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Sample records for 1h spin-lattice relaxation

  1. /sup 1/H and /sup 13/C spin-lattice relaxation in gaseous benzene

    SciTech Connect

    Folkendt, M.M.; Weiss-Lopez, B.E.; True, N.S.

    1988-08-25

    The nuclear spin-lattice relaxation time, T/sub 1/, measured for benzene protons at densities between 0.81 and 54.4 mol/m/sup 3/ (15 and 980 Torr) at 381 K exhibits a characteristic nonlinear density dependence. Analysis of the density-dependent T/sub 1/ data yields a spin-rotation coupling constant, C/sub eff/, of /vert bar/182.6 (0.4)/vert bar/ Hz and an angular momentum reorientation cross section, sigma, of 131 (1) /Angstrom//sup 2/. The /sup 13/C spin-lattice relaxation time of singly labeled /sup 13/C benzene is a linear function of density over the density range 1.07-75.12 mol/m/sup 3/ (20-1330 Torr). /sup 13/C T/sub 1/ values are shorter than /sup 1/H T/sub 1/ values by a factor of ca. 100 at comparable densities. The nuclear Overhauser enhancement factor, /eta/, is 0.0 /plus minus/ 0.02 at densities between 11 and 85.3 mol/m/sup 3/ (200 and 1500 Torr), demonstrating that dipole-dipole relaxation is relatively inefficient in this region. The spin-rotation coupling constant, C/sub eff/, for /sup 13/C nuclei in benzene is estimated to be /vert bar/1602 (68)/vert bar/ Hz.

  2. Miscibility of nifedipine and hydrophilic polymers as measured by (1)H-NMR spin-lattice relaxation.

    PubMed

    Aso, Yukio; Yoshioka, Sumie; Miyazaki, Tamaki; Kawanishi, Tohru; Tanaka, Kazuyuki; Kitamura, Satoshi; Takakura, Asako; Hayashi, Takashi; Muranushi, Noriyuki

    2007-08-01

    The miscibility of a drug with excipients in solid dispersions is considered to be one of the most important factors for preparation of stable amorphous solid dispersions. The purpose of the present study was to elucidate the feasibility of (1)H-NMR spin-lattice relaxation measurements to assess the miscibility of a drug with excipients. Solid dispersions of nifedipine with the hydrophilic polymers poly(vinylpyrrolidone) (PVP), hydroxypropylmethylcellulose (HPMC) and alpha,beta-poly(N-5-hydroxypentyl)-L-aspartamide (PHPA) with various weight ratios were prepared by spray drying, and the spin-lattice relaxation decay of the solid dispersions in a laboratory frame (T(1) decay) and in a rotating frame (T(1rho) decay) were measured. T(1rho) decay of nifedipine-PVP solid dispersions (3 : 7, 5 : 5 and 7 : 3) was describable with a mono-exponential equation, whereas T(1rho) decay of nifedipine-PHPA solid dispersions (3 : 7, 4 : 6 and 5 : 5) was describable with a bi-exponential equation. Because a mono-exponential T(1rho) decay indicates that the domain sizes of nifedipine and polymer in solid dispersion are less than several nm, it is speculated that nifedipine is miscible with PVP but not miscible with PHPA. All the nifedipine-PVP solid dispersions studied showed a single glass transition temperature (T(g)), whereas two glass transitions were observed for the nifedipine-PHPA solid dispersion (3 : 7), thus supporting the above speculation. For nifedipine-HPMC solid dispersions (3 : 7 and 5 : 5), the miscibility of nifedipine and HPMC could not be determined by DSC measurements due to the lack of obviously evident T(g). In contrast, (1)H-NMR spin-lattice relaxation measurements showed that nifedipine and HPMC are miscible, since T(1rho) decay of the solid dispersions (3 : 7, 5 : 5 and 7 : 3) was describable with a mono-exponential equation. These results indicate that (1)H-NMR spin-lattice relaxation measurements are useful for assessing the miscibility of a drug and an

  3. ESR lineshape and 1H spin-lattice relaxation dispersion in propylene glycol solutions of nitroxide radicals - Joint analysis

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Hoffmann, S. K.; Goslar, J.; Lijewski, S.; Kubica-Misztal, A.; Korpała, A.; Oglodek, I.; Kowalewski, J.; Rössler, E. A.; Moscicki, J.

    2013-12-01

    Electron Spin Resonance (ESR) spectroscopy and Nuclear Magnetic Relaxation Dispersion (NMRD) experiments are reported for propylene glycol solutions of the nitroxide radical: 4-oxo-TEMPO-d16 containing 15N and 14N isotopes. The NMRD experiments refer to 1H spin-lattice relaxation measurements in a broad frequency range (10 kHz-20 MHz). A joint analysis of the ESR and NMRD data is performed. The ESR lineshapes give access to the nitrogen hyperfine tensor components and the rotational correlation time of the paramagnetic molecule. The NMRD data are interpreted in terms of the theory of paramagnetic relaxation enhancement in solutions of nitroxide radicals, recently presented by Kruk et al. [J. Chem. Phys. 138, 124506 (2013)]. The theory includes the effect of the electron spin relaxation on the 1H relaxation of the solvent. The 1H relaxation is caused by dipole-dipole interactions between the electron spin of the radical and the proton spins of the solvent molecules. These interactions are modulated by three dynamic processes: relative translational dynamics of the involved molecules, molecular rotation, and electron spin relaxation. The sensitivity to rotation originates from the non-central positions of the interacting spin in the molecules. The electronic relaxation is assumed to stem from the electron spin-nitrogen spin hyperfine coupling, modulated by rotation of the radical molecule. For the interpretation of the NMRD data, we use the nitrogen hyperfine coupling tensor obtained from ESR and fit the other relevant parameters. The consistency of the unified analysis of ESR and NMRD, evaluated by the agreement between the rotational correlation times obtained from ESR and NMRD, respectively, and the agreement of the translation diffusion coefficients with literature values obtained for pure propylene glycol, is demonstrated to be satisfactory.

  4. 1H and 2H NMR spin-lattice relaxation probing water: PEG molecular dynamics in solution.

    PubMed

    Clop, Eduardo M; Perillo, María A; Chattah, Ana K

    2012-10-04

    Nuclear magnetic resonance spin-lattice relaxation times (T(1)) measurements were performed in aqueous solutions of poly(ethylene glycol) (PEG) of 6000 Da molecular mass to study the dynamical relation between PEG and water molecules at different solute concentrations. (1)H-T(1) experiments were carried on at a low magnetic field in the time domain (20 MHz) and at a high field (400 MHz) to obtain spectral resolution. Two contributing components were identified in each proton system, PEG and water, presenting values of T(1) with very different orders of magnitude. The approximate matching between the shorter (1)H-T(1) values associated with water and PEG has lead us to conclude that there exists a network of interactions (hydrogen bonds) between the solute and the solvent, which results in the presence of an ordered and dehydrated structure of PEG folded or self-assembled in equilibrium with a more flexible monomer structure. Dynamic light scattering results were consistent with the formation of PEG aggregates, showing a mean size between 40 and 100 nm.

  5. 1H-19F spin-lattice relaxation spectroscopy: proton tunnelling in the hydrogen bond studied by field-cycling NMR.

    PubMed

    Noble, D L; Aibout, A; Horsewill, A J

    2009-12-01

    Proton tunnelling in the hydrogen bonds of two fluorine substituted benzoic acid dimers has been investigated using field-cycling NMR relaxometry. The close proximity of the (19)F nuclei to the hydrogen bond protons introduces heteronuclear (19)F-(1)H dipolar interactions into the spin-lattice relaxation processes. This renders the (1)H magnetisation-recovery biexponential and introduces multiple spectral density components into the relaxation matrix characterised by frequencies that are sums and differences of the (19)F and (1)H Larmor frequencies. Using field-cycling NMR pulse sequences that measure the spin-lattice relaxation and cross-relaxation rates we demonstrate how some of these multiple spectral density components can be separately resolved. This leads to an accurate determination of the correlation times that characterise the proton tunnelling motion. A broad spectrum of relaxation behaviour is illustrated and explored in the chosen samples and the investigation is used to explore the theory and practise of field-cycling NMR relaxometry in cases where heteronuclear interactions are significant.

  6. ESR lineshape and {sup 1}H spin-lattice relaxation dispersion in propylene glycol solutions of nitroxide radicals – Joint analysis

    SciTech Connect

    Kruk, D.; Hoffmann, S. K.; Goslar, J.; Lijewski, S.; Kubica-Misztal, A.; Korpała, A.; Oglodek, I.; Moscicki, J.; Kowalewski, J.; Rössler, E. A.

    2013-12-28

    Electron Spin Resonance (ESR) spectroscopy and Nuclear Magnetic Relaxation Dispersion (NMRD) experiments are reported for propylene glycol solutions of the nitroxide radical: 4-oxo-TEMPO-d{sub 16} containing {sup 15}N and {sup 14}N isotopes. The NMRD experiments refer to {sup 1}H spin-lattice relaxation measurements in a broad frequency range (10 kHz–20 MHz). A joint analysis of the ESR and NMRD data is performed. The ESR lineshapes give access to the nitrogen hyperfine tensor components and the rotational correlation time of the paramagnetic molecule. The NMRD data are interpreted in terms of the theory of paramagnetic relaxation enhancement in solutions of nitroxide radicals, recently presented by Kruk et al. [J. Chem. Phys. 138, 124506 (2013)]. The theory includes the effect of the electron spin relaxation on the {sup 1}H relaxation of the solvent. The {sup 1}H relaxation is caused by dipole-dipole interactions between the electron spin of the radical and the proton spins of the solvent molecules. These interactions are modulated by three dynamic processes: relative translational dynamics of the involved molecules, molecular rotation, and electron spin relaxation. The sensitivity to rotation originates from the non-central positions of the interacting spin in the molecules. The electronic relaxation is assumed to stem from the electron spin–nitrogen spin hyperfine coupling, modulated by rotation of the radical molecule. For the interpretation of the NMRD data, we use the nitrogen hyperfine coupling tensor obtained from ESR and fit the other relevant parameters. The consistency of the unified analysis of ESR and NMRD, evaluated by the agreement between the rotational correlation times obtained from ESR and NMRD, respectively, and the agreement of the translation diffusion coefficients with literature values obtained for pure propylene glycol, is demonstrated to be satisfactory.

  7. Inhomogeneous 1H NMR spin-lattice relaxation in the organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br

    NASA Astrophysics Data System (ADS)

    Gezo, Joseph Christopher

    The two-dimensional superconductors based on the organic molecule "ET" have been an active area of research since their discovery over two decades ago. The member of this family with the highest critical temperature, kappa-(ET)2Cu[N(CN)2]Br ( Tc=11.7 K), has seen renewed interest since the observation of an anomalous Nernst signal by Nam et al in 2007 [51]. A similar effect was seen earlier by Ong's group in some of the high-temperature cuprate superconductors by [78,84]. This is interpreted to be evidence of a picture of superconductivity in which the resistive transition is driven by thermal fluctuations in the phase of the superconducting order parameter. Below Tc, these fluctuations take the form of bound vortex-antivortex pairs that have no long-range effect on the phase. At Tc, they undergo a Kosterlitz-Thouless unbinding transition; the unbound vortices destroy long-range phase coherence. Previously reported proton NMR measurements on this material have shown a high sensitivity to vortex motion, but reported no interesting behavior above the phase transition [15,25,42]. In this thesis, we revisit the 1H NMR properties of kappa-(ET)2Cu[N(CN)2]Br, paying specific attention to the spin-lattice relaxation, to look for some fingerprint of the phenomenon observed by Nam et al.

  8. Molecular mobility of lyophilized poly(vinylpyrrolidone) and methylcellulose as determined by the laboratory and rotating frame spin-lattice relaxation times of 1H and 13C.

    PubMed

    Yoshioka, Sumie; Aso, Yukio; Kojima, Shigeo

    2003-11-01

    Laboratory- and rotating- frame spin-lattice relaxation times (T(1) and T(1rho)) of (1)H and (13)C in lyophilized poly(vinylpyrrolidone) (PVP) and methylcellulose (MC) are determined to examine feasibility of using T(1) and T(1rho) as a measure of molecular motions on large time scales related to the storage stability of lyophilized formulations. The T(1rho) of proton and carbon was found to reflect the mobility of PVP and MC backbones, indicating that it is useful as a measure of large-time-scale molecular motions. In contrast to the T(1rho), the T(1) of proton measured in the same temperature range reflected the mobility of PVP and MC side chains. The T(1) of proton may be useful as a measure of local molecular motions on a smaller-time-scale, although the measurement is interfered by moisture under some conditions. The temperature dependence of T(1) and T(1rho) indicated that methylene in the MC molecule had much higher mobility than that in the dextran molecule, also indicated that methylene in the PVP side chain had a higher mobility than that in the MC side chain.

  9. Interaction between reduced glutathione and PEO-PPO-PEO copolymers in aqueous solutions: studied by 1H NMR and spin-lattice relaxation.

    PubMed

    Jia, Lianwei; Guo, Chen; Yang, Liangrong; Xiang, Junfeng; Tang, Yalin; Liu, Huizhou

    2011-03-17

    In order to investigate the effect of PEO-PPO-PEO copolymers on the glutathione (GSH)/glutathione-S-transferase (GST) detoxification system, interaction between the copolymers and GSH is studied by NMR measurements. Selective rotating-frame nuclear Overhauser effect (ROE) experiment confirms that glutamyl (Glu) α-H of GSH has spatial contact with EO methylene protons. Spin-lattice relaxation times of GSH Glu α-H show a decrease when PEO-PPO-PEO copolymers are added, and the decrease is greater with copolymers possessing more EO units. Other protons of GSH show little change in the presence of the copolymers. The addition of GSH promotes the dehydration of PEO-PPO-PEO copolymers. This results from the breaking of hydrogen bonds between water and the polymers and the forming of hydrogen bonds between Glu α-carboxylate protons and oxygen atoms of EO units. The dissociation constant between GSH and P85 copolymer is determined by spin-lattice relaxation measurements, which shows the binding is of low affinity and the two molecules are in fast dissociation kinetics. This study suggests that GSH transporting or utilizing systems may be affected by treatment of PEO-PPO-PEO copolymers.

  10. Solid state {sup 1}H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: The relationship between structure and methyl group and t-butyl group rotation

    SciTech Connect

    Wang, Xianlong E-mail: pbeckman@brynmawr.edu; Mallory, Frank B.; Mallory, Clelia W.; Odhner, Hosanna R.; Beckmann, Peter A. E-mail: pbeckman@brynmawr.edu

    2014-05-21

    We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state {sup 1}H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the {sup 1}H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups.

  11. Nuclear spin-lattice relaxation in nanofluids with paramagnetic impurities.

    PubMed

    Furman, Gregory B; Goren, Shaul D; Meerovich, Victor M; Sokolovsky, Vladimir L

    2015-12-01

    We study the spin-lattice relaxation of the nuclear spins in a liquid or a gas entrapped in nanosized ellipsoidal cavities with paramagnetic impurities. Two cases are considered where the major axes of cavities are in orientational order and isotropically disordered. The evolution equation and analytical expression for spin lattice relaxation time are obtained which give the dependence of the relaxation time on the structural parameters of a nanocavity and the characteristics of a gas or a liquid confined in nanocavities. For the case of orientationally ordered cavities, the relaxation process is exponential. When the nanocavities are isotropically disordered, the time dependence of the magnetization is significantly non-exponential. As shown for this case, the relaxation process is characterized by two time constants. The measurements of the relaxation time, along with the information about the cavity size, allow determining the shape and orientation of the nanocavity and concentration of the paramagnetic impurities.

  12. Pressure and temperature effects on 2H spin-lattice relaxation times and 1H chemical shifts in tert-butyl alcohol- and urea-D2O solutions

    NASA Astrophysics Data System (ADS)

    Yoshida, Koji; Ibuki, Kazuyasu; Ueno, Masakatsu

    1998-01-01

    The pressure and temperature effects of hydrophobic hydration were studied by NMR spectroscopy. The 1H chemical shifts (δ) were measured at 7.7, 29.9, and 48.4 °C under high pressure up to 294 MPa for HDO contained as impurity in neat D2O, 1 mol kg-1 tert-butyl alcohol (TBA)-D2O, and 1 mol kg-1 urea-D2O solutions, for the methyl group of TBA in the TBA-D2O solution, and for the amino group of urea in the urea-D2O solution. The 2H spin-lattice relaxation times (T1) were measured under the same conditions as the chemical shift measurements for D2O in neat D2O, TBA-D2O and urea-D2O solutions with organic contents up to 8 mol%. The following features are observed for the pressure effect on δ (HDO) and 2H-T1 in TBA-D2O solutions: (1) The δ (HDO) exhibits a downfield shift relative to that in neat D2O, and the difference of δ (HDO) between TBA solution and neat D2O becomes larger with increasing pressure at lower temperature. (2) The decrement of the rotational correlation time of water in the hydration shell of TBA (τcs) relative to the value at atmospheric pressure is smaller than that in the bulk (τc0). (3) The pressure coefficients of T1 are positive in dilute solutions but are negative in more than 4 to 5 mol% solutions. These results suggest that the hydrophobic hydration shell of TBA is different than the open structure of water present in bulk, and resists pressure more strongly than the open structure of water in the bulk. In solutions of 4 to 5 mol%, the hydration shell collapses. On the other hand, the τcs in the hydration shell of urea is slightly larger than that in bulk water at lower pressure, but is obviously larger at higher pressure. In view of the rotational motion of water molecules, urea seems to strengthen the water structure slightly rather than weaken it, although δ (HDO) approaches that in the bulk with pressure. It is difficult to classify urea into a structure maker or a breaker.

  13. Probing the Nuclear Spin-Lattice Relaxation Time at the Nanoscale

    NASA Astrophysics Data System (ADS)

    Wagenaar, J. J. T.; den Haan, A. M. J.; de Voogd, J. M.; Bossoni, L.; de Jong, T. A.; de Wit, M.; Bastiaans, K. M.; Thoen, D. J.; Endo, A.; Klapwijk, T. M.; Zaanen, J.; Oosterkamp, T. H.

    2016-07-01

    Nuclear spin-lattice relaxation times are measured on copper using magnetic-resonance force microscopy performed at temperatures down to 42 mK. The low temperature is verified by comparison with the Korringa relation. Measuring spin-lattice relaxation times locally at very low temperatures opens up the possibility to measure the magnetic properties of inhomogeneous electron systems realized in oxide interfaces, topological insulators, and other strongly correlated electron systems such as high-Tc superconductors.

  14. Proton spin-lattice relaxation mechanisms and the metal-insulator transition in cerium hydrides

    NASA Astrophysics Data System (ADS)

    Zamir, D.; Barnes, R. G.; Salibi, N.; Cotts, R. M.; Phua, T.-T.; Torgeson, D. R.; Peterson, D. T.

    1984-01-01

    Nuclear-magnetic-resonance (NMR) experiments have been done on cerium hydride (CeHx) samples to search for correlations between NMR properties and known electrical conductivity changes as a function of hydrogen concentration and temperature. Data are presented for the 1H spin-lattice relaxation rate R1 (=1T1) and some line shapes for 2.10<=x<=2.92 for temperatures from about 100 to 375 K. Although two 1H resonances are observed at some temperatures, proton spin-lattice relaxation is characterized by a single relaxation time at each x and T. To a good approximation R1=AT+R, where AT is attributed to direct dipolar coupling between protons and the electronic magnetic dipole moment of Ce3+, and R is an essentially temperature-independent term attributed to indirect [Ruderman-Kittel-Kasuya-Yosida (RKKY)] coupling to the Ce3+ moment. The AT term is so large that for most experiments the proton-proton dipolar and proton-conduction-electron couplings are negligible. The x dependence of the constant A is consistent with the dipolar coupling. The constant R decreases in a steep manner as x is increased above x~2.65 just below the regime 2.75

  15. Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

    PubMed

    Marsh, Derek

    2016-11-01

    Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T1-exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate Wn commonly used in the CW-EPR literature for (14)N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised (14)N spin-lattice relaxation rate, b=Wn/(2We), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in (14)N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for (14)N-relaxation: T1n=1/Wn. Results are compared and contrasted with those for the two-level (15)N-nitroxide system.

  16. Nuclear spin-lattice relaxation in nitroxide spin-label EPR

    NASA Astrophysics Data System (ADS)

    Marsh, Derek

    2016-11-01

    Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T1-exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate Wn commonly used in the CW-EPR literature for 14N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14N spin-lattice relaxation rate, b = Wn/(2We), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14N-relaxation: T1n = 1/Wn. Results are compared and contrasted with those for the two-level 15N-nitroxide system.

  17. Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds

    NASA Astrophysics Data System (ADS)

    Panich, A. M.; Sergeev, N. A.; Shames, A. I.; Osipov, V. Yu; Boudou, J.-P.; Goren, S. D.

    2015-02-01

    Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and 13C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of 13C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment.

  18. Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds.

    PubMed

    Panich, A M; Sergeev, N A; Shames, A I; Osipov, V Yu; Boudou, J-P; Goren, S D

    2015-02-25

    Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and (13)C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of (13)C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment.

  19. Exchange-mediated spin-lattice relaxation of Fe3+ ions in borate glasses.

    PubMed

    Misra, Sushil K; Pilbrow, John R

    2007-03-01

    Spin-lattice relaxation times (T1) of two borate glasses doped with different concentrations of Fe2O3 were measured using the Electron Spin-Echo (ESE) technique at X-band (9.630 GHz) in the temperature range 2-6K. In comparison with a previous investigation of Fe3+-doped silicate glasses, the relaxation rates were comparable and differed by no more than a factor of two. The data presented here extend those previously reported for borate glasses in the 10-250K range but measured using the amplitude-modulation technique. The T1 values were found to depend on temperature (T) as T(n) with n approximately 1 for the 1% and 0.1% Fe2O3-doped glass samples. These results are consistent with spin-lattice relaxation as effected by exchange interaction of a Fe3+ spin exchange-coupled to another Fe3+ spin in an amorphous material.

  20. [Spin-lattice relaxation of water protons in plant and animal cells].

    PubMed

    Samuilov, F D; Nikiforov, E A; Nikiforova, V I

    2012-01-01

    NMR-spin echo method has been used to study spin-lattice relaxation time of protons T1 in plant and animal cells - muscle tissue of fish, the cells of which unlike plant cells have no developed system of vacuoles, plastids and a solid cell wall. According to the values of T1 time a new NMR parameter K, a coefficient of relaxation effectiveness of a cell structure, has been calculated. This parameter can be used for quantitative characterization of the influence of different cell structures, the tissue water interact with, for a time of spin-lattice relaxation of water protons. It has been ascertained that the values of K coefficient in animal tissue and in storing tissues of some plants differ little; it may be stipulated by permanent transmembrane water exchange which occurs at high rate in the living cell. It has been concluded that there exists a certain similarity between water state in protoplast of plant and animal cells.

  1. The Spin-Lattice Relaxation of Hyperpolarized 89Y Complexes

    NASA Astrophysics Data System (ADS)

    Jindal, Ashish; Lumata, Lloyd; Xing, Yixun; Merritt, Matthew; Zhao, Piyu; Malloy, Craig; Sherry, Dean; Kovacs, Zoltan

    2011-03-01

    The low sensitivity of NMR can be overcome by dynamic nuclear polarization (DNP). However, a limitation to the use of hyperpolarized materials is the signal decay due to T1 relaxation. Among NMR-active nuclei, 89 Y is potentially valuable in medical imaging because in chelated form, pH-sensitive agents can be developed. 89 Y also offers many attractive features -- 100 % abundance, a 1/2 spin, and a long T1 , up to 10 min. Yet, developing new 89 Y complexes with even longer T1 values is desirable. Designing such complexes relies upon understanding the mechanism(s) responsible for T1 relaxation. We report an approach to hyperpolarized T1 measurements that enabled an analysis of relaxation mechanisms by selective deuteration of the ligand backbone, the solvent or both. Hyperpolarized 89 Y -- DTPA, DOTA, EDTA, and deuterated EDTA complexes were studied. Results suggest that substitution of low-gamma nuclei on the ligand backbone as opposed to that of the solvent most effectively increase the 89 Y T1 . These results are encouraging for in vivo applications as the presence of bound water may not dramatically affect the T1 .

  2. 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

  3. An iterative linear method for calculation of spin-lattice relaxation times

    NASA Astrophysics Data System (ADS)

    Crouch, Ronald; Hurlbert, Stuart; Ragouzeos, Aris

    A simple algorithm for the calculation of spin-lattice relaxation times which can be run in a programmable calculator is presented. As was suggested by H. Hanssum et al., an experimentally determined inhomogeneity parameter ( I) can be used with this procedure to compensate for imperfections in the RF field. The effects of variation of pulse width and repetition rate on both I and T1 are investigated with simulated and experimental data sets. The superiority of this approach over three-parameter nonlinear fitting methods is demonstrated by comparisons between data sets generated with different pulse flip angles and sample volumes.

  4. Measurement of solute proton spin-lattice relaxation times in water using the 1,3,3,1 sequence

    SciTech Connect

    Sankar, S.S.; Mole, P.A.; Coulson, R.L.

    1986-12-01

    /sup 1/H NMR spin-lattice relaxation times (T1) of the N-CH3 proton resonances of phosphocreatine (PCr) and creatine (Cr) in water solutions were obtained using the 1,3,3,1 pulse sequence. These T1 values were equivalent to those obtained in D/sub 2/O and water using either the conventional inversion-recovery experiment or the 1,3,3,1 pulse sequence. Thus, the 1,3,3,1 sequence of proton NMR can provide an independent means along with phosphorous NMR for assess PCr and for the study of the creatine kinase reaction (PCr + ADP in equilibrium ATP + Cr) in aqueous solutions and perhaps in biological preparations.

  5. Ion distribution in copper exchanged zeolites by using Si-29 spin lattice relaxation analysis

    NASA Astrophysics Data System (ADS)

    Palamara, Joseph; Seidel, Karsten; Moini, Ahmad; Prasad, Subramanian

    2016-06-01

    Transition metal-containing zeolites, particularly those with smaller pore size, have found extensive application in the selective catalytic reduction (SCR) of environmental pollutants containing nitrogen oxides. We report these zeolites have dramatically faster silicon-29 (Si-29) spin lattice relaxation times (T1) compared to their sodium-containing counterparts. Paramagnetic doping allows one to acquire Si-29 MAS spectra in the order of tens of seconds without significantly affecting the spectral resolution. Moreover, relaxation times depend on the method of preparation and the next-nearest neighbor silicon Qn(mAl) sites, where n = 4 and m = 0-4, respectively. A clear trend is noted between the effectiveness of Cu exchange and the Si-29 NMR relaxation times. It is anticipated that the availability of this tool, and the enhanced understanding of the nature of the active sites, will provide the means for designing improved SCR catalysts.

  6. Nuclear spin-lattice relaxation of 205TI in TIMo 6Se 8

    NASA Astrophysics Data System (ADS)

    Nishihara, H.; Ohtani, T.; Sano, Y.; Nakamura, Y.

    1991-12-01

    Temperature dependence of the nuclear spin-lattice relaxation rate of 205TI has been studied in a superconducting Chevrel compound TIMo 6Se 8. The rate follows the Korringa relation in the normal state with (T 1T) -1=3.4×10 2 (sK) -1. It follows a power law with T 1-1=2.64×10 -3T 6.9 in the superconducting state. An enhancement of the relaxation rate just below T c was not observed. These suggest that TIMo 6Se 8 is a new example of gapless superconductors. The relaxation behaviors in this Chevrel compound, which has low T c but has high H C2 is discussed in comparison with those in high-Tc oxides.

  7. Revisiting spin-lattice relaxation time measurements for dilute spins in high-resolution solid-state NMR spectroscopy.

    PubMed

    Fu, Riqiang; Li, Jun; Cui, Jingyu; Peng, Xinhua

    2016-07-01

    Numerous nuclear magnetic resonance (NMR) measurements of spin-lattice relaxation times (T1S) for dilute spins such as (13)C have led to investigations of the motional dynamics of individual functional groups in solid materials. In this work, we revisit the Solomon equations and analyze how the heteronuclear cross relaxation between the dilute S (e.g. (13)C) and abundant I (e.g. (1)H) spins affects the measured T1S values in solid-state NMR in the absence of (1)H saturation during the recovery time. It is found theoretically that at the beginning of the S spin magnetization recovery, the existence of non-equilibrium I magnetization introduces the heteronuclear cross relaxation effect onto the recovery of the S spin magnetization and confirmed experimentally that such a heteronuclear cross relaxation effect results in the recovery overshoot phenomena for the dilute spins when T1S is on the same order of T1H, leading to inaccurate measurements of the T1S values. Even when T1S is ten times larger than T1H, the heteronuclear cross relaxation effect on the measured T1S values is still noticeable. Furthermore, this cross relaxation effect on recovery trajectory of the S spins can be manipulated and even suppressed by preparing the initial I and S magnetization, so as to obtain the accurate T1S values. A sample of natural abundance l-isoleucine powder has been used to demonstrate the T1S measurements and their corresponding measured T1C values under various experimental conditions.

  8. 1H relaxation dispersion in solutions of nitroxide radicals: influence of electron spin relaxation.

    PubMed

    Kruk, D; Korpała, A; Kubica, A; Kowalewski, J; Rössler, E A; Moscicki, J

    2013-03-28

    The work presents a theory of nuclear ((1)H) spin-lattice relaxation dispersion for solutions of (15)N and (14)N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)]. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The (1)H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the (1)H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against (1)H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-(15)N and 4-oxo-TEMPO-d16-(14)N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both (14)N and (15)N systems and explains the features of (1)H relaxation dispersion resulting from the electron spin relaxation.

  9. 1H relaxation dispersion in solutions of nitroxide radicals: Influence of electron spin relaxation

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Korpała, A.; Kubica, A.; Kowalewski, J.; Rössler, E. A.; Moscicki, J.

    2013-03-01

    The work presents a theory of nuclear (1H) spin-lattice relaxation dispersion for solutions of 15N and 14N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The 1H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the 1H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against 1H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both 14N and 15N systems and explains the features of 1H relaxation dispersion resulting from the electron spin relaxation.

  10. The spin-temperature theory of dynamic nuclear polarization and nuclear spin-lattice relaxation

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Wollan, D. S.

    1974-01-01

    A detailed derivation of the equations governing dynamic nuclear polarization (DNP) and nuclear spin lattice relaxation by use of the spin temperature theory has been carried to second order in a perturbation expansion of the density matrix. Nuclear spin diffusion in the rapid diffusion limit and the effects of the coupling of the electron dipole-dipole reservoir (EDDR) with the nuclear spins are incorporated. The complete expression for the dynamic nuclear polarization has been derived and then examined in detail for the limit of well resolved solid effect transitions. Exactly at the solid effect transition peaks, the conventional solid-effect DNP results are obtained, but with EDDR effects on the nuclear relaxation and DNP leakage factor included. Explicit EDDR contributions to DNP are discussed, and a new DNP effect is predicted.

  11. Unexpected proton spin-lattice relaxation in the solutions of polyolefin and tetrachloroethane.

    PubMed

    He, Yiyong; Qiu, Xiaohua; Zhou, Zhe

    2010-07-01

    'Unexpected' proton spin-lattice relaxation (T(1)) times are reported for the solutions of poly(ethylene-co-1-octene) and tetrachloroethane-d(2). For the residual protons of the deuterated solvent and the methyl and vinyl protons at the polymer chain ends, their T(1) relaxation times vary significantly with both the polymer concentration and molecular weight over a wide range. The T(1)s also decrease with increasing temperature at relative high temperatures. Such behaviors are in contrast to most reported polymer solutions in which the T(1) has nearly no concentration or molecular weight dependence in the dilute and semi-dilute regime, and normal dependence on temperature. Further investigation revealed that the paramagnetic oxygen effect did shorten the measured proton T(1)s, but cannot account for the unexpected T(1) dependences. Spin rotation is proposed to provide a reasonable explanation.

  12. Frequency dependence of electron spin-lattice relaxation for semiquinones in alcohol solutions.

    PubMed

    Elajaili, Hanan B; Biller, Joshua R; Eaton, Sandra S; Eaton, Gareth R

    2014-10-01

    The spin-lattice relaxation rates at 293 K for three anionic semiquinones (2,5-di-t-butyl-1,4-benzosemiquinone, 2,6-di-t-butyl-1,4-benzosemiquinone, and 2,3,5,6-tetramethoxy-1,4-benzosemiquinone) were studied at up to 8 frequencies between 250 MHz and 34 GHz in ethanol or methanol solution containing high concentrations of OH(-). The relaxation rates are about a factor of 2 faster at lower frequencies than at 9 or 34 GHz. However, in perdeuterated alcohols the relaxation rates exhibit little frequency dependence, which demonstrates that the dominant frequency-dependent contribution to relaxation is modulation of dipolar interactions with solvent nuclei. The relaxation rates were modeled as the sum of two frequency-independent contributions (spin rotation and a local mode) and two frequency-dependent contributions (modulation of dipolar interaction with solvent nuclei and a much smaller contribution from modulation of g anisotropy). The correlation time for modulation of the interaction with solvent nuclei is longer than the tumbling correlation time of the semiquinone and is consistent with hydrogen bonding of the alcohol to the oxygen atoms of the semiquinones.

  13. The effect of a broad activation energy distribution on deuteron spin-lattice relaxation.

    PubMed

    Ylinen, E E; Punkkinen, M; Birczyński, A; Lalowicz, Z T

    2015-10-01

    Deuteron NMR spectra and spin-lattice relaxation were studied experimentally in zeolite NaY(2.4) samples containing 100% or 200% of CD3OH or CD3OD molecules of the total coverage of Na atoms in the temperature range 20-150K. The activation energies describing the methyl and hydroxyl motions show broad distributions. The relaxation data were interpreted by improving a recent model (Stoch et al., 2013 [16]) in which the nonexponential relaxation curves are at first described by a sum of three exponentials with adjustable relaxation rates and weights. Then a broad distribution of activation energies (the mean activation energy A0 and the width σ) was assumed for each essentially different methyl and hydroxyl position. The correlation times were calculated from the Arrhenius equation (containing the pre-exponential factor τ0), individual relaxation rates computed and classified into three classes, and finally initial relaxation rates and weights for each class formed. These were compared with experimental data, motional parameters changed slightly and new improved rates and weights for each class calculated, etc. This method was improved by deriving for the deuterons of the A and E species methyl groups relaxation rates, which depend explicitly on the tunnel frequency ωt. The temperature dependence of ωt and of the low-temperature correlation time were obtained by using the solutions of the Mathieu equation for a threefold potential. These dependencies were included in the simulations and as the result sets of A0, σ and τ0 obtained, which describe the methyl and hydroxyl motions in different positions in zeolite.

  14. Quadratic Zeeman effect and spin-lattice relaxation of Tm3 +:YAG at high magnetic fields

    NASA Astrophysics Data System (ADS)

    Veissier, Lucile; Thiel, Charles W.; Lutz, Thomas; Barclay, Paul E.; Tittel, Wolfgang; Cone, Rufus L.

    2016-11-01

    Anisotropy of the quadratic Zeeman effect for the H36→H34 transition at 793 nm wavelength in 3+169Tm-doped Y3Al5O12 is studied, revealing shifts ranging from near zero up to +4.69 GHz/T 2 for ions in magnetically inequivalent sites. This large range of shifts is used to spectrally resolve different subsets of ions and study nuclear spin relaxation as a function of temperature, magnetic field strength, and orientation in a site-selective manner. A rapid decrease in spin lifetime is found at large magnetic fields, revealing the weak contribution of direct phonon absorption and emission to the nuclear spin-lattice relaxation rate. We furthermore confirm theoretical predictions for the phonon coupling strength, finding much smaller values than those estimated in the limited number of past studies of thulium in similar crystals. Finally, we observe a significant—and unexpected—magnetic field dependence of the two-phonon Orbach spin relaxation process at higher field strengths, which we explain through changes in the electronic energy-level splitting arising from the quadratic Zeeman effect.

  15. Different molecular motions in lyophilized protein formulations as determined by laboratory and rotating frame spin-lattice relaxation times.

    PubMed

    Yoshioka, Sumie; Aso, Yukio; Kojima, Shigeo

    2002-10-01

    The spin-lattice relaxation times in the laboratory and rotating frame (T(1) and T(1rho)) of protons and carbons in lyophilized bovine serum gamma-globulin formulation containing dextran were determined by (1)H solid-state pulsed nuclear magnetic resonance (NMR) and high-resolution (13)C solid-state NMR. The temperature dependence of T(1) and T(1rho) of dextran protons in the lyophilized formulation suggests that the correlation time, tau(c), of the methylene protons in dextran is approximately 10(-6) s at -100 degrees C and 60% relative humidity, and decreases to 10(-7) s at 0 degrees C. When temperature is increased from 0 degrees C, the increased motion of the methylene groups is reflected in T(1), but is too fast to be observed by changes in T(1rho). Thus, the motion of the methine groups rather than the methylene groups begins to be reflected in T(1rho). The correlation time of the methine protons as determined by T(1rho) was of the same order as that of the methine carbons as determined by T(1rho). As the temperature is increased past the glass/rubber transition temperature, both the methylene and methine motions are greatly enhanced, resulting in much shorter T(1) and T(1rho) relaxation times.

  16. Spin-lattice relaxation and the calculation of gain, pump power, and noise temperature in ruby

    NASA Technical Reports Server (NTRS)

    Lyons, J. R.

    1989-01-01

    The use of a quantitative analysis of the dominant source of relaxation in ruby spin systems to make predictions of key maser amplifier parameters is described. The spin-lattice Hamiltonian which describes the interaction of the electron spins with the thermal vibrations of the surrounding lattice is obtained from the literature. Taking into account the vibrational anisotropy of ruby, Fermi's rule is used to calculate the spin transition rates between the maser energy levels. The spin population rate equations are solved for the spin transition relaxation times, and a comparison with previous calculations is made. Predictions of ruby gain, inversion ratio, and noise temperature as a function of physical temperature are made for 8.4-GHz and 32-GHz maser pumping schemes. The theory predicts that ruby oriented at 90 deg will have approximately 50 percent higher gain in dB and slightly lower noise temperature than a 54.7-deg ruby at 32 GHz (assuming pump saturation). A specific calculation relating pump power to inversion ratio is given for a single channel of the 32-GHz reflected wave maser.

  17. Spin-lattice relaxation within a dimerized Ising chain in a magnetic field

    SciTech Connect

    Erdem, Rıza E-mail: rerdem29@hotmail.com; Gülpınar, Gül; Yalçın, Orhan; Pawlak, Andrzej

    2014-07-21

    A qualitative study of the spin-lattice relaxation within a dimerized Ising chain in a magnetic field is presented. We have first determined the time dependence of the deviation of the lattice distortion parameter δΔ from the equilibrium state within framework of a technique combining the statistical equilibrium theory based on the transfer matrix method and the linear theory of irreversible thermodynamics. We have shown that the time dependence of the lattice distortion parameter is characterized by a single time constant (τ) which diverges around the critical point in both dimerized (Δ≠0) and uniform (Δ=0) phase regions. When the temperature and magnetic field are fixed to certain values, the time τ depends only on exchange coupling between the spins. It is a characteristic time associated with the long wavelength fluctuations of distortion. We have also taken into account the effects of spatial fluctuations on the relaxation time using the full Landau-Ginzburg free energy functional. We have found an explicit expression for the relaxation time as a function of temperature, coupling constant and wave vector (q) and shown that the critical mode corresponds to the case q=0. Finally, our results are found to be in good qualitative agreement with the results obtained in recent experimental study on synchrotron x-ray scattering and muon spin relaxation in diluted material Cu{sub 1−y}Mg{sub y}GeO{sub 3} where the composition y is very close to 0.0209. These results can be considered as natural extensions of some previous works on static aspects of the problem.

  18. Anomalous nuclear spin-lattice relaxation of 3He in contact with ordered Al2O3 aerogel

    NASA Astrophysics Data System (ADS)

    Alakshin, E. M.; Zakharov, M. Yu.; Klochkov, A. V.; Kuzmin, V. V.; Safiullin, K. R.; Stanislavovas, A. A.; Tagirov, M. S.

    2016-09-01

    Spin-lattice relaxation of 3He in contact with the ordered Al2O3 fiber aerogel has been studied at the temperature of 1.6 K in fields of 0.1-0.5 T by the pulsed nuclear magnetic resonance (NMR) method. An additional mechanism of the relaxation of 3He in aerogels is found and it is shown that this relaxation mechanism is not associated with the adsorbed layer. A hypothesis about the influence of intrinsic paramagnetic centers on the relaxation of gaseous 3He is proposed.

  19. Measuring nanopore size from the spin-lattice relaxation of CF4 gas

    PubMed Central

    Kuethe, Dean O.; Montaño, Rebecca; Pietraß, Tanja

    2007-01-01

    The NMR 19F spin-lattice relaxation time constant T1 for CF4 gas is dominated by spin–rotation interaction, which is mediated by the molecular collision frequency. When confined to pores of approximately the same size or smaller than the bulk gas mean free path, additional collisions of molecules with the pore walls should substantially change T1. To develop a method for measuring the surface/volume ratio S/V by measuring how T1 changes with confinement, we prepared samples of known S/V from fumed silica of known mass-specific surface area and compressed to varying degrees into cylinders of known volume. We then measured T1 for CF4 in these samples at varying pressures, and developed mathematical models for the change in T1 to fit the data. Even though CF4 has a critical temperature below room temperature, we found that its density in pores was greater than that of the bulk gas and that it was necessary to take this absorption into account. We modeled adsorption in two ways, by assuming that the gas condenses on the pore walls, and by assuming that gas in a region near the wall is denser than the bulk gas because of a simplified attractive potential. Both models suggested the same two-parameter formula, to which we added a third parameter to successfully fit the data and thus achieved a rapid, precise way to measure S/V from the increase in T1 due to confinement in pores. PMID:17400493

  20. Capturing fast relaxing spins with SWIFT adiabatic rotating frame spin-lattice relaxation (T1ρ) mapping.

    PubMed

    Zhang, J; Nissi, M J; Idiyatullin, D; Michaeli, S; Garwood, M; Ellermann, J

    2016-04-01

    Rotating frame spin-lattice relaxation, with the characteristic time constant T1ρ, provides a means to access motion-restricted (slow) spin dynamics in MRI. As a result of their restricted motion, these spins are sometimes characterized by a short transverse relaxation time constant T2 and thus can be difficult to detect directly with conventional image acquisition techniques. Here, we introduce an approach for three-dimensional adiabatic T1ρ mapping based on a magnetization-prepared sweep imaging with Fourier transformation (MP-SWIFT) sequence, which captures signal from almost all water spin populations, including the extremely fast relaxing pool. A semi-analytical procedure for T1ρ mapping is described. Experiments on phantoms and musculoskeletal tissue specimens (tendon, articular and epiphyseal cartilages) were performed at 9.4 T for both the MP-SWIFT and fast spin echo (FSE) read outs. In the phantom with liquids having fast molecular tumbling and a single-valued T1ρ time constant, the measured T1ρ values obtained with MP-SWIFT and FSE were similar. Conversely, in normal musculoskeletal tissues, T1ρ values measured with MP-SWIFT were much shorter than the values obtained with FSE. Studies of biological tissue specimens demonstrated that T1ρ-weighted SWIFT provides higher contrast between normal and diseased tissues relative to conventional acquisitions. Adiabatic T1ρ mapping with SWIFT readout captures contributions from the otherwise undetected fast relaxing spins, allowing more informative T1ρ measurements of normal and diseased states.

  1. Electron spin-lattice relaxation in radicals containing two methyl groups, generated by /γ-irradiation of polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Harbridge, James R.; Eaton, Sandra S.; Eaton, Gareth R.

    2002-12-01

    The effects of methyl rotation on electron spin-lattice relaxation times were examined by pulsed electron paramagnetic resonance for the major radicals in γ-irradiated polycrystalline α-amino isobutyric acid, dimethyl-malonic acid, and L-valine. The dominant radical is the same in irradiated dimethyl-malonic acid and α-amino isobutyric acid. Continuous wave saturation recovery was measured between 10 and 295 K at S-band and X-band. Inversion recovery, echo-detected saturation recovery, and pulsed electron-electron double resonance (ELDOR) data were obtained between 77 and 295 K. For the radicals in the three solids, recovery time constants measured by the various techniques were not the same, because spectral diffusion processes contribute differently for each measurement. Hyperfine splitting due to the protons of two methyl groups is resolved in the EPR spectra for each of the samples. Pulsed ELDOR data were obtained to characterize the spectral diffusion processes that transfer magnetization between hyperfine lines. Time constants were obtained for electron spin-lattice relaxation ( T1e), nuclear spin relaxation ( T1n), cross-relaxation ( Tx1), and spin diffusion ( Ts). Between 77 and 295 K rapid cross-relaxation (Δ Ms=±1, Δ MI=∓1) was observed for each sample, which is attributed to methyl rotation at a rate that is approximately equal to the electron Larmor frequency. The large temperature range over which cross-relaxation was observed suggests that methyl groups in the radical and in the lattice, with different activation energies for rotation, contribute to the rapid cross-relaxation. Activation energies for methyl and amino group rotation between 160 and 1900 K (1.3-16 kJ/mol) were obtained by analysis of the temperature dependence of 1/ T1e at S-band and X-band in the temperature intervals where the dynamic process dominates T1e.

  2. 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.

  3. 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.

  4. Raman electron spin-lattice relaxation with the Debye-type and with real phonon spectra in crystals

    NASA Astrophysics Data System (ADS)

    Hoffmann, Stanislaw K.; Lijewski, Stefan

    2013-02-01

    Electron spin-lattice relaxation temperature dependence was measured for Ti2+ (S = 1) and for Cu2+ (S = 1/2) ions in SrF2 single crystal by electron spin echo method in temperature range 4-109 K. The spin relaxation was governed by the two-phonon Raman processes. The relaxation theory is outlined and presented in a form suitable for applying with real phonon spectra. The experimental relaxation results were described using Debye-type phonon spectrum and the real phonon spectrum of SrF2 crystal. The Debye approximation does not fit well the results for SrF2 both at low and at high temperature. The relaxation rate is faster than that predicted by Debye-type phonon spectrum at low temperatures where excess of lattice vibrations over the Debye model exists but is slower at higher temperatures (above 50 K) where density of phonon states continuously decreases when approaching to the maximal acoustic phonon frequency. The expected deviation from Debye approximation was analyzed also for Cu2+ in NaCl and MgSiO3 crystals for which phonon spectra are available. The fitting with the real phonon spectrum allowed us to calculate spin-phonon coupling parameter as 267 cm-1 for Ti2+ and 1285 cm-1 for Cu2+ in SrF2.

  5. Nuclear spin-lattice relaxation at field-induced level crossings in a Cr8F8 pivalate single crystal

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shoji

    2016-01-01

    We construct a microscopic theory for the proton spin-lattice relaxation-rate 1 / T1 measurements around field-induced level crossings in a single crystal of the trivalent chromium ion wheel complex [Cr8F8(OOCtBu)16] at sufficiently low temperatures [E. Micotti et al., Phys. Rev. B 72 (2005) 020405(R)]. Exactly diagonalizing a well-equipped spin Hamiltonian for the individual clusters and giving further consideration to their possible interactions, we reveal the mechanism of 1 / T1 being single-peaked normally at the first level crossing but double-peaked intriguingly around the second level crossing. We wipe out the doubt about poor crystallization and find out a solution-intramolecular alternating Dzyaloshinsky-Moriya interaction combined with intermolecular coupling of antiferromagnetic character, each of which is so weak as several tens of mK in magnitude.

  6. Electron spin-lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids.

    PubMed

    Sato, Hideo; Bottle, Steven E; Blinco, James P; Micallef, Aaron S; Eaton, Gareth R; Eaton, Sandra S

    2008-03-01

    Electron spin-lattice relaxation rates, 1/T1, at X-band of nitroxyl radicals (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidin-1-oxyl and 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-oxyl) in glass-forming solvents (decalin, glycerol, 3-methylpentane, o-terphenyl, 1-propanol, sorbitol, sucrose octaacetate, and 1:1 water:glycerol) at temperatures between 100 and 300K were measured by long-pulse saturation recovery to investigate the relaxation processes in slow-to-fast tumbling regimes. A subset of samples was also studied at lower temperatures or at Q-band. Tumbling correlation times were calculated from continuous wave lineshapes. Temperature dependence and isotope substitution (2H and 15N) were used to distinguish the contributions of various processes. Below about 100K relaxation is dominated by the Raman process. At higher temperatures, but below the glass transition temperature, a local mode process makes significant contributions. Above the glass transition temperature, increased rates of molecular tumbling modulate nuclear hyperfine and g anisotropy. The contribution from spin rotation is very small. Relaxation rates at X-band and Q-band are similar. The dependence of 1/T1 on tumbling correlation times fits better with the Cole-Davidson spectral density function than with the Bloembergen-Purcell-Pound model.

  7. Electron spin lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids

    NASA Astrophysics Data System (ADS)

    Sato, Hideo; Bottle, Steven E.; Blinco, James P.; Micallef, Aaron S.; Eaton, Gareth R.; Eaton, Sandra S.

    2008-03-01

    Electron spin-lattice relaxation rates, 1/ T1, at X-band of nitroxyl radicals (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidin-1-oxyl and 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-oxyl) in glass-forming solvents (decalin, glycerol, 3-methylpentane, o-terphenyl, 1-propanol, sorbitol, sucrose octaacetate, and 1:1 water:glycerol) at temperatures between 100 and 300 K were measured by long-pulse saturation recovery to investigate the relaxation processes in slow-to-fast tumbling regimes. A subset of samples was also studied at lower temperatures or at Q-band. Tumbling correlation times were calculated from continuous wave lineshapes. Temperature dependence and isotope substitution ( 2H and 15N) were used to distinguish the contributions of various processes. Below about 100 K relaxation is dominated by the Raman process. At higher temperatures, but below the glass transition temperature, a local mode process makes significant contributions. Above the glass transition temperature, increased rates of molecular tumbling modulate nuclear hyperfine and g anisotropy. The contribution from spin rotation is very small. Relaxation rates at X-band and Q-band are similar. The dependence of 1/ T1 on tumbling correlation times fits better with the Cole-Davidson spectral density function than with the Bloembergen-Purcell-Pound model.

  8. Korringa-Like Nuclear Spin-Lattice Relaxation in a 2DES at ν= 1/2

    NASA Astrophysics Data System (ADS)

    Tracy, L. A.; Pfeiffer, L. N.

    2005-03-01

    Via a resistively-detected NMR technique, the nuclear spin lattice relaxation time T1 of ^71Ga at low temperatures has been measured in a GaAs/AlGaAs heterostructure containing two weakly-coupled 2D electron systems (2DES), each at Landau level filling ν= 1/2. Incomplete electronic spin polarization, which has been reported previously [1,2] for low density 2DESs at ν= 1/2, should facilitate hyperfine- coupled nuclear spin relaxation owing to the presence of both electron spin states at the Fermi level. Within composite fermion theory, a Korringa law temperature dependence: T1T = constant, is expected for temperatures T<1 K. Our measurements made at temperatures in the range 35 mK relaxation mechanisms in this system.[1] I. V. Kukushkin, K. v. Klitzing, and K. Eberl. Phys. Rev. Lett. 82, 3665 (1999); A. E. Dementyev, et al., Phys. Rev. Lett. 83, 5074 (1999); S. Melinte, et al., Phys. Rev. Lett. 84, 354 (2000).[2] I.B. Spielman, L.A. Tracy, J.P. Eisenstein, L.N. Pfeiffer, K.W. West, condmat/0410092.This work was supported by the DOE, NSF, and NDSEG.

  9. Probing protein hydration and aging of food materials by the magnetic field dependence of proton spin-lattice relaxation times.

    PubMed

    Godefroy, Sophie; Korb, Jean-Pierre; Creamer, Lawrence K; Watkinson, Philip J; Callaghan, Paul T

    2003-11-15

    Most cheeses can be considered as solid emulsions of milk fat in a matrix of water and proteins. Regions of each of the phases can be liquid during processing and maturation. Identifying these regions and monitoring changes in them is important as a prelude to controlling the structure of the final cheese. We concentrate on the behavior of water in the vicinity of proteins as a function of cheese aging. Our method utilizes nuclear magnetic relaxation dispersion (NMRD) associated with the frequency dependence of water spin-lattice relaxation rates using the field cycling NMR technique. This method provides insight into the dynamical behavior of water molecules on a very large time scale. Moreover, we can distinguish between molecular motion in bulk and motion in the vicinity of a source of relaxation, such as proteins. A fit of our dispersion data using a theory developed by J.-P. Korb and R.G. Bryant (J. Chem. Phys. 115 (2001) 23) allowed us to determine the degree of hydration of proteins as a function of aging. In particular, we find that protein hydration increases with ripening.

  10. Rotating Frame Spin Lattice Relaxation in a Swine Model of Chronic, Left Ventricular Myocardial Infarction

    PubMed Central

    Witschey, Walter RT; Pilla, James J; Ferrari, Giovanni; Koomalsingh, Kevin; Haris, Mohammed; Hinmon, Robin; Zsido, Gerald; Gorman, Joseph H; Gorman, Robert C; Reddy, Ravinder

    2010-01-01

    T1ρ relaxation times were quantified in a swine model of chronic, left ventricular myocardial infarction. It was found that there were low frequency relaxation mechanisms that suppress endogenous contrast at low spin lock amplitudes and in T2-weighted images. A moderate amplitude spin locking pulse could overcome these relaxation mechanisms. Relaxation dispersion data was measured over a range of RF field amplitudes and a model was formulated to include dipole-dipole relaxation modulated by molecular rotation and an apparent exchange mechanism. These techniques may find some use in the clinic for the observation of chronic, left ventricular cardiac remodeling. PMID:20677236

  11. Nuclear Spin-Lattice Relaxation Times from Continuous Wave NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Wooten, Jan B.; And Others

    1979-01-01

    The experiment described, suitable for undergraduate physical chemistry laboratories, illustrates the general principles of relaxation and introduces the nmr concepts of saturation and spin-inversion. (BB)

  12. Measurement of electron spin-lattice relaxation times in radical doped butanol samples at 1 K using the NEDOR method

    NASA Astrophysics Data System (ADS)

    Hess, C.; Herick, J.; Berlin, A.; Meyer, W.; Reicherz, G.

    2012-12-01

    The electron spin-lattice relaxation time (T1e) of TEMPO- and trityl-doped butanol samples at 2.5 T and temperatures between 0.95 K and 2.17 K was studied by pulsed nuclear magnetic resonance (NMR) using the nuclear-electron double resonance (NEDOR) method. This method is based on the idea to measure the NMR lineshift produced by the local field of paramagnetic impurities, whose polarization can be manipulated. This is of technical advantage as measurements can be performed under conditions typically used for the dynamic nuclear polarization (DNP) process - in our case 2.5 T and temperatures around 1 K - where a direct measurement on the electronic spins would be far more complicated to perform. As T1e is a crucial parameter determining the overall efficiency of DNP, the effect of the radical type, its spin concentration, the temperature and the oxygen content on T1e has been investigated. For radical concentrations as used in DNP (several 1019 spins/cm3) the relaxation rate (T1e-1) has shown a linear dependence on the paramagnetic electron concentration for both radicals investigated. Experiments with perdeuterated and ordinary butanol have given no indication for any influence of the host materials isotopes. The measured temperature dependence has shown an exponential characteristic. It is further observed that the oxygen content in the butanol samples has a considerable effect on the electron relaxation time and thus influences the nuclear relaxation time and polarization rate during the DNP. The experiments also show a variation in the NMR linewidth, leading to comparable time constants as determined by the lineshift. NEDOR measurements were also performed on irradiated, crystal grains of 6LiD. These samples exhibited a linewidth behavior similar to that of the cylindrically shaped butanol samples.

  13. Li chemisorption on Ru(001): LDA theory of the coverage dependence of the spin lattice relaxation time.

    NASA Astrophysics Data System (ADS)

    Mannstadt, W.; Freeman, A. J.

    1997-03-01

    The chemisorption of alkali atoms on metals still remains a challenging topic after almost sixty years of study. Recently, a novel type of experiment, β-decay NMR, was developed and applied to investigate Li atoms chemisorbed on a Ru(001) surface( H. J. Jänsch et al., Phys.Rev.Lett. 25, 120 (1995)). Such measurements of the spin lattice relaxation time provide information about the local density of states (LDOS) at EF and at the Li nucleus. Through the LDOS, the very local electronic properties of the chemisorbed alkali atom is determined, which provides new physical insight into the chemisorption process. One striking result is a constancy of the LDOS at low coverage, Θ=0 - 0.15, while the work function changes by about 2 eV. We present the first ab initio LDA calculations of the LDOS, using our full potential linearized augmented plane wave (FLAPW) method for thin films(E.Wimmer,H.Krakauer,M.Weinert, A.J.Freeman, Phys.Rev.B 24, 864 (1981)), to determine the Li chemisorption on Ru(001) for three coverages, Θ=1.0, 0.25 and 0.11, including a structure optimization for each. The calculations show a constant value of the LDOS at Θ= 0.25 and 0.11 which increases at high coverage by about a factor of two. * Supported by A.v.Humboldt Foundation

  14. An NMR thermometer for cryogenic magic-angle spinning NMR: the spin-lattice relaxation of (127)I in cesium iodide.

    PubMed

    Sarkar, Riddhiman; Concistrè, Maria; Johannessen, Ole G; Beckett, Peter; Denning, Mark; Carravetta, Marina; Al-Mosawi, Maitham; Beduz, Carlo; Yang, Yifeng; Levitt, Malcolm H

    2011-10-01

    The accurate temperature measurement of solid samples under magic-angle spinning (MAS) is difficult in the cryogenic regime. It has been demonstrated by Thurber et al. (J. Magn. Reson., 196 (2009) 84-87) [10] that the temperature dependent spin-lattice relaxation time constant of (79)Br in KBr powder can be useful for measuring sample temperature under MAS over a wide temperature range (20-296 K). However the value of T(1) exceeds 3 min at temperatures below 20K, which is inconveniently long. In this communication, we show that the spin-lattice relaxation time constant of (127)I in CsI powder can be used to accurately measure sample temperature under MAS within a reasonable experimental time down to 10 K.

  15. Electron spin-lattice relaxation of the (4Fe-4S) ferredoxin from B. stearothermophilus. Comparison with other iron proteins

    NASA Astrophysics Data System (ADS)

    Bertrand, Patrick; Gayda, Jean-Pierre; Rao, K. Krishna

    1982-05-01

    The temperature dependence of the electron spin-lattice relaxation time T1 of the (4Fe-4S) ferredoxin from Bacillus stearothermophilus is studied in the range 1.2 to 40 K. This dependence is similar to that observed for the (2Fe-2S) ferredoxin from Spirulina maxima and can be interpreted with the same relaxation processes [J.P. Gayda, P. Bertrand, A. Deville, C. More, G. Roger, J.F. Gibson, and R. Cammack, Biochim. Biophys. Acta 581, 15 (1979)]. In particular, between 4 and 15 K, the data are well fitted by a second-order Raman process involving three-dimensional phonons, with a Debye temperature of about 60 K (45 cm-1). This would give an estimation of the highest frequency of the vibrations which can propagate through the three-dimensional proteinic medium. In the highest temperature range (T≳30 K) the results are interpreted with an Orbach process involving an excited level of energy 120 cm-1. This process could be induced by the localized vibrations of the active site. Finally, these results are compared to those recently reported for some hemoproteins [H.J. Stapleton, J.P. Allen, C.P. Flynn, D.G. Stinson, and S.R. Kurtz, Phys. Rev. Lett. 45, 1456 (1980)]. Below 15 K, the temperature dependence of T1 for these samples is similar to that observed for the iron-sulfur proteins and may be interpreted in the same way. Our interpretation is compared to the fractal model proposed by Stapleton et al.

  16. 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).

  17. Observation of the vortex lattice melting by NMR spin-lattice relaxation in the mixed state

    SciTech Connect

    Bulaevskii, L.N.; Hammel, P.C.; Vinokur, V.M.

    1994-01-01

    For anisotropic layered superconductors the effect of moving vortices on the nuclear spin magnetization is calculated. Current is supposed to flow along layers, and applied magnetic field is tilted with respect to c-axis. In the solid phase the motion of the vortex lattice produces an alternating magnetic field perpendicular to the applied field which causes the decay of the spin-echo amplitude. This decay rate will display an array of peaks as a function of frequency. In the liquid phase this alternating field contribute to the longitudinal relaxation rate W{sub 1} which has a single peak.

  18. Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains

    NASA Astrophysics Data System (ADS)

    Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.

    2016-10-01

    We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.

  19. Effects of diffusion in magnetically inhomogeneous media on rotating frame spin-lattice relaxation

    NASA Astrophysics Data System (ADS)

    Spear, John T.; Gore, John C.

    2014-12-01

    In an aqueous medium containing magnetic inhomogeneities, diffusion amongst the intrinsic susceptibility gradients contributes to the relaxation rate R1ρ of water protons to a degree that depends on the magnitude of the local field variations ΔBz, the geometry of the perturbers inducing these fields, and the rate of diffusion of water, D. This contribution can be reduced by using stronger locking fields, leading to a dispersion in R1ρ that can be analyzed to derive quantitative characteristics of the material. A theoretical expression was recently derived to describe these effects for the case of sinusoidal local field variations of a well-defined spatial frequency q. To evaluate the degree to which this dispersion may be extended to more realistic field patterns, finite difference Bloch-McConnell simulations were performed with a variety of three-dimensional structures to reveal how simple geometries affect the dispersion of spin-locking measurements. Dispersions were fit to the recently derived expression to obtain an estimate of the correlation time of the field variations experienced by the spins, and from this the mean squared gradient and an effective spatial frequency were obtained to describe the fields. This effective spatial frequency was shown to vary directly with the second moment of the spatial frequency power spectrum of the ΔBz field, which is a measure of the average spatial dimension of the field variations. These results suggest the theory may be more generally applied to more complex media to derive useful descriptors of the nature of field inhomogeneities. The simulation results also confirm that such diffusion effects disperse over a range of locking fields of lower amplitude than typical chemical exchange effects, and should be detectable in a variety of magnetically inhomogeneous media including regions of dense microvasculature within biological tissues.

  20. Membrane fluidity profiles as deduced by saturation-recovery EPR measurements of spin-lattice relaxation times of spin labels.

