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Sample records for spinning nmr investigation

  1. Theoretical investigations of quantum correlations in NMR multiple-pulse spin-locking experiments

    Science.gov (United States)

    Gerasev, S. A.; Fedorova, A. V.; Fel'dman, E. B.; Kuznetsova, E. I.

    2018-04-01

    Quantum correlations are investigated theoretically in a two-spin system with the dipole-dipole interactions in the NMR multiple-pulse spin-locking experiments. We consider two schemes of the multiple-pulse spin-locking. The first scheme consists of π /2-pulses only and the delays between the pulses can differ. The second scheme contains φ-pulses (0Quantum discord is obtained for the first scheme of the multiple-pulse spin-locking experiment at different temperatures.

  2. NMR Investigation of beta-Substituted High-Spin and Low-Spin Iron(III) Tetraphenylporphyrins.

    Science.gov (United States)

    Wojaczynski, Jacek; Latos-Grazynski, Lechoslaw; Hrycyk, Witold; Pacholska, Ewa; Rachlewicz, Krystyna; Szterenberg, Ludmila

    1996-11-06

    The NMR spectra of a series of beta-substituted iron(III) tetraphenylporphyrin (2-X-TPP) complexes have been studied to elucidate the relationship between the electron donating/withdrawing properties of the 2-substituent and the (1)H NMR spectral pattern. The electronic nature of the substituent has been significantly varied and covered the -0.6 to 0.8 Hammett constant range. Both high-spin and low-spin complexes of the general formula (2-X-TPP)Fe(III)Cl and [(2-X-TPP)Fe(III)(CN)(2)](-) have been investigated. The (1)H NMR data for the following substituents (X) have been reported: py(+), NO(2), CN, CH(3), BzO (C(6)H(5)COO), H, D, Br, Cl, CH(3), NH(2), NH(3)(+), NHCH(3), OH, and O(-). The (1)H NMR resonances for low-spin dicyano complexes have been completely assigned by a combination of two-dimensional COSY and NOESY experiments. In the case of selected high-spin complexes, the 3-H resonance has been identified by the selective deuteration of all but the 3-H position. The pattern of unambiguously assigned seven pyrrole resonances reflects the asymmetry imposed by 2-substitution and has been used as an unique (1)H NMR spectroscopic probe to map the spin density distribution. The pyrrole isotropic shifts of [(2-X-TPP)Fe(III)(CN)(2)](-) are dominated by the contact term. In order to quantify the substituent effect, the dependence of isotropic shift of all low-spin pyrrole resonances and 3-H high-spin pyrrole resonance versus Hammett constants has been studied. The electronic effect is strongly localized at the beta-substituted pyrrole. The major change of the isotropic shift has also been noted for only one of two adjacent pyrrole rings, i.e., at 7-H and 8-H positions. These neighboring protons, located on a single pyrrole ring, experienced opposite shift changes when electron withdrawing/donating properties were modified. Two other pyrrole rings for all investigated derivatives revealed considerably smaller, substituent related, isotropic shift changes. A long

  3. Investigation of Sodium Distribution in Phosphate Glasses Using Spin-Echo {sup 23}Na NMR

    Energy Technology Data Exchange (ETDEWEB)

    ALAM, TODD M.; BOYLE, TIMOTHY J.; BROW, RICHARD K.; CLICK, CAROL C.; CONZONE, SAM; McLAUGHLIN, JAY; ZWANZIGER, JOE

    1999-09-16

    The spatial arrangement of sodium cations for a series of sodium phosphate glasses, xNa{sub 2}O(100-x)P{sub 2}O{sub 5} (x<55), were investigated using {sup 23}Na spin-echo NMR spectroscopy. The spin-echo decay rate is a function of the Na-Na homonuclear dipolar coupling and is related to the spatial proximity of neighboring Na nuclei. The spin-echo decay rate in these sodium phosphate glasses increases non-linearly with higher sodium number density, and thus provides a measure of the Na-Na extended range order. The results of these {sup 23}Na NMR experiments are discussed within the context of several structural models, including a decimated crystal lattice model, cubic dilation lattice model, a hard sphere (HS) random distribution model and a pair-wise cluster hard sphere model. While the experimental {sup 23}Na spin-echo M{sub 2} are described adequately by both the decimated lattice and the random HS model, it is demonstrated that the slight non-linear behavior of M{sub 2} as a function of sodium number density is more correctly described by the random distribution in the HS model. At low sodium number densities the experimental M{sub 2} is inconsistent with models incorporating Na-Na clustering. The ability to distinguish between Na-Na clusters and non-clustered distributions becomes more difficult at higher sodium concentrations.

  4. NMR investigations of surfaces and interfaces using spin-polarized xenon

    Energy Technology Data Exchange (ETDEWEB)

    Gaede, Holly Caroline [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-07-01

    129Xe NMR is potentially useful for the investigation of material surfaces, but has been limited to high surface area samples in which sufficient xenon can be loaded to achieve acceptable signal to noise ratios. In Chapter 2 conventional 129Xe NMR is used to study a high surface area polymer, a catalyst, and a confined liquid crystal to determine the topology of these systems. Further information about the spatial proximity of different sites of the catalyst and liquid crystal systems is determined through two dimensional exchange NMR in Chapter 3. Lower surface area systems may be investigated with spin-polarized xenon, which may be achieved through optical pumping and spin exchange. Optically polarized xenon can be up to 105times more sensitive than thermally polarized xenon. In Chapter 4 highly polarized xenon is used to examine the surface of poly(acrylonitrile) and the formation of xenon clathrate hydrates. An attractive use of polarized xenon is as a magnetization source in cross polarization experiments. Cross polarization from adsorbed polarized xenon may allow detection of surface nuclei with drastic enhancements. A non-selective low field thermal mixing technique is used to enhance the 13C signal of CO2 of xenon occluded in solid CO2 by a factor of 200. High-field cross polarization from xenon to proton on the surface of high surface area polymers has enabled signal enhancements of ~1,000. These studies, together with investigations of the efficiency of the cross polarization process from polarized xenon, are discussed in Chapter 5. Another use of polarized xenon is as an imaging contrast agent in systems that are not compatible with traditional contrast agents. The resolution attainable with this method is determined through images of structured phantoms in Chapter 6.

  5. Exploring the Structure of a DNA Hairpin with the Help of NMR Spin-Spin Coupling Constants: An Experimental and Quantum Chemical Investigation

    Czech Academy of Sciences Publication Activity Database

    Sychrovský, Vladimír; Vacek, Jaroslav; Hobza, Pavel; Žídek, L.; Sklenář, V.; Cremer, D.

    2002-01-01

    Roč. 106, - (2002), s. 10242-10250 ISSN 1089-5639 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : DNA * help of NMR spin-spin coupling constants * quantum chemical investigation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.765, year: 2002

  6. Concentration profiling in rat tissue by high-resolution magic-angle spinning NMR spectroscopy: investigation of a model drug.

    Science.gov (United States)

    Lucas, Laura H; Wilson, Sarah F; Lunte, Craig E; Larive, Cynthia K

    2005-05-01

    The utility of high-resolution magic-angle spinning (HR-MAS) NMR for studying drug delivery in whole tissues was explored by dosing female Sprague-Dawley rats with topical or injectable benzoic acid (BA). In principle, HR-MAS NMR permits the detection of both intra- and extracellular compounds. This is an advantage over the previous detection of topically applied BA using microdialysis coupled to HPLC/UV as microdialysis samples only the extracellular space. Skin and muscle samples were analyzed by (1)H HR-MAS NMR, and BA levels were determined using an external standard solution added to the sample rotor. One to two percent of the BA topical dose was detected in the muscle, showing that BA penetrated through the dermal and subcutaneous layers. Since BA was not detected in the muscle in the microdialysis studies, the NMR spectra revealed the intracellular localization of BA. The amount of BA detected in muscle after subcutaneous injection correlated with the distance from the dosing site. Overall, the results suggest that HR-MAS NMR can distinguish differences in the local concentration of BA varying with tissue type, dosage method, and tissue proximity to the dosing site. The results illustrate the potential of this technique for quantitative analysis of drug delivery and distribution and the challenges to be addressed as the method is refined.

  7. 139La NMR investigation of the charge and spin order in a La1.885Sr0.115CuO4 single crystal

    Science.gov (United States)

    Arsenault, A.; Takahashi, S. K.; Imai, T.; He, W.; Lee, Y. S.; Fujita, M.

    2018-02-01

    139La NMR is suited for investigations into magnetic properties of La2CuO4 -based cuprates in the vicinity of their magnetic instabilities, owing to the modest hyperfine interactions between 139La nuclear spins and Cu electron spins. We report comprehensive 139La NMR measurements on a single-crystal sample of high-Tc superconductor La1.885Sr0.115CuO4 in a broad temperature range across the charge and spin order transitions (Tcharge≃80 K, Tspinneutron≃Tc=30 K). From the high-precision measurements of the linewidth for the nuclear spin Iz=+1 /2 to -1 /2 central transition, we show that paramagnetic line broadening sets in precisely at Tcharge due to enhanced spin correlations within the CuO2 planes. Additional paramagnetic line broadening ensues below ˜35 K, signaling that Cu spins in some segments of CuO2 planes are on the verge of three-dimensional magnetic order. A static hyperfine magnetic field arising from ordered Cu moments along the a b plane, however, begins to develop only below Tspinμ S R=15 -20 K, where earlier muon spin rotation measurements detected Larmor precession for a small volume fraction (˜20 % ) of the sample. Based on the measurement of 139La nuclear-spin-lattice relaxation rate 1 /T1 , we also show that charge order triggers enhancement of low-frequency Cu spin fluctuations inhomogeneously; a growing fraction of 139La sites is affected by enhanced low-frequency spin fluctuations toward the eventual magnetic order, whereas a diminishing fraction continues to exhibit a behavior analogous to the optimally superconducting phase even below Tcharge. These 139La NMR results corroborate our recent 63Cu NMR observation that a very broad, anomalous winglike signal gradually emerges below Tcharge, whereas the normally behaving, narrower main peak is gradually wiped out [T. Imai et al., Phys. Rev. B 96, 224508 (2017), 10.1103/PhysRevB.96.224508]. Furthermore, we show that the enhancement of low-energy spin excitations in the low-temperature regime

  8. Possible quadrupolar nematic phase in the frustrated spin chain LiCuSbO4: An NMR investigation

    Science.gov (United States)

    Bosiočić, M.; Bert, F.; Dutton, S. E.; Cava, R. J.; Baker, P. J.; Požek, M.; Mendels, P.

    2017-12-01

    The frustrated one-dimensional quantum magnet LiCuSbO4 is a rare realization of the J1-J2 spin chain model with an easily accessible saturation field, formerly estimated at 12 T. Exotic multipolar nematic phases were theoretically predicted in such compounds just below the saturation field, but without unambiguous experimental observation so far. In this paper we present extensive experimental research on the compound in a wide temperature (30 mK to 300 K) and field (0-13.3 T) range by muon spin rotation (μ SR ), 7Li nuclear magnetic resonance (NMR), and magnetic susceptibility (SQUID). μ SR experiments in zero magnetic field demonstrate the absence of long-range 3D ordering down to 30 mK. Together with former heat capacity data [Dutton et al., Phys. Rev. Lett. 108, 187206 (2012), 10.1103/PhysRevLett.108.187206], magnetic susceptibility measurements suggest a short-range-correlated vector chiral phase in the field range 0-4 T. At the intermediate-field values (5-12 T), the system enters a 3D-ordered spin density wave phase with 0.75 μB per copper site at lowest temperatures (125 mK), estimated by NMR. At still higher field, the magnetization is found to be saturated above 13 T where the spin lattice T1-1 relaxation reveals a spin gap estimated at 3.2(2) K. We narrow down the possibility of observing a multipolar nematic phase to the range 12.5-13 T.

  9. Probing Spin Crossover in a Solution by Paramagnetic NMR Spectroscopy.

    Science.gov (United States)

    Pavlov, Alexander A; Denisov, Gleb L; Kiskin, Mikhail A; Nelyubina, Yulia V; Novikov, Valentin V

    2017-12-18

    Spin transitions in spin-crossover compounds are now routinely studied in the solid state by magnetometry; however, only a few methods exist for studies in solution. The currently used Evans method, which relies on NMR spectroscopy to measure the magnetic susceptibility, requires the availability of a very pure sample of the paramagnetic compound and its exact concentration. To overcome these limitations, we propose an alternative NMR-based technique for evaluating spin-state populations by only using the chemical shifts of a spin-crossover compound; those can be routinely obtained for a solution that contains unknown impurities and paramagnetic admixtures or is contaminated otherwise.

  10. Investigation of zeolites by solid state quadrapole NMR

    International Nuclear Information System (INIS)

    Janssen, R.

    1990-01-01

    The subject of this thesis is the NMR investigation of zeolites. The nature and properties of zeolites are discussed. Some of the basic priniples of NMR techniques on quadrupole nuclei are presented. A special technique, namely a two-dimensional nutation experiment is discussed in detail. The theory of the nutation experiment for quadrupole spin species with spin quantum number 3/2 as well as 5/2 is presented. For both spin spcies the theoretical spectra are compared with experimental results. It is also shown that the nutation expeirment can be performed with several pulse schemes. It is shown how phase-sensitive pure-absorption nutation spectra can be obtained and an NMR-probe is presented that is capable of performing NMR experiments at high (up to 500 degree C) temperatures. The two-dimensional nutation NMR technique has been applied to sodium cations in zeolite NaA. For this purpose a numbre of zeolite samples were prepared that contained different amounts of water. With the aid of nutation NMR the hydration of the zeolite can be studied and conclusions can be drawn about the symmetry of the surrounding of the sodium cations. With the aid of an extension of the nutation NMR experiment: Rotary Echo Nutation NMR, it is shown that in zeolite NaA, in various stages of hydration, the sodium cations or water molecules are mobile. Proof is given by means of high-temperature 23 Na-NMR that dehydrates zeolite NaA undergoes a phase transition at ca. 120 degree C. In a high-temperature NMR investigation of zeolite ZSM-5 it is shown that the sodium ions start to execute motions when the temperature is increased. (author). 198 refs.; 72 figs.; 6 tabs

  11. Investigation of Silica-Supported Vanadium Oxide Catalysts by High-Field 51 V Magic-Angle Spinning NMR

    Energy Technology Data Exchange (ETDEWEB)

    Jaegers, Nicholas R.; Wan, Chuan; Hu, Mary Y.; Vasiliu, Monica; Dixon, David A.; Walter, Eric; Wachs, Israel E.; Wang, Yong; Hu, Jian Zhi

    2017-03-14

    Supported V2O5/SiO2 catalysts were studied using solid state 51V MAS NMR at a sample spinning rate of 36 kHz and at a magnetic field of 19.975 T for a better understanding of the coordination of the vanadium oxide as a function of environmental conditions . Structural transformations of the supported vanadium oxide species between the catalyst in the dehydrated state and hydrated state under an ambient environment were revisited to examine the degree of oligomerization and the effect of water. The experimental results indicate the existence of a single dehydrated surface vanadium oxide species that resonates at -675 ppm and two vanadium oxide species under ambient conditions that resonate at -566 and -610 ppm, respectively. No detectable structural difference was found as a function of vanadium oxide loading on SiO2 (3% V2O5/SiO2 and 8% V2O5/SiO2). Quantum chemistry simulations of the 51V NMR chemical shifts on predicted surface structures were used as an aide in understanding potential surface vanadium oxide species on the silica support. The results suggest the formation of isolated surface VO4 units for the dehydrated catalysts with the possibility of dimer and cyclic trimer presence. The absence of bridging V-O-V vibrations (~200-300 cm-1) in the Raman spectra [Gao et al. J. Phys. Chem. B 1998, 102, 10842-10852], however, indicates that the isolated surface VO4 sites are the dominant dehydrated surface vanadia species on silica. Upon exposure to water, hydrolysis of the bridging V-O-Si bonds is most likely responsible for the decreased electron shielding experienced by vanadium. No indicators for the presence of hydrated decavanadate clusters or hydrated vanadia gels previously proposed in the literature were detected in this study.

  12. High-resolution magic angle spinning proton NMR analysis of human prostate tissue with slow spinning rates.

    Science.gov (United States)

    Taylor, Jennifer L; Wu, Chin-Lee; Cory, David; Gonzalez, R Gilberto; Bielecki, Anthony; Cheng, Leo L

    2003-09-01

    The development of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy for intact tissue analysis and the correlations between the measured tissue metabolites and disease pathologies have inspired investigations of slow-spinning methodologies to maximize the protection of tissue pathology structures from HR-MAS centrifuging damage. Spinning sidebands produced by slow-rate spinning must be suppressed to prevent their complicating the spectral region of metabolites. Twenty-two human prostatectomy samples were analyzed on a 14.1T spectrometer, with HR-MAS spinning rates of 600 Hz, 700 Hz, and 3.0 kHz, a repetition time of 5 sec, and employing various rotor-synchronized suppression methods, including DANTE, WATERGATE, TOSS, and PASS pulse sequences. Among them, DANTE, as the simplest scheme, has shown the most potential in suppression of tissue water signals and spinning sidebands, as well as in quantifying metabolic concentrations. Copyright 2003 Wiley-Liss, Inc.

  13. NMR studies of selective population inversion and spin clustering

    Energy Technology Data Exchange (ETDEWEB)

    Baum, J.S.

    1986-02-01

    This work describes the development and application of selective excitation techniques in Nuclear Magnetic Resonance. Composite pulses and multiple-quantum methods are used to accomplish various goals, such as broadband and narrowband excitation in liquids, and collective excitation of groups of spins in solids. These methods are applied to a variety of problems, including non-invasive spatial localization, spin cluster size characterization in disordered solids and solid state NMR imaging.

  14. NMR studies of selective population inversion and spin clustering

    International Nuclear Information System (INIS)

    Baum, J.S.

    1986-02-01

    This work describes the development and application of selective excitation techniques in Nuclear Magnetic Resonance. Composite pulses and multiple-quantum methods are used to accomplish various goals, such as broadband and narrowband excitation in liquids, and collective excitation of groups of spins in solids. These methods are applied to a variety of problems, including non-invasive spatial localization, spin cluster size characterization in disordered solids and solid state NMR imaging

  15. Spin coherence transfer in chemical transformations monitoredNMR

    Energy Technology Data Exchange (ETDEWEB)

    Anwar, Sabieh M.; Hilty, Christian; Chu, Chester; Bouchard,Louis-S.; Pierce, Kimberly L.; Pines, Alexander

    2006-07-31

    We demonstrate the use of micro-scale nuclear magneticresonance (NMR) for studying the transfer of spin coherence innon-equilibrium chemical processes, using spatially separated NMRencoding and detection coils. As an example, we provide the map ofchemical shift correlations for the amino acid alanine as it transitionsfrom the zwitterionic to the anionic form. Our method is unique in thesense that it allows us to track the chemical migration of encodednuclear spins during the course of chemical transformations.

  16. Recent advances in solid-state NMR spectroscopy of spin I=1/2 nuclei.

    Science.gov (United States)

    Lesage, Anne

    2009-08-28

    This perspective contains a brief review of some of the most recent developments in solid-state NMR spectroscopy of spin I = 1/2 nuclei. Over the last few years, methodological advances have concerned both (1)H and lower gamma spin I = 1/2 nuclei (i.e. (13)C) and have led to the introduction of sophisticated high-resolution techniques that allow the structural investigation at an atomic level of wider and wider classes of materials. Significant developments have thus been reported in the characterisation of crystalline organic molecules, notably with the de novo structure determination of powders at natural isotopic abundance essentially by NMR alone. Key advances have been made in parallel in the structural characterisation of inorganic or hybrid frameworks, often in combination with first principle calculation of the NMR observed. Finally, progress has been reported in the structural investigation of proteins, which are not amenable to solution NMR or X-ray crystallography.

  17. Analysis of NMR shifts and spin-spin coupling constants in L-Alanyl-LAlanine zwitterion

    Czech Academy of Sciences Publication Activity Database

    Sychrovský, Vladimír; Špirko, Vladimír; Šebestík, Jaroslav; Kapitán, Josef; Buděšínský, Miloš; Bouř, Petr

    2005-01-01

    Roč. 59, 7/8 (2005), s. 453 ISSN 0009-4293. [International Conference on the Applications of Density Functional Theory in Chemistry and Physics /11./. 11.09.2005-15.09.2005, Geneva] Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR shifts * spin-spin coupling Subject RIV: CF - Physical ; Theoretical Chemistry

  18. Polymers under mechanical stress- an NMR investigation

    Energy Technology Data Exchange (ETDEWEB)

    Boehme, Ute; Scheler, Ulrich [Leibniz Institute of Polymer Research Dresden (Germany); Xu, Bo; Leisen, Johannes; Beckham, Haskell W. [Georgia Institute of Technology, Atlanta, Georgia (United States)

    2010-07-01

    Low-field NMR using permanent magnets in Halbach arrangements permit NMR investigation without the limits present in high-field NMR. The lower field in conjunction with confined stray field permit the application of NMR, in particular relaxation NMR in a stretching apparatus and a rheometer. Crystalline and amorphous fraction of semi-crystalline polymers are distinguished by their transverse relaxation times. Upon mechanical load the relaxation times of the amorphous fraction changes as seen in in-situ measurements on polypropylene rods. During the formation of a neck the crystalline fraction becomes more prominent.

  19. NMR in rotating magnetic fields: Magic angle field spinning

    Energy Technology Data Exchange (ETDEWEB)

    Sakellariou, D.; Meriles, C.; Martin, R.; Pines, A.

    2004-09-10

    Magic angle sample spinning has been one of the cornerstones in high-resolution solid state NMR. Spinning frequencies nowadays have increased by at least one order of magnitude over the ones used in the first experiments and the technique has gained tremendous popularity. It is currently a routine procedure in solid-state NMR, high-resolution liquid-state NMR and solid-state MRI. The technique enhances the spectral resolution by averaging away rank 2 anisotropic spin interactions thereby producing isotropic-like spectra with resolved chemical shifts and scalar couplings. Andrew proposed that it should be possible to induce similar effects in a static sample if the direction of the magnetic field is varied, e.g., magic-angle rotation of the B0 field (B0-MAS) and this has been recently demonstrated using electromagnetic field rotation. Here we discuss on the possibilities to perform field rotation using alternative hardware, together with spectroscopic methods to recover isotropic resolution even in cases where the field is not rotating at the magic angle. Extension to higher magnetic fields would be beneficial in situations where the physical manipulation of the sample is inconvenient or impossible. Such situations occur often in materials or biomedical samples where ''ex-situ'' NMR spectroscopy and imaging analysis is needed.

  20. Manifestations of classical physics in the quantum evolution of correlated spin states in pulsed NMR experiments.

    Science.gov (United States)

    Ligare, Martin

    2016-05-01

    Multiple-pulse NMR experiments are a powerful tool for the investigation of molecules with coupled nuclear spins. The product operator formalism provides a way to understand the quantum evolution of an ensemble of weakly coupled spins in such experiments using some of the more intuitive concepts of classical physics and semi-classical vector representations. In this paper I present a new way in which to interpret the quantum evolution of an ensemble of spins. I recast the quantum problem in terms of mixtures of pure states of two spins whose expectation values evolve identically to those of classical moments. Pictorial representations of these classically evolving states provide a way to calculate the time evolution of ensembles of weakly coupled spins without the full machinery of quantum mechanics, offering insight to anyone who understands precession of magnetic moments in magnetic fields.

  1. NMR evidence for peculiar spin gaps in a doped S=1/2 Heisenberg spin chain

    Energy Technology Data Exchange (ETDEWEB)

    Utz, Yannic; Rudisch, Christian; Hammerath, Franziska; Grafe, Hans-Joachim; Mohan, Ashwin; Ribeiro, Patrick; Hess, Christian; Wolter, Anja; Kataev, Vladislav; Nishimoto, Satoshi; Drechsler, Stefan-Ludwig; Buechner, Bernd [IFW Dresden (Germany); Singh, Surjeet [Indian Institute of Science Education and Research, Pune (India); Saint-Martin, Romuald; Revcolevschi, Alexandre [Laboratoire de Physico-Chimie de l' Etat Solide, Universite Paris-Sud, Orsay (France)

    2012-07-01

    We present {sup 63}Cu Nuclear Magnetic Resonance (NMR) measurements on undoped, Ca-doped and Ni-doped SrCuO{sub 2} single crystals. SrCuO{sub 2} is a good realization of a one-dimensional S=1/2 Heisenberg spin chain. This is manifested by the theoretically-expected temperature-independent NMR spin-lattice relaxation rate T{sub 1}{sup -1}. In Sr{sub 0.9}Ca{sub 0.1}CuO{sub 2} an exponential decrease of T{sub 1}{sup -1} below 90 K evidences the opening of a gap in the spin excitation spectrum, which amounts to {Delta}=50 K. DMRG calculations are presented to discuss the origin of this spin gap. New results on SrCu{sub 0.99}Ni{sub 0.01}O{sub 2} also indicate the presence of a spin gap, which is twice as large as in Sr{sub 0.9}Ca{sub 0.1}CuO{sub 2}, despite the minor doping level of Ni compared to Ca. We discuss different possible impacts of Ca (S=0) and Ni (S=1) doping on structural and magnetic properties of the parent compound.

  2. Spin-rotation and NMR shielding constants in HCl

    International Nuclear Information System (INIS)

    Jaszuński, Michał; Repisky, Michal; Demissie, Taye B.; Komorovsky, Stanislav; Malkin, Elena; Ruud, Kenneth; Garbacz, Piotr; Jackowski, Karol; Makulski, Włodzimierz

    2013-01-01

    The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of 1 H 35 Cl are C Cl   = −53.914 kHz and C H   = 42.672 kHz (for the lowest rovibrational level). For the chlorine shielding constant, the ab initio value computed including the relativistic corrections, σ(Cl) = 976.202 ppm, provides a new absolute shielding scale; for hydrogen we find σ(H) = 31.403 ppm (both at 300 K). Combining the theoretical results with our new gas-phase NMR experimental data allows us to improve the accuracy of the magnetic dipole moments of both chlorine isotopes. For the hydrogen shielding constant, including relativistic effects yields better agreement between experimental and computed values

  3. Spin Liquid State in the 3D Frustrated Antiferromagnet PbCuTe_{2}O_{6}: NMR and Muon Spin Relaxation Studies.

    Science.gov (United States)

    Khuntia, P; Bert, F; Mendels, P; Koteswararao, B; Mahajan, A V; Baenitz, M; Chou, F C; Baines, C; Amato, A; Furukawa, Y

    2016-03-11

    PbCuTe_{2}O_{6} is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu^{2+} ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointing to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T_{1} NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.

  4. Modeling optically pumped NMR and spin polarization in GaAs/AlGaAs quantum wells

    Science.gov (United States)

    Saha, D.; Wood, R.; Tokarski, J. T.; McCarthy, L. A.; Bowers, C. R.; Sesti, E. L.; Hayes, S. E.; Kuhns, P. L.; McGill, S. A.; Reyes, A. R.; Sanders, G. D.; Stanton, C. J.

    2014-08-01

    Optically-pumped nuclear magnetic resonance (OPNMR) spectroscopy is an emerging technique to probe electronic and nuclear spin properties in bulk and quantum well semiconductors. In OPNMR, one uses optical pumping with light to create spin-polarized electrons in a semiconductor. The electron spin can be transferred to the nuclear spin bath through the Fermi contact hyperfine interaction which can then be detected by conventional NMR. The resulting NMR signal can be enhanced four to five orders of magnitude or more over the thermal equilibrium signal. In previous work, we studied OPNMR in bulk GaAs where we investigated the strength of the OPNMR signal as a function of the pump laser frequency. This allowed us to study the spin-split valence band. Here we report on OPNMR studies in GaAs/AlGaAs quantum wells. We focus on theoretical calculations for the average electron spin polarization at different photon energies for different values of external magnetic field in both unstrained and strained quantum wells. Our calculations allow us to identify the Landau level transitions which are responsible for the peaks in the photon energy dependence of the OPNMR signal intensity. The calculations are based on the 8- band Pidgeon-Brown model generalized to include the effects of the quantum confinement potential as well as pseudomorphic strain at the interfaces. Optical properties are calculated within the golden rule approximation. Detailed comparison to experiment allows one to accurately determine valence band spin splitting in the quantum wells including the effects of strain.

  5. A General Protocol for Temperature Calibration of MAS NMR Probes at Arbitrary Spinning Speeds

    Science.gov (United States)

    Guan, Xudong; Stark, Ruth E.

    2010-01-01

    A protocol using 207Pb NMR of solid lead nitrate was developed to determine the temperature of magic-angle spinning (MAS) NMR probes over a range of nominal set temperatures and spinning speeds. Using BioMAS and fastMAS probes with typical sample spinning rates of 8 and 35 kHz, respectively, empirical equations were devised to predict the respective sample temperatures. These procedures provide a straightforward recipe for temperature calibration of any MAS probe. PMID:21036557

  6. 13C solid state NMR investigation of natural resins components

    International Nuclear Information System (INIS)

    Tavares, Maria I.B.; Bathista, Andre L.B.S.; Silva, Emerson O.; Priante Filho, Nicolau; Nogueira, Jose S.

    2001-01-01

    The objective of this work is to establish and analytical methodology as a routine using solid state nuclear magnetic resonance (NMR) techniques to investigate the mainly chemical components presented in natural resins in bulk. And also to evaluate the molecular behaviour of these resins. The routine solid state techniques allow us to assign the main compounds presented in the resins. Therefore, applying specialised techniques, like variable contact time, delayed contact time, dephasing time and proton spin lattice relaxation time in the rotating frame (T 1 H ρ), more information about chemical structure and molecular dynamic is available

  7. Structural investigations of substituted indolizine derivatives by NMR studies

    International Nuclear Information System (INIS)

    Furdui, Bianca; Dinica, Rodica; Demeunynck, Martine; Druta, Ioan

    2008-01-01

    Owing to the increasing importance of indolizine heterocycles in the field of biology and pharmacology we have synthesized and investigated the obtained heterocycles by NMR techniques. In order to investigate the substituent effects on the spectroscopic properties, a series of indolizine derivatives were studied by 1 H-NMR, 13 C-NMR and 2D NMR (GCOSY, GHMBC and GHMQC spectra). (authors)

  8. Alternating spin chain compound AgVOAsO4 probed by 75As NMR

    Science.gov (United States)

    Ahmed, N.; Khuntia, P.; Ranjith, K. M.; Rosner, H.; Baenitz, M.; Tsirlin, A. A.; Nath, R.

    2017-12-01

    75As NMR measurements were performed on a polycrystalline sample of spin-1/2 alternating spin chain Heisenberg antiferromagnet AgVOAsO4. The temperature-dependent NMR shift K (T ) , which is a direct measure of the intrinsic spin susceptibility, agrees very well with the spin-1/2 alternating-chain model, justifying the assignment of the spin lattice. From the analysis of K (T ) , magnetic exchange parameters were estimated as follows: the leading exchange J /kB≃38.4 K and the alternation ratio α =J'/J ≃0.69 . The transferred hyperfine coupling between the 75As nucleus and V4 + spins obtained by comparing the NMR shift with the bulk susceptibility amounts to Ahf≃3.3 TμB. The effect of interchain couplings on the low-temperature activated behavior of K (T ) and the spin-lattice relaxation rate 1 /T1 is identified.

  9. Low-frequency spin dynamics and NMR spin-lattice relaxation in antiferromagnetic rings

    Science.gov (United States)

    Itou, T.; Sagane, T.; Oyamada, A.; Maegawa, S.; Igarashi, S.; Yukawa, Y.

    2011-01-01

    We develop a general theory of the spin dynamics of Heisenberg antiferromagnetic rings (HAFRs) that explains the mechanism of NMR spin-lattice relaxation at low temperatures. In HAFRs, the imaginary parts of the q-summed dynamic spin susceptibilities parallel and perpendicular to an applied static field, χsum∥″(ω) and χsum⊥″(ω), are composed of the sum of many slightly broadened δ-functional modes at many frequencies. The NMR relaxation is caused by the quasielastic mode in χsum∥″(ω) at around zero frequency. This quasielastic mode is characterized by two physical quantities, intensity P0∥ and frequency width Γ0∥. Although P0∥ has to date been assumed to be identical to the uniform static susceptibility, we point out that the two quantities are not identical. Without making this unreliable assumption for P0∥, we demonstrate experimentally how P0∥ and Γ0∥ behave, by analyzing the NMR relaxation rates of two different nuclei, H1 and C13, in a real HAFR. This analysis is more rigorous and thus can be used to estimate Γ0∥ and P0∥ more precisely than previously possible. We find that the temperature dependence of P0∥ exhibits activation-type behavior reflecting the first excitation gap. We also find that Γ0∥ decreases monotonically on cooling but saturates to a nonzero value at zero temperature. This strongly suggests that Γ0∥ is dominated not only by the electron-phonon interactions but also by internanomagnet dipole interactions, which have been neglected to date.

  10. The eigenmode perspective of NMR spin relaxation in proteins

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Yury E., E-mail: shapiro@nmrsgi4.ls.biu.ac.il, E-mail: eva.meirovitch@biu.ac.il; Meirovitch, Eva, E-mail: shapiro@nmrsgi4.ls.biu.ac.il, E-mail: eva.meirovitch@biu.ac.il [The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900-02 (Israel)

    2013-12-14

    We developed in recent years the two-body (protein and probe) coupled-rotator slowly relaxing local structure (SRLS) approach for elucidating protein dynamics from NMR spin relaxation. So far we used as descriptors the set of physical parameters that enter the SRLS model. They include the global (protein-related) diffusion tensor, D{sub 1}, the local (probe-related) diffusion tensor, D{sub 2}, and the local coupling/ordering potential, u. As common in analyzes based on mesoscopic dynamic models, these parameters have been determined with data-fitting techniques. In this study, we describe structural dynamics in terms of the eigenmodes comprising the SRLS time correlation functions (TCFs) generated by using the best-fit parameters as input to the Smoluchowski equation. An eigenmode is a weighted exponential with decay constant given by an eigenvalue of the Smoluchowski operator, and weighting factor determined by the corresponding eigenvector. Obviously, both quantities depend on the SRLS parameters as determined by the SRLS model. Unlike the set of best-fit parameters, the eigenmodes represent patterns of motion of the probe-protein system. The following new information is obtained for the typical probe, the {sup 15}N−{sup 1}H bond. Two eigenmodes, associated with the protein and the probe, dominate when the time scale separation is large (i.e., D{sub 2} ≫ D{sub 1}), the tensorial properties are simple, and the local potential is either very strong or very weak. When the potential exceeds these limits while the remaining conditions are preserved, new eigenmodes arise. The multi-exponentiality of the TCFs is associated in this case with the restricted nature of the local motion. When the time scale separation is no longer large, the rotational degrees of freedom of the protein and the probe become statistically dependent (coupled dynamically). The multi-exponentiality of the TCFs is associated in this case with the restricted nature of both the local and the

  11. The eigenmode perspective of NMR spin relaxation in proteins

    Science.gov (United States)

    Shapiro, Yury E.; Meirovitch, Eva

    2013-12-01

    We developed in recent years the two-body (protein and probe) coupled-rotator slowly relaxing local structure (SRLS) approach for elucidating protein dynamics from NMR spin relaxation. So far we used as descriptors the set of physical parameters that enter the SRLS model. They include the global (protein-related) diffusion tensor, D1, the local (probe-related) diffusion tensor, D2, and the local coupling/ordering potential, u. As common in analyzes based on mesoscopic dynamic models, these parameters have been determined with data-fitting techniques. In this study, we describe structural dynamics in terms of the eigenmodes comprising the SRLS time correlation functions (TCFs) generated by using the best-fit parameters as input to the Smoluchowski equation. An eigenmode is a weighted exponential with decay constant given by an eigenvalue of the Smoluchowski operator, and weighting factor determined by the corresponding eigenvector. Obviously, both quantities depend on the SRLS parameters as determined by the SRLS model. Unlike the set of best-fit parameters, the eigenmodes represent patterns of motion of the probe-protein system. The following new information is obtained for the typical probe, the 15N-1H bond. Two eigenmodes, associated with the protein and the probe, dominate when the time scale separation is large (i.e., D2 ≫ D1), the tensorial properties are simple, and the local potential is either very strong or very weak. When the potential exceeds these limits while the remaining conditions are preserved, new eigenmodes arise. The multi-exponentiality of the TCFs is associated in this case with the restricted nature of the local motion. When the time scale separation is no longer large, the rotational degrees of freedom of the protein and the probe become statistically dependent (coupled dynamically). The multi-exponentiality of the TCFs is associated in this case with the restricted nature of both the local and the global motion. The effects of local

  12. Hydrogen and deuterium NMR of solids by magic angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Eckman, Richard Raymond [Univ. of California, Berkeley, CA (United States)

    1982-10-01

    The nuclear magnetic resonance of solids has long been characterized by very large spectral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. For example, the homonuclear dipolar broadening, HD, for hydrogen is usually several tens of kilohertz. For deuterium, HD is relatively small; however, the quadrupole interaction causes a broadening which can be hundreds of kilohertz in polycrystalline or amorphous solids. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, βm = Arccos(3-1/2), with respect to the direction of the external magnetic field. Two approaches have been developed for each nucleus. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of β. A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when HD was small. This often occurs naturally when the nuclei are semi-dilute or involved in

  13. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Shmyreva, Anna A. [Center for Magnetic Resonance, St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Safdari, Majid; Furó, István [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Dvinskikh, Sergey V., E-mail: sergeid@kth.se [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg 199034 (Russian Federation)

    2016-06-14

    Orders of magnitude decrease of {sup 207}Pb and {sup 199}Hg NMR longitudinal relaxation times T{sub 1} upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX{sub 2} (Me = Pb, Hg and X = Cl, Br, I). In lead(II) halides, the most dramatic decrease of T{sub 1} relative to that in a static sample is in PbI{sub 2}, while it is smaller but still significant in PbBr{sub 2}, and not detectable in PbCl{sub 2}. The effect is magnetic-field dependent but independent of the spinning speed in the range 200–15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  14. NMRbot: Python scripts enable high-throughput data collection on current Bruker BioSpin NMR spectrometers.

    Science.gov (United States)

    Clos, Lawrence J; Jofre, M Fransisca; Ellinger, James J; Westler, William M; Markley, John L

    2013-06-01

    To facilitate the high-throughput acquisition of nuclear magnetic resonance (NMR) experimental data on large sets of samples, we have developed a simple and straightforward automated methodology that capitalizes on recent advances in Bruker BioSpin NMR spectrometer hardware and software. Given the daunting challenge for non-NMR experts to collect quality spectra, our goal was to increase user accessibility, provide customized functionality, and improve the consistency and reliability of resultant data. This methodology, NMRbot, is encoded in a set of scripts written in the Python programming language accessible within the Bruker BioSpin TopSpin ™ software. NMRbot improves automated data acquisition and offers novel tools for use in optimizing experimental parameters on the fly. This automated procedure has been successfully implemented for investigations in metabolomics, small-molecule library profiling, and protein-ligand titrations on four Bruker BioSpin NMR spectrometers at the National Magnetic Resonance Facility at Madison. The investigators reported benefits from ease of setup, improved spectral quality, convenient customizations, and overall time savings.

  15. High resolution magic angle spinning NMR applied to the analysis of organic compounds bound to solid supports.

    Science.gov (United States)

    Espinosa, Juan F

    2011-01-01

    In situ structural characterization of organic compounds attached to solid supports can be achieved by high-resolution magic angle spinning NMR (HRMAS NMR), a technique that provides solution-like spectra for resin-bound molecules. This review outlines the principles of the technique, the influence of the solid support on data quality, and NMR experiments that are useful for obtaining valuable information. The review describes, with multiple examples mainly from the last 7 years, how HRMAS NMR has been applied to monitor solid-phase reactions, elucidate reaction products and quantify compound loading on a solid support. Other applications, such as conformational analysis of immobilized compounds and investigation of molecular interactions with compounds in solution, are also discussed.

  16. Spin Choreography: Basic Steps in High Resolution NMR (by Ray Freeman)

    Science.gov (United States)

    Minch, Michael J.

    1998-02-01

    There are three orientations that NMR courses may take. The traditional molecular structure course focuses on the interpretation of spectra and the use of chemical shifts, coupling constants, and nuclear Overhauser effects (NOE) to sort out subtle details of structure and stereochemistry. Courses can also focus on the fundamental quantum mechanics of observable NMR parameters and processes such a spin-spin splitting and relaxation. More recently there are courses devoted to the manipulation of nuclear spins and the basic steps of one- and two-dimensional NMR experiments. Freeman's book is directed towards the latter audience. Modern NMR methods offer a myriad ways to extract information about molecular structure and motion by observing the behavior of nuclear spins under a variety of conditions. In Freeman's words: "We can lead the spins through an intricate dance, carefully programmed in advance, to enhance, simplify, correlate, decouple, edit or assign NMR spectra." This is a carefully written, well-illustrated account of how this dance is choreographed by pulse programming, double resonance, and gradient effects. Although well written, this book is not an easy read; every word counts. It is recommended for graduate courses that emphasize the fundamentals of magnetic resonance. It is not a text on interpretation of spectra.

  17. NMR with generalized dynamics of spin and spatial coordinates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Jae

    1987-11-01

    This work is concerned with theoretical and experimental aspects of the generalized dynamics of nuclear spin and spatial coordinates under magnetic-field pulses and mechanical motions. The main text begins with an introduction to the concept of ''fictitious'' interactions. A systematic method for constructing fictitious spin-1/2 operators is given. The interaction of spins with a quantized-field is described. The concept of the fictitious interactions under the irradiation of multiple pulses is utilized to design sequences for selectively averaging linear and bilinear operators. Relations between the low-field sequences and high-field iterative schemes are clarified. These relations and the transformation properties of the spin operators are exploited to develop schemes for heteronuclear decoupling of multi-level systems. The resulting schemes are evaluated for heteronuclear decoupling of a dilute spin-1/2 from a spin-1 in liquid crystal samples and from a homonuclear spin-1/2 pair in liquids. A relation between the spin and the spatial variables is discussed. The transformation properties of the spin operators are applied to spatial coordinates and utilized to develop methods for removing the orientational dependence responsible for line broadening in a powder sample. Elimination of the second order quadrupole effects, as well as the first order anisotropies is discussed. It is shown that various sources of line broadening can effectively be eliminated by spinning and/or hopping the sample about judiciously chosen axes along with appropriate radio-frequency pulse sequences.

  18. NMR with generalized dynamics of spin and spatial coordinates

    International Nuclear Information System (INIS)

    Lee, Chang Jae.

    1987-11-01

    This work is concerned with theoretical and experimental aspects of the generalized dynamics of nuclear spin and spatial coordinates under magnetic-field pulses and mechanical motions. The main text begins with an introduction to the concept of ''fictitious'' interactions. A systematic method for constructing fictitious spin-1/2 operators is given. The interaction of spins with a quantized-field is described. The concept of the fictitious interactions under the irradiation of multiple pulses is utilized to design sequences for selectively averaging linear and bilinear operators. Relations between the low-field sequences and high-field iterative schemes are clarified. These relations and the transformation properties of the spin operators are exploited to develop schemes for heteronuclear decoupling of multi-level systems. The resulting schemes are evaluated for heteronuclear decoupling of a dilute spin-1/2 from a spin-1 in liquid crystal samples and from a homonuclear spin-1/2 pair in liquids. A relation between the spin and the spatial variables is discussed. The transformation properties of the spin operators are applied to spatial coordinates and utilized to develop methods for removing the orientational dependence responsible for line broadening in a powder sample. Elimination of the second order quadrupole effects, as well as the first order anisotropies is discussed. It is shown that various sources of line broadening can effectively be eliminated by spinning and/or hopping the sample about judiciously chosen axes along with appropriate radio-frequency pulse sequences

  19. Investigating albendazole desmotropes by solid-state NMR spectroscopy.

    Science.gov (United States)

    Chattah, Ana K; Zhang, Rongchun; Mroue, Kamal H; Pfund, Laura Y; Longhi, Marcela R; Ramamoorthy, Ayyalusamy; Garnero, Claudia

    2015-03-02

    Characterization of the molecular structure and physicochemical solid-state properties of the solid forms of pharmaceutical compounds is a key requirement for successful commercialization as potential active ingredients in drug products. These properties can ultimately have a critical effect on the solubility and bioavailability of the final drug product. Here, the desmotropy of Albendazole forms I and II was investigated at the atomic level. Ultrafast magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy, together with powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectroscopy, were performed on polycrystalline samples of the two solids in order to fully characterize and distinguish the two forms. High-resolution one-dimensional (1)H, (13)C, and (15)N together with two-dimensional (1)H/(1)H single quantum-single quantum, (1)H/(1)H single quantum-double quantum, and (1)H/(13)C chemical shift correlation solid-state NMR experiments under MAS conditions were extensively used to decipher the intramolecular and intermolecular hydrogen bonding interactions present in both solid forms. These experiments enabled the unequivocal identification of the tautomers of each desmotrope. Our results also revealed that both solid forms may be described as dimeric structures, with different intermolecular hydrogen bonds connecting the tautomers in each dimer.

  20. Comparative NMR investigation of the Re-based borides

    Science.gov (United States)

    Lue, C. S.; Tao, Y. F.; Su, T. H.

    2008-07-01

    We report a systematic study of the rhenium-based borides, ReB2 , Re7B3 , and Re3B , by means of the B11 nuclear magnetic resonance (NMR) spectroscopy. While Re7B3 and Re3B are superconductors, ReB2 exhibits no superconducting signature but is of current interest due to its superhard mechanical property. Since the major focus of this investigation is their electronic characteristics in the normal states, we performed the measurements at temperatures between 77 and 295 K. For Re7B3 and Re3B , s -character electrons were found to be responsible for the observed B11 NMR Knight shift and spin-lattice relaxation rate (1/T1) . From T1 analysis, we thus deduce the partial Bs Fermi-level density of states (DOS) of both borides. On the other hand, the relaxation rate of ReB2 is mainly associated with p electrons, similar to the cases of OsB2 and RuB2 . In addition, the extracted B2p Fermi-level DOS is in good agreement with the theoretical prediction from band-structure calculations.

  1. An NMR Investigation of Phase Structure and Chain Dynamics in the Polyethylene/Montmorillonite Nanocomposites

    Directory of Open Access Journals (Sweden)

    Wei Li

    2013-01-01

    Full Text Available Novel exfoliated and interacted polyethylene (PE/montmorillonite (MMT nanocomposites prepared by in situ polymerization were characterized by solid-state nuclear magnetic resonance (NMR. The phase structure and molecular mobility were investigated by proton and carbon NMR under static and magic-angle spinning (MAS conditions. The results showed that incorporation of MMT layer enhanced the polyethylene crystallinity behavior. The chain mobility of crystalline phase, interphase and amorphous phase was hindered in the nanocomposites. The phase structure and chain dynamics were also investigated upon changing the temperature. The orthorhombic and monoclinic phases were detected according to the 13CP/MAS NMR. Quantitative characterization of the phase structure was also conducted by 13C DP/MAS upon changing the temperature. Finally, the difference in the phase structure and chain dynamics in each phase of PE/nanocomposites was compared based on the NMR results when fiber filler was introduced.

  2. NMR in an electric field: A bulk probe of the hidden spin and orbital polarizations

    OpenAIRE

    Ramírez-Ruiz, Jorge; Boutin, Samuel; Garate, Ion

    2017-01-01

    Recent theoretical work has established the presence of hidden spin and orbital textures in non-magnetic materials with inversion symmetry. Here, we propose that these textures can be detected by nuclear magnetic resonance (NMR) measurements carried out in the presence of an electric field. In crystals with hidden polarizations, a uniform electric field produces a staggered magnetic field that points to opposite directions at atomic sites related by spatial inversion. As a result, the NMR res...

  3. LipSpin: A New Bioinformatics Tool for Quantitative 1H NMR Lipid Profiling.

    Science.gov (United States)

    Barrilero, Rubén; Gil, Miriam; Amigó, Núria; Dias, Cintia B; Wood, Lisa G; Garg, Manohar L; Ribalta, Josep; Heras, Mercedes; Vinaixa, Maria; Correig, Xavier

    2018-02-06

    The structural similarity among lipid species and the low sensitivity and spectral resolution of nuclear magnetic resonance (NMR) have traditionally hampered the routine use of 1 H NMR lipid profiling of complex biological samples in metabolomics, which remains mostly manual and lacks freely available bioinformatics tools. However, 1 H NMR lipid profiling provides fast quantitative screening of major lipid classes (fatty acids, glycerolipids, phospholipids, and sterols) and some individual species and has been used in several clinical and nutritional studies, leading to improved risk prediction models. In this Article, we present LipSpin, a free and open-source bioinformatics tool for quantitative 1 H NMR lipid profiling. LipSpin implements a constrained line shape fitting algorithm based on voigt profiles and spectral templates from spectra of lipid standards, which automates the analysis of severely overlapped spectral regions and lipid signals with complex coupling patterns. LipSpin provides the most detailed quantification of fatty acid families and choline phospholipids in serum lipid samples by 1 H NMR to date. Moreover, analytical and clinical results using LipSpin quantifications conform with other techniques commonly used for lipid analysis.

  4. NMR relaxation investigation of the native corn starch structure with plasticizers

    Science.gov (United States)

    Cioica, N.; Fechete, R.; Cota, C.; Nagy, E. M.; David, L.; Cozar, O.

    2013-07-01

    The influences of starch, glycerol and water ratios on the structure, morphology and dynamics of starch polymer chains were investigated by NMR relaxation method. The 1H NMR CPMG echo decays and saturation recovery build-up curves were recorded and analyzed using the UPIN algorithm in order to get the spin-spin T2 and spin-lattice T1 relaxation times distributions. Significant differences between the CPMG curves were observed for native starch and the formulas in which water is added, whether these have or not glycerol in composition. For the formula which contains both plasticizers (water and glycerol), the CPMG curves decay slowly, indicating the presence of more mobile components.

  5. β -detected NMR spin relaxation in a thin film heterostructure of ferromagnetic EuO

    Science.gov (United States)

    MacFarlane, W. A.; Song, Q.; Ingle, N. J. C.; Chow, K. H.; Egilmez, M.; Fan, I.; Hossain, M. D.; Kiefl, R. F.; Levy, C. D. P.; Morris, G. D.; Parolin, T. J.; Pearson, M. R.; Saadaoui, H.; Salman, Z.; Wang, D.

    2015-08-01

    We present β -detected NMR measurements of the spin-lattice relaxation of +8Li implanted into an epitaxial heterostructure based on a 100 nm thick film of ferromagnetic (FM) EuO as a function of temperature through its FM transition. In the FM state, the spin-lattice relaxation rate follows the same temperature dependence, determined by magnon scattering mechanisms, observed in the bulk by 153Eu NMR, but above 40 K, the signal is wiped out. We also find that +8Li stopped in material adjacent to the magnetic layer exhibits spin relaxation related to the critical slowing of the Eu spins. A particularly strong relaxation in the Au overlayer suggests an unusual strong nonlocal coupling mechanism to 8Li in the metal.

  6. Discrimination of Basal Cell Carcinoma from Normal Skin Tissue Using High-Resolution Magic Angle Spinning 1H NMR Spectroscopy.

    Science.gov (United States)

    Mun, Je-Ho; Lee, Heonho; Yoon, Dahye; Kim, Byung-Soo; Kim, Moon-Bum; Kim, Shukmann

    2016-01-01

    High-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy is a useful tool for investigating the metabolism of various cancers. Basal cell carcinoma (BCC) is the most common skin cancer. However, to our knowledge, data on metabolic profiling of BCC have not been reported in the literature. The objective of the present study was to investigate the metabolic profiling of cutaneous BCC using HR-MAS (1)H NMR spectroscopy. HR-MAS (1)H NMR spectroscopy was used to analyze the metabolite profile and metabolite intensity of histopathologically confirmed BCC tissues and normal skin tissue (NST) samples. The metabolic intensity normalized to the total spectral intensities in BCC and NST was compared, and multivariate analysis was performed with orthogonal partial least-squares discriminant analysis (OPLS-DA). P values analysis revealed 9 metabolites that showed statistically significant difference between BCC and NST. In multivariate analysis, the OPLS-DA models built with the HR-MAS NMR metabolic profiles revealed a clear separation of BCC from NST. The receiver operating characteristic curve generated from the results revealed an excellent discrimination of BCC from NST with an area under the curve (AUC) value of 0.961. The present study demonstrated that the metabolite profile and metabolite intensity differ between BCC and NST, and that HR-MAS (1)H NMR spectroscopy can be a valuable tool in the diagnosis of BCC.

  7. Microscopic Displacement Imaging with Pulsed Field Gradient Turbo Spin-Echo NMR

    NARCIS (Netherlands)

    Scheenen, T.W.J.; Dusschoten, van D.; Jager, de P.A.; As, van H.

    2000-01-01

    We present a pulse sequence that enables the accurate and spatially resolved measurements of the displacements of spins in a variety of (biological) systems. The pulse sequence combines pulsed field gradient (PFG) NMR with turbo spin–echo (TSE) imaging. It is shown here that by ensuring that the

  8. High-resolution NMR spectroscopy of biological tissues usingprojected Magic Angle Spinning

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Rachel W.; Jachmann, Rebecca C.; Sakellariou, Dimitris; Nielsen, Ulla Gro; Pines, Alexander

    2005-01-27

    High-resolution NMR spectra of materials subject toanisotropic broadening are usually obtained by rotating the sample aboutthe magic angle, which is 54.7 degrees to the static magnetic field. Inprojected Magic Angle Spinning (p-MAS), the sample is spun about twoangles, neither of which is the magic angle. This provides a method ofobtaining isotropic spectra while spinning at shallow angles. The p-MASexperiment may be used in situations where spinning the sample at themagic angle is not possible due to geometric or other constraints,allowing the choice of spinning angle to be determined by factors such asthe shape of the sample, rather than by the spin physics. The applicationof this technique to bovine tissue samples is demonstrated as a proof ofprinciple for future biological or medical applications.

  9. Microfabricated inserts for magic angle coil spinning (MACS wireless NMR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Vlad Badilita

    Full Text Available This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the "magic angle" of 54.74° with respect to the direction of the magnetic field (magic angle spinning - MAS, accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii given the high spinning rates (tens of kHz involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds.

  10. EPR and NMR spectroscopy on spin-labeled proteins

    NARCIS (Netherlands)

    Finiguerra, Michelina Giuseppina

    2011-01-01

    Spin labeling and electron paramagnetic resonance (EPR) have been employed to study structure and dynamics of proteins. The surface polarity of four single cysteine mutants of the Zn-azurin in frozen solution were studied using 275 GHz EPR (J-band), with the advantage compared to 9 GHz (X-band) and

  11. Nuclear spin singlet states as a contrast mechanism for NMR spectroscopy.

    Science.gov (United States)

    Devience, Stephen J; Walsworth, Ronald L; Rosen, Matthew S

    2013-10-01

    Nuclear magnetic resonance (NMR) spectra of complex chemical mixtures often contain unresolved or hidden spectral components, especially when strong background signals overlap weaker peaks. In this article we demonstrate a quantum filter utilizing nuclear spin singlet states, which allows undesired NMR spectral background to be removed and target spectral peaks to be uncovered. The quantum filter is implemented by creating a nuclear spin singlet state with spin quantum numbers j = 0, mz  = 0 in a target molecule, applying a continuous RF field to both preserve the singlet state and saturate the magnetization of undesired molecules and then mapping the target molecule singlet state back into an NMR observable state so that its spectrum can be read out unambiguously. The preparation of the target singlet state can be carefully controlled with pulse sequence parameters, so that spectral contrast can be achieved between molecules with very similar structures. We name this NMR contrast mechanism 'Suppression of Undesired Chemicals using Contrast-Enhancing Singlet States' (SUCCESS) and we demonstrate it in vitro for three target molecules relevant to neuroscience: aspartate, threonine and glutamine. Copyright © 2013 John Wiley & Sons, Ltd.

  12. SPINS: Standardized ProteIn NMR Storage. A data dictionary and object-oriented relational database for archiving protein NMR spectra

    International Nuclear Information System (INIS)

    Baran, Michael C.; Moseley, Hunter N.B.; Sahota, Gurmukh; Montelione, Gaetano T.

    2002-01-01

    Modern protein NMR spectroscopy laboratories have a rapidly growing need for an easily queried local archival system of raw experimental NMR datasets. SPINS (Standardized ProteIn Nmr Storage) is an object-oriented relational database that provides facilities for high-volume NMR data archival, organization of analyses, and dissemination of results to the public domain by automatic preparation of the header files required for submission of data to the BioMagResBank (BMRB). The current version of SPINS coordinates the process from data collection to BMRB deposition of raw NMR data by standardizing and integrating the storage and retrieval of these data in a local laboratory file system. Additional facilities include a data mining query tool, graphical database administration tools, and a NMRStar v2.1.1 file generator. SPINS also includes a user-friendly internet-based graphical user interface, which is optionally integrated with Varian VNMR NMR data collection software. This paper provides an overview of the data model underlying the SPINS database system, a description of its implementation in Oracle, and an outline of future plans for the SPINS project

  13. Solid state NMR, basic theory and recent progress for quadrupole nuclei with half-integer spin

    International Nuclear Information System (INIS)

    Dieter, F.

    1998-01-01

    This review describes the basic theory and some recently developed techniques for the study of quadrupole nuclei with half integer spins in powder materials. The latter is connected to the introduction of the double rotation (DOR) by A. Samoson et al. (1) and to the introduction of the multiple quantum magic-angle spinning (MQ MAS) technique by L. Frydman et. al. (2). For integer spins, especially the solid-state deuterium magnetic resonance, we refer to the review of G.L. Hoatson and R.L. Vold: '' 2 H-NMR Spectroscopy of Solids and Liquid Crystals'' (3). For single crystals we refer to O. Kanert and M. Mehring: ''Static quadrupole effects in disordered cubic solids''(4) and we would like also to mention the ''classic'' review of M.H. Cohen and F. Reif: ''Quadrupole effects in NMR studies of solids'' (5). Some more recent reviews in the field under study are D. Freude and J. Haase ''Quadrupole effects in solid-state NMR'' (6). Ch. Jager: ''Satellite Transition Spectroscopy of Quadrupolar Nuclei'' (7) and B.F. Chmelka and J.W. Zwanziger: ''Solid State NMR Line Narrowing Methods for Quadrupolar Nuclei - Double Rotation and Dynamic-Angle Spinning'' (8). A survey of nuclear quadrupole frequency data published before the end of 1982 is given by H. Chihara and N. Nakamura in Landolt-Bornstein, Vol. 20 (9). Values of the chemical shift of quadrupole nuclei in solids can be found in books such as ''Multinuclear NMR'' edited by J. Mason (10). In section 9 of ref (6) some electric field gradient and chemical shift data published from 1983 to 1992 for the most studied quadrupole nuclei sup 27 Al, sup 23 Na, and sup 17 O are given

  14. Fast method of NMR imaging based on trains of spin echoes

    International Nuclear Information System (INIS)

    Hennel, F.

    1993-01-01

    A theoretical introduction to Fourier NMR imaging and a discussion of fast methods are presented. Then an application of the method of echo-planar imaging (EPI) with spin echoes in a micro-imaging system is described together with introduced modifications of the sequence. A new technique for the measurement of flow profiles in liquids which results from a modification of x-pulsed EPI is presented. The development of new software for a NMR micro-imaging system is described, too. 51 refs, 29 refs

  15. (S)Pinning down protein interactions by NMR

    DEFF Research Database (Denmark)

    Teilum, Kaare; Kunze, Micha Ben Achim; Erlendsson, Simon

    2017-01-01

    Protein molecules are highly diverse communication platforms and their interaction repertoire stretches from atoms over small molecules such as sugars and lipids to macromolecules. An important route to understanding molecular communication is to quantitatively describe their interactions....... These types of analyses determine the amounts and proportions of individual constituents that participate in a reaction as well as their rates of reactions and their thermodynamics. Although many different methods are available, there is currently no single method able to quantitatively capture and describe...... all types of protein reactions, which can span orders of magnitudes in affinities, reaction rates and lifetimes of states. As the more versatile technique, solution NMR spectroscopy offers a remarkable catalogue of methods that can be successfully applied to the quantitative as well as qualitative...

  16. Coexistence of spin frozen state and persistent spin dynamics in NaSrCo{sub 2}F{sub 7} as probed by μSR and NMR

    Energy Technology Data Exchange (ETDEWEB)

    Dengre, Shanu; Sarkar, Rajib; Braeuninger, Sascha Albert; Brueckner, Felix; Materne, Philipp; Klauss, Hans-Henning [Institute for Solid State Physics, TU Dresden (Germany); Krizan, Jason W.; Cava, Robert J. [Department of Chemistry, Princeton University, Princeton, NJ (United States); Luetkens, Hubertus; Baines, Chris [Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institute, Villigen (Switzerland)

    2016-07-01

    {sup 23}Na -and {sup 19}F NMR, and μSR experiments are performed to explore the microscopic properties of NaSrCo{sub 2}F{sub 7}, which is a newly discovered magnetically frustrated pyrochlore with weak bond disorder and with a frustration index of f = 42. While {sup 23}Na and {sup 19}F NMR experiments clearly suggest the presence of quasi static field distribution below ∝3 K as reflected in the huge NMR line broadening and wipe out effect of NMR signal intensity, μSR experiments on the other hand remains passive to this spin frozen state. Both NMR and μSR results indicate the slowing down of the magnetic (spin) fluctuations upon cooling towards the NMR spin frozen state. μSR relaxation rate increases slightly below ∝ 3 K, and remains not only constant down to 20 mK, but also stands independent in longitudinal magnetic field upto 4000 G implying that the spin fluctuations are dynamic. These observations suggest the coexistence of partial spin frozen state and persistent spin dynamics in NaSrCo{sub 2}F{sub 7}.

  17. Unusual spin frozen state in a frustrated pyrochlore system NaCaCo{sub 2}F{sub 7} as observed by NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, R.; Brueckner, F.; Klauss, H.H. [IFP, TU Dresden (Germany); Krizan, J.W.; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, NJ (United States)

    2016-07-01

    We present {sup 23}Na -and {sup 19}F NMR results on the magnetically frustrated pyrochlore NaCaCo{sub 2}F{sub 7} with a frustration index of f = θ{sub CW}/T{sub f} ∝ 56. Recent neutron scattering experiments proposed XY like antiferromagnetic spin clusters at low energies in NaCaCo{sub 2}F{sub 7}. {sup 23}Na NMR -spectra reveal the presence of two magnetically non equivalent Na sites in conjunction with the local Co{sup 2+} spin structure. Below 3.6 K both the {sup 23}Na -and {sup 19}F spectra broaden due to the formation of static spin correlations. A huge reduction of the {sup 19}F -and {sup 23}Na NMR signal intensity hints at a quasi-static field distribution in NaCaCo{sub 2}F{sub 7} in this regime. The {sup 19}F spin-lattice relaxation rate {sup 19}(1/T{sub 1}) exhibits a peak at around 2.9 K, at the same temperature range where ac and dc susceptibility data show a broad maximum. The character of the spin fluctuation appears to be isotropic. The overall temperature dependence of {sup 19}(1/T{sub 1}) can be described by the BPP theory considering a fluctuating hyperfine field with an autocorrelation function. The correlation time of the autocorrelation function exhibits an activation behavior further indicating the spin-frozen state. While the present NMR studies suggest the spin frozen state at low temperatures, μSR investigations however reveal the presence of so called persistent spin dynamics down to 20 mK implying an exotic ground state in NaCaCo{sub 2}F{sub 7}.

  18. Impurity effects in a S=1/2 Heisenberg spin chain probed by {sup 63}Cu NMR

    Energy Technology Data Exchange (ETDEWEB)

    Utz, Yannic; Bruening, Eva Maria; Hammerath, Franziska; Rudisch, Christian; Grafe, Hans-Joachim; Mohan, Ashwin; Hess, Christian; Nishimoto, Satoshi; Drechsler, Stefan-Ludwig; Buechner, Bernd [IFW Dresden (Germany); Saint-Martin, Romuald; Revcolevschi, Alexandre [LPCES, Orsay (France)

    2013-07-01

    We present {sup 63}Cu NMR measurements on undoped, Ni doped and Mg doped SrCuO{sub 2} single crystals. SrCuO{sub 2} is a good realization of a one-dimensional S=1/2 Heisenberg spin chain. This is confirmed by the theoretically-expected temperature independent NMR spin-lattice relaxation rate T{sup -1}{sub 1}. Doping with Ni, which can be regarded as a S=1 impurity, has a major impact on the magnetic properties of the spin chains. On the one hand, this is manifested by unusual features in the NMR spectra below 100 K, revealing the existence of an impurity-induced local alternating magnetisation. On the other hand, exponentially decaying spin lattice relaxation rates towards low temperatures indicate the opening of a spin gap similar to Ca doped SrCuO{sub 2}. Mg doping (S=0) has, however, no influence on the magnetic properties of the spin chains. Neither the NMR spectra nor the spin lattice relaxation rates differ from those measured on pure SrCuO{sub 2}. While the different impact of Ni and Mg doping on the spin chains could be explained by their different impurity spins, the opening of a spin gap in case of Ni doping is totally unexpected and not yet understood.

  19. Solid and liquid 129Xe NMR signals enhanced by spin-exchange optical pumping under flow

    International Nuclear Information System (INIS)

    Zhou Xin; Luo Jun; Sun Xianping; Zeng Xizhi; Liu Maili; Liu Wuyang

    2002-01-01

    Laser-polarized 129 Xe gas was produced by spin-exchange with Cs atom optically pumped with diode laser array in a low field under flow. The nuclear spin polarizations of the solid and liquid 129 Xe frozen from the laser-polarized 129 Xe gas were 2.16% and 1.45% respectively in the SY-80M NMR spectrometer, which corresponded to the enhancements of 6000 and 5000 compared to those without optical pumping under the same conditions. It could provide the base and possibility for quantum computers using laser-enhanced solid and liquid 129 Xe. Polarization loss of transport and state change was also discussed

  20. Experimental Investigations of Flow past Spinning Cylinders

    Science.gov (United States)

    Carlucci, Pasquale; Buckley, Liam; Mehmedagic, Igbal; Carlucci, Donald; Thangam, Siva

    2015-11-01

    Experimental investigations of flow past spinning cylinders is presented in the context of their application and relevance to flow past projectiles. A subsonic wind tunnel is used to perform experiments on flow past spinning cylinders that are sting-mounted and oriented such that their axis of rotation is aligned with the mean flow. The experiments cover a Reynolds number range of up to 300000 and rotation numbers of up to 2 (based on cylinder diameter). The experimental validation of the tunnel characteristics and the benchmarking of the flow field in the tunnel are described. The experimental results for spinning cylinders with both rear-mounted and fore-mounted stings are presented along with available computational and experimental findings. This work was funded in part by U. S. Army ARDEC.

  1. Structural investigations on betacyanin pigments by LC NMR and 2D NMR spectroscopy.

    Science.gov (United States)

    Stintzing, Florian C; Conrad, Jürgen; Klaiber, Iris; Beifuss, Uwe; Carle, Reinhold

    2004-02-01

    Four betacyanin pigments were analysed by LC NMR and subjected to extensive NMR characterisation after isolation. Previously, low pH values were applied for NMR investigations of betalains resulting in rapid degradation of the purified substances thus preventing extensive NMR studies. Consequently, up to now only one single (13)C NMR spectrum of a betalain pigment, namely that of neobetanin (=14,15-dehydrobetanin), was available. Because of its sufficient stability under highly acidic conditions otherwise detrimental for betacyanins, this pigment remained an exemption. Since betalains are most stable in the pH range of 5-7, a new solvent system has been developed allowing improved data acquisition through improved pigment stability at near neutral pH. Thus, not only (1)H, but for the first time also partial (13)C data of betanin, isobetanin, phyllocactin and hylocerenin isolated from red-purple pitaya [Hylocereus polyrhizus (Weber) Britton & Rose, Cactaceae] could be indirectly obtained by gHSQC- and gHMQC-NMR experiments.

  2. .sup.57./sup.Fe NMR and spin structure of manganese ferrite

    Czech Academy of Sciences Publication Activity Database

    Štěpánková, H.; Sedlák, B.; Chlan, V.; Novák, Pavel; Šimša, Zdeněk

    2008-01-01

    Roč. 77, č. 9 (2008), 092416/1-092419/4 ISSN 1098-0121 R&D Projects: GA ČR GA202/08/0541; GA ČR GA202/06/0051 Institutional research plan: CEZ:AV0Z10100521 Keywords : NMR * manganese ferrite * spin structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

  3. pH control and rapid mixing in spinning NMR samples

    Science.gov (United States)

    Yesinowski, James P.; Sunberg, Richard J.; Benedict, James J.

    An apparatus is described which permits the acquisition of NMR spectra from spinning 20-mm sample tubes while: (1) constantly monitoring the pH; (2) adding reagents to maintain constant pH (pH-statting); (3) efficiently mixing the added reagent. The apparatus was built to study the spontaneous precipitation of calcium phosphates from supersaturated solutions using 31P NMR. Other applications include the rapid determination of NMR titration curves, and the minimization of temperature gradients in large sample tubes. The apparatus was used to measure the 31P chemical shift titration of dilute phosphoric acid, which yielded accurate shifts for the three species of protonated orthophosphate ion. The bulk magnetic susceptibility of 85% H 3PO 4 relative to a dilute aqueous sample was also measured, and is shown to contribute significantly to chemical shift measurements.

