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Sample records for nmr spin-hamiltonian parameters

  1. Optical spectra and spin-Hamiltonian parameters of trivalent ytterbium in lead tungstate

    Indian Academy of Sciences (India)

    W-L Feng; X-M Li

    2011-01-01

    By using crystal-?eld theory, the optical spectra and spin-Hamiltonian parameters (abbr. SH parameters, i.e. the anisotropic factors $g_{\\|} g_{\\perp}$, and hyper?ne structure constants $A_{\\|}, A_{\\perp}$) of 171Yb3+ and 173Yb3+ isotopes in the tetragonal PbWO4 are calculated. The theoretical results agree well with the experimental values. The crystal-?eld parameters and the signs of the hyper?ne structure constants for both 171Yb3+ and 173Yb3+ isotopes are determined. The validities of the theoretical results are discussed.

  2. Calculations of the electronic levels, spin-Hamiltonian parameters and vibrational spectra for the CrCl3 layered crystals

    Science.gov (United States)

    Avram, C. N.; Gruia, A. S.; Brik, M. G.; Barb, A. M.

    2015-12-01

    Calculations of the Cr3+ energy levels, spin-Hamiltonian parameters and vibrational spectra for the layered CrCl3 crystals are reported for the first time. The crystal field parameters and the energy level scheme were calculated in the framework of the Exchange Charge Model of crystal field. The spin-Hamiltonian parameters (zero-field splitting parameter D and g-factors) for Cr3+ ion in CrCl3 crystals were obtained using two independent techniques: i) semi-empirical crystal field theory and ii) density functional theory (DFT)-based model. In the first approach, the spin-Hamiltonian parameters were calculated from the perturbation theory method and the complete diagonalization (of energy matrix) method. The infrared (IR) and Raman frequencies were calculated for both experimental and fully optimized geometry of the crystal structure, using CRYSTAL09 software. The obtained results are discussed and compared with the experimental available data.

  3. Spin-Hamiltonian parameters of Gd3+ ion in the room temperature tetragonal phase of BaTiO3

    International Nuclear Information System (INIS)

    The spin-Hamiltonian parameters (g factors g verticalstrokeverticalstroke, g perpendicularto, and zero-field splittings b20, b40, b44, b60, b64) of the 4f7 Gd3+ ion in the tetragonal phase of a BaTiO3 crystal are calculated through the diagonalization (of energy matrix) method based on the one-electron crystal field mechanism. In the calculations, the crystal field parameters are estimated from the superposition model with the structural data of the studied crystal. It is found that by using three adjustable intrinsic parameters anti Ak(R0) (k = 2, 4, 6) in the superposition model, the seven calculated spin-Hamiltonian parameters are in good agreement with the experimental values, suggesting that the diagonalization method based on one-electron crystal field mechanism is effective in the studies of spin-Hamiltonian parameters for 4f7 ions in crystals.

  4. On the non-standard rhombic spin Hamiltonian parameters derived from Moessbauer spectroscopy and magnetism-related measurements

    International Nuclear Information System (INIS)

    The orthorhombic standardization of spin Hamiltonian parameters is increasingly adopted in the electron magnetic resonance area. The aim of this paper is to elucidate the ramifications of orthorhombic standardization for other spectroscopic and magnetic techniques, which also employ the spin Hamiltonian formalism. This is illustrated by examples derived from the Moessbauer spectroscopy, magnetic moments and magnetic susceptibility, photoinduced changes of magnetization, and other magnetism-related measurements. Implications of standardization in the studies of magnetic ordering, Haldane gap for integer spin systems, the macroscopic quantum tunnelling of magnetization, specific heat measurements, the spin wave theory, and inelastic neutron scattering are also discussed. Several sets of the non-standard zero-field splitting (ZFS) parameters for transition ions at orthorhombic symmetry sites, expressed in various notations and units, are standardized. Calculations are performed using the computer package CST, which yields the standardized ZFS parameter sets. The results are presented in a unified way in the extended Stevens notation bkq and units of cm-1 together with the conventional D and E parameters, which prevail in the studies dealt with in this paper. This enables a direct comparison with the available data for similar ion/host systems. The standardization reveals several inconsistencies in interpretation of the experimental data obtained by various techniques

  5. Factors influencing concentration of V (4) complexes and parameters of the spin-hamiltonian in phosphate-vanadate semiconductor glasses

    International Nuclear Information System (INIS)

    The dependence is studied of the parameters of the spin-Hamiltonian, the nature of the chemical bond, the concentration of unpaired electrons and the splitting of the energy levels of the 3d ion of V(4) in the field of oxygen ligands on the composition of semiconducting phosphate-vanadate glasses mV2O5x(100-m)P2O5(m=100-2) and nonsemiconducting phosphate-vanadate glasses 24 CaOxV2O5x25 P2O5 by the EPR and electron-absorption methods. The dependences of the component of the g-tensor and of the hyperfine structure constant of the complex VOO4O are considered

  6. Monoclinic and orthorhombic standardization of spin-Hamiltonian parameters for rare-earth centers in various crystals

    Science.gov (United States)

    Rudowicz, C. Z.; Madhu, S. B.

    2000-05-01

    In a previous paper the standardization of the spin-Hamiltonian (SH) parameters for transition-metal ions at orthorhombic symmetry sites was dealt with using the computer package CST. In this paper the non-standard SH parameters for rare-earth ions at monoclinic and orthorhombic symmetry sites in various crystals, identified in an extensive literature survey, have been unified and standardized. The original non-standard zero-field splitting (ZFS) parameter sets given in various (i) parameter and operator notations, (ii) units and (iii) conventions for the axis systems are converted and presented in a unified way. Both the monoclinic- and orthorhombic-type standardization provided by the CST package have been employed. All the standardized ZFS parameters are expressed in the extended Stevens’ (ES) notation bqk and in units of 10 -4 cm -1. The transformations Si required and the ratio ??? B22/ B02? b22/ b02 and ?? E/ D are also provided in the tables. Implications of the standardization for the axis system used and interpretation of the EPR results are discussed, thus revealing several inconsistencies in the original papers. It is concluded that the results presented may facilitate future determination of the ZFS parameters by EPR and increase the reliability of data.

  7. Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO

    International Nuclear Information System (INIS)

    The local structure distortion, the spin Hamiltonian (SH) parameters, and the electric fine structure of the ground state for Mn2+ (3d5) ion in ZnO crystals are systematically investigated, where spin–spin (SS), spin–other-orbit (SOO) and orbit–orbit (OO) magnetic interactions, besides the well-known spin-orbit (SO) coupling, are taken into account for the first time, by using the complete diagonalization method. The theoretical results of the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), the Zeeman g-factors: g// and g?, and the energy differences of the ground state: ?1 and ?2 for Mn2+ in Mn2+: ZnO are in good agreement with experimental measurements when the three O2– ions below the Mn2+ ion rotate by 1.085° away from the [111]-axis. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Mn2+ ions in Mn2+: ZnO crystals. It is found for Mn2+ ions in Mn2+: ZnO crystals that although the SO mechanism is the most important one, the contributions to the SH parameters, made by other four mechanisms, i.e. SS, SOO, OO, and SO?SS?SOO?OO mechanisms, are significant and should not be omitted, especially for calculating ZFS parameter D. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  8. Research on the optical band positions, spin-Hamiltonian parameters and atom-position parameter of Co2+ ion in CdSe crystal

    Science.gov (United States)

    Mei, Yang; Zheng, Wen-Chen; Peng, Ren-Ming; Wei, Cheng-Fu

    2015-10-01

    The optical band positions and EPR (or spin-Hamiltonian) parameters (g factors g//, g? and zero-field splitting D) of Co2+ ion in the trigonally-distorted tetrahedral Cd2+ site of CdSe crystal are calculated simultaneously from the complete diagonalization (of energy matrix) method (CDM) based on the two-spin-orbit-parameter model. This model contains the contributions to the spectral data from both the spin-orbit parameters of central dn ion (i.e., one-spin-orbit-parameter model) in the conventional crystal-field theory and that of ligand ions via covalence effect. The calculated 12 optical band positions and three spin-Hamiltonian parameters using four adjustable parameters show reasonable agreement with the experimental values. The local atom-position parameter uloc (where the corresponding parameter u in the host CdSe crystal is unlikely) in the Co2+ center is also estimated from the calculations. The calculations of these spectral data from the CDM based on the conventional one-spin-orbit parameter model are also made for comparison. It is found that the calculated optical band positions are also close to the experimental values, but the calculated spin-Hamiltonian parameters are in poor agreement with the observed values. So, for the unified and reasonable calculations of optical and EPR data of dn ions in crystals (in particular, in the cases of ligand with large spin-orbit parameter), the CDM based on the two-spin-orbit-parameter model should be applied.

  9. Local structure distortion and spin Hamiltonian parameters for Cr 4+ ions in Cr 4+:?-Al 2O 3 crystals

    Science.gov (United States)

    Yang, Zi-Yuan

    2010-01-01

    The relations between the spin Hamiltonian (SH) parameters and crystal structure of Cr 4+:?-Al 2O 3 crystals have been established. On the basis of this, the SH parameters including zero-field splitting parameter D and Zeeman g-factors ( g|| and g?) for Cr 4+ ions in Cr 4+:?-Al 2O 3 crystals, taking into account the spin-spin (SS), spin-other-orbit (SOO) and orbit-orbit (OO) magnetic interactions in addition to the spin-orbit (SO) magnetic interaction, are theoretically investigated using complete diagonalization method (CDM). The theoretical results are in excellent agreement with the experimental ones when the upper three O 2- ions rotate 0.94° toward [1 1 1] axis and the lower three O 2- ions rotate 0.92° toward it. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Cr 4+ ions in Cr 4+:?-Al 2O 3 crystals. This study shows that for Cr 4+:?-Al 2O 3 the contributions arising from SS, SOO, and OO interactions to the zero-field splitting (ZFS) parameter D are appreciable, whereas those to g|| and g? are quite small.

  10. Theoretical investigations on the spin Hamiltonian parameters and local structure for the tetragonal Pt3+ Center in BaTiO3

    International Nuclear Information System (INIS)

    The spin Hamiltonian parameters (g factors and the hyperfine structure constants) and the local structure for the tetragonal Pt3+ center in BaTiO3 are theoretically investigated from the improved perturbation formulas of these parameters for a 5d7 ion in a tetragonally elongated octahedron. The Jahn-Teller effect yields 0.05 ? longer Pt3+ - O2- bonds along the C4 axis. Under the uniaxial [001] stress of 0.17GPa, the impurity center shows a moderate decrease of 12% for the tetragonal elongation and a slight increase of 3% for the core polarization constant, leading to the decline of the anisotropy ?g (= g? - g//) and the increase of ?A (= A? - -A// ), respectively. The calculated spin Hamiltonian parameters show good agreement with the observed values. (author)

  11. Studies of the spin Hamiltonian parameters and defect structures for Ag2+ in NaF and CsCdF3 crystals

    Science.gov (United States)

    Zhang, Li-Juan; Wu, Shao-Yi; Ding, Chang-Chun; Hu, Xian-Fen; He, Jia-Jun

    2016-03-01

    The spin Hamiltonian parameters (g factors g//, g?, hyperfine structure constants A//, A? and superhyperfine parameters Az?, Ax? and Ay?) and defect structures for Ag2+ in NaF and CsCdF3 crystals are theoretically studied using the improved perturbation formulas of these quantities for a 4d9 ion in a tetragonally elongated octahedron. The contributions from both the crystal-field and charge transfer mechanisms are taken into account, and the relevant model parameters are quantitatively obtained from the cluster approach in a consistent way. The impurity centers are found to undergo the relative tetragonal elongations of about 9.4% and 8.2% for Ag2+ in NaF and CsCdF3, respectively, along the C4 axis due to the Jahn-Teller effect. By employing the few adjustable parameters, the calculated spin Hamiltonian parameters based on the above uniform formulas and the local tetragonal elongation distortions agree well with the experimental data. Despite dominant ionicity of the hosts, the charge transfer contributions are actually important to the spin Hamiltonian parameters (e.g., about 20% for the g-shifts) due to strong covalency of impurity Ag2+.

  12. Theoretical evaluation of the electron paramagnetic resonance spin Hamiltonian parameters for the impurity displacements for Fe3+ and Ru3+ in corundum

    Indian Academy of Sciences (India)

    Q Fu; S Y Wu; J Z Lin; J S Yao

    2007-03-01

    The impurity displacements for Fe3+ and Ru3+ in corundum (Al2O3) are theoretically studied using the perturbation formulas of the spin Hamiltonian parameters (zero-field splitting and anisotropic factors) for a 3d5 (with high spin $S = 5/2$) and a 4d5 (with low spin $S = 1/2$) ion in trigonal symmetry, respectively. According to the investigations, the nd5 ($n = 3$ and 4) impurity ions may not locate at the ideal Al3+ site but undergo axial displacements by about 0.132 Å and 0.170 Å for Fe3+ and Ru3+, respectively, away from the center of the ligand octahedron along the C3 axis. The calculated spin Hamiltonian parameters based on the above axial displacements show good agreement with the observed values. The validity of the results is discussed.

  13. Studies on the spin Hamiltonian parameters and local structure for Rh4+ and Ir4+ in TiO2

    Science.gov (United States)

    Li, L. L.; Wu, S. Y.; Xu, P.; Zhang, S. X.

    2010-07-01

    The spin Hamiltonian (SH) parameters ( g factors g x , g y and g z and the hyperfine structure constants A x , A y and A z ) and local structure for the rhombic Rh4+ and Ir4+ centers in TiO2 (rutile) are theoretically studied from the perturbation formulas of these parameters for a low spin ( S = 1/2) d 5 ion under rhombically distorted octahedra. In the calculations, the ligand orbital and spin-orbit coupling contributions as well as the influence of the local lattice distortions are taken into account using the cluster approach. The local axial elongation ratios are found to be about 1.7 and 3 times, respectively, larger for the Rh4+ and Ir4+ centers than that (?0.0075) for the host Ti4+ site in rutile, while the perpendicular distortion angles (?-0.28° and -0.42°, respectively) are more than one order in magnitude smaller than the host value (?-9.12°). This means that the impurity centers exhibit further elongations of the oxygen octahedra and much smaller perpendicular rhombic distortions as compared with those of the host Ti4+ site in TiO2. The above local lattice distortions can be mainly ascribed to the substitution of the host Ti4+ by the nd 5 impurities, which may induce different physical and chemical properties for the metal-ligand clusters. In addition, the influence of the Jahn-Teller effect on the local structure may not be completely excluded. The calculated SH parameters show reasonable agreement with the observed values.

  14. Theoretical studies of the spin Hamiltonian parameters and local structures for the tetragonal Cu2+ and Ni3+ centers in Mg2TiO4

    International Nuclear Information System (INIS)

    Highlights: ? Spin Hamiltonian parameters and local structures are analyzed for the impurity Cu2+ and Ni3+ centers in Mg2TiO4. ? Ligand orbital and spin-orbit coupling contributions are included from the cluster approach due to moderate covalency. ? Ligand octahedra experience relative elongations along C4 axis due to Jahn-Teller effect. - Abstract: The local structures of the two impurity Cu2+ (and Ni3+) centers with low spin (S = 1/2) in Mg2TiO4 are theoretically studied by using the perturbation formulas of the spin Hamiltonian parameters for 3d9 (and 3d7) ions in tetragonally elongated octahedra. In these formulas, the tetragonal field parameters are quantitatively determined using the superposition model and the local structures of the impurity Cu2+ (and Ni3+) centers, and the ligand orbital and spin–orbit coupling contributions are included on the basis of the cluster approach in view of moderate covalency for the studied systems. The [CuO6]10? and [NiO6]9?clusters on the substitutional Mg2+ site are found to suffer relative elongations by about ?ZCu (?3.2%) and ?ZNi (?0.7%) for the impurity Cu2+ and Ni3+ centers, respectively, along the C4 axis due to the Jahn–Teller effect. The calculated spin Hamiltonian parameters based on the above Jahn–Teller elongations show good agreement with the observed values. The results are discussed.

  15. Microscopic spin-Hamiltonian parameters and crystal field energy levels for the low C3 symmetry Ni2+ centre in LiNbO3 crystals

    International Nuclear Information System (INIS)

    The microscopic spin-Hamiltonian (MSH) parameters and the crystal field (CF) energy levels for Ni2+ ions in LiNbO3 crystals have been investigated using the crystal field analysis/microscopic spin-Hamiltonian package recently developed. The investigations considered for the first time the spin-spin (SS) and spin-other-orbit (SOO) interactions. The low-symmetry effects (LSE) arising from the additional terms (Im(B43)?0) induced at the C3 symmetry sites by the distortion angle ?, which have been omitted in earlier works, have also been dealt with. This study shows that for LiNbO3 : Ni2+ the contributions arising from SS and SOO interactions to the zero-field splitting parameter D are appreciable, whereas those to g|| and gp-erpendicular are quite small. Since the distortion angle ? ( congruent with 0.68 deg. ) for LiNbO3 : Ni2+ is rather small, the contributions to the spin-Hamiltonian (SH) parameters arising from LSE are also small. Feasibility of application of the superposition model is also discussed. A good overall agreement between the theoretical and experimental results for the SH parameters and the CF energy levels has been obtained

  16. Theoretical calculations of spin-Hamiltonian parameters for the (MoOX5)2? (X=Cl, Br) metallic complexes in solution or frozen-glass

    International Nuclear Information System (INIS)

    The spin-Hamiltonian parameters (g factors g//, g? and hyperfine structure constants A//, A?) of the (MoOX5)2? (X=Cl, Br) metallic complexes in solution or frozen-glass are calculated from the high-order perturbation formulas based on the two-mechanism model. In these formulas, the contributions to spin-Hamiltonian parameters due to both the widely-applied crystal-field (CF) mechanism and the charge-transfer (CT) mechanism (which is neglected in CF theory) are taken into account, and the needed CF and CT energy levels are obtained from the optical spectra. The calculated results with two adjustable parameters are in reasonable agreement with the experimental values. The calculations show that (i) the relative importance of CT mechanism in (MoOBr5)2? metallic complexes is larger than that in (MoOCl5)2? ones because of the stronger covalence of Mo5+–Br? combination, and (ii) in both (MoOCl5)2? and (MoOBr5)2? metallic complexes, the contributions to spin-Hamiltonian parameters due to CT mechanism should also be taken into account because of the high valence state of Mo5+ ion

  17. Local structure distortion and spin Hamiltonian parameters for Cr3+-VZn tetragonal defect centre in Cr3+ doped KZnF3 crystal

    Science.gov (United States)

    Yang, Zi-Yuan

    2011-09-01

    The quantitative relationship between the spin Hamiltonian parameters (D, g?, ?g) and the crystal structure parameters for the Cr3+-VZn tetragonal defect centre in a Cr3+:KZnF3 crystal is established by using the superposition model. On the above basis, the local structure distortion and the spin Hamiltonian parameter for the Cr3+-VZn tetragonal defect centre in the KZnF3 crystal are systematically investigated using the complete diagonalization method. It is found that the VZn vacancy and the differences in mass, radius and charge between the Cr3+ and the Zn2+ ions induce the local lattice distortion of the Cr3+ centre ions in the KZnF3 crystal. The local lattice distortion is shown to give rise to the tetragonal crystal field, which in turn results in the tetragonal zero-field splitting parameter D and the anisotropic g factor ?g. We find that the ligand F- ion along [001] and the other five F- ions move towards the central Cr3+ by distances of ?1 = 0.0121 nm and ?2 = 0.0026 nm, respectively. Our approach takes into account the spin—orbit interaction as well as the spin—spin, spin—other-orbit, and orbit—orbit interactions omitted in the previous studies. It is found that for the Cr3+ ions in the Cr3+:KZnF3 crystal, although the spin—orbit mechanism is the most important one, the contribution to the spin Hamiltonian parameters from the other three mechanisms, including spin—spin, spin—other-orbit, and orbit—orbit magnetic interactions, is appreciable and should not be omitted, especially for the zero-field splitting (ZFS) parameter D.

  18. Theoretical studies of the spin-Hamiltonian parameters for the orthorhombic Pr4+ centers in Sr2CeO4 crystals

    Indian Academy of Sciences (India)

    Wen-Lin Feng

    2008-04-01

    Theoretical studies of spin-Hamiltonian (SH) parameters associated with Pr4+ in Sr2CeO4 single crystals have been made by using the complete diagonalizing energy matrix method (CDM) for the $4f^{1}$ electronic configuration. The calculated results are in excellent agreement with the experimental data. The negative signs of the anisotropic $g_{i}$-factors and hyperfine structure constants $A_{i}$ (where $i = ||$ or $\\perp$) for the orthorhombic Pr4+ ion in Sr2CeO4 are suggested from the calculations. By comparing the results obtained by the CDM with the experimental data, one finds it is valid to interpret the SH parameters for $4f^{1}$ ions in crystals. The results are discussed.

  19. Theoretical investigations of the spin-Hamiltonian parameters and local structural distortion of Fe3+: ZnAl2O4 crystals

    Science.gov (United States)

    Yang, Zi-Yuan

    2014-10-01

    The relations between the spin-Hamiltonian (SH) parameters and the structural parameters of the Fe3+ ions in Fe3+: ZnAl2O4 crystals have been established by means of the microscopic spin Hamiltonian theory and the superposition model (SPM). On the basis of this, the local structure distortion, the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), and the Zeeman g-factors g factors: g//, g?, and ?g(=g// - g?) for Fe3+ ions in Fe3+: ZnAl2O4 crystals, for the first time taking into account the electronic magnetic interactions, i.e. the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) interactions, besides the well-known spin-orbit (SO) interaction, are theoretically investigated using complete diagonalization method (CDM). This investigation reveals that the local structure distortion effect plays an important role in explaining the spectroscopic properties of Fe3+ ions in Fe3+: ZnAl2O4 crystals. The theoretical second-order ZFS parameter D, the fourth-order ZFS parameter (a-F), and the Zeeman g-factors: g//, g?, and ?g of the ground state for Fe3+ ion in Fe3+: ZnAl2O4 crystals yield a good agreement with experiment findings by taking into account the lattice distortions: ?R = 0.0191 nm and ?? = 0.076°. In conclusion, our research shows that there is a slight local structure distortion for Fe3+ ions in Fe3+: ZnAl2O4 crystals, but the site of Fe3+ still retains D3d symmetry. On the other hand, it is found for Fe3+ ions in Fe3+: ZnAl2O4 crystals that the SO mechanism is the most important one, whereas the contributions to the SH parameters from other four mechanisms, including the SS, SOO, OO, and SO?SS?SOO?OO mechanisms are not appreciable, especially for the ZFS parameter D.

  20. Theoretical investigations of the spin-Hamiltonian parameters and local structural distortion of Fe(3+): ZnAl2O4 crystals.

    Science.gov (United States)

    Yang, Zi-Yuan

    2014-10-15

    The relations between the spin-Hamiltonian (SH) parameters and the structural parameters of the Fe(3+) ions in Fe(3+): ZnAl2O4 crystals have been established by means of the microscopic spin Hamiltonian theory and the superposition model (SPM). On the basis of this, the local structure distortion, the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), and the Zeeman g-factors g factors: g//, g?, and ?g(=g//-g?) for Fe(3+) ions in Fe(3+): ZnAl2O4 crystals, for the first time taking into account the electronic magnetic interactions, i.e. the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) interactions, besides the well-known spin-orbit (SO) interaction, are theoretically investigated using complete diagonalization method (CDM). This investigation reveals that the local structure distortion effect plays an important role in explaining the spectroscopic properties of Fe(3+) ions in Fe(3+): ZnAl2O4 crystals. The theoretical second-order ZFS parameter D, the fourth-order ZFS parameter (a-F), and the Zeeman g-factors: g//, g?, and ?g of the ground state for Fe(3+) ion in Fe(3+): ZnAl2O4 crystals yield a good agreement with experiment findings by taking into account the lattice distortions: ?R=0.0191nm and ??=0.076°. In conclusion, our research shows that there is a slight local structure distortion for Fe(3+) ions in Fe(3+): ZnAl2O4 crystals, but the site of Fe(3+) still retains D3d symmetry. On the other hand, it is found for Fe(3+) ions in Fe(3+): ZnAl2O4 crystals that the SO mechanism is the most important one, whereas the contributions to the SH parameters from other four mechanisms, including the SS, SOO, OO, and SO?SS?SOO?OO mechanisms are not appreciable, especially for the ZFS parameter D. PMID:24835727

  1. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO

    Science.gov (United States)

    Yang, Zi-Yuan

    2009-03-01

    The local structure distortion, the spin Hamiltonian (SH) parameters, and the electric fine structure of the ground state for Mn2+ (3d5) ion in ZnO crystals are systematically investigated, where spin-spin (SS), spin-other-orbit (SOO) and orbit-orbit (OO) magnetic interactions, besides the well-known spin-orbit (SO) coupling, are taken into account for the first time, by using the complete diagonalization method. The theoretical results of the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), the Zeeman g-factors: g// and gbot, and the energy differences of the ground state: ?1 and ?2 for Mn2+ in Mn2+: ZnO are in good agreement with experimental measurements when the three O2- ions below the Mn2+ ion rotate by 1.085° away from the [111]-axis. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Mn2+ ions in Mn2+: ZnO crystals. It is found for Mn2+ ions in Mn2+: ZnO crystals that although the SO mechanism is the most important one, the contributions to the SH parameters, made by other four mechanisms, i.e. SS, SOO, OO, and SO~SS~SOO~OO mechanisms, are significant and should not be omitted, especially for calculating ZFS parameter D.

  2. Theoretical studies of the spin-Hamiltonian parameters and the effects of the temperature and pressure on the zero-field splitting for Ni2+: Zn(BF4)2.6H2O crystal

    International Nuclear Information System (INIS)

    The spin-Hamiltonian parameters (the g factors gparallel , g perpendicular and the zero-field splitting D) and the effects of the temperature and pressure on D for Ni2+ ion at the trigonal Zn2+ site in the low- and room-temperature phase of Zn(BF4)2.6H2O crystal are calculated. The calculations are based on the microscopic spin Hamiltonian theory in teams of the diagonalization of the complete energy matrix of 3d 8 ions in trigonal symmetry. The crystal-field parameters related to the impurity structure are obtained from the superposition model. Thus, the local trigonal distortion angle ?, the local angular thermal expansion coefficient and local angular compressibility for Ni2+ impurity centers in Zn(BF4)2.6H2O crystal are estimated. The reasonableness of these local values is discussed

  3. Investigations of the spin Hamiltonian parameters and local structures for Fe3+, Cr3+ and Mn4+ in rutile TiO2 single crystal

    Science.gov (United States)

    Dong, Hui-Ning; Liu, Xu-Sheng; Zhou, Hong-Fei

    2015-11-01

    The spin Hamiltonian parameters (g factors, hyperfine structure constants and zero-field splittings (ZFSs)) and local structures for the rhombic substitutional Fe3+, Cr3+ and Mn4+ in rutile (TiO2) single crystal are theoretically investigated from the high order perturbation calculations based on the cluster approach including both the crystal-field (CF) and charge-transfer (CT) contributions to the g factors and hyperfine structure constants. The impurity centers are found to undergo the local axial distortions ?Z (?0.22, 0.14 and -0.18 ?) and the planar bond angle variations ?? (?4.3, 5.9 and 0.2°) for Fe3+, Cr3+ and Mn4+, respectively. The signs for ZFSs D and E are analyzed in the light of those for ?Z and rhombic distortion angle ?? (=??-?/4) related to an ideal octahedron. The magnitudes of ?Z and ?? are conveniently illustrated by the axial and perpendicular ZFS relative variations ?F and ?G for the deviations of D and E based on the local distortion parameters from those (DH and EH) based on the host structural data of Ti4+ site. The validity of the above local structures is discussed in view of size and charge mismatch of the various impurity centers. The CT contributions to g-shift are opposite in sign and about 13-56% in magnitude compared with the CF ones, indicating the increasing importance (Cr3+

  4. Cr 3+ centres in LiNbO 3: Experimental and theoretical investigation of spin hamiltonian parameters

    Science.gov (United States)

    Yeom, T. H.; Chang, Y. M.; Rudowicz, C.; Choh, S. H.

    1993-07-01

    X-band EPR spectra of Cr 3+ ions in ferroelectric LiNbO 3 single crystal at room temperature are analyzed assuming Cr 3+ enters either of the three possible sites: Li, Nb and structural vacancy (SV) site. The observed spectra can be resolved into (I) the main (Cr 13+) and (II) the weak (Cr II3+) spectra. The axial zero-field splitting parameter for a Cr 3+ centre at Li site ( DLi) as well as Nb site ( DNb) is calculated using the superposition model. The values DLi and DNb agree well with the experimental D value for Cr I3+ and Cr II3+, respectively. This confirms that the main spectra can be attributed to Cr I3+ at the Li site and the weak spectra to Cr II3+ at the Nb site. For Cr 3+ ion at the structural vacancy site the parameter DSV is calculated as a function of displacement of Cr 3+ ion from the centre of the oxygen octahedron along the [1 1 1] direction. Other weak and unresolve spectra also observed by us can possibly be due to Cr 3+ centres at vacancy site.

  5. Modeling local structure using crystal field and spin Hamiltonian parameters: the tetragonal FeK3+-OI2- defect center in KTaO3 crystal

    Science.gov (United States)

    Gnutek, P.; Y Yang, Z.; Rudowicz, C.

    2009-11-01

    The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g_{\\parallel } and g_{\\perp } , are theoretically investigated for the FeK3+-OI2- center in KTaO3 crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the FeK3+-OI2- defect center in KTaO3. This modeling reveals that the off-center displacement of the Fe3+ ions, ?1(Fe3+), combined with an inward relaxation of the nearest oxygen ligands, ?2(O2-), and the existence of the interstitial oxygen OI2- give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the FeK3+-OI2- center in KTaO3. Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of ?1(Fe3+) and ?2(O2-) as well as the possible location of OI2- ligands around Fe3+ ions in KTaO3. The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g_{\\parallel } and g_{\\perp } and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing in the literature indicates considerable advantages of our method and presumably higher reliability of our predictions.

  6. Modeling local structure using crystal field and spin Hamiltonian parameters: the tetragonal FeK3+-OI2- defect center in KTaO3 crystal

    International Nuclear Information System (INIS)

    The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g|| and gperpendicular, are theoretically investigated for the FeK3+-OI2- center in KTaO3 crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the FeK3+-OI2- defect center in KTaO3. This modeling reveals that the off-center displacement of the Fe3+ ions, ?1(Fe3+), combined with an inward relaxation of the nearest oxygen ligands, ?2(O2-), and the existence of the interstitial oxygen OI2- give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the FeK3+-OI2- center in KTaO3. Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of ?1(Fe3+) and ?2(O2-) as well as the possible location of OI2- ligands around Fe3+ ions in KTaO3. The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g|| and gperpendicular and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing in the literature indicates considerable advantages of our method and presumably higher reliability of our predictions.

  7. An investigation on the defect structures and spin Hamiltonian parameters for the two orthorhombic Ti3+ centers in ZnWO4

    Science.gov (United States)

    Ding, Chang-Chun; Wu, Shao-Yi; Zhu, Qing-Sheng; Zhang, Zhi-Hong; Teng, Bao-Hua; Wu, Ming-He

    2015-11-01

    By employing the perturbation formulae of the spin Hamiltonian parameters (SHPs) (g factors gxx, gyy, gzz, hyperfine structure constants Axx, Ayy, Azz and superhyperfine parameters Axx', Ayy', Azz') for a 3d1 ion in orthorhombically elongated octahedra and tetrahedra, the defect structures and the experimental EPR spectra are theoretically and systematically investigated for the two orthorhombic Ti3+ centers C1 and C2 in ZnWO4. Center C1 is ascribed to the impurity Ti3+ at host W6+ site associated with two nearest neighbor oxygen vacancies due to charge compensation. The resultant tetrahedral [TiO4]5- cluster is determined to undergo the local orthorhombic elongation distortion, characterized by the axial distortion angle ?? (=?-?0?-6.84°) of the local impurity-ligand bond angle ? related to ?0 (?54.74°) and the perpendicular distortion angle ?? (=?-?0?2.5°) related to ?0 (?45°) of an ideal tetrahedron because of the Jahn-Teller effect. Center C2 is attributed to Ti3+ on Zn2+ site, and this octahedral [TiO6]9- cluster may experience the local axial elongation ?Z (?0.001 ?) and the planar bond angle variation ?? (?9.1°) due to the Jahn-Teller effect, resulting in a more regular oxygen octahedron. All the calculated SHPs (i.e., g factors for both centers, the hyperfine structure constants for center C2 and superhyperfine parameters of next nearest neighbor ligand W for center C1) show good agreement with the observed values. However, the theoretical results based on the previous assignment of center C1 as Ti3+ on W6+ site with only one nearest planar oxygen vacancy (i.e., five-fold coordinated octahedral [TiO5]7- cluster) show much worse agreement with the experimental data. The defect structures and the SHPs (especially the g anisotropies) are discussed for both centers. The present studies on the superhyperfine parameters of ligand W6+ for center C1 would be helpful to further investigations on the superhyperfine interactions of cation ligands which were rather scarcely treated before.

  8. Theoretical studies of the spin Hamiltonian parameters and local structures for the tetragonal Cu{sup 2+} and Ni{sup 3+} centers in Mg{sub 2}TiO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hua-Ming, E-mail: huamingzhang66@gmail.com [Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, Nanchang 330063 (China); Wan, Xiong; Zhang, Zhi-Ming [Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, Nanchang 330063 (China)

    2013-02-05

    Highlights: Black-Right-Pointing-Pointer Spin Hamiltonian parameters and local structures are analyzed for the impurity Cu{sup 2+} and Ni{sup 3+} centers in Mg{sub 2}TiO{sub 4}. Black-Right-Pointing-Pointer Ligand orbital and spin-orbit coupling contributions are included from the cluster approach due to moderate covalency. Black-Right-Pointing-Pointer Ligand octahedra experience relative elongations along C{sub 4} axis due to Jahn-Teller effect. - Abstract: The local structures of the two impurity Cu{sup 2+} (and Ni{sup 3+}) centers with low spin (S = 1/2) in Mg{sub 2}TiO{sub 4} are theoretically studied by using the perturbation formulas of the spin Hamiltonian parameters for 3d{sup 9} (and 3d{sup 7}) ions in tetragonally elongated octahedra. In these formulas, the tetragonal field parameters are quantitatively determined using the superposition model and the local structures of the impurity Cu{sup 2+} (and Ni{sup 3+}) centers, and the ligand orbital and spin-orbit coupling contributions are included on the basis of the cluster approach in view of moderate covalency for the studied systems. The [CuO{sub 6}]{sup 10-} and [NiO{sub 6}]{sup 9-}clusters on the substitutional Mg{sup 2+} site are found to suffer relative elongations by about {Delta}Z{sub Cu} ( Almost-Equal-To 3.2%) and {Delta}Z{sub Ni} ( Almost-Equal-To 0.7%) for the impurity Cu{sup 2+} and Ni{sup 3+} centers, respectively, along the C{sub 4} axis due to the Jahn-Teller effect. The calculated spin Hamiltonian parameters based on the above Jahn-Teller elongations show good agreement with the observed values. The results are discussed.

  9. Theoretical analysis of the spin Hamiltonian parameters in Co(II)S4 complexes, using density functional theory and correlated ab initio methods.

    Science.gov (United States)

    Maganas, Dimitrios; Sottini, Silvia; Kyritsis, Panayotis; Groenen, Edgar J J; Neese, Frank

    2011-09-19

    A systematic Density Functional Theory (DFT) and multiconfigurational ab initio computational analysis of the Spin Hamiltonian (SH) parameters of tetracoordinate S = 3/2 Co((II))S(4)-containing complexes has been performed. The complexes under study bear either arylthiolato, ArS(-), or dithioimidodiphosphinato, [R(2)P(S)NP(S)R'(2)](-) ligands. These complexes were chosen because accurate structural and spectroscopic data are available, including extensive Electron Paramagnetic Resonance (EPR)/Electron Nuclear Double Resonance (ENDOR) studies. For comparison purposes, the [Co(PPh(3))(2)Cl(2)] complex, which was thoroughly studied in the past by High-Field and Frequency EPR and Variable Temperature, Variable Field Magnetic Circular Dichroism (MCD) spectroscopies, was included in the studied set. The magnitude of the computed axial zero-field splitting parameter D (ZFS), of the Co((II))S(4) systems, was found to be within ~10% of the experimental values, provided that the property calculation is taken beyond the accuracy obtained with a second-order treatment of the spin-orbit coupling interaction. This is achieved by quasi degenerate perturbation theory (QDPT), in conjunction with complete active space configuration interaction (CAS-CI). The accuracy was increased upon recovering dynamic correlation with multiconfigurational ab initio methods. Specifically, spectroscopy oriented configuration interaction (SORCI), and difference dedicated configuration interaction (DDCI) were employed for the calculation of the D-tensor. The sign and magnitude of parameter D was analyzed in the framework of Ligand Field Theory, to reveal the differences in the electronic structures of the investigated Co((II))S(4) systems. For the axial complexes, accurate effective g'-tensors were obtained in the QDPT studies. These provide a diagnostic tool for the adopted ground state configuration (±3/2 or ±1/2) and are hence indicative of the sign of D. On the other hand, for the rhombic complexes, the determination of the sign of D required the SH parameters to be derived along suitably constructed symmetry interconversion pathways. This procedure, which introduces a dynamic perspective into the theoretical investigation, helped to shed some light on unresolved issues of the corresponding experimental studies. The metal hyperfine and ligand super-hyperfine A-tensors of the C(2) [Co{(SPPh(2))(SP(i)Pr(2))N}(2)] complex were estimated by DFT calculations. The theoretical data were shown to be in good agreement with the available experimental data. Decomposition of the metal A-tensor into individual contributions revealed that, despite the large ZFS, the observed significant anisotropy should be largely attributed to spin-dipolar contributions. The analysis of both, metal and ligand A-tensors, is consistent with a highly covalent character of the Co-S bonds. PMID:21848258

  10. Theoretical investigations of the local structure distortion and the spin Hamiltonian parameters of Cr 3+ ions at tetragonal charge-compensation defect CrF 5 O site in Cr 3+ : KMgF 3 crystals

    Science.gov (United States)

    Zi-Yuan, Yang

    2011-10-01

    The local structure distortion and the spin Hamiltonian (SH) parameters, including the zero-field splitting (ZFS) parameter D and the Zeeman g-factors g? and g?, are theoretically investigated by means of complete diagonalization method (CDM) and the microscopic spin Hamiltonian theory for tetragonal charge compensation CrF 5O defect center in Cr 3+:KMgF 3 crystals. The superposition model (SPM) calculations are carried out to provide the crystal field (CF) parameters. This investigation reveals that the replacement of O 2- for F - and its induced lattice relaxation ? 1(O 2-) combined with an inward relaxation of the nearest five fluorine ? 2(F -) give rise to a strong tetragonal crystal field, which in turn results in the large ZFS and large anisotropic g-factor ?g. The experimental SH parameters D and ?g can be reproduced well by assuming that O 2- moves towards the central ion Cr 3+ by ? 1(O 2-)=0.172R 0 and the five F - ions towards the central ion Cr 3+ by ? 2(F -)=0.022 R0. Our approach takes into account the spin-orbit (SO) interaction as well as the spin-spin (SS), spin-other-orbit (SOO), and orbit-orbit (OO) interactions omitted in previous studies. This shows that although the SO interaction is the most important one, the contributions to the SH parameters from other three magnetic interactions are appreciable and should not be omitted, especially for the ZFS parameter D.

  11. Theoretical investigations of the microscopic spin Hamiltonian parameters including the spin-spin and spin-other-orbit interactions for Ni{sup 2+}(3d{sup 8}) ions in trigonal crystal fields

    Energy Technology Data Exchange (ETDEWEB)

    Yang Ziyuan [Microelectronics Institute, Xidian University, Xi' an 710071 (China); Hao Yue [Microelectronics Institute, Xidian University, Xi' an 710071 (China); Rudowicz, Czeslaw [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR (China); Yeung Yauyuen [Department of Science, Hong Kong Institute of Education, 10 Lo Ping Road, Tai Po, New Territories, Hong Kong SAR (China)

    2004-05-26

    The microscopic origin of the spin Hamiltonian (SH) parameters for Ni{sup 2+}(3d{sup 8}) ions in a trigonal type I symmetry (C{sub 3v},D{sub 3d},D{sub 3}) crystal field (CF) is studied. In addition to the spin-orbit (SO) interaction, we consider also the spin-spin (SS) and spin-other-orbit (SOO) interactions. The relative importance of the four (SO, SS, SOO, and combined SO-SS-SOO) contributions to the SH parameters is investigated using the CFA/MSH package and the complete diagonalization method (CDM). The SO mechanism is dominant for all CF parameter (CFP) ranges studied, except where the contributions D{sub SO} to the zero-field splitting (ZFS) parameter D change sign. For the trigonal CFP, v{sub c} {approx} 1200cm{sup -1}D due to the other three mechanisms exceeds D{sub SO}. Although vertical bar D{sub SOO} vertical bar is quite small, the combined vertical bar D{sub SO-SOO} vertical bar is appreciable. The SO-based perturbation theory (PT) works generally well for the g-factors: g{sub parallel} and g{sub perp}, while it fails for D in the vicinity of v{sub c} and for large vertical bar v' vertical bar and v>0. The high percentage discrepancy ratio {delta}{sub D} = 2020% for v{sub c} indicates unreliability of D{sub SO} (in PT). Applications to Ni{sup 2+} ions at trigonal symmetry sites in LiNbO{sub 3}, {alpha}-LiIO{sub 3}, and Al{sub 2}O{sub 3}, are provided. The theoretical SH parameters are in good agreement with the experimental data. The low symmetry (C{sub 3}) effects induced by the angle {psi} are tentatively studied, but appear to be quite small.

  12. Theoretical investigations of the microscopic spin Hamiltonian parameters including the spin-spin and spin-other-orbit interactions for Ni2+(3d8) ions in trigonal crystal fields

    International Nuclear Information System (INIS)

    The microscopic origin of the spin Hamiltonian (SH) parameters for Ni2+(3d8) ions in a trigonal type I symmetry (C3v,D3d,D3) crystal field (CF) is studied. In addition to the spin-orbit (SO) interaction, we consider also the spin-spin (SS) and spin-other-orbit (SOO) interactions. The relative importance of the four (SO, SS, SOO, and combined SO-SS-SOO) contributions to the SH parameters is investigated using the CFA/MSH package and the complete diagonalization method (CDM). The SO mechanism is dominant for all CF parameter (CFP) ranges studied, except where the contributions DSO to the zero-field splitting (ZFS) parameter D change sign. For the trigonal CFP, vc ? 1200cm-1D due to the other three mechanisms exceeds DSO. Although vertical bar DSOO vertical bar is quite small, the combined vertical bar DSO-SOO vertical bar is appreciable. The SO-based perturbation theory (PT) works generally well for the g-factors: gparallel and gperp, while it fails for D in the vicinity of vc and for large vertical bar v' vertical bar and v>0. The high percentage discrepancy ratio ?D = 2020% for vc indicates unreliability of DSO (in PT). Applications to Ni2+ ions at trigonal symmetry sites in LiNbO3, ?-LiIO3, and Al2O3, are provided. The theoretical SH parameters are in good agreement with the experimental data. The low symmetry (C3) effects induced by the angle ? are tentatively studied, but appear to be quite small

  13. Studies of the spin-Hamiltonian parameters and defect structure for the tetragonal Fe5+ center in SrTiO3 crystals using a two-mechanism model

    Science.gov (United States)

    Zheng, Wen-Chen; Wu, Xiao-Xuan; Fang, Wang

    2007-11-01

    The high order perturbation formulas for spin-Hamiltonian (SH) parameters (g factors g_{\\parallel }, g_{\\perp } and zero-field splitting D) for 3d3 ions in tetragonal symmetry are established using a cluster approach. In these formulas, not only is the contribution to the SH parameters from the crystal-field (CF) mechanism included, but so also is that from the charge-transfer (CT) mechanism (which is neglected in the widely used CF theory). From these formulas, the g shifts \\Delta g_{\\parallel } ({=}g_{\\parallel }-g_{e} , where ge?2.0023, the value for the free electron), \\Delta g_{\\perp } ({=}g_{\\perp }-g_{e} ) and the zero-field splitting D for the tetragonal Fe5+ center in SrTiO3 crystal are calculated. The results (in particular, the positive g shifts, which cannot be explained on the basis of the CF mechanism) are in good agreement with the observed values. The calculation results show that (i) the sign of ?giCT (i={\\parallel } or \\perp ) due to the CT mechanism is opposite to that of ?giCF due to the CF mechanism, but the sign of DCT is the same as that of DCF and (ii) the ratio |QCT/QCF| (which represents the relative importance of the CT mechanism) takes values of about 143%, 143% and 114% for Q=\\Delta g_{ \\parallel } , \\Delta g_{\\perp } and D, respectively. This suggests that the positive g shifts are due mainly to the contribution of the CT mechanism; therefore for the high valence state 3dn ions in crystals, the contribution to SH parameters from the CT mechanism should be taken into account. The defect structure of the Fe5+ center in SrTiO3 crystal is also obtained from the calculations. The result is consistent with the expectations based on charge compensation and electrostatic interaction.

  14. Spectroscopic properties of Fe2+ ions at tetragonal sites-Crystal field effects and microscopic modeling of spin Hamiltonian parameters for Fe2+ (S=2) ions in K2FeF4 and K2ZnF4

    International Nuclear Information System (INIS)

    Magnetic and spectroscopic properties of the planar antiferromagnet K2FeF4 are determined by the Fe2+ ions at tetragonal sites. The two-dimensional easy-plane anisotropy exhibited by K2FeF4 is due to the zero field splitting (ZFS) terms arising from the orbital singlet ground state of Fe2+ ions with the spin S=2. To provide insight into the single-ion magnetic anisotropy of K2FeF4, the crystal field theory and the microscopic spin Hamiltonian (MSH) approach based on the tensor method is adopted. Survey of available experimental data on the crystal field energy levels and free-ion parameters for Fe2+ ions in K2FeF4 and related compounds is carried out to provide input for microscopic modeling of the ZFS parameters and the Zeeman electronic ones. The ZFS parameters are expressed in the extended Stevens notation and include contributions up to the fourth-order using as perturbation the spin-orbit and electronic spin-spin couplings within the tetragonal crystal field states of the ground 5D multiplet. Modeling of the ZFS parameters and the Zeeman electronic ones is carried out. Variation of these parameters is studied taking into account reasonable ranges of the microscopic ones, i.e. the spin-orbit and spin-spin coupling constants, and the energy level splittings, suitable for Fe2+ ions in K2FeF4 and Fe2+:K2ZnF4. Conversions between the ZFS parameters in the extended Stevens notation and the conventional ones are considered to enable comparison with the data of others. Comparative analysis of the MSH formulas derived earlier and our more complete ones indicates the importance of terms omitted earlier as well as the fourth-order ZFS parameters and the spin-spin coupling related contributions. The results may be useful also for Fe2+ ions at axial symmetry sites in related systems, i.e. Fe:K2MnF4, Rb2Co1-xFexF4, Fe2+:Rb2CrCl4, and Fe2+:Rb2ZnCl4. - Highlights: ? Truncated zero field splitting (ZFS) terms for Fe2+ in K2FeF4 and A2MX4 analyzed. ? Relations between truncated ZFS parameters and proper ones derived. ? Truncation of 4th-rank operators significantly affects D values for S=2 systems. ? Origin of 2nd-rank rhombic ZFS E-term found controversial. ? Feedback for microscopic modeling for Fe2+ (S=2) ions in A2MX4 provided.

  15. Spectroscopic properties of Fe 2+ ions at tetragonal sites—Crystal field effects and microscopic modeling of spin Hamiltonian parameters for Fe 2+ ( S=2) ions in K 2FeF 4 and K 2ZnF 4

    Science.gov (United States)

    Rudowicz, C.; Piwowarska, D.

    2011-11-01

    Magnetic and spectroscopic properties of the planar antiferromagnet K 2FeF 4 are determined by the Fe 2+ ions at tetragonal sites. The two-dimensional easy-plane anisotropy exhibited by K 2FeF 4 is due to the zero field splitting (ZFS) terms arising from the orbital singlet ground state of Fe 2+ ions with the spin S=2. To provide insight into the single-ion magnetic anisotropy of K 2FeF 4, the crystal field theory and the microscopic spin Hamiltonian (MSH) approach based on the tensor method is adopted. Survey of available experimental data on the crystal field energy levels and free-ion parameters for Fe 2+ ions in K 2FeF 4 and related compounds is carried out to provide input for microscopic modeling of the ZFS parameters and the Zeeman electronic ones. The ZFS parameters are expressed in the extended Stevens notation and include contributions up to the fourth-order using as perturbation the spin-orbit and electronic spin-spin couplings within the tetragonal crystal field states of the ground 5D multiplet. Modeling of the ZFS parameters and the Zeeman electronic ones is carried out. Variation of these parameters is studied taking into account reasonable ranges of the microscopic ones, i.e. the spin-orbit and spin-spin coupling constants, and the energy level splittings, suitable for Fe 2+ ions in K 2FeF 4 and Fe 2+:K 2ZnF 4. Conversions between the ZFS parameters in the extended Stevens notation and the conventional ones are considered to enable comparison with the data of others. Comparative analysis of the MSH formulas derived earlier and our more complete ones indicates the importance of terms omitted earlier as well as the fourth-order ZFS parameters and the spin-spin coupling related contributions. The results may be useful also for Fe 2+ ions at axial symmetry sites in related systems, i.e. Fe:K 2MnF 4, Rb 2Co 1-xFe xF 4, Fe 2+:Rb 2CrCl 4, and Fe 2+:Rb 2ZnCl 4.

  16. Modeling local structure using crystal field and spin Hamiltonian parameters: the tetragonal Fe{sub K}{sup 3+}-O{sub I}{sup 2-} defect center in KTaO{sub 3} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gnutek, P; Rudowicz, C [Institute of Physics, West Pomeranian University of Technology, Aleja Piastow 17, 70-310 Szczecin (Poland); Yang, Z Y, E-mail: crudowicz@zut.edu.p [Department of Physics, Baoji University of Arts and Science, Baoji 721007 (China)

    2009-11-11

    The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g{sub ||} and g{sub perpendicular}, are theoretically investigated for the Fe{sub K}{sup 3+}-O{sub I}{sup 2-} center in KTaO{sub 3} crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the Fe{sub K}{sup 3+}-O{sub I}{sup 2-} defect center in KTaO{sub 3}. This modeling reveals that the off-center displacement of the Fe{sup 3+} ions, DELTA{sub 1}(Fe{sup 3+}), combined with an inward relaxation of the nearest oxygen ligands, DELTA{sub 2}(O{sup 2-}), and the existence of the interstitial oxygen O{sub I}{sup 2-} give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the Fe{sub K}{sup 3+}-O{sub I}{sup 2-} center in KTaO{sub 3}. Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of DELTA{sub 1}(Fe{sup 3+}) and DELTA{sub 2}(O{sup 2-}) as well as the possible location of O{sub I}{sup 2-} ligands around Fe{sup 3+} ions in KTaO{sub 3}. The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g{sub ||} and g{sub perpendicular} and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing in the literature indicates considerable advantages of our method and presumably higher reliability of our predictions.

  17. Gravitational spin Hamiltonians from the S matrix

    Science.gov (United States)

    Vaidya, Varun

    2015-01-01

    We utilize generalized unitarity and recursion relations combined with effective field theory techniques to compute spin-dependent interaction terms for an inspiralling binary system in the post-Newtonian (PN) approximation. Using these methods offers great computational advantage over traditional techniques involving Feynman diagrams, especially at higher orders in the PN expansion. As a specific example, we reproduce the spin-orbit (up to 2.5PN order) and the leading-order S2 (2PN) Hamiltonian for a binary system with one of the massive objects having nonzero spin using the S -matrix elements of elementary particles. For the same system, we also obtain the S3 (3.5PN) spin Hamiltonian for an arbitrary massive object, which was until now known only for a black hole. Furthermore, we derive the missing S4 Hamiltonian at leading order (4PN), again for an arbitrary massive object and establish that the minimal coupling of an elementary particle to gravity automatically captures the physics of a spinning black hole. Finally, the Kerr metric is obtained as a series in GN by comparing the action of a test particle in the vicinity of a spinning black hole to the derived potential.

  18. Gravitational spin Hamiltonians from the S matrix

    CERN Document Server

    Vaidya, Varun

    2014-01-01

    We utilize generalized unitarity and recursion relations combined with effective field theory(EFT) techniques to compute spin dependent interaction terms for inspiralling binary systems in the post newtonian(PN) approximation. Using these methods offers great computational advantage over traditional techniques involving feynman diagrams, especially at higher orders in the PN expansion. As a specific example, we reproduce the spin-orbit interaction up to 2.5 PN order as also the leading order $S^2$(3PN) hamiltonian for an arbitrary massive object. We also obtain the unknown $S^3$(3.5PN) spin hamiltonian for an arbitrary massive object in terms of its low frequency linear response to gravitational perturbations, which was till now known only for a black hole. Furthermore, we derive the missing $S^4$ Hamiltonian at leading order(4PN) for an arbitrary massive object and establish that a minimal coupling of a massive elementary particle to gravity leads to a black hole structure. Finally, the Kerr metric is obtain...

  19. On Spin Hamiltonian Fits to Mössbauer Spectra of High-Spin Fe(II) Porphyrinate Systems

    OpenAIRE

    Schulz, Charles E; Hu, Chuanjiang; Scheidt, W.Robert

    2006-01-01

    Fits to Mössbauer spectra of high-spin iron(II) porphyrinates have been applied to the Fe(II) model compounds octaethylporphyrin(1,2-dimethylimidazole) and tetra-paramethoxyporphyrin(1,2-dimethylimidazole). Mössbauer spectra have been measured on these compounds at 4.2 K in large applied fields. Spin Hamiltonians were used for fitting both the electronic and nuclear interactions. The fits are done by adjusting the Hamiltonian parameters to simultaneously minimize the total ?2 for three differ...

  20. On Spin Hamiltonian fits to Moessbauer spectra of high-spin Fe(II) porphyrinate systems

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, Charles E., E-mail: cschulz@knox.edu [Knox College, Department of Physics (United States); Hu Chuanjiang, E-mail: scheidt.1@nd.edu; Scheidt, W. Robert [University of Notre Dame, Department of Chemistry and Biochemistry (United States)

    2006-06-15

    Fits to Moessbauer spectra of high-spin iron(II) porphyrinates have been applied to the Fe(II) model compounds octaethylporphyrin(1,2-dimethylimidazole) and tetra-paramethoxyporphyrin(1,2-dimethylimidazole). Moessbauer spectra have been measured on these compounds at 4.2 K in large applied fields. Spin Hamiltonians were used for fitting both the electronic and nuclear interactions. The fits are done by adjusting the Hamiltonian parameters to simultaneously minimize the total {chi}{sup 2} for three different applied fields. In order to get best fits, the EFG tensor need to be rotated relative to the ZFS tensor. A comparative sensitivity analysis of their Spin Hamiltonian parameters has also been done on the ZFS parameters D, and the EFG asymmetry parameter {eta}. The best fits suggest that both systems definitely have a negative quadrupole splitting, and that largest EFG component is tilted far from the z-axis of the ZFS tensor, which is likely to be near the heme normal.

  1. On Spin Hamiltonian Fits to Mössbauer Spectra of High-Spin Fe(II) Porphyrinate Systems.

    Science.gov (United States)

    Schulz, Charles E; Hu, Chuanjiang; Scheidt, W Robert

    2006-06-01

    Fits to Mössbauer spectra of high-spin iron(II) porphyrinates have been applied to the Fe(II) model compounds octaethylporphyrin(1,2-dimethylimidazole) and tetra-paramethoxyporphyrin(1,2-dimethylimidazole). Mössbauer spectra have been measured on these compounds at 4.2 K in large applied fields. Spin Hamiltonians were used for fitting both the electronic and nuclear interactions. The fits are done by adjusting the Hamiltonian parameters to simultaneously minimize the total ?(2) for three different applied fields. In order to get best fits, the EFG tensor need to be rotated relative to the ZFS tensor. A comparative sensitivity analysis of their Spin Hamiltonian parameters has also been done on the ZFS parameters D, and the EFG asymmetry parameter ?. The best fits suggest that both systems definitely have a negative quadrupole splitting, and that largest EFG component is tilted far from the z-axis of the ZFS tensor, which is likely to be near the heme normal. PMID:18160971

  2. On Spin Hamiltonian fits to Moessbauer spectra of high-spin Fe(II) porphyrinate systems

    International Nuclear Information System (INIS)

    Fits to Moessbauer spectra of high-spin iron(II) porphyrinates have been applied to the Fe(II) model compounds octaethylporphyrin(1,2-dimethylimidazole) and tetra-paramethoxyporphyrin(1,2-dimethylimidazole). Moessbauer spectra have been measured on these compounds at 4.2 K in large applied fields. Spin Hamiltonians were used for fitting both the electronic and nuclear interactions. The fits are done by adjusting the Hamiltonian parameters to simultaneously minimize the total ?2 for three different applied fields. In order to get best fits, the EFG tensor need to be rotated relative to the ZFS tensor. A comparative sensitivity analysis of their Spin Hamiltonian parameters has also been done on the ZFS parameters D, and the EFG asymmetry parameter ?. The best fits suggest that both systems definitely have a negative quadrupole splitting, and that largest EFG component is tilted far from the z-axis of the ZFS tensor, which is likely to be near the heme normal.

  3. Electronic origins of NMR parameters

    International Nuclear Information System (INIS)

    The Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for the understanding of many theoretical aspects of molecular physics. In this work, many of these aspects as well as its applications will be discussed. (A.C.A.S.)