    PubMed

    Mainali, Laxman; Feix, Jimmy B; Hyde, James S; Subczynski, Witold K

    2011-10-01

    There are no easily obtainable EPR spectral parameters for lipid spin labels that describe profiles of membrane fluidity. The order parameter, which is most often used as a measure of membrane fluidity, describes the amplitude of wobbling motion of alkyl chains relative to the membrane normal and does not contain explicitly time or velocity. Thus, this parameter can be considered as nondynamic. The spin-lattice relaxation rate (T(1)(-1)) obtained from saturation-recovery EPR measurements of lipid spin labels in deoxygenated samples depends primarily on the rotational correlation time of the nitroxide moiety within the lipid bilayer. Thus, T(1)(-1) can be used as a convenient quantitative measure of membrane fluidity that reflects local membrane dynamics. T(1)(-1) profiles obtained for 1-palmitoyl-2-(n-doxylstearoyl)phosphatidylcholine (n-PC) spin labels in dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol are presented in parallel with profiles of the rotational diffusion coefficient, R(⊥), obtained from simulation of EPR spectra using Freed's model. These profiles are compared with profiles of the order parameter obtained directly from EPR spectra and with profiles of the order parameter obtained from simulation of EPR spectra. It is shown that T(1)(-1) and R(⊥) profiles reveal changes in membrane fluidity that depend on the motional properties of the lipid alkyl chain. We find that cholesterol has a rigidifying effect only to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. These effects cannot be differentiated by profiles of the order parameter. All profiles in this study were obtained at X-band (9.5 GHz).

  1. Sub-millisecond (125)Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum.

    PubMed

    Levin, E M; Cui, J-F; Schmidt-Rohr, K

    2016-09-01

    (125)Te NMR spectra and spin-lattice relaxation times, T1, have been measured for several GeTe-based materials with Te excess. The spectra show inhomogeneous broadening by several thousand ppm and a systematic variation in T1 relaxation time with resonance frequency. The quadratic dependence of the spin-lattice relaxation rate, 1/T1, on the Knight shift in the Korringa relation is found to be valid over a wide range of Knight shifts. This result confirms that T1 relaxation in GeTe-based materials is mostly dominated by hyperfine interaction between nuclei and free charge carriers. In GeTe with 2.5% excess of Te, about 15% of the material exhibits a Knight shift of ≥4500ppm and a T1 of only 0.3ms, indicating a high hole concentration that could correspond to close to 50% vacancies on the Ge sublattice in this component. Our findings provide a basis for determining the charge carrier concentration and its distribution in complex thermoelectric and phase-change tellurides, which should lead to a better understanding of electronic and thermal transport properties as well as chemical bonding in these materials.

  2. Measurement of sample temperatures under magic-angle spinning from the chemical shift and spin-lattice relaxation rate of 79Br in KBr powder

    NASA Astrophysics Data System (ADS)

    Thurber, Kent R.; Tycko, Robert

    2009-01-01

    Accurate determination of sample temperatures in solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS) can be problematic, particularly because frictional heating and heating by radio-frequency irradiation can make the internal sample temperature significantly different from the temperature outside the MAS rotor. This paper demonstrates the use of 79Br chemical shifts and spin-lattice relaxation rates in KBr powder as temperature-dependent parameters for the determination of internal sample temperatures. Advantages of this method include high signal-to-noise, proximity of the 79Br NMR frequency to that of 13C, applicability from 20 K to 320 K or higher, and simultaneity with adjustment of the MAS axis direction. We show that spin-lattice relaxation in KBr is driven by a quadrupolar mechanism. We demonstrate a simple approach to including KBr powder in hydrated samples, such as biological membrane samples, hydrated amyloid fibrils, and hydrated microcrystalline proteins, that allows direct assessment of the effects of frictional and radio-frequency heating under experimentally relevant conditions.

  3. Electron spin-lattice relaxation mechanisms of nitroxyl radicals in ionic liquids and conventional organic liquids: temperature dependence of a thermally activated process.

    PubMed

    Kundu, Krishnendu; Kattnig, Daniel R; Mladenova, Boryana Y; Grampp, Günter; Das, Ranjan

    2015-03-26

    During the past two decades, several studies have established a significant role played by a thermally activated process in the electron spin relaxation of nitroxyl free radicals in liquid solutions. Its role has been used to explain the spin relaxation behavior of these radicals in a wide range of viscosities and microwave frequencies. However, no temperature dependence of this process has been reported. In this work, our main aim was to investigate the temperature dependence of this process in neat solvents. Electron spin-lattice relaxation times of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 4-hydroxy-TEMPO (TEMPOL), in X-band microwave frequency, were measured by the pulse saturation recovery technique in three room-temperature ionic liquids ([bmim][BF4], [emim][BF4], and [bmim][PF6]), di-isononyl phthalate, and sec-butyl benzene. The ionic liquids provided a wide range of viscosity in a modest range of temperature. An auxiliary aim was to examine whether the dynamics of a probe molecule dissolved in ionic liquids was different from that in conventional molecular liquids, as claimed in several reports on fluorescence dynamics in ionic liquids. This was the reason for the inclusion of di-isononyl phthalate, whose viscosities are similar to that of the ionic liquids in similar temperatures, and sec-butyl benzene. Rotational correlation times of the nitroxyl radicals were determined from the hyperfine dependence of the electron paramagnetic resonance (EPR) line widths. Observation of highly well-resolved proton hyperfine lines, riding over the nitrogen hyperfine lines, in the low viscosity regime in all the solvents, gave more accurate values of the rotational correlation times than the values generally measured in the absence of these hyperfine lines and reported in the literature. The measured rotational correlation times obeyed a modified Stokes-Einstein-Debye relation of temperature dependence in all solvents. By separating the contributions of g

  4. 87Rb spin-lattice relaxation times in ferroelectric-paraelectric-incommensurate phases of Rb2CoBr4 using static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2017-04-01

    To better elucidate the structural properties of Rb2CoBr4 in paraelectric, incommensurate, and ferroelectric phases, we studied the 87Rb nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times in laboratory frame T1 and in rotating frame T1ρ. The resonance frequency and the chemical shift do not change abruptly near the phase transition temperature of Ti = 333 K and TC = 192 K, whereas T1 and T1ρ display discontinuous changes near Ti and TC. The abrupt changes in the relaxation times near these temperatures seem to be a result of the structural phase transitions. The results are distinctly different from those reported for Rb2CoCl4.

  5. A carbon-13 NMR spin-lattice relaxation study of the molecular conformation of the nootropic drug 2-oxopyrrolidin-1-ylacetamide

    NASA Astrophysics Data System (ADS)

    Baldo, M.; Grassi, A.; Guidoni, L.; Nicolini, M.; Pappalardo, G. C.; Viti, V.

    The spin-lattice relaxation times ( T1) of carbon-13 resonances of the drug 2-oxopyrrolidin- 1-ylacetamide ( 2OPYAC) were determined in CDCl 3 + DMSO and H 2O solutions to investigate the internal conformational flexibility. The measured T1s for the hydrogen-bearing carbon atoms of the 2-pyrrolidone ring fragment were diagnostic of a rigid conformation with respect to the acetamide linked moiety. The model of anisotropic reorientation of a rigid body was used to analyse the measured relaxation data in terms of a single conformation. Owing to the small number of T1 data available the fitting procedure for each of the possible conformations failed. The structure corresponding to the rigid conformation was therefore considered to be the one that is strongly stabilized by internal hydrogen bonding as predicted on the basis of theoretical MO ab initio quantum chemical calculations.

  6. Magnetic field induced anisotropy of 139La spin-lattice relaxation rates in stripe ordered La1.875Ba0.125CuO4

    DOE PAGES

    S. -H. Baek; Gu, G. D.; Utz, Y.; ...

    2015-10-26

    We report 139La nuclear magnetic resonance studies performed on a La1.875Ba0.125CuO4 single crystal. The data show that the structural phase transitions (high-temperature tetragonal → low-temperature orthorhombic → low-temperature tetragonal phase) are of the displacive type in this material. The 139La spin-lattice relaxation rate T–11 sharply upturns at the charge-ordering temperature TCO = 54 K, indicating that charge order triggers the slowing down of spin fluctuations. Detailed temperature and field dependencies of the T–11 below the spin-ordering temperature TSO=40 K reveal the development of enhanced spin fluctuations in the spin-ordered state for H ∥ [001], which are completely suppressed for largemore » fields along the CuO2 planes. Lastly, our results shed light on the unusual spin fluctuations in the charge and spin stripe ordered lanthanum cuprates.« less

  7. 11B and 27Al NMR spin-lattice relaxation and Knight shift of Mg1-xAlxB2: Evidence for an anisotropic Fermi surface

    NASA Astrophysics Data System (ADS)

    Papavassiliou, G.; Pissas, M.; Karayanni, M.; Fardis, M.; Koutandos, S.; Prassides, K.

    2002-10-01

    We report a detailed study of the 11B and 27Al NMR spin-lattice relaxation rates (1/T1) and the 27Al Knight shift (K) in Mg1-xAlxB2, 0<=x<=1. The evolution of (1/T1T) and K with x is in excellent agreement with the prediction of ab initio calculations of a highly anisotropic Fermi surface, consisting mainly of hole-type two-dimensional (2D) cylindrical sheets from bonding 2px,y boron orbitals. The density of states at the Fermi level also decreases sharply on Al doping and the 2D sheets collapse at x~0.55, where the superconducting phase disappears.

  8. NMR spin-lattice relaxation study of 7Li and 93Nb nuclei in Ti- or Fe-doped LiNbO3:Mg single crystals

    NASA Astrophysics Data System (ADS)

    Yeom, Tae Ho; Lim, Ae Ran

    2016-04-01

    In this study, to understand the effects of paramagnetic impurities, we investigated the temperature dependent of the spin-lattice relaxation times of pure LiNbO3, LiNbO3:Mg, LiNbO3:Mg/Ti, LiNbO3:Mg/Fe, and LiNbO3:Mg/Fe (thermally treated at 500°C) single crystals. The results for the LiNbO3:Mg single crystals doped with Fe3+ or Ti3+ are discussed with respect to the site distribution and atomic mobility of Li and Nb. In addition, the effects of a thermal treatment on LiNbO3:Mg/Fe single crystals were examined based on the T1 analysis of 7Li and 93Nb. It was found that the presence of impurities in the crystals induced systematic changes of activation energies concerning atomic mobility.

  9. 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.

  10. Molecular motions of [Beta]-carotene and a carotenoporphyrin dyad in solution. A carbon-13 NMR spin-lattice relaxation time study

    SciTech Connect

    Li, S.; Swindle, S.L.; Smith, S.K.; Nieman, R.A.; Moore, A.L.; Moore, T.A.; Gust, D. )

    1995-03-09

    Analysis of [sup 13]C NMR spin-lattice relaxation times (T[sub 1]) yields information concerning both overall tumbling of molecules in solution and internal rotations about single bonds. Relaxation time and nuclear Overhauser effect data have been obtained for [Beta]-carotene and two related molecules, squalane and squalene, for zinc meso-tetraphenylporphyrin, and for a dyad consisting of a porphyrin covalently linked to a carotenoid polyene through a trimethylene bridge. Squalane and squalene, which lack conjugated double bonds, behave essentially as limp string, with internal rotations at least as rapid as overall isotropic tumbling motions. In contrast, [Beta]-carotene reorients as a rigid rod, with internal motions which are too slow to affect relaxation times. Modeling it as an anisotropic rotor yields a rotational diffusion coefficient for motion about the major axis which is 14 times larger than that for rotation about axes perpendicular to that axis. The porphyrin reorients more nearly isotropically and features internal librational motions about the single bonds to the phenyl groups. The relaxation time data for the carotenoporphyrin are consistent with internal motions similar to those of a medieval military flail. 31 refs., 3 figs., 5 tabs.

  11. Anisotropy of spin-spin and spin-lattice relaxation times in liquids entrapped in nanocavities: Application to MRI study of biological systems

    NASA Astrophysics Data System (ADS)

    Furman, Gregory B.; Goren, Shaul D.; Meerovich, Victor M.; Sokolovsky, Vladimir L.

    2016-02-01

    Spin-spin and spin-lattice relaxations in liquid or gas entrapped in nanosized ellipsoidal cavities with different orientation ordering are theoretically investigated. The model is flexible in order to be applied to explain experimental results in cavities with various forms, from very prolate up to oblate ones, and different degree of ordering of nanocavities. In the framework of the considered model, the dipole-dipole interaction is determined by a single coupling constant, which depends on the form, size, and orientation of the cavity and number of nuclear spins in the cavity. It was shown that the transverse and longitudinal relaxation rates differently depend on the angle between the external magnetic field and cavity main axis. The calculation results for the local dipolar field, transverse and longitudinal relaxation times explain the angular dependencies observed in MRI experiments with biological objects: cartilage and tendon. Microstructure of these tissues can be characterized by the standard deviation of the Gaussian distribution of fibril orientations. The comparison of the theoretical and experimental results shows that the value of the standard deviation obtained at the matching of the calculation to experimental results can be used as a parameter characterizing the disorder in the biological sample.

  12. Anisotropy of spin-spin and spin-lattice relaxation times in liquids entrapped in nanocavities: Application to MRI study of biological systems.

    PubMed

    Furman, Gregory B; Goren, Shaul D; Meerovich, Victor M; Sokolovsky, Vladimir L

    2016-02-01

    Spin-spin and spin-lattice relaxations in liquid or gas entrapped in nanosized ellipsoidal cavities with different orientation ordering are theoretically investigated. The model is flexible in order to be applied to explain experimental results in cavities with various forms, from very prolate up to oblate ones, and different degree of ordering of nanocavities. In the framework of the considered model, the dipole-dipole interaction is determined by a single coupling constant, which depends on the form, size, and orientation of the cavity and number of nuclear spins in the cavity. It was shown that the transverse and longitudinal relaxation rates differently depend on the angle between the external magnetic field and cavity main axis. The calculation results for the local dipolar field, transverse and longitudinal relaxation times explain the angular dependencies observed in MRI experiments with biological objects: cartilage and tendon. Microstructure of these tissues can be characterized by the standard deviation of the Gaussian distribution of fibril orientations. The comparison of the theoretical and experimental results shows that the value of the standard deviation obtained at the matching of the calculation to experimental results can be used as a parameter characterizing the disorder in the biological sample.

  13. Long-range Li+ dynamics in the lithium argyrodite Li7PSe6 as probed by rotating-frame spin-lattice relaxation NMR.

    PubMed

    Epp, V; Gün, O; Deiseroth, H-J; Wilkening, M

    2013-05-21

    Lithium-rich argyrodites belong to a relatively new group of fast ion conducting solids. They might serve as powerful electrolytes in all-solid-state lithium-ion batteries being, from a medium-term point of view, the key technology when safe energy storage systems have to be developed. Spin-lattice relaxation (SLR) nuclear magnetic resonance (NMR) measurements carried out in the rotating frame of reference turned out to be the method of choice to study Li dynamics in argyrodites. When plotted as a function of the inverse temperature, the SLR rates log10(R1ρ) reveal an asymmetric diffusion-induced rate peak. The rate peak contains information on the Li jump rate, the activation energy of the hopping process as well as correlation effects. In particular, considering the high-temperature flank of the SLR NMR rate peak recorded in the rotating frame of reference, an activation energy of approximately 0.49 eV is found. This value represents long-range lithium jump diffusion in crystalline Li7PSe6. As an example, at 325 K the Li jump rate determined from SLR NMR is in the order of 1.4 × 10(5) s(-1). The pronounced asymmetry of the rate peak R1ρ(1/T) points to correlated Li motion. It is comparable to that which is typically found for structurally disordered materials showing a broad range of correlation times.

  14. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    SciTech Connect

    Meyer, Benjamin Michael

    2003-01-01

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, τ, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single distribution of

  15. Electron Spin-Lattice Relaxation in Two Heme Iron and Two Blue-Copper Proteins at Liquid Helium Temperatures

    NASA Astrophysics Data System (ADS)

    Thayer, Bradley Denton

    1990-01-01

    The relaxation rates in frozen aqueous solutions of whale ferri-myoglobin azide, bovine ferri-hemoglobin azide, cupric azurin (P. aeruginosa) and cupric spinach plastocyanin were measured at 9.5 GHz using the pulse-saturation recovery method. Measurements covered a temperature range of 1.4 K to as high as 22 K, with corresponding relaxation rates up to 10^5/sec. Improvements in the equipment and the methods of analysis have enabled more stringent tests of the temperature dependence of the rates. In particular, several models proposed in the literature to explain the anomalous temperature dependence of the Raman rates in proteins are shown to be insufficient, including two fractal models. In addition, it is shown that any model based exclusively on the protein structure fails due to the diversity of the data under various solvent conditions. A general functional form consistent with a crossover in the vibrational properties is proposed instead, similar to the localization crossover in amorphous materials. The effect on the relaxation rate of several cosolvents and solutes is also examined. The effect on the direct process is much more pronounced than on the Raman region. The differences are shown to be consistent with changes in the velocity of sound at room temperature caused by the addition of cosolvents and solutes. Finally, the EPR recovery form is analyzed. We propose that the deviations in the recovery from an exponential form are due to a distribution of relaxation rates. The source of the distribution is most likely sample heating in the lower temperatures and a distribution of conformations frozen in near the paramagnetic site in the higher temperatures. It is not likely that it is caused by spin-spin interactions. The exact form of the distribution is unclear, but the most successful functional form for the recoveries is a stretched exponential with an exponent ranging from 0.5 to 1.0. However, a simple exponential fit to a limited portion of the recovery

  16. Spin-lattice relaxation of coupled metal-radical spin-dimers in proteins: application to Fe(2+)-cofactor (Q(A)(-.), Q(B)(-.), phi(-.)) dimers in reaction centers from photosynthetic bacteria.

    PubMed Central

    Calvo, Rafael; Isaacson, Roger A; Abresch, Edward C; Okamura, Melvin Y; Feher, George

    2002-01-01

    The spin-lattice relaxation times (T(1)) for the reduced quinone acceptors Q(A)(-.) and Q(B)(-.), and the intermediate pheophytin acceptor phi(-.), were measured in native photosynthetic reaction centers (RC) containing a high spin Fe(2+) (S = 2) and in RCs in which Fe(2+) was replaced by diamagnetic Zn(2+). From these data, the contribution of the Fe(2+) to the spin-lattice relaxation of the cofactors was determined. To relate the spin-lattice relaxation rate to the spin-spin interaction between the Fe(2+) and the cofactors, we developed a spin-dimer model that takes into account the zero field splitting and the rhombicity of the Fe(2+) ion. The relaxation mechanism of the spin-dimer involves a two-phonon process that couples the fast relaxing Fe(2+) spin to the cofactor spin. The process is analogous to the one proposed by R. Orbach (Proc. R. Soc. A. (Lond.). 264:458-484) for rare earth ions. The spin-spin interactions are, in general, composed of exchange and dipolar contributions. For the spin dimers studied in this work the exchange interaction, J(o), is predominant. The values of J(o) for Q(A)(-.)Fe(2+), Q(B)(-.)Fe(2+), and phi(-.)Fe(2+) were determined to be (in kelvin) -0.58, -0.92, and -1.3 x 10(-3), respectively. The |J(o)| of the various cofactors (obtained in this work and those of others) could be fitted with the relation exp(-beta(J)d), where d is the distance between cofactor spins and beta(J) had a value of (0.66-0.86) A(-1). The relation between J(o) and the matrix element |V(ij)|(2) involved in electron transfer rates is discussed. PMID:12414679

  17. Nuclear spin lattice relaxation and conductivity studies of the non-Arrhenius conductivity behavior in lithium fast ion conducting sulfide glasses

    NASA Astrophysics Data System (ADS)

    Meyer, Benjamin Michael

    Homogeneous xB2O3 + (1-x)B 2S3 glasses were prepared between 0 ≤ x ≤ 0.80. Raman, IR, and 11B NMR spectroscopies show that the boron oxide structures of B2O3, especially the six-membered rings, quickly diminish with increasing sulfide content, whereas the corresponding sulfide structures in B2S3 remain relatively intense as oxide content is increased. Differential scanning calorimetry (DSC) and density measurements show that physical properties of these boron oxysulfide glasses heavily favor the B2S3 properties regardless of the amount of B2O3 added to the system. It is hypothesized that the stability of the thioboroxol ring group relative to that of the BS 3/2 trigonal group is a possible source of this behavior. The formation of mixed boron oxysulfide structures of composition BSzO3-z where 0 < z < 3 is proposed. Structural studies of the ternary xLi2S + (1-x)[0.5 B2S3 + 0.5 GeS2] glasses using IR, Raman, and 11B NMR show that these glasses do not have equal sharing of the lithium atoms between GeS2 and B2S3. The IR spectra indicates that the B2S3 glass network are under-doped in comparison to corresponding compositions in the xLi 2S + (1-x)B2S3 binary system. Additionally, the Raman spectra show that the GeS2 glass network is over-modified. 11Boron static NMR gives evidence that ˜80% of the boron atoms are in tetrahedral coordinated. A super macro tetrahedron is proposed as one of the structures in these glasses in which some of them may contain boron sites substituted by germanium atoms at lower Li2S content. Nuclear Spin Lattice Relaxation and ionic conductivity measurements of Li doped Li2S + GeS2 + B2S3 glasses were performed to investigate the ion hopping dynamics and the non-Arrhenius conductivity behavior that has been observed in some fast ion conducting glasses. A distribution of activation energies model was used to fit the NSLR results and conductivity results. Comparisons are made to previously studied binary lithium thio-germanate and binary

  18. Fast Li ion dynamics in the solid electrolyte Li7 P3 S11 as probed by (6,7) Li NMR spin-lattice relaxation.

    PubMed

    Wohlmuth, Dominik; Epp, Viktor; Wilkening, Martin

    2015-08-24

    The development of safe and long-lasting all-solid-state batteries with high energy density requires a thorough characterization of ion dynamics in solid electrolytes. Commonly, conductivity spectroscopy is used to study ion transport; much less frequently, however, atomic-scale methods such as nuclear magnetic resonance (NMR) are employed. Here, we studied long-range as well as short-range Li ion dynamics in the glass-ceramic Li7 P3 S11 . Li(+) diffusivity was probed by using a combination of different NMR techniques; the results are compared with those obtained from electrical conductivity measurements. Our NMR relaxometry data clearly reveal a very high Li(+) diffusivity, which is reflected in a so-called diffusion-induced (6) Li NMR spin-lattice relaxation peak showing up at temperatures as low as 313 K. At this temperature, the mean residence time between two successful Li jumps is in the order of 3×10(8) s(-1) , which corresponds to a Li(+) ion conductivity in the order of 10(-4) to 10(-3) S cm(-1) . Such a value is in perfect agreement with expectations for the crystalline but metastable glass ceramic Li7 P3 S11 . In contrast to conductivity measurements, NMR analysis reveals a range of activation energies with values ranging from 0.17 to 0.26 eV, characterizing Li diffusivity in the bulk. In our case, through-going Li ion transport, when probed by using macroscopic conductivity spectroscopy, however, seems to be influenced by blocking grain boundaries including, for example, amorphous regions surrounding the Li7 P3 S11 crystallites. As a result of this, long-range ion transport as seen by impedance spectroscopy is governed by an activation energy of approximately 0.38 eV. The findings emphasize how surface and grain boundary effects can drastically affect long-range ionic conduction. If we are to succeed in solid-state battery technology, such effects have to be brought under control by, for example, sophisticated densification or through the preparation

  19. 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.

  20. Dynamics of [C{sub 3}H{sub 5}N{sub 2}]{sub 6}[Bi{sub 4}Br{sub 18}] by means of {sup 1}H NMR relaxometry and quadrupole relaxation enhancement

    SciTech Connect

    Masierak, W.; Florek-Wojciechowska, M.; Oglodek, I.; Jakubas, R.; Privalov, A. F.; Kresse, B.; Fujara, F.; Kruk, D.

    2015-05-28

    {sup 1}H spin-lattice field cycling relaxation dispersion experiments in the intermediate phase II of the solid [C{sub 3}H{sub 5}N{sub 2}]{sub 6}[Bi{sub 4}Br{sub 18}] are presented. Two motional processes have been identified from the {sup 1}H spin-lattice relaxation dispersion profiles and quantitatively described. It has been concluded that these processes are associated with anisotropic reorientations of the imidazolium ring, characterized by correlation times of the order of 10{sup −8} s-10{sup −9} s and of about 10{sup −5} s. Moreover, quadrupole relaxation enhancement (QRE) effects originating from slowly fluctuating {sup 1}H-{sup 14}N dipolar interactions have been observed. From the positions of the relaxation maxima, the quadrupole coupling parameters for the {sup 14}N nuclei in [C{sub 3}H{sub 5}N{sub 2}]{sub 6}[Bi{sub 4}Br{sub 18}] have been determined. The {sup 1}H-{sup 14}N relaxation contribution associated with the slow dynamics has been described in terms of a theory of QRE [Kruk et al., Solid State Nucl. Magn. Reson. 40, 114 (2011)] based on the stochastic Liouville equation. The shape of the QRE maxima (often referred to as “quadrupole peaks”) has been consistently reproduced for the correlation time describing the slow dynamics and the determined quadrupole coupling parameters.

  1. sup 31 P and sup 1 H NMR studies of the structure of enzyme-bound substrate complexes of lobster muscle arginine kinase: Relaxation measurements with Mn(II) and Co(II)

    SciTech Connect

    Jarori, G.K.; Ray, B.D.; Rao, B.D.N. )

    1989-11-28

    The paramagnetic effects of Mn(II) and Co(II) on the spin-lattice relaxation rates of {sup 31}P nuclei of ATP and ADP and of Mn(II) on the spin-lattice relaxation rate of the {delta} protons of arginine bound to arginine kinase from lobster tail muscle have been measured. Temperature variation of {sup 31}P relaxation rates in E-MnADP and E-MnATP yields activation energies ({Delta}E) in the range 6-10 kcal/mol. Thus, the {sup 31}P relaxation rates in these complexes are exchange limited and cannot provide structural information. However, the relaxation rates in E-CoADP and E-CoATP exhibit frequency dependence and {Delta}E values in the range 1-2 kcal/mol; i.e., these rates depend upon {sup 31}P-Co(II) distances. These distances were calculated to be in the range 3.2-4.5 {angstrom}, appropriate for direct coordination between Co(II) and the phosphoryl groups. The paramagnetic effect of Mn(II) on the {sup 1}H spin-lattice relaxation rate of the {delta} protons of arginine in the E-MnADP-Arg complex was also measured at three frequencies. From the frequency dependence of the relaxation rate an effective {tau}{sub C} of 0.6 ns has also been calculated, which is most likely to be the electron spin relaxation rate ({tau}{sub S1}) for Mn(II) in this complex. The distance estimated on the basis of the reciprocal sixth root of the average relaxation rate of the {delta} protons was 10.9 {plus minus} 0.3 {angstrom}.

  2. Molecular determinants for drug-receptor interactions. 8. Anisotropic and internal motions in morphine, nalorphine, oxymorphone, naloxone and naltrexone in aqueous solution by carbon-13 NMR spin-lattice relaxation times

    NASA Astrophysics Data System (ADS)

    Grassi, Antonio; Perly, Bruno; Pappalardo, Giuseppe C.

    1989-02-01

    Carbon-13 NMR spin-lattice relaxation times ( T1) were measured for morphine, oxymorphone, nalorphine, naloxone and naltrexone as hydrochloride salts in 2H 2O solution. The data refer to the molecules in the N-equatorial configuration. The experimental T1 values were interpreted using a model of anisotropic reorientation of a rigid body with superimposed internal motions of the flexible N-methyl, N-methyl-allyl and N-methyl-cyclopropyl fragments. The calculated internal motional rates were found to markedly decrease on passing from agonists to mixed (nalorphine) and pure (naloxone, naltrexone) antagonists. For these latter the observed trend of the internal flexibility about NC and CC bonds of the N-substituents is discussed in terms of a correlation with their relative antagonistic potencies. In fact, such an evidence of decreasing internal conformational dynamics in the order nalorphine, naloxone, naltrexone, appeared interestingly in line with the "two-state" model of opiate receptor operation mode proposed by Snyder.

  3. Magnetic field induced anisotropy of 139La spin-lattice relaxation rates in stripe ordered La1.875Ba0.125CuO4

    SciTech Connect

    S. -H. Baek; Gu, G. D.; Utz, Y.; Hucker, M.; Buchner, B.; Grafe, H. -J.

    2015-10-26

    We report 139La nuclear magnetic resonance studies performed on a La1.875Ba0.125CuO4 single crystal. The data show that the structural phase transitions (high-temperature tetragonal → low-temperature orthorhombic → low-temperature tetragonal phase) are of the displacive type in this material. The 139La spin-lattice relaxation rate T–11 sharply upturns at the charge-ordering temperature TCO = 54 K, indicating that charge order triggers the slowing down of spin fluctuations. Detailed temperature and field dependencies of the T–11 below the spin-ordering temperature TSO=40 K reveal the development of enhanced spin fluctuations in the spin-ordered state for H ∥ [001], which are completely suppressed for large fields along the CuO2 planes. Lastly, our results shed light on the unusual spin fluctuations in the charge and spin stripe ordered lanthanum cuprates.

  4. A general model to calculate the spin-lattice (T1) relaxation time of blood, accounting for haematocrit, oxygen saturation and magnetic field strength.

    PubMed

    Hales, Patrick W; Kirkham, Fenella J; Clark, Christopher A

    2016-02-01

    Many MRI techniques require prior knowledge of the T1-relaxation time of blood (T1bl). An assumed/fixed value is often used; however, T1bl is sensitive to magnetic field (B0), haematocrit (Hct), and oxygen saturation (Y). We aimed to combine data from previous in vitro measurements into a mathematical model, to estimate T1bl as a function of B0, Hct, and Y. The model was shown to predict T1bl from in vivo studies with a good accuracy (± 87 ms). This model allows for improved estimation of T1bl between 1.5-7.0 T while accounting for variations in Hct and Y, leading to improved accuracy of MRI-derived perfusion measurements.

  5. Effect of H bond removal and changes in the position of the iron-sulphur head domain on the spin-lattice relaxation properties of the [2Fe-2S](2+) Rieske cluster in cytochrome bc(1).

    PubMed

    Sarewicz, Marcin; Dutka, Małgorzata; Pietras, Rafał; Borek, Arkadiusz; Osyczka, Artur

    2015-10-14

    Here, comparative electron spin-lattice relaxation studies of the 2Fe-2S iron-sulphur (Fe-S) cluster embedded in a large membrane protein complex - cytochrome bc1 - are reported. Structural modifications of the local environment alone (mutations S158A and Y160W removing specific H bonds between Fe-S and amino acid side chains) or in combination with changes in global protein conformation (mutations/inhibitors changing the position of the Fe-S binding domain within the protein complex) resulted in different redox potentials as well as g-, g-strain and the relaxation rates (T1(-1)) for the Fe-S cluster. The relaxation rates for T < 25 K were measured directly by inversion recovery, while for T > 60 K they were deduced from simulation of continuous wave EPR spectra of the cluster using a model that included anisotropy of Lorentzian broadening. In all cases, the relaxation rate involved contributions from direct, second-order Raman and Orbach processes, each dominating over different temperature ranges. The analysis of T1(-1) (T) over the range 5-120 K yielded the values of the Orbach energy (EOrb), Debye temperature θD and Raman process efficiency CRam for each variant of the protein. As the Orbach energy was generally higher for mutants S158A and Y160W, compared to wild-type protein (WT), it is suggested that H bond removal influences the geometry leading to increased strength of antiferromagnetic coupling between two Fe ions of the cluster. While θD was similar for all variants (∼107 K), the efficiency of the Raman process generally depends on the spin-orbit coupling that is lower for S158A and Y160W mutants, when compared to the WT. However, in several cases CRam did not only correlate with spin-orbit coupling but was also influenced by other factors - possibly the modification of protein rigidity and therefore the vibrational modes around the Fe-S cluster that change upon the movement of the iron-sulphur head domain.

  6. Molecular organization of cytochrome c2 near the binding domain of cytochrome bc1 studied by electron spin-lattice relaxation enhancement.

    PubMed

    Pietras, Rafał; Sarewicz, Marcin; Osyczka, Artur

    2014-06-19

    Measurements of specific interactions between proteins are challenging. In redox systems, interactions involve surfaces near the attachment sites of cofactors engaged in interprotein electron transfer (ET). Here we analyzed binding of cytochrome c2 to cytochrome bc1 by measuring paramagnetic relaxation enhancement (PRE) of spin label (SL) attached to cytochrome c2. PRE was exclusively induced by the iron atom of heme c1 of cytochrome bc1, which guaranteed that only the configurations with SL to heme c1 distances up to ∼30 Å were detected. Changes in PRE were used to qualitatively and quantitatively characterize the binding. Our data suggest that at low ionic strength and under an excess of cytochrome c2 over cytochrome bc1, several cytochrome c2 molecules gather near the binding domain forming a "cloud" of molecules. When the cytochrome bc1 concentration increases, the cloud disperses to populate additional available binding domains. An increase in ionic strength weakens the attractive forces and the average distance between cytochrome c2 and cytochrome bc1 increases. The spatial arrangement of the protein complex at various ionic strengths is different. Above 150 mM NaCl the lifetime of the complexes becomes so short that they are undetectable. All together the results indicate that cytochrome c2 molecules, over the range of salt concentration encompassing physiological ionic strength, do not form stable, long-lived complexes but rather constantly collide with the surface of cytochrome bc1 and ET takes place coincidentally with one of these collisions.

  7. Measurement of Ligand–Target Residence Times by 1H Relaxation Dispersion NMR Spectroscopy

    PubMed Central

    2016-01-01

    A ligand-observed 1H NMR relaxation experiment is introduced for measuring the binding kinetics of low-molecular-weight compounds to their biomolecular targets. We show that this approach, which does not require any isotope labeling, is applicable to ligand–target systems involving proteins and nucleic acids of variable molecular size. The experiment is particularly useful for the systematic investigation of low affinity molecules with residence times in the micro- to millisecond time regime. PMID:27933946

  8. SPILADY: A parallel CPU and GPU code for spin-lattice magnetic molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Ma, Pui-Wai; Dudarev, S. L.; Woo, C. H.

    2016-10-01

    Spin-lattice dynamics generalizes molecular dynamics to magnetic materials, where dynamic variables describing an evolving atomic system include not only coordinates and velocities of atoms but also directions and magnitudes of atomic magnetic moments (spins). Spin-lattice dynamics simulates the collective time evolution of spins and atoms, taking into account the effect of non-collinear magnetism on interatomic forces. Applications of the method include atomistic models for defects, dislocations and surfaces in magnetic materials, thermally activated diffusion of defects, magnetic phase transitions, and various magnetic and lattice relaxation phenomena. Spin-lattice dynamics retains all the capabilities of molecular dynamics, adding to them the treatment of non-collinear magnetic degrees of freedom. The spin-lattice dynamics time integration algorithm uses symplectic Suzuki-Trotter decomposition of atomic coordinate, velocity and spin evolution operators, and delivers highly accurate numerical solutions of dynamic evolution equations over extended intervals of time. The code is parallelized in coordinate and spin spaces, and is written in OpenMP C/C++ for CPU and in CUDA C/C++ for Nvidia GPU implementations. Temperatures of atoms and spins are controlled by Langevin thermostats. Conduction electrons are treated by coupling the discrete spin-lattice dynamics equations for atoms and spins to the heat transfer equation for the electrons. Worked examples include simulations of thermalization of ferromagnetic bcc iron, the dynamics of laser pulse demagnetization, and collision cascades.

  9. A subzero 1H NMR relaxation investigation of water dynamics in tomato pericarp.

    PubMed

    Foucat, Loïc; Lahaye, Marc

    2014-09-01

    (1)H NMR relaxation times (T1 and T2) were measured at low field (0.47 T) in pericarp tissues of three tomato genotypes (Ferum, LA0147 and Levovil) at subzero temperature (-20 °C) and two ripening stages (mature green and red). The unfrozen water dynamics was characterised by two T1 and three T2 components. The relaxation time values and their associated relative populations allowed differentiating the ripening stage of only LA0147 and Levovil lines. But the three genotypes were unequivocally discriminated at the red ripe stage. The unfrozen water distribution was discussed in terms of specific interactions, especially with sugars, in relation with their osmoprotectant effects.

  10. (1)H-(14)N cross-relaxation spectrum analysis in sildenafil and sildenafil citrate.

    PubMed

    Gregorovič, Alan; Apih, Tomaž; Seliger, Janez

    2016-09-01

    Here we describe a method for the extraction of (14)N quadrupole parameters from a (1)H-(14)N cross-relaxation spectrum by fitting the lineshapes of the (14)N quadrupole transitions. The procedures used typically to fit quadrupole lineshapes are not directly applicable to fit the (1)H-(14)N cross-relaxation spectrum, because the presence of proton homonuclear dipolar interaction broadens the lineshapes considerably and prevents a reliable determination of Cq and η from a single lineshape. Instead, one must fit two or even three lineshapes originating from the same nitrogen site simultaneously. The problem is to identify which lineshapes belong together when many are observed due to the existence of several nitrogen sites. We solve this problem by fitting the spectrum for all possible combinations and find the best-fitting one. This combination then most likely correctly identifies lineshapes belonging to the same nitrogen site. There are two main advantages of our method compared to the typically used method, which relies only on lineshape singularities: (i) the method is "automatic" and does not require knowledge of nitrogen quadrupole parameters in similar environments to aid dip pairing and (ii) the accuracy of quadrupole parameters is better, as proton linewidth is included in the fits. We use sildenafil and sildenafil citrate as model compounds, each with six non-equivalent nitrogen sites.

  11. 1H NMR study of the phase transitions of trissarcosine calcium chloride single crystals at low temperature

    NASA Astrophysics Data System (ADS)

    Lee, Kyuhong; Lee, Moohee; Lee, Kwang Sei; Lim, Ae Ran

    2005-10-01

    The 1H NMR line-width and spin lattice relaxation time T1 of TSCC single crystals were studied. Variations in the temperature dependence of the spin lattice relaxation time were observed near 65 and 130 K, indicating drastic alterations of the spin dynamics at the phase transition temperatures. The changes in the temperature dependence of T1 near 65 and 130 K correspond to phase transitions of the crystal. The anomalous decrease in T1 around 130 K is due to the critical slowing down of the soft mode. The abrupt change in relaxation time at 65 K is associated with a structural phase transition. The proton spin lattice relaxation time of this crystal also has a minimum value in the vicinity of 185 K, which is governed by the reorientation of the CH3 groups of the sarcosine molecules. From this result, we conclude that the two phase transitions at 65 and 130 K can be discerned from abrupt variations in the 1H NMR relaxation behavior, and that 1H nuclei play important roles in the phase transitions of the TSCC single crystal.

  12. Translational diffusion in paramagnetic liquids by 1H NMR relaxometry: nitroxide radicals in solution.

    PubMed

    Kruk, D; Korpała, A; Kubica, A; Meier, R; Rössler, E A; Moscicki, J

    2013-01-14

    For nitroxide radicals in solution one can identify three frequency regimes in which (1)H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the (1)H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)] with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for (14)N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to (15)N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)]). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of (1)H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data-(1)H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of (14)N and (15)N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in (1)H resonance frequency, 10 kHz-20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.

  13. Translational diffusion in paramagnetic liquids by 1H NMR relaxometry: Nitroxide radicals in solution

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Korpała, A.; Kubica, A.; Meier, R.; Rössler, E. A.; Moscicki, J.

    2013-01-01

    For nitroxide radicals in solution one can identify three frequency regimes in which 1H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the 1H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854 with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for 14N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to 15N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)], 10.1021/jp980397h). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of 1H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data—1H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of 14N and 15N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in 1H resonance frequency, 10 kHz-20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.

  14. Measurement of T1/T2 relaxation times in overlapped regions from homodecoupled 1H singlet signals

    NASA Astrophysics Data System (ADS)

    Castañar, Laura; Nolis, Pau; Virgili, Albert; Parella, Teodor

    2014-07-01

    The implementation of the HOmodecoupled Band-Selective (HOBS) technique in the conventional Inversion-Recovery and CPMG-based PROJECT experiments is described. The achievement of fully homodecoupled signals allows the distinction of overlapped 1H resonances with small chemical shift differences. It is shown that the corresponding T1 and T2 relaxation times can be individually measured from the resulting singlet lines using conventional exponential curve-fitting methods.

  15. Dipolar cross-relaxation modulates signal amplitudes in the 1H NMR spectrum of hyperpolarized [ 13C]formate

    NASA Astrophysics Data System (ADS)

    Merritt, Matthew E.; Harrison, Crystal; Mander, William; Malloy, Craig R.; Dean Sherry, A.

    2007-12-01

    The asymmetry in the doublet of a spin coupled to hyperpolarized 13C has been used previously to measure the initial polarization of 13C. We tested the hypothesis that a single observation of the 1H NMR spectrum of hyperpolarized 13C formate monitors 13C polarization. Depending on the microwave frequency during the polarization process, in-phase or out-of-phase doublets were observed in the 1H NMR spectrum. Even in this simple two-spin system, 13C polarization was not reflected in the relative area of the JCH doublet components due to strong heteronuclear cross-relaxation. The Solomon equations were used to model the proton signal as a function of time after polarization and to estimate 13C polarization from the 1H NMR spectra.

  16. Electronic states and molecular dynamics of single-component molecular conductors [M (tmdt) 2] (M =Ni , Pt) studied by 13C and 1H NMR

    NASA Astrophysics Data System (ADS)

    Takagi, Rina; Miyagawa, Kazuya; Yoshimura, Masahide; Gangi, Hiro; Kanoda, Kazushi; Zhou, Biao; Idobata, Yuki; Kobayashi, Akiko

    2016-01-01

    The molecular conductors [M(tmdt) 2] (M =Ni , Pt) consisting of single molecular species are investigated with 13C NMR and 1H NMR. The temperature dependences of the 13C NMR shift and relaxation rate provide microscopic evidence for the metallic nature with appreciable electron correlations. Both compounds exhibit an anomalous frequency-dependent enhancement in the 1H nuclear spin-lattice relaxation rate in a wide temperature range. These observations signify the presence of extraordinary molecular motions with low energy excitations.

  17. Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements.

    PubMed

    Pham, Tran N; Watson, Simon A; Edwards, Andrew J; Chavda, Manisha; Clawson, Jacalyn S; Strohmeier, Mark; Vogt, Frederick G

    2010-10-04

    Solid-state NMR (SSNMR) can provide detailed structural information about amorphous solid dispersions of pharmaceutical small molecules. In this study, the ability of SSNMR experiments based on dipolar correlation, spin diffusion, and relaxation measurements to characterize the structure of solid dispersions is explored. Observation of spin diffusion effects using the 2D (1)H-(13)C cross-polarization heteronuclear correlation (CP-HETCOR) experiment is shown to be a useful probe of association between the amorphous drug and polymer that is capable of directly proving glass solution formation. Dispersions of acetaminophen and indomethacin in different polymers are examined using this approach, as well as (1)H double-quantum correlation experiments to probe additional structural features. (1)H-(19)F CP-HETCOR serves a similar role for fluorinated drug molecules such as diflunisal in dispersions, providing a rapid means to prove the formation of a glass solution. Phase separation is detected using (13)C, (19)F, and (23)Na-detected (1)H T(1) experiments in crystalline and amorphous solid dispersions that contain small domains. (1)H T(1) measurements of amorphous nanosuspensions of trehalose and dextran illustrate the ability of SSNMR to detect domain size effects in dispersions that are not glass solutions via spin diffusion effects. Two previously unreported amorphous solid dispersions involving up to three components and containing voriconazole and telithromycin are analyzed using these experiments to demonstrate the general applicability of the approach.

  18. 7Li relaxation time measurements at very low magnetic field by 1H dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Zeghib, Nadir; Grucker, Daniel

    2001-09-01

    Dynamic nuclear polarization (DNP) of water protons was used to measure the relaxation time of lithium at very low magnetic field as a demonstration of the use of DNP for nuclei less abundant than water protons. Lithium (Li+) was chosen because it is an efficient treatment for manic-depressive illness, with an unknown action mechanism. After having recalled the theoretical basis of a three-spin system comprising two nuclei - the water proton of the solvent, the dissolved Li+ ion and the free electron of a free radical - we have developed a transient solution in order to optimize potential biological applications of Li DNP. The three-spin model has allowed computation of all the parameters of the system - the longitudinal relaxation rate per unit of free radical concentration, the dipolar and scalar part of the coupling between the nuclei and the electron, and the maximum signal enhancement achievable for both proton and lithium spins. All these measurements have been obtained solely through the detection of the proton resonance.

  19. 1H NMR relaxation of water: a probe for surfactant adsorption on kaolin.

    PubMed

    Totland, Christian; Lewis, Rhiannon T; Nerdal, Willy

    2011-11-01

    In this study, (1)H NMR is used to investigate properties of sodium dodecyl sulfate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), and dodecyl trimethyl ammonium bromide (DTAB) adsorbed on kaolin by NMR T(1) and T(2) measurements of the water proton resonance. The results show that adsorbed surfactants form a barrier between sample water and the paramagnetic species present on the clay surface, thus significantly increasing the proton T(1) values of water. This effect is attributed to the amount of adsorbed surfactants and the arrangement of the surfactant aggregates. The total surface area covered by the cationic (DTAB and TTAB) and anionic (SDS) surfactants could be estimated from the water T(1) data and found to correspond to the fractions of negatively and positively charged surface area, respectively. For selected samples, the amount of paramagnetic species on the clay surface was reduced by treatment with hydrofluoric (HF) acid. For these samples, T(1) and T(2) measurements were taken in the temperature range 278-338 K, revealing detailed information on molecular mobility and nuclear exchange for the sample water that is related to surfactant behavior both on the surface and in the aqueous phase.

  20. Magnetic hyperthermia efficiency and 1H-NMR relaxation properties of iron oxide/paclitaxel-loaded PLGA nanoparticles

    NASA Astrophysics Data System (ADS)

    Ruggiero, Maria R.; Geninatti Crich, Simonetta; Sieni, Elisabetta; Sgarbossa, Paolo; Forzan, Michele; Cavallari, Eleonora; Stefania, Rachele; Dughiero, Fabrizio; Aime, Silvio

    2016-07-01

    Magnetic iron oxide nanoparticles (Fe-NPs) can be exploited in biomedicine as agents for magnetic fluid hyperthermia (MFH) treatments and as contrast enhancers in magnetic resonance imaging. New, oleate-covered, iron oxide particles have been prepared either by co-precipitation or thermal decomposition methods and incorporated into poly(lactic-co-glycolic acid) nanoparticles (PLGA-Fe-NPs) to improve their biocompatibility and in vivo stability. Moreover, the PLGA-Fe-NPs have been loaded with paclitaxel to pursue an MFH-triggered drug release. Remarkably, it has been found that the nanoparticle formulations are characterized by peculiar 1H nuclear magnetic relaxation dispersion (NMRD) profiles that directly correlate with their heating potential when exposed to an alternating magnetic field. By prolonging the magnetic field exposure to 30 min, a significant drug release was observed for PLGA-Fe-NPs in the case of the larger-sized magnetic nanoparticles. Furthermore, the immobilization of lipophilic Fe-NPs in PLGA-NPs also made it possible to maintain Néel relaxation as the dominant relaxation contribution in the presence of large iron oxide cores (diameters of 15-20 nm), with the advantage of preserving their efficiency when they are entrapped in the intracellular environment. The results reported herein show that NMRD profiles are a useful tool for anticipating the heating capabilities of Fe-NPs designed for MFH applications.

  1. 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

  2. Spin-lattice coupling in molecular dynamics simulation of ferromagnetic iron

    NASA Astrophysics Data System (ADS)

    Ma, Pui Wai

    A model for magnetic iron where atoms are treated as classical particles with intrinsic spins is developed. The atoms interact via scalar many-body forces as well as via spin-dependent forces of the Heisenberg form. The coupling between the lattice and spin degrees of freedom is described by a coordinate-dependent exchange function, where the spin-orientation-dependent forces are proportional to the gradient of this function. A spin-lattice dynamics simulation approach extends the existing magnetic-potential treatment to the case where the strength of interaction between the atoms depends on the relative non-collinear orientations of their spins. An algorithm for integrating the linked spin-coordinate equations of motion is based on the 2nd order Suzuki-Trotter decomposition for the non-commuting evolution operators for both coordinates and spins. The notions of the spin thermostat and the spin temperature are introduced through the combined application of the Langevin spin dynamics and the fluctuation-dissipation theorem. We investigate several applications of the method, performing microcanonical ensemble simulations of adiabatic spin-lattice relaxation of periodic arrays of 180° domain-walls, and isothermal-isobaric ensemble dynamical simulations of thermally equilibrated homogeneous systems at various temperatures. The isothermal magnetization curve evaluated using the spin-lattice dynamics algorithm is well described by the mean-field approximation and agrees satisfactorily with the experimental data for a broad range of temperatures. The equilibrium time-correlation functions of spin orientations exhibit the presence of short-range magnetic order above the Curie temperature. Short-range order spin fluctuations are shown to contribute to the thermal expansion of the material. Simulations on thermal expansion and elastic response of bulk bcc iron, and magnetization in bcc iron thin films are also performed and the results discussed. Our analysis illustrates

  3. Imazalil-cyclomaltoheptaose (beta-cyclodextrin) inclusion complex: preparation by supercritical carbon dioxide and 13C CPMAS and 1H NMR characterization.

    PubMed

    Lai, Simona; Locci, Emanuela; Piras, Alessandra; Porcedda, Silvia; Lai, Adolfo; Marongiu, Bruno

    2003-10-10

    An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (beta-cyclodextrin, betaCD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the betaCD/IMZ complex was obtained from ROESY spectroscopy, while the dynamics of the inclusion complex in the kilohertz range was obtained from the proton spin-lattice relaxation times in the rotating frame, T(1rho) (1H).

  4. Spin-Lattice Coupling and Superconductivity in Fe Pnictides

    DOE PAGES

    Egami, T.; Fine, B. V.; Parshall, D.; ...

    2010-01-01

    We consider strong spin-lattice and spin-phonon coupling in iron pnictides and discuss its implications on superconductivity. Strong magneto-volume effect in iron compounds has long been known as the Invar effect. Fe pnictides also exhibit this effect, reflected in particular on the dependence of the magnetic moment on the atomic volume of Fe defined by the positions of the nearest neighbor atoms. Through the phenomenological Landau theory, developed on the basis of the calculations by the density functional theory (DFT) and the experimental results, we quantify the strength of the spin-lattice interaction as it relates to the Stoner criterion for themore » onset of magnetism. We suggest that the coupling between electrons and phonons through the spin channel may be sufficiently strong to be an important part of the superconductivity mechanism in Fe pnictides.« less

  5. Experimental NMR spin-lattice relaxometry study in the liquid crystalline nematic phase of propylcyano-phenylcyclohexane.

    PubMed

    Acosta, R H; Pusiol, D J

    2001-01-01

    The NMR spin-lattice proton relaxation dispersion T1(nu(L)) of the liquid crystal propylcyano-phenylcyclohexane is studied over several decades of Larmor frequencies and at different temperatures in the nematic mesophase. The results show that the order fluctuation of the local nematic director contribution to T1(nu(L)) undergoes a transition between two power regimes: from T1(nu(L)) protional to nu(1/2)L to nu(alpha)L (alpha approximately 1/3) on going from low to high Larmor frequencies.

  6. 1H NMR z-spectra of acetate methyl in stretched hydrogels: Quantum-mechanical description and Markov chain Monte Carlo relaxation-parameter estimation

    NASA Astrophysics Data System (ADS)

    Shishmarev, Dmitry; Chapman, Bogdan E.; Naumann, Christoph; Mamone, Salvatore; Kuchel, Philip W.

    2015-01-01

    The 1H NMR signal of the methyl group of sodium acetate is shown to be a triplet in the anisotropic environment of stretched gelatin gel. The multiplet structure of the signal is due to the intra-methyl residual dipolar couplings. The relaxation properties of the spin system were probed by recording steady-state irradiation envelopes ('z-spectra'). A quantum-mechanical model based on irreducible spherical tensors formed by the three magnetically equivalent spins of the methyl group was used to simulate and fit experimental z-spectra. The multiple parameter values of the relaxation model were estimated by using a Bayesian-based Markov chain Monte Carlo algorithm.

  7. NMR relaxation dispersion of vulcanized natural rubber.

    PubMed

    Kariyo, Sobiroh; Stapf, Siegfried

    2004-01-01

    The dependence of the 1H spin-lattice relaxation time on the magnetic field strength has been determined for linear and cross-linked polyisoprene for Larmor frequencies between 5 kHz and 20 MHz. Universal power-law relations are found for all temperatures and cross-link densities under investigation and are compared to published results of rotating-frame experiments on similar natural rubber samples. The shape of the individual dispersion functions can be superposed into a master curve using appropriate shift factors. While addition of filler particles even at large weight fractions has only a minor effect on the relaxation times, uniaxial deformation and swelling are demonstrated to alter the molecular dynamics significantly.

  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. 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

  10. Cross relaxation in nitroxide spin labels

    NASA Astrophysics Data System (ADS)

    Marsh, Derek

    2016-11-01

    Cross relaxation, and mI -dependence of the intrinsic electron spin-lattice relaxation rate We , are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We , the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI -dependent.

  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.

  12. Separation of Anisotropy and Exchange Broadening Using 15N CSA- 15N- 1H Dipole-Dipole Relaxation Cross-Correlation Experiments

    NASA Astrophysics Data System (ADS)

    Renner, Christian; Holak, Tad A.

    2000-08-01

    Based on the measurement of cross-correlation rates between 15N CSA and 15N-1H dipole-dipole relaxation we propose a procedure for separating exchange contributions to transverse relaxation rates (R2 = 1/T2) from effects caused by anisotropic rotational diffusion of the protein molecule. This approach determines the influence of anisotropy and chemical exchange processes independently and therefore circumvents difficulties associated with the currently standard use of T1/T2 ratios to determine the rotational diffusion tensor. We find from computer simulations that, in the presence of even small amounts of internal flexibility, fitting T1/T2 ratios tends to underestimate the anisotropy of overall tumbling. An additional problem exists when the N-H bond vector directions are not distributed homogeneously over the surface of a unit sphere, such as in helix bundles or β-sheets. Such a case was found in segment 4 of the gelation factor (ABP 120), an F-actin cross-linking protein, in which the diffusion tensor cannot be calculated from T1/T2 ratios. The 15N CSA tensor of the residues for this β-sheet protein was found to vary even within secondary structure elements. The use of a common value for the whole protein molecule therefore might be an oversimplification. Using our approach it is immediately apparent that no exchange broadening exists for segment 4 although strongly reduced T2 relaxation times for several residues could be mistaken as indications for exchange processes.

  13. Investigation of local symmetry in LiH3(SeO3)2 single crystals by 1H and 7Li nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2013-10-01

    The local environments of 1H and 7Li nuclei in LiH3(SeO3)2 crystals were investigated using FT NMR. The 7Li spectrum does changes from three resonance lines to one resonance line near Tm (=383 K). The variation in the splitting of the 7Li resonance lines with temperature indicates that the EFG at the Li sites produced by the (SeO3)2- groups varies with temperature. The changes in the temperature dependence of the intensity, line width, and spin-lattice relaxation time T1 near Tm for the 1H and 7Li nuclei coincide with the distortion of the structural framework surrounding each 1H and 7Li ion. Finally, the NMR results obtained here are compared to MH3(SeO3)2 (M = Na, K, and Cs) crystals previously reported.

  14. 13C-CPMAS and 1H-NMR study of the inclusion complexes of beta-cyclodextrin with carvacrol, thymol, and eugenol prepared in supercritical carbon dioxide.

    PubMed

    Locci, Emanuela; Lai, Simona; Piras, Alessandra; Marongiu, Bruno; Lai, Adolfo

    2004-09-01

    Beta-cyclodextrin (beta-CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (components of essential oils of vegetable origin) were prepared by the supercritical CO2 technique, and their structural characterization was achieved by means of 1H-NMR in aqueous solution and 13C-CPMAS NMR in the solid state. Evidence of the formation of the inclusion complexes for all the examined systems was obtained by 1H-NMR in solution, while 2D-ROESY-NMR experiments were used to investigate the geometry of inclusion. In addition, the dynamics of these inclusion complexes in the kHz timescale was investigated by analysis of the 1H and 13C spin-lattice relaxation times in the rotating frame.

  15. Self-Assembly of Peptide Amphiphiles Designed as Imaging Probes for 19F and Relaxation-Enhanced 1H imaging

    NASA Astrophysics Data System (ADS)

    Preslar, Adam Truett

    This work incorporates whole-body imaging functionality into peptide amphiphile (PA) nanostructures used for regenerative medicine to facilitate magnetic resonance imaging (MRI). Two strategies were employed: 1. Conjugation of gadolinium chelates to peptide nanostructures to monitor biomaterial degradation in vivo with MRI and inductively-coupled plasma-mass spectroscopy (ICP-MS) 2. Synthesis of perfluorinated moiety-bearing peptide amphiphiles for 19F-MRI. The Gd(III) chelate gadoteridol was conjugated by copper-catalyzed "click" chemistry to a series of PAs known to form cylindrical nanostructures. By fitting nuclear magnetic resonance dispersion (NMRD) profiles to the Solomon-Bloembergen-Morgan (SBM) equations, it was observed that the water exchange parameter (tauM) depended on thermal annealing or calcium ion cross-linking. The sequence C16V 3A3E3G(Gd) exhibited an acceleration of nearly 100 ns after thermal annealing and calcium addition. These gadolinium-labeled PAs were used to track in vivo degradation of gels within the tibialis anterior muscle in a murine model. The half-life of biomaterial degradation was determined to be 13.5 days by inductively coupled plasma mass spectrometry (ICP-MS) of Gd(III). Gel implants could be monitored by MRI for eight days before the signal dispersed due to implant degradation and dilution. Additionally, nanostructures incorporating highly fluorinated domains were investigated for use as MRI contrast agents. Short, perfluoroalkyane tails of seven or eight carbon atoms in length were grafted to PA sequences containing a V2A2 beta-sheet forming sequence. The V2A2 sequence is known to drive 1D nanostructure assembly. It was found that the sequences C7F13V2A 2E2 and C7F13V2A 2K3 formed 1D assemblies in water which transition from ribbon-like to cylindrical shape as pH increases from 4.5 to 8.0. Ribbon-like nanostructures had reduced magnetic resonance signal by T 2 relaxation quenching, whereas their cylindrical counterparts

  16. Spin-lattice distribution MRI maps nigral pathology in progressive supranuclear palsy (PSP) during life: a pilot study.

    PubMed

    Hutchinson, Michael; Raff, Ulrich; Chaná, Pedro; Huete, Isidro

    2014-01-01

    An MRI biomarker for Parkinsonism has long been sought, but almost all attempts at conventional field strengths have proved unsatisfactory, since patients and controls are not separated. The exception is Spin-Lattice Distribution MRI (SLD-MRI), a technique which detects changes in the substantia nigra (SN) due to changes in the spin-lattice relaxation time, T1. This easily separates patients with Parkinson's disease (PD) from control subjects at 1.5 Tesla, suggesting that it may be sensitive to presymptomatic disease. SLD-MRI demonstrates a topography of signal change within the SN which is the same as the known topography of pathological change, where the lateral portions of the nucleus are more affected than the medial. In a further step towards its validation, we apply SLD-MRI to a disease control, Progressive Supranuclear Palsy (PSP), the most common of the atypical forms of Parkinsonism. In PSP the topography of pathological change in the SN is reversed. We therefore hypothesized that PSP would show a topography of SLD-MRI signal change in the SN that is the reverse of PD (i.e. the medial portion is more affected than the lateral). All 7 patients showed such a topography of MR signal, and all patients were separated from control subjects. Although this is a step toward validation of SLD-MRI with respect to sensitivity and disease specificity, nevertheless we stress that this is a pilot project only. Validation will only be possible when comparing larger cohorts of PSP, PD and control subjects.

  17. THz-Driven Ultrafast Spin-Lattice Scattering in Amorphous Metallic Ferromagnets

    NASA Astrophysics Data System (ADS)

    Bonetti, S.; Hoffmann, M. C.; Sher, M.-J.; Chen, Z.; Yang, S.-H.; Samant, M. G.; Parkin, S. S. P.; Dürr, H. A.

    2016-08-01

    We use single-cycle THz fields and the femtosecond magneto-optical Kerr effect to, respectively, excite and probe the magnetization dynamics in two thin-film ferromagnets with different lattice structures: crystalline Fe and amorphous CoFeB. We observe Landau-Lifshitz-torque magnetization dynamics of comparable magnitude in both systems, but only the amorphous sample shows ultrafast demagnetization caused by the spin-lattice depolarization of the THz-induced ultrafast spin current. Quantitative modeling shows that such spin-lattice scattering events occur on similar time scales than the conventional spin conserving electronic scattering (˜30 fs ). This is significantly faster than optical laser-induced demagnetization. THz conductivity measurements point towards the influence of lattice disorder in amorphous CoFeB as the driving force for enhanced spin-lattice scattering.

  18. Conformational distribution of baclofen analogues by 1H and 13C NMR analysis and ab initio HF MO STO-3G or STO-3G* calculations

    NASA Astrophysics Data System (ADS)

    Vaccher, Claude; Berthelot, Pascal; Debaert, Michel; Vermeersch, Gaston; Guyon, René; Pirard, Bernard; Vercauteren, Daniel P.; Dory, Magdalena; Evrard, Guy; Durant, François

    1993-12-01

    The conformations of 3-(substituted furan-2-yl) and 3-(substituted thien-2-yl)-γ-aminobutyric acid 1-9 in solution (D 2O) are estimated from high-resolution (300 MHz) 1H NMR coupling data. Conformations and populations of conformers are calculated by means of a modified Karplus-like relationship for the vicinal coupling constants. The results are compared with X-ray crystallographic investigations (torsion angles) and ab initio HF MO ST-3G or STO-3G* calculations. 1H NMR spectral analysis shows how 1-9 in solution retain the preferred g- conformation around the C3C4 bond, as found in the solid state, while a partial rotation is set up around the C2C3 bond: the conformations about C2C3 are all highly populated in solution. The 13C spin-lattice relaxation times are also discussed.