  4. Multiple Quantum Coherences (MQ) NMR and Entanglement Dynamics in the Mixed-Three-Spin XXX Heisenberg Model with Single-Ion Anisotropy

    Science.gov (United States)

    Hamid, Arian Zad

    2016-12-01

    We analytically investigate Multiple Quantum (MQ) NMR dynamics in a mixed-three-spin (1/2,1,1/2) system with XXX Heisenberg model at the front of an external homogeneous magnetic field B. A single-ion anisotropy property ζ is considered for the spin-1. The intensities dependence of MQ NMR coherences on their orders (zeroth and second orders) for two pairs of spins (1,1/2) and (1/2,1/2) of the favorite tripartite system are obtained. It is also investigated dynamics of the pairwise quantum entanglement for the bipartite (sub)systems (1,1/2) and (1/2,1/2) permanently coupled by, respectively, coupling constants J}1 and J}2, by means of concurrence and fidelity. Then, some straightforward comparisons are done between these quantities and the intensities of MQ NMR coherences and ultimately some interesting results are reported. We also show that the time evolution of MQ coherences based on the reduced density matrix of the pair spins (1,1/2) is closely connected with the dynamics of the pairwise entanglement. Finally, we prove that one can introduce MQ coherence of the zeroth order corresponds to the pair spins (1,1/2) as an entanglement witness at some special time intervals.

  5. Structural Investigations of Portland Cement Components, Hydration, and Effects of Admixtures by Solid-State NMR Spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen Bengaard; Andersen, Morten D.; Jakobsen, Hans Jørgen

    2006-01-01

    been investigated in detail by 29Si and 27Al MAS NMR where the combination of the results for these spin-nuclei provides important information on the degree of Al-incorporation in the C-S-H structure and of the average chain lengths of tetrahedral SiO4 and AlO4 units. This presentation will illustrate...

  6. Trans and surface membrane bound zervamicin IIB: 13C-MAOSS-NMR at high spinning speed

    International Nuclear Information System (INIS)

    Raap, J.; Hollander, J.; Ovchinnikova, T. V.; Swischeva, N. V.; Skladnev, D.; Kiihne, S.

    2006-01-01

    Interactions between 15 N-labelled peptides or proteins and lipids can be investigated using membranes aligned on a thin polymer film, which is rolled into a cylinder and inserted into the MAS-NMR rotor. This can be spun at high speed, which is often useful at high field strengths. Unfortunately, substrate films like commercially available polycarbonate or PEEK produce severe overlap with peptide and protein signals in 13 C-MAOSS NMR spectra. We show that a simple house hold foil support allows clear observation of the carbonyl, aromatic and C α signals of peptides and proteins as well as the ester carbonyl and choline signals of phosphocholine lipids. The utility of the new substrate is validated in applications to the membrane active peptide zervamicin IIB. The stability and macroscopic ordering of thin PC10 bilayers was compared with that of thicker POPC bilayers, both supported on the household foil. Sidebands in the 31 P-spectra showed a high degree of alignment of both the supported POPC and PC10 lipid molecules. Compared with POPC, the PC10 lipids are slightly more disordered, most likely due to the increased mobilities of the shorter lipid molecules. This mobility prevents PC10 from forming stable vesicles for MAS studies. The 13 C-peptide peaks were selectively detected in a 13 C-detected 1 H-spin diffusion experiment. Qualitative analysis of build-up curves obtained for different mixing times allowed the transmembrane peptide in PC10 to be distinguished from the surface bound topology in POPC. The 13 C-MAOSS results thus independently confirms previous findings from 15 N spectroscopy [Bechinger, B., Skladnev, D.A., Ogrel, A., Li, X., Rogozhkina, E.V., Ovchinnikova, T.V., O'Neil, J.D.J. and Raap, J. (2001) Biochemistry, 40, 9428-9437]. In summary, application of house hold foil opens the possibility of measuring high resolution 13 C-NMR spectra of peptides and proteins in well ordered membranes, which are required to determine the secondary and

  7. Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Kanmi [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    on decoupling efficiency as well as scaling factors. Indirect detection with assistance of PMLGm$\\bar{x}$ during INEPTR transfer proved to offer the highest sensitivity gains of 3-10. In addition, the CRAMPS sequence was applied under fast MAS to increase the 1H resolution during t1 evolution in the traditional, 13C detected HETCOR scheme. Two naturally abundant solids, tripeptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (f-MLF-OH) and brown coal, with well ordered and highly disordered structures, respectively, are studied to confirm the capabilities of these techniques. Concomitantly, a simple optimization of 1H homonuclear dipolar decoupling at MAS rates exceeding 10 kHz was developed (Chapter 4). The fine-tuned decoupling efficiency can be obtained by minimizing the signal loss due to transverse relaxation in a simple spin-echo experiment, using directly the sample of interest. The excellent agreement between observed decoupling pattern and earlier theoretical predictions confirmed the utility of this strategy. The properties of naturally abundant surface-bound fluorocarbon groups in mesoporous silica nanoparticles (MSNs) were investigated by the above-mentioned multidimensional solid-state NMR experiments and theoretical modeling (Chapter 5). Two conformations of (pentafluorophenyl)propyl groups (abbreviated as PFP) were determined as PFP-prone and PFP-upright, whose aromatic rings are located above the siloxane bridges and in roughly upright position, respectively. Several 1D and 2D NMR techniques were implemented in the characterizations, including indirectly detected 1H{l_brace}13C{r_brace} and 19F{l_brace}13C{r_brace} 2D HETCOR, Carr-Purcell-Meiboom-Gill (CPMG) assisted 29Si direct polarization and 29Si19F 2D experiments, 2D double-quantum (DQ) 19F MAS NMR spectra and spin-echo measurements

  8. Degree of Biomimicry of Artificial Spider Silk Spinning Assessed by NMR Spectroscopy.

    Science.gov (United States)

    Otikovs, Martins; Andersson, Marlene; Jia, Qiupin; Nordling, Kerstin; Meng, Qing; Andreas, Loren B; Pintacuda, Guido; Johansson, Jan; Rising, Anna; Jaudzems, Kristaps

    2017-10-02

    Biomimetic spinning of artificial spider silk requires that the terminal domains of designed minispidroins undergo specific structural changes in concert with the β-sheet conversion of the repetitive region. Herein, we combine solution and solid-state NMR methods to probe domain-specific structural changes in the NT2RepCT minispidroin, which allows us to assess the degree of biomimicry of artificial silk spinning. In addition, we show that the structural effects of post-spinning procedures can be examined. By studying the impact of NT2RepCT fiber drying, we observed a reversible beta-to-alpha conversion. We think that this approach will be useful for guiding the optimization of artificial spider silk fibers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. I. Advances in NMR Signal Processing. II. Spin Dynamics in Quantum Dissipative Systems

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yung-Ya [Univ. of California, Berkeley, CA (United States)

    1998-11-01

    Part I. Advances in IVMR Signal Processing. Improvements of sensitivity and resolution are two major objects in the development of NMR/MRI. A signal enhancement method is first presented which recovers signal from noise by a judicious combination of a priordmowledge to define the desired feasible solutions and a set theoretic estimation for restoring signal properties that have been lost due to noise contamination. The effect of noise can be significantly mitigated through the process of iteratively modifying the noisy data set to the smallest degree necessary so that it possesses a collection of prescribed properties and also lies closest to the original data set. A novel detection-estimation scheme is then introduced to analyze noisy and/or strongly damped or truncated FIDs. Based on exponential modeling, the number of signals is detected based on information estimated using the matrix pencil method. theory and the spectral parameters are Part II. Spin Dynamics in body dipole-coupled systems Quantum Dissipative Systems. Spin dynamics in manyconstitutes one of the most fundamental problems in magnetic resonance and condensed-matter physics. Its many-spin nature precludes any rigorous treatment. ‘Therefore, the spin-boson model is adopted to describe in the rotating frame the influence of the dipolar local fields on a tagged spin. Based on the polaronic transform and a perturbation treatment, an analytical solution is derived, suggesting the existence of self-trapped states in the. strong coupling limit, i.e., when transverse local field >> longitudinal local field. Such nonlinear phenomena originate from the joint action of the lattice fluctuations and the reaction field. Under semiclassical approximation, it is found that the main effect of the reaction field is the renormalization of the Hamiltonian of interest. Its direct consequence is the two-step relaxation process: the spin is initially localized in a quasiequilibrium state, which is later detrapped by

  10. Two-dimensional NMR investigations of the dynamic conformations of phospholipids and liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Mei [Univ. of California, Berkeley, CA (United States). Applied Science and Technology

    1996-05-01

    Two-dimensional 13C, 1H, and 31P nuclear magnetic resonance (NMR) techniques are developed and used to study molecular structure and dynamics in liquid-crystalline systems, primarily phospholipids and nematic liquid crystals. NMR spectroscopy characterizes molecular conformation in terms of orientations and distances of molecular segments. In anisotropically mobile systems, this is achieved by measuring motionally-averaged nuclear dipolar couplings and chemical shift anisotropies. The short-range couplings yield useful bond order parameters, while the long-range interactions constrain the overall conformation. In this work, techniques for probing proton dipolar local fields are further developed to obtain highlyresolved dipolar couplings between protons and rare spins. By exploiting variable-angle sample spinning techniques, orientation-sensitive NMR spectra are resolved according to sitespecific isotropic chemical shifts. Moreover, the signs and magnitudes of various short-range dipolar couplings are obtained. They are used in novel theoretical analyses that provide information about segmental orientations and their distributions. Such information is obtained in a model-independent fashion or with physically reasonable assumptions. The structural investigation of phospholipids is focused on the dynam

  11. Multiple acquisitions via sequential transfer of orphan spin polarization (MAeSTOSO): How far can we push residual spin polarization in solid-state NMR?

    Science.gov (United States)

    Gopinath, T; Veglia, Gianluigi

    2016-06-01

    Conventional multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) experiments detect the signal arising from the decay of a single coherence transfer pathway (FID), resulting in one spectrum per acquisition time. Recently, we introduced two new strategies, namely DUMAS (DUal acquisition Magic Angle Spinning) and MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), that enable the simultaneous acquisitions of multidimensional ssNMR experiments using multiple coherence transfer pathways. Here, we combined the main elements of DUMAS and MEIOSIS to harness both orphan spin operators and residual polarization and increase the number of simultaneous acquisitions. We show that it is possible to acquire up to eight two-dimensional experiments using four acquisition periods per each scan. This new suite of pulse sequences, called MAeSTOSO for Multiple Acquisitions via Sequential Transfer of Orphan Spin pOlarization, relies on residual polarization of both (13)C and (15)N pathways and combines low- and high-sensitivity experiments into a single pulse sequence using one receiver and commercial ssNMR probes. The acquisition of multiple experiments does not affect the sensitivity of the main experiment; rather it recovers the lost coherences that are discarded, resulting in a significant gain in experimental time. Both merits and limitations of this approach are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. SOPPA and CCSD vibrational corrections to NMR indirect spin-spin coupling constants of small hydrocarbons

    Science.gov (United States)

    Faber, Rasmus; Sauer, Stephan P. A.

    2015-12-01

    We present zero-point vibrational corrections to the indirect nuclear spin-spin coupling constants in ethyne, ethene, cyclopropene and allene. The calculations have been carried out both at the level of the second order polarization propagator approximation (SOPPA) employing a new implementation in the DALTON program, at the density functional theory level with the B3LYP functional employing also the Dalton program and at the level of coupled cluster singles and doubles (CCSD) theory employing the implementation in the CFOUR program. Specialized coupling constant basis sets, aug-cc-pVTZ-J, have been employed in the calculations. We find that on average the SOPPA results for both the equilibrium geometry values and the zero-point vibrational corrections are in better agreement with the CCSD results than the corresponding B3LYP results. Furthermore we observed that the vibrational corrections are in the order of 5 Hz for the one-bond carbon-hydrogen couplings and about 1 Hz or smaller for the other couplings apart from the one-bond carbon-carbon coupling (11 Hz) and the two-bond carbon-hydrogen coupling (4 Hz) in ethyne. However, not for all couplings lead the inclusion of zero-point vibrational corrections to better agreement with experiment.

  13. SOPPA and CCSD vibrational corrections to NMR indirect spin-spin coupling constants of small hydrocarbons

    International Nuclear Information System (INIS)

    Faber, Rasmus; Sauer, Stephan P. A.

    2015-01-01

    We present zero-point vibrational corrections to the indirect nuclear spin-spin coupling constants in ethyne, ethene, cyclopropene and allene. The calculations have been carried out both at the level of the second order polarization propagator approximation (SOPPA) employing a new implementation in the DALTON program, at the density functional theory level with the B3LYP functional employing also the Dalton program and at the level of coupled cluster singles and doubles (CCSD) theory employing the implementation in the CFOUR program. Specialized coupling constant basis sets, aug-cc-pVTZ-J, have been employed in the calculations. We find that on average the SOPPA results for both the equilibrium geometry values and the zero-point vibrational corrections are in better agreement with the CCSD results than the corresponding B3LYP results. Furthermore we observed that the vibrational corrections are in the order of 5 Hz for the one-bond carbon-hydrogen couplings and about 1 Hz or smaller for the other couplings apart from the one-bond carbon-carbon coupling (11 Hz) and the two-bond carbon-hydrogen coupling (4 Hz) in ethyne. However, not for all couplings lead the inclusion of zero-point vibrational corrections to better agreement with experiment

  14. Probing the flexibility of internal rotation in silylated phenols with the NMR scalar spin-spin coupling constants.

    Science.gov (United States)

    Sychrovský, Vladimír; Benda, Ladislav; Prokop, Alexandr; Blechta, Vratislav; Schraml, Jan; Spirko, Vladimír

    2008-06-12

    The rotation of a trimethylsiloxy (TMSO) group in three silylated phenols (with three different ortho substituents -H, -CH3, and -C(CH3)3) was studied with the NMR (n)J(Si,C), n = 2, 3, 4, 5, scalar spin-spin coupling between the (29)Si nucleus of the TMSO group and the (13)C nuclei of the phenyl ring. The internal rotation potential calculated with the B3LYP and MP2 calculation methods including the effect of a solvent environment (gas phase, chloroform, and water) was used for the calculation of the dynamical averages of the scalar coupling constants in the framework of the rigid-bender formalism. Solvent effects, the quality of the rotational potential, and the applicability of the classical molecular dynamic to the problem is discussed. Quantum effects have a sizable impact on scalar couplings, particularly for the internal rotational states well localized within the wells of the potential surfaces for the TMSO group. The overall difference between the experimental and theoretical scalar couplings calculated for the global energy-minima structures (static model) decreases substantially for both model potentials (B3LYP, MP2) when the molecular motion of the TMSO group is taken into account. The calculated data indicate that the inclusion of molecular motion is necessary for the accurate calculation of the scalar coupling constants and their reliable structural interpretation for any system which possesses a large-amplitude motion.

  15. Magnetization and 13C NMR spin-lattice relaxation of nanodiamond powder

    Energy Technology Data Exchange (ETDEWEB)

    Levin, E.M.; Fang, X.W.; Bud' ko, S.L.; Straszheim, W.E.; McCallum, R.W.; Schmidt-Rohr, K.

    2008-02-15

    The bulk magnetization at temperatures of 1.8-400 K and in magnetic fields up to 70 kOe, the ambient temperature {sup 13}C NMR spin-lattice relaxation, T{sub 1,c}, and the elemental composition of three nanodiamond powder samples have been studied. The total magnetization of nanodiamond can be explained in terms of contributions from (1) the diamagnetic effect of carbon, (2) the paramagnetic effect of unpaired electrons present in nanodiamond grains, and (3) ferromagnetic-like and (4) superparamagnetic contributions from Fe-containing particles detected in spatially resolved energy-dispersive spectroscopy. Contributions (1) and (2) are intrinsic to nanodiamond, while contributions (3) and (4) arise from impurities naturally present in detonation nanodiamond samples. {sup 13}C NMR T{sub 1,c} relaxation would be unaffected by the presence of the ferromagnetic particles with the bulk magnetization of {approx} 0.01 emu/g at 300 K. Thus, a reduction of T{sub 1,c} by 3 orders of magnitude compared to natural and synthetic microdiamonds confirms the presence of unpaired electrons in the nanodiamond grains. The spin concentration in nanodiamond powder corresponds to {approx}30 unpaired electrons per {approx}4.6 nm diameter nanodiamond grain.

  16. Solid-state 13C magic angle spinning NMR spectroscopy characterization of particle size structural variations in synthetic nanodiamonds

    International Nuclear Information System (INIS)

    Alam, Todd M.

    2004-01-01

    Solid-state 13 C magic angle spinning (MAS) NMR spectroscopy has been used to quantify the different carbon species observed in synthetically produced nanodiamonds. Two different diamond-like carbon species were observed using 13 C MAS NMR, which have been attributed to a highly ordered crystalline diamond phase and a disordered crystalline diamond phase. The relative ratio of these different diamond phases was found to vary with the particle size of the nanodiamond materials

  17. Use of earth field spin echo NMR to search for liquid minerals

    Science.gov (United States)

    Stoeffl, Wolfgang

    2001-01-01

    An instrument for measuring the spatial, qualitative and quantitative parameters of an underground nuclear magnetic resonance (NMR) active liquid mineral deposit, including oil and water. A phased array of excitation and receiver antennas on the surface and/or in a borehole excites the NMR active nuclei in the deposit, and using known techniques from magnetic resonance imaging (MRI), the spatial and quantitative distribution of the deposit can be measured. A surface array may utilize, for example, four large (50-500 diameter) diameter wire loops laid on the ground surface, and a weak (1.5-2.5 kHz) alternating current (AC) field applied, matching the NMR frequency of hydrogen in the rather flat and uniform earth magnetic field. For a short duration (a few seconds) an additional gradient field can be generated, superimposed to the earth field, by applying direct current (DC) to the grid (wire loops), enhancing the position sensitivity of the spin-echo and also suppressing large surface water signals by shifting them to a different frequency. The surface coil excitation can be combined with downhole receivers, which are much more radio-quiet compared to surface receivers, and this combination also enhances the position resolution of the MRI significantly. A downhole receiver module, for example, may have a 5.5 inch diameter and fit in a standard six inch borehole having a one-quarter inch thick stainless steel casing. The receiver module may include more than one receiver units for improved penetration and better position resolution.

  18. A low-E magic angle spinning probe for biological solid state NMR at 750 MHz

    Science.gov (United States)

    McNeill, Seth A.; Gor'kov, Peter L.; Shetty, Kiran; Brey, William W.; Long, Joanna R.

    2009-04-01

    Crossed-coil NMR probes are a useful tool for reducing sample heating for biological solid state NMR. In a crossed-coil probe, the higher frequency 1H field, which is the primary source of sample heating in conventional probes, is produced by a separate low-inductance resonator. Because a smaller driving voltage is required, the electric field across the sample and the resultant heating is reduced. In this work we describe the development of a magic angle spinning (MAS) solid state NMR probe utilizing a dual resonator. This dual resonator approach, referred to as "low-E," was originally developed to reduce heating in samples of mechanically aligned membranes. The study of inherently dilute systems, such as proteins in lipid bilayers, via MAS techniques requires large sample volumes at high field to obtain spectra with adequate signal-to-noise ratio under physiologically relevant conditions. With the low-E approach, we are able to obtain homogeneous and sufficiently strong radiofrequency fields for both 1H and 13C frequencies in a 4 mm probe with a 1H frequency of 750 MHz. The performance of the probe using windowless dipolar recoupling sequences is demonstrated on model compounds as well as membrane-embedded peptides.

  19. Polarisation of a spin- {1}/{2} β-NMR probe 11Be using collinear laser optical pumping

    Science.gov (United States)

    Levy, C. D. P.; Pearson, M. R.; Morris, G. D.; Lassen, J.; Chow, K. H.; Hossain, M. D.; Kiefl, R. F.; Labbé, R.; MacFarlane, W. A.; Parolin, T. J.; Root, L.; Saadaoui, H.; Smadella, M.; Wang, D.

    2009-04-01

    Spin {1}/{2} probes have special importance in the field of NMR, since they have no electric quadrupole moment and are thus pure magnetic sensors. The absence of quadrupolar splittings greatly simplifies the NMR frequency spectrum. That the muon is spin {1}/{2} is one of the reasons it has become so useful as a magnetic probe. Until now there has been no spin {1}/{2} probe suitable for beta-detected NMR. Such a probe would be particularly useful in complex materials, which are in general non-cubic. In this paper we describe the development of a low energy beam of spin-polarised 11Be, which is the lightest spin {1}/{2} isotope suitable for β-NMR. The intensity of the 11Be+ beam-generated by a laser ionisation source-is about 106/s. The 11Be nuclei are polarised by collinear laser optical pumping with an externally frequency doubled dye laser tuned to the 2S- 2P transition of 11Be+ at 313 nm.

  20. O17 and V51 NMR for the zigzag spin-1 chain compound CaV2O4

    Science.gov (United States)

    Zong, X.; Suh, B. J.; Niazi, A.; Yan, J. Q.; Schlagel, D. L.; Lograsso, T. A.; Johnston, D. C.

    2008-01-01

    V51 NMR studies on CaV2O4 single crystals and O17 NMR studies on O17 -enriched powder samples are reported. The temperature dependences of the O17 NMR linewidth and nuclear spin-lattice relaxation rate give strong evidence for a long-range antiferromagnetic transition at TN=78K in the powder. Magnetic susceptibility measurements show that TN=69K in the crystals. A zero-field V51 NMR signal was observed at low temperatures ( f≈237MHz at 4.2K ) in the crystals. The field-swept spectra with the field in different directions suggest the presence of two antiferromagnetic substructures. Each substructure is collinear, with the easy axes of the two substructures separated by an angle of 19(1)°, and with their average direction pointing approximately along the b axis of the crystal structure. The two spin substructures contain equal numbers of spins. The temperature dependence of the ordered moment, measured up to 45K , shows the presence of an energy gap EG in the antiferromagnetic spin wave excitation spectrum. Antiferromagnetic spin wave theory suggests that EG/kB lies between 64 and 98K .

  1. Polarisation of a spin-1/2 beta-NMR probe {sup 11}Be using collinear laser optical pumping

    Energy Technology Data Exchange (ETDEWEB)

    Levy, C.D.P., E-mail: levy@triumf.c [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Pearson, M.R.; Morris, G.D.; Lassen, J. [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Chow, K.H. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); Hossain, M.D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Kiefl, R.F. [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Canadian Institute for Advanced Research, 180 Dundas Street West, Toronto, Ontario, M5G 1Z8 (Canada); Labbe, R. [Departement de Physique, Universite Laval, Quebec, G1K 7P4 (Canada); MacFarlane, W.A.; Parolin, T.J. [Chemistry Department, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Root, L. [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Saadaoui, H.; Smadella, M.; Wang, D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

    2009-04-15

    Spin 1/2 probes have special importance in the field of NMR, since they have no electric quadrupole moment and are thus pure magnetic sensors. The absence of quadrupolar splittings greatly simplifies the NMR frequency spectrum. That the muon is spin 1/2 is one of the reasons it has become so useful as a magnetic probe. Until now there has been no spin 1/2 probe suitable for beta-detected NMR. Such a probe would be particularly useful in complex materials, which are in general non-cubic. In this paper we describe the development of a low energy beam of spin-polarised {sup 11}Be, which is the lightest spin 1/2 isotope suitable for beta-NMR. The intensity of the {sup 11}Be{sup +} beam-generated by a laser ionisation source-is about 10{sup 6}/s. The {sup 11}Be nuclei are polarised by collinear laser optical pumping with an externally frequency doubled dye laser tuned to the {sup 2}S{sub 1/2}-{sup 2}P{sub 1/2} transition of {sup 11}Be{sup +} at 313 nm.

  2. Development and Investigation of NMR tools for chiral compound identification

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Todd Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Electronic, Optical and Nano Materials; Lansdon, Rick [Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States)

    2014-09-01

    The goal behind the assigned summer project was to investigate the ability of nuclear magnetic resonance spectroscopy (NMR) to identify enantiomers of select chiral organo-fluorophosphates (OFPs) compounds which are analogs of chemical warfare agents (CWAs, e.g. Sarin). This involved investigations utilizing chiral solvating agents (CSAs) and characterizing the binding phenomena with cyclodextrins. The resolution of OFPs enantiomers using NMR would be useful for research into toxicodynamics and toxicokinetics in biological systems due to the widely differing properties of the CWA enantiomers [1]. The optimization of decontamination abilities in the case of a CWA events, with this method’s potential rapidity and robustness, as well as the development of models correlating chiral compounds with CSAs for optimal resolution are all rational benefits of this research.

  3. Two-dimensional MAS NMR correlation protocols involving double-quantum filtering of quadrupolar spin-pairs

    Science.gov (United States)

    Edén, Mattias

    2010-05-01

    Three two-dimensional (2D) NMR homonuclear correlation techniques invoking double-quantum (2Q) filtration of the central transitions of half-integer spins are evaluated numerically and experimentally. They correlate directly detected single-quantum (1Q) coherences in the t2 domain with either of 1Q, two-spin 2Q or single-spin multiple-quantum coherence-evolutions in the indirect (t1) dimension. We employ experimental 23Na and 27Al NMR on sodium sulfite and the natural mineral sillimanite (SiAl2O5), in conjunction with simulated 2D spectra from pairs of dipolar-recoupled spins-3/2 and 5/2 at different external magnetic fields, to compare the correlation strategies from the viewpoints of 2D spectral resolution, signal sensitivity, implementational aspects and their relative merits for establishing internuclear proximities and quadrupolar tensor orientations.

  4. NMR

    International Nuclear Information System (INIS)

    Kneeland, J.B.; Lee, B.C.P.; Whalen, J.P.; Knowles, R.J.R.; Cahill, P.T.

    1984-01-01

    Although still quite new, NMR imaging has already emerged as a safe, noninvasive, painless, and effective diagnostic modality requiring no ionizing radiation. Also, NMR appears already to have established itself as the method of choice for the examination of the brain spinal cord (excluding herniated disks). Another area in which NMR excels is in the examination of the pelvis. The use of surface coils offers the promise of visualizing structures with resolution unobtainable by any other means. In addition, NMR, with its superb visualization of vascular structures and potential ability to measure flow, may soon revolutionize the diagnosis of cardiovascular disease. Finally, NMR, through biochemically and physiologically based T/sub 1/ and T/sub 2/ indices or through spectroscopy, may provide a means of monitoring therapeutic response so as to permit tailoring of treatment to the individual patient. In short, NMR is today probably at the same stage as the x-ray was in Roentgen's day

  5. NMR in an electric field: A bulk probe of the hidden spin and orbital polarizations

    Science.gov (United States)

    Ramírez-Ruiz, Jorge; Boutin, Samuel; Garate, Ion

    2017-12-01

    Recent theoretical work has established the presence of hidden spin and orbital textures in nonmagnetic materials with inversion symmetry. Here, we propose that these textures can be detected by nuclear magnetic resonance (NMR) measurements carried out in the presence of an electric field. In crystals with hidden polarizations, a uniform electric field produces a staggered magnetic field that points to opposite directions at atomic sites related by spatial inversion. As a result, the NMR resonance peak corresponding to inversion partner nuclei is split into two peaks. The magnitude of the splitting is proportional to the electric field and depends on the orientation of the electric field with respect to the crystallographic axes and the external magnetic field. As a case study, we present a theory of electric-field-induced splitting of NMR peaks for 77Se,125Te, and 209Bi in Bi2Se3 and Bi2Te3 . In conducting samples with current densities of ≃106A/cm 2 , the splitting for Bi can reach 100 kHz , which is comparable to or larger than the intrinsic width of the NMR lines. In order to observe the effect experimentally, the peak splitting must also exceed the linewidth produced by the Oersted field. In Bi2Se3 , this requires narrow wires of radius ≲1 μ m . We also discuss other potentially more promising candidate materials, such as SrRuO3 and BaIr2Ge2 , whose crystal symmetry enables strategies to suppress the linewidth produced by the Oersted field.

  6. Magic Angle Spinning NMR Structure Determination of Proteins from Pseudocontact Shifts

    KAUST Repository

    Li, Jianping

    2013-06-05

    Magic angle spinning solid-state NMR is a unique technique to study atomic-resolution structure of biomacromolecules which resist crystallization or are too large to study by solution NMR techniques. However, difficulties in obtaining sufficient number of long-range distance restraints using dipolar coupling based spectra hamper the process of structure determination of proteins in solid-state NMR. In this study it is shown that high-resolution structure of proteins in solid phase can be determined without the use of traditional dipolar-dipolar coupling based distance restraints by combining the measurements of pseudocontact shifts (PCSs) with Rosetta calculations. The PCSs were generated by chelating exogenous paramagnetic metal ions to a tag 4-mercaptomethyl-dipicolinic acid, which is covalently attached to different residue sites in a 56-residue immunoglobulin-binding domain of protein G (GB1). The long-range structural restraints with metal-nucleus distance of up to ∼20 Å are quantitatively extracted from experimentally observed PCSs, and these are in good agreement with the distances back-calculated using an X-ray structure model. Moreover, we demonstrate that using several paramagnetic ions with varied paramagnetic susceptibilities as well as the introduction of paramagnetic labels at different sites can dramatically increase the number of long-range restraints and cover different regions of the protein. The structure generated from solid-state NMR PCSs restraints combined with Rosetta calculations has 0.7 Å root-mean-square deviation relative to X-ray structure. © 2013 American Chemical Society.

  7. Interaction study of polyisobutylene with paraffins by NMR using the evaluation of spin-lattice relaxation times for hydrogen nuclei

    International Nuclear Information System (INIS)

    Marques, Rosana G.G.; Tavares, Maria I.B.

    2001-01-01

    The evaluation of spin-lattice relaxation times of 1 H for polyisobutylene/paraffin systems, were obtained using the classic inversion recovery technique, and also through Cross Polarization Magic Angle Spinning (CP/MAS) techniques varying the contact time and also by the delayed contact time pulse sequence. NMR results showed that the polyisobutylene/paraffin systems in which high molecular weight paraffins were used, is heterogeneous. However, for paraffins with low molecular weight, the system presents good homogeneity. (author)

  8. Gaussian-approximation formalism for evaluating decay of NMR spin echoes

    International Nuclear Information System (INIS)

    Recchia, C.H.; Gorny, K.; Pennington, C.H.

    1996-01-01

    We present a formalism for evaluating the amplitude of the NMR spin echo and stimulated echo as a function of pulse spacings, for situations in which the nuclear spins experience an effective longitudinal magnetic field h z (t) resulting from an arbitrary number of independent sources, each characterized by its own arbitrary time correlation function. The distribution of accumulated phase angles for the ensemble of nuclear spins at the time of the echo is approximated as a Gaussian. The development of the formalism is motivated by the need to understand the transverse relaxation of 89 Y in YBa 2 Cu 3 O 7 , in which the 89 Y experiences 63,65 Cu dipolar fields which fluctuate due to 63,65 Cu T 1 processes. The formalism is applied successfully to this example, and to the case of nuclei diffusing in a spatially varying magnetic field. Then we examine a situation in which the approximation fails emdash the classic problem of chemical exchange in dimethylformamide, where the methyl protons experience a chemical shift which fluctuates between two discrete values. In this case the Gaussian approximation yields a monotonic decay of the echo amplitude with increasing pulse spacing, while the exact solution yields distinct open-quote open-quote beats close-quote close-quote in the echo height, which we confirm experimentally. In light of this final example the limits of validity of the approximation are discussed. copyright 1996 The American Physical Society

  9. Investigating the lignocellulosic composition during delignification using confocal raman spectroscopy, cross-polarization magic angle spinning carbon 13 - nuclear magnetic resonance (CP/MAS 13C- NMR) spectroscopy and atomic force microscopy

    CSIR Research Space (South Africa)

    Chunilall, Viren

    2012-03-01

    Full Text Available in the distribution of lignin between the middle lamella and secondary cell wall layer for all clones and species investigated. The E. gc clone showed high levels of lignin in the secondary cell wall layer compared to the E. gu clone, E. dunnii and E. nitens species...

  10. J-Modulation in ID NMR 1H Spectrum of Taurine and Aspartate Using Spin-Echo Technique

    Science.gov (United States)

    Oturak, Halil; Sağlam, Adnan; Bahçeli, Semiha

    1999-05-01

    This study reports on a theoretical calculation of Hahn's spin-echo experiment in case of a model A2B2 spin system with a strongly coupling character and gives the experimental results of one-dimension 1H high-resolution NMR spectra of taurine and aspartate. The calculated amplitudes of the spin-echoes for two different proton groups of taurine are given. Using results of our calculations for taurine, the computer simulations of J-modulation are implemented. It is shown that the agreement be-tween the experimental and simulated spectra is good.

  11. NMR Investigation of Equilibrium Micelle of Two Head Surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Meong Soo; Nam, Ki Dae [School of Chemical Engineering, Chungbuk National University, Cheongju (Korea); Jeong, Hwan Kyeong [AMLCD Division Semiconductor Samsung Electronics, Chunan (Korea); Lee, Hyang Woo [Department of Cosmetology, Keochang Provincial College, Keochang (Korea)

    2001-06-01

    The two-headed surfactant, disodium 4-n-alkyl-3-sulfonato succinate, has been synthesized by the monoesterification of maleic anhydride and n-alkanol(C{sub 8} {approx} C{sub 12}) and addition of sodium bisulfite to the corresponding monoester. The equilibrium micellar properties formed by these aqueous compounds, and the conformations of the alkyl long chain length that comprised of the interior of micellar, have been investigated using a combination of 1-D NMR and homonuclear/heteronuclear 2-D NMR techniques. The cmc' and the aggregation numbers determined from the NMR experiments were in an agreement with previous results found in the literatures for other types of two-headed surfactant systems. The amphiphiles had high cmc' and low aggregation numbers compared to single-headed surfactants of a comparable chain length. All these results were attributed to the addition a second headgroup to a single-headed, single-tailed surfactant. 27 refs., 6 figs., 4 tabs.

  12. A small-diameter NMR logging tool for groundwater investigations

    Science.gov (United States)

    Walsh, David; Turner, Peter; Grunewald, Elliot; Zhang, Hong; Butler, James J.; Reboulet, Ed; Knobbe, Steve; Christy, Tom; Lane, John W.; Johnson, Carole D.; Munday, Tim; Fitzpatrick, Andrew

    2013-01-01

    A small-diameter nuclear magnetic resonance (NMR) logging tool has been developed and field tested at various sites in the United States and Australia. A novel design approach has produced relatively inexpensive, small-diameter probes that can be run in open or PVC-cased boreholes as small as 2 inches in diameter. The complete system, including surface electronics and various downhole probes, has been successfully tested in small-diameter monitoring wells in a range of hydrogeological settings. A variant of the probe that can be deployed by a direct-push machine has also been developed and tested in the field. The new NMR logging tool provides reliable, direct, and high-resolution information that is of importance for groundwater studies. Specifically, the technology provides direct measurement of total water content (total porosity in the saturated zone or moisture content in the unsaturated zone), and estimates of relative pore-size distribution (bound vs. mobile water content) and hydraulic conductivity. The NMR measurements show good agreement with ancillary data from lithologic logs, geophysical logs, and hydrogeologic measurements, and provide valuable information for groundwater investigations.

  13. Magic-angle spinning NMR of intact bacteriophages: Insights into the capsid, DNA and their interface

    Science.gov (United States)

    Abramov, Gili; Morag, Omry; Goldbourt, Amir

    2015-04-01

    Bacteriophages are viruses that infect bacteria. They are complex macromolecular assemblies, which are composed of multiple protein subunits that protect genomic material and deliver it to specific hosts. Various biophysical techniques have been used to characterize their structure in order to unravel phage morphogenesis. Yet, most bacteriophages are non-crystalline and have very high molecular weights, in the order of tens of MegaDaltons. Therefore, complete atomic-resolution characterization on such systems that encompass both capsid and DNA is scarce. In this perspective article we demonstrate how magic-angle spinning solid-state NMR has and is used to characterize in detail bacteriophage viruses, including filamentous and icosahedral phage. We discuss the process of sample preparation, spectral assignment of both capsid and DNA and the use of chemical shifts and dipolar couplings to probe the capsid-DNA interface, describe capsid structure and dynamics and extract structural differences between viruses.

  14. Fluorine dynamics in BaF{sub 2} superionic conductors investigated by NMR

    Energy Technology Data Exchange (ETDEWEB)

    Gumann, Patryk

    2008-07-01

    In this work the dynamics of fluorine in solid-state electrolytes having BaF{sub 2}-structure was investigated using three different NMR-methods: field cycling relaxometry, lineshape analysis, and static field gradient NMR. For this purpose a pure BaF{sub 2} crystal, as well as crystals doped with trivalent impurities (LaF{sub 3}), were studied as a function of temperature. Using MAS NMR it was possible to identify two lines in Ba{sub 0.9}La{sub 0.1}F{sub 2.1} having different chemical shift, and to refer them to the modified crystal structure. On this basis a model for the fluorine lineshape has been developed, taking into account three motional processes characterized by their correlation times. It includes jump diffusion of the fluorine ions among equivalent sites within two crystallographically distinct sublattices, and inter-lattice exchange processes. By measuring frequency and temperature-dependent spin lattice relaxation times, it was possible to gain information about fluorine dynamics on microscopic length scales. An attempt was also made to analyze the data for pure BaF{sub 2} and low admixture concentration samples with a non-exponential correlation function. (orig.)

  15. Segmental dynamics of polyethylene-alt-propylene studied by NMR spin echo techniques

    Science.gov (United States)

    Lozovoi, A.; Mattea, C.; Hofmann, M.; Saalwaechter, K.; Fatkullin, N.; Stapf, S.

    2017-06-01

    Segmental dynamics of a highly entangled melt of linear polyethylene-alt-propylene with a molecular weight of 200 kDa was studied with a novel proton nuclear magnetic resonance (NMR) approach based upon 1H → 2H isotope dilution as applied to a solid-echo build-up function ISE(t), which is constructed from the NMR spin echo signals arising from the Hahn echo (HE) and two variations of the solid-echo pulse sequence. The isotope dilution enables the separation of inter- and intramolecular contributions to this function and allows one to extract the segmental mean-squared displacements in the millisecond time range, which is hardly accessible by other experimental methods. The proposed technique in combination with time-temperature superposition yields information about segmental translation in polyethylene-alt-propylene over 6 decades in time from 10-6 s up to 1 s. The time dependence of the mean-squared displacement obtained in this time range clearly shows three regimes of power law with exponents, which are in good agreement with the tube-reptation model predictions for the Rouse model, incoherent reptation and coherent reptation regimes. The results at short times coincide with the fast-field cycling relaxometry and neutron spin echo data, yet, significantly extending the probed time range. Furthermore, the obtained data are verified as well by the use of the dipolar-correlation effect on the Hahn echo, which was developed before by the co-authors. At the same time, the amplitude ratio of the intermolecular part of the proton dynamic dipole-dipole correlation function over the intramolecular part obtained from the experimental data is not in agreement with the predictions of the tube-reptation model for the regimes of incoherent and coherent reptation.

  16. DRAMAtic transforms in magic angle spinning recoupling NMR: The Bessel function pathway.

    Science.gov (United States)

    Goodman, Russell; Hancock, Jason; Siemens, Mark; Jarrell, Harold; Siminovitch, David

    2005-07-01

    In magic angle spinning (MAS) NMR recoupling experiments, the extraction of multiple couplings or a coupling distribution from the observed dephasing signals remains a challenging problem. At least for REDOR experiments, the REDOR transform solves this problem, enabling the simultaneous measurement of multiple dipolar couplings. Focusing on the quadrupolar dephasing observed in QUADRAMA experiments as a representative example, we demonstrate that the same analytical form used for the mathematical description of REDOR dephasing also describes the dephasing observed in a wide variety of MAS NMR recoupling experiments. This fact immediately extends REDOR transform techniques to a much broader suite of recoupling experiments than had previously been realized, including those of DRAMA, MELODRAMA and QUADRAMA. As an illustration, we use the DRAMAtic transform to provide the first inversion of a QUADRAMA dephasing signal to extract the quadrupole coupling distribution. Using a complete elliptic integral of the first kind, we further develop a novel expression for the Pake-spun powder patterns of the corresponding recoupled lineshapes. Our methods and results reinforce the central role that Bessel functions can play in simplifying the integrals that define both the dephasing signals in the time domain, and their Fourier transforms in the frequency domain.

  17. Hydrogen and deuterium NMR of solids by magic-angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Eckman, R.R.

    1982-10-01

    The nuclear magnetic resonance of solids has long been characterized by very large specral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, ..beta../sub m/ = Arccos (3/sup -1/2/), with respect to the direction of the external magnetic field. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of ..beta... A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when H/sub D/ was small. This often occurs naturally when the nuclei are semi-dilute or involved in internal motion. In the general case of large H/sub D/, isotropic spectra were obtained by dilution of /sup 1/H with /sup 2/H combined with magic angle rotation. The resolution obtained represents the practical limit for proton NMR of solids.

  18. 1H magic-angle spinning NMR evolves as a powerful new tool for membrane proteins

    Science.gov (United States)

    Schubeis, Tobias; Le Marchand, Tanguy; Andreas, Loren B.; Pintacuda, Guido

    2018-02-01

    Building on a decade of continuous advances of the community, the recent development of very fast (60 kHz and above) magic-angle spinning (MAS) probes has revolutionised the field of solid-state NMR. This new spinning regime reduces the 1H-1H dipolar couplings, so that direct detection of the larger magnetic moment available from 1H is now possible at high resolution, not only in deuterated molecules but also in fully-protonated substrates. Such capabilities allow rapid "fingerprinting" of samples with a ten-fold reduction of the required sample amounts with respect to conventional approaches, and permit extensive, robust and expeditious assignment of small-to-medium sized proteins (up to ca. 300 residues), and the determination of inter-nuclear proximities, relative orientations of secondary structural elements, protein-cofactor interactions, local and global dynamics. Fast MAS and 1H detection techniques have nowadays been shown to be applicable to membrane-bound systems. This paper reviews the strategies underlying this recent leap forward in sensitivity and resolution, describing its potential for the detailed characterization of membrane proteins.

  19. On the use of ultracentrifugal devices for routine sample preparation in biomolecular magic-angle-spinning NMR.

    Science.gov (United States)

    Mandal, Abhishek; Boatz, Jennifer C; Wheeler, Travis B; van der Wel, Patrick C A

    2017-03-01

    A number of recent advances in the field of magic-angle-spinning (MAS) solid-state NMR have enabled its application to a range of biological systems of ever increasing complexity. To retain biological relevance, these samples are increasingly studied in a hydrated state. At the same time, experimental feasibility requires the sample preparation process to attain a high sample concentration within the final MAS rotor. We discuss these considerations, and how they have led to a number of different approaches to MAS NMR sample preparation. We describe our experience of how custom-made (or commercially available) ultracentrifugal devices can facilitate a simple, fast and reliable sample preparation process. A number of groups have since adopted such tools, in some cases to prepare samples for sedimentation-style MAS NMR experiments. Here we argue for a more widespread adoption of their use for routine MAS NMR sample preparation.

  20. On the use of ultracentrifugal devices for routine sample preparation in biomolecular magic-angle-spinning NMR

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Abhishek; Boatz, Jennifer C. [University of Pittsburgh School of Medicine, Department of Structural Biology (United States); Wheeler, Travis B. [University of Pittsburgh School of Medicine, Department of Cell Biology (United States); Wel, Patrick C. A. van der, E-mail: vanderwel@pitt.edu [University of Pittsburgh School of Medicine, Department of Structural Biology (United States)

    2017-03-15

    A number of recent advances in the field of magic-angle-spinning (MAS) solid-state NMR have enabled its application to a range of biological systems of ever increasing complexity. To retain biological relevance, these samples are increasingly studied in a hydrated state. At the same time, experimental feasibility requires the sample preparation process to attain a high sample concentration within the final MAS rotor. We discuss these considerations, and how they have led to a number of different approaches to MAS NMR sample preparation. We describe our experience of how custom-made (or commercially available) ultracentrifugal devices can facilitate a simple, fast and reliable sample preparation process. A number of groups have since adopted such tools, in some cases to prepare samples for sedimentation-style MAS NMR experiments. Here we argue for a more widespread adoption of their use for routine MAS NMR sample preparation.

  1. Simplifying the complex 1H NMR spectra of fluorine-substituted benzamides by spin system filtering and spin-state selection: multiple-quantum-single-quantum correlation.

    Science.gov (United States)

    Baishya, Bikash; Reddy, G N Manjunatha; Prabhu, Uday Ramesh; Row, T N Guru; Suryaprakash, N

    2008-10-23

    The proton NMR spectra of fluorine-substituted benzamides are very complex (Figure 1) due to severe overlap of (1)H resonances from the two aromatic rings, in addition to several short and long-range scalar couplings experienced by each proton. With no detectable scalar couplings between the inter-ring spins, the (1)H NMR spectra can be construed as an overlap of spectra from two independent phenyl rings. In the present study we demonstrate that it is possible to separate the individual spectrum for each aromatic ring by spin system filtering employing the multiple-quantum-single-quantum correlation methodology. Furthermore, the two spin states of fluorine are utilized to simplify the spectrum corresponding to each phenyl ring by the spin-state selection. The demonstrated technique reduces spectral complexity by a factor of 4, in addition to permitting the determination of long-range couplings of less than 0.2 Hz and the relative signs of heteronuclear couplings. The technique also aids the judicious choice of the spin-selective double-quantum-single-quantum J-resolved experiment to determine the long-range homonuclear couplings of smaller magnitudes.

  2. Theoretical and experimental investigation of the 1H NMR spectrum of putrescine

    Science.gov (United States)

    Allouche, A. R.; Graveron-Demilly, D.; Fauvelle, F.; Aubert-Frécon, M.

    2008-12-01

    Chemical shifts δ and spin-spin coupling constants J have been calculated for the putrescine molecule, a polyamine present in prostate tissue, through a DFT/B3LYP/6-311++G(d,p)/PCM/(GIAO) approach, which has been shown to be accurate in previous work. From δ and J values, calculated for the first time for the isolated and the solvated putrescine, the 1H NMR spectra have been simulated. Comparisons between the calculated and the experimental NMR spectra at 400 MHz show a good agreement and allow to propose reliable values for the NMR spin Hamiltonian parameters of putrescine to be used as good starting values for further quantitation methods of metabolites in prostate tissue.

  3. Magic angle spinning nuclear magnetic resonance apparatus and process for high-resolution in situ investigations

    Science.gov (United States)

    Hu, Jian Zhi; Sears, Jr., Jesse A.; Hoyt, David W.; Mehta, Hardeep S.; Peden, Charles H. F.

    2015-11-24

    A continuous-flow (CF) magic angle sample spinning (CF-MAS) NMR rotor and probe are described for investigating reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions in situ. The rotor includes a sample chamber of a flow-through design with a large sample volume that delivers a flow of reactants through a catalyst bed contained within the sample cell allowing in-situ investigations of reactants and products. Flow through the sample chamber improves diffusion of reactants and products through the catalyst. The large volume of the sample chamber enhances sensitivity permitting in situ .sup.13C CF-MAS studies at natural abundance.

  4. Resonances in field-cycling NMR on molecular crystals. (reversible) Spin dynamics or (irreversible) relaxation?; Resonanzen in Field-Cycling-NMR an Molekuelkristallen. (reversible) Spindynamik oder (irreversible) Relaxation?

    Energy Technology Data Exchange (ETDEWEB)

    Tacke, Christian

    2015-07-01

    Multi spin systems with spin 1/2 nuclei and dipolar coupled quadrupolar nuclei can show so called ''quadrupolar dips''. There are two main reasons for this behavior: polarization transfer and relaxation. They look quite alike and without additional research cannot be differentiated easily in most cases. These two phenomena have quite different physical and theoretical backgrounds. For no or very slow dynamics, polarization transfer will take place, which is energy conserving inside the spin system. This effect can entirely be described using quantum mechanics on the spin system. Detailed knowledge about the crystallography is needed, because this affects the relevant hamiltonians directly. For systems with fast enough dynamics, relaxation takes over, and the energy flows from the spin system to the lattice; thus a more complex theoretical description is needed. This description has to include a dynamic model, usually in the form of a spectral density function. Both models should include detailed modelling of the complete spin system. A software library was developed to be able to model complex spin systems. It allows to simulate polarization transfer or relaxation effects. NMR measurements were performed on the protonic conductor K{sub 3}H(SO{sub 4}){sub 2}. A single crystal shows sharp quadrupolar dips at room temperature. Dynamics could be excluded using relaxation measurements and literature values. Thus, a polarization transfer analysis was used to describe those dips with good agreement. As a second system, imidazolium based molecular crystals were analyzed. The quadrupolar dips were expected to be caused by polarization transfer; this was carefully analyzed and found not to be true. A relaxation based analysis shows good agreement with the measured data in the high temperature area. It leverages a two step spectral density function, which indicates two distinct dynamic processes happening in this system.

  5. Hydrogen cluster/network in tobermorite as studied by multiple-quantum spin counting {sup 1}H NMR

    Energy Technology Data Exchange (ETDEWEB)

    Mogami, Yuuki [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Yamazaki, Satoru; Matsuno, Shinya [Analysis and Simulation Center, Asahi Kasei Corporation, Fuji, Shizuoka 416-8501 (Japan); Matsui, Kunio [Products and Marketing Development Dept., Asahi Kasei Construction Materials Corporation, Sakai-machi, Ibaraki 306-0493 (Japan); Noda, Yasuto [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Takegoshi, K., E-mail: takeyan@kuchem.kyoto-u.ac.jp [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2014-12-15

    Proton multiple-quantum (MQ) spin-counting experiment has been employed to study arrangement of hydrogen atoms in 9 Å/11 Å natural/synthetic tobermorites. Even though all tobermorite samples give similar characterless, broad static-powder {sup 1}H NMR spectra, their MQ spin-counting spectra are markedly different; higher quanta in 11 Å tobermorite do not grow with the MQ excitation time, while those in 9 Å one do. A statistical analysis of the MQ results recently proposed [26] is applied to show that hydrogens align in 9 Å tobermorite one dimensionally, while in 11 Å tobermorite they exist as a cluster of 5–8 hydrogen atoms.

  6. Investigations of Flow past Spinning Cylinders

    Science.gov (United States)

    Mehmedagic, Igbal; Carlucci, Pasquale; Buckley, Liam; Carlucci, Donald; Aljallis, Elias; Thangam, Siva

    2013-11-01

    A subsonic wind tunnel is used to perform experiments on flow past spinning cylinders. The blunt cylinders are sting-mounted and oriented such that their axis of rotation is aligned with the mean flow. The experiments cover a Reynolds number range of up to 300000 and rotation numbers of up to 1.2 (based on cylinder diameter). The results for spinning cylinders with both rear-mounted and fore-mounted stings are presented. Computations are performed using a two-equation anisotropic turbulence model that is based on proper representation of the energy spectrum to capture rotation and curvature. The model performance is validated with benchmark experimental flows and implemented for analyzing the flow configuration used in the experimental study. Funded in part by U. S. Army, ARDEC.

  7. A High-Resolution Magic Angle Spinning NMR Study of the Enantiodiscrimination of 3,4-Methylenedioxymethamphetamine (MDMA by an Immobilized Polysaccharide-Based Chiral Phase.

    Directory of Open Access Journals (Sweden)

    Juliana C Barreiro

    Full Text Available This paper reports the investigation of the chiral interaction between 3,4-methylenedioxy-methamphetamine (MDMA enantiomers and an immobilized polysaccharide-based chiral phase. For that, suspended-state high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (1H HR-MAS NMR was used. 1H HR-MAS longitudinal relaxation time and Saturation Transfer Difference (STD NMR titration experiments were carried out yielding information at the molecular level of the transient diastereoisomeric complexes of MDMA enantiomers and the chiral stationary phase. The interaction of the enantiomers takes place through the aromatic moiety of MDMA and the aromatic group of the chiral selector by π-π stacking for both enantiomers; however, a stronger interaction was observed for the (R-enantiomer, which is the second one to elute at the chromatographic conditions.

  8. Absolute Quantification of Water in Microporous Solids with1H Magic Angle Spinning NMR and Standard Addition.

    Science.gov (United States)

    Houlleberghs, Maarten; Hoffmann, Andreas; Dom, Dirk; Kirschhock, Christine E A; Taulelle, Francis; Martens, Johan A; Breynaert, Eric

    2017-07-05

    Zeolites are microporous materials driving industrial scale adsorption, ion exchange, and catalytic processes. Their water content dramatically impacts their properties, but its quantification with Karl Fisher titration or thermal gravimetric analysis is problematic. When standard addition of water is combined with 1 H magic angle spinning (MAS) NMR detection, absolute quantification of water in microporous materials becomes possible. The method was demonstrated on five different, commercially available zeolites.

  9. Investigation of material properties by NMR in low and high magnetic fields

    International Nuclear Information System (INIS)

    Rata, D.G.

    2006-01-01

    In this work the experiments have been performed at both low and high field. The experiments cover various domains from simple relaxation experiments in low field to diffusion and spin-diffusion in high field. The applications of low-field investigations are: - quality control of chemical products. - water content determination inside of the walls of buildings. - determination of multilayer polymer coatings on a concrete. In high-field NMR several alkane molecules swollen at equilibrium in cross-linked natural rubber samples have been investigated and analyzed based on the assumptions of the Vrentras theory. A small diffusion anisotropy of the order of 10% has been discovered because of a deformation of free volume under compression. The anisotropy increases with the cross-link density and the compression ratio. The results presented in this study show that the solvent size influences the anisotropy of the diffusion process through the size parameter. The spin-diffusion measurements have been performed on Stanyl samples with different aged samples, at controlled temperature conditions. (orig.)

  10. Investigation of material properties by NMR in low and high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Rata, D.G.

    2006-07-10

    In this work the experiments have been performed at both low and high field. The experiments cover various domains from simple relaxation experiments in low field to diffusion and spin-diffusion in high field. The applications of low-field investigations are: - quality control of chemical products. - water content determination inside of the walls of buildings. - determination of multilayer polymer coatings on a concrete. In high-field NMR several alkane molecules swollen at equilibrium in cross-linked natural rubber samples have been investigated and analyzed based on the assumptions of the Vrentras theory. A small diffusion anisotropy of the order of 10% has been discovered because of a deformation of free volume under compression. The anisotropy increases with the cross-link density and the compression ratio. The results presented in this study show that the solvent size influences the anisotropy of the diffusion process through the size parameter. The spin-diffusion measurements have been performed on Stanyl samples with different aged samples, at controlled temperature conditions. (orig.)

  11. Relativistic Spin-Orbit Heavy Atom on the Light Atom NMR Chemical Shifts: General Trends Across the Periodic Table Explained.

    Science.gov (United States)

    Vícha, Jan; Komorovsky, Stanislav; Repisky, Michal; Marek, Radek; Straka, Michal

    2018-04-20

    The importance of relativistic effects on the NMR parameters in heavy-atom (HA) compounds, particularly the SO-HALA (Spin-Orbit Heavy Atom on the Light Atom) effect on NMR chemical shifts, has been known for about 40 years. Yet, a general correlation between the electronic-structure and SO-HALA effect have been missing. By analyzing 1H NMR chemical shifts of the 6th-period hydrides (Cs-At) we discovered general electronic-structure principles and mechanisms that dictate the size and sign of the SO-HALA NMR chemical shifts. In brief, partially occupied HA valence shells induce relativistic shielding at the light atom (LA) nuclei, while empty HA valence shells induce relativistic deshielding. In particular, the LA nucleus is relativistically shielded in 5d2-5d8 and 6p4 HA hydrides and deshielded in 4f0, 5d0, 6s0, 6p0 HA hydrides. This general and intuitive concept explains periodic trends in the 1H NMR chemical shifts along the 6th-period hydrides (Cs-At) studied in this work. We present substantial evidence that the introduced principles have a general validity across the periodic table and can be extended to non-hydride LAs. The decades-old question why compounds with occupied frontier π molecular orbitals (MOs) cause SO-HALA shielding at the LA nuclei, while the frontier σ MOs cause deshielding is answered. We further derive connection between the SO-HALA NMR chemical shifts and Spin-Orbit-induced Electron Deformation Density (SO-EDD), a property, which can be obtained easily from differential electron densities and can be represented graphically. SO-EDD provides an intuitive understanding of the SO-HALA effect in terms of the depletion/concentration of the electron density at LA nuclei caused by spin-orbit coupling due to HA in the presence of magnetic field. Using an analogy between SO-EDD concept and arguments from classic NMR theory, the complex question of the SO-HALA NMR chemical shifts becomes easily understandable for a wide chemical audience.

  12. Spin Dynamics and Quantum Tunneling in Fe8 Nanomagnet and in AFM Rings by NMR

    Energy Technology Data Exchange (ETDEWEB)

    Ho-Baek, Seung [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    In this thesis, our main interest has been to investigate the spin dynamics and quantum tunneling in single molecule magnets (SMMs), For this we have selected two different classes of SMMs: a ferrimagnetic total high spin S = 10 cluster Fe8 and antiferromagnetic (AFM) ring-type clusters. For Fe8, our efforts have been devoted to the investigation of the quantum tunneling of magnetization in the very low temperature region. The most remarkable experimental finding in Fe8 is that the nuclear spin-lattice relaxation rate (1/T{sub l}) at low temperatures takes place via strong collision mechanism, and thus it allows to measure directly the tunneling rate vs T and H for the first time. For AFM rings, we have shown that 1/T{sub l} probes the thermal fluctuations of the magnetization in the intermediate temperature range. We find that the fluctuations are dominated by a single characteristic frequency which has a power law T-dependence indicative of fluctuations due to electron-acoustic phonon interactions.

  13. Spin Dynamics and Quantum Tunneling in Fe8 Nanomagnet and in AFM Rings by NMR

    International Nuclear Information System (INIS)

    Seung-Ho-Baek

    2004-01-01

    In this thesis, our main interest has been to investigate the spin dynamics and quantum tunneling in single molecule magnets (SMMs), For this we have selected two different classes of SMMs: a ferrimagnetic total high spin S = 10 cluster Fe8 and antiferromagnetic (AFM) ring-type clusters. For Fe8, our efforts have been devoted to the investigation of the quantum tunneling of magnetization in the very low temperature region. The most remarkable experimental finding in Fe8 is that the nuclear spin-lattice relaxation rate (1/T l ) at low temperatures takes place via strong collision mechanism, and thus it allows to measure directly the tunneling rate vs T and H for the first time. For AFM rings, we have shown that 1/T l probes the thermal fluctuations of the magnetization in the intermediate temperature range. We find that the fluctuations are dominated by a single characteristic frequency which has a power law T-dependence indicative of fluctuations due to electron-acoustic phonon interactions

  14. Spin dynamics and quantum tunneling in Fe8 nanomagnet and in AFM rings by NMR

    Science.gov (United States)

    Baek, Seung-Ho

    In this thesis, our main interest has been to investigate the spin dynamics and quantum tunneling in single molecule magnets (SMMs). For this we have selected two different classes of SMMs: a ferromagnetic total high spin S = 10 cluster Fe8 and antiferromagnetic (AFM) ring-type clusters. For Fe8, our efforts have been devoted to the investigation of the quantum tunneling of magnetization in the very low temperature region. The most remarkable experimental finding in Fe8 is that the nuclear spin-lattice relaxation rate (1/T1) at low temperatures takes place via strong collision mechanism, and thus it allows to measure directly the tunneling rate vs. T and H for the first time. For AFM rings, we have shown that 1/T1 probes the thermal fluctuations of the magnetization in the intermediate temperature range. We find that the fluctuations are dominated by a single characteristic frequency which has a power-law T-dependence indicative of fluctuations due to electron-acoustic phonon interactions.

  15. Magic-Angle-Spinning Solid-State NMR of Membrane Proteins

    NARCIS (Netherlands)

    Baker, Lindsay A.; Folkers, Gert E.; Sinnige, Tessa; Houben, Klaartje; Kaplan, M.; van der Cruijsen, Elwin A W; Baldus, Marc

    2015-01-01

    Solid-state NMR spectroscopy (ssNMR) provides increasing possibilities to examine membrane proteins in different molecular settings, ranging from synthetic bilayers to whole cells. This flexibility often enables ssNMR experiments to be directly correlated with membrane protein function. In this

  16. Tunnel splitting in biaxial spin models investigated with spin-coherent-state path integrals

    International Nuclear Information System (INIS)

    Chen Zhide; Liang, J.-Q.; Pu, F.-C.

    2003-01-01

    Tunnel splitting in biaxial spin models is investigated with a full evaluation of the fluctuation functional integrals of the Euclidean kernel in the framework of spin-coherent-state path integrals which leads to a magnitude of tunnel splitting quantitatively comparable with the numerical results in terms of diagonalization of the Hamilton operator. An additional factor resulted from a global time transformation converting the position-dependent mass to a constant one seems to be equivalent to the semiclassical correction of the Lagrangian proposed by Enz and Schilling. A long standing question whether the spin-coherent-state representation of path integrals can result in an accurate tunnel splitting is therefore resolved

  17. Solid-state 27Al and 29Si NMR investigations on Si-substituted hydrogarnets

    International Nuclear Information System (INIS)

    Rivas Mercury, J.M.; Pena, P.; Aza, A.H. de; Turrillas, X.; Sobrados, I.; Sanz, J.

    2007-01-01

    Partially deuterated Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x hydrates prepared by a reaction in the presence of D 2 O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by 29 Si and 27 Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The 29 Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x was followed by 27 Al NMR spectroscopy: Si:OH ratios were determined quantitatively from octahedral Al signals ascribed to Al(OH) 6 and Al(OSi)(OH) 5 environments. The NMR data obtained were consistent with the concentrations of the Al and Si species deduced from transmission electron microscopy energy-dispersive spectrometry and Rietveld analysis of both X-ray and neutron diffraction data

  18. Importance of triples contributions to NMR spin-spin coupling constants computed at the CC3 and CCSDT levels

    DEFF Research Database (Denmark)

    Faber, Rasmus; Sauer, Stephan P. A.; Gauss, Jürgen

    2017-01-01

    that the most important contributions arising from connected triple excitations in the coupled cluster expansion are accounted for at the CC3 level. Thus we believe that the CC3 method will become the standard approach for calculation of reference values of nuclear spin-spin coupling constants....

  19. A Coin-Flipping Analogy and Web App for Teaching Spin-Spin Splitting in [superscript 1]H NMR Spectroscopy

    Science.gov (United States)

    Azman, Adam M.; Esteb, John J.

    2016-01-01

    A coin-flipping analogy and free corresponding web app have been developed to facilitate student understanding of the origins of spin-spin splitting. First-order splitting patterns can easily be derived and understood. "Complex" splitting patterns (e.g., doublet of quartets), are easily incorporated into the analogy. A study of the…

  20. NMR spin relaxation in proteins: The patterns of motion that dissipate power to the bath

    Science.gov (United States)

    Shapiro, Yury E.; Meirovitch, Eva

    2014-04-01

    We developed in recent years the two-body coupled-rotator slowly relaxing local structure (SRLS) approach for the analysis of NMR relaxation in proteins. The two bodies/rotators are the protein (diffusion tensor D1) and the spin-bearing probe, e.g., the 15N-1H bond (diffusion tensor, D2), coupled by a local potential (u). A Smoluchowski equation is solved to yield the generic time correlation functions (TCFs), which are sums of weighted exponentials (eigenmodes). By Fourier transformation one obtains the generic spectral density functions (SDFs) which underlie the experimental relaxation parameters. The typical paradigm is to characterize structural dynamics in terms of the best-fit values of D1, D2, and u. Additional approaches we pursued employ the SRLS TCFs, SDFs, or eigenmodes as descriptors. In this study we develop yet another perspective. We consider the SDF as function of the angular velocity associated with the fluctuating fields underlying NMR relaxation. A parameter called j-fraction, which represents the relative contribution of eigenmode, i, to a given value of the SDF function at a specific frequency, ω, is defined. j-fraction profiles of the dominant eigenmodes are derived for 0 ≤ ω ≤ 1012 rad/s. They reveal which patterns of motion actuate power dissipation at given ω-values, what are their rates, and what is their relative contribution. Simulations are carried out to determine the effect of timescale separation, D1/D2, axial potential strength, and local diffusion axiality. For D1/D2 ≤ 0.01 and strong local potential of 15 kBT, power is dissipated by global diffusion, renormalized (by the strong potential) local diffusion, and probe diffusion on the surface of a cone (to be called cone diffusion). For D1/D2 = 0.1, power is dissipated by mixed eigenmodes largely of a global-diffusion-type or cone-diffusion-type, and a nearly bare renormalized-local-diffusion eigenmode. For D1/D2 > 0.1, most eigenmodes are of a mixed type. The analysis is

  1. Contribution of proton NMR relaxation to the investigation of ...

    Indian Academy of Sciences (India)

    001 Lisboa, Portugal. *Author for correspondence. Abstract. We present in this work a review concerning wide frequency range T1 proton NMR relaxation studies performed in compounds exhibiting columnar mesophases, namely the Col ho.

  2. Multiple acquisition of magic angle spinning solid-state NMR experiments using one receiver: Application to microcrystalline and membrane protein preparations

    Science.gov (United States)

    Gopinath, T.; Veglia, Gianluigi

    2015-04-01

    Solid-state NMR spectroscopy of proteins is a notoriously low-throughput technique. Relatively low-sensitivity and poor resolution of protein samples require long acquisition times for multidimensional NMR experiments. To speed up data acquisition, we developed a family of experiments called Polarization Optimized Experiments (POE), in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. POE allow the concatenation of multiple 2D or 3D pulse sequences into a single experiment, thus potentially combining all of the aforementioned advances, boosting the capability of ssNMR spectrometers at least two-fold without the addition of any hardware. In this perspective, we describe the first generation of POE, such as dual acquisition MAS (or DUMAS) methods, and then illustrate the evolution of these experiments into MEIOSIS, a method that enables the simultaneous acquisition of multiple 2D and 3D spectra. Using these new pulse schemes for the solid-state NMR investigation of biopolymers makes it possible to obtain sequential resonance assignments, as well as distance restraints, in about half the experimental time. While designed for acquisition of heteronuclei, these new experiments can be easily implemented for proton detection and coupled with other recent advancements, such as dynamic nuclear polarization (DNP), to improve signal to noise. Finally, we illustrate the application of these methods to microcrystalline protein preparations as well as single and multi-span membrane proteins reconstituted in lipid membranes.

  3. Multiple acquisition of magic angle spinning solid-state NMR experiments using one receiver: application to microcrystalline and membrane protein preparations.

    Science.gov (United States)

    Gopinath, T; Veglia, Gianluigi

    2015-04-01

    Solid-state NMR spectroscopy of proteins is a notoriously low-throughput technique. Relatively low-sensitivity and poor resolution of protein samples require long acquisition times for multidimensional NMR experiments. To speed up data acquisition, we developed a family of experiments called Polarization Optimized Experiments (POE), in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. POE allow the concatenation of multiple 2D or 3D pulse sequences into a single experiment, thus potentially combining all of the aforementioned advances, boosting the capability of ssNMR spectrometers at least two-fold without the addition of any hardware. In this perspective, we describe the first generation of POE, such as dual acquisition MAS (or DUMAS) methods, and then illustrate the evolution of these experiments into MEIOSIS, a method that enables the simultaneous acquisition of multiple 2D and 3D spectra. Using these new pulse schemes for the solid-state NMR investigation of biopolymers makes it possible to obtain sequential resonance assignments, as well as distance restraints, in about half the experimental time. While designed for acquisition of heteronuclei, these new experiments can be easily implemented for proton detection and coupled with other recent advancements, such as dynamic nuclear polarization (DNP), to improve signal to noise. Finally, we illustrate the application of these methods to microcrystalline protein preparations as well as single and multi-span membrane proteins reconstituted in lipid membranes. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Effect of spatial spin modulation on relaxation and NMR frequencies of sup 5 sup 7 Fe nuclei in ferroelectric antiferromagnetic BiFeO sub 3

    CERN Document Server

    Zalessky, A V; Zvezdin, A K; Gippius, A A; Morozova, E N; Khozeev, D F; Bush, A S; Pokatilov, V S

    2002-01-01

    The NMR spectra on the iron nuclei in the BiFeO sub 3 antiferromagnetic sample enriched by the sup 5 sup 7 Fe (95.43%) with the spatially-modulated magnetic structure are studied. It is established that the cycloid-type spin modulation in the BiFeO sub 3 produces spatial modulation of the nuclear spin-spin relaxation velocity and leads to the spectral nonuniform widening of the NMR local line. It is determined also that the local magnetic moments of the iron ions on various cycloid sections differently depend on temperature which testifies to different character of the spin waves excitation. The analogy of the experimental results with the NMR regularities in the Bloch wall is discussed

  5. Mobility of TOAC spin-labelled peptides binding to the Src SH3 domain studied by paramagnetic NMR

    International Nuclear Information System (INIS)

    Lindfors, Hanna E.; Koning, Peter E. de; Wouter Drijfhout, Jan; Venezia, Brigida; Ubbink, Marcellus

    2008-01-01

    Paramagnetic relaxation enhancement provides a tool for studying the dynamics as well as the structure of macromolecular complexes. The application of side-chain coupled spin-labels is limited by the mobility of the free radical. The cyclic, rigid amino acid spin-label TOAC (2,2,6,6-Tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), which can be incorporated straightforwardly by peptide synthesis, provides an attractive alternative. In this study, TOAC was incorporated into a peptide derived from focal adhesion kinase (FAK), and the interaction of the peptide with the Src homology 3 (SH3) domain of Src kinase was studied, using paramagnetic NMR. Placing TOAC within the binding motif of the peptide has a considerable effect on the peptide-protein binding, lowering the affinity substantially. When the TOAC is positioned just outside the binding motif, the binding constant remains nearly unaffected. Although the SH3 domain binds weakly and transiently to proline-rich peptides from FAK, the interaction is not very dynamic and the relative position of the spin-label to the protein is well-defined. It is concluded that TOAC can be used to generate reliable paramagnetic NMR restraints

  6. Mobility of TOAC spin-labelled peptides binding to the Src SH3 domain studied by paramagnetic NMR

    Energy Technology Data Exchange (ETDEWEB)

    Lindfors, Hanna E. [Leiden University, Leiden Institute of Chemistry, Gorlaeus Laboratories (Netherlands); Koning, Peter E. de; Wouter Drijfhout, Jan [Leiden University Medical Centre, Department of Immunohematology and Blood Transfusion (Netherlands); Venezia, Brigida; Ubbink, Marcellus [Leiden University, Leiden Institute of Chemistry, Gorlaeus Laboratories (Netherlands)], E-mail: m.ubbink@chem.leidenuniv.nl

    2008-07-15

    Paramagnetic relaxation enhancement provides a tool for studying the dynamics as well as the structure of macromolecular complexes. The application of side-chain coupled spin-labels is limited by the mobility of the free radical. The cyclic, rigid amino acid spin-label TOAC (2,2,6,6-Tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), which can be incorporated straightforwardly by peptide synthesis, provides an attractive alternative. In this study, TOAC was incorporated into a peptide derived from focal adhesion kinase (FAK), and the interaction of the peptide with the Src homology 3 (SH3) domain of Src kinase was studied, using paramagnetic NMR. Placing TOAC within the binding motif of the peptide has a considerable effect on the peptide-protein binding, lowering the affinity substantially. When the TOAC is positioned just outside the binding motif, the binding constant remains nearly unaffected. Although the SH3 domain binds weakly and transiently to proline-rich peptides from FAK, the interaction is not very dynamic and the relative position of the spin-label to the protein is well-defined. It is concluded that TOAC can be used to generate reliable paramagnetic NMR restraints.

