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Sample records for resonance relaxation studies

  1. [Study of the algorithm for inversion of low field nuclear magnetic resonance relaxation distribution].

    PubMed

    Chen, Shanshan; Wang, Hongzhi; Yang, Peiqiang; Zhang, Xuelong

    2014-06-01

    It is difficult to reflect the properties of samples from the signal directly collected by the low field nuclear magnetic resonance (NMR) analyzer. People must obtain the relationship between the relaxation time and the original signal amplitude of every relaxation component by inversion algorithm. Consequently, the technology of T2 spectrum inversion is crucial to the application of NMR data. This study optimized the regularization factor selection method and presented the regularization algorithm for inversion of low field NMR relaxation distribution, which is based on the regularization theory of ill-posed inverse problem. The results of numerical simulation experiments by Matlab7.0 showed that this method could effectively analyze and process the NMR relaxation data.

  2. Resonant relaxation in electroweak baryogenesis

    NASA Astrophysics Data System (ADS)

    Lee, Christopher; Cirigliano, Vincenzo; Ramsey-Musolf, Michael J.

    2005-04-01

    We compute the leading, chiral charge-changing relaxation term in the quantum transport equations that govern electroweak baryogenesis using the closed time path formulation of nonequilibrium quantum field theory. We show that the relaxation transport coefficients may be resonantly enhanced under appropriate conditions on electroweak model parameters and that such enhancements can mitigate the impact of similar enhancements in the CP-violating source terms. We also develop a power counting in the time and energy scales entering electroweak baryogenesis and include effects through second order in ratios ɛ of the small and large scales. We illustrate the implications of the resonantly enhanced O(ɛ2) terms using the Minimal Supersymmetric Standard Model, focusing on the interplay between the requirements of baryogenesis and constraints obtained from collider studies, precision electroweak data, and electric dipole moment searches.

  3. 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.

  4. 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.

  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. Magnetic Resonance Fingerprinting with short relaxation intervals.

    PubMed

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

    2017-09-01

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

  7. Vibrational relaxation of nascent diiodide ions studied by femtosecond transient resonance impulsive stimulated Raman scattering (TRISRS); experiment and simulation

    NASA Astrophysics Data System (ADS)

    Banin, Uri; Kosloff, Ronnie; Ruhman, Sanford

    1994-06-01

    Impulsive stimulated Raman scattering performed with femtosecond pulses on resonance with an electronic transition, comprises an all time domain Raman technique providing vibrational dynamics of the ground state chromophore. We report the application of this technique to record transient Raman responses of nascent diiodide ions, undergoing rapid vibrational relaxation following triiodide photodissociation in ethanol solution. Like other Fourier spectroscopic methods, this spectroscopy maximizes high simultaneous time and frequency resolution, making it well adapted, and in the present study exclusively capable, for recovering vibrational dynamics of highly excited molecular populations in transition. Master equation simulations of vibrational relaxation, coupled to quantum wave-packet representation of the light-matter interactions, are combined to provide a semi-quantitative analysis of the experimental results. Previous assignment of spectral narrowing of the nascent diiodide absorption to vibrational relaxation is bourn out by simulations. Inherent limitations and fortitudes of the TRISRS method are theoretically investigated and discussed.

  8. Relaxation in the glass former acetylsalicylic acid studied by deuteron magnetic resonance and dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Nath, R.; El Goresy, T.; Geil, B.; Zimmermann, H.; Böhmer, R.

    2006-08-01

    Supercooled liquid and glassy acetylsalicylic acid was studied using dielectric spectroscopy and deuteron relaxometry in a wide temperature range. The supercooled liquid is characterized by major deviations from thermally activated behavior. In the glass the secondary relaxation exhibits the typical features of a Johari-Goldstein process. Via measurements of spin-lattice relaxation times the selectively deuterated methyl group was used as a sensitive probe of its local environments. There is a large difference in the mean activation energy in the glass with respect to that in crystalline acetylsalicylic acid. This can be understood by taking into account the broad energy barrier distribution in the glass.

  9. Ferromagnetic resonance study of structure and relaxation of magnetization in NiFe/Ru superlattices

    NASA Astrophysics Data System (ADS)

    Alayo, W.; Landi, S., Jr.; Pelegrini, F.; Baggio-Saitovitch, E.

    2014-01-01

    The structural properties and relaxation processes of magnetization in [Ni81Fe19(t1)/Ru(t2)]N superlattices (N=number of bilayers) were analyzed by ferromagnetic resonance (FMR) with a fixed microwave frequency. One series of samples was deposited with constant NiFe layer thickness (t1) and variable Ru layer thickness (t2); the other series, with constant t2 and variable t1. A single FMR mode was observed for t2<15 Å and t1>75 Å and it has been attributed to the resonance of the exchange-coupled NiFe layers across the Ru interlayers. For the other values of t1 and t2, several FMR modes appeared and they were associated to non-coupled magnetic phases with different effective magnetization formed during the multilayer growth. The FMR linewidths were analyzed as a function of the magnetic layer thickness and a strong dependence on t1-2 was observed. It was attributed to the contribution of the two-magnon scattering mechanism for the linewidth.

  10. 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

  11. Study of cross - relaxation and molecular dynamics in the solid 3-(trifluoromethyl) benzoic acid by solid state NMR off - resonance.

    PubMed

    Woźniak-Braszak, Aneta

    2017-02-01

    Molecular dynamics of the solid 3-(trifluoromethyl) benzoic acid containing proton (1)H and fluorine (19)F nuclei was explored by the solid-state NMR off - resonance technique. Contrary to the previous experiments the proton nuclei system I relaxed in the off - resonance effective field B→e while fluorine nuclei system S was saturated for short time in comparison to the relaxation time T1I. New cross - relaxation solid - state NMR off - resonance experiments were conducted on a homebuilt pulse spectrometer operating at the on-resonance frequency of 30.2MHz, at the off - resonance frequency varied between 30.2 and 30.6MHz for protons and at the frequency of 28.411MHz for fluorines, respectively. Based on the experimental data the dispersions of the proton off - resonance spin - lattice relaxation rate ρρ(I), the fluorine off - resonance spin - lattice relaxation rate ρρ(S) and the cross - relaxation rate σρ in the rotating frame were determined. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Primary and secondary relaxation process in plastically crystalline cyanocyclohexane studied by 2H nuclear magnetic resonance. II. Quantitative analysis

    NASA Astrophysics Data System (ADS)

    Micko, B.; Kruk, D.; Rössler, E. A.

    2013-02-01

    We analyze the results of our previously reported 2H nuclear magnetic resonance (NMR) experiments in the plastically crystalline (PC) phase of cyanocyclohexane (Part I of this work) to study the fast secondary relaxation (or β-process) in detail. Both, the occurrence of an additional minimum in the spin-lattice relaxation T1 and the pronounced effects arising in the solid-echo spectrum above the glass transition temperature Tg = 134 K, allow for a direct determination of the restricting geometry of the β-process in terms of the "wobbling-in-a-cone" model. Whereas at temperatures below Tg the reorientation is confined to rather small solid angles (below 10°), the spatial restriction decreases strongly with temperature above Tg, i.e., the distribution of cone angles shifts continuously towards higher values. The β-process in the PC phase of cyanocyclohexane proceeds via the same mechanism as found in structural glass formers. This is substantiated by demonstrating the very similar behavior (for T < Tg) of spin-lattice relaxation, stimulated echo decays, and spectral parameters when plotted as a function of ⟨log τβ⟩ (taken from dielectric spectroscopy). We do, however, not observe a clear-cut relation between the relaxation strength of the β-process observed by NMR (calculated within the wobbling-in-a-cone model) and dielectric spectroscopy.

  13. Diffusion, relaxation, and chemical exchange in casein gels: a nuclear magnetic resonance study.

    PubMed

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

    2005-01-15

    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.

  14. Design and synthesis of calcium responsive magnetic resonance imaging agent: Its relaxation and luminescence studies.

    PubMed

    Tanwar, Jyoti; Datta, Anupama; Chauhan, Kanchan; Kumaran, S Senthil; Tiwari, Anjani K; Kadiyala, K Ganesh; Pal, Sunil; Thirumal, M; Mishra, Anil K

    2014-07-23

    Calcium concentration modulation both inside and outside cell is of considerable interest for nervous system function in normal and pathological conditions. MRI has potential for very high spatial resolution at molecular/cellular level. Design, synthesis and evaluation of Gd-DO3A-AME-NPHE, a calcium responsive MRI contrast agent is presented. The probe is comprised of a Gd(3+)-DO3A core coupled to iminoacetate coordinating groups for calcium induced relaxivity switching. In the absence of Ca(2+) ions, inner sphere water binding to the Gd-DO3A-AME-NPHE is restricted with longitudinal relaxivity, r1 = 4.37 mM(-1) s(-1) at 4.7 T. However, addition of Ca(2+) triggers a marked enhancement in r1 = 6.99 mM(-1) s(-1) at 4.7 T (60% increase). The construct is highly selective for Ca(2+) over competitive metal ions at extracellular concentration. The r1 is modulated by changes in the hydration number (0.2 to 1.05), which was confirmed by luminescence emission lifetimes of the analogous Eu(3+) complex. T1 phantom images establish the capability of complex of visualizing changes in [Ca(2+)] by MRI.

  15. Off-resonance R1rho relaxation outside of the fast exchange limit: an experimental study of a cavity mutant of T4 lysozyme.

    PubMed

    Korzhnev, Dmitry M; Orekhov, Vladislav Yu; Dahlquist, Frederick W; Kay, Lewis E

    2003-05-01

    An (15)N off-resonance R(1rho) spin relaxation study of an L99A point mutant of T4 lysozyme is presented. Previous CPMG-based relaxation dispersion studies of exchange in this protein have established that the molecule interconverts between a populated ground state and an excited state (3.4%) with an exchange rate constant of 1450 s(-1) at 25 degrees C. It is shown that for the majority of residues in this protein the offset dependence of the R(1rho) relaxation rates cannot be well fit using models which are only valid in the fast exchange regime. In contrast, a recently derived expression by Trott and Palmer (J. Magn. Reson., 154, 157-160, 2002) which is valid over a wider window of exchange than other relations, is shown to fit the data well. Values of (signed) chemical shift differences between exchanging sites have been extracted and are in reasonable agreement with shift differences measured using CPMG methods. A set of simulations is presented which help establish the exchange regimes that are best suited to analysis by off-resonance R(1rho) techniques.

  16. 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.

  17. 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

  18. A two-dimensional Fourier transform electron-spin resonance (ESR) study of nuclear modulation and spin relaxation in irradiated malonic acid

    NASA Astrophysics Data System (ADS)

    Lee, Sanghyuk; Patyal, Baldev R.; Freed, Jack H.

    1993-03-01

    Nuclear modulation in electron-spin-echo spectroscopy is conventionally studied by one-dimensional electron-spin-echo envelope modulation (1D-ESEEM). Two-dimensional Fourier transform electron-spin resonance (2D-FTESR) studies of nuclear modulation have the promise of enhancing the spectral resolution and clarifying the key details of the relaxation processes. We present a 2D-FTESR study on single proton nuclear modulation from γ-irradiated malonic acid single crystals to test the validity of the Gamliel-Freed theory and to assess the value of the new methods. The two pulse spin-echo correlation spectroscopy (SECSY) spectra as a function of orientation of the single crystal show very good agreement with the Gamliel-Freed theory extended to the general case of nonaxially symmetric hyperfine interaction. It is very simply affected by spin relaxation, such that relative intensities are essentially unaffected. Thus SECSY-ESR can most reliably be utilized for studying nuclear modulation. Stimulated SECSY provides the simplest nuclear modulation patterns, which, however, do exhibit the suppression effect well known in three-pulse ESEEM studies. Two-dimensional electron-electron double resonance (2D-ELDOR) provides nuclear modulation patterns similar to that of SECSY-ESR, so the suppression effect is absent. Both three-pulse methods exhibit complex relaxation behavior which can affect relative intensities. This is a feature characteristic of three-pulse ESEEM, but is not well understood. It is shown how the 2D-FTESR methods enable one to obtain the details of the complex spin relaxation, and in the process, obtain very good agreement between experiment and theory. 2D-ELDOR exhibits exchange cross peaks as well as coherence peaks from the nuclear modulation. It is shown how experiments, as a function of mixing time, enable one to separate the effects of the two. It is pointed out that such experiments are in the spirit of 3D spectroscopy. A new observation of the

  19. 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

  20. Relaxation time based classification of magnetic resonance brain images

    NASA Astrophysics Data System (ADS)

    Baselice, Fabio; Ferraioli, Giampaolo; Pascazio, Vito

    2015-03-01

    Brain tissue classification in Magnetic Resonance Imaging is useful for a wide range of applications. Within this manuscript a novel approach for brain tissue joint segmentation and classification is presented. Starting from the relaxation time estimation, we propose a novel method for identifying the optimal decision regions. The approach exploits the statistical distribution of the involved signals in the complex domain. The technique, compared to classical threshold based ones, is able to improve the correct classification rate. The effectiveness of the approach is evaluated on a simulated case study.

  1. A study of coal extraction with electron paramagnetic resonance (EPR) and proton nuclear magnetic resonance relaxation techniques. Quarterly technical progress report, April 1, 1993--June 30, 1993

    SciTech Connect

    Doetschman, D.C.; Mehlenbacher, R.C.; Ito, O.

    1993-09-01

    An electron spin and proton magnetic relaxation study is presented on the effects of the solvent extraction of coal on the macromoleculer network of the coal and on the mobile molecular species that are initially within the coal. The eight Argonne Premium coals were extracted at room temperature with a 1:1 (v/v) N-methylpyrrolidinone (NMP)-CS2 solvent mixture under an inert atmosphere. As much solvent as possible was removed from extract and residue by treatment in a vacuum. The mobilization of molecular free radicals by the solvent and the exposure of free radicals in the macromoleculer matrix to solvent or to species dissolved in the solvent, results in a preferential survival of residue radicals of types that depend on the particular coal and results in the apparently fairly uniform loss of all types of radicals in bituminous coal extracts. The surviving extract and residue free radicals are more predominantly of the odd- alternate hydrocarbon free radical type. The spin-lattice relaxation (SLR) of these coal free radicals has previously been inferred (Doetschman and Dwyer, Energy Fuels, 1992, 6, 783) to be from the modulation of the intramolecular electron-nuclear dipole-interactions of the CH groups in a magnetic field by rocldng motions of the radical in the coal matrix. Such a modulation would depend not only on the rocking amplitude and frequency but also upon the electron spin density at the CH groups in the radical. The observed SLR rates decrease with coal rank in agreement with the smaller spin densities and the lower rocidng amplitudes that are expected for the larger polycondensed ring systems in coals of higher rank. The SLR rates are found to be generally faster in the extracts (than residues) where the molecular species would be expected to have a smaller polycondensed ring system than in the macromoleculer matrix of the residue.

  2. Paramagnetic Ce3 + optical emitters in garnets: Optically detected magnetic resonance study and evidence of Gd-Ce cross-relaxation effects

    NASA Astrophysics Data System (ADS)

    Tolmachev, D. O.; Gurin, A. S.; Uspenskaya, Yu. A.; Asatryan, G. R.; Badalyan, A. G.; Romanov, N. G.; Petrosyan, A. G.; Baranov, P. G.; Wieczorek, H.; Ronda, C.

    2017-06-01

    Paramagnetic Ce3 +optical emitters have been studied by means of optically detected magnetic resonance (ODMR) via Ce3 + spin-dependent emission in cerium-doped garnet crystals which were both gadolinium free and contain gadolinium in a concentration from the lowest (0.1%) to 100%, i.e., to the superparamagnetic state. It has been shown that the intensity of photoluminescence excited by circularly polarized light into Ce3 + absorption bands can be used for selective monitoring the population of the Ce3 + ground-state spin sublevels. Direct evidence of the cross-relaxation effects in garnet crystals containing two electron spin systems, i.e., the simplest one of Ce3 + ions with the effective spin S =1/2 and the system of Gd3 + ions with the maximum spin S =7/2 , has been demonstrated. Magnetic resonance of Gd3 + has been found by monitoring Ce3 + emission in cerium-doped garnet crystals with gadolinium concentrations of 0.1 at. %, 4%-8%, and 100%, which implies the impact of the Gd3 + spin polarization on the optical properties of Ce3 +. Strong internal magnetic fields in superparamagnetic crystals were shown to modify the processes of recombination between UV-radiation-induced electron and hole centers that lead to the recombination-induced Ce3 + emission. Observation of spikes and subsequent decay in the cross-relaxation-induced ODMR signals under pulsed microwave excitation is suggested to be an informative method to investigate transient processes in the many-spin system of Ce3 +, Gd3 +, and electron and hole radiation-induced centers.

  3. Relaxation filtered hyperfine (REFINE) spectroscopy: a novel tool for studying overlapping biological electron paramagnetic resonance signals applied to mitochondrial complex I.

    PubMed

    Maly, Thorsten; MacMillan, Fraser; Zwicker, Klaus; Kashani-Poor, Noushin; Brandt, Ulrich; Prisner, Thomas F

    2004-04-06

    A simple strategy to separate overlapping electron paramagnetic resonance (EPR) signals in biological systems is presented. Pulsed EPR methods (inversion- and saturation-recovery) allow the determination of the T(1) spin-lattice relaxation times of paramagnetic centers. T(1) may vary by several orders of magnitude depending on the species under investigation. These variations can be employed to study selectively individual species from a spectrum that results from an overlap of two species using an inversion-recovery filtered (IRf) pulsed EPR technique. The feasibility of such an IRf field-swept technique is demonstrated on model compounds (alpha,gamma-bisphenylene-beta-phenylallyl-benzolate, BDPA, and 2,2,6,6-tetramethyl-piperidine-1-oxyl, TEMPO) and a simple strategy for the successful analysis of such mixtures is presented. Complex I is a multisubunit membrane protein of the respiratory chain containing several iron-sulfur (FeS) centers, which are observable with EPR spectroscopy. It is not possible to investigate the functionally important FeS cluster N2 separately because this EPR signal always overlaps with the other FeS signals. This cluster can be studied selectively using the IRf field-swept technique and its EPR spectrum is in excellent agreement with previous cw-EPR data from the literature. In addition, the possibility to separate the hyperfine spectra of two spectrally overlapping paramagnetic species is demonstrated by applying this relaxation filter together with hyperfine spectroscopy (REFINE). For the first time, the application of this filter to a three-pulse electron spin-echo envelope modulation (ESEEM) pulse sequence is demonstrated to selectively observe hyperfine spectra on a system containing two paramagnetic species. Finally, REFINE is used to assign the observed nitrogen modulation in complex I to an individual iron-sulfur cluster.

  4. Geminate recombination and vibrational relaxation dynamics of aqueous chlorine dioxide: A time-resolved resonance Raman study

    NASA Astrophysics Data System (ADS)

    Hayes, Sophia C.; Philpott, Matthew J.; Reid, Philip J.

    1998-08-01

    The photochemical dynamics of aqueous chlorine dioxide (OClO) are investigated using time-resolved resonance Raman spectroscopy. Stokes and anti-Stokes spectra are measured as a function of time following photoexcitation of OClO using degenerate pump and probe wavelengths at 390 nm. The temporal evolution of OClO Stokes intensity is found to be consistent with the reformation of ground-state OClO by subpicosecond geminate recombination of the primary ClO and O photofragments. Anti-Stokes intensity is observed for transitions corresponding to the symmetric stretch of OClO demonstrating that upon geminate recombination, excess vibrational energy is deposited along this coordinate. Dissipation of this energy to the surrounding solvent occurs with a time constant of ˜9 ps. Finally, a delay in the appearance of OClO anti-Stokes intensity relative to geminate recombination is observed demonstrating that the excess vibrational energy available to OClO is initially deposited along the resonance Raman inactive asymmetric stretch coordinate with the exchange of energy between this coordinate and the symmetric stretch occurring with a time-constant of ˜5 ps.

  5. Paramagnetic nuclear magnetic resonance relaxation and molecular mechanics studies of the chloroperoxidase-indole complex: insights into the mechanism of chloroperoxidase-catalyzed regioselective oxidation of indole.

    PubMed

    Zhang, Rui; He, Qinghao; Chatfield, David; Wang, Xiaotang

    2013-05-28

    To unravel the mechanism of chloroperoxidase (CPO)-catalyzed regioselective oxidation of indole, we studied the structure of the CPO-indole complex using nuclear magnetic resonance (NMR) relaxation measurements and computational techniques. The dissociation constant (KD) of the CPO-indole complex was calculated to be approximately 21 mM. The distances (r) between protons of indole and the heme iron calculated via NMR relaxation measurements and molecular docking revealed that the pyrrole ring of indole is oriented toward the heme with its 2-H pointing directly at the heme iron. Both KD and r values are independent of pH in the range of 3.0-6.5. The stability and structure of the CPO-indole complex are also independent of the concentration of chloride or iodide ion. Molecular docking suggests the formation of a hydrogen bond between the NH group of indole and the carboxyl O of Glu 183 in the binding of indole to CPO. Simulated annealing of the CPO-indole complex using r values from NMR experiments as distance restraints reveals that the van der Waals interactions were much stronger than the Coulomb interactions in the binding of indole to CPO, indicating that the association of indole with CPO is primarily governed by hydrophobic rather than electrostatic interactions. This work provides the first experimental and theoretical evidence of the long-sought mechanism that leads to the "unexpected" regioselectivity of the CPO-catalyzed oxidation of indole. The structure of the CPO-indole complex will serve as a lighthouse in guiding the design of CPO mutants with tailor-made activities for biotechnological applications.

  6. Association of exposure to manganese and iron with relaxation rates R1 and R2*- magnetic resonance imaging results from the WELDOX II study.

    PubMed

    Pesch, Beate; Dydak, Ulrike; Lotz, Anne; Casjens, Swaantje; Quetscher, Clara; Lehnert, Martin; Abramowski, Jessica; Stewig, Christoph; Yeh, Chien-Lin; Weiss, Tobias; van Thriel, Christoph; Herrmann, Lennard; Muhlack, Siegfried; Woitalla, Dirk; Glaubitz, Benjamin; Schmidt-Wilcke, Tobias; Brüning, Thomas

    2017-08-25

    Magnetic resonance imaging is a non-invasive method that allows the indirect quantification of manganese (Mn) and iron (Fe) accumulation in the brain due to their paramagnetic features. The WELDOX II study aimed to explore the influence of airborne and systemic exposure to Mn and Fe on the brain deposition using the relaxation rates R1 and R2* as biomarkers of metal accumulation in regions of interest in 161 men, including active and former welders. We obtained data on the relaxation rates R1 and R2* in regions that included structures within the globus pallidus (GP), substantia nigra (SN), and white matter of the frontal lobe (FL) of both hemispheres, as well as Mn in whole blood (MnB), and serum ferritin (SF). The study subjects, all male, included 48 active and 20 former welders, 41 patients with Parkinson's disease (PD), 13 patients with hemochromatosis (HC), and 39 controls. Respirable Mn and Fe were measured during a working shift for welders. Mixed regression models were applied to estimate the effects of MnB and SF on R1 and R2*. Furthermore, we estimated the influence of airborne Mn and Fe on the relaxation rates in active welders. MnB and SF were significant predictors of R1 but not of R2* in the GP, and were marginally associated with R1 in the SN (SF) and FL (MnB). Being a welder or suffering from PD or HC elicited no additional group effect on R1 or R2* beyond the effects of MnB and SF. In active welders, shift concentrations of respirable Mn>100μg/m(3) were associated with stronger R1 signals in the GP. In addition to the effects of MnB and SF, the welding technique had no further influence on R1. MnB and SF were significant predictors of R1 but not of R2*, indicative of metal accumulation, especially in the GP. Also, high airborne Mn concentration was associated with higher R1 signals in this brain region. The negative results obtained for being a welder or for the techniques with higher exposure to ultrafine particles when the blood

  7. Vibrational relaxation of NO(X 2Π, υ = 1) studied by an IR-UV-double-resonance technique

    NASA Astrophysics Data System (ADS)

    Kosanetzky, J.; List, U.; Urban, W.; Vormann, H.; Fink, E. H.

    1980-09-01

    Pulses from a mechanically chopped CO-laser were used to optically pump the first vibrational level of NO molecules in their fundamental band near 5.3 μm. The population of NO (υ = 1) was followed by measuring the resonance fluorescence of NO-γ-bands from a microwave discharge lamp in the UV region. Analysis of the first order decays of NO(υ = 1) following the excitation pulses yielded rate constants for VT and VV energy transfer processes in collisions of NO(υ = 1) with ground state NO and added gas molecules He, Ne, Ar, Kr, Xe, H 2, HD, D 2, N 2, O 2 and N 2O.

  8. Cyclohexane revisited: High pressure nuclear magnetic resonance rotating frame relaxation study of the dynamical solvent effects on the conformational isomerization of cyclohexane

    NASA Astrophysics Data System (ADS)

    Campbell, D. M.; Mackowiak, M.; Jonas, J.

    1992-02-01

    The main goal of this study is to extend the dynamic range of isomerization rates for cyclohexane in order to determine with high accuracy whether the barrier height to isomerization is pressure dependent. Therefore, the effect of pressure and temperature on the conformational isomerization of cyclohexane in carbon disulfide solvent has been investigated using the NMR (nuclear magnetic resonance) rotating frame relaxation technique. This technique, used for the first time in pressure studies of chemical exchange, allows the measurement of isomerization dynamics over a wide range of pressures and temperatures. By combining the rotating frame and NMR line shape techniques and generating the isoviscosity plots, it is shown that the barrier height to isomerization is independent of pressure. Since the experimental isomerization rate is accelerated by pressure, the viscosity dependence of the reduced transmission coefficient shows that the isomerization falls into the energy controlled (inertial) regime of the Kramers model in agreement with our earlier experimental findings. These experimental results, as interpreted in terms of stochastic models of isomerization reactions, indicate a strong collisional coupling and the presence of dynamical solvent effects.

  9. 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. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  10. 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

  11. 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.

  12. Proton-nuclear magnetic resonance relaxation times in brain edema

    SciTech Connect

    Kamman, R.L.; Go, K.G.; Berendsen, H.J. )

    1990-01-01

    Proton relaxation times of protein solutions, bovine brain, and edematous feline brain tissue were studied as a function of water concentration, protein concentration, and temperature. In accordance with the fast proton exchange model for relaxation, a linear relation could be established between R1 and the inverse of the weight fraction of tissue water. This relation also applied to R2 of gray matter and of protein solutions. No straightforward relation with water content was found for R2 of white matter. Temperature-dependent studies indicated that in this case, the slow exchange model for relaxation had to be applied. The effect of macromolecules in physiological relevant concentrations on the total relaxation behavior of edematous tissue was weak. Total water content changes predominantly affected the relaxation rates. The linear relation may have high clinical potential for assessment of the status of cerebral edema on the basis of T1 and T2 readings from MR images.

  13. Coherence resonance in a unijunction transistor relaxation oscillator

    NASA Astrophysics Data System (ADS)

    Nurujjaman, Md.; Bhattacharya, P. S.; Iyengar, A. N. Sekar; Sarkar, Sandip

    2009-07-01

    The phenomenon of coherence resonance is investigated in an unijunction transistor relaxation oscillator and quantified by estimating the normal variance (NV). Depending on the measuring points, two types of NV curves have been obtained. We have observed that the degradations in coherency at higher noise amplitudes in our system is probably the result of direct interference of coherent oscillations and the stochastic perturbation. Degradation of coherency may be minimal if this direct interference of noise and coherent oscillations is eliminated.

  14. 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

  15. Investigation of intermolecular double-quantum off-resonance longitudinal relaxation in the tilted rotating frame

    NASA Astrophysics Data System (ADS)

    Cai, Honghao; Zheng, Bingwen; Ke, Hanping; Chen, Zhong

    2015-11-01

    A modified correlation spectroscopy revamped by asymmetric z-gradients echo detection (CRAZED) sequence was applied to investigate the behavior of intermolecular double-quantum longitudinal relaxation processes in the tilted rotating frame. Theoretical formalism based on dipolar field theory was presented in detail. Spectroscopic measurements and quantitative analysis demonstrated that the signal intensities and intermolecular double-quantum off-resonance longitudinal relaxation time in the rotating frame (T1ρ, DQC eff) are inversely correlated with the tilt angle (θ), while positively correlated with the effective frequency of spin-locking field (ωe). Magnetic resonance imaging experiments of an agarose phantom also prove the validity of the theoretical analysis and demonstrated the feasibility of imaging based on T1ρ, DQC eff . The rotating-frame double-quantum relaxation measurements are useful for probing slow-motion molecules and this study provides the guidance for optimization of the spin-lock experiments.

  16. 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.

  17. Feasibility for mapping cartilage t1 relaxation times in the distal metacarpus3/metatarsus3 of thoroughbred racehorses using delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC): normal cadaver study.

    PubMed

    Carstens, Ann; Kirberger, Robert M; Velleman, Mark; Dahlberg, Leif E; Fletcher, Lizelle; Lammentausta, Eveliina

    2013-01-01

    Osteoarthritis of the metacarpo/metatarsophalangeal joints is one of the major causes of poor performance in horses. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) may be a useful technique for noninvasively quantifying articular cartilage damage in horses. The purpose of this study was to describe dGEMRIC characteristics of the distal metacarpus3/metatarsus3 (Mc3/Mt3) articular cartilage in 20 cadaver specimens collected from normal Thoroughbred horses. For each specimen, T1 relaxation time was measured from scans acquired precontrast and at 30, 60, 120, and 180 min post intraarticular injection of Gd-DTPA(2-) (dGEMRIC series). For each scan, T1 relaxation times were calculated using five regions of interest (sites 1-5) in the cartilage. For all sites, a significant decrease in T1 relaxation times occurred between precontrast scans and 30, 60, 120, and 180 min scans of the dGEMRIC series (P < 0.0001). A significant increase in T1 relaxation times occurred between 60 and 180 min and between 120 and 180 min post Gd injection for all sites. For sites 1-4, a significant increase in T1 relaxation time occurred between 30 and 180 min postinjection (P < 0.05). Sites 1-5 differed significantly among one another for all times (P < 0.0001). Findings from this cadaver study indicated that dGEMRIC using intraarticular Gd-DTPA(2-) is a feasible technique for measuring and mapping changes in T1 relaxation times in equine metacarpo/metatarsophalangeal joint cartilage. Optimal times for postcontrast scans were 60-120 min. Future studies are needed to determine whether these findings are reproducible in live horses. © 2013 Veterinary Radiology & Ultrasound.

  18. Suppression of sodium nuclear magnetic resonance double-quantum coherence by chemical shift and relaxation reagents

    NASA Astrophysics Data System (ADS)

    Hutchison, Robert B.; Huntley, James J. A.; Jin, Haoran; Shapiro, Joseph I.

    1992-12-01

    An investigation into the signal suppression behavior of the paramagnetic shift and relaxation reagents, Dy(P3O10)27- and Gd(P3O10)27-, with regard to their use in the nuclear magnetic resonance spectroscopic study of sodium has been performed. Measurements of T1 and T2 relaxation time constants of sodium in normal saline, Krebs-Henseleit buffer, and human blood serum, as a function of concentration of these reagents showed that, although closely coupled in the saline and K-H buffer environments, in plasma T1 and T2 become decoupled, transverse relaxation dominating in comparison to longitudinal relaxation. Linewidth measurements further suggest that relaxation in the plasma milieu is controlled primarily by inherent T2 relaxation, rather than by field inhomogeneity or diffusion effects. Quantitative single-quantum (1Q) and double-quantum (2Q) intensity measurements, biexponential T2 relaxation measurements, and parametric studies of the preparation time of the 2Q pulse sequence, were obtained in suspensions of bovine serum albumin and human erythrocytes. The observed suppression of sodium 2Q coherence by paramagnetic shift and relaxation reagents was found to exhibit a complex behavior in albumin solutions, involving the biexponential T2 decay to be expected during the preparation time of the 2Q filter pulse sequence, as well as the optimum preparation time for production of the double-quantum coherence itself. The controlling factor for both of these effects is the biexponential amplitude function in the expression for the transverse magnetization observed following application of the 2Q pulse sequence. This in turn is determined entirely by the values for the slow and fast components of biexponential relaxation in sodium, which themselves depend upon the concentration of the macromolecular binding sites for quadrupolar interaction. A similar behavior has been observed in suspensions of human erythrocytes.

  19. Active site substitution A82W improves the regioselectivity of steroid hydroxylation by cytochrome P450 BM3 mutants as rationalized by spin relaxation nuclear magnetic resonance studies.

    PubMed

    Rea, V; Kolkman, A J; Vottero, E; Stronks, E J; Ampt, K A M; Honing, M; Vermeulen, N P E; Wijmenga, S S; Commandeur, J N M

    2012-01-24

    Cytochrome P450 BM3 from Bacillus megaterium is a monooxygenase with great potential for biotechnological applications. In this paper, we present engineered drug-metabolizing P450 BM3 mutants as a novel tool for regioselective hydroxylation of steroids at position 16β. In particular, we show that by replacing alanine at position 82 with a tryptophan in P450 BM3 mutants M01 and M11, the selectivity toward 16β-hydroxylation for both testosterone and norethisterone was strongly increased. The A82W mutation led to a ≤42-fold increase in V(max) for 16β-hydroxylation of these steroids. Moreover, this mutation improves the coupling efficiency of the enzyme, which might be explained by a more efficient exclusion of water from the active site. The substrate affinity for testosterone increased at least 9-fold in M11 with tryptophan at position 82. A change in the orientation of testosterone in the M11 A82W mutant as compared to the orientation in M11 was observed by T(1) paramagnetic relaxation nuclear magnetic resonance. Testosterone is oriented in M11 with both the A- and D-ring protons closest to the heme iron. Substituting alanine at position 82 with tryptophan results in increased A-ring proton-iron distances, consistent with the relative decrease in the level of A-ring hydroxylation at position 2β.

  20. Nuclear magnetic resonance and nuclear spin relaxation in AlAs quantum well probed by ESR

    NASA Astrophysics Data System (ADS)

    Shchepetilnikov, A. V.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Smirnov, D. S.; Tiemann, L.; Reichl, C.; Dietsche, W.; Wegscheider, W.

    2016-12-01

    The study of nuclear magnetic resonance and nuclear spin-lattice relaxation was conducted in an asymmetrically doped to n ˜1.8 ×1011cm-2 16 nm AlAs quantum well grown in the [001 ] direction. The dynamic polarization of nuclear spins due to a hyperfine interaction resulted in the so-called Overhauser shift of two-dimensional conduction electron spin resonance. The maximum shifts achieved in the experiments are several orders of magnitude smaller than in GaAs-based heterostructures, indicating that the hyperfine interaction is weak. The nuclear spin-lattice relaxation time extracted from the decay of the Overhauser shift over time turned out to depend on the filling factor of the two-dimensional electron system. This observation indicates that nuclear spin-lattice relaxation is mostly due to the interaction between electron and nuclear spins. The Overhauser shift diminishes resonantly when the rf radiation of certain frequencies was applied to the sample. This effect served as an indirect, yet powerful, method for nuclear magnetic resonance detection: NMR quadrupole splitting of 75As nuclei was clearly resolved. Theoretical calculations performed describe well these experimental findings.

  1. 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.

  2. Effect of near-resonant energy transfer on vibrational relaxation in liquid dichloromethane-benzene mixtures

    NASA Astrophysics Data System (ADS)

    Choi, Pak-Kon; Takagi, Kenshiro; Negishi, Katsuo

    1981-01-01

    The velocity and absorption of sound waves are measured in liquid dichloromethane-benzene mixtures in the frequency range from 3 MHz to 6 GHz using three ultrasonic techniques, high-resolution Bragg reflection, Brillouin scattering, and pulse-echo overlap. Vibrational double relaxation is observed in every mixture studied. The higher-frequency relaxation is assigned to the lowest mode of benzene, and the lower-frequency one to all but the lowest mode of both molecules. These modes of both molecules are shown to be coupled with each other by the near-resonant intermolecular vibrational-vibrational energy transfers between the second lowest mode (704 cm-1) of dichloromethane and the modes (707, 675 cm-1) of benzene. The concentration dependence of the relaxation frequency is analyzed with the binary collision theory, and the rates of vibrational-translational energy transfer in collisions between different kinds of molecules are estimated.

  3. 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

    2011-07-07

    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.

  4. 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.

  5. High-speed laser modulation beyond the relaxation resonance frequency limit.

    PubMed

    Sacher, Wesley D; Zhang, Eric J; Kruger, Brett A; Poon, Joyce K S

    2010-03-29

    We propose and show that for coupling modulated lasers (CMLs), in which the output coupler is modulated rather than the pump rate, the conventional relaxation resonance frequency limit to the laser modulation bandwidth can be circumvented. The modulation response is limited only by the coupler. Although CMLs are best suited to microcavities, as a proof-of-principle, a coupling-modulated erbium-doped fiber laser is modulated at 1 Gb/s, over 10000 times its relaxation resonance frequency.

  6. [A study on Korean concepts of relaxation].

    PubMed

    Park, J S

    1992-01-01

    Relaxation technique is an independent nursing intervention used in various stressful situations. The concept of relaxation must be explored for the meaning given by the people in their traditional thought and philosophy. Korean relaxation technique, wanting to become culturally acceptable and effective, is learning to recognize and develop Korean concepts, experiences, and musics of relaxation. This study was aimed at discovering Korean concepts, experiences and musics of relaxation and contributing the development of the relaxation technique for Korean people. The subjects were 59 nursing students, 39 hospitalized patients, 61 housewives, 21 rural residents and 16 researchers. Data were collected from September 4th to October 24th, 1991 by interviews or questionnaires. The data analysis was done by qualitative research method, and validity assured by conformation of the concept and category by 2 nursing scientists who had written a Master's thesis on the relaxation technique. The results of the study were summarized as follows; 1. The meaning of the relaxation concept; From 298 statements, 107 concepts were extracted and then 5 categories "Physical domain", "Psychological domain", "Complex domain", "Situation", and "environment" were organized. 'Don't have discomforts, 'don't have muscle tension', 'don't have energy (him in Korean)', 'don't have activities' subcategories were included in "Physical domain". 'Don't have anxiety', 'feel good', 'emotional stability', 'don't have wordly thoughts', 'feel one's brain muddled', 'loss of desire' subcategories were included in "physical domain" 'Comfort body and mind', 'don't have tension of body and mind', 'be sagged' 'liveliness of thoughts' subcategories were included in "Complex domain". 'Rest', 'sleep', 'others' subcategories were included in "Situation domain". And 'quite environment' & 'comfortable environment' subcategories were included in "Environmental domain". 2. The experiences of the relaxation; From 151

  7. Relaxation dispersion NMR spectroscopy for the study of protein allostery.

    PubMed

    Farber, Patrick J; Mittermaier, Anthony

    2015-06-01

    Allosteric transmission of information between distant sites in biological macromolecules often involves collective transitions between active and inactive conformations. Nuclear magnetic resonance (NMR) spectroscopy can yield detailed information on these dynamics. In particular, relaxation dispersion techniques provide structural, dynamic, and mechanistic information on conformational transitions occurring on the millisecond to microsecond timescales. In this review, we provide an overview of the theory and analysis of Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR experiments and briefly describe their application to the study of allosteric dynamics in the homeodomain from the PBX transcription factor (PBX-HD). CPMG NMR data show that local folding (helix/coil) transitions in one part of PBX-HD help to communicate information between two distant binding sites. Furthermore, the combination of CPMG and other spin relaxation data show that this region can also undergo local misfolding, reminiscent of conformational ensemble models of allostery.

  8. Pore structure of hydrating cement paste by magnetic resonance relaxation analysis and freezing.

    PubMed

    Jehng, J Y; Sprague, D T; Halperin, W P

    1996-01-01

    Nuclear magnetic resonance relaxation analysis has been applied to interpret the evolution of microstructure in a cement paste during hydration. 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 spin-spin relaxation analysis performed at room temperature. Both methods consistently show that hydrating cement pastes have two principal components in their size distribution. The NMR relaxation times provide a measure of the characteristic pore sizes. Their interpretation is made in the context of a fast exchange model. 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.A modified Gibbs-Thompson analysis was used to determine pore volume distributions from the distribution of thawing temperatures.

  9. Solid-state NMR relaxation studies of Australian spider silks.

    PubMed

    Kishore, A I; Herberstein, M E; Craig, C L; Separovic, F

    Solid-state NMR techniques were used to study two different types of spider silk from two Australian orb-web spider species, Nephila edulis and Argiope keyserlingi. A comparison of (13)C-T(1) and (1)H-T(1rho) solid-state NMR relaxation data of the Ala Calpha, Ala Cbeta, Gly Calpha, and carbonyl resonances revealed subtle differences between dragline and cocoon silk. (13)C-T(1rho) and (1)H-T(1) relaxation experiments showed significant differences between silks of the two species with possible structural variations. Comparison of our data to previous (13)C-T(1) relaxation studies of silk from Nephila clavipes (A. Simmons et al., Macromolecules, 1994, Vol. 27, pp. 5235-5237) also supports the finding that differences in molecular mobility of dragline silk exist between species. Interspecies differences in silk structure may be due to different functional properties. Relaxation studies performed on wet (supercontracted) and dry silks showed that the degree of hydration affects relaxation properties, and hence changes in molecular mobility are correlated with functional properties of silk. Copyright 2002 Wiley Periodicals, Inc.

  10. Complimentary effect of yogic sound resonance relaxation technique in patients with common neck pain.

    PubMed

    Yogitha, Bali; Nagarathna, R; John, Ebnezar; Nagendra, Hr

    2010-01-01

    Studies have shown that conventional treatment methods with drugs, physiotherapy and exercises for common neck pain (CNP) may be inadequate. Yoga techniques have been found to be effective complimentary therapies in chronic low back pain and also for stress reduction in other diseases. The aim of the study was to examine the complimentary role of a yogic relaxation called mind sound resonance technique (MSRT) in non-surgical management of CNP. In this randomized controlled study, 60 patients with CNP were assigned to two groups (yoga, n=30) and (control, n=30). The yoga group received yogic MSRT for 20 minutes in supine position after the conventional physiotherapy program for 30 minutes using pre-recorded audio CD and the control group had non-guided supine rest for 20 minutes (after physiotherapy), for 10 days. MSRT provides deep relaxation for both mind and body by introspective experience of the sound resonance in the whole body while repeating the syllables A, U, M and Om and a long chant (Mahamrityunjaya mantra) several times in a meaningful sequence. Both the groups had pre and post assessments using visual pain analog scale, tenderness scoring key, neck disability score (NDS) questionnaire, goniometric measurement of cervical spinal flexibility, and state and trait anxiety inventory-Y1 (STAI-Y1). Mann-Whitney U test showed significant difference between groups in pain (P<0.01), tenderness (P<0.01), neck movements (P<0.01). NDS (P<0.01) and state anxiety (STAI-Y1) showed higher reduction in yoga (P<0.01) than that in the control group. Wilcoxon's test showed a significant improvement in both groups on all variables (P<0.01). Yoga relaxation through MSRT adds significant complimentary benefits to conventional physiotherapy for CNP by reducing pain, tenderness, disability and state anxiety and providing improved flexibility.

  11. Complimentary effect of yogic sound resonance relaxation technique in patients with common neck pain

    PubMed Central

    Yogitha, Bali; Nagarathna, R; John, Ebnezar; Nagendra, HR

    2010-01-01

    Background: Studies have shown that conventional treatment methods with drugs, physiotherapy and exercises for common neck pain (CNP) may be inadequate. Yoga techniques have been found to be effective complimentary therapies in chronic low back pain and also for stress reduction in other diseases. Objective: The aim of the study was to examine the complimentary role of a yogic relaxation called mind sound resonance technique (MSRT) in non-surgical management of CNP. Materials and Methods: In this randomized controlled study, 60 patients with CNP were assigned to two groups (yoga, n=30) and (control, n=30). The yoga group received yogic MSRT for 20 minutes in supine position after the conventional physiotherapy program for 30 minutes using pre-recorded audio CD and the control group had non-guided supine rest for 20 minutes (after physiotherapy), for 10 days. MSRT provides deep relaxation for both mind and body by introspective experience of the sound resonance in the whole body while repeating the syllables A, U, M and Om and a long chant (Mahamrityunjaya mantra) several times in a meaningful sequence. Both the groups had pre and post assessments using visual pain analog scale, tenderness scoring key, neck disability score (NDS) questionnaire, goniometric measurement of cervical spinal flexibility, and state and trait anxiety inventory-Y1 (STAI-Y1). Results: Mann-Whitney U test showed significant difference between groups in pain (P<0.01), tenderness (P<0.01), neck movements (P<0.01). NDS (P<0.01) and state anxiety (STAI-Y1) showed higher reduction in yoga (P<0.01) than that in the control group. Wilcoxon’s test showed a significant improvement in both groups on all variables (P<0.01). Conclusions: Yoga relaxation through MSRT adds significant complimentary benefits to conventional physiotherapy for CNP by reducing pain, tenderness, disability and state anxiety and providing improved flexibility. PMID:20948897

  12. Dynamics of unloaded and green tea extract loaded lecithin based liposomal dispersions investigated by nuclear magnetic resonance T2 relaxation.

    PubMed

    Kirtil, Emrah; Dag, Damla; Guner, Selen; Unal, Kubra; Oztop, Mecit H

    2017-09-01

    Liposomes are lipid bilayer vesicles that can be used as encapsulation systems for bioactive agents to provide increased protection against environmental stresses (such as pH or temperature extremes). Time Domain Nuclear Magnetic Resonance (TD-NMR) that is based on differentiation of specimen contents with respect to magnetic relaxation rates provides detailed information on amount, state and distribution of water and oil and provide reproducible results on the samples. These make TD-NMR particularly suitable for time-dependent monitoring of emulsion system dynamics. In this study, spin-spin (T2) relaxation times and relaxation spectra were used for characterizing green tea extract loaded and unloaded liposomes prepared with soy (S75) and egg lecithins (E80) by different preparation methods (such as homogenization type, pressure and solvent type). Mean particle sizes of liposomes were found to be the most influential factor in shaping mono-exponential T2 relaxation times. The differences in particle sizes of E80 and S75 samples along with samples with different homogenization pressures could be monitored with T2 relaxation times. Additionally, T2 relaxation times were found to be correlated with particle shape irregularity, and chemical instability of samples due to lipid oxidation. With relaxation spectrum analysis, particular components in the sample could be distinguished (internal/external water and lipid bilayers), which gave more elaborate results on mechanisms of instability. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Studies of spin relaxation and molecular dynamics in liquid crystals by two-dimensional Fourier transform electron spin resonance. II. Perdeuterated-tempone in butoxy benzylidene octylaniline and dynamic cage effects

    NASA Astrophysics Data System (ADS)

    Sastry, V. S. S.; Polimeno, Antonino; Crepeau, Richard H.; Freed, Jack H.

    1996-10-01

    Two-dimensional Fourier transform (2D-FT)-electron spin resonance (ESR) studies on the small globular spin probe perdeuterated tempone (PDT) in the liquid crystal solvent 4O,8 (butoxy benzylidene octylaniline) are reported. These experiments, over the temperature range of 95 °C to 24 °C, cover the isotropic (I), nematic (N), smectic A (SA), smectic B (SB), and crystal (C) phases. The 2D-ELDOR (two-dimensional electron-electron double resonance) spectra confirm the anomalously rapid reorientation of PDT, especially in the lower temperature phases. The model of a slowly relaxing local structure (SRLS) leads to generally very good non-linear least squares (NLLS) global fits to the sets of 2D-ELDOR spectra obtained at each temperature. These fits are significantly better than those achieved by the standard model of Brownian reorientation in a macroscopic orienting potential. The SRLS model is able to account for anomalies first observed in an earlier 2D-ELDOR study on PDT in a different liquid crystal in its smectic phases. Although it is instructional to extract the various spectral densities from the COSY (correlation spectroscopy) and 2D-ELDOR spectra, the use of NLLS global fitting to a full set of 2D-ELDOR spectra is shown to be more reliable and convenient for obtaining optimum model parameters, especially in view of possible (incipient) slow motional effects from the SRLS or dynamic cage. The cage potential is found to remain fairly constant at about kBT over the various phases (with only a small drop in the SB phase), but its asymmetry increases with decreasing temperature T. This value is significantly larger than the weak macroscopic orienting potential which increases from 0.1 to 0.3kBT with decreasing T. The cage relaxation rate, given by Rc is about 3×107 s-1 in the I phase, but increases to about 108 s-1 in the SA, SB, and C phases. The rotational diffusion tensor for PDT shows only a small T-independent asymmetry, and its mean rotational diffusion

  14. Studies of spin relaxation and molecular dynamics in liquid crystals by two-dimensional Fourier transform electron spin resonance. I. Cholestane in butoxy benzylidene-octylaniline and dynamic cage effects

    NASA Astrophysics Data System (ADS)

    Sastry, V. S. S.; Polimeno, Antonino; Crepeau, Richard H.; Freed, Jack H.

    1996-10-01

    Two-dimensional Fourier transform (2D-FT) electron spin resonance (ESR) studies on the rigid rodlike cholestane (CSL) spin-label in the liquid crystal solvent 4O,8 (butoxy benzylidene octylaniline) are reported. These experiments were performed over a wide temperature range: 96 °C to 25 °C covering the isotropic (I), nematic (N), smectic A (SA), smectic B (SB), and crystal (C) phases. It is shown that 2D-FT-ESR, especially in the form of 2D-ELDOR (two-dimensional electron-electron double resonance) provides greatly enhanced sensitivity to rotational dynamics than previous cw-ESR studies on this and related systems. This sensitivity is enhanced by obtaining a series of 2D-ELDOR spectra as a function of mixing time, Tm, yielding essentially a three-dimensional experiment. Advantage is taken of this sensitivity to study the applicability of the model of a slowly relaxing local structure (SRLS). In this model, a dynamic cage of solvent molecules, which relaxes on a slower time scale than the CSL solute, provides a local orienting potential in addition to that of the macroscopic aligning potential in the liquid crystalline phase. The theory of Polimeno and Freed for SRLS in the ESR slow motional regime is extended by utilizing the theory of Lee et al. to include 2D-FT-ESR experiments, and it serves as the basis for the analysis of the 2D-ELDOR experiments. It is shown that the SRLS model leads to significantly improved non-linear least squares fits to experiment over those obtained with the standard model of Brownian reorientation in a macroscopic aligning potential. This is most evident for the SA phase, and the use of the SRLS model also removes the necessity of fitting with the unreasonably large CSL rotational asymmetries in the smectic phases that are required in both the cw-ESR and 2D-ELDOR fits with the standard model. The cage potential is found to vary from about kBT in the isotropic phase to greater than 2kBT in the N and SA phases, with an abrupt drop to

  15. Determining the relaxivity values of protein cage-templated nanoparticles using magnetic resonance imaging.

    PubMed

    Sana, Barindra; Lim, Sierin

    2015-01-01

    The application of magnetic resonance imaging (MRI) is often limited by low magnetic relaxivity of currently used contrast agents. This problem can be addressed by developing more sensitive contrast agents by synthesizing new types of metal complex or metallic nanoparticles. Protein cage has been used as a template in biological synthesis of magnetic nanoparticles. The magnetic nanoparticle-protein cage composites have been reported to have high magnetic relaxivity, which implies their potential application as an MRI contrast agent. The magnetic relaxivity is determined by measuring longitudinal and transverse magnetic relaxivities of the potential agent. The commonly performed techniques are field-cycling NMR relaxometry (also known as variable field relaxometry or nuclear magnetic relaxation dispersion (NMRD) profiling) and in vitro or in vivo MRI relaxometry. Here, we describe techniques for the synthesis of nanoparticle-protein cage composite and determination of their magnetic relaxivities by in vitro MR image acquisition and data processing. In this method, longitudinal and transverse relaxivities are calculated by measuring relaxation rates of water hydrogen nuclei at different nanoparticle-protein cage composite concentrations.