  4. Spectroscopic properties of Fe{sup 2+} ions at tetragonal sites-Crystal field effects and microscopic modeling of spin Hamiltonian parameters for Fe{sup 2+} (S=2) ions in K{sub 2}FeF{sub 4} and K{sub 2}ZnF{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Rudowicz, C., E-mail: crudowicz@zut.edu.pl [Modeling in Spectroscopy Group, Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland); Piwowarska, D. [Modeling in Spectroscopy Group, Institute of Physics, West Pomeranian University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland)

    2011-11-15

    Magnetic and spectroscopic properties of the planar antiferromagnet K{sub 2}FeF{sub 4} are determined by the Fe{sup 2+} ions at tetragonal sites. The two-dimensional easy-plane anisotropy exhibited by K{sub 2}FeF{sub 4} is due to the zero field splitting (ZFS) terms arising from the orbital singlet ground state of Fe{sup 2+} ions with the spin S=2. To provide insight into the single-ion magnetic anisotropy of K{sub 2}FeF{sub 4}, the crystal field theory and the microscopic spin Hamiltonian (MSH) approach based on the tensor method is adopted. Survey of available experimental data on the crystal field energy levels and free-ion parameters for Fe{sup 2+} ions in K{sub 2}FeF{sub 4} and related compounds is carried out to provide input for microscopic modeling of the ZFS parameters and the Zeeman electronic ones. The ZFS parameters are expressed in the extended Stevens notation and include contributions up to the fourth-order using as perturbation the spin-orbit and electronic spin-spin couplings within the tetragonal crystal field states of the ground {sup 5}D multiplet. Modeling of the ZFS parameters and the Zeeman electronic ones is carried out. Variation of these parameters is studied taking into account reasonable ranges of the microscopic ones, i.e. the spin-orbit and spin-spin coupling constants, and the energy level splittings, suitable for Fe{sup 2+} ions in K{sub 2}FeF{sub 4} and Fe{sup 2+}:K{sub 2}ZnF{sub 4}. Conversions between the ZFS parameters in the extended Stevens notation and the conventional ones are considered to enable comparison with the data of others. Comparative analysis of the MSH formulas derived earlier and our more complete ones indicates the importance of terms omitted earlier as well as the fourth-order ZFS parameters and the spin-spin coupling related contributions. The results may be useful also for Fe{sup 2+} ions at axial symmetry sites in related systems, i.e. Fe:K{sub 2}MnF{sub 4}, Rb{sub 2}Co{sub 1-x}Fe{sub x}F{sub 4}, Fe{sup 2+}:Rb{sub 2}CrCl{sub 4}, and Fe{sup 2+}:Rb{sub 2}ZnCl{sub 4}. - Highlights: > Truncated zero field splitting (ZFS) terms for Fe{sup 2+} in K{sub 2}FeF{sub 4} and A{sub 2}MX{sub 4} analyzed. > Relations between truncated ZFS parameters and proper ones derived. > Truncation of 4th-rank operators significantly affects D values for S=2 systems. > Origin of 2nd-rank rhombic ZFS E-term found controversial. > Feedback for microscopic modeling for Fe{sup 2+} (S=2) ions in A{sub 2}MX{sub 4} provided.

  5. Magnetic interactions and microscopic spin Hamiltonian approaches for 3d3 ions at trigonal symmetry sites

    International Nuclear Information System (INIS)

    The spin-Hamiltonian (SH) parameters (D, g//, and g-bar ) for 4A2(3d3)-state ions at trigonal symmetry sites, taking into account the spin-spin (SS), the spin-other-orbit (SOO), the orbit-orbit (OO) magnetic interactions besides the well-known spin-orbit (SO) magnetic interaction, are studied in the intermediate-field coupling scheme using the CDM/MSH (Complete Diagonalization Method/ Microscopic Spin Hamiltonian) program recently developed. It is shown that the SH parameters arise from five microscopic mechanisms including SO coupling mechanism, SS coupling mechanism, SOO coupling mechanism, OO coupling mechanism, and SO-SS-SOO-OO combined coupling mechanism. The relative importance of the five (SO, SS, SOO, OO and combined SO-SS-SOO-OO) contributions to the SH parameters is investigated. It is shown that the SO coupling mechanism in these coupling mechanisms is the most important one. The effect of the OO coupling mechanism on the energy levels is appreciable whereas that on the SH parameters is negligible. The contribution from the SS coupling mechanism to the zero-field splitting (ZFS) parameter D is appreciable but is quite small to g-factors: g// and g-bar . In contrast, the contribution from the SOO coupling mechanism to the ZFS parameter D is quite small but is appreciable to g-factors. Two perturbation theory method approaches have been examined using CDM/MSH program. It is found that the analytical expressions developed by Macfarlane for D, g//, and g-bar work well in most of the CF ranges considered whereas those developed by Zdansky for D do not work well in almost all the CF ranges considered. The illustrative evaluation is performed for typical laser material Cr3+: Al2O3. The good agreements between the theoretical values and the experimental finding are obtained. It is found that the percentage difference ?D(=|DTotal(CDM)-DSO(CDM)|/|DTotal(CDM)|x100%) reaches 20.9% for laser material Cr3+: Al2O3. The investigation indicates that the contribution to the ZFS parameter D from the SS and SOO magnetic interactions should not be omitted.

  6. Universal Theoretical Approach to Extract Anisotropic Spin Hamiltonians.

    Science.gov (United States)

    Maurice, Rémi; Bastardis, Roland; Graaf, Coen de; Suaud, Nicolas; Mallah, Talal; Guihéry, Nathalie

    2009-11-10

    Monometallic Ni(II) and Co(II) complexes with large magnetic anisotropy are studied using correlated wave function based ab initio calculations. Based on the effective Hamiltonian theory, we propose a scheme to extract both the parameters of the zero-field splitting (ZFS) tensor and the magnetic anisotropy axes. Contrarily to the usual theoretical procedure of extraction, the method presented here determines the sign and the magnitude of the ZFS parameters in any circumstances. While the energy levels provide enough information to extract the ZFS parameters in Ni(II) complexes, additional information contained in the wave functions must be used to extract the ZFS parameters of Co(II) complexes. The effective Hamiltonian procedure also enables us to confirm the validity of the standard model Hamiltonian to produce the magnetic anisotropy of monometallic complexes. The calculated ZFS parameters are in good agreement with high-field, high-frequency electron paramagnetic resonance spectroscopy and frequency domain magnetic resonance spectroscopy data. A methodological analysis of the results shows that the ligand-to-metal charge transfer configurations must be introduced in the reference space to obtain quantitative agreement with the experimental estimates of the ZFS parameters. PMID:26609979

  7. Noether's theorem and low symmetry aspects concerning the crystal (ligand) field Hamiltonians and spin Hamiltonians

    International Nuclear Information System (INIS)

    This review presents a concise summary of major findings arising from our recent studies concerning the symmetry properties of crystal/ligand field (CF/LF) Hamiltonians and spin Hamiltonians (SHs). First we provide a bird's-eye view of these studies. Then we overview (i) the pertinent basic concepts and notations (ii) the algebraic symmetry (AS) of Hamiltonians for continuous rotational symmetry (CRS) cases, and (iii) the concepts of the rotational invariants and moments of CF Hamiltonians. This enables a new look from the point of view of the Noether's theorem on the properties of CF/LF Hamiltonians and SHs invariant under CRS, i.e. hexagonal II, tetragonal II, trigonal II, monoclinic, and triclinic ones. An important theorem and a conjecture on the conserved quantities stipulated by Noether's theorem for the Hamiltonians in question formulated by us helps to elucidate the interrelationships and deeper meaning of the concepts involved. Implications of the existence of the conserved quantities for interpretation of experimental CF parameter (CFP) datasets are encapsulated in five corollaries. These considerations reveal that the feasibility of determination of CFPs from fitting experimental spectra and the reduction of the existing higher-order rotational invariants for hexagonal type II and cubic symmetry require reinterpretation. This novel approach enables adoption of better fitting strategies utilizing welldefined conserved quantities, which are invariant under CRS. The advantages of this approach are illustrated using the CFP datasets reported in literature for RE3+ (4fN) ions in LiYF4. This review deals also with the fundamental intricate aspects, hitherto not fully understood, concerning the CF Hamiltonians for the 'low symmetry' cases, including the CRS cases as well as orthorhombic ones. This includes: (1) selection of the axis systems, (2) types of CF parameters and their properties, (3) introduction of a new notion of a nominal axis system for the fitted CFP datasets, (4) implications of the Noether's theorem and the AS of CF Hamiltonians, (5) correlation properties among CFP datasets, (6) the rotational degrees of freedom and the reduction of the number of independent CFPs, and (7) extension of the multiple correlated fitting technique. Clarification of these intricate aspects enables us to provide a general framework aimed at achieving an increased compatibility and reliability of CFP datasets for transition ions at low symmetry sites in crystals. The usefulness of this framework is illustrated by reanalysis of the CFP datasets for Nd3+ (Pr3+ ) in NdGaO3 (PrGaO3) and RNiO3

  8. Spin Hamiltonian, order out of a Coulomb phase, and pseudocriticality in the frustrated pyrochlore Heisenberg antiferromagnet FeF3

    Science.gov (United States)

    Sadeghi, Azam; Alaei, Mojtaba; Shahbazi, Farhad; Gingras, Michel J. P.

    2015-04-01

    FeF3, with its half-filled Fe3 +3 d orbital, hence zero orbital angular momentum and S =5 /2 , is often put forward as a prototypical highly frustrated classical Heisenberg pyrochlore antiferromagnet. By employing ab initio density functional theory, we obtain an effective spin Hamiltonian for this material. This Hamiltonian contains nearest-neighbor antiferromagnetic Heisenberg, biquadratic, and Dzyaloshinskii-Moriya interactions as dominant terms and we use Monte Carlo simulations to investigate the nonzero temperature properties of this minimal model. We find that upon decreasing temperature, the system passes through a Coulomb phase, composed of short-range correlated coplanar states, before transforming into an "all-in/all-out" (AIAO) state via a very weakly first-order transition at a critical temperature Tc?22 K, in good agreement with the experimental value for a reasonable set of Coulomb interaction U and Hund's coupling JH describing the material. Despite the transition being first order, the AIAO order parameter evolves below Tc with a power-law behavior characterized by a pseudo "critical exponent" ? ?0.18 in accord with experiment. We comment on the origin of this unusual ? value.

  9. Rovibrational and temperature effects in theoretical studies of NMR parameters

    DEFF Research Database (Denmark)

    Faber, Rasmus; Kaminsky, Jakub

    2016-01-01

    The demand for high precision calculations of NMR shieldings (or their related values, chemical shifts ?) 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 for molecular equilibrium geometries creates a demand for zero point vibrational and temperature corrections. In this chapter we describe briefly the theory behind rovibrational corrections and review then some important contributions to this field.

  10. Derivation of the spin Hamiltonians for Fe in MgO

    Science.gov (United States)

    Ferrón, A.; Delgado, F.; Fernández-Rossier, J.

    2015-03-01

    A method to calculate the effective spin Hamiltonian for a transition metal impurity in a non-magnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO. In the first step we calculate the electronic structure employing standard density functional theory (DFT), based on generalized gradient approximation (GGA), using plane waves as a basis set. The corresponding basis of atomic-like maximally localized Wannier functions is derived and used to represent the DFT Hamiltonian, resulting in a tight-binding model for the atomic orbitals of the magnetic impurity. The third step is to solve, by exact numerical diagonalization, the N electron problem in the open shell of the magnetic atom, including both effects of spin-orbit and Coulomb repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is mapped into effective spin models that, in addition to the spin matrices S, can also include the orbital angular momentum L when appropriate. We successfully apply the method to Fe in MgO, considering both the undistorted and Jahn-Teller (JT) distorted cases. Implications for the influence of Fe impurities on the performance of magnetic tunnel junctions based on MgO are discussed.

  11. 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

    CERN Document Server

    Farberovich, Oleg V; Soldatov, Alexander V

    2014-01-01

    We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density functional scheme for calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange couplings parameters linking the nickel ions with a silicon substrate. In this article we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on a silicon surface. The solution of the problem of the entanglement between a spin states in N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement. We have studied the Rabi oscillations to evaluate the N-spin qubits syst...

  12. Modeling Ne-21 NMR parameters for carbon nanosystems.

    Czech Academy of Sciences Publication Activity Database

    Kupka, T.; Nieradka, M.; Kaminský, Jakub; Stobinski, L.

    2013-01-01

    Ro?. 51, ?. 10 (2013), s. 676-681. ISSN 0749-1581 R&D Projects: GA ?R GAP208/11/0105; GA MŠk(CZ) LH11033 Grant ostatní: AV ?R(CZ) M200551205 Institutional support: RVO:61388963 Keywords : Ne-21 NMR * GIAO NMR * molecular modeling * carbon nanostructures Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.559, year: 2013

  13. 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

  14. Limitations of the Giant Spin Hamiltonian in Explaining Magnetization Tunneling in a Single-Molecule Magnet

    CERN Document Server

    Wilson, A; Yang, E C; Nakano, M; Hendrickson, D N; Hill, S

    2006-01-01

    EPR studies of a Ni4 single-molecule magnet yield the zero-field-splitting (zfs) parameters, D, B40 and B44, based on a giant spin approximation (GSA) with S = 4. Experiments on an isostructural Ni-doped Zn4 crystal establish the Ni(II) ion zfs parameters. The 4th-order zfs parameters in the GSA arise from the interplay between the Heisenberg interaction, Js1.s2, and the 2nd-order single-ion anisotropy, giving rise to mixing of higher lying states into the S = 4 state. Consequently, J directly influences the zfs in the ground state, enabling its direct determination by EPR.

  15. Limitations of the Giant Spin Hamiltonian in Explaining Magnetization Tunneling in a Single-Molecule Magnet

    OpenAIRE

    Wilson, A; Lawrence, J; Yang, E-C.; Nakano, M; Hendrickson, D. N.; Hill, S

    2006-01-01

    EPR studies of a Ni4 single-molecule magnet yield the zero-field-splitting (zfs) parameters, D, B40 and B44, based on a giant spin approximation (GSA) with S = 4. Experiments on an isostructural Ni-doped Zn4 crystal establish the Ni(II) ion zfs parameters. The 4th-order zfs parameters in the GSA arise from the interplay between the Heisenberg interaction, Js1.s2, and the 2nd-order single-ion anisotropy, giving rise to mixing of higher lying states into the S = 4 state. Consequently, J directl...

  16. NMR and FTIR characterization of petroleum residues: structural parameters and correlations

    International Nuclear Information System (INIS)

    Heavy petroleum residues can be used as raw materials in the production of various carbon products, notably isotropic and anisotropic pitches and different types of coke. The chemical characterization of these residues, and carbon materials in general, is a challenge that has to be addressed in order to allow the adequate optimization of production processes. In this study, petroleum residues of different refineries were studied by NMR, FTIR and elemental analysis. Optimum parameters were determined for NMR analysis and diffuse reflectance spectroscopy (DRIFTS), a technique that is usually applied to solid materials but was shown to yield good quality spectra for these samples. Correlations were found between NMR and FTIR results for the aromaticity index, a structural parameter widely used in the study of mesophase formation in pitches, as well as between C/H ratios and the aromaticity index. Other structural parameters of interest were also obtained. (author)

  17. 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

    Science.gov (United States)

    Farberovich, Oleg V.; Mazalova, Victoria L.; Soldatov, Alexander V.

    2015-11-01

    We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals Jij of the nanosystem Ni7-Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni7-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 ?s). The comparison of the energy 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 Ni7 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.

  18. 1H and 13C NMR for determining average molecular parameters of asphaltenes from vacuum residue distillation

    International Nuclear Information System (INIS)

    The aim of this work was to obtain average molecular parameters by using some analytical techniques, namely NMR (1H and 13C NMR), vapor pressure osmometry (VPO), and elemental analysis. NMR provided particular information on important molecular parameters such as aromatic carbon fraction, aliphatic carbons fraction, alkyl-substituted aromatic carbons, unsubstituted aromatic carbons, among others. Molecular modeling was employed to build the structure of asphaltenes using the experimental data. (author)

  19. Microscopic spin Hamiltonian approaches for 3d8 and 3d2 ions in a trigonal crystal field - perturbation theory methods versus complete diagonalization methods

    International Nuclear Information System (INIS)

    In this paper, we critically review the existing microscopic spin Hamiltonian (MSH) approaches, namely the complete diagonalization method (CDM) and the perturbation theory method (PTM), for 3d8(3d2) ions in a trigonal (C3v, D3, D3d) symmetry crystal field (CF). A new CDM is presented and a CFA/MSH computer package based on our crystal-field analysis (CFA) package for 3dN ions is developed for numerical calculations. Our method takes into account the contribution to the SH parameters (D, gparallel and gperpendicular to) from all 45 CF states for 3d8(3d2) ions and is based on the complete diagonalization of the Hamiltonian including the electrostatic interactions, the CF terms (in the intermediate CF scheme) and the spin-orbit coupling. The CFA/MSH package enables us to study not only the CF energy levels and wavefunctions but also the SH parameters as functions of the CF parameters (B20, B40 and B43 or alternatively Dq, ? and ?') for 3d8(3d2) ions in trigonal symmetry. Extensive comparative studies of other MSH approaches are carried out using the CFA/MSH package. First, we check the accuracy of the approximate PTM based on the 'quasi-fourth-order' perturbation formulae developed by Petrosyan and Mirzakhanyan (PM). The present investigations indicate that the PM formulae for the g-factors (gparallel and gperpendicular to) indeed work well, especially for the cases of small v and ?' and large Dq, whereas the PM formula for the zero-field splitting (ZFS) exhibits serious shortcomings. Earlier criticism of the PM approach by Zhou et al (Zhou K W, Zhao S B, Wu P F and Xie J K 1990 Phys. Status Solidi b 162 193) is then revisited. Second, we carry out an extensive comparison of the results of the present CFA/MSH package and those of other CDMs based on the strong- and weak-CF schemes. The CF energy levels and the SH parameters for 3d2 and 3d8 ions at C3v symmetry sites in several crystals are calculated and analysed. Our investigations reveal serious inconsistencies in the CDM results of Zhou et al and Li (Li Y 1995 J. Phys.: Condens. Matter 7 4075) based on the strong-CF scheme for Ni2+ ions in LiNbO3 crystals. The correctness of our CFA/MSH package is verified by comparing our results with the predictions of Ma et al (Ma D P, Ma N, Ma X D and Zhang H M 1998 J. Phys. Chem. Solids 59 1211, Ma D P, Ma X D, Chen J R and Liu Y Y 1997 Phys. Rev. B 56 1780) and Macfarlane (Macfarlane R M 1964 J. Chem. Phys. 40 373) for ?-Al2O3:V3+(3d2) and MgO:Ni2+(3d8). It appears that the two independent approaches show perfect agreement with our approach, unlike those of Zhou et al and Li, which turn out to be unreliable. Our results reveal that the contributions to the ZFS parameter from the higher excited states cannot be neglected; also, the ZFS parameter is very sensitive to slight changes of the crystal structure. Hence our CFA/MSH package, which takes into account the contributions to the ZFS parameter from the higher excited states, can provide reliable results and proves to be a useful tool for the studies of the effect of the lattice distortions, defects and structural disorder on the spectroscopic properties of 3d2 and 3d8 ions at trigonal symmetry sites in crystals. (author)

  20. Magnetostructural correlations for Fe2+ ions at orthorhombic sites in FeCl2·4H2O and FeF2·4H2O crystals modeled by microscopic spin Hamiltonian approach

    Science.gov (United States)

    Zaj?c, Magdalena; Lipi?ski, Ignacy Eryk; Rudowicz, Czes?aw

    2016-03-01

    The microscopic spin Hamiltonian (MSH) theory developed up to the fourth-order perturbation theory for 3d4 and 3d6 ions with spin S=2 within the 5D approximation is employed to predict the zero field splitting (ZFS) parameters and the Zeeman electronic (Ze) ones. The SH parameters, measurable by electron magnetic resonance (EMR), are expressed in terms of the microscopic parameters, i.e. the spin-orbit (?), spin-spin (?) coupling constants, and the crystal-field (ligands-field) energy levels (?i) within the 5D multiplet. The energies, ?i, are indirectly related with structural data, thus enabling investigation of magnetostructural correlations. As a case study Fe2+ (3d6; S=2) ions at orthorhombic sites in FeCl2·4H2O and FeF2·4H2O crystals are considered. Calculations of the ZFS and Ze parameters are carried out for wide ranges of values of the microscopic parameters using the package MSH/VBA. Dependence of the theoretically determined ZFS parameters bkq (in the Stevens notation) and the Zeeman factors gi on ?, ?, and ?i is examined and suitable graphs are presented. The absolute value of dominant ZFS parameter |b20| is predicted to be in the range from nearly 8.5 to 1.4 cm-1. Matching the theoretical SH parameters and the experimental ones enables determination of the suitable values of ?, ?, and ?i. The fourth-rank ZFS parameters and the ?(spin-spin)-related contributions, considered for the first time here, are found important. The MSH predictions may be verified and fine-tuned by high-magnetic field and high-frequency EMR measurements. The method employed here and the present results may be also useful for other structurally related systems.

  1. Sensitivity of the NMR density matrix to pulse sequence parameters: a simplified analytic approach.

    Science.gov (United States)

    Momot, Konstantin I; Takegoshi, K

    2012-08-01

    We present a formalism for the analysis of sensitivity of nuclear magnetic resonance pulse sequences to variations of pulse sequence parameters, such as radiofrequency pulses, gradient pulses or evolution delays. The formalism enables the calculation of compact, analytic expressions for the derivatives of the density matrix and the observed signal with respect to the parameters varied. The analysis is based on two constructs computed in the course of modified density-matrix simulations: the error interrogation operators and error commutators. The approach presented is consequently named the Error Commutator Formalism (ECF). It is used to evaluate the sensitivity of the density matrix to parameter variation based on the simulations carried out for the ideal parameters, obviating the need for finite-difference calculations of signal errors. The ECF analysis therefore carries a computational cost comparable to a single density-matrix or product-operator simulation. Its application is illustrated using a number of examples from basic NMR spectroscopy. We show that the strength of the ECF is its ability to provide analytic insights into the propagation of errors through pulse sequences and the behaviour of signal errors under phase cycling. Furthermore, the approach is algorithmic and easily amenable to implementation in the form of a programming code. It is envisaged that it could be incorporated into standard NMR product-operator simulation packages. PMID:22750252

  2. Exact two-component relativistic theory for NMR parameters: general formulation and pilot application.

    Science.gov (United States)

    Sun, Qiming; Xiao, Yunlong; Liu, Wenjian

    2012-11-01

    The previously proposed exact two-component (X2C) relativistic theory of nuclear magnetic resonance (NMR) parameters [Q. Sun, W. Liu, Y. Xiao, and L. Cheng, J. Chem. Phys. 131, 081101 (2009)] is reformulated to accommodate two schemes for kinetic balance, five schemes for magnetic balance, and three schemes for decoupling in a unified manner, at both matrix and operator levels. In addition, three definitions of spin magnetization are considered in the coupled-perturbed Kohn-Sham equation. Apart from its simplicity, the most salient feature of X2C-NMR lies in that its diamagnetic and paramagnetic terms agree individually with the corresponding four-component counterparts for any finite basis. For practical applications, five approximate schemes for the first order coupling matrix X(10) and four approximate schemes for the treatment of two-electron integrals are introduced, which render the computations of X2C-NMR very much the same as those of approximate two-component approaches. PMID:23145715

  3. Noninvasive temperature distribution measurement by simultaneous use of multiple NMR parameters

    International Nuclear Information System (INIS)

    A noninvasive thermometry method using NMR parameters, M0, T1 and T2, is proposed. Based on phantom experiments using a CuSO4 solution and its gels, multiple regression temperature estimation using T1 and M0 is examined and showed estimation error reductions of 2-10 % comparing with T1 single. From in-vitro experiments with bovine tissues, it is found that the temperature dependence of each parameter greatly varies according to the kinds of the tissues. As a conclusion, by choosing the optimum parameters for each tissue and, if necessary, by adapting multiple regression, accurate and tissue insensitive temperature imaging inside a biological body is expected. (author)

  4. NMR Principles

    OpenAIRE

    Hore, PJ

    2010-01-01

    The basic theory behind NMR spectroscopy is described. The various NMR parameters that can be obtained from NMR spectra are explained, including the chemical shift, spin-spin coupling, and relaxation. Some explanation of the theory of how NMR is detected is also presented. © 1999 Elsevier Ltd All rights reserved.

  5. Thermal and solvent effects on NMR spectroscopy parameters of a prototypical Chagas disease drug

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    Full text. Hydrogen bonds in liquids can be of crucial importance for solvent effects in spectroscopy. We have herein computed the nuclear magnetic spin-spin coupling constants (SSCC) involving 15N and 1H nuclei motivated by the relevance of these couplings for the indirect detection of the 15N chemical shifts. Such nJ(N,H) couplings are now also taken as probes for obtaining structural information in proteins. In this work, we focus on the J-couplings; a complete analysis of the NMR spectral data for the compounds studied can be found in previous papers. Thermal and solvent effects on the SSCCs of metronidazole (1) were studied computationally with appropriate quantum-chemical methods. Metronidazole may serve as a model compound to investigate the influence of solvent molecules on the NMR spin-spin coupling constants in heterocyclic rings. We find a hydrogen bond between 1 and a solvent water molecule that is associated with a bond critical point between the imidazole N-3 atom and a water H atom. AIM analysis indicates this hydrogen bond to be mainly electrostatic in nature. Simple static SSCC calculations in vacuo underestimate the nJ(N-3,H) coupling constants because of the neglect of hydrogen bonding. PCM-based treatments perform reasonably well because of the electrostatic character of the hydrogen bond. For more reliable predictions, it is important to take into account the dynamics of the system and to include nearby solvent molecules explicitly. The reduction of the hyperconjugative interactions involving the sigma CH bond or the sigma {sup *}CH antibond (with the coupling nucleus H) that is found in solution appears to be correlated to the reduction of coupling pathways in the imidazole ring. Since nuclear spin orientation information is transferred electronically to the other nuclei in the molecule, experimentally determined J-couplings directly reflect the nature of the chemical bond involved.106,107 Unlike most other NMR properties, which can be understood on the basis of semiclassical physics, J-coupling is a purely quantum- mechanical phenomenon. The present results provide evidence that hyperconjugative effects in solute molecules are not due to changes in geometric parameters upon solvation, but arise from the direct response of the electronic wave function to the presence of the solvent, which can be represented by discrete molecules and/or the dielectric bulk. We believe that our findings may be helpful to rationalize the relation between NMR parameters and the interactions in hydrogen-bonded complexes. Further applications along these lines are in progress. (author)

  6. Thermal and solvent effects on NMR spectroscopy parameters of a prototypical Chagas disease drug

    International Nuclear Information System (INIS)

    Full text. Hydrogen bonds in liquids can be of crucial importance for solvent effects in spectroscopy. We have herein computed the nuclear magnetic spin-spin coupling constants (SSCC) involving 15N and 1H nuclei motivated by the relevance of these couplings for the indirect detection of the 15N chemical shifts. Such nJ(N,H) couplings are now also taken as probes for obtaining structural information in proteins. In this work, we focus on the J-couplings; a complete analysis of the NMR spectral data for the compounds studied can be found in previous papers. Thermal and solvent effects on the SSCCs of metronidazole (1) were studied computationally with appropriate quantum-chemical methods. Metronidazole may serve as a model compound to investigate the influence of solvent molecules on the NMR spin-spin coupling constants in heterocyclic rings. We find a hydrogen bond between 1 and a solvent water molecule that is associated with a bond critical point between the imidazole N-3 atom and a water H atom. AIM analysis indicates this hydrogen bond to be mainly electrostatic in nature. Simple static SSCC calculations in vacuo underestimate the nJ(N-3,H) coupling constants because of the neglect of hydrogen bonding. PCM-based treatments perform reasonably well because of the electrostatic character of the hydrogen bond. For more reliable predictions, it is important to take into account the dynamics of the system and to include nearby solvent molecules explicitly. The reduction of the hyperconjugative interactions involving the sigma CH bond or the sigma *CH antibond (with the coupling nucleus H) that is found in solution appears to be correlated to the reduction of coupling pathways in the imidazole ring. Since nuclear spin orientation information is transferred electronically to the other nuclei in the molecule, experimentally determined J-couplings directly reflect the nature of the chemical bond involved.106,107 Unlike most other NMR properties, which can be understood on the basis of semiclassical physics, J-coupling is a purely quantum- mechanical phenomenon. The present results provide evidence that hyperconjugative effects in solute molecules are not due to changes in geometric parameters upon solvation, but arise from the direct response of the electronic wave function to the presence of the solvent, which can be represented by discrete molecules and/or the dielectric bulk. We believe that our findings may be helpful to rationalize the relation between NMR parameters and the interactions in hydrogen-bonded complexes. Further applications along these lines are in progress. (author)

  7. Ab Initio Quality NMR Parameters in Solid-State Materials Using a High-Dimensional Neural-Network Representation.

    Science.gov (United States)

    Cuny, Jérôme; Xie, Yu; Pickard, Chris J; Hassanali, Ali A

    2016-02-01

    Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental tools to probe the local atomic order of a wide range of solid-state compounds. However, due to the complexity of the related spectra, in particular for amorphous materials, their interpretation in terms of structural information is often challenging. These difficulties can be overcome by combining molecular dynamics simulations to generate realistic structural models with an ab initio evaluation of the corresponding chemical shift and quadrupolar coupling tensors. However, due to computational constraints, this approach is limited to relatively small system sizes which, for amorphous materials, prevents an adequate statistical sampling of the distribution of the local environments that is required to quantitatively describe the system. In this work, we present an approach to efficiently and accurately predict the NMR parameters of very large systems. This is achieved by using a high-dimensional neural-network representation of NMR parameters that are calculated using an ab initio formalism. To illustrate the potential of this approach, we applied this neural-network NMR (NN-NMR) method on the (17)O and (29)Si quadrupolar coupling and chemical shift parameters of various crystalline silica polymorphs and silica glasses. This approach is, in principal, general and has the potential to be applied to predict the NMR properties of various materials. PMID:26730889

  8. Non-Linear Problems in NMR: Application of the DFM Variation of Parameters Method

    Science.gov (United States)

    Erker, Jay Charles

    This Dissertation introduces, develops, and applies the Dirac-McLachlan-Frenkel (DFM) time dependent variation of parameters approach to Nuclear Magnetic Resonance (NMR) problems. Although never explicitly used in the treatment of time domain NMR problems to date, the DFM approach has successfully predicted the dynamics of optically prepared wave packets on excited state molecular energy surfaces. Unlike the Floquet, average Hamiltonian, and Van Vleck transformation methods, the DFM approach is not restricted by either the size or symmetry of the time domain perturbation. A particularly attractive feature of the DFM method is that measured data can be used to motivate a parameterized trial function choice and that the DFM theory provides the machinery to provide the optimum, minimum error choices for these parameters. Indeed a poor parameterized trial function choice will lead to a poor match with real experiments, even with optimized parameters. Although there are many NMR problems available to demonstrate the application of the DFM variation of parameters, five separate cases that have escaped analytical solution and thus require numerical methods are considered here: molecular diffusion in a magnetic field gradient, radiation damping in the presence of inhomogeneous broadening, multi-site chemical exchange, and the combination of molecular diffusion in a magnetic field gradient with chemical exchange. The application to diffusion in a gradient is used as an example to develop the DFM method for application to NMR. The existence of a known analytical solution and experimental results allows for direct comparison between the theoretical results of the DFM method and Torrey's solution to the Bloch equations corrected for molecular diffusion. The framework of writing classical Bloch equations in matrix notation is then applied to problems without analytical solution. The second example includes the generation of a semi-analytical functional form for the free precession and spin echo signals for a single, radiation damped, symmetric, inhomogenously broadened line. Although an analytical solution for the dynamics of the radiation damped single isochromat with and without homogeneous broadening is well known, the corresponding case involving symmetric inhomogeneous broadening has escaped solution to date. Although, an analytical theorem was developed to describe the tip angle |??|of the on resonance central vector of the inhomogeneous distribution due to the cumulative effect of radiation damping feedback, no insight into the magnetization dynamics during radiation damping are offered. Several trial functions were optimized with the DFM approach to obtain semi-analytical estimates of the free precession and spin echo signals with symmetric inhomogeneous broadening for the first time. The effect of inhomogeneous distribution function asymmetry in addition to sample demagnetization can also be treated using this approach. Initial results describing multi-site chemical exchange will be presented. It will be shown that the simplest trial function leads to the original treatment by Meiboom. The concept of multi-site exchange is then expanded to a continuum of exchange by proposing a chemical shift distribution where amplitude is proportional to shift probability. As an example, a symmetric Gaussian distribution is used to reproduce the expected result of mimicking diffusion effects on relaxation times. Finally the DFM method is applied to the composite problem of molecular diffusion in a magnetic field gradient with chemical exchange. The modeling of biologically relevant ion channels, which originally motivated this work, is treated as a two site exchange problem where ions in solution have a much higher diffusion coefficient than bound ions. Simulations for both the application of static magnetic field gradients and RF magnetic field gradients are presented.

  9. Essential Parameters for Structural Analysis and Dereplication by 1H NMR Spectroscopy

    Science.gov (United States)

    2015-01-01

    The present study demonstrates the importance of adequate precision when reporting the ? and J parameters of frequency domain 1H NMR (HNMR) data. Using a variety of structural classes (terpenoids, phenolics, alkaloids) from different taxa (plants, cyanobacteria), this study develops rationales that explain the importance of enhanced precision in NMR spectroscopic analysis and rationalizes the need for reporting ?? and ?J values at the 0.1–1 ppb and 10 mHz level, respectively. Spectral simulations paired with iteration are shown to be essential tools for complete spectral interpretation, adequate precision, and unambiguous HNMR-driven dereplication and metabolomic analysis. The broader applicability of the recommendation relates to the physicochemical properties of hydrogen (1H) and its ubiquity in organic molecules, making HNMR spectra an integral component of structure elucidation and verification. Regardless of origin or molecular weight, the HNMR spectrum of a compound can be very complex and encode a wealth of structural information that is often obscured by limited spectral dispersion and the occurrence of higher order effects. This altogether limits spectral interpretation, confines decoding of the underlying spin parameters, and explains the major challenge associated with the translation of HNMR spectra into tabulated information. On the other hand, the reproducibility of the spectral data set of any (new) chemical entity is essential for its structure elucidation and subsequent dereplication. Handling and documenting HNMR data with adequate precision is critical for establishing unequivocal links between chemical structure, analytical data, metabolomes, and biological activity. Using the full potential of HNMR spectra will facilitate the general reproducibility for future studies of bioactive chemicals, especially of compounds obtained from the diversity of terrestrial and marine organisms. PMID:24895010

  10. Isotropic chemical shifts and quadrupolar parameters of oxygen-17 using dynamic-angle spinning NMR

    International Nuclear Information System (INIS)

    Several oxygen-17-enriched silicates were studied using dynamic-angle spinning (DAS) NMR spectroscopy at two magnetic field strengths. The DAS method averages second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra for half-odd integer spin quadrupolar nuclei such as oxygen-17. A narrow spectral line is observed for each distinct oxygen site in a powdered sample at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Using equations for the total shift observed at two field strengths, the chemical shift is uniquely determined together with a product of the quadrupolar coupling constant (CQ = e2qQ/h) and the quadrupolar asymmetry parameter (?). For one silicate, the authors demonstrate a computer program that uses the isotropic shifts and quadrupolar products as constraints and provides simulations of overlapped magic-angle spinning line shapes. In this way the quadrupolar parameters, CQ and ?, are determined separately for each crystallographic site. The silicates studied include the discrete orthosilicates larnite (Ca2SiO4) and forsterite (Mg2SiO4), as well as diopside (CaMgSi2O6), wollastonite (CaSiO3), and clinoenstatite (MgSiO3), which are minerals composed of chains of silicon-oxygen tetrahedra. 49 refs., 2 figs., 2 tabs

  11. General order parameter based correlation analysis of protein backbone motions between experimental NMR relaxation measurements and molecular dynamics simulations

    International Nuclear Information System (INIS)

    Internal backbone dynamic motions are essential for different protein functions and occur on a wide range of time scales, from femtoseconds to seconds. Molecular dynamic (MD) simulations and nuclear magnetic resonance (NMR) spin relaxation measurements are valuable tools to gain access to fast (nanosecond) internal motions. However, there exist few reports on correlation analysis between MD and NMR relaxation data. Here, backbone relaxation measurements of 15N-labeled SH3 (Src homology 3) domain proteins in aqueous buffer were used to generate general order parameters (S2) using a model-free approach. Simultaneously, 80 ns MD simulations of SH3 domain proteins in a defined hydrated box at neutral pH were conducted and the general order parameters (S2) were derived from the MD trajectory. Correlation analysis using the Gromos force field indicated that S2 values from NMR relaxation measurements and MD simulations were significantly different. MD simulations were performed on models with different charge states for three histidine residues, and with different water models, which were SPC (simple point charge) water model and SPC/E (extended simple point charge) water model. S2 parameters from MD simulations with charges for all three histidines and with the SPC/E water model correlated well with S2 calculated from the experimental NMR relaxation measurements, in a site-specific manner. - Highlights: • Correlation analysis between NMR relaxation measurements and MD simulations. • General order parameter (S2) as common reference between the two methods. • Different protein dynamics with different Histidine charge states in neutral pH. • Different protein dynamics with different water models

  12. Solid state NMR and bioequivalence comparison of the pharmacokinetic parameters of two formulations of clindamycin

    KAUST Repository

    Al-Talla, Zeyad

    2011-01-01

    Objective: The purpose of this study was to compare the pharmacokinetic parameters and determine the bioequivalence of a generic formulation of clindamycin that is sold in the local markets in the Middle East (Clindox® 150 mg capsule; test) with a reference formulation (Dalacin C® 150 mg capsule) in healthy adult male volunteers. Methods: A single-dose, open-label, 2-period crossover study was conducted. Healthy male volunteers were randomly assigned to oral administration of a single treatment of the reference and test formulations. The same groups were given the alternate formulation. After dosing, serial blood samples were withdrawn for a period of 24 h. Serum harvested from the blood samples was analyzed for clindamycin by high performance liquid chromatography (HPLC) with ultraviolet detection. Pharmacokinetic parameters, including AUC0-∞, AUC 0-t, Cmax, Ke, tmax and t 1/2 were determined from the serum concentrations for both formulations (test and reference). The products were tested for bioequivalence after log-transformation of the data. Results: 24 healthy adult male volunteers from Jordan (mean [SD] age, 28.8 (7.7) years (range 19-45 years); height, 175.8 (10.6) cm (range 159.0-192.0 cm); weight, 75.6 (11.0) kg (range 58-101 kg); and body mass index, 24.4 (1.8) kg/m2 (range 21.3-28 kg/m2)) were enrolled in and completed the study. The 13C NMR spectra for both Dalacin C® and Clindox® showed 18 distinct lines associated with the 18 different carbon atoms. Conclusion: The statistical comparison suggested that Clindox® capsules are bioequivalent to Dalacin C® capsules. The 13C CPMAS results confirmed that the two drugs exhibit typical clindamycin spectra. ©2011 Dustri-Verlag Dr. K. Feistle.

  13. Effects of Quantum Nuclear Delocalisation on NMR Parameters from Path Integral Molecular Dynamics.

    Czech Academy of Sciences Publication Activity Database

    Dra?ínský, Martin; Hodgkinson, P.

    2014-01-01

    Ro?. 20, ?. 8 (2014), s. 2201-2207. ISSN 0947-6539 Grant ostatní: Seventh Framework Programme of the European Union(XE) FP7-299242 People Institutional support: RVO:61388963 Keywords : density functional calculations * isotope effects * NMR spectroscopy * nuclear delocalisation * path integral molecular dynamics Subject RIV: CC - Organic Chemistry Impact factor: 5.731, year: 2014

  14. Ab initio DFT study of bisphosphonate derivatives as a drug for inhibition of cancer: NMR and NQR parameters.

    Science.gov (United States)

    Aghabozorg, Hussein; Sohrabi, Beheshteh; Mashkouri, Sara; Aghabozorg, Hamid Reza

    2012-03-01

    DFT computations were carried out to characterize the (17)Oand (2)H electric field gradient, EFG, in various bisphosphonate derivatives. The computations were performed at the B3LYP level with 6-311++G (d,P) standard basis set. Calculated EFG tensors were used to determine the (17)O and (2)H nuclear quadrupole coupling constant, ? and asymmetry parameter, ?. For better understanding of the bonding and electronic structure of bisphosphonates, isotropic and anisotropic NMR chemical shieldings were calculated for the (13)C, (17)O and (31)P nuclei using GIAO method for the optimized structure of intermediate bisphosphonates at B3LYP level of theory using 6-311++G (d, p) basis set. The results showed that various substituents have a strong effect on the nuclear quadrupole resonance (NQR) parameters (?, ?) of (17)O in contrast with (2)H NQR parameters. The NMR and NQR parameters were studied in order to find the correlation between electronic structure and the activity of the desired bisphosphonates. In addition, the effect of substitutions on the bisphosphonates polarity was investigated. Molecular polarity was determined via the DFT calculated dipole moment vectors and the results showed that substitution of bromine atom on the ring would increase the activity of bisphosphonates. PMID:21633790

  15. NMR Parameters Determination through ACE Committee Machine with Genetic Implanted Fuzzy Logic and Genetic Implanted Neural Network

    Directory of Open Access Journals (Sweden)

    Asoodeh Mojtaba

    2015-06-01

    Full Text Available Free fluid porosity and rock permeability, undoubtedly the most critical parameters of hydrocarbon reservoir, could be obtained by processing of nuclear magnetic resonance (NMR log. Despite conventional well logs (CWLs, NMR logging is very expensive and time-consuming. Therefore, idea of synthesizing NMR log from CWLs would be of a great appeal among reservoir engineers. For this purpose, three optimization strategies are followed. Firstly, artificial neural network (ANN is optimized by virtue of hybrid genetic algorithm-pattern search (GA-PS technique, then fuzzy logic (FL is optimized by means of GA-PS, and eventually an alternative condition expectation (ACE model is constructed using the concept of committee machine to combine outputs of optimized and non-optimized FL and ANN models. Results indicated that optimization of traditional ANN and FL model using GA-PS technique significantly enhances their performances. Furthermore, the ACE committee of aforementioned models produces more accurate and reliable results compared with a singular model performing alone.

  16. Comparative analysis of the microscopic spin-Hamiltonian expressions used for the non-Kramers Fe{sup 2+}(3d{sup 6}) ions with spin S=2 in reduced rubredoxin, desulforedoxin, and related systems

    Energy Technology Data Exchange (ETDEWEB)

    Rudowicz, C.; Sung, H.W.F

    2003-09-01

    The predictions based on the crystal-field (CF) and spin-Hamiltonian (SH) theory play important role in the studies of the spectroscopic properties of the non-Kramers Fe{sup 2+} (S=2) ions in reduced rubredoxin, desulforedoxin, and related mononuclear synthetic analogues. The complexity of such systems as well as the various approximations used in analysis of experimental data contribute to inconclusive results derived from electron magnetic resonance, Moessbauer, and optical spectroscopy studies as well as theoretical calculations. In this paper various microscopic spin-Hamiltonian (MSH) approaches used in the pertinent literature and their limitations are critically examined. The CF and SH theory pertinent for the non-Kramers (3d{sup 6}) Fe{sup 2+} ion with spin S=2 at tetragonal and the first- and second-kind orthorhombic symmetry sites are presented in the nutshell. As a benchmark we utilize the MSH expressions within the {sup 5}D approximation derived by computer up to fourth order of perturbation theory. This theoretical framework enables us to carry out a comparative analysis of the various, often inconsistent, second-order MSH expressions existing in the literature. The fourth-rank zero-field splitting terms are considered for the first time. The results of this study provide a starting point for detailed modeling of the spectroscopic properties of Fe{sup 2+} ion in complex biological systems and their synthetic analogues.

  17. Comparative analysis of the microscopic spin-Hamiltonian expressions used for the non-Kramers Fe2+(3d6) ions with spin S=2 in reduced rubredoxin, desulforedoxin, and related systems

    International Nuclear Information System (INIS)

    The predictions based on the crystal-field (CF) and spin-Hamiltonian (SH) theory play important role in the studies of the spectroscopic properties of the non-Kramers Fe2+ (S=2) ions in reduced rubredoxin, desulforedoxin, and related mononuclear synthetic analogues. The complexity of such systems as well as the various approximations used in analysis of experimental data contribute to inconclusive results derived from electron magnetic resonance, Moessbauer, and optical spectroscopy studies as well as theoretical calculations. In this paper various microscopic spin-Hamiltonian (MSH) approaches used in the pertinent literature and their limitations are critically examined. The CF and SH theory pertinent for the non-Kramers (3d6) Fe2+ ion with spin S=2 at tetragonal and the first- and second-kind orthorhombic symmetry sites are presented in the nutshell. As a benchmark we utilize the MSH expressions within the 5D approximation derived by computer up to fourth order of perturbation theory. This theoretical framework enables us to carry out a comparative analysis of the various, often inconsistent, second-order MSH expressions existing in the literature. The fourth-rank zero-field splitting terms are considered for the first time. The results of this study provide a starting point for detailed modeling of the spectroscopic properties of Fe2+ ion in complex biological systems and their synthetic analogues

  18. Effects of quantum nuclear delocalisation on NMR parameters from path integral molecular dynamics.

    Science.gov (United States)

    Dra?ínský, Martin; Hodgkinson, Paul

    2014-02-17

    The influence of nuclear delocalisation on NMR chemical shifts in molecular organic solids is explored using path integral molecular dynamics (PIMD) and density functional theory calculations of shielding tensors. Nuclear quantum effects are shown to explain previously observed systematic deviations in correlations between calculated and experimental chemical shifts, with particularly large PIMD-induced changes (up to 23?ppm) observed for carbon atoms in methyl groups. The PIMD approach also enables isotope substitution effects on chemical shifts and J?couplings to be predicted in excellent agreement with experiment for both isolated molecules and molecular crystals. An approach based on convoluting calculated shielding or coupling surfaces with probability distributions of selected bond distances and valence angles obtained from PIMD simulations is used to calculate isotope effects. PMID:24435841

  19. Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

    CERN Document Server

    Soncini, Alessandro

    2012-01-01

    We derive a general formula for the paramagnetic NMR nuclear shielding tensor of an open-shell molecule in a pure spin state, subject to a zero-field splitting (ZFS). Our findings are in contradiction with a previous proposal. We present a simple application of the newly derived formula to the case of a triplet ground state split by an easy-plane ZFS spin Hamiltonian. When $kT$ is much smaller than the ZFS gap, thus a single non-degenerate level is thermally populated, our approach correctly predicts a temperature-independent paramagnetic shift, while the previous theory leads to a Curie temperature dependence.

  20. Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

    OpenAIRE

    Soncini, Alessandro; Heuvel, Willem Van den

    2012-01-01

    We derive a general formula for the paramagnetic NMR nuclear shielding tensor of an open-shell molecule in a pure spin state, subject to a zero-field splitting (ZFS). Our findings are in contradiction with a previous proposal. We present a simple application of the newly derived formula to the case of a triplet ground state split by an easy-plane ZFS spin Hamiltonian. When $kT$ is much smaller than the ZFS gap, thus a single non-degenerate level is thermally populated, our approach correctly ...

  1. Communication: Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting

    Science.gov (United States)

    Soncini, Alessandro; Van den Heuvel, Willem

    2013-01-01

    We derive a general formula for the paramagnetic NMR nuclear shielding tensor of an open-shell molecule in a pure spin state, subject to a zero-field splitting (ZFS). Our findings are in contradiction with a previous proposal. We present a simple application of the newly derived formula to the case of a triplet ground state split by an easy-plane ZFS spin Hamiltonian. When kT is much smaller than the ZFS gap, thus a single non-degenerate level is thermally populated, our approach correctly predicts a temperature-independent paramagnetic shift, while the previous theory leads to a Curie temperature dependence.

  2. Computer simulation of NMR signals in a multi spin system with magnetic dipole interactions

    International Nuclear Information System (INIS)

    In order to carry out a computer simulation within the scope of the quantum theory of angle moment, an algorithm is proposed to build eigenfunctions of a spin Hamiltonian. The algorithm proposed is used to calculate the NMR spectrum and free induction signal for 1D chains, which consist of 2 /7 spins. It is proved that only magnetic dipole interaction between spins cause the signal of free induction decay, which is not related to the evolution of the density matrix towards an equilibrium or quasi equilibrium

  3. The effects of some parameters on the calculated 1H NMR relaxation times of cell water

    International Nuclear Information System (INIS)

    The effect of some parameters on the longitudinal and transverse relaxation times is calculated and a comparison between the calculated relaxation times with the results of different measurements is made. (M.S.)

  4. Clarification of terminological confusion concerning the crystal field quantities vs. the effective spin Hamiltonian and zero-field splitting quantities in the papers by Bayrakçeken et al. [Spectrochim. Acta Part A 66 (2007) 462 and 1291

    Science.gov (United States)

    Rudowicz, Czes?aw

    2008-12-01

    The physically distinct notions: crystal field (CF) [or equivalently ligand field (LF)] and effective spin Hamiltonian, which comprises zero-field splitting (ZFS) [or equivalently fine structure (FS)], are often confused each with other in literature. Confusion of the type X = Y consists in referral to the quantity Y by the name X of another well-defined quantity. Most prevailing is the CF = ZFS confusion, i.e. labeling the actual ZFS/FS quantities as purportedly the CF/LF ones. Unique cases of the inverse ZFS = CF confusion, identified in recent papers by Bayrakçeken et al. [Spectrochim. Acta A 66 (2007) 462 and 1291], is discussed here. To clarify this confusion, clear distinction between operators of various nature used in electron magnetic resonance (EMR), optical spectroscopy, and related studies is provided. Other deficiencies in the two papers in question, which overlap to a large extent, and misinterpretations therein are critically commented on.

  5. Structural refinement of the RT LaOF phases by coupling powder X-Ray diffraction, (19)F and (139)La solid state NMR and DFT calculations of the NMR parameters.

    Science.gov (United States)

    Dabachi, Jamal; Body, Monique; Dittmer, Jens; Fayon, Franck; Legein, Christophe

    2015-12-21

    The structures of the ?- and t-LaOF phases have been refined from XRPD patterns. For both phases, (19)F and (139)La solid-state NMR spectra recorded at high magnetic fields show the presence of a single F and a single La local environment, indicating a full anionic ordering in these oxyfluoride compounds. DFT calculations of the (19)F and (139)La chemical shielding tensors and of the (139)La EFG tensor have been performed for the proposed structural models. The observed good agreement between experimental and calculated NMR parameters for both phases highlights the accuracy of the structural data. PMID:26565802

  6. Quantifying Lipari-Szabo modelfree parameters from 13CO NMR relaxation experiments

    International Nuclear Information System (INIS)

    It is proposed to obtain effective Lipari-Szabo order parameters and local correlation times for relaxation vectors of protein 13CO nuclei by carrying out a 13CO-R1 auto relaxation experiment, a transverse 13CO CSA/13CO-13C CSA/dipolar cross correlation and a transverse 13CO CSA/13CO-15N CSA/dipolar cross correlation experiment. Given the global rotational correlation time from 15N relaxation experiments, a new program COMFORD (CO-Modelfree Fitting Of Relaxation Data) is presented to fit the 13CO data to an effective order parameter SCO2, an effective local correlation time and the orientation of the CSA tensor with respect to the molecular frame. It is shown that the effective SCO2 is least sensitive to rotational fluctuations about an imaginary C?-C? axis and most sensitive to rotational fluctuations about an imaginary axis parallel to the NH bond direction. As such, the SCO2 information is fully complementary to the 15N relaxation order parameter, which is least sensitive to fluctuations about the NH axis and most sensitive to fluctuations about the C?-C? axis. The new paradigm is applied on data of Ca2+ saturated Calmodulin, and on available literature data for Ubiquitin. Our data indicate that the SCO2 order parameters rapport on slower, and sometimes different, motions than the 15N relaxation order parameters. The CO local correlation times correlate well with the calmodulin's secondary structure

  7. Theoretical investigations of spin Hamilton parameters and Knight shifts for rhombic and tetragonal CuGeO3

    International Nuclear Information System (INIS)

    The spin Hamiltonian parameters (g factors and hyperfine structure constants) and the Knight shifts for Cu2+ in the spin-Pierels compound CuGeO3 of rhombic and tetragonal phases are theoretically investigated from the high order perturbation formulas of these parameters for a 3d9 ion under rhombically and tetragonally elongated octahedra in a uniform way. The approximately linear relationships between Knight shifts and g factors are found, i.e., Ki/(gi?gs)=Kj/(gj?gs) (with i, j=x, y and z; gs?2.0023). The theoretical results show good agreement with the observed values, and the improvements are achieved by adopting the fewer adjustable parameters as compared with the previous treatments. The anisotropies of the g factors and the Knight shifts are attributed to the local rhombic and tetragonal elongations of the Cu2+ sites. The studies in this work would be helpful to establish complete physical scheme for uniform investigations on EPR and NMR spectroscopic behaviours of Cu2+ (or other similar 3d9 ions) in compounds

  8. Calculated 13C NMR relaxation parameters for a restricted internal diffusion model. Application to methionine relaxation in dihydrofolate reductase

    International Nuclear Information System (INIS)

    13C NMR relaxation parameters, T1, T2, and NOE, have been calculated based on a model assuming internal rotational diffusion subject to boundary conditions limiting the range of motion. Numerical results are presented as a function of diffusion coefficients D0 and D/sub i/ and angle ? defined as in the free internal rotation calculation, as well as 2theta, the allowed range of motion. Relaxation times vary from values expected in the absence of internal motion to values slightly below those calculated using the free internal rotation model as the range is increased from 0 to 3600. The discrepancy in the latter comparison arises from the boundary condition preventing diffusion from 180+ to 180-. Changes in T2 are typically monotonic or nearly monotonic as a function of theta; however, changes in T1 and NOE values are markedly nonmonotonic for D0 approx. 6 s-1 and for certain values of D/sub i/. Criteria for the applicability of the present calculations to the analysis of 13C NMR relaxation data obtained in studies of macromolecules undergoing restricted internal motion have been suggested. The results have been generalized to the case of multiple internal rotations, specifically for the problem of one free and one restricted diffusional process. In general, two types of rotation are not commutative. This model has been applied to relaxation data recently obtained for the methionine methyl resonances of specifically 13C-labeled dihydrofolate reductase obtained from S. faecium. The results indicate that the data can be readily explained by assuming rapid free internal diffusion about the S--CH3 bond and restricted internal diffusion about the CH2--S bond of methionine, such that for the broadest resonances the motional range is restricted to approx. 900 and for the sharpest resonances the range is >1800. Restriction of the motion allows a significantly better fit of data than a model based on two free internal rotations

  9. Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules

    Science.gov (United States)

    Martin, Bob; Autschbach, Jochen

    2015-02-01

    Using a recently proposed equation for NMR nuclear magnetic shielding for molecules with unpaired electrons [A. Soncini and W. Van den Heuvel, J. Chem. Phys. 138, 021103 (2013)], equations for the temperature (T) dependent isotropic shielding for multiplets with an effective spin S equal to 1/2, 1, 3/2, 2, and 5/2 in terms of electron paramagnetic resonance spin Hamiltonian parameters are derived and then expanded in powers of 1/T. One simplifying assumption used is that a matrix derived from the zero-field splitting (ZFS) tensor and the Zeeman coupling matrix (g-tensor) share the same principal axis system. The influence of the rhombic ZFS parameter E is only investigated for S = 1. Expressions for paramagnetic contact shielding (from the isotropic part of the hyperfine coupling matrix) and pseudo-contact or dipolar shielding (from the anisotropic part of the hyperfine coupling matrix) are considered separately. The leading order is always 1/T. A temperature dependence of the contact shielding as 1/T and of the dipolar shielding as 1/T2, which is sometimes assumed in the assignment of paramagnetic chemical shifts, is shown to arise only if S ? 1 and zero-field splitting is appreciable, and only if the Zeeman coupling matrix is nearly isotropic (?g = 0). In such situations, an assignment of contact versus dipolar shifts may be possible based only on linear and quadratic fits of measured variable-temperature chemical shifts versus 1/T. Numerical data are provided for nickelocene (S = 1). Even under the assumption of ?g = 0, a different leading order of contact and dipolar shifts in powers of 1/T is not obtained for S = 3/2. When ?g is not very small, dipolar and contact shifts both depend in leading order in 1/T in all cases, with sizable contributions in order 1/Tn with n = 2 and higher.

  10. Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Bob; Autschbach, Jochen, E-mail: jochena@buffalo.edu [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States)

    2015-02-07

    Using a recently proposed equation for NMR nuclear magnetic shielding for molecules with unpaired electrons [A. Soncini and W. Van den Heuvel, J. Chem. Phys. 138, 021103 (2013)], equations for the temperature (T) dependent isotropic shielding for multiplets with an effective spin S equal to 1/2, 1, 3/2, 2, and 5/2 in terms of electron paramagnetic resonance spin Hamiltonian parameters are derived and then expanded in powers of 1/T. One simplifying assumption used is that a matrix derived from the zero-field splitting (ZFS) tensor and the Zeeman coupling matrix (g-tensor) share the same principal axis system. The influence of the rhombic ZFS parameter E is only investigated for S = 1. Expressions for paramagnetic contact shielding (from the isotropic part of the hyperfine coupling matrix) and pseudo-contact or dipolar shielding (from the anisotropic part of the hyperfine coupling matrix) are considered separately. The leading order is always 1/T. A temperature dependence of the contact shielding as 1/T and of the dipolar shielding as 1/T{sup 2}, which is sometimes assumed in the assignment of paramagnetic chemical shifts, is shown to arise only if S ? 1 and zero-field splitting is appreciable, and only if the Zeeman coupling matrix is nearly isotropic (?g = 0). In such situations, an assignment of contact versus dipolar shifts may be possible based only on linear and quadratic fits of measured variable-temperature chemical shifts versus 1/T. Numerical data are provided for nickelocene (S = 1). Even under the assumption of ?g = 0, a different leading order of contact and dipolar shifts in powers of 1/T is not obtained for S = 3/2. When ?g is not very small, dipolar and contact shifts both depend in leading order in 1/T in all cases, with sizable contributions in order 1/T{sup n} with n = 2 and higher.

  11. Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules.