  19. Efficiency of free-energy calculations of spin lattices by spectral quantum algorithms

    SciTech Connect

    Master, Cyrus P.; Yamaguchi, Fumiko; Yamamoto, Yoshihisa

    2003-03-01

    Ensemble quantum algorithms are well suited to calculate estimates of the energy spectra for spin-lattice systems. Based on the phase estimation algorithm, these algorithms efficiently estimate discrete Fourier coefficients of the density of states. Their efficiency in calculating the free energy per spin of general spin lattices to bounded error is examined. We find that the number of Fourier components required to bound the error in the free energy due to the broadening of the density of states scales polynomially with the number of spins in the lattice. However, the precision with which the Fourier components must be calculated is found to be an exponential function of the system size.

  20. High-field 1H T1 and T2 NMR relaxation time measurements of H2O in homeopathic preparations of quartz, sulfur, and copper sulfate

    NASA Astrophysics Data System (ADS)

    Baumgartner, Stephan; Wolf, Martin; Skrabal, Peter; Bangerter, Felix; Heusser, Peter; Thurneysen, André; Wolf, Ursula

    2009-09-01

    Quantitative meta-analyses of randomized clinical trials investigating the specific therapeutic efficacy of homeopathic remedies yielded statistically significant differences compared to placebo. Since the remedies used contained mostly only very low concentrations of pharmacologically active compounds, these effects cannot be accounted for within the framework of current pharmacology. Theories to explain clinical effects of homeopathic remedies are partially based upon changes in diluent structure. To investigate the latter, we measured for the first time high-field (600/500 MHz) 1H T1 and T2 nuclear magnetic resonance relaxation times of H2O in homeopathic preparations with concurrent contamination control by inductively coupled plasma mass spectrometry (ICP-MS). Homeopathic preparations of quartz (10 c-30 c, n = 21, corresponding to iterative dilutions of 100-10-100-30), sulfur (13 x-30 x, n = 18, 10-13-10-30), and copper sulfate (11 c-30 c, n = 20, 100-11-100-30) were compared to n = 10 independent controls each (analogously agitated dilution medium) in randomized and blinded experiments. In none of the samples, the concentration of any element analyzed by ICP-MS exceeded 10 ppb. In the first measurement series (600 MHz), there was a significant increase in T1 for all samples as a function of time, and there were no significant differences between homeopathic potencies and controls. In the second measurement series (500 MHz) 1 year after preparation, we observed statistically significant increased T1 relaxation times for homeopathic sulfur preparations compared to controls. Fifteen out of 18 correlations between sample triplicates were higher for controls than for homeopathic preparations. No conclusive explanation for these phenomena can be given at present. Possible hypotheses involve differential leaching from the measurement vessel walls or a change in water molecule dynamics, i.e., in rotational correlation time and/or diffusion. Homeopathic preparations

  1. 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.

  2. Mn2+ complexes with 12-membered pyridine based macrocycles bearing carboxylate or phosphonate pendant arm: crystallographic, thermodynamic, kinetic, redox, and 1H/17O relaxation studies.

    PubMed

    Drahoš, Bohuslav; Kotek, Jan; Císařová, Ivana; Hermann, Petr; Helm, Lothar; Lukeš, Ivan; Tóth, Éva

    2011-12-19

    potentials (E(ox) = 0.73 V for MnL(1) and E(ox) = 0.68 V for MnL(2)), in accordance with air-oxidation. The parameters governing the relaxivity of the Mn(2+) complexes were determined from variable-temperature (17)O NMR and (1)H NMRD data. The water exchange is extremely fast, k(ex) = 3.03 and 1.77 × 10(9) s(-1) for MnL(1) and MnL(2), respectively. Variable-pressure (17)O NMR measurements have been performed to assess the water exchange mechanism on MnL(1) and MnL(2) as well as on other Mn(2+) complexes. The negative activation volumes for both MnL(1) and MnL(2) complexes confirmed an associative mechanism of the water exchange as expected for a hexacoordinated Mn(2+) ion. The hydration number of q = 1 was confirmed for both complexes by (17)O chemical shifts. A relaxometric titration with phosphate, carbonate or citrate excluded the replacement of the coordinated water molecule by these small endogenous anions.

  3. Slow molecular dynamics of water in a lyotropic complex fluid studied by deuterium conventional and spin-lattice relaxometry NMR.

    PubMed

    Rodríguez, C R; Pusiol, D J; Figueiredo Neto, A M; Seitter, R-O

    2002-03-01

    A nuclear magnetic resonance study of protons and deuterons in the mesomorphic phases of the micellar lyotropic mixture potassium laurate/1-decanol/heavy water is reported. The slow dynamical behavior of water molecules has been investigated with deuterons spin-lattice relaxation dispersion in the Larmor frequency range 10(3)

  4. Low resolution 1H NMR assignment of proton populations in pound cake and its polymeric ingredients.

    PubMed

    Luyts, A; Wilderjans, E; Waterschoot, J; Van Haesendonck, I; Brijs, K; Courtin, C M; Hills, B; Delcour, J A

    2013-08-15

    Based on a model system approach, five different proton populations were distinguished in pound cake crumb using one dimensional low resolution (1)H NMR spectroscopy. In free induction decay (FID) measurements, proton populations were assigned to (i) non-exchanging CH protons of crystalline starch, proteins and crystalline fat and (ii) non-exchanging CH protons of amorphous starch and gluten, which are in little contact with water. In Carr-Purcell-Meiboom-Gill (CPMG) measurements, three proton populations were distinguished. The CPMG population with the lowest mobility and the FID population with the highest mobility represent the same proton population. The two CPMG proton populations with the highest mobility were assigned to exchanging protons (i.e., protons of water, starch, gluten, egg proteins and sugar) and protons of lipids (i.e., protons of egg yolk lipids and amorphous lipid fraction of margarine) respectively. Based on their spin-lattice relaxation times (T1), two dimensional (1)H NMR spectroscopy further resolved the two proton populations with the highest mobility into three and two proton populations, respectively.

  5. (1)H NMR at Larmor frequencies down to 3Hz by means of Field-Cycling techniques.

    PubMed

    Kresse, B; Becher, M; Privalov, A F; Hofmann, M; Rössler, E A; Vogel, M; Fujara, F

    2017-04-01

    Field-Cycling (FC) NMR experiments were carried out at (1)H Larmor frequencies down to about 3Hz. This could be achieved by fast switching a high polarizing magnetic field down to a low evolution field which is tilted with respect to the polarization field. Then, the low frequency Larmor precession of the nuclear spin magnetization about this evolution field is registered by means of FIDs in a high detection field. The crucial technical point of the experiment is the stabilization of the evolution field, which is achieved by compensating for temporal magnetic field fluctuations of all three spatial components. The paper reports on some other basic low field experiments such as the simultaneous measurement of the Larmor frequency and the spin-lattice relaxation time in such small fields as well as the irradiation of oscillating transversal magnetic field pulses at very low frequencies as a novel method for field calibration in low field FC NMR. The potential of low field FC is exemplified by the (1)H relaxation dispersion of water at frequencies below about 2kHz stemming from the slow proton exchange process.

  6. Dynamic structures of intact chicken erythrocyte chromatins as studied by 1H-31P cross-polarization NMR.

    PubMed Central

    Akutsu, H; Nishimoto, S; Kyogoku, Y

    1994-01-01

    The dynamic properties of DNA in intact chicken erythrocyte cells, nuclei, nondigested chromatins, digested soluble chromatins, H1, H5-depleted soluble chromatins and nucleosome cores were investigated by means of single-pulse and 1H-31P cross-polarization NMR. The temperature dependence of the phosphorus chemical shift anisotropy was identical for the former three in the presence of 3 mM MgCl2, suggesting that the local higher order structure is identical for these chromatins. The intrinsic phosphorus chemical shift anisotropy of the nucleosome cores was -159 ppm. The chemical shift anisotropy of DNA in the chromatins can be further averaged by the motion of the linker DNA. The spin-lattice relaxation time in the rotating frame of the proton spins (T1p) of the nondigested chromatins was measured at various locking fields. The result was analyzed on the assumption of the isotropic motion to get a rough value of the correlation time of the motion efficient for the relaxation, which was eventually ascribed to the segmental motion of the linker DNA with restricted amplitude. The 30 nm filament structure induced by NaCl was shown to be dynamically different from that induced by MgCl2. Side-by-side compaction of 30-nm filaments was suggested to be induced in the MgCl2 concentration range higher than 0.3 mM. Biological significance of the dynamic structure was discussed in connection with the results obtained. PMID:7948693

  7. Pressure-induced superconductivity in the antiferromagnet κ - (ET) 2C F3S O3 with quasi-one-dimensional triangular spin lattice

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Asai, Takayuki; Shimizu, Yasuhiro; Hayama, Hiromi; Yoshida, Yukihiro; Saito, Gunzi

    2016-07-01

    We report an antiferromagnetic (AF) ordering at ambient pressure and a superconducting transition under pressure for κ - (ET) 2C F3S O3 [ ET =bis (ethylenedithio)tetrathiafulvalene], which has a two-dimensional electronic system with quasi-one-dimensional triangular spin lattice. At ambient pressure, AF ordering was detected at TN=2.5 K by 1H NMR, subsequent to two structural phase transitions at 230 and 190 K. Under hydrostatic pressures, metallic behavior appeared above ˜1.1 GPa, and a superconducting transition (maximum onset Tc=4.8 K at ˜1.3 GPa) was observed up to 2.2 GPa. Superconductivity was also found under c -axis strain, which reduced t'/t , but was absent under b -axis strain which increased t'/t .

  8. Spin-Lattice-Coupled Order in Heisenberg Antiferromagnets on the Pyrochlore Lattice.

    PubMed

    Aoyama, Kazushi; Kawamura, Hikaru

    2016-06-24

    Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at the stronger SLC is cubic symmetric characterized by the magnetic (1/2,1/2,1/2) Bragg peaks, while that at the weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed.

  9. Spin-Lattice-Coupled Order in Heisenberg Antiferromagnets on the Pyrochlore Lattice

    NASA Astrophysics Data System (ADS)

    Aoyama, Kazushi; Kawamura, Hikaru

    2016-06-01

    Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at the stronger SLC is cubic symmetric characterized by the magnetic (1/2 ,1/2 ,1/2 ) Bragg peaks, while that at the weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed.

  10. Change of translational-rotational coupling in liquids revealed by field-cycling 1H NMR

    NASA Astrophysics Data System (ADS)

    Meier, R.; Schneider, E.; Rössler, E. A.

    2015-01-01

    Applying the field-cycling nuclear magnetic resonance technique, the frequency dependence of the 1H spin-lattice relaxation rate, R 1 ω = T1 - 1 ω , is measured for propylene glycol (PG) which is increasingly diluted with deuterated chloroform. A frequency range of 10 kHz-20 MHz and a broad temperature interval from 220 to about 100 K are covered. The results are compared to those of experiments, where glycerol and o-terphenyl are diluted with their deuterated counter-part. Reflecting intra- as well as intermolecular relaxation, the dispersion curves R 1 ω , x (x denotes mole fraction PG) allow to extract the rotational time constant τrot(T, x) and the self-diffusion coefficient D(T, x) in a single experiment. The Stokes-Einstein-Debye (SED) relation is tested in terms of the quantity D(T, x) τrot(T, x) which provides a measure of an effective hydrodynamic radius or equivalently of the spectral separation of the translational and the rotational relaxation contribution. In contrast to o-terphenyl, glycerol and PG show a spectral separation much larger than suggested by the SED relation. In the case of PG/chloroform mixtures, not only an acceleration of the PG dynamics is observed with increasing dilution but also the spectral separation of rotational and translational relaxation contributions continuously decreases. Finally, following a behavior similar to that of o-terphenyl already at about x = 0.6; i.e., while D(T, x) τrot(T, x) in the mixture is essentially temperature independent, it strongly increases with x signaling thus a change of translational-rotational coupling. This directly reflects the dissolution of the hydrogen-bond network and thus a change of solution structure.

  11. {sup 1}H NMR relaxometry and quadrupole relaxation enhancement as a sensitive probe of dynamical properties of solids—[C(NH{sub 2}){sub 3}]{sub 3}Bi{sub 2}I{sub 9} as an example

    SciTech Connect

    Florek-Wojciechowska, M.; Wojciechowski, M.; Brym, Sz.; Kruk, D.; Jakubas, R.

    2016-02-07

    {sup 1}H nuclear magnetic resonance relaxometry has been applied to reveal information on dynamics and structure of Gu{sub 3}Bi{sub 2}I{sub 9} ([Gu = C(NH{sub 2}){sub 3}] denotes guanidinium cation). The data have been analyzed in terms of a theory of quadrupole relaxation enhancement, which has been extended here by including effects associated with quadrupole ({sup 14}N) spin relaxation caused by a fast fluctuating component of the electric field gradient tensor. Two motional processes have been identified: a slow one occurring on a timescale of about 8 × 10{sup −6} s which has turned out to be (almost) temperature independent, and a fast process in the range of 10{sup −9} s. From the {sup 1}H-{sup 14}N relaxation contribution (that shows “quadrupole peaks”) the quadrupole parameters, which are a fingerprint of the arrangement of the anionic network, have been determined. It has been demonstrated that the magnitude of the quadrupole coupling considerably changes with temperature and the changes are not caused by phase transitions. At the same time, it has been shown that there is no evidence of abrupt changes in the cationic dynamics and the anionic substructure upon the phase transitions.

  12. Strong spin-lattice coupling in CrSiTe3

    DOE PAGES

    Casto, L. D.; Clune, A. J.; Yokosuk, M. O.; ...

    2015-03-19

    CrSiTe3 has attracted recent interest as a candidate single-layer ferromagnetic semiconductor, but relatively little is known about the bulk properties of this material. Here, we report single-crystal X-ray diffraction, magnetic properties, thermal conductivity, vibrational, and optical spectroscopies and compare our findings with complementary electronic structure and lattice dynamics principles calculations. The high temperature paramagnetic phase is characterized by strong spin-lattice interactions that give rise to glassy behavior, negative thermal expansion, and an optical response that reveals that CrSiTe3 is an indirect gap semiconductor with indirect and direct band gaps at 0.4 and 1.2 eV, respectively. Measurements of the phonons acrossmore » the 33 K ferromagnetic transition provide additional evidence for strong coupling between the magnetic and lattice degrees of freedom. In conclusion, the Si-Te stretching and Te displacement modes are sensitive to the magnetic ordering transition, a finding that we discuss in terms of the superexchange mechanism. Lastly, spin-lattice coupling constants are also extracted.« less

  13. Strong spin-lattice coupling in CrSiTe3

    SciTech Connect

    Casto, L. D.; Clune, A. J.; Yokosuk, M. O.; Musfeldt, J. L.; Williams, T. J.; Zhuang, H. L.; Lin, M. -W.; Xiao, K.; Hennig, R. G.; Sales, B. C.; Yan, J. -Q.; Mandrus, D.

    2015-03-19

    CrSiTe3 has attracted recent interest as a candidate single-layer ferromagnetic semiconductor, but relatively little is known about the bulk properties of this material. Here, we report single-crystal X-ray diffraction, magnetic properties, thermal conductivity, vibrational, and optical spectroscopies and compare our findings with complementary electronic structure and lattice dynamics principles calculations. The high temperature paramagnetic phase is characterized by strong spin-lattice interactions that give rise to glassy behavior, negative thermal expansion, and an optical response that reveals that CrSiTe3 is an indirect gap semiconductor with indirect and direct band gaps at 0.4 and 1.2 eV, respectively. Measurements of the phonons across the 33 K ferromagnetic transition provide additional evidence for strong coupling between the magnetic and lattice degrees of freedom. In conclusion, the Si-Te stretching and Te displacement modes are sensitive to the magnetic ordering transition, a finding that we discuss in terms of the superexchange mechanism. Lastly, spin-lattice coupling constants are also extracted.

  14. Modulation of spin dynamics via voltage control of spin-lattice coupling in multiferroics

    DOE PAGES

    Zhu, Mingmin; Zhou, Ziyao; Peng, Bin; ...

    2017-02-03

    Our work aims at magnonics manipulation by the magnetoelectric coupling effect and is motivated by the most recent progresses in both magnonics (spin dynamics) and multiferroics fields. Here, voltage control of magnonics, particularly the surface spin waves, is achieved in La0.7Sr0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 multiferroic heterostructures. With the electron spin resonance method, a large 135 Oe shift of surface spin wave resonance (≈7 times greater than conventional voltage-induced ferromagnetic resonance shift of 20 Oe) is determined. A model of the spin-lattice coupling effect, i.e., varying exchange stiffness due to voltage-induced anisotropic lattice changes, has been established to explain experiment results with good agreement.more » In addition, an “on” and “off” spin wave state switch near the critical angle upon applying a voltage is created. The modulation of spin dynamics by spin-lattice coupling effect provides a platform for realizing energy-efficient, tunable magnonics devices.« less

  15. Different structure of the complexes of two cytochrome P-450 isozymes with acetanilide by 1H-NMR relaxation and spectrophotometry.

    PubMed

    Woldman YaYu; Weiner, L M; Lyakhovich, V V

    1993-05-28

    The functional and spectral characteristics of the interaction of acetanilide with phenobarbital- and methylcholanthrene- induced rat liver microsomes, as well as with corresponding major isozymes (cytochromes P-450b and P-450c) have been compared. The magnitude of the reverse 1st type binding spectra proved to be negatively correlated with the acetanilide oxidation on isozymes under study. The data on paramagnetic relaxation of acetanilide protons in the presence of P-450 have shown the structure of the enzyme-substrate complex to be different for two isozymes, acetanilide molecule being closer to Fe ion in the active site in the case of P-450c, which is active towards acetanilide oxidation. For the P-450c-acetanilide complex the group oxidized (phenyl) is the closest to Fe ion.

  16. Structure vs. composition: A solid-state 1H and 29Si NMR study of quenched glasses along the Na 2O-SiO 2-H 2O join

    NASA Astrophysics Data System (ADS)

    Cody, George D.; Mysen, Bjorn O.; Lee, Sung Keun

    2005-05-01

    A suite of six hydrous (7 wt.% H 2O) sodium silicate glasses spanning sodium octasilicate to sodium disilicate in composition were analyzed using 29Si single pulse (SP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, 1H- 29Si cross polarization (CP) MAS NMR, and fast MAS 1H-NMR. From the 29Si SPMAS data it is observed that at low sodium compositions dissolved water significantly depolymerizes the silicate network. At higher sodium contents, however, dissolved H 2O does not affect a significant increase in depolymerization over that predicted based on the Na/Si ratio alone. The fast MAS 1H-NMR data reveal considerable complexity in proton environments in each of the glasses studied. The fast MAS 1H-NMR spectra of the highest sodium concentration glasses do not exhibit evidence of signficantly greater fractions of dissolved water as molecular H 2O than the lower sodium concentration glasses requiring that the decrease in polymerization at high sodium contents involves a change in sodium solution mechanism. Variable contact time 1H- 29Si cross polarization (CP) MAS NMR data reveal an increase in the rotating frame spin lattice relaxation rate constant ( T1ρ*) for various Q n species with increasing sodium content that correlates with a reduction in the average 1H- 29Si coupling strength. At the highest sodium concentration, however, T1ρ* drops significantly, consistent with a change in the Na 2O solution mechanism.

  17. 13C and 1H NMR (Nuclear Magnetic Resonance) studies of solid polyolefines

    NASA Technical Reports Server (NTRS)

    Cudby, M. E. A.; Harris, R. K.; Metcalfe, K.; Packer, K. J.; Smith, P. W. R.

    1983-01-01

    The basis of H-1 and C-13 high-resolution NMR investigations of solid polymers is outlined. The C-13 NMR spectra of solid syndiotactic and isotactic polypropene are discussed and their interpretation in terms of conformation and chain-packing effects are reviewed. The effects of decreasing temperature on the C-13 high-resolution spectrum of an annealed sample of isotactic polypropene is described and interpreted in terms of the crystal structure. The question of the proportion of the sample giving rise to C-13 signals is addressed and some results reported. The main cause for observing only part of the total sample is shown to be the H-1 rotating frame spin-lattice relaxation behavior. The H-1 spin-lattice relaxation and spectral characteristics of a number of polyolefin samples are summarized and the role of spin-diffusion discussed.

  18. Nonuniversal scaling of the magnetocaloric effect as an insight into spin-lattice interactions in manganites

    NASA Astrophysics Data System (ADS)

    Smith, Anders; Nielsen, Kaspar K.; Bez, Henrique N.; Bahl, Christian R. H.

    2016-08-01

    We measure the magnetocaloric effect of the manganite series La0.67Ca0.33 -xSrxMnO3 by determining the isothermal entropy change upon magnetization, using variable-field calorimetry. The results demonstrate that the field dependence of the magnetocaloric effect close to the critical temperature is not given uniquely by the critical exponents of the ferromagnetic-paramagnetic phase transition, i.e., the scaling is nonuniversal. A theoretical description based on the Bean-Rodbell model and taking into account compositional inhomogeneities is shown to be able to account for the observed field dependence. In this way the determination of the nonuniversal field dependence of the magnetocaloric effect close to a phase transition can be used as a method to gain insight into the strength of the spin-lattice interactions of magnetic materials. The approach is shown also to be applicable to first-order transitions.

  19. Measuring free energy in spin-lattice models using parallel tempering Monte Carlo

    NASA Astrophysics Data System (ADS)

    Wang, Wenlong

    2015-05-01

    An efficient and simple approach of measuring the absolute free energy as a function of temperature for spin lattice models using a two-stage parallel tempering Monte Carlo and the free energy perturbation method is discussed and the results are compared with those of population annealing Monte Carlo using the three-dimensional Edwards-Anderson Ising spin glass model as benchmark tests. This approach requires little modification of regular parallel tempering Monte Carlo codes with also little overhead. Numerical results show that parallel tempering, even though using a much less number of temperatures than population annealing, can nevertheless equally efficiently measure the absolute free energy by simulating each temperature for longer times.

  20. Nematic spin order and spin-lattice coupling in Fe-based Superconductors

    NASA Astrophysics Data System (ADS)

    Hu, Jiangping; Fang, Chen; Tsai, Wei-Feng; Yao, Hong; Kivelson, Steve

    2009-03-01

    We show that the structure transitions observed in Fe-based superconductors are magnetically driven. A quantum Heisenberg model (J1-J2-Jz) exhibits a sequence of two phase transitions: from a high temperature symmetric phase to a narrow region of intermediate ``nematic'' phase, and then to a low temperature spin ordered phase when Jz is small. Identifying phases by their broken symmetries, these phases correspond precisely to the sequence of structural (tetragonal to monoclinic) and magnetic transitions that have been recently revealed in neutron scattering studies of 1111 series of Fe- based superconductors. The structural transition can thus be identified with the existence of incipient (``fluctuating'') magnetic order. We also discuss the effect of spin-lattice coupling on the phase diagram of the model. [3pt] Reference: Chen Fang, Hong Yao, Wei-Feng Tsai, JiangPing Hu and Steven A. Kivelson, Phys. Rev. B 77 224509 (2008).

  1. Many-body interferometry of a Rydberg-dressed spin lattice

    NASA Astrophysics Data System (ADS)

    Zeiher, Johannes; van Bijnen, Rick; Schauß, Peter; Hild, Sebastian; Choi, Jae-Yoon; Pohl, Thomas; Bloch, Immanuel; Gross, Christian

    2016-12-01

    Ultracold atoms in optical lattices are ideal to study fundamentally new quantum many-body systems including frustrated or topological magnetic phases and supersolids. However, the necessary control of strong long-range interactions between distant ground state atoms has remained a long-standing goal. Optical dressing of ground state atoms via off-resonant laser coupling to Rydberg states is one way to tailor such interactions. Here we report the realization of coherent Rydberg dressing to implement a two-dimensional synthetic spin lattice. Our single-atom-resolved interferometric measurements of the many-body dynamics enable the microscopic probing of the interactions and reveal their highly tunable range and anisotropy. Our work marks the first step towards the use of laser-controlled Rydberg interactions for the study of exotic quantum magnets in optical lattices.

  2. (1)H relaxivity of water in aqueous suspensions of Gd(3+)-loaded NaY nanozeolites and AlTUD-1 mesoporous material: the influence of Si/Al ratio and pore size.

    PubMed

    Norek, Małgorzata; Neves, Isabel C; Peters, Joop A

    2007-07-23

    The results of a (1)H nuclear magnetic relaxation dispersion (NMRD) and EPR study on aqueous suspensions of Gd(3+)-loaded NaY nanozeolites and AlTUD-1 mesoporous material are described. Upon increase of the Si/Al ratio from 1.7 to 4.0 in the Gd(3+)-loaded zeolites, the relaxation rate per mM Gd(3+) (r1) at 40 MHz and 25 degrees C increases from 14 to 27 s(-)1 mM(-1). The NMRD and EPR data were fitted with a previously developed two-step model that considers the system as a concentrated aqueous solution of Gd(3+) in the interior of the zeolite that is in exchange with the bulk water outside the zeolite. The results show that the observed increase in relaxivity can mainly be attributed to the residence lifetime of the water protons in the interior of the material, which decreased from 0.3 to 0.2 micros, upon the increase of the Si/Al ratio. This can be explained by the decreased interaction of water with the zeolite walls as a result of the increased hydrophobicity. The importance of the exchange rate of water between the inside and the outside of the material was further demonstrated by the relatively high relaxivity (33 s(-1) mM(-1) at 40 MHz, 25 degrees C) observed for a suspension of the Gd(3+)-loaded mesoporous material AlTUD-1. Unfortunately, Gd(3+) leaches rather easily from that material, but not from the Gd(3+)-loaded NaY zeolites, which may have potential as contrast agents for magnetic resonance imaging.

  3. Change of translational-rotational coupling in liquids revealed by field-cycling {sup 1}H NMR

    SciTech Connect

    Meier, R.; Schneider, E.; Rössler, E. A.

    2015-01-21

    Applying the field-cycling nuclear magnetic resonance technique, the frequency dependence of the {sup 1}H spin-lattice relaxation rate, R{sub 1}(ω)=T{sub 1}{sup −1}(ω), is measured for propylene glycol (PG) which is increasingly diluted with deuterated chloroform. A frequency range of 10 kHz–20 MHz and a broad temperature interval from 220 to about 100 K are covered. The results are compared to those of experiments, where glycerol and o-terphenyl are diluted with their deuterated counter-part. Reflecting intra- as well as intermolecular relaxation, the dispersion curves R{sub 1}(ω,x) (x denotes mole fraction PG) allow to extract the rotational time constant τ{sub rot}(T, x) and the self-diffusion coefficient D(T, x) in a single experiment. The Stokes-Einstein-Debye (SED) relation is tested in terms of the quantity D(T, x) τ{sub rot}(T, x) which provides a measure of an effective hydrodynamic radius or equivalently of the spectral separation of the translational and the rotational relaxation contribution. In contrast to o-terphenyl, glycerol and PG show a spectral separation much larger than suggested by the SED relation. In the case of PG/chloroform mixtures, not only an acceleration of the PG dynamics is observed with increasing dilution but also the spectral separation of rotational and translational relaxation contributions continuously decreases. Finally, following a behavior similar to that of o-terphenyl already at about x = 0.6; i.e., while D(T, x) τ{sub rot}(T, x) in the mixture is essentially temperature independent, it strongly increases with x signaling thus a change of translational-rotational coupling. This directly reflects the dissolution of the hydrogen-bond network and thus a change of solution structure.

  4. Investigating the magnetovolume effect in isotropic body-centered-cubic iron using spin-lattice dynamics simulations

    SciTech Connect

    Chui, C. P.; Zhou, Yan

    2014-08-15

    The understanding of the magnetovolume effect lacks explicit consideration of spin-lattice coupling at the atomic level, despite abundant theoretical and experimental studies throughout the years. This research gap is filled by the recently developed spin-lattice dynamics technique implemented in this study, which investigates the magnetovolume effect of isotropic body-centered-cubic (BCC) iron, a topic that has previously been subject to macroscopic analysis only. This approach demonstrates the magnetic anomaly followed by the volumetric changes associated with the effect, each characterized by the corresponding field-induced inflection temperature. The temperature of the heat capacity peaks is useful in determining the temperature for retarding the atomic volume increase. Moreover, this work shows the correlation between the effects of temperature and field strength in determining the equilibrium atomic volume of a ferromagnetic material under a magnetic field.

  5. Spin-lattice coupling mediated multiferroicity in (ND4)2FeCl5.D2O

    NASA Astrophysics Data System (ADS)

    Tian, W.; Cao, Huibo; Wang, Jincheng; Ye, Feng; Matsuda, M.; Yan, J.-Q.; Liu, Yaohua; Garlea, V. O.; Agrawal, Harish K.; Chakoumakos, B. C.; Sales, B. C.; Fishman, Randy S.; Fernandez-Baca, J. A.

    2016-12-01

    We report a neutron diffraction study of the multiferroic mechanism in (ND4)2FeCl5.D2O , a molecular compound that exhibits magnetically induced ferroelectricity. This material exhibits two successive magnetic transitions on cooling: a long-range order transition to an incommensurate (IC) collinear sinusoidal spin state at TN=7.3 K, followed by a second transition to an IC cycloidal spin state at TF E=6.8 K, the latter of which is accompanied by spontaneous ferroelectric polarization. The cycloid structure is strongly distorted by spin-lattice coupling, as evidenced by the observations of both odd and even higher-order harmonics associated with the cycloid wave vector, and a weak commensurate phase that coexists with the IC phase. The second-order harmonic appears at TF E, thereby providing unambiguous evidence that the onset of the electric polarization is accompanied by a lattice modulation due to spin-lattice interaction. The neutron results, in conjunction with the negative thermal expansion and large magnetostriction observed in Ref. [19], indicate that spin-lattice coupling plays a critical role in the ferroelectric mechanism of (ND4)2FeCl5.D2O .

  6. Spin-lattice coupling mediated multiferroicity in (ND4)2FeCl5·D2O

    DOE PAGES

    Tian, Wei; Cao, Huibo; Wang, Jincheng; ...

    2016-12-07

    In this paper, we report a neutron diffraction study of the multiferroic mechanism in (ND4)2FeCl5 • D2O, a molecular compound that exhibits magnetically induced ferroelectricity. This material exhibits two successive magnetic transitions on cooling: a long-range order transition to an incommensurate (IC) collinear sinusoidal spin state at TN = 7.3 K, followed by a second transition to an IC cycloidal spin state at TFE = 6.8 K, the latter of which is accompanied by spontaneous ferroelectric polarization. The cycloid structure is strongly distorted by spin-lattice coupling, as evidenced by the observations of both odd and even higher-order harmonics associated withmore » the cycloid wave vector, and a weak commensurate phase that coexists with the IC phase. The second-order harmonic appears at TFE, thereby providing unambiguous evidence that the onset of the electric polarization is accompanied by a lattice modulation due to spin-lattice interaction. The neutron results, in conjunction with the negative thermal expansion and large magnetostriction observed, indicate that spin-lattice coupling plays a critical role in the ferroelectric mechanism of (ND4)2FeCl5 • D2O.« less

  7. Spin-lattice coupling mediated multiferroicity in (ND4)2FeCl5 • D2O

    DOE PAGES

    Tian, Wei; Cao, Huibo; Wang, Jincheng; ...

    2016-12-07

    In this paper, we report a neutron diffraction study of the multiferroic mechanism in (ND4)2FeCl5 • D2O, a molecular compound that exhibits magnetically induced ferroelectricity. This material exhibits two successive magnetic transitions on cooling: a long-range order transition to an incommensurate (IC) collinear sinusoidal spin state at TN = 7.3 K, followed by a second transition to an IC cycloidal spin state at TFE = 6.8 K, the latter of which is accompanied by spontaneous ferroelectric polarization. The cycloid structure is strongly distorted by spin-lattice coupling, as evidenced by the observations of both odd and even higher-order harmonics associated withmore » the cycloid wave vector, and a weak commensurate phase that coexists with the IC phase. The second-order harmonic appears at TFE, thereby providing unambiguous evidence that the onset of the electric polarization is accompanied by a lattice modulation due to spin-lattice interaction. The neutron results, in conjunction with the negative thermal expansion and large magnetostriction observed, indicate that spin-lattice coupling plays a critical role in the ferroelectric mechanism of (ND4)2FeCl5 • D2O.« less

  8. A strong ferroelectric ferromagnet created by means of spin-lattice coupling.

    PubMed

    Lee, June Hyuk; Fang, Lei; Vlahos, Eftihia; Ke, Xianglin; Jung, Young Woo; Kourkoutis, Lena Fitting; Kim, Jong-Woo; Ryan, Philip J; Heeg, Tassilo; Roeckerath, Martin; Goian, Veronica; Bernhagen, Margitta; Uecker, Reinhard; Hammel, P Chris; Rabe, Karin M; Kamba, Stanislav; Schubert, Jürgen; Freeland, John W; Muller, David A; Fennie, Craig J; Schiffer, Peter; Gopalan, Venkatraman; Johnston-Halperin, Ezekiel; Schlom, Darrell G

    2010-08-19

    -temperature manifestations of this spin-lattice coupling mechanism. Our work demonstrates that a single experimental parameter, strain, simultaneously controls multiple order parameters and is a viable alternative tuning parameter to composition for creating multiferroics.

  9. A strong ferroelectric ferromagnet created by means of spin-lattice coupling.

    SciTech Connect

    Lee, J. H.; Fang, L.; Vlahos, E.; Ke, X.; Jung, Y.W.; Fitting Kourkaoutis, L.; Kim, J. W.; Ryan, P.; Heeg, T.; Roeckerath, M.; Goian, V.; Bernhagen, M.; Uecker, R.; Hammel, P.C.; Rabe, K. M.; Kamba, S.; Schubert, J.; Freeland, J.W.; Muller, D.A.; Fennie, C.J.; Schiffer, P.; Gopalan, V.; Johnston-Halperin, E.; Schlom, D. G.

    2010-08-19

    -temperature manifestations of this spin-lattice coupling mechanism. Our work demonstrates that a single experimental parameter, strain, simultaneously controls multiple order parameters and is a viable alternative tuning parameter to composition for creating multiferroics.

  10. Effect of manganese on human placental spin-lattice (T1) and spin-spin (T2) relaxation times

    SciTech Connect

    Angtuaco, T.L.; Mattison, D.R.; Thomford, P.J.; Jordan, J.

    1986-01-01

    Human placentas were obtained immediately following delivery and incubated with manganese chloride (MnCl/sub 2/) in concentrations ranging from 0.002 to 2.0 mM. Proton density, T1 and T2 were measured at times ranging from 5-200 minutes. There was rapid uptake of manganese by the placenta producing a dose-dependent decrease in placental T1 and T2. The major effect of manganese uptake was shortening of T1 suggesting that the contrast between placenta and myometrium will be enhanced predominantly for T1-dependent imaging pulse sequences.

  11. Intercalation of aflatoxin B sub 1 in two oligodeoxynucleotide adducts: Comparative sup 1 H NMR analysis of d(ATC sup AFB GAT)ter dot d(ATCGAT) and d(AT sup ATB GCAT) sub 2

    SciTech Connect

    Gopalakrishnan, S.; Harris, T.M.; Stone, M.P. )

    1990-11-01

    8,9-Dihydro-8-(N7-guanyl-(d(ATCGAT)))-9-hydroxyaflatoxin B{sub 1}{center dot}d(ATCGAT) and 8,9-dihydro-8-(N7-guanyl-(d(ATGCAT)))-9-hydroxyafltoxin B{sub 1}{center dot}8,9-dihydro-8-(N7-guanyl-(d(ATGCAT)))-9-hydroxyaflatoxin B{sub 1} were prepared by direct addition of aflatoxin B{sub 1} 8,9-expoxide to d(ATCGAT){sub 2} and d(ATGCAT){sub 2}, respectively. {sup 1}H NOE experiments, nonselective {sup 1}H T{sub 1} relaxation measurements, and {sup 1}H chemical shift perturbations demonstrate that in both modified oligodeoxynucleotides the aflatoxin moiety is intercalated above the 5{prime}-face of the modified guanine. The oligodeoxynucleotides remain right-handed, and perturbation of the B-DNA structure is localized adjacent to the adducted guanine. Aflatoxin-oligodeoxynucleotide {sup 1}H NOEs are observed between aflatoxin and the 5{prime}-neighbor base pair and include both the major groove and the minor groove. The protons at C8 and C9 of the aflatoxin terminal furan ring exhibit slower spin-lattice relaxation as compared to other oligodeoxynucleotide protons, which supports the conclusion that they face into the major groove. Increased shielding is observed for aflatoxin protons. The difference in reaction stoichiometry is consistent with an intercalated transition-state complex between aflatoxin B{sub 1} 8,9-epoxide and B-DNA. Intercalation provides excellent positioning for nucleophilic attack by guanine N7 on aflatoxin B{sub 1} 8,9-epoxide, which probably accounts for the observed efficiency of adduct formation despite the relatively low DNA binding affinity observed for aflatoxin B{sub 1}.

  12. Molecular dynamics of poly(L-lactide) biopolymer studied by wide-line solid-state 1H and 2H NMR spectroscopy.

    PubMed

    Nozirov, Farhod; Nazirov, Alovidin; Jurga, Stefan; Fu, Riqiang

    2006-06-01

    The molecular dynamics of poly(L-lactide) (PLLA) biopolymer was characterized through analyses of 1H and 2H NMR line-shapes and spin-lattice relaxation times at different temperatures. At low temperatures (e.g. 90 K), the methyl group rotation is dominant leading to a significant reduction in the proton second moment. Fast methyl group reorientation occurs at ca. 130 K. In additional to the fast methyl group rotation, hydroxyl groups start to reorient as the temperature increases further, eventually leading to the breakdown of the segments of the biopolymer chains above its glass transition temperature Tg of 323 K. The analyses of the 2H NMR line-shapes indicate that both the methyl and hydroxyl reorientations can be described by the so-called cone model, in which the former has three equilibrium positions with theta(C-D) = 70.5 degrees and phi = 120 degrees while the latter one exhibits two equilibrium positions with theta(O-D) = 78 degrees and phi = 180 degrees .

  13. Coupled nuclear spin relaxation and internal rotations in magnesium fluosilicate hexahydrate.

    NASA Technical Reports Server (NTRS)

    Utton, D. B.; Tsang, T.

    1972-01-01

    Both proton and fluorine nuclear spin-lattice relaxations have been studied by the 180- to 90-deg pulse method in magnesium fluosilicate hexahydrate at 25 and 13 MHz over the temperature range from 170 to 350 K. Observed nonexponential behavior of the nuclear magnetic relaxation is explained by internal rotations of the doubly charged negative fluosilicate ions and doubly charged positive magnesium hexahydrate ions.

  14. Magnetic phase transition in coupled spin-lattice systems: A replica-exchange Wang-Landau study.

    PubMed

    Perera, Dilina; Vogel, Thomas; Landau, David P

    2016-10-01

    Coupled, dynamical spin-lattice models provide a unique test ground for simulations investigating the finite-temperature magnetic properties of materials under the direct influence of the lattice vibrations. These models are constructed by combining a coordinate-dependent interatomic potential with a Heisenberg-like spin Hamiltonian, facilitating the treatment of both the atomic coordinates and the spins as explicit phase variables. Using a model parameterized for bcc iron, we study the magnetic phase transition in these complex systems via the recently introduced, massively parallel replica-exchange Wang-Landau Monte Carlo method. Comparison with the results obtained from rigid lattice (spin-only) simulations shows that the transition temperature as well as the amplitude of the peak in the specific heat curve is marginally affected by the lattice vibrations. Moreover, the results were found to be sensitive to the particular choice of interatomic potential.

  15. Magnetic phase transition in coupled spin-lattice systems: A replica-exchange Wang-Landau study

    NASA Astrophysics Data System (ADS)

    Perera, Dilina; Vogel, Thomas; Landau, David P.

    2016-10-01

    Coupled, dynamical spin-lattice models provide a unique test ground for simulations investigating the finite-temperature magnetic properties of materials under the direct influence of the lattice vibrations. These models are constructed by combining a coordinate-dependent interatomic potential with a Heisenberg-like spin Hamiltonian, facilitating the treatment of both the atomic coordinates and the spins as explicit phase variables. Using a model parameterized for bcc iron, we study the magnetic phase transition in these complex systems via the recently introduced, massively parallel replica-exchange Wang-Landau Monte Carlo method. Comparison with the results obtained from rigid lattice (spin-only) simulations shows that the transition temperature as well as the amplitude of the peak in the specific heat curve is marginally affected by the lattice vibrations. Moreover, the results were found to be sensitive to the particular choice of interatomic potential.

  16. 1H and 13C MAS NMR analysis for the role of chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in [N(CH3)4]2CuCl4

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-01-01

    The spin-lattice relaxation times in the laboratory frame, T1, and in the rotating frame, T1ρ, for 1H and 13C in [N(CH3)4]2CuCl4 were measured by static NMR and magic angle spinning (MAS) NMR as functions of temperature. The intensities of the 1H and 13C signals changed near phase transition temperatures TC1 and TC3, which indicated that N(CH3)4 plays an important role in these phase transitions. It was thus apparent that the T1 and T1ρ for 1H are governed by the same molecular motions. Two inequivalent ions, a-N(CH3)4 and b-N(CH3)4, were identified by 13C cross-polarization (CP)/MAS NMR. From these results, the behaviors of these two chemically inequivalent N(CH3)4 groups in the paraelastic and ferroelastic phases are discussed.

  17. 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.

  18. The structure of polycaprolactone-clay nanocomposites investigated by 1H NMR relaxometry.

    PubMed

    Monteiro, Mariana S S B; Rodrigues, Claudia Lopes; Neto, Roberto P C; Tavares, Maria Inês Bruno

    2012-09-01

    Nanocomposites based on polycaprolactone (PCL), containing concentrations of 1, 3 and 5 wt% of sodium montmorillonite (NT-25) and organo-modified montmorillonite clay, with three different salts (Viscogel B7, Viscogel S4 and Viscogel B8), were prepared employing the solution intercalation method using chloroform. The PCL nanocomposites were characterized by relaxometry, through determination of the hydrogen spin-lattice relaxation times using low-field nuclear magnetic resonance (NMR). Conventional X-ray diffraction (XDR) was also used to measure the basal space of the nanoclay. The proton spin-lattice relaxation parameters showed that hybrid nanocomposites were formed, containing different parts of intercalated and exfoliated organoclay. The proton T1rhoH also indicated changes in the microstructure, organization and the molecular mobility of the hybrid materials. NMR relaxometry is a good way to evaluate nanomaterials because it provides complementary information, since it is measured in a different time scale. Furthermore, differential scanning calorimetry and thermogravimetric analysis were also used to investigate the crystallization and thermal behavior of the nanocomposites, respectively. All materials had low crystallization temperature (Tc) and the melting temperature (Tm) were very close to that of the PCL matrix, but the degree of crystallinity of the nanocomposites decreased. TGA analysis demonstrated that montmorillonite accelerates PCL's decomposition while unmodified montmorillonite has the opposite effect.

  19. 1H-NMR, dielectric and calorimetric studies of molecular motions in m-nitroaniline crystal

    NASA Astrophysics Data System (ADS)

    Szostak, M. Magdalena; Wójcik, Grażyna; Gallier, Jean; Bertault, Marcel; Freundlich, Piotr; Kołodziej, Hubert A.

    1998-04-01

    Spin-lattice relaxation time, T1, spin-lattice relaxation time in the rotating frame, T1 ρ, and the second moment of the resonance line measurements at 80 MHz and over the 190-380 K temperature range are reported for protons in the optically nonlinear material m-nitroaniline ( m-NA). T1 has also been measured for samples irradiated by low energy and low intensity radiation. The real and imaginary parts of electric permittivity as well as tan  δ have been recorded in the 80-380 K temperature range at frequencies ranging from 100 Hz to 1.0 MHz. DSC measurements have been performed in the 110-387 K temperature range. Two phase transitions have been found: A glassy to rotative transition at 160 K and a plastic to plastic transformation at 365 K. The main feature of the m-NA crystal is that its plasticity continues to grow as the temperature increases. The reorientations of phenyl rings, the -NH 2 group proton 180° jumps, the lattice distortions caused by anisotropic thermal expansion and the cooperative reorientations of big molecular aggregates are thought to be the reasons for phase transitions and for the subsequent intermolecular charge transfer. The results are discussed with respect to optical second harmonic generation and near-IR photochemical reaction found in the m-NA crystal.

  20. NMR relaxation rate and the libron energy of solid hydrogen

    NASA Technical Reports Server (NTRS)

    Sugawara, K.; Woollam, J. A.

    1978-01-01

    By taking the rotational relaxation of orthohydrogen (o-H2) in solid hydrogen into account, the authors have theoretically investigated the longitudinal NMR spin lattice relaxation rate of o-H2. The rate is characterized by an anomalous maximum, as a function of temperature, at temperatures close to the mean libron energy of o-H2. Application of the theory for o-H2 concentrations between 42% and 75% reveals a nearly concentration-independent mean libron energy equivalent to about 1 K. This qualitatively and quantitatively contradicts the conclusions of other theories, but agrees with recent experiments.

  1. 1H NMR spin-spin relaxation and imaging in porous systems: an application to the morphological study of white portland cement during hydration in the presence of organics.

    PubMed

    Gussoni, M; Greco, F; Bonazzi, F; Vezzoli, A; Botta, D; Dotelli, G; Natali Sora, I; Pelosato, R; Zetta, L

    2004-07-01

    Proton nuclear magnetic resonance (NMR) spin-spin relaxation and imaging have been applied to investigate white Portland cement pastes during hydration in the absence and in the presence of organic solvents. The main organic solvent investigated was methanol, alone or together with the organic waste 2-chloroaniline (2-CA), an aromatic amine representative of an important class of highly toxic compounds. For all the analysed samples, prepared with a solvent-to-cement ratio of 0.4, the decay of the echo magnetization has been fitted by adopting a model that combines an exponential component with a gaussian one. The calculated independent relaxation parameters have been discussed in terms of morphological and dynamical changes that occur during the cement hardening process and pore formation. Three kinds of water molecules: "solid-like" (chemically and physically bound), "liquid-like" (porous trapped) and "free" water, endowed with anisotropic, near isotropic and isotropic motion, respectively, were identified. Spin-echo images collected on the same samples during the hydration kinetics, allowed the changes of water and solvents spatial distribution in the porous network to be monitored, showing percolation phenomena and confirming the multimodal open channels structure of the hardened cement system. Both T(2) relaxation and imaging data indicated that a pronounced delay occurs in the cement hardening when organics are present.

  2. Geometrically frustrated GdInO3: An exotic system to study negative thermal expansion and spin-lattice coupling

    NASA Astrophysics Data System (ADS)

    Paul, Barnita; Chatterjee, Swastika; Roy, Anushree; Midya, A.; Mandal, P.; Grover, Vinita; Tyagi, A. K.

    2017-02-01

    In this article, we report negative thermal expansion and spin frustration in hexagonal GdInO3. Rietveld refinements of the x-ray diffraction patterns reveal that the negative thermal expansion in the temperature range of 50-100 K stems from the triangular lattice of Gd3 + ions. The downward deviation of the low-temperature inverse susceptibility (χ-1) versus T plot from the Curie-Weiss law and the large value of the ratio, | θCW|/ TN>28 , where θCW and TN are respectively Curie-Weiss and Neel temperature, indicate a strong spin frustration, which inhibits long-range magnetic ordering down to 1.8 K. Magnetostriction measurements clearly demonstrate a spin-lattice coupling in the system. Low-temperature anomalous phonon softening, as obtained from temperature-dependent Raman measurements, also reveals the same. Our experimental observations are supported by first-principles density functional theory calculations of the electronic and phonon dispersion in GdInO3. The calculations suggest that the GdInO3 lattice is highly frustrated at low temperature. Further, the calculated normal mode frequencies of the Gd-related Γ point phonon modes reveal significant magnetoelastic coupling in this system. The competitive role of magnetic interaction energy and thermal stabilization energy in determining the change in interatomic distances is the possible origin for the negative thermal expansion in GdInO3 over a limited range of temperature.

  3. Half-metallicity of a kagome spin lattice: the case of a manganese bis-dithiolene monolayer.

    PubMed

    Zhao, Mingwen; Wang, Aizhu; Zhang, Xiaoming

    2013-11-07

    The spin ordering in kagome lattices has long been studied in the search for real materials with a spin-liquid ground state. The synthesis of a nickel bis-dichiolene complex (Ni3C12S12) nanosheet (T. Kambe et al., J. Am. Chem. Soc., 2013, 135, 2462) paved a way for realizing real two-dimensional kagome lattices. Using first-principles calculations, we predicted that a ferromagnetic kagome spin lattice with S = 3/2 on lattice vertices can be achieved in an Mn3C12S12 monolayer formed by substituting Ni with Mn atoms in nonmagnetic Ni3C12S12. Monte Carlo simulations on the basis of the Ising model suggest that it has a Curie temperature of about 212 K. A ferromagnetic Mn3C12S12 monolayer is half metallic with high carrier mobility in one spin channel and a band gap of 1.54 eV in another spin channel, which is quite promising for spintronic device applications. Additionally, a small band gap opens up at the Dirac point of the kagome bands due to the spin-orbital coupling effects, which may be implementable for achieving a quantum anomalous Hall effect.

  4. 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

  5. Spin relaxation measurements using first-harmonic out-of-phase absorption EPR signals.

    PubMed

    Livshits, V A; Páli, T; Marsh, D

    1998-09-01

    The dependence on spin-lattice (T1) relaxation of the first-harmonic absorption EPR signal (V'1) detected in phase quadrature with the Zeeman modulation has been investigated both theoretically and experimentally for nitroxide spin labels. Spectral simulations were performed by iterative solution of the Bloch equations that contained explicitly both the modulation and microwave magnetic fields (T. Páli, V. A. Livshits, and D. Marsh, 1996, J. Magn. Reson. B 113, 151-159). It was found that, of the various non-linear EPR displays, the first-harmonic out-of-phase V'1-signal, recorded under conditions of partial saturation of the microwave absorption, is particularly favorable for determining spin-lattice relaxation enhancements because of its superior signal intensity and relative insensitivity to spin-spin (T2) relaxation. By varying the Zeeman modulation frequency it is also possible to tune the optimum sensitivity of the V'1-signal to different ranges of the T1-relaxation time. A Zeeman modulation frequency of 25 kHz appears to be particularly suited to spin label applications. Calibrations are given for the dependence on T1-relaxation time of both the amplitude and the second integral of the V'1-signal recorded under standard conditions. Experiments on different spin labels in solution and in membranes demonstrate the practical usable sensitivity of the V'1-signal, even at modulation frequencies of 25 kHz, and these are used to investigate the dependence on microwave field intensity, in comparison with theoretical predictions. The practicable sensitivity to spin-lattice relaxation enhancements is demonstrated experimentally for a spin-labeled membrane system in the presence of paramagnetic ions. The first-harmonic out-of-phase V'1-signal appears to be the non-linear CW EPR method of choice for determining T1-relaxation enhancements in spin-labeled systems.

  6. Enhancement of Paramagnetic Relaxation by Photoexcited Gold Nanorods

    PubMed Central

    Wen, Tao; Wamer, Wayne G.; Subczynski, Witold K.; Hou, Shuai; Wu, Xiaochun; Yin, Jun-Jie

    2016-01-01

    Electron spin resonance (ESR) spectroscopy was used to investigate the switchable, light-dependent effects of gold nanorods (GNRs) on paramagnetic properties of nitroxide spin probes. The photoexcited GNRs enhanced the spin-spin and spin-lattice relaxations of nitroxide spin probes. It was shown that molecular oxygen plays the key role in this process. Our results demonstrate that ESR is a powerful tool for investigating the events following photoexcitation of GNRs. The novel light-controlled effects observed for GNRs on paramagnetic properties and activities of surrounding molecules have a number of significant applications where oxygen sensing and oxygen activity is important. PMID:27071507

  7. Pulsed NMRON relaxation measurements and thermometric NMR in the quasi-2 dimensional femomagnet: Mn(COOCH 3) 2·4H 2O

    NASA Astrophysics Data System (ADS)

    Le Gros, M.; Kotlicld, A.; Turrell, B. G.

    1990-08-01

    The measurement of the field dependence of the nuclear spin-lattice relaxation time of 54Mn in the two manganese sites in the quasi-2 dimensional ferromagnet Mn(COOCH 3) 2·4H 20 obtained by the pulsed NMRON technique is reported. This technique allows the observation in low fields of the higher frequency resonance which previously could not be measured by CW methods. The anomaly in the 54Mn relaxation time observed in the 55Mn level crossing regime is discussed, and the thermometric observation of the field dependence and lice width of the resonance lines from the abundant 55Mn spin systems is reported and related to the 54Mn spin-lattice relaxation behavior.

  8. 1H and 19 F NMR Study of Cation and Anion Motions in Guanidinium Hexafluorozirconate

    NASA Astrophysics Data System (ADS)

    Grottel, M.; Kozak, A.; Pająk, Z.

    1996-09-01

    Proton and fluorine NMR second moments and spin-lattice relaxation times of polycrystalline guanidinium hexafluorozirconate and its deuterated analogue were studied in laboratory (60 MHz) and rotating (H1 = 20 G) frames over a wide range of temperature. An analysis of the experimental results enabled us to reveal a dynamical inequivalence of two crystallographically independent cations and an unexpected high mobility of nonspherical anion dimers. A comparison of the ions dynamics in 2:1 complex studied with the guanidinium 1:1 and 3:1 complexes has shown a significant contribution of the hydrogen bonds to the potential barriers hindering the anion reorientations. At low temperatures a proton motion in the hydrogen bond and at 400 K a solid-solid phase transition have been discerned.

  9. U1h Superstructure

    SciTech Connect

    Glen Sykes

    2000-11-01

    The U1H Shaft Project is a design build subcontract to supply the U. S. Department of Energy (DOE) a 1,045 ft. deep, 20 ft. diameter, concrete lined shaft for unspecified purposes. The subcontract awarded to Atkinson Construction by Bechtel Nevada to design and construct the shaft for the DOE has been split into phases with portions of the work being released as dictated by available funding. The first portion released included the design for the shaft, permanent hoist, headframe, and collar arrangement. The second release consisted of constructing the shaft collar to a depth of 110 ft., the service entry, utility trenches, and installation of the temporary sinking plant. The temporary sinking plant included the installation of the sinking headframe, the sinking hoist, two deck winches, the shaft form, the sinking work deck, and temporary utilities required to sink the shaft. Both the design and collar construction were completed on schedule. The third release consisted of excavating and lining the shaft to the station depth of approximately 950 feet. Work is currently proceeding on this production sinking phase. At a depth of approximately 600 feet, Atkinson has surpassed production expectation and is more than 3 months ahead of schedule. Atkinson has employed the use of a Bobcat 331 excavator as the primary means of excavation. the shaft is being excavated entirely in an alluvial deposit with varying degrees of calcium carbonate cementation. Several more work packages are expected to be released in the near future. The remaining work packages include, construction of the shaft station a depth of 975 ft. and construction of the shaft sump to a depth of 1,045 ft., installation of the loading pocket and station steel and equipment, installation of the shaft steel and guides, installation of the shaft utilities, and installation of the permanent headframe, hoist, collar utilities, and facilities.

  10. Quadrupolar relaxation of hyperpolarized krypton-83 as a probe for surfaces.

    PubMed

    Stupic, Karl F; Cleveland, Zackary I; Pavlovskaya, Galina E; Meersmann, Thomas

    2006-02-01

    This work reports the first systematic study of relaxation experienced by the hyperpolarized (hp) noble gas isotope (83)Kr (I=9/2) in contact with surfaces. The spin-lattice relaxation of (83)Kr is found to depend strongly on the chemical composition of the surfaces in the vicinity of the gas. This effect is caused by quadrupolar interactions during brief periods of surface adsorption that are the dominating source of longitudinal spin relaxation in the (83)Kr atoms. Simple model systems of closest packed glass beads with uniform but variable bead sizes are used for the relaxation measurements. The observed relaxation rates depend strongly on the chemical treatment of the glass surfaces and on the surface to volume ratio. Hp (83)Kr NMR relaxation measurements of porous polymers with pore sizes of 70-250 microm demonstrate the potential use of this new technique for material sciences applications.

  11. Introductory Chemistry: A Molar Relaxivity Experiment in the High School Classroom.

    PubMed

    Dawsey, Anna C; Hathaway, Kathryn L; Kim, Susie; Williams, Travis J

    2013-07-09

    Dotarem and Magnevist, two clinically available magnetic resonance imaging (MRI) contrast agents, were assessed in a high school science classroom with respect to which is the better contrast agent. Magnevist, the more efficacious contrast agent, has negative side effects because its gadolinium center can escape from its ligand. However, Dotarem, though a less efficacious contrast agent, is a safer drug choice. After the experiment, students are confronted with the FDA warning on Magnevist, which enabled a discussion of drug efficacy versus safety. We describe a laboratory experiment in which NMR spin lattice relaxation rate measurements are used to quantify the relaxivities of the active ingredients of Dotarem and Magnevist. The spin lattice relaxation rate gives the average amount of time it takes the excited nucleus to relax back to the original state. Students learn by constructing molar relaxivity curves based on inversion recovery data sets that Magnevist is more relaxive than Dotarem. This experiment is suitable for any analytical chemistry laboratory with access to NMR.

  12. Introductory Chemistry: A Molar Relaxivity Experiment in the High School Classroom

    PubMed Central

    Dawsey, Anna C.; Hathaway, Kathryn L.; Kim, Susie; Williams, Travis J.

    2013-01-01

    Dotarem and Magnevist, two clinically available magnetic resonance imaging (MRI) contrast agents, were assessed in a high school science classroom with respect to which is the better contrast agent. Magnevist, the more efficacious contrast agent, has negative side effects because its gadolinium center can escape from its ligand. However, Dotarem, though a less efficacious contrast agent, is a safer drug choice. After the experiment, students are confronted with the FDA warning on Magnevist, which enabled a discussion of drug efficacy versus safety. We describe a laboratory experiment in which NMR spin lattice relaxation rate measurements are used to quantify the relaxivities of the active ingredients of Dotarem and Magnevist. The spin lattice relaxation rate gives the average amount of time it takes the excited nucleus to relax back to the original state. Students learn by constructing molar relaxivity curves based on inversion recovery data sets that Magnevist is more relaxive than Dotarem. This experiment is suitable for any analytical chemistry laboratory with access to NMR. PMID:23929983

  13. 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.

  14. Proton magnetic relaxation dispersion in aqueous biopolymer systems

    NASA Astrophysics Data System (ADS)

    Conti, S.

    Investigation of the magnetic field dependence of proton spin-lattice relaxation in solutions of bovine fibrinogen has been performed for Larmor frequencies between 50 Hz and 60 MHz, and complemented with measurements of spin-spin relaxation rates at 2 kHz and 25 MHz. A thorough analysis of experimental data, including the effects of protein concentration, temperature, pH and isotopic dilution, leads to an overall relaxation scheme consistent with T1 and T2 values at both low and high magnetic fields. The scheme involves water molecules slightly anisotropically bound on proteins as well as slow exchanging protein protons magnetically coupled to solute nuclei. A coherent picture, reminiscent of the traditional hydration layer, can be obtained for bound water. A major conclusion is that transfer of single protons may contribute substantially to the chemical exchange between free and bound water.

  15. Distribution of NMR relaxations in a random Heisenberg chain.

    PubMed

    Shiroka, T; Casola, F; Glazkov, V; Zheludev, A; Prša, K; Ott, H-R; Mesot, J

    2011-04-01

    NMR measurements of the (29)Si spin-lattice relaxation time T(1) were used to probe the spin-1/2 random Heisenberg chain compound BaCu(2)(Si(1-x)Ge(x))(2)O(7). Remarkable differences between the pure (x=0) and the fully random (x=0.5) cases are observed, indicating that randomness generates a distribution of local magnetic relaxations. This distribution, which is reflected in a stretched exponential NMR relaxation, exhibits a progressive broadening with decreasing temperature, caused by a growing inequivalence of magnetic sites. Compelling independent evidence for the influence of randomness is also obtained from magnetization data and Monte Carlo calculations. These results suggest the formation of random-singlet states in this class of materials, as previously predicted by theory.

  16. Bicollinear antiferromagnetic order, monoclinic distortion, and reversed resistivity anisotropy in FeTe as a result of spin-lattice coupling

    DOE PAGES

    Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

    2016-09-08

    The bicollinear antiferromagnetic order experimentally observed in FeTe is shown to be stabilized by the coupling g~12 between monoclinic lattice distortions and the spin-nematic order parameter with B2g symmetry, within a three-orbital spin-fermion model studied with Monte Carlo techniques. A finite but small value of g~12 is required, with a concomitant lattice distortion compatible with experiments, and a tetragonal-monoclinic transition strongly first order. Remarkably, the bicollinear state found here displays a planar resistivity with the reversed puzzling anisotropy discovered in transport experiments. Orthorhombic distortions are also incorporated, and phase diagrams interpolating between pnictides and chalcogenides are presented. Here, we concludemore » that the spin-lattice coupling we introduce is sufficient to explain the challenging properties of FeTe.« less

  17. Bicollinear antiferromagnetic order, monoclinic distortion, and reversed resistivity anisotropy in FeTe as a result of spin-lattice coupling

    SciTech Connect

    Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

    2016-09-08

    The bicollinear antiferromagnetic order experimentally observed in FeTe is shown to be stabilized by the coupling g~12 between monoclinic lattice distortions and the spin-nematic order parameter with B2g symmetry, within a three-orbital spin-fermion model studied with Monte Carlo techniques. A finite but small value of g~12 is required, with a concomitant lattice distortion compatible with experiments, and a tetragonal-monoclinic transition strongly first order. Remarkably, the bicollinear state found here displays a planar resistivity with the reversed puzzling anisotropy discovered in transport experiments. Orthorhombic distortions are also incorporated, and phase diagrams interpolating between pnictides and chalcogenides are presented. Here, we conclude that the spin-lattice coupling we introduce is sufficient to explain the challenging properties of FeTe.

  18. Quantum decoherence and quasi-equilibrium in open quantum systems with few degrees of freedom: application to 1H NMR of nematic liquid crystals.

