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Sample records for 7li nmr spectra

  1. Quadrupolar transients, cosine correlation functions, and two-dimensional exchange spectra of non-selectively excited spin-3/2 nuclei: A 7Li NMR study of the superionic conductor lithium indium phosphate

    NASA Astrophysics Data System (ADS)

    Storek, M.; Böhmer, R.

    2015-11-01

    Cos-cos stimulated echoes of non-selectively excited spin-3/2 nuclei were not exploited in studies of slow motional processes in solids and solid-like samples, so far. Based on a theoretical analysis of the quadrupolar transients which hitherto obviously precluded the application of such echoes, their utility is demonstrated for the example of 7Li NMR on the polycrystalline fast ion conductor lithium indium phosphate. Quadrupolar transients can adversely affect the shape of two- and three-pulse echo spectra and strategies are successfully tested that mitigate their impact. Furthermore, by means of suitably adapted cos-cos echo sequences an effective suppression of central-line contributions to the NMR spectra is achieved. By combining cos-cos and sin-sin datasets static two-dimensional exchange spectra were recorded that display quadrupolarly modulated off-diagonal intensity indicative of ionic motion.

  2. 7Li NMR study of normal human erythrocytes

    NASA Astrophysics Data System (ADS)

    Pettegrew, J. W.; Post, J. F. M.; Panchalingam, K.; Withers, G.; Woessner, D. E.

    The biological action of lithium is of great interest because of the therapeutic efficacy of the cation in manic-depressive illness. To investigate possible molecular interactions of lithium, 7Li NMR studies were conducted on normal human erythrocytes which had been incubated with lithium chloride. The uptake of lithium ions was followed by 7Li NMR, using a dysprosium, tripolyphosphate shift reagent. Lithium uptake followed single-exponential kinetics with a time constant of 14.7 h. The intracellular lithium relaxation times were T 1 ⋍ 5 s and T 2 ⋍ 0.15 s, which implies a lengthening of the lithium correlation time. It was found that lithium does not interact significantly with hemoglobin, the erythrocyte membrane, or artificial phospholipid membranes. Based on measurements of lithium T1 and T2 in concentrated agar gels, the large difference between T1 and T2 for intracellular lithium ions may be due to diffusion of the hydrated lithium ion through heterogeneous electrostatic field gradients created by the erythrocyte membrane-associated cytoskeletal network. Lithium binding to the membrane-associated cytoskeleton, however, cannot be ruled out. Because of the large differences between T1 and T2 of intracellular lithium ions, 1Li NMR may be a sensitive and promising noninvasive method to probe the intracellular environment.

  3. Lithium Visibility in Rat Brain and Muscle in Vivoby 7Li NMR Imaging

    NASA Astrophysics Data System (ADS)

    Komoroski, Richard A.; Pearce, John M.; Newton, Joseph E. O.

    1998-07-01

    The apparent concentration of lithium (Li)in vivowas determined for several regions in the brain and muscle of rats by7Li NMR imaging at 4.7 T with inclusion of an external standard of known concentration and visibility. The average apparent concentrations were 10.1 mM for muscle, and 4.2-5.3 mM for various brain regions under the dosing conditions used. The results were compared to concentrations determinedin vitroby high-resolution7Li NMR spectroscopy of extracts of brain and muscle tissue from the same rats. The comparison provided estimates of the7Li NMR visibility of the Li cation in each tissue region. Although there was considerable scatter of the calculated visibilities among the five rats studied, the results suggested essentially full visibility (96%) for Li in muscle, and somewhat reduced visibility (74-93%) in the various brain regions.

  4. Report for in-situ 7Li NMR experiment in PNNL Phase -1

    SciTech Connect

    Hu, Jian Zhi

    2014-08-19

    To understand the detailed local structural evolution, an in-situ 7Li NMR study was performed. An operando identification of the lithium germanide phases under various cycling regimens permitted understanding of the kinetics of phase transition between different structural phases, including the amorphous phases, and how these correlated with capacity retention. Combining data from TEM and in-situ 7Li NMR, we discovered that the phase inter-conversion during cycling was mediated by co-existing amorphous and crystalline phases, and that the high capacity observed was correlated with an over-lithiated lithium germanide phase.

  5. Localization of vacancies and mobility of lithium ions in Li2ZrO3 as obtained by 6,7Li NMR

    NASA Astrophysics Data System (ADS)

    Baklanova, Ya. V.; Arapova, I. Yu.; Buzlukov, A. L.; Gerashenko, A. P.; Verkhovskii, S. V.; Mikhalev, K. N.; Denisova, Т. А.; Shein, I. R.; Maksimova, L. G.

    2013-12-01

    The 6,7Li NMR spectra and the 7Li spin-lattice relaxation rate were measured on polycrystalline samples of Li2ZrO3, synthesized at 1050 K and 1300 K. The 7Li NMR lines were attributed to corresponding structural positions of lithium Li1 and Li2 by comparing the EFG components with those obtained in the first-principles calculations of the charge density in Li2ZrO3. For both samples the line width of the central 7Li transition and the spin-lattice relaxation time decrease abruptly at the temperature increasing above ~500 K, whereas the EFG parameters are averaged (<νQ>=42 (5) kHz) owing to thermally activated diffusion of lithium ions.

  6. Localization of vacancies and mobility of lithium ions in Li{sub 2}ZrO{sub 3} as obtained by {sup 6,7}Li NMR

    SciTech Connect

    Baklanova, Ya. V.; Arapova, I. Yu.; Buzlukov, A.L.; Gerashenko, A.P.; Verkhovskii, S.V.; Mikhalev, K.N.; Denisova, T.A.; Shein, I.R.; Maksimova, L.G.

    2013-12-15

    The {sup 6,7}Li NMR spectra and the {sup 7}Li spin–lattice relaxation rate were measured on polycrystalline samples of Li{sub 2}ZrO{sub 3}, synthesized at 1050 K and 1300 K. The {sup 7}Li NMR lines were attributed to corresponding structural positions of lithium Li1 and Li2 by comparing the EFG components with those obtained in the first-principles calculations of the charge density in Li{sub 2}ZrO{sub 3}. For both samples the line width of the central {sup 7}Li transition and the spin–lattice relaxation time decrease abruptly at the temperature increasing above ∼500 K, whereas the EFG parameters are averaged (〈ν{sub Q}〉=42 (5) kHz) owing to thermally activated diffusion of lithium ions. - Graphical abstract: Path of lithium ion hopping in lithium zirconate Li{sub 2}ZrO{sub 3}. - Highlights: • Polycrystalline samples Li{sub 2}ZrO{sub 3} with monoclinic crystal structure synthesized at different temperatures were investigated by {sup 6,7}Li NMR spectroscopy. • Two {sup 6,7}Li NMR lines were attributed to the specific structural positions Li1 and Li2. • The distribution of vacancies was clarified for both lithium sites. • The activation energy and pathways of lithium diffusion in Li{sub 2}ZrO{sub 3} were defined.

  7. Investigations of Li-containing SiCN(O) ceramics via 7Li MAS NMR.

    PubMed

    Gumann, Sina; Nestle, Nikolaus; Liebau-Kunzmann, Verena; Riedel, Ralf

    2007-04-01

    Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20 with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400 degrees C in argon (DeltaT=200 degrees C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting SiCN(O):Li ceramics were basically amorphous up to temperatures of 1000 degrees C and formed LiSi(2)N(3), graphite and silicon carbide as crystalline phases at higher temperatures. (7)Li MAS NMR spectroscopy was carried out to investigate the structure of the Li-containing phases and to study the reaction path of metallic Li with polysilazane. Based on the NMR spectra, there is almost no difference found in the chemical shift of the SiCN(O):Li ceramics obtained at different temperatures. Accordingly, Li is assigned to be mainly coordinated to N and O present as contaminant element. Relaxation time measurements showed that the most mobile Li(+) species seems to be present in the product obtained in the pyrolysis temperature range between 600 and 1000 degrees C. PMID:17418540

  8. 7Li double quantum filtered NMR and multinuclear relaxation rates of clay suspensions: the effect of clay concentration and nonionic surfactants

    PubMed

    Grandjean; Robert

    1999-05-01

    7Li double quantum NMR spectra were used to investigate ordering process of synthetic Li+-saponites dispersed in water. Synthetic clays suspended in aqueous solutions of poly(ethylene glycol) monoalkyl ethers were also studied by 7Li, 23Na, and 13C NMR techniques. The strongest surfactant-Li+-saponite interaction occurs with the lowest charged clay. Laponite interacts more strongly with organic molecules than does a similarly charged saponite. The number of oxyethylene units rather than the chain length seems to govern the solid-surfactant interaction. Copyright 1999 Academic Press. PMID:10329224

  9. Supertransferred hyperfine fields at {sup 7}Li: Variable temperature {sup 7}Li NMR studies of LiMn{sub 2}O{sub 4}-based spinels

    SciTech Connect

    Gee, B.; Horne, C.R.; Cairns, E.J.; Reimer, J.A. |

    1998-12-10

    The temperature dependence of the {sup 7}Li NMR shift was measured for LiMn{sub 2}O{sub 4}, LiMn{sub 2{minus}y}Ni{sub y}O{sub 4} (y = 0.1, 0.25, 0.33), LiMn{sub 2{minus}y}Co{sub y}O{sub 4} (y = 0.25, 0.5, 1.0), Li[Mn{sub 2{minus}y}Li{sub y}]O{sub 4} (y = 0.1, 0.33), and {lambda}-MnO{sub 2} spinel oxides. The {sup 7}Li NMR shift can be separated into temperature-independent and -dependent components. The temperature-dependent shift follows the Curie-Weiss behavior of the bulk magnetic susceptibility. The temperature-independent shift is attributed to contributions from van Vleck and diamagnetic susceptibilities. Pauli susceptibility may also contribute to the temperature-independent shift in the nickel- and cobalt-substituted spinels. Supertransferred hyperfine (STH) coupling constants were derived from the {sup 7}Li NMR shifts and bulk magnetic susceptibility data. The progressive increase in average nominal manganese oxidation state from +3.5 to +4 results in an increase in the supertransferred hyperfine field at the {sup 7}Li nucleus in the lithium-substituted samples. Replacement of manganese by either cobalt or nickel also results in a larger STH field at the {sup 7}Li nuclei. The increase in STH field for the lithium-, nickel-, and cobalt-substituted spinel oxides may arise from a greater covalence in these materials relative to the parent LiMn{sub 2}O{sub 4} spinel oxide.

  10. Solid-state 23Na and 7Li NMR investigations of sodium- and lithium-reduced mesoporous titanium oxides.

    PubMed

    Lo, Andy Y H; Schurko, Robert W; Vettraino, Melissa; Skadtchenko, Boris O; Trudeau, Michel; Antonelli, David M

    2006-02-20

    Mesoporous titanium oxide synthesized using a dodecylamine template was treated with 0.2, 0.6, and 1.0 equiv of Li- or Na-naphthalene. The composite materials were characterized by nitrogen adsorption, powder X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis, and solid-state 23Na and 7Li NMR spectroscopy. In all cases the wormhole mesoporosity was retained as evidenced by BET surface areas from 400 to 700 m(2)/g, Horvath-Kawazoe pore sizes in the 20 Angstroms range, and a lack of hysteresis in the nitrogen adsorption isotherms. Variable-temperature conductivity studies show that the Li-reduced materials are semiconductors, with conductivity values 3 orders of magnitude higher than those of the Na-reduced materials. Electrochemical measurements demonstrate reversible intercalation/deintercalation of Li+ ions into pristine mesoporous Ti oxides with good cycling capacity. Solid-state 23Na NMR reveals two distinct Na environments: one corresponding to sodium ions in the mesoporous channels and the other corresponding to sodium ions intercalated into the metal framework. 23Na NMR spectra also indicate that the relative population of the framework site increases with increased reduction levels. Solid-state 7Li NMR spectra display a single broad resonance, which increases in breadth with increased reduction levels, though individual resonances inferring the presence of channel and framework Li species are not resolved. Comparisons of the lithium chemical shifts with published values suggests an "anatase-like structure" with no long-range order in the least-reduced samples but a "lithium titanate-like structure" with no long-range order in the higher reduced materials. PMID:16472000

  11. (7)Li in situ 1D NMR imaging of a lithium ion battery.

    PubMed

    Klamor, S; Zick, K; Oerther, T; Schappacher, F M; Winter, M; Brunklaus, G

    2015-02-14

    The spatial distribution of charge carriers in lithium ion batteries during current flow is of fundamental interest for a detailed understanding of transport properties and the development of strategies for future improvements of the electrolyte-electrode interface behaviour. In this work we explored the potential of (7)Li 1D in situ NMR imaging for the identification of concentration gradients under constant current load in a battery cell. An electrochemical cell based on PTFE body and a stack of glass microfiber discs that are soaked with a technically relevant electrolyte suitable for high-temperature application and squeezed between a Li metal and a nano-Si-graphite composite electrode was assembled to acquire (7)Li 1D in situ NMR profiles with an improved NMR pulse sequence as function of time and state of charge, thereby visualizing the course of ion concentration during charge and discharge. Surface localized changes of Li concentration were attributed to processes such as solid electrolyte interphase formation or full lithiation of the composite electrode. The method allows the extraction of lithium ion transport properties. PMID:25578436

  12. {sup 7}Li NMR study of poly(p-phenylene) electrochemically doped with lithium

    SciTech Connect

    Shteinberg, V.G.; Shumm, B.A.; Zueva, A.F.

    1994-09-01

    Lithium ions in electrochemically doped poly(p-phenylene) (PPP) were studied by {sup 7}Li NMR. Two types of lithium cations exhibiting different mobility are found to exist. The fraction of more mobile cations increases with temperature but does not exceed 0.5. In the PPP{sup -}-Li{sup +} system, ion mobility is considerably lower than that found in the previously studied PPP{sup +}-AsF{sub 6}{sup -} (BF{sub 4}{sup -}) system, and up to 400 K no chemical reactions of polymer destruction occur.

  13. Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Tessler, M.; Friedman, M.; Schmidt, S.; Shor, A.; Berkovits, D.; Cohen, D.; Feinberg, G.; Fiebiger, S.; Krása, A.; Paul, M.; Plag, R.; Plompen, A.; Reifarth, R.

    2016-01-01

    Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.

  14. Identification of Li-Ion Battery SEI Compounds through (7)Li and (13)C Solid-State MAS NMR Spectroscopy and MALDI-TOF Mass Spectrometry.

    PubMed

    Huff, Laura A; Tavassol, Hadi; Esbenshade, Jennifer L; Xing, Wenting; Chiang, Yet-Ming; Gewirth, Andrew A

    2016-01-13

    Solid-state (7)Li and (13)C MAS NMR spectra of cycled graphitic Li-ion anodes demonstrate SEI compound formation upon lithiation that is followed by changes in the SEI upon delithiation. Solid-state (13)C DPMAS NMR shows changes in peaks associated with organic solvent compounds (ethylene carbonate and dimethyl carbonate, EC/DMC) upon electrochemical cycling due to the formation of and subsequent changes in the SEI compounds. Solid-state (13)C NMR spin-lattice (T1) relaxation time measurements of lithiated Li-ion anodes and reference poly(ethylene oxide) (PEO) powders, along with MALDI-TOF mass spectrometry results, indicate that large-molecular-weight polymers are formed in the SEI layers of the discharged anodes. MALDI-TOF MS and NMR spectroscopy results additionally indicate that delithiated anodes exhibit a larger number of SEI products than is found in lithiated anodes. PMID:26653886

  15. Ionic Pathways in Li13Si4 investigated by (6)Li and (7)Li solid state NMR experiments.

    PubMed

    Dupke, Sven; Langer, Thorsten; Winter, Florian; Pöttgen, Rainer; Winter, Martin; Eckert, Hellmut

    2015-02-01

    Local environments and dynamics of lithium ions in the binary lithium silicide Li13Si4 have been studied by (6)Li MAS-NMR, (7)Li spin-lattice relaxation time and site-resolved (7)Li 2D exchange NMR measurements as a function of mixing time. Variable temperature experiments result in distinct differences in activation energies characterizing the transfer rates between the different lithium sites. Based on this information, a comprehensive picture of the preferred ionic transfer pathways in this silicide has been developed. With respect to local mobility, the results of the present study suggests the ordering Li6/Li7>Li5>Li1>Li4 >Li2/Li3. Mobility within the z=0.5 plane is distinctly higher than within the z=0 plane, and the ionic transfer between the planes is most facile via Li1/Li5 exchange. The lithium ionic mobility can be rationalized on the basis of the type of the coordinating silicide anions and the lithium-lithium distances within the structure. Lithium ions strongly interacting with the isolated Si(4-) anions have distinctly lower mobility than those the coordination of which is dominated by Si2(6-) dumbbells. PMID:25524128

  16. Investigation of Local Structure and Cation Ordering in Dielectric Oxide Microwave Ceramics with stoichiometry A(Lix(Nb,Ta)y) O3 Using 7Li and 93Nb solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kalfarisi, Rony

    The local structure and cation ordering in dielectric oxide microwave ceramics with stoichiometry A(Lix(Nb,Ta)y) O3 are investigated using 7Li and 93Nb solid-state NMR spectroscopy. For all samples, 7Li MAS NMR spectra show one strong and sharp resonance peak indicating one unique environment which corresponds to local lithium environment of nearest B-site neighbor (nBn) surrounded by 4 LiO6 octahedra and 2 NbO6 octahedra (TaO6 in some samples). In addition to this, 7Li MAS NMR spectrum of (Ca2/3La1/3) (Li1/3Nb2/3) O3 show one additional weak and broad resonance peak which can be assigned to nBn of 3 LiO6 octahedra and 3 NbO6 octahedra. 93Nb MAS NMR spectra of samples with niobium content, show a resonance peak with tail toward the low frequency limit, an evidence to the existence of chemical shifts and quadrupole couplings distributions. Both (Sr2/3La1/3) (Li1/3Nb2/3) O3 and Ca(Li1/4Nb3/4) O3 spectra show one broad resonance peak, which can be interpreted as one NbO6 octahedron nBn with many slight variations through out the sample. While (Ca2/3La1/3) (Li1/3Nb2/3) O3 spectra show four peaks correspond to four distinct NbO6 octahedra local nBn environments with the nBn configuration as: (i) 3 LiO6 and 3 NbO6; (ii) 2 LiO6 and 4 NbO6; (iii) 1 LiO6 and 5 NbO6; (iv) all 6 NbO6

  17. Lanthanide complexes of aminophosphonates as shift reagents for 7Li and 23Na NMR studies in biological systems.

    PubMed

    Ramasamy, R; Castro, M M; de Freitas, D M; Geraldes, C F

    1992-01-01

    A systematic NMR characterization of various Dy(III) complexes of linear and macrocyclic aminophosphonates as 7Li and 23Na NMR shift reagents for biological systems was undertaken. Their efficacy as shift reagents (SR) was tested under constant aqueous solution ionic strength conditions at pH 7.5 as a function of rho = [SR]/[M+]. Further characterization of the two best SRs, Dy(PcPcP)2(7-) and Dy(DOTP)5-, led to the conclusion that, although quite sensitive to solution pH and the presence of alkali metal ions and Mg2+ and Ca2+, these complexes were stable towards hydrolysis by phosphatases. The lack of precipitation of its solutions in the presence of Ca2+, allowed the choice of Dy(DOTP)5- as the best overall SR for biological studies. Other SRs, like Dy(TTHA)3-, although less sensitive to pH and to divalent ions, require significantly higher concentrations to yield the same shifts, leading to large bulk susceptibility artifacts in perfused tissues and organs. PMID:1467337

  18. Magnetic fluctuations and possible formation of a spin-singlet cluster under pressure in the heavy-fermion spinel LiV2O4 probed by 7Li and 51V NMR

    NASA Astrophysics Data System (ADS)

    Takeda, Hikaru; Kato, Yusuke; Yoshimura, Masahiro; Shimizu, Yasuhiro; Itoh, Masayuki; Niitaka, Seiji; Takagi, Hidenori

    2015-07-01

    7Li and 51V NMR measurements up to 9.8 GPa have been made to elucidate local magnetic properties of a heavy-fermion spinel oxide LiV2O4 which undergoes a metal-insulator transition above ˜7 GPa. The temperature T and pressure P dependences of the 7Li and 51V Knight shifts and the nuclear spin-lattice relaxation rates 1 /T1 show that in the metallic phase, there is a crossover from a high-T region with weak ferromagnetic fluctuations to a low-T one with antiferromagnetic (AFM) fluctuations. The AFM fluctuations are enhanced below 20 K and 1.5 GPa, where a heavy Fermi-liquid state with the modified Korringa relation is formed. The evolution of the magnetic fluctuations is discussed from the aspect of the competition among several magnetic interactions. Above PMI˜6.7 GPa, we find the coexistence of metallic and insulating phases due to the first-order metal-insulator transition. The 7Li and 51V NMR spectra coming from the insulating phase have T -independent small Knight shifts and 7(1 /T1 ) with the thermally activated T dependence, indicating the formation of a spin-singlet cluster. We propose a model of a spin-singlet tetramer as discussed in geometrically frustrated materials.

  19. 7Li NMR spectroscopy and ion conduction mechanism in mesoporous silica (SBA-15) composite poly(ethylene oxide) electrolyte

    NASA Astrophysics Data System (ADS)

    Reddy, M. Jaipal; Chu, Peter P.

    A composite of mesoporous silica (SBA-15) with a polyethylene oxide (PEO) polymer electrolyte is examined for use in various electrochemical devices. Incorporation of SBA-15 in a PEO:LiClO 4 polymer electrolyte facilitates salt dissociation, enhances ion conductivity, and improves miscibility between organic and inorganic moieties. Optimized conductivity is found at 10 wt.% SBA-15 composition, above this concentration the conductivity is reduced due to aggregation of a SBA-15:Li rich phase. Heating above melt temperature of PEO allows more of the polymer segments to interact with SBA-15. This results in a greater degree of disorder upon cooling, and the ion conductivity is enhanced. A 7Li MAS NMR study reveals three types of lithium-ion coordination. Two major types of conduction mechanism can be identified: one through conventional amorphous PEO; a second via hopping in a sequential manner by replacing the nearby vacancies ('holes') on the surface (both interior and exterior) of the SBA-15 channels.

  20. Competition between Na + and Li + for Unsealed and Cytoskeleton-Depleted Human Red Blood Cell Membrane: A 23Na Multiple Quantum Filtered and 7Li NMR Relaxation Study

    NASA Astrophysics Data System (ADS)

    Srinivasan, Chandra; Minadeo, Nicole; Toon, Jason; Graham, Daniel; Mota de Freitas, Duarte; Geraldes, Carlos F. G. C.

    1999-09-01

    Evidence for competition between Li+ and Na+ for binding sites of human unsealed and cytoskeleton-depleted human red blood cell (csdRBC) membranes was obtained from the effect of added Li+ upon the 23Na double quantum filtered (DQF) and triple quantum filtered (TQF) NMR signals of Na+-containing red blood cell (RBC) membrane suspensions. We found that, at low ionic strength, the observed quenching effect of Li+ on the 23Na TQF and DQF signal intensity probed Li+/Na+ competition for isotropic binding sites only. Membrane cytoskeleton depletion significantly decreased the isotropic signal intensity, strongly affecting the binding of Na+ to isotropic membrane sites, but had no effect on Li+/Na+ competition for those sites. Through the observed 23Na DQF NMR spectra, which allow probing of both isotropic and anisotropic Na+ motion, we found anisotropic membrane binding sites for Na+ when the total ionic strength was higher than 40 mM. This is a consequence of ionic strength effects on the conformation of the cytoskeleton, in particular on the dimer-tetramer equilibrium of spectrin. The determinant involvement of the cytoskeleton in the anisotropy of Na+ motion at the membrane surface was demonstrated by the isotropy of the DQF spectra of csdRBC membranes even at high ionic strength. Li+ addition initially quenched the isotropic signal the most, indicating preferential Li+/Na+ competition for the isotropic membrane sites. High ionic strength also increased the intensity of the anisotropic signal, due to its effect on the restructuring of the membrane cytoskeleton. Further Li+ addition competed with Na+ for those sites, quenching the anisotropic signal. 7Li T1 relaxation data for Li+-containing suspensions of unsealed and csdRBC membranes, in the absence and presence of Na+ at low ionic strength, showed that cytoskeleton depletion does not affect the affinity of Na+ for the RBC membrane, but increases the affinity of Li+ by 50%. This clearly indicates that cytoskeleton

  1. Li mobility in Nasicon-type materials LiM2(PO4)3, M = Ge, Ti, Sn, Zr and Hf, followed by 7Li NMR spectroscopy.

    PubMed

    Arbi, K; París, M A; Sanz, J

    2011-10-21

    Lithium mobility in LiM(2)(PO(4))(3) compounds, M = Ge and Sn, has been investigated by (7)Li Nuclear Magnetic Resonance (NMR) spectroscopy, and deduced information compared with that reported previously in Ti, Zr and Hf members of the series in the temperature range 100-500 K. From the analysis of (7)Li NMR quadrupole interactions (C(Q) and η parameters), spin-spin T(2)(-1) and spin-lattice T(1)(-1) relaxation rates, structural sites occupancy and mobility of lithium have been deduced. Below 250 K, Li ions are preferentially located at M(1) sites in rhombohedral phases, but occupy intermediate M(12) sites between M(1) and M(2) sites in triclinic ones. In high-temperature rhombohedral phases, a superionic state is achieved when residence times at M(1) and M(12) sites become similar and correlation effects on Li motion decrease. This state can be obtained by large order-disorder transformations in rhombohedral phases or by sharp first order transitions in triclinic ones. The presence of two relaxation mechanisms in T(1)(-1) plots of rhombohedral phases has been associated with departures of conductivity from the Arrhenius behavior. Long term mobility of lithium is discussed in terms of the cation vacancy distribution along conduction paths. PMID:21897945

  2. Coupling of Li motion and structural distortions in olivine LiMnPO4 from 7Li and 31P NMR

    NASA Astrophysics Data System (ADS)

    Rudisch, Christian; Grafe, Hans-Joachim; Geck, Jochen; Partzsch, Sven; Zimmermann, M. v.; Wizent, Nadja; Klingeler, Rüdiger; Büchner, Bernd

    2013-08-01

    We present a detailed 7Li- and 31P-NMR study on single crystalline LiMnPO4 in the paramagnetic and antiferromagnetic phase (AFM, TN˜34 K). This allows us to determine the spin directions in the field-induced spin-flop phase. In addition, the anisotropic dipolar hyperfine coupling tensor of the 7Li and 31P nuclei is also fully determined by orientation and temperature-dependent NMR experiments and compared to the calculated values from crystal structure data. Deviations of the experimental values from the theoretical ones are discussed in terms of Mn disorder which is induced by Li disorder. In fact, the disorder in the Mn sublattice is directly revealed by diffuse x-ray scattering data. The present results provide experimental evidence for the Li diffusion strongly coupling to structural distortions within the MnPO4 host, which is expected to significantly affect the Li mobility as well as the performance of batteries based on this material.

  3. Quantitative analysis of NMR spectra with chemometrics

    NASA Astrophysics Data System (ADS)

    Winning, H.; Larsen, F. H.; Bro, R.; Engelsen, S. B.

    2008-01-01

    The number of applications of chemometrics to series of NMR spectra is rapidly increasing due to an emerging interest for quantitative NMR spectroscopy e.g. in the pharmaceutical and food industries. This paper gives an analysis of advantages and limitations of applying the two most common chemometric procedures, Principal Component Analysis (PCA) and Multivariate Curve Resolution (MCR), to a designed set of 231 simple alcohol mixture (propanol, butanol and pentanol) 1H 400 MHz spectra. The study clearly demonstrates that the major advantage of chemometrics is the visualisation of larger data structures which adds a new exploratory dimension to NMR research. While robustness and powerful data visualisation and exploration are the main qualities of the PCA method, the study demonstrates that the bilinear MCR method is an even more powerful method for resolving pure component NMR spectra from mixtures when certain conditions are met.

  4. Lithium motion in the anode material LiC6 as seen via time-domain 7Li NMR

    NASA Astrophysics Data System (ADS)

    Langer, J.; Epp, V.; Heitjans, P.; Mautner, F. A.; Wilkening, M.

    2013-09-01

    Since the commercialization of rechargeable lithium-ion energy storage systems in the early 1990s, graphite intercalation compounds (GICs) have served as the number one negative electrode material in most of today's batteries. During charging the performance of a battery is closely tied with facile Li insertion into the graphite host structure. So far, only occasionally time-domain nuclear magnetic resonance (NMR) measurements have been reported to study Li self-diffusion parameters in GICs. Here, we used several NMR techniques to enlighten Li hopping motions from an atomic-scale point of view. Li self-diffusion in the stage-1 GIC LiC6 has been studied comparatively by temperature-variable spin-spin relaxation NMR as well as (rotating frame) spin-lattice relaxation NMR. The data collected yield information on both the relevant activation energies and jump rates, which can directly be transformed into Li self-diffusion coefficients. At room temperature the Li self-diffusion coefficient turns out to be 10-15m2s-1, thus, slightly lower than that for layer-structured cathode materials such as Lix≈0.7TiS2.

  5. Computational, electrochemical and {sup 7}Li NMR studies of lithiated disordered carbons electrodes in lithium ion cells.

    SciTech Connect

    Sandi, G.; Gerald, R., II; Scanlon, L. G.; Carrado, K. A.; Winans, R. E.

    1998-01-07

    Disordered carbons that deliver high reversible capacity in electrochemical cells have been synthesized by using inorganic clays as templates to control the pore size and the surface area. The capacities obtained were much higher than those calculated if the resultant carbon had a graphitic-like structure. Computational chemistry was used to investigate the nature of lithium bonding in a carbon lattice unlike graphite. The lithium intercalated fullerene Li{sub n}-C{sub 60} was used as a model for our (non-graphitic) disordered carbon lattice. A dilithium-C{sub 60} system with a charge and multiplicity of (0,1) and a trilithium-C{sub 60} system with a charge and multiplicity of (0,4) were investigated. The spatial distribution of lithium ions in an electrochemical cell containing this novel disordered carbon material was investigated in situ by Li-7 NMR using an electrochemical cell that was incorporated into a toroid cavity nuclear magnetic resonance (NMR) imager. The concentration of solvated Li{sup +} ions in the carbon anode appears to be larger than in the bulk electrolyte, is substantially lower near the copper/carbon interface, and does not change with cell charging.

  6. Two-dimensional diffusion in Li0.7NbS2 as directly probed by frequency-dependent 7Li NMR

    NASA Astrophysics Data System (ADS)

    Epp, V.; Nakhal, S.; Lerch, M.; Wilkening, M.

    2013-05-01

    Li ion diffusion in layer-structured Li0.7NbS2 has been complementary investigated by nuclear magnetic resonance (NMR) spectroscopy from an atomic scale point of view. In the present case, 7Li NMR spin-lattice relaxation (SLR) rates R1ρ probed in the rotating frame of reference proved very informative in characterizing the Li self-diffusion process in the van der Waals gap between the NbS2 layers. While temperature-variable SLRρ measurements were used to determine dynamic parameters such as jump rates (τ-1) and the activation energy (Ea), frequency-dependent measurements were used to specify the dimensionality of the diffusion process. In particular, the effect of annealing, i.e., the distribution of Li ions between the layers, on overall Li dynamics has been studied. When plotted in an Arrhenius diagram, the R1ρ rates of an annealed sample, which were recorded at a locking frequency of 20 kHz, pass through a diffusion-induced relaxation peak whose maximum shows up at 320 K. Employing an appropriate diffusion model and appropriately accounting for a non-diffusive background relaxation, a Li jump rate τ-1(300 K) ≈ 1.3 × 105 s-1 and an activation energy Ea of 0.43(2) eV can be deduced. Most importantly, in the high-T limit of the diffusion-induced rate peak, i.e., when ω1τ ≪ 1 holds, the rates follow a logarithmic frequency dependence. This points to a diffusion process of low dimensionality and is in good agreement with predictions of relaxation models developed for 2D diffusion.

  7. Measurement of neutron energy spectra and neutron dose rates from 7Li(p,n)7Be reaction induced on thin LiF target

    NASA Astrophysics Data System (ADS)

    Atanackovic, Jovica; Matysiak, Witold; Dubeau, Jacques; Witharana, Sampath; Waker, Anthony

    2015-02-01

    The measurements of neutron energy spectra and neutron dose rates were performed using the KN Van de Graaff accelerator, located at the McMaster University Accelerator Laboratory (MAL). Protons were accelerated on the thin lithium fluoride (LiF) target and produced mono-energetic neutrons which were measured using three different spectrometers: Bonner Sphere Spectrometer (BSS), Nested Neutron Spectrometer (NNS), and Rotational Proton Recoil Spectrometer (ROSPEC). The purpose of this work is (1) measurement and quantification of low energy accelerator neutron fields in terms of neutron fluence and dose, (2) comparison of results obtained by three different instruments, (3) comparison of measurements with Monte Carlo simulations based on theoretical neutron yields from 7Li(p,n)7Be nuclear reaction, and (4) comparison of results obtained using different neutron spectral unfolding methods. The nominal thickness of the LiF target used in the experiment was 50 μg /cm2, which corresponds to the linear thickness of 0.19 μm and results in approximately 6 keV energy loss for the proton energies used in the experiment (2.2, 2.3, 2.4 and 2.5 MeV). For each of the proton energies, neutron fluence per incident proton charge was measured and several dosimetric quantities of interest in radiation protection were derived. In addition, theoretical neutron yield calculations together with the results of Monte Carlo (MCNP) modeling of the neutron spectra are reported. Consistent neutron fluence spectra were obtained with three detectors and good agreement was observed between theoretically calculated and measured neutron fluences and derived dosimetric quantities for investigated proton energies at 2.3, 2.4 and 2.5 MeV. In the case of 2.2 MeV, some plausibly explainable discrepancies were observed.

  8. Correlations between lithium local structure and electrochemistry of layered LiCo(1-2x)Ni(x)Mn(x)O2 oxides: 7Li MAS NMR and EPR studies.

    PubMed

    Stoyanova, Radostina; Ivanova, Svetlana; Zhecheva, Ekaterina; Samoson, Ago; Simova, Svetlana; Tzvetkova, Pavleta; Barra, Anne-Laure

    2014-02-14

    Advanced (7)Li MAS NMR technologies and high frequency EPR are combined to identify structural motifs and their relation to electrochemical properties of layered lithium-cobalt-nickel-manganese oxides LiCo1-2xNixMnxO2 (0 < x ≤ 0.5) used as cathode materials in lithium ion batteries. Structural-chemical shift regularities were established by systematic variation of the ratio of diamagnetic Co(3+) to paramagnetic Ni/Mn ions with variable valences. While EPR allows identifying the oxidation state of transition metal ions inside the layers, (7)Li NMR probes the local structure of Li with respect to transition metal ions located in two adjacent layers. For assignment of the lithium chemical shifts, we examine first magnetically diluted LiCo1-2xNixMnxO2 with x = 0.02, where paramagnetic ions are stabilized only in Mn(4+) and Ni(3+) form. Then the studies are extended towards the intermediate compositions with x = 0.10 and 0.33, containing simultaneously paramagnetic Mn(4+), Ni(3+) and Ni(2+) ions and diamagnetic Co(3+) ions. The benefit of using NMR with ultrafast spinning rates is demonstrated for the end composition LiNi0.5Mn0.5O2 having only paramagnetic Ni(2+) and Mn(2+) ions. The local structure of Li is quantified in respect of the number of Ni(2+) and Mn(4+) neighbors. It has been demonstrated that Ni(2+) and Mn(4+) are non-randomly distributed around Li and their distribution depends on the method of synthesis. The extent of local cationic order and its effect on the electrochemical properties of LiNi0.5Mn0.5O2 are discussed. PMID:24356075

  9. Electrochemical lithiation/delithiation of SnP2O7 observed by in situ XRD and ex situ(7)Li/(31)P NMR, and (119)Sn Mössbauer spectroscopy.

    PubMed

    Bezza, Ilham; Kaus, Maximilian; Riekehr, Lars; Pfaffmann, Lukas; Doyle, Stephen; Indris, Sylvio; Ehrenberg, Helmut; Solhy, Abderrahim; Saadoune, Ismael

    2016-04-21

    SnP2O7 was prepared by a sol-gel route. The structural changes of tin pyrophosphate during the electrochemical lithiation were followed by using in situ XRD measurements that reveal the existence of a crystalline phase at the beginning of the discharge process. Nevertheless, it becomes amorphous after the full discharge as a result of a conversion reaction leading to the formation of LixSny alloys. The electrochemical tests show a high capacity with high retention upon cycling. To better understand the reaction mechanism of SnP2O7 with Li, several techniques were applied, such as ex situ(119)Sn Mössbauer and ex situ(7)Li and (31)P NMR spectroscopies with which we can follow the changes in the local environment of each element during cycling. PMID:27029601

  10. {sup 7}Li-nuclear magnetic resonance observation of lithium insertion into mesocarbon microbeads

    SciTech Connect

    Tatsumi, K.; Akai, T.; Imamura, T.; Zaghib, K.; Iwashita, N.; Higuchi, S.; Sawada, Y.

    1996-06-01

    The stacking order of graphite layers in mesocarbon microbeads (MCMBs) heat-treated between 700 and 3,000 C was examined by analyses of X-ray diffraction measurements, and lithium insertion into the MCMBs has been observed using solid-state {sup 7}Li-nuclear magnetic resonance ({sup 7}Li-NMR) spectroscopy. In MCMBs heat-treated above 2,000 C, the fully lithiated MCMBs showed two bands at ca. 45 ppm (vs. KiCl) and ca. 27 ppm in their {sup 7}Li-NMR spectra. The profile of the band at 45 ppm was very close to that for the first-stage lithium graphite intercalation compound (Li-GIC), though the other band at 27 ppm could not be assigned to any phases of Li-GICs. From these results, it is suggested that the structures of the MCMBs heat-treated above 2,000 C for lithium insertion are classified as graphitic structure, which has the AB stacking order of graphite layers, and turbostatic structure with a random stacking sequence of graphite layers; the fully lithiated compositions of both structures were estimated as LiC{sub 6} and ca. Li{sub 0.2}C{sub 6}, respectively. Although MCMB heat-treated at 700 C gave a higher capacity than LiC{sub 6}, the line shift in the {sup 7}Li-NMR spectra indicated that lithium stored in the MCMB displayed an ionic character. Capacity change of the MCMBs during charge-discharge cycling up to 20 cycles and capacity loss at higher current densities (<200 mA/g) were also examined.

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

    PubMed

    Wohlmuth, Dominik; Epp, Viktor; Wilkening, Martin

    2015-08-24

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

  12. Galactic evolution of 7Li

    NASA Astrophysics Data System (ADS)

    Matteucci, Francesca

    2010-04-01

    Lithium represents a key element in cosmology, as it is one of the few nuclei synthesized during the Big Bang. The primordial abundance of 7Li allows us to impose constraints on the primordial nucleosynthesis and on the baryon density of the universe. However, 7Li is not only produced during the Big Bang but also during galactic evolution: measures of stellar Li in our Galaxy suggest an almost constant Li abundance (the so-called Spite plateau) at low metallicities and a subsequent increase in the disk stars, leading to a Li abundance in Population I stars higher by a factor of ten than in Population II stars. This means that there must exist several possible stellar sources of 7Li: asymptotic giant branch stars, supernovae, novae, red giant stars. 7Li is also partly produced in spallation processes while 6Li is entirely produced by such processes. All of these sources have been included in galactic chemical evolution models and constraints have been derived on the primordial 7Li and its evolution, as well on stellar models. I will review these models and their results and what we have learned about 7Li evolution. Some still open problems, such as the disagreement between the primordial 7Li abundance as derived by WMAP and as measured in Population II stars, and the uncertainties about the main sources of stellar 7Li will be discussed.

  13. On the solid-state NMR spectra of naproxen

    NASA Astrophysics Data System (ADS)

    Czernek, Jiří

    2015-01-01

    Two previous measurements of the 13C and 1H NMR isotropic chemical shifts in crystalline naproxen, which is an important pharmaceutical compound, are confronted with the results obtained from several theoretical approaches capable of the proper treatment of solid-phase effects. In the underlying geometrical optimizations, two crystal structures are considered. The agreement between the data sets is quantified, including an evaluation of the similarity between the experimental solid-state NMR spectra. The 13C-1H heteronuclear correlations are analyzed, and their various assignments are discussed employing the statistical treatment of the differences between the measured and theoretical isotropic chemical shifts.

  14. ImatraNMR: novel software for batch integration and analysis of quantitative NMR spectra.

    PubMed

    Mäkelä, A V; Heikkilä, O; Kilpeläinen, I; Heikkinen, S

    2011-08-01

    Quantitative NMR spectroscopy is a useful and important tool for analysis of various mixtures. Recently, in addition of traditional quantitative 1D (1)H and (13)C NMR methods, a variety of pulse sequences aimed for quantitative or semiquantitative analysis have been developed. To obtain actual usable results from quantitative spectra, they must be processed and analyzed with suitable software. Currently, there are many processing packages available from spectrometer manufacturers and third party developers, and most of them are capable of analyzing and integration of quantitative spectra. However, they are mainly aimed for processing single or few spectra, and are slow and difficult to use when large numbers of spectra and signals are being analyzed, even when using pre-saved integration areas or custom scripting features. In this article, we present a novel software, ImatraNMR, designed for batch analysis of quantitative spectra. In addition to capability of analyzing large number of spectra, it provides results in text and CSV formats, allowing further data-analysis using spreadsheet programs or general analysis programs, such as Matlab. The software is written with Java, and thus it should run in any platform capable of providing Java Runtime Environment version 1.6 or newer, however, currently it has only been tested with Windows and Linux (Ubuntu 10.04). The software is free for non-commercial use, and is provided with source code upon request. PMID:21705250

  15. ImatraNMR: Novel software for batch integration and analysis of quantitative NMR spectra

    NASA Astrophysics Data System (ADS)

    Mäkelä, A. V.; Heikkilä, O.; Kilpeläinen, I.; Heikkinen, S.

    2011-08-01

    Quantitative NMR spectroscopy is a useful and important tool for analysis of various mixtures. Recently, in addition of traditional quantitative 1D 1H and 13C NMR methods, a variety of pulse sequences aimed for quantitative or semiquantitative analysis have been developed. To obtain actual usable results from quantitative spectra, they must be processed and analyzed with suitable software. Currently, there are many processing packages available from spectrometer manufacturers and third party developers, and most of them are capable of analyzing and integration of quantitative spectra. However, they are mainly aimed for processing single or few spectra, and are slow and difficult to use when large numbers of spectra and signals are being analyzed, even when using pre-saved integration areas or custom scripting features. In this article, we present a novel software, ImatraNMR, designed for batch analysis of quantitative spectra. In addition to capability of analyzing large number of spectra, it provides results in text and CSV formats, allowing further data-analysis using spreadsheet programs or general analysis programs, such as Matlab. The software is written with Java, and thus it should run in any platform capable of providing Java Runtime Environment version 1.6 or newer, however, currently it has only been tested with Windows and Linux (Ubuntu 10.04). The software is free for non-commercial use, and is provided with source code upon request.

  16. Sensitive, quantitative carbon-13 NMR spectra by mechanical sample translation

    NASA Astrophysics Data System (ADS)

    Donovan, Kevin J.; Allen, Mary; Martin, Rachel W.; Shaka, A. J.

    2009-04-01

    Collecting a truly quantitative carbon-13 spectrum is a time-consuming chore. Very long relaxation delays, required between transients to allow the z-magnetization, M z, of the spin with the longestT1 to return to the equilibrium value, M0, must precede each transient. These long delays also reduce sensitivity, as fewer transients per unit time can be acquired. In addition, sometimes T1 is not known to within even a factor of two: a conservative guess for the relaxation delay then leads to very low sensitivity. We demonstrate a fresh method to bypass these problems and collect quantitative carbon-13 spectra by swapping the sample volume after each acquisition with a different portion where the magnetization is already equilibrated to M0. Loading larger sample volumes of 10-20 mL into an unusually long (1520 mm) 5 mm OD. NMR tube and vertically sliding the tube between acquisitions accomplishes the swap. The relaxation delay can then be skipped altogether. The spectra are thus both quantitative, and far more sensitive. We demonstrate the moving tube technique on two small molecules (thymol and butylhydroxytoluene) and show good carbon-13 quantification. The gain in sensitivity can be as much as 10-fold for slowly-relaxing 13C resonances. These experiments show that quantitative, sensitive carbon-13 spectra are possible whenever sufficient sample volumes are available. The method is applicable to any slow-relaxing nuclear spin species, such as 29Si, 15N and other low-γ nuclei.

  17. {sup 19}F NMR spectra and structures of halogenated porphyrins

    SciTech Connect

    Birnbaum, E.R.; Hodge, J.A.; Grinstaff, M.W.

    1995-07-05

    Fluorine-19 NMR spectra of a series of halogenated porphyrins have been used to create a spectral library of different types of fluorine splitting patterns for tetrakis(pentafluorophenyl) porphyrins (TFPP) complexed with diamagnetic and paramagnetic metal ions. The paramagnetic shift, line broadening, and fine structure of the resonances form the peripheral pentafluorophenyl rings are dependent on the symmetry and core environment of the porphyrin macrocycles. In combination with crystal structure data, {sup 19}F NMR helps define the behavior of halogenated porphyrins in solution. Six new crystal structures for TFPP and octahalo-TFPP derivatives are reported: H{sub 2}TFPP in rhombohedral space group R3, a = 20.327(4) {Angstrom}, c = 15.261(2) {Angstrom}, {beta} = 103.87(2){degrees}, V = 2227.6(13) {Angstrom}{sup 3}, Z = 2; CuTFPP in rhombohedral space group R3, a = 20.358(5), c = 14.678(2) {Angstrom}, {alpha} = 88.97(1), {beta}=76.05(1){degrees}, {gamma} = 71.29(1){degrees}, V = 2181.4(6) {Angstrom}{sup 3}, Z = 2; ZnTFPPCl{sub 8} in tetragonal space group P42, c, a = 19.502(20), c = 10.916(8) {Angstrom}, V = 4152(6) {Angstrom}{sup 3}, Z = 2; H{sub 2}TFPPBr{sub 8} in monoclinic space group C2, a = 27.634(6) {Angstrom}, b = 6.926(2) {Angstrom}, c = 14.844(3) {Angstrom}, {beta} = 109.64(2){degrees}, V = 2675.8(11) {Angstrom}{sup 3}, Z = 2.

  18. Visualizing skin effects in conductors with MRI: (7)Li MRI experiments and calculations.

    PubMed

    Ilott, Andrew J; Chandrashekar, S; Klöckner, Andreas; Chang, Hee Jung; Trease, Nicole M; Grey, Clare P; Greengard, Leslie; Jerschow, Alexej

    2014-08-01

    While experiments on metals have been performed since the early days of NMR (and DNP), the use of bulk metal is normally avoided. Instead, often powders have been used in combination with low fields, so that skin depth effects could be neglected. Another complicating factor of acquiring NMR spectra or MRI images of bulk metal is the strong signal dependence on the orientation between the sample and the radio frequency (rf) coil, leading to non-intuitive image distortions and inaccurate quantification. Such factors are particularly important for NMR and MRI of batteries and other electrochemical devices. Here, we show results from a systematic study combining rf field calculations with experimental MRI of (7)Li metal to visualize skin depth effects directly and to analyze the rf field orientation effect on MRI of bulk metal. It is shown that a certain degree of selectivity can be achieved for particular faces of the metal, simply based on the orientation of the sample. By combining rf field calculations with bulk magnetic susceptibility calculations accurate NMR spectra can be obtained from first principles. Such analyses will become valuable in many applications involving battery systems, but also metals, in general. PMID:25036296

  19. Visualizing skin effects in conductors with MRI: 7Li MRI experiments and calculations

    NASA Astrophysics Data System (ADS)

    Ilott, Andrew J.; Chandrashekar, S.; Klöckner, Andreas; Chang, Hee Jung; Trease, Nicole M.; Grey, Clare P.; Greengard, Leslie; Jerschow, Alexej

    2014-08-01

    While experiments on metals have been performed since the early days of NMR (and DNP), the use of bulk metal is normally avoided. Instead, often powders have been used in combination with low fields, so that skin depth effects could be neglected. Another complicating factor of acquiring NMR spectra or MRI images of bulk metal is the strong signal dependence on the orientation between the sample and the radio frequency (rf) coil, leading to non-intuitive image distortions and inaccurate quantification. Such factors are particularly important for NMR and MRI of batteries and other electrochemical devices. Here, we show results from a systematic study combining rf field calculations with experimental MRI of 7Li metal to visualize skin depth effects directly and to analyze the rf field orientation effect on MRI of bulk metal. It is shown that a certain degree of selectivity can be achieved for particular faces of the metal, simply based on the orientation of the sample. By combining rf field calculations with bulk magnetic susceptibility calculations accurate NMR spectra can be obtained from first principles. Such analyses will become valuable in many applications involving battery systems, but also metals, in general.

  20. Access to experimentally infeasible spectra by pure-shift NMR covariance.

    PubMed

    Fredi, André; Nolis, Pau; Cobas, Carlos; Parella, Teodor

    2016-09-01

    Covariance processing is a versatile processing tool to generate synthetic NMR spectral representations without the need to acquire time-consuming experimental datasets. Here we show that even experimentally prohibited NMR spectra can be reconstructed by introducing key features of a reference 1D CHn-edited spectrum into standard 2D spectra. This general procedure is illustrated with the calculation of experimentally infeasible multiplicity-edited pure-shift NMR spectra of some very popular homonuclear (ME-psCOSY and ME-psTOCSY) and heteronuclear (ME-psHSQC-TOCSY and ME-psHMBC) experiments. PMID:27494746

  1. Access to experimentally infeasible spectra by pure-shift NMR covariance

    NASA Astrophysics Data System (ADS)

    Fredi, André; Nolis, Pau; Cobas, Carlos; Parella, Teodor

    2016-09-01

    Covariance processing is a versatile processing tool to generate synthetic NMR spectral representations without the need to acquire time-consuming experimental datasets. Here we show that even experimentally prohibited NMR spectra can be reconstructed by introducing key features of a reference 1D CHn-edited spectrum into standard 2D spectra. This general procedure is illustrated with the calculation of experimentally infeasible multiplicity-edited pure-shift NMR spectra of some very popular homonuclear (ME-psCOSY and ME-psTOCSY) and heteronuclear (ME-psHSQC-TOCSY and ME-psHMBC) experiments.

  2. Automated evaluation of chemical shift perturbation spectra: New approaches to quantitative analysis of receptor-ligand interaction NMR spectra

    PubMed Central

    Peng, Chen; Unger, Stephen W.; Filipp, Fabian V.; Sattler, Michael; Szalma, Sándor

    2016-01-01

    This paper presents new methods designed for quantitative analysis of chemical shift perturbation NMR spectra. The methods automatically trace the displacements of cross peaks between a perturbed test spectrum and the reference spectrum (or among a series of titration spectra), and measure the changes of chemical shifts, heights, and widths of the altered peaks. The methods are primary aimed at the 1H-15N HSQC spectra of relatively small proteins (<15 kDa) assuming fast exchange between free and ligand-bound states on the chemical shift time scale, or for comparing spectra of free and fully bound states in the slow exchange situation. Using the 1H-15N HSQC spectra from a titration experiment of the 74-residue Pex13p SH3 domain with a Pex14p peptide ligand (14 residues, Kd = ~ 40µM), we demonstrate the scope and limits of our automatic peak tracing (APET) algorithm for efficient scoring of high-throughput SAR by NMR type HSQC spectra, and progressive peak tracing (PROPET) algorithm for detailed analysis of ligand titration spectra. Simulated spectra with low signal-to-noise ratios (S/N ranged from 20 to 1) were used to demonstrate the reliability and reproducibility of the results when dealing with poor quality spectra. These algorithms have been implemented in a new software module, FELIX-Autoscreen, for streamlined processing, analysis and visualization of SAR by NMR and other high-throughput receptor/ligand interaction experiments. PMID:15243180

  3. Anisotropy of hyperfine interactions as a tool for interpretation of NMR spectra in magnetic materials.

    PubMed

    Chlan, V; Stěpánková, H; Rezníček, R; Novák, P

    2011-07-01

    Approach for interpretation of nuclear magnetic resonance (NMR) spectra in magnetic materials is presented, consisting in employing the anisotropy of hyperfine interaction. The anisotropic parts of hyperfine magnetic fields on (57)Fe nuclei are calculated ab initio for a model example of lithium ferrite and utilized to assign the experimental NMR spectral lines to iron sites in the crystal structure. PMID:21536415

  4. Proton NMR Spectra: Deceptively Simple and Deceptively Complex Examples.

    ERIC Educational Resources Information Center

    Gurst, J. E.; And Others

    1985-01-01

    Describes relatively simple nuclear magnetic resonance (NMR) experiments that demonstrate unexpected results of the deceptively simple and deceptively complex types. Background information, experimental procedures, and typical results obtained are included. (JN)

  5. Proton Fingerprints Portray Molecular Structures: Enhanced Description of the 1H NMR Spectra of Small Molecules

    PubMed Central

    Napolitano, José G.; Lankin, David C.; McAlpine, James B.; Niemitz, Matthias; Korhonen, Samuli-Petrus; Chen, Shao-Nong; Pauli, Guido F.

    2013-01-01

    The characteristic signals observed in NMR spectra encode essential information on the structure of small molecules. However, extracting all of this information from complex signal patterns is not trivial. This report demonstrates how computer-aided spectral analysis enables the complete interpretation of 1D 1H NMR data. The effectiveness of this approach is illustrated with a set of organic molecules, for which replicas of their 1H NMR spectra were generated. The potential impact of this methodology on organic chemistry research is discussed. PMID:24007197

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

    PubMed Central

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

    2015-01-01

    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

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

    PubMed

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

    2015-01-01

    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

  8. Lattice simulation method to model diffusion and NMR spectra in porous materials.

    PubMed

    Merlet, Céline; Forse, Alexander C; Griffin, John M; Frenkel, Daan; Grey, Clare P

    2015-03-01

    A coarse-grained simulation method to predict nuclear magnetic resonance (NMR) spectra of ions diffusing in porous carbons is proposed. The coarse-grained model uses input from molecular dynamics simulations such as the free-energy profile for ionic adsorption, and density-functional theory calculations are used to predict the NMR chemical shift of the diffusing ions. The approach is used to compute NMR spectra of ions in slit pores with pore widths ranging from 2 to 10 nm. As diffusion inside pores is fast, the NMR spectrum of an ion trapped in a single mesopore will be a sharp peak with a pore size dependent chemical shift. To account for the experimentally observed NMR line shapes, our simulations must model the relatively slow exchange between different pores. We show that the computed NMR line shapes depend on both the pore size distribution and the spatial arrangement of the pores. The technique presented in this work provides a tool to extract information about the spatial distribution of pore sizes from NMR spectra. Such information is difficult to obtain from other characterisation techniques. PMID:25747093

  9. Some plant leaves have orientation-dependent EPR and NMR spectra.

    PubMed

    McCain, D C; Selig, T C; Govindjee; Markley, J L

    1984-02-01

    Proton nuclear magnetic resonance ((1)H NMR) spectra of leaves from 50 plant species were obtained at a spectrometer frequency of 470 MHz. Water present in leaf samples gives rise to characteristic spectral patterns. Most species show only one broad (1)H NMR peak; however, the leaves of some plants display complex, orientation-dependent spectra in which a common three-line pattern is discerned. The pattern varies with the angle between the leaf surface and the external magnetic field. Proton relaxation measurements show the presence of at least two water compartments in the leaves. The compartments are responsible for different components of the spectral pattern. EPR spectra, obtained at 35 GHz and at a temperature of -180 degrees C, of plant leaf sections are dominated by the strong signals of manganous ions. We find that most plant leaves have isotropic Mn(2+) EPR spectra. However, in some species (including ones that exhibit orientation-dependent (1)H NMR spectra) we detect orientation-dependent intensities in the forbidden lines; the spectra indicate that Mn(2+) ions occupy binding sites with axial or lower symmetry on nonrandomly oriented membranes. Both the NMR and the EPR results suggest that the chloroplasts of some plants are preferentially aligned with respect to the leaf surface. PMID:16593413

  10. Effects of instrumental artifacts on triple quantum filtered NMR spectra for spin I = 3/2

    NASA Astrophysics Data System (ADS)

    Sun, Cheng; Wang, Xuefeng; Wang, Zhixiao

    2016-07-01

    In this work, the effects of various instrumental artifacts on the triple quantum filtered NMR spectra for spin I = 3/2 nuclei are investigated. The studied artifacts include finite pulse widths, phase errors, radio frequency field inhomogeneity and pulse transients, which are commonly encountered in practice. The triple quantum filtered spectra are numerically simulated, based on the evolution of the spin density operator under the Hamiltonian for the artifacts. The results show that the presence of the artifacts introduces a shape distortion in the spectrum as well as a variation in the peak intensity, compared with the spectrum without any artifacts. This work indicates that the existence of the instrumental artifacts may cause a misunderstanding of the triple quantum filtered NMR spectra in experiments. The results suggest that one be aware of the instrumental artifacts when performing the triple quantum filtered NMR experiments.

  11. Effects of instrumental artifacts on triple quantum filtered NMR spectra for spin I=3/2.

    PubMed

    Sun, Cheng; Wang, Xuefeng; Wang, Zhixiao

    2016-07-01

    In this work, the effects of various instrumental artifacts on the triple quantum filtered NMR spectra for spin I=3/2 nuclei are investigated. The studied artifacts include finite pulse widths, phase errors, radio frequency field inhomogeneity and pulse transients, which are commonly encountered in practice. The triple quantum filtered spectra are numerically simulated, based on the evolution of the spin density operator under the Hamiltonian for the artifacts. The results show that the presence of the artifacts introduces a shape distortion in the spectrum as well as a variation in the peak intensity, compared with the spectrum without any artifacts. This work indicates that the existence of the instrumental artifacts may cause a misunderstanding of the triple quantum filtered NMR spectra in experiments. The results suggest that one be aware of the instrumental artifacts when performing the triple quantum filtered NMR experiments. PMID:27149654

  12. PR-CALC: A program for the reconstruction of NMR spectra from projections

    PubMed Central

    Coggins, Brian E.; Zhou, Pei

    2013-01-01

    Projection-reconstruction NMR (PR-NMR) has attracted growing attention as a method for collecting multidimensional NMR data rapidly. The PR-NMR procedure involves measuring lower-dimensional projections of a higher-dimensional spectrum, which are then used for the mathematical reconstruction of the full spectrum. We describe here the program PR-CALC, for the reconstruction of NMR spectra from projection data. This program implements a number of reconstruction algorithms, highly optimized to achieve maximal performance, and manages the reconstruction process automatically, producing either full spectra or subsets, such as regions or slices, as requested. The ability to obtain subsets allows large spectra to be analyzed by reconstructing and examining only those subsets containing peaks, offering considerable savings in processing time and storage space. PR-CALC is straightforward to use, and integrates directly into the conventional pipeline for data processing and analysis. It was written in standard C++ and should run on any platform. The organization is flexible, and permits easy extension of capabilities, as well as reuse in new software. PR-CALC should facilitate the widespread utilization of PR-NMR in biomedical research. PMID:16604426

  13. RUBIDIUM, a program for computer-aided assignment of two-dimensional NMR spectra of polypeptides.

    PubMed

    Yu, C; Hwang, J F; Chen, T B; Soo, V W

    1992-01-01

    Taking advantage of the rule-based expert system technology, a program named RUBIDIUM (Rule-Based Identification In 2D NMR Spectrum) was developed to accomplish the automatic 1H NMR resonance assignments of polypeptides. Besides noise elimination and peak selection capabilities, RUBIDIUM detects the cross-peak patterns of amino acid residues in the COSY spectrum, assigning these patterns to amino acid types, performing sequential assignments using combined COSY/NOESY spectra, and finally, achieving the total assignment of the 1H NMR spectrum. PMID:1607394

  14. Genetic algorithm-based feature selection in high-resolution NMR spectra

    PubMed Central

    Cho, Hyun-Woo; Jeong, Myong K.; Park, Youngja; Ziegler, Thomas R.; Jones, Dean P.

    2011-01-01

    High-resolution nuclear magnetic resonance (NMR) spectroscopy has provided a new means for detection and recognition of metabolic changes in biological systems in response to pathophysiological stimuli and to the intake of toxins or nutrition. To identify meaningful patterns from NMR spectra, various statistical pattern recognition methods have been applied to reduce their complexity and uncover implicit metabolic patterns. In this paper, we present a genetic algorithm (GA)-based feature selection method to determine major metabolite features to play a significant role in discrimination of samples among different conditions in high-resolution NMR spectra. In addition, an orthogonal signal filter was employed as a preprocessor of NMR spectra in order to remove any unwanted variation of the data that is unrelated to the discrimination of different conditions. The results of k-nearest neighbors and the partial least squares discriminant analysis of the experimental NMR spectra from human plasma showed the potential advantage of the features obtained from GA-based feature selection combined with an orthogonal signal filter. PMID:21472035

  15. Application of quantitative artificial neural network analysis to 2D NMR spectra of hydrocarbon mixtures.

    PubMed

    Väänänen, Taito; Koskela, Harri; Hiltunen, Yrjö; Ala-Korpela, Mika

    2002-01-01

    Understanding relationships between the structure and composition of molecular mixtures and their chemical properties is a main industrial aim. One central field of research is oil chemistry where the key question is how the molecular characteristics of composite hydrocarbon mixtures can be associated with the macroscopic properties of the oil products. Apparently these relationships are complex and often nonlinear and therefore call for advanced spectroscopic techniques. An informative and an increasingly used approach is two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy. In the case of composite hydrocarbons the application of 2D NMR methodologies in a quantitative manner pose many technical difficulties, and, in any case, the resulting spectra contain many overlapping resonances that challenge the analytical work. Here, we present a general methodology, based on quantitative artificial neural network (ANN) analysis, to resolve overlapping information in 2D NMR spectra and to simultaneously assess the relative importance of multiple spectral variables on the sample properties. The results in a set of 2D NMR spectra of oil samples illustrate, first, that use of ANN analysis for quantitative purposes is feasible also in 2D and, second, that this methodology offers an intrinsic opportunity to assess the complex and nonlinear relationships between the molecular composition and sample properties. The presented ANN methodology is not limited to the analysis of NMR spectra but can also be applied in a manner similar to other (multidimensional) spectroscopic data. PMID:12444730

  16. An efficient spectra processing method for metabolite identification from 1H-NMR metabolomics data.

    PubMed

    Jacob, Daniel; Deborde, Catherine; Moing, Annick

    2013-06-01

    The spectra processing step is crucial in metabolomics approaches, especially for proton NMR metabolomics profiling. During this step, noise reduction, baseline correction, peak alignment and reduction of the 1D (1)H-NMR spectral data are required in order to allow biological information to be highlighted through further statistical analyses. Above all, data reduction (binning or bucketing) strongly impacts subsequent statistical data analysis and potential biomarker discovery. Here, we propose an efficient spectra processing method which also provides helpful support for compound identification using a new data reduction algorithm that produces relevant variables, called buckets. These buckets are the result of the extraction of all relevant peaks contained in the complex mixture spectra, rid of any non-significant signal. Taking advantage of the concentration variability of each compound in a series of samples and based on significant correlations that link these buckets together into clusters, the method further proposes automatic assignment of metabolites by matching these clusters with the spectra of reference compounds from the Human Metabolome Database or a home-made database. This new method is applied to a set of simulated (1)H-NMR spectra to determine the effect of some processing parameters and, as a proof of concept, to a tomato (1)H-NMR dataset to test its ability to recover the fruit extract compositions. The implementation code for both clustering and matching steps is available upon request to the corresponding author. PMID:23525538

  17. 13C-NMR spectra and contact time experiment for Skjervatjern fulvic and humic acids

    USGS Publications Warehouse

    Malcolm, R.L.

    1992-01-01

    The T(CP) and T(1p) time constants for Skjervatjern fulvic and humic acids were determined to be short with T(CP) values ranging from 0.14 ms to 0.53 ms and T(1p) values ranging from 3.3 ms to 5.9 ms. T(CP) or T(1p) time constants at a contact time of 1 ms are favorable for quantification of 13C-NMR spectra. Because of the short T(CP) values, correction factors for signal intensity for various regions of the 13C-NMR spectra would be necessary at contact times greater than 1.1 ms or less than 0.9 ms. T(CP) and T(1p) values have a limited non-homogeneity within Skjervatjern fulvic and humic acids. A pulse delay or repeat time of 700 ms is more than adequate for quantification of these 13C-NMR spectra. Paramagnetic effects in these humic substances are precluded due to low inorganic ash contents, low contents of Fe, Mn, and Co, and low organic free-radical contents. The observed T(CP) values suggest that all the carbon types in Skjervatjern fulvic and humic acids are fully cross-polarized before significant proton relaxation occurs. The 13C-NMR spectra for Skjervatjern fulvic acid is similar to most aquatic fulvic acids as it is predominantly aliphatic, low in aromaticity (fa1 = 24), low in phenolic content, high in carboxyl content, and has no resolution of a methoxyl peak. The 13C-NMR spectra for Skjervatjern humic acid is also similar to most other aquatic humic acids in that it is also predominantly aliphatic, high in aromaticity (fa1 = 38), moderate in phenolic content, moderate in carboxyl content, and has a clear resolution of a methoxyl carbon region. After the consideration of the necessary 13C-NMR experimental conditions, these spectra are considered to be quantitative. With careful consideration of the previously determined 13C-NMR experimental conditions, quantitative spectra can be obtained for humic substances in the future from the HUMEX site. Possible changes in humic substances due to acidification should be determined from 13C-NMR data.

  18. Macroscopic orientation effects in broadline NMR-spectra of model membranes at high magnetic field strength

    PubMed Central

    Brumm, T.; Möps, A.; Dolainsky, C.; Brückner, S.; Bayerl, T. M.

