WorldWideScience
1

Density functional theory (DFT) calculations of the proton nuclear magnetic resonance (NMR) spin-Hamiltonian parameters for serine  

International Nuclear Information System (INIS)

1H nuclear magnetic resonance spin-Hamiltonian parameters: chemical shifts ? and indirect spin–spin coupling constants J, have been calculated for serine, a brain metabolite. Serine molecules in the gas-phase as well as in solution in water have been investigated using density functional theory. Solvent and conformer effects as well as zero-point vibrational corrections have been taken into account. For the non-vibrating molecule, the best agreement is obtained when solvent and conformer effects are included. Zero-point vibrational corrections improve the agreement with experimental values, leading to a root mean square deviation of 0.05 ppm for chemical shifts and 0.7 Hz for spin–spin coupling constants

2

Research on the spin-Hamiltonian parameters and defect structure for Ni{sup +} ion in CdS  

Energy Technology Data Exchange (ETDEWEB)

The spin-Hamiltonian parameters (g factors g{sub //}, g{sub ?} and hyperfine structure constants A{sub //}, A{sub ?}) for Ni{sup +} in the trigonally-distorted tetrahedral Cd{sup 2+} site of CdS are calculated from the complete diagonalization (of energy matrix) method with the suitable parameters. In the method, the contributions to spin-Hamiltonian parameters from both the spin-orbit parameters of central d{sup n} ion and ligands are contained and the interactions among all the ground and excited states are considered. The calculated results show reasonable agreement with the experimental values. The defect structure of Ni{sup +} center, which is similar to those of other 3d{sup n} centers in CdS, is obtained from the calculation.

Zheng, Wen-Chen, E-mail: zhengwc1@163.com [Department of Material Science, Sichuan University, Chengdu 610064 (China); International Center for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); He, Lv [Department of Physics, Zhejiang Normal University, Jinhua 321004 (China); Li, Wei; Liu, Hong-Gang [Department of Material Science, Sichuan University, Chengdu 610064 (China)

2013-03-01

3

Investigation of the spin-Hamiltonian parameters for the trigonal U5+ center in CaF2 crystal.  

Science.gov (United States)

The spin-Hamiltonian parameters (g factor g(//), g(perpendicular) and hyperfine structure constants A(//), A(perpendicular)) of the trigonal U(5+) center in CaF(2) crystal have been calculated from the complete diagonalization (of energy matrix) method (CDM) for 5f(1) ions in trigonal crystal field and under an external magnetic field. In the calculation, the crystal-field parameters are estimated from the superposition model. From the calculations, these spin-Hamiltonian parameters are reasonably explained, and the defect model (i.e., the trigonal U(5+) center is attributed to U(5+) substituting for Ca(2+) in CaF(2) with six F(-) ions replaced by O(2-) and the other two F(-) sites vacant because of charge compensation) given in the previous paper is confirmed. The results are discussed. PMID:20308011

Zheng, Wen-Chen; Liu, Hong-Gang; Yang, Wei-Qing; Su, Ping

2010-06-01

4

Theoretical investigations of the spin Hamiltonian parameters and local angular variations for the trigonal V3+ centers in alum compounds  

Science.gov (United States)

The spin Hamiltonian parameters (zero-field splittings D, g factors g // and g ?) for V3+ in the alum compounds are theoretically studied using the perturbation formulas for these parameters for a 3d2 ion in the trigonally distorted octahedra. The contributions from the dynamical Jahn-Teller effect, the configuration interactions and the ligand orbital and spin-orbit coupling interactions are considered from the cluster approach in a uniform way. The angles in the deformed octahedra around V3+ ions are increased by 1.1°-2.7°, as compared with those ones for the host. The theoretical spin Hamiltonian parameters based on the above angular variations and the related effects show good agreement with the experimental data, which reveal that these effects (especially the Jahn-Teller effect) can bring forward significant influences on the spin Hamiltonian parameters, and should be taken into account in electron paramagnetic resonance (EPR) analysis. The contributions from the configuration interactions and the ligand orbital and spin-orbit coupling interactions are quantitatively involved from the cluster approach in a uniform way. The results are discussed.

Zhang, Zhi-Hong; Wu, Shao-Yi; Hu, Xian-Fen; Kuang, Min-Quan

2014-04-01

5

Modeling of crystal field and spin-Hamiltonian parameters for Ti{sup 3+}:MgO  

Energy Technology Data Exchange (ETDEWEB)

The aim of this paper is to model the crystal field parameters (CFPs) and spin-Hamiltonian parameters (g factors g{sub ||}, g{sub ?} and hyperfine structure constants A{sub ||}, A{sub ?}) for the Ti{sup 3+}:MgO system. The CFPs were modeled in the frame of superposition model of the crystal field theory, based on ab initio supercell calculations of Ti{sup 3+}:MgO geometry and crystal field parameter 10Dq. The obtained values were used to simulate the energy levels scheme, by diagonalizing the full energy matrix of the Hamiltonian. The EPR parameters have been calculated from both the complete diagonalization method and the perturbation theory method. All the obtained results (optical and EPR) were compared with experimental data and a good agreement is observed.

Barb, A.M.; Gruia, A.S.; Avram, C.N., E-mail: acalin@physics.uvt.ro

2013-12-01

6

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

7

Spin-Hamiltonian parameters and defect structure for the tetragonal Mo5+ center in the reduced BaTiO3:Mo crystal  

International Nuclear Information System (INIS)

The spin-Hamiltonian parameters (g factors g?, g? and hyperfine structure constants A?, A?) of the tetragonal Mo5+ center in reduced BaTiO3:Mo crystal with low temperature phase are calculated from the high-order perturbation formulas based on the two-mechanism model for d1 ions in octahedral clusters with the ground state 2B2 (|dxy?). In the model, both the contributions to spin-Hamiltonian parameters from the crystal-field (CF) mechanism and that from the charge-transfer (CT) mechanism (which is neglected in the widely-used crystal field theory) are considered. The calculated results are in reasonably agreement with the experimental values. The calculations show that for the spin-Hamiltonian parameters of BaTiO3:Mo5+, the relative importances of CT mechanism |QCT/QCF| are about 17%, 9%, 7% and 7% for Q=?g?, ?g?, A?(2), and A?(2) (where ?g=g?ge, ge?2.0023, the g factor of free electron), respectively. It appears that for the high valence state dn ion clusters in crystals, the precise and complete calculations of spin-Hamiltonian parameters should take both the CF and CT mechanisms into account. The tetragonally-compressed distortion of (MoO6)7? octahedral clusters in the low-temperature rhombohedral phase of BaTiO3 caused by the static Jahn–Teller effect is also acquired from the calculations. The results are discussed. - Highlights: • Spin-Hamiltonian parameters of Mo5+ in rhombohedral BaTiO3 are calculated. • The calculation is based on the two (CF and CT)-mechanism model. • Contribution due to the charge-transfer mechanism should be considered. • Calculation confirms the defect model and obtains the defect structural data

8

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 propnetic, and optical properties)

9

151,153Eu electron paramagnetic resonance in SrMoO4 and determination of signs of spin Hamiltonian parameters at different temperatures  

Science.gov (United States)

The electron paramagnetic resonance (EPR) spectra of Eu2+ impurity centers in SrMoO4 crystals have been studied in the temperature range of 1.8, 100-300 K. A hyperfine structure has been simulated for 151,153Eu of different EPR transitions observed experimentally at different temperatures and external magnetic field orientations. A unique set of all parameters of the spin Hamiltonian for the known sign of the hyperfine interaction parameters A i has been determined. It has been found that the diagonal parameters | bn 0| of the spin Hamiltonian decrease with increasing temperature; however, the parameter b4 4 increases. The results of the study have demonstrated that | b2 0( T)/ P2 0( T)| ˜ const for 151,153Eu in this single crystal.

Gorlov, A. D.

2014-11-01

10

Theoretical investigations of the local structure and the spin Hamiltonian parameters for Ti{sup 2+} in MgCl{sub 2}  

Energy Technology Data Exchange (ETDEWEB)

The local structure and spin Hamiltonian parameters (zero-field splitting and g factors) for Ti{sup 2+} in MgCl{sub 2} are theoretically studied using the perturbation formulas of these parameters for a 3d{sup 2} ion under trigonally distorted octahedra. The contributions from the dynamical Jahn–Teller effect, the configuration interactions and the ligand orbital and spin–orbit coupling interactions are quantitatively involved based on the cluster approach in a uniform way. The chlorine polyhedron around the impurity Ti{sup 2+} is found to transform from a slightly compressed octahedron in pure MgCl{sub 2} to a slightly elongated one, characterized by the local angular decrease of 0.3° related to the host bond angle 54.78° due to the Jahn–Teller effect. The calculated spin Hamiltonian parameters based on the above trigonal elongation show good agreement with the experimental data. The results are discussed.

Zhang, Zhi-Hong, E-mail: zhihongzhang723@gmail.com [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Wu, Shao-Yi [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Hu, Xian-Fen; Kuang, Min-Quan [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2013-07-15

11

Theoretical calculations of spin-Hamiltonian parameters for the rhombic-like Mo{sup 5+} centers in KTiOPO{sub 4} crystal  

Energy Technology Data Exchange (ETDEWEB)

The spin-Hamiltonian parameters (g factors g{sub i} and hyperfine structure constants A{sub i}, were i=x, y and z) for Mo{sup 5+} ion occupying the Ti(1) site with approximately rhombic symmetry in KTiOPO{sub 4} crystal are calculated from the high-order perturbation formulas based on the two-mechanism model. In the model, not only the contribution due to the conventional crystal-field (CF) mechanism, but also those due to the charge-transfer (CT) mechanism are included. The six calculated spin-Hamiltonian parameters with four adjustable parameters are in reasonable agreement with the experimental values. The calculations show that for more accurate calculations of spin-Hamiltonian parameters of the high valence d{sup n} ions (e.g., Mo{sup 5+} considered here) in crystals, the contribution from CT mechanism, which is ignored in the conventional crystal field theory, should be taken into account. The reasonable crystal field energy levels of Mo{sup 5+} in KTiOPO{sub 4} are also predicted from calculations.

Yang, Mei [School of Physics and Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Wen-Chen, Zheng, E-mail: zhengwc1@163.com [Department of Material Science, Sichuan University, Chengdu 610064 (China); Hong-Gang, Liu [Department of Material Science, Sichuan University, Chengdu 610064 (China)

2013-12-01

12

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

13

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

Science.gov (United States)

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.

Mei, Yang; Zheng, Wen-Chen; Zhang, Lin; Chen, Bo-Wei

2014-11-01

14

Theoretical studies of spin-Hamiltonian parameters of Mo{sup 5+} ion doped in K{sub 2}SnCl{sub 6} crystal  

Energy Technology Data Exchange (ETDEWEB)

The spin-Hamiltonian (SH) parameters (g factors g{sub //}, g{sub ?} and hyperfine structure constants A{sub //}, A{sub ?} ) of K{sub 2}SnCl{sub 6}: Mo{sup 5+} (4d{sup 1}) crystal are theoretically studied by the use of two microscopic spin-Hamiltonian (SH) methods, the high-order perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM) within the molecular orbital (MO) scheme. The contributions arising both from the crystal field and charge transfer excitations are taken into account. The investigations show that the charge transfer mechanism plays a decisive role in the understanding of the spin-Hamiltonian (SH) parameters for 4d{sup 1} ions in crystals with the strong coordinate covalence, especially for g{sub //}>g{sub ?} which cannot be explained in the frame work of traditional crystal field approximation (CFA). The local defect structure around Mo{sup 5+} impurity ion center is determined to be D{sub 4} {sub h} point group symmetry.

Fang, Wang, E-mail: mailfangwang@163.com; Yang, Da-Xiao; Chen, Heng-Jie; Tang, Hai-Yan

2013-11-15

15

Spin-Hamiltonian parameters and defect structure for the tetragonal Mo{sup 5+} center in the reduced BaTiO{sub 3}:Mo crystal  

Energy Technology Data Exchange (ETDEWEB)

The spin-Hamiltonian parameters (g factors g{sub ?}, g{sub ?} and hyperfine structure constants A{sub ?}, A{sub ?}) of the tetragonal Mo{sup 5+} center in reduced BaTiO{sub 3}:Mo crystal with low temperature phase are calculated from the high-order perturbation formulas based on the two-mechanism model for d{sup 1} ions in octahedral clusters with the ground state {sup 2}B{sub 2} (|d{sub xy}?). In the model, both the contributions to spin-Hamiltonian parameters from the crystal-field (CF) mechanism and that from the charge-transfer (CT) mechanism (which is neglected in the widely-used crystal field theory) are considered. The calculated results are in reasonably agreement with the experimental values. The calculations show that for the spin-Hamiltonian parameters of BaTiO{sub 3}:Mo{sup 5+}, the relative importances of CT mechanism |Q{sup CT}/Q{sup CF}| are about 17%, 9%, 7% and 7% for Q=?g{sub ?}, ?g{sub ?}, A{sub ?}{sup (2)}, and A{sub ?}{sup (2)} (where ?g=g?g{sub e}, g{sub e}?2.0023, the g factor of free electron), respectively. It appears that for the high valence state d{sup n} ion clusters in crystals, the precise and complete calculations of spin-Hamiltonian parameters should take both the CF and CT mechanisms into account. The tetragonally-compressed distortion of (MoO{sub 6}){sup 7?} octahedral clusters in the low-temperature rhombohedral phase of BaTiO{sub 3} caused by the static Jahn–Teller effect is also acquired from the calculations. The results are discussed. - Highlights: • Spin-Hamiltonian parameters of Mo{sup 5+} in rhombohedral BaTiO{sub 3} are calculated. • The calculation is based on the two (CF and CT)-mechanism model. • Contribution due to the charge-transfer mechanism should be considered. • Calculation confirms the defect model and obtains the defect structural data.

Mei, Yang [School of Physics and Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Zheng, Wen-Chen, E-mail: zhengwc1@163.com [Department of Material Science, Sichuan University, Chengdu 610064 (China)

2013-12-15

16

Theoretical study of the spin Hamiltonian parameters of vanadium ions V2+ in CsMgX3 (X=Cl,Br,I)  

International Nuclear Information System (INIS)

The spin Hamiltonian g factors and the hyperfine structure constants for V2+ in CsMgX3 (X=Cl,Br,I) are theoretically studied by using the perturbation formulas of these parameters for a 3d3 ion in octahedral symmetry, based on the cluster approach. In such formulas, the contributions from the s-orbitals of the ligands were usually neglected. Here they are taken into account. The theoretical results (particularly the g factor for CsMgI3) show a significant improvement compared with those in absence of the ligand s-orbital contributions in the previous studies. (orig.)

17

Theoretical studies of the spin-Hamiltonian parameters for the or- thorhombic Pr4+ centers in Sr2CeO4 crystals  

Science.gov (United States)

Theoretical studies of spin-Hamiltonian (SH) parameters associated with Pr^{4+} in Sr_{2}CeO_{4} 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 bot ) for the orthorhombic Pr^{4+} ion in Sr_{2}CeO_{4} 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.

Feng, Wen-Lin

2008-04-01

18

Studies of the spin-Hamiltonian parameters and defect structures for Gd3+ ions in zircon-structure silicates MSiO4 (M=Zr, Hf, Th).  

Science.gov (United States)

The spin-Hamiltonian parameters (g factors g?, g? and zero-field splittings b2(0), b4(0), b4(4), b6(0), b6(4)) for 4f7 ion Gd3+ at the tetragonal M4+ site of zircon-structure silicates MSiO4 (M=Zr, Hf, Th) are calculated from a diagonalization (of energy matrix) method. The Hamiltonian concerning this energy matrix contains the free-ion, crystal-field interaction and Zeeman interaction terms and the 56×56 energy matrix is constructed by considering the ground multiplet 8S7/2 and the excited multiplets 6L7/2 (L=P, D, F, G, H, I). The defect structures of Gd3+ centers in the three MSiO4 crystals are yielded from the calculation. The results are discussed. PMID:21665526

Yang, Wei-Qing; Zheng, Wen-Chen

2011-09-01

19

Theoretical studies on the spin Hamiltonian parameters for monovalent chromium in ZnX (X=S, Se, Te) and CdTe  

Science.gov (United States)

The spin Hamiltonian parameters (g factor and hyperfine structure constants) of Cr+ in ZnX (X = S, Se, Te) and CdTe are theoretically investigated, using the perturbation formulas of these parameters for a tetrahedral 3d5 cluster. Both the contributions from the crystal-field (CF) and charge transfer (CT) mechanisms are considered from the cluster approach. The calculated results show good agreement with the experimental data. The CT contribution to g-shift ?g (=g - g s, where g s =2.0023 is the spin only value) is opposite (positive) in sign related to the CF one, and its importance (characterized by the relative ratio (|?g CT/?g CF|) is 11%, 66% and 104% (71%) for ZnS, ZnSe and ZnTe (CdTe), respectively. ACT from the CT contribution to hyperfine structure constant is the same (positive) in sign and about 50-53% in magnitude as compared with ACF from the CF one.

Hu, Xian-Fen; Wu, Shao-Yi; Kuang, Min-Quan; Li, Guo-Liang

2014-03-01

20

Studies on the spin Hamiltonian parameters and local angular distortions for the tetragonal Cu2+ centers in the ZnX (X=O and S) nanocrystals  

Science.gov (United States)

The spin Hamiltonian parameters (g factors and hyperfine structure constants) and local structures are theoretically studied for the tetragonal Cu2+ centers in the ZnX (X=O and S) nanocrystals from the perturbation formulas of these parameters for a 3d9 ion in tetragonally distorted tetrahedra. The ligand orbital and spin-orbit coupling contributions are considered in view of strong covalency. Due to the Jahn-Teller effect, the local Cu2+?X2- bond angles between the four equivalent impurity-ligand bonds and the four-fold axis are found to be about 2.47° and 1.68° larger than that (?54.74°) for an ideal tetrahedron. This induces tetragonally compressed [CuX4]6- clusters on tetrahedral substitutional Zn2+ sites, different from the assignments (i.e., Cu2+ on tetragonally elongated octahedral and tetrahedral substitutional sites in the ZnO and ZnS nanocrystals, respectively) in the previous works. The calculated g factors for both systems and the parallel component of the hyperfine structure constants for the ZnS:Cu2+ nanocrystals based on the above local angular distortions are in good agreement with the observed values. The validity of the present assignments for the local structures of the Cu2+ centers is analyzed.

Li, Guo-Liang; Wu, Shao-Yi; Zhang, Zhi-Hong; Ding, Chang-Chun; Hu, Xian-Fen

2015-01-01

21

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)

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.

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

22

Theoretical investigations of the spin Hamiltonian parameters and local structures for the tetragonal V{sup 3+} and Ti{sup 2+} centers in MgO and CaO  

Energy Technology Data Exchange (ETDEWEB)

The spin Hamiltonian parameters (zero-field splitting D, g factor and hyperfine structure constant) and the local structures for MgO:V{sup 3+}, CaO:V{sup 3+} and CaO:Ti{sup 2+} are theoretically investigated from the perturbation formulas of these parameters for 3d{sup 2} ions under tetragonally distorted octahedra. The contributions from the dynamical Jahn-Teller effect, the configuration interactions and the ligand orbital and spin-orbit coupling interactions are quantitatively taken into account based on the cluster approach in a uniform way. The ligand octahedra are found to suffer the relative elongations of about 1.5%, 4.4% and 4.6% for MgO:V{sup 3+}, CaO:V{sup 3+} and CaO:Ti{sup 2+}, respectively, along the C{sub 4} axis due to the dynamical Jahn-Teller effect. The calculated spin Hamiltonian parameters based on the above local tetragonal elongations show reasonable agreement with the experimental data for all the systems. The results are discussed.

Zhang Zhihong, E-mail: zhihongzhang723@gmail.com [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Wu Shaoyi [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054 (China); International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Kuang Minquan; Hu Xianfen [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2013-01-01

23

Supersymmetric analysis of a spin Hamiltonian model  

Energy Technology Data Exchange (ETDEWEB)

The intertwining method has been applied to the effective potential of the spin Hamiltonian H=-{gamma}S{sub z}{sup 2}-BS{sub x}. The supersymmetric partner potentials, some of which are singular, are obtained by using low-lying states of this potential. Applying the intertwining method successively, hierarchy of effective potentials has been established. Supersymmetric partner of the transformed spin Hamiltonian's effective potential has also been constructed.

Demircioglu, B. [Saraykoey Nuclear Research and Training Center, Saraykoey /Ankara (Turkey); Bilge Ocak, S. [Saraykoey Nuclear Research and Training Center, Saraykoey/Ankara (Turkey)]. E-mail: semamuzo@yahoo.com; Kuru, S. [Department of Physics, Ankara University, Faculty of Science, 06100 Tandogan/Ankara (Turkey)

2006-04-17

24

Theoretical studies of the spin-Hamiltonian parameters of the oxycation MoO3+ in (NH4)2MoOCl5 and K2MoOF5 single crystals  

Science.gov (United States)

Theoretical formulae for the spin-Hamiltonian (SH) parameters (g tensor g//, g? and hyperfine structure A tensor A//, A?) of the ground state of oxycation MoO3+ in [MOX5]2- (M=Mo5+, Cr4+, V3+, X=F-, Cl- or Br- ) complexes are derived by the high-order perturbation method within the frame of molecular orbital (MO) scheme. In those formulae, the contributions to the SH parameters arising both from the crystal field (CF) and charge transfer (CT) excitations are taken into account, which are derived up to the third and second order, respectively. Those formulae are applied to calculate the SH of the oxycation MoO3+ in (NH4)2MoOCl5 and K2MoOF5 single crystals by the best match method, and the calculated results are in good agreement with the experimental data. The investigations show that the charge transfer mechanism play a decisive role in the understanding for the SH parameters for 4d1 ions in crystals with the strong coordinate covalence, especially for anomalously experimental results g//>g? which cannot be explained by the traditional CF approximation alone. The MO coefficients are determined and the results are discussed.

Fang, Wang; Chen, Heng-Jie; Tan, Ren-Bing; Yang, Wen-Yan; Tang, Hai-Yan

2014-10-01

25

Investigations on the spin Hamiltonian parameters for Yb{sup 3+} ion in Bi{sub 2}Sr{sub 2}YCu{sub 2}O{sub 8}  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • The EPR spectra are studied for the two orthorhombic Yb{sup 3+} centers in Bi{sub 2}Sr{sub 2}YCu{sub 2}O{sub 8}. • The contributions due to the admixtures of various states are taken into account. • The spin Hamiltonian parameters show good agreement with experimental data. -- Abstract: Many theoretical and experimental works have been done to understand the several characteristics of the Bi{sub 2}Sr{sub 2}YCu{sub 2}O{sub 8}. Since the electron paramagnetic resonance (EPR) is a powerful tool to analyze the electronic and magnetic properties of paramagnetic impurities in compounds, studies on the above EPR parameters would be helpful to the investigations of the characteristics for the superconductors. In this paper, EPR parameters anisotropic g factors g{sub x}, g{sub y}, g{sub z}, and the hyperfine structure constants A{sub x}, A{sub y} and A{sub z} of the two orthorhombic Yb{sup 3+} centers in Bi{sub 2}Sr{sub 2}YCu{sub 2}O{sub 8} are theoretically studied from the perturbation formulas of these parameters for a 4f{sup 13} ion in orthorhombic symmetry. In these formulas, the contributions due to the admixtures of various states are taken into account, and the orthorhombic field parameters are obtained from the superposition model and the local structure of the impurity Yb{sup 3+} ion occupying the host Bi{sup 3+} site. The calculated EPR parameters are reasonable agree with the observed values.

Dong, Hui-Ning, E-mail: donghn@163.com; Dong, Meng-Ran; Li, Jin-Jin; Liu, Jun

2013-10-15

26

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 theore3, 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

27

Parameters of Cu Nuclear Spin Hamiltonian in Mixed Crystals (CH3NH3)2Cu(Cl1-xBrx)4  

Science.gov (United States)

NMR measurements of Cu nuclei are carried out in the ferromagnetic region of these mixed crystals to clarify the dependences of the hyperfine field, Hhf, and the quadrupole frequency, ?Q, on the surrounding ligand ions. Since the Cu2+ ground state is given by d(x2-y2), the obtained values of Hhf and ?Q are due to the number, n, of Br- ions in the four ligands on the x- and y-axes and are fitted by the experimental formula, Hhf?{=}Hhf?(0)+khf?n (?: x, y, z) and ?Q{=}?Q(0)+kQn, where k is the proportional constant. The differences between the hyperfine field along the x-axis and the y-axis are observed and are interpreted by the deviation from the tetragonal crystalline field.

Kubo, Hidenori; Suzuki, Yoshio; Tanimoto, Mitsuho; Uryû, Norikiyo

1983-04-01

28

Theoretical Explanations of the Spin Hamiltonian Parameters for Cu2+ Ion in LaSrAl1-xCuxO4 Solid Solution  

Science.gov (United States)

It is of interest for layered oxides containing copper because they are related to high temperature superconductivity. Among them, LaSrAl1-xCuxO4 solid solution has received much attention due to its elastic and elasto-optic properties and application as promising substrate for high-Tc superconducting thin films. So many theoretical and experimental works have been done to understand the several characteristics of the LaSrAl1-xCuxO4 materials. In this paper, the electron paramagnetic resonance g factors g//, g? and hyperfine structure constants A//, A? for the tetragonal Cu2+ center in LaSrAl1-xCuxO4 solid solution are theoretically explained by the method of diagonalizing the full Hamiltonian matrix. The related crystal field parameters are calculated from the superposition model and the local structural parameters of the impurity Cu2+ occupying the host Al3+ site. The superposition model parameters used in this work are comparable with those for similar tetragonal (CuO6)10- clusters in the previous works. The calculated results are in reasonable agreement with the observed values. The results are discussed.

Dong, Hui-Ning; Keeble, David J.; Wu, Shao-Yi

29

Gravitational spin Hamiltonians from the S matrix  

CERN Document Server

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...

Vaidya, Varun

2014-01-01

30

Gravitational spin Hamiltonians from the S matrix  

Science.gov (United States)

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.

Vaidya, Varun

2015-01-01

31

Spin densities on atoms in conjugated molecules in the spin-Hamiltonian method  

International Nuclear Information System (INIS)

A method for calculating the spin densities on atoms (rho z) of covalent molecules with conjugated bonds has been proposed in the framework of the spin-Hamiltonian method. In the example of calculations of the ground states of polyene radicals and the lowest triplet term of 6-radialene it has been shown that the spin-Hamiltonian method occupies an intermediate position between the unrestricted Hartree-Fock method and the method of single-particle spin-pairing amplitudes with respect to the accuracy of the determination of rho z. An estimate of the ground-state energy of a model ferromagnetic organic compound has been obtained by extrapolating the numerical calculations for polyradicals consisting of allyl fragments

32

NMR of mixed crystals (CH sub(3)NH sub(3)) sub(2)Cu(C1 sub(1-x)Br sub(x)) sub(4)(0<=x<=1)  

International Nuclear Information System (INIS)

By applying an external field to the local symmetry axes, the NMR spectra of Cu nuclei are determined by the pulsed NMR method at 1.75K. The parameters of the nuclear spin Hamiltonian of Cu nuclei are estimated by the analysis of the spectra. It is shown that the hyperfine field and quadrupole frequency systematically depend on n of the complex (CuCl sub(4-n) Br sub(n)) sup(2-) (n=0,1,2,3,4). The depend ence on n is due to the small covalency effect with the ligand ions. (author)

33

The PAW/GIPAW approach for computing NMR parameters: a new dimension added to NMR study of solids.  

Science.gov (United States)

In 2001, Mauri and Pickard introduced the gauge including projected augmented wave (GIPAW) method that enabled for the first time the calculation of all-electron NMR parameters in solids, i.e. accounting for periodic boundary conditions. The GIPAW method roots in the plane wave pseudopotential formalism of the density functional theory (DFT), and avoids the use of the cluster approximation. This method has undoubtedly revitalized the interest in quantum chemical calculations in the solid-state NMR community. It has quickly evolved and improved so that the calculation of the key components of NMR interactions, namely the shielding and electric field gradient tensors, has now become a routine for most of the common nuclei studied in NMR. Availability of reliable implementations in several software packages (CASTEP, Quantum Espresso, PARATEC) make its usage more and more increasingly popular, maybe indispensable in near future for all material NMR studies. The majority of nuclei of the periodic table have already been investigated by GIPAW, and because of its high accuracy it is quickly becoming an essential tool for interpreting and understanding experimental NMR spectra, providing reliable assignments of the observed resonances to crystallographic sites or enabling a priori prediction of NMR data. The continuous increase of computing power makes ever larger (and thus more realistic) systems amenable to first-principles analysis. In the near future perspectives, as the incorporation of dynamical effects and/or disorder are still at their early developments, these areas will certainly be the prime target. PMID:21612895

Charpentier, Thibault

2011-07-01

34

Understanding visual map formation through vortex dynamics of spin Hamiltonian models  

CERN Document Server

We introduce a general method for cerebral cortical map generation and apply it to pattern formation in orientation and ocular dominance columns of the brain. From a known cortical structure, we build spin Hamiltonian models with long-range interactions of the Mexican hat type. These Hamiltonian models allow a coherent interpretation of the diverse phenomena in the map formation in the visual cortex with the help of relaxation dynamics of spins. In particular, we predict various phenomena of self-organization in orientation and ocular map formation including the pinwheel annihilation and its dependency on the columnar wave vector and boundary conditions.

Cho, M W; Cho, Myoung Won; Kim, Seunghwan

2003-01-01

35

Signal intensities derived from different NMR probes and parameters contribute to variations in quantification of metabolites.  

Science.gov (United States)

We discovered that serious issues could arise that may complicate interpretation of metabolomic data when identical samples are analyzed at more than one NMR facility, or using slightly different NMR parameters on the same instrument. This is important because cross-center validation metabolomics studies are essential for the reliable application of metabolomics to clinical biomarker discovery. To test the reproducibility of quantified metabolite data at multiple sites, technical replicates of urine samples were assayed by 1D-(1)H-NMR at the University of Alberta and the University of Michigan. Urine samples were obtained from healthy controls under a standard operating procedure for collection and processing. Subsequent analysis using standard statistical techniques revealed that quantitative data across sites can be achieved, but also that previously unrecognized NMR parameter differences can dramatically and widely perturb results. We present here a confirmed validation of NMR analysis at two sites, and report the range and magnitude that common NMR parameters involved in solvent suppression can have on quantitated metabolomics data. Specifically, saturation power levels greatly influenced peak height intensities in a frequency-dependent manner for a number of metabolites, which markedly impacted the quantification of metabolites. We also investigated other NMR parameters to determine their effects on further quantitative accuracy and precision. Collectively, these findings highlight the importance of and need for consistent use of NMR parameter settings within and across centers in order to generate reliable, reproducible quantified NMR metabolomics data. PMID:24465670

Lacy, Paige; McKay, Ryan T; Finkel, Michael; Karnovsky, Alla; Woehler, Scott; Lewis, Michael J; Chang, David; Stringer, Kathleen A

2014-01-01

36

Theory of half-metallic double perovskites. II. Effective spin Hamiltonian and disorder effects  

Science.gov (United States)

Double perovskites such as Sr2FeMoO6 are materials with half-metallic ground states and ferrimagnetic Tc's well above room temperature. This paper is the second of our comprehensive theory for half-metallic double perovskites. Here we derive an effective Hamiltonian for the Fe core spins by “integrating out” the itinerant Mo electrons and obtain an unusual double-square-root form of the spin-spin interaction. We validate the classical spin Hamiltonian by comparing its results with those of the full quantum treatment presented in a companion paper [O. N. Meetei , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.87.165104 87, 165104 (2013)]. We then use the effective Hamiltonian to compute magnetic properties as a function of temperature and disorder and discuss the effect of excess Mo, excess Fe, and antisite disorder on the magnetization and Tc. We conclude with a proposal to increase Tc without sacrificing carrier polarization.

Erten, Onur; Meetei, O. Nganba; Mukherjee, Anamitra; Randeria, Mohit; Trivedi, Nandini; Woodward, Patrick

2013-04-01

37

Extended Czjzek model applied to NMR parameter distributions in sodium metaphosphate glass  

International Nuclear Information System (INIS)

The extended Czjzek model (ECM) is applied to the distribution of NMR parameters of a simple glass model (sodium metaphosphate, NaPO3) obtained by molecular dynamics (MD) simulations. Accurate NMR tensors, electric field gradient (EFG) and chemical shift anisotropy (CSA) are calculated from density functional theory (DFT) within the well-established PAW/GIPAW framework. The theoretical results are compared to experimental high-resolution solid-state NMR data and are used to validate the considered structural model. The distributions of the calculated coupling constant CQ ? |Vzz| and the asymmetry parameter ?Q that characterize the quadrupolar interaction are discussed in terms of structural considerations with the help of a simple point charge model. Finally, the ECM analysis is shown to be relevant for studying the distribution of CSA tensor parameters and gives new insight into the structural characterization of disordered systems by solid-state NMR. (paper)

38

Theoretical and Experimental NMR Parameters of Substituted Purines  

International Nuclear Information System (INIS)

Structural modifications of the purine bases, nucleosides, and nucleotides have resulted in the discovery of thousands of biologically active compounds, including many clinically used drugs. The proper characterization of the electron density distribution in the variously substituted purine derivatives is of great importance and significance due to the governing effect of electron distribution on the intermolecular interactions. NMR chemical shifts and indirect spin-spin coupling constants represent very sensitive probes for studying the electron distribution in these heterocycles. The variously substituted purine derivatives were investigated theoretically by DFT (B3LYP/6-311+G**) and experimentally using 1H-, 13C-, and 15N-NMR spectroscopy in the solution. DFT calculations of chemical shifts and scalar coupling constants were used for supporting and explaining the experimental data. (author)

39

Structure simulation with calculated NMR parameters - integrating COSMOS into the CCPN framework.  