    PubMed

    Segnorile, Héctor H; Zamar, Ricardo C

    2011-12-28

    Explanation of decoherence and quasi-equilibrium in systems with few degrees of freedom demands a deep theoretical analysis that considers the observed system as an open quantum system. In this work, we study the problem of decoherence of an observed system of quantum interacting particles, coupled to a quantum lattice. Our strategy is based on treating the environment and the system-environment Hamiltonians fully quantum mechanically, which yields a representation of the time evolution operator useful for disentangling the different time scales underlying in the observed system dynamics. To describe the possible different stages of the dynamics of the observed system, we introduce quantum mechanical definitions of essentially isolated, essentially adiabatic, and thermal-contact system-environment interactions. This general approach is then applied to the study of decoherence and quasi-equilibrium in proton nuclear magnetic resonance ((1)H NMR) of nematic liquid crystals. A summary of the original results of this work is as follows. We calculate the decoherence function and apply it to describe the evolution of a coherent spin state, induced by the coupling with the molecular environment, in absence of spin-lattice relaxation. By assuming quantum energy conserving or non-demolition interactions, we identify an intermediate time scale, between those controlled by self-interactions and thermalization, where coherence decays irreversibly. This treatment is also adequate for explaining the buildup of quasi-equilibrium of the proton spin system, via the process we called eigen-selectivity. By analyzing a hypothetical time reversal experiment, we identify two sources of coherence loss which are of a very different nature and give rise to distinct time scales of the spin dynamics: (a) reversible or adiabatic quantum decoherence and (b) irreversible or essentially adiabatic quantum decoherence. Local irreversibility arises as a consequence of the uncertainty introduced by

  19. Proton magnetic relaxation and internal rotations in tetramethylammonium cadmium chloride

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Utton, D. B.

    1976-01-01

    Nuclear magnetic resonance (NMR) and relaxation studies of the proton spin-lattice relaxation time (PSLRT) and proton second moment (PSM) are reported. Tetramethylammonium cadmium chloride (TMCC) was selected as a diamagnetic member of the isomorphic series, and hence proton data relate directly to the motion of the tetramethylammonium ion in the absence of paramagnetic ions. In the model adopted, the correlation time for hindered motion of one of the methyl groups differs from that of the other three groups in the low-temperature phase below 104 K. PSLRT and PSM values agree closely with experimental data with this model. Crystallographic phase transitions in TMCC occur at 104 K and 119 K according to the PSLRT measurements. Dipolar interactions between adjacent protons account for the PSLR rates below 104 K.

  20. Local Spin Relaxation within the Random Heisenberg Chain

    NASA Astrophysics Data System (ADS)

    Herbrych, J.; Kokalj, J.; Prelovšek, P.

    2013-10-01

    Finite-temperature local dynamical spin correlations Snn(ω) are studied numerically within the random spin-1/2 antiferromagnetic Heisenberg chain. The aim is to explain measured NMR spin-lattice relaxation times in BaCu2(Si0.5Ge0.5)2O7, which is the realization of a random spin chain. In agreement with experiments we find that the distribution of relaxation times within the model shows a very large span similar to the stretched-exponential form. The distribution is strongly reduced with increasing T, but stays finite also in the high-T limit. Anomalous dynamical correlations can be associated with the random singlet concept but not directly with static quantities. Our results also reveal the crucial role of the spin anisotropy (interaction), since the behavior is in contrast with the ones for the XX model, where we do not find any significant T dependence of the distribution.

  1. 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.

  2. 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.

  3. Liquid-state paramagnetic relaxation from first principles

    NASA Astrophysics Data System (ADS)

    Rantaharju, Jyrki; Vaara, Juha

    2016-10-01

    We simulate nuclear and electron spin relaxation rates in a paramagnetic system from first principles. Sampling a molecular dynamics trajectory with quantum-chemical calculations produces a time series of the instantaneous parameters of the relevant spin Hamiltonian. The Hamiltonians are, in turn, used to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by studying the aqueous solution of the Ni2 + ion. Taking advantage of Kubo's theory, the spin-lattice (T1) and spin-spin (T2) relaxation rates are extracted from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available experimental data is obtained by the method.

  4. The relationship between reorientational molecular motions and phase transitions in [Mg(H2O)6](BF4)2, studied with the use of 1H and 19F NMR and FT-MIR

    NASA Astrophysics Data System (ADS)

    Mikuli, Edward; Hetmańczyk, Joanna; Grad, Bartłomiej; Kozak, Asja; Wasicki, Jan W.; Bilski, Paweł; Hołderna-Natkaniec, Krystyna; Medycki, Wojciech

    2015-02-01

    A 1H and 19F nuclear magnetic resonance study of [Mg(H2O)6](BF4)2 has confirmed the existence of two phase transitions at Tc1 ≈ 257 K and Tc2 ≈ 142 K, detected earlier by the DSC method. These transitions were reflected by changes in the temperature dependences of both proton and fluorine of second moments M2H and M2F and of spin-lattice relaxation times T1H and T1F. The study revealed anisotropic reorientations of whole [Mg(H2O)6]2+ cations, reorientations by 180° jumps of H2O ligands, and aniso- and isotropic reorientations of BF4- anions. The activation parameters for these motions were obtained. It was found that the phase transition at Tc1 is associated with the reorientation of the cation as a whole unit around the C3 axis and that at Tc2 with isotropic reorientation of the BF4- anions. The temperature dependence of the full width at half maximum value of the infrared band of ρt(H2O) mode (at ˜596 cm-1) indicated that in phases I and II, all H2O ligands in [Mg(H2O)6]2+ perform fast reorientational motions (180° jumps) with a mean value of activation energy equal to ca 10 kJ mole-1, what is fully consistent with NMR results. The phase transition at Tc1 is associated with a sudden change of speed of fast (τR ≈ 10-12 s) reorientational motions of H2O ligands. Below Tc2 (in phase III), the reorientations of certain part of the H2O ligands significantly slow down, while others continue their fast reorientation with an activation energy of ca 2 kJ mole-1. This fast reorientation cannot be evidenced in NMR relaxation experiments. Splitting of certain IR bands connected with H2O ligands at the observed phase transitions suggests a reduction of the symmetry of the octahedral [Mg(H2O)6]2+ complex cation.

  5. Understanding Structure-Property Correlation in Monocationic and Dicationic Ionic Liquids through Combined Fluorescence and Pulsed-Field Gradient (PFG) and Relaxation NMR Experiments.

    PubMed

    Kumar Sahu, Prabhat; Ghosh, Arindam; Sarkar, Moloy

    2015-11-05

    Steady state, time-resolved fluorescence and NMR experiments are carried out to gain deeper insights into the structure-property correlation in structurally similar monocationic and dicationic room-temperature ionic liquids (RTILs). The excitation wavelength dependent fluorescence response of fluorophore in 1-methy-3-propyllimidazolium bis(trifluoromethylsulfonyl)amide [C3MIm][NTf2] is found to be different from that of 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide [C6(MIm)2][NTf2]2 and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [C6MIm][NTf2]. The outcomes of the present solvent dynamics study in [C3MIm][NTf2] when compared with those in [C6(MIm)2][NTf2]2 and in [C6MIm][NTf2] from our previous studies (Phys. Chem. Chem. Phys. 2014, 16, 12918-12928) indicate the involvement of dipolar rotation of imidazolium cation during solvation. To correlate the findings of solvation dynamics study with the dipolar rotation of the imidazolium ring, pulsed-field gradient (PFG)-NMR technique for translational diffusion coefficient measurement and (1)H as well as (19)F spin-lattice relaxation measurements are employed. NMR investigation reveals that an ultrafast component of solvation can be related to the dipolar rotation of imidazolium cation; hence, the role of dipolar rotation of cations in governing the dynamics of solvation in ILs cannot be ignored. Analysis of the rotational relaxation dynamics data by the Stokes-Einstein-Debye hydrodynamic theory unveils distinctive features of solute-solvent interaction in [C3MIm][NTf2] and [C6(MIm)2][NTf2]2.

  6. 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.

  7. Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

    NASA Astrophysics Data System (ADS)

    Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

    2001-06-01

    Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used.

  8. Multi-scales nuclear spin relaxation of liquids in porous media

    NASA Astrophysics Data System (ADS)

    Korb, Jean-Pierre

    2010-03-01

    The magnetic field dependence of the nuclear spin-lattice relaxation rate 1/T(ω) is a rich source of dynamical information for characterizing the molecular dynamics of liquids in confined environments. Varying the magnetic field changes the Larmor frequency ω, and thus the fluctuations to which the nuclear spin relaxation is sensitive. Moreover, this method permits a more complete characterization of the dynamics than the usual measurements as a function of temperature at fixed magnetic field strength, because many common solvent liquids have phase transitions that may alter significantly the character of the dynamics over the temperature range usually studied. Further, the magnetic field dependence of the spin-lattice relaxation rate, 1/T(ω), provides a good test of the theories that relate the measurement to the microdynamical behavior of the liquid. This is especially true in spatially confined systems where the effects of reduced dimensionality may force more frequent reencounters of the studied proton spin-bearing molecules with paramagnetic impurities at the pore surfaces that may alter the correlation functions that enter the relaxation equations in a fundamental way. We show by low field NMR relaxation that changing the amount of surface paramagnetic impurities leads to striking different pore-size dependences of the relaxation times T and T of liquids in pores. Here, we focus mainly on high surface area porous materials including calibrated porous silica glasses, granular packings, heterogeneous catalytic materials, cement-based materials and natural porous materials such as clay minerals and rocks. Recent highlights NMR relaxation works are reviewed for these porous materials, like continuous characterization of the evolving microstructure of various cementitious materials and measurement of wettability in reservoir carbonate rocks. Although, the recent applications of 2-dimensional T-T and T-z-store-T correlation experiments for characterization of

  9. Proton-detected 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H-1H RFDR mixing on a natural abundant sample under ultrafast MAS

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-09-01

    In this contribution, we have demonstrated a proton detection-based approach on a natural abundant powdered L-Histidine HCl-H2O sample at ultrafast magic angle spinning (MAS) to accomplish 14N/14N correlation from a 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H finite-pulse radio frequency-driven recoupling (fp-RFDR). Herein the heteronuclear magnetization transfer between 14N and 1H has been achieved by HMQC experiment, whereas 14N/14N correlation is attained through enhanced 1H-1H spin diffusion process due to 1H-1H dipolar recoupling during the RFDR mixing. While the use of ultrafast MAS (90 kHz) provides sensitivity enhancement through increased 1H transverse relaxation time (T2), the use of micro-coil probe which can withstand strong 14N radio frequency (RF) fields further improves the sensitivity per unit sample volume.

  10. Spin-lattice coupling mediated multiferroicity in (ND4)2FeCl5 • D2O

    SciTech Connect

    Tian, Wei; Cao, Huibo; Wang, Jincheng; Ye, Feng; Matsuda, Masaaki; Yan, Jiaqiang; Liu, Yaohua; Garlea, Vasile O.; Agrawal, Harish K.; Chakoumakos, Bryan C.; Sales, Brian C.; Fishman, Randy Scott; Fernandez-Baca, Jaime A.

    2016-12-07

    In this paper, we report a neutron diffraction study of the multiferroic mechanism in (ND4)2FeCl5 • D2O, a molecular compound that exhibits magnetically induced ferroelectricity. This material exhibits two successive magnetic transitions on cooling: a long-range order transition to an incommensurate (IC) collinear sinusoidal spin state at TN = 7.3 K, followed by a second transition to an IC cycloidal spin state at TFE = 6.8 K, the latter of which is accompanied by spontaneous ferroelectric polarization. The cycloid structure is strongly distorted by spin-lattice coupling, as evidenced by the observations of both odd and even higher-order harmonics associated with the cycloid wave vector, and a weak commensurate phase that coexists with the IC phase. The second-order harmonic appears at TFE, thereby providing unambiguous evidence that the onset of the electric polarization is accompanied by a lattice modulation due to spin-lattice interaction. The neutron results, in conjunction with the negative thermal expansion and large magnetostriction observed, indicate that spin-lattice coupling plays a critical role in the ferroelectric mechanism of (ND4)2FeCl5 • D2O.

  11. Relaxation Times and Line Widths of Isotopically-Substituted Nitroxides in Aqueous Solution at X-band

    PubMed Central

    Biller, Joshua R.; Meyer, Virginia; Elajaili, Hanan; Rosen, Gerald M.; Kao, Joseph P.Y.; Eaton, Sandra S.; Eatona, Gareth R.

    2011-01-01

    Optimization of nitroxides as probes for EPR imaging requires detailed understanding of spectral properties. Spin lattice relaxation times, spin packet line widths, nuclear hyperfine splitting, and overall lineshapes were characterized for six low molecular weight nitroxides in dilute deoxygenated aqueous solution at X-band. The nitroxides included 6-member, unsaturated 5-member, or saturated 5-member rings, most of which were isotopically labeled. The spectra are near the fast tumbling limit with T1 ~ T2 in the range of 0.50 to 1.1 μs at ambient temperature. Both spin-lattice relaxation T1 and spin-spin relaxation T2 are longer for 15N- than for 14N-nitroxides. The dominant contributions to T1 are modulation of nitrogen hyperfine anisotropy and spin rotation. Dependence of T1 on nitrogen nuclear spin state mI was observed for both 14N and 15N. Unresolved hydrogen/deuterium hyperfine couplings dominate overall line widths. Lineshapes were simulated by including all nuclear hyperfine couplings and spin packet line widths that agreed with values obtained by electron spin echo. Line widths and relaxation times are predicted to be about the same at 250 MHz as at X-band. PMID:21843961

  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. 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.

  14. 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.

  15. Suppression of Raman electron spin relaxation of radicals in crystals. Comparison of Cu2+ and free radical relaxation in triglycine sulfate and Tutton salt single crystals.

    PubMed

    Hoffmann, S K; Goslar, J; Lijewski, S

    2011-08-31

    Electron spin-lattice relaxation was measured by the electron spin echo method in a broad temperature range above 4.2 K for Cu(2+) ions and free radicals produced by ionizing radiation in triglycine sulfate (TGS) and Tutton salt (NH4)(2)Zn(SO4)2 ⋅ 6H2O crystals. Localization of the paramagnetic centres in the crystal unit cells was determined from continuous wave electron paramagnetic resonance spectra. Various spin relaxation processes and mechanisms are outlined. Cu(2+) ions relax fast via two-phonon Raman processes in both crystals involving the whole phonon spectrum of the host lattice. This relaxation is slightly slower for TGS where Cu(2+) ions are in the interstitial position. The ordinary Raman processes do not contribute to the radical relaxation which relaxes via the local phonon mode. The local mode lies within the acoustic phonon band for radicals in TGS but within the optical phonon range in (NH4)(2)Zn(SO4)2 ⋅ 6H2O. In the latter the cross-relaxation was considered. A lack of phonons around the radical molecules suggested a local crystal amorphisation produced by x- or γ-rays.

  16. 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

  17. Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities

    SciTech Connect

    Meriles, Carlos A.; Doherty, Marcus W.

    2014-07-14

    Key to future spintronics and spin-based information processing technologies is the generation, manipulation, and detection of spin polarization in a solid state platform. Here, we theoretically explore an alternative route to spin injection via the use of dynamically polarized nitrogen-vacancy (NV) centers in diamond. We focus on the geometry where carriers and NV centers are confined to proximate, parallel layers and use a “trap-and-release” model to calculate the spin cross-relaxation probabilities between the charge carriers and neighboring NV centers. We identify near-unity regimes of carrier polarization depending on the NV spin state, applied magnetic field, and carrier g-factor. In particular, we find that unlike holes, electron spins are distinctively robust against spin-lattice relaxation by other, unpolarized paramagnetic centers. Further, the polarization process is only weakly dependent on the carrier hopping dynamics, which makes this approach potentially applicable over a broad range of temperatures.

  18. Paramagnetic relaxation in anisotropic materials in zero and weak constant fields

    SciTech Connect

    Fokina, N. P.; Khalvashi, E. Kh.; Khutsishvili, K. O.

    2014-12-21

    Paramagnetic relaxation in strongly anisotropic materials is analytically investigated in zero and weak constant magnetic fields. The objectives of the microscopic analytical investigation are (i) the weak-field electron paramagnetic resonance (EPR) linewidth and (ii) the electron spin relaxation rates given by a calorimetric Gorter type experiment in the zero constant field at the arbitrary low-frequency field directions, respectively, to the sample crystallographic axes. The EPR linewidth is calculated under the suggestion of its spin-phonon nature at the one-phonon mechanism of the spin-lattice relaxation in the case of the strong isotropic exchange interaction for the arbitrary direction Z of the constant magnetic field. The EPR linewidth is presented as the half sum of the zero-field relaxation rates, measured by the Gorter experiment with the low-frequency field oriented along the X, Y axes. With the help of the macroscopic consideration, it is shown that the zero-field relaxation rates describe the relaxation of the X and Y magnetization components in a zero or weak constant magnetic field. The relaxation rates of the magnetizations created along a,b,c crystallographic axes by a low-frequency field in a Gorter type experiment follow the obtained expressions in the particular cases and are in the experimentally confirmed relations with the EPR linewidth.

  19. NMR spin relaxation rates in the Heisenberg bilayer

    NASA Astrophysics Data System (ADS)

    Mendes, Tiago; Curro, Nicholas; Scalettar, Richard; Paiva, Thereza; Dos Santos, Raimundo R.

    One of the striking features of heavy fermions is the fact that in the vicinity of a quantum phase transition these systems exhibit the breakdown of Fermi-liquid behavior and superconductivity. Nuclear magnetic resonance (NMR) expirements play an important role in the study of these phenomena. Measurements of NMR spin relaxation rates and Knight shift, for instance, can be used to probe the electronic spin susceptibility of these systems. Here we studied the NMR response of the Heisenberg bilayer model. In this model, it is well known that the increase of the interplane coupling between the planes, Jperp, supresses the antiferromagnetic order at a quantum critical point (QCP). We use stochastic series expansion (SSE) and the maximum-entropy analytic continuation method to calculate the NMR spin lattice relaxation rate 1 /T1 and the spin echo decay 1 /T2 G as function of Jperp. The spin echo decay, T2 G increases for small Jperp, due to the increase of the order parameter, and then vanishes abruptly in the QCP. The effects of Jperp dilution disorder in the QCP and the relaxation rates are also discussed. This research was supported by the NNSA Grant Number DE-NA 0002908, and Ciência sem fronteiras program/CNPQ.

  20. Electron spin relaxation in x-lithium phthalocyanine.

    PubMed

    Sato, Hideo; Dalton, Lauraine A; Ha, Duc; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2007-07-19

    Continuous-wave linewidths and spin susceptibilities, spin-spin relaxation rates (1/T2), and spin-lattice relaxation rates (1/T1) for two sources of x-LiPc were measured at 9.5 GHz between 15 and 298 K. Relaxation rates at 34 GHz were measured between 80 and 298 K. Room-temperature relaxation rates also were measured at 250 MHz, 1.9 GHz, and 2.76 GHz. The temperature dependences of linewidths and spin susceptibilities are characteristic of 1-D organic conductors. The ratio of populations of localized and delocalized electrons varies with sample preparation. For a single needle between 15 and about 200 K, 1/T2 is higher for the parallel orientation, but 1/T1 is higher for the perpendicular orientation, consistent with predictions based on dipolar interactions. Between about 60 and 150 K, which is the temperature regime in which spin susceptibility is changing rapidly with temperature, 1/T1 exhibits a non-monotonic dependence on temperature and is lower at 34 GHz than at 9.5 GHz. In other organic conductors, this dependence has been attributed to a bottleneck mechanism of relaxation. At higher temperatures, 1/T1 becomes less orientation-dependent. At room temperature, T1 increases rapidly between 250 MHz (3.0 micros) and 2.76 GHz (6.3 micros) and then shows less frequency dependence up to 34 GHz (9.8 micros). The relaxation rate near room temperature might have a substantial contribution from spin hopping perpendicular to the stacking axis of the molecules.

  1. Nuclear Magnetic Spin-Noise and Unusual Relaxation of Oxygen-17 in Water

    NASA Astrophysics Data System (ADS)

    Bendet-Taicher, Eli

    Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) have evolved into widely used techniques, providing diagnostic power in medicine and material sciences due to their high precision and non-invasive nature. Due to the small population differences between spin energy states, a significant sensitivity problem for NMR arises. The low sensitivity of NMR is probably its greatest limitation for applications to biological systems. An alternative probe tuning strategy based on the spin-noise response for application in standard one-dimensional and common high-resolution multidimensional standard biomolecular NMR experiments has shown an increase of up to 50% signal-to-noise (SNR) in one-dimensional NMR experiments and an increase of up to 22% in multi-dimensional ones. The method requires the adjustment of the optimal tuning condition, which may be offset by several hundreds kHz from the conventional tuning settings using the noise response of the water protons as an indicator. This work is described in the first part of the thesis (chapters 2--3). The second part (Chapter 4) of the thesis deals with anomalous oxygen-17 NMR relaxation behavior in water. Oxygen-17 (17O), which has spin of 5/2 and a natural abundance of 0.0373% possesses an electric quadrupole moment. Spin-lattice and spin-spin relaxation occur by the quadrupole interaction, while the J-coupling to 1H spins and exchange are deciding factors. T1 and T2 of 17O in water have been previously measured over a large range of temperatures. The spin-spin relaxation times of 17O as a function of temperature show an anomalous behaviour, expressed by a local maximum at the temperature of maximum density (TMD) of water. It is shown that the same anomalous behaviour shifts to the respective temperatures of maximum density for H2O/D2O solutions with different compositions and salt concentrations. This phenomenon can be correlated to the pH dependency of T2 of 17O in water, and water proton exchange rates

  2. Electron spin relaxation in pseudo-Jahn-Teller low-symmetry Cu(II) complexes in diaqua(L-aspartate)Zn(II).H(2)O crystals.

    PubMed

    Hoffmann, S K; Hilczer, W; Goslar, J; Massa, M M; Calvo, R

    2001-11-01

    Low-temperature (4-55 K) pulsed EPR measurements were performed with the magnetic field directed along the z-axis of the g-factor of the low-symmetry octahedral complex [(63)Cu(L-aspartate)(2)(H2O)2] undergoing dynamic Jahn-Teller effect in diaqua(L-aspartate)Zn(II) hydrate single crystals. Spin-lattice relaxation time T(1) and phase memory time T(M) were determined by the electron spin echo (ESE) method. The relaxation rate 1/T(1) increases strongly over 5 decades in the temperature range 4-55 K. Various processes and mechanisms of T(1)-relaxation are discussed, and it is shown that the relaxation is governed mainly by Raman relaxation processes with the Debye temperature Theta(D)=204 K, with a detectable contribution from disorder in the doped Cu(2+) ions system below 12 K. An analytical approximation of the transport integral I(8) is given in temperature range T=0.025-10Theta(D) and applied for computer fitting procedures. Since the Jahn-Teller distorted configurations differ strongly in energy (delta(12)=240 cm(-1)), there is no influence of the classical vibronic dynamics mechanism on T(1). Dephasing of the ESE (phase relaxation) is governed by instantaneous diffusion and spectral diffusion below 20 K with resulting rigid lattice value 1/T(0)(M)=1.88 MHz. Above this temperature the relaxation rate 1/T(M) increases upon heating due to two mechanisms. The first is the phonon-controlled excitation to the first excited vibronic level of energy Delta=243 cm(-1), with subsequent tunneling to the neighbor potential well. This vibronic-type dynamics also produces a temperature-dependent broadening of lines in the ESEEM spectra. The second mechanism is produced by the spin-lattice relaxation. The increase in T(M) is described in terms of the spin packets forming inhomogeneously broadened EPR lines.

  3. Dynamical crossover in an Ising spin glass above T(g): a muon-spin-relaxation investigation of Fe0.05TiS2.

    PubMed

    Keren, Amit; Gulener, F; Campbell, Ian; Bazalitsky, Galina; Amato, Alex

    2002-09-02

    We investigate the temperature dependence of the spin-spin dynamical autocorrelation function of the Ising spin glass Fe0.05TiS2 through field dependent muon-spin lattice relaxation measurements. We successfully analyze the results using the Ogielski function, namely, t(-x)exp((-[t/tau](y)) as employed in numerical simulations. The experimental estimates of x, y, and tau are compared with those from simulations. Our major finding is that in this system the correlation function changes its nature from Ogielski to a form indistinguishable from pure stretched exponential upon cooling close to T(g), indicating a dynamical crossover.

  4. 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.

  5. The relationship between reorientational molecular motions and phase transitions in [Mg(H{sub 2}O){sub 6}](BF{sub 4}){sub 2}, studied with the use of {sup 1}H and {sup 19}F NMR and FT-MIR

    SciTech Connect

    Mikuli, Edward Hetmańczyk, Joanna; Grad, Bartłomiej; Kozak, Asja; Wąsicki, Jan W.; Bilski, Paweł; Hołderna-Natkaniec, Krystyna; Medycki, Wojciech

    2015-02-14

    A {sup 1}H and {sup 19}F nuclear magnetic resonance study of [Mg(H{sub 2}O){sub 6}](BF{sub 4}){sub 2} has confirmed the existence of two phase transitions at T{sub c1} ≈ 257 K and T{sub c2} ≈ 142 K, detected earlier by the DSC method. These transitions were reflected by changes in the temperature dependences of both proton and fluorine of second moments M{sub 2}{sup H} and M{sub 2}{sup F} and of spin-lattice relaxation times T{sub 1}{sup H} and T{sub 1}{sup F}. The study revealed anisotropic reorientations of whole [Mg(H{sub 2}O){sub 6}]{sup 2+} cations, reorientations by 180° jumps of H{sub 2}O ligands, and aniso- and isotropic reorientations of BF{sub 4}{sup −} anions. The activation parameters for these motions were obtained. It was found that the phase transition at T{sub c1} is associated with the reorientation of the cation as a whole unit around the C{sub 3} axis and that at T{sub c2} with isotropic reorientation of the BF{sub 4}{sup −} anions. The temperature dependence of the full width at half maximum value of the infrared band of ρ{sub t}(H{sub 2}O) mode (at ∼596 cm{sup −1}) indicated that in phases I and II, all H{sub 2}O ligands in [Mg(H{sub 2}O){sub 6}]{sup 2+} perform fast reorientational motions (180° jumps) with a mean value of activation energy equal to ca 10 kJ mole{sup −1}, what is fully consistent with NMR results. The phase transition at T{sub c1} is associated with a sudden change of speed of fast (τ{sub R} ≈ 10{sup −12} s) reorientational motions of H{sub 2}O ligands. Below T{sub c2} (in phase III), the reorientations of certain part of the H{sub 2}O ligands significantly slow down, while others continue their fast reorientation with an activation energy of ca 2 kJ mole{sup −1}. This fast reorientation cannot be evidenced in NMR relaxation experiments. Splitting of certain IR bands connected with H{sub 2}O ligands at the observed phase transitions suggests a reduction of the symmetry of the octahedral [Mg(H{sub 2}O

  6. Zero field splitting fluctuations induced phase relaxation of Gd3+ in frozen solutions at cryogenic temperatures

    PubMed Central

    Raitsimring, A.; Dalaloyan, A.; Collauto, A.; Feintuch, A.; Meade, T.; Goldfarb, D.

    2015-01-01

    Distance measurements using double electron–electron resonance (DEER) and Gd3+ chelates for spin labels (GdSL) have been shown to be an attractive alternative to nitroxide spin labels at W-band (95 GHz). The maximal distance that can be accessed by DEER measurements and the sensitivity of such measurements strongly depends on the phase relaxation of Gd3+ chelates in frozen, glassy solutions. In this work, we explore the phase relaxation of Gd3+-DOTA as a representative of GdSL in temperature and concentration ranges typically used for W-band DEER measurements. We observed that in addition to the usual mechanisms of phase relaxation known for nitroxide based spin labels, GdSL are subjected to an additional phase relaxation mechanism that features an increase in the relaxation rate from the center to the periphery of the EPR spectrum. Since the EPR spectrum of GdSL is the sum of subspectra of the individual EPR transitions, we attribute this field dependence to transition dependent phase relaxation. Using simulations of the EPR spectra and its decomposition into the individual transition subspectra, we isolated the phase relaxation of each transition and found that its rate increases with |ms|. We suggest that this mechanism is due to transient zero field splitting (tZFS), where its magnitude and correlation time are scaled down and distributed as compared with similar situations in liquids. This tZFS induced phase relaxation mechanism becomes dominant (or at least significant) when all other well-known phase relaxation mechanisms, such as spectral diffusion caused by nuclear spin diffusion, instantaneous and electron spin spectral diffusion, are significantly suppressed by matrix deuteration and low concentration, and when the temperature is sufficiently low to disable spin lattice interaction as a source of phase relaxation. PMID:25442776

  7. Zero field splitting fluctuations induced phase relaxation of Gd3+ in frozen solutions at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Raitsimring, A.; Dalaloyan, A.; Collauto, A.; Feintuch, A.; Meade, T.; Goldfarb, D.

    2014-11-01

    Distance measurements using double electron-electron resonance (DEER) and Gd3+ chelates for spin labels (GdSL) have been shown to be an attractive alternative to nitroxide spin labels at W-band (95 GHz). The maximal distance that can be accessed by DEER measurements and the sensitivity of such measurements strongly depends on the phase relaxation of Gd3+ chelates in frozen, glassy solutions. In this work, we explore the phase relaxation of Gd3+-DOTA as a representative of GdSL in temperature and concentration ranges typically used for W-band DEER measurements. We observed that in addition to the usual mechanisms of phase relaxation known for nitroxide based spin labels, GdSL are subjected to an additional phase relaxation mechanism that features an increase in the relaxation rate from the center to the periphery of the EPR spectrum. Since the EPR spectrum of GdSL is the sum of subspectra of the individual EPR transitions, we attribute this field dependence to transition dependent phase relaxation. Using simulations of the EPR spectra and its decomposition into the individual transition subspectra, we isolated the phase relaxation of each transition and found that its rate increases with |ms|. We suggest that this mechanism is due to transient zero field splitting (tZFS), where its magnitude and correlation time are scaled down and distributed as compared with similar situations in liquids. This tZFS induced phase relaxation mechanism becomes dominant (or at least significant) when all other well-known phase relaxation mechanisms, such as spectral diffusion caused by nuclear spin diffusion, instantaneous and electron spin spectral diffusion, are significantly suppressed by matrix deuteration and low concentration, and when the temperature is sufficiently low to disable spin lattice interaction as a source of phase relaxation.

  8. Nuclear Spin Relaxation Characteristic of Submonolayer He Films in Nanochannels

    NASA Astrophysics Data System (ADS)

    Matsushita, Taku; Kawai, Ryosuke; Kuze, Atsushi; Hieda, Mitsunori; Wada, Nobuo

    2014-04-01

    In order to obtain information on dynamics of helium films in the nondegenerate fluid region, we have performed a pulsed-NMR experiment at 3.29 MHz on He films adsorbed in straight 2.4 nm channels of FSM silicates down to 0.54 K. In general, the spin-lattice and spin-spin relaxation times and were explained in terms of the two-dimensional Bloembergen-Purcell-Pound model for dipolar relaxation. Temperature dependences of in submonolayer He films show a minimum, indicating that the dipolar-field correlation time is about s. The temperature of the minimum monotonically lowers with increasing coverage, suggesting that He adatoms become more mobile at higher coverages. The low-dimensional property of He adatoms is observed as the separation of and above where . On the other hand, several features specific to films in the nanochannel geometry were also found. Especially, the temperature dependence of becomes very small just below and shows a shoulder at lower temperatures. This anomaly has not been observed in He adsorbed in wider pores or on flat surfaces, so that it is considered to be characteristic of He films confined in narrow channels with a diameter of a few nm.

  9. NMR relaxation of the orientation of single segments in semiflexible dendrimers

    SciTech Connect

    Markelov, Denis A. Gotlib, Yuli Ya.; Dolgushev, Maxim; Blumen, Alexander

    2014-06-28

    We study the orientational properties of labeled segments in semiflexible dendrimers making use of the viscoelastic approach of Dolgushev and Blumen [J. Chem. Phys. 131, 044905 (2009)]. We focus on the segmental orientational autocorrelation functions (ACFs), which are fundamental for the frequency-dependent spin-lattice relaxation times T{sub 1}(ω). We show that semiflexibility leads to an increase of the contribution of large-scale motions to the ACF. This fact influences the position of the maxima of the [1/T{sub 1}]-functions. Thus, going from outer to inner segments, the maxima shift to lower frequencies. Remarkably, this feature is not obtained in the classical bead-spring model of flexible dendrimers, although many experiments on dendrimers manifest such a behavior.

  10. Nuclear magnetic relaxation dispersion investigations of water retention mechanism by cellulose ethers in mortars

    SciTech Connect

    Patural, Laetitia; Korb, Jean-Pierre; Govin, Alexandre; Grosseau, Philippe; Ruot, Bertrand; Deves, Olivier

    2012-10-15

    We show how nuclear magnetic spin-lattice relaxation dispersion of proton-water (NMRD) can be used to elucidate the effect of cellulose ethers on water retention and hydration delay of freshly-mixed white cement pastes. NMRD is useful to determine the surface diffusion coefficient of water, the specific area and the hydration kinetics of the cement-based material. In spite of modifications of the solution's viscosity, we show that the cellulosic derivatives do not modify the surface diffusion coefficient of water. Thus, the mobility of water present inside the medium is not affected by the presence of polymer. However, these admixtures modify significantly the surface fraction of mobile water molecules transiently present at solid surfaces. This quantity measured, for the first time, for all admixed cement pastes is thus relevant to explain the water retention mechanism.

  11. Mechanisms of relaxation and spin decoherence in nanomagnets

    NASA Astrophysics Data System (ADS)

    van Tol, Johan

    Relaxation in spin systems is of great interest with respect to various possible applications like quantum information processing and storage, spintronics, and dynamic nuclear polarization (DNP). The implementation of high frequencies and fields is crucial in the study of systems with large zero-field splitting or large interactions, as for example molecular magnets and low dimensional magnetic materials. Here we will focus on the implementation of pulsed Electron Paramagnetic Resonance (ERP) at multiple frequencies of 10, 95, 120, 240, and 336 GHz, and the relaxation and decoherence processes as a function of magnetic field and temperature. Firstly, at higher frequencies the direct single-phonon spin-lattice relaxation (SLR) is considerably enhanced, and will more often than not be the dominant relaxation mechanism at low temperatures, and can be much faster than at lower fields and frequencies. In principle the measurement of the SLR rates as a function of the frequency provides a means to map the phonon density of states. Secondly, the high electron spin polarization at high fields has a strong influence on the spin fluctuations in relatively concentrated spin systems, and the contribution of the electron-electron dipolar interactions to the coherence rate can be partially quenched at low temperatures. This not only allows the study of relatively concentrated spin systems by pulsed EPR (as for example magnetic nanoparticles and molecular magnets), it enables the separation of the contribution of the fluctuations of the electron spin system from other decoherence mechanisms. Besides choice of temperature and field, several strategies in sample design, pulse sequences, or clock transitions can be employed to extend the coherence time in nanomagnets. A review will be given of the decoherence mechanisms with an attempt at a quantitative comparison of experimental rates with theory.

  12. Water and Backbone Dynamics in a Hydrated Protein

    PubMed Central

    Diakova, Galina; Goddard, Yanina A.; Korb, Jean-Pierre; Bryant, Robert G.

    2010-01-01

    Abstract Rotational immobilization of proteins permits characterization of the internal peptide and water molecule dynamics by magnetic relaxation dispersion spectroscopy. Using different experimental approaches, we have extended measurements of the magnetic field dependence of the proton-spin-lattice-relaxation rate by one decade from 0.01 to 300 MHz for 1H and showed that the underlying dynamics driving the protein 1H spin-lattice relaxation is preserved over 4.5 decades in frequency. This extension is critical to understanding the role of 1H2O in the total proton-spin-relaxation process. The fact that the protein-proton-relaxation-dispersion profile is a power law in frequency with constant coefficient and exponent over nearly 5 decades indicates that the characteristics of the native protein structural fluctuations that cause proton nuclear spin-lattice relaxation are remarkably constant over this wide frequency and length-scale interval. Comparison of protein-proton-spin-lattice-relaxation rate constants in protein gels equilibrated with 2H2O rather than 1H2O shows that water protons make an important contribution to the total spin-lattice relaxation in the middle of this frequency range for hydrated proteins because of water molecule dynamics in the time range of tens of ns. This water contribution is with the motion of relatively rare, long-lived, and perhaps buried water molecules constrained by the confinement. The presence of water molecule reorientational dynamics in the tens of ns range that are sufficient to affect the spin-lattice relaxation driven by 1H dipole-dipole fluctuations should make the local dielectric properties in the protein frequency dependent in a regime relevant to catalytically important kinetic barriers to conformational rearrangements. PMID:20085726

  13. Characterization of the International Humic Substances Society standard and reference fulvic and humic acids by solution state carbon-13 (13C) and hydrogen-1 (1H) nuclear magnetic resonance spectrometry

    USGS Publications Warehouse

    Thorn, Kevin A.; Folan, Daniel W.; MacCarthy, Patrick

    1989-01-01

    Standard and reference samples of the International Humic Substances Society have been characterized by solution state carbon-13 and hydrogen-1 nuclear magnetic resonance (NMR) spectrometry. Samples included the Suwannee River, soil, and peat standard fulvic and humic acids, the Leonardite standard humic acid, the Nordic aquatic reference fulvic and humic acids, and the Summit Hill soil reference humic acid. Aqueous-solution carbon-13 NMR analyses included the measurement of spin-lattice relaxation times, measurement of nuclear Overhauser enhancement factors, measurement of quantitative carbon distributions, recording of attached proton test spectra, and recording of spectra under nonquantitative conditions. Distortionless enhancement by polarization transfer carbon-13 NMR spectra also were recorded on the Suwannee River fulvic acid in deuterated dimethyl sulfoxide. Hydrogen-1 NMR spectra were recorded on sodium salts of the samples in deuterium oxide. The carbon aromaticities of the samples ranged from 0.24 for the Suwannee River fulvic acid to 0.58 for the Leonardite humic acid.

  14. Effects of spin-lock field direction on the quantitative measurement of spin-lattice relaxation time constant in the rotating frame (T1ρ) in a clinical MRI system

    SciTech Connect

    Yee, Seonghwan; Gao, Jia-Hong

    2014-12-15

    Purpose: To investigate whether the direction of spin-lock field, either parallel or antiparallel to the rotating magnetization, has any effect on the spin-lock MRI signal and further on the quantitative measurement of T1ρ, in a clinical 3 T MRI system. Methods: The effects of inverted spin-lock field direction were investigated by acquiring a series of spin-lock MRI signals for an American College of Radiology MRI phantom, while the spin-lock field direction was switched between the parallel and antiparallel directions. The acquisition was performed for different spin-locking methods (i.e., for the single- and dual-field spin-locking methods) and for different levels of clinically feasible spin-lock field strength, ranging from 100 to 500 Hz, while the spin-lock duration was varied in the range from 0 to 100 ms. Results: When the spin-lock field was inverted into the antiparallel direction, the rate of MRI signal decay was altered and the T1ρ value, when compared to the value for the parallel field, was clearly different. Different degrees of such direction-dependency were observed for different spin-lock field strengths. In addition, the dependency was much smaller when the parallel and the antiparallel fields are mixed together in the dual-field method. Conclusions: The spin-lock field direction could impact the MRI signal and further the T1ρ measurement in a clinical MRI system.

  15. Natural relaxation

    NASA Astrophysics Data System (ADS)

    Marzola, Luca; Raidal, Martti

    2016-11-01

    Motivated by natural inflation, we propose a relaxation mechanism consistent with inflationary cosmology that explains the hierarchy between the electroweak scale and Planck scale. This scenario is based on a selection mechanism that identifies the low-scale dynamics as the one that is screened from UV physics. The scenario also predicts the near-criticality and metastability of the Standard Model (SM) vacuum state, explaining the Higgs boson mass observed at the Large Hadron Collider (LHC). Once Majorana right-handed neutrinos are introduced to provide a viable reheating channel, our framework yields a corresponding mass scale that allows for the seesaw mechanism as well as for standard thermal leptogenesis. We argue that considering singlet scalar dark matter extensions of the proposed scenario could solve the vacuum stability problem and discuss how the cosmological constant problem is possibly addressed.

  16. Hydration water dynamics in biopolymers from NMR relaxation in the rotating frame

    NASA Astrophysics Data System (ADS)

    Blicharska, Barbara; Peemoeller, Hartwig; Witek, Magdalena

    2010-12-01

    Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10 -5 s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R1ρ = 1/ T1ρ appears over a range of easily accessible B1 values. Measurements of T1ρ at constant temperature and different B1 values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R1 = 1/ T1. The T1ρ dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme).

  17. Spin dynamics simulation of electron spin relaxation in Ni{sup 2+}(aq)

    SciTech Connect

    Rantaharju, Jyrki Mareš, Jiří Vaara, Juha

    2014-07-07

    The ability to quantitatively predict and analyze the rate of electron spin relaxation of open-shell systems is important for electron paramagnetic resonance and paramagnetic nuclear magnetic resonance spectroscopies. We present a combined molecular dynamics (MD), quantum chemistry (QC), and spin dynamics simulation method for calculating such spin relaxation rates. The method is based on the sampling of a MD trajectory by QC calculations, to produce instantaneous parameters of the spin Hamiltonian used, in turn, to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by simulating the relaxation of electron spin in an aqueous solution of Ni{sup 2+} ion. The spin-lattice (T{sub 1}) and spin-spin (T{sub 2}) relaxation rates are extracted directly from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available, indirectly obtained experimental data is obtained by our method.

  18. Complex mechanism of relaxation in solid chloroxylenol (antibacterial/antifungal agent) studied by ¹H NMR spectroscopy and density functional theory calculations.

    PubMed

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Tomczak, Marzena Agnieszka; Medycki, Wojciech

    2014-03-27

    Molecular relaxation in antibacterial/antifungal agent: chloroxylenol (4-chloro-3,5-dimethylphenol, PCMX) in the solid state was studied by the (1)H NMR and quantum chemistry calculations. The temperature dependencies of the proton spin-lattice relaxation time (T1) in the ranges 15-273 K (at 24.667 MHz), 77-295 K (at 15 MHz), and 112-291 K at 90 MHz and the second moment (M2) of (1)H NMR resonant line in the range 106-380 K were measured. The two minima in the temperature dependence of T1 revealed two activation processes, whereas the M2 dependence in the studied range was quite flat and revealed the only significant reduction at 380 K. The low temperature part of T1(T) dependence indicated the occurrence of two processes characteristic of methyl bearing solids; the quantum mechanics governed incoherent tunneling (responsible for the low temperature flattening of T1) and the classical Arrhenius dependence governed hindered rotation (related to the wide low temperature minimum of 0.066 s at 57 K, 24.667 MHz). The 2D potential energy surface obtained using DFT/B3LYP/6-311++G(2d,p) calculations revealed the inequivalence of methyl groups and the lack of their interplay/coupling. The activation energies of classical hindered rotation are 3.35 and 2.5 kJ/mol, whereas temperatures at which the proton tunneling T(tun) finally ceases are 52 and 63 K, for inequivalent methyl groups. C(p)(T) required for the estimation of T(tun) was calculated purely theoretically on the basis of the Einstein and Debye models of specific heat and 51 modes of atomic vibrations, 4 internal rotations, and 3 torsions calculated by DFT. The -CH3 motion (tunneling and classical) results in the reduction in the (1)H NMR line second moment from 17.3 G(2) (rigid) to approximately 11.05 G(2). The pointed high temperature minimum T1(T) of 0.109 s at 89 K, 24.667 MHz, which shifts with frequency, was assigned to small-angle libration jumps, by the Θ2 = ±15° between two positions of equilibrium. The

  19. 1H-detected 1H- 1H correlation spectroscopy of a stereo-array isotope labeled amino acid under fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroki; Kainosho, Masatsune; Akutsu, Hideo; Fujiwara, Toshimichi

    2010-04-01

    The combined use of selective deuteration, stereo-array isotope labeling (SAIL), and fast magic-angle spinning effectively suppresses the 1H-1H dipolar couplings in organic solids. This method provided the high-field 1H NMR linewidths comparable to those achieved by combined rotation and multiple-pulse spectroscopy. This technique was applied to two-dimensional 1H-detected 1H-1H polarization transfer CHH experiments of valine. The signal sensitivity for the 1H-detected CHH experiments was greater than that for the 13C-detected 1H-1H polarization transfer experiments by a factor of 2-4. We obtained the 1H-1H distances in SAIL valine by CHH experiments with an accuracy of about 0.2 Å by using a theory developed for 1H-1H polarization transfer in 13C-labeled organic compounds.

  20. Electron spin relaxation of exchange coupled pairs of transition metal ions in solids. Ti2+-Ti2+ pairs and single Ti2+ ions in SrF2 crystals.

    PubMed

    Hoffmann, Stanislaw K; Lijewski, Stefan; Goslar, Janina; Ulanov, Volodia A

    2010-01-01

    EPR (X- and Q-band) and electron spin relaxation measured by electron spin echo method (X-band) were studied for Ti(2+)(S=1) and Ti(2+)-Ti(2+) pairs in SrF(2) crystal at room temperature and in the temperature range 4.2-115 K. EPR spectrum consists of a strong line from Ti(2+) and quartets 2:3:3:2 from titanium pairs (S=2). Spin-Hamiltonian parameters of the pairs are g( parallel)=1.883, g( perpendicular)=1.975 and D=0.036 cm(-1). Temperature behavior of the dimer spectrum indicates ferromagnetic coupling between Ti(2+). Spin-lattice relaxation of individuals Ti(2+) is dominated by the ordinary two-phonon Raman process involving the whole phonon spectrum up to the Debye temperature Theta(D)=380 K with spin-phonon coupling parameter equal to 215 cm(-1). Important contribution to the relaxation arises from local mode vibrations of energy 133 cm(-1). The pair relaxation is faster due to the exchange coupling modulation mechanism with the relaxation rate characteristic for ferromagnetic ground state of the pairs 1/T(1) is proportional to [exp(2J/kT)-1](-1) which allowed to estimate the exchange coupling J=36 cm(-1). The theories of electron-lattice relaxation governed by exchange interaction are outlined for extended spin systems, for clusters and for individual dimers. Electron spin echo decay is strongly modulated by coupling with surrounding (19)F nuclei. FT-spectrum of the modulations shows a dipolar splitting of the fluorine lines, which allows the evaluation of the off-center shift of Ti(2+) in pair as 0.132 nm. The electron spin echo dephasing is dominated by an instantaneous diffusion at low temperatures and by the spin-lattice relaxation processes above 18K.

  1. Characterization of heroin samples by 1H NMR and 2D DOSY 1H NMR.

    PubMed

    Balayssac, Stéphane; Retailleau, Emmanuel; Bertrand, Geneviève; Escot, Marie-Pierre; Martino, Robert; Malet-Martino, Myriam; Gilard, Véronique

    2014-01-01

    Twenty-four samples of heroin from different illicit drug seizures were analyzed using proton Nuclear Magnetic Resonance ((1)H NMR) and two-dimensional diffusion-ordered spectroscopy (2D DOSY) (1)H NMR. A careful assignment and quantification of (1)H signals enabled a comprehensive characterization of the substances present in the samples investigated: heroin, its main related impurities (6-acetylmorphine, acetylcodeine, morphine, noscapine and papaverine) and cutting agents (caffeine and acetaminophen in nearly all samples as well as lactose, lidocaine, mannitol, piracetam in one sample only), and hence to establish their spectral signatures. The good agreement between the amounts of heroin, noscapine, caffeine and acetaminophen determined by (1)H NMR and gas chromatography, the reference method in forensic laboratories, demonstrates the validity of the (1)H NMR technique. In this paper, 2D DOSY (1)H NMR offers a new approach for a whole characterization of the various components of these complex mixtures.

  2. Breathing and Relaxation

    MedlinePlus

    ... Home Health Insights Stress & Relaxation Breathing and Relaxation Breathing and Relaxation Make an Appointment Ask a Question ... level is often dependent on his or her breathing pattern. Therefore, people with chronic lung conditions may ...

  3. Relaxation Assessment with Varied Structured Milieu (RELAX).

    ERIC Educational Resources Information Center

    Cassel, Russell N.; Cassel, Susie L.

    1983-01-01

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

  4. Enhanced Y1H Assays for Arabidopis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transcription regulation plays a key role in development and response to environment. To understand this mechanism, we need to know which transcription factor (TFs) would bind to which promoter, thus regulate their target gene expression. Yeast one-hybrid (Y1H) technique can be used to map this kind...

  5. Intrinsic spin and momentum relaxation in organic single-crystalline semiconductors probed by ESR and Hall measurements

    NASA Astrophysics Data System (ADS)

    Tsurumi, Junto; Häusermann, Roger; Watanabe, Shun; Mitsui, Chikahiko; Okamoto, Toshihiro; Matsui, Hiroyuki; Takeya, Jun

    Spin and charge momentum relaxation mechanism has been argued among organic semiconductors with various methods, devices, and materials. However, little is known in organic single-crystalline semiconductors because it has been hard to obtain an ideal organic crystal with an excellent crystallinity and controllability required for accurate measurements. By using more than 1-inch sized single crystals which are fabricated via contentious edge-casting method developed by our group, we have successfully demonstrated a simultaneous determination of spin and momentum relaxation time for gate-induced charges of 3,11-didecyldinaphtho[2,3- d:2',3'- d']benzo[1,2- b:4,5- b']dithiophene, by combining electron spin resonance (ESR) and Hall effect measurements. The obtained temperature dependences of spin and momentum relaxation times are in good agreement in terms of power law with a factor of approximately -2. It is concluded that Elliott-Yafet spin relaxation mechanism can be dominant at room temperature regime (200 - 300 K). Probing characteristic time scales such as spin-lattice, spin-spin, and momentum relaxation times, demonstrated in the present work, would be a powerful tool to elucidate fundamental spin and charge transport mechanisms. We acknowledge the New Energy and Industrial Technology Developing Organization (NEDO) for financial support.

  6. Estimation of free copper ion concentrations in blood serum using T1 relaxation rates

    NASA Astrophysics Data System (ADS)

    Blicharska, Barbara; Witek, Magdalena; Fornal, Maria; MacKay, Alex L.

    2008-09-01

    The water proton relaxation rate constant R1 = 1/ T1 (at 60 MHz) of blood serum is substantially increased by the presence of free Cu 2+ ions at concentrations above normal physiological levels. Addition of chelating agents to serum containing paramagnetic Cu 2+ nulls this effect. This was demonstrated by looking at the effect of adding a chelating agent—D-penicillamine (D-PEN) to CuSO 4 and CuCl 2 aqueous solutions as well as to rabbit blood serum. We propose that the measurement of water proton spin-lattice relaxation rate constants before and after chelation may be used as an alternative approach for monitoring the presence of free copper ions in blood serum. This method may be used in the diagnosis of some diseases (leukaemia, liver diseases and particularly Wilson's disease) because, in contrast to conventional methods like spectrophotometry which records the total number of both bound and free ions, the proton relaxation technique is sensitive solely to free paramagnetic ions dissolved in blood serum. The change in R1 upon chelation was found to be less than 0.06 s -1 for serum from healthy subjects but greater than 0.06 s -1 for serum from untreated Wilson's patients.

  7. The effects of bone on proton NMR relaxation times of surrounding liquids

    NASA Technical Reports Server (NTRS)

    Davis, C. A.; Genant, H. K.; Dunham, J. S.

    1986-01-01

    Preliminary attempts by our group at UCSF to assess fat content of vertebral marrow in the lumbar spine using relaxation time information demonstrated that the presence of trabecular bone affects relaxation times. The objective of this work was a thorough study of the effects of bone on NMR relaxation characteristics of surrounding liquids. Trabecular bone from autopsy specimens was ground up and sifted into a series of powders with graded densities ranging from 0.3 gm/cc to 0.8 gm/cc. Each powder was placed first in n-saline and then in cottonseed oil. With spectroscopy, spin-lattice relaxation times (T1) and effective spin-spin relaxation times (T2*) were measured for each liquid in each bone powder. As bone density and surface to volume ratio increased, T1 decreased faster for saline than for oil. T2* decreased significantly for both water and oil as the surface to volume ratio increased. It was concluded that effects of water on T1 could be explained by a surface interaction at the bone/liquid interface, which restricted rotational and translational motion of nearby molecules. The T1s of oil were not affected since oil molecules are nonpolar, do not participate in significant intermolecular hydrogen bonding, and therefore would not be expected to interact strongly with the bone surface. Effects on T2* could be explained by local magnetic field inhomogeneities created by discontinuous magnetic susceptibility near the bone surface. These preliminary results suggest that water in contact with trabecular bone in vivo will exhibit shortened relaxation times.

  8. Dosimetry of {sup 60}Co and {sup 192}Ir gamma-irradiated agarose gels by proton relaxation time measurement and NMR imaging, in a 0-100 Gy dose range

    SciTech Connect

    Chalansonnet, A.; Briguet, A.; Bonnat, J.L.

    1997-05-01

    Localized irradiation of the skin and subcutaneous tissues with large single doses of gamma rays can induce immediate effects characterized by erythema, desquamation, and necrosis. Correlations between the evolution of the lesions and dosimetry studies have to be established by biophysical methods. NMR studies of the effects of an irradiated Fricke solution might be a means of controlling the delivered irradiation doses. After exposition to ionizing radiations, ferrous ions are transformed into ferric ions. Both are paramagnetic ions, and proton spin-lattice relaxation is accelerated depending on the oxidation reaction. In this study, solution of ammonium ferrous sulfate in an acid environment was incorporated into a gelling substance made with agarose, so that T{sub 1} weighted image contrast could be used to detect ferric ion formation. Experiments with {sup 192}Ir and {sup 90}Co gamma rays with doses in the 0 to 100 Gy range were conducted with Fe{sup 2+} concentrations of 0.5, 1, 1.5, and 2 mM in a gelling substance containing 4% agarose. A relationship was established between the amount of Fe{sup 3+} created and the spin-lattice proton relaxation rate, which led to a straightforward dose-effect relation. The use of such high doses allowed us to reproduce realistic conditions of accidental overexposure. A linear relationship was obtained between the doses absorbed and the NMR parameters measured (T{sub 1} and relative image intensity). 17 refs., 3 figs., 1 tab.

  9. Complete (1) H NMR assignment of cedranolides.

    PubMed

    Perez-Hernandez, Nury; Gordillo-Roman, Barbara; Arrieta-Baez, Daniel; Cerda-Garcia-Rojas, Carlos M; Joseph-Nathan, Pedro

    2017-03-01

    Complete and unambiguous (1) H NMR chemical shift assignment of α-cedrene (2) and cedrol (9), as well as for α-pipitzol (1), isocedrol (10), and the six related compounds 3-8 has been established by iterative full spin analysis using the PERCH NMR software (PERCH Solutions Ltd., Kuopio, Finland). The total sets of coupling constants are described and correlated with the conformational equilibria of the five-membered ring of 1-10, which were calculated using the complete basis set method. Copyright © 2015 John Wiley & Sons, Ltd.

  10. A classical description of relaxation of interacting pairs of unlike spins: Extension to T1 ϱ, T2, and T1 ϱoff, including contact interactions

    NASA Astrophysics Data System (ADS)

    Konig, Seymour H.

    A novel derivation of the equations that describe the spin-lattice magnetic relaxation of nuclear spin moments, in liquids, resulting from magnetic dipolar interactions with neighboring paramagnetic ions, the Solomon-Bloembergen-Morgan equations was previously presented (S. H. Koenig, J. Magn. Reson.31, 1 (1978)). The derivation involves a computation of the dissipative energy flow from the nuclear spins to the lattice rather than a computation of the lattice-produced fluctuations of the local field at the nuclear spins. Two advantages accrue: (1) the spectral densities that enter into the relaxation expressions can be directly related to well-defined absorption transitions and relaxation processes of the paramagnetic ions, clarifying the physical processes that produce relaxation, and (2) the derivation can be readily generalized to paramagnetic ions with arbitrary spin Hamiltonian, and to deviations of their susceptibility from Curie law behavior. The derivation is extended to include relaxation in liquids in the rotating frame: the on resonance T1 ϱ which reduces to T2 for small amplitude radiofrequency fields; and the off resonance T1 ϱoff, which reduces to T1. The results, which are given for contact as well as dipolar interactions, also describe relaxation of 13C and 15N nuclei by protons under conditions of proton-decoupling, a situation becoming increasingly important in the study of biological macromolecules by high-resolution NMR spectroscopy.

  11. Preliminary 1H NMR study on archaeological waterlogged wood.

    PubMed

    Maccotta, Antonella; Fantazzini, Paola; Garavaglia, Carla; Donato, Ines D; Perzia, Patrizia; Brai, Maria; Morreale, Filippa

    2005-01-01

    Magnetic Resonance Relaxation (MRR) and Magnetic Resonance Imaging (MRI) are powerful tools to obtain detailed information on the pore space structure that one is unlikely to obtain in other ways. These techniques are particularly suitable for Cultural Heritage materials, because they use water 1H nuclei as a probe. Interaction with water is one of the main causes of deterioration of materials. Porous structure in wood, for example, favours the penetration of water, which can carry polluting substances and promote mould growth. A particular case is waterlogged wood from underwater discoveries and moist sites; in fact, these finds are very fragile because of chemical, physical and biological decay from the long contact with the water. When wood artefacts are brought to the surface and directly dried in air, there is the collapse of the cellular structures, and wood loses its original form and dimensions and cannot be used for study and museum exhibits. In this work we have undertaken the study of some wood finds coming from Ercolano's harbour by MRR and MRI under different conditions, and we have obtained a characterization of pore space in wood and images of the spatial distribution of the confined water in the wood.

  12. Distinguishing magnetic vs. quadrupolar relaxation in b-NMR using 8Li and 9Li

    NASA Astrophysics Data System (ADS)

    Chatzichristos, A.; McFadden, R. M. L.; Karner, V. L.; Cortie, D. L.; Fang, A.; Levy, C. D. P.; Macfarlane, W. A.; Morris, G. D.; Pearson, M. R.; Salman, Z.; Kiefl, R. F.

    2016-09-01

    Beta-detected NMR is a powerful technique in condensed matter physics. It uses the parity violation of beta decay to detect the NMR signal from a beam of highly polarized radionuclides implanted in a sample material. Spin-lattice relaxation (SLR) is studied by monitoring the rate with which the asymmetry between the beta counts in two opposing detectors is lost. Unlike classical NMR, b-NMR can study thin films and near-surface effects. The most common b-NMR isotope at TRIUMF is 8Li, which has a quadrupole moment, thus it is sensitive to both magnetic fields and electric field gradients. A challenge with 8Li b-NMR is identifying the predominant mechanism of SLR in a given sample. It is possible to distinguish between SLR mechanisms by varying the probe isotope. For two isotopes with different nuclear moments, the ratio of SLR rates should be different in the limits of either pure magnetic or quadrupolar relaxation. This method has been used in classical NMR and we report its first application to b-NMR. We measured the SLR rates for 8Li and 8Li in Pt foil and SrTiO3. Pt is a test case for pure magnetic relaxation. SrTiO3 is a non-magnetic insulator, but the source of its relaxation is not well understood. Here we show that its relaxation is mainly quadrupolar. We thank TRIUMF's CMMS for their technical support. This work was supported by: NSERC Discovery Grants to R.F.K. and W.A.M.; and IsoSiM fellowships to A.C. and R.M.L.M.

  13. Multislice 1H magnetic resonance spectroscopic imaging: assessment of epilepsy, Alzheimer's disease, and amyotrophic lateral sclerosis

    NASA Astrophysics Data System (ADS)

    Weiner, Michael W.; Maudsley, Andrew A.; Schuff, Norbert; Soher, Brian J.; Vermathen, Peter P.; Fein, George; Laxer, Kenneth D.

    1998-07-01

    Proton magnetic resonance spectroscopic imaging (1H MRSI) with volume pre-selection (i.e. by PRESS) or multislice 1H MRSI was used to investigate changes in brain metabolites in Alzheimer's disease, epilepsy, and amyotrophic lateral sclerosis. Examples of results from several ongoing clinical studies are provided. Multislice 1H MRSI of the human brain, without volume pre-selection offers considerable advantages over previously available techniques. Furthermore, MRI tissue segmentation and completely automated spectra curve fitting greatly facilitate quantitative data analysis. Future efforts will be devoted to obtaining full brain coverage and data acquisition at short spin echo times (TE less than 30 ms) for the detection of metabolites with short T2 relaxation times.

  14. Latent Period of Relaxation.

    PubMed

    Kobayashi, M; Irisawa, H

    1961-10-27

    The latent period of relaxation of molluscan myocardium due to anodal current is much longer than that of contraction. Although the rate and the grade of relaxation are intimately related to both the stimulus condition and the muscle tension, the latent period of relaxation remains constant, except when the temperature of the bathing fluid is changed.

  15. 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.

  16. Spin relaxation mechanism in silver nanowires covered with MgO protection layer

    NASA Astrophysics Data System (ADS)

    Idzuchi, H.; Fukuma, Y.; Wang, L.; Otani, Y.

    2012-07-01

    Spin-flip mechanism in Ag nanowires with MgO surface protection layers has been investigated by nonlocal spin injection using permalloy/Ag lateral spin valves. The spin flip events mediated by surface scattering are effectively suppressed by the MgO capping layer. The spin relaxation process was found to be well described in the framework of Elliott-Yafet mechanism (R. J. Elliott, Phys. Rev. 96, 266 (1954); Y. Yafet, in Solid State Physics, edited by F. Seitz and D. Turnbull (Academic, New York, 1963), pp. 1-98) and then the probabilities of spin-filp scattering for phonon or impurity mediated momentum scattering is precisely determined in the nanowires. The temperature dependent spin-lattice relaxation follows the Bloch-Grüneisen theory (V. F. Bloch, Z. Phys. 59, 208 (1930); V. E. Grüneisen, Ann. Phys. 5, 530 (1933)) and falls on to a universal curve of Ag as in the conduction-electron-spin resonance data for bulk.

  17. 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.

  18. Higher triplet state of fullerene C{sub 70} revealed by electron spin relaxation

    SciTech Connect

    Uvarov, Mikhail N.; Behrends, Jan; Kulik, Leonid V.

    2015-12-28

    Spin-lattice relaxation times T{sub 1} of photoexcited triplets {sup 3}C{sub 70} in glassy decalin were obtained from electron spin echo inversion recovery dependences. In the range 30–100 K, the temperature dependence of T{sub 1} was fitted by the Arrhenius law with an activation energy of 172 cm{sup −1}. This indicates that the dominant relaxation process of {sup 3}C{sub 70} is described by an Orbach-Aminov mechanism involving the higher triplet state t{sub 2} which lies 172 cm{sup −1} above the lowest triplet state t{sub 1}. Chemical modification of C{sub 70} fullerene not only decreases the intrinsic triplet lifetime by about ten times but also increases T{sub 1} by several orders of magnitude. The reason for this is the presence of a low-lying excited triplet state in {sup 3}C{sub 70} and its absence in triplet C{sub 70} derivatives. The presence of the higher triplet state in C{sub 70} is in good agreement with the previous results from phosphorescence spectroscopy.