    Science.gov (United States)

    Martin, Bob; Autschbach, Jochen

    2015-02-01

    Using a recently proposed equation for NMR nuclear magnetic shielding for molecules with unpaired electrons [A. Soncini and W. Van den Heuvel, J. Chem. Phys. 138, 021103 (2013)], equations for the temperature (T) dependent isotropic shielding for multiplets with an effective spin S equal to 1/2, 1, 3/2, 2, and 5/2 in terms of electron paramagnetic resonance spin Hamiltonian parameters are derived and then expanded in powers of 1/T. One simplifying assumption used is that a matrix derived from the zero-field splitting (ZFS) tensor and the Zeeman coupling matrix (g-tensor) share the same principal axis system. The influence of the rhombic ZFS parameter E is only investigated for S = 1. Expressions for paramagnetic contact shielding (from the isotropic part of the hyperfine coupling matrix) and pseudo-contact or dipolar shielding (from the anisotropic part of the hyperfine coupling matrix) are considered separately. The leading order is always 1/T. A temperature dependence of the contact shielding as 1/T and of the dipolar shielding as 1/T(2), which is sometimes assumed in the assignment of paramagnetic chemical shifts, is shown to arise only if S ? 1 and zero-field splitting is appreciable, and only if the Zeeman coupling matrix is nearly isotropic (?g = 0). In such situations, an assignment of contact versus dipolar shifts may be possible based only on linear and quadratic fits of measured variable-temperature chemical shifts versus 1/T. Numerical data are provided for nickelocene (S = 1). Even under the assumption of ?g = 0, a different leading order of contact and dipolar shifts in powers of 1/T is not obtained for S = 3/2. When ?g is not very small, dipolar and contact shifts both depend in leading order in 1/T in all cases, with sizable contributions in order 1/T(n) with n = 2 and higher. PMID:25662637

  12. Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules

    International Nuclear Information System (INIS)

    Using a recently proposed equation for NMR nuclear magnetic shielding for molecules with unpaired electrons [A. Soncini and W. Van den Heuvel, J. Chem. Phys. 138, 021103 (2013)], equations for the temperature (T) dependent isotropic shielding for multiplets with an effective spin S equal to 1/2, 1, 3/2, 2, and 5/2 in terms of electron paramagnetic resonance spin Hamiltonian parameters are derived and then expanded in powers of 1/T. One simplifying assumption used is that a matrix derived from the zero-field splitting (ZFS) tensor and the Zeeman coupling matrix (g-tensor) share the same principal axis system. The influence of the rhombic ZFS parameter E is only investigated for S = 1. Expressions for paramagnetic contact shielding (from the isotropic part of the hyperfine coupling matrix) and pseudo-contact or dipolar shielding (from the anisotropic part of the hyperfine coupling matrix) are considered separately. The leading order is always 1/T. A temperature dependence of the contact shielding as 1/T and of the dipolar shielding as 1/T2, which is sometimes assumed in the assignment of paramagnetic chemical shifts, is shown to arise only if S ≥ 1 and zero-field splitting is appreciable, and only if the Zeeman coupling matrix is nearly isotropic (Δg = 0). In such situations, an assignment of contact versus dipolar shifts may be possible based only on linear and quadratic fits of measured variable-temperature chemical shifts versus 1/T. Numerical data are provided for nickelocene (S = 1). Even under the assumption of Δg = 0, a different leading order of contact and dipolar shifts in powers of 1/T is not obtained for S = 3/2. When Δg is not very small, dipolar and contact shifts both depend in leading order in 1/T in all cases, with sizable contributions in order 1/Tn with n = 2 and higher

  13. Spin-spin cross relaxation and spin-Hamiltonian spectroscopy by optical pumping of Pr/sup 3+/:LaF3

    International Nuclear Information System (INIS)

    We report the observation of an anticrossing in solid-state laser spectroscopy produced by cross relaxation. Spin-spin cross relaxation between the /sup 141/Pr- and /sup 19/F-spin reservoirs in Pr/sup 3+/:LaF3 and its influence on the /sup 141/Pr NMR spectrum is detected by means of optical pumping. The technique employed combines optical pumping and hole burning with either external magnetic field sweep or rf resonance saturation in order to produce slow transient changes in resonant laser transmission. At a certain value of the external Zeeman field, where the energy-level splittings of Pr and F spins match, a level repulsion and discontinuity of the Pr/sup 3+/ NMR lines is observed. This effect is interpreted as the ''anticrossing'' of the combined Pr-F spin-spin reservoir energy states. The Zeeman-quadrupole-Hamiltonian spectrum of the hyperfine optical ground states of Pr/sup 3+/:LaF3 is mapped out over a wide range of Zeeman magnetic fields. A new scheme is proposed for dynamic polarization of nuclei by means of optical pumping, based on resonant cross relaxation between rare spins and spin reservoirs

  14. The mechanism of paramagnetic NMR relaxation produced by Mn(II): Role of orthorhombic and fourth-order zero field splitting terms

    Science.gov (United States)

    Sharp, Robert

    2008-10-01

    Mn(II) is a spin-5/2 paramagnetic ion that mediates a characteristically large NMR paramagnetic relaxation enhancement (NMR-PRE) of nuclear spins in solution. In the range of high magnetic field strengths (above about 0.3 T), where the electronic Zeeman interaction provides the largest term of the electron spin Hamiltonian, NMR relaxation mechanism is well understood. In the lower field range, the physical picture is more complex because of the presence in the spin Hamiltonian of zero field splitting (ZFS) terms that are comparable to or greater than the Zeeman term. This work describes a systematic study of the relaxation mechanism in the low field range, particularly aspects involving the dependence of NMR-PRE on the orthorhombic (E) and fourth-order (aq(4), q =0,2,4) ZFS tensor components. It is shown that the fourfold (a4(4)) and twofold (a2(4)) fourth-order components exert large orientation-dependent influences on the NMR-PRE. Thus, fourth-order terms with magnitudes equal to only a few percent of the quadratic ZFS terms (D,E) produce large changes in the shape of the magnetic field profile of the PRE. Effects arising from the orthorhombic quadratic ZFS term (E) are much smaller than those of the fourth-order terms and can in most cases be neglected. However, effects due to a4(4) and a2(4) need to be included in simulations of low field data.

  15. 153Eu and 69,71Ga Zero-Field NMR Study of Antiferromagnetic State in EuGa4

    Science.gov (United States)

    Yogi, Mamoru; Nakamura, Saori; Higa, Nonoka; Niki, Haruo; Hirose, Yusuke; ?nuki, Yoshichika; Harima, Hisatomo

    2013-10-01

    We report 153Eu and 69,71Ga NMR under a zero magnetic field on the antiferromagnetic state of EuGa4 with TN? 16 K. We have successfully observed a 153Eu zero-field NMR signal with well-resolved nuclear quadrupole splitting in the antiferromagnetic state of EuGa4. 69,71Ga zero-field NMR spectra were also observed below TN. The internal field and nuclear quadrupole frequency are estimated from a simulation of the spectra by the exact diagonalization of the nuclear spin Hamiltonian matrix. The asymmetrically split zero-field NMR spectra were explained by considering a configuration of the magnetic moments of Eu2+ lying in the basal ab-plane. The temperature dependence of the internal field, which is proportional to the sublattice magnetization, can be explained by the Brillouin function with J=S=7/2.

  16. Compact NMR

    International Nuclear Information System (INIS)

    Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures, while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue. In both applications, the sample (or patient) is positioned inside a large, superconducting magnet to magnetize the atomic nuclei. Interrogating radio-frequency pulses result in frequency spectra that provide the chemist with molecular information, the medical doctor with anatomic images, and materials scientist with NMR relaxation parameters. Recent advances in magnet technology have led to a variety of small permanent magnets to allow compact and low-cost instruments. The goal of this book is to provide an introduction to the practical use of compact NMR at a level nearly as basic as the operation of a smart phone.

  17. Study of correlations in molecular motion by multiple quantum NMR

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH3 and CD3) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed

  18. A molecular dynamics study of the effects of fast molecular motions on solid-state NMR parameters.

    Czech Academy of Sciences Publication Activity Database

    Dra?ínský, Martin; Hodgkinson, P.

    2013-01-01

    Ro?. 15, ?. 43 (2013), s. 8705-8712. ISSN 1466-8033 Grant ostatní: Seventh Framework Programme of the European Union(XE) FP7-299242 People Institutional support: RVO:61388963 Keywords : molecular dynamics * DFT calculations * NMR spectroscopy Subject RIV: CC - Organic Chemistry Impact factor: 3.858, year: 2013

  19. Evaluation of Parameters Critical for Observing Nucleic Acids Inside Living Xenopus laevis Oocytes by In-Cell NMR Spectroscopy.

    Czech Academy of Sciences Publication Activity Database

    Hansel, R.; Foldynová, Silvie; Lohr, F.; Buck, J.; Bongartz, E.; Bamberg, E.; Schwalbe, H.; Dotsch, V.; Trantírek, Lukáš

    2009-01-01

    Ro?. 131, ?. 43 (2009), s. 15761-15768. ISSN 0002-7863 R&D Projects: GA AV ?R KAN200100801 Institutional research plan: CEZ:AV0Z60220518 Keywords : in- cell NMR * nucleic acid * Xenopus laevis * DNA * RNA Subject RIV: BO - Biophysics Impact factor: 8.580, year: 2009

  20. Gravitational spin Hamiltonians from the S matrix

    OpenAIRE

    Vaidya, Varun

    2014-01-01

    We utilize generalized unitarity and recursion relations combined with effective field theory(EFT) techniques to compute spin dependent interaction terms for inspiralling binary systems in the post newtonian(PN) approximation. Using these methods offers great computational advantage over traditional techniques involving feynman diagrams, especially at higher orders in the PN expansion. As a specific example, we reproduce the spin-orbit interaction up to 2.5 PN order as also the leading order ...

  1. Mechanical analogues of spin Hamiltonians and dynamics

    International Nuclear Information System (INIS)

    Bloch et al. mapped the precession of the spin-half in a magnetic field of variable magnitude and direction to the rotations of a rigid sphere rolling on a curved surface utilizing SU(2)–SO(3) isomorphism. This formalism is extended to study the behaviour of spin–orbit interactions and the mechanical analogy for Rashba–Dresselhauss spin–orbit interaction in two dimensions is presented by making its spin states isomorphic to the rotations of a rigid sphere rolling on a ring. The change in phase of spin is represented by the angle of rotation of sphere after a complete revolution. In order to develop the mechanical analogy for the spin filter, we find that perfect spin filtration of down spin makes the sphere to rotate at some unique angles and the perfect spin filtration of up spin causes the rotations with certain discrete frequencies.

  2. Optimisation of NMR dynamic models II. A new methodology for the dual optimisation of the model-free parameters and the Brownian rotational diffusion tensor

    International Nuclear Information System (INIS)

    Finding the dynamics of an entire macromolecule is a complex problem as the model-free parameter values are intricately linked to the Brownian rotational diffusion of the molecule, mathematically through the autocorrelation function of the motion and statistically through model selection. The solution to this problem was formulated using set theory as an element of the universal set U-the union of all model-free spaces (d'Auvergne EJ and Gooley PR (2007) Mol BioSyst 3(7), 483-494). The current procedure commonly used to find the universal solution is to initially estimate the diffusion tensor parameters, to optimise the model-free parameters of numerous models, and then to choose the best model via model selection. The global model is then optimised and the procedure repeated until convergence. In this paper a new methodology is presented which takes a different approach to this diffusion seeded model-free paradigm. Rather than starting with the diffusion tensor this iterative protocol begins by optimising the model-free parameters in the absence of any global model parameters, selecting between all the model-free models, and finally optimising the diffusion tensor. The new model-free optimisation protocol will be validated using synthetic data from Schurr JM et al. (1994) J Magn Reson B 105(3), 211-224 and the relaxation data of the bacteriorhodopsin (1-36)BR fragment from Orekhov VY (1999) J Biomol NMR 14(4), 345-356. To demonstrate the importance of this new procedure the NMR relaxation data of the Olfactory Marker Protein (OMP) of Gitti R et al. (2005) Biochem 44(28), 9673-9679 is reanalysed. The result is that the dynamics for certain secondary structural elements is very different from those originally reported

  3. Simulating Frequency-Domain Electron Paramagnetic Resonance: Bridging the Gap between Experiment and Magnetic Parameters for High-Spin Transition-Metal Ion Complexes.

    Science.gov (United States)

    Nehrkorn, Joscha; Telser, Joshua; Holldack, Karsten; Stoll, Stefan; Schnegg, Alexander

    2015-10-29

    We present a comparison of experimental and simulated frequency- and field-domain electron paramagnetic resonance (EPR) spectra of integer and half-integer high-spin transition-metal ion complexes. For the simulation of EPR spectra a new tool within the EPR simulation software EasySpin is introduced, which allows for field- and frequency-domain EPR simulations with the same theoretical model and the same set of spin Hamiltonian parameters. The utility of this approach is demonstrated on the integer-spin complexes NiBr2(PPh3)2 and [Tp2Mn]SbF6 (both S = 1) and the half-integer-spin Fe(III) porphyrins, hemin (Fe(PPIX)Cl) and Fe(TPP)Cl (both S = 5/2). We demonstrate that the combination of field- and frequency-domain EPR techniques allows the determination of spin Hamiltonian parameters, in particular large zero-field splittings, with high accuracy. PMID:26154490

  4. Starting Structure Dependence of NMR Order Parameters Derived from MD Simulations: Implications for Judging Force-Field Quality

    OpenAIRE

    Koller, Alrun N.; Schwalbe, Harald; Gohlke, Holger

    2008-01-01

    Comparing experimental generalized N-H S2 order parameters to those calculated from molecular dynamics trajectories is increasingly used to judge force-field quality and completeness of sampling. Herein we demonstrate for the well-investigated system hen egg white lysozyme that different experimental starting structures can lead to significant differences in molecular-dynamics-derived S2 parameters that can be even larger than S2 parameter deviations due to different force fields. Caution sho...

  5. Molecular modeling and experimental studies on structure and NMR parameters of 9-benzyl-3,6-diiodo-9H-carbazole

    DEFF Research Database (Denmark)

    Radula-Janik, Klaudia; Kupka, Teobald

    2015-01-01

    A combined experimental and theoretical study has been performed on 9-benzyl-3,6-diiodo-9H-carbazole. Experimental X-ray (100.0 K) and room-temperature 13C NMR studies were supported by advanced density functional theory (DFT) calculations. The non relativistic structure optimization was performed and the 13C nuclear magnetic shieldings were predicted at the relativistic level of theory using the Zeroth Order Regular Approximation (ZORA). The changes in the benzene and pyrrole rings compared to the unsubstituted carbazole or the parent molecules were discussed in terms of aromaticity changes using the harmonic oscillator model of aromaticity (HOMA) and the nucleus independent chemical shift (NICS) indexes. Theoretical relativistic calculations of chemical shifts of carbons C3 and C6, directly bonded to iodine atoms, produced a reasonable agreement with experiment (initial deviation from experiment of 41.57 ppm dropped to 5.6 ppm). A good linear correlation between experimental and theoretically predicted structural and NMR parameters was observed.

  6. Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole.

    Science.gov (United States)

    Balachandran, V; Karpagam, V; Revathi, B; Kavimani, M; Santhi, G

    2015-01-25

    The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d,p) and 6-311+G (d,p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations. PMID:25173520

  7. The mechanism of paramagnetic NMR relaxation produced by Mn(II): role of orthorhombic and fourth-order zero field splitting terms.

    Science.gov (United States)

    Sharp, Robert

    2008-10-14

    Mn(II) is a spin-5/2 paramagnetic ion that mediates a characteristically large NMR paramagnetic relaxation enhancement (NMR-PRE) of nuclear spins in solution. In the range of high magnetic field strengths (above about 0.3 T), where the electronic Zeeman interaction provides the largest term of the electron spin Hamiltonian, NMR relaxation mechanism is well understood. In the lower field range, the physical picture is more complex because of the presence in the spin Hamiltonian of zero field splitting (ZFS) terms that are comparable to or greater than the Zeeman term. This work describes a systematic study of the relaxation mechanism in the low field range, particularly aspects involving the dependence of NMR-PRE on the orthorhombic (E) and fourth-order (a(q)(4), q=0,2,4) ZFS tensor components. It is shown that the fourfold (a(4)(4)) and twofold (a(2)(4)) fourth-order components exert large orientation-dependent influences on the NMR-PRE. Thus, fourth-order terms with magnitudes equal to only a few percent of the quadratic ZFS terms (D,E) produce large changes in the shape of the magnetic field profile of the PRE. Effects arising from the orthorhombic quadratic ZFS term (E) are much smaller than those of the fourth-order terms and can in most cases be neglected. However, effects due to a(4)(4) and a(2)(4) need to be included in simulations of low field data. PMID:19045147

  8. Study of correlations in molecular motion by multiple quantum NMR

    Energy Technology Data Exchange (ETDEWEB)

    Tang, J.H.

    1981-11-01

    Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH/sub 3/ and CD/sub 3/) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed.

  9. NMR tomography

    International Nuclear Information System (INIS)

    Novel measuring techniques, shorter examination time, and special contrast media now increasingly recommend NMR imaging for an extended range of diagnostic problems. The new possibilities have been explained at the 2nd European NMR Symposium in Berlin. (orig.)

  10. NMR lineshape in anisotropic superconductors

    Science.gov (United States)

    Khusainov, Mansur; Efremova, Svetlana; Proshin, Yurii N.; Tsarevskii, Sergey L.

    2000-07-01

    It is shown that the NMR lineshape strongly differs for various angles between normal to the surface of the superconductor and the external magnetic field direction. Thus, the surface effects drastically change the conclusions concerning the vortex lattice and parameters of the superconductor that are usually extracted from the NMR line shape. The NMR probing in the inclined magnetic fields will provide more detailed information about the parameters of the superconductor, especially in strongly anisotropic high- Tc superconductors.

  11. Zero field splitting parameters of Mn2+ in Bis (L-asparaginato) Zn (II) at interstitial orthorhombic symmetry site

    Science.gov (United States)

    Pandey, Sangita; Kripal, Ram

    2012-06-01

    The superposition model is used to calculate the crystal field parameters (CFPs) of Mn2+ in Bis (L-asparaginato) Zn (II). The zero field splitting parameters (ZFSPs) D and E are then investigated using perturbation theory and microscopic spin Hamiltonian (SH) theory. The calculated ZFS parameters are compared with the experimental values obtained by electron paramagnetic resonance. Both the zero field splitting parameters (ZFSPs) D and E evaluated theoretically are in good agreement with the experimental values. The results support the notion that the Mn2+ ion occupies interstitial site in Bis (L-asparaginato) Zn (II).

  12. Zero field splitting parameters of Mn²? in Bis (L-asparaginato) Zn (II) at interstitial orthorhombic symmetry site.

    Science.gov (United States)

    Pandey, Sangita; Kripal, Ram

    2012-06-01

    The superposition model is used to calculate the crystal field parameters (CFPs) of Mn(2+) in Bis (L-asparaginato) Zn (II). The zero field splitting parameters (ZFSPs) D and E are then investigated using perturbation theory and microscopic spin Hamiltonian (SH) theory. The calculated ZFS parameters are compared with the experimental values obtained by electron paramagnetic resonance. Both the zero field splitting parameters (ZFSPs) D and E evaluated theoretically are in good agreement with the experimental values. The results support the notion that the Mn(2+) ion occupies interstitial site in Bis (L-asparaginato) Zn (II). PMID:22391223

  13. Supplementation of antipsychotic treatment with sarcosine - GlyT1 inhibitor - causes changes of glutamatergic (1)NMR spectroscopy parameters in the left hippocampus in patients with stable schizophrenia.

    Science.gov (United States)

    Strzelecki, Dominik; Podgórski, Micha?; Ka?u?y?ska, Olga; Gawlik-Kotelnicka, Oliwia; Stefa?czyk, Ludomir; Kotlicka-Antczak, Magdalena; Gmitrowicz, Agnieszka; Grzelak, Piotr

    2015-10-01

    Glutamatergic system, the main stimulating system of the brain, plays an important role in the pathogenesis of schizophrenia. Hippocampus, a structure crucial for memory and cognitive functions and rich in glutamatergic neurons, is a natural object of interest in studies on psychoses. Sarcosine, a glycine transporter (GlyT-1) inhibitor influences the function of NMDA receptor and glutamate-dependent transmission. The aim of the study was to assess the effects of sarcosine on metabolism parameters in the left hippocampus in patients with schizophrenia. Assessments were performed using proton nuclear magnetic resonance ((1)H NMR) spectroscopy (1.5T). Fifty patients diagnosed with schizophrenia (DSM-IV-TR), with dominant negative symptoms, in stable clinical condition and stable antipsychotics doses were treated either with sarcosine (n=25) or placebo (n=25). Spectroscopic parameters were evaluated within groups and between two groups before and after 6-month intervention. All patients were also assessed with the Positive and Negative Syndrome Scale (PANSS). In the sarcosine group, after 6-month treatment, we found significant decrease in hippocampal Glx/Cr (Glx-complex of glutamate, glutamine and GABA, Cr-creatine) and Glx/Cho (Cho-choline), while N-acetylaspartate (NAA), myo-inositol (mI), Cr and Cho parameters remained stable along the study and also did not differ significantly between both groups. This is the first study showing that a pharmacological intervention in schizophrenia, particularly augmentation of the antypsychotic treatment with sarcosine, may reverse the pathological increase in glutamatergic transmission in the hippocampus. The results confirm involvement of glutamatergic system in the pathogenesis of schizophrenia and demonstrate beneficial effects of GlyT-1 inhibitor on the metabolism in the hippocampus and symptoms of schizophrenia. PMID:26306650

  14. First-principles calculation of the 17O NMR parameters in Ca oxide and Ca aluminosilicates: the partially covalent nature of the Ca-O bond, a challenge for density functional theory.

    Science.gov (United States)

    Profeta, Mickaël; Benoit, Magali; Mauri, Francesco; Pickard, Chris J

    2004-10-01

    We apply density functional theory (DFT) to the calculation of the (17)O NMR parameters in Ca and Mg oxides and aluminosilicates. We study the accuracy of the Perdew, Burke, and Ernzerhof (PBE) generalized-gradient approximation to DFT in the description of these systems and the origin of the experimentally observed large dependence of the (17)O chemical shift on the alkaline earth ion. We find that (i) the partially covalent nature of the Ca-O bond has a huge impact on the O chemical shifts. The Ca-O covalence alone explains why in Ca oxides and aluminosilicates the (17)O chemical shifts are much more deshielded than those of the corresponding Mg compounds. (ii) The Ca-O covalence is overestimated by the PBE functional. Thus PBE-DFT is not able to reproduce the measured (17)O NMR parameters in Ca oxide and Ca aluminosilicates. (iii) It is possible to correct for the PBE-DFT deficiency in a simple and transferable way and to predict very accurate (17)O NMR parameters. Such accuracy allows us to assign the (17)O NMR spectra of two important model systems: the grossite aluminate (CaAl(4)O(7)) and the wollastonite (CaSiO(3)) silicate. PMID:15453796

  15. Assignment of the (13)C NMR spectrum by correlation to dipolar coupled proton-pairs and estimation of order parameters of a thiophene based liquid crystal.

    Science.gov (United States)

    Reddy, Y Jayasubba; Ramanathan, K V

    2015-01-14

    Materials with widely varying molecular topologies and exhibiting liquid crystalline properties have attracted considerable attention in recent years. (13)C NMR spectroscopy is a convenient method for studying such novel systems. In this approach the assignment of the spectrum is the first step which is a non-trivial problem. Towards this end, we propose here a method that enables the carbon skeleton of the different sub-units of the molecule to be traced unambiguously. The proposed method uses a heteronuclear correlation experiment to detect pairs of nearby carbons with attached protons in the liquid crystalline core through correlation of the carbon chemical shifts to the double-quantum coherences of protons generated through the dipolar coupling between them. Supplemented by experiments that identify non-protonated carbons, the method leads to a complete assignment of the spectrum. We initially apply this method for assigning the (13)C spectrum of the liquid crystal 4-n-pentyl-4'-cyanobiphenyl oriented in the magnetic field. We then utilize the method to assign the aromatic carbon signals of a thiophene based liquid crystal thereby enabling the local order-parameters of the molecule to be estimated and the mutual orientation of the different sub-units to be obtained. PMID:25429708

  16. Optimization of Experimental Parameters to Explore Small-Ligand/Aptamer Interactions through Use of (1) H?NMR Spectroscopy and Molecular Modeling.

    Science.gov (United States)

    Souard, Florence; Perrier, Sandrine; Noël, Vincent; Fave, Claire; Fiore, Emmanuelle; Peyrin, Eric; Garcia, Julian; Vanhaverbeke, Cécile

    2015-10-26

    Aptamers constitute an emerging class of molecules designed and selected to recognize any given target that ranges from small compounds to large biomolecules, and even cells. However, the underlying physicochemical principles that govern the ligand-binding process still have to be clarified. A major issue when dealing with short oligonucleotides is their intrinsic flexibility that renders their active conformation highly sensitive to experimental conditions. To overcome this problem and determine the best experimental parameters, an approach based on the design-of-experiments methodology has been developed. Here, the focus is on DNA aptamers that possess high specificity and affinity for small molecules, L-tyrosinamide, and adenosine monophosphate. Factors such as buffer, pH?value, ionic strength, Mg(2+) -ion concentration, and ligand/aptamer ratio have been considered to find the optimal experimental conditions. It was then possible to gain new insight into the conformational features of the two ligands by using ligand-observed NMR spectroscopic techniques and molecular mechanics. PMID:26356596

  17. Benford distributions in NMR

    CERN Document Server

    Bhole, Gaurav; Mahesh, T S

    2014-01-01

    Benford's Law is an empirical law which predicts the frequency of significant digits in databases corresponding to various phenomena, natural or artificial. Although counter intuitive at the first sight, it predicts a higher occurrence of digit 1, and decreasing occurrences to other larger digits. Here we report the Benford analysis of various NMR databases and draw several interesting inferences. We observe that, in general, NMR signals follow Benford distribution in time-domain as well as in frequency domain. Our survey included NMR signals of various nuclear species in a wide variety of molecules in different phases, namely liquid, liquid-crystalline, and solid. We also studied the dependence of Benford distribution on NMR parameters such as signal to noise ratio, number of scans, pulse angles, and apodization. In this process we also find that, under certain circumstances, the Benford analysis can distinguish a genuine spectrum from a visually identical simulated spectrum. Further we find that chemical-sh...

  18. Theoretical Studies of the Local Structure and Electron Paramagnetic Resonance Parameters for Tetragonal VO2+ in C6H7KO7

    Science.gov (United States)

    Zhou, Ping; Li, Ling

    2015-03-01

    The optical spectra, electron paramagnetic resonance parameters (i.e., the spin Hamiltonian parameters, including paramagnetic g factors and the hyperfine structure constants Ai) and the local distortion structure for the tetragonal VO2+ in C6H7KO7 are theoretically studied based on the crystal-field theory and three-order perturbation formulas of a 3d1 centre in tetragonal site. The magnitude of orbital reduction factor, core polarisation constant ?, and local structure parameters are obtained by fitting the calculated optical spectra and electron paramagnetic resonance parameters to the experimental values. The theoretical results are in reasonable agreement with the experimental values.

  19. Theoretical studies of the local structure and electron paramagnetic resonance parameters for tetragonal VO2+ in C6H7KO7

    International Nuclear Information System (INIS)

    The optical spectra, electron paramagnetic resonance parameters (i.e., the spin Hamiltonian parameters, including paramagnetic g factors and the hyperfine structure constants Ai) and the local distortion structure for the tetragonal VO2+ in C6H7KO7 are theoretically studied based on the crystal-field theory and three-order perturbation formulas of a 3d1 centre in tetragonal site. The magnitude of orbital reduction factor, core polarisation constant ?, and local structure parameters are obtained by fitting the calculated optical spectra and electron paramagnetic resonance parameters to the experimental values. The theoretical results are in reasonable agreement with the experimental values.

  20. Towards NMR imaging in solids

    International Nuclear Information System (INIS)

    The traditional NMR imaging usually gives the NMR spatial parameters distributiuon of water mobile molecules of the biological tissues. A new branch of great interest is NMR imaging of the spatial distribution of biological macromolecules like proteins, amino acids, etc. Which are assimilable to solid-like systems, with moderate NMR spectral broadening. The knowledge of the spatial broad band components distribution can be very useful because if could characterize the normal and pathologic state of living tissues in a specific way. In these sysmesn, however, very intense gradients are necessary to get agood spatial resolution

  1. Molecular modeling and experimental studies on structure and NMR parameters of 9-benzyl-3,6-diiodo-9H-carbazole

    DEFF Research Database (Denmark)

    Radula-Janik, Klaudia; Kupka, Teobald; Ejsmont, Krzysztof; Daszkiewicz, Zdzis?aw; Sauer, Stephan P. A.

    2015-01-01

    A combined experimental and theoretical study has been performed on 9-benzyl-3,6-diiodo-9H-carbazole. Experimental X-ray (100.0 K) and room-temperature 13C NMR studies were supported by advanced density functional theory (DFT) calculations. The non relativistic structure optimization was performed and the 13C nuclear magnetic shieldings were predicted at the relativistic level of theory using the Zeroth Order Regular Approximation (ZORA). The changes in the benzene and pyrrole rings compared to ...

  2. Nitroaniline diamine.poly(dA-dT) complexes: 1H and 19F NMR parameters for full intercalation of aromatic rings into DNA.

    OpenAIRE

    Patel, D. J.; Gabbay, E J

    1981-01-01

    High-resolution proton, fluorine, and phosphorus NMR studies have been undertaken on complexes of methyl- and trifluoromethyl-substituted nitroaniline diamines with the synthetic DNA poly(dA-dT) in 10 mM buffer solution. We demonstrate full intercalation of the nitroaniline group of these reporter molecules between base pairs, based on large upfield proton shifts (1.3-1.7 ppm) at all four aromatic proton markers on complex formation. The temperature and pH dependences of the thymidine H-3 Wat...

  3. The resolution of the identity approximation for calculations of spin-spin contribution to zero-field splitting parameters

    Science.gov (United States)

    Ganyushin, Dmitry; Gilka, Natalie; Taylor, Peter R.; Marian, Christel M.; Neese, Frank

    2010-04-01

    In this work, the resolution of the identity (RI) approximation is developed for the calculation of the electron-electron spin-spin coupling (SSC) interaction that is a central component of the zero-field splitting (ZFS) term in the effective spin Hamiltonian. The approximated integrals are then used in large-scale multireference configuration interaction treatments of the SSC interaction. The SSC contribution to the ZFS is treated using the Breit-Pauli spin-spin Hamiltonian in conjunction with first-order perturbation theory. Test calculations on a set of diatomic molecules reveal that the error of the RI approximation does not exceed 0.01 cm-1 even if standard auxiliary basis sets are used. This error of less than 1% is considered to be negligible compared to the presently achievable accuracy of the SSC calculations relative to experimental data. The present development allows the correlated ab initio calculation of ZFS parameters of larger systems such as linear polyenes and linear polyacenes. The basis set convergence of the calculated ZFS values was investigated, and the effect of electronic correlation on the calculated ZFS parameters is discussed.

  4. The automatic NMR gaussmeter

    International Nuclear Information System (INIS)

    The paper describes the automatic gaussmeter operating according to the principle of nuclear magnetic resonance. There have been discussed the operating principle, the block diagram and operating parameters of the meter. It can be applied to measurements of induction in electromagnets of wide-line radio-spectrometers EPR and NMR and in calibration stands of magnetic induction values. Frequency range of an autodyne oscillator from 0,6 up to 86 MHz for protons is corresponding to the field range from 0.016 up to 2T. Applicaton of other nuclei, such as 7Li and 2D is also foreseen. The induction measurement is carried over automatically, and the NMR signal and value of measured induction are displayed on a monitor screen. (author)

  5. Rheo-NMR - how nuclear magnetic resonance is providing new insight regarding complex fluid rheology

    International Nuclear Information System (INIS)

    Over the past five decades, NMR has revolutionised chemistry, and has found widespread application in condensed matter physics, in molecular biology, in medicine and in food technology. Most recently NMR has made a significant impact in chemical engineering, where it is being extensively used for the non-invasive study of dispersion and flow in porous media. One of the most recent applications of NMR in materials science concerns its use in the study of the mechanical properties of complex fluids. This particular aspect of NMR has been extensively developed in research carried out at Massey University in New Zealand. In this short article, some of the ideas behind this work and the applications which have resulted, will be described. These examples provide a glimpse of possible applications of Nuclear Magnetic Resonance to the study of complex fluid rheology. While this is a very new field of research in which only a handful of groups presently participate, the potential exists for a substantial increase in Rheo-NMR research activity. Systems studied to date include polymer melts and semi-dilute solutions, thermotropic and lyotropic liquid crystals and liquid crystalline polymers, micellar solutions, food materials and colloidal suspensions. Rheo-NMR suffers in a number of respects by comparison with optical methods. It is expensive, it is difficult to use, it suffers from poor signal-to-noise ratios and the effective interpretation of spectra often depends on familiarity with the nuclear spin Hamiltonian and the associated effects of spin dynamics. Nonetheless NMR offers some unique advantages, including the ability to work with opaque materials, the ability to combine velocimetry with localised spectroscopy, and the ability to access a wide range of molecular properties relating to organisation, orientation and dynamics. Rheo-NMR has been able to provide a direct window on a variety of behaviours, including slip, shear-thinning, shear banding, yield stress behaviour, nematic director alignment and shear-induced mesophase reorganisation. The unique information available with this method suggests that it is likely to become an important tool in elucidating die intriguing rheological behaviour of a wide range of complex fluids

  6. NMR espectroscopic parameters of HX and Si (Sn)X{sub 4} (X = H, F, Cl, Br and I) and SnBr{sub 4-n}I{sub n} model compounds

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, Alejandro F.; Gimenez, Carlos A. [Physics Department, Natural and Exact Science Faculty, Northeastern University of Argentina and Institute of Modelling and Innovation on Technology, IMIT Avda Libertad 5460, W3404AAS Corrientes (Argentina); Aucar, Gustavo A., E-mail: gaa@unne.edu.ar [Physics Department, Natural and Exact Science Faculty, Northeastern University of Argentina and Institute of Modelling and Innovation on Technology, IMIT Avda Libertad 5460, W3404AAS Corrientes (Argentina)

    2012-02-20

    Graphical abstract: Optimized fully relativistic calculations of NMR J-couplings (HBr, HI), chemical shifts (Si, Sn) and absolute shielding for reference compounds of heavy atoms (Si, Sn) are given. Highlights: Black-Right-Pointing-Pointer In this article we show a procedure to get accurate NMR {sigma}{sup Ref} of Si and Sn. Black-Right-Pointing-Pointer Calculations of {sigma} on more than three heavy-atom-containing molecules are given. Black-Right-Pointing-Pointer Our results are closer to {delta}{sup exp} than previous calculations for SnX{sub 4} (X = H, Cl, Br, I). Black-Right-Pointing-Pointer Optimized basis sets were considered for full R and NR calculations of NMR J and {sigma}. Black-Right-Pointing-Pointer Relativistic effects enlarge electron correlation effects on J-couplings. - Abstract: The NMR spectroscopic parameters are largely influenced by relativistic effects. They are highly dependent on the electronic behavior inside the spatial regions occupied by nuclei. Full relativistic calculations of indirect nuclear spin-spin couplings at random phase level of approach (RPA) in the title compounds with reoptimized Dyall cVTZ basis sets are given. A comparison with the results of calculations with other basis sets that are mostly used within the non-relativistic (NR) domain is presented. We analyzed the dependence of that couplings with the speed of light over the whole range of values, from the full relativistic to the NR regimes. Within this last regime, calculations at the second-order level of approach (SOPPA) indicated that electron correlation effects may not be as important for nuclear magnetic shieldings, but they must be included with care for J-coupling calculations. From these calculations, we determined that relativity enlarges the electron correlation effects of the J-couplings of HBr and HI. Because the results of nuclear magnetic shielding calculations within polarization propagators at the RPA level were reliable, we were able to show a new and easy procedure to obtain absolute nuclear magnetic shieldings on reference compounds for both Si and Sn nuclei: {sigma}[Si (CH{sub 3}){sub 4}] = 421.28 {+-} 29.33 ppm and {sigma}[Sn (CH{sub 3}){sub 4}] = 3814.96 {+-} 79.12 ppm. They were obtained from experimental chemical shifts and accurate nuclear magnetic shielding calculations on different molecular systems.

  7. NMR espectroscopic parameters of HX and Si (Sn)X4 (X = H, F, Cl, Br and I) and SnBr4−nIn model compounds

    International Nuclear Information System (INIS)

    Graphical abstract: Optimized fully relativistic calculations of NMR J-couplings (HBr, HI), chemical shifts (Si, Sn) and absolute shielding for reference compounds of heavy atoms (Si, Sn) are given. Highlights: ► In this article we show a procedure to get accurate NMR σRef of Si and Sn. ► Calculations of σ on more than three heavy-atom-containing molecules are given. ► Our results are closer to δexp than previous calculations for SnX4 (X = H, Cl, Br, I). ► Optimized basis sets were considered for full R and NR calculations of NMR J and σ. ► Relativistic effects enlarge electron correlation effects on J-couplings. - Abstract: The NMR spectroscopic parameters are largely influenced by relativistic effects. They are highly dependent on the electronic behavior inside the spatial regions occupied by nuclei. Full relativistic calculations of indirect nuclear spin–spin couplings at random phase level of approach (RPA) in the title compounds with reoptimized Dyall cVTZ basis sets are given. A comparison with the results of calculations with other basis sets that are mostly used within the non-relativistic (NR) domain is presented. We analyzed the dependence of that couplings with the speed of light over the whole range of values, from the full relativistic to the NR regimes. Within this last regime, calculations at the second-order level of approach (SOPPA) indicated that electron correlation effects may not be as important for nuclear magnetic shieldings, but they must be included with care for J-coupling calculations. From these calculations, we determined that relativity enlarges the electron correlation effects of the J-couplings of HBr and HI. Because the results of nuclear magnetic shielding calculations within polarization propagators at the RPA level were reliable, we were able to show a new and easy procedure to obtain absolute nuclear magnetic shieldings on reference compounds for both Si and Sn nuclei: σ[Si (CH3)4] = 421.28 ± 29.33 ppm and σ[Sn (CH3)4] = 3814.96 ± 79.12 ppm. They were obtained from experimental chemical shifts and accurate nuclear magnetic shielding calculations on different molecular systems.

  8. Minimalist Relativistic Force Field: Prediction of Proton-Proton Coupling Constants in (1)H NMR Spectra Is Perfected with NBO Hybridization Parameters.

    Science.gov (United States)

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-05-15

    We previously developed a reliable method for multiparametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. We now report that utilization of NBO hybridization coefficients for carbon atoms in the involved C-H bonds allows for a significant simplification of this parametric scheme, requiring only four general types of SSCCs: geminal, vicinal, 1,3-, and long-range constants. The method is optimized for inexpensive B3LYP/6-31G(d) molecular geometries. A new DU8 basis set, based on a training set of 475 experimental spin-spin coupling constants, is developed for hydrogen and common non-hydrogen atoms (Li, B, C, N, O, F, Si, P, S, Cl, Se, Br, I) to calculate Fermi contacts. On a test set of 919 SSCCs from a diverse collection of natural products and complex synthetic molecules the method gave excellent accuracy of 0.29 Hz (rmsd) with the maximum unsigned error not exceeding 1 Hz. PMID:25885091

  9. DFT study of NH3 adsorption on the (5,0), (8,0), (5,5) and (6,6) single-walled carbon nanotubes. Calculated binding energies, NMR and NQR parameters

    International Nuclear Information System (INIS)

    Behavior of a single NH3 molecule adsorbed on external surface of H-capped (5,5), (6,6), (5,0), and (8,0) single-walled carbon nanotubes (SWCNTs) is studied via DFT calculations. Binding energies clearly exhibit adsorption dependence on tube diameter. 13C, 15N and 1H chemical shielding tensors are calculated at the B3LYP level using GIAO method. NMR calculations reveal that 13C chemical shielding of (8,0) is more sensitive to NH3 adsorption compared to (5,5), (6,6) and (5,0) tubes. 15N and 1H chemical shielding correlate noticeably with diameter of the nanotubes. 14N and 2H nuclear quadrupole coupling constants, CQ, and asymmetry parameter, ?, reveal the remarkable effect of NH3 adsorption on electronic structure of the SWCNTs.

  10. NMR Studies of Peroxidases.

    Science.gov (United States)

    Veitch, Nigel Charles

    Available from UMI in association with The British Library. Requires signed TDF. Peroxidases are a haem-containing group of enzymes with a wide diversity of function within biological systems. While a common characteristic is the ability to catalyse the conversion of hydrogen peroxide to water, it is the accompanying processes of hormone synthesis and degradation which have generated such a high level of interest. However, information at the molecular level is limited to a single well-resolved crystal structure, that of yeast cytochrome c peroxidase. This thesis presents a strategy for the investigation of peroxidase structure and function based on proton nuclear magnetic resonance spectroscopy, a technique which has the ability to address aspects of both protein structure and protein dynamics in solution. The application of one- and two-dimensional NMR techniques has been developed in the context of plant peroxidases, notably the isoenzyme HRP-C derived from the horseradish root. Characterisation of the proton NMR spectra of HRP -C in resting and ligated states provided new information enabling the structure of the binding site for aromatic donor molecules, such as indole-3-propionic, ferulic and benzhydroxamic acids, to be resolved. In order to overcome difficulties encountered with a protein of the complexity of peroxidase, additional information was obtained from chemical shift parameters and the use of peroxidase variants produced by site-directed mutagenesis. A comparative study using NMR spectroscopy was undertaken for wild-type recombinant HRP-C expressed in Escherichia coli, and two protein variants with substitutions made to residues located on the distal side of the haem pocket, Phe41 to Val and Arg38 to Lys. NMR analyses of a plant peroxidase from barley grains and the fungal peroxidase from Coprinus cinereus were also successful using methods conceived with HRP-C. Examination of three specifically constructed recombinant protein variants of C. cinereus peroxidase was essential in confirming the identity of residues participating in the aromatic donor molecule binding site of peroxidases.

  11. Vibrational spectra, NBO analysis, first order hyperpolarizabilities, thermodynamic functions and NMR chemical shielding anisotropy (CSA) parameters of 5-nitro-2-furoic acid by ab initio HF and DFT calculations.

    Science.gov (United States)

    Balachandran, V; Rajeswari, S; Lalitha, S

    2013-09-01

    In this work, FT-IR and FT-Raman spectra are recorded on the solid phase of 5-nitro-2-furoic acid (abbreviated as NFA) in the regions 4000-400 cm(-1) and 3500-100 cm(-1) respectively. The geometrical parameters, vibrational assignments, HOMO-LUMO energies and NBO calculations are obtained for the monomer and dimer of NFA from HF and DFT (B3LYP) with 6-311++G (d, p) basis set calculations. Second order perturbation energies and electron density (ED) transfer from filled lone pairs of Lewis base to unfilled Lewis acid sites of NFA are discussed on the basis of NBO analysis. Intermolecular hydrogen bonds exist through COOH groups; give the evidence for the formation of dimer entities in the title molecule. The theoretically calculated harmonic frequencies are scaled by common scale factor. The observed and the calculated frequencies are found to be in good agreement. The thermodynamic functions were obtained for the range of temperature 100-1000 K. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The chemical parameters were calculated from the HOMO and LUMO values. The NMR chemical shielding anisotropy (CSA) parameters were also computed for the title molecule. PMID:23735205

  12. Electron paramagnetic resonance parameters for Co2+ doped in ZnO

    International Nuclear Information System (INIS)

    In ZnO, each Zn2+ ion is tetrahedral and surrounded by O2- ions, with a slight distortion of C3v symmetry along the c-axis of the crystal. If a Zn2+ ion is substituted by a transition metal ion, the electronic structure of the partly filled d shell can be described by ligand field theory for distorted tetrahedral complexes. The aim of this paper is twofold: to present a method of calculating the crystal field and spin Hamiltonian parameters of Co2+ doped in ZnO, and to simulate the optical energy level scheme, in the framework of the exchange charge model of the crystal field. The electron paramagnetic resonance parameters are also calculated for Co2+ doped in ZnO by using the density functionality theory method. The results are compared with experimental data and good agreement is observed.

  13. NMR and dynamics of biopolymers

    Energy Technology Data Exchange (ETDEWEB)

    Lian, L.Y.; Barsukov, I.L. [Leicester Univ. (United Kingdom)

    1994-12-31

    Several basic experimental analytical NMR techniques that are frequently used for the qualitative and quantitative analysis of dynamic and exchange processes, focusing on proteins systems, are described: chemical exchange (slow exchange, fast exchange, intermediate exchange), heteronuclear relaxation measurements (relaxation parameters, strategy of relaxation data analysis, experimental results and examples, motional model interpretation of relaxation data, homonuclear relaxation); slow large-scale exchange and hydrogen-deuterium exchange are also studied: mechanisms of hydrogen exchange in a native protein, methods for measuring amide exchange rates by NMR, interpretation of amide exchange rates. 9 fig., 3 tab., 56 ref.

  14. NMR characteristics of low-grade glioma

    International Nuclear Information System (INIS)

    Sixteen low-grade gliomas were evaluated both with nuclear magnetic resonance (NMR) imaging and with computed tomography (CT). In 13 cases (81 %), the NMR images were much better in tissue contrast than the contrast-enhanced CT images. The tumors were shown as well-circumscribed oval lesions in the NMR, though they appeared as ill-defined, irregular, low-attenuation areas in the CT. The extent of the lesion, which was supposed to represent the active tumor tissue, was greater in the NMR than in the CT, because NMR tissue parameters (T1, T2) are more sensitive to pathological changes in brain tissue than is the X-ray attenuation coefficient. Though, in an optic glioma and a brain-stem astrocytoma, the CT with contrast enhancement displayed the contour of the mass as well as did NMR, it was inferior to the NMR in showing the cephalocaudal extension of the tumors. Calcification does not give a proton NMR signal under the present measuring conditions; thus the calcified cystic wall of a hypothalamic astrocytoma was displayed only in the CT images. In conclusion, the NMR imaging was apparently superior to contrast-enhanced CT in demonstrating the lesions due to low-grade glioma. (author)

  15. Ligand-receptor Interactions by NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Novak. P.

    2008-04-01

    Full Text Available Today NMR spectroscopy is a method of choice for elucidation of interactions between biomolecules and the potential ligands. Knowledge on these interactions is an essential prerequisite for the rational drug design. The most important contribution of NMR to drug design a few years ago was the 3D structure determination of proteins. Besides delivering the 3D structures of the free proteins as a raw material for the modeling studies on ligand binding, NMR can directly yield valuable experimental data on the biologically important protein-ligand complexes. In addition to X-ray diffraction, NMR spectroscopy can provide information on the internal protein dynamics ordynamics of intermolecular interactions. Changes in NMR parameters allow us to detect ("SAR by NMR" and quantitatively determine binding affinities (titration, diffusion NMR experiments, etc. of potential ligands. Also, it is possible to determine the binding site and conformations of ligands, receptors and receptor-ligand complexes with the help of NMR methods such as tr-NOESY. Epitopes or functional groups responsible for binding of ligands to the receptor can be identified by employing STD or WaterLOGSY experiments. In this review are described some of the most frequent NMR methods for the characterization of the interactions between biomolecules and ligands, together with their advantages and disadvantages.

  16. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A

    1992-01-01

    The protean nature of the applications of NMR is regularly reflected in Annual Reports on NMR Spectroscopy. Volume 24 is no exception, and it is an ineluctable fact that all areas of science appear to benefit upon submission to the blandishments of NMR. The examples provided here encompass solid state NMR, solid state NMR imaging, NMR studies of interfaces, NMR investigations of cells and organisms, 199 Mercury NMR, and some applications of NMR to the area of coal science.

  17. NMR studies of metabolism

    International Nuclear Information System (INIS)

    In this paper, the authors present applications of NMR to the study of different aspects of metabolism. The authors begin with a brief outline of localization methods that are commonly used to obtain in vivo NMR spectra. The authors then describe in more detail metabolic information recently obtained by NMR of perfused organs, intact animals, and humans. Previous reviews have already covered the applications of NMR to the study of metabolism in microorganisms, isolated or cultivated cells, and tumors. NMR spectroscopy of the brain, and human in vivo NMR spectroscopy have also been reviewed

  18. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A

    1996-01-01

    In comparison with other methods currently available for investigating the structure and dynamics of molecular NMR is egregious. The widespread applicability of the series of NMR techniques now commonly available is exemplified in the topics appearing in Annual Reports on NMR Spectroscopy Volume 33.Key Features* Applications of field-cycling NMR* Progress of high resolution NMR in solids* High pressure NMR* Molybdenum NMR spectroscopy* Applications of NMR in oil shale research

  19. First Satellite NMR Spectroscopy

    Science.gov (United States)

    McDowell, A. F.; Conradi, Mark S.; Haase, J.

    1996-03-01

    A new NMR spectroscopic method that detects only the /pm 3/2 to /pm 1/2 transitions (i.e., first satellites) of half-integer quadrupolar spins is presented. The technique is based on a central transition signal enhancement method that makes use of adiabatic radiofrequency sweeps. A plot of the enhanced central transition signal versus the stop frequency of the sweep is an integrated version of the first satellite spectrum. To find the quadrupole parameters one can fit this integrated spectrum directly, or differentiate the data to reveal the traditional spectrum (of the first satellites). We demonstrate the technique for ^27Al in Al_2O3 and ^93Nb in LiNbO_3. The advantages of this new spectroscopy are discussed.

  20. NMR and NQR parameters of ethanol crystal

    CERN Document Server

    Milinkovic, M

    2012-01-01

    Electric field gradients and chemical shielding tensors of the stable monoclinic crystal phase of ethanol are computed. The projector-augmented wave (PAW) and gauge-including projector-augmented wave (GIPAW) models in the periodic plane-wave density functional theory are used. The crystal data from X-ray measurements, as well as the structures where either all atomic, or only hydrogen atom positions are optimized in the density functional theory are analyzed. These structural models are also studied by including the semi-empirical Van der Waals correction to the density functional theory. Infrared spectra of these five crystal models are calculated.

  1. NMR studies of multiphase flows II

    Energy Technology Data Exchange (ETDEWEB)

    Altobelli, S.A.; Caprihan, A.; Fukushima, E. [Lovelace Institutes, Albuquerque, NM (United States)] [and others

    1995-12-31

    NMR techniques for measurements of spatial distribution of material phase, velocity and velocity fluctuation are being developed and refined. Versions of these techniques which provide time average liquid fraction and fluid phase velocity have been applied to several concentrated suspension systems which will not be discussed extensively here. Technical developments required to further extend the use of NMR to the multi-phase flow arena and to provide measurements of previously unobtainable parameters are the focus of this report.

  2. Structure and Dynamics using NMR Spectroscopy

    OpenAIRE

    Klages, Jochen

    2009-01-01

    NMR spectroscopy is one of the few analytical methods that enable the determination of structure as well as dynamics of a molecule at atomic resolution. In the thesis presented here, on the hand methods for the quantification of so far difficult accessible NMR parameters have been developed, which allow an analysis in the above discussed manner. On the other hand, already established procedures have been used to investigate the structure and dynamics of the protein receptor BMPR-IA. For this ...

  3. An introduction to biological NMR spectroscopy

    International Nuclear Information System (INIS)

    NMR spectroscopy is a powerful tool for biologists interested in the structure, dynamics, and interactions of biological macromolecules. This review aims at presenting in an accessible manner the requirements and limitations of this technique. As an introduction, the history of NMR will highlight how the method evolved from physics to chemistry and finally to biology over several decades. We then introduce the NMR spectral parameters used in structural biology, namely the chemical shift, the J-coupling, nuclear Overhauser effects, and residual dipolar couplings. Resonance assignment, the required step for any further NMR study, bears a resemblance to jigsaw puzzle strategy. The NMR spectral parameters are then converted into angle and distances and used as input using restrained molecular dynamics to compute a bundle of structures. When interpreting a NMR-derived structure, the biologist has to judge its quality on the basis of the statistics provided. When the 3D structure is a priori known by other means, the molecular interaction with a partner can be mapped by NMR: information on the binding interface as well as on kinetic and thermodynamic constants can be gathered. NMR is suitable to monitor, over a wide range of frequencies, protein fluctuations that play a crucial role in their biological function. In the last section of this review, intrinsically disordered proteins, which have escaped the attention of classical structural biology, are discussed in the perspective of NMR, one of the rare available techniques able to describe structural ensembles. This Tutorial is part of the International Proteomics Tutorial Programme (IPTP 16 MCP). (authors)

  4. 11B NMR spectroscopy

    International Nuclear Information System (INIS)

    This paper covers developments in 11B NMR spectroscopy subsequent to a previous review in this series. In addition, it serves to complement the preceding chapter. As in previous years, a major use of 11B has been archival - that is, use for routine characterization of new compounds - although considerable efforts to elucidate correlations between structure and NMR parameters continue. However, some significant trends may be noted. First, availability of high-field spectrometers with multinuclear capability as well as software for sophisticated data manipulation is increasingly common, and, with these instruments, lack of chemical-shift dispersion in the face of relatively large linewidths presents much less of a problem than previously when complex polyboron compounds are to be characterized. Coupled with this, potent separation techniques, exemplified by thin-layer, high-pressure and ion-exchange chromatography, are able to unravel complex mixtures and make pure compounds available for study. Use of X-ray crystallographic facilities with which to structurally characterize compounds whose spectra are reported is today almost routine. Less routine is an appreciation of the fact that one crystal teased from a reaction mixture is not necessarily representative of the system from which it was extracted; use of X-ray powder-diffraction analysis to test this hypothesis is to be encouraged. Thus inability to separate mixtures, to secure high-resolution spectra and structural data are of decreasing importance in boron chemistry, leaving, perhaps, as the rate-limiting factors, creativity and the propensity to select for detailed study systems that offer new, significant and fundamental insights into the chemistry of boron and of the elements to which it bonds

  5. Small NMR biomolecular sensors

    Science.gov (United States)

    Sun, Nan; Liu, Yong; Qin, Ling; Lee, Hakho; Weissleder, Ralph; Ham, Donhee

    2013-06-01

    By combining the physics of nuclear magnetic resonance (NMR) and silicon radio-frequency (RF) integrated circuits, we recently created progressively smaller NMR systems, which we originally reported in Refs. [1-4]. Our strategy for NMR system miniaturization proved effective, culminating in the smallest prototype [3,4] that weighs 0.1 kg and can be held at the palm of the hand. These small, low-cost NMR systems can be useful as biomolecular sensors in the personalized medicine setting, and we demonstrated their ability to detect proteins, compounds, and human cancer cells. The present paper, which is not a new technical contribution, reviews these developments.

  6. Method of enhancing image signal-to-noise ratio by combining NMR images of differing pulse sequence timing

    Energy Technology Data Exchange (ETDEWEB)

    Mac Fall, J.R.; Glover, G.H.

    1987-11-24

    This patent describes a method for generating a computed NMR having improved signal-to-noise ratio relative to an acquired NMR image corresponding to substantially similar timing parameters. The method comprises the steps of: exciting, spatially encoding and detecting NMR signals in a sample object to obtain acquired images according to a timing parameter which varies between acquired images; fitting NMR data corresponding to each pixel of the acquired images into an equation relating NMR parameters of the object to the NMR signals in order to produce fitted equational and generating the computed image corresponding to a single value of the timing parameter using the fitted equations.

  7. Development of Halbach magnet for portable NMR device

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) has enormous potential for various applications in industry as the on-line or at-line test/control device of process environments. Advantage of NMR is its non-destructive nature, because it does not require the measurement probe to have a contact with the tested media. Despite of the recent progress in this direction, application of NMR in industry is still very limited. This is related to the technical and analytical complications of NMR as a method, and high cost of NMR analyzers available at the market. However in many applications, NMR is a very useful technique to test various products and to monitor quantitatively industrial processes. Fortunately usually there is no need in a high-field superconducting magnets to obtain the high-resolution spectra with the detailed information on chemical shifts and coupling-constant. NMR analyzers are designed to obtain the relaxation parameters by measuring the NMR spectra in the time domain rather than in frequency domain. Therefore it is possible to use small magnetic field (and low frequency of 2-60 MHz) in NMR systems, based on permanent magnet technology, which are specially designed for specific at-line and on-line process applications. In this work we present the permanent magnet system developed to use in the portative NMR devices. We discuss the experimental parameters of the designed Halbach magnet system and compare them with results of theoretical modelling.

  8. Theoretical studies of the local structure and electron paramagnetic resonance parameters for tetragonal VO{sup 2+} in C{sub 6}H{sub 7}KO{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ping [Chongqing Jiaotong Univ. (China). School of Science; Li, Ling [Sichuan University of Arts and Science, Dazhou (China). Dept. of Maths and Finance-Economics

    2015-07-01

    The optical spectra, electron paramagnetic resonance parameters (i.e., the spin Hamiltonian parameters, including paramagnetic g factors and the hyperfine structure constants A{sub i}) and the local distortion structure for the tetragonal VO{sup 2+} in C{sub 6}H{sub 7}KO{sub 7} are theoretically studied based on the crystal-field theory and three-order perturbation formulas of a 3d{sup 1} centre in tetragonal site. The magnitude of orbital reduction factor, core polarisation constant κ, and local structure parameters are obtained by fitting the calculated optical spectra and electron paramagnetic resonance parameters to the experimental values. The theoretical results are in reasonable agreement with the experimental values.

  9. Laser enhanced thin gas NMR signal in NMR spectrometers

    International Nuclear Information System (INIS)

    The NMR apparatus for measuring the laser enhanced thin gas NMR signal were sketched. The thin gas NMR signal in NMR spectrometers by spin exchange optical pumping methods using linearly polarized laser radiation have been greatly enhanced. The NMR signal of thin gas was first observed in this NMR spectrometer with high magnetic fields. A measured 129Xe decay rates as the function of Cs density with a magnetic field of 1.879 tesla were shown out

  10. 14 N NMR of tetrapropylammonium based crystals

    Science.gov (United States)

    Dib, E.; Mineva, T.; Gaveau, P.; Alonso, B.

    2015-07-01

    We have investigated using 14N NMR different types of materials containing tetrapropylammonium cations. We consider the tetrapropylammonium bromide crystal as well as two different microporous materials silicalite-1 and AlPO-5, with MFI and AFI topology respectively, where the tetrapropylammonium cation plays the role of structure directing agent. 14N NMR quadrupolar coupling parameters were determined experimentally for all the crystals. In addition calculations based on Density Functional Theory with empirical dispersion (DFT-D) were performed on the MFI type zeolite. The sensitivity of the 14N quadrupolar coupling parameters to the spatial distribution of the anions in the zeolite's framework is emphasized.

  11. Lectures on pulsed NMR

    International Nuclear Information System (INIS)

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs

  12. Lectures on pulsed NMR

    International Nuclear Information System (INIS)

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs

  13. Teaching NMR Using Online Textbooks

    OpenAIRE

    Joseph P. Hornak

    1999-01-01

    Nuclear magnetic resonance (NMR) spectroscopy has almost become an essential analytical tool for the chemist. High-resolution one- and multi-dimensional NMR, timedomain NMR, and NMR microscopy are but a few of the NMR techniques at a chemist's disposal to determine chemical structure and dynamics. Consequently, even small chemistry departments are finding it necessary to provide students with NMR training and experience in at least some of these techniques. The hands-on experience is readily ...

  14. NMR logging apparatus

    Science.gov (United States)

    Walsh, David O; Turner, Peter

    2014-05-27

    Technologies including NMR logging apparatus and methods are disclosed. Example NMR logging apparatus may include surface instrumentation and one or more downhole probes configured to fit within an earth borehole. The surface instrumentation may comprise a power amplifier, which may be coupled to the downhole probes via one or more transmission lines, and a controller configured to cause the power amplifier to generate a NMR activating pulse or sequence of pulses. Impedance matching means may be configured to match an output impedance of the power amplifier through a transmission line to a load impedance of a downhole probe. Methods may include deploying the various elements of disclosed NMR logging apparatus and using the apparatus to perform NMR measurements.

  15. Dynamics in solids studied by NMR crystalography and MD simulations.

    Czech Academy of Sciences Publication Activity Database

    Dra?ínský, Martin; Šála, Michal; Hodgkinson, P.