  16. 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.

  17. Nuclear magnetic resonance water relaxation time changes in bananas during ripening: a new mechanism.

    PubMed

    Ribeiro, Fayene Zeferino; Marconcini, Lucinéia Vizzotto; de Toledo, Ingrid Bertoni; de Vasconcellos Azeredo, Rodrigo Bagueira; Barbosa, Lucio Leonel; Colnago, Luiz Alberto

    2010-09-01

    Nuclear magnetic resonance studies of banana fragments during ripening show an increase on the water transverse relaxation time (T2) and a decrease in water self-diffusion coefficient (D). As T(2) and D are normally directly correlated, we studied these two properties in intact bananas during ripening, in an attempt to rule out the effect of injury on the apparent discrepancies in the behavior of T(2) and D. The results show that injury in bananas causes a decrease in T2 of the water in vacuoles (T(2vac)). They also show that T(2vac) increased and D decreased during ripening, ruling out the injury effect. To explain the apparent discrepancies, we propose a new hypothesis for the increase in T2 values, based on the reduction of Fe3+ ions to Fe2+ by galacturonic acid, produced by the hydrolysis of pectin and a decrease in internal oxygen concentration during ripening. As injury alters T2 values it is necessary to use intact bananas to study relaxation times during ripening. The novel interpretation for the increase in T(2vac) based on reduction of Fe+3 and O2 concentration is an alternative mechanism to that based on the hydrolysis of starch in amyloplasts. Copyright 2010 Society of Chemical Industry.

  18. Nuclear magnetic resonance and proton relaxation times in experimental heterotopic heart transplantation

    SciTech Connect

    Eugene, M.; Lechat, P.; Hadjiisky, P.; Teillac, A.; Grosgogeat, Y.; Cabrol, C.

    1986-01-01

    It should be possible to detect heart transplant rejection by nuclear magnetic resonance (NMR) imaging if it induces myocardial T1 and T2 proton relaxation time alterations or both. We studied 20 Lewis rats after a heterotopic heart transplantation. In vitro measurement of T1 and T2 was performed on a Minispec PC20 (Bruker) 3 to 9 days after transplantation. Histologic analysis allowed the quantification of rejection process based on cellular infiltration and myocardiolysis. Water content, a major determinant of relaxation time, was also studied. T1 and T2 were significantly prolonged in heterotopic vs orthotopic hearts (638 +/- 41 msec vs 606 +/- 22 msec for T1, p less than 0.01 and 58.2 +/- 8.4 msec vs 47.4 +/- 1.9 msec for T2, p less than 0.001). Water content was also increased in heterotopic hearts (76.4 +/- 2.3 vs 73.8 +/- 1.0, p less than 0.01). Most importantly, we found close correlations between T1 and especially T2 vs water content, cellular infiltration, and myocardiolysis. We conclude that rejection reaction should be noninvasively detected by NMR imaging, particularly with pulse sequences emphasizing T2.

  19. Effect of short-term unloading on T2 relaxation time in the lumbar intervertebral disc—in vivo magnetic resonance imaging study at 3.0 tesla

    PubMed Central

    Stelzeneder, David; Kovács, Balázs K.; Goed, Sabine; Welsch, Goetz H.; Hirschfeld, Clemens; Paternostro-Sluga, Tatjana; Friedrich, Klaus M.; Mamisch, Tallal C.; Trattnig, Siegfried

    2012-01-01

    Background context Diurnal changes in T2 values, indicative for changes in water content, have been reported in the lumbar intervertebral discs. However, data concerning short-term T2 changes are missing. Purpose The purpose of this study was to investigate the short-term effects of unloading on T2 values in lumbar intervertebral discs in vivo. Study design Experimental study with repeated measurements of lumbar discs T2 relaxation time during a period of 38 minutes of supine posture. Patient sample Forty-one patients with acute or chronic low back pain (visual analog scale ≥3). Outcome measures T2 relaxation time in the intervertebral disc, lumbar lordosis angle, and intervertebral disc height. Methods Forty-one patients (mean age, 41.6 years) were investigated in the supine position using a 3-tesla magnetic resonance system. Sagittal T2 mapping was performed immediately after unloading and after a mean delay of 38 minutes. No patient movement was allowed between the measurements. One region of interest (ROI) was manually placed in both the anterior and the posterior annulus fibrosus (AF) and three ROIs in the nucleus pulposus (NP). Results There was a statistically significant decrease in the anterior NP (−2.7 ms; p<.05) and an increase in T2 values in the posterior AF (+3.5 ms; p<.001). Discs with initially low T2 values in the NP showed minor increase in the posterior AF (+1.6 ms; p<.05), whereas a major increase in the posterior AF was found in discs with initially high T2 values in the NP (+6.8 ms; p=.001). Patients examined in the morning showed no differences, but those investigated in the afternoon showed a decrease in the anterior NP (−5.3 ms; p<.05) and an increase in the posterior AF (+7.8 ms; p=.002). No significant differences were observed in other regions. Correlation analysis showed moderate correlations between the time of investigation and T2 changes in the posterior AF (r=0.46; p=.002). Conclusions A shift of water from the anterior to

  20. Anisotropic anomalous diffusion filtering applied to relaxation time estimation in magnetic resonance imaging.

    PubMed

    Senra Filho, Antonio Carlos da S; Barbosa, Jeam Haroldo O; Salmon, Carlos E G; Murta, Luiz O

    2014-01-01

    Relaxometry mapping is a quantitative modality in magnetic resonance imaging (MRI) widely used in neuroscience studies. Despite its relevance and utility, voxel measurement of relaxation time in relaxometry MRI is compromised by noise that is inherent to MRI modality and acquisition hardware. In order to enhance signal to noise ratio (SNR) and quality of relaxometry mapping we propose application of anisotropic anomalous diffusion (AAD) filter that is consistent with inhomogeneous complex media. Here we evaluated AAD filter in comparison to two usual spatial filters: Gaussian and non local means (NLM) filters applied to real and simulated T2 relaxometry image sequences. The results demonstrate that AAD filter is comparatively more efficient in noise reducing and maintaining the image structural edges. AAD shows to be a robust and reliable spatial filter for brain image relaxometry.

  1. Clarification of the measurement of surface spin relaxation via conduction electron spin resonance

    NASA Astrophysics Data System (ADS)

    Eigler, D. M.; Schultz, S.

    1982-12-01

    We clarify the parameterization of the probability of transverse conduction electron spin relaxation. ɛ, at the surface of a metal. Using Walker's boundary condition on the transverse spin magnetization, we have calculated the ɛ and thickness dependence of the spin resonance linewidth. The results are discussed in simple physical terms. The recent work of Allam and Vigouroux is shown to contain errors.

  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. Copyright © 2015 Elsevier Inc. All rights reserved.

  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. Gradient-induced longitudinal relaxation of hyperpolarized noble gases in the fringe fields of superconducting magnets used for magnetic resonance

    NASA Astrophysics Data System (ADS)

    Zheng, Wangzhi; Cleveland, Zackary I.; Möller, Harald E.; Driehuys, Bastiaan

    2011-02-01

    When hyperpolarized noble gases are brought into the bore of a superconducting magnet for magnetic resonance imaging (MRI) or spectroscopy studies, the gases must pass through substantial field gradients, which can cause rapid longitudinal relaxation. In this communication, we present a means of calculating this spatially dependent relaxation rate in the fringe field of typical magnets. We then compare these predictions to experimental measurements of 3He relaxation at various positions near a medium-bore 2-T small animal MRI system. The calculated and measured relaxation rates on the central axis of the magnet agree well and show a maximum 3He relaxation rate of 3.83 × 10-3 s-1 (T1 = 4.4 min) at a distance of 47 cm from the magnet isocenter. We also show that if this magnet were self-shielded, its minimum T1 would drop to 1.2 min. In contrast, a typical self-shielded 1.5-T clinical MRI scanner will induce a minimum on-axis T1 of 12 min. Additionally, we show that the cylindrically symmetric fields of these magnets enable gradient-induced relaxation to be calculated using only knowledge of the on-axis longitudinal field, which can either be measured directly or calculated from a simple field model. Thus, while most MRI magnets employ complex and proprietary current configurations, we show that their fringe fields and the resulting gradient-induced relaxation are well approximated by simple solenoid models. Finally, our modeling also demonstrates that relaxation rates can increase by nearly an order of magnitude at radial distances equivalent to the solenoid radius.

  5. Gradient-induced longitudinal relaxation of hyperpolarized noble gases in the fringe fields of superconducting magnets used for magnetic resonance.

    PubMed

    Zheng, Wangzhi; Cleveland, Zackary I; Möller, Harald E; Driehuys, Bastiaan

    2011-02-01

    When hyperpolarized noble gases are brought into the bore of a superconducting magnet for magnetic resonance imaging (MRI) or spectroscopy studies, the gases must pass through substantial field gradients, which can cause rapid longitudinal relaxation. In this communication, we present a means of calculating this spatially dependent relaxation rate in the fringe field of typical magnets. We then compare these predictions to experimental measurements of (3)He relaxation at various positions near a medium-bore 2-T small animal MRI system. The calculated and measured relaxation rates on the central axis of the magnet agree well and show a maximum (3)He relaxation rate of 3.83×10(-3) s(-1) (T(1)=4.4 min) at a distance of 47 cm from the magnet isocenter. We also show that if this magnet were self-shielded, its minimum T(1) would drop to 1.2 min. In contrast, a typical self-shielded 1.5-T clinical MRI scanner will induce a minimum on-axis T(1) of 12 min. Additionally, we show that the cylindrically symmetric fields of these magnets enable gradient-induced relaxation to be calculated using only knowledge of the on-axis longitudinal field, which can either be measured directly or calculated from a simple field model. Thus, while most MRI magnets employ complex and proprietary current configurations, we show that their fringe fields and the resulting gradient-induced relaxation are well approximated by simple solenoid models. Finally, our modeling also demonstrates that relaxation rates can increase by nearly an order of magnitude at radial distances equivalent to the solenoid radius. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. Gradient-induced Longitudinal Relaxation of Hyperpolarized Noble Gases in the Fringe Fields of Superconducting Magnets Used for Magnetic Resonance

    PubMed Central

    Zheng, Wangzhi; Cleveland, Zackary I.; Möller, Harald E.; Driehuys, Bastiaan

    2010-01-01

    When hyperpolarized noble gases are brought into the bore of a superconducting magnet for magnetic resonance imaging (MRI) or spectroscopy studies, the gases must pass through substantial field gradients, which can cause rapid longitudinal relaxation. In this communication, we present a means of calculating this spatially dependent relaxation rate in the fringe field of typical magnets. We then compare these predictions to experimental measurements of 3He relaxation at various positions near a medium-bore 2-T small animal MRI system. The calculated and measured relaxation rates on the central axis of the magnet agree well and show a maximum 3He relaxation rate of 3.83 × 10−3 s−1 (T1 = 4.4 min) at a distance of 47 cm from the magnet isocenter. We also show that if this magnet were self-shielded, its minimum T1 would drop to 1.2 min. In contrast, a typical self-shielded 1.5-T clinical MRI scanner will induce a minimum on-axis T1 of 12 min. Additionally, we show that the cylindrically symmetric fields of these magnets enable gradient-induced relaxation to be calculated using only knowledge of the on-axis longitudinal field, which can either be measured directly or calculated from a simple field model. Thus, while most MRI magnets employ complex and proprietary current configurations, we show that their fringe fields and the resulting gradient induced relaxation are well approximated by simple solenoid models. Finally, our modeling also demonstrates that relaxation rates can increase by nearly an order of magnitude at radial distances equivalent to the solenoid radius. PMID:21134771

  7. 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

  8. Measurement of the true transverse nuclear magnetic resonance relaxation in the presence of field gradients.

    PubMed

    Mitchell, J; Chandrasekera, T C; Gladden, L F

    2013-08-21

    A measure of the nuclear spin transverse relaxation time T2, as determined using the nuclear magnetic resonance Carr-Purcell Meiboom-Gill (CPMG) experiment, provides unique information characterizing the microstructure of porous media which are themselves ubiquitous across fields of petrophysics, biophysics, and chemical engineering. However, the CPMG measurement is sensitive to diffusion in large magnetic field gradients. Under such conditions an effective relaxation time T2,eff is observed instead, described by a combination of relaxation and diffusion exponents. The relaxation exponent always varies as nte (where n is the number, and te is the temporal separation, of spin echoes). The diffusion exponent varies as nte (k), where 1 < k ≤ 3, although the exact analytic form is often unknown. Here we present a general approach to separating the influence of relaxation and diffusion by utilizing a composite diffusion exponent. Any T2,eff component with a power of k > 1 is removed to provide a measure of the true T2 relaxation time distribution from CPMG data acquired in the presence of a strong background gradient. We apply the technique to discriminate between the effects of relaxation and diffusion in porous media using catalysts and rocks as examples. The method is generally applicable to any CPMG measurements conducted in the presence of a static magnetic field gradient.

  9. 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

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

    PubMed

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

    2010-09-01

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

  11. 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.

  12. Relaxation and Saturation in High-Gradient Force-Detected Magnetic Resonance: Theory and Observation

    NASA Astrophysics Data System (ADS)

    Dougherty, William; Bruland, Kelly; Chao, Shih-Hui; Garbini, Joseph; Jensen, Seth; Sidles, John

    1999-05-01

    We have observed microwave power-scaling behavior of electron spin resonance in a field gradient of 250,000 Tesla per meter by the technique of magnetic resonance force microscopy (MRFM). Resonance was induced in a dilute sample of DPPH in polystyrene at 77 and 10 K by an amplitude-modulated microwave field in a polarizing field produced by a micrometer-scale SmCo magnet mounted on a force microscope cantilever. Microwave power-dependent spin-gradient forces of 10--10,000 attonewtons were observed, with an electron spin-moment sensitivity comparable to the most sensitive SQUIDs. At low power, data were in good accord with analytical expressions derived from the Bloch equations for high gradients. At high power, saturation effects modify the induced forces, creating a distinct ``knee" in the force-response curve. The values of spin-lattice relaxation times inferred from the phase lag of the cantilever response agree with published values for similar samples obtained by conventional resonance spectroscopy at 77 K, but were shorter than published values at 10 K. MRFM techniques allow the observation of magnetic resonance in external field gradients which can meet or exceed the local intermolecular gradients, providing an interesting experimental and theoretical regime in which to test models of spin diffusion and relaxation.

  13. Nuclear Quadrupole Resonance Study of Potassium - - Chloride.

    NASA Astrophysics Data System (ADS)

    Ramia, Maximo Elias

    Fast Fourier transform nuclear quadrupole resonance (NQR) was used to study the cubic antifluorite crystal potassium hexacloro-osmate, K(,2)OsCl(,6). The study of the ('35)Cl and ('37)Cl resonances were performed on three samples of K(,2)OsCl(,6), a powder sample, a powder sample recrystallized from D(,2)O and a single crystal sample. The studies were carried out in the temperature range 300 to 6K. A detailed study of the ('35)Cl and ('37)Cl NQR lineshapes, in the temperature range 70 to 300K, showed that the lineshapes reflect the strain fields produced by lattice dislocations and point defects. The temperature evolution of these strain fields give rise to a satellite line which previously was attributed to H('+) ion impurities present in the samples. A comprehensive study of the temperature evolution of the NQR spectrum in the vicinity of the phase transition revealed a drop of line intensity and the progressive appearance of an extra broad resonance component. Both effects are associated with the existence of precursor dynamic clusters at temperatures higher than T(,C). Qualitatively similar but quantitatively different behaviour was observed in the powder and single crystal samples. Although the precursor clusters are an intrinsic property of the phrase transition, their detailed dynamics is sample independent. A NQR study of the tetragonal phase showed that at the lowest temperature the ratio of line intensities is 2:1. The phase shift effect previously observed in the tetragonal phase of K(,2)ReCl(,6) was also observed in K(,2)OsCl(,6). The effect has been explained as an experimental artifact introduced by the truncation of the FID due to the spectrometer dead time. Spin-lattice relaxation measurements in the cubic phase show two component relaxation in the vicinity of T(,C). The behaviour is quantitatively different in the powder and single crystal samples. The short relaxation time is associated with dynamic clusters. Spin-lattice relaxation time

  14. 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.

  15. Nuclear magnetic resonance relaxation and diffusion measurements as a proxy for soil properties

    NASA Astrophysics Data System (ADS)

    Duschl, Markus; Pohlmeier, Andreas; Galvosas, Petrik; Vereecken, Harry

    2013-04-01

    Nuclear Magnetic Resonance (NMR) relaxation and NMR diffusion measurements are two of a series of fast and non-invasive NMR applications widely used e.g. as well logging tools in petroleum exploration [1]. For experiments with water, NMR relaxation measures the relaxation behaviour of former excited water molecules, and NMR diffusion evaluates the self-diffusion of water. Applied in porous media, both relaxation and diffusion measurements depend on intrinsic properties of the media like pore size distribution, connectivity and tortuosity of the pores, and water saturation [2, 3]. Thus, NMR can be used to characterise the pore space of porous media not only in consolidated sediments but also in soil. The physical principle behind is the relaxation of water molecules in an external magnetic field after excitation. In porous media water molecules in a surface layer of the pores relax faster than the molecules in bulk water because of interactions with the pore wall. Thus, the relaxation in smaller pores is generally faster than in bigger pores resulting in a relaxation time distribution for porous media with a range of pore sizes like soil [4]. In NMR diffusion experiments, there is an additional encoding of water molecules by application of a magnetic field gradient. Subsequent storage of the magnetization and decoding enables the determination of the mean square displacement and therefore of the self-diffusion of the water molecules [5]. Employing various relaxation and diffusion experiments, we get a measure of the surface to volume ratio of the pores and the tortuosity of the media. In this work, we show the characterisation of a set of sand and soil samples covering a wide range of textural classes by NMR methods. Relaxation times were monitored by the Carr-Purcell-Meiboom-Gill sequence and analysed using inverse Laplace transformation. Apparent self-diffusion constants were detected by a 13-intervall pulse sequence and variation of the storage time. We

  16. 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

  17. 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

  18. Vibrational Relaxation of the Backbone and Base Modes in LacDNA Complexes by UV Resonance Raman Spectroscopy.

    PubMed

    Muntean, Cristina M; Bratu, Ioan; Hernanz, Antonio

    2017-07-20

    Vibrational band shape analysis through time correlation function concept is widely used to obtain experimental information on the molecular dynamics of medium-size molecules in different environments. Interesting details are revealed by extending this technique to biomolecules such as functional groups of the nucleic acids in media approaching the physiological conditions. In this work a study into the UV resonance Raman (UVRR) vibrational half bandwidths of functional groups in LacDNA, upon lowering the pH (pH 6.4, pH 3.45) and in the presence of Mn(2+) and Ca(2+) ions, respectively, was of interest. The corresponding global relaxation times have been derived. Also, the 793 cm(-1) UVRR band, corresponding to ν (backbone O-P-O, dT) oscillator of LacDNA in aqueous solutions, was selected for band shape-analysis. Vibrational relaxation appears as the dominant relaxation process for this mode, with vibrational dephasing being the most efficient for this oscillator. Current theories developed for vibrational dephasing have been applied to this profile, and relevant relaxation parameters have been obtained and discussed. To our knowledge this is the first study on DNA oligomers vibrational band shape analysis through time correlation function concept.

  19. Stellar dynamics around a massive black hole - III. Resonant relaxation of razor-thin axisymmetric discs

    NASA Astrophysics Data System (ADS)

    Sridhar, S.; Touma, Jihad R.

    2017-02-01

    We study the resonant relaxation (RR) of an axisymmetric, low-mass (or Keplerian) stellar disc orbiting a more massive black hole (MBH). Our recent work on the general kinetic theory of RR is simplified in the standard manner by the neglect of 'gravitational polarization' and applied to a razor-thin axisymmetric disc. The wake of a stellar orbit is expressed in terms of the angular momenta exchanged with other orbits, and used to derive a kinetic equation for RR under the combined actions of self-gravity, 1 PN and 1.5 PN general relativistic effects of the MBH and an arbitrary external axisymmetric potential. This is a Fokker-Planck equation for the stellar distribution function (DF), wherein the diffusion coefficients are given self-consistently in terms of contributions from apsidal resonances between pairs of stellar orbits. The physical kinetics is studied for the two main cases of interest. (1) 'Lossless' discs in which the MBH is not a sink of stars, and disc mass, angular momentum and energy are conserved: we prove that general H-functions can increase or decrease during RR, but the Boltzmann entropy is (essentially) unique in being a non-decreasing function of time. Therefore, secular thermal equilibria are maximum entropy states, with DFs of the Boltzmann form; the two-ring correlation function at equilibrium is computed. (2) Discs that lose stars to the MBH through an 'empty loss cone': we derive expressions for the MBH feeding rates of mass, angular momentum and energy in terms of the diffusive fluxes at the loss-cone boundaries.

  20. 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

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

    PubMed Central

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

    2015-01-01

    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 108 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 108 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. PMID:26314913

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 108 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 108 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.

  3. 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.

  4. In Situ Measurement of Surface Functional Groups on Silica Nanoparticles Using Solvent Relaxation Nuclear Magnetic Resonance.

    PubMed

    Yuan, Li; Chen, Lan; Chen, Xiaohong; Liu, Renxiao; Ge, Guanglu

    2017-09-05

    In situ analysis and study on the surface of nanoparticles (NPs) is a key to obtain their important physicochemical properties for the subsequent applications. Of them, most works focus on the qualitative characterization whereas quantitative analysis and measurement on the NPs under their storage and usage conditions is still a challenge. In order to cope with this challenge, solvation relaxation-based nuclear magnetic resonance (NMR) technology has been applied to measure the wet specific surface area and, therefore, determine the number of the bound water molecules on the surface of silica NPs in solution and the hydrophilic groups of various types grafted on the surface of the NPs. By changing the surface functional group on silica particles, the fine distinction for the solvent-particle interaction with different surface group can be quantitatively differentiated by measuring the number of water molecules absorbed on the surface. The results show that the number of the surface hydroxyl, amine, and carboxyl group per nm(2) is 4.0, 3.7, and 2.3, respectively, for the silica particles with a diameter of 203 nm. The method reported here is the first attempt to determine in situ the number of bound solvent molecules and any solvophilic groups grafted on nanoparticles.

  5. 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. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. 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.

  7. Non-Debye relaxation and resonance phenomena in dielectric spectra of CaCu3Ti4O12 family functional ceramic materials

    NASA Astrophysics Data System (ADS)

    Turik, A. V.; Bogatin, A. S.

    2015-01-01

    Experimental data on dielectric spectra of calcium copper titanate, CaCu3Ti4O12 (CCTO) family functional ceramics have been studied and analyzed. It is shown that there are both non-Debye relaxation and resonance regions in their spectra. An occurrence of a retardation of complex permittivity and a relaxation of electric modulus is established. An average relaxation frequency of the electric modulus is considerably (in some cases several orders of magnitude) larger than the retardation frequency of the permittivity. A parallel connection of the capacity and complex conductivity is used to model and interpret experimental data on a negative permittivity in the infralow frequency range. Computer simulation enables us to reveal that the hopping conductivity, characteristic for disordered heterogeneous systems, is to be taken into account to describe adequately experimental data on passing the real part of the capacity (or permittivity) through zero. We have found a critical frequency at which the parallel resonance would take place.

  8. Paramagnetic viral nanoparticles as potential high-relaxivity magnetic resonance contrast agents.

    PubMed

    Allen, Mark; Bulte, Jeff W M; Liepold, Lars; Basu, Gautam; Zywicke, Holly A; Frank, Joseph A; Young, Mark; Douglas, Trevor

    2005-10-01

    In order to compensate for the inherent high threshold of detectability of MR contrast agents, there has been an active interest in the development of paramagnetic nanoparticles incorporating high payloads of Gd(3+) with high molecular relaxivities. Toward this end, the protein cage of Cowpea chlorotic mottle virus (CCMV), having 180 metal binding sites, is being explored. In vivo CCMV binds Ca(2+) at specific metal binding sites; however, Gd(3+) can also bind at these sites. Using fluorescence resonance energy transfer we have characterized the binding affinity of Gd(3+) to the metal binding sites by competition experiments with Tb(3+). The measured dissociation constant (K(d)) for Gd(3+) bound to the virus is 31 microM. The T(1) and T(2) relaxivities of solvent water protons in the presence of Gd(3+)-bound CCMV were 202 and 376 mM(-1) s(-1), respectively, at 61 MHz Larmor frequency. The unusually high relaxivity values of the Gd(3+)-CCMV are largely a result of the nanoparticle virus size and the large number of Gd(3+) ions bound to the virus. These preliminary results should encourage further investigations into the use of viral protein cages as a new platform for MR contrast agents. Copyright 2005 Wiley-Liss, Inc.

  9. Dispersion of T1 and T2 nuclear magnetic resonance relaxation in crude oils.

    PubMed

    Chen, Joseph J; Hürlimann, Martin; Paulsen, Jeffrey; Freed, Denise; Mandal, Soumyajit; Song, Yi-Qiao

    2014-09-15

    Crude oils, which are complex mixtures of hydrocarbons, can be characterized by nuclear magnetic resonance diffusion and relaxation methods to yield physical properties and chemical compositions. In particular, the field dependence, or dispersion, of T1 relaxation can be used to investigate the presence and dynamics of asphaltenes, the large molecules primarily responsible for the high viscosity in heavy crudes. However, the T2 relaxation dispersion of crude oils, which provides additional insight when measured alongside T1, has yet to be investigated systematically. Here we present the field dependence of T1-T2 correlations of several crude oils with disparate densities. While asphaltene and resin-containing crude oils exhibit significant T1 dispersion, minimal T2 dispersion is seen in all oils. This contrasting behavior between T1 and T2 cannot result from random molecular motions, and thus, we attribute our dispersion results to highly correlated molecular dynamics in asphaltene-containing crude oils. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Determination of T1 relaxation time of normal equine tendons using magic angle magnetic resonance imaging.

    PubMed

    Spriet, Mathieu; Wisner, Erik R; Anthenill, Lucy A; Buonocore, Michael H

    2011-01-01

    Seven isolated equine front limbs were used to establish the normal T1 relaxation time of equine superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), and suspensory ligament (SL) using magic angle magnetic resonance (MR) imaging. MR imaging of the metacarpi was performed with the limbs positioned at 55° (the magic angle) relative to the main magnetic field. Transverse spin-echo proton density and inversion recovery images were acquired. T1 relaxation time was calculated based on ratios of signal intensity determined from the different pulse sequences. T1 relaxation times for SDFT, DDFT, and SL were 288 (± 17), 244 (± 14), and 349 (± 16) ms, respectively. The difference in T1 values between SDFT, DDFT, and SL was statistically significant. T1 values of equine tendons can be determined with magic angle imaging on a clinical MR system using < 10 min total scan time. The knowledge of the normal range of T1 values may be useful to identify horses with chronic tendinopathy, where based on the human literature, an increased T1 value may be expected. © 2010 Veterinary Radiology & Ultrasound.

  11. Nonlinear Optical Studies of Relaxation in Semiconductor Microstructures.

    NASA Astrophysics Data System (ADS)

    Remillard, Jeffrey Thomas

    The purpose of this research is to study the relaxation of optically generated excitons and carriers in semiconductor microstructures using four wave mixing (FWM) spectroscopy. The systems studied include CdSSe microcrystallite doped glasses and GaAs/AlGaAs multiple quantum well structures (MQWS). Exposing a semiconductor to optical radiation near the fundamental band gap results in the creation of populations of elementary excitations including electrons, holes, and excitons, and also results in the creation of a superposition state between the ground and excited state of the solid. The work in this dissertation examines the relaxation of the populations of elementary excitations and the relaxation of the coherence between the ground and excited state using four wave mixing spectroscopy. First, the nonlinear optical response of simple two level systems is examined in order to provide insight into the types of line shapes expected from semiconductors. It is shown that the line shape is strongly dependent on how the system is coupled to the reservoir and the consequences of coupling to a reservoir are examined in a FWM measurement made in atomic sodium. The first semiconductor system studied is CdSSe microcrystallite doped glass. This system is shown to have a very slow component to the nonlinear response which has a optical intensity dependence and temperature dependence which suggests that the FWM response in these materials is trap mediated. Room temperature FWM measurements in GaAs MQWS enables the measurement of the carrier recombination time and the ambipolar diffusion coefficient. Using the technique of correlated optical fields, a slow component to the nonlinear response was measured showing an interference profile which suggests a possible shift of the exciton resonance due to the optically generated carriers. At low temperatures (2-20 K), measurements of the exciton line shape and relaxation time were made and evidence for exciton spectral diffusion was

  12. Cooking effects on water distribution in potatoes using nuclear magnetic resonance relaxation.

    PubMed

    Mortensen, Margit; Thybo, Anette K; Bertram, Hanne C; Andersen, Henrik J; Engelsen, Søren B

    2005-07-27

    Continuous low-field (LF) (1)H NMR relaxometry was used to monitor the structural changes during cooking of potatoes with two different dry matter (DM) contents. A principal component analysis of the relaxation decay curves revealed major events related to water mobility during cooking, which occur at 53 and 60 degrees C for potatoes with medium and low DM contents, respectively. Exponential analysis of the relaxation decays reveals two major water populations in the potato: a slow-relaxing (assigned to water in cytoplasm and extracellular cavities) water component, T(22) ( approximately 350-550 ms), and a fast-relaxing component (primarily assigned to water associated with starch and cell walls), T(21) ( approximately 45-65 ms). Significant DM dependent shifts in both the T(21) and T(22) relaxation time constants were observed during cooking, indicating that starch gelatinizes between 53 and 70 degrees C with water exchanging with the hydroxyls of starch (transition in T(21)) and cells start to disrupt with an increase in diffusion volumes at approximately 60 degrees C (transition in T(22)). The study reveals that continuous LF NMR measurement is an excellent and highly sensitive method to study changes in water mobility and water populations during the cooking of potatoes.

  13. 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

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

    PubMed

    Costabel, Stephan; Yaramanci, Ugur

    2013-04-01

    [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

  15. 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.

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

    PubMed

    Syryamina, V N; Dzuba, S A

    2012-10-14

    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)], 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.

  17. 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.

  18. Relaxation behavior study of ultrasmall superparamagnetic iron oxide nanoparticles at ultralow and ultrahigh magnetic fields.

    PubMed

    Wang, Wei; Dong, Hui; Pacheco, Victor; Willbold, Dieter; Zhang, Yi; Offenhaeusser, Andreas; Hartmann, Rudolf; Weirich, Thomas E; Ma, Peixiang; Krause, Hans-Joachim; Gu, Zhongwei

    2011-12-15

    Ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) have attracted attention because of their current and potential usefulness as contrast agents for magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR). USPIOs are usually used for their significant capacity to produce predominant proton relaxation effects, which result in signal reduction. However, most previous studies that utilized USPIOs have been focused on the relaxation behavior at commonly used magnetic fields of clinical MRI systems (typically 1-3 T). In this paper, magnetic relaxation processes of protons in water surrounding the USPIOs are studied at ultralow (≤10 mT) and ultrahigh magnetic fields (14.1 T). USPIOs used in our experiments were synthesized with a core size of 6 nm, and transferred from organic to water by ligand exchange. The proton spin-lattice relaxation time (T(1)) and spin-spin relaxation time (T(2)) were investigated at ultralow (212 μT for T(2) and 10 mT for T(1)) and at 14.1 T with different iron concentrations. At all of the fields, there is a linear relationship between the inverse of relaxation times and the iron concentration. The spin-spin relaxivity (r(2)) at 14.1 T is much larger than that value of the ultralow field. At ultralow field, however, the spin-lattice relaxivity (r(1)) is larger than the r(1) at ultrahigh field. The results provide a perspective on potential in vivo and in vitro applications of USPIOs in ultralow and ultrahigh field NMR and MRI.

  19. Simultaneous EEG/functional magnetic resonance imaging at 4 Tesla: correlates of brain activity to spontaneous alpha rhythm during relaxation.

    PubMed

    Difrancesco, Mark W; Holland, Scott K; Szaflarski, Jerzy P

    2008-10-01

    : Simultaneous EEG and functional magnetic resonance imaging have been applied to the study of brain states associated with alpha waves using a magnetic field strength of 1.5 Tesla and has been shown in recent years to be feasible up to 3 Tesla for other applications. This study demonstrates this technique's continued viability at a field strength of 4 Tesla, affording a proportionally greater sensitivity to changes in Blood Oxygen Level Dependent (BOLD) signal. In addition, for the study of alpha correlations, the authors used a larger number of subjects and scanning sessions than in the previous work. Random effects group regression analysis of 35 EEG/functional magnetic resonance imaging sessions against occipital alpha magnitude in a relaxed state detected bilateral widespread activation of dorsal thalamus and portions of the anterior cingulate and cerebellum. In the same group analysis, deactivations arose predominantly in the fusiform and adjacent visual association areas with a small activation cluster also detected in dorsolateral prefrontal cortex. This pattern is consistent with a correspondence between alpha magnitude variations and resting state network dynamics ascertained by recent studies of low frequency spontaneous BOLD fluctuations. The central role of the thalamus in resting state networks correlated with alpha activity is highlighted. Demonstrating the applicability of simultaneous EEG/functional magnetic resonance imaging up to 4 Tesla is particularly important for clinically relevant research involving challenging spontaneous EEG abnormalities, such as those of epilepsy.

  20. 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.

  1. Nonlinear optical studies of relaxation in semiconductor microstructures

    NASA Astrophysics Data System (ADS)

    Remillard, Jeffrey Thomas

    1990-11-01

    Exposing a semiconductor to optical radiation near the fundamental band gap results in the creation of populations or elementary excitations including electrons, holes, and excitons, and also results in the creation of a superposition state between the ground and excited state of the solid. The relaxation of optically generated excitons and carriers in semiconductor microstructures was studied using four wave mixing (FWM) spectroscopy. The systems studied include CdSSe microcrystallite doped glasses and GaA/AlGaAs multiple quantum well structures (MQWS). First, the nonlinear optical response of simple two level systems is examined in order to provide insight into the types of line shapes expected from semiconductors. It is shown that the line shape is strongly dependent on how the system is coupled to the reservoir and the consequences of coupling to a reservoir are examined in a FWM measurement made in atomic sodium. The first semiconductor system studied is CdSSe microcrystallite doped glass. This system is shown to have a very slow component to the nonlinear response which has an optical intensity dependence and temperature dependence which suggests that the FWM response in these materials is trap mediated. Room temperature FWM measurements in GaAs MQWS enables the measurement of the carrier recombination time and the ambipolar diffusion coefficient. Using the technique of correlated optical fields, a slow component to the nonlinear response was measured showing an interference profile which suggests a possible shift of the exciton resonance due to the optically generated carriers. At low temperatures, measurements of the exciton line shape and relaxation time were made and evidence for exciton spectral diffusion was found. The low temperature line shapes can be qualitatively reproduced using Modified Optical Bloch equations which include the effects of spectral diffusion.

  2. Monte Carlo study of vibrational relaxation processes

    NASA Technical Reports Server (NTRS)

    Boyd, Iain D.

    1991-01-01

    A new model is proposed for the computation of vibrational nonequilibrium in the direct simulation Monte Carlo method (DSMC). This model permits level to level vibrational transitions for the first time in a Monte Carlo flowfield simulation. The model follows the Landau-Teller theory for a harmonic oscillator in which the rates of transition are related to an experimental correlation for the vibrational relaxation time. The usual method for simulating such processes in the DSMC technique applies a constant exchange probability to each collision and the vibrational energy is treated as a continuum. A comparison of these two methods is made for the flow of nitrogen over a wedge. Significant differences exist for the vibrational temperatures computed. These arise as a consequence of the incorrect application of a constant exchange probability in the old method. It is found that the numerical performances of the two vibrational relaxation models are equal.

  3. Monitoring Complex Formation by Relaxation-Induced Pulse Electron Paramagnetic Resonance Distance Measurements.

    PubMed

    Giannoulis, Angeliki; Oranges, Maria; Bode, Bela E

    2017-09-06

    Biomolecular complexes are often multimers fueling the demand for methods that allow unraveling their composition and geometric arrangement. Pulse electron paramagnetic resonance (EPR) spectroscopy is increasingly applied for retrieving geometric information on the nanometer scale. The emerging RIDME (relaxation-induced dipolar modulation enhancement) technique offers improved sensitivity in distance experiments involving metal centers (e.g. on metalloproteins or proteins labelled with metal ions). Here, a mixture of a spin labelled ligand with increasing amounts of paramagnetic Cu(II) ions allowed accurate quantification of ligand-metal binding in the model complex formed. The distance measurement was highly accurate and critical aspects for identifying multimerization could be identified. The potential to quantify binding in addition to the high-precision distance measurement will further increase the scope of EPR applications. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  4. 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

  5. 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

  6. 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.

  7. Permeability of a growing biofilm in a porous media fluid flow analyzed by magnetic resonance displacement-relaxation correlations.

    PubMed

    Vogt, Sarah J; Sanderlin, Alexis B; Seymour, Joseph D; Codd, Sarah L

    2013-05-01

    Biofilm growth in porous media is difficult to study non-invasively due to the opaqueness and heterogeneity of the systems. Magnetic resonance is utilized to non-invasively study water dynamics within porous media. Displacement-relaxation correlation experiments were performed on fluid flow during biofilm growth in a model porous media of mono-dispersed polystyrene beads. The spin-spin T2 magnetic relaxation distinguishes between the biofilm phase and bulk fluid phase due to water-biopolymer interactions present in the biofilm, and the flow dynamics are measured using PGSE NMR experiments. By correlating these two measurements, the effects of biofilm growth on the fluid dynamics can be separated into a detailed analysis of both the biofilm phase and the fluid phase simultaneously within the same experiment. Within the displacement resolution of these experiments, no convective flow was measured through the biomass. An increased amount of longitudinal hydrodynamic dispersion indicates increased hydrodynamic mixing due to fluid channeling caused by biofilm growth. The effect of different biofilm growth conditions was measured by varying the strength of the bacterial growth medium. Copyright © 2012 Wiley Periodicals, Inc.

  8. Effects of Liver Fibrosis Progression on Tissue Relaxation Times in Different Mouse Models Assessed by Ultrahigh Field Magnetic Resonance Imaging

    PubMed Central

    Müller, Andreas; Hochrath, Katrin; Stroeder, Jonas; Hittatiya, Kanishka; Schneider, Günther; Lammert, Frank; Buecker, Arno

    2017-01-01

    Recently, clinical studies demonstrated that magnetic resonance relaxometry with determination of relaxation times T1 and T2⁎ may aid in staging and management of liver fibrosis in patients suffering from viral hepatitis and steatohepatitis. In the present study we investigated T1 and T2⁎ in different models of liver fibrosis to compare alternate pathophysiologies in their effects on relaxation times and to further develop noninvasive quantification methods of liver fibrosis. MRI was performed with a fast spin echo sequence for measurement of T1 and a multigradient echo sequence for determination of T2⁎. Toxic liver fibrosis was induced by injections of carbon tetrachloride (1.4 mL CCl4 per kg bodyweight and week, for 3 or 6 weeks) in BALB/cJ mice. Chronic sclerosing cholangitis was mimicked using the ATP-binding cassette transporter B4 knockout (Abcb4 −/−) mouse model. Untreated BALB/cJ mice served as controls. To assess hepatic fibrosis, we ascertained collagen contents and fibrosis scores after Sirius red staining. T1 and T2⁎ correlate differently to disease severity and etiology of liver fibrosis. T2⁎ shows significant decrease correlating with fibrosis in CCl4 treated animals, while demonstrating significant increase with disease severity in Abcb4 −/− mice. Measurements of T1 and T2⁎ may therefore facilitate discrimination between different stages and causes of liver fibrosis. PMID:28194423

  9. Effects of Liver Fibrosis Progression on Tissue Relaxation Times in Different Mouse Models Assessed by Ultrahigh Field Magnetic Resonance Imaging.

    PubMed

    Müller, Andreas; Hochrath, Katrin; Stroeder, Jonas; Hittatiya, Kanishka; Schneider, Günther; Lammert, Frank; Buecker, Arno; Fries, Peter

    2017-01-01

    Recently, clinical studies demonstrated that magnetic resonance relaxometry with determination of relaxation times T1 and T2(⁎) may aid in staging and management of liver fibrosis in patients suffering from viral hepatitis and steatohepatitis. In the present study we investigated T1 and T2(⁎) in different models of liver fibrosis to compare alternate pathophysiologies in their effects on relaxation times and to further develop noninvasive quantification methods of liver fibrosis. MRI was performed with a fast spin echo sequence for measurement of T1 and a multigradient echo sequence for determination of T2(⁎). Toxic liver fibrosis was induced by injections of carbon tetrachloride (1.4 mL CCl4 per kg bodyweight and week, for 3 or 6 weeks) in BALB/cJ mice. Chronic sclerosing cholangitis was mimicked using the ATP-binding cassette transporter B4 knockout (Abcb4 (-/-)) mouse model. Untreated BALB/cJ mice served as controls. To assess hepatic fibrosis, we ascertained collagen contents and fibrosis scores after Sirius red staining. T1 and T2(⁎) correlate differently to disease severity and etiology of liver fibrosis. T2(⁎) shows significant decrease correlating with fibrosis in CCl4 treated animals, while demonstrating significant increase with disease severity in Abcb4 (-/-) mice. Measurements of T1 and T2(⁎) may therefore facilitate discrimination between different stages and causes of liver fibrosis.

  10. Probing rotational relaxation in HBr (v=1) using double resonance spectroscopy.

    PubMed

    Kabir, Md Humayun; Antonov, Ivan O; Heaven, Michael C

    2009-02-21

    Rotational energy transfer in HBr(v=1)+HBr collisions has been investigated using an optical pump-probe double resonance technique at ambient temperature. Rotationally state selective excitation of v=1 for rotational levels in the range J=0-9 was achieved by stimulated Raman pumping, and the evolution of population was monitored using (2+1) resonantly enhanced multiphoton ionization spectroscopy of the g (3) summation (-)-X (1) summation (+)(0-1) band. Collision-induced population transfer events with DeltaJrelaxation processes. Rate constant matrices were generated using fitting and scaling functions. The rate coefficients were best represented by the statistical power exponential gap law.

  11. Relaxation process and ferromagnetic resonance investigation of ferrofluids with Mn-Zn and Mn-Fe mixed ferrite particles

    NASA Astrophysics Data System (ADS)

    Mălăescu, I.; Ştefu, N.; Gabor, L.

    2001-09-01

    The magnetic relaxation processes in two ferrofluids with Mn 0.4Zn 0.6Fe 2O 4 (sample F1) and Mn 0.6Fe 0.4Fe 2O 4 (sample F2) mixed ferrite particles, dispersed in n-decan and kerosene, respectively, are investigated through the determination of components χ' and χ'' of the complex magnetic susceptibility in the range of (2-30) MHz. The values of the saturation magnetization of the two ferrofluids are M∞=5.28 kA/m for sample F1 and M∞=10.99 kA/m for sample F2. A maximum of the imaginary component χ'' was observed for both samples at frequencies of tens MHz. This maximum was assigned to relaxation processes of Néel type. The effective anisotropy constant K of the particles from the studied samples was evaluated, using both static and dynamic measurements and the values were found to be K1=6.12×10 3 J m -3 for the ferrofluid F1, and K2=5.60×10 3 J m -3 for the ferrofluid F2. From ferromagnetic resonance measurements, and based on the theoretical values computed for the Lande factor ( g), the effective anisotropy constants for the mixed ferrite particles in the studied ferrofluids and the anisotropy field values were determined using a new method. The values obtained in this way for the anisotropy constants K1 and K2 are compared to the ones determined from magnetic relaxation measurements.

  12. 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.

  13. Facile Preparation of a New Gadofullerene-Based Magnetic Resonance Imaging Contrast Agent with High 1H Relaxivity

    PubMed Central

    Shu, Chunying; Corwin, Frank D.; Zhang, Jianfei; Chen, Zhijian; Reid, Jonathan E.; Sun, Minghao; Xu, Wei; Sim, Jae Hyun; Wang, Chunru; Fatouros, Panos P.; Esker, Alan R.; Gibson, Harry W.; Dorn, Harry C.

    2009-01-01

    A new magnetic resonance imaging (MRI) contrast agent based on the trimetallic nitride templated (TNT) metallofullerene, Gd3N@C80, was synthesized by a facile method in high yield. The observed longitudinal and transverse relaxivities, r1 and r2, for water hydrogens in the presence of the water-soluble gadofullerene 2, Gd3N@C80(OH)~26(CH2CH2COOM)~16 (M = Na or H), are 207 and 282 mM-1s-1 (per C80 cage) at 2.4 T, respectively; these values are 50 times larger than those of Gd3+ poly(aminocarboxylate) complexes, such as commercial Omniscan® and Magnevist®. This high 1H relaxivity for this new hydroxylated and carboxylated gadofullerene derivative provides high signal enhancement at significantly lower Gd concentration as demonstrated by in vitro and in vivo MRI studies. Dynamic light scattering data reveal a unimodal size distribution with an average hydrodynamic radius of ca. 78 nm in pure water (pH = 7), which is significantly different from other hydroxylated or carboxylated fullerene and metallofullerene derivatives reported to date. Agarose gel infusion results indicate that the gadofullerene 2 displayed diffusion properties different from that of commercial Omniscan® and those of PEG5000 modified Gd3N@C80. The reactive carboxyl functionality present on this highly efficient contrast agent may also serve as a precursor for biomarker tissue-targeting purposes. PMID:19445504

  14. 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

  15. 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.

  16. 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.

  17. 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. © 2011 American Chemical Society

  18. Broadband ferromagnetic resonance characterization of anisotropies and relaxation in exchange-biased IrMn/CoFe bilayers

    NASA Astrophysics Data System (ADS)

    Beik Mohammadi, Jamileh; Jones, Joshua Michael; Paul, Soumalya; Khodadadi, Behrouz; Mewes, Claudia K. A.; Mewes, Tim; Kaiser, Christian

    2017-02-01

    The magnetization dynamics of exchange-biased IrMn/CoFe bilayers have been investigated using broadband and in-plane angle-dependent ferromagnetic resonance spectroscopy. The interface energy of the exchange bias effect in these bilayers exceeds values previously reported for metallic antiferromagnets. A strong perpendicular magnetic anisotropy and a small in-plane uniaxial anisotropy are also observed in these films. The magnetization relaxation of the bilayers has a strong unidirectional contribution, which is in part caused by two-magnon scattering. However, a detailed analysis of in-plane angle- and thickness-dependent linewidth data strongly suggests the presence of a previously undescribed unidirectional relaxation mechanism.

  19. 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

  20. Fetal response to abbreviated relaxation techniques. A randomized controlled study.

    PubMed

    Fink, Nadine S; Urech, Corinne; Isabel, Fornaro; Meyer, Andrea; Hoesli, Irène; Bitzer, Johannes; Alder, Judith

    2011-02-01

    stress during pregnancy can have adverse effects on the course of pregnancy and on fetal development. There are few studies investigating the outcome of stress reduction interventions on maternal well-being and obstetric outcome. this study aims (1) to obtain fetal behavioral states (quiet/active sleep, quiet/active wakefulness), (2) to investigate the effects of maternal relaxation on fetal behavior as well as on uterine activity, and (3) to investigate maternal physiological and endocrine parameters as potential underlying mechanisms for maternal-fetal relaxation-transferral. the behavior of 33 fetuses was analyzed during laboratory relaxation/quiet rest (control group, CG) and controlled for baseline fetal behavior. Potential associations between relaxation/quiet rest and fetal behavior (fetal heart rate (FHR), FHR variation, FHR acceleration, and body movements) and uterine activity were studied, using a computerized cardiotocogram (CTG) system. Maternal heart rate, blood pressure, cortisol, and norepinephrine were measured. intervention (progressive muscle relaxation, PMR, and guided imagery, GI) showed changes in fetal behavior. The intervention groups had higher long-term variation during and after relaxation compared to the CG (p=.039). CG fetuses had more FHR acceleration, especially during and after quiet rest (p=.027). Women in the PMR group had significantly more uterine activity than women in the GI group (p=.011) and than CG women. Maternal heart rate, blood pressure, and stress hormones were not associated with fetal behavior. this study indicates that the fetus might participate in maternal relaxation and suggests that GI is superior to PMR. This could especially be true for women who tend to direct their attention to body sensations such as abdominal activity. 2010 Elsevier Ltd. All rights reserved.

  1. Magnetic resonance spectroscopy in vivo of neurochemicals in a transgenic model of Alzheimer's disease: a longitudinal study of metabolites, relaxation time, and behavioral analysis in TASTPM and wild-type mice.

    PubMed

    Forster, Duncan; Davies, Karen; Williams, Steve

    2013-04-01

    Alzheimer's disease (AD) is the most common form of dementia in the elderly. Due to ongoing advances in our understanding of the underlying pathology of AD, many potential new targets for therapeutics are becoming available. Transgenic mouse models of AD have helped in furthering our understanding of AD and also provide a vehicle for preclinical testing of new, putative disease-modifying therapeutics, which may have potential for translation to use in clinical trials. To identify possible translational biomarkers, we have studied the longitudinal cerebral metabolic pattern of the TASTPM transgenic AD mouse, a double transgenic mouse overexpressing human mutant amyloid precursor protein (hAPP695swe) and presenilin-1 (M146V) by (1) H magnetic resonance spectroscopy, along with concurrent brain T1 /T2 mapping and behavioral testing. We found significant differences in creatine, glutamate, N-acetylaspartate, choline-containing compounds, and myo-inositol between TASTPM and wild-type mice. In the case of N-acetylaspartate and myo-inositol, there were similarities to differences detected in human AD. T1 /T2 values were shorter overall in TASTPM mice, indicating possible differences in water content between TASTPM and wild-type mice. In older TASTPM mice, exploratory behavior became more random, indicating a possible memory deficiency. The decrease in behavioral performance correlated in the transgenic group with higher expression of myo-inositol.

