T 21, during growth should be ascribed mainly to a change in protein content, as the protein content explained 77% of the variation in the T 21 time constant. Partial least squares (PLS) regression revealed validated correlations in the region of 0.58 to 0.77 between NMR transverse relaxation data and muscle development for all the four muscle types, which indicates that NMR relaxation measurements may be used in the prediction of muscle developmental stage.

  5. Relaxation mechanisms affecting magneto-optical resonances in an extremely thin cell: Experiment and theory for the cesium D1 line

    NASA Astrophysics Data System (ADS)

    Auzinsh, M.; Berzins, A.; Ferber, R.; Gahbauer, F.; Kalnins, U.; Kalvans, L.; Rundans, R.; Sarkisyan, D.

    2015-02-01

    We have measured magneto-optical signals obtained by exciting the D1 line of cesium atoms confined to an extremely thin cell (ETC), whose walls are separated by less than 1 μ m , and developed an improved theoretical model to describe these signals with experimental precision. The theoretical model was based on the optical Bloch equations and included all neighboring hyperfine transitions, the mixing of the magnetic sublevels in an external magnetic field, and the Doppler effect, as in previous studies. However, in order to model the extreme conditions in the ETC more realistically, the model was extended to include a unified treatment of transit relaxation and wall collisions with relaxation rates that were obtained directly from the thermal velocities of the atoms and the length scales involved. Furthermore, the interactions of the atoms with different regions of the laser beam were modeled separately to account for the varying laser beam intensity over the beam profile as well as saturation effects that become important near the center of the beam at the relatively high laser intensities used during the experiments in order to obtain measurable signals. The model described the experimentally measured signals for laser intensities for magnetic fields up to 55 G and laser intensities up to 1 W/cm2 with excellent agreement.

  6. ELECTRON SPIN RESONANCE STUDIES ON MELANIN.

    PubMed

    BLOIS, M S; ZAHLAN, A B; MALING, J E

    1964-11-01

    Electron spin resonance (e.s.r.) observations of squid melanin have been conducted over the temperature range 500 degrees K to 4.2 degrees K, and the effect of various chemical treatments of the melanin upon the e.s.r. spectrum has been studied. The findings have shown that the paramagnetism of this melanin follows the Curie Law from 500 degrees K to 4.2 degrees K, that the spin signal can be eliminated by the addition of Cu(++) to the melanin, and that the optical and e.s.r. absorptions of melanin are independent since either can be reduced or eliminated without affecting the other. Similar studies on synthetic melanins produced by autoxidation or by enzymatic oxidation of a number of biphenols were carried out. It was found that the e.s.r. signals of these synthetic melanins were strikingly similar (with respect to line width, line shape, and g-value) with those of squid melanin. It is concluded that the unpaired electrons observed are associated with trapped free radicals in the melanin polymer, that the biosynthesis of melanin may involve a free radical mechanism, and that these physical data are in accord with the concept of Nicolaus that melanin is a highly irregular, three-dimensional, polymer. PMID:14232133

  7. Analytical and experimental study of resonance ignition tubes

    NASA Technical Reports Server (NTRS)

    Stabinsky, L.

    1973-01-01

    The application of the gas-dynamic resonance concept was investigated in relation to ignition of rocket propulsion systems. Analytical studies were conducted to delineate the potential uses of resonance ignition in oxygen/hydrogen bipropellant and hydrazine monopropellant rocket engines. Experimental studies were made to: (1) optimize the resonance igniter configuration, and (2) evaluate the ignition characteristics when operating with low temperature oxygen and hydrogen at the inlet to the igniter.

  8. RESPECT: Neutron resonance spin-echo spectrometer for extreme studies

    NASA Astrophysics Data System (ADS)

    Georgii, R.; Kindervater, J.; Pfleiderer, C.; Böni, P.

    2016-11-01

    We propose the design of a REsonance SPin-echo spECtrometer for exTreme studies, RESPECT, that is ideally suited for the exploration of non-dispersive processes such as diffusion, crystallization, slow dynamics, tunneling processes, crystal electric field excitations, and spin fluctuations. It is a variant of the conventional neutron spin-echo technique (NSE) by (i) replacing the long precession coils by pairs of longitudinal neutron spin-echo coils combined with RF-spin flippers and (ii) by stabilizing the neutron polarization with small longitudinal guide fields that can in addition be used as field subtraction coils thus allowing to adjust the field integrals over a range of 8 orders of magnitude. Therefore, the dynamic range of RESPECT can in principle be varied over 8 orders of magnitude in time, if neutrons with the required energy are made available. Similarly as for existing NSE-spectrometers, spin echo times of up to approximately 1 μs can be reached if the divergence and the correction elements are properly adjusted. Thanks to the optional use of neutron guides and the fact that the currents for the correction coils are much smaller than in standard NSE, intensity gains of at least one order of magnitude are expected, making the concept of RESPECT also competitive for operation at medium flux neutron sources. RESPECT can also be operated in a MIEZE configuration allowing the investigation of relaxation processes in depolarizing environments as they occur when magnetic fields are applied at the sample position, i.e. for the investigation of the dynamics of flux lines in superconductors, magnetic fluctuations in ferromagnetic materials, and samples containing hydrogen.

  9. Long-term aging of elastomers: Chemical stress relaxation of fluorosilicone rubber and other studies

    NASA Technical Reports Server (NTRS)

    Kalfayan, S. H.; Mazzeo, A. A.; Silver, R. H.

    1971-01-01

    Aerospace applications of elastomers are considered, including: propellant binders, bladder materials for liquid propellant expulsion systems, and fuel tank sealants for high-speed aircraft. A comprehensive molecular theory for mechanical properties of these materials has been developed but has only been tested experimentally in cases where chemical degradation processes are excluded. Hence, a study is being conducted to ascertain the nature, extent, and rate of chemical changes that take place in some elastomers of interest. Chemical changes that may take place in the fluorosilicone elastomer, LS 420, which is regarded as a fuel and high-temperature-resistant rubber are investigated. The kinetic analysis of the chemical stress relaxation and gel permeation chromatography studies comprise the major portion of the report.

  10. A study of trapped mode resonances in asymmetric X-shape resonator for frequency selective surface

    NASA Astrophysics Data System (ADS)

    Chen, Kejian; Liu, Hong; Wang, Yiqi; Zhu, Yiming

    2013-08-01

    FSS is a two-dimensional periodic array of resonating metallic-dielectric structures, When FSS device steps into Terahertz range from microwave range, it is studied as THz functional components (such as Terahertz filter, Terahertz biochemical sensor, etc.) to promote the functionality of the THz spectroscopy/imaging system. When the device requires a narrow band transmission window for frequency selecting or a high electric field concentration in certain area to improve its sensitivity for sensing, normally, a high quality (Q) resonant structure can give helps. Recently, high-Q resonance induced by trapped mode resonance i studied widely in FSS research areas. To induce trapped mode resonance, one can simply break the symmetric of the unit structure of FSS. In this paper, several asymmetric X-shaped resonators for FSS working in terahertz range have been studied numerically. To compare the behaviour of X-shape resonator under different conditions (with additional part: Heart lines, Shoulder lines, Wrap or Shoes squares), a common platform (θ=60, θis angle of X shape) which is suitable for most of cases was used to make the study more meaningful. As the field enhancement behaviour is related to the trapped mode introduced by the asymmetric structure, we propose such kind of device to be used as a high quality filter or as a sensing element for biochemical samples.

  11. Electron Paramagnetic Resonance and Electron-Nuclear Double Resonance Studies of the Reactions of Cryogenerated Hydroperoxoferric–Hemoprotein Intermediates

    PubMed Central

    2015-01-01

    The fleeting ferric peroxo and hydroperoxo intermediates of dioxygen activation by hemoproteins can be readily trapped and characterized during cryoradiolytic reduction of ferrous hemoprotein–O2 complexes at 77 K. Previous cryoannealing studies suggested that the relaxation of cryogenerated hydroperoxoferric intermediates of myoglobin (Mb), hemoglobin, and horseradish peroxidase (HRP), either trapped directly at 77 K or generated by cryoannealing of a trapped peroxo-ferric state, proceeds through dissociation of bound H2O2 and formation of the ferric heme without formation of the ferryl porphyrin π-cation radical intermediate, compound I (Cpd I). Herein we have reinvestigated the mechanism of decays of the cryogenerated hydroperoxyferric intermediates of α- and β-chains of human hemoglobin, HRP, and chloroperoxidase (CPO). The latter two proteins are well-known to form spectroscopically detectable quasistable Cpds I. Peroxoferric intermediates are trapped during 77 K cryoreduction of oxy Mb, α-chains, and β-chains of human hemoglobin and CPO. They convert into hydroperoxoferric intermediates during annealing at temperatures above 160 K. The hydroperoxoferric intermediate of HRP is trapped directly at 77 K. All studied hydroperoxoferric intermediates decay with measurable rates at temperatures above 170 K with appreciable solvent kinetic isotope effects. The hydroperoxoferric intermediate of β-chains converts to the S = 3/2 Cpd I, which in turn decays to an electron paramagnetic resonance (EPR)-silent product at temperature above 220 K. For all the other hemoproteins studied, cryoannealing of the hydroperoxo intermediate directly yields an EPR-silent majority product. In each case, a second follow-up 77 K γ-irradiation of the annealed samples yields low-spin EPR signals characteristic of cryoreduced ferrylheme (compound II, Cpd II). This indicates that in general the hydroperoxoferric intermediates relax to Cpd I during cryoanealing at low temperatures, but

  12. A proof-of-concept study on the combination of repetitive transcranial magnetic stimulation and relaxation techniques in chronic tinnitus.

    PubMed

    Kreuzer, Peter M; Poeppl, Timm B; Bulla, Jan; Schlee, Winfried; Lehner, Astrid; Langguth, Berthold; Schecklmann, Martin

    2016-10-01

    Interference of ongoing neuronal activity and brain stimulation motivated this study to combine repetitive transcranial magnetic stimulation (rTMS) and relaxation techniques in tinnitus patients. Forty-two patients were enrolled in this one-arm proof-of-concept study to receive ten sessions of rTMS applied to the left dorsolateral prefrontal cortex and temporo-parietal cortex. During stimulation, patients listened to five different kinds of relaxation audios. Variables of interest were tinnitus questionnaires, tinnitus numeric rating scales, depressivity, and quality of life. Results were compared to results of historical control groups having received the same rTMS protocol (active control) and sham treatment (placebo) without relaxation techniques. Thirty-eight patients completed the treatment, drop-out rates and adverse events were low. Responder rates (reduction in tinnitus questionnaire (TQ) score ≥5 points 10 weeks after treatment) were 44.7 % in the study, 27.8 % in the active control group, and 21.7 % in the placebo group, differing between groups on a near significant level. For the tinnitus handicap inventory (THI), the main effect of group was not significant. However, linear mixed model analyses showed that the relaxation/rTMS group differed significantly from the active control group showing steeper negative THI trend for the relaxation/rTMS group indicating better amelioration over the course of the trial. Deepness of relaxation during rTMS and selection of active relaxation vs. passive listening to music predicted larger TQ. All remaining secondary outcomes turned out non-significant. This combined treatment proved to be a safe, feasible and promising approach to enhance rTMS treatment effects in chronic tinnitus. PMID:27315823

  13. An optical-optical double resonance probe of the lowest triplet state of jet-cooled thiophosgene: Rovibronic structures and electronic relaxation

    NASA Astrophysics Data System (ADS)

    Fujiwara, Takashige; Lim, Edward C.; Judge, Richard H.; Moule, David C.

    2006-03-01

    The vibrational structure, rotational structure, and electronic relaxation of the "dark" T1A23(n,π*) state of jet-cooled thiophosgene have been investigated by two-color S2←T1←S0 optical-optical double resonance (OODR) spectroscopy, which monitors the S2→S0 fluorescence generated by S2←T1 excitation. This method is capable of isolating the T1 vibrational structure into a1, b1, and b2 symmetry blocks. The fluorescence-detected vibrational structure of the Tz spin state of T1 shows that the CS stretching frequency as well as the barrier height for pyramidal deformation are significantly greater in the A23(n,π*) state than in the corresponding A21(n,π*) state. The differing vibrational parameters of the T1 thiophosgene relative to the S1 thiophosgene can be attributed to the motions of unpaired electrons that are better correlated when they are in the excited singlet state than when they are in the triplet state of same electron configuration. A set of T1 structural parameters and the information concerning the T1 spin states have been obtained from least-square fittings of the rotationally resolved T1←S0 excitation spectrum. The nearly degenerate ∣x⟩ and ∣y⟩ spin states are well removed from ∣z⟩ spin component, indicating that T1 thiophosgene is a good example of case (ab) coupling. The decay of the ∣z⟩ spin state of T1 thiophosgene, obtained from time-resolved S2←T1←S0 OODR experiment, is characteristic of strong-coupling intermediate-case decay in which an initial rapid decay is followed by recurrences and/or a long-lived quasiexponential decay.

  14. Magnetic resonance imaging of the calcaneus: preliminary assessment of trabecular bone-dependent regional variations in marrow relaxation time compared with dual X-ray absorptiometry

    NASA Technical Reports Server (NTRS)

    Guglielmi, G.; Selby, K.; Blunt, B. A.; Jergas, M.; Newitt, D. C.; Genant, H. K.; Majumdar, S.

    1996-01-01

    RATIONALE AND OBJECTIVES: Marrow transverse relaxation time (T2*) in magnetic resonance (MR) imaging may be related to the density and structure of the surrounding trabecular network. We investigated regional variations of T2* in the human calcaneus and compared the findings with bone mineral density (BMD), as measured by dual X-ray absorpiometry (DXA). Short- and long-term precisions were evaluated first to determine whether MR imaging would be useful for the clinical assessment of disease status and progression in osteoporosis. METHODS: Gradient-recalled echo MR images of the calcaneus were acquired at 1.5 T from six volunteers. Measurements of T2* were compared with BMD and (for one volunteer) conventional radiography. RESULTS: T2* values showed significant regional variation; they typically were shortest in the superior region of the calcaneus. There was a linear correlation between MR and DXA measurements (r = .66 for 1/T2* versus BMD). Differences in T2* attributable to variations in analysis region-of-interest placement were not significant for five of the six volunteers. Sagittal MR images had short- and long-term precision errors of 4.2% and 3.3%, respectively. For DXA, the precision was 1.3% (coefficient of variation). CONCLUSION: MR imaging may be useful for trabecular bone assessment in the calcaneus. However, given the large regional variations in bone density and structure, the choice of an ROI is likely to play a major role in the accuracy, precision, and overall clinical efficacy of T2* measurements.

  15. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: The Effect of Orientation Relaxation on Polymer Melt Crystallization Studied by Monte Carlo Simulations

    NASA Astrophysics Data System (ADS)

    Wang, Mao-Xiang

    2009-07-01

    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.

  16. Study of the operation temperature in the spin-exchange relaxation free magnetometer

    SciTech Connect

    Fang, Jiancheng; Li, Rujie Duan, Lihong; Chen, Yao; Quan, Wei

    2015-07-15

    We study the influence of the cell temperature on the sensitivity of the spin-exchange relaxation free (SERF) magnetometer and analyze the possibility of operating at a low temperature. Utilizing a 25 × 25 × 25 mm{sup 3} Cs vapor cell with a heating temperature of 85 {sup ∘}C, which is almost half of the value of potassium, we obtain a linewidth of 1.37 Hz and achieve a magnetic field sensitivity of 55 fT/Hz{sup 1/2} in a single channel. Theoretical analysis shows that fundamental sensitivity limits of this device with an active volume of 1 cm{sup 3} could approach 1 fT/Hz{sup 1/2}. Taking advantage of the higher saturated vapor pressure, SERF magnetometer based on Cs opens up the possibility for low cost and portable sensors and is particularly appropriate for lower temperature applications.

  17. Study of the operation temperature in the spin-exchange relaxation free magnetometer.

    PubMed

    Fang, Jiancheng; Li, Rujie; Duan, Lihong; Chen, Yao; Quan, Wei

    2015-07-01

    We study the influence of the cell temperature on the sensitivity of the spin-exchange relaxation free (SERF) magnetometer and analyze the possibility of operating at a low temperature. Utilizing a 25 × 25 × 25 mm(3) Cs vapor cell with a heating temperature of 85 °C, which is almost half of the value of potassium, we obtain a linewidth of 1.37 Hz and achieve a magnetic field sensitivity of 55 fT/Hz(1/2) in a single channel. Theoretical analysis shows that fundamental sensitivity limits of this device with an active volume of 1 cm(3) could approach 1 fT/Hz(1/2). Taking advantage of the higher saturated vapor pressure, SERF magnetometer based on Cs opens up the possibility for low cost and portable sensors and is particularly appropriate for lower temperature applications.

  18. Molecular-dynamics study of amorphous SiO{sub 2} relaxation

    SciTech Connect

    Fadhilah, Irfan Muhammad; Rosandi, Yudi

    2015-09-30

    Using Molecular-Dynamics simulation we observed the generation of amorphous SiO{sub 2} target from a randomly distributed Si and O atoms. We applied a sequence of annealing of the target with various temperature and quenching to room temperature. The relaxation time required by the system to form SiO{sub 4} tetrahedral mesh after a relatively long simulation time, is studied. The final amorphous target was analyzed using the radial distribution function method, which can be compared with the available theoretical and experimental data. We found that up to 70% of the target atoms form the tetrahedral SiO{sub 4} molecules. The number of formed tetrahedral increases following the growth function and the rate of SiO{sub 4} formation follows Arrhenius law, depends on the annealing temperature. The local structure of amorphous SiO{sub 2} after this treatment agrees well with those reported in some literatures.

  19. Study on the temperature-dependent coupling among viscosity, conductivity and structural relaxation of ionic liquids.

    PubMed

    Yamaguchi, Tsuyoshi; Yonezawa, Takuya; Koda, Shinobu

    2015-07-15

    The frequency-dependent viscosity and conductivity of three imidazolium-based ionic liquids were measured at several temperatures in the MHz region, and the results are compared with the intermediate scattering functions determined by neutron spin echo spectroscopy. The relaxations of both the conductivity and the viscosity agree with that of the intermediate scattering function at the ionic correlation when the relaxation time is short. As the relaxation time increases, the relaxations of the two transport properties deviate to lower frequencies than that of the ionic structure. The deviation begins at a shorter relaxation time for viscosity than for conductivity, which explains the fractional Walden rule between the zero-frequency values of the shear viscosity and the molar conductivity.

  20. Methodology for solid state NMR off-resonance study of molecular dynamics in heteronuclear systems.

    PubMed

    Jurga, Kazimierz; Woźniak-Braszak, Aneta; Baranowski, Mikołaj

    2015-10-01

    Methodology for the study of dynamics in heteronuclear systems in the laboratory frame was described in the previous paper [1]. Now the methodology for the study of molecular dynamics in the solid state heteronuclear systems in the rotating frame is presented. The solid state NMR off-resonance experiments were carried out on a homemade pulse spectrometer operating at the frequency of 30.2 MHz for protons. This spectrometer includes a specially designed probe which contains two independently tuned and electrically isolated coils installed in the coaxial position on the dewar. A unique probe design allows working at three slightly differing frequencies off and on resonance for protons and at the frequency of 28.411 MHz for fluorine nuclei with complete absence of their electrical interference. The probe allows simultaneously creating rf magnetic fields at off-resonance frequencies within the range of 30.2-30.6 MHz and at the frequency of 28.411 MHz. Presented heteronuclear cross-relaxation off-resonance experiments in the rotating frame provide information about molecular dynamics.

  1. Study of acoustic resonance of cascades

    NASA Astrophysics Data System (ADS)

    Honjo, M.; Tominaga, T.

    Discrete sounds and vibrations from guide vanes due to acoustic resonance in the vane flow path, are experimentally investigated. Other causes of pure sounds in stationary vanes are considered, such as direct radiation from wake shedding vortices, bubble vortices or leading edges, and radial or axial modes of air columns. Two-dimensional cascade tests are performed under various conditions, and the data are compared with theoretical results of flat plate cascades. Three-dimensional ducted guide vane model tests are carried out to apply prototype guide vanes, and to confirm the resonance of the two-dimensional tests. Results show that frequency is more sensitive to chord length than pitch length, and the ratio of the fluctuation frequency to fluid sound velocity/pitch length is independent of the scale. Bubble vortices on concave surfaces or leading edges are not exciting sources; and under the limit of solidity, no exciting energy can generate acoustic resonance in correspondence to the mode.

  2. Effects of hydrophobic treatments of stone on pore water studied by continuous distribution analysis of NMR relaxation times.

    PubMed

    Appolonia, L; Borgia, G C; Bortolotti, V; Brown, R J; Fantazzini, P; Rezzaro, G

    2001-01-01

    The effects of protective hydrophobic products applied to porous media such as stone or mortar vary greatly with the product, the porous medium, and the mode of application. Nuclear Magnetic Resonance (NMR) measurements on fluids in the pore spaces of both treated and untreated samples can give information on the contact of the fluid with the internal surfaces, which is affected by all the above factors. Continuous distributions of relaxation times T(1) and T(2) of water in the pores of both synthetic and natural porous media were obtained before and after hydrophobic treatment. The synthetic porous media are ceramic filter materials characterized by narrow distributions of pore dimensions and show that the treatment does not produce large changes in the relaxation times of the water. For three travertine samples most of a long relaxation time component, presumably from the largest pores, remains after treatment, while the amplitude of an intermediate component is greatly reduced. For three pudding-stone samples, treatment leads to a substantial loss from the long component and an even greater loss from the intermediate component. PMID:11445343

  3. Resonant Auger studies of metallic systems

    SciTech Connect

    Coulthard, I.; Antel, W. J., Jr.; Frigo, S. P.; Freeland, J. W.; Moore, J.; Calaway, W. S.; Pellin, M. J.; Mendelsohn, M.; Sham, T. K.; Naftel, S. J.; Stampfl, A. P. J.

    1999-10-21

    Results of resonant Auger spectroscopy experiments are presented for Cu, Co, and oxidized Al. Sub-lifetime narrowing of Auger spectra and generation of sub-lifetime narrowed absorption spectra constructed from Auger yield measurements, were observed. Resonant Auger yields are used to identify three valence states of oxidized Al. Partial absorption yield spectra were derived giving detailed electronic information and thickness information for the various chemical states of the bulk metal, the passivating aluminum oxide layer, and the metal-oxide interface region. In addition, the total absorption yield spectrum for the oxidized Al sample was constructed from the partial yield data, supporting the consistency of the authors method.

  4. Spin-lattice relaxation study of the methyl proton dynamics in solid 9,10-dimethyltriptycene (DMT).

    PubMed

    Piślewski, N; Tritt-Goc, J; Bielejewski, M; Rachocki, A; Ratajczyk, T; Szymański, S

    2009-06-01

    Proton spin-lattice relaxation studies are performed for powder samples of 9,10-dimethyltriptycene (DMT) and its isotopomer DMT-d(12) in which all the non-methyl protons in the molecule are replaced by deuterons. The relaxation data are interpreted in terms of the conventional relaxation theory based on the random jump model in which the Pauli correlations between the relevant spin and torsional states are discarded. The Arrhenius activation energies, obtained from the relaxation data, 25.3 and 24.8 kJ mol(-1) for DMT and DMT-d(12), respectively, are very high as for the methyl groups. The validity of the jump model in the present case is considered from the perspective of Haupt theory in which the Pauli principle is explicitly invoked. To this purpose, the dynamic quantities entering the Haupt model are reinterpreted in the spirit of the damped quantum rotation (DQR) approach introduced recently for the purpose of NMR lineshape studies of hindered molecular rotators. Theoretical modelling of the relevant methyl group dynamics, based on the DQR theory, was performed. From these calculations it is inferred that direct assessments of the torsional barrier heights, based on the Arrhenius activation energies extracted from relaxation data, should be treated with caution.

  5. Experimental study of effect of stress-relaxation bone plate on fracture healing.

    PubMed

    Zhang, Xianlong; Zhang, Wei; Dai, Kerong

    2000-11-15

    OBJECTIVE: To study the change of the stress shi elding rate of stress-relaxation plate in vivo and its influence on fracture he aling. METHODS: The diaphyses of bilateral tibias in 70 New Zealand ra bbits were osteotomized and fixed with stress-relaxation plates (SRP, the SRP g roup) and rigid plates (RP, the RP group), respectively. The fracture healing pr ocess in these 2 groups was investigated by radiography, light and polarized l ight microscopy and biomechanical test at 2 to 48 weeks postoperatively. RESULTS: Early after fixation the stress shielding rate was abo ut 70% in both groups. While in the SRP group the stress shielding rate decrease d gradually as time passed, which was significantly lower than that of the RP gr oup (P<0.05) by the end of the 8th postoperative week, and stabilized at the level of about 27% at 36-48 weeks after fixation. Abund ant external callus associated with the formation of cartilaginous callus could be observed in the SRP group at 2-4 weeks postoperatively. The transformation o f the callus into the lamellar bone began at 8-12 weeks, the collagen gradually arranged in order, and the mechanical nature of the united bone was gradually s trengthened, too. In the RP group, the external callus was scarce at the early s tage of fracture healing, and the callus remodeling at the late stage of fractur e healing was dominated by bone absorption. The ultimate bending strength (UBS) was only 57.95% of that of the normal by 48 weeks. CONCLUSIONS: The decrease of the stress shielding rate of SRP i n vivo was well interrelated with the time of fixation. The application of SRP c ould promote the callus formation and bone reconstruction thus to favor the reco very of the mechanical strength of the united bone. PMID:11874675

  6. Unstable resonator alignment study using off-axis injection.

    PubMed

    Ferguson, T R; Ploor, M D

    1991-10-20

    A brief qualitative experiment and subsequent theoretical study provide new insight concerning off-axis injection of unstable resonators. Theoretical results for aligned resonators show that the regurgitated beam intensity distribution and direction of travel are sensitive to the size, tilt, and other parameters of the injected beam, to the coherence length and number of longitudinal modes of the injecting laser, to clipping and diffraction from apertures, and to resonator length tuning. It is concluded that visual observations of output asymmetries can be used to align the resonator to some degree, but precise alignment using measurement of output asymmetries by a detector array is questionable. PMID:20717200

  7. Antivascular Effects of Neoadjuvant Androgen Deprivation for Prostate Cancer: An In Vivo Human Study Using Susceptibility and Relaxivity Dynamic MRI

    SciTech Connect

    Alonzi, Roberto; Padhani, Anwar R.; Taylor, N. Jane; Collins, David J.; D'Arcy, James A.; Stirling, J. James; Saunders, Michele I.; Hoskin, Peter J.

    2011-07-01

    Purpose: The antivascular effects of androgen deprivation have been investigated in animal models; however, there has been minimal investigation in human prostate cancer. This study tested the hypothesis that androgen deprivation causes significant reductions in human prostate tumor blood flow and the induction of hypoxia at a magnitude and in a time scale relevant to the neoadjuvant setting before radiotherapy. Methods and Materials: Twenty patients were examined, each with five multi-parameter magnetic resonance imaging scans: two scans before the commencement of androgen suppression, one scan after 1 month of hormone treatment, and two further scans after 3 months of therapy. Quantitative parametric maps of the prostate informing on relative blood flow (rBF), relative blood volume (rBV), vascular permeability (transfer constant [K{sup trans}]), leakage space (v{sub e}) and blood oxygenation (intrinsic relaxivity [R{sub 2}*]) were calculated. Results: Tumor blood volume and blood flow decreased by 83% and 79%, respectively, in the first month (p < 0.0001), with 74% of patients showing significant changes. The proportion of individual patients who achieved significant changes in T1 kinetic parameter values after 3 months of androgen deprivation for tumor measurements was 68% for K{sup trans} and 53% for v{sub e} By 3 months, significant increases in R{sub 2}* had occurred in prostate tumor, with a rise of 41.1% (p < 0.0001). Conclusions: Androgen deprivation induces profound vascular collapse within 1 month of starting treatment. Increased R{sub 2}* in regions of prostate cancer and a decrease in blood volume suggest a reduction in tumor oxygenation.

  8. Vibrational relaxation of carbon monoxide studied by two-wavelength infrared emission

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.

    1973-01-01

    Experimental results are presented for the vibrational relaxation of pure carbon monoxide behind incident shock waves over the temperature range 4000 to 6300 K. The data were obtained as infrared emission from the fundamental and overtone vibrational band systems (in some of the experiments the two-band systems were recorded simultaneously). The data are consistent with present theories for the vibrational relaxation of diatomic molecules and can be interpreted in terms of an initial Boltzmann vibrational distribution relaxing toward final equilibrium via a continuous sequence of intermediate Boltzmann distributions.

  9. Dielectric relaxation studies of binary mixture of β-picoline and methanol using time domain reflectometry at different temperatures

    NASA Astrophysics Data System (ADS)

    Trivedi, C. M.; Rana, V. A.; Hudge, P. G.; Kumbharkhane, A. C.

    2016-08-01

    Complex permittivity spectra of binary mixtures of varying concentrations of β-picoline and Methanol (MeOH) have been obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15, 288.15, 293.15 and 298.15 K temperatures. The dielectric relaxation parameters namely static permittivity (ɛ0), high frequency limit permittivity (ɛ∞1) and the relaxation time (τ) were determined by fitting complex permittivity data to the single Debye/Cole-Davidson model. Complex nonlinear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E which contain information regarding molecular structure and interaction between polar-polar liquids were also determined. From the experimental data, parameters such as effective Kirkwood correlation factor (geff), Bruggeman factor (fB) and some thermo dynamical parameters have been calculated. Excess parameters were fitted to the Redlich-Kister polynomial equation. The values of static permittivity and relaxation time increase nonlinearly with increase in the mol-fraction of MeOH at all temperatures. The values of excess static permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E are negative for the studied β-picoline — MeOH system at all temperatures.

  10. Oxygen Mapping within Healthy and Acutely Infarcted Brain Tissue in Humans Using the NMR Relaxation of Lipids: A Proof-Of-Concept Translational Study.

    PubMed

    Colliez, Florence; Safronova, Marta M; Magat, Julie; Joudiou, Nicolas; Peeters, André P; Jordan, Bénédicte F; Gallez, Bernard; Duprez, Thierry

    2015-01-01

    The clinical applicability of brain oxygenation mapping using the MOBILE (Mapping of Oxygen By Imaging Lipids relaxation Enhancement) magnetic resonance (MR) technique was assessed in the clinical setting of normal brain and of acute cerebral ischemia as a founding proof-of-concept translational study. Changes in the oxygenation level within healthy brain tissue can be detected by analyzing the spin-lattice proton relaxation ('Global T1' combining water and lipid protons) because of the paramagnetic properties of molecular oxygen. It was hypothesized that selective measurement of the relaxation of the lipid protons ('Lipids T1') would result in enhanced sensitivity of pO2 mapping because of higher solubility of oxygen in lipids than in water, and this was demonstrated in pre-clinical models using the MOBILE technique. In the present study, 12 healthy volunteers and eight patients with acute (48-72 hours) brain infarction were examined with the same clinical 3T MR system. Both Lipids R1 (R1 = 1/T1) and Global R1 were significantly different in the infarcted area and the contralateral unaffected brain tissue, with a higher statistical significance for Lipids R1 (median difference: 0.408 s-1; p<0.0001) than for Global R1 (median difference: 0.154 s-1; p = 0.027). Both Lipids R1 and Global R1 values in the unaffected contralateral brain tissue of stroke patients were not significantly different from the R1 values calculated in the brain tissue of healthy volunteers. The main limitations of the present prototypic version of the MOBILE sequence are the long acquisition time (4 min), hampering robustness of data in uncooperative patients, and a 2 mm slice thickness precluding accurate measurements in small infarcts because of partial volume averaging effects. PMID:26267901

  11. An analogue study of the initial carryover effects of meditation, hypnosis, and relaxation using native college students.

    PubMed

    Colby, F

    1991-06-01

    An analogue study involving two experiments was conducted to test the initial carryover effects of hypnosis, meditation, and relaxation upon self-reports of awareness. In the first experiment, concentrative meditators reported fewer nonsensorial events than controls. In the second experiment, concentrative meditators again reported fewer nonsensorial events, but covariate analysis and pretest/posttest comparisons revealed that it was the controls who had changed, increasing their nonsensorial reports. In addition, the relaxation group increased its reports of somatic awareness. Results were discussed in terms of the effects of performance demands and the possibility that meditation and hypnosis might be able to disinhibit awareness processes otherwise inhibited by normal daily routines.

  12. Multicavity wave resonator design using chaos studies

    NASA Astrophysics Data System (ADS)

    Méndez-Bermúdez, J. A.; Luna-Acosta, G. A.

    2007-03-01

    We propose the construction of electromagnetic and electronic multicavity resonators based on the mechanism of dynamical tunneling proper of mixed chaotic systems. We use chaotic two-dimensional (2D) waveguides formed by a linear array of coupled cavities whose geometrical parameters are chosen to produce mixed phase space: chaotic regions surrounding islands of stability where ray (particle) motion is regular. Rays (particles) coming into the waveguide cannot penetrate into these islands but incoming plane waves tunnel into them at a certain discrete set of frequencies (energies) forming quasi-bound states. In this paper we demonstrate the tunneling mechanism in 2D waveguides and how it can be used to design multicavity resonators. We also discuss possible applications in the construction of microlasers and electro-optical beam splitters and switches.

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

    SciTech Connect

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

    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.

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

    PubMed

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

    2015-10-14

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

  15. Relaxation Time Distribution (RTD) of Spectral Induced Polarization (SIP) data from environmental studies

    NASA Astrophysics Data System (ADS)

    Ntarlagiannis, D.; Ustra, A.; Slater, L. D.; Zhang, C.; Mendonça, C. A.

    2015-12-01

    In this work we present an alternative formulation of the Debye Decomposition (DD) of complex conductivity spectra, with a new set of parameters that are directly related to the continuous Debye relaxation model. The procedure determines the relaxation time distribution (RTD) and two frequency-independent parameters that modulate the induced polarization spectra. The distribution of relaxation times quantifies the contribution of each distinct relaxation process, which can in turn be associated with specific polarization processes and characterized in terms of electrochemical and interfacial parameters as derived from mechanistic models. Synthetic tests show that the procedure can successfully fit spectral induced polarization (SIP) data and accurately recover the RTD. The procedure was applied to different data sets, focusing on environmental applications. We focus on data of sand-clay mixtures artificially contaminated with toluene, and crude oil-contaminated sands experiencing biodegradation. The results identify characteristic relaxation times that can be associated with distinct polarization processes resulting from either the contaminant itself or transformations associated with biodegradation. The inversion results provide information regarding the relative strength and dominant relaxation time of these polarization processes.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    PubMed

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

    2015-10-14

    Recent potential energy surfaces (PESs) for the N2 + N and N2 + N2 systems are used in molecular dynamics (MD) to simulate rates of vibrational and rotational relaxations for conditions that occur in hypersonic flows. For both chemical systems, it is found that the rotational relaxation number increases with the translational temperature and decreases as the rotational temperature approaches the translational temperature. The vibrational relaxation number is observed to decrease with translational temperature and approaches the rotational relaxation number in the high temperature region. The rotational and vibrational relaxation numbers are generally larger in the N2 + N2 system. MD-quasi-classical trajectory (QCT) with the PESs is also used to calculate the V-T transition cross sections, the collision cross section, and the dissociation cross section for each collision pair. Direct simulation Monte Carlo (DSMC) results for hypersonic flow over a blunt body with the total collision cross section from MD/QCT simulations, Larsen-Borgnakke with new relaxation numbers, and the N2 dissociation rate from MD/QCT show a profile with a decreased translational temperature and a rotational temperature close to vibrational temperature. The results demonstrate that many of the physical models employed in DSMC should be revised as fundamental potential energy surfaces suitable for high temperature conditions become available. PMID:26472383

  18. Longitudinal-relaxation-enhanced NMR experiments for the study of nucleic acids in solution.

    PubMed

    Farjon, Jonathan; Boisbouvier, Jérôme; Schanda, Paul; Pardi, Arthur; Simorre, Jean-Pierre; Brutscher, Bernhard

    2009-06-24

    Atomic-resolution information on the structure and dynamics of nucleic acids is essential for a better understanding of the mechanistic basis of many cellular processes. NMR spectroscopy is a powerful method for studying the structure and dynamics of nucleic acids; however, solution NMR studies are currently limited to relatively small nucleic acids at high concentrations. Thus, technological and methodological improvements that increase the experimental sensitivity and spectral resolution of NMR spectroscopy are required for studies of larger nucleic acids or protein-nucleic acid complexes. Here we introduce a series of imino-proton-detected NMR experiments that yield an over 2-fold increase in sensitivity compared to conventional pulse schemes. These methods can be applied to the detection of base pair interactions, RNA-ligand titration experiments, measurement of residual dipolar (15)N-(1)H couplings, and direct measurements of conformational transitions. These NMR experiments employ longitudinal spin relaxation enhancement techniques that have proven useful in protein NMR spectroscopy. The performance of these new experiments is demonstrated for a 10 kDa TAR-TAR*(GA) RNA kissing complex and a 26 kDa tRNA.