    Baveno : -, 2015. s. 20-21. [SMASH 2015. Small Molecule NMR Conference . 20.09.2015-23.09.2015, Baveno] R&D Projects: GA ?R GA15-11223S; GA ?R GA13-24880S Institutional support: RVO:61388963 Keywords : molecular dynamics * calculations of NMR parameters * path integral molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry

  16. Optimization and practical implementation of ultrafast 2D NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Queiroz Junior, Luiz H. K., E-mail: professorkeng@gmail.com [Universidade Federal de Sao Carlos (UFSC), SP (Brazil). Departamento de Quimica; Universidade Federal de Goias (UFGO), Goiania, GO (Brazil). Inst. de Quimica; Ferreira, Antonio G. [Universidade Federal de Sao Carlos (UFSC), SP (Brazil). Departamento de Quimica; Giraudeau, Patrick [Universite de Nantes (France). CNRS, Chimie et Interdisciplinarite: Synthese, Analyse, Modelisation

    2013-09-01

    Ultrafast 2D NMR is a powerful methodology that allows recording of a 2D NMR spectrum in a fraction of second. However, due to the numerous non-conventional parameters involved in this methodology its implementation is no trivial task. Here, an optimized experimental protocol is carefully described to ensure efficient implementation of ultrafast NMR. The ultrafast spectra resulting from this implementation are presented based on the example of two widely used 2D NMR experiments, COSY and HSQC, obtained in 0.2 s and 41 s, respectively. (author)

  17. Optimization and practical implementation of ultrafast 2D NMR experiments

    Directory of Open Access Journals (Sweden)

    Luiz H. K. Queiroz Júnior

    2013-01-01

    Full Text Available Ultrafast 2D NMR is a powerful methodology that allows recording of a 2D NMR spectrum in a fraction of second. However, due to the numerous non-conventional parameters involved in this methodology its implementation is no trivial task. Here, an optimized experimental protocol is carefully described to ensure efficient implementation of ultrafast NMR. The ultrafast spectra resulting from this implementation are presented based on the example of two widely used 2D NMR experiments, COSY and HSQC, obtained in 0.2 s and 41 s, respectively.

  18. Cation-? versus anion-? interactions: A theoretical NMR study

    Science.gov (United States)

    Ebrahimi, Ali; Khorassani, Mostafa Habibi; Masoodi, Hamid Reza

    2011-03-01

    The influences of cation-? and anion-? interactions on NMR data have been investigated in complexes of cations and anions with 1,3,5-trifluorobenzene (TFB). Cation-? interaction increases 1JC-F, 1JC-H and the chemical shifts of hydrogen and fluorine while it decreases 1JC-C. The changes are in reverse direction in the presence of anion-? interaction. The role of geometry and electronic effects on the NMR data was considered. The distance dependence of NMR parameters has been studied in these complexes. The NMR data have been investigated in isoelectronic complexes.

  19. Experimental studies on permeability by a pulsed NMR method

    International Nuclear Information System (INIS)

    The experimental data on the determination of permeability of sandstones saturated with a fluid by pulsed nuclear magnetic resonance method (NMR) are presented. The modernization of a standard pulsed NMR spectrometer operating according to the spin echo method is briefly described. The data obtained make it possible to conclude the necessity of further development of theoretical representations on the relation between NMR parameters of a fluid contained in rock and rock permeability. In this case the increase of the accuracy determination of the rock permeability by pulsed NMR method is assumed

  20. Optimization and practical implementation of ultrafast 2D NMR experiments

    Scientific Electronic Library Online (English)

    Luiz H. K., Queiroz Júnior; Antonio G., Ferreira; Patrick, Giraudeau.

    Full Text Available Ultrafast 2D NMR is a powerful methodology that allows recording of a 2D NMR spectrum in a fraction of second. However, due to the numerous non-conventional parameters involved in this methodology its implementation is no trivial task. Here, an optimized experimental protocol is carefully described [...] to ensure efficient implementation of ultrafast NMR. The ultrafast spectra resulting from this implementation are presented based on the example of two widely used 2D NMR experiments, COSY and HSQC, obtained in 0.2 s and 41 s, respectively.

  1. A variable temperature EPR study of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) single crystal at 170 GHz: zero-field splitting parameter and its absolute sign.

    Science.gov (United States)

    Misra, Sushil K; Andronenko, Serguei I; Chand, Prem; Earle, Keith A; Paschenko, Sergei V; Freed, Jack H

    2005-06-01

    EPR measurements have been carried out on a single crystal of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) at 170-GHz in the temperature range of 312-4.2K. The spectra have been analyzed (i) to estimate the spin-Hamiltonian parameters; (ii) to study the temperature variation of the zero-field splitting (ZFS) parameter; (iii) to confirm the negative absolute sign of the ZFS parameter unequivocally from the temperature-dependent relative intensities of hyperfine sextets at temperatures below 10K; and (iv) to detect the occurrence of a structural phase transition at 4.35K from the change in the structure of the EPR lines with temperature below 10K. PMID:15862243

  2. A variable temperature EPR study of Mn 2+-doped NH 4Cl 0.9I 0.1 single crystal at 170 GHz: Zero-field splitting parameter and its absolute sign

    Science.gov (United States)

    Misra, Sushil K.; Andronenko, Serguei I.; Chand, Prem; Earle, Keith A.; Paschenko, Sergei V.; Freed, Jack H.

    2005-06-01

    EPR measurements have been carried out on a single crystal of Mn 2+-doped NH 4Cl 0.9I 0.1 at 170-GHz in the temperature range of 312-4.2 K. The spectra have been analyzed (i) to estimate the spin-Hamiltonian parameters; (ii) to study the temperature variation of the zero-field splitting (ZFS) parameter; (iii) to confirm the negative absolute sign of the ZFS parameter unequivocally from the temperature-dependent relative intensities of hyperfine sextets at temperatures below 10 K; and (iv) to detect the occurrence of a structural phase transition at 4.35 K from the change in the structure of the EPR lines with temperature below 10 K.

  3. Rapid prediction of multi-dimensional NMR data sets

    Energy Technology Data Exchange (ETDEWEB)

    Gradmann, Sabine; Ader, Christian [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Heinrich, Ines [Max Planck Institute for Molecular Physiology, Department of Physical Biochemistry (Germany); Nand, Deepak [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Dittmann, Marc [Max Planck Institute for Molecular Physiology, Department of Physical Biochemistry (Germany); Cukkemane, Abhishek; Dijk, Marc van; Bonvin, Alexandre M. J. J. [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Engelhard, Martin [Max Planck Institute for Molecular Physiology, Department of Physical Biochemistry (Germany); Baldus, Marc, E-mail: m.baldus@uu.nl [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands)

    2012-12-15

    We present a computational environment for Fast Analysis of multidimensional NMR DAta Sets (FANDAS) that allows assembling multidimensional data sets from a variety of input parameters and facilitates comparing and modifying such 'in silico' data sets during the various stages of the NMR data analysis. The input parameters can vary from (partial) NMR assignments directly obtained from experiments to values retrieved from in silico prediction programs. The resulting predicted data sets enable a rapid evaluation of sample labeling in light of spectral resolution and structural content, using standard NMR software such as Sparky. In addition, direct comparison to experimental data sets can be used to validate NMR assignments, distinguish different molecular components, refine structural models or other parameters derived from NMR data. The method is demonstrated in the context of solid-state NMR data obtained for the cyclic nucleotide binding domain of a bacterial cyclic nucleotide-gated channel and on membrane-embedded sensory rhodopsin II. FANDAS is freely available as web portal under WeNMR (http://www.wenmr.eu/services/FANDAShttp://www.wenmr.eu/services/FANDAS).

  4. Proton NMR tomography

    International Nuclear Information System (INIS)

    In NMR imaging the accurate field-strength discrimination possible with nuclear magnetic resonance is converted by gradients in the magnetic field into spatial discrimination. An NMR tomograph consists of a large coil-magnet, gradient coils, r.f. equipment (for excitation and detection of the nuclear spin precession), program-control electronics and a computer for translating signals into images. Pulse NMR methods are used, generally with 900 and 1800 pulses for excitation. The best-known versions of NMR imaging are 2D projection reconstruction and 2D Fourier zeugmatography. In addition to proton-density images it is also possible to produce images that are sensitive to relaxation times; these generally provide much more information. (author)

  5. ?-NMR sample optimization

    CERN Document Server

    Zakoucka, Eva

    2013-01-01

    During my summer student programme I was working on sample optimization for a new ?-NMR project at the ISOLDE facility. The ?-NMR technique is well-established in solid-state physics and just recently it is being introduced for applications in biochemistry and life sciences. The ?-NMR collaboration will be applying for beam time to the INTC committee in September for three nuclei: Cu, Zn and Mg. Sample optimization for Mg was already performed last year during the summer student programme. Therefore sample optimization for Cu and Zn had to be completed as well for the project proposal. My part in the project was to perform thorough literature research on techniques studying Cu and Zn complexes in native conditions, search for relevant binding candidates for Cu and Zn applicable for ß-NMR and eventually evaluate selected binding candidates using UV-VIS spectrometry.

  6. Artificial intelligence in NMR imaging and image processing

    International Nuclear Information System (INIS)

    NMR tomography offers a wealth of information and data acquisition variants. Artificial intelligence is able to efficiently support the selection of measuring parameters and the evaluation of results. (orig.)

  7. NMR of peroxide borofluoric compounds. Hydroperoxofluoroborates

    International Nuclear Information System (INIS)

    Using the method of 1H and 19F NMR reactions between sodium, potassium and ammonium hydroxotrifluoroborates and hydrogen peroxide are studied. Mono-, di-, and trihydroperoxofluoroborates, stable in solutions, have been found for the first time, their NMR parameters and rate constants of formation reactions being determined. The high yield of boron complexes (75%) in the first moment after MBF3OH dissolution in H2O2 solutions is used for their separation from the solution using the method of cation substitution with the formation of less soluble compounds

  8. Lorentz-to-Gauss multiplication (LGM) in FT NMR

    Energy Technology Data Exchange (ETDEWEB)

    Makhiyanov, N. [Production Association ``Nizhnekamskneftekhym``, Nizhnekamsk, Tatarstan (Russian Federation); Kupka, T. [Uniwersytet Slaski, Katowice (Poland)]|[Zaklad Fizyki Ciala Stalego, Polska Akademia Nauk, Zabrze (Poland); Pasterna, G. [Institute of Nuclear Physics, Cracow (Poland); Dziegielewski, J.O. [Uniwersytet Slaski, Katowice (Poland)

    1994-12-31

    High resolution proton and carbon NMR spectra of macromolecules and biomolecules are often overcrowded and with many partly overlapped signals. Several data processing methods to resolve partly overlapped NMR peaks have been reported. Among the Lorentz-to-Gauss and CDRE (Convulsion Difference Resolution Enhancement) methods are wide used. In this work calculation of the best set of parameters were carried out from a raw spectral data (initial FID and the corresponding untreated spectrum) and a method of prediction of optimal Lorentz-to-Gauss method parameters are suggested. The feasibility of this approach to improve the quality of NMR spectra from various resonating nuclei was shown too. 8 refs, 1 fig.

  9. Calculation of 19F and 27Al NMR parameters for rosenbergite, AlF[F0.5(H2O)0.5]4.H2O, a possible model for Al hydroxyfluorides in solution.

    Science.gov (United States)

    Tossell, J A; Liu, Yun

    2004-10-01

    (19)F and (27)Al NMR chemical shifts are calculated for the F and Al atoms of the mineral rosenbergite, AlF[F(0.5)(H(2)O)(0.5)](4).H(2)O The structure of rosenbergite consists of infinite chains of F-corner-sharing Al[F(4)(H(2)O)(2)] octahedra and isolated water molecules. An F-centered molecular cluster of composition Al(2)F(3)(OH(2))(8) (3+) was initially used to model the mineral, with geometries taken both from the two different available x-ray crystal structures and from equilibrium geometries calculated at the 6-31G* B3LYP level (both with and without polarizable continuum solvation). Related Al(F)F(n) em leader clusters, with additional F(-) replacing H(2)O, were also studied. A larger Al-centered cluster model Al(3)F(4)(OH(2))(12) (5+) was also generated from one of the x-ray geometries and produced very similar bridging F shieldings but slightly different Al shieldings. The NMR shieldings were calculated using both HF and B3LYP GIAO methods, with 6-311+G(2df,p) basis sets, and the HF and B3LYP results averaged for the F shieldings as described in previous work. Calculated (19)F NMR shifts (relative to CCl(3)F) using this procedure were within a few ppm of experiment when either set of x-ray crystal structure coordinates was used, but differed by as much as 20 ppm for the energy-optimized geometries. Rosenbergite-like fragments with geometries optimized in water, simulated by a PCM, were used to model Al hydroxyfluoride species in solution. The (19)F NMR shifts for the bridging F atoms in several such model complexes are very similar to those usually attributed to monomeric species such as Al(OH(2))(5)F(2+) in solution, suggesting that the solution species are actually corner bridging oligomers. The F in the monomeric Al(OH(2))(5)F(2+) solution species is too strongly shielded by about 20 ppm to match the experimental peak usually assigned to it. PMID:15366039

  10. NMR studies of cation transport across membranes

    Energy Technology Data Exchange (ETDEWEB)

    Shochet, N.R.

    1985-01-01

    /sup 23/Na NMR Studies of cation transport across membranes were conducted both on model and biological membranes. Two ionophores, the carrier monensin and the channel-former gramicidin, were chosen to induce cation transport in large unilamellar phosphatidylcholine vesicles. The distinction between the NMR signals arising from the two sides of the membrane was achieved by the addition of an anionic paramagnetic shift reagent to the outer solution. The kinetics of the cation transport across the membrane was observed simultaneously monitoring the changes in the /sup 23/Na NMR signals of both compartments. Two mathematical models were developed for the estimation of the transport parameters of the monensin- and gramicidin-induced cation transport. The models were able to fit the experimental data very well. A new method for the estimation of the volume trapped inside the vesicles was developed. The method uses the relative areas of the intra- and extravesicular NMR signals arising from a suspension of vesicles bathed in the same medium they contain, as a measure for the relative volumes of these compartments. Sodium transport across biological membranes was studied by /sup 23/ NMR, using suspensions of cultured nerve cells. The sodium influx through voltage-gated channels was studied using the channel modifier batrachotoxin in combination with scorpion toxin.

  11. Teaching NMR Using Online Textbooks

    Directory of Open Access Journals (Sweden)

    Joseph P. Hornak

    1999-12-01

    Full Text Available Nuclear magnetic resonance (NMR spectroscopy has almost become an essential analytical tool for the chemist. High-resolution one- and multi-dimensional NMR, timedomain NMR, and NMR microscopy are but a few of the NMR techniques at a chemist's disposal to determine chemical structure and dynamics. Consequently, even small chemistry departments are finding it necessary to provide students with NMR training and experience in at least some of these techniques. The hands-on experience is readily provided with access to state-of-the-art commercial spectrometers. Instruction in the principles of NMR is more difficult to achieve as most instructors try to teach NMR using single organic or analytical chemistry book chapters with static figures. This paper describes an online textbook on NMR spectroscopy called The Basics of NMR (http://www.cis.rit.edu/htbooks/nmr/ suitable for use in teaching the principles of NMR spectroscopy. The book utilizes hypertext and animations to present the principles of NMR spectroscopy. The book can be used as a textbook associated with a lecture or as a stand-alone teaching tool. Conference participants are encouraged to review the textbook and evaluate its suitability for us in teaching NMR spectroscopy to undergraduate chemistry majors.

  12. Probing surface interactions by combining NMR cryoporometry and NMR relaxometry

    Science.gov (United States)

    Mitchell, J.; Stark, S. C.; Strange, J. H.

    2005-06-01

    To further expand on the understanding of surface interactions at the liquid/solid interface on pore walls, the nuclear magnetic resonance (NMR) techniques of cryoporometry and relaxometry have been combined. The combination of these techniques allows variations in NMR relaxation parameters from pore surface to volume ratio changes and from surface interaction changes to be distinguished. By studying a range of sol-gel silicas from two different sources, it was noted that the relaxation time measurements were not consistent with the pore diameters determined by cryoporometry and N2 gas adsorption. Instead distinctly different relaxivity constants were determined for each absorbate in each of the two brands of silica. It was clear that the relaxation times were modified by more than just the pore geometry. Independent experiments on the two brands of silica suggested that the relaxometry results were heavily influenced by the concentration of paramagnetic relaxation centres in the silica gels. The strength of surface interaction, and hence surface affinity, was seen to depend on the liquid in the pores. Using this difference in surface affinities, binary mixtures of alkanes placed in sol-gel silicas were separated via preferential absorption and their components identified using cryoporometry, whereas the components could not be distinguished in the bulk liquid.

  13. Probing surface interactions by combining NMR cryoporometry and NMR relaxometry

    International Nuclear Information System (INIS)

    To further expand on the understanding of surface interactions at the liquid/solid interface on pore walls, the nuclear magnetic resonance (NMR) techniques of cryoporometry and relaxometry have been combined. The combination of these techniques allows variations in NMR relaxation parameters from pore surface to volume ratio changes and from surface interaction changes to be distinguished. By studying a range of sol-gel silicas from two different sources, it was noted that the relaxation time measurements were not consistent with the pore diameters determined by cryoporometry and N2 gas adsorption. Instead distinctly different relaxivity constants were determined for each absorbate in each of the two brands of silica. It was clear that the relaxation times were modified by more than just the pore geometry. Independent experiments on the two brands of silica suggested that the relaxometry results were heavily influenced by the concentration of paramagnetic relaxation centres in the silica gels. The strength of surface interaction, and hence surface affinity, was seen to depend on the liquid in the pores. Using this difference in surface affinities, binary mixtures of alkanes placed in sol-gel silicas were separated via preferential absorption and their components identified using cryoporometry, whereas the components could not be distinguished in the bulk liquid

  14. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A

    1994-01-01

    This collection of reports demonstrate the extensive purview of NMR and its applications. The pellucid presentations provided include accounts on application of NMR spectroscopy to sciences and technologies of glassand ceramics; high-resolution solid-state NMR studies on ceramics; NMR studies of zeolite; NMR studies of higher-order structures of solid polymers; and organic thin films. Taken together with reviews in other volumes of this series, the present accountsably demonstrate that NMR is facile princeps when it comes to problem solving in most areas of science, including the medical sciences.

  15. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A

    1996-01-01

    NMR is used in all areas of modern science, and its applications continue to grow. In 1995 we celebrate the 50th anniversary of the discovery of NMR Spectroscopy and almost 30 years since the appearance of the firstvolume of Annual Reports on NMR Spectroscopy. During these years, a large and diverse collection of topics have been covered, and the contents of Volume 32 are no exception. This volume consists of reviews covering four, clearly distinct areas of science.* * Applications of NMR to Food Science* Gradient NMR* Pharmacetucial Applications of NMR* Forensic Science

  16. NMR for medical applications

    International Nuclear Information System (INIS)

    The new NMR imaging technique very rapidly met with great approval in the medical field, and the growing variety and frequency of applications meanwhile has led to aspects of safety of patients and personnel being given more attention than hitherto. The problems to be studied for this purpose are closely connected with the biological and biochemical effects of strong magnetic fields. The information presented in the document refers to results obtained by animal experiments for the study of magnetic field-induced biological effects. The contributions are original lectures presented to a conference organised by the German Society for Medical Physics, at Frankfurt/Main, on April 19, 1985, under the subject theme 'Topics on physical principles, technical aspects and biological effects of NMR for medical applications'. The lectures explain both fundamentals of NMR imaging and latest research results; the information is intended for engineers and physicians alike. (DG)

  17. NMR Aerosolomics: Novel NMR Method for Organic Aerosol Analysis.

    Czech Academy of Sciences Publication Activity Database

    Horník, Št?pán; Schwarz, Jaroslav; Sýkora, Jan

    - : -, 2015, s. 162. ISBN N. [Small Molecule NMR Conference - SMASH 2015. Baveno (IT), 20.09.2015-23.09.2015] Institutional support: RVO:67985858 Keywords : aerosol * analysis * NMR Subject RIV: CC - Organic Chemistry

  18. Wide line NMR spectrometer

    International Nuclear Information System (INIS)

    The modernized NMR wide line spectrometer operating on the frequency of approximately 20 MHz is described. The spectrometer modernization is accomplished on the IBM PC basis with application of the plate of the analog-to-digital converter. The spectrometer operates on the constant magnet. The temperature of the sample may change within the range from 150 up to 400 K. The registering system of the NMR spectrometer consists of the weak HF oscillations generator, HF amplifier, detector, LF amplifier, phase detector and self-recorder

  19. NMR imaging technique

    International Nuclear Information System (INIS)

    This invention provides a method that can be adapted to existing NMR tomographic scanners of producing spectra of any given point in the image of the specimen slice, the intensity distribution of a selected resonance within an area of the image of the specimen slice, or an entire NMR spectrum of the given area. The method comprises acquiring n projections of the specimen slice, where n is greater than 1. Each of the projections is then shifted by ? f for the point (the frequency offset of the signal arising from the point, from the true chemical shift)

  20. NMR studies of oriented molecules

    Energy Technology Data Exchange (ETDEWEB)

    Sinton, S.W.

    1981-11-01

    Deuterium and proton magnetic resonance are used in experiments on a number of compounds which either form liquid crystal mesophases themselves or are dissolved in a liquid crystal solvent. Proton multiple quantum NMR is used to simplify complicated spectra. The theory of nonselective multiple quantum NMR is briefly reviewed. Benzene dissolved in a liquid crystal are used to demonstrate several outcomes of the theory. Experimental studies include proton and deuterium single quantum (..delta..M = +-1) and proton multiple quantum spectra of several molecules which contain the biphenyl moiety. 4-Cyano-4'-n-pentyl-d/sub 11/-biphenyl (5CB-d/sub 11/) is studied as a pure compound in the nematic phase. The obtained chain order parameters and dipolar couplings agree closely with previous results. Models for the effective symmetry of the biphenyl group in 5CB-d/sub 11/ are tested against the experimental spectra. The dihedral angle, defined by the planes containing the rings of the biphenyl group, is found to be 30 +- 2/sup 0/ for 5DB-d/sub 11/. Experiments are also described for 4,4'-d/sub 2/-biphenyl, 4,4' - dibromo-biphenyl, and unsubstituted biphenyl.

  1. Earth’s field NMR flow meter: Preliminary quantitative measurements

    Science.gov (United States)

    Fridjonsson, Einar O.; Stanwix, Paul L.; Johns, Michael L.

    2014-08-01

    In this paper we demonstrate the use of Earth’s field NMR (EF NMR) combined with a pre-polarising permanent magnet for measuring fast fluid velocities. This time of flight measurement protocol has a considerable history in the literature; here we demonstrate that it is quantitative when employing the Earth’s magnetic field for signal detection. NMR signal intensities are measured as a function of flow rate (0-1 m/s) and separation distance between the permanent magnet and the EF NMR signal detection. These data are quantitatively described by a flow model, ultimately featuring no free parameters, that accounts for NMR signal modulation due to residence time inside the pre-polarising magnet, between the pre-polarising magnet and the detection RF coil and inside the detection coil respectively. The methodology is subsequently demonstrated with a metallic pipe in the pre-polarising region.

  2. NMR analysis of proteins structure; Structure des proteines par RMN

    Energy Technology Data Exchange (ETDEWEB)

    Malliavin, Th. [Institut de Biologie Physico-Chimique, Lab. de Biochimie Theorique, 75 - Paris (France); Dardel, F. [Paris-5 Univ., Faculte de Pharmacie, Lab. de Cristallographie et RMN Biologiques, 75 (France)

    2002-01-01

    The nuclear magnetic resonance (NMR) analysis of proteins aims at determining the 3-D folding of the polypeptide chain. Because of the high number of nuclei observed in the samples, the NMR protein spectra are extremely complex. The different steps of the structure determination are: the preparation of the samples, the acquisition and processing of the NMR signal, the analysis and attribution of spectra, and the calculation of the coordinates of the atoms using the NMR spectra parameters. Content: 1 - proteins and peptides (composition and structure, secondary, tertiary and quaternary structure); 2 - NMR of proteins in solution (characteristics, structures determination, homonuclear experiments, heteronuclear experiments, proteins with a size higher than 20 kDa, intermolecular interactions, stability factors, internal molecular dynamics); 3 - structures calculation (calculation framework, distance geometry, molecular dynamics and simulated annealing, quality of the structure obtained). (J.S.)

  3. International symposium on NMR spectroscopy

    International Nuclear Information System (INIS)

    The publication consists of 32 papers and presentations from the field of NMR spectroscopy applications submitted to the International Symposium on NMR Spectroscopy held at Smolenice between 29 Sep and 3 Oct, 1980. (B.S.)

  4. NMR Studies of Purines.

    Czech Academy of Sciences Publication Activity Database

    Dra?ínský, Martin; Pohl, Radek

    Vol. 82. Oxford : Academic Press, 2014 - (Webb, G.), s. 59-113 ISBN 978-0-12-800184-4 R&D Projects: GA ?R GA13-24880S Institutional support: RVO:61388963 Keywords : NMR spectroscopy * purines * DFT calculations * chemical shifts Subject RIV: CC - Organic Chemistry

  5. Modern NMR Spectroscopy.

    Science.gov (United States)

    Jelinski, Lynn W.

    1984-01-01

    Discusses direct chemical information that can be obtained from modern nuclear magnetic resonance (NMR) methods, concentrating on the types of problems that can be solved. Shows how selected methods provide information about polymers, bipolymers, biochemistry, small organic molecules, inorganic compounds, and compounds oriented in a magnetic…

  6. NMR for chemists and biologists

    CERN Document Server

    Carbajo, Rodrigo J

    2013-01-01

    This book offers a concise introduction to the field of nuclear magnetic resonance or NMR. It presents the basic foundations of NMR in a non-mathematical way and provides an overview of both recent and important biological applications of NMR.

  7. Fluid-Rock Characterization and Interactions in NMR Well Logging

    Energy Technology Data Exchange (ETDEWEB)

    George J. Hirasaki; Kishore K. Mohanty

    2005-09-05

    The objective of this report is to characterize the fluid properties and fluid-rock interactions that are needed for formation evaluation by NMR well logging. The advances made in the understanding of NMR fluid properties are summarized in a chapter written for an AAPG book on NMR well logging. This includes live oils, viscous oils, natural gas mixtures, and the relation between relaxation time and diffusivity. Oil based drilling fluids can have an adverse effect on NMR well logging if it alters the wettability of the formation. The effect of various surfactants on wettability and surface relaxivity are evaluated for silica sand. The relation between the relaxation time and diffusivity distinguishes the response of brine, oil, and gas in a NMR well log. A new NMR pulse sequence in the presence of a field gradient and a new inversion technique enables the T{sub 2} and diffusivity distributions to be displayed as a two-dimensional map. The objectives of pore morphology and rock characterization are to identify vug connectivity by using X-ray CT scan, and to improve NMR permeability correlation. Improved estimation of permeability from NMR response is possible by using estimated tortuosity as a parameter to interpolate between two existing permeability models.

  8. NMR studies of the helium distribution in uranium tritide

    International Nuclear Information System (INIS)

    The distribution of helium (3He) created in uranium tritide (UT3) by triton decay has been investigated by pulse NMR techniques. The line shapes and relaxation times for 3He nuclei have been measured during a 3-year period. NMR samples were prepared from five UT3 synthesis batches. Because UT3 is a highly paramagnetic material which ferromagnetically orders below approximately 180 K, inhomogeneous magnetic field effects contributed to the NMR parameters. Detailed analyses of the frequency, temperature, and age dependences of these NMR parameters indicate most 3He atoms are retained in microscopic gas bubbles with dimensions 3He atoms in the UT3 lattice. A simple model based upon the nucleation, growth, and subsequent rupture at critical dimensions of helium bubbles is presented. This model qualitatively describes the 3He relaxation times and the observed 3He retention in UT3 powders

  9. Solid-state 73Ge NMR spectroscopy of simple organogermanes.

    Science.gov (United States)

    Hanson, Margaret A; Sutrisno, Andre; Terskikh, Victor V; Baines, Kim M; Huang, Yining

    2012-10-22

    Germanium-73 is an extremely challenging nucleus to examine by NMR spectroscopy due to its unfavorable NMR properties. Through the use of an ultrahigh (21.1 T) magnetic field, a systematic study of a series of simple organogermanes was carried out. In those cases for which X-ray structural data were available, correlations were drawn between the NMR parameters and structural metrics. These data were combined with DFT calculations to obtain insight into the structures of several compounds with unknown crystal structures. PMID:23023927

  10. Longitudinal and Transverse NMR in Superfluid 3He in Anisotropic Aerogel

    OpenAIRE

    Dmitriev, V. V.; Krasnikhin, D. A.; Mulders, N; Zavjalov, V. V.; Zmeev, D. E.

    2007-01-01

    It was found that NMR properties of both superfluid phases of $^3$He in anisotropic aerogel can be described in terms of the bulk superfluid order parameters with the orbital order parameter vector fixed by anisotropy of the aerogel sample. It was also shown that by a proper squeezing it is possible to get the aerogel sample with isotropic NMR properties.

  11. 45scandium NMR investigations in aqueous solutions

    International Nuclear Information System (INIS)

    45Sc NMR chemical shifts, linewidths, and longitudinal relaxation rates have been measured in aqueous solutions on scandium chloride and sulphate as a function of the appropriate acid. A common typical behaviour of these parameters without sudden changes has been observed. Also signals in the basic range have been obtained. H2O-D2O solvent isotope effects on Larmor frequency and relaxation rates are presented. (orig.)

  12. Fluid-Rock Characterization and Interactions in NMR Well Logging

    Energy Technology Data Exchange (ETDEWEB)

    Hirasaki, George J.; Mohanty, Kishore K.

    2003-02-10

    The objective of this project was to characterize the fluid properties and fluid-rock interactions which are needed for formation evaluation by NMR well logging. NMR well logging is finding wide use in formation evaluation. The formation parameters commonly estimated were porosity, permeability, and capillary bound water. Special cases include estimation of oil viscosity, residual oil saturation, location of oil/water contact, and interpretation on whether the hydrocarbon is oil or gas.

  13. Some exercises in quantitative NMR imaging

    International Nuclear Information System (INIS)

    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 T1 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 T1, 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 T1 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.)

  14. NMR of unfolded proteins

    Indian Academy of Sciences (India)

    Amarnath Chtterjee; Ashutosh Kumar; Jeetender Chugh; Sudha Srivastava; Neel S Bhavesh; Ramakrishna V Hosur

    2005-01-01

    In the post-genomic era, as more and more genome sequences are becoming known and hectic efforts are underway to decode the information content in them, it is becoming increasingly evident that flexibility in proteins plays a crucial role in many of the biological functions. Many proteins have intrinsic disorder either wholly or in specific regions. It appears that this disorder may be important for regulatory functions of the proteins, on the one hand, and may help in directing the folding process to reach the compact native state, on the other. Nuclear magnetic resonance (NMR) has over the last two decades emerged as the sole, most powerful technique to help characterize these disordered protein systems. In this review, we first discuss the significance of disorder in proteins and then describe the recent developments in NMR methods for their characterization. A brief description of the results obtained on several disordered proteins is presented at the end.

  15. Solid state NMR probe

    International Nuclear Information System (INIS)

    This patent describes a system for in vivo sensing of RF energy emanating from an organism exposed to an NMR scanner comprising: means for receiving RF energy emanating from within an organism in response to the NMR scanner. The receiving means is dimensioned for insertion into the organism. The receiving means comprises: means for generating an electrical signal having a strength and frequency related to the strength and frequency, respectively of the RF energy. The frequency of the electrical signal is greater than the frequency of the RF energy means for inserting the receiving means into an oriface in the organism and for localizing the receiving means at an area of interest within the organism. The receiving means is incorporated within the inserting means

  16. NMR, water and plants

    International Nuclear Information System (INIS)

    This thesis describes the application of a non-destructive pulsed proton NMR method mainly to measure water transport in the xylem vessels of plant stems and in some model systems. The results are equally well applicable to liquid flow in other biological objects than plants, e.g. flow of blood and other body fluids in human and animals. The method is based on a pulse sequence of equidistant ? pulses in combination with a linear magnetic field gradient. (Auth.)

  17. Applications of Unilateral NMR in Nondestructive Testing

    OpenAIRE

    Sharma, Shatrughan

    2004-01-01

    Für die Messung mit NMR-Spektroskopie wird eine Probe in der Regel vorbereitet, gemessen und anschließend entsorgt. In dem Fall, dass Probe nicht zerstört werden darf, gewinnt die Relaxationsanalyse bei niedrigen Feldern, i.e. die niedrig-auflösende NMR, an Bedeutung. Für große Proben ist die unilaterale NMR mit inhomogenen Feldern die Methode der Wahl. Unilaterale NMR oder inside-out NMR ist eine etablierte Technik der niedrig-auflösende NMR. Die NMR-MOUSE(Mobile Universal Surface Explorer) ...

  18. Soils, Pores, and NMR

    Science.gov (United States)

    Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about the connectivity of the pore system. Examples are given for T1-T2 correlation of some soil samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a Natural soil: Comparison of Relaxometric Imaging, T1 - T2 Correlation and Fast-Field Cycling NMR." The Open Magnetic Resonance Journal: in print. Pohlmeier, A., S. Haber-Pohlmeier, et al. (2009). "A Fast Field Cycling NMR Relaxometry Study of Natural Soils." Vadose Zone J. 8: 735-742. Stingaciu, L. R., A. Pohlmeier, et al. (2009). "Characterization of unsaturated porous media by high-field and low-field NMR relaxometry." Water Resources Research 45: W08412

  19. NMR used for Saudi crude asphaltenes

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) spectroscopy with proton (/sup 1/H) and carbon 13 (/sup 13/C) has been used to determine the structural characteristics of asphaltenes from four commercial Saudi Arabian crude oils. These characteristics are important to refiners that have deep conversion processes to determine yields from the residual fractions of the Saudi crudes, and to determine the operating parameters of the process units. The spectra obtained give some structural similarities among the crude oils, as well as some differences. Values of various structural parameters have been tabulated from the spectra

  20. Multinuclear NMR of CaSiO(3) glass: simulation from first-principles.

    Science.gov (United States)

    Pedone, Alfonso; Charpentier, Thibault; Menziani, Maria Cristina

    2010-06-21

    An integrated computational method which couples classical molecular dynamics simulations with density functional theory calculations is used to simulate the solid-state NMR spectra of amorphous CaSiO(3). Two CaSiO(3) glass models are obtained by shell-model molecular dynamics simulations, successively relaxed at the GGA-PBE level of theory. The calculation of the NMR parameters (chemical shielding and quadrupolar parameters), which are then used to simulate solid-state 1D and 2D-NMR spectra of silicon-29, oxygen-17 and calcium-43, is achieved by the gauge including projector augmented-wave (GIPAW) and the projector augmented-wave (PAW) methods. It is shown that the limitations due to the finite size of the MD models can be overcome using a Kernel Estimation Density (KDE) approach to simulate the spectra since it better accounts for the disorder effects on the NMR parameter distribution. KDE allows reconstructing a smoothed NMR parameter distribution from the MD/GIPAW data. Simulated NMR spectra calculated with the present approach are found to be in excellent agreement with the experimental data. This further validates the CaSiO(3) structural model obtained by MD simulations allowing the inference of relationships between structural data and NMR response. The methods used to simulate 1D and 2D-NMR spectra from MD GIPAW data have been integrated in a package (called fpNMR) freely available on request. PMID:20383404

  1. NMR imaging of the spine

    Energy Technology Data Exchange (ETDEWEB)

    Han, J.S. (Case Western Reserve Univ. School of Medicine, Cleveland, OH); Kaufman, B.; El Yousef, S.J.; Benson, J.E.; Bonstelle, C.T.; Alfidi, R.J.; Haaga, J.R.; Yeung, H.; Huss, R.G.

    1983-12-01

    The usefulness of nuclear magnetic resonance (NMR) images in the evaluation of spinal disorders below the craniocervical junction was studied. Six normal subjects and 41 patients with various spinal abnormalities were examined. NMR proved capable of demonstrating important normal and pathologic anatomic structures; it was useful in the evaluation of syringohydromyelia and cystic spinal cord tumors, and the bright signal intensity of lipoma was quite impressive. In the evaluation of herniated disk, NMR images offered a new perspective by visualizing abnormal degradation of the signal intensity of the nucleus pulposus itself. NMR images were least valuable in the evaluation of spondylosis and spinal stenosis. Although NMR imaging of the spine is still in a very early developmental stage, the absence of both ionizing radiation and risks associated with contrast material makes it especially attractive as a new diagnostic method. This limited experience with currently available equipment suggests that, with technical refinement, the efficacy of NMR of the spine will increase.

  2. Automatic maximum entropy spectral reconstruction in NMR.

    Science.gov (United States)

    Mobli, Mehdi; Maciejewski, Mark W; Gryk, Michael R; Hoch, Jeffrey C

    2007-10-01

    Developments in superconducting magnets, cryogenic probes, isotope labeling strategies, and sophisticated pulse sequences together have enabled the application, in principle, of high-resolution NMR spectroscopy to biomolecular systems approaching 1 megadalton. In practice, however, conventional approaches to NMR that utilize the fast Fourier transform, which require data collected at uniform time intervals, result in prohibitively lengthy data collection times in order to achieve the full resolution afforded by high field magnets. A variety of approaches that involve nonuniform sampling have been proposed, each utilizing a non-Fourier method of spectrum analysis. A very general non-Fourier method that is capable of utilizing data collected using any of the proposed nonuniform sampling strategies is maximum entropy reconstruction. A limiting factor in the adoption of maximum entropy reconstruction in NMR has been the need to specify non-intuitive parameters. Here we describe a fully automated system for maximum entropy reconstruction that requires no user-specified parameters. A web-accessible script generator provides the user interface to the system. PMID:17701276

  3. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A

    2012-01-01

    Nuclear magnetic resonance (NMR) is an analytical tool used by chemists and physicists to study the structure and dynamics of molecules. In recent years, no other technique has gained such significance as NMR spectroscopy. It is used in all branches of science in which precise structural determination is required and in which the nature of interactions and reactions in solution is being studied. Annual Reports on NMR Spectroscopy has established itself as a premier means for the specialist and non-specialist alike to become familiar with new techniques and applications of NMR spectroscopy. N

  4. NMR imaging of the heart

    International Nuclear Information System (INIS)

    It is now possible to obtain satisfactory images of the heart by nuclear magnetic resonance (NMR). Proton images of the heart were first demonstrated by Damadian in 1977. Normal and abnormal cardiac NMR images, as well as good quality images of the pericardium, have since been achieved by other groups of workers. Technical advances, including gating of the examination by the patients' ECG, have led to considerable improvement in image quality over the past few years. The principles of NMR, of NMR technology, and cardiac imaging have been previously described

  5. Fully automated system for pulsed NMR measurements

    International Nuclear Information System (INIS)

    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

  6. Some nitrogen-14 NMR studies in solids

    Energy Technology Data Exchange (ETDEWEB)

    Pratum, T.K.

    1983-11-01

    The first order quadrupolar perturbation of the /sup 14/N NMR spectrum yields information regarding the static and dynamic properties of the surrounding electronic environment. Signal to noise problems caused by long /sup 14/N longitudinal relaxation times (T/sub 1/) and small equilibrium polarizations are reduced by rotating frame cross polarization (CP) experiments between /sup 14/N and /sup 1/H. Using quadrupolar echo and CP techniques, the /sup 14/N quadrupolar coupling constants (e/sup 2/qQ/h) and asymmetry parameters (eta) have been obtained for a variety of tetraalkylammonium compounds by observation of their quadrupolar powder patterns at various temperatures. For choline chloride and iodide the /sup 14/N NMR powder patterns exhibit the effects of anisotropic molecular motion, while choline bromide spectra show no such effects.

  7. DNA oligonucleotide conformations: high resolution NMR studies

    International Nuclear Information System (INIS)

    The present work describes a DNA double-helix model, which is well comparable with the models derived from fibre-diffraction studies. The model has a mononucleotide repeat with torsion angles in accordance with average geometries as derived from 1H NMR studies. Special attention was paid to reduce the number of short H-H nonbonding contacts, which are abundantly present in the 'classical' fibre-diffraction models. Chapter 3 describes the first complete assignment of a 1H NMR spectrum of a DNA tetramer, d(TAAT). Preliminary conformational data derived from the spectral parameters recorded at 27 0C are given. A more detailed analysis employing temperature-dependence studies is given in Chapter 4. (Auth.)

  8. Some nitrogen-14 NMR studies in solids

    International Nuclear Information System (INIS)

    The first order quadrupolar perturbation of the 14N NMR spectrum yields information regarding the static and dynamic properties of the surrounding electronic environment. Signal to noise problems caused by long 14N longitudinal relaxation times (T1) and small equilibrium polarizations are reduced by rotating frame cross polarization (CP) experiments between 14N and 1H. Using quadrupolar echo and CP techniques, the 14N quadrupolar coupling constants (e2qQ/h) and asymmetry parameters (eta) have been obtained for a variety of tetraalkylammonium compounds by observation of their quadrupolar powder patterns at various temperatures. For choline chloride and iodide the 14N NMR powder patterns exhibit the effects of anisotropic molecular motion, while choline bromide spectra show no such effects

  9. Measurement of magnetic field intensity by means of NMR. I

    International Nuclear Information System (INIS)

    The influence of various parameters (e.g. polarization and intensity of high frequency field, NMR relaxation times, signal-to-noise ratio of the measuring apparatus) on the determination of the NMR resonance point of a nuclear system with an accurately known value of the gyromagnetic factor is discussed. Special attention is given to the case of real field, which is not stable in time. It is shown that if the lowest obtainable uncertainty of field intensity NMR measurement is to be achieved the transverse NMR relaxation time of the nuclei in the sample has to be selected in correlation with the properties of the field (e.g. time instability, spatial inhomogeneity) and of the measuring equipment (e.g. signal-to-noise ratio). (author)

  10. Application of chemometrics to low-field H-1 NMR relaxation data of intact fish flesh

    DEFF Research Database (Denmark)

    Jepsen, Signe Munk; Pedersen, H.T.; Engelsen, S.B.

    1999-01-01

    The possibilities for application of low-field H-1 nuclear magnetic resonance (NMR) as a rapid method for simultaneous assessment of basic quality parameters in fish were explored. In a first experiment, 200 salmon (Salmo salar) samples mapping the variation over an entire fish were measured by NMR and subsequently analysed for oil or water content by standard chemical methods. In a second experiment, 58 differently thawed cod (Gadus morhua) samples were measured by NMR and subsequently analysed...

  11. NMR signatures of topological objects in rotating superfluid {sup 3}He-A

    Energy Technology Data Exchange (ETDEWEB)

    Ruutu, V.M.H.; Parts, U.; Krusius, M. [Helsinki Univ. of Technology, Espoo (Finland)

    1996-06-01

    NMR spectrometry can be used to identify different topological objects in the order parameter field of rotating superfluid {sup 3}He-A. The authors list their signatures in the cw NMR absorption line shape. Quantized vortex lines, domain walls, and their combination, the vortex sheet, all induce satellite peaks with specific intensities and frequency shifts in the NMR spectrum. Examples of spectra are presented to allow a comparison and to distinguish between different objects.

  12. NMR signatures of topological objects in rotating superfluid 3He-A

    International Nuclear Information System (INIS)

    NMR spectrometry can be used to identify different topological objects in the order parameter field of rotating superfluid 3He-A. The authors list their signatures in the cw NMR absorption line shape. Quantized vortex lines, domain walls, and their combination, the vortex sheet, all induce satellite peaks with specific intensities and frequency shifts in the NMR spectrum. Examples of spectra are presented to allow a comparison and to distinguish between different objects

  13. NMR signatures of topological objects in rotating superfluid3He-A

    Science.gov (United States)

    Ruutu, V. M. H.; Parts, Ü.; Krusius, M.

    1996-06-01

    NMR spectrometry can be used to identify different topological objects in the order parameter field of rotating superfluid3He-A. We list their signatures in the cw NMR absorption line shape. Quantized vortex lines, domain walls, and their combination, the vortex sheet, all induce satellite peaks with specific intensities and frequency shifts in the NMR spectrum. Examples of spectra are presented to allow a comparison and to distinguish between different objects.

  14. Analysis of porous media and objects of cultural heritage by mobile NMR

    OpenAIRE

    Haber, Agnes

    2012-01-01

    Low-field NMR techniques are used to study porous system, from simple to complex structures, and objects of cultural heritage. It is shown that NMR relaxometry can be used to study the fluid dynamics inside a porous system. A simple theoretical model for multi-site relaxation exchange NMR is used to extract exchange kinetic parameters when applied on a model porous systems. It provides a first step towards the study of more complex systems, where continuous relaxation distributions are presen...

  15. Achievement of 1020 MHz NMR

    Science.gov (United States)

    Hashi, Kenjiro; Ohki, Shinobu; Matsumoto, Shinji; Nishijima, Gen; Goto, Atsushi; Deguchi, Kenzo; Yamada, Kazuhiko; Noguchi, Takashi; Sakai, Shuji; Takahashi, Masato; Yanagisawa, Yoshinori; Iguchi, Seiya; Yamazaki, Toshio; Maeda, Hideaki; Tanaka, Ryoji; Nemoto, Takahiro; Suematsu, Hiroto; Miki, Takashi; Saito, Kazuyoshi; Shimizu, Tadashi

    2015-07-01

    We have successfully developed a 1020 MHz (24.0 T) NMR magnet, establishing the world's highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-Tc superconductors NbTi and Nb3Sn) outer coils and an HTS (high-Tc superconductor, Bi-2223) innermost coil, being operated at superfluid liquid helium temperature such as around 1.8 K and in a driven-mode by an external DC power supply. The drift of the magnetic field was initially ± 0.8 ppm/10 h without the 2H lock operation; it was then stabilized to be less than 1 ppb/10 h by using an NMR internal lock operation. The full-width at half maximum of a 1H spectrum taken for 1% CHCl3 in acetone-d6 was as low as 0.7 Hz (0.7 ppb), which was sufficient for solution NMR. On the contrary, the temporal field stability under the external lock operation for solid-state NMR was 170 ppb/10 h, sufficient for NMR measurements for quadrupolar nuclei such as 17O; a 17O NMR measurement for labeled tri-peptide clearly demonstrated the effect of high magnetic field on solid-state NMR spectra.

  16. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  17. Achievement of 1020MHz NMR.

    Science.gov (United States)

    Hashi, Kenjiro; Ohki, Shinobu; Matsumoto, Shinji; Nishijima, Gen; Goto, Atsushi; Deguchi, Kenzo; Yamada, Kazuhiko; Noguchi, Takashi; Sakai, Shuji; Takahashi, Masato; Yanagisawa, Yoshinori; Iguchi, Seiya; Yamazaki, Toshio; Maeda, Hideaki; Tanaka, Ryoji; Nemoto, Takahiro; Suematsu, Hiroto; Miki, Takashi; Saito, Kazuyoshi; Shimizu, Tadashi

    2015-07-01

    We have successfully developed a 1020MHz (24.0T) NMR magnet, establishing the world's highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-Tc superconductors NbTi and Nb3Sn) outer coils and an HTS (high-Tc superconductor, Bi-2223) innermost coil, being operated at superfluid liquid helium temperature such as around 1.8K and in a driven-mode by an external DC power supply. The drift of the magnetic field was initially ±0.8ppm/10h without the (2)H lock operation; it was then stabilized to be less than 1ppb/10h by using an NMR internal lock operation. The full-width at half maximum of a (1)H spectrum taken for 1% CHCl3 in acetone-d6 was as low as 0.7Hz (0.7ppb), which was sufficient for solution NMR. On the contrary, the temporal field stability under the external lock operation for solid-state NMR was 170ppb/10h, sufficient for NMR measurements for quadrupolar nuclei such as (17)O; a (17)O NMR measurement for labeled tri-peptide clearly demonstrated the effect of high magnetic field on solid-state NMR spectra. PMID:25978708

  18. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A

    1985-01-01

    The current extent of applications of NMR spectroscopy to molecular problems is indicated by the diversity of the reviews presented in this volume. Dr. H.W.E. Rattle reports on NMR of amino acids, peptides, and proteins, which brings his account in Volume 11A up to date.

  19. Phenomenological simulation and density functional theory prediction of 57Fe Mössbauer parameters: application to magnetically coupled diiron proteins

    International Nuclear Information System (INIS)

    The use of phenomenological spin Hamiltonians and of spin density functional theory for the analysis and interpretation of Mössbauer spectra of antiferromagnetic or ferromagnetic diiron centers is briefly discussed. The spectroscopic parameters of the hydroxylase component of methane monooxygenase (MMOH), an enzyme that catalyzes the conversion of methane to methanol, have been studied. In its reduced diferrous state (MMOHRed) the enzyme displays 57Fe Mössbauer and EPR parameters characteristic of two ferromagnetically coupled high spin ferrous ions. However, Mössbauer spectra recorded for MMOHRed from two different bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, display slightly different electric quadrupole splittings (?EQ) in apparent contradiction to their essentially identical active site crystallographic structures and biochemical functions. Herein, the Mössbauer spectral parameters of MMOHRed have been predicted and studied via spin density functional theory. The somewhat different ?EQ recorded for the two bacteria have been traced to the relative position of an essentially unbound water molecule within their diiron active sites. It is shown that the presence or absence of the unbound water molecule mainly affects the electric field gradient at only one iron ion of the binuclear active sites.

  20. Phenomenological simulation and density functional theory prediction of 57 Fe Mössbauer parameters: application to magnetically coupled diiron proteins

    Science.gov (United States)

    Rodriguez, Jorge H.

    2013-04-01

    The use of phenomenological spin Hamiltonians and of spin density functional theory for the analysis and interpretation of Mössbauer spectra of antiferromagnetic or ferromagnetic diiron centers is briefly discussed. The spectroscopic parameters of the hydroxylase component of methane monooxygenase (MMOH), an enzyme that catalyzes the conversion of methane to methanol, have been studied. In its reduced diferrous state (MMOH Red ) the enzyme displays 57Fe Mössbauer and EPR parameters characteristic of two ferromagnetically coupled high spin ferrous ions. However, Mössbauer spectra recorded for MMOH Red from two different bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, display slightly different electric quadrupole splittings (? E Q ) in apparent contradiction to their essentially identical active site crystallographic structures and biochemical functions. Herein, the Mössbauer spectral parameters of MMOH Red have been predicted and studied via spin density functional theory. The somewhat different ? E Q recorded for the two bacteria have been traced to the relative position of an essentially unbound water molecule within their diiron active sites. It is shown that the presence or absence of the unbound water molecule mainly affects the electric field gradient at only one iron ion of the binuclear active sites.

  1. Applications of unilateral NMR in nondestructive testing

    OpenAIRE

    Sharma, Shatrughan

    2004-01-01

    In general, in NMR spectroscopy a sample is prepared for the NMR measurement, positioned in the magnet, measured, and discarded. But when non-destructiveness of the sample is more important, it becomes important to rely on relaxation analysis at low resolution NMR. If the samples are big in size the unilateral or single-sided NMR in inhomogeneous fields is an important choice. Unilateral NMR or inside-out NMR is one recognized technique in the field of low resolution NMR. The NMR-MOUSE (Mobil...

  2. Carbon-13 NMR spectroscopy

    International Nuclear Information System (INIS)

    Features in this edition are references (over 1,000), profuse illustration, a discussion of modern pulse techniques for spectral analysis, and extensive and thorough cataloguing of chemical shift data (over 200 pages) in readily accessible form. An attractive feature is the use of structural formulae with shifts inscribed in the structure. This new edition has been completely revised to take into account new techniques and the increased use of computers. The new methods described include those for multiplicity analysis and two-dimensional homo- or hetero-nuclear shift correlations. New sections about coupling constants, organophosphorus and organometalic compounds as well as synthetic polymers have been added. As in the second edition, the authors survey the large number of /sup 13/C NMR applications to organic molecule and natural products in a representative and systematic rather than an exhaustive way

  3. A simulator for NMR imaging experiments: its interest for adjusting apparatus

    International Nuclear Information System (INIS)

    A computer method for simulating NMR imaging spectra is described. This tool was built in order to permit the analysis of complex results in NMR imaging experimentation. Indeed, the observed spectra provide only a global information whereas simulation allows one to unravel the role of the various parameters. Some examples of possible applications are given

  4. Toward a Generalized Algorithm for the Automated Analysis of Complex Anisotropic NMR Spectra

    Science.gov (United States)

    Castiglione, F.; Carravetta, M.; Celebre, G.; Longeri, M.

    1998-05-01

    An existing algorithm, founded on the works of Stephenson and Binsch, for the automatic analysis of isotropic or simple anisotropic NMR spectra has been improved to treat very complex NMR spectra of molecules dissolved in nematic solvents. The main options added to the original algorithm are a wider choice of smoothing functions; the use of the principal component regression method; and the possibility of selecting molecular coordinates, order parameters, and spectral parameters as variables of the problem. By means of these new options, it has been possible to analyze automatically NMR spectra (even depending on 27 spectral parameters) of 16 molecules in an anisotropic environment. Details of each case are discussed.

  5. NMR Logging to Estimate Hydraulic Conductivity in Unconsolidated Aquifers.

    Science.gov (United States)

    Knight, Rosemary; Walsh, David O; Butler, James J; Grunewald, Elliot; Liu, Gaisheng; Parsekian, Andrew D; Reboulet, Edward C; Knobbe, Steve; Barrows, Mercer

    2016-01-01

    Nuclear magnetic resonance (NMR) logging provides a new means of estimating the hydraulic conductivity (K) of unconsolidated aquifers. The estimation of K from the measured NMR parameters can be performed using the Schlumberger-Doll Research (SDR) equation, which is based on the Kozeny-Carman equation and initially developed for obtaining permeability from NMR logging in petroleum reservoirs. The SDR equation includes empirically determined constants. Decades of research for petroleum applications have resulted in standard values for these constants that can provide accurate estimates of permeability in consolidated formations. The question we asked: Can standard values for the constants be defined for hydrogeologic applications that would yield accurate estimates of K in unconsolidated aquifers? Working at 10 locations at three field sites in Kansas and Washington, USA, we acquired NMR and K data using direct-push methods over a 10- to 20-m depth interval in the shallow subsurface. Analysis of pairs of NMR and K data revealed that we could dramatically improve K estimates by replacing the standard petroleum constants with new constants, optimal for estimating K in the unconsolidated materials at the field sites. Most significant was the finding that there was little change in the SDR constants between sites. This suggests that we can define a new set of constants that can be used to obtain high resolution, cost-effective estimates of K from NMR logging in unconsolidated aquifers. This significant result has the potential to change dramatically the approach to determining K for hydrogeologic applications. PMID:25810149

  6. Solid-state NMR study of halogen-bonded adducts.

    Science.gov (United States)

    Bryce, David L; Viger-Gravel, Jasmine

    2015-01-01

    Nuclear magnetic resonance (NMR) spectroscopy offers unique insights into halogen bonds. NMR parameters such as chemical shifts, quadrupolar coupling constants, J coupling constants, and dipolar coupling constants are in principle sensitive to the formation and local structure of a halogen bond. Carrying out NMR experiments on halogen-bonded adducts in the solid state may provide several advantages over solution studies including (1) the absence of solvent which can interact with halogen bond donor sites and complicate spectral interpretation, (2) the lack of a need for single crystals or even long-range crystalline order, and (3) the potential to measure complete NMR interaction tensors rather than simply their isotropic values. In this chapter, we provide an overview of the NMR interactions and experiments which are relevant to the study of nuclei which are often found in halogen bonds (RX···Y) including (13)C, (35/37)Cl, (79/81)Br, (127)I, (77)Se, and (14/15)N. Experimental examples based on iodoperfluorobenzene halides, bis(trimethylammonium)alkane diiodide, and selenocyanate complexes, as well as haloanilinium halides, are discussed. Of particular interest is the sensitivity of the isotropic chemical shifts, the chemical shift tensor spans, and the halide nuclear electric quadrupolar coupling tensors to the halogen bond geometry in such compounds. Technical limitations associated with the NMR spectroscopy of covalently-bonded halogens are underlined. PMID:24760615

  7. NMR properties of partially saturated porous silica glasses

    Science.gov (United States)

    Wiens, Eugen; Klitzsch, Norbert; Mohnke, Oliver

    2010-05-01

    The signal responses of nuclear magnetic resonance (NMR) is sensitive to the inner surfaces of the water filled porous media. Therefore this method is well suited to noninvasively determine hydrological relevant parameters such as the pore radii distributions or hydraulic permeability of fully and partially saturated rocks and soils. NMR exploits the relaxation of the magnetization of fluids in the pore space of porous medium. In this work we study the dependence of NMR signals on the inner structure of fully and partially saturated artificial porous silica glasses (VitraPOR). The samples are characterized by an accurately defined pore space with well known pore radii distributions and surface properties. The mean pore sizes of the investigated samples range from 0.6 ?m to 25 ?m. Laboratory NMR saturation recovery (T1) and CPMG (T2) measurements as well as diffusion pulsed gradient mesurements have been carried out using a 3.91 MHz NMR spectrometer. A homogeneous partial saturation down to 5 vol.% has been realized by applying a uniform negative pressure gradient to the samples at each desaturation step. Additionally the corresponding water retention curves have been recorded and evaluated. On the basis of the results from these experiments the numerical simulation of the pore network using the Delaunay tesselation approach with subsequent simulations of NMR relaxation on the pore scale is performed in order to assess structure, state and thus transport properties of fully and partially saturated soils.

  8. Single-crystal27 Al NMR study of corundum ?-Al2O3

    International Nuclear Information System (INIS)

    27Al NMR chemical shielding, quadrupolar coupling, and dipolar coupling interactions for corundum (?-Al2O3) are determined from the single-crystal 27Al NMR spectra according to the rotation about three orthogonal axis. 27Al NMR parameters obtained in this work with high accuracy are as follows: ?iso =7.4(4) ppm, QCC=2.30(4) MHz, ?=0.08(3), and R=2.0(3) kHz. This work appears to be the first NMR measurement of an aluminum-aluminum dipolar coupling interaction in ?-Al2O3 crystals

  9. Quantitative calibration of radiofrequency NMR Stark effects

    Science.gov (United States)

    Tarasek, Matthew R.; Kempf, James G.

    2011-10-01

    Nuclear magnetic resonance (NMR) Stark responses can occur in quadrupolar nuclei for an electric field oscillating at twice the usual NMR frequency (2?0). Calibration of responses to an applied E field is needed to establish nuclear spins as probes of native E fields within material and molecular systems. We present an improved approach and apparatus for accurate measurement of quadrupolar Stark effects. Updated values of C14 (the response parameter in cubic crystals) were obtained for both 69Ga and 75As in GaAs. Keys to improvement include a modified implementation of voltage dividers to assess the 2?0 amplitude, |E|, and the stabilization of divider response by reduction of stray couplings in 2?0 circuitry. Finally, accuracy was enhanced by filtering sets of |E| through a linear response function that we established for the radiofrequency amplifier. Our approach is verified by two types of spectral results. Steady-state 2?0 excitation to presaturate NMR spectra yielded C14 = (2.59 ± 0.06) × 1012 m-1 for 69Ga at room-temperature and 14.1 T. For 75As, we obtained (3.1 ± 0.1) × 1012 m-1. Both values reconcile with earlier results from 77 K and below 1 T, whereas current experiments are at room temperature and 14.1 T. Finally, we present results where few-microsecond pulses of the 2?0 field induced small (tens of Hz) changes in high-resolution NMR line shapes. There too, spectra collected vs |E| agree with the model for response, further establishing the validity of our protocols to specify |E|.