  2. 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.

  3. Relaxation dynamics of a quantum emitter resonantly coupled to a coherent state of a localized surface plasmon.

    PubMed

    Nerkararyan, Khachatur V; Bozhevolnyi, Sergey I

    2015-01-01

    We investigate the relaxation dynamics of a quantum dipole emitter (QDE), e.g., a molecule or quantum dot, located near a metal nanoparticle (MNP) exhibiting a dipolar localized surface plasmon (LSP) resonance at the frequency of the QDE radiative transition. A generic three-level QDE, which is pumped with an external laser pulse and thereby brought into an optically active excited state, is considered to be weakly coupled to the resonant LSP described by a coherent state. It is shown that, under the condition of the QDE-MNP characteristic relaxation time being much shorter than that of the QDE in free space but much longer than the LSP lifetime, the QDE relaxation dynamics can be described analytically and feature, in general, non-exponential decay with complicated transient behaviour. The main physical consequence of this relaxation process is that the emission, being largely determined by the MNP, comes out with a substantial delay. It is also shown that energy dissipation in the QDE-MNP system is relatively weak with the probability of the photon emission being ∼0.75, a number which, rather surprisingly, does not explicitly depend on the metal absorption characteristics. A large number of QDE-MNP system parameters in our analytical description open new possibilities for controlling quantum emitter dynamics.

  4. 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

  5. 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.

  6. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1990-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have concentrated on a theoretical treatment of pairs of tightly coupled spin {1/2} nuclei under magic angle spinning conditions. The average Hamiltonian theory developed here is required for a quantitative understanding of two dimensional NMR experiments of such spin pairs in solids. These experiments in turn provide a means of determining connectivities between resonances in solid state NMR spectra. Development of these techniques will allow us to establish connectivities between functional components in coals. The complete description of these spin dynamics has turned out to be complex, and is necessary to provide a foundation upon which such experiments may be quantitatively interpreted in complex mixtures such as coals. 25 refs., 4 figs., 3 tabs.

  7. Effects of fiber type and diet on nuclear magnetic resonance (NMR) relaxation times of skeletal muscle

    SciTech Connect

    Mardini, I.A.; McCarter, R.J.; Fullerton, G.D.

    1986-03-01

    NMR studies of muscle have typically used muscles of mixed fiber composition and have not taken into account the metabolic state of the host. Samples of psoas (type IIB fibers) and soleus (type I fibers) muscles were obtained from 3 groups of rabbits: group C, fed regular chow; group DK fed a potassium deficient diet; and group HC fed a high cholesterol diet. The T/sub 1/ and T/sub 2/ relaxation times of psoas and soleus muscles were not significantly different for group C. Following dietary manipulation, (groups KD and HC), however, the relaxation times of the psoas and soleus muscles were significantly different. There was also a significant difference in water content of psoas muscles in groups KD and HC vs. group C but the observed differences in NMR results could be only partially accounted for by the shift in water content. The authors results suggest that (1) changes in ion or cholesterol concentration are capable of inducing changes in water bonding and structuring in muscle tissues; (2) diet must be added to the growing list of environmental factors that can cause NMR contrast changes; (3) selective use of muscles rich in one fiber type or another for NMR measurements could provide either control or diagnostic information, related to changes in body composition.

  8. The effect of diffusion in internal gradients on nuclear magnetic resonance transverse relaxation measurements

    SciTech Connect

    Muncaci, S.; Ardelean, I.; Boboia, S.

    2013-11-13

    In the present work we study the internal gradient effects on diffusion attenuation of the echo train appearing in the well-known Carr-Purcell-Meiboom-Gill (CPMG) technique, extensively used for transverse relaxation measurements. Our investigations are carried out on two porous ceramics, prepared with the same amount of magnetic impurities (Fe{sub 2}O{sub 3}) but different pore sizes. It is shown that diffusion effects on the CPMG echo train attenuation are strongly influenced by the pore size for the same magnetic susceptibility of the two samples. The experimental results were compared with a theoretical model taking into account the limit of free or restricted diffusion on echo train attenuation. The NMR experiments were performed on water filled samples using a low-field NMR instrument. The porous ceramics were prepared using both the replica technique and the powder compression technique. Magnetic susceptibility measurements indicated close values of the susceptibility constant for the two samples whereas the SEM images indicated different pore sizes. The results reported here may have impact in the interpretation of NMR relaxation measurements of water in soils or concrete samples.

  9. 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.

  10. 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.

  11. A quantitative analysis of cardiac myocyte relaxation: a simulation study.

    PubMed

    Niederer, S A; Hunter, P J; Smith, N P

    2006-03-01

    The determinants of relaxation in cardiac muscle are poorly understood, yet compromised relaxation accompanies various pathologies and impaired pump function. In this study, we develop a model of active contraction to elucidate the relative importance of the [Ca2+]i transient magnitude, the unbinding of Ca2+ from troponin C (TnC), and the length-dependence of tension and Ca2+ sensitivity on relaxation. Using the framework proposed by one of our researchers, we extensively reviewed experimental literature, to quantitatively characterize the binding of Ca2+ to TnC, the kinetics of tropomyosin, the availability of binding sites, and the kinetics of crossbridge binding after perturbations in sarcomere length. Model parameters were determined from multiple experimental results and modalities (skinned and intact preparations) and model results were validated against data from length step, caged Ca2+, isometric twitches, and the half-time to relaxation with increasing sarcomere length experiments. A factorial analysis found that the [Ca2+]i transient and the unbinding of Ca2+ from TnC were the primary determinants of relaxation, with a fivefold greater effect than that of length-dependent maximum tension and twice the effect of tension-dependent binding of Ca2+ to TnC and length-dependent Ca2+ sensitivity. The affects of the [Ca2+]i transient and the unbinding rate of Ca2+ from TnC were tightly coupled with the effect of increasing either factor, depending on the reference [Ca2+]i transient and unbinding rate.

  12. Stochastic resonance whole body vibration increases perceived muscle relaxation but not cardiovascular activation: A randomized controlled trial

    PubMed Central

    Elfering, Achim; Burger, Christian; Schade, Volker; Radlinger, Lorenz

    2016-01-01

    AIM To investigate the acute effects of stochastic resonance whole body vibration (SR-WBV), including muscle relaxation and cardiovascular activation. METHODS Sixty-four healthy students participated. The participants were randomly assigned to sham SR-WBV training at a low intensity (1.5 Hz) or a verum SR-WBV training at a higher intensity (5 Hz). Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR) and self-reported muscle relaxation were assessed before and immediately after SR-WBV. RESULTS Two factorial analyses of variance (ANOVA) showed a significant interaction between pre- vs post-SR-WBV measurements and SR-WBV conditions for muscle relaxation in the neck and back [F(1,55) = 3.35, P = 0.048, η2 = 0.07]. Muscle relaxation in the neck and back increased in verum SR-WBV, but not in sham SR-WBV. No significant changes between pre- and post-training levels of SBD, DBD and HR were observed either in sham or verum SR-WBV conditions. With verum SR-WBV, improved muscle relaxation was the most significant in participants who reported the experience of back, neck or shoulder pain more than once a month (P < 0.05). CONCLUSION A single session of SR-WBV increased muscle relaxation in young healthy individuals, while cardiovascular load was low. An increase in musculoskeletal relaxation in the neck and back is a potential mediator of pain reduction in preventive worksite SR-WBV trials. PMID:27900274

  13. Spin wave resonance and relaxation in microwave magnetic multilayer structures and devices

    NASA Astrophysics Data System (ADS)

    Wu, Cheng

    The continuous and increasing demand for higher frequency magnetic microwave structures triggered a tremendous development in the field of magnetization dynamics over the past decade. In order to develop smaller and faster devices, more efforts are required to achieve a better understanding of the complex magnetization precessional dynamics, the magnetization anisotropy, and the sources of spin scattering at the nanoscale. This thesis presents measurements of magnetic precession and relaxation dynamics in multilayer ferromagnetic films of CoFe/PtMn/CoFe in both frequency and time domain. First, we conducted the ferromagnetic resonance (FMR) measurements for samples with the ferromagnetic CoFe layer thicknesses varying from 10 A to 500 A. The magnetic anisotropic parameters were determined by rotating the field aligned axis with respect to the spectral field in the configurations of both in-plane and out-of-plane. Moreover, we identified a high-order standing spin wave in our spectra and found a "critical angle" in the multilayer samples. We included an effective surface anisotropy field to describe our results. This allows us to determine the exchange interaction stiffness in the CoFe layers. Next, we performed pump-probe Magneto-Optical Kerr Effect experiments in the multilayer films. Three precession modes were observed in the Voigt geometry. The modes are assigned to the exchange-dominated spin wave excitations and the non-homogeneous dipole mode. We developed a comprehensive model of the magnetic eigenmodes and their coupling to light to gain accurate values of the exchange, bulk and surface anisotropy constants. The results are consistent with those from the FMR measurements. Finally, the measured resonance linewidths of CoFe/PtMn/CoFe films were analyzed by the thickness dependence of the CoFe layers. We discussed the contribution of the Gilbert damping, two magnon scattering, as well as surface and interface to the FMR linewidth and concluded the two magnon

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

    SciTech Connect

    King, Jason Christopher

    1995-05-01

    Photodissociation of M(CO)6 (M=Cr,Mo,W) and the formation of solvated M(CO)5•S complex was studied in cyclohexane; rate-limiting step is vibrational energy relaxation from the new bond to the solvent. For both M=Cr and Mo, the primary relaxation occurs in 18 ps; for Cr, there is an additional vibrational relaxation (150 ps time scale) of a CO group poorly coupled to other modes. Relaxation of M=W occurs in 42 ps; several possible mechanisms for the longer cooling are discussed. Vibrational relaxation is also investigated for I2- and IBr- in nonpolar and slightly polar solvents. Attempts were made to discover the mechanism for the fast energy transfer in nonpolar solvent. The longer time scale dynamics of I3- and IBr2- were also studied; both formed a metastable complex following photodissociation and 90-95% return to ground state in 100 ps, implying a barrier to recombination of 4.3 kcal/mol and a barrier to escape of ≥5.5 kcal/mol. The more complex photochemistry of M3(CO)12 (M=Fe,Ru) is also investigated, using visible and ultraviolet radiations, dissociation, geminate recombination, vibrational relaxation, and bridging structures and their reactions were studied. Attempts were made to extend ultrafast spectroscopy into the mid-infrared, but signal-to-noise was poor.

  15. Investigation of vibrational relaxation of hydrogen selenide by the method of double IR resonance

    SciTech Connect

    Rutkovskii, K.S.

    1995-06-01

    Signals of transient absorption and relaxation processes in gaseous mixtures of H{sub 2}Se with He, Ar, and HCl are investigated by way of selective vibrational excitation. Noticeable disagreement between theoretical and experimental values of the vibrational relaxation rates is found. 9 refs., 1 fig., 3 tabs.

  16. Resonant spin amplification in nanostructures with anisotropic spin relaxation and spread of the electronic g factor

    SciTech Connect

    Glazov, M. M. Ivchenko, E. L.

    2008-08-15

    Spin dynamics of electrons in semiconductors and structures with quantum wells under conditions where pumping and probing are performed in the form of a periodical series of pulses is theoretically studied. It is shown that, at a fixed delay between the pump and probe pulses, the signal of spin amplification as a function of the magnetic field consists of a series of narrow peaks conditioned by commensurability of the period of spin precession and pulse repetition interval. In the case of anisotropic spin relaxation, the peak centered at the zero magnetic field is suppressed compared with the neighboring peaks. The role of inhomogeneous broadening of the frequency of the Larmor precession in the formation of the spin amplification signal is analyzed.

  17. Holographic Grating Relaxation Studies of Probe Diffusion in Amorphous Polymers

    DTIC Science & Technology

    1994-06-15

    Relaxation, Chromophore Diffusion in PS, PMMA, PVAc, Polybutadiene, Polyethylmethacryla ;% PRICE cooE Effects of Glass Transition, chain branching. 17...properties such as molecular weight, glass transition temperature (Tg) and chain conformation on the probe diffusion coefficient, and effects of polymer...crosslinking and plasticising on the same process are also studied. Page 4 Experimental Matels • Camphorquinone (CQ), thymorquinone (TM) and diacetyl (DA

  18. 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.

  19. Nuclear magnetic resonance studies of lens transparency

    SciTech Connect

    Beaulieu, C.F.

    1989-01-01

    Transparency of normal lens cytoplasm and loss of transparency in cataract were studied by nuclear magnetic resonance (NMR) methods. Phosphorus ({sup 31}P) NMR spectroscopy was used to measure the {sup 31}P constituents and pH of calf lens cortical and nuclear homogenates and intact lenses as a function of time after lens enucleation and in opacification produced by calcium. Transparency was measured with laser spectroscopy. Despite complete loss of adenosine triphosphate (ATP) within 18 hrs of enucleation, the homogenates and lenses remained 100% transparent. Additions of calcium to ATP-depleted cortical homogenates produced opacification as well as concentration-dependent changes in inorganic phosphate, sugar phosphates, glycerol phosphorylcholine and pH. {sup 1}H relaxation measurements of lens water at 200 MHz proton Larmor frequency studied temperature-dependent phase separation of lens nuclear homogenates. Preliminary measurements of T{sub 1} and T{sub 2} with non-equilibrium temperature changes showed a change in the slope of the temperature dependence of T{sub 1} and T{sub 2} at the phase separation temperature. Subsequent studies with equilibrium temperature changes showed no effect of phase separation on T{sub 1} or T{sub 2}, consistent with the phase separation being a low-energy process. {sup 1}H nuclear magnetic relaxation dispersion (NMRD) studies (measurements of the magnetic field dependence of the water proton 1/T{sub 1} relaxation rates) were performed on (1) calf lens nuclear and cortical homogenates (2) chicken lens homogenates, (3) native and heat-denatured egg white and (4) pure proteins including bovine {gamma}-II crystallin bovine serum albumin (BSA) and myoglobin. The NMRD profiles of all samples exhibited decreases in 1/T{sub 1} with increasing magnetic field.

  20. 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.

  1. Structure-redox-relaxivity relationships for redox responsive manganese-based magnetic resonance imaging probes.

    PubMed

    Gale, Eric M; Mukherjee, Shreya; Liu, Cynthia; Loving, Galen S; Caravan, Peter

    2014-10-06

    A library of 10 Mn-containing complexes capable of switching reversibly between the Mn(II) and Mn(III) oxidation states was prepared and evaluated for potential usage as MRI reporters of tissue redox activity. We synthesized N-(2-hydroxybenzyl)-N,N',N'-ethylenediaminetriacetic acid (HBET) and N-(2-hydroxybenzyl-N,N',N'-trans-1,2-cyclohexylenediaminetriacetic acid (CyHBET) ligands functionalized (-H, -OMe, -NO2) at the 5-position of the aromatic ring. The Mn(II) complexes of all ligands and the Mn(III) complexes of the 5-H and 5-NO2 functionalized ligands were synthesized and isolated, but the Mn(III) complexes with the 5-OMe functionalized ligands were unstable. (1)H relaxivity of the 10 isolable complexes was measured at pH 7.4 and 37 °C, 1.4 T. Thermodynamic stability, pH-dependent complex speciation, hydration state, water exchange kinetics of the Mn(II) complexes, and pseudo-first order reduction kinetics of the Mn(III) complexes were studied using a combination of pH-potentiometry, UV-vis spectroscopy, and (1)H and (17)O NMR measurements. The effects of ligand structural and electronic modifications on the Mn(II/III) redox couple were studied by cyclic voltammetry. The Mn(II) complexes are potent relaxation agents as compared to the corresponding Mn(III) species with [Mn(II)(CyHBET)(H2O)](2-) exhibiting a 7.5-fold higher relaxivity (3.3 mM(-1) s(-1)) than the oxidized form (0.4 mM(-1) s(-1)). At pH 7.4, Mn(II) exists as a mixture of fully deprotonated (ML) and monoprotonated (HML) complexes and Mn(II) complex stability decreases as the ligands become more electron-releasing (pMn for 10 μM [Mn(II)(CyHBET-R')(H2O)](2-) decreases from 7.6 to 6.2 as R' goes from -NO2 to -OMe, respectively). HML speciation increases as the electron-releasing nature of the phenolato-O donor increases. The presence of a water coligand is maintained upon conversion from HML to ML, but the water exchange rate of ML is faster by up to 2 orders of magnitude (k(ex)(310) for H

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

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung

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

  3. A Comparative Study of T1 and T2 Relaxation in Shale

    NASA Astrophysics Data System (ADS)

    Keating, K.; Obasi, C. C.; Pashin, J. C.

    2015-12-01

    Nuclear magnetic resonance (NMR) relaxation measurement have been used extensively in petroleum and, more recently, in groundwater resource evaluation to estimate the porosity, pore-size distributions, permeability, fluid saturation, and fluid mobility. In shale, the transverse decay rate of NMR signal is sensitive to the microporosity, but is also affected by the paramagnetic contributions of clay and other iron-bearing minerals. Furthermore, contrasts in the magnetic susceptibility of the mineral matrix and pore fluids that result in an inhomogeneous magnetic field within the pore space results in an extra term in transverse relaxation. These issues can cause errors in NMR-based estimates of pore-size distribution and permeability. In this study we compare T1 and T2 relaxation time distributions in order to study the molecular mechanism of relaxation in brine-saturated mixtures of clay and other common minerals. We collected measurements on a range of mixtures of clay minerals common in shale (illite, glauconite, celadonite, chamosite, montmorillonite and kaolinite) and pyrite. To constrain the interpretation of the NMR data, we measured the magnetic susceptibility and surface area of all samples. We are confident that by accounting for the presence and variations of clay and pyrite in shale, we can substantially improve both the NMR estimate of pore-size distribution and permeability.

  4. Relaxation of a granular step: An experimental study

    NASA Astrophysics Data System (ADS)

    Siavoshi, Saloome; Kudrolli, Arshad

    2003-03-01

    We study the evolution of a granular step as it relaxes under the influence of gravity. This evolution has been described by Boutreux and de Gennes (1997) using a continuum model that involves immobile and rolling regions. They predict that the step relaxes to an angle which is less than the angle of repose. We make a rectangular pile of height h and length l using steel beads between two vertical glass plates. The grains are initially held in place using magnetic fields produced by an electromagnet. When the current is switched off, the vertical front of the pile relaxes to an angle which is less than the angle of repose. We measure the surface profile of the pile and the velocity of the particles by using high speed imaging and direct particle tracking. We find that the initial failure of the pile occurs at the surface. The depth of the flow first increases and then decreases as the pile relaxes. We change system parameters by varying h,l and the particle diameter. We will discuss our experimental results and comparisons to continuum models. The study may also be relevant to the modeling of landslides.

  5. 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.

  6. Zero-field studies of spin-lattice relaxation processes in non-Kramers doublet of LiF:Ni2+

    NASA Astrophysics Data System (ADS)

    Azamat, D. V.; Badalyan, A. G.; Dejneka, A.; Jastrabik, L.; Lančok, J.

    2016-12-01

    We use the inversion recovery technique with electron-spin-echo detection in order to study the non-resonant cross-relaxation of Ni2+-VLi with a faster relaxers—the exchange-coupled clusters of Ni2+ ions. An analysis of the results revealed a very high relaxation rate in non-Kramers doublet of LiF:Ni2+. The effect of a magnetic field on the spin-lattice relaxation of Ni2+ has estimated by comparing the results obtained for non-Kramers doublet around zero-magnetic field and for resonance at 394 mT (X-band microwave frequency).

  7. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    SciTech Connect

    Sachleben, Joseph Robert

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and 13C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution 1H and 13C 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 Å. Internal motion is estimated to be slow with a correlation time > 10-8 s-1. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O2 and ultraviolet. A method for measuring 14N-1H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T1 and T2 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 13C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  8. 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.

  9. 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…

  10. 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…

  11. 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.

  12. Two-Photon Excitation and Relaxation of the 3d-4d Resonance in Atomic Kr

    SciTech Connect

    Meyer, M.; Cubaynes, D.; Richardson, V.; Costello, J. T.; Radcliffe, P.; Li, W. B.; Duesterer, S.; Fritzsche, S.; Mihelic, A.; Papamihail, K. G.; Lambropoulos, P.

    2010-05-28

    Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes.

  13. Magnetic resonance imaging (MRI) and relaxation spectrum analysis as methods to investigate swelling in whey protein gels.

    PubMed

    Oztop, Mecit H; Rosenberg, Moshe; Rosenberg, Yael; McCarthy, Kathryn L; McCarthy, Michael J

    2010-10-01

    Effective means for controlled delivery of nutrients and nutraceuticals are needed. Whey protein-based gels, as a model system and as a potential delivery system, exhibit pH-dependent swelling when placed in aqueous solutions. Understanding the physics that govern gel swelling is thus important when designing gel-based delivery platforms. The extent of swelling over time was monitored gravimetrically. In addition to gravimetric measurements, magnetic resonance imaging (MRI) a real-time noninvasive imaging technique that quantified changes in geometry and water content of these gels was utilized. Heat-set whey protein gels were prepared at pH 7 and swelling was monitored in aqueous solutions with pH values of 2.5, 7, and 10. Changes in dimension over time, as characterized by the number of voxels in an image, were correlated to gravimetric measurements. Excellent correlations between mass uptake and volume change (R(2)= 0.99) were obtained for the gels in aqueous solutions at pH 7 and 10, but not for gels in the aqueous solution at pH 2.5. To provide insight into the mechanisms for water uptake, nuclear magnetic resonance (NMR) relaxation times were measured in independent experiments. The relaxation spectrum for the spin-spin relaxation time (T(2)) showed the presence of 3 proton pools for pH 7 and 10 trials and 4 proton pools for pH 2.5 trials. Results demonstrate that MRI and NMR relaxation measurements provided information about swelling in whey protein gels that can constitute a new means for investigating and developing effective delivery systems for foods.

  14. Resonance Raman spectra of an O2-binding H-NOX domain reveal heme relaxation upon mutation†

    PubMed Central

    Tran, Rosalie; Boon, Elizabeth M.; Marletta, Michael A.; Mathies, Richard A.

    2009-01-01

    Resonance Raman spectra are measured for Tt H-NOX WT and three other Tt H-NOX proteins containing mutations at key conserved residues to determine the heme conformation in solution. The most dramatic changes in heme conformation occurred in the O2-bound forms, and the single Tt H-NOX P115A mutation was sufficient to generate a significant relaxation of the chromophore. Clear evidence of heme relaxation in the Tt H-NOX I5L, P115A, and I5L/P115A mutants in solution is demonstrated by the observation of reduced resonance Raman intensities for several out-of-plane low frequency modes (e.g. γ11, γ12, γ13, and γ15) in the 400–750 cm−1 region known to be sensitive to ruffling and saddling deformations, as well as increased vibrational frequencies for the core heme skeletal stretching modes, ν3, ν2, and ν10. In addition, all three mutants exhibited some degree of heme conformational heterogeneity based on several broad skeletal markers (e.g. ν10) in the high frequency region. These results are comparable to those observed by Olea et al. for Tt H-NOX P115A in crystal form, where four different heme structures were determined from a single unit cell. Based on the resonance Raman spectra, it is clear that the actual heme conformation for Tt H-NOX P115A in solution is considerably more relaxed than WT, with increased flexibility within the protein pocket, allowing for rapid sampling of alternate conformations. PMID:19653642

  15. Advanced new relaxation filter-selective signal excitation methods for (13)C solid-state nuclear magnetic resonance.

    PubMed

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

    2014-10-21

    We have developed new relaxation filter-selective signal excitation (RFS) methods for (13)C solid-state NMR, which enable extraction of the spectrum of a target component from a mixture of several components. These methods are based on the equalization of proton relaxation time in a single domain via rapid intraproton spin diffusion and the difference in proton relaxation time of individual components in the mixture. We recently reported two types of RFS methods using proton spin-lattice relaxation time in the rotating frame ((1)H T1rho) in (13)C solid-state nuclear magnetic resonance (NMR) spectroscopy. Here, to increase the availability of RFS methods, we focus on proton spin-lattice relaxation time ((1)H T1). Introduction of simple pulse sequences to one-dimensional experiments reduced data acquisition time and increased flexibility, and led to the development of two new types of RFS methods using (1)H T1. We then demonstrated these methods by selectively exciting the (13)C signals of target components in a commercially available drug and a number of physical mixtures, and we showed them to be applicable to the quantitative analysis of individual components in these solid mixtures with an experimental duration of 1.5 to about 10 h. The practicality and versatility of these four RFS methods were increased by combining two or more of them, or by using a flip-back pulse, which is an effective means of shortening experimental duration. These RFS methods are suitable for use in a broad range of fields.

  16. Femtosecond spectroscopic studies of the lattice relaxation initiated by interacting electron-hole pairs under relaxation in alkali halides

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Iwai, S.; Tokizaki, T.; Tanimura, K.; Nakamura, A.; Itoh, N.

    1994-05-01

    Femtosecond time-resolved spectroscopic studies have been carried out to reveal the relaxation of free electron-hole pairs in KBr. We find that a hole is relaxed to a self-trapped hole with a delay of 10 ps. Two relaxation channels of an electron-hole pair are found: one lasts for 40 ps and leads competitively to a self-trapped exciton (STE) or an F-H pair; the other terminates within 6 ps, bypasses the STE, and leads to an F-H pair. The former channel is ascribed to the interplay between an electron and a self-trapped hole, while the latter demonstrates the dynamic interplay of an electron and a hole during their lattice relaxation.

  17. Magnetic Resonance Studies of Photosensitizers and Their Effect in Tumors

    DTIC Science & Technology

    2003-08-01

    Presentations Research Colloquium Poster Session on "In Vivo Magnetic Resonance Measurements of Lithium in Rat Hind Limb" Presented at the University...Medical Center,August 2002 "The Effects of Fluoxetine on Lithium Blood Levels in Rats ." Presented at the University of Nebraska Medical Center,August...2002. Pharmacokinetics and relaxivity of Lithium in Rat Thigh Muscle by MR Studies E. Rzepkal , S. Ramaprasad’ ,Presented at the 1 1th ISMRM

  18. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1988-01-01

    This report covers the progress made on the title project during the current reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. This quarter we have focused on variable temperature spin lattice relaxation measurements for several of the Argonne coals. 5 figs.

  19. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1988-01-01

    This report covers the progress made on the title project during the current reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. This quarter we have focussed on spin lattice relaxation measurements for several of the Argonne coals. 2 figs., 1 tab.

  20. A chemical relaxation study of human prostatic acid phosphatase.

    PubMed

    Shear, D B; Kustin, K

    1968-01-01

    Chemical relaxation methods and a dilution technique were applied to the study of the hydrolysis of p-nitrophenyl phosphate by human prostatic acid phosphatase. Although the reaction mechanism was not elucidated, rate constants and equilibrium constants were obtained for the reaction of enzyme and p-nitrophenol to form a complex. A slow, 2-sec relaxation effect which showed no concentration dependence was observed in various reaction mixtures, including some lacking the substrate and products of the hydrolytic reaction. The conclusion drawn is that there are two forms of the prostatic enzyme, which are normally in equilibrium with each other, but which undergo a relatively slow interconversion when this equilibrium is perturbed. A preliminary calculation indicates that these forms are present in the equilibrium ratio of 2:1.

  1. Graphene oxide-Fe3O4 nanoparticle composite with high transverse proton relaxivity value for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The potential of graphene oxide-Fe3O4 nanoparticle (GO-Fe3O4) 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-Fe3O4 composites synthesized by precipitating Fe3O4 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-Fe3O4 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-Fe3O4 composites possessed good biocompatibility with normal cell lines, whereas they exhibited considerable toxicity towards breast cancer cells.

  2. 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.

  3. 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.

  4. Study of dielectric relaxations of anhydrous trehalose and maltose glasses

    NASA Astrophysics Data System (ADS)

    Kwon, Hyun-Joung; Seo, Jeong-Ah; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2011-01-01

    We investigated the frequency dependent dielectric relaxation behaviors of anhydrous trehalose and maltose glasses in the temperature range which covers a supercooled and glassy states. In addition to the α-, Johari-Goldstein (JG) β-, and γ-relaxations in a typical glass forming system, we observed an extra relaxation process between JG β- and γ-relaxations in the dielectric loss spectra. We found that the unknown extra relaxation is a unique property of disaccharide which might originate from the intramolecular motion of flexible glycosidic bond. We also found that the temperature dependence of the JG β-relaxation time changes at 0.95Tg and it might be universal.

  5. Magnetic Resonance Water Proton Relaxation in Protein Solutions and Tissue: T1ρ Dispersion Characterization

    PubMed Central

    Chen, Enn-Ling; Kim, Raymond J.

    2010-01-01

    Background Image contrast in clinical MRI is often determined by differences in tissue water proton relaxation behavior. However, many aspects of water proton relaxation in complex biological media, such as protein solutions and tissue are not well understood, perhaps due to the limited empirical data. Principal Findings Water proton T1, T2, and T1ρ of protein solutions and tissue were measured systematically under multiple conditions. Crosslinking or aggregation of protein decreased T2 and T1ρ, but did not change high-field T1. T1ρ dispersion profiles were similar for crosslinked protein solutions, myocardial tissue, and cartilage, and exhibited power law behavior with T1ρ(0) values that closely approximated T2. The T1ρ dispersion of mobile protein solutions was flat above 5 kHz, but showed a steep curve below 5 kHz that was sensitive to changes in pH. The T1ρ dispersion of crosslinked BSA and cartilage in DMSO solvent closely resembled that of water solvent above 5 kHz but showed decreased dispersion below 5 kHz. Conclusions Proton exchange is a minor pathway for tissue T1 and T1ρ relaxation above 5 kHz. Potential models for relaxation are discussed, however the same molecular mechanism appears to be responsible across 5 decades of frequencies from T1ρ to T1. PMID:20052404

  6. Analysis of Molecular Interaction of Drugs Within β-Cyclodextrin Cavity by Solution State Nuclear Magnetic Resonance (NMR) Relaxation.

    PubMed

    Kumar, Deepak; Krishnan, Yogeshwaran; Paranjothy, Manikandan; Pal, Samanwita

    2017-03-09

    The prime focus of the present study is to employ NMR relaxation measurement to address the intermolecular interactions as well as motional dynamics of drugs viz., paracetamol and aspirin encapsulated within β-cyclodextrin (β-CD) cavity. In this report we have attempted to demonstrate the applicability of nonselective (R1(ns) ), selective (R1(se)) and bi-selective (R1(bs)) spin-lattice relaxation rates to infer dynamical parameters e.g., molecular rotational correlation times (τc) and cross-relaxation rates (σij) of the encapsulated drugs. Molecular rotational correlation times of the free drugs were calculated using selective relaxation rate in the fast molecular motion time regime ( ωH(2)τc(2)<1 and R1(ns)/R1(se)≈ 1.500), whereas that of the 1:1 complexed drugs were found from the ratio of R1(ns)/R1(se) in the intermediate motion time regime ( ωH(2)τc(2)≈ 1 and R1(ns)/R1(se) ≈ 1.054) and compared with each other to confirm the formation of inclusion complexes. Furthermore the cross-relaxation rates have been used to evaluate the intermolecular proton distances. Also, density functional theory (DFT) calculations were performed to determine the minimum energy geometry of the inclusion complexes and the results compared with experiments. The report thus presents the possibility of utilizing NMR relaxation data, a more cost effective experiments to calculate internuclear distances in case of drug-supramolecule complexes that are generally addressed by extremely time consuming 2D Nuclear Overhauser Enhancement (NOE) based methods. Plausible mode of insertion of drug molecules into the β-CD cavity has also been described based on experimental NMR relaxation data analysis.

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

    DOE PAGES

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

    2017-04-03

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  9. The nuclear magnetic resonance relaxation data analysis in solids: General R1/R1ρ equations and the model-free approach

    NASA Astrophysics Data System (ADS)

    Kurbanov, Rauf; Zinkevich, Tatjana; Krushelnitsky, Alexey

    2011-11-01

    The advantage of the solid state NMR for studying molecular dynamics is the capability to study slow motions without limitations: in the liquid state, if orienting media are not used, all anisotropic magnetic interactions are averaged out by fast overall Brownian tumbling of a molecule and thus investigation of slow internal conformational motions (e.g., of proteins) in solution can be conducted using only isotropic interactions. One of the main tools for obtaining amplitudes and correlation times of molecular motions in the μs time scale is measuring relaxation rate R1ρ. Yet, there have been a couple of unresolved problems in the quantitative analysis of the relaxation rates. First, when the resonance offset of the spin-lock pulse is used, the spin-lock field can be oriented under an arbitrary angle in respect to B0. Second, the spin-lock frequency can be comparable or even less than the magic angle spinning rate. Up to now, there have been no equations for R1ρ that would be applicable for any values of the spin-lock frequency, magic angle spinning rate and resonance offset of the spin-lock pulse. In this work such equations were derived for two most important relaxation mechanisms: heteronuclear dipolar coupling and chemical shift anisotropy. The validity of the equations was checked by numerical simulation of the R1ρ experiment using SPINEVOLUTION program. In addition to that, the applicability of the well-known model-free approach to the solid state NMR relaxation data analysis was considered. For the wobbling in a cone at 30° and 90° cone angles and two-site jump models, it has been demonstrated that the auto-correlation functions G0(t), G1(t), G2(t), corresponding to different spherical harmonics, for isotropic samples (powders, polycrystals, etc.) are practically the same regardless of the correlation time of motion. This means that the model-free approach which is widely used in liquids can be equally applied, at least assuming these two motional

  10. Dielectric Relaxation in Dimethyl Sulfoxide/Water Mixtures Studied by Microwave Dielectric Relaxation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Zijie; Manias, Evangelos; MacDonald, Digby D.; Lanagan, Michael

    2009-10-01

    Dielectric spectra of dimethyl sulfoxide (DMSO)/water mixtures, over the entire concentration range, have been measured using the transmission line method at frequencies from 45 MHz to 26 GHz and at temperatures of 298-318 K. The relaxation times of the mixtures show a maximum at an intermediate molar fraction of DMSO. The specific structure of mixtures in different concentration regions was determined by the dielectric relaxation dynamics, obtained from the effect of temperature on the relaxation time. A water structure "breaking effect" is observed in dilute aqueous solutions. The average number of hydrogen bonds per water molecule in these mixtures is found to be reduced compared to pure water. The increase in the dielectric relaxation time in DMSO/water mixtures is attributed to the spatial (steric) constraints of DMSO molecules on the hydrogen-bond network, rather than being due to hydrophobic hydration of the methyl groups. The interaction between water and DMSO by hydrogen bonding reaches a maximum at a DMSO molar fraction of 0.33, reflected by the maximum activation enthalpy for dielectric relaxation in this concentration, suggesting the formation of a stoichiometric compound, H2O-DMSO-H2O. In highly concentrated solutions, negative activation entropies are observed, indicating the presence of aggregates of DMSO molecules. A distinct antiparallel arrangement of dipoles is obtained for neat DMSO in the liquid state according to the Kirkwood correlation factor (gK = 0.5), calculated from the static permittivity. The similarity of the dielectric behavior of pure DMSO and DMSO-rich mixtures suggests that dipole-dipole interactions contribute significantly to the rotational relaxation process in these solutions.

  11. Progress towards energy relaxation studies in an ultracold dual-species Yb/Ca plasma

    NASA Astrophysics Data System (ADS)

    Bergeson, Scott; Kleinert, Michaela

    2016-10-01

    Ultracold neutral plasmas provide a unique laboratory system for studying dynamics of strongly coupled Coulomb systems. The precision spectroscopy and imaging tools of atomic physics are brought to bear on these systems of resonantly-ionized laser-cooled atoms. We have simultaneously laser-cooled and trapped Yb and Ca atoms at densities of 1010cm-3 . The Yb and Ca atoms differ by a factor of 4 in mass. Using resonant laser excitation, we selectively ionize the two different species for the purpose of studying energy relaxation in a strongly coupled Coulomb system. The strong coupling parameter and ion mass ratio are expected to be relevant to equilibration studies in warm dense matter experiments. Sequential ionization of the two species allows the later-ionized system to abruptly perturb the first one. Adjusting the stoichiometry of the plasma allows us to carefully determine the amount of additional heat deposited into the plasma. Molecular dynamics simulations suggest that in some regimes, the energy relaxation is nearly chaotic. This talk will summarize our progress towards ultracold plasma work in this dual-species system. Supported in part by NSF (PHY-1500376) and AFOSR (FA9950-12-1-0308).

  12. Review of /sup 1/H nuclear magnetic resonance relaxation in pathology: are T1 and T2 diagnostic

    SciTech Connect

    Bottomley, P.A.; Hardy, C.J.; Argersinger, R.E.; Allen-Moore, G.

    1987-01-01

    The longitudinal (T1) and transverse (T2) proton (1H) nuclear magnetic resonance (NMR) relaxation times of pathological human and animal tissues in the frequency range 1-100 MHz are archived, reviewed, and analyzed as a function of tissue of origin, NMR frequency, temperature, species, and in vivo versus in vitro status. T1 data from specific disease states of the bone, brain, breast, kidney, liver, muscle, pancreas, and spleen can be characterized by simple dispersions of the form T1 = AvB in the range 1-100 MHz with A and B empirically determined pathology-dependent constants. Pathological tissue T2 values are essentially independent of NMR frequency. Raw relaxation data, best-fit T1 parameters A and B, and the mean T2 values, are tabulated along with standard deviations and sample size to establish the normal range of pathological tissue relaxation times applicable to NMR imaging or in vitro NMR examination. Statistical analysis of relaxation data, assumed independent, reveals that most tumor and edematous tissue T1 values and some breast, liver, and muscle tumor T2 values are significantly elevated relative to normal, but do not differ significantly from other tumors and pathologies. Statistically significant abnormalities in the T1 values of some brain, breast, and lung tumors, and most pathological tissue T2 values could not, however, be demonstrated in the presence of large statistical errors. Both T1 and T2 in uninvolved tissue from tumor-bearing animals or organs do not demonstrate statistically significant differences from normal when considered as a group, suggesting no appreciable systemic effects associated with the presence of tumors compared to the statistical uncertainty.261 references. (Abstract Truncated)

  13. An open-source software tool for the generation of relaxation time maps in magnetic resonance imaging.

    PubMed

    Messroghli, Daniel R; Rudolph, Andre; Abdel-Aty, Hassan; Wassmuth, Ralf; Kühne, Titus; Dietz, Rainer; Schulz-Menger, Jeanette

    2010-07-30

    In magnetic resonance (MR) imaging, T1, T2 and T2* relaxation times represent characteristic tissue properties that can be quantified with the help of specific imaging strategies. While there are basic software tools for specific pulse sequences, until now there is no universal software program available to automate pixel-wise mapping of relaxation times from various types of images or MR systems. Such a software program would allow researchers to test and compare new imaging strategies and thus would significantly facilitate research in the area of quantitative tissue characterization. After defining requirements for a universal MR mapping tool, a software program named MRmap was created using a high-level graphics language. Additional features include a manual registration tool for source images with motion artifacts and a tabular DICOM viewer to examine pulse sequence parameters. MRmap was successfully tested on three different computer platforms with image data from three different MR system manufacturers and five different sorts of pulse sequences: multi-image inversion recovery T1; Look-Locker/TOMROP T1; modified Look-Locker (MOLLI) T1; single-echo T2/T2*; and multi-echo T2/T2*. Computing times varied between 2 and 113 seconds. Estimates of relaxation times compared favorably to those obtained from non-automated curve fitting. Completed maps were exported in DICOM format and could be read in standard software packages used for analysis of clinical and research MR data. MRmap is a flexible cross-platform research tool that enables accurate mapping of relaxation times from various pulse sequences. The software allows researchers to optimize quantitative MR strategies in a manufacturer-independent fashion. The program and its source code were made available as open-source software on the internet.

  14. Effects of Studying to Music and Post-Study Relaxation on Reading Comprehension.

    ERIC Educational Resources Information Center

    Etaugh, Claire; Ptasnik, Patricia

    1982-01-01

    Twenty female and 20 male college students studied a passage in quiet surroundings or while listening to preferred music and then either relaxed or read unrelated material. Reading comprehension of the passage was facilitated by silent study for subjects who seldom listen to music and by poststudy relaxation. (Author)

  15. Instantaneous normal modes, resonances, and decay channels in the vibrational relaxation of the amide I mode of N-methylacetamide-D in liquid deuterated water.

    PubMed

    Bastida, Adolfo; Soler, Miguel Angel; Zúñiga, José; Requena, Alberto; Kalstein, Adrián; Fernández-Alberti, Sebastián

    2010-06-14

    A nonequilibrium molecular dynamics (MD) study of the vibrational relaxation of the amide I mode of deuterated N-methylacetamide (NMAD) in aqueous (D(2)O) solution is carried out using instantaneous normal modes (INMs). The identification of the INMs as they evolve over time, which is necessary to analyze the energy fluxes, is made by using a novel algorithm which allows us to assign unequivocally each INM to an individual equilibrium normal mode (ENM) or to a group of ENMs during the MD simulations. The time evolution of the energy stored in each INM is monitored and the occurrence of resonances during the relaxation process is then investigated. The decay of the amide I mode, initially excited with one vibrational quantum, is confirmed to fit well to a biexponential function, implying that the relaxation process involves at least two mechanisms with different rate constants. By freezing the internal motions of the solvent, it is shown that the intermolecular vibration-vibration channel to the bending modes of the solvent is closed. The INM analysis reveals then the existence of a major and faster decay channel, which corresponds to an intramolecular vibrational redistribution process and a minor, and slower, decay channel which involves the participation of the librational motions of the solvent. The faster relaxation pathway can be rationalized in turn using a sequential kinetic mechanism of the type P-->M+L-->L, where P (parent) is the initially excited amide I mode, and M (medium) and L (low) are specific midrange and lower-frequency NMAD vibrational modes, respectively.

  16. [Comparative study of the psychophysiologic relaxation effects of an optic-acoustic mind machine with relaxation music].

    PubMed

    Brauchli, P

    1993-01-01

    The present study was designed to test the effectiveness of an optical-acoustic mind machine (brain machine) in inducing relaxation. The mind machine used in this study stimulates the user with flickers of light and pulsating sounds. During the treatment the stimulation decreases from 10 to 2 hertz and increases again at half time. No other relaxation inducing effects were used. Sixteen subjects received two or three sessions of instruction with the mind machine. Afterwards the parameters listed below were continuously recorded during one session with the mind machine and one session with the presentation of relaxing environmental sounds, which was conducted one week later: Frontal EMG, SCL on the left hand, heart rate. Pre- and posttreatment samples of saliva were collected and assessed for salivary IgA (S-IgA) and salivary cortisol (S-cortisol). Changes in the subjects' self-report were measured with a bipolar adjective list. ANCOVA with repeated measures revealed a decrease for all electrophysiological parameters during the mind machine session. S-cortisol concentration decreases as S-IgA increases. The mind machine made the subjects feel warmer and calmer. The results of this with in design revealed no reliable differences between the mind machine and the relaxing sounds of nature on the physiological and self-esteem parameters. The significantly greater decrease of SCL during the mind machine session was due to the elevated baseline of this parameter. The results lead to the conclusion that the mind machine seems to be useful in inducing relaxation, but is no more effective than the relaxing nature sounds used in this study.

  17. NMR Relaxation and Diffusion Study of Ultrasound Recycling of Polyurethanes

    NASA Astrophysics Data System (ADS)

    von Meerwall, E.; Ghose, S.; Isayev, A. I.

    2004-04-01

    We have examined the effect of intense ultrasound on unfilled polyurethane foam and rubber using proton NMR transverse relaxation and pulsed-gradient diffusion studies, sol extraction, GPC characterization, and glass transition measurements. Results correlate well with ultrasound amplitude. The proton T2 relaxation at 70.5 deg. C exhibits three discrete components, due to heavily entangled sol and crosslinked network; unentangled polymeric sol plus dangling network chain ends; and oligomer remnants. Devulcanizing produces heavy sol, increases segmental mobility of all species, and generates more dangling chain ends. In foams, but not in rubber, additional light sol is generated at the expense of network. All mobilities are significantly lower than in the other rubbers we have studied, an effect unrelated to the glass transition, nearly constant at -60 deg. C. Diffusion measurements, possible only in foams, show a bimodal spectrum whose fast component slows markedly with ultrasound amplitude, attesting to the production of fragments heavier than the original oligomers, as confirmed by GPC analysis. This work is the first to study ultrasound devulcanization in industrial rubbery foams.

  18. 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.

  19. Nuclear-magnetic-resonance relaxation due to the translational diffusion of fluid confined to quasi-two-dimensional pores

    NASA Astrophysics Data System (ADS)

    Faux, D. A.; McDonald, P. J.; Howlett, N. C.

    2017-03-01

    Nuclear-magnetic-resonance (NMR) relaxation experimentation is an effective technique for nondestructively probing the dynamics of proton-bearing fluids in porous media. The frequency-dependent relaxation rate T1-1 can yield a wealth of information on the fluid dynamics within the pore provided data can be fit to a suitable spin diffusion model. A spin diffusion model yields the dipolar correlation function G (t ) describing the relative translational motion of pairs of 1H spins which then can be Fourier transformed to yield T1-1. G (t ) for spins confined to a quasi-two-dimensional (Q2D) pore of thickness h is determined using theoretical and Monte Carlo techniques. G (t ) shows a transition from three- to two-dimensional motion with the transition time proportional to h2. T1-1 is found to be independent of frequency over the range 0.01-100 MHz provided h ≳5 nm and increases with decreasing frequency and decreasing h for pores of thickness h <3 nm. T1-1 increases linearly with the bulk water diffusion correlation time τb allowing a simple and direct estimate of the bulk water diffusion coefficient from the high-frequency limit of T1-1 dispersion measurements in systems where the influence of paramagnetic impurities is negligible. Monte Carlo simulations of hydrated Q2D pores are executed for a range of surface-to-bulk desorption rates for a thin pore. G (t ) is found to decorrelate when spins move from the surface to the bulk, display three-dimensional properties at intermediate times, and finally show a bulk-mediated surface diffusion (Lévy) mechanism at longer times. The results may be used to interpret NMR relaxation rates in hydrated porous systems in which the paramagnetic impurity density is negligible.

  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. PP084. Magnetic resonance imaging measurements of T2 relaxation times within contrasting regions of murine placenta is dependent upon blood flow.

    PubMed

    Bobek, G; Stait-Gardner, T; Surmon, L; Makris, A; Price, W S; Hennessy, A

    2012-07-01

    It has been postulated that reduced placental perfusion as a result of abnormal placental implantation is the initiating event that leads to the maternal symptoms of preeclampsia. To be able to directly measure blood flow and perfusion in the placenta in experimental models of preeclampsia would provide valuable insight into the structural abnormalities of this syndrome. Magnetic resonance imaging (MRI) offers visualization of anatomy and analysis of changes in tissue morphology and function including blood flow and perfusion. The major source of image contrast in MRI comes from the variation in relaxation times between tissues. Previously, human placenta has appeared as fairly homogeneous in studies of T1 and T2 relaxation times, with no internal morphology apparent. The aim of this study was to investigate, using much higher field strengths (11.7Tesla) and much higher resolution than have been used previously, whether structural inhomogeneities in the placenta can be discerned by T2 mapping and whether T2 mapping is capable of detecting structural abnormalities that may affect blood flow in a preeclamptic placenta. Magnetic resonance images were acquired on an anaesthetised C57BL/6JArc mouse placed in a vertical animal probe using a Bruker Avance 11.7Tesla wide-bore spectrometer with micro-imaging probe capable of generating gradients of 0.45T/m. T2 measurements were acquired using an MSME sequence protocol (Bruker MSME-T2-map) with an in-plane resolution of 0.1-0.2mm. Matlab was used to generate R2 (i.e., 1/T2) maps from the acquired data with the T2 values being calculated from selected regions of interest within 5 individual placenta. Additional T2 measurements were acquired on the same slices immediately after blood flow was reduced to zero. Three distinct regions of T2 contrast were discerned in the mouse placenta, likely correlating to the labrynthine, junctional and decidual zones. The contrast between the inner two regions was substantially abrogated when

  2. Magnetic resonance fingerprinting using echo-planar imaging: Joint quantification of T1 and T2∗ relaxation times.

    PubMed

    Rieger, Benedikt; Zimmer, Fabian; Zapp, Jascha; Weingärtner, Sebastian; Schad, Lothar R

    2016-12-16

    To develop an implementation of the magnetic resonance fingerprinting (MRF) paradigm for quantitative imaging using echo-planar imaging (EPI) for simultaneous assessment of T1 and T2∗. The proposed MRF method (MRF-EPI) is based on the acquisition of 160 gradient-spoiled EPI images with rapid, parallel-imaging accelerated, Cartesian readout and a measurement time of 10 s per slice. Contrast variation is induced using an initial inversion pulse, and varying the flip angles, echo times, and repetition times throughout the sequence. Joint quantification of T1 and T2∗ is performed using dictionary matching with integrated B1+ correction. The quantification accuracy of the method was validated in phantom scans and in vivo in 6 healthy subjects. Joint T1 and T2∗ parameter maps acquired with MRF-EPI in phantoms are in good agreement with reference measurements, showing deviations under 5% and 4% for T1 and T2∗, respectively. In vivo baseline images were visually free of artifacts. In vivo relaxation times are in good agreement with gold-standard techniques (deviation T1 : 4 ± 2%, T2∗: 4 ± 5%). The visual quality was comparable to the in vivo gold standard, despite substantially shortened scan times. The proposed MRF-EPI method provides fast and accurate T1 and T2∗ quantification. This approach offers a rapid supplement to the non-Cartesian MRF portfolio, with potentially increased usability and robustness. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  3. β-detected nuclear quadrupole resonance and relaxation of 8Li+ in sapphire

    NASA Astrophysics Data System (ADS)

    Salman, Z.; Chow, K. H.; Hossain, M. D.; Kiefl, R. F.; Levy, C. D. P.; Parolin, T. J.; Pearson, M. R.; Saadaoui, H.; Wang, D.; MacFarlane, W. A.

    2014-12-01

    We report detailed behaviour of low energy 8Li implanted near the surface of α- Al2O3 single crystal, as revealed by beta-detected NQR of 8Li. We find that the implanted 8Li occupies at least two sites with non-cubic symmetry in the Al2O3 lattice. In both sites the 8Li experiences axially symmetric electric field gradient, with the main principal axis along the c-crystallographic direction. The temperature and field dependence of the spin lattice relaxation of 8Li in α-Al2O3, indicate that the 8Li diffusion is negligible on the scale of its lifetime, 1.21 s.