  7. Effectively doubling the magnetic field in spin-1/2-spin-1, HSQC, HDQC, coupled HSQC, and coupled HDQC in solution NMR.

    Science.gov (United States)

    Shekar, S Chandra; Backer, Jonathan M; Girvin, Mark E

    2008-05-14

    Pulse sequences for spin-1/2-spin-1 pair heteronuclear single quantum correlation (HSQC), heteronuclear double quantum correlation (HDQC), and coupled-HSQC, and coupled-HDQC NMR spectroscopies are outlined, and experimental realization for a (13)C-(2)H pair is demonstrated in solution state. In both the coupled versions, conditions for generation of in-phase and antiphase multiplets in either dimension are arrived at. The patterns and the intensity ratios are explained. The double quantum (2Q) experiments confirm doubling of both the shift frequency and the splitting due to coupling (to spin 1/2) of the 2Q coherence emanating from spin 1. The frequency doubling is equivalent to the corresponding single quantum (1Q) coherence at double the magnetic field strength. The coupling doubling, however, is independent of the magnetic field strength and a signature feature of the 2Q coherence. The ramification of the relative relaxation rates of 1Q and 2Q coherences is discussed.

  8. Effectively doubling the magnetic field in spin-1∕2–spin-1, HSQC, HDQC, coupled HSQC, and coupled HDQC in solution NMR

    Science.gov (United States)

    Chandra Shekar, S.; Backer, Jonathan M.; Girvin, Mark E.

    2008-01-01

    Pulse sequences for spin-1∕2–spin-1 pair heteronuclear single quantum correlation (HSQC), heteronuclear double quantum correlation (HDQC), and coupled-HSQC, and coupled-HDQC NMR spectroscopies are outlined, and experimental realization for a 13C–2H pair is demonstrated in solution state. In both the coupled versions, conditions for generation of in-phase and antiphase multiplets in either dimension are arrived at. The patterns and the intensity ratios are explained. The double quantum (2Q) experiments confirm doubling of both the shift frequency and the splitting due to coupling (to spin 1∕2) of the 2Q coherence emanating from spin 1. The frequency doubling is equivalent to the corresponding single quantum (1Q) coherence at double the magnetic field strength. The coupling doubling, however, is independent of the magnetic field strength and a signature feature of the 2Q coherence. The ramification of the relative relaxation rates of 1Q and 2Q coherences is discussed. PMID:18532820

  9. NMR investigation of actinide (4) beta-diketonates

    International Nuclear Information System (INIS)

    Shcherbakova, L.L.; Mishin, V.Ya.; Rubtsov, E.M.

    1984-01-01

    NMR spectra of dipivaloylmethanates (DPM) of tetravalent thorium, uranium, neptunium and plutonium in various solvents in the 153-353 K temperature range have been studied. The mentioned coordination compounds, as well as acetylacetonates, in solution have coordination number eight and do not form solvates with polar molecules. They are stable to hydrolysis and to moderate radiation loads. In the case of uranium- and neptunium compounds a photochemical instability is detected, which could be used for synthesis of previously unknown actinyl dipivaloylmethanates. According to low-temperature NMR spectra two types of stoichiometric softness of the compounds studied are found. A problem of contact and pseudocontact contributions to the paramagnetic shifts in actinide (4) β-diketonates is discussed. An exact characteristic behaviour of the NMR-shifts of signals of DPM tret-butyl groups of the β-diketonates under considerafion is of interest from the analytical viewpoint

  10. Applications of pulsed nuclear magnetic resonance to chemistry: multiple-pulse NMR, cross polarization, magic-angle spinning annd instrumental design

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, P.D.

    1979-07-01

    Pulsed Nuclear Magnetic Resonance (NMR) has been applied to: (1) Measurements of the prinicpal components of the proton shielding tensors of the hydrides of zirconium chloride and zirconium bromide. Multiple-Pulse techniques have been used to remove static homonuclear dipolar coupling. The anisotropies and isotropic shifts of these tensors have been used to infer the possible locations of the hydrogen within the sandwich-like layers of these unusual compounds. (2) Studies of the oscillatory transfer of magnetic polarization between /sup 1/H and /sup 29/Si in substituted silanes. The technique of J Cross Polarization has been used to enhance sensitivity. The /sup 29/Si NMR shifts of -Si-O- model compounds have been investigated as a possible probe for future studies of the environment of bound oxygen in coal-derived liquids. (3) Measurements of the aromatic fraction of /sup 13/C in whole coals. The techniques of /sup 1/H-/sup 13/C Cross Polarization and Magic-Angle Spinning have been used to enhance sensitivity and remove shift anisotropy. Additional topics described are: (4) Calculation and properties of the broadened lineshape of the shileding Powder Pattern. (5) Calculation of the oscillatory transfer of magnetic polarization for an I-S system. (6) Numerical convolution and its uses. (7) The technique of digital filtering applied in the frequency domain. (8) The designs and properties of four NMR probe-circuits. (9) The design of a single-coil double-resonance probe for combined Magic-Angle Spinning and Cross Polarization. (10) The designs of low Q and high Q rf power amplifiers with emphasis on the rf matching circuitry.

  11. Spin-echo based diagonal peak suppression in solid-state MAS NMR homonuclear chemical shift correlation spectra

    Science.gov (United States)

    Wang, Kaiyu; Zhang, Zhiyong; Ding, Xiaoyan; Tian, Fang; Huang, Yuqing; Chen, Zhong; Fu, Riqiang

    2018-02-01

    The feasibility of using the spin-echo based diagonal peak suppression method in solid-state MAS NMR homonuclear chemical shift correlation experiments is demonstrated. A complete phase cycling is designed in such a way that in the indirect dimension only the spin diffused signals are evolved, while all signals not involved in polarization transfer are refocused for cancellation. A data processing procedure is further introduced to reconstruct this acquired spectrum into a conventional two-dimensional homonuclear chemical shift correlation spectrum. A uniformly 13C, 15N labeled Fmoc-valine sample and the transmembrane domain of a human protein, LR11 (sorLA), in native Escherichia coli membranes have been used to illustrate the capability of the proposed method in comparison with standard 13C-13C chemical shift correlation experiments.

  12. NMR investigation of boron impurities in refined metallurgical grade silicon

    Energy Technology Data Exchange (ETDEWEB)

    Grafe, Hans-Joachim; Loeser, Wolfgang; Schmitz, Steffen; Sakaliyska, Miroslava [Leibniz Institute for Solid State and Materials Research (IFW), Dresden (Germany); Wurmehl, Sabine [Leibniz Institute for Solid State and Materials Research (IFW), Dresden (Germany); Institute for Solid State Physics, Technische Universitaet Dresden (Germany); Eisert, Stefan; Reichenbach, Birk; Mueller, Tim [Adensis GmbH, Dresden (Germany); Acker, Joerg; Rietig, Anja; Ducke, Jana [Department of Chemistry, Faculty for Natural Sciences, Brandenburg Technical University Cottbus-Senftenberg, Senftenberg (Germany)

    2015-09-15

    The nuclear magnetic resonance (NMR) method was applied for tracking boron impurities in the refining process of metallurgical grade (MG) silicon. From the NMR signal of the {sup 11}B isotope at an operating temperature 4.2 K, the boron concentration can be estimated down to the order of 1-10 wppm B. After melting and resolidification of MG-Si alloyed with Ca and Ti, a major fraction of B impurities remains in the Si solid solution as inferred from the characteristic NMR frequency. The alloying element Ti does not form substantial fractions of TiB{sub 2}. Acid leaching of crushed powders of MG-Si alloyed with Ca and Ti can diminish the initial impurity content of B suggesting its accumulation in the grain boundary phases. NMR signals of TiB{sub 2} at 4.2 K and room temperature (RT), and of poly-Si with different B doping at 4.2 K. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Contribution of proton NMR relaxation to the investigation of ...

    Indian Academy of Sciences (India)

    Centro de Fisica da Materia Condensada (UL), Av. Prof. Gama Pinto 2, 1699 Lisboa Cedex, Portugal. IST (UTL), Av. Rovisco Pais, 1049-001 Lisboa, Portugal. *Author for correspondence. Abstract. We present in this work a review concerning wide frequency range T1 proton NMR relaxation studies performed in compounds ...

  14. Structure of the Alanine Hydration Shell as Probed by NMR Chemical Shifts and Indirect Spin-Spin Coupling

    Czech Academy of Sciences Publication Activity Database

    Dračínský, Martin; Kaminský, Jakub; Bouř, Petr

    2009-01-01

    Roč. 113, č. 44 (2009), s. 14698-14707 ISSN 1520-6106 R&D Projects: GA ČR GA202/07/0732; GA AV ČR IAA400550702 Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR spectroscopy * CPMD * molecular dynamics * solvent effects Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.471, year: 2009

  15. NMR spin relaxation in proteins: The patterns of motion that dissipate power to the bath

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Yury E., E-mail: eva.meirovitch@biu.ac.il, E-mail: yuryeshapiro@gmail.com; Meirovitch, Eva, E-mail: eva.meirovitch@biu.ac.il, E-mail: yuryeshapiro@gmail.com [The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900-02 (Israel)

    2014-04-21

    We developed in recent years the two-body coupled-rotator slowly relaxing local structure (SRLS) approach for the analysis of NMR relaxation in proteins. The two bodies/rotators are the protein (diffusion tensor D{sub 1}) and the spin-bearing probe, e.g., the {sup 15}N−{sup 1}H bond (diffusion tensor, D{sub 2}), coupled by a local potential (u). A Smoluchowski equation is solved to yield the generic time correlation functions (TCFs), which are sums of weighted exponentials (eigenmodes). By Fourier transformation one obtains the generic spectral density functions (SDFs) which underlie the experimental relaxation parameters. The typical paradigm is to characterize structural dynamics in terms of the best-fit values of D{sub 1}, D{sub 2}, and u. Additional approaches we pursued employ the SRLS TCFs, SDFs, or eigenmodes as descriptors. In this study we develop yet another perspective. We consider the SDF as function of the angular velocity associated with the fluctuating fields underlying NMR relaxation. A parameter called j-fraction, which represents the relative contribution of eigenmode, i, to a given value of the SDF function at a specific frequency, ω, is defined. j-fraction profiles of the dominant eigenmodes are derived for 0 ≤ ω ≤ 10{sup 12} rad/s. They reveal which patterns of motion actuate power dissipation at given ω-values, what are their rates, and what is their relative contribution. Simulations are carried out to determine the effect of timescale separation, D{sub 1}/D{sub 2}, axial potential strength, and local diffusion axiality. For D{sub 1}/D{sub 2} ≤ 0.01 and strong local potential of 15 k{sub B}T, power is dissipated by global diffusion, renormalized (by the strong potential) local diffusion, and probe diffusion on the surface of a cone (to be called cone diffusion). For D{sub 1}/D{sub 2} = 0.1, power is dissipated by mixed eigenmodes largely of a global-diffusion-type or cone-diffusion-type, and a nearly bare renormalized

  16. Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization

    Energy Technology Data Exchange (ETDEWEB)

    Lafon, Olivier [Universite de Lille Nord de France; Thankamony, Aany S. Lilly [Universite de Lille Nord de France; Kokayashi, Takeshi [Ames Laboratory; Carnevale, Diego [Ecole Polytechnique Federale de Lausanne; Vitzthum, Veronika [Ecole Polytechnique Federale de Lausanne; Slowing, Igor I. [Ames Laboratory; Kandel, Kapil [Ames Laboratory; Vezin, Herve [Universite de Lille Nord de France; Amoureux, Jean-Paul [Universite de Lille Nord de France; Bodenhausen, Geoffrey [Ecole Polytechnique Federale de Lausanne; Pruski, Marek [Ames Laboratory

    2012-12-21

    We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of 13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements εon/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to εon/off ≈ 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated.

  17. NMR methods for the investigation of structure and transport

    CERN Document Server

    Hardy, Edme H

    2011-01-01

    Methods of nuclear magnetic resonance (NMR) are increasingly applied in engineering sciences. The book summarizes research in the field of chemical and process engineering performed at the Karlsruhe Institute of Technology (KIT). Fundamentals of the methods are exposed for readers with an engineering background. Applications cover the fields of mechanical process engineering (filtration, solid-liquid separation, powder mixing, rheometry), chemical process engineering (trickle-bed reactor, ceramic sponges), bioprocess engineering (biofilm growth), and food process engineering (microwave heating

  18. Structure, magnetization, and NMR studies of the spin-glass compound (LixV1-x)3BO5 ( x≈0.40 and 0.33)

    Science.gov (United States)

    Zong, X.; Niazi, A.; Borsa, F.; Ma, X.; Johnston, D. C.

    2007-08-01

    Structural and magnetic properties of (LixV1-x)3BO5 powders (x=0.33) and single crystals (x=0.40) were studied by x-ray diffraction, magnetization, and NMR measurements. Both powder and single crystal x-ray diffraction data are consistent with the previously reported structure of the system. Magnetization measurements show an overall antiferromagnetic interaction among vanadium spins and reveal a transition into a spin glass state at a sample and magnetic field dependent temperature below ˜10K . The high temperature (T>20K) susceptibility is analyzed using a linear spin trimer model suggested in the literature but such a model is found to be insufficient to explain the data. Li7 and B11 NMR studies indicate an inhomogeneous dynamics close to the zero-field spin-glass transition temperature. The distribution of electronic spin relaxation times is derived using a recently proposed method and the broad temperature-dependent distribution obtained gives a consistent description of the NMR results. The temperature dependence of the distribution indicates a strong slowing down of the local moment spin dynamics as the system cools toward the zero-field spin-glass transition temperature even in the presence of a strong applied magnetic field up to 4.7T .

  19. 139La and 63Cu NMR investigation of charge order in La2CuO4 +y (Tc=42 K)

    Science.gov (United States)

    Imai, T.; Lee, Y. S.

    2018-03-01

    We report 139La and 63Cu NMR investigation of the successive charge order, spin order, and superconducting transitions in superoxygenated La2CuO4 +y single crystal with stage-4 excess oxygen order at Tstage≃290 K. We show that the stage-4 order induces tilting of CuO6 octahedra below Tstage, which in turn causes 139La NMR line broadening. The structural distortion continues to develop far below Tstage, and completes at Tcharge≃60 K, where charge order sets in. This sequence is reminiscent of the the charge-order transition in Nd codoped La1.88Sr0.12CuO4 that sets in once the low-temperature tetragonal phase is established. We also show that the paramagnetic 63Cu NMR signals are progressively wiped out below Tcharge due to enhanced low-frequency spin fluctuations in charge-ordered domains, but the residual 63Cu NMR signals continue to exhibit the characteristics expected for optimally doped superconducting CuO2 planes. This indicates that charge order in La2CuO4 +y does not take place uniformly in space. In addition, unlike the typical second-order magnetic phase transitions, low-frequency Cu spin fluctuations as probed by 139La nuclear spin-lattice relaxation rate do not exhibit critical divergence at Tspin(≃Tc ) =42 K. These findings, including the spatially inhomogeneous nature of the charge-ordered state, are qualitatively similar to the case of La1.885Sr0.115CuO4 [Imai et al., Phys. Rev. B 96, 224508 (2017), 10.1103/PhysRevB.96.224508 and Arsenault et al., Phys. Rev. B 97, 064511 (2018), 10.1103/PhysRevB.97.064511], but both charge and spin order take place more sharply in the present case.

  20. Sensitivity and Resolution Enhanced Solid-State NMR for Paramagnetic Systems and Biomolecules under Very Fast Magic Angle Spinning

    KAUST Repository

    Parthasarathy, Sudhakar

    2013-09-17

    Recent research in fast magic angle spinning (MAS) methods has drastically improved the resolution and sensitivity of NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarize recent and ongoing developments in this area by presenting (13)C and (1)H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of at least 20 kHz allows us to overcome major difficulties in (1)H and (13)C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (∼ms/scan) with short (1)H T1 values, we can perform (1)H SSNMR microanalysis of paramagnetic systems on the microgram scale with greatly improved sensitivity over that observed for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ∼40 kHz can enhance the sensitivity and resolution of (13)C biomolecular SSNMR measurements. Low-power (1)H decoupling schemes under VFMAS offer excellent spectral resolution for (13)C SSNMR by nominal (1)H RF irradiation at ∼10 kHz. By combining the VFMAS approach with enhanced (1)H T1 relaxation by paramagnetic doping, we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments with (13)C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine (13)C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary (13)C SSNMR data of Aβ amyloid fibrils and GB1 microcrystals acquired at (1)H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and ultrahigh fields could allow for routine multidimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the

  1. Probing the flexibility of internal rotation in silylated phenols with the NMR scalar spin-spin coupling constants

    Czech Academy of Sciences Publication Activity Database

    Sychrovský, Vladimír; Benda, Ladislav; Prokop, Alexandr; Blechta, Vratislav; Schraml, Jan; Špirko, Vladimír

    2008-01-01

    Roč. 112, č. 23 (2008), s. 5167-5174 ISSN 1089-5639 R&D Projects: GA AV ČR IAA400550701; GA AV ČR IAA400550702; GA AV ČR IAA400720706; GA ČR GA203/06/0738; GA MŠk LC512 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z40720504 Keywords : dynamical averaging * Si-29 NMR spectroscopy * ab-initio calculations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.871, year: 2008

  2. Solid-State NMR, Crystallographic, and Computational Investigation of Bisphosphonates and Farnesyl Diphosphate Synthase-Bisphosphonate Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Mao,J.; Mukherjee, S.; Zhang, Y.; Cao, R.; Sanders, J.; Song, Y.; Zhang, Y.; Meints, G.; Gao, Y.; et al.

    2006-01-01

    Bisphosphonates are a class of molecules in widespread use in treating bone resorption diseases and are also of interest as immunomodulators and anti-infectives. They function by inhibiting the enzyme farnesyl diphosphate synthase (FPPS), but the details of how these molecules bind are not fully understood. Here, we report the results of a solid-state {sup 13}C, {sup 15}N, and {sup 31}P magic-angle sample spinning (MAS) NMR and quantum chemical investigation of several bisphosphonates, both as pure compounds and when bound to FPPS, to provide information about side-chain and phosphonate backbone protonation states when bound to the enzyme. We then used computational docking methods (with the charges assigned by NMR) to predict how several bisphosphonates bind to FPPS. Finally, we used X-ray crystallography to determine the structures of two potent bisphosphonate inhibitors, finding good agreement with the computational results, opening up the possibility of using the combination of NMR, quantum chemistry and molecular docking to facilitate the design of other, novel prenytransferase inhibitors.

  3. In situ structural characterization of a recombinant protein in native Escherichia coli membranes with solid-state magic-angle-spinning NMR.

    Science.gov (United States)

    Fu, Riqiang; Wang, Xingsheng; Li, Conggang; Santiago-Miranda, Adriana N; Pielak, Gary J; Tian, Fang

    2011-08-17

    The feasibility of using solid-state magic-angle-spinning NMR spectroscopy for in situ structural characterization of the LR11 (sorLA) transmembrane domain (TM) in native Escherichia coli membranes is presented. LR11 interacts with the human amyloid precursor protein (APP), a central player in the pathology of Alzheimer's disease. The background signals from E. coli lipids and membrane proteins had only minor effects on the LR11 TM resonances. Approximately 50% of the LR11 TM residues were assigned by using (13)C PARIS data. These assignments allowed comparisons of the secondary structure of the LR11 TM in native membrane environments and commonly used membrane mimics (e.g., micelles). In situ spectroscopy bypasses several obstacles in the preparation of membrane proteins for structural analysis and offers the opportunity to investigate how membrane heterogeneity, bilayer asymmetry, chemical gradients, and macromolecular crowding affect the protein structure.

  4. Determination of the 14N quadrupole coupling constant of nitroxide spin probes by W-band ELDOR-detected NMR

    Science.gov (United States)

    Florent, Marc; Kaminker, Ilia; Nagarajan, Vijayasarathi; Goldfarb, Daniella

    2011-06-01

    Nitroxide spin probe electron paramagnetic resonance (EPR) has proven to be a very successful method to probe local polarity and solvent hydrogen bonding properties at the molecular level. The g xx and the 14N hyperfine A zz principal values are the EPR parameters of the nitroxide spin probe that are sensitive to these properties and are therefore monitored experimentally. Recently, the 14N quadrupole interaction of nitroxides has been shown to be also highly sensitive to polarity and H-bonding (A. Savitsky et al., J. Phys. Chem. B 112 (2008) 9079). High-field electron spin echo envelope modulation (ESEEM) was used successfully to determine the P xx and P yy principal components of the 14N quadrupole tensor. The P zz value was calculated from the traceless character of the quadrupole tensor. We introduce here high-field (W-band, 95 GHz, 3.5 T) electron-electron double resonance (ELDOR)-detected NMR as a method to obtain the 14N P zz value directly, together with A zz. This is complemented by W-band hyperfine sublevel correlation (HYSCORE) measurements carried out along the g xx direction to determine the principal P xx and P yy components. Through measurements of TEMPOL dissolved in solvents of different polarities, we show that A zz increases, while | P zz| decreases with polarity, as predicted by Savitsky et al.

  5. Investigation of structural transition of regenerated silk fibroin aqueous solution by Rheo-NMR spectroscopy.

    Science.gov (United States)

    Ohgo, Kosuke; Bagusat, Frank; Asakura, Tetsuo; Scheler, Ulrich

    2008-03-26

    In this study we applied Rheo-NMR to investigate the structural change of Bombyx mori silk fibroin in aqueous solution under shear. Monitoring the time dependence of 1H solution NMR spectra of silk fibroin subjected to constant shear strain, signal intensities of random coil decreased suddenly during shear while peaks from beta-sheet structure did not arise in the solution spectra. After these experiments, an aggregate of silk was found in the Couette flow cell and its secondary structure was determined as beta-sheet by 13C solid-state NMR. In conclusion the moderate shear applied here triggered the change in the secondary structure.

  6. Investigation of a polymer-dispersed liquid crystal system by NMR diffusometry and relaxometry

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Mingxue

    2013-02-26

    Polymer-dispersed liquid crystals (PDLCs) are polymer composites containing a dispersion of liquid crystal droplets in polymer networks. PDLCs have attracted much attention due to their unique properties and potential usage. The properties of PDLCs depend on the degree of phase separation and the size of liquid crystal droplets. To investigate the structure will help us to better understand and optimize PDLCs.The main aim of this PhD thesis was to investigate PDLCs by NMR techniques. Diffusion constants and spin-lattice relaxation times in the laboratory (T{sub 1}) and rotating frame (T{sub 1{rho}}) were measured for PDLCs as well as precursor mixtures based on the trifunctional monomer trimethylolpropane triacrylate (TMPTA) and the commercial nematic mixture E7. The variation of the main dipolar splitting of {sup 1}H spectra with increasing temperature was analyzed to obtain the nematic-to-isotropic phase transition temperature and the nematic order parameter of E7 and, for comparison, the nematic liquid crystal 5CB.Diffusion constants in TMPTA/E7 mixtures, measured by pulsed-field gradient NMR, increase for both E7 and TMPTA as the mass fraction of E7 increases, due to the lower viscosity of E7. E7 in the PDLC diffuses more slowly than in the bulk because of the hindrance by the polymer matrix. T{sub 1} and T{sub 1{rho}} relaxation times in the liquid or liquid-crystalline phases of TMPTA and bulk E7 are higher than in the PDLC and the pure polymer, due to the lower mobility in the polymer samples. T{sub 1{rho}} in the PDLC is even shorter than in the pure polymer, indicating an anti-softening effect caused by E7 molecules. In bulk E7, the well-ordered rod-like molecules exhibit a unique H-C dipolar coupling, which leads to oscillations in the cross-polarization curve. However, in the PDLC, the anchoring effect at the boundary between the polymer and LC droplets disturbs the molecular order resulting in a smooth cross polarization curve.

  7. Investigation of a polymer-dispersed liquid crystal system by NMR diffusometry and relaxometry

    International Nuclear Information System (INIS)

    Tang, Mingxue

    2013-01-01

    Polymer-dispersed liquid crystals (PDLCs) are polymer composites containing a dispersion of liquid crystal droplets in polymer networks. PDLCs have attracted much attention due to their unique properties and potential usage. The properties of PDLCs depend on the degree of phase separation and the size of liquid crystal droplets. To investigate the structure will help us to better understand and optimize PDLCs.The main aim of this PhD thesis was to investigate PDLCs by NMR techniques. Diffusion constants and spin-lattice relaxation times in the laboratory (T 1 ) and rotating frame (T 1ρ ) were measured for PDLCs as well as precursor mixtures based on the trifunctional monomer trimethylolpropane triacrylate (TMPTA) and the commercial nematic mixture E7. The variation of the main dipolar splitting of 1 H spectra with increasing temperature was analyzed to obtain the nematic-to-isotropic phase transition temperature and the nematic order parameter of E7 and, for comparison, the nematic liquid crystal 5CB.Diffusion constants in TMPTA/E7 mixtures, measured by pulsed-field gradient NMR, increase for both E7 and TMPTA as the mass fraction of E7 increases, due to the lower viscosity of E7. E7 in the PDLC diffuses more slowly than in the bulk because of the hindrance by the polymer matrix. T 1 and T 1ρ relaxation times in the liquid or liquid-crystalline phases of TMPTA and bulk E7 are higher than in the PDLC and the pure polymer, due to the lower mobility in the polymer samples. T 1ρ in the PDLC is even shorter than in the pure polymer, indicating an anti-softening effect caused by E7 molecules. In bulk E7, the well-ordered rod-like molecules exhibit a unique H-C dipolar coupling, which leads to oscillations in the cross-polarization curve. However, in the PDLC, the anchoring effect at the boundary between the polymer and LC droplets disturbs the molecular order resulting in a smooth cross polarization curve.

  8. Solid state nuclear magnetic resonance: investigating the spins of nuclear related materials

    International Nuclear Information System (INIS)

    Charpentier, Th.

    2007-10-01

    The author reviews his successive research works: his research thesis work on the Multiple Quantum Magic Angle Spinning (MQMAS) which is a quadric-polar nucleus multi-quanta correlation spectroscopy method, the modelling of NMR spectra of disordered materials, the application to materials of interest for the nuclear industry (notably the glasses used for nuclear waste containment). He presents the various research projects in which he is involved: storing glasses, nuclear magnetic resonance in paramagnetism, solid hydrogen storing matrices, methodological and instrument developments in high magnetic field and high resolution solid NMR, long range distance measurement by solid state Tritium NMR (observing the structure and dynamics of biological complex systems at work)

  9. NMR relaxation in spin ice at low temperature due to diffusing emergent monopoles

    Science.gov (United States)

    Henley, Christopher L.

    2013-03-01

    At low temperatures, spin dynamics in ideal spin ice is due mainly to dilute, thermally excited magnetic ``monopole'' excitations. I consider how these will affect the longitudinal (T1) and dephasing (T2) relaxation functions of a nuclear spin in the spin-ice pyrochlore Dy2Ti2O4. Up to the time scale for nearby monopoles to be rearranged, a stretched-exponential form of the relaxation functions is expected, due to averaging over nuclei that have different local environments. ror the dephasing (T2) relaxation, the power of time in the stretched exponential is 3/2 in the case of diffusing monopoles, but 1/2 in the case of fixed, fluctuating magnetic impurities. The flip rate and density of fluctuating spins (whatever their nature) can be extracted from the measured relaxation times T1 and T2, and from known parameters. However, the actual experimental relaxation measured by Kitagawa and Takigawa becomes temperature independent in the very low T limit, and the T2 has a power t 1 / 2 in the exponential, neither of which can be explained by monopoles. I suggest the very low T behavior could be due to magnetic impurities on the (normally nonmagnetic) Ti sites. Supported by NSF grant DMR-1005466.

  10. Multinuclear solid-state high-resolution and C-13 -{Al-27} double-resonance magic-angle spinning NMR studies on aluminum alkoxides

    NARCIS (Netherlands)

    Abraham, A.; Prins, R.; Bokhoven, J.A. van; Eck, E.R.H. van; Kentgens, A.P.M.

    2006-01-01

    A combination of Al-27 magic-angle spinning (MAS)/multiple quantum (MQ)-MAS, C-13-H-1 CPMAS, and C-13-{Al-27} transfer of population in double-resonance (TRAPDOR) nuclear magnetic resonance (NMR) were used for the structural elucidation of the aluminum alkoxides aluminum ethoxide, aluminum

  11. NMR water-proton spin-lattice relaxation time of human red blood cells and red blood cell suspensions

    International Nuclear Information System (INIS)

    Sullivan, S.G.; Rosenthal, J.S.; Winston, A.; Stern, A.

    1988-01-01

    NMR water-proton spin-lattice relaxation times were studied as probes of water structure in human red blood cells and red blood cell suspensions. Normal saline had a relaxation time of about 3000 ms while packed red blood cells had a relaxation time of about 500 ms. The relaxation time of a red blood cell suspension at 50% hematocrit was about 750 ms showing that surface charges and polar groups of the red cell membrane effectively structure extracellular water. Incubation of red cells in hypotonic saline increases relaxation time whereas hypertonic saline decreases relaxation time. Relaxation times varied independently of mean corpuscular volume and mean corpuscular hemoglobin concentration in a sample population. Studies with lysates and resealed membrane ghosts show that hemoglobin is very effective in lowering water-proton relaxation time whereas resealed membrane ghosts in the absence of hemoglobin are less effective than intact red cells. 9 refs.; 3 figs.; 1 table

  12. A robust heteronuclear dipolar recoupling method comparable to TEDOR for proteins in magic-angle spinning solid-state NMR

    Science.gov (United States)

    Zhang, Zhengfeng; Li, Jianping; Chen, Yanke; Xie, Huayong; Yang, Jun

    2017-12-01

    In this letter, we propose a robust heteronuclear dipolar recoupling method for proteins in magic-angle spinning (MAS) solid-state NMR. This method is as simple, robust and efficient as the well-known TEDOR in the aspect of magnetization transfer between 15N and 13C. Deriving from our recent band-selective dual back-to-back pulses (DBP) (Zhang et al., 2016), this method uses new phase-cycling schemes to realize broadband DBP (Bro-DBP). For broadband 15N-13C magnetization transfer (simultaneous 15N → 13C‧ and 15N → 13Cα), Bro-DBP has almost the same 15N → 13Cα efficiency while offers 30-40% enhancement on 15N → 13C‧ transfer, compared to TEDOR. Besides, Bro-DBP can also be used as a carbonyl (13C‧)-selected method, whose 15N → 13C‧ efficiency is up to 1.7 times that of TEDOR and is also higher than that of band-selective DBP. The performance of Bro-DBP is demonstrated on the N-formyl-[U-13C,15N]-Met-Leu-Phe-OH (fMLF) peptide and the U-13C, 15N labeled β1 immunoglobulin binding domain of protein G (GB1) microcrystalline protein. Since Bro-DBP is as robust, simple and efficient as TEDOR, we believe it is very useful for protein studies in MAS solid-state NMR.

  13. Magic angle spinning NMR below 6 K with a computational fluid dynamics analysis of fluid flow and temperature gradients

    Science.gov (United States)

    Sesti, Erika L.; Alaniva, Nicholas; Rand, Peter W.; Choi, Eric J.; Albert, Brice J.; Saliba, Edward P.; Scott, Faith J.; Barnes, Alexander B.

    2018-01-01

    We report magic angle spinning (MAS) up to 8.5 kHz with a sample temperature below 6 K using liquid helium as a variable temperature fluid. Cross polarization 13C NMR spectra exhibit exquisite sensitivity with a single transient. Remarkably, 1H saturation recovery experiments show a 1H T1 of 21 s with MAS below 6 K in the presence of trityl radicals in a glassy matrix. Leveraging the thermal spin polarization available at 4.2 K versus 298 K should result in 71 times higher signal intensity. Taking the 1H longitudinal relaxation into account, signal averaging times are therefore predicted to be expedited by a factor of >500. Computer assisted design (CAD) and finite element analysis were employed in both the design and diagnostic stages of this cryogenic MAS technology development. Computational fluid dynamics (CFD) models describing temperature gradients and fluid flow are presented. The CFD models bearing and drive gas maintained at 100 K, while a colder helium variable temperature fluid stream cools the center of a zirconia rotor. Results from the CFD were used to optimize the helium exhaust path and determine the sample temperature. This novel cryogenic experimental platform will be integrated with pulsed dynamic nuclear polarization and electron decoupling to interrogate biomolecular structure within intact human cells.

  14. Protein residue linking in a single spectrum for magic-angle spinning NMR assignment

    Energy Technology Data Exchange (ETDEWEB)

    Andreas, Loren B.; Stanek, Jan; Marchand, Tanguy Le; Bertarello, Andrea; Paepe, Diane Cala-De; Lalli, Daniela; Krejčíková, Magdaléna; Doyen, Camille; Öster, Carl [Université de Lyon, Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques (CNRS, ENS Lyon, UCB Lyon 1) (France); Knott, Benno; Wegner, Sebastian; Engelke, Frank [Bruker Biospin (Germany); Felli, Isabella C.; Pierattelli, Roberta [University of Florence, Department of Chemistry “Ugo Schiff“and Magnetic Resonance Center (CERM) (Italy); Dixon, Nicholas E. [University of Wollongong, School of Chemistry (Australia); Emsley, Lyndon; Herrmann, Torsten; Pintacuda, Guido, E-mail: guido.pintacuda@ens-lyon.fr [Université de Lyon, Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques (CNRS, ENS Lyon, UCB Lyon 1) (France)

    2015-07-15

    Here we introduce a new pulse sequence for resonance assignment that halves the number of data sets required for sequential linking by directly correlating sequential amide resonances in a single diagonal-free spectrum. The method is demonstrated with both microcrystalline and sedimented deuterated proteins spinning at 60 and 111 kHz, and a fully protonated microcrystalline protein spinning at 111 kHz, with as little as 0.5 mg protein sample. We find that amide signals have a low chance of ambiguous linkage, which is further improved by linking in both forward and backward directions. The spectra obtained are amenable to automated resonance assignment using general-purpose software such as UNIO-MATCH.

  15. Numerical calculation of spin echo amplitude in pulsed NMR: effects of quadrupole interaction

    International Nuclear Information System (INIS)

    Sobral, R.R.

    1986-01-01

    The spin echo obtained by nuclear magnetic resonance, in systems which atomic nuclei interact with magnetic fields and electric field gradients, present oscillations in function of the time interval between two excitations pulses. Using the density matrix formalism, the amplitudes of these echo is calculated, analytically. In this work, echo amplitudes obtained under different excitation conditions for nuclei of different nuclear spin values are calculated. The numerical results are compared with disposable analytical solutions. Applications of this method to the case of electric field gradient without axial symmetry were studied. Within the used approximation limits, an expression for attnuation of oscillatory behaviour of echo amplitude in function of the time interval between experimentally observed pulses was obtained. (M.C.K.) [pt

  16. Optical Orientation and Inverse Spin Hall Effect as Effective Tools to Investigate Spin-Dependent Diffusion

    Directory of Open Access Journals (Sweden)

    Marco Finazzi

    2016-11-01

    Full Text Available In this work we address optical orientation, a process consisting in the excitation of spin polarized electrons across the gap of a semiconductor. We show that the combination of optical orientation with spin-dependent scattering leading to the inverse spin-Hall effect, i.e., to the conversion of a spin current into an electrical signal, represents a powerful tool to generate and detect spin currents in solids. We consider a few examples where these two phenomena together allow addressing the spin-dependent transport properties across homogeneous samples or metal/semiconductor Schottky junctions.

  17. {sup 119}Sn NMR investigations on superconducting Ca{sub 3}Ir{sub 4}Sn{sub 13}

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Rajib; Brueckner, Felix; Guenther, Marco; Klauss, Hans-Henning [IFP, TU Dresden (Germany); Petrovic, Cedomir; Wang, Kefeng [CMPMS, BNL, Upton, NY (United States); Luetkens, Hubertus; Biswas, Pabitra; Morenzoni, Elvezio; Amato, Alex [PSI, Villigen (Switzerland)

    2014-07-01

    Ca{sub 3}Ir{sub 4}Sn{sub 13} was found to exhibit superconducting transition with T{sub c} ∼ 7 K. It received considerable attention due to the possible coexistence of superconductivity and ferromagnetic spin fluctuation as well as the three-dimensional charge density wave (CDW) from the superlattice transition. While thermal, transport, and thermodynamic characterization of Ca{sub 3}Ir{sub 4}Sn{sub 13} single crystals suggest that it is a weakly correlated nodeless superconductor, recent μSR investigation reveals that the electron-phonon pairing interaction is in the strong-coupling limit. Here we present {sup 119}Sn NMR investigations on Ca{sub 3}Ir{sub 4}Sn{sub 13} polycrystalline samples and discuss the symmetry of the superconducting order parameter together with the normal state properties. Our preliminary results of spin-lattice relaxation rate (1/T{sub 1}) indicate that this is a BCS superconductor with weak-coupling limit.

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  19. ^51V NMR Study of the Magnetic Structure of the Frustrated Zig-Zag Spin-1 Chain Compound CaV2O4

    Science.gov (United States)

    Zong, X.; Suh, B. J.; Niazi, A.; Johnston, D. C.

    2007-03-01

    ^51V NMR measurements have been performed on a single crystal of orthorhombic (at room temperature) CaV2O4 in zero applied magnetic field and with a small perturbing field up to H = 2 T, at temperatures well below the N'eel temperature TN= 78 K@. The c-axis is parallel to the chains. At H = 0, a broad ^51V NMR spectrum with a peak at 237 MHz was observed. The effective local hyperfine field Heff = 21.2 T corresponding to the peak frequency 237 MHz is in good agreement with expectation for the V^3+ S = 1 spin state. In Hc, the spectrum splits into two parts that are equally separated from the peak position at zero field. The separation of the parts depends strongly both on the magnitude and direction of H with respect to the crystal axes. Our NMR results are consistent with a collinear antiferromagnetic spin structure with the spin direction along the b-axis, which together with the magnetization data suggest that the antiferromagnetic long-range order arises from an order-from-disorder mechanism. We also present the temperature and orientation dependence of the spin-lattice relaxation rate 1/T1.

  20. NMR study of the molecular nanomagnet [Fe8(N3C6H15)6O2(OH)12]·[Br8·9H2O] in the high-spin magnetic ground state

    International Nuclear Information System (INIS)

    Furukawa, Y.; Kumagai, K.; Lascialfari, A.; Aldrovandi, S.; Borsa, F.; Sessoli, R.; Gatteschi, D.

    2001-01-01

    The magnetic molecular cluster [Fe 8 (N 3 C 6 H 15 ) 6 O 2 (OH) 12 ] 8+ [Br 8 ·9H 2 O] 8- , in short Fe8, has been investigated at low temperature by 1 H-NMR and relaxation measurements. Some measurements of 2 D-NMR in partially deuterated Fe8 clusters will also be reported. Upon decreasing temperature the NMR spectra display a very broad and structured signal which is the result of the internal local fields at the proton sites due to the local moments of the Fe(III) ions in the total S=10 magnetic ground state. The proton and deuteron NMR spectra have been analyzed and the different resonance peaks have been attributed to the different proton groups in the molecule. The simulation of the spectra by using a dipolar hyperfine field and the accepted model for the orientation of the Fe(III) local moments do not agree with the experiments even when the magnitude of the local Fe(III) moments is allowed to vary. It is concluded that a positive contact hyperfine interaction of the same order of magnitude as the dipolar interaction is present for all proton sites except the water molecules. The temperature and magnetic field dependence of the nuclear spin-lattice relaxation rate is ascribed to the fluctuations of the local Fe(III) moments, which follow rigidly the fluctuations of the total ground state magnetization of the nanomagnet. By using a simple model already utilized for the Mn12 cluster, we derive the value of the spin phonon coupling constant which determines the lifetime broadening of the different magnetic quantum number m substates of the S=10 ground state. It is shown that the lifetime broadening decreases rapidly on lowering the temperature. When the lifetime becomes longer than the reciprocal of the frequency shift of the proton lines a structure emerges in the NMR spectrum reflecting the ''frozen'' local moment configuration

  1. An automated framework for NMR resonance assignment through simultaneous slice picking and spin system forming

    KAUST Repository

    Abbas, Ahmed

    2014-04-19

    Despite significant advances in automated nuclear magnetic resonance-based protein structure determination, the high numbers of false positives and false negatives among the peaks selected by fully automated methods remain a problem. These false positives and negatives impair the performance of resonance assignment methods. One of the main reasons for this problem is that the computational research community often considers peak picking and resonance assignment to be two separate problems, whereas spectroscopists use expert knowledge to pick peaks and assign their resonances at the same time. We propose a novel framework that simultaneously conducts slice picking and spin system forming, an essential step in resonance assignment. Our framework then employs a genetic algorithm, directed by both connectivity information and amino acid typing information from the spin systems, to assign the spin systems to residues. The inputs to our framework can be as few as two commonly used spectra, i.e., CBCA(CO)NH and HNCACB. Different from the existing peak picking and resonance assignment methods that treat peaks as the units, our method is based on \\'slices\\', which are one-dimensional vectors in three-dimensional spectra that correspond to certain (N, H) values. Experimental results on both benchmark simulated data sets and four real protein data sets demonstrate that our method significantly outperforms the state-of-the-art methods while using a less number of spectra than those methods. Our method is freely available at http://sfb.kaust.edu.sa/Pages/Software.aspx. © 2014 Springer Science+Business Media.

  2. 31P and 29Si NMR investigations of the structure of NASICON-compounds

    International Nuclear Information System (INIS)

    Jaeger, C.; Scheler, G.; Barth, S.; Feltz, A.

    1988-01-01

    First systematic NMR investigations of several NASICON compounds are described. In the original NASICON Na 1+x Zr 2 (SiO 4 ) x (PO 4 ) 3-x the observed down-field shift (for increasing x) of both 31 P and 29 Si MAS NMR lines is explained by a change of the net atomic charge of the zirconium atoms caused by the substitution of the lattice positions of phosphorus by silicon atoms. The 'von Alpen' compound Na 4 ZrSi 3 O 10 consists of two phases; the crystalline Na 4 Zr 2 (SiO 4 ) 3 and the glassy phase 2 Na 2 O · 3 SiO 2 . Moreover, it is shown that NMR can be used to investigate the statistical substitution of lattice positions of the zirconium atoms by magnesium atoms in the mixed crystals Na 1+2x Mg x Zr 2-x (PO 4 ) 3 . (author)

  3. Structural investigation of e-beam cured epoxy resins through solid state NMR

    International Nuclear Information System (INIS)

    Alessi, Sabina; Spinella, Alberto; Caponetti, Eugenio; Dispenza, Clelia; Spadaro, Giuseppe

    2012-01-01

    In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artefact, are obtained by solid state NMR, carried out at constant room temperature. - Highlights: ► The structure of two e-beam cured epoxy systems is investigated through solid state NMR. ► The aim is to have direct information about the structure without inducing modifications. ► The different molecular structures are able to emphasize the response of solid state NMR. ► T 1 H, T 1ρ H and T CH measurements indicate different cross-linking degrees. ► The NMR results are in agreement with DMTA analysis performed in a previous paper.

  4. Molecular motions in thermotropic liquid crystals studied by NMR spin-lattice relaxation

    International Nuclear Information System (INIS)

    Zamar, R.C.; Gonzalez, C.E.; Mensio, O.

    1998-01-01

    Nuclear magnetic resonance relaxation experiments with field cycling techniques proved to be a valuable tool for studying molecular motions in liquid crystals, allowing a very broad Larmor frequency variation, sufficient to separate the cooperative motions from the liquid like molecular diffusion. In new experiments combining NMR field cycling with the Jeener-Broekaert order-transfer pulse sequence, it is possible to measure the dipolar order relaxation time (T 1D ), in addition to the conventional Zeeman relaxation time (T 1Z ) in a frequency range of several decades. When applying this technique to nematic thermotropic liquid crystals, T 1D showed to depend almost exclusively on the order fluctuation of the director mechanism in the whole frequency range. This unique characteristic of T 1D makes dipolar order relaxation experiments specially useful for studying the frequency and temperature dependence of the spectral properties of the collective motions. (author)

  5. Magic-Angle-Spinning NMR Magnet Development: Field Analysis and Prototypes

    Science.gov (United States)

    Voccio, John; Hahn, Seungyong; Park, Dong Keun; Ling, Jiayin; Kim, Youngjae; Bascuñán, Juan; Iwasa, Yukikazu

    2013-01-01

    We are currently working on a program to complete a 1.5 T/75 mm RT bore magic-angle-spinning nuclear magnetic resonance magnet. The magic-angle-spinning magnet comprises a z-axis 0.866-T solenoid and an x-axis 1.225-T dipole, each to be wound with NbTi wire and operated at 4.2 K in persistent mode. A combination of the fields creates a 1.5-T field pointed at 54.74 degrees (magic angle) from the rotation (z) axis. In the first year of this 3-year program, we have completed magnetic analysis and design of both coils. Also, using a winding machine of our own design and fabrication, we have wound several prototype dipole coils with NbTi wire. As part of this development, we have repeatedly made successful persistent NbTi-NbTi joints with this multifilamentary NbTi wire. PMID:24058275

  6. Experimental investigation of axially aligned flow past spinning cylinders

    Science.gov (United States)

    Carlucci, Pasquale; Buckley, Liam; Mehmedagic, Igbal; Carlucci, Donald; Thangam, Siva

    2016-11-01

    Experimental and numerical results of ongoing subsonic investigations of the flow field about axially aligned spinning cylinders with variable inter-cylinder spacing are presented. The experimental design is capable of investigating wake dynamics of the modeled system up to a Reynolds Number of 300,000 and rotation numbers up to 2. The experimental results are used to validate and confirm numerical simulations with and without the effects of swirl. The focus of the overall effort is an understanding of the dynamics of multi-body problems in a flow field, as such we relate the ongoing effort to previous studies by both the authors and the community at large and our ongoing work in developing accurate plant models for use in engineering analysis and design. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.

  7. Spin glasses (II)

    International Nuclear Information System (INIS)

    Fischer, K.H.

    1985-01-01

    Experimental results of spin glass studies are reviewed and related to existing theories. Investigations of spin glasses are concentrated on atomic structure, metallurgical treatment, and high-temperature susceptibility of alloys, on magnetic properties at low temperature and near the freezing temperature, on anisotropy behaviour measured by ESR, NMR and torque, on specific heat, Moessbauer effect, neutron scattering and muon-spin depolarization experiments, ultrasound and transport properties. Some new theories of spin glasses are discussed which have been developed since Part I appeared

  8. Chemical profile of beans cultivars (Phaseolus vulgaris) by 1H NMR - high resolution magic angle spinning (HR-MAS);Perfil quimico de cultivares de feijao (Phaseolus vulgaris) pela tecnica de high resolution magic angle spinning (HR-MAS)

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Luciano Morais; Choze, Rafael; Cavalcante, Pedro Paulo Araujo; Santos, Suzana da Costa; Ferri, Pedro Henrique, E-mail: luciano@quimica.ufg.b [Universidade Federal de Goias (UFG), Goiania, GO (Brazil). Inst. de Quimica; Ferreira, Antonio Gilberto [Universidade Federal de Sao Carlos (UFScar), SP (Brazil). Dept. de Quimica

    2010-07-01

    The application of one-dimensional proton high-resolution magic angle spinning ({sup 1}H HR-MAS) NMR combined with a typical advantages of solid and liquid-state NMR techniques was used as input variables for the multivariate statistical analysis. In this paper, different cultivars of beans (Phaseolus vulgaris) developed and in development by EMBRAPA - Arroz e Feijao were analyzed by {sup 1}H HR-MAS, which have been demonstrated to be a valuable tool in its differentiation according chemical composition and avoid the manipulation of the samples as used in other techniques. (author)

  9. Correlating the P-31 NMR Chemical Shielding Tensor and the (2)J(P,C) Spin-Spin Coupling Constants with Torsion Angles zeta and alpha in the Backbone of Nucleic Acids

    Czech Academy of Sciences Publication Activity Database

    Benda, Ladislav; Sochorová Vokáčová, Zuzana; Straka, Michal; Sychrovský, Vladimír

    2012-01-01

    Roč. 116, č. 12 (2012), s. 3823-3833 ISSN 1520-6106 R&D Projects: GA ČR GAP205/10/0228; GA ČR GPP208/10/P398; GA ČR GA203/09/2037 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleic acids * phosphorus NMR * NMR calculations * cross-correlated relaxation * spin–spin coupling constants Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.607, year: 2012

  10. Joule heating and spin-transfer torque investigated on the atomic scale using a spin-polarized scanning tunneling microscope.

    Science.gov (United States)

    Krause, S; Herzog, G; Schlenhoff, A; Sonntag, A; Wiesendanger, R

    2011-10-28

    The influence of a high spin-polarized tunnel current onto the switching behavior of a superparamagnetic nanoisland on a nonmagnetic substrate is investigated by means of spin-polarized scanning tunneling microscopy. A detailed lifetime analysis allows for a quantification of the effective temperature rise of the nanoisland and the modification of the activation energy barrier for magnetization reversal, thereby using the nanoisland as a local thermometer and spin-transfer torque analyzer. Both the Joule heating and spin-transfer torque are found to scale linearly with the tunnel current. The results are compared to experiments performed on lithographically fabricated magneto-tunnel junctions, revealing a very high spin-transfer torque switching efficiency in our experiments.

  11. A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

    Energy Technology Data Exchange (ETDEWEB)

    Song, Xuerui; Zhang, Jian; Feng, Fupan; Wang, Junfeng; Zhang, Wenlong; Lou, Liren; Zhu, Wei; Wang, Guanzhong, E-mail: gzwang@ustc.edu.cn [Hefei National Laboratory for Physical Science at Microscale, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026 (China)

    2014-04-15

    We investigated the influence of spins on surface of nanodiamonds (NDs) to the longitudinal relaxation time (T{sub 1}) and transverse relaxation time (T{sub 2}) of nitrogen vacancy (NV) centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T{sub 1} and T{sub 2}, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T{sub 1} of NV center inside is highly dependent to the surface spins of the NDs. However, for the T{sub 2} of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T{sub 1} of an NV center in NDs is more sensitive to the change of the surface spin density than T{sub 2}.

  12. A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

    Directory of Open Access Journals (Sweden)

    Xuerui Song

    2014-04-01

    Full Text Available We investigated the influence of spins on surface of nanodiamonds (NDs to the longitudinal relaxation time (T1 and transverse relaxation time (T2 of nitrogen vacancy (NV centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T1 and T2, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T1 of NV center inside is highly dependent to the surface spins of the NDs. However, for the T2 of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T1 of an NV center in NDs is more sensitive to the change of the surface spin density than T2.

  13. NMR study of spin fluctuations and superconductivity in LaFeAsO1-xHx

    Science.gov (United States)

    Fujiwara, Naoki; Sakurai, Ryosuke; Iimura, Soushi; Matsuishi, Satoru; Hosono, Hideo; Yamakawa, Yoichi; Kontani, Hiroshi

    2013-03-01

    We have performed NMR measurements in LaFeAsO1-xHx, an isomorphic compound of LaFeAsO1-xFx. LaFeAsO1-xHx is most recently known for having double superconducting (SC) domes on H doping. LaFeAsO1-xHx is an electron- doped system, and protons act as H-1 as well as F-1. The first SC dome is very similar between F and H doping, suggesting that H doping supplies the same amount of electrons as F doping. Interestingly, an excess amount of H up to x=0.5 can be replaced with O2-. In the H-overdoped regime (x > 0 . 2), LaFeAsO1-xHx undergoes the second superconducting state. We measured the relaxation rate of LaFeAsO1-xHx for x=0.2 and 0.4, and fond an anomalous electronic state; spin fluctuations measured from 1 /T1 T is enhanced with increasing the doping level from x = 0 . 2 to 0.4. The enhancement of spin fluctuations with increasing carrier doping is a new phenomenon that has not observed in LaFeAsO1-xFx in which the upper limit of the doping level is at most x = 0 . 2 . We will discuss the phenomenon in relation to superconductivity. Grant (KAKENHI 23340101) from the Ministry of Education, Sports and Science, Japan

  14. Pneumatic switched angle spinning NMR probe with capacitively coupled double saddle coil.

    Science.gov (United States)

    Litvak, Ilya M; Espinosa, Catalina A; Shapiro, Rebecca A; Oldham, Andrew N; Duong, Vincent V; Martin, Rachel W

    2010-10-01

    Switched angle spinning (SAS) experiments can be used for generating isotropic-anisotropic correlations in oriented samples in a single experiment. In order for these methods to become widespread, specialized hardware is required. Here we describe the electronic and mechanical design and performance of a double-resonance SAS probe. Unlike many previous SAS probe implementations, the focus here is on systems where the dipolar couplings are partially averaged by molecular motion. This probe has a moving double saddle coil capacitively coupled to the stationary circuit. Angle switching is accomplished by a steam engine-type pneumatic mechanism. The speed and stability of the switching hardware for SAS experiments are demonstrated using spectra of model compounds. Copyright © 2010 Elsevier Inc. All rights reserved.

  15. 17O NMR investigation of oxidative degradation in polymers under γ-irradiation

    International Nuclear Information System (INIS)

    ALAM, TODD M.; CELINA, MATHIAS C.; ASSINK, ROGER A.; CLOUGH, ROGER LEE; GILLEN, KENNETH T.

    2000-01-01

    The γ-irradiated-oxidation of pentacontane (C 50 H 102 ) and the polymer polyisoprene was investigated as a function of oxidation level using 17 O nuclear magnetic resonance (NMR) spectroscopy. It is demonstrated that by using 17 O labeled O 2 gas during the γ-irradiation process, details about the oxidative degradation mechanisms can be directly obtained from the analysis of the 17 O NMR spectra. Production of carboxylic acids is the primary oxygen-containing functionality during the oxidation of pentacontane, while ethers and alcohols are the dominant oxidation product observed for polyisoprene. The formation of ester species during the oxidation process is very minor for both materials, with water also being produced in significant amounts during the radiolytic oxidation of polyisoprene. The ability to focus on the oxidative component of the degradation process using 17 O NMR spectroscopy demonstrates the selectivity of this technique over more conventional approaches

  16. Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe.

    Science.gov (United States)

    Nanni, Emilio A; Barnes, Alexander B; Matsuki, Yoh; Woskov, Paul P; Corzilius, Björn; Griffin, Robert G; Temkin, Richard J

    2011-05-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B(1S)) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4mm diameter sapphire rotor containing the sample. The predicted average B(1S) field is 13μT/W(1/2), where S denotes the electron spin. For a routinely achievable input power of 5W the corresponding value is γ(S)B(1S)=0.84MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ϵ) vs. ω(1S)/(2π) for a sample of (13)C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. HIV-1 Capsid Function is Regulated by Dynamics: Quantitative Atomic-Resolution Insights by Integrating Magic-Angle-Spinning NMR, QM/MM, and MD.

    Science.gov (United States)

    Zhang, Huilan; Hou, Guangjin; Lu, Manman; Ahn, Jinwoo; Byeon, In-Ja L; Langmead, Christopher J; Perilla, Juan R; Hung, Ivan; Gor'kov, Peter L; Gan, Zhehong; Brey, William W; Case, David A; Schulten, Klaus; Gronenborn, Angela M; Polenova, Tatyana

    2016-10-05

    HIV-1 CA capsid protein possesses intrinsic conformational flexibility, which is essential for its assembly into conical capsids and interactions with host factors. CA is dynamic in the assembled capsid, and residues in functionally important regions of the protein undergo motions spanning many decades of timescales. Chemical shift anisotropy (CSA) tensors, recorded in magic-angle-spinning NMR experiments, provide direct residue-specific probes of motions on nano- to microsecond timescales. We combined NMR, MD, and Density-Functional-Theory calculations, to gain quantitative understanding of internal backbone dynamics in CA assemblies, and found that the dynamically averaged 15 N CSA tensors calculated by this joined protocol are in remarkable agreement with experiment. Thus, quantitative atomic-level understanding of the relationships between CSA tensors, local backbone structure and motions in CA assemblies is achieved, demonstrating the power of integrating NMR experimental data and theory for characterizing atomic-resolution dynamics in biological systems.

  18. Exotic spin phases in the one-dimensional spin-1/2 quantum magnet LiCuSbO{sub 4} as seen by high-field NMR and ESR spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Iakovleva, Margarita [IFW Dresden, Dresden (Germany); TU Dresden, Dresden (Germany); Zavoisky Physical Technical Institute, Kazan (Russian Federation); Grafe, Hans-Joachim; Kataev, Vladislav; Alfonsov, Alexey; Sturza, Mihai I.; Wurmehl, Sabine [IFW Dresden, Dresden (Germany); Vavilova, Evgeniia [Zavoisky Physical Technical Institute, Kazan (Russian Federation); Nojiri, Hiroyuki [Institute of Materials Research, Sendai (Japan); Buechner, Bernd [IFW Dresden, Dresden (Germany); TU Dresden, Dresden (Germany)

    2016-07-01

    We will present our recent results of high-field NMR and sub-THz ESR studies of the quantum magnet LiCuSbO{sub 4} (LCSO) that presents an excellent model system of a one-dimensional spin-1/2 quantum magnet with frustrated exchange interactions. Such networks are predicted to exhibit a plethora of novel ground states beyond classical ferro- or antiferromagnetic phases. In LCSO the absence of a long-range magnetic order down to sub-Kelvin temperatures is suggestive of the realization of a quantum spin liquid state. Our NMR and ESR measurements in strong magnetic fields up to 16 Tesla reveal clear indications for the occurrence of an exotic field-induced hidden phase which we will discuss in terms of multipolar physics.

  19. Zero-field NMR study on a spin glass: iron-doped 2H-niobium diselenide

    International Nuclear Information System (INIS)

    Chen, M.C.

    1982-01-01

    Spin echoes are used to study the 93 Nb NQR in 2H-NbSe 2 Fe/sub x/. Measured are (intensity) x (temperature), and T/sub 1P/ (spin-lattice relaxation parameter) and T 2 (spin-spin relaxation time) as a function of temperature. Data reveal dramatic differences between non-spin glass samples (x = 0, 0.25%, 1% and 5%) and spin glass samples (x = 8%, 10% and 12%). All of the NQR results and the model calculation of the correlation times of Fe spins are best described by the phase transition picture of spin glasses

  20. Selectively dispersed isotope labeling for protein structure determination by magic angle spinning NMR

    Energy Technology Data Exchange (ETDEWEB)

    Eddy, Matthew T. [Massachusetts Institute of Technology, Department of Chemistry (United States); Belenky, Marina [Brandeis University, Department of Chemistry (United States); Sivertsen, Astrid C. [Massachusetts Institute of Technology, Francis Bitter Magnet Laboratory (United States); Griffin, Robert G. [Massachusetts Institute of Technology, Department of Chemistry (United States); Herzfeld, Judith, E-mail: herzfeld@brandeis.edu [Brandeis University, Department of Chemistry (United States)

    2013-10-15

    The power of nuclear magnetic resonance spectroscopy derives from its site-specific access to chemical, structural and dynamic information. However, the corresponding multiplicity of interactions can be difficult to tease apart. Complimentary approaches involve spectral editing on the one hand and selective isotope substitution on the other. Here we present a new 'redox' approach to the latter: acetate is chosen as the sole carbon source for the extreme oxidation numbers of its two carbons. Consistent with conventional anabolic pathways for the amino acids, [1-{sup 13}C] acetate does not label {alpha} carbons, labels other aliphatic carbons and the aromatic carbons very selectively, and labels the carboxyl carbons heavily. The benefits of this labeling scheme are exemplified by magic angle spinning spectra of microcrystalline immunoglobulin binding protein G (GB1): the elimination of most J-couplings and one- and two-bond dipolar couplings provides narrow signals and long-range, intra- and inter-residue, recoupling essential for distance constraints. Inverse redox labeling, from [2-{sup 13}C] acetate, is also expected to be useful: although it retains one-bond couplings in the sidechains, the removal of CA-CO coupling in the backbone should improve the resolution of NCACX spectra.

  1. Investigating Supermassive Black Hole Spin at Different Redshift

    Science.gov (United States)

    Sinanan-Singh, Jasmine

    2018-01-01

    Supermassive black hole (SMBH) spin encodes vital information about the history of SMBH growth. High spins indicate a history of growth through large mass accretion events, which spin-up the black hole; Intermediate spins indicate a history of galactic mergers, which don't tend to systemcatically spin-up or spin-down black holes; low spins are attributed to successive, small accretion events with random orientations. Examining spin over different redshifts will help us understand the relative growth of SMBHs by mergers or accretion over cosmic time, an important part of understanding how SMBHs and their host galaxies co-evolved over time. To study spin, we compute the Fe K alpha emission line from the X-ray spectra of AGN sources in the Chandra-COSMOS Legacy Survey. We stack rest frame AGN spectra to improve the signal-to-noise ratio since the photon counts are low for individual spectra, and then average the spectra using an unwieghted mean. Our method is derived from Corral et al. (2008). We test our method on the two brightest sources in the COSMOS Survey and compute the rest frame average Fe K alpha emission line for different redshift bins. The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

  2. Intramolecular Hydrogen Bonding Involving Organic Fluorine: NMR Investigations Corroborated by DFT-Based Theoretical Calculations

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar Mishra

    2017-03-01

    Full Text Available The combined utility of many one and two dimensional NMR methodologies and DFT-based theoretical calculations have been exploited to detect the intramolecular hydrogen bond (HB in number of different organic fluorine-containing derivatives of molecules, viz. benzanilides, hydrazides, imides, benzamides, and diphenyloxamides. The existence of two and three centered hydrogen bonds has been convincingly established in the investigated molecules. The NMR spectral parameters, viz., coupling mediated through hydrogen bond, one-bond NH scalar couplings, physical parameter dependent variation of chemical shifts of NH protons have paved the way for understanding the presence of hydrogen bond involving organic fluorine in all the investigated molecules. The experimental NMR findings are further corroborated by DFT-based theoretical calculations including NCI, QTAIM, MD simulations and NBO analysis. The monitoring of H/D exchange with NMR spectroscopy established the effect of intramolecular HB and the influence of electronegativity of various substituents on the chemical kinetics in the number of organic building blocks. The utility of DQ-SQ technique in determining the information about HB in various fluorine substituted molecules has been convincingly established.

  3. Unilateral NMR investigation of multifunctional treatments on stones based on colloidal inorganic and organic nanoparticles.

    Science.gov (United States)

    Di Tullio, Valeria; Cocca, Mariacristina; Avolio, Roberto; Gentile, Gennaro; Proietti, Noemi; Ragni, Pietro; Errico, Maria Emanuela; Capitani, Donatella; Avella, Maurizio

    2015-01-01

    Consolidation and protection are among the most important treatments usually carried out in conservation of stone artifacts and monuments. In this paper, portable unilateral NMR and conventional techniques were used for investigating new multifunctional treatments based on tetraethoxysilane, silica, and polytetrafluoroethylene nanoparticles. The study was carried out on a very complex and heterogeneous porous stone such as tuff. NMR study allowed to obtain detailed information on the penetration depth of treatments, the hydrophobic effect, and changes in the open porosity caused by treatments. Physical and chemical inhomogeneities between the impregnated layers of tuff and the layers underneath were also detected. The average pores radius and pores interconnection obtained from NMR diffusion measurements were used for the first time to compare effects of different consolidating and/or protective treatments on stone. Because unilateral NMR technique is neither destructive nor invasive, investigation of treatments can be also carried out and optimized directly on buildings and monuments of interest for Cultural Heritage. Copyright © 2014 John Wiley & Sons, Ltd.

  4. Molecular mobility in Medicago truncatula seed during early stage of germination: Neutron scattering and NMR investigations

    Energy Technology Data Exchange (ETDEWEB)

    Falourd, Xavier [UR1268 Biopolymères Interactions Assemblages, INRA, F-44316 Nantes (France); Natali, Francesca [CNR-IOM-OGG, c/o Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Peters, Judith [Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Université Joseph Fourier UFR PhITEM, BP 53, 38041 Grenoble Cedex 9 (France); Institut de Biologie Structurale, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1 (France); Foucat, Loïc, E-mail: Loic.Foucat@nantes.inra.fr [UR1268 Biopolymères Interactions Assemblages, INRA, F-44316 Nantes (France)

    2014-01-15

    Highlights: • Neutron scattering and NMR approaches were used to characterize seed germination. • A parallel between macromolecular motions and water dynamics was established. • Freezing/thawing cycle revealed a hysteresis connected to the seed hydration level. - Abstract: First hours of Medicago truncatula (MT) seeds germination were investigated using elastic incoherent neutron scattering (EINS) and nuclear magnetic resonance (NMR), to follow respectively how macromolecular motions and water mobility evolve when water permeates into the seed. From EINS results, it was shown that there is an increase in macromolecular mobility with the water uptake. Changes in NMR relaxation parameters reflected microstructural changes associated with the recovery of the metabolic processes. The EINS investigation of the effect of temperature on macromolecular motions showed that there is a relationship between the amount of water in the seeds and the effect of freezing–thawing cycle. The NMR relaxometry results obtained at 253 K allowed establishing possible link between the freezing of water molecules tightly bound to macromolecules and their drastic motion restriction around 250 K, as observed with EINS at the highest water content.

  5. Time-evolution of the entropy of fluctuations in some biological systems as investigated by NMR

    International Nuclear Information System (INIS)

    Lenk, R.

    1979-01-01

    A simple expression for the entropy of fluctuations has been developed, using the tunnelling-effect model. This gives the possibility to estimate the changes and evolution of entropy in non-crystalline and biological samples by NMR investigations. On the other hand, the oscillatory character of the time-evolution of some properties, experimentally found in the investigated samples of plants, is interpreted in terms of the generalized master equation with an exponential memory function. (Auth.)

  6. Implementation of picoSpin Benchtop NMR Instruments into Organic Chemistry Teaching Laboratories through Spectral Analysis of Fischer Esterification Products

    Science.gov (United States)

    Yearty, Kasey L.; Sharp, Joseph T.; Meehan, Emma K.; Wallace, Doyle R.; Jackson, Douglas M.; Morrison, Richard W.

    2017-01-01

    [Superscript 1]H NMR analysis is an important analytical technique presented in introductory organic chemistry courses. NMR instrument access is limited for undergraduate organic chemistry students due to the size of the instrument, price of NMR solvents, and the maintenance level required for instrument upkeep. The University of Georgia Chemistry…

  7. αB-Crystallin: A Hybrid Solid-Solution State NMR Investigation Reveals Structural Aspects of the Heterogeneous Oligomer

    OpenAIRE

    Jehle, Stefan; van Rossum, Barth; Stout, Joseph R.; Noguchi, Satoshi R.; Falber, Katja; Rehbein, Kristina; Oschkinat, Hartmut; Klevit, Rachel E.; Rajagopal, Ponni

    2008-01-01

    Atomic level structural information on αB-Crystallin (αB), a prominent member of the small Heat Shock Protein (sHSP) family has been a challenge to obtain due its polydisperse, oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on ∼ 580 kDa human αB assembled from 175-residue, 20 kDa subunits. An ∼100-residue α-crystallin domain is common to all sHSPs and solution-state NMR was performed on two different α-crystallin domain c...

  8. Muon spin rotation and other microscopic probes of spin-glass dynamics

    International Nuclear Information System (INIS)

    MacLaughlin, D.E.

    1980-01-01

    A number of different microscopic probe techniques have been employed to investigate the onset of the spin-glass state in dilute magnetic alloys. Among these are Moessbauer-effect spectroscopy, neutron scattering, ESR of the impurity spins, host NMR and, most recently, muon spin rotation and depolarization. Spin probes yield information on the microscopic static and dynamic behavior of the impurity spins, and give insight into both the spin freezing process and the nature of low-lying excitations in the ordered state. Microscopic probe experiments in spin glasses are surveyed, and the unique advantages of muon studies are emphasized

  9. Investigations on the local structure and the spin-Hamiltonian ...

    Indian Academy of Sciences (India)

    In the calculations, the contributions to the spin-Hamiltonian parameters from ligand orbital and spin-orbit coupling are included on the basis of the cluster approach ... Manuscript received: 23 October 2014; Manuscript revised: 23 November 2015; Accepted: 16 December 2015; Final version published online: 13 July 2016 ...