Science.gov (United States)

The Collaborative Computing Project for NMR (CCPN) has build a software framework consisting of the CCPN data model (with APIs) for NMR related data, the CcpNmr Analysis program and additional tools like CcpNmr FormatConverter. The open architecture allows for the integration of external software to extend the abilities of the CCPN framework with additional calculation methods. Recently, we have carried out the first steps for integrating our software Computer Simulation of Molecular Structures (COSMOS) into the CCPN framework. The COSMOS-NMR force field unites quantum chemical routines for the calculation of molecular properties with a molecular mechanics force field yielding the relative molecular energies. COSMOS-NMR allows introducing NMR parameters as constraints into molecular mechanics calculations. The resulting infrastructure will be made available for the NMR community. As a first application we have tested the evaluation of calculated protein structures using COSMOS-derived 13C C? and C? chemical shifts. In this paper we give an overview of the methodology and a roadmap for future developments and applications. PMID:22942007

Schneider, Olaf; Fogh, Rasmus H; Sternberg, Ulrich; Klenin, Konstantin; Kondov, Ivan

2012-01-01

40

Practical Model Fitting Approaches to the Direct Extraction of NMR Parameters Simultaneously from All Dimensions of Multidimensional NMR Spectra  

International Nuclear Information System (INIS)

A maximum likelihood (ML)-based approach has been established for the direct extraction of NMR parameters (e.g., frequency, amplitude, phase, and decay rate) simultaneously from all dimensions of a D-dimensional NMR spectrum. The approach, referred to here as HTFD-ML (hybrid time frequency domain maximum likelihood), constructs a time-domain model composed of a sum of exponentially-decaying sinusoidal signals. The apodized Fourier transform of this time-domain signal is a model spectrum that represents the 'best fit' to the equivalent frequency-domain data spectrum. The desired amplitude and frequency parameters can be extracted directly from the signal model constructed by the HTFD-ML algorithm. The HTFD-ML approach presented here, as embodied in the software package CHIFIT, is designed to meet the challenges posed by model fitting of D-dimensional NMR data sets, where each consists of many data points (108 is not uncommon) encoding information about numerous signals (up to 105 for a protein of moderate size) that exhibit spectral overlap. The suitability of the approach is demonstrated by its application to the concerted analysis of a series of ten 2D 1H-15N HSQC experiments measuring 15N T1 relaxation. In addition to demonstrating the practicality of performing maximum likelihood analysis on large, multidimensional NMR spectra, the results demonstrate that this parametric model-fitting approach provides more accurate amplitude and frequency estimates than those obtude and frequency estimates than those obtained from conventional peak-based analysis of the FT spectrum. The improved performance of the model fitting approach derives from its ability to take into account the simultaneous contributions of all signals in a crowded spectral region (deconvolution) as well as to incorporate prior knowledge in constructing models to fit the data

41

NMR  

International Nuclear Information System (INIS)

For the interpretation of NMR images, it is important to recognize the effect of tissue specific parameters on the image contrast. In this study, we prepared T1, T2-sensitivity (total relaxation sensitivity) map as a means of presentation of the correlation between T1, T2 change and signal intensity change of various tissues. Ratio between fractional rate changes of each relaxation time against entire relaxation time and those of signal intensity against entire signal intensity; (? intensity/intensity)/(? relaxation time/relaxation time), are measured respectively by means of logarithmic differentiation, by which the sensitivity of each T1 and T2 (S (int., T1) and, S (int., T2)) was calculated. The summation of respective relaxation sensitivity was designated as total relaxation sensitivity (S. total (int., T1, T2)). The resulting S. total (int., T1, T2) is classified into seven different color indices according to its value. The classified S. total are plotted on T1 axis (T1; 0< T1<1,000 msec) and T2 axis (T2; 0< T2<200 msec). We present T1, T2-sensitivity map under the pulse sequence which applied frequently on Asahi Mark-J system. The classified S. total express generally the degree of dependence of respective relaxation time and we discuss about the precaution and limitation of T1, T2-sensitivity map application. (author)

42

Method and apparatus for rapid NMR imaging of nuclear parameters with an object  

International Nuclear Information System (INIS)

An imaging NMR scanner obtains plural spin echo signals during each of successive measurement cycles permitting determination of the T2 parameter for each display pixel after but a single measurement sequence. The amplitude of the NMR spin echo responses is dependent on an ''a'' machine parameter (the elapsed time between initiation of a given measurement cycle and the occurrence of the NMR response) and upon a ''b'' machine parameter (the elapsed time between initiation of successive measurement cycles). These a and b machine time parameters are selectively controlled to enhance resultant image contrast between different types of tissue or other internal structures of an object under examination. Special phase control circuits ensure the repeatability of relative phasing between successive NMR responses from the same measured volume and/or of reference RF signals utilized to frequency translate and synchronously demodulate the NMR responses in the successive measurement cycles of a complete measurement sequence. Special sub-sequences of four measurement cycles are utilized to provide resultant combined spin echo measurements substantially independent of FID signal components

43

A long-wave action of spin Hamiltonians and the inverse problem of the calculus of variations  

OpenAIRE

We suggest a method of derivation of the long-wave action of the model spin Hamiltonians using the non-linear partial differential equations of motions of the individual spins. According to the Vainberg's theorem the set of these equations are (formal) potential if the symmetry analysis for the Frechet derivatives of the system is true. The case of Heisenberg (anti)ferromagnets is considered. It is shown the functional whose stationary points are described by the equations c...

Bostrem, I. G.; Ovchinnikov, A. S.; Egorov, R. F.

2003-01-01

44

31P NMR parameters of amorphous Ni-P alloys prepared by different methods  

International Nuclear Information System (INIS)

Room temperature 31P NMR parameters were studied on amorphous Ni-P alloys prepared by four methods (chemical reduction from chloridic and sulphuric bath, electrodeposition, melt quenching). Those of the NMR parameters which depend on the average properties of the electronic structure are the same for each kind of alloys with the same chemical composition. The field-dependent linewidth contribution which reflects the fluctuations in the electronic structure indicates that all the alloys have an inhomogeneous electronic structure and a higher degree of inhomogeneity is observed in samples prepared by chemical reduction from the chloridic bath in comparison with alloys obtained by the other methods. (author)

45

The NMR parameters of the SiC-doped BN nanotubes: A DFT study  

Science.gov (United States)

NMR parameters consisting of isotropic and anisotropic chemical shielding parameters have been calculated based on density functional theory (DFT) to investigate the properties of the electronic structures of the silicon-carbon (SiC) doped boron nitride nanotubes (BNNTs). The structures have been allowed to relax by performing all atomic optimization. Afterwards, the chemical shielding (CS) parameters have been calculated for the B-11, C-13, N-15, and Si-29 atoms in the pristine and the SiC-doped models of the (4,4) armchair and (6,0) zigzag BNNTs. The results indicated that the doping of the B and N atoms by the C and Si atoms, respectively, has more significant influence on the calculated NMR parameters than the doping of the B and N atoms by the Si and C atoms, respectively. In comparison to the pristine model, the band gaps detect more changes in the former model of the doping process.

Mirzaei, Mahmoud

2010-05-01

46

ESR and NMR study of mixed yttrium-lutetium-aluminum garnets  

International Nuclear Information System (INIS)

ESR of Mo3+ ions and NMR of 27Al nuclei is investigated in mixed single crystals of yttrium-lutetium-aluminium garnets (Ysub(1-x)Lusub(x))3Al5O12, where 0 3+ and 27Al compared with Y3Al5O12 and Lu3Al5O12 single crystals are revealed associated with symmetry and crystalline field parameter changes at isomorphous substitution of Y3+ ions in the rare-earth sublattice of the garnet by those of Lu3+. Symmetry, nearest coordination, and parameters of spin-Hamiltonians are estimated concerning all of Mo3+ and 27Al centres in (Ysub(1-x)Lusub(x))3Al5O12 at x < 0.15. (author)

47

Solid state NMR interaction parameters of oxygens linking titanium and silicon in crystalline cyclic titanodiphenylsiloxanes.  

Science.gov (United States)

17O static and magic angle spinning NMR spectra are reported from three crystalline cyclic titanodiphenylsiloxanes at magnetic fields of 5.6, 14.1, and 17.6 T. These compounds allow the NMR parameters characteristic of Ti-O-Si environments to be determined. It appears from these data that the quadrupole interaction (C(Q)) of such environments is in the range of 3-3.5 MHz and that Si-O-TiO3 sites are less shifted than Si-O-TiO5. The relatively large isotropic chemical range observed suggests that for structurally and atomically disordered titanosilicate-based materials the very highest applied magnetic field may not produce the best 17O solid state NMR spectra. There appears to be a correlation between the 17O shift and Ti-O bondlength. PMID:11235025

Gervais, C; Babonneau, F; Hoebbel, D; Smith, M E

2000-01-01

48

?-NMR  

Science.gov (United States)

The ?-NMR facility at ISAC is constructed specifically for experiments in condensed matter physics with radioactive ion beams. Using co-linear optical pumping, a 8Li + ion beam having a large nuclear spin polarisation and low energy (nominally 30 keV) can be generated. When implanted into materials these ions penetrate to shallow depths comparable to length scales of interest in the physics of surfaces and interfaces between materials. Such low-energy ions can be decelerated with simple electrostatic optics to enable depth-resolved studies of near-surface phenomena over the range of about 2-200 nm. Since the ?-NMR signal is extracted from the asymmetry intrinsic to beta-decay and therefore monitors the polarisation of the radioactive probe nuclear magnetic moments, this technique is fundamentally a probe of local magnetism. More generally though, any phenomena which affects the polarisation of the implanted spins by, for example, a change in resonance frequency, line width or relaxation rate can be studied. The ?-NMR program at ISAC currently supports a number of experiments in magnetism and superconductivity as well as novel ultra-thin heterostructures exhibiting properties that cannot occur in bulk materials. The general purpose zero/low field and high field spectrometers are configured to perform CW and pulsed RF nuclear magnetic resonance and spin relaxation experiments over a range of temperatures (3-300 K) and magnetic fields (0-9 T).

Morris, Gerald D.

2014-01-01

49

A long-wave action of spin Hamiltonians and the inverse problem of the calculus of variations  

CERN Document Server

We suggest a method of derivation of the long-wave action of the model spin Hamiltonians using the non-linear partial differential equations of motions of the individual spins. According to the Vainberg's theorem the set of these equations are (formal) potential if the symmetry analysis for the Frechet derivatives of the system is true. The case of Heisenberg (anti)ferromagnets is considered. It is shown the functional whose stationary points are described by the equations coincides with the long-wave action and includes the non-trivial topological term (Berry phase).

Bostrem, I G; Egorov, R F

2001-01-01

50

Crystal field constants calculation in the spin-Hamiltonian for Eu2+ in alkali-halide crystals  

International Nuclear Information System (INIS)

The spin-Hamiltonian constants b02 and b22 for the center Eu2+-vacancy in NaCl, KCl and KBr crystals are calculated. Agreement with experimental data for b02 is obtained by taking into account the second and the fourth orders of perturbations in H = Hsub(L-S) + Vsub(C) + Hsub(S-S). Different values of b02 in the succession NaCl, KCl, KBr are explained under the assumption that Cl- ions, which are located in XY plane in the first sphere of Eu2+ surrounding, are shifted. (Auth.)

51

NMR parameters and geometries of OHN and ODN hydrogen bonds of pyridine-acid complexes.  

Science.gov (United States)

In this paper, equations are proposed which relate various NMR parameters of OHN hydrogen-bonded pyridine-acid complexes to their bond valences which are in turn correlated with their hydrogen-bond geometries. As the valence bond model is strictly valid only for weak hydrogen bonds appropriate empirical correction factors are proposed which take into account anharmonic zero-point energy vibrations. The correction factors are different for OHN and ODN hydrogen bonds and depend on whether a double or a single well potential is realized in the strong hydrogen-bond regime. One correction factor was determined from the known experimental structure of a very strong OHN hydrogen bond between pentachlorophenol and 4-methylpyridine, determined by the neutron diffraction method. The remaining correction factors which allow one also to describe H/D isotope effects on the NMR parameters and geometries of OHN hydrogen bond were determined by analysing the NMR parameters of the series of protonated and deuterated pyridine- and collidine-acid complexes. The method may be used in the future to establish hydrogen-bond geometries in biologically relevant functional OHN hydrogen bonds. PMID:15372662

Limbach, Hans-Heinrich; Pietrzak, Mariusz; Sharif, Shasad; Tolstoy, Peter M; Shenderovich, Ilya G; Smirnov, Sergei N; Golubev, Nikolai S; Denisov, Gleb S

2004-10-11

52

Surface-induced order parameter distortion in superfluid ³He-B measured by nonlinear NMR.  

Science.gov (United States)

The B phase of superfluid 3He is a three-dimensional time-reversal invariant topological superfluid, predicted to support gapless Majorana surface states. We confine superfluid 3He into a thin nanofluidic slab geometry. In the presence of a weak symmetry-breaking magnetic field, we have observed two possible states of the confined 3He-B phase manifold, through the small tipping angle NMR response. Large tipping angle nonlinear NMR has allowed the identification of the order parameter of these states and enabled a measurement of the surface-induced gap distortion. The results for two different quasiparticle surface scattering boundary conditions are compared with the predictions of weak-coupling quasiclassical theory. We identify a textural domain wall between the two B phase states, the edge of which at the cavity surface is predicted to host gapless states, protected in the magnetic field. PMID:24476290

Levitin, Lev V; Bennett, Robert G; Surovtsev, Evgeny V; Parpia, Jeevak M; Cowan, Brian; Casey, Andrew J; Saunders, John

2013-12-01

53

Sensitivity of the NMR density matrix to pulse sequence parameters: A simplified analytic approach  

Science.gov (United States)

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.

Momot, Konstantin I.; Takegoshi, K.

2012-08-01

54

Temperature dependence of EPR spectrum parameters for Cdsub(v)Hgsub(1-v)Se crystals  

International Nuclear Information System (INIS)

The paper deals with the temperature dependence of g and A spin hamiltonian parameters. The experimental data for the temperature range 4.2K-380K have been given as well as some theoretical difficulties have been presented. (author)

55

NMR Principles  

OpenAIRE

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.

Hore, Pj

2010-01-01

56

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Resíduos pesados de petróleo podem ser usados como matéria-prima na produção de diversos materiais de carbono, como piches, isotrópicos e anisotrópicos, e diferentes tipos de coque. A caracterização química destes resíduos, e de materiais de carbono em geral, é um desafio que deve ser abordado para [...] que se possa otimizar adequadamente estes processos de produção. Neste trabalho, resíduos de petróleo de diferentes refinarias foram analisados por RMN, FTIR e análise elementar. Parâmetros de análise foram otimizados para a técnica de RMN e espectroscopia no infravermelho por refletância difusa, uma técnica geralmente aplicada a materiais sólidos, mas que gerou espectros de boa qualidade para estas amostras. Correlações foram encontradas entre os índices de aromaticidade por RMN e FTIR, um parâmetro largamente usado no estudo da formação da mesofase, bem como entre a razão C/H e o índice de aromaticidade. Outros parâmetros estruturais de interesse também foram determinados. Abstract in english 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 orde [...] r 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.

Alexandre T., Castro.

1181-11-01

57

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

Energy Technology Data Exchange (ETDEWEB)

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)

NONE

2011-07-01

58

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 lvent 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)

59

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

Science.gov (United States)

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.

Erker, Jay Charles

60

Modeling NMR and EPR parameters in the metal-organic framework Cu3(BTC)2  

International Nuclear Information System (INIS)

In the last decade metal-organic frameworks (MOF) have been the subject of intensive research activity due to their tunable porous structure promoting interesting properties and applications. A very powerful tool for characterization of the complex chemical and electronic structure of these nanoporous materials is magnetic resonance spectroscopy. The interpretative and analytical power of the applied NMR and EPR experimental techniques can be significantly enhanced by supplying a reliable theoretical treatment of the underlying spectroscopic parameters. We report on the application of density functional theory (DFT) for computing the magnetic resonance properties of Cu3(BTC)2(H2O)3 (BTC=benzene 1,3,5-tricarboxylate). The ADF 2008 code with Slater basis sets incorporating relativistic corrections has been used for geometry optimization of the MOF building block. We have performed gas phase calculations modeling both the ground singlet and the excited triple state of the Cu(II) ions from the paddle-wheel unit. The nuclear shielding tensors of C and H forming the BTC linkers, as well as the ESR g- and A-tensors of the Cu(II) ions in the paddle-wheel have been calculated and compared to experimental results from the literature.

61

{\\it Ab initio} $^{27}Al$ NMR chemical shifts and quadrupolar parameters for $Al_2O_3$ phases and their precursors  

OpenAIRE

The Gauge-Including Projector Augmented Wave (GIPAW) method, within the Density Functional Theory (DFT) Generalized Gradient Approximation (GGA) framework, is applied to compute solid state NMR parameters for $^{27}Al$ in the $\\alpha$, $\\theta$, and $\\kappa$ aluminium oxide phases and their gibbsite and boehmite precursors. The results for well-established crystalline phases compare very well with available experimental data and provide confidence in the accuracy of the meth...

Ferreira, Ary R.; Ku?c?u?kbenli, Emine; Leita?o, Alexandre A.; Gironcoli, Stefano

2011-01-01

62

First-principles quantum-mechanical methods for full prediction of NMR parameters in fluorides  

International Nuclear Information System (INIS)

19F magic angle spinning (MAS) NMR is a powerful structural tool for complex fluoride crystalline materials having multiple crystallographic sites since 19F (I=1/2) isotropic chemical shift (?iso) is very sensitive to the environment of the fluorine atom. However, in many cases, several fluorine sites have the same multiplicity preventing an unambiguous experimental assignment. Simulation of the response to an external magnetic field is then necessary to complete the analysis. The relation of the measured ?iso values with the calculated isotropic chemical shieldings (?iso) is needed to interpret of NMR spectra. 19F ?iso values were calculated for alkali, alkaline earth and rare earth of column IIIB fluoride compounds using the GIPAW method implemented in the CASTEP software. Using DFT-PBE, we have established a linear relation between 19F calculated ?iso and experimental ?iso values which enables full prediction of 19F NMR spectra. In the case of complex NMR spectra, this calibration curve is successfully applied for the attribution from first-principles quantum-mechanical of 19F chemical shifts.

63

Aziridine nitrogen inversion by dynamic NMR: activation parameters in a fused bicyclic structure.  

Science.gov (United States)

The nitrogen inversion of a N-phenyl aziridine fused to a succinimide ring is influenced by the presence of a phenyl ring in the succinimide moiety. The endo invertomer is favored, showing an unsymmetrical equilibrium in variable (1)H NMR studies. PMID:24125572

de Loera, Denisse; Liu, Fang; Houk, K N; Garcia-Garibay, Miguel A

2013-11-15

64

First-principles quantum-mechanical methods for full prediction of NMR parameters in fluorides  

Energy Technology Data Exchange (ETDEWEB)

{sup 19}F magic angle spinning (MAS) NMR is a powerful structural tool for complex fluoride crystalline materials having multiple crystallographic sites since {sup 19}F (I=1/{sub 2}) isotropic chemical shift ({delta}{sub iso}) is very sensitive to the environment of the fluorine atom. However, in many cases, several fluorine sites have the same multiplicity preventing an unambiguous experimental assignment. Simulation of the response to an external magnetic field is then necessary to complete the analysis. The relation of the measured {delta}{sub iso} values with the calculated isotropic chemical shieldings ({sigma}{sub iso}) is needed to interpret of NMR spectra. {sup 19}F {sigma}{sub iso} values were calculated for alkali, alkaline earth and rare earth of column IIIB fluoride compounds using the GIPAW method implemented in the CASTEP software. Using DFT-PBE, we have established a linear relation between {sup 19}F calculated {sigma}{sub iso} and experimental {delta}{sub iso} values which enables full prediction of {sup 19}F NMR spectra. In the case of complex NMR spectra, this calibration curve is successfully applied for the attribution from first-principles quantum-mechanical of {sup 19}F chemical shifts.

Sadoc, Aymeric; Boucher, Florent [Institut des Materiaux Jean Rouxel (IMN), Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes (France); Biswal, Mamata; Body, Monique; Legein, Christophe [Institut de Recherche en Ingenierie Moleculaire et Materiaux Fonctionnels (IRIM2F), Universite du Maine, CNRS, Avenue Olivier Messiaen, 72085 Le Mans (France)

2011-07-01

65

Structural investigations of ?-CaAlF5 by coupling powder XRD, NMR, EPR and spectroscopic parameter calculations  

International Nuclear Information System (INIS)

?-CaAlF5 was synthesized by solid-state reaction. The precise structure was refined from X-ray powder diffraction data in the monoclinic space group P21/c with lattice constants a=5.3361A, b=9.8298A, c=7.3271A, and ?=109.91o (Z=4). The structure exhibits isolated chains of AlF63- octahedra sharing opposite corners.19F and 27Al solid state NMR spectra were recorded using MAS and SATRAS techniques. An EPR spectrum was recorded for ?-CaAlF5:Cr3+. The experimental spectra were simulated in order to extract the NMR and EPR parameter values. Five fluorine sites and one low symmetry aluminium site were found in agreement with the refined structure. These parameters were calculated using empirical and ab-initio methods. The agreement obtained between the calculated 19F chemical shift values, 27Al quadrupolar parameters, Cr3+ EPR fine structure parameters and the experimental results demonstrates the complementarity of XRD, magnetic resonance experiments and theoretical methodologies

66

Identification of the order parameter of 3A using low-field NMR measurements  

Science.gov (United States)

We have made simultaneous measurements of the longitudinal and transverse NMR frequencies of 3A in fields of the order of 30 G in a parallel plate geometry, defined by Mylar films 100 ?m apart, so that l is well oriented perpendicular to the static magnetic field. Comparison of our measurements with the quadratic axial-state frequency relation indicates that the A phase is axial in the pressure range 22.6 to 29.3 bars.

Mullins, T. R.; Dmitriev, V. V.; Armstrong, A. J.; Manninen, A. J.; Hook, J. R.; Hall, H. E.

1994-06-01

67

N.M.R. proton lineshape in (TMTSF)2X : incommensurability of nesting vector and order parameter  

OpenAIRE

For the first time, in the SDW state of the organic conductors (TMTSF) 2PF 6 and (TMTSF)2ClO4, the nesting vector Q is determined from a detailed analysis of the methyl proton N.M.R. lineshape for various magnetic field orientations. The amplitude ? of the order parameter is determined with a precision superior to that of previous works which had obtained no information on the nesting vector and neglected the hyperfine coupling. In the paramagnetic metallic state, the fast rotational tunnell...

Delrieu, J. M.; Roger, M.; Toffano, Z.; Moradpour, A.; Bechgaard, K.

1986-01-01

68

Longitudinal NMR parameter measurements of Japanese pear fruit during the growing process using a mobile magnetic resonance imaging system  

Science.gov (United States)

Longitudinal nuclear magnetic resonance (NMR) parameter measurements of Japanese pear fruit (Pyrus pyrifolia Nakai, Kosui) were performed using an electrically mobile magnetic resonance imaging (MRI) system with a 0.2 T and 16 cm gap permanent magnet. To measure the relaxation times and apparent diffusion coefficients of the pear fruit in relation to their weight, seven pear fruits were harvested almost every week during the cell enlargement period and measured in a research orchard. To evaluate the in situ relaxation times, six pear fruits were longitudinally measured for about two months during the same period. The measurements for the harvested samples showed good agreement with the in situ measurements. From the measurements of the harvested samples, it is clear that the relaxation rates of the pear fruits linearly change with the inverse of the linear dimension of the fruits, demonstrating that the relaxation mechanism is a surface relaxation. We therefore conclude that the mobile MRI system is a useful device for measuring the NMR parameters of outdoor living plants.

Geya, Yuto; Kimura, Takeshi; Fujisaki, Hirotaka; Terada, Yasuhiko; Kose, Katsumi; Haishi, Tomoyuki; Gemma, Hiroshi; Sekozawa, Yoshihiko

2013-01-01

69

Dual Substituent Parameter Modeling of Theoretical, NMR and IR Spectral Data of 5-Substituted Indole-2,3-diones  

Directory of Open Access Journals (Sweden)

Full Text Available Correlations of AM1 and PM3 theoretical data, 13C-NMR substituent chemical shifts (13C-SCS and IR carbonyl group wave numbers [ν(C3═O] were studied using dual substituent parameter (DSP models for 5-substituted indole-2,3-diones. For the C7 atom a reverse substituent effect attributed to extended π-polarization was observed. On the other hand, the DSP approaches for the C3 atom showed normal substituent effects with some contribution of reverse effect supported strongly by 13C-SCS correlations. In the ν(C3═O and p(C3═O DSP correlations the field effect contribution predominates over the resonance effect, which justifies the using of earlier suggested vibrational coupling (V-C model for 5- and 6-substituted indole-2,3-diones.

Zora Šusteková

2002-11-01

70

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.)

71

Bromine NMR Study of Cupric Compounds (CnH2n+1NH3)2CuBr4 (n{=}1, 2)  

Science.gov (United States)

The spin structure of (CnH2n+1NH3)2CuBr4 (n{=}1, 2) is studied by Br NMR at 1.7 K. In (C2H5NH3)2CuBr4, the magnetic space group is Pb'c'a type and the moment direction inclines at an angle of 49.5° with the c-axis. A weak ferromagnetic moment appears along to the c-axis. The anisotropic exchange field is estimated to be 2.5 kOe. The inter-layer exchange field and the out-of-layer anisotropy field are much smaller than previously reported values. The parameters of Br nuclear spin Hamiltonian are also obtained. In (CH3NH3)2CuBr4, the moment direction inclines at 27° with the c-axis. It is difficult to interpret the NMR results by the two-sublattice model. A model of the four-sublattice antiferromagnet is developped.

Suzuki, Yoshio; Tsuru, Kazuo; Kimishima, Yoshihide; Kubo, Hidenori

1981-05-01

72

Bromine NMR study of cupric compounds (C sub(n)H sub(2n+1)NH sub(3))2CUBr4 (n = 1, 2)  

International Nuclear Information System (INIS)

The spin structure of (C sub(n)H sub(2n+1)NH3)2CuBr4 (n = 1, 2) is studied by Br NMR at 1.7 K. In (C2H5NH3)2CuBr4, the magnetic space group is Pb'c'a type and the moment direction inclines at an angle of 49.50 with the c-axis. A weak ferromagnetic moment appears along to the c-axis. The anisotropic exchange field is estimated to be 2.5 kOe. The inter-layer exchange field and the out-of-layer anisotropy field are much smaller than previously reported values. The parameters of Br nuclear spin Hamiltonian are also obtained. In (CH3NH3)2CuBr4, the moment direction inclines at 270 with the c-axis. It is difficult to interpret the NMR results by the two-sublattice model. A model of the four-sublattice antiferromagnet is developped. (author)

73

NMR order parameters calculated in an expanding reference frame: identifying sites of short- and long-range motion  

Energy Technology Data Exchange (ETDEWEB)

NMR order parameters are calculated from molecular dynamics computer simulations of ubiquitin and the apo (Ca{sup 2+}-free) state of calbindin D{sub 9k}. Calculations are performed in an expanding reference frame so as to discriminate between the effects of short- and long-range motions. This approach reveals that the dominant contributions to the order parameters are short-range. Longer-range contributions are limited to specific sites, many of which have been recognized in previous studies of correlated motions. These sites are identified on the basis of an effective reorientational number, n{sub eff}. Not only does this parameter identify sites of short- and long-range motion, it also provides a way of evaluating the separability condition that is key to the Lipari-Szabo model-free method. When analyzed in conjunction with the Prompers-Brueschweiler separability index, the n{sub eff} values indicate that longer-range motions play a more prominent role in apo calbindin than they do in ubiquitin.

Johnson, Eric, E-mail: eric_johnson@mail.msj.edu [College of Mount St. Joseph, Department of Chemistry and Physical Sciences (United States)

2011-05-15

74

NMR order parameters calculated in an expanding reference frame: identifying sites of short- and long-range motion.  

Science.gov (United States)

NMR order parameters are calculated from molecular dynamics computer simulations of ubiquitin and the apo (Ca(2+)-free) state of calbindin D(9k). Calculations are performed in an expanding reference frame so as to discriminate between the effects of short- and long-range motions. This approach reveals that the dominant contributions to the order parameters are short-range. Longer-range contributions are limited to specific sites, many of which have been recognized in previous studies of correlated motions. These sites are identified on the basis of an effective reorientational number, n ( eff ). Not only does this parameter identify sites of short- and long-range motion, it also provides a way of evaluating the separability condition that is key to the Lipari-Szabo model-free method. When analyzed in conjunction with the Prompers-Brüschweiler separability index, the n ( eff ) values indicate that longer-range motions play a more prominent role in apo calbindin than they do in ubiquitin. PMID:21503632

Johnson, Eric

2011-05-01

75

Investigations of the Local Structure and the EPR Parameters for the Tetragonal Ni+ Center in SrF2  

Directory of Open Access Journals (Sweden)

Full Text Available The local structure and the spin Hamiltonian parameters g factors g// and g? and the hyperfine structure constantsA// and A? of a tetragonal Ni+ center in SrF2 are investigated, using the high order perturbation formulas for a 3d9ion in tetragonally elongated octahedra. According to these studies, the impurity Ni+ is found to locate at thedistance of about 0.36 Å from the nearest fluorine plane. The obtained spin Hamiltonian parameters agree wellwith the experimental data.

Ji-zi Lin

2010-10-01

76

NMR paramagnetic relaxation of the spin 2 complex Mn(III)TSPP: a unique mechanism.  

Science.gov (United States)

The S = 2 complex, manganese(III) meso-tetra(4-sulfonatophenyl)porphine chloride (Mn(III)TSPP) is a highly efficient relaxation agent with respect to water protons and has been studied extensively as a possible MRI contrast agent. The NMR relaxation mechanism has several unique aspects, key among which is the unusual role of zero-field splitting (zfs) interactions and the effect of these interactions on the electron spin dynamics. The principal determinant of the shape of the R1 magnetic relaxation dispersion (MRD) profile is the tetragonal 4th-order zfs tensor component, B4(4), which splits the levels of the m(S) = +/-2 non-Kramers doublet. When the splitting due to B4(4) exceeds the Zeeman splitting, the matrix elements of (S(z)) are driven into coherent oscillation, with the result that the NMR paramagnetic relaxation enhancement is suppressed. To confirm the fundamental aspects of this mechanism, proton R1 MRD data have been collected on polyacrylamide gel samples in which Mn(III)TSPP is reorientationally immobilized. Solute immobilization suppresses time-dependence in the electron spin Hamiltonian that is caused by Brownian motion, simplifying the theoretical analysis. Simultaneous fits of both gel and solution data were achieved using a single set of parameters, all of which were known or tightly constrained from prior experiments except the 4th-order zfs parameter, B4(4), and the electron spin relaxation times, which were found to differ in the m(S) = +/-1 and m(S) = +/-2 doublet manifolds. In liquid samples, but not in the gels, the B4(4)-induced splitting of the m(S) = +/-2 non-Kramers doublet is partially collapsed due to Brownian motion. This phenomenon affects the magnitudes of both B4(4) and electron spin relaxation times in the liquid samples. PMID:16833659

Schaefle, Nathaniel; Sharp, Robert

2005-04-21

77

Factors determining the reliable description of global tumbling parameters in solution NMR  

International Nuclear Information System (INIS)

An accurate description of global tumbling of a protein is essential for correct analysis and interpretation of internal dynamics and thermodynamics. The accurate fitting of global tumbling parameters is affected by the number of experimental relaxation data points available for analysis, the distribution of data points over the domain of the function describing the tumbling, the measurement error associated with the data, the error associated with use of an approximate functional form, and errors in the protein structure. We present an analysis of the influence of these factors on the error in global tumbling parameters and the corresponding error in the calculated T1/T2 values. We find that reduction of experimental and approximation error can compensate for a less-than-ideal quantity or distribution of data points, and that accurate parameters can be obtained for proteins with highly anisotropic distributions of bond vectors, as illustrated using the helical bundle protein G-CSF. This indicates that proteins with anisotropic distributions, such as the helical bundle class of proteins, should not summarily be excluded when selecting proteins for dynamic and thermodynamic analyses of 15N backbone relaxation measurements

78

Factors determining the reliable description of global tumbling parameters in solution NMR  

Energy Technology Data Exchange (ETDEWEB)

An accurate description of global tumbling of a protein is essential for correct analysis and interpretation of internal dynamics and thermodynamics. The accurate fitting of global tumbling parameters is affected by the number of experimental relaxation data points available for analysis, the distribution of data points over the domain of the function describing the tumbling, the measurement error associated with the data, the error associated with use of an approximate functional form, and errors in the protein structure. We present an analysis of the influence of these factors on the error in global tumbling parameters and the corresponding error in the calculated T{sub 1}/T{sub 2} values. We find that reduction of experimental and approximation error can compensate for a less-than-ideal quantity or distribution of data points, and that accurate parameters can be obtained for proteins with highly anisotropic distributions of bond vectors, as illustrated using the helical bundle protein G-CSF. This indicates that proteins with anisotropic distributions, such as the helical bundle class of proteins, should not summarily be excluded when selecting proteins for dynamic and thermodynamic analyses of {sup 15}N backbone relaxation measurements.

Pawley, Norma H. [Los Alamos National Laboratory, Bioscience Division (United States); Gans, Jason D. [Cornell University, Department of Applied and Engineering Physics (United States); Nicholson, Linda K. [Cornell University, Department of Molecular Biology and Genetics (United States)], E-mail: lkn2@cornell.edu

2002-11-15

79

Dynamics, NMR parameters and hyperfine coupling constants of the Fe3O4(1 0 0)-water interface: Implications for MRI probes  

Science.gov (United States)

Magnetite is an iron oxide widely used as contrast agent in MRI, receiving considerable interest from nanoscience and nanotechnology. In this work, the face 1 0 0 of the magnetite structure was studied with water in order to obtain 1H hyperfine coupling constants (HFCCs). Molecular dynamics (MD) calculations were performed using the ReaxFF program and for statistical inefficiency, structures were selected for HFCC and NMR calculations. From our theoretical findings, the magnetite in solution considerably increases the 1H HFCC of water molecules. From our results, it is essential to incorporate the dynamics and solvent effects into NMR calculations of relaxation parameters.

Gonçalves, Mateus A.; Peixoto, Fernando C.; da Cunha, Elaine F. F.; Ramalho, Teodorico C.

2014-08-01

80

Effects of substituents on the NMR features of basic bicyclic ring systems of fluoroquinolone antibiotics and the relationships between NMR chemical shifts, molecular descriptors and drug-likeness parameters.  

Science.gov (United States)

In the present study, the NMR spectroscopic features of trovafloxacin (TVA) mesylate, pefloxacin (PFX) mesylate dihydrate and ciprofloxacin (CIP) hydrochloride monohydrate were studied in DMSO-d6 solution with the aim of investigating the effects of substituents and the type of salt on the NMR parameters of basic bicyclic fluoroquinolone and fluoronaphthyridone ring systems. For this purpose, the 1H- and 13C- one- and two-dimensional homo- and heteronuclear NMR methods were used. The analysis of 1H- and 13C-NMR spectra confirmed the structures of investigated fluoroquinolone salts. Relationships between 1H- and 13C-NMR chemical shifts of fluoronaphthyridone and fluoroquinolone ring systems, calculated molecular descriptors (MDs) and drug-likeness scores (DLSs), computed for monoprotonic cations of investigated fluoroquinolone salts (TVAH+, PFXH+ and CIPH+), were also explored. The topological polar surface area (TPSA), the parameter of lipophilicity (miLogP), the relative molecular mass (Mr) and the volume (V) of computed molecular descriptors (MDs), as well as the G protein-coupled receptor ligand-likeness (GPCR ligand-ls), the ion channel ligand-likeness (ICL-ls), the kinase inhibitor-likeness (KI-ls) and the nuclear receptor ligand-likeness (NRL-ls) were used in this study. The 1H-NMR chemical shifts of protons in COOH, H5 and NHn+, as well as 13C-NMR chemical shifts of C4, C5 and C11 shown to be good parameters in exploration of property-property and property-drug-likeness relationships for investigated fluoroquinolone salts. Thus, collinear relationships of 1H-NMR chemical shifts of protons in COOH, H5 and NHn+ with TPSA and miLogP, as well as with GPCR ligand-ls, KI-ls and NRL-ls were revealed (?, ppm H in COOH vs. TPSA, R = -0.9421; ?, ppm H in COOH vs. NRL-ls, R = -0.9216; ?, ppm H5 vs. miLogP, R = 0.9962; ?, ppm H5 vs. KI-ls, R = 0.9969; ?, ppm NHn+vs. TPSA, R = -0.9875 and ?, ppm NHn+vs. NRL-ls, R = -0.9948). The collinearities between, 13C-NMR chemical shifts of C4, C5 and C11 with KI-ls and NRL-ls, as well as with TPSA, miLogP, Mr and V were also revealed (?, ppm C4 vs. TPSA, R = 0.9964; ?, ppm C4 vs. miLogP, R = 0.9487; ?, ppm C4 vs.Mr, R = 0.9629; ?, ppm C4 vs. KI-ls, R = 0.9461; ?, ppm C4 vs. NRL-ls, R = 0.9996; ?, ppm C5 vs. miLogP, R = 0.9994; ?, ppm C5 vs. KI-ls, R = 0.9990; ?, ppm C5 vs. NRL-ls, R = 0.9510; ?, ppm C11 vs. TPSA, R = -0,9958; ?, ppm C11 vs. NRL-ls, R = -0.9994 and ?, ppm C11 vs. KI-ls, R = -0.9481). PMID:21134860

Taka?, Milena Jadrijevi?-Mladar

2010-09-01

81

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.

82

Compact NMR  

Energy Technology Data Exchange (ETDEWEB)

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.

Bluemich, Bernhard; Haber-Pohlmeier, Sabina; Zia, Wasif [RWTH Aachen Univ. (Germany). Inst. fuer Technische und Makromolekulare Chemie (ITMC)

2014-06-01

83

Dft Study on 4(5)-Imidazole-Carbaldehyde-N(5)-Phenylthiosemicarbazone (Imtph): Nmr Shielding Tensors, Thermodynamic Parameters, Nbo Analysis, Molecular Electrostatic Potential (Mep), Homo and Lumo Studies  

OpenAIRE

The density functional theory (DFT) calculations at the level of B3LYP/6-31G was carried out on the structure 4(5)-Imidazole-carbaldehyde-N(5)-phenylthiosemicarbazone (ImTPh) in gas phase using Gaussian 03. Dipole moment (Debye), energy of structure formation (HF; kcal/mol) and point group, NMR parameters such as isotropic shielding (?iso) and anisotropic shielding (?aniso), ?11, ?22 and ?33 obtained. Also thermodynamic properties and natural bond orbitals (NBO) were calculated. Besides,...