    1992-01-01

    The partial orientation of multilamellar vesicles (MLV) in high magnetic fields has been studied and a method to prevent such effects is herewith proposed. The orientation effect was measured with 2H-, 31P-NMR and electron microscopy on MLVs of dipalmitoyl phosphatidylcholine with 30 mol% cholesterol. We present the first freeze—etch electron microscopy data obtained from MLV samples that were frozen directly in the NMR magnet at a field strength of 9.4 Tesla. These experiments clearly show that the MLVs adopt an ellipsoidal (but not a cylindrical) shape in the magnetic field. Best fit 31P-NMR lineshape calculations assuming an ellipsoidal distribution of molecular director axes to the experimentally obtained spectra provide a quantitative measure of the average semiaxis ratio of the ellipsoidal MLVs and its change with temperature. The application of so-called spherical supported vesicles (SSV) is found to prevent any partial orientation effects so that undistorted NMR powder pattern of the bilayer can be measured independently of magnetic field strength and temperature. The usefulness of SSVs is further demonstrated by a direct comparison of spectral data such as 31P-and 2H-NMR lineshapes and relaxation times as well as 2H-NMR dePaked spectra obtained for both model systems. These experiments show that spectral data obtained from partially oriented MLVs are not unambiguous to interpret, in particular, if an external parameter such as temperature is varied. ImagesFIGURE 1 PMID:19431822

  19. Molecular dynamics in paramagnetic materials as studied by magic-angle spinning 2H NMR spectra.

    PubMed

    Mizuno, Motohiro; Suzuki, You; Endo, Kazunaka; Murakami, Miwa; Tansho, Masataka; Shimizu, Tadashi

    2007-12-20

    A magic-angle spinning (MAS) 2H NMR experiment was applied to study the molecular motion in paramagnetic compounds. The temperature dependences of 2H MAS NMR spectra were measured for paramagnetic [M(H2O)6][SiF6] (M=Ni2+, Mn2+, Co2+) and diamagnetic [Zn(H2O)6][SiF6]. The paramagnetic compounds exhibited an asymmetric line shape in 2H MAS NMR spectra because of the electron-nuclear dipolar coupling. The drastic changes in the shape of spinning sideband patterns and in the line width of spinning sidebands due to the 180 degrees flip of water molecules and the reorientation of [M(H2O)6]2+ about its C3 axis were observed. In the paramagnetic compounds, paramagnetic spin-spin relaxation and anisotropic g-factor result in additional linebroadening of each of the spinning sidebands. The spectral simulation of MAS 2H NMR, including the effects of paramagnetic shift and anisotropic spin-spin relaxation due to electron-nuclear dipolar coupling and anisotropic g-factor, was performed for several molecular motions. Information about molecular motions in the dynamic range of 10(2) s(-1)NMR spectra when these paramagnetic effects are taken into account. PMID:18027914

  20. Bulk magnetization and 1H NMR spectra of magnetically heterogeneous model systems

    SciTech Connect

    Levin, E M; Bud' ko, S L

    2011-04-28

    Bulk magnetization and ¹H static and magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of two magnetically heterogeneous model systems based on laponite (LAP) layered silicate or polystyrene (PS) with low and high proton concentration, respectively, and ferrimagnetic Fe₂O₃ nano- or micro-particles have been studied. In LAP+Fe₂O₃, a major contribution to the NMR signal broadening is due to the dipolar coupling between the magnetic moments of protons and magnetic particles. In PS+Fe₂O₃, due to the higher proton concentration in polystyrene and stronger proton–proton dipolar coupling, an additional broadening is observed, i.e. ¹H MAS NMR spectra of magnetically heterogeneous systems are sensitive to both proton–magnetic particles and proton–proton dipolar couplings. An increase of the volume magnetization by ~1 emu/cm³ affects the ¹H NMR signal width in a way that is similar to an increase of the proton concentration by ~2×10²²/cm³. ¹H MAS NMR spectra, along with bulk magnetization measurements, allow the accurate determination of the hydrogen concentration in magnetically heterogeneous systems.

  1. On the practical aspects of recording wideline QCPMG NMR spectra.

    PubMed

    Hung, Ivan; Gan, Zhehong

    2010-06-01

    The practical aspects of applying CPMG for acquisition of wideline powder patterns are examined. It is shown that most distortions/modulations of spikelet spectra can be traced to the incoherent signal averaging from multiple coherence transfer pathways. A strategy for minimizing these distortions/modulations is described. Also, a few interesting observations regarding the implementation of the wideline WURST-QCPMG experiment are presented, namely the accumulation of second-order signal phase and the effects of varying the sweep rate and rf field of chirp pulses. PMID:20359918

  2. Characterisation of the 1H and 13C NMR spectra of methylcitric acid

    NASA Astrophysics Data System (ADS)

    Krawczyk, Hanna; Martyniuk, Tomasz

    2007-06-01

    Methylcitric acid (MCA) was synthesised in Reformatsky reaction (2 RS, 3 RS stereoisomers) and in the nucleophilic addition (2 RS, 3 SR stereoisomers). The stereoselectivity of these reactions was analysed. 1H and 13C NMR spectra of diastereoisomers of methylcitric acid were recorded and interpreted. The values of 1H chemical shifts and 1H- 1H coupling constants were analysed. Proton-decoupled high-resolution 13C NMR spectra of MCA diastereoisomers were measured in a series of dilute water solutions of various acidities. These data may provide a basis for unequivocal determination of the presence of MCA in the urine samples of patients' suffering from propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency. NMR spectroscopy enables determination of MCA diastereoisomers in body fluids and can be a complementary and useful diagnostic tool.

  3. Molecular Structures from [superscript 1]H NMR Spectra: Education Aided by Internet Programs

    ERIC Educational Resources Information Center

    Debska, Barbara; Guzowska-Swider, Barbara

    2007-01-01

    The article presents the way in which freeware Internet programs can be applied to teach [superscript 1]H NMR spectroscopy. The computer programs described in this article are part of the educational curriculum that explores spectroscopy and spectra interpretation. (Contains 6 figures.)

  4. Differential Analysis of 2D NMR Spectra: New Natural Products from a Pilot-Scale Fungal Extract Library

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using a newly developed protocol for the differential analysis of arrays of 2D NMR spectra, we were able to rapidly identify two previously unreported indole alkaloids from a library of unfractionated fungal extracts. Differential analyses of NMR spectra thus constitute an effective tool for the non...

  5. A new method for the comparison of 1H NMR predictors based on tree-similarity of spectra

    PubMed Central

    2014-01-01

    A methodology based on spectral similarity is presented that allows to compare NMR predictors without the recourse to assigned experimental spectra, thereby making the task of benchmarking NMR predictors less tedious, faster, and less prone to human error. This approach was used to compare four popular NMR predictors using a dataset of 1000 molecules and their corresponding experimental spectra. The results found were consistent with those obtained by directly comparing deviations between predicted and experimental shifts. PMID:24666427

  6. Quadrupolar magic angle spinning NMR spectra fitted using the Pearson IV function.

    PubMed

    Mironenko, Roman M; Belskaya, Olga B; Talsi, Valentin P; Likholobov, Vladimir A

    2014-01-01

    The Pearson IV function was used to fit the asymmetric solid-state (27)Al NMR spectra of alumina based catalysts. A high convergence (correlation coefficient is no less than 0.997) between experimental and simulated spectra was achieved. The decomposition of the (27)Al NMR spectra of zinc/aluminum mixed oxides with different Zn/Al molar ratio revealed an increased fraction (6-9%) of pentacoordinated aluminum atoms in these oxides as compared to γ-Al2O3. As the Zn/Al ratio is raised, the fraction of [AlO6] octahedral units decreases, while the fraction of [AlO4] tetrahedra increases. PMID:25454293

  7. HyperBIRD: a sensitivity-enhanced approach to collecting homonuclear-decoupled proton NMR spectra.

    PubMed

    Donovan, Kevin J; Frydman, Lucio

    2015-01-01

    Samples prepared following dissolution dynamic nuclear polarization (DNP) enable the detection of NMR spectra from low-γ nuclei with outstanding sensitivity, yet have limited use for the enhancement of abundant species like (1)H nuclei. Small- and intermediate-sized molecules, however, show strong heteronuclear cross-relaxation effects: spontaneous processes with an inherent isotopic selectivity, whereby only the (13)C-bonded protons receive a polarization enhancement. These effects are here combined with a recently developed method that delivers homonuclear-decoupled (1)H spectra in natural abundance samples based on heteronuclear couplings to these same, (13)C-bonded nuclei. This results in the HyperBIRD methodology; a single-shot combination of these two effects that can simultaneously simplify and resolve complex, congested (1)H NMR spectra with many overlapping spin multiplets, while achieving 50-100 times sensitivity enhancements over conventional thermal counterparts. PMID:25256418

  8. Line shapes in CP/MAS NMR spectra of half-integer quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenobu; Hayamizu, Kikuko

    1993-02-01

    Cross polarization (CP) from 1H to quadrupolar nuclei with S = 3/2 has been carried out under magic-angle-spinning (MAS) conditions for powder samples of Na 2B 4O 7·10H 2O and H 3BO 3. The line shapes in the CP/MAS NMR spectra are different from those in the spectra measured with the single pulse sequence combined with 1H dipolar decoupling. Furthermore, the line shapes are found to be dependent on the measuring conditions such as the pulse amplitude for the quadrupolar nuclei. The spin-locking experiments demonstrate that line shapes in CP/MAS NMR spectra are largely dependent on the spin-locking efficiency.

  9. 29Si and 27Al MAS NMR spectra of mullites from different kaolinites.

    PubMed

    He, Hongping; Guo, Jiugao; Zhu, Jianxi; Yuan, Peng; Hu, Cheng

    2004-04-01

    Mullites synthesized from four kaolinites with different random defect densities have been studied by 27Al and 29Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) and X-ray diffraction (XRD). All these mullites show the same XRD pattern. However, 29Si and 27Al MAS NMR spectra reveal that the mullites derived from kaolinites with high defect densities, have a sillimanite-type Al/Si ordering scheme and are low in silica, whereas those mullites derived from kaolinites with low defect densities, consist of both sillimanite- and mullite-type Al/Si ordering schemes and are rich in silica. PMID:15084323

  10. Magnetic structure of low-dimensional LiCu{sub 2}O{sub 2} multiferroic according to {sup 63,65}Cu and {sup 7}Li NMR studies

    SciTech Connect

    Sadykov, A. F. Gerashchenko, A. P.; Piskunov, Yu. V.; Ogloblichev, V. V.; Smol'nikov, A. G.; Verkhovskii, S. V.; Yakubovskii, A. Yu.; Tishchenko, E. A.; Bush, A. A.

    2012-10-15

    The complex NMR study of the magnetic structure of LiCu{sub 2}O{sub 2} multiferroic has been performed. It has been shown that the spin spirals in LiCu{sub 2}O{sub 2} are beyond the ab, bc, and ac crystallographic planes. The external magnetic field applied along the c axis of the crystal does not change the spatial orientation of spirals in Cu{sup 2+} chains. A magnetic field of H{sub 0} = 94 kOe applied along the a and b axes rotates the planes of spin spirals in chains, tending to orient the normal n of spirals along the external magnetic field. The rotation angle of the planes of the magnetic moments are maximal at H{sub 0} Double-Vertical-Line b.

  11. Practical model fitting approaches to the direct extraction of NMR parameters simultaneously from all dimensions of multidimensional NMR spectra.

    PubMed

    Chylla, R A; Volkman, B F; Markley, J L

    1998-08-01

    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 (10(8) is not uncommon) encoding information about numerous signals (up to 10(5) 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 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. PMID:9751999

  12. Protein–RNA specificity by high-throughput principal component analysis of NMR spectra

    PubMed Central

    Collins, Katherine M.; Oregioni, Alain; Robertson, Laura E.; Kelly, Geoff; Ramos, Andres

    2015-01-01

    Defining the RNA target selectivity of the proteins regulating mRNA metabolism is a key issue in RNA biology. Here we present a novel use of principal component analysis (PCA) to extract the RNA sequence preference of RNA binding proteins. We show that PCA can be used to compare the changes in the nuclear magnetic resonance (NMR) spectrum of a protein upon binding a set of quasi-degenerate RNAs and define the nucleobase specificity. We couple this application of PCA to an automated NMR spectra recording and processing protocol and obtain an unbiased and high-throughput NMR method for the analysis of nucleobase preference in protein–RNA interactions. We test the method on the RNA binding domains of three important regulators of RNA metabolism. PMID:25586222

  13. Magnetic susceptibility effects on 13C MAS NMR spectra of carbon materials and graphite.

    PubMed

    Freita, J C; Emmerich, F G; Cernicchiaro, G R; Sampaio, L C; Bonagamba, T J

    2001-01-01

    13C high-resolution solid-state nuclear magnetic resonance (NMR) was employed to study carbon materials prepared through the thermal decomposition of four different organic precursors (rice hulls, endocarp of babassu coconut, peat, and PVC). For heat treatment temperatures (HTTs) above about 600 C, all materials presented 13C NMR spectra composed of a unique resonance line associated with carbon atoms in aromatic planes. With increasing HTT a continuous broadening of this resonance and a diamagnetic shift in its central frequency were verified for all samples. The evolution of the magnitude and anisotropy of the magnetic susceptibility of the heat-treated carbon samples with HTT explains well these findings. It is shown that these results are better understood when a comparison is made with the features of the 13C NMR spectrum of polycrystalline graphite, for which the magnetic susceptibility effect is also present and is much more pronounced. PMID:11529420

  14. A system to obtain radiotracer uptake data simultaneously with NMR spectra in a high field magnet

    SciTech Connect

    Buchanan, M.; Marsden, P.K.; Garlick, P.B.; Mielke, C.H.

    1996-06-01

    Radiotracer techniques and nuclear magnetic resonance (NMR) spectroscopy are two complementary methods that are widely used to investigate cardiac metabolism. The authors have now developed a novel gamma photon detector system that will operate within a wide-bore, 9.4 T magnet. With this detector in position, it is possible to acquire radiotracer uptake data while simultaneously collecting NMR spectra. The advantages of this new system are firstly, that it enables correlations between radiotracer and NMR data to be made on individual rat hearts, and secondly that it allows the number of experiments required to obtain results of statistical significance to be greatly decreased. The extension of the system, to one in which positron emission tomography (PET) and magnetic resonance imaging (MRI) data are acquired simultaneously, clearly has enormous clinical potential. The detector consists of a NaI(Tl) scintillation crystal coupled to a magnetic field-insensitive photomultiplier tube by a 72.5 cm long, acrylic light pipe. This detector configuration satisfies the two, conflicting requirements of the crystal being near the sample, and thus in a high magnetic field, and the PMT being in a low magnetic field and thus far from the sample. In this paper the authors present the technical specifications of their new system together with what they believe are the first examples of simultaneously acquired NMR spectra and {sup 18}F-fluorodeoxyglucose ({sup 18}FDG) uptake data, obtained from isolated, perfused rat hearts.

  15. Deuteron and triton magnetic moments from NMR spectra of the hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Puchalski, Mariusz; Komasa, Jacek; Pachucki, Krzysztof

    2015-08-01

    We present a theory and calculations of the nuclear magnetic shielding with finite nuclear mass effects and determine the magnetic moments of deuteron and triton using the known NMR spectra of HD and HT molecules. The results μd=0.857 438 234 6 (53 ) μN and μt=2.978 962 471 (10 ) μN are more accurate and in good agreement with the currently accepted values.

  16. High-resolution J-resolved NMR spectra of dilute spins in solids

    NASA Astrophysics Data System (ADS)

    Terao, T.; Miura, H.; Saika, A.

    1981-08-01

    A technique for obtaining J-resolved NMR spectra of dilute spins in solids has been developed. It is based on the observation that a combination of magic-angle irradiation and magic-angle spinning removes dipolar broadening, but leaves indirect spin-spin coupling. A preliminary application of this technique to adamantane clearly reveals the AX (J = 121 Hz) and AX (J = 135 Hz) multiplets in the methylene and methyne 13C spectrum, respectively.

  17. Automated recognition and assessment of cross peaks in two-dimensional NMR spectra of macromolecules

    NASA Astrophysics Data System (ADS)

    Glaser, S.; Kalbitzer, H. R.

    A generally applicable procedure for the automated recognition of cross peaks in two-dimensional NMR spectra is presented which exploits local and global spectral properties. It is mainly based on general symmetry considerations which apply for the two-dimensional homonuclear techniques commonly used for structural determination of macromolecules in solution. The corresponding PASCAL program has been tested on a double-quantumfiltered COSY spectrum of a small protein; the results show that the recognition of cross peaks and their assessment works effectively even on spectra with intense 1 noise and experimental artifacts as are typically obtained for biological macromolecules with relatively low solubility.

  18. Investigation of structure, vibrational and NMR spectra of oxycodone and naltrexone: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Tavakol, Hossein; Esfandyari, Maryam; Taheri, Salman; Heydari, Akbar

    2011-08-01

    In this work, two important opioid antagonists, naltrexone and oxycodone, were prepared from thebaine and were characterized by IR, 1H NMR and 13C NMR spectroscopy. Moreover, computational NMR and IR parameters were obtained using density functional theory (DFT) at B3LYP/6-311++G** level of theory. Complete NMR and vibrational assignment were carried out using the observed and calculated spectra. The IR frequencies and NMR chemical shifts, determined experimentally, were compared with those obtained theoretically from DFT calculations, showed good agreements. The RMS errors observed between experimental and calculated data for the IR absorptions are 85 and 105 cm -1, for the 1H NMR peaks are 0.87 and 0.17 ppm and for those of 13C NMR are 5.6 and 5.3 ppm, respectively for naltrexone and oxycodone.

  19. Distinguishing Vaccinium species by chemical fingerprinting based on NMR spectra, validated with spectra collected in different laboratories.

    PubMed

    Markus, Michelle A; Ferrier, Jonathan; Luchsinger, Sarah M; Yuk, Jimmy; Cuerrier, Alain; Balick, Michael J; Hicks, Joshua M; Killday, K Brian; Kirby, Christopher W; Berrue, Fabrice; Kerr, Russell G; Knagge, Kevin; Gödecke, Tanja; Ramirez, Benjamin E; Lankin, David C; Pauli, Guido F; Burton, Ian; Karakach, Tobias K; Arnason, John T; Colson, Kimberly L

    2014-06-01

    A method was developed to distinguish Vaccinium species based on leaf extracts using nuclear magnetic resonance spectroscopy. Reference spectra were measured on leaf extracts from several species, including lowbush blueberry (Vaccinium angustifolium), oval leaf huckleberry (Vaccinium ovalifolium), and cranberry (Vaccinium macrocarpon). Using principal component analysis, these leaf extracts were resolved in the scores plot. Analysis of variance statistical tests demonstrated that the three groups differ significantly on PC2, establishing that the three species can be distinguished by nuclear magnetic resonance. Soft independent modeling of class analogies models for each species also showed discrimination between species. To demonstrate the robustness of nuclear magnetic resonance spectroscopy for botanical identification, spectra of a sample of lowbush blueberry leaf extract were measured at five different sites, with different field strengths (600 versus 700 MHz), different probe types (cryogenic versus room temperature probes), different sample diameters (1.7 mm versus 5 mm), and different consoles (Avance I versus Avance III). Each laboratory independently demonstrated the linearity of their NMR measurements by acquiring a standard curve for chlorogenic acid (R(2) = 0.9782 to 0.9998). Spectra acquired on different spectrometers at different sites classifed into the expected group for the Vaccinium spp., confirming the utility of the method to distinguish Vaccinium species and demonstrating nuclear magnetic resonance fingerprinting for material validation of a natural health product. PMID:24963620

  20. Deuteron NMR spectra of ND4ClO4 single crystal at low temperatures.

    PubMed

    Birczyński, A; Lalowicz, Z T; Ingman, L P; Punkkinen, M; Ylinen, E E

    1993-03-01

    2H NMR spectra of ND4ClO4 single crystal were obtained at v0 = 44 MHz. Orientation and temperature (1.9-75 K) dependences were measured. Fitting the spectra gives the effective quadrupole coupling constants for all deuterons and the ground torsional level structure. The isotope reduction of the (A-T) and (A-E) tunnelling splittings, i.e., the ratios of the respective splittings for NH4+ and ND4+, were found to be different. The splittings at T = 24 K are about 60% of the helium temperature values. The spectrum undergoes intermediate narrowing by reorientations between 26 and 34 K and tunnelling related features in the spectra are eradicated. After reaching the extreme narrowing limit, a doublet with gradually decreasing separation was observed, what was attributed to averaging by torsional oscillations of increasing amplitude. At high temperatures (T > 75 K), the narrow spectrum reflects fast multiaxial reorientation of the ammonium ion. PMID:7834308

  1. Exploring the use of Generalized Indirect Covariance to reconstruct pure shift NMR spectra: Current Pros and Cons

    NASA Astrophysics Data System (ADS)

    Fredi, André; Nolis, Pau; Cobas, Carlos; Martin, Gary E.; Parella, Teodor

    2016-05-01

    The current Pros and Cons of a processing protocol to generate pure chemical shift NMR spectra using Generalized Indirect Covariance are presented and discussed. The transformation of any standard 2D homonuclear and heteronuclear spectrum to its pure shift counterpart by using a reference DIAG spectrum is described. Reconstructed pure shift NMR spectra of NOESY, HSQC, HSQC-TOCSY and HSQMBC experiments are reported for the target molecule strychnine.

  2. Chemical shift changes and line narrowing in 13C NMR spectra of hydrocarbon clathrate hydrates.

    PubMed

    Kida, Masato; Sakagami, Hirotoshi; Takahashi, Nobuo; Nagao, Jiro

    2013-05-23

    The solid-state (13)C NMR spectra of various guest hydrocarbons (methane, ethane, propane, adamantane) in clathrate hydrates were measured to elucidate the local structural environments around hydrocarbon molecules isolated in guest-host frameworks of clathrate hydrates. The results show that, depending on the cage environment, the trends in the (13)C chemical shift and line width change as a function of temperature. Shielding around the carbons of the guest normal alkanes in looser cage environments tends to decrease with increasing temperature, whereas shielding in tighter cage environments tends to increase continuously with increasing temperature. Furthermore, the (13)C NMR line widths suggest, because of the reorientation of the guest alkanes, that the local structures in structure II are more averaged than those in structure I. The differences between structures I and II tend to be very large in the lower temperature range examined in this study. The (13)C NMR spectra of adamantane guest molecules in structure H hydrate show that the local structures around adamantane guests trapped in structure H hydrate cages are averaged at the same level as in the α phase of solid adamantane. PMID:23607335

  3. Uncertainty measurement for automated macro program-processed quantitative proton NMR spectra.

    PubMed

    Hays, Patrick A; Schoenberger, Torsten

    2014-11-01

    The evaluation of a fully automated quantitative proton nuclear magnetic resonance spectroscopy (qNMR) processing program, including the determination of its processing uncertainty, and the calculations of the combined uncertainty of the qNMR result, is presented with details on the use of a trimmed purity average. Quantitative NMR spectra (1359) were collected over a 4-month period on various concentrations of pseudoephedrine HCl dissolved in D2O (0.0610 to 93.60 mg/mL) containing maleic acid (the internal standard) to yield signal-to-noise ratios ranging from 3 to 72,000 for analyte integral regions. The resulting 5436 purities exhibited a normal distribution about the best estimate of the true value. The median absolute deviation (MAD) statistical method was used to obtain a model of uncertainty relative to the signal-to-noise of the analyte's integral peaks. The model was then tested using different concentrations of known purity chloroquine diphosphate. qNMR results of numerous illicit heroin HCl samples were compared to those obtained by capillary electrophoresis. PMID:25273593

  4. Alternative approach to the standardization of NMR spectra. Direct measurement of nuclear magnetic shielding in molecules.

    PubMed

    Jackowski, Karol; Jaszuński, Michał; Wilczek, Marcin

    2010-02-25

    Exploring the relation between shielding constants, resonance frequencies and magnetic moments of the nuclei we demonstrate that nuclear magnetic shielding can be directly observed from NMR spectra. In this approach, the absolute shielding constants of all the nuclei can be related to a single reference scale, with atomic (3)He as the primary standard. The accuracy of the data obtained using our method is confirmed comparing the (1)H and (13)C shielding constants for a series of deuterated compounds with those determined analyzing the traditional chemical shifts. Since the use of helium-3 is not in general a practical alternative, we next transfer the reference standard to the (2)H signals of external lock solvents, in this way making the method easy and ready for application with most NMR spectrometers. Finally, we illustrate our new method with the measurements of the (2/1)H primary isotope effects in several liquid deuterated solvents. PMID:20112974

  5. Determination of orientational order parameters from 2H NMR spectra of magnetically partially oriented lipid bilayers.

    PubMed Central

    Schäfer, H; Mädler, B; Sternin, E

    1998-01-01

    The partial orientation of multilamellar vesicles (MLVs) in high magnetic fields is known to affect the shape of 2H NMR spectra. There are numerical methods for extracting either the orientational order parameters of lipid molecules for a random distribution of domain orientations in the sample, or the distribution of orientations for a known set of spectral anisotropies. A first attempt at determining the orientational order parameters in the presence of an unknown nonrandom distribution of orientations is presented. The numerical method is based on the Tikhonov regularization algorithm. It is tested using simulated partially oriented spectra. An experimental spectrum of a phospholipid-ether mixture in water is analyzed as an example. The experimental spectrum is consistent with an ellipsoidal shape of MLVs with a ratio of semiaxes of approximately 3.4. PMID:9533713

  6. Spectral investigations of 2,5-difluoroaniline by using mass, electronic absorption, NMR, and vibrational spectra

    NASA Astrophysics Data System (ADS)

    Kose, Etem; Karabacak, Mehmet; Bardak, Fehmi; Atac, Ahmet

    2016-11-01

    One of the most significant aromatic amines is aniline, a primary aromatic amine replacing one hydrogen atom of a benzene molecule with an amino group (NH2). This study reports experimental and theoretical investigation of 2,5-difluoroaniline molecule (2,5-DFA) by using mass, ultraviolet-visible (UV-vis), 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared and Raman (FT-IR and FT-Raman) spectra, and supported with theoretical calculations. Mass spectrum (MS) of 2,5-DFA is presented with their stabilities. The UV-vis spectra of the molecule are recorded in the range of 190-400 nm in water and ethanol solvents. The 1H and 13C NMR chemical shifts are recorded in CDCl3 solution. The vibrational spectra are recorded in the region 4000-400 cm-1 (FT-IR) and 4000-10 cm-1 (FT-Raman), respectively. Theoretical studies are underpinned the experimental results as described below; 2,5-DFA molecule is optimized by using B3LYP/6-311++G(d,p) basis set. The mass spectrum is evaluated and possible fragmentations are proposed based on the stable structure. The electronic properties, such as excitation energies, oscillator strengths, wavelengths, frontier molecular orbitals (FMO), HOMO and LUMO energies, are determined by time-dependent density functional theory (TD-DFT). The electrostatic potential surface (ESPs), density of state (DOS) diagrams are also prepared and evaluated. In addition to these, reduced density gradient (RDG) analysis is performed, and thermodynamic features are carried out theoretically. The NMR spectra (1H and 13C) are calculated by using the gauge-invariant atomic orbital (GIAO) method. The vibrational spectra of 2,5-DFA molecule are obtained by using DFT/B3LYP method with 6-311++G(d,p) basis set. Fundamental vibrations are assigned based on the potential energy distribution (PED) of the vibrational modes. The nonlinear optical properties (NLO) are also investigated. The theoretical and experimental results give a detailed description of

  7. Structures of Si-Carbohydrate Aqueous Complexes: Comparison of NMR Spectra and Molecular Orbital Results

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.; Heaney, P. J.

    2002-12-01

    Researchers recently have made the discovery that hypercoordinate Si-sorbitol complexes will readily form in biologically relevant fluids, and they have reported the first evidence for a transient organosilicon complex generated within the life cycle of an organism. These interpretations are based upon peak assignments of Si-29 NMR spectra that invoke Si-polyol complexes with Si in five- and six-fold coordination states. However, ab initio analyses of the proposed organosilicon structures do not reproduce the experimentally observed chemical shifts. We have successfully modeled one of the observed Si-29 chemical shifts with a 5-fold Si-disorbitol complex involving 5-membered ring configurations (i.e., Si-O-C-C-O), which yielded Si-29 chemical shifts that closely matched the observed values in the -100 to -102 ppm range. Likewise, Si-29 NMR peaks near -144 ppm were well fit by a model in which a 6-fold Si was complexed to three sorbitol molecules in a 5-membered ring configuration. The ability to simulate observed NMR signals using molecular orbital calculations provides strong support for the controversial role of hypercoordinate organosilicon species in the uptake and transport of silica by biological systems. The existence of such complexes in turn may explain other puzzles in Si biogeochemistry, such as the persistence of monomeric silica in concentrated biological fluids and the biofractionation of Si isotopes and Ge.

  8. Quantification of Human Brain Metabolites from in Vivo1H NMR Magnitude Spectra Using Automated Artificial Neural Network Analysis

    NASA Astrophysics Data System (ADS)

    Hiltunen, Yrjö; Kaartinen, Jouni; Pulkkinen, Juhani; Häkkinen, Anna-Maija; Lundbom, Nina; Kauppinen, Risto A.

    2002-01-01

    Long echo time (TE=270 ms) in vivo proton NMR spectra resembling human brain metabolite patterns were simulated for lineshape fitting (LF) and quantitative artificial neural network (ANN) analyses. A set of experimental in vivo1H NMR spectra were first analyzed by the LF method to match the signal-to-noise ratios and linewidths of simulated spectra to those in the experimental data. The performance of constructed ANNs was compared for the peak area determinations of choline-containing compounds (Cho), total creatine (Cr), and N-acetyl aspartate (NAA) signals using both manually phase-corrected and magnitude spectra as inputs. The peak area data from ANN and LF analyses for simulated spectra yielded high correlation coefficients demonstrating that the peak areas quantified with ANN gave similar results as LF analysis. Thus, a fully automated ANN method based on magnitude spectra has demonstrated potential for quantification of in vivo metabolites from long echo time spectroscopic imaging.

  9. Theoretical study of NMR, infrared and Raman spectra on triple-decker phthalocyanines

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsushi; Oku, Takeo

    2016-02-01

    Electronic structures and magnetic properties of multi-decker phthalocyanines were studied by theoretical calculation. Electronic structures, excited processes at multi-states, isotropic chemical shifts of 13C, 14N and 1H-nuclear magnetic resonance (NMR), principle V-tensor in electronic field gradient (EFG) tensor and asymmetry parameters (η), vibration mode in infrared (IR) and Raman spectra of triple-decker phthalocyanines were calculated by density functional theory (DFT) and time-dependent DFT using B3LYP as basis function. Electron density distribution was delocalized on the phthalocyanine rings with electron static potential. Considerable separation of chemical shifts in 13C, 14N and 1H-NMR was originated from nuclear spin interaction between nitrogen and carbon atoms, nuclear quadrupole interaction based on EFG and η of central metal under crystal field. Calculated optical absorption at multi-excited process was derived from overlapping π-orbital on the phthalocyanine rings. The vibration modes in IR and Raman spectra were based on in-plane deformation and stretching vibrations of metal-ligand coordination bond on the deformed structure.

  10. Deconvolution of Complex 1D NMR Spectra Using Objective Model Selection.

    PubMed

    Hughes, Travis S; Wilson, Henry D; de Vera, Ian Mitchelle S; Kojetin, Douglas J

    2015-01-01

    Fluorine (19F) NMR has emerged as a useful tool for characterization of slow dynamics in 19F-labeled proteins. One-dimensional (1D) 19F NMR spectra of proteins can be broad, irregular and complex, due to exchange of probe nuclei between distinct electrostatic environments; and therefore cannot be deconvoluted and analyzed in an objective way using currently available software. We have developed a Python-based deconvolution program, decon1d, which uses Bayesian information criteria (BIC) to objectively determine which model (number of peaks) would most likely produce the experimentally obtained data. The method also allows for fitting of intermediate exchange spectra, which is not supported by current software in the absence of a specific kinetic model. In current methods, determination of the deconvolution model best supported by the data is done manually through comparison of residual error values, which can be time consuming and requires model selection by the user. In contrast, the BIC method used by decond1d provides a quantitative method for model comparison that penalizes for model complexity helping to prevent over-fitting of the data and allows identification of the most parsimonious model. The decon1d program is freely available as a downloadable Python script at the project website (https://github.com/hughests/decon1d/). PMID:26241959

  11. Cu-NMR spectra in UCu4Ni uncover site disorder

    NASA Astrophysics Data System (ADS)

    Bernal, O. O.; Rose, D. A.; Wu, Hsin-Ju; Chiang, M.; MacLaughlin, D. E.; Stewart, G. R.; Kim, J. S.

    2012-12-01

    Cu-NMR measurements in a random powder of UCu4Ni reveal two types of spectral lines for each of the two isotopes of naturally abundant Cu in the material. These lines, which we label L1 and L2, point to the existence of two inequivalent Cu sites in the sample. We present a study of the NMR line shape in UCu4Ni at three different frequencies (in the range from 40-70 MHz) and two temperature values (10 K and 150 K), that allow us to assign the lines to particular Cu sites. L1 is strongly broadened as the frequency decreases, but changes less with increasing temperature. In contrast, the width of L2 grows in proportion to frequency and decreases noticeably with increasing temperature. This behavior indicates that the crystallographic site corresponding to L1 is exposed to electric field gradients and has lower point symmetry than the site corresponding to L2, which displays some anisotropy but no discernible quadrupole effects. By comparison with the Cu-NMR spectra in UCu4Pd, where only one type of Cu-NMR line has been observed clearly, we can associate L1 with Cu(16e) nuclei: Cu nuclei sitting at the 16e site (Wyckoff notation) in the AuBe5 structure of the parent compound UCu5. This leaves L2 as originating from Cu(4c) nuclei; i.e., those sitting at the 4c site of the same structure. Unlike in UCu4Pd, the appearance of signal from Cu(4c) nuclei in the Ni compound is clear evidence of site disorder in UCu4Ni.

  12. Analysis of the carbon-13 and proton NMR spectra of bovine chromaffin granules.

    PubMed

    Sharp, R R; Richards, E P

    1977-03-29

    Natural abundance carbon-13 and proton NMR spectra of bovine chromaffin granules have been obtained and analyzed using computer simulation techniques. High resolution spectra show the presence of a fluid aqueous phase containing epinephrine, ATP and a random coil protein. The protein spectrum contains unusually intense resonances due to glutamic acid and proline and has been simulated satisfactorily using the known amino acid composition of chromogranin A. The lipid phase of chromaffin granules gives rise to intense, but very broad, resonances in the carbon-13 spectrum. Protons in the lipid phase are also observable as a very rapid component of the proton-free induction decay (T2 approximately equal to 15 microns). Linewidths of the carbon-13 spectra have been used to set upper limits on rotational correlation times and on the motional anisotropy in the aqueous phase. These limits show that the aqueous phase is a simple solution (not a gel) that is isotropic over regions much larger than solute dimensions. No gel transition is observed between -3 and 25 degrees C. The carbon-13 spectra are definitely inconsistent with a lipoprotein matrix model and chromaffin granules previously proposed by Helle and Serck-Hanssen ((1975) Mol. Cell, Biochem. 6, 127-146). Relative carbon-13 intensities of ATP and epinephrine are not consistent with the known 1 : 4 mol ratio of these components. This fact suggests that epinephrine and ATP are not directly complexed in intact chromaffin granules. PMID:849474

  13. Automated data evaluation and modelling of simultaneous (19) F-(1) H medium-resolution NMR spectra for online reaction monitoring.

    PubMed

    Zientek, Nicolai; Laurain, Clément; Meyer, Klas; Paul, Andrea; Engel, Dirk; Guthausen, Gisela; Kraume, Matthias; Maiwald, Michael

    2016-06-01

    Medium-resolution nuclear magnetic resonance spectroscopy (MR-NMR) currently develops to an important analytical tool for both quality control and process monitoring. In contrast to high-resolution online NMR (HR-NMR), MR-NMR can be operated under rough environmental conditions. A continuous re-circulating stream of reaction mixture from the reaction vessel to the NMR spectrometer enables a non-invasive, volume integrating online analysis of reactants and products. Here, we investigate the esterification of 2,2,2-trifluoroethanol with acetic acid to 2,2,2-trifluoroethyl acetate both by (1) H HR-NMR (500 MHz) and (1) H and (19) F MR-NMR (43 MHz) as a model system. The parallel online measurement is realised by splitting the flow, which allows the adjustment of quantitative and independent flow rates, both in the HR-NMR probe as well as in the MR-NMR probe, in addition to a fast bypass line back to the reactor. One of the fundamental acceptance criteria for online MR-MNR spectroscopy is a robust data treatment and evaluation strategy with the potential for automation. The MR-NMR spectra are treated by an automated baseline and phase correction using the minimum entropy method. The evaluation strategies comprise (i) direct integration, (ii) automated line fitting, (iii) indirect hard modelling (IHM) and (iv) partial least squares regression (PLS-R). To assess the potential of these evaluation strategies for MR-NMR, prediction results are compared with the line fitting data derived from the quantitative HR-NMR spectroscopy. Although, superior results are obtained from both IHM and PLS-R for (1) H MR-NMR, especially the latter demands for elaborate data pretreatment, whereas IHM models needed no previous alignment. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25854892

  14. NMR Studies of the Li-Mg-N-H Phases.

    NASA Astrophysics Data System (ADS)

    Bowman, Robert; Reiter, J. W.; Kulleck, J. G.; Hwang, S.-J.; Luo, Weifang

    2007-03-01

    Solid state NMR including magic-angle-spinning (MAS) and cross-polarization (CP) MAS experiments have been used to characterize various amide and imide phases containing Li and/or Mg. MAS-NMR spectra for the ^1H, ^6Li, ^7Li, and ^15N nuclei have been obtained to improve understanding on formation, processing, and degradation behavior. Only limited information could be obtained from the proton and ^7Li MAS-NMR spectra to due large dipolar interactions and small chemical shifts. However, more success was obtained from the ^6Li and ^15N nuclei although their very long spin-lattice relaxation times did impact signal acquisition times. For example, three distinct ^6Li peaks were resolved from LiNH2 phases that were clearly separated from the LiH secondary phase in these samples. While the ^15N spectra for LiNH2 phase in isotopically enriched samples exhibited only a single peak at least three distinct ^15N peaks were observed from the similarly enriched Mg amide samples. These differences will be related to crystal structures. The NMR spectra also revealed very little motion in these hydrides upon to nearly 500 K.

  15. Spectroscopic separation of (13) C NMR spectra of complex isomeric mixtures by the CSSF-TOCSY-INEPT experiment.

    PubMed

    Yang, Lu; Moreno, Aitor; Fieber, Wolfgang; Brauchli, Robert; Sommer, Horst

    2015-04-01

    Isomeric mixtures from synthetic or natural origins can pose fundamental challenges for their chromatographic separation and spectroscopic identification. A novel 1D selective NMR experiment, chemical shift selective filter (CSSF)-TOCSY-INEPT, is presented that allows the extraction of (13) C NMR subspectra of discrete isomers in complex mixtures without physical separation. This is achieved via CSS excitation of proton signals in the (1) H NMR mixture spectrum, propagation of the selectivity by polarization transfer within coupled (1) H spins, and subsequent relaying of the magnetization from (1) H to (13) C by direct INEPT transfer to generate (13) C NMR subspectra. Simple consolidation of the subspectra yields (13) C NMR spectra for individual isomers. Alternatively, CSSF-INEPT with heteronuclear long-range transfer can correlate the isolated networks of coupled spins and therefore facilitate the reconstruction of the (13) C NMR spectra for isomers containing multiple spin systems. A proof-of-principle validation of the CSSF-TOCSY-INEPT experiment is demonstrated on three mixtures with different spectral and structural complexities. The results show that CSSF-TOCSY-INEPT is a versatile, powerful tool for deconvoluting isomeric mixtures within the NMR tube with unprecedented resolution and offers unique, unambiguous spectral information for structure elucidation. PMID:25616134

  16. Simulation of 2D NMR Spectra of Carbohydrates Using GODESS Software.

    PubMed

    Kapaev, Roman R; Toukach, Philip V

    2016-06-27

    Glycan Optimized Dual Empirical Spectrum Simulation (GODESS) is a web service, which has been recently shown to be one of the most accurate tools for simulation of (1)H and (13)C 1D NMR spectra of natural carbohydrates and their derivatives. The new version of GODESS supports visualization of the simulated (1)H and (13)C chemical shifts in the form of most 2D spin correlation spectra commonly used in carbohydrate research, such as (1)H-(1)H TOCSY, COSY/COSY-DQF/COSY-RCT, and (1)H-(13)C edHSQC, HSQC-COSY, HSQC-TOCSY, and HMBC. Peaks in the simulated 2D spectra are color-coded and labeled according to the signal assignment and can be exported in JCAMP-DX format. Peak widths are estimated empirically from the structural features. GODESS is available free of charge via the Internet at the platform of the Carbohydrate Structure Database project ( http://csdb.glycoscience.ru ). PMID:27227420

  17. Structural and dynamic characterization of Li(12)Si(7) and Li(12)Ge(7) using solid state NMR.

    PubMed

    Dupke, Sven; Langer, Thorsten; Pöttgen, Rainer; Winter, Martin; Eckert, Hellmut

    2012-04-01

    Local environments and lithium ion dynamics in the binary lithium silicide Li(12)Si(7), and the analogous germanium compound have been characterized by detailed (6)Li, (7)Li, and (29)Si variable temperature static and magic-angle spinning (MAS) NMR experiments. In the MAS-NMR spectra, individual lithium sites are generally well-resolved at temperatures below 200K, whereas at higher temperatures partial site averaging is observed on the kHz timescale. The observed lithium chemical shift ranges of up to 60 ppm indicate a significant amount of electronic charge stored on the lithium species, consistent with the expectation of the extended Zintl-Klemm-Bussmann concept used for the theoretical description of lithium silicides. Furthermore the strongly diamagnetic chemical shifts observed for the lithium ions situated directly above the five-membered Si(5) rings suggest the possibility of aromatic ring currents in these structural elements. This assignment is confirmed further by (29)Si{(7)Li} CPMAS-heteronuclear correlation experiments. The (29)Si MAS-NMR spectra of Li(12)Si(7), aided by 2-D J-resolved spectroscopy, are well suited for differentiating between the individual sites within the silicon framework, while further detailed connectivity information is available on the basis of 2-D INADEQUATE and radio frequency driven recoupling (RFDR) spectra. Variable temperature static (7)Li NMR spectra reveal the onset of strong motional narrowing effects, illustrating high lithium ionic mobilities in both of these compounds. PMID:21996453

  18. Non-Linear Signal Detection Improvement by Radiation Damping in Single-Pulse NMR Spectra

    PubMed Central

    Schlagnitweit, Judith; Morgan, Steven W; Nausner, Martin; Müller, Norbert; Desvaux, Hervé

    2012-01-01

    When NMR lines overlap and at least one of them is affected by radiation damping, the resonance line shapes of all lines are no longer Lorentzian. We report the appearance of narrow signal distortions, which resemble hole-burnt spectra. This new experimental phenomenon facilitates the detection of tiny signals hidden below the main resonance. Theoretical analysis based on modified Maxwell–Bloch equations shows that the presence of strong transverse magnetization creates a feedback through the coil, which influences the magnetization of all spins with overlapping resonance lines. In the time domain this leads to cross-precession terms between magnetization densities, which ultimately cause non-linear behavior. Numerical simulations corroborate this interpretation. PMID:22266720

  19. An analytical derivation of a popular approximation of the Voigt function for quantification of NMR spectra.

    PubMed

    Bruce, S D; Higinbotham, J; Marshall, I; Beswick, P H

    2000-01-01

    The approximation of the Voigt line shape by the linear summation of Lorentzian and Gaussian line shapes of equal width is well documented and has proved to be a useful function for modeling in vivo (1)H NMR spectra. We show that the error in determining peak areas is less than 0.72% over a range of simulated Voigt line shapes. Previous work has concentrated on empirical analysis of the Voigt function, yielding accurate expressions for recovering the intrinsic Lorentzian component of simulated line shapes. In this work, an analytical approach to the approximation is presented which is valid for the range of Voigt line shapes in which either the Lorentzian or Gaussian component is dominant. With an empirical analysis of the approximation, the direct recovery of T(2) values from simulated line shapes is also discussed. PMID:10617435

  20. Velocity autocorrelation spectra in molten polymers measured by NMR modulated gradient spin-echo

    NASA Astrophysics Data System (ADS)

    Stepišnik, Janez; Mohorič, Aleš; Mattea, Carlos; Stapf, Siegfried; Serša, Igor

    2014-04-01

    The segmental dynamics in molten linear polymers is studied by the NMR method of modulated gradient spin-echo, which directly probes a spectrum of molecular velocity autocorrelation function. Diffusion spectra of mono-disperse poly(isoprene-1.4) with different molecular masses, measured in the frequency range 0.1-10 kHz at a temperature of 26\\ ^{\\circ}\\text{C} , have a form similar to the spectrum of Rouse chain dynamics, which implicates the tube-Rouse motion as the dominant dynamic process in this frequency range. The scaling of the center-of-mass diffusion coefficient, given from the fitting parameters, changes from N^{-1} into N^{-2.4} at around N \\approx 3\\text{-}5 Kuhn steps, which is less than predicted by theory and simulations, while the correlation times of the tube-Rouse mode do not follow the anticipated scaling.

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

    SciTech Connect

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

    1988-03-01

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

  2. Main-chain-directed strategy for the assignment of /sup 1/H NMR spectra of proteins

    SciTech Connect

    Englander, S.W.; Wand, A.J.

    1987-09-22

    A strategy for assigning the resonances in two-dimensional (2D) NMR spectra of proteins is described. The method emphasizes the analysis of through-space relationships between protons by use of the two-dimensional nuclear Overhauser effect (NOE) experiment. NOE patterns used in the algorithm were derived from a statistical analysis of the combinations of short proton-proton distances observed in the high-resolution crystal structures of 21 proteins. One starts with a search for authentic main-chain NH-C/sub ..cap alpha../H-C/sub ..beta../H J-coupled units, which can be found with high reliability. The many main-chain units of a protein are then placed in their proper juxtaposition by recognition of predefined NOE connectivity patterns. To discover these connectivities, the 2D NOE spectrum is examined, in a prescribed order, for the distinct NOE patterns characteristic of helices, sheets, turns, and extended chain. Finally, the recognition of a few amino acid side-chain types places the discovered secondary structure elements within the polypeptide sequences. Unlike the sequential assignment approach, the main-chain-directed strategy does not rely on the difficult task of recognizing many side-chain spin systems in J-correlated spectra, the assignment process is not in general sequential with the polypeptide chain, and the prescribed connectivity patterns are cyclic rather than linear. The latter characteristic avoids ambiguous branch points in the analysis and imposed an internally confirmatory property on each forward step.

  3. 1H NMR spectra of humic and fulvic acids and their peracetic oxidation products

    NASA Astrophysics Data System (ADS)

    Ruggiero, P.; Interesse, F. S.; Cassidei, L.; Sciacovelli, O.

    1980-04-01

    1H NMR spectra of humic (HA) and fulvic (FA) acids and their oxidative degradation products are reported. The HA shows the presence of -( CH2) n - CH3 ( n > 6) chemical fragments belonging to n-alkanes and/or n-fatty acids physically adsorbed onto the macromolecule structure. These fragments are absent in the FA fraction. Both humic fractions reveal the presence of similar amounts of aromatic protons which partly undergo exchange phenomena. The importance of this experimental observation is discussed. Oxidative degradation seems to cause partial cleavage of aromatic rings, more pronounced in the FA than in the HA. The degraded FA shows a higher total acidity and a higher phenolic OH content than the degraded HA. Both degraded fractions display some sharp singlet signals at 1.9 and 3.9 ppm arising from protons belonging to repetitive chemical fragments probably formed during the oxidation reaction. Tentative assignments of these signals are given. A general analysis of the HA and FA degraded spectra seems to indicate that the chemical fragments which undergo peracetic oxidation are substantially similar. The extent of oxidation of the two humic fractions is different. The HA degradation products reveal the presence of oligomeric structures, whereas the degraded FA appears less resistant to the oxidizing agent.

  4. The NMR investigation of alkaloids. IX. /sup 13/C NMR spectra and stereochemistry of convolvine, convolamine, convoline, convolidine, subhirsine and 6-hydroxyhyoscyamine

    SciTech Connect

    Yagudaev, M.R.; Aripova, S.F.

    1986-07-01

    A correlation has been made on the basis of the results of a study of the C 13 NMR spectra, of the CSs of the C 13 carbon nuclei with the structure and stereochemistry of the tropane alkaloids convolvine, convolamine, convoline, convolidine, subhirsine, and 6-hydroxyhyoscyamine. It has been established that the N-CH/sub 3/ group in convolamine and the -OH group in convoline are oriented equatorially, and the N-CH/sub 3/ in hydroxyhyoscyamine axially.

  5. Spinning-frequency-dependent linewidths in 1H-decoupled 13C magic-angle spinning NMR spectra

    NASA Astrophysics Data System (ADS)

    Nakai, Toshihito; McDowell, Charles A.

    1994-09-01

    The broadenings observed in 13C MAS NMR spectra, which depend on the sample-spinning speed, were studied, using polycrystalline adamantane. Not only was a monotonic increase of the linewidths with the increase of the spinning frequency observed, but also a novel resonant feature was found. The phenomena were interpreted as originating from rotary-resonance 13C 1H recoupling.

  6. Complete assignment of (1)H and (13)C NMR spectra of standard neo-iota-carrabiose oligosaccharides.

    PubMed

    Jouanneau, Diane; Boulenguer, Patrick; Mazoyer, Jacques; Helbert, William

    2010-02-26

    Standard Eucheuma denticulatum iota-carrageenan was degraded with the Alteromonas fortis iota-carrageenase. The most abundant products, the neo-iota-carratetraose and neo-iota-carrahexaose were purified by permeation gel chromatography, and their corresponding (1)H and (13)C NMR spectra were fully assigned. PMID:20038459

  7. Method for determining molar concentrations of metabolites in complex solutions from two-dimensional 1H-13C NMR spectra.

    PubMed

    Lewis, Ian A; Schommer, Seth C; Hodis, Brendan; Robb, Kate A; Tonelli, Marco; Westler, William M; Sussman, Michael R; Markley, John L

    2007-12-15

    One-dimensional (1D) (1)H nuclear magnetic resonance (NMR) spectroscopy is used extensively for high-throughput analysis of metabolites in biological fluids and tissue extracts. Typically, such spectra are treated as multivariate statistical objects rather than as collections of quantifiable metabolites. We report here a two-dimensional (2D) (1)H-(13)C NMR strategy (fast metabolite quantification, FMQ, by NMR) for identifying and quantifying the approximately 40 most abundant metabolites in biological samples. To validate this technique, we prepared mixtures of synthetic compounds and extracts from Arabidopsis thaliana, Saccharomyces cerevisiae, and Medicago sativa. We show that accurate (technical error 2.7%) molar concentrations can be determined in 12 min using our quantitative 2D (1)H-(13)C NMR strategy. In contrast, traditional 1D (1)H NMR analysis resulted in 16.2% technical error under nearly ideal conditions. We propose FMQ by NMR as a practical alternative to 1D (1)H NMR for metabolomics studies in which 50-mg (extract dry weight) samples can be obtained. PMID:17985927

  8. Exploring Light Neutron Rich Nuclei via the ({sup 7}Li,{sup 7}Be) Reaction

    SciTech Connect

    Cavallaro, M.; Cappuzzello, F.; Cunsolo, A.; Foti, A.; Orrigo, S. E. A.; Rodrigues, M. R. D.; Borello-Lewin, T.; Lenske, H.; Petrascu, H.; Winfield, J. S.

    2008-11-11

    A systematic study of the nuclei that can be described as an integer number of {alpha} particles plus three neutrons via the ({sup 7}Li,{sup 7}Be) reaction at about 8 MeV/u has shown the presence of Bound States Embedded in the Continuum in the energy spectra. These are experimental signatures of the dynamical correlations of an easily polarizable core with a single-particle state of the valence neutron.

  9. Analysis of deuteron breakup reactions on {sup 7}Li for energies up to 100 MeV

    SciTech Connect

    Ye, Tao; Watanabe, Yukinobu; Ogata, Kazuyuki

    2009-07-15

    Inclusive nucleon spectra from deuteron breakup reactions on {sup 7}Li are analyzed in terms of the continuum discretized coupled channels theory for the elastic breakup process and the Glauber model for the nucleon stripping process. Both theoretical models use the same phenomenological nucleon optical potential of {sup 7}Li and have no other free parameters. The calculations reproduce well a prominent bump observed around half the incident energy in experimental inclusive spectra of 40-MeV (d,xn) and 100-MeV (d,xp) reactions at forward angles. The analysis shows that the stripping process is more important than the elastic breakup process in deuteron breakup reactions on {sup 7}Li.

  10. Deuteron NMR Spectra of ND4 Tunneling at Low Frequenciesin (ND4)2SnBr6

    NASA Astrophysics Data System (ADS)

    Lalowicz, Z. T.; Serafin, R.; Punkkinen, M.; Vuorimäki, A. H.; Ylinen, E. E.

    1995-05-01

    Deuteron NMR spectra of slowly tunneling ND4+ ions are analysed. Spectra are calculated as functions of the tunneling parameters which are the tunneling frequencies about the symmetry axes C2 and C3 of the tetrahedral ion. The structure and splittings within the ground torsional level (GTL) are obtained by fitting the spectra of (ND4)2SnBr6. Comparison with the GTL structure obtained before for NH4+ in the same compound gives the isotope reduction factor of the tunneling frequency about 200.

  11. Unified and Isomer-Specific NMR Metabolomics Database for the Accurate Analysis of 13C–1H HSQC Spectra

    PubMed Central

    2015-01-01

    A new metabolomics database and query algorithm for the analysis of 13C–1H HSQC spectra is introduced, which unifies NMR spectroscopic information on 555 metabolites from both the Biological Magnetic Resonance Data Bank (BMRB) and Human Metabolome Database (HMDB). The new database, termed Complex Mixture Analysis by NMR (COLMAR) 13C–1H HSQC database, can be queried via an interactive, easy to use web interface at http://spin.ccic.ohio-state.edu/index.php/hsqc/index. Our new HSQC database separately treats slowly exchanging isomers that belong to the same metabolite, which permits improved query in cases where lowly populated isomers are below the HSQC detection limit. The performance of our new database and query web server compares favorably with the one of existing web servers, especially for spectra of samples of high complexity, including metabolite mixtures from the model organisms Drosophila melanogaster and Escherichia coli. For such samples, our web server has on average a 37% higher accuracy (true positive rate) and a 82% lower false positive rate, which makes it a useful tool for the rapid and accurate identification of metabolites from 13C–1H HSQC spectra at natural abundance. This information can be combined and validated with NMR data from 2D TOCSY-type spectra that provide connectivity information not present in HSQC spectra. PMID:25333826

  12. Unified and isomer-specific NMR metabolomics database for the accurate analysis of (13)C-(1)H HSQC spectra.

    PubMed

    Bingol, Kerem; Li, Da-Wei; Bruschweiler-Li, Lei; Cabrera, Oscar A; Megraw, Timothy; Zhang, Fengli; Brüschweiler, Rafael

    2015-02-20

    A new metabolomics database and query algorithm for the analysis of (13)C-(1)H HSQC spectra is introduced, which unifies NMR spectroscopic information on 555 metabolites from both the Biological Magnetic Resonance Data Bank (BMRB) and Human Metabolome Database (HMDB). The new database, termed Complex Mixture Analysis by NMR (COLMAR) (13)C-(1)H HSQC database, can be queried via an interactive, easy to use web interface at http://spin.ccic.ohio-state.edu/index.php/hsqc/index . Our new HSQC database separately treats slowly exchanging isomers that belong to the same metabolite, which permits improved query in cases where lowly populated isomers are below the HSQC detection limit. The performance of our new database and query web server compares favorably with the one of existing web servers, especially for spectra of samples of high complexity, including metabolite mixtures from the model organisms Drosophila melanogaster and Escherichia coli. For such samples, our web server has on average a 37% higher accuracy (true positive rate) and a 82% lower false positive rate, which makes it a useful tool for the rapid and accurate identification of metabolites from (13)C-(1)H HSQC spectra at natural abundance. This information can be combined and validated with NMR data from 2D TOCSY-type spectra that provide connectivity information not present in HSQC spectra. PMID:25333826

  13. Resolution Improvements in in Vivo1H NMR Spectra with Increased Magnetic Field Strength

    NASA Astrophysics Data System (ADS)

    Gruetter, Rolf; Weisdorf, Sally A.; Rajanayagan, Vasantham; Terpstra, Melissa; Merkle, Hellmut; Truwit, Charles L.; Garwood, Michael; Nyberg, Scott L.; Ugurbil, Kâmil

    1998-11-01

    The measurement of cerebral metabolites using highly homologous localization techniques and similar shimming methods was performed in the human brain at 1.5 and 4 T as well as in the dog and rat brain at 9.4 T. In rat brain, improved resolution was achieved by shimming all first- and second-order shim coils using a fully adiabatic FASTMAP sequence. The spectra showed a clear improvement in spectral resolution for all metabolite resonances with increased field strength. Changes in cerebral glutamine content were clearly observed at 4 T compared to 1.5 T in patients with hepatic encephalopathy. At 9.4 T, glutamine H4 at 2.46 ppm was fully resolved from glutamate H4 at 2.37 ppm, as was the potential resonance from γ-amino-butyric acid at 2.30 ppm and N-acetyl-aspartyl-glutamate at 2.05 ppm. Singlet linewidths were found to be as low as 6 Hz (0.015 ppm) at 9.4 T, indicating a substantial decrease in ppm linewidth with field strength. Furthermore, the methylene peak of creatine was partially resolved from phosphocreatine, indicating a close to 1:1 relationship in gray matter. We conclude that increasing the magnetic field strength increases spectral resolution also for1H NMR, which can lead to more than linear sensitivity gains.

  14. Variations of pH as an additional tool in the analysis of crowded NMR spectra of fucosylated chondroitin sulfates.

    PubMed

    Ustyuzhanina, Nadezhda E; Dmitrenok, Andrey S; Bilan, Maria I; Shashkov, Alexander S; Gerbst, Alexey G; Usov, Anatolii I; Nifantiev, Nikolay E

    2016-03-24

    The influence of pH variation on chemical shift values in NMR spectra of fucosylated chondroitin sulfates was studied using polysaccharides isolated from three sea cucumber species Apostichopus japonicus, Actinopyga mauritiana and Cucumaria japonica. The signals of glucuronic acid residues were found to be the most sensitive to pH changes in comparison to the chemical shifts of the sulfated galactosamine and fucosyl units, most of which were altered insignificantly. It was shown that in the presence of imidazole-HCl buffer (pH 7.2) NMR spectra of the polysaccharides from A. japonicus and A. mauritiana were sufficiently resolved, whereas under acidic conditions their (1)H NMR spectra were complicated by overlapping of H-1 signals of GlcA and GalNAc. In the case of polysaccharide from C. japonica bearing 3-O-fucosylated and 3-O-sulfated glucuronic acid residues in the backbone, acidification of the medium led to separation of H-1 signals of GlcA3S and GalNAc. Therefore, the combination of data obtained at different pH values may be useful for interpretation of overcrowded spectra of fucosylated chondroitin sulfates. PMID:26895544

  15. NMR Spectra Transformed by Electron-Nuclear Coupling as Indicator of Structural Peculiarities of Magnetically Active Molecular Systems.

    PubMed

    Voronov, Vladimir K

    2016-09-01

    The peculiarities of nuclear spin relaxation in the paramagnetic systems have been analyzed taking into account the exchange processes. The analysis is based on the modified Solomon-Bloembergen equations. In this line, the conditions of detecting of the NMR signals of samples are discussed depending on resonance frequency of the NMR spectrometer and characteristic relaxation time. On this basis, (1)H NMR spectra of cobalt semiquinolate complex have been analyzed. It has been shown that the satellite signals observed in the spectrum are caused by hyperfine coupling of the tert-butyl group protons with α and β states (localized on pz orbital of the aromatic carbon) of unpaired electron spin. The relaxation process of the resonance protons is controlled by paramagnetic dipole-dipole coupling. The contact hyperfine coupling does not contribute to the paramagnetic broadening. A mechanism involving paramagnetic molecular structures, which are responsible for intramolecular exchange processes in the cobalt semiquinolate complex, is given. PMID:27513208

  16. AssignFit: A program for simultaneous assignment and structure refinement from solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Tian, Ye; Schwieters, Charles D.; Opella, Stanley J.; Marassi, Francesca M.

    2012-01-01

    AssignFit is a computer program developed within the XPLOR-NIH package for the assignment of dipolar coupling (DC) and chemical shift anisotropy (CSA) restraints derived from the solid-state NMR spectra of protein samples with uniaxial order. The method is based on minimizing the difference between experimentally observed solid-state NMR spectra and the frequencies back calculated from a structural model. Starting with a structural model and a set of DC and CSA restraints grouped only by amino acid type, as would be obtained by selective isotopic labeling, AssignFit generates all of the possible assignment permutations and calculates the corresponding atomic coordinates oriented in the alignment frame, together with the associated set of NMR frequencies, which are then compared with the experimental data for best fit. Incorporation of AssignFit in a simulated annealing refinement cycle provides an approach for simultaneous assignment and structure refinement (SASR) of proteins from solid-state NMR orientation restraints. The methods are demonstrated with data from two integral membrane proteins, one α-helical and one β-barrel, embedded in phospholipid bilayer membranes.

  17. Experimental and theoretical studies on compositions, structures, and IR and NMR spectra of functionalized protic ionic liquids.

    PubMed

    Cui, Yingna; Yin, Jingmei; Li, Changping; Li, Shenmin; Wang, Ailing; Yang, Guang; Jia, Yingping

    2016-07-20

    The compositions and structures of amine-based functionalized protic ionic liquids (PILs), namely N,N-dimethyl(cyanoethyl)ammonium propionate (DMCEAP) and N,N-dimethyl(hydroxyethyl)ammonium propionate (DMEOAP) have been investigated systematically by IR and (1)H NMR spectroscopy and density functional theory (DFT) calculations. Analysis of the IR spectra suggests that both DMCEAP and DMEOAP are composed of neutral and ionized species in the liquid phase, the former one mainly existing in the state of precursor molecules, and the latter mainly as ion-pairs. The ratio of precursor molecules to ion-pairs in the liquid phase depends on the types of precursors, especially the functional groups of cations. (1)H NMR spectra indicate that there is a dynamic equilibrium between the neutral and ionized species, probably due to the formation of some intermediates in the PILs. The DFT calculations have been carried out to reveal the conformation, and obtain the corresponding IR and (1)H NMR spectra of the neutral and ionized species, so that the theoretical support to the experimental results can be provided. The present study will help understand the properties of PILs and provide guidance for further applications of PILs. PMID:27385035

  18. Singular spectrum analysis for an automated solvent artifact removal and baseline correction of 1D NMR spectra

    NASA Astrophysics Data System (ADS)

    De Sanctis, Silvia; Malloni, Wilhelm M.; Kremer, Werner; Tomé, Ana M.; Lang, Elmar W.; Neidig, Klaus-Peter.; Kalbitzer, Hans Robert

    2011-06-01

    NMR spectroscopy in biology and medicine is generally performed in aqueous solutions, thus in 1H NMR spectroscopy, the dominant signal often stems from the partly suppressed solvent and can be many orders of magnitude larger than the resonances of interest. Strong solvent signals lead to a disappearance of weak resonances of interest close to the solvent artifact and to base plane variations all over the spectrum. The AUREMOL-SSA/ALS approach for automated solvent artifact removal and baseline correction has been originally developed for multi-dimensional NMR spectroscopy. Here, we describe the necessary adaptations for an automated application to one-dimensional NMR spectra. Its core algorithm is still based on singular spectrum analysis (SSA) applied on time domain signals (FIDs) and it is still combined with an automated baseline correction (ALS) in the frequency domain. However, both steps (SSA and ALS) have been modified in order to achieve optimal results when dealing with one-dimensional spectra. The performance of the method has been tested on one-dimensional synthetic and experimental spectra including the back-calculated spectrum of HPr protein and an experimental spectrum of a human urine sample. The latter has been recorded with the typically used NOESY-type 1D pulse sequence including water pre-saturation. Furthermore, the fully automated AUREMOL-SSA/ALS procedure includes the managing of oversampled, digitally filtered and zero-filled data and the correction of the frequency domain phase shift caused by the group delay time shift from the digital finite response filtering.

  19. Conformational studies of 3-aminomethylene-2,4-pentanedione using vibrational and NMR spectra, and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gróf, M.; Gatial, A.; Milata, V.; Prónayová, N.; Sümmchen, L.; Salzer, R.

    2007-10-01

    The IR, Raman and NMR spectra of 3-aminomethylene-2,4-pentanedione (AMP) H 2N sbnd CH dbnd C(COCH 3) 2 were measured. According to the NMR spectra in chloroform and more polar DMSO at room temperature, the sample exists as single entity. On the other hand vibrational spectra revealed that in less polar solutions AMP exists as two conformers with EZ or ZZ orientation of acetyl groups whereas in more polar solvent only one EZ conformer is observed. Such interpretation was confirmed also by the temperature-dependent measurements of IR spectra in chloroform. The observed IR and Raman bands were compared with harmonic vibrational frequencies, calculated using ab initio MP2 and B3LYP density functional methods in 6-31G ∗∗ basis set, and assigned on the basis of potential energy distribution. In addition, the geometries and relative energies of possible conformers of AMP were also evaluated at the same levels of theory and compared with the data from X-ray analysis which revealed that AMP exists in solid state as EZ conformer. The influence of environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using PCM, IPCM and ONSAGER models.

  20. 224} studied by NMR

    SciTech Connect

    Furukawa, Y; Fang, X; Kögerler, P

    2014-05-14

    7Li nuclear magnetic resonance (NMR) studies have been performed to investigate magnetic properties and spin dynamics of Mn3+ (S = 2) spins in the giant polyoxometalate molecule {Mn40W224}. The 7Li-NMR line width is proportional to the external magnetic field H as expected in a paramagnetic state above 3 K. Below this temperature the line width shows a sudden increase and is almost independent of H, which indicates freezing of the local Mn3+ spins. The temperature dependence of T1 for both 1H and 7Li reveals slow spin dynamics at low temperatures, consistent with spin freezing. The slow spin dynamics is also evidenced by the observation of a peak of 1/T2 around 3 K, where the fluctuation frequency of spins is of the order of ~200 kHz. An explicit form of the temperature dependence of the fluctuation frequency of Mn3+ spins is derived from the nuclear relaxation data.

  1. (6)Li, (7)Li Nuclear Magnetic Resonance Investigation of Lithium Coordination in Binary Phosphate Glasses

    SciTech Connect

    Alam, T.M.; Boyle, T.J.; Brow, R.K.; Conzone, S.

    1999-02-08

    {sup 6}Li and {sup 7}Li solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the local coordination environment of lithium in a series of xLi{sub 2}O {center_dot} (1-x)P{sub 2}O{sub 5} glasses, where 0.05 {le} x {le} 0.55. Both the {sup 6}Li and {sup 7}Li show chemical shift variations with changes in the Li{sub 2}O concentration, but the observed {sup 6}Li NMR chemical shifts closely approximate the true isotropic chemical shift and can provide a measure of the lithium bonding environment. The {sup 6}Li NMR results indicate that in this series of lithium phosphate glasses the Li atoms have an average coordination between four and five. The results for the metaphosphate glass agree with the coordination number and range of chemical shifts observed for crystalline LiPO{sub 3}. An increase in the {sup 6}Li NMR chemical shift with increasing Li{sub 2}O content was observed for the entire concentration range investigated, correlating with increased cross-linking of the phosphate tetrahedral network by O-Li-O bridges. The {sup 6}Li chemical shifts were also observed to vary monotonically through the anomalous glass transition temperature (T{sub g}) minimum. This continuous chemical shift variation shows that abrupt changes in the Li coordination environment do not occur as the Li{sub 2}O concentration is increased, and such abrupt changes can not be used to explain the T{sub g} minimum.

  2. EASY-GOING deconvolution: Combining accurate simulation and evolutionary algorithms for fast deconvolution of solid-state quadrupolar NMR spectra

    NASA Astrophysics Data System (ADS)

    Grimminck, Dennis L. A. G.; Polman, Ben J. W.; Kentgens, Arno P. M.; Leo Meerts, W.

    2011-08-01

    A fast and accurate fit program is presented for deconvolution of one-dimensional solid-state quadrupolar NMR spectra of powdered materials. Computational costs of the synthesis of theoretical spectra are reduced by the use of libraries containing simulated time/frequency domain data. These libraries are calculated once and with the use of second-party simulation software readily available in the NMR community, to ensure a maximum flexibility and accuracy with respect to experimental conditions. EASY-GOING deconvolution ( EGdeconv) is equipped with evolutionary algorithms that provide robust many-parameter fitting and offers efficient parallellised computing. The program supports quantification of relative chemical site abundances and (dis)order in the solid-state by incorporation of (extended) Czjzek and order parameter models. To illustrate EGdeconv's current capabilities, we provide three case studies. Given the program's simple concept it allows a straightforward extension to include other NMR interactions. The program is available as is for 64-bit Linux operating systems.