  10. Sub-minute kinetics of human red cell fumarase: 1 H spin-echo NMR spectroscopy and 13 C rapid-dissolution dynamic nuclear polarization.

    Science.gov (United States)

    Shishmarev, Dmitry; Wright, Alan J; Rodrigues, Tiago B; Pileio, Giuseppe; Stevanato, Gabriele; Brindle, Kevin M; Kuchel, Philip W

    2018-03-01

    Fumarate is an important probe of metabolism in hyperpolarized magnetic resonance imaging and spectroscopy. It is used to detect the release of fumarase in cancer tissues, which is associated with necrosis and drug treatment. Nevertheless, there are limited reports describing the detailed kinetic studies of this enzyme in various cells and tissues. Thus, we aimed to evaluate the sub-minute kinetics of human red blood cell fumarase using nuclear magnetic resonance (NMR) spectroscopy, and to provide a quantitative description of the enzyme that is relevant to the use of fumarate as a probe of cell rupture. The fumarase reaction was studied using time courses of 1 H spin-echo and 13 C-NMR spectra. 1 H-NMR experiments showed that the fumarase reaction in hemolysates is sufficiently rapid to make its kinetics amenable to study in a period of approximately 3 min, a timescale characteristic of hyperpolarized 13 C-NMR spectroscopy. The rapid-dissolution dynamic nuclear polarization (RD-DNP) technique was used to hyperpolarize [1,4- 13 C]fumarate, which was injected into concentrated hemolysates. The kinetic data were analyzed using recently developed FmR α analysis and modeling of the enzymatic reaction using Michaelis-Menten equations. In RD-DNP experiments, the decline in the 13 C-NMR signal from fumarate, and the concurrent rise and fall of that from malate, were captured with high spectral resolution and signal-to-noise ratio, which allowed the robust quantification of fumarase kinetics. The kinetic parameters obtained indicate the potential contribution of hemolysis to the overall rate of the fumarase reaction when 13 C-NMR RD-DNP is used to detect necrosis in animal models of implanted tumors. The analytical procedures developed will be applicable to studies of other rapid enzymatic reactions using conventional and hyperpolarized substrate NMR spectroscopy. Copyright © 2018 John Wiley & Sons, Ltd.

  11. Investigation of non-collinear spin states with scanning tunneling microscopy.

    Science.gov (United States)

    Wulfhekel, W; Gao, C L

    2010-03-05

    Most ferromagnetic and antiferromagnetic substances show a simple collinear arrangement of the local spins. Under certain circumstances, however, the spin configuration is non-collinear. Scanning tunneling microscopy with its potential atomic resolution is an ideal tool for investigating these complex spin structures. Non-collinearity can be due to topological frustration of the exchange interaction, due to relativistic spin-orbit coupling or can be found in excited states. Examples for all three cases are given, illustrating the capabilities of spin-polarized scanning tunneling microscopy.

  12. Molecular interactions in the ionic liquid emim acetate and water binary mixtures probed via NMR spin relaxation and exchange spectroscopy.

    Science.gov (United States)

    Allen, Jesse J; Bowser, Sage R; Damodaran, Krishnan

    2014-05-07

    Interactions of ionic liquids (ILs) with water are of great interest for many potential IL applications. 1-Ethyl-3-methylimidazolium (emim) acetate, in particular, has shown interesting interactions with water including hydrogen bonding and even chemical exchange. Previous studies have shown the unusual behavior of emim acetate when in the presence of 0.43 mole fraction of water, and a combination of NMR techniques is used herein to investigate the emim acetate-water system and the unusual behavior at 0.43 mole fraction of water. NMR relaxometry techniques are used to describe the effects of water on the molecular motion and interactions of emim acetate with water. A discontinuity is seen in nuclear relaxation behavior at the concentration of 0.43 mole fraction of water, and this is attributed to the formation of a hydrogen bonded network. EXSY measurements are used to determine the exchange rates between the H2 emim proton and water, which show a complex dependence on the concentration of the mixture. The findings support and expand our previous results, which suggested the presence of an extended hydrogen bonding network in the emim acetate-water system at concentrations close to 0.50 mole fraction of H2O.

  13. Surface Interactions and Confinement of Methane: A High Pressure Magic Angle Spinning NMR and Computational Chemistry Study

    Energy Technology Data Exchange (ETDEWEB)

    Ok, Salim; Hoyt, David W.; Andersen, Amity; Sheets, Julie; Welch, Susan A.; Cole, David R.; Mueller, Karl T.; Washton, Nancy M.

    2017-01-18

    Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nano-porous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) were observed with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed non-porous, 12 nm particle size silica and a mesoporous silica with 200 nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. For pure methane, no significant thermal effects were found for the observed 13C chemical shifts at all pressures studied here (28.2 bar, 32.6 bar, 56.4 bar, 65.1 bar, 112.7 bar, and 130.3 bar). However, the 13C chemical shifts of resonances arising from confined methane changed slightly with changes in temperature in mixtures with mesoporous silica. The chemical shift values of 13C nuclides in methane change measurably as a function of pressure both in the pure state and in mixtures with both silica matrices, with a more pronounced shift when meso-porous silica is present. Molecular-level simulations utilizing GCMC, MD and DFT confirm qualitatively that the experimentally measured changes are attributed to interactions of methane with the hydroxylated silica surfaces as well as densification of methane within nanopores and on pore surfaces.

  14. Surface Interactions and Confinement of Methane: A High Pressure Magic Angle Spinning NMR and Computational Chemistry Study

    International Nuclear Information System (INIS)

    Ok, Salim; Hoyt, David W.; Andersen, Amity; Sheets, Julie; Welch, Susan A.

    2017-01-01

    Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nanoporous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, we observed changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) with 13 C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed nonporous, 12 nm particle size silica and a mesoporous silica with 200 nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. There was no significant thermal effects were found for the observed 13 C chemical shifts at all pressures studied here (28.2, 32.6, 56.4, 65.1, 112.7, and 130.3 bar) for pure methane. However, the 13 C chemical shifts of resonances arising from confined methane changed slightly with changes in temperature in mixtures with mesoporous silica. The chemical shift values of 13 C nuclides in methane change measurably as a function of pressure both in the pure state and in mixtures with both silica matrices, with a more pronounced shift when meso-porous silica is present. Molecular-level simulations utilizing GCMC, MD, and DFT confirm qualitatively that the experimentally measured changes are attributed to interactions of methane with the hydroxylated silica surfaces as well as densification of methane within nanopores and on pore surfaces.

  15. Real-time protein NMR spectroscopy and investigation of assisted protein folding.

    Science.gov (United States)

    Kumar, Amit; Balbach, Jochen

    2015-10-01

    During protein-folding reactions toward the native structure, short-lived intermediate states can be populated. Such intermediates expose hydrophobic patches and can self-associate leading to non-productive protein misfolding. A major focus of current research is the characterization of short-lived intermediates and how molecular chaperones enable productive folding. Real-time NMR spectroscopy, together with the development of advanced methods, is reviewed here and the potential these methods have to characterize intermediate states as well as interactions with molecular chaperone proteins at single-residue resolution is highlighted. Various chaperone interactions can guide the protein-folding reaction and thus are important for protein structure formation, stability, and activity of their substrates. Chaperone-assisted protein folding, characterization of intermediates, and their molecular interactions using real-time NMR spectroscopy will be discussed. Additionally, recent advances in NMR methods employed for characterization of high-energy intermediates will be discussed. Real-time NMR combines high resolution with kinetic information of protein reactions, which can be employed not only for protein-folding studies and the characterization of folding intermediates but also to investigate the molecular mechanisms of assisted protein folding. Real-time NMR spectroscopy remains an effective tool to reveal structural details about the interaction between chaperones and transient intermediates. Methodologically, it provides in-depth understanding of how kinetic intermediates and their thermodynamics contribute to the protein-folding reaction. This review summarizes the most recent advances in this field. This article is part of a Special Issue titled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Investigating the Locomotion of the Sandfish in Desert Sand Using NMR-Imaging

    OpenAIRE

    Baumgartner, Werner; Fidler, Florian; Weth, Agnes; Habbecke, Martin; Jakob, Peter; Butenweg, Christoph; Böhme, Wolfgang

    2008-01-01

    The sandfish (Scincus scincus) is a lizard having the remarkable ability to move through desert sand for significant distances. It is well adapted to living in loose sand by virtue of a combination of morphological and behavioural specializations. We investigated the bodyform of the sandfish using 3D-laserscanning and explored its locomotion in loose desert sand using fast nuclear magnetic resonance (NMR) imaging. The sandfish exhibits an in-plane meandering motion with a frequency of about 3...

  17. NMR and Electrochemical Investigation of the Transport Properties of Methanol and Water in Nafion and Clay-Nanocomposites Membranes for DMFCs

    Directory of Open Access Journals (Sweden)

    Vincenzo Baglio

    2012-06-01

    Full Text Available Water and methanol transport behavior, solvents adsorption and electrochemical properties of filler-free Nafion and nanocomposites based on two smectite clays, were investigated using impedance spectroscopy, DMFC tests and NMR methods, including spin-lattice relaxation and pulsed-gradient spin-echo (PGSE diffusion under variable temperature conditions. Synthetic (Laponite and natural (Swy-2 smectite clays, with different structural and physical parameters, were incorporated into the Nafion for the creation of exfoliated nanocomposites. Transport mechanism of water and methanol appears to be influenced from the dimensions of the dispersed platelike silicate layers as well as from their cation exchange capacity (CEC. The details of the NMR results and the effect of the methanol solution concentration are discussed. Clays particles, and in particular Swy-2, demonstrate to be a potential physical barrier for methanol cross-over, reducing the methanol diffusion with an evident blocking effect yet nevertheless ensuring a high water mobility up to 130 °C and for several hours, proving the exceptional water retention property of these materials and their possible use in the DMFCs applications. Electrochemical behavior is investigated by cell resistance and polarization measurements. From these analyses it is derived that the addition of clay materials to recast Nafion decreases the ohmic losses at high temperatures extending in this way the operating range of a direct methanol fuel cell.

  18. Calorimetric investigation of an yttrium-dysprosium spin glass

    International Nuclear Information System (INIS)

    Wenger, L.E.

    1978-01-01

    In an effort to compare the spin glass characteristics of yttrium--rare earth alloys with those of the noble-metal spin glasses, the susceptibility and heat capacity of Y/sub 0.98/Dy/sub 0.02/ have been measured in the temperature range 2.5--40 K. The low-field ac susceptibility measurement shows the characteristic cusp-like peak at 7.64 K. The magnetic specific heat of the same sample shows a peak at 7.0 K and may be qualitatively described as a semi-cusp. The magnetic entropy change from absolute zero to 7 K is approximately 0.52 of cR ln(2J+1). These results are qualitatively different than previous calorimetric results on the archetypal spin glasses, AuFe and CuMn, where rounded maxima are observed at temperatures above the spin glass transition temperatures

  19. Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in static NMR of half-integer spin quadrupolar nuclei.

    Science.gov (United States)

    Bräuniger, Thomas; Hempel, Günter; Madhu, P K

    2006-07-01

    In solid-state NMR of quadrupolar nuclei with half-integer spin I, fast amplitude-modulated (FAM) pulse trains have been utilised to enhance the intensity of the central-transition signal, by transferring spin population from the satellite transitions. In this paper, the signal-enhancement performance of the recently introduced SW-FAM pulse train with swept modulation frequency [T. Bräuniger, K. Ramaswamy, P.K. Madhu, Enhancement of the central-transition signal in static and magic-angle-spinning NMR of quadrupolar nuclei by frequency-swept fast amplitude-modulated pulses, Chem. Phys. Lett. 383 (2004) 403-410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW1/tau-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SWtau-FAM). For static spectra of 27Al (I=5/2), better signal-enhancement performance is found for the SW1/tau-FAM sequence, as demonstrated both by experiments and numerical simulations.

  20. NMR on the antiferromagnetic S=1/2 Heisenberg spin chain Sr{sub 2}CuO{sub 3} under the impact of Ni impurities

    Energy Technology Data Exchange (ETDEWEB)

    Utz, Yannic; Hammerath, Franziska; Nishimoto, Satoshi; Drechsler, Stefan-Ludwig; Hess, Christian; Buechner, Bernd; Grafe, Hans-Joachim [IFW Dresden (Germany); Beesetty, Neela Sekhar; Saint-Martin, Romuald; Revcolevschi, Alexandre [SP2M-ICMMO UMR-CNRS, Universite Paris-Sud (France)

    2015-07-01

    We present {sup 63}Cu NMR measurements on single crystals of Sr{sub 2}CuO{sub 3} doped with different amounts of nickel and compare them to numerical DMRG results. The parent compound contains copper-oxygen chains with S=1/2 on the copper site coupled by a large antiferromagnetic exchange coupling J ∼ 2000 K and is known to be a good realization of the 1D Heisenberg model. The measurements show that replacing only a few of the S=1/2 Cu ions with S=1 Ni has a major impact on the magnetic properties of the spin chain system. An unusual line broadening in the low temperature NMR spectra reveals the existence of an impurity-induced local alternating magnetization (LAM), and exponentially decaying spin-lattice relaxation rates T{sup -1}{sub 1} towards low temperatures indicate the opening of a spin gap similar to Ca-doped Sr{sub 2}CuO{sub 3}. While the T{sup -1}{sub 1} measurements could be explained by pure chain segmentation, as expected for a S=0 impurity, the spectra can only be understood by taking the nickel.

  1. Investigating sorption on iron-oxyhydroxide soil minerals by solid-state NMR spectroscopy: a 6Li MAS NMR study of adsorption and absorption on goethite

    DEFF Research Database (Denmark)

    Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia

    2005-01-01

    High-resolution 2H MAS NMR spectra can be obtained for nanocrystalline particles of goethite (alpha-FeOOH, particle size approximately 4-10 nm) at room temperature, facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, th...... on the goethite surface. Even larger Li hyperfine shifts (289 ppm) were observed for Li+-exchanged goethite, which contains lithium ions in the tunnels of the goethite structure, confirming the Li assignment of the 145 ppm Li resonance to the surface sites. Udgivelsesdato: 2005-Oct-6...

  2. Spin excitations in the quasi-two-dimensional charge-ordered insulator α -(BEDT-TTF ) 2I3 probed via 13C NMR

    Science.gov (United States)

    Ishikawa, Kyohei; Hirata, Michihiro; Liu, Dong; Miyagawa, Kazuya; Tamura, Masafumi; Kanoda, Kazushi

    2016-08-01

    The spin excitations from the nonmagnetic charge-ordered insulating state of α -(BEDT-TTF ) 2I3 at ambient pressure have been investigated by probing the static and low-frequency dynamic spin susceptibilities via site-selective nuclear magnetic resonance at 13C sites. The site-dependent values of the shift and the spin-lattice relaxation rate 1 /T1 below the charge-ordering transition temperature (TCO≈135 K ) demonstrate a spin density imbalance in the unit cell, in accord with the charge-density ratio reported earlier. The shift and 1 /T1 show activated temperature dependence with a static (shift) gap ΔS≈47 -52 meV and a dynamic (1 /T1 ) gap ΔR≈40 meV . The sizes of the gaps are well described in terms of a localized spin model, where spin-1/2 antiferromagnetic dimer chains are weakly coupled with each other.

  3. Mapping protein–protein interactions by double-REDOR-filtered magic angle spinning NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Changmiao; Hou, Guangjin, E-mail: hou@udel.edu; Lu, Xingyu; Polenova, Tatyana, E-mail: tpolenov@udel.edu [University of Delaware, Department of Chemistry and Biochemistry (United States)

    2017-02-15

    REDOR-based experiments with simultaneous {sup 1}H–{sup 13}C and {sup 1}H−{sup 15}N dipolar dephasing are explored for investigating intermolecular protein–protein interfaces in complexes formed by a U–{sup 13}C,{sup 15}N-labeled protein and its natural abundance binding partner. The application of a double-REDOR filter (dREDOR) results in a complete dephasing of proton magnetization in the U–{sup 13}C,{sup 15}N-enriched molecule while the proton magnetization of the unlabeled binding partner is not dephased. This retained proton magnetization is then transferred across the intermolecular interface by {sup 1}H–{sup 13}C or {sup 1}H–{sup 15}N cross polarization, permitting to establish the residues of the U–{sup 13}C,{sup 15}N-labeled protein, which constitute the binding interface. To assign the interface residues, this dREDOR-CPMAS element is incorporated as a building block into {sup 13}C–{sup 13}C correlation experiments. We established the validity of this approach on U–{sup 13}C,{sup 15}N-histidine and on a structurally characterized complex of dynactin’s U–{sup 13}C,{sup 15}N-CAP-Gly domain with end-binding protein 1 (EB1). The approach introduced here is broadly applicable to the analysis of intermolecular interfaces when one of the binding partners in a complex cannot be isotopically labeled.

  4. Investigation of iron spin crossover pressure in Fe-bearing MgO using hybrid functional

    Science.gov (United States)

    Cheng, Ya; Wang, Xianlong; Zhang, Jie; Yang, Kaishuai; Zhang, Chuanguo; Zeng, Zhi; Lin, Haiqin

    2018-04-01

    Pressure-induced spin crossover behaviors of Fe-bearing MgO were widely investigated by using an LDA  +  U functional for describing the strongly correlated Fe–O bonding. Moreover, the simulated spin crossover pressures depend on the applied U values, which are sensitive to environments and parameters. In this work, the spin crossover pressures of (Mg1‑x ,Fe x )O are investigated by using the hybrid functional with a uniform parameter. Our results indicate that the spin crossover pressures increase with increasing iron concentration. For example, the spin crossover pressure of (Mg0.03125,Fe0.96875)O and FeO was 56 GPa and 127 GPa, respectively. The calculated crossover pressures agreed well with the experimental observations. Therefore, the hybrid functional should be an effective method for describing the pressure-induced spin crossover behaviors in transition metal oxides.

  5. Computational and Experimental Investigations of Flow past Spinning Cylinders

    Science.gov (United States)

    Mehmedagic, Igbal; Buckley, Liam; Carlucci, Pasquale; Carlucci, Donald; Aljalis, Elias; Thangam, Siva; Stevens-Ardec Collaboration

    2012-11-01

    An anisotropic two-equation Reynolds-stress model is developed by considering the modifications to the energy spectrum and through invariance based scaling. In this approach the effect of rotation is used to modify the energy spectrum, while the influence of swirl is modeled based on scaling laws. The resulting generalized model is validated for benchmark turbulent flows with swirl and curvature. The time-averaged equations of motion and energy are solved using the modeled form of transport equations for the turbulence kinetic energy and the scalar form of turbulence dissipation with an efficient finite-volume algorithm. Computations for flow past an axially rotating cylinder with a free-spinning base are performed along with experiments for a range of spin rates and free stream flow conditions. A subsonic wind tunnel with a forward-sting mounted spinning cylinder is used for experiments. The experimental results of Carlucci & Thangam (2001) are used to benchmark flow over spinning cylinders. The data is extended to munitions spinning in the wake of other munitions and applications involving the design of projectiles are discussed. This work was funded in part by U. S. Army ARDEC.

  6. 1H High Resolution Magic-Angle Coil Spinning (HR-MACS µNMR Metabolic Profiling of whole Saccharomyces cervisiae cells: A Demonstrative Study

    Directory of Open Access Journals (Sweden)

    Alan eWong

    2014-06-01

    Full Text Available The low sensitivity of Nuclear Magnetic Resonance (NMR is its prime shortcoming compared to other analytical methods for metabolomic studies. It relies on large sample volume (30–50 µl for HR-MAS for rich metabolic profiling, hindering high-throughput screening especially when the sample requires a labor-intensive preparation or is a sacred specimen. This is indeed the case for some living organisms. This study evaluates a 1H HR-MAS approach for metabolic profiling of small volume (250 nl whole bacterial cells, Saccharomyces cervisiae, using an emerging micro-NMR technology: high-resolution magic-angle coil spinning (HR-MACS. As a demonstrative study for whole cells, we perform two independent metabolomics studies identifying the significant metabolites associated with osmotic stress and aging.

  7. 1H High Resolution Magic-Angle Coil Spinning (HR-MACS) - NMR Metabolic Profiling of whole Saccharomyces cervisiae cells: A Demonstrative Study

    Science.gov (United States)

    Wong, Alan; Boutin, Celine; Aguiar, Pedro

    2014-06-01

    The low sensitivity of Nuclear Magnetic Resonance (NMR) is its prime shortcoming compared to other analytical methods for metabolomic studies. It relies on large sample volume (30-50 µl for HR-MAS) for rich metabolic profiling, hindering high-throughput screening especially when the sample requires a labor-intensive preparation or is a sacred specimen. This is indeed the case for some living organisms. This study evaluates a 1H HR-MAS approach for metabolic profiling of small volume (250 nl) whole bacterial cells, Saccharomyces cervisiae, using an emerging micro-NMR technology: high-resolution magic-angle coil spinning (HR-MACS). As a demonstrative study for whole cells, we perform two independent metabolomics studies identifying the significant metabolites associated with osmotic stress and aging.

  8. Investigation of Oxidative Degradation in Polymers Using (17)O NMR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Todd M.; Celina, Mathew; Assink, Roger A.; Clough, Roger L.; Gillen, Kenneth T.; Wheeler David R.

    1999-07-20

    The thermal oxidation of pentacontane (C{sub 50}H{sub 102}), and of the homopolymer polyisoprene, has been investigated using {sup 17}O NMR spectroscopy. By performing the oxidation using {sup 17}O labeled O{sub 2} gas, it is possible to easily identify degradation products, even at relatively low concentrations. It is demonstrated that details of the degradation mechanism can be obtained from analysis of the {sup 17}O NMR spectra as a function of total oxidation. Pentacontane reveals the widest variety of reaction products, and exhibits changes in the relative product distributions with increasing O{sub 2} consumption. At low levels of oxygen incorporation, peroxides are the major oxidation product, while at later stages of degradation these species are replaced by increasing concentrations of ketones, alcohols, carboxylic acids and esters. Analyzing the product distribution can help in identification of the different free-radical decomposition pathways of hydroperoxides, including recombination, proton abstraction and chain scission, as well as secondary reactions. The {sup 17}O NMR spectra of thermally oxidized polyisoprene reveal fewer degradation functionalities, but exhibit an increased complexity in the type of observed degradation species due to structural features such as unsaturation and methyl branching. Alcohols and ethers formed from hydrogen abstraction and free radical termination.

  9. Spin-cast bulk heterojunction solar cells: A dynamical investigation

    KAUST Repository

    Chou, Kang Wei

    2013-02-22

    Spin-coating is extensively used in the lab-based manufacture of organic solar cells, including most of the record-setting solution-processed cells. We report the first direct observation of photoactive layer formation as it occurs during spin-coating. The study provides new insight into mechanisms and kinetics of bulk heterojunction formation, which may be crucial for its successful transfer to scalable printing processes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Influence of water-insoluble nonionic copolymer E(6)P(39)E(6) on the microstructure and self-aggregation dynamics of aqueous SDS solution-NMR and SANS investigations.

    Science.gov (United States)

    Prameela, G K S; Phani Kumar, B V N; Aswal, V K; Mandal, Asit Baran

    2013-10-28

    The influence of water-insoluble nonionic triblock copolymer PEO-PPO-PEO [poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] i.e., E6P39E6 with molecular weight 2800, on the microstructure and self-aggregation dynamics of anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D2O) were investigated using high resolution nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS) measurements. Variable concentration and temperature proton ((1)H), carbon ((13)C) NMR chemical shifts, (1)H self-diffusion coefficients, (1)H spin-lattice and spin-spin relaxation rates data indicate that the higher hydrophobic nature of copolymer significantly influenced aggregation characteristics of SDS. The salient features of the NMR investigations include (i) the onset of mixed micelles at lower SDS concentrations (SDS free micelles at higher SDS concentrations (~30 mM), (ii) disintegration of copolymer-SDS mixed aggregate at moderate SDS concentrations (~10 mM) and still binding of a copolymer with SDS and (iii) preferential localization of the copolymer occurred at the SDS micelle surface. SANS investigations indicate prolate ellipsoidal shaped mixed aggregates with an increase in SDS aggregation number, while a contrasting behavior in the copolymer aggregation is observed. The aggregation features of SDS and the copolymer, the sizes of mixed aggregates and the degree of counterion dissociation (α) extracted from SANS data analysis corroborate reasonably well with those of (1)H NMR self-diffusion and sodium ((23)Na) spin-lattice relaxation data.

  11. Detailed NMR investigation of cyclodextrin-perfluorinated surfactant interactions in aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Weiss-Errico, Mary Jo; O’Shea, Kevin E., E-mail: osheak@fiu.edu

    2017-05-05

    Highlights: • Perfluorochemicals (PFCs) are strongly encapsulated by cyclodextrins (CDs). • Competition studies confirm strong CD:PFC host-guest interactions. • {sup 19}F NMR Spectroscopy demonstrates association constants up to 10{sup 5} M{sup −1}. • Position of CD along PFC chain is elucidated from NMR results. • CD:PFC complex is not disturbed under a variety of water quality conditions. - Abstract: Perfluorochemicals (PFCs) are contaminants of serious concern because of their toxicological properties, widespread presence in drinking water sources, and incredible stability in the environment. To assess the potential application of α-, β-, and γ-cyclodextrins for PFC remediation, we investigated their complexation with linear fluorinated carboxylic acids, sulfonates, and a sulfonamide with carbon backbones ranging from C4-C9. {sup 19}F Nuclear Magnetic Resonance (NMR) spectroscopy studies demonstrated β-CD formed the strongest complexes with these PFCs. The polar head group had a modest influence, but for PFCs with backbones longer than six carbons, strong association constants are observed for 1:1 (K{sub 1:1} ∼ 10{sup 5} M{sup −1}) and 2:1 (K{sub 2:1} ∼ 10{sup 3} M{sup −1}) β-CD:PFC complexes. Excess β-CD can be used to complex 99.5% of the longer chain PFCs. Competition studies with adamantane-carboxylic acid and phenol confirmed the nature and persistence of the β-CD:PFC complex. Detailed analyses of the individual NMR chemical shifts and Job plots indicate the favored positions of the β-CD along the PFC chain. Solution pH, ionic strength, and the presence of humic acid have modest influence on the β-CD:PFC complexes. The strong encapsulation of PFCs by β-CD under a variety of water quality conditions demonstrates the tremendous potential of CD-based materials for the environmental remediation of PFCs.

  12. Spin Labeling ESR Investigation of Covalently Bound Residues in Soil

    Science.gov (United States)

    Aleksandrova, Olga; Steinhoff, Heinz-Juergen; Klasmeier, Joerg; Schulz, Marcus; Matthies, Michael

    2013-04-01

    Organic xenobiotic chemicals, such as pesticides, biocides and veterinary pharmaceuticals, interact with soil, which results in the simultaneous formations of metabolites, mineralization products, and bound or non-extractable residues (NER). Substances or metabolites with reactive functional groups, such as aniline or phenol, have a tendency to give a larger proportion of NER. Despite numerous studies on NER, the majority of their chemical structures is still unknown. Reversible sequestration and irreversible formation of NER were also observed for veterinary antibiotic pharmaceuticals, after their application to soil with and without manure. For this purpose, we hypothesized a key role of specific functional groups of soil contaminants, via which contaminants are covalently bound to soil constituents, and advance a method of spin labeling ESR investigation of reaction products using a membrane method. Spin labels (SL) represent chemically stable paramagnetic molecules used as molecular labels and molecular probes for testing the covalent binding, structural properties, and molecular mobility of different physical, chemical, and biological systems. In the case of covalent binding of SL, their ESR spectra become broadened. We used stable nitroxide radicals (NR) as SL. These radicals modeled organic chemical contaminants and differed only in one functional group. The paramagnetic SL 4-Amino Tempo (4-amino-2,2,6,6-tetramethyl-1-piperidinylox) differed from Tempo (2,2,6,6-Tetramethylpiperidinooxy) in a substituent at the para-position of the piperidine ring, whereas Aniline Tempo (1-Piperidinyloxy, 2,2,6,-tetramethyl, 6-Aniline) differed from Tempo in an Aniline substituting one CH3 functional group. Before experimental analysis, we tested temporal changes in the concentration of both NR incubated with soil and found that the life-times of them in soil exceeded 3 days. We contaminated and labeled soil samples with NR, adding to soil the aqueous solution, which already

  13. $^{11}$B and $^{27}$Al NMR spin-lattice relaxation and Knight shift study of Mg$_{1-x}$Al$_x$B$_2$. Evidence for anisotropic Fermi surface

    OpenAIRE

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

    2002-01-01

    We report a detailed study of $^{11}$B and $^{27}$Al NMR spin-lattice relaxation rates ($1/T_1$), as well as of $^{27}$Al Knight shift (K) of Mg$_{1-x}$Al$_x$B$_2$, $0\\leq x\\leq 1$. The obtained ($1/T_1T$) and K vs. x plots are in excellent agreement with ab initio calculations. This asserts experimentally the prediction that the Fermi surface is highly anisotropic, consisting mainly of hole-type 2-D cylindrical sheets from bonding $2p_{x,y}$ boron orbitals. It is also shown that the density ...

  14. Investigation of exotic modes of spinning nuclei near Zr

    Indian Academy of Sciences (India)

    2014-04-01

    Apr 1, 2014 ... Recently, a digital data acquisition system with 96 channels has been set up for the. Indian National ... vibration with other modes, high spin states of neutron-rich nuclei in sd-shell and isomers near-shell .... and integrated polarization direction correlation (IPDCO) analysis of different transitions were carried ...

  15. Pseudogap Behavior of the Nuclear Spin-Lattice Relaxation Rate in FeSe Probed by 77Se-NMR

    Science.gov (United States)

    Shi, Anlu; Arai, Takeshi; Kitagawa, Shunsaku; Yamanaka, Takayoshi; Ishida, Kenji; Böhmer, Anna E.; Meingast, Christoph; Wolf, Thomas; Hirata, Michihiro; Sasaki, Takahiko

    2018-01-01

    We conducted 77Se-nuclear magnetic resonance studies of the iron-based superconductor FeSe in magnetic fields of 0.6 to 19 T to investigate the superconducting and normal-state properties. The nuclear spin-lattice relaxation rate divided by the temperature (T1T)-1 increases below the structural transition temperature Ts but starts to be suppressed below T*, well above the superconducting transition temperature Tc(H), resulting in a broad maximum of (T1T)-1 at Tp(H). This is similar to the pseudogap behavior in optimally doped cuprate superconductors. Because T* and Tp(H) decrease in the same manner as Tc(H) with increasing H, the pseudogap behavior in FeSe is ascribed to superconducting fluctuations, which presumably originate from the theoretically predicted preformed pair above Tc(H).

  16. Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements

    Science.gov (United States)

    Kurauskas, Vilius; Weber, Emmanuelle; Hessel, Audrey; Ayala, Isabel; Marion, Dominique; Schanda, Paul

    2016-01-01

    Transverse relaxation rate measurements in MAS solid-state NMR provide information about molecular motions occurring on nanoseconds-to-milliseconds (ns-ms) time scales. The measurement of heteronuclear (13C, 15N) relaxation rate constants in the presence of a spin-lock radio-frequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins has been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely (i) the role of CSA/dipolar cross-correlated relaxation (CCR), and (ii) the impact of fast proton spin flips (i.e. proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable, and that this cross-correlated relaxation rate constant depends on ns-ms motions, and can thus itself provide insight into dynamics. We find that proton spin-diffusion attenuates this cross-correlated relaxation, due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and the present manuscript reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation. PMID:27500976

  17. Selective and extensive 13C labeling of a membrane protein for solid-state NMR investigations

    International Nuclear Information System (INIS)

    Hong, M.; Jakes, K.

    1999-01-01

    The selective and extensive 13C labeling of mostly hydrophobic amino acid residues in a 25 kDa membrane protein, the colicin Ia channel domain, is reported. The novel 13C labeling approach takes advantage of the amino acid biosynthetic pathways in bacteria and suppresses the synthesis of the amino acid products of the citric acid cycle. The selectivity and extensiveness of labeling significantly simplify the solid-state NMR spectra, reduce line broadening, and should permit the simultaneous measurement of multiple structural constraints. We show the assignment of most 13C resonances to specific amino acid types based on the characteristic chemical shifts, the 13C labeling pattern, and the amino acid composition of the protein. The assignment is partly confirmed by a 2D homonuclear double-quantum-filter experiment under magic-angle spinning. The high sensitivity and spectral resolution attained with this 13C-labeling protocol, which is termed TEASE for ten-amino acid selective and extensive labeling, are demonstrated

  18. Experimental and Computational Investigations of Flow past Spinning Cylinders

    Science.gov (United States)

    Carlucci, Pasquale; Mehmedagic, Igbal; Buckley, Liam; Carlucci, Donald; Thangam, Siva

    2011-11-01

    Experiments are performed in a low speed subsonic wind tunnel to analyze flow past spinning cylinders. The sting-mounted cylinders are oriented such that their axis of rotation is aligned with the mean flow. Data from spinning cylinders with both rear-mounted and fore-mounted stings are presented for a Reynolds numbers of up to 260000 and rotation numbers of up to 1.2 (based on cylinder diameter). Computations are performed using a two-equation turbulence model that is capable of capturing the effects of swirl and curvature. The model performance was validated with benchmark experimental flows and implemented for analyzing the flow configuration used in the experimental study. The results are analyzed and the predictive capability of the model is discussed. Funded in part by U. S. Army, ARDEC.

  19. Investigations on the local structure and the spin-Hamiltonian ...

    Indian Academy of Sciences (India)

    MS received 23 October 2014; revised 23 November 2015; accepted 16 December 2015; published online 13 July 2016. Abstract. The spin-Hamiltonian parameters (g factors g , g⊥ and hyperfine ..... Here, t2 ≈ 3 and t4 ≈ 5 are the power-law expo- nents [10–13]. ¯A2(R) and ¯A4(R) are the intrinsic parameters, with the ...

  20. Optical investigation of spin injection from (Ga,Mn)As into n-GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Endres, Bernhard; Sperl, Matthias; Utz, Martin; Schuh, Dieter; Einwanger, Andreas; Ciorga, Mariusz; Back, Christian; Bayreuther, Guenther [Universitaet Regensburg (Germany)

    2011-07-01

    Spin injection from a Ga(Mn,As) contact into a n-GaAs channel through an Esaki diode structure was investigated. Details of the layer structure are described in Ref 1. After lithographic patterning the spin polarization in the GaAs was measured by p-MOKE at low temperatures across a cleaved edge as described in Ref. 2. From the distribution of the spin polarization below the injecting contact the spin diffusion length and the drift dependent spin decay length can be estimated, which are important parameters for the calculation of the spin lifetime from Hanle-measurements. However, several contributions to the Hanle curves as the stray field, dynamic nuclear polarization and a tilted magnetization of the injector make the calculation of the spin lifetime more complex. In this contribution the different parameters of the sample are characterized by fitting experimental data with a one-dimensional drift-diffusion equation. A spin diffusion length of about 5 {mu}m and a spin lifetime of 10 ns was observed.

  1. Molecular and electron-spin structures of a ring-shaped mixed-valence polyoxovanadate (IV, V) studied by (11)B and (23)Na solid-state NMR spectroscopy and DFT calculations.

    Science.gov (United States)

    Iijima, Takahiro; Yamase, Toshihiro; Nishimura, Katsuyuki

    2016-01-01

    (11)B and (23)Na solid-state nuclear magnetic resonance (NMR) spectra of ring-shaped paramagnetic crystals of H15[V7(IV)V5(V)B32O84Na4]·13H2O containing seven d(1) electrons from V(IV) were studied. Magic-angle-spinning (MAS) and multiple-quantum MAS NMR experiments were performed at moderate (9.4T) and ultrahigh magnetic fields (21.6T). The NMR parameters for quadrupole and isotropic chemical shift interactions were estimated by simulation of the NMR spectra and from relativistic density functional theory (DFT) calculations. Four Na ions incorporated into the framework were found to occupy four distinct sites with different populations. The DFT calculation showed that d(1) electrons with effectively one up-spin caused by strong antiferromagnetic interactions were delocalized over the 12V ions. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Solid-state NMR of inorganic semiconductors.

    Science.gov (United States)

    Yesinowski, James P

    2012-01-01

    Studies of inorganic semiconductors by solid-state NMR vary widely in terms of the nature of the samples investigated, the techniques employed to observe the NMR signal, and the types of information obtained. Compared with the NMR of diamagnetic non-semiconducting substances, important differences often result from the presence of electron or hole carriers that are the hallmark of semiconductors, and whose theoretical interpretation can be involved. This review aims to provide a broad perspective on the topic for the non-expert by providing: (1) a basic introduction to semiconductor physical concepts relevant to NMR, including common crystal structures and the various methods of making samples; (2) discussions of the NMR spin Hamiltonian, details of some of the NMR techniques and strategies used to make measurements and theoretically predict NMR parameters, and examples of how each of the terms in the Hamiltonian has provided useful information in bulk semiconductors; (3) a discussion of the additional considerations needed to interpret the NMR of nanoscale semiconductors, with selected examples. The area of semiconductor NMR is being revitalized by this interest in nanoscale semiconductors, the great improvements in NMR detection sensitivity and resolution that have occurred, and the current interest in optical pumping and spintronics-related studies. Promising directions for future research will be noted throughout.

  3. Magic angle spinning and oriented sample solid-state NMR structural restraints combine for influenza a M2 protein functional insights.

    Science.gov (United States)

    Can, Thach V; Sharma, Mukesh; Hung, Ivan; Gor'kov, Peter L; Brey, William W; Cross, Timothy A

    2012-06-06

    As a small tetrameric helical membrane protein, the M2 proton channel structure is highly sensitive to its environment. As a result, structural data from a lipid bilayer environment have proven to be essential for describing the conductance mechanism. While oriented sample solid-state NMR has provided a high-resolution backbone structure in lipid bilayers, quaternary packing of the helices and many of the side-chain conformations have been poorly restrained. Furthermore, the quaternary structural stability has remained a mystery. Here, the isotropic chemical shift data and interhelical cross peaks from magic angle spinning solid-state NMR of a liposomal preparation strongly support the quaternary structure of the transmembrane helical bundle as a dimer-of-dimers structure. The data also explain how the tetrameric stability is enhanced once two charges are absorbed by the His37 tetrad prior to activation of this proton channel. The combination of these two solid-state NMR techniques appears to be a powerful approach for characterizing helical membrane protein structure.

  4. Chemical Shifts of the Carbohydrate Binding Domain of Galectin-3 from Magic Angle Spinning NMR and Hybrid Quantum Mechanics/Molecular Mechanics Calculations.

    Science.gov (United States)

    Kraus, Jodi; Gupta, Rupal; Yehl, Jenna; Lu, Manman; Case, David A; Gronenborn, Angela M; Akke, Mikael; Polenova, Tatyana

    2018-03-22

    Magic angle spinning NMR spectroscopy is uniquely suited to probe the structure and dynamics of insoluble proteins and protein assemblies at atomic resolution, with NMR chemical shifts containing rich information about biomolecular structure. Access to this information, however, is problematic, since accurate quantum mechanical calculation of chemical shifts in proteins remains challenging, particularly for 15 N H . Here we report on isotropic chemical shift predictions for the carbohydrate recognition domain of microcrystalline galectin-3, obtained from using hybrid quantum mechanics/molecular mechanics (QM/MM) calculations, implemented using an automated fragmentation approach, and using very high resolution (0.86 Å lactose-bound and 1.25 Å apo form) X-ray crystal structures. The resolution of the X-ray crystal structure used as an input into the AF-NMR program did not affect the accuracy of the chemical shift calculations to any significant extent. Excellent agreement between experimental and computed shifts is obtained for 13 C α , while larger scatter is observed for 15 N H chemical shifts, which are influenced to a greater extent by electrostatic interactions, hydrogen bonding, and solvation.

  5. The Effect of Water Solvent on NMR Spin- Spin Couplings in DNA: Improvement of Calculated Values by Application of Two Solvent Models

    Czech Academy of Sciences Publication Activity Database

    Sychrovský, Vladimír; Schneider, Bohdan; Hobza, Pavel; Žídek, L.; Sklenář, V.

    2003-01-01

    Roč. 5, - (2003), s. 734-739 ISSN 1463-9076 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : NMR * DNA * water solvent Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.959, year: 2003

  6. A complete set of NMR chemical shifts and spin-spin coupling constants for L-Alanyl-L-Alanine zwitterion and analysis of its conformational behavior

    Czech Academy of Sciences Publication Activity Database

    Bouř, Petr; Buděšínský, Miloš; Špirko, Vladimír; Kapitán, Josef; Šebestík, Jaroslav; Sychrovský, Vladimír

    2005-01-01

    Roč. 127, - (2005), 17079-17089 ISSN 0002-7863 R&D Projects: GA AV ČR(CZ) IAA4055104; GA ČR(CZ) GA203/05/0388 Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR * chemical shifts * coupling constants Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.419, year: 2005

  7. Solid-state {sup 27}Al and {sup 29}Si NMR investigations on Si-substituted hydrogarnets

    Energy Technology Data Exchange (ETDEWEB)

    Rivas Mercury, J.M. [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain); Pena, P. [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain)]. E-mail: ppena@icv.csic.es; Aza, A.H. de [Instituto de Ceramica y Vidrio, CSIC, Kelsen, 5, 28049 Cantoblanco-Madrid (Spain); Turrillas, X. [Instituto de Ciencias de la Construccion Eduardo Torroja, CSIC, Serrano Galvache, 4, 28033 Madrid (Spain); Sobrados, I. [Instituto de Ciencia de Materiales, CSIC, Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco-Madrid (Spain); Sanz, J. [Instituto de Ciencia de Materiales, CSIC, Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco-Madrid (Spain)

    2007-02-15

    Partially deuterated Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-x}(OH){sub 4x} hydrates prepared by a reaction in the presence of D{sub 2}O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by {sup 29}Si and {sup 27}Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The {sup 29}Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-x}(OH){sub 4x} was followed by {sup 27}Al NMR spectroscopy: Si:OH ratios were determined quantitatively from octahedral Al signals ascribed to Al(OH){sub 6} and Al(OSi)(OH){sub 5} environments. The NMR data obtained were consistent with the concentrations of the Al and Si species deduced from transmission electron microscopy energy-dispersive spectrometry and Rietveld analysis of both X-ray and neutron diffraction data.

  8. Magic-angle-spinning NMR spectroscopy. January 1978-May 1988 (Citations from the INSPEC: Information Services for the Physics and Engineering Communities data base). Report for January 1978-May 1988

    International Nuclear Information System (INIS)

    1988-05-01

    This bibliography contains citations concerning the principles and applications of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) in high-resolution spectra analysis of solids. Magic-angle spinning NMR is a very powerful spectrographic technique for the study of structures, dynamics, and reactivity of solids, and polcrystalline and amorphous solids. Studies of various materials are presented, including zeolites, organic compounds and polymers, liquid crystals, silicate and borate glasses, and alumina and oxide films. Applications in conductive polymers, biological systems, and organic matrixes of composite materials are presented. (Contains 89 citations fully indexed and including a title list.)

  9. MAS NMR of HIV-1 protein assemblies

    Science.gov (United States)

    Suiter, Christopher L.; Quinn, Caitlin M.; Lu, Manman; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-04-01

    The negative global impact of the AIDS pandemic is well known. In this perspective article, the utility of magic angle spinning (MAS) NMR spectroscopy to answer pressing questions related to the structure and dynamics of HIV-1 protein assemblies is examined. In recent years, MAS NMR has undergone major technological developments enabling studies of large viral assemblies. We discuss some of these evolving methods and technologies and provide a perspective on the current state of MAS NMR as applied to the investigations into structure and dynamics of HIV-1 assemblies of CA capsid protein and of Gag maturation intermediates.

  10. Investigation of Liquid Sloshing in Spin-Stabilized Satellites.

    Science.gov (United States)

    1993-01-31

    of minimum moment of inertia include a spinning top or a The INTELSAT IV communications satellite also expert- football . However, systems containing a...result in the veiocity square term as :’ H "A. r" r0,, q Ia Cte & W’w :zI - - t’G, ~q.) -0.5,2 20iO,,~ - %ll[t -i::.:O, , 3v defining the following...expressed in matrix form is first gie algorithm. In the time integration of structure- media problems.mapped to a subsystem in which the specified

  11. Interaction study of polyisobutylene with paraffins by NMR using the evaluation of spin-lattice relaxation times for hydrogen nuclei; Estudo da interacao do poliisobutileno com parafinas por RMN no estado solido

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Rosana G.G. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas - CENPES]. E-mail: garrido@cenpes.petrobras.com.br; Tavares, Maria I.B. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Macromoleculas]. E-mail: mibt@ima.ufrj.br

    2001-07-01

    The evaluation of spin-lattice relaxation times of {sup 1}H for polyisobutylene/paraffin systems, were obtained using the classic inversion recovery technique, and also through Cross Polarization Magic Angle Spinning (CP/MAS) techniques varying the contact time and also by the delayed contact time pulse sequence. NMR results showed that the polyisobutylene/paraffin systems in which high molecular weight paraffins were used, is heterogeneous. However, for paraffins with low molecular weight, the system presents good homogeneity. (author)

  12. FT-IR, NMR spectroscopic and quantum mechanical investigations of two ferrocene derivatives

    Directory of Open Access Journals (Sweden)

    Ö. Alver

    2017-07-01

    Full Text Available New ferrocene derivatives as N-(3-piperidin-1-ylpropylferrocenamide (Fc-3ppa and N-(pyridine-3-ylmethylferrocenamide (Fc-3pica and structural investigations were carried out with 1H, 13C, DEPT 45 or 135, HETCOR, COSY NMR and FT-IR spectroscopic techniques. Characterization of Fc-3ppa (FeC19H26N2O and Fc-3pica (FeC17H16N2O was also supported by density functional theory (DFT used by B3LYP functional and 6-31G(d or 6-311++G(d,p basis sets. From the combination of all the results, it can be clearly seen that syntheses of Fc-3ppa and Fc-3pica have been successfully achieved. Theoretical values are successfully compared against experimental data and B3LYP method is able to provide satisfactory results for predicting NMR properties and vibrational frequencies of the synthesized ferrocene based systems.

  13. 31P magic angle spinning NMR study of flux-grown rare-earth element orthophosphate (monazite/xenotime) solid solutions: evidence of random cation distribution from paramagnetically shifted NMR resonances.

    Science.gov (United States)

    Palke, Aaron C; Stebbins, Jonathan F; Boatner, Lynn A

    2013-11-04

    We present (31)P magic angle spinning nuclear magnetic resonance spectra of flux-grown solid solutions of La(1-x)Ce(x)PO4 (x between 0.027 and 0.32) having the monoclinic monazite structure, and of Y(1-x)M(x)PO4 (M = V(n+), Ce(3+), Nd(3+), x between 0.001 and 0.014) having the tetragonal zircon structure. Paramagnetically shifted NMR resonances are observed in all samples due to the presence of paramagnetic V(n+), Ce(3+), and Nd(3+) in the diamagnetic LaPO4 or YPO4. As a first-order observation, the number and relative intensities of these peaks are related to the symmetry and structure of the diamagnetic host phase. The presence of paramagnetic shifts allows for increased resolution between NMR resonances for distinct atomic species which leads to the observation of low intensity peaks related to PO4 species having more than one paramagnetic neighbor two or four atomic bonds away. Through careful analysis of peak areas and comparison with predictions for simple models, it was determined that solid solutions in the systems examined here are characterized by complete disorder (random distribution) of diamagnetic La(3+) or Y(3+) with the paramagnetic substitutional species Ce(3+) and Nd(3+). The increased resolution given by the paramagnetic interactions also leads to the observation of splitting of specific resonances in the (31)P NMR spectra that may be caused by local, small-scale distortions from the substitution of ions having dissimilar ionic radii.

  14. Investigation of Current Induced Spin Polarization in III-V Semiconductor Epilayers

    Science.gov (United States)

    Luengo-Kovac, Marta

    In the development of a semiconductor spintronics device, a thorough understanding of spin dynamics in semiconductors is necessary. In particular, electrical control of electron spins is advantageous for its compatibility with present day electronics. In this thesis, we will discuss the electrical modification of the electron g-factor, which characterizes the strength of the interaction between a spin and a magnetic field, as well as investigate electrically generated spin polarizations as a function of various material parameters. We report on the modification of the electron g-factor by an in-plane electric field in an InGaAs epilayer. We performed external magnetic field scans of the Kerr rotation of the InGaAs film in order to measure the g-factor independently of the spin-orbit fields. The g-factor increases from -0.4473(0.0001) at 0 V/cm to -0.4419( 0.0001) at 50 V/cm applied along the [110] crystal axis. A comparison of temperature and voltage dependent photoluminescence measurements indicate that minimal channel heating occurs at these voltages. Possible explanations for this g-factor modification are discussed, including an increase in the electron temperature that is independent of the lattice temperature and the modification of the donor-bound electron wave function by the electric field. The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InGaAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the spin polarization mechanism is extrinsic. Temperature-dependent measurements of the spin dephasing rates and mobilities were used to characterize the relative strengths of the intrinsic D

  15. Experimental and theoretical investigation of the magnetization dynamics of an artificial square spin ice cluster

    Energy Technology Data Exchange (ETDEWEB)

    Pohlit, Merlin, E-mail: pohlit@physik.uni-frankfurt.de; Porrati, Fabrizio; Huth, Michael; Müller, Jens [Institute of Physics, Goethe-University Frankfurt, Frankfurt/Main (Germany); Stockem, Irina; Schröder, Christian [Bielefeld Institute for Applied Materials Research, FH Bielefeld-University of Applied Sciences, Bielefeld (Germany)

    2016-10-14

    We study the magnetization dynamics of a spin ice cluster which is a building block of an artificial square spin ice fabricated by focused electron-beam-induced deposition both experimentally and theoretically. The spin ice cluster is composed of twelve interacting Co nanoislands grown directly on top of a high-resolution micro-Hall sensor. By employing micromagnetic simulations and a macrospin model, we calculate the magnetization and the experimentally investigated stray field emanating from a single nanoisland. The parameters determined from a comparison with the experimental hysteresis loop are used to derive an effective single-dipole macrospin model that allows us to investigate the dynamics of the spin ice cluster. Our model reproduces the experimentally observed non-deterministic sequences in the magnetization curves as well as the distinct temperature dependence of the hysteresis loop.

  16. Spectroscopic (vibrational, NMR and UV-vis.) and quantum chemical investigations on 4-hexyloxy-3-methoxybenzaldehyde.

    Science.gov (United States)

    Abbas, Ashgar; Gökce, Halil; Bahçeli, Semiha

    2016-01-05

    In this study, the 4-hexyloxy-3-methoxybenzaldehyde compound as one of the derivatives of vanillin which is a well known flavoring agent, C14H20O3, has been investigated by experimentally and extensively utilizing density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. In this context, the optimized geometry, vibrational frequencies, (1)H and (13)C NMR chemical shifts, UV-vis. (in gas phase and in methanol solvent) spectra, HOMO-LUMO analysis, molecular electrostatic potential (MEP), thermodynamic parameters and atomic charges of 4-hexyloxy-3-methoxybenzaldehyde have been calculated. In addition, theoretically predicted IR, Raman and UV-vis. (in gas phase and in methanol solvent) spectra of the mentioned molecule have been constructed. The results calculated were compared with the experimental data. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Spectroscopic (vibrational, NMR and UV-vis.) and quantum chemical investigations on 4-hexyloxy-3-methoxybenzaldehyde

    Science.gov (United States)

    Abbas, Ashgar; Gökce, Halil; Bahçeli, Semiha

    2016-01-01

    In this study, the 4-hexyloxy-3-methoxybenzaldehyde compound as one of the derivatives of vanillin which is a well known flavoring agent, C14H20O3, has been investigated by experimentally and extensively utilizing density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. In this context, the optimized geometry, vibrational frequencies, 1H and 13C NMR chemical shifts, UV-vis. (in gas phase and in methanol solvent) spectra, HOMO-LUMO analysis, molecular electrostatic potential (MEP), thermodynamic parameters and atomic charges of 4-hexyloxy-3-methoxybenzaldehyde have been calculated. In addition, theoretically predicted IR, Raman and UV-vis. (in gas phase and in methanol solvent) spectra of the mentioned molecule have been constructed. The results calculated were compared with the experimental data.

  18. Superionic phase transitions and nuclear spin phonon relaxation by Raman processes in Me3H(SeO4)2 (Me = Na, K, and Rb) single crystals by 1H and Me NMR

    International Nuclear Information System (INIS)

    Lim, Ae Ran

    2007-01-01

    Me 3 H(SeO 4 ) 2 (Me = Na, K, and Rb) single crystals were grown by the slow evaporation method, and the relaxation times of the 1 H and Me nuclei in these crystals were investigated using FT NMR spectrometry. The 1 H T 1 NMR results for K 3 H(SeO 4 ) 2 and Rb 3 H(SeO 4 ) 2 single crystals were very different from those for Na 3 H(SeO 4 ) 2 crystals. Short 1 H relaxation times were found for K 3 H(SeO 4 ) 2 and Rb 3 H(SeO 4 ) 2 at high temperatures, but not for Na 3 H(SeO 4 ) 2 , which are attributed to the destruction and reconstruction of hydrogen bonds; thus K 3 H(SeO 4 ) 2 and Rb 3 H(SeO 4 ) 2 have superionic phases, whereas Na 3 H(SeO 4 ) 2 does not. The temperature dependence of the relaxation rate for the 23 Na nucleus in Na 3 H(SeO 4 ) 2 crystals was in accord with a Raman process for nuclear spin-lattice relaxation (T 1 -1 ∝T 2 . In contrast, the spin-lattice relaxation rates for the 39 K and 87 Rb nuclei in K 3 H(SeO 4 ) 2 and Rb 3 H(SeO 4 ) 2 single crystals exhibited a very strong temperature dependence, T 1 -1 ∝T 7 . The motions giving rise to this strong temperature dependence may be related to the high electrical conductivities of these crystals at high temperatures

  19. Broadband homonuclear correlation spectroscopy driven by combined R2nv sequences under fast magic angle spinning for NMR structural analysis of organic and biological solids

    Science.gov (United States)

    Hou, Guangjin; Yan, Si; Trébosc, Julien; Amoureux, Jean-Paul; Polenova, Tatyana

    2013-07-01

    We recently described a family of experiments for R2nv Driven Spin Diffusion (RDSD) spectroscopy suitable for homonuclear correlation experiments under fast MAS conditions [G. Hou, S. Yan, S.J. Sun, Y. Han, I.J. Byeon, J. Ahn, J. Concel, A. Samoson, A.M. Gronenborn, T. Polenova, Spin diffusion drive by R-symmetry sequencs: applications to homonuclear correlation spectroscopy in MAS NMR of biological and organic solids, J. Am. Chem. Soc. 133 (2011) 3943-3953]. In these RDSD experiments, since the broadened second-order rotational resonance conditions are dominated by the radio frequency field strength and the phase shifts, as well as the size of reintroduced dipolar couplings, the different R2nv sequences display unique polarization transfer behaviors and different recoupling frequency bandwidths. Herein, we present a series of modified R2nv sequences, dubbed COmbined R2nv-Driven (CORD), that yield broadband homonuclear dipolar recoupling and give rise to uniform distribution of cross peak intensities across the entire correlation spectrum. We report NMR experiments and numerical simulations demonstrating that these CORD spin diffusion sequences are suitable for broadband recoupling at a wide range of magnetic fields and MAS frequencies, including fast-MAS conditions (νr = 40 kHz and above). Since these CORD sequences are largely insensitive to dipolar truncation, they are well suited for the determination of long-range distance constraints, which are indispensable for the structural characterization of a broad range of systems. Using U-13C,15N-alanine and U-13C,15N-histidine, we show that under fast-MAS conditions, the CORD sequences display polarization transfer efficiencies within broadband frequency regions that are generally higher than those offered by other existing spin diffusion pulse schemes. A 89-residue U-13C,15N-dynein light chain (LC8) protein has also been used to demonstrate that the CORD sequences exhibit uniformly high cross peak intensities

  20. A 13C{31P} REDOR NMR Investigation of the Role of Glutamic Acid Residues in Statherin-Hydroxyapatite Recognition

    Science.gov (United States)

    Ndao, Moise; Ash, Jason T.; Breen, Nicholas F.; Goobes, Gil; Stayton, Patrick S.; Drobny, Gary P.

    2011-01-01

    The side chain carboxyl groups of acidic proteins found in the extra-cellular matrix (ECM) of mineralized tissues play a key role in promoting or inhibiting the growth of minerals such as hydroxyapatite (HAP), the principal mineral component of bone and teeth. Among the acidic proteins found in the saliva is statherin, a 43-residue tyrosine-rich peptide that is a potent lubricant in the salivary pellicle and an inhibitor of both HAP crystal nucleation and growth. Three acidic amino acids – D1, E4, and E5 – are located in the N-terminal 15 amino acid segment, with a fourth amino acid, E26, located outside the N-terminus. We have utilized 13C{31P} REDOR NMR to analyze the role played by acidic amino acids in the binding mechanism of statherin to the HAP surface by measuring the distance between the δ-carboxyl 13C spins of the three glutamic acid side chains of statherin (residues E4, E5, E26) and 31P spins of the phosphate groups at the HAP surface. 13C{31P} REDOR studies of glutamic-5-13C acid incorporated at positions E4 and E26 indicate a 13C–31P distance of more than 6.5 Å between the side chain carboxyl 13C spin of E4 and the closest 31P in the HAP surface. In contrast, the carboxyl 13C spin at E5 has a much shorter 13C–31P internuclear distance of 4.25±0.09 Å, indicating that the carboxyl group of this side chain interacts directly with the surface. 13C T1ρ and slow-spinning MAS studies indicate that the motions of the side chains of E4 and E5 are more restricted than that of E26. Together, these results provide further insight into the molecular interactions of statherin with HAP surfaces. PMID:19678690

  1. Anisotropic spin fluctuations in heavy-fermion superconductor CeCoIn sub 5. In-NQR and Co-NMR studies

    CERN Document Server

    Kawasaki, Y; Yashima, M

    2003-01-01

    We report In-NQR and Co-NMR experiments of CeCoIn sub 5 that undergoes a superconducting transition with a record high T sub c =2.3 K to date among heavy-fermion superconductors. At zero magnetic field, an anomalous temperature (T) dependence of nuclear spin-lattice relaxation rate 1/T sub 1 of sup 1 sup 1 sup 5 In is explained by the relation 1/T sub 1 propor to T centre dot chi sub Q (T) sup 3 sup / sup 4 based on the anisotropic spin-fluctuations model in case of the proximity to an antiferromagnetic (AFM) quantum critical point (QCP). The novel behavior of 1/T sub 1 - T sup 1 sup / sup 4 over a wide T range of T sub c < T < 40 K arises because the staggered susceptibility almost follows the Curie law chi sub Q (T) propor to 1/(T + theta) with theta=0.6 K and hence 1/T sub 1 propor to T/(T + 0.6) sup 3 sup / sup 4 - T sup 1 sup / sup 4 for theta < T. We highlight that the behavior 1/T sub 1 - T sup 1 sup / sup 4 is due to the proximity to the anisotropic AFM QCP relevant with its layered structure...

  2. A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance.

    Science.gov (United States)

    Tan, Kong Ooi; Agarwal, Vipin; Meier, Beat H; Ernst, Matthias

    2016-09-07

    We present a generalized theoretical framework that allows the approximate but rapid analysis of residual couplings of arbitrary decoupling sequences in solid-state NMR under magic-angle spinning conditions. It is a generalization of the tri-modal Floquet analysis of TPPM decoupling [Scholz et al., J. Chem. Phys. 130, 114510 (2009)] where three characteristic frequencies are used to describe the pulse sequence. Such an approach can be used to describe arbitrary periodic decoupling sequences that differ only in the magnitude of the Fourier coefficients of the interaction-frame transformation. It allows a ∼100 times faster calculation of second-order residual couplings as a function of pulse sequence parameters than full spin-dynamics simulations. By comparing the theoretical calculations with full numerical simulations, we show the potential of the new approach to examine the performance of decoupling sequences. We exemplify the usefulness of this framework by analyzing the performance of commonly used high-power decoupling sequences and low-power decoupling sequences such as amplitude-modulated XiX (AM-XiX) and its super-cycled variant SC-AM-XiX. In addition, the effect of chemical-shift offset is examined for both high- and low-power decoupling sequences. The results show that the cross-terms between the dipolar couplings are the main contributions to the line broadening when offset is present. We also show that the SC-AM-XIX shows a better offset compensation.

  3. Magic angle spinning NMR below 6 K with a computational fluid dynamics analysis of fluid flow and temperature gradients.

    Science.gov (United States)

    Sesti, Erika L; Alaniva, Nicholas; Rand, Peter W; Choi, Eric J; Albert, Brice J; Saliba, Edward P; Scott, Faith J; Barnes, Alexander B

    2018-01-01

    We report magic angle spinning (MAS) up to 8.5 kHz with a sample temperature below 6 K using liquid helium as a variable temperature fluid. Cross polarization 13 C NMR spectra exhibit exquisite sensitivity with a single transient. Remarkably, 1 H saturation recovery experiments show a 1 H T 1 of 21 s with MAS below 6 K in the presence of trityl radicals in a glassy matrix. Leveraging the thermal spin polarization available at 4.2 K versus 298 K should result in 71 times higher signal intensity. Taking the 1 H longitudinal relaxation into account, signal averaging times are therefore predicted to be expedited by a factor of >500. Computer assisted design (CAD) and finite element analysis were employed in both the design and diagnostic stages of this cryogenic MAS technology development. Computational fluid dynamics (CFD) models describing temperature gradients and fluid flow are presented. The CFD models bearing and drive gas maintained at 100 K, while a colder helium variable temperature fluid stream cools the center of a zirconia rotor. Results from the CFD were used to optimize the helium exhaust path and determine the sample temperature. This novel cryogenic experimental platform will be integrated with pulsed dynamic nuclear polarization and electron decoupling to interrogate biomolecular structure within intact human cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Analysis of φ and χ1 torsion angles for hen lysozyme in solution from 1H NMR spin-spin coupling constants

    International Nuclear Information System (INIS)

    Smith, L.J.; Sutcliffe, M.J.; Redfield, C.; Dobson, C.M.

    1991-01-01

    Three-bond 3 J HNα coupling constants have been determined for 106 residues and 3 J αβ coupling constants have been measured for 57 residues of the 129-residue protein hen egg white lysozyme. These NMR data have been compared with torsion angles defined in the tetragonal and the triclinic crystal forms of the protein. For most residues the measured 3 J HNα values were consistent with the φ torsion angles found in both crystal forms; the RMS difference between the coupling constants calculated by using the tetragonal crystal structure φ angles and the experimental 3 J HNα values is 0.88 Hz. Thus there appears to be no significant averaging of the φ torsion angle either in the interior or at the surface of the protein. For 41 of the residues where 3 J αβ coupling constants have been determined, the values are consistent with a single staggered conformation about the χ 1 torsion angle and there is complete agreement between the NMR data in solution and the torsion angles defined in the crystalline state. In contrast, for the other 16 residues where 3 J αβ coupling constant values have been measured, the data indicate extensive motional averaging about the χ 1 torsion angle. These residues occur largely on the surface of the protein and examination of the crystal structures shows that many of these residues adopt a different conformation in the triclinic and tetragonal crystal forms and have high crystallographic temperature factors. It appears, however, that in solution conformational flexibility of the side chains of surface residues is significantly more pronounced than in individual crystal structures

  5. Weak self-association of human growth hormone investigated by nitrogen-15 NMR relaxation.

    Science.gov (United States)

    Jensen, Malene Ringkjøbing; Kristensen, Søren M; Keeler, Camille; Christensen, Hans E M; Hodsdon, Michael E; Led, Jens J

    2008-10-01

    The self-association of human growth hormone(hGH) was investigated using 15N NMR relaxation.The investigation relies on the 15N R1 and R2 relaxation rates and the heteronuclear{1H}-15N NOEs of the backbone amide groups at multiple protein concentrations. It is shown that the rotational correlation time of hGH in solution depends strongly on its concentration, indicating a significant degree of self-association.The self-association is reversible and the monomers in the aggregates are noncovalently linked. Extrapolation of the relaxation data to zero concentration predicts a correlation time of 13.4 ns and a rotational diffusion anisotropy of 1.26 for monomeric hGH, in agreement with the rotational diffusion properties estimated by hydrodynamic calculations. Moreover, the extrapolation allows characterization of the backbone dynamics of monomeric hGH without interference from self-association phenomena, and it is found that hGH is considerably more flexible than originally thought. A concerted least-squares analysis of the 15N relaxations and their concentration dependence reveals that the self-association goes beyond a simple monomer-dimer equilibrium, and that tetramers or other multimeric states co-exist in fast exchange with the monomeric and dimeric hGH at sub-millimolar concentrations. Small changes in the 1H and 15N amide chemical shifts suggest that a region around the C-terminus is involved in the oligomer formation.

  6. Investigation of V@2]O@5]/Nb@2]O@5] Catalysts by $51]V Solid-State NMR

    NARCIS (Netherlands)

    Smits, R.H.H.; Smits, R.H.H.; Seshan, Kulathuiyer; Ross, J.R.H.; Ross, J.R.H.

    1995-01-01

    Vanadium-niobium oxide catalysts containing variable amounts of vanadium and prepared by coprecipitation were investigated using 51V solid-state NMR. It was found that, in samples containing less than about 8 mol % V2O5, vanadium occurs in three different oxygen environments: in isolated tetrahedra,

  7. 113Cd-NMR investigation of a cadmium-substituted copper, zinc-containing superoxide dismutase from yeast

    DEFF Research Database (Denmark)

    Kofod, Pauli; Bauer, Rogert; Danielsen, Eva

    1991-01-01

    113Cd nuclear magnetic resonance spectroscopy has been used to investigate the metal binding sites of cadmium-substituted copper,zinc-containing superoxide dismutase from baker's yeast. NMR signals were obtained for 113Cd(II) at the Cu site as well as for 113Cd(II) at the Zn site. The two subunits...

  8. Investigation of sea microorganisms of the genus Alteromonas by 31P-NMR of high resolution

    International Nuclear Information System (INIS)

    Ivanova, E.P.; Isakov, V.V.; Mikhajlov, V.V.; Sokolova, S.V.; Gorshkova, N.M.; Fedosov, Yu.V.; Kiprianova, E.A.

    1993-01-01

    Comparative analysis of the 31 P-NMR spectra of intact cells of bacteria belonging to the genus Alteromonas, the producers of alkaline phosphatase was carried out. Differences in the content of phosphate-containing compounds were detected in individual species of the genus Alteromonas. By comparing the data on 31 P-NMR spectra, the electron micrographs and phosphatase activities, the possibility of revealing the presence of capsules was shown. Peculiar features of the 31 P-NMR spectra of alteromonades, as compared with other taxonomic groups of microorganisms, have been discussed

  9. Optical pumping and xenon NMR

    International Nuclear Information System (INIS)

    Raftery, M.D.

    1991-11-01

    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping 129 Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the 131 Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen

  10. Equivalence of the Floquet-Magnus and Fer Expansions to Investigate the Dynamics of a Spin System in the Three-Level System.

    Science.gov (United States)

    Mananga, Eugene Stephane

    2017-08-17

    In this work, we investigated the orders to which the Floquet-Magnus expansion (FME) and Fer expansion (FE) are equivalent or different for the three-level system. Specifically, we performed the third-order calculations of both approaches based on elegant integrations formalism. We present an important close relationship between the Floquet-Magnus and Fer expansions. As the propagator from the FME takes the form of the evolution operator, which removes the constraint of a stroboscopic observation, we appreciated the effects of time-evolution under Hamiltonians with different orders separately. Our work unifies and generalizes existing results of Floquet-Magnus and Fer approaches and delivers illustrations of novel springs that boost previous applications that are based on the classical information. Due to the lack of an unequivocal relationship between the FME and FE, some disagreements between the results produced by these theories will be found, especially in NMR experiments. Our results can find applications in the optimization of NMR spectroscopy, quantum computation, quantum optical control, and coherence in optics and might bear new awareness in fundamental perusals of quantum spin dynamics. This work is an important theoretical and numerical contribution in the general field of spin dynamics.

  11. Plaster mortars with polymer fibers and additives investigated by 1H NMR relaxometry

    Science.gov (United States)

    Mustea, Andrei; Manea, Daniela L.; Jumate, Elena; Orbán, Yvette A.; Fechete, Radu

    2017-12-01

    Plaster mortars with polypropylene (pp) fibers and/or additives were investigated by 1H NMR relaxometry. Two recipes are proposed and are based on a commercially available mortar or are self-prepared and have different content of polypropylene fibers, which play the role of reinforcement agent, and/or Sika additive which is a waterproofing agent. The distributions of transverse relaxation times, T2 were obtained at 1, 3, 7 and 28 days after preparation. For the majority of T2-distributions four peaks are observed and, are associated with the hydration water (to the mineralogical components) and water in small, medium and large pores. The evolution in time, from 1 to 28 days, of the T2-distributions indicates the effects of pp fibers and Sika additive in the formation of pore microstructure. The degree of homogeneity of prepared receipts was evaluated from the relative peak-width and compared with mechanical measurements. Finally, we shown that the inverse of the transverse relaxation time values, T2-1, characteristic to the hydration water depends linearly on the resistance at compression measured for the 1÷28 days period, proving the important role of hydrations to the mechanical properties of the final product.