  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. 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.

  6. 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.

  7. 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

  8. Monochord sounds and progressive muscle relaxation reduce anxiety and improve relaxation during chemotherapy: a pilot EEG study.

    PubMed

    Lee, Eun-Jeong; Bhattacharya, Joydeep; Sohn, Christof; Verres, Rolf

    2012-12-01

    Chemotherapy is the most distressing form of cancer treatment in oncology, but listening to music can be an adjuvant during chemotherapy. Monochord (MC) sounds are used in music therapy for the alleviation of pain, enhanced body perception, and relaxation. This study investigated the relaxation effect of MC sounds for patients during chemotherapy compared with progressive muscle relaxation (PMR), an established relaxation technique. Two randomized groups of patients were observed during chemotherapy. One group listened to recorded MC sounds (n=20) and the other group listened to recorded PMR (n=20). Each session was investigated pre and post using Spielberger's State Anxiety Inventory (SAI) and a questionnaire about the patient's physical and psychological states. Further, for the first and the last session, multivariate electroencephalogram (EEG) signals were recorded. Patients in both MC and PMR groups showed significant improvement in their physical and psychological states and in state anxiety. The EEG data showed that the MC and the PMR groups were associated with an increase of posterior theta (3.5-7.5 Hz) and a decrease of midfrontal beta-2 band (20-29.5 Hz) activity during the end phase of relaxation treatment. Further, the MC group was associated with decreased alpha band (8-12 Hz) activity in comparison with PMR group. This study shows that both listening to recorded MC sounds and practising PMR have a useful and comparable effect on gynaecologic oncological patients during chemotherapy, with partially overlapping but also notably divergent neural correlates. Future research should establish the systematic use of MC in oncological contexts. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. 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)

  10. Deuterium-substitution effects on relaxation times and interligand nuclear Overhauser effects for assignment of ligand resonances and isomer identification in cobalt(III) complexes

    SciTech Connect

    Storm, C.B.; Turner, A.H.; Rowan, N.S.

    1985-04-10

    Relaxation time, T/sub 1/, and nuclear Overhauser effects are reported for nine imidazole complexes and one histidine complex of Co(III). From these values unequivocal resonance and isomer assignments can be made. The deuterium substitution effect of T/sub 1/'s has been used to determine intranuclear distances and molecular configurations.

  11. PARAMAGNETIC RELAXATION IN CRYSTALS.

    DTIC Science & Technology

    CRYSTALS, PARAMAGNETIC RESONANCE, RELAXATION TIME , CRYSTAL DEFECTS, QUARTZ, GLASS, STRAIN(MECHANICS), TEMPERATURE, NUCLEAR SPINS, HYDROGEN, CALCIUM COMPOUNDS, FLUORIDES, COLOR CENTERS, PHONONS, OXYGEN.

  12. Building 1D resonance broadened quasilinear (RBQ) code for fast ions Alfvénic relaxations

    NASA Astrophysics Data System (ADS)

    Gorelenkov, Nikolai; Duarte, Vinicius; Berk, Herbert

    2016-10-01

    The performance of the burning plasma is limited by the confinement of superalfvenic fusion products, e.g. alpha particles, which are capable of resonating with the Alfvénic eigenmodes (AEs). The effect of AEs on fast ions is evaluated using a resonance line broadened diffusion coefficient. The interaction of fast ions and AEs is captured for cases where there are either isolated or overlapping modes. A new code RBQ1D is being built which constructs diffusion coefficients based on realistic eigenfunctions that are determined by the ideal MHD code NOVA. The wave particle interaction can be reduced to one-dimensional dynamics where for the Alfvénic modes typically the particle kinetic energy is nearly constant. Hence to a good approximation the Quasi-Linear (QL) diffusion equation only contains derivatives in the angular momentum. The diffusion equation is then one dimensional that is efficiently solved simultaneously for all particles with the equation for the evolution of the wave angular momentum. The evolution of fast ion constants of motion is governed by the QL diffusion equations which are adapted to find the ion distribution function.

  13. Study of Mass Diffusion and Relaxation Processes in Polymer Systems by Laser Induced Holographic Grating Relaxation and Dynamic Light Scattering.

    NASA Astrophysics Data System (ADS)

    Xia, Jiulin

    The diffusion of dye molecules in various polymer systems is studied using the Laser Induced Holographic Grating Relaxation technique. The diffusion coefficients of camphorquinone (CQ), thymoquinone (TQ), diacetyl (DA) and azo compounds in these polymers are studied as a function of temperature, properties of both the polymers and the dye molecules. The effects of additives are also investigated. Due to the chemical reversibility of the azo compounds, the kinetics of their chemical processes are also analyzed. The mutual diffusion coefficients in poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) compatible polymer blends are measured by dynamic light scattering as a function of the molecular weight of PEO while keeping the molecular weight of PMMA fixed. The polymer chain relaxation processes of poly(isobornyl methacrylate) (PIMA) are also studied by using dynamic light scattering.

  14. 1H and 19F NMR relaxation studies of fleroxacin with Micrococcus luteus.

    PubMed

    Waibel, Benjamin; Holzgrabe, Ulrike

    2007-04-11

    In order to investigate and characterize interaction processes between the fluoroquinolone fleroxacin and bacterial cells we used non-selective (all resonances are excited), selective (observed resonance is excited) spin-lattice relaxation rates and spin-spin relaxation measurements. The signals of three hydrogens at different moieties of the fleroxacin molecule were considered to get an insight in the complexation behavior. The enhancement of selective relaxation rates was observed with increasing fleroxacin concentrations and keeping the bacterial mass constant. The obtained relaxation rates of the affected hydrogens were analyzed via a Lineweaver-Burk-plot to determine the KD values. Furthermore, 19F NMR spectra were recorded and spin-spin relaxation rates (R2) were determined by a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. Because of the dependency of the line width of NMR peaks on transversal relaxation time T2, we compared the line width at half-height at different fleroxacin concentrations in order to investigate the involvement of fluorine atoms in different positions in the complexation. All findings point to core quinolone moiety to be involved in the interaction with bacterial cells.

  15. Electron Tunneling in Lithium Ammonia Solutions Probed by Frequency-Dependent Electron-Spin Relaxation Studies

    PubMed Central

    Maeda, Kiminori; Lodge, Matthew T.J.; Harmer, Jeffrey; Freed, Jack H.; Edwards, Peter P.

    2012-01-01

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential

  16. Electron tunneling in lithium-ammonia solutions probed by frequency-dependent electron spin relaxation studies.

    PubMed

    Maeda, Kiminori; Lodge, Matthew T J; Harmer, Jeffrey; Freed, Jack H; Edwards, Peter P

    2012-06-06

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T(1)) and spin-spin (T(2)) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multiexponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1-10) × 10(-12) s over a temperature range 230-290 K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a time scale of ∼10(-13) s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great

  17. 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

  18. 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.

  19. Superparamagnetic behaviour and T 1, T 2 relaxivity of ZnFe2O4 nanoparticles for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Manjura Hoque, S.; Srivastava, C.; Venkatesha, N.; Kumar, P. S. Anil; Chattopadhyay, K.

    2013-05-01

    In the present study, ZnFe2O4 nanoparticles were synthesized by the chemical co-precipitation followed by calcinations at 473 and 673 K for 4 h. Particle sizes obtained were 4 and 6 nm for the calcination temperatures of 473 and 673 K, respectively. To study the origin of system's low temperature spin dynamic behaviour, temperature dependence of susceptibility ? was investigated as a function of particle size and frequency. Slight increase in the grain size from 4 nm at 473 K to 6 nm at 673 K has led to a peak shift of temperature dependence of susceptibility measured at a constant frequency of 400 Hz. Temperature dependence of ? at different frequencies also resulted in peak shift. Relaxation time dependence of peak temperature obeys a power law, which provides the fitting parameters within the range of superparamagnetic nature of the particles. Further, dependence of relaxation time and peak temperature obeys Vogel-Fulcher law rather than Néel-Brown equation demonstrating that the particles follow the behaviour of superparamagnetism of slightly interacting system. Spin-lattice, T 1 and spin-spin, T 2 relaxivity of proton of the water molecule in the presence of chitosan-coated superparamagnetic ZnFe2O4 nanoparticle yields the values of 0.002 and 0.360 s-1 per ppm.

  20. Relaxation dynamics of amorphous dibucaine using dielectric studies

    NASA Astrophysics Data System (ADS)

    Sahra, M.; Jumailath, K.; Thayyil, M. Shahin; Capaccioli, S.

    2015-06-01

    Using broadband dielectric spectroscopy the molecular mobility of dibucaine is investigated in the supercooled liquid and gassy states, over a wide temperature range for some test frequencies. Above the glass transition temperature Tg, the presence of structural α- relaxation peak was observed due to the cooperative motions of the molecule and upon cooling frozen kinetically to form the glass. The secondary relaxation process was perceivable below Tg due to localized motions. The peak loss frequency of α-relaxation process shows non-Arrhenius behavior and obeys Vogel-Fulcher-Tammann equation over the measured temperature range whereas the β- process shows Arrhenius behavior.

  1. Time-resolved photoluminescence study of excitonic relaxation in one-dimensional systems

    NASA Astrophysics Data System (ADS)

    Tanino, H.; Rühle, W. W.; Takahashi, K.

    1988-12-01

    Self-trapped exciton luminescence of quasi-one-dimensional (1D) halogen-bridged mixed-valence platinum complexes [Pt(II) (EA)4][Pt(IV)Cl2(EA)4] Cl4.4H2O (EA=ethylamine) and [Pt(II)(en)2] [Pt(IV)Cl2(en)2](ClO4)4 (en=1,2-diaminoethane) are studied by time-resolved photoluminescence experiments. The lifetimes of the luminescence of self-trapped exciton are exceptionally short, of the order of 100 psec. We interpret the short lifetime by a ``giant oscillator strength'' caused by a strong coupling between the electron and hole of the 1D charge transfer exciton and an extended polaronlike character of the 1D state. The lifetimes of the broad luminescence and of the resonant Raman lines during the barrier-free relaxation process are both faster than 7 psec.

  2. Intrinsic relaxation of the ferromagnetic resonance in substituted yttrium iron garnets

    SciTech Connect

    Roschmann, P.

    1984-09-01

    The intrinsic loss properties of the ferromagnetic resonance (FMR) in Ga, Al, Sc and V substituted iron garnets have been investigated at different temperatures from T=77 K up to the Curie temperature by FMR measurements as a function of frequency. After separation of masking two-magnon scattering contributions the intrinsic losses of the bulk single crystal materials were resolved in terms of the dimensionless Landau-Lifshitz damping parameter ..cap alpha.. /sub f/ . The results of ..cap alpha.. /sub f/ (T) obtained for different temperatures were found to increase linearly versus 1/4..pi..M /sub s/ (T), the reciprocal of the respective saturation magnetization. Apart from the region of magnetic compensation the intrinsic FMR losses for 100 K < T < T /sub c/ have been related directly to thermomagnetic properties of substituted YIG using nearly invariant matching parameters.

  3. Explicit calculation of nuclear-magnetic-resonance relaxation rates in small pores to elucidate molecular-scale fluid dynamics

    NASA Astrophysics Data System (ADS)

    Faux, D. A.; McDonald, P. J.

    2017-03-01

    Nuclear-magnetic-resonance (NMR) spin-lattice (T1-1) and spin-spin (T2-1) relaxation rate measurements can act as effective nondestructive probes of the nanoscale dynamics of 1H spins in porous media. In particular, fast-field-cycling T1-1 dispersion measurements contain information on the dynamics of diffusing spins over time scales spanning many orders of magnitude. Previously published experimental T1-1 dispersions from a plaster paste, synthetic saponite, mortar, and oil-bearing shale are reanalyzed using a model and associated theory which describe the relaxation rate contributions due to the interaction between spin ensembles in quasi-two-dimensional pores. Application of the model yields physically meaningful diffusion correlation times for all systems. In particular, the surface diffusion correlation time and the surface desorption time take similar values for each system, suggesting that surface mobility and desorption are linked processes. The bulk fluid diffusion correlation time is found to be two to five times the value for the pure liquid at room temperature for each system. Reanalysis of the oil-bearing shale yields diffusion time constants for both the oil and water constituents. The shale is found to be oil wetting and the water T1-1 dispersion is found to be associated with aqueous Mn2 + paramagnetic impurities in the bulk water. These results escalate the NMR T1-1 dispersion measurement technique as the primary probe of molecular-scale dynamics in porous media yielding diffusion parameters and a wealth of information on pore morphology.

  4. Deuterium magnetic resonance studies in amorphous and crystalline silicon

    NASA Astrophysics Data System (ADS)

    Borzi, Raffaella

    Hydrogenation is essential for useful amorphous silicon films and devices. We used deuteron magnetic resonance (DMR) to investigate the hydrogen microstructure in amorphous and crystalline silicon. DMR line shapes analyses and longitudinal relaxation time studies can distinguish silicon-bonded deuterons from molecular deuterons. Our comparisons between crystalline and amorphous silicon have yielded new perspectives on the characterization of molecular hydrogen sites including interstitial tetragonal T-sites, and microvoids. Quantitative analyses of DMR line shapes and spin populations show that the fraction of interstitially trapped molecular hydrogen increases with increasing photovoltaic quality of the films.

  5. Solvent dynamical behavior in an organogel phase as studied by NMR relaxation and diffusion experiments.

    PubMed

    Yemloul, Mehdi; Steiner, Emilie; Robert, Anthony; Bouguet-Bonnet, Sabine; Allix, Florent; Jamart-Grégoire, Brigitte; Canet, Daniel

    2011-03-24

    An organogelation process depends on the gelator-solvent pair. This study deals with the solvent dynamics once the gelation process is completed. The first approach used is relaxometry, i.e., the measurement of toluene proton longitudinal relaxation time T(1) as a function of the proton NMR resonance frequency (here in the 5 kHz to 400 MHz range). Pure toluene exhibits an unexpected T(1) variation, which has been identified as paramagnetic relaxation resulting from an interaction of toluene with dissolved oxygen. In the gel phase, this contribution is retrieved with, in addition, a strong decay at low frequencies assigned to toluene molecules within the gel fibers. Comparison of dispersion curves of pure toluene and toluene in the gel phase leads to an estimate of the proportion of toluene embedded within the organogel (found around 40%). The second approach is based on carbon-13 T(1) and nuclear Overhauser effect measurements, the combination of these two parameters providing direct information about the reorientation of C-H bonds. It appears clearly that reorientation of toluene is the same in pure liquid and in the gel phase. The only noticeable changes in carbon-13 longitudinal relaxation times are due to the so-called chemical shift anisotropy (csa) mechanism and reflect slight modifications of the toluene electronic distribution in the gel phase. NMR diffusion measurements by the pulse gradient spin-echo (PGSE) method allow us to determine the diffusion coefficient of toluene inside the organogel. It is roughly two-thirds of the one in pure toluene, thus indicating that self-diffusion is the only dynamical parameter to be slightly affected when the solvent is inside the gel structure. The whole set of experimental observations leads to the conclusion that, once the gel is formed, the solvent becomes essentially passive, although an important fraction is located within the gel structure.

  6. 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.

  7. 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.

  8. Ferromagnetic resonance observation of exchange and relaxation effects in CrO{sub 2}

    SciTech Connect

    Lubitz, P.; Rubinstein, M.; Osofsky, M. S.; Nadgorny, B. E.; Soulen, R. J.; Bussmann, K. M.; Gupta, A.

    2001-06-01

    Ferromagnetic resonance (FMR) was observed in epitaxial thin films of CrO{sub 2} grown on TiO{sub 2}. FMR spectra were taken at 9.5 and 35 GHz and at temperatures from 4 K to above the ordering temperature of 393 K. The spectra of these films are generally complicated because of surface roughness and the distribution of stresses and anisotropies through their thickness. The thinnest films, however, display typical spin wave spectra, which could be approximated using uniform magnetic material analyses. The exchange constant at 300 K, D{similar_to}70meVAa{sup 2}, is consistent with values derived from the temperature dependence of M at low temperatures. The temperature dependence of D was extracted from the spin wave spacing and is similar to other magnetic metals. Our data indicate a room temperature Gilbert damping parameter of at most 0.0023 near 300 K, which is less than those of metallic magnetic materials except possibly Fe. The small damping parameter suggests that intrinsic losses seen in other magnetic metals, which may arise from electronic transitions between bands of different spin character, are small in CrO{sub 2}. {copyright} 2001 American Institute of Physics.

  9. Glycans in magnetic resonance imaging: determinants of relaxivity to smart agents, and potential applications in biomedicine.

    PubMed

    Cipolla, Laura; Gregori, Maria; So, Po-Wah

    2011-01-01

    Carbohydrate chemistry and glycobiology have become a "hot" subject. These extensive, complex structures serve essential roles in cell surface phenomena, but we are only beginning to understand what some of these functions are; any advances in the development of synthetic and/or analytical tools for glycobiology are extremely useful for our understanding of the roles of carbohydrates in biology, and as biomarkers of physiological/pathological states. This review provides an outlook of the potential of carbohydrate chemistry/biology in magnetic resonance imaging (MRI), a major important and prominent technique in diagnostic clinical medicine and biomedical research. During the last 30 years, MRI has developed from an intriguing research project to an essential diagnostic method in the clinic. Although MRI contrast in endogenous tissues provides excellent sensitivity for detecting subtle changes in anatomy and function, MRI still has poor specificity for attributing image contrast to specific biological processes. To overcome this limitation, MRI methods are being developed that induce changes in MR image contrast in response to molecular compositions and functions that serve as early biomarkers of pathologies. Carbohydrates with their intriguing chemistry, not only can provide structures for novel MRI probes for imaging specific biological processes, but can themselves provide novel targets/biomarkers. For example, the glycan structure can simply provide a molecular scaffold for modulating the physicochemical properties of the imaging contrast agent, or can be used for the design of novel MR agents with the ability to disclose relevant physiological or pathological cellular events.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. A randomised controlled study of mindfulness meditation versus relaxation therapy in the management of tinnitus.

    PubMed

    Arif, M; Sadlier, M; Rajenderkumar, D; James, J; Tahir, T

    2017-06-01

    Psychotherapeutic interventions have been adopted effectively in the management of tinnitus for a long time. This study compared mindfulness meditation and relaxation therapy for management of tinnitus. In this randomised controlled trial, patients were recruited for five sessions of mindfulness meditation or five sessions of relaxation therapy. Patients' responses were evaluated using the Tinnitus Reaction Questionnaire as a primary outcome measure, and the Hospital Anxiety and Depression Scale, visual analogue scale and a health status indicator as secondary outcome measures. A total of 86 patients were recruited. Thirty-four patients completed mindfulness meditation and 27 patients completed relaxation therapy. Statistically significant improvement was seen in all outcome measures except the health status indicator in both treatment groups. The change in treatment scores was greater in the mindfulness meditation group than in the relaxation therapy group. This study suggests that although both mindfulness meditation and relaxation therapy are effective in the management of tinnitus, mindfulness meditation is superior to relaxation therapy.

  12. Role of strain relaxation in exciton resonance energies of ZnO epitaxial layers grown on SiC substrates

    NASA Astrophysics Data System (ADS)

    Almamun Ashrafi, Abm

    2004-03-01

    The wide bandgap ZnO semiconductor is currently the subject of interest for the study of physics as well as investigations in response to the industrial demand for applications in optoelectronics devices. The most exciting physical properties of ZnO are the largest exciton binding energy of 60 meV and this can be tuned up to 120 meV by controlling the ZnO active layers1. Towards these goals, a great deal of efforts has been made on ZnO layers grown mostly on Al2O3 substrates. It is noted that the lattice mismatch in ZnO/Al2O3 is 18structural defects, and higher residual carrier concentration. To overcome these basic but unavoidable problems for crystalline quality, nearly-matched SiC substrate may play a role including reproducible p-type conductivity in ZnO layers2. Considering the ZnO lattice constant, the estimated lattice mismatch between the ZnO and SiC is to be 5may explore the ZnO epitaxy with the superior crystalline as well as optical properties towards the study of quantum physics in nanoscale level where strain governs the local atomic mechanisms in principle. Recently, we have reported the superior ZnO crystalline quality grown on SiC substrates compared to the ZnO/Al2O3 samples by MOCVD3. In progress to these results, strain relaxation effects in exciton resonance energies of ZnO layers have been addressed in this letter. The surface morphology of ZnO layers grown on SiC exhibited hexagons geometry for the VI/II falux raio of 4 by reflecting the +c ZnO surface. From these layers, therefore, free exciton (FX) emission was appeared with A and B bands to the corresponding energies of 3.377 and 3.390 eV4. With the increase of temperature, however, the FXs emission showed the quenching of excitons energy as well as intensity which may be a subject of overlapping the A and donor-bound (D0X) excitons4. The deduced activation energies of A and D0X exciton emissions suggested a consistency with an inclusion of exciton-defect binding energy in optical bands. The

  13. 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.

  14. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coal models. Along the same lines the author are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. During the last quarter the authors has concentrated on improvements in cross polarization (CP) sequences with a goal of making the CP process insensitive to experimental conditions such as the Hartmann-Hahn mismatch. It has been found that the usual theories of CP are incorrect, and that the CP process is very heterogeneous in nature. This has significant implications on methods typically used in quantifying {sup 13}C CPMAS spectra of coals. 19 refs., 11 figs.

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

    NASA Astrophysics Data System (ADS)

    Kalogerakis, K. S.; Matsiev, D.

    2016-12-01

    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 fast 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.

  16. 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.

  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. Experimental study on relaxation time in direction changing movement

    NASA Astrophysics Data System (ADS)

    Liu, Chi; Song, Weiguo; Fu, Libi; Lian, Liping; Lo, Siuming

    2017-02-01

    Controlled experiments were conducted to clarify the movement characteristics of pedestrians in direction changing processes. We track pedestrians' trajectories and map them into real space coordinates by the direct linear transformation method. In the acceleration process, the relaxation time and free moving speed in our experiments respectively equal 0.659 s and 1.540 m/s, which are consistent with those for Chinese participants in other experiments. Meanwhile, the values of relaxation time in the direction changing process are calculated by a derived equation from the concept of the social force model. It is observed that the relaxation time is not an invariable parameter, and tends to increase with an increase in the angular difference. Furthermore, results show that pedestrians are insensitive to a tiny angular difference between instantaneous velocity and desired velocity. These experimental results presented in this work can be applied in model development and validation.

  19. Relationship between bolus transit and LES-relaxation studied with concurrent impedance and manometry.

    PubMed

    Nguyen, H N; Domingues, G R; Winograd, R; Lammert, F; Silny, J; Matern, S

    2006-01-01

    Neuromuscular mechanisms regulating esophageal bolus transport are well studied. However, detailed data about the relationship between bolus transit and lower esophageal sphincter (LES)-relaxation during conventional motility testing are still lacking. We performed systematic studies in 25 normal subjects, employing a catheter that integrates the two techniques impedancometry and manometry in a single instrument for simultaneous recording and analysis of the relationship between bolus transit and LES relaxation after swallowing saline or yogurt. 195 swallows were analyzed. LES relaxation occurred frequently later than UES relaxation. The mean latency between bolus entry into the esophagus and LES relaxation was 3.6 +0.2 sec. Two types of swallow-induced LES relaxation were observed: (a) LES relaxation preceding bolus transit (46 cases or 24%) and (b) LES relaxation occurring during bolus transit (149 cases or 76%). In the later case, during 114 (76%) cases of this deglutition, the position of the bolus was very close to the LES. During deglutition, LES relaxation seems to be modulated by bolus transit and occurs predominantly upon arrival of the bolus in the distal esophagus.

  20. 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.

  1. Thermal diffusivity and nuclear spin relaxation: a continuous wave free precession NMR study.

    PubMed

    Venâncio, Tiago; Engelsberg, Mario; Azeredo, Rodrigo B V; Colnago, Luiz A

    2006-07-01

    Continuous wave free precession (CWFP) nuclear magnetic resonance is capable of yielding quantitative and easily obtainable information concerning the kinetics of processes that change the relaxation rates of the nuclear spins through the action of some external agent. In the present application, heat flow from a natural rubber sample to a liquid nitrogen thermal bath caused a large temperature gradient leading to a non-equilibrium temperature distribution. The ensuing local changes in the relaxation rates could be monitored by the decay of the CWFP signals and, from the decays, it was possible to ascertain the prevalence of a diffusive process and to obtain an average value for the thermal diffusivity.

  2. 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.

  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. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concern how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. During the last quarter the authors have concentrated on improvements in cross polarization (CP) sequences with a goal of making the CP process insensitive to experimental conditions such as the magic angle spinning (MAS) rate. In order to be able to use fields the order of 7.0 T or higher, CP efficiency must be maintained at MAS rates of over 10 kHz. The standard sequences have severe limitations at these rates which lead to intensity distortions in {sup 13}C CPMAS spectra. Thus in order to be able to take advantage of the increases in sensitivity and resolution that accompany high field operation, improvements in the NMR methods are required. The new sequences the authors are developing will be especially important for quantitative analysis of coal structure by {sup 13}C solid state NMR at high field strengths. 13 refs., 7 figs., 2 tabs.

  5. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project during the past reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have been reinvestigating the prospects of using zero field NMR types of techniques for two dimensional NMR structural analysis of complex organic solids such as coals. Currently MAS spin rates are not sufficiently high to permit zero field in high field NMR for protons in typical organic solids, however they are compatible with {sup 13}C-{sup 13}C dipolar couplings. In collaboration with Dr. Robert Tycko of AT T Bell Laboratories, inventor of the zero field in high field NMR method, the authors have performed the first zero field in high field {sup 13}C NMR experiments. These results are described. 9 refs., 2 figs.

  6. Electron paramagnetic resonance study of the nuclear spin dynamics in an AlAs quantum well

    NASA Astrophysics Data System (ADS)

    Shchepetilnikov, A. V.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Tiemann, L.; Reichl, C.; Dietsche, W.; Wegscheider, W.

    2016-12-01

    The nuclear spin dynamics in an asymmetrically doped 16-nm AlAs quantum well grown along the [001] direction has been studied experimentally using the time decay of the Overhauser shift of paramagnetic resonance of conduction electrons. The nonzero spin polarization of nuclei causing the initial observed Overhauser shift is due the relaxation of the nonequilibrium spin polarization of electrons into the nuclear subsystem near electron paramagnetic resonance owing to the hyperfine interaction. The measured relaxation time of nuclear spins near the unity filling factor is (530 ± 30) min at the temperature T = 0.5 K. This value exceeds the characteristic spin relaxation times of nuclei in GaAs/AlGaAs heterostructures by more than an order of magnitude. This fact indicates the decrease in the strength of the hyperfine interaction in the AlAs quantum well in comparison with GaAs/AlGaAs heterostructures.

  7. 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.

  8. Dielectric relaxation studies of poly(propylene glycol) confined in vermiculite clay.

    PubMed

    Schwartz, G A; Bergman, R; Mattsson, J; Swenson, J

    2003-11-01

    The molecular dynamics of oligomeric poly(propylene glycol) (PPG) liquids (M(w)=1200, 2000 and 4000 g/mol) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy. In addition to the alpha-relaxation, the normal mode relaxation process was studied for all samples both in bulk and confinement. For the normal mode process the relaxation rate in the clay is drastically shifted to lower frequencies compared to that of the bulk material in contrast to the alpha-process whose relaxation time is only slightly affected by the confinement. Also the temperature dependence of the relaxation time for the normal mode process is strongly affected by the confinement. Moreover, in the clay the intensity of the normal mode is stronger than that of the alpha-process, in contrast to the bulk samples where the opposite is observed.

  9. 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.

  10. Secondary and primary relaxations in hyperbranched polyglycerol: A comparative study in the frequency and time domains

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    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 β and γ processes. The study of the evolution of these two fast processes with temperature in the time retardation spectra shows that the β absorption is swallowed by the α in the glass-liquid transition, the γ absorption being the only relaxation that remains operative in the liquid state. In heating, a temperature is reached at which the α absorption vanishes appearing the αγ relaxation. Two characteristics of α absorptions, decrease of the dielectric strength with increasing temperature and rather high activation energy, are displayed by the αγ process. Williams' ansatz seems to hold for these topologically complex macromolecules.

  11. Relaxation Models of the (110) Zinc-Blende III-V Semiconductor Surfaces: Density Functional Study

    SciTech Connect

    Ye, H.; Chen, G.; Wu, Y.; Zhu, Y.; Wei, S. H.

    2008-11-01

    Clean III-V zinc-blende (110) surfaces are the most extensively studied semiconductor surface. For conventional III-V compounds such as GaAs and InP, the surface relaxation follows a bond rotation relaxation model. However, for III-nitrides recent study indicates that they follow a bond-constricting relaxation model. First-principles atom relaxation calculations are performed to explore the origin of the difference between the two groups of materials. By analyzing the individual shift trends and ionic properties of the top layer anions and cations, we attribute the difference between the conventional and nitride III-V compounds to the strong electronegativity of N, which leads to the s{sup 2}p{sup 3} pyramid bond angle to be larger than the ideal one in bulk (109.5{sup o}). The general trends of the atomic relaxation at the III-nitrides (110) surfaces are explained.

  12. Enthalpy relaxation studies of two structurally related amorphous drugs and their binary dispersions.

    PubMed

    Bansal, Shyam Sunder; Kaushal, Aditya Mohan; Bansal, Arvind Kumar

    2010-11-01

    The purpose of the current study was to evaluate the enthalpy relaxation behavior of valdecoxib (VLB) and etoricoxib (ETB) and their binary dispersions to derive relaxation constants and to understand their molecular mobilities. Solid dispersions of VLB and ETB were prepared with 1%, 2%, 5%, 10%, 15%, and 20% (w/w) concentrations of polyvinylpyrrolidone (PVP) in situ using differential scanning calorimetry (DSC). Enthalpy relaxation studies were carried out with isothermal storage periods of 1, 2, 4, 6, 16, and 24 hours at 40°C and 0% relative humidity (RH). PVP increased the glass transition temperature (T(g)) and decreased the enthalpy relaxation. Significant differences between two drugs were observed with respect to their relaxation behavior which may be due to differences in intermolecular interactions as predicted by Couchman-Karasz equation and molecular mobility. Kohlrausch-Williams-Watts equation was found to be inadequate in describing complex molecular relaxations in binary dispersions. The enthalpy relaxation behavior of VLB and ETB was found to be significantly different. PVP stabilized VLB significantly; however, its effect on ETB was negligible. The extent of enthalpy relaxation was found to correlate with hydrogen bonding tendency of the drug molecules. The outcome can help in rational designing of amorphous systems with optimal performance.

  13. 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.

  14. 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.

  15. A new secondary relaxation in the rigid and planar 1-methylindole: Evidence from binary mixture studies

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Li, Xiangqian; Guo, Yuxing; Wu, Tao; Liu, Ying Dan; Ngai, K. L.; Wang, Li-Min

    2016-12-01

    Found in our recent dielectric study of a planar and rigid glass-former, 1-methylindole (1MID), is an unusual secondary relaxation unrelated in its dynamic properties to the structural α-relaxation. We speculated that it originates from the in-plane motion of the molecules, and the supposedly universal Johari-Goldstein (JG) β-relaxation with strong connection to the structural α-relaxation in rigid glass-formers is not resolved [X. Q. Li et al. J. Chem. Phys. 143, 104505 (2015)]. In this work, dielectric measurements are performed in binary mixtures of 1MID with two aromatics of weak polarity, ethylbenzene (EB) and triphenylethylene (TPE), in the highly viscous regimes near glass transition. EB and TPE have smaller and larger molecular sizes and glass transition temperatures Tg than 1MID, respectively. Strikingly, the results show that the resolved secondary relaxations of 1MID in the two mixtures share the same relaxation time and their temperature dependence as pure 1MID, independent of the mode and degree of dilution. The results indicate that the unusual secondary relaxation is not directly coupled with the α-relaxation, and support the in-plane-rotation interpretation of its origin. On the other hand, the supposedly universal and intermolecular JG β-relaxation coming from the out-of-plane motion of the planar molecule has weaker dielectric strength, and it cannot be resolved from the more intense in-plane-rotation secondary relaxation because the dipole moment of 1MID lies on the plane.

  16. Ionic Conductivity And Structural Relaxation Studies on Lithium Niobophosphate Glass

    SciTech Connect

    Dabas, Prashant; Hariharan, K.

    2011-07-15

    Niobium pentoxide (Nb{sub 2}O{sub 5}) increases the chemical and thermal stability of otherwise hygroscopic alkali phosphate glasses and also enhances the conduction characteristics. Ion dynamics and structural relaxation have been investigated for mol%50Li{sub 2}0-45P{sub 2}0{sub 5}-5Nb{sub 2}O{sub 5}. The non-linearity parameter 'x' in the Tool-Narayanaswamy model is evaluated using the dependence of fictive and glass transition temperatures on the cooling and heating rates.

  17. Investigation of ligand binding and protein dynamics in Bacillus subtilis chorismate mutase by transverse relaxation optimized spectroscopy-nuclear magnetic resonance.

    PubMed

    Eletsky, Alexander; Kienhöfer, Alexander; Hilvert, Donald; Pervushin, Konstantin

    2005-05-10

    The structural and dynamical consequences of ligand binding to a monofunctional chorismate mutase from Bacillus subtilis have been investigated by solution NMR spectroscopy. TROSY methods were employed to assign 98% of the backbone (1)H(N), (1)H(alpha), (15)N, (13)C', and (13)C(alpha) resonances as well as 86% of the side chain (13)C resonances of the 44 kDa trimeric enzyme at 20 degrees C. This information was used to map chemical shift perturbations and changes in intramolecular mobility caused by binding of prephenate or a transition state analogue to the X-ray structure. Model-free interpretation of backbone dynamics for the free enzyme and its complexes based on (15)N relaxation data measured at 600 and 900 MHz showed significant structural consolidation of the protein in the presence of a bound ligand. In agreement with earlier structural and biochemical studies, substantial ordering of 10 otherwise highly flexible residues at the C-terminus is particularly notable. The observed changes suggest direct contact between this protein segment and the bound ligand, providing support for the proposal that the C-terminus can serve as a lid for the active site, limiting diffusion into and out of the pocket and possibly imposing conformational control over substrate once bound. Other regions of the protein that experience substantial ligand-induced changes also border the active site or lie along the subunit interfaces, indicating that the enzyme adapts dynamically to ligands by a sort of induced fit mechanism. It is believed that the mutase-catalyzed chorismate-to-prephenate rearrangement is partially encounter controlled, and backbone motions on the millisecond time scale, as seen here, may contribute to the reaction barrier.

  18. Synthesis, characterization, and relaxation studies of Gd-DO3A conjugate of chlorambucil as a potential theranostic agent.

    PubMed

    Kaur, Jasleen; Tsvetkova, Yoanna; Arroub, Karim; Sahnoun, Sabri; Kiessling, Fabian; Mathur, Sanjay

    2017-02-01

    DO3A-based macrocycles serve as attractive templates from which clinically useful theranostic agents can be obtained after coupling with molecular targeted therapeutic drugs. In this study, we describe the chemical synthesis, relaxation, and cytotoxicity studies of a new DO3A conjugate of chlorambucil (CHL) as a magnetic resonance imaging (MRI) theranostic agent. A convenient route of synthesis is reported, which allowed conjugation of the macrocyclic ligand (DO3A) to the chemotherapeutic drug (CHL) via tyrosine for the preparation of an attractive chelate-drug ensemble (DO3A-TR-CHL). The structures of all intermediates and final compound have been determined by (1) H, (13) C NMR, and MS. The efficacy of DO3A-TR-CHL as a non-ionic magnetic contrast agent was tested by performing relaxometric studies on its gadolinium complex. The complex exhibited relaxivities (7.11 mm(-1) /s) higher than that of currently used MR contrast agents and showed enhanced contrast in T1 -weighted images. MTT assays revealed that both DO3A-TR-CHL and Gd(III)-DO3A-TR-CHL conjugates exhibited dose-dependent toxicity and an enhanced antiproliferative activity against tumor (A549 and HeLa) cell lines compared to that of parent drug (CHL), thereby demonstrating their potential to be used as a magnetic resonance imaging theranostic for improved molecular imaging and therapy of human cancers. © 2017 John Wiley & Sons A/S.

  19. Dielectric dispersion, relaxation dynamics and thermodynamic studies of Beta-Alanine in aqueous solutions using picoseconds time domain reflectometry

    NASA Astrophysics Data System (ADS)

    Vinoth, K.; Ganesh, T.; Senthilkumar, P.; Sylvester, M. Maria; Karunakaran, D. J. S. Anand; Hudge, Praveen; Kumbharkhane, A. C.

    2017-09-01

    The aqueous solution of beta-alanine characterised and studied by their dispersive dielectric properties and relaxation process in the frequency domain of 10×106 Hz to 30×109 Hz with varying concentration in mole fractions and temperatures. The molecular interaction and dielectric parameters are discussed in terms of counter-ion concentration theory. The static permittivity (ε0), high frequency dielectric permittivity (ε∞) and excess dielectric parameters are accomplished by frequency depended physical properties and relaxation time (τ). Molecular orientation, ordering and correlation factors are reported as confirmation of intermolecular interactions. Ionic conductivity and thermo dynamical properties are concluded with the behaviour of the mixture constituents. Solute-solvent, solute-solute interaction, structure making and breaking abilities of the solute in aqueous medium are interpreted. Fourier Transform Infrared (FTIR) spectra of beta- alanine single crystal and liquid state have been studied. The 13C Nuclear Magnetic Resonance (NMR) spectral studies give the signature for resonating frequencies and chemical shifts of beta-alanine.

  20. Spectroscopic studies of individual plasmon resonant nanoparticles

    NASA Astrophysics Data System (ADS)

    Mock, Jack J.; Smith, David R.; Barbic, Mladen; Oldenburg, Steven J.; Schultz, David A.; Schultz, Sheldon

    2003-11-01

    We present a detailed description of the apparatus and techniques that we have utilized in our experimental study of individual plas on resonant nanoparticles,along with a brief description of some major results. The apparatus consists of a spectroscopic system combined with a modified darkfield microscope, which enables the user to sequentially select individual resonant nanostructures in the microscopic field of view for spectroscopic study. Plasmon resonant nanostructures scatter light elastically,and typically have very large scattering cross-sections at their resonant optical wavelengths. In general, spectra can be obtained with acquisition times between .1 to 30 seconds,and color images can be captured using consumer digital color cameras. Spheres,tetrahedrons,and pentagonal platelets were fabricated using colloidal chemistry techniques. To produce highly anisotropic structures such as nanorods and "barbells", templates were used. Many of these nanostructures have been individually spectroscopically characterized,and their spectra correlated with their shape and size as determined by transmission electron icroscope (TEM). The unique shape,size, composition,and dielectric surroundings of the individual plasmon resonant nanostructures determine their plasmon resonant behavior. We will show how the composition of the substrate on which the particles are immobilized and the dielectric of the surrounding medium have a significant effect on the plasmon resonance of the individual particles.

  1. 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. Copyright © 2013 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  2. Ultrafast relaxation dynamics of nitric oxide synthase studied by visible broadband transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hung, Chih-Chang; Yabushita, Atsushi; Kobayashi, Takayoshi; Chen, Pei-Feng; Liang, Keng S.

    2017-09-01

    Ultrafast dynamics of endothelial nitric oxide synthase (eNOS) oxygenase domain was studied by transient absorption spectroscopy pumping at Soret band. The broadband visible probe spectrum has visualized the relaxation dynamics from the Soret band to Q-band and charge transfer (CT) band. Supported by two-dimensional correlation spectroscopy, global fitting analysis has successfully concluded the relaxation dynamics from the Soret band to be (1) electronic transition to Q-band (0.16 ps), (2) ligand dissociation and CT (0.94 ps), (3) relaxation of the CT state (4.0 ps), and (4) ligand rebinding (59 ps).

  3. Relaxation in distal and proximal arm muscles: a reaction time study.

    PubMed

    Buccolieri, A; Avanzino, L; Trompetto, C; Abbruzzese, G

    2003-02-01

    To investigate whether the same mechanisms underlie muscle relaxation in proximal and distal arm muscles of normal subjects. Fourteen healthy subjects were studied using a simple visual reaction time paradigm. Relaxation reaction time (R-RT) and contraction reaction time (C-RT) were compared across different tasks involving distal (first dorsal interosseus, FDI, flexor carpi radialis, FCR) and proximal (biceps brachii, BB, triceps brachii, TR) arm muscles. Changes of FCR H-reflex before and during voluntary relaxation were investigated in two subjects. No significant difference was observed between R-RT and C-RT in the distal muscles. The R-RT was significantly shorter than C-RT in both the BB and TR muscles. The relaxation latency (R-RT) was significantly correlated to the subjects' age in all the muscles except the FDI. No inhibition of the FCR H-reflex could be observed in the 20 ms preceding muscle relaxation. Our findings suggest that neural mechanisms contribute differently to the relaxation of muscles with a different functional role. Voluntary relaxation in distal arm muscles is mainly related to the reduction of motor cortical output, while in proximal muscles a spinal disfacilitation is also present and possibly sustained by the modulation of presynaptic inhibition.

  4. Nuclear magnetic resonance studies of biological systems

    SciTech Connect

    Antypas, W.G. Jr.

    1988-01-01

    The difference between intracellular and extracellular proton relaxation rates provides the basis for the determination of the mean hemoglobin concentration (MHC) in red blood cells. The observed water T{sub 1} relaxation data from red blood cell samples under various conditions were fit to the complete equation for the time-dependent decay of magnetization for a two-compartment system including chemical exchange. The MHC for each sample was calculated from the hematocrit and the intracellular water fraction as determined by NMR. The binding of the phosphorylcholine (PC) analogue, 2-(trimethylphosphonio)-ethylphosphate (phosphoryl-phosphocholine, PPC) to the PC binding myeloma proteins TEPC-15, McPC 603, and MOPC 167 was studied by {sup 31}P NMR.

  5. SS-HORSE method for studying resonances

    NASA Astrophysics Data System (ADS)

    Blokhintsev, L. D.; Mazur, A. I.; Mazur, I. A.; Savin, D. A.; Shirokov, A. M.

    2017-03-01

    A new method for analyzing resonance states based on the Harmonic-Oscillator Representation of Scattering Equations (HORSE) formalism and analytic properties of partial-wave scattering amplitudes is proposed. The method is tested by applying it to the model problem of neutral-particle scattering and can be used to study resonance states on the basis of microscopic calculations performed within various versions of the shell model.

  6. 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.

  7. Relaxation of Lattice Inperfections as Studied by Chlorine NQR

    NASA Astrophysics Data System (ADS)

    Hashimoto, Masao; Adachi, Masahiro; Mano, Koichi

    1986-02-01

    The intensities, linewidths, and frequencies of 35Cl NQR signals in 6-nitro-2,4-bis(trichlorom ethyl)-benzo[1,3]dioxine were found to vary remarkably depending on the crystallization methods and annealing. This finding was correlated to the degree of crystal disorder. For a sample obtained by slow crystallization from an ethanolic solution of the compound, the growth of the height of the NQR absorption signal due to annealing was measured as a function of the isothermal annealing time. A kinetic analysis of the growth process gave an activation energy of approx. 110 kJ/mole for the relaxation process of the imperfection dominating the NQR signals. The dimorphism of the compound and the magnitude of the activation energy suggest the presence of misoriented molecules accompanied by vacancies in the crystal lattice of the stable phase.

  8. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1992-05-27

    This report covers the progress made on the title project for the project period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins are particularly promising. Methods combining proton-proton spin diffusion with {sup 13}C CPMAS readout are being developed to determine the connectivity of functional groups in coals in a high sensitivity relay type of experiment. Additional work is aimed a delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

  9. 13C NMR Relaxation Study of Segmental Motion of Poly(l-histidine) in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Uchino, Shinichi; Hiraoki, Toshifumi; Tsutsumi, Akihiro

    2004-05-01

    To study the segmental motion of poly (l-histidine) (PLH) in aqueous solution, the 13C spin-lattice relaxation time (T1) was measured at six resonance frequencies (ωC/2π) ranging from 15 to 100 MHz at temperatures from 10 to 80°C. For backbone Cα, plots of log(T1/ωC) against log(ωC) gave the well-superposed master curve, showing that the time-temperature reduction rule is realized. The shift factor obeyed the Arrhenius-type temperature dependence with the activation energy of 25.0 kJmol-1. Using this activation energy for the temperature dependence of the correlation time, the master curve was well reproduced by the Dejean-Lauprêtre-Monnerie (DLM) model. One of the parameters relating to the segmental motion was τ0/τ1=15, where τ0 and τ1 are the correlation times for the isolated single and correlated pair conformational transitions, respectively. It was found that the spectral density function J(ωC) has the exponent to the correlation time τ1 as ωCJ(ωC)˜(ωCτ1)0.71 in the region of ωCτ1≪ 1.

  10. Relationship between the Carotid Plaque T1 Relaxation Time and the Plaque-to-Muscle Signal Intensity Ratio on Black-Blood Magnetic Resonance Imaging Scans.

    PubMed

    Eto, Ayumu; Kinoshita, Yoshimasa; Matsumoto, Yoshihisa; Kiyomi, Fumiaki; Iko, Minoru; Nii, Kouhei; Tsutsumi, Masanori; Sakamoto, Kimiya; Aikawa, Hiroshi; Kazekawa, Kiyoshi

    2016-11-01

    Black-blood magnetic resonance imaging (BB-MRI) is useful for the characterization and assessment of carotid artery plaques. The plaque-to-muscle signal intensity (SI) ratio (plaque/muscle ratio [PMR]) is used widely to evaluate plaques. However, the correlation between the PMR and the T1 relaxation time needs to be determined. We measured the T1 relaxation time of carotid plaques using T1 mapping and compared the results with the PMR on BB-MRI scans. Between April 2014 and July 2015, 20 patients with carotid artery stenosis were treated by carotid artery stenting. All patients underwent preoperative magnetic resonance plaque imaging. The ratio of the plaque SI to the sternocleidomastoid muscle was calculated on T1-weighted BB-MRI scans. T1 mapping was performed in the region where the vessel was narrowest using the inversion recovery technique. The T1 relaxation time was recorded to determine whether there was a correlation with the PMR. The plaque T1 value was 577.3 ± 143.2 milliseconds; the PMR value obtained on BB-MRI scans was 1.23 ± .27. There was a statistically significant decrease in the T1 value as the PMR increased (P < .0001). As the T1 relaxation time was well correlated with the PMR on BB-MRI scans, the evaluation of vulnerable plaques using the PMR was reliable and convenient. Copyright © 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  11. 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.

  12. Studies in protein dynamics using heteronuclear nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Vugmeyster, Liliya

    Dynamic processes in proteins are important for their biological function. Several issues in protein dynamics are addressed by applying existing NMR methodologies to investigate dynamics of several small proteins. Amide H/D exchange rates have been measured for the N-terminal domain of the ribosomal protein L9, residues 1--56. The results suggest that the structure of the domain is preserved in isolation and that the stability of the isolated domain is comparable to the stability of this domain in intact L9. Single domain proteins can fold in vitro at rates in excess of 1 x 104 s-1. Measurement of folding rates of this magnitude poses a considerable technical challenge. Off-resonance 15N R1rho measurements are shown to be capable of measuring such fast protein folding rates. The measurements were performed on a sample of the peripheral subunit-binding domain from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus 15N labeled at Ala 11. Fast intramolecular motions (on ps-ns time scale) can be studied by heteronuclear laboratory frame NMR relaxation. The temperature dependence of the backbone dynamics of the 36-resiude subdomain of the F-actin bundling protein villin has been investigated by studying the temperature dependence of order parameters obtained from 15N relaxation measurements. The results support the hypothesis that one of the possible mechanisms of thermostability is to lower the heat capacity difference between the folded and unfolded states by lowering the contribution from the backbone dynamics. A commonly used model-free approach for the interpretation of the relaxation data for macromolecules in solution is modified to correct for the decoupling approximation between the overall and internal motions.

  13. Study into the correlation of dominant pore throat size and SIP relaxation frequency

    NASA Astrophysics Data System (ADS)

    Kruschwitz, Sabine; Prinz, Carsten; Zimathies, Annett

    2016-12-01

    There is currently a debate within the SIP community about the characteristic textural length scale controlling relaxation time of consolidated porous media. One idea is that the relaxation time is dominated by the pore throat size distribution or more specifically the modal pore throat size as determined in mercury intrusion capillary pressure tests. Recently new studies on inverting pore size distributions from SIP data were published implying that the relaxation mechanisms and controlling length scale are well understood. In contrast new analytical model studies based on the Marshall-Madden membrane polarization theory suggested that two relaxation processes might compete: the one along the short narrow pore (the throat) with one across the wider pore in case the narrow pores become relatively long. This paper presents a first systematically focused study into the relationship of pore throat sizes and SIP relaxation times. The generality of predicted trends is investigated across a wide range of materials differing considerably in chemical composition, specific surface and pore space characteristics. Three different groups of relaxation behaviors can be clearly distinguished. The different behaviors are related to clay content and type, carbonate content, size of the grains and the wide pores in the samples.

  14. 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.

  15. A theoretical study of the stress relaxation in HMX on the picosecond time scale

    NASA Astrophysics Data System (ADS)

    Long, Yao; Chen, Jun

    2015-12-01

    The stress relaxation model of β-HMX on the picosecond time scale is studied by a theoretical approach. The relaxation of normal stress is contributed by lattice vibration, and the relaxation of shear stress is contributed by molecular rotation. Based on this model, the energy dissipation rule of the elastic wave and the profile of the shock wave are investigated. We find at low frequency the dissipation rate of the elastic wave is proportional to the power function of frequency, and under high speed shock loading the width of the stress relaxation zone is less than 0.3 μm there is a pressure peak with a height of 14 GPa near the wave front.

  16. A Molecular Dynamics Study of Relaxation Processes at a Detonation Wave Front

    NASA Astrophysics Data System (ADS)

    Kawakatsu, Toshihiro; Ueda, Akira

    1988-09-01

    Energy relaxation processes at a detonation wave front are studied with use of the molecular dynamics method. The model system is a hard disk system which undergoes an exothermic isomerization reaction \\includegraphics{dummy.eps}, where \\varDelta Q is a reaction heat. Computations are performed for several values of the molar fraction of each species. Almost all the chemical energy of A particles is released when the detonation wave front passes. It is found that this relaxation process is composed of two kinds of time regions; one is a rapid decay process caused by non-correlated reactive collisions and the other a slow relaxation by the thermodynamic relaxation and/or the cage effect of particles.

