Sample records for hr mas nmr

  1. Citron and lemon under the lens of HR-MAS NMR spectroscopy.

    PubMed

    Mucci, Adele; Parenti, Francesca; Righi, Valeria; Schenetti, Luisa

    2013-12-01

    High Resolution Magic Angle Spinning (HR-MAS) is an NMR technique that can be applied to semi-solid samples. Flavedo, albedo, pulp, seeds, and oil gland content of lemon and citron were studied through HR-MAS NMR spectroscopy, which was used directly on intact tissue specimens without any physicochemical manipulation. HR-MAS NMR proved to be a very suitable technique for detecting terpenes, sugars, organic acids, aminoacids and osmolites. It is valuable in observing changes in sugars, principal organic acids (mainly citric and malic) and ethanol contents of pulp specimens and this strongly point to its use to follow fruit ripening, or commercial assessment of fruit maturity. HR-MAS NMR was also used to derive the molar percentage of fatty acid components of lipids in seeds, which can change depending on the Citrus species and varieties. Finally, this technique was employed to elucidate the metabolic profile of mold flavedo. PMID:23871074

  2. Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples

    PubMed Central

    Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2013-01-01

    High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues. PMID:24284435

  3. Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples

    NASA Astrophysics Data System (ADS)

    Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2013-11-01

    High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues.

  4. Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples.

    PubMed

    Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2013-01-01

    High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues. PMID:24284435

  5. Molecular degradation of ancient documents revealed by 1H HR-MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Corsaro, Carmelo; Mallamace, Domenico; ?ojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

    2013-10-01

    For centuries mankind has stored its knowledge on paper, a remarkable biomaterial made of natural cellulose fibers. However, spontaneous cellulose degradation phenomena weaken and discolorate paper over time. The detailed knowledge of products arising from cellulose degradation is essential in understanding deterioration pathways and in improving durability of cultural heritage. In this study, for the first time, products of cellulose degradation were individually detected in solid paper samples by means of an extremely powerful proton HR-MAS NMR set-up, in combination to a wise use of both ancient and, as reference, artificially aged paper samples. Carboxylic acids, in addition to more complex dicarboxylic and hydroxy-carboxylic acids, were found in all samples studied. Since these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents. Furthermore, the identification of compounds used in ancient production techniques, also suggests for artifacts dating, authentication and provenance.

  6. Molecular degradation of ancient documents revealed by 1H HR-MAS NMR spectroscopy

    PubMed Central

    Corsaro, Carmelo; Mallamace, Domenico; ?ojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

    2013-01-01

    For centuries mankind has stored its knowledge on paper, a remarkable biomaterial made of natural cellulose fibers. However, spontaneous cellulose degradation phenomena weaken and discolorate paper over time. The detailed knowledge of products arising from cellulose degradation is essential in understanding deterioration pathways and in improving durability of cultural heritage. In this study, for the first time, products of cellulose degradation were individually detected in solid paper samples by means of an extremely powerful proton HR-MAS NMR set-up, in combination to a wise use of both ancient and, as reference, artificially aged paper samples. Carboxylic acids, in addition to more complex dicarboxylic and hydroxy-carboxylic acids, were found in all samples studied. Since these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents. Furthermore, the identification of compounds used in ancient production techniques, also suggests for artifacts dating, authentication and provenance. PMID:24104201

  7. HR-MAS NMR Tissue Metabolomic Signatures Cross-Validated by Mass Spectrometry Distinguish Bladder Cancer from Benign Disease

    PubMed Central

    Tripathi, Pratima; Somashekar, Bagganahalli S; Ponnusamy, M.; Gursky, Amy; Dailey, Stephen; Kunju, Priya; Lee, Cheryl T.; Chinnaiyan, Arul M.; Rajendiran, Thekkelnaycke M.; Ramamoorthy, Ayyalusamy

    2013-01-01

    Effective diagnosis and surveillance of Bladder Cancer (BCa) is currently challenged by detection methods that are of poor sensitivity, particularly for low-grade tumors, resulting in unnecessary invasive procedures and economic burden. We performed HR-MAS NMR-based global metabolomic profiling and applied unsupervised principal component analysis (PCA) and hierarchical clustering performed on NMR dataset of bladder derived tissues and identified metabolic signatures that differentiate BCa from benign disease. A partial least-square discriminant analysis (PLS-DA) model (leave-one-out cross-validation) was used as diagnostic model to distinguish benign and BCa tissues. Receiver operating characteristic curve generated either from PC1 loadings of PCA or from predicted Y-values resulted in an area under curve of 0.97. Relative quantification of more than fifteen tissue metabolites derived from HR-MAS NMR showed significant differences (P < 0.001) between benign and BCa samples. Noticeably, striking metabolic signatures were observed even for early stage BCa tissues (Ta-T1) demonstrating the sensitivity in detecting BCa. With the goal of cross-validating metabolic signatures derived from HR-MAS NMR, we utilized the same tissue samples to analyze eight metabolites through gas chromatography-mass spectrometry (GC-MS)-targeted analysis, which undoubtedly complements HR-MAS NMR derived metabolomic information. Cross-validation through GC-MS clearly demonstrates the utility of straightforward, non-destructive and rapid HR-MAS NMR technique for clinical diagnosis of BCa with even greater sensitivity. In addition to its utility as a diagnostic tool, these studies will lead to a better understanding of aberrant metabolic pathways in cancer as well as the design and implementation of personalized cancer therapy through metabolic modulation. PMID:23731241

  8. DRIFT and HR MAS NMR characterization of humic substances from a soil treated with different organic and mineral fertilizers

    NASA Astrophysics Data System (ADS)

    Ferrari, Erika; Francioso, Ornella; Nardi, Serenella; Saladini, Monica; Ferro, Nicola Dal; Morari, Francesco

    2011-07-01

    In this study, using DRIFT and HR MAS NMR, we analyzed the humic substances isolated from a soil treated, over 40 years, with different organic, mineral and organic plus mineral treatments and cultivated with maize as the main crop. As expected, the structure of humic substances was very complex but by combining both techniques (DRIFT and HR MAS NMR) additional information was obtained on aromatic and aliphatic components, the most recalcitrant parts of these macromolecules. In so doing we wanted to investigate the relationship between HS structure and long-term management practices. An elevated content of lignin, aminoacids, peptides and proteins was observed mainly for farmyard manure treatments with respect to mineral or liquid manure amendments; this supports how the different management practices have greatly influenced the humification process of cultivated soils.

  9. HR-MAS NMR spectroscopy of reconstructed human epidermis: potential for the in situ investigation of the chemical interactions between skin allergens and nucleophilic amino acids.

    PubMed

    Elbayed, Karim; Berl, Valérie; Debeuckelaere, Camille; Moussallieh, François-Marie; Piotto, Martial; Namer, Izzie-Jacques; Lepoittevin, Jean-Pierre

    2013-01-18

    High-resolution magic angle spinning (HR-MAS) is a nuclear magnetic resonance (NMR) technique that enables the characterization of metabolic phenotypes/metabolite profiles of cells, tissues, and organs, under both normal and pathological conditions, without resorting to time-consuming extraction techniques. In this article, we explore a new domain of application of HR-MAS, namely, reconstructed human epidermis (RHE) and the in situ observation of chemical interactions between skin sensitizers and nucleophilic amino acids. First, the preparation, storage, and analysis of RHE were optimized, and this work demonstrated that HR-MAS NMR was well adapted for investigating RHE with spectra of good quality allowing qualitative as well as quantitative studies of metabolites. Second, in order to study the response of RHE to chemical sensitizers, the ((13)C)methyldodecanesulfonate was chosen as an NMR probe, and we compared adducts formed on human serum albumin (HSA) in solution and adducts formed in RHE. Thus, while the modification of proteins or peptides in solution takes several days to lead to a significant amount of modification, in RHE the modifications of nucleophilic amino acids were observable already at 24 h. The chemioselectivity also appeared to be different with major modifications taking place on histidine, methionine, and cysteine residues in RHE, while on HSA, significant modifications were observed on lysine residues with the formation of methylated and dimethylated amino groups. We thus demonstrated that RHE could be used to investigate in situ chemical interactions taking place between skin sensitizers and nucleophilic amino acids. This opens perspectives for the molecular understanding of the skin immune system activation by sensitizing chemicals. PMID:23256819

  10. 1H HR-MAS NMR Based Metabolic Profiling of Cells in Response to Treatment with a Hexacationic Ruthenium Metallaprism as Potential Anticancer Drug

    PubMed Central

    Vermathen, Martina; Paul, Lydia E. H.; Diserens, Gaëlle

    2015-01-01

    1H high resolution magic angle spinning (HR-MAS) NMR spectroscopy was applied in combination with multivariate statistical analyses to study the metabolic response of whole cells to the treatment with a hexacationic ruthenium metallaprism [1]6+ as potential anticancer drug. Human ovarian cancer cells (A2780), the corresponding cisplatin resistant cells (A2780cisR), and human embryonic kidney cells (HEK-293) were each incubated for 24 h and 72 h with [1]6+ and compared to untreated cells. Different responses were obtained depending on the cell type and incubation time. Most pronounced changes were found for lipids, choline containing compounds, glutamate and glutathione, nucleotide sugars, lactate, and some amino acids. Possible contributions of these metabolites to physiologic processes are discussed. The time-dependent metabolic response patterns suggest that A2780 cells on one hand and HEK-293 cells and A2780cisR cells on the other hand may follow different cell death pathways and exist in different temporal stages thereof. PMID:26024484

  11. Rapid 3D MAS NMR Spectroscopy at Critical Sensitivity

    E-print Network

    Matsuki, Yoh

    Sensitive SIFTing: Multidimensional non-uniform sampling (NUS) NMR spectroscopy is extended to the severely sensitivity-limited regime typical of MAS NMR of biomacromolecules by the use of spectroscopy by the integration ...

  12. Spectral Editing in 13 C MAS NMR under Moderately Fast

    E-print Network

    Frydman, Lucio

    Spectral Editing in 13 C MAS NMR under Moderately Fast Spinning Conditions1 Enrico De Vita-angle spinning (10­14 kHz MAS), CH and CH2 moieties behave to a large extent as if they were effectively isolated), magic-angle spinning (MAS), and efficient forms of proton decoupling has made the acquisition of 13 C

  13. Protein MAS NMR methodology and structural analysis of protein assemblies

    E-print Network

    Bayro, Marvin J

    2010-01-01

    Methodological developments and applications of solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, with particular emphasis on the analysis of protein structure, are described in this thesis. ...

  14. The refocused INADEQUATE MAS NMR experiment in multiple spin-systems: Interpreting observed correlation

    E-print Network

    Baltisberger, Jay H.

    The refocused INADEQUATE MAS NMR experiment in multiple spin-systems: Interpreting observed The robustness of the refocused INADEQUATE MAS NMR pulse sequence for probing through-bond connectivities has

  15. Broadband solid-state MAS NMR of paramagnetic systems.

    PubMed

    Pell, Andrew J; Pintacuda, Guido

    2015-02-01

    The combination of new magnet and probe technology with increasingly sophisticated pulse sequences has resulted in an increase in the number of applications of solid-state nuclear magnetic resonance (NMR) spectroscopy to paramagnetic materials and biomolecules. The interaction between the paramagnetic metal ions and the NMR-active nuclei often yields crucial structural or electronic information about the system. In particular the application of magic-angle spinning (MAS) has been shown to be crucial to obtaining resolution that is sufficiently high for studying complex systems. However such systems are generally extremely difficult to study as the shifts and shift anisotropies resulting from the same paramagnetic interaction broaden the spectrum beyond excitation and detection, and the paramagnetic relaxation enhancement (PRE) shortens the lifetimes of the excited signals considerably. One specific area that has therefore been receiving significant attention in recent years, and for which great improvements have been seen, is the development of broadband NMR sequences. The development of new excitation and inversion sequences for paramagnetic systems under MAS has often made the difference between the spectrum being unobtainable, and a complete NMR study being possible. However the development of the new sequences must explicitly take account of the modulation of the anisotropic shift interactions due to the sample rotation, with the resulting spin dynamics often being complicated considerably. The NMR sequences can either be helped or hindered by MAS, with the efficiency of some pulse schemes being destroyed, and others being greatly enhanced. This review describes the pulse sequences that have recently been proposed for broadband excitation, inversion, and refocussing of the signal components of paramagnetic systems. In doing so we define exactly what is meant by "broadband" under spinning conditions, and what the perfect pulse scheme should deliver. We also give a unified description of the spin dynamics under MAS which highlights the strengths and weaknesses of the various schemes, and which can be used as guidance for future research in this area. All the reviewed pulse schemes are evaluated both with simulations and experimental data obtained on the battery material LiFe(0.5)Mn(0.5)PO(4) which is typical of the complexity of the paramagnetic systems that are currently under study. PMID:25669740

  16. Semi-parametric time-domain quantification of HR-MAS data from prostate tissue.

    PubMed

    Ratiney, Helene; Albers, Mark J; Rabeson, Herald; Kurhanewicz, John

    2010-12-01

    High Resolution--Magic Angle Spinning (HR-MAS) spectroscopy provides rich biochemical profiles that require accurate quantification to permit biomarker identification and to understand the underlying pathological mechanisms. Meanwhile, quantification of HR-MAS data from prostate tissue samples is challenging due to significant overlap between the resonant peaks, the presence of short T?* metabolites such as citrate or polyamines (T? from 25 to 100 msec) and macromolecules, and variations in chemical shifts and T?*s within a metabolite's spin systems. Since existing methods do not address these challenges completely, a new quantification method was developed and optimized for HR-MAS data acquired with an ultra short T(E) and over 30,000 data points. The proposed method, named HR-QUEST (High Resolution--QUEST), iteratively employs the QUEST time-domain semi-parametric strategy with a new model function that incorporates prior knowledge from whole and subdivided metabolite signals. With these features, HR-QUEST is able to independently fit the chemical shifts and T?*s of a metabolite's spin systems, a necessity for HR-MAS data. By using the iterative fitting approach, it is able to account for significant contributions from macromolecules and to handle shorter T? metabolites, such as citrate and polyamines. After subdividing the necessary metabolite basis signals, the root mean square (RMS) of the residual was reduced by 52% for measured HR-MAS data from prostate tissue. Monte Carlo studies on simulated spectra with varied macromolecular contributions showed that the iterative fitting approach (6 iterations) coupled with inclusion of long T? macromolecule components in the basis set improve the quality of the fit, as assessed by the reduction of the RMS of the residual and of the RMS error of the metabolite signal estimate, by 27% and 71% respectively. With this optimized configuration, HR-QUEST was applied to measured HR-MAS prostate data and reliably quantified 16 metabolites and reference signals with estimated Cramér Rao Bounds ?5%. PMID:20842756

  17. The Effect of Biradical Concentration on the Performance of DNP-MAS-NMR

    E-print Network

    Loening, Niko

    The Effect of Biradical Concentration on the Performance of DNP-MAS-NMR Sascha Langeaa,1 , Arne H intensity in solid-state MAS-NMR experiments can be enhanced by 2-3 orders of magnitude. DNP relies be enhanced by the use of cross polarization (CP) [7] and magic-angle spinning (MAS) [8]. Nevertheless

  18. Coherence selection in double CP MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Jen-Hsien; Chou, Fang-Chieh; Tzou, Der-Lii M.

    2008-11-01

    Applications of double cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy, via 1H/ 15N and then 15N/ 13C coherence transfers, for 13C coherence selection are demonstrated on a 15N/ 13C-labeled N-acetyl-glucosamine (GlcNAc) compound. The 15N/ 13C coherence transfer is very sensitive to the settings of the experimental parameters. To resolve explicitly these parameter dependences, we have systematically monitored the 13C{ 15N/ 1H} signal as a function of the rf field strength and the MAS frequency. The data reveal that the zero-quantum coherence transfer, with which the 13C effective rf field is larger than that of the 15N by the spinning frequency, would give better signal sensitivity. We demonstrate in one- and two-dimensional double CP experiments that spectral editing can be achieved by tailoring the experimental parameters, such as the rf field strengths and/or the MAS frequency.

  19. 1H MAS, 13C CP/MAS, and 2H NMR spectra studies of piperidinium ph{p}-chlorobenzoate

    NASA Astrophysics Data System (ADS)

    Nakano, Ryo; Honda, Hisashi; Ishimaru, Shin'ichi; Noro, Sumiko

    2013-05-01

    Anomalous H/D isotope effects were detected in the 1H MAS NMR spectra of piperidinium p-chlorobenzoate (C5H10NH2{+}\\cdot ClC6H4COO - ) upon deuterium substitution of hydrogen atoms which form two kinds of N-H⋯O H-bonds in the crystal; in contrast to these spectra, only slight chemical shifts were recorded in 13C CP/MAS NMR spectra. 2H NMR spectrum of the deuterated sample show quadrupole coupling constants of 148 and 108 kHz, and reveal that there are a few motions contributing to the electric-field modulation of the 2H nucleus. The 1H MAS NMR spectra of piperidinium p-chlrobenzoate- d 16 (C5D10ND2{+}\\cdot ClC6D4COO - ) and - d 14 (C5D10NH2{+}\\cdot ClC6D4COO - ) revealed that the change in the envelope is caused by chemical shifts of each signal upon deuteration. Calculations based on the density-functional-theory showed that the N-H distance along the crystallographic a-axis mainly contributes to the anomalous isotope effects on 1H MAS NMR envelopes.