Masoome Sheikhi; Mohammad Mahmoodi Hashemi; Majid Monajjemi

2014-01-01

84

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

CERN Document Server

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.

Soncini, Alessandro

2012-01-01

85

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

Science.gov (United States)

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.

Soncini, Alessandro; Van den Heuvel, Willem

2013-01-01

86

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

OpenAIRE

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 a...

Soncini, Alessandro; Heuvel, Willem Den

2012-01-01

87

Theoretical investigations of spin Hamilton parameters and Knight shifts for rhombic and tetragonal CuGeO{sub 3}  

Energy Technology Data Exchange (ETDEWEB)

The spin Hamiltonian parameters (g factors and hyperfine structure constants) and the Knight shifts for Cu{sup 2+} in the spin-Pierels compound CuGeO{sub 3} of rhombic and tetragonal phases are theoretically investigated from the high order perturbation formulas of these parameters for a 3d{sup 9} 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., K{sub i}/(g{sub i}?g{sub s})=K{sub j}/(g{sub j}?g{sub s}) (with i, j=x, y and z; g{sub s}?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 Cu{sup 2+} sites. The studies in this work would be helpful to establish complete physical scheme for uniform investigations on EPR and NMR spectroscopic behaviours of Cu{sup 2+} (or other similar 3d{sup 9} ions) in compounds.

Kuang, Min-Quan, E-mail: mqkuang@yeah.net [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Wu, Shao-Yi [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Hu, Xian-Fen; Song, Bo-Tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2013-05-15

88

Spectral assignments and NMR parameter-structure relationships in borates using high-resolution 11B NMR and density functional theory.  

Science.gov (United States)

High-resolution, solid-state (11)B NMR spectra have been obtained at high magnetic fields for a range of polycrystalline borates using double-rotation (DOR), multiple-quantum magic angle spinning and isotopic dilution. DOR linewidths can be less than 0.2 ppm in isotopically diluted samples, allowing highly accurate values for the isotropic chemical shift, ?iso, and electric field gradient to be obtained. The experimental values are used as a test of density functional calculations using both projector augmented wave based CASTEP and WIEN2k. The CASTEP calculations of ?iso are generally in very good agreement with experiment, having r.m.s. deviation 0.40 ppm. WIEN2k calculations of electric field gradient magnitude, CQ, and asymmetry, ?, are also in excellent agreement with experiment, with r.m.s. deviations 0.038 MHz and 0.042 respectively. However, whilst CASTEP gives a similar deviation for ? (0.043) it overestimates CQ by ?15%. After scaling of the calculated electric field gradient by 0.842 the deviation in CQ is practically identical to that of the WIEN2k calculations. The spectral assignments that follow from the experimental and computational results allow identification of correlations between ?iso and (a) the average B-O-B bond angle, ?[combining overline], for both three and four coordinated boron, giving ?iso(B(III)) = (185.1 -?[combining overline])/3.42 ppm and ?iso(B(IV)) = (130.2 -?[combining overline])/5.31 ppm; and (b) the ring-site T(3) unit trigonal planar angular deviation, Stri, giving ?iso(T(3)(ring)) = (1.642 × 10(-2)-Stri)/(8.339 × 10(-4)) ppm. PMID:23608768

Alderman, Oliver L G; Iuga, Dinu; Howes, Andrew P; Pike, Kevin J; Holland, Diane; Dupree, Ray

2013-06-01

89

NMR imaging of plants  

International Nuclear Information System (INIS)

The basic possibility to use NMR imaging for non-invasive investigation of plants as well as the influence of the NMR parameters spin density and spin-spin relaxation time T2 on the image contrast is demonstrated. The numerical calculation of the spatial distribution of the pure NMR parameters points to the possibility of drawing conclusions concerning the physical and chemical state of the biological system. The experiments were performed on a commercial NMR spectrometer using a home-made accessory unit. (author)

90

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

Science.gov (United States)

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.

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

2013-10-01

91

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

Science.gov (United States)

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.

Sharp, Robert

2008-10-01

92

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

Science.gov (United States)

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

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

2015-01-01

93

Dft Study on 4(5-Imidazole-Carbaldehyde-N(5-Phenylthiosemicarbazone (Imtph: Nmr Shielding Tensors, Thermodynamic Parameters, Nbo Analysis, Molecular Electrostatic Potential (Mep, Homo and Lumo Studies  

Directory of Open Access Journals (Sweden)

Full Text Available The density functional theory (DFT calculations at the level of B3LYP/6-31G was carried out on the structure 4(5-Imidazole-carbaldehyde-N(5-phenylthiosemicarbazone (ImTPh in gas phase using Gaussian 03. Dipole moment (Debye, energy of structure formation (HF; kcal/mol and point group, NMR parameters such as isotropic shielding (?iso and anisotropic shielding (?aniso, ?11, ?22 and ?33 obtained. Also thermodynamic properties and natural bond orbitals (NBO were calculated. Besides, the frontier molecular orbital (FMO analysis and the molecular electrostatic potential (MEP of the compound were investigated by theoretical calculations.

Masoome Sheikhi

2014-03-01

94

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

95

Thallium-205 NMR determination of the thermodynamic parameters for the binding of monovalent and divalent cations to gramicidin A and C incorporated into model phospholipid membranes: An equilibrium study  

International Nuclear Information System (INIS)

Thermodynamic parameters have been determined for the binding of monovalent and divalent cations to gramicidin A and C incorporated in lyso-?-phosphatidylcholine dispersions. The thermodynamic analyses used equilibrium constants derived from the analysis of Tl-205 NMR chemical shifts using a one-site binding model of the gramicidin channel. Initial experiments determined the thermodynamic parameters of the Tl+ ion binding to gramicidin A. Next, the competitive binding-Tl-205 NMR technique was used to obtain the thermodynamic parameters for the binding of Li+, Na+, K+, Rb+, Cs+, NH4+ and Ag+ cations to gramicidin A. A similar experiment for the binding of the Li+, Na+, K+ and Rb+ cations to gramicidin C was performed. Similar experiments determined the thermodynamic parameter for the Cd++, Mg++, Ca++, Sr++ and Ba++ cations. Thermodynamic parameters have also been determined for the binding of the Tl+ ion to gramicidin A incorporated into dimyristoylphosphatidylcholine vesicles using Tl-205 NMR spectroscopy

96

Texture in the superconducting order parameter of CeCoIn5; FFLO state as evidenced by ultrasound and NMR  

Science.gov (United States)

A myriad of fascinating properties have been proposed for unconventional superconductors in the presence of a strong magnetic field. Among the possible exotic superconducting (SC) phases, a spatially nonuniform SC state originating from the paramagnetism of conduction electrons has become a subject of particular interest after the pioneering work by Fulde and Ferrel and Larkin and Ovchinnikov (FFLO) in the mid-1960's. We present here ultrasound and NMR studies of the quasi-2D heavy-fermion superconductor CeCoIn5 with extremely large Pauli paramagnetic susceptibility, which is believed to host a FFLO state. Ultrasound velocity measurements reveal an unusual structural transformation of the flux line lattice (FLL) in the vicinity of the upper critical field and with a magnetic field applied parallel to the ab plane. The transition field coincides with that at which heat capacity measurements reveal a second order phase transition. The lowering of the sound velocity at the transition is consistent with the collapse of the FLL tilt modulus and a crossover to quasi two-dimensional FLL pinning. In the vicinity of the upper critical field , the ^115In NMR spectrum also exhibits a dramatic change below T^*(H) which well coincides with the position of reported anomalies in specific heat and ultrasound velocity. Below T^*(H) a new resonance line appears at higher frequency, which can be attributed to the normal quasiparticle sheets formed in the SC regime. The NMR spectrum also indicate that the vortex core structure of CeCoIn5 appears to be markedly different from that of ordinary superconductors. On the basis of these results, we were able to establish a clear evidence of the spatially inhomogeneous SC state at high field and low temperatures, precisely as expected in a FFLO state. In collaboration with T.Watanabe, Y.Kasahara, K.Izawa (Univ. of Tokyo), C.J. van der Beek(Ecole Polytechnique),K.Kakuyanagi, K.Kumagai (Hokkaido Univ.), M.Nohara, T.Hanaguri, H.Takagi,(Univ. of Tokyo) H.Shishido, R.Settai, and Y.Onuki(Osaka Univ.)

Matsuda, Yuji

2005-03-01

97

31P-NMR spectroscopy in measurements of physiological parameters and response to therapy of human melanoma xenografts  

International Nuclear Information System (INIS)

The aim of the study was to investigate whether ''31P-NMR spectroscopy can be utilized in prediction and monitoring of response to therapy or tumours. The specific aims were: 1) To investigate possible correlations between on the one hand bio energetics status, phospholipids resonance ratios, intracellular pH and phosphorus T1s and on the other hand tumour blood supply and oxygenation, tumour proliferation and necrotic fraction across tumour lines. 2) Reveal possible correlations between changes in tumour bio energetics status and phosphorus T1s and the changes in tumour blood flow, tumour oxygenation and necrotic fraction. 3) To investigate whether irradiation and hyperthermia treatment of tumours affect bio energetics status and phosphorus T1s. 4) To identify the tumour physiological factors that is effected by the treatment and influence the bio energetics status and phosphorus T1s. The results are presented in 8 papers with titles: 1)''31P-nuclear magnetic resonance spectroscopy in vivo of six human melanoma zeno graft lines: Tumour bio energetic status and blood supply. 2) ''31P NMR spectroscopy studies of phospholipid metabolism in human melanoma xenograft lines differing in rate of tumour cell proliferation. 3) ''31P-nuclear magnetic resonance spectroscopy in vivo of four human melanoma xenograft lines: Spin-lattice relaxation times. 4) Effect of melanin on phosphorus T1s in human melanoma xenografts studie/sub>s in human melanoma xenografts studied by ''31P MRS 5) Spin-lattice relaxation time of inorganic phosphate in human tumour xenografts measured in vivo by ''31P-magnetic resonance spectroscopy influence of oxygen tension. 6) Effects of hyperthermia on bio energetic status and phosphorus T1s in human melanoma xenografts monitored by ''31P-MRS. 7) Monitoring of tumour reoxygenation following irradiation by ''31P magnetic resonance spectroscopy an experimental study of human melanoma xenografts. 8) Radiation-induced changes in phosphorus T1 values in human melanoma xenografts studied by ''31P-MRS. Conclusions of the study are in brief: 1) There was neither a correlation between phospholipids resonance ratios and tumour proliferation, nor between bio energetic status, intracellular pH and tumour blood supply across tumour lines. Phosphorus T1s were closely associated to the fraction of necrotic tumour tissue across tumour lines. Even though phosphorus T1s were correlated to necrosis, ''31P-NMR spectroscopy is not likely to be utilized in treatment response prediction since tumour necrosis is ambiguously related to treatment response. 2) There were close correlations between changes in bio energetic status and intracellular pH and changes in tumour blood supply within tumour lines during unperturbed tumour growth. 3) There were dose-dependent changes in tumour bio energetic status and phosphorus T1s after irradiation. The change in bio energetic status was attributed to tumour reoxygenation, whereas altered phosphorus T1s were mainly attributed to increased tumour water content. 4) Following hyperthermia there were treatment-induced changes in bio energetic status and phosphorus T1s that were dependent on the thermal dose. Changes in bio energetic status reflected mainly the altered tumour blood flow induced by the treatment, whereas phosphorus T1s probably were influenced by both necrosis and oedema caused by the hyperthermia treatment. ''31P NMR spectroscopy can probably develop into a useful tool in monitoring of tumour response to irradiation and hyperthermia treatment, since blood flow and oxygenation are closely related to tumour response

98

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

DEFF Research Database (Denmark)

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.

Radula-Janik, Klaudia; Kupka, Teobald

2015-01-01

99

On the influence of vibrational modes and intramolecular isomerization processes on the NMR parameters of bullvalene: A Feynman path integral - ab initio investigation  

International Nuclear Information System (INIS)

The absolute isotropic shieldings and chemical shifts at the 13C and 1H nuclei of bullvalene have been theoretically studied under the conditions of thermal equilibrium. For temperatures T ? 400 K the present Monte Carlo simulations predict a bare vibrational nuclear dynamics. T values > 400 K allow the superposition of vibrational modes and an intramolecular isomerization, i.e. the so-called Cope rearrangement. This result can be correlated with the 'slow' and 'fast' isomerization regime of bullvalene. In the slow regime nuclear magnetic resonance (NMR) measures four different 13C and 1H signals, a splitting that is in line with the molecular C3v symmetry at the minimum of the potential energy surface (PES). In the fast regime only a single signal for the 13C and 1H nuclei is measured by NMR indicating that all bullvalene carbons and protons are equivalent in the NMR time-scale. To derive the NMR parameters of bullvalene we have combined the Feynman path integral quantum Monte Carlo (PIMC) formalism with a tight-binding (TB) Hamiltonian and the Gauge including atomic orbital (GIAO) approach in an ab initio Hartree-Fock formulation. The TB model has been used to calculate the ground state PES, the free energy barrier of the Cope rearrangement, the statistical weight of the nuclear configurations in thermal equilibrium as well as the radial distribution functions of the nuclei. The vibrationn functions of the nuclei. The vibrational modes in a highly anharmonic potential cause an elongation of all bond lengths in thermal equilibrium. This leads to a topology dependent deshielding of the bullvalene nuclei. The T dependence of the deshielding is characteristic for dominating zero-point fluctuations for all temperatures studied. The GIAO based chemical shifts at the 13C and 1H nuclei are compared with experiment. The PIMC - ab initio approach leads to theoretical results of good quality. The T gradient of the 13C and 1H chemical shifts can be reproduced qualitatively by the present PIMC - ab initio approach

100

Moving NMR  

Science.gov (United States)

Initiated by the use of NMR for well logging, portable NMR instruments are being developed for a variety of novel applications in materials testing and process analysis and control. Open sensors enable non-destructive testing of large objects, and small, cup-size magnets become available for high throughput analysis by NMR relaxation and spectroscopy. Some recent developments of mobile NMR are reviewed which delineate the direction into which portable NMR is moving.

Blümich, Bernhard; Casanova, Federico; Danieli, Ernesto; Gong, Qingxia; Greferath, Marcus; Haber, Agnes; Kolz, Jürgen; Perlo, Juan

2008-12-01

101

Improved determination of spin density T1 and T2 from a three-parameter fit to multiple-delay-multiple-echo (MDME) NMR images  

International Nuclear Information System (INIS)

A method is presented for simultaneously determining values of relative hydrogen spin density Nsub(r), T1 and T2 from a single set of NMR image intensities acquired in a short imaging time. Multiple-echo data are collected at multiple delays in virtually the same imaging time used to obtain T1 and a T2-weighted Nsub(r) from a separate saturation recovery (SR) T1 measurement. All three parameters are then determined by a three-parameter fit of a derived signal intensity equation to these multiple-delay-multiple-echo (MDME) data, providing an inherent correction of Nsub(r) for T1 and T2 weighting without the use of sequences with Tsub(D)>5T1, and without further data collection for a separate T2 measurement. It also provides an effective reduction in the noise of the separate T2 measurement. A three-parameter fit to MDME data appears to be superior to the separate T1 and T2 measurements currently used to determine all three parameters. Calculations performed on CrCl3 solutions produced T1 values from 21 ms to 3.4s, T2 values from 6 to 714 ms, and standard errors as low as 0.33%, with a net imaging time of the order of that required for routine low-noise signal intensity imaging. (author)

102

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

Science.gov (United States)

The (1)H NMR signal of the methyl group of sodium acetate is shown to be a triplet in the anisotropic environment of stretched gelatin gel. The multiplet structure of the signal is due to the intra-methyl residual dipolar couplings. The relaxation properties of the spin system were probed by recording steady-state irradiation envelopes ('z-spectra'). A quantum-mechanical model based on irreducible spherical tensors formed by the three magnetically equivalent spins of the methyl group was used to simulate and fit experimental z-spectra. The multiple parameter values of the relaxation model were estimated by using a Bayesian-based Markov chain Monte Carlo algorithm. PMID:25486634

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

2015-01-01

103

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

Science.gov (United States)

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

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

2015-01-25

104

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

Science.gov (United States)

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 1H and 13C 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.

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

2015-01-01

105

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)

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

Reddy, Y Jayasubba; Ramanathan, K V

2015-01-14

106

Study of correlations in molecular motion by multiple quantum NMR  

Energy Technology Data Exchange (ETDEWEB)

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.

Tang, J.H.

1981-11-01

107

Ground State wave function and hyperfine interaction parameter of complexes with a V4+ ion  

International Nuclear Information System (INIS)

The ground state wave function of V4+ ion doped in different crystal lattices has been determined with the help of the different spin-Hamiltonian parameters obtained from the EPR studies of the same. The ground state wave function comes out to be of the dsub(xy) type. The hyperfine interaction parameter and the fermi contact term for each of the above crystallices containing V4+ ion have also been estimated and the nature of chemical bonding in complexes has been explained on the basis of the hyperfine interaction parameter. (author)

108

Quantitative NMR  

Science.gov (United States)

This site features a learning module focused on principles and practice of NMR for quantitative analysis, an application less commonly associated with the technique than is structure determination. Links to simulation packages are included.

Korir, Albert K.; Larive, Cynthia K.

2011-07-18

109

NMR Animations  

Science.gov (United States)

This site features animated tutorials on NMR with sufficient depth to be useful to the non NMR savvy. The animations are accompanied by short descriptions so that the processes displayed can be understood by the viewer. This site goes beyond just showing precession. There are nice animations showing the effect of different pulses, including composite pulses on the magnetization, the effects of magnetic gradient pulses to measure diffusion and do coherence pathway selection.

2011-07-26

110

NMR tutorial  

Science.gov (United States)

This site provides an entry-level introduction to NMR in a text and figures format. The site also contains example structure elucidation problems using NMR, IR and MS data complete with hints and answers. Although the molecules included are somewhat simple, the examples do a good job of illustrating the structure elucidation process. The site also has data for several more complex structure determination problems.

Bogdal, Dariusz

2011-07-19

111

Characterizing ions in solution by NMR methods  

OpenAIRE

NMR experiments performed under the effect of electric fields, either continuous or pulsed, can provide quantitative parameters related to ion association and ion transport in solution.  Electrophoretic NMR (eNMR) is based on a diffusion pulse-sequence with electric fields applied in the form of pulses. Magnetic field gradients enable the measurement of the electrophoretic mobility of charged species, a parameter that can be related to ionic association. The effective charge of the tetrameth...

Giesecke, Marianne

2014-01-01

112

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.

113

Mechanical analogues of spin Hamiltonians and dynamics  

Energy Technology Data Exchange (ETDEWEB)

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.

Kaur, Harjeet, E-mail: harjeet_kaur17@yahoo.com [Department of Physics, Guru Nanak Dev University, Amritsar 143 005 (India); Jain, Sudhir R. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Malik, Sham S. [Department of Physics, Guru Nanak Dev University, Amritsar 143 005 (India)

2014-01-17

114

Mechanical analogues of spin Hamiltonians and dynamics  

Science.gov (United States)

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.

Kaur, Harjeet; Jain, Sudhir R.; Malik, Sham S.

2014-01-01

115

Exchange parameters of bcc solid 3He  

International Nuclear Information System (INIS)

Using the spin Hamiltonian, in which two-spin interactions up to third neighbors and two kinds of large folded and planar cyclic four-spin exchange terms are included, spin wave spectrum of uudd and pseudoferromagnetic (PF) phase of bcc solid 3He in finite magnetic field has been calculated. The necessary conditions for the exchange parameters to explain the first order phase transition from uudd to PF at magnetic field of about 0.4T and high temperature experimental results have been obtained within a framework of a three-parameter model. By a calculation using a mean field approximation, the new phase, double spiral spin configuration has been found, and the possibility of the appearance of this phase near T/sub N/ are discussed. 10 references, 5 figures

116

NMR for liquid fossil fuels  

International Nuclear Information System (INIS)

The book comprises two parts: the first part elements of relevant NMR phenomenology, including a definition of the most important NMR parameters, an introduction to Fourier transform NMR and a discussion of newer pulse techniques. Sufficient background material is presented to enable the reader to follow such techniques as spin echo, two-dimensional and polarization transfer experiments. These techniques are illustrated by extensive examples derived from fuel chemistry. The second part addresses the interpretation of NMR spectra and is based, to a very large extent, on the work of the authors who have used NMR in a variety of applications in fossil fuels. This part describes in detail the three basic methods for interpreting NMR spectra of liquid fuels: average structural parameter calculations, average molecule construction and functional group analysis. The use of NMR in engineering calculations is also presented and should be particularly useful to those interested in processing of fossil fuels. Extensive examples are drawn from petroleum, shale oils, coal liquids and model systems. Computer programs for performing the characterizations from the spectra are provided. 146 refs.; 64 figs.; 47 tabs

117

27Al NMR Study on CeRu2Al10 Single Crystal: I. Determination of the NQR Parameters for Five Non-Equivalent Al Sites in the Paramagnetic Region  

Science.gov (United States)

We performed 27Al (I=5/2) NMR measurements in CeRu2Al10 single crystal by rotating the crystal axes against applied field in the paramagnetic region. The angle dependence of the resonance peaks for each of the five nonequivalent Al site allows us to determine the NQR parameters (?Q and ?) as well as the direction of the maximal principal axis of the electric field gradient (EFG), including the Al(2) site not detected by the NQR experiment due to the smaller ?Q than the lower limit of the measurement, with the aid of the results of zero-field 27Al NQR measurement and band calculation. The NQR parameters are in agreement with those obtained by 27Al NQR measurements. Both NQR parameters and the direction of the maximal principal axis of the EFG show excellent agreement with those obtained by the band calculation except for those in the Al(2) site.

Tanida, Hiroshi; Tanaka, Daiki; Sera, Masafumi; Nishioka, Takashi; Kato, Harukazu; Matsumura, Masahiro; Harima, Hisatomo; Yasuoka, Hiroshi

2011-01-01

118

27Al NMR study on CeRu2Al10 single crystal. 1. Determination of the NQR parameters for five non-equivalent Al sites in the paramagnetic region  

International Nuclear Information System (INIS)

We performed 27Al (I=5/2) NMR measurements in CeRu2Al10 single crystal by rotating the crystal axes against applied field in the paramagnetic region. The angle dependence of the resonance peaks for each of the five nonequivalent Al site allows us to determine the NQR parameters (?Q and ?) as well as the direction of the maximal principal axis of the electric field gradient (EFG), including the Al(2) site not detected by the NQR experiment due to the smaller ?Q than the lower limit of the measurement, with the aid of the results of zero-field 27Al NQR measurement and band calculation. The NQR parameters are in agreement with those obtained by 27Al NQR measurements. Both NQR parameters and the direction of the maximal principal axis of the EFG show excellent agreement with those obtained by the band calculation except for those in the Al(2) site. (author)

119

Hochdruck NMR  

OpenAIRE

Ziel der Arbeit waren hochauflösende NMR-Messungen an Biopolymeren bei Drücken bis 200 MPa. Dazu wurde ein vorhandenes Drucksystem an die Hochfeldgeräte adaptiert. Als wesentliche Verbesserung wurden Saphirdruckkapillaren eingeführt. Zur Beschreibung des Verhaltens von entfalteten Proteinen wurden die chemischen Verschiebungen der Protonenresonanzen von Tetrapeptiden vermessen. Neben der Erstellung von Tabellen zu vergleichenden Untersuchungen des Druckverhaltens gefalteter Proteine, k...

Arnold, Martin Reinhard

2003-01-01

120

NMR GHZ  

CERN Document Server

We describe the creation of a Greenberger-Horne-Zeilinger (GHZ) state of the form |000>+|111> (three maximally entangled quantum bits) using Nuclear Magnetic Resonance (NMR). We have successfully carried out the experiment using the proton and carbon spins of trichloroethylene, and confirmed the result using state tomography. We have thus extended the space of entangled quantum states explored systematically to three quantum bits, an essential step for quantum computation.

Laflamme, R; Zurek, W H; Catasti, P; Mariappan, S V S

1998-01-01

121

NMR GHZ  

OpenAIRE

We describe the creation of a Greenberger-Horne-Zeilinger (GHZ) state of the form |000>+|111> (three maximally entangled quantum bits) using Nuclear Magnetic Resonance (NMR). We have successfully carried out the experiment using the proton and carbon spins of trichloroethylene, and confirmed the result using state tomography. We have thus extended the space of entangled quantum states explored systematically to three quantum bits, an essential step for quantum computation.

Laflamme, R.; Knill, E.; Zurek, W. H.; Catasti, P.; Mariappan, S. V. S.

1997-01-01

122

{sup 3}1P-NMR spectroscopy in measurements of physiological parameters and response to therapy of human melanoma xenografts  

Energy Technology Data Exchange (ETDEWEB)

The aim of the study was to investigate whether ''31P-NMR spectroscopy can be utilized in prediction and monitoring of response to therapy or tumours. The specific aims were: 1) To investigate possible correlations between on the one hand bio energetics status, phospholipids resonance ratios, intracellular pH and phosphorus T{sub 1}s and on the other hand tumour blood supply and oxygenation, tumour proliferation and necrotic fraction across tumour lines. 2) Reveal possible correlations between changes in tumour bio energetics status and phosphorus T{sub 1}s and the changes in tumour blood flow, tumour oxygenation and necrotic fraction. 3) To investigate whether irradiation and hyperthermia treatment of tumours affect bio energetics status and phosphorus T{sub 1}s. 4) To identify the tumour physiological factors that is effected by the treatment and influence the bio energetics status and phosphorus T{sub 1}s. The results are presented in 8 papers with titles: 1)''31P-nuclear magnetic resonance spectroscopy in vivo of six human melanoma zeno graft lines: Tumour bio energetic status and blood supply. 2) ''31P NMR spectroscopy studies of phospholipid metabolism in human melanoma xenograft lines differing in rate of tumour cell proliferation. 3) ''31P-nuclear magnetic resonance spectroscopy in vivo of four human melanoma xenograft lines: Spin-lattice relaxation times. 4) Effect of melanin on phosphorus T{sub 1}s in human melanoma xenografts studied by ''31P MRS 5) Spin-lattice relaxation time of inorganic phosphate in human tumour xenografts measured in vivo by ''31P-magnetic resonance spectroscopy influence of oxygen tension. 6) Effects of hyperthermia on bio energetic status and phosphorus T{sub 1}s in human melanoma xenografts monitored by ''31P-MRS. 7) Monitoring of tumour reoxygenation following irradiation by ''31P magnetic resonance spectroscopy an experimental study of human melanoma xenografts. 8) Radiation-induced changes in phosphorus T{sub 1} values in human melanoma xenografts studied by ''31P-MRS. Conclusions of the study are in brief: 1) There was neither a correlation between phospholipids resonance ratios and tumour proliferation, nor between bio energetic status, intracellular pH and tumour blood supply across tumour lines. Phosphorus T{sub 1}s were closely associated to the fraction of necrotic tumour tissue across tumour lines. Even though phosphorus T{sub 1}s were correlated to necrosis, ''31P-NMR spectroscopy is not likely to be utilized in treatment response prediction since tumour necrosis is ambiguously related to treatment response. 2) There were close correlations between changes in bio energetic status and intracellular pH and changes in tumour blood supply within tumour lines during unperturbed tumour growth. 3) There were dose-dependent changes in tumour bio energetic status and phosphorus T{sub 1}s after irradiation. The change in bio energetic status was attributed to tumour reoxygenation, whereas altered phosphorus T1s were mainly attributed to increased tumour water content. 4) Following hyperthermia there were treatment-induced changes in bio energetic status and phosphorus T{sub 1}s that were dependent on the thermal dose. Changes in bio energetic status reflected mainly the altered tumour blood flow induced by the treatment, whereas phosphorus T{sub 1}s probably were influenced by both necrosis and oedema caused by the hyperthermia treatment. ''31P NMR spectroscopy can probably develop into a useful tool in monitoring of tumour response to irradiation and hyperthermia treatment, since blood flow and oxygenation are closely related to tumour response.

Olsen, Dag Rune

1999-07-01

123

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)

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.

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

124

NMR spectroscopy  

International Nuclear Information System (INIS)

The book reviews the applications of NMR-spectroscopy in medicine and biology. The first chapter of about 40 pages summarizes the history of development and explains the chemical and physical fundamentals of this new and non-invasive method in an easily comprehensible manner. The other chapters summarize diagnostic results obtained with this method in organs and tissues, so that the reader will find a systematic overview of the available findings obtained in the various organ systems. It must be noted, however, that ongoing research work and new insight quite naturally will necessitate corrections to be done, as is the case here with some biochemical interpretations which would need adjustment to latest research results. NMR-spectroscopy is able to measure very fine energy differences on the molecular level, and thus offers insight into metabolic processes, with the advantage that there is no need of applying ionizing radiation in order to qualitatively or quantitatively analyse the metabolic processes in the various organ systems. (orig./DG) With 40 figs., 4 tabs

125

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.

126

Ferrimagnetism of the magnetoelectric compound Cu2OSeO3 probed by S77e NMR  

Science.gov (United States)

We present a thorough S77e nuclear-magnetic-resonance (NMR) study of a single crystal of the magnetoelectric compound Cu2OSeO3 . The temperature dependence of the local electronic moments extracted from the NMR data is fully consistent with a magnetic phase transition from the high- T paramagnetic phase to a low- T ferrimagnetic state with 3/4 of the Cu2+ ions aligned parallel and 1/4 aligned antiparallel to the applied field of 14.09 T. The transition to this 3up-1down magnetic state is not accompanied by any splitting of the NMR lines or any abrupt modification in their broadening, hence there is no observable reduction in the crystal symmetry from its high- T cubic P213 space group. These results are in agreement with high-resolution x-ray diffraction and magnetization data on powder samples reported previously by Bos [Phys. Rev. B 78, 094416 (2008)]10.1103/PhysRevB.78.094416. We also develop a mean-field theory description of the problem based on a microscopic spin Hamiltonian with one antiferromagnetic (Jafm?68K) and one ferromagnetic (Jfm?-50K) nearest-neighbor exchange interaction.

Belesi, M.; Rousochatzakis, I.; Wu, H. C.; Berger, H.; Shvets, I. V.; Mila, F.; Ansermet, J. P.

2010-09-01

127

NMR Studies of Peroxidases.  

Science.gov (United States)

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.

Veitch, Nigel Charles

128

NMR imaging of leg tumors  

International Nuclear Information System (INIS)

NMR images of 8 patients with neoplasms of the legs were obtained. Volumetric and/or planar NMR data were acquired using a saturation recovery (SR) approach, incorporating magnetization refocusing. NMR images revealed tumors in all patients and correlated well with the extent seen on CT. SR images with a short interpulse delay (tau) demonstrated a significant decrease in signal intensity (SI) in histologically normal fat (n = 4) and marrow (n = 1) adjacent to tumors, consistent with a prolonged T1. At certain values of tau, tumors on SR images could not be differentiated from normal muscle and marrow by SI alone. Using this sequence with fixed signal refocusing parameters, images representing several values of tau may be required to distinguish tumors from normal structures

129

Annual reports on NMR spectroscopy  

CERN Document Server

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.

Webb, Graham A

1992-01-01

130

1H and 13C{1H} NMR spectral parameters of sulfur mustards, nitrogen mustards, and lewisites: computing and predicting of reference spectra for chemical identification.  

Science.gov (United States)

The (1)H and (13)C{(1)H} chemical shifts and (1)H spin-spin couplings of sulfur mustards, nitrogen mustards, and lewisites scheduled in the Chemical Weapons Convention, and those of bis(2-chloromethyl)disulfide, were determined in CDCl(3), CD(2)Cl(2), and (CD(3))(2)CO. Accurate parameters of this kind of series can be used for evaluating the current molecular modeling programs and the chemical shift and coupling constant prediction possibilities of the programs. Several prediction tests were made with commercial programs, and the results are reported here. PMID:22374852

Haapaniemi, Esa; Mesilaakso, Markku

2012-03-01

131

Spectroscopic (FT-IR, FT-Raman and UV-Visible) investigations, NMR chemical shielding anisotropy (CSA) parameters of 2,6-Diamino-4-chloropyrimidine for dye sensitized solar cells using density functional theory  

Science.gov (United States)

The molecular structure, geometry optimization, vibrational frequencies of organic dye sensitizer 2,6-Diamino-4-chloropyrimidine (DACP) were studied based on Hartree-Fock (HF) and density functional theory (DFT) using B3LYP methods with 6-311++G(d,p) basis set. Ultraviolet-Visible (UV-Vis) spectrum was investigated by time dependent DFT (TD-DFT). Features of the electronic absorption spectrum in the UV-Visible regions were assigned based on TD-DFT calculation. The absorption bands are assigned to transitions. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer DACP is due to an electron injection process from excited dye to the semiconductor's conduction band. The observed and the calculated frequencies are found to be in good agreement. The energies of the frontier molecular orbitals (FMOS) have also been determined. The chemical shielding anisotropic (CSA) parameters are calculated from the NMR analysis, Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

Gladis Anitha, E.; Joseph Vedhagiri, S.; Parimala, K.

2015-02-01

132

Spectroscopic (FT-IR, FT-Raman and UV-Visible) investigations, NMR chemical shielding anisotropy (CSA) parameters of 2,6-Diamino-4-chloropyrimidine for dye sensitized solar cells using density functional theory.  

Science.gov (United States)

The molecular structure, geometry optimization, vibrational frequencies of organic dye sensitizer 2,6-Diamino-4-chloropyrimidine (DACP) were studied based on Hartree-Fock (HF) and density functional theory (DFT) using B3LYP methods with 6-311++G(d,p) basis set. Ultraviolet-Visible (UV-Vis) spectrum was investigated by time dependent DFT (TD-DFT). Features of the electronic absorption spectrum in the UV-Visible regions were assigned based on TD-DFT calculation. The absorption bands are assigned to transitions. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer DACP is due to an electron injection process from excited dye to the semiconductor's conduction band. The observed and the calculated frequencies are found to be in good agreement. The energies of the frontier molecular orbitals (FMOS) have also been determined. The chemical shielding anisotropic (CSA) parameters are calculated from the NMR analysis, Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. PMID:25459717

Gladis Anitha, E; Joseph Vedhagiri, S; Parimala, K

2014-10-24

133

Fundamentals of NMR  

Science.gov (United States)

This e-text presents an introduction to the fundamentals of NMR covering magnetic resonance, pulsed NMR, relaxation, chemical shift, spin-spin coupling, the nuclear Overhauser effect and chemical exchange. The document may be downloaded in PDF format.

James, Thomas L.

2011-03-30

134

NMR Quantum Computation  

OpenAIRE

In this article I will describe how NMR techniques may be used to build simple quantum information processing devices, such as small quantum computers, and show how these techniques are related to more conventional NMR experiments.

Jones, J. A.

2000-01-01

135

NMR Quantum Information Processing  

OpenAIRE

Nuclear Magnetic Resonance (NMR) has provided a valuable experimental testbed for quantum information processing (QIP). Here, we briefly review the use of nuclear spins as qubits, and discuss the current status of NMR-QIP. Advances in the techniques available for control are described along with the various implementations of quantum algorithms and quantum simulations that have been performed using NMR. The recent application of NMR control techniques to other quantum comput...

Ramanathan, Chandrasekhar; Boulant, Nicolas; Chen, Zhiying; Cory, David G.; Chuang, Isaac; Steffen, Matthias

2004-01-01

136

Identification and MS-assisted interpretation of genetically influenced NMR signals in human plasma  

OpenAIRE

Nuclear magnetic resonance spectroscopy (NMR) provides robust readouts of many metabolic parameters in one experiment. However, identification of clinically relevant markers in 1H NMR spectra is a major challenge. Association of NMR-derived quantities with genetic variants can uncover biologically relevant metabolic traits. Using NMR data of plasma samples from 1,757 individuals from the KORA study together with 655,658 genetic variants, we show that ratios between NMR intensities at two chem...