  19. Using the viscoelastic relaxation of large impact craters to study the thermal history of Mars

    NASA Astrophysics Data System (ADS)

    Karimi, Saman; Dombard, Andrew J.; Buczkowski, Debra L.; Robbins, Stuart J.; Williams, Rebecca M.

    2016-07-01

    We simulate the long-term deformation of Martian craters and investigate the role of lower crustal flow in the evolution of surface and subsurface topography. Using the finite element method and a viscoelastic rheological model, we model the deformation of more than 30 large craters and Quasi-Circular Depressions (QCDs), in the diameter range of ∼200-500 km, in both the Northern Lowlands and Southern Highlands. We determine the most appropriate background heat fluxes that produce the current topography beneath the impacts at the crust-mantle boundary (ranges from 40 to ∼90 mW m-2). Our study shows that a higher background heat flux leads to more relaxation at the surface and subsurface. By applying various viscous creep parameters for hydrous and anhydrous rheologies, we demonstrate that Mars's interior is wet to a certain degree, which is consistent with other estimates. Since craters and QCDs are distributed fairly equally on the surface of the Red Planet, this study provides a less regionally biased picture of the thermal history of early Mars than in previous studies. Based on our results, the ancient average background heat flux in the Northern Lowlands was higher than that of the Southern Highlands, which could indicate that whatever process formed the crustal dichotomy had a thermal signature at least through the middle Noachian.

  20. a Light Scattering Study of the Relaxations in Fragile Glass Formers.

    NASA Astrophysics Data System (ADS)

    Sidebottom, David Lee

    We have used photon correlation spectroscopy to explore the changes which occur in the low frequency portion of the mode structure of two fragile glasses during their liquid to glass transition. The two systems studied were salol and 2Ca(NO_3)_2 cdot 3KNO_3. We show that the start of the glass transition, marked by the temperature T^{*} where the viscosity first deviates from the liquid -like power law, is also associated with the initial development of a new relaxation mode (the structural mode). As the temperature decreases below T^{*} , the structural mode destroys progressively larger sized (q^{-1}) hydrodynamic diffusive modes. The new mode is seen to decay via a stretched exponential, exp(-(t/tau)^{ beta}). Recent models^1 that envision a de-percolation of the available phase space of the liquid predict that beta <=aves 1.0 when the fraction of available phase space reachs about 1/2, and drops to beta ~ 1/3 at the percolation threshold. This threshold is thought to coincide with the glass transition. However, for 2Ca(NO_3)_2 cdot 3KNO_3 studied in this work and by others, beta is seen to reach 1/3 well in advance of the glass transition. In fact a correlation is noted between the attainment of Arrhenius temperature dependence of the viscosity and the cessation of evolution of beta. As many properties of liquids and glasses depend upon the mode structure, a survey of the literature has been conducted to examine how these changes at T ^{*} affect both the specific heat and the speed of sound. We find that the specific heat is enhanced by the development of the structural mode, and that near T ^{*} the initial development of transverse modes produces an increase in the speed of sound. Furthermore, both of these properties display a frequency dependence that is a direct reflection of the magnitude of the average relaxation time of the structural mode. ftn^1F. Mezei, W. Knaak, and B. Farrago, Phys. Rev. Lett. 58, 571 (1987).

  1. A diffusion and T2 relaxation MRI study of the ovine lumbar intervertebral disc under compression in vitro

    NASA Astrophysics Data System (ADS)

    Drew, Simon C.; Silva, Pujitha; Crozier, Stuart; Pearcy, Mark J.

    2004-08-01

    The ovine lumbar intervertebral disc is a useful model for the human lumbar disc. We present preliminary estimates of diffusion coefficients and T2 relaxation times in a pilot MRI study of the ovine lumbar intervertebral disc during uniaxial compression in vitro, and identify factors that hamper the ability to accurately monitor the temporal evolution of the effective diffusion tensor at high spatial resolution.

  2. A study on the impact of lithium-ion cell relaxation on electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Barai, Anup; Chouchelamane, Gael H.; Guo, Yue; McGordon, Andrew; Jennings, Paul

    2015-04-01

    Lithium-ion (Li-ion) batteries are of great interest to the automotive industry due to their higher power and energy density, higher cell voltage, longer cycle life and lower self-discharge compared to other battery chemistries. Electrochemical impedance spectroscopy is a powerful tool employed to investigate the fundamental electrochemical reactions within a Li-ion battery cell, which relates to state of charge, internal temperature and state of health. Its effectiveness has established it as a core method to study electrochemical behaviour of batteries in both off-line and on-line applications. In this work it is shown that in addition to state of charge, internal temperature and state of health, the time period between the removal of an electrical load and the impedance measurement affects the results. The study of five commercially available cells of varying capacities and electrode chemistries show that, regardless of cell type, maximum impedance change takes place within the first 4 h of the relaxation period. The root cause of this impedance change has been discussed from an electrochemical perspective.

  3. Theoretical studies of collisional relaxation of highly excited SO{sub 2} in an Ar bath

    SciTech Connect

    Lendvay, G.; Schatz, G.C.; Harding, L.B.

    1995-12-31

    This paper describes molecular dynamics studies of collisional relaxation of highly excited SO{sub 2} in an Ar bath. Most of the calculations use a newly developed global ab initio potential surface for SO{sub 2} that correctly describes the superoxide (SOO) and ring isomers of SO{sub 2} that occur as secondary minima on the ground state potential surface at high energies (about 75% of the dissociation energy) above the C{sub 2v} minimum. Rate constants for the S + O{sub 2} and O + SO reactions are calculated to test this surface, and to examine the importance of electronically excited states in the O + SO recombination. The Ar + SO{sub 2} collisions are described by summing the ab initio potential with empirical intermolecular potentials. The resulting average vibrational energy transfer <{Delta}E> per collision is in good agreement with direct measurements (done at energies where the secondary minima are not populated) at 1000K, but the agreement is poorer at 300K. The agreement is significantly better than was obtained in a previous theoretical study, and our results indicate that the use of improved intramolecular and intermolecular potentials is crucial to obtaining the better results. The energy dependence of <{Delta}E> is found to be much stronger at energies where the secondary minima on the potential surface are accessible, however much of this effect is reproduced using a potential that has the same dissociation energy but not the secondary minima.

  4. Will C-Laurdan dethrone Laurdan in fluorescent solvent relaxation techniques for lipid membrane studies?

    PubMed

    Barucha-Kraszewska, Justyna; Kraszewski, Sebastian; Ramseyer, Christophe

    2013-01-29

    Development of fluorescence methods involves the necessity of understanding the fluorescent probes behavior in their ground and excited states. In the case of biological membranes, the position of the dyes in the lipid bilayer and their response after excitation are necessary parameters to correctly analyze the experiments. In the present work, we focus on two fluorescent markers, Laurdan (6-lauroyl-2-(N,N-dimethylamino)naphthalene) and its derivative C-Laurdan (6-dodecanoyl-2-[N-methyl-N-(carboxymethyl)amino]naphthalene), recently proposed for lipid raft visualization [Kim, H. M.; et al. ChemBioChem 2007, 8, 553]. C-Laurdan, by the presence of an additional carboxyl group, has an advantage over Laurdan since it has a higher sensitivity to the membrane polarity at the lipid headgroup region and a higher water solubility. This theoretical study, based on quantum mechanical (QM) and molecular dynamics (MD) simulations in a fully hydrated lipid membrane model, compare the equilibrium and dynamic properties of both probes taking into account their fluorescence lifetimes. C-Laurdan is found to be more stable than Laurdan in the headgroup region of the membrane and also much more aligned with the lipids. This study suggests that, besides the lipid raft imaging, the C-Laurdan marker can considerably extend the capabilities of fluorescent solvent relaxation method. PMID:23311388

  5. Half-Sarcomere Dynamics in Myofibrils during Activation and Relaxation Studied by Tracking Fluorescent Markers

    PubMed Central

    Telley, Ivo A.; Denoth, Jachen; Stüssi, Edgar; Pfitzer, Gabriele; Stehle, Robert

    2006-01-01

    To study the dynamics of individual half-sarcomeres in striated muscle contraction, myofibrils prepared from rabbit psoas muscle and left ventricles of guinea pig were immunostained with two conjugated antibody complexes consisting of a primary antibody against either α-actinin or myomesin and a secondary fluorescently labeled Fab-fragment. We simultaneously measured force kinetics and determined the positions of the Z-line and M-band signals by fluorescence video microscopy and sophisticated computer vision (tracking) algorithms. Upon calcium activation, sarcomeres and half-sarcomeres shortened nonuniformly. Shortening occurred first rapidly and exponentially during the force rise and then slowly during the force plateau. In psoas myofibrils, time-resolved displacements of the A-band in sarcomeres were observed, i.e., the two halves of individual sarcomeres behaved nonuniformly. Nonuniformity in length changes between the two halves of sarcomeres was comparable to that between two adjacent half-sarcomeres of neighboring sarcomeres. Sequential lengthening of half-sarcomeres was observed in cardiac myofibrils during the rapid phase of force relaxation. The independent dynamics of the halves in a sarcomere reveals the half-sarcomere as the functional unit rather than the structural unit, the sarcomere. The technique will facilitate the study of filament sliding within individual half-sarcomeres and the mechanics of intersegmental chemomechanical coupling in multisegmental striated muscles. PMID:16239326

  6. Photoionization studies of the 2p resonances of atomic calcium

    NASA Astrophysics Data System (ADS)

    Obst, B.; Hansen, J. E.; Sonntag, B.; Wernet, Ph.; Zimmermann, P.

    2002-06-01

    The Ca 2p resonances at 345-355 eV were studied by photoion and photoelectron spectroscopy using monochromatized synchrotron radiation and atomic-beam technique. The analysis of the excitation and decay of these resonances shows strong configuration mixing between the different subshells of the valence electrons 4s, 3d, and 4p. In the case of the 2p-13/2 resonance structure at 348 eV there are two excited states with nearly equal contributions from the configuration 2p53d4s2 and 2p53d24s, which gives rise to strong variations of the resonantly enhanced 3p4(3d,4s)3 photoelectron lines when scanning the photon energy across the resonance.

  7. Dynamics of an integral membrane peptide: a deuterium NMR relaxation study of gramicidin.

    PubMed Central

    Prosser, R S; Davis, J H

    1994-01-01

    Solid state deuterium (2H) NMR inversion-recovery and Jeener-Broekaert relaxation experiments were performed on oriented multilamellar dispersions consisting of 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine and 2H exchange-labeled gramicidin D, at a lipid to protein molar ratio (L/P) of 15:1, in order to study the dynamics of the channel conformation of the peptide in a liquid crystalline phase. Our dynamic model for the whole body motions of the peptide includes diffusion of the peptide around its helix axis and a wobbling diffusion around a second axis perpendicular to the local bilayer normal in a simple Maier-Saupe mean field potential. This anisotropic diffusion is characterized by the correlation times, tau R parallel and tau R perpendicular. Aligning the bilayer normal perpendicular to the magnetic field and graphing the relaxation rate, 1/T1Z, as a function of (1-S2N-2H), where S2N-2H represents the orientational order parameter, wer were able to estimate the correlation time, tau R parallel, for rotational diffusion. Although in the quadrupolar splitting, which varies as (3 cos2 theta D-1), has in general two possible solutions to theta D in the range 0 < or = theta D < or = 90 degrees, the 1/T1Z vs. (1-S2N-2H) curve can be used to determine a single value of theta D in this range. Thus, the 1/T1Z vs. (1-S2N-2H) profile can be used both to define the axial diffusion rate and to remove potential structural ambiguities in the splittings. The T1Z anisotropy permits us to solve for the two correlation times (tau R parallel = 6.8 x 10(-9) s and tau R perpendicular = 6 x 10(-6) s). The simulated parameters were corroborated by a Jeener-Broekaert experiment where the bilayer normal was parallel to the principal magnetic field. At this orientation the ratio, J2(2 omega 0)/J1(omega 0) was obtained in order to estimate the strength of the restoring potential in a model-independent fashion. This measurement yields the rms angle, 1/2 (= 16 +/- 2 degrees at

  8. Nuclear Quadrupole Resonance Studies in MICA

    NASA Astrophysics Data System (ADS)

    Sengupta, S.; Rhadakrishna, S.; Marino, R. A.

    1986-02-01

    Aluminum-27 NQR transitions were detected in Muscovite Mica at room temperature using double resonance by level crossing (DRLC) techniques. Three lines were observed with frequencies of 572.5, 1052.0, and 1624.5 kHz. These lines are assigned to the octahedrally coordinated site, AlO4(OH)2. The corresponding quadrupole coupling constant, e2q Q/h, and asymmetry parameter, η, are 3554.8 kHz and 0.265, respectively. The remaining tetrahedrally coordinated sites, AlO4, gave no discernible signal, perhaps due to the greater 27Al- 1H distance.

  9. Picosecond-time-resolved studies of nonradiative relaxation in ruby and alexandrite

    SciTech Connect

    Gayen, S.K.; Wang, W.B.; Petricevic, V.; Alfano, R.R.

    1985-01-01

    Dynamics of the nonradiative transitions between the /sup 4/T/sub 2/ pump band and the /sup 2/E storage level of the Cr/sup 3 +/ ion in ruby and alexandrite crystals is studied using the picosecond excite-and-probe absorption technique. A 527-nm picosecond pulse excites the /sup 4/T/sub 2/ state of the Cr/sup 3 +/ ion, and an infrared picosecond probe pulse monitors the subsequent growth and decay of population in the excited states as a function of pump-probe delay. An upper limit of 7 ps is determined for the nonradiative lifetime of the /sup 4/T/sub 2/ state in ruby. A vibrational relaxation time of 25 ps for the /sup 4/T/sub 2/ band in alexandrite is estimated. The time to attain thermal equilibrium population between the /sup 2/E and /sup 4/T/sub 2/ levels of alexandrite following excitation of /sup 4/T/sub 2/ band is estimated to be approx. 100 ps.

  10. [Time-resolved optical studies of charge relaxation and charge transfer at electrode interfaces

    SciTech Connect

    Not Available

    1992-01-01

    Key components were identified in a quantitative model of carrier relaxation in semiconductor electrodes: nonlinear aspects of nonradiative and radiative recombination, effect of space charge field on carrier dynamics, self-absorption effects in direct gas semiconductors, and influence of surface state population kinetics on charge carrier recombination. For CdSe, the first three are operative (no direct proof of the last one). A realistic kinetic model for carrier recombination in the bulk of CdSe was used which includes important nonlinear effects, both radiative and nonradiative. The change in interfacial recombination velocity with the chemical nature of the sinterface was studied (n-CdSe/silane interfaces). Temperature effect (278 to 328 K) on fluorescence decay of n-CdSe in contact with 0.5 M KOH was found to be weak. An analytical solution was obtained for time-resolved fluoresence from electrodes under potential bias, and is being tested. Fluorescence work on a different material, CdS, indicate different recombination kinetics; this material was used to directly pump an optical transition of a surface state.

  11. [Time-resolved optical studies of charge relaxation and charge transfer at electrode interfaces

    SciTech Connect

    Not Available

    1992-12-31

    Key components were identified in a quantitative model of carrier relaxation in semiconductor electrodes: nonlinear aspects of nonradiative and radiative recombination, effect of space charge field on carrier dynamics, self-absorption effects in direct gas semiconductors, and influence of surface state population kinetics on charge carrier recombination. For CdSe, the first three are operative (no direct proof of the last one). A realistic kinetic model for carrier recombination in the bulk of CdSe was used which includes important nonlinear effects, both radiative and nonradiative. The change in interfacial recombination velocity with the chemical nature of the sinterface was studied (n-CdSe/silane interfaces). Temperature effect (278 to 328 K) on fluorescence decay of n-CdSe in contact with 0.5 M KOH was found to be weak. An analytical solution was obtained for time-resolved fluoresence from electrodes under potential bias, and is being tested. Fluorescence work on a different material, CdS, indicate different recombination kinetics; this material was used to directly pump an optical transition of a surface state.

  12. Microviscosity of human erythrocytes studied using hypophosphite two-spin order relaxation.

    PubMed Central

    Price, W S; Perng, B C; Tsai, C L; Hwang, L P

    1992-01-01

    A new 31P NMR method is used to probe the cytoplasmic viscosity of human erythrocytes. The method is based on observing two-spin order relaxation of the 31P atom of the hypophosphite ion. This method is superior to our previous method, using the longitudinal relaxation time of the ion, because random field effects such as intermolecular dipole-dipole relaxation can be separated from intramolecular relaxation. This allows a more accurate determination of the effective reorientational correlation time from the measured intramolecular relaxation because it is now unaffected by random field effects. The new method also provides a means by which to estimate the random field effects. Both two-spin order and proton-decoupled T1 measurements were conducted on hypophosphite in water solutions at various temperatures, glycerol solutions of various viscosities, and in erythrocyte samples of various cell volumes. The results show that the effective reorientational correlation time of the hypophosphite ion varies from 7.2 to 15.2 ps in the cytoplasm of cells ranging in volume from 102 to 56 fl cells. PMID:1504239

  13. Relaxation System

    NASA Technical Reports Server (NTRS)

    1987-01-01

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

  14. Nuclear quadrupole resonance studies in semi-metallic structures

    NASA Technical Reports Server (NTRS)

    Murty, A. N.

    1974-01-01

    Both experimental and theoretical studies are presented on spectrum analysis of nuclear quadrupole resonance of antimony and arsenic tellurides. Numerical solutions for secular equations of the quadrupole interaction energy are also discussed.

  15. Another challenge to paramagnetic relaxation theory: a study of paramagnetic proton NMR relaxation in closely related series of pyridine-derivatised dysprosium complexes.

    PubMed

    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. PMID:26792243

  16. Another challenge to paramagnetic relaxation theory: a study of paramagnetic proton NMR relaxation in closely related series of pyridine-derivatised dysprosium complexes.

    PubMed

    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.

  17. Lattice relaxation studies in strained epitaxial Fe-Co-C films

    SciTech Connect

    Reichel, L. Schultz, L.; Fähler, S.

    2015-05-07

    Aiming at high magnetocrystalline anisotropies, small additions of carbon have been proposed to stabilize a tetragonal lattice distortion in Fe-Co. In the present work, the relaxation mechanisms of Fe-Co films containing 2 at. % C are examined in detail. Film growth on buffers with different lattice constants is compared by a combination of in situ reflection high energy electron diffraction and ex-situ X-ray diffraction measurements. It is shown that relaxation starts at a thickness around 2 nm and ends at a distortion of about 4%, which is independent from the chosen buffer. Integral XRD and magnetization measurements suggest that the relaxation occurs over the complete film thickness.

  18. Study of the relaxation dynamics associated with the Glass Transition in two polyols

    NASA Astrophysics Data System (ADS)

    Faivre, Annelise; David, Laurent; Vigier, Gerard; Jal, Jean-Francois

    1998-03-01

    In order to improve the understanding of the glass transition, the molecular mobility of two complementary molecular systems (Sorbitol and Maltitol) was investigated over temperatures ranging from well above Tg, to below Tg. Using various spectroscopic techniques including mechanical and dielectric spectroscopies, viscosity measurements, neutron spin echo (ILL Grenoble), the relaxation maps of these polyols were determined for a very large frequency range. The results reveal two relaxation processes: -the main alpha-relaxation, which exhibits a complex dynamic pattern comprising non-Arrhenius behaviour above Tg and Arrhenius behaviour below Tg, -the secondary beta process, which exhibits an Arrhenius behaviour over the entire time-temperature range, which happens to be the same for both polyols. We attempt to describe these data in the framework of a model relating the dynamic behaviour of the system to the state of disorder, as characterized by the density of nano-fluctuations.

  19. Acoustic and relaxation behaviors of polydimethylsiloxane studied by using brillouin and dielectric spectroscopies

    NASA Astrophysics Data System (ADS)

    Lee, Byoung Wan; Ko, Jae-Hyeon; Park, Jaehoon; Shin, Dong-Myeong; Hwang, Yoon-Hwae

    2016-04-01

    The temperature dependences of the acoustic properties and the dielectric relaxation times of polydimethylsiloxane were investigated by using high-resolution Brillouin and broadband dielectric spectroscopies. The longitudinal sound velocity showed a large increase upon approaching the glass transition temperature while the acoustic absorption coefficient exhibited a maximum at ~263 K. Comparison of these results with previous ultrasonic data revealed a substantial frequency dispersion of the acoustic properties of this silicone-based elastomer. The relaxation times derived from the acoustic absorption peaks were consistent with the temperature dependence of the dielectric relaxation time of the structural a process, indicating a strong coupling between the acoustic waves and the segmental motions of the main chains.

  20. A study of the aging of silicone breast implants using 29Si, 1H relaxation and DSC measurements.

    PubMed

    Birkefeld, Anja Britta; Eckert, Hellmut; Pfleiderer, Bettina

    2004-08-01

    In this study 26 previously implanted silicone breast implants from the same manufacturer (Dow Corning) were investigated with two different analytical methods to characterize potential aging processes such as migration of monomer material from the gel and shell to local and distant sites, chemical alterations of the polymer, and infiltration of body compounds such as lipids. (1)H and (29)Si NMR relaxation measurements (spin-lattice, T1, and spin-spin, T2, relaxation times) were used to study the molecular dynamics of polysiloxane chains, both in gels and in shells. In addition, changes in physical properties were monitored by differential scanning calorimetry (DSC). The results of these measurements indicate that NMR relaxation times are influenced by implant generation, implantation time, shell texture and implant status. (1)H T2 values of shells and gels show a tendency to increase with increasing implantation time, indicating higher mobility and possible disintegration of the polymer network of older implants. Furthermore, the data suggest that aging also involves the migration of low cyclic molecular weight (LMW) silicone and linear chain polymer material from the gels into the shells. The high "bleeding" rate of second-generation (G2) implants (implantation period around 1973-1985), exhibiting thin shells is reflected in reduced relaxation times of these devices, most likely due to a loss of low molecular weight fractions from the gels. Moreover, "gel bleeding" also influences the melting behavior observed in DSC studies. Increased shell rigidity (high Tm and Tg) tends to be correlated with longer (29)Si relaxation times of the corresponding gels, suggesting a reduced transfer of LMW silicones and linear chain polymer from the gel to the shell and to the outside. Remarkably, textured implants seem to be less susceptible to degradation processes than implants with thin shells.

  1. A study into stress relaxation in oxides formed on zirconium alloys

    NASA Astrophysics Data System (ADS)

    Platt, P.; Polatidis, E.; Frankel, P.; Klaus, M.; Gass, M.; Howells, R.; Preuss, M.

    2015-01-01

    Pressurised and boiling water reactors contain zirconium alloys, which are used as nuclear fuel cladding. Oxidation of these alloys, and the associated hydrogen pick-up, is a limiting factor in the lifetime of the fuel. To extend the burn-up of nuclear fuel requires control of the oxidation, and therefore development of a mechanistic understanding of the cladding corrosion process. Synchrotron X-ray diffraction (S-XRD) has been used to analyse oxide layers formed during in-situ air oxidation of Zircaloy-4 and ZIRLO™. Analysis shows that as the oxide thickness increases over time there is a relaxation of the stresses present in both the monoclinic and meta-stable tetragonal phases, and a reduction in the tetragonal phase fraction. To better understand the mechanisms behind stress relaxation in the oxide layer, finite element analysis has been used to simulate mechanical aspects of the oxidation process. This simulation was first developed based on stress relaxation in oxides formed in autoclave, and analysed ex-situ using S-XRD. Relaxation mechanisms include creep and hydrogen-induced lattice strain in the metal substrate and creep in the oxide layer. Subsequently the finite element analysis has been extended to stress relaxation observed by in-situ S-XRD oxidation experiments. Finite element analysis indicates that the impact of creep in the oxide is negligible, and the impact of both creep and hydrogen-induced lattice strain in the metal substrate metal is small. The implication is that stress relaxation must result from another source such as the development of roughness at the metal-oxide interface, or fracture in the oxide layer.

  2. Dynamic relaxation study and experimental verification of dielectric-elastomer minimum-energy structures

    NASA Astrophysics Data System (ADS)

    Siu, S.; Rhode-Barbarigos, L.; Wagner, S.; Adriaenssens, S.

    2013-10-01

    The shape of a dielectric elastomer minimum energy structure (DEMES) depends on the equilibrium between a pre-stretched membrane and an inextensible frame. The authors show that an extended dynamic relaxation method, a technique employed for the form-finding and analysis of pre-stressed structures, can be used to simulate DEMES equilibrium shapes. Physical models show excellent agreement with the shape of computed models. Dynamic relaxation, with its low computational cost, is a powerful form-finding technique that efficiently predicts the equilibrium shape as well as the elastic energy of DEMES.

  3. Stress reactivity to and recovery from a standardised exercise bout: a study of 31 runners practising relaxation techniques

    PubMed Central

    Solberg, E; Ingjer, F; Holen, A; Sundgot-Borgen, J; Nilsson, S; Holme, I

    2000-01-01

    Objective—To compare the efficacy in runners of two relaxation techniques with regard to exercise reactivity and recovery after exercise. Methods—Thirty one adult male runners were studied prospectively for six months in three groups practising either meditation (n = 11) or autogenic training (n = 11) or serving as controls (n = 10). Before and after the six months relaxation intervention, indicators of reactivity to exercise and metabolism after exercise (blood lactate concentration, heart rate (HR), and oxygen consumption (VO2)), were tested immediately after and 10 minutes after exercise. Resting HR was also assessed weekly at home during the trial. State anxiety was measured before and after the intervention. Results—After the relaxation training, blood lactate concentration after exercise was significantly (p<0.01) decreased in the meditation group compared with the control group. No difference was observed in lactate responses between the autogenic training group and the control group. There were no significant differences among the groups with regard to HR, VO2, or levels of anxiety. Conclusion—Meditation training may reduce the lactate response to a standardised exercise bout. Key Words: autogenic training; lactate; meditation; recovery; relaxation; psychology PMID:10953899

  4. Electron Paramagnetic Resonance Study of Pr

    SciTech Connect

    Tezuka, Keitaro; Hinatsu, Yukio

    2001-01-01

    Electron paramagnetic resonance (EPR) spectra of tetravalent praseodymium ions doped in the cubic perovskite compound BaHfO{sub 3} have been measured at 4.2 K. A very large hyperfine interaction with the {sup 141}Pr nucleus was observed in the spectrum of Pr{sup 4+}/ BaHfO{sub 3}. The results were analyzed based on the weak field approximation, and the g value (|g|=0.619) and a hyperfine coupling constant (A=0.0589 cm{sup {minus}1}) were obtained. The measured g value is much smaller than |-10/7|, which indicates that the crystal field effect on the behavior of a 4f electron is large. These g and A values were compared with the EPR results for other f{sup 1} ions in an octahedral crystal field.

  5. Measurement of Spin-Lattice Relaxation Times and Concentrations in Systems with Chemical Exchange Using the One-Pulse Sequence: Breakdown of the Ernst Model for Partial Saturation in Nuclear Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Spencer, Richard G. S.; Fishbein, Kenneth W.

    2000-01-01

    A fundamental problem in Fourier transform NMR spectroscopy is the calculation of observed resonance amplitudes for a repetitively pulsed sample, as first analyzed by Ernst and Anderson in 1966. Applications include determination of spin-lattice relaxation times (T1's) by progressive saturation and correction for partial saturation in order to determine the concentrations of the chemical constituents of a spectrum. Accordingly, the Ernst and Anderson formalism has been used in innumerable studies of chemical and, more recently, physiological systems. However, that formalism implicitly assumes that no chemical exchange occurs. Here, we present an analysis of N sites in an arbitrary chemical exchange network, explicitly focusing on the intermediate exchange rate regime in which the spin-lattice relaxation rates and the chemical exchange rates are comparable in magnitude. As a special case of particular importance, detailed results are provided for a system with three sites undergoing mutual exchange. Specific properties of the N-site network are then detailed. We find that (i) the Ernst and Anderson analysis describing the response of a system to repetitive pulsing is inapplicable to systems with chemical exchange and can result in large errors in T1 and concentration measurements; (ii) T1's for systems with arbitrary exchange networks may still be correctly determined from a one-pulse experiment using the Ernst formula, provided that a short interpulse delay time and a large flip angle are used; (iii) chemical concentrations for exchanging systems may be correctly determined from a one-pulse experiment either by using a short interpulse delay time with a large flip angle, as for measuring T1's, and correcting for partial saturation by use of the Ernst formula, or directly by using a long interpulse delay time to avoid saturation; (iv) there is a significant signal-to-noise penalty for performing one-pulse experiments under conditions which permit accurate

  6. Dynamics in supercooled polyalcohols: Primary and secondary relaxation

    NASA Astrophysics Data System (ADS)

    Döß, A.; Paluch, M.; Sillescu, H.; Hinze, G.

    2002-10-01

    We have studied details of the molecular dynamics in a series of pure polyalcohols by means of dielectric spectroscopy and 2H nuclear magnetic resonance (NMR). From glycerol to threitol, xylitol and sorbitol a systematic change in the dynamics of the primary and secondary relaxation is found. With increasing molecular weight and fragility an increase in the width of the α-peak is observed. Details of the molecular reorientation process responsible for the α-relaxation were exploited by two-dimensional NMR experiments. It is found that in the same sequence of polyalcohols the appearance of the secondary relaxation changes gradually from a wing type scenario to a pronounced β-peak. From NMR experiments using selectively deuterated samples the molecular origin of the secondary relaxation could be elucidated in more detail.

  7. Study of field shifts of Ramsey resonances on ultracold atoms and ions

    SciTech Connect

    Tabatchikova, K. S.; Taichenachev, A. V.; Dmitriev, A. K.; Yudin, V. I.

    2015-02-15

    The effect of the finite laser radiation line width and spontaneous relaxation of levels on the efficiency of the suppression of the field shift of the central resonance for the generalized Ramsey scheme with pulses of different lengths and with a phase jump in the second pulse has been considered. The optimal parameters of the scheme corresponding to the minimum frequency shift and maximum amplitude of the resonance have been determined.

  8. Study on contraction and relaxation of experimentally denervated and immobilized muscles: Comparison with dystrophic muscles

    NASA Technical Reports Server (NTRS)

    Takamori, M.; Tsujihata, M.; Mori, M.; Hazama, R.; Ide, Y.

    1980-01-01

    The contraction-relaxation mechanism of experimentally denervated and immobilized muscles of the rabbit is examined. Results are compared with those of human dystrophic muscles, in order to elucidate the role and extent of the neurotrophic factor, and the role played by the intrinsic activity of muscle in connection with pathogenesis and pathophysiology of this disease.

  9. Studies of chinese original quiet sitting by using functional magnetic resonance imaging.

    PubMed

    Liou, Chien-Hui; Hsieh, Chang-Wei; Hsieh, Chao-Hsien; Chen, Jyh-Horng; Wang, Chi-Hong; Lee, Si-Chen

    2005-01-01

    Since different meditations may activate different regions in brain, we can use functional magnetic resonance imaging (fMRI) to investigate it. Chinese original quiet sitting is mainly one kind of traditional Chinese meditation. It contains two different parts: a short period of keeping phrase and intake spiritual energy, and a long period of relaxation with no further action. In this paper, both those two stages were studied by fMRI. We performed two different paradigms and found the accurate positions in the brain. The pineal gland and the hypothalamus showed positive activation during the first and second stages of this meditation. The BOLD (Blood Oxygenation Level Dependent) signal changes had also been found.

  10. Photoionization and ion cyclotron resonance studies of the ion chemistry of ethylene oxide

    NASA Technical Reports Server (NTRS)

    Corderman, R. R.; Williamson, A. D.; Lebreton, P. R.; Buttrill, S. E., Jr.; Beauchamp, J. L.

    1976-01-01

    The formation of the ethylene oxide molecular ion and its subsequent ion-molecule reactions leading to the products C2H5O(+) and C3H5O(+) have been studied using time-resolved photoionization mass spectroscopy, ion cyclotron resonance spectroscopy, and photoelectron spectroscopy. An examination of the effects of internal energy on reactivity shows that the ratio of C3H5O(+) to C2H5O(+) increases by an order of magnitude with a single quantum of vibrational energy. The formation of (C2H4O/+/)-asterisk in a collision-induced isomerization is found which yields a ring-opened structure by C-C bond cleavage. The relaxed ring-opened C2H4O(+) ion reacts with neutral ethylene oxide by CH2(+) transfer to yield an intermediate product ion C3H6O(+) which gives C3H5O(+) by loss of H.

  11. Line-Mixing Relaxation Matrix model for spectroscopic and radiative transfer studies

    NASA Astrophysics Data System (ADS)

    Mendaza, Teresa; Martin-Torres, Javier

    2016-04-01

    We present a generic model to compute the Relaxation Matrix easily adaptable to any molecule and type of spectroscopic lines or bands in non-reactive molecule collisions regimes. It also provides the dipole moment of every transition and level population of the selected molecule. The model is based on the Energy-Corrected Sudden (ECS) approximation/theory introduced by DePristo (1980), and on previous Relaxation Matrix studies for the interaction between molecular ro-vibrational levels (Ben-Rueven, 1966), atoms (Rosenkranz, 1975), linear molecules (Strow and Reuter, 1994; Niro, Boulet and Hartmann, 2004), and symmetric but not linear molecules (Tran et al., 2006). The model is open source, and it is user-friendly. To the point that the user only has to select the wished molecule and vibrational band to perform the calculations. It reads the needed spectroscopic data from the HIgh-resolution TRANsmission molecular absorption (HITRAN) (Rothman et al., 2013) and ExoMol (Tennyson and Yurchenko, 2012). In this work we present an example of the calculations with our model for the case of the 2ν3 band of methane (CH4), and a comparison with a previous work (Tran et al., 2010). The data produced by our model can be used to characterise the line-mixing effects on ro-vibrational lines of the infrared emitters of any atmosphere, to calculate accurate absorption spectra, that are needed in the interpretation of atmospheric spectra, radiative transfer modelling and General Circulation Models (GCM). References [1] A.E. DePristo, Collisional influence on vibration-rotation spectral line shapes: A scaling theoretical analysis and simplification, J. Chem. Phys. 73(5), 1980. [2] A. Ben-Reuven, Impact broadening of microwave spectra, Phys. Rev. 145(1), 7-22, 1966. [3] P.W. Rosenkranz, Shape of the 5 mm Oxygen Band in the Atmosphere, IEEE Transactions on Antennas and Propagation, vol. AP-23, no. 4, pp. 498-506, 1975. [4] Strow, L.L., D.D. Tobin, and S.E. Hannon, A compilation of

  12. Interaction of magnetic resonators studied by the magnetic field enhancement

    NASA Astrophysics Data System (ADS)

    Hou, Yumin

    2013-12-01

    It is the first time that the magnetic field enhancement (MFE) is used to study the interaction of magnetic resonators (MRs), which is more sensitive than previous parameters-shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

  13. Interaction of magnetic resonators studied by the magnetic field enhancement

    SciTech Connect

    Hou, Yumin

    2013-12-15

    It is the first time that the magnetic field enhancement (MFE) is used to study the interaction of magnetic resonators (MRs), which is more sensitive than previous parameters–shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

  14. NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals

    SciTech Connect

    Lim, Ae Ran; Paik, Younkee; Lim, Kye-Young

    2011-06-15

    The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the {sup 87}Rb and {sup 133}Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T{sub 1} are related to variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}. We also compared these {sup 87}Rb and {sup 133}Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO{sub 4}){sub 2}.12H{sub 2}O and MAl(SO{sub 4}){sub 2}.12H{sub 2}O crystals. - Graphical Abstract: The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb, Cs, and NH{sub 4}) single crystals have been investigated. Highlights: > The physical properties and phase transition mechanisms of MCr(SO{sub 4}){sub 2}.12H{sub 2}O (M=Rb and Cs) crystals {yields} The NMR spectra and the spin-lattice relaxation times T{sub 1} of the {sup 87}Rb and {sup 133}Cs nuclei in the two crystals {yields} The variations in the symmetry of the octahedra of water molecules surrounding Rb{sup +} and Cs{sup +}.