  19. Transverse Relaxation and Magnetization Transfer in Skeletal Muscle: Effect of pH

    PubMed Central

    Louie, Elizabeth A.; Gochberg, Daniel F.; Does, Mark D.; Damon, Bruce M.

    2008-01-01

    Exercise increases the intracellular T2 (T2,i) of contracting muscles. The mechanism(s) for the T2,i increase have not been fully described, and may include increased intracellular free water and acidification. These changes may alter chemical exchange processes between intracellular free water and proteins. In this study, the hypotheses were tested that 1) pH changes T2,i by affecting the rate of magnetization transfer (MT) between free intracellular water and intracellular proteins and 2) the magnitude of the T2,i effect depends on acquisition mode (localized or non-localized) and echo spacing. Frog gastrocnemius muscles were excised and their intracellular pH was either kept at physiological pH (7.0) or modified to model exercising muscle (pH 6.5). The intracellular transverse relaxation rate (R2,i =1/T2,i) always decreased in the acidic muscles, but the changes were greater when measured using more rapid refocusing rates. The MT rate from the macromolecular proton pool to the free water proton pool, its reverse rate, and the spin-lattice relaxation rate of water decreased in acidic muscles. It is concluded that intracellular acidification alters the R2,i of muscle water in a refocusing rate-dependent manner and that the R2,i changes are correlated with changes in the MT rate between macromolecules and free intracellular water. PMID:19097244

  20. Higher triplet state of fullerene C70 revealed by electron spin relaxation

    NASA Astrophysics Data System (ADS)

    Uvarov, Mikhail N.; Behrends, Jan; Kulik, Leonid V.

    2015-12-01

    Spin-lattice relaxation times T1 of photoexcited triplets 3C70 in glassy decalin were obtained from electron spin echo inversion recovery dependences. In the range 30-100 K, the temperature dependence of T1 was fitted by the Arrhenius law with an activation energy of 172 cm-1. This indicates that the dominant relaxation process of 3C70 is described by an Orbach-Aminov mechanism involving the higher triplet state t2 which lies 172 cm-1 above the lowest triplet state t1. Chemical modification of C70 fullerene not only decreases the intrinsic triplet lifetime by about ten times but also increases T1 by several orders of magnitude. The reason for this is the presence of a low-lying excited triplet state in 3C70 and its absence in triplet C70 derivatives. The presence of the higher triplet state in C70 is in good agreement with the previous results from phosphorescence spectroscopy.

  1. Temperature dependence of proton NMR relaxation times at earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Niedbalski, Peter; Kiswandhi, Andhika; Parish, Christopher; Ferguson, Sarah; Cervantes, Eduardo; Oomen, Anisha; Krishnan, Anagha; Goyal, Aayush; Lumata, Lloyd

    The theoretical description of relaxation processes for protons, well established and experimentally verified at conventional nuclear magnetic resonance (NMR) fields, has remained untested at low fields despite significant advances in low field NMR technology. In this study, proton spin-lattice relaxation (T1) times in pure water and water doped with varying concentrations of the paramagnetic agent copper chloride have been measured from 6 to 92oC at earth's magnetic field (1700 Hz). Results show a linear increase of T1 with temperature for each of the samples studied. Increasing the concentration of the copper chloride greatly reduced T1 and reduced dependence on temperature. The consistency of the results with theory is an important confirmation of past results, while the ability of an ultra-low field NMR system to do contrast-enhanced magnetic resonance imaging (MRI) is promising for future applicability to low-cost medical imaging and chemical identification. This work is supported by US Dept of Defense Award No. W81XWH-14-1-0048 and the Robert A. Welch Foundation Grant No. AT-1877.

  2. Temperature dependence of relaxation times in proton components of fatty acids.

    PubMed

    Kuroda, Kagayaki; Iwabuchi, Taku; Obara, Makoto; Honda, Masatoshi; Saito, Kensuke; Imai, Yutaka

    2011-01-01

    We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T(1), of both the methylene (CH(2)) chain and terminal methyl (CH(3)) was linearly related to temperature (r>0.98, P<0.001) in samples of animal fat. The temperature coefficients for the 2 primary proton components differed significantly; in 5 bovine fat samples, the coefficient at 30 °C was 1.79±0.07 (%/°C) for methylene and 2.98±0.38 (%/°C) for methyl. Numerical simulations based on such a difference demonstrated the possibility of considerable error from inconsistent ratios in fatty acid components when calibrating and estimating temperature. The error reached 3.3 °C per 15 °C in temperature elevation when we used a pure CH(2) signal for calibration and observed the signal with 18% of CH(3) to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T(1) of CH(2) seems promising in terms of reliability and reproducibility in measuring temperature of fat.

  3. Kinetics of the in vivo31P 1H nuclear overhauser effect of the human-calf-muscle phosphocreatine resonance

    NASA Astrophysics Data System (ADS)

    Bachert, Peter; Bellemann, Matthias E.

    In 31P 1H double-resonance experiments in a 1.5 T whole-body MR system, we observed in vivo the truncated driven, transient, and steady-state 31P- 1H nuclear Overhauser effect of the phosphocreatine resonance in 31P MR spectra of human gastrocnemius muscle. Maximum signal enhancements of 0.52 ± 0.01, 0.20 ± 0.01, and 0.79 ± 0.02 were measured, respectively. Fitting the data with theoretical functions which solve the multispin Solomon equations for N protons (S spins) dipolar coupled to a 31P nucleus (I spin) yields cross-relaxation times {2}/{[Σ i=1-N σIS(i) ] } in the order of 20 s. In vivo experiments are feasible for studying relaxation mechanisms in coupled 31P 1H spin systems in intact tissue.

  4. 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.

  5. Crystalline 1H-1,2,3-triazol-5-ylidenes

    SciTech Connect

    Bertrand, Guy; Gulsado-Barrios, Gregorio; Bouffard, Jean; Donnadieu, Bruno

    2016-08-02

    The present invention provides novel and stable crystalline 1H-1,2,3 triazolium carbenes and metal complexes of 1H-1,2,3 triazolium carbenes. The present invention also provides methods of making 1H-1,2,3 triazolium carbenes and metal complexes of 1H-1,2,3 triazolium carbenes. The present invention also provides methods of using 1H-1,2,3 triazolium carbenes and metal complexes of 1H-1,2,3 triazolium carbenes in catalytic reactions.

  6. Spatially localized sup 1 H NMR spectra of metabolites in the human brain

    SciTech Connect

    Hanstock, C.C. ); Rothman, D.L.; Jue, T.; Shulman, R.G. ); Prichard, J.W. )

    1988-03-01

    Using a surface coil, the authors have obtained {sup 1}H NMR spectra from metabolites in the human brain. Localization was achieved by combining depth pulses with image-selected in vivo spectroscopy magnetic field gradient methods. {sup 1}H spectra in which total creatine (3.03 ppm) has a signal/noise ratio of 95:1 were obtained in 4 min from 14 ml of brain. A resonance at 2.02 ppm consisting predominantly of N-acetylaspartate was measured relative to the creatine peak in gray and white matter, and the ratio was lower in the white matter. The spin-spin relaxation times of N-acetylaspartate and creatine were measured in white and gray matter and while creatine relaxation times were the same in both, the N-acetylaspartate relaxation time was longer in white matter. Lactate was detected in the normoxic brain and the average of three measurements was {approx}0.5 mM from comparison with the creatine plus phosphocreatine peak, which was assumed to be 10.5 mM.

  7. 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.

  8. 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…

  9. Relaxation of magnetotail plasmas

    NASA Technical Reports Server (NTRS)

    Bhattacharjee, A.

    1987-01-01

    A quasi-thermodynamic model is presented for the relaxation of magnetotail plasmas during substorms, followed by quiet times. It is proposed that the plasma relaxes to a state of low-potential energy subject to a small number of global constraints. The constraints are exactly preserved by all ideal motions and, approximately, by a wide class of motions of the plasma undergoing magnetic reconnection. A variational principle which minimizes the free energy predicts the relaxed state. Exact, two-dimensional solutions of the relaxed state are obtained. A universal feature of the exact solutions is a chain of magnetic islands along the tail axis. Sufficient conditions for the stability of relaxed states are obtained from the second variation of the free-energy functional.

  10. The Effects of Dissolved Oxygen upon Amide Proton Relaxation and Chemical Shift in a Perdeuterated Protein

    NASA Astrophysics Data System (ADS)

    Ulmer, Tobias S.; Campbell, Iain D.; Boyd, Jonathan

    2002-08-01

    The effects of dissolved molecular oxygen upon amide proton ( 1H N) longitudinal and transverse relaxation rates and chemical shifts were studied for a small protein domain, the second type 2 module of fibronectin ( 2F2)—isotopically enriched to 99% 2H, 98% 15N. Longitudinal relaxation rate enhancements, R O 2( 1H N), of individual backbone 1H N nuclei varied up to 14 fold between a degassed and oxygenated (1 bar) solution, indicating that the oxygen distribution within the protein is inhomogeneous. On average, smaller relaxation rate enhancements were observed for 1H N nuclei associated with the core of the protein compared to 1H N nuclei closer to the surface, suggesting restricted oxygen accessibility to some regions. In agreement with an O 2- 1H N hyperfine interaction in the extreme narrowing limit, the 1H N transverse relaxation rates showed no significant change, up to an oxygen pressure of 9.5 bar (the maximum pressure used in this study). For most 1H N resonances, small Δδ O 2( 1H N) hyperfine chemical shifts could be detected between oxygen pressures of 1 bar and 9.5 bar.

  11. Dielectric relaxation near 25 K in multiferroic BiFeO3 ceramics

    NASA Astrophysics Data System (ADS)

    Ramachandran, B.; Dixit, A.; Naik, R.; Lawes, G.; Ramachandra Rao, M. S.

    2011-11-01

    Our investigations using low-temperature Raman spectroscopy, dielectric, and magnetodielectric studies of as-prepared and vacuum-annealed BiFeO3 ceramics revealed two dielectric anomalies near 25 and 281 K. Systematic studies were carried out to probe the anomaly near 25 K which exhibits clear frequency dependence and falls close to a previously observed magnetic transition. The low-temperature dielectric relaxation behavior yielded characteristic energy scales of ˜30 and ˜34 meV for the as-prepared and vacuum-annealed BiFeO3 samples, respectively. Raman spectra showed hardening of the E(TO6) and E(TO9) modes near 25 K, and the Raman shift in phonon frequencies is found to be broader in the vacuum-annealed BiFeO3 than in the as-prepared BiFeO3. We observed a linear magnetodielectric coupling in both samples at 25 K. These experimental results suggest that coupling among spin, lattice, and dielectric properties persist to low temperatures in BiFeO3.

  12. 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.

  13. Lattice dynamics, phase transitions and spin relaxation in [Fe(C5H5)2] PF6

    NASA Astrophysics Data System (ADS)

    Herber, R. H.; Felner, I.; Nowik, I.

    2016-12-01

    The organometallic compound ferrocenium hexafluorophosphate, [Fe(C5H5)2] PF6, has been studied by Mössbauer spectroscopy in the past, mainly to determine the crystal structure at high temperatures. Here we present studies at 95 K to 305 K and analyze the spectra in terms of spin relaxation theory which yields accurately the hyperfine interaction parameters and the spin-spin and spin-lattice relaxation rates in this paramagnetic compound. The spectral area under the resonance curve yields the recoil free fraction and thus the mean square of the vibration amplitude . One observes a large discontinuity in the slope of versus T at ˜210 K, indicative of a phase transition. The analysis of the spectra proves that the quadrupole interaction is small but certainly negative, ½e2qQ = -0.12(2) mm/s, and causes the asymmetry observed in the spectra. The detailed analysis yields also, for the first time, the fluctuating effective magnetic hyperfine field, H eff = 180(50) kOe.

  14. Hyperpolarized 13C NMR lifetimes in the liquid-state: relating structures and T1 relaxation times

    NASA Astrophysics Data System (ADS)

    Parish, Christopher; Niedbalski, Peter; Hashami, Zohreh; Fidelino, Leila; Kovacs, Zoltan; Lumata, Lloyd

    Among the various attempts to solve the insensitivity problem in nuclear magnetic resonance (NMR), the physics-based technique dissolution dynamic nuclear polarization (DNP) is probably the most successful method of hyperpolarization or amplifying NMR signals. Using this technique, liquid-state NMR signal enhancements of several thousand-fold are expected for low-gamma nuclei such as carbon-13. The lifetimes of these hyperpolarized 13C NMR signals are directly related to their 13C spin-lattice relaxation times T1. Depending upon the 13C isotopic location, the lifetimes of hyperpolarized 13C compounds can range from a few seconds to minutes. In this study, we have investigated the hyperpolarized 13C NMR lifetimes of several 13C compounds with various chemical structures from glucose, acetate, citric acid, naphthalene to tetramethylallene and their deuterated analogs at 9.4 T and 25 deg C. Our results show that the 13C T1s of these compounds can range from a few seconds to more than 60 s at this field. Correlations between the chemical structures and T1 relaxation times will be discussed and corresponding implications of these results on 13C DNP experiments will be revealed. US Dept of Defense Award No. W81XWH-14-1-0048 and Robert A. Welch Foundation Grant No. AT-1877.

  15. Water and salt distribution in Atlantic salmon (Salmo salar) studied by low-field 1H NMR, 1H and 23Na MRI and light microscopy: effects of raw material quality and brine salting.

    PubMed

    Aursand, Ida G; Veliyulin, Emil; Böcker, Ulrike; Ofstad, Ragni; Rustad, Turid; Erikson, Ulf

    2009-01-14

    The effect of different Atlantic salmon raw materials (prerigor, postrigor and frozen/thawed) on water mobility and salt uptake after brine salting was investigated by using LF 1H NMR T2 relaxation,1H and 23Na MRI and light microscopy. Distributed exponential analysis of the T2 relaxation data revealed two main water pools in all raw materials, T21 and T22, with relaxation times in the range of 20-100 ms and 100-300 ms, respectively. Raw material differences were reflected in the T2 relaxation data. Light microscopy demonstrated structural differences between unsalted and salted raw materials. For prerigor fillets, salting induced a decrease in T21 population coupled with a more open microstructure compared to unsalted fillets, whereas for frozen/thawed fillets, an increase in T21 population coupled with salt-induced swelling of myofibers was observed. The result implies that the T21 population was directly affected by the density of the muscle myofiber lattice. MR imaging revealed significant differences in salt uptake between raw materials, prerigor salted fillets gained least salt (1.3-1.6% NaCl), whereas the frozen/thawed fillets gained most salt (2.7-2.9% NaCl), and obtained the most even salt distribution due to the more open microstructure. This study demonstrates the advantage of LF NMR T2 relaxation and 1H and 23Na MRI as effective tools for understanding of the relationship between the microstructure of fish muscle, its water mobility and its salt uptake.

  16. Relaxation techniques for stress

    MedlinePlus

    ... problems such as high blood pressure, stomachaches, headaches, anxiety, and depression. Using relaxation techniques can help you feel calm. These exercises can also help you manage stress and ease ...

  17. The in vivo relaxivity of MRI contrast agents

    NASA Astrophysics Data System (ADS)

    Shuter, Borys

    1999-11-01

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

  18. Determining diffusion coefficients of ionic liquids by means of field cycling nuclear magnetic resonance relaxometry.

    PubMed

    Kruk, D; Meier, R; Rachocki, A; Korpała, A; Singh, R K; Rössler, E A

    2014-06-28

    Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220-258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243-318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258-323 K). The dispersion of (1)H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz-20 MHz, and the studies are complemented by (19)F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the (1)H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the (1)H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the (19)F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.

  19. Very short NMR relaxation times of anions in ionic liquids: new pulse sequence to eliminate the acoustic ringing.

    PubMed

    Klimavicius, Vytautas; Gdaniec, Zofia; Balevicius, Vytautas

    2014-11-11

    NMR relaxation processes of anions were studied in two neat imidazolium-based room temperature ionic liquids (RTILs) 1-decyl-3-methyl-imidazolium bromide- and chloride. The spin-lattice and spin-spin relaxations of 81Br and 35Cl nuclei were found to be extremely fast due to very strong quadrupolar interactions. The determined relaxation rates are comparable with those observed in the solids or in some critical organic solute/water/salt systems. In order to eliminate the acoustic ringing of the probe-head during relaxation times measurements the novel pulse sequence has been devised. It is based on the conventional inversion recovery pulse sequence, however, instead of the last 90° pulse the subsequence of three 90° pulses applied along axes to fulfill the phase cycling condition is used. Using this pulse sequence it was possible to measure T1 for both studied nuclei. The viscosity measurements have been carried out and the rotational correlation times were calculated. The effective 35Cl quadrupolar coupling constant was found to be almost one order lower than that for 81Br, i.e. 1.8 MHz and 16.0 MHz, respectively. Taking into account the facts that the ratio of (Q(35Cl)/Q(81Br))2≈0.1 and EFG tensors on the anions are quite similar, analogous structural organizations are expected for both RTILs. The observed T1/T2 (1.27-1.44) ratios were found to be not sufficiently high to confirm the presence of long-living (on the time scale of ≥10(-8) s) mesoscopic structures or heterogeneities in the studied neat ionic liquids.

  20. Differential protonation and dynamic structure of doxylamine succinate in solution using 1H and 13C NMR.

    PubMed

    Somashekar, B S; Nagana Gowda, G A; Ramesha, A R; Khetrapal, C L

    2004-07-01

    A protonation and dynamic structural study of doxylamine succinate, a 1:1 salt of succinic acid with dimethyl-[2-(1-phenyl-1-pyridin-2-yl-ethoxy)ethyl]amine, in solution using one- and two-dimensional 1H and 13C NMR experiments at variable temperature and concentration is presented. The two acidic protons of the salt doxylamine succinate are in 'intermediate' exchange at room temperature, as evidenced by the appearance of a broad signal. This signal evolves into two distinct signals below about -30 degrees C. A two-dimensional 1H-1H double quantum filtered correlation experiment carried out at -55 degrees C shows protonation of one of the acidic protons to the dimethylamine nitrogen. A two-dimensional rotating frame 1H-1H NOE experiment at the same temperature reveals that the other proton remains with the succinate moiety. Comparison of the 1H and 13C chemical shifts and the 13C T1 relaxation times of the salt with those of the free base further substantiate the findings.

  1. Dipolar nuclear spin relaxation in liquids and plane fluids undergoing chemical reactions

    NASA Astrophysics Data System (ADS)

    Fries, P. H.

    We describe the correlated translational and rotational relative brownian motions of two reacting groups of atoms, alternatively bound and free, by the normalized solutions of a set of coupled diffusion equations. Under equilibrium conditions we calculate the spectral densities j(ω) characteristic of the fluctuations of the intermolecular dipolar coupling between spins of these diffusing groups of atoms. When ωτ << 1, where τ is the translational correlation time, the form of the spectral density j2(ω) in three-dimensional liquids is j2(0) - α3ω1/2. The coefficient α3 is independent of the molecular local order, of the diffusional rotation speed of the spin-carrying groups of atoms and of their association and dissociation rates. In plane fluids, when ωτ << 1, the spectral density j(0)(ω) may be written as -a2 ln (ωτ) where the dependence of a2 on the average relative distribution of the interacting spins varies with the rate of the chemical reactions. In both three- and two-dimensional fluids spectral densities show an ω-3/2 or ω-2 behaviour for ωτ >> 1 according to the magnitude of the association rate of the reacting groups of atoms. In liquid glycerol we analyse the low- and high-frequency limits of the experimental proton relaxation rate 1/T1 and 1/T1ρ measured by Harmon, Harmon and Burnett, and Lenk. We also discuss the proton spin-lattice relaxation times measured by Kleinberg and Silbernagel in layered intercalation compounds TiS2-NH3 and TaS2-NH3.

  2. Teaching 1H NMR Spectrometry Using Computer Modeling.

    ERIC Educational Resources Information Center

    Habata, Yoichi; Akabori, Sadatoshi

    2001-01-01

    Molecular modeling by computer is used to display stereochemistry, molecular orbitals, structure of transition states, and progress of reactions. Describes new ideas for teaching 1H NMR spectroscopy using computer modeling. (Contains 12 references.) (ASK)

  3. Water distribution in brine salted cod (Gadus morhua) and salmon (Salmo salar): a low-field 1H NMR study.

    PubMed

    Aursand, Ida G; Gallart-Jornet, Lorena; Erikson, Ulf; Axelson, David E; Rustad, Turid

    2008-08-13

    Low-field (LF) (1)H NMR T 2 relaxation measurements were used to study changes in water distribution in lean (Atlantic cod) and fatty (Atlantic salmon) fish during salting in 15% NaCl and 25% NaCl brines. The NMR data were treated by PCA, continuous distribution analysis, and biexponential fitting and compared with physicochemical data. Two main water pools were observed in unsalted fish, T 21, with relaxation times in the range 20-100 ms, and T 22, with relaxation times in the range 100-300 ms. Pronounced changes in T 2 relaxation data were observed during salting, revealing changes in the water properties. Salting in 15% brine lead to a shift toward longer relaxation times, reflecting increased water mobility, whereas, salting in saturated brines had the opposite effect. Water mobility changes were observed earlier in the salting process for cod compared to salmon. Good linear correlations ( F

  4. Non-Korringa nuclear relaxation in the ferromagnetic phase of the bilayered manganite La{sub1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7}.

    SciTech Connect

    Hoch, M. J. R.; Kuhns, P. L.; Moulton, W. G.; Lu, J.; Reyes, A. P.; Mitchell, J. F.; Materials Science Division; Florida State Univ.

    2009-01-01

    In contrast to ferromagnetic (FM) three-dimensional manganites, {sup 55}Mn NMR spectra obtained for the FM phase of the colossal magnetoresistance bilayer manganite La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} show a broad distribution of hyperfine fields at Mn sites. The hyperfine distribution reflects variations in the electronic structure at the local level. {sup 55}Mn spin-lattice relaxation rates have a surprisingly weak dependence both on temperature and on applied magnetic field. Significant departures of the relaxation rate from Korringa temperature dependence below 40 K provide evidence for non Fermi liquid behavior in this quasi-two-dimensional metal. At temperatures approaching T{sub c} from below, in the range where colossal magnetoresistance appears, further anomalous and field-dependent behavior is found in the relaxation rate temperature dependence. The results provide evidence for changes in the electronic structure with temperature in this poorly metallic system. At low temperatures the changes are possibly linked to orbital ordering effects. In addition, statistical fluctuations in dopant concentration may play some role in inducing local variations in the electronic structure. Above 90 K the emergence of polarons is likely to be responsible for the observed decrease in the relaxation rate.

  5. Relaxation in quantum glasses

    NASA Astrophysics Data System (ADS)

    Ancona Torres, Carlos E.

    The Ising model in transverse field provides the simplest description of a quantum glass. I study two systems that are realizations of the Ising model in transverse field, LiHoxY1-- xF4 and Rb1-- x(NH4)xH2PO 4. In the spin glass LiHoxY1-- xF4, applying a magnetic field Ht transverse to the Ising direction introduces tunneling between the bare Ising eigenstates. In addition, the coupling between the transverse dipolar interaction and the transverse field introduces entanglement or tunable random fields depending on the concentration. By comparing the classical and quantum transitions in LiHo0.198Y0.802F4 and LiHo 0.167Y0.833F4, I characterize the crossover from random field dominated behavior in the 19.8% sample to entanglement dominated behavior in the 16.7% sample. The quantum transition in the 19.8% sample is dominated by the limit on its correlation length caused by the random fields, while the dominant effect in the 16.7% sample is the enhanced tunneling rate introduced by entanglement. The proton glass Rb1--x(NH 4)xH2PO4 relaxes through tunneling of protons in the hydrogen bonds of the crystal, yielding an effective Ising model in transverse field. Since this field cannot be tuned directly, I combine bulk dielectric susceptibility measurements with neutron Compton scattering measurements of the local tunneling potential in two different concentrations, x = 35% and 72%. I find that tunneling drives the fastest relaxation processes at temperatures as high as 20 K and explicitly calculate the tunneling rate from the tunneling potential of the hydrogen bond. Moreover, the structural mechanism for the glassy relaxation allows a real-space picture of the relaxation dynamics to be correlated to the free energy description of aging. I find that the glassy relaxation is driven by the sequential diffusion of defects called Takagi configurations with a classical to quantum crossover in the relaxation at 3 K. I relate the relaxation rate to the quantum action of tunneling

  6. Syntheses, structures, and 1H, 13C{1H} and 119Sn{1H} NMR chemical shifts of a family of trimethyltin alkoxide, amide, halide and cyclopentadienyl compounds

    DOE PAGES

    Lichtscheidl, Alejandro G.; Janicke, Michael T.; Scott, Brian L.; ...

    2015-08-21

    The synthesis and full characterization, including Nuclear Magnetic Resonance (NMR) data (1H, 13C{1H} and 119Sn{1H}), for a series of Me3SnX (X = O-2,6-tBu2C6H3 (1), (Me3Sn)N(2,6-iPr2C6H3) (3), NH-2,4,6-tBu3C6H2 (4), N(SiMe3)2 (5), NEt2, C5Me5 (6), Cl, Br, I, and SnMe3) compounds in benzene-d6, toluene-d8, dichloromethane-d2, chloroform-d1, acetonitrile-d3, and tetrahydrofuran-d8 are reported. The X-ray crystal structures of Me3Sn(O-2,6-tBu2C6H3) (1), Me3Sn(O-2,6-iPr2C6H3) (2), and (Me3Sn)(NH-2,4,6-tBu3C6H2) (4) are also presented. As a result, these compiled data complement existing literature data and ease the characterization of these compounds by routine NMR experiments.

  7. Sensitivity of proton NMR relaxation times in a HTPB based polyurethane elastomer to thermo-oxidative aging.

    SciTech Connect

    Assink, Roger Alan; Mowery, Daniel Michael; Celina, Mathias Christopher

    2004-09-01

    Solid-state {sup 1}H NMR relaxometry studies were conducted on a hydroxy-terminated polybutadiene (HTPB) based polyurethane elastomer thermo-oxidatively aged at 80 C. The {sup 1}H T{sub 1}, T{sub 2}, and T{sub 1{rho}} relaxation times of samples thermally aged for various periods of time were determined as a function of NMR measurement temperature. The response of each measurement was calculated from a best-fit linear function of the relaxation time vs. aging time. It was found that the T{sub 2,H} and T{sub 1{rho},H} relaxation times exhibited the largest response to thermal degradation, whereas T{sub 1,H} showed minimal change. All of the NMR relaxation measurements on solid samples showed significantly less sensitivity to thermal aging than the T{sub 2,H} relaxation times of solvent-swollen samples.

  8. Hair Dye and Hair Relaxers

    MedlinePlus

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

  9. A Comparison of Relaxation Strategies.

    ERIC Educational Resources Information Center

    Matthews, Doris B.

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

  10. Relaxation from particle production

    NASA Astrophysics Data System (ADS)

    Hook, Anson; Marques-Tavares, Gustavo

    2016-12-01

    We consider using particle production as a friction force by which to implement a "Relaxion" solution to the electroweak hierarchy problem. Using this approach, we are able to avoid superplanckian field excursions and avoid any conflict with the strong CP problem. The relaxation mechanism can work before, during or after inflation allowing for inflationary dynamics to play an important role or to be completely decoupled.

  11. Detection of cerebral NAD(+) by in vivo (1)H NMR spectroscopy.

    PubMed

    de Graaf, Robin A; Behar, Kevin L

    2014-07-01

    Nicotinamide adenine dinucleotide (NAD(+)) plays a central role in cellular metabolism both as a coenzyme for electron-transfer enzymes as well as a substrate for a wide range of metabolic pathways. In the current study NAD(+) was detected on rat brain in vivo at 11.7T by 3D localized (1)H MRS of the NAD(+) nicotinamide protons in the 8.7-9.5 ppm spectral region. Avoiding water perturbation was critical to the detection of NAD(+) as strong, possibly indirect cross-relaxation between NAD(+) and water would lead to a several-fold reduction of the NAD(+) intensity in the presence of water suppression. Water perturbation was minimized through the use of localization by adiabatic spin-echo refocusing (LASER) in combination with frequency-selective excitation. The NAD(+) concentration in the rat cerebral cortex was determined at 296 ± 28 μm, which is in good agreement with recently published (31) P NMR-based results as well as results from brain extracts in vitro (355 ± 34 μm). The T1 relaxation time constants of the NAD(+) nicotinamide protons as measured by inversion recovery were 280 ± 65 and 1136 ± 122 ms in the absence and presence of water inversion, respectively. This confirms the strong interaction between NAD(+) nicotinamide and water protons as observed during water suppression. The T2 relaxation time constants of the NAD(+) nicotinamide protons were determined at 60 ± 13 ms after confounding effects of scalar coupling evolution were taken into account. The simplicity of the MR sequence together with the robustness of NAD(+) signal detection and quantification makes the presented method a convenient choice for studies on NAD(+) metabolism and function. As the method does not critically rely on magnetic field homogeneity and spectral resolution it should find immediate applications in rodents and humans even at lower magnetic fields.

  12. Chain Dynamics, Relaxation Times, and Conductivities of Bithiophene--Acene Copolymers Measured Using High Frequency Saturation Transfer EPR.

    PubMed

    Fraind, Alicia M; Ryzhkov, Lev R; Tovar, John D

    2016-02-11

    We present a study to probe the formation of localized aromatic sextets and their effects on the charge transport properties in polymers with acene cores. Bithiophene-acene copolymers containing benzene, naphthalene, or anthracene as acene cores were synthesized using Yamamoto polymerization. Drop-casted polymer films were chemically doped and analyzed using high frequency saturation transfer EPR (HF ST-EPR), a method which has proven useful in the study of conducting polymers. The spin-spin and spin-lattice relaxation times were determined for these polymers at low temperatures (4 to 20 K) and used to obtain inter- and intrachain spin diffusion rates and conductivities. Similar interchain spin diffusion rates were seen across all polymer systems; however, anthracene containing polymer poly(hexylTTATT) was found to have the largest intrachain spin diffusion rate. The poly(hexylTTATT) intrachain spin diffusion rate may be artificially high if the anthracene ring restricts the diffusion of spin to the hexylated quaterthiophene segment in poly(hexylTTATT) whereas the spins diffuse through the acene cores in the benzene and naphthalene derivatives. Alternatively, as both the spin diffusion rates and conductivities vary unpredictably with temperature, it is possible that the π-electron localization previously seen in the anthracene core could be relieved at lower temperatures.

  13. PREFACE: Muon spin rotation, relaxation or resonance

    NASA Astrophysics Data System (ADS)

    Heffner, Robert H.; Nagamine, Kanetada

    2004-10-01

    ), is currently being built to replace the current Japanese muSR capability at KEK. These muSR institutions provide scientists a variety of sample environments, including a range of temperatures, magnetic fields and applied pressure. In addition, very low-energy muon beams (< 1 keV) have been developed for studies of thin films and nano-materials. In 2002 this world-wide community founded the International Society of muSR Spectroscopy (http://musr.org/~isms/) in order to promote the health of this growing field of research. The 20 papers presented in this volume are intended to highlight some of the current muSR research activities of interest to condensed matter physicists. It is not an exhaustive review. In particular, the active and exciting area of muonium chemistry is left to a future volume. The group of papers in section I addresses the physics of strongly correlated electrons in solids, one of the most active fields of condensed matter research today. Strong electron correlations arise from (Coulomb) interactions which render Landau's theory of electron transport for weakly interacting systems invalid. Included in this category are unconventional heavy-fermion superconductors, high-temperature copper-oxide superconductors, non-Fermi liquid (NFL) systems and systems with strong electron-lattice-spin coupling, such as the colossal magnetoresistance manganites. Two key properties often make the muon a unique probe of these materials: (1) the muon's large magnetic moment (~3 mup) renders it extremely sensitive to the tiny magnetic fields (~1 Gauss) found, for example, in many NFL systems and in superconductors possessing time-reversal-violating order parameters, and (2) the muon's spin 1/2 creates a simple muSR lineshape (no quadrupolar coupling), ideal for measuring spin-lattice-relaxation, local susceptibilities and magnetic-field distributions in ordered magnets and superconductors. Section II contains studies which exploit the unique sensitivities of muSR just

  14. Softening temperature of lyophilized bovine serum albumin and gamma-globulin as measured by spin-spin relaxation time of protein protons.

    PubMed

    Yoshioka, S; Aso, Y; Kojima, S

    1997-04-01

    We investigated the usefulness of the spin-spin relaxation time (T2) of protein protons as a probe for evaluating the molecular flexibility of freeze-dried protein formulations. It is proposed that the microscopic softening temperature determined from changes in the T2 of protein protons (Ts(T2)) is an important characteristic of freeze-dried protein formulations, the glass transition temperature (Tg) of which is generally difficult to determine by differential scanning calorimetry. We determined the molecular flexibility of lyophilized bovine serum albumin (BSA) and bovine gamma-globulin (BGG) by measuring the T2 of protein and water protons as well as the spin-lattice relaxation time (T1) of the latter as a function of temperature. The flexibility of freeze-dried BSA and BGG cakes markedly varied at temperatures above and below the Ts(T2), affecting the stability of the proteins. The denaturation and subsequent aggregation of lyophilized BSA and BGG cakes with a relatively high water content was enhanced in the softened state at temperatures above the Ts(T2). Lyophilized cakes with an extremely low water content were significantly denatured, even in the unsoftened state at temperatures below the Ts(T2), probably due to the thermodynamically unstable structures of protein molecules generated by a loss of structural water.

  15. Transverse spin relaxation and magnetic correlation in Pr1-xCaxMnO3: Influence of particle size variation and chemical doping

    NASA Astrophysics Data System (ADS)

    Shukla, Vinay Kumar; Mukhopadhyay, Soumik

    2017-03-01

    The short ranged magnetic correlations and dynamics of hole doped Pr1-xCaxMnO3 (0.33 < x < 0.5) of different crystallite sizes have been investigated using electron spin resonance spectroscopy. The major contribution to the temperature dependence of paramagnetic line-width is attributed to the spin-lattice relaxation dominated by thermally activated hopping of small polarons with the typical activation energy of 20-50 meV. Irrespective of the crystallite size and dopant concentration, the transverse spin relaxation time (t2) follows a universal scaling behaviour of the type t 2 ˜ ( T / T 0 ) n in the paramagnetic regime, where T0 and n are the scaling parameters. Using the temperature dependence of t2, we construct a phase diagram which shows that near half-doping, the magnetic correlations associated with charge ordering not only survives even down to the crystallite size of 22 nm but is also actually enhanced. We conclude that the eventual suppression of charge ordering with reduction in the particle size is possibly more to do with the greater influence of chemical disorder than any intrinsic effect.

  16. Observation of zero-point quantum fluctuations of a single-molecule magnet through the relaxation of its nuclear spin bath.

    PubMed

    Morello, A; Millán, A; de Jongh, L J

    2014-03-21

    A single-molecule magnet placed in a magnetic field perpendicular to its anisotropy axis can be truncated to an effective two-level system, with easily tunable energy splitting. The quantum coherence of the molecular spin is largely determined by the dynamics of the surrounding nuclear spin bath. Here we report the measurement of the nuclear spin-lattice relaxation rate 1/T1n in a single crystal of the single-molecule magnet Mn12-ac, at T ≈ 30 mK in perpendicular fields B⊥ up to 9 T. The relaxation channel at B ≈ 0 is dominated by incoherent quantum tunneling of the Mn12-ac spin S, aided by the nuclear bath itself. However for B⊥>5 T we observe an increase of 1/T1n by several orders of magnitude up to the highest field, despite the fact that the molecular spin is in its quantum mechanical ground state. This striking observation is a consequence of the zero-point quantum fluctuations of S, which allow it to mediate the transfer of energy from the excited nuclear spin bath to the crystal lattice at much higher rates. Our experiment highlights the importance of quantum fluctuations in the interaction between an "effective two-level system" and its surrounding spin bath.

  17. Novel 1H low field nuclear magnetic resonance applications for the field of biodiesel

    PubMed Central

    2013-01-01

    Background Biodiesel production has increased dramatically over the last decade, raising the need for new rapid and non-destructive analytical tools and technologies. 1H Low Field Nuclear Magnetic Resonance (LF-NMR) applications, which offer great potential to the field of biodiesel, have been developed by the Phyto Lipid Biotechnology Lab research team in the last few years. Results Supervised and un-supervised chemometric tools are suggested for screening new alternative biodiesel feedstocks according to oil content and viscosity. The tools allowed assignment into viscosity groups of biodiesel-petrodiesel samples whose viscosity is unknown, and uncovered biodiesel samples that have residues of unreacted acylglycerol and/or methanol, and poorly separated and cleaned glycerol and water. In the case of composite materials, relaxation time distribution, and cross-correlation methods were successfully applied to differentiate components. Continuous distributed methods were also applied to calculate the yield of the transesterification reaction, and thus monitor the progress of the common and in-situ transesterification reactions, offering a tool for optimization of reaction parameters. Conclusions Comprehensive applied tools are detailed for the characterization of new alternative biodiesel resources in their whole conformation, monitoring of the biodiesel transesterification reaction, and quality evaluation of the final product, using a non-invasive and non-destructive technology that is new to the biodiesel research area. A new integrated computational-experimental approach for analysis of 1H LF-NMR relaxometry data is also presented, suggesting improved solution stability and peak resolution. PMID:23590829

  18. Applications of 1H-NMR to Biodiesel Research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodiesel is an alternative diesel fuel derived from vegetable oils, animal fats, or used cooking oils. It is produced by reacting these materials with an alcohol in the presence of a catalyst to give the corresponding mono-alkyl esters. 1H-NMR is a routine analytical method that has been used for...

  19. Nuclear receptor NR1H3 in familial multiple sclerosis

    PubMed Central

    Wang, Zhe; Sadovnick, A. Dessa; Traboulsee, Anthony L.; Ross, Jay P.; Bernales, Cecily Q.; Encarnacion, Mary; Yee, Irene M.; de Lemos, Madonna; Greenwood, Talitha; Lee, Joshua D.; Wright, Galen; Ross, Colin J.; Zhang, Si; Song, Weihong; Vilariño-Güell, Carles

    2016-01-01

    SUMMARY Multiple sclerosis (MS) is an inflammatory disease characterized by myelin loss and neuronal dysfunction. Despite the aggregation observed in some families, pathogenic mutations have remained elusive. In this study we describe the identification of NR1H3 p.Arg415Gln in seven MS patients from two multi-incident families presenting severe and progressive disease, with an average age at onset of 34 years. Additionally, association analysis of common variants in NR1H3 identified rs2279238 conferring a 1.35-fold increased risk of developing progressive MS. The p.Arg415Gln position is highly conserved in orthologs and paralogs, and disrupts NR1H3 heterodimerization and transcriptional activation of target genes. Protein expression analysis revealed that mutant NR1H3 (LXRA) alters gene expression profiles, suggesting a disruption in transcriptional regulation as one of the mechanisms underlying MS pathogenesis. Our study indicates that pharmacological activation of LXRA or its targets may lead to effective treatments for the highly debilitating and currently untreatable progressive phase of MS. PMID:27253448

  20. Complete 1H and 13C spectral assignment of floridoside.

    PubMed

    Simon-Colin, Christelle; Kervarec, Nelly; Pichon, Roger; Deslandes, Eric

    2002-02-11

    Floridoside (2-O-alpha-D-galactopyranosylglycerol) was extracted from the red marine alga Rhodymenia palmata, and purified by ion-exchange chromatography: 1D and 2D NMR spectroscopy experiments were used to unambiguously assign the complete 1H and 13C spectra.

  1. Dynamic Nuclear Polarization of β-Cyclodextrin Macromolecules.

    PubMed

    Caracciolo, Filippo; Carretta, Pietro; Filibian, Marta; Melone, Lucio

    2017-03-30

    (1)H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of β-cyclodextrins doped with different concentrations of the TEMPO radical. Nuclear polarization increased up to 10% in the optimal case, with a behavior of the buildup rate (1/TPOL) and of the nuclear spin-lattice relaxation rate (1/T1n) consistent with a thermal mixing regime. The temperature dependence of 1/T1n and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics. The high-temperature relaxation is driven by molecular motions, and 1/T1n was studied at room temperature in liquid solutions for dilution levels close to the ones typically used for in vivo studies.

  2. Progressive muscle relaxation, yoga stretching, and ABC relaxation theory.

    PubMed

    Ghoncheh, Shahyad; Smith, Jonathan C

    2004-01-01

    This study compared the psychological effects of progressive muscle relaxation (PMR) and yoga stretching (hatha) exercises. Forty participants were randomly divided into two groups and taught PMR or yoga stretching exercises. Both groups practiced once a week for five weeks and were given the Smith Relaxation States Inventory before and after each session. As hypothesized, practitioners of PMR displayed higher levels of relaxation states (R-States) Physical Relaxation and Disengagement at Week 4 and higher levels of Mental Quiet and Joy as a posttraining aftereffect at Week 5. Contrary to what was hypothesized, groups did not display different levels of R-States Energized or Aware. Results suggest the value of supplementing traditional somatic conceptualizations of relaxation with the psychological approach embodied in ABC relaxation theory. Clinical and research implications are discussed.

  3. Quantification of (1) H-MRS signals based on sparse metabolite profiles in the time-frequency domain.

    PubMed

    Parto Dezfouli, Mohammad Ali; Parto Dezfouli, Mohsen; Ahmadian, Alireza; Frangi, Alejandro F; Esmaeili Rad, Melika; Saligheh Rad, Hamidreza

    2017-02-01

    MRS is an analytical approach used for both quantitative and qualitative analysis of human body metabolites. The accurate and robust quantification capability of proton MRS ((1) H-MRS) enables the accurate estimation of living tissue metabolite concentrations. However, such methods can be efficiently employed for quantification of metabolite concentrations only if the overlapping nature of metabolites, existing static field inhomogeneity and low signal-to-noise ratio (SNR) are taken into consideration. Representation of (1) H-MRS signals in the time-frequency domain enables us to handle the baseline and noise better. This is possible because the MRS signal of each metabolite is sparsely represented, with only a few peaks, in the frequency domain, but still along with specific time-domain features such as distinct decay constant associated with T2 relaxation rate. The baseline, however, has a smooth behavior in the frequency domain. In this study, we proposed a quantification method using continuous wavelet transformation of (1) H-MRS signals in combination with sparse representation of features in the time-frequency domain. Estimation of the sparse representations of MR spectra is performed according to the dictionaries constructed from metabolite profiles. Results on simulated and phantom data show that the proposed method is able to quantify the concentration of metabolites in (1) H-MRS signals with high accuracy and robustness. This is achieved for both low SNR (5 dB) and low signal-to-baseline ratio (-5 dB) regimes.

  4. HIST1H2AA — EDRN Public Portal

    Cancer.gov

    HIST1H2AA, a member of the histone 2A family, is a core component of the nucleosome. The nucleosome is a histone octamer containing two molecules each of H2A, H2B, H3 and H4 assembled in one H3-H4 heterotetramer and two H2A-H2B heterodimers. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template (the octamer wraps approximately 147 bp of DNA). Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. The HIST1H2AA gene is intronless and encodes a member of the histone H2A family. Transcripts from this gene contain a palindromic termination element.

  5. Quantitative produced water analysis using mobile 1H NMR

    NASA Astrophysics Data System (ADS)

    Wagner, Lisabeth; Kalli, Chris; Fridjonsson, Einar O.; May, Eric F.; Stanwix, Paul L.; Graham, Brendan F.; Carroll, Matthew R. J.; Johns, Michael L.

    2016-10-01

    Measurement of oil contamination of produced water is required in the oil and gas industry to the (ppm) level prior to discharge in order to meet typical environmental legislative requirements. Here we present the use of compact, mobile 1H nuclear magnetic resonance (NMR) spectroscopy, in combination with solid phase extraction (SPE), to meet this metrology need. The NMR hardware employed featured a sufficiently homogeneous magnetic field, such that chemical shift differences could be used to unambiguously differentiate, and hence quantitatively detect, the required oil and solvent NMR signals. A solvent system consisting of 1% v/v chloroform in tetrachloroethylene was deployed, this provided a comparable 1H NMR signal intensity for the oil and the solvent (chloroform) and hence an internal reference 1H signal from the chloroform resulting in the measurement being effectively self-calibrating. The measurement process was applied to water contaminated with hexane or crude oil over the range 1-30 ppm. The results were validated against known solubility limits as well as infrared analysis and gas chromatography.

  6. Ultrasonic degradation of 1-H-benzotriazole in water.

    PubMed

    Zúñiga-Benítez, Henry; Soltan, Jafar; Peñuela, Gustavo

    2014-01-01

    This paper reports on the effect of different parameters of ultrasonic power, pollutant initial concentration, pH and the presence of co-existing chemical species (oxygen, nitrogen, ozone, and radical scavengers) on the ultrasonic degradation of the endocrine disruptor 1-H-benzotriazole. Increasing the 1-H-benzotriazole initial concentration from 41.97 to 167.88 μM increased the pollutant degradation rate by 40%. Likewise, a high applied ultrasonic power enhanced the extent of 1-H-benzotriazole removal and its initial degradation rate, which was accelerated in the presence of ozone and oxygen, but inhibited by nitrogen. The most favorable pH for the ultrasonic degradation was acidic media, reaching ∼90% pollutant removal in 2 h. The hydroxyl free radical concentration in the reaction medium was proportional to the ultrasound power and the irradiation time. Kinetic models based on a Langmuir-type mechanism were used to predict the pollutant sonochemical degradation. It was concluded that degradation takes place at both the bubble-liquid interfacial region and in the bulk solution, and OH radicals were the main species responsible for the reaction. Hydroxyl free radicals were generated by water pyrolysis and then diffused into the interfacial region and the bulk solution where most of the solute molecules were present.

  7. Ultrafast Relaxation in Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takayoshi

    The following sections are included: * INTRODUCTION * EXPERIMENTAL * Samples * Femtosecond experimental apparatus * RESULTS AND DISCUSSION * Poly(phenylacetylenes) * Blue-phase PDA-3BCMU * Red-phase PDA-4BCMU * Blue-phase PDA-DFMP * P3MT * P3DT * PTV * RELAXATION MECHANISMS * Review of the previous works * Symmetry of the lower electronic excited states * Primary relaxation processes * Theoretical studies of nonlinear excitations * Mechanism of relaxation in polymers with a weakly nondegenerate ground state (poly(phenylacetylene)s) * Dual peak component with power-law decay * Single-peak component with an exponential decay * Hot self-trapped exciton * Transition to the electron-hole threshold * Transition to a biexciton state * Mechanism of relaxation in polymers with a strongly or moderately nondegenerate ground state * Classifications of polymers * Femtosecond relaxation * Picosecond relaxation * CONCLUSION * Acknowledgments * REFERENCES

  8. Relaxing music for anxiety control.

    PubMed

    Elliott, Dave; Polman, Remco; McGregor, Richard

    2011-01-01

    The purpose of this investigation was to determine the characteristics of relaxing music for anxiety control. Undergraduate students (N=84) were instructed to imagine themselves in an anxiety producing situation while listening to a selection of 30 music compositions. For each composition, level of relaxation, the factors that either enhanced or detracted from its relaxing potential and the emotional labels attached were assessed. Participants were also asked to state which music components (e.g., tempo, melody) were most conducive to relaxation. Additional information was obtained through the use of a focus group of 6 undergraduate music students. This paper presents details on the characteristics of relaxing-music for anxiety control and emotional labels attached to the relaxing compositions. Furthermore, an importance value has been attached to each of the music components under scrutiny, thus providing an indication of which music components should receive greatest attention when selecting music for anxiety control.

  9. ABC relaxation theory and the factor structure of relaxation states, recalled relaxation activities, dispositions, and motivations.

    PubMed

    Smith, J C; Wedell, A B; Kolotylo, C J; Lewis, J E; Byers, K Y; Segin, C M

    2000-06-01

    ABC Relaxation Theory proposes 15 psychological relaxation-related states (R-States): Sleepiness, Disengagement, Physical Relaxation, Mental Quiet, Rested/Refreshed, At Ease/At Peace, Energized, Aware, Joy, Thankfulness and Love, Prayerfulness, Childlike Innocence, Awe and Wonder, Mystery, and Timeless/Boundless/Infinite. The present study summarizes the results of 13 separate factor analyses of immediate relaxation-related states, states associated with recalled relaxation activities, relaxation dispositions, and relaxation motivations on a combined sample of 1,904 individuals (group average ages ranged from 28-40 yr.). Four exploratory factor analyses of Smith Relaxation Inventories yielded 15 items that most consistently and exclusively load (generally at least .70) on six replicated factors. These items included happy, joyful, energized, rested, at peace, warm, limp, silent, quiet, dozing, drowsy, prayerful, mystery, distant, and indifferent. Subsequent factor analyses restricted to these items and specifying six factors were performed on 13 different data sets. Each yielded the same six-factor solution: Factor 1: Centered Positive Affect, Factor 2: Sleepiness, Factor 3: Disengagement, Factor 4: Physical Relaxation, Factor 5: Mental Quiet, and Factor 6: Spiritual. Implications for ABC Relaxation Theory are discussed.

  10. Transverse relaxation of scalar-coupled protons.

    PubMed

    Segawa, Takuya F; Baishya, Bikash; Bodenhausen, Geoffrey

    2010-10-25

    In a preliminary communication (B. Baishya, T. F. Segawa, G. Bodenhausen, J. Am. Chem. Soc. 2009, 131, 17538-17539), we recently demonstrated that it is possible to obtain clean echo decays of protons in biomolecules despite the presence of homonuclear scalar couplings. These unmodulated decays allow one to determine apparent transverse relaxation rates R(2) (app) of individual protons. Herein, we report the observation of R(2) (app) for three methyl protons, four amide H(N) protons, and all 11 backbone H(α) protons in cyclosporin A. If the proton resonances overlap, their R(2) (app) rates can be measured by transferring their magnetization to neighboring (13)C nuclei, which are less prone to overlap. The R(2) (app) rates of protons attached to (13)C are faster than those attached to (12)C because of (13)C-(1)H dipolar interactions. The differences of these rates allow the determination of local correlation functions. Backbone H(N) and H(α) protons that have fast decay rates R(2) (app) also feature fast longitudinal relaxation rates R(1) and intense NOESY cross peaks that are typical of crowded environments. Variations of R(2) (app) rates of backbone H(α) protons in similar amino acids reflect differences in local environments.

  11. Proton-detected 3D (1)H/(13)C/(1)H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz.

    PubMed

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-28

    A proton-detected 3D (1)H/(13)C/(1)H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of (13)C-(1)H connectivities, and proximities of (13)C-(1)H and (1)H-(1)H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including (1)H-(1)H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) (1)H/(1)H and 2D (13)C/(1)H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of (1)H-(1)H proximity and (13)C-(1)H connectivity. In addition, the 2D (F1/F2) (1)H/(13)C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of (1)H-(1)H dipolar couplings, enables the measurement of proximities between (13)C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of (1)H-(1)H-(13)C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H2O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  12. Proton-detected 3D 1H/13C/1H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

    A proton-detected 3D 1H/13C/1H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of 13C-1H connectivities, and proximities of 13C-1H and 1H-1H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including 1H-1H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) 1H/1H and 2D 13C/1H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of 1H-1H proximity and 13C-1H connectivity. In addition, the 2D (F1/F2) 1H/13C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of 1H-1H dipolar couplings, enables the measurement of proximities between 13C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of 1H-1H-13C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ṡ H2O ṡ HCl demonstrate the efficiency of the 3D experiment.

  13. Sodium-23 magnetic resonance imaging during and after transient cerebral ischemia: multinuclear stroke protocols for double-tuned 23Na/1H resonator systems

    NASA Astrophysics Data System (ADS)

    Wetterling, Friedrich; Ansar, Saema; Handwerker, Eva

    2012-11-01

    A double-tuned 23Na/1H resonator system was developed to record multinuclear MR image data during and after transient cerebral ischemia. 1H-diffusion-, 1H perfusion, 1H T2-, 1H arterial blood flow- and 23Na spin density-weighted images were then acquired at three time points in a rodent stroke model: (I) during 90 min artery occlusion, (II) directly after arterial reperfusion and (III) one day after arterial reperfusion. Normal 23Na was detected in hypoperfused stroke tissue which exhibited a low 1H apparent diffusion coefficient (ADC) and no changes in 1H T2 relaxation time during transient ischemia, while 23Na increased and ADC values recovered to normal values directly after arterial reperfusion. For the first time, a similar imaging protocol was set-up on a clinical 3T MRI site in conjunction with a commercial double-tuned 1H/23Na birdcage resonator avoiding a time-consuming exchange of resonators or MRI systems. Multinuclear 23Na/1H MRI data sets were obtained from one stroke patient during both the acute and non-acute stroke phases with an aquisition time of 22 min. The lesion exhibiting low ADC was found to be larger compared to the lesion with high 23Na at 9 h after symptom onset. It is hoped that the presented pilot data demonstrate that fast multinuclear 23Na/1H MRI preclinical and clinical protocols can enable a better understanding of how temporal and regional MRI parameter changes link to pathophysiological variations in ischemic stroke tissue.

  14. Complete assignment of NMR data of 22 phenyl-1H-pyrazoles' derivatives.

    PubMed

    de Oliveira, Aline Lima; Alves de Oliveira, Carlos Henrique; Mairink, Laura Maia; Pazini, Francine; Menegatti, Ricardo; Lião, Luciano Morais

    2011-08-01

    Complete assignment of (1)H and (13)C NMR chemical shifts and J((1)H/(1)H and (1)H/(19)F) coupling constants for 22 1-phenyl-1H-pyrazoles' derivates were performed using the concerted application of (1)H 1D and (1)H, (13)C 2D gs-HSQC and gs-HMBC experiments. All 1-phenyl-1H-pyrazoles' derivatives were synthesized as described by Finar and co-workers. The formylated 1-phenyl-1H-pyrazoles' derivatives were performed under Duff's conditions.

  15. Differentiation between cortical atrophy and hydrocephalus using 1H MRS.

    PubMed

    Bluml, S; McComb, J G; Ross, B D

    1997-03-01

    Quantitative 1H MRS to determine cerebral metabolite patterns and MRI to determine CSF flow were applied to 12 patients with ventricular dilation-Group A, cortical atrophy (N = 5); or Group B, hydrocephalus (N = 7)- and in 9 normal controls. While mean brain water (Group A = 80% +/- 6; Group B = 86% +/- 5; normal = 85% +/- 4) did not differ between the two groups of patients and controls, 1H MRS distinguished those patients with cortical atrophy (Group A) (N-acetylaspartate/ creatine (NAA/Cr) = 0.69 +/- 0.17, versus normal = 1.06 +/- 0.16; P < 0.002; [NAA] = 5.9 +/- 1.3 mmoles/kg, versus normal 8.0 +/- 1.4; P < 0.02) from those with hydrocephalus (Group B) (NAA/Cr = 1.16 +/- 0.11; [NAA] = 9.2 +/- 1.2; P > 0.13 and P > 0.07). Lactate levels were elevated in 3/5 patients with cortical atrophy, but in 0/7 of those with hydrocephalus. Mean absolute concentrations (mmoles/kg) of the five major cerebral osmolytes were 41 +/- 4 (Group A), 43 +/- 6 (Group B), and 42 +/- 4 (normal), so that despite massive brain deformation, constant osmolality was maintained. 1H MRS may directly benefit surgical planning in hydrocephalus infants by clearly identifying those with cortical atrophy who do not require CSF diversion. Thinning of the cortical mantle in hydrocephalus may result from osmotically driven reduction in individual cell volumes, (shrinkage), rather than brain-compression.

  16. In vivo1H NMR spectroscopy of the human brain at 9.4 T: Initial results

    NASA Astrophysics Data System (ADS)

    Deelchand, Dinesh Kumar; Moortele, Pierre-François Van de; Adriany, Gregor; Iltis, Isabelle; Andersen, Peter; Strupp, John P.; Thomas Vaughan, J.; Uğurbil, Kâmil; Henry, Pierre-Gilles

    2010-09-01

    In vivo proton NMR spectroscopy allows non-invasive detection and quantification of a wide range of biochemical compounds in the brain. Higher field strength is generally considered advantageous for spectroscopy due to increased signal-to-noise and increased spectral dispersion. So far 1H NMR spectra have been reported in the human brain up to 7 T. In this study we show that excellent quality short echo time STEAM and LASER 1H NMR spectra can be measured in the human brain at 9.4 T. The information content of the human brain spectra appears very similar to that measured in the past decade in rodent brains at the same field strength, in spite of broader linewidth in human brain. Compared to lower fields, the T1 relaxation times of metabolites were slightly longer while T2 relaxation values of metabolites were shorter (<100 ms) at 9.4 T. The linewidth of the total creatine (tCr) resonance at 3.03 ppm increased linearly with magnetic field (1.35 Hz/T from 1.5 T to 9.4 T), with a minimum achievable tCr linewidth of around 12.5 Hz at 9.4 T. At very high field, B0 microsusceptibility effects are the main contributor to the minimum achievable linewidth.

  17. (1)H nuclear magnetic resonance (NMR) as a tool to measure dehydration in mice.

    PubMed

    Li, Matthew; Vassiliou, Christophoros C; Colucci, Lina A; Cima, Michael J

    2015-08-01

    Dehydration is a prevalent pathology, where loss of bodily water can result in variable symptoms. Symptoms can range from simple thirst to dire scenarios involving loss of consciousness. Clinical methods exist that assess dehydration from qualitative weight changes to more quantitative osmolality measurements. These methods are imprecise, invasive, and/or easily confounded, despite being practiced clinically. We investigate a non-invasive, non-imaging (1)H NMR method of assessing dehydration that attempts to address issues with existing clinical methods. Dehydration was achieved by exposing mice (n = 16) to a thermally elevated environment (37 °C) for up to 7.5 h (0.11-13% weight loss). Whole body NMR measurements were made using a Bruker LF50 BCA-Analyzer before and after dehydration. Physical lean tissue, adipose, and free water compartment approximations had NMR values extracted from relaxation data through a multi-exponential fitting method. Changes in before/after NMR values were compared with clinically practiced metrics of weight loss (percent dehydration) as well as blood and urine osmolality. A linear correlation between tissue relaxometry and both animal percent dehydration and urine osmolality was observed in lean tissue, but not adipose or free fluids. Calculated R(2) values for percent dehydration were 0.8619 (lean, P < 0.0001), 0.5609 (adipose, P = 0.0008), and 0.0644 (free fluids, P = 0.3445). R(2) values for urine osmolality were 0.7760 (lean, P < 0.0001), 0.5005 (adipose, P = 0.0022), and 0.0568 (free fluids, P = 0.3739). These results suggest that non-imaging (1)H NMR methods are capable of non-invasively assessing dehydration in live animals.

  18. Probing Structure Property Relationships in Complex Engineering Silicones by 1H NMR

    SciTech Connect

    Chinn, S C; Gjersing, E L; Maxwell, R S; Eastwood, E; Bowen, D; Stephens, T

    2006-07-14

    It is generally accepted that the properties of polymeric materials are controlled by the network structure and the reactions by which they have been constructed. These properties include the bulk moduli at creation, but also the properties as a function of age during use. In order to interpret mechanical properties and predict the time dependent changes in these properties, detailed knowledge of the effect of structural changes must be obtained. The degree and type of crosslinking, the molecular weight between crosslinks, the number of elastically ineffective chains (loops, dangling chain ends, sol-fraction) must be characterized. A number of theoretical and experimental efforts have been reported in the last few years on model networks prepared by endlinking reactions and the relationships of those structures with the ultimate mechanical properties. A range of experimental methods have been used to investigate structure including rheometric, scattering, infrared, {sup 29}Si MAS and CPMAS, {sup 1}H relaxation measurements, and recently {sup 1}H multiple quantum methods. Characterization of the growth of multiple quantum coherences have recently been shown to provide detailed insight into silicone network structure by the ability to selective probe the individual components of the polymer network, such as the polymer-filler interface or network chains. We have employed recently developed MQ methods to investigate the structure-property relationships in a series of complex, endlinked filled-PDMS blends. Here, a systematic study of the relationship between the molecular formulation, as dictated by the amount and type of crosslinks present and by the remaining network chains, and the segmental dynamics as observed by MQ NMR was performed.

  19. Development of relaxation turbulence models

    NASA Technical Reports Server (NTRS)

    Hung, C. M.

    1976-01-01

    Relaxation turbulence models have been intensively studied. The complete time dependent mass averaged Navier-Stokes equations have been solved for flow into a two dimensional compression corner. A new numerical scheme has been incorporated into the developed computed code with an attendant order of magnitude reduction in computation time. Computed solutions are compared with experimental measurements of Law for supersonic flow. Details of the relaxation process have been studied; several different relaxation models, including different relaxation processes and varying relaxation length, are tested and compared. Then a parametric study has been conducted in which both Reynolds number and wedge angle are varied. To assess effects of Reynolds number and wedge angle, the parametric study includes the comparison of computed separation location and upstream extent of pressure rise; numerical results are also compared with the measurements of surface pressure, skin friction and mean velocity field.