Raffler, Johannes; Ro?misch-margl, Werner; Petersen, Ann-kristin; Pagel, Philipp; Blo?chl, Florian; Hengstenberg, Christian; Illig, Thomas; Meisinger, Christa; Stark, Klaus; Wichmann, H-erich; Adamski, Jerzy; Gieger, Christian; Kastenmu?ller, Gabi; Suhre, Karsten

2013-01-01

137

NMR studies of multiphase flows II  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1995-12-31

138

Application of the NMR-MOUSE to food emulsions  

Science.gov (United States)

The application of the NMR-MObile Universal Surface Explorer (NMR-MOUSE) to study food systems is evaluated using oil-in-water emulsions, and the results are compared to those obtained using a conventional low-field NMR (LF-NMR) instrument. The NMR-MOUSE is a small and portable LF-NMR system with a one-sided magnet layout that is used to replace the conventional magnet and probe on a LF-NMR instrument. The high magnetic field gradients associated with the one-sided MOUSE magnet result in NMR signal decays being dominated by molecular diffusion effects, which makes it possible to discriminate between the NMR signals from oil and water. Different data acquisition parameters as well as different approaches to the analysis of the NMR data from a range of oil-in-water emulsions are evaluated, and it is demonstrated how the concentration of oil and water can be determined from the NMR-MOUSE signals. From these model systems it is concluded that the NMR-MOUSE has good potential for the quantitative analysis of intact food products.

Pedersen, H. T.; Ablett, S.; Martin, D. R.; Mallett, M. J. D.; Engelsen, S. B.

2003-11-01

139

An introduction to biological NMR spectroscopy.  

Science.gov (United States)

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). PMID:23831612

Marion, Dominique

2013-11-01

140

NMR and NQR parameters of ethanol crystal  

OpenAIRE

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 structura...

Milinkovic, M.; Bilalbegovic, G.

2012-01-01

141

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.retical modelling.

142

NMR crystallography of ?-poly(L-lactide).  

Science.gov (United States)

A complementary approach that combines NMR measurements, analysis of X-ray and neutron powder diffraction data and advanced quantum mechanical calculations was employed to study the ?-polymorph of L-polylactide. Such a strategy, which is known as NMR crystallography, to the best of our knowledge, is used here for the first time for the fine refinement of the crystal structure of a synthetic polymer. The GIPAW method was used to compute the NMR shielding parameters for the different models, which included the ?-PLLA structure obtained by 2-dimensional wide-angle X-ray diffraction (WAXD) at -150 °C (model M1) and at 25 °C (model M2), neutron diffraction (WAND) measurements (model M3) and the fully optimized geometry of the PLLA chains in the unit cell with defined size (model M4). The influence of changes in the chain conformation on the (13)C ?(ii) NMR shielding parameters is shown. The correlation between the ?(ii) and ?(ii) values for the M1-M4 models revealed that the M4 model provided the best fit. Moreover, a comparison of the experimental (13)C NMR spectra with the spectra calculated using the M1-M4 models strongly supports the data for the M4 model. The GIPAW method, via verification using NMR measurements, was shown to be capable of the fine refinement of the crystal structures of polymers when coarse X-ray diffraction data for powdered samples are available. PMID:23340670

Pawlak, Tomasz; Jaworska, Magdalena; Potrzebowski, Marek J

2013-03-01

143

NMR imaging and pharmaceutical sciences  

International Nuclear Information System (INIS)

Described is the technique of NMR-imaging in diagnostic medicine. Proton and phosphorus NMR in diagnosis of abnormal tissue pathology. Discussed is the value of NMR to the pharmaceutical sciences. NMR may play an important role in monitoring the response of tissues to drugs, determining the localization of drugs, performing real time pharmacokinetics and testing the use of NMR contrast pharmaceuticals

144

Diffusion NMR of molecular cages and capsules.  

Science.gov (United States)

In the last decade diffusion NMR and diffusion ordered spectroscopy (DOSY) have become important analytical tools for the characterization of supramolecular systems in solution. Diffusion NMR can be used to glean information on the (effective) size and shape of molecular species, as well as to probe inter-molecular interactions and can be used to estimate the association constant (Ka) of a complex. In addition, the diffusion coefficient, as obtained from diffusion NMR, is a much more intuitive parameter than the chemical shift for probing self-association, aggregation and inter-molecular interactions. The diffusion coefficient may be an even more important analytical parameter in systems in which the formed supramolecular entity has the same symmetry as its building units, when there is a large change in the molecular weight, where many molecular species are involved in the formation of the supramolecular systems, and when proton transfer may occur which, in turn, may affect the chemical shift. Some of the self-assembled molecular capsules and cages prepared in the last decade represent such supramolecular systems and in the present review, following a short introduction on diffusion NMR, we survey the contribution of diffusion NMR and DOSY in the field of molecular containers and capsules. We will first focus on the role played by diffusion NMR in the field of hydrogen bond driven self-assembled capsules. We then survey the contributions of diffusion NMR and DOSY to the study and characterization of metal-ligand cages and capsules. Finally, we describe a few recent applications of diffusion NMR in the field of hydrophobic, electrostatic and covalent containers. PMID:25110858

Avram, Liat; Cohen, Yoram

2014-12-22

145

NMR and protein dynamics  

OpenAIRE

NMR techniques can give insight into a wide variety of motional events that occur in proteins over a range of timescales. In the first section of this article an overview of the results of dynamics studies, using NMR methods, on both small globular and larger multi-domain proteins is presented including the findings from investigations of non-native partly folded states. The second section of the article then concentrates on two topics where NMR can give residue specific quantitative data, na...

Smith, Lj; Dobson, Cm

1996-01-01

146

Elemental analysis by NMR.  

Science.gov (United States)

We explore the possibility for elemental analysis by NMR. To keep the efficiency of the signal acquisition common for all spin species, we propose to fix the frequency and vary the magnetic field to cover the isotopes involved in a sample. We introduce constant-frequency receptivity for quantitative elemental analysis in the frequency-fixed NMR experiment. Field-variable NMR experiments are demonstrated using a cryogen-free superconducting magnet. In addition to elemental analysis in liquid solution, solid-state NMR under magic-angle spinning is also described. PMID:23036840

Takeda, Kazuyuki; Ichijo, Naoki; Noda, Yasuto; Takegoshi, K

2012-11-01

147

Understanding NMR Spectroscopy  

Science.gov (United States)

This site provides links to a series of PDF files that represent chapters of an e-text on the basics of NMR. While many other textbooks on NMR are available, the chief merit of this one is that it has a nice chapter on the NMR instrumentation (ch. 5) which should be accessible to undergraduates. The text also provides a relatively mathematics-free or maybe more accurately Dirac bracket notation-free introduction to 1-D and 2-D (COSY and NOESY) experiments that would be appreciated by advanced undergraduates or beginning graduate students involved in undergraduate research experiences using NMR.

Keeler, James

2011-04-15

148

Optimization and practical implementation of ultrafast 2D NMR experiments  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

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

149

Optimization and practical implementation of ultrafast 2D NMR experiments  

Directory of Open Access Journals (Sweden)

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.

Luiz H. K. Queiroz Júnior

2013-01-01

150

Teaching NMR Using Online Textbooks  

OpenAIRE

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 ...

Hornak, Joseph P.

1999-01-01

151

NMR imaging system software  

International Nuclear Information System (INIS)

FTI program used for NMR imaging i.e. for obtaining, recording and decoding of two-dimensional object image is described. The NMR apparatus connected on line with MERA 400 microcomputer is presented. The exemplary image is give. 3 refs., 3 figs. (A.S.)

152

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

153

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

154

NMR Spectroscopy - Theory  

Science.gov (United States)

This web site begins with a simple quantum description of NMR and proceeds to introduce resonance absorption, relaxation, chemical shifts, and scalar couplings. This site will be useful for advanced undergraduate students needing a description of NMR that is more detailed than that given in most introductory Organic texts.

Lord, J. R.

2011-06-30

155

Databases and Software for NMR-Based Metabolomics.  

Science.gov (United States)

New software and increasingly sophisticated NMR metabolite spectral databases are advancing the unique abilities of NMR spectroscopy to identify and quantify small molecules in solution for studies of metabolite biomarkers and metabolic flux. Public and commercial databases now contain experimental 1D (1)H, (13)C and 2D (1)H-(13)C spectra and extracted spectral parameters for over a thousand compounds and theoretical data for thousands more. Public databases containing experimental NMR data from complex metabolic studies are emerging. These databases are providing information vital for the construction and testing of new computational algorithms for NMR-based chemometric and quantitative metabolomics studies. In this review we focus on database and software tools that support a quantitative NMR approach to the analysis of 1D and 2D NMR spectra of complex biological mixtures. PMID:24260723

Ellinger, James J; Chylla, Roger A; Ulrich, Eldon L; Markley, John L

2013-01-01

156

Basics of NMR  

Science.gov (United States)

Dr. Joseph Hornak of the Rochester Institute of Technology presents this high quality hypertextbook for in-depth coverage of the physics and technique behind Nuclear Magnetic Resonance (NMR) (For Dr. Hornak's Basics of MRI, see the August 4, 1999 Scout Report for Science & Engineering). The material is presented in a detailed and clear manner without over simplifying the concepts. Chapters include "The Mathematics of NMR," "Spin Physics," "NMR Spectroscopy," "Fourier Transforms," "Pulse Sequences," and much more. A chapter on "NMR Hardware" offers an overview of components (like the superconducting magnet and various coils) used in most NMR systems. The "Practical Considerations" chapter emphasizes spectroscopic techniques. With the screen split into two separate frames, explanatory graphics can be viewed alongside the text. A glossary and a list of symbols are also included in this carefully produced textbook.

Hornak, Joseph P.

157

Solid state NMR  

Energy Technology Data Exchange (ETDEWEB)

This series presents critical reviews of the present position and future trends in modern chemical research. Short and concise reports on chemistry. Each written by the world renowned experts. Still valid and useful after 5 or 10 years. More information as well as the electronic version of the whole content available at: springerlink.com. Dipolar Recoupling, by Niels Chr. Nielsen, Lasse A. Strassoe and Anders B. Nielsen. - Solid-State NMR Techniques for the Structural Determination of Amyloid Fibrils, by Jerry C. C. Chan. - Solid-State {sup 19}F-NMR of Peptides in Native Membranes, by Katja Koch, Sergii Afonin, Marco Ieronimo, Marina Berditsch and Anne S. Ulrich. - Probing Quadrupolar Nuclei by Solid-State NMR Spectroscopy: Recent Advances, by Christian Fernandez and Marek Pruski. - Solid State NMR of Porous Materials Zeolites and Related Materials, by Hubert Koller and Mark Weiss. - Solid-State NMR of Inorganic Semiconductors, by James P. Yesinowski.

Chan, Jerry C.C. (ed.) [National Taiwan Univ., Taipei (China). Dept. of Chemistry

2012-07-01

158

NMR logging apparatus  

Science.gov (United States)

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.

Walsh, David O; Turner, Peter

2014-05-27

159

In situ NMR systems.  

Science.gov (United States)

In situ NMR is becoming an established technology for applications in bioprocessing and metabolic engineering. The in situ NMR biosensor acts as a noninvasive pH, ion, and concentration meter, with 31P and 13C as the two main isotopes of study. A substantial data base now exists for phosphorus and carbon spectra of bacteria and yeast. In situ NMR can provide many of the state variables needed for modeling glycolytic pathway function. NMR micro-reactor technology has improved significantly in the last decade. Several designs for immobilized cell reactors have been tested, and in particular, considerable gains have been made in the feasibility of studying aerobic, chemostat cultures with in situ NMR. Acquisition of 31P spectra from cell suspensions of 3-5% v/v under controlled conditions can be made in 3-7 minute time resolution in several systems. PMID:11471540

Shanks, J V

2001-01-01

160

Liquid-Liquid extraction and NMR  

Energy Technology Data Exchange (ETDEWEB)

This paper offers an overview of the possibilities for the use of NMR techniques in solvent extraction studies for new extraction systems (monoamides, malonamides and picolinamides) and tri-n-butylphosphate (TBP) properties investigations. We have used NMR spectroscopy with monoamides to identify the structural parameters that control monoamide selectivity and efficiency. Distances between the carbon atoms of the monoamide ligands and the lanthanides(lII) or actinides(IV) metallic centres were determined through the analysis of the {sup 13}C T{sub 1} NMR relaxation time data. The conformational data obtained by NMR measurements related to lanthanide nitrate monoamide solvates were then compared with the corresponding distribution coefficients. Dynamic information on the extractant were also obtained and gave an indication of the time scale of different motions in liquid phases as well as the influence of a metal ion in the media. From {sup 1}H, {sup 2}H and {sup 13}C NMR spectra analyses, extractants in organic phases show some weak interactions such as malonamide dimer formations. These were observed for diluted benzenic solutions but for more concentrated solutions, micellar formation were observed. This may explain: decantation problems and the large amount of extracted water observed. Nitric acid extraction mechanisms can be also determined by NMR. The case of the picolinamide extractants, analysed from {sup 1}H and {sup 13}C NMR spectra is a good example. A relatively straightforward mechanism results of this and protonation sites are determined. {sup 31}P NMR was found useful for practical and basic research dealing with the hydrolytic and radiolytic degradations of the TBP : each organophosphorus TBP degradation product was identified and quantified. A chemical exchange between dibutylphosphoric acid (HDBP) and DBP:Zr(NO{sub 3}){sub 4} system was pointed out and allows us to understand the original Zr(IV) property that induces demixion of HDBP from aqueous nitric solutions. (authors) 3 refs., 2 tabs., 3 figs.

Berthon, C.; Vaufrey, F.; Livet, J.; Madic, C. [CEA, Centre d`Etudes Nucleaires de Fontenay-aux-Roses, DCC/DRDD/SEMP/SEC, Fontenay-aux-Rose (France); Hudson, M.J. [University of Reading, Berkshire (United Kingdom). Department of Chemistry

1996-12-31

161

Rapid prediction of multi-dimensional NMR data sets  

Energy Technology Data Exchange (ETDEWEB)

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).

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

162

39K NMR in polycrystalline potassium perbromate  

International Nuclear Information System (INIS)

Asymmetry parameter of electric field gradient (EFG) 0.47(5) and quadrupole bond constant 0.80(5) MHz in polycrystal compound KBrO4 at 296 K were determined by 39K NMR method. It is shown that the values of EFG in cationic positions of alkali metal perbromates are bound linearly with reciprocal volume of the crystal unit cell

163

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.)

164

NMR Stark Spectroscopy: New Methods to Calibrate NMR Sensitivity to Electric Fields  

Science.gov (United States)

The influence of electrostatics on NMR parameters is well accepted. Thus, NMR is a promising route to probe electrical features within molecules and materials. However, applications of NMR Stark effects (E-field induced changes in spin energy levels) have been elusive. I have developed new approaches to resolve NMR Stark effects from an applied E field. This calibrates nuclear probes whose spectral response might later be used to evaluate internal E fields that are critical to function, such as those due to local charge distributions or sample structure. I will present two novel experimental approaches for direct calibration of NMR quadrupolar Stark effects (QSEs). In the first, steady-state (few-second) excitation by an E field at twice the NMR frequency (2? 0) is used to saturate spin magnetization. The extent of saturation vs. E-field amplitude calibrates the QSE response rate, while measurements vs sample orientation determine tensorial character. The second method instead synchronizes short (few µs) pulses of the 2?0 E field with a multiple-pulse NMR sequence. This, “POWER” (Perturbations Observed With Enhanced Resolution) approach enables more accurate measure of small QSEs (i.e. few Hz spectral changes). A 2nd key advantage is the ability to define tensorial response without reorienting the sample, but instead varying the phase of the 2?0 field. I will describe these experiments and my home-built NMR “Stark probe”, employed on a conventional wide-bore solid-state NMR system. Results with GaAs demonstrate each method, while extensions to a wider array of molecular and material systems may now be possible using these methods.

Tarasek, Matthew R.

165

Theoretical and experimental insights into applicability of solid-state 93Nb NMR in catalysis.  

Science.gov (United States)

Ab initio DFT calculations of (93)Nb NMR parameters using the NMR-CASTEP code were performed for a series of over fifty individual niobates, and a good agreement has been found with experimental NMR parameters. New experimental and calculated (93)Nb NMR data were obtained for several compounds, AlNbO4, VNb9O25, K8Nb6O19 and Cs3NbO8, which are of particular interest for catalysis. Several interesting trends have been identified between (93)Nb NMR parameters and the specifics of niobium site environments in niobates. These trends may serve as useful guidelines in interpreting (93)Nb NMR spectra of complex niobium oxide systems, including amorphous samples and niobium-based multicomponent heterogeneous catalysts. Potential applications of (93)Nb NMR to study solid polyoxoniobates are discussed. PMID:23450163

Papulovskiy, Evgeniy; Shubin, Alexandre A; Terskikh, Victor V; Pickard, Chris J; Lapina, Olga B

2013-04-14

166

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

International Nuclear Information System (INIS)

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

167

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

168

Applications of NMR in biological metabolic research  

International Nuclear Information System (INIS)

The nuclear magnetic resonance has become a powerful means of studying biological metabolism in non-invasive and non-destructive way. Being used to study the metabolic processes of living system in normal physiological conditions as well as in molecular level, the method is better than other conventional approaches. Using important parameters such as NMR-chemical shifts, longitudinal relaxation time and transverse relaxation time, it is possible to probe the metabolic processes as well as conformation, concentration, transportation and distribution of reacting and resulting substances. The NMR spectroscopy of 1H, 31P and 13C nuclei has already been widely used in metabolic researches

169

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

170

Benford distributions in NMR  

OpenAIRE

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-d...

Bhole, Gaurav; Shukla, Abhishek; Mahesh, T. S.

2014-01-01

171

Proteins Studied by NMR  

OpenAIRE

Nuclear magnetic resonance (NMR) spectroscopy is a powerful method for the study of the structure, dynamics, activity, and folding of proteins in solution. Peptides and small proteins (<10 kDa) can be studied in detail using 1H NMR and two-dimensional methods including COSY (correlation spectroscopy) and TOCSY (total correlation spectroscopy), which provide 'through-bond' correlations, and NOESY (nuclear Overhauser effect spectroscopy), which provides 'through-space' information. For larger p...

Redfield, C.

2010-01-01

172

Quantum computation using NMR  

OpenAIRE

This article reviews recent work done by us an some initial steps towards the implementation of quantum computation using liquid state NMR. We describe how special kinds of states required for such computation (called pseudo-pure states) can be created from a thermal ensemble of spins. We demonstrate the implementation of several quantum logic gates through one- and two-dimensional NMR methods, using transition- and spin- selective pulses. Finally, we discuss the implementation of the Deutsch...

Dorai, Kavita; Mahesh, Ts; Arvind; Kumar, Anil

2000-01-01

173

Silver and Gold NMR  

OpenAIRE

Silver and gold, together with copper, form the transition metal group IB elements in the periodic table and possess very different nuclear magnetic resonance (NMR) spectroscopic properties. While there is only one gold isotope (197Au), which has a spin of 3/2 and therefore a quadrupole moment, silver occurs in two isotopic forms (109Ag and 109Au), both of which have a spin 1/2 and similar NMR spectroscopic properties. The unfavorable properties of g...

Zangger, Klaus; Armitage, Lan M.

1999-01-01

174

Renal transplant NMR  

International Nuclear Information System (INIS)

The preliminary results of NMR evaluation of renal transplants (Txs) are reported including correlation with nuclear medicine (NM) and ultrasound (US). Thirteen Txs (8 cadaver (Cd), 5 living related doner (LRD) in 13 patients (6M, 7F) ranging in age from 25-47 (x 35) were evaluated by NM (32), NMR (15) and US (5). Clinical diagnoses included: rejection (8), ATN (2), infarction (1), and normal (2). Of the 8 patients with rejection (5) Cd; 3 LRD) pathologic proof was obtained in 3. An experimental 0.12 T resistive magnet (GE) was used with a partial saturation technique with repetition time (TR) of 143 and 286 msec to provide T1 weighting. T2 weighted information was obtained with a spin echo technique with echo times (TE) of 20, 40, 60 and 80 msec. The NMR appearance of normal Txs consisted of a uniform signal intensity (Tx> pelvic musculature), well-defined internal architecture with good cortical medullary differentiation and normal appearing vessels. The NMR appearance of abnormal transplants consisted of a heterogeneous or overall decrease in signal intensity (kidney muscle) with poor cortical medullary differentiation with or without a halo of decreased signal intensity. Although NMR was able to differentiate normal from abnormal, it was unable to clearly discriminate between ATN and rejection. Advantages of NMR included the ability to demonstrate regional anatomy, vasculature, post operative fluid collections and hematomas, and associated avascular necrosis of ths, and associated avascular necrosis of the hips

175

Renal transplant NMR  

Energy Technology Data Exchange (ETDEWEB)

The preliminary results of NMR evaluation of renal transplants (Txs) are reported including correlation with nuclear medicine (NM) and ultrasound (US). Thirteen Txs (8 cadaver (Cd), 5 living related doner (LRD) in 13 patients (6M, 7F) ranging in age from 25-47 (x 35) were evaluated by NM (32), NMR (15) and US (5). Clinical diagnoses included: rejection (8), ATN (2), infarction (1), and normal (2). Of the 8 patients with rejection (5) Cd; 3 LRD) pathologic proof was obtained in 3. An experimental 0.12 T resistive magnet (GE) was used with a partial saturation technique with repetition time (TR) of 143 and 286 msec to provide T1 weighting. T2 weighted information was obtained with a spin echo technique with echo times (TE) of 20, 40, 60 and 80 msec. The NMR appearance of normal Txs consisted of a uniform signal intensity (Tx> pelvic musculature), well-defined internal architecture with good cortical medullary differentiation and normal appearing vessels. The NMR appearance of abnormal transplants consisted of a heterogeneous or overall decrease in signal intensity (kidney muscle) with poor cortical medullary differentiation with or without a halo of decreased signal intensity. Although NMR was able to differentiate normal from abnormal, it was unable to clearly discriminate between ATN and rejection. Advantages of NMR included the ability to demonstrate regional anatomy, vasculature, post operative fluid collections and hematomas, and associated avascular necrosis of the hips.

Velchik, M.G.; Kressel, H.; Thickman, D.; Alavi, A.

1985-05-01

176

Applications of NMR to biological systems  

International Nuclear Information System (INIS)

This work describes the application of nuclear magnetic resonance spectrometry (NMR) for the study of three biological systems, namely, the pulmonary surfactant-associated protein, SPL(pVal), the myocardial calcium slow channel of the perfused guinea pig heart, and the intracellular buffering system of the Leishmania donovani promastigote. Investigations of structural features of bovine SPL(pVal) were performed using one and two-dimensional 1H-NMR techniques. Delayed Fourier transform 1H-NMR has been used to study the effects of bovine SPL(pVal) and temperature upon model membrane structure. A model describing the mechanism by which the SPL(pVal) lowers the membrane surface tension has been proposed. In order to study the dependence of the myocardial calcium slow channel activity on adenosine triphosphate levels and intracellular pH, and in vivo 31P-NMR probe capable of simultaneously and noninvasively monitoring these three parameters was designed. In vivo 31P-NMR was also applied for the study of the Leishmania donovani promastigote's ability to maintain a pH gradient across its cellular membrane at low extracellular pH

177

NMR studies of cation transport across membranes  

Energy Technology Data Exchange (ETDEWEB)

/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.

Shochet, N.R.

1985-01-01

178

Ga NMR study of GdGa2-xAlx  

Science.gov (United States)

69Ga and 71Ga NMR signals in GdGa2-xAlx (x = 0.1, 0.25, 0.5, 0.75,1) have been observed at a low temperature in a zero magnetic field. Gd NMR signals were observed only for the samples with x <= 0.5 in the frequency range less than 110MHz, but Ga NMR signals have been observed for all samples in the frequency range higher than Gd NMR frequencies. The features of the observed Ga NMR spectra of the samples with low Al concentration are quite different from those of highly Al concentrated samples. This difference is attributed to the change of the magnetic structure of these compounds. NMR parameters calculated from the Ga NMR results are reported, too. The magnetic structures of these compounds are discussed on the basis of the Ga NMR results.

Hamasaki, T.; Zenmyo, K.; Kubo, H.

2009-03-01

179

Ga NMR study of GdGa2-xAlx  

International Nuclear Information System (INIS)

69Ga and 71Ga NMR signals in GdGa2-xAlx (x = 0.1, 0.25, 0.5, 0.75,1) have been observed at a low temperature in a zero magnetic field. Gd NMR signals were observed only for the samples with x ? 0.5 in the frequency range less than 110MHz, but Ga NMR signals have been observed for all samples in the frequency range higher than Gd NMR frequencies. The features of the observed Ga NMR spectra of the samples with low Al concentration are quite different from those of highly Al concentrated samples. This difference is attributed to the change of the magnetic structure of these compounds. NMR parameters calculated from the Ga NMR results are reported, too. The magnetic structures of these compounds are discussed on the basis of the Ga NMR results.

180

Ga NMR study of GdGa{sub 2-x}Al{sub x}  

Energy Technology Data Exchange (ETDEWEB)

{sup 69}Ga and {sup 71}Ga NMR signals in GdGa{sub 2-x}Al{sub x} (x = 0.1, 0.25, 0.5, 0.75,1) have been observed at a low temperature in a zero magnetic field. Gd NMR signals were observed only for the samples with x <= 0.5 in the frequency range less than 110MHz, but Ga NMR signals have been observed for all samples in the frequency range higher than Gd NMR frequencies. The features of the observed Ga NMR spectra of the samples with low Al concentration are quite different from those of highly Al concentrated samples. This difference is attributed to the change of the magnetic structure of these compounds. NMR parameters calculated from the Ga NMR results are reported, too. The magnetic structures of these compounds are discussed on the basis of the Ga NMR results.

Hamasaki, T [Kyushu Sangyo University, Fukuoka 813-8503 (Japan); Zenmyo, K; Kubo, H, E-mail: hamasaki@ip.kyusan-u.ac.j [Fukuoka Institute of Technology, Fukuoka 811-0295 (Japan)

2009-03-01

181

Teaching NMR Using Online Textbooks  

Directory of Open Access Journals (Sweden)

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.

Joseph P. Hornak

1999-12-01

182

Quantum spin Hamiltonians for the SU(2)k WZW model  

International Nuclear Information System (INIS)

We propose to use null vectors in conformal field theories to derive model Hamiltonians of quantum spin chains and the corresponding ground state wavefunction(s). The approach is quite general, and we illustrate it by constructing a family of Hamiltonians whose ground states are the chiral correlators of the SU(2)k WZW model for integer values of the level k. The simplest example corresponds to k = 1 and is essentially a nonuniform generalization of the Haldane–Shastry model with long-range exchange couplings. At level k = 2, we analyse the model for N spin 1 fields. We find that the Renyi entropy and the two-point spin correlator show, respectively, logarithmic growth and algebraic decay. Furthermore, we use the null vectors to derive a set of algebraic, linear equations relating spin correlators within each model. At level k = 1, these equations allow us to compute the two-point spin correlators analytically for the finite chain uniform Haldane–Shastry model and to obtain numerical results for the nonuniform case and for higher-point spin correlators in a very simple way and without resorting to Monte Carlo techniques

183

Annual reports on NMR spectroscopy  

CERN Document Server

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.

Webb, Graham A

1994-01-01

184

NMR and pet imaging in beam localization  

International Nuclear Information System (INIS)

Positron emission tomography (PET) and nuclear magnetic resonance (NMR) imaging are the most recent developments in diagnostic imaging and the authors have used these techniques at LBL for pre-treatment and follow-up imaging of cerebral tumors and tumors of the head and neck. The data obtained by these two techniques are very different. In NMR imaging, the image signal is determined by mobile proton density and T1 and T2 relaxation parameters. Proton density is most commonly altered by changes in tissue water and NMR is very sensitive to such changes. There are also significant differences in free proton content and relaxation parameters between different normal tissues, so that NMR images are rich in anatomic detail. In PET, images are by definition functional rather than anatomic, as they always reflect the biological behavior of injected positron-emitting radionuclides and different molecules act as tracers of different physiologic functions. The tracers that we use most commonly in cerebral tumor imaging are three: (i) Rubidium-82 (Rb), which is excluded from the normal brain by the blood-brain barrier (BBB), (ii) F-18-2 fluoro-deoxyglucose (FDG), which reflects glucose uptake, and (iii) I-122-HIPDM, which demonstrates brain tissue perfusion

185

NMR studies of oriented molecules  

Energy Technology Data Exchange (ETDEWEB)

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.

Sinton, S.W.

1981-11-01

186

Fluid-Rock Characterization and Interactions in NMR Well Logging  

Energy Technology Data Exchange (ETDEWEB)

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.

George J. Hirasaki; Kishore K. Mohanty

2005-09-05

187

Fourier transform NMR  

International Nuclear Information System (INIS)

This paper discusses the concept of Fourier transformation one of the many precious legacies of the French mathematician Jean Baptiste Joseph Fourier, essential for understanding the link between continuous-wave (CW) and Fourier transform (FT) NMR. Although in modern FT NMR the methods used to obtain a frequency spectrum from the time-domain signal may vary greatly, from the efficient Cooley-Tukey algorithm to very elaborate iterative least-square methods based other maximum entropy method or on linear prediction, the principles for Fourier transformation are unchanged and give invaluable insight into the interconnection of many pairs of physical entities called Fourier pairs

188

Longitudinal and Transverse NMR in Superfluid 3He in Anisotropic Aerogel  

OpenAIRE

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.

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

2007-01-01

189

Boolean logic gate design principles in unconventional computers: an NMR case study  

CERN Document Server

We present a general method for analysing novel computational substrates to determine which of their parameters can be manipulated to exhibit the complete set of 2-input boolean logical operations. We demonstrate this approach with an NMR-based case study, showing which NMR parameters can be used to perform boolean logic.

Bechmann, Matthias; Stepney, Susan

2011-01-01

190

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.)

191

On the use of ultracentrifugal devices for sedimented solute NMR  

International Nuclear Information System (INIS)

We have recently proposed sedimented solute NMR (SedNMR) as a solid-state method to access biomolecules without the need of crystallization or other sample manipulation. The drawback of SedNMR is that samples are intrinsically diluted and this is detrimental for the signal intensity. Ultracentrifugal devices can be used to increase the amount of sample inside the rotor, overcoming the intrinsic sensitivity limitation of the method. We designed two different devices and we here report the directions for using such devices and the relevant equations for determining the parameters for sedimentation.

192

NMR contribution to the actinides chemistry in aqueous solution  

International Nuclear Information System (INIS)

Multi-nuclei NMR utilization, for actinides aqueous solutions studies, give data on the formed complexes. With the NMR parameters, such as chemical displacements, it is possible to accede to the complex structure, to the determination of the equilibrium constants and so to follow the whole chemical equilibriums occurring in aqueous solutions, with the mi-height width of the NMR signals: to the ligand-metal exchange speed, and with the Sz component of the total magnetization of the electronic spin: to some data on the actinides paramagnetic effects. (A.B.). 6 refs., 3 figs

193

Mössbauer and NMR study of novel Tin(IV)-lactames  

International Nuclear Information System (INIS)

N-tributylstannylated 2-pyrrolidinone was reacted with tributyltin triflate in different molar ratios and the complex formation monitored using 1H-NMR, 13C-NMR and 119Sn Mössbauer spectroscopy. Comparing the carbon NMR and tin Mössbauer results, a reaction scheme is suggested for the complexation which assumes the formation of a simultaneously O- and N-tributylstannylated pyrrolidinone cation. The formation of the only O-stannylated pyrrolidinone is also assumed to account for the non-constant Mössbauer parameters of the two tin environments in the distannylated pyrrolidinone cation when the ratio of tributyltin triflate is increased in the reaction.

194

The current situation and perspectives of NMR tomography  

International Nuclear Information System (INIS)

The work accomplished by research teams in the USA and Great Britain in the first ten years following the discovery of NMR as a diagnostic tool has developed this technique to a method offering a high standard of image quality, with a high signal-to-noise ratio and good spatial resolution. Achievements in terms of biochemical information and accuracy of parameter measurement, however, still called for further research, so that in the last few years work has been devoted to enhancing the specificity and quantification of the NMR imaging method, and to rapid NMR tomography. (orig./TRV)

195

Robustness of quantum discord to sudden death in NMR  

CERN Document Server

We investigate the dynamics of entanglement and quantum discord of two qubits in liquid state homonuclear NMR. Applying a phenomenological description for NMR under relaxation process, and taking a group of typical parameters of NMR, we show that when a zero initial state $|00> $ experiences a relaxation process, its entanglement disappears completely after a sequence of so-called sudden deaths and revivals, while the quantum discord retains remarkable values after a sequence of oscillations. That is to say, the quantum discord is more robust than entanglement.

Xu, Jianwei

2011-01-01

196

Assessment of DFT functionals with NMR chemical shifts  

OpenAIRE

Density-functional theory (DFT) calculations of the magnetic shielding for nuclear magnetic resonance (NMR) in solids provide an important contribution for understanding the experimentally observed chemical shifts. It is known that the calculated NMR shielding parameters for a particular nucleus in a series of compounds correlate well with the experimentally measured chemical shifts; however, the slope of a linear fit often differs from the ideal value of 1.0. Focusing on a series of ionic co...

Laskowski, Robert; Blaha, Peter; Tran, Fabien

2013-01-01

197

First Principles NMR Study of Fluorapatite under Pressure  

OpenAIRE

NMR is the technique of election to probe the local properties of materials. Herein we present the results of density functional theory (DFT) \\textit{ab initio} calculations of the NMR parameters for fluorapatite (FAp), a calcium orthophosphate mineral belonging to the apatite family, by using the GIPAW method [Pickard and Mauri, 2001]. Understanding the local effects of pressure on apatites is particularly relevant because of their important role in many solid state and bio...

Pavan, Barbara; Ceresoli, Davide; Tecklenburg, Mary M. J.; Fornari, Marco

2012-01-01

198

"Pure by NMR"?  

OpenAIRE

Integration of a (13)C-(1)H satellite peak of a given (12)C-(1)H parent resonance within a quantitative (1)H NMR spectrum and comparison to the minor component represents a simple protocol for the accurate determination of diastereoisomeric ratios of up to 1000:1 (i.e., 99.8% de).

Claridge, Td; Davies, Sg; Polywka, Me; Roberts, Pm; Russell, Aj; Savory, Ed; Smith, Ad

2008-01-01

199

Festkörper-NMR-Spektroskopie  

OpenAIRE

Die innerhalb dieser Arbeit mittels moderner Festkörper-NMR-Methoden untersuchte molekulare Dynamik in Poly(methacrylat)-Schmelzen und Polyphenylen-Dendrimeren ist durch eine bemerkenswerte Anisotropie gekennzeichnet.Die Anisotropie der molekularen Dynamik zeigt sich in geschmolzenen, ataktischen und isotaktischen Poly(ethylmethacrylaten) (PEMA) durch die Zeitskalenseparation der segmentellen alpha-Relaxation von einem etwa zwei Größenordnungen langsameren Relaxationsprozeß, welcher die I...

Wind, Michael

2002-01-01

200

A Review of the Principles and Applications of the NMR Technique for Near-Surface Characterization  

Science.gov (United States)

This paper presents a comprehensive review of the recent advances in nuclear magnetic resonance (NMR) measurements for near-surface characterization using laboratory, borehole, and field technologies. During the last decade, NMR has become increasingly popular in near-surface geophysics due to substantial improvements in instrumentation, data processing, forward modeling, inversion, and measurement techniques. This paper starts with a description of the principal theory and applications of NMR. It presents a basic overview of near-surface NMR theory in terms of its physical background and discusses how NMR relaxation times are related to different relaxation processes occurring in porous media. As a next step, the recent and seminal near-surface NMR developments at each scale are discussed, and the limitations and challenges of the measurement are examined. To represent the growth of applications of near-surface NMR, case studies in a variety of different near-surface environments are reviewed and, as examples, two recent case studies are discussed in detail. Finally, this review demonstrates that there is a need for continued research in near-surface NMR and highlights necessary directions for future research. These recommendations include improving the signal-to-noise ratio, reducing the effective measurement dead time, and improving production rate of surface NMR (SNMR), reducing the minimum echo time of borehole NMR (BNMR) measurements, improving petrophysical NMR models of hydraulic conductivity and vadose zone parameters, and understanding the scale dependency of NMR properties.