  15. Group hypnotherapy versus group relaxation for smoking cessation: an RCT study protocol

    PubMed Central

    2012-01-01

    Background A significant number of smokers would like to stop smoking. Despite the demonstrated efficacy of pharmacological smoking cessation treatments, many smokers are unwilling to use them; however, they are inclined to try alternative methods. Hypnosis has a long-standing reputation in smoking cessation therapy, but its efficacy has not been scientifically proven. We designed this randomised controlled trial to evaluate the effects of group hypnosis as a method for smoking cessation, and we will compare the results of group hypnosis with group relaxation. Methods/Design This is a randomised controlled trial (RCT) to compare the efficacy of a single session of hypnosis with that of relaxation performed in groups of 8-15 smokers. We intend to include at least 220 participants in our trial. The inclusion criteria include smoking at least 5 cigarettes per day, not using other cessation methods and being willing to quit smoking. The intervention is performed by a trained hypnotist/relaxation therapist. Both groups first receive 40 min of mental preparation that is based on motivational interviewing. Then, a state of deep relaxation is induced in the hypnosis condition, and superficial relaxation is induced in the control condition. Suggestions are made in the hypnosis condition that aim to switch the mental self-image of the participants from that of smokers to that of non-smokers. Each intervention lasts for 40 min. The participants also complete questionnaires that assess their smoking status and symptoms of depression and anxiety at baseline, 2 weeks and 6 months post-intervention. In addition, saliva samples are collected to assess cotinine levels at baseline and at 6 months post-intervention. We also assess nicotine withdrawal symptoms at 2 weeks post-intervention. Discussion To the best of our knowledge, this RCT is the first to test the efficacy of group hypnosis versus group relaxation. Issues requiring discussion in the outcome paper include the lack of

  16. Magnetic resonance studies of isotopically labeled paramagnetic proteins: (2FE-2S) ferredoxins

    SciTech Connect

    Cheng, H.; Xia, B.; Chae, Y.K.; Westler, W.M.; Markley, J.L.

    1994-12-01

    Recent developments in NMR spectroscopy, especially multidimensional, multinuclear NMR techniques, have made NMR the most versatile tool available for studying protein structure and function in solution. Unlike diamagnetic proteins, paramagnetic proteins contain centers with unpaired electrons. These unpaired electrons interact with magnetic nuclei either through chemical bonds by a contact mechanism or through space by a pseudocontact mechanism. Such interactions make the acquisition and analysis of NMR spectra of paramagnetic proteins more challenging than those of diamagnetic proteins. Some NMR signals from paramagnetic proteins are shifted outside the chemical shift region characteristic of diamagnetic proteins; these {open_quotes}hyperfine-shifted{close_quotes} resonances originate from nuclei that interact with unpaired electrons from the paramagnetic center. The large chemical shift dispersion in spectra of paramagnetic proteins makes it difficult to excite the entire spectral window and leads to distortions in the baseline. Interactions with paramagnetic centers shorten T{sub 1} and T{sub 2} relaxation times of nuclei; the consequences are line broadening and lower spectral sensitivity. Scalar (through bond) and dipolar (through space) interactions between pairs of nuclei are what give rise to crosspeak signals in multi-dimensional NMR spectra of small diamagnetic proteins. When such interactions involve a nucleus that is strongly relaxed by interaction with a paramagnetic center, specialized methods may be needed for its detection or it may be completely undetectable by present nD NMR methods.

  17. New insight into relaxation dynamics of an epoxy/hydroxy functionalized polybutadiene from dielectric and mechanical spectroscopy studies.

    PubMed

    Hensel-Bielowka, S; Wojnarowska, Z; Knapik, J; Paluch, M

    2014-01-01

    Dielectric and mechanical spectroscopy methods have been employed to describe the temperature dependencies of the segmental and macromolecular relaxation rates in epoxy/hydroxy functionalized polybutadiene. Dielectric studies on the dynamics of segments of the polymer as well as the mobility of small ions trapped in the system have been carried out both as a function of temperature and pressure under isobaric and isothermal conditions, respectively. PMID:25100898

  18. Experimental study of resonance crossing with a Paul trap

    NASA Astrophysics Data System (ADS)

    Takeuchi, H.; Fukushima, K.; Ito, K.; Moriya, K.; Okamoto, H.; Sugimoto, H.

    2012-07-01

    The effect of resonance crossing on beam stability is studied systematically by employing a novel tabletop experimental tool and a multiparticle simulation code. A large number of ions are confined in a compact linear Paul trap to reproduce the collective beam behavior. We can prove that the ion plasma in the trap is physically equivalent to a charged-particle beam propagating through a strong focusing channel. The plasma confinement force is quickly ramped such that the trap operating point traverses linear and nonlinear resonance stop bands. Assuming a nonscaling fixed field alternating gradient accelerator composed of many identical FODO cells, we measure how much ion losses occur under diverse conditions. It is experimentally and numerically demonstrated that too slow resonance crossing leads to significant ion losses as expected. Particular attention must be paid to the linear coherent resonance excited at a quarter-integer tune. When the beam intensity is high, this type of linear stop band can seriously affect the beam quality even for rather fast resonance crossing. A scaling law is given of the emittance growth caused by the quarter-integer resonance crossing.

  19. Study of spatial spin-modulated structures by Mössbauer spectroscopy using SpectrRelax

    SciTech Connect

    Matsnev, Mikhail E. Rusakov, Vyacheslav S.

    2014-10-27

    SpectrRelax is an application for analysis and fitting of absorption and emission Mössbauer spectra. It includes a large selection of static and relaxation spectrum models, and allows fitting and searching for optimal model parameters. Recently, we have added new models for Mössbauer spectra of nuclides in spatial spin modulated structures. In these structures, spin density or direction changes in a periodic way along a single direction, and this wave is incommensurate with the underlying lattice. The models include Spin/Charge density wave, where the shape of this wave is represented as a sum of odd harmonics, Anharmonic spin modulation where the spin direction has a cycloidal type modulation, and a Spiral-like spin structure, in which magnetic moments rotate in a plane perpendicular to the wave propagation vector, forming a spiral.

  20. [Etomidate and suxamethonium. The duration of relaxation and pseudocholinesterase activity. A clinical experimental study (author's transl)].

    PubMed

    Doenicke, A; Dittmann-Kessler, I; Sramoto, A; Beyer, E

    1980-03-01

    In ten health volunteers general anaesthesia was induced with etomidate (0.3 mg per kg body weight) and continued with NWO/O2 inhalation. Together with etomidate, suxamethonium (1.5 mg per kg body weight) was given simultaneously and the same dose reinjected as soon as the original muscle tone had returned completely. At equal intervals after the first and second injection the pseudocholinesterase was spectrophotometrically measured. No significant alteration of the enzyme activity was detectable at any time. Etomidate therefore does not inhibit the pseudocholinesterase. The two phases of relaxation were registered with the "finger-twitch" method and their duration compared. Etomidate did not prolong the time of relaxation after suxamethonium.

  1. Tuning the relaxation rates of dual-mode T1/T2 nanoparticle contrast agents: a study into the ideal system

    NASA Astrophysics Data System (ADS)

    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

  2. Water interactions with varying molecular states of bovine casein: 2H NMR relaxation studies

    SciTech Connect

    Kumosinski, T.F.; Pessen, H.; Prestrelski, S.J.; Farrell, H.M. Jr.

    1987-09-01

    The caseins occur in milk as spherical colloidal complexes of protein and salts with an average diameter of 1200 A, the casein micelles. Removal of Ca2+ is thought to result in their dissociation into smaller protein complexes stabilized by hydrophobic interactions and called submicelles. Whether these submicelles actually occur within the micelles as discrete particles interconnected by calcium phosphate salt bridges has been the subject of much controversy. A variety of physical measurements have shown that casein micelles contain an inordinately high amount of trapped water (2 to 7 g H/sub 2/O/g protein). With this in mind it was of interest to determine if NMR relaxation measurements could detect the presence of this trapped water within the micelles, and to evaluate whether it is a continuum with picosecond correlation times or is associated in part with discrete submicellar structures with nanosecond motions. For this purpose the variations in /sup 2/H NMR longitudinal and transverse relaxation rates of water with protein concentration were determined for bovine casein at various temperatures, under both submicellar and micellar conditions. D/sub 2/O was used instead of H/sub 2/O to eliminate cross-relaxation effects. From the protein concentration dependence of the relaxation rates, the second virial coefficient of the protein was obtained by nonlinear regression analysis. Using either an isotropic tumbling or an intermediate asymmetry model, degrees of hydration, v, and correlation times, tau c, were calculated for the caseins; from the latter parameter the Stokes radius, r, was obtained. Next, estimates of molecular weights were obtained from r and the partial specific volume. Values were in the range of those published from other methodologies for the submicelles.

  3. Superspin relaxation in Fe3O4/hexane magnetic fluids: A dynamic susceptibility study

    NASA Astrophysics Data System (ADS)

    Botez, Cristian E.; Morris, Joshua L.; Eastman, Michael P.

    2012-07-01

    We have used frequency-resolved (100 Hz < f < 10,000 Hz) ac magnetic susceptibility measurements to directly determine the Néel and Brown relaxation times in 30-nm-size Fe3O4/hexane magnetic fluids at temperatures between 200 and 300 K. Our data collected on both powder and magnetic fluid samples allow the separation of the contributions from the Néel and Brown relaxation mechanisms that act concomitantly within the above-mentioned temperature range. At all temperatures we find that the Brown relaxation times (τB) are shorter than their Néel counterparts (τN), evidence that the Brown mechanism yields the major contribution towards the system's overall superspin dynamics. τB exhibits a steep two-order-of-magnitude decrease upon heating, from τB = 1 × 10-3 s at T = 237 K to τB = 1.5 × 10-5 s at T = 270 K, a behavior mostly driven by the heating-induced reduction of the liquid carrier's viscosity.

  4. Wannier interpolation study of the Elliot-Yafet spin relaxation in metals

    NASA Astrophysics Data System (ADS)

    Roman, Eric; Souza, Ivo; Yates, Jonathan

    2007-03-01

    Energy states of nonmagnetic metals may be chosen to be purely spin up and down in the absence of spin-orbit coupling. Spin-orbit coupling mixes the two states by a small amount b^2. A spin-conserving interaction (e.g. electron-phonon) causes transitions between the two states, and flips the electron's spin. Some insight into this Elliot-Yafet spin relaxation mechanism can be obtained by averaging b^2 over the Fermi surface. In trivalent metals, such as aluminum, b^21 almost everywhere on the Fermi surface, except at small ``hot spot'' regions. Although the small regions of large b^2 dominate the spin relaxation process, they are difficult to capture numerically. We describe a Wannier interpolation strategy to compute . We validate it by performing ab initio calculations on aluminum, finding good agreement with previous results.^1 We also discuss interpolating ab initio electron-phonon matrix elements to compute the spin relaxation rate. J. Fabian and S. Das Sarma, Phys. Rev. Lett. 81, 5624 (1998). X. Wang, J. Yates, I. Souza, and D. Vanderbilt, Phys. Rev. B, in press (cond-mat/0608257).

  5. Venlafaxine versus applied relaxation for generalized anxiety disorder: a randomized controlled study on clinical and electrophysiological outcomes.

    PubMed

    Zullino, Daniele; Chatton, Anne; Fresard, Emmanuelle; Stankovic, Miroslava; Bondolfi, Guido; Borgeat, François; Khazaal, Yasser

    2015-03-01

    Some components of generalized anxiety disorder, such as physical symptoms, are thought to reflect autonomic nervous system arousal. This study primarily assessed the relationships between psychophysiological and clinical measures using venlafaxine extended release or applied relaxation, and secondarily, the impact of combination treatment in patients not remitting after 8 weeks. Fifty-eight patients were randomly assigned to 8 weeks of treatment with either venlafaxine or applied relaxation (Phase I). Non-remitted patients received combination treatment for an additional 8 weeks (Phase II). Assessments included the Hamilton Anxiety Scale (HAM-A), Beck Depression Inventory, Penn State Worry Questionnaire and the Stroop Color-Word Task coupled with electrophysiological measures (skin conductance and frontalis electromyography (EMG)). In Phase 1, a time effect was found for the clinical and skin conductance measures. Thirteen patients from each group were in remission. In Phase 2, seven additional patients remitted. Baseline psychophysiological measures were not associated with baseline clinical variables or with clinical outcomes. Independently of treatment allocation, a reduction in frontal EMG values at week 4 was significantly associated with a decrease in HAM-A scores at week 8. At week 4, responders from the applied relaxation group had lower electrophysiological activity than the venlafaxine group. Baseline psychophysiological measures were not linked with clinical measures at study inclusion or with treatment response. Frontal EMG response at week 4 is a possible predictor of treatment response. Treatment combination enhances treatment response after initial failure. PMID:25464934

  6. A molecular dynamics simulation study of the α-relaxation in a 1,4-polybutadiene melt as probed by the coherent dynamic structure factor

    NASA Astrophysics Data System (ADS)

    Smith, Grant D.; Bedrov, Dmitry; Paul, Wolfgang

    2004-09-01

    The dynamic coherent structure factor Scoh(q,t) for a 1,4-polybutadiene (PBD) melt has been investigated using atomistic molecular dynamics simulations. The relaxation of Scoh(q,t) at q=1.44 Å-1 and q=2.72 Å-1, corresponding to the first and second peaks in the static structure factor for PBD, was studied in detail over a wide range of temperature. It was found that time-temperature superposition holds for the α-relaxation for both q values over a wide temperature range and that the α-relaxation can be well described by a stretched (Kohlrauch-William-Watts) exponential with temperature independent but q dependent amplitude and stretching exponent. The α-relaxation times for both q values were found to exhibit the same non-Arrhenius temperature dependence, indicating that the same physical processes are responsible for relaxation on both length scales. The α-relaxation time was found to depend strongly upon the dynamical range of data utilized in determining the relaxation time, accounting for qualitative discrepancies between α-relaxation times reported here and those extracted for PBD from experimentally measured Scoh(q,t).

  7. Water vapor absorption in porous media polluted by calcium nitrate studied by time domain nuclear magnetic resonance.

    PubMed

    Gombia, Mirko; Bortolotti, Villiam; Brown, Robert J S; Camaiti, Mara; Cavallero, Luisa; Fantazzini, Paola

    2009-08-01

    Nuclear magnetic resonance relaxation analysis of liquid water (1)H nuclei in real porous media, selected for their similar composition (carbonate rocks) and different pore space architecture, polluted with calcium nitrate, is presented to study the kinetics of water condensation and salt deliquescence inside the pore space. These phenomena are responsible for deterioration of porous materials when exposed to environmental injury by pollution in a humid atmosphere. The theory is well described for simple pore geometries, but it is not yet well understood in real porous media with wide distributions of pore sizes and connections. The experiment is performed by following in time the formation of liquid water inside the pore space by T(1) and T(2) relaxation time distributions. The distributions allow one to see the effects of both the salt concentration and the pore space structure on the amount of water vapor condensed and its kinetics. It is shown that, for a given lithotype, even with different amounts of pollutant, the rate-average relaxation time T(1ra) tends to increase monotonically with NMR signal, proportional to the amount of liquid water. T(1ra) is often inversely associated with surface-to-volume ratio. This suggests a trend toward the filling of larger pores as amounts of liquid water increase, but it does not indicate a strict sequential filling of pores in order of size and starting with the smallest; in fact, relaxation time distributions show clearly that this is not the case. Increased amounts of salt lead to both markedly increased rates and markedly increased amounts of water absorption. NMR measurements of amounts of water, together with relaxation time distributions, give the possibility of information on the effect of pollution in porous materials exposed to humid atmospheres but sheltered from liquid water, even before the absorption of large amounts of moisture and subsequent damage. These phenomena are of importance also in other fields

  8. Water vapor absorption in porous media polluted by calcium nitrate studied by time domain nuclear magnetic resonance.

    PubMed

    Gombia, Mirko; Bortolotti, Villiam; Brown, Robert J S; Camaiti, Mara; Cavallero, Luisa; Fantazzini, Paola

    2009-08-01

    Nuclear magnetic resonance relaxation analysis of liquid water (1)H nuclei in real porous media, selected for their similar composition (carbonate rocks) and different pore space architecture, polluted with calcium nitrate, is presented to study the kinetics of water condensation and salt deliquescence inside the pore space. These phenomena are responsible for deterioration of porous materials when exposed to environmental injury by pollution in a humid atmosphere. The theory is well described for simple pore geometries, but it is not yet well understood in real porous media with wide distributions of pore sizes and connections. The experiment is performed by following in time the formation of liquid water inside the pore space by T(1) and T(2) relaxation time distributions. The distributions allow one to see the effects of both the salt concentration and the pore space structure on the amount of water vapor condensed and its kinetics. It is shown that, for a given lithotype, even with different amounts of pollutant, the rate-average relaxation time T(1ra) tends to increase monotonically with NMR signal, proportional to the amount of liquid water. T(1ra) is often inversely associated with surface-to-volume ratio. This suggests a trend toward the filling of larger pores as amounts of liquid water increase, but it does not indicate a strict sequential filling of pores in order of size and starting with the smallest; in fact, relaxation time distributions show clearly that this is not the case. Increased amounts of salt lead to both markedly increased rates and markedly increased amounts of water absorption. NMR measurements of amounts of water, together with relaxation time distributions, give the possibility of information on the effect of pollution in porous materials exposed to humid atmospheres but sheltered from liquid water, even before the absorption of large amounts of moisture and subsequent damage. These phenomena are of importance also in other fields

  9. Studying the ρ resonance parameters with staggered fermions

    NASA Astrophysics Data System (ADS)

    Fu, Ziwen; Wang, Lingyun

    2016-08-01

    We deliver a lattice study of ρ resonance parameters with p -wave π π scattering phases, which are extracted by finite-size methods at one center-of-mass frame and four moving frames for six lattice ensembles from the MILC Collaboration with pion masses ranging from 346 to 176 MeV. The effective range formula is applied to describe the scattering phases as a function of the energy covering the resonance region; this allows us to extract ρ resonance parameters and to investigate the quark-mass dependence. Lattice studies with three flavors of Asqtad-improved staggered fermions enable us to use the moving-wall source technique on large lattice spatial dimensions (L =64 ) and small light u /d quarks. Numerical computations are carried out at two lattice spacings, a ≈0.12 and 0.09 fm.

  10. Psychological profile and self-administered relaxation in patients with craniofacial pain: a prospective in-office study

    PubMed Central

    2013-01-01

    Introduction The objective of this study was to evaluate the psychological profile of craniofacial pain sufferers and the impact of patient subtype classification on the short-time effectiveness of a self-administered relaxation training. Methods One hundred unselected in-office patients (67% females) suffering from chronic facial pain and/or headache with the presumptive diagnose of temporo-mandibular disorder (TMD) completed a questionnaire battery comprising craniofacial pain perception, somatic complaints, irrational beliefs, and pain behavior and were classified into subtypes using cluster analysis. They underwent a self-administered progressive relaxation training and were re-evaluated for pain perception after 3 months. Results Pain was mild to moderate in the majority of patients. Symptom domains comprised parafunctional activities, temporo-mandibular pain and dysfunction, fronto-temporal headache, head/neck and neck/back pain. Three patient subtypes were identified regarding symptom/dysfunction level: (i) low burden (mild/moderate), (ii) psychosocial dysfunction (moderate/high), (iii) adaptive coping (moderate/mild). Self-rated adherence to the recommended relaxation training was moderate throughout the sample, but self-rated relief was significantly different between clusters. At follow-up, pain intensity was significantly decreased in all patients, whereas pain-related interference was improved only in dysfunctional and adaptive patients. Improvement of symptom domains varied between clusters and was most comprehensive in adaptive patients. Conclusions In conclusion, craniofacial pain sufferers can be divided in meaningful subtypes based on their pain perception, irrational beliefs, and pain behaviour. A self-administered relaxation training generally yielded positive effects on pain perception, however the benefit may be greater in patients with more marked symptom impact (both dysfunctional and adaptive). PMID:24382096

  11. A molecular dynamics study of dislocation density generation and plastic relaxation during shock of single crystal Cu

    NASA Astrophysics Data System (ADS)

    Sichani, Mehrdad M.; Spearot, Douglas E.

    2016-07-01

    The molecular dynamics simulation method is used to investigate the dependence of crystal orientation and shock wave strength on dislocation density evolution in single crystal Cu. Four different shock directions <100>, <110>, <111>, and <321> are selected to study the role of crystal orientation on dislocation generation immediately behind the shock front and plastic relaxation as the system reaches the hydrostatic state. Dislocation density evolution is analyzed for particle velocities between the Hugoniot elastic limit ( up H E L ) for each orientation up to a maximum of 1.5 km/s. Generally, dislocation density increases with increasing particle velocity for all shock orientations. Plastic relaxation for shock in the <110>, <111>, and <321> directions is primarily due to a reduction in the Shockley partial dislocation density. In addition, plastic anisotropy between these orientations is less apparent at particle velocities above 1.1 km/s. In contrast, plastic relaxation is limited for shock in the <100> orientation. This is partially due to the emergence of sessile stair-rod dislocations with Burgers vectors of 1/3<100> and 1/6<110>. The nucleation of 1/6<110> dislocations at lower particle velocities is mainly due to the reaction between Shockley partial dislocations and twin boundaries. On the other hand, for the particle velocities above 1.1 km/s, the nucleation of 1/3<100> dislocations is predominantly due to reaction between Shockley partial dislocations at stacking fault intersections. Both mechanisms promote greater dislocation densities after relaxation for shock pressures above 34 GPa compared to the other three shock orientations.

  12. Enhancing relaxation states and positive emotions in physicians through a mindfulness training program: A one-year study.

    PubMed

    Amutio, Alberto; Martínez-Taboada, Cristina; Hermosilla, Daniel; Delgado, Luis Carlos

    2015-01-01

    Previous research on mindfulness has focused mainly on stress-related negative symptoms and short-term effects. In contrast, the present article focuses on the impact of a mindfulness-based stress reduction (MBSR) program on improving well-being (i.e. relaxation states and related positive emotions) in a longitudinal study for a period of one year. A randomized controlled trial in a sample of 42 physicians was used. The intervention group participated in an 8-week MBSR program, with an additional 10-month maintenance period and completed measures of mindfulness and relaxation at pre-intervention, post-intervention and after 10 months. Heart rate measures were also obtained. Significant improvements in favor of the experimental group compared with the control group on the levels of mindfulness and relaxation (including positive emotional states, such as at ease/peace, renewal, energy, optimism, happiness, acceptance, and even transcendence) were obtained after eight weeks. Remarkably, change magnitudes (effect size) significantly increased at the end of the maintenance period after a year, especially for mindfulness and positive energy. Additionally, heart rate significantly decreased for the intervention group and maintained a year after the beginning of the treatment. Results are relevant in terms of practical consequences for improving health and well-being in this population and also in terms of cost-efficiency.

  13. Effect of Stimulative and Sedative Music Videos on Depressive Symptoms and Physiological Relaxation in Older Adults: A Pilot Study.

    PubMed

    Huang, Chiung-Yu; Hsieh, Yuan-Mei; Lai, Hui-Ling

    2016-09-01

    Music has been found to improve depressive symptoms and relaxation. However, few studies related to this issue have been conducted using music videos (MVs). The aim was to compare the effects of stimulative and sedative MVs on depressive symptoms and physiological relaxation (i.e., electromyography, heart rate variability, and skin conductance) in older adults with depressive symptoms. Using a 2-week crossover design, interventions alternated between watching a stimulative and sedative MV and vice versa. Each intervention lasted for 30 minutes on 1 day during the first week, and was then alternated to another intervention for 1 day during the following week. Stimulative MVs were more effective in treating depressive symptoms than sedative MVs. Stimulative and sedative MVs had beneficial effects on depressive symptoms and physiological relaxation compared with baseline data. These findings add new knowledge to the literature for health care providers to improve psychophysiological health in older adults with depressive symptoms. [Res Gerontol Nurs. 2016; 9(5):233-242.]. PMID:27637111

  14. Teaching to Relax: Development of a Program to Potentiate Stress-Results of a Feasibility Study with Medical Undergraduate Students.

    PubMed

    Scholz, Michael; Neumann, Carolin; Wild, Katharina; Garreis, Fabian; Hammer, Christian M; Ropohl, Axel; Paulsen, Friedrich; Burger, Pascal H M

    2016-09-01

    Medical students are a population at risk for the development of stress-related risk states (e.g. burnout) and manifest mental disorders (e.g. depression). Still the learning of coping mechanisms against stress is not an integral part of the medical curriculum. In a pilot study we developed an elective course for learning relaxation techniques (Relacs) which was geared to the clinical practice of autogenic training (AT) with psychiatric patients. The course focussed on an innovative and mostly communicative transfer of knowledge about AT, progressive muscle relaxation and medical hypnosis and stressed the principle of repeated and supervised exercises in small student groups alongside self-administered exercise. 42 students took part in this course and showed a very high acceptance for the topic and positive evaluation. Moreover, we found a distinct improvement of the participants' mental parameters (burnout, anxiety) and a good knowledge about the course's contents within the final exams at the end of the semester. The structure and realisation of the course is easily adaptable and very effective regarding the improvement of the students' mental health. Due to our results and the commonly known prevalence of stress-related disorders in medical students we postulate the integration of courses on relaxation strategies in the medical curriculum. PMID:26800974

  15. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    SciTech Connect

    Benjamin Michael Meyer

    2003-05-31

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, {tau}, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single distribution

  16. Preliminary Study of Oxygen-Enhanced Longitudinal Relaxation in MRI: A Potential Novel Biomarker of Oxygenation Changes in Solid Tumors

    SciTech Connect

    O'Connor, James P.B.; Naish, Josephine H.; Parker, Geoff J.M.; Waterton, John C.; Watson, Yvonne; Jayson, Gordon C.; Buonaccorsi, Giovanni A.; Cheung, Sue; Buckley, David L.; McGrath, Deirdre M.; West, Catharine M.L.; Davidson, Susan E.; Roberts, Caleb; Mills, Samantha J.; Mitchell, Claire L.; Hope, Lynn; Ton, N. Chan; Jackson, Alan

    2009-11-15

    Purpose: There is considerable interest in developing non-invasive methods of mapping tumor hypoxia. Changes in tissue oxygen concentration produce proportional changes in the magnetic resonance imaging (MRI) longitudinal relaxation rate (R{sub 1}). This technique has been used previously to evaluate oxygen delivery to healthy tissues and is distinct from blood oxygenation level-dependent (BOLD) imaging. Here we report application of this method to detect alteration in tumor oxygenation status. Methods and materials: Ten patients with advanced cancer of the abdomen and pelvis underwent serial measurement of tumor R{sub 1} while breathing medical air (21% oxygen) followed by 100% oxygen (oxygen-enhanced MRI). Gadolinium-based dynamic contrast-enhanced MRI was then performed to compare the spatial distribution of perfusion with that of oxygen-induced DELTAR{sub 1}. Results: DELTAR{sub 1} showed significant increases of 0.021 to 0.058 s{sup -1} in eight patients with either locally recurrent tumor from cervical and hepatocellular carcinomas or metastases from ovarian and colorectal carcinomas. In general, there was congruency between perfusion and oxygen concentration. However, regional mismatch was observed in some tumor cores. Here, moderate gadolinium uptake (consistent with moderate perfusion) was associated with low area under the DELTAR{sub 1} curve (consistent with minimal increase in oxygen concentration). Conclusions: These results provide evidence that oxygen-enhanced longitudinal relaxation can monitor changes in tumor oxygen concentration. The technique shows promise in identifying hypoxic regions within tumors and may enable spatial mapping of change in tumor oxygen concentration.

  17. Progressive muscle relaxation, yoga stretching, and ABC relaxation theory.

    PubMed

    Ghoncheh, Shahyad; Smith, Jonathan C

    2004-01-01

    This study compared the psychological effects of progressive muscle relaxation (PMR) and yoga stretching (hatha) exercises. Forty participants were randomly divided into two groups and taught PMR or yoga stretching exercises. Both groups practiced once a week for five weeks and were given the Smith Relaxation States Inventory before and after each session. As hypothesized, practitioners of PMR displayed higher levels of relaxation states (R-States) Physical Relaxation and Disengagement at Week 4 and higher levels of Mental Quiet and Joy as a posttraining aftereffect at Week 5. Contrary to what was hypothesized, groups did not display different levels of R-States Energized or Aware. Results suggest the value of supplementing traditional somatic conceptualizations of relaxation with the psychological approach embodied in ABC relaxation theory. Clinical and research implications are discussed.

  18. Fim study on the relaxation and crystallization processes of a Cu-Zr amorphous alloy

    NASA Astrophysics Data System (ADS)

    H, Lu; Lu, Hua; D, S. Tang; Tang, Disheng; Y, Y. Xiong; Xiong, Yanyun

    1987-09-01

    The relaxation of the Cu-50at.%Zr amorphous alloy was revealed by FIM as a process of formation of clusters consisting of 2, 3, or 4 atoms, which afterwards migrate towards some definite centers, predominantly the quenched-in "embryos", to construct ordered structure. This dynamic picture, so far as we know, is observed for the first time. Crystallized regions were determined by atom-probe analysis as Cu10Zr7 phase, and the coexisting phase CuZr2 was not revealed simultaneously.

  19. Ultrafast Optical Reflectivity Study of Photo-Carrier Relaxation Dynamics in Perovskite Iridates

    NASA Astrophysics Data System (ADS)

    Chu, Hao; Zhao, Liuyan; Hogan, Tom; Wilson, Stephen; Hsieh, David; Caltech Collaboration; University of California, Santa Barbara Collaboration

    The Ruddlesden-Popper series of perovskite iridates Srn+1IrnO3n+1 lie close to a localization-delocalization boundary, evolving from a Mott-like magnetic insulator in the single layer (n=1) compound to a paramagnetic semi-metal in the infinite layer (n= ∞) compound. We will discuss the insulator-to-metal transition in perovskite iridates from the point of view of time-resolved optical reflectivity measurements. This technique probes the relaxation dynamics of photo-generated carriers, which are strongly affected by the presence of a charge gap.

  20. Experimental study on resonant frequency of the thermoacoustic cooling system

    NASA Astrophysics Data System (ADS)

    Sakamoto, Shin-ichi; Hirano, Hiroyuki; Fujita, Takashi; Watanabe, Yoshiaki

    2006-05-01

    The purpose of our study is to construct a new cooling system applying the thermoacoustic effect. Stainless loop-tube is employed as our thermoacoustic cooling system and temperature decrease of 40 degrees C from the room temperature has been confirmed. In this paper, it is investigated that the relation between the viscosity boundary layer and the resonant frequency of the generated sound is investigated. Also, the sound pressure and temperature variation are observed with various total lengths of the loop-tube, with the view toward improvement in the cooling effect of the thermoacoustic cooling system. It was generally considered that the sound generated in the thermoacoustic cooling system is resonated with the tube length by 1 wavelength. However, when the total length of the loop-tube is over 2600 mm and inner pressure is 0.1 MPa, the resonant wavelength is 2. This is resulted from the influence of the viscosity boundary layer. It is found that the loop-tube decides the resonant frequency so that the thickness of the viscosity boundary layer is smaller than the stack channel radius. As a result, the resonant wavelength is 2 in a certain condition. The frequency is an important parameter for the thermoacoustic cooling system. From obtained results, one of the factors to select the frequency is found.

  1. Magnetic resonance spectroscopy and imaging for the study of fossils.

    PubMed

    Giovannetti, Giulio; Guerrini, Andrea; Salvadori, Piero A

    2016-07-01

    Computed tomography (CT) has long been used for investigating palaeontological specimens, as it is a nondestructive technique which avoids the need to dissolve or ionize the fossil sample. However, magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) have recently gained ground as analytical tools for examination of palaeontological samples, by nondestructively providing information about the structure and composition of fossils. While MRI techniques are able to reveal the three-dimensional geometry of the trace fossil, MRS can provide information on the chemical composition of the samples. The multidimensional nature of MR (magnetic resonance) signals has potential to provide rich three-dimensional data on the palaeontological specimens and also to help in elucidating paleopathological and paleoecological questions. In this work the verified applications and the emerging uses of MRI and MRS in paleontology are reviewed, with particular attention to fossil spores, fossil plants, ambers, fossil invertebrates, and fossil vertebrate studies.

  2. Strategy for the study of paramagnetic proteins with slow electronic relaxation rates by nmr spectroscopy: application to oxidized human [2Fe-2S] ferredoxin.

    PubMed

    Machonkin, Timothy E; Westler, William M; Markley, John L

    2004-05-01

    NMR studies of paramagnetic proteins are hampered by the rapid relaxation of nuclei near the paramagnetic center, which prevents the application of conventional methods to investigations of the most interesting regions of such molecules. This problem is particularly acute in systems with slow electronic relaxation rates. We present a strategy that can be used with a protein with slow electronic relaxation to identify and assign resonances from nuclei near the paramagnetic center. Oxidized human [2Fe-2S] ferredoxin (adrenodoxin) was used to test the approach. The strategy involves six steps: (1) NMR signals from (1)H, (13)C, and (15)N nuclei unaffected or minimally affected by paramagnetic effects are assigned by standard multinuclear two- and three-dimensional (2D and 3D) spectroscopic methods with protein samples labeled uniformly with (13)C and (15)N. (2) The very broad, hyperfine-shifted signals from carbons in the residues that ligate the metal center are classified by amino acid and atom type by selective (13)C labeling and one-dimensional (1D) (13)C NMR spectroscopy. (3) Spin systems involving carbons near the paramagnetic center that are broadened but not hyperfine-shifted are elucidated by (13)C[(13)C] constant time correlation spectroscopy (CT-COSY). (4) Signals from amide nitrogens affected by the paramagnetic center are assigned to amino acid type by selective (15)N labeling and 1D (15)N NMR spectroscopy. (5) Sequence-specific assignments of these carbon and nitrogen signals are determined by 1D (13)C[(15)N] difference decoupling experiments. (6) Signals from (1)H nuclei in these spin systems are assigned by paramagnetic-optimized 2D and 3D (1)H[(13)C] experiments. For oxidized human ferredoxin, this strategy led to assignments (to amino acid and atom type) for 88% of the carbons in the [2Fe-2S] cluster-binding loops (residues 43-58 and 89-94). These included complete carbon spin-system assignments for eight of the 22 residues and partial assignments for

  3. Experiment study of an electron cyclotron resonant ion source based on a tapered resonance cavity

    NASA Astrophysics Data System (ADS)

    Yang, Juan; Shi, Feng; Jin, Yizhou; Wang, Yunmin; Komurasaki, Kimiya

    2013-12-01

    Electron cyclotron resonant plasma is one type of magnetised plasma generated by continuous microwave energy. It has the property of high degree of ionization and large volume at low gas pressure, which makes it useful for space propulsion and material processing. This article presents the experiment study of the plasma properties and ion beam extraction from an electron cyclotron resonant ion source based on a tapered resonance cavity. Optical emission spectroscopy based on a simple collisional radiation model was used for plasma diagnosis. Experiment results show that, at microwave power setting ranging from 7.06 to 17.40 W and mass flow rate ranging from 1 to 10 sccm, argon gas can be ionized. Ion beam of 109.1 mA from the ion source can be extracted at microwave power of 30 W, mass flow rate of 10 sccm, and accel voltage of 800 V. The diagnosed plasma temperature and density are 2.4-5.2 eV and 2 × 1016-4.8 × 1017 m-3, respectively.