  12. Investigating the locomotion of the sandfish in desert sand using NMR-imaging.

    Science.gov (United States)

    Baumgartner, Werner; Fidler, Florian; Weth, Agnes; Habbecke, Martin; Jakob, Peter; Butenweg, Christoph; Böhme, Wolfgang

    2008-10-01

    The sandfish (Scincus scincus) is a lizard having the remarkable ability to move through desert sand for significant distances. It is well adapted to living in loose sand by virtue of a combination of morphological and behavioural specializations. We investigated the bodyform of the sandfish using 3D-laserscanning and explored its locomotion in loose desert sand using fast nuclear magnetic resonance (NMR) imaging. The sandfish exhibits an in-plane meandering motion with a frequency of about 3 Hz and an amplitude of about half its body length accompanied by swimming-like (or trotting) movements of its limbs. No torsion of the body was observed, a movement required for a digging-behaviour. Simple calculations based on the Janssen model for granular material related to our findings on bodyform and locomotor behaviour render a local decompaction of the sand surrounding the moving sandfish very likely. Thus the sand locally behaves as a viscous fluid and not as a solid material. In this fluidised sand the sandfish is able to "swim" using its limbs.

  13. Investigating the locomotion of the sandfish in desert sand using NMR-imaging.

    Directory of Open Access Journals (Sweden)

    Werner Baumgartner

    Full Text Available The sandfish (Scincus scincus is a lizard having the remarkable ability to move through desert sand for significant distances. It is well adapted to living in loose sand by virtue of a combination of morphological and behavioural specializations. We investigated the bodyform of the sandfish using 3D-laserscanning and explored its locomotion in loose desert sand using fast nuclear magnetic resonance (NMR imaging. The sandfish exhibits an in-plane meandering motion with a frequency of about 3 Hz and an amplitude of about half its body length accompanied by swimming-like (or trotting movements of its limbs. No torsion of the body was observed, a movement required for a digging-behaviour. Simple calculations based on the Janssen model for granular material related to our findings on bodyform and locomotor behaviour render a local decompaction of the sand surrounding the moving sandfish very likely. Thus the sand locally behaves as a viscous fluid and not as a solid material. In this fluidised sand the sandfish is able to "swim" using its limbs.

  14. Synthesis of Radiation Curable Palm Oil-Based Epoxy Acrylate: NMR and FTIR Spectroscopic Investigations.

    Science.gov (United States)

    Salih, Ashraf M; Ahmad, Mansor Bin; Ibrahim, Nor Azowa; Dahlan, Khairul Zaman Hj Mohd; Tajau, Rida; Mahmood, Mohd Hilmi; Yunus, Wan Md Zin Wan

    2015-08-04

    Over the past few decades, there has been an increasing demand for bio-based polymers and resins in industrial applications, due to their potential lower cost and environmental impact compared with petroleum-based counterparts. The present research concerns the synthesis of epoxidized palm oil acrylate (EPOLA) from an epoxidized palm oil product (EPOP) as environmentally friendly material. EPOP was acrylated by acrylic acid via a ring opening reaction. The kinetics of the acrylation reaction were monitored throughout the reaction course and the acid value of the reaction mixture reached 10 mg KOH/g after 16 h, indicating the consumption of the acrylic acid. The obtained epoxy acrylate was investigated intensively by means of FTIR and NMR spectroscopy, and the results revealed that the ring opening reaction was completed successfully with an acrylation yield about 82%. The UV free radical polymerization of EPOLA was carried out using two types of photoinitiators. The radiation curing behavior was determined by following the conversion of the acrylate groups. The cross-linking density and the hardness of the cured EPOLA films were measured to evaluate the effect of the photoinitiator on the solid film characteristics, besides, the thermal and mechanical properties were also evaluated.

  15. Proton NMR investigation of heme pocket mobility in hemoglobin via hydrogen isotope exchange kinetics

    International Nuclear Information System (INIS)

    Han, K.

    1985-01-01

    Dynamic mobility of heme cavity, the active site of Hb, was investigated by analyzing the hydrogen isotope exchange kinetics of the proximal histidyl ring NH of various kinds of Hbs with the aid of the high field Fourier Transform 1 H NMR spectroscopy. The exchange reaction occurs faster in oxy or R-state Hb than in deoxy or T-state Hb and there exists a good correlation between the oxygen affinity of Hb and the heme pocket mobility reflected in the hydrogen exchange rate. The effect of pH on the exchange is dramatically different for the two subunits of Hb A. Studying the exchange characteristics of mutant Hbs and chemically modified Hbs not only showed the existence of three well-defined localized paths for transmission of conformational changes between different heme pockets through a 1 b 2 subunit interface, but also indicated that the heme pocket mobility is regulated by the quaternary state of Hb as well as by the ligation state of Hb. Finally, the effect of the quaternary state on the heme pocket mobility is separated from that of the ligation by following the exchange reactions in Hbs where only their quaternary structure transition can be achieved without changing their ligation states by adjusting experimental conditions such as adding inositol hexaphosphate

  16. Synthesis of Radiation Curable Palm Oil–Based Epoxy Acrylate: NMR and FTIR Spectroscopic Investigations

    Directory of Open Access Journals (Sweden)

    Ashraf M. Salih

    2015-08-01

    Full Text Available Over the past few decades, there has been an increasing demand for bio-based polymers and resins in industrial applications, due to their potential lower cost and environmental impact compared with petroleum-based counterparts. The present research concerns the synthesis of epoxidized palm oil acrylate (EPOLA from an epoxidized palm oil product (EPOP as environmentally friendly material. EPOP was acrylated by acrylic acid via a ring opening reaction. The kinetics of the acrylation reaction were monitored throughout the reaction course and the acid value of the reaction mixture reached 10 mg KOH/g after 16 h, indicating the consumption of the acrylic acid. The obtained epoxy acrylate was investigated intensively by means of FTIR and NMR spectroscopy, and the results revealed that the ring opening reaction was completed successfully with an acrylation yield about 82%. The UV free radical polymerization of EPOLA was carried out using two types of photoinitiators. The radiation curing behavior was determined by following the conversion of the acrylate groups. The cross-linking density and the hardness of the cured EPOLA films were measured to evaluate the effect of the photoinitiator on the solid film characteristics, besides, the thermal and mechanical properties were also evaluated.

  17. An investigation into the effects of pore connectivity on T2 NMR relaxation

    Science.gov (United States)

    Ghomeshi, Shahin; Kryuchkov, Sergey; Kantzas, Apostolos

    2018-04-01

    Nuclear Magnetic Resonance (NMR) is a powerful technique used to characterize fluids and flow in porous media. The NMR relaxation curves are closely related to pore geometry, and the inversion of the NMR relaxometry data is known to give useful information with regards to pore size distribution (PSD) through the relative amplitudes of the fluids stored in the small and large pores. While this information is crucial, the main challenge for the successful use of the NMR measurements is the proper interpretation of the measured signals. Natural porous media patterns consist of complex pore structures with many interconnected or "coupled" regions, as well as isolated pores. This connectivity along the throats changes the relaxation distribution and in order to properly interpret this data, a thorough understanding of the effects of pore connectivity on the NMR relaxation distribution is warranted. In this paper we address two main points. The first pertains to the fact that there is a discrepancy between the relaxation distribution obtained from experiments, and the ones obtained from solving the mathematical models of diffusion process in the digitized images of the pore space. There are several reasons that may attribute to this such as the lack of a proper incorporation of surface roughness into the model. However, here we are more interested in the effects of pore connectivity and to understand why the typical NMR relaxation distribution obtained from experiments are wider, while the numerical simulations predict that a wider NMR relaxation distribution may indicate poor connectivity. Secondly, by not taking into account the pore coupling effects, from our experience in interpreting the data, we tend to underestimate the pore volume of small pores and overestimate the amplitudes in the large pores. The role of pore coupling becomes even more prominent in rocks with small pore sizes such as for example in shales, clay in sandstones, and in the microstructures of

  18. Magic angle spinning NMR reveals sequence-dependent structural plasticity, dynamics, and the spacer peptide 1 conformation in HIV-1 capsid protein assemblies.

    Science.gov (United States)

    Han, Yun; Hou, Guangjin; Suiter, Christopher L; Ahn, Jinwoo; Byeon, In-Ja L; Lipton, Andrew S; Burton, Sarah; Hung, Ivan; Gor'kov, Peter L; Gan, Zhehong; Brey, William; Rice, David; Gronenborn, Angela M; Polenova, Tatyana

    2013-11-27

    A key stage in HIV-1 maturation toward an infectious virion requires sequential proteolytic cleavage of the Gag polyprotein leading to the formation of a conical capsid core that encloses the viral RNA genome and a small complement of proteins. The final step of this process involves severing the SP1 peptide from the CA-SP1 maturation intermediate, which triggers the condensation of the CA protein into the capsid shell. The details of the overall mechanism, including the conformation of the SP1 peptide in CA-SP1, are still under intense debate. In this report, we examine tubular assemblies of CA and the CA-SP1 maturation intermediate using magic angle spinning (MAS) NMR spectroscopy. At magnetic fields of 19.9 T and above, outstanding quality 2D and 3D MAS NMR spectra were obtained for tubular CA and CA-SP1 assemblies, permitting resonance assignments for subsequent detailed structural characterization. Dipolar- and scalar-based correlation experiments unequivocally indicate that SP1 peptide is in a random coil conformation and mobile in the assembled CA-SP1. Analysis of two CA protein sequence variants reveals that, unexpectedly, the conformations of the SP1 tail, the functionally important CypA loop, and the loop preceding helix 8 are modulated by residue variations at distal sites. These findings provide support for the role of SP1 as a trigger of the disassembly of the immature CA capsid for its subsequent de novo reassembly into mature cores and establish the importance of sequence-dependent conformational plasticity in CA assembly.

  19. Integrating High-Resolution and Solid-State Magic Angle Spinning NMR Spectroscopy and a Transcriptomic Analysis of Soybean Tissues in Response to Water Deficiency.

    Science.gov (United States)

    Coutinho, Isabel D; Moraes, Tiago Bueno; Mertz-Henning, Liliane Marcia; Nepomuceno, Alexandre Lima; Giordani, Willian; Marcolino-Gomes, Juliana; Santagneli, Silvia; Colnago, Luiz Alberto

    2017-11-01

    Solid-state NMR (SSNMR) spectroscopy methods provide chemical environment and ultrastructural details that are not easily accessible by other non-destructive, high-resolution spectral techniques. High-resolution magic angle spinning (HR-MAS) has been widely used to obtain the metabolic profile of a heterogeneous sample, combining the resolution enhancement provided by MAS in SSNMR with the shimming and locking procedures in liquid-state NMR. In this work, we explored the feasibility of using the HR-MAS and SSNMR techniques to identify metabolic changes in soybean leaves subjected to water-deficient conditions. Control and water-deficient soybean leaves were analysed using one-dimensional (1D) HR-MAS and SSNMR. Total RNA was extracted from the leaves for the transcriptomic analysis. The 1 H HR-MAS and CP-MAS 13 C{ 1 H} spectra of soybean leaves grown with and without water deficiency stress revealed striking differences in metabolites. A total of 30 metabolites were identified, and the impact of water deficiency on the metabolite profile of soybean leaves was to induce amino acid synthesis. High expression levels of genes required for amino acid biosynthesis were highly correlated with the compounds identified by 1 H HR-MAS. The integration of the 1 H HR-MAS and SSNMR spectra with the transcriptomic data provided a complete picture of the major changes in the metabolic profile of soybeans in response to water deficiency. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  20. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Guangjin, E-mail: hou@udel.edu, E-mail: tpolenov@udel.edu; Lu, Xingyu, E-mail: luxingyu@udel.edu, E-mail: lexvega@comcast.net; Vega, Alexander J., E-mail: luxingyu@udel.edu, E-mail: lexvega@comcast.net; Polenova, Tatyana, E-mail: hou@udel.edu, E-mail: tpolenov@udel.edu [Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, Pennsylvania 15261 (United States)

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear {sup 1}H-X (X = {sup 13}C, {sup 15}N, {sup 31}P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the {sup 1}H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the {sup 1}H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from {sup 1}H chemical shift anisotropy, while keeping the {sup 1}H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [{sup 15}N]-N-acetyl-valine and [U-{sup 13}C,{sup 15}N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate {sup 1}H-{sup 15}N dipolar couplings in the context of 3D experiments is presented on U-{sup 13}C,{sup 15}N-enriched dynein light chain protein LC8.

  1. 13C and 29Si NMR as a probe to investigate polysiloxanes used in dental applications

    International Nuclear Information System (INIS)

    Silva, Naira Machado da; Tavares, Maria Ines B.

    2001-01-01

    The properties of dental mould polymeric materials are strongly influenced by the chemical structure of both the polymer and the catalyst used in the crosslink reaction between them. In order to characterize and suggest some modifications on the materials interfacial interactions, mixtures of Polymer-catalyst were prepared. The polymer and the catalyst chemical structures were obtained by 13 C, 1 H and 129 Si NMR analysis in solution state. From the solution NMR results it was obtained the structure of the polymer and the catalyst and also the kind of the crosslink reaction taken. The CPMAS 1 '3C NMR analysis in the solid state were used to identify chemical structure of the polymeric dental moulded sample. (author)

  2. 1H-NMR spectroscopic investigation of reversed micellization in metal/organophosphorous surfactant system

    International Nuclear Information System (INIS)

    Gaonkar, A.G.; Neuman, R.D.; Garver, T.M. Jr.

    1988-01-01

    Evidence for the formation of reversed micellar aggregates in the extraction system di(2-ethyl-hexyl)phosphoric acid (HDEHP)/benzene/0.05 mol dm -3 CaCl 2 was obtained from proton magnetic resonance ( 1 H-NMR) spectroscopy. 1 H-NMR measurements indicate that the critical reversed micellar concentration is 6-11x10 -3 F and that the equilibrium constant for reversed micellization is 2.4x10 12 (mol/l) -5.6 . The interfacial tension, equilibrium calcium distribution coefficient and apparent molecular weight of the species in the equilibrated organic phase were also determined and are compared to the 1 H-NMR results. 21 refs.; 5 figs

  3. Pairwise NMR experiments for the determination of protein backbone dihedral angle Φ based on cross-correlated spin relaxation

    International Nuclear Information System (INIS)

    Takahashi, Hideo; Shimada, Ichio

    2007-01-01

    Novel cross-correlated spin relaxation (CCR) experiments are described, which measure pairwise CCR rates for obtaining peptide dihedral angles Φ. The experiments utilize intra-HNCA type coherence transfer to refocus 2-bond J NCα coupling evolution and generate the N (i)-C α (i) or C'(i-1)-C α (i) multiple quantum coherences which are required for measuring the desired CCR rates. The contribution from other coherences is also discussed and an appropriate setting of the evolution delays is presented. These CCR experiments were applied to 15 N- and 13 C-labeled human ubiquitin. The relevant CCR rates showed a high degree of correlation with the Φ angles observed in the X-ray structure. By utilizing these CCR experiments in combination with those previously established for obtaining dihedral angle Ψ, we can determine high resolution structures of peptides that bind weakly to large target molecules

  4. Quantum model of a solid-state spin qubit: Ni cluster on a silicon surface by the generalized spin Hamiltonian and X-ray absorption spectroscopy investigations

    Energy Technology Data Exchange (ETDEWEB)

    Farberovich, Oleg V. [School of Physics and Astronomy, Beverly and Raymond Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel); Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Voronezh State University, Voronezh 394000 (Russian Federation); Mazalova, Victoria L., E-mail: mazalova@sfedu.ru [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Soldatov, Alexander V. [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation)

    2015-11-15

    pattern with the anisotropic exchange models conventionally used for the analysis of this system and, with the results of the experimental XANES spectra, shows that our complex investigations provide a good description of the pattern of the spin levels and the spin structures of the nanomagnetic Ni{sub 7} qubit. The results are discussed in the view of the general problem of the solid-state spin qubits and the spin structure of the Ni cluster. - Highlights: • We present the model of the quantum solid-state qubit. • We have studied the Rabi oscillations and the electron spin decoherence. • The quantum entanglement is important for a quantum computation. • We have analyzed a behavior of the entanglement in the finite clusters.

  5. Developments in Solid-State NMR

    Indian Academy of Sciences (India)

    reso/020/11/1040-1052. Keywords. NMR; solid state; anisotropy; magic angle spinning dipolar coupling; quadrupolar coupling; chemical shift. Author Affiliations. K V Ramanathan1. NMR Research Center, Indian Institute of Science, Bengaluru ...

  6. Magic angle spinning 31P NMR spectroscopy reveals two essentially identical ionization states for the cardiolipin phosphates in phospholipid liposomes.

    Science.gov (United States)

    Kooijman, E E; Swim, L A; Graber, Z T; Tyurina, Y Y; Bayır, H; Kagan, V E

    2017-01-01

    Specific membrane lipid composition is crucial for optimized structural and functional organization of biological membranes. Cardiolipin is a unique phospholipid and important component of the inner mitochondrial membrane. It is involved in energy metabolism, inner mitochondrial membrane transport, regulation of multiple metabolic reactions and apoptotic cell death. The physico-chemical properties of cardiolipin have been studied extensively but despite all these efforts there is still lingering controversy regarding the ionization of the two phosphate groups of cardiolipin. Results obtained in the 1990s and early 2000s suggested that cardiolipin has two disparate pKa values where one of the protons was proposed to be stabilized by an intramolecular hydrogen bond. This has led to extensive speculations on the roles of these two putative ionization states of cardiolipin in mitochondria. More recently the notion of two pKa values has been challenged and rejected by several groups. These studies relied on external measurements of proton adsorption or electrophoretic mobility of membranes but did not take into account the low pH phase behavior and chemical stability of cardiolipin. Here we used 31 P NMR to show that in the physiologically relevant membrane phospholipid environment, cardiolipin carries two negative charges at physiological pH. We additionally demonstrate the pH dependent phase behavior and chemical stability of cardiolipin containing membranes. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. NMR relaxometry as a versatile tool to study Li ion dynamics in potential battery materials.

    Science.gov (United States)

    Kuhn, A; Kunze, M; Sreeraj, P; Wiemhöfer, H D; Thangadurai, V; Wilkening, M; Heitjans, P

    2012-04-01

    NMR spin relaxometry is known to be a powerful tool for the investigation of Li(+) dynamics in (non-paramagnetic) crystalline and amorphous solids. As long as significant structural changes are absent in a relatively wide temperature range, with NMR spin-lattice (as well as spin-spin) relaxation measurements information on Li self-diffusion parameters such as jump rates and activation energies are accessible. Diffusion-induced NMR relaxation rates are governed by a motional correlation function describing the ion dynamics present. Besides the mean correlation rate of the dynamic process, the motional correlation function (i) reflects deviations from random motion (so-called correlation effects) and (ii) gives insights into the dimensionality of the hopping process. In favorable cases, i.e., when temperature- and frequency-dependent NMR relaxation rates are available over a large dynamic range, NMR spin relaxometry is able to provide a comprehensive picture of the relevant Li dynamic processes. In the present contribution, we exemplarily present two recent variable-temperature (7)Li NMR spin-lattice relaxation studies focussing on Li(+) dynamics in crystalline ion conductors which are of relevance for battery applications, viz. Li(7) La(3)Zr(2)O(12) and Li(12)Si(7). Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Atomic-resolution structure of the CAP-Gly domain of dynactin on polymeric microtubules determined by magic angle spinning NMR spectroscopy.

    Science.gov (United States)

    Yan, Si; Guo, Changmiao; Hou, Guangjin; Zhang, Huilan; Lu, Xingyu; Williams, John Charles; Polenova, Tatyana

    2015-11-24

    Microtubules and their associated proteins perform a broad array of essential physiological functions, including mitosis, polarization and differentiation, cell migration, and vesicle and organelle transport. As such, they have been extensively studied at multiple levels of resolution (e.g., from structural biology to cell biology). Despite these efforts, there remain significant gaps in our knowledge concerning how microtubule-binding proteins bind to microtubules, how dynamics connect different conformational states, and how these interactions and dynamics affect cellular processes. Structures of microtubule-associated proteins assembled on polymeric microtubules are not known at atomic resolution. Here, we report a structure of the cytoskeleton-associated protein glycine-rich (CAP-Gly) domain of dynactin motor on polymeric microtubules, solved by magic angle spinning NMR spectroscopy. We present the intermolecular interface of CAP-Gly with microtubules, derived by recording direct dipolar contacts between CAP-Gly and tubulin using double rotational echo double resonance (dREDOR)-filtered experiments. Our results indicate that the structure adopted by CAP-Gly varies, particularly around its loop regions, permitting its interaction with multiple binding partners and with the microtubules. To our knowledge, this study reports the first atomic-resolution structure of a microtubule-associated protein on polymeric microtubules. Our approach lays the foundation for atomic-resolution structural analysis of other microtubule-associated motors.

  9. Diffusional behavior of n-paraffins with various chain lengths in urea adduct channels by pulsed field-gradient spin-echo NMR spectroscopy

    International Nuclear Information System (INIS)

    Kim, Sunmi; Kuroki, Shigeki; Ando, Isao

    2006-01-01

    The diffusion coefficients (D) of n-paraffin molecules (n-C n H 2n+2 ) with various chain-lengths (n = 8, 12, 21, 26, 28 and 32) in the long channels of a deuterated urea-d 4 adduct have been measured at 25 deg. C by means of pulsed field-gradient spin-echo 1 H NMR method. The aim is to clarify diffusional behavior of the n-paraffin molecules in the urea adduct channels. From the experimental results, it is found that n-paraffin molecules are diffusing in the long channels and have two kinds of diffusion components, namely a fast (D ∼ 10 -10 m 2 /s) and a slow diffusion component (D ∼ 10 -11 m 2 /s). The diffusing-time (Δ) dependence of the diffusion coefficients of the n-paraffins shows some likely evidence of restricted diffusion since the n-paraffin molecules are confined in the urea channel. The diffusion coefficients (D) decrease as the carbon number increases from 8 to 28, and very slowly decreases as the carbon number increases from 28 to 32

  10. High resolution NMR theory and chemical applications

    CERN Document Server

    Becker, Edwin D

    1969-01-01

    High Resolution NMR: Theory and Chemical Applications focuses on the applications of nuclear magnetic resonance (NMR), as well as chemical shifts, lattices, and couplings. The book first offers information on the theory of NMR, including nuclear spin and magnetic moment, spin lattice relaxation, line widths, saturation, quantum mechanical description of NMR, and ringing. The text then ponders on instrumentation and techniques and chemical shifts. Discussions focus on the origin of chemical shifts, reference compounds, empirical correlations of chemical shifts, modulation and phase detection,

  11. NMR investigations of temperature-induced phase transition in aqueous polymer solutions

    Czech Academy of Sciences Publication Activity Database

    Spěváček, Jiří

    2011-01-01

    Roč. 305, č. 1 (2011), s. 18-25 ISSN 1022-1360 R&D Projects: GA ČR GA202/09/1281 Institutional research plan: CEZ:AV0Z40500505 Keywords : aqueous polymer solutions * cooperative effects * NMR Subject RIV: CD - Macromolecular Chemistry

  12. Influence of water on stability of geopolymers investigated by NMR solid state spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Kobera, Libor; Brus, Jiří; Urbanová, Martina; Slavík, R.

    2008-01-01

    Roč. 33, - (2008), s. 86 ISSN 1896-2203. [Mid-European Clay Conference MECC 08 /4./. 22.09.2008-27.09.2008, Zakopane] R&D Projects: GA AV ČR IAA400500602 Institutional research plan: CEZ:AV0Z40500505 Keywords : stability * NMR * solid state spectroscopy * geopolymer Subject RIV: CD - Macromolecular Chemistry

  13. Structural investigation of bistrifluron using x-ray crystallography, NMR spectroscopy, and molecular modeling

    CERN Document Server

    Moon, J K; Rhee, S K; Kim, G B; Yun, H S; Chung, B J; Lee, S S; Lim, Y H

    2002-01-01

    A new insecticide, bistrifluron acts as an inhibitor of insect development and interferes with the cuticle formation of insects. Since it shows low acute oral and dermal toxicities, it can be one of potent insecticides. Based on X-ray crystallography, NMR spectroscopy and molecular modeling, the structural studies of bistrifluron have been carried out.

  14. Role of hydration in the phase transition of polypeptides investigated by NMR and Raman spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Dybal, Jiří; Schmidt, Pavel; Kříž, Jaroslav; Kurková, Dana; Rodriguez-Cabello, J. C.; Alonso, M.

    2004-01-01

    Roč. 205, - (2004), s. 143-150 ISSN 1022-1360 R&D Projects: GA AV ČR IAA4050208 Institutional research plan: CEZ:AV0Z4050913 Keywords : NMR * quantum chemistry * Raman spectroscopy Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.691, year: 2004

  15. Conformational Properties and orientational order of a de Vries liquid crystal investigated through NMR spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Domenici, V.; Lelli, M.; Cifelli, M.; Hamplová, Věra; Marchetti, A.; Veracini, C.A.

    2014-01-01

    Roč. 15, č. 7 (2014), s. 1485-1495 ISSN 1439-4235 Institutional support: RVO:68378271 Keywords : conformations * liquid crystals * orientational order * phase transitions * solid-state NMR spectroscopy Subject RIV: CC - Organic Chemistry Impact factor: 3.419, year: 2014

  16. Solid state NMR investigations and MD simulations of triblock copolymers in lipid bilayers

    Czech Academy of Sciences Publication Activity Database

    Baerenwald, R.; Ferreira, T. M.; Ollila, Samuli; Saalwaechter, K.

    2017-01-01

    Roč. 46, Suppl 1 (2017), S117 ISSN 0175-7571. [IUPAB congress /19./ and EBSA congress /11./. 16.07.2017-20.07.2017, Edinburgh] Institutional support: RVO:61388963 Keywords : solid state NMR * molecular dynamic simulations Subject RIV: BO - Biophysics

  17. The local physical structure of amorphous hydrogenated boron carbide: insights from magic angle spinning solid-state NMR spectroscopy.

    Science.gov (United States)

    Paquette, Michelle M; Li, Wenjing; Sky Driver, M; Karki, Sudarshan; Caruso, A N; Oyler, Nathan A

    2011-11-02

    Magic angle spinning solid-state nuclear magnetic resonance spectroscopy techniques are applied to the elucidation of the local physical structure of an intermediate product in the plasma-enhanced chemical vapour deposition of thin-film amorphous hydrogenated boron carbide (B(x)C:H(y)) from an orthocarborane precursor. Experimental chemical shifts are compared with theoretical shift predictions from ab initio calculations of model molecular compounds to assign atomic chemical environments, while Lee-Goldburg cross-polarization and heteronuclear recoupling experiments are used to confirm atomic connectivities. A model for the B(x)C:H(y) intermediate is proposed wherein the solid is dominated by predominantly hydrogenated carborane icosahedra that are lightly cross-linked via nonhydrogenated intraicosahedral B atoms, either directly through B-B bonds or through extraicosahedral hydrocarbon chains. While there is no clear evidence for extraicosahedral B aside from boron oxides, ∼40% of the C is found to exist as extraicosahedral hydrocarbon species that are intimately bound within the icosahedral network rather than in segregated phases.

  18. Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

    Science.gov (United States)

    Herlitschke, M.; Disch, S.; Sergueev, I.; Schlage, K.; Wetterskog, E.; Bergström, L.; Hermann, R. P.

    2016-04-01

    The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4 nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.

  19. Nuclear magnetic resonance (NMR): principles and applications

    International Nuclear Information System (INIS)

    Quibilan, E.I.

    The basis for the phenomenon of nuclear magnetic resonance (NMR) is the ability of certain nuclei possessing both intrinsic angular momentum or ''spin'' I and magnetic moment to absorb electromagnetic energy in the radio frequency range. In principle, there are approximately 200 nuclei which may be investigated using the NMR technique. The NMR spectrum consists of intensity peaks along an axis calibrated in terms of the steady magnetic field or the frequency of the radiofrequency electromagnetic radiation. Analysis of the number, spacing, position and intensity of the lines in an NMR spectrum consists of intensity peaks along an axis calibrated in terms of the steady magnetic field or the frequency of the radiofrequency electromagnetic radiation. Analysis of the number, spacing, position and intensity of the lines in an NMR spectrum provides a variety of qualitative and quantitative analytical applications. The most obvious applications consist of the measurements of nuclear properties, such as spin number and nuclear magnetic moment. In liquids, the fine structure of resonance spectra provides a tool for chemical identification and molecular structure analysis. Other applications include the measurements of self-diffusion coefficients, magnetic fields and field homogeneity, inter-nuclear distances, and, in some cases, the water content of biological materials. (author)

  20. Investigation of hydrolysis of heteropolyacid H3PW12O40 by 31P NMR method

    International Nuclear Information System (INIS)

    Maksimovskaya, R.I.

    1998-01-01

    The composition of water solutions of heteropolyacid (H 3 PW 12 O 40 (PW 12 )) is studied at different concentrations and pH through the NMR 31 P method with the purpose of clarification of actual mechanism of the heteropolyacid hydrolysis. The NMR 31 P data showed that the PW 11 M (M=Li = , K + , Na + , Mg 2+ , Ca 2+ ) complexes are the only product of the first stage of hydrolysis by M-base titration. This stage ends by pH≤5. By further pH growth these complexes retain the composition up to their decomposition. Diagrams of the solution distribution relative to different forms within the range of pH 1-9 and more exactly defined scheme of the H 3 PW 12 O 40 alkali hydrolysis are presented. At the same time the heteropolyacid demonstrates high stability to acid hydrolysis

  1. Structural investigation of molten fluorides of nuclear interest by NMR and XAFS spectroscopies

    International Nuclear Information System (INIS)

    Pauvert, Olivier

    2009-01-01

    In the frame of the renewal of the different nuclear plans, the molten salt reactor is one of the six concepts of reactors of 4. generation. This reactor has the particularity to use a liquid fuel based on LiF-ThF 4 mixtures. In order to develop and to optimize this concept, it is important to characterize the structure of the melt and to describe its physical and chemical properties. Our work has been based on the study of the system MF-ZrF 4 (M = Li, Na, K) selected as a model of ThF 4 based systems. We have combined two spectroscopic techniques, the Nuclear Magnetic Resonance and the X-ray Absorption at high temperature, with molecular dynamics calculations. We particularly focused on the local environments of the fluorine and the zirconium. In order to interpret the NMR data obtain in the molten state, we performed a preliminary study on zirconium halides and rare earth and alkali fluoro zirconates using the 91 Zr solid-state NMR at very high magnetic fields. New correlations between structural parameters and NMR data have been established. At high temperature, in MF-ZrF 4 melts we have shown the coexistence of three different kind of Zr-based complexes with different proportions depending on the amount of ZrF 4 and on the nature of the alkali. Depending on the ZrF 4 content, three kinds of fluorine have been characterized: form free fluorines at low amount of zirconium fluorides, fluorines involved in Zr-based complexes and bridging fluorines at higher ZrF 4 content. This original and innovative approach of molten fluorides mixtures, combining NMR and EXAFS at high temperature with molecular dynamics calculations, is very efficient to describe their speciation and thus their fluoro-acidity. (author)

  2. NMR and Theoretical Investigation of Cation Binding With Sol-Gel Silicates

    Science.gov (United States)

    1993-07-12

    sturation . (bottom spectrum). The corresponding 2’Si NMR spec- trum (Figure 2) shows no hydrolyzed TEOS. Thus, as replaced by Si-O-Si bonds. Evidently the...Q(M) and Q(O) are the (36) Do Jong, B. H. W. S.; Brown . G. L Geochim. Cosmochim. Acto1980. 44. 1627. (37) McCormick, A. V.; Bell, A. T.; Radke, C. J

  3. Investigation of chemometric instrumental transfer methods for high-resolution NMR.

    Science.gov (United States)

    Alam, Todd M; Alam, M Kathleen; McIntyre, Sarah K; Volk, David E; Neerathilingam, Muniasamy; Luxon, Bruce A

    2009-06-01

    The implementation of direct standardization (DS), piecewise direct standardization (PDS), and double-window piecewise direct standardization (DWPDS) instrumental transfer techniques for high-resolution (1)H NMR spectral data was explored. The ability to transfer a multivariate calibration model developed for a "master or target" NMR instrument configuration to seven different ("secondary") NMR instrument configurations was measured. Partial least-squares (PLS) calibration of glucose, glycine, and citrate metabolite relative concentrations in model mixtures following mapping of the secondary instrumental configurations using DS, PDS, or DWPDS instrumental transfer allowed the performance of the different transfer methods to be assessed. Results from these studies suggest that DS and PDS transfer techniques produce similar improvements in the error of prediction compared to each other and provide a significant improvement over standard spectral preprocessing techniques including reference deconvolution and spectral binning. The DS instrumental transfer method produced the largest percent improvement in the predictions of concentrations for these model mixtures but, in general, required that additional transfer calibration standards be used. Limitations of the different instrumental transfer methods with respect to sample subset selection are also discussed.

  4. Bis(pentamethylcyclopentadienyl)ytterbium: An investigation of weak interactions in solution using multinuclear NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, David Joel [Univ. of California, Berkeley, CA (United States)

    1995-07-01

    NMR spectroscopy is ideal for studying weak interactions (formation enthalpy ≤20 kcal/mol) in solution. The metallocene bis(pentamethylcyclopentadienyl)ytterbium, Cp*2Yb, is ideal for this purpose. cis-P2PtH2complexes (P = phosphine) were used to produce slow-exchange Cp*2YbL adducts for NMR study. Reversible formation of (P2PtH)2 complexes from cis-P2PtH2 complexes were also studied, followed by interactions of Cp*2Yb with phosphines, R3PX complexes. A NMR study was done on the interactions of Cp*2Yb with H2, CH4, Xe, CO, silanes, stannanes, C6H6, and toluene.

  5. Relaxation-compensated difference spin diffusion NMR for detecting 13C–13C long-range correlations in proteins and polysaccharides

    International Nuclear Information System (INIS)

    Wang, Tuo; Williams, Jonathan K.; Schmidt-Rohr, Klaus; Hong, Mei

    2015-01-01

    The measurement of long-range distances remains a challenge in solid-state NMR structure determination of biological macromolecules. In 2D and 3D correlation spectra of uniformly 13 C-labeled biomolecules, inter-residue, inter-segmental, and intermolecular 13 C– 13 C cross peaks that provide important long-range distance constraints for three-dimensional structures often overlap with short-range cross peaks that only reflect the covalent structure of the molecule. It is therefore desirable to develop new approaches to obtain spectra containing only long-range cross peaks. Here we show that a relaxation-compensated modification of the commonly used 2D 1 H-driven spin diffusion (PDSD) experiment allows the clean detection of such long-range cross peaks. By adding a z-filter to keep the total z-period of the experiment constant, we compensate for 13 C T 1 relaxation. As a result, the difference spectrum between a long- and a scaled short-mixing time spectrum show only long-range correlation signals. We show that one- and two-bond cross peaks equalize within a few tens of milliseconds. Within ∼200 ms, the intensity equilibrates within an amino acid residue and a monosaccharide to a value that reflects the number of spins in the local network. With T 1 relaxation compensation, at longer mixing times, inter-residue and inter-segmental cross peaks increase in intensity whereas intra-segmental cross-peak intensities remain unchanged relative to each other and can all be subtracted out. Without relaxation compensation, the difference 2D spectra exhibit both negative and positive intensities due to heterogeneous T 1 relaxation in most biomolecules, which can cause peak cancellation. We demonstrate this relaxation-compensated difference PDSD approach on amino acids, monosaccharides, a crystalline model peptide, a membrane-bound peptide and a plant cell wall sample. The resulting difference spectra yield clean multi-bond, inter-residue and intermolecular correlation peaks

  6. NMR imaging of human atherosclerosis

    International Nuclear Information System (INIS)

    Toussaint, J.F.

    1995-01-01

    Diagnosis and prognosis of atherosclerosis can no longer be evaluated with morphological parameters only. A description of atherosclerotic plaque composition is necessary to study the mechanisms of plaque rupture, which depends on collagenous cap and lipid core thicknesses. NMR, as a biochemical imaging technique, allows visualization of these components using T1 contrast (mobile lipids), T2 contrast (cap vs. core), spin density (calcifications), diffusion imaging, 1H and 13C spectroscopy. Today, these imaging sequences allow to study in vitro the effects of interventional techniques such as angioplasty or atherectomy. Clinical investigations begin, which will attempt to develop in vivo microscopy and test the ability of NMR to predict plaque rupture. (author). 13 refs., 7 figs

  7. Fourier Analysis and Structure Determination. Part II: Pulse NMR and NMR Imaging.

    Science.gov (United States)

    Chesick, John P.

    1989-01-01

    Uses simple pulse NMR experiments to discuss Fourier transforms. Studies the generation of spin echoes used in the imaging procedure. Shows that pulse NMR experiments give signals that are additions of sinusoids of differing amplitudes, frequencies, and phases. (MVL)

  8. αB-Crystallin. A Hybrid Solid-State/Solution-State NMR Investigation Reveals Structural Aspects of the Heterogeneous Oligomer

    Energy Technology Data Exchange (ETDEWEB)

    Jehle, Stefan [Freie Univ., Berlin (Germany); Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); van Rossum, Barth [Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Stout, Joseph R. [Univ. of Washington, Seattle, WA (United States); Noguchi, Satoshi M. [Univ. of Washington, Seattle, WA (United States); Falber, Katja [Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Rehbein, Kristina [Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Oschkinat, Hartmut [Freie Univ., Berlin (Germany); Leibniz Inst. for Molecular Pharmacology, Berlin (Germany); Klevit, Rachel E. [Univ. of Washington, Seattle, WA (United States); Rajagopal, Ponni [Univ. of Washington, Seattle, WA (United States)

    2008-11-14

    Atomic-level structural information on αB-Crystallin (αB), a prominent member of the small heat-shock protein family, has been a challenge to obtain due its polydisperse oligomeric nature. We show that magic-angle spinning solid-state NMR can be used to obtain high-resolution information on an ~580-kDa human αB assembled from 175-residue 20-kDa subunits. An ~100-residue α-crystallin domain is common to all small heat-shock proteins, and solution-state NMR was performed on two different α- crystallin domain constructs isolated from αB. In vitro, the chaperone-like activities of full-length αB and the isolated α-crystallin domain are identical. Chemical shifts of the backbone and Cβ resonances have been obtained for residues 64–162 (α-crystallin domain plus part of the C-terminus) in αB and the isolated α-crystallin domain by solid-state and solution-state NMR, respectively. Both sets of data strongly predict six β-strands in the α-crystallin domain. A majority of residues in the α-crystallin domain have similar chemical shifts in both solid-state and solution-state, indicating similar structures for the domain in its isolated and oligomeric forms. Sites of intersubunit interaction are identified from chemical shift differences that cluster to specific regions of the α-crystallin domain. Multiple signals are observed for the resonances of M68 in the oligomer, identifying the region containing this residue as existing in heterogeneous environments within αB. Evidence for a novel dimerization motif in the human α-crystallin domain is obtained by a comparison of (i) solid-state and solution-state chemical shift data and (ii) 1H–15N heteronuclear single quantum coherence spectra as a function of pH. The isolated α-crystallin domain undergoes a dimer–monomer transition over the pH range 7.5–6.8. This steep pHdependent switch may be important for αB to function optimally (e.g., to preserve the filament integrity

  9. 1H NMR investigation of self-association of vanillin in aqueous solution

    International Nuclear Information System (INIS)

    Bogdan, Mircea; Floare, Calin G; PIrnau, Adrian

    2009-01-01

    A self-association of vanillin have been studied by 1 H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  10. {sup 1}H NMR investigation of self-association of vanillin in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bogdan, Mircea; Floare, Calin G; PIrnau, Adrian, E-mail: mircea.bogdan@itim-cj.r [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)

    2009-08-01

    A self-association of vanillin have been studied by {sup 1}H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  11. Investigation of zeolitic imidazolate frameworks using 13C and 15N solid-state NMR spectroscopy

    OpenAIRE

    Sneddon, Scott; Kahr, Juergen; Orsi, Angelica F.; Price, David J.; Dawson, Daniel M.; Wright, Paul A.; Ashbrook, Sharon E.

    2017-01-01

    The authors are grateful to EPSRC computational support through the Collaborative Computational Project on NMR Crystallography (CCP-NC), via EP/M022501/1, and for other support through EP/G062129/1 (JK) and EP/M506631/1 (SS). AFO acknowledges funding from the European Community Seventh Framework Program (FP7/2007-2013 [grant agreement number 608490], Project M4CO2). SEA would also like to thank the Royal Society and Wolfson Foundation for a merit award. AFO would also like to acknowledge the ...

  12. Pathogenesis of rheumatoid arthritis and cartilage degradation - investigations by in vitro 1H NMR spetroscopy

    International Nuclear Information System (INIS)

    Schiller, J.; Arnhold, J.; Arnold, K.

    2000-01-01

    Degenerative joint diseases like rheumatoid arthritis are accompanied by a progradient degradation of the articular cartilage matrix. Although the details of cartilage destruction are not yet completely understood, it is assumed that secreted products of stimulated neutrophilic granulocytes are massively involved in such processes. This paper discusses the in vitro application of high-resolution proton NMR spectroscopy (600 MHz) for the study of pathologically changed human synovial fluids and the detection of metabolites and degradation products in fluids obtained by punctuation. Additionally, it is explained what resonances may serve as indicators for the different pathological processes of cartilage degradation (effects of reactive oxygen species and enzymes). (orig.) [de

  13. Investigation of the spin Seebeck effect and anomalous Nernst effect in a bulk carbon material

    Science.gov (United States)

    Wongjom, Poramed; Pinitsoontorn, Supree

    2018-03-01

    Since the discovery of the spin Seebeck effect (SSE) in 2008, it has become one of the most active topics in the spin caloritronics research field. It opened up a new way to create the spin current by a combination of magnetic fields and heat. The SSE was observed in many kinds of materials including metallic, semiconductor, or insulating magnets, as well as non-magnetic materials. On the other hand, carbon-based materials have become one of the most exciting research areas recently due to its low cost, abundance and some exceptional functionalities. In this work, we have investigated the possibility of the SSE in bulk carbon materials for the first time. Thin platinum film (Pt), coated on the smoothened surface of the bulk carbon, was used as the spin detector via the inverse spin Hall effect (ISHE). The experiment for observing longitudinal SSE in the bulk carbon was set up by applying a magnetic field up to 30 kOe to the sample with the direction perpendicular to the applied temperature gradient. The induced voltage from the SSE was extracted. However, for conductive materials, e.g. carbon, the voltage signal under this set up could be a combination of the SSE and the anomalous Nernst effect (ANE). Therefore, two measurement configurations were carried out, i.e. the in-plane magnetization (IM), and the perpendicular-to-plane magnetization (PM). For the IM configuration, the SSE + ANE signals were detected where as the only ANE signal existed in the PM configuration. The results showed that there were the differences between the voltage signals from the IM and PM configurations implying the possibility of the SSE in the bulk carbon material. Moreover, it was found that the difference in the IM and PM signals was a function of the magnetic field strength, temperature difference, and measurement temperature. Although the magnitude of the possible SSE voltage in this experiment was rather low (less than 0.5 μV at 50 K), this research showed that potential of using

  14. 2-mm Band and X-band electron spin resonance and electron spin-echo investigations of some carbonaceous materials

    Energy Technology Data Exchange (ETDEWEB)

    Tsvetkov, Y.D.; Dzuba, S.A.; Gulin, V.I. [Institute of Chemical Kinetics and Combustion, Novosibirsk (Russian Federation)

    1993-12-31

    Argonne Premium coal samples were studied by using 2-mm band and X-band continuous-wave electron spin resonance (CW ESR) and X-band electron spin-echo (ESE) spectroscopy. The line widths and g factors (Lande g factor, spectroscopic splitting factor) were determined. The correlation between {Delta}g = g{sub {parallel}} - g{sub {perpendicular}} and the carbon content in coal samples was established. Paramagnetic centers in coals could be attributed to radicals with partial redistribution of spin density from polycyclic {pi}-system to peroxide-type structures. The degree of this redistribution depends on the degree of carbonization. Phase relaxation times, T{sub 2}, for these coals were determined by using ESE spectroscopy. 5 refs., 2 figs., 3 tabs.

  15. Investigation of spin correlations in top-pair production with the CMS detector at the LHC

    International Nuclear Information System (INIS)

    Davids, Martina

    2011-01-01

    In spring 2010 the Large Hadron Collider (LHC) started its operation with a center-of-mass energy of 7 TeV, that will be increased up to 14 TeV in the following years. Considering a medium energy of √(s)=10 TeV and a luminosity of L=10 33 cm -2 s -1 some million top quarks are produced per year. This offers the opportunity to investigate spin-correlations between the top quarks from pair production. As the spinconfiguration of the top-quark pair depends on the production mechanism, a measurement of such effects is a unique tool to study the contributions of the production processes and spin effects. This allows to test the Standard Model. This thesis investigates dileptonic top-pair decays at the Compact Muon Solenoid based on simulated events. A quantitative measure of spin correlations is the asymmetry A, that manifests itself in the angular distribution of the two leptons. A full kinematic reconstruction of the top pair is necessary to determine this distribution. The MC generators Pythia, MC rate at NLO, and TopReX are tested with respect to their treatment of spin-correlations. Pythia is used to generate uncorrelated samples. MC rate at NLO reproduces the Standard Model prediction. These samples are used to determine the sensitivity of the present analysis. Due to an incorrect implementation of the helicity states, TopReX is not usable. A full event selection and reconstruction are adapted. The reconstructed angular distribution shows a significant distortion. A template method is implemented to determine the asymmetry. Here, the angular distribution is decomposed into a flat, a completely asymmetric, and a background part, that are fitted by a binned χ 2 approach to toy-data. An ensemble study is performed to estimate the statistical uncertainty. As the main systematic uncertainties, generator effects, the jet energy scale and uncertainties in the cross sections or selection efficiency are investigated. Considering an integrated luminosity of L int =1 fb

  16. NMR spectroscopic study and DFT calculations of GIAO NMR ...

    African Journals Online (AJOL)

    1H, proton coupled and decoupled 13C, DEPT, HETCOR NMR spectra, the magnitude of one bond 1JCH coupling constants and 13C NMR spin-lattice relaxation time (T1) of 1,9-diaminononane (danon, C9H22N2) have been reported for the first time. 1H, 13C NMR chemical shifts and 1JCH coupling constants of danon ...

  17. Integrating solid-state NMR and computational modeling to investigate the structure and dynamics of membrane-associated ghrelin.

    Directory of Open Access Journals (Sweden)

    Gerrit Vortmeier

    Full Text Available The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide's secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide's positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8-17 form an α-helix, while residues 21-23 and 26-27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane.

  18. Integrating Solid-State NMR and Computational Modeling to Investigate the Structure and Dynamics of Membrane-Associated Ghrelin

    Science.gov (United States)

    Els-Heindl, Sylvia; Chollet, Constance; Scheidt, Holger A.; Beck-Sickinger, Annette G.; Meiler, Jens; Huster, Daniel

    2015-01-01

    The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide’s secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide’s positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8–17 form an α-helix, while residues 21–23 and 26–27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane. PMID:25803439

  19. Urine metabolite analysis as a function of deoxynivalenol exposure: an NMR-based metabolomics investigation.

    Science.gov (United States)

    Hopton, R P; Turner, E; Burley, V J; Turner, P C; Fisher, J

    2010-02-01

    Deoxynivalenol (DON) is a toxic fungal metabolite that frequently contaminates cereal crops including wheat, maize and barley. Despite knowledge of frequent exposure through diet, our understanding of the potential consequences of human exposure remains limited, in part due to the lack of validated exposure biomarkers. In this study, we interrogated the urinary metabolome using nuclear magnetic resonance (NMR) spectroscopy to compare individuals with known low and high DON exposure through consumption of their normal diet. Urine samples from 22 adults from the UK (seven males, 15 females; age range = 21-59 years) had previously determined urinary DON levels using an established liquid chromatography-mass spectrometry (LC-MS) assay. Urine samples were subsequently analysed using an NMR-based metabolomics approach coupled with multivariate statistical analysis. Metabolic profiling suggested that hippurate levels could be used to distinguish between groups with low (3.6 ng DON mg(-1) creatinine: 95% CI = 2.6, 5.0 ng mg(-1)) and high (11.1 ng mg(-1): 95% CI = 8.1, 15.5 ng mg(-1)) DON exposure, with the concentration of hippurate being significantly (1.5 times) higher for people with high DON exposure than for those with low DON exposure (p = 0.047). This, to our knowledge, is the first report of a metabolomics-derived biomarker of DON exposure in humans.

  20. 31P MAS refocused INADEQUATE spin-echo (REINE) NMR spectroscopy: revealing J coupling and chemical shift two-dimensional correlations in disordered solids.

    Science.gov (United States)

    Guerry, Paul; Smith, Mark E; Brown, Steven P

    2009-08-26

    Two-dimensional (2D) variations in (2)J(P(1),P(1)), (2)J(P(1),P(2)), and (2)J(P(2),P(2)) are obtained--using the REINE (REfocused INADEQUATE spin-Echo) pulse sequence presented by Cadars et al. (Phys. Chem. Chem. Phys. 2007, 9, 92-103)--from pixel-by-pixel fittings of the spin-echo modulation for the 2D correlation peaks due to linked phosphate tetrahedra (P(1)-P(1), P(1)-P(2), P(2)-P(1), and P(2)-P(2)) in a (31)P refocused INADEQUATE solid-state MAS NMR spectrum of a cadmium phosphate glass, 0.575CdO-0.425P(2)O(5). In particular, separate variations for each 2D (31)P REINE peak are obtained which reveal correlations between the J couplings and the (31)P chemical shifts of the coupled nuclei that are much clearer than those evident in previously presented 2D z-filtered (31)P spin-echo spectra. Notably, such correlations between the J couplings and the (31)P chemical shifts are observed even though the conditional probability distributions extracted using the protocol of Cadars et al. (J. Am. Chem. Soc. 2005, 127, 4466-4476) indicate that there is no marked correlation between the (31)P chemical shifts of neighboring phosphate tetrahedra. For 2D peaks at the P(2) (31)P chemical shift in the direct dimension, there can be contributions from chains of three units (P(1)-P(2)-P(1)), chains of four units (P(1)-P(2)-P(2)-P(1)), or longer chains or rings (-P(2)-P(2)-P(2)-): for the representative glass considered here, best fits are obtained assuming a glass comprised predominantly of chains of four units. The following variations are found: (2)J(P(1),P(1)) = 13.4 +/- 0.3 to 14.8 +/- 0.5 Hz, (2)J(P(1),P(2)) = 15.0 +/- 0.3 to 18.2 +/- 0.3 Hz, and (2)J(P(2),P(2)) = 5.9 +/- 0.6 to 9.1 +/- 0.9 Hz from the fits to the P(1)-P(1), P(1)-P(2), and P(2)-P(2) peaks, respectively. The correlation of a particular J coupling with the (31)P chemical shifts of the considered nucleus and the coupled nucleus is quantified by the coefficients C(F(2)) and C(F(1)) that correspond to the

  1. Proton dynamics investigation for dimethyl ammonium cation

    International Nuclear Information System (INIS)

    Pislewski, N.; Tritt-Goc, J.; Jakubas, R.

    1995-01-01

    Proton dynamics in dimethyl ammonium cation has been investigated by means of NMR and spin echo methods in polycrystalline salts [NH 2 (CH 3 ) 2 ] + Bi 2 J 9 - and [NH 2 (CH 3 ) 2 ] + SbJ 9 - . Spin-lattice relaxation time as well as second moment of NMR line have been measured for influence study of crystal structure changes on proton dynamics

  2. Cadmium-113 NMR spin-lattice relaxation and exchange kinetics in concanavalin A: A double saturation transfer experiment

    Science.gov (United States)

    Ellis, Paul D.; Yang, Ping P.; Palmert, Allen R.

    The field dependence of the 113Cd relaxation rate in cadmium-substituted Concanavalin A was investigated at three magnetic field strengths, 2.3, 4.7, and 9.4 T. Because of the anomalously large relaxation rate observed for the resonance corresponding to free cadmium in the system and our prior knowledge that cadmium is undergoing chemical exchange in this system, a detailed analysis was undertaken of the relaxation data obtained at 9.4 T to investigate the relative importance of chemical exchange dynamics upon the observed relaxation time constants. The differential equations for the resulting restricted three-site exchange network can be solved in closed form by employing a double saturation transfer experiment in conjunction with a saturation-recovery T1 experiment. The analysis of these data demonstrate that chemical exchange processes contribute 14, 75, and 20% to the observed relaxation time constants for the 113Cd resonances for the S1 site, free cadmium and the S2 site respectively. If the possibility of exchange contributions to the NOE were ignored, then the observed field dependence of T1 could not be discussed in terms of conventional single correlation time theories of relaxation. In this case the data could be discussed in terms of correlation times involving overall motion of the protein coupled with correlation times describing "internal motions." These internal motions may be the result of the formation of "abortive" complexes with exogenous ligands for those metalloproteins where the metal can be readily removed from the protein. However, for Con A, it is shown that the weak field dependence observed for the heteronuclear NOE is not due to internal motions, but rather to exchange processes.

  3. Early {sup 8}Li{sup +}{beta}-NMR investigations in GaAs and Ge

    Energy Technology Data Exchange (ETDEWEB)

    Chow, K.H. [Department of Physics, University of Alberta, Edmonton, AB, T6G 2J1 (Canada)]. E-mail: kimchow@phys.ualberta.ca; Salman, Z. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); MacFarlane, W.A. [Department of Chemistry, University of British Columbia, Vancouver, V6T 1Z1 (Canada); Campbell, Brendan [Department of Physics, University of Alberta, Edmonton, AB, T6G 2J1 (Canada); Keeler, T.A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Kiefl, R.F. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Kreitzman, S.R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); Levy, C.D.P. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); Morris, G.D. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); Parolin, T.J. [Department of Chemistry, University of British Columbia, Vancouver, V6T 1Z1 (Canada); Daviel, S. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); Yamani, Z. [National Research Council, Steacie Institute for Molecular Sciences, Neutron Program for Materials Research, Chalk River Laboratories, Chalk River, ON, K0J 1J0 (Canada)

    2006-03-31

    In this paper, we describe initial studies of the structure and dynamics associated with Li+8 in bulk crystalline GaAs and Ge. At low temperatures in GaAs, the amplitude of the Li+8 resonance signal at {approx}3T indicates that a large fraction (at least 70%) of the Li end up in locations with cubic symmetry (i.e. the tetrahedral interstitial and substitutional sites). The linewidth of the {beta}-NMR Li+8 resonance increases dramatically above 150K, reaches a maximum at about 290K, and decreases again. This suggests that the Li starts to change its location, probably from an interstitial to a substitutional site, at {approx}150K. Experiments in Ge are also described. In this sample, a narrow resonance is seen at low temperatures that is likely due to Li located at an interstitial site. Near room temperature, it appears that Li is converting to another site.

  4. Investigating the Mechanisms of Amylolysis of Starch Granules by Solution-State NMR

    Science.gov (United States)

    2015-01-01

    Starch is a prominent component of the human diet and is hydrolyzed by α-amylase post-ingestion. Probing the mechanism of this process has proven challenging, due to the intrinsic heterogeneity of individual starch granules. By means of solution-state NMR, we demonstrate that flexible polysaccharide chains protruding from the solvent-exposed surfaces of waxy rice starch granules are highly mobile and that during hydrothermal treatment, when the granules swell, the number of flexible residues on the exposed surfaces increases by a factor of 15. Moreover, we show that these flexible chains are the primary substrates for α-amylase, being cleaved in the initial stages of hydrolysis. These findings allow us to conclude that the quantity of flexible α-glucan chains protruding from the granule surface will greatly influence the rate of energy acquisition from digestion of starch. PMID:25815624

  5. NMR spectroscopy using liquid crystal solvents

    CERN Document Server

    Emsley, JW

    2013-01-01

    NMR Spectroscopy using Liquid Crystal Solvents covers the importance of using a liquid crystal solvent in NMR to derive nuclear dipolar spin-spin coupling constants. This book is composed of ten chapters, and begins with a brief description of the features and benefits of liquid crystal in NMR spectroscopic analysis. The succeeding chapters deal with the mode of operation of nuclear spin Hamiltonian for partially oriented molecules and the analysis of NMR spectra of partially oriented molecules, as well as the determination of rigid molecule structure. These topics are followed by discussions

  6. Time domain NMR evaluation of poly(vinyl alcohol) xerogels

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Elton Jorge da Rocha; Cavalcante, Maxwell de Paula; Tavares, Maria Ines Bruno, E-mail: mibt@ima.ufrj.br [Universidade Federal do Rio de Janeiro (IMA/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Tecnologia. Instituto de Macromoleculas Professora Eloisa Mano

    2016-05-15

    Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO{sub 2}), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO{sub 2} does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO{sub 2}. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials. (author)

  7. Some exercises in quantitative NMR imaging

    International Nuclear Information System (INIS)

    Bakker, C.J.G.

    1985-01-01

    The articles represented in this thesis result from a series of investigations that evaluate the potential of NMR imaging as a quantitative research tool. In the first article the possible use of proton spin-lattice relaxation time T 1 in tissue characterization, tumor recognition and monitoring tissue response to radiotherapy is explored. The next article addresses the question whether water proton spin-lattice relaxation curves of biological tissues are adequately described by a single time constant T 1 , and analyzes the implications of multi-exponentiality for quantitative NMR imaging. In the third article the use of NMR imaging as a quantitative research tool is discussed on the basis of phantom experiments. The fourth article describes a method which enables unambiguous retrieval of sign information in a set of magnetic resonance images of the inversion recovery type. The next article shows how this method can be adapted to allow accurate calculation of T 1 pictures on a pixel-by-pixel basis. The sixth article, finally, describes a simulation procedure which enables a straightforward determination of NMR imaging pulse sequence parameters for optimal tissue contrast. (orig.)

  8. Congested ferrocenyl polyphosphanes bearing electron-donating or electron-withdrawing phosphanyl groups: assessment of metallocene conformation from NMR spin couplings and use in palladium-catalyzed chloroarenes activation.

    Science.gov (United States)

    Mom, Sophal; Beaupérin, Matthieu; Roy, David; Royer, Sylviane; Amardeil, Régine; Cattey, Hélène; Doucet, Henri; Hierso, J-C

    2011-11-21

    The synthesis of novel substituted cyclopentadienyl salts that incorporate both a congested branched alkyl group (tert-butyl, (triphenyl)methyl, or tri(4-tert-butyl)phenylmethyl) and a phosphanyl group is reported. The introduction of either electron-withdrawing or electron-donating substituents (furyl, i-propyl, cyclohexyl, tert-butyl) on P atoms was generally achieved in high yield. The modular synthesis of ferrocenyl polyphosphanes from an assembly of these cyclopentadienyl salts was investigated, leading to the formation of new triphosphanes (denoted as 9-12) and diphosphanes (denoted as 14-16). The resulting phosphanes are not sensitive to air or moisture, even when electron-rich substituents are present. This set of polyphosphanes displays varied conformational features, which are discussed in the light of their multinuclear NMR characterization in solution and of the X-ray solid state structure of the representative triphosphane 1,2-bis(diphenylphosphanyl)-1'-(diisopropylphosphanyl)-3'-(triphenyl)methyl-4-tert-butyl ferrocene, 11. In particular, the existence of a range of significantly different nonbonded ("through-space", TS) spin-spin coupling constants between heteroannular P atoms, for the triphosphanes of this class, allowed their preferred conformation in solution to be appraised. The study evidences an unanticipated flexibility of the ferrocene platform, despite the presence of very congested tert-butyl and trityl groups. Herein, we show that, contrary to our first belief, the preferred conformation for the backbone of ferrocenyl polyphosphanes can not only depend on the hindrance of the groups decorating the cyclopentadienyl rings but is also a function of the substituents of the phosphanyl groups. The interest of these robust phosphanes as ligands was illustrated in palladium catalysis for the arylation of n-butyl furan with chloroarenes, using direct C-H activation of the heteroaromatic in the presence of low metal/ligand loadings (0.5-1.0 mol

  9. The magnetic structure on the ground state of the equilateral triangular spin tube

    International Nuclear Information System (INIS)

    Matsui, Kazuki; Goto, Takayuki; Manaka, Hirotaka; Miura, Yoko

    2016-01-01

    The ground state of the frustrated equilateral triangular spin tube CsCrF 4 is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by 19 F-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120°-type structure in ab-plane does not accord with the NMR spectra of ordered state.

  10. The magnetic structure on the ground state of the equilateral triangular spin tube

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, Kazuki, E-mail: k703861@eagle.sophia.ac.jp; Goto, Takayuki [Sophia University, Physics Division (Japan); Manaka, Hirotaka [Kagoshima University, Graduate School of Science and Engineering (Japan); Miura, Yoko [Suzuka National College of Technology (Japan)

    2016-12-15

    The ground state of the frustrated equilateral triangular spin tube CsCrF{sub 4} is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by {sup 19}F-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120°-type structure in ab-plane does not accord with the NMR spectra of ordered state.

  11. Molecular simulations and solid-state NMR investigate dynamical structure in rhodopsin activation.

    Science.gov (United States)

    Mertz, Blake; Struts, Andrey V; Feller, Scott E; Brown, Michael F

    2012-02-01

    Rhodopsin has served as the primary model for studying G protein-coupled receptors (GPCRs)-the largest group in the human genome, and consequently a primary target for pharmaceutical development. Understanding the functions and activation mechanisms of GPCRs has proven to be extraordinarily difficult, as they are part of a complex signaling cascade and reside within the cell membrane. Although X-ray crystallography has recently solved several GPCR structures that may resemble the activated conformation, the dynamics and mechanism of rhodopsin activation continue to remain elusive. Notably solid-state ((2))H NMR spectroscopy provides key information pertinent to how local dynamics of the retinal ligand change during rhodopsin activation. When combined with molecular mechanics simulations of proteolipid membranes, a new paradigm for the rhodopsin activation process emerges. Experiment and simulation both suggest that retinal isomerization initiates the rhodopsin photocascade to yield not a single activated structure, but rather an ensemble of activated conformational states. This article is part of a Special Issue entitled: Membrane protein structure and function. Copyright © 2011. Published by Elsevier B.V.

  12. Structural Investigation of the Interaction between LolA and LolB Using NMR

    Science.gov (United States)

    Nakada, Shingo; Sakakura, Masayoshi; Takahashi, Hideo; Okuda, Suguru; Tokuda, Hajime; Shimada, Ichio

    2009-01-01

    Lipoproteins that play critical roles in various cellular functions of Gram-negative bacteria are localized in the cells inner and outer membranes. Lol proteins (LolA, LolB, LolC, LolD, and LolE) are involved in the transportation of outer membrane-directed lipoproteins from the inner to the outer membrane. LolA is a periplasmic chaperone that transports lipoproteins, and LolB is an outer membrane receptor that accepts lipoproteins. To clarify the structural basis for the lipoprotein transfer from LolA to LolB, we examined the interaction between LolA and mLolB, a soluble mutant of LolB, using solution NMR spectroscopy. We determined the interaction mode between LolA and mLolB with conformational changes of LolA. Based upon the observations, we propose that the LolA·LolB complex forms a tunnel-like structure, where the hydrophobic insides of LolA and LolB are connected, which enables lipoproteins to transfer from LolA to LolB. PMID:19546215

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

    Directory of Open Access Journals (Sweden)

    Tae Ho Yeom

    2016-04-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

  15. NMR (¹H, ROESY) spectroscopic and molecular modelling investigations of supramolecular complex of β-cyclodextrin and curcumin.

    Science.gov (United States)

    Jahed, Vahid; Zarrabi, Ali; Bordbar, Abdol-Khalegh; Hafezi, Mohammad Sadegh

    2014-12-15

    In this paper we have investigated the solubility enhancement of curcumin through inclusion complexation by β-cyclodextrin as well as the topology and geometry of interaction between curcumin and carrier. For this purpose, the phase solubility of curcumin was assessed using Higuchi and Connors method, and the inclusion complex was characterised by 1D (1)H and 2D ROESY NMR analysis, and finally confirmed by molecular modelling. The phase solubility diagram demonstrated the AL-type which confirms an increase in curcumin solubility by increasing the concentration of β-cyclodextrin. (1)H NMR and ROESY spectra results showed a cross-peak between H-3 proton of β-cyclodextrin and the aromatic rings group of curcumin. This revealed the hydrophobic interactions between aromatic rings of curcumin and the cavity of β-cyclodextrin. Finally, the enthalpy of formation was obtained from molecular modelling results which in turn indicated that the process is exothermic and low-energy interactions are involved in the inclusion complex formation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

    Directory of Open Access Journals (Sweden)

    Cesar Garcias-Morales

    2015-10-01

    Full Text Available This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt a chair–boat conformation, while those in 2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ones, compounds 3–8, adopt a chair–chair conformation because of stereoelectronic effects. These stereoelectronic effects were analyzed by the 1JC–H coupling constants, which were measured in the 13C satellites of the 1H NMR spectra obtained with the hetero-dqf pulse sequence. In the solid state, these stereoelectronic effects were investigated by measurement of X-ray diffraction data, the molecular geometry (torsional bond angles and bond distances, and inter- and intramolecular interactions, and by natural bond orbital analysis, which was performed using density functional theory at the ωB97XD/6311++G(d,p level. We found that one of the main factors influencing the conformational stability of 3–8 is the interaction between the lone-pair electrons of nitrogen and the antibonding sigma orbital of C(7–Heq (nN→σ*C–H(7eq, a type of hyperconjugative interaction.

  17. Does aluminium bind to histidine? An NMR investigation of amyloid β12 and amyloid β16 fragments.

    Science.gov (United States)

    Narayan, Priya; Krishnarjuna, Bankala; Vishwanathan, Vinaya; Jagadeesh Kumar, Dasappa; Babu, Sudhir; Ramanathan, Krishna Venkatachala; Easwaran, Kalpathy Ramaier Katchap; Nagendra, Holenarasipur Gundurao; Raghothama, Srinivasarao

    2013-07-01

    Aluminium and zinc are known to be the major triggering agents for aggregation of amyloid peptides leading to plaque formation in Alzheimer's disease. While zinc binding to histidine in Aβ (amyloid β) fragments has been implicated as responsible for aggregation, not much information is available on the interaction of aluminium with histidine. In the NMR study of the N-terminal Aβ fragments, DAEFRHDSGYEV (Aβ12) and DAEFRHDSGYEVHHQK (Aβ16) presented here, the interactions of the fragments with aluminium have been investigated. Significant chemical shifts were observed for few residues near the C-terminus when aluminium chloride was titrated with Aβ12 and Aβ16 peptides. Surprisingly, it is nonhistidine residues which seem to be involved in aluminium binding. Based on NMR constrained structure obtained by molecular modelling, aluminium-binding pockets in Aβ12 were around charged residues such as Asp, Glu. The results are discussed in terms of native structure propagation, and the relevance of histidine residues in the sequences for metal-binding interactions. We expect that the study of such short amyloid peptide fragments will not only provide clues for plaque formation in aggregated conditions but also facilitate design of potential drugs for these targets. © 2013 John Wiley & Sons A/S.

  18. Spin dynamics in the strongly magnetically frustrated compounds YBaCo{sub 3}AlO{sub 7} and YBaCo{sub 3}FeO{sub 7} probed by NMR and ESR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Iakovleva, Margarita [IFW Dresden, Dresden (Germany); TU Dresden, Dresden (Germany); E. K. Zavoisky Physical-Technical Institute, Kazan (Russian Federation); Zeisner, Julian; Zimmermann, Stephan; Buechner, Bernd [IFW Dresden, Dresden (Germany); TU Dresden, Dresden (Germany); Valldor, Martin [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany); Vavilova, Evgeniia [E. K. Zavoisky Physical-Technical Institute, Kazan (Russian Federation); Grafe, Hans-Joachim; Alfonsov, Alexey; Kataev, Vladislav [IFW Dresden, Dresden (Germany)

    2016-07-01

    In the Swedenborgite type compounds YBaCo{sub 3}AlO{sub 7} and YBaCo{sub 3}FeO{sub 7} the magnetic lattice can be described as a stacking of kagome layers, where unconventional ground states such as a spin liquid state can be expected due to the strong geometrical frustration. We performed a combined experimental study of magnetic properties of single crystals of YBaCo{sub 3}AlO{sub 7} and YBaCo{sub 3}FeO{sub 7} with high field ESR and high field NMR spectroscopy. The experimental results show the occurrence of short-range quasi static electron spin correlations at T{sup *} ∼ 22 K for YBaCo{sub 3}AlO{sub 7} and T{sup *} ∼ 60K for YBaCo{sub 3}FeO{sub 7} but not a long-range antiferromagnetic order. We compare our results with AC and DC susceptibility measurements and discuss a possible competition between a spin glass-like state due to intrinsic structural disorder and a spin liquid state arising from strong magnetic frustration in this materials.

  19. Structure and Permeability of Porous Silicon Investigated by Self-Diffusion NMR Measurements of Ethanol and Heptane

    Directory of Open Access Journals (Sweden)

    Puibasset J.

    2016-07-01

    Full Text Available The adsorption and phase transitions of confined fluids in nanoporous materials have been studied intensely because of both their fundamental interest and their crucial role in many technologies. Questions relating to the influence of the confinement of fluids, and the disorder or elastic deformation of porous solids on the liquid-gas phase transition are still under debate. Model systems are needed to understand the adsorption phenomenon. In this context, Porous Silicon (PoSi, which is a single crystal obtained by etching a (100 silicon wafer is an excellent candidate. Indeed, it consists of non-connected tubular pores running parallel to the [100] axis perpendicular to the wafer surface, with transverse sections with a polygonal shape of nanometric size whose areas are widely distributed. Once detached from the wafer, free PoSi membranes can be considered a nanoscale disordered honeycomb. Adsorption/desorption experiments have been performed to characterize the structure: they have shown that evaporation occurs collectively, an intriguing observation generally associated with a disordered pore structure with many interconnections through narrow necks. The characterization of fluid mobility inside the pores should give complementary information about the pore structure and topology. This paper focuses on the dynamics of a fluid confined inside the structure of porous silicon, and in particular the self-diffusion measurements (pulsed field gradient spin echo Nuclear Magnetic Resonance (NMR. The results show a strong anisotropy of the self-diffusion tensor, as expected in this highly anisotropic structure. However, a non-zero self-diffusion in the directions perpendicular to the pore axis is observed. In order to interpret these puzzling results, molecular and Brownian dynamics calculations are underway.