Behroozmand, Ahmad A.; Keating, Kristina; Auken, Esben

2015-01-01

201

Study of liquid crystalline order by NMR  

OpenAIRE

The liquid crystalline phase represents a unique state of matter where partial order exists on molecular and supra-molecular levels and is responsible for several interesting properties observed in this phase. Hence a detailed study of ordering in liquid crystals is of significant scientific and technological interest. NMR provides several parameters that can be used to obtain information about the liquid crystalline phase. Of these, the measurement of dipolar couplings between nuclei has ...

Ramanathan, Kv

2009-01-01

202

Annual reports on NMR spectroscopy  

CERN Document Server

Commencing with Volume 21, the aim of this series is to produce a larger number of, relatively short but, timely and authoritative reviews. These will concentrate, in particular, on areas of NMR where recent progress, and developments, are of special interest and will reflect the many NMR developments occurring in the primary scientific literature. The present volume demonstrates the advances which can be made by the application of NMR techniques in many diverse areas of chemistry. Of particular significance is the account of Graphics-Aided NMR which will become an inprotant development in the use of NMR spectroscopy.

Webb, Graham A

1989-01-01

203

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.)

204

Modeling of NMR processing, toward efficient unattended processing of NMR experiments  

Science.gov (United States)

Many alternative processing techniques have recently been proposed in the literature. Most of these techniques rely on specific acquisition protocols as well as on specific data processing techniques, the need for an efficient versatile and expandable NMR processing tool would be a particularly timely addition to the modern NMR spectroscopy laboratory. The work presented here consists in a modeling of the various possible NMR data processing approaches. This modeling presents a common working frame for most of the modern acquisition/processing protocols. Two different data modeling approaches are presented, strong modeling and weak modeling, depending whether the system under study or the measurement is modeled. The emphasis is placed on the weak modeling approach. This modeling is implemented in a computer program developed in python and called NPK standing (standing for NMR Processing Kernel), organized in four logical layers (i) mathematical kernel; (ii) elementary actions; (iii) processing phases; (iv) processing strategies. This organisation, along with default values for most processing parameters allows the use of the program in an unattended manner, producing close to optimal spectra. Examples are shown for 1D and 2D processing, and liquid and solid NMR spectroscopy. NPK is available from the site: http://abcis.cbs.cnrs.fr/NPK

Tramesel, Dominique; Catherinot, Vincent; Delsuc, Marc-André

2007-09-01

205

Rekonstruktion von Proteinstrukturen aus unvollständigen NMR-Daten  

OpenAIRE

Gegenstand dieser Arbeit ist die Anwendung der Bayes'schen Wahrscheinlichkeitstheorie auf das Problem der makromolekularen Strukturbestimmung aus NMR-Daten. Ausgehend vom Prinzip der Inferentiellen Strukturbestimmung (ISD), habe ich wahrscheinlichkeitstheoretische Modelle für Messungen skalarer und dipolarer Kopplungen entwickelt. Es zeigt sich, daß die Regeln der Wahrscheinlichkeitstheorie zusätzliche Parameter wie die Fehler der Datensätze sowie Parameter der Theorie (Karplus-Koeffiz...

Habeck, Michael

2004-01-01

206

Benchmarking NMR experiments: A relational database of protein pulse sequences  

Science.gov (United States)

Systematic benchmarking of multi-dimensional protein NMR experiments is a critical prerequisite for optimal allocation of NMR resources for structural analysis of challenging proteins, e.g. large proteins with limited solubility or proteins prone to aggregation. We propose a set of benchmarking parameters for essential protein NMR experiments organized into a lightweight (single XML file) relational database (RDB), which includes all the necessary auxiliaries (waveforms, decoupling sequences, calibration tables, setup algorithms and an RDB management system). The database is interfaced to the Spinach library ( http://spindynamics.org), which enables accurate simulation and benchmarking of NMR experiments on large spin systems. A key feature is the ability to use a single user-specified spin system to simulate the majority of deposited solution state NMR experiments, thus providing the (hitherto unavailable) unified framework for pulse sequence evaluation. This development enables predicting relative sensitivity of deposited implementations of NMR experiments, thus providing a basis for comparison, optimization and, eventually, automation of NMR analysis. The benchmarking is demonstrated with two proteins, of 170 amino acids I domain of ?X?2 Integrin and 440 amino acids NS3 helicase.

Senthamarai, Russell R. P.; Kuprov, Ilya; Pervushin, Konstantin

2010-03-01

207

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

208

NMR tomography today  

International Nuclear Information System (INIS)

In NMR tomography, superconducting magnets achieving high homogeneity have come to the fore, all the more as the magnetic stray field, e.g. in a 2 tesla magnet with direct flux feedback could be reduced to the values of a 0.5 tesla magnet without additional magnetic shielding. In addition, consumption of cryogenic agents could be cut back. Examination conditions have been improved by faster switches to stronger gradients and advanced high-frequency systems with antennas adapted to organ conditions (surface coils). This also brought about better imaging quality and higher local resolution values up to less than one mm. Efforts for further improvements will concentrate on the software and measuring methods and are expected to achieve shorter examination times and at the same time better images, as the potentials of NMR tomography are far from being depleted today. It remains to be seen whether and when spectroscopy will become as important in clinical diagnostics as imaging is now. (orig.)

209

?-nmr of Palladium foil  

International Nuclear Information System (INIS)

Beta-detected NMR (?-nmr) of low-energy implanted 8Li+ was studied in metallic palladium. The resonance was found to have a large negative shift with respect to the reference signal in the cubic insulator MgO. This shift exhibited significant temperature dependence on cooling below room temperature, approximately proportionate to the temperature-dependent spin susceptibility of pure Pd. Thus it is tentatively attributed to a Knight shift (K) caused by a large negative hyperfine coupling; a phenomenon common in transition metal ions, but not in alkalis. However, the spin-lattice relaxation of 8Li is much slower than expected from the Korringa law for such a large K. We compare results from samples of very different thicknesses: 12.5?m foil and a 100nm thin film

210

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.)

211

NMR quantum information processing  

OpenAIRE

Quantum computing exploits fundamentally new models of computation based on quantum mechanical properties instead of classical physics, and it is believed that quantum computers are able to dramatically improve computational power for particular tasks. At present, nuclear magnetic resonance (NMR) has been one of the most successful platforms amongst all current implementations. It has demonstrated universal controls on the largest number of qubits, and many advanced techniqu...

Ramanathan, Chandrasekhar; Boulant, Nicolas; Chen, Zhiying; Cory, David G.; Chuang, Isaac; Steffen, Matthias

2015-01-01

212

NMR studies of metalloproteins  

OpenAIRE

Metalloproteins represent a large share of the proteomes, with the intrinsic metal ions providing catalytic, regulatory, and structural roles critical to protein functions. Structural characterization of metalloproteins and identification of metal coordination features including numbers and types of ligands and metal-ligand geometry, and mapping the structural and dynamic changes upon metal binding are significant for understanding biological functions of metalloproteins. NMR spectroscopy has...

Li, H.; Sun, H.

2011-01-01

213

SOLID STATE NMR  

OpenAIRE

The chapter is reporting a short introduction of solid state NMR tchnique and then is presenting some recent results where the development of new pulse sequences have brought some insights to various aspects of the characterization of solid state materials. Finally the attention will be focused on the information that the technique can provide in the field of crystal engineering, in the detection of polymorphism and in the dynamic processes occurring in the solid state.

Gobetto, Roberto

2007-01-01

214

OPTIMIZING SPATIALLY LOCALIZED NMR  

OpenAIRE

Fourier-series windowing, a technique used to obtain spatially localized in vivo NMR spectra, is extended to fields-of-view containing a number of arbitrarily shaped regions of interest. For each volume, k-space weighting functions are derived and then combined to give an overall k-space sampling pattern - the number of signal acquisitions per phase-encoding vector - which can then be used to obtain spatially localized spectra of optimal sensitivity, consistent with a specified degree of loca...

Hodgkinson, P.; Hore, P.

1995-01-01

215

Multiplex NMR: A novel methodology for high -throughput NMR analysis  

OpenAIRE

In this thesis, multiplex NMR methodology is described, which has the potential to significantly increase the throughput of NMR measurements. This novel methodology has possible applications in areas where large numbers of samples need to be analyzed. Multiple-coil NMR probes have been constructed to analyze multiple samples simultaneously using parallel detecting microcoils that were incorporated into a single RF circuit. Linear field gradients generated either by offsetting Z1 shim from its...

Hou, Ting

2002-01-01

216

Study of a Conformational Equilibrium of Lisinopril by HPLC, NMR, and DFT  

OpenAIRE

The isomerization of lisinopril has been investigated using chromatographic, NMR spectroscopic, and theoretical calculations. The NMR data, particularly the NOEDIFF experiments, show that the major species that was eluted first is the trans form. The proportion was 77% and 23% for the trans and cis, respectively. The thermodynamic parameters (?H, ?S, and ?G) were determined by varying the temperature in the NMR experiments. The interpretations of the experimental data were further supporte...

Sondes Bouabdallah; Med Thaieb Ben Dhia; Med Rida Driss

2014-01-01

217

Study of a Conformational Equilibrium of Lisinopril by HPLC, NMR, and DFT  

Science.gov (United States)

The isomerization of lisinopril has been investigated using chromatographic, NMR spectroscopic, and theoretical calculations. The NMR data, particularly the NOEDIFF experiments, show that the major species that was eluted first is the trans form. The proportion was 77% and 23% for the trans and cis, respectively. The thermodynamic parameters (?H, ?S, and ?G) were determined by varying the temperature in the NMR experiments. The interpretations of the experimental data were further supported by DFT/B3LYP calculations. PMID:24707291

Bouabdallah, Sondes; Ben Dhia, Med Thaieb; Driss, Med Rida

2014-01-01

218

Automatic maximum entropy spectral reconstruction in NMR  

International Nuclear Information System (INIS)

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

219

Lyotropic mesophases studied by 31P-NMR  

International Nuclear Information System (INIS)

The 31P-NMR is a powerful method to study liquid crystalline systems. Information about the phase states is obtained by only ''a look'' if the screening tensor of the anisotropy of chemical shift is known. The line shapes indicate also very simply mixed and transition states. If the screening tensor is known detailed information about dynamical and conformation states can be obtained. Finally the 31P-NMR can give valuable insight into very complex systems as biological systems. Liquid crystalline mesophases and their properties (structure, dynamical processes) are studied by different physical methods as X-ray-, neutron- and light-scattering, NMR etc. Each method is based on special parameters which are sensitive to certain properties. Each method yields therefore only information about these properties. If the molecules forming liquid-crystalline mesophases contain 31P-atoms the 31P-NMR can be used as a powerful physical technique. (author)

220

Fully automated system for pulsed NMR measurements  

Energy Technology Data Exchange (ETDEWEB)

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.

Cantor, David Milton

1977-01-01

221

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

222

Some nitrogen-14 NMR studies in solids  

Energy Technology Data Exchange (ETDEWEB)

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.

Pratum, T.K.

1983-11-01

223

Static properties of the S=1 one-dimensional antiferromagnet AgVP2S6  

Science.gov (United States)

NMR frequency shift has been measured at 51V and 31P sites in a single crystal of the one-dimensional spin-1 antiferromagnet AgVP2S6. Parameters in the single-ion spin Hamiltonian were determined from the orbital (van Vleck) shift at V sites. Temperature dependence of the spin shift (spin susceptibility) is consistent with the theoretical prediction and the magnitude of the Haldane gap determined from neutron-scattering experiments.

Takigawa, M.; Asano, T.; Ajiro, Y.; Mekata, M.

1995-11-01

224

NMR spectroscopic investigations of proteins  

OpenAIRE

NMR-spektroskopische Untersuchungen zur Struktur und Wirkungsweise des Membranproteins EmrE und der N-terminalen Domäne des VAT-Proteins wurden durchgeführt. Den Schwerpunkt bilden die Studien an dem multidrug- Transportprotein EmrE. Die Untersuchungen erfolgten mit den Methoden der hochauflösenden NMR-Spektroskopie in isotroper Lösung und der Festkörper- MAS-NMR-Spektroskopie. Zusätzlich konnte die Struktur von VAT-N in Lösung bestimmt werden, die als allgemeines Modell für die N-ter...

Gro?ger, Adriane

2007-01-01

225

Annual reports on NMR spectroscopy  

CERN Document Server

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 NMR to polymer science.

Webb, Graham A

1994-01-01

226

Annual reports on NMR spectroscopy  

CERN Document Server

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 NMR to polymer science.

Webb, Graham A

1995-01-01

227

NMR molecular photography  

OpenAIRE

A procedure is described for storing a 2D pattern consisting of 32x32 = 1024 bits in a spin state of a molecular system and then retrieving the stored information as a stack of NMR spectra. The system used is a nematic liquid crystal, the protons of which act as spin clusters with strong intramolecular interactions. The technique used is a programmable multi-frequency irradiation with low amplitude. When it is applied to the liquid crystal, a large number of coherent long-li...

Khitrin, Anatoly K.; Ermakov, Vladimir L.; Fung, B. M.

2002-01-01

228

NMR, Water and Plants  

OpenAIRE

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 (Chapter 8). The method is based on a pulse sequence of equidistant ?pulses in combination with a linear magnetic field gradient G.Following a general intro...

As, H.

1982-01-01

229

NMR studies of fast-ion conductors  

International Nuclear Information System (INIS)

NMR principles are reviewed, and NMR techniques which are likely to give a major contribution to studies of fast ion transport in solids are discussed. The NMR correlation function is defined, and examples are given and discussed

230

New nuclear quadrupole resonance technique in ?-NMR  

International Nuclear Information System (INIS)

The ?-NMR technique has been modified in order to detect efficiently the nuclear quadrupole effects in the NMR spectra. ?-NMR is detected as a function of coupling frequency; all RFs that correspond to the coupling frequency were applied simultaneously. (orig.)

231

A combined ??Se NMR and molecular dynamics contribution to the structural understanding of the chalcogenide glasses.  

Science.gov (United States)

Solid-state (77)Se NMR measurements, first-principles molecular dynamics and DFT calculations of NMR parameters were performed to gain insight into the structure of selenium-rich GexSe(1-x) glasses. We recorded the fully-relaxed NMR spectra on natural abundance and 100% isotopically enriched GeSe4 samples, which led us to reconsider the level of structural heterogeneity in this material. In this paper, we propose an alternative procedure to initialise molecular dynamics runs for the chalcogenide glasses. The (77)Se NMR spectra calculated on the basis of the structural models deduced from these simulations are consistent with the experimental spectrum. PMID:25050418

Sykina, Kateryna; Bureau, Bruno; Le Pollès, Laurent; Roiland, Claire; Deschamps, Michaël; Pickard, Chris J; Furet, Eric

2014-09-01

232

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

233

THz Dynamic Nuclear Polarization NMR.  

Science.gov (United States)

Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140-600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

Nanni, Emilio A; Barnes, Alexander B; Griffin, Robert G; Temkin, Richard J

2011-08-29

234

Annual reports on NMR spectroscopy  

CERN Document Server

NMR spectroscopy has grown to be a vitally important technique with applications in many areas of science. Annual Reports on NMR Spectroscopy is quickly becoming the source for the latest information on current progress, both experimental and theoretical. Chemists in a variety of disciplines will be interested in this up-to-date, comprehensive series.

Webb, Graham A

1986-01-01

235

Nuclear magnetic resonance (NMR) tomography  

International Nuclear Information System (INIS)

A brief survey of the working principle of the NMR technique in diagnostical medicine is given. Its clinical usefulness for locating tumors, diagnosing various other diseases, such as some mental illnesses and multiple sclerosis, and its possibilities for studying biochemical processes in vivo are mentioned. The price of NMR image scanners and the problems of the strong magnetic field around the machines are mentioned

236

NMR Spectroscopy in Ionic Liquds  

Science.gov (United States)

Today, NMR spectroscopy is the most important analytical tool for synthetically working chemists. This review describes the development of NMR spectroscopic methods for use in ionic liquid media and the state-of-the art in terms of routine analytics as well as modern advanced techniques.

Giernoth, Ralf

237

Annual reports on NMR spectroscopy  

CERN Document Server

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.

Webb, Graham A

1985-01-01

238

Annual reports on NMR spectroscopy  

CERN Document Server

This book is part of a series on spectroscopy, and covers NMR studiesof isolated spin-pairs in the solid state, the oxidation state dependence of transition metal shieldings, the Cinderella nuclei, nuclear spin relaxation in organic systems, solutions of macromolecules and aggregates and the NMR of coals and coal products. Related titlesare volumes 20, 21 and 22 in the series.

1991-01-01

239

Identification and MS-assisted interpretation of genetically influenced NMR signals in human plasma.  

Science.gov (United States)

Nuclear magnetic resonance spectroscopy (NMR) provides robust readouts of many metabolic parameters in one experiment. However, identification of clinically relevant markers in (1)H NMR spectra is a major challenge. Association of NMR-derived quantities with genetic variants can uncover biologically relevant metabolic traits. Using NMR data of plasma samples from 1,757 individuals from the KORA study together with 655,658 genetic variants, we show that ratios between NMR intensities at two chemical shift positions can provide informative and robust biomarkers. We report seven loci of genetic association with NMR-derived traits (APOA1, CETP, CPS1, GCKR, FADS1, LIPC, PYROXD2) and characterize these traits biochemically using mass spectrometry. These ratios may now be used in clinical studies. PMID:23414815

Raffler, Johannes; Römisch-Margl, Werner; Petersen, Ann-Kristin; Pagel, Philipp; Blöchl, Florian; Hengstenberg, Christian; Illig, Thomas; Meisinger, Christa; Stark, Klaus; Wichmann, H-Erich; Adamski, Jerzy; Gieger, Christian; Kastenmüller, Gabi; Suhre, Karsten

2013-01-01

240

Protein NMR Structures Refined without NOE Data  

Science.gov (United States)

The refinement of low-quality structures is an important challenge in protein structure prediction. Many studies have been conducted on protein structure refinement; the refinement of structures derived from NMR spectroscopy has been especially intensively studied. In this study, we generated flat-bottom distance potential instead of NOE data because NOE data have ambiguity and uncertainty. The potential was derived from distance information from given structures and prevented structural dislocation during the refinement process. A simulated annealing protocol was used to minimize the potential energy of the structure. The protocol was tested on 134 NMR structures in the Protein Data Bank (PDB) that also have X-ray structures. Among them, 50 structures were used as a training set to find the optimal “width” parameter in the flat-bottom distance potential functions. In the validation set (the other 84 structures), most of the 12 quality assessment scores of the refined structures were significantly improved (total score increased from 1.215 to 2.044). Moreover, the secondary structure similarity of the refined structure was improved over that of the original structure. Finally, we demonstrate that the combination of two energy potentials, statistical torsion angle potential (STAP) and the flat-bottom distance potential, can drive the refinement of NMR structures. PMID:25279564

Ryu, Hyojung; Kim, Tae-Rae; Ahn, SeonJoo; Ji, Sunyoung; Lee, Jinhyuk

2014-01-01

241

Fundamentals of Protein NMR Spectroscopy  

CERN Document Server

NMR spectroscopy has proven to be a powerful technique to study the structure and dynamics of biological macromolecules. Fundamentals of Protein NMR Spectroscopy is a comprehensive textbook that guides the reader from a basic understanding of the phenomenological properties of magnetic resonance to the application and interpretation of modern multi-dimensional NMR experiments on 15N/13C-labeled proteins. Beginning with elementary quantum mechanics, a set of practical rules is presented and used to describe many commonly employed multi-dimensional, multi-nuclear NMR pulse sequences. A modular analysis of NMR pulse sequence building blocks also provides a basis for understanding and developing novel pulse programs. This text not only covers topics from chemical shift assignment to protein structure refinement, as well as the analysis of protein dynamics and chemical kinetics, but also provides a practical guide to many aspects of modern spectrometer hardware, sample preparation, experimental set-up, and data pr...

Rule, Gordon S

2006-01-01

242

Structural Biology: Practical NMR Applications  

CERN Document Server

This textbook begins with an overview of NMR development and applications in biological systems. It describes recent developments in instrument hardware and methodology. Chapters highlight the scope and limitation of NMR methods. While detailed math and quantum mechanics dealing with NMR theory have been addressed in several well-known NMR volumes, chapter two of this volume illustrates the fundamental principles and concepts of NMR spectroscopy in a more descriptive manner. Topics such as instrument setup, data acquisition, and data processing using a variety of offline software are discussed. Chapters further discuss several routine stategies for preparing samples, especially for macromolecules and complexes. The target market for such a volume includes researchers in the field of biochemistry, chemistry, structural biology and biophysics.

Teng, Quincy

2005-01-01

243

NMR imaging of the kidney  

International Nuclear Information System (INIS)

NMR imaging was performed in 18 patients suffering from various renal disorders. 2 scanners were used, a 0.14T resistive prototype system and the superconducting Gyroscan S5. NMR imaging proved to be a very sensitive technique. Tumours as small as 5-10 mm were detected. Solid tumours and cysts could be distinguished. As a result of the excellent contrast resolution and tissue differentiation NMR imaging appears to be very accurate in the staging of renal cell carcinoma. Blood vessels within a tumour may be visible as little black dots. Because of their short T1 hemorrhagic cysts can be differentiated from simple cysts. Further prospective follow-up studies are required before a definite statement can be made as to the value of NMR imaging in diffuse parenchymal disease. Calcifications were not detected. NMR imaging does not seem to be any more specific as to tissue characterisation than other imaging modalities

244

Flow units from integrated WFT and NMR data  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1997-08-01

245

Solid state NMR of sulfa-drugs  

Energy Technology Data Exchange (ETDEWEB)

This work has been a study of systems, mostly of sulfa-drugs, showing polymorphic behaviour. Using different means as solid state NMR, X-ray analysis, * and theoretical calculations, we have seen how it is possible to understand results obtained from the different techniques, proving how the study of polymorphic systems needs cooperative advice from the different techniques that are able to detect polymorphic differences. Within the sulfa-drugs I have been mostly concentrating on sulfanilamide, studying {sup 13}C and {sup 15}N solid state NMR spectra of the different polymorphs. The NMR parameters that have been most interesting to study, have been the relaxation times that have revealed complicated motion of the molecule despite it being a small molecule. In order to obtain detailed information from {sup 15}N spectra it has been necessary to enrich the samples and this has enabled a study of the shielding tensors of the nitrogens in the molecule. {sup 13}C spectra were also recorded of systems studied sulfathiazole solvates, that proved to show some of the same solid state effects in the NMR spectra as sulfanilamide. Shielding calculations have proved to be still limited in order to obtain reliable information on the shielding of both {sup 13}C and {sup 15}N nuclei but considering hydrogen-bonded molecules, as opposed to isolated molecules, seemed to have improved the calculations quite a lot, so that some idea of intermolecular effects could be deducted. Exact positions of the hydrogen has proved to be essential as well in order to improve the calculations. Finally a case study for the REDOR pulse sequence has been carried out. Different attempts to understand the effects influencing this particular experiment have been carried out on 20% and 99% doubly enriched glycine, as well as on a particular sample, doubly enriched BRL55834, but the internuclear distances measured with this technique still displayed some uncertainties that made results not thoroughly reliable. (author)

Portieri, A

2001-07-01

246

Solid state NMR of sulfa-drugs  

International Nuclear Information System (INIS)

This work has been a study of systems, mostly of sulfa-drugs, showing polymorphic behaviour. Using different means as solid state NMR, X-ray analysis, * and theoretical calculations, we have seen how it is possible to understand results obtained from the different techniques, proving how the study of polymorphic systems needs cooperative advice from the different techniques that are able to detect polymorphic differences. Within the sulfa-drugs I have been mostly concentrating on sulfanilamide, studying 13C and 15N solid state NMR spectra of the different polymorphs. The NMR parameters that have been most interesting to study, have been the relaxation times that have revealed complicated motion of the molecule despite it being a small molecule. In order to obtain detailed information from 15N spectra it has been necessary to enrich the samples and this has enabled a study of the shielding tensors of the nitrogens in the molecule. 13C spectra were also recorded of systems studied sulfathiazole solvates, that proved to show some of the same solid state effects in the NMR spectra as sulfanilamide. Shielding calculations have proved to be still limited in order to obtain reliable information on the shielding of both 13C and 15N nuclei but considering hydrogen-bonded molecules, as opposed to isolated molecules, seemed to have improved the calculations quite a lot, so that some idea of intermolecular effects that some idea of intermolecular effects could be deducted. Exact positions of the hydrogen has proved to be essential as well in order to improve the calculations. Finally a case study for the REDOR pulse sequence has been carried out. Different attempts to understand the effects influencing this particular experiment have been carried out on 20% and 99% doubly enriched glycine, as well as on a particular sample, doubly enriched BRL55834, but the internuclear distances measured with this technique still displayed some uncertainties that made results not thoroughly reliable. (author)

247

DFT- NMR Study of 4-Phenoxychlorophenylglioxime  

International Nuclear Information System (INIS)

We present the results of density functional theory (DFT) calculations of chemical shifts and shielding constants in suggested anti-, amphi-, and syn-, geometrical isomers of 4 -phenoxychlorophenylglioxime. In this study, our main scope is to determine anti-, amphi-, and syn- isomer structure of 4- phenoxychlorophenylglioxime computationally using DFT NMR parameter( chemical shift and shielding constant) calculation. In order to achieve this goal, chemical shifts and shielding constants calculations of 4- phenoxychlorophenylglioxime's geometrical isomers are performed using different DFT functionals in combination with Gaussian basis sets. Theoretically calculated values are compared with the experimentally observed values

248

Constants of NMR spectra  

International Nuclear Information System (INIS)

The NMR (nuclear magnetic resonance) spectroscopy is a method for studying matter. It has been developed in a lot of fields of physics, physical chemistry, chemistry and biology. It concerns both the solid state and the liquid state. The study in solution of synthesis organic molecules or of organic molecules of natural origin and of biological molecules is particularly stressed on but it is also possible to study inorganic molecules. The originality of this method is to give both data on each atoms of the studied structure, on the atoms sequence in this structure, on the conformation and on the related configurations. It allows to reveal the interactions between separate molecules too. It is also a precious tool for the analysis of molecular movements. The development of this method for the study of condensed phases is particularly studied nowadays and the data obtained are for a lot of fields as acute as those obtained at the liquid state. (O.M.)

249

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

250

Carbon-13 NMR spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

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.

Breitmaier, E.; Voelter, W.

1987-01-01

251

NMR flow tube for online NMR reaction monitoring.  

Science.gov (United States)

In this paper we describe the development of a 5 mm NMR flow tube that can be used in a standard 5 mm NMR probe, enabling the user to conduct experiments on flowing samples or, more specifically, on flowing reaction mixtures. This enables reaction monitoring or kinetic experiments to be conducted by flowing reaction mixtures from a reaction vessel to detection in the coil area of the NMR, without the need for a specialized flow NMR probe. One of the key benefits of this flow tube is that it provides flexibility to be used across a range of available spectrometers of varying magnetic field strengths with a standard 5 mm probe setup. The applicability of this flow tube to reaction monitoring is demonstrated using the reaction of p-phenylenediamine and isobutyraldehyde to form the diimine product. PMID:25375410

Foley, David A; Bez, Eckhard; Codina, Anna; Colson, Kimberly L; Fey, Michael; Krull, Robert; Piroli, Don; Zell, Mark T; Marquez, Brian L

2014-12-16

252

NMR measurement of pore structure  

Energy Technology Data Exchange (ETDEWEB)

An attempt was made to pursue [sup 129]Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, [sup 13]CO[sub 2], and [sup 15]N[sub 2]. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10[sup [minus]2] to 10[sup [minus]6]s.

Earl, W.L. (Los Alamos National Lab., NM (United States)); Kim, Yong-Wah (Los Alamos National Lab., NM (United States) New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics); Smith, D.M. (New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics)

1993-05-31

253

NMR measurement of pore structure  

Energy Technology Data Exchange (ETDEWEB)

An attempt was made to pursue {sup 129}Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, {sup 13}CO{sub 2}, and {sup 15}N{sub 2}. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10{sup {minus}2} to 10{sup {minus}6}s.

Earl, W.L. [Los Alamos National Lab., NM (United States); Kim, Yong-Wah [Los Alamos National Lab., NM (United States)]|[New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics; Smith, D.M. [New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics

1993-05-31

254

SEnD NMR: Sensitivity Enhanced n-Dimensional NMR  

OpenAIRE

Sparse sampling offers tremendous potential for overcoming the time limitations imposed by traditional Cartesian sampling of indirectly detected dimensions of multidimensional NMR data. However, in many instances sensitivity rather than time remains of foremost importance when collecting data on protein samples. Here we explore how to optimize the collection of radial sampled multidimensional NMR data to achieve maximal signal-to-noise. A method is presented that exploits a rigorous definitio...

Gledhill, John M.; Wand, A. Joshua

2010-01-01

255

FAST-NMR - Functional Annotation Screening Technology Using NMR Spectroscopy  

OpenAIRE

An abundance of protein structures emerging from structural genomics and the Protein Structure Initiative (PSI) are not amenable to ready functional assignment because of a lack of sequence and structural homology to proteins of known function. We describe a high-throughput NMR methodology (FAST-NMR) to annotate the biological function of novel proteins through the structural and sequence analysis of protein-ligand interactions. This is based on basic tenets of biochemistry where proteins wit...

Mercier, Kelly A.; Baran, Michael; Ramanathan, Viswanathan; Revesz, Peter; Xiao, Rong; Montelione, Gaetano T.; Powers, Robert

2006-01-01

256

Ab initio simulation of paramagnetic NMR spectra: the 31P NMR in oxovanadium phosphates.  

Science.gov (United States)

A theoretical analysis of the temperature-dependent (31)P NMR signals for the ambient pressure vanadyl pyrophosphate AP-(VO)(2)P(2)O(7) and the oxovanadium hemihydrate hydrogenophosphate VO(HPO(4)).0.5H(2)O phases is reported. The ab initio calculation of the magnetic exchange parameters and the hyperfine constants gives access to an original ab initio simulation of NMR spectra. Such a strategy allows one to clarify the crystallographic nature of the different experimentally studied phases. For the vanadyl pyrophosphate ambient pressure structure, our simulations strongly support the presence of a monoclinic phase. Based on this assumption, hyperfine constants are extracted from the fit of the experimental data. These values are directly compared to the ab initio ones. PMID:12656632

Petit, Sébastien; Borshch, Serguei A; Robert, Vincent

2003-04-01

257

Inverse methods in two-dimensional NMR spectral analysis  

Science.gov (United States)

Solid-state NMR is a valuable technique for the study of disordered materials. Analysis of such spectra usually involves solution of so-called ill-posed inverse problems. Here we present a strategy for the analysis of two-parameter two-dimensional NMR problems and test it on 2D DECODER and DOQSY experiments. Using Monte Carlo tests, constraints are determined for the resolution and accuracy of the analysis for both experiments. The methods are finally applied to spectra of spider dragline silk, a heterogeneous solid fibrous protein.

van Beek, Jacco D.; Meier, Beat H.; Schäfer, Hartmut

2003-05-01

258

Possible Observation of Parity Nonconservation by High-Resolution NMR  

International Nuclear Information System (INIS)

In achiral conditions, a difference in the NMR spectra of the d, l forms of a chiral molecule should be a manifestation of the never observed parity nonconservation in molecules. The involved NMR parameters depend on the never measured nuclear-spin-dependent PNC potential. Calculations performed with a relativistically parameterized extended Huckel method show a difference of a few mHz in the metal resonance frequency of enantiomers, containing Pt or Pb. A discussion of the various possible limiting factors shows that such a difference could be observed

259

NMR of superfluid 3He in anisotropic aerogel  

CERN Document Server

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.

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

2006-01-01

260

NMR spectroscopy of muscle proteins  

International Nuclear Information System (INIS)

Author reviews various experimental techniques used for study of the structure of muscle proteins. Difficulties of application of NMR are described. Studies of the influence of Ca2+ on flexibility of actin polymer are presented

261

Compact orthogonal NMR field sensor  

Science.gov (United States)

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.

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

2009-02-03

262

Transformer-coupled NMR probe  

Science.gov (United States)

In this study, we propose an NMR probe circuit that uses a transformer with a ferromagnetic core for impedance matching. The ferromagnetic core provides a strong but confined coupling that result in efficient energy transfer between the sample coil and NMR spectrometer, while not disturbing the B1 field generated by the sample coil. We built a transformer-coupled NMR probe and found that it offers comparable performance (loss probe operates over a wide frequency range (500 kHz-5 MHz in this example) without the need for matching adjustments. Such probes could be useful for low-field mobile NMR applications of multi-frequency operation, such as imaging, relaxation, and diffusion measurements, as well as NQR.

Utsuzawa, Shin; Mandal, Soumyajit; Song, Yi-Qiao

2012-03-01

263

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

Science.gov (United States)

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

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

264

NMR characterization of thin films  

Science.gov (United States)

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.

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

265

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

266

Katheter fuer NMR-Untersuchungen  

OpenAIRE

DE 10142394 A UPAB: 20030320 NOVELTY - Catheter comprises a catheter body (1) made of flexible material with a measurement tip, an unfolding NMR probe (2) and a guide channel for insertion of a guide element for mechanical stabilization of the catheter and or a cleaning or suction channel, whereby a control channel with a control element is designed to control the positioning of the measurement tip from the distal end of the catheter body. USE - Catheter for insertion of NMR probes into body ...

Benecke, M.; Manz, B.

2002-01-01

267

PROBING PLANT METABOLISM WITH NMR.  

OpenAIRE

Analytical methods for probing plant metabolism are taking on new significance in the era of functional genomics and metabolic engineering. Among the available methods, nuclear magnetic resonance (NMR) spectroscopy is a technique that can provide insights into the integration and regulation of plant metabolism through a combination of in vivo and in vitro measurements. Thus NMR can be used to identify, quantify, and localize metabolites, to define the intracellular environment, and to explore...

Ratcliffe, Rg; Shachar-hill, Y.

2001-01-01

268

Computergestützte Analyse von NMR- Spektren  

OpenAIRE

Das Ziel der Arbeit war die Entwicklung, Erprobung und Anwendung von Programmen, um die zeitraubende Arbeit der, mit der Proteinstrukturaufklärung verbundenen, Auswertung von NMR- Spektren zu beschleunigen, und die Qualität der ermittelten Strukturen zu sichern. Außerdem wurde in einer großangelegten Messreihe (NMR- NOESY- Spektren) eine Temperaturreihe von 10°C bis 50°C des Proteins Saratin (Wirkstoff aus der Arzneimittelforschung, neuer Blutgerinnungshemmer) erzeugt, daraus 41 räu...

Kirchho?fer, Renate

2006-01-01

269

NMR spectroscopy in bioinorganic chemistry  

OpenAIRE

Multinuclear and multidimensional nuclear magnetic resonance (NMR) spectroscopy is applied in our groups to gain insights into the role of metal ions for the function and structure of large biomolecules. Specifically, NMR is used i) to investigate how metal ions bind to nucleic acids and thereby control the folding and structure of RNAs, ii) to characterize how metal ions are able to stabilize modified nucleic acids to be used as potential nanowires, and iii) to characterize the formation, st...

Donghi, Daniela; Johannsen, Silke; Sigel, Roland K. O.; Freisinger, Eva

2012-01-01

270

Optical pumping and xenon NMR  

Energy Technology Data Exchange (ETDEWEB)

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.

Raftery, M.D.

1991-11-01

271

Optical pumping and xenon NMR  

Energy Technology Data Exchange (ETDEWEB)

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.

Raftery, M.D.

1991-11-01

272

Variable-temperature NMR and conformational analysis of Oenothein B  

International Nuclear Information System (INIS)

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)

273

Variable-temperature NMR and conformational analysis of Oenothein B  

Energy Technology Data Exchange (ETDEWEB)

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)

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

274

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

Energy Technology Data Exchange (ETDEWEB)

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.

Krishnan, V V

2005-04-26

275

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

Energy Technology Data Exchange (ETDEWEB)

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.

Matwiyoff, N.A.