  4. Experiment study of an electron cyclotron resonant ion source based on a tapered resonance cavity

    SciTech Connect

    Yang, Juan; Shi, Feng; Jin, Yizhou; Wang, Yunmin; Komurasaki, Kimiya

    2013-12-15

    Electron cyclotron resonant plasma is one type of magnetised plasma generated by continuous microwave energy. It has the property of high degree of ionization and large volume at low gas pressure, which makes it useful for space propulsion and material processing. This article presents the experiment study of the plasma properties and ion beam extraction from an electron cyclotron resonant ion source based on a tapered resonance cavity. Optical emission spectroscopy based on a simple collisional radiation model was used for plasma diagnosis. Experiment results show that, at microwave power setting ranging from 7.06 to 17.40 W and mass flow rate ranging from 1 to 10 sccm, argon gas can be ionized. Ion beam of 109.1 mA from the ion source can be extracted at microwave power of 30 W, mass flow rate of 10 sccm, and accel voltage of 800 V. The diagnosed plasma temperature and density are 2.4–5.2 eV and 2 × 10{sup 16}–4.8 × 10{sup 17} m{sup −3}, respectively.

  5. Magnetic resonance studies of photo-induced electron transfer reactions

    SciTech Connect

    van Willigen, H.

    1990-12-01

    During the period covered by this report research has been concerned with the application of Fourier Transform Electron Paramagnetic Resonance (FT EPR) in the study of photo-induced electron transfer reactions. Donor molecules used in this investigation have been various porphyrins, whereas quinones were used as acceptor molecules.

  6. Magnetic Resonance Perfusion Imaging in the Study of Language

    ERIC Educational Resources Information Center

    Hillis, Argye E.

    2007-01-01

    This paper provides a brief review of various uses of magnetic resonance perfusion imaging in the investigation of brain/language relationships. The reviewed studies illustrate how perfusion imaging can reveal areas of brain where dysfunction due to low blood flow is associated with specific language deficits, and where restoration of blood flow…

  7. Bone tissue and porous media: common features and differences studied by NMR relaxation.

    PubMed

    Fantazzini, Paola; Brown, Robert James Sidford; Borgia, Giulio Cesare

    2003-01-01

    Despite significant differences between bone tissues and other porous media such as oilfield rocks, there are common features as well as differences in the response of NMR relaxation measurements to the internal structures of the materials. Internal surfaces contribute to both transverse (T2) and longitudinal (T1) relaxation of pore fluids, and in both cases the effects depend on, among other things, local surface-to-volume ratio (S/V). In both cases variations in local S/V can lead to distributions of relaxation times, sometimes over decades. As in rocks, it is useful to take bone data under different conditions of cleaning, saturation, and desaturation. T1 and T2 distributions are computed using UPEN. In trabecular bone it is easy to see differences in dimensions of intertrabecular spaces in samples that have been de-fatted and saturated with water, with longer T1 and T2 for larger pores. Both T1 and T2 distributions for these water-saturated samples are bimodal, separating or partly separating inter- and intratrabecular water. The T1 peak times have a ratio of from 10 to 30, depending on pore size, but for the smaller separations the distributions may not have deep minima. The T2 peak times have ratios of over 1000, with intratrabecular water represented by large peaks at a fraction of a ms, which we can observe only by single spin echoes. CPMG data show peaks at about a second, tapering down to small amplitudes by a ms. In all samples the free induction decay (FID) from an inversion-recovery (IR) T1 measurement shows an approximately Gaussian (solid-like) component, exp[-1/2 (T/TGC), with TGC approximately 11.7+/-0.7 micros (GC for "Gaussian Component"), and a liquid-like component (LLC) with initially simple-exponential decay at the rate-average time T(2-FID) for the first 100 micros. Averaging and smoothing procedures are adopted to derive T(2-FID) as a function of IR time and to get T1 distributions for both the GC and the LLC. It appears that contact with

  8. Muon Spin Rotation/Relaxation Study of Ba2CoO4

    SciTech Connect

    Russo, P. L.; Sugiyama, J.; Brewer, J.; Ansaldo, E. J.; Stubbs, S. L.; Chow, K. H.; Jin, Rongying; Sha, Hao; Zhang, Jiandi

    2009-01-01

    A positive muon spin rotation and relaxation ({mu}{sup +}SR) experiment on a single crystal of Ba{sub 2}CoO{sub 4} indicates the existence of an antiferromagnetic (AF) transition occurring at T{sub N} {approx} 24 K. Weak transverse field measurements show that the paramagnetic volume fraction of the sample decreases rapidly at the magnetic transition, indicating a bulk effect which cannot be due to the presence of impurities. Zero-field measurements reveal the presence of a magnetically ordered state below T{sub N} with at least three crystallographically inequivalent muon sites. The results are compared to recent magnetic susceptibility and neutron measurements. Of the two AF spin structures proposed to explain recent neutron experiments, the {mu}{sup +}SR results clearly exclude the one involving AF order along the c axis while supporting that with AF order in the ab plane.

  9. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study

    PubMed Central

    Zhou, Li-li; Liu, Rang-su; Tian, Ze-an; Liu, Hai-rong; Hou, Zhao-yang; Peng, Ping

    2016-01-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90–150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule. PMID:27526660

  10. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study.

    PubMed

    Zhou, Li-Li; Liu, Rang-Su; Tian, Ze-An; Liu, Hai-Rong; Hou, Zhao-Yang; Peng, Ping

    2016-01-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90-150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule. PMID:27526660

  11. A Study of Successive Over-relaxation Method Parallelization over Modern HPC Languages

    SciTech Connect

    Mittal, Sparsh

    2014-01-01

    Successive over-relaxation (SOR) is a computationally intensive, yet extremely important iterative solver for solving linear systems. Due to recent trends of exponential growth in amount of data generated and increasing problem sizes, serial platforms have proved to be insucient in providing the required computational power. In this paper, we present parallel implementations of red-black SOR method using three modern programming languages namely Chapel, D and Go. We employ SOR method for solving 2D steady-state heat conduction problem. We discuss the optimizations incorporated and the features of these languages which are crucial for improving the program performance. Experiments have been performed using 2, 4, and 8 threads and performance results are compared with serial execution. The analysis of results provides important insights into working of SOR method.

  12. Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets

    NASA Astrophysics Data System (ADS)

    Salman, Z.; Parolin, T. J.; Chow, K. H.; Keeler, T. A.; Miller, R. I.; Wang, D.; Macfarlane, W. A.

    2006-05-01

    We present longitudinal field muon spin relaxation (μSR) measurements in the unilluminated state of the photosensitive molecular magnetic Co-Fe Prussian Blue analogues M1-2xCo1+x[Fe(CN)6]•zH2O , where M=K and Rb with x=0.4 and ≃0.17 , respectively. These results are compared to those obtained in the x=0.5 stoichiometric limit Co1.5[Fe(CN)6]•6H2O , which is not photosensitive. We find evidence for correlation between the range of magnetic ordering and the value of x in the unilluminated state, which can be explained using a site percolation model.

  13. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Zhou, Li-Li; Liu, Rang-Su; Tian, Ze-An; Liu, Hai-Rong; Hou, Zhao-Yang; Peng, Ping

    2016-08-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90–150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule.

  14. A Computational and Experimental Study of Resonators in Three Dimensions

    NASA Technical Reports Server (NTRS)

    Tam, C. K. W.; Ju, H.; Jones, Michael G.; Watson, Willie R.; Parrott, Tony L.

    2009-01-01

    In a previous work by the present authors, a computational and experimental investigation of the acoustic properties of two-dimensional slit resonators was carried out. The present paper reports the results of a study extending the previous work to three dimensions. This investigation has two basic objectives. The first is to validate the computed results from direct numerical simulations of the flow and acoustic fields of slit resonators in three dimensions by comparing with experimental measurements in a normal incidence impedance tube. The second objective is to study the flow physics of resonant liners responsible for sound wave dissipation. Extensive comparisons are provided between computed and measured acoustic liner properties with both discrete frequency and broadband sound sources. Good agreements are found over a wide range of frequencies and sound pressure levels. Direct numerical simulation confirms the previous finding in two dimensions that vortex shedding is the dominant dissipation mechanism at high sound pressure intensity. However, it is observed that the behavior of the shed vortices in three dimensions is quite different from those of two dimensions. In three dimensions, the shed vortices tend to evolve into ring (circular in plan form) vortices, even though the slit resonator opening from which the vortices are shed has an aspect ratio of 2.5. Under the excitation of discrete frequency sound, the shed vortices align themselves into two regularly spaced vortex trains moving away from the resonator opening in opposite directions. This is different from the chaotic shedding of vortices found in two-dimensional simulations. The effect of slit aspect ratio at a fixed porosity is briefly studied. For the range of liners considered in this investigation, it is found that the absorption coefficient of a liner increases when the open area of the single slit is subdivided into multiple, smaller slits.

  15. Fundamental studies of stress distributions and stress relaxation in oxide scales on high temperature alloys. [Final progress report

    SciTech Connect

    Shores, D.A.; Stout, J.H.; Gerberich, W.W.

    1993-06-01

    This report summarizes a three-year study of stresses arising in the oxide scale and underlying metal during high temperature oxidation and of scale cracking. In-situ XRD was developed to measure strains during oxidation over 1000{degrees}C on pure metals. Acoustic emission was used to observe scale fracture during isothermal oxidation and cooling, and statistical analysis was used to infer mechanical aspects of cracking. A microscratch technique was used to measure the fracture toughness of scale/metal interface. A theoretical model was evaluated for the development and relaxation of stresses in scale and metal substrate during oxidation.

  16. Application of MOBILE (mapping of oxygen by imaging lipids relaxation enhancement) to study variations in tumor oxygenation.

    PubMed

    Jordan, Bénédicte F; Magat, Julie; Colliez, Florence; Ozel, Elif; Fruytier, Anne-Catherine; Marchand, Valérie; Mignion, Lionel; Gallez, Bernard

    2013-01-01

    The aim of the study was to sensitively monitor changes in tumor oxygen using the MOBILE (mapping of oxygen by imaging lipids relaxation enhancement) technique. This method was applied in mammary tumor mouse models on an 11.7T Bruker MRI system. MOBILE was compared with functional imaging R2*, R1 of water and with pO2 measurements (using EPR oximetry and O2-dependent fluorescence quenching measurements). MOBILE was shown to be capable to monitor changes in oxygenation in tumor tissues.

  17. Muon spin relaxation study of Zr(H2PO4)(PO4).2H2O.

    PubMed

    Clayden, Nigel J; Cottrell, Stephen P

    2006-07-14

    Muon spin relaxation has been used to study the muon dynamics in the layered zirconium phosphate Zr(H(2)PO(4))(PO(4)).2H(2)O as a function of temperature. Radiofrequency decoupling was used to establish the origin of the local dipolar field as coupling with (1)H spins. Muons were trapped at two sites, one identified as HMuO and the other consistent with PO-Mu on the basis of their zero-field second moments. Although a small decrease in the local nuclear dipolar field was seen with temperature, the muons remained essentially static over the temperature range 20-300 K.

  18. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite

    NASA Astrophysics Data System (ADS)

    Reddy, S. Lakshmi; Fayazuddin, Md.; Frost, Ray L.; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals.

  19. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite.

    PubMed

    Reddy, S Lakshmi; Fayazuddin, Md; Frost, Ray L; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals. PMID:17324611

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

    ERIC Educational Resources Information Center

    Hites, Lacey S.; Lundervold, Duane A.

    2013-01-01

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

  1. Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn.

    PubMed

    Baker, Michael L; Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J; Barker, Claire; Blundell, Stephen J; Carretta, Stefano; Collison, David; Güdel, Hans U; Guidi, Tatiana; McInnes, Eric J L; Möller, Johannes S; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L; Santini, Paolo; Tuna, Floriana; Tregenna-Piggott, Philip L W; Vitorica-Yrezabal, Iñigo J; Timco, Grigore A; Winpenny, Richard E P

    2016-01-26

    The spin dynamics of Cr8 Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8 Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8 Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8 Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities. PMID:26748964

  2. Studies of a Large Odd‐Numbered Odd‐Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8Mn

    PubMed Central

    Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J.; Barker, Claire; Carretta, Stefano; Collison, David; Güdel, Hans U.; Guidi, Tatiana; McInnes, Eric J. L.; Möller, Johannes S.; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L.; Santini, Paolo; Tuna, Floriana; Tregenna‐Piggott, Philip L. W.; Vitorica‐Yrezabal, Iñigo J.; Timco, Grigore A.

    2016-01-01

    Abstract The spin dynamics of Cr8Mn, a nine‐membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8Mn is a rare example of a large odd‐membered AF ring, and has an odd‐number of 3d‐electrons present. Odd‐membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated‐spin ground states. The chemical synthesis and structures of two Cr8Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground‐spin‐state crossing from S=1/2 to S=3/2 in Cr8Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin‐pair correlations and scalar‐spin chirality, shows a non‐collinear spin structure that fluctuates between non‐planar states of opposite chiralities. PMID:26748964

  3. Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn.

    PubMed

    Baker, Michael L; Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J; Barker, Claire; Blundell, Stephen J; Carretta, Stefano; Collison, David; Güdel, Hans U; Guidi, Tatiana; McInnes, Eric J L; Möller, Johannes S; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L; Santini, Paolo; Tuna, Floriana; Tregenna-Piggott, Philip L W; Vitorica-Yrezabal, Iñigo J; Timco, Grigore A; Winpenny, Richard E P

    2016-01-26

    The spin dynamics of Cr8 Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8 Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8 Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8 Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities.

  4. Curie-type paramagnetic NMR relaxation in the aqueous solution of Ni(II).

    PubMed

    Mareš, Jiří; Hanni, Matti; Lantto, Perttu; Lounila, Juhani; Vaara, Juha

    2014-04-21

    Ni(2+)(aq) has been used for many decades as a model system for paramagnetic nuclear magnetic resonance (pNMR) relaxation studies. More recently, its magnetic properties and also nuclear magnetic relaxation rates have been studied computationally. We have calculated electron paramagnetic resonance and NMR parameters using quantum-mechanical (QM) computation of molecular dynamics snapshots, obtained using a polarizable empirical force field. Statistical averages of hyperfine coupling, g- and zero-field splitting tensors, as well as the pNMR shielding terms, are compared to the available experimental and computational data. In accordance with our previous work, the isotropic hyperfine coupling as well as nuclear shielding values agree well with experimental measurements for the (17)O nuclei of water molecules in the first solvation shell of the nickel ion, whereas larger deviations are found for (1)H centers. We report, for the first time, the Curie-type contribution to the pNMR relaxation rate using QM calculations together with Redfield relaxation theory. The Curie relaxation mechanism is analogous to chemical shift anisotropy relaxation, well-known in diamagnetic NMR. Due to the predominance of other types of paramagnetic relaxation mechanisms for this system, it is possible to extract the Curie term only computationally. The Curie mechanism alone would result in around 16 and 20 s(-1) of relaxation rates (R1 and R2 respectively) for the (1)H nuclei of water molecules bonded to the Ni(2+) center, in a magnetic field of 11.7 T. The corresponding (17)O relaxation rates are around 33 and 38 s(-1). We also report the Curie contribution to the relaxation rate for molecules beyond the first solvation shell in a 1 M solution of Ni(2+) in water.

  5. Backbone dynamics of free barnase and its complex with barstar determined by 15N NMR relaxation study.

    PubMed

    Sahu, S C; Bhuyan, A K; Udgaonkar, J B; Hosur, R V

    2000-10-01

    Backbone dynamics of uniformly 15N-labeled free barnase and its complex with unlabelled barstar have been studied at 40 degrees C, pH 6.6, using 15N relaxation data obtained from proton-detected 2D [1H]-15N NMR spectroscopy. 15N spin-lattice relaxation rate constants (R1), spin-spin relaxation rate constants (R2), and steady-state heteronuclear [1H]-15N NOEs have been measured at a magnetic field strength of 14.1 Tesla for 91 residues of free barnase and for 90 residues out of a total of 106 in the complex (excluding three prolines and the N-terminal residue) backbone amide 15N sites of barnase. The primary relaxation data for both the cases have been analyzed in the framework of the model-free formalism using both isotropic and axially symmetric models of the rotational diffusion tensor. As per the latter, the overall rotational correlation times (tau(m)) are 5.0 and 9.5 ns for the free and complexed barnase, respectively. The average order parameter is found to be 0.80 for free barnase and 0.86 for the complex. However, the changes are not uniform along the backbone and for about 5 residues near the binding interface there is actually a significant decrease in the order parameters on complex formation. These residues are not involved in the actual binding. For the residues where the order parameter increases, the magnitudes vary significantly. It is observed that the complex has much less internal mobility, compared to free barnase. From the changes in the order parameters, the entropic contribution of NH bond vector motion to the free energy of complex formation has been calculated. It is apparent that these motion's cause significant unfavorable contributions and therefore must be compensated by many other favorable contributions to effect tight complex formation. The observed variations in the motion and their different locations with regard to the binding interface may have important implications for remote effects and regulation of the enzyme action. PMID

  6. Fundamentals of ionic conductivity relaxation gained from study of procaine hydrochloride and procainamide hydrochloride at ambient and elevated pressure.

    PubMed

    Wojnarowska, Z; Swiety-Pospiech, A; Grzybowska, K; Hawelek, L; Paluch, M; Ngai, K L

    2012-04-28

    The pharmaceuticals, procaine hydrochloride and procainamide hydrochloride, are glass-forming as well as ionically conducting materials. We have made dielectric measurements at ambient and elevated pressures to characterize the dynamics of the ion conductivity relaxation in these pharmaceuticals, and calorimetric measurements for the structural relaxation. Perhaps due to their special chemical and physical structures, novel features are found in the ionic conductivity relaxation of these pharmaceuticals. Data of conductivity relaxation in most ionic conductors when represented by the electric loss modulus usually show a single resolved peak in the electric modulus loss M(")(f) spectra. However, in procaine hydrochloride and procainamide hydrochloride we find in addition another resolved loss peak at higher frequencies over a temperature range spanning across T(g). The situation is analogous to many non-ionic glass-formers showing the presence of the structural α-relaxation together with the Johari-Goldstein (JG) β-relaxation. Naturally the analogy leads us to name the slower and faster processes resolved in procaine hydrochloride and procainamide hydrochloride as the primary α-conductivity relaxation and the secondary β-conductivity relaxation, respectively. The analogy of the β-conductivity relaxation in procaine HCl and procainamide HCl with JG β-relaxation in non-ionic glass-formers goes further by the finding that the β-conductivity is strongly related to the α-conductivity relaxation at temperatures above and below T(g). At elevated pressure but compensated by raising temperature to maintain α-conductivity relaxation time constant, the data show invariance of the ratio between the β- and the α-conductivity relaxation times to changes of thermodynamic condition. This property indicates that the β-conductivity relaxation has fundamental importance and is indispensable as the precursor of the α-conductivity relaxation, analogous to the relation found

  7. Fundamentals of ionic conductivity relaxation gained from study of procaine hydrochloride and procainamide hydrochloride at ambient and elevated pressure

    NASA Astrophysics Data System (ADS)

    Wojnarowska, Z.; Swiety-Pospiech, A.; Grzybowska, K.; Hawelek, L.; Paluch, M.; Ngai, K. L.

    2012-04-01

    The pharmaceuticals, procaine hydrochloride and procainamide hydrochloride, are glass-forming as well as ionically conducting materials. We have made dielectric measurements at ambient and elevated pressures to characterize the dynamics of the ion conductivity relaxation in these pharmaceuticals, and calorimetric measurements for the structural relaxation. Perhaps due to their special chemical and physical structures, novel features are found in the ionic conductivity relaxation of these pharmaceuticals. Data of conductivity relaxation in most ionic conductors when represented by the electric loss modulus usually show a single resolved peak in the electric modulus loss M″(f ) spectra. However, in procaine hydrochloride and procainamide hydrochloride we find in addition another resolved loss peak at higher frequencies over a temperature range spanning across Tg. The situation is analogous to many non-ionic glass-formers showing the presence of the structural α-relaxation together with the Johari-Goldstein (JG) β-relaxation. Naturally the analogy leads us to name the slower and faster processes resolved in procaine hydrochloride and procainamide hydrochloride as the primary α-conductivity relaxation and the secondary β-conductivity relaxation, respectively. The analogy of the β-conductivity relaxation in procaine HCl and procainamide HCl with JG β-relaxation in non-ionic glass-formers goes further by the finding that the β-conductivity is strongly related to the α-conductivity relaxation at temperatures above and below Tg. At elevated pressure but compensated by raising temperature to maintain α-conductivity relaxation time constant, the data show invariance of the ratio between the β- and the α-conductivity relaxation times to changes of thermodynamic condition. This property indicates that the β-conductivity relaxation has fundamental importance and is indispensable as the precursor of the α-conductivity relaxation, analogous to the relation found

  8. Study of metalloproteins using continuous wave electron paramagnetic resonance (EPR).

    PubMed

    Gambarelli, Serge; Maurel, Vincent

    2014-01-01

    Electron paramagnetic resonance (EPR) is an invaluable tool when studying systems with paramagnetic centers. It is a sensitive spectroscopic method, which can be used with dilute samples in aqueous buffer solutions. Here, we describe the basic procedure for recording an X-band EPR spectrum of a metalloprotein sample at low temperature. We also discuss basic optimization techniques to provide spectra with a high signal to noise ratio and minimum distortion.

  9. Breathing and Relaxation

    MedlinePlus

    ... Top Doctors in the Nation Departments & Divisions Home Health Insights Stress & Relaxation Breathing and Relaxation Breathing and Relaxation Make ... Management Assess Your Stress Coping Strategies Identifying ... & Programs Health Insights Doctors & Departments Research & Science Education & Training Make ...

  10. Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study

    PubMed Central

    Bricker, William P.; Shenai, Prathamesh M.; Ghosh, Avishek; Liu, Zhengtang; Enriquez, Miriam Grace M.; Lambrev, Petar H.; Tan, Howe-Siang; Lo, Cynthia S.; Tretiak, Sergei; Fernandez-Alberti, Sebastian; Zhao, Yang

    2015-01-01

    Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function. PMID:26346438

  11. Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study.

    PubMed

    Bricker, William P; Shenai, Prathamesh M; Ghosh, Avishek; Liu, Zhengtang; Enriquez, Miriam Grace M; Lambrev, Petar H; Tan, Howe-Siang; Lo, Cynthia S; Tretiak, Sergei; Fernandez-Alberti, Sebastian; Zhao, Yang

    2015-01-01

    Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function. PMID:26346438

  12. Calorimetric studies of the heat capacity and relaxation of amorphous Si prepared by electron beam evaporation

    NASA Astrophysics Data System (ADS)

    Tsang, K. H.; Kui, H. W.; Chik, K. P.

    1993-10-01

    The heat capacity of a-Si thin film prepared by electron beam evaporation method was measured from 360 to 820 K by a differential scanning calorimeter. For the as-prepared a-Si specimen, two novel irreversible endothermic processes and one irreversible broad exothermic reaction were found. The origins of the endothermic reactions were not known. It is suggested that they may be caused by a change in the number and distribution of voids that occurs at approximately 465 K and the creation of dangling bonds at the higher temperature regime (≳620 K). The exothermic reaction is attributed to heat release during structural relaxation. When measuring the heat capacity of a-Si, Ca-Sip, these irreversible reactions were first eliminated by annealing the specimens at high temperatures. The heat capacity of crystalline Si, Cc-Sip, was also measured and the difference, ΔCSip=Ca-Sip -Cc-Sip, was used to evaluate the thermodynamic melting temperature of the a-Si, Tal, which is determined to be 1400 K.

  13. Computational Study of Atomistic Strain Relaxation Mechanisms in Biaxially Strained Ultra-Thin Metallic Films

    NASA Astrophysics Data System (ADS)

    Gungor, M. Rauf; Maroudas, Dimitrios

    2005-03-01

    Understanding the mechanical response under certain loading conditions of nanometer-scale-thick metallic films is fundamentally and technologically important. In this presentation, we report a comprehensive computational analysis on the atomistic mechanisms of strain relaxation under a wide range of applied biaxial tensile strain in free-standing ultra-thin Cu films based on multi-million-atom molecular-dynamics simulations. Our analysis reveals that after an elastic response at low strain (< 2%), plastic deformation occurs accompanied by dislocation emission from the void surface, void surface morphological transition, dislocation jogging, vacancy generation and migration along dislocation cores, as well as formation and propagation of threading dislocation loops from the film's surfaces. At higher (> 6%) strain levels, a transition to a new plastic deformation regime gives rise to a practically uniform distribution of dislocations in the metallic thin film. Under such conditions, dislocations are emitted from the thin film's surfaces and inhibit void growth due to their interactions with the dislocations emitted from the void surface and the resulting pinning of the latter defects.

  14. Non-radiative relaxation of photoexcited chlorophylls: Theoretical and experimental study

    SciTech Connect

    Bricker, William P.; Shenai, Prathamesh M.; Ghosh, Avishek; Liu, Zhengtang; Enriquez, Miriam Grace M.; Lambrev, Petar H.; Tan, Howe -Siang; Lo, Cynthia S.; Tretiak, Sergei; Fernandez-Alberti, Sebastian; Zhao, Yang

    2015-09-08

    Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. With modeling this process, non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

  15. Non-radiative relaxation of photoexcited chlorophylls: Theoretical and experimental study

    DOE PAGES

    Bricker, William P.; Shenai, Prathamesh M.; Ghosh, Avishek; Liu, Zhengtang; Enriquez, Miriam Grace M.; Lambrev, Petar H.; Tan, Howe -Siang; Lo, Cynthia S.; Tretiak, Sergei; Fernandez-Alberti, Sebastian; et al

    2015-09-08

    Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. With modeling this process, non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are ablemore » to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.« less

  16. High-field small animal magnetic resonance oncology studies

    NASA Astrophysics Data System (ADS)

    Bokacheva, Louisa; Ackerstaff, Ellen; LeKaye, H. Carl; Zakian, Kristen; Koutcher, Jason A.

    2014-01-01

    This review focuses on the applications of high magnetic field magnetic resonance imaging (MRI) and spectroscopy (MRS) to cancer studies in small animals. High-field MRI can provide information about tumor physiology, the microenvironment, metabolism, vascularity and cellularity. Such studies are invaluable for understanding tumor growth and proliferation, response to treatment and drug development. The MR techniques reviewed here include 1H, 31P, chemical exchange saturation transfer imaging and hyperpolarized 13C MRS as well as diffusion-weighted, blood oxygen level dependent contrast imaging and dynamic contrast-enhanced MRI. These methods have been proven effective in animal studies and are highly relevant to human clinical studies.

  17. Relaxation Assessment with Varied Structured Milieu (RELAX).

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Cassel, Susie L.

    1983-01-01

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

  18. Study of proton resonance structure in 27P via resonant elastic scattering of 26Si+p

    NASA Astrophysics Data System (ADS)

    Jung, H. S.; Lee, C. S.; Kwon, Y. K.; Moon, J. Y.; Lee, J. H.; Yun, C. C.; Kubono, S.; Yamaguchi, H.; Hashimoto, T.; Kahl, D.; Hayakawa, S.; Choi, Seonho; Kim, M. J.; Kim, Y. H.; Kim, Y. K.; Park, J. S.; Kim, E. J.; Moon, C.-B.; Teranishi, T.; Wakabayashi, Y.; Iwasa, N.; Yamada, T.; Togano, Y.; Kato, S.; Cherubini, S.; Rapisarda, G. G.

    2012-11-01

    A measurement of resonant elastic scattering of 26Si+p was performed with a thick target using a 26Si radioactive ion beam at the CRIB (CNS Radioactive Ion Beam separator) of the Center for Nuclear Study (CNS), the University of Tokyo. The excitation function of 27P was measured successfully with the inverse kinematics method through a covered the range of excitation energies from Ex ~ 2.3 to 3.8 MeV, providing information about the resonance structure of this nucleus. The properties of these resonances are important to better determine the production rates of 26Si(p,g)27P reaction, which is one of the astrophysically important nuclear reactions to understand the production of the 26Al. Some new resonant states have been investigated, and determined their resonance parameters, such as excitation energies, proton partial widths, and spin-parities by R-matrix calculation.

  19. Temperature-dependent microwave dielectric relaxation studies of hydrogen bonded polar binary mixtures of propan-1-ol and propionaldehyde.

    PubMed

    Vishwam, T; Parvateesam, K; Sreeharisastry, S; Murthy, V R K

    2013-10-01

    The molecular interaction between the polar systems of propan-1-ol and propionaldehyde for various mole fractions at different temperatures were studied by determining the frequency dependent complex dielectric permittivity by using the open-ended coaxial probe technique method in the microwave frequency range from 20 MHz to 20 GHz. The geometries are optimized at HF, B3LYP and MP2 with 6-311G and 6-311G+ basis sets. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method and compared with the theoretical results. Conformational analysis of the formation of hydrogen bond between the propan-1-ol and propionaldehyde is supported by the FT-IR and molecular polarizability calculations. The average relaxation times are calculated from their respective Cole-Cole plots. The activation entropy, activation enthalpy and Kirkwood correlation 'g' factor, excess permittivity (ε(E)), excess inverse relaxation time (1/τ)(E), Bruggeman parameter (f(B)) have also been determined for propan-1-ol and propionaldehyde and the results were correlated.

  20. The effects of relaxation response meditation on the symptoms of irritable bowel syndrome: results of a controlled treatment study.

    PubMed

    Keefer, L; Blanchard, E B

    2001-07-01

    In this study, Herbert Benson's (1975) Relaxation Response Meditation program was tested as a possible treatment for Irritable Bowel Syndrome (IBS). Participants were 16 adults who were matched into pairs based on presence of Axis I disorder, primary IBS symptoms and demographic features and randomized to either a six week meditation condition or a six week wait list symptom monitoring condition. Thirteen participants completed treatment and follow-up. All subjects assigned to the Wait List were subsequently treated. Patients in the treatment condition were taught the meditation technique and asked to practice it twice a day for 15 minutes. Composite Primary IBS Symptom Reduction (CPSR) scores were calculated for each patient from end of baseline to two weeks post-treatment (or to post wait list). One tailed independent sample t-tests revealed that Meditation was superior to the control (P=0.04). Significant within-subject improvements were noted for flatulence (P=0.03) and belching (P=0.02) by post-treatment. By three month follow-up, significant improvements in flatulence (P<0.01), belching (P=0.02), bloating (P=0.05), and diarrhea (P=0.03) were shown by symptom diary. Constipation approached significance (P=0.07). Benson's Relaxation Response Meditation appears to be a viable treatment for IBS.

  1. Scissors mode of Gd nuclei studied from resonance neutron capture

    NASA Astrophysics Data System (ADS)

    Kroll, J.; Baramsai, B.; Becker, J. A.; Bečvár, F.; Bredeweg, T. A.; Couture, A.; Chyzh, A.; Dashdorj, D.; Haight, R. C.; Heil, M.; Jandel, M.; Käppeler, F.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Parker, W.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Vieira, D. J.; Walker, C. L.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.

    2012-10-01

    Spectra of γ rays following the neutron capture at isolated resonances of stable Gd nuclei weremeasured. The objectives were to get new information on photon strength of 153,155-159Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength ΣB(M1)↑, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum ΣB(M1)↑ increases with A and for 157,159Gd it is significantly higher compared to 156,158Gd.

  2. Scissors Mode of 162 Dy Studied from Resonance Neutron Capture

    DOE PAGES

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O’Donnell, J. M.; Rundberg, R. S.; et al

    2015-05-28

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions,more » (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.« less

  3. Scissors Mode of 162Dy Studied from Resonance Neutron Capture

    NASA Astrophysics Data System (ADS)

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Wilhelmy, J. B.

    2015-05-01

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ') reactions.

  4. Scissors mode of Gd nuclei studied from resonance neutron capture

    SciTech Connect

    Kroll, J.; Baramsai, B.; Becker, J. A.; and others

    2012-10-20

    Spectra of {gamma} rays following the neutron capture at isolated resonances of stable Gd nuclei were measured. The objectives were to get new information on photon strength of {sup 153,155-159}Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength {Sigma}B(M1){up_arrow}, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum {Sigma}B(M1){up_arrow} increases with A and for {sup 157,159}Gd it is significantly higher compared to {sup 156,158}Gd.

  5. Magnetic material arrangement in oriented termites: a magnetic resonance study

    NASA Astrophysics Data System (ADS)

    Alves, O. C.; Wajnberg, E.; de Oliveira, J. F.; Esquivel, D. M. S.

    2004-06-01

    Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite, the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g=2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite's body (abdomen + thorax). From the temperature dependence of the resonant field and from the spectral linewidths, we estimate the existence of magnetic nanoparticles 18.5 ± 0.3 nm in diameter and an effective magnetic anisotropy constant, Keff between 2.1 and 3.2 × 10 4 erg/cm 3. A sudden change in the double integrated spectra at about 100 K for N.o. with the long body axis oriented perpendicular to the magnetic field can be attributed to the Verwey transition, and suggests an organized film-like particle system.

  6. Experimental Resonance Enhanced Multiphoton Ionization (REMPI) studies of small molecules

    NASA Technical Reports Server (NTRS)

    Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.; Ohalloran, M. A.; Tomkins, F. S.

    1987-01-01

    Resonance enhanced multiphoton ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of exciting opportunities for both basic and applied science. On the applied side, REMPI has great potential as an ultrasensitive, highly selective detector for trace, reactive, or transient species. On the basic side, REMPI affords an unprecedented means of exploring excited state physics and chemistry at the quantum-state-specific level. An overview of current studies of excited molecular states is given to illustrate the principles and prospects of REMPI.