  20. MAS NMR studies of carbon-13 spin exchange in durene.

    PubMed

    Reichert, D; Hempel, G; Poupko, R; Luz, Z; Olejniczak, Z; Tekely, P

    1998-12-01

    One- (1-D) and two-dimensional (2-D) carbon-13 NMR exchange measurements in powder samples of isotopically normal durene under magic angle spinning (MAS) are reported. The experiments include rotor synchronized 2-D exchange (RS2DE), 1-D magnetization transfer (MT) and time reverse ODESSA (tr-ODESSA). The latter two experiments were performed as a function of several external parameters, including proton decoupling field during mixing time, sample spinning rate and partly, of temperature. The effects of these parameters on the spin exchange induced by spin diffusion and by chemical, or physical exchange, is discussed. Spin exchange between all types of carbons in the durene molecules occurs on the time scale of seconds. From the dependence of the spin exchange rate on the external parameters it is concluded that the process is dominated by spin diffusion. On the basis of these results an upper limit of 10(-16) cm2 s(-1) can be set for the self-diffusion constant in crystalline durene. PMID:10023843

  1. DNP-Enhanced MAS NMR of Bovine Serum Albumin Sediments and Solutions

    E-print Network

    Ravera, Enrico

    Protein sedimentation sans cryoprotection is a new approach to magic angle spinning (MAS) and dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy of proteins. It increases the sensitivity of ...

  2. Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy

    E-print Network

    Debelouchina, Galia T.

    Protein magic angle spinning (MAS) NMR spectroscopy has generated structural models of several amyloid fibril systems, thus providing valuable information regarding the forces and interactions that confer the extraordinary ...

  3. 1H, 13C and 31P MAS NMR studies of lyophilized brain tumors

    Microsoft Academic Search

    R. Marsza?ek; M. Pisklak; D. Horszty?ski; I. Wawer

    2010-01-01

    1H, 13C and 31P magic angle spinning magnetic resonance spectra (MAS NMR) of lyophilized brain tissue specimens were recorded. Among the 35 cases of brain tumors there were 24 glioblastomas, seven meningiomas and a few other types. 1H NMR measurements were performed with a MAS speed of 33kHz. The intense CH3, CH2 and CH? peaks in the 1H spectrum result

  4. A software framework for analysing solid-state MAS NMR data.

    PubMed

    Stevens, Tim J; Fogh, Rasmus H; Boucher, Wayne; Higman, Victoria A; Eisenmenger, Frank; Bardiaux, Benjamin; van Rossum, Barth-Jan; Oschkinat, Hartmut; Laue, Ernest D

    2011-12-01

    Solid-state magic-angle-spinning (MAS) NMR of proteins has undergone many rapid methodological developments in recent years, enabling detailed studies of protein structure, function and dynamics. Software development, however, has not kept pace with these advances and data analysis is mostly performed using tools developed for solution NMR which do not directly address solid-state specific issues. Here we present additions to the CcpNmr Analysis software package which enable easier identification of spinning side bands, straightforward analysis of double quantum spectra, automatic consideration of non-uniform labelling schemes, as well as extension of other existing features to the needs of solid-state MAS data. To underpin this, we have updated and extended the CCPN data model and experiment descriptions to include transfer types and nomenclature appropriate for solid-state NMR experiments, as well as a set of experiment prototypes covering the experiments commonly employed by solid-sate MAS protein NMR spectroscopists. This work not only improves solid-state MAS NMR data analysis but provides a platform for anyone who uses the CCPN data model for programming, data transfer, or data archival involving solid-state MAS NMR data. PMID:21953355

  5. Investigation of domain size in polymer membranes using double quantum filtered spin diffusion MAS NMR.

    SciTech Connect

    Fujimoto, Cy H.; Alam, Todd Michael; Cherry, Brian Ray; Cornelius, Christopher James

    2005-02-01

    Solid-state {sup 1}H magic angle spinning (MAS) NMR was used to investigate sulfonated Diels-Alder poly(phenlylene) polymer membranes. Under high spinning speed {sup 1}H MAS conditions, the proton environments of the sulfonic acid and phenylene polymer backbone are resolved. A double-quantum (DQ) filter using the rotor-synchronized back-to-back (BABA) NMR multiple-pulse sequence allowed the selective suppression of the sulfonic proton environment in the {sup 1}H MAS NMR spectra. This DQ filter in conjunction with a spin diffusion NMR experiment was then used to measure the domain size of the sulfonic acid component within the membrane. In addition, the temperature dependence of the sulfonic acid spin-spin relaxation time (T{sub 2}) was determined, providing an estimate of the activation energy for the proton dynamics of the dehydrated membrane.

  6. Reduction of spin diffusion artifacts from 2D zfr-INADEQUATE MAS NMR spectra Jay H. Baltisberger

    E-print Network

    Baltisberger, Jay H.

    Reduction of spin diffusion artifacts from 2D zfr-INADEQUATE MAS NMR spectra Jay H. Baltisberger s t r a c t The primary shortcoming of the z-filtered refocused INADEQUATE MAS NMR pulse sequence and diversity of experiments that work well under MAS conditions has been a continued goal of many researchers

  7. 1H, 13C and 31P MAS NMR studies of lyophilized brain tumors.

    PubMed

    Marsza?ek, R; Pisklak, M; Horszty?ski, D; Wawer, I

    2010-01-01

    (1)H, (13)C and (31)P magic angle spinning magnetic resonance spectra (MAS NMR) of lyophilized brain tissue specimens were recorded. Among the 35 cases of brain tumors there were 24 glioblastomas, seven meningiomas and a few other types. (1)H NMR measurements were performed with a MAS speed of 33 kHz. The intense CH(3), CH(2) and CH peaks in the (1)H spectrum result from fatty acid residues of phospholipids, which are "mobile enough" besides the anhydrous environment. (13)C CPMAS spectra revealed the resonances of creatine and guanidine carbons; the high intensity signals arise from carbonyl groups and methylene carbons of lipids. In particular we found a fraction of mobile lipids, characterized by narrow resonances and long T(1rho)(H) Overlapped resonances of phospholipids head groups contributed to the peak at 4-7 ppm in the (31)P MAS NMR spectra. Our results indicate that (1)H and (13)C MAS NMR are able to characterize tumor types: differentiate glioblastomas from meningiomas and shed light on tumor biochemical characteristics. However, water soluble metabolites are not observed and macromolecules yield broad overlapped resonances. Generally, lyophilization significantly decreases discriminative potential of NMR analysis. PMID:20133109

  8. Determination of metabolite concentrations in human brain tumour biopsy samples using HR-MAS and ERETIC measurements.

    PubMed

    Martínez-Bisbal, M Carmen; Monleon, Daniel; Assemat, Olivier; Piotto, Martial; Piquer, José; Llácer, José Luis; Celda, Bernardo

    2009-02-01

    Accurate determination of the concentration of the metabolites contained in intact human biopsies of 10 glioblastoma multiforme samples was achieved using one-dimensional (1)H high-resolution magic angle spinning (HR-MAS) NMR combined with ERETIC (electronic reference to in vivo concentrations) measurements. The amount of sample used ranged from 6.8 to 12.9 mg. Metabolite concentrations were measured in each sample using two methods: with DSS (2,2-dimethyl-2-silapentane-5-sulfonate sodium salt) as an internal reference and with ERETIC as an external electronically generated reference. The ERETIC signal was shown to be highly reproducible and did not affect the spectral quality. The concentrations calculated by the ERETIC method in model solutions were shown to be independent of the salt concentration in the range typically found in biological samples (0-250 mM). The ERETIC method proved to be straightforward to use in tissues and much more robust than the internal standard method. The concentrations calculated using the internal DSS concentration were systematically found to be higher than those determined using the ERETIC technique. These results indicate a possible interaction of the DSS molecules with the biopsy sample. Moreover, variations in the sample preparation process, with possible loss of DSS solution, may hamper the quantification process, as happens in one of the ten samples analysed. In this study, the ERETIC method was validated on model solutions and used in brain tumour tissues. Calculated metabolite concentrations obtained with the ERETIC procedure matched the values determined in the same type of tumours by in vivo, ex vivo and in vitro methodologies. PMID:18833546

  9. Optimized multiple quantum MAS lineshape simulations in solid state NMR

    NASA Astrophysics Data System (ADS)

    Brouwer, William J.; Davis, Michael C.; Mueller, Karl T.

    2009-10-01

    The majority of nuclei available for study in solid state Nuclear Magnetic Resonance have half-integer spin I>1/2, with corresponding electric quadrupole moment. As such, they may couple with a surrounding electric field gradient. This effect introduces anisotropic line broadening to spectra, arising from distinct chemical species within polycrystalline solids. In Multiple Quantum Magic Angle Spinning (MQMAS) experiments, a second frequency dimension is created, devoid of quadrupolar anisotropy. As a result, the center of gravity of peaks in the high resolution dimension is a function of isotropic second order quadrupole and chemical shift alone. However, for complex materials, these parameters take on a stochastic nature due in turn to structural and chemical disorder. Lineshapes may still overlap in the isotropic dimension, complicating the task of assignment and interpretation. A distributed computational approach is presented here which permits simulation of the two-dimensional MQMAS spectrum, generated by random variates from model distributions of isotropic chemical and quadrupole shifts. Owing to the non-convex nature of the residual sum of squares (RSS) function between experimental and simulated spectra, simulated annealing is used to optimize the simulation parameters. In this manner, local chemical environments for disordered materials may be characterized, and via a re-sampling approach, error estimates for parameters produced. Program summaryProgram title: mqmasOPT Catalogue identifier: AEEC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3650 No. of bytes in distributed program, including test data, etc.: 73 853 Distribution format: tar.gz Programming language: C, OCTAVE Computer: UNIX/Linux Operating system: UNIX/Linux Has the code been vectorised or parallelized?: Yes RAM: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 3.5M, SMP AMD opteron Classification: 2.3 External routines: OCTAVE ( http://www.gnu.org/software/octave/), GNU Scientific Library ( http://www.gnu.org/software/gsl/), OPENMP ( http://openmp.org/wp/) Nature of problem: The optimal simulation and modeling of multiple quantum magic angle spinning NMR spectra, for general systems, especially those with mild to significant disorder. The approach outlined and implemented in C and OCTAVE also produces model parameter error estimates. Solution method: A model for each distinct chemical site is first proposed, for the individual contribution of crystallite orientations to the spectrum. This model is averaged over all powder angles [1], as well as the (stochastic) parameters; isotropic chemical shift and quadrupole coupling constant. The latter is accomplished via sampling from a bi-variate Gaussian distribution, using the Box-Muller algorithm to transform Sobol (quasi) random numbers [2]. A simulated annealing optimization is performed, and finally the non-linear jackknife [3] is applied in developing model parameter error estimates. Additional comments: The distribution contains a script, mqmasOpt.m, which runs in the OCTAVE language workspace. Running time: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 58.35 seconds, SMP AMD opteron. References:S.K. Zaremba, Annali di Matematica Pura ed Applicata 73 (1966) 293. H. Niederreiter, Random Number Generation and Quasi-Monte Carlo Methods, SIAM, 1992. T. Fox, D. Hinkley, K. Larntz, Technometrics 22 (1980) 29.

  10. Powder MAS NMR lineshapes of quadrupolar nuclei in the presence of second-order quadrupole interaction.

    PubMed

    Ajoy, G; Ramakrishna, J; Bahçeli, S; Klinowski, J

    2000-07-01

    We derive a complete analytical solution for the powder magic angle spinning (MAS) nuclear magnetic resonance (NMR) lineshape in the presence of second-order quadrupole interaction, considering a radiofrequency (rf) pulse of finite width, a finite MAS frequency, and a non-zero asymmetry parameter. (Ix) is calculated using two approaches. The first applies time-dependent perturbation theory in the presence of the rf pulse and stationary perturbation theory (SPT) in its absence. The second is based on the Magnus expansion of the density matrix in the interaction representation during the pulse and SPT in its absence. We solve the problem in the laboratory frame using the properties of the Fourier transform and spin operators. Diagonalisation is not required. Both approaches agree well with each other under all conditions and also with the transition probability approach for the central transition. The Magnus expansion exists at all times and the effect of the non-secular terms is negligible. We describe an analytical method of averaging (Ix) over the Euler angles and simulate the 11B MAS NMR lineshapes for crystalline and vitreous B2O3. A critical analysis is given of all earlier calculations of the MAS NMR lineshape. PMID:10928635

  11. Solid-state variable-temperature 1H MAS NMR studies on deuterated polyethylene.

    PubMed

    Chen, Q; Hurosu, H; Ando, I; Wu, X

    1997-02-01

    Solid-state variable-temperature/magic angle spinning (VT/MAS) 1H NMR measurements were carried out on deuterated polyethylene. From these experimental results it was found that the 1H chemical shift induced by conformational and morphological changes of the polyethylene sample is within the linewidth of approximately 0.5 ppm. Furthermore, from MAS/dipolar decoupling experiments it was found that the resonance frequency of the proton varies linearly with the inverse square of the deuterium decoupling power. This experimental finding is discussed theoretically. PMID:9176937

  12. Study on crystallographically inequivalent protons in RbH2AsO4 using static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Lee, Kwang-Sei

    2015-02-01

    Two inequivalent protons from 1H NMR spectra of RbH2AsO4 in the paraelectric phase were distinguished using static NMR and MAS NMR. From the 1H spin-lattice relaxation times in the laboratory frame, T1, and rotating frame, T1?, of the two crystallographically inequivalent hydrogen sites, i.e., H(1) and H(2), the temperature dependences of T1 and T1? for H(1) were related to the reorientational motion. The shorter H(1) bonds give rise to stronger H-bonds, and protons involved in stronger H-bonds have long relaxation times. Consequently, the RbH2AsO4 structure has two crystallographically inequivalent sites with two different hydrogen-bond lengths.

  13. Decomposition of adsorbed VX on activated carbons studied by {sup 31}P MAS NMR

    SciTech Connect

    Ishay Columbus; Daniel Waysbort; Liora Shmueli; Ido Nir; Doron Kaplan [Israel Institute for Biological Research, Ness Ziona (Israel). Departments of Organic Chemistry and Physical Chemistry

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. Four types of activated carbon were used, including coal-based BPL. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) ((DES){sub 2}). Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. 17 refs., 6 figs., 3 tabs.

  14. Physical properties of the nonlinear optical material Li2B4O7 studied by static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2015-07-01

    The mechanisms behind the nonlinear optical (NLO) properties of Li2B4O7 are characterized by 7Li static nuclear magnetic resonance (NMR) and magic-angle spinning (MAS) NMR. Furthermore, the structural nature of 3-coordinate BO3 and 4-coordinate BO4 groups is also characterized by the same method. For 7Li and 11B, the spin-lattice relaxation time T1 in laboratory frame gradually decreases with increasing temperature, whereas the spin-lattice relaxation time T1? in rotating frame, which differs from T1, is nearly constant. In addition, the activation energies of 7Li and 11B, which are obtained via the values of T1 and T1?, are also compared.

  15. Characterization of plasma-sprayed hydroxyapatite by 31 P-MAS-NMR and the effect of subsequent annealing

    Microsoft Academic Search

    J. Vogel; C. Rüssel; G. Günther; P. Hartmann; F. Vizethum; N. Bergner

    1996-01-01

    The characterization of plasma spray induced changes become complicated by the formation of amorphous phases.31P magic angle spinning (MAS)-nuclear magnetic resonance (NMR) measurements are suited to detect both crystalline and amorphous calcium phosphates. Therefore, we used31P-MAS-NMR and X-ray diffraction (XRD) to characterize plasma-sprayed hydroxyapatite. Besides small quantities of nearly unchanged crystalline apatite, disordered partly X-ray amorphous apatite was detected. Additionally,

  16. 99Tc-MAS-NMR on a Cationic Framework Material for Trapping TcO{sub 4}{sup –}

    SciTech Connect

    Yu, P.; Wang, Shuao; Alekseev, Evgeny V.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.; Phillips, Brian L.; Casey, William H.

    2010-08-09

    {sup 99}Tc?magic-angle spinning (MAS) NMR spectra show that TcO{sub 4}{sup ?} ions, which are generated by nuclear fission and can contaminate the environment, can be trapped within the channels and cavities of a cationic framework material (see picture). These spectra are among the first {sup 99}Tc?MAS?NMR spectra reported to date, and show that the TcO{sub 4}{sup ?} ions can be efficiently removed from simulated nuclear waste solutions.