  20. Neutron spin-echo investigation of the microemulsion dynamics. in bicontinuous lamellar and droplet phases

    CERN Document Server

    Mihailescu, M; Endo, H; Allgaier, J; Gompper, G; Stellbrink, J; Richter, D; Jakobs, B; Sottmann, T; Faragó, B

    2002-01-01

    Using neutron spin-echo (NSE) spectroscopy in combination with dynamic light scattering (DLS), we performed an extensive investigation of the bicontinuous phase in ternary water-surfactant-oil microemulsions, with extension to lamellar and droplet phases. The dynamical behavior of surfactant monolayers of decyl-polyglycol-ether (C sub 1 sub 0 E sub 4) molecules, or mixtures of surfactant with long amphiphilic block-copolymers of type poly-ethylene propylene/poly-ethylene oxide (PEP-PEO) was studied, under comparable conditions. The investigation techniques provide access to different length scales relative to the characteristic periodicity length of the microemulsion structure. Information on the elastic bending modulus is obtained from the local scale dynamics in view of existing theoretical descriptions and is found to be in accordance with small angle neutron scattering (SANS) studies. Evidence for the modified elastic properties and additional interaction of the amphiphilic layers due to the polymer is mo...

  1. Investigation of thermalization in giant-spin models by different Lindblad schemes

    Energy Technology Data Exchange (ETDEWEB)

    Beckmann, Christian; Schnack, Jürgen, E-mail: jschnack@uni-bielefeld.de

    2017-09-01

    Highlights: • The non-equilibrium magnetization is investigated with quantum master equations that rest on Lindblad schemes. • It is studied how different couplings to the bath modify the magnetization. • Various field protocols are employed; relaxation times are deduced. • Result: the time evolution depends strongly on the details of the transition operator used in the Lindblad term. - Abstract: The theoretical understanding of time-dependence in magnetic quantum systems is of great importance in particular for cases where a unitary time evolution is accompanied by relaxation processes. A key example is given by the dynamics of single-molecule magnets where quantum tunneling of the magnetization competes with thermal relaxation over the anisotropy barrier. In this article we investigate how good a Lindblad approach describes the relaxation in giant spin models and how the result depends on the employed operator that transmits the action of the thermal bath.

  2. Micromagnetic investigation of the dynamics of magnetization switching induced by a spin polarized current

    Science.gov (United States)

    Lee, Kyung-Jin; Dieny, Bernard

    2006-03-01

    Using micromagnetic modeling, we tested a prediction of single-domain spin-torque theory which switching current density depends only weakly on magnetic cell size. The switching time and current density are strongly affected by the cell size for low spin polarization. Larger samples with a small length-to-width ratio and small spin polarization can exhibit a nonmonotonous dependence of switching time on current. Excitation of incoherent spin waves caused by the circular Oersted field due to the current is responsible for this nonmonotonous dependence. However, the magnetic dynamics recovers a single-domain-like behavior when the spin polarization is high and/or the cell size is small.

  3. Nuclear Magnetic Resonance spectroscopy of marine microalgae: Metabolic profiling and species discrimination from High-Resolution Magic Angle Spinning NMR analysis of whole-cell samples

    OpenAIRE

    Chauton, Matilde Skogen

    2005-01-01

    Based on what is said about the background and structure, this thesis presents a discussion of the use of NMR spectroscopy as a tool for species discrimination and metabolic profiling of microalgae. The results of various analyses including NMR and statistics are evaluated from what is known from already established identification methods such as pigment chromatography and chemotaxonomy, and the chemical composition of microalgal cells. The main focus is on the application of HR MAS on whole ...

  4. L-glutamine: Dynamical properties investigation by means of INS, IR, RAMAN, {sup 1}H NMR and DFT techniques

    Energy Technology Data Exchange (ETDEWEB)

    Pawlukojć, A., E-mail: andrzej@jinr.ru [Institute of Nuclear Chemistry and Technology, Dorodna 16 str., 03-195 Warsaw (Poland); Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Hołderna-Natkaniec, K. [Faculty of Physics, A. Mickiewicz University, 61-614 Poznań (Poland); Bator, G. [Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383 Wroclaw (Poland); Natkaniec, I. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Faculty of Physics, A. Mickiewicz University, 61-614 Poznań (Poland)

    2014-10-31

    Graphical abstract: - Highlights: • The L-glutamine was investigated by INS, IR, Raman and {sup 1}H NMR spectroscopy. • DFT calculations for the solids state model were performed. • The NH{sub 3}{sup +} torsional vibration mode is observed in the INS spectra. • Activation energy for the NH{sub 3}{sup +} group reorientation is obtained. - Abstract: Vibrational spectra of L-glutamine in the solid state were studied using the inelastic neutron scattering (INS), infrared (IR), Raman and {sup 1}H NMR spectroscopy techniques. DFT calculation using CASTEP code with the periodic boundary conditions was used to determine and describe the normal modes in the vibrational spectra of pure L-glutamine. An excellent agreement between the calculated and experimental INS, IR and Raman data has been found. Bands assigned to the stretching vibrations of the NH{sub 3}{sup +} group in hydrogen bonds are observed at 2400, 2618 and 2619 cm{sup −1}, while the NH{sub 3}{sup +} torsion vibration mode is observed at 441 cm{sup −1}. The band at 2041 cm{sup −1} is assigned to combinations of the NH{sub 3}{sup +} bending symmetry vibration and the CO{sub 2}{sup -} rocking vibration and can be used as an “indicator band” for the identification of the NH{sub 3}{sup +} groups in amino acid. For the L-glutamine an activation energy needed for the NH{sub 3}{sup +} group reorientation was obtained as 7.4 kcal/mol. It was found, that the combination three spectroscopic methods (INS, IR and Raman) with calculations for the crystal state proved to be an effective tool to investigate dynamical properties of amino acid crystals.

  5. L-glutamine: Dynamical properties investigation by means of INS, IR, RAMAN, 1H NMR and DFT techniques

    International Nuclear Information System (INIS)

    Pawlukojć, A.; Hołderna-Natkaniec, K.; Bator, G.; Natkaniec, I.

    2014-01-01

    Graphical abstract: - Highlights: • The L-glutamine was investigated by INS, IR, Raman and 1 H NMR spectroscopy. • DFT calculations for the solids state model were performed. • The NH 3 + torsional vibration mode is observed in the INS spectra. • Activation energy for the NH 3 + group reorientation is obtained. - Abstract: Vibrational spectra of L-glutamine in the solid state were studied using the inelastic neutron scattering (INS), infrared (IR), Raman and 1 H NMR spectroscopy techniques. DFT calculation using CASTEP code with the periodic boundary conditions was used to determine and describe the normal modes in the vibrational spectra of pure L-glutamine. An excellent agreement between the calculated and experimental INS, IR and Raman data has been found. Bands assigned to the stretching vibrations of the NH 3 + group in hydrogen bonds are observed at 2400, 2618 and 2619 cm −1 , while the NH 3 + torsion vibration mode is observed at 441 cm −1 . The band at 2041 cm −1 is assigned to combinations of the NH 3 + bending symmetry vibration and the CO 2 - rocking vibration and can be used as an “indicator band” for the identification of the NH 3 + groups in amino acid. For the L-glutamine an activation energy needed for the NH 3 + group reorientation was obtained as 7.4 kcal/mol. It was found, that the combination three spectroscopic methods (INS, IR and Raman) with calculations for the crystal state proved to be an effective tool to investigate dynamical properties of amino acid crystals

  6. Marking of metabolites in the diagnostics of metabolic diseases and in the investigation of xenobiotics metabolism using NMR spectroscopy.

    Science.gov (United States)

    Krawczyk, Hanna

    2016-10-25

    There are currently no sound estimates of the number of children born with a serious congenital disorder attributable to genetic or environmental causes (World Health Organization) but there is a supposed number of babies born with birth defects per year: in the world approximately 7.9 million children (6% of births). There is conducted population-based screening by the individual countries. The specialised methods are used when it is not possible to diagnose disease in screening. In recent years in the diagnostics of these disorders the methods of Magnetic Resonance Spectroscopy of the brain (in vivo 1 H-MRS) and high resolution NMR spectroscopy gain in importance. The manuscript focused on developing the method of marking the metabolic diseases markers of various origins using NMR spectroscopy (including synthesis of markers). Considering the disorders occurring among children, according to Hoffman, Zschocke, Nyhan, there are three following groups of inherited metabolic diseases: disorders of intermediary metabolism, disorders of the biosynthesis and breakdown of complex molecules and neurotransmitter defects and related disorders. The presented investigation is focused on: a study of selected compounds that cause disorders of intermediary metabolism, a study of compounds that cause disorders of the biosynthesis and breakdown of complex molecules and a study of compounds that cause neurotransmitter defects and related disorders. In the subsequent chapter of manuscript there are presented the results of investigation concerning the metabolism of xenobiotics that could potentially be used in therapy of inherited metabolic diseases, basing on stilbene derivatives. In the last chapter there are presented the results of experiments with creatinine- the metabolite produced in muscles. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Experimental investigation of transverse spin asymmetries in muon-p SIDIS processes: Sivers asymmetries

    CERN Document Server

    Adolph, C.; Alexakhin, V.Yu.; Alexandrov, Yu.; Alexeev, G.D.; Amoroso, A.; Antonov, A.A.; Austregesilo, A.; Badelek, B.; Balestra, F.; Barth, J.; Baum, G.; Bedfer, Y.; Bernhard, J.; Bertini, R.; Bettinelli, M.; Bicker, K.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bordalo, P.; Bradamante, F.; Braun, C.; Bravar, A.; Bressan, A.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S.U.; Cicuttin, A.; Crespo, M.L.; Dalla Torre, S.; Das, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Dhara, L.; Donskov, S.V.; Doshita, N.; Duic, V.; Dunnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Filin, A.; Finger, M.; Fischer, H.; Franco, C.; von Hohenesche, N.du Fresne; Friedrich, J.M.; Frolov, V.; Garfagnini, R.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Geyer, R.; Giorgi, M.; Gnesi, I.; Gobbo, B.; Goertz, S.; Grabmuller, S.; Grasso, A.; Grube, B.; Gushterski, R.; Guskov, A.; Guthorl, T.; Haas, F.; von Harrach, D.; Heinsius, F.H.; Herrmann, F.; Hess, C.; Hinterberger, F.; Horikawa, N.; Hoppner, Ch.; d'Hose, N.; Ishimoto, S.; Ivanov, O.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Joosten, R.; Kabuss, E.; Kang, D.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu.A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koblitz, S.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Korzenev, A.; Kotzinian, A.M.; Kouznetsov, O.; Kramer, M.; Kroumchtein, Z.V.; Kunne, F.; Kurek, K.; Lauser, L.; Lednev, A.A.; Lehmann, A.; Levorato, S.; Lichtenstadt, J.; Liska, T.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G.K.; Mann, A.; Marchand, C.; Martin, A.; Marzec, J.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu.V.; Moinester, M.A.; Morreale, A.; Mutter, A.; Nagaytsev, A.; Nagel, T.; Negrini, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V.I.; Nowak, W.D.; Nunes, A.S.; Olshevsky, A.G.; Ostrick, M.; Padee, A.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Perevalova, E.; Pesaro, G.; Peshekhonov, D.V.; Piragino, G.; Platchkov, S.; Pochodzalla, J.; Polak, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Rajotte, J.F.; Ramos, S.; Rapatsky, V.; Reicherz, G.; Richter, A.; Rocco, E.; Rondio, E.; Rossiyskaya, N.S.; Ryabchikov, D.I.; Samoylenko, V.D.; Sandacz, A.; Sapozhnikov, M.G.; Sarkar, S.; Savin, I.A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schluter, T.; Schmidt, K.; Schmitt, L.; Schonning, K.; Schopferer, S.; Schott, M.; Schroder, W.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sissakian, A.N.; Slunecka, M.; Smirnov, G.I.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Sznajder, P.; Takekawa, S.; Wolbeek, J.Ter; Tessaro, S.; Tessarotto, F.; Tkatchev, L.G.; Uhl, S.; Uman, I.; Vandenbroucke, M.; Virius, M.; Vlassov, N.V.; Wang, L.; Wilfert, M.; Windmolders, R.; Wislicki, W.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zhuravlev, N.; Zvyagin, A.

    2012-10-31

    The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Sivers asymmetry of the proton has been extracted in the Bjorken x range 0.003 0.03. The asymmetry is different from zero and positive also in the low x region, where sea-quarks dominate. The kinematic dependence of the asymmetry has also been investigated and results are given for various intervals of hadron and virtual photon fractional energy. In contrast to the case of the Collins asymmetry, the results on the Sivers asymmetry suggest a strong dependence on the four-momentum transfer to the nucleon, in agreement with the most recent calculations.

  8. NMR-spectroscopy

    International Nuclear Information System (INIS)

    Lundin, A.G.; Fedin, Eh.I.

    1986-01-01

    Physical foundations are given and the most important areas of nuclear magnetic resonance (NMR) application in physics, chemistry, biology are described. A detailed review of the investigations conducted and the NMR applications in different science and technology fields is presented. The method basic experimental variants, including such new ones as high resolution in a solid body; rare isotope resonance; two-dimensional and multi-quantum fourier-spectroscopy; large molecule NMR; NMR tomography and NMR intrascopy etc. are considered. The instruments are briefly described. NMR is characterized as one of the most important investigation methods of the material composition, its molecular and crystal structure, visualization of the living organism and nonmetallic object inner structure

  9. Magnetism of the spin-trimer compound CaNi 3(P 2O 7)2: Microscopic insight from combined 31P NMR and first-principles studies

    Science.gov (United States)

    Majumder, M.; Kanungo, S.; Ghoshray, A.; Ghosh, M.; Ghoshray, K.

    2015-03-01

    Magnetization, 31P nuclear magnetic resonance study, and first-principles electronic structure calculations have been performed in the spin-1 trimer chain compound CaNi3(P2O7 )2. Two separate spectra arising from magnetically and crystallographically inequivalent P sites are observed. In the ordered state, the resonance lines for both the P sites (P1 and P2) are found to be split into two, which is clear microscopic evidence of the development of two-sublattice AFM order below TM. A nonnegligible contribution of ferromagnetic hyperfine field and dipolar field have also been seen in the ordered state. The first-principles calculations show that the intratrimer (J1) and intertrimer interactions (J2) are of weak ferromagnetic type with the values 2.85 and 1.49 meV, respectively, whereas the interchain interaction (J3) is of strong antiferromagnetic type with a value of 5.63 meV. The anisotropy of the imaginary part of dynamical spin susceptibility around TM along with the exponential decrement of 1 /T1 below TM indicate the probable participation of the Ni -3 d electron's orbital degrees of freedom in the ferrimagnetic transition. The dominance of orbital fluctuations over the spin fluctuations seems to be responsible for showing low value of the binding energy u of the local spin configuration (estimated from local spin models) and an unusually weak exponent in the power-law behavior of 1 /T1 below 50 K, in the paramagnetic state. Electronic structure calculations also reveal the importance of orbital degrees of freedom of Ni -3 d moments, which is consistent with our NMR data analysis.

  10. Dynamical Monte Carlo investigation of spin reversals and nonequilibrium magnetization of single-molecule magnets

    OpenAIRE

    Liu, Gui-Bin; Liu, Bang-Gui

    2010-01-01

    In this paper, we combine thermal effects with Landau-Zener (LZ) quantum tunneling effects in a dynamical Monte Carlo (DMC) framework to produce satisfactory magnetization curves of single-molecule magnet (SMM) systems. We use the giant spin approximation for SMM spins and consider regular lattices of SMMs with magnetic dipolar interactions (MDI). We calculate spin reversal probabilities from thermal-activated barrier hurdling, direct LZ tunneling, and thermal-assisted LZ tunnelings in the pr...

  11. Electron spin interactions in chemistry and biology fundamentals, methods, reactions mechanisms, magnetic phenomena, structure investigation

    CERN Document Server

    Likhtenshtein, Gertz

    2016-01-01

    This book presents the versatile and pivotal role of electron spin interactions in nature. It provides the background, methodologies and tools for basic areas related to spin interactions, such as spin chemistry and biology, electron transfer, light energy conversion, photochemistry, radical reactions, magneto-chemistry and magneto-biology. The book also includes an overview of designing advanced magnetic materials, optical and spintronic devices and photo catalysts. This monograph appeals to scientists and graduate students working in the areas related to spin interactions physics, biophysics, chemistry and chemical engineering.

  12. HPLC-NMR INVESTIGATION OF THE ISOMERIZATION OF ALACHLOR-ETHANE SULFONIC ACID. (R829008)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

    Directory of Open Access Journals (Sweden)

    Srinivasa Rao Singamaneni

    2014-04-01

    Full Text Available Electronic spin transport properties of graphene nanoribbons (GNRs are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element spin-sensitive techniques such as electron spin resonance (ESR spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW, pulse and hyperfine sublevel correlation (HYSCORE ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs, which were subsequently chemically converted (CCGNRs with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH3 adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns and fast (39 ns components. HYSCORE ESR data demonstrate the explicit presence of protons and 13C atoms. With the provided identification of intrinsic point magnetic defects such as proton and 13C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic-based transport properties of CCGNRs.

  14. Investigations on resolution enhancement in EPR by means of electron spin echoes

    International Nuclear Information System (INIS)

    Merks, R.P.J.

    1979-01-01

    The electron spin echo technique has been applied in four types of experiments: the measurement of electric field induced shifts of the EPR line; the detection of electron spin echo ENDOR; a relaxation measurement and the measurement of hyperfine interactions via the nuclear modulation effect. (Auth.)

  15. Improved resolution and simplification of the spin-diffusion-based NMR method for the structural analysis of mixed-linker MOFs

    Science.gov (United States)

    Krajnc, Andraž; Bueken, Bart; De Vos, Dirk; Mali, Gregor

    2017-06-01

    Nuclear magnetic resonance spectroscopy combined with modeling represents a powerful tool for the structural analysis of heterogeneous materials. In this contribution we describe an upgraded method, particularly suited for the structural analysis of mixed-linker metal-organic framework materials, which is based on the measurement and modeling of proton spin diffusion among constituents. We tested the method on a UiO-66-type metal-organic material, in which the organic building units were 1,4-benzenedicarboxylate and trans-1,4-cyclohexanedicarboxylate anions distributed within the framework in an unknown manner. We showed that resolution of the signals of different building units could be significantly enhanced by the carbon-detected version of the proton spin-diffusion measurement. Because this kind of measurement is much more time consuming than the proton-detected measurement and because one has to carry out several two-dimensional measurements to extract spin-diffusion curves, we inspected the possibility of reducing the number of such measurements. This could be done by limiting the analysis to short mixing times, for which, as shown in this contribution, linear approximation is valid. When working in the linear regime, only a few experimental points are needed to determine the slope of spin-diffusion curves. Usage of short spin-diffusion mixing times significantly shortened the total measurement time and also markedly simplified the modeling of spin-diffusion curves.

  16. Rhodospirillum rubrum CO-dehydrogenase. Part 2: Spectroscopic investigation and assignment of spin-spin coupling signals

    Energy Technology Data Exchange (ETDEWEB)

    Heo, J.; Staples, C.R.; Telser, J.; Ludden, P.W.

    1999-12-08

    solely from the [Fe{sub 4}S{sub 4}]{sup 1+} clusters. These resonances are attributed in fully reduced CODH to spin-spin coupling between [Fe{sub 4}S{sub 4}]{sub C}{sup 1+} (S = 1/2) and [Fe{sub 4}S{sub 4}]{sub B}{sup 1+} (S = 1/2). When CODH was poised at a calculated potential of {minus}326 mV, the UV-visible absorption spectrum indicated that only one of the [Fe{sub 4}S{sub 4}] clusters was reduced. However, the EPR spectrum was much different than that observed at ca. {minus}295 mV. The EPR spectrum of CODH at {minus}326 mV exhibited resonances arising from a slow-relaxing [Fe{sub 4}S{sub 4}]{sup 1+} (S = 1/2) cluster (g{sub z,y,x} = 2.04, 1.93, 1.89) and a very minor amount of a fast-relaxing [Fe{sub 4}S{sub 4}]{sup 1+} (S = 1/2) cluster. None of the C{sub red1} coupling signal was present. The fast-relaxing cluster is assigned to [Fe{sub 4}S{sub 4}]{sub C}{sup 1+}, while the slow-relaxing cluster is assigned to uncoupled [Fe{sub 4}S{sub 4}]{sub C}{sup 1+}. The observation of uncoupled [Fe{sub 4}S{sub 4}]{sub C}{sup 1+} at slightly lower potentials suggests the reduction of [(CO{sub L})Fe{sup 3+}-Ni{sup 2+}-H{minus}]{sup 4+} (S = 1/2) to [(CO{sub L})Fe{sup 2+}-Ni{sup 2+}-H{minus}]{sup 3+} (S = 0). Treatment of CODH with its physiological product (CO{sub 2}) while poised at {minus}326 mV with 99% reduced phenosafranin results in accumulation of oxidized dye, the production of CO, and the appearance of a new species with g{sub x} = 1.75. This species has relaxation properties unlike C{sub red2A}. Based upon the method of generation and the relaxation properties of the species, the g = 1.75 feature is assigned to [Fe{sub 4}S{sub 4}]{sub C}{sup 1+} (S = 1/2) spin-coupling with [Fe{sup 2+}-Ni{sup 2+}]{sup 4+} (S = 1) (and is referred to as C{sub red2B}). Based on the data presented in this and Part 1, a mechanism for the oxidation of CO to CO{sub 2} by R.rubrum CODH is proposed.

  17. The combined use of quantum chemical calculations and CP/MAS NMR spectroscopy to investigate soil bound residues of labeled xenobiotics

    Science.gov (United States)

    Lewandowski, Hans; Philipp, Herbert; Meier, Robert J.; Narres, Hans-Dieter; Berns, Anne E.

    2010-05-01

    Application of solid state Nuclear Magnetic Resonance (NMR) spectroscopy to 13C- and 15N-labeled compounds is a powerful tool to study the interactions of xenobiotics with soil and its components. The type of interaction with soil components, like organic matter or the mineral phase, influences binding and release of a xenobiotic and its metabolites in soil. As such interactions to the soil matrix cause shifts in the initial positions of the NMR signals of the investigated labeled compound, NMR can be used to elucidate the binding type of bound residues. Density functional theory (DFT) calculations are excellent suited to support such NMR studies of xenobiotics. In a first step, DFT calculations were used to support the interpretation of the spectra of labeled xenobiotics, their metabolites and reaction products synthesized through reaction with model substances (representing specific functionalities of humic substances). In a second step, they allow to evaluate the influence of possible bonds on the initial chemical shift (e.g. towards higher or lower field). This can be especially helpful in the case of bonds like van-der-Waals interactions, for which it is difficult to prepare defined model substances. CP/MAS-NMR spectroscopy and DFT calculations were applied to study the interactions of several labeled xenobiotics and soil organic matter.

  18. Methods of dilatometric investigations under extreme conditions and the case of spin-ice compounds

    Science.gov (United States)

    Doerr, M.; Granovsky, S.; Rotter, M.; Stöter, T.; Wang, Z.-S.; Zherlitsyn, S.; Wosnitza, J.

    2017-10-01

    We give an overview on how dilatometric methods have been developed in the last decade. The concept of capacitive dilatometry was successfully adapted to dilution refrigerators with a resolution of 10-9. Miniaturized dilatometers with an overall diameter of 18 mm or less are optimally suited for measuring longitudinal and transversal components of the striction tensor. Going to another extreme, to the highest (pulsed) fields, optical methods, such as the FBG technology, were developed for investigations up to 100 T. As examples for utilizing dilatometry at low temperatures we show results for the spin-ice materials Dy2Ti2O7 and Ho2Ti2O7. To characterise the magneto-elastic coupling in these materials, we investigated the thermal expansion and magnetostriction between 80 mK and 15 K and in magnetic fields aligned along the [111] direction and found field-induced phases and strong correlations below 500 mK. Our data demonstrate, that the formation of the field-induced phase is strongly influenced by lattice distortions: any change in interatomic distances will result in a variation of the exchange couplings.

  19. Investigation of bistable perception with the "silhouette spinner": sit still, spin the dancer with your will.

    Science.gov (United States)

    Liu, Chao-Hsuan; Tzeng, Ovid J L; Hung, Daisy L; Tseng, Philip; Juan, Chi-Hung

    2012-05-01

    Many studies have used static and non-biologically related stimuli to investigate bistable perception and found that the percept is usually dominated by their intrinsic nature with some influence of voluntary control from the viewer. Here we used a dynamic stimulus of a rotating human body, the silhouette spinner illusion, to investigate how the viewers' intentions may affect their percepts. In two experiments, we manipulated observer intention (active or passive), fixation position (body or feet), and spinning velocity (fast, medium, or slow). Our results showed that the normalized alternating rate between two bistable percepts was greater when (1) participants actively attempted to switch percepts, (2) when participants fixated at the spinner's feet rather than the body, inducing as many as 25 switches of the bistable percepts within 1 min, and (3) when they watched the spinner at high velocity. These results suggest that a dynamic biologically-bistable percept can be quickly alternated by the viewers' intention. Furthermore, the higher alternating rate in the feet condition compared to the body condition suggests a role for biological meaningfulness in determining bistable percepts, where 'biologically plausible' interpretations are favored by the visual system. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Communication: Proton NMR dipolar-correlation effect as a method for investigating segmental diffusion in polymer melts

    International Nuclear Information System (INIS)

    Lozovoi, A.; Mattea, C.; Stapf, S.; Herrmann, A.; Rössler, E. A.; Fatkullin, N.

    2016-01-01

    A simple and fast method for the investigation of segmental diffusion in high molar mass polymer melts is presented. The method is based on a special function, called proton dipolar-correlation build-up function, which is constructed from Hahn Echo signals measured at times t and t/2. The initial rise of this function contains additive contributions from both inter- and intramolecular magnetic dipole-dipole interactions. The intermolecular contribution depends on the relative mean squared displacements (MSDs) of polymer segments from different macromolecules, while the intramolecular part reflects segmental reorientations. Separation of both contributions via isotope dilution provides access to segmental displacements in polymer melts at millisecond range, which is hardly accessible by other methods. The feasibility of the method is illustrated by investigating protonated and deuterated polybutadiene melts with molecular mass 196 000 g/mol at different temperatures. The observed exponent of the power law of the segmental MSD is close to 0.32 ± 0.03 at times when the root MSD is in between 45 Å and 75 Å, and the intermolecular proton dipole-dipole contribution to the total proton Hahn Echo NMR signal is larger than 50% and increases with time.

  1. NMR Investigation of the complexation of (S-2-isopropyl- 1-(o-nitrophenylsulfonylaziridine with -cyclodextrin

    Directory of Open Access Journals (Sweden)

    Mohamed Z. Sliman

    2014-07-01

    Full Text Available Aziridines are known to undergo hydrolysis in the presence of cyclodextrins, whereas the latter are largely investigated as potential vectors of biologically active compounds. Despite this easy cyclodextrin-induced cleavage of aziridines in aqueous medium, it was of interest to find out a model aziridine derivative that would be sufficiently water-stable and form a stable complex with b-cyclodextrin in aqueous medium, so that it could be used as a reference in future formulations or vectorization work. Among compounds we have investigated, we found out that only (S-2-isopropyl-1-(o-nitrophenylsulfonylaziridine complied with the above-mentioned solubility and stability requirements. NMR studies of the inclusion complex of this derivative with b-cyclodextrin provided useful parameters related to the stoichiometry of the complex and the association constant Ka. The geometry of the complex was assessed by 2D-ROESY experiments, suggesting a deep insertion of the aziridine into the cavity of b-cyclodextrin.

  2. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  3. What Is the True Color of Fresh Meat? A Biophysical Undergraduate Laboratory Experiment Investigating the Effects of Ligand Binding on Myoglobin Using Optical, EPR, and NMR Spectroscopy

    Science.gov (United States)

    Linenberger, Kimberly; Bretz, Stacey Lowery; Crowder, Michael W.; McCarrick, Robert; Lorigan, Gary A.; Tierney, David L.

    2011-01-01

    With an increased focus on integrated upper-level laboratories, we present an experiment integrating concepts from inorganic, biological, and physical chemistry content areas. Students investigate the effects of ligand strength on the spectroscopic properties of the heme center in myoglobin using UV-vis, [superscript 1]H NMR, and EPR…

  4. Spin Labeling ESR Investigation of a Role of Humic Acids at Covalent Binding of Xenobiotics to Soil

    Science.gov (United States)

    Aleksandrova, Olga

    2014-05-01

    The environmental risk of organic xenobiotic chemicals released into soils is controlled by their sorption and binding processes. However, the molecular mechanisms of reversible and irreversible interactions of xenobiotics with soil constituents and an influence of humic substances on this interaction are only partly understood. New methods and approaches aimed at understanding of molecular mechanisms in the soil environment and a role of humic substances in the sorption and binding processes are today required to manage and keep the quality of soil used and fertilized in agricultural industry. The paper presents a new approach of using stable ESR spin labels to investigate a role of humic substances in the interactions of organic xenobiotic chemicals with constituents of natural soil via the typical functional groups of xenobiotics, such as Amines. At the experiment, the nitroxide spin labels, such as TEMPO (2,2,6,6-Tetramethylpiperidin-1-oxyl), Amino-TEMPO (4-amino-2,2,6,6-Tetramethylpiperidin-1-oxyl) and Aniline spin labels (2,5,5-Trimethyl-2-(3-aminophenyl)pyrrolidin-1-oxyl), were added to samples of different natural soils, such luvisol, cambisol and chernozem. Amino-TEMPO and Aniline spin labels include the aliphatic amino and aromatic amino functional groups, respectively. A significant broadening of the ESR spectrum of Aniline spin labels incubated in different soils indicated a stable effect of covalent binding of the spin labels to soil constituents via the aromatic amino, whereas the ESR spectra of the other two spin labels were not broadened that pointed at the absence of covalent binding of spin labels via the aliphatic amino. As shown, a part of bound spin labels via the aromatic amino increased with increasing of the concentration of humic acids in soil. The same broadened signals were also be detected with the humic acids extracted from the investigated soils. A strong covalent binding of spin labels to humic substances via the aromatic amines was

  5. High-resolution magic angle spinning (1)H NMR spectroscopy of metabolic changes in rabbit lens after treatment with dexamethasone combined with UVB exposure

    Czech Academy of Sciences Publication Activity Database

    Seather, O.; Risa, O.; Čejková, Jitka; Krane, J.; Midelfart, A.

    2004-01-01

    Roč. 242, - (2004), s. 1000-1007 ISSN 0721-832X R&D Projects: GA ČR GA304/03/0419 Institutional research plan: CEZ:AV0Z5008914 Keywords : HR-MAS 1H NMR Subject RIV: FF - HEENT, Dentistry Impact factor: 1.513, year: 2004

  6. NMR investigation of reaction between α-oxides and uranium tetrachloride

    International Nuclear Information System (INIS)

    Minevich, V.Ya.; Shupik, A.N.; Khvostik, G.M.; Sokolov, V.N.; Kondratenkov, G.P.

    1983-01-01

    The PMR method has been used to study equilibrium stage of certain α-oxide interaction (propylene oxide (PO), epichlorohydrin (ECH)) with uranium (4) tetrachloride. Mechanism of PO complexing with uranium tetrachloride is chosen based on investigating the dependence of chemical shifts of α-oxide proton signals on the relation of components in the system. Equilibrium constants and formation heat of complexes of different composition are estimated. It is shown that despite the fact that THF is a stronger donor than PO and ECH the complexes of the latter are most stable as compared to the similar THF complexes that is probably, associated with additional interaction of UCl 4 with α-oxides with participation of the π-electron system of the epoxide

  7. Investigation of proton spin relaxation in water with dispersed silicon nanoparticles for potential magnetic resonance imaging applications

    Science.gov (United States)

    Kargina, Yu. V.; Gongalsky, M. B.; Perepukhov, A. M.; Gippius, A. A.; Minnekhanov, A. A.; Zvereva, E. A.; Maximychev, A. V.; Timoshenko, V. Yu.

    2018-03-01

    Porous and nonporous silicon (Si) nanoparticles (NPs) prepared by ball-milling of electrochemically etched porous Si layers and crystalline Si wafers were studied as potential agents for enhancement of the proton spin relaxation in aqueous media. While nonporous Si NPs did not significantly influence the spin relaxation, the porous ones resulted in strong shortening of the transverse relaxation times. In order to investigate an effect of the electron spin density in porous Si NPs on the proton spin relaxation, we use thermal annealing of the NPs in vacuum or in air. The transverse relaxation rate of about 0.5 l/(g s) was achieved for microporous Si NPs, which were thermally annealing in vacuum to obtain the electron spin density of the order of 1017 g-1. The transverse relaxation rate was found to be almost proportional to the concentration of porous Si NPs in the range from 0.1 to 20 g/l. The obtained results are discussed in view of possible biomedical applications of Si NPs as contrast agents for magnetic resonance imaging.

  8. Experimental investigation shell model excitations of 89Zr up to high spin and its comparison with 88,90Zr

    International Nuclear Information System (INIS)

    Saha, S.; Palit, R.; Sethi, J.

    2012-01-01

    The excited states of nuclei near N=50 closed shell provide suitable laboratory for testing the interactions of shell model states, possible presence of high spin isomers and help in understanding the shape transition as the higher orbitals are occupied. In particular, the structure of N = 49 isotones (and Z =32 to 46) with one hole in N=50 shell gap have been investigated using different reactions. Interestingly, the high spin states in these isotones have contribution from particle excitations across the respective proton and neutron shell gaps and provide suitable testing ground for the prediction of shell model interactions describing theses excitations across the shell gap. In the literature, extensive study of the high spin states of heavier N = 49 isotones starting with 91 Mo up to 95 Pd are available. Limited information existed on the high spin states of lighter isotones. Therefore, the motivation of the present work is to extend the high spin structure of 89 Zr and to characterize the structure of these levels through comparison with the large scale shell model calculations based on two new residual interactions in f 5/2 pg 9/2 model space

  9. Evidence for an internal-field-induced spin-flop configuration in the extended kagome YBaCo4O7

    Science.gov (United States)

    Hoch, M. J. R.; Kuhns, P. L.; Yuan, S.; Besara, T.; Whalen, J. B.; Siegrist, T.; Reyes, A. P.; Brooks, J. S.; Zheng, H.; Mitchell, J. F.

    2013-02-01

    The spin structure and spin dynamics in the extended kagome frustrated antiferromagnet YBaCo4O7 have been investigated using zero field and low applied field 59Co NMR. The YBaCo4O7 lattice is made up of bipyramid Co-ion units that form alternating planes of edge-sharing spin triangles and corner-sharing kagome spin triangles in an unusual exchange topology. Our low-temperature spin configuration results, based on hyperfine field orientations, are consistent with those from neutron scattering for the triangle spins which order antiferromagnetically below 106 K. For the kagome spins at low temperatures the static hyperfine fields are found to be oriented orthogonal to those of the triangle spins in a spin-flop configuration that is in disagreement with the neutron findings. Nuclear relaxation rate measurements made as a function of temperature show that inhomogeneous dynamic spin disorder occurs in kagome planes well below the Néel point.

  10. NMR investigation of intramolecular dynamics of heteroleptic triple-decker (porphyrinato)(phthalocyaninato) lanthanides.

    Science.gov (United States)

    Birin, Kirill P; Gorbunova, Yulia G; Tsivadze, Aslan Yu

    2011-11-21

    Intramolecular dynamics of meso-aryl substituents of porphyrin deck in the triple-decker lanthanide (porphyrinato)(phthalocyaninates) of symmetrical type [Br(4)TPP]Ln[(15C5)(4)Pc]Ln[Br(4)TPP] (Ln = La, Nd, Eu; [Br(4)TPP] = tetrakis-5,10,15,20-(4-bromophenyl)-porphyrinato-ligand; [(15C5)(4)Pc] = tetrakis-(15-crown-5)-phthalocyaninato-ligand) are investigated. Attempts to achieve coalescence were not successful, although the trend of exchanging protons to coalescence point was observed in the case of Nd and Eu complexes. The analysis of NOESY cross-peaks between exchanging protons allowed to evaluate the rotation rate constants at different temperatures. The activation barrier of the meso-aryl substituent rotation was calculated with Arrhenius equation based on determined rate constants. The rate constants are lower and activation barriers are higher than ones found previously for related compounds. This journal is © The Royal Society of Chemistry 2011

  11. Capillary electrophoresis of clenbuterol enantiomers and NMR investigation of the clenbuterol/carboxymethyl-β-cyclodextrin complex.

    Science.gov (United States)

    Zhou, Jie; Li, Yinghui; Liu, Qian; Fu, Guangjun; Zhang, Zhenzhong

    2013-03-01

    A capillary electrophoretic method has been established for the separation of the enantiomers of clenbuterol. The effects of pH value, composition of the background electrolyte, concentration of carboxymethyl-β-cyclodextrin (CM-β-CD), capillary temperature and running voltage have been investigated. The two enantiomers were separated in an uncoated capillary with phosphate buffer (50 mmol/L, pH 3.5) containing 10 mmol/L CM-β-CD. The capillary temperature was at 15°C and applied voltage was at 20 kV. The inclusion complex of CM-β-CD and clenbuterol was synthesized and characterized by two-dimensional rotating frame spectroscopy (2D ROESY). Based on the 2D ROESY analysis, an inclusion structure of the clenbuterol/CM-β-CD complex was proposed, in which clenbuterol penetrated CM-β-CD in a tilted manner due to the interaction of intermolecular hydrogen bonds between clenbuterol and CM-β-CD.

  12. Experimental investigation of transverse spin asymmetries in muon-p SIDIS processes: Collins asymmetries

    CERN Document Server

    Adolph, C.; Alexakhin, V.Yu.; Alexandrov, Yu.; Alexeev, G.D.; Amoroso, A.; Antonov, A.A.; Austregesilo, A.; Badelek, B.; Balestra, F.; Barth, J.; Baum, G.; Bedfer, Y.; Bernhard, J.; Bertini, R.; Bettinelli, M.; Bicker, K.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bordalo, P.; Bradamante, F.; Braun, C.; Bravar, A.; Bressan, A.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S.U.; Cicuttin, A.; Crespo, M.L.; Dalla Torre, S.; Das, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Dhara, L.; Donskov, S.V.; Doshita, N.; Duic, V.; Dunnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Filin, A.; Finger, M.; Fischer, H.; Franco, C.; von Hohenesche, N.du Fresne; Friedrich, J.M.; Frolov, V.; Garfagnini, R.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Geyer, R.; Giorgi, M.; Gnesi, I.; Gobbo, B.; Goertz, S.; Grabmuller, S.; Grasso, A.; Grube, B.; Gushterski, R.; Guskov, A.; Guthorl, T.; Haas, F.; von Harrach, D.; Heinsius, F.H.; Herrmann, F.; Hess, C.; Hinterberger, F.; Horikawa, N.; Hoppner, Ch.; d'Hose, N.; Ishimoto, S.; Ivanov, O.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Joosten, R.; Kabuss, E.; Kang, D.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu.A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koblitz, S.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Korzenev, A.; Kotzinian, A.M.; Kouznetsov, O.; Kramer, M.; Kroumchtein, Z.V.; Kunne, F.; Kurek, K.; Lauser, L.; Lednev, A.A.; Lehmann, A.; Levorato, S.; Lichtenstadt, J.; Liska, T.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G.K.; Mann, A.; Marchand, C.; Martin, A.; Marzec, J.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu.V.; Moinester, M.A.; Morreale, A.; Mutter, A.; Nagaytsev, A.; Nagel, T.; Negrini, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V.I.; Nowak, W.D.; Nunes, A.S.; Olshevsky, A.G.; Ostrick, M.; Padee, A.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Perevalova, E.; Pesaro, G.; Peshekhonov, D.V.; Piragino, G.; Platchkov, S.; Pochodzalla, J.; Polak, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Rajotte, J.F.; Ramos, S.; Rapatsky, V.; Reicherz, G.; Richter, A.; Rocco, E.; Rondio, E.; Rossiyskaya, N.S.; Ryabchikov, D.I.; Samoylenko, V.D.; Sandacz, A.; Sapozhnikov, M.G.; Sarkar, S.; Savin, I.A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schluter, T.; Schmidt, K.; Schmitt, L.; Schonning, K.; Schopferer, S.; Schott, M.; Schroder, W.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sissakian, A.N.; Slunecka, M.; Smirnov, G.I.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Sznajder, P.; Takekawa, S.; Wolbeek, J.Ter; Tessaro, S.; Tessarotto, F.; Tkatchev, L.G.; Uhl, S.; Uman, I.; Vandenbroucke, M.; Virius, M.; Vlassov, N.V.; Wang, L.; Wilfert, M.; Windmolders, R.; Wislicki, W.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zhuravlev, N.; Zvyagin, A.

    2012-10-31

    The COMPASS Collaboration at CERN has measured the transverse spin azimuthal asymmetry of charged hadrons produced in semi-inclusive deep inelastic scattering using a 160 GeV positive muon beam and a transversely polarised NH_3 target. The Collins asymmetry of the proton was extracted in the Bjorken x range 0.003investigations of the dependence on the ki...

  13. Investigations of the polymer/magnetic interface of organic spin-valves

    Energy Technology Data Exchange (ETDEWEB)

    Morley, N.A., E-mail: n.a.morley@sheffield.ac.uk [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Dost, R.; Lingam, A.S.V. [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Barlow, A.J. [National EPSRC XPS Users’ Service, School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2015-12-30

    Graphical abstract: - Highlights: • Metal carbide and sulphide species are detected at a polymer–magnetic interface. • Top magnetic electrodes on P3HT have uniaxial anisotropy. • Top magnetic electrodes on PBTTT are isotropic. - Abstract: This work investigates the top interface of an organic spin-valve, to determine the interactions between the polymer and top magnetic electrode. The polymers studied are regio-regular poly(3-hexylthiophene) (RR-P3HT) and poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT) and the magnetic top electrodes are NiFe and Fe. X-ray photoelectron spectroscopy (XPS) is used to determine the bonding at the interface, along with the extent of how oxidised the magnetic layers are, while atomic force microscopy (AFM) is used to determine the surface roughness. A magneto-optic Kerr effect (MOKE) magnetometer is used to study the magnetic properties of the top electrode. It is shown that at the organic–magnetic interface the magnetic atoms interact with the polymer, as metallic–sulphide and metallic-carbide species are present at the interface. It is also shown that the structure of the polymer influences the anisotropy of the magnetic electrode, such that the magnetic electrodes grown on RR-P3HT have uniaxial anisotropy, while those grown on PBTTT are isotropic.

  14. Gas chromatographic and electron spin resonance investigations of gamma-irradiated frog legs

    International Nuclear Information System (INIS)

    Morehouse, K.M.; Ku, Yuoh; Albrecht, H.L.; Yang, G.C.

    1991-01-01

    Several very sensitive techniques to measure radiation-induced products in frog legs were investigated. Presented here are results from the use of electron spin resonance (ESR) spectroscopy and capillary gas chromatography (GC) to measure radiolysis products in γ-irradiated frog legs. When bone is irradiated, a characteristic ESR signal develops and is easily measured. The intensity of the ESR signal is dose-dependent and stable for several months at room temperature. When triglycerides or fatty acids are irradiated, some of the major stable products formed are hydrocarbons with one less carbon than the precursor fatty acids. These hydrocarbons are formed as the result of the loss of CO 2 during various free radical reactions. A capillary GC procedure was developed to monitor the formation of these hydrocarbons in γ-irradiated frog legs. Since frog legs contain large amounts of palmitic, stearic, oleic, and linoleic acids, the formation of the hydrocarbons (pentadecane, heptadecane, 8-heptadecene, and 6,9-heptadecadiene, respectively) from the decarboxylation of these fatty acids was monitored. The yields of these hydrocarbons were found to be linear with applied dose. A sample from a lot of imported frog legs that were believed to have been treated with ionizing radiation was also analyzed. The ESR technique, in conjunction with the GC data on the hydrocarbons, appears to be a useful approach for identifying and monitoring frog legs that have been treated with ionizing radiation. (author)

  15. Investigation of the field dependent spin structure of exchange coupled magnetic heterostructures

    International Nuclear Information System (INIS)

    Gurieva, Tatiana

    2016-05-01

    This thesis describes the investigation of the field dependent magnetic spin structure of an antiferromagnetically (AF) coupled Fe/Cr heterostructure sandwiched between a hardmagnetic FePt buffer layer and a softmagnetic Fe top layer. The depth-resolved experimental studies of this system were performed via Magneto-optical Kerr effect (MOKE), Vibrating Sample Magnetometry (VSM) and various measuring methods based on nuclear resonant scattering (NRS) technique. Nucleation and evolution of the magnetic spiral structure in the AF coupled Fe/Cr multilayer structure in an azimuthally rotating external magnetic field were observed using NRS. During the experiment a number of time-dependent magnetic side effects (magnetic after-effect, domain-wall creep effect) caused by the non-ideal structure of a real sample were observed and later explained. Creation of the magnetic spiral structure in rotating external magnetic field was simulated using a one-dimensional micromagnetic model.The cross-sectional magnetic X-ray diffraction technique was conceived and is theoretically described in the present work. This method allows to determine the magnetization state of an individual layer in the magnetic heterostructure. It is also applicable in studies of the magnetic structure of tiny samples where conventional x-ray reflectometry fails.

  16. Theoretical investigation on spin-forbidden cooling transitions of gallium hydride.

    Science.gov (United States)

    Zhang, Yun-Guang; Zhang, Hua; Song, Hai-Yang; Yu, You; Wan, Ming-Jie

    2017-09-20

    Herein, the spin-forbidden cooling of a gallium hydride molecule is investigated using ab initio quantum chemistry. The cooling transition and the corresponding potential energy curves including , a 3 Π 0 - , a 3 Π 0 + , a 3 Π 1 , a 3 Π 2 , A 1 Π 1 , , 1 3 Σ, , , and 2 3 Σ states are simulated based on the multi-reference configuration interaction approach plus Davidson corrections method. By solving the nuclear Schrödinger equation, we calculate the spectroscopic constants of these states, which are in good agreement with the available experimental values. Based on the transition data, there seems to be a theoretical puzzle: highly diagonally distributed Franck-Condon factor f 00 for transitions , , and for the gallium hydride molecule but the intervening state A 1 Π 1 for transition is prohibitive to laser cooling. In addition, the transition does not have a suitable rate of optical cycling owing to a large radiative lifetime for state. Our theoretical simulation indicates the solution to the puzzle: the transition has a high emission rate, and there is a suitable radiative lifetime for a 3 Π 1 state, which can ensure rapid and efficient laser cooling of gallium hydride. The proposed laser drives transition by using three wavelengths (main pump laser λ 00 ; two repumping lasers λ 10 and λ 21 ). These results demonstrate the possibility of laser-cooling the gallium hydride molecule, and a sub-microkelvin cool temperature can be reached for this molecule.

  17. FTIR, FT-Raman, FT-NMR, UV-visible and quantum chemical investigations of 2-amino-4-methylbenzothiazole.

    Science.gov (United States)

    Arjunan, V; Sakiladevi, S; Rani, T; Mythili, C V; Mohan, S

    2012-03-01

    The FT-IR (4000-400 cm(-1)) and FT-Raman (4000-100 cm(-1)) spectral measurements and complete assignments of the observed spectra of 2-amino-4-methylbenzothiazole (2A4MBT) have been proposed. Ab initio and DFT calculations have been performed and the structural parameters of the compound were determined from the optimised geometry with 6-31G(d,p), 6-311++G(d,p) and cc-pVDZ basis sets and giving energies, harmonic vibrational frequencies, depolarisation ratios, IR intensities and Raman activities. (1)H and (13)C NMR spectra were recorded and (1)H and (13)C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-visible spectrum of the compound was also recorded and the electronic properties, such as HOMO, LUMO and band gap energies were measured by time-dependent DFT (TD-DFT) approach. The geometric parameters, energies, harmonic vibrational frequencies, IR intensities, Raman activities chemical shifts and absorption wavelengths were compared with the available experimental data of the molecule. The influences of methyl and amino groups on the skeletal modes and on the proton chemical shifts have been investigated. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. The influence of silanized nano-SiO{sub 2} on the hydration of cement paste: NMR investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bede, A., E-mail: Andrea.Bede@phys.utcluj.ro; Pop, A.; Ardelean, I. [Technical University of Cluj-Napoca, Department of Physics and Chemistry, 400114 Cluj-Napoca (Romania); Moldovan, M. [“Babes-Bolyai” University, “Raluca Ripan” Chemistry Research Institute, Department of Polymer Composites, 400294 Cluj-Napoca (Romania)

    2015-12-23

    It is known that by adding a small amount of nanoparticles to the cement-based materials a strong influence on the workability, strength and durability is obtained. These characteristics of the material are fundamentally determined by the hydration process taking place after mixing the cement grains with water. In the present study the influence introduced by the addition of nano-silica with silanized surfaces on the hydration process was investigated using low-field nuclear magnetic resonance (NMR) relaxometry. The cement samples were prepared using gray cement at a water-to-cement ratio of 0.4 and a 5% addition of nanosilica. The surface of the nanoparticles was modified using a coating of Silane A174. The cement pastes were monitored during their standard curing time of 28 days. It was established that, by using unmodified nanosilica particles, an acceleration of the hydration process takes place as compared with the pure cement paste. On the other side, by adding silanized nanoparticles, the dormancy stage significantly extends and the hydration process is slower. This slowing down process could enhance the mechanical strength of cement based materials as a result of a better compaction of the hydrated samples.

  19. L-glutamine: Dynamical properties investigation by means of INS, IR, RAMAN, 1H NMR and DFT techniques

    Science.gov (United States)

    Pawlukojć, A.; Hołderna-Natkaniec, K.; Bator, G.; Natkaniec, I.

    2014-10-01

    Vibrational spectra of L-glutamine in the solid state were studied using the inelastic neutron scattering (INS), infrared (IR), Raman and 1H NMR spectroscopy techniques. DFT calculation using CASTEP code with the periodic boundary conditions was used to determine and describe the normal modes in the vibrational spectra of pure L-glutamine. An excellent agreement between the calculated and experimental INS, IR and Raman data has been found. Bands assigned to the stretching vibrations of the NH3+ group in hydrogen bonds are observed at 2400, 2618 and 2619 cm-1, while the NH3+ torsion vibration mode is observed at 441 cm-1. The band at 2041 cm-1 is assigned to combinations of the NH3+ bending symmetry vibration and the CO2- rocking vibration and can be used as an "indicator band" for the identification of the NH3+ groups in amino acid. For the L-glutamine an activation energy needed for the NH3+ group reorientation was obtained as 7.4 kcal/mol. It was found, that the combination three spectroscopic methods (INS, IR and Raman) with calculations for the crystal state proved to be an effective tool to investigate dynamical properties of amino acid crystals.

  20. Early Stages of Biomineral Formation—A Solid-State NMR Investigation of the Mandibles of Minipigs

    Directory of Open Access Journals (Sweden)

    Anastasia Vyalikh

    2017-11-01

    Full Text Available Solid-state nuclear magnetic resonance (NMR spectroscopy allows for the identification of inorganic species during the biomineral formation, when crystallite particles visible in direct imaging techniques have not yet been formed. The bone blocks surrounding dental implants in minipigs were dissected after the healing periods of two, four, and eight weeks, and newly formed tissues formed around the implants were investigated ex vivo. Two-dimensional 31P-1H heteronuclear correlation (HETCOR spectroscopy is based on the distance-dependent heteronuclear dipolar coupling between phosphate- and hydrogen-containing species and provides sufficient spectral resolution for the identification of different phosphate minerals. The nature of inorganic species present at different mineralization stages has been determined based on the 31P chemical shift information. After a healing time of two weeks, pre-stages of mineralization with a rather unstructured distribution of structural motives were found. After four weeks, different structures, which can be described as nanocrystals exhibiting a high surface-to-volume ratio were detected. They grew and, after eight weeks, showed chemical structures similar to those of matured bone. In addition to hydroxyapatite, amorphous calcium phosphate, and octacalcium phosphate, observed in a reference sample of mature bone, signatures of ß-tricalcium phosphate and brushite-like structures were determined at the earlier stages of bone healing.

  1. Spin polarized tunnelling investigation of nanometre Co clusters by means of a Ni bulk tip

    International Nuclear Information System (INIS)

    Rastei, M V; Bucher, J P

    2006-01-01

    A massive Ni tip is used in spin polarized scanning tunnelling microscopy (SP STM) to explore the magnetization state of nanometre Co clusters, self-organized on the Au(111) surface. Constant current STM images taken at 4.6 K show a bimodal distribution of the cluster heights, accounting for the spin polarization of the STM junction. The spin polarization of the tunnel junction as a function of the bias voltage is found to depend on the local density of states of the sample examined. Changing the vacuum barrier parameters by bringing the tip closer to the surface leads to a reduction in the tunnelling magnetoresistance that may be attributed to spin flip effects. (letter to the editor)

  2. Structure and dynamics of the ApA, ApC, CpA and CpC RNA dinucleoside monophosphates resolved with NMR scalar spin-spin couplings

    Czech Academy of Sciences Publication Activity Database

    Vokáčová, Zuzana; Buděšínský, Miloš; Rosenberg, Ivan; Schneider, Bohdan; Šponer, Jiří; Sychrovský, Vladimír

    2009-01-01

    Roč. 113, č. 4 (2009), s. 1182-1191 ISSN 1520-6106 R&D Projects: GA AV ČR IAA400550701 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50040507; CEZ:AV0Z50520701 Keywords : RNA * NMR * MD Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.471, year: 2009

  3. Lithium ion diffusion measurements on a garnet-type solid conductor Li6.6La3Zr1.6Ta0.4O12 by using a pulsed-gradient spin-echo NMR method.

    Science.gov (United States)

    Hayamizu, Kikuko; Matsuda, Yasuaki; Matsui, Masaki; Imanishi, Nobuyuki

    2015-09-01

    The garnet-type solid conductor Li7-xLa3Zr2-xTaxO12 is known to have high ionic conductivity. We synthesized a series of compositions of this conductor and found that cubic Li6.6La3Zr1.6Ta0.4O12 (LLZO-Ta) has a high ionic conductivity of 3.7×10(-4)Scm(-1) at room temperature. The (7)Li NMR spectrum of LLZO-Ta was composed of narrow and broad components, and the linewidth of the narrow component varied from 0.69kHz (300K) to 0.32kHz (400K). We carried out lithium ion diffusion measurements using pulsed-field spin-echo (PGSE) NMR spectroscopy and found that echo signals were observed at T≥313K with reasonable sensitivity. The lithium diffusion behavior was measured by varying the observation time and pulsed-field gradient (PFG) strength between 313 and 384K. We found that lithium diffusion depended significantly on the observation time and strength of the PFG, which is quite different from lithium ion diffusion in liquids. It was shown that lithium ion migration in the solid conductor was distributed widely in both time and space. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. A solid-state NMR and DFT study of compositional modulations in AlxGa1-xAs

    NARCIS (Netherlands)

    Knijn, Paulus J.; Bentum, P. Jan M. van; Eck, Ernst R.H. van; Fang, Changming; Grimminck, Dennis L.A.G.; Groot, Robert A. de; Havenith, Remco W.A.; Marsman, Martijn; Meerts, W. Leo; Wijs, Gilles A. de; Kentgens, Arno P.M.

    2010-01-01

    We have conducted 75As and 69Ga Nuclear Magnetic Resonance (NMR) experiments to investigate order/disorder in AlxGa1-xAs lift-off films with x ~ 0.297 and 0.489. We were able to identify all possible As(AlnGa4-n) sites with n = 0–4 coordinations in 75As NMR spectra using spin-echo experiments at

  5. New techniques in NMR spectroscopy

    International Nuclear Information System (INIS)

    Hughes, C.E.

    1998-10-01

    In 1989, Soerensen introduced a method, the unitary bound, for calculating the maximum efficiencies of coherence transfer processes in NMR. This thesis applies this method to quadrupolar nuclei, an area not investigated by Soerensen. In doing so, several questions are raised, and answered, as to the implications of the unitary bound for coherence transfer processes in all areas of NMR. These include discussions of when such processes can be reversed without loss of signal and when sequential coherence transfer steps can be carried out with both steps having the maximum efficiency. One area of NMR of quadrupolar nuclei which has attracted some interest over the past few years has been the selective excitation of 23 Na nuclei in ordered environments. This was hinted at by Jaccard et al. in 1986 and demonstrated in biological systems by Eliav et al. in 1992, who achieved the selective excitation using a double-quantum filtration (DQF) experiment. The following year, Kemp-Harper and Wimperis demonstrated that the Jeener-Broekaert experiment could be used to achieve the same selectivity through excitation of quadrupolar order. The unitary bound shows that neither of these experiments achieve the maximum coherence transfer efficiency. This thesis sets out to improve upon the efficiency of these two experiments. Two multiple-pulse experiments are investigated. One seeks to improve upon the efficiency of the Jeener-Broekaert experiment for spin I = 3/2 nuclei by 33% to achieve the unitary bound efficiency. The other seeks to improve the efficiency of the selective DQF experiment by 41% to achieve the bound for spin I= 3/2 nuclei. 23 Na NMR spectra of cartilage and a lyotropic liquid crystal are presented which show that, although the new version of the Jeener-Broekaert experiment achieves no greater efficiency in practical application than the original, the new DQF experiment produces up to half of the expected improvement in efficiency. Alternative techniques to the

  6. Interaction Study of an Amorphous Solid Dispersion of Cyclosporin A in Poly-Alpha-Cyclodextrin with Model Membranes by 1H-, 2H-, 31P-NMR and Electron Spin Resonance

    Directory of Open Access Journals (Sweden)

    Jean-Claude Debouzy

    2014-01-01

    Full Text Available The properties of an amorphous solid dispersion of cyclosporine A (ASD prepared with the copolymer alpha cyclodextrin (POLYA and cyclosporine A (CYSP were investigated by 1H-NMR in solution and its membrane interactions were studied by 1H-NMR in small unilamellar vesicles and by 31P 2H NMR in phospholipidic dispersions of DMPC (dimyristoylphosphatidylcholine in comparison with those of POLYA and CYSP alone. 1H-NMR chemical shift variations showed that CYSP really interacts with POLYA, with possible adduct formation, dispersion in the solid matrix of the POLYA, and also complex formation. A coarse approach to the latter mechanism was tested using the continuous variations method, indicating an apparent 1 : 1 stoichiometry. Calculations gave an apparent association constant of log Ka = 4.5. A study of the interactions with phospholipidic dispersions of DMPC showed that only limited interactions occurred at the polar head group level (31P. Conversely, by comparison with the expected chain rigidification induced by CYSP, POLYA induced an increase in the fluidity of the layer while ASD formation led to these effects almost being overcome at 298 K. At higher temperature, while the effect of CYSP seems to vanish, a resulting global increase in chain fluidity was found in the presence of ASD.

  7. Experimental investigation of new low-dimensional spin systems in vanadium oxides

    International Nuclear Information System (INIS)

    Kaul, E.E.

    2005-01-01

    In this dissertation we reported our experimental investigation of the magnetic properties of nine low-dimensional vanadium compounds. Two of these materials are completely new (Pb 2 V 5 O 12 and Pb 2 VO(PO 4 ) 2 ) and were found during our search for new low-dimensional vanadium oxides. Among the other seven vanadium compounds studied, three were physically investigated for the first time (Sr 2 VO(PO 4 ) 2 , BaZnVO(PO 4 ) 2 and SrZnVO(PO 4 ) 2 ). Two had hitherto only preliminary, and wrongly interpreted, susceptibility measurements reported in the literature (Sr 2 V 3 O 9 and Ba 2 V 3 O 9 ) while the remaining two (Li 2 VOSiO 4 and Li 2 VOGeO 4 ) were previously investigated in some detail but the interpretation of the data was controversial. We investigated the magnetic properties of these materials by means of magnetic susceptibility and specific heat (C p (T)) measurements (as well as single crystal ESR measurements in the case of Sr 2 V 3 O 9 ). We synthesized the samples necessary for our physical studies. That required a search of the optimal synthesis conditions for obtaining pure, high quality, polycrystalline samples. Single crystals of Sr 2 V 3 O 9 and Pb 2 VO(PO 4 ) 2 were also successfully grown. Pb 2 VO(PO 4 ) 2 , BaZnVO(PO 4 ) 2 , SrZnVO(PO 4 ) 2 , Li 2 VOSiO 4 and Li 2 VOGeO 4 were found to be experimental examples of frustrated square-lattice systems which are described by theJ 1 -J 2 model. We found that Li 2 VOSiO 4 and Li 2 VOGeO 4 posses a weakly frustrated antiferromagnetic square lattice while Pb 2 VO(PO 4 ) 2 , BaZnVO(PO 4 ) 2 and SrZnVO(PO 4 ) 2 form a more strongly frustrated ferromagnetic square lattice. Pb 2 V 5 O 12 is structurally and compositionally related to the two dimensional A 2+ V 4+ n O 2n+1 vanadates. Its structure consists of layers formed by edge- and corner-shared square VO 5 pyramids. The basic structural units are plaquettes consisting of six corner-shared pyramids pointing in the same direction, which form a spin

  8. Complex methyl groups dynamics in [(CH3)4P]3Sb2Br9 (PBA) from low to high temperatures by proton spin-lattice relaxation and narrowing of proton NMR spectrum.

    Science.gov (United States)

    Latanowicz, L; Medycki, W; Jakubas, R

    2009-11-01

    Molecular dynamics of a polycrystalline sample of [(CH(3))(4)P](3)Sb(2)Br(9) (PBA) has been studied on the basis of the T(1) (24.7 MHz) relaxation time measurement, the proton second moment of NMR and the earlier published T(1) (90 MHz) relaxation times. The study was performed in a wide range of temperatures (30-337 K). The tunnel splitting omega(T) of the methyl groups was estimated as of low frequency (from kHz to few MHz). The proton spin pairs of the methyl group are known to perform a complex internal motion being a resultant of four components. Three of them involve mass transportation over and through the potential barrier and are characterized by the correlation times tau(3) and tau(T)of the jumps over the barrier and tunnel jumps in the threefold potential of the methyl group and tau(iso) the correlation time of isotropic rotation of the whole TMP cation. For tau(3) and tau(iso) the Arrhenius temperature dependence was assumed, while for tau(T)--the Schrödinger one. The fourth motion causes fluctuations of the tunnel splitting frequency, omega(T), and it is related to the lifetime of the methyl spin at the energy level. The correlation function for this fourth motion (tau(omega) correlation time) has been proposed by Müller-Warmuth et al. In this paper a formula for the correlation function and spectral density of the complex motion made of the above-mentioned four components was derived and used in interpretation of the T(1) relaxation time. The second moment of proton NMR line at temperatures below 50K is four times lower than its value for the rigid structure. The three components of the internal motion characterized by tau(T), tau(H), and tau(iso) were proved to reduce the second moment of the NMR line. The tunnel jumps of the methyl group reduce M(2) at almost 0K, the classical jumps over the barrier reduce M(2) in the vicinity of 50K, while the isotropic motion near 150K. Results of the study on the dynamics of CH(3) groups of TMP cation based on

  9. Ultrafast electron, lattice and spin dynamics on rare earth metal surfaces. Investigated with linear and nonlinear optical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Radu, I.E.

    2006-03-15

    This thesis presents the femtosecond laser-induced electron, lattice and spin dynamics on two representative rare-earth systems: The ferromagnetic gadolinium Gd(0001) and the paramagnetic yttrium Y(0001) metals. The employed investigation tools are the time-resolved linear reflectivity and second-harmonic generation, which provide complementary information about the bulk and surface/interface dynamics, respectively. The femtosecond laser excitation of the exchange-split surface state of Gd(0001) triggers simultaneously the coherent vibrational dynamics of the lattice and spin subsystems in the surface region at a frequency of 3 THz. The coherent optical phonon corresponds to the vibration of the topmost atomic layer against the underlying bulk along the normal direction to the surface. The coupling mechanism between phonons and magnons is attributed to the modulation of the exchange interaction J between neighbour atoms due to the coherent lattice vibration. This leads to an oscillatory motion of the magnetic moments having the same frequency as the lattice vibration. Thus these results reveal a new type of phonon-magnon coupling mediated by the modulation of the exchange interaction and not by the conventional spin-orbit interaction. Moreover, we show that coherent spin dynamics in the THz frequency domain is achievable, which is at least one order of magnitude faster than previously reported. The laser-induced (de)magnetization dynamics of the ferromagnetic Gd(0001) thin films have been studied. Upon photo-excitation, the nonlinear magneto-optics measurements performed in this work show a sudden drop in the spin polarization of the surface state by more than 50% in a <100 fs time interval. Under comparable experimental conditions, the time-resolved photoemission studies reveal a constant exchange splitting of the surface state. The ultrafast decrease of spin polarization can be explained by the quasi-elastic spin-flip scattering of the hot electrons among spin

  10. Investigation on spin-flip reaction of Re + CH3CN by relativistic density functional theory.

    Science.gov (United States)

    Xiao, Yi; Ji, Wen-Xin; Wei-Xu; Chen, Xian-Yang; Wang, Shu-Guang

    2014-07-07

    To explore the integrated reaction mechanisms for Re atom with acetonitrile theoretically, density functional theory with zero-order regular approximation (ZORA) relativistic corrections has been employed at the BP86/TZ2P level. There have been three adiabatic potential energy surfaces in the study along sextet, quartet and doublet spin states. However, the detailed minimum energy reaction pathway altogether contains six stationary states () to (), five transition states (), and two intersystem crossings with spin inversion (marked by ⇒): (6)Re + CH3CN → η(1)-ReNCCH3 () → ⇒ η(2)-Re(NC)CH3 () → → η(3)-HRe(NCCH2) () → → CH3-ReNC () → → CH2[double bond, length as m-dash]Re(H)NC () ⇒ → CH[triple bond, length as m-dash]Re(H)2NC (). Thereinto, the lowest energy crossing points (LECP) have been determined by the DFT fractional-occupation-number (FON) approach. The first spin inversion has transferred the potential energy surfaces from high-spin sextet to the quartet intermediate () with the subsequent C-C bond breakage. The second one from the quartet to the low-spin doublet state accompanies the C-H activation, decreasing the transition barrier by 157 kJ mol(-1). The overall reaction could be exothermic by about 210 kJ mol(-1). Harmonic vibration frequencies and NBO, WBO analysis are also applied to verified the experimental observed information.

  11. Structure and dynamics of the ApA, ApC, CpA and CpC RNA dinucleoside monophosphates resolved with NMR scalar spin-spin couplings

    Czech Academy of Sciences Publication Activity Database

    Vokáčová, Zuzana; Schneider, Bohdan; Buděšínský, Miloš; Rosenberg, Ivan; Šponer, Jiří; Sychrovský, Vladimír

    2009-01-01

    Roč. 16, 1a (2009), b52-b52 ISSN 1211-5894. [Meeting of the Czechoslovak and Slovak Biologists /7./. 12.03.2009-14.03.2009, Nové Hrady] R&D Projects: GA AV ČR IAA400550701 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50040507 Keywords : NMR * dinucleoside monophosphate Subject RIV: CF - Physical ; Theoretical Chemistry

  12. In-depth investigation of spin-on doped solar cells with thermally grown oxide passivation

    Directory of Open Access Journals (Sweden)

    Samir Mahmmod Ahmad

    Full Text Available Solar cell industrial manufacturing, based largely on proven semiconductor processing technologies supported by significant advancements in automation, has reached a plateau in terms of cost and efficiency. However, solar cell manufacturing cost (dollar/watt is still substantially higher than fossil fuels. The route to lowering cost may not lie with continuing automation and economies of scale. Alternate fabrication processes with lower cost and environmental-sustainability coupled with self-reliance, simplicity, and affordability may lead to price compatibility with carbon-based fuels. In this paper, a custom-designed formulation of phosphoric acid has been investigated, for n-type doping in p-type substrates, as a function of concentration and drive-in temperature. For post-diffusion surface passivation and anti-reflection, thermally-grown oxide films in 50–150-nm thickness were grown. These fabrication methods facilitate process simplicity, reduced costs, and environmental sustainability by elimination of poisonous chemicals and toxic gases (POCl3, SiH4, NH3. Simultaneous fire-through contact formation process based on screen-printed front surface Ag and back surface through thermally grown oxide films was optimized as a function of the peak temperature in conveyor belt furnace. Highest efficiency solar cells fabricated exhibited efficiency of ∼13%. Analysis of results based on internal quantum efficiency and minority carried measurements reveals three contributing factors: high front surface recombination, low minority carrier lifetime, and higher reflection. Solar cell simulations based on PC1D showed that, with improved passivation, lower reflection, and high lifetimes, efficiency can be enhanced to match with commercially-produced PECVD SiN-coated solar cells. Keywords: Crystalline Si solar cells, Phosphoric acid spin-on doping, Screen printing, Thermal oxide passivation

  13. Investigations of low- and high-spin states of sup 1 sup 3 sup 2 La

    CERN Document Server

    Kumar, V; Singh, R P; Muralithar, S; Bhowmik, R K

    2003-01-01

    The fusion evaporation reaction sup 1 sup 2 sup 2 Sn( sup 1 sup 4 N,4n) sup 1 sup 3 sup 2 La was used to populate the high-spin states of sup 1 sup 3 sup 2 La at the beam energy of 60 MeV. A new band consisting of mostly E2 transitions has been discovered. This band has the interesting links to the ground state 2 sup - and the isomeric state 6 sup -. A new transition of energy 351 keV connecting the low-spin states of the positive-parity band based on the pi h sub 1 sub 1 sub / sub 2 x nu h sub 1 sub 1 sub / sub 2 particle configuration, has been found. This has played a very important role in resolving the existing ambiguities and inconsistencies in the spin assignment of the band head. (orig.)