  10. Introduction to the conformational investigation of peptides and proteins by using two-dimensional proton NMR experiments

    International Nuclear Information System (INIS)

    This report presents the elementary bases for an initiation to the conformational study of peptides and proteins by using two-dimensional proton NMR experiments. First, some general features of protein structures are summarized. A second chapter is devoted to the basic NMR experiments and to the spectral parameters which provide a structural information. This description is illustrated by NMR spectra of peptides. The third chapter concerns the most standard two-dimensional proton NMR experiments and their use for a conformational study of peptides and proteins. Lastly, an example of NMR structural investigation of a peptide is reported

  11. NMR-tomography of the heart

    International Nuclear Information System (INIS)

    The NMR-tomography as a non-invasive imaging process is examined regarding to the value to answer clinical issues. This method allows an evaluation of qualitative, quantitative, morphological and functional parameters. The diagnostic use on the heart shows early myocardial changes, thrombosis, changes in the dynamics of the left ventricle (EDV, ESV, EF), the quantitative wall movement and the blood flow in a shunt defect. The placed value of echocardiography, myocardial scintigraphy and coronary angiography in the diagnosis of acquired valvular heart disease, myocardial perfusion and coronary heart disease is not lowered by the above mentioned method. (orig.)

  12. Flow units from integrated WFT and NMR data

    Energy Technology Data Exchange (ETDEWEB)

    Kasap, E.; Altunbay, M.; Georgi, D.

    1997-08-01

    Reliable and continuous permeability profiles are vital as both hard and soft data required for delineating reservoir architecture. They can improve the vertical resolution of seismic data, well-to-well stratigraphic correlations, and kriging between the well locations. In conditional simulations, permeability profiles are imposed as the conditioning data. Variograms, covariance functions and other geostatistical indicators are more reliable when based on good quality permeability data. Nuclear Magnetic Resonance (NMR) logging and Wireline Formation Tests (WFT) separately generate a wealth of information, and their synthesis extends the value of this information further by providing continuous and accurate permeability profiles without increasing the cost. NMR and WFT data present a unique combination because WFTs provide discrete, in situ permeability based on fluid-flow, whilst NMR responds to the fluids in the pore space and yields effective porosity, pore-size distribution, bound and moveable fluid saturations, and permeability. The NMR permeability is derived from the T{sub 2}-distribution data. Several equations have been proposed to transform T{sub 2} data to permeability. Regardless of the transform model used, the NMR-derived permeabilities depend on interpretation parameters that may be rock specific. The objective of this study is to integrate WFT permeabilities with NMR-derived, T{sub 2} distribution-based permeabilities and thereby arrive at core quality, continuously measured permeability profiles. We outlined the procedures to integrate NMR and WFT data and applied the procedure to a field case. Finally, this study advocates the use of hydraulic unit concepts to extend the WFT-NMR derived, core quality permeabilities to uncored intervals or uncored wells.

  13. Two dimensional solid state NMR

    International Nuclear Information System (INIS)

    This thesis illustrates, by discussing some existing and newly developed 2D solid state experiments, that two-dimensional NMR of solids is a useful and important extension of NMR techniques. Chapter 1 gives an overview of spin interactions and averaging techniques important in solid state NMR. As 2D NMR is already an established technique in solutions, only the basics of two dimensional NMR are presented in chapter 2, with an emphasis on the aspects important for solid spectra. The following chapters discuss the theoretical background and applications of specific 2D solid state experiments. An application of 2D-J resolved NMR, analogous to J-resolved spectroscopy in solutions, to natural rubber is given in chapter 3. In chapter 4 the anisotropic chemical shift is mapped out against the heteronuclear dipolar interaction to obtain information about the orientation of the shielding tensor in poly-(oxymethylene). Chapter 5 concentrates on the study of super-slow molecular motions in polymers using a variant of the 2D exchange experiment developed by us. Finally chapter 6 discusses a new experiment, 2D nutation NMR, which makes it possible to study the quadrupole interaction of half-integer spins. 230 refs.; 48 figs.; 8 tabs

  14. NMR for chemists and biologists

    CERN Document Server

    Carbajo, Rodrigo J

    2013-01-01

    This book intends to be an easy and concise introduction to the field of nuclear magnetic resonance or NMR, which has revolutionized life sciences in the last twenty years. A significant part of the progress observed in scientific areas like Chemistry, Biology or Medicine can be ascribed to the development experienced by NMR in recent times. Many of the books currently available on NMR deal with the theoretical basis and some of its main applications, but they generally demand a strong background in Physics and Mathematics for a full understanding. This book is aimed to a wide scientific audie

  15. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A; McCarthy, M J

    1995-01-01

    Over recent years, no other technique has grown to such importance as that of NMR spectroscopy. It is used in all branches of science where precise structural determination is required and where the nature of interactions and reactions in solution is being studied. Annual Reports on NMR Spectroscopy has established itself as a means for the specialist and non-specialist alike to become familiar with new applications of the technique in all branches of chemistry, including biochemistry, and pharmaceutics. This volume focuses on theoretical aspects of NMR nuclear shielding and on applications of

  16. Dynamic NMR of nano- and microstructured materials

    International Nuclear Information System (INIS)

    The fast technological advancement which took place over the past few decades sustained the development of various categories of advanced polymeric, composite and porous materials, with complex physical and chemical properties determined by their structure and dynamics at nano- and micrometer levels. This brought forth the necessity of combining different methods of analysis, which cover multiple length scales, in order to allow for a comprehensive characterization and a valid prediction of a material's macroscopic behaviour. The purpose of this work was to characterize the structure and dynamics of various types of nano- and micro structured systems, such as silane crosslinked poly(ethylene), cement-in-polymer dispersion with different compositions or model and natural porous media, using a combination of nuclear magnetic resonance (NMR) methods that provide relevant information on different length scales of interest. Data processing and interpretation was facilitated by self-made computational procedures and mathematical models. The different subjects approached in this work are briefly presented in Chapter 1 (Introduction) and discussed in detail further on in an order according to the length scale of the motion probed. In Chapter 2 proton NMR wideline spectroscopy is used to obtain information on the phase composition, molecular mobility and domain sizes of crosslinked poly(ethylene) (PE), a polymer commonly used in a broad range of applications, from day-to-day life basic commodities like water and sewage pipes, to insulating coatings for medium and high voltage wires. Due to its industrial importance, this type of PE has been previously characterized using a variety of methods. The novelty brought by this study is the quantitative analysis of the spin diffusion (SD) coefficients and domain sizes of different phases by a dedicated software developed for solving the spin diffusion equations for a lamellar morphology, using as input data extracted from NMR double quantum filtered SD experiments and including a series of bonds for and minimizing uncertainties in the estimation of essential parameters. Recently developed cement-in-polymer dispersions (c/p) with different compositions and cement to polymer ratios are investigated in Chapters 3 and 4, by a vast array of NMR techniques, that probe, on different length scales, the structure of the investigated specimens, as well as the dynamics of water transport inside the materials. Chapter 3 presents the results obtained using multinuclear solid state magic angle spinning NMR to probe, at nanometer level, the structure of cement-in-polymer dispersions. The hydration effects and crystallization of the inorganic matrix are probed by 29Si NMR while the chemical reactions of the organic phase are quantified by 13C cross-polarization; the results are correlated with data offered by other analysis techniques. The study of hydrated c/p is continued in Chapter 4, where proton NMR imaging is employed to obtain information about the microstructural changes which take place upon exposure to water at different temperatures. The water transport in the c/p matrix is monitored on line and the hydration phenomenon, together with information about the physical suffered by the samples are discussed with regard to polymer type, amount and curing conditions. A simple mathematical model of diffusion in a cylindrical system, involving time dependent diffusion coefficients and variable surface concentrations, is used to predict the manner in which the water amount inside the organic/cementitious pastes evolves in time. Further on, the effects of diffusive and advective transport in model and natural porous media are systematically investigated in Chapters 5 and 6. NMR exchange relaxometry is known as a very powerful tool for probing the structure and dynamics of fully or partially hydrated porous systems, but, until know, no information existed on how the effects of slow advective transport - a phenomenon of considerable interest for different branches of science and industry - are reflected i

  17. Dynamic NMR of nano- and microstructured materials

    Energy Technology Data Exchange (ETDEWEB)

    Olaru, Maria Alexandra

    2013-07-01

    The fast technological advancement which took place over the past few decades sustained the development of various categories of advanced polymeric, composite and porous materials, with complex physical and chemical properties determined by their structure and dynamics at nano- and micrometer levels. This brought forth the necessity of combining different methods of analysis, which cover multiple length scales, in order to allow for a comprehensive characterization and a valid prediction of a material's macroscopic behaviour. The purpose of this work was to characterize the structure and dynamics of various types of nano- and micro structured systems, such as silane crosslinked poly(ethylene), cement-in-polymer dispersion with different compositions or model and natural porous media, using a combination of nuclear magnetic resonance (NMR) methods that provide relevant information on different length scales of interest. Data processing and interpretation was facilitated by self-made computational procedures and mathematical models. The different subjects approached in this work are briefly presented in Chapter 1 (Introduction) and discussed in detail further on in an order according to the length scale of the motion probed. In Chapter 2 proton NMR wideline spectroscopy is used to obtain information on the phase composition, molecular mobility and domain sizes of crosslinked poly(ethylene) (PE), a polymer commonly used in a broad range of applications, from day-to-day life basic commodities like water and sewage pipes, to insulating coatings for medium and high voltage wires. Due to its industrial importance, this type of PE has been previously characterized using a variety of methods. The novelty brought by this study is the quantitative analysis of the spin diffusion (SD) coefficients and domain sizes of different phases by a dedicated software developed for solving the spin diffusion equations for a lamellar morphology, using as input data extracted from NMR double quantum filtered SD experiments and including a series of bonds for and minimizing uncertainties in the estimation of essential parameters. Recently developed cement-in-polymer dispersions (c/p) with different compositions and cement to polymer ratios are investigated in Chapters 3 and 4, by a vast array of NMR techniques, that probe, on different length scales, the structure of the investigated specimens, as well as the dynamics of water transport inside the materials. Chapter 3 presents the results obtained using multinuclear solid state magic angle spinning NMR to probe, at nanometer level, the structure of cement-in-polymer dispersions. The hydration effects and crystallization of the inorganic matrix are probed by {sup 29}Si NMR while the chemical reactions of the organic phase are quantified by {sup 13}C cross-polarization; the results are correlated with data offered by other analysis techniques. The study of hydrated c/p is continued in Chapter 4, where proton NMR imaging is employed to obtain information about the microstructural changes which take place upon exposure to water at different temperatures. The water transport in the c/p matrix is monitored on line and the hydration phenomenon, together with information about the physical suffered by the samples are discussed with regard to polymer type, amount and curing conditions. A simple mathematical model of diffusion in a cylindrical system, involving time dependent diffusion coefficients and variable surface concentrations, is used to predict the manner in which the water amount inside the organic/cementitious pastes evolves in time. Further on, the effects of diffusive and advective transport in model and natural porous media are systematically investigated in Chapters 5 and 6. NMR exchange relaxometry is known as a very powerful tool for probing the structure and dynamics of fully or partially hydrated porous systems, but, until know, no information existed on how the effects of slow advective transport - a phenomenon of considerable interest for different branches of science and industry

  18. Compact orthogonal NMR field sensor

    Science.gov (United States)

    Gerald, II, Rex E. (Brookfield, IL); Rathke, Jerome W. (Homer Glen, IL)

    2009-02-03

    A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

  19. Truncated forms of zero-field splitting (ZFS) Hamiltonians and implications for interpretation of ZFS parameters for Fe 2+( S=2) ions in KFeF

    Science.gov (United States)

    Rudowicz, C.; Piwowarska, D.

    2011-06-01

    We investigate truncated forms of zero-field splitting (ZFS) Hamiltonians utilized for Fe 2+ ions with spin S=2 at tetragonal sites in K 2FeF 4 and A 2MX 4 compounds. The ZFS terms determine the easy-plane anisotropy in K 2FeF 4. This type of truncation consists in omission of some operator parts in the fourth-rank ZFS terms. Relationships between improper (truncated) ZFS parameters and the proper (full) ones are derived. An important implication of this truncation is an additional contribution to the second-rank axial ZFS parameter D, which significantly affects D values for S=2 systems. This hinders comparisons of seemingly compatible ' D' values from various sources. The origin of the second-rank rhombic ZFS E-term is also considered and found controversial. Using proper conversions, we analyze discrepancies existing in literature. A survey of available ZFS parameter values provides feedback for microscopic modeling of spin Hamiltonian parameters for Fe 2+(S=2) ions in A 2MX 4 systems.

  20. Interpretations of NMR images

    International Nuclear Information System (INIS)

    Two color display schemes are generally considered in medical images: pseudo-color and color composite. Psuedo-color technique maps the intensity means of a single monochrome image into a three dimensional color space, the gray level is thus replaced by the assigned color. Such a psuedo-color assignment is somewhat arbitrary but may be advantageous if the monochrome image is composed of simple intensity patterns. A good example of psuedo-color application is in nuclear medicine: The change of gray levels can be simply determined and the isocounts from two regions with different surroundings can be readily recognized. However, the use of psuedo-color in CT or MR imaging is controversial because it does not give additional information and may exaggerate insignificant gray scale differences. The color composite technique maps three parametric image data into a three dimensional color space, and thus three monochrome images are merged to form a single color image. The color composite technique increases the number of ways information can be displayed and provides both quantitative and qualitative data about the object or event represented. This paper describes the application of color composite in NMR images

  1. NMR imaging of cerebral infarction

    International Nuclear Information System (INIS)

    One hundred and five patients with cerebral infarction were studied by nuclear magnetic resonance (NMR) CT (resistive type of magnet with strength of 0.1 tesla) and X-ray CT. Pulse sequences used saturation recovery (Tr = 600 mSec), Inversion recovery (Tr = 500 mSec, Td = 300 mSec) and spin echo (Tr = 1500 mSec, Te = 40, 80, 120, 160 mSec). Fifteen cases were examined by NMR-CT within 24 hours from onset. Proton NMR imaging could not detect cerebral ischemia as early as 2 hours after onset, but except could detect the lesions in Se image the area of cerebral infarct 3 hours after onset. After 5 hours from onset image changes in SE were evident and corresponded to the area of cerebral infarct, but image changes in IR could not fully delineate the infarcted area. NMR images of 41 year-old woman with cerebral embolism by MCA trunck occlusion associated with mitral stenosis were presented, and NMR-CT was examined 10 hours, 9th and 43th days after episode of MCA occlusion. Sixty patents (64 times) with lacunar infarction were studied by NMR-CT and X-ray CT. The inversion recovery images were used mainly for detection of lesions and comparison with X-ray CT. In 160 lesions which were detected by NMR-CT or X-ray CT, could 156 lesions be detected by NMR-CT and 78 lesions by X-ray CT. Inversion recovery images were more useful for detection of lacunes than X-ray CT. Calculated T1 and T2 values prolonged with time course from onset. (author)

  2. Optical pumping and xenon NMR

    Energy Technology Data Exchange (ETDEWEB)

    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 {sup 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 {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  3. Optical pumping and xenon NMR

    Energy Technology Data Exchange (ETDEWEB)

    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 [sup 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 [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  4. NMR characterization of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gerald, II, Rex E. (Brookfield, IL); Klingler, Robert J. (Glenview, IL); Rathke, Jerome W. (Homer Glen, IL); Diaz, Rocio (Chicago, IL); Vukovic, Lela (Westchester, IL)

    2008-11-25

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  5. NMR characterization of thin films

    Science.gov (United States)

    Gerald II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2010-06-15

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  6. Optical pumping and xenon NMR

    International Nuclear Information System (INIS)

    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 129Xe 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 131Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen

  7. Carbon-13 NMR studies of liquid crystals

    International Nuclear Information System (INIS)

    High resolution, proton decoupled 13C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = less than P2(costheta) greater than are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so, with temperature in the smectic-A phase. In the nematic series studied, the ordering exhibits an even-odd alternation along the series and qualitative agreement with a recent theory due to Marcelja is found. In both phases, the spectra show that the molecule rotates rapidly about its long axis. Tentative conclusions about molecular conformational motion and 14N spin relaxation are presented for both nematic and smectic-A phases. In the smectic-A phase, the sample is rotated about an axis perpendicular to H0 and the resulting spectra are dicusssed. The theory of observed chemical shifts in liquid crystals is discussed and equations are derived which relate the nmr spectra of liquid-crystals to the order parameters. A model for the smectic-C phase due to Luz and Meiboom and Doane is described and lineshapes are determined on the basis of this model for special cases. The dependence of the order parameters on the molecular potential which give rise to the various degrees of order in the different liquid crystalline phases is examined. To a good approximation the functional dependence of the order parameters on the molecular potential is shown to be a simple one in the limit of small tilt angle in the smectic-C phase

  8. Recent progress in NMR microscopy towards cellular imaging

    International Nuclear Information System (INIS)

    Recent advances in NMR microscopy based on fundamental physical parameters and experimental factors are discussed. We consider fundamental resolution limits due to molecular diffusion and the experimental system bandwidth, as well as practical resolution limits arising from poor signal-to-noise ratio due to small imaging voxel size and finite line broadening due to signal attenuation brought about by diffusion. Several microscopic imaging pulse sequences are presented and applied to elucidating cellular imaging problems such as the cell lineage patterns in Xenopus laevis embryos. Experimental results obtained with 7.0 T NMR microscopy system are presented. (author)

  9. NMR and spin relaxation in systems with magnetic nanoparticles

    Science.gov (United States)

    Noginova, N.; Weaver, T.; King, M.; Bourlinos, A. B.; Giannelis, E. P.; Atsarkin, V. A.

    2007-02-01

    The 1H NMR spectra and spin dynamics of the host systems have been studied in liquid and solid suspensions of ?-Fe2O3 nanoparticles. Significant broadening of 1H NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T1/T2 depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of T1 upon the nanoparticle concentration. We explain the experimental results taking into account the predomination of self-diffusion as a source of the relaxation in liquid suspensions, and estimate effective parameters of relaxation in the systems under study.

  10. NMR and spin relaxation in systems with magnetic nanoparticles

    International Nuclear Information System (INIS)

    The 1H NMR spectra and spin dynamics of the host systems have been studied in liquid and solid suspensions of ?-Fe2O3 nanoparticles. Significant broadening of 1H NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T1/T2 depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of T1 upon the nanoparticle concentration. We explain the experimental results taking into account the predomination of self-diffusion as a source of the relaxation in liquid suspensions, and estimate effective parameters of relaxation in the systems under study

  11. NMR of superfluid 3He in anisotropic aerogel

    CERN Document Server

    Kunimatsu, T; Izumina, K; Matsubara, A; Sasaki, Y; Kubota, M; Ishikawa, O; Mizusaki, T; Bunkov, Yu M; Bunkov, Yu.M.

    2006-01-01

    We report on orientation of the order parameter in the 3He-A and 3He-B phases caused by aerogel anisotropy. In 3He-A we have observed relatively homogeneous NMR line with an anomalously large negative frequency shift. We can attribute this effect to an orientation of orbital momentum along the axis of density anisotropy. The similar orientation effect we have seen in 3He-B. We can measure the A-phase Leggett frequency, which shows the same energy gap suppression as in the B-phase. We observe a correlation of A - B transition temperature and NMR frequency shift.

  12. Solution of the inverse problem of NMR relaxation

    International Nuclear Information System (INIS)

    The solution of the NMR relaxation inverse problem for the two-component system with magnetization exchange between two components is given. The method for identification of the two-component system parameters by decrease in the cross-sectional magnetization and additional determination of one out of the system three components: population and relaxation time is proposed. The component population may be evaluated thereby through the method differing from the NMR, which provides for an additional advantage. Analytical expressions are obtained for these three cases and their properties are studied in detail. It is shown, that minimal calculational errors occur by measuring the long-time relaxation

  13. A comprehensive NMR study of cubic and hexagonal boron nitride.

    Science.gov (United States)

    Jeschke, G; Hoffbauer, W; Jansen, M

    1998-08-01

    A variety of techniques and measurements on all NMR accessible nuclei allow one to obtain a complete and precise set of chemical shift and quadrupole coupling parameters for both boron and nitrogen in cubic and hexagonal boron nitride. For hexagonal boron nitride, 11B to 15N cross polarization under magic angle sample spinning conditions is demonstrated at natural isotope abundance. The presented approach for NMR characterization of the crystalline boron nitrides should also be applicable to structurally related composite materials, nanotubes, and amorphous ceramics. PMID:9808290

  14. Static and dynamic NMR properties of gas-phase xenon

    OpenAIRE

    Hanni, M. (Matti)

    2011-01-01

    Abstract This thesis presents computational studies of both the static and dynamic parameters of the nuclear magnetic resonance (NMR) spectroscopy of gaseous xenon. First, state-of-the-art static magnetic resonance parameters are computed in small xenon clusters by using methods of quantum chemistry, and second, time-dependent relaxation phenomena are investigated via molecular dynamics simulations at different experimental conditions. Based on the underlying quantum and ...

  15. Spin Hamiltonian of the Highly Frustrated Gd3Ga5O12 Garnet Antiferromagnet

    CERN Document Server

    Yavorskii, T; Gingras, M J P; Yavors'kii, Taras; Enjalran, Matthew; Gingras, Michel J.P.

    2005-01-01

    Gadolinium Gallium Garnet (GGG) is a fascinating magnetic material that displays an ordered phase in an applied magnetic field, but lacks long-range order and shows spin glass behavior in zero field. We investigate GGG in the zero field regime using a variational mean-field theory approach. We reproduce the spin liquid like correlations and the positions of sharp peaks seen in powder neutron diffraction measurements on GGG. Contrary to the current belief, our results speak in favor of a scenario where GGG is on the verge of developing true conventional long-range magnetic order in zero magnetic field.

  16. A spin Hamiltonian for non-relativistic electrons and their interaction with an external field

    Energy Technology Data Exchange (ETDEWEB)

    Santos, E S; Rivelino, R [Instituto de Fisica, Universidade Federal da Bahia, 40210-340, Salvador, Bahia (Brazil); De Montigny, M [Theoretical Physics Institute, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada); De Melo, G R, E-mail: esdras.santos@ufba.b, E-mail: rivelino@ufba.b, E-mail: montigny@phys.ualberta.c, E-mail: gmelo@ift.unesp.b [Instituto de Fisica Teorica, Universidade Estadual Paulista, 01140-070, Sao Paulo, SP (Brazil)

    2010-08-20

    We investigate the spin of the electron in a non-relativistic context by using the Galilean covariant Pauli-Dirac equation. From a non-relativistic Lagrangian density, we find an appropriate Dirac-like Hamiltonian in the momentum representation, which includes the spin operator in the Galilean covariant framework. Within this formalism, we show that the total angular momentum appears as a constant of motion. Additionally, we propose a non-minimal coupling that describes the Galilean interaction between an electron and the electromagnetic field. Thereby, we obtain, in a natural way, the Hamiltonian including all the essential interaction terms for the electron in a general vector field.

  17. NMR line shape in anisotropic superconductors in a tilted magnetic field

    Science.gov (United States)

    Efremova, S. A.; Proshin, Yu. N.; Tsarevskii, S. L.

    1998-06-01

    NMR line shape has been constructed for anisotropic type-II superconductors in tilted magnetic fields, with inclusion of vortex-lattice magnetic-field nonuniformities and of the skin effect near the superconductor surface. The NMR line shape parameters are shown to change considerably when the external magnetic field changes direction. This makes it possible to obtain more detailed information about the characteristics of a superconductor, in particular, its anisotropy parameter.

  18. Medical applications of NMR imaging and NMR spectroscopy with stable isotopes. Summary

    International Nuclear Information System (INIS)

    The current status of NMR imaging and NMR spectroscopy are summarized. For the most part examples from the March 1983 Puerto Rico symposium are used to illustrate the utility of NMR in medicine. 18 refs., 5 figs

  19. jsNMR: an embedded platform-independent NMR spectrum viewer.

    Science.gov (United States)

    Vosegaard, Thomas

    2015-04-01

    jsNMR is a lightweight NMR spectrum viewer written in JavaScript/HyperText Markup Language (HTML), which provides a cross-platform spectrum visualizer that runs on all computer architectures including mobile devices. Experimental (and simulated) datasets are easily opened in jsNMR by (i) drag and drop on a jsNMR browser window, (ii) by preparing a jsNMR file from the jsNMR web site, or (iii) by mailing the raw data to the jsNMR web portal. jsNMR embeds the original data in the HTML file, so a jsNMR file is a self-transforming dataset that may be exported to various formats, e.g. comma-separated values. The main applications of jsNMR are to provide easy access to NMR data without the need for dedicated software installed and to provide the possibility to visualize NMR spectra on web sites. PMID:25641013

  20. The inherent accuracy of 1H NMR spectroscopy to quantify plasma lipoproteins is subclass dependent.

    Science.gov (United States)

    Ala-Korpela, Mika; Lankinen, Niko; Salminen, Aino; Suna, Teemu; Soininen, Pasi; Laatikainen, Reino; Ingman, Petri; Jauhiainen, Matti; Taskinen, Marja-Riitta; Héberger, Károly; Kaski, Kimmo

    2007-02-01

    Proton NMR spectroscopy as a means to quantify lipoprotein subclasses has received wide clinical interest. The experimental part is a fast routine procedure that contrasts favourably to other lipoprotein measurement protocols. The difficulties in using (1)H NMR, however, are in uncovering the subclass specific information from the overlapping data. The NMR-based quantification has been evaluated only in relation to biochemical measures, thereby leaving the inherent capability of NMR rather vague due to biological variation and diversity among the biochemical experiments. Here we will assess the use of (1)H NMR spectroscopy of plasma per se. This necessitates data for which the inherent parameters, namely the shapes and areas of the (1)H NMR signals of the subclasses are available. This was achieved through isolation and (1)H NMR experiments of 11 subclasses--VLDL1, VLDL2, IDL, LDL1, LDL2, LDL3, HDL(2b), HDL(2a), HDL(3a), HDL(3b) and HDL(3c)--and the subsequent modelling of the spectra. The subclass models were used to simulate biochemically representative sets of spectra with known subclass concentrations. The spectral analyses revealed 10-fold differences in the quantification accuracy of different subclasses by (1)H NMR. This finding has critical significance since the usage of (1)H NMR methodology in the clinical arena is rapidly increasing. PMID:16730730

  1. Spectrometer with direct NMR detection in a rotating coordinate system

    International Nuclear Information System (INIS)

    A spectrometer with direct NMR detection in efficient magnetic field in a rotating coordinate system (rcs) during nuclear spin system irradiation by strong high-frequency field is described. The detection is carried out at comparatively low frequency in the 10-100 kHz range using the inductance coil oriented parallel to constant magnetic field. The concrete spectrometer parameters are presented as applied to 1H and 19F NMR of solids under ''magic'' angle conditions. The spectrometer permits to obtain the NMR frequency spetrum in rcs, lateral and longitudinal relaxation curves in rcs and double-rotating coordinate system, echo signals in rcs, The detection is continuous and is carried out in one pass. With respect to the spectra resolution in solids the spectrometer is by two-three order in excess of traditional wide-line spectrometers with continuous irradiation

  2. AUREMOL: Automatic protein structure determination from NMR data

    Energy Technology Data Exchange (ETDEWEB)

    Donaubauer, Harald; Harsch, Tobias; Malloni, Willhelm; Sanctis, Silvia de; Kieninger, Baerbel; Danilova, Nina; Brunner, Konrad; Gronwald, Wolfram; Trenner, Jochen; Kalbitzer, Hans Robert [University of Regensburg (Germany); Neidig, Klaus-Peter [Bruker BioSpin (Germany)

    2010-07-01

    Several approaches to the problem of automated protein structure determination from NMR data exist. The concept for automation is a molecule centred approach where all of the available a priori information is used to eliminate as many free parameters as possible and reduce the amount of information and experimental data. Using a starting structure and as much additional information as possible, like predicted chemical shifts and backbone torsion angles, the assignment and the structure itself are refined in an iterative process. Therefore we are developing AUREMOL, which goal is the reliable and automatic structure determination of biological macro molecules such as proteins from NMR data. In AUREMOL included modules are RELAX, which uses complete relaxation formalism to calculate a simulated NOESY NMR spectrum, SIBASA (simulated based sequential assignment), which bases on simulated annealing to determine the chemical shifts of these signals, KNOWNOE, REFINE, which calculates intermolecular distances from a NOESY spectrum and the structure evaluation RFAC.

  3. Ligand screening by saturation-transfer difference (STD) NMR spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, V V

    2005-04-26

    NMR based methods to screen for high-affinity ligands have become an indispensable tool for designing rationalized drugs, as these offer a combination of good experimental design of the screening process and data interpretation methods, which together provide unprecedented information on the complex nature of protein-ligand interactions. These methods rely on measuring direct changes in the spectral parameters, that are often simpler than the complex experimental procedures used to study structure and dynamics of proteins. The goal of this review article is to provide the basic details of NMR based ligand-screening methods, with particular focus on the saturation transfer difference (STD) experiment. In addition, we provide an overview of other NMR experimental methods and a practical guide on how to go about designing and implementing them.

  4. AUREMOL: Automatic protein structure determination from NMR data

    International Nuclear Information System (INIS)

    Several approaches to the problem of automated protein structure determination from NMR data exist. The concept for automation is a molecule centred approach where all of the available a priori information is used to eliminate as many free parameters as possible and reduce the amount of information and experimental data. Using a starting structure and as much additional information as possible, like predicted chemical shifts and backbone torsion angles, the assignment and the structure itself are refined in an iterative process. Therefore we are developing AUREMOL, which goal is the reliable and automatic structure determination of biological macro molecules such as proteins from NMR data. In AUREMOL included modules are RELAX, which uses complete relaxation formalism to calculate a simulated NOESY NMR spectrum, SIBASA (simulated based sequential assignment), which bases on simulated annealing to determine the chemical shifts of these signals, KNOWNOE, REFINE, which calculates intermolecular distances from a NOESY spectrum and the structure evaluation RFAC.

  5. Variable-temperature NMR and conformational analysis of Oenothein B

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Suzana C.; Carvalho, Ariadne G.; Fortes, Gilmara A.C.; Ferri, Pedro H.; Oliveira, Anselmo E. de, E-mail: suzana.quimica.ufg@hotmail.com [Universidade Federal de Goias (UFGO), Goiania, GO (Brazil). Instituto de Quimica

    2014-02-15

    Oenothein B is a dimeric hydrolyzable tannin with a wide range of biological activities, such as antitumour, anti-inflammatory and antiviral. Its nuclear magnetic resonance (NMR) at room temperature show duplications and broadening of signals. Experiments of 1D and 2D NMR at lower temperatures were useful for the complete NMR assignments of all hydrogens and carbons. The 3D structure of the most stable conformer was determined for the first time by nuclear Overhauser effect spectroscopy (NOESY) experiment (-20 deg C) and density functional theory (DFT)(B3LYP/6-31G)/ polarizable continuum model (PCM) quantum chemical calculations. The favoured conformation showed a highly compacted geometry and a lack of symmetry, in which the two valoneoyl groups showed distinct conformational parameters and stabilities. (author)

  6. Ensemble Calculation for Intrinsically Disordered Proteins Using NMR Parameters.

    Science.gov (United States)

    Kragelj, Jaka; Blackledge, Martin; Jensen, Malene Ringkjøbing

    2015-01-01

    Intrinsically disordered proteins (IDPs) perform their function despite their lack of well-defined tertiary structure. Residual structure has been observed in IDPs, commonly described as transient/dynamic or expressed in terms of fractional populations. In order to understand how the protein primary sequence dictates the dynamic and structural properties of IDPs and in general to understand how IDPs function, atomic-level descriptions are needed. Nuclear magnetic resonance spectroscopy provides information about local and long-range structure in IDPs at amino acid specific resolution and can be used in combination with ensemble descriptions to represent the dynamic nature of IDPs. In this chapter we describe sample-and-select approaches for ensemble modelling of local structural propensities in IDPs with specific emphasis on validation of these ensembles. PMID:26387101

  7. NMR-aided differentiation of enantiomers: Signal enantioresolution.

    Science.gov (United States)

    Pérez-Trujillo, Míriam; Parella, Teodor; Kuhn, Lars T

    2015-05-30

    NMR-aided enantiodiscrimination using chiral auxiliaries (CAs) is a recognized method for differentiating enantiomers and for measuring enantiomeric ratios (er). Up to the present, the study, optimization, and comparison of such methods have been performed based on the enantiodifferentiation of NMR signals via analyzing non-equivalent chemical-shift values (???) of the diastereoisomeric species formed. However, a poor and non-reliable comparison of results is often obtained via the analysis of ??? exclusively. In here, the concept of enantioresolution of an individual NMR signal and its importance for NMR-aided enantiodifferentiation studies is introduced and discussed. In addition, the enantioresolution quotient, E, is proposed as the parameter to describe its quantification. Complementary to measuring ???, the experimental determination of E allows a more reliable interpretation of the results and opens up new possibilities for the study of enantiodifferentiation data derived from novel NMR experiments, setup improvements or new CAs. Finally, the different relationships between signal enantiodifferentiation, signal enantioresolution, and other main experimental issues of enantiodifferentiation experiments are addressed. PMID:25998459

  8. NMR signal analysis to attribute the components to the solid/liquid phases present in mixes and ice creams

    OpenAIRE

    Mariette, F.; Lucas, T.

    2005-01-01

    The NMR relaxation signals from complex products like ice cream are hard to interpret because of the multi-exponential behaviour of the relaxation signal and the difficulty of attributing the NMR relaxation components to specific molecule fractions. An attribution of the NMR relaxation parameters is proposed, however, based on an approach that combines quantitative analysis of the spin-spin and spin-lattice relaxation times and the signal intensities with characterization of the ice cream com...

  9. NMR studies of actinide dioxides

    International Nuclear Information System (INIS)

    17O NMR measurements have been performed on a series of the actinide dioxides, UO2, NpO2 and PuO2. Although the 17O NMR spectra in these materials are similar at higher temperatures, the low-temperature spectra present are significantly different. In UO2 we have observed a wide spectrum, forming a rectangular shape below TN=30 K. In NpO2, on the other hand, the spectra broaden rather gradually and exhibit a two-peak structure below T0=26 K. In PuO2, neither spectrum broadening nor splitting has been observed. We show that these NMR spectra clearly indicate the different nature of the low-temperature magnetic ground states in these actinide compounds

  10. Quantitative chemical analysis by NMR

    International Nuclear Information System (INIS)

    This paper reports that nuclear magnetic resonance (NMR) spectroscopy offers several important advantages as a technique for quantitative chemical analysis, including the ease with which multicomponent mixtures can be analyzed, the nondestructive nature of NMR, and the direct proportionality of the integrated resonance intensity (I) and concentration (C) of nuclei giving the resonance: I = kC. With proper attention to experimental conditions, the proportionality constant is the same for all resonances in a spectrum. Thus NMR differs substantially from chromatographic methods and from together spectroscopic methods, which require a predetermined response factor for each compound being determined. Relative concentrations can be obtained directly from relative resonance intensities while absolute concentrations can be obtained by adding a known concentration of another compound as an internal intensity standard

  11. Solid state NMR of polymers

    International Nuclear Information System (INIS)

    The solid state NMR is used not so much in distinguishing chemical species and analyzing components and chemical structure as in collecting the various kind of informations of solid state of polymer, such as conformation, phase structure, a kind of molecular motion, velocity and compatibility by the measurement of relaxation time and linear analysis. The report introduces the interest papers from 1993 to 1995 applied the solid state NMR to synthetic polymers. On the measurement methods, CP/MAS, pulse NMR, heteronuclear correlation (HETCOR) method, wide-line separation (WISE), 2D exchange method and new rotational echo double resonance (REDOR) method are explained. The examples of application such as chemical component, chemical structure, conformation, crosslinked molecule, polymer gel, solid state structure, molecular motion, copolymer, phase structure of polymer blend and orientation are explained, too. (S.Y.)

  12. NMR investigation of coal extracts

    International Nuclear Information System (INIS)

    Proton NMR spectroscopy was used for the evaluation of 10% coal extract solutions in deuterated pyridine. Four types of Czechoslovak coal were analyzed. Agreement was found between the aromaticity of coal extracts calculated from 1H NMR data using Brown's method and Ladner's and Williams' method and the characterization of an average molecule of the coal extract by the number of non-bridge carbon atoms of aromatic rings, by the overall number of aromatic ring carbon atoms and the number of aromatic rings, determined by the Williams and Ferris methods. The methods for calculating carbon distribution from 1H NMR data, however, contain some constants theoretically estimated or experimentally found using the method which still remain to be verified. (M.K.)

  13. Bootstrap calibration and uncertainty estimation of downhole NMR hydraulic conductivity estimates in an unconsolidated aquifer.

    Science.gov (United States)

    Parsekian, A D; Dlubac, K; Grunewald, E; Butler, J J; Knight, R; Walsh, D O

    2015-01-01

    Characterization of hydraulic conductivity (K) in aquifers is critical for evaluation, management, and remediation of groundwater resources. While estimates of K have been traditionally obtained using hydraulic tests over discrete intervals in wells, geophysical measurements are emerging as an alternative way to estimate this parameter. Nuclear magnetic resonance (NMR) logging, a technology once largely applied to characterization of deep consolidated rock petroleum reservoirs, is beginning to see use in near-surface unconsolidated aquifers. Using a well-known rock physics relationship-the Schlumberger Doll Research (SDR) equation--K and porosity can be estimated from NMR water content and relaxation time. Calibration of SDR parameters is necessary for this transformation because NMR relaxation properties are, in part, a function of magnetic mineralization and pore space geometry, which are locally variable quantities. Here, we present a statistically based method for calibrating SDR parameters that establishes a range for the estimated parameters and simultaneously estimates the uncertainty of the resulting K values. We used co-located logging NMR and direct K measurements in an unconsolidated fluvial aquifer in Lawrence, Kansas, USA to demonstrate that K can be estimated using logging NMR to a similar level of uncertainty as with traditional direct hydraulic measurements in unconsolidated sediments under field conditions. Results of this study provide a benchmark for future calibrations of NMR to obtain K in unconsolidated sediments and suggest a method for evaluating uncertainty in both K and SDR parameter values. PMID:24520904

  14. Two-dimensional NMR spectrometry

    International Nuclear Information System (INIS)

    This article is the second in a two-part series. In part one (ANALYTICAL CHEMISTRY, May 15) the authors discussed one-dimensional nuclear magnetic resonance (NMR) spectra and some relatively advanced nuclear spin gymnastics experiments that provide a capability for selective sensitivity enhancements. In this article and overview and some applications of two-dimensional NMR experiments are presented. These powerful experiments are important complements to the one-dimensional experiments. As in the more sophisticated one-dimensional experiments, the two-dimensional experiments involve three distinct time periods: a preparation period, t0; an evolution period, t1; and a detection period, t2

  15. High resolution NMR in metals

    International Nuclear Information System (INIS)

    With the advent of multiple pulse NMR a number of high resolution NMR experiments in solids have been performed. We report here on performing such experiments in metals where information of different kind can be obtained: 1) Anisotropy of the Knight shift in non-cubic solids; 2) Distribution of Knight shifts due to crystal defects; 3) Bulk Knight shift anisotropy dependent on the shape and susceptibility of the sample. Examples of the different contributions are exemplified in the case of Be9 and Al27 powder samples. (author)

  16. NMR relaxation times of trabecular bone-reproducibility, relationships to tissue structure and effects of sample freezing

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) spectroscopy provides a potential tool for non-invasive evaluation of the trabecular bone structure. The objective of this study was to determine the reproducibility of the NMR relaxation parameters (T2, Carr-Purcel-T2, T1?) for fat and water and relate those to the structural parameters obtained by micro-computed tomography (?CT). Especially, we aimed to evaluate the effect of freezing on the relaxation parameters. For storing bone samples, freezing is the standard procedure during which the biochemical and cellular organization of the bone marrow may be affected. Bovine trabecular bone samples were stored at -20 0C for 7 days and measured by NMR spectroscopy before and after freezing. The reproducibility of NMR relaxation parameters, as expressed by the coefficient of variation, ranged from 3.1% to 27.9%. In fresh samples, some correlations between NMR and structural parameters (Tb.N, Tb.Sp) were significant (e.g. the relaxation rate for T2 of fat versus Tb.Sp: r = -0.716, p < 0.01). Freezing did not significantly change the NMR relaxation times but the correlations between relaxation parameters and the ?CT structural parameters were not statistically significant after freezing, suggesting some nonsystematic alterations of the marrow structure. Therefore, the use of frozen bone samples for NMR relaxation studies may provide inferior information about the trabecular bone structure.

  17. Pulsed zero field NMR of solids and liquid crystals

    International Nuclear Information System (INIS)

    This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs

  18. Pulsed zero field NMR of solids and liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Thayer, A.M.

    1987-02-01

    This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs.

  19. NMR velocity mapping and RHEO-NMR in complex liquids

    International Nuclear Information System (INIS)

    By using the NMR technique, we have determined the velocity distribution and the rate of strain in a micelle solution (cetylpyridinium chloride and sodium salicylate) below and above a critical shear rate and have studied the isotropic and stress-induced ordered nematic phases in a micelle solution CTAB/D2O in a cylindric Couette cell.

  20. Push-through Direction Injectin NMR Automation

    Science.gov (United States)

    Nuclear magnetic resonance (NMR) and mass spectrometry (MS) are the two major spectroscopic techniques successfully used in metabolomics studies. The non-invasive, quantitative and reproducible characteristics make NMR spectroscopy an excellent technique for detection of endogeno...

  1. Solution NMR of large molecules and assemblies†

    OpenAIRE

    Mark P. Foster; McElroy, Craig A.; Amero, Carlos D

    2007-01-01

    Solution NMR spectroscopy represents a powerful tool for examining the structure and function of biological macromolecules. The advent of multidimensional (2D–4D) NMR, together with the widespread use of uniform isotopic labeling of proteins and RNA with the NMR-active isotopes, 15N and 13C, opened the door to detailed analyses of macromolecular structure, dynamics and interactions of smaller macromolecules (< ~25 kDa). Over the past 10 years, advances in NMR and isotope labeling methods have...

  2. ?-NMR of a thin Pt film

    International Nuclear Information System (INIS)

    We report beta-detected NMR (?-NMR) measurements on a 50 nm thick platinum (Pt) film grown on a magnesium oxide (MgO) substrate. The frequency of the ?-NMR resonance in Pt was compared to the MgO reference frequency to estimate the Knight shift at various temperatures (100-300 K). The Knight shift was found to be negative and strongly temperature dependent. The implications are discussed and compared to other transition metals that have been studied via ?-NMR previously.

  3. Concretes damaging: the NMR lights

    International Nuclear Information System (INIS)

    The damaging of cement-based materials (concrete, mortars, etc..) is a major concern for applications like road salting or wastes confinement. The NMR study of the calcium hydrate silicates (CHS) of concretes allows to determine the causes of their damaging: de-cohesion of CHS chains, hydration of alkaline ions. Short note. (J.S.)

  4. The physics of NMR tomography

    International Nuclear Information System (INIS)

    The nuclear magnetic resonance properties of the nuclei of atoms is a convenient means for elucidating the morphology and pathophysiology of the human body. The fundamental principles of Larmor precession are discussed from the classical as well as from the quantum mechanical point of view. In this paper, principles of NMR medical imaging and its clinical applications are discussed. (orig.)

  5. EPR OF Mn2+ IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.; Laursen, Ib; Johnsen, O.

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters ha...

  6. Epr of Mn2+ Impurities in Calcite: A Detailed Study Pertinent to Marble Provenance Determination

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.; Laursen, I.; Johnsen, O.

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters ha...

  7. An AMBER/DYANA/MOLMOL Phosphorylated Amino Acid Library Set and Incorporation into NMR Structure Calculations

    International Nuclear Information System (INIS)

    Protein structure determination using Nuclear Magnetic Resonance (NMR) requires the use of molecular dynamics programs that incorporate both NMR experimental and implicit atomic data. Atomic parameters for each amino acid type are encoded in libraries used by structure calculation programs such as DYANA and AMBER. However, only a few non-standard amino acid library sets are included in these programs or the molecular visualization program MOLMOL. Our laboratory is calculating the phosphorylated and non-phosphorylated states of peptides and proteins using NMR methods. To calculate chemically correct structures, we have extended the available molecular libraries for these programs to include the modified amino acids phosphoserine, phosphothreonine, and phosphotyrosine

  8. Polymers under mechanical stress- an NMR investigation

    International Nuclear Information System (INIS)

    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.

  9. 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.

  10. Bone marrow NMR imaging and scintigraphy in AIDS patients

    International Nuclear Information System (INIS)

    The examinations were carried out in order to ascertain whether bone marrow abnormalities can be detected in AIDS patients by means of magnetic resonance imaging or scintiscanning. In 16 of the 19 patients the NMR image and/or the scintiscan distinctly revealed bone marrow abnormalities, but there was no exact correlation to be found to immunological parameters, the peripheral blood picture, or the clinical stage of the HIV infection. (orig.)

  11. NMR in ferro- and antiferromagnets in conditions of magnon ''bottleneck''. Derivation of equations of motion

    International Nuclear Information System (INIS)

    The equations are derived describing the NMR under magnon ''battleneck'' conditions for an arbitrary relationship between the NMR line width and the width magnon line. The expression is obtained for the ''bottleneck'' parameter. The calculation is made for uniaxial ferromagnetics (both one-domain and multidomain) and antiferromagnetics of the ''light plane'' type. The equations obtained are compared with the corresponding equations of the phonon ''bottleneck'' theory

  12. NMR assessment of ice creams: Effect of formulation on liquid and solid fat

    OpenAIRE

    Lucas, T.; Le Ray, D; Barey, P.; Mariette, F.

    2005-01-01

    The capacity of low field NMR spectrometry to characterize the different behaviours of fat protons in unfrozen ice cream mix and in ice cream was investigated. Various formulations comprising different types of fat, protein and emulsifier were tested. The NMR parameters attributed to fat were sensitive both to the type of fat and also to the components located at the fat globule interface. In the unfrozen ice cream mix and to a lesser extent in ice cream, liquid fat was more sensitiv...

  13. Multinuclear NMR studies of gaseous and liquid sevoflurane

    Science.gov (United States)

    Maci?ga, E.; Makulski, W.; Jackowski, K.; Blicharska, B.

    2006-03-01

    For the first time, a small amount of sevoflurane ((CF 3) 2CHOCH 2F) in carbon dioxide and xenon as the gaseous solvents has been studied using 19F and 1H NMR spectra. Density-dependent 19F and 1H nuclear magnetic shielding was observed when the pressure of each solvent was increased. After extrapolation of the results to the zero-density limit it was possible to determine the appropriate shielding constants free from intermolecular interactions, ?0(F) and ?0(H). Similar procedure has also been applied for the investigation of fluorine-proton spin-spin couplings and the 2J 0(FH) and 3J 0(FH) constants of an isolated (CF 3) 2CHOCH 2F molecule were also obtained. Additionally, high-resolution 1H, 13C, 17O and 19F NMR spectra of pure liquid sevoflurane were also recorded and all the 1H- 13C, 1H- 19F and 19F- 13C spin-spin coupling constants and NMR chemical shifts were measured. It is shown that the experimental NMR parameters are suitable for comparison with the results of recent quantum-chemical calculations.

  14. Profiling formulated monoclonal antibodies by (1)H NMR spectroscopy.

    Science.gov (United States)

    Poppe, Leszek; Jordan, John B; Lawson, Ken; Jerums, Matthew; Apostol, Izydor; Schnier, Paul D

    2013-10-15

    Nuclear magnetic resonance (NMR) is arguably the most direct methodology for characterizing the higher-order structure of proteins in solution. Structural characterization of proteins by NMR typically utilizes heteronuclear experiments. However, for formulated monoclonal antibody (mAb) therapeutics, the use of these approaches is not currently tenable due to the requirements of isotope labeling, the large size of the proteins, and the restraints imposed by various formulations. Here, we present a new strategy to characterize formulated mAbs using (1)H NMR. This method, based on the pulsed field gradient stimulated echo (PGSTE) experiment, facilitates the use of (1)H NMR to generate highly resolved spectra of intact mAbs in their formulation buffers. This method of data acquisition, along with postacquisition signal processing, allows the generation of structural and hydrodynamic profiles of antibodies. We demonstrate how variation of the PGSTE pulse sequence parameters allows proton relaxation rates and relative diffusion coefficients to be obtained in a simple fashion. This new methodology can be used as a robust way to compare and characterize mAb therapeutics. PMID:24006877

  15. Pulsed NMR-relaxation meter

    International Nuclear Information System (INIS)

    Pulsed NMR-relaxation meter is designed to determine times of spin-lattice and spin-spin relaxation when investigating physico-chemical properties of solids and liquids. The device includes small-scale magnetic system with NMR-transducer, two-channel shaper of high-power radiopulses, programmer and analog-to-digital converter. High-frequency amplifier is based on field transistors with low level of self-noise. Unit operating frequency is 20 MHz, pass band may change discretely within 10-700 kHz limits. Magnetic system has the following dimensions: diameter - 165 mm, length - 110 mm, interpole gap -12 mm. Homogeneity of magnetic field constitutes 10-4

  16. NMR study of vanadium hydrides

    International Nuclear Information System (INIS)

    The nuclear magnetic resonance (NMR) method was used to study the position and the diffusion mobility of hydrogen in ? and ? vanadium hydrides in the temperature range of inception of hydrogen brittleness of metallic vanadium (130-450 K). An NMR analysis of 15V at various temperatures in ? and ?-hydrides has shown that the ?-hydride suffers a phase transformation in 190-230 K temperature range; the phase composition of the VHsub(0.84); VHsub(1.21); VHsub(1.75) hydrides was investigated. The variation of the width of the line as a function of the temperature is due only to the temperature-dependent dipole-dipole contribution. The activation energies of the self-diffusion of hydrogen in ?'-hydride and in ?-hydride were calculated. It was established that hydrogen occupies mainly tetrahedral positions in the ?'-vanadium hydride

  17. In vivo localized 1H NMR spectroscopy: an experimental characterization of the PRESS technique

    International Nuclear Information System (INIS)

    The aim of this study was the experimental characterization of the PRESS technique for image-guided in vivo 1H NMR spectroscopy, as implemented on a commercially available 1.5 T NMR whole-body system. Three characterization parameters were defined and evaluated in test object measurements: selection efficiency, suppression efficiency and contamination. Characterization parameters were evaluated in different experimental conditions. The profile of signal intensity across the volume of interest (VOI) was investigated. Results show that characterization parameters are slightly affected by echo time, while they are not affected by changes in repetition time. (author)

  18. Measurement of deformations by NMR

    Science.gov (United States)

    Bytchenkoff, Dimitri; Rodts, Stéphane

    2015-12-01

    Two NMR data acquisition protocols together with corresponding data processing algorithms for locating macroscopic objects, measuring distances between them or monitoring their displacements or deformations with microscopic precision are presented and discussed. The performance of the methods is demonstrated by applying them to the measurement of deformations of a freely supported beam under loading. We believe that our methods will find their applications in mechanics, civil engineering and medicine.

  19. NMR-Based Milk Metabolomics.

    Science.gov (United States)

    Sundekilde, Ulrik K; Larsen, Lotte B; Bertram, Hanne C

    2013-01-01

    Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR)-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits. PMID:24957988

  20. NMR-Based Milk Metabolomics

    Directory of Open Access Journals (Sweden)

    Hanne C. Bertram

    2013-04-01

    Full Text Available Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits.

  1. NMR-based milk metabolomics

    DEFF Research Database (Denmark)

    Sundekilde, Ulrik; Larsen, Lotte Bach

    2013-01-01

    Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR)-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits.

  2. High resolution NMR in solids

    International Nuclear Information System (INIS)

    The NMR spectra of solids, typically three orders of magnitude broader than those of fluids, arise from a variety of nuclear interactions of a mainly static and anisotropic character. These include direct magnetic dipolar interactions, indirect electron-coupled interactions, chemical and Knight shift interactions, and electric quadrupolar interactions. In isotropic mobile fluids the rapid random motion of the nuclei effectively removes the anisotropic interactions leaving a spectrum generated by the isotropic shifts and isotropic electron-coupled interactions, often exhibiting a wealth of fine structure rich in structural information. In recent years, considerable effort has been directed to techniques for the artificial removal of anisotropic sources of broadening in solids in order to obtain high-resolution NMR spectra for solids also. The methods all involve imposing a time-dependence on the anisotropic nuclear interactions. The following approaches to high resolution NMR in solids are discussed: (1) Random motion method, (2) Specimen rotation method, (3) Magnetic field rotation method, (4) Rotating frame method, (5) Multiple pulse methods, (6) High magnetic field method, (7) Double resonance rare spin methods. The paper discusses the various techniques and compares the situation in which they are effective, giving examples. A fuller account is given of the specimen rotation method. (author)

  3. Efficient design of multituned transmission line NMR probes: the electrical engineering approach.

    Science.gov (United States)

    Frydel, J A; Krzystyniak, M; Pienkowski, D; Pietrzak, M; de Sousa Amadeu, N; Ratajczyk, T; Idzik, K; Gutmann, T; Tietze, D; Voigt, S; Fenn, A; Limbach, H H; Buntkowsky, G

    2011-01-01

    Transmission line-based multi-channel solid state NMR probes have many advantages regarding the cost of construction, number of RF-channels, and achievable RF-power levels. Nevertheless, these probes are only rarely employed in solid state-NMR-labs, mainly owing to the difficult experimental determination of the necessary RF-parameters. Here, the efficient design of multi-channel solid state MAS-NMR probes employing transmission line theory and modern techniques of electrical engineering is presented. As technical realization a five-channel ((1)H, (31)P, (13)C, (2)H and (15)N) probe for operation at 7 Tesla is described. This very cost efficient design goal is a multi port single coil transmission line probe based on the design developed by Schaefer and McKay. The electrical performance of the probe is determined by measuring of Scattering matrix parameters (S-parameters) in particular input/output ports. These parameters are compared to the calculated parameters of the design employing the S-matrix formalism. It is shown that the S-matrix formalism provides an excellent tool for examination of transmission line probes and thus the tool for a rational design of these probes. On the other hand, the resulting design provides excellent electrical performance. From a point of view of Nuclear Magnetic Resonance (NMR), calibration spectra of particular ports (channels) are of great importance. The estimation of the π/2 pulses length for all five NMR channels is presented. PMID:21316931

  4. Isotope alternation system: two-level, NMR-controlled rapid switching

    International Nuclear Information System (INIS)

    In the sequential transmission method of normalization in AMS the magnetic parameters of the accelerator must be alternated between their values for the lighter and the heavier isotopes with as little loss of time as possible. Rapid changing of these parameters has been effected through a combination of computer control and nuclear magnetic resonance (NMR) search and lock control

  5. Measurements of Boar Spermatozoa Motility Using PFG NMR Method

    International Nuclear Information System (INIS)

    The evaluation of spermatozoa motility, viability and morphology is an essential parameter in the examination of sperm quality and in the establishment of correlations between sperm quality and fertility. Until now, assessment of sperm quality has been based on subjective evaluation of parameters, such as motility and viability, and on objective parameters, such as semen concentration and morphology abnormalities. When subjective optical microscopic evaluation was used in humans and animals, variations of 30 to 60% have been reported in the estimation of the motility parameters of the same ejaculates. To overcome this variability, different systems have been proposed such as turbidimetry, laser-Doppler spectroscopy, and photometric methods. Other accurate techniques, such as flow cytometry, which allows the evaluation of concentration, and cellulose-acetate/nitrate filter measure only a single semen parameter. The more recent track semen analysis system, based on individual spermatozoon evaluation, offers an accurate calculation of different semen parameters. Although some interesting results have already been obtained, many questions remain, which have to be answered to allow for further development in veterinary medicine, clinical fertility settings, physiological, and toxicology research activities. Pulsed field gradient nuclear magnetic resonance (PFG NMR) techniques have been presented demonstrating the potential to study flow and transport processes in complex systems. By PFG NMR, the molecular displacement can be measured that occurs during a time interval D, between two consecutive magnetic field gradient pulses. In this poster we present the results of PFG-NMR obtained for a number of samples of boar spermatozoa with varying motility and discuss whether this method can be useful for fast and reliable spermatozoa motility evaluation. (author)

  6. Advanced NMR technology for bioscience and biotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Hammel, P.C.; Hernandez, G.; Trewhella, J.; Unkefer, C.J. [Los Alamos National Lab., NM (US); Boumenthal, D.K. [Univ. of Utah, Salt Lake City, UT (US); Kennedy, M.A. [Pacific Northwest National Lab., Richland, WA (US); Moore, G.J. [Wayne State Univ., Detroit, MI (US)

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). NMR plays critical roles in bioscience and biotechnology in both imaging and structure determination. NMR is limited, however, by the inherent low sensitivity of the NMR experiment and the demands for spectral resolution required to study biomolecules. The authors addressed both of these issues by working on the development of NMR force microscopy for molecular imaging, and high field NMR with isotope labeling to overcome limitations in the size of biomolecules that can be studied using NMR. A novel rf coil design for NMR force microscopy was developed that increases the limits of sensitivity in magnetic resonance detection for imaging, and the authors demonstrated sub-surface spatial imaging capabilities. The authors also made advances in the miniaturization of two critical NMR force microscope components. They completed high field NMR and isotope labeling studies of a muscle protein complex which is responsible for regulating muscle contraction and is too large for study using conventional NMR approaches.

  7. Ordering and intramolecular mobility in the nematic phase of PAA investigated by means of NMR lineshape analysis and computer simulations of the lineshape

    OpenAIRE

    Limmer, St.; Schmiedel, H.; Hillner, B.; Lösche, A.; Grande, S

    1980-01-01

    We have recorded the 1H- and 2H-NMR spectra of PAA, PAA-d6, and PAA-d8. The order parameter S = Szz = 1/2. has been determined from the different types of NMR experiments and shown to be quite sufficient for the interpretation of both proton and deuterium NMR data since the values of the tentatively calculated second order parameter Sxx- Syy (from 2H- resonance of PAA-d8) are very small. From a comparison of the proton NMR spectra of PAA-d6 and PAA and theoretical spectra com...