  17. 1 H MAS NMR spectra of hydroxyl species on diatomite surface

    Microsoft Academic Search

    Yuan Peng; Wu Daqing; Chen Zhong; Chen Zhiwei; Lin Zhongyu; Diao Guiyi; Peng Jinlian

    2001-01-01

    High spinning speed1H magic-angle spinning nuclear magnetic resonance (1H MAS NMR) was used to detect surface hydroxyl groups of diatomite, which include isolated hydroxyl groups and hydrogen-bonded\\u000a hydroxyl groups, and water adsorbed on diatomite surface that include pore water and hydrogen-bonded water. The corresponding\\u000a proton chemical shifts of above species are ca. 2.0, 6.0–7.1, 4.9 and 3.0 respectively. Accompanied by

  18. The effect of biradical concentration on the performance of DNP-MAS-NMR

    NASA Astrophysics Data System (ADS)

    Lange, Sascha; Linden, Arne H.; Akbey, Ümit; Trent Franks, W.; Loening, Nikolaus M.; van Rossum, Barth-Jan; Oschkinat, Hartmut

    2012-03-01

    With the technique of dynamic nuclear polarization (DNP) signal intensity in solid-state MAS-NMR experiments can be enhanced by 2-3 orders of magnitude. DNP relies on the transfer of electron spin polarization from unpaired electrons to nuclear spins. For this reason, stable organic biradicals such as TOTAPOL are commonly added to samples used in DNP experiments. We investigated the effects of biradical concentration on the relaxation, enhancement, and intensity of NMR signals, employing a series of samples with various TOTAPOL concentrations and uniformly 13C, 15N labeled proline. A considerable decrease of the NMR relaxation times (T1, T2?, and T1?) is observed with increasing amounts of biradical due to paramagnetic relaxation enhancement (PRE). For nuclei in close proximity to the radical, decreasing T1? reduces cross-polarization efficiency and decreases in T2? broaden the signal. Additionally, paramagnetic shifts of 1H signals can cause further line broadening by impairing decoupling. On average, the combination of these paramagnetic effects (PE; relaxation enhancement, paramagnetic shifts) quenches NMR-signals from nuclei closer than 10 Å to the biradical centers. On the other hand, shorter T1 times allow the repetition rate of the experiment to be increased, which can partially compensate for intensity loss. Therefore, it is desirable to optimize the radical concentration to prevent additional line broadening and to maximize the signal-to-noise observed per unit time for the signals of interest.

  19. 1H high resolution magic-angle coil spinning (HR-MACS) ?NMR metabolic profiling of whole Saccharomyces cervisiae cells: a demonstrative study

    PubMed Central

    Wong, Alan; Boutin, Céline; Aguiar, Pedro M.

    2014-01-01

    The low sensitivity and thus need for large sample volume is one of the major drawbacks of Nuclear Magnetic Resonance (NMR) spectroscopy. This is especially problematic for performing rich metabolic profiling of scarce samples such as whole cells or living organisms. This study evaluates a 1H HR-MAS approach for metabolic profiling of small volumes (250 nl) of whole cells. We have applied an emerging micro-NMR technology, high-resolution magic-angle coil spinning (HR-MACS), to study whole Saccharomyces cervisiae cells. We find that high-resolution high-sensitivity spectra can be obtained with only 19 million cells and, as a demonstration of the metabolic profiling potential, we perform two independent metabolomics studies identifying the significant metabolites associated with osmotic stress and aging. PMID:24971307

  20. High magnetic field solid-state NMR analyses by combining MAS, MQ-MAS, homo-nuclear and hetero-nuclear correlation experiments.

    PubMed

    Lin, Xiongchao; Ideta, Keiko; Miyawaki, Jin; Nishiyama, Yusuke; Mochida, Isao; Yoon, Seong-Ho

    2012-04-01

    A general strategy of structural analysis of alumina silicate by combining various solid-state NMR measurements such as single pulse, multi-quantum magic angle spinning, double-quantum homo-nuclear correlation under magic angle spinning (DQ-MAS), and cross-polarization hetero-nuclear correlation (CP-HETCOR) was evaluated with the aid of high magnetic field NMR (800?MHz for (1) H Larmor frequency) by using anorthite as a model material. The high magnetic field greatly enhanced resolution of (27) Al in single pulse, DQ-MAS, and even in triple-quantum magic angle spinning NMR spectra. The spatial proximities through dipolar couplings were probed by the DQ-MAS methods for homo-nuclear correlations between both (27) Al-(27) Al and (29) Si-(29) Si and by CP-HETCOR for hetero-nuclear correlations between (27) Al-(29) Si in the anorthite framework. By combining various NMR methodologies, we elucidated detailed spatial correlations among various aluminum and silicon species in anorthite that was hard to be determined using conventional analytical methods at low magnetic field. Moreover, the presented approach is applicable to analyze other alumina-silicate minerals. PMID:22392761

  1. 1H, 13C MAS NMR and GIAO-CPHF calculations of chloramphenicol, thiamphenicol and their pyrrole analogues

    NASA Astrophysics Data System (ADS)

    ?o?ek, Teresa; Paradowska, Katarzyna; Krajewska, Dorota; Ró?a?ski, Andrzej; Wawer, Iwona

    2003-02-01

    The 13C CP MAS and 1H MAS NMR and ab initio (GIAO-CPHF) calculations were used to obtain structural information on two known antibiotics: chloramphenicol, and thiamphenicol, and two new analogues: DL- threo-1-(1-methyl-4-nitro-pyrrole-2-yl)-2-dichloroacetamidopropane-1,3-diol and DL- threo-1-(1-methylsulfonylpyrrole-3-yl)-2-dichloroacetamidopropane-1,3-diol.

  2. Thermal maturity of type II kerogen from the New Albany Shale assessed by 13C CP/MAS NMR.

    PubMed

    Werner-Zwanziger, Ulrike; Lis, Grzegorz; Mastalerz, Maria; Schimmelmann, Arndt

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. PMID:15589735

  3. Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy

    PubMed Central

    Debelouchina, Galia T.; Bayro, Marvin J.; Fitzpatrick, Anthony W.; Ladizhansky, Vladimir; Colvin, Michael T.; Caporini, Marc A.; Jaroniec, Christopher P.; Bajaj, Vikram S.; Rosay, Melanie; MacPhee, Cait E.; Vendruscolo, Michele; Maas, Werner E.; Dobson, Christopher M.; Griffin, Robert G.

    2014-01-01

    Protein magic angle spinning (MAS) NMR spectroscopy has generated structural models of several amyloid fibril systems, thus providing valuable information regarding the forces and interactions that confer the extraordinary stability of the amyloid architecture. Despite these advances, however, obtaining atomic resolution information describing the higher levels of structural organization within the fibrils remains a significant challenge. Here, we detail MAS NMR experiments and sample labeling schemes designed specifically to probe such higher order amyloid structure and we have applied them to the fibrils formed by an eleven-residue segment of the amyloidogenic protein transthyretin (TTR(105-115)). These experiments have allowed us to define unambiguously not only the arrangement of the peptide ?-strands into ?-sheets but also the ?-sheet interfaces within each protofilament, and in addition to identify the nature of the protofilament-to-protofilament contacts that lead to the formation of the complete fibril. Our efforts have resulted in 111 quantitative distance and torsion angle restraints (10 per residue) that describe the various levels of structure organization. The experiments benefited extensively from the use of dynamic nuclear polarization (DNP), which in some cases allowed us to shorten the data acquisition time from days to hours and to improve significantly the signal-to-noise ratios of the spectra. The ?-sheet interface and protofilament interactions identified here revealed local variations in the structure that result in multiple peaks for the exposed N- and C-termini of the peptide and in inhomogeneous line-broadening for the side-chains buried within the interior of the fibrils. PMID:24304221

  4. Assignment of non-crystalline forms in cellulose I by CP\\/MAS 13C NMR spectroscopy

    Microsoft Academic Search

    Kristina Wickholm; Per Tomas Larsson; Tommy Iversen

    1998-01-01

    Non-crystalline forms of cellulose in birch pulp, cotton linters and Cladophora sp were studied by CP\\/MAS 13C NMR spectroscopy. New assignments were made for the NMR-signals in the lower shift part of the C-4 region (80–86ppm). These signals were assigned to cellulose at accessible fibril surfaces, cellulose at inaccessible fibril surfaces and hemicellulose. Also, further evidence was found for para-crystalline

  5. Low Temperature 1H MAS NMR Spectroscopy Studies of Proton Motion in Zeolite

    SciTech Connect

    Huo, H.; Peng, L; Grey, C

    2009-01-01

    Low temperature {sup 1}H MAS NMR spectroscopy is used to study protonic motion in zeolite HZSM-5 in both samples that have been dried using procedures that are standard in the literature and samples that have been more carefully dehydrated. A significant enhancement of proton mobility is seen for the ''standard'' dehydrated HZSM-5 sample in comparison to that seen for the much drier sample. This is ascribed to a vehicle-hopping mechanism involving the residual water that is present in these zeolites. A gradual change of the framework structure is observed on cooling to approximately 213 K, as monitored via the change in {sup 1}H chemical shift values of the Broensted acid resonances and by X-ray diffraction. A more sudden change in structure is seen by differential scanning calorimetry and NMR at approximately 220?230 K, which is associated with changes in both the mobility and the modes of binding of the residual water to the Broensted acid sites and the zeolite framework.

  6. Magnesium Silicate Dissolution Investigated by 29Si MAS, 1H-29Si CP MAS, 25Mg QCPMG, and 1H-25Mg CP QCPMG NMR

    SciTech Connect

    Davis, Michael C.; Brouwer, William J.; Wesolowski, David J.; Anovitz, Lawrence M.; Lipton, Andrew S.; Mueller, Karl T.

    2009-08-01

    Olivine has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of magnesium with respect to silica during weathering under acidic conditions, which has been correlated to the formation of a silicon rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. In particular, the fate of magnesium in the system is not understood and spectroscopic interrogations through nuclear magnetic resonance can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced spectroscopic techniques (29Si MAS, 1H-29Si CP MAS, 25Mg QCPMG, and 1H-25Mg 2 CP QCPMG NMR) to probe leached layer formation and possible secondary phase precipitation during the dissolution of forsterite at 150 oC.

  7. Disordering and the progress of hydration at the surface of diopside: A cross-polarization MAS-NMR study

    SciTech Connect

    Peck, J.A.; Farnan, I.; Stebbins, J.F. (Stanford Univ., CA (USA))

    1988-12-01

    Samples of synthetic crystalline diopside were prepared with different volumes of surface phase by varying the time of grinding of each sample, and then investigated using {sup 29}Si MAS-NMR. Hydration of the surface, which begins during grinding in laboratory air, allows the surface phase to be detected using {sup 1}H-{sup 29}Si CP MAS-NMR. The surface phase appears to be structurally similar to diopside glass. Several hours of reaction with aqueous solution promotes the formation of Q{sub 2}-(OH){sub 2}, which is indicated by the appearance of a peak in the CP-MAS spectrum at {minus}93 ppm. The progress of hydration appears to be relatively independent of the pH of the aqueous solution.

  8. Signal intensities in 1H-13C CP and INEPT MAS NMR of liquid crystals

    NASA Astrophysics Data System (ADS)

    Nowacka, A.; Bongartz, N. A.; Ollila, O. H. S.; Nylander, T.; Topgaard, D.

    2013-05-01

    Spectral editing with CP and INEPT in 13C MAS NMR enables identification of rigid and mobile molecular segments in concentrated assemblies of surfactants, lipids, and/or proteins. In order to get stricter definitions of the terms "rigid" and "mobile", as well as resolving some ambiguities in the interpretation of CP and INEPT data, we have developed a theoretical model for calculating the CP and INEPT intensities as a function of rotational correlation time ?c and C-H bond order parameter SCH, taking the effects of MAS into account. According to the model, the range of ?c can at typical experimental settings (5 kHz MAS, 1 ms ramped CP at 80-100 kHz B1 fields) be divided into four regimes: fast (?c < 1 ns), fast-intermediate (?c ? 0.1 ?s), intermediate (?c ? 1 ?s), and slow (?c > 0.1 ms). In the fast regime, the CP and INEPT intensities are independent of ?c, but strongly dependent on |SCH|, with a cross-over from dominating INEPT to dominating CP at |SCH| > 0.1. In the intermediate regime, neither CP nor INEPT yield signal on account of fast T1? and T2 relaxation. In both the fast-intermediate and slow regimes, there is exclusively CP signal. The theoretical predictions are tested by experiments on the glass-forming surfactant n-octyl-?-D-maltoside, for which ?c can be varied continuously in the nano- to millisecond range by changing the temperature and the hydration level. The atomistic details of the surfactant dynamics are investigated with MD simulations. Based on the theoretical model, we propose a procedure for calculating CP and INEPT intensities directly from MD simulation trajectories. While MD shows that there is a continuous gradient of ?c from the surfactant polar headgroup towards the methyl group at the end of the hydrocarbon chain, analysis of the experimental CP and INEPT data indicates that this gradient gets steeper with decreasing temperature and hydration level, eventually spanning four orders of magnitude at completely dry conditions.

  9. Molybdenum modified phosphate glasses studied by 31P MAS NMR and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Szumera, Magdalena

    2015-02-01

    Glasses have been synthesized in the system P2O5sbnd SiO2sbnd K2Osbnd MgOsbnd CaO modified by addition of MoO3. Glasses were prepared by conventional fusion method from 40 g batches. The influence of Mo-cations on the analysed glass structure was investigated by means of Raman and 31P MAS-NMR techniques. It has been found that molybdate units can form Mo[MoO4/MoO6]sbnd Osbnd P and/or Mo[MoO4/MoO6]sbnd Osbnd Si bonds with non-bridging oxygens atoms of Q2 methaphosphate units, resulting in the transformation of chain methaphosphate structure into pyrophosphate and finally into orthophosphate structure. It has been also found that increasing amount of MoO3 in the structure of investigated glasses causes their gradual depolymerization and molybdenum ions in the analysed glass matrix act as modifying cations.

  10. Hydration properties of regioselectively etherified celluloses monitored by 2H and 13C solid-state MAS NMR spectroscopy.

    PubMed

    Larsen, Flemming H; Schöbitz, Michael; Schaller, Jens

    2012-06-20

    The hydration properties of 2,3-O-hydroxypropylcellulose (HPC) and 2,3-O-hydroxyethylcellulose (HEC) were analyzed by multi-nuclear solid-state MAS NMR spectroscopy. By 13C single-pulse (SP) MAS and cross-polarization (CP) MAS NMR, differences between the immobile regions and all parts of the polysaccharides were detected as a function of hydration. Complementary information about the water environments was observed by 2H MAS NMR. By this approach it was demonstrated that side chains in 2,3-O-HPC and 2,3-O-HEC were easier to hydrate than the cellulose backbone. Furthermore the motion of water was more restricted (slower) in 2,3-O-HPC than in 2,3-O-HEC. For both polysaccharides the hydration could be explained by a two-step process: in step one increased ordering of the immobile regions occurs after which the entire polymer is hydrated in step two. PMID:24750769

  11. Effects of T 2-relaxation in MAS NMR spectra of the satellite transitions for quadrupolar nuclei: a 27Al MAS and single-crystal NMR study of alum KAl(SO 4) 2 · 12H 2O

    Microsoft Academic Search

    Morten Daugaard Andersen; Hans J. Jakobsen; Jørgen Skibsted

    2005-01-01

    Asymmetries in the manifold of spinning sidebands (ssbs) from the satellite transitions have been observed in variable-temperature 27Al MAS NMR spectra of alum (KAl(SO4)2·12H2O), recorded in the temperature range from ?76 to 92°C. The asymmetries decrease with increasing temperature and reflect the fact that the ssbs exhibit systematically different linewidths for different spectral regions of the manifold. From spin-echo 27Al

  12. Effects of T2-relaxation in MAS NMR spectra of the satellite transitions for quadrupolar nuclei: a 27Al MAS and single-crystal NMR study of alum KAl(SO4)2 · 12H2O

    Microsoft Academic Search

    Morten Daugaard Andersen; Hans J. Jakobsen; Jørgen Skibsted

    2005-01-01

    Asymmetries in the manifold of spinning sidebands (ssbs) from the satellite transitions have been observed in variable-temperature 27Al MAS NMR spectra of alum (KAl(SO4)2 · 12H2O), recorded in the temperature range from -76 to 92 °C. The asymmetries decrease with increasing temperature and reflect the fact that the ssbs exhibit systematically different linewidths for different spectral regions of the manifold.

  13. Microscopic structural analysis of fractured silk fibers from Bombyx mori and Samia cynthia ricini using 13C CP\\/MAS NMR with a 1 mm microcoil MAS NMR probehead

    Microsoft Academic Search

    Kazuo Yamauchi; Shizuo Yamasaki; Rui Takahashi; Tetsuo Asakura

    2010-01-01

    Conformational changes have been studied in silk fibers from the domestic silkworm Bombyx mori and a wild silkworm Samia cynthia ricini as a result of fractured by stretching. About 300 samples consisting of only the fractured regions of [1-13C]Ala or [1-13C]Gly labeled silk fibers were collected and observed by 13C CP\\/MAS NMR spectra. The total amount of these fractured fibers

  14. Magnesium silicate dissolution investigated by Si-29 MAS, H-1-Si-29 CPMAS, Mg-25 QCPMG NMR.

    SciTech Connect

    Davis, M C [Oak Ridge National Laboratory (ORNL); Wesolowski, David J [ORNL

    2009-09-01

    Olivine-(Mg,Fe){sub 2}SiO{sub 4}-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg{sub 2}SiO{sub 4}) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ({sup 29}Si MAS, {sup 1}H-{sup 29}Si CP MAS, {sup 25}Mg QCPMG, and {sup 1}H-{sup 25}Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 C.