  17. Structural and microscopic relaxations in glycerol: An inelastic x-ray scattering study

    SciTech Connect

    Cunsolo, A.; Leu, B. M.; Said, A. H.; Cai, Y. Q.

    2011-05-10

    The THz dynamics of liquid glycerol has been probed by inelastic x-ray scattering at different pressure spanning the 0.66-3 Kbar range. A comparison with ultrasound absorption results available in literature leads us to identify the presence of two different relaxations, a structural (slow) relaxation and a microscopic (fast) one. Although the former has been already thoroughly studied in glycerol by lower frequency spectroscopic techniques, no hints on the latter are so far available in literature. We observe that the characteristic timescale of this fast relaxation ranges in the sub-picosecond, tends to decrease with increasing the wave-vector and seems rather insensitive to pressure changes. Finally, the timescale and strength of the fast relaxation have a direct link revealing the microscopic, single particle, nature of the involved process.

  18. Nuclear and Electron Relaxation. Chianti Workshop on Magnetic Resonance (3rd) Held in San Miniato, Pisa, Italy on May 28-June 2, 1989

    DTIC Science & Technology

    1989-06-01

    OZ oT 0 ID cm1 relea~el LC NELAXATO 7- -;; a 3 d Chianti Workshop on Magnetic Resonance NUCLEAR AND ELECTRON RELAXATION San Miniato (Pisa) - Italy...by the oartecipants at the 2 nd Workshop. The success of the present Workshop as it appears from this collection of abstracts seems great. There is a ...the red fluid necessary to keep us in the excited state in a pleasent and happy atmosphere. Finally, I would like to acknowledge the Cassa di

  19. 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

  20. Nonequilibrium relaxation study of Ising spin glass models

    NASA Astrophysics Data System (ADS)

    Ozeki, Yukiyasu; Ito, Nobuyasu

    2001-07-01

    As an analysis of equilibrium phase transitions, the nonequilibrium relaxation method is extended to the spin glass (SG) transition. The +/-J Ising SG model is analyzed for three-dimensional (cubic) lattices up to the linear size of L=127 and for four-dimensional (hypercubic) lattice up to L=41. These sizes of systems are quite large as compared with those calculated, so far, by equilibrium simulations. As a dynamical order parameter, we calculate the clone correlation function (CCF) Q(t,tw)≡[F], which is a spin correlation of two replicas produced after the waiting time tw from a simple starting state. It is found that the CCF shows an exponential decay in the paramagnetic phase, and a power-law decay after aginglike development (t>>tw) in the SG phase. This provides a reliable upper bound of the transition temperature Tg. It is also found that a scaling relation, Q(t,tw)=t-λqwq¯(t/tw), holds just around the transition point providing the lower bound of Tg. Together with these two bounds, we propose a new dynamical way for the estimation of Tg from much larger systems. In the SG phase, the power-law behavior of the CCF for t>>tw suggests that the SG phase in short-range Ising models has a rugged phase space.

  1. Polarizability anisotropy relaxation in nanoconfinement: molecular simulation study of acetonitrile in silica pores.

    PubMed

    Milischuk, Anatoli A; Ladanyi, Branka M

    2013-12-12

    We present the results of a molecular simulation study of polarizability anisotropy relaxation of liquid acetonitrile confined in approximately cylindrical silica pores of diameters in the range of 20-40 Å. Grand Canonical Monte Carlo simulation is used to determine the density of acetonitrile in pores in equilibrium with the bulk liquid, and canonical-ensemble molecular dynamics is then used to calculate the trajectories of the filled pores prepared in this way. We find that the pores are wetting, partially due to hydrogen bonding between acetonitrile nitrogen and pore silanol groups and that acetonitrile molecules have preferential orientations relative to the interface. The mobility of molecules in interfacial regions is considerably reduced and dependent mainly on their proximity to the interface. We include the contributions of molecular and interaction-induced polarizabilities to the collective polarizability anisotropy relaxation. We find that this relaxation includes a slowly relaxing component absent from the corresponding process in bulk acetonitrile and that the amplitude of this component increases as the pore diameter decreases. These results are in agreement with optical Kerr effect experiments on acetonitrile in silica pores in a similar diameter range. Further analysis of our data indicates that collective reorientation and predominantly translational "collision-induced" polarizability dynamics both contribute to the slowly relaxing portion of polarizability anisotropy decay. We further find that pore anisotropy plays a role, giving rise to different relaxation rates of polarizability anisotropy components with a different mix of axial and radial character and that collective reorientation contributing to polarizability anisotropy relaxation is somewhat faster at long times than single-molecule orientational relaxation.

  2. Spectral density mapping at multiple magnetic fields suitable for (13)C NMR relaxation studies.

    PubMed

    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 (15)N relaxation rates, introduce significant systematic errors when applied to (13)C 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 (13)C frequencies can be obtained from data acquired at three magnetic fields for uniformly (13)C-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. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. 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.

  4. 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.

  5. IR theory of weak H-bonds: Davydov coupling, Fermi resonances and direct relaxations. I. Basis equations within the linear response theory

    NASA Astrophysics Data System (ADS)

    Chamma, D.; Henri-Rousseau, O.

    1999-09-01

    Infrared and Raman spectral densities of cyclic H-bonded dimers, such as encountered in carboxylic acids, are obtained in a full quantum mechanical way by introducing relaxation effects towards the surroundings in the model of Wójcik [Mol. Phys. 36 (1978) 1757] which accounts for the possibility of simultaneous Davydov coupling (between the two hydrogen bonds involved in a cyclic dimer) and Fermi coupling (between each hydrogen bond and one or several bending modes). The relaxations of the fast stretching modes of the H-bonds and of the bending modes are assumed to be of direct type, and are taken into account in the spirit of the Green formalism by insertion of imaginary damping parameters in the effective hamiltonians. Then, the spectral density is obtained within the framework of the linear response theory by Fourier transform of the time-dependent autocorrelation function either of the dipole moment operator, in the infrared case, or of the tensor of the polarizabilities in the Raman case. Extension to non-resonant fast stretching and bending modes, and to several Fermi resonances is also performed according to Henri-Rousseau and Chamma [Chem. Phys. 229 (1998) 37]. In the undamped case, the equivalence of the present work is established with the theory of Maréchal and Witkowski [J. Chem. Phys. 48 (1968) 3697] by neglecting the Fermi resonances. Moreover, one-to-one correspondences are also shown with the work of Henri-Rousseau and Chamma [Chem. Phys. 229 (1998) 37] by ignoring Davydov coupling, and with that of Rösch and Ratner [J. Chem. Phys. 61 (1974) 3344] by neglecting both Davydov and Fermi couplings. Finally, the use of the symmetry properties which appear in cyclic dimers when neglecting the Fermi resonances, initially performed by Maréchal and Witkowski [J. Chem. Phys. 48 (1968) 3697], is discussed, showing the equivalence with the results of the non-symmetrized treatment.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. Studying IDP stability and dynamics by fast relaxation imaging in living cells.

    PubMed

    Dhar, Apratim; Prigozhin, Maxim; Gelman, Hannah; Gruebele, Martin

    2012-01-01

    Fast relaxation imaging (FReI) temperature-tunes living cells and applies small temperature jumps to them, to monitor biomolecular stability and kinetics in vivo. The folding or aggregation state of a target protein is monitored by Förster resonance energy transfer (FRET). Intrinsically disordered proteins near the structured-unstructured boundary are particularly sensitive to their environment. We describe, using the IDP α-synuclein as an example, how FReI can be used to measure IDP stability and folding inside the cell.

  11. Nuclear Magnetic Resonance Technology for Medical Studies

    NASA Astrophysics Data System (ADS)

    Budinger, Thomas F.; Lauterbur, Paul C.

    1984-10-01

    Nuclear magnetic resonance proton imaging provides anatomical definition of normal and abnormal tissues with a contrast and detection sensitivity superior to those of x-ray computed tomography in the human head and pelvis and parts of the cardiovascular and musculoskeletal systems. Recent improvements in technology should lead to advances in diagnostic imaging of the breast and regions of the abdomen. Selected-region nuclear magnetic resonance spectroscopy of protons, carbon-13, and phosphorus-31 has developed into a basic science tool for in vivo studies on man and a unique tool for clinical diagnoses of metabolic disorders. At present, nuclear magnetic resonance is considered safe if access to the magnet environment is controlled. Technological advances employing field strengths over 2 teslas will require biophysical studies of heating and static field effects.

  12. Characterization of brain tumours with spin-spin relaxation: pilot case study reveals unique T 2 distribution profiles of glioblastoma, oligodendroglioma and meningioma.

    PubMed

    Laule, Cornelia; Bjarnason, Thorarin A; Vavasour, Irene M; Traboulsee, Anthony L; Wayne Moore, G R; Li, David K B; MacKay, Alex L

    2017-09-11

    Prolonged spin-spin relaxation times in tumour tissue have been observed since some of the earliest nuclear magnetic resonance investigations of the brain. Over the last three decades, numerous studies have sought to characterize tumour morphology and malignancy using quantitative assessment of T 2 relaxation times, although attempts to categorize and differentiate tumours have had limited success. However, previous work must be interpreted with caution as relaxation data were typically acquired using a variety of multiple echo sequences with a range of echoes and T 2 decay curves and were frequently fit with monoexponential analysis. We defined the distribution of T 2 components in three different human brain tumours (glioblastoma, oligodendroglioma, meningioma) using a multi-echo sequence with a greater number of echoes and a longer acquisition window than previously used (48 echoes, data collection out to 1120 ms) with no a priori assumptions about the number of exponential components contributing to the T 2 decay. T 2 relaxation times were increased in tumour tissue and each tumour showed a distinct T 2 distribution profile. Tumours have complex and unique compartmentalization characteristics. Quantitative assessment of T 2 relaxation in brain cancer may be useful in evaluating different grades of brain tumours on the basis of their T 2 distribution profile, and has the potential to be a non-invasive diagnostic tool which may also be useful in monitoring therapy. Further study with a larger sample size and varying grades of tumours is warranted.

  13. 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.

  14. Promoting sleep for hospitalized patients with advanced cancer with relaxation therapy: experience of a randomized study.

    PubMed

    Ducloux, Dominique; Guisado, Huguette; Pautex, Sophie

    2013-09-01

    Sleep disorders are frequent in patients with advanced cancer receiving palliative care. The objective of this study was to demonstrate whether relaxation therapy can improve their satisfaction with sleep. Few studies have investigated the effectiveness of relaxation in patients hospitalized with an advanced chronic disease. Prospective randomized study with an immediate intervention group (IIG; relaxation days 3-6) and a delayed intervention group (DIG; relaxation days 6-9). The main measure was the overall satisfaction of sleep measured on a Numerical Rating Scale of Satisfaction of Sleep (NRSSS) between 0 and 10. Totally 18 (IIG: 9; DIG: 9) patients were included in this study (mean age 66 ± 10.7). The NRSSS improved in both the groups (almost statistically significant) between the day of inclusion and day 2. Because of the dropout of the patients during the last days of the study, we analyzed the improvement in sleep satisfaction only between day 2 and 5. The NRSSS D5 for the immediate and delayed groups were 4.0 ± 23 and 3.8 ± 2.3, respectively. There was no significant improvement in both the groups. The results demonstrated the difficulty to include patients with advanced cancer in a randomized study with a DIG. We were not able to demonstrate the effectiveness of relaxation therapy on sleep satisfaction. Techniques that can be easily used to improve sleep in patients with an advanced cancer should be developed and used already early in the disease.

  15. A laboratory study of the influence of iron(II) bearing minerals on the nuclear magnetic resonance measurement.

    NASA Astrophysics Data System (ADS)

    Keating, K.; Knight, R.

    2008-12-01

    Proton nuclear magnetic resonance (NMR) relaxation is a geophysical technique which can be used to measure water content and estimate hydraulic conductivity in the top 100 m of Earth's surface. We conducted a laboratory study to measure the effect of the concentration of iron(II) minerals on NMR relaxation rates of water-saturated sand mixtures. We measured mixtures of quartz sand (diameter < 420μm) and four different iron(II) minerals in granular form (diameters ranging from 45 to 53μm): troilite (FeS), pyrite (FeS2), siderite (Fe(II)CO3), and vivianite (Fe(II)PO4+nH2O). The iron(II) minerals were mixed with quartz to concentrations of 1 and 2% by weight iron. The NMR response of the water-saturated samples was measured and used to calculate four averaged relaxation rates for each iron(II) mineral mixture: the total mean log, bulk fluid, surface, and diffusion relaxation rates. The surface area of the samples was also measured and used to calculate the surface relaxivity. The results of this study are: 1) The mean log and surface relaxation rates of all the samples increase with iron(II) concentration. 2) For the troilite, pyrite and siderite mixtures the surface relaxivity increased with concentration of iron(II); for the vivianite mixtures the surface relaxivity remained constant for iron(II) concentrations of 1 and 2%. 3) The diffusion relaxation rate was non-zero and was slower than the surface relaxation rate for the troilite and vivianite mixtures; the diffusion relaxation rate was zero for the siderite and pyrite mixtures. The results of this study allow us to correct for the presence of iron(II) minerals in the interpretation of NMR data.

  16. Robust postfabrication trimming of ultracompact resonators on silicon on insulator with relaxed requirements on resolution and alignment.

    PubMed

    Alipour, Payam; Atabaki, Amir H; Askari, Murtaza; Adibi, Ali; Eftekhar, Ali A

    2015-10-01

    One of the main drawbacks of the high-index-contrast silicon-on-insulator platform in integrated photonics is the high sensitivity of the resonance wavelength of resonators to dimensional variations caused by fabrication imperfection. In this work, we experimentally demonstrate an accurate postfabrication trimming technique for compensating the fabrication-induced variations in the resonance properties of nanophotonic devices. Using this technique, we reduce the variation of the resonance wavelength of 4 μm diameter microdonut resonators by more than 1 order of magnitude to about 25 pm, which is adequate for most interconnect, optical signal processing, and sensing applications. In addition, our proposed technique has improved misalignment toleration and throughput compared to previous reports.

  17. Luminescent and Optically Detected Magnetic Resonance Studies of CdS/PVA Nanocomposite

    NASA Astrophysics Data System (ADS)

    Rudko, Galyna Yu.; Vorona, Igor P.; Fediv, Volodymyr I.; Kovalchuk, Andrii; Stehr, Jan E.; Shanina, Bela D.; Chen, WeiMin M.; Buyanova, Irina A.

    2017-02-01

    A series of solid nanocomposites containing CdS nanoparticles in polymeric matrix with varied conditions on the interface particle/polymer was fabricated and studied by photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. The results revealed interface-related features in both PL and ODMR spectra. The revealed paramagnetic centers are concluded to be involved in the processes of photo-excited carriers relaxation.

  18. 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.

  19. Probing the Residual Structure of the Low Populated Denatured State of ADA2h under Folding Conditions by Relaxation Dispersion Nuclear Magnetic Resonance Spectroscopy.

    PubMed

    Pustovalova, Yulia; Kukic, Predrag; Vendruscolo, Michele; Korzhnev, Dmitry M

    2015-08-04

    The structural characterization of low populated states of proteins with accuracy comparable to that achievable for native states is important for understanding the mechanisms of protein folding and function, as well as misfolding and aggregation. Because of the transient nature of these low populated states, they are seldom detected directly under conditions that favor folding. The activation domain of human procarboxypeptidase A2 (ADA2h) is an α/β-protein that forms amyloid fibrils at low pH, presumably initiated from a denatured state with a considerable amount of residual structure. Here we used Carr-Parcell-Meiboom-Gill relaxation dispersion (CPMG RD) nuclear magnetic resonance (NMR) spectroscopy to characterize the structure of the denatured state of the ADA2h I71V mutant under conditions that favor folding. Under these conditions, the lifetime of the denatured state of I71V ADA2h is on the order of milliseconds and its population is approximately several percent, which makes this mutant amenable to studies by CPMG RD methods. The nearly complete set of CPMG RD-derived backbone (15)N, (13)C, and (1)H NMR chemical shifts in the I71V ADA2h denatured state reveals that it retains a significant fraction (up to 50-60%) of nativelike α-helical structure, while the regions encompassing native β-strands are structured to a much lesser extent. The nativelike α-helical structure of the denatured state can bring together hydrophobic residues on the same sides of α-helices, making them available for intra- or intermolecular interactions. CPMG RD data analysis thus allowed a detailed structural characterization of the ADA2h denatured state under folding conditions not previously achieved for this protein.

  20. 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%.

  1. Resonance Raman spectroscopy study of protonated porphyrin

    NASA Astrophysics Data System (ADS)

    Gorski, A.; Starukhin, A.; Stavrov, S.; Gawinkowski, S.; Waluk, J.

    2017-02-01

    Resonance Raman microscopy was used to study the resonance Raman scattering of the diacid (diprotonated form) of free-base porphyrin (21H,23H-porphine) in a crystal powder and KBr pellets. Intensive lines in the spectral range between 100 ÷ 1000 cm- 1 have been detected and assigned as spectral manifestation of out-of-plane modes. The Raman spectra were simulated by means of DFT methods and compared with the experimental data. It is evident from experimental and theoretical results that the activation of out-of-plane modes arises from saddle distortion of the porphyrin macrocycle upon formation of its diprotonated form.

  2. Effect of intra-abdominal hypertension on left ventricular relaxation: a preliminary animal study.

    PubMed

    Mahjoub, Y; Lorne, E; Maizel, J; Plantefève, G; Massy, Z A; Dupont, H; Slama, M

    2012-02-01

    In the intensive care unit, intra-abdominal hypertension (IAH) is a frequently encountered, life-threatening condition. The aim of this animal study was to evaluate the effect of IAH on left ventricular (LV) relaxation (i.e. the active phase of diastole). Seven male rabbits were anaesthetized before mechanical ventilation. A 20 mm Hg increase in intra-abdominal pressure (IAP) was then induced by intraperitoneal infusion of 1.5% glycine solution. Haemodynamic parameters were recorded and the relaxation time constant tau (considered to be the best index of left ventricle relaxation) was calculated. All haemodynamic measurements were recorded at baseline and then after induction of IAH. A 20 mm Hg increase in IAP was not followed by a significant change in arterial pressure, but was associated with increases in central venous pressure (from 2 [-2 to 6] to 7 [-2 to 12] mm Hg, P= 0.03), LV end-diastolic pressure (from 7 [6-8] to 15 [11-19] mm Hg, P= 0.04) and the relaxation time constant tau (from 16 [14-18] to 43 [34-52] ms, P= 0.048). In this animal study, a 20 mm Hg increase in IAP impaired LV relaxation. Further studies are necessary to identify the causes of this impairment.

  3. Nuclear magnetic relaxation studies of water in frozen biological tissues. Cross-relaxation effects between protein and bound water protons

    NASA Astrophysics Data System (ADS)

    Escanyé, J. M.; Canet, D.; Robert, J.

    Water proton longitudinal relaxation has been investigated in frozen mouse tissues including tumors. The nonfreezable water which gives rise to a relatively sharp NMR signal at this temperature (263 K) is identified as water bound to macromolecules. Measurements have been carried out by the nonselective inversion-recovery method at 90 and 6 MHz. Partially selective inversion has been achieved at 90 MHz by the DANTE sequence. The experimental data are analyzed by means of Solomon-type equations. This analysis provides the cross-relaxation term from which the dipolar contribution to water relaxation rate, arising from interactions with macromolecular protons, is calculated. This contribution seems to be dominant. The number of water protons interacting with a given macromolecular proton is found to be of the order of 10. The data at both frequencies can be consistently interpreted in terms of water diffusion, with a characteristic time of about 10 -9 sec. These conclusions are valid for all the tissues investigated here, their relaxation parameters exhibiting only slight differences.

  4. Fast Scanning Calorimetry study of non-equilibrium relaxation in fragile organic liquids

    NASA Astrophysics Data System (ADS)

    Sadtchenko, Vlad; Bhattacharya, Deepanjan; O'Reilly, Liam

    2013-03-01

    Fast scanning calorimetry (FSC), capable of heating rates in excess of 1000000 K/s, was combined with vapor deposition technique to investigate non-equilibrium relaxation in micrometer thick viscous liquid films of several organic compounds (e.g.2-ethyl-1-hexanol, Toluene, and 1-propanol) under high vacuum conditions. Rapid heating of samples, vapor deposited at temperatures above their standard glass softening transition (Tg), resulted in observable endotherms which onset temperatures were strongly dependent on heating rate and the deposition temperature. Furthermore, all of the studied compounds were characterized by distinct critical deposition temperatures at which observation of endotherm became impossible. Based on the results of these studies, we have developed a simple model which makes it possible to infer the equilibrium enthalpy relaxation times for liquids from FSC data. We will discuss implications of these studies for contemporary models of non-equilibrium relaxation in glasses and supercooled liquids. Supported by NSF Grant 1012692.

  5. Microwave dielectric relaxation spectroscopy study of alkan-1-ol/alkylbenzoate binary solvents.

    PubMed

    Navarro, Ana M; García, Begoña; Ibeas, Saturnino; Hoyuelos, Francisco J; Peñacoba, Indalecio A; Leal, José M

    2013-10-03

    The structure and dynamics of alkan-1-ol/alkylbenzoate binary mixtures have been studied by microwave dielectric relaxation spectroscopy in the 200 MHz to 20 GHz frequency range. The binary mixtures of methanol, ethanol, propan-1-ol, butan-1-ol, and pentan-1-ol with methyl, ethyl, propyl, and butyl benzoates were studied at 298.15 K. The relaxational response of the pure alcohols, pure esters, and their binary mixtures over the full composition range is properly described by the Havriliak-Negami model. The alcohol content, alcohol length, and alkyl side-chain effects on the relaxational properties have been studied for these mixtures over the whole composition range. From the experimental readings, the effective and the corrective Kirkwood and Bruggeman correlation factors have been calculated. The data gathered have been interpreted in terms of the alkyl side-chain effect and their reliance on the mixture composition.

  6. Concentration dependence of nitroxyl spin probes in liposomal solution: electron spin resonance and overhauser-enhanced magnetic resonance studies.

    PubMed

    Meenakumari, V; Utsumi, Hideo; Jawahar, A; Franklin Benial, A Milton

    2016-12-21

    In this work, the detailed studies of electron spin resonance (ESR) and overhauser-enhanced magnetic resonance imaging (OMRI) were carried out for permeable nitroxyl spin probe, MC-PROXYL as a function of agent concentration in liposomal solution. In order to compare the impermeable nature of nitroxyl radical, the study was also carried out only at 2 mM concentration of carboxy-PROXYL. The ESR parameters were estimated using L-band and 300 MHz ESR spectrometers. The line width broadening was measured as a function of agent concentration in liposomal solution. The estimated rotational correlation time is proportional to the agent concentration, which indicates that less mobile nature of nitroxyl spin probe in liposomal solution. The partition parameter and permeability values indicate that the diffusion of nitroxyl spin probe distribution into the lipid phase is maximum at 2 mM concentration of MC-PROXYL. The dynamic nuclear polarization (DNP) parameters such as DNP factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for 2 mM MC-PROXYL in 400 mM liposomal dispersion. The spin lattice relaxation time was shortened in liposomal solution, which leads to the high relaxivity. Reduction in coupling factor is due to less interaction between the electron and nuclear spins, which causes the reduction in enhancement. The leakage factor increases with increasing agent concentration. The increase in DNP enhancement was significant up to 2 mM in liposomal solution. These results paves the way for choosing optimum agent concentration and OMRI scan parameters used in intra and extra membrane water by loading the liposome vesicles with a lipid permeable nitroxyl spin probes in OMRI experiments.

  7. Sorption selectivity in natural organic matter studied with nitroxyl paramagnetic relaxation probes.

    PubMed

    Lattao, Charisma; Cao, Xiaoyan; Li, Yuan; Mao, Jingdong; Schmidt-Rohr, Klaus; Chappell, Mark A; Miller, Lesley F; dela Cruz, Albert Leo; Pignatello, Joseph J

    2012-12-04

    Sorption site selectivity and mechanism in natural organic matter (NOM) were addressed spectroscopically by the sorption of paramagnetic nitroxyl compounds (spin probes) of different polarity, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and HTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl). The sorbents were Pahokee peat, Beulah-Zap lignite, and a polystyrene-poly(vinyl methyl ether) (PS-PVME) polymer blend representing the mixed aliphatic-aromatic, polar-nonpolar character of NOM. Nuclear-electron spin interaction serves as an efficient relaxation pathway, resulting in attenuation of the (13)C-CP/TOSS NMR signal for (13)C nuclei in proximity to the N-O· group (r(-6) dependence). In the natural solids the spin probes sorbed more specifically (greater isotherm nonlinearity) and had lower rotational mobility (broader electron paramagnetic resonance signals) than in PS-PVME. Titration with spin probe indicated almost no selectivity for the different carbon functional groups of PS-PVME, and little to no selectivity for the different carbon moieties of Pahokee and Beulah, including aromatic, alkyl, O-alkyl, di-O-alkyl, and O-methyl. In any case, sorption site selectivity of spin probes to NOM was always weaker than partition selectivity found in model solvent-water (toluene, hexadecane, anisole, octanol) and cellulose-water systems. The results indicate little or no preferential sorption in NOM based on functional group chemistry or putative microdomain character, but rather are consistent with the filling of pores whose walls have an average chemical environment reflecting the bulk chemical composition of the solid. This work demonstrates for the first time the use of paramagnetic probes to study sorption specificity.

  8. A study of relaxation techniques for the transient analysis of digital circuits

    NASA Astrophysics Data System (ADS)

    Chia, W. K.

    1985-06-01

    In the VLSI microelectronics era, the cost of the immense CPU time and memory storage for a standard circuit simulator has become prohibitive. In order to achieve dramatic improvement in the performance of the circuit simulator, there are two principal points of departure from the standard simulation approach, namely, tearing decomposition and relaxation decomposition. This research is to study the numerical convergence and stability properties of several of the relaxation algorithms that have been proposed for the simulation of VLSI circuits. The time-point Gauss-Seidel method with prediction, the exploitation of latency and event scheduling algorithms are implemented into a general purpose circuit simulator SLATE-R (a Simulator with Latency and Tearing--Relaxed version). The performance of the SLATE-R program in the analysis of various types of integrated circuit technologies is studied.

  9. 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.

  10. Identification of the chromophore in the apatite pigment [Sr10(PO4)6(Cu(x)OH(1-x-y))2]: linear OCuO- featuring a resonance Raman effect, an extreme magnetic anisotropy, and slow spin relaxation.

    PubMed

    Kazin, Pavel E; Zykin, Mikhail A; Zubavichus, Yan V; Magdysyuk, Oxana V; Dinnebier, Robert E; Jansen, Martin

    2014-01-03

    A new chromophore has been identified in copper-doped apatite pigments having the general composition [Sr(10)(PO(4))(6)(Cu(x)OH(1-x-y))(2)], in which x=0.1, 0.3 and y=0.01-0.42. By using X-ray absorption spectroscopy, low-temperature magnetization measurements, and synchrotron X-ray powder structure refinement, it has been shown that the oxygenated compounds contain simultaneously diamagnetic Cu(1+) and paramagnetic Cu(3+) with S=1. Cu(3+) is located at the same crystallographic position as Cu(1+), being linearly coordinated by two oxygen atoms and forming the OCuO(-) anion. The Raman spectroscopy study of [A(10)(PO(4))(6)(Cu(x)OH(1-x-y))(2)], in which A=Ca, Sr, Ba, reveals resonance bands at 651-656 cm(-1) assigned to the symmetric stretching vibration (ν(1)) of OCuO(-). The strontium apatite pigment exhibits a strong paramagnetic anisotropy with an unprecedentedly large negative zero-field splitting parameter (D) of ≈-400 cm(-1). The extreme magnetic anisotropy causes slow magnetization relaxation with relaxation times (τ) up to 0.3 s at T=2 K, which relates the compounds to single-ion magnets. At low temperature, τ is limited by a spin quantum-tunneling, whereas at high temperature a thermally activated relaxation prevails with U(eff)≈48 cm(-1). Strong dependence of τ on the paramagnetic center concentration at low temperature suggests that the spin-spin relaxation dominates in the spin quantum-tunneling process. The compound is the first example of a d-metal-based single-ion magnet with S=1, the smallest spin at which an energy barrier arises for the spin flipping.

  11. Nuclear Magnetic Resonance Studies in Heavy Fermion Materials

    NASA Astrophysics Data System (ADS)

    Shirer, Kent Robert

    29Si, 31P, and 115In nuclear magnetic resonance studies of heavy fermion materials URu2Si 2, CeRhIn5, and URu2Si2- xPx were conducted as a function of temperature, pressure, and, in the case of URu2Si2- xPx, doping. Knight shift measurements in these systems probe the hybridization between conduction and local f-electrons which is described by the heavy fermion coherence temperature, T*, and can be captured by a two fluid model. This model takes the dual nature of the local moments and the heavy electron fluid into account. In URu2Si2 in a pressure range from 0-9.1 kbar, spin-lattice-relaxation data were taken and suggest a partial suppression of the density of states below 30 K. The data are analyzed in terms of a two component spin-fermion model. The spin-lattice-relaxation behavior is then compared to other materials that demonstrate precursor fluctuations in a pseudogap regime above a ground state with long-range order. Nuclear magnetic resonance data in CeRhIn5 for both the In(1) and In(2) sites are also taken under hydrostatic pressure. The Knight shift data reveal a suppression of the hyperfine coupling to the In(1) site as a function of pressure, and the electric field gradient at the In(2) site exhibits a change of slope. These changes to these coupling constants reflect alterations to the electronic structure at the quantum critical point. Finally, we report 31P nuclear magnetic resonance measurements in single crystals of URu2Si2-xP x with x = 0.09, 0.33. In the case of the x = 0.09 doping, we find no evidence for a phase transition, though the material still exhibits heavy fermion coherence. In the x = 0.33 doping, we find that it undergoes an antiferromagnetic (AFM) phase transition. When we include the pure compound in our analysis, we find that the hyperfine couplings and coherence temperatures evolve with doping. We compare this evolution with the trends seen in other compounds.

  12. Charge-carrier relaxation in disordered organic semiconductors studied by dark injection: Experiment and modeling

    NASA Astrophysics Data System (ADS)

    Mesta, M.; Schaefer, C.; de Groot, J.; Cottaar, J.; Coehoorn, R.; Bobbert, P. A.

    2013-11-01

    Understanding of stationary charge transport in disordered organic semiconductors has matured during recent years. However, charge-carrier relaxation in nonstationary situations is still poorly understood. Such relaxation can be studied in dark injection experiments, in which the bias applied over an unilluminated organic semiconductor device is abruptly increased. The resulting transient current reveals both charge-carrier transport and relaxation characteristics. We performed such experiments on hole-only devices of a polyfluorene-based organic semiconductor. Modeling the dark injection by solving a one-dimensional master equation using the equilibrium carrier mobility leads to a too-slow current transient, since this approach does not account for carrier relaxation. Modeling by solving a three-dimensional time-dependent master equation does take into account all carrier transport and relaxation effects. With this modeling, the time scale of the current transient is found to be in agreement with experiment. With a disorder strength somewhat smaller than extracted from the temperature-dependent stationary current-voltage characteristics, also the shape of the experimental transients is well described.

  13. T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study.

    PubMed

    Mamisch, Tallal Charles; Hughes, Timothy; Mosher, Timothy J; Mueller, Christoph; Trattnig, Siegfried; Boesch, Chris; Welsch, Goetz Hannes

    2012-03-01

    T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage. The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue. There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX. Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface.

  14. High pressure studies on structural and secondary relaxation dynamics in silyl derivative of D-glucose

    NASA Astrophysics Data System (ADS)

    Minecka, Aldona; Kamińska, Ewa; Tarnacka, Magdalena; Dzienia, Andrzej; Madejczyk, Olga; Waliłko, Patrycja; Kasprzycka, Anna; Kamiński, Kamil; Paluch, Marian

    2017-08-01

    In this paper, broadband dielectric spectroscopy was applied to investigate molecular dynamics of 1,2,3,4,6-penta-O-(trimethylsilyl)-D-glucopyranose (S-GLU) at ambient and elevated pressures. Our studies showed that apart from the structural relaxation, one well resolved asymmetric secondary process (initially labeled as β) is observed in the spectra measured at p = 0.1 MPa. Analysis with the use of the coupling model and criterion proposed by Ngai and Capaccioli indicated that the β-process in S-GLU is probably a Johari-Goldstein relaxation of intermolecular origin. Further high pressure experiments demonstrated that there are in fact two secondary processes contributing to the β-relaxation. Therefore, one can postulate that the coupling model is a necessary, but not sufficient criterion to identify the true nature of the given secondary relaxation process. The role of pressure experiments in better understanding of the molecular origin of local mobility seems to be much more important. Interestingly, our research also revealed that the structural relaxation in S-GLU is very sensitive to compression. It was reflected in an extremely high pressure coefficient of the glass transition temperature (dTg/dp = 412 K/GPa). According to the literature data, such a high value of dTg/dp has not been obtained so far for any H-bonded, van der Waals, or polymeric glass-formers.

  15. Chemical shift and spin-lattice relaxation time for two crystallographically inequivalent 133Cs sites in Cs2BBr4 (B=57Co, 63Cu, and 65Zn) using magic-angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Kim, Sun Ha

    2017-05-01

    The structural geometry around the 133Cs nuclei in Cs2BBr4 (B = 57Co, 63Cu, and 65Zn) was investigated by examining the chemical shifts and spin-lattice relaxation times in a rotating frame. Two crystallographically inequivalent Cs(1) and Cs(2) sites were differentiated. The spin-lattice relaxation times T1ρ of 133Cs nuclei in three crystals were measured to obtain detailed information about their structural dynamics. Cs(1) surrounded by eleven bromide ions was found to have a longer relaxation time than Cs(2) surrounded by nine bromide ions. The nuclear magnetic resonance (NMR) results were compared to previously reported results for Cs2BCl4. The halogen species in Cs2BX4 (X = Br, Cl) was not found to influence the relaxation time, whereas the B metal ion (B = Co, Cu, and Zn) was found to alter the relaxation time mechanism.

  16. Effects of Mind Sound Resonance Technique (Yogic Relaxation) on Psychological States, Sleep Quality, and Cognitive Functions in Female Teachers: A Randomized, Controlled Trial.

    PubMed

    Rao, Manas; Metri, Kashinath G; Raghuram, Nagaratna; Hongasandra, Nagendra R

    2017-01-01

    Context • Several studies have revealed a high rate of physical and psychological problems from stress among schoolteachers. Yoga is one of the mind-body interventions known to alleviate stress and effects. The mind sound resonance technique (MSRT), a yoga-based, mindfulness relaxation is recognized as having a positive influence on physical and psychological health. Objectives • The study intended to examine the effects of an MSRT intervention for 1 mo on perceived stress, quality of sleep, cognitive function, state and trait anxiety, psychological distress, and fatigue among female teachers. Design • The study was a randomized, controlled trial. Setting • The study occurred at 2 primary schools in Bangalore City, India. Participants • Sixty female teachers, aged between 30 and 55 y, from the 2 schools were enrolled in the study. Intervention • The participants were randomly divided into an MSRT group (n = 30) and a control group (n = 30). Participants in the MSRT group participated in MSRT for 30 min/d, 5 d/wk, for the duration of 1 mo. The participants in the control group followed their normal daily routines. Outcome measures • Perceived stress, sleep quality, cognitive function, anxiety, psychological distress, fatigue, and self-esteem were assessed using standardized assessment tools at baseline and after 1 mo of the intervention. Results • In the MSRT group, a significant reduction occurred for 5 variables: (1) 47.01% for perceived stress (P < .001), (2) 28.76% for state anxiety (P < .001), (3) 13.35% for trait anxiety (P < .001), (4) 32.90% for psychological distress (P < .001), and (5) 44.79% for fatigue (P < .001). A significant improvement occurred for that group for 2 variables: (1) 44.94% for quality of sleep (P < .001), and (2) 12.12% for self-esteem (P < .001). An 11.88% increase occurred for the group for cognitive function, but the change was not significant (P = .111). On the other hand, the control group showed significant

  17. Low-temperature nuclear quadrupole resonance studies of antimony and application to thermometry

    NASA Astrophysics Data System (ADS)

    Genio, Edgar Baylon

    1997-11-01

    The spin-lattice retaxation time, Tsb1, of finely divided powdered metallic antinomy immersed in liquid sp3He was measured using pulsed Nuclear Quadrupole Resonance (NQR) techniques. In this technique, the nuclear quadrupole resonant antinomy nuclei were saturated using an RF pulse. The recovery back to equilibrium was monitored using short inspection pulses and the magnetization recovery follows a recovery curve characterized by the relaxation time Tsb1. Tsb1 measurements were performed at temperatures ranging from 150 mK to 1.25 mK. Temperatures down to 11 mK were achieved by using a dilution refrigerator. Lower temperatures were achieved using adiabatic nuclear demagnetization of a copper bundle starting at 8.5 Tesla (7.5 Tesla average field over the copper bundle). The sample was cooled by immersion in liquid sp3He which is in thermal contact with silver sinter packed in the bottom of a silver cell. This cell was bolted onto a cold plate attached to the copper bundle. It was found that a low temperatures starting near 75 mK, the measured total relaxation was significantly enhanced with respect to the Korringa relaxation, the dominant relaxation mechanism expected for a metal at these temperatures. This enhancement is attributed to a surface relaxation mechanism mediated by the surface sp3He atoms. In systems immersed in liquid sp3He, a surface relaxation mechanism is present due to a modulation of the interaction between the solid-like sp3He atoms on the surface and the surface spins. This modulation is due to the quantum zero-point motion of the sp3He atoms on the surface. This phenomenon has been well studied in insulating systems using Nuclear Magnetic Resonance. The measurements undertaken in this study demonstrate that this phenomenon is present in a metallic and quadrupolar system. This surface relaxation mechanism becomes the dominant relaxation mechanism at low temperatures. Considering the surface and bulk spins as belonging to different phases, a two

  18. Auto-assembling of ditopic macrocyclic lanthanide chelates with transition-metal ions. Rigid multimetallic high relaxivity contrast agents for magnetic resonance imaging.

    PubMed

    Paris, Jérôme; Gameiro, Cristiana; Humblet, Valérie; Mohapatra, Prasanta K; Jacques, Vincent; Desreux, Jean F

    2006-06-26

    PhenHDO3A is a ditopic ligand featuring a tetraazacyclododecane unit substituted by three acetate arms and one 6-hydroxy-5,6-dihydro-1,10-phenanthroline group (PhenHDO3A = rel-10-[(5R,6R)-5,6-dihydro-6-hydroxy-1,10-phenantholin-5-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid). This ligand was specially designed so as to obtain highly stable heteropolymetallic assemblies. PhenHDO3A has been prepared starting from phenanthroline epoxide and either a triprotected tetraazacyclododecane or tert-butyl triester of N,N',N' '-tetraazacyclododecane-triacetic acid. The latter yields PhenHDO3A in a single step. PhenHDO3A forms kinetically stable lanthanide complexes (acid-catalyzed kinetic constant kH = (1.2 +/- 0.2) x 10(-3) s(-1) M(-1)) whose solution structure has been deduced from a quantitative analysis of the paramagnetic shifts and the longitudinal relaxation times of the proton nuclei of YbPhenHDO3A. The alcohol group of the dihydro-phenanthroline unit remains coordinated to the encapsulated metal ion despite the steric crowding brought about by this group. Furthermore, the complexes are monohydrated, as shown by luminescence lifetime measurements on EuPhenHDO3A solutions. Relaxivity titrations at 20 MHz clearly indicate that the phenanthroline unit of GdPhenHDO3A is available for the spontaneous formation of highly stable tris complexes with the Fe2+ and Ni2+ ions. The water-exchange times and the rotational correlation times of GdPhenHDO3A and Fe(GdPhenHDO3A)32+ have been deduced from variable temperature 17O NMR studies and from nuclear relaxation dispersion curves. Despite rather slow water-exchange rates (taum0 = 1.0-1.2 x 10(-6) s), relaxivity gains of 90% have been observed upon the formation of the heterometallic tris complexes. The latter rotate about four times more slowly (taur0= 398 ps) than the monomeric unit (taur0 = 105 ps) and their relaxivity is, accordingly, twice as high. The relaxivity of the tris complexes between 10 and 50 MHz is

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

    PubMed

    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. Copyright © 2012 Elsevier Inc. All rights reserved.

  20. 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.

  1. Albumin binding, relaxivity, and water exchange kinetics of the diastereoisomers of MS-325, a gadolinium(III)-based magnetic resonance angiography contrast agent.

    PubMed

    Caravan, Peter; Parigi, Giacomo; Chasse, Jaclyn M; Cloutier, Normand J; Ellison, Jeffrey J; Lauffer, Randall B; Luchinat, Claudio; McDermid, Sarah A; Spiller, Marga; McMurry, Thomas J

    2007-08-06

    The amphiphilic gadolinium complex MS-325 ((trisodium-{(2-(R)-[(4,4-diphenylcyclohexyl) phosphonooxymethyl] diethylenetriaminepentaacetato) (aquo)gadolinium(III)}) is a contrast agent for magnetic resonance angiography (MRA). MS-325 consists of two slowly interconverting diastereoisomers, A and B (65:35 ratio), which can be isolated at pH > 8.5 (TyeklAr, Z.; Dunham, S. U.; Midelfort, K.; Scott, D. M.; Sajiki, H.; Ong, K.; Lauffer, R. B.; Caravan, P.; McMurry, T. J. Inorg. Chem. 2007, 46, 6621-6631). MS-325 binds to human serum albumin (HSA) in plasma resulting in an extended plasma half-life, retention of the agent within the blood compartment, and an increased relaxation rate of water protons in plasma. Under physiological conditions (37 degrees C, pH 7.4, phosphate buffered saline (PBS), 4.5% HSA, 0.05 mM complex), there is no statistical difference in HSA affinity or relaxivity between the two isomers (A 88.6 +/- 0.6% bound, r1 = 42.0 +/- 1.0 mM(-1) s(-1) at 20 MHz; B 90.2 +/- 0.6% bound, r1 = 38.3 +/- 1.0 mM(-1) s(-1) at 20 MHz; errors represent 1 standard deviation). At lower temperatures, isomer A has a higher relaxivity than isomer B. The water exchange rates in the absence of HSA at 298 K, kA298 = 5.9 +/- 2.8 x 10(6) s(-1), kB298 = 3.2 +/- 1.8 x 10(6) s(-1), and heats of activation, DeltaHA = 56 +/- 8 kJ/mol, DeltaHB = 59 +/- 11 kJ/mol, were determined by variable-temperature 17O NMR at 7.05 T. Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded over the frequency range of 0.01-50 MHz at 5, 15, 25, and 35 degrees C in a 4.5% HSA in PBS solution for each isomer (0.1 mM). Differences in the relaxivity in HSA between the two isomers could be attributed to the differing water exchange rates.

  2. 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.

  3. High Pressure Light Scattering Study of Relaxation in the Glass Former Cumene

    NASA Astrophysics Data System (ADS)

    Ransom, Tim; Lyon, Kevin; Oliver, William

    2014-03-01

    To understand relaxation dynamics in glassy systems, a light scattering study on Cumene has been carried out in a diamond anvil cell (DAC) at pressures from 0.2 GPa to 2.5 GPa isothermally at 75 °C. Polarized and depolarized spectra were taken in both near-backscattering and equal-angle 60° forward-scattering geometries at several free spectral ranges from 0.5 GHz to 300 GHz. Depolarized backscattering spectra are converted into susceptibility featuring the evolution of the α-relaxation peak, yielding structural relaxation times τα from 10 ps to 1 ns. We have also developed photon correlation spectroscopy (PCS) in a DAC, giving τα from ~ 1 μs to 1 s. We fit τα over these many decades with a modified VFTH equation τα =τ0 exp[DP/(P0-P)] giving parameters τ0 = 9.2 ps, D = 17.5, and P0 = 4.5 GPa at 75°C. After the α-relaxation peak moves into lower frequencies (P ~ 1 GPa), we observe the emergence of the β-relaxation minimum region. We fit the β-minimum to a power law scaling form χ''(ω) = b(ω/ωmin)a + a(ωmin/ ω)b. Polarized backscattering and forward scattering gives frequency shift ωB and linewidth ΓB values of the longitudinal acoustic modes at two different q. We observe that the usual peak in linewidths does not coincide with ωBτalpha ~ 1, indicating that the longitudinal acoustic modes do not couple with structural relaxation. Tansverse acoustic modes also appear in the depolarized forward scattering spectra. NSF Grant Number: DMR 0552944.

  4. Study of the kinetics and mechanism of heterogeneous catalytic reactions by the relaxation method

    SciTech Connect

    Bal`zhinimaev, B.S.; Pinaeva, L.G.

    1995-01-01

    The main results of studying reaction mechanisms by relaxation methods are presented for SO{sub 2} oxidation, o-xylene oxidation, and ethylene epoxidation. It is shown that reaction mechanisms can be efficiently investigated, and qualitative correlations between the characteristics of catalytic activity and the composition and structure of the adsorption layer can be found by combining kinetic methods with physical methods.

  5. 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.

  6. Conformational flexibility of a human immunoglobulin light chain variable domain by relaxation dispersion nuclear magnetic resonance spectroscopy: implications for protein misfolding and amyloid assembly.

    PubMed

    Mukherjee, Sujoy; Pondaven, Simon P; Jaroniec, Christopher P

    2011-07-05

    The conformational flexibility of a human immunoglobulin κIV light-chain variable domain, LEN, which can undergo conversion to amyloid under destabilizing conditions, was investigated at physiological and acidic pH on a residue-specific basis by multidimensional solution-state nuclear magnetic resonance (NMR) methods. Measurements of backbone chemical shifts and amide (15)N longitudinal and transverse spin relaxation rates and steady-state nuclear Overhauser enhancements indicate that, on the whole, LEN retains its native three-dimensional fold and dimeric state at pH 2 and that the protein backbone exhibits limited fast motions on the picosecond to nanosecond time scale. On the other hand, (15)N Carr--Purcell--Meiboom--Gill (CPMG) relaxation dispersion NMR data show that LEN experiences considerable slower, millisecond time scale dynamics, confined primarily to three contiguous segments of about 5-20 residues and encompassing the N-terminal β-strand and complementarity determining loop regions 2 and 3 in the vicinity of the dimer interface. Quantitative analysis of the CPMG relaxation dispersion data reveals that at physiological pH these slow backbone motions are associated with relatively low excited-state protein conformer populations, in the ~2-4% range. Upon acidification, the minor conformer populations increase significantly, to ~10-15%, with most residues involved in stabilizing interactions across the dimer interface displaying increased flexibility. These findings provide molecular-level insights about partial protein unfolding at low pH and point to the LEN dimer dissociation, initiated by increased conformational flexibility in several well-defined regions, as being one of the important early events leading to amyloid assembly.

  7. 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)

  8. 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)

  9. New techniques for cartilage magnetic resonance imaging relaxation time analysis: texture analysis of flattened cartilage and localized intra- and inter-subject comparisons.

    PubMed

    Carballido-Gamio, Julio; Link, Thomas M; Majumdar, Sharmila

    2008-06-01

    MR relaxation time measurements of knee cartilage have shown potential to characterize knee osteoarthritis (OA). In this work, techniques that allow localized intra- and inter-subject comparisons of cartilage relaxation times, as well as cartilage flattening for texture analysis parallel and perpendicular to the natural cartilage layers, are presented. The localized comparisons are based on the registration of bone structures and the assignment of relaxation time feature vectors to each point in the bone-cartilage interface. Cartilage flattening was accomplished with Bezier splines and warping, and texture analysis was performed with second-order texture measures using gray-level co-occurrence matrices (GLCM). In a cohort of five normal subjects the performance and reproducibility of the techniques were evaluated using T1rho maps of femoral knee cartilage. The feasibility of creating a mean cartilage relaxation time map is also presented. Successful localized intra- and inter-subject T1rho comparisons were obtained with reproducibility similar to that reported in the literature for regional T2. Improvement of the reproducibility of GLCM features was obtained by flattening the T1rho maps. The results indicate that the presented techniques have potential in longitudinal and population studies of knee OA at different stages of the disease.

  10. New Techniques for Cartilage Magnetic Resonance Imaging Relaxation Time Analysis: Texture Analysis of Flattened Cartilage and Localized Intra- and Inter-subject Comparisons

    PubMed Central

    Carballido-Gamio, Julio; Link, Thomas M.; Majumdar, Sharmila

    2010-01-01

    MR relaxation time measurements of knee cartilage have shown potential to characterize knee osteoarthritis (OA). In this work, techniques that allow localized intra- and inter-subject comparisons of cartilage relaxation times, as well as cartilage flattening for texture analysis parallel and perpendicular to the natural cartilage layers, are presented. The localized comparisons are based on the registration of bone structures and the assignment of relaxation time feature vectors to each point in the bone– cartilage interface. Cartilage flattening was accomplished with Bezier splines and warping, and texture analysis was performed with second-order texture measures using gray-level co-occurrence matrices (GLCM). In a cohort of five normal subjects the performance and reproducibility of the techniques were evaluated using T1ρ maps of femoral knee cartilage. The feasibility of creating a mean cartilage relaxation time map is also presented. Successful localized intra- and inter-subject T1ρ comparisons were obtained with reproducibility similar to that reported in the literature for regional T2. Improvement of the reproducibility of GLCM features was obtained by flattening the T1ρ maps. The results indicate that the presented techniques have potential in longitudinal and population studies of knee OA at different stages of the disease. PMID:18506807

  11. Cross-correlation trajectory study of vibrational relaxation of DF(v = 1 to 7) by DF(v = 0) and of HF by HF

    SciTech Connect

    Coltrin, M.E.; Marcus, R.A.

    1982-03-01

    Three-dimensional quasiclassical trajectories and a cross-correlation method of analysis are used to study the vibrational relaxation of DF(v/sub 1/ = 1 to 7) by DF(v/sub 2/ = 0). Rate constants are calculated for V--V and V--R, T energy transfer. As was seen in earlier studies on HF--HF, the V--R, T mechanism becomes increasingly important at higher initial v/sub 1/, as the V--V transfer moves further off resonance and also becomes increasingly endothermic. Both factors contribute to the decrease of V--V transfer rates with increasing v/sub 1/ for the higher values of v/sub 1/. Comparisons are made with results of a classical path study of vibrational relaxation in DF--DF and with experiment where possible. New results on the HF--HF V--V transfer rates are presented.

  12. (1)H NMR Relaxation Study of a Magnetic Ionic Liquid as a Potential Contrast Agent.