  3. An inversion method of 2D NMR relaxation spectra in low fields based on LSQR and L-curve

    NASA Astrophysics Data System (ADS)

    Su, Guanqun; Zhou, Xiaolong; Wang, Lijia; Wang, Yuanjun; Nie, Shengdong

    2016-04-01

    The low-field nuclear magnetic resonance (NMR) inversion method based on traditional least-squares QR decomposition (LSQR) always produces some oscillating spectra. Moreover, the solution obtained by traditional LSQR algorithm often cannot reflect the true distribution of all the components. Hence, a good solution requires some manual intervention, for especially low signal-to-noise ratio (SNR) data. An approach based on the LSQR algorithm and L-curve is presented to solve this problem. The L-curve method is applied to obtain an improved initial optimal solution by balancing the residual and the complexity of the solutions instead of manually adjusting the smoothing parameters. First, the traditional LSQR algorithm is used on 2D NMR T1-T2 data to obtain its resultant spectra and corresponding residuals, whose norms are utilized to plot the L-curve. Second, the corner of the L-curve as the initial optimal solution for the non-negative constraint is located. Finally, a 2D map is corrected and calculated iteratively based on the initial optimal solution. The proposed approach is tested on both simulated and measured data. The results show that this algorithm is robust, accurate and promising for the NMR analysis.

  4. Quantitative Quantum Mechanical Spectral Analysis (qQMSA) of 1H NMR spectra of complex mixtures and biofluids

    NASA Astrophysics Data System (ADS)

    Tiainen, Mika; Soininen, Pasi; Laatikainen, Reino

    2014-05-01

    The quantitative interpretation of 1H NMR spectra of mixtures like the biofluids is a demanding task due to spectral complexity and overlap. Complications may arise also from water suppression, T2-editing, protein interactions, relaxation differences of the species, experimental artifacts and, furthermore, the spectra may contain unknown components and macromolecular background which cannot be easily separated from baseline. In this work, tools and strategies for quantitative Quantum Mechanical Spectral Analysis (qQMSA) of 1H NMR spectra from complex mixtures were developed and systematically assessed. In the present approach, the signals of well-defined, stoichiometric components are described by a QM model, while the background is described by a multiterm baseline function and the unknown signals using optimizable and adjustable lines, regular multiplets or any spectral structures which can be composed from spectral lines. Any prior knowledge available from the spectrum can also be added to the model. Fitting strategies for weak and strongly overlapping spectral systems were developed and assessed using two basic model systems, the metabolite mixtures without and with macromolecular (serum) background. The analyses show that if the spectra are measured in high-throughput manner, the consistent absolute quantification demands some calibration to compensate the different response factors of the protons and compounds. On the other hand, the results show that also the T2-edited spectra can be measured so that they obey well the QM rules. In general, qQMSA exploits and interprets the spectral information in maximal way taking full advantage from the QM properties of the spectra and, at the same time, offers chemical confidence which means that individual components can be identified with high confidence on the basis of their accurate spectral parameters.

  5. Constraining Oxygen-17 NMR Spectra of High Pressure Crystals and Glasses: New Data for Jadeite, Pyrope, Grossular, and Mullite

    NASA Astrophysics Data System (ADS)

    Kelsey, K. E.; Stebbins, J. F.; Du, L.; Hankins, B.

    2005-12-01

    17O NMR is a direct way of analyzing the immediate environment around oxygen atoms and can provide information on cation ordering, mixing, and network connectivity in glasses and disordered crystals. Due to overlapping peaks and lack of data on crystalline model compounds, 17O NMR spectra of high pressure glasses have been difficult to interpret. Additionally, data on crystalline model compounds are needed to test the validity of quantum chemical calculations. In this study, 17O NMR spectra were collected for crystalline jadeite, pyrope, grossular, and mullite in order to determine the parameters for oxygen bonded to [6]Al in a variety of environments. Jadeite contains three oxygen sites: oxygen bonded to [4]Si, Na, and two [6]Al atoms (O1), oxygen bonded to [4]Si, Na, and [6]Al atoms (O2), and oxygen bonded to two [4]Si and two Na atoms (O3). The NMR parameters for O1 are CQ = 3.3 MHz, δ = 64 ppm, and ν = 0.9; for O2 are CQ = 4.1 MHz, δ = 59 ppm, and ν = 0.15; and for O3 are CQ = 5.0 MHz, δ = 60 ppm, and ν = 0.15. The parameters for O2 are similar to interpretations of recent data for this kind of site in high pressure sodium aluminosilicate glasses (δ = 59 ppm) and to quantum chemical calculations (Lee et al., 2004, J. Phys. Chem., 108, 5897). Pyrope and grossular each contain one oxygen site, oxygen bonded to [4]Si, [6]Al, and two M2+ cations. The 17O NMR parameters for pyrope are CQ = 3.4 MHz, δ = 84 ppm, and ν = 0.3 and for grossular are CQ = 4.1 MHz, δ = 102 ppm, and ν = 0.4. In grossular, the NMR peak for oxygens bonded to [4]Si, Ca, and high coordinated Al seems to fall between those for "normal" bridging and non bridging oxygens, as reported for high pressure CAS glasses by Allwardt et al. (2005). These data will also be useful to help understand Ca-Mg ordering in the pyrope-grossular solid solutions. Mullite contains four oxygen environments: oxygen bonded to three tetrahedral Al or Si (Oc*), oxygen bonded to two tetrahedral Al or Si (Oc), and

  6. The cosmological 7Li problem from a nuclear physics perspective

    NASA Astrophysics Data System (ADS)

    Broggini, C.; Canton, L.; Fiorentini, G.; Villante, F. L.

    2012-06-01

    The primordial abundance of 7Li as predicted by Big Bang Nucleosynthesis (BBN) is more than a factor 2 larger than what has been observed in metal-poor halo stars. Herein, we analyze the possibility that this discrepancy originates from incorrect assumptions about the nuclear reaction cross sections relevant for BBN. To do this, we introduce an efficient method to calculate the changes in the 7Li abundance produced by arbitrary (temperature dependent) modifications of the nuclear reaction rates. Then, considering that 7Li is mainly produced from 7Be via the electron capture process 7Be+e- → 7Li+νe, we assess the impact of the various channels of 7Be destruction. Differently from previous analysis, we consider the role of unknown resonances by using a complete formalism which takes into account the effect of Coulomb and centrifugal barrier penetration and that does not rely on the use of the narrow-resonance approximation. As a result of this, the possibility of a nuclear physics solution to the 7Li problem is significantly suppressed. Given the present experimental and theoretical constraints, it is unlikely that the 7Be+n destruction rate is underestimated by the 2.5 factor required to solve the problem. We exclude, moreover, that resonant destruction in the channels 7Be+t and 7Be+3He can explain the 7Li puzzle. New unknown resonances in 7Be+d and 7Be+α could potentially produce significant effects. Recent experimental results have ruled out such a possibility for 7Be+d. On the other hand, for the 7Be+α channel very favorable conditions are required. The possible existence of a partially suitable resonant level in 11C is studied in the framework of a coupled-channel model and the possibility of a direct measurement is considered.

  7. Ab initio study of 59Co NMR spectra in Co2FeAl1-xSix Heusler alloys

    NASA Astrophysics Data System (ADS)

    Nishihara, H.; Sato, K.; Akai, H.; Takiguchi, C.; Geshi, M.; Kanomata, T.; Sakon, T.; Wada, T.

    2015-05-01

    Ab initio electronic structure calculation of a series of Co2FeAl1-xSix Heusler alloys has been performed, using the Korringa-Kohn-Rostoker-coherent potential approximation method to explain experimental 59Co NMR spectra. Two prominent features are explained semi-quantitatively-a global shift of the 59Co resonance line due to alloying with Al and Si atoms in Co2FeAl1-xSix, and the effect of local disorder in creating distinct satellite lines of 59Co NMR in Co2FeAl. The importance is stressed of the positive contribution to the 59Co hyperfine field from valence electron polarization, which emerges from the half-metallic band structure inherent in Co-based Heusler alloys.

  8. Computer-assisted assignment of 2D 1H NMR spectra of proteins: basic algorithms and application to phoratoxin B.

    PubMed

    Kleywegt, G J; Boelens, R; Cox, M; Llinás, M; Kaptein, R

    1991-05-01

    A suite of computer programs (CLAIRE) is described which can be of assistance in the process of assigning 2D 1H NMR spectra of proteins. The programs embody a software implementation of the sequential assignment approach first developed by Wüthrich and co-workers (K. Wüthrich, G. Wider, G. Wagner and W. Braun (1982) J. Mol. Biol. 155, 311). After data-abstraction (peakpicking), the software can be used to detect patterns (spin systems), to find cross peaks between patterns in 2D NOE data sets and to generate assignments that are consistent with all available data and which satisfy a number of constraints imposed by the user. An interactive graphics program called CONPAT is used to control the entire assignment process as well as to provide the essential feedback from the experimental NMR spectra. The algorithms are described in detail and the approach is demonstrated on a set of spectra from the mistletoe protein phoratoxin B, a homolog of crambin. The results obtained compare well with those reported earlier based entirely on a manual assignment process. PMID:1841687

  9. Optimized Spectral Editing of 13C MAS NMR Spectra of Rigid Solids Using Cross-Polarization Methods

    NASA Astrophysics Data System (ADS)

    Sangill, R.; Rastrupandersen, N.; Bildsoe, H.; Jakobsen, H. J.; Nielsen, N. C.

    Combinations of 13C magic-angle spinning (MAS) NMR experiments employing cross polarization (CP), cross polarization-depolarization (CPD), and cross polarization-depolarization-repolarization are analyzed quantitatively to derive simple and general procedures for optimized spectral editing of 13C CP/MAS NMR spectra of rigid solids by separation of the 13C resonances into CH n subspectra ( n = 0, 1, 2, and 3). Special attention is devoted to a differentiation by CPD/MAS of CH and CH 2 resonances since these groups behave quite similarly during spin lock under Hartmann-Hahn match and are therefore generally difficult to distinguish unambiguously. A general procedure for the design of subexperiments and linear combinations of their spectra to provide optimized signal-to-noise ratios for the edited subspectra is described. The technique is illustrated by a series of edited 13C CP/MAS spectra for a number of rigid solids ranging from simple organic compounds (sucrose and l-menthol) to complex pharmaceutical products (calcipotriol monohydrate and vitamin D 3) and polymers (polypropylene, polyvinyl alcohol, polyvinyl chloride, and polystyrene).

  10. Constraining 17O and 27Al NMR spectra of high-pressure crystals and glasses: New data for jadeite, pyrope, grossular, and mullite

    USGS Publications Warehouse

    Kelsey, K.E.; Stebbins, J.F.; Du, L.-S.; Hankins, B.

    2007-01-01

    The 17O NMR spectra of glasses quenched from melts at high pressure are often difficult to interpret due to overlapping peaks and lack of crystalline model compounds. High-pressure aluminosilicate glasses often contain significant amounts of [5]Al and [6]Al, thus these high-pressure glasses must contain oxygen bonded to high-coordinated aluminum. The 17O NMR parameters for the minerals jadeite, pyrope, grossular, and mullite are presented to assist interpretation of glass spectra and to help test quantum chemical calculations. The 17O NMR parameters for jadeite and grossular support previous peak assignments of oxygen bonded to Si and high-coordinated Al in high-pressure glasses as well as quantum chemical calculations. The oxygen tricluster in mullite is very similar to the previously observed tricluster in grossite (CaAl4 O7) and suspected triclusters in glasses. We also present 27Al NMR spectra for pyrope, grossular, and mullite.

  11. Characterisation of the 1H and 13C NMR spectra of N-acetylaspartylglutamate and its detection in urine from patients with Canavan disease.

    PubMed

    Krawczyk, Hanna; Gradowska, Wanda

    2003-03-10

    1H and 13C NMR spectra of N-acetylaspartylglutamate (NAAG) have been recorded and interpreted. The values of the 1H chemical shifts and 1H-(1)H coupling constants at different pH were obtained by iterative computer fitting of 1-D 1H NMR spectra. This provided information on the solution conformation of the investigated molecule. Proton-decoupled high resolution 13C NMR spectra of NAAG have been measured in a series of dilute water solution of various acidity. These data have provided a basis for unequivocal determination of the presence of NAAG in the urine sample of a patient suffering from Canavan disease. NMR spectroscopy provides a possibility of detecting NAAG in body fluids. PMID:12615232

  12. Barrier distributions for the 7Li+27Al reaction

    NASA Astrophysics Data System (ADS)

    Cárdenas, W. H. Z.

    2010-08-01

    Barrier distributions can be obtained from the first derivative of the elastic and quasielastic (QEL) backward angle excitation functions [1]. In this work we present a study of the barrier distribution for the 7Li+27Al reaction from a Coupled-Channels Born Approximation (CCBA) calculations using the code FRESCO [2].

  13. Probing protein structure by solvent perturbation of NMR spectra: the surface accessibility of bovine pancreatic trypsin inhibitor.

    PubMed Central

    Molinari, H; Esposito, G; Ragona, L; Pegna, M; Niccolai, N; Brunne, R M; Lesk, A M; Zetta, L

    1997-01-01

    In the absence of specific interactions, the relative attenuation of protein NMR signals due to added stable free radicals such as TEMPOL should reflect the solvent accessibility of the molecular surface. The quantitative correlation between observed attenuation and surface accessibility was investigated with a model system, i.e., the small protein bovine pancreatic trypsin inhibitor. A detailed discussion is presented on the reliability and limits of the approach, and guidelines are provided for data acquisition, treatment, and interpretation. The NMR-derived accessibilities are compared with those obtained from x-ray diffraction and molecular dynamics data. Although the time-averaged accessibilities from molecular dynamics are ideally suited to fit the NMR data, better agreement was observed between the paramagnetic attenuations of the fingerprint cross-peaks of homonuclear proton spectra and the total NH and H alpha accessibilities calculated from x-ray coordinates, than from time-averaged molecular dynamics simulations. In addition, the solvent perturbation response appears to be a promising approach for detecting the thermal conformational evolution of secondary structure elements in proteins. PMID:9199802

  14. Fast acquisition of high-resolution NMR spectra in inhomogeneous fields via intermolecular double-quantum coherences

    PubMed Central

    Chen, Zhong; Cai, Shuhui; Chen, Zhiwei; Zhong, Jianhui

    2009-01-01

    A pulse sequence, IDEAL-II, is proposed based on the concept of intermolecular dipolar-interaction enhanced all lines [Z. Chen et al., J. Am. Chem. Soc. 126, 446 (2004)] for obtaining one-dimensional (1D) high-resolution liquid NMR spectra in inhomogeneous fields via two-dimensional acquisitions. With the new acquisition scheme, the range of magnetic field inhomogeneity rather than chemical shift is sampled in the indirect dimension. This enables a great reduction in acquisition time and amount of data, much improved over the original IDEAL implementation. It is applicable to both isolated and J-coupled spin systems in liquid. For the latter, apparent J coupling constants are magnified threefold in spectra obtained with this sequence. This allows a more accurate measurement of J coupling constants in the cases of small J coupling constants or large inhomogeneous fields. Analytical expression was derived based on intermolecular multiple-quantum coherence treatments. Solution samples that were purposely deshimmed and biological samples with intrinsic field inhomogeneities were tested. Experimental results demonstrate that this sequence retains useful structural information including chemical shifts, relative peak areas, and multiplet patterns of J coupling even when the field inhomogeneity is severe enough to almost erase all spectroscopic information with conventional 1D single-quantum coherence techniques. This sequence is more applicable to weakly coupled and uncoupled spin systems, potentially useful for studying metabolites in in vivo NMR spectroscopy and for characterizing technologically important new materials in combinatorial chemistry. PMID:19256612

  15. Site-resolved 2H relaxation experiments in solid materials by global line-shape analysis of MAS NMR spectra

    NASA Astrophysics Data System (ADS)

    Lindh, E. L.; Stilbs, P.; Furó, I.

    2016-07-01

    We investigate a way one can achieve good spectral resolution in 2H MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the 2H MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two 2H spin populations with similar chemical shifts but different quadrupole splittings. In 2H-exchanged cellulose containing two 2H spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics.

  16. Site-resolved (2)H relaxation experiments in solid materials by global line-shape analysis of MAS NMR spectra.

    PubMed

    Lindh, E L; Stilbs, P; Furó, I

    2016-07-01

    We investigate a way one can achieve good spectral resolution in (2)H MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the (2)H MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two (2)H spin populations with similar chemical shifts but different quadrupole splittings. In (2)H-exchanged cellulose containing two (2)H spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics. PMID:27152833

  17. Metabonomics classifies pathways affected by bioactive compounds. Artificial neural network classification of NMR spectra of plant extracts.

    PubMed

    Ott, Karl-Heinz; Araníbar, Nelly; Singh, Bijay; Stockton, Gerald W

    2003-03-01

    The biochemical mode-of-action (MOA) for herbicides and other bioactive compounds can be rapidly and simultaneously classified by automated pattern recognition of the metabonome that is embodied in the 1H NMR spectrum of a crude plant extract. The ca. 300 herbicides that are used in agriculture today affect less than 30 different biochemical pathways. In this report, 19 of the most interesting MOAs were automatically classified. Corn (Zea mays) plants were treated with various herbicides such as imazethapyr, glyphosate, sethoxydim, and diuron, which represent various biochemical modes-of-action such as inhibition of specific enzymes (acetohydroxy acid synthase [AHAS], protoporphyrin IX oxidase [PROTOX], 5-enolpyruvylshikimate-3-phosphate synthase [EPSPS], acetyl CoA carboxylase [ACC-ase], etc.), or protein complexes (photosystems I and II), or major biological process such as oxidative phosphorylation, auxin transport, microtubule growth, and mitosis. Crude isolates from the treated plants were subjected to 1H NMR spectroscopy, and the spectra were classified by artificial neural network analysis to discriminate the herbicide modes-of-action. We demonstrate the use and refinement of the method, and present cross-validated assignments for the metabolite NMR profiles of over 400 plant isolates. The MOA screen also recognizes when a new mode-of-action is present, which is considered extremely important for the herbicide discovery process, and can be used to study deviations in the metabolism of compounds from a chemical synthesis program. The combination of NMR metabolite profiling and neural network classification is expected to be similarly relevant to other metabonomic profiling applications, such as in drug discovery. PMID:12590124

  18. Magnetism, optical absorbance, and 19F NMR spectra of nafion films with self-assembling paramagnetic networks

    SciTech Connect

    Levin, E. M.; Chen, Q.; Bud'ko, S. L.

    2012-01-15

    Magnetization, optical absorbance, and {sup 19}F NMR spectra of Nafion transparent films as received and doped with Mn{sup 2+}, Co{sup 2+}, Fe{sup 2+}, and Fe{sup 3+} ions with and without treatment in 1H-1,2,4-triazole (trz) have been studied. Doping of Nafion with Fe{sup 2+} and Co{sup 2+} and their bridging to nitrogen of triazole yields a hybrid self-assembling paramagnetic system that exhibits interesting magnetic and optical properties. These include spin crossover phenomena between high-spin (HS) and low-spin (LS) states in Nafion-Fe{sup 2+}-trz and Nafion-Co{sup 2+}-trz accompanied by thermochromic effects in the visible range induced by temperature. A large shift of the magnetization curve induced by a magnetic field in the vicinity of the HS {leftrightarrow} LS, {approx}220 K, observed for Nafion-Fe{sup 2+}-trz has a rate of {approx}6 K/kOe, which is about three orders of magnitude larger than that in bulk spin crossover Fe{sup 2+} materials. Selective response of {sup 19}F NMR signals on doping with paramagnetic ions demonstrates that NMR can be used as spatially resolved method to study Nafion film with paramagnetic network. Both chemical shift and width of {sup 19}F NMR signals show that SO groups of Nafion, Fe or Co ions, and nitrogen of triazole are bonded whereas they form a spin crossover system. Based on a model of nanosize cylinders proposed for Nafion [K. Schmidt-Rohr and Q. Chen, Nat Mater (2008), 75], we suggest that paramagnetic ions are located inside these cylinders, forming self-assembling magnetically and optically active nanoscale networks.

  19. Cross polarization and magic angle sample spinning NMR spectra of model organic compounds. 1. Highly protonated molecules

    SciTech Connect

    Alemany, L.B.; Grant, D.M.; Pugmire, R.J.; Alger, T.D.; Zilm, K.W.

    1983-04-20

    CP/MAS /sup 13/C NMR spectra were obtained at various contact times on ten solid organic compounds containing a variety of simple functional groups. The spectra show that signal intensities that agree with atomic ratios can be obtained with a contact time of 2.25 ms and often with a contact time as short as about 1 ms. Computer analysis of signal intensities obtained at a minimum of ten different contact times provides T/sub CH/ data that are consistent with these experimental results. The experimental results are also consistent with the previously reported lack of significant variation in the spectra of complex organic solids obtained with contact times of about 1 to 3 ms. In general, nonprotonated carbon atoms polarize more slowly than protonated carbon atoms. The compounds exhibit a wide range of proton spin lattice relaxation times. Some compounds exhibit more resonances than are found in the /sup 13/C(/sup 1/H) spectra of the compounds in solution because the crystalline environment removes the nominal spatial equivalence found for carbon atoms related to each other by unimolecular symmetry elements.

  20. The Chemical Shift Baseline for High-Pressure NMR Spectra of Proteins.

    PubMed

    Frach, Roland; Kibies, Patrick; Böttcher, Saraphina; Pongratz, Tim; Strohfeldt, Steven; Kurrmann, Simon; Koehler, Joerg; Hofmann, Martin; Kremer, Werner; Kalbitzer, Hans Robert; Reiser, Oliver; Horinek, Dominik; Kast, Stefan M

    2016-07-18

    High-pressure (HP) NMR spectroscopy is an important method for detecting rare functional states of proteins by analyzing the pressure response of chemical shifts. However, for the analysis of the shifts it is mandatory to understand the origin of the observed pressure dependence. Here we present experimental HP NMR data on the (15) N-enriched peptide bond model, N-methylacetamide (NMA), in water, combined with quantum-chemical computations of the magnetic parameters using a pressure-sensitive solvation model. Theoretical analysis of NMA and the experimentally used internal reference standard 4,4-dimethyl-4-silapentane-1-sulfonic (DSS) reveal that a substantial part of observed shifts can be attributed to purely solvent-induced electronic polarization of the backbone. DSS is only marginally responsive to pressure changes and is therefore a reliable sensor for variations in the local magnetic field caused by pressure-induced changes of the magnetic susceptibility of the solvent. PMID:27282319

  1. An Ultra-high-Resolution Survey of the Interstellar 7Li/6Li Isotope Ratio in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Knauth, David C.; Federman, S. R.; Lambert, David L.

    2003-03-01

    In an effort to probe the extent of variations in the interstellar 7Li/6Li ratio seen previously, ultra-high-resolution (R~360,000), high signal-to-noise spectra of stars in the Perseus OB2 and Scorpius OB2 associations were obtained. These measurements confirm our earlier findings of an interstellar 7Li/6Li ratio of about 2 toward ο Per, the value predicted from models of Galactic cosmic-ray spallation reactions. Observations of other nearby stars yield limits consistent with the isotopic ratio of ~12 seen in carbonaceous chondrite meteorites. If this ratio originally represented the gas toward ο Per, then to decrease the original isotope ratio to its current value an order of magnitude increase in the Li abundance is expected, but it is not seen. The elemental K/Li ratio is not unusual, although Li and K are formed via different nucleosynthetic pathways. Several proposals to account for the low 7Li/6Li ratio were considered, but none seems satisfactory. Analysis of the Li and K abundances from our survey highlighted two sight lines where depletion effects are prevalent. There is evidence for enhanced depletion toward X Per, since both abundances are lower by a factor of 4 when compared to other sight lines. Moreover, a smaller Li/H abundance is observed toward 20 Aql, but the K/H abundance is normal, suggesting enhanced Li depletion (relative to K) in this direction. Our results suggest that the 7Li/6Li ratio has not changed significantly during the last 4.5 billion years and that a ratio of ~12 represents most gas in the solar neighborhood. In addition, there appears to be a constant stellar contribution of 7Li, indicating that one or two processes dominate its production in the Galaxy.

  2. Cucurbitacins from Cayaponia racemosa: isolation and total assignment of 1H and 13C NMR spectra.

    PubMed

    Chaves, Davina C; Assunção, João Carlos C; Braz-Filho, Raimundo; Lemos, Telma L G; Monte, Francisco J Q

    2007-05-01

    Two new cucurbitane-type triterpenoids, 2beta,3beta,16alpha,20(R),25-pentahydroxy-9-methyl-19-norlanost-5-en-7,22-dione and 2beta,3beta,16alpha,20(R),25-pentahydroxy-9-methyl-19-norlanost-5-en-7,11,22-trione, were isolated from fruits of Cayaponia racemosa. The total (1)H and (13)C chemical shift assignment of these two closely related compounds is described, making use of one- and two-dimensional NMR techniques. PMID:17372957

  3. Target structure independent 7Li elastic scattering at lowmomentum transfers

    SciTech Connect

    Momotyuk, O.A.; Keeley, N.; Kemper, K.W.; Roeder, B.T.; Crisp,A.M.; Cluff, W.; Schmidt, B.G.; Wiedeking, M.; Marechal, F.; Rusek, K.; Mezhevych, S.Yu.; Liendo, J.

    2006-07-20

    Analyzing powers and cross sections for the elastic scattering of polarized 7Li by targets of 6Li, 7Li and 12C are shown to depend only on the properties of the projectile for momentum transfers of less than 1.0 fm-1. The result of a detailed analysis of the experimental data within the framework of the coupled channels model with ground state reorientation and transitions to the excited states of the projectile and targets included in the coupling schemes are presented. This work suggests that nuclear properties of weakly-bound nuclei can be tested by elastic scattering experiments, independent of the target used, if data are acquired for momentum transfers less than {approx}1.0 fm-1.

  4. Population of Nuclei Via 7Li-Induced Binary Reactions

    SciTech Connect

    Clark, Rodney M.; Phair, Larry W.; Descovich, M.; Cromaz, Mario; Deleplanque, M.A.; Fall on, Paul; Lee, I-Yang; Macchiavelli, A.O.; McMahan, Margaret A.; Moretto, Luciano G.; Rodriguez-Vieitez, E.; Sinha,Shrabani; Stephens, Frank S.; Ward, David; Wiedeking, Mathis

    2005-08-08

    The authors have investigated the population of nuclei formed in binary reactions involving {sup 7}Li beams on targets of {sup 160}Gd and {sup 184}W. The {sup 7}Li + {sup 184}W data were taken in the first experiment using the LIBERACE Ge-array in combination with the STARS Si {Delta}E-E telescope system at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. By using the Wilczynski binary transfer model, in combination with a standard evaporation model, they are able to reproduce the experimental results. This is a useful method for predicting the population of neutron-rich heavy nuclei formed in binary reactions involving beams of weakly bound nuclei formed in binary reactions involving beams of weakly bound nuclei and will be of use in future spectroscopic studies.

  5. Population of Nuclei Via 7Li-Induced Binary Reactions

    SciTech Connect

    Clark, R M; Phair, L W; Descovich, M; Cromaz, M; Deleplanque, M A; Fallon, P; Lee, I Y; Macchiavelli, A O; McMahan, M A; Moretto, L G; Rodriguez-Vieitez, E; Sinha, S; Stephens, F S; Ward, D; Wiedeking, M; Bernstein, L A; Burke, J T; Church, J A

    2005-08-09

    The authors have investigated the population of nuclei formed in binary reactions involving {sup 7}Li beams on targets of {sup 160}Gd and {sup 184}W. The {sup 7}Li + {sup 184}W data were taken in the first experiment using the LIBERACE Ge-array in combination with the STARS Si {Delta}E-E telescope system at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. By using the Wilczynski binary transfer model, in combination with a standard evaporation model, they are able to reproduce the experimental results. This is a useful method for predicting the population of neutron-rich heavy nuclei formed in binary reactions involving beams of weakly bound nuclei and will be of use in future spectroscopic studies.

  6. Modified Prony Method to Resolve and Quantify in Vivo31P NMR Spectra of Tumors

    NASA Astrophysics Data System (ADS)

    Barone, P.; Guidoni, L.; Ragona, R.; Viti, V.; Furman, E.; Degani, H.

    Prony's method, successfully used in processing NMR signals, performs poorly at low signal-to-noise ratios. To overcome this problem, a statistical approach has been adopted by using Prony's method as a sampling device from the distribution associated with the true spectrum. Specifically, Prony's method is applied for each regression order p and number of data points n, both considered in a suitable range, and the estimates of frequencies, amplitudes, and decay factors are pooled separately. A histogram of the pooled frequencies is computed and, looking at the histogram, a lower and an upper frequency bound for each line of interest is determined. All frequency estimates in each of the determined intervals as well as associated decay factors and amplitudes are considered to be independent normal variates. A mean value and a corresponding 95% confidence interval are computed for each parameter. 31P NMR signals from MCF7 human breast cancer cells, inoculated into athymic mice and which developed into tumors, have been processed with traditional methods and with this modified Prony's method. The main components of the phosphomonoester peak, namely those deriving from phosphorylcholine and phosphorylethanolamine, are always well resolved with this new approach and their relative amplitudes can be consequently evaluated. Peak intensities of these two signals show different behavior during treatment of tumors with the antiestrogenic drug tamoxifen. The results of this new approach are compared with those obtainable with traditional techniques.

  7. A novel approach to the rapid assignment of (13)C NMR spectra of major components of vegetable oils such as avocado, mango kernel and macadamia nut oils.

    PubMed

    Retief, Liezel; McKenzie, Jean M; Koch, Klaus R

    2009-09-01

    Assignment of (13)C nuclear magnetic resonance (NMR) spectra of major fatty acid components of South African produced vegetable oils was attempted using a method in which the vegetable oil was spiked with a standard triacylglycerol. This proved to be inadequate and therefore a new rapid and potentially generic graphical linear correlation method is proposed for assignment of the (13)C NMR spectra of major fatty acid components of apricot kernel, avocado pear, grapeseed, macadamia nut, mango kernel and marula vegetable oils. In this graphical correlation method, chemical shifts of fatty acids present in a known standard triacylglycerol is plotted against the corresponding chemical shifts of fatty acids present in the vegetable oils. This new approach (under carefully defined conditions and concentrations) was found especially useful for spectrally crowded regions where significant peak overlap occurs and was validated with the well-known (13)C NMR spectrum of olive oil which has been extensively reported in the literature. In this way, a full assignment of the (13)C{1H} NMR spectra of the vegetable oils, as well as tripalmitolein was readily achieved and the resonances belonging to the palmitoleic acid component of the triacylglycerols in the case of macadamia nut and avocado pear oil resonances were also assigned for the first time in the (13)C NMR spectra of these oils. PMID:19544589

  8. Analysis of 31P MAS NMR spectra and transversal relaxation of bacteriophage M13 and tobacco mosaic virus.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1994-01-01

    Phosphorus magic angle spinning nuclear magnetic resonance (NMR) spectra and transversal relaxation of M13 and TMV are analyzed by use of a model, which includes both local backbone motions of the encapsulated nucleic acid molecules and overall rotational diffusion of the rod-shaped virions about their length axis. Backbone motions influence the sideband intensities by causing a fast restricted reorientation of the phosphodiesters. To evaluate their influence on the observed sideband patterns, we extend the model that we used previously to analyze nonspinning 31P NMR lineshapes (Magusin, P.C.M.M., and M. A. Hemminga. 1993a. Biophys. J. 64:1861-1868) to magic angle spinning NMR experiments. Backbone motions also influence the conformation of the phosphodiesters, causing conformational averaging of the isotropic chemical shift, which offers a possible explanation for the various linewidths of the centerband and the sidebands observed for M13 gels under various conditions. The change of the experimental lineshape of M13 as a function of temperature and hydration is interpreted in terms of fast restricted fluctuation of the dihedral angles between the POC and the OCH planes on both sides of the 31P nucleus in the nucleic acid backbone. Backbone motions also seem to be the main cause of transversal relaxation measured at spinning rates of 4 kHz or higher. At spinning rates less than 2 kHz, transversal relaxation is significantly faster. This effect is assigned to slow, overall rotation of the rod-shaped M13 phage about its length axis. Equations are derived to simulate the observed dependence of T2e on the spinning rate. PMID:8038391

  9. Molecular structure, vibrational spectra and DFT molecular orbital calculations (TD-DFT and NMR) of the antiproliferative drug Methotrexate

    NASA Astrophysics Data System (ADS)

    Ayyappan, S.; Sundaraganesan, N.; Aroulmoji, V.; Murano, E.; Sebastian, S.

    2010-09-01

    The FT-IR and FT-Raman spectral studies of the Methotrexate (MTX) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of MTX have been investigated with the help of B3LYP density functional theory (DFT) using 6-31G(d) as basis set. Detailed analysis of the vibrational spectra has been made with the aid of theoretically predicted vibrational frequencies. The vibrational analysis confirms the differently acting ring modes, steric repulsion, conjugation and back-donation. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complement with the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. Good correlations between the experimental 1H and 13C NMR chemical shifts in DMSO solution and calculated GIAO shielding tensors were found.

  10. Weighted least-squares deconvolution method for discovery of group differences between complex biofluid 1H NMR spectra

    NASA Astrophysics Data System (ADS)

    Gipson, Geoffrey T.; Tatsuoka, Kay S.; Sweatman, Brian C.; Connor, Susan C.

    2006-12-01

    Biomarker discovery through analysis of high-throughput NMR data is a challenging, time-consuming process due to the requirement of sophisticated, dataset specific preprocessing techniques and the inherent complexity of the data. Here, we demonstrate the use of weighted, constrained least-squares for fitting a linear mixture of reference standard data to complex urine NMR spectra as an automated way of utilizing current assignment knowledge and the ability to deconvolve confounded spectral regions. Following the least-squares fit, univariate statistics were used to identify metabolites associated with group differences. This method was evaluated through applications on simulated datasets and a murine diabetes dataset. Furthermore, we examined the differential ability of various weighting metrics to correctly identify discriminative markers. Our findings suggest that the weighted least-squares approach is effective for identifying biochemical discriminators of varying physiological states. Additionally, the superiority of specific weighting metrics is demonstrated in particular datasets. An additional strength of this methodology is the ability for individual investigators to couple this analysis with laboratory specific preprocessing techniques.

  11. Importance of Tensor Asymmetry for the Analysis of 2H-NMR Spectra from Deuterated Aromatic Rings

    PubMed Central

    Pulay, Peter; Scherer, Erin M.; van der Wel, Patrick C. A.; Koeppe, Roger E.

    2008-01-01

    We have used ab initio calculations to compute all of the tensor elements of the electric field gradient for each carbon-deuterium bond in the ring of deuterated 3-methyl-indole. Previous analyses have ignored the smaller tensor elements perpendicular to principal component Vzz which is aligned with the C-2H bond (local bond z-axis). At each ring position, the smallest element Vxx is in the molecular plane and Vyy is normal to the plane of the ring. The asymmetry parameter η = (|Vyy|-|Vxx|)/|Vzz| ranges from 0.07 at C4 to 0.11 at C2. We used the perpendicular (off-bond) tensor elements, in concert with an improved understanding of the indole ring geometry1, to analyze prototype 2H-NMR spectra from well-oriented, hydrated peptide/lipid samples. For each of the 4 tryptophans of membrane-spanning gramicidin A (gA)2 channels, the inclusion of the perpendicular elements changes the deduced ring tilt by nearly 10° and increases the ring principal order parameter Szz for overall ‘wobble’ with respect to the membrane normal (molecular z-axis). With the improved analysis, the magnitude of Szz for the outermost indole rings of Trp13 and Trp15 is indistinguishable from that observed previously for backbone atoms (0.93 ± 0.03). For the Trp9 and Trp11 rings, which are slightly more buried within the membrane, Szz is slightly lower (0.86 ± 0.03). The results show that the perpendicular elements are important for the detailed analysis of 2H-NMR spectra from aromatic ring systems. PMID:16332101

  12. The effect of sample hydration on 13C CPMAS NMR spectra of fulvic acids

    USGS Publications Warehouse

    Hatcher, P.G.; Wilson, M.A.

    1991-01-01

    Three fulvic acids, two of which have been well studied by a number of other groups (Armadale and Suwannee river fulvic acids) have been examined by high resolution solid-state 13C-NMR techniques to delineate the effect of absorbed water. Two main effects of absorbed water were observed: (1) changes in spin lattice relaxation times in the rotating frame and cross polarization times and (2) total loss of signal so that some fulvic acid is effectively in solution. These results suggest that discrepancies in the literature concerning observed relative signal intensities from different structural groups are due to absorbed water and emphasize the necessity for proper precautionary drying before spectroscopic analysis. ?? 1991.

  13. Theory of damped quantum rotation in NMR spectra. I. Fundamental aspects.

    PubMed

    Ratajczyk, T; Szymański, S

    2005-11-22

    The damped quantum rotation (DQR) theory, formulated originally for methyl-like atomic groupings, is now extended to hindered (N>3)-fold molecular rotors, such as the cyclopentadienyl, benzene, and cycloheptatrienyl rings in solid phase environments. It heightens the significance of the Pauli principle in shaping up the stochastic dynamics of such objects, reflected in NMR line shapes. The corresponding NMR line-shape equation is derived; its stochastic part is shown for the first time to have the double commutator form for any values of the quantum-mechanical (coherence-damping) rate constants entering it. Constraints on the relative magnitudes of such constants are determined under which the DQR line-shape equation is converted into the phenomenological Alexander-Binsch equation describing classical jumps of the rotor. When all the quantum rate constants happen to be equal, the phenomenological model of equal jump rates between any two of the N (equivalent) orientations of the rotor is reproduced. On the other hand, the seemingly most plausible (for N>3) nearest-neighbor hopping model does not have any peculiar grounds in the DQR approach. For the special instances of stochastic molecular motions addressed in this work, the extended DQR formalism affords a quantification of the "degree of classicality" represented by a complete set of the relevant quantum rate constants. In view of our earlier experimental findings for the methyl rotors, the very occurrence of the nonclassical DQR effects seems unquestionable even for the objects of the size of benzene. The question of under what circumstances such effects can be big enough to be detected experimentally will be addressed in Part II of this work. PMID:16351283

  14. Neutron characterization study for D-T, p-7Li neutron sources with new BCA based direct collision coupling method

    NASA Astrophysics Data System (ADS)

    Wang, Guan-bo; Yang, Xin; Qian, Da-zhi; Li, Run-dong; Tang, Bin

    2014-09-01

    The T(D,n)4He and 7Li(p,n)7Be neutron sources have been used for decades in nuclear physics research, stellar nucleosynthesis research and neutron therapy research. In this work, the neutron characterization including neutron yield, spectra, and angular distribution for D-T and p-7Li sources have been studied with our new binary collision approximation (BCA) based direct collision coupling method. Distinguished from the traditional path integration method for getting the neutron weight, the new model establishes a relationship between the scattering cross section and the impact parameter, which allows the secondary neutron generation carrying out jointly with ions BCA tracking. The experimental measurements of neutron characterizations have been employed for these two reactions, and the new algorithm is validated.

  15. Sensitivity Gains, Linearity, and Spectral Reproducibility in Nonuniformly Sampled Multidimensional MAS NMR Spectra of High Dynamic Range.

    SciTech Connect

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David M.; Hoch, Jeffrey C.; Rovnyak, David S.; Polenova, Tatyana E.

    2014-04-22

    Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C–13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C,15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C–13C MAS correlation experiments that yield high quality artifact-free datasets.

  16. Toward dynamic isotopomer analysis in the rat brain in vivo: automatic quantitation of 13C NMR spectra using LCModel.

    PubMed

    Henry, Pierre-Gilles; Oz, Gülin; Provencher, Stephen; Gruetter, Rolf

    2003-01-01

    The LCModel method was adapted to analyze localized in vivo (13)C NMR spectra obtained from the rat brain in vivo at 9.4 T. Prior knowledge of chemical-shifts, J-coupling constants and J-evolution was included in the analysis. Up to 50 different isotopomer signals corresponding to 10 metabolites were quantified simultaneously in 400 microl volumes in the rat brain in vivo during infusion of [1,6-(13)C(2)]glucose. The analysis remained accurate even at low signal-to-noise ratio of the order of 3:1. The relative distribution of isotopomers in glutamate, glutamine and aspartate determined in vivo in 22 min was in excellent agreement with that measured in brain extracts. Quantitation of time series of (13)C spectra yielded time courses of total (13)C label incorporation into up to 16 carbon positions, as well as time courses of individual isotopomer signals, with a temporal resolution as low as 5 min (dynamic isotopomer analysis). The possibility of measuring in vivo a wealth of information that was hitherto accessible only in extracts is likely to expand the scope of metabolic studies in the intact brain. PMID:14679502

  17. Vibrational spectra, molecular structure, NBO, UV, NMR, first order hyperpolarizability, analysis of 4-Methoxy-4'-Nitrobiphenyl by density functional theory.

    PubMed

    Govindarasu, K; Kavitha, E

    2014-03-25

    In this study, geometrical optimization, spectroscopic analysis, electronic structure and nuclear magnetic resonance studies of 4-Methoxy-4'-Nitrobiphenyl (abbreviated as 4M4'NBPL) were investigated by utilizing HF and DFT/B3LYP with 6-31G(d,p) as basis set. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the 4M4'NBPL have been calculated with the help of density functional theory computations. The FT-IR and FT-Raman spectra were recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1) respectively. Natural Bond Orbital (NBO) analysis is also used to explain the molecular stability. The UV-Vis absorption spectra of the title compound dissolved in chloroform were recorded in the range of 200-800 cm(-1). The HOMO-LUMO energy gap explains the charge interaction taking place within the molecule. Good correlation between the experimental (1)H and (13)C NMR chemical shifts in chloroform solution and calculated GIAO shielding tensors were found. The dipole moment, linear polarizability and first order hyperpolarizability values were also computed. The linear polarizability and first order hyperpolarizability of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The chemical reactivity and thermodynamic properties of 4M4'NBPL at different temperature are calculated. In addition, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations. PMID:24299985

  18. Vibrational spectra, molecular structure, NBO, UV, NMR, first order hyperpolarizability, analysis of 4-Methoxy-4";-Nitrobiphenyl by density functional theory

    NASA Astrophysics Data System (ADS)

    Govindarasu, K.; Kavitha, E.

    2014-03-01

    In this study, geometrical optimization, spectroscopic analysis, electronic structure and nuclear magnetic resonance studies of 4-Methoxy-4";-Nitrobiphenyl (abbreviated as 4M4";NBPL) were investigated by utilizing HF and DFT/B3LYP with 6-31G(d,p) as basis set. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the 4M4";NBPL have been calculated with the help of density functional theory computations. The FT-IR and FT-Raman spectra were recorded in the region 4000-400 cm-1 and 3500-50 cm-1 respectively. Natural Bond Orbital (NBO) analysis is also used to explain the molecular stability. The UV-Vis absorption spectra of the title compound dissolved in chloroform were recorded in the range of 200-800 cm-1. The HOMO-LUMO energy gap explains the charge interaction taking place within the molecule. Good correlation between the experimental 1H and 13C NMR chemical shifts in chloroform solution and calculated GIAO shielding tensors were found. The dipole moment, linear polarizability and first order hyperpolarizability values were also computed. The linear polarizability and first order hyperpolarizability of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The chemical reactivity and thermodynamic properties of 4M4";NBPL at different temperature are calculated. In addition, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

  19. Towards high resolution ^1H NMR spectra of tannin colloidal aggregates

    NASA Astrophysics Data System (ADS)

    Mirabel, M.; Glories, Y.; Pianet, I.; Dufourc, E. J.

    1999-10-01

    The time dependent colloidal formation of tannins in hydro-alcoholic medium has been studied by 1H-NMR. Line broadening observed with time can be cancelled by making use of magic angle sample spinning (MASS) thus yielding sharp lines that allow structural studies. We used as an example catechin, a constitutive monomer of Bordeaux young red wine tannins. Chemical shift variations of polyphenol protons allow monitoring the time course of aggregation. La formation de tanins colloïdaux au cours du temps, en milieu hydroalcoolique, a été suivie par RMN-^1H. Un élargissement marqué des résonances est observé et peut être supprimé par la rotation de l'échantillon à l'angle magique ce qui ouvre tout un champ d'études structurales sur ces composés colloïdaux. L'exemple proposé est celui de la catéchine, monomère constitutif de tannins présents en grande quantité dans les vins rouges jeunes de Bordeaux. Des variations du déplacement chimique de certains protons polyphénoliques permettent de suivre l'évolution temporelle de l'agrégation.

  20. Relativistic force field: parametric computations of proton-proton coupling constants in (1)H NMR spectra.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2014-09-01

    Spin-spin coupling constants in (1)H NMR carry a wealth of structural information and offer a powerful tool for deciphering molecular structures. However, accurate ab initio or DFT calculations of spin-spin coupling constants have been very challenging and expensive. Scaling of (easy) Fermi contacts, fc, especially in the context of recent findings by Bally and Rablen (Bally, T.; Rablen, P. R. J. Org. Chem. 2011, 76, 4818), offers a framework for achieving practical evaluation of spin-spin coupling constants. We report a faster and more precise parametrization approach utilizing a new basis set for hydrogen atoms optimized in conjunction with (i) inexpensive B3LYP/6-31G(d) molecular geometries, (ii) inexpensive 4-31G basis set for carbon atoms in fc calculations, and (iii) individual parametrization for different atom types/hybridizations, not unlike a force field in molecular mechanics, but designed for the fc's. With the training set of 608 experimental constants we achieved rmsd <0.19 Hz. The methodology performs very well as we illustrate with a set of complex organic natural products, including strychnine (rmsd 0.19 Hz), morphine (rmsd 0.24 Hz), etc. This precision is achieved with much shorter computational times: accurate spin-spin coupling constants for the two conformers of strychnine were computed in parallel on two 16-core nodes of a Linux cluster within 10 min. PMID:25158224

  1. A Discovery-Based Hydrochlorination of Carvone Utilizing a Guided-Inquiry Approach to Determine the Product Structure from [superscript 13]C NMR Spectra

    ERIC Educational Resources Information Center

    Pelter, Michael W.; Walker, Natalie M.

    2012-01-01

    This experiment describes a discovery-based method for the regio- and stereoselective hydrochlorination of carvone, appropriate for a 3-h second-semester organic chemistry laboratory. The product is identified through interpretation of the [superscript 13]C NMR and DEPT spectra are obtained on an Anasazi EFT-60 at 15 MHz as neat samples. A…

  2. Quantitative analysis of ³¹P NMR spectra of soil extracts--dealing with overlap of broad and sharp signals.

    PubMed

    Doolette, Ashlea L; Smernik, Ronald J

    2015-09-01

    Solution (31)P NMR analysis following extraction with a mixture of sodium hydroxide and ethylenediaminetetraacetic acid is the most widely used method for detailed characterization of soil organic P. However, quantitative analysis of the (31)P NMR spectra is complicated by severe spectral overlap in the monoester region. Various deconvolution procedures have been developed for the task, yet none of these are widely accepted or implemented. In this mini-review, we first describe and compare these varying approaches. We then review approaches to similar issues of spectral overlap in biomedical science applications including NMR-based metabolic profiling and analyzing (31)P magnetic resonance spectra of ex vivo and in vivo intact tissues. The greater maturity and resourcing of this biomedical research means that a wider variety of approaches has been developed. Of particular relevance are approaches to dealing with overlap of broad and sharp signals. Although the existence of this problem is still debated in the context of soil analyses, not only is it well-recognized in biomedical applications, but multiple approaches have been developed to deal with it, including T2 editing and time-domain fitting. Perhaps the most transferable concept is the incorporation of 'prior knowledge' in the fitting of spectra. This is well established in biomedical applications but barely touched in soil analyses. We argue that shortcuts to dealing with overlap in the monoester region (31)P NMR soil spectra are likely to be found in the biomedical literature, although some degree of adaptation will be necessary. PMID:25854619

  3. Ab Initio Molecular Dynamics Simulations and GIPAW NMR Calculations of a Lithium Borate Glass Melt.

    PubMed

    Ohkubo, Takahiro; Tsuchida, Eiji; Takahashi, Takafumi; Iwadate, Yasuhiko

    2016-04-14

    The atomic structure of a molten 0.3Li2O-0.7B2O3 glass at 1250 K was investigated using ab initio molecular dynamics (AIMD) simulations. The gauge including projector augmented wave (GIPAW) method was then employed for computing the chemical shift and quadrupolar coupling constant of (11)B, (17)O, and (7)Li from 764 AIMD derived structures. The chemical shift and quadrupolar coupling constant distributions were directly estimated from the dynamical structure of the molten glass. (11)B NMR parameters of well-known structural units such as the three-coordinated ring, nonring, and four-coordinated tetrahedron were found to be in good agreement with the experimental results. In this study, more detailed classification of B units was presented based on the number of O species bonded to the B atoms. This highlights the limitations of (11)B NMR sensitivity for resolving (11)B local environment using the experimentally obtained spectra only. The (17)O NMR parameter distributions can theoretically resolve the bridging and nonbridging O atoms with different structural units such as nonring, single boroxol ring, and double boroxol ring. Slight but clear differences in the number of bridging O atoms surrounding Li that have not been reported experimentally were observed in the theoretically obtained (7)Li NMR parameters. PMID:27010637

  4. A General Method for Extracting Individual Coupling Constants from Crowded (1)H NMR Spectra.

    PubMed

    Sinnaeve, Davy; Foroozandeh, Mohammadali; Nilsson, Mathias; Morris, Gareth A

    2016-01-18

    Couplings between protons, whether scalar or dipolar, provide a wealth of structural information. Unfortunately, the high number of (1)H-(1)H couplings gives rise to complex multiplets and severe overlap in crowded spectra, greatly complicating their measurement. Many different methods exist for disentangling couplings, but none approaches optimum resolution. Here, we present a general new 2D J-resolved method, PSYCHEDELIC, in which all homonuclear couplings are suppressed in F2, and only the couplings to chosen spins appear, as simple doublets, in F1. This approaches the theoretical limit for resolving (1)H-(1)H couplings, with close to natural linewidths and with only chemical shifts in F2. With the same high sensitivity and spectral purity as the parent PSYCHE pure shift experiment, PSYCHEDELIC offers a robust method for chemists seeking to exploit couplings for structural, conformational, or stereochemical analyses. PMID:26636773

  5. Communication: Permanent dipoles contribute to electric polarization in chiral NMR spectra

    SciTech Connect

    Buckingham, A. David

    2014-01-07

    Nuclear magnetic resonance spectroscopy is blind to chirality because the spectra of a molecule and its mirror image are identical unless the environment is chiral. However, precessing nuclear magnetic moments in chiral molecules in a strong magnetic field induce an electric polarization through the nuclear magnetic shielding polarizability. This effect is equal and opposite for a molecule and its mirror image but is small and has not yet been observed. It is shown that the permanent electric dipole moment of a chiral molecule is partially oriented through the antisymmetric part of the nuclear magnetic shielding tensor, causing the electric dipole to precess with the nuclear magnetic moment and producing a much larger temperature-dependent electric polarization with better prospects of detection.

  6. X-ray and DFT studies of the structure, vibrational and NMR spectra of 2-amino-pyridine betaine hydrochloride

    NASA Astrophysics Data System (ADS)

    Szafran, M.; Kowalczyk, I.; Koput, J.; Katrusiak, A.

    2005-06-01

    The effect of hydrogen bonding, inter- and intramolecular electrostatic interactions on the conformation of 2-amino-pyridine betaine hydrochloride (1-carboxymethyl-2-amino-pyridinium chloride), 2-NH 2PBH⋯Cl(c), in the crystal and its isolated molecules has been studied by X-ray diffraction, FT-IR, Raman, 1H and 13C NMR spectroscopies, and by DFT calculations. In the crystal, the Cl - anion is connected with protonated betaine via hydrogen bond, O-H⋯Cl -= 2.975(2) Å, two N(12)-H⋯Cl - hydrogen bonds and two N(1) H⋯Cl - intermolecular electrostatic interactions. Two minima are located in the potential energy surface at the B3LYP/6-31G(d,p) level, 2-NH 2PBH⋯Cl(t) and 2-NH 2PB⋯HCl(c), with the latter being 20,7 kcal/mol higher in energy. The optimized bond lengths and angles of 2-NH 2PBH⋯Cl(t) at B3LYP level of theory are in good agreement with X-ray data, except for the conformation of the COOH group, which is cis ( syn) in the crystal and trans ( anti) in the single molecule. The probable assignments for the anharmonic experimental solid state vibrational spectra of 2-NH 2PBH⋯Cl(c) and 2-ND 2PBD⋯Cl(c) based on the calculated B3LYP/6-31G(d,p) harmonic frequencies have been made. 1H and 13C NMR screening constants for both single molecules have been calculated in the GIAO/B3LYP/6-31G(d,p) approach. Linear correlation between the calculated and experimental 1H chemical shifts holds only for cis conformer. The lack of such a correlation for trans conformer indicates that it is absent in D 2O solution.

  7. Automated Quantification of Human Brain Metabolites by Artificial Neural Network Analysis from in VivoSingle-Voxel 1H NMR Spectra

    NASA Astrophysics Data System (ADS)

    Kaartinen, Jouni; Mierisová, Šarka; Oja, Joni M. E.; Usenius, Jukka-Pekka; Kauppinen, Risto A.; Hiltunen, Yrjö

    1998-09-01

    A real-time automated way of quantifying metabolites fromin vivoNMR spectra using an artificial neural network (ANN) analysis is presented. The spectral training and test sets for ANN containing peaks at the chemical shift ranges resembling long echo time proton NMR spectra from human brain were simulated. The performance of the ANN constructed was compared with an established lineshape fitting (LF) analysis using both simulated and experimental spectral data as inputs. The correspondence between the ANN and LF analyses showed correlation coefficients of order of 0.915-0.997 for spectra with large variations in both signal-to-noise and peak areas. Water suppressed1H NMR spectra from 24 healthy subjects were collected and choline-containing compounds (Cho), total creatine (Cr), and N-acetyl aspartate (NAA) were quantified with both methods. The ANN quantified these spectra with an accuracy similar to LF analysis (correlation coefficients of 0.915-0.951). These results show that LF and ANN are equally good quantifiers; however, the ANN analyses are more easily automated than LF analyses.

  8. Metastable charged sparticles and the cosmological {sup 7}Li problem

    SciTech Connect

    Cyburt, Richard H.; Ellis, John; Luo, Feng; Fields, Brian D.; Olive, Keith A.; Spanos, Vassilis C. E-mail: John.Ellis@cern.ch E-mail: feng.luo@kcl.ac.uk E-mail: spanos@inp.demokritos.gr

    2012-12-01

    We consider the effects of metastable charged sparticles on Big-Bang Nucleosynthesis (BBN), including bound-state reaction rates and chemical effects. We make a new analysis of the bound states of negatively-charged massive particles with the light nuclei most prominent in BBN, and present a new code to track their abundances, paying particular attention to that of {sup 7}Li. Assuming, as an example, that the gravitino is the lightest supersymmetric particle (LSP), and that the lighter stau slepton, τ-tilde {sub 1}, is the metastable next-to-lightest sparticle within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), we analyze the possible effects on the standard BBN abundances of τ-tilde {sub 1} bound states and decays for representative values of the gravitino mass. Taking into account the constraint on the CMSSM parameter space imposed by the discovery of the Higgs boson at the LHC, we delineate regions in which the fit to the measured light-element abundances is as good as in standard BBN. We also identify regions of the CMSSM parameter space in which the bound state properties, chemistry and decays of metastable charged sparticles can solve the cosmological {sup 7}Li problem.

  9. The crystal structure of ^7Li2ND

    NASA Astrophysics Data System (ADS)

    Tsubota, Masami; Sorby, Magnus H.; Hino, Satoshi; Ichikawa, Takayuki; Hauback, Bjorn C.; Kojima, Yoshitsugu

    2008-03-01

    Recently much attention has been given to reversible hydrogen storage materials possessing high gravimetric capacity. Lithium amide/imide systems are promising candidates. Chen et al.[1] found that a mixture of lithium amide and lithium hydride can reversibly store hydrogen up to 6.5 mass% forming lithium imide (Li2NH). Among them, the crystal structure of Li2NH is still controversial. Balogh et al.[2] have reported a cubic structure model. However, this model differs significantly from theoretical structure models. In this work, the crystal structure of the isotopically substituted ^7Li2ND has been investigated by powder neutron and synchrotron X-ray diffraction experiments. In our data some peaks, which should be a single peak for cubic symmetry, were obviously split indicating a lower symmetry than cubic for lithium imide. The structure of ^7Li2ND will be described. [1] P. Chen et al., J. Phys. Chem. B 107 (2003) 10967. [2] M.P. Balogh et al., J. Alloys Compd. 420 (2006) 326.

  10. Automated assignment of NMR chemical shifts based on a known structure and 4D spectra.

    PubMed

    Trautwein, Matthias; Fredriksson, Kai; Möller, Heiko M; Exner, Thomas E

    2016-08-01

    Apart from their central role during 3D structure determination of proteins the backbone chemical shift assignment is the basis for a number of applications, like chemical shift perturbation mapping and studies on the dynamics of proteins. This assignment is not a trivial task even if a 3D protein structure is known and needs almost as much effort as the assignment for structure prediction if performed manually. We present here a new algorithm based solely on 4D [(1)H,(15)N]-HSQC-NOESY-[(1)H,(15)N]-HSQC spectra which is able to assign a large percentage of chemical shifts (73-82 %) unambiguously, demonstrated with proteins up to a size of 250 residues. For the remaining residues, a small number of possible assignments is filtered out. This is done by comparing distances in the 3D structure to restraints obtained from the peak volumes in the 4D spectrum. Using dead-end elimination, assignments are removed in which at least one of the restraints is violated. Including additional information from chemical shift predictions, a complete unambiguous assignment was obtained for Ubiquitin and 95 % of the residues were correctly assigned in the 251 residue-long N-terminal domain of enzyme I. The program including source code is available at https://github.com/thomasexner/4Dassign . PMID:27484442

  11. Antioxidant activity, NMR, X-ray, ECD and UV/vis spectra of (+)-terrein: Experimental and theoretical approaches

    NASA Astrophysics Data System (ADS)

    Trabolsy, Zuhra Bashir Khalifa Al; Anouar, El Hassane; Zakaria, Nur Shahidatul Shida; Zulkeflee, Manar; Hasan, Mizaton Hazizul; Zin, Maisarah Mohd; Ahmad, Rohaya; Sultan, Sadia; Weber, Jean-Frédéric F.

    2014-02-01

    Fungal metabolite terrein isolated from Aspergillus terreus is endowed with diverse biological and antioxidant activities. To determine the stereochemistry of the isolated terrein, we combined spectroscopic methods (CD and NMR spectra) and theoretical calculations (DFT and TD-DFT methods). Stereochemistry effects on the antioxidant activity of isolated terrein were evaluated by calculating bond dissociation enthalpies (BDEs), ionization potentials (IPs) and spin density delocalization of terrein and isoterrein stereoisomers with B3P86/6-31+G (d, p) method in gas and polarizable continuum model. The results showed a good agreement between experimental data and theoretical calculations which confirmed the (+)-terrein stereochemistry of isolated metabolite. Theoretical calculations showed that the antioxidant activity is relatively influenced by isomeric geometry of the terrein (a variation of 2 kcal/mol between BDEs of terrein and isoterrein isomers), while chirality has no influence on the antioxidant activity [0.2 kcal/mol difference between BDEs of (+)- and (-)-terrein]. The low antioxidant activity of (+)-terrein with respect to trolox and ascorbic acid was explained by the positive free Gibbs energy of the hydrogen atom transfer (HAT) mechanism and high BDE values of the 2-OH active site.

  12. MetaboID: A graphical user interface package for assignment of 1H NMR spectra of bodyfluids and tissues

    NASA Astrophysics Data System (ADS)

    MacKinnon, Neil; Somashekar, Bagganahalli S.; Tripathi, Pratima; Ge, Wencheng; Rajendiran, Thekkelnaycke M.; Chinnaiyan, Arul M.; Ramamoorthy, Ayyalusamy

    2013-01-01

    Nuclear magnetic resonance based measurements of small molecule mixtures continues to be confronted with the challenge of spectral assignment. While multi-dimensional experiments are capable of addressing this challenge, the imposed time constraint becomes prohibitive, particularly with the large sample sets commonly encountered in metabolomic studies. Thus, one-dimensional spectral assignment is routinely performed, guided by two-dimensional experiments on a selected sample subset; however, a publicly available graphical interface for aiding in this process is currently unavailable. We have collected spectral information for 360 unique compounds from publicly available databases including chemical shift lists and authentic full resolution spectra, supplemented with spectral information for 25 compounds collected in-house at a proton NMR frequency of 900 MHz. This library serves as the basis for MetaboID, a Matlab-based user interface designed to aid in the one-dimensional spectral assignment process. The tools of MetaboID were built to guide resonance assignment in order of increasing confidence, starting from cursory compound searches based on chemical shift positions to analysis of authentic spike experiments. Together, these tools streamline the often repetitive task of spectral assignment. The overarching goal of the integrated toolbox of MetaboID is to centralize the one dimensional spectral assignment process, from providing access to large chemical shift libraries to providing a straightforward, intuitive means of spectral comparison. Such a toolbox is expected to be attractive to both experienced and new metabolomic researchers as well as general complex mixture analysts.

  13. The infrared, Raman, NMR and UV spectra, ab initio calculations and spectral assignments of 2-amino-4-chloro-6-methoxypyrimidine

    NASA Astrophysics Data System (ADS)

    Cinar, Z.; Karabacak, M.; Cinar, M.; Kurt, M.; Chinna babu, P.; Sundaraganesan, N.

    2013-12-01

    The 2-amino-4-chloro-6-methoxypyrimidine abbreviated as ACMP have been investigated by both the experimental and theoretical methods; through this work we provide the essential fact about the structural and vibrational insights. The optimized molecular structure, atomic charges, vibrational frequencies and ultraviolet spectral interpretation of ACMP have been studied by performing DFT/B3LYP/6-311++G(df,pd) level of theory. The FT-IR, FT-Raman spectra were recorded in the region 4000-400 cm-1 and 4000-50 cm-1 respectively. The UV absorption spectrum of the compound that dissolved in ethanol and water solution were recorded in the range of 200-400 nm. The scaled wavenumbers are compared with the experimental values. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. Based on the UV spectrum and TD-DFT calculations, the electronic structure and the assignments of the absorption bands were carried out. The 1H, 13C and DEPT 135 nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated using with the Gauge Including Atomic Orbital (GIAO) method and compared with experimental results. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

  14. Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Joshi, Bhawani Datt; Srivastava, Anubha; Honorato, Sara Braga; Tandon, Poonam; Pessoa, Otília Deusdênia Loiola; Fechine, Pierre Basílio Almeida; Ayala, Alejandro Pedro

    2013-09-01

    Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as “pau branco”. Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d, p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The 13C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d, p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A.

  15. The D 1Σ+ state of 7LiH

    NASA Astrophysics Data System (ADS)

    Huang, Yen-Ling; Luh, Wei-Tzou; Jeung, Gwang-Hi; Gadéa, F. Xavier

    2000-07-01

    The 7LiH D 1Σ+ excited electronic state has been observed for the first time by a pulsed optical-optical double resonance fluorescence depletion spectroscopic technique. Several rovibrational levels of the A 1Σ+ and B 1Π electronic states have been used as the intermediate states. Among 22 vibrational levels, 128 rovibrational levels have been observed. The spectral assignment is identified by the observed rotational structures and term values and by a comparison between the derived vibrational and rotational constants with the theoretical values. An ab initio adiabatic potential energy curve for the D 1Σ+ state and relevant D 1Σ+-A1Σ+ and D 1Σ+-B 1Π transition moment functions are presented. An overall measure of three different aspects, the energetics, the spectral line shape, and the transition probability, strongly favors the argument that the vibronic approach is a better approach for characterizing the excited D 1Σ+ electronic state.

  16. Quantitative (13)C Solid-State NMR Spectra by Multiple-Contact Cross-polarization for Drug Delivery: From Active Principles to Excipients and Drug Carriers.

    PubMed

    Saïdi, Fadila; Taulelle, Francis; Martineau, Charlotte

    2016-08-01

    In this contribution, we present an analysis of the main parameters influencing the efficiency of the (1)H → (13)C multiple-contact cross-polarization nuclear magnetic resonance (NMR) experiment in the context of solid pharmaceutical materials. Using the optimum experimental conditions, quantitative (13)C NMR spectra are then obtained for porous metal-organic frameworks (potential drug carriers) and for components present in drug formulations (active principle ingredient and excipients, amorphous or crystalline). Finally, we show that mixtures of components can also be quantified with this method and, hence, that it represents an ideal tool for quantification of pharmaceutical formulations by (13)C cross-polarization under magic-angle spinning NMR in the industry as it is robust and easy to set up, much faster than direct (13)C polarization and is efficient for samples at natural abundance. PMID:27372550

  17. An approach to the simultaneous quantitative analysis of metabolites in table wines by (1)H NMR self-constructed three-dimensional spectra.

    PubMed

    Li, Bao Qiong; Xu, Min Li; Wang, Xue; Zhai, Hong Lin; Chen, Jing; Liu, Jin Jin

    2017-02-01

    Wine consists of several hundred components with different concentrations, including water, ethanol, glycerol, organic acids and sugars. Accurate quantification of target compounds in such complex samples is a difficult task based on conventional (1)H NMR spectra due to some challenges. In this paper, the three-dimensional spectrum was constructed firstly by simply repeating (1)H NMR spectrum itself so as to extract the features of target compounds by Tchebichef moment method. A proof-of-concept model system, the determination of five metabolites in wines was utilized to evaluate the performance of the proposed strategy. The results indicate that the proposed approach can provide accurate and reliable concentration predictions, probably the best results ever achieved using PLS and interval-PLS methods. Our novel strategy has not only good performance but also does not require laborious multi-step and subjective pretreatments. Therefore, it is expected that the proposed method could extend the application of conventional (1)H NMR. PMID:27596391

  18. Evaluation of the reliability of the maximum entropy method for reconstructing 3D and 4D NOESY-type NMR spectra of proteins.