  15. Characterization of the surface of positive electrodes for Li-ion batteries using 7 Li MAS NMR

    Microsoft Academic Search

    Nicolas Dupré; Julie Oliveri; Jeremy Degryse; Jean-Frédéric Martin; Dominique Guyomard

    2008-01-01

    The growth and evolution of the interphase, due to contact with the ambient atmosphere or electrolyte, are followed using\\u000a 7Li magic-angle spinning nuclear magnetic resonance (MAS NMR) in the case of two materials amongst the most promising candidates\\u000a for positive electrodes for lithium batteries: LiFePO4 and LiMn0.5Ni0.5O2. The use of appropriate experimental conditions to acquire the NMR signal allows observing

  16. MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

    Microsoft Academic Search

    Madhumita Goswami; Govind P. Kothiyal; Lionel Montagne; Laurent Delevoye

    2008-01-01

    Lithium zinc silicate glasses of composition (mol%): 17.5Li2O–(72?x)SiO2–xZnO?5.1Na2O?1.3P2O5?4.1B2O3, 5.5?x?17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. 29Si and 31P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q2, Q3 and Q4 sites are identified from 29Si MAS-NMR, which relative intensities are found to

  17. Thermal maturity of type II kerogen from the New Albany Shale assessed by13C CP/MAS NMR

    USGS Publications Warehouse

    Werner-Zwanziger, U.; Lis, G.; Mastalerz, Maria; Schimmelmann, A.

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. ?? 2004 Elsevier Inc. All rights reserved.

  18. DETERMINATION OF BRANCHING RATIOS IN STARCH OF INTACT FLOURS BY GEL-STATE 1H MAS NMR SSPECTROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    1H MAS NMR was employed to determine the ratio of alpha 1-4 to alpha 1-6 branching in the starch of rice flour. Samples investigated were exchanged (2X) in D2O with freeze drying, gelatinized with 90/10 percent DMSO/ D2O freeze dried again, finally moistened with D2O, and placed in a spherical 4 mm ...

  19. Spectral editing through laser-flash excitation in two-dimensional photo-CIDNP MAS NMR experiments.

    PubMed

    Sai Sankar Gupta, Karthick Babu; Daviso, Eugenio; Jeschke, Gunnar; Alia, A; Ernst, Matthias; Matysik, Jörg

    2014-09-01

    In solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR experiments, strong signal enhancement is observed from molecules forming a spin-correlated radical pair in a rigid matrix. Two-dimensional (13)C-(13)C dipolar-assisted rotational resonance (DARR) photo-CIDNP MAS NMR experiments have been applied to obtain exact chemical shift assignments from those cofactors. Under continuous illumination, the signals are enhanced via three-spin mixing (TSM) and differential decay (DD) and their intensity corresponds to the electron spin density in pz orbitals. In multiple-(13)C labelled samples, spin diffusion leads to propagation of signal enhancement to all (13)C spins. Under steady-state conditions, direct signal assignment is possible due to the uniform signal intensity. The original intensities, however, are inaccessible and the information of the local electron spin density is lost. Upon laser-flash illumination, the signal is enhanced via the classical radical pair mechanism (RPM). The obtained intensities are related to isotropic hyperfine interactions aiso and both enhanced absorptive and emissive lines can be observed due to differences in the sign of the local isotropic hyperfine interaction. Exploiting the mechanism of the polarization, selectivity can be increased by the novel time-resolved two-dimensional dipolar-assisted rotational resonance (DARR) MAS NMR experiment which simplifies the signal assignment compared to complex spectra of the same RCs obtained by continuous illumination. Here we present two-dimensional time-resolved photo-CIDNP MAS NMR experiments providing both directly: signal assignment and spectral editing by sign and strength of aiso. Hence, this experiment provides a direct key to the electronic structure of the correlated radical pair. PMID:25063951

  20. MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

    SciTech Connect

    Goswami, Madhumita [UCCS-Unite de Catalyse et Chimie du Solide, UMR CNRS 8181, Ecole Nationale Superieure de Chimie de Lille, Universite des Sciences et Technologies de Lille, BP 108, 59652 Villeneuve d'Ascq Cedex (France); Kothiyal, Govind P. [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Montagne, Lionel [UCCS-Unite de Catalyse et Chimie du Solide, UMR CNRS 8181, Ecole Nationale Superieure de Chimie de Lille, Universite des Sciences et Technologies de Lille, BP 108, 59652 Villeneuve d'Ascq Cedex (France)], E-mail: lionel.montagne@univ-lille1.fr; Delevoye, Laurent [UCCS-Unite de Catalyse et Chimie du Solide, UMR CNRS 8181, Ecole Nationale Superieure de Chimie de Lille, Universite des Sciences et Technologies de Lille, BP 108, 59652 Villeneuve d'Ascq Cedex (France)

    2008-02-15

    Lithium zinc silicate glasses of composition (mol%): 17.5Li{sub 2}O-(72-x)SiO{sub 2}-xZnO-5.1Na{sub 2}O-1.3P{sub 2}O{sub 5}-4.1B{sub 2}O{sub 3}, 5.5{<=}x{<=}17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. {sup 29}Si and {sup 31}P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q{sup 2}, Q{sup 3} and Q{sup 4} sites are identified from {sup 29}Si MAS-NMR, which relative intensities are found to vary with the ZnO content, indicating a network depolymerization by ZnO. Moreover, well separated Q{sup 3} and Q{sup 4} resonances for low ZnO content indicates the occurrence of phase separation. From {sup 31}P MAS-NMR, it is seen that phosphorus is mainly present in the form of ortho-(Q{sup 0}) and pyro-phosphate (Q{sup 1}) structural units and variation of ZnO content did not have much effect on these resonances, which provides an additional evidence for phase separation in the glass. On conversion to glass-ceramics, lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), lithium zinc ortho-silicate (Li{sub 3}Zn{sub 0.5}SiO{sub 4}), tridymite (SiO{sub 2}) and cristobalite (SiO{sub 2}) were identified as major silicate crystalline phases. Using {sup 29}Si MAS-NMR, quantification of these silicate crystalline phases is carried out and correlated with the ZnO content in the glass-ceramics samples. In addition, {sup 31}P spectra unambiguously revealed the presence of crystalline Li{sub 3}PO{sub 4} and (Na,Li){sub 3}PO{sub 4} in the glass-ceramics. - Graphical abstract: {sup 29}Si and {sup 31}P MAS-NMR analyses were carried out on multi-component Li{sub 2}O-SiO{sub 2}-ZnO-Na{sub 2}O-P{sub 2}O{sub 5}-B{sub 2}O{sub 3} glasses and glass-ceramics developed for sealing application. Structural data are reported, including phase separation process and quantification of amorphous and crystalline phases.

  1. Study of phase transition mechanisms in [N(CH3)4]2ZnCl4 by static NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Lim, Kye-Young

    2014-05-01

    The temperature dependences of chemical shifts, intensities, the spin-lattice relaxation time in laboratory frame T1, and in rotating frame T1? were measured for 1H and 13C in [N(CH3)4]2ZnCl4 by single-crystal NMR and MAS NMR. The unit cell in phase I contains two chemically inequivalent types of N(CH3)4 ions. However, the two chemically different ions N(CH3)4 cannot be practically identified from the 13C NMR spectrum. The structural changes for 1H and 13C were measured near Ti and TC4. The existence of chemically equivalent N(CH3)4 ions in phase I and the existence of the ferroelastic characteristic of the N(CH3)4 ions in phases IV and V are discussed.

  2. Detailed analysis of the TIMES and TIMES0 high-resolution MAS methods for high-resolution proton NMR

    NASA Astrophysics Data System (ADS)

    Lu, Xingyu; Lafon, Olivier; Trébosc, Julien; Thankamony, Aany Sofia Lilly; Nishiyama, Yusuke; Gan, Zhehong; Madhu, P. K.; Amoureux, Jean-Paul

    2012-10-01

    We analyze and compare the specifications of TIMES and TIMES0 proton high-resolution NMR methods for solid-state samples. This comparison is performed in terms of resolution versus magic-angle spinning (MAS) spinning speed, ?R, rf-field amplitude, ?1, and tilt-angle for the effective rf-field, ?p. The chemical-shift and homo-nuclear dipolar scaling factors are calculated for both methods. For all MAS speeds, the best resolution is always observed with rf-field of ?1 ? 120-130 kHz. At slow MAS speed (?R ? 10 kHz), the best resolution is observed for a tilt-angle of ?P ? 90°. At moderate spinning speed (15 ? ?R ? 35 kHz), ?P ? 55° gives the best resolution. At higher MAS speed (?R ? 60 kHz), with TIMES and TIMES0 the best resolution is obtained for ?P ? 40°; but we then recommend TIMES0, owing to its simpler set-up. We also show that in addition to the usual high rf-field regime (?1 ? 120-130 kHz), another low rf-regime (?1 ? 40-50 kHz) exists at MAS speed higher than ?R ? 60 kHz, which also gives a good 1H resolution. This low rf-regime should be useful for multi-dimensional analyses of bio-molecules with 1H detection under high-resolution, in order to limit the heating of the sample.

  3. Determination of the structural changes by Raman and {sup 13}C CP/MAS NMR spectroscopy on native corn starch with plasticizers

    SciTech Connect

    Cozar, O. [Academy of Romanian Scientists, Splaiul Independentei 54, 050094, Bucharest, Romania and National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch (Romania)] [Academy of Romanian Scientists, Splaiul Independentei 54, 050094, Bucharest, Romania and National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch (Romania); Filip, C.; Tripon, C. [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania); Cioica, N.; Co?a, C.; Nagy, E. M. [National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch, RO-400458 Cluj-Napoca (Romania)] [National Institute of Research-Development for Machines and Installations Designed to Agriculture and Food Industry - INMA Bucure?ti - Cluj-Napoca Branch, RO-400458 Cluj-Napoca (Romania)

    2013-11-13

    The plasticizing - antiplasticizing effect of water and glycerol contents on native corn starch samples is investigated by FT-Raman and {sup 13}C CP/MAS NMR spectroscopy. The presence of both amorphous and crystalline structural phases was evidenced in pure native corn starch and also in the samples containing plasticizers. Among the crystalline starch structures, the A- and V- types were suggested by CP/MAS NMR spectra.

  4. Solid-state dynamics in the closo-carboranes: a (11)B MAS NMR and molecular dynamics study.

    PubMed

    Ahumada, Hernán; Kurkiewicz, Teresa; Thrippleton, Michael J; Wimperis, Stephen

    2015-03-19

    This work explores the dynamic behavior of the three closo-carborane isomers (formula C2B10H12) using modern solid-state magic angle spinning (MAS) NMR techniques and relates the experimental measurements to theoretical results obtained using molecular dynamics simulations. At high temperatures and at B0 = 9.4 T, the (11)B MAS line widths are narrow (40-90 Hz) for the three isomers. The rotational correlation times (?c) calculated by molecular dynamics are on the picosecond time scale, showing a quasi-isotropic rotation at these temperatures, typical for liquid systems. For all three isomers, the values of the (11)B spin-lattice relaxation times (T1) show discontinuities as the temperature is decreased, confirming the phase changes reported in the literature. At low temperatures, the (11)B MAS spectra of all three isomers exhibit much broader lines. The simulations showed that the molecular reorientation was anisotropic around different symmetry axes for each isomer, and this was supported by the values of the reduced quadrupolar parameter PQ(eff) derived from "dynamic shift" measurements using (11)B MQMAS NMR spectroscopy. The behavior of PQ(eff) as a function of temperature for p-carborane suggests that molecular reorientation is about the C5 symmetry axis of the molecule at low temperatures, and this was supported by the molecular dynamics simulations. PMID:25710751

  5. Conformation analysis and molecular mobility of ethylene and tetrafluoroethylene copolymer using solid-state 19F MAS and 1H --> 19F CP/MAS NMR spectroscopy.

    PubMed

    Aimi, Keitaro; Ando, Shinji

    2004-07-01

    The changes in the conformation and molecular mobility accompanied by a phase transition in the crystalline domain were analyzed for ethylene (E) and tetrafluoroethylene (TFE) copolymer, ETFE, using variable-temperature (VT) solid-state 19F magic angle spinning (MAS) and 1H --> 19F cross-polarization (CP)/MAS NMR spectroscopy. The shifts of the signals for fluorines in TFE units to higher frequency and the continuing decrease and increase in the T1rho(F) values suggest that conformational exchange motions exist in the crystalline domain between 42 and 145 degrees C. Quantum chemical calculations of magnetic shielding constants showed that the high-frequency shift of TFE units should be induced by trans to gauche conformational changes at the CH2-CF2 linkage in the E-TFE unit. Although the 19F signals of the crystalline domain are substantially overlapped with those of the amorphous domain at ambient probe temperature (68 degrees C), they were successfully distinguished by using the dipolar filter and spin-lock pulse sequences at 145 degrees C. The dipolar coupling constants for the crystalline domain, which can be estimated by fitting the dipolar oscillation behaviors in the 1H --> 19F CP curve, showed a significant decrease with increasing temperature from 42 to 145 degrees C. This is due to the averaging of 1H-19F dipolar interactions originating from the molecular motion in the crystalline domain. The increase in molecular mobility in the crystalline domain was clearly shown by VT T1rho(F) and 1H --> 19F CP measurements in the phase transition temperature range. PMID:15181627

  6. 29 Si MAS-NMR spectroscopy of mica-type silicates: Observed and predicted distribution of tetrahedral Al-Si

    Microsoft Academic Search

    C. P. Herrero; M. Gregorkiewitz; J. Sanz; J. M. Serratosa

    1987-01-01

    29Si MAS-NMR spectra were obtained for vermiculite with tetrahedral composition x=Al\\/(Al+Si)=0.28, a synthetic mica with x=0.43, and margarite with x=0.5. Comparison between the observed and Monte-Carlo simulated spectra was used to test different Al-Si distribution schemes in the tetrahedral sheet. The results of this analysis are interpreted including earlier data corresponding to lower Al for Si substitutions (0.12=x=0.28), and it

  7. Long-Range Correlations between Aliphatic [superscript 13]C Nucleic in Protein MAS NMR Spectroscopy

    E-print Network

    Bayro, Marvin?J.

    Highly efficient polarization transfer can be achieved in the magic-angle spinning NMR analysis of proteins by the combination of [superscript 13]C labeling at alternating positions and band-selective radio-frequency-driven ...

  8. Examining microstructural composition of hardened cement paste cured under high temperature and pressure using nanoindentation and 29Si MAS NMR

    NASA Astrophysics Data System (ADS)

    Kim, Jung J.; Rahman, Muhammad K.; Reda Taha, Mahmoud M.

    2012-12-01

    Microstructural composition of the hardened cement pastes are analyzed using nanoindentation and 29Si MAS NMR after curing time periods of 7 and 28 days. Two curing conditions, room condition (20°C with 0.1 MPa pressure) and an elevated condition (80°C with 10 MPa pressure) are prepared to hydrate cement pastes [water to cement ( w/ c) ratio of 0.45]. The degree of hydration of the cement paste quantified using nanoindentation was compared with that from 29Si MAS NMR. From nanoindentation of the hardened cement pastes, microstructural hydration products are characterized with respect to the corresponding modulus of elasticity. A hydration product, which has a relatively high modulus of elasticity over other known hydration products, was found in the hardened cement paste cured in elevated temperature and pressure. The effect of high pressure on the composition of the hydration product is discussed and it is hypothesized that the packing density of calcium-silicate-hydrate (C-S-H) might increase when a cement paste is hydrated under high temperature and pressure.

  9. Enhanced In situ Continuous-Flow MAS NMR for Reaction Kinetics in the Nanocages

    E-print Network

    Bao, Xinhe

    kinetics in the nanospace. Methanol conversion in CHA nanocages has been investigated in detail for proof batchlike or continuous-flow mode.5-11 Most of these studies are focused on the reactant transformation and easily. It has been shown that laser- hyperpolarized (HP) 129 Xe NMR technique is powerful in studying

  10. Phase cycling schemes for finite-pulse-RFDR MAS solid state NMR experiments

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Sun, Pingchuan; Ramamoorthy, Ayyalusamy

    2015-03-01

    The finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used in 2D homonuclear chemical shift correlation experiments under magic angle spinning (MAS). A recent study demonstrated the advantages of using a short phase cycle, XY4, and its super-cycle, XY414, for the fp-RFDR pulse sequence employed in 2D 1H/1H single-quantum/single-quantum correlation experiments under ultrafast MAS conditions. In this study, we report a comprehensive analysis on the dipolar recoupling efficiencies of XY4, XY412, XY413, XY414, and XY814 phase cycles under different spinning speeds ranging from 10 to 100 kHz. The theoretical calculations reveal the presence of second-order terms (T10T2,±2, T1,±1T2,±1, etc.) in the recoupled homonuclear dipolar coupling Hamiltonian only when the basic XY4 phase cycle is utilized, making it advantageous for proton-proton magnetization transfer under ultrafast MAS conditions. It is also found that the recoupling efficiency of fp-RFDR is quite dependent on the duty factor (?180/?R) as well as on the strength of homonuclear dipolar couplings. The rate of longitudinal magnetization transfer increases linearly with the duty factor of fp-RFDR for all the XY-based phase cycles investigated in this study. Examination of the performances of different phase cycles against chemical shift offset and RF field inhomogeneity effects revealed that XY414 is the most tolerant phase cycle, while the shortest phase cycle XY4 suppressed the RF field inhomogeneity effects most efficiently under slow spinning speeds. Our results suggest that the difference in the fp-RFDR recoupling efficiencies decreases with the increasing MAS speed, while ultrafast (>60 kHz) spinning speed is advantageous as it recouples a large amount of homonuclear dipolar couplings and therefore enable fast magnetization exchange. The effects of higher-order terms and cross terms between various interactions in the effective Hamiltonian of fp-RFDR are also analyzed using numerical simulations for various phase cycles. Results obtained via numerical simulations are in excellent agreement with ultrafast MAS experimental results from the powder samples of glycine and L-alanine.