    PubMed

    Daniel, Carla I; Vaca Chávez, Fabián; Portugal, Carla A M; Crespo, João G; Sebastião, Pedro J

    2015-09-03

    A proton nuclear magnetic relaxation dispersion (1)H NMRD study of the molecular dynamics in mixtures of magnetic ionic liquid [P66614][FeCl4] with [P66614][Cl] ionic liquid and mixtures of [P66614][FeCl4] with dimethyl sulfoxide (DMSO) is presented. The proton spin-lattice relaxation rate, R1, was measured in the frequency range of 8 kHz-300 MHz. The viscosity of the binary mixtures was measured as a function of an applied magnetic field, B, in the range of 0-2 T. In the case of DMSO/[P66614][FeCl4] the viscosity was found to be independent from the magnetic field, while in the case of the [P66614][Cl]/[P66614][FeCl4] system viscosity decreased with the increase of the magnetic field strength. The spin-lattice relaxation results were analyzed for all systems taking into account the relaxation mechanisms associated with the molecular motions with correlation times in a range between 10(-11) and 10(-7)s, usually observed by NMRD, and the paramagnetic relaxation contributions associated with the presence of the magnetic ions in the systems. In the case of the DMSO/[P66614][FeCl4] system the R1 dispersion shows the relaxation enhancement due to the presence of the magnetic ions, similar to that reported for contrast agents. For the [P66614][Cl]/[P66614][FeCl4] system, the R1 dispersion presents a much larger paramagnetic relaxation contribution, in comparison with that observed for the DMSO/[P66614][FeCl4] mixtures but different from that reported for other magnetic ionic liquid system. In the [P66614][Cl]/[P66614][FeCl4] system the relaxation enhancement associated with the paramagnetic ions is clearly not proportional to the concentration of magnetic ions, in contrast with what is observed for the DMSO/[P66614][FeCl4] system.

  13. Using bio-functionalized magnetic nanoparticles and dynamic nuclear magnetic resonance to characterize the time-dependent spin-spin relaxation time for sensitive bio-detection.

    PubMed

    Liao, Shu-Hsien; Chen, Kuen-Lin; Wang, Chun-Min; Chieh, Jen-Jie; Horng, Herng-Er; Wang, Li-Min; Wu, C H; Yang, Hong-Chang

    2014-11-12

    In this work, we report the use of bio-functionalized magnetic nanoparticles (BMNs) and dynamic magnetic resonance (DMR) to characterize the time-dependent spin-spin relaxation time for sensitive bio-detection. The biomarkers are the human C-reactive protein (CRP) while the BMNs are the anti-CRP bound onto dextran-coated Fe3O4 particles labeled as Fe3O4-antiCRP. It was found the time-dependent spin-spin relaxation time, T2, of protons decreases as time evolves. Additionally, the ΔT2 of of protons in BMNs increases as the concentration of CRP increases. We attribute these to the formation of the magnetic clusters that deteriorate the field homogeneity of nearby protons. A sensitivity better than 0.1 μg/mL for assaying CRP is achieved, which is much higher than that required by the clinical criteria (0.5 mg/dL). The present MR-detection platform shows promise for further use in detecting tumors, viruses, and proteins.

  14. Effect of velocity cross-relaxation and mode separation upon the power spectrum of a chemical oxygen-iodine laser resonator

    NASA Astrophysics Data System (ADS)

    Copeland, Drew A.

    1990-06-01

    A gain model for optical extraction from the CW chemical oxygen-iodine laser medium is described. It uses a simplified, temperatuire-dependent, chemical kinetics package which consists of several reactions between molecular oxygen, atomic and molecular iodine, water, and helium. The Heidner I2 dissociation mechanism is included to allow for incomplete dissociation. Gas flow is treated using a premixed, one-dimensional stream-tube model which accounts for gas expansion and heat release in the cavity. Collisional cross-relaxation effects upon the Doppler-broadened line are treated using a Fokker-Planck diffusion model of the velocity distribution of the upper and lower laser levels. This model, in conjunction with geometric optics, multimode model of an unstable standing-wave confocal resonator, is used to examine the influence of incomplete velocity cross-relaxation and longitudinal mode separation upon the output power and mode spectrum of the laser. It is shown that lasing will occur on all available modes even when the mode separation is less than the collision linewidth.

  15. Zinc chloride modified electronic transport and relaxation studies in barium-tellurite glasses

    NASA Astrophysics Data System (ADS)

    Dhankhar, Sunil; Kundu, R. S.; Rani, Sunita; Sharma, Preeti; Murugavel, S.; Punia, Rajesh; Kishore, N.

    2017-06-01

    The ac conductivity of halide based tellurium glasses having composition 70 TeO2-(30-x) BaO-x ZnCl2; x = 5, 10, 15, 20 and 25 has been investigated in the frequency range 10-1 Hz to 105Hz and in the temperature range 453 K to 553 K. The frequency and temperature dependent ac conductivity show mixed behaviour with increase in halide content and found to obey Jonscher's universal power law. The values of dc conductivity, crossover frequency and frequency exponent have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. For determining the conduction mechanism in studied glass system, frequency exponent has been analyzed by various theoretical models. In presently studied glasses, the ac conduction takes place via overlapping large polaron tunneling (OLPT). The values of activation energy for dc conduction (W) and the one associated with relaxation process (ER) are found to increase with increase in x up to glass sample with x = 15 and thereafter it decrease with increase in zinc chloride content. DC conduction takes place via variable range hopping (VRH) as proposed by Mott with some modification suggested by Punia et al. The value of real part of modulus (M') is observed to decrease with increase in temperature. The value of stretched exponent (β) obtained from fitting of M'' reveals the presence of non-Debye type of relaxation in presently studied glass samples. Scaling spectra of ac conductivity and values of electric modulus (M' and M'') collapse into a single master curve for all the compositions and temperatures. The values of relaxation energy (ER) for all the studied glass compositions are almost equal to W, suggesting that polarons have to overcome same barrier while relaxing and conducting. The conduction and relaxation processes in the studied glass samples are composition and temperature independent. [Figure not available: see fulltext.

  16. Zinc chloride modified electronic transport and relaxation studies in barium-tellurite glasses

    NASA Astrophysics Data System (ADS)

    Dhankhar, Sunil; Kundu, R. S.; Rani, Sunita; Sharma, Preeti; Murugavel, S.; Punia, Rajesh; Kishore, N.

    2017-09-01

    The ac conductivity of halide based tellurium glasses having composition 70 TeO2-(30-x) BaO-x ZnCl2; x = 5, 10, 15, 20 and 25 has been investigated in the frequency range 10-1 Hz to 105Hz and in the temperature range 453 K to 553 K. The frequency and temperature dependent ac conductivity show mixed behaviour with increase in halide content and found to obey Jonscher's universal power law. The values of dc conductivity, crossover frequency and frequency exponent have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. For determining the conduction mechanism in studied glass system, frequency exponent has been analyzed by various theoretical models. In presently studied glasses, the ac conduction takes place via overlapping large polaron tunneling (OLPT). The values of activation energy for dc conduction (W) and the one associated with relaxation process ( E R) are found to increase with increase in x up to glass sample with x = 15 and thereafter it decrease with increase in zinc chloride content. DC conduction takes place via variable range hopping (VRH) as proposed by Mott with some modification suggested by Punia et al. The value of real part of modulus ( M') is observed to decrease with increase in temperature. The value of stretched exponent (β) obtained from fitting of M'' reveals the presence of non-Debye type of relaxation in presently studied glass samples. Scaling spectra of ac conductivity and values of electric modulus ( M' and M'') collapse into a single master curve for all the compositions and temperatures. The values of relaxation energy ( E R) for all the studied glass compositions are almost equal to W, suggesting that polarons have to overcome same barrier while relaxing and conducting. The conduction and relaxation processes in the studied glass samples are composition and temperature independent. [Figure not available: see fulltext.

  17. Transmission-line resonators for the study of individual two-level tunneling systems

    NASA Astrophysics Data System (ADS)

    Brehm, Jan David; Bilmes, Alexander; Weiss, Georg; Ustinov, Alexey V.; Lisenfeld, Jürgen

    2017-09-01

    Parasitic two-level tunneling systems (TLS) emerge in amorphous dielectrics and constitute a serious nuisance for various microfabricated devices, where they act as a source of noise and decoherence. Here, we demonstrate a new test bed for the study of TLS in various materials which provides access to properties of individual TLS as well as their ensemble response. We terminate a superconducting transmission-line resonator with a capacitor that hosts TLS in its dielectric. By tuning TLS via applied mechanical strain, we observe the signatures of individual TLS strongly coupled to the resonator in its transmission characteristics and extract the coupling components of their dipole moments and energy relaxation rates. The strong and well-defined coupling to the TLS bath results in pronounced resonator frequency fluctuations and excess phase noise, through which we can study TLS ensemble effects such as spectral diffusion, and probe theoretical models of TLS interactions.

  18. Study on the cyclic GMP-dependency of relaxations to endogenous and exogenous nitric oxide in the mouse gastrointestinal tract.

    PubMed

    De Man, J G; De Winter, B Y; Herman, A G; Pelckmans, P A

    2007-01-01

    cGMP mediates nitrergic relaxations of intestinal smooth muscle, but several studies have indicated that cGMP-independent mechanisms may also be involved. We addressed this contention by studying the effect of ODQ and ns2028, specific inhibitors of soluble guanylate cyclase, on nitrergic relaxations of the mouse gut. Mouse gastric fundus and small intestinal muscle preparations were mounted in organ baths to study relaxations to exogenous NO, NO donors and electrical field stimulation (EFS) of enteric nerves. In gastric fundus longitudinal muscle strips, ODQ and NS2028 abolished the L-nitroarginine-sensitive relaxations to EFS and the relaxations to NO and NO donors, glyceryl trinitrate (GTN), SIN-1 and sodium nitroprusside (SNP). EFS of intestinal segments and muscle strips showed L-nitroarginine-resistant relaxations, which were abolished by the purinoceptor blocker suramin. In the presence of suramin, ODQ and NS2028 abolished all relaxations to EFS in intestinal segments and strips. ODQ and NS2028 abolished the relaxations to exogenous NO and to the NO donors GTN, SIN-1 and SNP in circular and longitudinal intestinal muscle strips. Intestinal segments showed residual relaxations to NO and GTN. Our results indicate that relaxations to endogenous NO in the mouse gastric fundus and small intestine are completely dependent on cGMP. ODQ and NS2028 incompletely blocked nitrergic relaxations to exogenous NO in intact intestinal segments. However, it is unlikely that this is due to the involvement of cGMP-independent pathways because ODQ and NS2028 abolished all relaxations to endogenous and exogenous NO in intestinal muscle strips.

  19. 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.

  20. Molecular mobility and structure of elastin deduced from the solvent and temperature dependence of 13C magnetic resonance relaxation data.

    PubMed

    Lyerla, J R; Torchia, D A

    1975-11-18

    13C relaxation parameters, T1, line width, and NOE, have been determined for backbone carbons of ligamentum nuchae elastin swollen by 0.15 M NaCl, 0.15 M NaCl-formamide, 0.15 M NaCl-ethanol, dimethyl sulfoxide, and formamide. The data have been analyzed in terms of (a) a single correlation time model and (b) a model employing a log-chi2 distribution of correlation times used by Schaefer (1973) to analyze solid cis-polyisoprene 13C relaxation data. Employing the latter mode, one obtains an approximately self-consistent quantitative analysis of all the elastin data. An average backbone correlation time, tau, of ca. 2 nsec is calculated for elastin swollen in the presence of polar organic solvents at 37 degrees, in approximate agreement with tau of 0.4 nsec obtained for bulk cis-polyisoprene at 35 degrees. The influence of solvent and temperature on elastin spectra indicate that the larger tau value (approximately 80 nsec) obtained for elastin swollen by 0.15 M NaCl at 37 degrees is a consequence of weak interchain polar and hydrophobic interactions, a result which is in accord with the reported viscoelastic behavior exhibited by water-swollen elastin at 37 degrees. The results obtained further suggest that Gly, Pro, and Val residues are significantly more mobile than Ala residues, which are located in the cross-link regions. Hence, the NMR data support the view that water-swollen elastin is composed of a network of mobile chains, except possibly in the cross-link regions.

  1. Magnetic Field Strength Dependence of Transverse Relaxation and Signal-to-Noise Ratio for Hyperpolarized Xenon-129 and Helium-3 Gas Magnetic Resonance Imaging of Lungs

    NASA Astrophysics Data System (ADS)

    Dominguez-Viqueira, William

    Magnetic resonance (MR) imaging with hyperpolarized noble gases (HNG), 3He or 129Xe, has become a promising approach for studying lung anatomy and function. Unlike conventional MR imaging, the magnetization in HNG MR is independent of the magnetic field strength. This means that no improvement in signal-to-noise ratio (SNR) is expected with increasing clinical field strength above ˜0.25T. Furthermore, it has been predicted that the SNR may decline at clinical field strength due to decreases in the apparent transverse relaxation time (T2*), caused by the increased magnetic susceptibility induced field gradients at the air-tissue interface. In this thesis the magnetic field strength dependence of T2* and SNR in HNG MR is investigated experimentally in rodent and human lungs. For rodent imaging, a novel broad-band (0.1-100MHz) variable field strength MR imaging system for rodents was built. This system permitted imaging of 129Xe, 3He and 1H at low magnetic field strengths (3-73.5mT) to experimentally investigate the field dependence of HNG imaging SNR in rodent lungs. In vivo 129Xe and 3He signals were acquired at 73.5mT and T 2* was estimated to be approximately 180+/-8 ms, in good agreement with previously reported values. At 73.5mT, image noise is dominated by losses originated from the radiofrequency (RF) coils. To address this issue, RF coils were built using different types of copper wire and compared in phantoms and in vivo in rat lungs using hyperpolarized 3He and 129Xe gas. An SNR improvement of up to 200% was obtained with Litz wire compared to conventional copper wire. This improvement demonstrated the feasibility of HNG lung imaging in rodents at 73.5mT with SNR comparable to that obtained at clinical field strengths. To verify the SNR field dependence in humans, hyperpolarized 3He lung imaging at two commonly used clinical field strengths (1.5T and 3T) was performed in the same volunteers and compared. No significant differences in SNR were obtained

  2. Impact of electron-impurity scattering on the spin relaxation time in graphene: a first-principles study.

    PubMed

    Fedorov, Dmitry V; Gradhand, Martin; Ostanin, Sergey; Maznichenko, Igor V; Ernst, Arthur; Fabian, Jaroslav; Mertig, Ingrid

    2013-04-12

    The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.

  3. Dynamic study of interaction between beta-cyclodextrin and aspirin by the ultrasonic relaxation method.

    PubMed

    Fukahori, Takanori; Kondo, Minako; Nishikawa, Sadakatsu

    2006-03-09

    A single ultrasonic relaxational phenomenon was observed in aqueous solutions containing both beta-cyclodextrin (beta-CD) as host and nonionized or ionized acetylsalicylic acid (aspirin) as guest. The observed relaxation was responsible for a dynamic complexation reaction between beta-CD and aspirin molecules, concomitant with a volume change during the reaction. The kinetic and equilibrium constants for the complexation in the acid (nonionized) form of the aspirin system were derived from the guest concentration dependence of the relaxation frequency. The equilibrium constant for the carboxylate (ionized) form of aspirin was determined from the concentration dependence of a maximum absorption per wavelength, and the rate constants were calculated by using the determined equilibrium constant and the observed relaxation frequencies, which remained nearly almost constant over the concentration range studied. The results showed that the effect of charge on the aspirin molecule was reflected only in the dissociation process from the beta-CD cavity, while no remarkable change was seen in the association process whose rate was diffusion controlled. The results could be explained on the basis of the difference of the hydrophobic moieties in the two guests that were included in the host cavity. The results of the standard volume change for the complexation reaction were closely related to the number of expelled water molecules originally located in the beta-CD cavity and the volume of the aspirin molecule incorporated into the beta-CD cavity.

  4. Proton and tritium NMR relaxation studies of peptide inhibitor binding to bacterial collagenase: Conformation and dynamics

    SciTech Connect

    Dive, V.; Lai, A.; Valensin, G.; Saba, G.; Yiotakis, A.; Toma, F. )

    1991-02-15

    The interaction of succinyl-Pro-Ala, a competitive inhibitor of Achromobacter iophagus collagenase, with the enzyme was studied by longitudinal proton and tritium relaxation. Specific deuterium and tritium labeling of the succinyl part at vicinal positions allowed the measurement of the cross-relaxation rates of individual proton or tritium spin pairs in the inhibitor-enzyme complex as well as in the free inhibitor. Overall correlation times, internuclear distances, and qualitative information on the internal mobility in Suc1 (as provided by the generalized order parameter S2) could be deduced by the comparison of proton and tritium cross-relaxation of spin pairs at complementary positions in the -CH2- CH2- moiety as analyzed in terms of the model-free approach by Lipari and Szabo. The conformational and motional parameters of the inhibitor in the free and enzyme-bound state were directly compared by this method. The measurement of proton cross-relaxation in the Ala residue provided additional information on the inhibitor binding. The determination of the order parameter in different parts of the inhibitor molecule in the bound state indicates that the succinyl and alanyl residues are primarily involved in the interaction with the enzyme activity site. The succinyl moiety, characterized in solution by the conformational equilibrium among the three staggered rotamers--i.e., trans: 50%; g+: 20%; g-: 30%--adopted in the bound state the unique trans conformation.

  5. Noise and relaxation studies of acetylcholine induced currents in the presence of procaine.

    PubMed Central

    Marty, A

    1978-01-01

    1. The effects of procaine on the excitatory effects of acetylcholine (ACh) on Aplysia neurones were studied by analysing the current relaxations induced by voltage steps. Procaine was applied by perfusion and ACh was applied iontophoretically under two sets of experimental conditions designed to produce very different ACh concentrations at the membrane. 2. When ACh was applied at high concentration, the current relaxation following a hyperpolarizing step showed two components at procaine concentrations of about 2 X 10(-5) M; a fast increase was followed by a slow decrease. At high procaine concentrations (greater than 10(-4) M), the relaxation has only one component, corresponding to an exponential current decrease. 3. When ACh was applied at low concentrations, the current relaxation usually showed two components. At low procaine concentrations a fast increase was followed by a slower one; at higher procaine concentrations, a fast decrease preceded the slow increase. 4. All the results can be accounted for by assuming that procaine binds preferentially to the activated receptor-channel complex and converts it into a non-conducting complex. The association and dissociation constants were calculated to be (at 12 degrees C, -80 mV) 1.3 X 10(6) M-1 sec-1 and 10 sec-1. PMID:671293

  6. In-Vivo Like Studies of the hIAPP Amyloid Precursors Using Dielectric Relaxation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hirai, Yusuke; Mahommed Assiri, Reem; Barry, Donal; Despa, Florin; Stroe, Izabela

    2013-03-01

    Recent studies show that the amyloid formation in Type II diabetic disease involves aggregation of monomers of the human islet amyloid polypeptide (hIAPP) into oligomers, protofibrils, and fibrils. Here we present data showing that Dielectric Relaxation Spectroscopy is a very sensitive technique to detect the hIAPP precursors. We measured the dielectric response of amyloidogenic hIAPP and non-amyloidogenic rIAPP as a function of frequency (10-3 Hz to 107 Hz), temperature (193K to 283K), and incubation time (0-120 h). To mimic in-vivo like conditions, the proteins were measured in bovine serum albumin. Our results show that the dielectric signal of amyloidogenic hIAPP shifts towards the dielectric signal of the background, as predicted by theoretical calculations. No similar shift is observed for the non-amyloidogenic rIAPP. In addition, the dielectric signal of both the hIAPP and the rIAPP shows two relaxation processes over the measured temperature range. We used two Havrilik-Negami functions plus conductivity to fit the two relaxation processes we determined the relaxation time for both processes and calculated the corresponding activation energies. This work was supported by the Kalenian Award.

  7. Theoretical study of geometry relaxation following core excitation: H2O, NH3, and CH4

    NASA Astrophysics Data System (ADS)

    Takahashi, Osamu; Kunitake, Naoto; Takaki, Saya

    2015-10-01

    Single core-hole (SCH) and double core-hole excited state molecular dynamics (MD) calculations for neutral and cationic H2O, NH3, and CH4 have been performed to examine geometry relaxation after core excitation. We observed faster X-H (X = C, N, O) bond elongation for the core-ionized state produced from the valence cationic molecule and the double-core-ionized state produced from the ground and valence cationic molecules than for the first resonant SCH state. Using the results of SCH MD simulations of the ground and valence cationic molecules, Auger decay spectra calculations were performed. We found that fast bond scission leads to peak broadening of the spectra.

  8. a Dynamic Light Scattering Study of the Relaxation Dynamics in Aqueous Polymer Gelatin Solutions and Gels.

    NASA Astrophysics Data System (ADS)

    Ren, Shangzhi

    1992-01-01

    The dynamics of the molecular relaxations in semi -dilute polymer solutions and gels has important implications in fundamental physics and technological applications. Dynamic Light Scattering (DLS) techniques directly probe such dynamics by monitoring and analyzing the pattern of fluctuations of the light scattered from polymer molecules. We have employed the DLS to explore the molecular relaxation behavior of thermally reversible, semi-dilute, aqueous gelatin solutions and gels. Our experiment results indicate that there are three relaxation modes in the DLS spectrum for the semi-dilute aqueous gelatin solutions: a fast exponential cooperative diffusion mode, an intermediate power-law mode, and a stretched exponential slow mode. When the system evolves from sol to gel under a thermal quench, the fast mode remains unchanged while the characteristic relaxation time of the slow mode diverges, leaving the power-law intermediate mode most apparent for ~ 5 decades in correlation time. The power -law mode is novel in the experimental studies of the relaxation dynamics in linear polymer chain systems and is found to be q dependent. The DLS data is analyzed under a new scheme separating the dynamic scattering component from the static counterpart developed under the growing chain crosslinking. It is the first attempt ever made to deal with the non-ergodicity effect in the DLS studies not only for the gels, as suggested by Pusey and van Megen (80), but also for the DLS during the sol-gel transitions. We have considered a possible interpretation for the observed relaxation based on anomalous diffusion of < x^2>~ lnt and < x^2 >~ t^beta, with < {rm x}^2> being mean-square-displacement and 0~ lnt behavior is associated with the intermediate power-law relaxation mode while the < x^2>~ t^beta behavior is

  9. A proton NMR relaxation study of water dynamics in bovine serum albumin nanoparticles.

    PubMed

    Belotti, Monica; Martinelli, Andrea; Gianferri, Raffaella; Brosio, Elvino

    2010-01-14

    Water dynamics and compartmentation in glutaraldehyde cross-linked bovine serum albumin nanoparticles have been investigated by an integrated nuclear magnetic resonance (NMR) protocol based on water relaxation times and self-diffusion coefficients measurements. Multi-exponentially of water relaxation curves has been accounted for according to a diffusive and chemical exchange model (see B. P. Hills, S. F. Takacs and P. S. Belton, Mol. Phys., 1989, 67(4), 903, and Mol. Phys., 1989, 67(4), 913; E. Brosio, M. Belotti and R. Gianferri, in Food Science and Technology: New Research, ed. L. V. Greco and M. N. Bruno, Nova Science Publishers, Hauppauge (NY), 2008) that made it possible to single out water molecules in the molecular spaces in the interior of albumin nanoparticles, in the meso-cavities formed by packed nanoparticles and in the meniscus on top of the nanoparticles suspension. A quantitative rationalization of T(2) values of water different components allowed morphological information to be acquired as for the size of water filled compartments, while self-diffusion coefficient measurements of water excess or fluxed packed nanoparticles suspensions are describers of transport properties of soft biomaterials. The paper reports an NMR approach that can be seen as a general and relevant method to characterize excess-water-swollen soft biomaterials.

  10. In Vivo Natural-Abundance 13C Nuclear Magnetic Resonance Studies of Living Ectomycorrhizal Fungi 1

    PubMed Central

    Martin, Francis; Canet, Daniel; Marchal, Jean-Pierre; Brondeau, Jean

    1984-01-01

    Natural-abundance 13C nuclear magnetic resonance spectroscopy has been used to study intact mycelia of the ectomycorrhizal fungi Cenococcum graniforme (Ascomycetes) and Hebeloma crustuliniforme (Basidiomycetes). A number of sharp resonances are observed in living fungi. These signals primarily arise from fatty acyl chains and carbohydrate nuclei. The spectra are interpreted in terms of relative concentrations of the major fatty acids present in the fungal triglycerides. The small line width of fatty acids (mainly oleic, linoleic, and palmitic acids) resonances and spin-lattice relaxation time are indicative of fast rotational reorientations and are consequently thought to arise from fatty acyl chains in fat droplets. We were able to locate the site of lipids accumulation within mycelia using light microscopy and histological staining. Many lipid droplets were observed in mycelia of both species. These results suggest that fatty acids droplets could be involved in carbon storage and metabolism from ectomycorrhizal fungi. PMID:16663561

  11. 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

  12. Two-spin relaxation of P dimers in silicon

    NASA Astrophysics Data System (ADS)

    Borhani, Massoud; Hu, Xuedong

    2010-12-01

    We study two-electron singlet-triplet relaxation of donor-bound electrons in Silicon. Hyperfine interaction of the electrons with the phosphorus (P) nuclei, in combination with the electron-phonon interaction, lead to relaxation of the triplet states. Within the Heitler-London and effective-mass approximations, we calculate the triplet relaxation rates in the presence of an applied magnetic field. This relaxation mechanism affects the resonance peaks in current electron-spin-resonance experiments on P dimers. Moreover, the estimated time scales for the spin decay put an upper bound on the gate pulses needed to perform fault-tolerant two-qubit operations in donor-spin-based quantum computers. We have found the optimal regimes though, which mitigate this relaxation mechanism, yet permit sufficiently fast two-qubit operations.

  13. The First Study of Cartilage by Magnetic Resonance

    PubMed Central

    Xia, Yang; Stilbs, Peter

    2016-01-01

    Objective To recap the historical journey leading to the first cartilage research article using nuclear magnetic resonance (NMR), published in 1955 by 2 Swedish researchers, Erik Odeblad and Gunnar Lindström. Design Extensive Internet search utilizing both English and Swedish websites, and reading the dissertations available at the Royal Institute of Technology (Stockholm, Sweden) and via interlibrary loans at Oakland University (Michigan, USA). Results Using a primitive NMR instrument that Lindström built for his graduate research at the Nobel Institute for Physics (Stockholm, Sweden), Odeblad and Lindström studied the characteristics of the NMR signal in calf cartilage. The authors wrote, “In cartilage and fibrous tissue, in which the proton signals probably arise from highly viscous water with short spin-lattice relaxation time, the signals were also larger than would correspond to the water content.” The authors speculated the signal differences between water and biological tissues could be attributed to the absorption and organization of the water molecules to the proteins in the tissue, which was remarkably accurate. Conclusions It is quite certain that Odeblad and Lindström published the first biomedical study using NMR in 1955. In this article, cartilage and a number of other biological tissues were examined for the first time using NMR. PMID:27688837

  14. Electron spin resonance study of ion-implanted polymers

    NASA Astrophysics Data System (ADS)

    Wasserman, B.; Dresselhaus, M. S.; Braunstein, G.; Wnek, G. E.; Roth, G.

    1985-03-01

    The effect of ion implantation on the polymers PAN (polyacrylonitrile), PPO (poly 2,6-dimethylphenylene oxide) and PPS (p-polyphenylene sulfide) is studied using electron spin resonance. ESR measurements on these polymers were performed as a function of ion species and fluence in the temperature range 10 study (84Kr,80Br,75As,40Ar and14N). It is therefore concluded that the carrier concentration is related to the structural damage and not to chemical doping effects. From the shape of the ESR line, the ratio of the relaxation times for one-dimensional to three-dimensional spin diffusion is determined to be larger than 1000. The temperature dependence of the unpaired carrier concentration shows a strong deviation from a Curie law behavior, which can be explained by assuming that a defect band is formed with a bandgap due to strong Coulomb interaction between electrons on the defect sites.

  15. Multinuclear nuclear magnetic resonance spectroscopic study of cartilage proteoglycans

    SciTech Connect

    Lerner, L.

    1985-01-01

    Hyaline cartilage is a composite material whose major function is to withstand compression while retaining flexibility. Its mechanical properties are affected by tissue hydration and ionic composition. Models of the mechanical behavior of cartilage have incorporated certain assumptions about the interactions of the major components of cartilage: collagen, proteoglycans, water, and cations. To determine the validity of these assumption, the authors have used nuclear magnetic resonance spectroscopy (NMR). Two approaches have been used: (a) natural abundance carbon-13 NMR; and (b) NMR of sodium-23, potassium-39, magnesium-25, and calcium-43. Evidence from studies in intact tissues are reinforced by extensive measurements on solutions of proteoglycans and other relevant macromolecules. Based on the measurements of NMR relaxation rates and lineshapes reported here, it is concluded that neither sodium nor potassium interact strongly with bovine nasal proteoglycan aggregates or their substituent glycosaminoglycan chains in solution. Proteoglycans do bind magnesium and calcium. Therefore there is a qualitative difference between monovalent and divalent cations, which is not taken into account by polyelectrolyte models or models for the ionic dependence of mechanical properties. Cation binding to heparin, which has a higher charge density than cartilage proteoglycans, was also studied. The results presented here establish that heparin binds sodium, magnesium, and calcium.

  16. 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.

  17. Relaxant effects of metoclopramide and magnesium sulfate on isolated pregnant myometrium: an in vitro study.

    PubMed

    Tang, Y Y; Du, Y; Ni, J; Ma, Y S; Lin, X M; Zhou, J

    2014-05-01

    Metoclopramide and magnesium sulfate are extensively used agents in obstetrics. In this study, the relaxant properties of metoclopramide and magnesium sulfate on pregnant myometrium, together with the possible reversing influences of oxytocin and cabergoline (a dopamine D2 receptor agonist), were investigated. Myometrial strips from 24 parturients were randomly allocated to four groups: control (Group CON), magnesium sulfate and oxytocin (Group MSO), metoclopramide and oxytocin (Group MEO), and metoclopramide and cabergoline (Group MEC). Myometrial strips were mounted on a myograph bathed in Krebs buffer. Saline (Group CON) and five incremental doses of magnesium sulfate (Group MSO) or metoclopramide (Groups MEO and MEC) were sequentially microinjected into the bath. Subsequently, oxytocin (Groups CON, MSO and MEO) or cabergoline (Group MEC) was microinjected into the bath. The myometrial contractile characteristics after each drug injection, including contractile force, interval and duration, were analyzed. Magnesium sulfate was more potent for prolonging myometrial contractile interval than reducing contractile force. Metoclopramide relaxed myometrial contractions by inhibiting contractile force and prolonging contractile interval in a concentration-dependent manner. Oxytocin reversed both the inhibited contractile force and the prolonged contractile interval caused by a high concentration of magnesium sulfate but accelerated the contractile interval and had no significant effect on the contractile force suppressed by metoclopramide. The relaxant effects of metoclopramide were completely reversed by cabergoline. Both magnesium sulfate and metoclopramide relaxed myometrial contractions, and exhibited different responses to subsequent oxytocin treatment. The relaxant mechanism of metoclopramide may be via blockade of dopamine D2 receptor, which requires further investigation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.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

  20. Nuclear magnetic resonance study of potassium dihydrophosphate

    NASA Astrophysics Data System (ADS)

    Uskova, N. I.; Podorozhkin, D. Yu.; Charnaya, E. V.; Nefedov, D. Yu.; Baryshnikov, S. V.; Bugaev, A. S.; Lee, M. K.; Chang, L. J.

    2016-04-01

    A powder sample of potassium dihydrophosphate KH2PO4 has been studied by the 31P NMR method in a wide temperature range covering the ferroelectric phase transition. Changes in the position and shape of the resonance line at the transition to the ferroelectric phase have been revealed. The parameters of the chemical shift tensor of 31P (isotropic shift, anisotropy, and asymmetry) in the ferroelectric phase have been calculated from the experimental data. A sharp increase in the anisotropy of the tensor at the phase transition has been demonstrated. Dielectric measurements have also been carried out to verify the transition temperature.

  1. 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.

  2. 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. Copyright © 2012 Wiley Periodicals, Inc.

  3. 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

  4. Effect of massage therapy on pain, anxiety, relaxation, and tension after colorectal surgery: A randomized study.

    PubMed

    Dreyer, Nikol E; Cutshall, Susanne M; Huebner, Marianne; Foss, Diane M; Lovely, Jenna K; Bauer, Brent A; Cima, Robert R

    2015-08-01

    The purpose of this randomized controlled trial was to evaluate the effect of postoperative massage in patients undergoing abdominal colorectal surgery. One hundred twenty-seven patients were randomized to receive a 20-min massage (n = 61) or social visit and relaxation session (no massage; n = 66) on postoperative days 2 and 3. Vital signs and psychological well-being (pain, tension, anxiety, satisfaction with care, relaxation) were assessed before and after each intervention. The study results indicated that postoperative massage significantly improved the patients' perception of pain, tension, and anxiety, but overall satisfaction was unchanged. In conclusion, massage may be beneficial during postoperative recovery for patients undergoing abdominal colorectal surgery. Further studies are warranted to optimize timing and duration and to determine other benefits in this clinical setting.

  5. Study of clinical anaesthesia with pedius A anaesthesia system using ketamine or halothane with muscle relaxant.

    PubMed

    Das, S K; Das, S

    1995-10-01

    In pedius anaesthesia system, oxygen enriched air and air are generated through an electrically driven oxygen generator 'Permox', obviating the need of compressed gas cylinder or pipe line. Effect of anaesthesia with pedius A anaesthesia system using ketamine or halothane with muscle relaxant in 2 groups of patients had been studied. Both groups had satisfactory results clinically. It appears that if the cases are carefully selected, both the agents have got equal effectiveness.

  6. 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.

  7. Exchange-dependent relaxation in the rotating frame for slow and intermediate exchange -- modeling off-resonant spin-lock and chemical exchange saturation transfer.

    PubMed

    Zaiss, Moritz; Bachert, Peter

    2013-05-01

    Chemical exchange observed by NMR saturation transfer (CEST) and spin-lock (SL) experiments provide an MRI contrast by indirect detection of exchanging protons. The determination of the relative concentrations and exchange rates is commonly achieved by numerical integration of the Bloch-McConnell equations. We derive an analytical solution of the Bloch-McConnell equations that describes the magnetization of coupled spin populations under radiofrequency irradiation. As CEST and off-resonant SL are equivalent, their steady-state magnetization and dynamics can be predicted by the same single eigenvalue: the longitudinal relaxation rate in the rotating frame R1ρ . For the case of slowly exchanging systems, e.g. amide protons, the saturation of the small proton pool is affected by transverse relaxation (R2b ). It turns out, that R2b is also significant for intermediate exchange, such as amine- or hydroxyl-exchange or paramagnetic CEST agents, if pools are only partially saturated. We propose a solution for R1ρ that includes R2 of the exchanging pool by extending existing approaches, and verify it by numerical simulations. With the appropriate projection factors, we obtain an analytical solution for CEST and SL for nonzero R2 of the exchanging pool, exchange rates in the range 1-10(4) Hz, B1 from 0.1 to 20 μT and arbitrary chemical shift differences between the exchanging pools, whilst considering the dilution by direct water saturation across the entire Z-spectra. This allows the optimization of irradiation parameters and the quantification of pH-dependent exchange rates and metabolite concentrations. In addition, we propose evaluation methods that correct for concomitant direct saturation effects. It is shown that existing theoretical treatments for CEST are special cases of this approach.

  8. Evaluating the Uncertainty in Exchange Parameters Determined from Off-Resonance R1ρ Relaxation Dispersion for Systems in Fast Exchange

    PubMed Central

    Bothe, Jameson R.; Stein, Zachary W.; Al-Hashimi, Hashim M.

    2014-01-01

    Spin relaxation in the rotating frame (R1ρ) is a powerful NMR technique for characterizing fast microsecond timescale exchange processes directed toward short-lived excited states in biomolecules. At the limit of fast exchange, only kex = k1 + k−1 and Φıx = pGpE(Δω)2 can be determined from R1ρ data limiting the ability to characterize the structure and energetics of the excited state conformation. Here, we use simulations to examine the uncertainty with which exchange parameters can be determined for two state systems in intermediate-to-fast exchange using off-resonance R1ρ relaxation dispersion. R1ρ data computed by solving the Bloch-McConnell equations reveals small but significant asymmetry with respect to offset (R1ρ(ΔΩ) ≠ R1ρ(−ΔΩ)), which is a hallmark of slow-to-intermediate exchange, even under conditions of fast exchange for free precession chemical exchange line broadening (kex/Δω > 10). A grid search analysis combined with bootstrap and Monte-Carlo based statistical approaches for estimating uncertainty in exchange parameters reveals that both the sign and magnitude of Δω can be determined at a useful level of uncertainty for systems in fast exchange (kex/Δω < 10) but that this depends on the uncertainty in the R1ρ data and requires a thorough examination of the multidimensional variation of χ2 as a function of exchange parameters. Results from simulations are complemented by analysis of experimental R1ρ data measured in three nucleic acid systems with exchange processes occurring on the slow (kex/Δω = 0.2; pE = ~ 0.7%), fast (kex/Δω = ~10–16; pE = ~13%) and very fast (kex = 39,000 s−1) chemical shift timescales. PMID:24819426

  9. Control of dipolar relaxation in external fields

    NASA Astrophysics Data System (ADS)

    Pasquiou, B.; Bismut, G.; Beaufils, Q.; Crubellier, A.; Maréchal, E.; Pedri, P.; Vernac, L.; Gorceix, O.; Laburthe-Tolra, B.

    2010-04-01

    We study dipolar relaxation in both ultracold thermal and Bose-condensed Cr atom gases. We show three different ways to control dipolar relaxation, making use of either a static magnetic field, an oscillatory magnetic field, or an optical lattice to reduce the dimensionality of the gas from three-dimensional (3D) to two-dimensional (2D). Although dipolar relaxation generally increases as a function of a static magnetic-field intensity, we find a range of nonzero magnetic-field intensities where dipolar relaxation is strongly reduced. We use this resonant reduction to accurately determine the S=6 scattering length of Cr atoms: a6=103±4a0. We compare this new measurement to another new determination of a6, which we perform by analyzing the precise spectroscopy of a Feshbach resonance in d-wave collisions, yielding a6=102.5±0.4a0. These two measurements provide, by far, the most precise determination of a6 to date. We then show that, although dipolar interactions are long-range interactions, dipolar relaxation only involves the incoming partial wave l=0 for large enough magnetic-field intensities, which has interesting consequences on the stability of dipolar Fermi gases. We then study ultracold Cr gases in a one-dimensional (1D) optical lattice resulting in a collection of independent 2D gases. We show that dipolar relaxation is modified when the atoms collide in reduced dimensionality at low magnetic-field intensities, and that the corresponding dipolar relaxation rate parameter is reduced by a factor up to 7 compared to the 3D case. Finally, we study dipolar relaxation in the presence of rf oscillating magnetic fields, and we show that both the output channel energy and the transition amplitude can be controlled by means of the rf frequency and Rabi frequency.

  10. Exercise and relaxation intervention for patients with advanced lung cancer: a qualitative feasibility study.

    PubMed

    Adamsen, L; Stage, M; Laursen, J; Rørth, M; Quist, M

    2012-12-01

    Lung cancer patients experience loss of physical capacity, dyspnea, pain, reduced energy and psychological distress. The aim of this study was to explore feasibility, health benefits and barriers of exercise in former sedentary patients with advanced stage lung cancer, non-small cell lung cancer (NSCLC) (III-IV) and small cell lung cancer (SCLC) (ED), undergoing chemotherapy. The intervention consisted of a hospital-based, supervised, group exercise and relaxation program comprising resistance-, cardiovascular- and relaxation training 4 h weekly, 6 weeks, and a concurrent unsupervised home-based exercise program. An explorative study using individual semi-structured interviews (n=15) and one focus group interview (n=8) was conducted among the participants. Throughout the intervention the patients experienced increased muscle strength, improvement in wellbeing, breathlessness and energy. The group exercise and relaxation intervention showed an adherence rate of 76%, whereas the patients failed to comply with the home-based exercise. The hospital-based intervention initiated at time of diagnosis encouraged former sedentary lung cancer patients to participation and was undertaken safely by cancer patients with advanced stages of disease, during treatment. The patients experienced physical, functional and emotional benefits. This study confirmed that supervised training in peer-groups was beneficial, even in a cancer population with full-blown symptom burden and poor prognosis.

  11. Radiation belts study in RESONANCE project

    NASA Astrophysics Data System (ADS)

    Mogilevsky, Mikhail; Demekhov, Andrei; Zelenyi, Lev; Petrukovich, Anatoly; Shklyar, David

    The Earth’s inner magnetosphere is an important part of space weather framework. Outer radiation belt is a home for numerous communication and navigation satellites. But besides this practical problem, this region is a theoretical nugget. Hot magnetospheric, cold plas¬mospheric, and, in contrast, high energy plasma coexist here. Such non-equilibrium state of plasma is glued by various plasma oscillations actively interacting with particles and resulting, in particular, in spatial and velocity diffusion. Diffusion influences acceleration and precipitation of particles and defines their life¬time in the Earth’s magnetosphere. The project RESONANCE is aimed to study the whole complex of these issues, both practical (space weather), and fundamental (nonlinear plasma dynamics). The project RESONANCE is a part of the Russian Federal State Program. Lavochkin Association is responsi¬ble for preparation and testing of the satellites. Space Research Institute of the Russian Academy of Sciences is a leading scientific organization. Besides Russian scientists, specialists from Austria, Bulgaria, Czech Re¬public, Finland, France, Germany, Greece, Poland, Slovakia, Ukraine, USA take part.

  12. Muon spin relaxation studies of superconductivity in a crystalline array of weakly coupled metal nanoparticles.

    PubMed

    Bono, D; Schnepf, A; Hartig, J; Schnöckel, H; Nieuwenhuys, G J; Amato, A; de Jongh, L J

    2006-08-18

    We report muon-spin-relaxation studies in weak transverse fields of the superconductivity in the metal cluster compound, Ga84[N(SiMe3)2]20-Li6Br2(thf)20.2 toluene. The temperature and field dependence of the muon-spin-relaxation rate and Knight shift clearly evidence type II bulk superconductivity below Tc approximately 7.8 K, with Bc1 approximately 0.06 T, Bc2 approximately 0.26 T, kappa approximately 2, and weak flux pinning. The data are well described by the s-wave BCS model with weak electron-phonon coupling in the clean limit. A qualitative explanation for the conduction mechanism in this novel type of narrow-band superconductor is presented.

  13. Hypnotic relaxation therapy for treatment of hot flashes following prostate cancer surgery: a case study.

    PubMed

    Elkins, Gary R; Kendrick, Cassie; Koep, Lauren

    2014-01-01

    This case study reports on a 69-year-old African American male who presented with hot flashes following a diagnosis of prostate cancer and subsequent prostatectomy. Measures include both self-reported and physiologically measured hot flash frequency and sleep quality. The intervention involved 7 weekly sessions of hypnotic relaxation therapy directed toward alleviation of hot flashes. Posttreatment self-reported hot flashes decreased 94%; physiologically measured hot flashes decreased 100%; and sleep quality improved 87.5%. At week 12, both self-reported and physiologically measured hot flashes decreased 95% and sleep quality improved 37.5% over baseline, suggesting hypnotic relaxation therapy may be an effective intervention for men with hot flashes following treatment for prostate cancer.

  14. Molecular motion of micellar solutes: a /sup 13/C NMR relaxation study

    SciTech Connect

    Stark, R.E.; Kasakevich, M.L.; Granger, J.W.

    1982-02-04

    A series of simple NMR relaxation experiments have been performed on nitrobenzene and aniline dissolved in the ionic detergents sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB). Using /sup 13/C relaxation rates at various molecular sites, and comparing data obtained in organic media with those for micellar solutions, the viscosity at the solubilization site was estimated and a detailed picture of motional restrictions imposed by the micellar enviroment was derived. Viscosities of 8 to 17 cp indicate a rather fluid environment for solubilized nitrobenzene; both additives exhibit altered motional preferences in CTAB solutions only. As an aid in interpretation of the NMR data, quasi-elastic light scattering and other physical techniques have been used to evaluate the influence of organic solutes on micellar size and shape. The NMR methods are examined critically in terms of their general usefulness for studies of solubilization in detergent mice

  15. 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.

  16. Feasibility Study of Real-Time Scheduling Using the Lagrangean Relaxation Method Under an APS Environment

    NASA Astrophysics Data System (ADS)

    Shin, Kaikou; Kuroda, Mitsuru; Natsuyama, Kouichi

    Advanced Planning and Scheduling (APS) has been widely recognized as a promising method for solving real production planning and scheduling problems. Based on the proposal of a real-time job shop scheduling mechanism under an APS environment, which adopts the Lagrangean relaxation method as the optimization logic, the present paper describes a feasibility study of this mechanism by evaluating its calculation speed and re-scheduling quality. Numerical experiments have been carried out for various models having different scales, as well as different densities and strengths of random events, such as the arrival of new jobs or changes to the due dates for existing jobs. The results of experiments show that the proposed scheduling mechanism has the potential to satisfy the real-time scheduling requirements, not only in terms of calculation speed and solution quality, but also with respect to predictability of the calculation load. Finally, an improvement to the Lagrangean relaxation method is proposed to improve re-scheduling quality.

  17. Molecular dynamics study of the weakly solvent dependent relaxation dynamics following chlorine dioxide photoexcitation

    NASA Astrophysics Data System (ADS)

    Brooksby, Craig; Prezhdo, Oleg V.; Reid, Philip J.

    2003-11-01

    The solvation dynamics following photoexcitation of chlorine dioxide (OClO) in different solvents are investigated by classical molecular dynamics. Following previous work on the aqueous response to OClO photoexcitation [J. Chem. Phys. 118, 4563 (2003)], the present study considers the response of chloroform and cyclohexane; these three liquids present unique solvent environments that differ significantly in both polarity and structure. The study is designed to ascertain the origin of the solvent-invariant homogeneous linewidth associated with OClO photoexcitation and to confirm, at the molecular level, whether the relaxation dynamics are similar across dissimilar solvents due to chance or a common relaxation origin. The results obtained here are used to predict the time scale of solvent-induced optical dephasing, and excellent agreement with experiment is observed for all solvents. Analysis demonstrates that the solvation dynamics of OClO are dominated by short-ranged mechanical solute-solvent interactions regardless of the identity and electrostatic properties of the solvent. Low-frequency translational motions dominate the coupling spectrum, and virtually no contribution to energy gap relaxation is achieved through intramolecular solvent motions. The invariant homogeneous linewidth is attributed to the similarity in the primary response of all solvents to OClO photoexcitation.

  18. 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.

  19. Electronic relaxation dynamics of PCDA-PDA studied by transient absorption spectroscopy.

    PubMed

    Joung, Joonyoung F; Baek, Junwoo; Kim, Youngseo; Lee, Songyi; Kim, Myung Hwa; Yoon, Juyoung; Park, Sungnam

    2016-08-17

    Photo-curable polymers originating from 10,12-pentacosadiynoic acid (PCDA-PDA) are commonly used polydiacetylenes (PDAs). PCDA-PDA exhibits thermochromic properties undergoing a unique colorimetric transition from blue to red as the temperature is increased from low to high. In this work, we have carefully studied the temperature-dependent optical properties of PCDA-PDA by using UV-visible absorption, FTIR, Raman, and transient absorption (TA) spectroscopy in combination with quantum chemical calculations. Temperature-dependent UV-visible absorption spectra indicate that PCDA-PDA exhibits reversible thermochromic properties up to 60 °C and its thermochromic properties become irreversible above 60 °C. Such distinct thermochromic properties are also manifested in TA signals so that the electronically excited PCDA-PDA relaxes to the ground state via an intermediate state at 20 °C (blue form) but it relaxes directly back to the ground state at 80 °C (red form). The electronic relaxation dynamics of PCDA-PDA are comprehensively analyzed based on different kinetic models by using the global fitting analysis method. The intermediate state in the blue form of PCDA-PDA is clearly found to be responsible for fluorescence quenching. FTIR and Raman spectroscopy and quantum chemical calculations confirm that the H-bonds between the carboxylic acid groups in PCDA-PDA are broken at high temperatures leading to an irreversible structural change of PCDA-PDA.

  20. The geometry relaxation and intersystem crossing of quaterthiophene studied by femtosecond spectroscopy.

    PubMed

    Sun, Si-mei; Zhang, Song; Liu, Kai; Wang, Ya-ping; Zhang, Bing

    2015-04-01

    Quaterthiophene is used as a fluorescent marker for biological applications, but the intrinsic excited state dynamics for its high triplet-formation yield are still under debate due to the complexity of the molecule structure and the undetermined energy level order. In this work, ultrafast geometry relaxation and intersystem crossing of quaterthiophene in 1,4-dioxane are studied by femtosecond time-resolved spectroscopy combined with quantum calculations. Transient absorption spectra at a pump wavelength of 400 nm are completely recorded up to the delay time of 1 ns. The kinetic traces of excited state absorption indicate that geometry relaxation occurs on the S1 potential energy surface with a time constant of ∼70 ps. Two triplet-triplet absorption bands centered at 563 nm and 600 nm show a direct dynamical conversion. The intersystem crossing is determined to be ∼398 ps. The high triplet yield is measured as ∼0.7 via the efficient intersystem crossing. On the basis of quantum chemical calculations, a general mechanism is proposed to describe the geometry relaxation and intersystem crossing processes.

  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. Nuclear magnetic relaxation study of poly(ethylene oxide)-lithium salt based electrolytes

    NASA Astrophysics Data System (ADS)

    Donoso, J. P.; Bonagamba, T. J.; Panepucci, H. C.; Oliveira, L. N.; Gorecki, W.; Berthier, C.; Armand, M.

    1993-06-01

    We have studied the low-temperature NMR line shape for three nuclei (1H, 7Li, and 19F) in poly(ethylene oxide)-lithium salts (LiClO4, LiBF4, and LiAsF6) solid polymer ionic conductors and measured their spin-lattice relaxation rates as functions of frequency and temperature. The three nuclei probe the dynamics of the polymer segments, the cations, and the anions. We find that the Li+ cations follow the segmental motion of the chain, while the anions move independently. Homonuclear interactions and heteronuclear interactions with the polymer and the anion contribute to the 7Li line shape. When the heteronuclear contributions were selectively eliminated by the decoupling method, it was found that the Li-H interaction accounts for 80%-90% of the linewidth. Additional evidence for the correlation between the cationic and the polymeric motions is provided by the remarkably similar temperature dependences of the measured relaxation rates for 7Li and 1H, which differ significantly from the dependence for 19F. The frequency dependence of the relaxation rates is poorly described by the Bloembergen, Purcell, and Pound model; a recently developed graphical procedure nevertheless shows that the motion of the protons and the anions is governed by a single time scale, while the 7Li ions are affected by an additional scale, associated with the coupling of its quadrupolar moment to the electric-field gradient.