  8. Insight into sodium silicate glass structural organization by multinuclear NMR combined with first-principles calculations

    International Nuclear Information System (INIS)

    Short and medium range order of silica and sodium silicate glasses have been investigated from a quantitative analysis of 29Si MAS NMR and 23Na, 17O MQMAS NMR spectra. The method described enables the extraction of the underlying 17O NMR parameter distributions of bridging oxygens (BOs) and non-bridging oxygens (NBOs), and yields site populations which are confirmed by 29Si NMR data. The extracted NMR parameter distributions and their variations with respect to the glass chemical composition can then be analyzed in terms of local structural features (bond angles and bond lengths, coordination numbers) with the help of molecular dynamics simulations combined with first-principles calculations of NMR parameters. Correlations of relevant structural parameters with 23Na, 29Si and 17O NMR interactions (isotropic chemical shift ?(iso), quadrupolar coupling constant C(Q) and quadrupolar asymmetry parameter ?Q are re-examined and their applicability is discussed. These data offer better insights into the structural organization of the glass network, including both chemical and topological disorder. Adding sodium to pure silica significantly diminishes the Si-O-Si bond angles and leads to a longer mean Si-O bond length with a slight decrease of the mean Na-O bond length. Moreover, the present data are in favor of a homogeneous distribution of Na around both oxygen species in the silicate network. Finally, our approach was found to be sensitive enough to investigate the effect of addition of a small quantity of molybdenum oxide (about 1 mol%) on the 17O MAS spectrum, opening new possibilities for investigating the Mo environment in silicate glasses. (authors)

  9. NMR of glycans: shedding new light on old problems.

    Science.gov (United States)

    Battistel, Marcos D; Azurmendi, Hugo F; Yu, Bingwu; Freedberg, Darón I

    2014-05-01

    The diversity in molecular arrangements and dynamics displayed by glycans renders traditional NMR strategies, employed for proteins and nucleic acids, insufficient. Because of the unique properties of glycans, structural studies often require the adoption of a different repertoire of tailor-made experiments and protocols. We present an account of recent developments in NMR techniques that will deepen our understanding of structure-function relations in glycans. We open with a survey and comparison of methods utilized to determine the structure of proteins, nucleic acids and carbohydrates. Next, we discuss the structural information obtained from traditional NMR techniques like chemical shifts, NOEs/ROEs, and coupling-constants, along with the limitations imposed by the unique intrinsic characteristics of glycan structure on these approaches: flexibility, range of conformers, signal overlap, and non-first-order scalar (strong) coupling. Novel experiments taking advantage of isotopic labeling are presented as an option for overcoming spectral overlap and raising sensitivity. Computational tools used to explore conformational averaging in conjunction with NMR parameters are described. In addition, recent developments in hydroxyl detection and hydrogen bond detection in protonated solvents, in contrast to traditional sample preparations in D2O for carbohydrates, further increase the tools available for both structure information and chemical shift assignments. We also include previously unpublished data in this context. Accurate determination of couplings in carbohydrates has been historically challenging due to the common presence of strong-couplings. We present new strategies proposed for dealing with their influence on NMR signals. We close with a discussion of residual dipolar couplings (RDCs) and the advantages of using (13)C isotope labeling that allows gathering one-bond (13)C-(13)C couplings with a recently improved constant-time COSY technique, in addition to the commonly measured (1)H-(13)C RDCs. PMID:24815364

  10. NMR metabolomics for assessment of exercise effects with mouse biofluids

    Energy Technology Data Exchange (ETDEWEB)

    Le Moyec, Laurence; Mille-Hamard, Laurence; Breuneval, Carole; Petot, Helene; Billat, Veronique L. [Universite Evry Val d' Essonne, UBIAE INSERM U902, Evry Cedex (France); Triba, Mohamed N. [Universite Paris 13, CSPBAT UMR 7244, Bobigny (France)

    2012-08-15

    Exercise modulates the metabolome in urine or blood as demonstrated previously for humans and animal models. Using nuclear magnetic resonance (NMR) metabolomics, the present study compares the metabolic consequences of an exhaustive exercise at peak velocity (Vp) and at critical velocity (Vc) on mice. Since small-volume samples (blood and urine) were collected, dilution was necessary to acquire NMR spectra. Consequently, specific processing methods were applied before statistical analysis. According to the type of exercise (control group, Vp group and Vc group), 26 male mice were divided into three groups. Mice were sacrificed 2 h after the end of exercise, and urine and blood samples were drawn from each mouse. Proton NMR spectra were acquired with urine and deproteinized blood. The NMR data were aligned with the icoshift method and normalised using the probabilistic quotient method. Finally, data were analysed with the orthogonal projection of latent-structure analysis. The spectra obtained with deproteinized blood can neither discriminate the control mice from exercised mice nor discriminate according to the duration of the exercise. With urine samples, a significant statistical model can be estimated when comparing the control mice to both groups, Vc and Vp. The best model is obtained according to the exercise duration with all mice. Taking into account the spectral regions having the highest correlations, the discriminant metabolites are allantoin, inosine and branched-chain amino acids. In conclusion, metabolomic profiles assessed with NMR are highly dependent on the exercise. These results show that urine samples are more informative than blood samples and that the duration of the exercise is a more important parameter to influence the metabolomic status than the exercise velocity. (orig.)

  11. Improvements in Technique of NMR Imaging and NMR Diffusion Measurements in the Presence of Background Gradients.

    Science.gov (United States)

    Lian, Jianyu

    In this work, modification of the cosine current distribution rf coil, PCOS, has been introduced and tested. The coil produces a very homogeneous rf magnetic field, and it is inexpensive to build and easy to tune for multiple resonance frequency. The geometrical parameters of the coil are optimized to produce the most homogeneous rf field over a large volume. To avoid rf field distortion when the coil length is comparable to a quarter wavelength, a parallel PCOS coil is proposed and discussed. For testing rf coils and correcting B _1 in NMR experiments, a simple, rugged and accurate NMR rf field mapping technique has been developed. The method has been tested and used in 1D, 2D, 3D and in vivo rf mapping experiments. The method has been proven to be very useful in the design of rf coils. To preserve the linear relation between rf output applied on an rf coil and modulating input for an rf modulating -amplifying system of NMR imaging spectrometer, a quadrature feedback loop is employed in an rf modulator with two orthogonal rf channels to correct the amplitude and phase non-linearities caused by the rf components in the rf system. The modulator is very linear over a large range and it can generate an arbitrary rf shape. A diffusion imaging sequence has been developed for measuring and imaging diffusion in the presence of background gradients. Cross terms between the diffusion sensitizing gradients and background gradients or imaging gradients can complicate diffusion measurement and make the interpretation of NMR diffusion data ambiguous, but these have been eliminated in this method. Further, the background gradients has been measured and imaged. A dipole random distribution model has been established to study background magnetic fields Delta B and background magnetic gradients G_0 produced by small particles in a sample when it is in a B_0 field. From this model, the minimum distance that a spin can approach a particle can be determined by measuring and . From this model, the particle concentration in a sample can be determined by measuring the lineshape of a free induction decay (fid).

  12. Rheo-NMR of shear banded flow in wormlike micelles

    Science.gov (United States)

    Callaghan, Paul

    2008-03-01

    Rheo-NMR gives access to detailed information about the flow field generated by the device used to induce deformational flow. It also provides information about colloidal or molecular organisation and dynamics, under conditions of flow. In particular, NMR offers the possibility of measuring nuclear spin relaxation times and molecular self-diffusion coefficients, sensitive respectively to molecular brownian motions and their restrictions due to local structure. Furthermore, through the use of orientation-dependent terms in the spin interactions, such as the nuclear quadrupole or dipolar interactions, NMR permits the measurement of molecular order parameters. When combined with imaging methods, NMR in principle allows such measurements to be spatially localized, often with resolution down to a few 10s of microns In the study of shear banding phenomena in wormlike micelles, Rheo-NMR has proven of especial value, not only indicating the clear existence of shear bands, but also that they are associated with fluctuations, and sometimes, with molecular alignment. The subtlety of the correspondence (or lack of correspondence) between birefringence effects and shear banded flow has also been revealed. Recent measurements of shear-banded flow under Couette flow of the micellar system 10% w/v cetylpyridinium chloride and sodium salicylate (CPyCl/NaSal) molar ratio 2:1 in 0.5 M NaCl in ^1H2O, indicate that shear banding fluctuations are consistent with the shear stress fluctuations observed in rheological measurements. Furthermore we find a coupling between flow fluctuations in the gradient and vorticity directions. Using ^2H NMR spectroscopy on a deuterated probe molecule (n-decane) in the wormlike micellar interior, direct measurement of the shear-induced nematic phase transition is reported. More recently we have used Rheo-NMR to investigate the flow and alignment properties of worm-like micelles formed by a 5% w/w solution of the BASF difunctional block copolymer non-ionic surfactant, Pluronic P105 in water along with 4.3% w/v 1-phenylethanol-d5. A variety of shear-banding and alignment behaviours are observed, along with both stable and fluctuating flows.

  13. NMR spectroscopy and imaging of hyperpolarized gases

    OpenAIRE

    Zänker, Paul-Philipp

    2007-01-01

    Since the discovery of the nuclear magnetic resonance (NMR) phenomenon, countless NMR techniques have been developed that are today indispensable tools in physics, chemistry, biology, and medicine. As one of the main obstacles in NMR is its notorious lack of sensitivity, different hyperpolarization (HP) methods have been established to increase signals up to several orders of magnitude. In this work, different aspects of magnetic resonance, using HP noble gases, are studied, hereby combining ...

  14. High resolution NMR theory and chemical applications

    CERN Document Server

    Meurant, Gerard

    2013-01-01

    High Resolution NMR: Theory and Chemical Applications, Second Edition covers the significant progress in understanding the NMR phenomena, instrumentation, and applications in chemical and biochemistry. This edition is divided into 14 chapters and begins with the historical developments and theoretical aspects of NMR. Considerable chapters are devoted to the basic principles, chemical shifts, coupling constants, and analysis of complex spectra. Other chapters contain expanded topics on carbon-13, nuclear Overhauser effect, relaxation mechanisms, and the use of superconducting magnets. The remai

  15. Applications of Concatenated Composite Pulses to NMR

    CERN Document Server

    Bando, Masamitsu; Kondo, Yasushi; Nemoto, Nobuaki; Nakahara, Mikio; Shikano, Yutaka

    2015-01-01

    ConCatenated Composite Pulses (CCCPs) are derived from various composite pulses widely employed in NMR and have been developed as high-precision unitary operations in Quantum Information Processing (QIP). CCCPs are robust against two systematic errors, pulse-length and off-resonance errors, in NMR simultaneously. We show experiments that demonstrate CCCPs are powerful and versatile tools not only in QIP but also in NMR measurements.

  16. 1H HR-MAS NMR and S180 cells: metabolite assignment and evaluation of pulse sequence

    Scientific Electronic Library Online (English)

    Aline L. de, Oliveira; Bruno César B., Martinelli; Luciano M., Lião; Flávia C., Pereira; Elisangela P., Silveira-Lacerda; Glaucia B., Alcantara.

    2014-06-01

    Full Text Available Ressonância magnética nuclear de ¹H de alta resolução com giro no ângulo mágico (HR-MAS NMR) é uma técnica empregada na avaliação de células e tecidos intactos. Entretanto, parâmetros bem estabelecidos de NMR são cruciais para a obtenção de resultados confiáveis. A fim de discutir as principais etap [...] as envolvidas na otimização das análises de HR-MAS NMR, este artigo avaliou diferentes sequências de pulsos e parâmetros de NMR usando células de sarcoma 180 (S180). O completo assinalamento dos metabólitos de S180 é também apresentado para auxiliar estudos futuros. Abstract in english High resolution magic angle spinning ¹H nuclear magnetic resonance spectroscopy (HR-MAS NMR) is a useful technique for evaluation of intact cells and tissues. However, optimal NMR parameters are crucial in obtaining reliable results. To identify the key steps for the optimization of HR-MAS NMR param [...] eters, we assessed different pulse sequences and NMR parameters using sarcoma 180 (S180) cells. A complete assignment of the metabolites of S180 is given to assist future studies.

  17. A new inversion method for (T2, D) 2D NMR logging and fluid typing

    Science.gov (United States)

    Tan, Maojin; Zou, Youlong; Zhou, Cancan

    2013-02-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.

  18. Deuteron NMR resolved mesogen vs. crosslinker molecular order and reorientational exchange in liquid single crystal elastomers.

    Science.gov (United States)

    Milavec, J; Domenici, V; Zupan?i?, B; Rešeti?, A; Bubnov, A; Zalar, B

    2016-01-27

    Differences in the temperature behaviour of orientational ordering of structurally equivalent side-chain liquid single crystal elastomers (LSCEs) with (2)H-labelled crosslinker and mesogen have been studied by deuteron quadrupole-perturbed NMR. The impact of nematic director reorientations on the deuteron NMR spectral shapes was analyzed in terms of a discrete reorientational exchange model. This provided for the determination of the degree of nematic director alignment and for the quantification of the influence of the reorientational exchange on the (2)H NMR spectra in terms of two parameters, the nematic director orientational dispersion parameter ?? and the motional effectiveness parameter ?. A comparative analysis of model simulations and experimental spectra reveals that mesogenic molecules in LSCEs exhibit faster reorientational dynamics as compared to crosslinker molecules and that mesogens and crosslinkers exhibit a similar and rather substantial static director orientational disorder. PMID:26778188

  19. Dynamic pulsed-field-gradient NMR

    CERN Document Server

    Sorland, Geir Humborstad

    2014-01-01

    Dealing with the basics, theory and applications of dynamic pulsed-field-gradient NMR NMR (PFG NMR), this book describes the essential theory behind diffusion in heterogeneous media that can be combined with NMR measurements to extract important information of the system being investigated. This information could be the surface to volume ratio, droplet size distribution in emulsions, brine profiles, fat content in food stuff, permeability/connectivity in porous materials and medical applications currently being developed. Besides theory and applications it will provide the readers with backgro

  20. NMR studies of isotopically labeled RNA

    Energy Technology Data Exchange (ETDEWEB)

    Pardi, A. [Univ. of Colorado, Boulder, CO (United States)

    1994-12-01

    In summary, the ability to generate NMR quantities of {sup 15}N and {sup 13}C-labeled RNAs has led to the development of heteronuclear multi-dimensional NMR techniques for simplifying the resonance assignment and structure determination of RNAs. These methods for synthesizing isotopically labeled RNAs are only several years old, and thus there are still relatively few applications of heteronuclear multi-dimensional NMR techniques to RNA. However, given the critical role that RNAs play in cellular function, one can expect to see an increasing number of NMR structural studies of biologically active RNAs.

  1. The fluorescence properties and NMR analysis of protopine and allocryptopine

    Energy Technology Data Exchange (ETDEWEB)

    Kubala, Martin, E-mail: mkubala@prfnw.upol.c [Department of Biophysics, Faculty of Science, Palacky University, tr. 17. listopadu 12, CZ-77146 Olomouc (Czech Republic); Vacek, Jan [Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, CZ-77515 Olomouc (Czech Republic); Popa, Igor [Department of Inorganic Chemistry, Faculty of Science, Palacky University, tr. 17. listopadu 12, CZ-77146 Olomouc (Czech Republic); Janovska, Marika [Department of Biophysics, Faculty of Science, Palacky University, tr. 17. listopadu 12, CZ-77146 Olomouc (Czech Republic); Kosina, Pavel; Ulrichova, Jitka [Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, CZ-77515 Olomouc (Czech Republic); Travnicek, Zdenek [Department of Inorganic Chemistry, Faculty of Science, Palacky University, tr. 17. listopadu 12, CZ-77146 Olomouc (Czech Republic); Simanek, Vilim [Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, CZ-77515 Olomouc (Czech Republic)

    2011-07-15

    The fluorescence properties of protopine and allocryptopine in aqueous and organic environments are described for the first time. The fluorescence of alkaloids and their pH-dependent interconversion to cationic forms (transannular interaction) were studied using steady-state and time-resolved fluorescence techniques. For the analysis of tricyclic base and cis/trans tetracyclic cations of the alkaloids, NMR and X-ray crystallography were used. - Highlights: {yields} We describe fundamental fluorescence characteristics of alkaloids protopine and allocryptopine. {yields} We analyzed the pH-dependent transitions and cis/trans isomerization. {yields} These two alkaloids can be better distinguished by their fluorescence decay characteristics. {yields} The fluorescence parameters are related to the NMR and crystallographic structural data.

  2. The fluorescence properties and NMR analysis of protopine and allocryptopine

    International Nuclear Information System (INIS)

    The fluorescence properties of protopine and allocryptopine in aqueous and organic environments are described for the first time. The fluorescence of alkaloids and their pH-dependent interconversion to cationic forms (transannular interaction) were studied using steady-state and time-resolved fluorescence techniques. For the analysis of tricyclic base and cis/trans tetracyclic cations of the alkaloids, NMR and X-ray crystallography were used. - Highlights: ? We describe fundamental fluorescence characteristics of alkaloids protopine and allocryptopine. ? We analyzed the pH-dependent transitions and cis/trans isomerization. ? These two alkaloids can be better distinguished by their fluorescence decay characteristics. ? The fluorescence parameters are related to the NMR and crystallographic structural data.

  3. Solid State NMR Investigations of Zeolite - Intercalate Structures

    Energy Technology Data Exchange (ETDEWEB)

    Fyfe, Colin A.; Diaz, Anix; Brouwer, Darren H.; Lee, Joseph; Schneider, Celine M.; Scheffler, Franziska A.; Darton, Richard J.

    2006-07-24

    We will describe two topics in which structural information on complexes of zeolites is obtained from solid state NMR. In the first, recent work on the determination of the complete three-dimensional structures of the complexes of zeolites with organic sorbates will be briefly reported. The method has been optimized and the presentation of the results systematized. In the second topic, we will describe how solid state NMR can be used in the reverse sense to probe for the existence and structures of “nanocrystals” whose dimensions are too small to give proper Bragg scattering and which have been proposed to be the synthesis route for the formation of zeolite ZSM-5. In this study, the spectral parameters of “probe” template molecules are used as being diagnostic of whether the local environment of the framework has been formed. These are independent of the “crystal” dimensions and this general approach may be applicable to other similar “nano” systems.

  4. Transverse NMR relaxation as a probe of mesoscopic structure

    CERN Document Server

    Kiselev, V G; Kiselev, Valerij G.; Novikov, Dmitry S.

    2002-01-01

    We show that transverse NMR signal relaxation averaged over a macroscopic volume is extremely sensitive to structure of mesoscopic paramagnetic inhomogeneities. Such a sensitivity is proposed as a novel kind of contrast in the NMR measurements. We model the medium by a suspension of arbitrary shaped mesoscopic paramagnetic objects, and find transverse relaxation without adjustable parameters in the case when the dephasing effect of an individual object is small. Results indicate a strong relaxation rate dependence on the shape of the objects. As a major application we consider transverse spin relaxation in the whole blood, for which our theory agrees well with experiments and Monte-Carlo simulations. Applications to a wide range of problems in complex systems (porous media, biological systems, diffusion limited reaction rates) are discussed.

  5. Short recovery time NMR probe

    Energy Technology Data Exchange (ETDEWEB)

    Ramia, M.E.; Martin, C.A.; Jeandrevin, S., E-mail: ramia@famaf.unc.edu.ar [Universidad Nacional de Cordoba, (Argentina). Facultad de Matematica, Astronomia y Fisica

    2011-07-01

    A NMR probe for low frequency and short recovery time is presented in this work. The probe contains the tuning circuit, diode expanders and quarter wavelength networks to protect the receiver from both the amplifier noise and the coil ringing following the transmitter power pulse. It also possesses a coil damper which is activated by of non active components. The probe performance shows a recovery time of about of 15?s a sensitive Q factor reduction and an increase of the signal to noise ratio of about 68% during the reception at a work frequency of 2 MHz. (author)

  6. Tantalum-181 solution NMR spectroscopy

    Science.gov (United States)

    Rehder, Dieter; Basler, Wolf

    The 181Ta NMR spectra of solutions of [Et 4N][TaL 6] (L = Cl -, CO) and K 2[TaF 7] have been obtained. The shift range encompasses 3450 ppm, limited by [TaCl 6] - at the low-field and [Ta(CO) 6] - at the high-field side. The shielding sensitivity of the 181Ta nucleus is about 1.6 times that of 93Nb and 0.6 times that of 183W. Half widths are 4.3 (L = Cl -), 6.7 (L = CO) and 29 kHz ([TaF 7] -).

  7. Access to NMR Spectroscopy for Two-Year College Students: The NMR Site at Trinity University

    Science.gov (United States)

    Mills, Nancy S.; Shanklin, Michael

    2011-01-01

    Students at two-year colleges and small four-year colleges have often obtained their exposure to NMR spectroscopy through "canned" spectra because the cost of an NMR spectrometer, particularly a high-field spectrometer, is prohibitive in these environments. This article describes the design of a NMR site at Trinity University in which spectral…

  8. NMR paramagnetic relaxation enhancement: test of the controlling influence of zfs rhombicity for S = 1.

    Science.gov (United States)

    Miller, J C; Lohr, L L; Sharp, R R

    2001-02-01

    Prior theoretical work has predicted that the NMR paramagnetic relaxation enhancement (NMR-PRE) produced by electron spin S = 1 ions is highly sensitive to orthorhombic terms in the static zero field splitting (zfs) tensor. Zfs orthorhombicity (which implies chemical inequivalence of the three principal directions of the zfs-principal axis system and is described by the zfs E-parameter) is predicted to suppress the NMR-PRE profoundly relative to the reference cylindrical zfs-limit situation. This expectation was tested experimentally by a comparison of the zfs-limit NMR-PRE produced by [Ni(II)(en)(3)](2+) (en = ethylenediamine), a trigonal complex which lacks zfs-rhombicity, with the zfs-limit NMR-PRE produced by two orthorhombic complexes, [Ni(II)(en)(2)(H(2)O)(2)](2+) and [Ni(II)(en)(H(2)O)(4)](2+). As predicted, the zfs-limit NMR-PRE produced by the orthorhombic complexes in the proton resonance of a dioxane probe species in the solvent was strongly suppressed (by factors of approximately 5 and 7, respectively) relative to the comparable measurement on the trigonal complex. The suppression of the NMR-PRE due to the orthorhombic zfs terms is counteracted by an applied Zeeman field, leading to a predicted rise in the NMR-PRE with increasing Zeeman field strength; this rise occurs when the Zeeman energy is comparable to the orthorhombic zfs splitting, 2E. This second prediction of theory was likewise confirmed: the expected rhombicity-induced magnetic field dependence in the NMR-PRE was observed for the orthorhombic complexes but not for the trigonal complex. PMID:11237632

  9. Parameter Estimation

    DEFF Research Database (Denmark)

    Sales-Cruz, Mauricio; Heitzig, Martina; Cameron, Ian; Gani, Rafiqul

    In this chapter the importance of parameter estimation in model development is illustrated through various applications related to reaction systems. In particular, rate constants in a reaction system are obtained through parameter estimation methods. These approaches often require the application...... of optimisation techniques coupled with dynamic solution of the underlying model. Linear and nonlinear approaches to parameter estimation are investigated. There is also the application of maximum likelihood principles in the estimation of parameters, as well as the use of orthogonal collocation to...... generate a set of algebraic equations as the basis for parameter estimation.These approaches are illustrated using estimations of kinetic constants from reaction system models....

  10. Method for enhancing NMR imaging; and diagnostic use

    International Nuclear Information System (INIS)

    This patent describes a method for nuclear magnetic resonance (NMR) imagining of a patient comprising, prior to the NMR imaging of a patient, administering to the patient ferromagnetic, paramagnetic or diamagnetic particles effective to enhance an NMR image

  11. Early history of NMR at Los Alamos

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) spectroscopy has developed into an important research tool in chemistry. More recently, NMR imaging and in vivo spectroscopy promise to produce a revolution in medicine and biochemistry. Early experiments at Los Alamos led to DOE programs involving stable isotopes of importance to biology and to medicine. These events are briefly recounted. 2 refs

  12. A Guided Inquiry Approach to NMR Spectroscopy

    Science.gov (United States)

    Parmentier, Laura E.; Lisensky, George C.; Spencer, Brock

    1998-04-01

    We present a novel way to introduce NMR spectroscopy into the general chemistry curriculum as part of a week-long aspirin project in our one-semester introductory course. Aspirin is synthesized by reacting salicylic acid and acetic anhydride. Purity is determined by titration and IR and NMR spectroscopy. Students compare IR and NMR spectra of their aspirin product to a series of reference spectra obtained by the class. Students are able to interpret the IR spectra of their aspirin using IR data from previous experiments. NMR is introduced by having students collect 1H NMR spectra of a series of reference compounds chosen to include some of the structural features of aspirin and compare spectra and structures of the reference compounds to develop a correlation chart for chemical shifts. This process is done in small groups using shared class data and is guided by a series of questions designed to relate the different kinds of hydrogen atoms to number and position of peaks in the NMR spectrum. Students then identify the peaks in the NMR spectrum of their aspirin product and relate percent purity by titration with spectral results and percent yield. This is an enjoyable project that combines the synthesis of a familiar material with a guided inquiry-based introduction to NMR spectroscopy.

  13. NMR Spectroscopy and Its Value: A Primer

    Science.gov (United States)

    Veeraraghavan, Sudha

    2008-01-01

    Nuclear magnetic resonance (NMR) spectroscopy is widely used by chemists. Furthermore, the use of NMR spectroscopy to solve structures of macromolecules or to examine protein-ligand interactions is popular. Yet, few students entering graduate education in biological sciences have been introduced to this method or its utility. Over the last six…

  14. Using Cloud Storage for NMR Data Distribution

    Science.gov (United States)

    Soulsby, David

    2012-01-01

    An approach using Google Groups as method for distributing student-acquired NMR data has been implemented. We describe how to configure NMR spectrometer software so that data is uploaded to a laboratory section specific Google Group, thereby removing bottlenecks associated with printing and processing at the spectrometer workstation. Outside of…

  15. Characterization of natural bentonite by NMR

    International Nuclear Information System (INIS)

    Solid state NMR as well as several other instrumental chemical analysis techniques were used in order to characterize two natural occurring bentonite. The methodology is described. The NMR spectra, together with the other used techniques suggest that the observed differences are due to iron inclusions in tetrahedral and octahedral sites

  16. An Inversion Recovery NMR Kinetics Experiment

    Science.gov (United States)

    Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this…

  17. NMR investigation into water content of foodstuffs

    International Nuclear Information System (INIS)

    The applications are briefly discussed of NMR methods in measuring water content in food and food products. The NMR methods allow measuring water content in different fractions; physical (energy) water mobility from relaxation characteristics and mechanical water mobility from the self-diffusion coefficient; correlation time and coordination number pertaining to one molecule for each fraction. (B.S.)

  18. 2D NMR studies of biomolecules

    International Nuclear Information System (INIS)

    The work described in this thesis comprises two related subjects. The first part describes methods to derive high-resolution structures of proteins in solution using two-dimensional (2-D) NMR. The second part describes 2-D NMR studies on the interaction between proteins and DNA. (author). 261 refs.; 52 figs.; 23 tabs

  19. An Inexpensive High-Throughput NMR Tube Cleaning Apparatus

    OpenAIRE

    Zhang, Bo; Hodgson, James; Hancock, Walter; Powers, Robert

    2011-01-01

    Large scale Nuclear Magnetic Resonance (NMR) tube cleaning is currently a bottleneck in high throughput NMR ligand affinity screens. Expensive alternatives include discarding the NMR tubes after a single use (~$2 to $8/tube), using commercial NMR tube cleaners (~$15K) or abandoning NMR tubes for flow probe technology (~$75K). Instead, we describe a relatively inexpensive (~$400) and easily constructed apparatus that can clean 180 NMR tubes an hour while using a modest amount of solvent. The a...

  20. Carbon-13 NMR spectroscopy of biological systems

    CERN Document Server

    Beckmann, Nicolau

    1995-01-01

    This book is intended to provide an in-depth understanding of 13C NMR as a tool in biological research. 13C NMR has provided unique information concerning complex biological systems, from proteins and nucleic acids to animals and humans. The subjects addressed include multidimensional heteronuclear techniques for structural studies of molecules in the liquid and solid states, the investigation of interactions in model membranes, the elucidation of metabolic pathwaysin vitro and in vivo on animals, and noninvasive metabolic studies performed on humans. The book is a unique mix of NMR methods and biological applications which makes it a convenient reference for those interested in research in this interdisciplinary area of physics, chemistry, biology, and medicine.Key Features* An interdisciplinary text with emphasis on both 13C NMR methodology and the relevant biological and biomedical issues* State-of-the-art 13C NMR techniques are described; Whenever possible, their advantages over other approaches are empha...

  1. NMR and MRI apparatus and method

    Science.gov (United States)

    Clarke, John; Kelso, Nathan; Lee, SeungKyun; Moessle, Michael; Myers, Whittier; McDermott, Robert; ten Haken, Bernard; Pines, Alexander; Trabesinger, Andreas

    2007-03-06

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. Additional signal to noise benefits are obtained by use of a low noise polarization coil, comprising litz wire or superconducting materials. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  2. NMR imaging of the brain: current status and perspectives

    International Nuclear Information System (INIS)

    Recent developments in NMR imaging of the brain are summarised and preliminary results from cranial examination of 230 patients and 60 volunteers at Hammersmith Hospital are discussed. An NMR scanner is described and three pulse sequences which produce images with varying dependence on the basic imaging parameters proton density, T1 and T2 are outlined. The first of these pulse sequences, Repeated Free Induction Decay, produces images which demonstrate changes in proton density although these have limited diagnostic utility. The second sequence, Inversion-recovery, produces images which depend on T1. These show a high level of grey white matter contrast giving considerable anatomical detail. In addition pathological changes such as infarction, haemorrhage, demyelination and malignancy produce changes in T1 enabling lesions to be localised. The third sequence, Spin-echo, produces images dependent on T2. Whilst these display little grey-white matter contrast they frequently highlight pathological changes in the brain. Images of these three basic types can also be produced in transverse coronal and sagittal planes. Although much more work remains to be done, NMR imaging appears likely to play a major role in neurological diagnosis within the foreseeable future

  3. A frequency determination method for digitized NMR signals

    CERN Document Server

    Yan, H; Khatiwada, R; Smith, E; Snow, W M; Fu, C B; Chu, P -H; Gao, H; Zheng, W

    2013-01-01

    We present a high precision frequency determination method for digitized NMR FID signals. The method employs high precision numerical integration rather than simple summation as in many other techniques. With no independent knowledge of the other parameters of a NMR FID signal (phase $\\phi$, amplitude $A$, and transverse relaxation time $T_{2}$) this method can determine the signal frequency $f_{0}$ with a precision of $1/(8\\pi^{2}f_{0}^{2}T_{2}^{2})$ if the observation time $T$ is long enough. The method is especially convenient when the detailed shape of the observed FT NMR spectrum is not well defined. When $T_{2}$ is $+\\infty$ and the signal becomes pure sinusoidal, the precision of the method is $3/(2\\pi^{2}f_{0}^{2}T^{2})$ which is one order more precise than a typical frequency counter. Analysis of this method shows that the integration reduces the noise by bandwidth narrowing as in a lock-in amplifier, and no extra signal filters are needed. For a pure sinusoidal signal we find from numerical simulati...

  4. High resolution NMR microscopy of plants and fungi.

    Science.gov (United States)

    Köckenberger, W; De Panfilis, C; Santoro, D; Dahiya, P; Rawsthorne, S

    2004-05-01

    Nuclear magnetic resonance (NMR) microscopy is a completely noninvasive technique that can be used to acquire images with high spatial resolution through opaque objects such as plant organs and tissue parts. The image contrast can be chosen to represent the anatomical details or to visualize the spatial distribution of a range of physico-chemical parameters such as the apparent diffusion constant of water or the velocity of water flow within plants in vivo. In addition, images can be generated which show the spatial distribution of metabolites. Furthermore, it is possible to detect chemical compounds labelled with the stable isotope (13)C and to generate images showing the spatial distribution of the (13)C label in the intact plant. The ability to monitor water flow and transport of (13)C-labelled tracer in intact plants with NMR microscopy favours the use of this technique in the investigation of long-distance transport processes in plants. A short introduction into the technical principles of NMR microscopy is provided and the problems associated with applications to plants are summarized. The potential of the technique is explained with applications to Zinnia elegans plants, wheat grains and Brassica napus siliques. PMID:15102065

  5. KAIS resistive NMR-CT and its clinical application

    International Nuclear Information System (INIS)

    This paper contains the results of clinical studies with 0.1 and 0.15 Tesla KAIS NMR tomograph which was developed by Korean Advanced Institute of Science. A variety of imaging modes such as saturation recover (SR), spin echo (SE), and inversion recovery (IR) as well as echo and repetition times were applied. Clinical imagings were performed on 22 patients with diseases of brain (15 cases), cervical spine (2 cases), chest (2 cases), pancreas (2 cases), and kidney (1 case). In SR imaging, we have obtained images strongly dependent on the hydrogen nuclei density. SE with long echo time and IR are effective for T2 and T1 dependent images, respectively. Results of clinical NMR imaging are presented and compared with X-CT and the other radiological examinations. Obtained results appear promising and with further examinations along with parameter adjustment, it is expected that the NMR imaging will not only substitute many conventional diagnostic methods such as X-ray CT but also be useful for the early detection of tumor and other lesions not obtainable with other modalities

  6. 93Nb NMR chemical shift scale for niobia systems.

    Science.gov (United States)

    Lapina, Olga B; Khabibulin, Dzhalil F; Romanenko, Konstantin V; Gan, Zhehong; Zuev, Mikhail G; Krasil'nikov, Vladimir N; Fedorov, Vladimir E

    2005-09-01

    93Nb solid-state NMR spectra of a series of inorganic niobates with Nb in different oxygen coordination environments were measured. For all studied compounds the chemical shielding and quadrupole tensor parameters were determined using conventional and ultrahigh field NMR facilities, ultrahigh speed MAS, DQ STMAS, solid-echo and computer modeling. It has been demonstrated that the 93Nb isotropic chemical shift is sensitive to the coordination number of Nb sites. For the first time the 93Nb NMR chemical shift scale for NbOx polyhedra in solid materials has been proposed: for four-coordinated Nb sites, the isotropic shifts occur from -650 to -950 ppm; five-coordinated Nb sites have the isotropic shifts in the range of -900 to -980 ppm; for six-coordinated Nb sites the isotropic shifts vary from -900 to -1360 ppm; the shifts from -1200 to -1600 ppm are typical for seven-coordinated Nb sites; for eight-coordinated Nb sites the shifts are higher than -1400 ppm. The possible correlation between the value of the isotropic chemical shift and the ionic character of the NbOx-MOy polyhedra association has been suggested. The magnitude of the 93Nb quadrupole coupling constant depends on the local symmetry of Nb sites and may vary from hundreds of kHz to hundreds of MHz. PMID:16216475

  7. NMR study of the alkaline isomerization of fefficytochrome c

    International Nuclear Information System (INIS)

    The pH-induced isomerization of horse heart cytochrome c has been studied by 1H NMR. We find that the transition occuring in D2O with a pKa measuresd as 9.5 ± 0.1 is from the native species to a mixture of two basic forms which have very similar NMR spectra. The heme methyl peaks of these two forms have been assigned by 2D exchange NMR. The forward rate constant (native to alkaline cytochrome c) has a value of 4.0 ± 0.6 s-1 at 27 deg C and is independent of pH; the reverse rate constant is pH-dependent. The activation parameters are ?H 12.8 ± 0.8 kcal-mol1, ?S = -12.9 ± 2.0 e.u. for the forward reaction and ?H = 6.0 ± 0.3 kcal-mol-1, ?S = - 35.1 ± 1.3 e.u. for the reverse reaction (Ph = 9.28). ?H and ?S for the isomerization are 6.7 ± 0.6 kcal-mol-1 and 21.9 ± 1.0 e.u., respectively. (author). 26 refs.; 5 figs

  8. NMR studies of molecules in liquid crystals and graphite

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, M.E.

    1992-06-01

    NMR experiments to measure proton dipole couplings were performed on a series of n-alkanes (n-hexane through n-decane) dissolved in nematic liquid crystals. Computer modeling of the experimental NMR-spectra was done using several different models for intermolecular interactions in these systems. The model of Photinos et al. was found to be best in describing the intermolecular interactions in these systems and can provide a statistical picture of the conformation and orientation of the alkane molecules in their partially-oriented environment. Order parameters and conformational distributions for the alkanes can be calculated from the modeling. The alkanes are found to have conformational distributions very much like those found in liquid alkanes. Proton NMR spectra of tetrahydrofuran (THF) intercalated in two graphite intercalation compounds were also measured. Computer simulations of these spectra provide a picture of THF in the constrained environment between the graphene layers where the THF is oriented at a particular angle, can translate and rotate freely, but does not appear to pseudorotate.

  9. Utilization of NMR in determination of hydrogen structure in solids

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) methods offer many opportunities for obtaining information on structures and atom locations in metal-hydrogen systems. Nuclei interact with the microscopic local environment via their magnetic dipole and electric quadrupole moments, and since these moment properties are invariable for a given nuclear species, the interactions serve to probe the magnitudes and symmetries of the electric and magnetic fields at the nuclear sites. A variety of experimental techniques may be utilized, including both steady-state (wide-line) and transient (pulsed) measurements. These techniques may be applied to study the NMR of all three hydrogen isotopes (1H, 2D, 3T). In addition to structural aspects, NMR measurements provide information pertaining to electronic structure and hydrogen diffusion in metal-hydrogen systems. This review concentrates on the utilization of wide-line methods which yield parameters characterizing the steady-state interactions of nuclei with their environment. Pulse experiments which measure nuclear spin relaxation times also furnish information on structures and phases

  10. NMR-based milk metabolomics

    DEFF Research Database (Denmark)

    Sundekilde, Ulrik; Larsen, Lotte Bach; Bertram, Hanne Christine S.

    2013-01-01

    Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality...... and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR)-based metabolomics trends in milk research, including...... applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers...

  11. Autodyne detector for acoustic NMR

    International Nuclear Information System (INIS)

    A high-sensitivity circuit for investigating direct acoustic nuclear magnetic resonance is described. The circuit contains an autodyne, an acoustic resonator, a calibrator, and a rectifier. To increase the generation stability, the circuit uses parametric negative feedback from the rectifier output to the autodyne amplifier. The autodyne uses a differential amplifier assembled on field transistors and acting as an amplifier and summator simultaneously. Besides, both halves of the amplifier have a capacitive current coupling, which reduces the noise level and increases the stability of circuit operation. The circuit described was used to determine the coefficient of resonance absorption of ultrasound by the nuclear-spin system of 75As. During the measurements the power introduced into the specimen was equal to 1 ?w. The circuit can readily be adapted for investigating the ordinary NMR

  12. Chiral discrimination in NMR spectroscopy.

    Science.gov (United States)

    Buckingham, A David

    2015-11-01

    Nuclear magnetic resonance is the most important form of molecular spectroscopy in chemistry and biochemistry but it is normally blind to chirality. It was predicted in 2004 that precessing nuclear spins in chiral molecules in a liquid in a strong magnetic field induce a rotating electric polarization that is of opposite sign for enantiomers. This polarization arises from the distortion of the electronic structure by the nuclear magnetic moment in the presence of the strong magnetic field and is equivalent to the linear effect of an electric field on the nuclear shielding tensor. The polarization is strongly enhanced in dipolar molecules through the partial orientation of the permanent dipole through the antisymmetric part of the nuclear magnetic shielding tensor. Alternatively, an applied electric field will induce a chirally sensitive magnetization perpendicular to the field and to the nuclear spin. Progress towards the experimental realization of chiral discrimination by NMR is assessed. PMID:26537400

  13. Parameter libraries

    International Nuclear Information System (INIS)

    Full text: Recommendations for future parameter libraries: 1. The existing parameter library should be updated, extended and corrected regularly based on the latest measurements, evaluations and theoretical studies by international collaborations (through CRPs or other activities). What parts of the parameter library to be updated and corrected should be taken into account in setting up the activity. 2. New parameters should be added according to the new mechanisms or approaches introduced in the nuclear reaction model code and the updated results from nuclear theory studies. 3. Information on the range of parameters, especially for nuclear reaction model parameters used for covariance evaluations and sensitivity studies of nuclear data should be recommended. The information which can be used for this purpose should be considered based on the nuclear reaction models such like OM, DWBA, H-F and exciton model, etc. which are popular in the nuclear reaction model codes. 4. The model parameters (global and local) and related information for the unstable nuclei model calculations should be recommended and the uncertainties from the parameters for the model calculations of unstable nuclei should be studied and analyzed. 5. If some parameter systematics could be provided, it would help the nuclear data evaluators and nuclear data users to perform the model calculations. 6. CRPs and collaborations should be considered to address the above items. (author)

  14. sup 1 sup 1 B nutation NMR study of powdered borosilicates

    CERN Document Server

    Woo, A J; Han, D Y

    1998-01-01

    In this work, we applied the 1D sup 1 sup 1 B nutation NMR method for the analysis of the local structural environments in powdered borosilicates (SiO sub 2 -B sub 2 O sub 3). Spin dynamics during a rf irradiation for spin I=3/2 was analytically calculated with a density matrix formalism. Spectral simulation programs were written in MATLAB on a PC. Two borosilicates prepared by the sol-gel process at different stabilization temperature were used for the 1D sup 1 sup 1 B nutation NMR experiment. The sup 1 sup 1 B NMR parameters, quadrupole coupling constants (e sup 2 qQ/h) and asymmetry parameters (eta), for each borosilicate were extracted from the nonlinear least-squares fitting. The effects of heat treatments on the local structures of boron sites in borosilicates were discussed.

  15. Bituminous ore characterization by integrating low-field NMR with density and particle size distribution measurements

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) imaging is often used to determine the content of oil sands ore. However, it is difficult for current NMR spectrometers to differentiate bitumen spectra and clay-bound water signals. This paper provided details of a novel method for determining the fluid and solids content of oil sands using low-field NMR. The method involved the integration of a density measurement to an NMR algorithm combined with laboratory oil sands evaluations. Thawed raw oil sands samples were weighed and injected with nitrogen to calculate the gas occupied volume. An independent solid content estimate was made by measuring both the weight and the bulk density of an ore sample. The sample was then placed into an NMR spectrometer and exposed to different CPMG parameters. Bitumen and water content were determined using the NMR algorithm. Particle size distribution analysis using Dean-Stark extraction showed that the method correlated with the fast relaxation components of water spectra in both oil sands and water-saturated sand extracted from the ore. A vacuum saturation step was then followed by a centrifugal desaturation of the sand to irreducible saturation. The method was then tested with samples of 4 Athabasca oil sands. It was concluded that use of the new method will accelerate core analysis times

  16. Theoretical and experimental NMR studies on muscimol from fly agaric mushroom (Amanita muscaria).

    Science.gov (United States)

    Kupka, Teobald; Wieczorek, Piotr P

    2016-01-15

    In this article we report results of combined theoretical and experimental NMR studies on muscimol, the bioactive alkaloid from fly agaric mushroom (Amanita muscaria). The assignment of (1)H and (13)C NMR spectra of muscimol in DMSO-d6 was supported by additional two-dimensional heteronuclear correlated spectra (2D NMR) and gauge independent atomic orbital (GIAO) NMR calculations using density functional theory (DFT). The effect of solvent in theoretical calculations was included via polarized continuum model (PCM) and the hybrid three-parameter B3LYP density functional in combination with 6-311++G(3df,2pd) basis set enabled calculation of reliable structures of non-ionized (neutral) molecule and its NH and zwitterionic forms in the gas phase, chloroform, DMSO and water. GIAO NMR calculations, using equilibrium and rovibrationally averaged geometry, at B3LYP/6-31G* and B3LYP/aug-cc-pVTZ-J levels of theory provided muscimol nuclear magnetic shieldings. The theoretical proton and carbon chemical shifts were critically compared with experimental NMR spectra measured in DMSO. Our results provide useful information on its structure in solution. We believe that such data could improve the understanding of basic features of muscimol at atomistic level and provide another tool in studies related to GABA analogs. PMID:26312739

  17. Analysis of porous media and objects of cultural heritage by mobile NMR

    Energy Technology Data Exchange (ETDEWEB)

    Haber, Agnes

    2012-11-01

    Low-field NMR techniques are used to study porous system, from simple to complex structures, and objects of cultural heritage. It is shown that NMR relaxometry can be used to study the fluid dynamics inside a porous system. A simple theoretical model for multi-site relaxation exchange NMR is used to extract exchange kinetic parameters when applied on a model porous systems. It provides a first step towards the study of more complex systems, where continuous relaxation distributions are present, such as soil systems or building materials. Moisture migration is observed in the soil systems with the help of 1D and 2D NMR relaxometry methods. In case of the concrete samples, the difference in composition makes a significant difference in the ability of water uptake. The single-sided NMR sensor proves to be a useful tool for on-site measurements. This is very important also in the case of the cultural heritage objects, as most of the objects can not be moved out of their environment. Mobile NMR turns out to be a simple but reliable and powerful tool to investigate moisture distributions and pore structures in porous media as well as the conservation state and history of objects of cultural heritage.

  18. Analysis of porous media and objects of cultural heritage by mobile NMR

    International Nuclear Information System (INIS)

    Low-field NMR techniques are used to study porous system, from simple to complex structures, and objects of cultural heritage. It is shown that NMR relaxometry can be used to study the fluid dynamics inside a porous system. A simple theoretical model for multi-site relaxation exchange NMR is used to extract exchange kinetic parameters when applied on a model porous systems. It provides a first step towards the study of more complex systems, where continuous relaxation distributions are present, such as soil systems or building materials. Moisture migration is observed in the soil systems with the help of 1D and 2D NMR relaxometry methods. In case of the concrete samples, the difference in composition makes a significant difference in the ability of water uptake. The single-sided NMR sensor proves to be a useful tool for on-site measurements. This is very important also in the case of the cultural heritage objects, as most of the objects can not be moved out of their environment. Mobile NMR turns out to be a simple but reliable and powerful tool to investigate moisture distributions and pore structures in porous media as well as the conservation state and history of objects of cultural heritage.

  19. Theoretical and experimental NMR studies on muscimol from fly agaric mushroom (Amanita muscaria)

    Science.gov (United States)

    Kupka, Teobald; Wieczorek, Piotr P.

    2016-01-01

    In this article we report results of combined theoretical and experimental NMR studies on muscimol, the bioactive alkaloid from fly agaric mushroom (Amanita muscaria). The assignment of 1H and 13C NMR spectra of muscimol in DMSO-d6 was supported by additional two-dimensional heteronuclear correlated spectra (2D NMR) and gauge independent atomic orbital (GIAO) NMR calculations using density functional theory (DFT). The effect of solvent in theoretical calculations was included via polarized continuum model (PCM) and the hybrid three-parameter B3LYP density functional in combination with 6-311++G(3df,2pd) basis set enabled calculation of reliable structures of non-ionized (neutral) molecule and its NH and zwitterionic forms in the gas phase, chloroform, DMSO and water. GIAO NMR calculations, using equilibrium and rovibrationally averaged geometry, at B3LYP/6-31G* and B3LYP/aug-cc-pVTZ-J levels of theory provided muscimol nuclear magnetic shieldings. The theoretical proton and carbon chemical shifts were critically compared with experimental NMR spectra measured in DMSO. Our results provide useful information on its structure in solution. We believe that such data could improve the understanding of basic features of muscimol at atomistic level and provide another tool in studies related to GABA analogs.

  20. Non-uniform sampling of NMR relaxation data

    DEFF Research Database (Denmark)

    Linnet, Troels E; Teilum, Kaare

    2016-01-01

    The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors in the...... extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of (15)N Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion datasets for four different proteins and performing a full data analysis of the resulting non-uniform sampled datasets, we have compared the performance of...

  1. NMR in solid ionic and nanoionics

    International Nuclear Information System (INIS)

    Full text: Nuclear Magnetic Resonance (NMR) is a spectroscopic technique which employs magnetic nuclei to study, among others, the dynamics of condensed matter at the atomic level. Thus, NMR has been and still is a successful instrument in the research field of solid electrolytes also known as solid ionics. This paper presents the typical NMR experiments performed in solid ionics together with some examples from nanoionics. The experiments to be discussed comprise: (i) measurements of the diffusion coefficient employing the pulsed-field gradient and the static fringe-field method; (ii) the experimentally related NMR imaging; (iii) double resonance experiments like spin-echo double resonance (SEDOR) and two-dimensional Fourier transform NMR (2D-FT NMR); (iv) various types of nuclear relaxation, in particular spin-lattice relaxation. The NMR techniques yield information on topics like the following: type and number of mobile atoms and defects, diffusion pathways (e.g. dimensionality restrictions), atomic jump frequencies, activation energy and activation volume of these movements, diffusion coefficient with activation energy and prefactor, correlation effects in atomic movements, space correlation factor, cooperative phenomena, symmetry of atomic sites, behavior at phase transitions. These applications will be illustrated by giving examples from crystals, glasses, and polymers. (author)

  2. Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds

    OpenAIRE

    Perić, Berislav; Gautier, Régis; Pickard, Chris,; Bosiočić, Marko; Grbić, Mihael,; Požek, Miroslav

    2014-01-01

    : Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-sta...

  3. Median Modified Wiener Filter for nonlinear adaptive spatial denoising of protein NMR multidimensional spectra

    KAUST Repository

    Cannistraci, Carlo Vittorio

    2015-01-26

    Denoising multidimensional NMR-spectra is a fundamental step in NMR protein structure determination. The state-of-the-art method uses wavelet-denoising, which may suffer when applied to non-stationary signals affected by Gaussian-white-noise mixed with strong impulsive artifacts, like those in multi-dimensional NMR-spectra. Regrettably, Wavelet\\'s performance depends on a combinatorial search of wavelet shapes and parameters; and multi-dimensional extension of wavelet-denoising is highly non-trivial, which hampers its application to multidimensional NMR-spectra. Here, we endorse a diverse philosophy of denoising NMR-spectra: less is more! We consider spatial filters that have only one parameter to tune: the window-size. We propose, for the first time, the 3D extension of the median-modified-Wiener-filter (MMWF), an adaptive variant of the median-filter, and also its novel variation named MMWF*. We test the proposed filters and the Wiener-filter, an adaptive variant of the mean-filter, on a benchmark set that contains 16 two-dimensional and three-dimensional NMR-spectra extracted from eight proteins. Our results demonstrate that the adaptive spatial filters significantly outperform their non-adaptive versions. The performance of the new MMWF* on 2D/3D-spectra is even better than wavelet-denoising. Noticeably, MMWF* produces stable high performance almost invariant for diverse window-size settings: this signifies a consistent advantage in the implementation of automatic pipelines for protein NMR-spectra analysis.

  4. Time domain NMR applied to food products

    OpenAIRE

    Van Duynhoven, J.; Voda, A.; Witek, M.M.; As, H. van

    2010-01-01

    Time-domain NMR is being used throughout all areas of food science and technology. A wide range of one- and two-dimensional relaxometric and diffusometric applications have been implemented on cost-effective, robust and easy-to-use benchtop NMR equipment. Time-domain NMR applications do not only cover research and development but also quality and process control in the food supply chain. Here the opportunity to further downsize and tailor equipment has allowed for “mobile” sensor applications...

  5. Probing porous media with gas diffusion NMR

    Science.gov (United States)

    Mair, R. W.; Wong, G. P.; Hoffmann, D.; Hurlimann, M. D.; Patz, S.; Schwartz, L. M.; Walsworth, R. L.

    1999-01-01

    We show that gas diffusion nuclear magnetic resonance (GD-NMR) provides a powerful technique for probing the structure of porous media. In random packs of glass beads, using both laser-polarized and thermally polarized xenon gas, we find that GD-NMR can accurately measure the pore space surface-area-to-volume ratio, S/V rho, and the tortuosity, alpha (the latter quantity being directly related to the system's transport properties). We also show that GD-NMR provides a good measure of the tortuosity of sandstone and complex carbonate rocks.

  6. 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.

  7. Scalar operators in solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Boqin

    1991-11-01

    Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.

  8. Resistive NMR of brain stem gliomas

    International Nuclear Information System (INIS)

    The NMR and CT findings in 22 patients with primary brain stem tumors were compared to determine the value of each study in identifying, and delineating the extent and relationships of the tumor to brain anatomy. NMR was found to be distinctly superior to CT in showing involvement of the medulla and upper cervical cord. NMR eliminates the need for intrathecal enhanced metrizamide CT, and in the future should be the only initial diagnostic test needed for the evaluation of intrinsic brain stem tumors. (orig.)

  9. NMR imaging of the brain: initial impressions

    International Nuclear Information System (INIS)

    An NMR imaging system designed and built by Thorn-EMI Ltd was installed at Hammersmith Hospital in March 1981. In the first year of operation 180 patients and 40 volunteers have had cranial examinations and initial impressions bases on this experience are presented. Patients with a wide variety of neurological diseases have been studied to provide a basis for diagnostic interpretation, to define distinctive features, and to evaluate different types of scanning sequences. NMR imaging appears to be of considerable value in neurological diagnosis and has a number of advantages over CT. The detailed evaluation of NMR imaging will require much more work but the initial results are very promising

  10. Graphical programming for broadband pulse NMR spectroscopy

    International Nuclear Information System (INIS)

    In a broadband pulsed nuclear magnetic resonance (NMR) spectrometer we often need to sweep the excitation frequency over a wide range, and acquire the spin echo components in quadrature for further spectral analysis. Computer languages such as C or Pascal have been traditionally applied to the development of software control of laboratory equipment, and consequently, the automatization of NMR experiments. However, the use of graphical languages have proved to be a flexible and convenient way for experiment and data acquisition control. In our application we use the graphical language Labview for the automatic control of a broadband pulse NMR spectrometer, dedicated to the study of magnetic metal systems. (author)

  11. Introduction to some basic aspects of NMR

    International Nuclear Information System (INIS)

    The principal interactions are reviewed that are experienced by nuclear spins making magnetic resonance feasible and which disturb it in a way that gives access to the properties of bulk matter. The interactions leading to NMR include Zeeman interaction, dipole-dipole interactions, and exchange interactions. Spin-lattice relaxation relevant to NMR is revisited next. It is followed by an overview of spin temperature. Finally, the care of periodic Hamiltonian is discussed in detail as another contribution to NMR. (R.P.) 48 refs., 12 figs

  12. Assessment of structural changes of human teeth by low-field nuclear magnetic resonance (NMR)

    International Nuclear Information System (INIS)

    A technique of low-field pulsed proton nuclear magnetic resonance (NMR) spin relaxation is described for assessment of age-related structural changes (dentin and pulp) of human teeth in vitro. The technique involves spin–spin relaxation measurement and inversion spin–spin spectral analysis methods. The spin–spin relaxation decay curve is converted into a T2 distribution spectrum by a sum of single exponential decays. The NMR spectra from the extracted dentin-portion-only and dental pulp-cells-only were compared with the whole extracted teeth spectra, for the dentin and pulp peak assignments. While dentin and pulp are highly significant parameters in determining tooth quality, variations in these parameters with age can be used as an effective tool for estimating tooth quality. Here we propose an NMR calibration method—the ratio of the amount of dentin to the amount of pulp obtained from NMR T2 distribution spectra can be used for measuring the age-related structural changes in teeth while eliminating any variations in size of teeth. Eight teeth (third molars) extracted from humans, aged among 17–67 years old, were tested in this study. It is found that the intensity ratio of dentin to pulp sensitively changes from 0.48 to 3.2 approaching a linear growth with age. This indicates that age-related structural changes in human teeth can be detected using the low-field NMR technique

  13. Numerical simulation of ( T 2, T 1) 2D NMR and fluid responses

    Science.gov (United States)

    Tan, Mao-Jin; Zou, You-Long; Zhang, Jin-Yan; Zhao, Xin

    2012-12-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology is limited for fluid typing, while two-dimensional nuclear magnetic resonance (2D NMR) logging can provide more parameters including longitudinal relaxation time ( T 1) and transverse relaxation time ( T 2) relative to fluid types in porous media. Based on the 2D NMR relaxation mechanism in a gradient magnetic field, echo train simulation and 2D NMR inversion are discussed in detail. For 2D NMR inversion, a hybrid inversion method is proposed based on the damping least squares method (LSQR) and an improved truncated singular value decomposition (TSVD) algorithm. A series of spin echoes are first simulated with multiple waiting times ( T W s) in a gradient magnetic field for given fluid models and these synthesized echo trains are inverted by the hybrid method. The inversion results are consistent with given models. Moreover, the numerical simulation of various fluid models such as the gas-water, light oil-water, and vicious oil-water models were carried out with different echo spacings ( T E s) and T W s by this hybrid method. Finally, the influences of different signal-to-noise ratios (SNRs) on inversion results in various fluid models are studied. The numerical simulations show that the hybrid method and optimized observation parameters are applicable to fluid typing of gas-water and oil-water models.

  14. Assessment of structural changes of human teeth by low-field nuclear magnetic resonance (NMR)

    Science.gov (United States)

    Ni, Qingwen; Chen, Shuo

    2010-01-01

    A technique of low-field pulsed proton nuclear magnetic resonance (NMR) spin relaxation is described for assessment of age-related structural changes (dentin and pulp) of human teeth in vitro. The technique involves spin-spin relaxation measurement and inversion spin-spin spectral analysis methods. The spin-spin relaxation decay curve is converted into a T2 distribution spectrum by a sum of single exponential decays. The NMR spectra from the extracted dentin-portion-only and dental pulp-cells-only were compared with the whole extracted teeth spectra, for the dentin and pulp peak assignments. While dentin and pulp are highly significant parameters in determining tooth quality, variations in these parameters with age can be used as an effective tool for estimating tooth quality. Here we propose an NMR calibration method—the ratio of the amount of dentin to the amount of pulp obtained from NMR T2 distribution spectra can be used for measuring the age-related structural changes in teeth while eliminating any variations in size of teeth. Eight teeth (third molars) extracted from humans, aged among 17-67 years old, were tested in this study. It is found that the intensity ratio of dentin to pulp sensitively changes from 0.48 to 3.2 approaching a linear growth with age. This indicates that age-related structural changes in human teeth can be detected using the low-field NMR technique.

  15. Magnetic and high-frequency EPR studies of an octahedral Fe(III) compound with unusual zero-field splitting parameters.