  14. Investigation of the chemomarkers correlated with flower colour in different organs of Catharanthus roseus using NMR-based metabolomics.

    Science.gov (United States)

    Pan, Qifang; Dai, Yuntao; Nuringtyas, Tri Rini; Mustafa, Natali Rianika; Schulte, Anna Elisabeth; Verpoorte, Robert; Choi, Young Hae

    2014-01-01

    Flower colour is a complex phenomenon that involves a wide range of secondary metabolites of flowers, for example phenolics and carotenoids as well as co-pigments. Biosynthesis of these metabolites, though, occurs through complicated pathways in many other plant organs. The analysis of the metabolic profile of leaves, stems and roots, for example, therefore may allow the identification of chemomarkers related to the final expression of flower colour. To investigate the metabolic profile of leaves, stems, roots and flowers of Catharanthus roseus and the possible correlation with four flower colours (orange, pink, purple and red). (1) H-NMR and multivariate data analysis were used to characterise the metabolites in the organs. The results showed that flower colour is characterised by a special pattern of metabolites such as anthocyanins, flavonoids, organic acids and sugars. The leaves, stems and roots also exhibit differences in their metabolic profiles according to the flower colour. Plants with orange flowers featured a relatively high level of kaempferol analogues in all organs except roots. Red-flowered plants showed a high level of malic acid, fumaric acid and asparagine in both flowers and leaves, and purple and pink flowering plants exhibited high levels of sucrose, glucose and 2,3-dihydroxy benzoic acid. High concentrations of quercetin analogues were detected in flowers and leaves of purple-flowered plants. There is a correlation between the metabolites specifically associated to the expression of different flower colours and the metabolite profile of other plant organs and it is therefore possible to predict the flower colours by detecting specific metabolites in leaves, stems or roots. This may have interesting application in the plant breeding industry. Copyright © 2013 John Wiley & Sons, Ltd.

  15. 1H NMR-based metabolomics investigation of copper-laden rat: a model of Wilson's disease.

    Directory of Open Access Journals (Sweden)

    Jingjing Xu

    Full Text Available Wilson's disease (WD, also known as hepatoleticular degeneration (HLD, is a rare autosomal recessive genetic disorder of copper metabolism, which causes copper to accumulate in body tissues. In this study, rats fed with copper-laden diet are used to render the clinical manifestations of WD, and their copper toxicity-induced organ lesions are studied. To investigate metabolic behaviors of 'decoppering' process, penicillamine (PA was used for treating copper-laden rats as this chelating agent could eliminate excess copper through the urine. To date, there has been limited metabolomics study on WD, while metabolic impacts of copper accumulation and PA administration have yet to be established.A combination of 1HNMR spectroscopy and multivariate statistical analysis was applied to examine the metabolic profiles of the urine and blood serum samples collected from the copper-laden rat model of WD with PA treatment.Copper accumulation in the copper-laden rats is associated with increased lactate, creatinine, valine and leucine, as well as decreased levels of glucose and taurine in the blood serum. There were also significant changes in p-hydroxyphenylacetate (p-HPA, creatinine, alpha-ketoglutarate (α-KG, dimethylamine, N-acetylglutamate (NAG, N-acetylglycoprotein (NAC in the urine of these rats. Notably, the changes in p-HPA, glucose, lactate, taurine, valine, leucine, and NAG were found reversed following PA treatment. Nevertheless, there were no changes for dimethylamine, α-KG, and NAC as a result of the treatment. Compared with the controls, the concentrations of hippurate, formate, alanine, and lactate were changed when PA was applied and this is probably due to its side effect. A tool named SMPDB (Small Molecule Pathway Database is introduced to identify the metabolic pathway influenced by the copper-laden diet.The study has shown the potential application of NMR-based metabolomic analysis in providing further insights into the molecular

  16. An NMR-based metabolomic approach to investigate the effects of supplementation with glutamic acid in piglets challenged with deoxynivalenol.

    Science.gov (United States)

    Wu, Miaomiao; Xiao, Hao; Ren, Wenkai; Yin, Jie; Hu, Jiayu; Duan, Jielin; Liu, Gang; Tan, Bie; Xiong, Xia; Oso, Abimbola Oladele; Adeola, Olayiwola; Yao, Kang; Yin, Yulong; Li, Tiejun

    2014-01-01

    Deoxynivalenol (DON) has various toxicological effects in humans and pigs that result from the ingestion of contaminated cereal products. This study was conducted to investigate the protective effects of dietary supplementation with glutamic acid on piglets challenged with DON. A total of 20 piglets weaned at 28 d of age were randomly assigned to receive 1 of 4 treatments (5 piglets/treatment): 1) basal diet, negative control (NC); 2) basal diet +4 mg/kg DON (DON); 3) basal diet +2% (g/g) glutamic acid (GLU); 4) basal diet +4 mg/kg DON +2% glutamic acid (DG). A 7-d adaptation period was followed by 30 days of treatment. A metabolite analysis using nuclear magnetic resonance spectroscopy (1H-NMR)-based metabolomic technology and the determination of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities for plasma, as well as the activity of Caspase-3 and the proliferation of epithelial cells were conducted. The results showed that contents of low-density lipoprotein, alanine, arginine, acetate, glycoprotein, trimethylamine-N-oxide (TMAO), glycine, lactate, and urea, as well as the glutamate/creatinine ratio were higher but high-density lipoprotein, proline, citrate, choline, unsaturated lipids and fumarate were lower in piglets of DON treatment than that of NC treatment (Pglutamic acid increased the plasma concentrations of proline, citrate, creatinine, unsaturated lipids, and fumarate, and decreased the concentrations of alanine, glycoprotein, TMAO, glycine, and lactate, as well as the glutamate/creatinine ratio (Pglutamic acid to DON treatment increased the plasma activities of SOD and GSH-Px and the proliferating cell nuclear antigen (PCNA) labeling indexes for the jejunum and ileum (Pglutamic acid has the potential to repair the injuries associated with oxidative stress as well as the disturbances of energy and amino acid metabolism induced by DON.

  17. Relation Between Acid and Catalytic Properties of Chlorinated Gamma-Alumina. a 31p Mas Nmr and Ftir Investigation

    Directory of Open Access Journals (Sweden)

    Guillaume D.

    1999-07-01

    Full Text Available In this paper, we have studied the effect of chlorine on the surface properties of gamma-alumina, especially on their acid properties. The use of FTIR spectroscopy and 31P MAS NMR of adsorbed trimethylphosphine allows to propose a chlorination mechanism. To correlate the surface properties of these chlorinated gamma-alumina with their catalytic properties, we have used a model reaction, the cracking of n-heptane under reforming conditions. The analysis of the correlation between acid properties determined by 31P MAS NMR and the catalytic results (in terms of activities and selectivities allows to identify which sites are involved in the cracking reaction.

  18. On investigation of optical and spin properties of NV centers in aggregates of detonation nanodiamonds

    Science.gov (United States)

    Bolshedvorskii, S. V.; Vorobyov, V. V.; Soshenko, V. V.; Zeleneev, A.; Sorokin, V. N.; Smolyaninov, A. N.; Akimov, A. V.

    2018-02-01

    Quickly developing application of nitrogen-vacancy color centers in diamond sets demands on cheap and high optical and spin properties nanodiamonds. Among other types, detonation nanodiamonds are easiest for production but often show no NV color centers inside. In this work we show, that aggregates of detonation nanodiamonds could be as good, or even better in terms of brightness and spin properties, than more expensive single crystal nanodiamonds. This way aggregates of detonation nanodiamonds could efficiently serve as cheap and bright source of single photon radiation or sensitive element of biocompatible sensor.

  19. All optical method for investigation of spin and charge transport in semiconductors: Combination of spatially and time-resolved luminescence

    Energy Technology Data Exchange (ETDEWEB)

    Cadiz, F.; Paget, D.; Grebenkov, D.; Korb, J. P.; Rowe, A. C. H. [Physique de la matière condensée, Ecole Polytechnique, CNRS, 91128 Palaiseau (France); Barate, P.; Amand, T. [Université de Toulouse, INSA-CNRS-UPS, 31077 Toulouse Cedex (France); Arscott, S.; Peytavit, E. [Institut d' Electronique, de Microélectronique et de Nanotechnologie (IEMN), University of Lille, CNRS, Avenue Poincaré, Cité Scientifique, 59652 Villeneuve d' Ascq (France)

    2014-07-14

    A new approach is demonstrated for investigating charge and spin diffusion as well as surface and bulk recombination in unpassivated doped semiconductors. This approach consists in using two complementary, conceptually related, techniques, which are time-resolved photoluminescence (TRPL) and spatially resolved microluminescence (μPL) and is applied here to p{sup +} GaAs. Analysis of the sole TRPL signal is limited by the finite risetime. On the other hand, it is shown that joint TRPL and μPL can be used to determine the diffusion constant, the bulk recombination time, and the spin relaxation time. As an illustration, the temperature variation of these quantities is investigated for p{sup +} GaAs.

  20. Two-dimensional spin diffusion in multiterminal lateral spin valves

    Science.gov (United States)

    Saha, D.; Basu, D.; Holub, M.; Bhattacharya, P.

    2008-01-01

    The effects of two-dimensional spin diffusion on spin extraction in lateral semiconductor spin valves have been investigated experimentally and theoretically. A ferromagnetic collector terminal of variable size is placed between the ferromagnetic electron spin injector and detector of a conventional lateral spin valve for spin extraction. It is observed that transverse spin diffusion beneath the collector terminal plays an important role along with the conventional longitudinal spin diffusion in describing the overall transport of spin carriers. Two-dimensional spin diffusion reduces the perturbation of the channel electrochemical potentials and improves spin extraction.

  1. 29Si NMR and SAXS investigation of the hybrid organic-inorganic glasses obtained by consolidation of the melting gels

    Science.gov (United States)

    Jitianu, Andrei; Cadars, Sylvian; Zhang, Fan; Rodriguez, Gabriela; Picard, Quentin; Aparicio, Mario; Mosa, Jadra; Klein, Lisa C.

    2017-01-01

    This study is focused on structural characterization of hybrid glasses obtained by consolidation of melting gels. The melting gels were prepared in molar ratios of methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DMDES) of 75%MTES-25%DMDES and 65%MTES-35%DMDES. Following consolidation, the hybrid glasses were characterized using Raman, 29Si and 13C Nuclear Magnetic Resonance (NMR) spectroscopies, synchrotron Small Angle X-Ray Scattering (SAXS) and scanning electron microscopy (SEM). Raman spectroscopy revealed the presence of Si-C bonds in the hybrid glasses and 8-membered ring structures in the Si-O-Si network. Qualitative NMR spectroscopy identified the main molecular species, while quantitative NMR data showed that the ratio of trimers (T) to dimers (D) varied between 4.6 and 3.8. Two-dimensional 29Si NMR data were used to identify two distinct types of T3 environments. SAXS data showed that the glasses are homogeneous across the nm to micrometer length scales. The scattering cross section was one thousand times lower than what is expected when phase separation occurs. The SEM images show a uniform surface without defects, in agreement with the SAXS results, which further supports that the hybrid glasses are nonporous. PMID:28262904

  2. Investigating the reactivity of pMDI with wood cell walls using high-resolution solution-state NMR spectroscopy

    Science.gov (United States)

    Daniel J. Yelle; John Ralph; Charles R. Frihart

    2009-01-01

    The objectives of this study are the following: (1) Use solution-state NMR to assign contours in HSQC spectra of the reaction products between pMDI model compounds and: (a) lignin model compounds, (b) milled-wood lignin, (c) ball-milled wood, (d) microtomed loblolly pine; (2) Determine where and to what degree urethane formation occurs with loblolly pine cell wall...

  3. Spins of adsorbed molecules investigated by the detection of Kondo resonance

    Science.gov (United States)

    Komeda, Tadahiro

    2014-12-01

    Surface magnetism has been one of the platforms to explore the magnetism in low dimensions. It is also a key component for the development of quantum information processes, which utilizes the spin degree of freedom. The Kondo resonance is a phenomenon that is caused by an interaction between an isolated spin and conduction electrons. First observed in the 1930s as an anomalous increase in the low-temperature resistance of metals embedded with magnetic atoms, the Kondo physics mainly studied the effects of bulk magnetic impurities in the resistivity. In the last 15 years it has undergone a revival by a scanning tunneling microscope (STM) which enables the measurement of the Kondo resonance at surfaces using an atomic scale point contact. The detection of the Kondo resonance can be a powerful tool to explore surface magnetism. In this article, I review recent studies of the surface spin of adsorbed molecules by the detection of the Kondo resonance. Researches on metal phthalocyanine (MPc) and porphyrin molecules will be examined. In addition, the Kondo resonance for double-decker lanthanoide Pc molecules will be discussed. Some of the double-decker Pc molecules show single-molecule magnet (SMM) behavior, which attracts attention as a material for electronic devices. For both classes, the ligand plays a crucial role in determining the parameters of the Kondo resonance, such as the Kondo temperature and the change of the shape from peak to Fano-dip. In addition, the spin in delocalized molecular orbital forms the Kondo resonance, which shows significant differences from the Kondo resonance formed by the metal spins. Since molecular orbital can be tuned in a flexible manner by the design of the molecule, the Kondo resonance formed by delocalized molecular orbital might expand the knowledge of this field.

  4. Bulk carbohydrate grain filling of barley ß-glucan mutants studied by 1H HR MAS NMR

    DEFF Research Database (Denmark)

    Seefeldt, Helene Fast; Larsen, Flemming Hofmann; Viereck, Nanna

    2008-01-01

    ) during grain filling. For the first time, 1H HR MAS NMR spectra of flour from immature barley seeds are analyzed. Spectral assignments are made using two-dimensional (2D) NMR methods. Both α- and β-glucan biosynthesis were characterized by inspection of the spectra as well as by calibration......Temporal and genotypic differences in bulk carbohydrate accumulation in three barley genotypes differing in the content of mixed linkage β-(1→3),(1→4)-D-glucan (β-glucan) and starch were investigated using proton high-resolution, magic angle spinning, nuclear magnetic resonance (1H HR MAS NMR...

  5. THz Dynamic Nuclear Polarization NMR.

    Science.gov (United States)

    Nanni, Emilio A; Barnes, Alexander B; Griffin, Robert G; Temkin, Richard J

    2011-08-29

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140-600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology.

  6. The characterisation of polymers using pulsed NMR

    International Nuclear Information System (INIS)

    Charlesby, A.

    1983-01-01

    Broad line pulsed NMR is applied to obtain information on radiation-induced polymer changes and other aspects of polymer science based on the interpretation of spin-spin relaxation curves. Calculations are made to determine the molecular weight, the crosslink density of simple, low molecular weight, flexible polymers. For higher molecular weight polymers, a conclusion can be drawn on the concentrations of entangled and crosslinked units by means of pulsed NMR. Some typical applications of the technique are illustrated by the examples of polyethylenes, rubbers, filled polymeric systems and aqueous polyethylene oxide solutions. The morphology of polymers can be followed by pulsed NMR. (V.N.)

  7. Investigation of Landau level spin reversal in (110) oriented p-type GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Isik, Nebile

    2009-09-01

    In this thesis, the Landau level crossing or anticrossing of hole levels has been investigated in p-type GaAs 400 Aa wide quantum wells. In magneto-transport measurements, this is evidenced with the presence of an anomalous peak in the longitudinal resistance measurements at {nu}=1. In the transversal resistance measurements, no signature of this anomalous peak is observed. By increasing the hole density in the quantum well by applying a top gate voltage, the position of the anomalous peak shifts to higher magnetic fields. At very high densities, anomalous peak disappears. By applying a back gate voltage, the electric field in the quantum well is tuned. A consequence is that the geometry of the quantum well is tuned from square to triangular. The anomalous peak position is shown to depend also on the back gate voltage applied. Temperature dependence of the peak height is consistent with thermal activation energy gap ({delta}/2= 135 {mu}eV). The activation energy gap as a function of the magnetic field has a parabolic like dependence, with the minimum of 135 {mu}eV at 4 T. The peak magnitude is observed to decrease with increasing temperature. An additional peak is observed at {nu}=2 minimum. This additional peak at {nu}=2 might be due to the higher Landau level crossing. The p-type quantum wells have been investigated by photoluminescence spectroscopy, as a function of the magnetic field. The polarization of the emitted light has been analyzed in order to distinguish between the transitions related to spin of electron {+-} 1/2 and spin of hole -+ 3/2. The transition energies of the lowest electron Landau levels with spin {+-} 1/2 and hole Landau levels with spin -+ 3/2 versus magnetic field show crossing at 4 T. The heavy hole Landau levels with spins {+-} 3/2 are obtained by the substraction of transition energies from the sum of lowest electron Landau level energy and the energy gap of GaAs. The heavy hole Landau levels show a crossing at 4 T. However, due to the

  8. Rovibrational and temperature effects in theoretical studies of NMR parameters

    DEFF Research Database (Denmark)

    Faber, Rasmus; Kaminsky, Jakub; Sauer, Stephan P. A.

    2016-01-01

    The demand for high precision calculations of NMR shieldings (or their related values, chemical shifts δ) and spin-spin coupling constants facilitating and supporting detailed interpretations of NMR spectra increases hand in hand with the development of computational techniques and hardware...... resources. Highly sophisticated calculations including even relativistic effects are nowadays possible for these properties. However, NMR parameters depend not only on molecular structure and environment but also on molecular flexibility and temperature and the apparent success of theoretical predictions...

  9. Numerical Investigations of Post-Newtonian Hamiltonian Dynamics for Spinning Compact Binaries

    Science.gov (United States)

    Zhong, S. Y.

    2012-03-01

    Spinning compact binaries, consisting of neutron stars or black holes, not only have rich dynamic phenomena of resonance and chaos, but also are the most promising source for detecting gravitational waves. There should be a certain relation between the dynamics of the gravitational bodies and the gravitational waveforms. Based on the least-squares correction, several manifold correction schemes like the single-scaling method and the dual-scaling method are designed to suppress numerical errors from 6 integrals of motion in a conservative post-Newtonian (PN) Hamiltonian of spinning compact binaries. Taking a fifth order Runge-Kutta algorithm as a basic integrator, we wonder whether the PN contributions, the spin effects, and the classification of orbits exert some influences on these correction schemes and the Nacozy's approach. It is found that they are almost the same in correcting the integrals for the pure Kepler problem. Once the third-order PN contributions are added to the pure orbital part, there are explicit differences of correction effectiveness among these methods. As an interesting case, the efficiency of correction is better for chaotic eccentric orbits than for quasicircular regular ones. In all cases tested, the new momentum-position dual-scaling scheme does always have the optimal performance. It costs a little but not much expensive additional computational cost when the spin effects exist, and several time-saving techniques are used. The corrected numerical results are more accurate than the uncorrected ones, so that chaos from the numerical errors can be avoided. See Phys. Rev. D 81, 104037 (2010) for more details. Lubich et al. (Phys. Rev. D 81, 104025 (2010)) presented a noncanonically symplectic integrator for the PN Hamiltonian of a spinning compact binary. However, the Euler mixed integrator is problematic because of its bad numerical stability.We improved the work by constructing the second-order and the fourth-order fixed symplectic

  10. Small angle neutron scattering investigations of spin disorder in nanocomposite soft magnets

    International Nuclear Information System (INIS)

    Vecchini, C.; Moze, O.; Suzuki, K.; Cadogan, J.M.; Pranzas, K.; Michels, A.; Weissmueller, J.

    2006-01-01

    The technique of SANS (small angle neutron scattering) furnishes unique information on the characteristic magnetic length scales and local magnetic anisotropies at the nanoscale in nanocomposite ferromagnets. Such information is not presently available using any other microscopic technique. The basic principles and results of the technique will be presented with regard to a unique and unexpected observation of a dipole field controlled spin disorder in a prototypical soft nanocomposite ferromagnet of the Nanoperm type

  11. Investigation of spin-zero bosons in q-deformed relativistic quantum mechanics

    Science.gov (United States)

    Sobhani, H.; Chung, W. S.; Hassanabadi, H.

    2018-04-01

    In this article, Scattering states of Klein-Gordon equation for three scatter potentials of single and double Dirac delta and a potential well in the q-deformed formalism of relativistic quantum mechanics have been derived. At first, we discussed how q-deformed formalism can be constructed and used. Postulates of this q-deformed quantum mechanics are noted. Then scattering problems for spin-zero bosons are studied.

  12. Dynamical Monte Carlo investigation of spin reversal and nonequilibrium magnetization of single-molecule magnets

    Science.gov (United States)

    Liu, Gui-Bin; Liu, Bang-Gui

    2010-10-01

    In this paper, we combine thermal effects with Landau-Zener (LZ) quantum tunneling effects in a dynamical Monte Carlo (DMC) framework to produce satisfactory magnetization curves of single-molecule magnet (SMM) systems. We use the giant spin approximation for SMM spins and consider regular lattices of SMMs with magnetic dipolar interactions (MDIs). We calculate spin-reversal probabilities from thermal-activated barrier hurdling, direct LZ tunneling, and thermal-assisted LZ tunnelings in the presence of sweeping magnetic fields. We do systematical DMC simulations for Mn12 systems with various temperatures and sweeping rates. Our simulations produce clear step structures in low-temperature magnetization curves, and our results show that the thermally activated barrier hurdling becomes dominating at high temperature near 3 K and the thermal-assisted tunnelings play important roles at intermediate temperature. These are consistent with corresponding experimental results on good Mn12 samples (with less disorders) in the presence of little misalignments between the easy axis and applied magnetic fields, and therefore our magnetization curves are satisfactory. Furthermore, our DMC results show that the MDI, with the thermal effects, have important effects on the LZ tunneling processes, but both the MDI and the LZ tunneling give place to the thermal-activated barrier hurdling effect in determining the magnetization curves when the temperature is near 3 K. This DMC approach can be applicable to other SMM systems and could be used to study other properties of SMM systems.

  13. 15N NMR spectroscopic investigation of nitrous and nitric acids in sulfuric acid solutions of varying acidities

    International Nuclear Information System (INIS)

    Prakash, G.K.S.; Heiliger, L.; Olah, G.A.

    1990-01-01

    Both nitrous and nitric acids were studied in sulfuric acid solutions of varying acid strengths by 15 N NMR spectroscopy. The study gives new insights into the nature of intermediates present at different acid strengths. Furthermore, we have also discovered a novel redox reaction between NO 2 + and NO + ions involving the intermediacy of their respective acids. A mechanism is proposed to explain the observed results. 13 refs., 2 figs., 1 tab

  14. 15N NMR investigation of the reduction and binding of TNT in an aerobic bench scale reactor simulating windrow composting

    Science.gov (United States)

    Thorn, K.A.; Pennington, J.C.; Hayes, C.A.

    2002-01-01

    T15NT was added to a soil of low organic carbon content and composted for 20 days in an aerobic bench scale reactor. The finished whole compost and fulvic acid, humic acid, humin, and lignocellulose fractions extracted from the compost were analyzed by solid-state CP/MAS and DP/MAS 15N NMR. 15N NMR spectra provided direct spectroscopic evidence for reduction of TNT followed by covalent binding of the reduced metabolites to organic matter of the composted soil, with the majority of metabolite found in the lignocellulose fraction, by mass also the major fraction of the compost. In general, the types of bonds formed between soil organic matter and reduced TNT amines in controlled laboratory reactions were observed in the spectra of the whole compost and fractions, confirming that during composting TNT is reduced to amines that form covalent bonds with organic matter through aminohydroquinone, aminoquinone, heterocyclic, and imine linkages, among others. Concentrations of imine nitrogens in the compost spectra suggestthat covalent binding bythe diamines 2,4DANT and 2,6DANT is a significant process in the transformation of TNT into bound residues. Liquid-phase 15N NMR spectra of the fulvic acid and humin fractions provided possible evidence for involvement of phenoloxidase enzymes in covalent bond formation.

  15. Deuteron NMR (Nuclear Magnetic Resonance) in relation to the glass transition in polymers

    Science.gov (United States)

    Roessler, E.; Sillescu, H.; Spiess, H. W.; Wallwitz, R.

    1983-01-01

    H-2NMR is introduced as a tool for investigating slow molecular motion in the glass transition region of amorphous polymers. In particular, we compare H-2 spin alignment echo spectra of chain deuterated polystyrene with model calculations for restricted rotational Brownian motion. Molecular motion in the polyztyrene-toluene system has been investigated by analyzing H-2NMR of partially deuterated polystyrene and toluene, respectively. The diluent mobility in the mixed glass has been decomposed into solid and liquid components where the respective average correlation times differ by more than 5 decades.

  16. 89Y NMR observation of ferromagnetic and antiferromagnetic spin fluctuations in the collapsed tetragonal phase of YFe2(Ge,Si)2

    Science.gov (United States)

    Srpčič, J.; Jeglič, P.; Felner, I.; Lv, Bing; Chu, C. W.; Arčon, D.

    2017-11-01

    The surprising discovery of tripling the superconducting critical temperature of KFe2As2 at high pressures has led to an intriguing question of how the superconductivity in the collapsed tetragonal phase differs from that in the noncollapsed phases of Fe-based superconductors. Here we report a 89Y nuclear magnetic resonance study of YFe2GexSi2 -x compounds whose electronic structure is similar to that of iron-pnictide collapsed tetragonal phases already at ambient pressure. We find that Fe(Ge,Si) layers show ferromagnetic spin fluctuations, whereas the layers are coupled antiferromagnetically. Furthermore, localized moments attributed either to Fe interstitial or antisite defects may account for magnetic impurity pair-breaking effects, thus explaining the substantial variation of superconductivity among different YFe2Ge2 samples.

  17. Cellulose Structural Polymorphism in Plant Primary Cell Walls Investigated by High-Field 2D Solid-State NMR Spectroscopy and Density Functional Theory Calculations.

    Science.gov (United States)

    Wang, Tuo; Yang, Hui; Kubicki, James D; Hong, Mei

    2016-06-13

    The native cellulose of bacterial, algal, and animal origins has been well studied structurally using X-ray and neutron diffraction and solid-state NMR spectroscopy, and is known to consist of varying proportions of two allomorphs, Iα and Iβ, which differ in hydrogen bonding, chain packing, and local conformation. In comparison, cellulose structure in plant primary cell walls is much less understood because plant cellulose has lower crystallinity and extensive interactions with matrix polysaccharides. Here we have combined two-dimensional magic-angle-spinning (MAS) solid-state nuclear magnetic resonance (solid-state NMR) spectroscopy at high magnetic fields with density functional theory (DFT) calculations to obtain detailed information about the structural polymorphism and spatial distributions of plant primary-wall cellulose. 2D (13)C-(13)C correlation spectra of uniformly (13)C-labeled cell walls of several model plants resolved seven sets of cellulose chemical shifts. Among these, five sets (denoted a-e) belong to cellulose in the interior of the microfibril while two sets (f and g) can be assigned to surface cellulose. Importantly, most of the interior cellulose (13)C chemical shifts differ significantly from the (13)C chemical shifts of the Iα and Iβ allomorphs, indicating that plant primary-wall cellulose has different conformations, packing, and hydrogen bonding from celluloses of other organisms. 2D (13)C-(13)C correlation experiments with long mixing times and with water polarization transfer revealed the spatial distributions and matrix-polysaccharide interactions of these cellulose structures. Celluloses f and g are well mixed chains on the microfibril surface, celluloses a and b are interior chains that are in molecular contact with the surface chains, while cellulose c resides in the core of the microfibril, outside spin diffusion contact with the surface. Interestingly, cellulose d, whose chemical shifts differ most significantly from those of

  18. A neutron scattering investigation of a Au-Fe spin glass alloy

    International Nuclear Information System (INIS)

    Murani, A.P.

    1978-01-01

    Neutron scattering measurements on a Au-Fe alloy containing 10 at.% Fe have been made using two different techniques which together help to illuminate some interesting dynamical properties of the spin glass alloy system. Time-of-flight measurements of the scattering function S(q,ω) reveal a broad, q-dependent, quasi-elastic line and a central elastic peak which at high temperatures is due mainly to the nuclear incoherent scattering from the sample. The line width of the quasi-elastic spectrum diminishes gradually with decreasing temperature, appears to go through a minimum especially at the higher q-values but always remains finite as T→0K. Below some relatively high temperature the integrated quasi-elastic scattering intensity begins to decrease with decreasing temperature accompanied by a continuous increase of the elastic scattering intensity. The static susceptibility chi(q) obtained from the broad quasi-elastic spectrum has a maximum which occurs at a temperature a little higher than that observed in the low field a.c. susceptibility. On the other hand measurements at very low q-values (0.005 -1 ) of the total scattering cross-section (which is mainly quasi-elastic) shows a series of q-dependent maxima at lower temperatures which extrapolate smoothly as q→0 to the temperature of the maximum in the a.c. susceptibility. We believe the results demonstrate the gradual process of freezing of spins over a wide temperature range and also reveal the presence of relatively rapid dynamical fluctuations in the spin system at low temperatures. (author)

  19. An electron spin resonance (ESR) investigation of the dosimetric potential of potassium tartrate

    International Nuclear Information System (INIS)

    Korkmaz, G.; Oezsayin, F.; Polat, M.

    2012-01-01

    While unirradiated potassium tartrate (PT) samples do not exhibit any electron spin resonance signal, irradiated ones contain many resonance signals. A power function of the radiation dose was found to describe well the dose-response curve of the central resonance signal, and adjusting the microwave power and modulation amplitude to be 2 mW and 1 mT, respectively, was found to increase the sensitivity of PT. The radiation sensitivity of PT and the accuracy of the measured radiation dose were found to be G = 0.42 and 6%, respectively. (authors)

  20. Multinuclear MAS NMR studies on coked zeolites H-ZSM-5

    International Nuclear Information System (INIS)

    Ernst, H.; Freude, D.; Hunger, M.; Pfeifer, H.

    1991-01-01

    During the cracking process carbonaceous materials are deposited on the outer or inner surface of the catalyst. These deposits are in many cases the main cause of catalyst deactivation. Magic angle spinning (MAS) NMR investigations and catalytic n-hexane cracking were carried out on H-ZSM-5 zeolites after a mild hydrothermal de-alumination. By 13 C CP MAS NMR it could be shown that the enhanced catalytic activity does not enhance the coke formation and that the chemical nature of these deposits is essentially aromatic. From 1 H MAS NMR studies performed on shallow-bed activated sealed samples and 27 Al and 29 Si MAS NMR on rehydrated samples it follows that for high coke concentrations the catalyst deactivation is caused mainly by blocking of Broensted acid sites. (author). 27 refs.; 3 figs.; 2 tabs

  1. Analysis of the Electronic Structure of the Special Pair of a Bacterial Photosynthetic Reaction Center by 13 C Photochemically Induced Dynamic Nuclear Polarization Magic-Angle Spinning NMR Using a Double-Quantum Axis.

    Science.gov (United States)

    Najdanova, Marija; Gräsing, Daniel; Alia, A; Matysik, Jörg

    2018-01-01

    The origin of the functional symmetry break in bacterial photosynthesis challenges since several decades. Although structurally very similar, the two branches of cofactors in the reaction center (RC) protein complex act very differently. Upon photochemical excitation, an electron is transported along one branch, while the other remains inactive. Photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) 13 C NMR revealed that the two bacteriochlorophyll cofactors forming the "Special Pair" donor dimer are already well distinguished in the electronic ground state. These previous studies are relying solely on 13 C- 13 C correlation experiments as radio-frequency-driven recoupling (RFDR) and dipolar-assisted rotational resonance (DARR). Obviously, the chemical-shift assignment is difficult in a dimer of tetrapyrrole macrocycles, having eight pyrrole rings of similar chemical shifts. To overcome this problem, an INADEQUATE type of experiment using a POST C7 symmetry-based approach is applied to selectively isotope-labeled bacterial RC of Rhodobacter (R.) sphaeroides wild type (WT). We, therefore, were able to distinguish unresolved sites of the macromolecular dimer. The obtained chemical-shift pattern is in-line with a concentric assembly of negative charge within the common center of the Special Pair supermolecule in the electronic ground state. © 2017 The American Society of Photobiology.

  2. Reversible binding of the HPLC6 isoform of type I antifreeze proteins to ice surfaces and the antifreeze mechanism studied by multiple quantum filtering-spin exchange NMR experiment.

    Science.gov (United States)

    Ba, Yong; Wongskhaluang, Jeff; Li, Jiabo

    2003-01-15

    Antifreeze proteins (AFPs) protect organisms from freezing damage by inhibiting the growth of seed-ice crystals. It has long been hypothesized that irreversible binding of AFPs to ice surfaces is responsible for inhibiting the growth of seed-ice crystals as such a mechanism supports the popularly accepted Kelvin effect for the explanation of local freezing-point depression. However, whether the binding is reversible or irreversible is still under debate due to the lack of direct experimental evidence. Here, we report the first direct experimental result, by using the newly developed multiple quantum (MQ) filtering-spin exchange NMR experiment, that shows that the binding of HPLC6 peptides to ice surfaces is reversible. It was found that the reversible process can be explained by the model of monolayer adsorption. These results suggest that the Kelvin effect is not suitable for explaining the antifreeze mechanism, and direct interactions between the peptides and the ice-surface binding sites are the driving forces for the binding of AFPs to ice surfaces. We propose that there exists a concentration gradient of AFP from an ice-binding surface to the solution due to the affinity of ice surfaces to AFPs. This concentration gradient creates a dense layer of AFP in contact with the ice-binding surface, which depresses the local freezing point because of the colligative property, but not the Kelvin effect.

  3. Metabolic profiling of apples from different production systems before and after controlled atmosphere (CA) storage studied by 1H high resolution-magic angle spinning (HR-MAS) NMR.

    Science.gov (United States)

    Vermathen, Martina; Marzorati, Mattia; Diserens, Gaëlle; Baumgartner, Daniel; Good, Claudia; Gasser, Franz; Vermathen, Peter

    2017-10-15

    Determination of metabolic alterations in apples induced by such processes as different crop protection strategies or storage, are of interest to assess correlations with fruit quality or fruit disorders. Preliminary results proposed the metabolic discrimination of apples from organic (BIO), integrated (IP) and low-input (LI) production. To determine contributions of temporal metabolic developments and to define the type of metabolic changes during storage, 1 H high resolution-magic angle spinning (HR-MAS) NMR spectroscopy of apple pulp was performed before and after two time points of controlled atmosphere storage. Statistical analysis revealed similar metabolic changes over time for IP-, LI- and BIO-samples, mainly decreasing lipid and sucrose, and increasing fructose, glucose and acetaldehyde levels, which are potential contributors to fruit aroma. Across the production systems, BIO apples had consistently higher levels of fructose and monomeric phenolic compounds but lower levels of condensed polyphenols than LI and IP apples, while the remaining metabolites assimilated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Combination of LC-ICP-MS, LC-MS and NMR for investigation of the oxidative degradation of selenomethionine

    DEFF Research Database (Denmark)

    Gammelgaard, B.; Cornett, Claus; Olsen, J.

    2003-01-01

    Selenomethionine (SeMet) was oxidized by heating an acidic solution with hydrogen peroxide. Samples were taken before and during the oxidation process. The oxidation products were separated by cation exchange chromatography followed by ICP-MS detection to identify the selenium containing compounds...... as well as electrospray ionization MS detection to determine the masses of the degradation products. Furthermore, the samples were analyzed by Se-77-NMR. The first appearing degradation product was selenomethionine selenoxide, which was converted via the deaminated selenoxide to methane seleninic acid...

  5. Magnus expansion paradoxes in the study of equilibrium magnetization and entanglement in multi-pulse spin locking

    Science.gov (United States)

    Kuznetsova, E. I.; Fel'dman, E. B.; Feldman, D. E.

    2016-06-01

    Divergence of the Magnus expansion leads to paradoxes in the spin dynamics of solid-state NMR and in quantum informatics. This review presents results on quasi-equilibrium magnetization in a system of dipole-dipole (DD) coupled spins at times T_2\\ll t \\ll T1ρ in multiple-pulse spin locking ( T_2 is the transverse spin relaxation time and T1ρ is the rotating-frame spin-lattice relaxation time). It is shown how contradictions between the results obtained with the Magnus expansion and experimental data can be removed. Systems of two and three DD coupled spins in multi-pulse spin locking are considered, and the entanglement evolution is investigated using both the Magnus expansion and the exact solution. The critical temperature for an entangled state is also found.

  6. Solid state NMR study of cumbaru flour

    International Nuclear Information System (INIS)

    Nogueira, Jose S.; Bathista, Andre L.B.S.; Silva, Emerson O.; Priante Filho, Nicolau; Tavares, Maria I.B.

    2001-01-01

    The polysaccharide obtained by seed of Dipteryx alata Vog, has been characterised by 13 C solid state, using the basic routine techniques, like MAS and CPMAS and by the proton spin-lattice relaxation time in the rotating frame parameter (T 1 H ρ). Knowing that the chemical structure and molecular dynamic are extremely necessary route to obtain information on the polysaccharides, this work contributes to the classification of the seed containing in the cumbaru fruit to get response on its application. To obtain the initial responses for our purposes some solid state NMR techniques were chosen. The CPMAS 13 C NMR spectrum of the polysaccharide was investigated to know if it has some crystallinity. The MAS 13 C NMR spectrum showed the presence of domains with distinct molecular mobility, because these domains will differ basically in the distribution size and chain packing. The variable contact time experiment was used to analyse the distribution form of 13 C decays, which give us more information about sample heterogeneity. The T 1 H ρHr values were obtained from the variable contact time and by delayed contact time experiment, because these parameter indicate the order of polysaccharides. From the values of this parameter, we found that this polysaccharide is completely non-ordered. (author)

  7. Investigation of uranium (VI) extraction mechanisms from phosphoric and sulfuric media by {sup 31}P-NMR

    Energy Technology Data Exchange (ETDEWEB)

    Fries, B.; Marie, C.; Pacary, V.; Berthon, C.; Miguirditchian, M.; Charbonnel, M.C. [CEA, Centre de Marcoule, Nuclear Energy Divison, RadioChemistry and Processes Department - DRCP, F-30207 Bagnols-sur-Ceze (France); Mokhtari, H. [AREVA Mines, Process and Analysis Department - SEPA, F-87250 Bessines-sur-Gartempe (France)

    2016-07-01

    Phosphate rocks contain uranium (∼1000 ppm on average) and are considered as a secondary source for uranium production. Uranium extraction using DEHCNPB (butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid, a bifunctional cationic extractant) has been studied to better understand mechanism differences depending on the original acidic solution (phosphoric or sulfuric). Solvent extraction batch experiments were carried out and the organic phases were probed using {sup 31}P-NMR. This technique enabled to demonstrate that phosphoric acid is poorly extracted by DEHCNPB ([H{sub 3}PO{sub 4}]{sub org} < 2 mM), using direct quantification in the organic phase by {sup 31}P-NMR spectra integration. Moreover, in the presence of uranium in the initial phosphoric acid solution, uranyl extraction by DEHCNPB competes with H{sub 3}PO{sub 4} extraction. Average stoichiometries of U(VI)-DEHCNPB complexes in organic phases were also determined using slope analysis on uranium distribution data. Uranium seems to be extracted from a phosphoric medium by two extractant molecules, whereas more than three DEHCNPB on average would be necessary to extract uranium from a sulfuric medium. Thus, uranium is extracted according to different mechanisms depending on the nature of the initial solution. (authors)

  8. Inelastic neutron scattering investigation of magnetostructural excitations in the spin-Peierls organic system (TMTTF) 2P F6

    Science.gov (United States)

    Pouget, J. P.; Foury-Leylekian, P.; Petit, S.; Hennion, B.; Coulon, C.; Bourbonnais, C.

    2017-07-01

    One-dimensional (1D) conductors such as Bechgaard and Fabre salts are a prototypal example of correlated systems where the phase diagram is controlled by sizable electron-electron repulsions. In deuterated (TMTTF) 2P F6 , where this interaction achieves charge localization at ambient pressure on donor stacks, magnetostructural coupling plays a decisive role to stabilize a spin-Peierls (SPs) ground state at TSP=13 K . In this paper, we present the first inelastic neutron scattering investigation of SP magnetic excitations in organics. Our paper reveals the presence above TSP of sizable critical fluctuations leading to the formation of a pseudogap in the 1D antiferromagnetic (AF) S =1 /2 magnetic excitation spectrum of the donor stack, concomitant with the local formation of singlet of paired spins into dimers below TSPMF≈40 K . In addition, the inelastic neutron scattering investigation allows us also to probe the SP critical lattice dynamics and to show that at ambient pressure these dynamics are of relaxation or order-disorder type. Below TSP, our paper reveals the emergence of a two gap SP magnetic excitation spectrum towards a well-defined S =1 magnon mode and a continuum of two excitations, as theoretically predicted. Our measurements allow us to locate the ambient pressure SP phase of (TMTTF) 2P F6 in the classical (adiabatic) limit close to the classical/quantum crossover line. Then we provide arguments suggesting that pressurized (TMTTF) 2P F6 shifts to the quantum (antiadiabatic) SP gapped phase, which ends in a quantum critical point allowing the stabilization of an AF phase that competes with superconductivity at higher pressure. Finally, we propose that the magnetostructural coupling mechanism in the Fabre salts is caused by dimer charge/spin fluctuations driven by the coupling of donors with anions.

  9. 1H and 10B NMR and MRI investigation of boron- and gadolinium–boron compounds in boron neutron capture therapy

    International Nuclear Information System (INIS)

    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.

    2011-01-01

    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.

  10. The stoichiometry of synthetic alunite as a function of hydrothermal ageing investigated by solid-state NMR spectroscopy, powder X-ray diffraction, and infrared spectroscopy

    DEFF Research Database (Denmark)

    Grube, Elisabeth; Nielsen, U. G.

    2014-01-01

    The stoichiometry of a series of synthetic alunite (nominally KAl3(SO4)2(OH)6) samples prepared by hydrothermal methods as a function of reaction time (1 – 31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic...... of potassium defects present, from 17.261(1) to 17.324(5) Å. Solid-state 27Al MAS NMR revealed a decrease in the defect concentration as a function of time and showed the presence of 7-10 % impurities in the samples....

  11. 1H and 10B NMR and MRI investigation of boron- and gadolinium-boron compounds in boron neutron capture therapy.

    Science.gov (United States)

    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. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Density functional theory and QM/MM illustration of the behavior of B23N23 nano-cone: EPR & NMR investigation

    OpenAIRE

    Samira Bagheri; Alireza Ziglari

    2015-01-01

    In this work, the B23N23 nano-cone has been investigated using the DFT exchange-correlation functional of theory by electron paramagnetic resonance of EPR2 and EPR3 basis sets. The results of ab initio and QM/MM calculations of NMR chemical shift values of σiso, σaniso, Δσ, δ and η parameters of with GIAO and CSGT approximations of B23N23 have been obtained. The relative energies have been compared between EPR2 and EPR3 methods. Also, Atoms charge transfers have considered to full alternat...

  13. Organic free radicals in clathrate hydrates investigated by muon spin spectroscopy.

    Science.gov (United States)

    Percival, Paul W; Mozafari, Mina; Brodovitch, Jean-Claude; Chandrasena, Lalangi

    2014-02-20

    Very little is known about the behavior of free H atoms and small organic radicals inside clathrate hydrate structures despite the relevance of such species to combustion of hydrocarbon hydrates. Muonium is an H atom analog, essentially a light isotope of hydrogen, and can be used to probe the chemistry of H atoms and transient free radicals. We demonstrate the first application of muon spin spectroscopy to characterize radicals in clathrate hydrates. Atomic muonium was detected in hydrates of cyclopentane and tetrahydrofuran, and muoniated free radicals were detected in the hydrates of cyclopentene and 2,5-dihydrofuran, indicating rapid addition of muonium to the organic guest. Muon avoided level-crossing spectra of the radicals in hydrates are markedly different to those of the same radicals in pure organic liquids at the same temperature, and this can be explained by limited mobility of the enclathrated radicals, leading to anisotropy in the hyperfine interactions.

  14. Solid-State NMR Investigation of Drug-Excipient Interactions and Phase Behavior in Indomethacin-Eudragit E Amorphous Solid Dispersions.

    Science.gov (United States)

    Lubach, Joseph W; Hau, Jonathan

    2018-02-20

    To investigate the nature of drug-excipient interactions between indomethacin (IMC) and methacrylate copolymer Eudragit® E (EE) in the amorphous state, and evaluate the effects on formulation and stability of these amorphous systems. Amorphous solid dispersions containing IMC and EE were spray dried with drug loadings from 20% to 90%. PXRD was used to confirm the amorphous nature of the dispersions, and DSC was used to measure glass transition temperatures (T g ). 13 C and 15 N solid-state NMR was utilized to investigate changes in local structure and protonation state, while 1 H T 1 and T 1ρ relaxation measurements were used to probe miscibility and phase behavior of the dispersions. T g values for IMC-EE solid dispersions showed significant positive deviations from predicted values in the drug loading range of 40-90%, indicating a relatively strong drug-excipient interaction. 15 N solid-state NMR exhibited a change in protonation state of the EE basic amine, with two distinct populations for the EE amine at -360.7 ppm (unprotonated) and -344.4 ppm (protonated). Additionally, 1 H relaxation measurements showed phase separation at high drug load, indicating an amorphous ionic complex and free IMC-rich phase. PXRD data showed all ASDs up to 90% drug load remained physically stable after 2 years. 15 N solid-state NMR experiments show a change in protonation state of EE, indicating that an ionic complex indeed forms between IMC and EE in amorphous solid dispersions. Phase behavior was determined to exhibit nanoscale phase separation at high drug load between the amorphous ionic complex and excess free IMC.

  15. Probing oxidative degradation in polymers using {sup 17}O NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Alam, T.M.; Click, C.A.; Assink, R.A.

    1997-09-01

    Understanding the mechanism of oxidative degradation remains an important goal in being able to predict the aging process in polymer materials. Nuclear magnetic resonance (NMR) spectroscopy has previously been utilized to investigate polymer degradation, including both proton ({sup 1}H) and carbon ({sup 13}C) studies. These previous NMR studies, as well as other spectroscopic investigations, are complicated by the almost overwhelming signal arising from the native undegraded polymer. This makes the identification and quantification of degradation species at small concentrations difficult. In this note we discuss recent investigation into the use of oxygen ({sup 17}O) NMR spectroscopy to probe the oxidative degradation process in polymers at a molecular level. Due to the low natural abundance (0.037%) and a nuclear spin of I=5/2 possessing an appreciable quadrupolar moment, the use of {sup 17}O NMR in polymer investigations has been limited. By utilizing synthetically enriched oxygen gas during the accelerated aging process, both the difficulties of low natural abundance and background interference signals are eliminated. For enriched samples {sup 17}O NMR spectra now provide a unique probe since all of the observed NMR resonances are the direct result of oxidative degradation.

  16. Application of NMR screening techniques for observing ligand binding with a protein receptor.

    Science.gov (United States)

    Shimotakahara, Sakurako; Furihata, Kazuo; Tashiro, Mitsuru

    2005-01-01

    Water ligand observed via gradient spectroscopy (WaterLOGSY), saturation transfer difference and NOE pumping NMR techniques were used to identify ligand binding with a receptor. Although these experiments were originally designed to observe ligands in complexes, their application is limited by the affinity of ligands towards target molecules. Here the improved WaterLOGSY pulse sequence was developed by incorporating the double pulsed field gradient spin-echo and gradient-tailored excitation WATERGATE sequences. The efficiency of these ligand-observed NMR screening techniques was investigated using the ribonuclease T1-inhibitor system. Copyright 2004 John Wiley & Sons, Ltd.

  17. Lipophilic Bisphosphonates as Dual Farnesyl/Geranylgeranyl Diphosphate Synthase Inhibitors: An X-ray and NMR Investigation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Cao, R; Yin, F; Hudock, M; Guo, R; Song, Y; No, J; Bergan, K; Leon, A; et al,

    2009-01-01

    Considerable effort has focused on the development of selective protein farnesyl transferase (FTase) and protein geranylgeranyl transferase (GGTase) inhibitors as cancer chemotherapeutics. Here, we report a new strategy for anticancer therapeutic agents involving inhibition of farnesyl diphosphate synthase (FPPS) and geranylgeranyl diphosphate synthase (GGPPS), the two enzymes upstream of FTase and GGTase, by lipophilic bisphosphonates. Due to dual site targeting and decreased polarity, the compounds have activities far greater than do current bisphosphonate drugs in inhibiting tumor cell growth and invasiveness, both in vitro and in vivo. We explore how these compounds inhibit cell growth and how cell activity can be predicted based on enzyme inhibition data, and using X-ray diffraction, solid state NMR, and isothermal titration calorimetry, we show how these compounds bind to FPPS and/or GGPPS.

  18. NMR-Based Metabonomic Investigation of Heat Stress in Myotubes Reveals a Time-Dependent Change in the Metabolites

    DEFF Research Database (Denmark)

    Straadt, Ida K; Young, Jette F; Bross, Peter

    2010-01-01

    NMR-based metabonomics was applied to elucidate the time-dependent stress responses in mouse myotubes after heat exposure of either 42 or 45 degrees C for 1 h. Principal component analysis (PCA) revealed that the gradual time-dependent changes in metabolites contributing to the clustering...... and separation of the control samples from the different time points after heat stress primarily are in the metabolites glucose, leucine, lysine, phenylalanine, creatine, glutamine, and acetate. In addition, PC scores revealed a maximum change in metabolite composition 4 h after the stress exposure; thereafter......, samples returned toward control samples, however, without reaching the control samples even 10 h after stress. The results also indicate that the myotubes efficiently regulate the pH level by release of lactate to the culture medium at a heat stress level of 42 degrees C, which is a temperature level...

  19. Preparation of Uniformly 13C,15N-Labeled Recombinant Human Amylin for Solid-State NMR Investigation

    DEFF Research Database (Denmark)

    Kosicka, Iga; Kristensen, Torsten; Bjerring, Morten

    2014-01-01

    of amyloidogenic proteins in large amounts remains challenging due to their aggregation potential, toxicity for cells and difficult purification. In this work, we report a method for the production of large amounts of uniformly labeled 13C,15N-human amylin, being one of the most amyloidogenic peptides known....... This method utilizes inclusion bodies-directed expression and cheap chemical cleavage with cyanogen bromide in order to minimize the cost of the procedure compared to the use of less efficient proteolytic enzymes. We demonstrate the formation of amylin fibrils in vitro characterized using biophysical methods...... and electron microscopy, show toxicity towards human cells, and demonstrate that produced material may form the basis for structure determination using solid-state NMR....

  20. NMR investigation of the porosity of hypercrosslinked polystyrene and the properties of water confined in its nanopores

    Science.gov (United States)

    Babushkina, T. A.; Klimova, T. P.; Tsyurupa, M. P.; Blinnikova, Z. K.; Davankov, V. A.

    2012-10-01

    The melting of water frozen preliminarily at 180 K in a free internal volume of water-swollen hypercrosslinked polystyrene networks with degrees of crosslinking ranging from 43 to 500% is studied by NMR. It is found that ice melts within a narrow range of low temperatures, 195-225 K, demonstrating that the pores in the networks are small and uniform in size. It is, however, impossible to calculate the pore size via the Gibbs-Thomson equation, since the structure of water (and hence its properties) depend on a sample's rate of freezing. We conclude that the activation of the orientational motions of water molecules starts to manifest itself already at 200 K; upon reaching 220-230 K, the total mobility of water molecules is due largely to translational motions with an activation energy of 27-28 kJ/mol.

  1. Crystal structure, magnetism, {sup 89}Y solid state NMR, and {sup 121}Sb Moessbauer spectroscopic investigations of YIrSb

    Energy Technology Data Exchange (ETDEWEB)

    Benndorf, Christopher [Institut fuer Physikalische Chemie, Universitaet Muenster (Germany); Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Heletta, Lukas; Block, Theresa; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Universitaet Muenster (Germany); Institute of Physics in Sao Carlos, University of Sao Paulo, Sao Carlos (Brazil)

    2017-02-15

    The ternary antimonide YIrSb was synthesized from the binary precursor YIr and elemental antimony by a diffusion controlled solid-state reaction. Single crystals were obtained by a flux technique with elemental bismuth as an inert solvent. The YIrSb structure (TiNiSi type, space group Pnma) was refined from single-crystal X-ray diffractometer data: a = 711.06(9), b = 447.74(5), c = 784.20(8) pm, wR{sub 2} = 0.0455, 535 F{sup 2} values, 20 variables. {sup 89}Y solid state MAS NMR and {sup 121}Sb Moessbauer spectra show single resonance lines in agreement with single-crystal X-ray data. YIrSb is a Pauli paramagnet. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. NMR-based metabolomic investigation of bioactivity of chemical constituents in black raspberry (Rubus occidentalis L.) fruit extracts.

    Science.gov (United States)

    Paudel, Liladhar; Wyzgoski, Faith J; Giusti, M Monica; Johnson, Jodee L; Rinaldi, Peter L; Scheerens, Joseph C; Chanon, Ann M; Bomser, Joshua A; Miller, A Raymond; Hardy, James K; Reese, R Neil

    2014-02-26

    Black raspberry (Rubus occidentalis L.) (BR) fruit extracts with differing compound profiles have shown variable antiproliferative activities against HT-29 colon cancer cell lines. This study used partial least-squares (PLS) regression analysis to develop a high-resolution (1)H NMR-based multivariate statistical model for discerning the biological activity of BR constituents. This model identified specific bioactive compounds and ascertained their relative contribution against cancer cell proliferation. Cyanidin 3-rutinoside and cyanidin 3-xylosylrutinoside were the predominant contributors to the extract bioactivity, but salicylic acid derivatives (e.g., salicylic acid glucosyl ester), quercetin 3-glucoside, quercetin 3-rutinoside, p-coumaric acid, epicatechin, methyl ellagic acid derivatives (e.g., methyl ellagic acetyl pentose), and citric acid derivatives also contributed significantly to the antiproliferative activity of the berry extracts. This approach enabled the identification of new bioactive components in BR fruits and demonstrates the utility of the method for assessing chemopreventive compounds in foods and food products.

  3. Computer studies of multiple-quantum spin dynamics

    International Nuclear Information System (INIS)

    Murdoch, J.B.

    1982-11-01

    The excitation and detection of multiple-quantum (MQ) transitions in Fourier transform NMR spectroscopy is an interesting problem in the quantum mechanical dynamics of spin systems as well as an important new technique for investigation of molecular structure. In particular, multiple-quantum spectroscopy can be used to simplify overly complex spectra or to separate the various interactions between a nucleus and its environment. The emphasis of this work is on computer simulation of spin-system evolution to better relate theory and experiment

  4. Computer studies of multiple-quantum spin dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Murdoch, J.B.

    1982-11-01

    The excitation and detection of multiple-quantum (MQ) transitions in Fourier transform NMR spectroscopy is an interesting problem in the quantum mechanical dynamics of spin systems as well as an important new technique for investigation of molecular structure. In particular, multiple-quantum spectroscopy can be used to simplify overly complex spectra or to separate the various interactions between a nucleus and its environment. The emphasis of this work is on computer simulation of spin-system evolution to better relate theory and experiment.

  5. NMR-based metabolite profiling of human milk: A pilot study of methods for investigating compositional changes during lactation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Junfang [Department of Chemistry, Umeå University (Sweden); Domellöf, Magnus [Department of Clinical Sciences, Pediatrics, Umeå University (Sweden); Zivkovic, Angela M. [Foods for Health Institute, University of California, Davis, CA (United States); Department of Nutrition, University of California, Davis, CA (United States); Larsson, Göran [Department of Medical Biochemistry and Biophysics, Unit of Research, Education and Development-Östersund, Umeå University (Sweden); Öhman, Anders, E-mail: anders.ohman01@umu.se [Department of Pharmacology and Clinical Neuroscience, Umeå University (Sweden); Nording, Malin L., E-mail: malin.nording@umu.se [Department of Chemistry, Umeå University (Sweden)

    2016-01-15

    Low-molecular-weight metabolites in human milk are gaining increasing interest in studies of infant nutrition. In the present study, the milk metabolome from a single mother was explored at different stages of lactation. Metabolites were extracted from sample aliquots using either methanol/water (MeOH/H{sub 2}O) extraction or ultrafiltration. Nuclear magnetic resonance (NMR) spectroscopy was used for metabolite identification and quantification, and multi- and univariate statistical data analyses were used to detect changes over time of lactation. Compared to MeOH/H{sub 2}O extraction, ultrafiltration more efficiently reduced the interference from lipid and protein resonances, thereby enabling the identification and quantification of 36 metabolites. The human milk metabolomes at the early (9–24 days after delivery) and late (31–87 days after delivery) stages of lactation were distinctly different according to multi- and univariate statistics. The late lactation stage was characterized by significantly elevated concentrations of lactose, choline, alanine, glutamate, and glutamine, as well as by reduced levels of citrate, phosphocholine, glycerophosphocholine, and N-acetylglucosamine. Our results indicate that there are significant compositional changes of the human milk metabolome also in different phases of the matured lactation stage. These findings complement temporal studies on the colostrum and transitional metabolome in providing a better understanding of the nutritional variations received by an infant. - Highlights: • 36 metabolites were simultaneously quantified in human milk by NMR. • Ultrafiltration more efficiently reduces interferences than MeOH/H{sub 2}O extraction. • Compositional changes of the human milk exist during the matured lactation stage.

  6. NMR-based metabolite profiling of human milk: A pilot study of methods for investigating compositional changes during lactation

    International Nuclear Information System (INIS)

    Wu, Junfang; Domellöf, Magnus; Zivkovic, Angela M.; Larsson, Göran; Öhman, Anders; Nording, Malin L.

    2016-01-01

    Low-molecular-weight metabolites in human milk are gaining increasing interest in studies of infant nutrition. In the present study, the milk metabolome from a single mother was explored at different stages of lactation. Metabolites were extracted from sample aliquots using either methanol/water (MeOH/H 2 O) extraction or ultrafiltration. Nuclear magnetic resonance (NMR) spectroscopy was used for metabolite identification and quantification, and multi- and univariate statistical data analyses were used to detect changes over time of lactation. Compared to MeOH/H 2 O extraction, ultrafiltration more efficiently reduced the interference from lipid and protein resonances, thereby enabling the identification and quantification of 36 metabolites. The human milk metabolomes at the early (9–24 days after delivery) and late (31–87 days after delivery) stages of lactation were distinctly different according to multi- and univariate statistics. The late lactation stage was characterized by significantly elevated concentrations of lactose, choline, alanine, glutamate, and glutamine, as well as by reduced levels of citrate, phosphocholine, glycerophosphocholine, and N-acetylglucosamine. Our results indicate that there are significant compositional changes of the human milk metabolome also in different phases of the matured lactation stage. These findings complement temporal studies on the colostrum and transitional metabolome in providing a better understanding of the nutritional variations received by an infant. - Highlights: • 36 metabolites were simultaneously quantified in human milk by NMR. • Ultrafiltration more efficiently reduces interferences than MeOH/H 2 O extraction. • Compositional changes of the human milk exist during the matured lactation stage.

  7. FT-IR and FT-Raman, NMR and UV spectroscopic investigation and hybrid computational (HF and DFT) analysis on the molecular structure of mesitylene.

    Science.gov (United States)

    Kose, E; Atac, A; Karabacak, M; Nagabalasubramanian, P B; Asiri, A M; Periandy, S

    2013-12-01

    The spectroscopic properties of mesitylene were investigated by FT-IR, FT-Raman, UV, (1)H and (13)C NMR techniques. The geometrical parameters and energies have been obtained from density functional theory (DFT) B3LYP method and Hartree-Fock (HF) method with 6-311++G(d,p) and 6-311G(d,p) basis sets calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were presented. (13)C and (1)H NMR chemical shifts were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, oscillator strength, wavelengths, HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed. Reduced density gradient (RDG) of the mesitylene was also given to investigate interactions of the molecule. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Neutron spin echo investigation of elementary excitations in superfluid 4He

    International Nuclear Information System (INIS)

    Mezei, F.

    1980-01-01

    The present work represents the first experimental evidence for the application of Neutron Spin Echo (NSE) in high resolution study of both optical-like (non dispersive) and dispersive elementary excitations. The results obtained proved to be relevant contributions concerning the temperature dependence of the energy and linewidth of the roton excitation between 0.96 and 1.4 K; the temperature dependence of the linewidth of the 1.1 A -1 and 1.72 A -1 phonons and the suggested onset of three-phonon decay between 2.1 A -1 and 2.4 A -1 . The energy transfer resolution achieved in this work was 10-40 times superiour to those in previous similar neutron scattering experiments. In this paper most of the attention will be paid to the experimental aspects. In the first section the details of the NSE experiment are described, with particular emphasis on the first demonstration of the general scheme of NSE focussing, which involves the tuning of both the ratio of the precession fields H 0 /H 1 and their geometrical assymetry ('tilt angle'). The second section gives the experimental results without, however, a detailed discussion of their significance for the understanding of superfluid 4 He, which will be published elsewhere. (orig.)

  9. Morphology and side-chain dynamics in hydrated hard α-keratin fibres by 1H solid-state NMR

    Science.gov (United States)

    Melian, Claudiu; Demco, Dan E.; Istrate, Monica; Balaceanu, Andreea; Moldovan, Dumitrita; Fechete, Radu; Popescu, Crisan; Möller, Martin

    2009-10-01

    The effect of hydration on phase composition, aminoacids side-chain dynamics, and domain thickness of hard α-keratin was investigated by 1H solid-state NMR. Decomposition of wide-line 1H NMR spectra was used to determine the phase composition and to obtain information on molecular motion. Proton spin-diffusion NMR experiments using a double-quantum dipolar filter were used to estimate the rigid domain sizes for the hydrated Caucasian hair fibres. The relative domain sizes were obtained from the solution of spin-diffusion equation for cylindrical morphologies in the initial-rate approximation by a novel approach. A qualitative model describing the morphological and molecular dynamics changes induced by hydration was developed.

  10. Investigating correlations in the altered metabolic profiles of obese and diabetic subjects in a South Indian Asian population using an NMR-based metabolomic approach.

    Science.gov (United States)

    Gogna, Navdeep; Krishna, Murahari; Oommen, Anup Mammen; Dorai, Kavita

    2015-02-01

    It is well known that obesity/high body mass index (BMI) plays a key role in the evolution of insulin resistance and type-2 diabetes mellitus (T2DM). However, the exact mechanism underlying its contribution is still not fully understood. This work focuses on an NMR-based metabolomic investigation of the serum profiles of diabetic, obese South Indian Asian subjects. (1)H 1D and 2D NMR experiments were performed to profile the altered metabolic patterns of obese diabetic subjects and multivariate statistical methods were used to identify metabolites that contributed significantly to the differences in the samples of four different subject groups: diabetic and non-diabetic with low and high BMIs. Our analysis revealed that the T2DM-high BMI group has higher concentrations of saturated fatty acids, certain amino acids (leucine, isoleucine, lysine, proline, threonine, valine, glutamine, phenylalanine, histidine), lactic acid, 3-hydroxybutyric acid, choline, 3,7-dimethyluric acid, pantothenic acid, myoinositol, sorbitol, glycerol, and glucose, as compared to the non-diabetic-low BMI (control) group. Of these 19 identified significant metabolites, the levels of saturated fatty acids, lactate, valine, isoleucine, and phenylalanine are also higher in obese non-diabetic subjects as compared to control subjects, implying that this set of metabolites could be identified as potential biomarkers for the onset of diabetes in subjects with a high BMI. Our work validates the utility of NMR-based metabolomics in conjunction with multivariate statistical analysis to provide insights into the underlying metabolic pathways that are perturbed in diabetic subjects with a high BMI.

  11. Investigation of the spin-1 honeycomb antiferromagnet BaNi2V2O8 with easy-plane anisotropy

    Science.gov (United States)

    Klyushina, E. S.; Lake, B.; Islam, A. T. M. N.; Park, J. T.; Schneidewind, A.; Guidi, T.; Goremychkin, E. A.; Klemke, B.; Mânsson, M.

    2017-12-01

    The magnetic properties of the two-dimensional, S =1 honeycomb antiferromagnet BaNi2V2O8 have been comprehensively studied using dc susceptibility measurements and inelastic neutron scattering techniques. The magnetic excitation spectrum is found to be dispersionless within experimental resolution between the honeycomb layers, while it disperses strongly within the honeycomb plane where it consists of two gapped spin-wave modes. The magnetic excitations are compared to linear spin-wave theory allowing the Hamiltonian to be determined. The first- and second-neighbor magnetic exchange interactions are antiferromagnetic and lie within the ranges 10.90 meV ≤Jn≤13.35 meV and 0.85 meV ≤Jn n≤1.65 meV, respectively. The interplane coupling Jout is four orders of magnitude weaker than the intraplane interactions, confirming the highly two-dimensional magnetic behavior of this compound. The sizes of the energy gaps are used to extract the magnetic anisotropies and reveal substantial easy-plane anisotropy and a very weak in-plane easy-axis anisotropy. Together these results reveal that BaNi2V2O8 is a candidate compound for the investigation of vortex excitations and Berezinsky-Kosterliz-Thouless phenomenon.

  12. EPR investigation of zinc/iodine exchange between propargyl iodides and diethylzinc: detection of propargyl radical by spin trapping.

    Science.gov (United States)

    Maury, Julien; Jammi, Suribabu; Vibert, François; Marque, Sylvain R A; Siri, Didier; Feray, Laurence; Bertrand, Michèle

    2012-10-19

    The production of propargyl radicals in the reaction of dialkylzincs with propargyl iodides in nondegassed medium was investigated by EPR using tri-tert-butylnitrosobenzene (TTBNB) as a spin trap. The radical mechanism and the nature of the observed species were confirmed by the trapping of propargyl radicals generated by an alternative pathway: i.e., upon irradiation of propargyl iodides in the presence of hexa-n-butyldistannane. In dialkylzinc-mediated experiments a high concentration of adduct was instantaneously observed, whereas no spontaneous production of spin adduct was detected in a blank experiment performed with the propargylic iodide and TTBNB in the absence of diethylzinc. Under irradiation in the presence of distannane, two different species were observed at the very beginning of the irradiation; the nitroxide resulting from the trapping of propargyl radical at the propargyl carbon remained the only species detected after irradiating for several minutes. The absence of adducts resulting from the trapping of allenyl canonical forms was supported by DFT calculations and by the preparation of an authentic sample.

  13. NMR imaging studies of coal

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Z.R.; Zhang, P.Z.; Ding, G.L.; Li, L.Y.; Ye, C.H. [University of Science and Technology, Beijing (China). Dept. of Chemistry

    1996-06-01

    The permeation transportation and swelling behavior of solvents into coal are investigated by NMR imaging using pyridine-d{sub 5} and acetone-d{sub 6}. Images of coal swollen with deuterated solvents illuminate proton distributions of mobile phases within the coal macromolecular networks. More information about the chemical and physical structure of coal can be obtained using NMR imaging techniques.

  14. NMR imaging of osteoarticular pathology

    Energy Technology Data Exchange (ETDEWEB)

    Frocrain, L.; Duvauferrier, R.; Gagey, N. and others

    1987-01-01

    NMR imaging is assuming an increasingly important role in the diagnosis of osteo-articular disorders. Semiological descriptions of the mean pathological disorders of the locomotor system are presented. Some investigation strategies are proposed to compare NMR imaging with other imaging techniques in various pathological states.

  15. Matrix-assisted relaxation in Fe(phen)2(NCS)2 spin-crossover microparticles, experimental and theoretical investigations

    International Nuclear Information System (INIS)

    Enachescu, Cristian; Stancu, Alexandru; Tanasa, Radu; Tissot, Antoine; Laisney, Jérôme; Boillot, Marie-Laure

    2016-01-01

    In this study, we present the influence of the embedding matrix on the relaxation of Fe(phen) 2 (NCS) 2 (phen = 1,10-phenanthroline) spin-transition microparticles as revealed by experiments and provide an explanation within the framework of an elastic model based on a Monte-Carlo method. Experiments show that the shape of the high-spin → low-spin relaxation curves is drastically changed when the particles are dispersed in glycerol. This effect was considered in the model by means of interactions between the microparticles and the matrix. A faster start of the relaxation for microparticles embedded in glycerol is due to an initial positive local pressure acting on the edge spin-crossover molecules from the matrix side. This local pressure diminishes and eventually becomes negative during relaxation, as an effect of the decrease of the volume of spin-crossover microparticles from high-spin to low-spin.

  16. Nano-Mole Scale Side-Chain Signal Assignment by 1H-Detected Protein Solid-State NMR by Ultra-Fast Magic-Angle Spinning and Stereo-Array Isotope Labeling

    KAUST Repository

    Wang, Songlin

    2015-04-09

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52–57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems.

  17. Theoretical Investigation of Dynamic Properties of Magnetic Molecule Systems as Probed by NMR and Pulsed Fields Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Rousochatzakis, Ioannis [Iowa State Univ., Ames, IA (United States)

    2005-12-17

    The field of molecular magnetism[l-6] has become a subject of intense theoretical and experimental interest and has rapidly evolved during the last years. This inter-disciplinary field concerns magnetic systems at the molecular or "nanoscopic" level, whose realization has become feasible due to recent advances in the field of chemical synthesis. The present theoretical work provides a first step towards exploiting the possibilities that are offered by probing magnetic molecules using external magnetic fields with high sweep rates. These probes, apart for providing information specific to magnetic molecules, offer the possibility of conducting a detailed study of the relaxational behavior of interacting spin systems as a result of their coupling with a "heat bath" and in particular the excitations of the host lattice. Development of a broad theoretical framework for dealing with relaxational phenomena induced by dynamical magnetic fields is indeed a worthy goal.