1983-01-01

276

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

277

Distinguishing Individual Lipid Headgroup Mobility and Phase Transitions in Raft-Forming Lipid Mixtures with 31P MAS NMR  

OpenAIRE

A model membrane system composed of egg sphingomyelin (SM), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol was studied with static and magic angle spinning 31P NMR spectroscopy. This model membrane system is of significant biological relevance since it is known to form lipid rafts. 31P NMR under magic angle spinning conditions resolves the SM and DOPC headgroup resonances allowing for extraction of the 31P NMR parameters for the individual lipid components. The isotropic che...

Holland, Gregory P.; Mcintyre, Sarah K.; Alam, Todd M.

2006-01-01

278

NMR-based analysis of protein-ligand interactions.  

Science.gov (United States)

Physiological processes are mainly controlled by intermolecular recognition mechanisms involving protein-protein and protein-ligand (low molecular weight molecules) interactions. One of the most important tools for probing these interactions is high-field solution nuclear magnetic resonance (NMR) through protein-observed and ligand-observed experiments, where the protein receptor or the organic compounds are selectively detected. NMR binding experiments rely on comparison of NMR parameters of the free and bound states of the molecules. Ligand-observed methods are not limited by the protein molecular size and therefore have great applicability for analysing protein-ligand interactions. The use of these NMR techniques has considerably expanded in recent years, both in chemical biology and in drug discovery. We review here three major ligand-observed NMR methods that depend on the nuclear Overhauser effect-transferred nuclear Overhauser effect spectroscopy, saturation transfer difference spectroscopy and water-ligand interactions observed via gradient spectroscopy experiments-with the aim of reporting recent developments and applications for the characterization of protein-ligand complexes, including affinity measurements and structural determination. PMID:23591643

Cala, Olivier; Guillière, Florence; Krimm, Isabelle

2014-02-01

279

NMR of a Phospholipid: Modules for Advanced Laboratory Courses  

Science.gov (United States)

A laboratory project is described that builds upon the NMR experience undergraduates receive in organic chemistry with a battery of NMR experiments that investigate egg phosphatidylcholine (egg PC). This material, often labeled in health food stores as lecithin, is a major constituent of mammalian cell membranes. The NMR experiments may be used to make resonance assignments, to study molecular organization in model membranes, to test the effects of instrumental parameters, and to investigate the physics of nuclear spin systems. A suite of modular NMR exercises is described, so that the instructor may tailor the laboratory sessions to biochemistry, instrumental analysis, or physical chemistry. The experiments include solution-state one-dimensional (1D) 1H, 13C, and 31P experiments; two-dimensional (2D) TOtal Correlated SpectroscopY (TOCSY); and the spectral editing technique of Distortionless Enhancement by Polarization Transfer (DEPT). To demonstrate the differences between solution and solid-state NMR spectroscopy and instrumentation, a second set of experiments generates 1H, 13C, and 31P spectra of egg PC dispersed in aqueous solution, under both static and magic-angle spinning conditions.

Gaede, Holly C.; Stark, Ruth E.

2001-09-01

280

Application of Solution NMR Spectroscopy to Study Protein Dynamics  

Directory of Open Access Journals (Sweden)

Full Text Available Recent advances in spectroscopic methods allow the identification of minute fluctuations in a protein structure. These dynamic properties have been identified as keys to some biological processes. The consequences of this structural flexibility can be far?reaching and they add a new dimension to the structure-function relationship of biomolecules. Nuclear Magnetic Resonance (NMR spectroscopy allows the study of structure as well as dynamics of biomolecules in a very broad range of timescales at atomic level. A number of new NMR methods have been developed recently to allow the measurements of time scales and spatial fluctuations, which in turn provide the thermodynamics associated with the biological processes. Since NMR parameters reflect ensemble measurements, structural ensemble approaches in analyzing NMR data have also been developed. These new methods in some instances can even highlight previously hidden conformational features of the biomolecules. In this review we describe several solution NMR methods to study protein dynamics and discuss their impact on important biological processes.

Christoph Göbl

2012-03-01

281

NMR of Solid Phosphorus and Nitrogen Compounds.  

Science.gov (United States)

Available from UMI in association with The British Library. Requires signed TDF. The main thrust of this work is the determination of solid structure using the technique of solid-state nuclear magnetic resonance spectroscopy. High-resolution ^{31} P NMR spectra have been obtained for a number of solid diphosphine disulphides under conditions of crosspolarization, high-power proton decoupling and magic-angle rotation. The results yield crystallographic information about the size of the asymmetric unit and are consistent with data from X-ray diffraction when known. In one case, evidence of morphological variation is obtained. Shielding tensor information was extracted from magic-angle spinning spectra wherever possible. Attempts to correlate tensor data with structural parameters met with little success. Fifty-one solid phosphonic, aminophosphonic and phosphinic acid compounds have been studied using high -resolution ^{13}C, ^{31}P, ^{15 }N and ^{23}Na NMR spectroscopy via the techniques noted above. Again, results yielded crystallographic information about the size of the asymmetric unit. Agreement was found with the limited amount of crystallographic information available. Additionally, ^1H CRAMPS results provided chemical shift information on the hydrogen-bonded acid protons. Comparison of these data with oxygen-oxygen bond lengths from known diffraction studies indicates a possible correlation between the ^1H shift and the oxygen-oxygen bond distance. Shielding tensor data was determined from static and slow-spinning MAS spectra. One empirical correlation was found. The asymmetry parameter was related to structural factors. A number of methods are currently used to determine the principal components of the shielding tensor from slow -speed magic-angle spinning experiments. Two of these are examined and their limitations discussed. A computer program to simulate and fit spinning sideband spectra is presented. The advantages and disadvantages of such a program are examined and several examples given. A survey of the literature of solid-state nitrogen NMR is presented. The experimental considerations of natural abundance nitrogen-15 NMR are examined. The viability of running nitrogen-15 at natural abundance and with reasonable utilization of spectrometer resources is discussed.

Merwin, Lawrence Hale

282

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

Science.gov (United States)

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

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

2015-01-01

283

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

Energy Technology Data Exchange (ETDEWEB)

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 (T{sub 2}, Carr-Purcel-T{sub 2}, T{sub 1}{rho}) for fat and water and relate those to the structural parameters obtained by micro-computed tomography ({mu}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 {sup 0}C 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 T{sub 2} 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 {mu}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.

Prantner, Viktoria; Isaksson, Hanna; Nissi, Mikko J; Jurvelin, Jukka S [Department of Physics and Mathematics, University of Eastern Finland, PO Box 1627, 70211 Kuopio (Finland); Naervaeinen, Johanna; Groehn, Olli H J [Department of Neurobiology, A I Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, 70211 Kuopio (Finland); Lammentausta, Eveliina [Department of Diagnostic Radiology, Oulu University Hospital, PO Box 50, 90029 OYS, Oulu (Finland); Avela, Janne, E-mail: hanna.isaksson@uef.f [Department of Biology of Physical Activity, University of Jyvaeskylae, PO Box 35, 40014 Jyvaeskylae (Finland)

2010-12-07

284

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 structmation about the trabecular bone structure.

285

95Mo nuclear magnetic resonance parameters of molybdenum hexacarbonyl from density functional theory: appraisal of computational and geometrical parameters.  

OpenAIRE

Solid-state (95)Mo nuclear magnetic resonance (NMR) properties of molybdenum hexacarbonyl have been computed using density functional theory (DFT) based methods. Both quadrupolar coupling and chemical shift parameters were evaluated and compared with parameters of high precision determined using single-crystal (95)Mo NMR experiments. Within a molecular approach, the effects of major computational parameters, i.e. basis set, exchange-correlation functional, treatment of relativity, have been e...

Cuny, Je?ro?me; Sykina, Kateryna; Fontaine, Bruno; Le Polle?s, Laurent; Pickard, Chris J.; Gautier, Re?gis

2011-01-01

286

Electric field gradient calculations in paramagnetic compounds using the PAW approach. Application to ²³Na NMR in layered vanadium phosphates.  

OpenAIRE

This article presents ab initio calculations of electric field gradient (EFG) parameters as a tool for the structural characterization of paramagnetic crystalline compounds. Previously reported ²³Na NMR parameters of vanadium + IV containing vanado-phosphate compounds were computed within density functional theory using both cluster and fully periodic approaches. Quadrupolar parameter values measured by ²³Na NMR experiments were reproduced with a level of accuracy comparable to that achie...

Cuny, J.; Yates, Jr; Gautier, R.; Furet, E.; Le Fur, E.; Le Polle?s, L.

2010-01-01

287

In vivo applications of NMR to medicine  

International Nuclear Information System (INIS)

The two in vivo applications of nuclear magnetic resonance (NMR) to medicine, namely NMR imaging and localized NMR spectroscopy are described. A brief outline of the principles of NMR for spins I = 1/2, is followed by an account of NMR image formation using protons. The question of tissue discrimination is dealt with during a discussion of nuclear relaxation, before the phenomenon of chemical shielding is described, together with illustrations of the usefulness of 31P and 13C NMR spectra obtained in vivo. (author)

288

Carbon-13 NMR of flavinoids  

International Nuclear Information System (INIS)

The present book has been written with the objective of introducing the organic chemists with the conceptual and experimental basis required for interpretation of 13C NMR spectra of a flavonoid and to a discussion of general usefulness of the technique in solving flavonoid structural problem. After a brief general introduction to the essential aspects of flavonoids and 13C NMR spectroscopy, considerable emphasis has been placed in chapter 2 on the various experimental methods and the interpretation of spectral details which enable individual resonance lines to be associated with the appropriate carbons in a molecule. The whole bulk of the literature, published on 13C NMR of flavonoids in the major journals upto 1986 alongwith some recent references of 1987 has been classified in several categories such as: flavonoids, isflavonoids, other flavonoids, flavonoid glycosides, chalconoids and flavanoids. Each category constitutes a chapter. Finally the last chapter is devoted largely to a discussion for the differentiation of various categories and subcategories of flavonoids and for the establishment of aromatic substitution pattern in these compounds. It should be emphasized that the book is a data book and only concerned with the actual analysis of 13C NMR spectra, thus a reasonable familiarity with basic instrumentation of 13C NMR and general pattern of nuclear chemical shifts has been assumed. (author). refs.; figsts has been assumed. (author). refs.; figs.; tabs

289

Optimal control in NMR spectroscopy: Numerical implementation in SIMPSON  

Science.gov (United States)

We present the implementation of optimal control into the open source simulation package SIMPSON for development and optimization of nuclear magnetic resonance experiments for a wide range of applications, including liquid- and solid-state NMR, magnetic resonance imaging, quantum computation, and combinations between NMR and other spectroscopies. Optimal control enables efficient optimization of NMR experiments in terms of amplitudes, phases, offsets etc. for hundreds-to-thousands of pulses to fully exploit the experimentally available high degree of freedom in pulse sequences to combat variations/limitations in experimental or spin system parameters or design experiments with specific properties typically not covered as easily by standard design procedures. This facilitates straightforward optimization of experiments under consideration of rf and static field inhomogeneities, limitations in available or desired rf field strengths (e.g., for reduction of sample heating), spread in resonance offsets or coupling parameters, variations in spin systems etc. to meet the actual experimental conditions as close as possible. The paper provides a brief account on the relevant theory and in particular the computational interface relevant for optimization of state-to-state transfer (on the density operator level) and the effective Hamiltonian on the level of propagators along with several representative examples within liquid- and solid-state NMR spectroscopy.

Tošner, Zden?k; Vosegaard, Thomas; Kehlet, Cindie; Khaneja, Navin; Glaser, Steffen J.; Nielsen, Niels Chr.

2009-04-01

290

Bildgebendes NMR-Verfahren sowie NMR-Vorrichtung  

OpenAIRE

WO2003102617 A UPAB: 20040120 NOVELTY - The object being examined (O) is placed in a given volume in the NMR nuclear magnetic resonance machine (1). It is supported on a flat surface (3) of a magnet (2) and a hydraulic or piezoelectric actuator may be used. Several coils subjected to high- frequency current may surround the volume occupied by the object. There is a high-frequency surface coil (7). The coils are connected to a receiver circuit (8). USE - NMR device producing image of object oc...

Volke, F.; Benecke, M.

2004-01-01

291

NMR Analysis of 2-(2?, 3?-dihydro-1?H-inden-1?-yl-1H-indene  

Directory of Open Access Journals (Sweden)

Full Text Available 1H, 13C and two dimensional NMR analyses were applied to determine the NMR parameters of 2-(2?,3?-dihydro-1?H-inden-1?-yl-1H-indene. The chemical shifts of all the H- and C-atoms, as well as the appropriate coupling constants were determined and the complete NMR resonance assignments of the molecule are given. The predicted patterns of the four different H atoms of the two methylene groups of the indane structural element coincided completely with the complex patterns in the NMR spectra.

PETER SPITELLER

2001-12-01

292

NMR Analysis of 2-(2?, 3?-dihydro-1?H-inden-1?-yl)-1H-indene  

OpenAIRE

1H, 13C and two dimensional NMR analyses were applied to determine the NMR parameters of 2-(2?,3?-dihydro-1?H-inden-1?-yl)-1H-indene. The chemical shifts of all the H- and C-atoms, as well as the appropriate coupling constants were determined and the complete NMR resonance assignments of the molecule are given. The predicted patterns of the four different H atoms of the two methylene groups of the indane structural element coincided completely with the complex patterns in the NMR spectra.

PETER SPITELLER; JOVAN JOVANOVIC; MICHAEL SPITELLER

2001-01-01

293

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

294

Radiofrequency and magnet technology in medical NMR  

International Nuclear Information System (INIS)

Nuclear magnetic resonance (NMR) is briefly described, particularly its rf and magnet aspects. Particular attention is given to the duplexer, the rf coils, and new kinds of magnets for remote sensing NMR

295

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...

296

A SENSITIVE NMR THERMOMETER FOR MULTINUCLEI FT NMR  

Science.gov (United States)

A pernicious problem in multinuclei FT NMR is accurate measurement of sample temperature. This arises from several factors including widespread use of high-power decoupling, large sample tubes (with potentially large temperature gradients across the sample volume), and lack of su...

297

NMR STUDIES OF THE STRUCTURE OF GLASS  

OpenAIRE

Over the past 25 years, wide-line Nuclear Magnetic Resonance (NMR) techniques have been used successfully to study the structure of glasses on an atomic scale [1]. Analysis of the quadrupolar structure in NMR spectra of borate glasses has yielded quantitative determinations of the relative numbers of boron atoms in various oxygen environments. After a brief discussion of the relevant as ects of NMR theory, this paper will present some of the most recent studies : B11 NMR in sodium borosilicat...

Bray, P.; . W.

1982-01-01

298

?-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.

299

High resolution NMR theory and chemical applications  

CERN Document Server

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

Becker, Edwin D

1969-01-01

300

Indirect use of deuterium in solution NMR studies of protein structure and hydrogen bonding.  

Science.gov (United States)

A description of the utility of deuteration in protein NMR is provided with an emphasis on quantitative evaluation of the effects of deuteration on a number of NMR parameters of proteins: (1) chemical shifts, (2) scalar coupling constants, (3) relaxation properties (R1 and R2 rates) of nuclei directly attached to one or more deuterons as well as protons of methyl groups in a highly deuterated environment, (4) scalar relaxation of 15N and 13C nuclei in 15N-D and 13C-D spin systems as a measure of hydrogen bonding strength, and (5) NOE-based applications of deuteration in NMR studies of protein structure. The discussion is restricted to the 'indirect' use of deuterium in the sense that the description of NMR parameters and properties of the nuclei affected by nearby deuterons (15N, 13C, 1H) is provided rather than those of deuterium itself. PMID:24411830

Tugarinov, Vitali

2014-02-01

301

9Be-NMR studies of the heavy-Fermion superconductor UBe13  

Science.gov (United States)

Field-angle dependence of 9Be-NMR measurements has been carried out for a single crystal UBe13 in the temperature range of 0.35-1.5 K. For H?[0 0 1], we observed that 9Be-NMR spectra consisted of 10 lines; one line comes from a Be(I) site located in the cubic symmetry, while nine lines come from Be(II) sites located in the lower symmetry. From the field angle dependence of the NMR spectra, we determined NQR parameters such as the nuclear quadrupole frequency (?Q?84 kHz)and the asymmetry parameter (??0.21). In the superconducting state, we found that 9Be-NMR Knight shift for H?[0 0 1] does not change at all. This result is consistent with the spin-triplet pairing state in UBe13.

Tou, H.; Tsugawa, N.; Sera, M.; Haga, Y.; ?nuki, Y.

2007-03-01

302

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

303

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

Science.gov (United States)

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.

Rodriguez, Jorge H.

2013-04-01

304

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.

305

Phenomenological simulation and density functional theory prediction of {sup 57}Fe Moessbauer parameters: application to magnetically coupled diiron proteins  

Energy Technology Data Exchange (ETDEWEB)

The use of phenomenological spin Hamiltonians and of spin density functional theory for the analysis and interpretation of Moessbauer 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{sub Red}) the enzyme displays {sup 57}Fe Moessbauer and EPR parameters characteristic of two ferromagnetically coupled high spin ferrous ions. However, Moessbauer spectra recorded for MMOH{sub Red} from two different bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b, display slightly different electric quadrupole splittings ({Delta}E{sub Q}) in apparent contradiction to their essentially identical active site crystallographic structures and biochemical functions. Herein, the Moessbauer spectral parameters of MMOH{sub Red} have been predicted and studied via spin density functional theory. The somewhat different {Delta}E{sub 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.

Rodriguez, Jorge H., E-mail: jhrodrig@purdue.edu [Purdue University, Department of Physics (United States)

2013-04-15

306

Interactions between cations and peat organic matter monitored with NMR wideline, static and FFC NMR relaxometry  

Science.gov (United States)

The molecular size of humic substances is still under debate and is believed to range up to several hundred thousands Dalton, although a number of recent studies suggest much lower molecular weights. Nowadays an increasing number of authors suggest a model of molecular aggregates. One explanation why results on the molecular mass of humic materials are contradictory, may be that individual OM molecules are linked via intermolecular interactions, by bridges of water molecules or by cations bridging cation exchange sites (Schaumann, 2006a, b). Properties of such cross-linked systems can be similar to macromolecular systems revealing covalent cross-links. In this context, multivalent cations play an important ecological role, serving as reversible cross-linking agent. Formation and disruption of such cation bridges may close or open sorption sites in soil organic matter. Although cross-linking by multivalent cations has been proposed in many studies, the cross-linking effect has not yet been demonstrated on the molecular scale. The objective of this study was to investigate the interactions between cations and peat organic matter using NMR wideline techniques as well as static and fast field cycling (FFC) NMR relaxometry. Peat treated with solutions containing either Na+, Ca2+ or Al3+ was investigated in air-dried state for longitudinal relaxation times (T1) and NMR wideline characteristics. T1 distributions were separated into two Gaussian functions which were interpreted to represent two proton populations belonging to two environments of differing mobility. The relaxation rates (R1 = T1-1) in the cation treated samples spread over a range of 87-123 s-1 (R1a: fast component) and 32-42 s-1 (R1b: slow component). The rates in all treatments are significantly different from each other. and decrease in the order conditioned sample > desalinated sample > Na-treated sample. The treatment with multivalent cations affects R1a and R1b in different ways and needs more detailed explanation. Wideline proton NMR spectra can be used to quantify proton containing material, mainly water, based on their mobility. Spectra were decomposed into a Gaussian and Lorentzian line and changes to mobility after heat treatment indicate the water binding strength. In this study, differences in the various NMR parameters on the cation treatments will be presented and discussed with respect to the crosslinking hypothesis.

Schaumann, Gabriele E.; Conte, Pellegrino; Jäger, Alexander; Alonzo, Giuseppe; Bertmer, Marko

2010-05-01

307

The physics of NMR tomography.  

Science.gov (United States)

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. PMID:3714509

Akber, S F

1986-02-01

308

Membranes Studied by NMR Spectroscopy  

OpenAIRE

The use of NMR spectroscopy to study the structures and dynamics of membrane systems is described. The principal nuclei used are 1H, 2H, 13C and 31P. Both oriented and nonoriented systems can be investigated. In addition, peptides and proteins embedded in membranes can be studied. © 1999 Elsevier Ltd All rights reserved.

Watts, A.; Opella, Sj

2010-01-01

309

Ultra-high resolution NMR  

International Nuclear Information System (INIS)

Chromatography is nearly always the method of choice for the analysis of complex mixtures. Chromatography alone, however, is often inadequate; it is frequently necessary to use a hyphenated procedure in which chromatography is used for separation of the mixture into pure substances and then mass spectrometry, infrared spectroscopy, or some other spectroscopic method is used for structural identification of each component. Although nuclear magnetic resonance (NMR) spectroscopy has been very successful in structural determinations of pure compounds, it is seldom used for identification of specific molecules in complex mixtures. Here the authors show that methodology recently developed in their laboratory increases the power NMR for analysis of complex mixtures. They wish to emphasize that, because of the low sensitivity of NMR spectroscopy, the large amounts of material required for an analysis will restrict the applicability of the methods presented below. Nevertheless, the examples in this report illustrate the many important analytical problems that can be solved by means of ultra-high resolution NMR methods

310

Receiver gain function: the actual NMR receiver gain  

OpenAIRE

The observed NMR signal size depends on the receiver gain parameter. We propose a receiver gain function to characterize how much the raw FID is amplified by the receiver as a function of the receiver gain setting. Although the receiver is linear for a fixed gain setting, the actual gain of the receiver may differ from what the gain setting suggests. Nevertheless, for a given receiver, we demonstrate that the receiver gain function can be calibrated. Such a calibration enables accurate compar...

Mo, Huaping; Harwood, John S.; Raftery, Daniel

2010-01-01

311

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.)

312

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.

313

Noise figure characterization of preamplifiers at NMR frequencies.  

Science.gov (United States)

A method for characterizing the noise figure of preamplifiers at NMR frequencies is presented. The noise figure of preamplifiers as used for NMR and MRI detection varies with source impedance and with the operating frequency. Therefore, to characterize a preamplifier's noise behavior, it is necessary to perform noise measurements at the targeted frequency while varying the source impedance with high accuracy. At high radiofrequencies, such impedance variation is typically achieved with transmission-line tuners, which however are not available for the relatively low range of typical NMR frequencies. To solve this issue, this work describes an alternative approach that relies on lumped-element circuits for impedance manipulation. It is shown that, using a fixed-impedance noise source and suitable ENR correction, this approach permits noise figure characterization for NMR and MRI purposes. The method is demonstrated for two preamplifiers, a generic BF998 MOSFET module and an MRI-dedicated, integrated preamplifier, which were both studied at 128MHz, i.e., at the Larmor frequency of protons at 3 Tesla. Variations in noise figure of 0.01dB or less over repeated measurements reflect high precision even for small noise figures in the order of 0.4dB. For validation, large sets of measured noise figure values are shown to be consistent with the general noise-parameter model of linear two-ports. Finally, the measured noise characteristics of the superior preamplifier are illustrated by SNR measurements in MRI data. PMID:21439871

Nordmeyer-Massner, J A; De Zanche, N; Pruessmann, K P

2011-05-01

314

New methodological approaches in solid-state NMR  

International Nuclear Information System (INIS)

Full text: Spectacular advances in solid-state NMR methodology, instrumentation and sample preparation have made possible studies of structure and dynamics on increasingly complex molecular systems, such as proteins that cannot be investigated by X-ray, or solution-state NMR (amyloid fibrils, membrane proteins embedded in native environments, protein aggregates), other large biomolecular systems (DNA, RNA, carbohydrates), functionalized polymeric materials, selfassembled and inclusion molecular complexes, molecular nano-devices, etc. Many of these applications rely on the development of solid-state NMR techniques tailored to specifically address characteristic structural and dynamical features of larger and larger molecules, where often the dynamics of abundant spins, for instance, 1H, or 13C(15N) in uniformly labeled samples, represents a major challenge. To account for a broad range of multi-spin processes in such systems that may influence the efficiency of the proposed experimental scheme, or the reliability of the extracted parameters from the measured data, adequate theoretical tools are also highly desirable. In this context, here, we present some of our recent developments that address exactly these issues, namely: (i) elaboration of viable approaches for symbolic algebra computation of dynamics in extended spin networks, within a framework called SD-CAS (Spin Dynamics by Computer Algebra System), and (ii) development of new sora System), and (ii) development of new solid-state NMR methods for structural investigation of complex molecular systems. (author)

315

Xenon NMR of phase biaxiality in liquid crystals.  

Science.gov (United States)

Biaxial thermotropic nematic liquid crystals would be of great importance in liquid crystal display technology. Less than a decade ago, such liquid crystals were suggested. The biaxiality of the phases was confirmed using (2)H NMR spectroscopy of deuterated probe molecules. The spectra were collected from a sample rotating around an axis perpendicular to the external magnetic field, resulting in a two-dimensional powder pattern. We have proposed an alternate technique that is based on the second order quadrupole shift detectable in (131)Xe NMR spectra of dissolved xenon. The method has many advantages, such as the NMR spectra are taken from a static sample and the (131)Xe quadrupole coupling tensor is extremely sensitive to the symmetry of the phase. In the present study, we report results obtained on a 600-MHz NMR spectrometer. Together with the data of our earlier study, they confirm that the asymmetry parameter of the (131)Xe quadrupole coupling tensor in the nematic phase of a ferroelectric liquid crystal is 0.85 and in the smectic A phase ca 0.62, indicating significant phase biaxiality. PMID:24771455

Jokisaari, Jukka; Zhu, Jianfeng

2014-10-01

316

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

317

Recognition of lumbar disk herniation with NMR  

International Nuclear Information System (INIS)

Fifteen nuclear magnetic resonance (NMR) studies of 14 patients with herniated lumbar intervertebral disks were performed on the UCSF NMR imager. Computed tomographic (CT) scans done on a GE CT/T 8800 or comparable scanner were available at the time of NMR scan interpretation. Of the 16 posterior disk ruptures seen at CT, 12 were recognized on NMR. Diminished nucleus pulposus signal intensity was present in all ruptured disks. In one patient, NMR scans before and after chymopapain injection showed retraction of the protruding part of the disk and loss of signal intensity after chemonucleolysis. Postoperative fibrosis demonstrated by CT in one patient and at surgery in another showed intermediate to high signal intensity on NMR, easily distinguishing it from nearby thecal sac and disk. While CT remains the method of choice for evaluation of the patient with suspected lumbar disk rupture, the results of this study suggest that NMR may play a role in evaluating this common clinical problem

318

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 thn 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)

319

Natural abundance (25)Mg solid-state NMR of mg oxyanion systems: a combined experimental and computational study.  

OpenAIRE

Solid-state (25)Mg magic angle spinning nuclear magnetic resonance (MAS NMR) data are reported from a range of organic and inorganic magnesium-oxyanion compounds at natural abundance. To constrain the determination of the NMR interaction parameters (delta(iso), chi(Q), eta(Q)) data have been collected at three external magnetic fields (11.7, 14.1 and 18.8 T). Corresponding NMR parameters have also been calculated by using density functional theory (DFT) methods using the GIPAW approach, with ...

Cahill, Ls; Hanna, Jv; Wong, A.; Freitas, Jc; Yates, Jr; Harris, Rk; Smith, Me

2009-01-01

320

Experience with NMR-CT  

International Nuclear Information System (INIS)

Characteristics of NMR-CT and images from various pulse sequences were examined using a NMR-CT system of 0.15 Tesla resistive magnet on 55 patients with intracranial diseases. Short spin echo (SE) imaging clearly visualized anatomic location. Long SE imaging visualized lesions as high intensity areas, yielding high sensitivity in the detection of intracranial lesions. Inversion recovery (IR) imaging visualized white matter and gray matter as signal intensity areas of varying degree, allowing contrast discrimination of white and gray matter. T1 images, prepared from long SE and IR images, were similar to CT cisternographic images with metrizamide, clearly visualizing the relation between brain tissues and subarachnoid space. Short and long SE imagings were considered useful for scout view and screening, respectively. In patients with brain tumors, no definite correlation between T1 values and tissue findings was observed. (Namekawa, K.)

321

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

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

1135-11-01

322

NMR Studies of Inclusion Compounds  

OpenAIRE

This thesis presents the application of some of the NMR methods in studying host-guest complexes, mainly in solution. The general focus of the work is on investigating the reorientational dynamics of some small molecules that are bound inside cavities of larger moieties. In the current work, these moieties belong to two groups: cryptophanes and cyclodextrins. Depending on the structure of the cavities, properties of the guest molecules and the formed complexes vary. Chloroform and dichloromet...

Nikkhou Aski, Sahar

2008-01-01

323

NMR study of Mediterranean foodstuff  

OpenAIRE

Oggetto di studio dell’attività di dottorato è stata l’identificazione del profilo metabolico di oli d’oliva aromatizzati, gelatine reale e di estratti di campioni di spigola e di lattuga tramite spettroscopia di Risonanza Magnetica Nucleare. Il profilo metabolico è stato ottenuto tramite esperimenti NMR 1D e 2D ed è stato utilizzato insieme ad una appropriata analisi statistica per raggruppare i campioni secondo il problema specifico. Sono stati caratterizzati oli di oliva aromatiz...

D Amico, Irene

2010-01-01

324

Metabolomics: NMR base genetic diversity  

OpenAIRE

Metabolomics is the systematic identification and quantitation of all metabolites in a givenorganism or biological sample. The enhanced resolution provided by nuclear magnetic resonance (NMR)spectroscopy, allows the simultaneous determination and comparison of thousands of chemical entities,which has lead to an expansion of small molecule biochemistry studies in bacteria, plants, and mammals.Continued development of these analytical platforms will accelerate the widespread use of metabolomics...

Kapoor R.A.; Ladak S.S.; Gomase V.S.*

2009-01-01

325

Scalable NMR spectroscopy with semiconductor chips.  

Science.gov (United States)

State-of-the-art NMR spectrometers using superconducting magnets have enabled, with their ultrafine spectral resolution, the determination of the structure of large molecules such as proteins, which is one of the most profound applications of modern NMR spectroscopy. Many chemical and biotechnological applications, however, involve only small-to-medium size molecules, for which the ultrafine resolution of the bulky, expensive, and high-maintenance NMR spectrometers is not required. For these applications, there is a critical need for portable, affordable, and low-maintenance NMR spectrometers to enable in-field, on-demand, or online applications (e.g., quality control, chemical reaction monitoring) and co-use of NMR with other analytical methods (e.g., chromatography, electrophoresis). As a critical step toward NMR spectrometer miniaturization, small permanent magnets with high field homogeneity have been developed. In contrast, NMR spectrometer electronics capable of modern multidimensional spectroscopy have thus far remained bulky. Complementing the magnet miniaturization, here we integrate the NMR spectrometer electronics into 4-mm(2) silicon chips. Furthermore, we perform various multidimensional NMR spectroscopies by operating these spectrometer electronics chips together with a compact permanent magnet. This combination of the spectrometer-electronics-on-a-chip with a permanent magnet represents a useful step toward miniaturization of the overall NMR spectrometer into a portable platform. PMID:25092330

Ha, Dongwan; Paulsen, Jeffrey; Sun, Nan; Song, Yi-Qiao; Ham, Donhee

2014-08-19

326

Advanced NMR technology for bioscience and biotechnology  

Energy Technology Data Exchange (ETDEWEB)

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.

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

327

NMR probes HTGR fuel synthesis  

Energy Technology Data Exchange (ETDEWEB)

Schemes for the synthesis of microspherical nuclear fuel particles of uranium dioxide using the sol-gel process were developed by scientists at Oak Ridge National Laboratory and General Atomics for use in high temperature gas cooled reactors (HTGR). When coated with ceramic layers of pyrolytic carbon and silicon carbide, the microspherical particle retains volatile fission products very effectively. Researchers at Savannah River have developed a new method using carbon-13 and oxygen-17 nuclear magnetic resonance (NMR) for monitoring particle fuel manufacture by this synthesis process. NMR is an electromagnetic method developed in the 1950s based upon the quantized nuclear spin properties of nuclei with non-zero nuclear magnetic moments. Early examples of highly sensitive nuclei included hydrogen-1, carbon-13, fluorine-19 and phosphorus-31. Modern NMR methods based upon Fourier-Transform signal accumulation, homogenous-field superconducting magnets and modern computers have extended the method to a much longer list of useful nuclei of interest to the nuclear industry including deuterium, tritium, lithium-7, boron-10 and -11, nitrogen-14 and -15, oxygen-17, sodium-23 and caesium-133. (Author).

King, C.M.; Thompson, M.C. (Westinghouse Savannah River Co., Aiken, SC (United States))

1992-10-01

328

NMR-based milk metabolomics  

DEFF Research Database (Denmark)

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.

Sundekilde, Ulrik; Larsen, Lotte Bach

2013-01-01

329

NMR-Based Milk Metabolomics  

Directory of Open Access Journals (Sweden)

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.

Hanne C. Bertram

2013-04-01

330

Rheo-NMR of shear banded flow in wormlike micelles  

Science.gov (United States)

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.

Callaghan, Paul

2008-03-01

331

Structure and NMR assignment in calcined and as-synthesized forms of AlPO-14: a combined study by first-principles calculations and high-resolution 27Al-31P MAS NMR correlation.  

Science.gov (United States)

The high-resolution 27Al and 31P NMR spectra of two as-synthesized forms of the microporous aluminophosphate AlPO-14 and the corresponding calcined-dehydrated form were assigned using both "first-principles" calculations of NMR parameters (GIPAW, as implemented in NMR-CASTEP) and a 27Al-31P heteronuclear correlation NMR experiment (MQ-J-HETCOR) that exploits 27Al multiple-quantum coherences and J couplings to identify Al-O-P linkages. NMR parameters calculated from published AlPO-14 crystal structures, which are derived from powder X-ray diffraction (XRD) data, are in poor agreement with experiment and it was necessary to optimize the structure geometry using energy minimization before satisfactory agreement was obtained. Comparison of simulated powder XRD patterns from the experimental and the energy-minimized structures shows that the changes in relative atomic positions in the optimized structure are relatively small and yield only minor adjustments in the Bragg peak intensities. These results indicate that a combination of NMR spectroscopy and first-principles calculation of NMR parameters may soon be considered a generally useful step in the refinement of the structures of microporous materials derived from powder diffraction data. PMID:18956112

Ashbrook, Sharon E; Cutajar, Marica; Pickard, Chris J; Walton, Richard I; Wimperis, Stephen

2008-10-01

332

Field-swept 33S NMR study of elemental sulfur  

Science.gov (United States)

Field-swept 33S NMR spectra of a cyclic octaatomic molecule of elemental sulfur, ?-S8, are presented. The spectra were acquired at a Larmor frequency of 16.2 MHz and using a superconducting magnet at between 6.32 and 0.50 T. Methods were developed for analyzing the field-swept 33S NMR spectra in which both Zeeman and quadrupole interactions were dominant. The quadrupole coupling constant, CQ, and the asymmetry parameter, ?Q, for ?-S8 were found to be 43.68 MHz and 0.57, respectively. T1 measurements of ?-S8 were conducted using the nuclear quadrupole resonance signals, and the activation energy was determined to be 54(1) kJ mol-1 from these T1 measurements. The molecular motion was assigned to ring-puckering of ?-S8 molecules within the crystal structure.

Yamada, Kazuhiko; Kitagawa, Kentaro; Takahashi, Masato

2015-01-01

333

Antiferro multipolar ordering and it's identification by NMR experiment  

International Nuclear Information System (INIS)

The antiferro-ordering of multipolar moments often plays important roles in the low temperature phase transition of f-electron systems. The splitting of NMR spectra, which is analyzed in terms of the invariant hyperfine coupling between the nuclear spin and the multipolar moments of magnetic ions, gives important information about the multipolar ordering. Experimental and theoretical studies on CeB6 and NpO2 are presented as typical examples. The study on the low temperature phase of PrFe4P12, whose nature has been controversial, are reviewed. It was concluded that it has an antiferro order with the order-parameter characterized by the identity representation of the point group. The large anisotropy of NMR splitting in the magnetic field direction dependence suggests important roles of moments with higher ranks in PrFe4P12. (author)

334

Technical and clinical aspects of NMR imaging  

International Nuclear Information System (INIS)

In NMR imaging any scanning plane and slice thickness can be selected electronically and this has allowed high quality coronal and sagittal images to be obtained directly. The absence of any moving parts in the equipment promotes a high reliability. NMR imaging has a greater potential than CT for the selective examination of tissue characteristics since unlike the CT where x-ray attenuation co-efficients alone determine image contrast at least four separate variable contribute to the NMR signal. The outstanding attraction of NMR imaging is the avoidance of exposure to ionizing radiation. The RF photons used in NMR have energies some 1010 times smaller than x-ray photons. So far no hazard has been established by any of the groups working in this field. The present NMR images should be compared with CT scans at a comparable stage in their development and not with the higher quality images currently available. (J.P.N.)