  11. 27Al and 29Si MAS NMR investigations of cordierite glass, mu- and alpha-cordierite.

    PubMed

    Storek, W; Müller, R; Kunath-Fandrei, G

    1997-12-01

    27Al and 29Si Magic-Angle Spinning NMR results are reported for conventionally prepared glass of cordierite stoichiometry (2MgO.2Al2O3.5SiO2), the metastable high-quartz solid solution (mu-cordierite) and the high-temperature polymorph of cordierite (alpha-cordierite). Both, 27Al two-dimensional (2D) quadrupole nutation experiments and 27Al satellite transition spectroscopy (SATRAS) have been applied to identify two different tetrahedrally-coordinated aluminium sites (AlO4). SATRAS has been used to extract the quadrupole interaction parameters and their distribution, the isotropic chemical shifts and the relative populations of the different Al sites. Both, the 27Al and 29Si NMR results, lead to the conclusion that a perfect Si/Al disorder does not exist in these investigated cordierite samples. PMID:9477452

  12. 17O MAS NMR and first principles calculations of ZrO2 polymorphs

    NASA Astrophysics Data System (ADS)

    Pimentel, Helio R. X.; Aguiar, Daniel L. M.; San Gil, Rosane A. S.; Souza, Eugenio F.; Ferreira, Ary R.; Leitão, Alexandre A.; Alencastro, Ricardo B.; Menezes, Sônia M. C.; Chiaro, Sandra S. X.

    2013-01-01

    DFT has been used for the first time to calculate 17O NMR magnetic response of the monoclinic and tetragonal ZrO2 phases. The calculated values were compared with those obtained by solid state 17O NMR after in situ17O isotopic enrichment of the boehmite samples inside ZrO2 rotors. The theoretical and experimental results indicated that after drying (120 °C) and calcination (500 °C/3 h) under ambient pressure, part of the ceramic structure of the ZrO2 rotor was exchanged, generating Zr17O2 species. A good correlation between DFT and experimental data for monoclinic and tetragonal ZrO2 polymorphs was achieved.

  13. Solid state 31P and 207Pb MAS NMR studies on polycrystalline O,O'-dialkyldithiophosphate lead(II) complexes.

    PubMed

    Larsson, Anna-Carin; Ivanov, Alexander V; Pike, Kevin J; Forsling, Willis; Antzutkin, Oleg N

    2005-11-01

    A number of lead(II) O,O'-dialkyldithiophosphate complexes were studied by (13)C, (31)P, and (207)Pb MAS NMR. Simulations of (31)P chemical shift anisotropy using spinning sideband analysis reveal a linear relationship between the SPS bond angle and the principal values delta(22) and delta(33) of the (31)P chemical shift tensor. The (31)P CSA data were used to assign ligands with different structural functions. In the cases of diethyldithiophosphate and di-iso-butyldithiophosphate lead(II) complexes, (2)J((31)P, (207)Pb)-couplings were resolved and used to confirm the suggested assignment of the ligands. The SIMPSON computer program was used to calculate (31)P and (207)Pb spectral sideband patterns. PMID:16102989

  14. A Timesaving Strategy for MAS NMR Spectroscopy by Combining Non-Uniform Sampling and Paramagnetic Relaxation Assisted Condensed Data Collection

    PubMed Central

    Sun, Shangjin; Yan, Si; Guo, Changmiao; Li, Mingyue; Hoch, Jeffrey C.; Williams, John C.; Polenova, Tatyana

    2012-01-01

    We present a timesaving strategy for acquiring 3D magic angle spinning NMR spectra for chemical shift assignments in proteins and protein assemblies in the solid state. By simultaneous application of non-uniform sampling (NUS) and paramagnetic-relaxation-assisted condensed data collection (PACC), we can attain 16-fold time reduction in the 3D experiments without sacrificing the signal-to-noise ratio or the resolution. We demonstrate that with appropriate concentration of paramagnetic dopant introduced into the sample the overwhelming majority of chemical shifts are not perturbed, with the exception of a limited number of shifts corresponding to residues located at the surface of the protein, which exhibit small perturbations. This approach enables multi-dimensional MAS spectroscopy in samples of intrinsically low sensitivity and/or high spectral congestion where traditional experiments fail, and is especially beneficial for structural and dynamics studies of large proteins and protein assemblies. PMID:23094591

  15. Ultra-high resolution in MAS solid-state NMR of perdeuterated proteins: implications for structure and dynamics.

    PubMed

    Reif, Bernd

    2012-03-01

    High resolution proton spectra are obtained in MAS solid-state NMR in case samples are prepared using perdeuterated protein and D(2)O in the recrystallization buffer. Deuteration reduces drastically (1)H, (1)H dipolar interactions and allows to obtain amide proton line widths on the order of 20 Hz. Similarly, high-resolution proton spectra of aliphatic groups can be obtained if specifically labeled precursors for biosynthesis of methyl containing side chains are used, or if limited amounts of H(2)O in the bacterial growth medium is employed. This review summarizes recent spectroscopic developments to access structure and dynamics of biomacromolecules in the solid-state, and shows a number of applications to amyloid fibrils and membrane proteins. PMID:22280934

  16. Simple and accurate determination of X-H distances under ultra-fast MAS NMR

    NASA Astrophysics Data System (ADS)

    Paluch, Piotr; Pawlak, Tomasz; Amoureux, Jean-Paul; Potrzebowski, Marek J.

    2013-08-01

    We demonstrate that a very simple experiment, Cross-Polarization with Variable Contact-time (CP-VC), is very efficient at ultra-fast MAS (?R ? 60 kHz) to measure accurately the C-H and N-H distances, and to analyze the dynamics of bio-molecules. This experiment can be performed with samples that are either 13C or 15N labeled or without any labeling. The method is very robust experimentally with respect to imperfect Hartman-Hahn setting, and presents a large scaling factor allowing a better dipolar determination, especially for long C-H or N-H distances, or for CH3 or NH3 moieties with three-site hopping. At ultra-fast MAS, it can be used quantitatively in a 2D way, because its scaling factor is then little dependent on the offsets. This robustness with respect to offset is related to the ultra-fast spinning speed, and hence to the related small rotor diameter. Indeed, these two specifications lead to efficient n = ±1 zero-quantum Hartman-Hahn CP-transfers with large RF-fields on proton and carbon or nitrogen channels, and large dipolar scaling factor.

  17. A MAS NMR study of the bacterial ABC transporter ArtMP.

    PubMed

    Lange, Vivien; Becker-Baldus, Johanna; Kunert, Britta; van Rossum, Barth-Jan; Casagrande, Fabio; Engel, Andreas; Roske, Yvette; Scheffel, Frank M; Schneider, Erwin; Oschkinat, Hartmut

    2010-03-01

    ATP-binding cassette (ABC) transport systems facilitate the translocation of substances, like amino acids, across cell membranes energised by ATP hydrolysis. This work describes first structural studies on the ABC transporter ArtMP from Geobacillus stearothermophilus in native lipid environment by magic-angle spinning NMR spectroscopy. The 2D crystals of ArtMP and 3D crystals of isolated ArtP were prepared in different nucleotide-bound or -unbound states. From selectively (13)C,(15)N-labelled ArtP, several sequence-specific assignments were obtained, most of which could be transferred to spectra of ArtMP. Residues Tyr133 and Pro134 protrude directly into the ATP-binding pocket at the interface of the ArtP subunits, and hence, are sensitive monitors for structural changes during nucleotide binding and hydrolysis. Distinct sets of NMR shifts were obtained for ArtP with different phosphorylation states of the ligand. Indications were found for an asymmetric or inhomogeneous state of the ArtP dimer bound with triphosphorylated nucleotides. With this investigation, a model system was established for screening all functional states occurring in one ABC transporter in native lipid environment. PMID:20099290

  18. Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range

    PubMed Central

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David; Hoch, Jeffrey C.; Rovnyak, David

    2014-01-01

    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. PMID:24752819

  19. Red coralline algae assessed as marine pH proxies using 11B MAS NMR.

    PubMed

    Cusack, M; Kamenos, N A; Rollion-Bard, C; Tricot, G

    2015-01-01

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions. PMID:25640229

  20. A CP/MAS NMR Characterization of the structure and dynamics of HF doped polyaniline

    NASA Astrophysics Data System (ADS)

    Espe, M. P.; Schaefer, J.; Mattes, B.

    1996-03-01

    Solid-state NMR relaxation studies show that polyaniline undergoes 180^o phenyl ring flips over a broad frequency range. However, lack of cooperative main-chain motion is evident as only approx 20% of the phenyl rings flip. The ^15N and ^19F spectra of the doped polymer reveal the presence of both localized and delocalized bipolarons. There are three different fluorine environments, two assigned to localized bipolarons and one to localizaed bipolarons. Rotational-echo double resonance (REDOR) experiments have been used to measure the N..F distance of 3.1 angstroms; the same distance is observed for both bipolaron forms. The REDOR results also show that there are regions of the polymer where, possibly connected to long-range structural order, there is strong F-F interaction.

  1. Aluminum coordinations for aluminosilicate glasses at 1 atm. and 3GPa: a 27Al MAS NMR study

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Stebbins, J. F.; Withers, A. C.; Hirschmann, M. M.

    2003-12-01

    In this study, we used 27Al MAS NMR to investigate the distribution of different aluminum coordinations in ambient pressure and moderate pressure (3GPa) aluminosilicate glasses with compositions of Mx+(9-3x)Al2Si6O18, where M= Ca2+, Na+, and K+. These spectra were collected at 18.8 Tesla to minimize the peak broadening due to second-order quadrupolar effects, which causes overlapping peaks for different coordinations of Al. Aluminum is thought to be mostly tetrahedrally coordinated in ambient-pressure aluminosilicate glasses where M+(2-x)O >= Al2O3, but 27Al NMR studies have shown that small concentrations of high-coordinated Al are present in both charge balanced (Toplis et al. 2000; Stebbins et al. 2001) and "depolymerized" (M+(2-x)O > Al2O3) aluminosilicate glasses (Stebbins and Farnan 1992). The 27Al spectra of samples of this study show that these ambient pressure glasses all contain [5]Al. Interestingly, the NAS (Na-aluminosilicate) glass contains more [5]Al than the KAS glass (0.6 vs. 0.3, respectively), which is opposite of that observed for SiO[5] groups in binary silicate glasses (Stebbins and McMillan 1993). The CAS glass spectrum shows a shoulder at 25 ppm, but the [4]Al peak is too broad to assign a reliable percentage for the amount of [5]Al. Previous studies of high-pressure glasses have shown that Al transforms to higher coordinations with increasing pressures (Yarger et al. 1995). In this study, we observe that the 27Al MAS spectrum of the 3 GPa NAS glass shows that 7% [5]Al and 1% [6]Al species exist. Additionally, the spectra of the KAS glass shows that 2% [5]Al and possibly some [6]Al are present at 3 GPa. These spectra clearly show for the first time that pressure induced Al-coordination changes occur in aluminosilicate glasses at pressures of 3 GPa. Recent 27Al NMR spectra of high-pressure "depolymerized" aluminosilicate glasses with different fictive temperatures have shown that the amount of high-coordinated Al increases with increasing temperature, which suggests that these results represent a minimum value for the melt (Allwardt et al 2003). Further work will focus on obtaining data at higher pressures to determine the pressure dependence for the generation of these species.

  2. A highly sensitive method for in vitro testing of fluorinated drug candidates using high-resolution continuum source molecular absorption spectrometry (HR-CS MAS).

    PubMed

    Würtenberger, Irene; Gust, Ronald

    2014-05-01

    We report here the development, optimization, and evaluation of a highly sensitive method for the determination of fluorine in biological matrices employing highresolution continuum source molecular absorption spectrometry (HR-CS MAS), suitable for pharmacological testing of fluorine-containing drug candidates. For this purpose, the most important parameters were studied in detail and subsequently optimized using a multivariate approach based on experimental design methodology. We developed a new approach employing a graphite tube lined with tantalum foil, thereby significantly enhancing sensitivity, while interferences from phosphorus monoxide (PO) molecular absorption due to the complex phosphate-rich matrix were completely eliminated. The limit of detection and the characteristic mass were 5.79 and 6.08 pg F, respectively. In order to evaluate the accuracy of the procedure, a recovery test was performed using spiked samples from three bioassays (i.e., DNA binding, protein binding, and cellular uptake) and the recovery rates ranged from 97.4 to 106.4%. The proposed method is applicable for preclinical in vitro testing of fluorinated drug molecules and thereby establishes HR-CS atomic absorption spectrometry instrumentation as a universal tool in medicinal chemistry. PMID:24760395

  3. FT-RAMAN AND 13C CP-MAS NMR SPECTROSCOPIC ASSESSMENT OF CONFORMATIONAL CHANGES IN PROTEIN AND STARCH UNDER VARIOUS PARABOILING CONDITIONS FOR RICE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FT-Raman and solid-state 13C CP-MAS NMR spectroscopies were employed to assess the conformational changes to protein and starch in rice under variable conditions of parboiling. TOX 3108 rice from Ghana, was parboiled by the soaking-steaming-drying method under conditions that mimicked various local...

  4. CHANGES IN PROTEIN AND STARCH CONFORMATION DURING VARIABLE TEMPERATURE PARBOILING OF RICE: FT-RAMAN AND 13C CP-MAS NMR SPECTROSCOPIC ASSESSMENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FT-Raman and solid-state 13C cross polarization magic-angle spinning (CP-MAS) NMR spectroscopies were employed to assess the conformational changes to protein and starch in paddy rice under variable conditions of parboiling. Rice variety, TOX 3108 from Ghana, was parboiled by the soaking-steaming-d...

  5. Practical aspects of high-sensitivity multidimensional 13C MAS NMR spectroscopy of perdeuterated proteins

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; van Rossum, Barth-Jan; Oschkinat, Hartmut

    2012-04-01

    The double nucleus enhanced recoupling (DONER) experiment employs simultaneous irradiation of protons and deuterons to promote spin diffusion processes in a perdeuterated protein. This results in 4-5 times higher sensitivity in 2D 13C-13C correlation experiments as compared to PDSD [1]. Here, a quantitative comparison of PDSD, 1H-DARR, 2H-DARR, and 1H + 2H DONER has been performed to analyze the influence of spin diffusion on polarization transfer processes. Cross peak buildup curves were analyzed to obtain guidelines for choosing the best experimental parameters. The largest cross peak intensities were observed for the DONER experiments. The fastest build-up rate was observed in the 2H-DARR experiment within a buildup range of ˜18-45 ms, whereas values between 24 and 69 ms are observed for the DONER experiment. Furthermore, the effects of direct excitation and cross polarization (CP) are compared. A comparison between DONER and RFDR experiments reveal ˜50% more intense cross peaks in the C?-CO and C?-Calip regions of the 2D 13C-13C DONER spectrum applying proton CP (1H-13C). As a parameter determining the S/N in 13C-13C correlation experiments, proton CP efficiency is investigated using deuterated samples with proton/deuterium ratios at 20%, 40%, and 100% H2O. Sufficiently strong 13C CPMAS signal intensity is observed for such proteins even with very low proton concentration. The effect of proton and/or deuterium decoupling is analyzed at various MAS spinning frequencies. Deuterium decoupling was found most crucial for obtaining high resolution. Long range correlations are readily observed representing distances up to ˜6 Å by using DONER approach.

  6. Roles of chemically inequivalent N(CH3)4 ions in phase transition temperatures in [N(CH3)4]2CoCl4 by single-crystal NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-06-01

    The temperature dependences of the 1H and 13C spin-lattice relaxation time in the laboratory frame, T1, and in the rotating frame, T1?, in [N(CH3)4]2CoCl4 were measured by static nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR. In the ferroelastic phase, 1H T1? underwent molecular motion according to the Bloembergen-Purcell-Pound theory. Two inequivalent ions, a-N(CH3)4 and b-N(CH3)4, were identified by 13C cross polarization (CP)/MAS NMR. On the basis of the 13C NMR results, the existence of two chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in the ferroelectric phase and the existence of the ferroelastic twin structure of the N(CH3)4 ions in the ferroelastic phase were discussed.