    Science.gov (United States)

    Solano-Peralta, Alejandro; Saucedo-Vázquez, Juan P; Escudero, Roberto; Höpfl, Herbert; El-Mkami, Hassane; Smith, Graham M; Sosa-Torres, Martha E

    2009-03-01

    Temperature-dependent magnetic susceptibility and multi-frequency EPR (9.4, 34.5, 94 and 188 GHz) spectroscopic measurements have been carried out together with an X-ray study at 100 K to study [Fe(DMSO)(6)](NO(3))(3). The iron(III) ion remains high-spin (S = 5/2) in the temperature range studied, therefore, the EPR data were interpreted using the conventional S = 5/2 spin Hamiltonian. A full analysis of EPR spectra at 95 GHz of a powdered sample at 290 K revealed that they are extremely sensitive to D and E values. The zfs parameters were precisely determined: D = + 0.1730 cm(-1), E = 0.00 cm(-1) and lambda = |E/D| = 0.00. A sequence of the spectra neatly shows that the compound has a clear magnetic dependence on temperature. The study at 5 K, showed that the zfs parameters increase: D = + 0.1970 cm(-1), E = 0.017 cm(-1) and lambda = |E/D| = 0.086. These data indicate that as the temperature decreases the D tensor increases slightly showing an increase in the rhombicity. These results confirm that |2D| is congruent to h nu at X-band in this case. Additionally, it has been shown by X-ray crystal analysis of [Fe(DMSO)(6)](NO(3))(3) at 100 K that this is involved in a hydrogen bonding network, consisting of C-H...O interactions between the nitrate anions and the methyl groups of the coordinated DMSO molecules, thus suggesting that the differences found in the spectroscopic parameters D and E at different temperatures must be due to these supramolecular interactions. PMID:19421612

  16. Solid-state NMR of polymers

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) spectroscopy has emerged as one of the most important methods for the solid-state characterisation of polymers. The popularity of NMR is due to the fact that many molecular level features can be measured from the NMR spectra, including the polymer chain conformation, the morphology and the dynamics. The spectral features and relaxation times are affected by local interactions, so they provide information about the structure of polymers on a length scale (2-200 A) that is difficult to measure by other methods. In favourable cases, the NMR experiments provide a molecular-level explanation for the transitions observed by differential scanning calorimetry (DSC) and other methods, and the NMR properties can often be related to the bulk properties. Solid-state NMR has long been of interest in polymer science, and the first solid-state NMR studies of polymers were reported approximately a year after the discovery of nuclear resonance in bulk matter. It was reported in this initial study that the proton line width for natural rubber at room temperature is more like that of a mobile liquid than of a solid, but that the resonance broadens near the glass transition temperature (Tg). This was recognised as being related to a change in chain dynamics above and below the Tg. NMR methods developed rapidly after these initial observations, first for polymers in solution and, more recently, for polymers in the solid-state. Solid-state NMR studies of polymers were developed more slowly than their solution-state counterparts because solid-state NMR requires more specialised equipment. Solid-state NMR is now such an important tool that most modern spectrometers are capable of performing these studies. The interest in the NMR of solid polymers is due in part to the fact that most polymers are used in the solid state, and in many cases the NMR properties can be directly related to the macroscopic properties. Polymers have restricted mobility in solids, for example, and the chemical shifts can be directly related to the chain conformation. Solid-state NMR is also an efficient way to monitor the reactivity of polymers, since chemical changes often result in large spectral changes. The relaxation times in solids depend not only on the chain dynamics, but also on the morphology over a length scale of 20-200 A. NMR has been extensively used to measure the length scale of mixing in blends and multiphase polymers, and the domain sizes in semicrystalline polymers. Solid-state NMR methods have been greatly expanded with the introduction of multi-dimensional NMR. These studies have led to a molecular level understanding of the dynamics traditionally observed by dielectric and dynamic-mechanical spectroscopy, and a better understanding of the relationship between polymer morphology and macroscopic properties

  17. Lipid Dynamics Studied by Calculation of 31P Solid-State NMR Spectra Using Ensembles from Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Hansen, Sara Krogh; Vestergaard, Mikkel; Thøgersen, Lea; Schiøtt, Birgit; Nielsen, Niels Christian; Vosegaard, Thomas

    2014-01-01

    We present a method to calculate 31P solid-state NMR spectra based on the dynamic input from extended molecular dynamics (MD) simulations. The dynamic information confered by MD simulations is much more comprehensive than the information provided by traditional NMR dynamics models based on, for example, order parameters. Therefore, valuable insight into the dynamics of biomolecules may be achieved by the present method. We have applied this method to study the dynamics of lipid bilayers containi...

  18. NMR study of the ma?etic metals cobalt and nickel in the paramagnetic and ferromagnetic states

    International Nuclear Information System (INIS)

    Results of NMR measurements in the 3d - electron transition metals nickel and cobalt are presented. Measurements were performed in the paramagnetic and ferromagnetic states, as close as possible, experimentally to the Curie transition temperature Tsub(c). It is shown that NMR is a powerful tool to study the behavior of magnetic metals. The developed experimental technique enables measurements in an extended temperature range in metals with strongly temperature dependent parameters. (B.G.)

  19. The Corset Effect, Field-Cycling NMR Relaxometry, Transverse NMR Relaxation, Field-Gradient NMR Diffusometry, and Incoherent Neutron Scattering

    OpenAIRE

    Kimmich, Rainer; Fatkullin, Nail

    2010-01-01

    The corset effect is an experimentally established dynamic confinement phenomenon first observed by field-cycling NMR relaxometry and transverse NMR relaxation in polymer melts in pores with dimensions ranging from a few nanometers up to 0.06 micrometers or even more. The techniques employed are specifically sensitive to rotational fluctuations of polymer segments. It will be shown that neutron scattering and other methods probing translational fluctuations are not suitable ...

  20. Stereochemistry of tropane N-oxide derivatives studied by experimental and theoretical NMR.

    Czech Academy of Sciences Publication Activity Database

    Pohl, Radek; Dra?ínský, Martin; Slav?tínská, Lenka; Bud?šínský, Miloš

    Frankfurt am Main : Cuvillier Verlag Göttingen, 2011. s. 279-279. [EUROMAR 2011. Magnetic Resonance Conference. 21.08.2011-25.08.2011, Frankfurt am Main] Institutional research plan: CEZ:AV0Z40550506 Keywords : stereochemistry * calculation of the NMR parameters * DFT GIAO Subject RIV: CC - Organic Chemistry

  1. Structural 1H NMR analysis of asphaltic-resinous petroleum fractions

    International Nuclear Information System (INIS)

    A mathematical analysis is given of NMR spectra of asphaltic-resinous petroleum fractions. The method was used in evaluating the basic structural parameters of the Romashkino oil. The method is not demanding on experiments and is recommended for permanent use in evaluating raw materials for technological processing. (M.K.)

  2. NMR Analysis of Unknowns: An Introduction to 2D NMR Spectroscopy

    Science.gov (United States)

    Alonso, David E.; Warren, Steven E.

    2005-01-01

    A study combined 1D (one-dimensional) and 2D (two-dimensional) NMR spectroscopy to solve structural organic problems of three unknowns, which include 2-, 3-, and 4-heptanone. Results showed [to the first power]H NMR and [to the thirteenth power]C NMR signal assignments for 2- and 3-heptanone were more challenging than for 4-heptanone owing to the…

  3. Indicator dilution approach to NMR signal-flow curves

    International Nuclear Information System (INIS)

    An indicator dilution model for the dependence of NMR signal on flow rate is presented. The model explains the enhancement in NMR signal observed at low flow rates and the reduction in NMR signal at high flow rates. It also produces an excellent fit to original NMR flow data, which are also presented. (author)

  4. Structural investigations of substituted indolizine derivatives by NMR studies

    International Nuclear Information System (INIS)

    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 1H-NMR, 13C-NMR and 2D NMR (GCOSY, GHMBC and GHMQC spectra). (authors)

  5. NMR study of Albemoschus esculentus characterization

    Energy Technology Data Exchange (ETDEWEB)

    Bathista, A.L.B.S; Silva, E.O.; Nogueira, Jose de S. [Mato Grosso Univ., Cuiaba, MT (Brazil). Dept. de Fisica]. E-mail: nogueira@cpd.ufmt.br; Tavares, M.I.B. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Macromoleculas]. E-mail: mibt@ima.ufrj.br

    2001-07-01

    The investigation of the main compounds presented in the Albemoschus esculentus has been carried out employing nuclear magnetic resonance spectroscopy (NMR), using solution and solid state NMR when it one was necessary. The evaluation of NMR data allowed us to characterize the main type of components presented in this kind of sample. It was necessary to use a total information from solid state NMR and also the solution response. From these information we could get that four main components were presented in this sample. One in the shell, that is cellulose, another one between the shell and seeds that is a polysaccharide and in the seed two components were found one is a starch and the second one is an oil, a triacylglycerol. These components are responsible by its physical chemistry properties. (author)

  6. NMR study of Albemoschus esculentus characterization

    International Nuclear Information System (INIS)

    The investigation of the main compounds presented in the Albemoschus esculentus has been carried out employing nuclear magnetic resonance spectroscopy (NMR), using solution and solid state NMR when it one was necessary. The evaluation of NMR data allowed us to characterize the main type of components presented in this kind of sample. It was necessary to use a total information from solid state NMR and also the solution response. From these information we could get that four main components were presented in this sample. One in the shell, that is cellulose, another one between the shell and seeds that is a polysaccharide and in the seed two components were found one is a starch and the second one is an oil, a triacylglycerol. These components are responsible by its physical chemistry properties. (author)

  7. Bayesian Peak Picking for NMR Spectra

    KAUST Repository

    Cheng, Yichen

    2014-02-01

    Protein structure determination is a very important topic in structural genomics, which helps people to understand varieties of biological functions such as protein-protein interactions, protein–DNA interactions and so on. Nowadays, nuclear magnetic resonance (NMR) has often been used to determine the three-dimensional structures of protein in vivo. This study aims to automate the peak picking step, the most important and tricky step in NMR structure determination. We propose to model the NMR spectrum by a mixture of bivariate Gaussian densities and use the stochastic approximation Monte Carlo algorithm as the computational tool to solve the problem. Under the Bayesian framework, the peak picking problem is casted as a variable selection problem. The proposed method can automatically distinguish true peaks from false ones without preprocessing the data. To the best of our knowledge, this is the first effort in the literature that tackles the peak picking problem for NMR spectrum data using Bayesian method.

  8. Sodium NMR/MRI for anisotropic systems.

    Science.gov (United States)

    Eliav, U; Navon, G

    2016-02-01

    Sodium ((23) Na) plays a central role in many physiological processes, and its high NMR sensitivity makes it an attractive nucleus for biomedical NMR and MRI research. Many biological tissues contain structures such as fibers and membranes that impose anisotropic translational and rotational motions on the sodium ions. Translational motion can be studied by diffusion measurements. Anisotropic rotational motion results in non-vanishing quadrupolar interaction that it is best studied by exploiting multiple quantum coherences for (23) Na NMR spectroscopy and MRI. The current review covers the application of the various NMR techniques to the study of (23) Na in anisotropic compartments in cartilage, tendon, intervertebral discs, red blood cells, nervous system and muscles. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26105084

  9. NMR spectroscopy of biofluids and extracts.

    Science.gov (United States)

    Le Gall, Gwénaëlle

    2015-01-01

    Metabonomics-based proton nuclear magnetic resonance ((1)H NMR) spectroscopy is a cross-disciplinary science that overlaps with analytical chemistry, biology, and statistical analysis. Applying (1)H NMR on cell extracts provides a rapid and comprehensive screening of the most abundant metabolites allowing the quantitation of typically 20-70 compounds including amino and organic acids, sugars, amines, nucleosides, phenolic compounds, osmolytes, and lipids produced at sublevel millimolar concentrations. The method is particularly suited for high-throughput analysis (up to 100 samples/24 h), and the powerful structural elucidation of NMR is a great asset for the identification of unknown compounds. This chapter describes procedures for recording metabolite profiles using (1)H NMR, depicts the preprocessing steps leading to data analysis, and presents methods of metabolite identification in spectral profiles of extracts from plants, food, microbes, and mammalian systems. PMID:25677144

  10. NMR and optical studies of piezoelectric polymers

    International Nuclear Information System (INIS)

    Progress is reported in several areas dealing with piezoelectric (electroactive) polymers (mostly vinylidene fluoride, trifluoroethylene, copolymers, PVF2) and liquid crystals. Optical studies, neutron scattering, NMR, thermal, theory and modeling were done

  11. NMR in the SPINE Structural Proteomics project.

    Science.gov (United States)

    Ab, E; Atkinson, A R; Banci, L; Bertini, I; Ciofi-Baffoni, S; Brunner, K; Diercks, T; Dötsch, V; Engelke, F; Folkers, G E; Griesinger, C; Gronwald, W; Günther, U; Habeck, M; de Jong, R N; Kalbitzer, H R; Kieffer, B; Leeflang, B R; Loss, S; Luchinat, C; Marquardsen, T; Moskau, D; Neidig, K P; Nilges, M; Piccioli, M; Pierattelli, R; Rieping, W; Schippmann, T; Schwalbe, H; Travé, G; Trenner, J; Wöhnert, J; Zweckstetter, M; Kaptein, R

    2006-10-01

    This paper describes the developments, role and contributions of the NMR spectroscopy groups in the Structural Proteomics In Europe (SPINE) consortium. Focusing on the development of high-throughput (HTP) pipelines for NMR structure determinations of proteins, all aspects from sample preparation, data acquisition, data processing, data analysis to structure determination have been improved with respect to sensitivity, automation, speed, robustness and validation. Specific highlights are protonless (13)C-direct detection methods and inferential structure determinations (ISD). In addition to technological improvements, these methods have been applied to deliver over 60 NMR structures of proteins, among which are five that failed to crystallize. The inclusion of NMR spectroscopy in structural proteomics pipelines improves the success rate for protein structure determinations. PMID:17001092

  12. Introduction to NMR Quantum Information Processing

    CERN Document Server

    Laflamme, R; Cory, D G; Fortunato, E M; Havel, T F; Miquel, C; Martínez, R; Negrevergne, C; Ortiz, G; Pravia, M A; Sharf, Y; Sinha, S; Somma, R D; Viola, L

    2002-01-01

    After a general introduction to nuclear magnetic resonance (NMR), we give the basics of implementing quantum algorithms. We describe how qubits are realized and controlled with RF pulses, their internal interactions, and gradient fields. A peculiarity of NMR is that the internal interactions (given by the internal Hamiltonian) are always on. We discuss how they can be effectively turned off with the help of a standard NMR method called ``refocusing''. Liquid state NMR experiments are done at room temperature, leading to an extremely mixed (that is, nearly random) initial state. Despite this high degree of randomness, it is possible to investigate QIP because the relaxation time (the time scale over which useful signal from a computation is lost) is sufficiently long. We explain how this feature leads to the crucial ability of simulating a pure (non-random) state by using ``pseudopure'' states. We discuss how the ``answer'' provided by a computation is obtained by measurement and how this measurement differs f...

  13. Fast and Ultrafast quantitative 2D NMR

    International Nuclear Information System (INIS)

    Two dimensional (2D) NMR shows a high potential for quantitative analysis of complex mixtures, as it considerably reduces spectral overlap. However, two major aspects should be considered to obtain accurate and precise results by quantitative 2D NMR. First, the peak volumes depend on a number of factors which require the use of calibration or correction strategies. Second, the quantitative performances -and therefore the application- of 2D NMR are limited by long experiment durations. However, the recent development of meticulous analytical procedures, associated with novel methodological developments, lead to repeatable and reproducible results in a reasonable time, compatible with routine analysis. This article highlights some of the most recent developments in this area, illustrated by their application to complex samples where 1D NMR fails due to spectral overlap. (authors)

  14. NMR studies of cerebral metabolism in vivo

    International Nuclear Information System (INIS)

    The nature and extent of the potential synergism between PET and NMR methods is not yet well appreciated in the biomedical community. The long-range interest of medical neurobiology will be well served by efforts of PET and NMR scientists to follow each others' work so that opportunities for productive interchange can be efficiently exploited. Appreciation of the synergism by the rest of the biomedical community will follow naturally. PET is said by the people doing it to be still in its infancy, for they are more concerned with advancing their discipline than with admiring its already impressive achievements. On the scale of the same developmental metaphor, many NMR methods for studying the living human brain are still in utero. The best way to provide the reader a sense of the current status and future course of NMR research in medical neurobiology is by discussion of published in vivo studies. Such a discussion, adapted from another article is what follows

  15. NMR study of hydride systems

    International Nuclear Information System (INIS)

    The hydrides of thorium (ThH2, Th4H15 and Th4D15) and the intermetallic compound system (Zr(Vsub(1-x)Cosub(x))2 and its hydrides were investigated using the nuclear magnetic resonance (NMR) technique. From the results for the thorium hydride samples it was concluded that the density of states at the Fermi level n(Esub(f)) is higher in Th4H15 than in ThH2; there is an indirect reaction between the protons and the d electrons belonging to the Th atoms in Th4H15; n(E) has a sharp structure near Esub(f). It was also found that the hydrogen diffusion mechanism changes with temperature. From the results for the intermetallic compound system conclusions were drawn concerning variations in the electronic structure, which explain the behavior of the system. In hydrogen diffusion studies in several samples it was found that Co atoms slow the diffusion rate. Quadrupole spectra obtained at low temperatures show that the H atoms preferably occupy tetrahedral sites formed by three V atoms and one Z atom. (H.K.)

  16. NMR Quantum Information Processing and Entanglement

    CERN Document Server

    Laflamme, R; Negrevergne, C; Viola, L; Laflamme, Raymond; Cory, David G.; Negrevergne, Camille; Viola, Lorenza

    2001-01-01

    In this essay we discuss the issue of quantum information and recent nuclear magnetic resonance (NMR) experiments. We explain why these experiments should be regarded as quantum information processing (QIP) despite the fact that, in present liquid state NMR experiments, no entanglement is found. We comment on how these experiments contribute to the future of QIP and include a brief discussion on the origin of the power of quantum computers.

  17. Frontiers of NMR in Molecular Biology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-08-25

    NMR spectroscopy is expanding the horizons of structural biology by determining the structures and describing the dynamics of blobular proteins in aqueous solution, as well as other classes of proteins including membrane proteins and the polypeptides that form the aggregates diagnostic of prion and amyloid diseases. Significant results are also emerging on DNA and RNA oligomers and their complexes with proteins. This meeting focused attention on key structural questions emanating from molecular biology and how NMR spectroscopy can be used to answer them.

  18. Oriented solid-state NMR spectrosocpy

    DEFF Research Database (Denmark)

    Bertelsen, Kresten

    2010-01-01

    This thesis is concerned with driving forward oriented solid-state NMR spectroscopy as a viable technique for studying peptides in membrane bilayers. I will show that structural heterogeneity is an intrinsic part of the peptide/lipid system and that NMR can be used to characterize static and dynamic structural features of the peptides and its local surroundings. In fact one need to take into account the dynamical features of the system in order to correctly predict the structure from oriented so...

  19. 15N NMR spectroscopy of carbon azides

    International Nuclear Information System (INIS)

    The following triply 15N labelled azides CH3N3, C6H5N3, O2NC6H4N3, (O2N)3C6H2N3, NCN3, and (NCN3)3 were investigated by 15N NMR and partially by vibrational and 13C NMR spectroscopy. The signals of the ?- and ?-N atom show an overcrossing. 1J(15N-13C) is zero for the arylazides. (orig.)

  20. NMR of porous Bio-systems

    OpenAIRE

    Snaar, E.J.M.

    2002-01-01

    The structure and dynamics of water diffusion and -transport at a microscale in heterogeneous porous media have been investigated using various 1H NMR techniques. In particular in biological porous media the dynamics are usually very complex since it is intimately related to the microstructure (close environment). Fortunately, there is an almost endless variety of NMR pulse sequences available for measuring spin density, relaxation, and diffusion, although finding the most suitable sequence f...

  1. Applications of 1H-NMR relaxometry in experimental liver studies

    International Nuclear Information System (INIS)

    Purpose of this study was to investigate applications of proton nuclear magnetic resonance (1H-NMR) relaxometry in experimental medicine. Relaxometry was performed by measurements of spin-lattice (T1) and spin-spin (T2) relaxation time parameters on liver biopsies up to four hours after biopsy excision. Variations of relaxation times due to species and strain, different sample handling and different liver damage models, ethionine fatty liver and paracetamol liver necrosis, were investigated. Cell integrity effects were studied on homogenized liver samples. Relaxation time parameters, especially 'main' components T1A and T2A of biexponential model fit, were identified to react very sensitive after tissue damages as well as to cell viability. Thus, investigation of stored liver grafts was performed in order to evaluate the possibility of a rapid liver graft viability testing method for human liver transplantation surgery by 1H-NMR relaxometry. Another series of measurements was performed to investigate the applicability of isoflurane anesthesia for in vivo NMR experiments. This study proved the good appropriateness of isoflurane for that purpose provided that physiological monitoring and individual adjustment of anesthesia are performed. In these investigations it could be revealed that mainly T1A and T2A are influenced by tissue condition and that different information is inherent in these two parameters, with T2A reflecting tissue viability and changes of tissue conditions very sensitively but rather unspecifically in respect to the damage applied. Based on these results the following future applications of 1H-NMR relaxometry are suggested : (1) model investigations, (2) investigation of given pathologies, (3) investigation of basic requirements for in vivo NMR and (4) application in a liver graft viability testing protocol, which seems to be the most important future application of 1H-NMR relaxometry in medicine. (author)

  2. Multidimensional NMR spectroscopy in a single scan.

    Science.gov (United States)

    Gal, Maayan; Frydman, Lucio

    2015-11-01

    Multidimensional NMR has become one of the most widespread spectroscopic tools available to study diverse structural and functional aspects of organic and biomolecules. A main feature of multidimensional NMR is the relatively long acquisition times that these experiments demand. For decades, scientists have been working on a variety of alternatives that would enable NMR to overcome this limitation, and deliver its data in shorter acquisition times. Counting among these methodologies is the so-called ultrafast (UF) NMR approach, which in principle allows one to collect arbitrary multidimensional correlations in a single sub-second transient. By contrast to conventional acquisitions, a main feature of UF NMR is a spatiotemporal manipulation of the spins that imprints the chemical shift and/or J-coupling evolutions being sought, into a spatial pattern. Subsequent gradient-based manipulations enable the reading out of this information and its multidimensional correlation into patterns that are identical to those afforded by conventional techniques. The current review focuses on the fundamental principles of this spatiotemporal UF NMR manipulation, and on a few of the methodological extensions that this form of spectroscopy has undergone during the years. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26249041

  3. A microscale protein NMR sample screening pipeline

    International Nuclear Information System (INIS)

    As part of efforts to develop improved methods for NMR protein sample preparation and structure determination, the Northeast Structural Genomics Consortium (NESG) has implemented an NMR screening pipeline for protein target selection, construct optimization, and buffer optimization, incorporating efficient microscale NMR screening of proteins using a micro-cryoprobe. The process is feasible because the newest generation probe requires only small amounts of protein, typically 30-200 ?g in 8-35 ?l volume. Extensive automation has been made possible by the combination of database tools, mechanization of key process steps, and the use of a micro-cryoprobe that gives excellent data while requiring little optimization and manual setup. In this perspective, we describe the overall process used by the NESG for screening NMR samples as part of a sample optimization process, assessing optimal construct design and solution conditions, as well as for determining protein rotational correlation times in order to assess protein oligomerization states. Database infrastructure has been developed to allow for flexible implementation of new screening protocols and harvesting of the resulting output. The NESG micro NMR screening pipeline has also been used for detergent screening of membrane proteins. Descriptions of the individual steps in the NESG NMR sample design, production, and screening pipeline are presented in the format of a standard operating procedure.

  4. A new laboratory approach to shale analysis using NMR relaxometry

    Science.gov (United States)

    Washburn, Kathryn E.; Birdwell, Justin E.

    2013-01-01

    Low-field nuclear magnetic resonance (LF-NMR) relaxometry is a non-invasive technique commonly used to assess hydrogen-bearing fluids in petroleum reservoir rocks. Measurements made using LF-NMR provide information on rock porosity, pore-size distributions, and in some cases, fluid types and saturations (Timur, 1967; Kenyon et al., 1986; Straley et al., 1994; Brown, 2001; Jackson, 2001; Kleinberg, 2001; Hurlimann et al., 2002). Recent improvements in LF-NMR instrument electronics have made it possible to apply methods used to measure pore fluids to assess highly viscous and even solid organic phases within reservoir rocks. T1 and T2 relaxation responses behave very differently in solids and liquids; therefore the relationship between these two modes of relaxation can be used to differentiate organic phases in rock samples or to characterize extracted organic materials. Using T1-T2 correlation data, organic components present in shales, such as kerogen and bitumen, can be examined in laboratory relaxometry measurements. In addition, implementation of a solid-echo pulse sequence to refocus T2 relaxation caused by homonuclear dipolar coupling during correlation measurements allows for improved resolution of solid-phase protons. LF-NMR measurements of T1 and T2 relaxation time distributions were carried out on raw oil shale samples from the Eocene Green River Formation and pyrolyzed samples of these shales processed by hydrous pyrolysis and techniques meant to mimic surface and in-situ retorting. Samples processed using the In Situ Simulator approach ranged from bitumen and early oil generation through to depletion of petroleum generating potential. The standard T1-T2 correlation plots revealed distinct peaks representative of solid- and liquid-like organic phases; results on the pyrolyzed shales reflect changes that occurred during thermal processing. The solid-echo T1 and T2 measurements were used to improve assessment of the solid organic phases, specifically kerogen, thermally degraded kerogen, and char. Integrated peak areas from the LF-NMR results representative of kerogen and bitumen were found to be well correlated with S1 and S2 parameters from Rock-Eval programmed pyrolysis. This study demonstrates that LFNMR relaxometry can provide a wide range of information on shales and other reservoir rocks that goes well beyond porosity and pore-fluid analysis.

  5. Grape juice quality control by means of ¹H nmr spectroscopy and chemometric analyses

    Scientific Electronic Library Online (English)

    Caroline Werner Pereira da Silva, Grandizoli; Francinete Ramos, Campos; Fabio, Simonelli; Andersson, Barison.

    Full Text Available This work shows the application of ¹H NMR spectroscopy and chemometrics for quality control of grape juice. A wide range of quality assurance parameters were assessed by single ¹H NMR experiments acquired directly from juice. The investigation revealed that conditions and time of storage should be r [...] evised and indicated on all labels. The sterilization process of homemade grape juices was efficient, making it possible to store them for long periods without additives. Furthermore, chemometric analysis classified the best commercial grape juices to be similar to homemade grape juices, indicating that this approach can be used to determine the authenticity after adulteration.

  6. Grape juice quality control by means of ¹H nmr spectroscopy and chemometric analyses

    Directory of Open Access Journals (Sweden)

    Caroline Werner Pereira da Silva Grandizoli

    2014-01-01

    Full Text Available This work shows the application of ¹H NMR spectroscopy and chemometrics for quality control of grape juice. A wide range of quality assurance parameters were assessed by single ¹H NMR experiments acquired directly from juice. The investigation revealed that conditions and time of storage should be revised and indicated on all labels. The sterilization process of homemade grape juices was efficient, making it possible to store them for long periods without additives. Furthermore, chemometric analysis classified the best commercial grape juices to be similar to homemade grape juices, indicating that this approach can be used to determine the authenticity after adulteration.

  7. 93Nb and 17O NMR chemical shifts of niobiophosphate compounds.

    Science.gov (United States)

    Flambard, A; Montagne, L; Delevoye, L; Steuernagel, S

    2007-10-01

    Niobiophosphate compounds with a large range of niobium and oxygen environments were studied with (93)Nb and (17)O solid-state NMR. (93)Nb isotropic chemical shift of pure niobate Nb(ONb)(6), pure phosphate Nb(OP)(6) and mixed phosphate-niobate Nb(OP)(x)(ONb)((6-x)) (1NMR spectra of a series of enriched samples provided the chemical shift and quadrupolar parameters for 4 types of oxygen environment (P-O-P, P-O-Na, P-O-Nb and Nb-O-Nb). Finally, Nb-O-Nb sites were characterized by a large (17)O chemical shift anisotropy. PMID:17728114

  8. NMR-Based Multi Parametric Quality Control of Fruit Juices: SGF Profiling

    OpenAIRE

    Fang Fang; Anna Minoja; Ute C. Marx; Monika Mörtter; Hartmut Schäfer; Eberhard Humpfer; Susanne Koswig; Peter Rinke; Manfred Spraul; Birk Schütz

    2009-01-01

    With SGF Profiling™ we introduce an NMR-based screening method for the quality control of fruit juices. This method has been developed in a joint effort by Bruker BioSpin GmbH and SGF International e.V. The system is fully automated with respect to sample transfer, measurement, data analysis and reporting and is set up on an Avance 400 MHz flow-injection NMR spectrometer. For each fruit juice a multitude of parameters related to quality and authenticity are evaluated simultaneously from a sin...

  9. Validation of quantitative 1H NMR method for the analysis of pharmaceutical formulations

    International Nuclear Information System (INIS)

    The need for effective and reliable quality control in products from pharmaceutical industries renders the analyses of their active ingredients and constituents of great importance. This study presents the theoretical basis of ¹H NMR for quantitative analyses and an example of the method validation according to Resolution RE N. 899 by the Brazilian National Health Surveillance Agency (ANVISA), in which the compound paracetamol was the active ingredient. All evaluated parameters (selectivity, linearity, accuracy, repeatability and robustness) showed satisfactory results. It was concluded that a single NMR measurement provides structural and quantitative information of active components and excipients in the sample. (author)

  10. Solid-state 13C NMR spectroscopic, chemolytic and biological assessment of pretreated municipal solid waste

    OpenAIRE

    M. Pichler; Knicker, Heike; Kögel-Knabner, I.

    2001-01-01

    In Central Europe, composting and anaerobic digestion of municipal solid waste (MSW) is used as pretreatment before landfilling to reduce landfill emissions. MSW samples were analyzed before, during, and after pretreatment to assess the stability of the organic matter. Chemolytic, nuclear magnetic resonance (NMR) spectroscopic, and respiration parameters were correlated to evaluate a substitution of the time-consuming respiration analysis by chemical parameters. 13C cross polarization magic a...

  11. Superposition model analysis of the zero-field splitting parameters of Fe 3+ doped in TlInS 2 crystal - Low symmetry aspects

    Science.gov (United States)

    Gnutek, Pawe?; Aç?kgöz, Muhammed; Rudowicz, Czes?aw

    2010-07-01

    In this study, using the superposition model (SPM) and crystallographic data, the second- and fourth-rank zero-field splitting (ZFS) parameters (ZFSPs) have been calculated for Fe 3+ ions at two In sites in TlInS 2 single crystal. Since crystallographic data indicate C1 site symmetry, a full triclinic ZFS Hamiltonian has been employed. Model parameters were adjusted so to obtain best agreement between the SPM calculated ZFSPs and the second-rank ZFSPs measured by electron magnetic resonance (EMR). The effects of site symmetry on the theoretically predicted ZFSPs and interpretation of the available experimental ZFSPs have been considered. The experimental second-rank ZFSPs were obtained using approximated orthorhombic spin Hamiltonian. Hence, to facilitate comparison with the SPM calculated ZFSPs, the ascent in symmetry method has been applied to the crystallographic data to quantify the structural approximation from triclinic to orthorhombic and to tetragonal site symmetry. Our considerations provide additional structural information, especially concerning the low site symmetry aspects, pertinent for Fe 3+ impurity centers in TlInS 2 and related crystals. Our SPM analysis of ZFSPs indicates that satisfactory so tentative agreement can be achieved between the theoretical predictions and the experimentally measured values of the second-rank ZFSPs. The procedure proposed here may serve as a general framework for modelling of ZFSPs for other ion-host systems. More accurate modelling for Fe 3+ ions in TlInS 2 may be carried out when better quality EMR results taking into account the low symmetry effects in EMR spectra and the values of the fourth-rank ZFSPs become available. The results of SPM calculations support earlier suggestions that Fe 3+ ions substitute for In 3+ ions in TlInS 2.

  12. Single-sided NMR tomography

    Energy Technology Data Exchange (ETDEWEB)

    Perlo, J.F.

    2006-07-01

    MRI is one of the most powerful non-invasive imaging techniques. Its main advantage arises from the diversity of contrasts that can be used to enhance the discrimination of different regions in the object. In the last years special effort has been undertaken to achieve spatial localization with open systems instead of conventional closed geometries. However, the low and strongly inhomogeneous fields generated by open magnets had precluded the use of such systems. Two crucial points had been clearly identified; methods commonly used for imaging do not work in strongly inhomogeneous fields, and the extremely poor sensitivity, which extends the experimental times to impractical limits. In this thesis both points are addressed by new developments of both hardware and methodologies. One of the main needs for improving the signal-to-noise ratio was to have an analytical or numerical method to quantify it. The well known formulation for the signal-to-noise ratio obtained by Hoult et al. is not appropriate for single-sided NMR. In chapter 2 an expression for the SNR in strongly inhomogeneous field is derived. Furthermore, this expression is the product of terms that depend separately on the magnet, the rf coil, and the spectrometer capabilities. By means of that, different magnets and rf coils are discussed in details. Moreover, a fast and accurate numerical method to calculate magnetic fields based on the analogy of a magnetic dipole and a coil is presented. The combination of these numerical tools with experimental data has shown to be a tremendously useful approach during this thesis. (orig.)

  13. Single-sided NMR tomography

    International Nuclear Information System (INIS)

    MRI is one of the most powerful non-invasive imaging techniques. Its main advantage arises from the diversity of contrasts that can be used to enhance the discrimination of different regions in the object. In the last years special effort has been undertaken to achieve spatial localization with open systems instead of conventional closed geometries. However, the low and strongly inhomogeneous fields generated by open magnets had precluded the use of such systems. Two crucial points had been clearly identified; methods commonly used for imaging do not work in strongly inhomogeneous fields, and the extremely poor sensitivity, which extends the experimental times to impractical limits. In this thesis both points are addressed by new developments of both hardware and methodologies. One of the main needs for improving the signal-to-noise ratio was to have an analytical or numerical method to quantify it. The well known formulation for the signal-to-noise ratio obtained by Hoult et al. is not appropriate for single-sided NMR. In chapter 2 an expression for the SNR in strongly inhomogeneous field is derived. Furthermore, this expression is the product of terms that depend separately on the magnet, the rf coil, and the spectrometer capabilities. By means of that, different magnets and rf coils are discussed in details. Moreover, a fast and accurate numerical method to calculate magnetic fields based on the analogy of a magnetic dipole and a coil is presented. The combination of these numerical tools with experimental data has shown to be a tremendously useful approach during this thesis. (orig.)

  14. Molecular dynamics of solid cortisol studied by NMR

    Science.gov (United States)

    Andrew, E. R.

    Polycrystalline cortisol (hydrocortisone; 11?,17?,21-trihydroxy-4-preg- nene-3,20-dione; C21H30O5) has been investigated by continuous and pulse proton NMR methods between 78 and 400 K at Larmor frequencies of 7, 25 and 60 MHz. A reduced value of second moment was found above 90 K and is ascribed to reorientation of two methyl groups. A single asymmetric minimum was found in the temperature dependence of the spin-lattice relaxation times and this also is attributed to reorientation of two methyl groups. The asymmetry suggests an asymmetric distribution of correlation times of the motion. Using the Cole-Davidson distribution, the best computer fit yields the following parameters characterizing the motion: Ea = 11?8 ± 0?1 kJ mol-1, ?0 = 4?6 ± 0?4) x 10-13s, distribution parameter ? = 0?62.

  15. Quantitative Analysis of STD-NMR Spectra of Reversibly Forming Ligand-Receptor Complexes

    Science.gov (United States)

    Krishna, N. Rama; Jayalakshmi, V.

    We describe our work on the quantitative analysis of STD-NMR spectra of reversibly forming ligand-receptor complexes. This analysis is based on the theory of complete relaxation and conformational exchange matrix analysis of saturation transfer (CORCEMA-ST) effects. As part of this work, we have developed two separate versions of the CORCEMA-ST program. The first version predicts the expected STD intensities for a given model of a ligand-protein complex, and compares them quantitatively with the experimental data. This version is very useful for rapidly determining if a model for a given ligand-protein complex is compatible with the STD-NMR data obtained in solution. It is also useful in determining the optimal experimental conditions for undertaking the STD-NMR measurements on a given complex by computer simulations. In the second version of the CORCEMA-ST program, we have implemented a torsion angle refinement feature for the bound ligand within the protein binding pocket. In this approach, the global minimum for the bound ligand conformation is obtained by a hybrid structure refinement protocol involving CORCEMA-ST calculation of intensities and simulated annealing refinement of torsion angles of the bound ligand using STD-NMR intensities as experimental constraints to minimize a pseudo-energy function. This procedure is useful in refining and improving the initial models based on crystallography, computer docking, or other procedures to generate models for the bound ligand within the protein binding pocket compatible with solution STD-NMR data. In this chapter we describe the properties of the STD-NMR spectra, including the dependence of the intensities on various parameters. We also describe the results of the CORCEMA-ST analyses of experimental STD-NMR data on some ligand-protein complexes to illustrate the quantitative analysis of the data using this method. This CORCEMA-ST program is likely to be useful in structure-based drug design efforts.

  16. HPLC-NMR revisited: Using time-slice HPLC-SPE-NMR with database assisted dereplication

    DEFF Research Database (Denmark)

    Johansen, Kenneth; Wubshet, Sileshi Gizachew; Nyberg, Nils

    2013-01-01

    Time based trapping of chromatographically separated compounds on to solid-phase extraction cartridges (SPE) and subsequent elution to NMR-tubes was done to emulate the function of HPLC–NMR for dereplication purposes. Sufficient mass sensitivity was obtained by the use of a state-of-the-art HPLC...

  17. Use of NMR and NMR Prediction Software to Identify Components in Red Bull Energy Drinks

    Science.gov (United States)

    Simpson, Andre J.; Shirzadi, Azadeh; Burrow, Timothy E.; Dicks, Andrew P.; Lefebvre, Brent; Corrin, Tricia

    2009-01-01

    A laboratory experiment designed as part of an upper-level undergraduate analytical chemistry course is described. Students investigate two popular soft drinks (Red Bull Energy Drink and sugar-free Red Bull Energy Drink) by NMR spectroscopy. With assistance of modern NMR prediction software they identify and quantify major components in each…

  18. The NMR study of biologically active metallated alkanol ammoinium ionic liquids

    Science.gov (United States)

    Ushakov, I. A.; Voronov, V. K.; Adamovich, S. N.; Mirskov, R. G.; Mirskova, A. N.

    2016-01-01

    The 1H, 13C, 15N, and 111Cd NMR spectra of a series of metallated alkanol ammonium ionic liquids (MAIL) series [n N(CH2CH2OH;)3M]+ · mX-, where M = Cd, Mg, Zn, Fe, Rh; X = Cl, OOCCH3, obtained in a wide range of temperatures of the studied samples, have been analyzed. It is found that, under biomimetic conditions (H2O, 25 °C), the compounds studied exist as mono- bi- and the tricyclic structures, which are in equilibrium. Shift of the equilibrium depends upon nature of a metal and effects all the parameters of the NMR spectra. Peculiarities of ligand exchange, typical for the studied compounds, have been studied in a wide range of temperatures. It is found that the NMR data can be used to control structure of the compounds formed in the course of synthesis.

  19. Identifying Stereoisomers by ab-initio Calculation of Secondary Isotope Shifts on NMR Chemical Shieldings

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Böhm

    2014-04-01

    Full Text Available We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2Hethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

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

    Science.gov (United States)

    Falourd, Xavier; Natali, Francesca; Peters, Judith; Foucat, Loïc

    2014-01-01

    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.

  1. NMR-Based Multi Parametric Quality Control of Fruit Juices: SGF Profiling

    Directory of Open Access Journals (Sweden)

    Fang Fang

    2009-11-01

    Full Text Available With SGF Profiling™ we introduce an NMR-based screening method for the quality control of fruit juices. This method has been developed in a joint effort by Bruker BioSpin GmbH and SGF International e.V. The system is fully automated with respect to sample transfer, measurement, data analysis and reporting and is set up on an Avance 400 MHz flow-injection NMR spectrometer. For each fruit juice a multitude of parameters related to quality and authenticity are evaluated simultaneously from a single data set acquired within a few minutes. This multimarker/multi-aspect NMR screening approach features low cost-per-sample and is highly competitive with conventional and targeted fruit juice quality control methods.

  2. NMR Structural Study of the Prototropic Equilibrium in Solution of Schiff Bases as Model Compounds

    Directory of Open Access Journals (Sweden)

    David Ortegón-Reyna

    2013-12-01

    Full Text Available An NMR titration method has been used to simultaneously measure the acid dissociation constant (pKa and the intramolecular NHO prototropic constant ?KNHO on a set of Schiff bases. The model compounds were synthesized from benzylamine and substituted ortho-hydroxyaldehydes, appropriately substituted with electron-donating and electron-withdrawing groups to modulate the acidity of the intramolecular NHO hydrogen bond. The structure in solution was established by 1H-, 13C- and 15N-NMR spectroscopy. The physicochemical parameters of the intramolecular NHO hydrogen bond (pKa, ?KNHO and ??G° were obtained from 1H-NMR titration data and pH measurements. The Henderson–Hasselbalch data analysis indicated that the systems are weakly acidic, and the predominant NHO equilibrium was established using Polster–Lachmann ?-diagram analysis and Perrin model data linearization.

  3. AEM and NMR: Tools for the Future of Groundwater Management

    Science.gov (United States)

    Abraham, J. D.; Cannia, J. C.; Lawrie, K.

    2012-12-01

    Within the world, understanding groundwater resources and their management are growing in importance to society as groundwater resources are stressed by drought and continued development. To minimize conflicts, tools and techniques need to be applied to support knowledge-based decisions and management. Airborne electromagnetic (AEM) surveys provide high-quality subsurface data not available from any other source for building the complex hydrogeologic frameworks needed by water-resource managers for effective groundwater management. Traditionally, point data, such as borehole logs, borehole geophysics, surface geophysics, and aquifer tests were interpolated over long distances to create hydrogeologic frameworks. These methods have enjoyed a long history of being the best available technology to inform our understanding of groundwater and how it moves. The AEM techniques proivde pathway for geoscientists to follow to develop more accurate descriptions of the hydrogeological framework. However, the critical and challenging measurements in characterizing aquifers include effective porosity and hydraulic conductivity. These parameters are not reliable derived from AEM. Typically, values for effective porosity and hydraulic conductivity are derived by lithological comparisons with published data; direct measurements of hydraulic conductivity acquired by a few constant head aquifer tests or slug tests; and expensive and time consuming laboratory measurements of cores which can be biased by sampling and the difficulty of making measurements on unconsolidated materials. Aquifer tests are considered to be the best method to gather information on hydraulic conductivity but are rare because of cost and difficult logistics. Also they are unique in design and interpretation from site to site. Nuclear Magnetic Resonance (NMR) can provide a direct measurement of the presence of water in the pore space of aquifer materials. Detection and direct measurement is possible due to the nuclear magnetization of the hydrogen (protons) in the water. These measurements are the basis of the familiar MRI (magnetic resonance imaging) in medical applications. NMR is also widely used in logging applications within the petroleum industry. Effective porosity values were derived directly from the borehole and surface NMR data, and hydraulic conductivity values were calculated using empirical relationships calibrated and verified with few laboratory permeameter and aquifer tests. NMR provides measurements of the effective porosity and hydraulic conductivity at a resolution not possible using traditional methods. Unlike aquifer tests, NMR logs are not unique in design and are applied in similar fashion from borehole to borehole providing a standard way of measuring hydraulic properties. When the hydraulic properties from the NMR are integrated with hydrogeological framework interpretations of AEM data large areas can be characterized. This allows a much more robust method for conceptualizing groundwater models then simply using previously published data for assigning effective porosity and hydraulic conductivity. Examples from the North Platte River Basin in Nebraska and the Murray Darling Basin of Australia illustrate that borehole and surface NMR allows superior, rapid measurements of the complexities of aquifers within when integrated with AEM.

  4. Microscopic origins of the zero-field splitting parameters for {sup 6}S(3d{sup 5}) state ions at tetragonal symmetry crystal field

    Energy Technology Data Exchange (ETDEWEB)

    Yang Ziyuan, E-mail: yziyuan@tom.co [Department of Physics and Information Technology, Baoji University of Arts and Science, Baoji, 721007 Shaanxi (China)

    2010-12-01

    The microscopic origin of the zero-field splitting (ZFS) parameters including D and (a+2F/3), for {sup 6}S(3d{sup 5}) state ion at tetragonal symmetry crystal field (CF), taking into account the electronic magnetic interactions, i.e. the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) interactions, besides the well-known spin-orbit (SO) interaction, have been investigated using the complete diagonalization method (CDM) and the microscopic spin Hamiltonian theory. Although the SO mechanism is the most important one, the contributions to the ZFS parameters D and (a+2F/3) due to the four additional mechanisms: SS, SOO, OO, and the combined SO{approx}SS{approx}SOO{approx}OO coupling mechanism, are appreciable and shall not be omitted. The individual contributions to the ZFS parameters arising from the spin quartet states and the spin doublet states have been analyzed. It is shown that the ZFS parameters D and (a+2F/3) arise from the spin quartet states as well as the combined effects between the spin doublet states and the spin quartets states, whereas the contributions to D and (a+2F/3) from the spin doublet states are zero. Our investigations show that the rank-2 ZFS parameter D primarily results from the spin quartet states, whereas the rank-4 ZFS parameter (a+2F/3) primarily results from the combined effects between the spin doublet states and the spin quartet states. The contributions to the rank-2 ZFS parameter D from the net spin quartet states exceed 95% and the contributions to the rank-4 ZFS parameter (a+2F/3) from the combined effects between the spin doublet states and the spin quartet states exceed 88.2% for the selected ranges of the crystal field parameters. The dependence of the ZFS parameters D and (a+2F/3) on the CF parameters Dq, B{sub 20}, and B{sup l}{sub 40} for {sup 6}S(3d{sup 5}) state ions at tetragonal symmetry have been studied. It is found that the relations hold: |D(-Dq)|{approx}-|D(Dq)|, (a+2F/3)(-Dq){approx}(a+2F/3)(-Dq) for |Dq|>800 cm{sup -1}. The illustrative evaluation is performed for typical crystal materials: Mn{sup 2+}: Rb{sub 2}CdF{sub 4}, Mn{sup 2+}: K{sub 2}MgF{sub 4}, and Mn{sup 2+}: K{sub 2}ZnF{sub 4} crystals. The good agreements between the theoretical values and the experimental finding are obtained.

  5. Microscopic origins of the zero-field splitting parameters for 6S(3d 5) state ions at tetragonal symmetry crystal field

    Science.gov (United States)

    Yang, Zi-Yuan

    2010-12-01

    The microscopic origin of the zero-field splitting (ZFS) parameters including D and ( a+2 F/3), for 6S(3d 5) state ion at tetragonal symmetry crystal field (CF), taking into account the electronic magnetic interactions, i.e. the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) interactions, besides the well-known spin-orbit (SO) interaction, have been investigated using the complete diagonalization method (CDM) and the microscopic spin Hamiltonian theory. Although the SO mechanism is the most important one, the contributions to the ZFS parameters D and ( a+2 F/3) due to the four additional mechanisms: SS, SOO, OO, and the combined SO?SS?SOO?OO coupling mechanism, are appreciable and shall not be omitted. The individual contributions to the ZFS parameters arising from the spin quartet states and the spin doublet states have been analyzed. It is shown that the ZFS parameters D and ( a+2 F/3) arise from the spin quartet states as well as the combined effects between the spin doublet states and the spin quartets states, whereas the contributions to D and ( a+2 F/3) from the spin doublet states are zero. Our investigations show that the rank-2 ZFS parameter D primarily results from the spin quartet states, whereas the rank-4 ZFS parameter ( a+2 F/3) primarily results from the combined effects between the spin doublet states and the spin quartet states. The contributions to the rank-2 ZFS parameter D from the net spin quartet states exceed 95% and the contributions to the rank-4 ZFS parameter ( a+2 F/3) from the combined effects between the spin doublet states and the spin quartet states exceed 88.2% for the selected ranges of the crystal field parameters. The dependence of the ZFS parameters D and ( a+2 F/3) on the CF parameters Dq, B20, and Bl40 for 6S(3d 5) state ions at tetragonal symmetry have been studied. It is found that the relations hold: | D(- Dq)|?-| D( Dq)|, ( a+2 F/3)(- Dq)?( a+2 F/3)(- Dq) for | Dq|>800 cm -1. The illustrative evaluation is performed for typical crystal materials: Mn 2+: Rb 2CdF 4, Mn 2+: K 2MgF 4, and Mn 2+: K 2ZnF 4 crystals. The good agreements between the theoretical values and the experimental finding are obtained.

  6. Microscopic origins of the zero-field splitting parameters for 6S(3d5) state ions at tetragonal symmetry crystal field

    International Nuclear Information System (INIS)

    The microscopic origin of the zero-field splitting (ZFS) parameters including D and (a+2F/3), for 6S(3d5) state ion at tetragonal symmetry crystal field (CF), taking into account the electronic magnetic interactions, i.e. the spin-spin (SS), the spin-other-orbit (SOO), and the orbit-orbit (OO) interactions, besides the well-known spin-orbit (SO) interaction, have been investigated using the complete diagonalization method (CDM) and the microscopic spin Hamiltonian theory. Although the SO mechanism is the most important one, the contributions to the ZFS parameters D and (a+2F/3) due to the four additional mechanisms: SS, SOO, OO, and the combined SO?SS?SOO?OO coupling mechanism, are appreciable and shall not be omitted. The individual contributions to the ZFS parameters arising from the spin quartet states and the spin doublet states have been analyzed. It is shown that the ZFS parameters D and (a+2F/3) arise from the spin quartet states as well as the combined effects between the spin doublet states and the spin quartets states, whereas the contributions to D and (a+2F/3) from the spin doublet states are zero. Our investigations show that the rank-2 ZFS parameter D primarily results from the spin quartet states, whereas the rank-4 ZFS parameter (a+2F/3) primarily results from the combined effects between the spin doublet states and the spin quartet states. The contributions to the rank-2 ZFS parameter D from the net spin quartet states exceed 95% and the contributions to the rank-4 ZFS parameter (a+2F/3) from the combined effects between the spin doublet states and the spin quartet states exceed 88.2% for the selected ranges of the crystal field parameters. The dependence of the ZFS parameters D and (a+2F/3) on the CF parameters Dq, B20, and Bl40 for 6S(3d5) state ions at tetragonal symmetry have been studied. It is found that the relations hold: |D(-Dq)|?-|D(Dq)|, (a+2F/3)(-Dq)?(a+2F/3)(-Dq) for |Dq|>800 cm-1. The illustrative evaluation is performed for typical crystal materials: Mn2+: Rb2CdF4, Mn2+: K2MgF4, and Mn2+: K2ZnF4 crystals. The good agreements between the theoretical values and the experimental finding are obtained.

  7. Nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

    Science.gov (United States)

    Fukushima, Eiichi (Los Alamos, NM); Roeder, Stephen B. W. (La Mesa, CA); Assink, Roger A. (Albuquerque, NM); Gibson, Atholl A. V. (Bryan, TX)

    1986-01-01

    An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio-frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

  8. NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds

    KAUST Repository

    Zhang, Xiaoming

    2016-03-16

    Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that 209Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by 209Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states.

  9. Wine analysis to check quality and authenticity by fully-automated 1H-NMR

    Directory of Open Access Journals (Sweden)

    Spraul Manfred

    2015-01-01

    Full Text Available Fully-automated high resolution 1H-NMR spectroscopy offers unique screening capabilities for food quality and safety by combining non-targeted and targeted screening in one analysis (15–20 min from acquisition to report. The advantage of high resolution 1H-NMR is its absolute reproducibility and transferability from laboratory to laboratory, which is not equaled by any other method currently used in food analysis. NMR reproducibility allows statistical investigations e.g. for detection of variety, geographical origin and adulterations, where smallest changes of many ingredients at the same time must be recorded. Reproducibility and transferability of the solutions shown are user-, instrument- and laboratory-independent. Sample prepara- tion, measurement and processing are based on strict standard operation procedures which are substantial for this fully automated solution. The non-targeted approach to the data allows detecting even unknown deviations, if they are visible in the 1H-NMR spectra of e.g. fruit juice, wine or honey. The same data acquired in high-throughput mode are also subjected to quantification of multiple compounds. This 1H-NMR methodology will shortly be introduced, then results on wine will be presented and the advantages of the solutions shown. The method has been proven on juice, honey and wine, where so far unknown frauds could be detected, while at the same time generating targeted parameters are obtained.

  10. Early non-destructive biofouling detection in spiral wound RO Membranes using a mobile earth's field NMR

    KAUST Repository

    Fridjonsson, E.O.

    2015-04-20

    We demonstrate the use of Earth\\'s field (EF) Nuclear Magnetic Resonance (NMR) to provide early non-destructive detection of active biofouling of a commercial spiral wound reverse osmosis (RO) membrane module. The RO membrane module was actively biofouled to different extents, by the addition of biodegradable nutrients to the feed stream, as revealed by a subtle feed-channel pressure drop increase. Easily accessible EF NMR parameters (signal relaxation parameters T1, T2 and the total NMR signal modified to be sensitive to stagnant fluid only) were measured and analysed in terms of their ability to detect the onset of biofouling. The EF NMR showed that fouling near the membrane module entrance significantly distorted the flow field through the whole membrane module. The total NMR signal is shown to be suitable for non-destructive early biofouling detection of spiral wound membrane modules, it was readily deployed at high (operational) flow rates, was particularly sensitive to flow field changes due to biofouling and could be deployed at any position along the membrane module axis. In addition to providing early fouling detection, the mobile EF NMR apparatus could also be used to (i) evaluate the production process of spiral wound membrane modules, and (ii) provide an in-situ determination of module cleaning process efficiency.

  11. BOOK REVIEW: NMR Imaging of Materials

    Science.gov (United States)

    Blümich, Bernhard

    2003-09-01

    Magnetic resonance imaging (MRI) of materials is a field of increasing importance. Applications extend from fundamental science like the characterization of fluid transport in porous rock, catalyst pellets and hemodialysers into various fields of engineering for process optimization and product quality control. While the results of MRI imaging are being appreciated by a growing community, the methods of imaging are far more diverse for materials applications than for medical imaging of human beings. Blümich has delivered the first book in this field. It was published in hardback three years ago and is now offered as a paperback for nearly half the price. The text provides an introduction to MRI imaging of materials covering solid-state NMR spectroscopy, imaging methods for liquid and solid samples, and unusual MRI in terms of specialized approaches to spatial resolution such as an MRI surface scanner. The book represents an excellent and thorough treatment which will help to grow research in materials MRI. Blümich developed the treatise over many years for his research students, graduates in chemistry, physics and engineering. But it may also be useful for medical students looking for a less formal discussion of solid-state NMR spectroscopy. The structure of this book is easy to perceive. The first three chapters cover an introduction, the fundamentals and methods of solid-state NMR spectroscopy. The book starts at the ground level where no previous knowledge about NMR is assumed. Chapter 4 discusses a wide variety of transformations beyond the Fourier transformation. In particular, the Hadamard transformation and the 'wavelet' transformation are missing from most related books. This chapter also includes a description of noise-correlation spectroscopy, which promises the imaging of large objects without the need for extremely powerful radio-frequency transmitters. Chapters 5 and 6 cover basic imaging methods. The following chapter about the use of relaxation and spectroscopic methods to weight or filter the spin signals represents the core of the book. This is a subject where Blümich is deeply involved with substantial contributions. The chapter includes a lot of ideas to provide MR contrast between different regions based on their mobility, diffusion, spin couplings or NMR spectra. After describing NMR imaging methods for solids with broad lines, Blümich spends time on applications in the last two chapters of the book. This part is really fun to read. It underlines the effort to bring NMR into many kinds of manufacturing. Car tyres and high-voltage cables are just two such areas. Elastomeric materials, green-state ceramics and food science represent other interesting fields of applications. This part of the book represents a personal but nevertheless extensive compilation of modern applications. As a matter of course the MOUSE is presented, a portable permanent-magnet based NMR developed by Blümich and his co-workers. Thus the book is not only of interest to NMR spectroscopists but also to people in material science and chemical engineering. The bibliography and indexing are excellent and may serve as an attractive reference source for NMR spectroscopists. The book is the first on the subject and likely to become the standard text for NMR imaging of materials as the books by Abragam, Slicher and Ernst et al are for NMR spectroscopy. The purchase of this beautiful book for people dealing with NMR spectroscopy or medical MRI is highly recommended. Ralf Ludwig

  12. NMR methodologies in the analysis of blueberries.

    Science.gov (United States)

    Capitani, Donatella; Sobolev, Anatoly P; Delfini, Maurizio; Vista, Silvia; Antiochia, Riccarda; Proietti, Noemi; Bubici, Salvatore; Ferrante, Gianni; Carradori, Simone; De Salvador, Flavio Roberto; Mannina, Luisa

    2014-06-01

    An NMR analytical protocol based on complementary high and low field measurements is proposed for blueberry characterization. Untargeted NMR metabolite profiling of blueberries aqueous and organic extracts as well as targeted NMR analysis focused on anthocyanins and other phenols are reported. Bligh-Dyer and microwave-assisted extractions were carried out and compared showing a better recovery of lipidic fraction in the case of microwave procedure. Water-soluble metabolites belonging to different classes such as sugars, amino acids, organic acids, and phenolic compounds, as well as metabolites soluble in organic solvent such as triglycerides, sterols, and fatty acids, were identified. Five anthocyanins (malvidin-3-glucoside, malvidin-3-galactoside, delphinidin-3-glucoside, delphinidin-3-galactoside, and petunidin-3-glucoside) and 3-O-?-l-rhamnopyranosyl quercetin were identified in solid phase extract. The water status of fresh and withered blueberries was monitored by portable NMR and fast-field cycling NMR. (1) H depth profiles, T2 transverse relaxation times and dispersion profiles were found to be sensitive to the withering. PMID:24668393

  13. Clinical trial of NMR-CT, (3)

    International Nuclear Information System (INIS)

    The present ongoing clinical study, which began last summer, utilizes an NMR-CT scanner with a resistive megnet providing a low-grade static magnetic field (0.1 Tesla). Our main purpose is to determine the potential of this type of NMR-CT system in particular its spatial and contrast resolution, and the utility of its Tl image in differential diagnosis and detection of lesions. The NMR-CT system used in this study is based on four vertical coil air-core magnets operating at about 0.1 Tesla and giving a proton resonance frequency of 4.5 MHz. Examination of patients with hepatic and pancreatic disease indicated that the NMR-CT is suitable for survey studies on solid tumors, hemangioma and cystic lesions. The NMR-CT also provided very useful Tl data. The Tl of solid tumor was found to be 300 to 500 msec; that of hemangioma was 500 to 700 msec, and that of cystic lesion was usually over 800 msec. The detection of hepatoma in the cirrhotic liver was found to be difficult in some cases because of the similarity of their spin-lattice relaxation times and the small degree of contrast between tumor and cirrhotic liver parenchyma. Differential diagnosis of solid tumor, hemangioma, and cystic disease can be performed through reference to their discrete Tl values. The borders of these lesions are apparently clearer than with X-ray CT imaging. (author)

  14. NMR spectra simulation for quantum computing

    International Nuclear Information System (INIS)

    Full text: Pulse NMR is one of the most serious candidates as an experimental technique for implementing quantum algorithms. To the present date, this technique is in fact the only one where full demonstrations of quantum algorithms implementations have been carried out, in spite of various technical difficulties. On NMR quantum computers, gates and subroutines are encoded as radiofrequency pulse sequences. A 'program output' is read directly on the measured spectra. On this work we simulate NMR spectra and show their evolution during algorithms implementations for two and three qubits systems. We will focus on Grover search, Quantum Fourier Transform, Shor factorization and Teleportation algorithms. Calculated spectra are compared to experimental data extracted from the literature. The main difficulties associated to the use of NMR to quantum computing, such as the exponential decrease of the signal upon increasing the number of qubits could, in principle, be partially removed by using ferromagnetic materials. However, broad NMR linewidths in these materials can mask logical operation. Some simulations are also presented to illustrate this point. (author)

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

    International Nuclear Information System (INIS)

    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)

  16. Variable-temperature NMR and conformational analysis of oenothein B

    Scientific Electronic Library Online (English)

    Suzana C., Santos; Ariadne G., Carvalho; Gilmara A. C., Fortes; Pedro H., Ferri; Anselmo E. de, Oliveira.