  7. Muon spin relaxation and rotation studies of the filled skutterudite alloys praseodymium osmium ruthenium antimonide and praseodymium lanthanum osmium antimonide

    NASA Astrophysics Data System (ADS)

    Shu, Lei

    Some filled skutterudite compounds have recently been found to exhibit very interesting properties. The first Pr-based heavy-fermion superconductor, PrOs4Sb12, is an intriguing material due to the unusual properties of both its normal and superconducting states. Comprehensive muon spin rotation and relaxation studies and magnetic susceptibility measurements, described in this dissertation, have been performed to investigate the microscopic properties of PrOs4Sb12 and its Ru and La doped alloys. The temperature dependence of penetration depth measured in the vortex state of PrOs4Sb12 using transverse-field muon spin rotation (TF-muSR) is weaker than those measured by radiofrequency measurements. A scenario based on two-band superconductivity in PrOs4Sb 12, is proposed to resolve this difference. TF-muSR experiments also suggest the suppression of superfluid density with Ru doping, probably due to impurity scattering. In addition, magnetic susceptibility data as well as analysis of the muSR data in PrOs4Sb12 reveal a nearly linear relation of mu+ Knight shift vs. magnetic susceptibility. This suggests that the muon charge does not affect the crystalline electric field splitting of Pr3+ near neighbors. Additional evidence comes from the fact that the superconducting transition temperature Tc measured from muSR is consistent with the bulk superconducting values. Zero-field muon spin relaxation (ZF-muSR) experiments have been carried out in the Pr(Os1-xRux) 4Sb12 and Pr1-yLayOs 4Sb12 alloy systems to investigate the time-reversal symmetry (TRS) breaking found in an earlier ZF-muSR study of the end compound PrOs 4Sb12. The results from measurements at KEK, Japan, suggest that Ru doping is considerably more efficient than La doping in suppressing TRS breaking superconducting in PrOs4Sb12. However, we think that the spontaneous local field that indicates TRS breaking detected by ZF-muSR may depend on sample quality if those fields are from inhomogeneity in the

  8. Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3(NIT(C6H4OPh))]: A μ{sup +} spin relaxation study

    SciTech Connect

    Arosio, Paolo Orsini, Francesco; Corti, Maurizio; Mariani, Manuel; Bogani, Lapo; Caneschi, Andrea; Lago, Jorge; Lascialfari, Alessandro

    2015-05-07

    The spin dynamics of the molecular magnetic chain [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] were investigated by means of the Muon Spin Relaxation (μ{sup +}SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ{sup +}SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λ{sub interm}(T), associated with the intermediate relaxing component. The experimental λ{sub interm}(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ{sub 0} exp(Δ/k{sub B}T), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state.

  9. Using Nice-Ohvms Lineshapes to Study Relaxation Rates and Transition Dipole Moments

    NASA Astrophysics Data System (ADS)

    Hodges, James N.; McCall, Benjamin J.

    2016-06-01

    Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy (NICE-OHVMS) is a successful technique that we have developed to sensitively, precisely, and accurately record transitions of molecular ions. It has been used exclusively as a method for precise transition frequency measurement via saturation and fitting of the resultant Lamb dips. NICE-OHVMS has been employed to improve the uncertainties on H_3^+, CH_5^+, HeH^+, and OH^+, reducing the transition frequency uncertainties by two orders of magnitude. Because NICE-OHVMS is a saturation technique, this provides a unique opportunity to access information about the ratio of the transition dipole moment to the relaxation rate of the transition. This can be done in two ways, either through comparison of Lamb dip depth to the transition profile or comparison of the absorption intensity and dispersion intensity. Due to the complexity of the modulation scheme, there are many parameters that affect the apparent intensity of the recorded lineshape. A complete understanding of the lineshape is required to make the measurements of interest. Here we present a model that accounts for the heterodyne modulation and velocity modulation, assuming that the fundamental lineshape is represented by a Voigt profile. Fits to data are made and interpreted in order to extract the saturation parameter. K.N. Crabtree et al., Chem. Phys. Lett. 551, 1 (2012). J.N. Hodges et al., J. Chem. Phys. 139, 164201 (2013). A.J. Perry et al., J. Mol. Spectrosc. 317, 71 (2015). A.J. Perry et al., J. Chem. Phys. 141, 101101 (2014). C.R. Marcus et al., Astrophys. J. 817, 138 (2016).

  10. Elastic relaxations associated with the Pm3m-R3c transition in LaA103 III: superattenuation of acoustic resonances

    SciTech Connect

    Darling, Timothy W; Carpenter, M A; Buckley, A; Taylor, P A; Mcknight, R E A

    2009-01-01

    Resonant Ultrasound Spectroscopy has been used to characterize elastic softening and a variety of new acoustic dissipation processes associated with the Pm{bar 3}m {leftrightarrow} R{bar 3}c transition in single crystal and ceramic samples of LaAlO{sub 3}. Softening of the cubic structure ahead of the transition point is not accompanied by an increase in dissipation but follows different temperature dependences for the bulk modulus, 1/3(C{sub 11} + 2C{sub 12}), and the shear components 1/2(C{sub 11}-C{sub 12}) and C{sub 44} as if the tilting instability contains two slightly different critical temperatures. The transition itself is marked by the complete disappearance of resonance peaks (superattenuation), which then reappear below {approx}700 K in spectra from single crystals. Comparison with low frequency, high stress data from the literature indicate that the dissipation is not due to macroscopic displacement of needle twins. An alternative mechanism, local bowing of twin walls under low dynamic stress, is proposed. Pinning of the walls with respect to this displacement process occurs below {approx}350 K. Anelasticity maps, analogous to plastic deformation mechanism maps, are proposed to display dispersion relations and temperature/frequency/stress fields for different twin wall related dissipation mechanisms. An additional dissipation process, with an activation energy of 43 {+-} 6 kJ.mole{sup -1}, occurs in the vicinity of 250 K. The mechanism for this is not known, but it is associated with C{sub 44} and therefore appears to be related in some way to the cubic {leftrightarrow} rhombohedral transition at {approx}817 K. Slight softening in the temperature interval {approx}220 {yields} 70 K of resonance peaks determined by shear elastic constants hints at an incipient E{sub g} ferroelastic instability in LaAlO{sub 3}. The softening interval ends with a further dissipation peak at {approx} 60 K, the origin of which is discussed in terms of freezing of atomic

  11. In utero eyeball development study by magnetic resonance imaging.

    PubMed

    Brémond-Gignac, D S; Benali, K; Deplus, S; Cussenot, O; Ferkdadji, L; Elmaleh, M; Lassau, J P

    1997-01-01

    The aim of this study was to measure fetal ocular development and to determine a growth curve by means of measurements in utero. Fetal ocular development was recorded by analysis of the results of magnetic resonance imaging (MRI). An anatomic study allowed definition of the best contrasted MRI sequences for calculation of the ocular surface. Biometric analysis of the values of the ocular surface in the neuro-ocular plane in 35 fetuses allowed establishment of a linear model of ocular growth curve in utero. Evaluation of ocular development may allow the detection and confirmation of malformational ocular anomalies such as microphthalmia.

  12. In vivo Carbon-13 Nuclear Magnetic Resonance Studies of Mammals

    NASA Astrophysics Data System (ADS)

    Alger, J. R.; Sillerud, L. O.; Behar, K. L.; Gillies, R. J.; Shulman, R. G.; Gordon, R. E.; Shaw, D.; Hanley, P. E.

    1981-11-01

    Natural abundance carbon-13 nuclear magnetic resonances (NMR) from human arm and rat tissues have been observed in vivo. These signals arise primarily from triglycerides in fatty tissue. Carbon-13 NMR was also used to follow, in a living rat, the conversion of C-1--labeled glucose, which was introduced into the stomach, to C-1--labeled liver glycogen. The carbon-13 sensitivity and resolution obtained shows that natural abundance carbon-13 NMR will be valuable in the study of disorders in fat metabolism, and that experiments with substrates labeled with carbon-13 can be used to study carbohydrate metabolism in vivo.

  13. Plasmon-mediated energy relaxation in graphene

    NASA Astrophysics Data System (ADS)

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    2015-12-01

    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.

  14. Plasmon-mediated energy relaxation in graphene

    SciTech Connect

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    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.

  15. Methodology to study polymers interaction by surface plasmon resonance imaging.

    PubMed

    Vollmer, N; Trombini, F; Hely, M; Bellon, S; Mercier, K; Cazeneuve, C

    2015-01-01

    The surface plasmon resonance (SPR) technique has been primarily used in the field of biology, in particular for the study of antibody-antigen interactions. Recently, polymers were introduced to form inclusion complexes. We describe here, a methodology based on surface plasmon resonance imaging to study water-resistant and reversible inclusion complexes using systems which are compatible with a cosmetic use. The purpose of this study is to follow in real time the interaction between two polymers. To carry out this study: •A biochip based on a covalent binding of one "host polymer" on a gold-activated surface was developed.•The binding of the host polymer to a guest polymer was monitored.•The presence of interactions between the β-cyclodextrins groups of the host polymer and the adamantyl functional groups of the guest polymer and the possibility of dissociating the complex were established. This technique allowed carrying out parallel assays for optimizing the amount of complexes formed, the host polymer being spotted at five concentrations. It was then possible to study the influence of the concentration in host system for two concentrations of the guest polymer. The concentration in the host polymer yielding the highest immobilization of the guest system was further determined. PMID:26150967

  16. Study of the Ground State Properties of LiHoxY1-xF4 Using Muon Spin Relaxation

    SciTech Connect

    Rodriguez, Jose A.; Aczel, Adam A.; Carlo, Jeremy; Dunsiger, Sarah; Macdougall, Gregory J; Russo, Peter L.; Savici, Andrei T; Uemura, Yasutomo J.; Wiebe, Christopher; Luke, Graeme M.

    2010-09-01

    LiHoxY1-xF4 is an insulator where the magnetic Ho3+ ions have an Ising character and interact mainly through magnetic dipolar fields. We used the muon spin relaxation technique to study the nature of its ground state for samples with x 0.25. In contrast with some previous works, we did not find canonical spin glass behavior down to 15 mK. Instead, below 300 mK we observed temperature-independent dynamic magnetism characterized by a single correlation time. The 300 mK energy scale corresponds to the Ho3+ hyperfine interaction strength, suggesting that this interaction may be involved in the dynamic behavior of the system.

  17. Preliminaries toward studying resonant extraction from the Debuncher

    SciTech Connect

    Michelotti, Leo; Johnstone, John; /Fermilab

    2009-06-01

    A recent proposal to detect {mu} {yields} e direct conversion at Fermilab asks for slow extraction of protons from the antiproton source, specifically from the Debuncher. [1] A third-integer resonance originally was considered for this, partly because of the Debuncher's three-fold symmetry and partly because its operational horizontal tune, {nu}{sub x} {approx} 9.765, is already within 0.1 of {nu}{sub x} = 29/3. Using a half integer resonance, {nu}{sub x} = 19/2, though not part of the original proposal, has been suggested more recently because (a) Fermilab has had a good deal of experience with half-integer extraction from the Tevatron, the Main Injector and the erstwhile Main Ring, and (b) for reasons we shall examine later, it depopulates the entire bunch without an abort at the end. This memo presents considerations preliminary to studying both possibilities. It is meant only as a starting point for investigations to be carried out in the future. The working constraints and assumptions have oscillated between two extremes: (1) making minimal changes in the antiproton source to minimize cost and (2) building another machine in the same tunnel. In this memo we adopt an attitude aligned more toward the first. The assumed parameters are listed in Table 1. A few are not (easily) subject to change, such as those related to the beam's momentum and revolution frequency and the acceptance of the debuncher. Two resonance exemplars are presented in the next section, with an explanation of the analytic and semi-analytic calculations that can be done for each. Section 3 contains preliminary numerical work that was done to validate the exemplars within the context of extraction from the Debuncher. A final section contains a summary. Following the bibliography, appendices contain (a) a qualitative, conceptual discussion of extraction for the novice, (b) a telegraphic review of the perturbative incantations used to filter the exemplars as principal resonances of quadrupole

  18. Nuclear quadrupole resonance studies project. [spectrometer design and spectrum analysis

    NASA Technical Reports Server (NTRS)

    Murty, A. N.

    1978-01-01

    The participation of undergraduates in nuclear quadrupole resonance research at Grambling University was made possible by NASA grants. Expanded laboratory capabilities include (1) facilities for high and low temperature generation and measurement; (2) facilities for radio frequency generation and measurement with the modern spectrum analyzers, precision frequency counters and standard signal generators; (3) vacuum and glass blowing facilities; and (4) miscellaneous electronic and machine shop facilities. Experiments carried out over a five year period are described and their results analyzed. Theoretical studies on solid state crystalline electrostatic fields, field gradients, and antishielding factors are included.

  19. A New Tissue Resonator Indenter Device and Reliability Study

    PubMed Central

    Jia, Ming; Zu, Jean W.; Hariri, Alireza

    2011-01-01

    Knowledge of tissue mechanical properties is widely required by medical applications, such as disease diagnostics, surgery operation, simulation, planning, and training. A new portable device, called Tissue Resonator Indenter Device (TRID), has been developed for measurement of regional viscoelastic properties of soft tissues at the Bio-instrument and Biomechanics Lab of the University of Toronto. As a device for soft tissue properties in-vivo measurements, the reliability of TRID is crucial. This paper presents TRID’s working principle and the experimental study of TRID’s reliability with respect to inter-reliability, intra-reliability, and the indenter misalignment effect as well. PMID:22346623

  20. Tunnel-diode resonator and nuclear magnetic resonance studies of low-dimensional magnetic and superconducting systems

    NASA Astrophysics Data System (ADS)

    Yeninas, Steven Lee

    This thesis emphasizes two frequency-domain techniques which uniquely employ radio frequency (RF) excitations to investigate the static and dynamic properties of novel magnetic and superconducting materials. The first technique is a tunnel-diode resonator (TDR) which detects bulk changes in the dynamic susceptibility, chi = dM/dH. The capability of TDR to operate at low temperatures (less than 100 mK) and high fields (up to 65 T in pulsed fields) was critical for investigations of the antiferromagnetically correlated magnetic molecules Cr12Cu2 and Cr12 Ln4 (Ln = Y, Eu, Gd, Tb, Dy, Ho, Er, Yb), and the superconductor SrFe2(As1--xPx) 2 (x = 0.35). Investigations of Cr12Cu 2 and Cr12Ln4 demonstrates the first implementation of TDR to experimentally investigate the lowlying energy spectra of magnetic molecules in pulsed magnetic fields. Zeeman splitting of the quantum spin states results in transitions between field-dependent ground state energy levels observed as peaks in dM/dH at 600 mK, and demonstrate good agreement with theoretical calculations using a isotropic Heisenberg spin Hamiltonian. Increasing temperature to 2.5 K, TDR reveals a rich spectrum of frequency-dependent level crossings from thermally populated excited states which cannot be observed by conventional static magnetometry techniques. The last study presented uses TDR in pulsed fields to determine the temperature-dependent upper-critical field Hc2 to investigate the effects of columnar defects arising from heavy ion irradiation of SrFe2(As 1--xPx)2. Results suggest irradiation uniformly suppresses Tc and Hc2, and does not introduce additional features on H c2(T) and the shapes of the anisotropic Hc2 curves indicates a nodal superconducting gap. The second technique is nuclear magnetic resonance (NMR) which yields site specific magnetic and electronic information arising from hyperfine interactions for select magnetic nuclei. NMR spectra and nuclear spin-lattice relaxation measurements are reported

  1. Protein dynamics from nuclear magnetic relaxation.

    PubMed

    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.

  2. Extended nuclear quadrupole resonance study of the heavy-fermion superconductor PuCoGa5

    NASA Astrophysics Data System (ADS)

    Koutroulakis, G.; Yasuoka, H.; Tobash, P. H.; Mitchell, J. N.; Bauer, E. D.; Thompson, J. D.

    2016-10-01

    PuCoGa5 has emerged as a prototypical heavy-fermion superconductor, with its transition temperature (Tc≃18.5 K) being the highest amongst such materials. Nonetheless, a clear description as to what drives the superconducting pairing is still lacking, rendered complicated by the notoriously intricate nature of plutonium's 5 f valence electrons. Here, we present a detailed Ga,7169 nuclear quadrupole resonance (NQR) study of PuCoGa5, concentrating on the system's normal state properties near to Tc and aiming to detect distinct signatures of possible pairing mechanisms. In particular, the quadrupole frequency and spin-lattice relaxation rate were measured for the two crystallographically inequivalent Ga sites and for both Ga isotopes, in the temperature range 1.6-300 K. No evidence of significant charge fluctuations is found from the NQR observables. On the contrary, the low-energy dynamics is dominated by anisotropic spin fluctuations with strong, nearly critical, in-plane character, which are effectively identical to the case of the sister compound PuCoIn5. These findings are discussed within the context of different theoretical proposals for the unconventional pairing mechanism in heavy-fermion superconductors.

  3. Modelling studies in aqueous solution of lanthanide (III) chelates designed for nuclear magnetic resonance biomedical applications

    NASA Astrophysics Data System (ADS)

    Henriques, E. S.; Geraldes, C. F. G. C.; Ramos, M. J.

    Molecular dynamics simulations and complementary modelling studies have been carried out for the [Gd(DOTA)·(H2O)]- and [Tm(DOTP)]5- chelates in aqueous media, to provide a better understanding of several structural and dynamical properties of these versatile nuclear magnetic resonance (NMR) probes, including coordination shells and corresponding water exchange mechanisms, and interactions of these complexes with alkali metal ions. This knowledge is of key importance in the areas of 1H relaxation and shift reagents for NMR applications in medical diagnosis. A new refinement of our own previously developed set of parameters for these Ln(III) chelates has been used, and is reported here. Calculations of water mean residence times suggest a reassessment of the characterization of the chelates' second coordination shell, one where the simple spherical distribution model is discarded in favour of a more detailed approach. Na+ probe interaction maps are in good agreement with the available site location predictions derived from 23Na NMR shifts.

  4. A 300 MHz and 600 MHz proton NMR study of a 12 base pair restriction fragment: investigation of structure by relaxation measurements.

    PubMed Central

    Early, T A; Kearns, D R; Hillen, W; Wells, R D

    1980-01-01

    The 1H NMR spectrum of a 12 base pair DNA restriction fragment has been measured at 300 and 600 MHz and resonances from over 70 protons are individually resolved. Relaxation rate measurements have been carried out at 300 MHz and compared with the theoretical predictions obtained using an isotropic rigid rotor model with coordinates derived from a Dreiding model of DNA. The model gives results that are in excellent agreement with experiment for most protons when a 7 nsec rotational correlation time is used, although agreement is improved for certain base protons by using a shorter correlation time for the sugar group, or by increasing the sugar-base interproton distances. A comparison of non-selective and selective spin-lattice relaxation rates for carbon bound protons indicates that there is extensive spin diffusion even in this short DNA fragment. Examination of the spin-spin relaxation rates for the same type of proton on different base pairs reveals little sequence effect on conformation. PMID:6258152

  5. Electron spin-lattice and spin-spin relaxation study of a trinuclear iron(III) complex and its relevance in quantum computing.

    PubMed

    Mitrikas, George; Sanakis, Yiannis; Raptopoulou, Catherine P; Kordas, George; Papavassiliou, Georgios

    2008-02-01

    Electron spins of molecular magnets are promising candidates for large scale quantum information processing because they exhibit a large number of low-lying excited states. In this paper X-band pulse electron paramagnetic resonance spectroscopy is used to determine the intrinsic relaxation times T1 and T2 of a molecular magnet with an S = 1/2 ground state, namely the neutral trinuclear oxo-centered iron (III) complex, [Fe3(micro3-O)(O2CPh)5(salox)(EtOH)(EtOH)(H2O)]. The temperature dependence of the spin-lattice relaxation time T1 between 4.5 and 11 K shows that the Orbach relaxation process is dominant with the first excited state lying 57 cm(-1) above the ground state, whereas the phase memory time T(M) is of the order of 2.6 micros and exhibits a modest temperature dependence. These results together with previous magnetic measurements give further insight into the magnetic properties of the complex. The coherent manipulation of the electron spins is also examined by means of transient nutation experiments.

  6. Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy.

    PubMed

    Wilkinson, Iain; Boguslavskiy, Andrey E; Mikosch, Jochen; Bertrand, Julien B; Wörner, Hans Jakob; Villeneuve, David M; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

    2014-05-28

    The excited state dynamics of isolated sulfur dioxide molecules have been investigated using the time-resolved photoelectron spectroscopy and time-resolved photoelectron-photoion coincidence techniques. Excited state wavepackets were prepared in the spectroscopically complex, electronically mixed (B̃)(1)B1/(Ã)(1)A2, Clements manifold following broadband excitation at a range of photon energies between 4.03 eV and 4.28 eV (308 nm and 290 nm, respectively). The resulting wavepacket dynamics were monitored using a multiphoton ionisation probe. The extensive literature associated with the Clements bands has been summarised and a detailed time domain description of the ultrafast relaxation pathways occurring from the optically bright (B̃)(1)B1 diabatic state is presented. Signatures of the oscillatory motion on the (B̃)(1)B1/(Ã)(1)A2 lower adiabatic surface responsible for the Clements band structure were observed. The recorded spectra also indicate that a component of the excited state wavepacket undergoes intersystem crossing from the Clements manifold to the underlying triplet states on a sub-picosecond time scale. Photoelectron signal growth time constants have been predominantly associated with intersystem crossing to the (c̃)(3)B2 state and were measured to vary between 750 and 150 fs over the implemented pump photon energy range. Additionally, pump beam intensity studies were performed. These experiments highlighted parallel relaxation processes that occurred at the one- and two-pump-photon levels of excitation on similar time scales, obscuring the Clements band dynamics when high pump beam intensities were implemented. Hence, the Clements band dynamics may be difficult to disentangle from higher order processes when ultrashort laser pulses and less-differential probe techniques are implemented.

  7. Resonance Energy Transfer-Based Approaches to Study GPCRs.

    PubMed

    Ayoub, Mohammed Akli

    2016-01-01

    Since their discovery, G protein-coupled receptors (GPCRs) constitute one of the most studied proteins leading to important discoveries and perspectives in terms of their biology and implication in physiology and pathophysiology. This is mostly linked to the remarkable advances in the development and application of the biophysical resonance energy transfer (RET)-based approaches, including bioluminescence and fluorescence resonance energy transfer (BRET and FRET, respectively). Indeed, BRET and FRET have been extensively applied to study different aspects of GPCR functioning such as their activation and regulation either statically or dynamically, in real-time and intact cells. Consequently, our view on GPCRs has considerably changed opening new challenges for the study of GPCRs in their native tissues in the aim to get more knowledge on how these receptors control the biological responses. Moreover, the technological aspect of this field of research promises further developments for robust and reliable new RET-based assays that may be compatible with high-throughput screening as well as drug discovery programs.

  8. High Field Small Animal Magnetic Resonance Oncology Studies

    PubMed Central

    Bokacheva, Louisa; Ackerstaff, Ellen; LeKaye, H. Carl; Zakian, Kristen; Koutcher, Jason A.

    2014-01-01

    This review focuses on the applications of high magnetic field magnetic resonance imaging (MRI) and spectroscopy (MRS) to cancer studies in small animals. High field MRI can provide information about tumor physiology, the microenvironment, metabolism, vascularity and cellularity. Such studies are invaluable for understanding tumor growth and proliferation, response to treatment and drug development. The MR techniques reviewed here include 1H, 31P, Chemical Exchange Saturation Transfer (CEST) imaging, and hyperpolarized 13C MR spectroscopy as well as diffusion-weighted, Blood Oxygen Level Dependent (BOLD) contrast imaging, and dynamic contrast-enhanced MR imaging. These methods have been proven effective in animal studies and are highly relevant to human clinical studies. PMID:24374985

  9. [Indications for relaxation in geriatrics].

    PubMed

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

    1975-11-01

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

  10. Study of nucleon resonances at EBAC@Jlab

    SciTech Connect

    Hiroyuki Kamano

    2010-05-01

    We present the dynamical origin of the P11 nucleon resonances resulting from a dynamical coupled-channels (DCC) analysis of meson production reactions off a nucleon target, which is conducted in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Two resonance poles are found in the energy region where the Roper resonance P11(1440) is supposed to be observed. Furthermore, the two resonance poles and the next higher resonance pole corresponding to P11(1710) are found to originate from a single bare state.

  11. Conformational stability and thermal pathways of relaxation in triclosan (antibacterial/excipient/contaminant) in solid-state: combined spectroscopic ((1)H NMR) and computational (periodic DFT) study.

    PubMed

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Tomczak, Marzena Agnieszka; Medycki, Wojciech

    2015-05-21

    The mechanism of molecular dynamics in the antibacterial/antifungal agent, triclosan (5-chloro-2-(2',4'-dichlorophenoxy)-phenol), in solid state was studied by (1)H NMR spectroscopy and periodic density functional theory (DFT) calculations. Temperature dependencies of the proton spin-lattice relaxation time (T1) in the ranges 86-293 and 90-250 K (at 15 and 24.667 MHz, respectively) and the second moment (M2) of the (1)H NMR resonant line in the range 103-300 K were measured. Two minima in the temperature dependence of T1 revealed a classical Arrhenius governed activation processes. The low temperature shallow minimum T1(T) of 71 s at 115 K, 15 MHz, which shifts with frequency, was assigned to classical hindered jumps of hydroxyl group around OC axis and with respect to a 5-chloro-2-phenol ring. The activation energy of this motion estimated on the basis of the fit of the theoretical model to the experimental points is 9.68 kJ/mol. The pointed high temperature minimum T1(T) of 59 s at 190 K, 15 MHz, which also shifts with frequency, was assigned to the small angle librations by Θlib= ± 9° between two positions of equilibrium differing in energy by 7.42 kJ/mol. The activation energy of this motion estimated on the basis of the fit of the theoretical model to the experimental points is 31.1 kJ/mol. Both motions result in a negligible reduction in the (1)H NMR line second moment, thus the second moment delivers an irrelevant description of the molecular motions in triclosan.

  12. Study on electrostatic resonance of nanoprisms with sharp corners

    NASA Astrophysics Data System (ADS)

    Chan, Wai Soen; Ng, Ka Ki; Yu, Kin Wah

    2015-03-01

    We have studied the electrostatic resonance of metal nanoprisms with sharp corners numerically. We consider an infinite metal cylinder with polygonal base, e.g. square. The incident electric field lies in the plane of cross-section of the cylinder. Yu and co-workers proposed Green's function formalism (GFF) to numerically calculate the electric potential and field distribution in plasmonic systems. We will adopt the scheme to demonstrate the effect of sharp corners, particularly on the effect of electrostatic resonance spectrum, as in the spectral analysis proposed by Bergman and Milton. Hetherington and Thorpe investigated the conductivity of a sheet containing dilute inclusion with sharp corners, they made use of a conformal mapping approach to calculate the conductivity from circular inclusions. Helsing, McPhedran and Milton also investigated the optical properties of a metamaterial lattice with inclusions having sharp corners. We study the possibility of improving numerical accuracy by combining the conformal mapping approach and GFF. We may extend similar approach to investigate the properties of plasmonic systems, for examples nanoboties and nanostars.

  13. A comparative study of the effects of problem-solving skills training and relaxation on the score of self-esteem in women with postpartum depression

    PubMed Central

    Nasiri, Saeideh; Kordi, Masoumeh; Gharavi, Morteza Modares

    2015-01-01

    Background: Self-esteem is a determinant factor of mental health. Individuals with low self-esteem have depression, and low self-esteem is one of main symptoms of depression. Aim of this study is to compare the effects of problem-solving skills and relaxation on the score of self-esteem in women with postpartum depression. Materials and Methods: This clinical trial was performed on 80 women. Sampling was done in Mashhad healthy centers from December 2009 to June 2010. Women were randomly divided and assigned to problem-solving skills (n = 26), relaxation (n = 26), and control groups (n = 28). Interventions were implemented for 6 weeks and the subjects again completed Eysenck self-esteem scale 9 weeks after delivery. Data analysis was done by descriptive statistics, Kruskal–Wallis test, and analysis of variance (ANOVA) test by SPSS software. Results: The findings showed that the mean of self-esteem scale scores was 117.9 ± 9.7 after intervention in the problem-solving group, 117.0 ± 11.8 in the relaxation group, and 113.5 ± 10.4 in the control group and there was significant difference between the groups of relaxation and problem solving, and also between intervention groups and control group. Conclusions: According to the results, problem-solving skills and relaxation can be used to prevent and recover from postpartum depression. PMID:25709699

  14. Basic study on the most relaxing respiration period in children to aid the development of a respiration-leading stuffed toy.

    PubMed

    Uratani, Hiroki; Yoshino, Kohzoh; Ohsuga, Mieko

    2014-01-01

    Following natural disasters, accidents, and shocking incidents, some children experience post-traumatic stress disorder (PTSD). The respiration control method, which relaxes the body and mind, may efficiently prevent PTSD. Therefore, we developed a stuffed toy that leads children's respiration using the up-and-down movement of the abdomen to help them relax. We investigated the most appropriate respiration period for children's relaxation. Data from studies on heart rate variability (HRV) biofeedback training suggest that breathing at the respiration period at which HRV is the highest is effective for improving chronic diseases. Therefore, we measured the relationship between the respiration period and physiological indices, including HRV. The participants were 10 children aged 5-12 years. HRV was the highest at a 10-12-s respiration period in all 10 children. However, the most suitable respiration period for smooth breathing and relaxation was different from that at which HRV is the highest. Therefore, the most relaxing respiration periods for children need to be determined by indices other than HRV. PMID:25570724

  15. [Preparation of and study on magnetic resonance imaging performance of metal porphyrin modified by low molecular weight chitosan].

    PubMed

    Yu, Dong-Jun; Li, Min-Zhi; Huang, Xian-Zhu; Zhu, Wei-Hua; Huang, Yan; Zhang, Qi; Liu, Qing

    2013-10-01

    The functional complex Mn-TCPP-CS20 as a potential magnetic resonance imaging (MRI) contrast agent was synthesized through tetra(4-carboxyphenyl) Mn(II)-porphyrin (Mn-TCPP) modified by CS20, which was low degree of polymerization and narrow distribution. The results showed that Mn-TCPP-CS20 had good water-solubility and structural stability. The chemical structures of the products were characterized with Fourier transform infrared spectra (FTIR), UV-Vis spectra, mass spectrum (MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results showed that Mn-TCPP was successfully linked to CS20 by an amide function. The relaxation properties in vitro of the functional complex Mn-TCPP-CS20 as the potential MRI contrast agent were preliminarily studied. It was found that the longitudinal relaxivity (r1) of the synthesized Mn-TCPP-CS20 (6.11 mmol(-1) x L x s(-1)) was higher than that of the commercial contrast agent Gd-DTPA (r1 = 3.59 mmol(-1) x L x s(-1)). Besides, the imaging effect of Mn-TCPP-CS20 was superior to that of Gd-DTPA in the same condition. These studies suggested that Mn-TCPP-CS20 has the advantage of becoming a potential tissue-targeting contrast agent.

  16. Nuclear quadrupole resonance study of local bonding in glassy As{sub x}Se{sub 1-x}

    SciTech Connect

    Ahn, Eungho; Williams, G. A.; Taylor, P. C.

    2006-11-01

    Nuclear quadrupole resonance (NQR) experiments were performed on glassy As{sub x}Se{sub 1-x} to study the local structural order. The bonding in As{sub x}Se{sub 1-x} is governed by preferential bonding (chemical ordering) between arsenic and selenium at arsenic concentrations x{<=}0.40; however, the bonding for higher arsenic concentrations is governed mostly by statistical considerations. At concentrations x{>=}0.45 the glasses are inhomogeneous with the presence of local regions of different composition. Measurements of the NQR spin echo intensity identify regions formed by arsenic atoms bonded to zero, one, two, or three selenium atoms. The NQR spectral line shapes and the longitudinal relaxation times suggest that these regions have a more ordered structure as compared to the homogeneous samples with low arsenic content. The existence of a small concentration of crystalline inclusions in amorphous As{sub 0.60}Se{sub 0.40} is also suggested.

  17. Progressive muscle relaxation, breathing exercises, and ABC relaxation theory.

    PubMed

    Matsumoto, M; Smith, J C

    2001-12-01

    This study compared the psychological effects of Progressive Muscle Relaxation (PMR) and breathing exercises. Forty-two students were divided randomly into two groups and taught PMR or breathing exercises. Both groups practiced for five weeks and were given the Smith Relaxation States Inventory before and after each session. As hypothesized, PMR practitioners displayed greater increments in relaxation states (R-States) Physical Relaxation and Disengagement, while breathing practitioners displayed higher levels of R-State Strength and Awareness. Slight differences emerged at Weeks 1 and 2; major differences emerged at Weeks 4 and 5. A delayed and potentially reinforcing aftereffect emerged for PMR only after five weeks of training--increased levels of Mental Quiet and Joy. Clinical and theoretical implications are discussed.

  18. X-ray diffraction study of stress relaxation in cubic boron nitride films grown with simultaneous medium-energy ion bombardment

    SciTech Connect

    Abendroth, B.; Gago, R.; Eichhorn, F.; Moeller, W.

    2004-12-13

    Relaxation of the intrinsic stress of cubic boron nitride (cBN) thin films has been studied by x-ray diffraction (XRD) using synchrotron light. The stress relaxation has been attained by simultaneous medium-energy ion bombardment (2-10 keV) during magnetron sputter deposition, and was confirmed macroscopically by substrate curvature measurements. In order to investigate the stress-release mechanisms, XRD measurements were performed in in-plane and out-of-plane geometry. The analysis shows a pronounced biaxial state of compressive stress in the cBN films grown without medium-energy ion bombardment. This stress is partially released during the medium-energy ion bombardment. It is suggested that the main path for stress relaxation is the elimination of strain within the cBN grains due to annealing of interstitials.

  19. Study to eliminate ground resonance using active controls

    NASA Technical Reports Server (NTRS)

    Straub, F. K.

    1984-01-01

    The effectiveness of active control blade feathering in increasing rotor body damping and the possibility to eliminate ground resonance instabilities were investigated. An analytical model representing rotor flapping and lead-lag degrees of freedom and body pitch, roll, longitudinal and lateral motion is developed. Active control blade feathering is implemented as state variable feedback through a conventional swashplate. The influence of various feedback states, feedback gain, and weighting between the cyclic controls is studied through stability and response analyses. It is shown that blade cyclic inplane motion, roll rate and roll acceleration feedback can add considerable damping to the system and eliminate ground resonance instabilities, which the feedback phase is also a powerful parameter, if chosen properly, it maximizes augmentation of the inherent regressing lag mode damping. It is shown that rotor configuration parameters, like blade root hinge offset, flapping stiffness, and precone considerably influence the control effectiveness. It is found that active control is particularly powerful for hingeless and bearingless rotor systems.

  20. Study on enthalpy relaxation of glassy polystyrene using a structure-dependent Kohlrausch stretch exponent combined with coupling model.

    PubMed

    Liu, Guodong; Zuo, Yang; Lin, Jingjing; Zhao, Dongmei

    2014-07-01

    In this paper the enthalpy relaxation of polystyrene (PS) was restudied using a structure-dependent Kohlrausch stretch exponent β with incorporation of a coupling model (CM). The structure dependence of β is described in 3 semi-phenomenological equations. The temperature and structure dependence of the relaxation time of the Johari-Goldstein (JG) relaxation (τ JG) is presented using the traditional Tools-Narayanaswamy-Moynihan (TNM) and Adam-Gibbs-Vogel (AGV) equations. The fitting results of heat capacity data are much better than the conventional TNM and Adam-Gibbs (AG) models when the structure dependence of β is described using an exponential equation and τ JG is calculated using the AGV equation, although there are one fewer fitting parameters in the new model. The results indicate that both the structure dependence of β and the CM model may play considerable roles in the investigation on the structure relaxation process in polymers around the glass transition.

  1. Femtosecond chirp-free studies of energy relaxation in semiconductor quantum dots: Search for a phonon bottleneck

    SciTech Connect

    Klimov, V.; McBranch, D.

    1997-08-01

    Contrary to the predictions of phonon bottleneck theories, we observe very fast subpicosecond energy relaxation in strongly confined semiconductor nanocrystals with electron level spacing as large as 20 LO phonon energies.

  2. Nuclear magnetic resonance studies of macroscopic morphology and dynamics

    SciTech Connect

    Barrall, G A

    1995-09-01

    Nuclear magnetic resonance techniques are traditionally used to study molecular level structure and dynamics with a noted exception in medically applied NMR imaging (MRI). In this work, new experimental methods and theory are presented relevant to the study of macroscopic morphology and dynamics using NMR field gradient techniques and solid state two-dimensional exchange NMR. The goal in this work is not to take some particular system and study it in great detail, rather it is to show the utility of a number of new and novel techniques using ideal systems primarily as a proof of principle. By taking advantage of the analogy between NMR imaging and diffraction, one may simplify the experiments necessary for characterizing the statistical properties of the sample morphology. For a sample composed of many small features, e.g. a porous medium, the NMR diffraction techniques take advantage of both the narrow spatial range and spatial isotropy of the sample`s density autocorrelation function to obtain high resolution structural information in considerably less time than that required by conventional NMR imaging approaches. The time savings of the technique indicates that NMR diffraction is capable of finer spatial resolution than conventional NMR imaging techniques. Radio frequency NMR imaging with a coaxial resonator represents the first use of cylindrically symmetric field gradients in imaging. The apparatus as built has achieved resolution at the micron level for water samples, and has the potential to be very useful in the imaging of circularly symmetric systems. The study of displacement probability densities in flow through a random porous medium has revealed the presence of features related to the interconnectedness of the void volumes. The pulsed gradient techniques used have proven successful at measuring flow properties for time and length scales considerably shorter than those studied by more conventional techniques.