    PubMed

    Shigemitsu, Yoshiki; Ikeya, Teppei; Yamamoto, Akihiro; Tsuchie, Yuusuke; Mishima, Masaki; Smith, Brian O; Güntert, Peter; Ito, Yutaka

    2015-02-01

    Despite their advantages in analysis, 4D NMR experiments are still infrequently used as a routine tool in protein NMR projects due to the long duration of the measurement and limited digital resolution. Recently, new acquisition techniques for speeding up multidimensional NMR experiments, such as nonlinear sampling, in combination with non-Fourier transform data processing methods have been proposed to be beneficial for 4D NMR experiments. Maximum entropy (MaxEnt) methods have been utilised for reconstructing nonlinearly sampled multi-dimensional NMR data. However, the artefacts arising from MaxEnt processing, particularly, in NOESY spectra have not yet been clearly assessed in comparison with other methods, such as quantitative maximum entropy, multidimensional decomposition, and compressed sensing. We compared MaxEnt with other methods in reconstructing 3D NOESY data acquired with variously reduced sparse sampling schedules and found that MaxEnt is robust, quick and competitive with other methods. Next, nonlinear sampling and MaxEnt processing were applied to 4D NOESY experiments, and the effect of the artefacts of MaxEnt was evaluated by calculating 3D structures from the NOE-derived distance restraints. Our results demonstrated that sufficiently converged and accurate structures (RMSD of 0.91Å to the mean and 1.36Å to the reference structures) were obtained even with NOESY spectra reconstructed from 1.6% randomly selected sampling points for indirect dimensions. This suggests that 3D MaxEnt processing in combination with nonlinear sampling schedules is still a useful and advantageous option for rapid acquisition of high-resolution 4D NOESY spectra of proteins. PMID:25545060

  19. A study of the molecular conformations and the vibrational, 1H and 13C NMR spectra of the anticancer drug tamoxifen and triphenylethylene

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Khan, Ibrahim

    2016-08-01

    The structural stability and the vibrational spectra of the anticancer drug tamoxifen and triphenylethylene were investigated by the DFT B3LYP/6-311G (d,p) calculations. Tamoxifen and triphenylethylene were predicted to exist predominantly as non-planar structures. The vibrational frequencies and the 1H and 13C NMR chemical shifts of the low energy structures of tamoxifen and triphenylethylene were computed at the DFT B3LYP level of theory. Complete vibrational assignments were provided by combined theoretical and experimental data of tamoxifen and triphenylethylene. The 1H and 13C NMR spectra of both molecules were interpreted by experimental and DFT calculated chemical shifts of the two molecules. The RMSD between experimental and theoretical 1H and 13C chemical shifts for tamoxifen is 0.29 and 4.72 ppm, whereas for triphenylethylene, it is 0.16 and 2.70 ppm, respectively.

  20. Systematic comparison of sets of (13)C NMR spectra that are potentially identical. Confirmation of the configuration of a cuticular hydrocarbon from the cane beetle Antitrogus parvulus.

    PubMed

    Basar, Norazah; Damodaran, Krishnan; Liu, Hao; Morris, Gareth A; Sirat, Hasnah M; Thomas, Eric J; Curran, Dennis P

    2014-08-15

    A systematic process is introduced to compare (13)C NMR spectra of two (or more) candidate samples of known structure to a natural product sample of unknown structure. The process is designed for the case where the spectra involved can reasonably be expected to be very similar, perhaps even identical. It is first validated by using published (13)C NMR data sets for the natural product 4,6,8,10,16,18-hexamethyldocosane. Then the stereoselective total syntheses of two candidate isomers of the related 4,6,8,10,16-pentamethyldocosane natural product are described, and the process is applied to confidently assign the configuration of the natural product as (4S,6R,8R,10S,16S). This is accomplished even though the chemical shift differences between this isomer and its (16R)-epimer are only ±5-10 ppb (±0.005-0.01 ppm). PMID:25019530

  1. Systematic Comparison of Sets of 13C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

    PubMed Central

    2015-01-01

    A systematic process is introduced to compare 13C NMR spectra of two (or more) candidate samples of known structure to a natural product sample of unknown structure. The process is designed for the case where the spectra involved can reasonably be expected to be very similar, perhaps even identical. It is first validated by using published 13C NMR data sets for the natural product 4,6,8,10,16,18-hexamethyldocosane. Then the stereoselective total syntheses of two candidate isomers of the related 4,6,8,10,16-pentamethyldocosane natural product are described, and the process is applied to confidently assign the configuration of the natural product as (4S,6R,8R,10S,16S). This is accomplished even though the chemical shift differences between this isomer and its (16R)-epimer are only ±5–10 ppb (±0.005–0.01 ppm). PMID:25019530

  2. Cellobiose as a model system to reveal cellulose dissolution mechanism in acetate-based ionic liquids: Density functional theory study substantiated by NMR spectra.

    PubMed

    Cao, Bobo; Du, Jiuyao; Du, Dongmei; Sun, Haitao; Zhu, Xiao; Fu, Hui

    2016-09-20

    Cellulose dissolution mechanism in acetate-based ionic liquids was systematically studied in Nuclear Magnetic Resonance (NMR) spectra and Density Functional Theory (DFT) methods by using cellobiose and 1-butyl-3-methylimidazolium acetate (BmimAc) as a model system. The solubility of cellulose in ionic liquid increased with temperature increase in the range of 90-140°C. NMR spectra suggested OAc(-) preferred to form stronger hydrogen bonds with hydrogen of hydroxyl in cellulose. Electrostatic potential method was employed to predict the most possible reaction sites and locate the most stable configuration. Atoms in molecules (AIM) theory was used to study the features of bonds at bond critical points and the variations of bond types. Simultaneously, noncovalent interactions were characterized and visualized by employing reduced density gradient analysis combined with Visual Molecular Dynamics (VMD) program. Natural bond orbital (NBO) theory was applied to study the noncovalent nature and characterize the orbital interactions between cellobiose and Bmim[OAc]. PMID:27261759

  3. Simplification of the 1H NMR spectra of enantiomers dissolved in chiral liquid crystals, combining variable angle sample spinning and selective refocusing experiments.

    PubMed

    Beguin, Laetitia; Courtieu, Jacques; Ziani, Latifa; Merlet, Denis

    2006-12-01

    This work presents a technique to simplify overcrowded proton spectra in chiral liquid crystal solvents using rotation of the sample near the magic angle, VASS, combined with homonuclear selective refocusing 2D NMR experiments, SERF. This methodology provides a powerful tool to visualise enantiomers out of unresolved proton spectra. A modified SERF sequence is presented where the resulting 2D spectrum can be phased to increase the resolution. Accurate enantiomeric excesses are determined that are not possible to measure on static samples. Two examples are presented. PMID:16991108

  4. A Simple Approach for Obtaining High Resolution, High Sensitivity ¹H NMR Metabolite Spectra of Biofluids with Limited Mass Supply

    SciTech Connect

    Hu, Jian Zhi; Rommereim, Donald N.; Wind, Robert A.; Minard, Kevin R.; Sears, Jesse A.

    2006-11-01

    A simple approach is reported that yields high resolution, high sensitivity ¹H NMR spectra of biofluids with limited mass supply. This is achieved by spinning a capillary sample tube containing a biofluid at the magic angle at a frequency of about 80Hz. A 2D pulse sequence called ¹H PASS is then used to produce a high-resolution ¹H NMR spectrum that is free from magnetic susceptibility induced line broadening. With this new approach a high resolution ¹H NMR spectrum of biofluids with a volume less than 1.0 µl can be easily achieved at a magnetic field strength as low as 7.05T. Furthermore, the methodology facilitates easy sample handling, i.e., the samples can be directly collected into inexpensive and disposable capillary tubes at the site of collection and subsequently used for NMR measurements. In addition, slow magic angle spinning improves magnetic field shimming and is especially suitable for high throughput investigations. In this paper first results are shown obtained in a magnetic field of 7.05T on urine samples collected from mice using a modified commercial NMR probe.

  5. Spectroscopic characterization of the first singlet (Ã 1B1) excited state of 7Li16O7Li

    NASA Astrophysics Data System (ADS)

    Bellert, D.; Winn, D. K.; Breckenridge, W. H.

    2003-11-01

    Using laser induced fluorescence (LIF) and resonance enhanced two-photon ionization (R2PI) spectroscopy, several (ν1',ν2',ν3') vibrational bands of the à 1B1(K'=1)←X˜ 1Σg+(0,0,0) perpendicular transition of the 7Li16O7Li molecule have been rotationally resolved and analyzed to yield effective A',B',C' values. The estimated geometry of the à 1B1 state does not vary with ν1' (symmetric stretch mode), but θ' increases and R' decreases slightly as ν2' (bending mode) increases. Extrapolation leads to an estimate for the (0,0,0) state of θ0'=105±5°, R0'=1.86±0.04 Å, and for the potential minimum θe'=102±5°, Re'=1.87±0.04 Å. The strongly bent nature of the à 1B1 state is due to promotion of an O-2 p-electron (b1) from the strongly ionic, linear Li+O-2Li+ ground state to an a1 molecular orbital which has Li/Li bonding character. The Ã1B1 state thus has an approximately Li+1/2O-1Li+1/2 charge distribution, so that the ionic bonding is less strong than in the linear ground state, where (from this study and an earlier stimulation-emission pumping study) R0″=1.611±0.003 Å. In fact, the Li-Li distance in the à 1B1 state, ˜3.0 Å, is quite similar to that of the Li2+1 ion, so the bonding may be described as that of Li2+1 bound ionically to the O-1 ion.

  6. First determination of the 8Li valence neutron asymptotic normalization coefficient using the 7Li(8Li,7Li)8Li reaction

    NASA Astrophysics Data System (ADS)

    Howell, D.; Davids, B.; Greene, J. P.; Kanungo, R.; Mythili, S.; Ruiz, C.; Ruprecht, G.; Thompson, I. J.

    2013-08-01

    We report here a determination of the asymptotic normalization coefficient of the valence neutron in 8Li from a measurement of the angular distribution of the 7Li(8Li,7Li)8Li reaction at 11 MeV. Using isospin symmetry the 8B ANC has also been calculated and used to infer a value for S17(0) of 20.2 ± 4.4 eV b.

  7. 4 f-4 f hypersensitivity in the absorption spectra and NMR studies on paramagnetic lanthanide chloride complexes with 1,10-phenanthroline in non-aqueous solutions

    NASA Astrophysics Data System (ADS)

    Hussain, H. A.; Iftikhar, K.

    2003-03-01

    The optical absorption and NMR studies of trivalent lanthanide chloride complexes with 1,10-phenanthroline (phen) are presented and discussed. The 1H NMR spectra of the complexes of La, Pr, Nd, Eu and Yb have been studied in methanol- d4. The resonances of phen in the NMR spectra of the paramagnetic complexes have been shifted to lower as well as higher fields, which is a manifestation of dipolar interaction. The H (2) protons of the heterocyclic amine display broad resonances. The degree of broadening in Pr, Nd, and Yb complexes follows the order Prspectra of Pr, Nd, Ho and Er complexes have been investigated in methanol, pyridine, DMSO and DMF, which reveal that the hypersensitive transitions exhibit larger variation in oscillator strength values and band shapes. The change in the coordination geometry of the complexes and relative basicity of ligand are found responsible for oscillator strength and band shape variation. The interelectronic repulsion and covalency parameters show covalent nature of bonding between the metal and the ligand.

  8. Synthesis and NMR Spectral Analysis of Amine Heterocycles: The Effect of Asymmetry on the [superscript 1]H and [superscript 13]C NMR Spectra of N,O-Acetals

    ERIC Educational Resources Information Center

    Saba, Shahrokh; Ciaccio, James A.; Espinal, Jennifer; Aman, Courtney E.

    2007-01-01

    The stereochemical investigation is conducted to give students the combined experience of chemical synthesis of amines and N-heterocycles and structural stereochemical analysis using NMR spectroscopy. Students are introduced to the concept of topicity-stereochemical relationships between ligands within a molecule by synthesizing N,O-acetals.

  9. Reaction mechanism of 7Li(3He,p)9Be and 7Li(3H,n)9Be and primordial nucleosynthesis of 9Be

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Kajino, T.; Kubo, K.-I.

    1993-02-01

    We investigate in a unified way the reaction mechanism of 7Li(3H,n)9Be and 7Li(3He, p)9Be at the low energies Ec.m.<=2 MeV of astrophysical interest. Assuming charge independence of the nuclear reaction amplitudes and taking account of the effects from different isospin contribution, Coulomb interaction, and associated kinematical conditions properly, we constrain the upper and lower bounds of the total cross section of 7Li(3H,n)9Be theoretically by using knowledge of the 7Li(3He, p)9Be reaction. It is found that the total cross section of 7Li(3H,n)9Be at Gamow window energy E~250 keV is dominated by the near-threshold T=1 resonance whose resonance parameters are not determined at all experimentally, although the direct reaction process makes progressively important contributions at higher energies 500 keV<=Ec.m.. Primordial abundance of 9Be calculated in the inhomogeneous and standard big-bang models by using the inferred reaction cross section for 7Li(3H,n)9Be is compared with recent results of astronomical observations.

  10. Paramagnetic effects on the NMR spectra of isotropic bicelles with headgroup modified chelator lipids and metal ions.

    PubMed

    Tang, Ming; Mao, Kevin; Li, Stacey; Zhuang, Jianqin; Diallo, Koumba

    2016-06-21

    We characterized the paramagnetic effects of nine metal ions on NMR signals of isotropic bicelles with headgroup-modified lipids. We found that Mn(2+), Gd(3+) and Dy(3+) show evidence for influencing NMR signals on the surface more than inside and on the disc edge, providing distance information in the bilayers. PMID:27240538

  11. Chromatographic NMR in NMR solvents

    NASA Astrophysics Data System (ADS)

    Carrara, Caroline; Viel, Stéphane; Delaurent, Corinne; Ziarelli, Fabio; Excoffier, Grégory; Caldarelli, Stefano

    2008-10-01

    Recently, it was demonstrated that pseudo-chromatographic NMR experiments could be performed using typical chromatographic solids and solvents. This first setup yielded improved separation of the spectral components of the NMR spectra of mixtures using PFG self-diffusion measurements. The method (dubbed Chromatographic NMR) was successively shown to possess, in favorable cases, superior resolving power on non-functionalized silica, compared to its LC counterpart. To further investigate the applicability of the method, we studied here the feasibility of Chromatographic NMR in common deuterated solvents. Two examples are provided, using deuterated chloroform and water, for homologous compounds soluble in these solvents, namely aromatic molecules and alcohols, respectively.

  12. Use of 7Li(p,n) reaction as a neutron source in a PGNAA setup.

    PubMed

    Naqvi, A A; Nagadi, M M

    2005-03-01

    The performance of a 7Li(p,n) reaction-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup has been determined for analysis of Portland cement samples using Monte Carlo study. The calculations were carried out for a 7Li(p,n) reaction-based PGNAA setup with an external moderator similar to the one used in a previous 2.8 MeV neutrons-based PGNAA setup. The optimum values of geometry parameters of the 7Li(p,n) reaction-based setup are different from those of the 2.8 MeV neutrons-based setup resulting in better performance of the 7Li(p,n) reaction-based setup. The prompt gamma-ray yield from the 7Li(p,n) reaction-based setup is 60-70% higher than that from the 2.8 MeV neutrons-based setup. Although the performances of the 7Li(p,n) reaction-based setup is comparable with that of a previously studied 3H(p,n) reaction-based setup, yet performance of the 7Li(p,n) reaction-based setup is superior to that of the 3H(p,n) reaction-based setup because it has less radiation hazard due to utilization of non-radioactive neutron producing target. This study has provided a theoretical base for experimental test of a 7Li(p,n) reaction-based PGNAA setup. PMID:15607917

  13. Prospects of lithium enrichment on 7Li isotope by method of controlled ions electro-migration

    NASA Astrophysics Data System (ADS)

    Martoyan, G. A.; Kalugin, M. M.; Gabrielyan, A. V.; Martoyan, A. G.

    2016-01-01

    This paper deals with a new electro-membrane method of enrichment of 7Li isotope. The data are presented on the importance and application fields regarding the use of 7Li isotopes. Existing methods and criteria of separation of lithium isotopes are discussed. The principle of new technology, regimes of enrichment experiments, and analysis details of obtained products are briefly described.

  14. A New 6Li Detection in a Halo Subgiant, and Constraints for the Depletion of the Big Bang 7Li Abundance

    NASA Astrophysics Data System (ADS)

    Deliyannis, C. P.; Ryan, S. G.

    2000-05-01

    We present measurements of the 6Li/7Li isotope ratio in ten metal-poor stars derived from very high resolution (100,000) and S/N (300-800/pixel) McDonald 2.7-meter coude spectra, including two possible 6Li detections. We present specific new evidence that we have indeed detected the 6Li absorption feature, and not a convective asymmetry of the 7Li feature. One of our detections argues in favor of a protostellar (and not a surface-spallated) origin for this 6Li. We find that 6Li has either not evolved strongly with metallicity, in contrast to what is observed for Be and B, or else concurrent 6Li production is matched by stellar depletion. While such fine-tuning seems unlikely, no models can explain the origin of 6Li without such depletion. In the context of the observed 9Be/7Li depletion correlation and its slow-mixing explanation, taking our data at face value implies that the Big Bang 7Li abundance is no more than 0.2-0.3 dex higher than the values observed in the halo Li plateau.

  15. Non-Gaussian error distribution of 7Li abundance measurements

    NASA Astrophysics Data System (ADS)

    Crandall, Sara; Houston, Stephen; Ratra, Bharat

    2015-07-01

    We construct the error distribution of 7Li abundance measurements for 66 observations (with error bars) used by Spite et al. (2012) that give A(Li) = 2.21 ± 0.065 (median and 1σ symmetrized error). This error distribution is somewhat non-Gaussian, with larger probability in the tails than is predicted by a Gaussian distribution. The 95.4% confidence limits are 3.0σ in terms of the quoted errors. We fit the data to four commonly used distributions: Gaussian, Cauchy, Student’s t and double exponential with the center of the distribution found with both weighted mean and median statistics. It is reasonably well described by a widened n = 8 Student’s t distribution. Assuming Gaussianity, the observed A(Li) is 6.5σ away from that expected from standard Big Bang Nucleosynthesis (BBN) given the Planck observations. Accounting for the non-Gaussianity of the observed A(Li) error distribution reduces the discrepancy to 4.9σ, which is still significant.

  16. Studies of the Efimov Effect in 7 Li

    NASA Astrophysics Data System (ADS)

    Luo, D.; Nguyen, J. H. V.; Hulet, R. G.

    2016-05-01

    Ultracold atomic gases provide an ideal environment to study few body physics in the universal regime. Passive techniques, such as monitoring loss of the atomic sample while varying the hold time allows us to explore properties such as the scaling behavior of Efimov trimers. In our experiment, we explore how the Efimov states are affected by non-zero temperature. We measure the three-body loss rate for a 7 Li atom gas at different scattering lengths and extract the location and width of an Efimov recombination minimum for various temperatures. Alternatively, we may perform more active experiments such as creating dimers using RF-field modulation as a probe of molecular binding energies. We use RF-association to form Feshbach dimers and Efimov trimers, and find a strong enhancement of the dimer formation rate at the atom-dimer resonance, which could be explained by an avalanche mechanism. In the past the enhancement in the three-body recombination rate at the same location had also been observed, and attributed to the avalanche. We explore the link between these findings with a side-by-side comparison of the dimer-formation rate and the three-body loss rate. Work supported by the NSF, an ARO MURI Grant, and the Welch Foundation.

  17. Test of level density models from reactions of {sup 6}Li on {sup 58}Fe and {sup 7}Li on {sup 57}Fe

    SciTech Connect

    Oginni, B. M.; Grimes, S. M.; Voinov, A. V.; Adekola, A. S.; Brune, C. R.; Carter, D. E.; Heinen, Z.; Jacobs, D.; Massey, T. N.; O'Donnell, J. E.; Schiller, A.

    2009-09-15

    The reactions of {sup 6}Li on {sup 58}Fe and {sup 7}Li on {sup 57}Fe have been studied at 15 MeV beam energy. These two reactions produce the same compound nucleus, {sup 64}Cu. The charged particle spectra were measured at backward angles. The data obtained have been compared with Hauser-Feshbach model calculations. The level density parameters of {sup 63}Ni and {sup 60}Co have been obtained from the particle evaporation spectra. We also find contributions from the break up of the lithium projectiles to the low energy region of the {alpha} spectra.

  18. Conformational and isomerizational studies of 3- N, N-dimethylhydrazino-2-methylsulfonyl propenenitrile using NMR and vibrational spectra, X-ray analysis and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gróf, M.; Gatial, A.; Milata, V.; Prónayová, N.; Kožíšek, J.; Breza, M.; Matějka, P.

    2008-11-01

    The IR, Raman and NMR spectra of 3- N, N-dimethylhydrazino-2-methylsulfonyl propenenitrile (DMHSP) [(H 3C) 2N sbnd NH sbnd CH dbnd C(CN) (SO 2CH 3)] as a solid and in different solvents were measured. The spectra and X-ray analysis revealed that DMHSP was prepared as a pure E-isomer and E- syn conformer with the syn orientation of N, N-dimethylhydrazino group towards the C dbnd C double bond in the solid state. Due to the low barrier practically free isomerization process occurred in solutions at room temperature. DMHSP exists in more polar solvents as pure E-isomer in conformational equilibrium between E- syn and E- anti but in a less polar solvent the presence of Z-isomer was observed as well. From the IR and NMR temperature dependence spectra in polar solvents the energy difference between E- anti and E- syn of Δ H = 2.3 ± 0.9 kJ/mol and Δ H = 3.2 ± 0.4 kJ/mol, respectively, was estimated with the syn one being more stable. The geometries and relative energies of possible conformers of DMHSP were evaluated using ab initio MP2 and B3LYP density functional methods in 6-31G ∗∗ basis set and compared with the X-ray data. The interpretation of NMR spectra was supported by ab initio MP2 calculations. The influence of solvent polarity on the conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using PCM model. In addition, the observed IR and Raman bands were compared also with harmonic vibrational frequencies, calculated on the same levels of theory, and assigned on the base of potential energy distribution.

  19. Bond pathway analysis of NMR spectra for Li1.2Mn0.4Co0.4O2: pristine material

    NASA Astrophysics Data System (ADS)

    Iddir, Hakim; Key, Baris; Dogan, Fulya; Russell, John; Long, Brandon; Bareno, Javier; Croy, Jason; Benedek, Roy

    2015-03-01

    NMR has been applied extensively to lithium ion battery cathode materials, of which layered-layered composites xLi2MnO3 . (1 - x) Li MO2 (M = Mn,Co,Ni) are of particular interest, owing to their high energy density. In this work, NMR spectra are measured for the model layered-layered system xLi2MnO3 . (1 - x) LiCoO2 and Bond-Pathway-model analysis is applied to elucidate the atomic arrangement and domain structure of this material (in its pristine state, before electrochemical cycling). The simplest structural element of a domain consists of a stripe of composition LiMn2 parallel to an in-layer crystallographic axis in a metal layer of the composite. A simple model of the composite structure may be constructed by a superposition of such stripes in an LiCoO background. We show that such a model can account for most of the features of the observed NMR spectra. Support from the Vehicle Technologies Program U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy.

  20. Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Gopinath, T.; Veglia, Gianluigi

    2013-05-01

    We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

  1. On 7LI Enrichment by Low-Mass Metal-Poor Red Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    de la Reza, Ramiro; da Silva, Licio; Drake, Natalia A.; Terra, Marco A.

    2000-06-01

    First-ascent red giants with strong and very strong Li lines have just been discovered in globular clusters. Using the stellar internal prompt 7Li enrichment-mass-loss scenario, we explore the possibility of 7Li enrichment in the interstellar matter of the globular cluster M3 produced by these Li-rich giants. We found that enrichment as large as 70% or more compared to the initial 7Li content of M3 can be obtained during the entire life of this cluster. However, because M3 will cross into the Galactic plane several times, the new 7Li will be very probably removed by ram pressure into the disk. Globular clusters appear then as possible new sources of 7Li in the Galactic disk. It is also suggested that the known Na/Al variations in stars of globular clusters could be somehow related to the 7Li variations and that the cool bottom process mixing mechanism acting in the case of 7Li could also play a role in the case of Na and Al surface enrichments.

  2. Interpreting the Paramagnetic NMR Spectra of Potential Ru(III) Metallodrugs: Synergy between Experiment and Relativistic DFT Calculations.

    PubMed

    Novotný, Jan; Sojka, Martin; Komorovsky, Stanislav; Nečas, Marek; Marek, Radek

    2016-07-13

    Ruthenium-based compounds are potential candidates for use as anticancer metallodrugs. The central ruthenium atom can be in the oxidation state +2 (e.g., RAPTA, RAED) or +3 (e.g., NAMI, KP). In this study we focus on paramagnetic NAMI analogs of a general structure [4-R-pyH](+)trans-[Ru(III)Cl4(DMSO)(4-R-py)](-), where 4-R-py stands for a 4-substituted pyridine. As paramagnetic systems are generally considered difficult to characterize in detail by NMR spectroscopy, we performed a systematic structural and methodological NMR study of complexes containing variously substituted pyridines. The effect of the paramagnetic nature of these complexes on the (1)H and (13)C NMR chemical shifts was systematically investigated by temperature-dependent NMR experiments and density-functional theory (DFT) calculations. To understand the electronic factors influencing the orbital (δ(orb), temperature-independent) and paramagnetic (δ(para), temperature-dependent) contributions to the total NMR chemical shifts, a relativistic two-component DFT approach was used. The paramagnetic contributions to the (13)C NMR chemical shifts are correlated with the distribution of spin density in the ligand moiety and the (13)C isotropic hyperfine coupling constants, Aiso((13)C), for the individual carbon atoms. To analyze the mechanism of spin distribution in the ligand, the contributions of molecular spin-orbitals (MSOs) to the hyperfine coupling constants and the spatial distribution of the z-component of the spin density in the MSOs calculated at the relativistic four-component DFT level are discussed and rationalized. The significant effects of the substituent and the solvent on δ(para), particularly the contact contribution, are demonstrated. This work should contribute to further understanding of the link between the electronic structure and the NMR chemical shifts in open-shell systems, including the ruthenium-based metallodrugs investigated in this account. PMID:27312929

  3. The conformational stability, solvation and the assignments of the experimental infrared, Raman, 1H and 13C NMR spectra of the local anesthetic drug lidocaine

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

    2015-05-01

    The structure, vibrational and 1H and 13C NMR spectra of the local anesthetic drug lidocaine were investigated by the B3LYP/6-311G∗∗ calculations. The molecule was predicted to have the non-planar cis (NCCN ∼ 0°) structures being about 2-6 kcal/mol lower in energy than the corresponding trans (NCCN ∼ 180°) forms. The calculated NCCN (9.6°) and CNCC (-132.2°) torsional angles were in a good qualitative agreement with the reported X-ray angles (3.1 and 13.0°, -102.67 and -77.9°, respectively, for H-bonded dimers). The Gibbs energy of solution of lidocaine in formamide, water, dimethylsulfoxide, acetonitrile, methanol, ethanol and chloroform solutions was estimated at the B3LYP level. The predicted affinity of lidocaine toward the alcohols, acetonitrile and chloroform solutions was in excellent agreement with the reported experimental solubility of the drug in organic solvents. The analysis of the observed vibrational spectra is consistent with the presence of lidocaine in only one conformation at room temperature. The 1H and 13C NMR spectra of lidocaine were interpreted by experimental and DFT calculated chemical shifts of the drug. The RMSD between experimental and theoretical 1H and 13C chemical shifts for lidocaine is 0.47 and 8.26 ppm, respectively.

  4. A study of the experimental and theoretical infrared, Raman, 1H and 13C NMR spectra of the biochemicals valeric and valproic acids

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

    2014-10-01

    The structural stability, vibrational, 1H and 13C NMR spectra of valeric and valproic acids were investigated by the B3LYP calculations with the 6-311G** basis set. Valeric acid is predicted to exist predominantly in the planar cis form (80% abundance). Valproic acid is predicted to have an equilibrium mixture of 68% gauche-1 and 32% gauche-2 structures at 298.15 K. The spectral feature of the Osbnd H stretching mode in the infrared spectra of both acids suggests the presence of strong H-bonding in the condensed phase of valeric acid and weak H-bonding in the case of valproic acid. The harmonic and anharmonic vibrational wavenumbers were computed at the B3LYP level of theory and tentative vibrational assignments were provided on the basis of combined theoretical and experimental infrared and Raman data of the molecules. Not all of the calculated anharmonic wavenumbers showed a consistent trend with the observed wavenumbers. The 1H and 13C NMR spectra of both acids were interpreted by experimental and DFT calculated chemical shifts of the two acids. The RMSD between experimental and theoretical 1H and 13C chemical shifts for valeric acid is 1.8 and 3.8 ppm, whereas for valproic acid, it is 1.4 and 4.5 ppm, respectively.

  5. Quantum-chemical analyses of aromaticity, UV spectra, and NMR chemical shifts in plumbacyclopentadienylidenes stabilized by Lewis bases.

    PubMed

    Kawamura, Toshiaki; Abe, Minori; Saito, Masaichi; Hada, Masahiko

    2014-04-30

    We carried out a series of zeroth-order regular approximation (ZORA)-density functional theory (DFT) and ZORA-time-dependent (TD)-DFT calculations for molecular geometries, NMR chemical shifts, nucleus-independent chemical shifts (NICS), and electronic transition energies of plumbacyclopentadienylidenes stabilized by several Lewis bases, (Ph)2 ((t) BuMe2 Si)2 C4 PbL1 L2 (L1, L2 = tetrahydrofuran, Pyridine, N-heterocyclic carbene), and their model molecules. We mainly discussed the Lewis-base effect on the aromaticity of these complexes. The NICS was used to examine the aromaticity. The NICS values showed that the aromaticity of these complexes increases when the donation from the Lewis bases to Pb becomes large. This trend seems to be reasonable when the 4n-Huckel rule is applied to the fractional π-electron number. The calculated (13)C- and (207)Pb-NMR chemical shifts and the calculated UV transition energies reasonably reproduced the experimental trends. We found a specific relationship between the (13)C-NMR chemical shifts and the transition energies. As we expected, the relativistic effect was essential to reproduce a trend not only in the (207)Pb-NMR chemical shifts and J[Pb-C] but also in the (13)C-NMR chemical shifts of carbons adjacent to the lead atom. PMID:24643814

  6. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    USGS Publications Warehouse

    Thorn, K.A.; Cox, L.G.

    2009-01-01

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS 15N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by 15N NMR. Liquid state 15N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (1H-15N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  7. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    SciTech Connect

    Thorn, Kevin A.; Cox, Larry G.

    2009-02-28

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS ¹⁵N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by ¹⁵N NMR. Liquid state ¹⁵N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (¹H–¹⁵N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  8. Interaction of loosely bound radioactive 7Be and stable 7Li with 9Be

    NASA Astrophysics Data System (ADS)

    Verma, S.; Das, J. J.; Jhingan, A.; Kalita, K.; Barua, S.; Golda, K. S.; Madhavan, N.; Sugathan, P.; Nath, S.; Varughese, T.; Gehlot, J.; Mandal, S.; Ranjit; Sahu, P. K.; John, B.; Nayak, B. K.; Jha, V.; Saxena, A.; Datta, S. K.; Singh, R.

    2010-06-01

    Quasielastic scattering angular distributions have been measured for the 7Be + 9Be system at E lab = 17 , 19 and 21MeV in the angular range θ_{{cm}}^{} = 24° - 57° . An optical model (OM) analysis of these data has been carried out in order to extract optical potential parameters and reaction cross-sections. One-proton stripping cross-sections were also measured for this system at E lab = 19 and 21MeV. These transfer angular-distribution data were compared with the finite-range distorted-wave Born approximation (FRDWBA) calculations. For the 7Li + 9Be system quasielastic scattering angular distributions were measured and emitted light charged particles were detected at E lab = 15.75 , 24.00 and 30.00MeV in the angular range θ_{{cm}}^{} = 7° - 70° . Fusion cross-sections were obtained by reproducing the measured α -evaporation spectra from the compound nucleus at backward angles with the statistical model calculations. The ratios of the experimental fusion cross-sections to the total reaction cross-sections (obtained from OM analysis) were found to be small. This result suggests that the break-up process has a strong influence on the fusion process leading to a reduction in the fusion cross-section.

  9. Absolute nutrient concentration measurements in cell culture media: (1)H q-NMR spectra and data to compare the efficiency of pH-controlled protein precipitation versus CPMG or post-processing filtering approaches.

    PubMed

    Goldoni, Luca; Beringhelli, Tiziana; Rocchia, Walter; Realini, Natalia; Piomelli, Daniele

    2016-09-01

    The NMR spectra and data reported in this article refer to the research article titled "A simple and accurate protocol for absolute polar metabolite quantification in cell cultures using q-NMR" [1]. We provide the (1)H q-NMR spectra of cell culture media (DMEM) after removal of serum proteins, which show the different efficiency of various precipitating solvents, the solvent/DMEM ratios, and pH of the solution. We compare the data of the absolute nutrient concentrations, measured by PULCON external standard method, before and after precipitation of serum proteins and those obtained using CPMG (Carr-Purcell-Meiboom-Gill) sequence or applying post-processing filtering algorithms to remove, from the (1)H q-NMR spectra, the proteins signal contribution. For each of these approaches, the percent error in the absolute value of every measurement for all the nutrients is also plotted as accuracy assessment. PMID:27331118

  10. Influence of inner-sphere processes on the paramagnetic shifts in the {sup 1}H NMR spectra of some mixed-ligand complexes of rare-earth elements

    SciTech Connect

    Khachatryan, A.S.; Vashchuk, A.V.; Panyushkin, V.T.

    1995-12-20

    Concentration dependences of the observed chemical shifts in the NMR spectra of 1:1:1 and 1:2:1 mixed-ligand complexes of rare-earth elements with acetylacetone and acrylic, methacrylic, maleic, and fumaric acids were analyzed. The complexes undergo inner-sphere structural transformations involving different modes of coordination of the unsaturated acid, which is capable of coordination to the central ion through both the carboxylic group and {pi} electrons of the double bond. The possibility of determining equilibrium constants and limiting chemical shifts of the isomeric forms of the complexes was demonstrated. 9 refs., 4 figs.

  11. Bare-Minimum Fluorous Mixture Synthesis of a Stereoisomer Library of 4,8,12-Trimethylnonadecanols and Predictions of NMR Spectra of Saturated Oligoisoprenoid Stereoisomers

    PubMed Central

    Yeh, Edmund A.-H.; Kumli, Eveline; Damodaran, Krishnan; Curran, Dennis P.

    2013-01-01

    All four diastereomers of a typical saturated oligoisoprenoid, 4,8,12-trimethylnonadecanol, are made by an iterative three step cycle with the aid of traceless thionocarbonate fluorous tags to encode configurations. The tags have a minimum number of total fluorine atoms, starting at zero and increasing in increments of one. With suitable acquisition and data processing, each diastereomer exhibited characteristic chemical shifts of methyl resonances in its 1H and 13C NMR spectra. Together, these shifts provide a basis to predict the appearance of the methyl region of the spectrum of every stereoisomer of higher saturated oligoisoprenoids. PMID:23297872

  12. NMR profiling of biomolecules at natural abundance using 2D 1H-15N and 1H-13C multiplicity-separated (MS) HSQC spectra

    NASA Astrophysics Data System (ADS)

    Chen, Kang; Freedberg, Darón I.; Keire, David A.

    2015-02-01

    2D NMR 1H-X (X = 15N or 13C) HSQC spectra contain cross-peaks for all XHn moieties. Multiplicity-edited1H-13C HSQC pulse sequences generate opposite signs between peaks of CH2 and CH/CH3 at a cost of lower signal-to-noise due to the 13C T2 relaxation during an additional 1/1JCH period. Such CHn-editing experiments are useful in assignment of chemical shifts and have been successfully applied to small molecules and small proteins (e.g. ubiquitin) dissolved in deuterated solvents where, generally, peak overlap is minimal. By contrast, for larger biomolecules, peak overlap in 2D HSQC spectra is unavoidable and peaks with opposite phases cancel each other out in the edited spectra. However, there is an increasing need for using NMR to profile biomolecules at natural abundance dissolved in water (e.g., protein therapeutics) where NMR experiments beyond 2D are impractical. Therefore, the existing 2D multiplicity-edited HSQC methods must be improved to acquire data on nuclei other than 13C (i.e.15N), to resolve more peaks, to reduce T2 losses and to accommodate water suppression approaches. To meet these needs, a multiplicity-separated1H-X HSQC (MS-HSQC) experiment was developed and tested on 500 and 700 MHz NMR spectrometers equipped with room temperature probes using RNase A (14 kDa) and retroviral capsid (26 kDa) proteins dissolved in 95% H2O/5% D2O. In this pulse sequence, the 1/1JXH editing-period is incorporated into the semi-constant time (semi-CT) X resonance chemical shift evolution period, which increases sensitivity, and importantly, the sum and the difference of the interleaved 1JXH-active and the 1JXH-inactive HSQC experiments yield two separate spectra for XH2 and XH/XH3. Furthermore we demonstrate improved water suppression using triple xyz-gradients instead of the more widely used z-gradient only water-suppression approach.

  13. Toward an in Vivo Neurochemical Profile: Quantification of 18 Metabolites in Short-Echo-Time 1H NMR Spectra of the Rat Brain

    NASA Astrophysics Data System (ADS)

    Pfeuffer, Josef; Tkáč , Ivan; Provencher, Stephen W.; Gruetter, Rolf

    1999-11-01

    Localized in vivo1H NMR spectroscopy was performed with 2-ms echo time in the rat brain at 9.4 T. Frequency domain analysis with LCModel showed that the in vivo spectra can be explained by 18 metabolite model solution spectra and a highly structured background, which was attributed to resonances with fivefold shorter in vivo T1 than metabolites. The high spectral resolution (full width at half maximum approximately 0.025 ppm) and sensitivity (signal-to-noise ratio approximately 45 from a 63-μL volume, 512 scans) was used for the simultaneous measurement of the concentrations of metabolites previously difficult to quantify in 1H spectra. The strongly represented signals of N-acetylaspartate, glutamate, taurine, myo-inositol, creatine, phosphocreatine, glutamine, and lactate were quantified with Cramér-Rao lower bounds below 4%. Choline groups, phosphorylethanolamine, glucose, glutathione, γ-aminobutyric acid, N-acetylaspartylglutamate, and alanine were below 13%, whereas aspartate and scyllo-inositol were below 22%. Intra-assay variation was assessed from a time series of 3-min spectra, and the coefficient of variation was similar to the calculated Cramér-Rao lower bounds. Interassay variation was determined from 31 pooled spectra, and the coefficient of variation for total creatine was 7%. Tissue concentrations were found to be in very good agreement with neurochemical data from the literature.

  14. Using a Problem Solving-Cooperative Learning Approach to Improve Students' Skills for Interpreting [Superscript 1]H NMR Spectra of Unknown Compounds in an Organic Spectroscopy Course

    ERIC Educational Resources Information Center

    Angawi, Rihab F.

    2014-01-01

    To address third- and fourth-year chemistry students' difficulties with the challenge of interpreting [superscript 1]H NMR spectra, a problem solving-cooperative learning technique was incorporated in a Spectra of Organic Compounds course. Using this approach helped students deepen their understanding of the basics of [superscript 1]H NMR…

  15. Electrical conductivity, differential scanning calorimetry, X-ray diffraction, and 7Li nuclear magnetic resonance studies of n-C x H(2 x+1)OSO3Li ( x = 12, 14, 16, 18, and 20)

    NASA Astrophysics Data System (ADS)

    Hirakawa, Satoru; Morimoto, Yoshiaki; Honda, Hisashi

    2015-04-01

    Electrical conductivity ( σ), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) measurements of n-C x H (2 x+1) OSO 3Li ( x= 12, 14, 16, 18, and 20) crystals were performed as a function of temperature. In addition, σ, DSC, and XRD observations of n-C x H (2 x+1) OSO 3Na and n-C x H (2 x+1) OSO 3K ( x= 12, 14, 16, 18, and 20) crystals were carried out for comparison. DSC results of the salts revealed several solid-solid phase transitions with large entropy changes (Δ S). For n-C 18 H 37 OSO 3Li and n-C 20 H 41 OSO 3Li salts, each melting point produced a small Δ S mp value compared with the total entropy change in the solid phases (Δ S tr1+Δ S tr2). Additionally, Li + ion diffusion was detected in the highest temperature solid phases. For K salts, larger σ values were detected for potassium alkylsulfates compared with those reported for alkyl carboxylate. 7Li NMR spectra of n-C 18 H 37 OSO 3Li crystals recorded in the low-temperature phase showed large asymmetry parameters, suggesting the Li + ions are localized at asymmetric sites in the crystals.

  16. Strategy for Enhancement of (13)C-Photo-CIDNP NMR Spectra by Exploiting Fractional (13)C-Labeling of Tryptophan.

    PubMed

    Eisenreich, Wolfgang; Joshi, Monika; Illarionov, Boris; Kacprzak, Sylwia; Lukaschek, Michail; Kothe, Gerd; Budisa, Nediljko; Fischer, Markus; Bacher, Adelbert; Weber, Stefan

    2015-10-29

    The photo-CIDNP effect has proven to be useful to strongly enhance NMR signals of photochemically active proteins simply by irradiation with light. The evolving characteristic patterns of enhanced absorptive and emissive NMR lines can be exploited to elucidate the photochemistry and photophysics of light-driven protein reactions. In particular, by the assignment of (13)C NMR resonances, redox-active amino acids may be identified and thereby electron-transfer pathways unraveled, in favorable cases, even with (13)C at natural abundance. If signal enhancement is weak, uniform (13)C isotope labeling is traditionally applied to increase the signal strength of protein (13)C NMR. However, this typically leads to cross relaxation, which transfers light-induced nuclear-spin polarization to adjacent (13)C nuclei, thereby preventing an unambiguous analysis of the photo-CIDNP effect. In this contribution, two isotope labeling strategies are presented; one leads to specific but ubiquitous (13)C labeling in tryptophan, and the other is based on fractional isotope labeling affording sets of isotopologs with low probability of next-neighbor isotope accumulation within individual tryptophan molecules. Consequently, cross relaxation is largely avoided while the signal enhancement by (13)C enrichment is preserved. This results in significantly simplified polarization patterns that are easier to analyze with respect to the generation of light-generated nuclear-spin polarization. PMID:26244593

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

    PubMed

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

    2015-01-01

    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

  18. Structure of pyridine and quinoline vinyl ethers according to data from /sup 1/H and /sup 13/C NMR spectra and quantum-chemical calculations

    SciTech Connect

    Afonin, A.V.; Voronov, V.K.; Andriankov, M.A.; Danovich, D.K.

    1987-08-10

    A systematic investigation of the structure of the vinyl ethers of heterocyclic compounds has not been undertaken. The present work was devoted to investigation of the stereochemical and electronic structure of the vinyl ethers of pyridine and quinoline. The PMR spectra of the samples were recorded for 5% solutions in deuterochloroform on a Tesla BS-497 spectrometer at 100 MHz. The /sup 13/C NMR spectra were recorded on a Tesla BS-567A spectrometer at 25.1 MHz in deuterochloroform with the samples at concentrations of 30%. The internal standard was HMDS. The vinyl ethers of pyridine and quinoline exist preferentially in the nonplanar S-trans conformation. In the vinyl esters of pyridine and quinoline the p-..pi.. conjugation is concurrent in nature and depends on the position of the vinyloxy group in the heterocycle.

  19. Nucleon and triton production from nucleon-induced reactions on 7Li

    NASA Astrophysics Data System (ADS)

    Watanabe, Yukinobu; Guo, Hairui; Nagaoka, Kohei; Matsumoto, Takuma; Ogata, Kazuyuki; Yahiro, Masanobu

    2016-06-01

    Nucleon (N) and triton production from nucleon-induced reactions on 7Li at an incident energy of 14 MeV are analyzed by using three-body continuum discretized coupled channels method (CDCC), final state interaction (FSI) model, and sequential decay (SD) model. The CDCC is used to describe nucleon and triton production via breakup continuum channels, 7Li(N,N')7Li*→ t + α. Triton production from p(n) + 7Li → t + 5Li(5He) channel and nucleon production from sequential decay of the ground-state 5Li(5He) are calculated by the FSI model and the SD model, respectively. The calculated double differential cross sections for both nucleon and triton production are in good agreement with experimental ones except at relatively low nucleon emission energies.

  20. Simulation of the neutron spectrum from the 7Li(p,n) reaction with a liquid-lithium target at Soreq Applied Research Accelerator Facility

    NASA Astrophysics Data System (ADS)

    Friedman, M.; Cohen, D.; Paul, M.; Berkovits, D.; Eisen, Y.; Feinberg, G.; Giorginis, G.; Halfon, S.; Krása, A.; Plompen, A. J. M.; Shor, A.

    2013-01-01

    The 7Li(p,n)7Be reaction has been used for the last 25 years to produce quasi-Maxwellian neutrons in order to measure Maxwellian-Averaged Cross-Sections in the relevant temperatures for stellar nucleosynthesis. A liquid-lithium target at the Soreq Applied Research Accelerator Facility is expected to allow us to perform such measurements at higher neutron intensities. Here we describe a Monte Carlo tool, SimLiT, developed to evaluate neutron spectra, intensities and angular distributions resulting from this reaction. We also demonstrate the feasibility to couple SimLiT with an advanced transport code, resulting in a powerful tool for planning and analysis of experiments using the 7Li(p,n) reaction as a neutron source.

  1. Stopping powers of MeV-energy ions 7LI, 12C, 16O and 28Si in some common target materials

    NASA Astrophysics Data System (ADS)

    Lin, E. K.; Sun, H. L.; Yu, Y. C.; Wang, C. W.; Liu, T. Y.; Chiou, J. W.; Lee, C. S.

    1997-02-01

    Stopping powers for 0.4-8.5 MeV 7Li-ions, 0.4-10 MeV 12C-ions, 0.3-14 MeV 16O-ions and 0.5-11.5 MeV 28Si ions in four commonly used materials (Al, Cu, Ag and Au) have been determined by using the backscattering method. Elastic backscattering spectra were measured at a laboratory detection angle 170° using a passivated implanted planar Si (PIPS) detector. Energy dependence of stopping powers were obtained and compared to the semiempirical model (TRIM-91 and SRIM-96) predictions. The SRIM-96 calculations generally reproduce the experimental data more closely and lead to a significant improvement of the agreement of the 7Li data when compared to TRIM-91.

  2. Combined experimental (FT-IR, UV-visible spectra, NMR) and theoretical studies on the molecular structure, vibrational spectra, HOMO, LUMO, MESP surfaces, reactivity descriptor and molecular docking of Phomarin

    NASA Astrophysics Data System (ADS)

    Kumar, Abhishek; Srivastava, Ambrish Kumar; Gangwar, Shashi; Misra, Neeraj; Mondal, Avijit; Brahmachari, Goutam

    2015-09-01

    Phomarin is an important natural product belonging to anthraquinone series of compounds. The equilibrium geometry of phomarin has been determined and analyzed at DFT method employing B3LYP/6-311++G(d,p) level of computation. The reactivity of molecule using various descriptors such as Fukui functions, local softness, electrophilicity, electronegativity, Hardness, HOMO-LUMO gap are calculated and discussed. The infrared and UV-vis spectra of phomarin are calculated and compared with the experimentally observed ones. Moreover, 1H and 13C NMR spectra have been calculated by using the gauge independent atomic orbital method. We also notice that phomarin shows remarkable biological activities against malaria parasite. The study suggests further investigation on phomarin for their pharmacological importance.

  3. Dynamic effects in MAS and MQMAS NMR spectra of half-integer quadrupolar nuclei: calculations and an application to the double perovskite cryolite.

    PubMed

    Kotecha, Mrignayani; Chaudhuri, Santanu; Grey, Clare P; Frydman, Lucio

    2005-11-30

    Dynamic processes such as chemical exchange or rotations between inequivalent orientations can affect the magic-angle spinning (MAS) and the multiple-quantum (MQ) MAS NMR spectra of half-integer quadrupolar nuclei. The present paper discusses such dynamic multisite MAS and MQMAS effects and applies them to study the dynamic processes that occur in the double perovskite cryolite, Na3AlF6. Dynamic line shape simulations invoking a second-order broadening of the central transition and relying on the semiclassical Bloch-McConnell formalism for chemical exchange were performed for a variety of exchange models possessing different symmetries. Fitting experimental variable-temperature cryolite 23Na NMR data with this formalism revealed that the two inequivalent sodium sites in this mineral undergo an exchange characterized by a broad distribution of rates. To further assess this dynamic process a variety of 27Al and 19F MAS NMR studies were also undertaken; quantitative 27Al-19F dipolar coupling measurements then revealed a dynamic motion of the AlF6 octahedra that were qualitatively consistent with predictions stemming from molecular dynamic simulations on this double perovskite. PMID:16305261

  4. Local structure and lithium mobility in intercalated Li3Al(x)Ti(2-x)(PO4)3 NASICON type materials: a combined neutron diffraction and NMR study.

    PubMed

    Arbi, K; Hoelzel, M; Kuhn, A; García-Alvarado, F; Sanz, J

    2014-09-14

    The structural features of intercalated Li3AlxTi2-x(PO4)3 compounds, with x = 0 and 0.2, have been deduced by Rietveld analysis of neutron diffraction (ND) patterns recorded between 100 and 500 K. The Li insertion decreases the symmetry from R3̄c to R3̄ in analyzed compounds. In pristine Li1+xAlxTi2-x(PO4)3 samples, Li occupies mainly six-fold M1 sites at ternary axes; but in lithiated Li3AlxTi2-x(PO4)3 samples, Li is located near M2 positions at M3/M3' four-fold coordinated sites. In both cases, Li arrangement minimizes electrostatic Li-Li repulsions. The insertion of lithium resulted in the reduction of Ti(4+) to Ti(3+) that shifts (7)Li, (27)Al and (31)P MAS-NMR resonances towards more positive chemical shifts, improving the resolution of different sites. The detection of twelve components in (7)Li MAS-NMR spectra recorded at room temperature suggests the location of Li(+) ions at three-oxygen faces that define M2 cavities. From (7)Li MAS-NMR spectra, the occupancy of sites and mobility of lithium were investigated in the temperature range 100-500 K. The correlation between structural information, deduced by neutron diffraction, and lithium mobility, deduced by NMR spectroscopy, provides new insights into structural factors that affect lithium mobility in materials with NASICON structure. PMID:25070935

  5. Conformational and isomerizational studies of 3- N, N-dimethylhydrazino-2-acetyl propenenitrile using X-ray analysis, NMR and vibrational spectra, and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gróf, M.; Gatial, A.; Milata, V.; Prónayová, N.; Kožíšek, J.; Breza, M.; Matějka, P.

    2009-12-01

    The IR, Raman and NMR spectra of 3- N, N-dimethylhydrazino-2-acetyl propenenitrile (DMHAP) [(H 3C) 2N sbnd NH sbnd CH dbnd C(CN)(COCH 3)] were measured. X-ray analysis revealed that DMHAP exists in solid state as ZZa conformer. Vibrational and NMR spectra confirmed the existence of only one ZZa conformer with an intramolecular hydrogen bond in less polar solvents and next two EZa and EZs conformers of E-isomer with Z-orientation of acetyl group and anti and syn orientation of dimethylhydrazino group in more polar environments. The observed IR and Raman bands were compared with harmonic vibrational frequencies, calculated using ab initio MP2 and DFT/B3LYP methods in 6-31G∗∗ basis set, and assigned on the basis of potential energy distribution. In addition, the geometries and relative energies of the possible isomers and conformers of DMHAP were also evaluated on the same levels and compared with the X-ray data. The influence of environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model.

  6. IR and NMR spectra, intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution

    NASA Astrophysics Data System (ADS)

    Zvereva, Elena E.; Katsyuba, Sergey A.; Vandyukov, Alexander E.; Chernova, Alla V.; Kovalenko, Valery I.; Solovieva, Svetlana E.; Antipin, Igor S.; Konovalov, Alexander I.

    2010-02-01

    It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10-20 cm -1) red shift of the IR bands of the NH 2 stretching vibrations, which suggests rather weak NH⋯N hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.

  7. IR and NMR spectra, intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution.

    PubMed

    Zvereva, Elena E; Katsyuba, Sergey A; Vandyukov, Alexander E; Chernova, Alla V; Kovalenko, Valery I; Solovieva, Svetlana E; Antipin, Igor S; Konovalov, Alexander I

    2010-02-01

    It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10-20 cm(-1)) red shift of the IR bands of the NH(2) stretching vibrations, which suggests rather weak NHcdots, three dots, centeredN hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes. PMID:20042365

  8. Off-resonance effects on 2D NMR nutation spectra of I = 3/2 quadrupolar nuclei in static samples.

    PubMed

    Xia, Y; Deng, F; Ye, C

    1995-12-01

    The off-resonance effects on 2D NMR nutation of I = 3/2 quadrupolar nuclei are demonstrated with perturbation theory and numerical calculation in static samples. The off-resonant (delta omega) rf field (omega 1) enlarges a nutation frequency and consequently increases the measurement range of nuclear quadrupolar interaction parameters. When omega e > omega Qmax, and arctg(omega 1/delta omega) = +/- 54.7 degrees (magic angle), the satellite lines (produced by coherence transfers) in a nutation spectrum are superimposed with the line of central transition, and hence the nutation spectrum is simplified and its sensitivity is enhanced. The nuclear quadrupolar interaction parameters of 23Na nuclei in Na omega molecular sieve are obtained using 2D NMR nutation. PMID:9053113

  9. Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra

    SciTech Connect

    Bernal, Andrés; Patiny, Luc; Castillo, Andrés M.; González, Fabio; Wist, Julien

    2015-02-21

    Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruning of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems.

  10. Processes controlling δ7Li in rivers illuminated by study of streams and groundwaters draining basalts

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Ming; Wanner, Christoph; Rudnick, Roberta L.; McDonough, William F.

    2015-01-01

    We evaluate the factors influencing the abundance, [Li], and isotopic composition of riverine Li delivered to the oceans through analyses and modeling of [Li] and δ7Li in streams and groundwaters draining a single continental lithology, the Columbia River Basalts (CRBs). The streams were sampled in different climate zones that lie east (dry), and west (wet) of the Cascades Mountains, and during two different seasons (summer and late winter) in order to evaluate climatic and seasonal influences on Li isotopes in rivers. Dissolved Li (δLi7dis = + 9.3 to +30.4) is systematically heavier than that of fresh or weathered CRBs (-4.7 to +6.0, Liu et al., 2013), suspended loads (-5.9 to -0.3), and shallow groundwaters (+6.7 to +9.4), consistent with previous studies showing that Li isotope fractionation is affected by equilibration between stream water and secondary minerals. However, the lack of correlation between δ7Lidis and climate zone, the uniform secondary minerals and bedrock, coupled with the highly variable (> 20 ‰) δLi7dis indicate that other factors exert a strong control on δ7Lidis. In particular, the heavier Li in streams compared to the shallow groundwaters that feed them indicates that continued isotopic fractionation between stream water and suspended and/or bed loads has a major influence on riverine δ7Li. Seasonal δ7Li variation is observed only for streams west of the Cascades, where the difference in precipitation rate between the dry and wet seasons is greatest. Reactive transport model simulations reveal that riverine δ7Li is strongly controlled by subsurface residence times and the Li isotope fractionation occurring within rivers. The latter explains why there is no positive correlation between δ7Li and traditional weathering proxies such as Si or normalized Si in rivers, as riverine Li isotope fractionation drives δ7Li to higher values during transport, whereas the concentrations of major cations and anions are diluted. The varying

  11. New high S/N observations of the (6Li) /(7) Li blend in HD 84937 and two other metal-poor stars

    NASA Astrophysics Data System (ADS)

    Cayrel, R.; Spite, M.; Spite, F.; Vangioni-Flam, E.; Cassé, M.; Audouze, J.

    1999-03-01

    High signal to noise ratio spectra have been obtained with the GECKO spectrograph at CFHT, at a spectral resolution of 100 000, for three metal-poor stars in order to obtain more accurate abundances of the very fragile element (6) Li. For two newly observed stars, BD +42 2667 and BD +36 2165 it appears that the first may have a detectable amount of (6) Li, whereas no (6) Li is found in the second one. The S/N ratio of only a few hundreds obtained for these two faint stars preclude however a firm conclusion. For the third star, the well known object HD84937, a very high S/N of 650 per pixel (over 1000 per resolved spectral element) was obtained, yielding greatly improved accuracy over previous determinations. A value of (6) Li / (7) Li = 0.052 +/- 0.019 (one sigma) is obtained. We also conclude that the no- (6) Li assumption is ruled out at the 95 per cent level, even in the most permissive case, when a variation of all the other free parameters (wavelength zero-point, continuum location, macroturbulent broadening, abundance of (7) Li) is allowed. The possibility that the (6) Li feature is an artifact due to a once suspected binarity of HD 84937 is discussed, with the conclusion that this assumption is ruled out by the extant data on the radial velocity of the object. The (6) Li abundance is compared with recent models of formation of the light elements Li, Be and B. This comparison shows that (6) Li is either undepleted, or only moderately depleted in HD 84937, from its initial value. Under the assumption that the atmospheric depletion of (6) Li and (7) Li in stars is by slow mixing with hot layers (underneath the convective zone), in which these elements can burn, we conclude that the depletion of (7) Li by this mechanism in HD 84937 is less than 0.1 dex. This new upper limit to the efficiency of the depletion of (7) Li by slow mixing burning, in a star located on the Spite plateau, leads to a more secure estimation of the primordial abundance of (7) Li. However

  12. Elastic recoil detection analysis of hydrogen with 7Li ions using a polyimide foil as a thick hydrogen reference

    NASA Astrophysics Data System (ADS)

    Pelicon, Primož; Razpet, Alenka; Markelj, Sabina; Čadež, Iztok; Budnar, Miloš

    2005-01-01

    Elastic recoil detection analysis (ERDA) with an absorber foil using a 4.2 MeV 7Li2+ beam was utilized for evaluation of hydrogen depth profiles. Since recoil cross-sections when using Li ions as projectiles are not well known, the energy dependent ratio between the experimental yield and the yield calculated using the Rutherford recoil cross-section was obtained from an ERDA spectrum of a thick polyimide (Kapton) sample. It was estimated that this ratio does not significantly depend on sample composition. Therefore it was used for correction of measured spectra analyzed by existing simulation and evaluation programs in which the Rutherford recoil cross-sections were applied. The correction procedure has been verified in round-robin measurements of well-characterized Si:H thin layers. Application of the method for determination of a hydrogen depth concentration profile in hydrogen-containing graphite samples is presented.

  13. NMR study of new ruthenates with high magnetic ordering

    NASA Astrophysics Data System (ADS)

    Paulose, P. L.; Chakrabarty, Tanmoy

    The Ru based compounds, Ca3LiRuO6 and Ca3NaRuO6 show unusually high magnetic ordering temperature. Extended super exchange model is invoked to explain the magnetic behavior in the isostructural compound Ca3LiOsO6. We have carried out NMR investigation on these two Ru-based compounds. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature (TC) of 115 K which is explored by the temperature dependence of 7Li NMR line shift, line-width and spin-lattice relaxation rate (1/T1) . Above TC, a broad maximum is observed in the evolution of line-width of the spectra. We speculate that this feature might be attributed to some low-dimensional magnetic behavior. Contrastingly, Ca3NaRuO6 with similar structure and local geometry of the Ru5+ ions is a conventional antiferromagnet with a transition temperature of 90 K. The temperature dependence of 23Na NMR line shift and 1/T1 is studied across magnetic transition in Ca3NaRuO6. The temperature variation of line-width is found to be different compared to Ca3LiRuO6. In both these systems, 1/T1 decreases significantly below ordering temperature, characteristic of many antiferromagnetic systems.

  14. Elastic scattering and fusion cross sections for {sup 7}Be,{sup 7}Li+{sup 27}Al systems

    SciTech Connect

    Kalita, K.; Verma, S.; Singh, R.; Das, J.J.; Jhingan, A.; Madhavan, N.; Nath, S.; Varughese, T.; Sugathan, P.; Parkar, V.V.; Mahata, K.; Ramachandran, K.; Shrivastava, A.; Chatterjee, A.; Kailas, S.; Barua, S.; Basu, P.; Majumdar, H.; Sinha, M.; Bhattacharya, R.

    2006-02-15

    Quasi-elastic-scattering and transfer reaction cross-section measurements were made for the {sup 7}Be+{sup 27}Al system at E{sub lab}=17, 19, and 21 MeV in the angular range {theta}{sub c.m.}=12 deg. An optical model (OM) analysis of the quasi-elastic scattering data was carried out. The fusion cross sections were derived at these energies by subtraction of the integrated transfer cross sections from the reaction cross sections obtained from the fits to quasi-elastic-scattering data. These fusion cross sections were found to be consistent with those obtained from the coupled-channels calculations. Elastic scattering and fusion cross sections were measured for the {sup 7}Li+{sup 27}Al system at E{sub lab}=10, 13, 16, 19, and 24 MeV. For elastic scattering the angular coverages were in the {theta}{sub lab}=12 deg. - 72 deg. range and for fusion the {alpha}-evaporation spectra from the compound nucleus were measured in the angular range {theta}{sub lab}=52 deg. - 132 deg. (142 deg. at 10 MeV). The elastic-scattering angular distributions were subjected to OM analysis. The {alpha}-evaporation spectra were reproduced with the statistical model calculations, and the fusion cross sections were extracted from them. The fusion cross sections were also extracted by subtraction of the integrated inelastic-scattering cross sections from the reaction cross sections obtained from the OM fits to the elastic-scattering data, and these fusion data were found to be consistent. The CCDEF calculations describe these data quite well. A comparison of the fusion data for the {sup 7}Be+{sup 27}Al and {sup 7}Li+{sup 27}Al systems shows a similar and consistent behavior.

  15. 1H NMR spectra of alcohols and diols in chloroform: DFT/GIAO calculation of chemical shifts.

    PubMed

    Lomas, John S

    2014-12-01

    Proton nuclear magnetic resonance (NMR) shifts of aliphatic alcohols in chloroform have been computed on the basis of density functional theory, the solvent being included by the integral-equation-formalism polarisable continuum model of Gaussian 09. Relative energies of all conformers are calculated at the Perdew, Burke and Ernzerhof (PBE)0/6-311+G(d,p) level, and NMR shifts by the gauge-including atomic orbital method with the PBE0/6-311+G(d,p) geometry and the cc-pVTZ basis set. The 208 computed CH proton NMR shifts for 34 alcohols correlate very well with the experimental values, with a gradient of 1.00 ± 0.01 and intercept close to zero; the overall root mean square difference (RMSD) is 0.08 ppm. Shifts for CH protons of diols in chloroform are well correlated with the theoretical values for (isotropic) benzene, with similar gradient and intercept (1.02 ± 0.01, -0.13 ppm), but the overall RMSD is slightly higher, 0.12 ppm. This approach generally gives slightly better results than the CHARGE model of Abraham et al. The shifts of unsaturated alcohols in benzene have been re-examined with Gaussian 09, but the overall fit for CH protons is not improved, and OH proton shifts are worse. Shifts of vinyl protons in alkenols are systematically overestimated, and the correlation of computed shifts against the experimental data for unsaturated alcohols follows a quadratic equation. Splitting the 20 compounds studied into two sets, and applying empirical scaling based on the quadratic for the first set to the second set, gives an RMSD of 0.10 ppm. A multi-standard approach gives a similar result. PMID:25199903

  16. Experimental and theoretical investigation of the molecular structure, conformational stability, hyperpolarizability, electrostatic potential, thermodynamic properties and NMR spectra of pharmaceutical important molecule: 4'-methylpropiophenone.

    PubMed

    Karunakaran, V; Balachandran, V

    2014-07-15

    Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra) of 4'-methylpropiophenone (MPP). The FT-IR and FT-Raman spectra of 4'-methylpropiophenone (MPP) have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the infrared and Raman spectra of MPP are also reported based on total energy distribution (TED). The observed and the calculated frequencies are found to be in good agreement. The (1)H and (13)C NMR chemical shifts have been calculated by Gauge-Independent Atomic Orbital (GIAO) method with B3LYP/6-311++G(d,p). The natural bond orbital (NBO), natural hybrid orbital (NHO) analysis and electronic properties, such as HOMO and LUMO energies, were performed by DFT approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) of the novel molecular system and related properties (βtot, α0 and Δα) of MPP are calculated using DFT/6-311++G(d,p) method on the finite-field approach. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The thermodynamic functions of the title compound were also performed at the above method and basis set. PMID:24657464

  17. Experimental and theoretical investigation of the molecular structure, conformational stability, hyperpolarizability, electrostatic potential, thermodynamic properties and NMR spectra of pharmaceutical important molecule: 4‧-Methylpropiophenone

    NASA Astrophysics Data System (ADS)

    Karunakaran, V.; Balachandran, V.

    2014-07-01

    Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra) of 4‧-methylpropiophenone (MPP). The FT-IR and FT-Raman spectra of 4‧-methylpropiophenone (MPP) have been recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the infrared and Raman spectra of MPP are also reported based on total energy distribution (TED). The observed and the calculated frequencies are found to be in good agreement. The 1H and 13C NMR chemical shifts have been calculated by Gauge-Independent Atomic Orbital (GIAO) method with B3LYP/6-311++G(d,p). The natural bond orbital (NBO), natural hybrid orbital (NHO) analysis and electronic properties, such as HOMO and LUMO energies, were performed by DFT approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) of the novel molecular system and related properties (βtot, α0 and Δα) of MPP are calculated using DFT/6-311++G(d,p) method on the finite-field approach. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The thermodynamic functions of the title compound were also performed at the above method and basis set.

  18. In situ7Li and 133Cs nuclear magnetic resonance investigations on the role of Cs+ additive in lithium-metal deposition process

    NASA Astrophysics Data System (ADS)

    Hu, Jian Zhi; Zhao, Zhenchao; Hu, Mary Y.; Feng, Ju; Deng, Xuchu; Chen, Xilin; Xu, Wu; Liu, Jun; Zhang, Ji-Guang

    2016-02-01

    Cesium ion (Cs+) has been reported to be an effective electrolyte additive to suppress Li dendrite growth which prevents the application of lithium (Li) metal as an anode for rechargeable Li batteries. In this work, we investigated the effect of Cs+ additive on Li depositions using quantitative in situ7Li and 133Cs nuclear magnetic resonance (NMR) with planar symmetric Li cells. It's found that the addition of Cs+ can significantly enhance both the formation of well aligned Li nanorods and reversibility of the Li electrode. In situ133Cs NMR directly confirms that Cs+ migrates to Li electrode to form a positively charged electrostatic shield during the charging process. Much more electrochemical "active" Li was found in Li films deposited with Cs+ additive, while more electrochemical "dead" and thicker Li rods were identified in Li films deposited without Cs+. Combining the in situ and the previous ex-situ results, a Li deposition model has been proposed to explain these observations.

  19. Quantification of the Contribution of Extracellular Sodium to 23Na Multiple-Quantum-Filtered NMR Spectra of Suspensions of Human Red Blood Cells

    NASA Astrophysics Data System (ADS)

    Knubovets, Tatyana; Shinar, Hadassah; Navon, Gil

    1998-03-01

    23Na double-quantum-filtered (DQF) NMR enables the detection of anisotropic motion of sodium ions due to their interaction with ordered structures in biological tissues. Using the technique, anisotropic motion was found for sodium ions in mammalian red blood cell suspensions (RBC) and the effect was shown to correlate with the integrity of membrane cytoskeleton. In the present study relative contributions to the DQF and triple-quantum-filtered (TQF) spectra of sodium bound to anisotropic and isotropic binding sites in the intra- and extracellular sodium pools (Na content being 15 and 150 mM, respectively) of human RBC were quantified for different hematocrits. DQF spectra were measured by a modified Jeener-Broekaert pulse sequence which enabled exclusive detection of anisotropically moving sodium ions. The relative contributions of the extracellular sodium to the TQF and DQF spectra decreased as the hematocrit increased, but their efficiency relative to the sodium content increased. The contribution of the extracellular sodium to the TQF signal was found to dominate the spectrum of the RBC suspension at all hematocrits studied. The contribution of the extracellular sodium to the DQF was significantly smaller than that to the TQF and was only 22% at a high hematocrit of about 90%.