  20. The 1H NMR Profile of Healthy Dog Cerebrospinal Fluid

    PubMed Central

    Musteata, Mihai; Nicolescu, Alina; Solcan, Gheorghe; Deleanu, Calin

    2013-01-01

    The availability of data for reference values in cerebrospinal fluid for healthy humans is limited due to obvious practical and ethical issues. The variability of reported values for metabolites in human cerebrospinal fluid is quite large. Dogs present great similarities with humans, including in cases of central nervous system pathologies. The paper presents the first study on healthy dog cerebrospinal fluid metabolomic profile using 1H NMR spectroscopy. A number of 13 metabolites have been identified and quantified from cerebrospinal fluid collected from a group of 10 mix breed healthy dogs. The biological variability as resulting from the relative standard deviation of the physiological concentrations of the identified metabolites had a mean of 18.20% (range between 9.3% and 44.8%). The reported concentrations for metabolites may be used as normal reference values. The homogeneity of the obtained results and the low biologic variability show that the 1H NMR analysis of the dog’s cerebrospinal fluid is reliable in designing and interpreting clinical and therapeutic trials in dogs with central nervous system pathologies. PMID:24376499

  1. 23Na and 1H NMR Microimaging of Intact Plants

    NASA Astrophysics Data System (ADS)

    Olt, Silvia; Krötz, Eva; Komor, Ewald; Rokitta, Markus; Haase, Axel

    2000-06-01

    23Na NMR microimaging is described to map, for the first time, the sodium distribution in living plants. As an example, the response of 6-day-old seedlings of Ricinus communis to exposure to sodium chloride concentrations from 5 to 300 mM was observed in vivo using 23Na as well as 1H NMR microimaging. Experiments were performed at 11.75 T with a double resonant 23Na-1H probehead. The probehead was homebuilt and equipped with a climate chamber. T1 and T2 of 23Na were measured in the cross section of the hypocotyl. Within 85 min 23Na images with an in-plane resolution of 156 × 156 μm were acquired. With this spatial information, the different types of tissue in the hypocotyl can be discerned. The measurement time appears to be short compared to the time scale of sodium uptake and accumulation in the plant so that the kinetics of salt stress can be followed. In conclusion, 23Na NMR microimaging promises great potential for physiological studies of the consequences of salt stress on the macroscopic level and thus may become a unique tool for characterizing plants with respect to salt tolerance and salt sensitivity.

  2. 23Na and (1)H NMR microimaging of intact plants.

    PubMed

    Olt, S; Krötz, E; Komor, E; Rokitta, M; Haase, A

    2000-06-01

    (23)Na NMR microimaging is described to map, for the first time, the sodium distribution in living plants. As an example, the response of 6-day-old seedlings of Ricinus communis to exposure to sodium chloride concentrations from 5 to 300 mM was observed in vivo using (23)Na as well as (1)H NMR microimaging. Experiments were performed at 11.75 T with a double resonant (23)Na-(1)H probehead. The probehead was homebuilt and equipped with a climate chamber. T(1) and T(2) of (23)Na were measured in the cross section of the hypocotyl. Within 85 min (23)Na images with an in-plane resolution of 156 x 156 micrometer were acquired. With this spatial information, the different types of tissue in the hypocotyl can be discerned. The measurement time appears to be short compared to the time scale of sodium uptake and accumulation in the plant so that the kinetics of salt stress can be followed. In conclusion, (23)Na NMR microimaging promises great potential for physiological studies of the consequences of salt stress on the macroscopic level and thus may become a unique tool for characterizing plants with respect to salt tolerance and salt sensitivity.

  3. Metabolomic insight into soy sauce through (1)H NMR spectroscopy.

    PubMed

    Ko, Bong-Kuk; Ahn, Hyuk-Jin; van den Berg, Frans; Lee, Cherl-Ho; Hong, Young-Shick

    2009-08-12

    Soy sauce, a well-known seasoning in Asia and throughout the world, consists of many metabolites that are produced during fermentation or aging and that have various health benefits. However, their comprehensive assessment has been limited due to targeted or instrumentally specific analysis. This paper presents for the first time a metabolic characterization of soy sauce, especially that aged up to 12 years, to obtain a global understanding of the metabolic variations through (1)H NMR spectroscopy coupled with multivariate pattern recognition techniques. Elevated amino acids and organic acids and the consumption of carbohydrate were associated with continuous involvement of microflora in aging for 12 years. In particular, continuous increases in the levels of betaine were found during aging for up to 12 years, demonstrating that microbial- or enzyme-related metabolites were also coupled with osmotolerant or halophilic bacteria present during aging. This work provides global insights into soy sauce through a (1)H NMR-based metabolomic approach that enhances the current understanding of the holistic metabolome and allows assessment of soy sauce quality.

  4. New approach for understanding experimental NMR relaxivity properties of magnetic nanoparticles: focus on cobalt ferrite.

    PubMed

    Rollet, Anne-Laure; Neveu, Sophie; Porion, Patrice; Dupuis, Vincent; Cherrak, Nadine; Levitz, Pierre

    2016-12-07

    Relaxivities r1 and r2 of cobalt ferrite magnetic nanoparticles (MNPs) have been investigated in the aim of improving the models of NMR relaxation induced by magnetic nanoparticles. On one hand a large set of relaxivity data has been collected for cobalt ferrite MNP dispersions. On the other hand the relaxivity has been calculated for dispersions of cobalt ferrite MNPs with size ranging from 5 to 13 nm, without using any fitting procedure. The model is based on the magnetic dipolar interaction between the magnetic moments of the MNPs and the (1)H nuclei. It takes into account both the longitudinal and transversal contributions of the magnetic moments of MNPs leading to three contributions in the relaxation equations. The comparison of the experimental and theoretical data shows a good agreement of the NMR profiles as well as the temperature dependence.

  5. Genetic Variation in Myosin 1H Contributes to Mandibular Prognathism

    PubMed Central

    Tassopoulou-Fishell, Maria; Deeley, Kathleen; Harvey, Erika M.; Sciote, James; Vieira, Alexandre R.

    2013-01-01

    Introduction Several candidate loci have been suggested as influencing mandibular prognathism (1p22.1, 1p22.2, 1p36, 3q26.2, 5p13-p12, 6q25, 11q22.2-q22.3, 12q23, 12q13.13, and 19p13.2). The goal of this study was to replicate these results in a well-characterized homogeneous sample set. Methods Thirty-three single nucleotide polymorphisms spanning all candidate regions were studied in 44 prognathic and 35 Class I subjects from the University of Pittsburgh School of Dental Medicine Dental Registry and DNA Repository. The 44 mandibular prognathism subjects had an average age of 18.4 years, 31 were females and 13 males, and 24 were White, 15 African American, two Hispanic, and three Asian. The 35 Class I subjects had an average age of 17.6 years, 27 were females and 9 males, and 27 were White, six African Americans, one Hispanic, and two Asian. Skeletal mandibular prognathism diagnosis included cephalometric values indicative of Class III such as ANB smaller than two degrees, negative Witts appraisal, and positive A–B plane. Additional mandibular prognathism criteria included negative OJ and visually prognathic (concave) profile as determined by the subject's clinical evaluation. Orthognathic subjects without jaw deformations were used as a comparison group. Mandibular prognathism and orthognathic subjects were matched based on race, sex and age. Genetic markers were tested by polymerase chain reaction using TaqMan chemistry. Chi-square and Fisher exact tests were used to determine overrepresentation of marker allele with alpha of 0.05. Results An association was unveiled between a marker in MYO1H (rs10850110) and the mandibular prognathism phenotype (p=0.03). MYO1H is a Class-I myosin that is in a different protein group than the myosin isoforms of muscle sarcomeres, which are the basis of skeletal muscle fiber typing. Class I myosins are necessary for cell motility, phagocytosis and vesicle transport. Conclusions More strict clinical definitions may increase

  6. Dynamics of helical worm-like chains. VIII. Higher-order subspace approximations to dielectric and magnetic relaxation and fluorescence depolarization for flexible chains

    NASA Astrophysics Data System (ADS)

    Yamakawa, Hiromi; Yoshizaki, Takenao; Fujii, Motoharu

    1986-04-01

    Following the general scheme developed in the preceding paper (paper VII), dielectric and magnetic relaxation and fluorescence depolarization for flexible chain polymers in dilute solution are reinvestigated on the basis of the discrete helical worm-like chain in the higher-order subspace approximation. A comparison of theory with experiment is made with respect to the dielectric correlation time τD, the spin-lattice relaxation time T1, the spin-spin relaxation time T2, the nuclear Overhauser enhancement (NOE), the fluorescence emission anisotropy r(t), the average fluorescence anisotropy r¯, and the fluorescence correlation time τF. It is found that there is agreement between the diameters of the chains determined from these dynamic properties and those from chemical structures, better than in the previous crude subspace approximation, indicating that the theory is remarkably improved in the present approximation. The magnetic correlation time τM is in general not an observable, and therefore an empirical equation to be used for its determination from the observed T1 is constructed. It is then found that there is good correlation between the dynamic chain stiffness τX/τ0X and the static chain stiffness λ-1, where τ0X is the correlation time of the isolated subbody (monomer unit) with X=D, M, and F; τX/τ0X is a monotonically increasing function of λ-1 nearly independent of X as far as perpendicular dipoles are concerned. An explanation of this result is given. However, the dependence of τX on temperature cannot be explained very satisfactorily.

  7. 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.

  8. Curie-type paramagnetic NMR relaxation in the aqueous solution of Ni(II).

    PubMed

    Mareš, Jiří; Hanni, Matti; Lantto, Perttu; Lounila, Juhani; Vaara, Juha

    2014-04-21

    Ni(2+)(aq) has been used for many decades as a model system for paramagnetic nuclear magnetic resonance (pNMR) relaxation studies. More recently, its magnetic properties and also nuclear magnetic relaxation rates have been studied computationally. We have calculated electron paramagnetic resonance and NMR parameters using quantum-mechanical (QM) computation of molecular dynamics snapshots, obtained using a polarizable empirical force field. Statistical averages of hyperfine coupling, g- and zero-field splitting tensors, as well as the pNMR shielding terms, are compared to the available experimental and computational data. In accordance with our previous work, the isotropic hyperfine coupling as well as nuclear shielding values agree well with experimental measurements for the (17)O nuclei of water molecules in the first solvation shell of the nickel ion, whereas larger deviations are found for (1)H centers. We report, for the first time, the Curie-type contribution to the pNMR relaxation rate using QM calculations together with Redfield relaxation theory. The Curie relaxation mechanism is analogous to chemical shift anisotropy relaxation, well-known in diamagnetic NMR. Due to the predominance of other types of paramagnetic relaxation mechanisms for this system, it is possible to extract the Curie term only computationally. The Curie mechanism alone would result in around 16 and 20 s(-1) of relaxation rates (R1 and R2 respectively) for the (1)H nuclei of water molecules bonded to the Ni(2+) center, in a magnetic field of 11.7 T. The corresponding (17)O relaxation rates are around 33 and 38 s(-1). We also report the Curie contribution to the relaxation rate for molecules beyond the first solvation shell in a 1 M solution of Ni(2+) in water.

  9. Crystal structure of 1H,1'H-[2,2'-biimid-azol]-3-ium hydrogen tartrate hemi-hydrate.

    PubMed

    Gao, Xiao-Li; Bian, Li-Fang; Guo, Shao-Wei

    2014-11-01

    In the crystal of the title hydrated salt, C6H7N4 (+)·C4H5O6 (-)·0.5H2O, the bi-imidazole monocation, 1H,1'H-[2,2'-biimidazol]-3-ium, is hydrogen bonded, via N-H⋯O, O-H⋯O and O-H⋯N hydrogen bonds, to the hydrogen tartrate anion and the water mol-ecule, which is located on a twofold rotation axis, forming sheets parallel to (001). The sheets are linked via C-H⋯O hydrogen bonds, forming a three-dimensional structure. There are also C=O⋯π inter-actions present [O⋯π distances are 3.00 (9) and 3.21 (7) Å], involving the carbonyl O atoms and the imidazolium ring, which may help to consolidate the structure. In the cation, the dihedral angle between the rings is 11.6 (2)°.

  10. One dimensional 1H, 2H and 3H

    NASA Astrophysics Data System (ADS)

    Vidal, A. J.; Astrakharchik, G. E.; Vranješ Markić, L.; Boronat, J.

    2016-05-01

    The ground-state properties of one-dimensional electron-spin-polarized hydrogen 1H, deuterium 2H, and tritium 3H are obtained by means of quantum Monte Carlo methods. The equations of state of the three isotopes are calculated for a wide range of linear densities. The pair correlation function and the static structure factor are obtained and interpreted within the framework of the Luttinger liquid theory. We report the density dependence of the Luttinger parameter and use it to identify different physical regimes: Bogoliubov Bose gas, super-Tonks-Girardeau gas, and quasi-crystal regimes for bosons; repulsive, attractive Fermi gas, and quasi-crystal regimes for fermions. We find that the tritium isotope is the one with the richest behavior. Our results show unambiguously the relevant role of the isotope mass in the properties of this quantum system.

  11. Progressive muscle relaxation, breathing exercises, and ABC relaxation theory.

    PubMed

    Matsumoto, M; Smith, J C

    2001-12-01

    This study compared the psychological effects of Progressive Muscle Relaxation (PMR) and breathing exercises. Forty-two students were divided randomly into two groups and taught PMR or breathing exercises. Both groups practiced for five weeks and were given the Smith Relaxation States Inventory before and after each session. As hypothesized, PMR practitioners displayed greater increments in relaxation states (R-States) Physical Relaxation and Disengagement, while breathing practitioners displayed higher levels of R-State Strength and Awareness. Slight differences emerged at Weeks 1 and 2; major differences emerged at Weeks 4 and 5. A delayed and potentially reinforcing aftereffect emerged for PMR only after five weeks of training--increased levels of Mental Quiet and Joy. Clinical and theoretical implications are discussed.

  12. Arrangement and mobility of water in vermiculite hydrates followed by 1H NMR spectroscopy.

    PubMed

    Sanz, J; Herrero, C P; Serratosa, J M

    2006-04-20

    The arrangement of water molecules in one- and two-layer hydrates of high-charged vermiculites, saturated with alkaline (Li(+), Na(+)) and alkali-earth (Mg(2+), Ca(2+), Ba(2+)) cations, has been analyzed with (1)H NMR spectroscopy. Two different orientations for water molecules have been found, depending on the hydration state and the sites occupied by interlayer cations. As the amount of water increases, hydrogen bond interactions between water molecules increase at expenses of water-silicate interactions. This interaction favors water mobility in vermiculites. A comparison of the temperature dependence of relaxation times T(1) and T(2) for one and two-layer hydrates of Na-vermiculite shows that the rotations of water molecules around C(2)-axes and that of cation hydration shells around the c-axis is favored in the two-layer hydrate. In both hydrates, the anisotropic diffusion of water takes place at room temperature, preserving the orientation of water molecules relative to the silicate layers. Information obtained by NMR spectroscopy is compatible with that deduced by infrared spectroscopy and with structural studies carried out with X-ray and neutron diffraction techniques on single-crystals of vermiculite.

  13. Stress relaxation in heterogeneous polymers

    NASA Astrophysics Data System (ADS)

    Witten, T. A.

    1992-05-01

    When heterogeneous polymers such as diblock copolymers form a microdomain phase, an imposed strain gives rise to stress from two sources, and several mechanisms of stress relaxation. The release of stress by disentanglement is strongly influenced by the effective confinement of the junction points to the domain boundaries and by the stretching of the chains. Using accepted notions of entangled chain kinetics, it is argued that the relaxation time for sliding stress is exponential in the chainlength to the 7/9 power. A method for calculating the frequency-dependent dynamic modulus is sketched. Despite the slow relaxation implied by these mechanisms, it appears possible to create domains of high energy.

  14. Isotope Effects in Collisional VT Relaxation of Molecular Hydrogen

    NASA Technical Reports Server (NTRS)

    Bieniek, R. J.

    2006-01-01

    A simple exponential-potential model of molecular collisions leads to a two-parameter analytic expression for rates of collisionally induced vibrational-translation (VT) energy exchange that has been shown to be accurate over variations of orders of magnitude as a function of temperature in a variety of systems. This includes excellent agreement with reported experimental and theoretical results for the fundamental self-relaxation rate of molecular hydrogen H2(v = 1) + H2 yields H2(v = 0) + H2. The analytic rate successfully follows the five-orders-of-magnitude change in experimental values for the temperature range 50-2000 K. This approach is now applied to isotope effects in the vibrational relaxation rates of excited HD and D2 in collision with H2: HD(v = 1)+H2 yields HD(v = 0)+H2 and D2(v = 1)+H2 yields D2(v = 0)+H2. The simplicity of the analytic expression for the thermal rate lends itself to convenient application in modeling the evolving vibrational populations of molecular hydrogen in shocked astrophysical environments.

  15. Effective rotational correlation times of proteins from NMR relaxation interference

    NASA Astrophysics Data System (ADS)

    Lee, Donghan; Hilty, Christian; Wider, Gerhard; Wüthrich, Kurt

    2006-01-01

    Knowledge of the effective rotational correlation times, τc, for the modulation of anisotropic spin-spin interactions in macromolecules subject to Brownian motion in solution is of key interest for the practice of NMR spectroscopy in structural biology. The value of τc enables an estimate of the NMR spin relaxation rates, and indicates possible aggregation of the macromolecular species. This paper reports a novel NMR pulse scheme, [ 15N, 1H]-TRACT, which is based on transverse relaxation-optimized spectroscopy and permits to determine τc for 15N- 1H bonds without interference from dipole-dipole coupling of the amide proton with remote protons. [ 15N, 1H]-TRACT is highly efficient since only a series of one-dimensional NMR spectra need to be recorded. Its use is suggested for a quick estimate of the rotational correlation time, to monitor sample quality and to determine optimal parameters for complex multidimensional NMR experiments. Practical applications are illustrated with the 110 kDa 7,8-dihydroneopterin aldolase from Staphylococcus aureus, the uniformly 15N-labeled Escherichia coli outer membrane protein X (OmpX) in 60 kDa mixed OmpX/DHPC micelles with approximately 90 molecules of unlabeled 1,2-dihexanoyl- sn-glycero-3-phosphocholine (DHPC), and the 16 kDa pheromone-binding protein from Bombyx mori, which cover a wide range of correlation times.

  16. Dispersion of Relaxation Rates in the Rotating Frame Under the Action of Spin-Locking Pulses and Diffusion in Inhomogeneous Magnetic Fields

    PubMed Central

    Spear, John T.; Zu, Zhongliang; Gore, John C.

    2013-01-01

    Purpose A method is described for characterizing magnetically inhomogeneous media and the spatial scales of intrinsic susceptibility variations within samples. The rate of spin-lattice relaxation in the rotating frame, R1ρ, is affected by diffusion effects to a degree that depends on the magnitude of an applied spin-locking field. Appropriate analysis of the dispersion of R1ρ with locking field may be used to characterize susceptibility variations in inhomogeneous tissues. Theory and Methods The contribution of diffusion to R1ρ is quantified by an analytic expression derived by analyzing of the effects of diffusion through periodic variations of magnetic susceptibility and is used to predict the effects of inhomogeneities in simple phantoms. The theory is further applied to imaging to derive parametric images that portray the dimensions of susceptibility inhomogeneities independent of their magnitude. Results Significant dispersion of R1ρ with locking field was predicted and measured experimentally for suspensions of microspheres ranging from 1 to 90 µm in diameter. For scales of practical interest, these dispersion effects occur at much lower locking fields than the range in which chemical exchange effects cause similar dispersion. Conclusion There is good agreement between theory and experiment, and the method has potential for quantitative tissue characterization and functional imaging. PMID:23804212

  17. Stress Relaxation of Interim Restoratives.

    DTIC Science & Technology

    1978-05-18

    unmodified zinc oxide- eugenol cement were more favorable than those of IRM and Cavit. The plastic behavior of gutta-percha temporary stopping precluded assessment of its relaxation at temperatures in excess of 22P C. (Author)

  18. Relaxation labeling using modular operators

    SciTech Connect

    Duncan, J.S.; Frei, W.

    1983-01-01

    Probabilistic relaxation labeling has been shown to be useful in image processing, pattern recognition, and artificial intelligence. The approaches taken to date have been encumbered with computationally extensive summations which generally prevent real-time operation and/or easy hardware implementation. The authors present a new and unique approach to the relaxation labeling problem using modular, VLSI-oriented hierarchical complex operators. One of the fundamental concepts of this work is the representation of the probability distribution of the possible labels for a given object (pixel) as an ellipse, which may be summed with neighboring object's distribution ellipses, resulting in a new, relaxed label space. The mathematical development of the elliptical approach will be presented and compared to more classical approaches, and a hardware block diagram that shows the implementation of the relaxation scheme using vlsi chips will be presented. Finally, results will be shown which illustrate applications of the modular scheme, iteratively, to both edges and lines. 13 references.

  19. Liver Metabolite Concentrations Measured with 1H MR Spectroscopy

    PubMed Central

    Pettigrew, Roderic I.; Gharib, Ahmed M.

    2012-01-01

    Purpose: To determine the feasibility of measuring choline and glycogen concentrations in normal human liver in vivo with proton (hydrogen 1 [1H]) magnetic resonance (MR) spectroscopy. Materials and Methods: Signed consent to participate in an institutional review board–approved and HIPAA-compliant study was obtained from 46 subjects (mean age, 46 years ± 17 [standard deviation]; 24 women) consecutively recruited during 285 days. Navigator-gated MR images were used to select 8-mL volumes for point-resolved spectroscopy (PRESS) with a 35-msec echo time. Line widths were minimized with fast breath-hold B0 field mapping and further manual shimming. Navigator-gated spectra were recorded with and without water suppression to determine metabolite concentrations with water signals as an internal reference. In three subjects, echo time was varied to determine the glycogen and choline T2. Linear regression analysis was used to examine relations between choline, hepatic lipid content, body mass index, glycogen content, and age. Results: Choline concentrations could be determined in 46 of 48 studies and was found to be 8.6 mmol per kilogram of wet weight ± 3.1 (range, 3.8–17.6; n = 44). Twenty-seven spectra in 25 individuals with narrow line widths and low lipid content were adequate for quantitation of glycogen. The glycogen (glucosyl unit) concentration was 38.1 mmol/kg wet weight ± 14.4. The T2 of combined glycogen peaks in the liver of three subjects was 36 msec ± 8. Choline levels showed a weak but significant correlation with glycogen (r2 = 0.15; P < .05) but not with lipid content. Conclusion: Navigator-gated and gradient-echo shimmed PRESS 1H MR spectroscopy may allow quantification of liver metabolites that are important for understanding and identifying disorders of glucose and lipid metabolism. © RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112344/-/DC1 PMID:22891360

  20. Hexamethyldisiloxane-based nanoprobes for (1) H MRI oximetry.

    PubMed

    Gulaka, Praveen K; Rastogi, Ujjawal; McKay, Madalyn A; Wang, Xianghui; Mason, Ralph P; Kodibagkar, Vikram D

    2011-12-01

    Quantitative in vivo oximetry has been reported using (19) F MRI in conjunction with reporter molecules, such as perfluorocarbons, for tissue oxygenation (pO(2) ). Recently, hexamethyldisiloxane (HMDSO) has been proposed as a promising alternative reporter molecule for (1) H MRI-based measurement of pO(2) . To aid biocompatibility for potential systemic administration, we prepared various nanoemulsion formulations using a wide range of HMDSO volume fractions and HMDSO to surfactant ratios. Calibration curves (R(1) versus pO(2) ) for all emulsion formulations were found to be linear and similar to neat HMDSO for low surfactant concentrations (<10% v/v). A small temperature dependence in the calibration curves was observed, similar to previous reports on neat HMDSO, and was characterized to be approximately 1 Torr/ °C under hypoxic conditions. To demonstrate application in vivo, 100 µL of this nanoemulsion was administered to healthy rat thigh muscle (Fisher 344, n=6). Dynamic changes in mean thigh tissue pO(2) were measured using the PISTOL (proton imaging of siloxanes to map tissue oxygenation levels) technique in response to oxygen challenge. Changing the inhaled gas to oxygen for 30 min increased the mean pO(2) significantly (p<0.001) from 39 ± 7 to 275 ± 27 Torr. When the breathing gas was switched back to air, the tissue pO(2) decreased to a mean value of 45 ± 6 Torr, not significantly different from baseline (p>0.05), in 25 min. A first-order exponential fit to this part of the pO(2) data (i.e. after oxygen challenge) yielded an oxygen consumption-related kinetic parameter k=0.21 ± 0.04 min(-1) . These results demonstrate the feasibility of using HMDSO nanoemulsions as nanoprobes of pO(2) and their utility to assess oxygen dynamics in vivo, further developing quantitative (1) H MRI oximetry.

  1. Vacancy Relaxation in Cubic Crystals

    NASA Technical Reports Server (NTRS)

    Girifalco, L. A.; Weizer, V. G.

    1960-01-01

    The configuration of the atoms surrounding a vacancy in four face-centered cubic and three body-centered cubic metals has been computed, using a pairwise, central-force model in which the energy of interaction between two atoms was taken to have the form of a Morse function. Only radial relaxations were considered. The first and second nearest-neighbor relaxations for the face-centered systems were found to be: Pb (1.42,-0.43), Ni (2.14,-0.39), Cu(2.24,-0.40) and Ca (2.73,-0.41, expressed in percentages of normal distances. For the body-centered systems the relaxations out to the fourth nearest neighbors to the vacancy were: Fe (6.07,-2.12, -0.25, -), Ba (7.85, -2.70, 0.70, -0.33) and Na (10.80, -3.14, 3.43, -0.20). The positive signs indicate relaxation toward the vacancy and the negative signs indicate relaxation away from the vacancy. The energies of relaxation (eV) are: Pb (0.162), Ni (0.626), Cu (0.560), Ca (0.400), Fe (1.410), Ba (0.950) and Na (0.172).

  2. Improved TROSY-HNCA experiment with suppression of conformational exchange induced relaxation.

    PubMed

    Pervushin, K; Gallius, V; Ritter, C

    2001-10-01

    A general method for improving of the sensitivity of the TROSY-type triple resonance experiments in the presence of conformational exchange-induced (CSX) relaxation is proposed based on the use of CPMG-INEPT (Müller et al., J. Am. Chem. Soc., 1995, 117, 11043-11048) during the N-C polarization transfer periods. Significantly improved sensitivity is demonstrated for the majority of cross-peaks in the new [15N,1H]-TROSY-XY-HNCA experiment, measured with partially folded RNase AS-Protein, with negligible loss of sensitivity for resonances unaffected by CSX relaxation. In addition, a comparison of cross-peak amplitudes in [15N,1N]-TROSY-XY-HNCA and conventional [15N,1H]-TROSY-HNCA spectra provides a quick and sensitive estimation of the CSX relaxation contribution.

  3. Hyperpolarized nanodiamond with long spin-relaxation times

    NASA Astrophysics Data System (ADS)

    Rej, Ewa; Gaebel, Torsten; Boele, Thomas; Waddington, David E. J.; Reilly, David J.

    2015-10-01

    The use of hyperpolarized agents in magnetic resonance, such as 13C-labelled compounds, enables powerful new imaging and detection modalities that stem from a 10,000-fold boost in signal. A major challenge for the future of the hyperpolarization technique is the inherently short spin-relaxation times, typically <60 s for 13C liquid-state compounds, which limit the time that the signal remains boosted. Here we demonstrate that 1.1% natural abundance 13C spins in synthetic nanodiamond can be hyperpolarized at cryogenic and room temperature without the use of free radicals, and, owing to their solid-state environment, exhibit relaxation times exceeding 1 h. Combined with the already established applications of nanodiamonds in the life sciences as inexpensive fluorescent markers and non-cytotoxic substrates for gene and drug delivery, these results extend the theranostic capabilities of nanoscale diamonds into the domain of hyperpolarized magnetic resonance.

  4. Mapping of prostate cancer by 1H MRSI.

    PubMed

    Kobus, Thiele; Wright, Alan J; Scheenen, Tom W J; Heerschap, Arend

    2014-01-01

    In many studies, it has been demonstrated that (1)H MRSI of the human prostate has great potential to aid prostate cancer management, e.g. in the detection and localisation of cancer foci in the prostate or in the assessment of its aggressiveness. It is particularly powerful in combination with T2 -weighted MRI. Nevertheless, the technique is currently mainly used in a research setting. This review provides an overview of the state-of-the-art of three-dimensional MRSI, including the specific hardware required, dedicated data acquisition sequences and information on the spectral content with background on the MR-visible metabolites. In clinical practice, it is important that relevant MRSI results become available rapidly, reliably and in an easy digestible way. However, this functionality is currently not fully available for prostate MRSI, which is a major obstacle for routine use by inexperienced clinicians. Routine use requires more automation in the processing of raw data than is currently available. Therefore, we pay specific attention in this review on the status and prospects of the automated handling of prostate MRSI data, including quality control. The clinical potential of three-dimensional MRSI of the prostate is illustrated with literature examples on prostate cancer detection, its localisation in the prostate, its role in the assessment of cancer aggressiveness and in the selection and monitoring of therapy.

  5. 3-hydroxy-2(1H)-pyridinone chelating agents

    DOEpatents

    Raymond, K.N.; Xu, J.

    1997-04-29

    Disclosed is a series of improved metal chelating agents, which are highly effective upon both injection and oral administration; several of the most effective are of low toxicity. These chelating agents incorporate within their structure 1-hydroxy-2-pyridinone (1,2-HOPO) and 3-hydroxy-2-pyridinone (3,2-HOPO) moieties with a substituted carbamoyl group ortho to the hydroxy or oxo groups of the hydroxypyridinone ring. The electron-withdrawing carbamoyl group increases the acidity of the hydroxypyridinones. In the metal complexes of the chelating agents, the amide protons form very strong hydrogen bonds with its adjacent HOPO oxygen donor, making these complexes very stable at physiological conditions. The terminal N-substituents provides a certain degree of lipophilicity to the 3,2-HOPO, increasing oral activity. Also disclosed is a method of making the chelating agents and a method of producing a known compound, 3-hydroxy-1-alkyl-2(1H)pyridinone, used as a precursor to the chelating agent, safely and in large quantities. 2 figs.

  6. 3-hydroxy-2(1H)-pyridinone chelating agents

    DOEpatents

    Raymond, Kenneth N.; Xu, Jide

    1997-01-01

    Disclosed is a series of improved metal chelating agents, which are highly effective upon both injection and oral administration; several of the most effective are of low toxicity. These chelating agents incorporate within their structure 1-hydroxy-2-pyridinone (1,2-HOPO) and 3-hydroxy-2-pyridinone (3,2-HOPO) moieties with a substituted carbamoyl group ortho to the hydroxy or oxo groups of the hydroxypyridinone ring. The electron-withdrawing carbamoyl group increases the acidity of the hydroxypyridinones. In the metal complexes of said chelating agents, the amide protons form very strong hydrogen bonds with its adjacent HOPO oxygen donor, making these complexes very stable at physiological conditions. The terminal N-substituents provides a certain degree of lipophilicity to said 3,2-HOPO, increasing oral activity. Also disclosed is a method of making the chelating agents and a method of producing a known compound, 3-hydroxy-1-alkyl-2(1H)pyridinone, used as a precursor to the chelating agent, safely and in large quantities.

  7. 1H NMR Metabolomics Analysis of Glioblastoma Subtypes

    PubMed Central

    Cuperlovic-Culf, Miroslava; Ferguson, Dean; Culf, Adrian; Morin, Pier; Touaibia, Mohamed

    2012-01-01

    Glioblastoma multiforme (GBM) is the most common form of malignant glioma, characterized by unpredictable clinical behaviors that suggest distinct molecular subtypes. With the tumor metabolic phenotype being one of the hallmarks of cancer, we have set upon to investigate whether GBMs show differences in their metabolic profiles. 1H NMR analysis was performed on metabolite extracts from a selection of nine glioblastoma cell lines. Analysis was performed directly on spectral data and on relative concentrations of metabolites obtained from spectra using a multivariate regression method developed in this work. Both qualitative and quantitative sample clustering have shown that cell lines can be divided into four groups for which the most significantly different metabolites have been determined. Analysis shows that some of the major cancer metabolic markers (such as choline, lactate, and glutamine) have significantly dissimilar concentrations in different GBM groups. The obtained lists of metabolic markers for subgroups were correlated with gene expression data for the same cell lines. Metabolic analysis generally agrees with gene expression measurements, and in several cases, we have shown in detail how the metabolic results can be correlated with the analysis of gene expression. Combined gene expression and metabolomics analysis have shown differential expression of transporters of metabolic markers in these cells as well as some of the major metabolic pathways leading to accumulation of metabolites. Obtained lists of marker metabolites can be leveraged for subtype determination in glioblastomas. PMID:22528487

  8. Molecular dynamics simulations of NMR relaxation and diffusion of bulk hydrocarbons and water

    NASA Astrophysics Data System (ADS)

    Singer, Philip M.; Asthagiri, Dilip; Chapman, Walter G.; Hirasaki, George J.

    2017-04-01

    Molecular dynamics (MD) simulations are used to investigate 1H nuclear magnetic resonance (NMR) relaxation and diffusion of bulk n-C5H12 to n-C17H36 hydrocarbons and bulk water. The MD simulations of the 1H NMR relaxation times T1,2 in the fast motion regime where T1 =T2 agree with measured (de-oxygenated) T2 data at ambient conditions, without any adjustable parameters in the interpretation of the simulation data. Likewise, the translational diffusion DT coefficients calculated using simulation configurations agree with measured diffusion data at ambient conditions. The agreement between the predicted and experimentally measured NMR relaxation times and diffusion coefficient also validate the forcefields used in the simulation. The molecular simulations naturally separate intramolecular from intermolecular dipole-dipole interactions helping bring new insight into the two NMR relaxation mechanisms as a function of molecular chain-length (i.e. carbon number). Comparison of the MD simulation results of the two relaxation mechanisms with traditional hard-sphere models used in interpreting NMR data reveals important limitations in the latter. With increasing chain length, there is substantial deviation in the molecular size inferred on the basis of the radius of gyration from simulation and the fitted hard-sphere radii required to rationalize the relaxation times. This deviation is characteristic of the local nature of the NMR measurement, one that is well-captured by molecular simulations.

  9. Nitrergic relaxation of the horse corpus cavernosum. Role of cGMP.

    PubMed

    Recio, P; López, P G; Hernández, M; Prieto, D; Contreras, J; García-Sacristán, A

    1998-06-12

    The involvement of nitric oxide (NO) and the mechanisms mediating neurogenic relaxation were investigated in the horse corpus cavernosum. NADPH-diaphorase activity was expressed in nerve fibres around arteries and muscular bundles in the horse trabecular tissue. Relaxations in response to electrical field stimulation were tetrodotoxin (10(-6) M)-sensitive, indicating their neurogenic origin. The NO synthase inhibitor, L-NO-arginine (L-NO-Arg, 3 x 10(-5) M), abolished the electrically induced relaxations, which were significantly reversed by L-arginine (3 x 10(-3) M). Exogenous NO (10(-6)-10(-3) M) evoked relaxations which were unaffected by L-NO-Arg. 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 5 x 10(-6) M), an inhibitor of guanylate cyclase activation by NO, reduced the relaxations in response to electrical stimulation and exogenous NO. Iberiotoxin (3 x 10(-8) M) or apamin (5 x 10(-7) M), inhibitors of large and small conductance Ca2+-activated K+ channels, respectively, and glibenclamide (3 x 10(-6) M), a blocker of ATP-sensitive K+ channels, failed to modify the relaxations with NO. It is suggested that NO is present in nerve fibres of the horse corpus cavernosum and relaxes smooth muscle through a guanylate cyclase-dependent mechanism. Neither Ca2+-activated nor ATP-sensitive K+ channels seem to be involved in these relaxations.

  10. Relaxation schemes for Chebyshev spectral multigrid methods

    NASA Technical Reports Server (NTRS)

    Kang, Yimin; Fulton, Scott R.

    1993-01-01

    Two relaxation schemes for Chebyshev spectral multigrid methods are presented for elliptic equations with Dirichlet boundary conditions. The first scheme is a pointwise-preconditioned Richardson relaxation scheme and the second is a line relaxation scheme. The line relaxation scheme provides an efficient and relatively simple approach for solving two-dimensional spectral equations. Numerical examples and comparisons with other methods are given.

  11. Nuclear Spin Relaxation and Molecular Interactions of a Novel Triazolium-Based Ionic Liquid

    SciTech Connect

    Allen, Jesse J; Schneider, Yanika; Kail, Brian W; Luebke, David R; Nulwala, Hunaid; Damodaran, Krishnan

    2013-04-11

    Nuclear spin relaxation, small-angle X-ray scattering (SAXS), and electrospray ionization mass spectrometry (ESI-MS) techniques are used to determine supramolecular arrangement of 3-methyl-1-octyl-4-phenyl-1H-triazol-1,2,3-ium bis(trifluoromethanesulfonyl)imide [OMPhTz][Tf{sub 2}N], an example of a triazolium-based ionic liquid. The results obtained showed first-order thermodynamic dependence for nuclear spin relaxation of the anion. First-order relaxation dependence is interpreted as through-bond dipolar relaxation. Greater than first-order dependence was found in the aliphatic protons, aromatic carbons (including nearest neighbors), and carbons at the end of the aliphatic tail. Greater than first order thermodynamic dependence of spin relaxation rates is interpreted as relaxation resulting from at least one mechanism additional to through-bond dipolar relaxation. In rigid portions of the cation, an additional spin relaxation mechanism is attributed to anisotropic effects, while greater than first order thermodynamic dependence of the octyl side chain’s spin relaxation rates is attributed to cation–cation interactions. Little interaction between the anion and the cation was observed by spin relaxation studies or by ESI-MS. No extended supramolecular structure was observed in this study, which was further supported by MS and SAXS. nuclear Overhauser enhancement (NOE) factors are used in conjunction with spin–lattice relaxation time (T{sub 1}) measurements to calculate rotational correlation times for C–H bonds (the time it takes for the vector represented by the bond between the two atoms to rotate by one radian). The rotational correlation times are used to represent segmental reorientation dynamics of the cation. A combination of techniques is used to determine the segmental interactions and dynamics of this example of a triazolium-based ionic liquid.

  12. String order and symmetries in quantum spin lattices.

    PubMed

    Pérez-García, D; Wolf, M M; Sanz, M; Verstraete, F; Cirac, J I

    2008-04-25

    We show that the existence of string order in a given quantum state is intimately related to the presence of a local symmetry by proving that both concepts are equivalent within the framework of finitely correlated states. Once this connection is established, we provide a complete characterization of local symmetries in these states. The results allow us to understand in a straightforward way many of the properties of string order parameters, like their robustness or fragility under perturbations and their typical disappearance beyond strictly one-dimensional lattices. We propose and discuss an alternative definition, ideally suited for detecting phase transitions, and generalizations to two and more spatial dimensions.

  13. Ellipsoidal Relaxation of Deformed Vesicles

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Lira, Rafael B.; Riske, Karin A.; Dimova, Rumiana; Lin, Hao

    2015-09-01

    Theoretical analysis and experimental quantification on the ellipsoidal relaxation of vesicles are presented. The current work reveals the simplicity and universal aspects of this process. The Helfrich formula is shown to apply to the dynamic relaxation of moderate-to-high tension membranes, and a closed-form solution is derived which predicts the vesicle aspect ratio as a function of time. Scattered data are unified by a time scale, which leads to a similarity behavior, governed by a distinctive solution for each vesicle type. Two separate regimes in the relaxation are identified, namely, the "entropic" and the "constant-tension" regimes. The bending rigidity and the initial membrane tension can be simultaneously extracted from the data analysis, posing the current approach as an effective means for the mechanical analysis of biomembranes.

  14. Relaxed Poisson cure rate models.

    PubMed

    Rodrigues, Josemar; Cordeiro, Gauss M; Cancho, Vicente G; Balakrishnan, N

    2016-03-01

    The purpose of this article is to make the standard promotion cure rate model (Yakovlev and Tsodikov, ) more flexible by assuming that the number of lesions or altered cells after a treatment follows a fractional Poisson distribution (Laskin, ). It is proved that the well-known Mittag-Leffler relaxation function (Berberan-Santos, ) is a simple way to obtain a new cure rate model that is a compromise between the promotion and geometric cure rate models allowing for superdispersion. So, the relaxed cure rate model developed here can be considered as a natural and less restrictive extension of the popular Poisson cure rate model at the cost of an additional parameter, but a competitor to negative-binomial cure rate models (Rodrigues et al., ). Some mathematical properties of a proper relaxed Poisson density are explored. A simulation study and an illustration of the proposed cure rate model from the Bayesian point of view are finally presented.

  15. Derivatives of pyrazinecarboxylic acid: 1H, 13C and 15N NMR spectroscopic investigations.

    PubMed

    Holzer, Wolfgang; Eller, Gernot A; Datterl, Barbara; Habicht, Daniela

    2009-07-01

    NMR spectroscopic studies are undertaken with derivatives of 2-pyrazinecarboxylic acid. Complete and unambiguous assignment of chemical shifts ((1)H, (13)C, (15)N) and coupling constants ((1)H,(1)H; (13)C,(1)H; (15)N,(1)H) is achieved by combined application of various 1D and 2D NMR spectroscopic techniques. Unequivocal mapping of (13)C,(1)H spin coupling constants is accomplished by 2D (delta,J) long-range INEPT spectra with selective excitation. Phenomena such as the tautomerism of 3-hydroxy-2-pyrazinecarboxylic acid are discussed.

  16. Local spin dynamics of iron oxide magnetic nanoparticles dispersed in different solvents with variable size and shape: A 1H NMR study

    NASA Astrophysics Data System (ADS)

    Basini, M.; Orlando, T.; Arosio, P.; Casula, M. F.; Espa, D.; Murgia, S.; Sangregorio, C.; Innocenti, C.; Lascialfari, A.

    2017-01-01

    Colloidal magnetic nanoparticles (MNPs) based on a nearly monodisperse iron oxide core and capped by oleic acid have been used as model systems for investigating the superparamagnetic spin dynamics by means of magnetometry measurements and nuclear magnetic resonance (1H NMR) relaxometry. The key magnetic properties (saturation magnetization, coercive field, and frequency dependent "blocking" temperature) of MNPs with different core size (3.5 nm, 8.5 nm, and 17.5 nm), shape (spherical and cubic), and dispersant (hexane and water-based formulation) have been determined. 1H NMR dispersion profiles obtained by measuring the r1 (longitudinal) and r2 (transverse) nuclear relaxivities in the frequency range 0.01-60 MHz confirmed that in all samples the physical mechanisms that drive the nuclear relaxation are the Néel reversal at low temperature and the Curie relaxation at high frequency. The magnetization reversal time at room temperature extracted from the fitting of NMR data falls in the typical range of superparamagnetic systems (10-9-10-10 s). Furthermore, from the distance of minimum approach we could conclude that water molecules do not arrive in close vicinity of the magnetic core. Our findings contribute to elucidate the local spin dynamics mechanisms in colloidal superparamagnetic nanoparticles which are useful in biomedical application as, e.g., contrast agents for magnetic resonance imaging.

  17. A mixed relaxed clock model

    PubMed Central

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  18. A mixed relaxed clock model.

    PubMed

    Lartillot, Nicolas; Phillips, Matthew J; Ronquist, Fredrik

    2016-07-19

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees.This article is part of the themed issue 'Dating species divergences using rocks and clocks'.

  19. Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair

    NASA Astrophysics Data System (ADS)

    Chang, Zhiwei; Halle, Bertil

    2013-10-01

    In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water 1H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft

  20. Analog circuits for relaxation networks.

    PubMed

    Card, H

    1993-12-01

    Selected examples are presented of recent advances, primarily from the U.S. and Canada, in analog circuits for relaxation networks. Relaxation networks having feedback connections exhibit potentially greater computational power per neuron than feedforward networks. They are also more poorly understood especially with respect to learning algorithms. Examples are described of analog circuits for (i) supervised learning in deterministic Boltzmann machines, (ii) unsupervised competitive learning and feature maps and (iii) networks with resistive grids for vision and audition tasks. We also discuss recent progress on in-circuit learning and synaptic weight storage mechanisms.

  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. Synthesis of 1H-indazoles and 1H-pyrazoles via FeBr3/O2 mediated intramolecular C-H amination.

    PubMed

    Zhang, Tianshui; Bao, Weiliang

    2013-02-01

    A new synthesis of substituted 1H-indazoles and 1H-pyrazoles from arylhydrazones via FeBr(3)/O(2) mediated C-H activation/C-N bond formation reactions is reported. The corresponding 1,3-diaryl-substituted indazoles and trisubstituted pyrazoles were obtained in moderate to excellent yields under mild conditions.

  3. "Stressing" Relaxation in the Classroom.

    ERIC Educational Resources Information Center

    Prager-Decker, Iris

    A rationale is offered for incorporating relaxation training in elementary school classroom activities. Cited are research studies which focus on the reaction of children to stressful life changes and resulting behavioral and physical disorders. A list is given of significant life events which may be factors in causing diseases or misbehavior in…

  4. Theory of nuclear magnetic relaxation

    NASA Technical Reports Server (NTRS)

    Mcconnell, J.

    1983-01-01

    A theory of nuclear magnetic interaction is based on the study of the stochastic rotation operator. The theory is applied explicitly to relaxation by anisotropic chemical shift and to spin-rotational interactions. It is applicable also to dipole-dipole and quadrupole interactions.

  5. Relaxation properties in classical diamagnetism

    NASA Astrophysics Data System (ADS)

    Carati, A.; Benfenati, F.; Galgani, L.

    2011-06-01

    It is an old result of Bohr that, according to classical statistical mechanics, at equilibrium a system of electrons in a static magnetic field presents no magnetization. Thus a magnetization can occur only in an out of equilibrium state, such as that produced through the Foucault currents when a magnetic field is switched on. It was suggested by Bohr that, after the establishment of such a nonequilibrium state, the system of electrons would quickly relax back to equilibrium. In the present paper, we study numerically the relaxation to equilibrium in a modified Bohr model, which is mathematically equivalent to a billiard with obstacles, immersed in a magnetic field that is adiabatically switched on. We show that it is not guaranteed that equilibrium is attained within the typical time scales of microscopic dynamics. Depending on the values of the parameters, one has a relaxation either to equilibrium or to a diamagnetic (presumably metastable) state. The analogy with the relaxation properties in the Fermi Pasta Ulam problem is also pointed out.

  6. Distributed Relaxation for Conservative Discretizations

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.

    2001-01-01

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

  7. Enhancement of T1 and T2 relaxation by paramagnetic silica-coated nanocrystals

    SciTech Connect

    Gerion, D; Herberg, J; Gjersing, E; Ramon, E; Maxwell, R; Gray, J W; Budinger, T F; Chen, F F

    2006-08-28

    We present the first comprehensive investigation on water-soluble nanoparticles embedded into a paramagnetic shell and their properties as an MRI contrast agent. The nanoprobes are constructed with an inorganic core embedded into an ultra-thin silica shell covalently linked to chelated Gd{sup 3+} paramagnetic ions that act as an MRI contrast agent. The chelator contains the molecule DOTA and the inorganic core contains a fluorescent CdSe/ZnS qdots in Au nanoparticles. Optical properties of the cores (fluorescence emission or plasmon position) are not affected by the neither the silica shell nor the presence of the chelated paramagnetic ions. The resulting complex is a MRI/fluorescence probe with a diameter of 8 to 15 nm. This probe is highly soluble in high ionic strength buffers at pH ranging from {approx}4 to 11. In MRI experiments at clinical field strengths of 60 MHz, the QDs probes posses spin-lattice (T{sub 1}) and a spin-spin (T{sub 2}) relaxivities of 1018.6 +/- 19.4 mM{sup -1} s{sup -1} and 2438.1 +/- 46.3 mM{sup -1} s{sup -1} respectively for probes having {approx}8 nm. This increase in relaxivity has been correlated to the number of paramagnetic ions covalently linked to the silica shell, ranging from approximately 45 to over 320. We found that each bound chelated paramagnetic species contributes by over 23 mM{sup -1} s{sup -1} to the total T{sub 1} and by over 54 mM{sup -1} s{sup -1} to the total T{sub 2} relaxivity respectively. The contrast power is modulated by the number of paramagnetic moieties linked to the silica shell and is only limited by the number of chelated paramagnetic species that can be packed on the surface. So far, the sensitivity of our probes is in the 100 nM range for 8-10 nm particles and reaches 10 nM for particles with approximately 15-18 nm in diameter. The sensitivities values in solutions are equivalent of those obtained with small superparamagnetic iron oxide nanoparticles of 7 nm diameter clustered into a 100 nm polymeric

  8. Comparative Relaxant Effects of Ataciguat and Zaprinast on Sheep Sphincter of Oddi

    PubMed Central

    Çakmak, Erol; Yönem, Özlem; Saraç, Bülent; Parlak, Mesut; Çelik, Cumali; Ataseven, Hilmi; Bağcivan, İhsan

    2016-01-01

    Background: Relaxing the sphincter of Oddi (SO) is an important process during endoscopic retrograde cholangiopancreatography (ERCP) procedures. This issue suggests that the easier the sphincterotomy and cannulation, the more post-ERCP complications decrease. Aims: To compare the relaxant effects of ataciguat (a novel soluble guanylyl cyclase activator) and zaprinast (an inhibitor of phosphodiesterase 5) on sheep SO in vitro, thus testing whether they can be used during ERCP. Study Design: Animal experimentation. Methods: Sheep SO rings were placed in tissue baths and their isometric tension to ataciguat and zaprinast were tested. We also tested their isometric tension against ataciguat in the presence of 1H-(1,2,4) oxadiazole (4,3-a) quinoxalin-1-one (ODQ) which is a soluble guanylyl cyclase inhibitor. Results: Ataciguat and zaprinast both triggered concentration addicted relaxation on sheep SO rings (p=0.0018, p=0.0025 respectively) but the relaxation of the ataciguat was significantly greater than that of zaprinast at all concentrations (p=0.0024). It was observed that decreased relaxation responses were initiated by ataciguat in the presence of ODQ (p=0.0012). Conclusion: Ataciguat and zaprinast both have relaxing effects on sphincter of Oddi, although that of zaprinast is lower. We believe that ataciguat and zaprinast can be used in ERCP procedures in order to relax the sphincter of Oddi and thus can be used locally in order to decrease complications. PMID:27606143

  9. Relaxation processes in non-Debye dielectrics

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    The specific features of the relaxation processes in non-Debye dielectrics have been investigated. The nature of the difference between the relaxation frequencies of the dielectric constant and dielectric loss (conductivity) has been explained. It has been shown that the average relaxation frequency of the conductivity is considerably (in some cases, by several orders of magnitude) higher than the relaxation frequency of the dielectric constant owing to an increase in the conductivity spectra of the statistical weight of the relaxation processes with short relaxation times.

  10. Noninvasive monitoring of moisture uptake in Ca(NO3)2 -polluted calcareous stones by 1H-NMR relaxometry.

    PubMed

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

    2015-01-01

    NMR transverse relaxation time (T(2)) distribution of (1)H nuclei of water has been used to monitor the moisture condensation kinetics in Ca(NO(3))(2)  · (4)H(2)O-polluted Lecce stone, a calcareous stone with highly regular porous structure often utilized as basic material in Baroque buildings. Polluted samples have been exposed to water vapor adsorption at controlled relative humidity to mimic environmental conditions. In presence of pollutants, the T(2) distributions of water in stone exhibit a range of relaxation time values and amplitudes not observed in the unpolluted case. These characteristics could be exploited for in situ noninvasive detection of salt pollution in Lecce stone or as damage precursors in architectural buildings of cultural heritage interest.

  11. Equivalent Relaxations of Optimal Power Flow

    SciTech Connect

    Bose, S; Low, SH; Teeraratkul, T; Hassibi, B

    2015-03-01

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

  12. Anomalous dielectric relaxation of water confined in graphite oxide

    SciTech Connect

    Yu, Ji; Tian, Yuchen; Gu, Min; Tang, Tong B.

    2015-09-28

    Nonmonotonic thermal dependence of dielectric relaxation of water has been observed in hydrated graphite oxide (GO). Graphite oxide prepared via Hummers method then imbued with specific water contents were characterized, with {sup 13}C and {sup 1}H nuclear magnetic resonance spectroscopies, X-ray photoelectron spectroscopy, ambient- and variable-temperature X-ray diffractometries, as well as thermogravimetric analysis. Pressed pellets provided with either conducting or blocking electrodes yielded dielectric loss, which was shown to originate from dielectric relaxation of the confined water. Three relaxation processes were observed in impedance spectroscopy. Our previous work has identified two different types of water in GO, namely, intercalated water and water in inter-grain voids. P{sub 1} expresses the reorientation of water confined inside inter-grain voids, and P{sub 2}, the rotation of intercalated water molecules confined in interlayers. The present work reveals a new process P{sub 3}, which also relates to intercalated water. It slows down with temperature, and this apparent anomaly is explained by the decrease in water content and consequent narrowing of interlayer spacing in graphite oxide, as confirmed by characterization techniques. The present study should contribute to our understanding of surface water dynamics.

  13. Anomalous dielectric relaxation of water confined in graphite oxide

    NASA Astrophysics Data System (ADS)

    Yu, Ji; Tian, Yuchen; Gu, Min; Tang, Tong B.

    2015-09-01

    Nonmonotonic thermal dependence of dielectric relaxation of water has been observed in hydrated graphite oxide (GO). Graphite oxide prepared via Hummers method then imbued with specific water contents were characterized, with 13C and 1H nuclear magnetic resonance spectroscopies, X-ray photoelectron spectroscopy, ambient- and variable-temperature X-ray diffractometries, as well as thermogravimetric analysis. Pressed pellets provided with either conducting or blocking electrodes yielded dielectric loss, which was shown to originate from dielectric relaxation of the confined water. Three relaxation processes were observed in impedance spectroscopy. Our previous work has identified two different types of water in GO, namely, intercalated water and water in inter-grain voids. P1 expresses the reorientation of water confined inside inter-grain voids, and P2, the rotation of intercalated water molecules confined in interlayers. The present work reveals a new process P3, which also relates to intercalated water. It slows down with temperature, and this apparent anomaly is explained by the decrease in water content and consequent narrowing of interlayer spacing in graphite oxide, as confirmed by characterization techniques. The present study should contribute to our understanding of surface water dynamics.

  14. 1H and 10B NMR and MRI investigation of boron- and gadolinium-boron compounds in boron neutron capture therapy.

    PubMed

    Bonora, M; Corti, M; Borsa, F; Bortolussi, S; Protti, N; Santoro, D; Stella, S; Altieri, S; Zonta, C; Clerici, A M; Cansolino, L; Ferrari, C; Dionigi, P; Porta, A; Zanoni, G; Vidari, G

    2011-12-01

    (10)B molecular compounds suitable for Boron Neutron Capture Therapy (BNCT) are tagged with a Gd(III) paramagnetic ion. The newly synthesized molecule, Gd-BPA, is investigated as contrast agent in Magnetic Resonance Imaging (MRI) with the final aim of mapping the boron distribution in tissues. Preliminary Nuclear Magnetic Resonance (NMR) measurements, which include (1)H and (10)B relaxometry in animal tissues, proton relaxivity of the paramagnetic Gd-BPA molecule in water and its absorption in tumoral living cells, are reported.

  15. Plasmon-mediated energy relaxation in graphene

    SciTech Connect

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    2015-12-28

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  16. Kinetic activation-relaxation technique.

    PubMed

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

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).

  17. Models of violently relaxed galaxies

    NASA Astrophysics Data System (ADS)

    Merritt, David; Tremaine, Scott; Johnstone, Doug

    1989-02-01

    The properties of spherical self-gravitating models derived from two distribution functions that incorporate, in a crude way, the physics of violent relaxation are investigated. The first distribution function is identical to the one discussed by Stiavelli and Bertin (1985) except for a change in the sign of the 'temperature', i.e., e exp(-aE) to e exp(+aE). It is shown that these 'negative temperature' models provide a much better description of the end-state of violent relaxation than 'positive temperature' models. The second distribution function is similar to the first except for a different dependence on angular momentum. Both distribution functions yield single-parameter families of models with surface density profiles very similar to the R exp 1/4 law. Furthermore, the central concentration of models in both families increases monotonically with the velocity anisotropy, as expected in systems that formed through cold collapse.

  18. Kinetic activation-relaxation technique

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).

  19. 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.

  20. Relaxation: A Fourth "R" for Education.

    ERIC Educational Resources Information Center

    Frederick, A. B.

    Relaxation training helps the individual handle tension through concentrating upon efficient use of muscles. A program of progressive relaxation can be easily incorporated into elementary and secondary schools. Objectives of such a program include the following: (a) to learn to relax technically for purposes of complete rest (deep muscle…

  1. Arresting relaxation in Pickering Emulsions

    NASA Astrophysics Data System (ADS)

    Atherton, Tim; Burke, Chris

    2015-03-01

    Pickering emulsions consist of droplets of one fluid dispersed in a host fluid and stabilized by colloidal particles absorbed at the fluid-fluid interface. Everyday materials such as crude oil and food products like salad dressing are examples of these materials. Particles can stabilize non spherical droplet shapes in these emulsions through the following sequence: first, an isolated droplet is deformed, e.g. by an electric field, increasing the surface area above the equilibrium value; additional particles are then adsorbed to the interface reducing the surface tension. The droplet is then allowed to relax toward a sphere. If more particles were adsorbed than can be accommodated by the surface area of the spherical ground state, relaxation of the droplet is arrested at some non-spherical shape. Because the energetic cost of removing adsorbed colloids exceeds the interfacial driving force, these configurations can remain stable over long timescales. In this presentation, we present a computational study of the ordering present in anisotropic droplets produced through the mechanism of arrested relaxation and discuss the interplay between the geometry of the droplet, the dynamical process that produced it, and the structure of the defects observed.

  2. A study of dipolar interactions and dynamic processes of water molecules in tendon by 1H and 2H homonuclear and heteronuclear multiple-quantum-filtered NMR spectroscopy.

    PubMed

    Eliav, U; Navon, G

    1999-04-01

    The effect of proton exchange on the measurement of 1H-1H, 1H-2H, and 2H-2H residual dipolar interactions in water molecules in bovine Achilles tendons was investigated using double-quantum-filtered (DQF) NMR and new pulse sequences based on heteronuclear and homonuclear multiple-quantum filtering (MQF). Derivation of theoretical expressions for these techniques allowed evaluation of the 1H-1H and 1H-2H residual dipolar interactions and the proton exchange rate at a temperature of 24 degrees C and above, where no dipolar splitting is evident. The values obtained for these parameters at 24 degrees C were 300 and 50 Hz and 3000 s-1, respectively. The results for the residual dipolar interactions were verified by repeating the above measurements at a temperature of 1.5 degrees C, where the spectra of the H2O molecules were well resolved, so that the 1H-1H dipolar interaction could be determined directly from the observed splitting. Analysis of the MQF experiments at 1.5 degrees C, where the proton exchange was in the intermediate regime for the 1H-2H dipolar interaction, confirmed the result obtained at 24 degrees C for this interaction. A strong dependence of the intensities of the MQF signals on the proton exchange rate, in the intermediate and the fast exchange regimes, was observed and theoretically interpreted. This leads to the conclusion that the MQF techniques are mostly useful for tissues where the residual dipolar interaction is not significantly smaller than the proton exchange rate. Dependence of the relaxation times and signal intensities of the MQF experiments on the orientation of the tendon with respect to the magnetic field was observed and analyzed. One of the results of the theoretical analysis is that, in the fast exchange regime, the signal decay rates in the MQF experiments as well as in the spin echo or CPMG pulse sequences (T2) depend on the orientation as the square of the second-rank Legendre polynomial.

  3. Effects of Various Forms of Relaxation Training on Physiological and Self-Report Measures of Relaxation

    ERIC Educational Resources Information Center

    Reinking, Richard H.; Kohl, Marilyn L.

    1975-01-01

    Examines relative effectiveness of four types of relaxation training including Jacobson-Wolpe and electromyograph (EMG) feedback. Dependent measures are EMG recordings and self-report measures of relaxation. All groups reported increased relaxation, but EMG groups were superior in EMG measures of speed of learning and depth of relaxation.…

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

    ERIC Educational Resources Information Center

    Hites, Lacey S.; Lundervold, Duane A.

    2013-01-01

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

  5. Effects of Progressive Relaxation versus Biofeedback-Assisted Relaxation with College Students.

    ERIC Educational Resources Information Center

    See, John D.; Czerlinsky, Thomas

    1990-01-01

    Examined use of biofeedback, relaxation training, or both in a college relaxation class with an enrollment of 33 students. Results indicated students receiving relaxation training plus biofeedback improved significantly more on psychological variables than did students receiving only relaxation training. (Author/ABL)

  6. Proton-detected 3D (15)N/(1)H/(1)H isotropic/anisotropic/isotropic chemical shift correlation solid-state NMR at 70kHz MAS.

    PubMed

    Pandey, Manoj Kumar; Yarava, Jayasubba Reddy; Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2016-01-01

    Chemical shift anisotropy (CSA) tensors offer a wealth of information for structural and dynamics studies of a variety of chemical and biological systems. In particular, CSA of amide protons can provide piercing insights into hydrogen-bonding interactions that vary with the backbone conformation of a protein and dynamics. However, the narrow span of amide proton resonances makes it very difficult to measure (1)H CSAs of proteins even by using the recently proposed 2D (1)H/(1)H anisotropic/isotropic chemical shift (CSA/CS) correlation technique. Such difficulties due to overlapping proton resonances can in general be overcome by utilizing the broad span of isotropic chemical shifts of low-gamma nuclei like (15)N. In this context, we demonstrate a proton-detected 3D (15)N/(1)H/(1)H CS/CSA/CS correlation experiment at fast MAS frequency (70kHz) to measure (1)H CSA values of unresolved amide protons of N-acetyl-(15)N-l-valyl-(15)N-l-leucine (NAVL).

  7. Dynamics of Glass Relaxation at Room Temperature

    NASA Astrophysics Data System (ADS)

    Welch, Roger C.; Smith, John R.; Potuzak, Marcel; Guo, Xiaoju; Bowden, Bradley F.; Kiczenski, T. J.; Allan, Douglas C.; King, Ellyn A.; Ellison, Adam J.; Mauro, John C.

    2013-06-01

    The problem of glass relaxation under ambient conditions has intrigued scientists and the general public for centuries, most notably in the legend of flowing cathedral glass windows. Here we report quantitative measurement of glass relaxation at room temperature. We find that Corning® Gorilla® Glass shows measurable and reproducible relaxation at room temperature. Remarkably, this relaxation follows a stretched exponential decay rather than simple exponential relaxation, and the value of the stretching exponent (β=3/7) follows a theoretical prediction made by Phillips for homogeneous glasses.

  8. Time of relaxation in dusty plasma model

    NASA Astrophysics Data System (ADS)

    Timofeev, A. V.

    2015-11-01

    Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.

  9. [Study on derivatives of 5-amino-4-acylamino-1H-pyrazole as inhibitors of furin].

    PubMed

    Kibirev, V K; Osadchuk, T V; Vadziuk, O B; Shablykin, O V; Kozachenko, A P; Chumachenko, S A; Popil'nichenko, S V; Brovarets, V S

    2011-01-01

    A series of 5-amino-1H-pyrazoles was synthesized and studied as inhibitors of furin. The most potent compound, 5-amino-4-acetylamino-3-(4-methylphenylamino)1H-pyrazole, was found to retard the activity of furin by mixed-type inhibition with K = 288 microM. These findings permit to plan new ways for chemical modifications of the 5-amino-1H-pyrazole structure and design more potent furin inhibitors of non-peptide nature.