335

Construction of a NMR permanent magnet  

International Nuclear Information System (INIS)

Viewing the development of the pulsed, low resolution NMR spectrometers for quantitative analysis, the electronic part of a NMR spectrometer has first been constructed, based on a 1.4 Tesla magnet of a 60 MHz Varian device, with a gap increased to 23 mm, therefore reducing the field to .66 Tesla (28 MHz for the hydrogen). For the complete construction of the spectrometer in Brazil, a permanent magnet for NMR has also been constructed

336

Applications of NMR in Dairy Research  

Directory of Open Access Journals (Sweden)

Full Text Available NMR is a robust analytical technique that has been employed to investigate the properties of many substances of agricultural relevance. NMR was first used to investigate the properties of milk in the 1950s and has since been employed in a wide range of studies; including properties analysis of specific milk proteins to metabolomics techniques used to monitor the health of dairy cows. In this brief review, we highlight the different uses of NMR in the dairy industry.

Anthony D. Maher

2014-03-01

337

Applications of NMR in Dairy Research  

Science.gov (United States)

NMR is a robust analytical technique that has been employed to investigate the properties of many substances of agricultural relevance. NMR was first used to investigate the properties of milk in the 1950s and has since been employed in a wide range of studies; including properties analysis of specific milk proteins to metabolomics techniques used to monitor the health of dairy cows. In this brief review, we highlight the different uses of NMR in the dairy industry. PMID:24958391

Maher, Anthony D.; Rochfort, Simone J.

2014-01-01

338

Moderne Festkörper-NMR an Funktionspolymeren  

OpenAIRE

In dieser Arbeit wurden drei häufig verwandte Polymere bzw. Komposite aus verschiedenen Kunststoffbereichen, nämlich Naturkautschuk, auf hydrophile Kieselsäure gepfropftes PDMS (Polydimethylsiloxan) und Ton-Polyamid-Nanokomposite auf deren mikroskopische Strukturen mit der modernen Festkörper-NMR-Technik untersucht. Neben der multinuklearen NMR-Spektroskopie zur Strukturaufklärung, die man normalerweise von der NMR in der Chemie kennt, ist es in dieser Arbeit desweiteren gelungen, eine K...

Wang, Mingfei

2004-01-01

339

NMR exposure sensitizes tumor cells to apoptosis.  

Science.gov (United States)

NMR technology has dramatically contributed to the revolution of image diagnostic. NMR apparatuses use combinations of microwaves over a homogeneous strong (1 Tesla) static magnetic field. We had previously shown that low intensity (0.3-66 mT) static magnetic fields deeply affect apoptosis in a Ca2+ dependent fashion (Fanelli et al., 1999 FASEBJ., 13;95-102). The rationale of the present study is to examine whether exposure to the static magnetic fields of NMR can affect apoptosis induced on reporter tumor cells of haematopoietic origin. The impressive result was the strong increase (1.8-2.5 fold) of damage-induced apoptosis by NMR. This potentiation is due to cytosolic Ca2+ overload consequent to NMR-promoted Ca2+ influx, since it is prevented by intracellular (BAPTA-AM) and extracellular (EGTA) Ca2+ chelation or by inhibition of plasma membrane L-type Ca2+ channels. Three-days follow up of treated cultures shows that NMR decrease long term cell survival, thus increasing the efficiency of cytocidal treatments. Importantly, mononuclear white blood cells are not sensitised to apoptosis by NMR, showing that NMR may increase the differential cytotoxicity of antitumor drugs on tumor vs normal cells. This strong, differential potentiating effect of NMR on tumor cell apoptosis may have important implications, being in fact a possible adjuvant for antitumor therapies. PMID:16528477

Ghibelli, L; Cerella, C; Cordisco, S; Clavarino, G; Marazzi, S; De Nicola, M; Nuccitelli, S; D'Alessio, M; Magrini, A; Bergamaschi, A; Guerrisi, V; Porfiri, L M

2006-03-01

340

NMR studies of isotopically labeled RNA  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1994-12-01

341

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

Science.gov (United States)

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…

Mills, Nancy S.; Shanklin, Michael

2011-01-01

342

Short recovery time NMR probe  

International Nuclear Information System (INIS)

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)

343

NUTATION NMR STUDIES OF POLYACETYLENE  

OpenAIRE

Using nutation NMR spectroscopy we have been able to determine directly the carbon-carbon bond lengths in polyacetylene. For trans-polyacetylene we find double and single bond lengths of 1.36 and 1.44 Å respectively ; the double bond in cis-polyacetylene is found to be 1.38 Å. Interestingly, at 77°K we do not observe a rapid interchange of the single and double bonds in trans-polyacetylene in the manner predicted for chains containing a soliton defect, suggesting that the majority of the c...

Clarke, T.; Kendrick, R.; Yannoni, C.

1983-01-01

344

An Inexpensive High-Throughput NMR Tube Cleaning Apparatus  

OpenAIRE

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...

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

2011-01-01

345

The eNMR platform for structural biology  

OpenAIRE

The e-NMR project is a European cooperation initiative that aims at providing the bio-NMR user community with a software platform integrating and streamlining the computational approaches necessary for the analysis of bio-NMR data. The e-NMR platform is based on a Grid computational infrastructure. A main focus of the current implementation of the e-NMR platform is on streamlining structure determination protocols. Indeed, to facilitate the use of NMR spectroscopy in t...

Bonvin, A. M. J. J.; Rosato, A.; Wassenaar, T. A.

2010-01-01

346

Parameter Estimation  

DEFF Research Database (Denmark)

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.

Sales-Cruz, Mauricio; Heitzig, Martina

2011-01-01

347

Picoliter H-1 NMR Spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

A RF probe that fits inside the bore of a small gradient coil package is described for routine 1H-NMR microscopy measurements on small samples. The probe operates at 500 MHz and houses a 267-um-diameter solenoid transceiver. When used in three dimensional chemical shift imaging (3D-CSI) experiments, the measured signal-to-noise ratio (SNR) is shown to be within 20-30 percent of theoretical limits formulated by only considering the solenoid's resistive losses. This is illustrated using a 100-um-diameter globule of triacylglycerols ({approx}900mM) that may be an oocyte precursor in young Xenopus Laevis frogs, and water sample containing choline at a concentration often found in live cells ({approx}33mM). In chemical shift images generated using a few thousand scans, the choline methyl line is found to have an acceptable SNR in resolved from just 5 picoliters in the Xenopus globule. It is concluded that the probe's sensitivity is sufficient for performing 1H-NMR on picoliter-scale volumes in biological cells and tissues.

Minard, Kevin R.(BATTELLE (PACIFIC NW LAB)); Wind, Robert A.(BATTELLE (PACIFIC NW LAB))

2002-02-01

348

Picoliter 1H NMR Spectroscopy  

Science.gov (United States)

In this study, a 267-?m-diameter solenoid transceiver is used to acquire localized 1H NMR spectra and the measured signal-to-noise ratio (SNR) at 500 MHz is shown to be within 20-30% of theoretical limits formulated by considering only its resistive losses. This is illustrated using a 100-?m-diameter globule of triacylglycerols (˜900 mM) that may be an oocyte precursor in young Xenopus laevis frogs and a water sample containing choline at a concentration often found in live mammalian cells (˜33 mM). In chemical shift imaging (CSI) experiments performed using a few thousand total scans, the choline methyl line is shown to have an acceptable SNR in resolved volume elements containing only 50 pL of sample, and localized spectra are resolved from just 5 pL in the Xenopus globule. These findings demonstrate the feasibility of performing 1H NMR on picoliter-scale sample volumes in biological cells and tissues and illustrate how the achieved SNR in spectroscopic images can be predicted with reasonable accuracy at microscopic spatial resolutions.

Minard, Kevin R.; Wind, Robert A.

2002-02-01

349

Determination of cyclopeptide conformations in solution using NMR data and conformational energy calculations.  

Science.gov (United States)

The three-dimensional structure of the cyclic analogs of bradykinin and substance P C-terminal hexapeptide was studied using conformational energy calculations. Initial conformations for energy minimization were selected with the aid of the measured intensities of local nuclear Overhauser effects (NOEs) and other 1H-NMR data. Expected values of the 1H-NMR parameters for low-energy conformations of the cyclopeptides were calculated and compared with those observed experimentally using semiquantitative gradation of NOE intensities. Several low-energy structures of the cyclic bradykinin analog, possessing similar backbone conformations stabilized by two beta-turns, are in agreement with experimental data. None of the low-energy conformations of the substance P cyclic hexapeptide were in satisfactory agreement with the experimental set of NOEs. The agreement was achieved only by averaging of the calculated 1H-NMR parameters over several combinations of the low-energy conformations. PMID:2466496

Shenderovich, M D; Nikiforovich, G V; Saulitis, J B; Chipens, G I

1988-08-01

350

sup 1 sup 1 B nutation NMR study of powdered borosilicates  

CERN Document Server

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.

Woo, A J; Han, D Y

1998-01-01

351

Interface card for NMR data acquisition  

International Nuclear Information System (INIS)

A NMR spectrometer constructed by NPDIA is being used for analysis of seed oil contents in projects of oil seeds improvement. Some improvements have been introduced in this spectrometer, and this work presents an IBM-Pc compatible interface card. This interface has some characteristics which are exclusive for NMR

352

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

353

Using Cloud Storage for NMR Data Distribution  

Science.gov (United States)

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…

Soulsby, David

2012-01-01

354

An Inversion Recovery NMR Kinetics Experiment  

Science.gov (United States)

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…

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

2011-01-01

355

NMR Spectroscopy and Its Value: A Primer  

Science.gov (United States)

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…

Veeraraghavan, Sudha

2008-01-01

356

Electrical conductivity effects on NMR images  

International Nuclear Information System (INIS)

NMR image distorsions due to the amplitude attenuation and phase shift of the radiofrequency field in a slightly conducting sample are examined. The geometry of the NMR coil is also taken into account. An image correction is proposed when appreciable skin effect occurs

357

NMR studies on irradiated lecithin systems  

International Nuclear Information System (INIS)

By means of NMR and u.v. spectroscopy we have examined the radiation damage of liposomes under different experimental conditions including addition of a nitro compound as an effector with the aim of minimizing irradiation effects. Some NMR spectroscopic results were derived from partially relaxed spectra. This method seems to be useful for the detection of different radiation effects. (author)

358

Enzyme dynamics from NMR spectroscopy.  

Science.gov (United States)

Conspectus Biological activities of enzymes, including regulation or coordination of mechanistic stages preceding or following the chemical step, may depend upon kinetic or equilibrium changes in protein conformations. Exchange of more open or flexible conformational states with more closed or constrained states can influence inhibition, allosteric regulation, substrate recognition, formation of the Michaelis complex, side reactions, and product release. NMR spectroscopy has long been applied to the study of conformational dynamic processes in enzymes because these phenomena can be characterized over multiple time scales with atomic site resolution. Laboratory-frame spin-relaxation measurements, sensitive to reorientational motions on picosecond-nanosecond time scales, and rotating-frame relaxation-dispersion measurements, sensitive to chemical exchange processes on microsecond-millisecond time scales, provide information on both conformational distributions and kinetics. This Account reviews NMR spin relaxation studies of the enzymes ribonuclease HI from mesophilic (Escherichia coli) and thermophilic (Thermus thermophilus) bacteria, E. coli AlkB, and Saccharomyces cerevisiae triosephosphate isomerase to illustrate the contributions of conformational flexibility and dynamics to diverse steps in enzyme mechanism. Spin relaxation measurements and molecular dynamics (MD) simulations of the bacterial ribonuclease H enzymes show that the handle region, one of three loop regions that interact with substrates, interconverts between two conformations. Comparison of these conformations with the structure of the complex between Homo sapiens ribonuclease H and a DNA:RNA substrate suggests that the more closed state is inhibitory to binding. The large population of the closed conformation in T. thermophilus ribonuclease H contributes to the increased Michaelis constant compared with the E. coli enzyme. NMR spin relaxation and fluorescence spectroscopy have characterized a conformational transition in AlkB between an open state, in which the side chains of methionine residues in the active site are disordered, and a closed state, in which these residues are ordered. The open state is highly populated in the AlkB/Zn(II) complex, and the closed state is highly populated in the AlkB/Zn(II)/2OG/substrate complex, in which 2OG is the 2-oxoglutarate cosubstrate and the substrate is a methylated DNA oligonucleotide. The equilibrium is shifted to approximately equal populations of the two conformations in the AlkB/Zn(II)/2OG complex. The conformational shift induced by 2OG ensures that 2OG binds to AlkB/Zn(II) prior to the substrate. In addition, the opening rate of the closed conformation limits premature release of substrate, preventing generation of toxic side products by reaction with water. Closure of active site loop 6 in triosephosphate isomerase is critical for forming the Michaelis complex, but reopening of the loop after the reaction is (partially) rate limiting. NMR spin relaxation and MD simulations of triosephosphate isomerase in complex with glycerol 3-phosphate demonstrate that closure of loop 6 is a highly correlated rigid-body motion. The MD simulations also indicate that motions of Gly173 in the most flexible region of loop 6 contribute to opening of the active site loop for product release. Considered together, these three enzyme systems illustrate the power of NMR spin relaxation investigations in providing global insights into the role of conformational dynamic processes in the mechanisms of enzymes from initial activation to final product release. PMID:25574774

Palmer, Arthur G

2015-02-17

359

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

360

High-resolution solid-state NMR spectroscopy as a tool for investigation of enantioselective inclusion complexation.  

Science.gov (United States)

In this paper, we showed the application of solid state-NMR (SS NMR) spectroscopy in structural studies of chiral compounds employing sample of (E)-1-diphenylphosphinoylpent-3-en-2-ol 1 as a model compound. Racemate of 1 was fully characterized by NMR techniques (both in liquid and solid phase) and X-ray crystallography. Theoretical calculations employing the GIAO approach were used to explain the influence of hydrogen bonding on 31P NMR shielding parameter in racemate. Enantioselective inclusion complexation (EIC) method with TADDOL as host molecule was applied to separate of enantiomers. The formation of host-guest complex and decomplexation procedure was monitored by means of the SS NMR. The liquid-state NMR, due to similarity of 13C and 31P spectral parameters was not able to distinguish racemate from enantiomer. In the solid phase, owing to distinction of hydrogen bonding and molecular packing in the crystal lattice, racemate and enantiomers were easy recognized by NMR spectroscopy. PMID:17537616

Gajda, J; Jeziorna, A; Ciesielski, W; Potrzebowski, W M; Prezdo, W W; Potrzebowski, M J

2007-05-01

361

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

362

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

363

A frequency determination method for digitized NMR signals  

CERN Document Server

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...

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

2013-01-01

364

1H NMR spectroscopic identification of a glue sniffing biomarker.  

Science.gov (United States)

Organic solvent abuse typically involves sniffing organic solvents to experience the mind-altering conditions they induce. In Republic of Korea, organic solvent abuse is a serious social problem, especially among teenagers. Several studies have addressed the effects of organic solvent abuse on mind and body, but there are no simple methods by which such abuse can be positively identified. In this report, we describe a method for analyzing toluene metabolites (toluene is the main ingredient of glue) in glue-sniffers' urine using (1)H NMR spectroscopy. Toluene is a commonly used solvent in the rubber, paint, plastics, leather, printing, and chemical industries. Inhaled toluene is metabolized to hippuric acid in the liver and excreted in the urine. Hippuric acid is known as a good biomarker for biological monitoring of toluene exposure. We have scanned hippuric acid and other toluene metabolites by NMR spectroscopy and performed statistical multivariate analysis of the data. Based on this analysis, we sought to determine parameters by which glue-sniffing (toluene inhalation) behavior may be verified. We also demonstrate the use of a pattern recognition method for accurate and efficient analysis of NMR data. In comparison to conventional methods, such as mass spectroscopy coupled with liquid chromatography or gas chromatography, nuclear magnetic resonance spectroscopy has several advantages, including simple sample preparation, non-destructive sampling, accuracy, short acquisition time, and reproducibility in the determination of urinary hippuric acid. PMID:21316881

Kwon, Bobae; Kim, Siwon; Kim, Sosun; Lee, Dong-Kye; Park, Yu-Jin; Kim, Myung-Duck; Lee, Jae-Shin; Kim, Suhkmann

2011-06-15

365

Carbon-13 NMR spectroscopy of biological systems  

CERN Document Server

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...

Beckmann, Nicolau

1995-01-01

366

Identification and analysis of drugs in the solid state by 13C CPMAS NMR: suxamethonium chloride and hydrocortisonum (Codhydrine)  

International Nuclear Information System (INIS)

Cross-polarization (CP) magic angle spinning (MAS) 13C NMR spectroscopy has become a routine tool in pharmacy, employed to identify and characterize drugs in the solid phase. 13C CPMAS NMR spectra were recorded for solid hydrocortisone 21-hemisuccinate and suxamethonium chloride. White crystalline substances, such as these two drugs, can be easily distinguished; and solid-state 13NMR spectra of remarkably good quality are obtained in less than half an hour. 13C CPMAS chemical shifts for solid suxamethonium chloride and hydrocortisone sodium hemisuccinate are given, as well as cross-polarization kinetic parameters for suxamethonium chloride. (author)

367

High-resolution (19)F MAS NMR spectroscopy: structural disorder and unusual J couplings in a fluorinated hydroxy-silicate.  

OpenAIRE

High-resolution (19)F magic angle spinning (MAS) NMR spectroscopy is used to study disorder and bonding in a crystalline solid. (19)F MAS NMR reveals four distinct F sites in a 50% fluorine-substituted deuterated hydrous magnesium silicate (clinohumite, 4Mg(2)SiO(4)·Mg(OD(1-x)F(x))(2) with x = 0.5), indicating extensive structural disorder. The four (19)F peaks can be assigned using density functional theory (DFT) calculations of NMR parameters for a number of structural models with a range ...

Griffin, Jm; Yates, Jr; Berry, Aj; Wimperis, S.; Ashbrook, Se

2010-01-01

368

Crystallinity and compositional changes in carbonated apatites: Evidence from 31P solid-state NMR, Raman, and AFM analysis  

OpenAIRE

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43? ?1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO32? range investigated. Comparison...

Mcelderry, John-david P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; Mcnerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M. Banaszak; Tecklenburg, Mary M. J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

2013-01-01

369

Contribution of first-principles calculations to multinuclear NMR analysis of borosilicate glasses  

International Nuclear Information System (INIS)

Boron-11 and silicon-29 NMR spectra of xSiO2-(1-x)B2O3 glasses (x= 0. 40, 0. 80 and 0. 83) have been calculated using a combination of molecular dynamics (MD) simulations with density functional theory (DFT) calculations of NMR parameters. Structure models of 200 atoms have been generated using classical force fields and subsequently relaxed at the PBE-GGAlevel of DFT theory. The gauge including projector augmented wave (GIPAW) method is then employed for computing the shielding and electric field gradient tensors for each silicon and boron atom. Silicon-29 MAS and boron-11 MQMAS NMR spectra of two glasses (x = 0. 40 and 0. 80) have been acquired and theoretical spectra are found to well agree with the experimental data. For boron-11, the NMR parameter distributions have been analysed using a Kernel density estimation (KDE) approach which is shown to highlight its main features. Accordingly, a new analytical model that incorporates the observed correlations between the NMR parameters is introduced. It significantly improves the fit of the B-11 MQMAS spectra and yields, therefore, more reliable NMR parameter distributions. A new analytical model for a quantitative description of the dependence of the silicon-29 and boron-11 isotropic chemical shift upon the bond angles is proposed, which incorporates possibly the effect of SiO2-B2O3 intermixing. Combining all the above procedures, we show how distributio above procedures, we show how distributions of Si-O-T and B-O-T (T= Si, B) bond angles can be estimated from the distribution of isotropic chemical shift of silicon-29 and boron-11, respectively. (authors)

370

A HTS dc SQUID-NMR: fabrication of the SQUID and application to low-field NMR for fruit quality detection  

Science.gov (United States)

Superconducting Quantum Interference Devices (SQUIDs) have made the detection of low-field (LF) and ultra-low field nuclear magnetic resonance (ULF-NMR) a reality. The latter has been proven to be a potential tool for non-destructive quality testing of horticultural products, amongst many other applications. High-Temperature Superconductor (HTS) dc SQUIDS are likely to allow for the development of not only low-cost NMR systems but also prototypes that are mobile and easily maintainable. A HTS dc SQUID was manufactured on an YBCO thin film, using a novel laser based lithography method. The lithography was implemented by a new laser system developed in-house, as a model of low-cost lithography systems. The junctions of the dc SQUID were tested and displayed normal I-V characteristics in the acceptable range for the application. In order to determine the viability of low-field NMR for non-destructive quality measurement of horticultural products, a commercial HTS dc SQUID-NMR system was used to measure quality parameters of banana during ripening. The trend of color change and sugar increase of the banana during ripening were the most highly correlated attributes to the SQUID-NMR measured parameter, average T1 (spin-lattice relaxation time). Further studies were done, that involved processing of the NMR signal into relaxation time resolved spectra. A spectral signature of banana was obtained, where each peak is a T1 value corresponding to a proton pool, and is reported here. These results will potentially lead to deeper understanding of the quality of the samples under study.

Isingizwe Nturambirwe, J. Frédéric; Perold, Willem J.; Opara, Linus U.

2014-06-01

371

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

Science.gov (United States)

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. PMID:25619991

Cannistraci, Carlo Vittorio; Abbas, Ahmed; Gao, Xin

2015-01-01

372

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

KAUST Repository

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.

Cannistraci, Carlo Vittorio

2015-01-26

373

A rapid coal characterisation analysis by low-resolution NMR spectroscopy and partial least-squares regression  

OpenAIRE

1H-NMR spectroscopy is a potentially useful technique for the characterisation of coal. A novel technique was applied to distinguish, characterise and determine quantitatively five different classes of proton containing components from air-dried Australian bituminous coals. The five different classes of protons are described by 14 fitted NMR parameters, which are the signal amplitudes, spin-lattice relaxation times and spin-spin relaxation times. To establish the mathematical relationship bet...

Harmer, Jr; Callcott, Tg; Maeder, M.; Smith, Be

2001-01-01

374

NMR and dielectric spectroscopy investigation of protein dynamical structure.  

Science.gov (United States)

The general approach to globular proteins dynamical structure investigation by NMR and time domain dielectric spectroscopy (TDDS) is presented. The information on macromolecular dynamical behavior in the case of these two methods is obtained in terms of correlation function and its parameters of atom motions. The interpretation of experimental results in the present work will be carried out in the framework of model-free approach which is common both for magnetic and dielectric relaxation. The lysozyme pH-dependence investigation is presented as an example.

Fedotov, V. D.; Feldman, Yu. D.; Krushelnitsky, A. G.; Ermolina, I. V.

1990-03-01

375

Synthesis, IR and NMR spectral correlations in some symmetrical diimines  

Directory of Open Access Journals (Sweden)

Full Text Available A series of diimines have been synthesized by coupling of diamine with substituted benzaldehydes. The purities of these diimines were checked by their analytical and spectroscopic data. The spectral frequencies ?CN (cm-1, NMR chemical shifts (?, ppm of C-H and C=N of these diimines have been correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituents on the above spectral data has been studied. DOI: http://dx.doi.org/10.4314/bcse.v28i1.9

G. Thirunarayanan

2014-01-01

376

NMR of superfluid 3He in anisotropic aerogel  

OpenAIRE

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-...

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

2006-01-01

377

NMR spectroscopic characterization of ?-cyclodextrin inclusion complex with vanillin  

International Nuclear Information System (INIS)

The inclusion of vanillin by ?-cyclodextrin was investigated by 1H NMR. The continuous variation technique was used to evidence the formation of soluble 1:1 complex in aqueous solution. The association constant of vanillin with ?-cyclodextrin has been obtained at 298 K by fitting the experimental chemical shifts differences, ??obs ?free - ?obs of the observed guest and host protons, with a non-linear regression method. Besides the effective association constant, the fitting procedure allows a precise determination of all chemical shift parameters characterizing the pure complex. They can by used for an analysis of the geometry of the molecular complex in solution.

378

NMR spectroscopic characterization of ?-cyclodextrin inclusion complex with vanillin  

Science.gov (United States)

The inclusion of vanillin by ?-cyclodextrin was investigated by 1H NMR. The continuous variation technique was used to evidence the formation of soluble 1:1 complex in aqueous solution. The association constant of vanillin with ?-cyclodextrin has been obtained at 298 K by fitting the experimental chemical shifts differences, ??obs = ?free - ?obs of the observed guest and host protons, with a non-linear regression method. Besides the effective association constant, the fitting procedure allows a precise determination of all chemical shift parameters characterizing the pure complex. They can by used for an analysis of the geometry of the molecular complex in solution.

Pîrnau, Adrian; Bogdan, Mircea; Floare, Calin G.

2009-08-01

379

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

380

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

Science.gov (United States)

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.

Ni, Qingwen; Chen, Shuo

2010-01-01

381

Improved Characterization of Healthy and Malignant Tissue by NMR Line-Shape Relaxation Correlations  

OpenAIRE

We performed a relaxation-line-shape correlation NMR experiment on muscle, liver, kidney, and spleen tissues of healthy mice and of mouse tumor tissue. In each tissue studied, five spin groups were resolved and characterized by their relaxation parameters. We report a previously uncharacterized semi-solid spin group and discuss briefly the value of this method for the identification of malignant tissues.

Peemoeller, H.; Shenoy, R. K.; Pintar, M. M.; Kydon, D. W.; Inch, W. R.

1982-01-01

382

31P solid state NMR geometrical effects on the chemical shift tensor  

International Nuclear Information System (INIS)

The principal components of the 31P chemical shift tensor sigma of four cyclic organophosphorus compounds of different size, where the phorphorus atoms have the same chemical environment are reported from solid state NMR studies. The sigma tensors show a large anisotropy. The asymmetry parameter eta shows a linear variation as a function of the intracyclic bond angle around the phosphorus. (orig.)

383

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.)

384

Background suppression in MAS NMR  

Science.gov (United States)

Pulse sequences for suppressing background signals from spinning modules used in magic-angle spinning NMR are described. These pulse sequences are based on spatially selective composite 90° pulses originally reported by Bax, which provide for no net excitation of spins outside the homogeneous region of the coil. We have achieved essentially complete suppression of background signals originating from our Vespel spinning module (which uses a free-standing coil) in both 1H and 13C spectra without notable loss in signal intensity. Successful modification of both Bloch decay and cross-polarization pulse sequences to include spatially selective pulses was essential to acquire background-free spectra for weak samples. Background suppression was also found to be particularly valuable for both T1 and T1 ?, relaxation measurements.

White, Jeffery L.; Beck, Larry W.; Ferguson, David B.; Haw, James F.

385

Hyperpolarized Hadamard spectroscopy using flow NMR.  

Science.gov (United States)

The emergence of the dissolution dynamic nuclear polarization (D-DNP) technique provides an important breakthrough to overcome inherent sensitivity limitations in nuclear magnetic resonance (NMR) experiments. In dissolution DNP, only a small amount of frozen sample is polarized, dissolved, and injected into an NMR spectrometer. Although substantially enhanced NMR signals can be obtained, the single scan nature of this technique a priori impedes the use of correlation experiments, which represent some of the most powerful applications of NMR spectroscopy. Here, an alternative method for multiscan spectroscopy from D-DNP samples utilizing a flow NMR probe is described. Multiple hyperpolarized segments of sample are sequentially injected using a purpose designed device. Hadamard spectroscopy can then be applied for obtaining chemical shift correlation information even from a small number of scans. This capability is demonstrated with a four-scan data set for obtaining the [(13)C,(1)H] correlations in the test molecule 1-butanol. Because of the effects of spin-lattice relaxation and concentration gradients in the D-DNP experiment, the subtractive process for Hadamard reconstruction requires an additional step of intensity scaling. For this purpose, a reconstruction procedure was developed that uses entropy maximization and is robust with respect to noise and signal overlap. In a broader sense, the multiscan NMR as described here is amenable to various correlation NMR experiments, and increases the versatility of D-DNP in small-molecule characterization. PMID:23834163

Chen, Hsueh-Ying; Hilty, Christian

2013-08-01

386

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

387

NMR-Profiles of Protein Solutions  

OpenAIRE

NMR-Profiles are quantitative one-dimensional presentations of two-dimensional [15N,1H]-correlation spectra used to monitor the quality of protein solutions prior to and during NMR structure determinations and functional studies. In our current use in structural genomics projects, a NMR-Profile is recorded at the outset of a structure determination, using a uniformly 15N-labeled micro-scale sample of the protein. We thus assess the extent to which polypeptide backbone resonance assignments ca...

Pedrini, Bill; Serrano, Pedro; Mohanty, Biswaranjan; Geralt, Michael; Wu?thrich, Kurt

2013-01-01

388

NMR-spektroskopische Untersuchungen an Fettsäurebindungsproteinen  

OpenAIRE

Ziel dieser Arbeit war es, mit der Methode der NMR-Spektroskopie strukturelle und funktionelle Eigenschaften von Fettsäurebindungsproteinen zu untersuchen. NMR-Spektren von Proteinen mit hohem -Faltblattanteil, wie H-FABP, zeigen häufig eine große Dispersion mit einer typischen Verteilung tief- und hochfeldverschobener Signale. Es wurden 1D/2D 1H-NMR Spektren für den Wildtyp und mehrere Mutanten (F4E, F4S, F4S/W8E, W8E, F16E, F16S, K21I, F64S, L66G und E72S) des humanen H-FABP aufgenommen...

Rademacher, Martin

2003-01-01

389

NMR data handbook for biomedical applications  

International Nuclear Information System (INIS)

The text is divided into 10 chapters, each of which covers a specific block of material and has its own references. The volume is meant to serve as a laboratory handbook and a desk reference, containing basic NMR theory, useful formulae and physical constants, and compiled data from the NMR literature. The volume attempts to cover the development of biological NMR through several decades of in vitro experiments that have laid the groundwork for and pointed to profitable areas of investigation for new in vivo techniques

390

Motions and entropies in proteins as seen in NMR relaxation experiments and molecular dynamics simulations.  

Science.gov (United States)

Molecular dynamics simulations of E. coli glutaredoxin1 in water have been performed to relate the dynamical parameters and entropy obtained in NMR relaxation experiments, with results extracted from simulated trajectory data. NMR relaxation is the most widely used experimental method to obtain data on dynamics of proteins, but it is limited to relatively short timescales and to motions of backbone amides or in some cases (13)C-H vectors. By relating the experimental data to the all-atom picture obtained in molecular dynamics simulations, valuable insights on the interpretation of the experiment can be gained. We have estimated the internal dynamics and their timescales by calculating the generalized order parameters (O) for different time windows. We then calculate the quasiharmonic entropy (S) and compare it to the entropy calculated from the NMR-derived generalized order parameter of the amide vectors. Special emphasis is put on characterizing dynamics that are not expressed through the motions of the amide group. The NMR and MD methods suffer from complementary limitations, with NMR being restricted to local vectors and dynamics on a timescale determined by the rotational diffusion of the solute, while in simulations, it may be difficult to obtain sufficient sampling to ensure convergence of the results. We also evaluate the amount of sampling obtained with molecular dynamics simulations and how it is affected by the length of individual simulations, by clustering of the sampled conformations. We find that two structural turns act as hinges, allowing the ? helix between them to undergo large, long timescale motions that cannot be detected in the time window of the NMR dipolar relaxation experiments. We also show that the entropy obtained from the amide vector does not account for correlated motions of adjacent residues. Finally, we show that the sampling in a total of 100 ns molecular dynamics simulation can be increased by around 50%, by dividing the trajectory into 10 replicas with different starting velocities. PMID:25350574

Allnér, Olof; Foloppe, Nicolas; Nilsson, Lennart

2015-01-22

391

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 id 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)

392

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)

393

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)

394

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

OpenAIRE

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 ...

Kimmich, Rainer; Fatkullin, Nail

2010-01-01

395

ADAPT-NMR Enhancer: complete package for reduced dimensionality in protein NMR spectroscopy  

OpenAIRE

Summary: ADAPT-nuclear magnetic resonance (ADAPT-NMR) offers an automated approach to the concurrent acquisition and processing of protein NMR data with the goal of complete backbone and side chain assignments. What the approach lacks is a useful graphical interface for reviewing results and for searching for missing peaks that may have prevented assignments or led to incorrect assignments. Because most of the data ADAPT-NMR collects are 2D tilted planes used to find peaks in 3...

Lee, Woonghee; Bahrami, Arash; Markley, John L.

2013-01-01

396

Substituent Effects in the 13C-NMR Spectra of Six-Membered Nitrogen Heteroaromatic Compounds  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: It is shown that the 13C-NMR chemical shifts of carbon atoms in substituted sixmembered heteroaromatic compounds correlate with the correponding "additivity parameters" for substituted benzene derivatives. Thus, for precalculation of chemical shifts in such compounds, just one set of parameters can be used. The differences between experimental chemical shifts and those calculated from correlation with the common set may provide insights into intramolecular interactions not reported in the literature.

Janusz Oszczapowicz

2005-01-01

397

31P NMR knights shifts in the UPY (Y = S, Se, Te) compounds  

International Nuclear Information System (INIS)

Nuclear magnetic resonance of 31P measurements have been made for UPY (where Y = S, Se and Te) compounds. The resonance lines show the effect of anisotropic Knight shifts. In the UPS, the NMR data indicate an axial symmetry of the phosphorus environment whereas for UPSe and UPTe the symmetry is lower than the axial one. The result for UPSe disagrees with earlier structural studies. An analysis of NMR spectra indicates that both the asymmetry parameter epsilon and the isotropic component of the Knight shift increase with the increase of atomic weight of the Y element. (orig.)

398

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

OpenAIRE

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 s...

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

2009-01-01

399

Benchmarks for the 13C NMR chemical shielding tensors in peptides in the solid state  

Science.gov (United States)

The benchmark set is proposed, which comprises 126 principal elements of chemical shielding tensors, and the respective isotropic chemical shielding values, of all 42 13C nuclei in crystalline Tyr-D-Ala-Phe and Tyr-Ala-Phe tripeptides with known, but highly dissimilar structures. These data are obtained by both the NMR measurements and the density functional theory in the pseudopotential plane-wave scheme. Using the CASTEP program, several computational strategies are employed, for which the level of agreement between calculations and experiment is established. This set is mainly intended for the validation of methods capable of predicting the 13C NMR parameters in solid-state systems.

Czernek, Ji?í; Pawlak, Tomasz; Potrzebowski, Marek J.

2012-02-01

400

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)

401

(35)Cl solid-state NMR of halide ionic liquids at ultrahigh fields.  

Science.gov (United States)

This Letter describes recent work investigating the solid-state NMR spectra of (35)Cl nuclei in an assortment of ionic liquids under static and MAS conditions at field strengths of 9.4 and 21.1 T. At high field it was possible to resolve and extract information from multiple unique crystallographic sites and to resolve otherwise complex spectra that were analyzed to extract information regarding the electric field gradient (EFG) and chemical shift tensors, including their relative orientation. The NMR parameters were found to be typical of organic salts in general. PMID:19007195

Gordon, Peter G; Brouwer, Darren H; Ripmeester, John A

2008-12-11

402

A new laboratory approach to shale analysis using NMR relaxometry  

Science.gov (United States)

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.

Washburn, Kathryn E.; Birdwell, Justin E.