  20. Tensor analyzing powers and energy dependence of the {sup 7}Li+{sup 16}O interaction

    SciTech Connect

    Rudchik, A. T.; Rudchik, A. A.; Chesnokova, V. D.; Kyryanchuk, V. M.; Ponkratenko, O. A.; Kemper, K. W.; Crisp, A. M.; Marechal, F.; Roeder, B. T.; Momotyuk, O. A.; Rusek, K.

    2007-02-15

    The differential cross section angular distribution and the analyzing powers {sup T}T{sub 10},{sup T}T{sub 20}, for {sup 7}Li+{sup 16}O elastic scattering were measured at E{sub lab}({sup 7}Li(vector sign)) = 42 MeV. These and previously published {sup 7}Li+{sup 16}O scattering data measured at E{sub c.m.} = 6.26-34.78 MeV were analyzed with the optical model and coupled-reaction channels (CRC) methods to determine the energy dependence of the parameters of the scattering potential. It was found that the optical model potentials are energy independent for {sup 7}Li laboratory bombarding energies above 28 MeV, except for a slight decrease in the real potential strength as the bombarding energy increases. The calculations presented show that the tensor analyzing power {sup T}T{sub 20} arises from a coherent combination of contributions from the ground-state reorientation and central scattering potential. The energy-dependent CRC potentials were shown to describe the data for the {sup 16}O({sup 7}Li,t){sup 20}Ne reaction.

  1. Molecular dynamics and information on possible sites of interaction of intramyocellular metabolites in vivo from resolved dipolar couplings in localized 1H NMR spectra

    NASA Astrophysics Data System (ADS)

    Schröder, Leif; Schmitz, Christian; Bachert, Peter

    2004-12-01

    Proton NMR resonances of the endogenous metabolites creatine and phosphocreatine ((P)Cr), taurine (Tau), and carnosine (Cs, β-alanyl- L-histidine) were studied with regard to residual dipolar couplings and molecular mobility. We present an analysis of the direct 1H- 1H interaction that provides information on motional reorientation of subgroups in these molecules in vivo. For this purpose, localized 1H NMR experiments were performed on m. gastrocnemius of healthy volunteers using a 1.5-T clinical whole-body MR scanner. We evaluated the observable dipolar coupling strength SD0 ( S = order parameter) of the (P)Cr-methyl triplet and the Tau-methylene doublet by means of the apparent line splitting. These were compared to the dipolar coupling strength of the (P)Cr-methylene doublet. In contrast to the aliphatic protons of (P)Cr and Tau, the aromatic H2 ( δ = 8 ppm) and H4 ( δ = 7 ppm) protons of the imidazole ring of Cs exhibit second-order spectra at 1.5 T. This effect is the consequence of incomplete transition from Zeeman to Paschen-Back regime and allows a determination of SD0 from H2 and H4 of Cs as an alternative to evaluating the multiplet splitting which can be measured directly in high-resolution 1H NMR spectra. Experimental data showed striking differences in the mobility of the metabolites when the dipolar coupling constant D0 (calculated with the internuclear distance known from molecular geometry in the case of complete absence of molecular dynamics and motion) is used for comparison. The aliphatic signals involve very small order parameters S ≈ (1.4 - 3) × 10 -4 indicating rapid reorientation of the corresponding subgroups in these metabolites. In contrast, analysis of the Cs resonances yielded S ≈ (113 - 137) × 10 -4. Thus, the immobilization of the Cs imidazole ring owing to an anisotropic cellular substructure in human m. gastrocnemius is much more effective than for (P)Cr and Tau subgroups. Furthermore, 1H NMR experiments on aqueous model

  2. Indole-containing new types of dyes and their UV-vis and NMR spectra and electronic structures: Experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Kuzu, Burak; Menges, Nurettin

    2016-06-01

    Indole containing dyes were synthesized via a simple method with high yield. These molecules have different colors and UV-vis spectra of them were recorded. Impact of solvents on absorbances was investigated and it was observed that basic solvent such as DMF and pyridine have blue shift. TD-DFT calculations were done and results were compared with experimental data. NMR data of molecules were analyzed and tautomeric forms of colorants and their ratio were determined. It was find out that two tautomers might be formed in solution, called indole and indolenine form. HOMO-LUMO and energy gaps were calculated and plotted. Furthermore, molecular electrostatic potentials were simulated to find out electrophilic and nucleophilic regions.

  3. Indole-containing new types of dyes and their UV-vis and NMR spectra and electronic structures: Experimental and theoretical study.

    PubMed

    Kuzu, Burak; Menges, Nurettin

    2016-06-01

    Indole containing dyes were synthesized via a simple method with high yield. These molecules have different colors and UV-vis spectra of them were recorded. Impact of solvents on absorbances was investigated and it was observed that basic solvent such as DMF and pyridine have blue shift. TD-DFT calculations were done and results were compared with experimental data. NMR data of molecules were analyzed and tautomeric forms of colorants and their ratio were determined. It was find out that two tautomers might be formed in solution, called indole and indolenine form. HOMO-LUMO and energy gaps were calculated and plotted. Furthermore, molecular electrostatic potentials were simulated to find out electrophilic and nucleophilic regions. PMID:26985875

  4. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples. PMID:23913630

  5. Facilitating quality control for spectra assignments of small organic molecules: nmrshiftdb2--a free in-house NMR database with integrated LIMS for academic service laboratories.

    PubMed

    Kuhn, Stefan; Schlörer, Nils E

    2015-08-01

    nmrshiftdb2 supports with its laboratory information management system the integration of an electronic lab administration and management into academic NMR facilities. Also, it offers the setup of a local database, while full access to nmrshiftdb2's World Wide Web database is granted. This freely available system allows on the one hand the submission of orders for measurement, transfers recorded data automatically or manually, and enables download of spectra via web interface, as well as the integrated access to prediction, search, and assignment tools of the NMR database for lab users. On the other hand, for the staff and lab administration, flow of all orders can be supervised; administrative tools also include user and hardware management, a statistic functionality for accounting purposes, and a 'QuickCheck' function for assignment control, to facilitate quality control of assignments submitted to the (local) database. Laboratory information management system and database are based on a web interface as front end and are therefore independent of the operating system in use. PMID:25998807

  6. Crystal structure and theoretical study of IR and 1H and 13C NMR spectra of cordatin, a natural product with antiulcerogenic activity

    NASA Astrophysics Data System (ADS)

    Brasil, Davi S. B.; Alves, Cláudio N.; Guilhon, Giselle M. S. P.; Muller, Adolfo H.; Secco, Ricardo De S.; Peris, Gabriel; Llusar, Rosa

    Cordatin is a furan diterpenoid with a clerodane skeleton isolated from Croton palanostigma Klotzsch (Euphorbiaceae). This natural product shows significant antiulcerogenic activity, similar to cimetidine (Tagamet®), a compound used for the treatment of peptic ulcers. The crystal structure of cordatin was obtained by X-ray diffraction and its geometrical parameters were compared with theoretical calculations at the B3LYP theory level. The IR and NMR (1H and 13C chemical shifts and coupling constants) spectra were obtained and compared with the theoretical calculations. The B3LYP theory level, with the 6-31G(d,p) and 6-311G(d,p) basis set, provided IR absorption values close to the experimental data. Moreover, theoretical NMR parameters obtained in both gas phase and chloroform solvent at the B3PW91/DGDZVP, B3LYP/6-311+G(2d,p), and B3PW91/6-311+G(2d,p) levels showed good correlations with the experimental results.

  7. Demystifying fluorine chemical shifts: electronic structure calculations address origins of seemingly anomalous (19)F-NMR spectra of fluorohistidine isomers and analogues.

    PubMed

    Kasireddy, Chandana; Bann, James G; Mitchell-Koch, Katie R

    2015-11-11

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of (19)F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in (19)F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F isomer results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of (19)F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra. PMID:26524669

  8. FT-IR, FT-Raman, NMR and UV-Vis spectra and DFT calculations of 5-bromo-2-ethoxyphenylboronic acid (monomer and dimer structures)

    NASA Astrophysics Data System (ADS)

    Sas, E. B.; Kose, E.; Kurt, M.; Karabacak, M.

    2015-02-01

    In this study, the Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of 5-bromo-2-ethoxyphenylboronic acid (5Br2EPBA) are recorded in the solid phase in the region 4000-400 cm-1 and 3500-10 cm-1, respectively. The 1H, 13C and DEPT nuclear magnetic resonance (NMR) spectra are recorded in DMSO solution. The UV-Vis absorption spectrum of 5Br2EPBA is saved in the range of 200-400 nm in ethanol and water. The following theoretical calculations for monomeric and dimeric structures are supported by experimental results. The molecular geometry and vibrational frequencies in the ground state are calculated by using DFT methods with 6-31G(d,p) and 6-311G(d,p) basis sets. There are four conformers for the present molecule. The computational results diagnose the most stable conformer of 5Br2EPBA as Trans-Cis (TC) form. The complete assignments are performed on the basis of the total energy distribution (TED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method in parallel quantum solutions (PQS) program. The 1H and 13C NMR chemical shifts of 5Br2EPBA molecule are calculated by using the Gauge Invariant Atomic Orbital (GIAO) method in DMSO and gas phase for monomer and dimer structures of the most stable conformer. Moreover, electronic properties, such as the HOMO and LUMO energies (by TD-DFT and CIS methods) and molecular electrostatic potential surface (MEPs) are investigated. Stability of the molecule arising from hyper-conjugative interactions, charge delocalization is analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) properties and thermodynamic features are presented. All calculated results are compared with the experimental data of the title molecule. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the title molecule.

  9. FT-IR, FT-Raman, NMR and UV-Vis spectra and DFT calculations of 5-bromo-2-ethoxyphenylboronic acid (monomer and dimer structures).

    PubMed

    Sas, E B; Kose, E; Kurt, M; Karabacak, M

    2015-02-25

    In this study, the Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of 5-bromo-2-ethoxyphenylboronic acid (5Br2EPBA) are recorded in the solid phase in the region 4000-400 cm(-1) and 3500-10 cm(-1), respectively. The (1)H, (13)C and DEPT nuclear magnetic resonance (NMR) spectra are recorded in DMSO solution. The UV-Vis absorption spectrum of 5Br2EPBA is saved in the range of 200-400 nm in ethanol and water. The following theoretical calculations for monomeric and dimeric structures are supported by experimental results. The molecular geometry and vibrational frequencies in the ground state are calculated by using DFT methods with 6-31G(d,p) and 6-311G(d,p) basis sets. There are four conformers for the present molecule. The computational results diagnose the most stable conformer of 5Br2EPBA as Trans-Cis (TC) form. The complete assignments are performed on the basis of the total energy distribution (TED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method in parallel quantum solutions (PQS) program. The (1)H and (13)C NMR chemical shifts of 5Br2EPBA molecule are calculated by using the Gauge Invariant Atomic Orbital (GIAO) method in DMSO and gas phase for monomer and dimer structures of the most stable conformer. Moreover, electronic properties, such as the HOMO and LUMO energies (by TD-DFT and CIS methods) and molecular electrostatic potential surface (MEPs) are investigated. Stability of the molecule arising from hyper-conjugative interactions, charge delocalization is analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) properties and thermodynamic features are presented. All calculated results are compared with the experimental data of the title molecule. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the title molecule. PMID:25305625

  10. Organic Matter Composition, Recycling Susceptibility and the Effectiveness of the Biological Pump - An Evaluation using NMR Spectra of Marine Plankton

    NASA Astrophysics Data System (ADS)

    Paytan, A.; Cade-Menun, B.

    2005-12-01

    The degree of organic matter biodegradation and recycling depends on the "reactivity" of compounds synthesized by the biota, which in turn is controlled by the structural characteristics of these compounds. Thus, abundance of a wide-range of organic compounds in seawater would lend itself to different susceptibility for biodegradation, which in turn is important for estimating the potential for rapid regeneration in the euphotic zone and thus the effectiveness of the biological pump. We employed 13C and 31P NMR spectroscopy on cultures of phytoplankton dominating blooms in the Southern Ocean grown under five light levels at 3oC. We found differences in both C and P compounds synthesized by the different taxa as well as for each species at various light levels. Results suggest variability in synthesized organic compounds by different taxa and by a single species grown in different environmental conditions. understanding of the oceanic C cycle in general and C sequestration effectiveness in particular.

  11. The dipole moment of 7LiH and 7LiD in the excited A 1Σ + state: A test of the born-oppenheimer approximation

    NASA Astrophysics Data System (ADS)

    Brieger, M.; Renn, A.; Sodeik, A.; Hese, A.

    1983-02-01

    Continuing our Stark quantum beat experiments on 7LiH at electric field strengths of 100 kV/cm and above, we were le to observe quantum beat signals for the vibrational level v' = 5 of the A 1v+ state. The evaluation of these signals yields a field reduced splitting Δ W/ E2 = 1.157(70) kHz/(kV/cm) 2 which would correspond to an "effective" value of 1μ eff( v' = 5)1 = 0.051 (5) D for the dipole moment, if the ordinarily used formula were applicable. A serious check of all available data, however, shows that neighbouring vibrational levels of the A 1v+ state and also the sum over the levels of the electronic ground state X 1Σ +, though counteracting, have the main effect on the residual splitting thus preventing a straightforward evaluation for the dipole moment. Taking account of these polarizability effects and including the possibility for a slight shift of the theoretical dipole moment function a value of 1μ( v' = 5)1 = 0.089(14) D is the most probable one. In the case of 7LiD according to the usual formula an "effective" value of 1μ eff( v' = 6)1 = 0.425(20) D was deduced from a beat signal obtained at an electric field strength of 24 kV/cm. Here the influence of neighbouring vibrational levels and electronic states is only of minor importance leading to a corrected value of 1μ( v' = 6)1 = 0.43(2) D for the dipole moment. This value differs by 13% from the theoretical one calculated on the basis of the dipole moment function of 7LiH and the adiabatically corrected potential energy curve of 7LiD, thus indicating non-adiabatic effects.

  12. Spectrally edited 2D 13Csbnd 13C NMR spectra without diagonal ridge for characterizing 13C-enriched low-temperature carbon materials

    NASA Astrophysics Data System (ADS)

    Johnson, Robert L.; Anderson, Jason M.; Shanks, Brent H.; Fang, Xiaowen; Hong, Mei; Schmidt-Rohr, Klaus

    2013-09-01

    Two robust combinations of spectral editing techniques with 2D 13Csbnd 13C NMR have been developed for characterizing the aromatic components of 13C-enriched low-temperature carbon materials. One method (exchange with protonated and nonprotonated spectral editing, EXPANSE) selects cross peaks of protonated and nearby nonprotonated carbons, while the other technique, dipolar-dephased double-quantum/single-quantum (DQ/SQ) NMR, selects signals of bonded nonprotonated carbons. Both spectra are free of a diagonal ridge, which has many advantages: Cross peaks on the diagonal or of small intensity can be detected, and residual spinning sidebands or truncation artifacts associated with the diagonal ridge are avoided. In the DQ/SQ experiment, dipolar dephasing of the double-quantum coherence removes protonated-carbon signals; this approach also eliminates the need for high-power proton decoupling. The initial magnetization is generated with minimal fluctuation by combining direct polarization, cross polarization, and equilibration by 13C spin diffusion. The dipolar dephased DQ/SQ spectrum shows signals from all linkages between aromatic rings, including a distinctive peak from polycondensed aromatics. In EXPANSE NMR, signals of protonated carbons are selected in the first spectral dimension by short cross polarization combined with dipolar dephasing difference. This removes ambiguities of peak assignment to overlapping signals of nonprotonated and protonated aromatic carbons, e.g. near 125 ppm. Spin diffusion is enhanced by dipolar-assisted rotational resonance. Before detection, Csbnd H dipolar dephasing by gated decoupling is applied, which selects signals of nonprotonated carbons. Thus, only cross peaks due to magnetization originating from protonated C and ending on nearby nonprotonated C are retained. Combined with the chemical shifts deduced from the cross-peak position, this double spectral editing defines the bonding environment of aromatic, COO, and Cdbnd O carbons

  13. Nuclear structure constrains on resonant energies: A solution of the cosmological 7Li problem?

    NASA Astrophysics Data System (ADS)

    Civitarese, O.; Mosquera, M. E.

    2013-01-01

    In this work, we study the cosmological 7Li problem from a nuclear structure point of view, by including resonances in the reactions which populate beryllium. The calculation of primordial abundances is performed by solving the balance equations semi-analytically. It is found that the primordial abundance of lithium is indeed reduced, as a consequence of the presence of resonant channels in the relevant cross sections. We set limits on the resonant energy for each reaction relevant for the chain leading to 7Li, by performing a statistical analysis of the available observational data.

  14. Effect of breakup coupling on fusion for 6,7Li+24Mg systems

    NASA Astrophysics Data System (ADS)

    Pradhan, M. K.; Mukherjee, A.; Dasmahapatra, B.

    2015-01-01

    To study the effect of breakup coupling on fusion we have derived fusion cross sections in the framework of continuum discretised coupled channels (CDCC) method using the coupled channels code FRESCO for the systems 6,7Li+24Mg. The CDCC predicted fusion cross sections for the 7Li+24Mg system agree well with the experimental fusion data whereas for the 6Li+24Mg system the agreement is reasonable at below barrier energies. However, within the limits of the present work no definite conclusion could be obtained from the quality of agreement at above barrier energies for the 6Li+24Mg system.

  15. NMR of 133Cs+ in stretched hydrogels: One-dimensional, z- and NOESY spectra, and probing the ion's environment in erythrocytes

    NASA Astrophysics Data System (ADS)

    Kuchel, Philip W.; Shishmarev, Dmitry; Puckeridge, Max; Levitt, Malcolm H.; Naumann, Christoph; Chapman, Bogdan E.

    2015-12-01

    133Cs nuclear magnetic resonance (NMR) spectroscopy was conducted on 133Cs+ in gelatin hydrogels that were either relaxed or stretched. Stretching generated a septet from this spin-7/2 nucleus, and its nuclear magnetic relaxation was studied via z-spectra, and two-dimensional nuclear Overhauser (NOESY) spectroscopy. Various spectral features were well simulated by using Mathematica and the software package SpinDynamica. Spectra of CsCl in suspensions of human erythrocytes embedded in gelatin gel showed separation of the resonances from the cation inside and outside the cells. Upon stretching the sample, the extracellular 133Cs+ signal split into a septet, while the intracellular peak was unchanged, revealing different alignment/ordering properties of the environment inside and around the cells. Differential interference contrast light microscopy confirmed that the cells were stretched when the overall sample was elongated. Analysis of the various spectral features of 133Cs+ reported here opens up applications of this K+ congener for studies of cation-handling by metabolically-active cells and tissues in aligned states.

  16. Studies on vibrational, NMR spectra and quantum chemical calculations of N-Succinopyridine: An organic nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Kannan, V.; Thirupugalmani, K.; Brahadeeswaran, S.

    2013-10-01

    Single crystals of N-Succinopyridine (NSP) have been grown from water using solution growth method by isothermal solvent evaporation technique. The solid state Fourier Transform Infrared (FTIR) spectrum of the grown crystal shows a broad absorption extending from 3450 down to 400 cm-1, due to H-bond vibrations and other characteristic vibrations. Fourier Transform Raman (FT-Raman) spectrum of NSP single crystal shows Raman intensities ranging from 3100 to 100 cm-1 due the characteristics vibrations of functional groups present in NSP. The proton and carbon positions of NSP have been described by 1H and 13C NMR spectrum respectively. Ab initio quantum chemical calculations on NSP have been performed by density functional theory (DFT) calculations using B3LYP method with 6-311++G(d,p) basis set. The predicted first hyperpolarizability is found to be 1.29 times greater than that of urea and suggests that the title compound could be an attractive material for nonlinear optical applications. The calculated HOMO-LUMO energies show that charge transfers occur within the molecule and other related molecular properties. Molecular properties such as Mulliken population analysis, thermodynamic functions and perturbation theory energy analysis have also been reported. Electrostatic potential map (ESP) of NSP obtained by electron density isosurface provided the information about the size, shape, charge density distribution and site of chemical reactivity of the title molecule. The molecular stability and bond strength have been investigated through the Natural Bond Orbital (NBO) analysis.

  17. Removal of t1 noise from metabolomic 2D 1H- 13C HSQC NMR spectra by Correlated Trace Denoising

    NASA Astrophysics Data System (ADS)

    Poulding, Simon; Charlton, Adrian J.; Donarski, James; Wilson, Julie C.

    2007-12-01

    The presence of t1 noise artefacts in 2D phase-cycled Heteronuclear Single Quantum Coherence (HSQC) spectra constrains the use of this experiment despite its superior sensitivity. This paper proposes a new processing algorithm, working in the frequency-domain, for reducing t1 noise. The algorithm has been developed for use in contexts, such as metabolomic studies, where existing denoising techniques cannot always be applied. Two test cases are presented that show the algorithm to be effective in improving the SNR of peaks embedded within t1 noise by a factor of more than 2, while retaining the intensity and shape of genuine peaks.

  18. In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.

    PubMed

    Blanc, Frédéric; Leskes, Michal; Grey, Clare P

    2013-09-17

    Electrochemical cells, in the form of batteries (or supercapacitors) and fuel cells, are efficient devices for energy storage and conversion. These devices show considerable promise for use in portable and static devices to power electronics and various modes of transport and to produce and store electricity both locally and on the grid. For example, high power and energy density lithium-ion batteries are being developed for use in hybrid electric vehicles where they improve the efficiency of fuel use and help to reduce greenhouse gas emissions. To gain insight into the chemical reactions involving the multiple components (electrodes, electrolytes, interfaces) in the electrochemical cells and to determine how cells operate and how they fail, researchers ideally should employ techniques that allow real-time characterization of the behavior of the cells under operating conditions. This Account reviews the recent use of in situ solid-state NMR spectroscopy, a technique that probes local structure and dynamics, to study these devices. In situ NMR studies of lithium-ion batteries are performed on the entire battery, by using a coin cell design, a flat sealed plastic bag, or a cylindrical cell. The battery is placed inside the NMR coil, leads are connected to a potentiostat, and the NMR spectra are recorded as a function of state of charge. (7)Li is used for many of these experiments because of its high sensitivity, straightforward spectral interpretation, and relevance to these devices. For example, (7)Li spectroscopy was used to detect intermediates formed during electrochemical cycling such as LixC and LiySiz species in batteries with carbon and silicon anodes, respectively. It was also used to observe and quantify the formation and growth of metallic lithium microstructures, which can cause short circuits and battery failure. This approach can be utilized to identify conditions that promote dendrite formation and whether different electrolytes and additives can help

  19. Rapid acquisition of multidimensional solid-state NMR spectra of proteins facilitated by covalently bound paramagnetic tags.

    PubMed

    Nadaud, Philippe S; Helmus, Jonathan J; Sengupta, Ishita; Jaroniec, Christopher P

    2010-07-21

    We describe a condensed data collection approach that facilitates rapid acquisition of multidimensional magic-angle spinning solid-state nuclear magnetic resonance (SSNMR) spectra of proteins by combining rapid sample spinning, optimized low-power radio frequency pulse schemes and covalently attached paramagnetic tags to enhance protein (1)H spin-lattice relaxation. Using EDTA-Cu(2+)-modified K28C and N8C mutants of the B1 immunoglobulin binding domain of protein G as models, we demonstrate that high resolution and sensitivity 2D and 3D SSNMR chemical shift correlation spectra can be recorded in as little as several minutes and several hours, respectively, for samples containing approximately 0.1-0.2 micromol of (13)C,(15)N- or (2)H,(13)C,(15)N-labeled protein. This mode of data acquisition is naturally suited toward the structural SSNMR studies of paramagnetic proteins, for which the typical (1)H longitudinal relaxation time constants are inherently a factor of at least approximately 3-4 lower relative to their diamagnetic counterparts. To illustrate this, we demonstrate the rapid site-specific determination of backbone amide (15)N longitudinal paramagnetic relaxation enhancements using a pseudo-3D SSNMR experiment based on (15)N-(13)C correlation spectroscopy, and we show that such measurements yield valuable long-range (15)N-Cu(2+) distance restraints which report on the three-dimensional protein fold. PMID:20583834

  20. FTIR, FT-RAMAN, NMR, spectra, normal co-ordinate analysis, NBO, NLO and DFT calculation of N,N-diethyl-4-methylpiperazine-1-carboxamide molecule

    NASA Astrophysics Data System (ADS)

    Muthu, S.; Elamurugu Porchelvi, E.

    2013-11-01

    The Fourier Transform Infrared (FT-IR) and FT-Raman of N,N-diethyl-4-methylpiperazine-1-carboxamide (NND4MC) have been recorded and analyzed. The structure of the compound was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) and 6-311G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electronic dipole moment (μD) and the first hyperpolarizability (βtot) values of the investigated molecule were computed using Density Functional Theory (DFT/B3LYP) with 6-31G(d,p) and 6-311G(d,p) basis sets. The calculated results also show that the NND4MC molecule may have microscopy nonlinear optical (NLO) behavior with non zero values. Mulliken atomic charges of NND4MC were calculated. The 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. The UV-Vis spectrum of the compound was recorded. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. A study on the electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) were also performed.

  1. FTIR, FT-RAMAN, NMR, spectra, normal co-ordinate analysis, NBO, NLO and DFT calculation of N,N-diethyl-4-methylpiperazine-1-carboxamide molecule.

    PubMed

    Muthu, S; Elamurugu Porchelvi, E

    2013-11-01

    The Fourier Transform Infrared (FT-IR) and FT-Raman of N,N-diethyl-4-methylpiperazine-1-carboxamide (NND4MC) have been recorded and analyzed. The structure of the compound was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) and 6-311G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ(*) and π(*) antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electronic dipole moment (μD) and the first hyperpolarizability (βtot) values of the investigated molecule were computed using Density Functional Theory (DFT/B3LYP) with 6-31G(d,p) and 6-311G(d,p) basis sets. The calculated results also show that the NND4MC molecule may have microscopy nonlinear optical (NLO) behavior with non zero values. Mulliken atomic charges of NND4MC were calculated. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. The UV-Vis spectrum of the compound was recorded. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. A study on the electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) were also performed. PMID:23845985

  2. Probing the influential factors of NMR T1-T2 spectra in the characterization of the kerogen by numerical simulation.

    PubMed

    Ge, Xinmin; Fan, Yiren; Chen, Hua; Deng, Shaogui; Cao, Yingchang; Zahid, Muhammad Aleem

    2015-11-01

    The low field nuclear magnetic resonance (NMR) spectroscopy has been widely used to characterize the longitudinal and transversal relaxation (T1-T2) spectrum of unconventional resources such as shale gas and tight oil containing significant proportions of kerogen and bitumen. However, it requires exquisite design of the acquisition model and the inversion algorithm due to the fast relaxation nature of the kerogen and bitumen. A new direct two dimensional (2D) inversion algorithm combined the iterative truncated singular value decomposition (TSVD) and the Akaiake Information Criterion (AIC) is presented to perform the data inversion efficiently. The fluid component decomposition (FCD) is applied to construct the forward T1-T2 model of the kerogen, and numerical simulations are conducted to investigate factors which may influence inversion results including echo spacing, recovery time series, signal to noise ratio (SNR), and the maximal iteration time. Results show that the T2 component is heavily impaired by the echo spacing, whereas the T1 component is influenced by the recovery time series but with limited effects. The inversion precision is greatly affected by the quality of the data. The inversed spectrum deviates from the model seriously when the SNR of the artificial noise is lower than 50, and the T2 component is more sensitive to the noise than the T1 component. What's more, the maximal iteration time can also affect the inversion result, especially when the maximal iteration time is smaller than 500. Proper acquisition and inversion parameters for the characterization of the kerogen are obtained considering the precision and the computational cost. PMID:26397220

  3. Probing the influential factors of NMR T1-T2 spectra in the characterization of the kerogen by numerical simulation

    NASA Astrophysics Data System (ADS)

    Ge, Xinmin; Fan, Yiren; Chen, Hua; Deng, Shaogui; Cao, Yingchang; Zahid, Muhammad Aleem

    2015-11-01

    The low field nuclear magnetic resonance (NMR) spectroscopy has been widely used to characterize the longitudinal and transversal relaxation (T1-T2) spectrum of unconventional resources such as shale gas and tight oil containing significant proportions of kerogen and bitumen. However, it requires exquisite design of the acquisition model and the inversion algorithm due to the fast relaxation nature of the kerogen and bitumen. A new direct two dimensional (2D) inversion algorithm combined the iterative truncated singular value decomposition (TSVD) and the Akaiake Information Criterion (AIC) is presented to perform the data inversion efficiently. The fluid component decomposition (FCD) is applied to construct the forward T1-T2 model of the kerogen, and numerical simulations are conducted to investigate factors which may influence inversion results including echo spacing, recovery time series, signal to noise ratio (SNR), and the maximal iteration time. Results show that the T2 component is heavily impaired by the echo spacing, whereas the T1 component is influenced by the recovery time series but with limited effects. The inversion precision is greatly affected by the quality of the data. The inversed spectrum deviates from the model seriously when the SNR of the artificial noise is lower than 50, and the T2 component is more sensitive to the noise than the T1 component. What's more, the maximal iteration time can also affect the inversion result, especially when the maximal iteration time is smaller than 500. Proper acquisition and inversion parameters for the characterization of the kerogen are obtained considering the precision and the computational cost.

  4. Barrier distributions for the {sup 7}Li+{sup 27}Al reaction

    SciTech Connect

    Cardenas, W. H. Z.

    2010-08-04

    Barrier distributions can be obtained from the first derivative of the elastic and quasielastic (QEL) backward angle excitation functions [1]. In this work we present a study of the barrier distribution for the {sup 7}Li+{sup 27}Al reaction from a Coupled-Channels Born Approximation (CCBA) calculations using the code FRESCO [2].

  5. Assignment of the sup 1 H and sup 15 N NMR spectra of Rhodobacter capsulatus ferrocytochrome c sub 2

    SciTech Connect

    Gooley, P.R.; Caffrey, M.S.; Cusanovich, M.A.; MacKenzie, N.E. )

    1990-03-06

    The peptide resonances of the {sup 1}H and {sup 15}N nuclear magnetic resonance spectra of ferrocytochrome c{sub 2} from Rhodobacter capsulatus are sequentially assigned by a combination of 2D {sup 1}H-{sup 1}H and {sup 1}H-{sup 15}N spectroscopy, the latter performed on {sup 15}N-enriched protein. Short-range nuclear Overhauser effect (NOE) data show {alpha}-helices from residues 3-17, 55-65, 69-88, and 103-115. Within the latter two {alpha}-helices, there are three single 3{sub 10} turns, 70-72, 76-78, and 107-109. In addition {alpha}H-NH{sub i+1} and {alpha}H-NH{sub i+2} NOEs indicate that the N-terminal helix (3-17) is distorted. Compared to horse or tuna cytochrome c and cytochrome c{sub 2} of Rhodospirillium rubrum, there is a 6-residue insertion at residues 23-29 in R. capsulatus cytochrome c{sub 2}. The NOE data show that this insertion forms a loop, probably an {Omega} loop. {sup 1}H-{sup 15}N heteronuclear multiple quantum correlation experiments are used to follow NH exchange over a period of 40 h. As the 2D spectra are acquired in short time periods (30 min), rates for intermediate exchanging protons can be measured. Comparison of the NH exchange data for the N-terminal helix of cytochrome c{sub 2} of R. capsulatus with the highly homologous horse heart cytochrome c shows that this helix is less stable in cytochrome c{sub 2}.

  6. Structural characterization, solvent effects on nuclear magnetic shielding tensors, experimental and theoretical DFT studies on the vibrational and NMR spectra of 3-(acrylamido)phenylboronic acid

    NASA Astrophysics Data System (ADS)

    Alver, Özgür; Kaya, Mehmet Fatih; Dikmen, Gökhan

    2015-12-01

    Structural elucidation of 3-(acrylamido)phenylboronic acid (C9H10BNO3) was carried out with 1H, 13C and HETCOR NMR techniques. Solvent effects on nuclear magnetic shielding tensors were examined with deuterated dimethyl sulfoxide, acetone, methanol and water solvents. The correct order of appearance of carbon and hydrogen atoms on NMR scale from highest magnetic field region to the lowest one were investigated using different types of theoretical levels and the details of the levels were presented in this study. Stable structural conformers and vibrational band analysis of the title molecule (C9H10BNO3) were studied both experimental and theoretical viewpoints using FT-IR, Raman spectroscopic methods and density functional theory (DFT). FT-IR and Raman spectra were obtained in the region of 4000-400 cm-1, and 3700-10 cm-1, respectively. Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-31++G(d, p) basis set was included in the search for optimized structures and vibrational wavenumbers. Experimental and theoretical results show that after application of a suitable scaling factor density functional B3LYP method resulted in acceptable results for predicting vibrational wavenumbers except OH and NH stretching modes which is most likely arising from increasing unharmonicity in the high wave number region and possible intra and inter molecular interaction at OH edges those of which are not fully taken into consideration in theoretical processes. To make a more quantitative vibrational assignments, potential energy distribution (PED) values were calculated using VEDA 4 (Vibrational Energy Distribution Analysis) program.

  7. Bayesian reconstruction of projection reconstruction NMR (PR-NMR).

    PubMed

    Yoon, Ji Won

    2014-11-01

    Projection reconstruction nuclear magnetic resonance (PR-NMR) is a technique for generating multidimensional NMR spectra. A small number of projections from lower-dimensional NMR spectra are used to reconstruct the multidimensional NMR spectra. In our previous work, it was shown that multidimensional NMR spectra are efficiently reconstructed using peak-by-peak based reversible jump Markov chain Monte Carlo (RJMCMC) algorithm. We propose an extended and generalized RJMCMC algorithm replacing a simple linear model with a linear mixed model to reconstruct close NMR spectra into true spectra. This statistical method generates samples in a Bayesian scheme. Our proposed algorithm is tested on a set of six projections derived from the three-dimensional 700 MHz HNCO spectrum of a protein HasA. PMID:25218584

  8. Line shift, line asymmetry, and the ^6Li/^7Li isotopic ratio determination

    NASA Astrophysics Data System (ADS)

    Cayrel, R.; Steffen, M.; Chand, H.; Bonifacio, P.; Spite, M.; Spite, F.; Petitjean, P.; Ludwig, H.-G.; Caffau, E.

    2007-10-01

    Context: Line asymmetries are generated by convective Doppler shifts in stellar atmospheres, especially in metal-poor stars, where convective motions penetrate to higher atmospheric levels. Such asymmetries are usually neglected in abundance analyses. The determination of the ^6Li/^7Li isotopic ratio is prone to suffering from such asymmetries, as the contribution of ^6Li is a slight blending reinforcement of the red wing of each component of the corresponding ^7Li line, with respect to its blue wing. Aims: The present paper studies the halo star HD 74000 and estimates the impact of convection-related asymmetries on the Li isotopic ratio determination. Methods: Two methods are used to meet this aim. The first, which is purely empirical, consists in deriving a template profile from another element that can be assumed to originate in the same stellar atmospheric layers as Li I, producing absorption lines of approximately the same equivalent width as individual components of the ^7Li I resonance line. The second method consists in conducting the abundance analysis based on NLTE line formation in a 3D hydrodynamical model atmosphere, taking into account the effects of photospheric convection. Results: The results of the first method show that the convective asymmetry generates an excess absorption in the red wing of the ^7Li absorption feature that mimics the presence of ^6Li at a level comparable to the hitherto published values. This opens the possibility that only an upper limit on ^6Li/^7Li has thus far been derived. The second method confirms these findings. Conclusions: From this work, it appears that a systematic reappraisal of former determinations of ^6Li abundances in halo stars is warranted. Based on observations carried out at the European Southern Observatory (ESO), under prog. ID 75.D-0600. Tables 1-3, and additional references are only available in electronic form at http://www.aanda.org

  9. The cosmological {sup 7}Li problem from a nuclear physics perspective

    SciTech Connect

    Broggini, C.; Canton, L.; Fiorentini, G.; Villante, F.L. E-mail: luciano.canton@pd.infn.it E-mail: francesco.villante@lngs.infn.it

    2012-06-01

    The primordial abundance of {sup 7}Li as predicted by Big Bang Nucleosynthesis (BBN) is more than a factor 2 larger than what has been observed in metal-poor halo stars. Herein, we analyze the possibility that this discrepancy originates from incorrect assumptions about the nuclear reaction cross sections relevant for BBN. To do this, we introduce an efficient method to calculate the changes in the {sup 7}Li abundance produced by arbitrary (temperature dependent) modifications of the nuclear reaction rates. Then, considering that {sup 7}Li is mainly produced from {sup 7}Be via the electron capture process {sup 7}Be+e{sup −} → {sup 7}Li+ν{sub e}, we assess the impact of the various channels of {sup 7}Be destruction. Differently from previous analysis, we consider the role of unknown resonances by using a complete formalism which takes into account the effect of Coulomb and centrifugal barrier penetration and that does not rely on the use of the narrow-resonance approximation. As a result of this, the possibility of a nuclear physics solution to the {sup 7}Li problem is significantly suppressed. Given the present experimental and theoretical constraints, it is unlikely that the {sup 7}Be+n destruction rate is underestimated by the 2.5 factor required to solve the problem. We exclude, moreover, that resonant destruction in the channels {sup 7}Be+t and {sup 7}Be+{sup 3}He can explain the {sup 7}Li puzzle. New unknown resonances in {sup 7}Be+d and {sup 7}Be+α could potentially produce significant effects. Recent experimental results have ruled out such a possibility for {sup 7}Be+d. On the other hand, for the {sup 7}Be+α channel very favorable conditions are required. The possible existence of a partially suitable resonant level in {sup 11}C is studied in the framework of a coupled-channel model and the possibility of a direct measurement is considered.

  10. NMR, UV, FT-IR, FT-Raman spectra and molecular structure (monomeric and dimeric structures) investigation of nicotinic acid N-oxide: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Atac, Ahmet; Karabacak, Mehmet; Karaca, Caglar; Kose, Etem

    2012-01-01

    In this work, the experimental and theoretical UV, NMR, and vibrational features of nicotinic acid N-oxide (abbreviated as NANO, C 6H 5NO 3) were studied. The ultraviolet (UV) absorption spectrum of studied compound that dissolved in water was examined in the range of 200-800 nm. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm -1 and 3500-50 cm -1, respectively. The 1H and 13C NMR spectra in DMSO were recorded. The geometrical parameters, energies and the spectroscopic properties of NANO were obtained for all four conformers from density functional theory (DFT) B3LYP/6-311++G(d,p) basis set calculations. There are four conformers, C n, n = 1-4 for this molecule. The computational results identified the most stable conformer of title molecule as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. 13C and 1H nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, absorption wavelengths, HOMO and LUMO energies, were performed by CIS approach. Finally the calculation results were applied to simulate infrared, Raman, and UV spectra of the title compound which show good agreement with observed spectra.

  11. Particle Leaking, Cross-Section Ratio 10B(n,{alpha})/238U(n,fission), and Excitation Function of the Reaction 10B(n,{alpha})7Li at MeV Energies

    SciTech Connect

    Giorginis, Georgios; Khryachkov, Vitali

    2005-05-24

    The 10B(n,{alpha})7Li reaction was studied in the energy range between 1.5 MeV and 5.6 MeV at the 7-MV Van de Graaff accelerator of IRMM by using a gridded ionisation chamber, signal digitisation, and an intrinsic 238U neutron monitor. The aim was to obtain accurate data for the IAEA Coordinated Research Project (CRP) on the improvement of standard cross sections for light elements. The effect of particle leaking was discovered and its implications investigated. The determination of the cross section {sigma}({alpha}0+{alpha}1) strongly benefits from it but measurements of angular distributions, individual cross sections {sigma}({alpha}0) and {sigma}({alpha}1), and the branching ratio {alpha}0/{alpha}1 are negatively affected. The correct number of reaction events was obtained by identification of unknown particle signatures in the energy spectra as 10B(n,{alpha})7Li events in the form of quasi 7Li+{alpha} particles created by particle leaking. The cross-section ratio 10B(n,{alpha})7Li/238U(n,fission) was measured and the excitation function of 10B(n,{alpha})7Li determined by simultaneously detecting the charged particles from the boron disintegration in the forward hemisphere and the 238U fission fragments in the backward hemisphere. The IRMM cross sections are compared to experimental data of other groups and to predictions of the ENDF/B-VI.8, JENDL-3.3, and JEF-2.2 evaluations.

  12. Experimental signatures for distinguishing breakup fusion and transfer in {sup 7}Li+{sup 165}Ho

    SciTech Connect

    Tripathi, V.; Navin, A.; Mahata, K.; Ramachandran, K.; Shrivastava, A.; Chatterjee, A.; Kailas, S.; Nanal, V.; Pillay, R.G.

    2005-07-01

    Reactions involving weakly bound nuclei of {sup 7}Li show large yields of {alpha} particles that have their origin in elastic breakup, breakup followed by fusion, or triton transfer. The latter two processes, breakup fusion and transfer, have similar characteristics and produce the same residual fragments. We report here results of exclusive measurements of charged particles and characteristic {gamma} rays from the heavy residues in the {sup 7}Li+{sup 165}Ho system at 42 MeV (E/V{sub b}{approx_equal}1.6) to look for experimental signatures to differentiate between transfer and breakup fusion. Such a distinction is essential for a better theoretical understanding of both the fusion process and direct reactions involving weakly bound stable and unstable beams.

  13. A 2D MOT design optimized for dual-species 6 Li-7 Li experiments

    NASA Astrophysics Data System (ADS)

    Cai, Yanping; Evans, Jesse; Wright, Kevin

    2016-05-01

    We have built a 2D MOT optimized for simultaneous capture and cooling of 6 Li and 7 Li. The design includes a vapor source located very close to the capture region, which reduces depletion of the low-velocity part of the oven flux. The source is angled so that the most probable longitudinal velocity of captured atoms is near optimal for transferring to a 3D MOT, even without a push beam. Because 6 Li D2 repump light can impede capture and cooling of 7 Li, we have characterized the system performance with 6 Li repumped on both the D1 and D2 transitions. This design provides ample cold atom flux to load a dual-species 3D MOT for quantum degenerate gas experiments.

  14. Coupled channel effect in elastic scattering and fusion for 6,7Li+28Si

    NASA Astrophysics Data System (ADS)

    Sinha, Mandira; Roy, Subinit; Basu, P.; Majumdar, H.; Santra, S.; Parkar, V. V.; Golda, K. S.; Kailas, S.

    2011-10-01

    The fusion excitation and elastic angular distribution were measured for 6,7Li+28Si from below to above Coulomb barrier (≤ 3Vb) energies. The barrier distribution derived from the fusion data was found to be broad and asymmetric at the sub-barrier region, compared to 1D BPM estimation. Effect of rotational coupling on fusion was found to be not so dominant. Phenomenological optical potential parameters, with surface and volume type imaginary potentials, were obtained from f tting of elastic scattering data and energy dependence of real and imaginary surface strengths were investigated around the barrier. CDCC calculations considering only breakup of projectile were performed for 6,7Li+28Si with the elastic scattering data, using the code FRESCO. The effects of breakup of projectile on elastic cross section do not agree with the energy dependence of real and imaginary strength with volume type imaginary potential around the barrier.

  15. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    -MAS-13C-NMR spectrum of HA. The CP-MAS- 13C-NMR spectra of the HA were quite similar to each other. These spectra exhibited signals for alkyl (0~50 ppm), O-alkyl (50~110 ppm), aromatic (110~160 ppm) and carbonyl (160~200 ppm) regions. The signals in carbonyl C region concentrated between 172 ppm and 173 ppm, and with a small signal occurred in the region of 190~200 ppm, indicating that there was carbonyl C of carboxylic acid, ester and amide, but a little amount carbonyl C of ketonic compounds. In the region of aromatic C, the most obvious peaks were the absorption at 131~133 ppm and 114~117 ppm. The former was mainly the aromatic C substituted by -COOH or -COOMe and the unsubstituted aromatic meta to carbons bearing an oxygen or nitrogen atom; the latter was mainly the unsubstituted aromatic C ortho and para to carbons bearing an oxygen and nitrogen atom. There was a small peak at 152-154ppm, which was the signal of phenolic OH. The signal at 55~56 ppm was methoxyl C. The signals at 71~73 ppm were due to the -CH(OH)- in carbohydrate. The peak at 102~103 ppm was generally assigned to double oxygen-C in polysaccharide (possibly acetal). The maximum absorption at 30 ppm was the contribution of the polymethylene chain -(CH2)n- in saturated hydrocarbons (Wilson, 1981). After OM application, the contents of alkyl C and O-alkyl C increased and the contents of aromatic C and carbonxyl C except to 1986 decreased. Compared with 1986, the contents of O-alkyl C increased and the contents of alkyl C decreased for the same treatment CKbr and O2. Aromaticity decreased significantly in OM treatments, indicating that the OM decreased the content of aromatic C and was simplified the molecular structure. The relative content of O-alkyl C increased indicating that OM application increased the content of methoxyl C and -CH(OH)- in carbohydrate. Alkyl C was probably derived from compounds of plants with high resistance to degradation, such as cutin and suberin (Baldock et al., 1992; Preston

  16. An update on the big bang nucleosynthesis prediction for {sup 7}Li: the problem worsens

    SciTech Connect

    Cyburt, Richard H; Fields, Brian D; Olive, Keith A E-mail: bdfields@uiuc.edu

    2008-11-15

    The lithium problem arises from the significant discrepancy between the primordial {sup 7}Li abundance as predicted by big bang nucleosynthesis (BBN) theory and the Wilkinson Microwave Anisotropy Probe (WMAP) baryon density, and the pre-Galactic lithium abundance inferred from observations of metal-poor (Population II) stars. This problem has loomed for the past decade, with a persistent discrepancy of a factor of 2-3 in {sup 7}Li/H. Recent developments have sharpened all aspects of the Li problem. Namely: (1) BBN theory predictions have sharpened due to new nuclear data; in particular, the uncertainty on the reaction rate for{sup 3}He({alpha},{gamma}){sup 7}Be has reduced to 7.4%, nearly a factor of 2 tighter than previous determinations. (2) The WMAP five-year data set now yields a cosmic baryon density with an uncertainty reduced to 2.7%. (3) Observations of metal-poor stars have tested for systematic effects. With these, we now find that the BBN+WMAP predicts{sup 7}Li/H = (5.24{sub -0.67}{sup +0.71}) Multiplication-Sign 10{sup -10}. The central value represents an increase by 23%, most of which is due to the upward shift in the{sup 3}He({alpha},{gamma}){sup 7}Be rate. More significant is the reduction in the{sup 7}Li/H uncertainty by almost a factor of 2, tracking the reduction in the{sup 3}He({alpha},{gamma}){sup 7}Be error bar. These changes exacerbate the Li problem; the discrepancy is now a factor 2.4 or 4.2{sigma} (from globular cluster stars) to 4.3 or 5.3{sigma} (from halo field stars). Possible resolutions to the lithium problem are briefly reviewed, and key experimental and astronomical measurements highlighted.

  17. New measurement of the 10B(n,α)7 Li through the Trojan Horse Method

    NASA Astrophysics Data System (ADS)

    Spartá, Roberta

    2016-04-01

    B(n,α) Li reaction cross section has been measured using the Trojan Horse method, with the specific aim to separate the α1 contribution (coming from the first Li excited level) by the αo (related to the Li ground state), using a very thin target. Preliminary results are shown of the three-body B(d,α7 Li)H cross section.

  18. ^7Li BEC in a millimeter-scale Ioffe-Pritchard trap

    NASA Astrophysics Data System (ADS)

    Liu, Mingchang; Wang, Ruquan; Minardi, Francesco; Kasevich, Mark

    2006-05-01

    A millimeter-scale Ioffe-Pritchard type magnetic trap with excellent optical access has been used to demonstrate Bose-Einstein condensation in^ 7Li. The trap utilizes a novel combination of free space and substrate patterned current carrying elements to produce the required fields. Substrate electrodes are fabricated with using the direct-bond copper (DBC) process on a ceramic substrate. DBC fabrication enables excellent thermal dissipation together with high current capacity vias and surface conductors. With 100A trapping current, which dissipates less than 10W the trap provides 400G/Cm magnetic gradient in the radial direction, 50Hz trapping frequency in axial direction and 80G trap depth for ^7Li. With conventional water cooling, lifetime for the trap is over 1 minute and BEC regime is reached after 35s forced evaporation. The demonstrated performance for ^7Li is expected to scale well to other alkalis and this compact configuration may serve as an excellent platform for mobile ultra-cold atom sensors.

  19. Electron affinity of (7)Li calculated with the inclusion of nuclear motion and relativistic corrections.

    PubMed

    Stanke, Monika; Kedziera, Dariusz; Bubin, Sergiy; Adamowicz, Ludwik

    2007-10-01

    Explicitly correlated Gaussian functions have been used to perform very accurate variational calculations for the ground states of (7)Li and (7)Li(-). The nuclear motion has been explicitly included in the calculations (i.e., they have been done without assuming the Born-Oppenheimer (BO) approximation). An approach based on the analytical energy gradient calculated with respect to the Gaussian exponential parameters was employed. This led to a noticeable improvement of the previously determined variational upper bound to the nonrelativistic energy of Li(-). The Li energy obtained in the calculations matches those of the most accurate results obtained with Hylleraas functions. The finite-mass (non-BO) wave functions were used to calculate the alpha(2) relativistic corrections (alpha=1c). With those corrections and the alpha(3) and alpha(4) corrections taken from Pachucki and Komasa [J. Chem. Phys. 125, 204304 (2006)], the electron affinity (EA) of (7)Li was determined. It agrees very well with the most recent experimental EA. PMID:17919011

  20. {sup 7}Li(p,n) NUCLEAR DATA LIBRARY FOR INCIDENT PROTON ENERGIES TO 150 MEV

    SciTech Connect

    S. MASHNIK; ET AL

    2000-11-01

    Researchers at Los Alamos National Laboratory are considering the possibility of using the Low Energy Demonstration Accelerator (LEDA), constructed at LANSCE for the Accelerator Production of Tritium program (APT), as a neutron source. Evaluated nuclear data are needed for the p+{sup 7}Li reaction, to predict neutron production from thin and thick lithium targets. In this report we describe evaluation methods that make use of experimental data, and nuclear model calculations, to develop an ENDF-formatted data library for incident protons with energies up to 150 MeV. The important {sup 7}Li(p,n{sub 0}) and {sup 7}Li(p,n{sub 1}) reactions are evaluated from the experimental data, with their angular distributions represented using Lengendre polynomial expansions. The decay of the remaining reaction flux is estimated from GNASH nuclear model calculations. This leads to the emission of lower-energy neutrons and other charged particles and gamma-rays from preequilibrium and compound nucleus decay processes. The evaluated ENDF-data are described in detail, and illustrated in numerous figures. We also illustrate the use of these data in a representative application by a radiation transport simulation with the code MCNPX.

  1. 4T 7Li 3D MRSI in the brains of bipolar disorder subjects

    PubMed Central

    Lee, Jing-Huei; Adler, Caleb; Norris, Matthew; Chu, Wen-Jang; Fugate, Elizabeth M; Strakowski, Stephen M.; Komoroski, Richard A.

    2012-01-01

    This work demonstrates the first whole brain “high spatial resolution” 7Li MRSI in bipolar disorder subjects. The in vivo quantification is validated by a phantom containing 5 mM lithium salt using the identical RF sequence and imaging protocol. This study is the first demonstration of the 7Li distribution in the brain of bipolar disorder patients on lithium therapy using a 3D MRSI approach. The results show that brain lithium level is strongly correlated with serum lithium concentration. The brain-to-serum lithium ratio for the average brain and the local maximum were 0.39 ± 0.08 (r = 0.93) and 0.92 ± 0.16 (r= 0.90), respectively. The lithium distribution is found to be non-uniform throughout the brain for all patients, which is somewhat unexpected and highly intriguing. This uneven distribution is more evident in subjects at a higher therapeutic serum lithium level. This finding may suggest that lithium targets specific brain tissues and/or certain enzymatic and macromolecular sites that are associated with therapeutic effect. Further investigations of bipolar disorder patients on lithium therapy using 3D 7Li MRSI are warranted. PMID:22692991

  2. Probing the cluster structure of 7Li via elastic scattering on protons and deuterons in inverse kinematics

    NASA Astrophysics Data System (ADS)

    Pakou, A.; Soukeras, V.; Cappuzzello, F.; Acosta, L.; Agodi, C.; Aslanoglou, X.; Calabrese, S.; Carbone, D.; Cavallaro, M.; Foti, A.; Keeley, N.; Marquinez-Duran, G.; Martel, I.; Mazzocco, M.; Parascandolo, C.; Pierroutsakou, D.; Rusek, K.; Sgouros, O.; Strano, E.; Zagatto, V. A. B.

    2016-07-01

    Elastic scattering measurements were performed for the 7Li+p system in inverse kinematics at energies of 16, 25, 35, and 38.1 MeV and for the 7Li+d system at 38.1 MeV. The heavy ejectiles were detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud in Catania, Italy. The results are analyzed using the Jeukenne-Lejeune-Mahaux and continuum discretized coupled channel frameworks. In the latter case the cluster structure of 7Li proves to be critical for the theoretical interpretation of the experimental results.

  3. Ferroelastic phase transitions by 14N NMR spectra in [N(CH3)4]2CoCl4 and [N(CH3)4]2ZnCl4 single crystals

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-09-01

    Changes in the structural geometry of [N(CH3)4]2BCl4 (B=Co and Zn) crystals near the phase transition temperatures were studied by analyzing the 14N nuclear magnetic resonance (NMR) spectra. Two physically inequivalent a-N(1)(CH3)4 and b-N(2)(CH3)4 groups were observed in these spectra. Abrupt changes in the resonance frequency and splitting of 14N NMR signals near the phase transition temperatures were attributed to structural phase transitions, and the primary mechanism of these phase transitions exhibited ferroelastic characteristics. In addition, ferroelasticity of [N(CH3)4]2BCl4 was identified at low temperatures using optical polarizing microscopy.

  4. Probing the fusion of 7Li with 64Ni at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Shaikh, Md. Moin; Roy, Subinit; Rajbanshi, S.; Mukherjee, A.; Pradhan, M. K.; Basu, P.; Nanal, V.; Pal, S.; Shrivastava, A.; Saha, S.; Pillay, R. G.

    2016-04-01

    Background: The stable isotopes of Li, 6Li6 and 7Li, have two-body cluster structures of α +d and α +t with α -separation energies or breakup thresholds at 1.47 and 2.47 MeV, respectively. The weak binding of these projectiles introduces several new reaction channels not usually observed in the case of strongly bound projectiles. The impact of these breakup or breakup-like reaction channels on fusion, the dominant reaction process at near-barrier energies, with different target masses is of current interest. Purpose: Our purpose is to explore the fusion, at above and below the Coulmb barrier, of 7Li with 64Ni target in order to understand the effect of breakup or breakup-like processes with medium-mass target in comparison with 6Li, which has a lower breakup threshold. Measurement: The total fusion (TF) excitation of the weakly bound projectile 7Li with the medium-mass target 64Ni has been measured at the near-barrier energies (0.8 to 2 VB). The measurement was performed using the online characteristic γ -ray detection method. The complete fusion (CF) excitation function for the system was obtained using the x n -evaporation channels with the help of statistical model predictions. Results: At the above barrier energies CF cross sections exhibit an average suppression of about 6.5% compared to the one-dimensional barrier penetration model (1DBPM) predictions, while the model describes the measured TF cross section well. But below the barrier, both TF and CF show enhancements compared to 1DBPM predictions. Unlike 6Li, enhancement of CF for 7Li could not be explained by inelastic coupling alone. Conclusion: Whereas the σTF cross sections are almost the same for both the systems in the above barrier region, the suppression of σCF at above the barrier is less for the 7Li+64Ni system than for the 6+64Ni system. Also direct cluster transfer has been identified as the probable source for producing large enhancement in TF cross sections.

  5. Vibrational spectra, molecular structure, NBO, NMR, UV, first order hyperpolarizability, analysis of (S)-(-)-N-(5-Nitro-2-pyridyl) alaninol by Density functional theory.

    PubMed

    Govindarasu, K; Kavitha, E

    2014-06-01

    In this study, geometrical optimization, spectroscopic analysis, electronic structure and nuclear magnetic resonance studies of (S)-(-)-N-(5-Nitro-2-pyridyl) alaninol (abbreviated as SN5N2PLA) were investigated by utilizing HF and DFT/B3LYP with 6-31G(d,p) as basis set. The Fourier transform infrared (FT-IR) and FT-Raman spectra of SN5N2PLA were recorded in the region 4000-400cm(-1) and 3500-50cm(-1), respectively. Complete vibrational assignments, analysis and correlation of the fundamental modes for the title compound were carried out. UV-Visible spectrum of the compound that dissolved in methanol were recorded in the region 200-800nm and the electronic properties HOMO and LUMO energies were measured by TD-DFT approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The molecular stability and bond strength have been investigated by applying the Natural Bond Orbital (NBO) analysis. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of SN5N2PLA were calculated using the GIAO method in methanol solution and compared with the measured experimental data. The dipole moment, polarizability and first order hyperpolarizability values were also computed. The polarizability and first hyperpolarizability of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The Chemical reactivity and Thermodynamic properties of SN5N2PLA at different temperature are calculated. In addition, molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs) analysis were investigated using theoretical calculations. PMID:24657932

  6. Phosphorus-31 NMR spectra of ethidium, quinacrine, and daunomycin complexes with poly(adenylic acid)ter dot poly(uridylic acid) RNA duplex and calf thymus DNA

    SciTech Connect

    Gorenstein, D.G.; Lai, K. )

    1989-04-04

    {sup 31}P NMR provides a convenient monitor of the phosphate ester backbone conformational changes upon binding of the intercalating drugs ethidium, quinacrine, and daunomycin to sonicated poly(A){center dot}poly(U) and calf thymus DNA. {sup 31}P chemical shifts can also be used to assess differences in the duplex unwinding angles in the presence of the drug. Thus a new {sup 31}P signal, 1.8-2.2 ppm downfield from the double-stranded helix signals, is observed in the ethidium ion-poly(A){center dot}poly(U) complex. This signal arises from phosphates which are in perturbed environments due to intercalation of the drug. This is in keeping with the hypothesis that the P-O ester torsional angle in phosphates linking the intercalated base pairs is more trans-like. Similar though smaller deshielding of the {sup 31}P signals is observed in sonicated poly(A){center dot}poly(U)-quinacrine complexes as well as in the daunomycin complexes. The effect of added ethidium ion, quinacrine, and daunomycin on the {sup 31}P spectra of sonicated calf thymus DNA is consistent with Wilson and Jones' (1982) earlier study. In these drug-DNA complexes the drug produces a gradual downfield shift in the DNA {sup 31}P signal without the appearance of a separate downfield peak. These differences are attributed to differences in the rate of chemical exchange of the drug between free and bound duplex states. The previous correlation of {sup 31}P chemical shift with drug duplex unwinding angle is confirmed for both the RNA and DNA duplexes.

  7. Application of unsymmetrical indirect covariance NMR methods to the computation of the (13)C <--> (15)N HSQC-IMPEACH and (13)C <--> (15)N HMBC-IMPEACH correlation spectra.

    PubMed

    Martin, Gary E; Hilton, Bruce D; Irish, Patrick A; Blinov, Kirill A; Williams, Antony J

    2007-10-01

    Utilization of long-range (1)H--(15)N heteronuclear chemical shift correlation has continually grown in importance since the first applications were reported in 1995. More recently, indirect covariance NMR methods have been introduced followed by the development of unsymmetrical indirect covariance processing methods. The latter technique has been shown to allow the calculation of hyphenated 2D NMR data matrices from more readily acquired nonhyphenated 2D NMR spectra. We recently reported the use of unsymmetrical indirect covariance processing to combine (1)H--(13)C GHSQC and (1)H--(15)N GHMBC long-range spectra to yield a (13)C--(15)N HSQC-HMBC chemical shift correlation spectrum that could not be acquired in a reasonable period of time without resorting to (15)N-labeled molecules. We now report the unsymmetrical indirect covariance processing of (1)H--(13)C GHMBC and (1)H--(15)N IMPEACH spectra to afford a (13)C--(15)N HMBC-IMPEACH spectrum that has the potential to span as many as six to eight bonds. Correlations for carbon resonances long-range coupled to a protonated carbon in the (1)H--(13)C HMBC spectrum are transferred via the long-range (1)H--(15)N coupling pathway in the (1)H--(15)N IMPEACH spectrum to afford a much broader range of correlation possibilities in the (13)C--(15)N HMBC-IMPEACH correlation spectrum. The indole alkaloid vincamine is used as a model compound to illustrate the application of the method. PMID:17729230

  8. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    -MAS-13C-NMR spectrum of HA. The CP-MAS- 13C-NMR spectra of the HA were quite similar to each other

  9. What can d7Li tell us about sources and flow pathes of river water (Western Pamir, Tajikistan)?

    NASA Astrophysics Data System (ADS)

    Meier, Christiane; Knoche, Malte; Osenbrück, Karsten; Seitz, Hans-Michael; Weise, Stephan M.

    2015-04-01

    The high alpine regions in Central Asia are the headwaters for big river systems such as the Amu Darya, which is intensively used for agricultural purposes. For the local water resources management it is important to understand the key factors and processes of runoff generation. It is assumed, that the dominant factors for runoff generation are glacier and snow melt in the Pamir Mountains. However the influence of ground water to river water is also an important factor but still not well understood. We investigated the River Gunt catchment as an exemplary catchment for the Pamir Mountains to identify the origin and to quantify the portion of ground water. Thereby we analyzed water samples of river water, subsurface water, thermal water and glacier water for 7Li. We detected a wide range of 7Li values (from +7‰ to +30‰), whereas the highest values were measured in the glacier melt water at the glacier snout (7Li = +28.8‰) which are similar to the 7Li value of sea water, the lowest values were found in the samples of thermal water and springs in solid rock (7Li between +8‰ and +11‰), the samples of river water are more or less placed on a mixing line in between. We assume that tributaries showing an isotope signature similar to the glacier ones are mainly controlled by melt water while water samples with 7Li values comparable to the 7Li values of subsurface water samples pass through the underground or have a strong interaction between river water and river bed. The water samples of the main stream Gunt also show low 7Li values so we assume a strong contribution of subsurface water to the total runoff or an intensive water-rock-interaction in its riverbed.

  10. Beam shaping assembly optimization for (7)Li(p,n)(7)Be accelerator based BNCT.

    PubMed

    Minsky, D M; Kreiner, A J

    2014-06-01

    Within the framework of accelerator-based BNCT, a project to develop a folded Tandem-ElectroStatic-Quadrupole accelerator is under way at the Atomic Energy Commission of Argentina. The proposed accelerator is conceived to deliver a proton beam of 30mA at about 2.5MeV. In this work we explore a Beam Shaping Assembly (BSA) design based on the (7)Li(p,n)(7)Be neutron production reaction to obtain neutron beams to treat deep seated tumors. PMID:24345525

  11. Spectroscopic study of the C 1Σ+ state of 7LiH

    NASA Astrophysics Data System (ADS)

    Chen, Jye-Jong; Luh, Wei-Tzou; Jeung, Gwang-Hi

    1999-03-01

    Forty-two vibrational (v=2-43) levels of the 7LiH C 1Σ+ excited electronic state have been observed by a pulsed optical-optical double resonance fluorescence depletion spectroscopic technique. The absolute vibrational numbering of the C 1Σ+ state is identified with the measurements of the isotopic shifts between 7LiH and 6LiH among several rotation-vibration bands of the C 1Σ+-A 1Σ+ electronic system, and it is further demonstrated by the consistency between observed spectral intensities and calculated ones. The highest observed quasi bound rotational level for the v=43 level is J=8. The spectral term values for those vibrational levels lying above v=33 occur in an irregular order. The level of v=34 lies mainly in the inner, tiny well. The term values for the observed rovibrational levels (2⩽v⩽32, 0⩽J⩽11) in the outer ionic well are described by a set of Dunham-type coefficients, with which a Rydberg-Klein-Rees (RKR) potential energy curve is constructed. This RKR potential is combined with an ab initio potential to construct an effective hybrid potential. The calculated electronic transition moment function for the C-A transition is also given.

  12. Corrosion barriers processed by Al electroplating and their resistance against flowing Pb-15.7Li

    NASA Astrophysics Data System (ADS)

    Krauss, Wolfgang; Konys, Jürgen; Wulf, Sven-Erik

    2014-12-01

    In the HCLL blanket design, ferritic-martensitic steels are in direct contact with the flowing liquid breeder Pb-15.7Li and have to withstand severe corrosion attack. Beyond corrosion, T-permeation from the breeder into the RAFM-steels is also an important issue and has to be reduced significantly. Earlier work showed that Al-based coatings can act as barriers for both, however, applied processes e.g. HDA or VPS exhibited strong drawbacks in the past. Meanwhile new industrial relevant coating processes, using electroplating technology are under development and called ECA (electrochemical aluminization) and ECX (electrochemical deposition from ionic liquids) process. In this study electrochemically Al-coated and heat-treated Eurofer samples were tested in PICOLO loop for exposure times up to 12,000 h (ECA) and 2000 h (first results ECX) respectively to determine corrosion properties in flowing Pb-15.7Li (550 °C, 0.1 m/s). Cross section analysis afterward corrosion testing proved the ability of thin Al-based barriers made by electrochemical techniques to protect the bare Eurofer from corrosion attack even at exposure times of 12,000 h. Determined radial corrosion rates lay between 10 and 20 μm/a. First results for ECX coated samples (2000 h) revealed more homogeneous corrosion behavior of the barrier layer itself compared to ECA.

  13. Astrophysical S factors for radiative proton capture by {sup 3}H and {sup 7}Li nuclei

    SciTech Connect

    Dubovichenko, S. B.

    2011-03-15

    Within the potential cluster model where orbital states are classified according to Young diagrams and isospin, astrophysical S factors are considered for radiative proton capture by {sup 3}H and {sup 7}Li nuclei at energies of up to 1 and 10 keV, respectively. It is shown that the approach used, which takes into account only the E1 transition for the p{sup 3}H capture process, makes it possible to describe well the most recent experimental data at c.m. energies in the range from 50 keV to 5MeV. In the case of proton capture by {sup 7}Li nuclei, an M1 processwas taken into account in addition to the E1 transition, and a general behavior and the magnitude of the experimental S factor could be correctly reproduced owing to this at astrophysical energies, including the region around the resonance at 0.441 MeV (in the laboratory frame).

  14. FT-IR, FT-Raman, UV, NMR spectra and molecular structure investigation of (E)-2-(3-chloropyrazin-2-yl)-1-(3-ethyl-2, 6-diphenyl piperidin-4-ylidene) hydrazine: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Therasa Alphonsa, A.; Loganathan, C.; Athavan Alias Anand, S.; Kabilan, S.

    2015-11-01

    This work presents the characterization of (E)-2-(3-chloropyrazin-2-yl)-1-(3-ethyl-2, 6-diphenyl piperidin-4-ylidene) hydrazine (HDE) by quantum chemical calculations and spectral techniques. The structure was investigated by FT-IR, FT-Raman, UV-vis and NMR techniques. The geometrical parameters and energies have been obtained from Density functional theory (DFT) B3LYP (6-31G (d, p)) basis set calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge-independent atomic orbital method (GIAO). The electronic properties such as excitation energies, wavelength, HOMO, LUMO energies performed by Time dependent density functional theory (TD-DFT) results complements with the experimental findings. NBO analysis has been performed for analyzing charge delocalization throughout the molecule. The calculation results were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. To provide information about the interactions between human cytochrome protein and the novel compound theoretically, docking studies were carried out using Schrödinger software.