  3. Study of dielectric relaxation process in nanocomposite of Li{sub 2}O−SiO{sub 2} nanoglass-CuO nanoparticles

    SciTech Connect

    Saha, Dhriti Ranjan Chakravorty, Dipankar

    2014-04-24

    Dielectric behaviour of a nanocomposite consisting of 23Li{sub 2}O⋅77SiO{sub 2} nanoglass within the pores of compacted CuO nanoparticles was studied. Real and imaginary parts of dielectric permittivity of the material were measured over the temperature range 313 to 363 K. The results indicated a relaxation behaviour. The data were explained by a space charge polarization model developed in the case of a laminar conductor. The activation energy of the relaxation process was in close agreement with that of lithium ion conduction in the nanoglass.

  4. In-situ electron paramagnetic resonance studies of paramagnetic point defects in superconducting microwave resonators

    NASA Astrophysics Data System (ADS)

    Zhang, Shengke; Kopas, Cameron; Wagner, Brian; Queen, Daniel; Newman, N.

    2016-09-01

    The physical nature and concentration of paramagnetic point defects in the dielectrics of superconducting planar microwave resonators have been determined using in-situ electron paramagnetic resonance spectroscopy. To perform this work, the quality factor of parallel plate and stripline resonators was measured as a function of the magnitude of a magnetic-field applied parallel to the electrode surfaces. YBa2Cu3O7-δ thin film electrodes proved to be a preferred choice over Nb and MgB2 because they are readily available and have a small surface resistance (Rs) up to high temperatures (˜77 K) and magnetic fields (i.e., <1 T). Stripline resonators with a widely used high performance microwave dielectric, Co2+-doped Ba(Zn1/3Nb2/3)O3, are shown to have losses dominated by d-electron spin-excitations in exchange-coupled Co2+ point-defect clusters, even in the absence of an applied magnetic field. A significant enhanced microwave loss in stripline and parallel plate resonators is found to correlate with the presence of paramagnetic Mn2+ dopants in Ba(Zn1/3Ta2/3)O3 ceramics and dangling bond states in amorphous Si thin films, although the identification of the dominant loss mechanism(s) in these dielectrics requires further investigation.

  5. Mechanism of stress relaxation in nanocrystalline Fe-N thin films

    NASA Astrophysics Data System (ADS)

    Gupta, Ranjeeta; Gupta, Ajay; Leitenberger, W.; Rüffer, R.

    2012-02-01

    The mechanism of stress relaxation in nanocrystalline Fe-N thin film has been studied. The as-deposited film possesses a strong in-plane compressive stress which relaxes with thermal annealing. Precise diffusion measurements using nuclear resonance reflectivity show that stress relaxation does not involve any long-range diffusion of Fe atoms. Rather, a redistribution of nitrogen atoms at various interstitial sites, as evidenced by conversion electron Mössbauer spectroscopy, is responsible for the relaxation of internal stresses. On the other hand, formation of the γ'-Fe4N phase at temperatures above 523 K involves long-range rearrangement of Fe atoms. The activation energy for Fe self-diffusion is found to be 0.38±0.04 eV.

  6. Petrographic and ferromagnetic resonance studies of experimentally shocked regolith analogs

    NASA Technical Reports Server (NTRS)

    Gibbons, R. V.; Morris, R. V.; Horz, F.; Thompson, T. D.

    1975-01-01

    Studies of porous aggregates of a regolith analog system composed of a 50:50-wt% mixture of labradorite and bronzite shocked at approximately 100-kbar intervals up to approximately 500 kbar are described, and characteristics of the well-indurated 'rock' formed at all pressures are reported. Ferromagnetic resonance studies of diopside and bronzite that were shocked at approximately 500 kbar are also reported. The formation of metallic particles in the superparamagnetic and single-domain size range as well as the metal fractionation are characterized, and the results suggest that the superparamagnetic and single-domain metallic particles in lunar soils may be produced by shock-induced dissemination of meteoritic and indigenous metal.

  7. Relaxation times estimation in MRI

    NASA Astrophysics Data System (ADS)

    Baselice, Fabio; Caivano, Rocchina; Cammarota, Aldo; Ferraioli, Giampaolo; Pascazio, Vito

    2014-03-01

    Magnetic Resonance Imaging is a very powerful techniques for soft tissue diagnosis. At the present, the clinical evaluation is mainly conducted exploiting the amplitude of the recorded MR image which, in some specific cases, is modified by using contrast enhancements. Nevertheless, spin-lattice (T1) and spin-spin (T2) relaxation times can play an important role in many pathology diagnosis, such as cancer, Alzheimer or Parkinson diseases. Different algorithms for relaxation time estimation have been proposed in literature. In particular, the two most adopted approaches are based on Least Squares (LS) and on Maximum Likelihood (ML) techniques. As the amplitude noise is not zero mean, the first one produces a biased estimator, while the ML is unbiased but at the cost of high computational effort. Recently the attention has been focused on the estimation in the complex, instead of the amplitude, domain. The advantage of working with real and imaginary decomposition of the available data is mainly the possibility of achieving higher quality estimations. Moreover, the zero mean complex noise makes the Least Square estimation unbiased, achieving low computational times. First results of complex domain relaxation times estimation on real datasets are presented. In particular, a patient with an occipital lesion has been imaged on a 3.0T scanner. Globally, the evaluation of relaxation times allow us to establish a more precise topography of biologically active foci, also with respect to contrast enhanced images.

  8. Determination of the Maier-Saupe strength parameter from dielectric relaxation experiments: a molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Bates, Martin A.; Luckhurst, Geoffrey R.

    Molecular dynamics simulations have been performed to investigate the rotational motion in the nematic and isotropic phases of a model mesogenic system in which the interactions between the molecules are represented by the Gay-Berne potential. First-rank end-over-end rotational relaxation times, analogous to those measured using dielectric relaxation spectroscopy for real mesogens with a longitudinal electric dipole, have been determined as a function of temperature and density. The relaxation times at temperatures throughout the nematic region are found to be larger than the values extrapolated from the isotropic phase to the same temperature. The simulation results are compared with the extended Debye theory for dielectric relaxation in the nematic phase. This relates the reduction in the relaxation rate to the retardation factor which depends on the Maier-Saupe strength parameter, and in turn is defined uniquely by the second-rank orientational order parameter. The simulations indicate that the retardation factor at constant strength parameter is density dependent, a feature neglected in the relaxation theory. We compare the simulation results where possible with experiment.

  9. Bottom-up study of the MRI positive contrast created by the Off-Resonance Saturation sequence

    NASA Astrophysics Data System (ADS)

    Delangre, S.; Vuong, Q. L.; Henrard, D.; Po, C.; Gallez, B.; Gossuin, Y.

    2015-05-01

    Superparamagnetic iron oxide nanoparticles (SPM particles) are used in MRI to highlight regions such as tumors through negative contrast. Unfortunately, sources as air bubbles or tissues interfaces also lead to negative contrast, which complicates the image interpretation. New MRI sequences creating positive contrast in the particle surrounding, such as the Off-Resonance Saturation sequence (ORS), have thus been developed. However, a theoretical study of the ORS sequence is still lacking, which hampers the optimization of this sequence. For this reason, this work provides a self-consistent analytical expression able to predict the dependence of the contrast on the sequence parameters and the SPM particles properties. This expression was validated by numerical simulations and experiments on agarose gel phantoms on a 11.7 T scanner system. It provides a fundamental understanding of the mechanisms leading to positive contrast, which could allow the improvement of the sequence for future in vivo applications. The influence of the SPM particle relaxivities, the SPM particle concentration, the echo time and the saturation pulse parameters on the contrast were investigated. The best contrast was achieved with SPM particles possessing the smallest transverse relaxivity, an optimal particle concentration and for low echo times.

  10. Relaxation Paths and Dynamics of β-apo-8'-carotenal: An Ultrafast Electronic and Vibrational Study

    NASA Astrophysics Data System (ADS)

    Van Tassle, A. J.; Prantil, M. A.; Burchfield, J. M.; Fleming, G. R.

    Results of infrared and visible transient absorption measurements following either two-photon excitation to the forbidden S1 state or one-photon excitation to the S2 state of the carotenoid β-apo-8'-carotenal are presented. This technique enables the study and comparison of subsequent structural dynamics with and without interference from higher states.

  11. Dynamic NMR of low-sensitivity fast-relaxing nuclei: (17)O NMR and DFT study of acetoxysilanes.

    PubMed

    Fusaro, Luca; Mameli, Giulia; Mocci, Francesca; Luhmer, Michel; Cerioni, Giovanni

    2012-02-01

    (17)O NMR is not routinely used for structure characterization, and kinetic studies of fluxional organic compounds are seldom undertaken because poor sensitivity and fast quadrupole relaxation are frequently regarded as intractable issues. This work shows how, nowadays, quantitative (17)O dynamic NMR studies on small organic molecules are feasible without enrichment being needed. It reports on acetoxysilanes, a class of fluxional compounds whose structure and dynamics were to be clarified. Natural abundance (17)O NMR spectra were recorded over a wide range of temperatures using standard instrumentation. The analysis relies on simple linewidth measurements and directly provides the activation parameters. The activation enthalpy is found to decrease with increasing number of acetoxy groups bound to silicon. Density functional theory calculations properly predict this trend and show that a single oxygen atom of the acetoxy group is bound to silicon, excluding chelation as binding mode, and that the dynamic process involves the shift of the silicon atom between the two oxygen atoms of the acetoxy group.

  12. Application of fluorescence resonance energy transfer in protein studies

    PubMed Central

    Ma, Linlin; Yang, Fan; Zheng, Jie

    2014-01-01

    Since the physical process of fluorescence resonance energy transfer (FRET) was elucidated more than six decades ago, this peculiar fluorescence phenomenon has turned into a powerful tool for biomedical research due to its compatibility in scale with biological molecules as well as rapid developments in novel fluorophores and optical detection techniques. A wide variety of FRET approaches have been devised, each with its own advantages and drawbacks. Especially in the last decade or so, we are witnessing a flourish of FRET applications in biological investigations, many of which exemplify clever experimental design and rigorous analysis. Here we review the current stage of FRET methods development with the main focus on its applications in protein studies in biological systems, by summarizing the basic components of FRET techniques, most established quantification methods, as well as potential pitfalls, illustrated by example applications. PMID:25368432

  13. Model and full scale study of twin supersonic plume resonance

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Manning, James C.; Ponton, Michael K.

    1987-01-01

    This paper examines the effect of both nozzle geometry and scale on the twin supersonic plume resonance phenomenon associated with aircraft having engine nozzle center-to-center spacings less than two diameters. Exit plane near field dynamic pressures were measured for both single and dual nozzle operation in 4.7 percent model and full scale under static conditions. The frequencies associated with this phenomenon were predicted to within 5 percent for a full scale F-15 aircraft. Amplitude levels associated with this phenomenon were found to dominate the dynamic pressure fluctuations in the inter-nozzle region, and reach a level near the structural design limit for this aircraft. The model scale studies, which involved both axisymmetric and rectangular geometry, indicated that amplitude levels could be expected to be much higher in flight. High amplitude levels would likely occur in the overexpanded region for axisymmetric geometry, and in the underexpanded region for rectangular geometry.

  14. A Computational and Experimental Study of Slit Resonators

    NASA Technical Reports Server (NTRS)

    Tam, C. K. W.; Ju, H.; Jones, M. G.; Watson, W. R.; Parrott, T. L.

    2003-01-01

    Computational and experimental studies are carried out to offer validation of the results obtained from direct numerical simulation (DNS) of the flow and acoustic fields of slit resonators. The test cases include slits with 90-degree corners and slits with 45-degree bevel angle housed inside an acoustic impedance tube. Three slit widths are used. Six frequencies from 0.5 to 3.0 kHz are chosen. Good agreement is found between computed and measured reflection factors. In addition, incident sound waves having white noise spectrum and a prescribed pseudo-random noise spectrum are used in subsequent series of tests. The computed broadband results are again found to agree well with experimental data. It is believed the present results provide strong support that DNS can eventually be a useful and accurate prediction tool for liner aeroacoustics. The usage of DNS as a design tool is discussed and illustrated by a simple example.

  15. Laser desorption studies of high mass biomolecules in Fourier-transform ion cyclotron resonance mass spectrometry.

    PubMed Central

    Solouki, T; Russell, D H

    1992-01-01

    Matrix-assisted laser desorption ionization is used to obtain Fourier-transform ion cyclotron resonance mass spectra of model peptides (e.g., gramicidin S, angiotensin I, renin substrate, melittin, and bovine insulin). Matrix-assisted laser desorption ionization yields ions having appreciable kinetic energies. Two methods for trapping the high kinetic energy ions are described: (i) the ion signal for [M+H]+ ions is shown to increase with increasing trapping voltages, and (ii) collisional relaxation is used for the detection of [M+H]+ ions of bovine insulin. Images PMID:1378614

  16. Dielectric relaxation studies in Se90Cd8Sb2 glassy alloy

    NASA Astrophysics Data System (ADS)

    Shukla, Nitesh; Rao, Vandita; Dwivedi, D. K.

    2016-05-01

    Se90Cd8Sb2 chalcogenide semiconducting alloy was prepared by melt quench technique. The prepared glassy alloy has been characterized by techniques such as scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX).Dielectric properties of Se90Cd8Sb2 chalcogenide semiconductor have been studied using impedance spectroscopic technique in the frequency range 5×102Hz - 1×105Hz and in temperature range 303-318K. It is found that dielectric constant ɛ' and dielectric loss factor ɛ″ are dependent on frequency and temperature.

  17. Biaxial stress relaxation in glassy polymers - Polymethylmethacrylate.

    NASA Technical Reports Server (NTRS)

    Sternstein, S. S.; Ho, T. C.

    1972-01-01

    Biaxial stress relaxation studies were performed on glassy polymethylmethacrylate in combined torsion-tension strain fields using a specially designed apparatus with exceptionally high stiffness and low cross talk between the torsional and tensile load measuring transducers. It was found that at low strain levels uniaxial tension relaxation is slower than pure torsion relaxation; tensile-component relaxation rates are unaffected by the level of torsional strain; torsional-component relaxation rates decrease as tensile strain is increased; uniaxial tension relaxation rates approach the pure torsion rates at higher strains (about 2%). A phenomenological treatment is presented which shows that relaxation rates can be coupled to the strain fields in which they are observed and yet be consistent with the concepts of linear viscoelasticity and the Boltzmann superposition integral.

  18. Resonant micro and nanoelectromechanical systems: Actuation and biological sensing studies

    NASA Astrophysics Data System (ADS)

    Ilic, Bojan

    This thesis explores various actuation mechanisms of resonant nanoelectro-mechanical systems (NEMS) with emphasis directed towards detection of biomolecules. Arrays of bulk and surface micromachined devices, made using conventional thin film fabrication methods, are used to explore the mass loading effects of selective molecular immobilization on the surface of the NEMS resonators. Experimentally measured shift in the first eigenfrequency is correlated to the amount of mass loading from the binding events and verified using theoretical constructs. Under ambient conditions where considerable damping occurs, immunospecific detection of single Escherichia coli O157:H7 cells is demonstrated by measuring the out of plane vibrational resonant mode using an optical deflection system with thermal noise as an excitation mechanism. Further sensitivity enhancement utilizing vacuum encapsulation in conjunction with piezoelectric actuation and tailoring of the cantilever dimensions is demonstrated by measuring mass loading of a nonpathogenic insect baculovirus, single Aminopropyltriethoxysilane (APTS), Hexamethyldisilazane (HMDS) and Octade-cyltrichlorosilane (OTS) monolayers. To highlight the lower detectable mass limit, surface machined NEMS oscillators with integrated circular Au contacts and sub-attogram mass detection sensitivity are used for selective immobilization of dinitrophenyl poly(ethylene glycol) undecanthiol based molecules. Experimental and theoretical elucidation of optical actuation of NEMS cantilevers at large distances from the clamped end is presented. These observations are considered within the theoretical framework of heat transfer and used to measure binding events of single double-stranded deoxyribonucleic acid (dsDNA) molecules to localized gold nanodots near the free end of a NEMS oscillator. Because this method allows direct coupling of energy into the device layer, several modes of in-plane vibrations are observed and employed in shaking off

  19. Magnetic resonance imaging of experimental cerebral oedema.

    PubMed Central

    Barnes, D; McDonald, W I; Tofts, P S; Johnson, G; Landon, D N

    1986-01-01

    Triethyl tin(TET)-induced cerebral oedema has been studied in cats by magnetic resonance imaging (MRI), and the findings correlated with the histology and fine structure of the cerebrum following perfusion-fixation. MRI is a sensitive technique for detecting cerebral oedema, and the distribution and severity of the changes correlate closely with the morphological abnormalities. The relaxation times, T1 and T2 increase progressively as the oedema develops, and the proportional increase in T2 is approximately twice that in T1. Analysis of the magnetisation decay curves reveals slowly-relaxing and rapidly-relaxing components which probably correspond to oedema fluid and intracellular water respectively. The image appearances taken in conjunction with relaxation data provide a basis for determining the nature of the oedema in vivo. Images PMID:3806109

  20. Study of proton resonance structure in {sup 27}P via resonant elastic scattering of {sup 26}Si+p

    SciTech Connect

    Jung, H. S.; Lee, C. S.; Kwon, Y. K.; Moon, J. Y.; Lee, J. H.; Yun, C. C.; Kubono, S.; Yamaguchi, H.; Hashimoto, T.; Kahl, D.; Hayakawa, S.; Choi, Seonho; Kim, M. J.; Kim, Y. H.; Kim, Y. K.; Park, J. S.; Kim, E. J.; Moon, C.-B.; Teranishi, T.; Wakabayashi, Y.; and others

    2012-11-12

    A measurement of resonant elastic scattering of {sup 26}Si+p was performed with a thick target using a {sup 26}Si radioactive ion beam at the CRIB (CNS Radioactive Ion Beam separator) of the Center for Nuclear Study (CNS), the University of Tokyo. The excitation function of {sup 27}P was measured successfully with the inverse kinematics method through a covered the range of excitation energies from E{sub x}{approx} 2.3 to 3.8 MeV, providing information about the resonance structure of this nucleus. The properties of these resonances are important to better determine the production rates of {sup 26}Si(p,g){sup 27}P reaction, which is one of the astrophysically important nuclear reactions to understand the production of the {sup 26}Al. Some new resonant states have been investigated, and determined their resonance parameters, such as excitation energies, proton partial widths, and spin-parities by R-matrix calculation.

  1. Study of the Fermi velocity and scattering time by periodic orbit resonance in the quasi-one-dimensional conductor (TMTSF)2ClO4

    NASA Astrophysics Data System (ADS)

    Takahashi, S.; Takasaki, S.

    2005-03-01

    (TMTSF)2ClO4 belongs to the family of quasi-one- dimensional (Q1D) Bechgaard salts, and is one of the most widely studied organic conductors because of its variety of exotic ground states, which may be tuned by applying pressure, magnetic field, or by employing different cooling processes (relaxed and quenched states). These phases include: metallic, insulating, p-wave superconducting, and field-induced-spin-density-wave. We recently observed periodic orbit resonances (POR) in (TMTSF)2ClO4 (a form of Q1D cyclotron resonance).^1 Studies of the angle-dependence of the POR enable us to determine the Fermi velocity, vF, and the scattering time, τ. In this talk, we will discuss the dependence of vF and τ on the cooling process, and their relation to the superconducting critical temperature.^1S. Takahashi et al., cond-mat/0404545 (2004)

  2. Nanoparticle aggregation and relaxation effects in ferrofluids: studied through anisotropic light scattering

    NASA Astrophysics Data System (ADS)

    Rablau, Corneliu; Vaishnava, Prem; Sudakar, Chandran; Tackett, Ronald; Lawes, Gavin; Naik, Ratna

    2008-08-01

    We have investigated the aggregation and dissociation dynamics of 6-nm size Fe3O4 nanoparticles coated by tetra methyl ammonium hydroxide (TMAH) and the same size γ-Fe2O3 nanoparticles precipitated inside an alginate hydrogel matrix, both in aqueous suspensions, using dc magnetic-field-induced time-dependent light scattering patterns. For the Fe3O4 ferrofluid, a strong anisotropy in light scattering was observed for light propagating perpendicular to the magnetic field. This behavior is attributed to the aggregation of the nanoparticles into chain-like and column-like structures oriented parallel to the magnetic field. A significantly different behavior is observed for the aqueous suspension of γ-Fe2O3 nanoparticles precipitated in alginate hydrogel, for which the application of the dc magnetic field produced little to no change in the light scattering patterns. We attribute this difference to the constrained random distribution of γ-Fe2O3 nanoparticles precipitated in the alginate matrix. Correlating the results from this investigation with our previous study of magneto-thermal measurements in ac fields [Vaishnava et al., J. Appl. Phys. 102, 063914 (2007)], we conclude that for a ferrofluid to exhibit significant thermal effects under an ac magnetic field, it should exhibit optical anisotropy by developing a chain like structure under the influence of a dc magnetic field.

  3. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems.

    PubMed

    Baranowski, M; Woźniak-Braszak, A; Jurga, K

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal. PMID:26705906

  4. Slow Relaxation of Magnetization in an Isostructural Series of Zinc-Lanthanide Complexes: An Integrated EPR and AC Susceptibility Study.

    PubMed

    Amjad, Asma; Madalan, Augustin M; Andruh, Marius; Caneschi, Andrea; Sorace, Lorenzo

    2016-08-26

    We report the synthesis, structure, and spectroscopic and dynamic magnetic properties of a series of heterodinuclear complexes, [ZnLn(LH4 )2 ](NO3 )3 ⋅6 H2 O (Ln=Nd, Tb, Dy, Ho, Er, and Yb), with the singly deprotonated form of a new compartmentalized Schiff-base ligand, LH5 . The Ln(III) ions in these systems show a distorted square-antiprism geometry with an LnO8 coordination sphere. EPR spectroscopy and DC magnetic studies have shown that the anisotropic nature of the complexes is far more complicated than predicted on the basis of a simple electrostatic model. Among the investigated systems, only the Dy(III) derivative showed single-ion magnet behavior, in zero and an applied magnetic field, both in pure polycrystalline samples and in a series of polycrystalline samples with different degrees of dilution at the single-crystal level in the isostructural Y(III) derivative. The rich dynamics observed as functions of frequency, field, and temperature reveals that multiple relaxation mechanisms are at play, resulting in a barrier of 189 cm(-1) , which is among the highest reported for a dinuclear Zn-Dy system. Analysis of the dynamic behavior as a function of dilution degree further evidenced the persistence of non-negligible intermolecular interactions, even at the lowest concentration of 1 %. PMID:27465998

  5. The relaxation exercise and social support trial-resst: study protocol for a randomized community based trial

    PubMed Central

    2011-01-01

    Background Studies suggests a possible link between vaginal discharge and common mental distress, as well as highlight the implications of the subjective burden of disease and its link with mental health. Methods/Design This is a community-based intervention trial that aims to evaluate the impact of a psycho-social intervention on medically unexplained vaginal discharge (MUVD) in a group of married, low-income Lebanese women, aged 18-49, and suffering from low to moderate levels of anxiety and/or depression. The intervention consisted of 12 sessions of structured social support, problem solving techniques, group discussions and trainer-supervised relaxation exercises (twice per week over six weeks). Women were recruited from Hey el Selloum, a southern disadvantaged suburb of Beirut, Lebanon, during an open recruitment campaign. The primary outcome was self-reported MUVD, upon ruling out reproductive tract infections (RTIs), through lab analysis. Anxiety and/or depression symptoms were the secondary outcomes for this trial. These were assessed using an Arabic validated version of the Hopkins Symptoms Checklist-25 (HSCL-25). Assessments were done at baseline and six months using face-to face interviews, pelvic examinations and laboratory tests. Women were randomized into either intervention or control group. Intent to treat analysis will be used. Discussion The results will indicate whether the proposed psychosocial intervention was effective in reducing MUVD (possibly mediated by common mental distress). Trial Registration The trial is registered at the Wellcome Trust Registry, ISRCTN assigned: ISRCTN: ISRCTN98441241 PMID:21864414

  6. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems

    NASA Astrophysics Data System (ADS)

    Baranowski, M.; Woźniak-Braszak, A.; Jurga, K.

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2 MHz and 28.411 MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins 1H are polarized in the magnetic field B0 while fluorine spins 19F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

  7. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems.

    PubMed

    Baranowski, M; Woźniak-Braszak, A; Jurga, K

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

  8. Rouse Mode Analysis of Chain Relaxation in Polymer Nanocomposites

    PubMed Central

    Kalathi, Jagannathan T.; Rubinstein, Michael; Grest, Gary S.

    2016-01-01

    Large-scale Molecular Dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer-solvent system. However, for NPs larger than half the entanglement mesh size, effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Thus, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect. PMID:25939276

  9. Rouse mode analysis of chain relaxation in polymer nanocomposites

    DOE PAGES

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; Grest, Gary S.

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, asmore » in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.« less

  10. Rouse mode analysis of chain relaxation in polymer nanocomposites

    SciTech Connect

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; Grest, Gary S.

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.

  11. The fluorinated (10, 0) boron nitride nanotube: a computational nuclear magnetic resonance and nuclear quadrupole resonance study.

    PubMed

    Seif, Ahmad; Boshra, Asadollah; Bodaghi, Ali

    2010-01-01

    Quantum chemical calculations at the level of density functional theory (DFT) were carried out to investigate the influence of fluorination boron and nitrogen nuclear magnetic resonance (NMR) and also nuclear quadrupole resonance (NQR) parameters in the (10, 0) single-wall boron nitride nanotube (SWBNNT). To achieve this aim three models of (10, 0) boron nitride nanotubes (BNNTs), raw and two F-attached (exohedral and endohedral) derivatives were studied. The results of calculations showed that while the boron atom chemically bonded to F atom has the largest chemical shielding isotropy (CSI); it has the smallest quadrupole coupling constant (CQ) value among the other boron nuclei.

  12. Interference effect on resonance studies in searches of heavy particles

    NASA Astrophysics Data System (ADS)

    Bian, Ligong; Liu, Da; Shu, Jing; Zhang, Yongchao

    2016-05-01

    The interference between resonance signal and continuum background can be either constructive or destructive, depending on the relative sign of couplings between the signal and background amplitudes. Different interference schemes lead to asymmetric distortions of the resonance line shape, which could be distinguished in experiments, when the internal resonance width is larger than the detector resolution. Interpreting the ATLAS diboson excesses by means of a toy W‧ model as an illustrative example (though it is disfavored by the 13 TeV data), we find that the signs of resonance couplings can only be revealed in the line shape measurements up to a high confidence level at a high luminosity, which could bring us further information on the underlying theory beyond resonance searches at future lepton and hadron colliders.

  13. Resonant soft x-ray fluorescence studies of novel materials

    SciTech Connect

    Carlisle, J.A.; Terminello, L.J.; Hudson, E.A.; Shirley, E.L.; Jia, J.J.; Callcott, T.A.; Himpsel, F.J.; Ederer, D.L.; Perera, R.C.C.

    1995-02-08

    The authors are using resonant soft x-ray fluorescence at the Advanced Light Source to probe the electronic and geometric structure of novel materials. In the resonant process, a core electron is excited by a photon whose energy is near the core binding energy. In this energy regime the absorption and emission processes are coupled, and this coupling manifests itself in several ways. In boron nitride (BN), the resonant emission spectra reflect the influence of a ``spectator`` electron in an unoccupied excitonic state. The resonant emission can be used to distinguish between the various bulk phases of BN, and can also be used to probe the electronic structure of a monolayer of BN buried in a bulk environment, where it is inaccessible to electron spectroscopies. For highly-oriented pyrolytic graphite (HOPG) a coherent absorption-emission process takes place in the resonant regime, whereby crystalline momentum is conserved between the core excited electron and the valence hole which remains after emission.

  14. /sup 13/C nuclear magnetic resonance studies of cardiac metabolism

    SciTech Connect

    Seeholzer, S.H.

    1985-01-01

    The last decade has witnessed the increasing use of Nuclear Magnetic Resonance (NMR) techniques for following the metabolic fate of compounds specifically labeled with /sup 13/C. The goals of the present study are: (1) to develop reliable quantitative procedures for measuring the /sup 13/C enrichment of specific carbon sites in compounds enriched by the metabolism of /sup 13/C-labeled substrates in rat heart, and (2) to use these quantitative measurements of fractional /sup 13/C enrichment within the context of a mathematical flux model describing the carbon flow through the TCA cycle and ancillary pathways, as a means for obtaining unknown flux parameters. Rat hearts have been perfused in vitro with various combinations of glucose, acetate, pyruvate, and propionate to achieve steady state flux conditions, followed by perfusion with the same substrates labeled with /sup 13/C in specific carbon sites. The hearts were frozen at different times after addition of /sup 13/C-labeled substrates and neutralized perchloric acid extracts were used to obtain high resolution proton-decoupled /sup 13/C NMR spectra at 90.55 MHz. The fractional /sup 13/C enrichment (F.E.) of individual carbon sites in different metabolites was calculated from the area of the resolved resonances after correction for saturation and nuclear Overhauser effects. These F.E. measurements by /sup 13/C NMR were validated by the analysis of /sup 13/C-/sup 1/H scalar coupling patterns observed in /sup 1/H NMR spectra of the extracted metabolites. The results obtained from perfusion of hearts glucose plus either (2-/sup 13/C) acetate or (3-/sup 13/C) pyruvate are similar to those obtained by previous investigators using /sup 14/C-labeled substrates.

  15. Nuclear magnetic resonance study of the collagen matrix in tendon

    NASA Astrophysics Data System (ADS)

    Krasnosselskaia, Lada Vadimovna

    Understanding of complex interactions of water with macromolecules is a prerequisite for quantitative musculoskeletal imaging and this dissertation presents a study on NMR characteristics of water in anisotropic environment of the collagen extracellular matrix of tendon. The first chapter of the dissertation analyzes a "magic angle" effect, a well known in clinical practice artifact of a sudden signal increase in normal tendons and ligaments at the orientation of 55° with respect to the static magnetic field of an MRI scanner. The physical basis of the orientation dependence of the free induction decay is studied in ex-vivo mammalian tissue at the field strength of 2 Tesla. Obtained quantitative measures are related to the model of heterogeneous water phases in the collagen extracellular matrix of tendon. A novel effect of central frequency shift of the water signal is reported and hypothesis on the origin of the effect is put forward. Clinical applications of NMR and MRI constantly benefit from adopting methods and techniques from the field of NMR of liquids, solids and liquid crystals. In the second chapter, a pseudo solid echo technique is evaluated for the purpose of detecting slow motions in the collagen matrix at different hydration and temperatures, at the field strength of 11.74 Tesla (500 MHz). The pseudo solid echo is shown capable in detecting motions on the scale of 10-3-10-6 seconds. 1H spin-lattice relaxation study at different levels of hydration and temperatures is presented in the third chapter. Predictions of the molecular model of collagen hydration are verified at the field strength of 11.74 Tesla (500 MHz) and temperature of 6°C, 26°C and 37°C. In the fourth chapter, an efficient adaptive mesh numerical code is developed on the basis of the octal tree data structure for assessment of the bulk magnetic susceptibility effects. The code allows calculation of the microscopic magnetic field as "seen by the nucleus" for uniformly magnetized

  16. Ferromagnetic resonance studies of thermal effects on lunar metallic Fe phases

    NASA Technical Reports Server (NTRS)

    Tsay, F.-D.; Live, D. H.

    1974-01-01

    Ferromagnetic resonance results of annealing experiments are discussed which illustrate the thermal effects on lunar metallic iron phases already present in a lunar fines sample. Spectral features of ferromagnetic resonance produced in the sample by heat treatments at temperatures between 600 and 1025 C are described which resemble those detected in lunar breccias and crystalline rocks. A correlation is shown to exist between these features and the degree of thermal metamorphism. It is noted that this correlation can be used as a built-in geothermometer or probe to investigate the thermal history and degree of metamorphism of a lunar sample containing metallic iron phases. The thermal history of a metaclastic rock is analyzed in this way, and it is shown that thermal metamorphism is an effective process for increasing relaxation times or the stability of the natural remanent magnetization carried by single-domain metallic iron particles.

  17. An ab initio study of multiple phonon scattering resonances in silicon germanium alloys

    NASA Astrophysics Data System (ADS)

    Mendoza, Jonathan; Esfarjani, Keivan; Chen, Gang

    2015-05-01

    We have computed phonon scattering rates and density of states in silicon germanium alloys using Green's function calculations and density functional theory. This method contrasts with the virtual crystal approximation (VCA) used in conjunction with Fermi's golden rule, which cannot capture resonance states occurring through the interaction of substitutional impurities with the host lattice. These resonances are demonstrated by density of states and scattering rate calculations in the dilute limit and show broadening as the concentration increases. Although these deviations become significant from the VCA at high frequencies, the relaxation times obtained for these phonon modes are small in both the full scattering theory and the VCA, resulting in their negligible contribution to thermal transport.

  18. The effects of soy on freezable bread dough: a magnetic resonance study.

    PubMed

    Simmons, Amber L; Vodovotz, Yael

    2012-11-15

    Hygroscopic soy ingredients were hypothesised to slow the rate of water migration in unleavened bread dough during frozen storage. Thawed soy (18% dry weight) and wheat dough samples were assessed using non-destructive nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) for up to 8 wks frozen storage time. MRI suggested a spatially homogeneous, net increase in proton mobility with frozen storage and, with solution state proton NMR, distinct "free" and "bound" states were discerned. T(2) relaxation times of the majority proton population suggested increased mobility with frozen storage time, and statistical difference from the fresh sample was seen later for the soy samples than the wheat samples. As seen by (13)C-solid state NMR, the crystallinity of the starch was not affected by either soy addition or frozen storage. In conclusion, addition of soy to bakery products led to slightly enhanced preservation of "fresh" characteristics of the dough during frozen storage. PMID:22868142

  19. Resonant Ultrasound Studies of Complex Transition Metal Oxides

    SciTech Connect

    Dr. Henry Bass; Dr. J. R. Gladden

    2008-08-18

    Department of Energy EPSCoR The University of Mississippi Award: DE-FG02-04ER46121 Resonant Ultrasound Spectroscopy Studies of Complex Transition Metal Oxides The central thrust of this DOE funded research program has been to apply resonant ultrasound spectroscopy (RUS), an elegant and efficient method for determining the elastic stiffness constants of a crystal, to the complex and poorly understood class of materials known as transition metal oxides (TMOs). Perhaps the most interesting and challenging feature of TMOs is their strongly correlated behavior in which spin, lattice, and charge degrees of freedom are strongly coupled. Elastic constants are a measure of the interatomic potentials in a crystal and are thus sensitive probes into the atomic environment. This sensitivity makes RUS an ideal tool to study the coupling of phase transition order parameters to lattice strains. The most significant result of the project has been the construction of a high temperature RUS apparatus capable of making elastic constant measurements at temperatures as high as 1000 degrees Celsius. We have designed and built novel acoustic transducers which can operate as high as 600 degrees Celsius based on lithium niobate piezoelectric elements. For measurement between 600 to 1000 C, a buffer rod system is used in which the samples under test and transducers are separated by a rod with low acoustic attenuation. The high temperature RUS system has been used to study the charge order (CO) transition in transition metal oxides for which we have discovered a new transition occurring about 35 C below the CO transition. While the CO transition exhibits a linear coupling between the strain and order parameter, this new precursor transition shows a different coupling indicating a fundamentally different mechanism. We have also begun a study, in collaboration with the Jet Propulsion Laboratory, to study novel thermoelectric materials at elevated temperatures. These materials include silicon

  20. Theoretical studies of the properties of magnetic resonance signal formed under the influence of distant dipolar field

    NASA Astrophysics Data System (ADS)

    Wong, Chung Ki

    This dissertation studies the properties of nuclear magnetic resonance (NMR) signals of biological samples formed under the influence of distant dipolar field (DDF). The use of DDF effect for magnetic resonance imaging (MRI) has aroused substantial research interests in recent years because of the unique contrast features of DDF signal. The main research activities on this topic are to improve the DDF signal level, and to characterize the use of DDF effect on probing tissue structures and functional MRI in brain studies. Issues of both directions are addressed in this dissertation. After a brief introduction to basic spin dynamics related to MR, the classical Bloch equation with the nonlinear DDF effect incorporated is solved analytically. The mechanism of separating the DDF signal from the whole signal of the sample based on the correlation spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) is first reviewed. That the sensitivity of the signal to physical parameters such as static magnetic field and transverse relaxation time are examined, and parameters for optimal signal-to-noise and contrast are obtained. The technique of multiple spin-echo acquisition to increase the signal magnitude and time efficiency is analyzed, and optimal conditions are found. Finally the problem of the sensitivity of DDF signal to variations in local magnetic field on a particular length scale is treated using a perturbation method. The results suggest that such sensitivity exists in a simple field distribution.