2013-01-01

403

NMR imaging of the abdomen: technical considerations  

International Nuclear Information System (INIS)

Evaluation of nuclear magnetic resonance (NMR) imaging of the abdomen was done in 41 patients with focal and diffuse disorders of the liver and retroperitoneal and vascular abnormalities. Spin-echo technique was used in each situation with varying time to echo (TE) and repetition rates (TR). No single pulsing technique was optimal in all situations. Three false-negative NMR studies of 22 patients with focal lesions of the liver were attributed to incomplete coverage of the involved area or inappropriate pulsing technique. When appropriate technique was achieved, NMR was equal to computed tomography (CT) in detecting abdominal disorders, except in fatty infiltration of the liver. NMR was superior to CT in imaging vascular anatomy because of the inherent increased contrast produced by the absence of signal from flowing blood and the flexibility of imaging planes

404

A 2H NMR study on biosynthesis  

International Nuclear Information System (INIS)

A 2H NMR study on griseofulvin reports evidence of participation of medium water into the methlyl group of chain-starter, with use of various kinds of acetate precursors, as a result of hydrogen exchange. (Auth.)

405

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

406

Nuclear magnetic resonance (NMR) theory and applications  

International Nuclear Information System (INIS)

Over the past years, techniques of nuclear magnetic resonance (NMR) have developed into several areas of applications. The relaxation times and the proton density have been measured and applied under various conditions to study the state of water in tissues and natural products. The fat and water content as well as their distribution have been determined by NMR methods. The shifts of the ATP spectral peaks may be applied to determine the functional state of an organ. In recent years a more significant innovation has emerged. The NMR signals, through mathematical manipulation have been successfully transformed into magnetic Resonance Images. It is very likely that, with the present rapid progress in instrumentation and computer engineering the magnetic resonance imaging (MRI) may supercede, in every aspect, those imaging modalities in current use. This paper describes briefly the theory of NMR and its applications in industries and medicine. Emphasis is given to the relationship between the relaxation times and the physical phenomena observed

407

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

408

NMR studies on irradiated lecithin systems  

International Nuclear Information System (INIS)

By means of NMR and UV spectroscopy we have examined the radiation damage of liposomes under different experimental conditions including an addition of a nitro compound as an effector with the aim to minimize the irradiation effects. (author)

409

33S NMR cryogenic probe for taurine detection  

Science.gov (United States)

With the goal of a S33 nuclear magnetic resonance (NMR) probe applicable to in vivo NMR on taurine-biological samples, we have developed the S33 NMR cryogenic probe, which is applicable to taurine solutions. The NMR sensitivity gain relative to a conventional broadband probe is as large as 3.5. This work suggests that improvements in the preamplifier could allow NMR measurements on 100 ?M taurine solutions, which is the level of sensitivity necessary for biological samples.

Hobo, Fumio; Takahashi, Masato; Maeda, Hideaki

2009-03-01

410

WeNMR: structural biology on the grid  

OpenAIRE

The WeNMR (http://www.wenmr.eu) project is an EU-funded international effort to streamline and automate structure determination from Nuclear Magnetic Resonance (NMR) data. Conventionally calculation of structure requires the use of various softwares, considerable user expertise and ample computational resources. To facilitate the use of NMR spectroscopy in life sciences the eNMR/WeNMR consortium has set out to provide protocolized services through easy-to-use web interfac...

Wassenaar, Tsjerk A.; Dijk, Marc; Loureiro-ferreira, Nuno; Schot, Gijs; Vries, Sjoerd J.; Schmitz, Christophe; Zwan, Johan; Boelens, Rolf; Giachetti, Andrea; Ferella, Lucio; Rosato, Antonio; Bertini, Ivano; Herrmann, Torsten; Jonker, Hendrik R. A.; Bagaria, Anurag

2011-01-01

411

Solid-state NMR spectroscopy on complex biomolecules  

OpenAIRE

Biomolecular applications of NMR spectroscopy are often merely associated with soluble molecules or magnetic resonance imaging. However, since the late 1970s, solid-state NMR (ssNMR) spectroscopy has demonstrated its ability to provide atomic-level insight into complex biomolecular systems ranging from lipid bilayers to complex biomaterials. In the last decade, progress in the areas of NMR spectroscopy, biophysics, and molecular biology have significantly expanded the repertoire of ssNMR spec...

Renault, M. A. M.; Cukkemane, A. A.; Baldus, M.

2010-01-01

412

NMR methods for fast data acquisition  

OpenAIRE

NMR spectroscopy has witnessed tremendous advancements in recent years with the development of new methodologies for structure determination and availability of high-field strength spectrometers equipped with cryogenic probes. Supported by these advancements, a new dimension in NMR research has emerged which aims to increase the speed with data is collected and analyzed. Several novel methodologies have been proposed in this direction. This review focuses on the principles on which these d...

Atreya, Hanudatta S.

2010-01-01

413

Spatially resolved 2D Laplace NMR  

OpenAIRE

Within the past decade, 2D Laplace nuclear magnetic resonance (NMR) has been proved to be a powerful method to investigate porous materials. However, it gives information only about integral characteristics of a given sample with regard to pore-size and pore connectivity. It is therefore desirable to combine MRI with 2D-Laplace NMR to generate information about fluid transport within defined areas of a sample. Spatially resolved D-T2 correlation maps were measured for four different samples: ...

Zhang, Yan

2014-01-01

414

NMR method of assay for gentamicin  

International Nuclear Information System (INIS)

Nuclear Magnetic Resonance (NMR) has been used successfully to assay gentamicin dosage forms. The method gives 100.5% accuracy with a variation of 2.3% for pure samples. It is a fast method of analysis. An assay which normally takes 14 or 18 hours by microbiological or ion exchange chromatographic methods respectively can now be performed in 30 minutes by the use of NMR. (author). 8 refs.; 3 tabs.; 1 fig

415

NMR of porous Bio-systems  

OpenAIRE

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 mo...

Snaar, E. J. M.

2002-01-01

416

Theoretical NMR correlations based Structure Discussion  

OpenAIRE

Abstract The constitutional assignment of natural products by NMR spectroscopy is usually based on 2D NMR experiments like COSY, HSQC, and HMBC. The actual difficulty of the structure elucidation problem depends more on the type of the investigated molecule than on its size. The moment HMBC data is involved in the process or a large number of heteroatoms is present, a possibility of multiple solutions fitting the same data set exists. A structure elucidation software can be used to ...

Junker Jochen

2011-01-01

417

Scalable NMR Spectroscopy with Semiconductor Chips  

OpenAIRE

Conventional nuclear magnetic resonance (NMR) spectrometers—the electronic brain that orchestrates and monitors nuclear spin motions—are bulky, expensive, thus, not scalable. In this thesis, we report on scalable 4-mm2 silicon spectrometer chips that perform a broad range of two-dimensional NMR spectroscopy—e.g., correlation spectroscopy, J-resolved spectroscopy, and heteronuclear quantum coherence spectroscopy—as well as one-dimensional spectroscopy and relaxometry. I...

Ha, Dongwan

2014-01-01

418

NMR Quantum Computation: a Critical Evaluation  

OpenAIRE

Liquid state nuclear magnetic resonance (NMR) techniques have produced some spectacular successes in the construction of small quantum computers, and NMR is currently by far the leading technology for quantum computation. There are, however, a number of significant problems with any attempt to scale up the technology to produce computers of any useful size. While it is probable that some of these will be successfully sidestepped during the next few years, it is unlikely that...

Jones, Ja

2000-01-01

419

beta-NMR of Palladium foil  

OpenAIRE

Beta-detected NMR (beta-NMR) of low-energy implanted Li-8(+) was studied in metallic palladium. The resonance was found to have a large negative shift with respect to the reference signal in the cubic insulator MgO. This shift exhibited significant temperature dependence on cooling below room temperature, approximately proportionate to the temperature-dependent spin susceptibility of pure Pd. Thus it is tentatively attributed to a Knight shift (K) caused by a large negative hyperfine coupling...

Parolin, Tj; Salman, Z.; Chakhalian, J.; Wang, D.; Keeler, Ta; Hossain, M.; Kiefl, Rf; Chow, Kh; Morris, Gd; Miller, Ri; Macfarlane, Wa

2006-01-01

420

NMR studies of organic polymorphs & solvates.  

OpenAIRE

This review article describes the applications of NMR to the study of polymorphs and related forms (solvates) of organic (especially pharmaceutical) compounds, for which it is of increasing academic and practical importance. The nature of the systems covered is briefly introduced, as are the techniques constituting solid-state NMR. The methodologies involved are then reviewed under a number of different headings, ranging from spectral editing through relaxation times to shielding tensors and ...

Harris, R. K.

2006-01-01

421

Annual Reports on NMR Spectroscopy. Volume 58  

OpenAIRE

A novel NMR technique for imaging materials exhibiting extremely short T2 relaxation times is described and some examples of its application to materials of scientific and industrial interest are presented. The technique employs continuous wave (CW) radiofrequency irradiation of the sample together with continual detection, and thus the experimental deadtime inherent in pulsed techniques is effectively eliminated. The mechanisms which broaden the NMR linewidths of materials in the solid state...

Fagan, Andrew John

2005-01-01

422

Carbon-13 NMR characterization of actinyl(VI) carbonate complexes in aqueous solution  

International Nuclear Information System (INIS)

The uranyl(VI) carbonate system has been re-examined using 13C NMR of 99.9% 13C-enriched UVIO2 (13CO3)34- in millimolar concentrations. By careful control of carbonate ion concentration, we have confirmed the existence of the trimer, and observed dynamic equilibrium between the monomer and the timer. In addition, the ligand exchange reaction between free and coordinated carbonate on PuVIO2(13CO3)34- and AmVIO2(13CO3)34- systems has been examined by variable temperature 13C NMR line-broadening techniques 13C NMR line-broadening techniques. A modified Carr-Purcell-Meiboom-Gill NMR pulse sequence was written to allow for experimental determination of ligand exchange parameters for paramagnetic actinide complexes. Preliminary Eyring analysis has provided activation parameters of ?Gdouble-dagger295 = 56 kJ/M, ?Hdouble-dagger = 38 kJ/M, and ?Sdouble-dagger = -60 J/M-K for the plutonyl triscarbonate system, suggesting an associative transition state for the plutonyl (VI) carbonate complex self-exchange reaction. Experiments for determination of the activation parameters for the americium (VI) carbonate system are in progress

423

NMR analysis of carbohydrate-binding interactions in solution: an approach using analysis of saturation transfer difference NMR spectroscopy.  

Science.gov (United States)

One of the most commonly used ligand-based NMR methods for detecting ligand binding is saturation transfer difference (STD) nuclear magnetic resonance (NMR) spectroscopy. The STD NMR method is an invaluable technique for assessing carbohydrate-lectin interactions in solution, because STD NMR can be used to detect weak ligand binding (Kd ca. 10(-3)-10(-8) M). STD NMR spectra identify the binding epitope of a carbohydrate ligand when bound to lectin. Further, the STD NMR method uses 1H-detected NMR spectra of only the carbohydrate, and so only small quantities of non-labeled lectin are required. In this chapter, I describe a protocol for the STD NMR method, including the experimental procedures used to acquire, process, and analyze STD NMR data, using STD NMR studies for methyl-?-D-galactopyranoside (?-Me-Gal) binding to the C-terminal domain of an R-type lectin from earthworm (EW29Ch) as an example. PMID:25117260

Hemmi, Hikaru

2014-01-01

424

27Al NMR/NQR studies of YbAl3C3  

International Nuclear Information System (INIS)

The phase transition at T*=80 K in YbAl3C3 has been studied by 27Al nuclear quadrupole resonance (NQR) measurement and nuclear magnetic resonance (NMR) measurement up to 30T. The NQR and NMR spectra reveal clear anomalies just below T*, which provides the first microscopic evidence for symmetry lowering in the low-temperature phase below T*. The transition is characterized by marked changes in the 27Al-NQR frequencies ?Q's without significant changes in the lattice parameters. The field dependence of the transition is also investigated. The NMR line exhibits field-induced rapid broadening below T*, which almost vanishes in zero field. Moreover, we found that T* increases by 10 K at 30T. These unique magnetic properties are consistent with the scheme that the microscopic mechanism underlying the phase transition involves Yb-4f electrons rather than the scheme of a simple structural phase transition. (author)

425

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

Directory of Open Access Journals (Sweden)

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.

Fang Fang

2009-11-01

426

63,65Cu NMR Method in a Local Field for Investigation of Copper Ore Concentrates  

Science.gov (United States)

To choose the most efficient method and ore beneficiation flow diagram, it is important to know physical and chemical properties of ore concentrates. The feasibility of application of the 63,65Cu nuclear magnetic resonance (NMR) method in a local field aimed at studying the properties of copper ore concentrates in the copper-iron-sulfur system is demonstrated. 63,65Cu NMR spectrum is measured in a local field for a copper concentrate sample and relaxation parameters (times T1 and T2) are obtained. The spectrum obtained was used to identify a mineral (chalcopyrite) contained in the concentrate. Based on the experimental data, comparative characteristics of natural chalcopyrite and beneficiated copper concentrate are given. The feasibility of application of the NMR method in a local field to explore mineral deposits is analyzed.

Gavrilenko, A. N.; Starykh, R. V.; Khabibullin, I. Kh.; Matukhin, V. L.

2015-01-01

427

A simulated annealing approach for solving zeolite crystal structures from two-dimensional NMR correlation spectra.  

Science.gov (United States)

An improved NMR crystallography strategy is presented for determining the structures of network materials such as zeolites from just a single two-dimensional (2D) NMR correlation spectrum that probes nearest-neighbor interactions, combined with the unit cell parameters and space group information measured in a diffraction experiment. The correlation information contained within a 2D spectrum is converted into a "connectivity matrix" which is incorporated into a cost function whose minimum is searched for using a simulated annealing algorithm. The algorithm was extensively tested on over 150 zeolite frameworks from the International Zeolite Association database of zeolite structures and shown to be very robust and efficient in reconstructing the structures from connectivity information. The structure determination of the pure silica zeolites ITQ-4, Ferrierite, and Sigma-2 from experimental 2D (29)Si double-quantum NMR spectra and powder X-ray diffraction data using this improved approach is also presented. PMID:25466355

Brouwer, Darren H; Horvath, Matthew

2014-10-29

428

A new de-noising method of NMR FID signals based on wavelet transform  

International Nuclear Information System (INIS)

Taking aim at the de-noising of clinical NMR FID signals, the paper analyzes the wavelet transform characteristic of available signals and noises separately based on wavelet transform technology. With the principles of three de-noising methods wavelet-based, wavelet transform modulus maxima, threshold shrinkage, and translation invariance. Effective solutions for selecting method of wavelet basis function, optimized thresholding function and wavelet decomposing parameters are put forward, so as the distinguishing method between signals and noises. Taking brain gliomas as an example, the paper implements effective experimental solutions based on the wavelet transform de-noising technology. About 30 clinical NMR data obtained from the NMR devices have been de-noised to provide high quality data and validated the new method. (authors)

429

Residual broadening in high-resolution NMR of quadrupolar nuclei in solids  

CERN Document Server

amorphous materials. The spectra of these compounds show significant additional broadening due to the presence of distributions of chemical shift and quadrupolar parameters. A lineshape-fitting routine is proposed, tested and applied to obtain quantitative estimates of these distributions in the sup 2 sup 7 AI MQMAS NMR spectra of a series of amorphous aluminosilicate compounds. Solid-state NMR spectra of quadrupolar nuclei are often poorly resolved due to the presence of anisotropic second-order quadrupolar broadening, even under conventional magic angle spinning (MAS) conditions. The two-dimensional multiple-quantum MAS (MQMAS) experiment is one of several techniques which have been designed to remove this broadening and provide high-resolution NMR spectra of half-integer quadrupolar nuclei. This thesis demonstrates that, in the absence of this pure quadrupolar broadening, it is possible to observe a weak quadrupolar-dipolar interaction which also survives conventional MAS and is the result of dipolar coupl...

McManus, J

2001-01-01

430

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

Directory of Open Access Journals (Sweden)

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.

Karl-Heinz Böhm

2014-04-01

431

Optically detected NMR of optically hyperpolarized 31P neutral donors in 28Si  

CERN Document Server

The electron and nuclear spins of the shallow donor 31P are promising qubit candidates invoked in many proposed Si-based quantum computing schemes. We have recently shown that the near-elimination of inhomogeneous broadening in highly isotopically enriched 28Si enables an optical readout of both the donor electron and nuclear spins by resolving the donor hyperfine splitting in the near-gap donor bound exciton transitions. We have also shown that pumping these same transitions can very quickly produce large electron and nuclear hyperpolarizations at low magnetic fields, where the equilibrium electron and nuclear polarizations are near zero. Here we show preliminary results of the measurement of 31P neutral donor NMR parameters using this optical nuclear hyperpolarization mechanism for preparation of the 31P nuclear spin system, followed by optical readout of the resulting nuclear spin population after manipulation with NMR pulse sequences. This allows for the observation of single-shot NMR signals with very hi...

Steger, M; Yang, A; Saeedi, K; Hayden, M E; Thewalt, M L W; Itoh, K M; Riemann, H; Abrosimov, N V; Becker, P; Pohl, H -J

2010-01-01

432

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

Directory of Open Access Journals (Sweden)

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.

David Ortegón-Reyna

2013-12-01

433

NMR structural study of the prototropic equilibrium in solution of Schiff bases as model compounds.  

Science.gov (United States)

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. PMID:24384925

Ortegón-Reyna, David; Garcías-Morales, Cesar; Padilla-Martínez, Itzia; García-Báez, Efren; Aríza-Castolo, Armando; Peraza-Campos, Ana; Martínez-Martínez, Francisco

2013-01-01

434

Probing acid-amide intermolecular hydrogen bonding by NMR spectroscopy and DFT calculations  

Science.gov (United States)

Benzene carboxylic acids and benzamide act as their self-complement in molecular recognition to form inter-molecular hydrogen bonded dimers between amide and carboxylic acid groups, which have been investigated by 1H, 13C and 15N NMR spectroscopy. Extensive NMR studies using diffusion ordered spectroscopy (DOSY), variable temperature 1D, 2D NMR, established the formation of heterodimers of benzamide with benzoic acid, salicylic acid and phenyl acetic acid in deuterated chloroform solution. Association constants for the complex formation in the solution state have been determined. The results are ascertained by X-ray diffraction in the solid state. Intermolecular interactions in solution and in solid state were found to be similar. The structural parameters obtained by X-ray diffraction studies are compared with those obtained by DFT calculations.

Chaudhari, Sachin Rama; Suryaprakash, N.

2012-05-01

435

A simple method for analyzing 51V solid-state NMR spectra of complex systems.  

Science.gov (United States)

Five vanadium complexes as models for biological systems were investigated using (51)V-MAS-NMR spectroscopy. All spectra show an uncommon line shape, which can be attributed to a shorter relaxation time of the satellite transition in contrast to the central one. A method for the reliable analysis of such kind of spectra is presented for the first time and the most important NMR parameters of the investigated complexes (quadrupolar coupling constant C(Q), asymmetry of the EFG tensor ?(Q), isotropic chemical shift ?(iso), chemical shift anisotropy ?(?) and asymmetry of the CSA tensor ?(?)) are presented. These results are of particular importance with respect to the analysis of the (51)V-MAS-NMR spectra of vanadium moieties in biological matrices such as vanadium chloroperoxidase, which show hitherto unexplained low intensity of the satellite sideband pattern. PMID:21601435

Fenn, Annika; Wächtler, Maria; Breitzke, Hergen; Buchholz, Axel; Lippold, Ines; Plass, Winfried; Buntkowsky, Gerd

2011-09-01

436

NMR Studies on the Internal Structure of High-Tc Superconductors and Other Anorganic Compounds  

International Nuclear Information System (INIS)

Spatially-resolved NMR is used to probe internal structures in highly correlated superconductors of optimally-doped Tl2Ba2CuO6+? (Tc 85 K) and a heavy fermion superconductor CeCoIn5 (Tc = 2.3 K). The characteristic change of the properties of 205Tl-NMR in the vortex state provides a clear evidence of the antiferromagnetic order in the vortex cores below 20 K in Tl2Ba2CuO6+?. We also obtain anomalous 115In-NMR spectra of CeCoIn5, which provides a microscopic evidence for the occurrence of a spatially-modulated superconducting order parameter expected in a Fulde-Ferrel-Larkin-Ovchinnkov (FFLO) state.

437

Zero field NMR and NQR  

International Nuclear Information System (INIS)

Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field. Comparison is made to previous frequency domain and high field methods. A general density operator formalism is given for the experiments where the evolution period is initiated by a sudden switching to zero field and is terminated by a sudden restoration of the field. Analytical expressions for the signals are given for a variety of simple dipolar and quadrupolar systems and numerical simulations are reported for up to six coupled spin-1/2 nuclei. Experimental results are reported or reviewed for 1H, 2D, 7Li, 13C, and 27Al nuclei in a variety of polycrystalline materials. The effects of molecular motion and bodily sample rotation are described. Various extensions of the method are discussed, including demagnetized initial conditions and correlation by two-dimensional Fourier transformation of zero field spectra with themselves or with high field spectra

438

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.)

439

Natural attenuation of oil spills in Patagonian soils. Characterization by 1H NMR spectroscopy.  

Science.gov (United States)

The natural attenuation of oil spill contaminated soils, with different exposure times, in Patagonian environment was evaluated by the use of several parameters to quantify the degree of changes in the composition. Column (CC) and gas chromatography (GC); UV-visible and 1H NMR techniques were used to determine compositional and structural indexes. The results show that the nC18/Phytane GC index, that was 1.5 for crude oil, decreased with exposure time to values between 0.97-0.17 in the residues. The percentages for the four aliphatic (H1-H4) and the aromatic (H(A)), proton types, determined by 1H NMR, were: 12.9-34.4 (H1), 43.3-60.2 (H2), 4.24-24.2 (H), 1.33-17.9 (H4), and 0.44-4.81 (HA), in crude oil and residues, respectively. Furthermore, the characterization of significant 1H NMR signals indicated the presence of carboxylic acid hydrogens in the polar fraction of the crude oil and of residues of two years age. The Principal Components Analysis (PCA) of the parameters determined by CC, GC and NMR showed that the first three principal components (1st, 2nd, and 3 rd PC), accounted for more than 84% of variance. The 1st PC is largely influenced by H, H,, H, H, and the nC,,/Phytane GC parameter, in the order given. The evaluation of the different parameters by PCA suggests that 1H NMR is more useful than GC to evaluate the degree of the chemical transformations of oil spills in soils PMID:18610542

Ríos, S M; Nudelman, N S

2008-01-01

440

Experimental and calculated 1H, 13C and 31P NMR spectra of (hydroxypyridin-3-yl-methyl)phosphonic acid  

Science.gov (United States)

(Hydroxypyridin-3-yl-methyl)phosphonic acid named also 3-pyridylmethyl(hydroxy)-phosphonic acid, MC5, is biologically active compound and exhibits metal binding ability attributable to the presence of the phosphonic group and the pyridine nitrogen. Its proton NMR data have been previously reported, only. Thus, in this work we offer interpretation of 1H, 13C and 31P NMR spectra of this compound dissolved in D 2O in the pD range between 1.5 and 9.0. Additionally, to support our interpretation of the obtained data, we calculated NMR spectra of all expected forms that are the result of consecutive deprotonation of MC5. Theoretical calculations of the NMR spectra as well as structural parameters of the compounds (cation, zwitteranion, and two anions) were performed at the B3PW91 level with the 6-311G** and 6-311++G**basis sets.

Chruszcz, Katarzyna; Bara?ska, Ma?gorzata; Czarniecki, Krzysztof; Proniewicz, Leonard M.

2003-06-01

441

Effective chiral-spin Hamiltonian for odd-numbered coupled Heisenberg chains  

International Nuclear Information System (INIS)

An L x ? system of odd number of coupled Heisenberg spin chains is studied using a degenerate perturbation theory, where L is the number of coupled chains. An effective chain Hamiltonian is derived explicitly in terms of two spin half degrees of freedom of a closed chain of L sites, valid in the regime the inter-chain coupling is stronger than the intra-chain coupling. The spin gap has been calculated numerically using the effective Hamiltonian for L = 3,5,7,9 for a finite chain up to ten sites. It is suggested that the ground state of the effective Hamiltonian is correlated, by examining various variational trial states for the effective-spin chain Hamiltonian. (author). 11 refs, 1 fig., 1 tab

442

Spin Hamiltonian of the Highly Frustrated Gd3Ga5O12 Garnet Antiferromagnet  

CERN Document Server

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.

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

2005-01-01

443

Investigation of ferroelectric nanostructured systems by ESR and NMR methods  

International Nuclear Information System (INIS)

Full text: The theoretical and experimental investigation of ferroelectric nanopowders is performed. Since the most prominent size effect in ferroelectric nanomaterials was known to be size driven ferroelectric-paraelectric phase transition at some critical particle size R = Rcr the study of this effect manifestation in radiospectroscopy spectra was the main goal of the paper. In the theoretical part, the size effect of the parameters of the central transition +1/2 -1/2 lines which are known to be the most intensive for powder sample both in ESR and NMR are considered for the materials with ferroelectric tetragonal phase at room temperature and cubic paraelectric phase in the bulk. Therefore the transformation of axial symmetry spectra into cubic symmetry ones can be expected at R ? Rcr. For this transformation description the spontaneous polarization inhomogeneity inside a particle and distribution of particle sizes calculated previously were taken into account. Both these factors lead to inhomogeneous broadening of the lines. In ESR spectra the transformation of the spectra from axial symmetry to cubic symmetry lines was obtained with decreasing of nanoparticle sizes with practically complete disappearance of axial spectra at R ? Rcr. The method of Rcr value extraction from the ratio of the different symmetry spectra intensities was proposed. Size effect in NMR spectra for nuclei with quadrupole moments was consideei with quadrupole moments was considered, i.e. +1/2 -1/2 transition perturbed by second order quadrupole interaction of the nuclei with electric field gradient was calculated. Allowing for the absence of cubic symmetry in the vicinity of surface even in paraelectric phase, namely at R ? Rcr (P = 0), we described this size effect in core and shell model. Measurements of Fe3+ ESR spectra and 137Ba NMR spectra in nanopowder of BaTiO3 were carried out. The samples were prepared by rate-controlled method. Laser granulometry method analysis had shown that the particles sizes are distributed around two maxima with R bar ? 160 nm and R bar ? 40 nm. The decrease of intensity of axial symmetry ESR lines of Fe3+ and appearance of cubic symmetry line was observed with the average sizes decrease with complete disappearance of axial spectra at R bar ? 40 nm. NMR spectra practically did not change in all the samples although the essential narrowing of the line was expected at R ? Rcr. The comparison of the theory with experiment was carried out. The theory fits experimental data pretty good. The value of critical size Rcr ? 40 nm was extracted from ESR data. The asymmetry and broadening of right hand side shoulder of ESR cubic symmetry line was shown to be related to contribution of paramagnetic centers in the vicinity of the particles surface with lower than cubic symmetry. Such type of contribution to NMR line can be the main reason of absence of the pronounced size effect, namely the narrowing of the line, in NMR spectra of nuclei with quadrupole mechanism that defined the spectra main characteristics. The nuclei with chemical shift mechanism can be more sensitive for size effect investigations by NMR method. (author)

444

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

Science.gov (United States)

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…

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

2009-01-01

445

Gallium doped in armchair and zigzag models of boron phosphide nanotubes (BPNTs): A NMR study  

International Nuclear Information System (INIS)

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.

446

NMR-CT of craniocerebral trauma  

International Nuclear Information System (INIS)

The rapid development of NMR imaging has been documented by many recent reports, but there have been fewer clinical studies. We applied NMR-CT to craniocerebral disease from July, 1983; our preliminary results are presented here. The device operates with a main magnetic field of 0.1T produced by the surrounding magnet. The data-accumulating time for protons and the T1 image was 4 minutes, while that of the IR image was 2 minutes. X-ray CT was performed with GE CT/T. Six patients with craniocerebral traumas were imaged with both NMR-CT and X-ray CT on the same day. A proton image, a T1 image, and an IR image were obtained and then compared with the image of the X-ray CT. All of the pathological changes in the brain were made visible by the NMR-CT. In some cases, the NMR-CT was more useful than the X-ray CT in demonstrating craniocerebral traumas. The advantages of the NMR-CT over the X-ray CT were as follows: a) the absence of bone artifacts, and b) important information for diagnosis could be obtained by measuring the T1 value. However, very small lesions were not clearly visible, and the data-accumulating time was longer than in the case of the X-ray CT. Much more clinical evaluation is required, but NMR-CT seems to be becoming a very important technique for craniocerebral traumas. (author)

447

NMR studies of phase behaviour in polyacrylonitrile solutions  

International Nuclear Information System (INIS)

The aim of the thesis was to study the phase behaviour of aqueous polyacrylonitrile/NaSCN solutions using a variety of nuclear magnetic resonance techniques. Polyacrylonitrile (PAN) is the basis of the acrylic fibre industry, as such fibres contain at least 85% PAN. Despite this industrial importance, the available literature describing the phase behaviour of PAN in solution is far from comprehensive. Bulk 1H NMR relaxation measurements were carried out over a wide range of concentrations and temperatures to probe the molecular dynamics of the PAN and water molecules. The relaxation data was found to be biexponential decay for all samples, the relative amplitudes of which were shown to be equal to the ratio of PAN protons to water protons. Both species were found to be in the regime of rapid molecular motion. Bulk 1H NMR self diffusion measurements, using the PFGSTE technique, exhibited a bi-exponential decay of the echo amplitudes. By careful selection of the observation time, ?, it was possible to independently probe the water and PAN translational diffusion. A background gradient, resulting from inhomogeneities of the magnetic field, complicated the analysis of the data and a novel polynomial least squares fitting procedure was devised to overcome this effect. The measured attenuation of the water diffusion coefficients (D?10-6-10-5cm2s-1) with increasing PAN volume fraction was modelled according volume fraction was modelled according to various theories, including free volume and scaling laws. The study of the PAN diffusion coefficient (D?10-7-10-6cm2s-1) was limited by the experimental constraints of the NMR spectrometer. A 1H NMR one-dimensional imaging technique was used to study the non-solvent induced phase separation (coagulation) of a PAN solution. The time dependence of the measured profiles allowed observation of the coagulation process. A diffusion model was developed to fit the experimental data using a semi-infinite diffusion framework. The fitting parameters represented the diffusion coefficients of the water molecules in the solution /coagulated PAN network, and in the bulk non-solvent /solvent. PAN films were cast at a range of temperatures in non-solvent baths. This was a scaling up of the dimensions of the fibre spinning process and was used to investigate the range of morphologies which can be formed in the wet-spinning of acrylic fibres. Before any drying processes, water molecules were confined in the porous structure of the saturated films, and their NMR relaxation and self diffusion behaviour was investigated. Parameters describing the pore size and the tortuosity were derived from these studies and scanning electron microscopy was used as a comparative technique. The pore sizes predicted from the NMR data span a smaller spatial range than those observed from SEM. This is explained by the fundamental differences between the two techniques. (author)

448

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

Science.gov (United States)

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.

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

449

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

Science.gov (United States)

Twenty-four samples of heroin from different illicit drug seizures were analyzed using proton Nuclear Magnetic Resonance ((1)H NMR) and two-dimensional diffusion-ordered spectroscopy (2D DOSY) (1)H NMR. A careful assignment and quantification of (1)H signals enabled a comprehensive characterization of the substances present in the samples investigated: heroin, its main related impurities (6-acetylmorphine, acetylcodeine, morphine, noscapine and papaverine) and cutting agents (caffeine and acetaminophen in nearly all samples as well as lactose, lidocaine, mannitol, piracetam in one sample only), and hence to establish their spectral signatures. The good agreement between the amounts of heroin, noscapine, caffeine and acetaminophen determined by (1)H NMR and gas chromatography, the reference method in forensic laboratories, demonstrates the validity of the (1)H NMR technique. In this paper, 2D DOSY (1)H NMR offers a new approach for a whole characterization of the various components of these complex mixtures. PMID:24378299

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

2014-01-01

450

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)

451

Stacked planar micro coils for single-sided NMR applications  

Science.gov (United States)

This paper describes planar micro structured coils fabricated in a novel multilayer assembly for single-sided NMR experiments. By arranging the coil's turns in both lateral and vertical directions, all relevant coil parameters can be tailored to a specific application. To this end, we implemented an optimization algorithm based on simulations applying finite element methods (FEMs), which maximizes the coil's sensitivity and thus signal-to-noise ratio (SNR) while incorporating boundary conditions such as the coil's electrical properties and a localized sensitivity needed for single-sided applications. Utilizing thin-film technology and microstructuring techniques, the planar character is kept by a sub-millimeter overall thickness. The coils are adapted to the Profile NMR-MOUSE® magnet with a homogeneous slice of about 200 ?m in height and a uniform depth gradient of about 20 T/m. The final design of a coil with 20 turns, separated in four layers with five turns each, and an outer dimension of 4 × 4 mm2 is able to measure a sample volume almost five times smaller than that of a state-of-the-art 14 × 16 mm2 Profile NMR-MOUSE® coil with the same SNR. This allows for volume-limited measurements with high SNR and enables different future developments. The minimal dead time of 4 ?s facilitates further improvements of the SNR by echo adding techniques and the characterization of samples with short T2 relaxation times. Measurements on solid polymers like polyethylene (PE) and polypropylene (PP) with T2 components as short as 200 ?s approve the overall beneficial coil properties. Furthermore the ability to perform depth profiling with microscopic resolution is demonstrated.

Watzlaw, Jan; Glöggler, Stefan; Blümich, Bernhard; Mokwa, Wilfried; Schnakenberg, Uwe

2013-05-01

452

Variable-temperature NMR and conformational analysis of oenothein B  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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.

Suzana C., Santos; Ariadne G., Carvalho; Gilmara A. C., Fortes; Pedro H., Ferri; Anselmo E. de, Oliveira.

2014-02-01

453

Measuring the contrast-enhancement in the skin and subcutaneous fatty tissue with the NMR-Mouse registered: a feasibility study  

International Nuclear Information System (INIS)

Purpose: the NMR-Mouse registered is an open and mobile sensor for measuring NMR relaxation parameters in organic matters. T1-measurements of the subcutaneous fatty tissue and the skin are reported. Material and method: for the first time, the NMR-Mouse registered was employed to measure the signal recovery following saturation of the skin and the subcutaneous fatty tissue of three patients, before and after administering a contrast agent. Results: despite a low signal-to-noise ratio, changes in the relaxation behaviour of the skin could be detected. Malignant tissue exhibits faster signal recovery than scar tissue and healthy tissue, which only show a small difference. Conclusions: changes in the relaxation behavior can be monitored with the NMR-Mouse registered. Before the clinical use of the NMR-Mouse, sensitivity, sensor mounting device, and sensor tuning must be improved. Further investigations need to be performed on a statistically relevant number of patients. (orig.)

454

Rotational dynamics in a crystalline molecular gyroscope by variable-temperature 13C NMR, 2H NMR, X-ray diffraction, and force field calculations.  

Science.gov (United States)

A combination of solid-state 13C CPMAS NMR, 2H NMR, X-ray-determined anisotropic displacement parameters (ADPs), and molecular mechanics calculations were used to analyze the rotational dynamics of 1,4-bis[3,3,3-tris(m-methoxyphenyl)propynyl]benzene (3A), a structure that emulates a gyroscope with a p-phenylene group acting as a rotator and two m-methoxy-substituted trityl groups acting as a stator. The line shape analysis of VT 13C CPMAS and broad-band 2H NMR data were in remarkable agreement with each other, with rotational barriers of 11.3 and 11.5 kcal/mol, respectively. The barriers obtained by analysis of ADPs obtained by single-crystal X-ray diffraction at 100 and 200 K, assuming a sinusoidal potential, were 10.3 and 10.1 kcal, respectively. A similar analysis of an X-ray structure solved from data acquired at 300 K suggested a barrier of only 8.0 kcal/mol. Finally, a rotational potential calculated with a finite cluster model using molecular mechanics revealed a symmetric but nonsinusoidal potential that accounts relatively well for the X-ray-derived values and the NMR experimental results. It is speculated that the discrepancy between the barriers derived from low and high-temperature X-ray data may be due to an increase in anharmonicity, or to disorder, at the higher temperature values. PMID:17243820

Khuong, Tinh-Alfredo V; Dang, Hung; Jarowski, Peter D; Maverick, Emily F; Garcia-Garibay, Miguel A

2007-01-31

455

NMR methodologies in the analysis of blueberries.  

Science.gov (United States)

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

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

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