  15. PIC microcontroller based external fast analog to digital converter to acquire wide-lined solid NMR spectra by BRUKER DRX and Avance-I spectrometers.

    PubMed

    Koczor, Bálint; Rohonczy, János

    2015-01-01

    Concerning many former liquid or hybrid liquid/solid NMR consoles, the built in Analog-to-Digital Converters (ADCs) are incapable of digitizing the fids at sampling rates in the MHz range. Regarding both strong anisotropic interactions in the solid state and wide chemical shift dispersion nuclei in solution phase such as (195)Pt, (119)Sn, (207)Pb etc., the spectrum range of interest might be in the MHz range. As determining the informative tensor components of anisotropic NMR interactions requires nonlinear fitting over the whole spectrum including the asymptotic baseline, it is prohibited by low sampling rates of the ADCs. Wide spectrum width is also useful in solution NMR, since windowing of wide chemical shift ranges is avoidable. We built an external analog to digital converter with 10 MHz maximal sampling rate, which can work simultaneously with the built in ADC of the spectrometer. The ADC was tested on both Bruker DRX and Avance-I NMR consoles. In addition to the analog channels it only requires three external digital lines of the NMR console. The ADC sends data to PC via USB. The whole process is controlled by software written in JAVA which is implemented under TopSpin. PMID:25727157

  16. Comparative NMR studies on Ca3LiRuO6 and Ca3NaRuO6

    NASA Astrophysics Data System (ADS)

    Chakrabarty, T.; Paulose, P. L.

    2016-06-01

    We report a comparative study of two ruthanate compounds, Ca3LiRuO6 and Ca3NaRuO6 by magnetic measurements, heat capacity and NMR. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature of 115 K. The 7Li NMR linewidth of Ca3LiRuO6 displays a broad shoulder above the magnetic ordering temperature. Anomalous shoulder of this type is observed in the susceptibility data also. The origin of these phenomena is not clear but could possibly be attributed to low dimensional magnetism. A contrasting magnetic behavior is seen in Ca3NaRuO6, an antiferromagnet with a transition temperature at 87 K. The NMR study shows that the Knight shift is proportional to the magnetic susceptibility. Also, in Ca3NaRuO6, the Knight shift and the linewidth of the spectra change differently compared to Ca3LiRuO6. The heat capacity of both compounds show a λ-type anomaly at respective magnetic transition temperatures. However, in both the systems the entropy change (Δ S) is much less than that of an ordered S  =  3/2 system.

  17. Comparative NMR studies on Ca3LiRuO6 and Ca3NaRuO6.

    PubMed

    Chakrabarty, T; Paulose, P L

    2016-06-15

    We report a comparative study of two ruthanate compounds, Ca3LiRuO6 and Ca3NaRuO6 by magnetic measurements, heat capacity and NMR. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature of 115 K. The (7)Li NMR linewidth of Ca3LiRuO6 displays a broad shoulder above the magnetic ordering temperature. Anomalous shoulder of this type is observed in the susceptibility data also. The origin of these phenomena is not clear but could possibly be attributed to low dimensional magnetism. A contrasting magnetic behavior is seen in Ca3NaRuO6, an antiferromagnet with a transition temperature at 87 K. The NMR study shows that the Knight shift is proportional to the magnetic susceptibility. Also, in Ca3NaRuO6, the Knight shift and the linewidth of the spectra change differently compared to Ca3LiRuO6. The heat capacity of both compounds show a λ-type anomaly at respective magnetic transition temperatures. However, in both the systems the entropy change ([Formula: see text]S) is much less than that of an ordered S  =  3/2 system. PMID:27157888

  18. Vector analyzing power of {pi}{sup +7}Li scattering in the region of the {delta}{sub 33} resonance

    SciTech Connect

    Ibraeva, E. T.; Zhusupov, M. A.; Zaykin, A. Yu.; Imambekov, O.

    2006-04-15

    Within Glauber diffraction theory, the vector analyzing power iT{sub 11} is calculated at three energies of positively charged pions, 134, 164, and 194 MeV, incident to {sup 7}Li nuclei. These energy values lie in the region of the {delta}{sub 33} resonance in {pi}{sup {+-}}N interaction, the resonance maximum being at 180 MeV. The calculation of iT{sub 11} was performed with several model {sup 7}Li wave functions, including the {alpha}t-cluster and shell-model ones. The properties of {pi}{sup +7}Li scattering are found to be sensitive to the structural features of the target nucleus. A comparison of the results of the calculations with experimental data shows that the wave functions in question and the potentials used to calculate them are quite appropriate.

  19. Automated structure verification based on a combination of 1D (1)H NMR and 2D (1)H - (13)C HSQC spectra.

    PubMed

    Golotvin, Sergey S; Vodopianov, Eugene; Pol, Rostislav; Lefebvre, Brent A; Williams, Antony J; Rutkowske, Randy D; Spitzer, Timothy D

    2007-10-01

    A method for structure validation based on the simultaneous analysis of a 1D (1)H NMR and 2D (1)H - (13)C single-bond correlation spectrum such as HSQC or HMQC is presented here. When compared with the validation of a structure by a 1D (1)H NMR spectrum alone, the advantage of including a 2D HSQC spectrum in structure validation is that it adds not only the information of (13)C shifts, but also which proton shifts they are directly coupled to, and an indication of which methylene protons are diastereotopic. The lack of corresponding peaks in the 2D spectrum that appear in the 1D (1)H spectrum, also gives a clear picture of which protons are attached to heteroatoms. For all these benefits, combined NMR verification was expected and found by all metrics to be superior to validation by 1D (1)H NMR alone. Using multiple real-life data sets of chemical structures and the corresponding 1D and 2D data, it was possible to unambiguously identify at least 90% of the correct structures. As part of this test, challenging incorrect structures, mostly regioisomers, were also matched with each spectrum set. For these incorrect structures, the false positive rate was observed as low as 6%. PMID:17694570

  20. High-resolution solid-state 13C CP MAS NMR spectra of some β-cyclodextrin inclusion complexes with nitriles

    NASA Astrophysics Data System (ADS)

    Okazaki, M.; McDowell, C. A.

    1983-11-01

    β-cyclodextrin inclusion complexes of 3-aminobenzonitrile, 4-aminobenzonitrile, and adamantane-1-carbonitrile were studied by means of high-resolution solid-state CP MAS 13C NMR spectroscopy. The interactions between the host and guest molecules are discussed.

  1. A new approach to the optimisation of non-uniform sampling schedules for use in the rapid acquisition of 2D NMR spectra of small molecules.

    PubMed

    Sidebottom, Philip J

    2016-08-01

    Non-uniform sampling allows the routine, rapid acquisition of 2D NMR data. When the number of points in the NUS schedule is low, the quality of the data obtained is very dependent of the schedule used. A simple proceedure for finding optimium schedules has been developed and is demonstrated for the multiplicity edited HSQC experiment. PMID:27160788

  2. Measurement of fusion excitation function for 7Li+64Ni near the barrier

    NASA Astrophysics Data System (ADS)

    Moin Shaikh, Md.; Roy, Subinit; Rajbanshi, S.; Mukherjee, A.; Pradhan, M. K.; Basu, P.; Pal, S.; Nanal, V.; Shrivastava, A.; Saha, S.; Pillay, R. G.

    2016-05-01

    Total fusion (TF) excitation function has been measured for the system 7Li + 64Ni at the energies near the Coulomb barrier of the system. The evaporation residue (ER) cross sections have been estimated through the online detection of characteristic γ-rays of the ERs. The summed ER cross sections yielding the experimental TF cross section have been compared with the theoretical one dimensional barrier penetration model (1DBPM) prediction. The measured and the model cross sections are very close to each other at above barrier energies. However, an enhancement of the experimental TF cross section with respect to the 1DBPM prediction is observed at below barrier energies. Coupled channels (CC) calculation with inelastic excitations alone could not explain the enhancement. The origin of the enhancement is identified as due to the enhanced population of the αxn channels.

  3. 7Li-induced reactions for fast-timing with LaBr3:Ce detectors

    NASA Astrophysics Data System (ADS)

    Mason, P. J. R.; Podolyàk, Zs.; Mǎrginean, N.; Regan, P. H.; Alexander, T.; Algora, A.; Alharbi, T.; Bowry, M.; Britton, R.; Bucurescu, D.; Bruce, A. M.; Bunce, M.; Cǎta-Danil, G.; Cǎta-Danil, I.; Cooper, N.; Deleanu, D.; Delion, D.; Filipescu, D.; Gelletly, W.; Glodariu, T.; Gheorghe, I.; Ghiťǎ, D.; Ilie, G.; Ivanova, D.; Kisyov, S.; Lalkovski, S.; Lica, R.; Liddick, S. N.; Mǎrginean, R.; Mihai, C.; Mulholland, K.; Negret, A.; Nita, C. R.; Rice, S.; Roberts, O. J.; Sava, T.; Smith, J. F.; Söderström, P.-A.; Stevenson, P. D.; Stroe, L.; Toma, S.; Townsley, C.; Werner, V.; Wilson, E.; Wood, R. T.; Zamfir, N. V.; Zhekova, M.

    2012-10-01

    7Li induced-reactions have been used with a 186W target to populate nuclei around A˜180-190 at the National Institute of Physics and Nuclear Engineering in Bucharest, Romania. An array of high-purity germanium (HPGe) and cerium-doped lanthanum bromide (LaBr3:Ce) detectors have been used to measure sub-nanosecond half-lives with fast-timing techniques. The yrast 2+ state in 190Os was measured to be t1/2 = 375(20)ps, in excellent agreement with the literature value. The previously unreported half-life of the 564-keV state in 189Ir has also been measured and a value of t1/2 = 540(100)ps ps obtained.

  4. TLD efficiency of 7LiF for doses deposited by high-LET particles

    NASA Technical Reports Server (NTRS)

    Benton, E. R.; Frank, A. L.; Benton, E. V.

    2000-01-01

    The efficiency of 7 LiF TLDs (TLD-700) in registering dose from high-LET (> or = 10 keV/micrometers) charged particles (relative to 137Cs gamma rays) has been measured for a number of accelerated heavy ions at various particle accelerator facilities. These measured efficiency values have been compared with similar results obtained from the open literature and a dose efficiency function has been fitted to the combined data set. While it was found that the dose efficiency is not only a function of LET, but also of the charge of the incident particle, the fitted function can be used to correct the undermeasured value of dose from exposures made in mixed radiation fields where LET information is available. This LET-dependent dose efficiency function is used in our laboratory in determining total absorbed dose and dose equivalent from combined TLD and CR-39 plastic nuclear track detector measurements.

  5. New method to evaluate the 7Li(p, n)7Be reaction near threshold

    NASA Astrophysics Data System (ADS)

    Herrera, María S.; Moreno, Gustavo A.; Kreiner, Andrés J.

    2015-04-01

    In this work a complete description of the 7Li(p, n)7Be reaction near threshold is given using center-of-mass and relative coordinates. It is shown that this standard approach, not used before in this context, leads to a simple mathematical representation which gives easy access to all relevant quantities in the reaction and allows a precise numerical implementation. It also allows in a simple way to include proton beam-energy spread affects. The method, implemented as a C++ code, was validated both with numerical and experimental data finding a good agreement. This tool is also used here to analyze scattered published measurements such as (p, n) cross sections, differential and total neutron yields for thick targets. Using these data we derive a consistent set of parameters to evaluate neutron production near threshold. Sensitivity of the results to data uncertainty and the possibility of incorporating new measurements are also discussed.

  6. Optimization of the {sup 7}Li(p,n) proton beam energy for BNCT applications

    SciTech Connect

    Bleuel, D.L.; Donahue, R.J.

    1996-02-01

    The reaction {sup 7}Li(p,n){sup 7} Be has been proposed as an accelerator-based source of neutrons for Boron Neutron Capture Therapy (BNCT). This reaction has a large steep resonance for proton energies of about 2.3 MeV which ends at about 2.5 MeV. It has generally been accepted that one should use 2.5 MeV protons to get the highest yield of neutrons for BNCT. This paper suggests that for BNCT the optimum proton energy may be about 2.3 MeV and that a proton energy of about 2.2 MeV will provide the same useful neutron fluence outside a thinner moderator as the neutron fluence from a 2.5 MeV proton beam with a thicker moderator.

  7. Lithium-7 NMR studies of Li(1-x)CoO2 battery cathodes

    NASA Astrophysics Data System (ADS)

    Ouyang, B.; Cao, X.; Lin, H. W.; Slane, S.; Kostov, S.

    1995-05-01

    Lithium-deficient cathode materials Li(1-x)CoO2, where x = 0.1, 0.4 and 0.6 were prepared electrochemically from the stoichiometric parent compound (x = 0.0). The materials were observed to be air-stable, and x-ray diffraction characterization yielded good agreement with the in situ studies of Dahn and co-workers, regarding changes in lattice parameters. In addition to both static and magic angle spinning (MAS) Li-7 NMR, measurements, the samples were investigated by EPR and cobalt K-edge NEXAFS. The removal of Li is accompanied by compensating electrons from the Co d-orbitals, as evidenced by both shifts in the NEXAFS peak and the observation of EPR signals due to spins localized on the Co ions. These spins, in turn, result in dramatic 7Li chemical shifts (89 ppm for x = 0.6) and line broadening. Whereas MAS analysis of Li(0.9)CoO2 indicates two magnetically inequivalent Li sites, the spectra become too broad to resolve different sites for higher values of x. Finally NMR linewidth and spin- lattice relaxation measurements as a function of temperature suggest a modest increase in Li(+) ion mobility for Li-deficient samples as compared to the parent compound.

  8. Quasi-Elastic Barrier Distribution for the {sup 7}Li+{sup 144}Sm Weakly Bound System

    SciTech Connect

    Otomar, D. R.; Gomes, P. R. S.; Lubian, J.; Monteiro, D. S.

    2009-06-03

    We have measured the excitation function of quasielastic and elastic scattering, at backward angles, for a range of energies from below to above the Coulomb barrier, for the {sup 7}Li+{sup 144}Sm system. Barrier distributions were exctracted from these excitation functions by a numerical method. From the theoretical analysis one concluded that the quadrupole and octupole excitations of {sup 144}Sm and the one-neutron transfer (stripping) channel are important reaction processes. Nevertheless, the agreement with the experimental results is poor. The discrepancy is attributed to the {sup 7}Li break-up channel that was not taken into account in the coupling scheme.

  9. An atomic beam of 6Li — 7Li for high resolution spectroscopy from matrix isolation sublimation

    NASA Astrophysics Data System (ADS)

    Oliveira, A. N.; Sacramento, R. L.; Silva, B. A.; Uhlmann, F. O.; Wolff, W.; Cesar, C. L.

    2016-07-01

    We propose the Matrix Isolation Sublimation (MlSu) technique for generating cold lithium atoms for the measurement of the 6Li - 7Li isotope shift in D1 and D2 transitions. The technique is capable of generating cold 6Li and 7Li beams at 4 K with forward velocity of 125 m/s. Using this beam we offer a distinguished source of lithium atoms for transitions measurements, adding a new possibility to make high resolution spectroscopy towards improving the experimental checks of the theory.

  10. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine.

    PubMed

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-15

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm(-1) and 4000-10 cm(-1), respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results. PMID:24813280

  11. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine

    NASA Astrophysics Data System (ADS)

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-01

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm-1 and 4000-10 cm-1, respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results.

  12. Fast neutron measurements with 7Li and 6Li enriched CLYC scintillators

    NASA Astrophysics Data System (ADS)

    Giaz, A.; Blasi, N.; Boiano, C.; Brambilla, S.; Camera, F.; Cattadori, C.; Ceruti, S.; Gramegna, F.; Marchi, T.; Mattei, I.; Mentana, A.; Million, B.; Pellegri, L.; Rebai, M.; Riboldi, S.; Salamida, F.; Tardocchi, M.

    2016-07-01

    The recently developed Cs2LiYCl6:Ce (CLYC) crystals are interesting scintillation detectors not only for their gamma energy resolution (<5% at 662 keV) but also for their capability to identify and measure the energy of both gamma rays and fast/thermal neutrons. The thermal neutrons were detected by the 6Li(n,α)t reaction while for the fast neutrons the 35Cl(n,p)35S and 35Cl(n,α)32P neutron-capture reactions were exploited. The energy of the outgoing proton or α particle scales linearly with the incident neutron energy. The kinetic energy of the fast neutrons can be measured using both the Time Of Flight (TOF) technique and using the CLYC energy signal. In this work, the response to monochromatic fast neutrons (1.9-3.8 MeV) of two CLYC 1″×1″ crystals was measured using both the TOF and the energy signal. The observables were combined to identify fast neutrons, to subtract the thermal neutron background and to identify different fast neutron-capture reactions on 35Cl, in other words to understand if the detected particle is an α or a proton. We performed a dedicated measurement at the CN accelerator facility of the INFN Legnaro National Laboratories (Italy), where the fast neutrons were produced by impinging a proton beam (4.5, 5.0 and 5.5 MeV) on a 7LiF target. We tested a CLYC detector 6Li-enriched at about 95%, which is ideal for thermal neutron measurements, in parallel with another CLYC detector 7Li-enriched at more than 99%, which is suitable for fast neutron measurements.

  13. Asymptotic and near-target direct breakup of 6Li and 7Li

    NASA Astrophysics Data System (ADS)

    Kalkal, Sunil; Simpson, E. C.; Luong, D. H.; Cook, K. J.; Dasgupta, M.; Hinde, D. J.; Carter, I. P.; Jeung, D. Y.; Mohanto, G.; Palshetkar, C. S.; Prasad, E.; Rafferty, D. C.; Simenel, C.; Vo-Phuoc, K.; Williams, E.; Gasques, L. R.; Gomes, P. R. S.; Linares, R.

    2016-04-01

    Background: Li,76 and 9Be are weakly bound against breakup into their cluster constituents. Breakup location is important for determining the role of breakup in above-barrier complete fusion suppression. Recent works have pointed out that experimental observables can be used to separate near-target and asymptotic breakup. Purpose: Our purpose is to distinguish near-target and asymptotic direct breakup of Li,76 in reactions with nuclei in different mass regions. Method: Charged particle coincidence measurements are carried out with pulsed Li,76 beams on 58Ni and 64Zn targets at sub-barrier energies and compared with previous measurements using 208Pb and 209Bi targets. A detector array providing a large angular coverage is used, along with time-of-flight information to give definitive particle identification of the direct breakup fragments. Results: In interactions of 6Li with 58Ni and 64Zn, direct breakup occurs only asymptotically far away from the target. However, in interactions with 208Pb and 209Bi, near-target breakup occurs in addition to asymptotic breakup. Direct breakup of 7Li into α -t is not observed in interactions with 58Ni and 64Zn. However, near-target dominated direct breakup was observed in measurements with 208Pb and 209Bi. A modified version of the Monte Carlo classical trajectory model code platypus, which explicitly takes into account lifetimes associated with unbound states, is used to simulate sub-barrier breakup reactions. Conclusions: Near-target breakup in interactions with Li,76 is an important mechanism only for the heavy targets 208Pb and 209Bi. There is insignificant near-target direct breakup of 6Li and no direct breakup of 7Li in reactions with 58Ni and 64Zn. Therefore, direct breakup is unlikely to suppress the above-barrier fusion cross section in reactions of Li,76 with 58Ni and 64Zn nuclei.

  14. Response of an FBX dosimeter to high LET 7Li and 12C ions

    NASA Astrophysics Data System (ADS)

    Bhat, N. N.; Choudhary, D.; Sarma, A.; Gupta, B. L.; Siddappa, K.

    2003-12-01

    We have carried out systematic studies on the response of ferrous sulphate-benzoic acid-xylenol orange (FBX)—a highly sensitive chemical dosimeter in liquid form to accelerated charged particles of different LET. Dosimeters were exposed in the form of thin layers to graded fluence of 7Li ion beam with three different energies Viz, 46, 38 and 27 MeV corresponding to average LETs of 6.3, 7.5 and 11 eV Å -1 and 12C ion beam with energy 45.6 MeV corresponding to average LET of 52.5 eV Å -1. From the investigations, the corresponding G(Fe +3) values were found to be (51.7±1.3)×10 -7, (35.4±0.7)×10 -7, (19.3±0.6)×10 -7 and (8.4±0.1)×10 -7 mol J -1, respectively. For gamma radiation, with estimated LET of 0.02 eV Å -1, G(Fe +3) value was observed to be (56.1±0.4)×10 -7 mol J -1. Clearly, G(Fe +3) values were found to decrease with increasing LET of the particle beam. However, the dosimeter showed no dependence on LET up to about 6 eV Å -1 unlike the Fricke dosimeter. The results confirm the response of FBX dosimeter is non-linear for doses exceeding 5 Gy for 60Co gamma rays. More importantly, the present study using 7Li and 12C ions clearly shows that response of the FBX dosimeter is linear for high LET radiations at low as well as high doses.

  15. Synthesis, experimental spectra (IR & Raman and NMR), vibrational analysis and theoretical DFT investigations of N-(5-(4-methylbenzoyl)-2-oxo-4-(4-methylphenyl)pyrimidine-1(2H)-yl)-4-methylbenzamide

    NASA Astrophysics Data System (ADS)

    Aydın, Lütfiye; Şahan, Emine; Önal, Zülbiye; Özpozan, Talat

    2014-08-01

    The title molecule, N-(5-(4-methylbenzoyl)-2-oxo-4-(4-methylphenyl)pyrimidine-1(2H)-yl)-4-methylbenzamide (C27H23N3O3), was synthesized and characterized by elemental analysis, IR, Raman, 1H and 13C NMR spectral data. To determine conformational flexibility, potential energy surfaces of the title compound were obtained by DFT regarding the selected degree of torsional freedom, which was varied from 0° to 360° in 6° and 20° steps. The ten conformers of the title compound were determined and it was found that the conformer 1 basis the most stable one. All conformers were also optimized by using the density functional theory (DFT/B3LYP) method with the 6-31G(d,p), 6-311G(d,p) and cc-pVDZ basis sets in the ground state. Potential energy distribution was calculated with the 6-31G(d,p) basis set. The vibrational spectra were recorded in solid phase IR and Raman spectra were compared based on the results of the theoretical calculations. The formation of hydrogen bonds was explained using natural bond orbital (NBO) analysis and spectroscopic analysis. NMR analysis and frontier molecular orbitals (FMOs) were also investigated by DFT.

  16. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: A combined experimental and density functional methods

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wang, Xueliang

    2015-01-01

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method.

  17. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: a combined experimental and density functional methods.

    PubMed

    Wang, Tao; Wang, Xueliang

    2015-01-25

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method. PMID:25123947

  18. Relationships Between Base-Catalyzed Hydrolysis Rates or Glutathione Reactivity for Acrylates and Methacrylates and Their NMR Spectra or Heat of Formation

    PubMed Central

    Fujisawa, Seiichiro; Kadoma, Yoshinori

    2012-01-01

    The NMR chemical shift, i.e., the π-electron density of the double bond, of acrylates and methacrylates is related to the reactivity of their monomers. We investigated quantitative structure-property relationships (QSPRs) between the base-catalyzed hydrolysis rate constants (k1) or the rate constant with glutathione (GSH) (log kGSH) for acrylates and methacrylates and the 13C NMR chemical shifts of their α,β-unsaturated carbonyl groups (δCα and δCβ) or heat of formation (Hf) calculated by the semi-empirical MO method. Reported data for the independent variables were employed. A significant linear relationship between k1 and δCβ, but not δCα, was obtained for methacrylates (r2 = 0.93), but not for acrylates. Also, a significant relationship between k1 and Hf was obtained for both acrylates and methacrylates (r2 = 0.89). By contrast, log kGSH for acrylates and methacrylates was linearly related to their δCβ (r2 = 0.99), but not to Hf. These findings indicate that the 13C NMR chemical shifts and calculated Hf values for acrylates and methacrylates could be valuable for estimating the hydrolysis rate constants and GSH reactivity of these compounds. Also, these data for monomers may be an important tool for examining mechanisms of reactivity. PMID:22754331

  19. Moving NMR

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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.

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

    PubMed

    Vosegaard, Thomas

    2015-04-01

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

  1. The contribution of magnetic susceptibility effects to transmembrane chemical shift differences in the 31P NMR spectra of oxygenated erythrocyte suspensions.

    PubMed

    Kirk, K; Kuchel, P W

    1988-01-01

    Triethyl phosphate, dimethyl methylphosphonate, and the hypophosphite ion all contain the phosphoryl functional group. When added to an oxygenated erythrocyte suspension, the former compound gives rise to a single 31P NMR resonance, whereas the latter compounds give rise to separate intra- and extracellular 31P NMR resonances. On the basis of experiments with intact oxygenated cell suspensions (in which the hematocrit was varied) and with oxygenated cell lysates (in which the lysate concentration was varied), it was concluded that the chemical shifts of the intra- and extracellular populations of triethyl phosphate differ as a consequence of the diamagnetic susceptibility of intracellular oxyhemoglobin but that this difference is averaged by the rapid exchange of the compound across the cell membrane. The difference in the magnetic susceptibility of the intra- and extracellular compartments contributes to the observed separation of the intra- and extracellular resonances of dimethyl methylphosphonate and hypophosphite. The magnitude of this contribution is, however, substantially less than that calculated using a simple two-compartment model and varies with the hematocrit of the suspension. Furthermore, it is insufficient to fully account for the transmembrane chemical shift differences observed for dimethyl methylphosphonate and hypophosphite. An additional effect is operating to move the intracellular resonances of these compounds to a lower chemical shift. The effect is mediated by an intracellular component, and the magnitude of the resultant chemical shift variations depends upon the chemical structure of the phosphoryl compound involved. PMID:3275636

  2. /sup 13/C and /sup 1/H NMR spectra and structure of the products from the condensation of 1,3-dicarbonyl compounds with aldehydes

    SciTech Connect

    Emelina, E.E.; Gindin, V.A.; Ershov, B.A.

    1988-05-20

    The structure of the diadducts formed in the reaction of 1,3-dicarbonyl compounds with aldehydes in a ratio of 2:1 under the conditions of the Knoevenagel condensation was studied by /sup 13/C and /sup 1/H NMR spectroscopy. It was shown that acyclic tetracarbonyl compounds are formed in the absence of a catalyst while substituted cyclohexanones are formed in the presence of piperidine. The acyclic tetracarbonyl compounds exist mainly in the tetraketo form in solution, and the presence of the monoenol form was established for dimethyl 2,4-diacetylpentanedioate in CD/sub 2/Cl/sub 2/. The most characteristic signals which distinguish between the cyclic diadducts and the acyclic products are the signals of the C/sup 5/ (delta 72 ppm) and C/sup 6/ (delta 52 ppm) atoms. The presence of a keto-enol equilibrium in 2,4-diacetyl-5-hydroxy-3-(p-methoxyphenyl)-5-methylcyclohexanone was demonstrated by /sup 13/C NMR.

  3. Contribution of magnetic susceptibility effects to transmembrane chemical shift differences in the /sup 31/P NMR spectra of oxygenated erythrocyte suspensions

    SciTech Connect

    Kirk, K.; Kuchel, P.W.

    1988-01-05

    Triethyl phosphate, dimethyl methylphosphonate, and the hypophosphite ion all contain the phosphoryl functional group. When added to an oxygenated erythrocyte suspension, the former compound gives rise to a single /sup 31/P NMR resonance, whereas the latter compounds give rise to separate intra- and extracellular /sup 31/P NMR resonances. On the basis of experiments with intact oxygenated cell suspensions (in which the hematocrit was varied) and with oxygenated cell lysates (in which the lysate concentration was varied) it was concluded that the chemical shifts of the intra- and extracellular populations of triethyl phosphate differ as a consequence of the diamagnetic susceptibility of intracellular oxyhemoglobin but that this difference is averaged by the rapid exchange of the compound across the cell membrane. The difference is the magnetic susceptibility of the intra- and extracellular compartments contributes to the observed separation of the intra- and extracellular resonances of dimethyl methylphosphonate and hypophosphite. The magnitude of this contribution is, however, substantially less than that calculated using a simple two-compartment model and varies with the hematocrit of the suspension. Furthermore, it is insufficient to fully account for the transmembrane chemical shift differences observed for dimethyl methylphosphonate and hypophosphite. An additional effect is operating to move the intracellular resonances of these compounds to a lower chemical shift. The effect is mediated by an intracellular component, and the magnitude of the resultant chemical shift variations depends upon the chemical structure of the phosphoryl compound involved.

  4. Neutron Interactions With 7Be and the Primordial 7Li Problem

    NASA Astrophysics Data System (ADS)

    Kading, Emily E.; Gai, Moshe; Kahn, Merav; Lee, Morit; Tessler, Moshe; Paul, Michael; Weiss, Aryeh; Berkovitz, Dan; Halfon, Shlomi; Kijel, Danny; Kreisel, Arik; Shor, Asher; Silverman, Ido; Weissman, Leonid; Hass, Michael; Mukul, Ish; Maugeri, Emilio A.; Dressler, Rugard; Schumann, Dorothea; Heinitz, Stephan; Stora, Thierry; Ticehurst, David; Howell, Calvin R.

    2015-10-01

    We study the interaction of neutrons with 7Be to estimate the direct destruction of 7Be during BBN; i.e. the predicted primordial 7Li. We plan to use a 7Be target (15 GBq) prepared by electro-deposition at PSI. The intense neutron flux of up to 5×1010 n/sec/cm2 are produced with proton beams and a high power liquid-lithium target (LiLiT) from the SARAF (phase I) facility in Israel. The outgoing particles will be measured using CR-39 plates that were tested to be insensitive to the large neutron flux and were calibrated with protons and alpha-particles from the TUNL. In a separate stage implanted 7Be target will be prepared at the ISOLDE facility of CERN. The results of the calibration of the CR-39 plates and the test experiment at SARAF with 10B target as well as a very low activity 7Be test target prepared at PSI, will be presented. Supported in part by the US-Israel Binational Science Foundation Proposal No. 2012098, the USDOE Grants No. DE-FG02-94ER40870, DE-FG02-97ER41033, and the Pazi Foundation, Israel.

  5. Systematics of the breakup probability function for 6Li and 7Li projectiles

    NASA Astrophysics Data System (ADS)

    Capurro, O. A.; Pacheco, A. J.; Arazi, A.; Carnelli, P. F. F.; Fernández Niello, J. O.; Martinez Heimann, D.

    2016-01-01

    Experimental non-capture breakup cross sections can be used to determine the probability of projectile and ejectile fragmentation in nuclear reactions involving weakly bound nuclei. Recently, the probability of both type of dissociations has been analyzed in nuclear reactions involving 9Be projectiles onto various heavy targets at sub-barrier energies. In the present work we extend this kind of systematic analysis to the case of 6Li and 7Li projectiles with the purpose of investigating general features of projectile-like breakup probabilities for reactions induced by stable weakly bound nuclei. For that purpose we have obtained the probabilities of projectile and ejectile breakup for a large number of systems, starting from a compilation of the corresponding reported non-capture breakup cross sections. We parametrize the results in accordance with the previous studies for the case of beryllium projectiles, and we discuss their systematic behavior as a function of the projectile, the target mass and the reaction Q-value.

  6. Optimization of the {sup 7}Li(p,n) proton beam energy for BNCT applications

    SciTech Connect

    Bleuel, B.L.; Donahue, R.J.

    1996-05-01

    The reaction {sup 7}Li(p,n){sup 7} Be has been proposed as an accelerator-based source of neutrons for Boron Neutron Capture Therapy (BNCT). This reaction has a large steep resonance for proton energies of about 2.3 MeV which ends at about 2.5 MeV. It has generally been accepted that one should use 2.5 MeV protons to get the highest yield of neutrons for BNCT. This paper suggests that for BNCT the optimum proton energy may be about 2.3 MeV and that a proton energy of about 2.2 MeV will provide the same useful neutron flux outside a thinner moderator as the neutron flux from a 2.5 MeV proton beam with a, thicker moderator. These results are based on optimization of the useful neutron spectrum in air at the point of irradiation, not on depth-dose profiles in tissue/tumor.

  7. Exclusive Measurements of Breakup Reactions in the {sup 7}Li+{sup 144}Sm System

    SciTech Connect

    Heimann, D. Martinez; Pacheco, A. J.; Arazi, A.; Figueira, J. M.; Negri, A.; Capurro, O. A.; Carnelli, P.; Fimiani, L.; Grinberg, P.; Marti, G. V.; Testoni, J. E.; Monteiro, D. S.; Marta, H. D.

    2009-03-04

    Breakup reactions induced by a 30 MeV {sup 7}Li beam on a {sup 144}Sm target were measured through the coincident detection of the light particles emitted in the reaction plane. The emphasis of the measurements and data analysis was placed in the complete characterization of the reaction by means of the identification of the breakup products and the experimental extraction of the physically relevant magnitudes. The coincident yield of the emitted light particles was compared with the results of kinematical calculations that were done assuming different distributions for these magnitudes and taking into account the geometric response of the detection system. The results of this comparison indicate in all cases a clear dominance of a process compatible with the breakup of {sup 6}Li through the 3{sup +} resonant state at 2.186 MeV following one-neutron transfer from the projectile to the target, over the breakup of the projectile itself. Relative cross sections as a function of the emission angle of the {sup 6}Li and the in-plane anisotropy of the subsequent emission of breakup products were extracted from the data.

  8. Comparison of corrosion behavior of EUROFER and CLAM steels in flowing Pb-15.7Li

    NASA Astrophysics Data System (ADS)

    Konys, J.; Krauss, W.; Zhu, Z.; Huang, Q.

    2014-12-01

    Ferritic martensitic steels are envisaged to be applied as structural materials in HCLL blanket systems. Their compatibility with the liquid breeder, which is in direct contact with the structural alloy, will be essential for reliable and safe operation of the designed blankets. Formerly performed corrosion tests of RAFM steels in PICOLO loop of KIT were mainly done at high flow velocities, e.g., 0.22 m/s and delivered severe attack with material loss rates above 400 μm/yr at 823 K. Meanwhile, flow velocities for corrosion testing have been reduced into the 'cm range' to be near fusion relevant conditions. Among the international ITER-partners, many varieties of RAFM steels have been developed and manufactured within the last decade, e.g., the so-called Chinese Low Activation Martensitic steel (CLAM). In this paper, the long term corrosion behavior of EUROFER and CLAM steel in flowing Pb-15.7Li will be presented at a flow velocity of about 0.10 m/s and compared with earlier obtained results of RAFM steels exposed at other operation parameters of PICOLO loop. The observed corrosion attack is near 220 μm/yr and fits well to predictions made by MATLIM-modeling for low flow velocities in the turbulent flow regime.

  9. The 10B(n,α0)7Li and 10B(n,αlγ)7Li alpha-particle angular distributions, branching ratios and cross-sections measurements for En < 3 MeV

    NASA Astrophysics Data System (ADS)

    Hambsch, F. J.; Ruskov, I.; Vidali, M.

    2010-01-01

    The 10B(n,α0)7Li and 10B(n,αiγ)7Li angular distributions have been measured at the GELINA time-of-flight spectrometer in the incident neutron energy range from 0.1 keV to 1 MeV by means of a twin Frisch-grid ionization chamber. With this type of detector it is possible to measure the angular distribution of the charged reaction fragments in a close to 2×2π solid angle with ~100% efficiency and a clear separation of both reaction channels: emission to the 7Li ground state (α0) or to its first excited state (α1). A strong angular anisotropy was observed at ~ 520 keV. In order to extend the energy range up to 2.5-3 MeV and to measure, also, the reaction cross sections, a double twin Frisch-grid ionization chamber was constructed. It is loaded with two very thin 94% 10B-enriched samples, mounted back-to-back with 235U samples on the common cathodes. New data acquisition, visualization and analysis software is used in a new set of long-term measurements, which are still going on.

  10. Production cross section of At radionuclides from 7Li+natPb and 9Be+natTl reactions

    NASA Astrophysics Data System (ADS)

    Maiti, Moumita; Lahiri, Susanta

    2011-12-01

    Earlier we reported theoretical studies on the probable production of astatine radionuclides from 6,7Li- and 9Be-induced reactions on natural lead and thallium targets, respectively. The production of astatine radionuclides were investigated experimentally with two heavy-ion-induced reactions: 9Be + natTl and 7Li + natPb. Formation cross sections of the evaporation residues, 207,208,209,210At, produced in the (HI,xn) channel, were measured by the stacked-foil technique followed by off-line γ spectrometry at low incident energies (<50 MeV). Measured excitation functions were interpreted in terms of a compound nuclear reaction mechanism using Weisskopf-Ewing and Hauser-Feshbach models. Measured cross-section values are lower than the respective theoretical predictions.

  11. Multinuclear NMR Imaging of Fluid Phases in Berea Sandstone

    NASA Astrophysics Data System (ADS)

    Sarkar, S. N.; Dechter, J. J.; Komoroski, R. A.

    Multinuclear NMR of 7Li, 19F, and 1H has been investigated as a method for discriminating multiple fluid phases in porous rock. Good 7Li NMR images from LiCl brine in saturated Berea sandstone were obtained within a few hours at 1 × 1 × 5 mm 3 resolution using a low-TE, 3D volume imaging sequence. At 4.7 T, the 7Li T1 was 750 ms, and T2 was 10 ms. High-quality 19F and 1H images of a model fluorinated injectant (trifluorotoluene) in Berea were obtained at 0.4 × 0.4 × 3 mm 3 resolution in a few hours. Fluorine-19 imaging was found to be easier than 1H imaging due to the narrower 19F resonance and comparable T1 and T2 in Berea sandstone. Lithium-7 and 19F imaging offer alternatives for discriminating aqueous and organic phases unambiguously in flooded oil cores, especially where 1H signals for the two phases are unresolved.

  12. Microanalytical techniques for boron analysis using the 10B(n,alpha)7Li reaction.

    PubMed

    Fairchild, R G; Gabel, D; Laster, B H; Greenberg, D; Kiszenick, W; Micca, P L

    1986-01-01

    In order to predict the efficacy of boronated compounds for neutron capture therapy (NCT), it is mandatory that the boron concentration in tissues be known. Various techniques for measurement of trace amounts of boron (1-100 ppm) are available, including chemical and physical procedures. Experience has shown that, with the polyhedral boranes and carboranes in particular, the usual colorimetric and spark emission spectroscopic methods are not reliable. Although these compounds may be traced with additional radiolabels, direct physical detection of boron by nondestructive methods is clearly preferable. Boron analysis via detection of the prompt-gamma ray from the 10B(n, alpha)7Li reaction has been shown to be a reliable technique. Two prompt-gamma facilities developed at Brookhaven National Laboratory are described. One, at the 60-MW high flux beam reactor, uses sophisticated beam extraction techniques to enhance thermal neutron intensity and reduce fast neutron and gamma contamination. The other was constructed at Brookhaven's 5-MW medical research reactor and uses conventional shielding and electronics to provide an "on-line" boron analysis facility adjacent to beams designed for NCT, thus satisfying one of the requisites for clinical application of this procedure. Technical restrictions attendant upon the synthesis and testing of boronated biomolecules often require the measurement of trace amounts of boron in extremely small (mg) samples. A track-etching technique capable of detecting ng amounts of boron in mg liquid or cell samples is described. Thus it is possible to measure the boron content in small amounts (mg samples) of antibodies, or boron uptake in cells grown in tissue culture. PMID:3951409

  13. Cross sections for neutron-producing reactions induced by 14. 1 MeV neutrons incident on /sup 6/Li, /sup 7/Li, /sup 10/B, /sup 11/B, and carbon

    SciTech Connect

    Drosg, M.; Lisowski, P.W.; Drake, D.M.; Hardekopf, R.A.; Muellner, M.

    1988-10-01

    Using the time-of-flight technique, we have measured neutron emission spectra for /sup 6/Li, /sup 7/Li, /sup 10/B, /sup 11/B and carbon at an incident neutron energy of 14.1 MeV and at 10 angles between 30/degree/ and 143/degree/. Double differential cross sections and their integrated values have been extracted and are presented in tables and graphs. The nonelastic portion of the neutron emission spectra is noticeably higher than expected which may be due to uncertainties in the input library (ENDF/B-IV) used in the Monte Carlo correction for multiple scattering. In particular, the library for /sup 11/B appears to be very unrealistic with an integrated elastic cross section which should be higher by 50%. 20 refs., 1 fig., 12 tabs.

  14. QUANTITATIVE 15N NMR SPECTROSCOPY

    EPA Science Inventory

    Line intensities in 15N NMR spectra are strongly influenced by spin-lattice and spin-spin relaxation times, relaxation mechanisms and experimental conditions. Special care has to be taken in using 15N spectra for quantitative purposes. Quantitative aspects are discussed for the 1...

  15. Fragmentation of {sup 7}Li relativistic nuclei on a proton into the {sup 3}H + {sup 4}He channel

    SciTech Connect

    Peresadko, N. G.; Alexandrov, Yu. A. Gerasimov, S. G.; Dronov, V. A.; Larionova, V. G.; Pisetskaya, A. V.; Tamm, E. I.; Fetisov, V. N.; Kharlamov, S. P.; Shesterkina, L. N.

    2010-11-15

    In a track nuclear photoemulsion exposed to a beam of {sup 7}Li nuclei accelerated to a momentum of 3 GeV/c per nucleon at the synchrophasotron of the Joint Institute for Nuclear Research (JINR, Dubna), 13 events in which {sup 7}Li nuclei interacting with protons break up into {sup 3}H and {sup 4}He fragments were detected among 3730 inelastic-interaction events. For this fragmentation channel, the cross section was found to be 8 {+-} 2 mb. The average value of the fragment total transverse momentum was 214 {+-} 5 MeV/c. This value exceeds markedly the average value of the transverse-momentum transfer in the coherent dissociation of {sup 7}Li nuclei on track-emulsion nuclei (166{+-}5MeV/c). The recoil-proton transverse momentum was on average 98% of the total proton momentum. The longitudinal-momentum distribution of protons was characterized by a variance of 16 MeV/c and a mean value of 37 {+-} 2MeV/c.

  16. Threshold behavior of interaction potential for the system 7Li + 64Ni: Comparison with 6Li + 64Ni

    NASA Astrophysics Data System (ADS)

    Shaikh, Md. Moin; Das, Mili; Roy, Subinit; Sinha, M.; Pradhan, M. K.; Basu, P.; Datta, U.; Ramachandran, K.; Shrivastava, A.

    2016-09-01

    The elastic scattering angular distributions for the system 7Li + 64Ni were measured in the bombarding energy range of 12 MeV ≤Elab ≤ 26.4 MeV. A phenomenological optical model analysis was performed for the measured data. The strengths of the fitted potential components at the surface were estimated to extract their variation with energy. Further analyses of the measured angular distributions were performed with a hybrid potential composed of a renormalized folded real and a phenomenological imaginary potential. Both the model potentials predict similar energy dependent behavior for the effective interaction potential around the barrier. Unlike the heavy targets, 7Li + 64Ni does not show a normal threshold behavior. It also does not clearly exhibit a behavior similar to 6Li + 64Ni. The real potential for 7Li + 64Ni does not exhibit any significant energy dependence and the imaginary potential strength remains almost independent of energy above the Coulomb barrier (∼ 14 MeV). However, at energies below the barrier, a sudden drop in the imaginary potential strength is observed.

  17. Cumulative “roof effect” in high-resolution in vivo 31P NMR spectra of human calf muscle and the Clebsch Gordan coefficients of ATP at 1.5 T

    NASA Astrophysics Data System (ADS)

    Schröder, Leif; Schmitz, Christian; Bachert, Peter

    2005-05-01

    NMR spectra of non-weakly coupled spin systems exhibit asymmetries in line intensities known as "roof effect" in 1D spectroscopy. Due to limited spectral resolution, this effect has not been paid much attention so far in in vivo spectroscopy. But when high-quality spectra are obtained, this effect should be taken into account to explain the quantum-mechanical fine structure of the system. Adenosine 5'-triphosphate (ATP) represents a 31P spin system with multiple line splittings which are caused by J-couplings of medium strength at 1.5 T. We analyzed the ATP roof effect in vivo, especially for the β-ATP multiplet. The intensities of its outer resonances deviate by ca. 12.5% from a symmetrical triplet. As this asymmetry reflects the transition from Paschen-Back to Zeeman effect with total spin that is largely broken up, the Clebsch-Gordan coefficients of the system can be indicated in analogy to the hyperfine structure of hydrogen. Taking the roof effect into account, the χ2 of fitting in vivo ATP resonances is reduced by ca. 9% ( p < 0.005).

  18. Vibrational analysis using FT-IR, FT-Raman spectra and HF-DFT methods and NBO, NLO, NMR, HOMO-LUMO, UV and electronic transitions studies on 2,2,4-trimethyl pentane

    NASA Astrophysics Data System (ADS)

    Suvitha, A.; Periandy, S.; Govindarajan, M.; Gayathri, P.

    2015-03-01

    In this work, the vibrational spectral analysis was carried out by using Raman and infrared spectroscopy in the range 100-4000 cm-1and 50-4000 cm-1, respectively, for 2,2,4-Trimethyl Pentane, TMP (C8H18) molecule. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and geometrical parameter calculations based on Hartree Fock (HF) and density functional theory (DFT) method with 6-311++G(d,p) basis set. The scaled B3LYP/6-311++G(d,p) results shows the best agreement with the experimental values over the other method. The calculated HOMO and LUMO energies shows that charge transfer within the molecule. The physical reactions of single bond hydrocarbon TMP were investigated. The results of the calculations were applied to simulate spectra of the title compound, which shows the excellent agreement with observed spectra. Besides, Mulliken atomic charges, UV, frontier molecular orbital (FMO), MEP, NLO activity, Natural Bond-Orbital (NBO) analysis, NMR and thermodynamic properties of title molecule were also performed.

  19. FT-IR, FT-Raman, NMR spectra, density functional computations of the vibrational assignments (for monomer and dimer) and molecular geometry of anticancer drug 7-amino-2-methylchromone

    NASA Astrophysics Data System (ADS)

    Mariappan, G.; Sundaraganesan, N.

    2014-04-01

    Vibrational assignments for the 7-amino-2-methylchromone (abbreviated as 7A2MC) molecule using a combination of experimental vibrational spectroscopic measurements and ab initio computational methods are reported. The optimized geometry, intermolecular hydrogen bonding, first order hyperpolarizability and harmonic vibrational wavenumbers of 7A2MC have been investigated with the help of B3LYP density functional theory method. The calculated molecular geometry parameters, the theoretically computed vibrational frequencies for monomer and dimer and relative peak intensities were compared with experimental data. DFT calculations using the B3LYP method and 6-31 + G(d,p) basis set were found to yield results that are very comparable to experimental IR and Raman spectra. Detailed vibrational assignments were performed with DFT calculations and the potential energy distribution (PED) obtained from the Vibrational Energy Distribution Analysis (VEDA) program. Natural Bond Orbital (NBO) study revealed the characteristics of the electronic delocalization of the molecular structure. 13C and 1H NMR spectra have been recorded and 13C and 1H nuclear magnetic resonance chemical shifts of the molecule have been calculated using the gauge independent atomic orbital (GIAO) method. Furthermore, All the possible calculated values are analyzed using correlation coefficients linear fitting equation and are shown strong correlation with the experimental data.

  20. Hydrothermal synthesis, X-ray structure refinement, 31P NMR spectra and vibrational study of NaLa(HPO4)2

    NASA Astrophysics Data System (ADS)

    Ben Hassen, C.; Boujelbene, M.; Mhiri, T.

    2013-10-01

    NaLa(HPO4)2 was obtained by hydrothermal synthesis. The structure of NaLa(HPO4)2 was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed a space group P21/c (No. 14), with lattice parameters of a = 9.7151(17) Å, b = 8.320(12) Å, c = 9.83(2) Å, beta = 114.65(17)°, V = 722 (8) Å3 and Z = 4. Final refinement led to RF = 4.86% and RB = 12.35%.The existence of bound O-H and bound P-O in the structure has been confirmed by IR and Raman spectroscopy. The existence of two crystallographically independent phosphorus atoms in the structure has been confirmed by NMR spectrum. The structure is characterized by LaO6 octahedra which are solely connected to six adjacent HPO4 tetrahedra via common O-corners. This structure contains twelve- and four-membered rings forming channels along [1 1¯ 1]. The cross sections of the channels are given by twelve-membered rings consisting of four lanthanum coordination octahedral and eight hydrogenphosphate groups as well as four-membered rings consisting of two lanthanum coordination octahedra and two hydrogenphosphate tetrahedra. Sodium ions are located within those channels of the twelve-membered rings.

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

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-05-15

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

  2. A sequential assignment procedure for proteins that have intermediate line widths in MAS NMR spectra: amyloid fibrils of human CA150.WW2.

    PubMed

    Becker, Johanna; Ferguson, Neil; Flinders, Jeremy; van Rossum, Barth-Jan; Fersht, Alan R; Oschkinat, Hartmut

    2008-08-11

    The second WW domain (WW2) of CA150, a human transcriptional activator, forms amyloid fibrils in vitro under physiological conditions. Based on experimental constraints from MAS NMR spectroscopy experiments, alanine scanning and electron microscopy, a structural model of CA150.WW2 amyloid fibrils was calculated earlier. Here, the assignment strategy is presented and suggested as a general approach for proteins that show intermediate line width. The (13)C,(13)C correlation experiments were recorded on fully or partially (13)C-labelled fibrils. The earlier (13)C assignment (26 residues) was extended to 34 of the 40 residues by direct (13)C-excitation experiments by using a deuterated sample that showed strongly improved line width. A 3D HNC-TEDOR (transferred-echo double-resonance) experiment with deuterated CA150.WW2 fibrils yielded 14 amide nitrogen and proton resonance assignments. The obtained chemical shifts were compared with the chemical shifts determined with the natively folded WW domain. TALOS (Torsion angle likelihood obtained from shift and sequence similarity) predictions confirmed that, under physiological conditions, the fibrillar form of CA150.WW2 adopts a significantly different beta structure than the native WW-domain fold. PMID:18642254

  3. High-Speed Magic-Angle Spinning 13C MAS NMR Spectra of Adamantane: Self-Decoupling of the Heteronuclear Scalar Interaction and Proton Spin Diffusion

    NASA Astrophysics Data System (ADS)

    Ernst, Matthias; Verhoeven, Aswin; Meier, Beat H.

    1998-02-01

    We have investigated the carbon line shape of solid adamantane under high-speed magic-angle sample spinning (MAS) acquired without proton decoupling. The CH-group shows a spinning-speed-dependent line broadening while the CH2-group consists of a spinning-speed-independent sharp component and a spinning-speed-dependent broader part. These phenomena can be explained by self-decoupling of theJ-interaction due to proton spin diffusion. Such a self-decoupling process can be described by a magnetization exchange process between the multiplet lines. Changing the spin-diffusion rate constant by off-resonance irradiation of the protons allows us to observe the full range from slow exchange to coalescence to fast exchange of the carbon spectra. One of the multiplet components in the CH2-group corresponds to a group spin of the protons of zero and therefore does not couple to the other protons. This gives rise to the sharp central line. The magnetization exchange rate constant between the different multiplet lines can be determined from the spectra and is a measure for the spinning-speed-dependent proton spin-diffusion rate constant. Even at an MAS speed of 30 kHz, proton spin diffusion is still observable despite the relatively weak intermolecular proton dipolar-coupling network in adamantane which results in a static proton line width of only 14 kHz (full width at half height).

  4. The relationship between environmental abundant electromagnetic fields and packaging shape to their effects on the 17O NMR and Raman spectra of H2O-NaCl

    NASA Astrophysics Data System (ADS)

    Abdelsamie, Maher A. A.; Rahman, Russly B. Abdul; Mustafa, Shuhaimi; Hashim, Dzulkifly

    2015-07-01

    In this study, two identical groups of four containers with different packaging shapes made of polymethyl methacrylate (PMMA) were used to store H2O-NaCl solution for seven days at ambient room temperature (25 °C). Faraday shield was used to shield one group. The surrounding electromagnetic fields were measured during the storage period by using R&S®TS-EMF EMF measurement system. Samples of H2O-NaCl were collected at the end of the storage period and examined by 17Oxygene nuclear magnetic resonance spectroscopy (17O NMR) and Raman spectroscopy. Electromagnetic simulation was used to explore the relationship between the packaging shape of H2O-NaCl containers and the environmentally abundant electromagnetic fields to their effects on the cluster size of water. The study showed variations in the cluster size of water stored inside the two groups of containers. It was observed that the cluster size of water stored in the unshielded containers was lower than that of the shielded containers. The cluster size of water stored in the unshielded pyramidal container was lower than the cluster size of water stored in the unshielded rectangular, square, and cylindrical containers. The EM simulation results showed significant variations in the total specific absorption rate SAR and maximum point SAR values induced in the H2O-NaCl solution in the unshielded container models at 2400 MHz for both vertical and horizontal polarization. It can be concluded that the variations in the values of SAR induced in H2O-NaCl solution are directly related to the variations in the cluster size of the stored water.

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

    ERIC Educational Resources Information Center

    Mills, Nancy S.; Shanklin, Michael

    2011-01-01

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

  6. Improved information on the 7Li+p{yields}{alpha}+{alpha} reaction via the Trojan Horse Method applied to the 3He break-up

    SciTech Connect

    Tumino, A.; Spitaleri, C.; Sergi, M. L.; Cherubini, S.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Romano, S.; Tudisco, S.; Kroha, V.; Burjan, V.; Novac, J.; Vincour, J.; Fulop, S.; Somorjai, E.

    2006-04-26

    The astrophysically relevant 7Li+p{yields}{alpha}+{alpha} reaction was investigated via the THM by selecting the quasi-free contribution to the measured 3He+7Li{yields}{alpha}+{alpha}+d three-body process. This investigation is mainly aimed at testing the validity of the pole approximation in the THM against the bound structure of the Trojan-horse nucleus. The three-body experiment was performed at 33 MeV, corresponding to a 7Li-p relative energy ranging from 0.2 to 7 MeV. The quasi-free 7Li+p cross-section was compared with the free reaction cross-section as well as with indirect data from a previous THM experiment. The good agreement between data sets throughout the energy range investigated provided a very important validity test of the pole approximation for the THM.

  7. 1H NMR, electronic-absorption and resonance-Raman spectra of isomeric okenone as compared with those of isomeric β-carotene, canthaxanthin, β-apo-8'-carotenal and spheroidene

    NASA Astrophysics Data System (ADS)

    Fujii, Ritsuko; Chen, Chun-Hai; Mizoguchi, Tadashi; Koyama, Yasushi

    1998-05-01

    Eleven cis- trans isomers of okenone were isolated by means of HPLC using a silica-gel column from an isomeric mixture which was obtained by iodine-sensitized photo-isomerization of the all- trans isomer. The configurations of eight isomers among them were determined by NMR spectroscopy using the isomerization shifts of the olefinic 1Hs and the 1H- 1H NOE correlations to be all- trans, 7- cis, 7- cis,8-s- cis, 9- cis, 9'- cis, 13- cis, 13'- cis and 9,9'-di- cis, and their electronic-absorption and resonance-Raman spectra were recorded. Based on the results: (1) the chemical shifts of the olefinic 1Hs in NMR; (2) the wavelength of the A g-→B u+ transition; and (3) the relative intensity of the A g-→A g+ versus the A g-→B u+ transition in electronic absorption; (4) the CC stretching frequency; and (5) the relative intensity of the C10-C11 (C10'-C11') versus the C14-C15 (C14'-C15') stretching vibration in resonance Raman were compared among the all- trans, 7- cis, 9- cis (9'- cis) and 13- cis (13'- cis) isomers of β-carotene, canthaxanthin, β-apo-8'-carotenal, neurosporene, spheroidene and okenone. Relevance of the systematic changes in the above five different parameters originally found in β-carotene was examined in the rest of the carotenoids, and the effects of the peripheral groups on them were explained in terms of the length and asymmetry of the conjugated system consisting of the CC and CO bonds.

  8. Simulations of molecular dynamics in solid-state NMR spectra of spin-1 nuclei including effects of CSA- and EFG-terms up to second order.

    PubMed

    Larsen, Flemming H

    2007-04-01

    By numerical simulations MAS and QCPMG methods for acquiring spectra of spin-1 nuclei were compared in order to determine the most sensitive experiment for analysis of molecular dynamics. To comply with the large quadrupolar constants for 14N and the CSA reported for 6Li both of these interactions are included up to second order. For 2H and 6Li both QCPMG and single-pulse MAS experiments were suitable for dynamics studies whereas the single-pulse MAS experiment were the method of choice for investigation of 14N dynamics for C(Q)'s larger than 750kHz at 14.1T. This property prohibits excitation of the 14N lineshape using either single hard or softer composite rf-pulses. Focusing on 14N it was demonstrated that the centerband lineshape is sensitive toward both off-MAS and CSA effects. In addition, excitation by real-time pulses showed that proper lineshapes corresponding to a site with a C(Q) of 3MHz may be excited by a very short pulse. PMID:17418539

  9. Destructions of {sup 7}Be and {sup 7}Li in Big Bang nucleosynthesis through reactions with exotic long-lived sub-strongly interacting massive particles

    SciTech Connect

    Kusakabe, Motohiko; Kawasaki, Masahiro

    2012-11-12

    An observed plateau abundance of {sup 7}Li in metal-poor halo stars indicates its primordial origin. The {sup 7}Li abundances are about a factor of three smaller than that predicted in standard big bang nucleosynthesis (BBN) model. In addition, some of the stars possibly contain {sup 6}Li in abundances larger than standard BBN prediction. Particle models sometimes include heavy longlived colored particles which are confined in exotic strongly interacting massive particles (SIMPs). We have found reactions which destroy {sup 7}Be and {sup 7}Li during BBN in the scenario of BBN affected by a long-lived sub-strongly interactingmassive particle (sub-SIMP, X). The reactions are non radiative X captures of {sup 7}Be and {sup 7}Li which can operate if the X particle interacts with nuclei strongly enough to drive {sup 7}Be destruction but not strongly enough to form a bound state with {sup 4}He of relative angular momentum L = 1. The processes can be a cause of the {sup 7}Li problem. In this paper we suggest new possible reactions for {sup 6}Li production. Especially, a {sup 6}Li production through the deuteron capture of {sup 4}He bound to X can operate in the parameter region solving the {sup 7}Li problem.

  10. Irradiation characteristics of BNCT using near-threshold 7Li(p, n)7Be direct neutrons: application to intra-operative BNCT for malignant brain tumours.

    PubMed

    Tanaka, Kenichi; Kobayashi, Tooru; Sakurai, Yoshinori; Nakagawa, Yoshinobu; Ishikawa, Masayori; Hoshi, Masaharu

    2002-08-21

    A calculation method for the dosage of neutrons by near-threshold 7Li(p, n)7Be and gamma rays by 7Li(p, p'gamma)7Li was validated through experiments with variable distance between the Li target and the phantom, focusing on large angular dependence. The production of neutrons and gamma rays in the Li target was calculated by Lee's method and their transport in the phantom was calculated using the MCNP-4B code. The dosage in intra-operative boron neutron capture therapy (BNCT) using near-threshold 7Li(p, n)7Be direct neutrons was evaluated using the validated calculation method. The effectiveness of the usage of the direct neutrons was confirmed from the existence of the region satisfying the requirements of the protocol utilized in intra-operative BNCT for brain tumours in Japan. The boron-dose enhancer (BDE) introduced in this paper to increase the contribution of the 10B(n, alpha)7Li dose in the living body was effective. The void utilized to increase the dose in deep regions was also effective with BDE. For the investigation of 1.900 MeV proton beams, for example, it was found that intraoperative BNCT using near-threshold 7Li(p, n)7Be direct neutrons is feasible. PMID:12222863

  11. Non-thermal processes in standard big bang nucleosynthesis: II. Two-body disintegration of D, 7Li, 7Be nuclei by fast neutrons

    NASA Astrophysics Data System (ADS)

    Voronchev, Victor T.; Nakamura, Makoto; Nakao, Yasuyuki

    2009-05-01

    Continuing the analysis of non-thermal effects in standard big bang nucleosynthesis (JCAP05(2008)010), we examine the role of suprathermal nuclear reactions induced in the early universe plasma by energetic nucleons of various origins. The processes of present interest are break-ups of D, 7Li, 7Be nuclei induced by 14-MeV neutrons generated in the plasma via the T(d, n)4He reaction. It is shown that this reaction forms the ensemble of fast neutrons whose fraction in the plasma neutron component is at the level of 0.01 %. In spite of the small percentage, such neutrons can effectively destroy the loosely bound D, 7Li, 7Be nuclei. It is found that at temperatures T9 < 0.8 the n-induced non-thermal break-ups of D and 7Li dominate over other reactions occurring in the n+D and n+7Li systems. However, the non-thermal neutronic effects prove to be insufficiently strong to modify the standard picture of nucleosynthesis. The D, 3He, 4He abundances are obtained to remain unchanged, and only a little effect is marked for primordial 7Li. The 0.01 % fraction of plasma neutrons (fast DT neutrons) reduces the 7Li abundance by 0.02 %.

  12. Microscopic Calculation of Astrophysical S-factor and Branching Ratio for the 3H(α, γ)7Li Reaction

    NASA Astrophysics Data System (ADS)

    Solovyev, Alexander S.; Igashov, Sergey Yu.; Tchuvill'sky, Yury M.

    2015-01-01

    In the present work the radiative capture reaction 3H(α, γ)7Li has been investigated. The astrophysical S-factor and the branching ratio of the reaction have been calculated within a microscopic approach - the algebraic version of the resonating-group model. The lowest compatible with the Pauli exclusion principle wave functions of the translation-invariant oscillator shell model are adopted as the internal wave functions of the colliding clusters. The modified Hasegawa-Nagata NN-potential was employed in the calculations. The results are in good agreement with the experimental data.

  13. R-matrix Analysis for the 8Be System and Features in the p+7Li Reaction Over Resonance Region

    NASA Astrophysics Data System (ADS)

    Kunieda, Satoshi

    2016-06-01

    A comprehensive R-matrix analysis is currently underway for the 8Be compound system toward a consistent evaluation of the p+7Li reaction cross-sections over the resonance energy region. In this analysis, the energy eigenvalues are fixed to the level energies given in ENSDF, and we searched for values of the boundary condition parameters as well as the reduced-width amplitudes. It is found that some additional levels are necessary to fit the resonant shape of experimental cross-sections. Besides, the channel radii obtained may be consistent with well-known physical pictures of the atomic nucleus.

  14. Epithermal neutron beams from the 7 Li(p,n) reaction near the threshold for neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Porras, I.; Praena, J.; Arias de Saavedra, F.; Pedrosa, M.; Esquinas, P.; L. Jiménez-Bonilla, P.

    2016-11-01

    Two applications for neutron capture therapy of epithermal neutron beams calculated from the 7Li ( p , n reaction are discussed. In particular, i) for a proton beam of 1920 keV of a 30 mA, a neutron beam of adequate features for BNCT is found at an angle of 80° from the forward direction; and ii) for a proton beam of 1910 keV, a neutron beam is obtained at the forward direction suitable for performing radiobiology experiments for the determination of the biological weighting factors of the fast dose component in neutron capture therapy.

  15. Elastic Scattering Of {sup 6,7}Li+{sup 80}Se At Near And Above Barrier Energies

    SciTech Connect

    Fimiani, L.; Marti, G. V.; Capurro, O. A.; Barbara, E. de; Testoni, J. E.; Zalazar, L.; Arazi, A.; Cardona, M. A.; Carnelli, P.; Figueira, J. M.; Hojman, D.; Martinez Heimann, D.; Negri, A. E.; Pacheco, A. J.; Fernandez Niello, J. O.

    2010-08-04

    In this work we propose to study the elastic scattering of the weakly bound projectiles {sup 6,7}Li on an intermediate mass target {sup 80}Se. From the experimental results presented here, precise angular distributions at energies below, around and above the nominal Coulomb barriers of the systems were obtained. The final goal of our work is to determine the characteristic parameters of the optical potential and use them to address the question of whether the usual threshold anomaly or the breakup threshold anomaly are present or not in these systems.

  16. Quasi-elastic Scattering Measurements in the {sup 6,7}Li+{sup 144}Sm Systems

    SciTech Connect

    Capurro, O. A.; Arazi, A.; Fernandez Niello, J. O.; Figueira, J. M.; Marti, G. V.; Martinez Heimann, D.; Negri, A. E.; Pacheco, A. J.; Monteiro, D. S.; Otomar, D. R.; Gomes, P. R. S.

    2009-06-03

    In the present work, results of measurements of quasi-elastic scattering cross sections using a silicon-telescope detector at backward angles are reported. They allowed us to deduce fusion barrier distributions from the first derivative of the corresponding excitation function (-d(d{sigma}{sub qes}/d{sigma}{sub Rut})/dE). We report data for the systems {sup 6,7}Li on {sup 144}Sm which are characterized by loosely bound projectiles onto a closed neutron shell target. The experimental excitation functions and the associated barrier distributions are compared for both systems.

  17. Breakup Reactions and Exclusive Measurements in the {sup 6,7}Li+{sup 144}Sm Systems

    SciTech Connect

    Heimann, D. Martinez; Pacheco, A. J.; Arazi, A.; Figueira, J. M.; Negri, A. E.; Capurro, O. A.; Carnelli, P.; Fimiani, L.; Grinberg, P.; Marti, G. V.; Testoni, J. E.; Monteiro, D. S.; Marta, H. D.

    2009-06-03

    The breakup of the projectile-like nuclei in reactions induced by 30 MeV {sup 6}Li and {sup 7}Li beams on a {sup 144}Sm target have been measured through the coincident detection of the in-plane emitted light particles. The primary ion that undergoes breakup has been identified and the physically meaningful variables that characterize the reaction have been obtained on a purely experimental basis. Distributions have been obtained for both the binary emission angle and for the breakup emission angle in the reference frame of the breakup products.

  18. 19F-decoupling of half-integer spin quadrupolar nuclei in solid-state NMR: application of frequency-swept decoupling methods.

    PubMed

    Chandran, C Vinod; Hempel, Günter; Bräuniger, Thomas

    2011-09-01

    In solid-state NMR studies of minerals and ion conductors, quadrupolar nuclei like (7)Li, (23)Na or (133)Cs are frequently situated in close proximity to fluorine, so that application of (19)F decoupling is beneficial for spectral resolution. Here, we compare the decoupling efficiency of various multi-pulse decoupling sequences by acquiring (19)F-decoupled (23)Na-NMR spectra of cryolite (Na(3)AlF(6)). Whereas the MAS spectrum is only marginally affected by application of (19)F decoupling, the 3Q-filtered (23)Na signal is very sensitive to it, as the de-phasing caused by the dipolar interaction between sodium and fluorine is three-fold magnified. Experimentally, we find that at moderate MAS speeds, the decoupling efficiencies of the frequency-swept decoupling schemes SW(f)-TPPM and SW(f)-SPINAL are significantly better than the conventional TPPM and SPINAL sequences. The frequency-swept sequences are therefore the methods of choice for efficient decoupling of quadrupolar nuclei with half-integer spin from fluorine. PMID:21856132

  19. A Guided Inquiry Approach to NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

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

    1998-04-01

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

  20. Paramagnetic shimming for wide-range variable-field NMR.

    PubMed

    Ichijo, Naoki; Takeda, Kazuyuki; Takegoshi, K

    2014-09-01

    We propose a new passive shimming strategy for variable-field NMR experiments, in which the magnetic field produced by paramagnetic shim pieces placed inside the magnet bore compensates the inhomogeneity of a variable-field magnet for a wide range of magnet currents. Paramagnetic shimming is demonstrated in (7)Li, (87)Rb, and (45)Sc NMR of a liquid solution sample in magnetic fields of 3.4, 4.0, and 5.4T at a fixed carrier frequency of 56.0MHz. Since both the main-field inhomogeneity and the paramagnetic magnetization are proportional to the main-magnet current, the resonance lines are equally narrowed by the improved field homogeneity with an identical configuration of the paramagnetic shim pieces. Paramagnetic shimming presented in this work opens the possibility of high-resolution variable-field NMR experiments. PMID:25080372

  1. On the hyperfine structures of the ground state(s) in the 6Li and 7Li atoms

    NASA Astrophysics Data System (ADS)

    Frolov, A. M.