  18. Spectroscopic (FT-IR, FT-Raman, UV and NMR) investigation on 1-phenyl-2-nitropropene by quantum computational calculations.

    Science.gov (United States)

    Xavier, S; Periandy, S

    2015-01-01

    In this paper, the spectral analysis of 1-phenyl-2-nitropropene is carried out using the FTIR, FT Raman, FT NMR and UV-Vis spectra of the compound with the help of quantum mechanical computations using ab-initio and density functional theories. The FT-IR (4000-400 cm(-1)) and FT-Raman (4000-100 cm(-1)) spectra were recorded in solid phase, the (1)H and (13)C NMR spectra were recorded in CDCl3 solution phase and the UV-Vis (200-800 nm) spectrum was recorded in ethanol solution phase. The different conformers of the compound and their minimum energies are studied using B3LYP functional with 6-311+G(d,p) basis set and two stable conformers with lowest energy were identified and the same was used for further computations. The computed wavenumbers from different methods are scaled so as to agree with the experimental values and the scaling factors are reported. All the modes of vibrations are assigned and the structure the molecule is analyzed in terms of parameters like bond length, bond angle and dihedral angle predicted by both B3LYP and B3PW91 methods with 6-311+G(d,p) and 6-311++G(d,p) basis sets. The values of dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the molecule are reported, using which the non-linear property of the molecule is discussed. The HOMO-LUMO mappings are reported which reveals the different charge transfer possibilities within the molecule. The isotropic chemical shifts predicted for (1)H and (13)C atoms using gauge invariant atomic orbital (GIAO) theory show good agreement with experimental shifts. NBO analysis is carried out to picture the charge transfer between the localized bonds and lone pairs. The local reactivity of the molecule has been studied using the Fukui function. The thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Optical investigation of the strong spin-orbit-coupled magnetic semimetal YbMnBi2

    Science.gov (United States)

    Chaudhuri, Dipanjan; Cheng, Bing; Yaresko, Alexander; Gibson, Quinn D.; Cava, R. J.; Armitage, N. P.

    2017-08-01

    Strong spin-orbit coupling (SOC) can result in ground states with nontrivial topological properties. The situation is even richer in magnetic systems where the magnetic ordering can potentially have strong influence over the electronic band structure. The class of A MnBi2 (A = Sr, Ca) compounds are important in this context as they are known to host massive Dirac fermions with strongly anisotropic dispersion, which is believed to be due to the interplay between strong SOC and magnetic degrees of freedom. We report the optical conductivity of YbMnBi2, a newly discovered member of this family and a proposed Weyl semimetal (WSM) candidate with broken time reversal symmetry. Together with density functional theory (DFT) band-structure calculations, we show that the complex conductivity can be interpreted as the sum of an intraband Drude response and interband transitions. We argue that the canting of the magnetic moments that has been proposed to be essential for the realization of the WSM in an otherwise antiferromagnetically ordered system is not necessary to explain the optical conductivity. We believe our data is explained qualitatively by the uncanted magnetic structure with a small offset of the chemical potential from strict stochiometry. We find no definitive evidence of a bulk Weyl nodes. Instead, we see signatures of a gapped Dirac dispersion, common in other members of A MnBi2 family or compounds with similar 2D network of Bi atoms. We speculate that the evidence for a WSM seen in ARPES arises through a surface magnetic phase. Such an assumption reconciles all known experimental data.

  20. Structural properties of carbon nanotubes derived from 13C NMR

    KAUST Repository

    Abou-Hamad, E.

    2011-10-10

    We present a detailed experimental and theoretical study on how structural properties of carbon nanotubes can be derived from 13C NMR investigations. Magic angle spinning solid state NMR experiments have been performed on single- and multiwalled carbon nanotubes with diameters in the range from 0.7 to 100 nm and with number of walls from 1 to 90. We provide models on how diameter and the number of nanotube walls influence NMR linewidth and line position. Both models are supported by theoretical calculations. Increasing the diameter D, from the smallest investigated nanotube, which in our study corresponds to the inner nanotube of a double-walled tube to the largest studied diameter, corresponding to large multiwalled nanotubes, leads to a 23.5 ppm diamagnetic shift of the isotropic NMR line position δ. We show that the isotropic line follows the relation δ = 18.3/D + 102.5 ppm, where D is the diameter of the tube and NMR line position δ is relative to tetramethylsilane. The relation asymptotically tends to approach the line position expected in graphene. A characteristic broadening of the line shape is observed with the increasing number of walls. This feature can be rationalized by an isotropic shift distribution originating from different diamagnetic shielding of the encapsulated nanotubes together with a heterogeneity of the samples. Based on our results, NMR is shown to be a nondestructive spectroscopic method that can be used as a complementary method to, for example, transmission electron microscopy to obtain structural information for carbon nanotubes, especially bulk samples.

  1. Experimental and NMR theoretical methodology applied to geometric analysis of the bioactive clerodane trans-dehydrocrotonin

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Breno Almeida; Firme, Caio Lima, E-mail: firme.caio@gmail.com, E-mail: caiofirme@quimica.ufrn.br [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Instituto de Quimica; Maciel, Maria Aparecida Medeiros [Universidade Potiguar, Natal, RN (Brazil). Programa de Pos-graduacao em Biotecnologia; Kaiser, Carlos R. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Instituto de Quimica; Schilling, Eduardo; Bortoluzzi, Adailton J. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Departamento de Quimica

    2014-04-15

    trans-Dehydrocrotonin (t-DCTN) a bioactive 19-nor-diterpenoid clerodane type isolated from Croton cajucara Benth, is one of the most investigated clerodane in the current literature. In this work, a new approach joining X-ray diffraction data, nuclear magnetic resonance (NMR) data and theoretical calculations was applied to the thorough characterization of t-DCTN. For that, the geometry of t-DCTN was reevaluated by X-ray diffraction as well as {sup 1}H and {sup 13}C NMR data, whose geometrical parameters where compared to those obtained from B3LYP/6-311G++(d,p) level of theory. From the evaluation of both calculated and experimental values of {sup 1}H and {sup 13}C NMR chemical shifts and spin-spin coupling constants, it was found very good correlations between theoretical and experimental magnetic properties of t-DCTN. Additionally, the delocalization indexes between hydrogen atoms correlated accurately with theoretical and experimental spin-spin coupling constants. An additional topological analysis from quantum theory of atoms in molecules (QTAIM) showed intramolecular interactions for t-DCTN. (author)

  2. Spin-Mechatronics

    Science.gov (United States)

    Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

    2017-01-01

    We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.

  3. Proton NMR investigation of the electron-exchange reaction between hexaammineruthenium(II) and hexaammineruthenium(III) ions

    Energy Technology Data Exchange (ETDEWEB)

    Smolenaers, P.J.; Beattie, J.K.

    1986-06-18

    The rate of the electron-self-exchange reaction between (Ru(NH/sub 3/)/sub 6/)/sup 3 +/ and (Ru(NH/sub 3/)/sub 6/)/sup 2 +/ has been measured by proton NMR line broadening. The system is complicated by the equation of (Ru(NH/sub 3/)/sub 6/)/sup 2 +/, which results in reduction of the small amount of (Ru(NH/sub 3/)/sub 6/)/sup 3 +/ present. To reduce this difficulty, measurements were performed at 4/sup 0/C. Rate constants are (6.6 +/- 1.0) x 10/sup 3/ and (9.9 +/- 0.2) X 10/sup 3/ M/sup -1/ s/sup -1/ for solutions of 0.125 and 0.250 M (Ru(NH/sub 3/)/sub 6/)Cl/sub 2/, respectively. These rate constants are in order-of-magnitude agreement with those previously reported. The reaction appears to be catalyzed by chloride ion. A rate constant for the uncatalyzed reaction at 4/sup 0/C and an ionic strength approx.0.5 M is estimated to be 3.3 x 10/sup 3/ M/sup -1/ s/sup -1/. The activation enthalpy is about 5 kcal mol/sup -1/.

  4. Structural investigations of borosilicate glasses containing MoO{sub 3} by MAS NMR and Raman spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Caurant, D., E-mail: daniel-caurant@enscp.f [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Ecole Nationale Superieure de Chimie de Paris (ENSCP, ParisTech), 11 rue Pierre et Marie Curie, 75231 Paris (France); Majerus, O.; Fadel, E.; Quintas, A. [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Ecole Nationale Superieure de Chimie de Paris (ENSCP, ParisTech), 11 rue Pierre et Marie Curie, 75231 Paris (France); Gervais, C. [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Universite Pierre et Marie Curie, 75252 Paris (France); Charpentier, T. [CEA, IRAMIS, Service Interdisciplinaire sur les Systemes Moleculaires et Materiaux, CEA Saclay, 91191 Gif-sur-Yvette (France); Neuville, D. [Physique des Mineraux et des Magmas, UMR-CNRS 7047, Institut de Physique du Globe, place Jussieu, 75252 Paris (France)

    2010-01-01

    High molybdenum concentration in glass compositions may lead to alkali and alkaline-earth molybdates crystallization during melt cooling that must be controlled particularly during the preparation of highly radioactive nuclear glassy waste forms. To understand the effect of molybdenum addition on the structure of a simplified nuclear glass and to know how composition changes can affect molybdates crystallization tendency, the structure of two glass series belonging to the SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-CaO-MoO{sub 3} system was studied by {sup 29}Si, {sup 11}B, {sup 23}Na MAS NMR and Raman spectroscopies by increasing MoO{sub 3} or B{sub 2}O{sub 3} concentrations. Increasing MoO{sub 3} amount induced an increase of the silicate network reticulation but no significant effect was observed on the proportion of BO{sub 4}{sup -} units and on the distribution of Na{sup +} cations in glass structure. By increasing B{sub 2}O{sub 3} concentration, a strong evolution of the distribution of Na{sup +} cations was observed that could explain the evolution of the nature of molybdate crystals (CaMoO{sub 4} or Na{sub 2}MoO{sub 4}) formed during melt cooling.

  5. Molecular vibrational investigation [FT-IR, FT-Raman, UV-Visible and NMR] on Bis(thiourea) Nickel chloride using HF and DFT calculations.

    Science.gov (United States)

    Anand, S; Sundararajan, R S; Ramachandraraja, C; Ramalingam, S; Durga, R

    2015-03-05

    In the present research work, the FT-IR, FT-Raman spectra of the Bis(thiourea) Nickel chloride (BTNC) were recorded and analyzed. The observed fundamental frequencies in finger print and functional group regions were assigned according to their uniqueness region. The computational calculations were carried out by HF and DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The present organo-metallic compound was made up of covalent and coordination covalent bonds. The modified vibrational pattern of the complex molecule associated with ligand group was analyzed. Furthermore, the (13)C NMR and (1)H NMR spectral data were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP/6-311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A investigation on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  6. Molecular vibrational investigation [FT-IR, FT-Raman, UV-Visible and NMR] on Bis(thiourea) Nickel chloride using HF and DFT calculations

    Science.gov (United States)

    Anand, S.; Sundararajan, R. S.; Ramachandraraja, C.; Ramalingam, S.; Durga, R.

    2015-03-01

    In the present research work, the FT-IR, FT-Raman spectra of the Bis(thiourea) Nickel chloride (BTNC) were recorded and analyzed. The observed fundamental frequencies in finger print and functional group regions were assigned according to their uniqueness region. The computational calculations were carried out by HF and DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The present organo-metallic compound was made up of covalent and coordination covalent bonds. The modified vibrational pattern of the complex molecule associated with ligand group was analyzed. Furthermore, the 13C NMR and 1H NMR spectral data were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP/6-311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A investigation on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed.

  7. Fused-Ring Derivatives of Quinoxalines: Spectroscopic Characterization and Photoinduced Processes Investigated by EPR Spin Trapping Technique

    Directory of Open Access Journals (Sweden)

    Zuzana Barbieriková

    2014-08-01

    Full Text Available 10-Ethyl-7-oxo-7,10-dihydropyrido[2,3-f]quinoxaline derivatives, synthesized as promising biologically/photobiologically active compounds were characterized by UV/vis, FT-IR and fluorescent spectroscopy. Photoinduced processes of these derivatives were studied by EPR spectroscopy, monitoring in situ the generation of reactive intermediates upon UVA (λmax = 365 nm irradiation. The formation of reactive oxygen species and further oxygen- and carbon-centered radical intermediates was detected and possible reaction routes were suggested. To quantify the investigated processes, the quantum yields of the superoxide radical anion spin-adduct and 4-oxo-2,2,6,6-tetramethylpiperidine N-oxyl generation were determined, reflecting the activation of molecular oxygen by the excited state of the quinoxaline derivative.

  8. Structural NMR assignment

    International Nuclear Information System (INIS)

    Procter, J.B.; Torda, A.E.

    1999-01-01

    Full text: General automated NMR assignment approaches are aimed at full heteronuclear assignment, which is needed for structure determination. Usually, full assignment requires at least as much spectral information as is used for structure generation. For large proteins, obtaining sufficient spectral information may require a number of sample preparations and many spectra, resulting in a significant overhead for the use of NMR in biochemical investigation. For a protein of biochemical interest one may already have an x-ray crystal structure, but spectral assignment is still needed to use NMR as a structural probe for ligand binding studies. In this situation it may be possible to use much less spectral information to make an assignment based purely on the correspondence of structural data to the measurements contained in a few simple spectra. We introduce a framework to accomplish this 'structural assignment', and give some observations on the practical requirements for a structural assignment to succeed

  9. Discrimination of sugarcane according to cultivar by 1H NMR and chemometric analyses

    Energy Technology Data Exchange (ETDEWEB)

    Alves Filho, Elenilson G.; Silva, Lorena M.A.; Choze, Rafael; Liao, Luciano M. [Laboratorio de Ressonancia Magnetica Nuclear, Instituto de Quimica, Universidade Federal de Goias (UFG), Goiania, GO (Brazil); Honda, Neli K.; Alcantara, Glaucia B. [Departamento de Quimica, Universidade Federal de Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil)

    2012-07-01

    Several technologies for the development of new sugarcane cultivars have mainly focused on the increase in productivity and greater disease resistance. Sugarcane cultivars are usually identified by the organography of the leaves and stems, the analysis of peroxidase and esterase isoenzyme activities and the total soluble protein as well as soluble solid content. Nuclear magnetic resonance (NMR) associated with chemometric analysis has proven to be a valuable tool for cultivar assessment. Thus, this article describes the potential of chemometric analysis applied to 1H high resolution magic angle spinning (HRMAS) and NMR in solution for the investigation of sugarcane cultivars. For this purpose, leaves from eight different cultivars of sugarcane were investigated by {sup 1}H NMR spectroscopy in combination with chemometric analysis. The approach shows to be a useful tool for the distinction and classification of different sugarcane cultivars as well as to access the differences on its chemical composition. (author)

  10. 13C NMR studies of the molecular flexibility of antidepressants

    International Nuclear Information System (INIS)

    Munro, S.L.; Andrews, P.R.; Craik, D.J.; Gale, D.J.

    1986-01-01

    The solution dynamics of a series of clinically potent antidepressants have been investigated by measuring 13 C NMR relaxation parameters. Correlation times and internal motional rates were calculated from spin-lattice relaxation times and nuclear Overhauser effects for the protonated carbons in mianserin, imipramine-like antidepressants, and amitriptyline-like antidepressants. These data were interpreted in terms of overall molecular tumbling, internal rotations, and inherent flexibility of these structures. Of particular interest was the conformational variability of the tricyclic nucleus of the tricyclic antidepressants, where the data indicated a fivefold difference in mobility of the dimethylene bridge of imipramine-like antidepressants relative to amitriptyline-like compounds. The implications of such a difference in internal motions is discussed in relation to previous NMR studies and to the reported differences in pharmacological activity of these antidepressants

  11. Investigation of spin-gapless semiconductivity and half-metallicity in Ti2MnAl-based compounds

    International Nuclear Information System (INIS)

    Lukashev, P.; Staten, B.; Hurley, N.; Kharel, P.; Gilbert, S.; Fuglsby, R.; Huh, Y.; Valloppilly, S.; Zhang, W.; Skomski, R.; Sellmyer, D. J.; Yang, K.

    2016-01-01

    The increasing interest in spin-based electronics has led to a vigorous search for new materials that can provide a high degree of spin polarization in electron transport. An ideal candidate would act as an insulator for one spin channel and a conductor or semiconductor for the opposite spin channel, corresponding to the respective cases of half-metallicity and spin-gapless semiconductivity. Our first-principle electronic-structure calculations indicate that the metallic Heusler compound Ti 2 MnAl becomes half-metallic and spin-gapless semiconducting if half of the Al atoms are replaced by Sn and In, respectively. These electronic structures are associated with structural transitions from the regular cubic Heusler structure to the inverted cubic Heusler structure.

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

    Science.gov (United States)

    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.

  13. $\\beta$-NMR of copper isotopes in ionic liquids

    CERN Multimedia

    We propose to test the feasibility of spin-polarization and $\\beta$-NMR studies on several short-lived copper isotopes, $^{58}$ Cu, $^{74}$Cu and $^{75}$Cu in crystals and liquids. The motivation is given by biological studies of Cu with $\\beta$-NMR in liquid samples, since Cu is present in a large number of enzymes involved in electron transfer and activation of oxygen. The technique is based on spin-polarization via optical pumping in the new VITO beamline. We will use the existing lasers, NMR magnet and NMR chambers and we will prepare a new optical pumping system. The studies will be devoted to tests of achieved $\\beta$-asymmetry in solid hosts, the behaviour of asymmetry when increasing vacuum, and finally NMR scans in ionic liquids. The achieved spin polarization will be also relevant for the plans to measure with high precision the magnetic moments of neutron-rich Cu isotopes.

  14. Graphical programming for pulse automated NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Belmonte, S.B. [Universidade do Estado, Rio de Janeiro, RJ (Brazil); Oliveira, I.S.; Guimaraes, A.P. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1999-01-01

    We describe a software program designed to control a broadband pulse Nuclear Magnetic Resonance (NMR) spectrometer used in zero-field NMR studies of magnetic metals. The software is written in the graphical language LabVIEW. This type of programming allows modifications and the inclusion of new routines to be easily made by the non-specialist, without changing the basic structure of the program. The program corrects for differences in the gain of the two acquisition channels [U (phase) and V (quadrature)], and automatic baseline subtraction. We present examples of measurements of NMR spectra, spin-echo decay (T{sub 2}), and quadrupolar oscillations, performed in magnetic intermetallic compounds. (author)

  15. Investigation of the Maximum Spin-Up Coefficients of Friction Obtained During Tests of a Landing Gear Having a Static-Load Rating of 20,000 Pounds

    Science.gov (United States)

    Batterson, Sidney A.

    1959-01-01

    An experimental investigation was made at the Langley landing loads track to obtain data on the maximum spin-up coefficients of friction developed by a landing gear having a static-load rating of 20,000 pounds. The forward speeds ranged from 0 to approximately 180 feet per second and the sinking speeds, from 2.7 feet per second to 9.4 feet per second. The results indicated the variation of the maximum spin-up coefficient of friction with forward speed and vertical load. Data obtained during this investigation are also compared with some results previously obtained for nonrolling tires to show the effect of forward speed.

  16. 2D-NMR investigation and in vitro evaluation of antioxidant, antigenotoxic and estrogenic/antiestrogenic activities of strawberry grape.

    Science.gov (United States)

    D'Abrosca, Brigida; Lavorgna, Margherita; Scognamiglio, Monica; Russo, Chiara; Graziani, Vittoria; Piscitelli, Concetta; Fiorentino, Antonio; Isidori, Marina

    2017-07-01

    Strawberry grape is considered beneficial due to its extensive phytochemical properties. To expand the knowledge about the chemical constituents and the biological activities of the whole plant, 2D-NMR investigation has been carried out on pulp, peel, seeds, stalks and leaves. Catechin and epicatechin were identified as the main constituents of the seed extract, quercetin and ferulic acid were detected in the leaves and malvidin and cyanidin glucopyranoside in the peels. The leaf, stalk and seed extracts were found to be very rich in phytochemicals and were tested for their ability to reduce the mutagenicity and genotoxicity of standard agents via Salmonella mutagenicity assay and SOS chromotest, respectively. Moreover, the estrogen/antiestrogen-like activity was evaluated on the MCF-7 estrogen-responsive cells. Seed and stalk extracts had an elevated antimutagenic/antigenotoxic activity. Stalk extracts highly reduced the proliferative effect of natural estrogen, 17β-estradiol. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. An investigation of the transmission of electronic effects in a series of 5- and 6-substituted benzazoles by the methods of basic deuterium exchange and nmr spectroscopy

    International Nuclear Information System (INIS)

    Tupitsyn, I.F.; Belyashova, A.I.; Zatsepina, N.N.

    1985-01-01

    The kinetics of deuterium exchange at the methyl groups in 5- and 6-substituted 2-methylbenzothiazoles, 6-substituted 2-methylbenzoxazoles, and 5-substituted 1,2-dimethylbenzimidazoles have been studied. A quantitative estimate of the influence of the substituents on the free energy of activation of deuterium exchange and on the chemical shifts in the 1 H, 13 C, and 19 F NMR spectra of the benzazoles investigated and of the substituted quinolines and napthalenes used as standard systems has been made with the aid of correlation analysis. It has been shown that the decrease in the transmission capacity of the benzazole nucleus in the transition state of the reaction as compared with the initial state is due to the influence of cross-conjugation effects disturbing the additive nature of the electronic interactions. The question of the probable structure of the transition state of the reaction is discussed

  18. Temperature dependent spin and orbital magnetization in TbCo{sub 2}: Magnetic Compton scattering and first-principles investigations

    Energy Technology Data Exchange (ETDEWEB)

    Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, M.L. Sukhadia University, Udaipur 313001 (India); Mund, H.S. [Department of Physics, M.L. Sukhadia University, Udaipur 313001 (India); Sahariya, Jagrati [Department of Physics, Manipal University Jaipur, Jaipur 303007 (India); Dashora, Alpa [Department of Physics, University of Mumbai, Vidyanagri, Santacruz (E), Mumbai 400098 (India); Halder, Madhumita; Yusuf, S.M. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute, SPring8, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

    2015-06-05

    Highlights: • Presented temperature dependent spin momentum densities in TbCo{sub 2}. • Explored spin and orbital magnetic moments at different sites. • Contribution of local and itinerant moments in TbCo{sub 2} is explained. • First-principles calculations are performed to supplement the experiment. - Abstract: Spin-polarized Compton profiles of TbCo{sub 2} have been measured to elucidate the interesting behavior of spin and orbital moments at different temperatures. The magnetic Compton profiles (MCPs) have been analyzed in terms of site specific spin moments due to Tb-4f electrons, Co and itinerant electrons. The temperature dependence of the orbital moment has been deduced using Compton and magnetometry data ranging between 6 and 300 K. The present data exhibit a decrease in the ratio of orbital to spin moments from 43.9% to 35.0% (while going from 6 to 300 K). First-principles calculations within DFT + U scheme have also been performed to confirm the spin-, orbital- and site specific-magnetic moments in TbCo{sub 2}. An antiparallel exchange coupling between the Tb-4f and Co spin moments is found. The orbital moment is found to have a parallel coupling with the Tb spin moment, as evident from the experimental MCPs. From first-principles data it is seen that the orbital moments of Tb and Co sites are antiparallel to each other, as in the case of their spin magnetic moments. The present experimental study also shows an existence of an itinerant moment which is coupled ferromagnetically with the Tb-4f spin moment.

  19. Nonadiabatic Spin Torque Investigated Using Thermally Activated Magnetic Domain Wall Dynamics

    DEFF Research Database (Denmark)

    Eltschka, M.; Woetzel, Mathias; Rhensius, J.

    2010-01-01

    Using transmission electron microscopy, we investigate the thermally activated motion of domain walls (DWs) between two positions in Permalloy (Ni80Fe20) nanowires at room temperature. We show that this purely thermal motion is well described by an Arrhenius law, allowing for a description...

  20. Optimized strategy of 1H and 13C solid-state NMR methods to investigate water dynamics in soil organic matter as well as the influence of crystallinity of poly(methylene) segments

    Science.gov (United States)

    Bertmer, Marko; Jaeger, Alexander; Schwarz, Jette; Schaumann, Gabriele

    2010-05-01

    Water plays a crucial role in soil organic matter (SOM) having various different functions such as transport of material, elution of ,e. g., pollutants in soil, and also the sequestration of humic substances. Furthermore, the generation and quantification of hydrophilic and hydrophobic regions in soil has several effects on SOM which can also include the storage amount and time of certain material, especially chemical pollutants. The importance of water in soil is also documented by the multitude of scientific approaches to characterize soils including diffusion NMR to study the water channel structure in soil. Our focus is on the study of water dynamics and soil structure to elucidate mechanisms of physicochemical aging. The approach uses the application of various solid-state NMR techniques - including 1H and 13C NMR - to get a multitude of information on SOM. In non-rotating samples, 1H lines are usually very broad and unstructured. Nevertheless, this rather simple technique allows for a differentiation of 1H containing chemicals based on their dynamics in soil. This includes rather solid soil components and solid as well as mobile water molecules. Based on an optimized 1H solid-state NMR strategy to study soil material together with a straightforward lineshape analysis, a series of soils and peats are characterized. Although even 1H NMR with sample spinning (MAS) often gives only limited information on different structures, we present results on the application of 2D 1H-1H phase-modulated Lee-Goldburg sequences (PMLG), that show already at medium spinning speeds the separation of functional groups. Their quantification can be correlated with sample composition, type of sample conditioning, and other parameters such as cation type or concentration and heat treatment. We are especially interested to correlate NMR data with DSC measurements based on a certain heat treatment of the soils. Our proposed model describes the presence of water in soil as a matrix

  1. Low energy nuclear spin excitations in Ho metal investigated by high resolution neutron spectroscopy.

    Science.gov (United States)

    Chatterji, Tapan; Jalarvo, Niina

    2013-04-17

    We have investigated the low energy excitations in metallic Ho by high resolution neutron spectroscopy. We found at T = 3 K clear inelastic peaks in the energy loss and energy gain sides, along with the central elastic peak. The energy of this low energy excitation, which is 26.59 ± 0.02 μeV at T = 3 K, decreased continuously and became zero at TN ≈ 130 K. By fitting the data in the temperature range 100-127.5 K with a power law we obtained the power-law exponent β = 0.37 ± 0.02, which agrees with the expected value β = 0.367 for a three-dimensional Heisenberg model. Thus the energy of the low energy excitations can be associated with the order parameter.

  2. Electronic [UV-Visible] and vibrational [FT-IR, FT-Raman] investigation and NMR-mass spectroscopic analysis of terephthalic acid using quantum Gaussian calculations.

    Science.gov (United States)

    Karthikeyan, N; Prince, J Joseph; Ramalingam, S; Periandy, S

    2015-03-15

    In this research work, the vibrational IR, polarization Raman, NMR and mass spectra of terephthalic acid (TA) were recorded. The observed fundamental peaks (IR, Raman) were assigned according to their distinctiveness region. The hybrid computational calculations were carried out for calculating geometrical and vibrational parameters by DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The molecular mass spectral data related to base molecule and substitutional group of the compound was analyzed. The modification of the chemical property by the reaction mechanism of the injection of dicarboxylic group in the base molecule was investigated. The (13)C and (1)H NMR spectra were simulated by using the gauge independent atomic orbital (GIAO) method and the absolute chemical shifts related to TMS were compared with experimental spectra. The study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, were performed by hybrid Gaussian calculation methods. The orbital energies of different levels of HOMO and LUMO were calculated and the molecular orbital lobe overlapping showed the inter charge transformation between the base molecule and ligand group. From the frontier molecular orbitals (FMO), the possibility of electrophilic and nucleophilic hit also analyzed. The NLO activity of the title compound related to Polarizability and hyperpolarizability were also discussed. The present molecule was fragmented with respect to atomic mass and the mass variation depends on the substitutions have also been studied. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  3. Electronic [UV-Visible] and vibrational [FT-IR, FT-Raman] investigation and NMR-mass spectroscopic analysis of terephthalic acid using quantum Gaussian calculations

    Science.gov (United States)

    Karthikeyan, N.; Joseph Prince, J.; Ramalingam, S.; Periandy, S.

    2015-03-01

    In this research work, the vibrational IR, polarization Raman, NMR and mass spectra of terephthalic acid (TA) were recorded. The observed fundamental peaks (IR, Raman) were assigned according to their distinctiveness region. The hybrid computational calculations were carried out for calculating geometrical and vibrational parameters by DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The molecular mass spectral data related to base molecule and substitutional group of the compound was analyzed. The modification of the chemical property by the reaction mechanism of the injection of dicarboxylic group in the base molecule was investigated. The 13C and 1H NMR spectra were simulated by using the gauge independent atomic orbital (GIAO) method and the absolute chemical shifts related to TMS were compared with experimental spectra. The study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, were performed by hybrid Gaussian calculation methods. The orbital energies of different levels of HOMO and LUMO were calculated and the molecular orbital lobe overlapping showed the inter charge transformation between the base molecule and ligand group. From the frontier molecular orbitals (FMO), the possibility of electrophilic and nucleophilic hit also analyzed. The NLO activity of the title compound related to Polarizability and hyperpolarizability were also discussed. The present molecule was fragmented with respect to atomic mass and the mass variation depends on the substitutions have also been studied.

  4. Structural changes of humic acids from sinking organic matter and surface sediments investigated by advanced solid-state NMR: Insights into sources, preservation and molecularly uncharacterized components

    Science.gov (United States)

    Mao, Jingdong; Tremblay, Luc; Gagné, Jean-Pierre

    2011-12-01

    Knowledge of the structural changes that particulate organic matter (POM) undergoes in natural systems is essential for determining its reactivity and fate. In the present study, we used advanced solid-state NMR techniques to investigate the chemical structures of sinking particulate matter collected at different depths as well as humic acids (HAs) extracted from these samples and underlying sediments from the Saguenay Fjord and the St. Lawrence Lower Estuary (Canada). Compared to bulk POM, HAs contain more non-polar alkyls, aromatics, and aromatic C-O, but less carbohydrates (or carbohydrate-like structures). In the two locations studied, the C and N contents of the samples (POM and HAs) decreased with depth and after deposition onto sediments, leaving N-poor but O-enriched HAs and suggesting the involvement of partial oxidation reactions during POM microbial degradation. Advanced NMR techniques revealed that, compared to the water-column HAs, sedimentary HAs contained more protonated aromatics, non-protonated aromatics, aromatic C-O, carbohydrates (excluding anomerics), anomerics, OC q, O-C q-O, OCH, and OCH 3 groups, but less non-polar alkyls, NCH, and mobile CH 2 groups. These results are consistent with the relatively high reactivity of lipids and proteins or peptides. In contrast, carbohydrate-like structures were selectively preserved and appeared to be involved in substitution and copolymerization reactions. Some of these trends support the selective degradation (or selective preservation) theory. The results provide insights into mechanisms that likely contribute to the preservation of POM and the formation of molecules that escape characterization by traditional methods. Despite the depletion of non-polar alkyls with depth in HAs, a significant portion of their general structure survived and can be assigned to a model phospholipid. In addition, little changes in the connectivities of different functional groups were observed. Substituted and copolymerized

  5. Complete 1H NMR assignments of pyrrolizidine alkaloids and a new eudesmanoid from Senecio polypodioides.

    Science.gov (United States)

    Villanueva-Cañongo, Claudia; Pérez-Hernández, Nury; Hernández-Carlos, Beatriz; Cedillo-Portugal, Ernestina; Joseph-Nathan, Pedro; Burgueño-Tapia, Eleuterio

    2014-05-01

    Chemical investigation of the aerial parts of Senecio polypodioides lead to the isolation of the new eudesmanoid 1β-angeloyloxyeudesm-7-ene-4β,9α-diol (1) and the known dirhamnosyl flavonoid lespidin (3), while from roots, the known 7β-angeloyloxy-1-methylene-8α-pyrrolizidine (5) and sarracine N-oxide (6), as well as the new neosarracine N-oxide (8), were obtained. The structure of 1 and 8 was elucidated by spectral means. Complete assignments of the (1)H NMR data for 5, 6, sarracine (7), and 8 were made using one-dimensional and two-dimensional NMR experiments and by application of the iterative full spin analysis of the PERCH NMR software. Copyright © 2014 John Wiley & Sons, Ltd.

  6. NMR system and method having a permanent magnet providing a rotating magnetic field

    Science.gov (United States)

    Schlueter, Ross D [Berkeley, CA; Budinger, Thomas F [Berkeley, CA

    2009-05-19

    Disclosed herein are systems and methods for generating a rotating magnetic field. The rotating magnetic field can be used to obtain rotating-field NMR spectra, such as magic angle spinning spectra, without having to physically rotate the sample. This result allows magic angle spinning NMR to be conducted on biological samples such as live animals, including humans.

  7. Neutron Scattering Investigation of the Temperature Dependence of Long-Wavelength Spin Waves in Ferromagnetic Rb2CrCI4

    DEFF Research Database (Denmark)

    Hutchings, M T; Als-Nielsen, Jens Aage; Lindgård, Per-Anker

    1981-01-01

    The long-wavelength spin waves in Rb2CrCl4, a nearly two-dimensional ferromagnet, have been investigated at several temperatures below Tc=52.4K using neutron inelastic scattering techniques. The data have been analysed in terms of a Hartree-Fock theory using matching-matrix elements to give...

  8. NMR study of strongly correlated electron systems

    Science.gov (United States)

    Kitaoka, Y.; Tou, H.; Zheng, G.-q.; Ishida, K.; Asayama, K.; Kobayashi, T. C.; Kohda, A.; Takeshita, N.; Amaya, K.; Onuki, Y.; Geibel, G.; Schank, C.; Steglich, F.

    1995-02-01

    Various types of ground states in strongly correlated electron systems have been systematically investigated by means of NMR/NQR at low temperatures under high magnetic field and pressure. We focus on two well-known heavy-electron families, CeCu 2X 2 (X = Si and Ge) (Ce(122)) and UM 2Al 3 (M = Ni and Pd) (U(123)). The Cu NQR experiments on CeCu 2X 2 under high pressure indicate that the physical property of CeCu 2Ge 2 at high pressure, i.e. above the transition at 7.6 GPa from antiferromagnetic (AF) to superconductivity, are clearly related to tha CeCu 2Si 2 at ambient pressure. In addition to the H-T phase diagram established below 7 T, NMR and specific heat experiments on polycrystal CeCu 2.05Si 2 have revealed the presence of a new phase above 7 T. In a high-quality polycrystal of UPd 2Al 3 with a record high- Tc of 2 K at ambient pressure and the narrowest Al NQR line width, the nuclear-spin lattice relaxation rate, 27(1/ T1) measured in zero field has been found to obey the T3 law down to 0.13 K, giving strong evidence that the energy gap vanishes along lines on the Fermi surface. Thus it seems that all heavy-electron superconductors exhibit lines of zero gap, regardless of their different magnetic properties.

  9. Investigations into light-front interactions for massless fields (I): non-constructibility of higher spin quartic amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson, Anders K.H. [Academy of Textiles, Engineering and Economics, University of Borås,Allégatan 1, SE-50190 Borås (Sweden)

    2016-12-27

    The dynamical commutators of the light-front Poincaré algebra yield first order differential equations in the p{sup +} momenta for the interaction vertex operators. The homogeneous solution to the equation for the quartic vertex is studied. Consequences as regards the constructibility assumption of quartic higher spin amplitudes from cubic amplitudes are discussed. The existence of quartic contact interactions unrelated to cubic interactions by Poincaré symmetry indicates that the higher spin S-matrix is not constructible. Thus quartic amplitude based no-go results derived by BCFW recursion for Minkowski higher spin massless fields may be circumvented.

  10. Application of spin-sensitive electron spectroscopies to investigations of electronic and magnetic properties of solid surfaces and epitaxial systems: Progress report, 1 January 1987-31 December 1987

    International Nuclear Information System (INIS)

    Walters, G.K.; Dunning, F.B.

    1987-08-01

    Research during the second year of this grant has focussed on: (1) investigation of surface magnetic structure of Ni(lll) by Spin-Polarized Low Energy Electron Diffraction (SPLEED) and overhaul of the apparatus to incorporate additional spin-dependent electron spectroscopies and epitaxial growth capabilities; and (2) investigation of dynamics of metastable atom deexcitation at magnetic and adsorbate-covered surfaces using Spin-Polarized Metastable Deexcitation Spectroscopy (SPMDS)

  11. In child and adult migraineurs the somatosensory cortex stands out … again: An arterial spin labeling investigation.

    Science.gov (United States)

    Youssef, Andrew M; Ludwick, Allison; Wilcox, Sophie L; Lebel, Alyssa; Peng, Ke; Colon, Elisabeth; Danehy, Amy; Burstein, Rami; Becerra, Lino; Borsook, David

    2017-08-01

    Over the past decade, human brain imaging investigations have reported altered regional cerebral blood flow (rCBF) in the interictal phase of migraine. However, there have been conflicting findings across different investigations, making the use of perfusion imaging in migraine pathophysiology more difficult to define. These inconsistencies may reflect technical constraints with traditional perfusion imaging methods such as single-photon emission computed tomography and positron emission tomography. Comparatively, pseudocontinuous arterial spin labeling (pCASL) is a recently developed magnetic resonance imaging technique that is noninvasive and offers superior spatial resolution and increased sensitivity. Using pCASL, we have previously shown increased rCBF within the primary somatosensory cortex (S1) in adult migraineurs, where blood flow was positively associated with migraine frequency. Whether these observations are present in pediatric and young adult populations remains unknown. This is an important question given the age-related variants of migraine prevalence, symptomology, and treatments. In this investigation, we used pCASL to quantitatively compare and contrast blood flow within S1 in pediatric and young adult migraineurs as compared with healthy controls. In migraine patients, we found significant resting rCBF increases within bilateral S1 as compared with healthy controls. Furthermore, within the right S1, we report a positive correlation between blood flow value with migraine attack frequency and cutaneous allodynia symptom profile. Our results reveal that pediatric and young adult migraineurs exhibit analogous rCBF changes with adult migraineurs, further supporting the possibility that these alterations within S1 are a consequence of repeated migraine attacks. Hum Brain Mapp 38:4078-4087, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  12. Toward increased concentration sensitivity for continuous wave EPR investigations of spin-labeled biological macromolecules at high fields

    Science.gov (United States)

    Song, Likai; Liu, Zhanglong; Kaur, Pavanjeet; Esquiaqui, Jackie M.; Hunter, Robert I.; Hill, Stephen; Smith, Graham M.; Fanucci, Gail E.

    2016-04-01

    High-field, high-frequency electron paramagnetic resonance (EPR) spectroscopy at W-(∼94 GHz) and D-band (∼140 GHz) is important for investigating the conformational dynamics of flexible biological macromolecules because this frequency range has increased spectral sensitivity to nitroxide motion over the 100 ps to 2 ns regime. However, low concentration sensitivity remains a roadblock for studying aqueous samples at high magnetic fields. Here, we examine the sensitivity of a non-resonant thin-layer cylindrical sample holder, coupled to a quasi-optical induction-mode W-band EPR spectrometer (HiPER), for continuous wave (CW) EPR analyses of: (i) the aqueous nitroxide standard, TEMPO; (ii) the unstructured to α-helical transition of a model IDP protein; and (iii) the base-stacking transition in a kink-turn motif of a large 232 nt RNA. For sample volumes of ∼50 μL, concentration sensitivities of 2-20 μM were achieved, representing a ∼10-fold enhancement compared to a cylindrical TE011 resonator on a commercial Bruker W-band spectrometer. These results therefore highlight the sensitivity of the thin-layer sample holders employed in HiPER for spin-labeling studies of biological macromolecules at high fields, where applications can extend to other systems that are facilitated by the modest sample volumes and ease of sample loading and geometry.

  13. Investigating the compatibility of PEEK polymer for the fabrication of sample cells for use in muon spin spectroscopy

    International Nuclear Information System (INIS)

    Chandrasena, L; McKenzie, I; Brodovitch, J-C; Mozafari, M; Percival, P W; Cottrell, S P

    2014-01-01

    Polyether ether ketone (PEEK) is a thermoplastic polymer with a wide range of applications due to its chemical inertness and thermal stability, and for these reasons sample cells for gas and liquid phase μSR have been constructed from PEEK. Muon levelcrossing resonance (μLCR) studies of PEEK revealed a broad, strong μLCR signal that, we hypothesize, is due to multiple overlapping resonances from the various muonium (Mu) adducts of PEEK. To investigate this, two monomer units from PEEK (4,4'-dihydroxybenzophenone and para-dimethoxybenzene) were studied in solution using transverse-field muon spin rotation (TF-μSR) and μLCR. Two different muoniated radicals were formed by Mu addition to 4,4 / - dihydroxybenzophenone and one radical was formed in para-dimethoxybenzene. The μSR spectra were assigned by comparing the experimentally measured muon and proton hyperfine coupling constants with values calculated for the possible structures using Gaussian-09 software with the B3LYP functional and 6-31G basis set. Good agreement was found for cyclohexadienyl- type radicals formed by Mu addition to the benzene rings of the monomer units. We can also infer that these radicals are being formed in PEEK, and based on this we conclude that sample cells made of PEEK are unsuitable for many types of μSR experiment

  14. Self-condensation of n-(N-propyl)butanimine: NMR and mass spectral analyses and investigation by theoretical calculation

    Energy Technology Data Exchange (ETDEWEB)

    Manfrini, Rozangela Magalhaes; Teixeira, Flavia Rodrigues; Pilo-Veloso, Dorila; Alcantara, Antonio Flavio de Carvalho, E-mail: aalcantara@zeus.qui.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Inst. de Ciencias Exatas. Dept. de Quimica; Nelson, David Lee [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Fac. de Farmacia. Dept. de Quimica; Siqueira, Ezequias Pessoa de [Centro de Pesquisas Rene Rachou (FIOCRUZ), Belo Horizonte, MG (Brazil)

    2012-07-01

    The stability of N-propylbutanimine (1) was investigated under different experimental conditions. The acid-catalyzed self-condensation that produced the E-enimine (4) and Z-inimine (5) was studied by experimental analyses and theoretical calculations. Since the calculations for the energy of 5 indicated that it had a lower energy than 4, yet 4 was the principal product, the self-condensation of 1 must be kinetically controlled. (author)

  15. nmr spectroscopic study and dft calculations of vibrational analyses ...

    African Journals Online (AJOL)

    Preferred Customer

    Furthermore, GIAO/DFT (Gauge Including Atomic Orbitals/Density. Functional Theory) approach is extensively used for the calculations of chemical shifts for various types of compounds [14-20]. During the last decade an important breakthrough in the calculation of NMR spin-spin coupling constants took place when the ...

  16. Investigation of tautomeric transformations of adducts of 7,8-dicarba-nido-undecaborana(11) with derivatives of pyridine by 11B NMR spectroscopy method

    International Nuclear Information System (INIS)

    Volkov, O.V.; Il'inchik, E.A.; Volkov, V.V.

    1999-01-01

    Tautomeric transformations are investigated in solutions of o-carborane(12) derivatives 7,8-C 2 B 9 H 11 ·Py(X), where Py(X)=4-picoline (4-CH 3 -C 5 H 4 N), 3-picoline (3-CH 3 -C 5 H 4 N), 4-stilbazol (4-C 6 H 5 -C 2 H 2 -C 5 H 4 N), 3-bromopyridine (3-Br-C 5 H 4 N) and 7,8-C 2 B 9 H 10 I·C 5 H 5 N. Uncovered tautomeric transformations are bound with migration of bridge hydrogen of C 2 B 9 H 11 cluster assisting in structure of these compounds. Signal of boron nuclei in 11 B NMR spectra is observed in the region of high field of spectrum if the nearest two atoms of boron are bounded by bridge hydrogen additionally. That permits to fix happening dynamic structural transformations of adducts investigated. The dependence of tautomeric equilibrium on nature of substituents introduced in heterocyclic ligand and carborane cluster. Increase of electron-acceptor properties of substituent induces displacement of equilibrium in the direction of tautomer bridge hydrogen in which is removed from boron atom bounded with substituent [ru

  17. Investigation of the preventive effect of Sijunzi decoction on mitomycin C-induced immunotoxicity in rats by 1H NMR and MS-based untargeted metabolomic analysis.

    Science.gov (United States)

    Guan, Zhibo; Wu, Juan; Wang, Cancan; Zhang, Fang; Wang, Yinan; Wang, Miao; Zhao, Min; Zhao, Chunjie

    2018-01-10

    Sijunzi decoction (SJZD) is a well known traditional Chinese prescription used for the treatment of gastrointestinal disorders and immunity enhancement. It has been found to indeed improve life quality of chemotherapy patients and extensive used in clinical conbined with chemotherapeutics for the treatment of cancer. The aim of this study was to investigate the preventive effect of the immunotoxicity of SJZD on mitomycin C (MMC) and the metabolic mechanism of action. NMR and MS-based metabolomics approaches were combined for monitoring MMC-induced immunotoxicity and the protective effect of SJZD. Body weight change and mortality, histopathological observations and relative viscera weight determinations of spleen and thymus, sternum micronucleus assay and hematological analysis were used to confirm the immunotoxicity and attenuation effects. An OPLS-DA approach was used to screen potential biomarkers of immunotoxicity and the MetaboAnalyst and KEGG PATHWAY Database were used to investigate the metabolic pathways. 8 biomarkers in plasma samples, 19 in urine samples and 10 in spleen samples were identified as being primarily involved in amino acid metabolism, carbohydrate metabolism and lipid metabolism. The most critical pathway was alanine, aspartate and glutamate metabolism. The variations in biomarkers revealed the preventive effect of the immunotoxicity of SJZD on MMC and significant for speculating the possible metabolic mechanism. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

  18. Ground State of Quasi-One Dimensional Competing Spin Chain Cs2Cu2Mo3O12 at zero and Finite Fields

    Science.gov (United States)

    Matsui, Kazuki; Goto, Takayuki; Angel, Julia; Watanabe, Isao; Sasaki, Takahiko; Hase, Masashi

    The ground state of competing-spin-chain Cs2Cu2Mo3O12 with the ferromagnetic exchange interaction J1 = -93 K on nearest-neighboring spins and the antiferromagnetic one J2 = +33 K on next-nearest-neighboring spins was investigated by ZF/LF-μSR and 133Cs-NMR in the 3He temperature range. The zero-field μSR relaxation rate λ shows a significant increase below 1.85 K, suggesting the existence of magnetic order, which is consistent with the recent report on the specific heat. However, LF decoupling data at the lowest temperature 0.3 K indicate that the spins fluctuate dynamically, suggesting that the system is in a quasi-static ordered state under zero field. This idea is further supported by the fact that the broadening in NMR spectra below TN is weakened at low field below 2 T.

  19. Nuclear spin: Fifty years of ups and downs

    Energy Technology Data Exchange (ETDEWEB)

    Pines, A. [Lawrence Berkeley National Lab., CA (United States)

    1996-12-31

    Rumors of its demise notwithstanding, nuclear magnetic resonance (NMR) continues to flourish fifty years after our birth. The lecture will be a reminiscence about moments of excitation, coherence and relaxation in the history of NMR which produced, among other developments, spin echoes and time reversal, Fourier transform and multidimensional spectroscopy, magnetic resonance imaging, and high resolution solid state NMR. Applications of modern NMR spectroscopy cut across the boundaries of physics, chemistry, materials, biology and medicine.

  20. Investigation of nuclei near N = 82 and Z = 64 VIA radioactive decay of high-spin isomers

    International Nuclear Information System (INIS)

    Toth, K.S.

    1979-01-01

    An island of very high spin isomers was found recently in neutron-deficient Gd-Lu nuclei near the N = 82 closed shell in (H.I.,xn) measurements. This exciting discovery has led to a large number of experiments trying to identify the structures of these isomers and the nuclei in which they occur. These attempts have been helped in many instances by available spectroscopic information at low excitation energies. A systematic investigation of the low-lying structure of nuclei near N = 82 and Z greater than or equal to 64 was carried out. Heavy-ion beams were used to produce proton-rich isotopes which were then transported, with the use of gas-jet systems, to shielded areas where singles and coincidence γ-ray measurements could be made. Earlier investigations dealt with the decay of terbium ( 146-149 Tb) and dysprosium ( 147-152 Dy) nuclei. During the past two years the research program was extended to holmium nuclides (A less than or equal to 152) produced in 10 B bombardments of samarium. Two new isotopes, 149 Ho and 148 Ho, were identified. The decay data of 21-s 149 Ho supplement in-beam results and locate the hg/ 2 neutron state in 149 Dy to be at 1091 keV. The most intense γ-ray associated with 9-s 148 Ho has an energy of 1688 keV. It is possibly the first-excited to ground-state transition in 148 Dy. Recent in-beam measurements have shown that the first-excited state in 146 Gd is, unespectedly, 3 - in contrast to doubly evenN = 82 nuclei below gadolinium where it is 2 + . It would be interesting to determine whether the 1688-keV level in 148 Dy, the next nucleus in this isotonic series, is 2reverse arrow or 3 - in character. 12 references

  1. Solid-state NMR basic principles and practice

    CERN Document Server

    Apperley, David C; Hodgkinson, Paul

    2014-01-01

    Nuclear Magnetic Resonance (NMR) has proved to be a uniquely powerful and versatile tool for analyzing and characterizing chemicals and materials of all kinds. This book focuses on the latest developments and applications for "solid-state" NMR, which has found new uses from archaeology to crystallography to biomaterials and pharmaceutical science research. The book will provide materials engineers, analytical chemists, and physicists, in and out of lab, a survey of the techniques and the essential tools of solid-state NMR, together with a practical guide on applications. In this concise introduction to the growing field of solid-state nuclear magnetic resonance spectroscopy The reader will find: * Basic NMR concepts for solids, including guidance on the spin-1/2 nuclei concept * Coverage of the quantum mechanics aspects of solid state NMR and an introduction to the concept of quadrupolar nuclei * An understanding relaxation, exchange and quantitation in NMR * An analysis and interpretation of NMR data, with e...

  2. Fully automated system for pulsed NMR measurements

    International Nuclear Information System (INIS)

    Cantor, D.M.

    1977-01-01

    A system is described which places many of the complex, tedious operations for pulsed NMR experiments under computer control. It automatically optimizes the experiment parameters of pulse length and phase, and precision, accuracy, and measurement speed are improved. The hardware interface between the computer and the NMR instrument is described. Design features, justification of the choices made between alternative design strategies, and details of the implementation of design goals are presented. Software features common to all the available experiments are discussed. Optimization of pulse lengths and phases is performed via a sequential search technique called Uniplex. Measurements of the spin-lattice and spin-spin relaxation times and of diffusion constants are automatic. Options for expansion of the system are explored along with some of the limitations of the system

  3. Effective Floquet Hamiltonian for spin I = 1 in magic angle spinning ...

    Indian Academy of Sciences (India)

    WINTEC

    Floquet Hamiltonians; contact transformations in NMR; Spin-1 MAS NMR; effective Ham- iltonians. 1. Introduction. Solid state nuclear magnetic resonance spectroscopy is an important technique to study structures, dyna- mics and electric charge distribution around nuclei in solids. It is also more difficult to perform and ana-.

  4. Nuclear Spin-Spin Coupling in HD, HT, and DT

    Science.gov (United States)

    Puchalski, Mariusz; Komasa, Jacek; Pachucki, Krzysztof

    2018-02-01

    The interaction between nuclear spins in a molecule is exceptionally sensitive to the physics beyond the standard model. However, all present calculations of the nuclear spin-spin coupling constant J are burdened by computational difficulties, which hinders the comparison to experimental results. Here, we present a variational approach and calculate the constant J in the hydrogen molecule with the controlled numerical precision, using the adiabatic approximation. The apparent discrepancy with experimental result is removed by an analysis of nonadiabatic effects based on the experimental values of the J constant for HD, HT, and DT molecules. This study significantly improves the reliability of the NMR theory for searching new physics in the spin-spin coupling.

  5. Spin drift and spin diffusion currents in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Idrish Miah, M [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au

    2008-09-15

    On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  6. Spin drift and spin diffusion currents in semiconductors

    Directory of Open Access Journals (Sweden)

    M Idrish Miah

    2008-01-01

    Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  7. Spin drift and spin diffusion currents in semiconductors

    International Nuclear Information System (INIS)

    Idrish Miah, M

    2008-01-01

    On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  8. Structural Characterization of Febuxostat/l-Pyroglutamic Acid Cocrystal Using Solid-State 13C-NMR and Investigational Study of Its Water Solubility

    Directory of Open Access Journals (Sweden)

    Ji-Hun An

    2017-12-01

    Full Text Available Febuxostat (FB is a poorly water-soluble drug that belongs to BCS class II. The drug is employed for the treatment of inflammatory disease arthritis urica (gout, and the free base, FB form-A, is most preferred for drug formulation. In order to achieve a goal of improving the water solubility of FB form-A, this study was carried out using the cocrystallization technique called the liquid-assisted grinding method to produce FB cocrystals. Here, five amino acids containing amine (NH, oxygen (O, and hydroxyl (OH functional groups, and possessing difference of pKa less than 3 with FB, were selected as coformers. Then, solvents including methanol, ethanol, isopropyl alcohol, n-hexane, dichloromethane, and acetone were used for the cocrystal screening. As a result, a cocrystal was obtained when acetone and l-pyroglutamic acid (PG of 0.5 eq. were employed as solvent and coformer, respectively. The ratio of 2:1, which is the ratio of FB to PG within FB-PG cocrystal, was predicted by means of solid-state CP/MAS 13C-NMR, solution-state NMR (1H, 13C, and 2D and FT-IR. Moreover, Powder X-ray Diffraction (PXRD, Differential Scanning Calorimetry (DSC, and Thermogravimetric Analysis (TGA were used to investigate the characteristics of FB-PG cocrystal. In addition, comparative solubility tests between FB-PG cocrystal and FB form-A were conducted in deionized water and under simulated gastrointestinal pH (1.2, 4, and 6.8 conditions. The result revealed that FB-PG cocrystal has a solubility of four-fold higher than FB form-A in deionized water and two-fold and five-fold greater than FB form-A at simulated gastrointestinal pH 1.2 and pH 4, respectively. Besides, solubilities of FB-PG cocrystal and FB form-A at pH 6.8 were similar to the results measured in deionized water. Therefore, it is postulated that FB-PG cocrystal has a potential overcoming the limitations related to the low aqueous solubility of FB form-A. Accordingly, FB-PG cocrystal is suggested as an

  9. Spectroscopic (FTIR, FT-Raman, UV and NMR) investigation and NLO, HOMO-LUMO, NBO analysis of 2-Benzylpyridine based on quantum chemical calculations.

    Science.gov (United States)

    Mathammal, R; Sudha, N; Guru Prasad, L; Ganga, N; Krishnakumar, V

    2015-02-25

    In this work, the vibrational characteristics of 2-Benzylpyridine have been investigated. The structure of the molecule has been optimized and the structural characteristics of the molecule have been determined by density functional theory B3LYP method with 6-31G(d,p) basis set. The infrared and Raman spectra have been simulated from calculated intensities. Both the experimental and theoretical vibrational data confirms the presence of functional groups in the title compound. The (1)H and (13)C NMR spectra were recorded and (1)H and (13)C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital method. UV-Visible spectrum of the title compound was recorded in the region 190-1100 nm and the electronic properties HOMO and LUMO energies were calculated by CIS approach. Nonlinear optical and thermodynamic properties were interpreted. All the calculated results were compared with the available experimental data of the title molecule. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Metabolic Effects of a 24-Week Energy-Restricted Intervention Combined with Low or High Dairy Intake in Overweight Women: An NMR-Based Metabolomics Investigation

    Directory of Open Access Journals (Sweden)

    Hong Zheng

    2016-02-01

    Full Text Available We investigated the effect of a 24-week energy-restricted intervention with low or high dairy intake (LD or HD on the metabolic profiles of urine, blood and feces in overweight/obese women by NMR spectroscopy combined with ANOVA-simultaneous component analysis (ASCA. A significant effect of dairy intake was found on the urine metabolome. HD intake increased urinary citrate, creatinine and urea excretion, and decreased urinary excretion of trimethylamine-N-oxide (TMAO and hippurate relative to the LD intake, suggesting that HD intake was associated with alterations in protein catabolism, energy metabolism and gut microbial activity. In addition, a significant time effect on the blood metabolome was attributed to a decrease in blood lipid and lipoprotein levels due to the energy restriction. For the fecal metabolome, a trend for a diet effect was found and a series of metabolites, such as acetate, butyrate, propionate, malonate, cholesterol and glycerol tended to be affected. Overall, even though these effects were not accompanied by a higher weight loss, the present metabolomics data reveal that a high dairy intake is associated with endogenous metabolic effects and effects on gut microbial activity that potentially impact body weight regulation and health. Moreover, ASCA has a great potential for exploring the effect of intervention factors and identifying altered metabolites in a multi-factorial metabolomic study.

  11. Dynamics of bio-membranes investigated by neutron spin echo: Effects of phospholipid conformations and presence of lidocaine

    Science.gov (United States)

    Yi, Zheng

    Bio-membranes of the natural living cells are made of bilayers of phospholipids molecules embedded with other constituents, such as cholesterol and membrane proteins, which help to accomplish a broad range of functions. Vesicles made of lipid bilayers can serve as good model systems for bio-membranes. Therefore these systems have been extensively characterized and much is known about their shape, size, porosity and functionality. In this dissertation we report the studies of the effects of the phosoholipid conformation, such as hydrocarbon number and presence of double bond in hydrophobic tails on dynamics of phospholipids bilayers studied by neutron spin echo (NSE) technique. We have investigated how lidocaine, the most medically used local anesthetics (LA), influence the structural and dynamical properties of model bio-membranes by small angle neutron scattering (SANS), NSE and differential scanning calorimetry (DSC). To investigate the influence of phospholipid conformation on bio-membranes, the bending elasticities kappac of seven saturated and monounsaturated phospholipid bilayers were investigated by NSE spectroscopy. kappa c of phosphatidylcholines (PCS) in liquid crystalline (L alpha) phase ranges from 0.38x10-19 J for 1,2-Dimyristoyl- sn-Glycero-3-Phosphocholine (14:0 PC) to 0.64x10-19 J for 1,2-Dieicosenoyl-sn-Glycero-3-Phosphocholine (20:1 PC). It was confirmed that when the area modulus KA varies little with chain unsaturation or length, the elastic ratios (kappac/ KA)1/2 of bilayers varies linearly with lipid hydrophobic thickness d. For the study of the influence of LA on bio-membranes, SANS measurements have been performed on 14:0 PC bilayers with different concentrations of lidocaine to determine the bilayer thickness dL as a function of the lidocaine concentration. NSE has been used to study the influence of lidocaine on the bending elasticity of 14:0 PC bilayers in Lalpha and ripple gel (Pbeta') phases. Our results confirmed that the molecules of

  12. A 13C and 1H NMR spectroscopic investigation of the structure of the iminium ion with a dipolar form in metal complexes of 2-N-substituted N-confused porphyrins.

    Science.gov (United States)

    Chang, Wen-Pin; Lin, Wen-Chain; Chen, Jyh-Horung; Wang, Shin-Shin; Tung, Jo-Yu

    2012-11-21

    The crystal structures of chloro(2-aza-2-ethoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′N′′) zinc(II) [Zn(2-NCH2COOC2H5NCTPP)Cl; 4], (2-aza-2-ethoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′N′′) palladium(II) [Pd(2-NCH2COOC2H5NCTPP); 5], bromo(2-aza-2-ethoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′N′′) manganese(III) [Mn(2-NCH2COOC2H5NCTPP)Br; 6], [2-aza-(3′-phenoxypropyl)-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′N′′] nickel(II) [Ni(2-NCH2CH2CH2OC6H5NCTPP); 7] and chloro(2-aza-2-methoxycarbonylmethyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′N′′) zinc(II) [Zn(2-NCH2COOCH3NCTPP)Cl; 8] have been established. The g value of 9.54, which was measured from the parallel polarization of the X-band EPR spectra in CHCl3 at 4 K, is consistent with the high spin mononuclear manganese(III) centre (S = 2) in 6. The magnitude of the axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) centre in 6 was determined approximately to be 1.63 cm(−1) by paramagnetic susceptibility measurements. The NMR spectroscopic investigation of the iminium ion with a dipolar canonical contribution to the metal complexes 5–7, Pd(2-NCH2C6H5NCTPP) (10) and Ni(2-NCH2C6H5NCTPP) (11) in CDCl3 is reported. A resonance between the dipolar canonical form II and covalent canonical form I exists for complexes 5–7, 10 and 11 in CDCl3. To develop the correlations between δ13C [C(3)], δ1H [H(3)] and the canonical form II in 5–7, 10 and 11, this work thoroughly examines the 13C and 1H NMR of N+=CH(Ar) fragment on seven metal complexes of 2-N substituted N-confused porphyrin. According to these results, the 13C [C(3)] and 1H [H(3)] chemical shifts of the N+=CH(Ar) fragment at 20 °C in CDCl3 are separately located at 152.6 ± 0.5 and 8.30 ± 0.15 ppm respectively for the iminium ion. This exists as a dipolar canonical form II for complexes 5–7, 10 and 11, and the N–CH(Ar) group

  13. NMR spectroscopy applied to the eye: Drugs and metabolic studies

    International Nuclear Information System (INIS)

    Saether, Oddbjoern

    2005-01-01

    NMR spectroscopy has been extensively applied in biomedical research during the last decades. It has proved to be an analytical tool of great value. From being mainly used in chemistry, technological developments have expanded the application of NMR spectroscopy to a great wealth of disciplines. With this method, biochemical information can be obtained by analysing tissue extracts. Moreover, NMR spectroscopy is increasingly employed for pharmacokinetic studies and analysis of biofluids. Technological progress has provided increased sensitivity and resolution in the spectra, which enable even more of the complexity of biological samples to be elucidated. With the implementation of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy in biomedicine, intact tissue samples or biopsies can be investigated. Thus, NMR spectroscopy has an ever-increasing impact in metabolic screening of human samples and in animal models, and methods are also increasingly realised in vivo. The present work, NMR spectroscopy applied to eye research, consists of two main parts. Firstly, the feasibility to monitor fluorinated ophthalmic drugs directly in the eye was assessed. Secondly, HR-MAS H1 NMR spectroscopy was applied for metabolic profiling of the anterior eye segment, specifically to analyse metabolic changes in intact corneal and lenticular samples after cataractogenic insults. This work included metabonomics with the application of pattern recognition methods to analyse HR-MAS spectra of eye tissues. Optimisation strategies were explored for F19 NMR detection of fluorinated drugs in a phantom eye. S/N gains in F19 NMR spectroscopy were achieved by implementing time-share H1 decoupling at 2.35 T. The method is advantageous for compounds displaying broad spectral coupling patterns, though detection of drugs at concentrations encountered in the anterior eye segment after topical application was not feasible. Higher magnetic fields and technological improvements could enable

  14. NMR spectroscopy applied to the eye: Drugs and metabolic studies

    Energy Technology Data Exchange (ETDEWEB)

    Saether, Oddbjoern

    2005-07-01

    NMR spectroscopy has been extensively applied in biomedical research during the last decades. It has proved to be an analytical tool of great value. From being mainly used in chemistry, technological developments have expanded the application of NMR spectroscopy to a great wealth of disciplines. With this method, biochemical information can be obtained by analysing tissue extracts. Moreover, NMR spectroscopy is increasingly employed for pharmacokinetic studies and analysis of biofluids. Technological progress has provided increased sensitivity and resolution in the spectra, which enable even more of the complexity of biological samples to be elucidated. With the implementation of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy in biomedicine, intact tissue samples or biopsies can be investigated. Thus, NMR spectroscopy has an ever-increasing impact in metabolic screening of human samples and in animal models, and methods are also increasingly realised in vivo. The present work, NMR spectroscopy applied to eye research, consists of two main parts. Firstly, the feasibility to monitor fluorinated ophthalmic drugs directly in the eye was assessed. Secondly, HR-MAS H1 NMR spectroscopy was applied for metabolic profiling of the anterior eye segment, specifically to analyse metabolic changes in intact corneal and lenticular samples after cataractogenic insults. This work included metabonomics with the application of pattern recognition methods to analyse HR-MAS spectra of eye tissues. Optimisation strategies were explored for F19 NMR detection of fluorinated drugs in a phantom eye. S/N gains in F19 NMR spectroscopy were achieved by implementing time-share H1 decoupling at 2.35 T. The method is advantageous for compounds displaying broad spectral coupling patterns, though detection of drugs at concentrations encountered in the anterior eye segment after topical application was not feasible. Higher magnetic fields and technological improvements could enable

  15. Liquid and gas phase NMR spectra of 13CH313CHO acetaldehyde

    Science.gov (United States)

    Makulski, Włodzimierz; Wikieł, Agata J.

    2018-01-01

    The gas phase NMR experiments perform a vital role in establishing the magnetic shielding and spin-spin coupling constants which are free from intermolecular interactions, equivalent to the parameter of isolated molecules. This work is concerned with an acetaldehyde molecule. Small amounts of acetaldehyde 13CH313CHO in gaseous matrices of CO2 and Xe were studied using high-precision 1H and 13C NMR measurements. Results were extrapolated to the zero-density limit permitting the determinations of the 1H and 13C absolute nuclear magnetic shielding of an isolated acetaldehyde molecule. The difference between the experimental and recent theoretical DFT results is discussed. Several samples of 13CH313CHO dissolved in popular organic and inorganic solvents were also investigated. Gas-to-solution shifts show the influence of the association process when acetaldehyde is transferred from gas to liquid state. Several spin-spin coupling constants in the gas phase and in different solvents were precisely measured.

  16. Spin and Maximal Acceleration

    Directory of Open Access Journals (Sweden)

    Giorgio Papini

    2017-12-01

    Full Text Available We study the spin current tensor of a Dirac particle at accelerations close to the upper limit introduced by Caianiello. Continual interchange between particle spin and angular momentum is possible only when the acceleration is time-dependent. This represents a stringent limit on the effect that maximal acceleration may have on spin physics in astrophysical applications. We also investigate some dynamical consequences of maximal acceleration.

  17. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2012-01-01

    In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

  18. Dynamic NMR Study of Model CMP Slurry Containing Silica Particles as Abrasives

    Science.gov (United States)

    Odeh, F.; Al-Bawab, A.; Li, Y.

    2018-02-01

    Chemical mechanical planarization (CMP) should provide a good surface planarity with minimal surface defectivity. Since CMP slurries are multi-component systems, it is very important to understand the various processes and interactions taking place in such slurries. Several techniques have been employed for such task, however, most of them lack the molecular recognition to investigate molecular interactions without adding probes which in turn increase complexity and might alter the microenvironment of the slurry. Nuclear magnetic resonance (NMR) is a powerful technique that can be employed in such study. The longitudinal relaxation times (T1) of the different components of CMP slurries were measured using Spin Echo-NMR (SE-NMR) at a constant temperature. The fact that NMR is non-invasive and gives information on the molecular level gives more advantage to the technique. The model CMP slurry was prepared in D2O to enable monitoring of T1 for the various components' protons. SE-NMR provide a very powerful tool to study the various interactions and adsorption processes that take place in a model CMP silica based slurry which contains BTA and/or glycine and/or Cu+2 ions. It was found that BTA is very competitive towards complexation with Cu+2 ions and BTA-Cu complex adsorbs on silica surface.

  19. Element-selective investigation of femtosecond spin dynamics in NiPd magnetic alloys using extreme ultraviolet radiation

    Science.gov (United States)

    Gang, Seung-gi; Adam, Roman; Plötzing, Moritz; von Witzleben, Moritz; Weier, Christian; Parlak, Umut; Bürgler, Daniel E.; Schneider, Claus M.; Rusz, Jan; Maldonado, Pablo; Oppeneer, Peter M.

    2018-02-01

    We studied femtosecond spin dynamics in NixPd1 -x magnetic thin films by optically pumping the system with infrared (1.55 eV) laser pulses and subsequently recording the reflectivity of extreme ultraviolet (XUV) pulses synchronized with the pump pulse train. XUV light in the energy range from 20 to 72 eV was produced by laser high-harmonic generation. The reflectivity of XUV radiation at characteristic resonant energies allowed separate detection of the spin dynamics in the elemental subsystems at the M2 ,3 absorption edges of Ni (68.0 and 66.2 eV) and N2 ,3 edges of Pd (55.7 and 50.9 eV). The measurements were performed in transversal magneto-optical Kerr effect geometry. In static measurements, we observed a magnetic signature of the Pd subsystem due to an induced magnetization. Calculated magneto-optical asymmetries based on density functional theory show close agreement with the measured results. Femtosecond spin dynamics measured at the Ni absorption edges indicates that increasing the Pd concentration, which causes a decrease in the Curie temperature TC, results in a drop of the demagnetization time τM, contrary to the τM˜1 /TC scaling expected for single-species materials. This observation is ascribed to the increase of the Pd-mediated spin-orbit coupling in the alloy.

  20. The dynamics in polyethyleneoxide–alkali iodide complexes investigated by neutron spin-echo spectroscopy and molecular dynamics simulations

    NARCIS (Netherlands)

    Mos, B.; Verkerk, P.; Pouget, S.; Van Zon, A.; Bel, G.J.; De Leeuw, S.W.; Eisenbach, C.D.

    2000-01-01

    We determined the self part of the intermediate scattering function in liquid polyethyleneoxide (PEO) and PEO–alkali iodide complexes by means of neutron spin-echo spectroscopy and molecular dynamics (MD) computer simulations. We present the first accurate quantitative results on the segmental