  10. H-1 Relaxation Times of Metabolites in Biological Samples Obtained with Nondestructive Ex-vivo Slow-MAS NMR

    SciTech Connect

    Hu, Jian Zhi; Wind, Robert A.; Rommereim, Donald N.

    2006-03-01

    Methods suitable for measuring 1H relaxation times such as T1, T2 and T1p, in small sized biological objects including live cells, excised organs and tissues, oil seeds etc., were developed in this work. This was achieved by combining inversion-recovery, spin-echo, or spin lock segment with the phase-adjusted spinning sideband (PASS) technique that was applied at slow sample spinning rate. Here, 2D-PASS was used to produce a high-resolution 1H spectrum free from the magnetic susceptibility broadening so that the relaxation parameters of individual metabolite can be determined. Because of the slow spinning employed, tissue and cell damage due to sample spinning is minimized. The methodologies were demonstrated by measuring 1H T1, T2 and T1p of metabolites in excised rat livers and sesame seeds at spinning rates of as low as 40 Hz.

  11. 4(1H)-Pyridone and 4(1H)-Quinolone Derivatives as Antimalarials with Erythrocytic, Exoerythrocytic, and Transmission Blocking Activities

    PubMed Central

    Monastyrskyi, Andrii; Kyle, Dennis E.; Manetsch, Roman

    2015-01-01

    Infectious diseases are the second leading cause of deaths in the world with malaria being responsible for approximately the same amount of deaths as cancer in 2012. Despite the success in malaria prevention and control measures decreasing the disease mortality rate by 45% since 2000, the development of single-dose therapeutics with radical cure potential is required to completely eradicate this deadly condition. Targeting multiple stages of the malaria parasite is becoming a primary requirement for new candidates in antimalarial drug discovery and development. Recently, 4(1H)-pyridone, 4(1H)-quinolone, 1,2,3,4-tetrahydroacridone, and phenoxyethoxy-4(1H)-quinolone chemotypes have been shown to be antimalarials with blood stage activity, liver stage activity, and transmission blocking activity. Advancements in structure-activity relationship and structure-property relationship studies, biological evaluation in vitro and in vivo, as well as pharmacokinetics of the 4(1H)-pyridone and 4(1H)-quinolone chemotypes will be discussed. PMID:25116582

  12. Quantitative Quantum Mechanical Spectral Analysis (qQMSA) of (1)H NMR spectra of complex mixtures and biofluids.

    PubMed

    Tiainen, Mika; Soininen, Pasi; Laatikainen, Reino

    2014-05-01

    The quantitative interpretation of (1)H NMR spectra of mixtures like the biofluids is a demanding task due to spectral complexity and overlap. Complications may arise also from water suppression, T2-editing, protein interactions, relaxation differences of the species, experimental artifacts and, furthermore, the spectra may contain unknown components and macromolecular background which cannot be easily separated from baseline. In this work, tools and strategies for quantitative Quantum Mechanical Spectral Analysis (qQMSA) of (1)H NMR spectra from complex mixtures were developed and systematically assessed. In the present approach, the signals of well-defined, stoichiometric components are described by a QM model, while the background is described by a multiterm baseline function and the unknown signals using optimizable and adjustable lines, regular multiplets or any spectral structures which can be composed from spectral lines. Any prior knowledge available from the spectrum can also be added to the model. Fitting strategies for weak and strongly overlapping spectral systems were developed and assessed using two basic model systems, the metabolite mixtures without and with macromolecular (serum) background. The analyses show that if the spectra are measured in high-throughput manner, the consistent absolute quantification demands some calibration to compensate the different response factors of the protons and compounds. On the other hand, the results show that also the T2-edited spectra can be measured so that they obey well the QM rules. In general, qQMSA exploits and interprets the spectral information in maximal way taking full advantage from the QM properties of the spectra and, at the same time, offers chemical confidence which means that individual components can be identified with high confidence on the basis of their accurate spectral parameters.

  13. Relaxation damping in oscillating contacts

    PubMed Central

    Popov, M.; Popov, V.L.; Pohrt, R.

    2015-01-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed. PMID:26549011

  14. Vicinal 1H-1H NMR coupling constants from density functional theory as reliable tools for stereochemical analysis of highly flexible multichiral center molecules.

    PubMed

    López-Vallejo, Fabian; Fragoso-Serrano, Mabel; Suárez-Ortiz, Gloria Alejandra; Hernández-Rojas, Adriana C; Cerda-García-Rojas, Carlos M; Pereda-Miranda, Rogelio

    2011-08-05

    A protocol for stereochemical analysis, based on the systematic comparison between theoretical and experimental vicinal (1)H-(1)H NMR coupling constants, was developed and applied to a series of flexible compounds (1-8) derived from the 6-heptenyl-5,6-dihydro-2H-pyran-2-one framework. The method included a broad conformational search, followed by geometry optimization at the DFT B3LYP/DGDZVP level, calculation of the vibrational frequencies, thermochemical parameters, magnetic shielding tensors, and the total NMR spin-spin coupling constants. Three scaling factors, depending on the carbon atom hybridizations, were found for the (1)H-C-C-(1)H vicinal coupling constants: f((sp3)-(sp3)) = 0.910, f((sp3)-(sp2)) = 0.929, and f((sp2)-(sp2))= 0.977. A remarkable correlation between the theoretical (J(pre)) and experimental (1)H-(1)H NMR (J(exp)) coupling constants for spicigerolide (1), a cytotoxic natural product, and some of its synthetic stereoisomers (2-4) demonstrated the predictive value of this approach for the stereochemical assignment of highly flexible compounds containing multiple chiral centers. The stereochemistry of two natural 6-heptenyl-5,6-dihydro-2H-pyran-2-ones (14 and 15) containing diverse functional groups in the heptenyl side chain was also analyzed by application of this combined theoretical and experimental approach, confirming its reliability. Additionally, a geometrical analysis for the conformations of 1-8 revealed that weak hydrogen bonds substantially guide the conformational behavior of the tetraacyloxy-6-heptenyl-2H-pyran-2-ones.

  15. A classical approach in simple nuclear fusion reaction {sub 1}H{sup 2}+{sub 1}H{sup 3} using two-dimension granular molecular dynamics model

    SciTech Connect

    Viridi, S.; Kurniadi, R.; Waris, A.; Perkasa, Y. S.

    2012-06-06

    Molecular dynamics in 2-D accompanied by granular model provides an opportunity to investigate binding between nuclei particles and its properties that arises during collision in a fusion reaction. A fully classical approach is used to observe the influence of initial angle of nucleus orientation to the product yielded by the reaction. As an example, a simplest fusion reaction between {sub 1}H{sup 2} and {sub 1}H{sup 3} is observed. Several products of the fusion reaction have been obtained, even the unreported ones, including temporary {sub 2}He{sup 4} nucleus.

  16. Temperature imaging by 1H NMR and suppression of convection in NMR probes

    PubMed

    Hedin; Furo

    1998-03-01

    A simple arrangement for suppressing convection in NMR probes is tested experimentally. Diffusion experiments are used to determine the onset of convection and 1H temperature imaging helps to rationalize the somewhat surprising results. A convenient new 1H NMR thermometer, CH2Br2 dissolved in a nematic thermotropic liquid crystal, is presented. Copyright 1998 Academic Press.

  17. Complete Genome Sequence of a Bovine Viral Diarrhea Virus Subgenotype 1h Strain Isolated in Italy.

    PubMed

    Bazzucchi, Moira; Bertolotti, Luigi; Giammarioli, Monica; Casciari, Cristina; Rossi, Elisabetta; Rosati, Sergio; De Mia, Gian Mario

    2017-02-23

    We sequenced the complete genome of bovine viral diarrhea virus (BVDV) strain UM/126/07. It belongs to subgenotype 1h. The complete genome is composed of 12,196 nucleotides organized as one open reading frame encoding 3,898 amino acids. This is the first report of a full-length sequence of BVDV-1h.

  18. A critical evaluation of heteronuclear TOCSY (HEHAHA) experiments for 1H,6Li spin pairs.

    PubMed

    Bergander, Klaus; Hüls, Dietmar; Glaser, Steffen J; Günther, Harald; Luy, Burkhard

    2014-12-01

    Heteronuclear TOCSY (HEHAHA) experiments for (1) H,(6) Li spin pairs in organolithium compounds with adjacent strongly coupled (1) H,(1) H spin systems showed unexpected cross peak behaviour: for n-butyllithium (1) H,(6) Li cross peaks were completely missing, whereas for the dimer of (Z)-2-lithio-1-(o-lithiophenyl)ethane, a cross peak for remote protons was observed even at very short mixing times. It was assumed that strong magnetization transfer within the proton spin systems was responsible for these results, which prevented unambiguous chemical shift assignments. Selective experiments with the (6) Li,(1) H-HET-PLUSH-TACSY sequence then showed the expected (6) Li,(1) H cross peaks for the transfer via the directly coupled (1) H and (6) Li nuclei. For n-butyllithium transfer to H(Cα) via an unresolved heteronuclear coupling constant below 0.1 Hz is unambiguously observed. Cross peaks in the 2D (6) Li,(1) H-HET-PLUSH-TACSY spectra for the dimer of (Z)-2-lithio-1-(o-lithiophenyl)ethane are readily explained by the measured coupling network and the corresponding active mixing conditions.

  19. Reliability of ^1^H NMR analysis for assessment of lipid oxidation at frying temperatures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The reliability of a method using ^1^H NMR analysis for assessment of oil oxidation at a frying temperature was examined. During heating and frying at 180 °C, changes of soybean oil signals in the ^1^H NMR spectrum including olefinic (5.16-5.30 ppm), bisallylic (2.70-2.88 ppm), and allylic (1.94-2.1...

  20. An oxazolo[3,2-b]indazole route to 1H-indazolones.

    PubMed

    Oakdale, James S; Solano, Danielle M; Fettinger, James C; Haddadin, Makhluf J; Kurth, Mark J

    2009-07-02

    The novel heterocycle 2,3-dihydrooxazolo[3,2-b]indazole has been synthesized and utilized to provide easy access to 1H-indazolones, particularly the previously unreported 2-(2-alkoxyethyl)-1H-indazol-3(2H)-ones. Mechanistic as well as optimization and reaction scope studies are reported.

  1. Complete Genome Sequence of a Bovine Viral Diarrhea Virus Subgenotype 1h Strain Isolated in Italy

    PubMed Central

    Bazzucchi, Moira; Bertolotti, Luigi; Casciari, Cristina; Rossi, Elisabetta; Rosati, Sergio; De Mia, Gian Mario

    2017-01-01

    ABSTRACT We sequenced the complete genome of bovine viral diarrhea virus (BVDV) strain UM/126/07. It belongs to subgenotype 1h. The complete genome is composed of 12,196 nucleotides organized as one open reading frame encoding 3,898 amino acids. This is the first report of a full-length sequence of BVDV-1h. PMID:28232427

  2. Relaxation of liquid bridge after droplets coalescence

    NASA Astrophysics Data System (ADS)

    Zheng, Jiangen; Shi, Haiyang; Chen, Guo; Huang, Yingzhou; Wei, Hua; Wang, Shuxia; Wen, Weijia

    2016-11-01

    We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.

  3. Conservation of magnetic helicity during plasma relaxation

    SciTech Connect

    Ji, H.; Prager, S.C.; Sarff, J.S.

    1994-07-01

    Decay of the total magnetic helicity during the sawtooth relaxation in the MST Reversed-Field Pinch is much larger than the MHD prediction. However, the helicity decay (3--4%) is smaller than the magnetic energy decay (7--9%), modestly supportive of the helicity conservation hypothesis in Taylor`s relaxation theory. Enhanced fluctuation-induced helicity transport during the relaxation is observed.

  4. Dielectric relaxation in a protein matrix

    SciTech Connect

    Pierce, D.W.; Boxer, S.G.

    1992-06-25

    The dielectric relaxation of a sperm whale ApoMb-DANCA complex is measured by the fluorescence dynamic Stokes shift method. Emission energy increases with decreasing temperature, suggesting that the relaxation activation energies of the rate-limiting motions either depend on the conformational substrate or different types of protein motions with different frequencies participate in the reaction. Experimental data suggest that there may be relaxations on a scale of <100 ps. 61 refs., 7 figs., 2 tabs.

  5. Paley-Wiener criterion for relaxation functions

    NASA Astrophysics Data System (ADS)

    Ngai, K. L.; Rajagopal, A. K.; Rendell, R. W.; Teitler, S.

    1983-11-01

    It is shown how the Paley-Wiener theorem in Fourier-transform theory can provide the bound for physically acceptable relaxation functions for long times. In principle the linear exponential decay function, and hence also a superposition of linear exponential decay functions, does not provide an acceptable description of relaxation phenomenon although the Paley-Wiener bound can be made to approach arbitrarily close to linear exponential. A class of relaxation functions proposed recently obeys the Paley-Wiener bound. The general necessity for time-dependent relaxation rates is emphasized and discussed.

  6. Elucidating connectivity and metal-binding structures of unlabeled paramagnetic complexes by 13C and 1H solid-state NMR under fast magic angle spinning.

    PubMed

    Wickramasinghe, Nalinda P; Shaibat, Medhat A; Ishii, Yoshitaka

    2007-08-23

    Characterizing paramagnetic complexes in solids is an essential step toward understanding their molecular functions. However, methodologies to characterize chemical and electronic structures of paramagnetic systems at the molecular level have been notably limited, particularly for noncrystalline solids. We present an approach to obtain connectivities of chemical groups and metal-binding structures for unlabeled paramagnetic complexes by 13C and 1H high-resolution solid-state NMR (SSNMR) using very fast magic angle spinning (VFMAS, spinning speed >or=20 kHz). It is experimentally shown for unlabeled Cu(II)(Ala-Thr) that 2D 13C/1H correlation SSNMR under VFMAS provides the connectivity of chemical groups and assignments for the characterization of unlabeled paramagnetic systems in solids. We demonstrate that on the basis of the assignments provided by the VFMAS approach multiple 13C-metal distances can be simultaneously elucidated by a combination of measurements of 13C anisotropic hyperfine shifts and 13C T1 relaxation due to hyperfine interactions for this peptide-Cu(II) complex. It is also shown that an analysis of 1H anisotropic hyperfine shifts allows for the determination of electron-spin states in Fe(III)-chloroprotoporphyin-IX in solid states.

  7. 1H NMR, 13C NMR and mass spectral studies of some Schiff bases derived from 3-amino-1,2,4-triazole.

    PubMed

    Issa, Y M; Hassib, H B; Abdelaal, H E

    2009-11-01

    Heterocyclic Schiff bases derived from 3-amino-1,2,4-triazole and different substituted aromatic aldehydes are prepared and subjected to (1)H NMR, (13)C NMR and mass spectral analyses. (1)H NMR spectra in DMSO exhibit a sharp singlet within the 9.35-8.90ppm region which corresponds to the azomethine proton. The position of this signal is largely dependent on the nature of the substituents on the benzal moiety. It is observed that the shape, position and the integration value of the signal of the aromatic proton of the triazole ring ((5)C) are clearly affected by the rate of exchange, relaxation time, concentration of solution as well as the solvent used. (13)C NMR is taken as substantial support for the results reached from (1)H NMR studies. The mass spectral results are taken as a tool to confirm the structure of the investigated compounds. The base peak (100%), mostly the M-1 peak, indicates the facile loss of hydrogen radical. The fragmentation pattern of the unsubstituted Schiff base is taken as the general scheme. Differences in the other schemes result from the effect of the electronegativity of the substituents attached to the aromatic ring.

  8. Myocardial contraction-relaxation coupling

    PubMed Central

    2010-01-01

    Since the pioneering work of Henry Pickering Bowditch in the late 1800s to early 1900s, cardiac muscle contraction has remained an intensely studied topic for several reasons. The heart is located centrally in our body, and its pumping motion demands the attention of the observer. The contraction of the heart encompasses a complex interplay of mechanical, chemical, and electrical properties, and its function can thus be studied from any of these viewpoints. In addition, diseases of the heart are currently killing more people in the Westernized world than any other disease. When combined with the increasing emphasis of research to be clinically relevant, this contributes to the heart remaining a topic of continued basic and clinical investigation. Yet, there are significant aspects of cardiac muscle contraction that are still not well understood. A big complication of the study of cardiac muscle contraction is that there exists no equilibrium among many of the important governing parameters, which include pre- and afterload, intracellular ion concentrations, membrane potential, and velocity and direction of movement. Thus the classic approach of perturbing an equilibrium or a steady state to learn about the role of the perturbing factor in the system cannot be unambiguously interpreted, since each of the parameters that govern contraction are constantly changing, as well as constantly changing their interaction with each other. In this review, presented as the 54th Bowditch Lecture at Experimental Biology meeting in Anaheim in April 2010, I will revisit several governing factors of cardiac muscle relaxation by applying newly developed tools and protocols to isolated cardiac muscle tissue in which the dynamic interactions between the governing factors of contraction and relaxation can be studied. PMID:20852049

  9. Increasing 14N NQR signal by 1H-14N level crossing with small magnetic fields.

    PubMed

    Thurber, Kent R; Sauer, Karen L; Buess, Michael L; Klug, Christopher A; Miller, Joel B

    2005-11-01

    NQR detection of materials, such as TNT, is hindered by the low signal-to-noise ratio at low NQR frequencies. Sweeping small (0-26 mT) magnetic fields to shift the (1)H NMR frequency relative to the (14)N NQR frequencies can provide a significant increase of the (14)N NQR signal-to-noise ratio. Three effects of (1)H-(14)N level crossing are demonstrated in diglycine hydrochloride and TNT. These effects are (1) transferring (1)H polarization to one or more of the (14)N transitions, including the use of an adiabatic flip of the (1)H polarization during the field sweep, (2) shortening the effective (14)N T(1) by the interaction of (1)H with the (14)N transitions, (3) "level transfer" effect where the third (14)N (spin 1) energy level or other (14)N sites with different NQR frequency are used as a reservoir of polarization which is transferred to the measured (14)N transition by the (1)H. The (14)N NQR signal-to-noise ratio can be increased by a factor of 2.5 for one (14)N site in diglycine hydrochloride (and 2.2 in TNT), even though the maximum (1)H frequency used in this work, 111 6 kHz, is only 30% larger than the measured (14)N frequencies (834 kHz for diglycine hydrochloride and 843 kHz for TNT).

  10. Evaluation of short-TE (1)H MRSI for quantification of metabolites in the prostate.

    PubMed

    Basharat, Meer; Jafar, Maysam; deSouza, Nandita M; Payne, Geoffrey S

    2014-04-01

    Back-to-back (1)H MRSI scans, using an endorectal and phased-array coil combination, were performed on 18 low-risk patients with prostate cancer at 3 T, employing TEs of 32 and 100 ms in order to compare metabolite visualization at each TE. Outer-volume suppression of lipid signals was performed using regional saturation (REST) slabs and the quantification of spectra at both TEs was achieved with the quantitation using quantum estimation (QUEST) routine. Metabolite nulling experiments in an additional five patients found that there were negligible macromolecule background signals in prostate spectra at TE = 32 ms. Metabolite visibility was judged using the criterion Cramér-Rao lower bound (CRLB)/amplitude < 20%, and metabolite concentrations were corrected for relaxation effects and referenced to the data acquired in corresponding water-unsuppressed MRSI scans. For the first time, the prostate metabolites spermine and myo-inositol were quantified individually in vivo, together with citrate, choline and creatine. All five metabolite visibilities were higher in TE = 32 ms MRSI than in TE = 100 ms MRSI. At TE = 32 ms, citrate was visible in 99.0% of lipid-free spectra, whereas, at TE = 100 ms, no metabolite simulation of citrate matched the in vivo peaks. Spermine, choline and creatine were visualised separately in 30.4% more spectra at TE = 32 ms than at TE = 100 ms, and myo-inositol in 72.5% more spectra. T2 values were calculated for spermine (53 ± 16 ms), choline (62 ± 17 ms) and myo-inositol (90 ± 48 ms). Data from the TE = 32 ms spectra showed that the concentrations of citrate and spermine secretions were positively correlated in both the peripheral zone and central gland (R(2)  = 0.73 and R(2)  = 0.43, respectively), and that the citrate content was significantly higher in the former at 64 ± 22 mm than in the latter at 32 ± 16 mm (p = 0.01). However, lipid

  11. 1H NMR investigation of thermally triggered insulin release from poly(N-isopropylacrylamide) microgels.

    PubMed

    Nolan, Christine M; Gelbaum, Leslie T; Lyon, L Andrew

    2006-10-01

    We describe investigations of insulin release from thermoresponsive microgels using variable temperature (1)H NMR. Microgel particles composed of poly(N-isopropylacrylamide) were loaded with the peptide via a swelling technique, and this method was compared to simple equilibrium partitioning. Variable temperature (1)H NMR studies suggest that the swelling loading method results in enhanced entrapment of the peptide versus equilibrium partitioning. A centrifugation-loading assay supports this finding. Pseudo-temperature jump (1)H NMR measurements suggest that the insulin release rate is partially decoupled from microgel collapse. These types of direct release investigations could prove to be useful methods in the future design of controlled macromolecule drug delivery devices.

  12. Intermolecular Interactions between Eosin Y and Caffeine Using 1H-NMR Spectroscopy

    PubMed Central

    Okuom, Macduff O.; Wilson, Mark V.; Jackson, Abby; Holmes, Andrea E.

    2014-01-01

    DETECHIP has been used in testing analytes including caffeine, cocaine, and tetrahydrocannabinol (THC) from marijuana, as well as date rape and club drugs such as flunitrazepam, gamma-hydroxybutyric acid (GHB), and methamphetamine. This study investigates the intermolecular interaction between DETECHIP sensor eosin Y (DC1) and the analyte (caffeine) that is responsible for the fluorescence and color changes observed in the actual array. Using 1H-NMR, 1H-COSY, and 1H-DOSY NMR methods, a proton exchange from C-8 of caffeine to eosin Y is proposed. PMID:25018772

  13. Conformational evaluation and detailed 1H and 13C NMR assignments of eremophilanolides.

    PubMed

    Burgueño-Tapia, Eleuterio; Hernández, Luis R; Reséndiz-Villalobos, Adriana Y; Joseph-Nathan, Pedro

    2004-10-01

    Extensive application of 1D and 2D NMR methodology, combined with molecular modeling, allowed the complete 1H and 13C NMR assignments of eremophilanolides from Senecio toluccanus. Comparison of the experimental 1H, 1H coupling constant values with those generated employing a generalized Karplus-type relationship, using dihedral angles extracted from MMX and DFT calculations, revealed that the epoxidized eremophilanolides 1 and 2 show conformational rigidity at room temperature, whereas molecules 3-6, containing an isolated double bond, are conformationally mobile.

  14. H2 Receptor-Mediated Relaxation of Circular Smooth Muscle in Human Gastric Corpus: the Role of Nitric Oxide (NO).

    PubMed

    Lee, Sang Eok; Kim, Dae Hoon; Kim, Young Chul; Han, Joung-Ho; Choi, Woong; Kim, Chan Hyung; Jeong, Hye Won; Park, Seon-Mee; Yun, Sei Jin; Choi, Song-Yi; Sung, Rohyun; Kim, Young Ho; Yoo, Ra Young; Sun, Park Hee; Kim, Heon; Song, Young-Jin; Xu, Wen-Xie; Yun, Hyo-Yung; Lee, Sang Jin

    2014-10-01

    This study was designed to examine the effects of histamine on gastric motility and its specific receptor in the circular smooth muscle of the human gastric corpus. Histamine mainly produced tonic relaxation in a concentration-dependent and reversible manner, although histamine enhanced contractility in a minor portion of tissues tested. Histamine-induced tonic relaxation was nerve-insensitive because pretreatment with nerve blockers cocktail (NBC) did not inhibit relaxation. Additionally, K(+) channel blockers, such as tetraethylammonium (TEA), apamin (APA), and glibenclamide (Glib), had no effect. However, N(G)-nitro-L-arginine methyl ester (L-NAME) and 1H-(1,2,4)oxadiazolo (4,3-A) quinoxalin-1-one (ODQ), an inhibitor of soluble guanylate cyclase (sGC), did inhibit histamine-induced tonic relaxation. In particular, histamine-induced tonic relaxation was converted to tonic contraction by pretreatment with L-NAME. Ranitidine, the H2 receptor blocker, inhibited histamine-induced tonic relaxation. These findings suggest that histamine produced relaxation in circular smooth muscle of human gastric smooth muscle through H2 receptor and NO/sGC pathways.

  15. Mechanical spectroscopy of Snoek type relaxation

    NASA Astrophysics Data System (ADS)

    Golovin, S. A.; Golovin, I. S.

    2012-09-01

    A review is presented for work in the area of elasticity for metals and alloys with a body-centered cubic lattice caused by diffusion under stress of interstitial atoms, i.e., Snoek relaxation in metals and Snoek type relaxation in alloys. Practical possibilities in analyzing materials of this class by mechanical spectroscopy are demonstrated.

  16. Analysis of sawtooth relaxation oscillations in tokamaks

    SciTech Connect

    Yamazaki, K.; McGuire, K.; Okabayashi, M.

    1982-07-01

    Sawtooth relaxation oscillations are analyzed using the Kadomtsev's disruption model and a thermal relaxation model. The sawtooth period is found to be very sensitive to the thermal conduction loss. Qualitative agreement between these calculations and the sawtooth period observed in several tokamaks is demonstrated.

  17. Dielectric relaxations in partly deuterated ammonium dichromate

    NASA Astrophysics Data System (ADS)

    Gilchrist, John le G.

    1987-12-01

    Two dielectric relaxations in partly deuterated ammonium dichromate are attributed to reorientations of mixed-isotope ammonium ions. Loss peaks were observed between 20 and 40 K and obey the Arrhenius law with activation energy 1.5 kcal/mol for the stronger relaxation. The dipole moment is of the order of 0.015 D.

  18. On relaxations and aging of various glasses

    PubMed Central

    Amir, Ariel; Oreg, Yuval; Imry, Yoseph

    2012-01-01

    Slow relaxation occurs in many physical and biological systems. “Creep” is an example from everyday life. When stretching a rubber band, for example, the recovery to its equilibrium length is not, as one might think, exponential: The relaxation is slow, in many cases logarithmic, and can still be observed after many hours. The form of the relaxation also depends on the duration of the stretching, the “waiting time.” This ubiquitous phenomenon is called aging, and is abundant both in natural and technological applications. Here, we suggest a general mechanism for slow relaxations and aging, which predicts logarithmic relaxations, and a particular aging dependence on the waiting time. We demonstrate the generality of the approach by comparing our predictions to experimental data on a diverse range of physical phenomena, from conductance in granular metals to disordered insulators and dirty semiconductors, to the low temperature dielectric properties of glasses. PMID:22315418

  19. Enthalpy relaxation and annealing effect in polystyrene.

    PubMed

    Sakatsuji, Waki; Konishi, Takashi; Miyamoto, Yoshihisa

    2013-07-01

    The effects of thermal history on the enthalpy relaxation in polystyrene are studied by differential scanning calorimetry. The temperature dependence of the specific heat in the liquid and the glassy states, that of relaxation time, and the exponent of the Kohlrausch-Williams-Watts function are determined by measurements of the thermal response against sinusoidal temperature variation. A phenomenological model equation previously proposed to interpret the memory effect in the frozen state is applied to the enthalpy relaxation and the evolution of entropy under a given thermal history is calculated. The annealing below the glass transition temperature produces two effects on enthalpy relaxation: the decay of excess entropy with annealing time in the early stage of annealing and the increase in relaxation time due to physical aging in the later stage. The crossover of these effects is reflected in the variation of temperature of the maximum specific heat observed in the heating process after annealing and cooling.

  20. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples.

  1. Deproto-metallation using a mixed lithium-zinc base and computed CH acidity of 1-aryl 1H-benzotriazoles and 1-aryl 1H-indazoles.

    PubMed

    Nagaradja, Elisabeth; Chevallier, Floris; Roisnel, Thierry; Dorcet, Vincent; Halauko, Yury S; Ivashkevich, Oleg A; Matulis, Vadim E; Mongin, Florence

    2014-03-07

    1-Aryl-1H-benzotriazoles and -1H-indazoles were synthesized, and their deproto-metallation using the base prepared by mixing LiTMP with ZnCl2·TMEDA (1/3 equiv.) was studied. In the indazole series, reactions occurring at the 3 position were followed by ring opening, and functionalization of the substrate was only found possible (on the sulfur ring) using 2-thienyl as aryl group. In the benzotriazole series, either mono- or bis-deprotonation (depending on the amount of base employed) was achieved with phenyl, 4-methoxyphenyl and 2-thienyl as aryl group, and bis-deprotonation in the case of 4-chlorophenyl and 4-trifluoromethylphenyl. The experimental results were analyzed with the help of the CH acidities of the substrates, determined in THF solution using the DFT B3LYP method.

  2. 1H NMR quantitative determination of photosynthetic pigments from green beans (Phaseolus vulgaris L.).

    PubMed

    Valverde, Juan; This, Hervé

    2008-01-23

    Using 1H nuclear magnetic resonance spectroscopy (1D and 2D), the two types of photosynthetic pigments (chlorophylls, their derivatives, and carotenoids) of "green beans" (immature pods of Phaseolus vulgaris L.) were analyzed. Compared to other analytical methods (light spectroscopy or chromatography), 1H NMR spectroscopy is a fast analytical way that provides more information on chlorophyll derivatives (allomers and epimers) than ultraviolet-visible spectroscopy. Moreover, it gives a large amount of data without prior chromatographic separation.

  3. Practical Methylation Procedure for (1H)-1,2,4-Triazole (Postprint)

    DTIC Science & Technology

    2007-09-01

    Francis Group, LLC. 14. ABSTRACT Conversion of (1H)-1,2,4-triazole to its sodium salt with methanolic sodium methoxide is followed by reaction ...From - To) 04-06-2007 Journal Article 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Practical Methylation Procedure for (1H)-1,2,4-Triazole (Postprint...continuous extraction (chloroform/water) with a final short-path distillation under a controlled vacuum to obtain spectroscopically pure 1- methyl -1,2,4

  4. The quantitation of nuclear Overhauser effect methods for total conformational analysis of peptides in solution. Application to gramicidin S.

    PubMed Central

    Jones, C R; Sikakana, C T; Hehir, S; Kuo, M C; Gibbons, W A

    1978-01-01

    The [1H:1H] nuclear Overhauser effects (NOE's) and spin-lattice relaxation times (T1's) are reported for the backbone protons of the decapeptide gramicidin S. Several methods for calculating interproton distances from these measurements are presented. Ratios of interproton distances were obtained from [1H:1H] NOE's and from the combination of [1H:1H]NOE'S and T1 values. Actual proton-proton distances were calculated from these ratios either by using the known distance between two geminal protons or distances derived from scalar coupling constants. The interproton distances calculated for gramicidin S are consistent with a II' beta-turn/antiparallel beta-sheet conformation. PMID:83886

  5. 1H and 31P nuclear magnetic resonance and kinetic studies of the active site structure of chloroplast CF1 ATP synthase.

    PubMed

    Devlin, C C; Grisham, C M

    1990-07-03

    The interaction of nucleotides and nucleotide analogues and their metal complexes with Mn2+ bound to both the latent and dithiothreitol-activated CF1 ATP synthase has been examined by means of steady-state kinetics, water proton relaxation rate (PRR) measurements, and 1H and 31P nuclear relaxation measurements. Titration of both the latent and activated Mn(2+)-CF1 complexes with ATP, ADP, Pi, Co(NH3)4ATP, Co(NH3)4ADP, and Co(NH3)4AMPPCP leads to increases in the water relaxation enhancement, consistent with enhanced metal binding and a high ternary complex enhancement. Steady-state kinetic studies are consistent with competitive inhibition of CF1 by Co(NH3)4AMPPCP with respect to CaATP. The data are consistent with a Ki for Co(NH3)4AMPPCP of 650 microM, in good agreement with a previous Ki of 724 microM for Cr(H2O)4ATP [Frasch, W., & Selman, B. (1982) Biochemistry 21, 3636-3643], and a best fit KD of 209 microM from the water PRR measurements. 1H and 31P nuclear relaxation measurements in solutions of CF1 and Co(NH3)4AMPPCP were used to determine the conformation of the bound substrate analogue and the arrangement with respect to this structure of high- and low-affinity sites for Mn2+. The bound nucleotide analogue adopts a bent conformation, with the low-affinity Mn2+ site situated between the adenine and triphosphate moieties and the high-affinity metal site located on the far side of the triphosphate chain. The low-affinity metal forms a distorted inner-sphere complex with the beta-P and gamma-P of the substrate. The distances from Mn2+ to the triphosphate chain are too large for first coordination sphere complexes but are appropriate for second-sphere complexes involving, for example, intervening hydrogen-bonded water molecules or residues from the protein.

  6. sup 1 H and sup 31 P nuclear magnetic resonance and kinetic studies of the active site structure of chloroplast CF sub 1 ATP synthase

    SciTech Connect

    Devlin, C.C.; Grisham, C.M. )

    1990-07-03

    The interaction of nucleotides and nucleotide analogues and their complexes with Mn{sup 2+} bound to both the latent and dithiothreitol-activated CF{sub 1} ATP synthase has been examined by means of steady-state kinetics, water proton relaxation rate (PRR) measurements, and {sup 1}H and {sup 31}P nuclear relaxation measurements. Titration of both the latent and activated Mn{sup 2+}-CF{sub 1} complexes with ATP, ADP, P{sub i}, Co(NH{sub 3}){sub 4}ATP, Co(NH{sub 3}){sub 4}ADP, and Co(NH{sub 3}){sub 4}AMPPCP leads to increases in the water relaxation enhancement, consistent with enhanced metal binding and a high ternary complex enhancement. Steady-state kinetic studies are consistent with competitive inhibition of CF{sub 1} by Co(NH{sub 3}){sub 4}AMPPCP with respect to CaATP. {sup 1}H and {sup 31}P nuclear relaxation measurements in solutions of CF{sub 1} and Co(NH{sub 3}){sub 4}AMPPCP were used to determine the conformation of the bound substrate analogue and the arrangement with respect to this structure of high- and low-affinity sites for Mn{sup 2+}. The bound nucleotide analogue adopts a bent conformation, with the low-affinity sites for Mn{sup 2+}. The bound nucleotide analogue adopts a bent conformation, with the low-affinity Mn{sup 2+} site situated between the adenine and triphosphate moieties and the high-affinity metal site located on the far side of the triphosphate chain. The low-affinity metal forms a distorted inner-sphere complex with the {beta}-P and {gamma}-P of the substrate. The distances from Mn{sup 2+} to the triphosphate chain are too large for first coordination sphere complexes but are appropriate for second-sphere complexes involving, for example, intervening hydrogen-bonded water molecules or residues from the protein.

  7. Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-10-28

    A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  8. Alternative determination of blood alcohol concentration by (1)H NMR spectroscopy.

    PubMed

    Zailer, Elina; Diehl, Bernd W K

    2016-02-05

    A rapid, accurate and specific proton nuclear magnetic resonance ((1)H NMR) spectroscopic method is developed to determine ethanol in blood, known as the blood alcohol concentration (BAC). The limits of detection and quantification are 0.02g/L and 0.07g/L, respectively. The (1)H NMR spectra show linearity for whole blood and serum samples of a concentration range of 0.00-3.00g/L (R(2)>0.9995). The (1)H NMR method is applied and validated for whole blood as the sample media. Real driving under influence case samples are analyzed with the reference enzyme-based alcohol dehydrogenase and headspace gas chromatography techniques by the Forensic Medicine in Bonn. The reference results are compared with the (1)H NMR spectroscopic results. The validation and comparison indicate that (1)H NMR is suitable for the quantification of BAC in whole blood. This technique has the advantages of automated analysis with good measurement precision and fast sample throughput. A drop of blood (V=20μL) is adequate for an analysis leading to a possible simplification of the sample collection. Due to the non-destructive method, follow-up examinations by (1)H NMR spectroscopy or DNA determinations by different techniques (PCR, in situ hybridization) are possible in resolving legal disputes.

  9. Postseismic relaxation and transient creep

    USGS Publications Warehouse

    Savage, J.C.; Svarc, J.L.; Yu, S.-B.

    2005-01-01

    Postseismic deformation has been observed in the epicentral area following the 1992 Landers (M = 7.3), 1999 Chi-Chi (M = 7.6), 1999 Hector Mine (M = 7.1), 2002 Denali (M = 7.9), 2003 San Simeon (M = 6.5), and 2004 Parkfield (M = 6.0) earthquakes. The observations consist of repeated GPS measurements of the position of one monument relative to another (separation ???100 km). The early observations (t < 0.1 year) are well fit by the function a' + c'log(t), where t is the time after the earthquake and a' and c' are constants chosen to fit the data. Because a log(t) time dependence is characteristic of transient (primary) creep, the early postseismic response may be governed by transient creep as Benioff proposed in 1951. That inference is provisional as the stress conditions prevailing in postseismic relaxation are not identical to the constant stress condition in creep experiments. The observed logarithmic time dependence includes no characteristic time that might aid in identifying the micromechanical cause.

  10. Supervised Discrete Hashing With Relaxation.

    PubMed

    Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu

    2016-12-29

    Data-dependent hashing has recently attracted attention due to being able to support efficient retrieval and storage of high-dimensional data, such as documents, images, and videos. In this paper, we propose a novel learning-based hashing method called ''supervised discrete hashing with relaxation'' (SDHR) based on ''supervised discrete hashing'' (SDH). SDH uses ordinary least squares regression and traditional zero-one matrix encoding of class label information as the regression target (code words), thus fixing the regression target. In SDHR, the regression target is instead optimized. The optimized regression target matrix satisfies a large margin constraint for correct classification of each example. Compared with SDH, which uses the traditional zero-one matrix, SDHR utilizes the learned regression target matrix and, therefore, more accurately measures the classification error of the regression model and is more flexible. As expected, SDHR generally outperforms SDH. Experimental results on two large-scale image data sets (CIFAR-10 and MNIST) and a large-scale and challenging face data set (FRGC) demonstrate the effectiveness and efficiency of SDHR.

  11. Nonlinear electrochemical relaxation around conductors.

    PubMed

    Chu, Kevin T; Bazant, Martin Z

    2006-07-01

    We analyze the simplest problem of electrochemical relaxation in more than one dimension-the response of an uncharged, ideally polarizable metallic sphere (or cylinder) in a symmetric, binary electrolyte to a uniform electric field. In order to go beyond the circuit approximation for thin double layers, our analysis is based on the Poisson-Nernst-Planck (PNP) equations of dilute solution theory. Unlike most previous studies, however, we focus on the nonlinear regime, where the applied voltage across the conductor is larger than the thermal voltage. In such strong electric fields, the classical model predicts that the double layer adsorbs enough ions to produce bulk concentration gradients and surface conduction. Our analysis begins with a general derivation of surface conservation laws in the thin double-layer limit, which provide effective boundary conditions on the quasineutral bulk. We solve the resulting nonlinear partial differential equations numerically for strong fields and also perform a time-dependent asymptotic analysis for weaker fields, where bulk diffusion and surface conduction arise as first-order corrections. We also derive various dimensionless parameters comparing surface to bulk transport processes, which generalize the Bikerman-Dukhin number. Our results have basic relevance for double-layer charging dynamics and nonlinear electrokinetics in the ubiquitous PNP approximation.

  12. Multifrequency Pulsed EPR and the Characterization of Molecular Dynamics

    PubMed Central

    Eaton, Sandra S.; Eaton, Gareth R.

    2017-01-01

    In fluid solution motion-dependent processes dominate electron spin lattice relaxation for nitroxides and semiquinones at frequencies between 250 MHz and 34 GHz. For triarylmethyl radicals motion-dependent processes dominate spin lattice relaxation at frequencies below about 3 GHz. The frequency dependence of relaxation provides invaluable information about dynamic processes occurring with characteristic times on the order of the electron Zeeman frequency. Relaxation mechanisms, methods of measuring spin-lattice relaxation, and motional processes for nitroxide, semiquinone, and triarylmethyl radicals are discussed. PMID:26478481

  13. Plasma Relaxation Dynamics Moderated by Current Sheets

    NASA Astrophysics Data System (ADS)

    Dewar, Robert; Bhattacharjee, Amitava; Yoshida, Zensho

    2014-10-01

    Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor-relaxed equilibrium model all these constraints are relaxed save for global magnetic flux and helicity. A Lagrangian is presented that leads to a new variational formulation of magnetized fluid dynamics, relaxed MHD (RxMHD), all static solutions of which are Taylor equilibrium states. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-relaxed MHD (MRxMHD), is developed. These concepts are illustrated using a simple two-region slab model similar to that proposed by Hahm and Kulsrud--the formation of an initial shielding current sheet after perturbation by boundary rippling is calculated using MRxMHD and the final island state, after the current sheet has relaxed through a reconnection sequence, is calculated using RxMHD. Australian Research Council Grant DP110102881.

  14. Relaxation processes in disaccharide sugar glasses

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  15. Relaxation of impact basins on icy satellites

    NASA Technical Reports Server (NTRS)

    Thomas, Paul J.; Squyres, Steven W.

    1988-01-01

    The problem of relaxation of very large impact craters on icy satellites is addressed and the extent to which such studies can help place constraints on the nature of such satellite interiors is investigated. Very general calculations aimed at understanding the nature of relaxation of large impact structures, including the directions, relaxation velocities, and stress levels, are presented. The dependence of relaxation on such factors as silicate core size and viscosity gradients in the ice is examined. The general results are used to address whether comparing the current morphology of impact basins to estimates of their original shape will yield an understanding of the thermal and mechanical structure of the interiors of the icy satellites. It is found that the relaxation rates derived from models of satellite interiors can provide constraints on viscous layer thicknesses. High thermal gradients can permit substantial relaxation even in thin viscous layers. Finally, the constraints on the internal structure of Tethys arising from the extremely relaxed state of the Odysseus basin and the existence of Ithaca Chasma are discussed.

  16. [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

  17. Le Chatelier's principle with multiple relaxation channels

    NASA Astrophysics Data System (ADS)

    Gilmore, R.; Levine, R. D.

    1986-05-01

    Le Chatelier's principle is discussed within the constrained variational approach to thermodynamics. The formulation is general enough to encompass systems not in thermal (or chemical) equilibrium. Particular attention is given to systems with multiple constraints which can be relaxed. The moderation of the initial perturbation increases as additional constraints are removed. This result is studied in particular when the (coupled) relaxation channels have widely different time scales. A series of inequalities is derived which describes the successive moderation as each successive relaxation channel opens up. These inequalities are interpreted within the metric-geometry representation of thermodynamics.

  18. Relaxation time in disordered molecular systems

    SciTech Connect

    Rocha, Rodrigo P.; Freire, José A.

    2015-05-28

    Relaxation time is the typical time it takes for a closed physical system to attain thermal equilibrium. The equilibrium is brought about by the action of a thermal reservoir inducing changes in the system micro-states. The relaxation time is intuitively expected to increase with system disorder. We derive a simple analytical expression for this dependence in the context of electronic equilibration in an amorphous molecular system model. We find that the disorder dramatically enhances the relaxation time but does not affect its independence of the nature of the initial state.

  19. Neural control of muscle relaxation in echinoderms.

    PubMed

    Elphick, M R; Melarange, R

    2001-03-01

    Smooth muscle relaxation in vertebrates is regulated by a variety of neuronal signalling molecules, including neuropeptides and nitric oxide (NO). The physiology of muscle relaxation in echinoderms is of particular interest because these animals are evolutionarily more closely related to the vertebrates than to the majority of invertebrate phyla. However, whilst in vertebrates there is a clear structural and functional distinction between visceral smooth muscle and skeletal striated muscle, this does not apply to echinoderms, in which the majority of muscles, whether associated with the body wall skeleton and its appendages or with visceral organs, are made up of non-striated fibres. The mechanisms by which the nervous system controls muscle relaxation in echinoderms were, until recently, unknown. Using the cardiac stomach of the starfish Asterias rubens as a model, it has been established that the NO-cGMP signalling pathway mediates relaxation. NO also causes relaxation of sea urchin tube feet, and NO may therefore function as a 'universal' muscle relaxant in echinoderms. The first neuropeptides to be identified in echinoderms were two related peptides isolated from Asterias rubens known as SALMFamide-1 (S1) and SALMFamide-2 (S2). Both S1 and S2 cause relaxation of the starfish cardiac stomach, but with S2 being approximately ten times more potent than S1. SALMFamide neuropeptides have also been isolated from sea cucumbers, in which they cause relaxation of both gut and body wall muscle. Therefore, like NO, SALMFamides may also function as 'universal' muscle relaxants in echinoderms. The mechanisms by which SALMFamides cause relaxation of echinoderm muscle are not known, but several candidate signal transduction pathways are discussed here. The SALMFamides do not, however, appear to act by promoting release of NO, and muscle relaxation in echinoderms is therefore probably regulated by at least two neuronal signalling systems acting in parallel. Recently, other

  20. Characterization of Free Surface-Bound and Entrapped Water Environments in Poly(N-Isopropyl Acrylamide) Hydrogels via 1H HRMAS PFG NMR Spectroscopy

    DOE PAGES

    Alam, Todd Michael; Childress, Kimberly Kay; Pastoor, Kevin; ...

    2014-09-19

    We found that different water environments in poly(N-isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using 1H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro-gels. For photo-initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spin R2 relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. Furthermore, by combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self-diffusion rate for these differentmore » water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described.« less

  1. Vibrational and theoretical analysis of pentyl-4-benzoyl-1-[2,4-dinitrophenyl]-5-phenyl-1H-pyrazole-3-carboxylate

    NASA Astrophysics Data System (ADS)

    Arı, Hatice; Büyükmumcu, Zeki; Özpozan, Talat; İlhan, İlhan Özer; Bahadır, Özlem

    2013-06-01

    Infrared spectrum of the compound, pentyl-4-benzoyl-1-[2,4-dinitrophenyl]-5-phenyl-1H-pyrazole-3-carboxylate (PBDPPC) has been measured. Conformational search through relaxed scan has been carried out to find the most stable conformational isomer. After the full geometry optimization for the most stable conformer using B3LYP and BLYP hybrid functionals of Density Functional Theory (DFT), vibrational normal modes have been calculated at the same theoretical levels. Potential Energy Distribution (PED) of each normal mode has been calculated by means of VEDA4 to obtain contributions of internal coordinates to the normal modes. Natural Bond Orbital (NBO) analysis has been performed to get insights into the possible hydrogen bonding sites for all the conformational isomers.

  2. Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for spin I = 1

    NASA Astrophysics Data System (ADS)

    Nilsson, Tomas; Halle, Bertil

    2012-08-01

    The frequency dependence of the longitudinal relaxation rate, known as the magnetic relaxation dispersion (MRD), can provide a frequency-resolved characterization of molecular motions in complex biological and colloidal systems on time scales ranging from 1 ns to 100 μs. The conformational dynamics of immobilized proteins and other biopolymers can thus be probed in vitro or in vivo by exploiting internal water molecules or labile hydrogens that exchange with a dominant bulk water pool. Numerous water 1H and 2H MRD studies of such systems have been reported, but the widely different theoretical models currently used to analyze the MRD data have resulted in divergent views of the underlying molecular motions. We have argued that the essential mechanism responsible for the main dispersion is the exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings when internal water molecules or labile hydrogens escape from orientationally confining macromolecular sites. In the EMOR model, the exchange process is thus not just a means of mixing spin populations but it is also the direct cause of spin relaxation. Although the EMOR theory has been used in several studies to analyze water 2H MRD data from immobilized biopolymers, the fully developed theory has not been described. Here, we present a comprehensive account of a generalized version of the EMOR theory for spin I = 1 nuclides like 2H. As compared to a previously described version of the EMOR theory, the present version incorporates three generalizations that are all essential in applications to experimental data: (i) a biaxial (residual) electric field gradient tensor, (ii) direct and indirect effects of internal motions, and (iii) multiple sites with different exchange rates. In addition, we describe and assess different approximations to the exact EMOR theory that are useful in various regimes. In particular, we consider the experimentally important

  3. Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: longitudinal relaxation dispersion for spin I = 1.

    PubMed

    Nilsson, Tomas; Halle, Bertil

    2012-08-07

    The frequency dependence of the longitudinal relaxation rate, known as the magnetic relaxation dispersion (MRD), can provide a frequency-resolved characterization of molecular motions in complex biological and colloidal systems on time scales ranging from 1 ns to 100 μs. The conformational dynamics of immobilized proteins and other biopolymers can thus be probed in vitro or in vivo by exploiting internal water molecules or labile hydrogens that exchange with a dominant bulk water pool. Numerous water (1)H and (2)H MRD studies of such systems have been reported, but the widely different theoretical models currently used to analyze the MRD data have resulted in divergent views of the underlying molecular motions. We have argued that the essential mechanism responsible for the main dispersion is the exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings when internal water molecules or labile hydrogens escape from orientationally confining macromolecular sites. In the EMOR model, the exchange process is thus not just a means of mixing spin populations but it is also the direct cause of spin relaxation. Although the EMOR theory has been used in several studies to analyze water (2)H MRD data from immobilized biopolymers, the fully developed theory has not been described. Here, we present a comprehensive account of a generalized version of the EMOR theory for spin I = 1 nuclides like (2)H. As compared to a previously described version of the EMOR theory, the present version incorporates three generalizations that are all essential in applications to experimental data: (i) a biaxial (residual) electric field gradient tensor, (ii) direct and indirect effects of internal motions, and (iii) multiple sites with different exchange rates. In addition, we describe and assess different approximations to the exact EMOR theory that are useful in various regimes. In particular, we consider the experimentally

  4. Quantitative Determination of Carthamin in Carthamus Red by 1H-NMR Spectroscopy.

    PubMed

    Yoshida, Takamitsu; Terasaka, Kazuyoshi; Kato, Setsuko; Bai, Fan; Sugimoto, Naoki; Akiyama, Hiroshi; Yamazaki, Takeshi; Mizukami, Hajime

    2013-01-01

    Carthamus Red is a food colorant prepared from the petals of Carthamus tinctorius (Asteraceae) whose major pigment is carthamin. Since an authentic carthamin standard is difficult to obtain commercially for the preparation of calibration curves in HPLC assays, we applied (1)H-NMR spectroscopy to the quantitative determination of carthamin in commercial preparations of Carthamus Red. Carthamus Red was repeatedly extracted in methanol and the extract was dissolved in pyridine-d(5) containing hexamethyldisilane (HMD) prior to (1)H-NMR spectroscopic analysis. The carthamin contents were calculated from the ratios of singlet signal intensities at approximately σ: 9.3 derived from H-16 of carthamin to those of the HMD signal at σ: 0. The integral ratios exhibited good repeatability among NMR spectroscopic analyses. Both the intra-day and inter-day assay variations had coefficients of variation of <5%. Based on the coefficient of absorption, the carthamin contents of commercial preparations determined by (1)H-NMR spectroscopy correlated well with those determined by colorimetry, although the latter were always approximately 1.3-fold higher than the former, irrespective of the Carthamus Red preparations. In conclusion, the quantitative (1)H-NMR spectroscopy used in the present study is simple and rapid, requiring no carthamin standard for calibration. After HMD concentration has been corrected using certified reference materials, the carthamin contents determined by (1)H-NMR spectroscopy are System of Units (SI)-traceable.

  5. A disc wind interpretation of the strong Fe Kα features in 1H 0707-495

    NASA Astrophysics Data System (ADS)

    Hagino, Kouichi; Odaka, Hirokazu; Done, Chris; Tomaru, Ryota; Watanabe, Shin; Takahashi, Tadayuki

    2016-10-01

    1H 0707-495 is the most convincing example of a supermassive black hole with an X-ray spectrum being dominated by extremely smeared, relativistic reflection, with the additional requirement of strongly supersolar iron abundance. However, here we show that the iron features in its 2-10 keV spectrum are rather similar to the archetypal wind dominated source, PDS 456. We fit all the 2-10 keV spectra from 1H 0707-495 using the same wind model as used for PDS 456, but viewed at higher inclination so that the iron absorption line is broader but not so blueshifted. This gives a good overall fit to the data from 1H 0707-495, and an extrapolation of this model to higher energies also gives a good match to the NuSTAR data. Small remaining residuals indicate that the iron line emission is stronger than in PDS 456. This is consistent with the wider angle wind expected from a continuum-driven wind from the super-Eddington mass accretion rate in 1H 0707-495, and/or the presence of residual reflection from the underlying disc though the presence of the absorption line in the model removes the requirement for highly relativistic smearing, and highly supersolar iron abundance. We suggest that the spectrum of 1H 0707-495 is sculpted more by absorption in a wind than by extreme relativistic effects in strong gravity.

  6. The structure and properties of 5,6-dinitro-1H-benzotriazole

    NASA Astrophysics Data System (ADS)

    Santa María, Dolores; Claramunt, Rosa M.; Torralba, M. Carmen; Torres, M. Rosario; Alkorta, Ibon; Elguero, José

    2016-06-01

    5,6-Dinitro-1H-benzotriazole crystallizes in the monoclinic system, space group P21/c. The asymmetric unit contains the planar 1H-tautomer together with a water molecule of crystallization. Each water molecule is hydrogen bonded to three adjacent 5,6-dinitrobenzotriazoles forming a tape along the b-axis of the crystal. These tapes stack along the c-axis through hydrogen bonds involving the water molecules and one of the nitro groups leading to a bidimensional structure. Solid-state 13C and 15N CPMAS NMR allow to confirm that the tautomer present is the 1H one. In DMSO-d6 solution the results are quite different and, based on GIAO/B3LYP/6-311++G(d,p) calculations, lead us to conclude that the major tautomer is the 5,6-dinitro-2H-benzotriazole, a surprising result that contradicts the rule that the major tautomer in solution coincides with the one present in the crystal. An anhydrous pseudopolymorph of 5,6-dinitro-1H-benzotriazole has been obtained as a non-crystalline form and from solid-state NMR and theoretical calculations, we conclude that it is an 1H-tautomer.

  7. Elastic and magnetoelastic relaxation behaviour of multiferroic (ferromagnetic + ferroelectric + ferroelastic) Pb(Fe0.5Nb0.5)O3 perovskite

    NASA Astrophysics Data System (ADS)

    Carpenter, M. A.; Schiemer, J. A.; Lascu, I.; Harrison, R. J.; Kumar, A.; Katiyar, R. S.; Ortega, N.; Sanchez, D. A.; Salazar Mejia, C.; Schnelle, W.; Echizen, M.; Shinohara, H.; Heap, A. J. F.; Nagaratnam, R.; Dutton, S. E.; Scott, J. F.

    2015-07-01

    Resonant Ultrasound Spectroscopy has been used to characterize elastic and anelastic anomalies in a polycrystalline sample of multiferroic Pb(Fe0.5Nb0.5)O3 (PFN). Elastic softening begins at ~550 K, which is close to the Burns temperature marking the development of dynamical polar nanoregions. A small increase in acoustic loss at ~425 K coincides with the value of T* reported for polar nanoregions starting to acquire a static or quasi-static component. Softening of the shear modulus by ~30-35% through ~395-320 K, together with a peak in acoustic loss, is due to classical strain/order parameter coupling through the cubic → tetragonal → monoclinic transition sequence of ferroelectric/ferroelastic transitions. A plateau of high acoustic loss below ~320 K is due to the mobility under stress of a ferroelastic microstructure but, instead of the typical effects of freezing of twin wall motion at some low temperature, there is a steady decrease in loss and increase in elastic stiffness below ~85 K. This is attributed to freezing of a succession of strain-coupled defects with a range of relaxation times and is consistent with a report in the literature that PFN develops a tweed microstructure over a wide temperature interval. No overt anomaly was observed near the expected Néel point, ~145 K, consistent with weak/absent spin/lattice coupling but heat capacity measurements showed that the antiferromagnetic transition is actually smeared out or suppressed. Instead, the sample is weakly ferromagnetic up to ~560 K, though it has not been possible to exclude definitively the possibility that this could be due to some magnetic impurity. Overall, evidence from the RUS data is of a permeating influence of static and dynamic strain relaxation effects which are attributed to local strain heterogeneity on a mesoscopic length scale. These, in turn, must have a role in determining the magnetic properties and multiferroic character of PFN.

  8. Selective excitation enables assignment of proton resonances and (1)H-(1)H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-21

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of (1)H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as (13)C or (15)N. In this method, after the initial preparation of proton magnetization and cross-polarization to (13)C nuclei, transverse magnetization of desired (13)C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific (13)C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of (1)H-(1)H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  9. Selective excitation enables assignment of proton resonances and 1H-1H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-01

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of 1H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as 13C or 15N. In this method, after the initial preparation of proton magnetization and cross-polarization to 13C nuclei, transverse magnetization of desired 13C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific 13C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of 1H-1H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  10. Selective excitation enables assignment of proton resonances and {sup 1}H-{sup 1}H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-21

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of {sup 1}H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as {sup 13}C or {sup 15}N. In this method, after the initial preparation of proton magnetization and cross-polarization to {sup 13}C nuclei, transverse magnetization of desired {sup 13}C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific {sup 13}C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of {sup 1}H-{sup 1}H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  11. Dynamics-based selective 2D {sup 1}H/{sup 1}H chemical shift correlation spectroscopy under ultrafast MAS conditions

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-05-28

    Dynamics plays important roles in determining the physical, chemical, and functional properties of a variety of chemical and biological materials. However, a material (such as a polymer) generally has mobile and rigid regions in order to have high strength and toughness at the same time. Therefore, it is difficult to measure the role of mobile phase without being affected by the rigid components. Herein, we propose a highly sensitive solid-state NMR approach that utilizes a dipolar-coupling based filter (composed of 12 equally spaced 90° RF pulses) to selectively measure the correlation of {sup 1}H chemical shifts from the mobile regions of a material. It is interesting to find that the rotor-synchronized dipolar filter strength decreases with increasing inter-pulse delay between the 90° pulses, whereas the dipolar filter strength increases with increasing inter-pulse delay under static conditions. In this study, we also demonstrate the unique advantages of proton-detection under ultrafast magic-angle-spinning conditions to enhance the spectral resolution and sensitivity for studies on small molecules as well as multi-phase polymers. Our results further demonstrate the use of finite-pulse radio-frequency driven recoupling pulse sequence to efficiently recouple weak proton-proton dipolar couplings in the dynamic regions of a molecule and to facilitate the fast acquisition of {sup 1}H/{sup 1}H correlation spectrum compared to the traditional 2D NOESY (Nuclear Overhauser effect spectroscopy) experiment. We believe that the proposed approach is beneficial to study mobile components in multi-phase systems, such as block copolymers, polymer blends, nanocomposites, heterogeneous amyloid mixture of oligomers and fibers, and other materials.

  12. Spin dynamics in CuO and Cu[sub 1[minus][ital x

    SciTech Connect

    Carretta, P.; Corti, M.; Rigamonti, A. )

    1993-08-01

    [sup 63]Cu nuclear quadrupole resonance (NQR), nuclear antiferromagnetic resonance (AFNMR), and spin-lattice relaxation, as well as [sup 7]Li NMR and relaxation measurements in CuO and in Cu[sub 1[minus][ital x

  13. Correlation of lactate and pH in human skeletal muscle after exercise by 1H NMR.

    PubMed

    Pan, J W; Hamm, J R; Hetherington, H P; Rothman, D L; Shulman, R G

    1991-07-01

    We have made in vivo 1H NMR measurements of the time course of pH and lactate in human skeletal muscle after exercise. Spectra were obtained in a 4.7-T 30-cm bore Bruker Biospec spectrometer with a 2.5-cm diameter single surface coil. pH was determined from the shift of the endogenous carnosine H-C2 peak while lactate concentrations were determined by comparison with endogenous total creatine, taken to be 28.5 mM/kg wet wt. Fitting the data shows that the exponential decay of lactate (-0.094 +/- 0.014 min-1. t1/2 = 10.6 min) is slower than that of pH (-0.147 +/- 0.015 min-1, t1/2 = 4.7 min), n = 7 with two different volunteers. These values are significantly different with P less than 0.0005. Relaxation times of lactate and creatine were also measured for lactate quantitation; creatine T1, 1.23 +/- 12 s, T2, 136.2 +/- 26.4 ms (both in resting human muscle); lactate T1 (in postmortem rabbit muscle), 1.0 +/- 11 s and T2, 80 ms (in postexercise human muscle). At the end of intense exercise, the lactate level reached was 25.3 +/- 4.0 mM and the average pH drop was 1.0 pH unit. We discuss the implications of these measurements in conjunction with existing data on other sources of H+ flux, phosphocreatine resynthesis, H+ transport, and contribution of inorganic phosphate to buffering.

  14. Vibrational energy relaxation in liquid oxygen

    NASA Astrophysics Data System (ADS)

    Everitt, K. F.; Egorov, S. A.; Skinner, J. L.

    1998-09-01

    We consider theoretically the relaxation from the first excited vibrational state to the ground state of oxygen molecules in neat liquid oxygen. The relaxation rate constant is related in the usual way to the Fourier transform of a certain quantum mechanical force-force time-correlation function. A result from Egelstaff allows one instead to relate the rate constant (approximately) to the Fourier transform of a classical force-force time-correlation function. This Fourier transform is then evaluated approximately by calculating three equilibrium averages from a classical molecular dynamics simulation. Our results for the relaxation times (at two different temperatures) are within a factor of 5 of the experimental relaxation times, which are in the ms range.

  15. Energy landscape of relaxed amorphous silicon

    NASA Astrophysics Data System (ADS)

    Valiquette, Francis; Mousseau, Normand

    2003-09-01

    We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.

  16. Relaxation dynamics of a multihierarchical polymer network

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  17. The Irreversible Thermodynamics of Chemical Relaxation.

    ERIC Educational Resources Information Center

    Schelly, Z. A.

    1980-01-01

    Discusses the thermodynamics of relaxation methods, considering (1) mode of perturbation of chemical equilibria, (2) enforced change of the concentrations, and (3) chemical contributions to equations of state. (CS)

  18. Slow spin relaxation in dipolar spin ice.

    NASA Astrophysics Data System (ADS)

    Orendac, Martin; Sedlakova, Lucia; Orendacova, Alzbeta; Vrabel, Peter; Feher, Alexander; Pajerowski, Daniel M.; Cohen, Justin D.; Meisel, Mark W.; Shirai, Masae; Bramwell, Steven T.