    2016-06-01

    Hyperfine structure of the ground 22 S-states of the three-electron atoms and ions is investigated. By using our recent numerical values for the doublet electron density at the atomic nucleus we determine the hyperfine structure of the ground (doublet) 22 S-state(s) in the 6Li and 7Li atoms. Our predicted values (228.2058MHz and 803.5581MHz, respectivly) agree well with the experimental values 228.20528(8) MHz (6Li) and 803.50404(48) MHz (7Li (R.G. Schlecht and D.W. McColm, Phys. Rev. 142, 11 (1966))). The hyperfine structures of a number of lithium isotopes with short life-times, including 8Li, 9Li and 11Li atoms are also predicted. The same method is used to obtain the hyperfine structures of the three-electron 7Be+ and 9Be+ ions in their ground 22 S-states. Finally, we conclude that our approach can be generalized to describe the hyperfine structure in the triplet n 3 S-states of the four-electron atoms and ions.

  2. Using the Doppler broadened γ line of the 10B(n,αγ)7Li reaction for thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Ben-Galim, Y.; Wengrowicz, U.; Moreh, R.; Orion, I.; Raveh, A.

    2016-02-01

    When a thermal neutron is absorbed by 10B in the 10B(n,α)7Li reaction, there is a chance of 94% that a 478 keV photon be emitted by an excited 7Li nucleus. This reaction is exothermic with a Q-value of 2.31 MeV and the nuclei are emitted with kinetic energies of E(α)=1.47 MeV and E(7Li*)=0.84 MeV. This implies that the 478 keV γ line is emitted by a moving 7Li nucleus and hence is expected to be Doppler broadened. In the present work we suggest to use this broadening of the γ line as a fingerprint for the detection of thermal neutrons using a high resolution gamma spectrometer. We thus developed a Monte Carlo program using a MATLAB code based on a High Purity Germanium (HPGe) detector coupled with a Boron Carbide (B4C) sheet to calculate the γ line broadening. Our simulation shows that the FWHM width of the resulting γ line is 12.6 keV, in good agreement with our measurement. Hence the broadened γ line emitted by the 10B(n,αγ)7Li reaction and detected by a HPGe detector shows that this method is an effective tool for neutron detection while maintaining good gamma discrimination.

  3. An Integrated Laboratory Project in NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Hudson, Reggie L.; Pendley, Bradford D.

    1988-01-01

    Describes an advanced NMR project that can be done with a 60-MHz continuous-wave proton spectrometer. Points out the main purposes are to give students experience in second-order NMR analysis, the simplification of spectra by raising the frequency, and the effect of non-hydrogen nuclei on proton resonances. (MVL)

  4. Automated protein NMR resonance assignments.

    PubMed

    Wan, Xiang; Xu, Dong; Slupsky, Carolyn M; Lin, Guohui

    2003-01-01

    NMR resonance peak assignment is one of the key steps in solving an NMR protein structure. The assignment process links resonance peaks to individual residues of the target protein sequence, providing the prerequisite for establishing intra- and inter-residue spatial relationships between atoms. The assignment process is tedious and time-consuming, which could take many weeks. Though there exist a number of computer programs to assist the assignment process, many NMR labs are still doing the assignments manually to ensure quality. This paper presents (1) a new scoring system for mapping spin systems to residues, (2) an automated adjacency information extraction procedure from NMR spectra, and (3) a very fast assignment algorithm based on our previous proposed greedy filtering method and a maximum matching algorithm to automate the assignment process. The computational tests on 70 instances of (pseudo) experimental NMR data of 14 proteins demonstrate that the new score scheme has much better discerning power with the aid of adjacency information between spin systems simulated across various NMR spectra. Typically, with automated extraction of adjacency information, our method achieves nearly complete assignments for most of the proteins. The experiment shows very promising perspective that the fast automated assignment algorithm together with the new score scheme and automated adjacency extraction may be ready for practical use. PMID:16452794

  5. 1H and 13C NMR spectra, structure and physicochemical features of phenyl acridine-9-carboxylates and 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulphonates--alkyl substituted in the phenyl fragment.

    PubMed

    Krzymiński, K; Malecha, P; Zadykowicz, B; Wróblewska, A; Błażejowski, J

    2011-01-01

    The 1H and 13C NMR spectra of twelve phenyl acridine-9-carboxylates--alkyl-substituted in the phenyl fragment--and their 10-methyl-9-(phenoxycarbonyl)acridinium salts dissolved in CD3CN, CD3OD, CDCl3 and DMSO-d6 were recorded in order to examine the influence of the structure of these compounds and the properties of the solvents on chemical shifts and 1H-(1)H coupling constants. Experimental data were compared with 1H and 13C chemical shifts predicted at the GIAO/DFT level of theory for DFT(B3LYP)/6-31G** optimised geometries of molecules, as well as with values of 1H chemical shifts and 1H-(1)H coupling constants, estimated using ACD/HNMR database software to ensure that the assignment was correct. To investigate the relations between chemical shifts and selected structural or physicochemical characteristics of the target compounds, the values of several of these parameters were determined at the DFT or HF levels of theory. The HOMO and LUMO energies obtained at the HF level yielded the ionisation potentials and electron affinities of molecules. The DFT method provided atomic partial charges, dipole moments, LCAO coefficients of pz LUMO of selected C atoms, and angles reflecting characteristic structural features of the compounds. It was found that the experimentally determined 1H and 13C chemical shifts of certain atoms relate to the predicted dipole moments, the angles between the acridine and phenyl moieties, and the LCAO coefficients of the pz LUMO of the C atoms believed to participate in the initial step of the oxidation of the target compounds. The spectral and physicochemical characteristics of the target compounds were investigated in the context of their chemiluminogenic ability. PMID:21134782

  6. Three-body effects in the /sup 7/Li (/ital d/,. cap alpha cap alpha. /ital n/) reaction

    SciTech Connect

    Arena, N.; Cavallaro, S.; Fazio, G.; Giardina, G.; Italiano, A.; Herman, M.; Bruno, M.; Cannata, F.; D'Agostino, M.

    1989-07-01

    Measurements of the differential cross sections for the/sup 7/Li(/ital d/,..cap alpha cap alpha..n) reaction have been performed at deuteron incident energy /ital E/(/ital d/)=6.8 MeV. The kinematical configurations were chosen so as to optimize the population of the /sup 5/He/sup **/ 3/2/sup +/ state with 16.76 MeV excitation energy. The parameters of this resonance are deduced from the experimental data; deviations from the standard values indicate the relevance of three-body effects and/or rescattering. Some phenomenological considerations give a qualitative explanation of the results obtained. In particular, as far as the width is concerned, we observe a broadening with respect to the standard value, which may be related to the presence of a shadow pole.

  7. Transport properties derived from ion-atom collisions: 6Li-6Li+ and 6Li-7Li+ Cases

    NASA Astrophysics Data System (ADS)

    Bouledroua, Moncef; Bouchelaghem, Fouzia; LPR Team

    2014-10-01

    This investigation treats quantum-mechanically the ion- atom collisions and computes the transport coefficients, such as the coefficients of mobility and diffusion. For the case of lithium, the calculations start by determining the gerade and ungerade potential curves through which ionic lithium approaches ground lithium. Then, by considering the isotopic effects and nuclear spins, the elastic and charge-transfer cross sections are calculated for the case of 6Li+and7Li+ colliding with 6Li. Finally, the temperature-dependent diffusion and mobility coefficients are analyzed, and the results are contrasted with those obtained from literature. The main results of this work have been recently published in. This work has been realized within the frames of the CNEPRU Project D01120110036 of the Algerian Ministry of Higher Education.

  8. Elastic and inelastic angular distributions of the 7Li+120Sn system for energies near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Zagatto, V. A. B.; Oliveira, J. R. B.; Gasques, L. R.; Alcántara-Núñez, J. A.; Duarte, J. G.; Aguiar, V. P.; Medina, N. H.; Seale, W. A.; Pires, K. C. C.; Freitas, A.; Lubian, J.; Shorto, J. M. B.; Genezini, F. A.; Rossi, E. S., Jr.

    2016-06-01

    The reaction of 7Li+120Sn has been measured at bombarding energies of 21, 24 and 27 MeV. The {2}+\\to {0}+ γ -ray transition in 120Sn was observed and the angular distribution for the 2+ excited state was obtained. Coupled channels and coupled-reaction channels calculations, including the dynamical polarization potential due to the projectile break-up, obtained from continuum discretized coupled channel calculations, were performed. The comparison between the existing experimental elastic angular distribution with the coupled-reaction channels calculations indicates that the 1n stripping transfer is the most intense channel to be coupled and the 2n stripping reaction occurs sequentially rather than directly, however, further data must be analyzed to confirm this indication. The experimental elastic and inelastic scattering data were well described by the calculations, but some discrepancies in these channels may indicate the need for corrections to the nuclear potential and/or the necessity to incorporate further channels.

  9. On optimizing the {sup 7}Li(p,n) proton beam energy and moderator material for BNCT

    SciTech Connect

    Bleuel, D.L.; Donahue, R.J.; Ludewigt, B.A.

    1996-09-01

    The reaction {sup 7}Li(p,n){sup 7}Be has been proposed as an accelerator-based source of neutrons for Boron Neutron Capture Therapy (BNCT). This reaction has a large steep resonance for proton energies around 2.3 MeV which ends at approximately 2.5 MeV. It is generally accepted that the use of 2.5 MeV protons produces the highest yield of neutrons for BNCT. This paper suggests that for BNCT the optimum proton energy may be as low as 2.2-2.3 MeV. The evaluation of the clinical usefulness of the epithermal neutron beams investigated here has been based on depth-dose distributions in a head phantom.

  10. R-matrix analysis of reactions in the 9B compound system applied to the 7Li problem in BBN

    NASA Astrophysics Data System (ADS)

    Paris, M.; Hale, G.; Hayes-Sterbenz, A.; Jungman, G.

    2016-01-01

    Recent activity in solving the ‘lithium problem’ in big bang nucleosynthesis has focused on the role that putative resonances may play in resonance-enhanced destruction of 7Li. Particular attention has been paid to the reactions involving the 9B compound nuclear system, d+7Be → 9B. These reactions are analyzed via the multichannel, two-body unitary R-matrix method using the code EDA developed by Hale and collaborators. We employ much of the known elastic and reaction data, in a four-channel treatment. The data include elastic 3He +6Li differential cross sections from 0.7 to 2.0 MeV, integrated reaction cross sections for energies from 0.7 to 5.0 MeV for 6Li(3He,p)8Be* and from 0.4 to 5.0 MeV for the 6Li(3He,d)7Be reaction. Capture data have been added to an earlier analysis with integrated cross section measurements from 0.7 to 0.825 MeV for 6Li(3He,γ)9B. The resulting resonance parameters are compared with tabulated values, and previously unidentified resonances are noted. Our results show that there are no near d+7Be threshold resonances with widths that are 10’s of keV and reduce the likelihood that a resonance-enhanced mass-7 destruction mechanism, as suggested in recently published work, can explain the 7Li problem.

  11. Applications of Diffusion Ordered Spectroscopy (DOSY-NMR)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffusion-ordered NMR (DOSY-NMR) is a powerful, but under-utilized, technique for the investigation of mixtures based on translational diffusion rates. DOSY spectra allow for determination by NMR of components that may differ in molecular weight, geometry or complexation. Typical applications coul...

  12. Scalar operators in solid-state NMR

    SciTech Connect

    Sun, Boqin

    1991-11-01

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

  13. Solid-state NMR and Membrane Proteins

    PubMed Central

    Opella, Stanley J.

    2015-01-01

    The native environment for a membrane protein is a phospholipid bilayer. Because the protein is immobilized on NMR timescales by the interactions within a bilayer membrane, solid-state NMR methods are essential to obtain high-resolution spectra. Approaches have been developed for both unoriented and oriented samples, however, they all rest on the foundation of the most fundamental aspects solid-state NMR, and the chemical shift and homo- and hetero-nuclear dipole-dipole interactions. Solid-state NMR has advanced sufficiently to enable the structures of membrane proteins to be determined under near-native conditions in phospholipid bilayers. PMID:25681966

  14. Cross-section measurement for the /sup 7/Li(n,n't)/sup 4/He reaction at 14. 74 MeV

    SciTech Connect

    Smith, D.L.; Meadows, J.W.; Bretscher, M.M.; Cox, S.A.

    1984-09-01

    The cross section for the /sup 7/Li(n,n't)/sup 4/He reaction is measured at an average neutron energy of 14.74 MeV, with a resolution of 0.324 MeV, relative to the /sup 238/U neutron-fission cross section. Tritium activities for the irradiated lithium-metal samples (enriched to 99.95% in /sup 7/Li) are deduced using a liquid-scintillation counting method which relies upon the tritiated-water standard from the US National Bureau of Standards. The measured cross section ratio of /sup 7/Li(n,n't)/sup 4/He to /sup 238/U neutron fission is 0.2523 (+- 2.2%). The derived /sup 7/Li(n,n't)/sup 4/He reaction cross section is 0.301 (+- 5.3%) barn, based on the ENDF/B-V value of 1.193 (+- 4.8%) barn for the /sup 238/U neutron-fission cross section. 59 references.

  15. Vector analyzing power measurement of pion scattering from polarized [sup 7]Li in the region of the [Delta][sub 33] resonance

    SciTech Connect

    Meier, R.; Boschitz, E.; Brinkmoeller, B.; Buehler, J.; Ritt, S.; Wessler, M. ); Konter, J.A.; Mango, S.; van den Brandt, B. ); Efimovykh, V.A.; Kovalev, A.I.; Prokofiev, A.N.; Polyakov, V.V. ); Chaumette, P.; Deregel, J.; Durand, G.; Fabre, J. ); Mach, R. ); Tacik, R. )

    1994-01-01

    The inclusive vector analyzing power [ital iT][sub 11] of [pi][sup +][r arrow][sup 7]Li elastic scattering and inelastic scattering to the 0.47 MeV excited state was measured at several angles for [ital T][sub [pi

  16. Understanding the directed ortho lithiation of (R)-Ph₂P(=NCO₂Me)NHCH(Me)Ph. NMR spectroscopic and computational study of the structure of the N-lithiated species.

    PubMed

    Casimiro, M; García-López, J; Iglesias, M J; López-Ortiz, F

    2014-10-14

    A multinuclear magnetic resonance ((1)H, (7)Li, (13)C, (15)N, (31)P) and DFT computational study at the M06-2X(SMD,THF)/6-311+G(d,p)//B3LYP/6-31G(d) level of the structure of a N-lithiated phosphinimidic amide (R)-Ph2P(=NCO2Me)NHCH(Me)Ph 13 has been performed. In THF solution it exists as an equilibrium mixture of monomers and dimers. The monomers consist of a six-membered ring formed by coordination of the lithium atom with the deprotonated nitrogen and the oxygen atom of the carbonyl group. This coordination mode is in contrast to the standard N,N-chelation observed in N-lithiated N,N'-bis(trimethylsilyl)phosphinimidic amides. The calculations showed that the metallacycle adopts a twist-boat conformation and that the lithium atom is in a tetrahedral environment involving O,N-chelation by the ligand and coordination to two/one THF molecules in the monomer/dimer. Dimerization takes place through O-Li bridges. For all species two series of isomers have been identified, which originated by restricted rotation of the methoxy group and ring inversion. The twist-boat conformational interconversion seems to be operating for explaining the pattern of signals observed in the (7)Li and (31)P NMR spectra. The structure found for the most stable dimer is analogous to the molecular structure reported for a related C(α)-lithiated phosphazene 20. The structural study revealed that the chiral side-arm of the N-lithiated species is oriented to the outer face of the pro-S P-phenyl ring, which shows one ortho-proton very close to the nitrogen atom of the carbamate moiety. In this conformation, proton abstraction by a base is highly favoured, in agreement with the experimental results. PMID:24849316

  17. NMR Studies of Peroxidases.

    NASA Astrophysics Data System (ADS)

    Veitch, Nigel Charles

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

  18. Non-Destructive Monitoring of Charge-Discharge Cycles on Lithium Ion Batteries using 7Li Stray-Field Imaging

    PubMed Central

    Tang, Joel A.; Dugar, Sneha; Zhong, Guiming; Dalal, Naresh S.; Zheng, Jim P.; Yang, Yong; Fu, Riqiang

    2013-01-01

    Magnetic resonance imaging provides a noninvasive method for in situ monitoring of electrochemical processes involved in charge/discharge cycling of batteries. Determining how the electrochemical processes become irreversible, ultimately resulting in degraded battery performance, will aid in developing new battery materials and designing better batteries. Here we introduce the use of an alternative in situ diagnostic tool to monitor the electrochemical processes. Utilizing a very large field-gradient in the fringe field of a magnet, stray-field-imaging (STRAFI) technique significantly improves the image resolution. These STRAFI images enable the real time monitoring of the electrodes at a micron level. It is demonstrated by two prototype half-cells, graphite∥Li and LiFePO4∥Li, that the high-resolution 7Li STRAFI profiles allow one to visualize in situ Li-ions transfer between the electrodes during charge/discharge cyclings as well as the formation and changes of irreversible microstructures of the Li components, and particularly reveal a non-uniform Li-ion distribution in the graphite. PMID:24005580

  19. Central nervous system radiation syndrome in mice from preferential 10B(n, alpha)7Li irradiation of brain vasculature.

    PubMed

    Slatkin, D N; Stoner, R D; Rosander, K M; Kalef-Ezra, J A; Laissue, J A

    1988-06-01

    Ionizing radiations were directed at the heads of anesthetized mice in doses that evoked the acute central nervous system (CNS) radiation syndrome. Irradiations were done using either a predominantly thermal neutron field at a nuclear reactor after intraperitoneal injection of 10B-enriched boric acid or 250-kilovolt-peak x-rays with and without previous intraperitoneal injection of equivalent unenriched boric acid. Since 10B concentrations were approximately equal to 3-fold higher in blood than in cerebral parenchyma during the reactor irradiations, more radiation from alpha and 7Li particles was absorbed by brain endothelial cells than by brain parenchymal cells. Comparison of the LD50 dose for CNS radiation lethality from the reactor experiments with the LD50 dose from the x-ray experiments gives results compatible with morphologic evidence that endothelial cell damage is a major determinant of acute lethality from the CNS radiation syndrome. It was also observed that boric acid is a low linear energy transfer radiation-enhancement agent in vivo. PMID:3375251

  20. Central nervous system radiation syndrome in mice from preferential 10B(n, alpha)7Li irradiation of brain vasculature.

    PubMed Central

    Slatkin, D N; Stoner, R D; Rosander, K M; Kalef-Ezra, J A; Laissue, J A

    1988-01-01

    Ionizing radiations were directed at the heads of anesthetized mice in doses that evoked the acute central nervous system (CNS) radiation syndrome. Irradiations were done using either a predominantly thermal neutron field at a nuclear reactor after intraperitoneal injection of 10B-enriched boric acid or 250-kilovolt-peak x-rays with and without previous intraperitoneal injection of equivalent unenriched boric acid. Since 10B concentrations were approximately equal to 3-fold higher in blood than in cerebral parenchyma during the reactor irradiations, more radiation from alpha and 7Li particles was absorbed by brain endothelial cells than by brain parenchymal cells. Comparison of the LD50 dose for CNS radiation lethality from the reactor experiments with the LD50 dose from the x-ray experiments gives results compatible with morphologic evidence that endothelial cell damage is a major determinant of acute lethality from the CNS radiation syndrome. It was also observed that boric acid is a low linear energy transfer radiation-enhancement agent in vivo. Images PMID:3375251

  1. Assigning the NMR Spectrum of Glycidol: An Advanced Organic Chemistry Exercise

    ERIC Educational Resources Information Center

    Helms, Eric; Arpaia, Nicholas; Widener, Melissa

    2007-01-01

    Various one- and two-dimensional NMR experiments have been found to be extremely useful for assigning the proton and carbon NMR spectra of glycidol. The technique provides extremely valuable information aiding in the complete assignment of the peaks.

  2. Cross-section measurement for the 10B(n, alpha)7Li reaction at 4.0 and 5.0 MeV.

    PubMed

    Zhang, Guohui; Guo, Li'an; Cao, Rongtai; Zhang, Jiaguo; Chen, Jinxiang

    2008-10-01

    Cross-sections of the (10)B(n, alpha)(7)Li reaction were measured at En=4.0 and 5.0 MeV. A gridded ionization chamber (GIC) was used as charged particle detector. Neutrons were produced through the D(d, n)(3)He reaction with a deuterium gas target. Experiments were performed at the 4.5 MV Van de Graaff accelerator of Peking University. Cross-section data of the (238)U(n, f) reaction were employed as standard. The measured cross-sections of the (10)B(n, alpha)(7)Li reaction at 4.0 and 5.0 MeV are 211+/-17 and 169+/-14 mb, respectively, and they are compared with existing results of measurements and evaluations. PMID:18387305

  3. 3He (α , γ)7Be and 3H (α , γ)7Li astrophysical S factors from the no-core shell model with continuum

    NASA Astrophysics Data System (ADS)

    Dohet-Eraly, Jérémy; Navrátil, Petr; Quaglioni, Sofia; Horiuchi, Wataru; Hupin, Guillaume; Raimondi, Francesco

    2016-06-01

    The 3He(α , γ)7Be and 3H(α , γ)7Li astrophysical S factors are calculated within the no-core shell model with continuum using a renormalized chiral nucleon-nucleon interaction. The 3He(α , γ)7Be astrophysical S factors agree reasonably well with the experimental data while the 3H(α , γ)7Li ones are overestimated. The seven-nucleon bound and resonance states and the α + 3He/3H elastic scattering are also studied and compared with experiment. The low-lying resonance properties are rather well reproduced by our approach. At low energies, the s-wave phase shift, which is non-resonant, is overestimated.

  4. Neutron beam optimization based on a 7Li(p,n)7Be reaction for treatment of deep-seated brain tumors by BNCT

    NASA Astrophysics Data System (ADS)

    Zahra Ahmadi, Ganjeh; S. Farhad, Masoudi

    2014-10-01

    Neutron beam optimization for accelerator-based Boron Neutron Capture Therapy (BNCT) is investigated using a 7Li(p,n)7Be reaction. Design and optimization have been carried out for the target, cooling system, moderator, filter, reflector, and collimator to achieve a high flux of epithermal neutron and satisfy the IAEA criteria. Also, the performance of the designed beam in tissue is assessed by using a simulated Snyder head phantom. The results show that the optimization of the collimator and reflector is critical to finding the best neutron beam based on the 7Li(p,n)7Be reaction. Our designed beam has 2.49×109n/cm2s epithermal neutron flux and is suitable for BNCT of deep-seated brain tumors.

  5. Trojan horse particle invariance studied with the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He reactions

    SciTech Connect

    Pizzone, R. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Bertulani, C.; Mukhamedzhanov, A.; Blokhintsev, L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Kiss, G. G.; Li, C.; Tumino, A.

    2011-04-15

    The Trojan horse nucleus invariance for the binary reaction cross section extracted from the Trojan horse reaction was tested using the quasifree {sup 3}He({sup 6}Li,{alpha}{alpha})H and {sup 3}He({sup 7}Li,{alpha}{alpha}){sup 2}H reactions. The cross sections for the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He binary processes were extracted in the framework of the plane wave approximation. They are compared with direct behaviors as well as with cross sections extracted from previous indirect investigations of the same binary reactions using deuteron as the Trojan horse nucleus instead of {sup 3}He. The very good agreement confirms the applicability of the plane wave approximation which suggests the independence of the binary indirect cross section on the chosen Trojan horse nucleus, at least for the investigated cases.

  6. A new measurement of the 7Li(d,p)8Li cross section and consequences for 7Be(p,γ)8B

    NASA Astrophysics Data System (ADS)

    Weissman, L.; Broude, C.; Goldring, G.; Hadar, R.; Hass, M.; Schwamm, F.; Shaanan, M.

    1998-02-01

    A novel scheme for measuring the cross section of the 7Be(p,γ)8B reaction, the major source of high energy neutrinos from the sun, is presented. The scheme involves a strictly uniform particle beam and overcomes some of the recognized experimental uncertainties of previous measurements. A new measurement of σ[7Li(d,p)8Li] has been carried out using this setup, and the present value of σ[7Li(d,p)8Li] = 155(8) mb at the top of the Ed(lab.) = 776 keV resonance is compared with previous measurements. A new issue regarding both the (d,p) and (p,γ) reactions has been examined: reaction-product nuclei which are backscattered out of the target. Measurements and simulations carried out in the course of this investigation are presented and discussed in the context of possible effects on the measured cross sections of these reactions.

  7. [sup 26]Mg([sup 6]L[rvec i],[sup 7]Li)[sup 25]Mg reaction at 60 MeV

    SciTech Connect

    Ward, R.P.; Clarke, N.M. School of Physics and Space Research, University of Birmingham, Edgbaston, Birmingham B15 2TT ); Pearce, K.I.; Pinder, C.N. ); Blyth, C.O.; Choi, H.D.; Dee, P.R.; Roman, S.; Tungate, G. ); Davis, N.J. )

    1995-03-01

    Angular distributions of differential cross section and vector analyzing power have been measured for the [sup 26]Mg([sup 6]L[rvec i],[sup 7]Li)[sup 25]Mg reaction at 60 MeV bombarding energy. Finite-range distorted-wave Born approximation calculations were found to reproduce much of the structure of the data, although the predictions were approximately 3[degree] out of phase with the data. Finite-range coupled-channels Born approximation calculations including inelastic excitations in [sup 6]Li and [sup 7]Li, using coupling schemes derived from elastic scattering analyses, modified the predictions only slightly and did not remove the phase discrepancy.

  8. Characteristics of BDE dependent on 10B concentration for accelerator-based BNCT using near-threshold 7Li(p,n)7Be direct neutrons.

    PubMed

    Tanaka, K; Kobayashi, T; Bengua, G; Nakagawa, Y; Endo, S; Hoshi, M

    2004-11-01

    The characteristics boron-dose enhancer (BDE) was evaluated as to the dependence on the (10)B concentration for BNCT using near-threshold (7)Li(p,n)(7)Be direct neutrons. The treatable protocol depth (TPD) was utilized as an evaluation index. MCNP-4B calculations were performed for near-threshold (7)Li(p,n)(7)Be at a proton energy of 1.900MeV and for a polyethylene BDE. Consequently, the TPD was increased by increasing T/N ratio, i.e., the ratio of the (10)B concentration in the tumor ((10)B(Tumor)) to that in the normal tissue ((10)B(Normal)), and by increasing (10)B(Tumor) and (10)B(Normal) for constant T/N ratio. It has been found that the BDE becomes unnecessary from the viewpoint of increasing the TPD, when (10)B(Tumor) is over a certain level. PMID:15308161

  9. Modern NMR spectroscopy: a guide for chemists

    SciTech Connect

    Sanders, J.K.M.; Hunter, B.K.

    1988-01-01

    The aim of the authors of Modern NMR Spectroscopy is to bridge the communication gap between the chemist and the spectroscopist. The approach is nonmathematical, descriptive, and pictorial. To illustrate the ideas introduced in the text, the authors provide original spectra obtained specially for this purpose. Examples include spectroscopy of protons, carbon, and less receptive nuclei of interest to inorganic chemists. The authors succeed in making high-resolution NMR spectroscopy comprehensible for the average student or chemist.

  10. Probing Cancer Cell Metabolism Using NMR Spectroscopy.

    PubMed

    Hollinshead, Kate E R; Williams, Debbie S; Tennant, Daniel A; Ludwig, Christian

    2016-01-01

    Altered cellular metabolism is now accepted to be at the core of many diseases including cancer. Over the past 20 years, NMR has become a core technology to study these metabolic perturbations in detail. This chapter reviews current NMR-based methods for steady-state metabolism and, in particular, the use of non-radioactive stable isotope-enriched tracers. Opportunities and challenges for each method, such as 1D (1)H NMR spectroscopy and (13)C carbon-based NMR spectroscopic methods, are discussed. Ultimately, the combination of NMR and mass spectra as orthogonal technologies are required to compensate for the drawbacks of each technique when used singly are discussed. PMID:27325263

  11. /sup 7/Be(n,p)/sup 7/Li total cross section from 25 meV to 13. 5 keV

    SciTech Connect

    Koehler, P.E.; Bowman, C.D.; Steinkruger, F.J.; Moody, D.C.; Hale, G.M.; Starner, J.W.; Wender, S.A.; Haight, R.C.; Lisowski, P.W.; Talbert, W.L.

    1988-03-01

    The total /sup 7/Be(n,p)/sup 7/Li cross section has been measured from 25 meV to 13.5 keV. These energies correspond to temperatures of T = 2.9 x 10/sup -7/ to 0.16 GK. For thermal neutrons the cross sections to the ground state (p/sub 0/) and the first excited state (p/sub 1/) of /sup 7/BLi are 38 400 +- 800 b and 420 +- 120 b, respectively. This result for the total /sup 7/Be(n,p)/sup 7/Li thermal cross section is about 25% lower, and is approximately a factor of 10 more precise than previous published measurements. For energies above 100 eV, a significant departure from a 1v shape for the total cross section is observed. The data were analyzed using a single-level approximation, and were also analyzed together with other data using multilevel-multichannel R-matrix theory. Results are presented for the properties of the 2/sup -/ threshold state and for a possible nearby 2/sup -/ state. The astrophysical reaction rate, N/sub A/<..sigma..v>, was calculated from the measured cross sections for the combined p/sub 0/ and p/sub 1/ transitions. The resulting reaction rate is approximately 60--80 % of the rate currently in use. This reduction in the /sup 7/Be(n,p)/sup 7/Li reaction rate could result in a calculated increase in the production of /sup 7/Li during the big bang by as much as 20%

  12. Au, Bi, Co and Nb cross-section measured by quasimonoenergetic neutrons from p + 7Li reaction in the energy range of 18-36 MeV

    NASA Astrophysics Data System (ADS)

    Majerle, M.; Bém, P.; Novák, J.; Šimečková, E.; Štefánik, M.

    2016-09-01

    Au, Bi, Co and Nb samples were irradiated several times with quasi-monoenergetic neutrons from p + 7Li reaction in the energy range of 18-36 MeV. The activities of the samples were measured with the HPGe detector and the reaction rates were calculated. The cross-sections were extracted using the SAND-II method with the reference cross-sections from the EAF-2010 database. The uncertainties of the final results are discussed.

  13. Exchange Effects in the Radiative Capture Reactions 3H(α, γ)7Li and 3He(α, γ)7Be

    NASA Astrophysics Data System (ADS)

    Solovyev, A. S.; Igashov, S. Yu.; Tchuvil'sky, Yu. M.

    2016-05-01

    The mirror 3H(α, γ)7Li and 3He(α, γ)7Be reactions have been considered using the algebraic versions of the resonating group model and of the orthogonality conditions model. Exchange effects in interaction of the colliding nuclei and influence of the corresponding exchange terms in matrix elements of the interaction potential on calculated astrophysical S-factors for the reactions have been studied.

  14. Synthesis and optical characterization of LiKB4O7, Li2B6O10, and LiCsB6O10 glasses

    SciTech Connect

    Adamiv, V.; Teslyuk, I.; Dyachok, Ya.; Romanyuk, G.; Krupych, O.; Mys, O.; Martynyuk-Lototska, I.; Burak, Ya.; Vlokh, R.

    2010-10-01

    In the current work we report on the synthesis of LiKB4O7, Li2B6O10, and LiCsB6O10 borate glasses. The results for their piezo-optic, acousto-optic, acoustic, elastic, refractive, optical transmission, and optical resistance properties are also presented. It is shown that some of these glasses represent efficient acousto-optic materials that are transparent down to the vacuum ultraviolet range and highly resistant to laser radiation.

  15. LEGO-NMR spectroscopy: a method to visualize individual subunits in large heteromeric complexes.

    PubMed

    Mund, Markus; Overbeck, Jan H; Ullmann, Janina; Sprangers, Remco

    2013-10-18

    Seeing the big picture: Asymmetric macromolecular complexes that are NMR active in only a subset of their subunits can be prepared, thus decreasing NMR spectral complexity. For the hetero heptameric LSm1-7 and LSm2-8 rings NMR spectra of the individual subunits of the complete complex are obtained, showing a conserved RNA binding site. This LEGO-NMR technique makes large asymmetric complexes accessible to detailed NMR spectroscopic studies. PMID:23946163

  16. Synthesis and x-ray structural characterization of binuclear iridium(I) and rhodium(I) hydroxypyridinate complexes. 1. Complete assignment of the /sup 1/H NMR spectra by two-dimensional and NOE techniques. The nature of inside and outside /sup 1/H chemical shift differences

    SciTech Connect

    Rodman, G.S.; Mann, K.R.

    1988-09-21

    Six new d/sup 8/-d/sup 8/ complexes, (Ir(COD)(..mu..-hp))/sub 2/, (Ir(COD)(..mu..-mhp))/sub 2/, (Ir(COD)(..mu..-chp))/sub 2/, (Ir(COD)(..mu..-2hq))/sub 2/, (Rh(COD)(..mu..-hp))/sub 2/, and (Rh(COD)(..mu..-mhp))/sub 2/ (hp = 2-hydroxyphridinate, mhp = 6-methyl-2-hydroxypyridinate, chp = 6-chloro-2-hydroxypyridinate, 2hq = 2-hydroxyquinolate, COD = 1,5-cyclooctadiene), were synthesized and characterized by /sup 1/H NMR, /sup 13/C NMR, and IR spectroscopy and FAB mass spectrometry. X-ray crystallographic analyses of the isostructural (M(COD)(..mu..-mhp))/sub 2/ (M = Ir and Rh) complexes confirmed the binuclear nature of the complexes. The complete assignment of the /sup 1/H NMR spectrum of (Ir(COD)(..mu..-hp))/sub 2/ (and by analogy, the spectra of the other five complexes) was carried out with selective decoupling, nuclear Overhauser effect (NOE), and two-dimensional NMR techniques. The NOE observed between hp proton H5 and COD proton H15 allowed the precise assignment of all 12 COD resonances. Olefinic proton H12 (trans to N and outside) resonates downfield of olefinic proton H11 (trans to N and inside). Olefininc proton H15 (trans to O and outside) resonates upfield of olefinic proton H16 (trans to O and inside). The endo methylene protons resonate upfield of the exo methylene protons. The inside/outside chemical shift differences observed for these compounds are ascribed to steric and magnetic anisotropy effects. The crystallographic data are presented. The molecular structure of the complexes is discussed in detail. 39 references, 5 figures, 9 tables.

  17. NMR studies of bond arrangements in alkali phosphate glasses

    SciTech Connect

    Alam, T.M.; Brow, R.K.

    1998-01-01

    Solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has become a powerful tool for the investigation of local structure and medium range order in glasses. Previous {sup 31}P MAS NMR studies have detailed the local structure for a series of phosphate glasses. Phosphate tetrahedra within the glass network are commonly described using the Q{sup n} notation, where n = 0, 1, 2, 3 and represents the number of bridging oxygens attached to the phosphate. Using {sup 31}P MAS NMR different phosphate environments are readily identified and quantified. In this paper, the authors present a brief description of recent one dimensional (1D) {sup 6}Li, {sup 7}Li and {sup 31}P MAS experiments along with two-dimensional (2D) {sup 31}P exchange NMR experiments for a series of lithium ultraphosphate glasses. From the 2D exchange experiments the connectivities between different Q{sup n} phosphate tetrahedra were directly measured, while the 1D experiments provided a measure of the P-O-P bond angle distribution and lithium coordination number as a function of Li{sub 2}O concentration.

  18. Partial diagenetic overprint of Late Jurassic belemnites from New Zealand: Implications for the preservation potential of δ7Li values in calcite fossils

    NASA Astrophysics Data System (ADS)

    Ullmann, Clemens V.; Campbell, Hamish J.; Frei, Robert; Hesselbo, Stephen P.; Pogge von Strandmann, Philip A. E.; Korte, Christoph

    2013-11-01

    The preservation potential and trends of alteration of many isotopic systems (e.g. Li, Mg, Ca) that are measured in fossil carbonates are little explored, yet extensive paleoenvironmental interpretations have been made on the basis of these records. Here we present a geochemical dataset for a Late Jurassic (˜153 Ma) belemnite (Belemnopsis sp.) from New Zealand that has been partially overprinted by alteration. We report the physical pathways and settings of alteration, the resulting elemental and isotopic trends including δ7Li values and Li/Ca ratios, and assess whether remnants of the primary shell composition have been preserved or can be extrapolated from the measured values. The δ18O and δ13C values as well as Sr/Ca and Mn/Ca ratios were analysed along two profiles. In addition, 6 samples were analysed for 87Sr/86Sr, Sr/Ca and Mn/Ca ratios. Five samples from the same specimen and 2 from the surrounding sediment were analysed for δ7Li values, Li/Ca, Sr/Ca and Mn/Ca ratios and are compared to results for 6 other Late Jurassic belemnite rostra (Belemnopsis sp. andHibolithes sp.) from the same region. The 87Sr/86Sr ratios are lower (less radiogenic) in the most altered part of the rostrum, whereas δ7Li values become more positive with progressive alteration. The direction and magnitude of the trends in the geochemical record indicate that one main phase of alteration that occurred in the Late Cretaceous caused most of the diagenetic signature in the calcite. Despite relatively deep burial, down to 4 km, and thus elevated temperatures, this diagenetic signature has subsequently been preserved even for the highly mobile element lithium, suggesting that primary lithium-isotope values can be maintained over geological timescales, at least in thick macrofossil shells. Our best δ7Li estimate for pristine Late Jurassic (˜155-148 Ma) belemnites is +27 ± 1‰, which points to a Late Jurassic seawater δ7Li of ˜29-32‰, compatible with the modern value of 31‰.

  19. Nondestructive high-resolution solid-state NMR of rotating thin films at the magic-angle.

    PubMed

    Inukai, Munehiro; Noda, Yasuto; Takeda, Kazuyuki

    2011-12-01

    We present a new approach to nondestructive magic-angle spinning (MAS) nuclear magnetic resonance (NMR) for thin films. In this scheme, the sample put on the top of a rotor is spun using the conventional MAS system, and the NMR signals are detected with an additional coil. Stable spinning of disk-shaped samples with diameters of 7 mm and 12 mm at 14.2 and 7 kHz are feasible. We present 7Li MAS NMR experiments of a thin-film sample of LiCoO2 with a thickness of 200 nm. Taking advantage of the nondestructive feature of the experiment, we also demonstrate ex situ experiments, by tracing conformation change upon annealing for various durations. This approach opens the door for in situ MAS NMR of thin-film devices as well. PMID:21958755

  20. Nondestructive high-resolution solid-state NMR of rotating thin films at the magic-angle

    NASA Astrophysics Data System (ADS)

    Inukai, Munehiro; Noda, Yasuto; Takeda, Kazuyuki

    2011-12-01

    We present a new approach to nondestructive magic-angle spinning (MAS) nuclear magnetic resonance (NMR) for thin films. In this scheme, the sample put on the top of a rotor is spun using the conventional MAS system, and the NMR signals are detected with an additional coil. Stable spinning of disk-shaped samples with diameters of 7 mm and 12 mm at 14.2 and 7 kHz are feasible. We present 7Li MAS NMR experiments of a thin-film sample of LiCoO 2 with a thickness of 200 nm. Taking advantage of the nondestructive feature of the experiment, we also demonstrate ex situ experiments, by tracing conformation change upon annealing for various durations. This approach opens the door for in situ MAS NMR of thin-film devices as well.

  1. GEL-STATE NMR OF BALL-MILLED WHOLE CELL WALLS IN DMSO-d6 USING 2D SOLUTION-STATE NMR SPECTROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant cell walls were used for obtaining 2D solution-state NMR spectra without actual solubilization or structural modification. Ball-milled whole cell walls were swelled directly in the NMR tube with DMSO-d6 where they formed a gel. There are relatively few gel-state NMR studies. Most have involved...

  2. NMR study of some coumarins and furocoumarins methylated

    NASA Astrophysics Data System (ADS)

    Miranda, R.; Santana, L.; Uriarte, E.; Zagotto, G.

    1994-01-01

    The 1H and 13C NMR spectra of various methylcoumarins and methylfurocoumarins are reported. All signals were assigned and the influence on chemical shifts of methylation at various positions was determined.

  3. Coupled channels description of single and mutual excitation in the scattering of 7Li from 12C and 24, 26Mg

    NASA Astrophysics Data System (ADS)

    Cook, J.; Clarice, N. M.; Coopersmith, J.; Griffiths, R. J.

    1982-09-01

    Coupled channels calculations have been made for the scattering of 7Li from 12C at 63 and 79 MeV and from 24,26Mg at 88 MeV. The calculations describe, simultaneously, the elastic scattering, excitation of 7Li to the 478 keV {1}/{2}- state, excitation of the target to its first 2 + state, and the mutual excitation of both projectile and target to their {1}/{2}- and 2 + states respectively. The potentials have been calculated by a double folding model using the M3Y effective interaction for the real part, and a gaussian effective interaction for the imaginary part. Realistic densities have been used for the ground states of 7Li, 12C and 24, 26Mg and also the transition densities to the excited states using a microscopic plus macroscopic prescription. For the mutual excitation, both one-step processes with l = 0, 2 and 4 and two-step processes were included. The calculations show that the two-step processes are the dominant contribution to the mutual excitation, but at forward angles, the oscillations in the data are only reproduced with the coherent addition of the one-step processes, which are dominated by the l = 4 contribution. Even when coupling to all single and mutual excitations are included the real potential still requires a normalization of about 0.6. The addition of the quadrupole re-orientation matrix element for the ground state does not significantly change this value. These calculations confirm that the coupling to the first excited inelastic levels of target and ejectile is not the source of the anomalous M3Y normalization, and that the dominant mode for mutual excitation is a two-step process. However, direct one-step mutual excitation is important for small angles (θ ≲ 20°).

  4. Development of Halbach magnet for portable NMR device

    NASA Astrophysics Data System (ADS)

    Doğan, N.; Topkaya, R.; Subaşi, H.; Yerli, Y.; Rameev, B.

    2009-03-01

    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.

  5. Two-dimensional NMR spectrometry

    SciTech Connect

    Farrar, T.C.

    1987-06-01

    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, t/sub 0/; an evolution period, t/sub 1/; and a detection period, t/sub 2/.

  6. NMR investigation of Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Son, Kwanghyo; Jang, Zeehoon

    2013-01-01

    109Ag nuclear magnetic resonance (NMR) and relaxation measurements have been performed on two powder samples of Ag nanoparticles with average sizes of 20 nm and 80 nm. The measurements have been done in an external field of 9.4 T and in the temperature range 10 K < T < 280 K. The 109Ag NMR spectra for both samples have close to Lorentzian shapes and turn out to be mixtures of homogeneous and inhomogeneous lines. The linewidth Δ ν at room temperature is 1.3 kHz for both samples and gradually increases with decreasing temperature. Both the Knight shift ( K) and the nuclear spin-lattice relaxation rate (1/ T 1) are observed to be almost identical to the values reported for the bulk Ag metal, whereby the Korringa ratio R(= K 2 T 1 T/S) is found to be 2.0 for both samples in the investigated temperature range.

  7. Synthesis and optical characterization of LiKB4O7, Li2B6O10, and LiCsB6O10 glasses.

    PubMed

    Adamiv, V; Teslyuk, I; Dyachok, Ya; Romanyuk, G; Krupych, O; Mys, O; Martynyuk-Lototska, I; Burak, Ya; Vlokh, R

    2010-10-01

    In the current work we report on the synthesis of LiKB(4)O(7), Li(2)B(6)O(10), and LiCsB(6)O(10) borate glasses. The results for their piezo-optic, acousto-optic, acoustic, elastic, refractive, optical transmission, and optical resistance properties are also presented. It is shown that some of these glasses represent efficient acousto-optic materials that are transparent down to the vacuum ultraviolet range and highly resistant to laser radiation. PMID:20885472

  8. Elastic Scattering of 7Li+27Al at Backward Angles in the 7-11 MeV Energy Range for Application in RBS

    NASA Astrophysics Data System (ADS)

    Carnelli, P. F. F.; Abriola, D.; Arazi, A.; Capurro, O. A.; Cardona, M. A.; Fernández Niello, J. O.; Figueira, J. M.; Fimiani, L.; Grinberg, P.; Hojman, D.; Martí, G. V.; Martinez Heimann, D.; Negri, A. E.; Pacheco, A. J.

    2010-08-01

    We have measured elastic excitation functions for the 7Li+27Al system, in an energy range close to its Coulomb barrier (Elab = 8.4 MeV) in steps of 0.25 MeV. For this purpose, an array of eight surface-barrier detectors was used. To get an insight on the background composition (mainly α particles), a telescope-detector was used for atomic-number identification. Identical measurements for the 6Li+27Al system are planned for the near future.

  9. Fusion and direct reactions around the barrier for the systems {sup 7,9}Be,{sup 7}Li+{sup 238}U

    SciTech Connect

    Raabe, R.; Angulo, C.; Charvet, J. L.; Jouanne, C.; Nalpas, L.; Figuera, P.; Pierroutsakou, D.; Romoli, M.; Sida, J. L.

    2006-10-15

    We present new cross section data for the complete fusion of the weakly bound systems {sup 7,9}Be and {sup 7}Li on {sup 238}U at energies around the Coulomb barrier. In the same measurement, yields for direct processes and incomplete fusion are detected. For all systems, a suppression of the complete fusion cross section around and above the barrier is observed. At energies below the barrier, the fusion of the {sup 7}Be+{sup 238}U system shows no enhancement with respect to simple model predictions.

  10. Breakup coupling effects on near-barrier quasi-elastic scattering of {sup 6,7}Li on {sup 144}Sm

    SciTech Connect

    Otomar, D. R.; Lubian, J.; Gomes, P. R. S.; Monteiro, D. S.; Niello, J. O. Fernandez; Guimaraes, V.; Chamon, L. C.

    2009-09-15

    Excitation functions of quasi-elastic scattering at backward angles have been measured for the {sup 6,7}Li+{sup 144}Sm systems at near-barrier energies, and fusion barrier distributions have been extracted from the first derivatives of the experimental cross sections with respect to the bombarding energies. The data have been analyzed in the framework of continuum discretized coupled-channel calculations, and the results have been obtained in terms of the influence exerted by the inclusion of different reaction channels, with emphasis on the role played by the projectile breakup.

  11. Elastic Scattering of {sup 7}Li+{sup 27}Al at Backward Angles in the 7-11 MeV Energy Range for Application in RBS

    SciTech Connect

    Carnelli, P. F. F.; Arazi, A.; Cardona, M. A.; Figueira, J. M.; Hojman, D.; Martinez Heimann, D.; Negri, A. E.; Pacheco, A. J.; Abriola, D.; Capurro, O. A.; Fimiani, L.; Grinberg, P.; Marti, G. V.; Fernandez Niello, J. O.

    2010-08-04

    We have measured elastic excitation functions for the {sup 7}Li+{sup 27}Al system, in an energy range close to its Coulomb barrier (E{sub lab} = 8.4 MeV) in steps of 0.25 MeV. For this purpose, an array of eight surface-barrier detectors was used. To get an insight on the background composition (mainly {alpha} particles), a telescope-detector was used for atomic-number identification. Identical measurements for the {sup 6}Li+{sup 27}Al system are planned for the near future.

  12. Study of the {sup 19}O states via the ({sup 7}Li,{sup 7}Be) reaction at 52 MeV

    SciTech Connect

    Cavallaro, M.; Cappuzzello, F.; Cunsolo, A.; Carbone, D.; Foti, A.; Lenske, H.

    2010-04-30

    The {sup 19}F({sup 7}Li,{sup 7}Be){sup 19}O reaction at 52 MeV incident energy has been performed at INFN-LNS in Catania using the MAGNEX large acceptance spectrometer. The use of an algebraic ray-reconstruction technique has allowed to extract the {sup 19}O excitation energy spectrum and the experimental angular distributions. A theoretical analysis based on the Quasi-particle Random Phase Approximation has described the transitions to the 1p-1h states of the {sup 19}O, in close agreement with the experimental cross sections without using any scaling factor.

  13. Quantum effects in the case of (6)Li+ and (7)Li+ ions evolving in a neutral (6)Li gas at a wide range of temperatures.

    PubMed

    Bouchelaghem, F; Bouledroua, M

    2014-02-01

    This work deals with the quantum-mechanical calculation of the temperature-dependent mobility of ionic lithium atoms diffusing in their parent gas. The computation of the quantal phase shifts in connection with the gerade and ungerade potential-energy curves, through which Li(+) approaches Li(2s), leads to the computation of the charge-transfer and diffusion cross sections. The behavior of the coefficients of diffusion and mobility with temperature is also examined. Throughout this work, the isotopic effects in the (6)Li(+)-(6)Li and (7)Li(+)-(6)Li collisions are emphasized. PMID:24326775

  14. Increasing the quantitative bandwidth of NMR measurements.

    PubMed

    Power, J E; Foroozandeh, M; Adams, R W; Nilsson, M; Coombes, S R; Phillips, A R; Morris, G A

    2016-02-18

    The frequency range of quantitative NMR is increased from tens to hundreds of kHz by a new pulse sequence, CHORUS. It uses chirp pulses to excite uniformly over very large bandwidths, yielding accurate integrals even for nuclei such as (19)F that have very wide spectra. PMID:26789115

  15. An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR

    NASA Astrophysics Data System (ADS)

    Kempf, J. G.; Marohn, J. A.; Carson, P. J.; Shykind, D. A.; Hwang, J. Y.; Miller, M. A.; Weitekamp, D. P.

    2008-06-01

    Optical nuclear magnetic resonance (ONMR) is a powerful probe of electronic properties in III-V semiconductors. Larmor-beat detection (LBD) is a sensitivity optimized, time-domain NMR version of optical detection based on the Hanle effect. Combining LBD ONMR with the line-narrowing method of POWER (perturbations observed with enhanced resolution) NMR further enables atomically detailed views of local electronic features in III-Vs. POWER NMR spectra display the distribution of resonance shifts or line splittings introduced by a perturbation, such as optical excitation or application of an electric field, that is synchronized with a NMR multiple-pulse time-suspension sequence. Meanwhile, ONMR provides the requisite sensitivity and spatial selectivity to isolate local signals within macroscopic samples. Optical NMR, LBD, and the POWER method each introduce unique demands on instrumentation. Here, we detail the design and implementation of our system, including cryogenic, optical, and radio-frequency components. The result is a flexible, low-cost system with important applications in semiconductor electronics and spin physics. We also demonstrate the performance of our systems with high-resolution ONMR spectra of an epitaxial AlGaAs /GaAs heterojunction. NMR linewidths down to 4.1Hz full width at half maximum were obtained, a 103-fold resolution enhancement relative any previous optically detected NMR experiment.

  16. NMR studies of oriented molecules

    SciTech Connect

    Sinton, S.W.

    1981-11-01

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

  17. Normal coordinate analysis, molecular structure, vibrational, electronic spectra and NMR investigation of 4-Amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione by ab initio HF and DFT method

    NASA Astrophysics Data System (ADS)

    Bahgat, Khaled; Fraihat, Safwan

    2015-01-01

    In the present work, the characterization of 4-Amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione (APTT) molecule was carried out by quantum chemical method and vibrational spectral techniques. The FT-IR (4000-400 cm-1) and FT-Raman (4000-100 cm-1) spectra of APTT were recorded in solid phase. The UV-Vis absorption spectrum of the APTT was recorded in the range of 200-400 nm. The molecular geometry, harmonic vibrational frequencies and bonding features of APTT in the ground state have been calculated by HF and DFT methods using 6-311++G(d,p) basis set. The complete vibrational frequency assignments were made by normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMF). The molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO) and natural localized molecular orbital (NLMO) analysis. The electronic properties, such as excitation energies, absorption wavelength, HOMO and LUMO energies were performed by time depended DFT (TD-DFT) approach. The 1H and 13C nuclear magnetic resonance chemical shift of the molecule were calculated using the gauge-including atomic orbital (GIAO) method and compared with experimental results. Finally, the calculation results were analyzed to simulate infrared, FT-Raman and UV spectra of the title compound which shows better agreement with observed spectra.

  18. Evaluation of the /sup 7/Li(n,n't)/sup 4/He cross section for ENDF/B-VI and application to uncertainty analysis

    SciTech Connect

    Young, P.G.; Davidson, J.W.; Muir, D.W.

    1988-01-01

    A new covariance analysis of n+/sup 7/Li cross section data has been completed for Version VI of ENDF/B. The analysis updates our 1981 work for ENDF/B-V.2 to include new data that has become available since that time and to incorporate cross correlations between different experiments. The bulk of the new measured data consists of some 10 new (or newly revised) tritium-production measurements involving about 70 new data points. The new analysis results in only small changes in the previous evaluation of the tritium-production cross section but significantly reduces the magnitudes of uncertainties due to the more extensive and accurate data base that was used. A two-dimensional sensitivity and uncertainty analysis of the Lithium Blanket Module experiments at the LOTUS facility was performed in order to assess the effects of the new /sup 7/Li cross sections on tritium breeding uncertainty in a realistic system. 4 refs., 6 figs., 3 tabs.

  19. NMR analysis of biodiesel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodiesel is usually analyzed by the various methods called for in standards such as ASTM D6751 and EN 14214. Nuclear magnetic resonance (NMR) is not one of these methods. However, NMR, with 1H-NMR commonly applied, can be useful in a variety of applications related to biodiesel. These include monit...

  20. Organic Spectroscopy Laboratory: Utilizing IR and NMR in the Identification of an Unknown Substance

    ERIC Educational Resources Information Center

    Glagovich, Neil M.; Shine, Timothy D.

    2005-01-01

    A laboratory experiment that emphasizes the interpretation of both infrared (IR) and nuclear magnetic resonance (NMR) spectra in the elucidation of the structure of an unknown compound was developed. The method helps students determine [to the first power]H- and [to the thirteenth power]C-NMR spectra from the structures of compounds and to…

  1. Hyperpolarized NMR of plant and cancer cell extracts at natural abundance.

    PubMed

    Dumez, Jean-Nicolas; Milani, Jonas; Vuichoud, Basile; Bornet, Aurélien; Lalande-Martin, Julie; Tea, Illa; Yon, Maxime; Maucourt, Mickaël; Deborde, Catherine; Moing, Annick; Frydman, Lucio; Bodenhausen, Geoffrey; Jannin, Sami; Giraudeau, Patrick

    2015-09-01

    Natural abundance (13)C NMR spectra of biological extracts are recorded in a single scan provided that the samples are hyperpolarized by dissolution dynamic nuclear polarization combined with cross polarization. Heteronuclear 2D correlation spectra of hyperpolarized breast cancer cell extracts can also be obtained in a single scan. Hyperpolarized NMR of extracts opens many perspectives for metabolomics. PMID:26215673

  2. NMR system and method having a permanent magnet providing a rotating magnetic field

    DOEpatents

    Schlueter, Ross D [Berkeley, CA; Budinger, Thomas F [Berkeley, CA

    2009-05-19

    Disclosed herein are systems and methods for generating a rotating magnetic field. The rotating magnetic field can be used to obtain rotating-field NMR spectra, such as magic angle spinning spectra, without having to physically rotate the sample. This result allows magic angle spinning NMR to be conducted on biological samples such as live animals, including humans.

  3. Background suppression in MAS NMR

    NASA Astrophysics Data System (ADS)

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

    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 ϱ, relaxation measurements.

  4. 11B and constraints on neutrino oscillations and spectra from neutrino nucleosynthesis.

    PubMed

    Austin, Sam M; Heger, Alexander; Tur, Clarisse

    2011-04-15

    We study the sensitivity to variations in the triple-alpha and 12C(α,γ)16O reaction rates, of the yield of the neutrino-process isotopes 7Li, 11B, 19F, 138La, and 180Ta in core-collapse supernovae. Compared to solar abundances, less than 15% of 7Li, about 25%-80% of 19F, and about half of 138La is produced in these stars. Over a range of ±2σ for each helium-burning rate, 11B is overproduced and the yield varies by an amount larger than the variation caused by the effects of neutrino oscillations. The total 11B yield, however, may eventually provide constraints on supernova neutrino spectra. PMID:21568548

  5. 1H NMR relaxation in urea

    NASA Astrophysics Data System (ADS)

    Taylor, R. E.; Bacher, Alfred D.; Dybowski, C.

    2007-11-01

    Proton NMR spin-lattice relaxation times T1 were measured for urea as a function of temperature. An activation energy of 46.3 ± 4.7 kJ/mol was extracted and compared with the range of 38-65 kJ/mol previously reported in the literature as measured by different magnetic resonance techniques. In addition, proton NMR spin-lattice relaxation times in the rotating frame T1 ρ were measured as a function of temperature. These measurements provide acquisition conditions for the 13C and 15N CP/MAS spectra of pure urea in the crystalline phase.

  6. Nuclear magnetic resonance characterization of a paramagnetic DNA-drug complex with high spin cobalt; assignment of the 1H and 31P NMR spectra, and determination of electronic, spectroscopic and molecular properties.

    PubMed

    Gochin, M

    1998-08-01

    The proton NMR spectrum of the ternary complex between the octamer duplex d(TTGGCCAA)2, two molecules of the drug chromomycin-A3, and a divalent cobalt ion has been assigned. Assignment procedures used standard two-dimensional techniques and relied upon the expected NOE contacts observed in the equivalent diamagnetic complex containing zinc. The magnetic susceptibility tensor for the cobalt was determined and used to calculate shifts for all nuclei, aiding in the assignment process and verification. Relaxation, susceptibility, temperature and field dependence studies of the paramagnetic spectrum enabled determination of electronic properties of the octahedral cobalt complex. The electronic relaxation tau(s) was determined to be 2.5 +/- 1.5 ps; the effective isotropic g value was found to be 2.6 +/- 0.2, indicating strong spin-orbit coupling. The magnetic susceptibility tensor was determined to be chi(xx) = 8.9 x 10(-3) cm3/mol, chi(yy) = 9.5 x 10(-3) cm3/mol, chi(zz) = 12.8 * 10(-3) cm3/mol. A tentative rotational correlation time of 8 ns was obtained for the complex. Both macroscopic and microscopic susceptibility measurements revealed deviations from Curie behavior over the temperature range accessible in the study. Non-selective relaxation rates were found to be inaccurate for defining distances from the metal center. However, pseudocontact shifts could be calculated with high accuracy using the dipolar shift equation. Isotropic hyperfine shifts were factored into contact and dipolar terms, revealing that the dipolar shift predominates and that contact shifts are relatively small. PMID:9751997

  7. Evaluation of the characteristics of boron-dose enhancer (BDE) materials for BNCT using near threshold 7Li(p,n)7Be direct neutrons

    NASA Astrophysics Data System (ADS)

    Bengua, Gerard; Kobayashi, Tooru; Tanaka, Kenichi; Nakagawa, Yoshinobu

    2004-03-01

    The characteristics of a number of candidate boron-dose enhancer (BDE) materials for boron neutron capture therapy (BNCT) using near threshold 7Li(p,n)7Be direct neutrons were evaluated based on the treatable protocol depth (TPD), defined in this paper. Simulation calculations were carried out by means of MCNP-4B transport code for candidate BDE materials, namely, (C2H4)n, (C2H3F)n, (C2H2F2)n, (C2HF3)n, (C2D4)n, (C2F4)n, beryllium metal, graphite, D2O and 7LiF. Dose protocols applied were those used for intra-operative BNCT treatment for brain tumour currently used in Japan. The maximum TPD (TPDmax) for each BDE material was found to be between 4 cm and 5 cm in the order of (C2H4)n < (C2H3F)n < (C2H2F2)n < (C2HF3)n < beryllium metal < (C2D4)n < graphite < (C2F4)n < D2O < 7LiF. Based on the small and arbitrary variations in the TPDmax for these materials, an explicit advantage of a candidate BDE material could not be established from the TPDmax alone. The dependence of TPD on BDE thickness was found to be influenced by the type of BDE material. For materials with hydrogen, sharp variations in TPD were observed, while those without hydrogen exhibited more moderate fluctuations in TPD as the BDE thickness was varied. The BDE thickness corresponding to TPDmax (BDE(TPDmax)) was also found to depend on the type of BDE material used. Thicker BDE(TPDmax), obtained mostly for BDE materials without hydrogen, significantly reduced the dose rates within the phantom. The TPDmax, the dependence of TPD on BDE thickness and the BDE (TPDmax) were ascertained as appropriate optimization criteria in choosing suitable BDE materials for BNCT. Among the candidate BDE materials considered in this study, (C2H4)n was judged as the suitable material for near-surface tumours and beryllium metal for deeper tumours based on these optimization criteria and other practical considerations.

  8. Isotopic splitting patterns in the (13) C NMR spectra of some partially deuterated 1-aryl-2-(phenyldiazenyl)butane-1,3-dione and 4-hydroxy-3-(phenyldiazenyl)-2H-chromen-2-one: evidence for elucidation of tautomeric forms.

    PubMed

    Noroozi Pesyan, Nader; Rashidnejad, Hamid

    2016-05-01

    Nuclear magnetic resonance spectra of synthesized azo dyes derived from aniline derivatives in reaction with benzoylacetone and 4-hydroxycoumarin were studied in both CDCl3 and (CD3 )2 SO (two drops of D2 O were added into solutions of dyes). All dyes showed intramolecular hydrogen bonding. Dyes derived from o-nitro aniline in the reaction with benzoylacetone, and 4-hydroxycoumarin showed bifurcated intramolecular hydrogen bonds. The solvent-substrate proton exchange of dyes derived from benzoylacetone and 4-hydroxycoumarin was examined in the presence of two drops of D2 O. Among ten dye samples, two dyes derived from benzoylacetone did not show deuteration, three dyes showed partial deuteration and five dyes showed full deuteration under similar conditions. For the partially deuterated dyes the β-isotope effect in (13) C splitting was investigated and was used for the determination of the predominant tautomeric form. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26776053

  9. A novel laser-collider used to produce monoenergetic 13.3 MeV 7Li (d, n) neutrons

    NASA Astrophysics Data System (ADS)

    Zhao, J. R.; Zhang, X. P.; Yuan, D. W.; Li, Y. T.; Li, D. Z.; Rhee, Y. J.; Zhang, Z.; Li, F.; Zhu, B. J.; Li, Yan F.; Han, B.; Liu, C.; Ma, Y.; Li, Yi F.; Tao, M. Z.; Li, M. H.; Guo, X.; Huang, X. G.; Fu, S. Z.; Zhu, J. Q.; Zhao, G.; Chen, L. M.; Fu, C. B.; Zhang, J.

    2016-06-01

    Neutron energy is directly correlated with the energy of the incident ions in experiments involving laser-driven nuclear reactions. Using high-energy incident ions reduces the energy concentration of the generated neutrons. A novel “laser-collider” method was used at the Shenguang II laser facility to produce monoenergetic neutrons via 7Li (d, n) nuclear reactions. The specially designed K-shaped target significantly increased the numbers of incident d and Li ions at the keV level. Ultimately, 13.3 MeV neutrons were obtained. Considering the time resolution of the neutron detector, we demonstrated that the produced neutrons were monoenergetic. Interferometry and a Multi hydro-dynamics simulation confirmed the monoenergetic nature of these neutrons.

  10. A Comprehensive Theoretical Analysis of 6,7Li + 64Zn Elastic Scattering in a Wide Angular Range Around the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Ibraheem, Awad A.; Aygun, M.

    2016-06-01

    In this paper, the elastic scattering angular distributions of 6,7Li on 64Zn have been investigated by using various nuclear potentials. For this, we use the phenomenological Woods-Saxon potential, the real double folding potential with the density-independent M3Y effective interaction supplemented with an imaginary part in Woods-Saxon form and the double folding potentials multiplied with a normalization factor of the real and imaginary parts via the density-independent and CDM3Y6 density-dependent versions of the M3Y effective interaction have been used. The results have been compared with each other as well as with the experimental data. It has been observed that the agreement between the theoretical results and earlier reported data is perfect. Finally, the change of the total reaction cross sections with energy has been investigated.

  11. A novel laser-collider used to produce monoenergetic 13.3 MeV 7Li (d, n) neutrons

    PubMed Central

    Zhao, J. R.; Zhang, X. P.; Yuan, D. W.; Li, Y. T.; Li, D. Z.; Rhee, Y. J.; Zhang, Z.; Li, F.; Zhu, B. J.; Li, Yan F.; Han, B.; Liu, C.; Ma, Y.; Li, Yi F.; Tao, M. Z.; Li, M. H.; Guo, X.; Huang, X. G.; Fu, S. Z.; Zhu, J. Q.; Zhao, G.; Chen, L. M.; Fu, C. B.; Zhang, J.

    2016-01-01

    Neutron energy is directly correlated with the energy of the incident ions in experiments involving laser-driven nuclear reactions. Using high-energy incident ions reduces the energy concentration of the generated neutrons. A novel “laser-collider” method was used at the Shenguang II laser facility to produce monoenergetic neutrons via 7Li (d, n) nuclear reactions. The specially designed K-shaped target significantly increased the numbers of incident d and Li ions at the keV level. Ultimately, 13.3 MeV neutrons were obtained. Considering the time resolution of the neutron detector, we demonstrated that the produced neutrons were monoenergetic. Interferometry and a Multi hydro-dynamics simulation confirmed the monoenergetic nature of these neutrons. PMID:27250660

  12. A novel laser-collider used to produce monoenergetic 13.3 MeV (7)Li (d, n) neutrons.

    PubMed

    Zhao, J R; Zhang, X P; Yuan, D W; Li, Y T; Li, D Z; Rhee, Y J; Zhang, Z; Li, F; Zhu, B J; Li, Yan F; Han, B; Liu, C; Ma, Y; Li, Yi F; Tao, M Z; Li, M H; Guo, X; Huang, X G; Fu, S Z; Zhu, J Q; Zhao, G; Chen, L M; Fu, C B; Zhang, J

    2016-01-01

    Neutron energy is directly correlated with the energy of the incident ions in experiments involving laser-driven nuclear reactions. Using high-energy incident ions reduces the energy concentration of the generated neutrons. A novel "laser-collider" method was used at the Shenguang II laser facility to produce monoenergetic neutrons via (7)Li (d, n) nuclear reactions. The specially designed K-shaped target significantly increased the numbers of incident d and Li ions at the keV level. Ultimately, 13.3 MeV neutrons were obtained. Considering the time resolution of the neutron detector, we demonstrated that the produced neutrons were monoenergetic. Interferometry and a Multi hydro-dynamics simulation confirmed the monoenergetic nature of these neutrons. PMID:27250660

  13. Radiative neutron capture by {sup 2}H, {sup 7}Li, {sup 14}C, and {sup 14}N nuclei at astrophysical energies

    SciTech Connect

    Dubovichenko, S. B.