  3. 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.

  4. 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.

  5. On the lorentzian versus Gaussian character of time-domain spin-echo signals from the brain as sampled by means of gradient-echoes: Implications for quantitative transverse relaxation studies.

    PubMed

    Mulkern, Robert V; Balasubramanian, Mukund; Mitsouras, Dimitrios

    2014-07-30

    To determine whether Lorentzian or Gaussian intra-voxel frequency distributions are better suited for modeling data acquired with gradient-echo sampling of single spin-echoes for the simultaneous characterization of irreversible and reversible relaxation rates. Clinical studies (e.g., of brain iron deposition) using such acquisition schemes have typically assumed Lorentzian distributions. Theoretical expressions of the time-domain spin-echo signal for intra-voxel Lorentzian and Gaussian distributions were used to fit data from a human brain scanned at both 1.5 Tesla (T) and 3T, resulting in maps of irreversible and reversible relaxation rates for each model. The relative merits of the Lorentzian versus Gaussian model were compared by means of quality of fit considerations. Lorentzian fits were equivalent to Gaussian fits primarily in regions of the brain where irreversible relaxation dominated. In the multiple brain regions where reversible relaxation effects become prominent, however, Gaussian fits were clearly superior. The widespread assumption that a Lorentzian distribution is suitable for quantitative transverse relaxation studies of the brain should be reconsidered, particularly at 3T and higher field strengths as reversible relaxation effects become more prominent. Gaussian distributions offer alternate fits of experimental data that should prove quite useful in general. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

  6. Two-dimensional longitudinal and transverse relaxation time correlation as a low-resolution nuclear magnetic resonance characterization of ancient ceramics

    NASA Astrophysics Data System (ADS)

    Casieri, Cinzia; Terenzi, Camilla; De Luca, Francesco

    2009-02-01

    Longitudinal and transverse relaxation time correlation (T1-T2) is employed as a nuclear magnetic resonance noninvasive characterization tool for archeological ceramics. This paper is aimed at investigating whether the most relevant firing-induced changes in ceramics, including those involving pore space properties and paramagnetic mineral structures, could be used as markers of the firing process and therefore of ceramics themselves. Ancient ceramics are made up of naturally available clays, often rich in iron impurities, which undergo relevant modifications of pore distribution upon firing. The firing process also assists chemical and physical rearrangement of iron-bearing species, yielding mineral structures with different magnetic properties. That being so, T1-T2 maps are expected to show the interdependence between ceramic structure and firing technology. T1 and T2 distributions are basically proportional to pore-size distribution, but T2, which is also sensitive to magnetic susceptibility effects, may give information on the porous matrix composition as well. Such a methodology has first been employed on laboratory-prepared ceramic samples, with different paramagnetic compositions and controlled firing temperatures, in order to tackle the problem of model-ceramic selection. Then, the T1-T2 correlation approach has been used on medieval ceramic findings in order to get information about their thermal and compositional history. The information obtained by means of two-dimensional correlation maps proves coherent with archeological dating, thus illustrating the capabilities of this method.

  7. 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.

  8. Relaxation of hyperpolarized 129 Xe in a deflating polymer bag

    NASA Astrophysics Data System (ADS)

    Möller, Harald E.; Cleveland, Zackary I.; Driehuys, Bastiaan

    2011-09-01

    In magnetic resonance imaging with hyperpolarized (HP) noble gases, data is often acquired during prolonged gas delivery from a storage reservoir. However, little is known about the extent to which relaxation within the reservoir will limit the useful acquisition time. For quantitative characterization, 129Xe relaxation was studied in a bag made of polyvinyl fluoride (Tedlar). Particular emphasis was on wall relaxation, as this mechanism is expected to dominate. The HP 129Xe magnetization dynamics in the deflating bag were accurately described by a model assuming dissolution of Xe in the polymer matrix and dipolar relaxation with neighboring nuclear spins. In particular, the wall relaxation rate changed linearly with the surface-to-volume ratio and exhibited a relaxivity of κ = 0.392 ± 0.008 cm/h, which is in reasonable agreement with κ = 0.331 ± 0.051 cm/h measured in a static Tedlar bag. Estimates for the bulk gas-phase 129Xe relaxation yielded T1bulk=2.55±0.22 h, which is dominated by intrinsic Xe-Xe relaxation, with small additional contributions from magnetic field inhomogeneities and oxygen-induced relaxation. Calculations based on these findings indicate that relaxation may limit HP 129Xe experiments when slow gas delivery rates are employed as, for example, in mouse imaging or vascular infusion experiments.

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

    SciTech Connect

    Black, Bruce Elmer

    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 11B and 27Al NQR resonances. The scope of this study was increased to include 23Na, 51V, and 55Mn NQR transitions. Also, a technique was presented to observe 14N 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 14N 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.

  10. Magnetic relaxations in a Tb-based single molecule magnet studied by quasielastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Kofu, Maiko; Kajiwara, Takashi; Gardner, Jason S.; Simeoni, Giovanna G.; Tyagi, Madhusudan; Faraone, Antonio; Nakajima, Kenji; Ohira-Kawamura, Seiko; Nakano, Motohiro; Yamamuro, Osamu

    2013-12-01

    By using ac magnetic susceptibility and quasielatic neutron scattering (QENS) techniques, we have investigated a magnetization relaxation phenomenon of a rare-earth based single molecule magnet, TbCuC19H20N3O16. We clearly identified and characterized two magnetic relaxations. The slower relaxation observed in the ac susceptibility is at the ms timescale around T=2 K and its activation energy is 16 K. On the other hand, the faster relaxation in the QENS measurements occurs on the timescale between ns and ps with activation energy of 174 K. The slower relaxation may occur through thermally activated tunneling among magnetic substates. We discuss two possible origins for the faster relaxation; one is a thermally activated tunneling between the higher excited states, the other is the magnetic relaxation coupled with the motion of ligands around the magnetic ions. This is the first clear observation of magnetic relaxation on the single molecule magnet revealed by QENS.

  11. Study of spin resonances in the accelerators with snakes

    SciTech Connect

    Lee, S.Y.

    1988-01-01

    Spin resonances in the circular accelerators with snakes are studied to understand the nature of snake resonances. We analyze the effect of snake configuration, and the snake superperiod on the resonance. Defining the critical resonance strength epsilon/sub c/ as the maximum tolerable resonance strength without losing the beam polarization after passing through the resonance, we found that epsilon/sub c/ is a sensitive function of the snake configuration, the snake superperiod at the first order snake resonance, the higher order snake resonance conditions and the spin matching condition. Under properly designed snake configuration, the critical resonance strength epsilon/sub c/ is found to vary linearly with N/sub S/ as = (1/..pi..)sin/sup /minus/1/(/vert bar/cos ..pi nu../sub z//vert bar//sup /1/2//)N/sub S/, where ..nu../sub z/ and N/sub S/ are the betatron tune and the number of snakes respectively. We also study the effect of overlapping intrinsic and imperfection resonances. The imperfection resonance should be corrected to a magnitude of insignificance (e.g., epsilonless than or equal to0.1 for two snakes case) to maintain proper polarization. 23 refs., 25 figs.

  12. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Nuclear-quadrupole-resonance study of overdoped Y1- xCaxBa2Cu3O7

    NASA Astrophysics Data System (ADS)

    Williams, G. V.; Krämer, S.; Mehring, M.

    2001-03-01

    We have performed a 63,65Cu nuclear-quadrupole-resonance study of overdoped Y1-xCaxBa2Cu3O7 and find that the temperature dependence of the Cu spin-lattice and spin-spin relaxation rates are similar to that in lightly overdoped YBa2Cu3O7. We show that the data can be interpreted within the Millis, Monien, and Pines model in terms of no significant decrease in the antiferromagnetic correlation length, at least for p<0.233. Furthermore, the isotopic ratios of the spin-lattice and spin-spin relaxation rates do not change with increasing hole concentration, indicating that magnetic relaxation is still dominant in the overdoped region.

  14. Translation and reorientation of CD4 molecules in nanoscale cages of zeolites as studied by deuteron spin-lattice relaxation

    NASA Astrophysics Data System (ADS)

    Birczyński, A.; Punkkinen, M.; Szymocha, A. M.; Lalowicz, Z. T.

    2007-11-01

    Deuteron spin-lattice relaxation was applied to study translational and rotational mobility of CD4 molecules trapped in the cages of zeolites. Tetrahedral methane molecules are treated as quantum rotators. Relaxation rates related to the intraquadrupole interaction are derived for the T and A +E symmetry species in the presence of large tunneling splittings, consistently with the assumption that A and E species molecules relax at the same rate. An exchange model is presented, which describes the effect on relaxation of CD4 jumping between two positions characterized by different potentials. While staying at either position bonded to an atom or ion at the cage wall, the molecule has some freedom to move in the vicinity. This causes a time-dependent external electric field gradient, which contributes to the deuteron relaxation rate via the electric quadrupole interaction. Spin conversion transitions couple the relaxation of magnetizations MT and MAE, which is taken into account by reapplying the presented model under somewhat different conditions. Such a two-step procedure leads to successful fits with the experimental results obtained in the range of temperatures roughly 20-200K for zeolites HY, NaA, and NaMordenite. At higher temperatures CD4 molecules fly freely across zeolite cages and relaxation changes accordingly, while incoherent tunneling dominates for immobile molecules below 20K.

  15. Comment on ``Study of dielectric relaxations of anhydrous trehalose and maltose glasses'' [J. Chem. Phys. 134, 014508 (2011)

    NASA Astrophysics Data System (ADS)

    Kaminski, K.; Wlodarczyk, P.; Paluch, M.

    2011-10-01

    Very recently Kwon et al. [H.-J. Kwon, J.-A. Seo, H. K. Kim, and Y. H. Hwang, J. Chem. Phys. 134, 014508 (2011)] published an article on the study of dielectric relaxation in trehalose and maltose glasses. They carried out broadband dielectric measurements at very wide range of temperatures covering supercooled liquid as well as glassy state of both saccharides. It is worth to mention that authors have also applied a new method for obtaining anhydrous glasses of trehalose and maltose that enables avoiding their caramelization. Four relaxation processes were identified in dielectric spectra of both saccharides. The slower one was identified as structural relaxation process the next one, not observed by the others, was assigned as Johari-Goldstein (JG) β-relaxation, while the last two secondary modes were of the same nature as found by Kaminski et al. [K. Kaminski, E. Kaminska, P. Wlodarczyk, S. Pawlus, D. Kimla, A. Kasprzycka, M. Paluch, J. Ziolo, W. Szeja, and K. L. Ngai, J. Phys. Chem. B 112, 12816 (2008)]. In this comment we show that the authors mistakenly assigned the slowest relaxation process as structural mode of disaccharides. We have proven that this relaxation process is an effect of formation of thin layer of air or water between plate of capacitor and sample. The same effect can be observed if plates of capacitor are oxidized. Thus, we concluded that their slowest mode is connected to the dc conduction process while their β JG process is primary relaxation of trehalose and maltose.

  16. Nonlinear Optical Studies of Resonant Systems

    DTIC Science & Technology

    1989-06-14

    1986), Appl. Phys. Lett. 49, 1275 Cohen , E., and M.D. Sturge (1982), Phys. Rev. B 25, 3828. Cohen - Tannoudji , Claude (1977), in Frontiers in Laser...evaluation of this term including the use of reservoir theory in the density matrix ( Cohen - Tannoudji , 1977). For many cases of interest, the...review of relaxation, see Cohen -Tan -iAi, 1977). The velocity term on the left hand side describes motion of tb ’enter of mass for gas phase systems

  17. 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.

  18. Cross-relaxation in nuclear polarization. A flash-CIDNP study

    NASA Astrophysics Data System (ADS)

    Yurkovskaya, A. V.; Tsentalovich, Yu. P.; Sagdeev, R. Z.

    1990-08-01

    CIDNP with microsecond time resolution was used to study the kinetics of nuclear polarization formation during the photolysis of acetone in isopropanol over a wide temperature range. The coincidence of signs of multiplet effects of CIDNP (A/E) for cage and escape reaction products as well as the presence of net polarization (E) changing its sign with decreasing temperature have been revealed. The account of scalar electron-nuclear cross-relaxation has been shown to be necessary for the interpretation of the results obtained.

  19. Vibrational energy transport in molecules studied by relaxation-assisted two-dimensional infrared spectroscopy.

    PubMed

    Rubtsova, Natalia I; Rubtsov, Igor V

    2015-04-01

    This review presents an overview of the relaxation-assisted two-dimensional infrared (RA 2DIR) spectroscopy method for measuring structures and energy transport dynamics in molecules. The method strongly enhances the range of accessible distances compared to traditional 2DIR and offers new structural reporters, such as the energy transport time, cross-peak amplification factors, and connectivity patterns. The use of the method for assigning vibrational modes with various levels of delocalization is illustrated. RA 2DIR relies on vibrational energy transport in molecules; as such, the transport mechanism can be conveniently studied by the method. Applications to identify diffusive and ballistic energy transport are demonstrated.

  20. 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.

  1. Contrast-enhanced magnetic resonance tomoangiography: a new imaging technique for studying thoracic great vessels.

    PubMed

    Revel, D; Loubeyre, P; Delignette, A; Douek, P; Amiel, M

    1993-01-01

    The authors propose a new imaging approach for studying thoracic great vessels, using high-speed MR imaging combined with intravenous rapid bolus injection of a paramagnetic contrast media. The decrease of the T1 relaxation time of flowing blood induced by the contrast agent (Gd-DOTA) caused an increased signal intensity within the vessel lumen for a time period allowing multiplanar imaging of various vascular structures. The intraluminal signal enhancement is mainly related to the blood concentration of the contrast agent as in conventional X-ray angiography. Information on the aorta and pulmonary arteries obtained by the so-called contrast-enhanced magnetic resonance tomoangiography appears complementary to that obtained with other vascular MR imaging procedures such as cine-MRI and magnetic resonance angiography (MRA).

  2. Measurement of longitudinal relaxation times for spin-decoupled protons.

    NASA Technical Reports Server (NTRS)

    Gerace, M. J.; Kuhlmann, K. F.

    1972-01-01

    Description of an experimental method for the determination of the longitudinal relaxation time for spin-decoupled protons by a modified version of the saturation recovery technique reported by Van Geet and Hume (1965). The described method should facilitate relaxation studies of chemically shifted protons (or fluorines) and can be applied to more complicated spin systems with the aid of triple resonance and noise-decoupling techniques.

  3. 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.

  4. Endotracheal intubation without muscle relaxants in children using remifentanil and propofol: Comparative study

    PubMed Central

    Naziri, Freshteh; Amiri, Hakimeh Alereza; Rabiee, Mozaffar; Banihashem, Nadia; Nejad, Farhad Mohammad; Shirkhani, Ziba; Solimanian, Sedigheh

    2015-01-01

    Introduction: Endotracheal intubation is essential during general anesthesia and muscle relaxant drugs provide ideal conditions for this purpose. The objective of this study was to evaluate the intubating condition of remifentanil combined with propofol without muscle relaxant. Materials and Methods: In this prospective randomized study, 60 children aged 3-12 years, American Society of Anesthesiologists physical status I and II were included. All the children were premedicated with 0.05 mg/kg midazolam and 1.5 mg/kg lidocaine 5 min before the induction of anesthesia with 3 mg/kg propofol. Then, they were allocated randomly to receive either 2 μg/kg remifentanil (group R) or 1.5 mg/kg succinylcholine (group S). Tracheal intubation was attempted 90 s after the administration of propofol. The quality of intubation was assessed by using Copenhagen score based on jaw relaxation, ease of laryngoscopy, position of vocal cord, coughing and limb movement. Heart rate and blood pressure were recorded before and after induction, and 1, 3, 5 min after intubation. Results: There was no significant difference in intubating condition between the two groups (P = 0.11). Intubation condition was excellent in 26 of 30 (86.7%) patients in the group R compared with 30 (100%) patients in the group S. We observed significant difference in heart rate and systolic blood pressure over time between two groups (P = 0.02, P = 0.03 respectively). After intubation, we had higher heart rate and systolic blood pressure with a significant difference in group S compared with group R (P = 0.006, P = 0.018). None of the children had a chest rigidity, laryngospasm, and hypoxia. Conclusions: In premedicated children, propofol-remifentanil combination provides adequate conditions for tracheal intubation that is comparable with succinylcholine. Hemodynamic response to laryngoscopy and tracheal intubation was controlled better in group R. PMID:26543458

  5. Electron spin relaxation and K39 pulsed ENDOR studies on Cr5+ -doped K3NbO8 at 9.7 and 240 GHz

    NASA Astrophysics Data System (ADS)

    Nellutla, S.; Morley, G. W.; van Tol, J.; Pati, M.; Dalal, N. S.

    2008-08-01

    Cr5+ -doped K3NbO8 , considered to be useful as an electron spin qubit, has been investigated by pulsed X band (˜9.7GHz) and 240 GHz electron paramagnetic resonance and electron nuclear double resonance (ENDOR). Comparison of the low temperature electronic spin-lattice relaxation rate 1/T1 at 9.7 and 240 GHz shows that it is 250 times faster at 240 GHz than at X band. On the other hand, spin-spin relaxation rate 1/T2 appears largely frequency independent and is very likely related to the superhyperfine (SHF) coupling of the Cr5+ electron with the surrounding potassium and niobium nuclei. This coupling was investigated by hyperfine sublevel correlation spectroscopy at 9.7 GHz and pulsed Mims ENDOR at 240 GHz. The use of high frequency and field enabled us to unambiguously measure the hyperfine and quadrupole couplings of the K39 in spite of its small magnetic moment. We find that the largest K39 SHF coupling is positive, with 0.522 and 0.20 MHz as its isotropic and dipolar parts, respectively. N93b ENDOR was dominantly due to its quadrupolar interaction with a coupling of about 0.8 MHz and a SHF coupling of about 0.08 MHz. The significance of these data to spin qubit studies is pointed out.

  6. Study of resonances for the restricted 3-body problem

    NASA Astrophysics Data System (ADS)

    Quarles, B.; Musielak, Z. E.; Cuntz, M.

    2012-08-01

    Our aim is to identify and classify mean-motion resonances (MMRs) for the coplanar circular restricted three-body problem (CR3BP) for mass ratios between 0.10 and 0.50. Our methods include the maximum Lyapunov exponent, which is used as an indicator for the location of the resonances, the Fast Fourier Transform (FFT) used for determining what kind of resonances are present, and the inspection of the orbital elements to classify the periodicity. We show that the 2:1 resonance occurs the most frequently. Among other resonances, the 3:1 resonance is the second most common, and furthermore both 3:2 and 5:3 resonances occur more often than the 4:1 resonance. Moreover, the resonances in the coplanar CR3BP are classified based on the behaviour of the orbits. We show that orbital stability is ensured for high values of resonance (i.e., high ratios) where only a single resonance is present. The resonances attained are consistent with the previously established resonances for the solar system, i.e., specifically, in regards to the asteroid belt. Previous work employed digital filtering and Lyapunov characteristic exponents to determine stochasticity of the eccentricity, which is found to be consistent with our usage of Lyapunov exponents as an alternate approach based on varying the mass ratio instead of the eccentricity. Our results are expected to be of principal interest to future studies, including augmentations to observed or proposed resonances, of extra-solar planets in binary stellar systems.

  7. 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

  8. Solution dynamics of the trp repressor: a study of amide proton exchange by T1 relaxation.

    PubMed

    Gryk, M R; Finucane, M D; Zheng, Z; Jardetzky, O

    1995-03-10

    The amide proton exchange rates of Escherichia coli trp repressor have been measured through their effects on the longitudinal relaxation rates of the amide protons. Three types of exchange regimes have been observed: (1) slow exchange (on a minute/hour time-scale), measurable by isotope exchange, but not by relaxation techniques in the core of the molecule; (2) relatively rapid exchange, with the rates on a T1 relaxation time-scale (seconds) in the DNA-binding region and (3) very fast exchange at the N and C termini. The results have been analyzed in terms of the two-site exchange model originally proposed by Linderstrøm-Lang, and of a three-site extension of the model. The values of the intrinsic exchange rates calculated using the two-state model agree with the values expected from the studies of Englander and co-workers for the very fast case of the chain terminals, but disagree with the literature values by two orders of magnitude in the intermediate case found in the DNA-binding region. The implication of these findings is that the "open" state of the two-state model in the DNA-binding region is not completely open and has an intrinsic exchange rate different from that of a random coil peptide. Alternatively, if the literature values of the intrinsic exchange rates are assumed to apply to the open states in all parts of the repressor molecule, two "closed" helical states have to be postulated, in slow exchange with each other, with only one of them in rapid exchange with the open state and hence with the solvent. Kinetically, the two models are indistinguishable.

  9. Relaxation of surface steps after thermal quenches: a numerical study within the terrace-step-kink model.

    PubMed

    Bustingorry, S; Centres, P M

    2011-07-01

    We study the out-of-equilibrium relaxation of surface steps after thermal quenches using numerical simulations of the terrace-step-kink model for a vicinal surface. We analyze both single and interacting steps in a situation where the temperature is suddenly changed at a given quench time. We focus on a physically relevant range of temperatures and show that the relaxation of the roughness is compatible with a power-law behavior with an effective relaxation exponent close to γ = 1/2 in all cases. This value is consistent with a one-dimensional Edwards-Wilkinson equation. In particular, this means that, although the case of interacting steps is effectively a two-dimensional system, its relaxation is dominated by short length-scale fluctuations, where steps are not interacting.

  10. Emission Mössbauer spectroscopy study of fluence dependence of paramagnetic relaxation in Mn/Fe implanted ZnO

    NASA Astrophysics Data System (ADS)

    Masenda, H.; Geburt, S.; Bharuth-Ram, K.; Naidoo, D.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Mølholt, T. E.; Ncube, M.; Shayestehaminzadeh, S.; Gislason, H. P.; Langouche, G.; Ólafsson, S.; Ronning, C.

    2016-12-01

    Emission Mössbauer Spectroscopy following the implantation of radioactive precursor isotope 57Mn+ ( T 1/2= 1.5 min) into ZnO single crystals at ISOLDE/CERN shows that a large fraction of 57Fe atoms produced in the 57Mn beta decay is created as paramagnetic Fe3+ with relatively long spin-lattice relaxation times. Here we report on ZnO pre-implanted with 56Fe to fluences of 2×1013, 5×10 13 and 8 × 1013 ions/cm2 in order to investigate the dependence of the paramagnetic relaxation rate of Fe3+ on fluence. The spectra are dominated by magnetic features displaying paramagnetic relaxation effects. The extracted spin-lattice relaxation rates show a slight increase with increasing ion fluence at corresponding temperatures and the area fraction of Fe3+ at room temperature reaches a maximum contribution of 80(3)% in the studied fluence range.

  11. Relaxed heaps

    SciTech Connect

    Driscoll, J.R. ); Gabow, H.N.; Shrairman, R. ); Tarjan, R.E. )

    1988-11-01

    The relaxed heap is a priority queue data structure that achieves the same amortized time bounds as the Fibonacci heap - a sequence of m decrease key and n delete min operations takes time O(m + n log n). A variant of relaxed heaps achieves similar bounds in the worst case - O(1) time for decrease key and O(log n) for delete min. Relaxed heaps give a processor-efficient parallel implementation of Dijkstra's shortest path algorithm, and hence other algorithms in network optimization. A relaxed heap is a type of binomial queue that allows heap order to be violated.

  12. Molecular motions in glassy crystal cyanoadamantane : a proton spin-lattice relaxation study

    NASA Astrophysics Data System (ADS)

    Amoureux, J. P.; Decressain, R.; Sahour, M.; Cochon, E.

    1992-02-01

    Cyanoadamantane C{10}H{15}CN exhibits four different solid phases : two cubic plastic (I and I'), one cubic glassy (Ig) and one monoclinic ordered (II). In cubic plastic phases (I, I') three types of motion coexist : a uniaxial rotation of the molecule around its C—CequivN axis, a tumbling reorientation of this dipolar axis between the <~ngle 001rangle directions and a vacancy self-diffusion. In the cubic glassy state (Ig) the tumbling motion is frozen and therefore only the uniaxial rotation survives. In the ordered phase (II), the molecules only perform a 3-fold uniaxial rotation among identical positions. These different molecular motions in the four solid phases have been studied by the analysis of the T_{1 z} and T_{1 ρ} spin-lattice relaxation times in ^1H-NMR. The derived residence time are compared, when possible, to values previously deduced from quasi-elastic neutron scattering, dielectric relaxation and second moment of the ^1H-NMR lineshape. Le cyanoadamantane C{10}H{15}CN possède quatre phases solides différentes : deux plastiques cubiques (I et I'), une vitreuse cubique (Ig) et une ordonnée monoclinique (II). Dans les phases plastiques cubiques (I, I') trois types de mouvements coexistent : une rotation uniaxiale de la molécule autour de son axe C—CequivN, un basculement de cet axe dipolaire entre les directions <~ngle 001rangle et une diffusion moléculaire. Dans l'état vitreux cubique (Ig), le mouvement de basculement est gelé et seule la rotation uniaxiale subsiste. Enfin dans la phase ordonnée (II), les molécules effectuent une rotation uniaxiale d'ordre 3 entre positions indiscernables. Ces différents mouvements dans les quatre phases solides ont été évalués par l'analyse des temps de relaxation spin-réseau T_{1 z} et T_{1 ρ} en ^1H-RMN. Les temps de résidence qui en sont déduits sont comparés (lorsque cela est possible) aux valeurs correspondantes déduites précédemment par diffusion quasi-élastique des neutrons, par

  13. 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.

  14. Thermally activated spin fluctuations in stoichiometric LiCoO2 clarified by electron paramagnetic resonance and muon-spin rotation and relaxation measurements

    NASA Astrophysics Data System (ADS)

    Mukai, Kazuhiko; Aoki, Yoshifumi; Andreica, Daniel; Amato, Alex; Watanabe, Isao; Giblin, Sean R.; Sugiyama, Jun

    2014-03-01

    Lithium cobalt dioxide (LiCoO2) belongs to a family of layered CoO2-based materials and has considerable interests in both fundamental physics and technological applications in lithium-ion batteries. We report the results of structural, electrochemical, magnetic susceptibility (χ), electron paramagnetic resonance (EPR), and muon-spin rotation and relaxation (μSR) measurements on powder Lix0CoO2 samples, where the nominal Li/Co ratios (x0) were 0.95, 1.00, 1.02, 1.05, and 1.10, respectively. Structural, electrochemical, and χ measurements suggested that the sample with x0 = 1.02 is very close to single stoichiometric LiCoO2 (ST-LCO) phase and that the Co ions in the x0 = 1.02 sample are in a nonmagnetic low-spin state with S = 0 (t2g6). However, both EPR and μSR revealed that the x0 = 1.02 (ST-LCO) sample includes a large amount of nonordered magnetic phase in the temperature (T) range between 100 and 500 K. The volume fraction of such magnetic phase was found to be ˜45 vol% at 300 K by μSR, indicating an intrinsic bulk feature for ST-LCO. In fact, structural and photoelectron spectroscopic analyses clearly excluded the possibility that the nonordered magnetism is caused by impurities, defects, or surfaces. Because EPR and μSR sense static and dynamic nature of local magnetic environments, we concluded that Co spins in ST-LCO are fluctuating in the EPR and μSR time-windows. We also proposed possible origins of such nonordered magnetism, that is, a spin-state transition and charge disproportionation.

  15. The effect of body-mind relaxation meditation induction on major depressive disorder: A resting-state fMRI study.

    PubMed

    Chen, Fangfang; Lv, Xueyu; Fang, Jiliang; Yu, Shan; Sui, Jing; Fan, Lingzhong; Li, Tao; Hong, Yang; Wang, XiaoLing; Wang, Weidong; Jiang, Tianzi

    2015-09-01

    Meditation has been increasingly evaluated as an important complementary therapeutic tool for the treatment of depression. The present study employed resting-state functional magnetic resonance imaging (rs-fMRI) to examine the effect of body-mind relaxation meditation induction (BMRMI) on the brain activity of depressed patients and to investigate possible mechanisms of action for this complex intervention. 21 major depressive disorder patients (MDDs) and 24 age and gender-matched healthy controls (HCs) received rs-fMRI scans at baseline and after listening to a selection of audio designed to induce body-mind relaxation meditation. The rs-fMRI data were analyzed using Matlab toolbox to obtain the amplitude of low-frequency fluctuations (ALFF) of the BOLD signal for the whole brain. A mixed-design repeated measures analysis of variance (ANOVA) was performed on the whole brain to find which brain regions were affected by the BMRMI. An additional functional connectivity analysis was used to identify any atypical connection patterns after the BMRMI. After the BMRMI experience, both the MDDs and HCs showed decreased ALFF values in the bilateral frontal pole (BA10). Additionally, increased functional connectivity from the right dorsal medial prefrontal cortex (dmPFC) to the left dorsal lateral prefrontal cortex (dlPFC) and the left lateral orbitofrontal cortex (OFC) was identified only in the MDDs after the BMRMI. In order to exclude the impact of other events on the participants׳ brain activity, the Hamilton Rating Scales for Depression (HDRS) was not measured after the body-mind relaxation induction. Our findings support the hypothesis that body-mind relaxation meditation induction may regulate the activities of the prefrontal cortex and thus may have the potential to help patients construct reappraisal strategies that can modulate the brain activity in multiple emotion-processing systems. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Understanding long-time vacancy aggregation in iron: A kinetic activation-relaxation technique study

    NASA Astrophysics Data System (ADS)

    Brommer, Peter; Béland, Laurent Karim; Joly, Jean-François; Mousseau, Normand

    2014-10-01

    Vacancy diffusion and clustering processes in body-centered-cubic (bcc) Fe are studied using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities. For monovacancies and divacancies, k-ART recovers previously published results while clustering in a 50-vacancy simulation box agrees with experimental estimates. Applying k-ART to the study of clustering pathways for systems containing from one to six vacancies, we find a rich set of diffusion mechanisms. In particular, we show that the path followed to reach a hexavacancy cluster influences greatly the associated mean-square displacement. Aggregation in a 50-vacancy box also shows a notable dispersion in relaxation time associated with effective barriers varying from 0.84 to 1.1 eV depending on the exact pathway selected. We isolate the effects of long-range elastic interactions between defects by comparing to simulations where those effects are deliberately suppressed. This allows us to demonstrate that in bcc Fe, suppressing long-range interactions mainly influences kinetics in the first 0.3 ms, slowing down quick energy release cascades seen more frequently in full simulations, whereas long-term behavior and final state are not significantly affected.

  17. Electroencephalographic (EEG) measurements of mindfulness-based Triarchic body-pathway relaxation technique: a pilot study.

    PubMed

    Chan, Agnes S; Han, Yvonne M Y; Cheung, Mei-Chun

    2008-03-01

    The "Triarchic body-pathway relaxation technique" (TBRT) is a form of ancient Chinese mindfulness-based meditation professed to give rise to positive emotions and a specific state of consciousness in which deep relaxation and internalized attention coexist. The purpose of this study was to examine the EEG pattern generated during the practice of this mindfulness exercise, and compare it to music listening which has been shown to induce positive emotions. Nineteen college students (aged 19-22 years) participated in the study. Each participant listened to both the TBRT and music audiotapes while EEG was recorded. The order of presentation was counterbalanced to avoid order effect. Two EEG indicators were used: (1) alpha asymmetry index, an indicator for left-sided anterior activation, as measure of positive emotions, and (2) frontal midline theta activity, as a measure for internalized attention. Increased left-sided activation, a pattern associated with positive emotions, was found during both TBRT exercise and music conditions. However, only TBRT exercise was shown to exhibit greater frontal midline theta power, a pattern associated with internalized attention. These results provided evidence to support that the TBRT gives rise to positive emotional experience, accompanied by focused internalized attention.

  18. QSAR study on the relaxant agents from some Mexican medicinal plants and synthetic related organic compounds.

    PubMed

    Ramírez-Galicia, Guillermo; Garduño-Juarez, Ramón; Hemmateenejad, Bahram; Deeb, Omar; Estrada-Soto, Samuel

    2007-08-01

    Quantitative Structure-Activity Relationship studies were performed to describe and predict the antispasmodic activity of some molecules isolated from Mexican Medicinal Flora as well as for some synthetic ones based on stilbenoid bioisosteres. The relaxant activity of these molecules was taken from experiments on rat and guinea-pig ileum tissues. Given that there is some evidence of species-specific on the relaxant effects, two data sets were proposed, one for rat ileum and the other for guinea-pig ileum. These data were statistically treated in order to find a Quantitative Structure-Activity Relationship model that could describe the corresponding biological models. The goodness of prediction for the best models was measured in terms of the Leave-One-Out Cross-Validation R(2) (LOO q(2)) and the correlation coefficients of regressions through the origin (RTO R(2)0). Results show that papaverine activity could not be used as reference in rat ileum tests; however, this molecule can be used as a good reference molecule in guinea-pig ileum tests. Our study shows that MATS5p and R8m+ descriptors are the most important descriptors in predicting the rat ileum activity and that atomic polarizability is the main atomic property. On the other hand, the R3u GETAWAY descriptor turns out to be important in predicting the guinea-pig ileum activity where the influence/distance of substituents on these molecules could describe the observed activity.

  19. 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.

  20. Thermal Properties of Whispering Gallery Mode Resonators

    DTIC Science & Technology

    2014-12-22

    F01m 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 ABSTRACT Number of Papers published in peer-reviewed journals: Thermal Properties of Whispering...Gallery Mode Resonators Report Title In this project, we studied the thermal properties of ultra-high-quality whispering-gallery-mode microtoroid...resonators. More specifically, we measured the thermal relaxation time of the resonator to estimate the response time of the resonator based infrared (IR

  1. Proton NMR T1, T2, and T1 rho relaxation studies of native and reconstituted sarcoplasmic reticulum and phospholipid vesicles.

    PubMed Central

    Deese, A J; Dratz, E A; Hymel, L; Fleischer, S

    1982-01-01

    The phospholipids protons of native and reconstituted sarcoplasmic reticulum (SR) membrane vesicles yield well-resolved nuclear magnetic resonance (NMR) spectra. Resonance area measurements, guided by the line shape theory of Bloom and co-workers, imply that we are observing a large fraction of the lipid intensity and that the protein does not appear to reduce the percent of the signal that is well resolved. We have measured the spin-lattice (T1) and spin-spin (T2) relaxation rates of the choline, methylene, and terminal methyl protons at 360 MHz and the spin-lattice relaxation rate in the rotating frame (T1 rho) at 100 MHz. Both the T1 and T2 relaxation rates are single exponential processes for all of the resonances if the residual water proton signal is thoroughly eliminated by selective saturation. The T1 and T2 relaxation rates increase as the protein concentration increases, and T2 rate decrease with increasing temperature. This implies that the protein is reducing both high frequency (e.g., trans-gauche methylene isomerizations) and low frequency (e.g., large amplitude, chain wagging) lipid motions, from the center of the bilayer to the surface. It is possible that spin diffusion contributes to the effect of protein on lipid T1's although some of the protein-induced T1 change is due to motional effects. The T2 relaxation times are observed to be near 1 ms for the membranes with highest protein concentration and approximately 10 ms for the lipids devoid of protein. This result, combined with the observation that the T2 rates are monophasic, suggests that at least two lipid environments exist in the presence of protein, and that the lipids are exchanging between these environments at a rate greater than 1/T2 or 10(3) s-1. The choline resonance yields single exponential T1 rho relaxation in the presence and absence of protein, whereas the other resonances measured exhibit biexponential relaxation. Protein significantly increases the single T1 rho relaxation

  2. Ultrasound Treatment of Butyl Gum and Rubber, Studied by NMR Relaxation

    NASA Astrophysics Data System (ADS)

    von Meerwall, E. D.; Feng, Wenlai; Isayev, A. I.

    2004-10-01

    We have examined the effects of intense ultrasound on butyl gum and unfilled vulcanizates using proton transverse NMR relaxation, sol extraction, GPC analysis, and glass transition measurements. At 100 deg.C the spin echo decays exhibit three components, due to entangled molecules and network, unentangled sol plus dangling chain ends, and oligomer remnants; two components suffice to describe most vulcanizates. Compared to other rubbers we have studied, all component spin relaxation times are shorter and less sensitive to ultrasound, and the fraction of the short-T2 component is significantly higher. In the gums sonication produces chain scission but no significant crosslinking. In sol extracted from sonicated rubber, the T2 component amplitudes correlate well with the trimodal molecular-weight distribution. In spite of the low glass transition temperatures (near -60 deg.C) even the longest T2 up to 120 deg.C was too short to permit pulsed-gradient diffusion measurements. The low extractable sol fraction at standard ultrasound settings confirms the conclusion that in butyl rubber sonication is less effective for network destruction than in other rubbers.

  3. Relaxation NMR as a tool to study the dispersion and formulation behavior of nanostructured carbon materials.

    PubMed

    Fairhurst, David; Cosgrove, Terence; Prescott, Stuart W

    2016-06-01

    Solvent relaxation NMR has been used to estimate the surface areas and wettability of various types of nanostructured carbon materials in a range of solvents including water, ethanol, and tetrahydrofuran. We illustrate the application of the technique through several short case studies using samples including nanocarbon blacks, graphene oxide, nanographites, and porous graphenes. The technique is shown to give a good measure of surface area, correlating well with conventional surface area estimates obtained by nitrogen adsorption, transmission electron microscopy, or light scattering for the non-porous samples. NMR relaxation has advantages in terms of speed of analysis and being able to use concentrated, wet, and opaque samples. For samples that are porous, two distinct surface areas can be estimated assuming the two environments ('inner' and 'outer') have the same surface chemistry, and that there is a slow exchange of solvent molecules between them. Furthermore, we show that differences in wettability and dispersability between samples dispersed in water, ethanol, and cyclopentanone can be observed, along with changes to the surface chemistry of the interface. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  4. Multi-Component T2 Relaxation Studies of the Avian Egg

    PubMed Central

    Mitsouras, Dimitris; Mulkern, Robert V.; Maier, Stephan E.

    2015-01-01

    Purpose To investigate the tissue-like multiexponential T2 signal decays in avian eggs. Methods Transverse relaxation studies of raw, soft-boiled and hard-boiled eggs were performed at 3 Tesla using a 3D Carr-Purcell-Meiboom-Gill (CPMG) imaging sequence. Signal decays over a TE range of 11 to 354 ms were fitted assuming single- and multi-component signal decays with up to three separately decaying components. Fat saturation was used to facilitate spectral assignment of observed decay components. Results Egg white, yolk and the centrally located latebra all demonstrate nonmonoexponential T2 decays. Specifically, egg white exhibits two-component decays with intermediate and long T2 times. Meanwhile, yolk and latebra are generally best characterized with triexponential decays, with short, intermediate and very long T2 decay times. Fat saturation revealed that the intermediate component of yolk could be attributed to lipids. Cooking of the egg profoundly altered the decay curves. Conclusion Avian egg T2 decay curves cover a wide range of decay times. Observed T2 components in yolk and latebra as short as 10 ms, may prove valuable for testing clinical sequences designed to measure short T2 components, such as myelin-associated water in the brain. Thus we propose that the egg can be a versatile and widely available MR transverse relaxation phantom. PMID:26037128

  5. Active site dynamics in NADH oxidase from Thermus thermophilus studied by NMR spin relaxation.

    PubMed

    Miletti, Teresa; Farber, Patrick J; Mittermaier, Anthony

    2011-09-01

    We have characterized the backbone dynamics of NADH oxidase from Thermus thermophilus (NOX) using a recently-developed suite of NMR experiments designed to isolate exchange broadening, together with (15)N R (1), R (1ρ ), and {(1)H}-(15)N steady-state NOE relaxation measurements performed at 11.7 and 18.8 T. NOX is a 54 kDa homodimeric enzyme that belongs to a family of structurally homologous flavin reductases and nitroreductases with many potential biotechnology applications. Prior studies have suggested that flexibility is involved in the catalytic mechanism of the enzyme. The active site residue W47 was previously identified as being particularly important, as its level of solvent exposure correlates with enzyme activity, and it was observed to undergo "gating" motions in computer simulations. The NMR data are consistent with these findings. Signals from W47 are dynamically broadened beyond detection and several other residues in the active site have significant R ( ex ) contributions to transverse relaxation rates. In addition, the backbone of S193, whose side chain hydroxyl proton hydrogen bonds directly with the FMN cofactor, exhibits extensive mobility on the ns-ps timescale. We hypothesize that these motions may facilitate structural rearrangements of the active site that allow NOX to accept both FMN and FAD as cofactors.

  6. Exercise as migraine prophylaxis: A randomized study using relaxation and topiramate as controls

    PubMed Central

    Varkey, Emma; Cider, Åsa; Carlsson, Jane; Linde, Mattias

    2011-01-01

    Aim: Scientific evidence regarding exercise in migraine prophylaxis is required. Therefore this study aimed to evaluate the effects of exercise in migraine prevention. Methods: In a randomized, controlled trial of adults with migraine, exercising for 40 minutes three times a week was compared to relaxation according to a recorded programme or daily topiramate use, which was slowly increased to the individual’s highest tolerable dose (maximum 200 mg/day). The treatment period lasted for 3 months, and migraine status, quality of life, level of physical activity, and oxygen uptake were evaluated. The primary efficacy variable was the mean reduction of the frequency of migraine attacks during the final month of treatment compared with the baseline. Results: Ninety-one patients were randomized and included in the intention-to-treat analysis. The primary efficacy variable showed a mean reduction of 0.93 (95% confidence interval (CI) 0.31–1.54) attacks in the exercise group, 0.83 (95% CI 0.22–1.45) attacks in the relaxation group, and 0.97 (95% CI 0.36–1.58) attacks in the topiramate group. No significant difference was observed between the groups (p = 0.95). Conclusion: Exercise may be an option for the prophylactic treatment of migraine in patients who do not benefit from or do not want to take daily medication. PMID:21890526

  7. Spin relaxation studies of Li(+) ion dynamics in polymer gel electrolytes.

    PubMed

    Brinkkötter, M; Gouverneur, M; Sebastião, P J; Vaca Chávez, F; Schönhoff, M

    2017-03-08

    Two ternary polymer gel electrolyte systems are compared, containing either polyethylene oxide (PEO) or the poly-ionic liquid poly(diallyldimethylammonium) bis(trifluoromethyl sulfonyl)imide (PDADMA-TFSI). Both gel types are based on the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl sulfonyl)imide (P14TFSI) and LiTFSI. We study the influence of the polymers on the local lithium ion dynamics at different polymer concentrations using (7)Li spin-lattice relaxation data in dependence on frequency and temperature. In all cases the relaxation rates are well described by the Cole-Davidson motional model with Arrhenius dependence of the correlation time and a temperature dependent quadrupole coupling constant. For both polymers the correlation times are found to increase with polymer concentration. The activation energy of local motions slightly increases with increasing PEO concentration, and slightly decreases with increasing PDADMA-TFSI concentration. Thus the local Li(+) motion is reduced by the presence of either polymer; however, the reduction is less effective in the PDADMA(+) samples. We thus conclude that mechanical stabilization of a liquid electrolyte by a polymer can be achieved at a lower decrease of Li(+) motion when a cationic polymer is used instead of PEO.

  8. 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.

  9. Monte Carlo method for studies of spin relaxation in degenerate electron gas: Application to monolayer graphene

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

    Monte Carlo method allowing to account for the effect of Pauli Exclusion Principle in the case of spin polarized electron gas is demonstrated. Modeling requires calculation of electron states occupancy accounting for the direction of the spin of the scattered electron. As an example of application, calculations for the case of spin and energy relaxation of initially polarized electrons in monolayer graphene have been performed. Model includes D'yakonov-Perel' and Elliot-Yafet relaxation mechanisms. It is demonstrated that electron distribution function and energy relaxation follow the spin polarization relaxation and they are mainly governed by spin related scattering processes.

  10. Novel nuclear magnetic resonance techniques for studying biological molecules

    SciTech Connect

    Laws, David Douglas

    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 (Φ/Ψ) dihedral angles by comparing experimentally determined 13Ca, 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 α-helical and β-sheet conformers in the solid state, the aggregates formed from the PrP 89-143 mutants appear to be mostly β-sheet.

  11. 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.

  12. Study of charge-carrier relaxation in a disordered organic semiconductor by simulating impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Mesta, M.; Cottaar, J.; Coehoorn, R.; Bobbert, P. A.

    2014-05-01

    Impedance spectroscopy is a very sensitive probe of nonstationary charge transport governed by charge-carrier relaxation in devices of disordered organic semiconductors. We simulate impedance spectroscopy measurements of hole-only devices of a polyfluorene-based disordered organic semiconductor by solving a time-dependent three-dimensional master equation for the occupational probabilities of transport sites in the semiconductor. We focus on the capacitance-voltage characteristics at different frequencies. In order to obtain good agreement with the measured characteristics, we have to assume a lower strength of a Gaussian energy disorder than obtained from best fits to the stationary current density-voltage characteristics. This lower disorder strength is in agreement with dark-injection studies of nonstationary charge transport on the same devices. The results add to solving the puzzle of reconciling nonstationary with stationary charge-transport studies of disordered organic semiconductors.

  13. TEACHING NEUROMUSCULAR RELAXATION.

    ERIC Educational Resources Information Center

    NORRIS, JEANNE E.; STEINHAUS, ARTHUR H.

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

  14. Proton relaxation times in cancer diagnosis

    SciTech Connect

    Santhana Mariappan, S.V.; Subramanian, S.; Chandrakumar, N.; Rajalakshmi, K.R.; Sukumaran, S.S.

    1988-10-01

    Proton nuclear magnetic resonance relaxation parameters (T1, T2) were measured for over 100 malignant and normal tissue samples of various organs of the human body. The purpose of this study was to estimate the reliability of the NMR technique in discriminating normal from malignant tissues. Breast and cervix samples were analyzed by using the malignancy index concept and we were able to distinguish malignant and normal tissue in 17 out of 18 breast samples and 5 out of 7 cervix samples. Since the relaxation data of a normal control population of the other organs were not available, the data for these are reported without any further analysis. The distinction between carcinomas and sarcomas was also made by using the estimated relaxation parameters. Malignancy indices of breast tissue samples for linear least-squares and nonlinear two-parameter and three-parameter least-squares procedures were calculated and used to evaluate the relative efficiencies in discriminating malignant from normal tissues.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Matsuoka, T.; Koda, S.

    2007-08-01

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

  17. Diffusion, Structural Relaxation and Rheological Properties of a Simple Glass Forming Model: A Molecular Dynamics Study

    NASA Astrophysics Data System (ADS)

    Varnik, Fathollah

    2008-02-01

    Via large scale molecular dynamics simulations, we study diffusion in melts undergoing strong shear flow and its relation to the rheological response in a well established glass forming model system, namely the 80:20 binary Lennard-Jones system first introduced by Kob and Andersen [W. Kob and H.C. Andersen, PRL 73, 1376 (1994)]. In previous works [F. Varnik JCP 125, 164514 (2006) and F. Varnik and O. Henrich PRB 73, 174209 (2006)], the interplay between the dynamics of structural relaxation on the length scale of the average interparticle distance and the stress response of the model was studied. Here we focus on the large scale dynamics under homogeneous shear by evaluating the time dependence of the mean square displacements for temperatures ranging from the supercooled state to far below the mode coupling critical temperature of the model. Particularly long simulations are performed allowing an accurate determination of the diffusion constant. For low temperatures and at not too high shear rates, the mean square displacements exhibit the well known two step relaxation behavior with a long time diffusive motion along the spatial directions perpendicular to the flow. In the flow direction, on the other hand, a third regime follows the diffusive motion, where Taylor dispersion with the typical t3 time dependence clearly dominates the long time behavior of the particle displacements. At the lowest studied temperatures, the cross over from the diffusive regime to the regime where the contribution of Taylor dispersion becomes significant, occurs at length scales of the order of a particle diameter but is shifted towards progressively larger displacements as temperature increases.

  18. Kinetic studies of desensitization and resensitization of the relaxation response to beta-2 adrenoceptor agonists in isolated guinea pig trachea.

    PubMed

    Wachsman, D E; Kavaler, J P; Sugár, I P; Schachter, E N; Gonsiorek, W; Maayani, S

    1997-01-01

    Activation of beta-2 adrenoceptors (BAR) in smooth muscle preparations is associated with a rapid, reversible and incomplete receptor desensitization, resulting in a steady-state relaxation response to BAR agonists. Based on results from cell culture studies, we hypothesize that, in the isolated guinea pig trachea, this steady state is a result of a concurrent resensitization of desensitizing BAR. In tracheal segments maintained at mechanical tone (4-6 g), isoproterenol (ISO) and the partial BAR agonist salbutamol (SALB) elicited a monotonic, rapid (1-3 min) and reproducible relaxation response that could be maintained for up to 45 min and was completely reversed by propranolol. Similarly, tissues preconstricted with 0.1 microM carbachol (CARB) responded with a sustained relaxation response to ISO. In contrast, in tissues preconstricted with 0.3 to 10 microM CARB or with 75 mM KCl, the relaxation elicited by ISO was followed by a slow (20-30 min) and partial restoration of muscle tone ("fade"). The relaxation and fade were observed when CARB-constricted tissues were relaxed with SALB (0.2 or 10 microM) or 10 microM salmeterol. No response to SALB was observed when tissues were preconstricted with KCl. The fade met criteria for its classification as a homologous desensitization of the relaxation response at the BAR level. In desensitized washed tissues, a complete recovery of the original relaxation response could be detected within 60 min of drug removal. A propranolol- and ICI 118-551-sensitive steady state was achieved 30 to 35 min after the addition of BAR agonists to the isolated tissues. A three-compartment phenomenological kinetic model accurately described the observed data, defining one steady-state and three rate constants, describing relaxation (k1), desensitization (k2) and resensitization (k3). The values of k2 and k3 for the response to SALB and to salmeterol were significantly larger than those observed for ISO. In the presence of KCl, the values of k

  19. Nuclear quadrupole resonance studies of amorphous, orthorhombic, and rhombohedral arsenic

    SciTech Connect

    Jellison, G.E. Jr.; Petersen, G.L.; Taylor, P.C.

    1980-10-15

    Pulsed nuclear quadrupole resonance (NQR) experiments have been performed on three forms of elemental arsenic: amorphous (a), rhombohedral (rh), and orthorhombic (or). The temperature dependence of the spin-lattice relaxation time (T/sub 1/) provides evidence for the existence of disorder (tunneling) modes in a-As. It is found that the NQR line shape of a-As is highly asymmetric, and this asymmetry is attributed to a distribution of dihedral angles in a-As. The observed NQR frequencies indicate that the amount of bonding s admixture is different in each material (rh-As:3%, or-As:7%, a-As:10%). Simple calculations in comparison with x-ray results indicate that the bonding configurations in these three forms of arsenic do not necessarily correspond to maximum overlap of bonding orbitals on adjacent atoms.