  1. Zen meditation and ABC relaxation theory: an exploration of relaxation states, beliefs, dispositions, and motivations.

    PubMed

    Gillani, N B; Smith, J C

    2001-06-01

    This study is an attempt to rigorously map the psychological effects of Zen meditation among experienced practitioners. Fifty-nine Zen meditators with at least six years of experience practiced an hour of traditional Zazen seated meditation. A control group of 24 college students spent 60 min silently reading popular magazines. Before relaxation, all participants took the Smith Relaxation States Inventory (SRSI), the Smith Relaxation Dispositions/Motivations Inventory (SRD/MI), and the Smith Relaxation Beliefs Inventory (SRBI). After practice, participants again took the SRSI. Analyses revealed that meditators are less likely to believe in God, more likely to believe in Inner Wisdom, and more likely to display the relaxation dispositions Mental Quiet, Mental Relaxation, and Timeless/Boundless/Infinite. Pre- and postsession analyses revealed that meditators showed greater increments in the relaxation states Mental Quiet, Love and Thankfulness, and Prayerfulness, as well as reduced Worry. Results support Smith's ABC Relaxation Theory.

  2. Simultaneous Study of Brownian and Néel Relaxation Phenomena in Ferrofluids by Mössbauer Spectroscopy.

    PubMed

    Landers, J; Salamon, S; Remmer, H; Ludwig, F; Wende, H

    2016-02-10

    We demonstrate the ability of Mössbauer spectroscopy to simultaneously investigate Brownian motion and Néel relaxation in ferrofluidic samples. For this purpose, Mössbauer spectra of coated iron oxide nanoparticles with core diameters of 6.0-26.4 nm dissolved in 70 vol % glycerol solution were recorded in the temperature range of 234-287 K and compared to low-temperature spectra without Brownian motion. By comparison to theory, we were able to determine the particle coating thickness and the dynamic viscosity of the fluid from the broadening of the absorption lines (Brownian motion), as well as the state of Néel relaxation. Results from Mössbauer spectroscopy were crosschecked by AC-susceptometry at several temperatures for Brownian motion and in the high-frequency regime (100 Hz-1 MHz) for Néel relaxation. PMID:26788750

  3. Dielectric relaxation study of binary mixture of sulfolane and N,N-dimethylformamide in benzene solution using microwave absorption data

    NASA Astrophysics Data System (ADS)

    Singh, Dalip; Thakur, Nagesh; Sharma, D. R.

    2012-12-01

    The dielectric constant (ɛ') and dielectric loss (ɛ″) for dilute solutions of the binary mixture of different molar concentrations of sulfolane and DMF in benzene solution has been measured at 9.885 GHz and different temperatures (25, 30, 35, 40°C) by using standard microwave techniques. Following the single frequency concentration variational method, the dielectric relaxation time (τ) and dipole moment (μ) have been calculated. It is found that dielectric relaxation process can be treated as the rate process, just like the viscous flow. The presence of solute-solute molecular associations in benzene solution has been proposed. Energy parameters (Δ H ɛ, Δ F ɛ, Δ S ɛ) for dielectric relaxation process of binary mixture at 50% mole fraction in benzene at 25, 30, 35, and 40°C have been calculated and compared with the corresponding energy parameters (Δ H η, Δ F η, Δ S η) for the viscous flow.

  4. Nitrergic Pathway Is the Main Contributing Mechanism in the Human Gastric Fundus Relaxation: An In Vitro Study

    PubMed Central

    Ko, Eun-Ju; Lee, Ji-Yeon; Ahn, Ki Duck; Bae, Je Moon; Rhee, Poong-Lyul

    2016-01-01

    Background Human gastric fundus relaxation is mediated by intrinsic inhibitory pathway. We investigated the roles of nitrergic and purinergic pathways, two known inhibitory factors in gastric motility, on spontaneous and nerve-evoked contractions in human gastric fundus muscles. Methods Gastric fundus muscle strips (12 circular and 13 longitudinal) were obtained from patients without previous gastrointestinal motility disorder who underwent gastrectomy for stomach cancer. Using these specimens, we examined basal tone, peak, amplitude, and frequency of spontaneous contractions, and peak and nadir values under electrical field stimulation (EFS, 150 V, 0.3 ms, 10 Hz, 20 s). To examine responses to purinergic and nitrergic inhibition without cholinergic innervation, atropine (muscarinic antagonist, 1 μM), MRS2500 (a purinergic P2Y1 receptor antagonist, 1 μM), and N-nitro-L-arginine (L-NNA, a nitric oxide synthase inhibitor, 100 μM) were added sequentially for spontaneous and electrically-stimulated contractions. Tetrodotoxin was used to confirm any neuronal involvement. Results In spontaneous contraction, L-NNA increased basal tone and peak in both muscle layers, while amplitude and frequency were unaffected. EFS (up to 10 Hz) uniformly induced initial contraction and subsequent relaxation in a frequency-dependent manner. Atropine abolished initial on-contraction and induced only relaxation during EFS. While MRS2500 showed no additional influence, L-NNA reversed relaxation (p = 0.012 in circular muscle, and p = 0.006 in longitudinal muscle). Tetrodotoxin abolished any EFS-induced motor response. Conclusions The relaxation of human gastric fundus muscle is reduced by nitrergic inhibition. Hence, nitrergic pathway appears to be the main mechanism for the human gastric fundus relaxation. PMID:27589594

  5. Distance determination from dysprosium induced relaxation enhancement: a case study on membrane-inserted WALP23 polypeptides

    NASA Astrophysics Data System (ADS)

    Lueders, Petra; Razzaghi, Sahand; Jäger, Heidrun; Tschaggelar, René; Hemminga, Marcus A.; Yulikov, Maxim; Jeschke, Gunnar

    2013-10-01

    Membrane incorporated synthetic α-helical polypeptides labelled with Dy(III) chelate complexes and nitroxide radicals were studied by the inversion recovery (IR) technique and Dy(III)-nitroxide distances were obtained. A comparison of obtained distances with the previously reported Gd(III)-nitroxide double electron-electron resonance (DEER) calibration data was performed and revealed reliability of the IR-based technique for the distance determination in membrane-incorporated biomacromolecules. The presented distance determination technique is 'spectroscopically orthogonal' to DEER-based distance measurements and can be potentially combined with DEER to study multiply spin-labelled biomacromolecules. The key steps of the data processing, the types of obtained distance information and the areas of possible application of the technique are discussed.

  6. Complex mechanism of relaxation in solid chloroxylenol (antibacterial/antifungal agent) studied by ¹H NMR spectroscopy and density functional theory calculations.

    PubMed

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Tomczak, Marzena Agnieszka; Medycki, Wojciech

    2014-03-27

    Molecular relaxation in antibacterial/antifungal agent: chloroxylenol (4-chloro-3,5-dimethylphenol, PCMX) in the solid state was studied by the (1)H NMR and quantum chemistry calculations. The temperature dependencies of the proton spin-lattice relaxation time (T1) in the ranges 15-273 K (at 24.667 MHz), 77-295 K (at 15 MHz), and 112-291 K at 90 MHz and the second moment (M2) of (1)H NMR resonant line in the range 106-380 K were measured. The two minima in the temperature dependence of T1 revealed two activation processes, whereas the M2 dependence in the studied range was quite flat and revealed the only significant reduction at 380 K. The low temperature part of T1(T) dependence indicated the occurrence of two processes characteristic of methyl bearing solids; the quantum mechanics governed incoherent tunneling (responsible for the low temperature flattening of T1) and the classical Arrhenius dependence governed hindered rotation (related to the wide low temperature minimum of 0.066 s at 57 K, 24.667 MHz). The 2D potential energy surface obtained using DFT/B3LYP/6-311++G(2d,p) calculations revealed the inequivalence of methyl groups and the lack of their interplay/coupling. The activation energies of classical hindered rotation are 3.35 and 2.5 kJ/mol, whereas temperatures at which the proton tunneling T(tun) finally ceases are 52 and 63 K, for inequivalent methyl groups. C(p)(T) required for the estimation of T(tun) was calculated purely theoretically on the basis of the Einstein and Debye models of specific heat and 51 modes of atomic vibrations, 4 internal rotations, and 3 torsions calculated by DFT. The -CH3 motion (tunneling and classical) results in the reduction in the (1)H NMR line second moment from 17.3 G(2) (rigid) to approximately 11.05 G(2). The pointed high temperature minimum T1(T) of 0.109 s at 89 K, 24.667 MHz, which shifts with frequency, was assigned to small-angle libration jumps, by the Θ2 = ±15° between two positions of equilibrium. The

  7. Feasibility studies for light scattering experiments to determine the velocity relaxation of small particles in a fluid

    NASA Technical Reports Server (NTRS)

    Acquista, C.; Narducci, L. M.

    1980-01-01

    An approach for measuring the non-Markoffian component in the relaxation mechanism of a Brownian particle is proposed which combines desirable features of both the shock wave experiment and conventional light scattering experiments. It is suggested that the radiation pressure generated by a C.W. laser be used to guide an individual spherical particle to terminal velocity. At an appropriate time, the beam intensity is suddenly lowered to a value at which the radiation pressure is negligible, and the ensuing velocity relaxation is measured directly.

  8. Study on vibrational relaxation dynamics of phenol-water complex by picosecond time-resolved IR-UV pump-probe spectroscopy in a supersonic molecular beam

    NASA Astrophysics Data System (ADS)

    Miyazaki, Yasunori; Inokuchi, Yoshiya; Ebata, Takayuki; Petković, Milena

    2013-06-01

    A comparative study of vibrational energy relaxation (VER) between the monohydrated complexes of phenol-d0 and phenol-d1 is investigated in a supersonic molecular beam. The direct time-resolved measurement of energy redistribution from the phenolic OH/OD stretching mode of the phenol-d0-H2O/phenol-d1-D2O is performed by picosecond IR-UV pump-probe spectroscopy. Two complexes follow the same relaxation process that begins with the intramolecular vibrational energy redistribution (IVR) and the intermolecular vibrational energy redistribution (IVR), which is followed by the vibrational predissociation (VP). The difference in the relaxation lifetimes between them is discussed by anharmonic force field and RRKM calculations. Anharmonic analysis implies that intra- (IVR) and intermolecular (IVR) relaxations occur in parallel in the complexes. The RRKM-predicted dissociation (VP) lifetimes show qualitative agreement with the observed results, suggesting that VP takes place after the statistical energy distribution in the complexes.

  9. Critical relaxation with overdamped quasiparticles in open quantum systems

    NASA Astrophysics Data System (ADS)

    Lang, Johannes; Piazza, Francesco

    2016-09-01

    We study the late-time relaxation following a quench in an open quantum many-body system. We consider the open Dicke model, describing the infinite-range interactions between N atoms and a single, lossy electromagnetic mode. We show that the dynamical phase transition at a critical atom-light coupling is characterized by the interplay between reservoir-driven and intrinsic relaxation processes in the absence of number conservation. Above the critical coupling, small fluctuations in the occupation of the dominant quasiparticle mode start to grow in time, while the quasiparticle lifetime remains finite due to losses. Near the critical interaction strength, we observe a crossover between exponential and power-law 1 /τ relaxation, the latter driven by collisions between quasiparticles. For a quench exactly to the critical coupling, the power-law relaxation extends to infinite times, but the finite lifetime of quasiparticles prevents aging from appearing in two-times response and correlation functions. We predict our results to be accessible to quench experiments with ultracold bosons in optical resonators.

  10. Geometric Magnetic Frustration in Li3Mg2OsO6 Studied with Muon Spin Relaxation

    NASA Astrophysics Data System (ADS)

    Carlo, J. P.; Derakhshan, S.; Greedan, J. E.

    Geometric frustration manifests when the spatial arrangement of ions inhibits magnetic order. Typically associated with antiferromagnetically (AF)-correlated moments on triangular or tetrahedral lattices, frustration occurs in a variety of structures and systems, resulting in rich phase diagrams and exotic ground states. As a window to exotic physics revealed by the cancellation of normally dominant interactions, the research community has taken great interest in frustrated systems. One family of recent interest are the rock-salt ordered oxides A5BO6, in which the B sites are occupied by magnetic ions comprising a network of interlocked tetrahedra, and nonmagnetic ions on the A sites control the B oxidation state through charge neutrality. Here we will discuss studies of Li3Mg2OsO6 using muon spin relaxation (μSR), a highly sensitive local probe of magnetism. Previous studies of this family included Li5OsO6, which exhibits AF order below 50K with minimal evidence for frustration, and Li4MgReO6, which exhibits glassy magnetism. Li3Mg2RuO6, meanwhile, exhibits long-range AF, with the ordering temperature suppressed by frustration. But its isoelectronic twin, Li3Mg2OsO6 (5d3 vs. 4d3) exhibits very different behavior, revealed by μSR to be a glassy ground state below 12K. Understanding why such similar systems exhibit diverse ground-state behavior is key to understanding the nature of geometric magnetic frustration. Financial support from the Research Corporation for Science Advancement.

  11. The Relaxation Response Resiliency Enhancement Program in the Management of Chronic Refractory Temporomandibular Joint Disorder: Results from a Pilot Study

    PubMed Central

    Vranceanu, Ana-Maria; Shaefer, Jeffery R.; Saadi, Ashkan Fahandej; Slawsby, Ellen; Sarin, Jaya; Scult, Matthew; Benson, Herbert; Denninger, John W.

    2015-01-01

    Objectives This is an open-pilot study to evaluate the feasibility, acceptability and efficacy of a pain-specific version of an established mind–body medicine program, the Relaxation Response [RR] Resiliency Program [R3P], in patients with chronic temporomandibular disorder [TMD]. Methods Male and female with at least a six-month history of pain involving the masticatory muscles were sought in the Orofacial Pain Centers of the Massachusetts General Hospital [MGH] or through an advertisement sent to MGH employees from 2008 to 2010. Eligible participants underwent the R3P intervention [eight group sessions] after standard medical management. Pre- and post-group patients underwent objective measures of impairment [vertical and lateral range of motion with and without pain, temporomandibular joint and muscle pain palpation, and algometer measures] and completed psychosocial measures [Symptom Severity Index, Perceived Stress Scale, the Symptom Checklist-90-Revised and Short Form 36 Health Survey]. Results Twenty-four subjects [16 females, 90% from MGH Orofacial Pain Centers,10% from among MGH employees], mean age 38 years, met eligibility criteria and participated in the study. The intervention was highly feasible and accepted by patients, as evidenced by a 92% rate of completion. Paired t-test analyses revealed improvement on self-reported pain measures: pain intensity [p<0.02], pain frequency [p<0.002], pain duration [p<0.027], pain tolerability [p<0.009] and on several objective tests. Conclusions The pain specific R3P is efficacious in reducing objective and subjective symptoms in patients with chronic refractory TMD. The comprehensive intervention, which combines educational information about pain with RR, cognitive behavioral and resiliency-enhancement skills, is accepted by patients and may be more efficacious than other treatments with fewer elements. PMID:26568669

  12. Nucleon Resonance Structure Studies via Exclusive KY Electroproduction

    NASA Astrophysics Data System (ADS)

    Carman, Daniel S.

    2016-10-01

    Studying the structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The electrocouplings of N^* states in the mass range below 1.8 GeV have been determined from analyses of CLAS π N, η N, and π π N data. This work has made it clear that consistent results from independent analyses of several exclusive channels with different couplings and non-resonant backgrounds but the same N^* electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying N^* states preferentially decay through the π π N channel instead of π N. Data from the KY channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying N^* states against those determined from the π N and π π {N} channels. A program to study excited N^* state structure in both non-strange and strange exclusive electroproduction channels using CLAS12 will measure differential cross sections and polarization observables to be used as input to extract the γ _v{it{NN}}^* electrocoupling amplitudes for the most prominent N^* states in the range of invariant energy W up 3 GeV in the virtually unexplored domain of momentum transfers Q^2 up to 12 GeV^2.

  13. Study of a possible S = + 1 dynamically generated baryonic resonance

    NASA Astrophysics Data System (ADS)

    Sarkar, Sourav; Oset, E.; Vicente Vacas, M. J.

    2005-05-01

    Starting from the lowest-order chiral Lagrangian for the interaction of the baryon decuplet with the octet of pseudoscalar mesons we find an attractive interaction in the ΔK channel with L = 0 and I = 1, while the interaction is repulsive for I = 2. The attractive interaction leads to a pole in the second Riemann sheet of the complex plane and manifests itself in a large strength of the ΔK scattering amplitude close to the ΔK threshold, which is not the case for I = 2. However, we also make a study of uncertainties in the model and conclude that the existence of this pole depends sensitively upon the input used and can disappear within reasonable variations of the input parameters. We take advantage to study the stability of the other poles obtained for the {{3}/{2}}- dynamically generated resonances of the model and conclude that they are stable and not contingent to reasonable changes in the input of the theory.

  14. Nucleon resonance structure studies via exclusive KY electroproduction

    DOE PAGES

    Carman, Daniel S.

    2016-06-16

    Studying the structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The electrocouplings ofmore » $N^*$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $$\\pi N$$, $$\\eta N$$, and $$\\pi \\pi N$$ data. This work has made it clear that consistent results from independent analyses of several exclusive channels with different couplings and non-resonant backgrounds but the same $N^*$ electro excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying $N^*$ states preferentially decay through the $$\\pi \\pi N$$ channel instead of $$\\pi N$$. Data from the $KY$ channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying $N^*$ states against those determined from the $$\\pi N$$ and $$\\pi \\pi N$$ channels. Lastly, a program to study excited $N^*$ state structure in both non-strange and strange exclusive electroproduction channels using CLAS12 will measure differential cross sections and polarization observables to be used as input to extract the $$\\gamma_vNN^*$$ electrocoupling amplitudes for the most prominent $N^*$ states in the range of invariant energy $W$ up 3~GeV in the virtually unexplored domain of momentum transfers $Q^2$ up to 12~GeV$^2$.« less

  15. Study of waveguide resonators for FEL operating at submillimeter wavelengths

    SciTech Connect

    Yakover, I.M.; Pinhasi, Y.; Gover, A.

    1995-12-31

    This paper presents theoretical results of waveguide resonator study for FEL operating at the submillimeter wavelength region. Because of increased ohmic losses it is harder to obtain high Q waveguide cavities at these wavelengths. The following unconventional multimode waveguides: metal-dielectric, corrugated and curved parallel plates, were considered. The type and structure of the operating modes were determined and their attenuation constant, effective mode area and wave impedance were calculated. On the basis of this analysis small-signal gain simulations were made. We have performed a parametric study of the various FEL oscillator cavity designs based on the parameters of the Israeli Tandem FEL experiment. It was found that an FEL utilizing unconventional waveguides has much better performance in comparison to an FEL based on conventional multimode rectangular and circular waveguides. In particular, promising design parameters for a sub-mm wavelength FEL utilizing a metal-dielectric waveguide were identified: gain of 45%/Amp and ohmic losses of 2% at frequency 300 GHz, and gain of 20%/Amp and ohmic losses 1% at frequency 675 GHz.

  16. Nucleon Resonance Structure Studies via Exclusive KY Electroproduction

    NASA Astrophysics Data System (ADS)

    Carman, Daniel S.

    2016-06-01

    Studying the structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The electrocouplings of N^* states in the mass range below 1.8 GeV have been determined from analyses of CLAS π N , η N , and π π N data. This work has made it clear that consistent results from independent analyses of several exclusive channels with different couplings and non-resonant backgrounds but the same N^* electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying N^* states preferentially decay through the π π N channel instead of π N . Data from the KY channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying N^* states against those determined from the π N and π π {N} channels. A program to study excited N^* state structure in both non-strange and strange exclusive electroproduction channels using CLAS12 will measure differential cross sections and polarization observables to be used as input to extract the γ _v{{NN}}^* electrocoupling amplitudes for the most prominent N^* states in the range of invariant energy W up 3 GeV in the virtually unexplored domain of momentum transfers Q^2 up to 12 GeV^2.

  17. Using surface plasmon resonance imaging to study bacterial biofilmsa

    PubMed Central

    Abadian, Pegah N.; Tandogan, Nil; Jamieson, John J.; Goluch, Edgar D.

    2014-01-01

    This paper describes the use of Surface Plasmon Resonance imaging (SPRi) as an emerging technique to study bacterial physiology in real-time without labels. The overwhelming majority of bacteria on earth exist in large multicellular communities known as biofilms. Biofilms are especially problematic because they facilitate the survival of pathogens, leading to chronic and recurring infections as well as costly industrial complications. Monitoring biofilm accumulation and removal is therefore critical in these and other applications. SPRi uniquely provides label-free, high-resolution images of biomass coverage on large channel surfaces up to 1 cm2 in real time, which allow quantitative assessment of biofilm dynamics. The rapid imaging capabilities of this technique are particularly relevant for multicellular bacterial studies, as these cells can swim several body lengths per second and divide multiple times per hour. We present here the first application of SPRi to image Escherichia coli and Pseudomonas aeruginosa cells moving, attaching, and forming biofilms across a large surface. This is also the first time that biofilm removal has been visualized with SPRi, which has important implications for monitoring the biofouling and regeneration of fluidic systems. Initial images of the removal process show that the biofilm releases from the surface as a wave along the direction of the fluid flow. PMID:24753735

  18. Polaron hopping in olivine phosphates studied by nuclear resonant scattering

    NASA Astrophysics Data System (ADS)

    Tracy, Sally June

    Valence fluctuations of Fe2+ and Fe3+ were studied in a solid solution of LixFePO4 by nuclear resonant forward scattering of synchrotron x rays while the sample was heated in a diamond-anvil pressure cell. The spectra acquired at different temperatures and pressures were analyzed for the frequencies of valence changes using the Blume-Tjon model of a system with a fluctuating Hamiltonian. These frequencies were analyzed to obtain activation energies and an activation volume for polaron hopping. There was a large suppression of hopping frequency with pressure, giving an anomalously large activation volume. This large, positive value is typical of ion diffusion, which indicates correlated motions of polarons, and Li+ ions that alter the dynamics of both. In a parallel study of NaxFePO4, the interplay between sodium ordering and electron mobility was investigated using a combination of synchrotron x-ray diffraction and nuclear resonant scattering. Conventional Mossbauer spectra were collected while the sample was heated in a resistive furnace. An analysis of the temperature evolution of the spectral shapes was used to identify the onset of fast electron hopping and determine the polaron hopping rate. Synchrotron x-ray diffraction measurements were carried out in the same temperature range. Reitveld analysis of the diffraction patterns was used to determine the temperature of sodium redistribution on the lattice. The diffraction analysis also provides new information about the phase stability of the system. The temperature evolution of the iron site occupancies from the Mossbauer measurements, combined with the synchrotron diffraction results give strong evidence for a relationship between the onset of fast electron dynamics and the redistribution of sodium in the lattice. Measurements of activation barriers for polaron hopping gave fundamental insights about the correlation between electronic carriers and mobile ions. This work established that polaron-ion interactions

  19. The electron spin resonance study of heavily nitrogen doped 6H SiC crystals

    SciTech Connect

    Savchenko, D. V.

    2015-01-28

    The magnetic and electronic properties of heavily doped n-type 6H SiC samples with a nitrogen concentration of 10{sup 19} and 4 × 10{sup 19 }cm{sup −3} were studied with electron spin resonance (ESR) at 5–150 K. The observed ESR line with a Dysonian lineshape was attributed to the conduction electrons (CE). The CE ESR (CESR) line was fitted by Lorentzian (insulating phase) (T < 40 K) and by Dysonian lineshape (metallic phase) above 40 K, demonstrating that Mott insulator-metal (IM) transition takes place at ∼40 K, accompanied by significant change in the microwave conductivity. The temperature dependence of CESR linewidth follows the linear Korringa law below 40 K, caused by the coupling of the localized electrons (LE) and CE, and is described by the exponential law above 40 K related to the direct relaxation of the LE magnetic moments via excited levels driven by the exchange interaction of LE with CE. The g-factor of the CESR line (g{sub ‖} = 2.0047(3), g{sub ⊥} = 2.0034(3)) is governed by the coupling of the LE of nitrogen donors at hexagonal and quasi-cubic sites with the CE. The sharp drop in CESR line intensity (25–30 K) was explained by the formation of antiferromagnetic ordering in the spin system close to the IM transition. The second broad ESR line overlapped with CESR signal (5–25 K) was attributed to the exchange line caused by the hopping motion of electrons between occupied and non-occupied positions of the nitrogen donors. Two mechanisms of conduction, hopping and band conduction, were distinguished in the range of T = 10–25 K and T > 50 K, respectively.

  20. Internal rotation potential and relaxation of structure in nitrobenzene studied by microwave spectroscopy supported by quantum chemistry

    NASA Astrophysics Data System (ADS)

    Larsen, Niels Wessel

    2010-01-01

    Rotational constants for the vibrational ground state and three torsionally excited states of nine nitrobenzene isotopologues were used to investigate the internal rotation potential and the structure of nitrobenzene. Relaxation parameters were calculated by the B3LYP and MP2(full) methods with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. The four sets of relaxation parameters all led to a clear improvement in the fit to rotational constants as compared with fits without relaxation of structure. The improvement was different from set to set, with B3LYP/aug-cc-PVDZ as a surprising winner. However, letting three of the relaxation parameters vary freely, gave virtually identical results for the molecular structure and potential function in all cases. Assuming higher order potential coefficient to vanish, the resultant potential parameters were, with 1 σ uncertainties, V2 = 1678 ± 19 cm -1 and V4 = -207 ± 6 cm -1. The barrier to internal rotation was estimated to 1575 ± 150 cm -1. A small change in structure upon ortho deuteration was found.

  1. Relaxation of a qubit measured by a driven Duffing oscillator

    SciTech Connect

    Serban, I.; Dykman, M. I.; Wilhelm, F. K.

    2010-02-15

    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 quasienergy resonances. Coupling to the driven oscillator changes the effective temperature of the qubit.

  2. Relaxation oscillations in a laser with a Gaussian mirror.

    PubMed

    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. PMID:11921794

  3. Proton magnetic relaxation and internal rotations in tetramethylammonium cadmium chloride

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Utton, D. B.

    1976-01-01

    Nuclear magnetic resonance (NMR) and relaxation studies of the proton spin-lattice relaxation time (PSLRT) and proton second moment (PSM) are reported. Tetramethylammonium cadmium chloride (TMCC) was selected as a diamagnetic member of the isomorphic series, and hence proton data relate directly to the motion of the tetramethylammonium ion in the absence of paramagnetic ions. In the model adopted, the correlation time for hindered motion of one of the methyl groups differs from that of the other three groups in the low-temperature phase below 104 K. PSLRT and PSM values agree closely with experimental data with this model. Crystallographic phase transitions in TMCC occur at 104 K and 119 K according to the PSLRT measurements. Dipolar interactions between adjacent protons account for the PSLR rates below 104 K.

  4. Finite-element modeling method for the study of dielectric relaxation at high frequencies of heterostructures made of multilayered particle

    NASA Astrophysics Data System (ADS)

    Fourn, Cédric; Lasquellec, Sophie; Brosseau, Christian

    2007-12-01

    There has been much recent interest in how morphological descriptors may affect the electromagnetic wave transport in particulate composite mediums. In this work, we present results of finite-element simulations that model the permittivity of two-dimensional (or cross sections of infinite three-dimensional parallel, infinitely long, identical, circular cylinders, where the properties and characteristics are invariant along the perpendicular cross-sectional plane) three-phase heterostructures made of a multilayered discoidal particle. While strictly valid only in a direct current situation, our analysis can be extended to treat electric fields that oscillate with time provided that the wavelengths and attenuation lengths associated with the fields are much larger than the microstructure dimension in order that the homogeneous (effective medium) representation of the composite structure makes sense. From simulations over a range of parameters, our analysis evaluates the effect of the surface fraction of inclusion, the conductivity, and thickness (relative to the particle radius) of the particle conductive coating on the effective complex permittivity of isotropic heterostructures in which the filler particles have a core-shell structure. Four main effects are found. First, the importance of the surface fraction of inclusion on the effective complex permittivity at high frequencies (from microwave to infrared) is illustrated over a broad range of coating thicknesses and conductivities. Second, the encapsulation phase (metallic coating) conductivity is identified as the key property controlling the dielectric relaxation due to interfacial polarization. Third, a simple parametrization of the high-frequency effective permittivity spectrum allowed us to obtain a reliable modelization of the Debye-type relaxation processes. From the least-squares fit of the effective complex permittivity data, we extract information on these relaxation processes, i.e., relaxation

  5. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    DOE PAGES

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; East, William E.; Blandford, Roger D.

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focusmore » on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less

  6. Kinetic Study of Radiation-reaction-limited Particle Acceleration During the Relaxation of Unstable Force-free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; East, William E.; Blandford, Roger D.

    2016-09-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The “flares” are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. Higher magnetization studies are promising and will be carried out in the future.

  7. Synchronization of pairwise-coupled, identical, relaxation oscillators based on metal-insulator phase transition devices: A model study

    NASA Astrophysics Data System (ADS)

    Parihar, Abhinav; Shukla, Nikhil; Datta, Suman; Raychowdhury, Arijit

    2015-02-01

    Computing with networks of synchronous oscillators has attracted wide-spread attention as novel materials and device topologies have enabled realization of compact, scalable and low-power coupled oscillatory systems. Of particular interest are compact and low-power relaxation oscillators that have been recently demonstrated using MIT (metal-insulator-transition) devices using properties of correlated oxides. Further the computational capability of pairwise coupled relaxation oscillators has also been shown to outperform traditional Boolean digital logic circuits. This paper presents an analysis of the dynamics and synchronization of a system of two such identical coupled relaxation oscillators implemented with MIT devices. We focus on two implementations of the oscillator: (a) a D-D configuration where complementary MIT devices (D) are connected in series to provide oscillations and (b) a D-R configuration where it is composed of a resistor (R) in series with a voltage-triggered state changing MIT device (D). The MIT device acts like a hysteresis resistor with different resistances in the two different states. The synchronization dynamics of such a system has been analyzed with purely charge based coupling using a resistive (RC) and a capacitive (CC) element in parallel. It is shown that in a D-D configuration symmetric, identical and capacitively coupled relaxation oscillator system synchronizes to an anti-phase locking state, whereas when coupled resistively the system locks in phase. Further, we demonstrate that for certain range of values of RC and CC, a bistable system is possible which can have potential applications in associative computing. In D-R configuration, we demonstrate the existence of rich dynamics including non-monotonic flows and complex phase relationship governed by the ratios of the coupling impedance. Finally, the developed theoretical formulations have been shown to explain experimentally measured waveforms of such pairwise coupled

  8. A Study of Standing Pressure Waves Within Open and Closed Acoustic Resonators

    NASA Technical Reports Server (NTRS)

    Daniels, C.; Steinetz, B.; Finkbeiner, J.; Raman, G.; Li, X.

    2002-01-01

    The first section of the results presented herein was conducted on an axisymmetric resonator configured with open ventilation ports on either end of the resonator, but otherwise closed and free from obstruction. The remaining section presents the results of a similar resonator shape that was closed, but contained an axisymmetric blockage centrally located through the axis of the resonator. Ambient air was used as the working fluid. In each of the studies, the resonator was oscillated at the resonant frequency of the fluid contained within the cavity while the dynamic pressure, static pressure, and temperature of the fluid were recorded at both ends of the resonator. The baseline results showed a marked reduction in the amplitude of the dynamic pressure waveforms over previous studies due to the use of air instead of refrigerant as the working fluid. A sharp reduction in the amplitude of the acoustic pressure waves was expected and recorded when the configuration of the resonators was modified from closed to open. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic pressure amplitudes varied little from baseline measurements.

  9. [Diagnosis. Radiological study. Ultrasound, computed tomography and magnetic resonance imaging].

    PubMed

    Gallo Vallejo, Francisco Javier; Giner Ruiz, Vicente

    2014-01-01

    Because of its low cost, availability in primary care and ease of interpretation, simple X-ray should be the first-line imaging technique used by family physicians for the diagnosis and/or follow-up of patients with osteoarthritis. Nevertheless, this technique should only be used if there are sound indications and if the results will influence decision-making. Despite the increase of indications in patients with rheumatological disease, the role of ultrasound in patients with osteoarthritis continues to be limited. Computed tomography (CT) is of some -although limited- use in osteoarthritis, especially in the study of complex joints (such as the sacroiliac joint and facet joints). Magnetic resonance imaging (MRI) has represented a major advance in the evaluation of joint cartilage and subchondral bone in patients with osteoarthritis but, because of its high cost and diagnostic-prognostic yield, this technique should only be used in highly selected patients. The indications for ultrasound, CT and MRI in patients with osteoarthritis continue to be limited in primary care and often coincide with situations in which the patient may require hospital referral. Patient safety should be bourne in mind. Patients should be protected from excessive ionizing radiation due to unnecessary repeat X-rays or inadequate views or to requests for tests such as CT, when not indicated.

  10. Mapping Depression in Schizophrenia: A Functional Magnetic Resonance Imaging Study.

    PubMed

    Kumari, Veena; Peters, Emmanuelle; Guinn, Ashley; Fannon, Dominic; Russell, Tamara; Sumich, Alexander; Kuipers, Elizabeth; Williams, Steven C R; Ffytche, Dominic H

    2016-05-01

    Depressive symptoms are common in schizophrenia, often left untreated, and associated with a high relapse rate, suicidal ideation, increased mortality, reduced social adjustment and poor quality of life. The neural mechanisms underlying depression in psychosis are poorly understood. Given reports of altered brain response to negative facial affect in depressive disorders, we examined brain response to emotive facial expressions in relation to levels of depression in people with psychosis. Seventy outpatients (final N= 63) and 20 healthy participants underwent functional magnetic resonance imaging during an implicit affect processing task involving presentation of facial expressions of fear, anger, happiness as well as neutral expressions and a (no face) control condition. All patients completed Beck Depression Inventory (BDI-II) and had their symptoms assessed on the Positive and Negative Syndrome Scale (PANSS). In patients, depression (BDI-II) scores associated positively with activation of the left thalamus, extending to the putamen-globus pallidus, insula, inferior-middle frontal and para-post-pre-central gyri during fearful expressions. Furthermore, patients with moderate-to-severe depression had significantly higher activity in these brain regions during fearful expressions relative to patients with no, minimal, or mild depression and healthy participants. The study provides first evidence of enhanced brain response to fearful facial expressions, which signal an uncertain source of threat in the environment, in patients with psychosis and a high level of self-reported depression. PMID:26712855

  11. Electron Spin Resonance (ESR) studies of returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Tsay, Fun-Dow; Kim, Soon Sam; Liang, Ranty H.