    2009-03-01

    Spin relaxation in dipolar spin ice Dy2Ti2O7 and Ho2Ti2O7 was investigated using the magnetocaloric effect and susceptibility. The magnetocaloric behavior of Dy2Ti2O7 at temperatures where the orientation of spins is governed by ``ice rules`` (T < Tice) revealed thermally activated relaxation; however, the resulting temperature dependence of the relaxation time is more complicated than anticipated by a mere extrapolation of the corresponding high temperature data [1]. A susceptibility study of Ho2Ti2O7 was performed at T > Tice and in high magnetic fields, and the results suggest a slow relaxation of spins analogous to the behavior reported in a highly polarized cooperative paramagnet [2]. [1] J. Snyder et al., Phys. Rev. Lett. 91 (2003) 107201. [2] B. G. Ueland et al., Phys. Rev. Lett. 96 (2006) 027216.

  19. Nanoscale electrodeposition of Al on n -Si(1 1 1) : H from an ionic liquid

    NASA Astrophysics Data System (ADS)

    Aravinda, C. L.; Burger, B.; Freyland, W.

    2007-02-01

    The H-terminated Si(1 1 1)/ionic liquid interface has been imaged by scanning tunneling microscopy (STM) for the first time. Employing the ionic liquid AlCl-[Cmim]+ nanoscale electrodeposition of Al on Si(1 1 1) : H substrates has been investigated by in situ electrochemical scanning probe techniques at room temperature. No underpotential deposition of Al is found. Nucleation of Al begins at the Nernst potential with the formation of large islands spread all over the substrate. Under the influence of the scanning STM tip, these islands are easily disturbed which makes it difficult to image the initial stages of electrochemical phase formation. We explain this by a relatively high mobility of the islands due to the poor wetting of Al on the Si(1 1 1) : H substrate. The 3D growth of Al on Si(1 1 1) : H follows a Volmer-Weber growth mode. Scanning tunneling spectra of larger Al clusters show clearly metallic characteristics.

  20. Aminosilanes derived from 1H-benzimidazole-2(3H)-thione.

    PubMed

    Palomo-Molina, Juliana; García-Báez, Efrén V; Contreras, Rosalinda; Pineda-Urbina, Kayim; Ramos-Organillo, Angel

    2015-09-01

    Two new molecular structures, namely 1,3-bis(trimethylsilyl)-1H-benzimidazole-2(3H)-thione, C13H22N2SSi2, (2), and 1-trimethylsilyl-1H-benzimidazole-2(3H)-thione, C10H14N2SSi, (3), are reported. Both systems were derived from 1H-benzimidazole-2(3H)-thione. Noncovalent C-H···π interactions between the centroid of the benzmidazole system and the SiMe3 groups form helicoidal arrangements in (2). Dimerization of (3) results in the formation of R2(2)(8) rings via N-H···S interactions, along with parallel π-π interactions between imidazole and benzene rings.

  1. Amino­silanes derived from 1H-benzimidazole-2(3H)-thione

    PubMed Central

    Palomo-Molina, Juliana; García-Báez, Efrén V.; Contreras, Rosalinda; Pineda-Urbina, Kayim; Ramos-Organillo, Angel

    2015-01-01

    Two new mol­ecular structures, namely 1,3-bis­(tri­methyl­silyl)-1H-benzimidazole-2(3H)-thione, C13H22N2SSi2, (2), and 1-tri­methyl­silyl-1H-benzimidazole-2(3H)-thione, C10H14N2SSi, (3), are reported. Both systems were derived from 1H-benzimidazole-2(3H)-thione. Noncovalent C—H⋯π inter­actions between the centroid of the benzmidazole system and the SiMe3 groups form helicoidal arrangements in (2). Dimerization of (3) results in the formation of R 2 2(8) rings via N—H⋯S inter­actions, along with parallel π–π inter­actions between imidazole and benzene rings. PMID:26322611

  2. Measurement of rates of transport across erythrocyte membranes by 1H nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Guy, Robert D.; Tahir Razi, M.; Rabenstein, Dallas L.

    The use of 1H NMR to monitor the transport of small molecules across the membrane of erythrocytes is evaluated. Cells are separated, as a function of time, from a suspension medium containing the small molecule of interest, and then analyzed for the small molecule by 1H NMR. 1H NMR spectra of either the intact cells or cell lysate are measured by the protein saturation pulse/Fourier transform (PSP/FT) technique. With this technique, interfering hemoglobin resonances are suppressed with a selective presaturation pulse and high-resolution spectra are obtained for small molecules. The detection limit is on the order of 0. 10 m M Membrane transport rates were measured for alanine, penicillamine, N-acetylpenicillamine, and S-methylcysteine.

  3. Congenital Cataracts and Gut Dysmotility in a DYNC1H1 Dyneinopathy Patient

    PubMed Central

    Gelineau-Morel, Rose; Lukacs, Marshall; Weaver, K. Nicole; Hufnagel, Robert B.; Gilbert, Donald L.; Stottmann, Rolf W.

    2016-01-01

    Whole exome sequencing continues to end the diagnostic odyssey for a number of patients and expands our knowledge of phenotypes associated with gene mutations. We describe an 11-year-old female patient with a constellation of symptoms including congenital cataracts, gut dysmotility, sensory neuropathy, and bifrontal polymicrogyria. Whole exome sequencing was performed and identified a de novo heterozygous missense mutation in the ATPase motor domain of cytoplasmic dynein heavy chain 1 (DYNC1H1), which is known to be involved in neuronal migration and retrograde axonal transport. The mutation was found to be highly damaging by multiple prediction programs. The residue is highly conserved, and reported mutations in this gene result in a variety of phenotypes similar to that of our patient. We report only the second case of congenital cataracts and the first of gut dysmotility in a patient with DYNC1H1, thus expanding the spectrum of disease seen in DYNC1H1 dyneinopathies. PMID:27754416

  4. 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.

  5. Long-range surface-induced water structures and the effect of 1-butanol studied by 1H nuclear magnetic resonance.

    PubMed

    Totland, Christian; Lewis, Rhiannon T; Nerdal, Willy

    2013-09-03

    Thin films of water between glass plates were investigated in this study with regard to water structure and dynamics in the temperature range of 278-313 K. We further investigated how addition of 1-butanol (0.05 and 0.5 M) affects the range and properties of the surface-induced water structures. From the observation of two (1)H nuclear magnetic resonance (NMR) water resonances and two relaxation components, it was found that the interfacial water exists in a two-state mixture in dynamic equilibrium, with the respective structures interpreted as being high-density water (HDW) and low-density water (LDW). In the absence of 1-butanol, the LDW state is more pronounced, with a further shift in equilibrium toward the LDW state with an increase in temperature. However, in water film samples containing 1-butanol, the HDW state dominates at low temperatures while the LDW state becomes more visible at higher temperatures. Furthermore, the addition of 1-butanol significantly increased the extent of the surface-induced water structures. NMR relaxation shows that the dynamics of water in the HDW state is significantly affected by the presence of 1-butanol and further indicates that the distribution of values for the enthalpy of activation associated with translational motion of water molecules in the HDW state is narrower in the 0.05 M 1-butanol sample than in the 0.5 M 1-butanol sample.

  6. Relativistic Force Field: Parametrization of (13)C-(1)H Nuclear Spin-Spin Coupling Constants.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-11-06

    Previously, we reported a reliable DU8 method for natural bond orbital (NBO)-aided parametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. As sophisticated NMR experiments for precise measurements of carbon-proton SSCCs are becoming more user-friendly and broadly utilized by the organic chemistry community to guide and inform the process of structure determination of complex organic compounds, we have now developed a fast and accurate method for computing (13)C-(1)H SSCCs. Fermi contacts computed with the DU8 basis set are scaled using selected NBO parameters in conjunction with empirical scaling coefficients. The method is optimized for inexpensive B3LYP/6-31G(d) geometries. The parametric scaling is based on a carefully selected training set of 274 ((3)J), 193 ((2)J), and 143 ((1)J) experimental (13)C-(1)H spin-spin coupling constants reported in the literature. The DU8 basis set, optimized for computing Fermi contacts, which by design had evolved from optimization of a collection of inexpensive 3-21G*, 4-21G, and 6-31G(d) bases, offers very short computational (wall) times even for relatively large organic molecules containing 15-20 carbon atoms. The most informative SSCCs for structure determination, i.e., (3)J, were computed with an accuracy of 0.41 Hz (rmsd). The new unified approach for computing (1)H-(1)H and (13)C-(1)H SSCCs is termed "DU8c".

  7. 40 CFR 721.1750 - 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium salts. 721.1750 Section 721.1750... 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium...-tyl-oxy)-, sodium salt (PMN P-92-35), and 1H-benzotriazole, 5-(pentyloxy)- , potassium salt (PMN...

  8. 40 CFR 721.1750 - 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium salts. 721.1750 Section 721.1750... 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium...-tyl-oxy)-, sodium salt (PMN P-92-35), and 1H-benzotriazole, 5-(pentyloxy)- , potassium salt (PMN...

  9. 40 CFR 721.1750 - 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium salts. 721.1750 Section 721.1750... 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium...-tyl-oxy)-, sodium salt (PMN P-92-35), and 1H-benzotriazole, 5-(pentyloxy)- , potassium salt (PMN...

  10. 40 CFR 721.1750 - 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium salts. 721.1750 Section 721.1750... 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium...-tyl-oxy)-, sodium salt (PMN P-92-35), and 1H-benzotriazole, 5-(pentyloxy)- , potassium salt (PMN...

  11. 40 CFR 721.1750 - 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium salts. 721.1750 Section 721.1750... 1H-Benzotriazole, 5-(pen-tyl-oxy)- and 1H-ben-zo-tri-a-zole, 5-(pen-tyl-oxy)-, sodium and potassium...-tyl-oxy)-, sodium salt (PMN P-92-35), and 1H-benzotriazole, 5-(pentyloxy)- , potassium salt (PMN...

  12. Peroxynitrite-induced relaxation in isolated rat aortic rings and mechanisms of action.

    PubMed

    Li, Jianfeng; Li, Wenyan; Altura, Bella T; Altura, Burton M

    2005-12-15

    The present study was designed to evaluate the effects of peroxynitrite (ONOO-), the product of superoxide and nitric oxide, on isolated segments of rat aorta. In the absence of any vasoactive agent, ONOO- (from 10(-8) to 10(-4) M) failed to alter the basal tension. In phenylephrine (PE; 5 x 10(-7) M)-precontracted rat aortic rings (RAR), ONOO- elicited concentration-dependent relaxation at concentrations of from 10(-8) to 10(-4) M. The effective concentrations producing approximately 50% of maximal relaxation (ED50) to ONOO- were 1.84 x 10(-5) M and 1.96 x 10(-5) M in intact and denuded RAR, respectively (P > 0.05). No significant differences in the relaxation responses were found between RAR with or without endothelium (P > 0.05). The presence of either 5 microM methylene blue (MB) or 5 microM 1H-[1,2,4]oxadiazolo-[4,3-alpha]quinoxalin-1-one (ODQ) significantly inhibited the relaxations induced by ONOO-. Sildenafil (10(-7) M), on the other hand, significantly potentiated the ONOO--induced relaxations. Tetraethylammonium chloride (T-2265) significantly decreased the ONOO--induced relaxations in a concentration-dependent manner. However, ONOO- had no effect on RAR precontracted by high KCL (40 mM, n = 6, P > 0.05). Addition of calyculin A also significantly decreased the ONOO--induced relaxation in a dose-dependent manner. Furthermore, ONOO- significantly inhibited calcium-induced contractions of K+-depolarized aortic rings in a concentration-related manner. Lastly, a variety of other pharmacological agents and antagonists including L-NMMA, L-arginine, indomethacin, atropine, naloxone, diphenhydramine, cimetine, glibenclamide, haloperidol, superoxide dismutase (SOD), and catalase did not influence the relaxant effects of ONOO- on RAR. Our new results suggest that ONOO--triggered relaxation on rat aortic rings is mediated by elevation of cGMP levels, membrane hyperpolarization via K+-channel activation, activation of myosin phosphatase activity, and interference

  13. Peroxynitrite-induced relaxation in isolated rat aortic rings and mechanisms of action

    SciTech Connect

    Li Jianfeng; Li Wenyan; Altura, Bella T.; Altura, Burton M. . E-mail: baltura@downstate.edu

    2005-12-15

    The present study was designed to evaluate the effects of peroxynitrite (ONOO{sup -}), the product of superoxide and nitric oxide, on isolated segments of rat aorta. In the absence of any vasoactive agent, ONOO{sup -} (from 10{sup -8} to 10{sup -4} M) failed to alter the basal tension. In phenylephrine (PE; 5 x 10{sup -7} M)-precontracted rat aortic rings (RAR), ONOO{sup -} elicited concentration-dependent relaxation at concentrations of from 10{sup -8} to 10{sup -4} M. The effective concentrations producing approximately 50% of maximal relaxation (ED{sub 5}) to ONOO{sup -} were 1.84 x 10{sup -5} M and 1.96 x 10{sup -5} M in intact and denuded RAR, respectively (P > 0.05). No significant differences in the relaxation responses were found between RAR with or without endothelium (P > 0.05). The presence of either 5 {mu}M methylene blue (MB) or 5 {mu}M 1H-[1,2,4]oxadiazolo-[4,3-{alpha}]quinoxalin-1-one (ODQ) significantly inhibited the relaxations induced by ONOO{sup -}. Sildenafil (10{sup -7} M), on the other hand, significantly potentiated the ONOO{sup -}-induced relaxations. Tetraethylammonium chloride (T-2265) significantly decreased the ONOO{sup -}-induced relaxations in a concentration-dependent manner. However, ONOO{sup -} had no effect on RAR precontracted by high KCL (40 mM, n = 6, P > 0.05). Addition of calyculin A also significantly decreased the ONOO{sup -}-induced relaxation in a dose-dependent manner. Furthermore, ONOO{sup -} significantly inhibited calcium-induced contractions of K{sup +}-depolarized aortic rings in a concentration-related manner. Lastly, a variety of other pharmacological agents and antagonists including L-NMMA, L-arginine, indomethacin, atropine, naloxone, diphenhydramine, cimetine, glibenclamide, haloperidol, superoxide dismutase (SOD), and catalase did not influence the relaxant effects of ONOO{sup -} on RAR. Our new results suggest that ONOO{sup -}-triggered relaxation on rat aortic rings is mediated by elevation of cGMP levels

  14. On convex relaxation of graph isomorphism

    PubMed Central

    Aflalo, Yonathan; Bronstein, Alexander; Kimmel, Ron

    2015-01-01

    We consider the problem of exact and inexact matching of weighted undirected graphs, in which a bijective correspondence is sought to minimize a quadratic weight disagreement. This computationally challenging problem is often relaxed as a convex quadratic program, in which the space of permutations is replaced by the space of doubly stochastic matrices. However, the applicability of such a relaxation is poorly understood. We define a broad class of friendly graphs characterized by an easily verifiable spectral property. We prove that for friendly graphs, the convex relaxation is guaranteed to find the exact isomorphism or certify its inexistence. This result is further extended to approximately isomorphic graphs, for which we develop an explicit bound on the amount of weight disagreement under which the relaxation is guaranteed to find the globally optimal approximate isomorphism. We also show that in many cases, the graph matching problem can be further harmlessly relaxed to a convex quadratic program with only n separable linear equality constraints, which is substantially more efficient than the standard relaxation involving 2n equality and n2 inequality constraints. Finally, we show that our results are still valid for unfriendly graphs if additional information in the form of seeds or attributes is allowed, with the latter satisfying an easy to verify spectral characteristic. PMID:25713342

  15. Ultrasonic relaxations in lanthanide phosphate glasses

    NASA Astrophysics Data System (ADS)

    Carini, G.; D'angelo, G.; Federico, M.; Tripodo, G.; Saunders, G. A.; Senin, H. B.

    1994-08-01

    The attenuation and velocity of ultrasonic waves of frequencies in the range of 10 to 90 MHz have been measured in La2O3-P2O5 and Sm2O3-P2O5 glasses with high lanthanide concentrations as a function of temperature between 1.5 and 400 K. Two distinct features characterize the attenuation behavior: (i) a plateau at temperatures below 15 K and (ii) a broad high-temperature peak. The former feature is interpreted in terms of the phonon-assisted relaxation of two-level systems and the latter by assuming the existence of a distribution of thermally activated relaxing centers. For both these mechanisms the product of the deformation potential squared and the density of relaxing particles decreases with increasing lanthanide-ion concentration. This result, taken together with previous observations of the properties of oxide glasses, provides physical insight into the microscopic origin of the relaxation effects and suggests that the source of the low- and high-temperature attenuation mechanisms is the same. At temperatures below 100 K, the sound velocity, after the subtraction of the relaxation and anharmonic contributions, follows a linear law as predicted by the soft-potential model for the relaxation of soft harmonic oscillators. An encouraging agreement is obtained between the parameters regulating this mechanism and those determined from the acoustic attenuation plateau.

  16. Dielectric relaxation spectroscopy of phlogopite mica

    NASA Astrophysics Data System (ADS)

    Kaur, Navjeet; Singh, Mohan; Singh, Anupinder; Awasthi, A. M.; Singh, Lakhwant

    2012-11-01

    An in-depth investigation of the dielectric characteristics of annealed phlogopite mica has been conducted in the frequency range 0.1 Hz-10 MHz and over the temperature range 653-873 K through the framework of dielectric permittivity, electric modulus and conductivity formalisms. These formalisms show qualitative similarities in relaxation processes. The frequency dependence of the M″ and dc conductivity is found to obey an Arrhenius law and the activation energy of the phlogopite mica calculated both from dc conductivity and the modulus spectrum is similar, indicating that same type of charge carriers are involved in the relaxation phenomena. The electric modulus and conductivity data have been fitted with the Havriliak-Negami function. Scaling of M‧, M″, ac conductivity has also been performed in order to obtain insight into the relaxation mechanisms. The scaling behaviour indicates that the relaxation describes the same mechanism at different temperatures. The relaxation mechanism was also examined using the Cole-Cole approach. The study elaborates that the investigation regarding the temperature and frequency dependence of dielectric relaxation in the phlogopite mica will be helpful for various cutting edge applications of this material in electrical engineering.

  17. Elevated Glutamatergic Compounds in Pregenual Anterior Cingulate in Pediatric Autism Spectrum Disorder Demonstrated by 1H MRS and 1H MRSI

    PubMed Central

    Bejjani, Anthony; O'Neill, Joseph; Kim, John A.; Frew, Andrew J.; Yee, Victor W.; Ly, Ronald; Kitchen, Christina; Salamon, Noriko; McCracken, James T.; Toga, Arthur W.; Alger, Jeffry R.; Levitt, Jennifer G.

    2012-01-01

    Recent research in autism spectrum disorder (ASD) has aroused interest in anterior cingulate cortex and in the neurometabolite glutamate. We report two studies of pregenual anterior cingulate cortex (pACC) in pediatric ASD. First, we acquired in vivo single-voxel proton magnetic resonance spectroscopy (1H MRS) in 8 children with ASD and 10 typically developing controls who were well matched for age, but with fewer males and higher IQ. In the ASD group in midline pACC, we found mean 17.7% elevation of glutamate + glutamine (Glx) (p<0.05) and 21.2% (p<0.001) decrement in creatine + phosphocreatine (Cr). We then performed a larger (26 subjects with ASD, 16 controls) follow-up study in samples now matched for age, gender, and IQ using proton magnetic resonance spectroscopic imaging (1H MRSI). Higher spatial resolution enabled bilateral pACC acquisition. Significant effects were restricted to right pACC where Glx (9.5%, p<0.05), Cr (6.7%, p<0.05), and N-acetyl-aspartate + N-acetyl-aspartyl-glutamate (10.2%, p<0.01) in the ASD sample were elevated above control. These two independent studies suggest hyperglutamatergia and other neurometabolic abnormalities in pACC in ASD, with possible right-lateralization. The hyperglutamatergic state may reflect an imbalance of excitation over inhibition in the brain as proposed in recent neurodevelopmental models of ASD. PMID:22848344

  18. Two configurations of the four-ring birdcage coil for 1H imaging and 1H-decoupled 31P spectroscopy of the human head.

    PubMed

    Murphy-Boesch, J; Srinivasan, R; Carvajal, L; Brown, T R

    1994-02-01

    The four-ring birdcage resonator, a new class of dual-tuned birdcage resonators, is described. We report two configurations of the coil: the low-pass, high-pass (LP-HP) and the low-pass, low-pass (LP-LP), both of which can be operated in dual quadrature mode at 1.5 T. As head coils, both configurations exhibit greatly reduced tuning interactions between frequencies, permitting rapid, noniterative tuning. Compared with single-tuned, two-ring birdcage resonators of similar volume, the sensitivity and transmitter efficiencies of the resonators are better than 85% for the proton frequency and the same to within 5% for the phosphorus frequency. Circuit models have been developed to refine coil tuning and aid the calculation of B1 field contour plots. Both configurations have been used for integrated examinations involving acquisition of high-quality 1H images and 1H-decoupled 31P CSI spectra of the human head. A scaled-down version of the LP-LP configuration has been demonstrated for use with the human calf.

  19. Two Configurations of the Four-Ring Birdcage Coil for 1H Imaging and 1H-Decoupled 31P Spectroscopy of the Human Head

    NASA Astrophysics Data System (ADS)

    Murphyboesch, J.; Srinivasan, R.; Carvajal, L.; Brown, T. R.

    The four-ring birdcage resonator, a new class of dual-tuned birdeage resonators, is described. We report two configurations of the coil: the low-pass, high-pass (LP-HP) and the low-pass, low-pass (LP-LP), both of which can be operated in dual quadrature mode at 1.5 T. As head coils, both configurations exhibit greatly reduced tuning interactions between frequencies, permitting rapid, noniterative tuning. Compared with single-tuned, two-ring birdcage resonators of similar volume, the sensitivity and transmitter efficiencies of the resonators are better than 85% for the proton frequency and the same to within 5% for the phosphorus frequency. Circuit models have been developed to refine coil tuning and aid the calculation of B1 field contour plots. Both configurations have been used for integrated examinations involving acquisition of high-quality 1H images and 1H-decoupled 31P CSI spectra of the human head. A scaled-down version of the LP-LP configuration has been demonstrated for use with the human calf.

  20. (1)H chemical shift differences of Prelog-Djerassi lactone derivatives: DFT and NMR conformational studies.

    PubMed

    Aímola, Túlio J; Lima, Dimas J P; Dias, Luiz C; Tormena, Cláudio F; Ferreira, Marco A B

    2015-02-21

    This work reports an experimental and theoretical study of the conformational preferences of several Prelog-Djerassi lactone derivatives, to elucidate the (1)H NMR chemical shift differences in the lactonic core that are associated with the relative stereochemistry of these derivatives. The boat-like conformation of explains the anomalous (1)H chemical shift between H-5a and H-5b, in which the two methyl groups (C-8 and C-9) face H-5b, leading to its higher shielding effect.

  1. A practical, metal-free synthesis of 1H-indazoles.

    PubMed

    Counceller, Carla M; Eichman, Chad C; Wray, Brenda C; Stambuli, James P

    2008-03-06

    The synthesis of 1H-indazoles is achieved from o-aminobenzoximes by the selective activation of the oxime in the presence of the amino group. The reaction occurs with a variety of substituted o-aminobenzoximes using a slight excess of methanesulfonyl chloride and triethylamine at 0-23 degrees C and is amenable to scale-up. The synthesis of 1H-indazoles under these conditions is extremely mild compared with previous synthetic approaches and affords the desired compounds in good to excellent yields.

  2. Ex vivo relaxation effect of Cuscuta chinensis extract on rabbit corpus cavernosum.

    PubMed

    Sun, Kai; Zhao, Chen; Chen, Xiang-Feng; Kim, Hye-Kyung; Choi, Bo-Ram; Huang, Yi-Ran; Park, Jong-Kwan

    2013-01-01

    The effect of Cuscuta chinensis extract on the rabbit penile corpus cavernosum (PCC) was evaluated in the present study. Penises obtained from healthy male New Zealand white rabbits (2.5-3.0 kg) were precontracted with phenylephrine (Phe, 10 µmol l(-1)) and then treated with various concentrations of Cuscuta chinensis extract (1, 2, 3, 4 and 5 mg ml(-1)). The change in penile tension was recorded, and cyclic nucleotides in the PCC were measured by radioimmunoassay (RIA). The interaction between Cuscuta chinensis and sildenafil was also evaluated. The result indicated that the PCC relaxation induced by Cuscuta chinensis extract was concentration-dependent. Pre-treatment with an nitric oxide synthase (NOS) inhibitor (Nω nitro-L-arginine-methyl ester, L-NAME), a guanylyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ), or a protein kinase A inhibitor (KT 5720) did not completely inhibit the relaxation. Incubation of penile cavernous tissue with the Cuscuta chinensis extract significantly increased cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) in the PCC. Moreover, the Cuscuta chinensis extract significantly enhanced sildenafil-induced PCC relaxation. In conclusion, the Cuscuta chinensis extract exerts a relaxing effect on penile cavernous tissue in part by activating the NO-cGMP pathway, and it may improve erectile dysfunction (ED), which does not completely respond to sildenafil citrate.

  3. 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.

  4. Irisin relaxes mouse mesenteric arteries through endothelium-dependent and endothelium-independent mechanisms.

    PubMed

    Jiang, Miao; Wan, Fangzhu; Wang, Fang; Wu, Qi

    2015-12-25

    Irisin, a newly discovered myokine, has been shown to produce modest weight loss and improve glucose intolerance in mice. The purpose of this study was to investigate the effects of irisin on vascular activity and the mechanisms involved. Experiments were performed on mouse mesenteric arteries. We demonstrated that irisin induced relaxation in mesenteric arteries with or without endothelium in a concentration-dependent manner. It was further demonstrated that the irisin-induced vasorelaxation effects on endothelium-intact mesenteric arteries were reduced by pretreatment with Nω-nitro-L-arginine methyl ester (L-NAME) or 1H-[1, 2, 4] oxadizolo [4, 3-a] quinoxalin-1-one (ODQ). However, pretreatment with indomethacin (INDO), a nonselective cyclooxygenase inhibitor did not modulate irisin-induced relaxation. In addition, the contraction due to extracellular Ca(2+) influx and intracellular Ca(2+) release was also inhibited by irisin. In summary, these results suggested that the endothelium-dependent relaxation of irisin is mediated by the nitric oxide (NO)-guanosine 3', 5'-cyclic phosphate (cGMP)-dependent pathway but not the prostaglandin I2 (PGI2)-cyclic adenosine monophosphate (cAMP)-dependent mechanism. Endothelium-independent relaxation may be depend on inhibiting Ca(2+) influx through blocking VDCCs and intracellular Ca(2+) release through both IP3R and RyR channels.

  5. Probing molecular dynamics in chromatographic systems using high-resolution 1H magic-angle-spinning NMR spectroscopy: interaction between p-Xylene and C18-bonded silica.

    PubMed

    Coen, Muireann; Wilson, Ian D; Nicholson, Jeremy K; Tang, Huiru; Lindon, John C

    2004-06-01

    The exact nature of the interaction between small molecules and chromatographic solid phases has been the subject of much research, but detailed understanding of the molecular dynamics in such systems remains elusive. High-resolution (1)H magic-angle-spinning (MAS) NMR spectroscopy has been applied to the investigation of C18-bonded silica material as used in chromatographic separation techniques together with an adsorbed model analyte, p-xylene. Two distinct p-xylene and water environments were identified within the C18-bonded silica through the measurement of (1)H NMR chemical shifts, T(1) and T(2) relaxation times and diffusion coefficients, including their temperature dependence. The results have been analyzed in terms of two environments, p-xylene within the C18 chains, in slow exchange on the NMR time scale with p-xylene in a more mobile state adsorbed as a layer in close proximity to the C18 particles, but which is distinct from free liquid p-xylene. The techniques used here could have more general applications, including the study of drug molecules bound into phospholipid membranes in micelles or vesicles.

  6. Evaluation of full-resolution J-resolved 1H NMR projections of biofluids for metabonomics information retrieval and biomarker identification.

    PubMed

    Fonville, Judith M; Maher, Anthony D; Coen, Muireann; Holmes, Elaine; Lindon, John C; Nicholson, Jeremy K

    2010-03-01

    Spectroscopic profiling of biological samples is an integral part of metabolically driven top-down systems biology and can be used for identifying biomarkers of toxicity and disease. However, optimal biomarker information recovery and resonance assignment still pose significant challenges in NMR-based complex mixture analysis. The reduced signal overlap as achieved when projecting two-dimensional (2D) J-resolved (JRES) NMR spectra can be exploited to mitigate this problem and, here, full-resolution (1)H JRES projections have been evaluated as a tool for metabolic screening and biomarker identification. We show that the recoverable information content in JRES projections is intrinsically different from that in the conventional one-dimensional (1D) and Carr-Purcell-Meiboom-Gill (CPMG) spectra, because of the combined result of reduction of the over-representation of highly split multiplet peaks and relaxation editing. Principal component and correlation analyses of full-resolution JRES spectral data demonstrated that peak alignment is necessary. The application of statistical total correlation spectroscopy (STOCSY) to JRES projections improved the identification of previously overlapped small molecule resonances in JRES (1)H NMR spectra, compared to conventional 1D and CPMG spectra. These approaches are demonstrated using a galactosamine-induced hepatotoxicity study in rats and show that JRES projections have a useful and complementary role to standard one-dimensional experiments in complex mixture analysis for improved biomarker identification.

  7. Quantitative analysis of four major diterpenoids in Andrographis paniculata by 1H NMR and its application for quality control of commercial preparations.

    PubMed

    Yang, Minghua; Wang, Junsong; Kong, Lingyi

    2012-11-01

    A quantitative proton nuclear magnetic resonance technique (qHNMR) has been successfully introduced to quantify andrographolide, dehydroandrographolide, deoxyandrographolide and neoandrographolide in Andrographis paniculata, a commonly used important traditional Chinese medicine. Creative use of trifluoroacetic acid-d, which satisfactorily resolved the overlapping signals of these compounds in crowded regions of δ 4.5-5.6 ppm in (1)H NMR spectrum, made their quantification possible. Optimization of other experimental conditions, including internal standard, NMR pulse sequence, and NMR relaxation delay time, finally established the (1)H NMR based quantification approach, which was validated with satisfactory accuracy, precision, repeatability, and recovery. Except for deoxyandrographolide and neoandrographolide in two compound recipes, this method was successfully applied to quantify the four major components in fourteen raw herb materials and five commercial preparations, providing quantification results in good agreement with those determined by HPLC. The inherent advantages of qHNMR, such as its rapidity and simplicity, make itself a feasible alternative to HPLC for the quality control of A. paniculata raw material and herbal preparations.

  8. Measurement of the 14N nuclear quadrupole resonance frequencies by the solid effect

    NASA Astrophysics Data System (ADS)

    Seliger, J.; Žagar, V.

    2008-07-01

    1H- 14N nuclear quadrupole double resonance using magnetic field cycling between high and low magnetic field and solid effect in the low magnetic field is analyzed in details. The transition probabilities per unit time for the solid-effect transitions are calculated. The double resonance spectra are calculated in the limiting cases of fast and slow nitrogen spin-lattice relaxation. The double resonance spectra are measured in histamine and quinolinic acid. The experimental spectra are analyzed and the 14N NQR frequencies are determined.

  9. Spectroscopic and theoretical study on the interaction between diperoxovanadate and oxazole

    NASA Astrophysics Data System (ADS)

    Zeng, Birong; Zhu, Xiongbin; Yu, Xianyong; Cai, Shuhui; Chen, Zhong

    2008-01-01

    Detailed investigations were carried out to explore the interaction systems of NH 4VO 3/H 2O 2/oxazole in aqueous solution under physiological conditions by a combined use of multinuclear NMR ( 1H, 13C, 14N and 51V), diffusion ordered spectroscopy (DOSY), variable temperature NMR, electrospray ionization mass spectrometry (ESI-MS), spin-lattice relaxation and density functional calculations. The results indicated the formation of a new peroxovanadate species [OV(O 2) 2(oxazole)] - with oxazole coordinating to vanadium through nitrogen atom. The solution structure of the new species was predicted from theoretical calculations.

  10. Synthesis of chlorambucil-tempol adduct and its delivery using fluoroalkyl double-ended poly (ethylene glycol) micelles.

    PubMed

    Prabhutendolkar, Anuja; Liu, Xiangli; Mathias, Errol V; Ba, Yong; Kornfield, Julie A

    2006-01-01

    In our pursuit to find potent anticancer drugs, we have covalently bonded free radical tempol to chlorambucil giving a chlorambucil-tempol (CT) adduct in which both of the anticancer active sites in tempol and chlorambucil were left intact. Analysis using NMR, Maldi-TOF, and EPR verified the designed chemical structure. Because the CT adduct is more hydrophobic than chlorambucil, its delivery also was investigated using fluoroalkyl double-ended poly (ethylene glycol) (Rf-PEG) micelles. Results from EPR spectra and(19) F and(1) H NMR spin lattice relaxation times show that the Rf-PEG micelles are able to encapsulate CT into the Rf cores of the micelles.

  11. BOOK REVIEW: Magnetohydrodynamics of Plasma Relaxation

    NASA Astrophysics Data System (ADS)

    Connor, J. W.

    1998-06-01

    This monograph on magnetohydrodynamic (MHD) relaxation in plasmas by Ortolani and Schnack occupies a fascinating niche in the plasma physics literature. It is rare in the complex and often technically sophisticated subject of plasma physics to be able to isolate a topic and deal with it comprehensively in a mere 180 pages. Furthermore, it brings a refreshingly original and personal approach to the treatment of plasma relaxation, synthesizing the experiences of the two authors to produce a very readable account of phenomena appearing in such diverse situations as laboratory reversed field pinches (RFPs) and the solar corona. Its novelty lies in that, while it does acknowledge the seminal Taylor theory of relaxation as a general guide, it emphasizes the role of large scale numerical MHD simulations in developing a picture for the relaxation phenomena observed in experiment and nature. Nevertheless, the volume has some minor shortcomings: a tendency to repetitiveness and some omissions that prevent it being entirely self-contained. The monograph is divided into nine chapters, with the first a readable, `chatty', introduction to the physics and phenomena of relaxation discussed in the later chapters. Chapter 2 develops the tools for describing relaxation processes, namely the resistive MHD model, leading to a discussion of resistive instabilities and the stability properties of RFPs. This chapter demonstrates the authors' confessed desire to avoid mathematical detail with a rather simplified discussion of Δ' and magnetic islands; it also sets the stage for their own belief, or thesis, that numerical simulation of the non-linear consequences of the MHD model is the best approach to explaining the physics of relaxation. Nevertheless, in Chapter 3 they provide a reasonably good account and critique of one analytic approach that is available, and which is the commonly accepted picture for relaxation in pinches - the Taylor relaxation theory based on the conservation of

  12. Solid state and solution properties of lanthanide(III) complexes of a tetraiminodiphenolate macrocyclic ligand. X-ray structure, 1H NMR and luminescence spectral studies

    NASA Astrophysics Data System (ADS)

    Bag, Pradip; Dutta, Supriya; Flörke, Ulrich; Nag, Kamalaksha

    2008-11-01

    The lanthanide(III) complexes of composition [Ln(LH 2)(H 2O) 3Cl]Cl 2 (Ln = La-Lu and Y, 1- 15) derived from the tetraiminodiphenolate macrocyclic ligand L 2- have been prepared and characterized. In these compounds, the two uncoordinated imine nitrogens of the macrocycle are protonated and hydrogen-bonded with the metal-bound phenolate oxygens and thereby provide a zwitterionic structure to the ligand. The X-ray crystal structure of the compounds of La and Nd have been determined and they are found to be isostructural. The coordination polyhedra for the eight-coordinated metal centre in the complex cation [Ln(N 2O 2)(O 3Cl)] 2+ can be described as distorted square antiprism. Intermolecular hydrogen-bondings involving the three coordinated water molecules and the two uncoordinated chloride ions give rise to the 2-D network in which the chlorides are triply hydrogen-bridged and the water molecules are doubly hydrogen-bridged. Moreover, the aromatic rings in this network are involved in π-π interaction in two different ways. 1H NMR spectra of the complexes in (CD 3) 2SO have been studied. The spectral assignments for the paramagnetic complexes of Ce-Eu have been made from { 1H- 1H} COSY spectra and longitudinal relaxation time ( T1) measurements. It is inferred that the complex species [Ln(LH 2){(CD 3) 2SO} 4] 3+ that exist in solution are isostructural for the compounds of La-Eu. The contact and pseudo-contact contribution to the isotropic paramagnetic shifts in the complexes of Ce-Eu have been estimated. The luminescence spectra of the complexes of La, Sm, Eu and Tb have been studied in methanol-ethanol (1:4) glassy matrix and in the solid state at 77 K, and the quantum yields have been estimated.

  13. Molecular Structures from [superscript 1]H NMR Spectra: Education Aided by Internet Programs

    ERIC Educational Resources Information Center

    Debska, Barbara; Guzowska-Swider, Barbara

    2007-01-01

    The article presents the way in which freeware Internet programs can be applied to teach [superscript 1]H NMR spectroscopy. The computer programs described in this article are part of the educational curriculum that explores spectroscopy and spectra interpretation. (Contains 6 figures.)

  14. Simultaneous imaging of 13C metabolism and 1H structure: technical considerations and potential applications.

    PubMed

    Gordon, Jeremy W; Fain, Sean B; Niles, David J; Ludwig, Kai D; Johnson, Kevin M; Peterson, Eric T

    2015-05-01

    Real-time imaging of (13)C metabolism in vivo has been enabled by recent advances in hyperpolarization. As a result of the inherently low natural abundance of endogenous (13)C nuclei, hyperpolarized (13)C images lack structural information that could be used to aid in motion detection and anatomical registration. Motion before or during the (13)C acquisition can therefore result in artifacts and misregistration that may obscure measures of metabolism. In this work, we demonstrate a method to simultaneously image both (1)H and (13)C nuclei using a dual-nucleus spectral-spatial radiofrequency excitation and a fully coincident readout for rapid multinuclear spectroscopic imaging. With the appropriate multinuclear hardware, and the means to simultaneously excite and receive on both channels, this technique is straightforward to implement requiring little to no increase in scan time. Phantom and in vivo experiments were performed with both Cartesian and spiral trajectories to validate and illustrate the utility of simultaneous acquisitions. Motion compensation of dynamic metabolic measurements acquired during free breathing was demonstrated using motion tracking derived from (1)H data. Simultaneous multinuclear imaging provides structural (1)H and metabolic (13)C images that are correlated both spatially and temporally, and are therefore amenable to joint (1)H and (13)C analysis and correction of structure-function images.

  15. Antifungal properties of wheat histones (H1-H4) and purified wheat histone H1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wheat (Triticum sp.) histones H1, H2, H3, and H4 were extracted. H1 was further purified. Their activities against fungi with varying degrees of wheat pathogenicity were determined. They included Aspergillus flavus, A. fumigatus, A. niger, F. oxysporum, F. verticillioides, F. solani, F. graminearu...

  16. 32 CFR 1630.15 - Class 1-H: Registrant not subject to processing for induction.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... for induction. 1630.15 Section 1630.15 National Defense Other Regulations Relating to National Defense... induction. In Class 1-H shall be placed any registrant who is not eligible for Class 1-A and is not currently subject to processing for induction....

  17. 32 CFR 1630.15 - Class 1-H: Registrant not subject to processing for induction.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... for induction. 1630.15 Section 1630.15 National Defense Other Regulations Relating to National Defense... induction. In Class 1-H shall be placed any registrant who is not eligible for Class 1-A and is not currently subject to processing for induction....

  18. NMR resonance splitting of urea in stretched hydrogels: proton exchange and (1)H/(2)H isotopologues.

    PubMed

    Kuchel, Philip W; Naumann, Christoph; Chapman, Bogdan E; Shishmarev, Dmitry; Håkansson, Pär; Bacskay, George; Hush, Noel S

    2014-10-01

    Urea at ∼12 M in concentrated gelatin gel, that was stretched, gave (1)H and (2)H NMR spectral splitting patterns that varied in a predictable way with changes in the relative proportions of (1)H2O and (2)H2O in the medium. This required consideration of the combinatorics of the two amide groups in urea that have a total of four protonation/deuteration sites giving rise to 16 different isotopologues, if all the atoms were separately identifiable. The rate constant that characterized the exchange of the protons with water was estimated by back-transformation analysis of 2D-EXSY spectra. There was no (1)H NMR spectral evidence that the chiral gelatin medium had caused in-equivalence in the protons bonded to each amide nitrogen atom. The spectral splitting patterns in (1)H and (2)H NMR spectra were accounted for by intra-molecular scalar and dipolar interactions, and quadrupolar interactions with the electric field gradients of the gelatin matrix, respectively.

  19. Investigation of 1H MRS for quantification of hepatic triglyceride in lean and obese cats.

    PubMed

    Clark, M H; Larsen, R; Lu, W; Hoenig, M

    2013-10-01

    (1)H magnetic resonance spectroscopy ((1)H MRS) is the preferred technique for noninvasive quantification of hepatic triglyceride in humans. Domestic cats are subject to liver lipid accumulation, but MRS has not been investigated for quantification of liver fat in cats. The purpose of this project was to explore a technique for (1)H MRS measurement of hepatic triglyceride in lean and obese cats. Hepatic (1)H MRS was performed, using a 3T imaging unit and a single-voxel spin-echo spectroscopy sequence, on 6 lean (3.3-4.6 kg) and 12 obese cats (5.2-9.8 kg). Median liver fat percentages in lean and obese cats were 1.3% and 6.8%, respectively. Results are biologically plausible, based on chemical assay in a separate group of cats; however, full validation of the method is necessary before other conclusions can be drawn. This report should provide a foundation for the further development of spectroscopic techniques for studying hepatic lipid accumulation in cats.

  20. Experimental test of Bell's inequality via the 1H(d,2He)n reaction

    SciTech Connect

    Saito, T.; Sakai, H.; Kuboki, H.; Sasano, M.; Yako, K.; Ikeda, T.; Itoh, K.; Kawabata, T.; Maeda, Y.; Suda, K.; Uesaka, T.; Matsui, N.; Satou, Y.; Sekiguchi, K.; Tamii, A.

    2005-05-06

    To test Bell's inequality, measurements of spin correlations between two protons in the spin singlet state have been performed. Proton pairs in the singlet state were produced by the 1H(d,2He)n reaction at Ed = 270 MeV.

  1. Complete Assignment of (1)H-NMR Resonances of the King Cobra Neurotoxin CM-11.

    PubMed

    Pang, Yu-Xi; Liu, Wei-Dong; Liu, Ai-Zhuo; Pei, Feng-Kui

    1997-01-01

    The king cobra (Ophiophagus Hannah) neurotoxin CM-Il is long-chain peptide with 72 amino acid residues. Its complete assignment of (1)H-NMR resonances was obtained using various 2D-NMR technologies, including DQF-COSY, clean-TOCSY and NOESY.

  2. Synthesis of stereospecifically deuterated desoxypodophyllotoxins and 1H-nmr assignment of desoxypodophyllotoxin

    NASA Technical Reports Server (NTRS)

    Pullockaran, A. J.; Kingston, D. G.; Lewis, N. G.

    1989-01-01

    [4 beta- 2H1]Desoxypodophyllotoxin [3], [4 alpha- 2H1]desoxypodophyllotoxin [4], and [4, 4- 2 H2]desoxypodophyllotoxin [9] were prepared from podophyllotoxin [1] via its chloride [5]. A complete assignment of the 1H-nmr spectrum of desoxypodophyllotoxin [2] was made on the basis of the spectra of the deuterated compounds [3] and [4].

  3. Aminosilanes derived from 1H-benzimidazole-2(3H)-thione

    SciTech Connect

    Palomo-Molina, Juliana; García-Báez, Efrén V.; Pineda-Urbina, Kayim; Ramos-Organillo, Angel

    2015-08-12

    In two trimethylsilyl-substituted 1H-benzimidazole-2(3H)-thiones, noncovalent C—H⋯π interactions between the centroid of the benzmidazole system and the SiMe{sub 3} groups form helicoidal arrangements in one, and dimerization results in the formation of R{sub s} {sup 2}(8) rings via N—H⋯S interactions, along with parallel π–π interactions between imidazole and benzene rings, in the second compound. Two new molecular structures, namely 1,3-bis(trimethylsilyl)-1H-benzimidazole-2(3H)-thione, C{sub 13}H{sub 22}N{sub 2}SSi{sub 2}, (2), and 1-trimethylsilyl-1H-benzimidazole-2(3H)-thione, C{sub 10}H{sub 14}N{sub 2}SSi, (3), are reported. Both systems were derived from 1H-benzimidazole-2(3H)-thione. Noncovalent C—H⋯π interactions between the centroid of the benzmidazole system and the SiMe{sub 3} groups form helicoidal arrangements in (2). Dimerization of (3) results in the formation of R{sub 2}{sup 2}(8) rings via N—H⋯S interactions, along with parallel π–π interactions between imidazole and benzene rings.

  4. Synthesis of 1H-indazoles from N-tosylhydrazones and nitroaromatic compounds.

    PubMed

    Liu, Zhenxing; Wang, Long; Tan, Haocheng; Zhou, Shiyi; Fu, Tianren; Xia, Ying; Zhang, Yan; Wang, Jianbo

    2014-05-21

    A new method for the synthesis of 1H-indazoles from readily available N-tosylhydrazones and nitroaromatic compounds has been developed. This transformation occurs under transition-metal-free conditions and shows a wide substrate scope. The method has been successfully applied to the formal synthesis of a bioactive compound, WAY-169916.

  5. Synthesis of 1H-Indazoles from Imidates and Nitrosobenzenes via Synergistic Rhodium/Copper Catalysis.

    PubMed

    Wang, Qiang; Li, Xingwei

    2016-05-06

    Nitrosobenzenes have been used as a convenient aminating reagent for the efficient synthesis of 1H-indazoles via rhodium and copper catalyzed C-H activation and C-N/N-N coupling. The reaction occurred under redox-neutral conditions with high efficiency and functional group tolerance. Moreover, a rhodacyclic imidate complex has been identified as a key intermediate.

  6. One-pot synthesis of novel 2,3-dihydro-1H-indazoles.

    PubMed

    Breton, Gary W; Lepore, Antonio J

    2011-11-16

    A copper(I)-mediated one-pot synthesis of 2,3-dihydro-1H-indazole heterocycles has been developed. This synthetic route provides the desired indazoles in moderate to good yields (55%-72%) which are substantially better than those achievable with an alternative two-step reaction sequence. The reaction is tolerant of functionality on the aromatic ring.

  7. Mutations in the tail domain of DYNC1H1 cause dominant spinal muscular atrophy

    PubMed Central

    Harms, M.B.; Ori-McKenney, K.M.; Scoto, M.; Tuck, E.P.; Bell, S.; Ma, D.; Masi, S.; Allred, P.; Al-Lozi, M.; Reilly, M.M.; Miller, L.J.; Jani-Acsadi, A.; Pestronk, A.; Shy, M.E.; Muntoni, F.; Vallee, R.B.

    2012-01-01

    Objective: To identify the gene responsible for 14q32-linked dominant spinal muscular atrophy with lower extremity predominance (SMA-LED, OMIM 158600). Methods: Target exon capture and next generation sequencing was used to analyze the 73 genes in the 14q32 linkage interval in 3 SMA-LED family members. Candidate gene sequencing in additional dominant SMA families used PCR and pooled target capture methods. Patient fibroblasts were biochemically analyzed. Results: Regional exome sequencing of all candidate genes in the 14q32 interval in the original SMA-LED family identified only one missense mutation that segregated with disease state—a mutation in the tail domain of DYNC1H1 (I584L). Sequencing of DYNC1H1 in 32 additional probands with lower extremity predominant SMA found 2 additional heterozygous tail domain mutations (K671E and Y970C), confirming that multiple different mutations in the same domain can cause a similar phenotype. Biochemical analysis of dynein purified from patient-derived fibroblasts demonstrated that the I584L mutation dominantly disrupted dynein complex stability and function. Conclusions: We demonstrate that mutations in the tail domain of the heavy chain of cytoplasmic dynein (DYNC1H1) cause spinal muscular atrophy and provide experimental evidence that a human DYNC1H1 mutation disrupts dynein complex assembly and function. DYNC1H1 mutations were recently found in a family with Charcot-Marie-Tooth disease (type 2O) and in a child with mental retardation. Both of these phenotypes show partial overlap with the spinal muscular atrophy patients described here, indicating that dynein dysfunction is associated with a range of phenotypes in humans involving neuronal development and maintenance. PMID:22459677

  8. MTR and In-vivo 1H-MRS studies on mouse brain with parkinson's disease

    NASA Astrophysics Data System (ADS)

    Yoon, Moon-Hyun; Kim, Hyeon-Jin; Chung, Jin-Yeung; Doo, Ah-Reum; Park, Hi-Joon; Kim, Seung-Nam; Choe, Bo-Young

    2012-12-01

    The aim of this study was to investigate whether the changes in the magnetization transfer ratio (MTR) histogram are related to specific characteristics of Parkinson's disease (PD) and to investigate whether the MTR histogram parameters are associated with neurochemical dysfunction by performing in vivo proton magnetic resonance spectroscopy (1H-MRS). MTR and in vivo 1H-MRS studies were performed on control mice (n = 10) and 1-methyl-1,2,3,6-tetrahydropyridine intoxicated mice (n = 10). All the MTR and in vivo 1H-MRS experiments were performed on a 9.4 T MRI/MRS system (Bruker Biospin, Germany) using a standard head coil. The protondensity fast spin echo (FSE) images and the T2-weighted spin echo (SE) images were acquired with no gap. Outer volume suppression (OVS), combined with the ultra-short echo-time stimulated echo acquisition mode (STEAM), was used for the localized in-vivo 1H-MRS. The quantitative analysis of metabolites was performed from the 1H spectra obtained in vivo on the striatum (ST) by using jMRUI (Lyon, France). The peak height of the MTR histograms in the PD model group was significantly lower than that in the control group (p < 0.05). The midbrain MTR values for volume were lower in the PD group than the control group(p < 0.05). The complex peak (Glx: glutamine+glutamate+ GABA)/creatine (Cr) ratio of the right ST in the PD group was significantly increased as compared to that of the control group. The present study revealed that the peak height of the MTR histogram was significantly decreased in the ST and substantia nigra, and a significant increase in the Gl x /Cr ratio was found in the ST of the PD group, as compared with that of the control group. These findings could reflect the early phase of neuronal dysfunction of neurotransmitters.

  9. Novel mutations expand the clinical spectrum of DYNC1H1-associated spinal muscular atrophy

    PubMed Central

    Scoto, Mariacristina; Rossor, Alexander M.; Harms, Matthew B.; Cirak, Sebahattin; Calissano, Mattia; Robb, Stephanie; Manzur, Adnan Y.; Martínez Arroyo, Amaia; Rodriguez Sanz, Aida; Mansour, Sahar; Fallon, Penny; Hadjikoumi, Irene; Klein, Andrea; Yang, Michele; De Visser, Marianne; Overweg-Plandsoen, W.C.G. (Truus); Baas, Frank; Taylor, J. Paul; Benatar, Michael; Connolly, Anne M.; Al-Lozi, Muhammad T.; Nixon, John; de Goede, Christian G.E.L.; Foley, A. Reghan; Mcwilliam, Catherine; Pitt, Matthew; Sewry, Caroline; Phadke, Rahul; Hafezparast, Majid; Chong, W.K. “Kling”; Mercuri, Eugenio; Baloh, Robert H.; Reilly, Mary M.

    2015-01-01

    Objective: To expand the clinical phenotype of autosomal dominant congenital spinal muscular atrophy with lower extremity predominance (SMA-LED) due to mutations in the dynein, cytoplasmic 1, heavy chain 1 (DYNC1H1) gene. Methods: Patients with a phenotype suggestive of a motor, non–length-dependent neuronopathy predominantly affecting the lower limbs were identified at participating neuromuscular centers and referred for targeted sequencing of DYNC1H1. Results: We report a cohort of 30 cases of SMA-LED from 16 families, carrying mutations in the tail and motor domains of DYNC1H1, including 10 novel mutations. These patients are characterized by congenital or childhood-onset lower limb wasting and weakness frequently associated with cognitive impairment. The clinical severity is variable, ranging from generalized arthrogryposis and inability to ambulate to exclusive and mild lower limb weakness. In many individuals with cognitive impairment (9/30 had cognitive impairment) who underwent brain MRI, there was an underlying structural malformation resulting in polymicrogyric appearance. The lower limb muscle MRI shows a distinctive pattern suggestive of denervation characterized by sparing and relative hypertrophy of the adductor longus and semitendinosus muscles at the thigh level, and diffuse involvement with relative sparing of the anterior-medial muscles at the calf level. Proximal muscle histopathology did not always show classic neurogenic features. Conclusion: Our report expands the clinical spectrum of DYNC1H1-related SMA-LED to include generalized arthrogryposis. In addition, we report that the neurogenic peripheral pathology and the CNS neuronal migration defects are often associated, reinforcing the importance of DYNC1H1 in both central and peripheral neuronal functions. PMID:25609763

  10. A Comparative Evaluation of Three Relaxation Training Procedures.

    ERIC Educational Resources Information Center

    Brandon, Jeffrey E.

    Comparison was made between the effectiveness of three relaxation training procedures: (1) Behavioral Relaxation Training, which consisted of training in relaxing specific parts of the body and controlling breathing; (2) Meditation (based on Benson's procedure for eliciting the relaxation response); and (3) Seashore Sounds "Attention Focusing,"…

  11. Electrical Relaxation in Rare Earth Doped Cubic Lead Fluoride.

    DTIC Science & Technology

    1982-11-01

    PAGE (W v,. Data Fleted ) READ INSTRUCTIONSREPORT DOCUMENTATION PAGE BEFRE CMPETINGFORSORE OMPLETIN FO M 1. REPORT NUMBER j2. GOVT ACCESSION NO. 3...For the smallest rare earths, however, at least nine .* relaxations are found. The concentration studies indicate multiple relaxations for certain...relaxations are found. The concentration studies indicate multiple relaxations for certain sites. Both simple sites and clusters are observed for

  12. Fractal geometry impact on nuclear relaxation in irregular pores.

    PubMed

    Sapoval, B; Russ, S; Petit, D; Korb, J P

    1996-01-01

    We apply a fractal description of pore surface irregularity to study the nuclear relaxation of a confined liquid. From the introduction of a length characteristic of diffusive and surface relaxing properties we describe three different relaxation regimes. These regimes show that the nuclear relaxation can be drastically modified by pore surface irregularity.

  13. Structural, electronic and vibrational properties of N,N'-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN2) crystal.

    PubMed

    Colle, Renato; Grosso, Giuseppe; Cassinese, Antonio; Centore, Roberto

    2013-09-21

    We present a theoretical and experimental investigation of the crystalline structure of N,N'-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN2) that has been deduced combining experimental XRD data, obtained from powders, with global-optimization algorithms which allow to identify Bravais lattice, primitive cell parameters, and space group of the crystal. The XRD spectrum calculated for the proposed crystalline structure very well reproduces the measured XRD data. Our results suggest the triclinic lattice structure of spatial groups P1 and P1, respectively, for the crystalline PDI-FCN2-1,7 and PDI-FCN2-1,6 isomers. In both cases, the primitive cell contains a single molecule. On the proposed crystalline structures, KS-DFT cell energy calculations, including van der Waals interactions, have been performed to assign the minimum energy geometrical structure and orientation of the molecule inside the corresponding primitive cell. These calculations evidence the molecular packing that characterizes the strong anisotropy of the PDI-FCN2 crystal. Electronic band-structures calculated for both isomers within the Kohn-Sham density-functional theory indicate that the crystalline P1 structure is an indirect gap semiconductor, while the P1 structure is a direct gap semiconductor. The electronic band structure calculations on the optimized crystal geometries highlight strong anisotropy in the dispersion curves E(k), which roots at the molecular packing in the crystal. Finally, the vibrational spectrum of both crystalline isomers has been calculated in the harmonic approximation and the dominant vibrational frequencies have been associated to collective motions of selected atoms in the molecules.

  14. Structural, electronic and vibrational properties of N,N'-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN2) crystal

    NASA Astrophysics Data System (ADS)

    Colle, Renato; Grosso, Giuseppe; Cassinese, Antonio; Centore, Roberto

    2013-09-01

    We present a theoretical and experimental investigation of the crystalline structure of N,N'-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN2) that has been deduced combining experimental XRD data, obtained from powders, with global-optimization algorithms which allow to identify Bravais lattice, primitive cell parameters, and space group of the crystal. The XRD spectrum calculated for the proposed crystalline structure very well reproduces the measured XRD data. Our results suggest the triclinic lattice structure of spatial groups Poverline{1} and P1, respectively, for the crystalline PDI-FCN2-1,7 and PDI-FCN2-1,6 isomers. In both cases, the primitive cell contains a single molecule. On the proposed crystalline structures, KS-DFT cell energy calculations, including van der Waals interactions, have been performed to assign the minimum energy geometrical structure and orientation of the molecule inside the corresponding primitive cell. These calculations evidence the molecular packing that characterizes the strong anisotropy of the PDI-FCN2 crystal. Electronic band-structures calculated for both isomers within the Kohn-Sham density-functional theory indicate that the crystalline Poverline{1} structure is an indirect gap semiconductor, while the P1 structure is a direct gap semiconductor. The electronic band structure calculations on the optimized crystal geometries highlight strong anisotropy in the dispersion curves E(k), which roots at the molecular packing in the crystal. Finally, the vibrational spectrum of both crystalline isomers has been calculated in the harmonic approximation and the dominant vibrational frequencies have been associated to collective motions of selected atoms in the molecules.

  15. Evidence for a conserved binding motif of the dinuclear metal site in mammalian and plant purple acid phosphatases: 1H NMR studies of the di-iron derivative of the Fe(III)Zn(II) enzyme from kidney bean.

    PubMed

    Battistuzzi, G; Dietrich, M; Löcke, R; Witzel, H

    1997-05-01

    The di-iron core of mammalian purple acid phosphatases has been reproduced in the plant enzyme from kidney bean (Mr 111000) upon insertion of an Fe(II) ion in place of the native zinc(II) in the dinuclear Fe(III)Zn(II) core. The shortening of the electronic relaxation time of the metal centre allows detection of hyperfine-shifted 1H NMR resonances, although severe broadening due to Curie relaxation prevents independent signal assignment. Nevertheless, comparison of the spectral features of the structurally characterized plant enzyme with those of the mammalian species, which were previously extensively assigned, is consistent with a close similarity of the metal-binding sites, also suggested by previous sequence-alignment studies. Some differences appear to be mainly localized at the M(II) site. Spectral comparison was also carried out on the Fe(III)Co(II) derivatives.

  16. Backbone 1H, 13C and 15N assignments of YibK and avariant containing a unique cysteine residue at C-terminus in 8 M urea-denatured states [corrected].

    PubMed

    Hsieh, Shu-Ju Micky; Mallam, Anna L; Jackson, Sophie E; Hsu, Shang-Te Danny

    2014-10-01

    YibK is a tRNA methyltransferase from Haemophilus influenzae, which forms a stable homodimer in solution and contains a deep trefoil 31 knot encompassing the C-terminal helix that threads through a long loop. It has been a model system for investigating knotted protein folding pathways. Recent data have shown that the polypeptide chain of YibK remains loosely knotted under highly denaturing conditions. Here, we report (1)H, (13)C and (15)N chemical shift assignments for YibK and its variant in the presence of 8 M urea. This work forms the basis for further analysis using NMR techniques such as paramagnetic relaxation enhancement, residual dipolar couplings and spin-relaxation dynamics analysis.

  17. {sup 1}H NMR relaxometry as an indicator of setting and water depletion during cement hydration

    SciTech Connect

    Wang, Biyun; Faure, Paméla; Thiéry, Mickaël; Baroghel-Bouny, Véronique

    2013-03-15

    Proton nuclear magnetic resonance relaxometry has been used to detect setting and microstructure evolution during cement hydration. NMR measurements were performed since casting, during setting and until hardening (from 0 to 3 days). The mobility of water molecules was assessed by an analysis focused on the diagram of longitudinal relaxation time T{sub 1} generated by an Inversion Recovery sequence. The initial stiffening of the solid network was identified by an analysis of the relaxation rate 1/T{sub 1}. The kinetics of water depletion was investigated by using a simple one-pulse acquisition sequence. In parallel, conventional techniques (Vicat needle and temperature monitoring), as well as numerical simulations of hydration, were used to complement and validate these NMR results. Cement pastes and mortars with different water-to-cement ratios made of grey or white OPCs were tested. Furthermore, the effects of the addition of sand, super-plasticizer and silica fume on the hydration kinetics were investigated.

  18. Convex relaxations for gas expansion planning

    SciTech Connect

    Borraz-Sanchez, Conrado; Bent, Russell Whitford; Backhaus, Scott N.; Hijazi, Hassan; Van Hentenryck, Pascal

    2016-01-01

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

  19. Doppler effect induced spin relaxation boom

    NASA Astrophysics Data System (ADS)

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-03-01

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.

  20. Doppler effect induced spin relaxation boom.

    PubMed

    Zhao, Xinyu; Huang, Peihao; Hu, Xuedong

    2016-03-21

    We study an electron spin qubit confined in a moving quantum dot (QD), with our attention on both spin relaxation, and the product of spin relaxation, the emitted phonons. We find that Doppler effect leads to several interesting phenomena. In particular, spin relaxation rate peaks when the QD motion is in the transonic regime, which we term a spin relaxation boom in analogy to the classical sonic boom. This peak indicates that a moving spin qubit may have even lower relaxation rate than a static qubit, pointing at the possibility of coherence-preserving transport for a spin qubit. We also find that the emitted phonons become strongly directional and narrow in their frequency range as the qubit reaches the supersonic regime, similar to Cherenkov radiation. In other words, fast moving excited spin qubits can act as a source of non-classical phonons. Compared to classical Cherenkov radiation, we show that quantum dot confinement produces a small but important correction on the Cherenkov angle. Taking together, these results have important implications to both spin-based quantum information processing and coherent phonon dynamics in semiconductor nanostructures.