  7. Solid-state 19F MAS NMR study on the conformation and molecular mobility of poly(chlorotrifluoroethylene).

    PubMed

    Tatsuno, Hiroto; Aimi, Keitaro; Ando, Shinji

    2007-05-01

    The temperature dependence of molecular mobility and conformational changes of poly(chlorotrifluoro- ethylene) (PCTFE) have been investigated by solid-state (19)F magic angle spinning (MAS) NMR spectroscopy. The pulse techniques of dipolar-filter and T(1rho)-filter allow selective observation of the amorphous and crystalline domains, respectively. The temperature dependence of T(1rho) (F) revealed that the segmental motion in the amorphous domain becomes vigorous above ca 80 degrees C, which is well above the glass transition (T(g)) temperature (52 degrees C) and more close to the beta-relaxation temperature (95 degrees C). On the other hand, vigorous molecular motions in the crystalline domain occur above 120 degrees C, which is much below the melting temperature (212 degrees C). This indicates that the polymer chains in the PCTFE crystallites are more mobile than those of typical semicrystalline fluoropolymers like poly(vinylidene fluoride) (PVDF), which can be associated with structural imperfections in the crystallites. In addition, the density functional theory (DFT) calculations of (19)F magnetic shielding suggest that the high-frequency shifts observed for the crystalline signals above 80 degrees C can be ascribed to the conformational change around meso diads toward more twisted and/or helical conformations in the main chain. PMID:17372960

  8. Magnesium silicate dissolution investigated by S1-29 MAS, H-1 Si-29 CPMAS, Mg-25 QCPMG, and H-1 Mg-25 CP QCPMG NMR

    SciTech Connect

    Davis, M C [Oak Ridge National Laboratory (ORNL); Brouwer, Piet W [ORNL; Wesolowski, David J [ORNL; Anovitz, Lawrence {Larry} M [ORNL

    2009-07-01

    Olivine-(Mg,Fe){sub 2}SiO{sub 4}-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg2SiO4) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ({sup 29}Si MAS, {sup 1}H-{sup 29}Si CP MAS, {sup 25}Mg QCPMG, and {sup 1}H-{sup 25}Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 C.

  9. Magnesium silicate dissolution investigated by 29Si MAS, 1H-29Si CPMAS, 25Mg QCPMG, and 1H-25Mg CP QCPMG NMR.

    PubMed

    Davis, Michael C; Brouwer, William J; Wesolowski, David J; Anovitz, Lawrence M; Lipton, Andrew S; Mueller, Karl T

    2009-08-28

    Olivine-(Mg,Fe)(2)SiO(4)-has been the subject of frequent investigation in the earth sciences because of its simple structure and rapid dissolution kinetics. Several studies have observed a preferential release of the divalent cation with respect to silicon during weathering under acidic conditions, which has been correlated to the formation of a silicon-rich leached layer. While leached layer formation has been inferred through the changing solution chemistry, a thorough spectroscopic investigation of olivine reacted under acidic conditions has not been conducted. The pure magnesium end member of the olivine series (forsterite-Mg(2)SiO(4)) was chosen for detailed investigations in this study because paramagnetic iron hinders NMR investigations by providing an extra mode of relaxation for neighboring nuclei, causing lineshapes to become significantly broadened and unobservable in the NMR spectrum. For reacting forsterite, spectroscopic interrogations using nuclear magnetic resonance (NMR) can elucidate the changing magnesium coordination and bonding environment. In this study, we combine analysis of the changing solution chemistry with advanced NMR techniques ((29)Si MAS, (1)H-(29)Si CP MAS, (25)Mg QCPMG, and (1)H-(25)Mg CP QCPMG NMR) to probe leached layer formation and secondary phase precipitation during the dissolution of forsterite at 150 degrees C. PMID:19652836

  10. Effect of the SiO 2\\/Na 2O ratio on the alkali activation of fly ash. Part II: 29Si MAS-NMR Survey

    Microsoft Academic Search

    M. Criado; A. Fernández-Jiménez; A. Palomo; I. Sobrados; J. Sanz

    2008-01-01

    29Si MAS-NMR spectroscopy was used to characterize the reaction products resulting from the alkali activation of a type F fly ash. Specifically, analyses focused on the degree of polymerization of the activating solution (SiO2\\/Na2O ratio=0.0, 0.19, 0.69 and 1.17) and thermal curing time (from 8h to 180 days at 85°C). The results obtained showed that the degree of polymerization of

  11. CP-MAS 13C NMR and FT-IR investigation of the degradation reactions of polymer constituents in wood welding

    Microsoft Academic Search

    L. Delmotte; C. Ganne-Chedeville; J. M. Leban; A. Pizzi; F. Pichelin

    2008-01-01

    The essential chemical modifications involving the polymeric constituents of wood in friction welding occur in the first 5–6s slowing down or even stopping afterwards. FT-IR and CP-MAS 13C NMR of the welded area of wood have shown dehydration and an apparent increase in the crystallinity of cellulose. A certain level of hemicelluloses degradation occurs, accompanied by the generation of some

  12. Local Ca-Mg distribution of Mg-rich pyrope-grossular garnets synthesized at different temperatures revealed by 29Si MAS NMR spectroscopy

    Microsoft Academic Search

    ANNE BOSENICK; CHARLES A. GEIGER; BRIAN L. PHILLIPS

    Pyrope-grossular solid solutions, (Mg,Ca) 3Al2Si3O12, of composition Py85Gr15 and Py75Gr25 were synthesized at 1000, 1200, and 1400 °C and 30 kbars in a piston-cylinder device. The synthetic garnets were characterized using optical, microprobe, and X-ray methods and their Ca-Mg distribu- tions were investigated using 29 Si MAS NMR spectroscopy. The syntheses produced 100% garnet except for those undertaken at 1000

  13. Investigation of cation environment and framework changes in silicotitanate exchange materials using solid-state 23Na, 29Si, and 133Cs MAS NMR

    NASA Astrophysics Data System (ADS)

    Cherry, Brian R.; Nyman, May; Alam, Todd M.

    2004-06-01

    Crystalline silicotitanate (CST), HNa 3Ti 4Si 2O 14·4H 2O and the Nb-substituted CST (Nb-CST), HNa 2Ti 3NbSi 2O 14·4H 2O, are highly selective Cs + sorbents, which makes them attractive materials for the selective removal of radioactive species from nuclear waste solutions. The structural basis for the improved Cs + selectivity in the niobium analogs was investigated through a series of solid-state magic angle spinning (MAS) NMR experiments. Changes in the local environment of the Na + and Cs + cations in both CST and Nb-CST materials as a function of weight percent cesium exchange were investigated using 23Na and 133Cs MAS NMR. Framework changes induced by Cs + loading and hydration state were investigated with 29Si MAS NMR. Multiple Cs + environments were observed in the CST and Nb-CST material. The relative population of these different Cs + environments varies with the extent of Cs + loading. Marked changes in the framework Si environment were noted with the initial incorporation of Cs +, however with increased Cs + loading the impact to the Si environment becomes less pronounced. The Cs + environment and Si framework structure were influenced by the Nb-substitution and were greatly affected by the amount of water present in the materials. The increased Cs + selectivity of the Nb-CST materials arises from both the chemistry and geometry of the tunnels and pores.

  14. Synthesis, characterization, and {sup 1}H and {sup 71}Ga MAS NMR spectroscopy of a novel Mg/Ga double layered hydroxide

    SciTech Connect

    Aramendia, M.A.; Borau, V.; Jimenez, C. [Cordoba Univ. (Spain)] [and others] [Cordoba Univ. (Spain); and others

    1997-06-01

    A new brucite-like layered Mg/Ga double hydroxide (LDH) of composition [Mg{sub 0.174}Ga{sub 0.256}(OH){sub 2}](CO{sub 3}){sub 0}.134 {center_dot}mH{sub 2}O was synthesized by coprecipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073K were characterized by X-ray diffraction, diffuse reflectance infrared spectroscopy, high-resolution solid-state nuclear magnetic resonance (MAS NMR), and thermogravimetric analysis. The surface properties of the solid (specific surface) and its basicity were also determined. The Mg /Ga LDH was found to be stable up to 523 K and to decompose into a mixture of periclase MgO and amorphous Ga{sub 2}O{sub 3} at 823 K. Its changes with temperature were monitored by using {sup 1}H and {sup 71}Ga MAS NMR; {sup 1}H MAS NMR spectra revealed the loss of interlayer OH groups supporting the brucite-like structure on calcination at 823 K.

  15. Sensitivity enhancement in natural-abundance solid-state 33S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions.

    PubMed

    Hansen, Michael Ryan; Brorson, Michael; Bildsøe, Henrik; Skibsted, Jørgen; Jakobsen, Hans J

    2008-02-01

    The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state (33)S (spin I=3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH(4))(2)WS(4) and (NH(4))(2)MoS(4). These materials all exhibit (33)S quadrupole coupling constants (C(Q)) in the range 0.1-1.0 MHz, with precise C(Q) values being determined from analysis of the PT enhanced (33)S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I=3/2 nuclei with similar C(Q) values (0.3-1.2 MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance (33)S MAS NMR, a time saving which is extremely welcome for this important low-gamma nucleus. PMID:18082436

  16. Sensitivity enhancement in natural-abundance solid-state 33S MAS NMR spectroscopy employing adiabatic inversion pulses to the satellite transitions

    NASA Astrophysics Data System (ADS)

    Hansen, Michael Ryan; Brorson, Michael; Bildsøe, Henrik; Skibsted, Jørgen; Jakobsen, Hans J.

    2008-02-01

    The WURST (wideband uniform rate smooth truncation) and hyperbolic secant (HS) pulse elements have each been employed as pairs of inversion pulses to induce population transfer (PT) between the four energy levels in natural abundance solid-state 33S (spin I = 3/2) MAS NMR, thereby leading to a significant gain in intensity for the central transition (CT). The pair of inversion pulses are applied to the satellite transitions for a series of inorganic sulfates, the sulfate ions in the two cementitious materials ettringite and thaumasite, and the two tetrathiometallates (NH 4) 2WS 4 and (NH 4) 2MoS 4. These materials all exhibit 33S quadrupole coupling constants ( CQ) in the range 0.1-1.0 MHz, with precise CQ values being determined from analysis of the PT enhanced 33S MAS NMR spectra. The enhancement factors for the WURST and HS elements are quite similar and are all in the range 1.74-2.25 for the studied samples, in excellent agreement with earlier reports on HS enhancement factors (1.6-2.4) observed for other spin I = 3/2 nuclei with similar CQ values (0.3-1.2 MHz). Thus, a time saving in instrument time by a factor up to five has been achieved in natural abundance 33S MAS NMR, a time saving which is extremely welcome for this important low-? nucleus.

  17. Evaluation of Lactate and Alanine as Metabolic Biomarkers of Prostate Cancer Using 1H HR-MAS Spectroscopy of Biopsy Tissues

    PubMed Central

    Tessem, May-Britt; Swanson, Mark G.; Keshari, Kayvan R.; Albers, Mark J.; Joun, David; Tabatabai, Z. Laura; Simko, Jeffry P.; Shinohara, Katsuto; Nelson, Sarah J.; Vigneron, Daniel B.; Gribbestad, Ingrid S.; Kurhanewicz, John

    2008-01-01

    The goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using 1H high-resolution magic angle spinning (HR-MAS) spectroscopy of snap-frozen transrectal ultrasound (TRUS)-guided prostate biopsy tissues. A long-echo-time rotor-synchronized Carr-Purcell-Meiboom-Gill (CPMG) sequence including an electronic reference to access in vivo concentrations (ERETIC) standard was used to determine the concentrations of lactate and alanine in 82 benign and 16 malignant biopsies (mean 26.5% ± 17.2% of core). Low concentrations of lactate (0.61 ± 0.28 mmol/kg) and alanine (0.14 ± 0.06 mmol/kg) were observed in benign prostate biopsies, and there was no significant difference between benign predominantly glandular (N = 54) and stromal (N = 28) biopsies between patients with (N = 38) and without (N = 44) a positive clinical biopsy. In biopsies containing prostate cancer there was a highly significant (P < 0.0001) increase in lactate (1.59 ± 0.61 mmol/kg) and alanine (0.26 ± 0.07 mmol/kg), and minimal overlap with lactate concentrations in benign biopsies. This study demonstrates for the first time very low concentrations of lactate and alanine in benign prostate biopsy tissues. The significant increase in the concentration of both lactate and alanine in biopsy tissue containing as little as 5% cancer could be exploited in hyperpolarized 13C spectroscopic imaging (SI) studies of prostate cancer patients. PMID:18727052

  18. (sup 6)Li and (sup 7)MAS NMR and In Situ X-Ray Diffraction Studies of Lithium Manganate Cathode Materials

    SciTech Connect

    Lee, Young Joo; Wang, Francis; Grey, Clare P.; Mukerjee, Sanjeev; McBreen, James

    1998-11-30

    {sup 6}Li MAS NMR spectra of lithium manganese oxides with differing manganese oxidation states (LiMn{sub 2}O{sub 4}, Li{sub 4}Mn{sub 5}O{sub 12}, Li{sub 2}Mn{sub 4}O{sub 9}, and Li{sub 2}Mn{sub 2}O{sub 4}) are presented. Improved understanding of the lithium NMR spectra of these model compounds is used to interpret the local structure of the Li{sub x}Mn{sub 2}O{sub 4} cathode materials following electrochemical Li{sup +} deintercalation to various charging levels. In situ x-ray diffraction patterns of the same material during charging are also reported for comparison. Evidence for two-phase behavior for x <0.4 (Li{sub x}Mn{sub 2}O{sub 4}) is seen by both NMR and diffraction.

  19. A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission.

    PubMed

    Pike, Kevin J; Kemp, Thomas F; Takahashi, Hiroki; Day, Robert; Howes, Andrew P; Kryukov, Eugeny V; MacDonald, James F; Collis, Alana E C; Bolton, David R; Wylde, Richard J; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M; Newton, Mark E; Dupree, Ray; Smith, Mark E

    2012-02-01

    A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE(13) fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz (1)H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE(16) second-harmonic mode of the gyrotron) for DNP at 14.1T (600 MHz (1)H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ~1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz (1)H and double channel HX mode for 284 MHz (1)H, with MAS sample temperatures ?85 K. Initial data at 6.7 T and ~1 W pulsed microwave power are presented with (13)C enhancements of 60 for a frozen urea solution ((1)H-(13)C CP), 16 for bacteriorhodopsin in purple membrane ((1)H-(13)C CP) and 22 for (15)N in a frozen glycine solution ((1)H-(15)N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design. PMID:22218011

  20. The guest ordering and dynamics in urea inclusion compounds studied by solid-state 1H and 13C MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Xiaorong; Müller, Klaus

    2011-12-01

    Urea inclusion compounds with different guest species were studied by 13C CP MAS and 1H MAS NMR spectroscopy. It is possible to arrange the asymmetric guest species in three different ways: head-head, head-tail and tail-tail. 13C CP MAS NMR studies indicate that the preference arrangement is determined by the interaction strength of the end functional groups. 13C relaxation experiments are used to study the dynamic properties of urea inclusion compounds. 13C relaxation studies on urea inclusion compounds with n-alkane or decanoic acid show that the 13C T1 and 13C T1? values exhibit the position dependence towards the center of the chain, indicating internal chain mobility. The analysis of variable-temperature 13C T1? experiments on urea inclusion compounds with hexadecane and pentadecane, for the first time, suggests that chain fluctuations and lateral motion of n-alkane guests may contribute to the 13C T1? relaxation.

  1. Obtaining aluminas from the thermal decomposition of their different precursors: An {sup 27}Al MAS NMR and X-ray powder diffraction studies

    SciTech Connect

    Chagas, L.H.; De Carvalho, G.S.G. [Universidade Federal de Juiz de Fora, Departamento de Química, Grupo de Físico-Química de Sólidos e Interfaces, 36036-330 Juiz de Fora, MG (Brazil); San Gil, R.A.S. [Universidade Federal do Rio de Janeiro, Instituto de Química, 21949-900 Rio de Janeiro, RJ (Brazil); Chiaro, S.S.X. [PETROBRAS-CENPES, 21941-915 Rio de Janeiro, RJ (Brazil); Leitão, A.A. [Universidade Federal de Juiz de Fora, Departamento de Química, Grupo de Físico-Química de Sólidos e Interfaces, 36036-330 Juiz de Fora, MG (Brazil); Diniz, R., E-mail: renata.diniz@ufjf.edu.br [Universidade Federal de Juiz de Fora, Departamento de Química, Grupo de Físico-Química de Sólidos e Interfaces, 36036-330 Juiz de Fora, MG (Brazil)

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized three precursors of alumina from different methods. • The calcination of the precursors generated several alumina polymorphs. • XRD and NMR were used for structural investigation of the polymorphs. • The synthesis route determines the structural and textural properties of the solids. - Abstract: A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. The characteristics of the four precursors were investigated by thermal, vibrational and X-ray powder diffraction (XRD) analysis. Additionally, the nuclear magnetic resonance, with magic angle spinning ({sup 27}Al MAS NMR), was used to verify the coordination of aluminum cations. Each precursor was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and {sup 27}Al MAS NMR. Due to interest in catalysis supports, special attention was given to the ?-Al{sub 2}O{sub 3} phase, which in addition to structural investigation was subjected to textural analysis. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties, which in turn can significantly influence the performance of a supported catalyst.