  20. 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.

  1. 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.

  2. Use of a relaxation technique by mothers of children with autism: a case-series study.

    PubMed

    Gika, Danai M; Artemiadis, Artemios K; Alexopoulos, Evangelos C; Darviri, Christina; Chrousos, George P; Papanikolaou, Katerina

    2012-12-01

    Mothers of children with autism are subject to considerable stress by having to adjust to the disorder and to cope with practical and social issues. Evidence on the effects of relaxation training on stress of these mothers is scarce. The purpose of this pilot case-series study was to examine the role of a simple 6-week daily stress management technique on mothers of children with autism. Mothers' stress measurements and children's functionality were assessed using validated instruments. Participants were 11 mothers of children with autism seen consecutively in the autism clinic of a children's hospital. Statistically significant median reductions of perceived and parental stress were noted after the 6-week intervention. Median stress scores were lower by 37.1% and 33% from the baseline values of the perceived stress scale and parental stress index, respectively. Stress was not significantly correlated with children's functioning. Stress management seems to have benefits for mothers of children with autism.

  3. Microwave dielectric relaxation studies of hydrogen bonded polar binary mixtures of isobutanol and aniline

    NASA Astrophysics Data System (ADS)

    Vishwam, T.; Murthy, V. R. K.

    2013-03-01

    The molecular interaction between the polar systems of isobutanol and aniline 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 and B3LYP with 6-31G and 6-31G+ 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 isobutanol and aniline 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 permittivities (ɛE), Bruggeman parameters (fB) have also been determined for isobutanol and aniline and the results were correlated.

  4. 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.

  5. Study of relaxation kinetics in argon afterglow by the breakdown time delay measurements

    SciTech Connect

    Markovic, V.Lj.; Gocic, S.R.; Stamenkovic, S.N.; Petrovic, Z.Lj.

    2005-07-15

    In this paper the afterglow kinetics in argon is studied by the breakdown time delay measurements as a function of relaxation time t{sub d}({tau}) ('memory curve'). Measurements were carried out at the pressure of 1.33 mbar in a gas tube with gold-plated copper cathode and approximate and exact numerical models are developed to follow metastable and charged particle decay. It was found that the early afterglow kinetics is governed by the charged particle decay up to hundreds of milliseconds, extending from ambipolar to the free diffusion limit. Quenching processes reduce the effective lifetime of metastable states several orders of magnitude below that relevant for the time scale of the observations if realistic abundances and processes are included in the model. Nitrogen atoms originating from impurities and recombining on the cathode surface can determine the breakdown time delay down to that defined by the level of cosmic rays and natural radioactivity.

  6. Relaxation Biodynamics: Experimental Studies and Modeling of Biogeochemical Processes in Northern Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Panikov, N. S.; Pankratov, T.

    2001-12-01

    Relaxation phenomenon in physics and chemistry stands for delay between the application of an external stress to a system and its response. When an equilibrated nuclear, atomic or molecular system is subjected to an abrupt physical change (sudden rise in temperature or pressure), it takes time for the system to re-equilibrate under the new conditions. This period (relaxation time) can provide a powerful insight into mechanisms of chemical reaction. Our intention is to extend such approach to analysis of the complex biological phenomena related mainly to microbial growth and activity in the soil. We will show how this information can be used for better understanding the biogeochemical processes in northern terrestrial ecosystems such as aerobic and anaerobic decomposition of organic matter, gas (CO2 and CH4) emission to atmosphere, migration and transformation of biogenic elements, etc. The major source of experimental data is laboratory soil incubation under controlled environmental conditions with abrupt changes in one of the key parameters: temperature (including the water-to-ice phase transition), soil moisture, light (illumination of planted soil), supply of organic substrate and mineral nutrients. The state of biological component before and after abrupt changes was followed by continuous recording of gas (CO2, CH4) exchange rate and (in some special experiments), chemical analysis of the soil solution, and the characterization of soil community (microbial and plants biomass, species composition, change of life forms, etc.) The obtained dynamic data were fit to simulation models (sets of differential equations) describing the C- and energy flow through the studied microcosm systems. The comparison of predicted and observed relaxation dynamics allowed us to discard wrong assumptions on the nature of regulatory mechanisms involved in the functioning of the soil community. Finally, the conclusions derived from the lab experiments are projected to field

  7. Collisional cross-section of water molecules in vapour studied by means of 1H relaxation in NMR

    PubMed Central

    Mammoli, Daniele; Canet, Estel; Buratto, Roberto; Miéville, Pascal; Helm, Lothar; Bodenhausen, Geoffrey

    2016-01-01

    In gas phase, collisions that affect the rotational angular momentum lead to the return of the magnetization to its equilibrium (relaxation) in Nuclear Magnetic Resonance (NMR). To the best of our knowledge, the longitudinal relaxation rates R1 = 1/T1 of protons in H2O and HDO have never been measured in gas phase. We report R1 in gas phase in a field of 18.8 T, i.e., at a proton Larmor frequency ν0 = 800 MHz, at temperatures between 353 and 373 K and pressures between 9 and 101 kPa. By assuming that spin rotation is the dominant relaxation mechanism, we estimated the effective cross-section σJ for the transfer of angular momentum due to H2O-H2O and HDO-D2O collisions. Our results allow one to test theoretical predictions of the intermolecular potential of water in gas phase. PMID:28008913

  8. Collisional cross-section of water molecules in vapour studied by means of 1H relaxation in NMR

    NASA Astrophysics Data System (ADS)

    Mammoli, Daniele; Canet, Estel; Buratto, Roberto; Miéville, Pascal; Helm, Lothar; Bodenhausen, Geoffrey

    2016-12-01

    In gas phase, collisions that affect the rotational angular momentum lead to the return of the magnetization to its equilibrium (relaxation) in Nuclear Magnetic Resonance (NMR). To the best of our knowledge, the longitudinal relaxation rates R1 = 1/T1 of protons in H2O and HDO have never been measured in gas phase. We report R1 in gas phase in a field of 18.8 T, i.e., at a proton Larmor frequency ν0 = 800 MHz, at temperatures between 353 and 373 K and pressures between 9 and 101 kPa. By assuming that spin rotation is the dominant relaxation mechanism, we estimated the effective cross-section σJ for the transfer of angular momentum due to H2O-H2O and HDO-D2O collisions. Our results allow one to test theoretical predictions of the intermolecular potential of water in gas phase.

  9. Temperature and concentration-dependent relaxation of ferrofluids characterized with a high-Tc SQUID-based nuclear magnetic resonance spectrometer

    NASA Astrophysics Data System (ADS)

    Yang, Hong-Chang; Liu, Chieh-Wen; Liao, S. H.; Chen, Hsin-Hsien; Chen, M. J.; Chen, K. L.; Horng, Herng-Er; Yang, S. Y.; Wang, L. M.

    2012-05-01

    We investigated the relaxation of protons in magnetic fluids using a high-Tc SQUID magnetometer. It was found that the longitudinal relaxation rate, 1/T1, is slower than the transverse relaxation rate, 1/T2, for ferrofluids in the same field. This is due to the fact that the 1/T1 process involves returning the magnetization to the z-direction, which automatically involves the loss of magnetization in the x-y plane governed by the 1/T2 process. Additionally, 1/T1 and 1/T2 at high temperatures are slower than the corresponding relaxation rates at low temperatures, which is due to the enhanced Brownian motion of nanoparticles at high temperatures.

  10. Nonlinear Optical Studies of Resonant Systems

    DTIC Science & Technology

    1992-08-01

    hh1 Exciton . 2ps D-a " - 4ps b) EIIE 2 FPD from hhl Exciton -2 ps SPE from Stokes -4 ps /shifted resonance " -15 0 5 15 Reference Delay ( ps ) Figure 1...left and right axes. 4 S.T. Cundiff, H. Wang and D.G. Steel Picosecond Photon Echoes... 2 aSPE from 0 ps -_ __ hh1 Exciton . 2ps -2 CO ’- 4ps -b) ELE 2...methods which we have developed based on four - wave mixing as well as coherent transient techniques such as photon echoes. Accesion Fo’- -... NTIS Cn,7

  11. How Do You #relax When You’re #stressed? A Content Analysis and Infodemiology Study of Stress-Related Tweets

    PubMed Central

    Ritchart, Amanda; Perry, Nicholas; Chaparro, Juan D; Conway, Mike

    2017-01-01

    Background Stress is a contributing factor to many major health problems in the United States, such as heart disease, depression, and autoimmune diseases. Relaxation is often recommended in mental health treatment as a frontline strategy to reduce stress, thereby improving health conditions. Twitter is a microblog platform that allows users to post their own personal messages (tweets), including their expressions about feelings and actions related to stress and stress management (eg, relaxing). While Twitter is increasingly used as a source of data for understanding mental health from a population perspective, the specific issue of stress—as manifested on Twitter—has not yet been the focus of any systematic study. Objective The objective of our study was to understand how people express their feelings of stress and relaxation through Twitter messages. In addition, we aimed at investigating automated natural language processing methods to (1) classify stress versus nonstress and relaxation versus nonrelaxation tweets, and (2) identify first-hand experience—that is, who is the experiencer—in stress and relaxation tweets. Methods We first performed a qualitative content analysis of 1326 and 781 tweets containing the keywords “stress” and “relax,” respectively. We then investigated the use of machine learning algorithms—in particular naive Bayes and support vector machines—to automatically classify tweets as stress versus nonstress and relaxation versus nonrelaxation. Finally, we applied these classifiers to sample datasets drawn from 4 cities in the United States (Los Angeles, New York, San Diego, and San Francisco) obtained from Twitter’s streaming application programming interface, with the goal of evaluating the extent of any correlation between our automatic classification of tweets and results from public stress surveys. Results Content analysis showed that the most frequent topic of stress tweets was education, followed by work and social

  12. 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.

  13. Density-functional theory study of vibrational relaxation of CO stretching excitation on Si(100)

    NASA Astrophysics Data System (ADS)

    Sakong, Sung; Kratzer, Peter; Han, Xu; Laß, Kristian; Weingart, Oliver; Hasselbrink, Eckart

    2008-11-01

    A first-principles theory is presented for calculating the lifetime of adsorbate vibrations on semiconductor or insulator surfaces, where dissipation of the vibrational energy to substrate phonons is the dominant relaxation mechanism. As an example, we study the stretching vibration of CO/Si(100), where a lifetime of 2.3 ns has been measured recently [K. Laß, X. Han, and E. Hasselbrink, J. Chem. Phys. 123, 051102 (2005)]. Density-functional theory (DFT) calculations for the local modes of the adsorbate, including their anharmonic coupling, are combined with force field calculations for the substrate phonons. Using the DFT-Perdew-Burke-Ernzerhof functional, we have determined the most stable adsorption site for CO on top of the lower Si atom of the Si surface dimer, the local normal modes of CO, and the multidimensional potential energy surface for the CO vibrations. The anharmonic stretching frequency of adsorbed CO obtained in DFT-PBE is 5% lower than the experimental value, while the B3LYP functional reproduces the CO stretching frequency with only 1.4% error. The coupling between the anharmonic vibrational modes and the phonon continuum is evaluated within first-order perturbation theory, and transition rates for the CO vibrational relaxation are calculated using Fermi's golden rule. The lifetime of 0.5 ns obtained with DFT-PBE is in qualitative agreement with experiment, while using vibrational frequencies from the B3LYP functional gives a much too long lifetime as compared to experiment. We find that the numerical value of the lifetime is very sensitive to the harmonic frequencies used as input to the calculation of the transition rate. An empirical adjustment of these frequencies yields excellent agreement between our theory and experiment. From these calculations we conclude that the most probable microscopic decay channel of the CO stretching mode is into four lateral shift/bending quanta and one phonon.

  14. Atomic structure relaxation in nanocrystalline NiO studied by EXAFS spectroscopy: Role of nickel vacancies

    NASA Astrophysics Data System (ADS)

    Anspoks, A.; Kalinko, A.; Kalendarev, R.; Kuzmin, A.

    2012-11-01

    Nanocrystalline NiO samples have been studied using the Ni K-edge extended x-ray absorption fine structure (EXAFS) spectroscopy and recently developed modeling technique, combining classical molecular dynamics with ab initio multiple-scattering EXAFS calculations (MD-EXAFS). Conventional analysis of the EXAFS signals from the first two coordination shells of nickel revealed that (i) the second shell average distance R(Ni-Ni2) expands in nanocrystalline NiO compared to microcrystalline NiO, in agreement with overall unit cell volume expansion observed by x-ray diffraction; (ii) on the contrary, the first shell average distance R(Ni-O1) in nanocrystalline NiO shrinks compared to microcrystalline NiO; (iii) the thermal contribution into the mean-square relative displacement σ2 is close in both microcrystalline and nanocrystalline NiO and can be described by the Debye model; (iv) the static disorder is additionally present in nanocrystalline NiO in both the first Ni-O1 and second Ni-Ni2 shells due to nanocrystal structure relaxation. Within the MD-EXAFS method, the force-field potential models have been developed for nanosized NiO using as a criterion the agreement between the experimental and theoretical EXAFS spectra. The best solutions have been obtained for the 3D cubic-shaped nanoparticle models with nonzero Ni vacancy concentration Cvac: Cvac≈0.4-1.2% for NiO nanoparticles having the cube size of L≈3.6-4.2 nm and Cvac≈1.6-2.0% for NiO thin film composed of cubic nanograins with a size of L≈1.3-2.1 nm. Thus our results show that the Ni vacancies in nanosized NiO play important role in its atomic structure relaxation along with the size reduction effect.

  15. NUCLEAR MAGNETIC RELAXATION IN LIQUID METALS, ALLOYS, AND SALTS.

    DTIC Science & Technology

    NUCLEAR MAGNETIC RESONANCE, *ALKALI METAL ALLOYS, *LIQUID METALS, * SALTS , NUCLEAR MAGNETIC RESONANCE, NUCLEAR MAGNETIC RESONANCE, RELAXATION TIME... SODIUM , GALLIUM, SODIUM ALLOYS, THALLIUM, THALLIUM COMPOUNDS, MELTING, NUCLEAR SPINS, QUANTUM THEORY, OPERATORS(MATHEMATICS), BIBLIOGRAPHIES, INTEGRAL EQUATIONS, TEST EQUIPMENT, MATHEMATICAL ANALYSIS.

  16. 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.

  17. [Physical and mental reactions to forest relaxation video--studies on gender differences].

    PubMed

    Tsujiura, Yoshiko; Toyoda, Kumiko

    2013-01-01

    To explore gender differences in physical and mental relaxation in subjects who watched a forest relaxation video. The subjects were 12 males and 12 females in their 20's, with an average age of 21.67 ± 1.00 and 21.42 ± 1.56, respectively. They rested for 5 minutes, and then watched either a forest relaxation video or control video (grey screen, no sound). After the video session, they rested again for 5 minutes. Thus, the total experimental duration was 20 minutes. Before and after the video session, subjects completed visual analog scales (VAS) on mood and Profile of Mood States (POMS) questionnaires. Subjects also pointed out the most comfortable scenes on the video. In addition, we measured their heart rates. Analyses were based on the semantic differential (SD) technique. The heart rate of male subjects decreased just after watching the relaxation video (p<0.05-0.01), and the LnHF increased (p<0.05-0.01), indicating significant activation of the parasympathetic nervous system. Regarding VAS scales, the "refreshment" score increased in male subjects (p<0.01). In females, all three scores for "pleasantness", "calmness", and "refreshment" increased after watching the relaxation video (p<0.05-0.001). In addition, the "tension-anxiety" score of the POMS decreased after watching the video (p<0.05). Both male and female subjects felt relaxed after the forest relaxation video. Especially, heart rate changes suggested that male subjects experienced relaxation after the video, whereas female subjects experienced mental relaxation.

  18. 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.

  19. Monte Carlo study of non-diffusive relaxation of a transient thermal grating in thin membranes

    NASA Astrophysics Data System (ADS)

    Zeng, Lingping; Chiloyan, Vazrik; Huberman, Samuel; Maznev, Alex A.; Peraud, Jean-Philippe M.; Hadjiconstantinou, Nicolas G.; Nelson, Keith A.; Chen, Gang

    2016-02-01

    The impact of boundary scattering on non-diffusive thermal relaxation of a transient grating in thin membranes is rigorously analyzed using the multidimensional phonon Boltzmann equation. The gray Boltzmann simulation results indicate that approximating models derived from previously reported one-dimensional relaxation model and Fuchs-Sondheimer model fail to describe the thermal relaxation of membranes with thickness comparable with phonon mean free path. Effective thermal conductivities from spectral Boltzmann simulations free of any fitting parameters are shown to agree reasonably well with experimental results. These findings are important for improving our fundamental understanding of non-diffusive thermal transport in membranes and other nanostructures.

  20. 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.

  1. 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.

  2. Double-resonance 14N nuclear-magnetic-resonance probe for single-crystal studies

    NASA Astrophysics Data System (ADS)

    Naito, Akira; McDowell, Charles A.

    1989-06-01

    A double-resonance 14N nuclear-magnetic-resonance (NMR) probe suitable for single-crystal studies is described. The 14N and 1H sample coils are wound as coaxial solenoids and used instead of a doubly tuned single coil to tune over the required frequency range of the 14N channel. The choice of materials for the probe body and the wire size for the sample and impedance matching coils were chosen carefully to minimize spurious ringing phenomena, which is troublesome in probe designs for solid-state NMR. The probe has a very accurate goniometer since the resolution of 14N NMR signals is high.

  3. Photoluminescent and Slow Magnetic Relaxation Studies on Lanthanide(III)-2,5-pyrazinedicarboxylate Frameworks.

    PubMed

    Marinho, Maria Vanda; Reis, Daniella O; Oliveira, Willian X C; Marques, Lippy F; Stumpf, Humberto O; Déniz, Mariadel; Pasán, Jorge; Ruiz-Pérez, Catalina; Cano, Joan; Lloret, Francesc; Julve, Miguel

    2017-02-20

    In the series described in this work, the hydrothermal synthesis led to oxidation of the 5-methyl-pyrazinecarboxylate anion to the 2,5-pyrazinedicarboxylate dianion (2,5-pzdc) allowing the preparation of three-dimensional (3D) lanthanide(III) organic frameworks of formula {[Ln2(2,5-pzdc)3(H2O)4]·6H2O}n [Ln = Ce (1), Pr (2), Nd (3), and Eu (4)] and {[Er2(2,5-pzdc)3(H2O)4]·5H2O}n (5). Single-crystal X-ray diffraction on 1-5 reveals that they crystallize in the triclinic system, P1̅ space group with the series 1-4 being isostructural. The crystal structure of the five compounds are 3D with the lanthanide(III) ions linked through 2,5-pzdc(2-) dianions acting as two- and fourfold connectors, building a binodal 4,4-connected (4·6(4)8)(4(2)6(2)8(2))-mog network. The photophysical properties of the Nd(III) (3) and Eu(III) (4) complexes exhibit sensitized photoluminescence in the near-infrared and visible regions, respectively. The photoluminescence intensity and lifetime of 4 were very sensitive due to the luminescence quenching of the (5)D0 level by O-H oscillators of four water molecules in the first coordination sphere leading to a quantum efficiency of 11%. Variable-temperature magnetic susceptibility measurements for 1-5 reveal behaviors as expected for the ground terms of the magnetically isolated rare-earth ions [(2)F5/2, (2)H4, (4)I9/2, (7)F0, and (4)I15/2 for Ce(III), Pr(III), Nd(III), Eu(III), and Er(III), respectively] with MJ = 0 (2 and 4) and ±1/2 (1, 3, and 5). Q-band electron paramagnetic resonance measurements at low temperature corroborate these facts. Frequency-dependent alternating-current magnetic susceptibility signals under external direct-current fields in the range of 100-2500 G were observed for the Kramers ions of 1, 3, and 5, indicating slow magnetic relaxation (single-ion magnet) behavior. In these compounds, τ(-1) decreases with decreasing temperature at any magnetic field, but no Arrhenius law can simulate such a dependence in all the

  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. Resonance Raman studies of the purple membrane.

    PubMed

    Aton, B; Doukas, A G; Callender, R H; Becher, B; Ebrey, T G

    1977-06-28

    The individual resonance Raman spectra of the PM568 and M412 forms of light-adapted purple membrane from Halobacterium halobium have been measured using the newly developed flow technique. For comparison purposes, the Raman spectra of the model chromophores, all-trans- and 13-cis retinal n-butylamine, both as protonated and unprotonated Schiff bases, have also been obtained. In agreement with previous work, the Raman data indicate that the retinal chromophore is linked to the purple membrane protein via a protonated. Schiff base in the case of the PM568 and an unprotonated Schiff base for the M412 form. The basic mechanism for color regulation in both forms appears to be electron delocalization. The spectral features of the two forms are different from each other and different from the model compound spectra.

  6. Unraveling electron and hole relaxation dynamics in colloidal CdTe nanorods: a two-dimensional electronic spectroscopy study

    NASA Astrophysics Data System (ADS)

    Stoll, Tatjana; Branchi, Federico; Rehault, Julien; Kriegel, Ilka; Scotognella, Francesco; Tassone, Francesco; Cerullo, Giulio

    2017-02-01

    In this work we study the ultrafast exciton dynamics in CdTe nanorods by using two-dimensional electronic spectroscopy (2DES). By simultaneously exciting the lowest three excitonic transitions (i.e. S1, S2 and S3) we extract the electron and hole relaxation pathways, owing to the combined temporal and spectral resolution of 2DES. In particular, we directly observe hot hole relaxation from the second to the first exciton state in about 30 fs by excitation of the S2 transition. Additionally, we extract a direct charge relaxation to S1 by disentangling the overlapping bleach and excited state induced energy level shifts after excitation of S3.

  7. 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.].

  8. [Stabilizing splint versus relaxing appliances in the treatment of myofacial pain. Preliminary results of a prospective randomized study].

    PubMed

    Siegert, R; Gundlach, K K

    1989-11-01

    Both stabilizing splints and relaxing appliances have been recommended for the treatment of myofacial pain. It was the goal of the present study to compare the therapeutic effect of these two types of appliances. 26 patients with myofacial pain, whose symptoms were not overshadowed by arthropathy and in whom previous physiotherapy had failed to bring about sufficient pain relief, were divided into two prospectively randomized groups. They received either a stabilizing splint or a relaxing appliance. The therapeutic effect was assessed with the aid of the patients' subjective reports and the Helkimo indices. In spite of the small number of patients the statistical evaluation of the results showed stabilizing splints to be significantly (p less than 0.03) superior to relaxing appliances in the treatment of myofacial pain.

  9. Electrically detected magnetic resonance studies of phosphorus doped diamond

    NASA Astrophysics Data System (ADS)

    Graf, T.; Brandt, M. S.; Nebel, C. E.; Stutzmann, M.; Koizumi, S.

    2001-12-01

    Phosphorus doped n-type epitaxial diamond films have been studied by electron spin resonance (ESR) and electrically detected magnetic resonance (EDMR). At low electric field, the dominant defects influencing the electronic transport are carbon dangling bonds, while at higher fields the anisotropic spin resonance signal of a new phosphorus-related center with g⊥=2.0026, g||=2.0042, Aiso=17.6 G, and Aaniso=1.8 G is observed. These results indicate that room temperature conductivity in this film is dominated by hopping via phosphorus-related defect centers rather than via hydrogenic donor states of phosphorus atoms on substitutional sites.

  10. Use of cross-correlated NMR relaxation for the study of motional anisotropy of liquid crystals

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Rangeet; Kumar, Anil

    2003-04-01

    A method to measure the rotational diffusion coefficients of a liquid crystal based on the measurements of auto and cross-correlated relaxation is presented here. We report the measurements of cross-correlations between the relaxation processes originating from the chemical shift anisotropy (CSA) of 13C and its dipolar coupling with the attached proton, for various carbons in a liquid crystal. The spectral densities are expressed as a function of motional parameters, using extended Lipari-Szabo model-free approach. These motional parameters were extracted from the measured self-relaxation, cross-relaxation and the cross-correlation rates. The potential of this method is demonstrated by the determination of the rotational diffusion coefficients of N-4-methoxybenzylidene-4-butylaniline (MBBA) at 297 K undergoing magic angle sample spinning.

  11. Identification of the slower secondary relaxation's nature in maltose by means of theoretical and dielectric studies

    NASA Astrophysics Data System (ADS)

    Wlodarczyk, P.; Kaminski, K.; Adrjanowicz, K.; Wojnarowska, Z.; Czarnota, B.; Paluch, M.; Ziolo, J.; Pilch, J.

    2009-09-01

    Dielectric relaxation measurements on maltose were performed at ambient and increasing pressure. The loss spectra collected below glass transition of this disaccharide revealed presence of two well separated secondary relaxations. Activation energies determined for both modes are Ea=73 kJ/mol and 47 kJ/mol for the slower (β) and faster (γ) relaxation, respectively. From high pressure measurements activation volume ΔV =15.6 ml/mol for the slower secondary relaxation was estimated. Both quantities: activation energy and activation volume for α-process derived from dielectric data, were compared to those obtained from the conformational calculations with use of density functional theory (DFT). We found out satisfactory agreement between both quantities for the molecular motion related to the rotation of the two monosaccharide units around glycosidic linkage in this disaccharide.

  12. Coherent spectral hole burning in crystals with nonlinear relaxation

    SciTech Connect

    Shakhmuratov, R.N.; Khasanshin, R.A.

    1995-09-01

    Absorption of the probe field by crystals excited by a powerful pumping wave is considered. The case is studied when pumping affects the phase relaxation, slowing it down considerably for resonant ions. This is shown to result in the appearance of a rectangular hole in the broad spectral contour, which is typical for the population hole burning. 28 refs., 8 figs.

  13. A study of the main resonances outside the geostationary ring

    NASA Astrophysics Data System (ADS)

    Celletti, Alessandra; Galeş, Cătălin

    2015-08-01

    We investigate the dynamics of satellites and space debris in external resonances, namely in the region outside the geostationary ring. Precisely, we focus on the 1:2, 1:3, 2:3 resonances, which are located at about 66 931.4 km, 87 705.0 km, 55 250.7 km, respectively. Some of these resonances have been already exploited in space missions, like XMM-Newton and Integral. Our study is mainly based on a Hamiltonian approach, which allows us to get fast and reliable information on the dynamics in the resonant regions. Significative results are obtained even by considering just the effect of the geopotential in the Hamiltonian formulation. For objects (typically space debris) with high area-to-mass ratio the Hamiltonian includes also the effect of the solar radiation pressure. In addition, we perform a comparison with the numerical integration in Cartesian variables, including the geopotential, the gravitational attraction of Sun and Moon, and the solar radiation pressure. We implement some simple mathematical tools that allows us to get information on the terms which are dominant in the Fourier series expansion of the Hamiltonian around a given resonance, on the amplitude of the resonant islands and on the location of the equilibrium points. We also compute the Fast Lyapunov Indicators, which provide a cartography of the resonant regions, yielding the main dynamical features associated to the external resonances. We apply these techniques to analyze the 1:2, 1:3, 2:3 resonances; we consider also the case of objects with large area-to-mass ratio and we provide an application to the case studies given by XMM-Newton and Integral.

  14. Relaxivity of Gd-based contrast agents on X nuclei with long intrinsic relaxation times in aqueous solutions

    PubMed Central

    van Heeswijk, Ruud B.; Laus, Sabrina; Morgenthaler, Florence D.; Gruetter, Rolf

    2007-01-01

    The relaxivity of commercially available gadolinium-based contrast agents was studied for X-nuclei resonances with long intrinsic relaxation times ranging between 6 and several hundred seconds. Omniscan in pure 13C formic acid had a relaxivity of 2.9 mM-1 s-1, whereas its relaxivity on glutamate C1 and C5 in aqueous solution was ∼0.5 mM-1 s-1. Both relaxivities allow the preparation of solutions with a predetermined short T1 suggest that in vitro substantial sensitivity gains in their measurement can be achieved. 6Li has a long intrinsic relaxation time, on the order of several minutes, which was strongly affected by the contrast agents. Relaxivity ranged from ∼0.1 mM-1 s-1 for Omniscan to 0.3 for Magnevist, whereas the relaxivity of Gd-DOTP was at 11 mM-1 s-1 two orders of magnitude higher. Overall these experiments suggest that the presence of 0.1-10 μM contrast agents should be detectable, provided sufficient sensitivity is available, such as that afforded by hyperpolarization, recently introduced to in vivo imaging. PMID:17448617

  15. Method of Relaxation Moments for Studying Nonlinear Locally Nonequilibrium Processes of Transfer of Polymeric Systems

    NASA Astrophysics Data System (ADS)

    Popov, V. I.

    2015-01-01

    A method for simulating the processes of transfer of thermodynamic systems with polymeric microstructure is considered. The method is based on the classical locally equilibrium medium-state entropy concept expanded by the introduction of a structural tensor parameter whose evolution characterizes the nonlinear anisotropic relaxation properties of a thermodynamic system and the associated transfer phenomena. The dynamic, thermal, and mass transfer characteristics of macrotransfer are determined by corresponding integrals of relaxation moments.

  16. Photon-echo studies of collisional relaxation in weakly ionized noble-gas mixtures.

    PubMed

    Woodworth, M R

    1983-06-01

    Photon-echo relaxation rates are measured in weakly ionized plasmas of binary mixtures of noble gases, in which the photon echo generated on a transition in one noble-gas species is damped primarily by atoms of the second species. The special cases of pure krypton and xenon are extensions of previous work in pure helium, neon, and argon. With the exception of mixtures with helium as the perturber, measured relaxation rates are consistent with collisional line-broadening calculations.

  17. Transitions and relaxations in gamma-irradiated polypropylene studied by positron annihilation lifetime spectroscopy

    NASA Astrophysics Data System (ADS)

    Djourelov, N.; Suzuki, T.; Shantarovich, V. P.; Dobreva, T.; Ito, Y.

    2005-01-01

    The changes in the relaxation and transition temperatures in PP due to gamma irradiation in a vacuum were measured by means of positron annihilation lifetime spectroscopy. It was shown that the gamma and beta relaxation temperatures, as well as the melting point follow the changes in the crystallinity with the irradiation dose. For the glass transition temperatures and premelting point, after irradiation dose of 88 kGy, an inverse of the changes was observed.

  18. 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.

  19. Ultrasonic studies of relaxation phenomena in crude oils and their solutions

    NASA Astrophysics Data System (ADS)

    Bucek, M.; Marczak, W.

    2005-10-01

    Asphaltenes are operationally defined as non-volatile and polar components of crude oils soluble in toluene and insoluble in n-heptane. They gradually plug production wells and pipes because of flocculation and precipitation causing technical problems and financial losses. The flocculation is reversible. Absorption of ultrasound have been measured in three crude oils and their mixtures with toluene at frequencies from 2.4 to 80 MHz at T = 298.15 K. Processes with relaxation times in the interval from 10 to 100 ns were found in the crude oils. The relaxation may be due to aggregation of asphaltenes, that in favourable conditions may lead to flocculation. Relaxation processes in the solutions are faster, with relaxation times partly outside the measurement range. Most probably, the molecules of asphaltenes easier translate and rotate in the solutions than in viscous crude oils. If the proposed model is correct, one may expect relaxation times shorter in deasphaltenated oils. On the other hand, the relaxation may be ascribed to bending long hydrocarbon chains. That process is also rather slow.

  20. A numerical study of the South China Sea Warm Current during winter monsoon relaxation

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; Ding, Yang; Bao, Xianwen; Bi, Congcong; Li, Ruixiang; Zhang, Cunjie; Shen, Biao; Wan, Kai

    2017-06-01

    Using a Finite-Volume Community Ocean Model, we investigated the dynamic mechanism of the South China Sea Warm Current (SCSWC) in the northern South China Sea (NSCS) during winter monsoon relaxation. The model reproduces the mean surface circulation of the NSCS during winter, while model-simulated subtidal currents generally capture its current pattern. The model shows that the current over the continental shelf is generally southwestward, under a strong winter monsoon condition, but a northeastward counter-wind current usually develops between 50- and 100-m isobaths, when the monsoon relaxes. Model experiments, focusing on the wind relaxation process, show that sea level is elevated in the northwestern South China Sea (SCS), related to the persistent northeasterly monsoon. Following wind relaxation, a high sea level band builds up along the mid-shelf, and a northeastward current develops, having an obvious vertical barotropic structure. Momentum balance analysis indicates that an along-shelf pressure gradient provides the initial driving force for the SCSWC during the first few days following wind relaxation. The SCSWC subsequently reaches a steady quasi-geostrophic balance in the cross-shelf direction, mainly linked to sea level adjustment over the shelf. Lagrangian particle tracking experiments show that both the southwestward coastal current and slope current contribute to the northeastward movement of the SCSWC during winter monsoon relaxation.

  1. 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.

  2. 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.

  3. 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.

  4. Diffusion-relaxation correlation spectroscopic imaging: A multidimensional approach for probing microstructure.

    PubMed

    Kim, Daeun; Doyle, Eamon K; Wisnowski, Jessica L; Kim, Joong Hee; Haldar, Justin P

    2017-03-19

    To propose and evaluate a novel multidimensional approach for imaging subvoxel tissue compartments called Diffusion-Relaxation Correlation Spectroscopic Imaging. Multiexponential modeling of MR diffusion or relaxation data is commonly used to infer the many different microscopic tissue compartments that contribute signal to macroscopic MR imaging voxels. However, multiexponential estimation is known to be difficult and ill-posed. Observing that this ill-posedness is theoretically reduced in higher dimensions, diffusion-relaxation correlation spectroscopic imaging uses a novel multidimensional imaging experiment that jointly encodes diffusion and relaxation information, and then uses a novel constrained reconstruction technique to generate a multidimensional diffusion-relaxation correlation spectrum for every voxel. The peaks of the multidimensional spectrum are expected to correspond to the distinct tissue microenvironments that are present within each macroscopic imaging voxel. Using numerical simulations, experiment data from a custom-built phantom, and experiment data from a mouse model of traumatic spinal cord injury, diffusion-relaxation correlation spectroscopic imaging is demonstrated to provide substantially better multicompartment resolving power compared to conventional diffusion- and relaxation-based methods. The diffusion-relaxation correlation spectroscopic imaging approach provides powerful new capabilities for resolving the different components of multicompartment tissue models, and can be leveraged to significantly expand the insights provided by MRI in studies of tissue microstructure. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  5. A study of T₁ relaxation time as a measure of liver fibrosis and the influence of confounding histological factors.

    PubMed

    Hoad, Caroline L; Palaniyappan, Naaventhan; Kaye, Philip; Chernova, Yulia; James, Martin W; Costigan, Carolyn; Austin, Andrew; Marciani, Luca; Gowland, Penny A; Guha, Indra N; Francis, Susan T; Aithal, Guruprasad P

    2015-06-01

    Liver biopsy is the standard test for the assessment of fibrosis in liver tissue of patients with chronic liver disease. Recent studies have used a non-invasive measure of T1 relaxation time to estimate the degree of fibrosis in a single slice of the liver. Here, we extend this work to measure T1 of the whole liver and investigate the effects of additional histological factors such as steatosis, inflammation and iron accumulation on the relationship between liver T1 and fibrosis. We prospectively enrolled patients who had previously undergone liver biopsy to have MR scans. A non-breath-holding, fast scanning protocol was used to acquire MR relaxation time data (T1 and T2*), and blood serum was used to determine the enhanced liver fibrosis (ELF) score. Areas under the receiver operator curves (AUROCs) for T1 to detect advanced fibrosis and cirrhosis were derived in a training cohort and then validated in a second cohort. Combining the cohorts, the influence of various histology factors on liver T1 relaxation time was investigated. The AUROCs (95% confidence interval (CI)) for detecting advanced fibrosis (F ≥ 3) and cirrhosis (F = 4) for the training cohort were 0.81 (0.65-0.96) and 0.92 (0.81-1.0) respectively (p < 0.01). Inflammation and iron accumulation were shown to significantly alter T1 in opposing directions in the absence of advanced fibrosis; inflammation increasing T1 and iron decreasing T1. A decision tree model was developed to allow the assessment of early liver disease based on relaxation times and ELF, and to screen for the need for biopsy. T1 relaxation time increases with advanced fibrosis in liver patients, but is also influenced by iron accumulation and inflammation. Together with ELF, relaxation time measures provide a marker to stratify patients with suspected liver disease for biopsy.

  6. 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).

  7. Relaxation enhanced compressed sensing three-dimensional black-blood vessel wall MR imaging: Preliminary studies.

    PubMed

    Li, Bo; Li, Hao; Li, Jun; Zhang, Yuchen; Wang, Xiaoying; Zhang, Jue; Dong, Li; Fang, Jing

    2015-09-01

    In this study, we sought to investigate the feasibility of a new technique termed relaxation enhanced compressed sensing three-dimensional motion-sensitizing driven equilibrium prepared 3D rapid gradient echo sequence (RECS-3D MERGE). The RECS-3D MERGE sequence consisted of a 3D MERGE sequence for imaging, a period of delay time (TD) for relaxation enhancement, and a pseudo-centric phase encoding order used for under-sampling acquisition to maintain scan efficiency. Seven healthy volunteers and six patients with 40% to 75% carotid artery stenosis were recruited in this study. Healthy subjects underwent 3D MERGE, RECS-3D MERGE and two-dimensional (2D) T1-weighted double inversion recovery fast spin echo (T1W DIR-FSE) scans. The signal ratio (SR) values of 21 RECS-3D MERGE scans were compared in order to determine the optimal scan parameter set of acceleration factor (AF) and delay time (TD) for RECS-3D MERGE sequence. Patients then underwent 3D MERGE, RECS-3D MERGE using the aforementioned optimal scan parameter set and 2D T1W DIR-FSE scans. Two radiologists, blinded to the imaging technique, qualitatively graded each image on a six-point ordinal scale. The highest value of SR occurred with the scan parameter set of 3-fold AF and 800ms TD. Compared to 3D MERGE, RECS-3D MERGE with the parameter set significantly improved the image quality for both healthy subjects and patients experiments, while the scan efficiency was not sacrificed. And no significant differences were observed in the subjective scores of RECS-3D MERGE and 2D T1W DIR-FSE image qualities. RECS-3D MERGE technique achieved significant improvement in black-blood image quality compared with 3D MERGE. And the image quality of this 3D rapid carotid black-blood imaging technique is comparable to 2D T1W DIR-FSE while it has much higher scan efficiency. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. Rapid Parametric Mapping of the Longitudinal Relaxation Time T1 Using Two-Dimensional Variable Flip Angle Magnetic Resonance Imaging at 1.5 Tesla, 3 Tesla, and 7 Tesla

    PubMed Central

    Dieringer, Matthias A.; Deimling, Michael; Santoro, Davide; Wuerfel, Jens; Madai, Vince I.; Sobesky, Jan; von Knobelsdorff-Brenkenhoff, Florian; Schulz-Menger, Jeanette; Niendorf, Thoralf

    2014-01-01

    Introduction Visual but subjective reading of longitudinal relaxation time (T1) weighted magnetic resonance images is commonly used for the detection of brain pathologies. For this non-quantitative measure, diagnostic quality depends on hardware configuration, imaging parameters, radio frequency transmission field (B1+) uniformity, as well as observer experience. Parametric quantification of the tissue T1 relaxation parameter offsets the propensity for these effects, but is typically time consuming. For this reason, this study examines the feasibility of rapid 2D T1 quantification using a variable flip angles (VFA) approach at magnetic field strengths of 1.5 Tesla, 3 Tesla, and 7 Tesla. These efforts include validation in phantom experiments and application for brain T1 mapping. Methods T1 quantification included simulations of the Bloch equations to correct for slice profile imperfections, and a correction for B1+. Fast gradient echo acquisitions were conducted using three adjusted flip angles for the proposed T1 quantification approach that was benchmarked against slice profile uncorrected 2D VFA and an inversion-recovery spin-echo based reference method. Brain T1 mapping was performed in six healthy subjects, one multiple sclerosis patient, and one stroke patient. Results Phantom experiments showed a mean T1 estimation error of (-63±1.5)% for slice profile uncorrected 2D VFA and (0.2±1.4)% for the proposed approach compared to the reference method. Scan time for single slice T1 mapping including B1+ mapping could be reduced to 5 seconds using an in-plane resolution of (2×2) mm2, which equals a scan time reduction of more than 99% compared to the reference method. Conclusion Our results demonstrate that rapid 2D T1 quantification using a variable flip angle approach is feasible at 1.5T/3T/7T. It represents a valuable alternative for rapid T1 mapping due to the gain in speed versus conventional approaches. This progress may serve to enhance the capabilities of

  9. Rapid parametric mapping of the longitudinal relaxation time T1 using two-dimensional variable flip angle magnetic resonance imaging at 1.5 Tesla, 3 Tesla, and 7 Tesla.

    PubMed

    Dieringer, Matthias A; Deimling, Michael; Santoro, Davide; Wuerfel, Jens; Madai, Vince I; Sobesky, Jan; von Knobelsdorff-Brenkenhoff, Florian; Schulz-Menger, Jeanette; Niendorf, Thoralf

    2014-01-01

    Visual but subjective reading of longitudinal relaxation time (T1) weighted magnetic resonance images is commonly used for the detection of brain pathologies. For this non-quantitative measure, diagnostic quality depends on hardware configuration, imaging parameters, radio frequency transmission field (B1+) uniformity, as well as observer experience. Parametric quantification of the tissue T1 relaxation parameter offsets the propensity for these effects, but is typically time consuming. For this reason, this study examines the feasibility of rapid 2D T1 quantification using a variable flip angles (VFA) approach at magnetic field strengths of 1.5 Tesla, 3 Tesla, and 7 Tesla. These efforts include validation in phantom experiments and application for brain T1 mapping. T1 quantification included simulations of the Bloch equations to correct for slice profile imperfections, and a correction for B1+. Fast gradient echo acquisitions were conducted using three adjusted flip angles for the proposed T1 quantification approach that was benchmarked against slice profile uncorrected 2D VFA and an inversion-recovery spin-echo based reference method. Brain T1 mapping was performed in six healthy subjects, one multiple sclerosis patient, and one stroke patient. Phantom experiments showed a mean T1 estimation error of (-63±1.5)% for slice profile uncorrected 2D VFA and (0.2±1.4)% for the proposed approach compared to the reference method. Scan time for single slice T1 mapping including B1+ mapping could be reduced to 5 seconds using an in-plane resolution of (2×2) mm2, which equals a scan time reduction of more than 99% compared to the reference method. Our results demonstrate that rapid 2D T1 quantification using a variable flip angle approach is feasible at 1.5T/3T/7T. It represents a valuable alternative for rapid T1 mapping due to the gain in speed versus conventional approaches. This progress may serve to enhance the capabilities of parametric MR based lesion detection and

  10. Anisotropic Rotational Diffusion Studied by Nuclear Spin Relaxation and Molecular Dynamics Simulation: An Undergraduate Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Fuson, Michael M.

    2017-01-01

    Laboratories studying the anisotropic rotational diffusion of bromobenzene using nuclear spin relaxation and molecular dynamics simulations are described. For many undergraduates, visualizing molecular motion is challenging. Undergraduates rarely encounter laboratories that directly assess molecular motion, and so the concept remains an…

  11. Ferromagnetic resonance studies of lunar core stratigraphy

    NASA Technical Reports Server (NTRS)

    Housley, R. M.; Cirlin, E. H.; Goldberg, I. B.; Crowe, H.

    1976-01-01

    We first review the evidence which links the characteristic ferromagnetic resonance observed in lunar fines samples with agglutinatic glass produced primarily by micrometeorite impacts and present new results on Apollo 15, 16, and 17 breccias which support this link by showing that only regolith breccias contribute significantly to the characteristic FMR intensity. We then provide a calibration of the amount of Fe metal in the form of uniformly magnetized spheres required to give our observed FMR intensities and discuss the theoretical magnetic behavior to be expected of Fe spheres as a function of size. Finally, we present FMR results on samples from every 5 mm interval in the core segments 60003, 60009, and 70009. These results lead us to suggest: (1) that secondary mixing may generally be extensive during regolith deposition so that buried regolith surfaces are hard to recognize or define; and (2) that local grinding of rocks and pebbles during deposition may lead to short scale fluctuations in grain size, composition, and apparent exposure age of samples.

  12. Activated mechanisms in proteins: a multiple-temperature activation-relaxation technique study

    NASA Astrophysics Data System (ADS)

    Malek, Rachid; Mousseau, Normand; Derreumaux, Philippe

    2001-03-01

    The low-temperature dynamics of proteins is controlled by a complex activated dynamics taking place over long time-scales compared with the period of thermal oscillations. In view of the range of relevant time scales, the numerical study of these processes remains a challenge and numerous methods have been introduced to address this problem. We introduce here a mixture of two algorithms, the activation-relaxation technique (ART)^1,2 coupled with the parallel tempering method, and use it to study the structure of the energy landscape around the native state of a 38-residue polypeptide. While ART samples rapidly the local energy landscape, the parallel tempering, which sets up exchanges of configuration between simultaneous runs at multiple temperatures, generates a very efficient sampling of energy basins separated by high barriers^(3). Results show the nature of the barriers and local minima surrounding the native state of this 38-residue peptide, modeled with off-lattice OPEP-like interactions^4. (1) G.T. Barkema and N. Mousseau, PRL 77, 4358 (1996) (2) N. Mousseau and G.T. Barkema, PRE 57, 2419 (1998) (3) E. Marinari and G. Parisi, Europhys. Lett., 19 (6), 451 (1992) (4) Ph. Derreumaux, J. Chem. Phys. 111, 2301 (1999); PRB 85, 206 (2000)

  13. 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.

  14. Aromatherapy massage seems to enhance relaxation in children with burns: an observational pilot study.

    PubMed

    O'Flaherty, Linda-Anne; van Dijk, Monique; Albertyn, Rene; Millar, Alastair; Rode, Heinz

    2012-09-01

    This observational pilot study investigated effects of aromatherapy massage in paediatric burn patients. The setting was a 17 beds level I burn unit in Cape Town, South Africa. Between January and October 2009 heart rates and respiratory rates of patients who underwent aromatherapy massage sessions were read before and after the sessions. Primary outcomes were decline in heart rates and respiratory rates, a sign of relaxation. Behavioural responses (sleep/awake state, facial expression, body posture) were documented as secondary outcomes. A convenience sample of 71 paediatric burn patients (median age 3 years) underwent a total of 126 massage sessions. Mean heart rate decreased significantly from 118 (SD 20) to 109 (SD 21), t=9.8, p<0.001. Mean respiratory rate decreased significantly from 34 (SD 8) to 30 (SD 8), t=10.2, p<0.001. Most massage sessions (92.8%) elicited positive behaviour to the massage, e.g. the child fell asleep, calmed or asked to continue. Nine patients (7.2%) with a median age of 15 months who underwent a single massage session did not show positive behaviour but cried, wriggled or were distressed. Aromatherapy massage seems to be a helpful nonpharmacological approach to reduce hospitalized paediatric burn patients' distress. Future studies with better research designs and validated outcome measures should confirm our findings. Copyright © 2012 Elsevier Ltd and ISBI. All rights reserved.

  15. 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.

  16. 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.

  17. Nuclear Magnetic Resonance Studies of the 122 Iron-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Dioguardi, Adam Paul

    Extensive 75As nuclear magnetic resonance (NMR) studies were conducted on a variety of 122 iron-based superconductors. NMR frequency swept spectra and the spin-lattice relaxation rate (T 1-1) were measured in CaFe2As2 as a function of temperature. The temperature dependence of the internal hyperfine field was extracted from the spectra, and T1 -1 exhibits an anomalous peak attributed to the glassy freezing of domain walls associated with filamentary superconductivity. The field dependence of T1-1 and subsequent bulk resistivity and magnetization measurements also show signatures of filamentary superconductivity nucleated at antiphase domain walls. Systematic doping-dependent NMR studies were also carried out on Ni- and Co-doped BaFe2As2. In the Ni-doped variant, local magnetic inhomogeneities were observed via field swept NMR spectral analyses, and the doping dependence of the Neel temperature TN was confirmed by fits to (T 1T)-1(T). Spectral wipeout and stretched exponential relaxation behavior in the Co-doped variant reveal inhomogeneous behavior and the emergence of a cluster spin glass state. The NMR measurements bring into question the details of the phase transition from coexisting antiferromagnetism and superconductivity to pure superconductivity.

  18. Shock tube study of dissociation and relaxation in 1,1-difluoroethane and vinyl fluoride.

    PubMed

    Xu, Hui; Kiefer, John H; Sivaramakrishnan, Raghu; Giri, Binod R; Tranter, Robert S

    2007-08-21

    This paper reports measurements of the thermal dissociation of 1,1-difluoroethane in the shock tube. The experiments employ laser-schlieren measurements of rate for the dominant HF elimination using 10% 1,1-difluoroethane in Kr over 1500-2000 K and 43 < P < 424 torr. The vinyl fluoride product of this process then dissociates affecting the late observations. We thus include a laser schlieren study (1717-2332 K, 75 < P < 482 torr in 10 and 4% vinyl fluoride in Kr) of this dissociation. This latter work also includes a set of experiments using shock-tube time-of-flight mass spectrometry (4% vinyl fluoride in neon, 1500-1980 K, 500 < P < 1300 torr). These time-of-flight experiments confirm the theoretical expectation that the only reaction in vinyl fluoride is HF elimination. The dissociation experiments are augmented by laser schlieren measurements of vibrational relaxation (1-20% C(2)H(3)F in Kr, 415-1975 K, 5 < P < 50 torr, and 2 and 5% C(2)H(4)F(2) in Kr, 700-1350 K, 6 < P < 22 torr). These experiments exhibit very rapid relaxation, and incubation delays should be negligible in dissociation. An RRKM model of dissociation in 1,1-difluoroethane based on a G3B3 calculation of barrier and other properties fits the experiments but requires a very large DeltaE(down) of 1600 cm(-1), similar to that found in a previous examination of 1,1,1-trifluoroethane. Dissociation of vinyl fluoride is complicated by the presence of two parallel HF eliminations, both three-center and four-center. Structure calculations find nearly equal barriers for these, and TST calculations show almost identical k(infinity). An RRKM fit to the observed falloff again requires an unusually large DeltaE(down) and the experiments actually support a slightly reduced barrier. These large energy-transfer parameters now seem routine in these large fluorinated species. It is perhaps a surprising result for which there is as yet no explanation.

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

    SciTech Connect

    Hou, Yumin

    2013-12-15