    2013-07-15

    The possibility of describing experimental data on the total cross sections for the n{sup 2}H, n{sup 7}Li, n{sup 14}C, and n{sup 14}N radiative-capture processes within the potential cluster model involving forbidden states and their classification according to Young's tableaux is considered. It is shown that this model and the methods used here to construct potentials make it possible to describe correctly the behavior of the experimental cross sections at energies between 5 to 10 meV (5 Multiplication-Sign 10{sup -3}-10 Multiplication-Sign 10{sup -3} eV) and 1 to 15MeV.

  14. Search for solar axion emission from {sup 7}Li and D(p, γ){sup 3}He nuclear decays with the CAST γ-ray calorimeter

    SciTech Connect

    Andriamonje, S.; Aune, S.; Dafni, T.; Ferrer-Ribas, E.; Autiero, D.; Barth, K.; Davenport, M.; Lella, L. Di; Belov, A.; Beltrán, B.; Carmona, J.M.; Cebrián, S.; Bräuninger, H.; Englhauser, J.; Friedrich, P.; Collar, J.I.; Eleftheriadis, C.; Fanourakis, G.; Fischer, H.; Franz, J.; Collaboration: CAST collaboration; and others

    2010-03-01

    We present the results of a search for a high-energy axion emission signal from {sup 7}Li (0.478 MeV) and D(p, γ){sup 3}He (5.5 MeV) nuclear transitions using a low-background γ-ray calorimeter during Phase I of the CAST experiment. These so-called ''hadronic axions'' could provide a solution to the long-standing strong-CP problem and can be emitted from the solar core from nuclear M1 transitions. This is the first such search for high-energy pseudoscalar bosons with couplings to nucleons conducted using a helioscope approach. No excess signal above background was found.

  15. Width measurement of the {sup 6}Li{sub 4.31} state by the {sup 7}Li({sup 3}He, {alpha}d){alpha} reaction

    SciTech Connect

    Arena, N.; Cavallaro, S.; D`Agostino, P.; D`Arrigo, A.; Fazio, G.; Giardina, G.; Sacchi, M.; Eremin, N.V.; Klochko, T.U.; Lombardi, M.

    1995-02-01

    The J{sup {pi}} = 2{sup +}, T = 0 {sup 6}Li state at E{sub x} = 4.31 MeV was populated by the {sup 7}Li({sup 3}He, {alpha}d){alpha} reaction performed at 4, 5, and 6 MeV {sup 3}He incident energies. The values obtained for {Gamma}({sup 6}Li{sub 4.31}) were compared with those deduced from the above reaction at E({sup 3}He) = 2.5 MeV. In contrast to the findings of other authors, no dependence of the above parameter on incident energy was observed. 23 refs., 1 fig., 2 tabs.

  16. A Comprehensive Theoretical Analysis of 6,7Li + 64Zn Elastic Scattering in a Wide Angular Range Around the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Ibraheem, Awad A.; Aygun, M.

    2016-08-01

    In this paper, the elastic scattering angular distributions of 6,7Li on 64Zn have been investigated by using various nuclear potentials. For this, we use the phenomenological Woods-Saxon potential, the real double folding potential with the density-independent M3Y effective interaction supplemented with an imaginary part in Woods-Saxon form and the double folding potentials multiplied with a normalization factor of the real and imaginary parts via the density-independent and CDM3Y6 density-dependent versions of the M3Y effective interaction have been used. The results have been compared with each other as well as with the experimental data. It has been observed that the agreement between the theoretical results and earlier reported data is perfect. Finally, the change of the total reaction cross sections with energy has been investigated.

  17. Measurement of the 477.6-keV γ -ray production cross section following inelastic neutron scattering by 7Li

    NASA Astrophysics Data System (ADS)

    Nyman, M.; Belloni, F.; Ichinkhorloo, D.; Pirovano, E.; Plompen, A. J. M.; Rouki, C.

    2016-02-01

    The γ -ray production cross section for the 477.6-keV 1 /2-→3 /2g.s . - transition in 7Li following inelastic neutron scattering has been measured from the reaction threshold up to 18 MeV. This cross section is interesting as a possible standard for other γ -ray production cross-section measurements. The experiment was conducted at the GELINA pulsed white neutron source with the GAINS spectrometer consisting of 12 high-purity germanium detectors. The time-of-flight method was used for neutron energy determination. The sample was an optical-quality lithium fluoride disk and the neutron flux was monitored using a 235U fission chamber. Previous measurements of this cross section are reviewed and compared with our results. Recently, the examined cross section has been calculated using the continuum-discretized coupled-channels method. The results are found to be in reasonable agreement with the experimental data.

  18. Astrophysical SE2 factor of the 12C(α, γ)16O reaction through the 12C(11B, 7Li)16O transfer reaction

    NASA Astrophysics Data System (ADS)

    Guo, B.; Du, X. C.; Li, Z. H.; Li, Y. J.; Pang, D. Y.; Su, J.; Yan, S. Q.; Fan, Q. W.; Gan, L.; Han, Z. Y.; Li, E. T.; Li, X. Y.; Lian, G.; Liu, J. C.; Pei, C. J.; Qiao, L. H.; Shen, Y. P.; Su, Y.; Wang, Y. B.; Zeng, S.; Zhou, Y.; Liu, W. P.

    2016-02-01

    The 12C(α, γ)16O reaction plays a key role in the evolution of stars with masses of M > 0.55 M⊙. At the Gamow peak (Ec.m. = 300 ke V, T9 = 0.2), the cross section of the 12C(α, γ)16O reaction is so small (about 10-17 barn) that the direct measurement in ground laboratory is not feasible with the existing technology. Up to now, the cross sections at lower energies can only be extrapolated from the data at higher energies. However, two subthreshold resonances, locating at Ex = 7.117 MeV and Ex = 6.917 MeV, make this extrapolation more complicated. In this work the 6.917 MeV subthreshold resonance in the 12C(α, γ)16O reaction was investigated via the 12C(11B, 7Li)16O reaction. The experiment was performed using the Q3D magnetic spectrograph at HI-13 tandem accelerator. We measured the angular distribution of the 12C(11B, 7Li)16O transfer reaction leading to the 6.917 MeV state. Based on DWBA analysis, we derived the square of ANC of the 6.917 MeV level in 16O to be (2.45± 0.28) ×1010 fm-1, with which the reduced-α width can be computed. Finally, we calculated the astrophysical SE2 factor of the 6.917 MeV resonance to be 67.6 ± 7.7 ke V b.

  19. Two dimensional NMR spectroscopy

    SciTech Connect

    Schram, J.; Bellama, J.M.

    1988-01-01

    Two dimensional NMR represents a significant achievement in the continuing effort to increase solution in NMR spectroscopy. This book explains the fundamentals of this new technique and its analytical applications. It presents the necessary information, in pictorial form, for reading the ''2D NMR,'' and enables the practicing chemist to solve problems and run experiments on a commercial spectrometer by using the software provided by the manufacturer.

  20. A modularized pulse programmer for NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Mao, Wenping; Bao, Qingjia; Yang, Liang; Chen, Yiqun; Liu, Chaoyang; Qiu, Jianqing; Ye, Chaohui

    2011-02-01

    A modularized pulse programmer for a NMR spectrometer is described. It consists of a networked PCI-104 single-board computer and a field programmable gate array (FPGA). The PCI-104 is dedicated to translate the pulse sequence elements from the host computer into 48-bit binary words and download these words to the FPGA, while the FPGA functions as a sequencer to execute these binary words. High-resolution NMR spectra obtained on a home-built spectrometer with four pulse programmers working concurrently demonstrate the effectiveness of the pulse programmer. Advantages of the module include (1) once designed it can be duplicated and used to construct a scalable NMR/MRI system with multiple transmitter and receiver channels, (2) it is a totally programmable system in which all specific applications are determined by software, and (3) it provides enough reserve for possible new pulse sequences.

  1. 15N and13C NMR investigation of hydroxylamine-derivatized humic substances

    USGS Publications Warehouse

    Thorn, K.A.; Arterburn, J.B.; Mikita, M.A.

    1992-01-01

    Five fulvic and humic acid samples of diverse origins were derivatized with 15N-labeled hydroxylamine and analyzed by liquid-phase 15N NMR spectrometry. The 15N NMR spectra indicated that hydroxylamine reacted similarly with all samples and could discriminate among carbonyl functional groups. Oximes were the major derivatives; resonances attributable to hydroxamic acids, the reaction products of hydroxylamine with esters, and resonances attributable to the tautomeric equilibrium position between the nitrosophenol and monoxime derivatives of quinones, the first direct spectroscopic evidence for quinones, also were evident. The 15N NMR spectra also suggested the presence of nitriles, oxazoles, oxazolines, isocyanides, amides, and lactams, which may all be explained in terms of Beckmann reactions of the initial oxime derivatives. INEPT and ACOUSTIC 15N NMR spectra provided complementary information on the derivatized samples. 13C NMR spectra of derivatized samples indicated that the ketone/quinone functionality is incompletely derivatized with hydroxylamine. ?? 1991 American Chemical Society.

  2. Ultra-wideline solid-state NMR spectroscopy.

    PubMed

    Schurko, Robert W

    2013-09-17

    Although solid-state NMR (SSNMR) provides rich information about molecular structure and dynamics, the small spin population differences between pairs of spin states that give rise to NMR transitions make it an inherently insensitive spectroscopic technique in terms of signal acquisition. Scientists have continuously addressed this issue via improvements in NMR hardware and probes, increases in the strength of the magnetic field, and the development of innovative pulse sequences and acquisition methodologies. As a result, researchers can now study NMR-active nuclides previously thought to be unobservable or too unreceptive for routine examination via SSNMR. Several factors can make it extremely challenging to detect signal or acquire spectra using SSNMR: (i) low gyromagnetic ratios (i.e., low Larmor frequencies), (ii) low natural abundances or dilution of the nuclide of interest (e.g., metal nuclides in proteins or in organometallic catalysts supported on silica), (iii) inconvenient relaxation characteristics (e.g., very long longitudinal or very short transverse relaxation times), and/or (iv) extremely broad powder patterns arising from large anisotropic NMR interactions. Our research group has been particularly interested in efficient acquisition of broad NMR powder patterns for a variety of spin-1/2 and quadrupolar (spin > 1/2) nuclides. Traditionally, researchers have used the term "wideline" NMR to refer to experiments yielding broad (1)H and (2)H SSNMR spectra ranging from tens of kHz to ∼250 kHz in breadth. With modern FT NMR hardware, uniform excitation in these spectral ranges is relatively easy, allowing for the acquisition of high quality spectra. However, spectra that range in breadth from ca. 250 kHz to tens of MHz cannot be uniformly excited with conventional, high-power rectangular pulses. Rather, researchers must apply special methodologies to acquire such spectra, which have inherently low S/N because the signal intensity is spread across such

  3. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1988-08-01

    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.

  4. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1986-09-01

    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.

  5. Detection of Taurine in Biological Tissues by 33S NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Musio, Roberta; Sciacovelli, Oronzo

    2001-12-01

    The potential of 33S NMR spectroscopy for biochemical investigations on taurine (2-aminoethanesulfonic acid) is explored. It is demonstrated that 33S NMR spectroscopy allows the selective and unequivocal identification of taurine in biological samples. 33S NMR spectra of homogenated and intact tissues are reported for the first time, together with the spectrum of a living mollusc. Emphasis is placed on the importance of choosing appropriate signal processing methods to improve the quality of the 33S NMR spectra of biological tissues.

  6. Analysis of multiple pulse NMR in solids

    NASA Technical Reports Server (NTRS)

    Rhim, W.-K.; Elleman, D. D.; Vaughan, R. W.

    1973-01-01

    The general problems associated with the removal of the effects of dipolar broadening from solid-state NMR spectra are analyzed. The effects of finite pulse width and H sub 1 inhomogeneity are shown to have limited the resolution of previous pulse cycles, and a new eight-pulse cycle designed to minimize these problems is discussed. Spectra for F-19 in CaF2 taken with this cycle are presented which show residual linewidth near 10 Hz. The feasibility of measuring proton chemical shift tensors is discussed.

  7. Conformation of the nootropic agents 1-(4-methoxybenzoyl)-5-oxo-2-pyrrolidinepropanoic acid (CI-933) and 4-hydroxymethyl-1-benzyl-pyrrolidin-2-one (WEB-1868): X-ray crystal structures, theoretical MO calculations (AM-1) and 600 MHZ 1H NMR spectra

    NASA Astrophysics Data System (ADS)

    Amato, Maria E.; Bandoli, Giuliano; Djedaïni, Florence; Dolmella, Alessandro; Grassi, Antonio; Pappalardo, Giuseppe C.

    1990-05-01

    The crystal and molecular structures of the cognition activators 1-(4-methoxybenzoyl)-5-oxo-2-pyrrolidinepropanoic acid (CI-933) ( 1) and 4-hydroxymethyl-1-benzyl-pyrrolidin-2-one (WEB-1868) ( 2) have been determined by X-ray analysis. The conformations of the isolated molecules 1 and 2 have been deduced from AM1-type theoretical calculations. Whilst in 1 there are no hydrogen bonds, in 2 stabilization of the crystal occurs through effective inter- and intramolecular ? bonds. The five-membered ring in both 1 and 2 adopts an envelope conformation in the solid with C(3) at the flap displaced from the C(1), C(2), C(4), N(5) mean plane. Bond distances and angles are normal and comparable with previously known similar structures. In the crystal, the torsion angles C(1)-N(5)-C(6)-C(7) and N(5)-C(6)-C(7)-C(8) in 1 are 43.1° and 44.8°, respectively; the same torsion angles in 2 are -101° and 42°, respectively. Results of theoretical calculations correlate well with the conformation of 1 in the solid, whilst in the case of 2 these indicate that the conformation in the crystal should not be retained by the isolated molecule. The complete analysis of the very high field (600 MHz) 1H NMR spectra of both compounds in CDCl 3, gives results well in line with the above established conformational features.

  8. NMR logging apparatus

    DOEpatents

    Walsh, David O; Turner, Peter

    2014-05-27

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

  9. Silver and Gold NMR

    PubMed Central

    Zangger, Klaus

    1999-01-01

    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 gold have prevented its NMR spectroscopic investigation thus far. On the other hand, there are several reports of silver NMR. However, the low sensitivity of silver, combined with its long relaxation times have rendered the direct detection of silver possible only with concentrations greater than a few tenth molar. Reviewed here are the general limitations of silver NMR and some techniques to partially overcome these limitations, as well as a summary of currently available chemical shift and scalar coupling data on 109Ag. PMID:18475898

  10. Diffraction dissociation of {sup 7}Li and {sup 7}Be relativistic nuclei on proton targets through the {sup 3}H({sup 3}He)+{sup 4}He channels

    SciTech Connect

    Fetisov, V. N.

    2015-07-15

    For the fragmentation of {sup 7}Li and {sup 7}Be relativistic nuclei (with momenta of, respectively, P = 3 GeV/c and P = 1.6 GeV/c per nucleon) on proton targets through the {sup 3}H({sup 3}He) + {sup 4}He channels, the differential cross sections with respect to the momentum transfer Q to the fragments were calculated on the basis of the cluster version of Akhiezer–Glauber–Sitenko diffraction theory by employing the twobody cluster model for the {sup 7}Li ({sup 3}H + {sup 4}He) and {sup 7}Be ({sup 3}He + {sup 4}He) nuclei. These calculations, performed in the impulse approximation in the interaction of intranuclear clusters with the target nucleus, explained a strong suppression of the cross sections for reactions on protons at Q lower than 100 MeV/c and higher than 350 MeV/c and the observed irregularities in the behavior off the cross section for {sup 7}Li fragmentation on complex track-emulsion nuclei. Cross-section values close to their experimental counterparts were obtained upon setting the coefficient of two-body clustering in the {sup 7}Li and {sup 7}Be nuclei to k ≃ 0.7.

  11. Rapid characterization of molecular diffusion by NMR spectroscopy.

    PubMed

    Pudakalakatti, Shivanand M; Chandra, Kousik; Thirupathi, Ravula; Atreya, Hanudatta S

    2014-11-24

    An NMR-based approach for rapid characterization of translational diffusion of molecules has been developed. Unlike the conventional method of acquiring a series of 2D (13)C and (1)H spectra, the proposed approach involves a single 2D NMR spectrum, which can be acquired in minutes. Using this method, it was possible to detect the presence of intermediate oligomeric species of diphenylalanine in solution during the process of its self-assembly to form nanotubular structures. PMID:25331210

  12. Optimization of a neutron production target and a beam shaping assembly based on the 7Li( p, n) 7Be reaction for BNCT

    NASA Astrophysics Data System (ADS)

    Burlon, A. A.; Kreiner, A. J.; Valda, A. A.; Minsky, D. M.; Somacal, H. R.; Debray, M. E.; Stoliar, P.

    2005-02-01

    In this work a thick LiF target was studied through the 7Li( p, n) 7Be reaction as a neutron source for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT) to provide a testing ground for numerical simulations aimed at producing an optimized neutron production target and beam shaping assembly design. Proton beams in the 1.88-2.0 MeV energy range were produced with the tandem accelerator TANDAR ( TANDem ARgentino) at the Comisión Nacional de Energía Atómica (CNEA) in Buenos Aires, Argentina. A cylindrical water-filled head-phantom, containing a boric acid sample, was irradiated to study the resulting neutron flux. The dose deposited in the boric acid sample was inferred through the Compton-suppressed detection of the gamma radiation produced from the 10B( n, αγ) 7Li capture reaction. The thermal neutron flux was evaluated using bare and Cd-covered activation gold foils. In all cases, Monte Carlo simulations have been done showing good agreement with the experimental results. Extensive MCNP simulation trials have then been performed after the preliminary calculation tool validation in order to optimize a neutron beam shaping assembly. These simulations include a thick Li metal target (instead of LiF), a whole-body phantom, two different moderator-reflector assemblies (Al/AlF 3/LiF, Fluental ®, as moderator and lead as reflector and a combination of Al, PTFE (polytetrafluoroethylene) and LiF as moderator and lead as reflector) and the treatment room. The doses were evaluated for proton bombarding energies of 1.92 MeV (near to the threshold of the reaction), 2.0 MeV, 2.3 MeV (near the reaction resonance) and 2.5 MeV, and for three Fluental ® and Al/PTFE/LiF moderator thicknesses (18, 26 and 34 cm). In a later instance, the effect of the specific skin radiosensitivity (an RBE of 2.5 for the 10B( n, α) 7Li reaction) and a 10B uptake 50% greater than the healthy tissue one, was considered for the scalp. To evaluate the doses in the phantom, a comparison of

  13. Design and applications of an in situ electrochemical NMR cell

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaocan; Zwanziger, Josef W.

    2011-01-01

    A device using a three-electrode electrochemical cell (referred to as an ECNMR cell) was successfully constructed that could be used in a standard 5 mm NMR probe to acquire high-resolution NMR spectra while the working electrode was held at a constant electrical potential. The working electrode was a 20 nm thick gold film thermally coated on the outside of an inner 3 mm glass tube. An underlayer consisting of (3-mercaptopropyl)trimethoxy-silane was coated on the glass surface in order to improve its adhesion to gold. Tests showed prolonged life of the gold film. Details of the design and construction of the ECNMR cell are described. The ECNMR cell could be routinely used in a multi-user service high-resolution NMR instrument under oxygen-free conditions in both aqueous and non-aqueous solvents. Different approaches were applied to suppress the noise transmitted between the potentiostat and the NMR spectrometer. These approaches were shown to be effective in reducing background noise in the NMR spectra. The electrochemical and NMR performance of the ECNMR cell is presented. The reduction of 1,4-benzoquinone in both aqueous and non-aqueous solvents was used for testing. The evolution of the in situ ECNMR spectra with time demonstrated that use of the ECNMR cell was feasible. Studies of caffeic acid and 9-chloroanthracene using this ECNMR cell were undertaken to explore its applications, such as monitoring reactions and studying their reaction mechanisms.

  14. Capillary toroid cavity detector for high pressure NMR

    SciTech Connect

    Gerald, II, Rex E.; Chen, Michael J.; Klingler, Robert J.; Rathke, Jerome W.; ter Horst, Marc

    2007-09-11

    A Toroid Cavity Detector (TCD) is provided for implementing nuclear magnetic resonance (NMR) studies of chemical reactions under conditions of high pressures and temperatures. A toroid cavity contains an elongated central conductor extending within the toroid cavity. The toroid cavity and central conductor generate an RF magnetic field for NMR analysis. A flow-through capillary sample container is located within the toroid cavity adjacent to the central conductor to subject a sample material flowing through the capillary to a static magnetic field and to enable NMR spectra to be recorded of the material in the capillary under a temperature and high pressure environment.

  15. Structural biology applications of solid state MAS DNP NMR.

    PubMed

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance. PMID:27095695

  16. NMR studies on polyphosphide Ce6Ni6P17

    NASA Astrophysics Data System (ADS)

    Koyama, T.; Yamada, H.; Ueda, K.; Mito, T.; Aoyama, Y.; Nakano, T.; Takeda, N.

    2016-02-01

    We report the result of 31P nuclear magnetic resonance (NMR) studies on Ce6Ni6P17. The observed NMR spectra show a Lorentzian-type and an asymmetric shapes, reflecting the local symmetry around each P site in the cubic unit cell. We have identified the observed NMR lines corresponding to three inequivalent P sites and deduced the temperature dependence of the Knight shift for each site. The Knight shifts increase with decreasing temperature down to 1.5 K, indicating a localized spin system of Ce6Ni6P17. Antiferromagnetic correlation between 4f spins is suggested from the negative sign of the Weiss-temperature.

  17. Structural biology applications of solid state MAS DNP NMR

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.

  18. Monoterpene Unknowns Identified Using IR, [to the first power]H-NMR, [to the thirteenth power]C-NMR, DEPT, COSY, and HETCOR

    ERIC Educational Resources Information Center

    Alty, Lisa T.

    2005-01-01

    A study identifies a compound from a set of monoterpenes using infrared (IR) and one-dimensional (1D) nuclear magnetic resonance (NMR) techniques. After identifying the unknown, each carbon and proton signal can be interpreted and assigned to the structure using the information in the two-dimensional (2D) NMR spectra, correlation spectroscopy…

  19. High-resolution NMR spectroscopy under the fume hood.

    PubMed

    Küster, Simon K; Danieli, Ernesto; Blümich, Bernhard; Casanova, Federico

    2011-08-01

    This work reports the possibility to acquire high-resolution (1)H NMR spectra with a fist-sized NMR magnet directly installed under the fume hood. The small NMR sensor based on permanent magnets was used to monitor the trimerization of propionaldehyde catalyzed by indium trichloride in real time by continuously circulating the reaction mixture through the magnet bore in a closed loop with the help of a peristaltic pump. Thanks to the chemical selectivity of NMR spectroscopy the progress of the reaction can be monitored on-line by determining the concentrations of both reactant and product from the area under their respective lines in the NMR spectra as a function of time. This in situ measurement demonstrates that NMR probes can be used in chemistry laboratories, e.g. for reaction optimization, or installed at specific points of interest along industrial process lines. Therefore, it will open the door for the implementation of feedback control based on spectroscopic NMR data. PMID:21698335

  20. NMR data visualization, processing, and analysis on mobile devices.

    PubMed

    Cobas, Carlos; Iglesias, Isaac; Seoane, Felipe

    2015-08-01

    Touch-screen computers are emerging as a popular platform for many applications, including those in chemistry and analytical sciences. In this work, we present our implementation of a new NMR 'app' designed for hand-held and portable touch-controlled devices, such as smartphones and tablets. It features a flexible architecture formed by a powerful NMR processing and analysis kernel and an intuitive user interface that makes full use of the smart devices haptic capabilities. Routine 1D and 2D NMR spectra acquired in most NMR instruments can be processed in a fully unattended way. More advanced experiments such as non-uniform sampled NMR spectra are also supported through a very efficient parallelized Modified Iterative Soft Thresholding algorithm. Specific technical development features as well as the overall feasibility of using NMR software apps will also be discussed. All aspects considered the functionalities of the app allowing it to work as a stand-alone tool or as a 'companion' to more advanced desktop applications such as Mnova NMR. PMID:25924947

  1. Performance Assessment in Fingerprinting and Multi Component Quantitative NMR Analyses.

    PubMed

    Gallo, Vito; Intini, Nicola; Mastrorilli, Piero; Latronico, Mario; Scapicchio, Pasquale; Triggiani, Maurizio; Bevilacqua, Vitoantonio; Fanizzi, Paolo; Acquotti, Domenico; Airoldi, Cristina; Arnesano, Fabio; Assfalg, Michael; Benevelli, Francesca; Bertelli, Davide; Cagliani, Laura R; Casadei, Luca; Cesare Marincola, Flaminia; Colafemmina, Giuseppe; Consonni, Roberto; Cosentino, Cesare; Davalli, Silvia; De Pascali, Sandra A; D'Aiuto, Virginia; Faccini, Andrea; Gobetto, Roberto; Lamanna, Raffaele; Liguori, Francesca; Longobardi, Francesco; Mallamace, Domenico; Mazzei, Pierluigi; Menegazzo, Ileana; Milone, Salvatore; Mucci, Adele; Napoli, Claudia; Pertinhez, Thelma; Rizzuti, Antonino; Rocchigiani, Luca; Schievano, Elisabetta; Sciubba, Fabio; Sobolev, Anatoly; Tenori, Leonardo; Valerio, Mariacristina

    2015-07-01

    An interlaboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for multicomponent quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. A total of 36 NMR data sets (corresponding to 1260 NMR spectra) were produced by 30 participants using 34 NMR spectrometers. The calibration line method was chosen for the quantification of a five-component model mixture. Results show that quantitative NMR is a robust quantification tool and that 26 out of 36 data sets resulted in statistically equivalent calibration lines for all considered NMR signals. The performance of each laboratory was assessed by means of a new performance index (named Qp-score) which is related to the difference between the experimental and the consensus values of the slope of the calibration lines. Laboratories endowed with a Qp-score falling within the suitable acceptability range are qualified to produce NMR spectra that can be considered statistically equivalent in terms of relative intensities of the signals. In addition, the specific response of nuclei to the experimental excitation/relaxation conditions was addressed by means of the parameter named NR. NR is related to the difference between the theoretical and the consensus slopes of the calibration lines and is specific for each signal produced by a well-defined set of acquisition parameters. PMID:26020452

  2. Li NMR study of heavy-fermion LiV2O4 containing magnetic defects

    SciTech Connect

    Zong, X.; Das, S.; Borsa, F.; Vannette, M.; Prozorov, R.; Schmalian, J.; Johnston, D.

    2008-04-21

    We present a systematic study of the variations of the {sup 7}Li NMR properties versus magnetic defect concentration up to 0.83 mol% within the spinel structure of polycrystalline powder samples and a collection of small single crystals of LiV2O4 in the temperature range from 0.5 to 4.2 K. We also report static magnetization measurements and ac magnetic susceptibility measurements at 14 MHz on the samples at low temperatures. Both the NMR spectrum and nuclear spin-lattice relaxation rate are inhomogeneous in the presence of the magnetic defects. The NMR data for the powders are well explained by assuming that (i) there is a random distribution of magnetic point defects, (ii) the same heavy Fermi liquid is present in the samples containing the magnetic defects as in magnetically pure LiV2O4, and (iii) the influences of the magnetic defects and of the Fermi liquid on the magnetization and NMR properties are separable. In the single crystals, somewhat different behaviors are observed. Remarkably, the magnetic defects in the powder samples show evidence of spin freezing below T {approx} 1.0 K, whereas in the single crystals with similar magnetic defect concentration no spin freezing was found down to 0.5 K. Thus different types of magnetic defects and/or interactions between them appear to arise in the powders versus the crystals, possibly due to the substantially different synthesis conditions of the powders and crystals.

  3. Structural Evolution and Li Dynamics in Nanophase Li3PS4 by Solid-State and Pulsed Field Gradient NMR

    SciTech Connect

    Gobet, Mallory; Greenbaum, Steve; Sahu, Gayatri; Liang, Chengdu

    2014-01-01

    The ceramic lithium ion conductor -Li3PS4 has a disordered and nanoporous structure that leads to an enhancement in ionic conductivity by some three orders of magnitude compared to the crystalline phase. The phase is prepared by thermal treatment of an inorganic-organic complex based on Li3PS4 and THF. Multinuclear (1H, 6,7Li, 31P) solid state NMR spectroscopy is used to characterize the structural phase evolution of the starting material at various steps in the thermal treatment. The phase formed after high temperature treatment is recognized as spectroscopically distinct from the bulk -Li3PS4 compound. Also formed is an amorphous lithium thiophosphate phase that is metastable as verified by annealing over an extended period. Lithium ion self-diffusion coefficients are measurable by standard pulsed gradient NMR methods at 100oC and with values consistent with the high ionic conductivity previously reported for this material.

  4. Li dynamics in carbon-rich polymer-derived SiCN ceramics probed by NMR

    NASA Astrophysics Data System (ADS)

    Baek, Seung-Ho; Reinold, Lukas; Graczyk-Zajac, Magdalena; Riedel, Ralf; Hammerath, Franziska; Buechner, Bernd; Grafe, Hajo

    2014-03-01

    We report 7Li, 29Si, and 13C NMR studies of two different carbon-rich SiCN ceramics SiCN-1 and SiCN-3 derived from the preceramic polymers polyphenylvinylsilylcarbodiimide and polyphenylvinylsilazane, respectively. From the spectral analysis of the three nuclei at room temperature, we find that only the 13C spectrum is strongly influenced by Li insertion/extraction, suggesting that carbon phases are the major electrochemically active sites for Li storage. Temperature and Larmor frequency (ωL) dependences of the 7Li linewidth and spin-lattice relaxation rates T1-1 are described by an activated law with the activation energy EA of 0.31 eV and the correlation time τ0 in the high temperature limit of 1.3 ps. The 3 / 2 power law dependence of T1-1 on ωL which deviates from the standard Bloembergen, Purcell, and Pound (BPP) model implies that the Li motion on the μs timescale is governed by continuum diffusion mechanism rather than jump diffusion. On the other hand, the rotating frame relaxation rate T1ρ-1 results suggest that the slow motion of Li on the ms timescale may be affected by complex diffusion and/or non-diffusion processes.

  5. A microdosimetric study of {sup 10}B(n,{alpha}){sup 7}Li and {sup 157}Gd(n,{gamma}) reactions for neutron capture therapy

    SciTech Connect

    Wang, C.K.C.; Sutton, M.; Evans, T.M.; Laster, B.H.

    1999-01-01

    This paper presents the microdosimetric analysis for the most interesting cell survival experiment recently performed at the Brookhaven National Laboratory (BNL). In this experiment, the cells were first treated with a gadolinium (Gd) labeled tumor-seeking boronated porphyrin (Gd-BOPP) or with BOPP alone, and then irradiated with thermal neutrons. The resulting cell-survival curves indicate that the {sup 157}Gd(n,{gamma}) reactions are very effective in cell killing. The death of a cell treated with Gd-BOPP was attributed to either the {sup 10}B(n,{alpha}){sup 7}Li reactions or the {sup 157}Gd(n,{gamma}) reactions (or both). However, the quantitative relationship between the two types of reaction and the cell-survival fraction was not clear. This paper presents the microdosimetric analysis for the BNL experiment based on the measured experimental parameters, and the results clearly suggest a quantitative relationship between the two types of reaction and the cell survival fraction. The results also suggest new research in gadolinium neutron capture therapy (GdNCT) which may lead to a more practical modality than the boron neutron capture therapy (BNCT) for treating cancers.

  6. A microdosimetric study of {sup 10}B(n,{alpha}){sup 7}Li and {sup 157}Gd(n,{gamma}) reactions for neutron capture therapy

    SciTech Connect

    Wang, C.K.C.; Sutton, M.; Evans, T.M.; Laster, B.H.

    1996-12-31

    This paper presents the microdosimetric analysis for the most interesting cell survival experiment recently performed at the Brookhaven National Laboratory (BNL). In this experiment, the cells were first treated with a gadolinium (Gd) labeled tumor-seeking boronated porphyrin (Gd-BOPP) or with BOPP alone, and then irradiated with thermal neutrons. The resulting cell survival curves indicate that the {sup 157}Gd(n,{gamma}) reactions is very effective in cell killing. The death of a cell treated with GD-BOPP were attributed to either the {sup 10}B(n,{alpha}) {sup 7}Li reactions or the {sup 157}Gd(n,{gamma}) reactions (or both). However, the quantitative relationship between the two types of reaction and the cell survival fraction was not clear. This paper presents the microdosimetric analysis for the BNL experiment based on the measured experimental parameters, and the results clearly suggest a quantitative relationship between the two types of reaction and the cell survival fraction. The results also suggest new research in Gadolinium neutron capture therapy (GDNCT) which may lead to a more practical modality than the boron neutron capture therapy (BNCT) for treating cancers.

  7. Mechanical Property and Intergranular Corrosion Sensitivity of Zn-Free and Zn-Microalloyed Al-2.7Cu-1.7Li-0.3Mg Alloys

    NASA Astrophysics Data System (ADS)

    Li, Jin-feng; Xu, Long; Cai, Chao; Chen, Yong-lai; Zhang, Xu-hu; Zheng, Zi-qiao

    2014-11-01

    The influence of 0.72 pct Zn addition on the tensile properties of Al-2.7Cu-1.7Li-0.3Mg alloys was investigated. Their intergranular corrosion (IGC) dependence on aging [T6 type at 423 K (150 °C) and 448 K (175 °C) and T8 type at 423 K (150 °C)] time was studied. An IGC diagram associated with aging process was established. The addition of 0.72 pct Zn enhanced the strength of the Al-Li alloy with T6 type aging at 448 K (175 °C). With aging process, the corrosion mode of the T6-aged Al-Li alloys was changed in the following order: pitting and local IGC (initial aging stage), general IGC (underaging stage), local IGC (near peak-aging stage), and pitting (overaging stage) again. The IGC depth was increased first and then decreased with aging time extension. The corrosion potential change of grains and the microstructure variation were used to explain the IGC sensitivity of the Al-Li alloy with different tempers. Meanwhile, 0.72 pct Zn addition decreased the IGC sensitivity of the Al-Li alloy, especially the T6-aged Al-Li alloy.

  8. Mechanical Property and Intergranular Corrosion Sensitivity of Zn-Free and Zn-Microalloyed Al-2.7Cu-1.7Li-0.3Mg Alloys

    NASA Astrophysics Data System (ADS)

    Li, Jin-feng; Xu, Long; Cai, Chao; Chen, Yong-lai; Zhang, Xu-hu; Zheng, Zi-qiao

    2014-09-01

    The influence of 0.72 pct Zn addition on the tensile properties of Al-2.7Cu-1.7Li-0.3Mg alloys was investigated. Their intergranular corrosion (IGC) dependence on aging [T6 type at 423 K (150 °C) and 448 K (175 °C) and T8 type at 423 K (150 °C)] time was studied. An IGC diagram associated with aging process was established. The addition of 0.72 pct Zn enhanced the strength of the Al-Li alloy with T6 type aging at 448 K (175 °C). With aging process, the corrosion mode of the T6-aged Al-Li alloys was changed in the following order: pitting and local IGC (initial aging stage), general IGC (underaging stage), local IGC (near peak-aging stage), and pitting (overaging stage) again. The IGC depth was increased first and then decreased with aging time extension. The corrosion potential change of grains and the microstructure variation were used to explain the IGC sensitivity of the Al-Li alloy with different tempers. Meanwhile, 0.72 pct Zn addition decreased the IGC sensitivity of the Al-Li alloy, especially the T6-aged Al-Li alloy.

  9. Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B1Π of 7LiH

    NASA Astrophysics Data System (ADS)

    Shi, De-Heng; Liu, Yu-Fang; Sun, Jin-Feng; Zhu, Zun-Lue; Yang, Xiang-Dong

    2006-12-01

    The reasonable dissociation limit of the second excited singlet state B1Π of 7LiH molecule is obtained. The accurate dissociation energy and equilibrium geometry of the B1Π state are calculated using a symmetry-adapted-cluster configuration-interaction method in full active space. The whole potential energy curve for the B1Π state is obtained over the internuclear distance ranging from about 0.10 nm to 0.54 nm, and has a least-square fit to the analytic Murrell-Sorbie function form. The vertical excitation energy is calculated from the ground state to the B1Π state and compared with previous theoretical results. The equilibrium internuclear distance obtained by geometry optimization is found to be quite different from that obtained by single-point energy scanning under the same calculation condition. Based on the analytic potential energy function, the harmonic frequency value of the B1Π state is estimated. A comparison of the theoretical calculations of dissociation energies, equilibrium interatomic distances and the analytic potential energy function with those obtained by previous theoretical results clearly shows that the present work is more comprehensive and in better agreement with experiments than previous theories, thus it is an improvement on previous theories.

  10. Development of liquid-lithium film jet-flow for the target of (7)Li(p,n)(7)Be reactions for BNCT.

    PubMed

    Kobayashi, Tooru; Miura, Kuniaki; Hayashizaki, Noriyosu; Aritomi, Masanori

    2014-06-01

    A feasibility study on liquid lithium target in the form of a flowing film was performed to evaluate its potential use as a neutron generation target of (7)Li(p,n)(7)Be reaction in BNCT. The target is a windowless-type flowing film on a concave wall. Its configuration was adapted for a proton beam which is 30mm in diameter and with energy and current of up to 3MeV and 20mA, respectively. The flowing film of liquid lithium was 0.6mm in thickness, 50mm in width and 50mm in length. The shapes of the nozzle and concave back wall, which create a stable flowing film jet, were decided based on water experiments. A lithium hydrodynamic experiment was performed to observe the stability of liquid lithium flow behavior. The flowing film of liquid lithium was found to be feasible at temperatures below the liquid lithium boiling saturation of 342°C at the surface pressure of 1×10(-3)Pa. Using a proto-type liquid lithium-circulating loop for BNCT, the stability of the film flow was confirmed for velocities up to 30m/s at 220°C and 250°C in vacuum at a pressure lower than 10(-3) Pa. It is expected that for practical use, a flowing liquid lithium target of a windowless type can solve the problem of radiation damage and target cooling. PMID:24412425

  11. Metals, a Plasma of the Poor Man: Electron Screening in 7Li(p,{alpha}){alpha} and 6Li(p,{alpha})3He for Different Environments

    SciTech Connect

    Rolfs, C.

    2006-05-24

    The electron screening in the 7Li(p,{alpha}){alpha} reaction has been studied at Ep = 30 to 100 keV for different environments: Li2WO4 insulator, Li metal, and PdLi alloys. For the insulator a screening potential energy of Ue = 185{+-}150 eV was observed, consistent with previous work and the atomic adiabatic limit. However, for the Li metal and the PdLi alloys we find large values of Ue = 1280{+-}60 and 3790{+-}330 eV, respectively: the values can be explained by the plasma model of Debye applied to the quasi-free metallic electrons in these samples. Similar results have been found for the 6Li(p,{alpha})3He reaction supporting the hypothesis of the isotopic independence of the electron screening effect. The data together with previous studies of d(d,p)t and 9Be(p,{alpha})6Li in metals verify the Debye model scaling Ue {proportional_to} Zt (charge number of target)

  12. Li(+) Local Structure in Li-Tetraglyme Solvate Ionic Liquid Revealed by Neutron Total Scattering Experiments with the (6/7)Li Isotopic Substitution Technique.

    PubMed

    Saito, Soshi; Watanabe, Hikari; Hayashi, Yutaka; Matsugami, Masaru; Tsuzuki, Seiji; Seki, Shiro; Canongia Lopes, José N; Atkin, Rob; Ueno, Kazuhide; Dokko, Kaoru; Watanabe, Masayoshi; Kameda, Yasuo; Umebayashi, Yasuhiro

    2016-07-21

    Equimolar mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraglyme (G4: CH3O-(CH2CH2O)4-CH3) yield the solvate (or chelate) ionic liquid [Li(G4)][TFSA], which is a homogeneous transparent solution at room temperature. Solvate ionic liquids (SILs) are currently attracting increasing research interest, especially as new electrolytes for Li-sulfur batteries. Here, we performed neutron total scattering experiments with (6/7)Li isotopic substitution to reveal the Li(+) solvation/local structure in [Li(G4)][TFSA] SILs. The experimental interference function and radial distribution function around Li(+) agree well with predictions from ab initio calculations and MD simulations. The model solvation/local structure was optimized with nonlinear least-squares analysis to yield structural parameters. The refined Li(+) solvation/local structure in the [Li(G4)][TFSA] SIL shows that lithium cations are not coordinated to all five oxygen atoms of the G4 molecule (deficient five-coordination) but only to four of them (actual four-coordination). The solvate cation is thus considerably distorted, which can be ascribed to the limited phase space of the ethylene oxide chain and competition for coordination sites from the TFSA anion. PMID:27388117

  13. Formation of ultracold (7)Li(85)Rb molecules in the lowest triplet electronic state by photoassociation and their detection by ionization spectroscopy.

    PubMed

    Altaf, Adeel; Dutta, Sourav; Lorenz, John; Pérez-Ríos, Jesús; Chen, Yong P; Elliott, D S

    2015-03-21

    We report the formation of ultracold (7)Li(85)Rb molecules in the a(3)Σ(+) electronic state by photoassociation (PA) and their detection via resonantly enhanced multiphoton ionization (REMPI). With our dual-species Li and Rb magneto-optical trap apparatus, we detect PA resonances with binding energies up to ∼62 cm(-1) below the (7)Li 2s (2)S1/2 + (85)Rb 5p (2)P1/2 asymptote. In addition, we use REMPI spectroscopy to probe the a(3)Σ(+) state and excited electronic 3(3)Π and 4(3)Σ(+) states and identify a(3)Σ(+) (v″ = 7-13), 3(3)Π (vΠ' = 0-10), and 4(3)Σ(+) (vΣ' = 0-5) vibrational levels. Our line assignments agree well with ab initio calculations. These preliminary spectroscopic studies on previously unobserved electronic states are crucial to discovering transition pathways for transferring ultracold LiRb molecules created via PA to deeply bound rovibrational levels of the electronic ground state. PMID:25796252

  14. Formation of ultracold {sup 7}Li{sup 85}Rb molecules in the lowest triplet electronic state by photoassociation and their detection by ionization spectroscopy

    SciTech Connect

    Altaf, Adeel Dutta, Sourav; Lorenz, John; Pérez-Ríos, Jesús; Chen, Yong P.; Elliott, D. S.

    2015-03-21

    We report the formation of ultracold {sup 7}Li{sup 85}Rb molecules in the a{sup 3}Σ{sup +} electronic state by photoassociation (PA) and their detection via resonantly enhanced multiphoton ionization (REMPI). With our dual-species Li and Rb magneto-optical trap apparatus, we detect PA resonances with binding energies up to ∼62 cm{sup −1} below the {sup 7}Li 2s {sup 2}S{sub 1/2} + {sup 85}Rb 5p {sup 2}P{sub 1/2} asymptote. In addition, we use REMPI spectroscopy to probe the a{sup 3}Σ{sup +} state and excited electronic 3{sup 3}Π and 4{sup 3}Σ{sup +} states and identify a{sup 3}Σ{sup +} (v″ = 7–13), 3{sup 3}Π (v{sub Π}′ = 0–10), and 4{sup 3}Σ{sup +} (v{sub Σ}′ = 0–5) vibrational levels. Our line assignments agree well with ab initio calculations. These preliminary spectroscopic studies on previously unobserved electronic states are crucial to discovering transition pathways for transferring ultracold LiRb molecules created via PA to deeply bound rovibrational levels of the electronic ground state.

  15. Ultrafast multidimensional Laplace NMR for a rapid and sensitive chemical analysis

    NASA Astrophysics Data System (ADS)

    Ahola, Susanna; Zhivonitko, Vladimir V.; Mankinen, Otto; Zhang, Guannan; Kantola, Anu M.; Chen, Hsueh-Ying; Hilty, Christian; Koptyug, Igor V.; Telkki, Ville-Veikko

    2015-09-01

    Traditional nuclear magnetic resonance (NMR) spectroscopy relies on the versatile chemical information conveyed by spectra. To complement conventional NMR, Laplace NMR explores diffusion and relaxation phenomena to reveal details on molecular motions. Under a broad concept of ultrafast multidimensional Laplace NMR, here we introduce an ultrafast diffusion-relaxation correlation experiment enhancing the resolution and information content of corresponding 1D experiments as well as reducing the experiment time by one to two orders of magnitude or more as compared with its conventional 2D counterpart. We demonstrate that the method allows one to distinguish identical molecules in different physical environments and provides chemical resolution missing in NMR spectra. Although the sensitivity of the new method is reduced due to spatial encoding, the single-scan approach enables one to use hyperpolarized substances to boost the sensitivity by several orders of magnitude, significantly enhancing the overall sensitivity of multidimensional Laplace NMR.

  16. Ultrafast multidimensional Laplace NMR for a rapid and sensitive chemical analysis

    PubMed Central

    Ahola, Susanna; Zhivonitko, Vladimir V; Mankinen, Otto; Zhang, Guannan; Kantola, Anu M.; Chen, Hsueh-Ying; Hilty, Christian; Koptyug, Igor V.; Telkki, Ville-Veikko

    2015-01-01

    Traditional nuclear magnetic resonance (NMR) spectroscopy relies on the versatile chemical information conveyed by spectra. To complement conventional NMR, Laplace NMR explores diffusion and relaxation phenomena to reveal details on molecular motions. Under a broad concept of ultrafast multidimensional Laplace NMR, here we introduce an ultrafast diffusion-relaxation correlation experiment enhancing the resolution and information content of corresponding 1D experiments as well as reducing the experiment time by one to two orders of magnitude or more as compared with its conventional 2D counterpart. We demonstrate that the method allows one to distinguish identical molecules in different physical environments and provides chemical resolution missing in NMR spectra. Although the sensitivity of the new method is reduced due to spatial encoding, the single-scan approach enables one to use hyperpolarized substances to boost the sensitivity by several orders of magnitude, significantly enhancing the overall sensitivity of multidimensional Laplace NMR. PMID:26381101

  17. NMR studies of the conformation and motion of tetrahydrofuran in graphite intercalation compounds

    SciTech Connect

    Caplan, D. F.

    1991-11-01

    The behavior of tetrahydrofuran (THF) molecules intercalated in graphite layers in compounds Cs(THF){sub 1.3}C{sub 24} and K(THF){sub 2.5}C{sub 24} was studied by proton NMR. The graphite layers in these compounds impose a uniform ordering on the THF molecules, giving rise to sharp NMR spectra. Experimental and simulated proton NMR spectra were used to investigate geometry, orientation and conformation of intercalated THF, and to determine whether pseudorotation, a large amplitude low-frequency vibration observed in gaseous THF, can also occur in the constrained environment provided by the graphite intercalation compounds. Deuterium and multiple quantum proton NMR spectra were also simulated in order to determine if these techniques could further refine the proton NMR results.

  18. An NMR Study of Microvoids in Polymers

    NASA Technical Reports Server (NTRS)

    Toy, James; Mattrix, Larry

    1996-01-01

    An understanding of polymer defect structures, like microvoids in polymeric matrices, is most crucial to their fabrication and application potential. In this project guest atoms are introduced into the microvoids in PMR-15 and NMR is used to determine microvoid sizes and locations. Xenon is a relatively inert probe that would normally not be found naturally in polymer or in NMR probe materials. There are two NMR active Xenon isotopes, Xe-129 and Xe-131. The Xe atom has a very high polarizability, which makes it sensitive to the intracrystalline environment of polymers. Interactions between the Xe atoms and the host matrix perturb and Xe electron cloud, deshielding the nuclei, and thereby expanding the range of the observed NMR chemical shifts. This chemical shift range which may be as large as 5000 ppm, permits subtle structural and chemical effects to be studied with high sensitivity. The Xe-129-NMR line shape has been found to vary in response to changes in the pore symmetry of the framework hosts in Zeolites and Clathrasil compounds. Before exposure to Xe gas, the PMR-15 samples were dried in a vacuum oven at 150 C for 48 hours. The samples were then exposed to Xe gas at 30 psi for 72 hours and sealed in glass tubes with 1 atmosphere of Xenon gas. Xenon gas at 1 atmosphere was used to tune up the spectrometer and to set up the appropriate NMR parameters. A series of spectra were obtained interspersed with applications of vacuum and heating to drive out the adsorbed Xe and determine the role of Xe-Xe interactions in the observed chemical shift.

  19. Automated protein fold determination using a minimal NMR constraint strategy

    PubMed Central

    Zheng, Deyou; Huang, Yuanpeng J.; Moseley, Hunter N.B.; Xiao, Rong; Aramini, James; Swapna, G.V.T.; Montelione, Gaetano T.

    2003-01-01

    Determination of precise and accurate protein structures by NMR generally requires weeks or even months to acquire and interpret all the necessary NMR data. However, even medium-accuracy fold information can often provide key clues about protein evolution and biochemical function(s). In this article we describe a largely automatic strategy for rapid determination of medium-accuracy protein backbone structures. Our strategy derives from ideas originally introduced by other groups for determining medium-accuracy NMR structures of large proteins using deuterated, 13C-, 15N-enriched protein samples with selective protonation of side-chain methyl groups (13CH3). Data collection includes acquiring NMR spectra for automatically determining assignments of backbone and side-chain 15N, HN resonances, and side-chain 13CH3 methyl resonances. These assignments are determined automatically by the program AutoAssign using backbone triple resonance NMR data, together with Spin System Type Assignment Constraints (STACs) derived from side-chain triple-resonance experiments. The program AutoStructure then derives conformational constraints using these chemical shifts, amide 1H/2H exchange, nuclear Overhauser effect spectroscopy (NOESY), and residual dipolar coupling data. The total time required for collecting such NMR data can potentially be as short as a few days. Here we demonstrate an integrated set of NMR software which can process these NMR spectra, carry out resonance assignments, interpret NOESY data, and generate medium-accuracy structures within a few days. The feasibility of this combined data collection and analysis strategy starting from raw NMR time domain data was illustrated by automatic analysis of a medium accuracy structure of the Z domain of Staphylococcal protein A. PMID:12761394

  20. Three-Dimensional Maximum-Quantum Correlation HMQC NMR Spectroscopy (3D MAXY-HMQC)

    NASA Astrophysics Data System (ADS)

    Liu, Maili; Mao, Xi-An; Ye, Chaohui; Nicholson, Jeremy K.; Lindon, John C.

    1997-11-01

    The extension of two-dimensional maximum-quantum correlation spectroscopy (2D MAXY NMR), which can be used to simplify complex NMR spectra, to three dimensions (3D) is described. A new pulse sequence for 3D MAXY-HMQC is presented and exemplified using the steroid drug dexamethasone. The sensitivity and coherence transfer efficiency of the MAXY NMR approach has also been assessed in relation to other HMQC- and HSQC-based 3D methods.

  1. Isolation and 2D NMR Studies of Alkaloids from Comptonella sessilifoliola1.

    PubMed

    Pusset, J; Lopez, J L; Pais, M; Neirabeyeh, M A; Veillon, J M

    1991-04-01

    Six known furanoquinoline alkaloids have been isolated from the wood and trunk bark of COMPTONELLA SESSILIFOLIOLA (Guillaumin) Hartley (Rutaceae). 2D NMR experiments gave the assignment of all the signals for both (1)H- and (13)C-NMR spectra. Pteleine and kokusaginine were used as models. The two-dimensional carbon-proton correlation experiments, performed for the first time on furanoquinoline alkaloids, led us to correct (13)C-NMR assignments previously described in the literature. PMID:17226139

  2. Slow-MAS NMR: A New Technology for In Vivo Metabolomic Studies

    SciTech Connect

    Wind, Robert A.; Hu, Jian Zhi; Majors, Paul D.

    2005-08-01

    Improvements in the ability to obtain detailed in vivo metabolic information have been identified as key elements of better understanding the efficacy and toxicity of new therapies. A new NMR technology called LOCMAT is discussed that yields substantially increased spectral resolution of spatially localized in vivo 1H NMR metabolite spectra, as illustrated by measurements in the liver and heart of a live mouse. Thus, LOCMAT promises to significantly enhance the utility of NMR spectroscopy for biomedical research.

  3. Development and applications of NMR (nuclear magnetic resonance) in low fields and zero field

    SciTech Connect

    Bielecki, A.

    1987-05-01

    This dissertation is about nuclear magnetic resonance (NMR) spectroscopy in the absence of applied magnetic fields. NMR is usually done in large magnetic fields, often as large as can be practically attained. The motivation for going the opposite way, toward zero field, is that for certain types of materials, particularly powdered or polycrystalline solids, the NMR spectra in zero field are easier to interpret than those obtained in high field. 92 refs., 60 figs., 1 tab.

  4. Experimental and theoretical study of the intramolecular C-H···N and C-H···S hydrogen bonding effects in the 1H and 13C NMR spectra of the 2-(alkylsulfanyl)-5-amino-1-vinylpyrroles: a particular state of amine nitrogen.

    PubMed

    Afonin, Andrei V; Pavlov, Dmitry V; Albanov, Alexander I; Tarasova, Ol'ga A; Nedolya, Nina A

    2013-07-01

    In the (1)H NMR spectra of the 1-vinylpyrroles with amino- and alkylsulfanyl groups in 5 and 2 positions, an extraordinarily large difference between resonance positions of the HA and HB terminal methylene protons of the vinyl group is discovered. Also, the one-bond (1)J(C(β),H(B)) coupling constant is surprisingly greater than the (1)J(C(β),H(A)) coupling constant in pyrroles under investigation, while in all known cases, there was a reverse relationship between these coupling constants. These spectral anomalies are substantiated by quantum chemical calculations. The calculations show that the amine nitrogen lone pair is removed from the conjugation with the π-system of the pyrrole ring so that it is directed toward the HB hydrogen. These factors are favorable to the emergence of the intramolecular C-HB •••N hydrogen bonding in the s-cis(N) conformation. On the other hand, the spatial proximity of the sulfur to the HB hydrogen provides an opportunity of the intramolecular C-HB •••S hydrogen bonding in the s-cis(S) conformation. Presence of the hydrogen bond critical points as well as ring critical point for corresponding chelate ring revealed by a quantum theory of atoms in molecules (QTAIM) approach confirms the existence of the weak intramolecular C-H•••N and C-H•••S hydrogen bonding. Therefore, an unusual high-frequency shift of the HB signal and the increase in the (1)J(C(β),H(B)) coupling constant can be explained by the effects of hydrogen bonding. PMID:23695830

  5. BOOK REVIEW: NMR Imaging of Materials

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard

    2003-09-01

    spectroscopic methods to weight or filter the spin signals represents the core of the book. This is a subject where Blümich is deeply involved with substantial contributions. The chapter includes a lot of ideas to provide MR contrast between different regions based on their mobility, diffusion, spin couplings or NMR spectra. After describing NMR imaging methods for solids with broad lines, Blümich spends time on applications in the last two chapters of the book. This part is really fun to read. It underlines the effort to bring NMR into many kinds of manufacturing. Car tyres and high-voltage cables are just two such areas. Elastomeric materials, green-state ceramics and food science represent other interesting fields of applications. This part of the book represents a personal but nevertheless extensive compilation of modern applications. As a matter of course the MOUSE is presented, a portable permanent-magnet based NMR developed by Blümich and his co-workers. Thus the book is not only of interest to NMR spectroscopists but also to people in material science and chemical engineering. The bibliography and indexing are excellent and may serve as an attractive reference source for NMR spectroscopists. The book is the first on the subject and likely to become the standard text for NMR imaging of materials as the books by Abragam, Slicher and Ernst et al are for NMR spectroscopy. The purchase of this beautiful book for people dealing with NMR spectroscopy or medical MRI is highly recommended. Ralf Ludwig

  6. SQUID detected NMR in microtesla magnetic fields

    NASA Astrophysics Data System (ADS)

    Matlachov, Andrei N.; Volegov, Petr L.; Espy, Michelle A.; George, John S.; Kraus, Robert H.

    2004-09-01

    We have built an NMR system that employs a superconducting quantum interference device (SQUID) detector and operates in measurement fields of 2-25 μT. The system uses a pre-polarizing field from 4 to 30 mT generated by simple room-temperature wire-wound coils that are turned off during measurements. The instrument has an open geometry with samples located outside the cryostat at room-temperature. This removes constraints on sample size and allows us to obtain signals from living tissue. We have obtained 1H NMR spectra from a variety of samples including water, mineral oil, and a live frog. We also acquired gradient encoded free induction decay (FID) data from a water-plastic phantom in the μT regime, from which simple projection images were reconstructed. NMR signals from samples inside metallic containers have also been acquired. This is possible because the penetration skin depth is much greater at the low operating frequencies of this system than for conventional systems. Advantages to ultra-low field NMR measurements include lower susceptibility artifacts caused by high strength polarizing and measurement fields, and negligible line width broadening due to measurement field inhomogeneity, reducing the burden of producing highly homogeneous fields.

  7. /sup 29/Si NMR study of the surface of pyrogenic silica modified by methylchlorosilanes

    SciTech Connect

    Brie, V.V.; Gorlov, Yu.I.; Chuiko, A.A.

    1986-11-01

    Cross-polarization /sup 29/Si NMR spectra have been used for aerosil modified by methyl-chlorosilanes to identify surface organosilicon compounds and their reactions during hydrolysis and methanolysis.

  8. On the microscopic fluctuations driving the NMR relaxation of quadrupolar ions in water

    SciTech Connect

    Carof, Antoine; Salanne, Mathieu; Rotenberg, Benjamin; Charpentier, Thibault

    2015-11-21

    Nuclear Magnetic Resonance (NMR) relaxation is sensitive to the local structure and dynamics around the probed nuclei. The Electric Field Gradient (EFG) is the key microscopic quantity to understand the NMR relaxation of quadrupolar ions, such as {sup 7}Li{sup +}, {sup 23}Na{sup +}, {sup 25}Mg{sup 2+}, {sup 35}Cl{sup −}, {sup 39}K{sup +}, or {sup 133}Cs{sup +}. Using molecular dynamics simulations, we investigate the statistical and dynamical properties of the EFG experienced by alkaline, alkaline Earth, and chloride ions at infinite dilution in water. Specifically, we analyze the effect of the ionic charge and size on the distribution of the EFG tensor and on the multi-step decay of its auto-correlation function. The main contribution to the NMR relaxation time arises from the slowest mode, with a characteristic time on the picosecond time scale. The first solvation shell of the ion plays a dominant role in the fluctuations of the EFG, all the more that the ion radius is small and its charge is large. We propose an analysis based on a simplified charge distribution around the ion, which demonstrates that the auto-correlation of the EFG, hence the NMR relaxation time, reflects primarily the collective translational motion of water molecules in the first solvation shell of the cations. Our findings provide a microscopic route to the quantitative interpretation of NMR relaxation measurements and open the way to the design of improved analytical theories for NMR relaxation for small ionic solutes, which should focus on water density fluctuations around the ion.

  9. An Analysis of a Commercial Furniture Refinisher: A Comprehensive Introductory NMR Experiment.

    ERIC Educational Resources Information Center

    Markow, Peter G.; Cramer, John A.

    1983-01-01

    Describes a comprehensive nuclear magnetic resonance (NMR) experiment designed to introduce undergraduate organic chemistry students to measurement/interpretation of NMR parameters. Students investigate chemical shift analysis, spin-spin coupling, peak integrations, effect of deuterium oxide extraction, and comparisons with literature spectra;…

  10. Experimental Determination of pK[subscript a] Values by Use of NMR Chemical Shifts, Revisited

    ERIC Educational Resources Information Center

    Gift, Alan D.; Stewart, Sarah M.; Bokashanga, Patrick Kwete

    2012-01-01

    This laboratory experiment, using proton NMR spectroscopy to determine the dissociation constant for heterocyclic bases, has been modified from a previously described experiment. A solution of a substituted pyridine is prepared using deuterium oxide (D[subscript 2]O) as the solvent. The pH of the solution is adjusted and proton NMR spectra are…

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

    PubMed

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

    2013-04-14

    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

  12. NMR Observation of Impurity-Pair Ordering in Weakly Disordered Solid Solutions

    NASA Astrophysics Data System (ADS)

    Ailion, David; Zalar, Bostjan; Lebar, Andrija

    2007-03-01

    Breaking of the average cubic symmetry in Li-doped potassium tantalate (K1-xLixTaO3) was observed with quadrupole-perturbed ^7LiNMR at temperatures (150-400 K) far above the nominal glass transition temperature (80 K). The observed spectrum consists of contributions from both isolated Li ions (i.e., with no nearest neighbor Li) and from Li pairs. The isolated Li ions move among six equivalent off-center sites in a potential having cubic symmetry. These have zero average electric-field gradient and, hence, exhibit no quadrupole splitting. In addition, very low intensity, but well resolved, quadrupole satellites having a temperature-dependent splitting were observed. This splitting indicates that the various Li pair configurations are not all equally probable. These are the first observations of biased Li-ion ordering that persists in the paraelectric phase at temperatures high above the glass phase.

  13. NMR imaging microscopy

    SciTech Connect

    Not Available

    1986-10-01

    In the past several years, proton nuclear magnetic resonance (NMR) imaging has become an established technique in diagnostic medicine and biomedical research. Although much of the work in this field has been directed toward development of whole-body imagers, James Aguayo, Stephen Blackband, and Joseph Schoeninger of the Johns Hopkins University School of Medicine working with Markus Hintermann and Mark Mattingly of Bruker Medical Instruments, recently developed a small-bore NMR microscope with sufficient resolution to image a single African clawed toad cell (Nature 1986, 322, 190-91). This improved resolution should lead to increased use of NMR imaging for chemical, as well as biological or physiological, applications. The future of NMR microscopy, like that of many other newly emerging techniques, is ripe with possibilities. Because of its high cost, however, it is likely to remain primarily a research tool for some time. ''It's like having a camera,'' says Smith. ''You've got a way to look at things at very fine levels, and people are going to find lots of uses for it. But it is a very expensive technique - it costs $100,000 to add imaging capability once you have a high-resolution NMR, which itself is at least a $300,000 instrument. If it can answer even a few questions that can't be answered any other way, though, it may be well worth the cost.''

  14. Ab initio calculation of accurate dissociation energy, potential energy curve and dipole moment function for the A1Σ+ state 7LiH molecule

    NASA Astrophysics Data System (ADS)

    Shi, De-Heng; Liu, Yu-Fang; Sun, Jin-Feng; Yang, Xiang-Dong; Zhu, Zun-Lue

    2006-05-01

    The reasonable dissociation limit of the A1Σ+ state 7LiH molecule is obtained. The accurate dissociation energy and the equilibrium geometry of this state are calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space for the first time. The whole potential energy curve and the dipole moment function for the A1Σ+ state are calculated over a wide internuclear separation range from about 0.1 to 1.4 nm. The calculated equilibrium geometry and dissociation energy of this potential energy curve are of Re=0.2487 nm and De=1.064 eV, respectively. The unusual negative values of the anharmonicity constant and the vibration-rotational coupling constant are of ωeχe=-4.7158cm-1 and αe=-0.08649cm-1, respectively. The vertical excitation energy from the ground to the A1Σ+ state is calculated and the value is of 3.613 eV at 0.15875 nm (the equilibrium position of the ground state). The highly anomalous shape of this potential energy curve, which is exceptionally flat over a wide radial range around the equilibrium position, is discussed in detail. The harmonic frequency value of 502.47cm-1 about this state is approximately estimated. Careful comparison of the theoretical determinations with those obtained by previous theories about the A1Σ+ state dissociation energy clearly shows that the present calculations are much closer to the experiments than previous theories, thus represents an improvement.

  15. Near-threshold (7)Li(p,n)(7)Be neutrons on the practical conditions using thick Li-target and Gaussian proton energies for BNCT.

    PubMed

    Kobayashi, Tooru; Hayashizaki, Noriyosu; Katabuchi, Tatsuya; Tanaka, Kenichi; Bengua, Gerard; Nakao, Noriaki; Kosako, Kazuaki

    2014-06-01

    The near threshold (7)Li(p,n)(7)Be neutrons generated by incident proton energy having Gaussian distribution with mean energies from 1.85 to 1.95MeV, were studied as a practical neutron source for BNCT wherein an RFQ accelerator and a thick Li-target are used. Gaussian energy distributions with the standard deviation of 0, 10, 20 and 40keV for mean proton energies from 1.85 to 1.95MeV were surveyed in 0.01MeV increments. A thick liquid Li-target whose dimensions were established in our previous experiments (i.e., 1mm-thick with 50mm width and 50mm length) was considered in this study. The suitable incident proton energy and physical dimensions of Pb layer which serves as a gamma absorber and a Polyethylene layer which is used as a BDE were surveyed by means of the concepts of TPD. Dose distribution were calculated by using MCNP5. A proton beam with mean energy of 1.92MeV and a Gaussian energy distribution with a standard deviation of 20keV at a current of 10mA was selected from the viewpoint of irradiation time and practically achievable proton current. The suitable thicknesses of Pb gamma absorber was estimated to be about 3cm. The estimated thickness of the polyethylene BDE was about 24mm for an ideal proton current of 13mA, and was 18mm for a practical proton current of 10mA. PMID:24491682

  16. Nuclear spin noise in NMR revisited

    SciTech Connect

    Ferrand, Guillaume; Luong, Michel

    2015-09-07

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a “bump” or as a “dip” superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  17. Some nitrogen-14 NMR studies in solids

    SciTech Connect

    Pratum, T.K.

    1983-11-01

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

  18. NMR spectral analysis using prior knowledge

    NASA Astrophysics Data System (ADS)

    Kasai, Takuma; Nagata, Kenji; Okada, Masato; Kigawa, Takanori

    2016-03-01

    Signal assignment is a fundamental step for analyses of protein structure and dynamics with nuclear magnetic resonance (NMR). Main-chain signal assignment is achieved with a sequential assignment method and/or an amino-acid selective stable isotope labeling (AASIL) method. Combinatorial selective labeling (CSL) methods, as well as our labeling strategy, stable isotope encoding (SiCode), were developed to reduce the required number of labeled samples, since one of the drawbacks of AASIL is that many samples are needed. Signal overlapping in NMR spectra interferes with amino-acid determination by CSL and SiCode. Since spectral deconvolution by peak fitting with a gradient method cannot resolve closely overlapped signals, we developed a new method to perform both peak fitting and amino acid determination simultaneously, with a replica exchange Monte Carlo method, incorporating prior knowledge of stable-isotope labeling ratios and the amino-acid sequence of the protein.

  19. Nuclear spin noise in NMR revisited

    NASA Astrophysics Data System (ADS)

    Ferrand, Guillaume; Huber, Gaspard; Luong, Michel; Desvaux, Hervé

    2015-09-01

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a "bump" or as a "dip" superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  20. NMR and protein folding: equilibrium and stopped-flow studies.

    PubMed Central

    Frieden, C.; Hoeltzli, S. D.; Ropson, I. J.

    1993-01-01

    NMR studies are now unraveling the structure of intermediates of protein folding using hydrogen-deuterium exchange methodologies. These studies provide information about the time dependence of formation of secondary structure. They require the ability to assign specific resonances in the NMR spectra to specific amide protons of a protein followed by experiments involving competition between folding and exchange reactions. Another approach is to use 19F-substituted amino acids to follow changes in side-chain environment upon folding. Current techniques of molecular biology allow assignments of 19F resonances to specific amino acids by site-directed mutagenesis. It is possible to follow changes and to analyze results from 19F spectra in real time using a stopped-flow device incorporated into the NMR spectrometer. PMID:8298453