  2. Application of High-Resolution 1H MAS NMR Spectroscopy to the Analysis of Intact Bones from Mice Exposed to Gamma Radiation

    PubMed Central

    Zhang, Qibin; Hu, Jian Zhi; Rommereim, Donald N.; Murphy, Mark K.; Phipps, Richard P.; Huso, David L.; Dicello, John F.

    2009-01-01

    Herein we demonstrate that high-resolution magic angle spinning (MAS) 1H NMR can be used to profile the pathology of bone marrow rapidly and with minimal sample preparation. The spectral resolution obtained allows several metabolites to be analyzed quantitatively. The level of NMR-detectable metabolites in the epiphysis + metaphysis sections of mouse femur were significantly higher than that observed in the diaphysis of the same femur. The major metabolite damage to bone marrow resulting from either 3.0 Gy or 7.8 Gy of whole-body ? radiation 4 days after exposure were (1) decreased total choline content, (2) increased fatty acids in bone marrow, and (3) decreased creatine content. These results suggest that the membrane choline phospholipid metabolism (MCPM) pathway and the fatty acid biosynthesis pathway were altered as a result of radiation exposure. We also found that the metabolic damage induced by radiation in the epiphysis + metaphysis sections of mouse femur was higher than that of the diaphysis of the same femur. Traditional histopathology analysis was also carried out to correlate radiation damage with changes in metabolites. Importantly, the molecular information gleaned from high-resolution MAS 1H NMR complements the pathology data. PMID:19883229

  3. Direct quantification of M/G ratio from (13)C CP-MAS NMR spectra of alginate powders by multivariate curve resolution.

    PubMed

    Salomonsen, Tina; Jensen, Henrik Max; Larsen, Flemming Hofmann; Steuernagel, Stefan; Engelsen, Søren Balling

    2009-10-12

    Multivariate curve resolution (MCR) was applied to (13)C cross-polarisation (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of non-depolymerised alginate powders obtained from brown seaweed plus a pure mannuronate sample isolated from Pseudomonas fluorescens for estimation of the mannuronic acid/guluronic acid ratio (M/G ratio). An excellent MCR model with a correlation coefficient of r(2)=0.99 was established between the estimated M/G ratios and the M/G ratios obtained from the traditional (1)H solution state NMR method. The new method allows for successful determination of the M/G ratio independent of the calcium content (at least up to 2.4%, which was the upper limit in this study) with a root mean square error of prediction of 0.05. It is thus concluded that (13)C CP-MAS NMR in combination with multivariate curve resolution is a reliable, convenient (no sample preparation is required) and relatively rapid method for M/G ratio determinations of alginates and it may serve as a good alternative to the chemical techniques traditionally used. PMID:19619871

  4. Solid-state single and triple-quantum 93Nb MAS NMR studies of ferroelectric Pb(Mg1/3Nb2/3)O3 and a related pyrochlore.

    PubMed

    Cruz, L P; Rocha, J; Pedrosa de Jesus, J D; Savariault, J M; Galy, J

    1999-12-01

    Pb(Mg1/3Nb2/3)O3 (PMN), a well-known relaxor ferroelectric material, and a related pyrochlore phase have been studied by single- and triple-quantum 93Nb MAS NMR spectroscopy. The assignment of the NMR resonances has been attempted. PMID:10672939

  5. MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P 2O 5 and TiO 2 nucleants

    Microsoft Academic Search

    A. Ananthanarayanan; G. P. Kothiyal; L. Montagne; B. Revel

    2010-01-01

    Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li2O–4.0Al2O3–68.6SiO2–3.0K2O–2.6B2O3–0.5P2O5–0.9TiO2 was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by 29Si, 31P, 11B and 27Al MAS-NMR. XRD and 29Si NMR showed that lithium metasilicate (Li2SiO3) is the first phase to c form followed by cristobalite (SiO2) and lithium

  6. Satellite transitions acquired in real time by magic angle spinning (STARTMAS): ``Ultrafast'' high-resolution MAS NMR spectroscopy of spin I =3/2 nuclei

    NASA Astrophysics Data System (ADS)

    Thrippleton, Michael J.; Ball, Thomas J.; Wimperis, Stephen

    2008-01-01

    The satellite transitions acquired in real time by magic angle spinning (STARTMAS) NMR experiment combines a train of pulses with sample rotation at the magic angle to refocus the first- and second-order quadrupolar broadening of spin I =3/2 nuclei in a series of echoes, while allowing the isotropic chemical and quadrupolar shifts to evolve. The result is real-time isotropic NMR spectra at high spinning rates using conventional MAS equipment. In this paper we describe in detail how STARTMAS data can be acquired and processed with ease on commercial equipment. We also discuss the advantages and limitations of the approach and illustrate the discussion with numerical simulations and experimental data from four different powdered solids.

  7. H/D isotope effect of 1H MAS NMR spectra and 79Br NQR frequencies of piperidinium p-bromobenzoate and pyrrolidinium p-bromobenzoate

    NASA Astrophysics Data System (ADS)

    Honda, Hisashi; Kyo, Shinshin; Akaho, Yousuke; Takamizawa, Satoshi; Terao, Hiromitsu

    2010-04-01

    H/D isotope effects onto 79Br NQR frequencies of piperidinium p-bromobenzoate were studied by deuterium substitution of hydrogen atoms which form two kinds of N-H?O type hydrogen bonds, and the isotope shift of ca. 100 kHz were detected for a whole observed temperature range. In addition, 1H MAS NMR spectra measurements of piperidinium and pyrrolidinium p-bromobenzoate were carried out and little isotope changes of NMR line shape were detected. In order to reveal effects of molecular arrangements into the obtained isotope shift of NQR frequencies, single-crystal X-ray measurement of piperidinium p-bromobenzoate- d2 and density-functional-theory calculation were carried out. Our estimation showed the dihedral-angle change between piperidine and benzene ring contributes to isotope shift rather than those of N-H lengths by deuterium substitution.

  8. The structure of aluminosilicate glasses: High-resolution {sup 17}O and {sup 27}Al MAS and 3QMAS NMR study

    SciTech Connect

    Lee, S.K.; Stebbins, J.F.

    2000-05-04

    The authors investigate short-range order and local atomic configuration in charge-balanced aluminosilicate glasses as functions of composition, using {sup 17}O and {sup 27}Al MAS and triple-quantum magic angle spinning (3QMAS) NMR spectroscopy. Enhanced resolution in {sup 17}O and {sup 27}Al 3QMAS spectra, compared to MAS NMR, allows the quantification of the spectra and the extent of disorder using a semiempirical function relating 3QMAS efficiency to a quadrupolar coupling constant (C{sub q}). The variations with the Si/Al ratio (R) in peak positions and widths in the isotropic dimension of {sup 27}Al 3QMAS NMR spectra in both Na and Ca-aluminosilicate glasses can be ascribed to variations in the populations of Al sites with varying numbers of Al vs Si neighbors with composition. In the {sup 17}O 3QMAS spectra, variations of populations of three clearly resolved oxygen sites (Al-O-Al, Si-O-Al, and Si-O-Si) with R and cation field strength are consistent with the predictions given in previous results from {sup 29}Si MAS NMR. The quadrupolar coupling product (P{sub q}) of each oxygen site does not vary significantly with R, but it increases with cation field strength. On the other hand, isotropic chemical shifts ({delta}{sub iso}{sup CS}) increase with decreasing R and increasing cation field strength. These trends suggest that the configuration and framework connectivity in aluminosilicate glasses and melts are relatively constant with R but can be perturbed by high field strength cations with increased Al-O-Al and angular disorder, manifested by the increased variation of {delta}{sub iso}{sup CS} and the formation of non-bridging oxygen (NBO). The extent of disorder in aluminosilicate glasses is reflected in calculated configurational enthalpy, which increases with increasing cation field strength, consistent with the excess enthalpy of mixing data from calorimetry. The method and results given here provide improved prospects for the quantitative application of 3QMAS NMR and add to a more complete understanding of framework site connectivity in aluminosilicate glasses.

  9. ¹H-MAS-NMR chemical shifts in hydrogen-bonded complexes of chlorophenols (pentachlorophenol, 2,4,6-trichlorophenol, 2,6-dichlorophenol, 3,5-dichlorophenol, and p-chlorophenol) and amine, and H/D isotope effects on ¹H-MAS-NMR spectra.

    PubMed

    Honda, Hisashi

    2013-01-01

    Chemical shifts (CS) of the ¹H nucleus in N···H···O type hydrogen bonds (H-bond) were observed in some complexes between chlorophenols [pentachlorophenol (PCP), 2,4,6-tricholorophenol (TCP), 2,6-dichlorophenol (26DCP), 3,5-dichlorophenol (35DCP), and p-chlorophenol (pCP)] and nitrogen-base (N-Base) by solid-state high-resolution ¹H-NMR with the magic-angle-spinning (MAS) method. Employing N-Bases with a wide range of pKa values (0.65-10.75), ¹H-MAS-NMR CS values of bridging H atoms in H-bonds were obtained as a function of the N-Base's pKa. The result showed that the CS values were increased with increasing pKa values in a range of DpKa < 0 [DpKa = pKa(N-Base)-pKa(chlorophenols)] and decreased when DpKa > 2: The maximum CS values was recorded in the PCP (pKa = 5.26)-4-methylpyridine (6.03), TCP (6.59)-imidazole (6.99), 26DCP (7.02)-2-amino-4-methylpyridine (7.38), 35DCP (8.04)-4-dimethylaminopyridine (9.61), and pCP (9.47)-4-dimethylaminopyridine (9.61) complexes. The largest CS value of 18.6 ppm was recorded in TCP-imidazole crystals. In addition, H/D isotope effects on ¹H-MAS-NMR spectra were observed in PCP-2-amino-3-methylpyridine. Based on the results of CS simulation using a B3LYP/6-311+G** function, it can be explained that a little changes of the N-H length in H-bond contribute to the H/D isotope shift of the ¹H-MAS-NMR peaks. PMID:23609627

  10. Bonding Preferences of Non-Bridging Oxygens in Calcium Aluminosilicate Glass: Evidence from O-17 MAS and 3QMAS NMR on Calcium Aluminate Glass

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Lee, S.; Stebbins, J.

    2001-12-01

    Non-bridging oxygens (NBO's) play a significant role in the thermodynamic and transport properties in glasses and silicate melts. Previous oxygen-17 (O-17) triple quantum magic angle spinning (3QMAS NMR) data have shown the presence of NBO's in several calcium aluminosilicate (CAS) glasses on the CaAl2O4-SiO2 join (Stebbins and Xu 1997). The observed chemical shifts of these glasses are similar to those for the NBO in calcium silicate glasses (Stebbins et al. 1997 and Stebbins et al 1999); however, a recent O-17 MAS NMR study of crystalline CaAl2O4 showed that the NBO peak in an associated impurity phase is shifted to a higher frequency by 30 to 40 ppm from that of CAS and Ca-silicate glasses (Stebbins et al. in press). This finding suggests that Si is the preferred network cation for NBO's in aluminosilicate glasses and melts at the glass transition temperature. The preference for Si over that of Al as the network cation host for NBO's has also been suggested by Raman and other spectroscopic techniques (Mysen 1988). To investigate this apparent preference for Si-NBO, O-17 3QMAS and MAS experiments were conducted to examine the location of the NBO peak in the spectra of a calcium aluminate glass. Since the CaAl2O4 glass is difficult to make by conventional cooling methods, the binary eutectic composition (63CaO-37Al2O3) was chosen. The resulting O-17 MAS spectrum shows an intense, relatively narrow peak centered at 72 ppm, which nearly coincides with the peak location and width of the Al-O-Al peak in the crystalline Ca-aluminates (Stebbins et al. in press.) (70 ppm). There is a broader, less intense peak centered at 155 ppm that is assigned to the Al-NBO peak. This peak is in approximately the same location as that for a Ca-aluminate phase reported by Stebbins et al. (in press) (137 ppm). In addition, our 3QMAS data show that the peak maximum of the NBO in the Ca-aluminate (-85 and 150 ppm in isotropic and MAS dimensions, respectively) differs significantly from that of the calcium aluminosilicates and Ca-silicates of Stebbins et al. (1997 and 1999) (approximately -61 and 95 ppm in isotropic and MAS dimensions, respectively). Our data, when combined with previous data on CAS and CS glasses, strongly suggests that most of the NBO's in calcium aluminosilicate glasses are bonded to Si, not Al.

  11. A Raman and MAS NMR study of mixed alkali Na–K and Na–Li aluminoborosilicate glasses

    Microsoft Academic Search

    N. Ollier; T. Charpentier; B. Boizot; G. Wallez; D. Ghaleb

    2004-01-01

    Structural studies of two types of aluminoborosilicate glasses (Na\\/K and Na\\/Li) using Raman and NMR spectroscopy are presented. Both types of glasses display a mixed alkali effect (MAE) according to electrical conductivity and Tg measurements. Concerning the glass structure and more particularly the silicate network, our results show that the MAE slightly affects the glass polymerization degree, which displays a

  12. Observation of 1H-13C and 1H-1H proximities in a paramagnetic solid by NMR at high magnetic field under ultra-fast MAS.

    PubMed

    Li, Shenhui; Trébosc, Julien; Lafon, Olivier; Zhou, Lei; Shen, Ming; Pourpoint, Frédérique; Amoureux, Jean-Paul; Deng, Feng

    2015-02-01

    The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of (1)H and (13)C signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) (1)H-(13)C correlations with (1)H detection and (ii) (1)H-(1)H double-quantum?single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of l-alanine at high magnetic field (18.8 T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5 kHz. Compared to (13)C detection, we show that (1)H detection leads to a 3-fold enhancement in sensitivity for (1)H-(13)C 2D correlation experiments. By combining (1)H-(13)C and (1)H-(1)H 2D correlation experiments with the analysis of (13)C longitudinal relaxation times, we have been able to assign the (1)H and (13)C signals of each l-alanine ligand. PMID:25557861

  13. The chemical state of Sn in Sn-montmorillonite; A multinuclear MAS NMR and 119Sn Mössbauer spectroscopic study

    Microsoft Academic Search

    I. Hannus; I. Pálinkó; K. Lázár; J. B. Nagy; I. Kiricsi

    1995-01-01

    The incorporation of Sn was attempted in-between the layers of Na-montmorillonite through the hydrolysis of (NH4)2SnCl6 in an aqueous environment under reflux. Intercalation was successful and the resulting structure was characterized by X-ray fluorescence (XRF) spectroscopy, X-ray diffractometry (XRD), surface area (BET) and thermogravimetric measurements, infrared (IR), 119Sn Mössbauer and multinuclear (27Al, 29Si and 119Sn) magic angle spinning (MAS) spectroscopies.

  14. Correlations between 11B NMR parameters and structural characters in borate and borosilicate minerals investigated by high-resolution MAS NMR and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Zhou, Bing; Sun, Zhaohua; Yao, Yefeng; Pan, Yuanming

    2012-05-01

    Borates consisting of diverse fundamental building blocks (FBB) formed from complex polymerization of planar triangular [B?3] groups and tetrahedral [B?4] groups, where ? = O and OH, provide an excellent opportunity for investigation of correlations between the NMR parameters and local structures. However, previous studies suggested that the 11B NMR parameters in borates are insensitive to local structural environments other than the B coordination number, in contrast to those documented for 29Si, 23Na and 27Al in silicates, and no correlation between 11B chemical shifts and the sum of bond valences has been established for borate minerals with hydroxyl groups or molecular water in the structures. In this study, high-resolution NMR spectra have been acquired at the ultra high field of 21 T as well as at 14 T for selected borate and borosilicate minerals, and have been used to extract high-precision NMR parameters by using combined ab initio theoretical calculations and spectral simulations. These new NMR parameters reveal subtle correlations with various structural characters, especially the effects of the 11B chemical shifts from the bridging oxygen atom(s), site symmetry, symmetry of FBB, the sum of bond valences, as well as the next-nearest-neighbor cations and hydrogen bonding. Also, these results provide new insights into the shielding mechanism for 11B in borate and borosilicate minerals. In particular, this study demonstrates that the small variation in 11B chemical shifts can still be used to probe the local structural environments and that the established correlations can be used to investigate the structural details in borates and amorphous materials.