    1989-01-01

    The most important objective of the Comet Nucleus Sample Returm Mission is to return samples which could reflect formation conditions and evolutionary processes in the early solar nebula. It is expected that the returned samples will consist of fine-grained silicate materials mixed with ices composed of simple molecules such as H2O, NH3, CH4 as well as organics and/or more complex compounds. Because of the exposure to ionizing radiation from cosmic-ray, gamma-ray, and solar wind protons at low temperature, free radicals are expected to be formed and trapped in the solid ice matrices. The kind of trapped radical species together with their concentration and thermal stability can be used as a dosimeter as well as a geothermometer to determine thermal and radiation histories as well as outgassing and other possible alternation effects since the nucleus material was formed. Since free radicals that are known to contain unpaired electrons are all paramagnetic in nature, they can be readily detected and characterized in their native form by the Electron Spin Resonance (ESR) method. In fact, ESR has been shown to be a non-destructive, highly sensitive tool for the detection and characterization of paramagnetic, ferromagnetic, and radiation damage centers in terrestrial and extraterrestrial geological samples. The potential use of ESR as an effective method in the study of returned comet nucleus samples, in particular, in the analysis of fine-grained solid state icy samples is discussed.

  12. Achromatic synesthesias - a functional magnetic resonance imaging study.

    PubMed

    Melero, H; Ríos-Lago, M; Peña-Melián, A; Álvarez-Linera, J

    2014-09-01

    Grapheme-color synesthetes experience consistent, automatic and idiosyncratic colors associated with specific letters and numbers. Frequently, these specific associations exhibit achromatic synesthetic qualities (e.g. white, black or gray). In this study, we have investigated for the first time the neural basis of achromatic synesthesias, their relationship to chromatic synesthesias and the achromatic congruency effect in order to understand not only synesthetic color but also other components of the synesthetic experience. To achieve this aim, functional magnetic resonance imaging experiments were performed in a group of associator grapheme-color synesthetes and matched controls who were stimulated with real chromatic and achromatic stimuli (Mondrians), and with letters and numbers that elicited different types of grapheme-color synesthesias (i.e. chromatic and achromatic inducers which elicited chromatic but also achromatic synesthesias, as well as congruent and incongruent ones). The information derived from the analysis of Mondrians and chromatic/achromatic synesthesias suggests that real and synesthetic colors/achromaticity do not fully share neural mechanisms. The whole-brain analysis of BOLD signals in response to the complete set of synesthetic inducers revealed that the functional peculiarities of the synesthetic brain are distributed, and reflect different components of the synesthetic experience: a perceptual component, an (attentional) feature binding component, and an emotional component. Additionally, the inclusion of achromatic experiences has provided new evidence in favor of the emotional binding theory, a line of interpretation which constitutes a bridge between grapheme-color synesthesia and other developmental modalities of the phenomenon.

  13. Fluorescence resonance energy transfer studies on anthrax lethal toxin.

    PubMed

    Croney, John C; Cunningham, Kristina M; Collier, R John; Jameson, David M

    2003-08-28

    Anthrax lethal toxin is a binary bacterial toxin consisting of two proteins, protective antigen (PA) and lethal factor (LF), that self-assemble on receptor-bearing eukaryotic cells to form toxic, non-covalent complexes. PA(63), a proteolytically activated form of PA, spontaneously oligomerizes to form ring-shaped heptamers that bind LF and translocate it into the cell. Site-directed mutagenesis was used to substitute cysteine for each of three residues (N209, E614 and E733) at various levels on the lateral face of the PA(63) heptamer and for one residue (E126) on LF(N), the 30 kDa N-terminal PA binding domain of LF. Cysteine residues in PA were labeled with IAEDANS and that in LF(N) was labeled with Alexa 488 maleimide. The mutagenesis and labeling did not significantly affect function. Time-resolved fluorescence methods were used to study fluorescence resonance energy transfer (FRET) between the AEDANS and Alexa 488 probes after the complex assembled in solution. The results clearly indicate energy transfer between AEDANS labeled at residue N209C on PA and the Alexa 488-labeled LF(N), whereas transfer from residue E614C on PA was slight, and none was observed from residue E733C. These results support a model in which LF(N) binds near the top of the ring-shaped (PA(63))(7) heptamer.

  14. Mapping Depression in Schizophrenia: A Functional Magnetic Resonance Imaging Study

    PubMed Central

    Kumari, Veena; Peters, Emmanuelle; Guinn, Ashley; Fannon, Dominic; Russell, Tamara; Sumich, Alexander; Kuipers, Elizabeth; Williams, Steven C. R.; ffytche, Dominic H.

    2016-01-01

    Depressive symptoms are common in schizophrenia, often left untreated, and associated with a high relapse rate, suicidal ideation, increased mortality, reduced social adjustment and poor quality of life. The neural mechanisms underlying depression in psychosis are poorly understood. Given reports of altered brain response to negative facial affect in depressive disorders, we examined brain response to emotive facial expressions in relation to levels of depression in people with psychosis. Seventy outpatients (final N = 63) and 20 healthy participants underwent functional magnetic resonance imaging during an implicit affect processing task involving presentation of facial expressions of fear, anger, happiness as well as neutral expressions and a (no face) control condition. All patients completed Beck Depression Inventory (BDI-II) and had their symptoms assessed on the Positive and Negative Syndrome Scale (PANSS). In patients, depression (BDI-II) scores associated positively with activation of the left thalamus, extending to the putamen-globus pallidus, insula, inferior-middle frontal and para-post-pre-central gyri during fearful expressions. Furthermore, patients with moderate-to-severe depression had significantly higher activity in these brain regions during fearful expressions relative to patients with no, minimal, or mild depression and healthy participants. The study provides first evidence of enhanced brain response to fearful facial expressions, which signal an uncertain source of threat in the environment, in patients with psychosis and a high level of self-reported depression. PMID:26712855

  15. Nuclear magnetic resonance studies of bovine γB-crystallin

    NASA Astrophysics Data System (ADS)

    Thurston, George; Mills, Jeffrey; Michel, Lea; Mathews, Kaylee; Zanet, John; Payan, Angel; van Nostrand, Keith; Kotlarchyk, Michael; Ross, David; Wahle, Christopher; Hamilton, John

    Anisotropy of shape and/or interactions play an important role in determining the properties of concentrated solutions of the eye lens protein, γB-crystallin, including its liquid-liquid phase transition. We are studying γB anisotropic interactions with use of nuclear magnetic resonance (NMR) concentration- and temperature-dependent chemical shift perturbations (CSPs). We analyze two-dimensional heteronuclear spin quantum coherence (HSQC) spectra on backbone nitrogen and attached hydrogen nuclei for CSPs, up to 3 percent volume fraction. Cumulative distribution functions of the CSPs show a concentration and temperature-dependent spread. Many peaks that are highly shifted with either concentration or temperature are close (i) crystal intermolecular contacts (ii) locations of cataractogenic point mutations of a homologous human protein, human γD-crystallin, and (iii) charged amino-acid residues. We also discuss the concentration- and temperature-dependence of NMR and quasielastic light scattering measurements of rotational and translational diffusion of γB crystallin in solution, affected by interprotein attractions. Supported by NIH EY018249.

  16. Fluorescence resonance energy transfer in the studies of guanine quadruplexes.

    PubMed

    Juskowiak, Bernard; Takenaka, Shigeori

    2006-01-01

    A guanine (G)-quadruplex DNA motif has recently emerged as a biologically important structure that is believed to interfere with telomere maintenance by telomerase. G-quadruplexes exhibit four-stranded structures containing one or more nucleic acid strands with central channel able to accommodate metal cations. Coordination of certain metal cations stabilizes G-quadruplex as with some promising small organic molecules that promote the formation and/or stabilization of G-quadruplex. Among many techniques employed to explore properties of G-quadruplexes, the fluorescence resonance energy transfer (FRET) technique has been recognized as a powerful tool to study G-quadruplex formation. This review summarizes the current developments in the uses of FRET technique for the fundamental structural investigations and its practical applications. Applications include FRET-based selection of efficient quadruplex-binding ligands, design of a nanomolecular machine, and a molecular aptamer beacon for protein recognition. We also describe a technique for detection of potassium ions in aqueous solution with the use of quadruplex-based sensor (potassium-sensing oligonucleotide).

  17. Achromatic synesthesias - a functional magnetic resonance imaging study.

    PubMed

    Melero, H; Ríos-Lago, M; Peña-Melián, A; Álvarez-Linera, J

    2014-09-01

    Grapheme-color synesthetes experience consistent, automatic and idiosyncratic colors associated with specific letters and numbers. Frequently, these specific associations exhibit achromatic synesthetic qualities (e.g. white, black or gray). In this study, we have investigated for the first time the neural basis of achromatic synesthesias, their relationship to chromatic synesthesias and the achromatic congruency effect in order to understand not only synesthetic color but also other components of the synesthetic experience. To achieve this aim, functional magnetic resonance imaging experiments were performed in a group of associator grapheme-color synesthetes and matched controls who were stimulated with real chromatic and achromatic stimuli (Mondrians), and with letters and numbers that elicited different types of grapheme-color synesthesias (i.e. chromatic and achromatic inducers which elicited chromatic but also achromatic synesthesias, as well as congruent and incongruent ones). The information derived from the analysis of Mondrians and chromatic/achromatic synesthesias suggests that real and synesthetic colors/achromaticity do not fully share neural mechanisms. The whole-brain analysis of BOLD signals in response to the complete set of synesthetic inducers revealed that the functional peculiarities of the synesthetic brain are distributed, and reflect different components of the synesthetic experience: a perceptual component, an (attentional) feature binding component, and an emotional component. Additionally, the inclusion of achromatic experiences has provided new evidence in favor of the emotional binding theory, a line of interpretation which constitutes a bridge between grapheme-color synesthesia and other developmental modalities of the phenomenon. PMID:24845620

  18. Spin relaxation in metallic ferromagnets

    NASA Astrophysics Data System (ADS)

    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.

  19. Single-point magnetic resonance imaging study of water adsorption in pellets of zeolite 4A.

    PubMed

    Prado, P J; Balcom, B J; Jama, M

    1999-03-01

    The water uptake process in commercial type particles of zeolite 4A has been studied using a single-point MRI method. True proton density, T1, T2, and T*2 relaxation times were obtained with submillimetric resolution, overcoming the restrictions of short T*2 signals. The molecular mobility in nonequilibrium conditions has been characterized by relaxation time mapping. A clear reduction of the water sorption rate was observed by comparing MRI profiles of a loosely packed bed and gravimetric measurements of spread particles from the same sieved zeolite batch.

  20. Electron spin resonance studies of the ovary of the rat

    NASA Astrophysics Data System (ADS)

    Andersen, Roy S.; Curtis, Joseph C.

    1988-11-01

    Electron spin resonance spectra of rat ovaries, isolated ovarian compartments, and ovarian subcellular fractions were compared with spectra of rat adrenals. Rat ovaries were found to exhibit ESR signals similar to those previously described in studies of mammalian adrenal and testis. Observations were made at 113 K in an anaerobic environment. ESR signals of the low-spin ferric cytochrome P-450, the non-heme protein ferredoxin, and the non-heme glycoprotein transferrin were consistently observed in whole ovaries. The first two signals were detected in mitochondrial fractions isolated from ovaries, while only cytochrome P-450 was detected in microsomal fractions. Signals from ferredoxin and cytochrome P-450 were also consistently observed in both whole adrenals and adrenal mitochondrial fractions. However, in the microsomal fraction only cytochrome P-450 was present. The g values for the cytochrome P-450 and ferredoxin signals found in this study of ovaries were identical to those previously reported and also found in this study in spectra of rat adrenals. The concentration of ferredoxin per milligram wet mass in rat ovaries appears to be only one-sixth of that in the rat adrenal. The concentration of cytochrome P-450 appears to be only one-ninth of that in the adrenal. Signals from ferredoxin were detected in all ovarian compartments except granulosa cells isolated from Graafian follicles. The third signal, that of transferrin, while often observed in the spectra of whole ovaries, has been attributed to residual blood in the tissues examined. The effects of oxygen on these spectra has been found to be considerable and is discussed.

  1. Cerebellum and speech perception: a functional magnetic resonance imaging study.

    PubMed

    Mathiak, Klaus; Hertrich, Ingo; Grodd, Wolfgang; Ackermann, Hermann

    2002-08-15

    A variety of data indicate that the cerebellum participates in perceptual tasks requiring the precise representation of temporal information. Access to the word form of a lexical item requires, among other functions, the processing of durational parameters of verbal utterances. Therefore, cerebellar dysfunctions must be expected to impair word recognition. In order to specify the topography of the assumed cerebellar speech perception mechanism, a functional magnetic resonance imaging study was performed using the German lexical items "Boden" ([bodn], Engl. "floor") and "Boten" ([botn], "messengers") as test materials. The contrast in sound structure of these two lexical items can be signaled either by the length of the wordmedial pause (closure time, CLT; an exclusively temporal measure) or by the aspiration noise of wordmedial "d" or "t" (voice onset time, VOT; an intrasegmental cue). A previous study found bilateral cerebellar disorders to compromise word recognition based on CLT whereas the encoding of VOT remained unimpaired. In the present study, two series of "Boden - Boten" utterances were resynthesized, systematically varying either in CLT or VOT. Subjects had to identify both words "Boden" and "Boten" by analysis of either the durational parameter CLT or the VOT aspiration segment. In a subtraction design, CLT categorization as compared to VOT identification (CLT - VOT) yielded a significant hemodynamic response of the right cerebellar hemisphere (neocerebellum Crus I) and the frontal lobe (anterior to Broca's area). The reversed contrast ( VOT - CLT) resulted in a single activation cluster located at the level of the supratemporal plane of the dominant hemisphere. These findings provide first evidence for a distinct contribution of the right cerebellar hemisphere to speech perception in terms of encoding of durational parameters of verbal utterances. Verbal working memory tasks, lexical response selection, and auditory imagery of word strings have been

  2. Interflavin electron transfer in human cytochrome P450 reductase is enhanced by coenzyme binding. Relaxation kinetic studies with coenzyme analogues.

    PubMed

    Gutierrez, Aldo; Munro, Andrew W; Grunau, Alex; Wolf, C Roland; Scrutton, Nigel S; Roberts, Gordon C K

    2003-06-01

    The role of coenzyme binding in regulating interflavin electron transfer in human cytochrome P450 reductase (CPR) has been studied using temperature-jump spectroscopy. Previous studies [Gutierrez, A., Paine, M., Wolf, C.R., Scrutton, N.S., & Roberts, G.C.K. Biochemistry (2002) 41, 4626-4637] have shown that the observed rate, 1/tau, of interflavin electron transfer (FADsq - FMNsq-->FADox - FMNhq) in CPR reduced at the two-electron level with NADPH is 55 +/- 2 s-1, whereas with dithionite-reduced enzyme the observed rate is 11 +/- 0.5 s-1, suggesting that NADPH (or NADP+) binding has an important role in controlling the rate of internal electron transfer. In relaxation experiments performed with CPR reduced at the two-electron level with NADH, the observed rate of internal electron transfer (1/tau = 18 +/- 0.7 s-1) is intermediate in value between those seen with dithionite-reduced and NADPH-reduced enzyme, indicating that the presence of the 2'-phosphate is important for enhancing internal electron transfer. To investigate this further, temperature jump experiments were performed with dithionite-reduced enzyme in the presence of 2',5'-ADP and 2'-AMP. These two ligands increase the observed rate of interflavin electron transfer in two-electron reduced CPR from 1/tau = 11 s-1 to 35 +/- 0.2 s-1 and 32 +/- 0.6 s-1, respectively. Reduction of CPR at the two-electron level by NADPH, NADH or dithionite generates the same spectral species, consistent with an electron distribution that is equivalent regardless of reductant at the initiation of the temperature jump. Spectroelectrochemical experiments establish that the redox potentials of the flavins of CPR are unchanged on binding 2',5'-ADP, supporting the view that enhanced rates of interdomain electron transfer have their origin in a conformational change produced by binding NADPH or its fragments. Addition of 2',5'-ADP either to the isolated FAD-domain or to full-length CPR (in their oxidized and reduced forms) leads to

  3. Study of the onset of the acoustic streaming in parallel plate resonators with pulse ultrasound.

    PubMed

    Castro, Angelica; Hoyos, Mauricio

    2016-03-01

    In a previous study, we introduced pulse mode ultrasound as a new method for reducing and controlling the acoustic streaming in parallel plate resonators (Hoyos and Castro, 2013). Here, by modifying other parameters such as the resonator geometry and the particle size, we have found a threshold for particle manipulation with ultrasonic standing waves in confined resonators without the influence of the acoustic streaming. We demonstrate that pulse mode ultrasound open the possibility of manipulating particles smaller than 1 μm size.

  4. Experimental and theoretical studies of the influence of a tensile load on the relaxation of residual stresses in a hardened cylindrical specimen under creep conditions

    NASA Astrophysics Data System (ADS)

    Radchenko, V. P.; Kocherov, E. P.; Saushkin, M. N.; Smyslov, V. A.

    2015-03-01

    This paper presents an experimental and theoretical study of the influence of a tensile load on the relaxation of residual stresses in a hardened cylindrical specimen of ZhS6KP alloy under creep conditions at 800°C. An experimental study was conducted to investigate the distribution of the axial residual stress tensor component across the thickness of the hardened layer after hardening by air shot blasting using microbeads and after creep loading for 50 and 200 h under a tensile load of 150 and 250 MPa. A detailed theoretical analysis of the problem was performed. In all loading regimes, the calculated and experimental values of the residual stresses were found to be in good agreement. It was shown that at low tensile load, the relaxation rate decreased in comparison with the case of thermal exposure in the absence of a tensile load and, with increasing load intensity, it increased.

  5. Carbon-13 NMR relaxation study of molecular dynamics and organization of sodium poly(styrenesulfonate) and dodecyltrimethylammonium bromide aggregates in aqueous solution

    SciTech Connect

    Gao, Zhisheng; Wasylishen, R.E.; Kwak, J.C.T. )

    1990-01-25

    Aqueous solutions of aggregates of sodium poly(styrenesulfonate) (PSS) and dodecyltrimethylammonium bromide (DTAB) have been studied by {sup 13}C NMR relaxation measurements at 8.48 T. The relaxation data are interpreted by use of a two-step model. Correlation times for fast motion and order parameters have been calculated as a function of carbon position on the alkyl chain of DTAB in the PSS-DTAB aggregates. A micellar solution of DTAB is also studied for comparison. Slightly larger order parameters are observed for the surfactant alkyl chain (except the last three carbons C10, C11, and C12) in the PSS-DTAB aggregates compared with those in DTAB micelles. On the other hand, for the carbons near the headgroup of DTAB, the correlation times for fast motion in the PSS-DTAB aggregates are much longer than those in the DTAB micelles.

  6. Fluorescence Resonance Energy Transfer Studies of DNA Polymerase β

    PubMed Central

    Towle-Weicksel, Jamie B.; Dalal, Shibani; Sohl, Christal D.; Doublié, Sylvie; Anderson, Karen S.; Sweasy, Joann B.

    2014-01-01

    During DNA repair, DNA polymerase β (Pol β) is a highly dynamic enzyme that is able to select the correct nucleotide opposite a templating base from a pool of four different deoxynucleoside triphosphates (dNTPs). To gain insight into nucleotide selection, we use a fluorescence resonance energy transfer (FRET)-based system to monitor movement of the Pol β fingers domain during catalysis in the presence of either correct or incorrect dNTPs. By labeling the fingers domain with ((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid (IAEDANS) and the DNA substrate with Dabcyl, we are able to observe rapid fingers closing in the presence of correct dNTPs as the IAEDANS comes into contact with a Dabcyl-labeled, one-base gapped DNA. Our findings show that not only do the fingers close after binding to the correct dNTP, but that there is a second conformational change associated with a non-covalent step not previously reported for Pol β. Further analyses suggest that this conformational change corresponds to the binding of the catalytic metal into the polymerase active site. FRET studies with incorrect dNTP result in no changes in fluorescence, indicating that the fingers do not close in the presence of incorrect dNTP. Together, our results show that nucleotide selection initially occurs in an open fingers conformation and that the catalytic pathways of correct and incorrect dNTPs differ from each other. Overall, this study provides new insight into the mechanism of substrate choice by a polymerase that plays a critical role in maintaining genome stability. PMID:24764311

  7. Proton nuclear magnetic resonance studies on the variant-3 neurotoxin from Centruroides sculpturatus Ewing: Sequential assignment of resonances

    SciTech Connect

    Nettesheim, D.G.; Klevit, R.E.; Drobny, G.; Watt, D.D.; Krishna, N.R. )

    1989-02-21

    The authors report the sequential assignment of resonances to specific residues in the proton nuclear magnetic resonance spectrum of the variant-3 neurotoxin from the scorpion Centruroides sculpturatus Ewing (range southwestern U.S.A.). A combination of two-dimensional NMR experiments such as 2D-COSY, 2D-NOESY, and single- and double-RELAY coherence transfer spectroscopy has been employed on samples of the protein dissolved in D{sub 2}O and in H{sub 2}O for assignment purposes. These studies provide a basis for the determination of the solution-phase conformation of this protein and for undertaking detailed structure-function studies of these neurotoxins that modulate the flow of sodium current by binding to the sodium channels of excitable membranes.

  8. Phase transitions in semidefinite relaxations

    PubMed Central

    Javanmard, Adel; Montanari, Andrea; Ricci-Tersenghi, Federico

    2016-01-01

    Statistical inference problems arising within signal processing, data mining, and machine learning naturally give rise to hard combinatorial optimization problems. These problems become intractable when the dimensionality of the data is large, as is often the case for modern datasets. A popular idea is to construct convex relaxations of these combinatorial problems, which can be solved efficiently for large-scale datasets. Semidefinite programming (SDP) relaxations are among the most powerful methods in this family and are surprisingly well suited for a broad range of problems where data take the form of matrices or graphs. It has been observed several times that when the statistical noise is small enough, SDP relaxations correctly detect the underlying combinatorial structures. In this paper we develop asymptotic predictions for several detection thresholds, as well as for the estimation error above these thresholds. We study some classical SDP relaxations for statistical problems motivated by graph synchronization and community detection in networks. We map these optimization problems to statistical mechanics models with vector spins and use nonrigorous techniques from statistical mechanics to characterize the corresponding phase transitions. Our results clarify the effectiveness of SDP relaxations in solving high-dimensional statistical problems. PMID:27001856

  9. Phase transitions in semidefinite relaxations.

    PubMed

    Javanmard, Adel; Montanari, Andrea; Ricci-Tersenghi, Federico

    2016-04-19

    Statistical inference problems arising within signal processing, data mining, and machine learning naturally give rise to hard combinatorial optimization problems. These problems become intractable when the dimensionality of the data is large, as is often the case for modern datasets. A popular idea is to construct convex relaxations of these combinatorial problems, which can be solved efficiently for large-scale datasets. Semidefinite programming (SDP) relaxations are among the most powerful methods in this family and are surprisingly well suited for a broad range of problems where data take the form of matrices or graphs. It has been observed several times that when the statistical noise is small enough, SDP relaxations correctly detect the underlying combinatorial structures. In this paper we develop asymptotic predictions for several detection thresholds, as well as for the estimation error above these thresholds. We study some classical SDP relaxations for statistical problems motivated by graph synchronization and community detection in networks. We map these optimization problems to statistical mechanics models with vector spins and use nonrigorous techniques from statistical mechanics to characterize the corresponding phase transitions. Our results clarify the effectiveness of SDP relaxations in solving high-dimensional statistical problems. PMID:27001856

  10. Study of the baryon resonances structure via η photoproduction

    NASA Astrophysics Data System (ADS)

    Li, Zhenping; Saghai, Bijan

    1998-12-01

    Within a quark model the process γp-->ηp, for Eγlab < 1.2 GeV, is investigated. We find that the recent data from GRAAL on the polarized beam asymmetry require significant contributions from the resonances D13(1520), F15(1680), and to a lesser extent from P13(1720) in addition to those from the dominant S11(1535) resonance, implied by the Mainz differential cross-section data. The contributions from the resonances S11(1650), D13(1700) and D15(1675) are found consistently small but sensitive to the polarized target asymmetry measured recently at ELSA. These results are shown to be consistent with the quark model predictions.

  11. Inter-study reproducibility of cardiovascular magnetic resonance tagging

    PubMed Central

    2013-01-01

    Background The aim of this study is to determine the test-retest reliability of the measurement of regional myocardial function by cardiovascular magnetic resonance (CMR) tagging using spatial modulation of magnetization. Methods Twenty-five participants underwent CMR tagging twice over 12 ± 7 days. To assess the role of slice orientation on strain measurement, two healthy volunteers had a first exam, followed by image acquisition repeated with slices rotated ±15 degrees out of true short axis, followed by a second exam in the true short axis plane. To assess the role of slice location, two healthy volunteers had whole heart tagging. The harmonic phase (HARP) method was used to analyze the tagged images. Peak midwall circumferential strain (Ecc), radial strain (Err), Lambda 1, Lambda 2, and Angle α were determined in basal, mid and apical slices. LV torsion, systolic and early diastolic circumferential strain and torsion rates were also determined. Results LV Ecc and torsion had excellent intra-, interobserver, and inter-study intra-class correlation coefficients (ICC range, 0.7 to 0.9). Err, Lambda 1, Lambda 2 and angle had excellent intra- and interobserver ICC than inter-study ICC. Angle had least inter-study reproducibility. Torsion rates had superior intra-, interobserver, and inter-study reproducibility to strain rates. The measurements of LV Ecc were comparable in all three slices with different short axis orientations (standard deviation of mean Ecc was 0.09, 0.18 and 0.16 at basal, mid and apical slices, respectively). The mean difference in LV Ecc between slices was more pronounced in most of the basal slices compared to the rest of the heart. Conclusions Intraobserver and interobserver reproducibility of all strain and torsion parameters was excellent. Inter-study reproducibility of CMR tagging by SPAMM varied between different parameters as described in the results above and was superior for Ecc and LV torsion. The variation in LV Ecc

  12. Field Line Resonance at Mercury's Magnetosphere: A Simulation Study

    SciTech Connect

    Eun-Hwa Kim, Jay R. Johnson, and Dong-Hun Lee

    2008-05-22

    Ultra low frequency (ULF) waves, which are assumed to be standing waves on the field, are observed by the Mariner 10 spacecraft at Mercury. These waves are oscillating at 38% of the proton gyrofrequency. It is well known that the heavy ions, such as Na+, are abundant in Mercury's magnetosphere. Because the presence of different ion species has an influence on the plasma dispersion characteristics near the ion gyro-frequencies, such relatively high frequencies of magnetospheric eigenoscillations at Mercury require a multi-fluid treatment for the plasma. Thus ULF waves at Mercury may have a distinct difference from typical ULF oscillations at Earth, which are often described in terms of magnetohydrodynamics (MHD). By adopting a multi-fluid numerical wave model, we examine how magnetic eigenoscillations occur in Mercury's magnetosphere. Because protons and sodium ions are the main constituents at Mercury, we assume an electron-proton- sodium plasma in our model. The frequency spectra and time histories of the electromagnetic fields at the ion-ion hybrid (IIH) and cavity resonances are presented. Our results show: (1) The observed ULF waves are likely compressional waves rather than FLR. (2) Resonant absorption occurs at the IIH resonance, thus incoming compressional waves are converted into the IIH resonance. (3) The IIH resonance is strongly guided by the background magnetic field and shows linear polarization in the east-west meridian. (4) Both the Alfvén and the IIH are suggested as a mechanism for FLR at Mercury. (5) The resonance frequency enables us to estimate the local heavy ion concentration ratio.

  13. Temperature dependence of proton relaxation times in vitro.

    PubMed

    Nelson, T R; Tung, S M

    1987-01-01

    Accurate measurement of tissue relaxation characteristics is dependent on many factors, including field strength and temperature. The purpose of this study was to evaluate the relationship between sample temperature, viscosity and proton spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). A review of two basic models of relaxation the simple molecular motion model and the fast exchange two state model is given with reference to their thermal dependencies. The temperature dependence for both T1 and T2 was studied on a 0.15 Tesla whole body magnetic resonance imager. Thirteen samples comprising both simple and complex materials were investigated by using a standard spin-echo (SE) technique and a modified Carr-Purcell-Meiboom-Gill (CPMG) multi-echo sequence. A simple linear relationship between T1 and temperature was observed for all samples over the range of 20 degrees C to 50 degrees C. There is an inverse relationship between viscosity and T1 and T2. A quantity called the temperature dependence coefficient (TDC) is introduced and defined as the percent rate of change of the proton relaxation time referenced to a specific temperature. The large TDC found for T1 values, e.g. 2.37%/degrees C for CuSO4 solutions and 3.59%/degrees C for light vegetable oils at 22 degrees C, indicates that a temperature correction should be made when comparing in-vivo and in-vitro T1 times. The T2 temperature dependence is relatively small. PMID:3041151

  14. Dynamics of imidazolium ionic liquids from a combined dielectric relaxation and optical Kerr effect study: evidence for mesoscopic aggregation.

    PubMed

    Turton, David A; Hunger, Johannes; Stoppa, Alexander; Hefter, Glenn; Thoman, Andreas; Walther, Markus; Buchner, Richard; Wynne, Klaas

    2009-08-12

    We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based room-temperature ionic liquids (RTILs) [emim][BF(4)], [emim][DCA], and [bmim][DCA] at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in accordance with recent simulations that have reported mesoscopic structure arising from aggregates or clusters--structure that explains the anomalous and inconveniently high viscosities of these liquids.

  15. Domain reversal and relaxation in LiNbO3 single crystals studied by piezoresponse force microscope

    NASA Astrophysics Data System (ADS)

    Kan, Yi; Lu, Xiaomei; Wu, Xiumei; Zhu, Jinsong

    2006-12-01

    The LiNbO3 crystal was polarized and characterized by the piezoresponse force mode of scanning probe microscope. By using the Kolmogorov-Avrami-Ishibashi [Izv. Akad. Nauk, USSR: Ser. Math. 3, 355 (1937); J. Chem. Phys. 8, 212 (1940); J. Phys. Soc. Jpn. 63, 1031 (1994); 63, 1601 (1994)] theory to analyze the relaxation process after domain switching, it was found that (1) the percent of final switched domains after poling increased with the enhancing poling voltage, (2) the nucleation time was a constant to a certain sample, (3) the dimension of domain growth decreased with the enhancing poling voltage, and (4) the relaxation time had a maximum at a medial voltage. The corresponding mechanism for domain switching was discussed, which is hopefully useful for domain engineering.

  16. Temperature relaxation in dense plasma mixtures

    NASA Astrophysics Data System (ADS)

    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.

  17. A multinuclear NMR relaxation study of the interaction of divalent metal ions with L-aspartic acid.

    PubMed

    Khazaeli, S; Viola, R E

    1984-09-01

    Carbon-13 spin-lattice relaxation times, T1, have been measured for aqueous solutions of L-aspartic acid, L-alanine, O-phospho-L-serine, and 2-mercapto-L-succinic acid in the presence of the paramagnetic metal ions, Cu2+ and Mn2+, and Mg2+ as a diamagnetic control, at ambient temperature and neutral pH. Nitrogen-15, oxygen-17 and proton relaxation times were also obtained for L-aspartic acid and phosphorus-31 relaxation times for O-phospho-L-serine under similar conditions. The structures of these complexes in solution were determined from the various metal ion-nuclei distances calculated from the paramagnetically-induced relaxation. These results indicate that the Cu2+ interaction with L-aspartic acid is through alpha-amino and beta-carboxyl groups while Mn2+ coordinates most strongly through alpha- and beta-carboxyl groups, with the possibility of a weak interaction through the amino group. An examination of the coordination of these divalent metal ions to an analog of L-aspartic acid in which the beta-carboxyl group is replaced by a phosphate group (O-phospho-L-serine) indicated that Cu2+ coordination is now probably through the alpha-amino and phosphate groups, while this analog is a monodentate ligand for Mn2+ coordinating through the phosphate group. Removal of the beta-carboxyl group (L-alanine) also results in Cu2+ coordination through the alpha-carboxyl and alpha-amino groups, and the same ligand interactions are observed with Mn2+. Replacement of the alpha-amino group of L-aspartic acid with an -SH group (2-mercapto-L-succinate) is sufficient to eliminate any specific coordination with either Cu2+ or Mn2+. PMID:6491655

  18. Bilingual brain organization: a functional magnetic resonance adaptation study.

    PubMed

    Klein, Denise; Zatorre, Robert J; Chen, Jen-Kai; Milner, Brenda; Crane, Joelle; Belin, Pascal; Bouffard, Marc

    2006-05-15

    We used functional magnetic resonance adaptation (fMRA) to examine whether intra-voxel functional specificity may be present for first (L1)- and second (L2)-language processing. We examined within- and across-language adaptation for spoken words in English-French bilinguals who had acquired their L2 after the age of 4 years. Subjects listened to words presented binaurally through earphones. In two control conditions (one for each language), six identical words were presented to obtain maximal adaptation. The remaining six conditions each consisted of five words that were identical followed by a sixth word that differed. There were thus a total of eight experimental conditions: no-change (sixth word identical to first five); a change in meaning (different final word in L1); a change in language (final item translated into L2); a change in meaning and language (different final word in L2). The same four conditions were presented in L2. The study also included a silent baseline. At the neural level, within- and across-language word changes resulted in release from adaptation. This was true for separate analyses of L1 and L2. We saw no evidence for greater recovery from adaptation in across-language relative to within-language conditions. While many brain regions were common to L1 and L2, we did observe differences in adaptation for forward translation (L1 to L2) as compared to backward translation (L2 to L1). The results support the idea that, at the lexical level, the neural substrates for L1 and L2 in bilinguals are shared, but with some populations of neurons within these shared regions showing language-specific responses.

  19. Theory of the spin relaxation of conduction electrons in silicon.

    PubMed

    Cheng, J L; Wu, M W; Fabian, J

    2010-01-01

    A realistic pseudopotential model is introduced to investigate the phonon-induced spin relaxation of conduction electrons in bulk silicon. We find a surprisingly subtle interference of the Elliott and Yafet processes affecting the spin relaxation over a wide temperature range, suppressing the significance of the intravalley spin-flip scattering, previously considered dominant, above roughly 120 K. The calculated spin relaxation times T1 agree with the spin resonance and spin injection data, following a T(-3) temperature dependence. The valley anisotropy of T1 and the spin relaxation rates for hot electrons are predicted.

  20. Diffuse phase transition and high-temperature dielectric relaxation study on (Bi0.5Na0.5)1-xBaxTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Liu, Qiu-Xiang; Tang, Xin-Gui; Jiang, Yan-Ping; Yue, Jing-Long; Li, Jin-Kai

    2016-09-01

    Lead free (Bi0.5Na0.5)1-xBaxTiO3 (x=0.6, 0.7, 0.8, 0.9) ferroelectric ceramics were synthesized by the traditional solid state reaction method. Sintering was carried out at 1200 °C for 2 h in air atmosphere. The structural, microstructure and Ferroelectric of ceramics were investigated. In dielectric studies, a diffuse phase transition was exhibited and a dielectric relaxation behavious was observed at high temperature range. Impedance analysis characterized grain and grain boundaries resistivities of the ceramics and calculated activation energy and the activation energy for conduction. Polaron theory indicates that the relaxation of the samples at high temperatures was associated with the hopping ions caused by oxygen vacancies.