    2014-02-01

    Full Text Available Oenoteína B é um tanino hidrolisável dimérico com um amplo espectro de atividades biológicas, tais como antitumoral, anti-inflamatória e anti-viral. Seus espectros de ressonância magnética nuclear (RMN) à temperatura ambiente apresentam duplicações e alargamento de sinais. Experimentos de RMN uni e [...] bidimensionais a baixas temperaturas foram úteis no assinalamento de todos os sinais de hidrogênios e carbonos sem a necessidade de derivatização. A estrutura tridimensional do confôrmero mais estável foi determinada pela primeira vez através do experimento de espectroscopia de efeito nuclear Overhauser (NOESY) (-20 ºC) e cálculos computacionais usando métodos de teoria do funcional de densidade (DFT) (B3LYP/6-31G) e modelo contínuo polarizado (PCM). A conformação mais favorecida apresentou uma geometria altamente compactada e sem simetria, onde os dois grupos valoneoila mostraram diferentes parâmetros conformacionais e estabilidades. Abstract in english Oenothein B is a dimeric hydrolysable tannin with a wide range of biological activities, such as antitumour, anti-inflammatory and antiviral. Its nuclear magnetic resonance (NMR) at room temperature show duplications and broadening of signals. Experiments of 1D and 2D NMR at lower temperatures were [...] useful for the complete NMR assignments of all hydrogens and carbons. The 3D structure of the most stable conformer was determined for the first time by nuclear Overhauser effect spectroscopy (NOESY) experiment (-20 ºC) and density functional theory (DFT)(B3LYP/6-31G)/ polarizable continuum model (PCM) quantum chemical calculations. The favoured conformation showed a highly compacted geometry and a lack of symmetry, in which the two valoneoyl groups showed distinct conformational parameters and stabilities.

  17. Gallium doped in armchair and zigzag models of boron phosphide nanotubes (BPNTs): A NMR study

    Science.gov (United States)

    Rezaei-Sameti, M.

    2012-09-01

    The electrical properties and NMR parameters of the pristine and Ga-doped structures of two representative (8, 0) zigzag and (4, 4) armchair of boron phosphide nanotubes (BPNTs) have been investigated. The structural geometries of above nanotubes have been allowed to relax by optimization and then the isotropic and anisotropic chemical shielding parameters (CSI and CSA) of 11B and 31P have been calculated based on DFT theory. The results reveal that the influence of Ga-doping was more significant on the geometries of the zigzag model than the armchair one. The difference of band gap energies between the pristine and Ga-doped armchair BPNTs was larger than the zigzag model. Significant differences of NMR parameters of those nuclei directly contributed to the Ga-doping atoms have been observed.

  18. EPR OF Mn2+ IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters having the correct signs as well as magnitudes. We present data that determine the sign of the axial anisotropy parameter and thereby facilitate future quantum mechanical characterizations of marble electron paramagnetic resonance spectra that supplement provenance determination.

  19. EPR OF Mn2+ IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.; Laursen, Ib; Johnsen, O.

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters having the correct signs as well as magnitudes. We present data that determine the sign of the axial anisotropy parameter and thereby facilitate future quantum mechanical characterizations of marble electr...

  20. Muscular pathology: echographic and NMR imaging aspects

    International Nuclear Information System (INIS)

    A comparison of echographic techniques and NMR imaging has been done for the diagnosis of muscular trauma and tumor pathologies. In traumatic pathology, the echographic analysis allows to determine the complete assessment of recent muscular injuries. NMR imaging can be used in granuloma or fibrous callosity appreciation and for the analysis of deep injury (muscles and muscles-tendon junctions) and of muscular aponeurosis. Echography must be used together with color coding Doppler technique in the diagnosis of tumor pathology and for the study of slow fluxes. The recently available energy Doppler technique seems to be powerful in the study of vascularization of small expansive formations, but their extension to adjacent bone or tissue can only be appreciated using NMR imaging. (J.S.)

  1. Gas NMR Characterization of Oil Shale

    Science.gov (United States)

    Sorte, Eric; Laicher, Gernot; Saam, Brian

    2007-10-01

    Accurate descriptions and simulations of oil reservoirs such as carbonate-rich sedimentary rock are important for the efficient development and conversion of recoverable energy reserves. These descriptions depend on reliable measures of the properties of the formation rock such as absolute and effective porosity, mineralogical composition, permeability, and tortuosity. NMR signal relaxation time (T1 and T2) and measurements of restricted diffusion of gases in porous media can be used to probe multi-pore media, yielding valuable petrophysical information and allowing the characterization of internal topology and pore size distribution. We employ NMR techniques on imbibed fluorinated and hyperpolarized noble gases - gases with the unique properties of being chemically inert and minimally invasive while exhibiting favorable NMR properties - at various pressure and temperatures to characterize the shale heterogeneity. We show current results of our characterizations and explore ideas for future work.

  2. A modularized pulse programmer for NMR spectroscopy

    International Nuclear Information System (INIS)

    A modularized pulse programmer for a NMR spectrometer is described. It consists of a networked PCI-104 single-board computer and a field programmable gate array (FPGA). The PCI-104 is dedicated to translate the pulse sequence elements from the host computer into 48-bit binary words and download these words to the FPGA, while the FPGA functions as a sequencer to execute these binary words. High-resolution NMR spectra obtained on a home-built spectrometer with four pulse programmers working concurrently demonstrate the effectiveness of the pulse programmer. Advantages of the module include (1) once designed it can be duplicated and used to construct a scalable NMR/MRI system with multiple transmitter and receiver channels, (2) it is a totally programmable system in which all specific applications are determined by software, and (3) it provides enough reserve for possible new pulse sequences

  3. Deuterium NMR, induced and intrinsic cholesteric lyomesophases

    International Nuclear Information System (INIS)

    Induced and intrinsic cholesteric lyotropic mesophases were studied. Induced cholesteric lyomesophases based on potassium laurate (KL) system, with small amounts of cholesterol added, were studied by deuterium NMR and by polarizing microscopy. Order profiles obtained from deuterium NMR of KL perdenderated chains in both induced cholesteric and normal mesophases were compared. The intrinsic cholesteric lyotropic mesophases were based on the amphiphile potassium N-lauroyl serinate (KLNS) in the resolved levo form. The study of the type I intrinsic cholesteric mesophase was made by optical microscopy under polarized light and the type II intrinsic cholesteric lyomesophase was characterized by deuterium NMR. The new texture was explained by the use of the theory of disclinations developed for thermotropic liquid crystals, specially for cholesteric type. (M.J.C.)

  4. Characterization by NMR of ozonized methyl linoleate

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, Maritza F. [National Center for Scientific Research, Havana (Cuba). Ozone Research Center. Dept. of Ozonized Substances]. E-mail: maritza.diaz@cnic.edu.cu; Gavin, Jose A. [University of the Laguna, Tenerife (Spain)

    2007-07-01

    In the present study ozonized methyl linoleate with peroxide index of 1,800 mmol-equiv kg{sup -1} was chemically characterized. Ozonation of methyl linoleate produced hydroperoxides, ozonides and aldehydes which were identified by {sup 1}H and {sup 13}C NMR two-dimensional. The standard methyl linoleate and ozonized methyl linoleate shown very similar {sup 1}H NMR spectra except for the signals at {delta} 9.7 and {delta} 9.6 that correspond to aldehydic hydrogen, {delta} 5.7 and {delta} 5.5 (olefinic signals from hydroperoxides) and {delta} 5.2 ppm (multiplet from ozonides methynic hydrogen). Other resonance assignments are based on the connectivities provided by the hydrogen scalar coupling constants. These results indicate that NMR spectroscopy can provide valuable information about the amount of formed oxygenated compounds in the ozonized methyl linoleate in order to use it to follow up ozone therapy and chemistry of ozonized vegetable oil. (author)

  5. Application of site-specific natural isotope fractionation (SNIF-NMR) of hydrogen to the characterization of European beers

    Energy Technology Data Exchange (ETDEWEB)

    Martin, G.J.; Benbernou, M.; Lantier, F. (Nantes Univ., 44 (France))

    More than one hundred samples of European beers have been investigated by the new SNIF-NMR method which is based on 2H NMR at the natural abundance level and enables site-specific natural isotope fractionation factors in ethanol to be determined. The relative (R) and absolute (D/H)sub(i) parameters are shown to be characteristic of the country where the beers are brewed and the observed variations are explained in terms of cereal composition, water resource, and manufacturing processing (fermentation, yeast, temperature cycle). These new parameters find analytical and mechanistic applications in the identification of a beer and in the investigation of a fermentation process.

  6. Application of site-specific natural isotope fractionation (SNIF-NMR) of hydrogen to the characterization of European beers

    International Nuclear Information System (INIS)

    More than one hundred samples of European beers have been investigated by the new SNIF-NMR method which is based on 2H NMR at the natural abundance level and enables site-specific natural isotope fractionation factors in ethanol to be determined. The relative (R) and absolute (D/H)sub(i) parameters are shown to be characteristic of the country where the beers are brewed and the observed variations are explained in terms of cereal composition, water resource, and manufacturing processing (fermentation, yeast, temperature cycle). These new parameters find analytical and mechanistic applications in the identification of a beer and in the investigation of a fermentation process. (author)

  7. Fast multidimensional NMR spectroscopy for sparse spectra.

    Science.gov (United States)

    Merhej, Dany; Ratiney, Hélène; Diab, Chaouki; Khalil, Mohamad; Sdika, Michaël; Prost, Rémy

    2014-06-01

    Multidimensional NMR spectroscopy is widely used for studies of molecular and biomolecular structure. A major disadvantage of multidimensional NMR is the long acquisition time which, regardless of sensitivity considerations, may be needed to obtain the final multidimensional frequency domain coefficients. In this article, a method for under-sampling multidimensional NMR acquisition of sparse spectra is presented. The approach is presented in the case of two-dimensional NMR acquisitions. It relies on prior knowledge about the support in the two-dimensional frequency domain to recover an over-determined system from the under-determined system induced in the linear acquisition model when under-sampled acquisitions are performed. This over-determined system can then be solved with linear least squares. The prior knowledge is obtained efficiently at a low cost from the one-dimensional NMR acquisition, which is generally acquired as a first step in multidimensional NMR. If this one-dimensional acquisition is intrinsically sparse, it is possible to reconstruct the corresponding two-dimensional acquisition from far fewer observations than those imposed by the Nyquist criterion, and subsequently to reduce the acquisition time. Further improvements are obtained by optimizing the sampling procedure for the least-squares reconstruction using the sequential backward selection algorithm. Theoretical and experimental results are given in the case of a traditional acquisition scheme, which demonstrate reliable and fast reconstructions with acceleration factors in the range 3-6. The proposed method outperforms the CS methods (OMP, L1) in terms of the reconstruction performance, implementation and computation time. The approach can be easily extended to higher dimensions and spectroscopic imaging. PMID:24664959

  8. 1 MHz bandwidth true NMR SQUID amplifier

    Science.gov (United States)

    Thomasson, S. L.; Gould, C. M.

    1995-10-01

    We have developed an integrated dc SQUID magnetometer with additional positive feedback (APF) for low frequency true NMR applications. The APF scheme allows direct coupled read out from the SQUID to room temperature electronics and eliminates the need for the conventional modulation scheme, thereby greatly simplifying the flux-locked loop electronics. We have configured our SQUID system for the specific needs of sensitive NMR measurements which include large bandwidth and high slew rate. We have achieved a bandwidth of 1.2 MHz and a slew rate greater than 105?0/s for frequencies above 10 kHz.

  9. 1 MHz bandwidth true NMR SQUID amplifier

    International Nuclear Information System (INIS)

    We have developed an integrated dc SQUID magnetometer with additional positive feedback (APF) for low frequency true NMR applications. The APF scheme allows direct coupled read out from the SQUID to room temperature electronics and eliminates the need for the conventional modulation scheme, thereby greatly simplifying the flux-locked loop electronics. We have configured our SQUID system for the specific needs of sensitive NMR measurements which include large bandwidth and high slew rate. We have achieved a bandwidth of 1.2 MHz and a slew rate greater than 105?0/s for frequencies above 10 kHz

  10. 13C NMR Metabolomics: INADEQUATE Network Analysis

    Science.gov (United States)

    Clendinen, Chaevien S.; Pasquel, Christian; Ajredini, Ramadan; Edison, Arthur S.

    2015-01-01

    The many advantages of 13C NMR are often overshadowed by its intrinsically low sensitivity. Given that carbon makes up the backbone of most biologically relevant molecules, 13C NMR offers a straightforward measurement of these compounds. Two-dimensional 13C-13C correlation experiments like INADEQUATE (incredible natural abundance double quantum transfer experiment) are ideal for the structural elucidation of natural products and have great but untapped potential for metabolomics analysis. We demonstrate a new and semi-automated approach called INETA (INADEQUATE network analysis) for the untargeted analysis of INADEQUATE datasets using an in silico INADEQUATE database. We demonstrate this approach using isotopically labeled Caenorhabditis elegans mixtures. PMID:25932900

  11. Using NMR to Measure Fractal Dimensions

    CERN Document Server

    Candela, D; Wong, Po-zen

    2002-01-01

    A comment is made on the recent PFG NMR measurements by Stallmach, et al. on water-saturated sands [Phys. Rev. Lett. 88, 105505 (2002)]. It is pointed out that the usual law for the time-dependent diffusion coefficient D(t) used by these authors is not valid for a fractal surface. It is shown that (1-D(t)/D0) \\~ t^[(3-Ds)/2] at short times for a surface of fractal dimension Ds, where D0 is the bulk diffusion coefficient. Preliminary PFG NMR data on water saturated limestone and plastic beads are presented to illustrate this analysis.

  12. Tritiation methods and tritium NMR spectroscopy

    International Nuclear Information System (INIS)

    We have used a simple process for the production of highly tritiated water and characterized the product species by 1H and 3H NMR spectroscopy. The water is readily manipulated and used in subsequent reactions either as T2O, CH3COOT or CF3COOT. Development of tritiated diimide has progressed to the point where cis-hydrogenated products at 1-20 Ci/mmole S.A. are possible. Tri-n-butyl tin tritide has been produced at >95% tritium content and well characterized by multinuclear NMR techniques. 27 refs., 3 figs

  13. NMR characterization of high cis polybutadiene

    International Nuclear Information System (INIS)

    In this work a laboratory scale process was studied for the production of polybutadiene with high content of cis-1,4 repeating units. A Ziegler-Natta catalytic system constituted of neodymium versatate (Nd), tert-butyl chloride (Cl) and an organo aluminium compound (Al) was used. The influence of the organo aluminium (co catalyst) type, Al/Nd and Cl/Nd molar ratios on the polymer microstructure was verified. The polymers microstructures were characterized by 13C nuclear magnetic resonance (NMR). The maximum content of cis-1,4 repeating units determined by 13C-NMR was 97.37%. (author)

  14. NMR characterization of high cis polybutadiene

    Energy Technology Data Exchange (ETDEWEB)

    Fraga, L.A.; Tavares, M.I.B. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Macromoleculas Professora Eloisa Mano]. E-mail: mibt@ima.ufrj.br; Coutinho, F.M.B.; Costa, M.A.S. [Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Inst. de Quimica

    2004-07-01

    In this work a laboratory scale process was studied for the production of polybutadiene with high content of cis-1,4 repeating units. A Ziegler-Natta catalytic system constituted of neodymium versatate (Nd), tert-butyl chloride (Cl) and an organo aluminium compound (Al) was used. The influence of the organo aluminium (co catalyst) type, Al/Nd and Cl/Nd molar ratios on the polymer microstructure was verified. The polymers microstructures were characterized by {sup 13}C nuclear magnetic resonance (NMR). The maximum content of cis-1,4 repeating units determined by {sup 13}C-NMR was 97.37%. (author)

  15. Structural fidelity and NMR relaxation analysis in a prototype RNA hairpin.

    Science.gov (United States)

    Giamba?u, George M; York, Darrin M; Case, David A

    2015-05-01

    RNA hairpins are widespread and very stable motifs that contribute decisively to RNA folding and biological function. The GTP1G2C3A4C5U6U7C8G9G10U11G12C13C14 construct (with a central UUCG tetraloop) has been extensively studied by solution NMR, and offers and excellent opportunity to evaluate the structure and dynamical description afforded by molecular dynamics (MD) simulations. Here, we compare average structural parameters and NMR relaxation rates estimated from a series of multiple independent explicit solvent MD simulations using the two most recent RNA AMBER force fields (ff99 and ff10). Predicted overall tumbling times are ?20% faster than those inferred from analysis of NMR data and follow the same trend when temperature and ionic strength is varied. The Watson-Crick stem and the "canonical" UUCG loop structure are maintained in most simulations including the characteristic syn conformation along the glycosidic bond of G9, although some key hydrogen bonds in the loop are partially disrupted. Our analysis pinpoints G9-G10 backbone conformations as a locus of discrepancies between experiment and simulation. In general the results for the more recent force-field parameters (ff10) are closer to experiment than those for the older ones (ff99). This work provides a comprehensive and detailed comparison of state of the art MD simulations against a wide variety of solution NMR measurements. PMID:25805858

  16. NMR-based metabolomics of mammalian cell and tissue cultures

    International Nuclear Information System (INIS)

    NMR spectroscopy was used to evaluate growth media and the cellular metabolome in two systems of interest to biomedical research. The first of these was a Chinese hamster ovary cell line engineered to express a recombinant protein. Here, NMR spectroscopy and a quantum mechanical total line shape analysis were utilized to quantify 30 metabolites such as amino acids, Krebs cycle intermediates, activated sugars, cofactors, and others in both media and cell extracts. The impact of bioreactor scale and addition of anti-apoptotic agents to the media on the extracellular and intracellular metabolome indicated changes in metabolic pathways of energy utilization. These results shed light into culture parameters that can be manipulated to optimize growth and protein production. Second, metabolomic analysis was performed on the superfusion media in a common model used for drug metabolism and toxicology studies, in vitro liver slices. In this study, it is demonstrated that two of the 48 standard media components, choline and histidine are depleted at a faster rate than many other nutrients. Augmenting the starting media with extra choline and histidine improves the long-term liver slice viability as measured by higher tissues levels of lactate dehydrogenase (LDH), glutathione and ATP, as well as lower LDH levels in the media at time points out to 94 h after initiation of incubation. In both models, media components and cellular metabolites are measured over time and correlated with currently accepted endpoint measures.

  17. NMR-based metabolomics of mammalian cell and tissue cultures

    Energy Technology Data Exchange (ETDEWEB)

    Aranibar, Nelly; Borys, Michael; Mackin, Nancy A.; Ly, Van; Abu-Absi, Nicholas; Abu-Absi, Susan [Bristol-Myers Squibb Company (United States); Niemitz, Matthias [PERCH Solutions Ltd. (Finland); Schilling, Bernhard; Li, Zheng Jian; Brock, Barry; Russell, Reb J.; Tymiak, Adrienne; Reily, Michael D., E-mail: michael.reily@bms.com [Bristol-Myers Squibb Company (United States)

    2011-04-15

    NMR spectroscopy was used to evaluate growth media and the cellular metabolome in two systems of interest to biomedical research. The first of these was a Chinese hamster ovary cell line engineered to express a recombinant protein. Here, NMR spectroscopy and a quantum mechanical total line shape analysis were utilized to quantify 30 metabolites such as amino acids, Krebs cycle intermediates, activated sugars, cofactors, and others in both media and cell extracts. The impact of bioreactor scale and addition of anti-apoptotic agents to the media on the extracellular and intracellular metabolome indicated changes in metabolic pathways of energy utilization. These results shed light into culture parameters that can be manipulated to optimize growth and protein production. Second, metabolomic analysis was performed on the superfusion media in a common model used for drug metabolism and toxicology studies, in vitro liver slices. In this study, it is demonstrated that two of the 48 standard media components, choline and histidine are depleted at a faster rate than many other nutrients. Augmenting the starting media with extra choline and histidine improves the long-term liver slice viability as measured by higher tissues levels of lactate dehydrogenase (LDH), glutathione and ATP, as well as lower LDH levels in the media at time points out to 94 h after initiation of incubation. In both models, media components and cellular metabolites are measured over time and correlated with currently accepted endpoint measures.

  18. Conventions and nomenclature for double diffusion encoding NMR and MRI.

    Science.gov (United States)

    Shemesh, Noam; Jespersen, Sune N; Alexander, Daniel C; Cohen, Yoram; Drobnjak, Ivana; Dyrby, Tim B; Finsterbusch, Jurgen; Koch, Martin A; Kuder, Tristan; Laun, Fredrik; Lawrenz, Marco; Lundell, Henrik; Mitra, Partha P; Nilsson, Markus; Özarslan, Evren; Topgaard, Daniel; Westin, Carl-Fredrik

    2016-01-01

    Stejskal and Tanner's ingenious pulsed field gradient design from 1965 has made diffusion NMR and MRI the mainstay of most studies seeking to resolve microstructural information in porous systems in general and biological systems in particular. Methods extending beyond Stejskal and Tanner's design, such as double diffusion encoding (DDE) NMR and MRI, may provide novel quantifiable metrics that are less easily inferred from conventional diffusion acquisitions. Despite the growing interest on the topic, the terminology for the pulse sequences, their parameters, and the metrics that can be derived from them remains inconsistent and disparate among groups active in DDE. Here, we present a consensus of those groups on terminology for DDE sequences and associated concepts. Furthermore, the regimes in which DDE metrics appear to provide microstructural information that cannot be achieved using more conventional counterparts (in a model-free fashion) are elucidated. We highlight in particular DDE's potential for determining microscopic diffusion anisotropy and microscopic fractional anisotropy, which offer metrics of microscopic features independent of orientation dispersion and thus provide information complementary to the standard, macroscopic, fractional anisotropy conventionally obtained by diffusion MR. Finally, we discuss future vistas and perspectives for DDE. Magn Reson Med 75:82-87, 2016. © 2015 Wiley Periodicals, Inc. PMID:26418050

  19. Tailoring broadband inversion pulses for MAS Solid state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Riedel, Kerstin; Herbst, Christian; Leppert, Joerg; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai [Fritz Lipmann Institute, Research group-Molecular Biophysics/NMR spectroscopy, Leibniz Institute for Age Research (Germany)], E-mail: raman@fli-leibniz.de

    2006-08-15

    A simple approach is demonstrated for designing optimised broadband inversion pulses for MAS solid state NMR studies of biological systems. The method involves a two step numerical optimisation procedure and takes into account experimental requirements such as the pulse length, resonance offset range and extent of H{sub 1} inhomogeneity compensation needed. A simulated annealing protocol is used initially to find appropriate values for the parameters that define the well known tanh/tan adiabatic pulse such that a satisfactory spin inversion is achieved with minimum RF field strength. This information is then used in the subsequent stage of refinement where the RF pulse characteristics are further tailored via a local optimisation procedure without imposing any restrictions on the amplitude and frequency modulation profiles. We demonstrate that this approach constitutes a generally applicable tool for obtaining pulses with good inversion characteristics. At moderate MAS frequencies the efficacy of the method is experimentally demonstrated for generating double-quantum NMR spectra via the zero-quantum dipolar recoupling scheme RFDR.

  20. Tailoring broadband inversion pulses for MAS Solid state NMR

    International Nuclear Information System (INIS)

    A simple approach is demonstrated for designing optimised broadband inversion pulses for MAS solid state NMR studies of biological systems. The method involves a two step numerical optimisation procedure and takes into account experimental requirements such as the pulse length, resonance offset range and extent of H1 inhomogeneity compensation needed. A simulated annealing protocol is used initially to find appropriate values for the parameters that define the well known tanh/tan adiabatic pulse such that a satisfactory spin inversion is achieved with minimum RF field strength. This information is then used in the subsequent stage of refinement where the RF pulse characteristics are further tailored via a local optimisation procedure without imposing any restrictions on the amplitude and frequency modulation profiles. We demonstrate that this approach constitutes a generally applicable tool for obtaining pulses with good inversion characteristics. At moderate MAS frequencies the efficacy of the method is experimentally demonstrated for generating double-quantum NMR spectra via the zero-quantum dipolar recoupling scheme RFDR

  1. Solid State Multinuclear NMR Studies of Relaxor Ferroelectrics

    Science.gov (United States)

    Hoatson, Gina; Zhou, Donghua; Fayon, Franck; Massiot, Dominique; Gan, Zhehong; Vold, Robert

    2002-03-01

    Multinuclear (207Pb, 45Sc, 93Nb) NMR has been used to investigate the local structure and cation disorder in solid solutions of (1-x) Pb(Mg1/3Nb2/3)O3: x Pb(Sc1/2Nb1/2)O3, as a function of concentration. The relaxor ferroelectrics have been well characterized by X-ray and dielectric response measurements(1). MAS, and 3QMAS spectra are presented for 93Nb at 14.0 and 19.6 Tesla. The 93Nb MAS lineshapes have been assigned to species with different arrangements of the nearest B-cation neighbors. It is necessary to include distributions of the electric field gradient parameters and dispersions in isotropic chemical shifts; these have been estimated from the data. The relative intensities of each spectral component are analyzed and the data strongly supports the modified Random Site model. To explain NMR intensities and to validate the model, Monte Carlo simulations will be presented. (1) P. K., Davies, L. Farber, M. Valant, and M. A. Akabas, AIP Conf. Proc. 535 (2000) 38-46.

  2. “In-plant” NMR: Analysis of the Intact Plant Vesicularia dubyana by High Resolution NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Viktor P. Kutyshenko

    2015-03-01

    Full Text Available We present here the concept of “in-plant” NMR and show that high-resolution NMR spectroscopy is suitable for the analysis of intact plants and can be used to follow the changes in the intraorganismal molecular composition over long time periods. The NMR-based analysis of the effect of different concentrations of heavy water on the aquatic plant Vesicularia dubyana revealed that due to the presence of specific adaptive mechanisms this plant can sustain the presence of up to 85% of D2O. However, it dies in 100% heavy water.

  3. Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.

    Science.gov (United States)

    Perić, Berislav; Gautier, Régis; Pickard, Chris J; Bosiočić, Marko; Grbić, Mihael S; Požek, Miroslav

    2014-01-01

    Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined δiso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and δ33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (δ11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements. PMID:24581866

  4. THE ROLE OF SUPERCONDUCTING MAGNETS IN NMR MEDICAL IMAGING

    OpenAIRE

    GREEN, M; Singer, J

    1984-01-01

    Modern medicine has become dependent on x-rays and various imaging techniques for the diagnosis of diseases. Within the last five yers, an imaging technique which uses NMR (Nuclear Magnetic Resonance) has been developed. NMR imaging will produce detailed pictures of soft tissues without the use of dangerous ionizing radiation. NMR imaging can be particularly useful for the detection of cancer and certain cardiovascular diseases. NMR imaging may well provide the first large-scale use of superc...

  5. SPE-NMR metabolite sub-profiling of urine

    OpenAIRE

    Jacobs, D M; Spiesser, L.; Garnier, M.; Roo, N., de; Dorsten, F., van; Hollebrands, B.; van Velzen, E; Draijer, R.; Duynhoven, J.P.M. van

    2012-01-01

    NMR-based metabolite profiling of urine is a fast and reproducible method for detection of numerous metabolites with diverse chemical properties. However, signal overlap in the (1)H NMR profiles of human urine may hamper quantification and identification of metabolites. Therefore, a new method has been developed using automated solid-phase extraction (SPE) combined with NMR metabolite profiling. SPE-NMR of urine resulted in three fractions with complementary and reproducible sub-profiles. The...

  6. Solid-state NMR of proteins sedimented by ultracentrifugation

    OpenAIRE

    2011-01-01

    Relatively large proteins in solution, spun in NMR rotors for solid samples at typical ultracentrifugation speeds, sediment at the rotor wall. The sedimented proteins provide high-quality solid-state-like NMR spectra suitable for structural investigation. The proteins fully revert to the native solution state when spinning is stopped, allowing one to study them in both conditions. Transiently sedimented proteins can be considered a novel phase as far as NMR is concerned. NMR of transiently se...

  7. 57Fe NMR study of manganese ferrites.

    Czech Academy of Sciences Publication Activity Database

    Chlan, V.; Procházka, V.; Št?pánková, H.; Sedlák, B.; Novák, Pavel; Šimša, Zden?k; Brabers, V.A.M.

    2008-01-01

    Ro?. 320, ?. 11 (2008), e96-e99. ISSN 0304-8853 R&D Projects: GA ?R GA202/06/0051 Institutional research plan: CEZ:AV0Z10100521 Keywords : manganate ferrites * NMR Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.283, year: 2008

  8. NMR blood vessel imaging method and apparatus

    International Nuclear Information System (INIS)

    A high speed method of forming computed images of blood vessels based on measurements of characteristics of a body is described comprising the steps of: subjecting a predetermined body area containing blood vessels of interest to, successively, applications of a short repetition time (TR) NMR pulse sequence during the period of high blood velocity and then to corresponding applications during the period of low blood velocity for successive heart beat cycles; weighting the collected imaging data from each application of the NMR pulse sequence according to whether the data was acquired during the period of high blood velocity or a period of low blood velocity of the corresponding heart beat cycle; accumulating weighted imaging data from a plurality of NMR pulse sequences corresponding to high blood velocity periods and from a plurality of NMR pulse sequences corresponding to low blood velocity periods; subtracting the weighted imaging data corresponding to each specific phase encoding acquired during the high blood velocity periods from the weighted imaging data for the same phase encoding corresponding to low blood velocity periods in order to compute blood vessel imaging data; and forming an image of the blood vessels of interest from the blood vessel imaging data

  9. Hydrate Shell Growth Measured Using NMR.

    Science.gov (United States)

    Haber, Agnes; Akhfash, Masoumeh; Loh, Charles K; Aman, Zachary M; Fridjonsson, Einar O; May, Eric F; Johns, Michael L

    2015-08-18

    Benchtop nuclear magnetic resonance (NMR) pulsed field gradient (PFG) and relaxation measurements were used to monitor the clathrate hydrate shell growth occurring in water droplets dispersed in a continuous cyclopentane phase. These techniques allowed the growth of hydrate inside the opaque exterior shell to be monitored and, hence, information about the evolution of the shell's morphology to be deduced. NMR relaxation measurements were primarily used to monitor the hydrate shell growth kinetics, while PFG NMR diffusion experiments were used to determine the nominal droplet size distribution (DSD) of the unconverted water inside the shell core. A comparison of mean droplet sizes obtained directly via PFG NMR and independently deduced from relaxation measurements showed that the assumption of the shell model-a perfect spherical core of unconverted water-for these hydrate droplet systems is correct, but only after approximately 24 h of shell growth. Initially, hydrate growth is faster and heat-transfer-limited, leading to porous shells with surface areas larger than that of spheres with equivalent volumes. Subsequently, the hydrate growth rate becomes mass-transfer-limited, and the shells become thicker, spherical, and less porous. PMID:26102311

  10. Strukturní charakterizace glukan? 13 C NMR spectroscopy.

    Czech Academy of Sciences Publication Activity Database

    Sp?vá?ek, Ji?í

    2005-01-01

    Ro?. 99, ?. 9 (2005), s. 668. ISSN 0009-2770. [Struktura a biologické ú?inky polysacharid? a jejich derivát?. 11.11.2005, Praha] R&D Projects: GA ?R(CZ) GA525/05/0273 Keywords : solid state 13C NMR * cellulose * chitin Subject RIV: GM - Food Processing

  11. Gate controlled amplifier for platinum NMR thermometry

    Science.gov (United States)

    Jinzaki, Y.; Okuda, Y.; Ikushima, A. J.

    A 250 kHz pulsed NMR circuit for measurement of platinum nuclear susceptibility is described. The nuclear free induction decay signal is detected using the single-coil method. Saturation of the amplifier is avoided by gating the rf pulse. This system is used for nuclear thermometry below 30 mK.

  12. Novel NMR Method for Organic Aerosol Analysis.

    Czech Academy of Sciences Publication Activity Database

    Horník, Št?pán

    Prague : Institute of Chemical Process Fundamental of the CAS, v. v. i, 2015 - (Bendová, M.; Wagner, Z.), s. 20-21 ISBN 978-80-86186-70-2. [Bažant Postgraduate Conference 2015. Prague (CZ)] Institutional support: RVO:67985858 Keywords : nmr method * organic aerosol composition * analysis Subject RIV: CF - Physical ; Theoretical Chemistry

  13. Structural Studies of Biological Solids Using NMR

    Science.gov (United States)

    Ramamoorthy, Ayyalusamy

    2011-03-01

    High-resolution structure and dynamics of biological molecules are important in understanding their function. While studies have been successful in solving the structures of water-soluble biomolecules, it has been proven difficult to determine the structures of membrane proteins and fibril systems. Recent studies have shown that solid-state NMR is a promising technique and could be highly valuable in studying such non-crystalline and non-soluble biosystems. I will present strategies to study the structures of such challenging systems and also about the applications of solid-state NMR to study the modes of membrane-peptide interactions for a better assessment of the prospects of antimicrobial peptides as substitutes to antibiotics in the control of human disease. Our studies on the mechanism of membrane disruption by LL-37 (a human antimicrobial peptide), analogs of the naturally occurring antimicrobial peptide magainin2 extracted from the skin of the African frog Xenopus Laevis, and pardaxin will be presented. Solid-state NMR experiments were used to determine the secondary structure, dynamics and topology of these peptides in lipid bilayers. Similarities and difference in the cell-lysing mechanism, and their dependence on the membrane composition, of these peptides will be discussed. Atomic-level resolution NMR structures of amyloidogenic proteins revealing the misfolding pathway and early intermediates that play key roles in amyloid toxicity will also be presented.

  14. NMR analysis of a fluorocarbon copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R.E.; Smith, C.H.

    1987-10-01

    Vinylidene fluoride (VF/sub 2/) can be copolymerized with chlorotrifluoroethylene (CTFE) in an aqueous emulsion using a peroxide chain initiator. The physical properties of the resulting fluorocarbon polymer depend on the ratio of VF/sub 2/ to CTFE and the randomness of the copolymerization. When CTFE and VF are polymerized in an approximately 3:1 mole ratio, the resulting polymer is soluble in acetone (and other solvents) at room temperature. Using proton and fluorine-19 NMR, the mole ratio of CTFE to VF/sub 2/, the emulsifier (perfluorodecanoate) concentration, and the randomness of copolymerization can be determined. A trifluorotoluene internal standard is added to a d/sub 6/-acetone solution of the fluoropolymer. Proton NMR is used to determine the amount of VF/sub 2/. Fluorine-19 NMR is used to measure the amount of emulsifier and the randomness of copolymerization. Each analysis requires about 5 minutes, and is quite precise, with relative standard deviations from 3 to 10% (10 replicates analyzed). In addition, the results from NMR analyses agree well with wet chemical analyses. 4 refs., 3 figs., 3 tabs.

  15. NMR analysis of a fluorocarbon copolymer

    International Nuclear Information System (INIS)

    Vinylidene fluoride (VF2) can be copolymerized with chlorotrifluoroethylene (CTFE) in an aqueous emulsion using a peroxide chain initiator. The physical properties of the resulting fluorocarbon polymer depend on the ratio of VF2 to CTFE and the randomness of the copolymerization. When CTFE and VF are polymerized in an approximately 3:1 mole ratio, the resulting polymer is soluble in acetone (and other solvents) at room temperature. Using proton and fluorine-19 NMR, the mole ratio of CTFE to VF2, the emulsifier (perfluorodecanoate) concentration, and the randomness of copolymerization can be determined. A trifluorotoluene internal standard is added to a d6-acetone solution of the fluoropolymer. Proton NMR is used to determine the amount of VF2. Fluorine-19 NMR is used to measure the amount of emulsifier and the randomness of copolymerization. Each analysis requires about 5 minutes, and is quite precise, with relative standard deviations from 3 to 10% (10 replicates analyzed). In addition, the results from NMR analyses agree well with wet chemical analyses. 4 refs., 3 figs., 3 tabs

  16. The bar coil for NMR tomograph

    International Nuclear Information System (INIS)

    The bar coil (bi-planar) for the NMR tomograph, designed for medical diagnostics, has been described. The tests of coil shown that it generates good homogenous magnetic field in a big volume what results in improving of the signal-to-noise ratio

  17. Kvantitativní 31P NMR spektroskopie huminových kyselin.

    Czech Academy of Sciences Publication Activity Database

    Novák, František; Hrabal, R.; Bartošová, I.; Kal?ík, Ji?í

    2005-01-01

    Ro?. 99, - (2005), s. 236-245. ISSN 0009-2770 R&D Projects: GA ?R(CZ) GA206/02/1504 Institutional research plan: CEZ:AV0Z6066911 Keywords : 31P NMR spectroscopy * humic acids Subject RIV: EH - Ecology, Behaviour Impact factor: 0.445, year: 2005

  18. The precision of NMR structure ensembles revisited

    International Nuclear Information System (INIS)

    Biomolecular structures provide the basis for many studies in research areas such as structure-based drug design and homology modeling. In order to use molecular coordinates it is important that they are reliable in terms of accurate description of the experimental data and in terms of the overall and local geometry. Besides these primary quality criteria an indication is needed for the uncertainty in the atomic coordinates that may arise from the dynamic behavior of the considered molecules as well as from experimental- and computational procedures.In contrast to the crystallographic B-factor, a good measure for the uncertainty in NMR-derived atomic coordinates is still not available. It has become clear in recent years that the widely used atomic Root Mean Square Deviation (RMSD), which is a measure for the precision of the data, overestimates the accuracy of NMR structure ensembles and therefore is a problematic measure for the uncertainty in the atomic coordinates.In this study we report a method that yields a more realistic estimate of the uncertainty in the atomic coordinates by maximizing the RMSD of an ensemble of structures, while maintaining the accordance with the experimentally derived data. The results indicate that the RMSD of most NMR structure ensembles can be significantly increased compromising neither geometric quality nor NMR data. This maximized RMSD therefore seems a better estimate of the true uncertainty in the atomic coordinates

  19. 13C NMR of tunnelling methyl groups

    Science.gov (United States)

    Detken, A.

    The dipolar interactions between the protons and the central 13C nucleus of a 13CH3 group are used to study rotational tunnelling and incoherent dynamics of such groups in molecular solids. Single-crystal 13C NMR spectra are derived for arbitrary values of the tunnel frequency upsilon t. Similarities to ESR and 2H NMR are pointed out. The method is applied to three different materials. In the hydroquinone/acetonitrile clathrate, the unique features in the 13C NMR spectra which arise from tunnelling with a tunnel frequency that is much larger than the dipolar coupling between the methyl protons and the 13C nucleus are demonstrated, and the effects of incoherent dynamics are studied. The broadening of the 13C resonances is related to the width of the quasi-elastic line in neutron scattering. Selective magnetization transfer experiments for studying slow incoherent dynamics are proposed. For the strongly hindered methyl groups of L-alanine, an upper limit for upsilon is derived from the 13C NMR spectrum. In aspirinTM (acetylsalicylic acid), incoherent reorientations dominate the spectra down to the lowest temperatures studied; their rate apparently increases with decreasing temperature below 25K.

  20. NMR analog of Bell's inequalities violation test

    International Nuclear Information System (INIS)

    In this paper, we present an analog of Bell's inequalities violation test for N qubits to be performed in a nuclear magnetic resonance (NMR) quantum computer. This can be used to simulate or predict the results for different Bell's inequality tests, with distinct configurations and a larger number of qubits. To demonstrate our scheme, we implemented a simulation of the violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality using a two-qubit NMR system and compared the results to those of a photon experiment. The experimental results are well described by the quantum mechanics theory and a local realistic hidden variables model (LRHVM) that was specifically developed for NMR. That is why we refer to this experiment as a simulation of Bell's inequality violation. Our result shows explicitly how the two theories can be compatible with each other due to the detection loophole. In the last part of this work, we discuss the possibility of testing some fundamental features of quantum mechanics using NMR with highly polarized spins, where a strong discrepancy between quantum mechanics and hidden variables models can be expected

  1. Hyperpolarized NMR Probes for Biological Assays

    Directory of Open Access Journals (Sweden)

    Sebastian Meier

    2014-01-01

    Full Text Available During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and detected with high sensitivity and contrast against background signals using high resolution NMR spectroscopy. A variety of natural, derivatized and designed hyperpolarized probes has emerged for diverse biological studies including assays of intracellular reaction progression, pathway kinetics, probe uptake and export, pH, redox state, reactive oxygen species, ion concentrations, drug efficacy or oncogenic signaling. These probes are readily used directly under natural conditions in biofluids and are often directly developed and optimized for cellular assays, thus leaving little doubt about their specificity and utility under biologically relevant conditions. Hyperpolarized molecular probes for biological NMR spectroscopy enable the unbiased detection of complex processes by virtue of the high spectral resolution, structural specificity and quantifiability of NMR signals. Here, we provide a survey of strategies used for the selection, design and use of hyperpolarized NMR probes in biological assays, and describe current limitations and developments.

  2. Composite pulses in NMR quantum computation

    OpenAIRE

    Jones, Jonathan A.

    2009-01-01

    I describe the use of techniques based on composite rotations to combat systematic errors in quantum logic gates. Although developed and described within the context of Nuclear Magnetic Resonance (NMR) quantum computing these sequences should be applicable to other implementations of quantum computation.

  3. NMR in the elucidation of complex structures

    International Nuclear Information System (INIS)

    The author is interested in developing ideas and procedures whereby the process of structural elucidation by means of NMR spectroscopy are considered. In this paper he demonstrates how it is possible to construct a structural elucidation argument for a reasonable complex molecule without having to invent 'candidate structures' or refer to a 'working structure'. (A.S.). 36 refs.; 6 figs

  4. Method of producing images by NMR techniques

    International Nuclear Information System (INIS)

    The patent relates to methods of producing images of samples by NMR techniques. The method involves free induction signals, which are generated by gyro-magnetically excited nuclei in a sample. Fourier transformation of the signals yields the image. (U.K.)

  5. Compression of NMR data. Application to two-dimensional NMR spectroscopy and imaging

    Science.gov (United States)

    Zolnai, Zsolt; Macura, Slobodan; Markley, John L.

    The important information in a high-resolution two-dimensional NMR spectrum or 2D NMR image is localized in a small fraction of the overall data block. Hence data files should be subject to compression by suitable manipulation. We propose two methods for data compression: elimination of background noise and logarithmic scaling of the data. By combining the two methods, one can obtain a compression factor of 30 or more without significant loss of spectral information content. The method is particularly suitable for the storage of massive data sets. One or more two-dimensional spectra can be reduced and stored on one floppy disk. These methods and their versatility are demonstrated via compression of two-dimensional NMR spectra of a small protein (turkey ovomucoid third domain) and via compression of the NMR image of a phantom.

  6. Lithological control on gas hydrate saturation as revealed by signal classification of NMR logging data

    Science.gov (United States)

    Bauer, Klaus; Kulenkampff, Johannes; Henninges, Jan; Spangenberg, Erik

    2015-09-01

    In this paper, nuclear magnetic resonance (NMR) downhole logging data are analyzed with a new strategy to study gas hydrate-bearing sediments in the Mackenzie Delta (NW Canada). In NMR logging, transverse relaxation time (T2) distribution curves are usually used to determine single-valued parameters such as apparent total porosity or hydrocarbon saturation. Our approach analyzes the entire T2 distribution curves as quasi-continuous signals to characterize the rock formation. We apply self-organizing maps, a neural network clustering technique, to subdivide the data set of NMR curves into classes with a similar and distinctive signal shape. The method includes (1) preparation of data vectors, (2) unsupervised learning, (3) cluster definition, and (4) classification and depth mapping of all NMR signals. Each signal class thus represents a specific pore size distribution which can be interpreted in terms of distinct lithologies and reservoir types. A key step in the interpretation strategy is to reconcile the NMR classes with other log data not considered in the clustering analysis, such as gamma ray, hydrate saturation, and other logs. Our results defined six main lithologies within the target zone. Gas hydrate layers were recognized by their low signal amplitudes for all relaxation times. Most importantly, two subtypes of hydrate-bearing shaly sands were identified. They show distinct NMR signals and differ in hydrate saturation and gamma ray values. An inverse linear relationship between hydrate saturation and clay content was concluded. Finally, we infer that the gas hydrate is not grain coating, but rather, pore filling with matrix support is the preferred growth habit model for the studied formation.

  7. Performance of the WeNMR CS-Rosetta3 web server in CASD-NMR

    International Nuclear Information System (INIS)

    We present here the performance of the WeNMR CS-Rosetta3 web server in CASD-NMR, the critical assessment of automated structure determination by NMR. The CS-Rosetta server uses only chemical shifts for structure prediction, in combination, when available, with a post-scoring procedure based on unassigned NOE lists (Huang et al. in J Am Chem Soc 127:1665–1674, 2005b, doi: 10.1021/ja047109h 10.1021/ja047109h ). We compare the original submissions using a previous version of the server based on Rosetta version 2.6 with recalculated targets using the new R3FP fragment picker for fragment selection and implementing a new annotation of prediction reliability (van der Schot et al. in J Biomol NMR 57:27–35, 2013, doi: 10.1007/s10858-013-9762-6 10.1007/s10858-013-9762-6 ), both implemented in the CS-Rosetta3 WeNMR server. In this second round of CASD-NMR, the WeNMR CS-Rosetta server has demonstrated a much better performance than in the first round since only converged targets were submitted. Further, recalculation of all CASD-NMR targets using the new version of the server demonstrates that our new annotation of prediction quality is giving reliable results. Predictions annotated as weak are often found to provide useful models, but only for a fraction of the sequence, and should therefore only be used with caution

  8. Genetic algorithms and solid state NMR pulse sequences

    CERN Document Server

    Bechmann, Matthias; Sebald, Angelika

    2013-01-01

    The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C7 dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is found to be robust over a wide range of parameters, requires only minimal a priori knowledge of the spin system for experimental implementations with buildup rates being solely determined by the magnitude of the dipolar coupling interaction, but is found to be less broadbanded than the original C7 pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.

  9. Genetic algorithms and solid state NMR pulse sequences

    Science.gov (United States)

    Bechmann, Matthias; Clark, John; Sebald, Angelika

    2013-03-01

    The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C721 dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is found to be robust over a wide range of parameters, requires only minimal a priori knowledge of the spin system for experimental implementations with buildup rates being solely determined by the magnitude of the dipolar coupling interaction, but is found to be less broadbanded than the original C721 pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.

  10. Pulsed NMR experiments in superfluid 3He confined in aerogel

    International Nuclear Information System (INIS)

    Pulsed NMR experiments have been performed in both B and supercooled A phases of superfluid 3He in aerogel. Dependencies of spin precession frequency on tipping angle in B-phase of superfluid 3He in aerogel are found to be different for pure 3He and for the cell preplated with 4He. A sharp increase of the frequency for tipping angles greater than 104 deg. was observed in low temperature superfluid phase of 3He in 4He preplated aerogel as it is expected for the B-phase structure of the order parameter. Dependencies of the frequency on the tipping angle in supercooled A-phase are similar for both pure 3He and 4He preplated aerogel

  11. Basic facts and perspectives of Overhauser DNP NMR

    Science.gov (United States)

    Ravera, Enrico; Luchinat, Claudio; Parigi, Giacomo

    2016-03-01

    After the first surprisingly large 1H DNP enhancements of the water signal in aqueous solutions of nitroxide radicals observed at high magnetic fields, Overhauser DNP is gaining increasing attention for a number of applications now flourishing, showing the potentialities of this mechanism in solution and solid state NMR as well as in MRI. Unexpected Overhauser DNP enhancements in insulating solids were recently measured at 100 K, with a magnitude which increases with the applied magnetic field. We recapitulate here the theoretical premises of Overhauser DNP in solution and analyze the effects of the various parameters on the efficacy of the mechanism, underlining the link between the DNP enhancements and the field dependent relaxation properties. Promisingly, more effective DNP enhancements are expected by exploiting the potentialities offered by 13C detection and the use of supercritical fluids.

  12. Physiological parameters

    International Nuclear Information System (INIS)

    The physiological characteristics of man depend on the intake, metabolism and excretion of stable elements from food, water, and air. The physiological behavior of natural radionuclides and radionuclides from nuclear weapons testing and from the utilization of nuclear energy is believed to follow the pattern of stable elements. Hence information on the normal physiological processes occurring in the human body plays an important role in the assessment of the radiation dose received by man. Two important physiological parameters needed for internal dose determination are the pulmonary function and the water balance. In the Coordinated Research Programme on the characterization of Asian population, five participants submitted data on these physiological characteristics - China, India, Japan, Philippines and Viet Nam. During the CRP, data on other pertinent characteristics such as physical and dietary were simultaneously being collected. Hence, the information on the physiological characteristics alone, coming from the five participants were not complete and are probably not sufficient to establish standard values for the Reference Asian Man. Nonetheless, the data collected is a valuable contribution to this research programme

  13. Simultaneous multinuclear NMR studies of brain metabolism

    International Nuclear Information System (INIS)

    The brain is a complex metabolic system with intricate interactions between the various metabolic pathways to provide the tight regulation necessary to maintain homeostasis. A major problem faced by investigators studying metabolic regulation in vivo, is the inability to noninvasively follow the evolution of changes in metabolite concentrations during imposed metabolic stress. The work described in this thesis develops in vivo NMR spectroscopy into a technique to simultaneously monitor levels of high energy phosphate metabolites, intracellular pH, lactate concentrations and ionic equilibria in a time resolved fashion, and applies this technique to study metabolic regulation in the brain. The basic technique involves frequency interleaved NMR data acquisition, allowing spectra from several nuclei to be acquired in the same time it would take to acquire a spectrum from a single nucleus. In order to permit such frequency time shared use of the NMR spectrometer, it is necessary to develop multiple tuned NMR probes, capable of operating at several different frequencies with high sensitivity. Probes using multiple-pole tuning networks and coupled tank circuits individually or in combination are described. Applications of double (31P, 1H) and triple 23Na, 1H, 31P) nuclear NMR to study metabolic regulation in cat brain models of hypoxic ischemia and global seizure are described. The results are consistent with regulation of oxidative metabolism in the brain in vivo by the phosphorylation ratio, a potent regulator of in vitro mitochondrial function. Measurements of the brain buffering capacity and post isochemic lactate efflux are presented. A close correlation between the transmembrane Na+ gradient and the energy state is established

  14. Zur Bestimmung chemischer Verschiebungen der NMR-Frequenzen bei Quadrupolkernen aus den MAS-NMR-Spektren

    Science.gov (United States)

    Müller, D.

    Die allgemeinen Ausdrücke für den NMR-Zentralübergang für Quadrupolkerne mit halbzahligem Spin bei Probenrotation, die von BEHRENS [1, 2] unter Berücksichtigung von Quadrupolwechselwirkungseffekten 2. Ordnung für beliebige Neigungswinkel der Rotationsachse abgeleitet wurden, werden für den praktisch interessierenden Fall der Probenrotation um den magischen Winkel (magic angle spinning, MAS) in einer den Ausgangsformeln für das Ruhespektrum (ohne Probenrotation) analogen Form dargestellt. Am Beispiel der 27Al-NMR-Spektren zweier Aluminate wird die Theorie überprüft und zur exakten Ermittlung der chemischen Verschiebungswerte aus den MAS-Spektren eingesetzt.Translated AbstractDetermination of Chemical Shifts of NMR-Frequencies of Quadrupolar Nuclei from the MAS-NMR SpectraThe general expressions for the NMR central transition of rotating samples with quadrupolar nuclei of half-integer spins, derived by BEHRENS [1, 2] for arbitrary angles of inclination of the spinning axis considering second-order quadrupolar effects, are presented for the practically interesting case of magic angle spinning (MAS) in a form analogous to the expressions for the resting sample. The theory is tested and used for the exact determination of the chemical shift values from the MAS-27Al-NMR spectra of two representative aluminates.

  15. OPENCORE NMR: Open-source core modules for implementing an integrated FPGA-based NMR spectrometer

    Science.gov (United States)

    Takeda, Kazuyuki

    2008-06-01

    A tool kit for implementing an integrated FPGA-based NMR spectrometer [K. Takeda, A highly integrated FPGA-based nuclear magnetic resonance spectrometer, Rev. Sci. Instrum. 78 (2007) 033103], referred to as the OPENCORE NMR spectrometer, is open to public. The system is composed of an FPGA chip and several peripheral boards for USB communication, direct-digital synthesis (DDS), RF transmission, signal acquisition, etc. Inside the FPGA chip have been implemented a number of digital modules including three pulse programmers, the digital part of DDS, a digital quadrature demodulator, dual digital low-pass filters, and a PC interface. These FPGA core modules are written in VHDL, and their source codes are available on our website. This work aims at providing sufficient information with which one can, given some facility in circuit board manufacturing, reproduce the OPENCORE NMR spectrometer presented here. Also, the users are encouraged to modify the design of spectrometer according to their own specific needs. A home-built NMR spectrometer can serve complementary roles to a sophisticated commercial spectrometer, should one comes across such new ideas that require heavy modification to hardware inside the spectrometer. This work can lower the barrier of building a handmade NMR spectrometer in the laboratory, and promote novel and exciting NMR experiments.

  16. 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. PMID:14759534

  17. Clinical application and evaluation of the diagnostic significance of NMR-tomography

    International Nuclear Information System (INIS)

    Aim of the project was the clinical application and evaluation of the diagnostic significance of NMR-tomography. About 3 000 patients have been examined especially with diseases of the brain. In 75% of all cases pathological findings could be detected. A subgroup of these patients was used for comprehensive studies with regard to tissue characterization based on the calculation of relaxation time parameters. With methods of image processing and classification techniques we tried to get a clear correlation between combined NMR-parameters and human tissue types. The results show that this procedure is able to improve the detectibility and the association to finding groups and tumorgradings in certain cases. (orig./ECB) With 134 refs., 17 tabs., 86 figs

  18. Solution conformation and dynamics of a tetrasaccharide related to the Lewis{sup X} antigen deduced by NMR relaxation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Poveda, Ana [Universidad Autonoma de Madrid, Servicio Interdepartamental de Investigacion (Spain); Asensio, Juan Luis; Martin-Pastor, Manuel; Jimenez-Barbero, Jesus [Instituto de Quimica Organica, CSIC, Grupo de Carbohidratos (Spain)

    1997-07-15

    {sup 1}H-NMR cross-relaxation rates and nonselective longitudinal relaxation times have been obtained at two magnetic fields (7.0 and 11.8 T) and at a variety of temperatures for the branched tetrasaccharide methyl 3-O-{alpha}-N-acetyl-galactosaminyl-{beta}-galactopyranosyl-(1{sup {yields}}4)[3-O-{alpha}-fucosyl] -glucopyranoside (1), an inhibitor of astrocyte growth. In addition, {sup 13}C-NMR relaxation data have also been recorded at both fields. The {sup 1}H-NMR relaxation data have been interpreted using different motional models to obtain proton-proton correlation times. The results indicate that the GalNAc and Fuc rings display more extensive local motion than the two inner Glc and Gal moieties, since those present significantly shorter local correlation times. The{sup 13}C-NMR relaxation parameters have been interpreted in terms of the Lipari-Szabo model-free approach. Thus, order parameters and internal motion correlation times have been deduced. As obtained for the{sup 1}H-NMR relaxation data, the two outer residues possess smaller order parameters than the two inner rings. Internal correlation times are in the order of 100 ps. The hydroxymethyl groups have also different behaviour,with the exocyclic carbon on the glucopyranoside unit showing the highestS{sup 2}. Molecular dynamics simulations using a solvated system have also been performed and internal motion correlation functions have been deduced from these calculations. Order parameters and interproton distances have been compared to those inferred from the NMR measurements. The obtained results are in fair agreement with the experimental data.

  19. Solution conformation and dynamics of a tetrasaccharide related to the LewisX antigen deduced by NMR relaxation measurements

    International Nuclear Information System (INIS)

    1H-NMR cross-relaxation rates and nonselective longitudinal relaxation times have been obtained at two magnetic fields (7.0 and 11.8 T) and at a variety of temperatures for the branched tetrasaccharide methyl 3-O-?-N-acetyl-galactosaminyl-?-galactopyranosyl-(1?4)[3-O-?-fucosyl] -glucopyranoside (1), an inhibitor of astrocyte growth. In addition, 13C-NMR relaxation data have also been recorded at both fields. The 1H-NMR relaxation data have been interpreted using different motional models to obtain proton-proton correlation times. The results indicate that the GalNAc and Fuc rings display more extensive local motion than the two inner Glc and Gal moieties, since those present significantly shorter local correlation times. The13C-NMR relaxation parameters have been interpreted in terms of the Lipari-Szabo model-free approach. Thus, order parameters and internal motion correlation times have been deduced. As obtained for the1H-NMR relaxation data, the two outer residues possess smaller order parameters than the two inner rings. Internal correlation times are in the order of 100 ps. The hydroxymethyl groups have also different behaviour,with the exocyclic carbon on the glucopyranoside unit showing the highestS2. Molecular dynamics simulations using a solvated system have also been performed and internal motion correlation functions have been deduced from these calculations. Order parameters and interproton distances have been compared to those inferred from the NMR measurements. The obtained results are in fair agreement with the experimental data

  20. Constraining 17O and 27Al NMR spectra of high-pressure crystals and glasses: New data for jadeite, pyrope, grossular, and mullite

    Science.gov (United States)

    Kelsey, K.E.; Stebbins, J.F.; Du, L.-S.; Hankins, B.

    2007-01-01

    The 17O NMR spectra of glasses quenched from melts at high pressure are often difficult to interpret due to overlapping peaks and lack of crystalline model compounds. High-pressure aluminosilicate glasses often contain significant amounts of [5]Al and [6]Al, thus these high-pressure glasses must contain oxygen bonded to high-coordinated aluminum. The 17O NMR parameters for the minerals jadeite, pyrope, grossular, and mullite are presented to assist interpretation of glass spectra and to help test quantum chemical calculations. The 17O NMR parameters for jadeite and grossular support previous peak assignments of oxygen bonded to Si and high-coordinated Al in high-pressure glasses as well as quantum chemical calculations. The oxygen tricluster in mullite is very similar to the previously observed tricluster in grossite (CaAl4 O7) and suspected triclusters in glasses. We also present 27Al NMR spectra for pyrope, grossular, and mullite.