  15. Complete protocol for slow-spinning high-resolution magic-angle spinning NMR analysis of fragile tissues.

    PubMed

    André, Marion; Dumez, Jean-Nicolas; Rezig, Lamya; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2014-11-01

    High-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) is an essential tool to characterize a variety of semisolid systems, including biological tissues, with virtually no sample preparation. The "non-destructive" nature of NMR is typically compromised, however, by the extreme centrifugal forces experienced under conventional HR-MAS frequencies of several kilohertz. These features limit the usefulness of current HR-MAS approaches for fragile samples. Here, we introduce a full protocol for acquiring high-quality HR-MAS NMR spectra of biological tissues at low spinning rates (down to a few hundred hertz). The protocol first consists of a carefully designed sample preparation, which yields spectra without significant spinning sidebands at low spinning frequency for several types of sample holders, including the standard disposable inserts classically used in HR-MAS NMR-based metabolomics. Suppression of broad spectral features is then achieved using a modified version of the recently introduced PROJECT experiment with added water suppression and rotor synchronization, which deposits limited power in the sample and which can be suitably rotor-synchronized at low spinning rates. The performance of the slow HR-MAS NMR procedure is demonstrated on conventional (liver tissue) and very delicate (fish eggs) samples, for which the slow-spinning conditions are shown to preserve the structural integrity and to minimize intercompartmental leaks of metabolites. Taken together, these results expand the applicability and reliability of HR-MAS NMR spectroscopy. These results have been obtained at 400 and 600 MHz and suggest that high-quality slow HR-MAS spectra can be expected at higher magnetic fields using the described protocol. PMID:25286333

  16. MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass–ceramics having different Li 2O\\/Al 2O 3 ratio

    Microsoft Academic Search

    A. Ananthanarayanan; G. P. Kothiyal; L. Montagne; B. Revel

    2010-01-01

    Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi2O–71.7SiO2–(17.7?x)Al2O3–4.9K2O–3.2B2O3–2.5P2O5 (5.1?x?12.6) upon heat treatment were studied. 29Si, 27Al, 31P and 11B MAS-NMR were employed for structural characterization of both LAS glasses and glass–ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO3 and

  17. Asymmetric simultaneous phase-inversion cross-polarization in solid-state MAS NMR: Relaxing selective polarization transfer condition between two dilute spins

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengfeng; Fu, Riqiang; Li, Jianping; Yang, Jun

    2014-05-01

    Double cross polarization (DCP) has been widely used for heteronuclear polarization transfer between 13C and 15N in solid-state magic-angle spinning (MAS) NMR. However, DCP is such sensitive to experimental settings that small variations or deviations in RF fields would deteriorate its efficiency. Here, we report on asymmetric simultaneous phase-inversion cross polarization (referred as aSPICP) for selective polarization transfer between low-? 13C and 15N spins. We have demonstrated through simulations and experiments using biological solids that the asymmetric duration in the simultaneous phase-inversion cross polarization scheme leads to efficient polarization transfer between 13C and 15N even with large chemical shift anisotropies in the presence of B1 field variations or mismatch of the Hartmann-Hahn conditions. This could be very useful in the aspect of long-duration experiments for membrane protein studies at high fields.

  18. Study of superionic phase transition of (NH4)4LiH3(SO4)4 by 1H MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2013-04-01

    The temperature dependences of the line width, chemical shift, and spin-lattice relaxation time in the rotating frame, T1?, of the ammonium protons and hydrogen-bond protons in (NH4)4LiH3(SO4)4 are investigated by 1H MAS NMR. The change in the chemical shift for hydrogen-bond protons near the superionic phase transition TS (=405 K) indicates both H-bond breaking and new H-bond formation. Further, 1H T1? for the hydrogen-bond protons changes significantly near TS, and these protons play a more prominent role than the ammonium protons. Between TC (=232 K) and TS, molecular motions of the ammonium and hydrogen-bond protons occurred. The hydrogen-bond protons significantly influence the superionic phase transition of (NH4)4LiH3(SO4)4.

  19. 13C CP MAS NMR and GIAO-CHF/DFT calculations of flavonoids: Morin, kaempferol, tricin, genistein, formononetin and 3,7-dihydroxyflavone

    NASA Astrophysics Data System (ADS)

    Zieli?ska, Agnieszka; Paradowska, Katarzyna; Jakowski, Jacek; Wawer, Iwona

    2008-02-01

    13C CP MAS NMR spectra of the flavonoids: morin, kaempferol, 3,7-dihydroxyflavone, tricin and isoflavones: genistein and formononetin were recorded to characterize solid-state conformations. Intramolecular hydrogen bonds forming five-, six- and seven-membered rings are present in the two morin molecules in the crystals - their 13C resonances have been assigned with the aid of the calculated shielding constants. Linear relationships between the calculated shielding constants ?DFT (ppm) and chemical shifts ( ?CPMAS, ppm) were obtained for all studied compounds. Higher correlation coefficients suggest that the conformation with "clockwise" orientation of both OH groups is more probable in the solid 3,7-dihydroxyflavone, whereas in the solid formononetin the OH and OCH 3 substituents are directed "anticlockwise". The barrier to the rotation of phenyl ring B decreases in the order: morin (2'-OH, 3-OH) > kaempferol (3-OH) > tricin.

  20. Studies using {sup 27}Al MAS NMR of AF{sub m} and AF{sub t} phases and the formation of Friedel's salt

    SciTech Connect

    Jones, M.R.; Macphee, D.E.; Chudek, J.A.; Hunter, G.; Lannegrand, R.; Talero, R.; Scrimgeour, S.N

    2003-02-01

    This paper describes the application of the magic angle spinning (MAS) NMR spectroscopy to study the chemical environment of {sup 27}Al-bearing phases in Portland cement-based concrete. A specific methodology is described that allows reliable spectra to be determined for combinations of different types of cements and fillers (in this case, Portland cement, fly ash, slag, silica fume, metakaolin and limestone filler). As well as the study of 'molecular structure' of cement matrix, the paper reviews the mechanism of Friedel's salt formation in cement systems. Mechanisms based on ion exchange of chloride for hydroxide in hydroxy-AF{sub m} and on chloride absorption on formation are discussed. Finally, the nature of the chloride/hydrate binding phenomena are described to provide a reasonable robust and fundamental picture of the role different cements can play in the provision of overall concrete durability to chloride ingress from a chemical perspective.

  1. Structural elucidation of b-(Y,Sc){sub 2}Si{sub 2}O{sub 7} : combined use of {sub 89}Y MAS NMR and powder diffraction.

    SciTech Connect

    Allix, M.; Alba, M. D.; Florian, P.; Fernandez-Carrion, A. J.; Suchomel, M. R.; Escudero, A.; Suard, E.; Becerro, A. I. (X-Ray Science Division); (CNRS); (Univ. d'Orleans); (Inst de Ciencia de Materiales de Sevilla); (Inst. Laue-Langevin)

    2011-08-01

    Although the structures of pure Sc{sub 2}Si{sub 2}O{sub 7} and {beta}-Y{sub 2}Si{sub 2}O{sub 7} have been described in the literature using the C2/m space group, {sup 29}Si magic angle spinning (MAS) NMR measurements of the intermediate members of the Sc{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} system indicate a lowering of the symmetry to the C2 space group. Indeed, these compositions exhibit a unique Si crystallographic site and an Si-O-Si angle lower than 180{sup o}, incompatible with the C2/m space group. C2 is the only possible alternative. Space group Cm can be discarded with regard to its two different Si sites per unit cell. Moreover, {sup 89}Y MAS NMR data have revealed the existence of two different Y sites in the structure of the intermediate members of the Sc{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} system, confirming the lowering of the symmetry to the C2 space group. The viability of the C2 model has therefore been tested and confirmed by refinement of synchrotron and neutron powder diffraction data for the different members of the system. The structural evolutions across the Sc{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} system are discussed.

  2. Composite-180° pulse-based symmetry sequences to recouple proton chemical shift anisotropy tensors under ultrafast MAS solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Malon, Michal; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-01-01

    There is considerable interest in the measurement of proton (1H) chemical shift anisotropy (CSA) tensors to obtain deeper insights into H-bonding interactions which find numerous applications in chemical and biological systems. However, the presence of strong 1H/1H dipolar interaction makes it difficult to determine small size 1H CSAs from the homogeneously broadened NMR spectra. Previously reported pulse sequences for 1H CSA recoupling are prone to the effects of radio frequency field (B1) inhomogeneity. In the present work we have carried out a systematic study using both numerical and experimental approaches to evaluate ?-encoded radio frequency (RF) pulse sequences based on R-symmetries that recouple 1H CSA in the indirect dimension of a 2D 1H/1H anisotropic/isotropic chemical shift correlation experiment under ultrafast magic angle spinning (MAS) frequencies. The spectral resolution and sensitivity can be significantly improved in both frequency dimensions of the 2D 1H/1H correlation spectrum without decoupling 1H/1H dipolar couplings but by using ultrafast MAS rates up to 70 kHz. We successfully demonstrate that with a reasonable RF field requirement (<200 kHz) a set of symmetry-based recoupling sequences, with a series of phase-alternating 270°0-90°180 composite-180° pulses, are more robust in combating B1 inhomogeneity effects. In addition, our results show that the new pulse sequences render remarkable 1H CSA recoupling efficiency and undistorted CSA lineshapes. Experimental results on citric acid and malonic acid comparing the efficiencies of these newly developed pulse sequences with that of previously reported CSA recoupling pulse sequences are also reported under ultrafast MAS conditions.

  3. Boron isotopes as pH proxy: A new look at boron speciation in deep-sea corals using 11B MAS NMR and EELS

    NASA Astrophysics Data System (ADS)

    Rollion-Bard, Claire; Blamart, Dominique; Trebosc, Julien; Tricot, Grégory; Mussi, Alexandre; Cuif, Jean-Pierre

    2011-02-01

    Dissolved boron in modern seawater occurs in the form of two species, trigonal boric acid B(OH) 3 and tetrahedral borate ion B(OH)4-. One of the key assumption in the use of boron isotopic compositions of carbonates as pH proxy is that only borate ions, B(OH)4-, are incorporated into the carbonate. Here, we investigate the speciation of boron in deep-sea coral microstructures ( Lophelia pertusa specimen) by using high field magic angle spinning nuclear magnetic resonance ( 11B MAS NMR) and electron energy-loss spectroscopy (EELS). We observe both boron coordination species, but in different proportions depending on the coral microstructure, i.e. centres of calcification versus fibres. These results suggest that careful sampling is necessary before performing boron isotopic measurements in deep-sea corals. By combining the proportions of B(OH) 3 and B(OH)4- determined by NMR and our previous ion microprobe boron isotope measurements, we propose a new equation for the relation between seawater pH and boron isotopic composition in deep-sea corals.

  4. Analysis of mercerization process based on the intensity change of deconvoluted resonances of (13)C CP/MAS NMR: Cellulose mercerized under cooling and non-cooling conditions.

    PubMed

    Miura, Kento; Nakano, Takato

    2015-08-01

    The area intensity change of C1, C4, and C6 in spectrum obtained by (13)C CP/MAS NMR and the mutual relationship between their changes were examined for cellulose samples treated with various concentrations of aqueous NaOH solutions under non-cooling and cooling conditions. The area intensity of C1-up and C6-down changed cooperatively with that of C4-down which corresponds to the crystallinity of samples: "-up" and "-down" are the up- and down- field component in a splitting peak of NMR spectrum, respectively. The intensity change of C1-up starts to decrease with decreasing in that of C4-down after that of C6-down is almost complete. These changes were more clearly observed for samples treated under cooling condition. It can be suggested that their characteristic change relates closely to the change in conformation of cellulose chains by induced decrystallization and the subsequent crystallization of cellulose II, and presumed that their changes at microscopic level relate to the macroscopic morphological changes such as contraction along the length of cellulose chains and recovery along the length. PMID:26042706

  5. Refinement of borate structures from 11B MAS NMR spectroscopy and density functional theory calculations of 11B electric field gradients.

    PubMed

    Hansen, Michael Ryan; Madsen, Georg K H; Jakobsen, Hans J; Skibsted, Jørgen

    2005-03-10

    The refinement of borate structures using DFT calculations combined with experimental (11)B quadrupole coupling parameters from solid-state NMR spectroscopy is presented. The (11)B electric field gradient (EFG) tensors, calculated using the WIEN2k software for trigonal and tetrahedral boron sites in a series of model compounds, exhibit a convincing linear correlation with the quadrupole coupling tensor elements, determined from (11)B MAS NMR spectra of the central or satellite transitions. The model compounds include Li(2)B(4)O(7), Mg(2)B(2)O(5), Mg(3)B(2)O(6), NH(4)B(C(6)H(5))(4), and colemanite (CaB(3)O(4)(OH)(3).H(2)O). The (11)B quadrupole moment, Q = 0.0409 +/- 0.0002 barn, derived from the linear correlation, is in excellent agreement with the accepted value for Q((11)B). This demonstrates that DFT (WIEN2k) calculations can provide precise (11)B quadrupole coupling parameters on an absolute scale. On the other hand, DFT calculations based on the reported crystal structures for datolite (CaBSiO(4)(OH)) and danburite (CaB(2)Si(2)O(8)) cannot reproduce the experimental (11)B quadrupole coupling parameters to the same high precision. However, optimization of these structures by minimization of the forces between the atoms (obtained by DFT) results in a significant improvement between the calculated and experimental (11)B quadrupole coupling parameters, which indicates that reliable refinements of the borate structures are obtained by this method. Finally, the DFT calculations also provide important structural information about the sign and orientation of the EFG tensor elements in the crystal frame, a kind of information that cannot be achieved from (11)B NMR experiments on powdered samples. PMID:16833533

  6. Proton-detected MAS NMR experiments based on dipolar transfers for backbone assignment of highly deuterated proteins

    NASA Astrophysics Data System (ADS)

    Chevelkov, Veniamin; Habenstein, Birgit; Loquet, Antoine; Giller, Karin; Becker, Stefan; Lange, Adam

    2014-05-01

    Proton-detected solid-state NMR was applied to a highly deuterated insoluble, non-crystalline biological assembly, the Salmonella typhimurium type iii secretion system (T3SS) needle. Spectra of very high resolution and sensitivity were obtained at a low protonation level of 10-20% at exchangeable amide positions. We developed efficient experimental protocols for resonance assignment tailored for this system and the employed experimental conditions. Using exclusively dipolar-based interspin magnetization transfers, we recorded two sets of 3D spectra allowing for an almost complete backbone resonance assignment of the needle subunit PrgI. The additional information provided by the well-resolved proton dimension revealed the presence of two sets of resonances in the N-terminal helix of PrgI, while in previous studies employing 13C detection only a single set of resonances was observed.

  7. High-temperature behavior of NH4H2PO4 studied by single-crystal and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Lee, Kwang-Sei

    2013-07-01

    To confirm a high-temperature behavior of NH4H2PO4, the temperature dependences of the line-width, resonance frequency, and spin-lattice relaxation times in the laboratory frame, T1, and in the rotating frame, T1?, were investigated using a Fourier transform NMR spectrometer. The hydrogen bonds both in O-H-O between two PO4 groups and in N-H-O between NH4 and PO4 were distinguished, and the T1 values of both types of hydrogen-bond proton and 31P ions were described by the Bloembergen-Purcell-Pound theory. In addition, the T1? values of both types of hydrogen-bond proton and of 31P ions exhibited strong temperature dependences at high temperature; the changes in T1? at high temperature were related to variations in the symmetry.

  8. Dipolar Assisted Assignment Protocol (DAAP) for MAS solid-state NMR of Rotationally Aligned Membrane Proteins in Phospholipid Bilayers

    PubMed Central

    Das, Bibhuti B.; Zhang, Hua; Opella, Stanley J.

    2014-01-01

    A method for making resonance assignments in magic angle spinning solid-state NMR spectra of membrane proteins that utilizes the range of hetero-nuclear dipolar coupling frequencies in combination with conventional chemical shift based assignment methods is demonstrated. The dipolar assisted assignment protocol (DAAP) takes advantage of the rotational alignment of the membrane proteins in liquid crystalline phospholipid bilayers. Improved resolution is obtained by combining the magnetically inequivalent heteronuclear dipolar frequencies with isotropic chemical shift frequencies. Spectra with both dipolar and chemical shift frequency axes assist with resonance assignments. DAAP can be readily extended to three- and four- dimensional experiments and to include both backbone and side chain sites in proteins. PMID:24698983

  9. MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P{sub 2}O{sub 5} and TiO{sub 2} nucleants

    SciTech Connect

    Ananthanarayanan, A. [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Universite Lille Nord de France - UMR CNRS 8181, USTL, 59655 Villeneuve d'Ascq (France); Kothiyal, G.P. [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Montagne, L., E-mail: lionel.montagne@univ-lille1.f [Universite Lille Nord de France - UMR CNRS 8181, USTL, 59655 Villeneuve d'Ascq (France); Revel, B. [Universite Lille Nord de France - UMR CNRS 8181, USTL, 59655 Villeneuve d'Ascq (France)

    2010-06-15

    Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li{sub 2}O-4.0Al{sub 2}O{sub 3}-68.6SiO{sub 2}-3.0K{sub 2}O-2.6B{sub 2}O{sub 3}-0.5P{sub 2}O{sub 5}-0.9TiO{sub 2} was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by {sup 29}Si, {sup 31}P, {sup 11}B and {sup 27}Al MAS-NMR. XRD and {sup 29}Si NMR showed that lithium metasilicate (Li{sub 2}SiO{sub 3}) is the first phase to c form followed by cristobalite (SiO{sub 2}) and lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}). {sup 29}Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 {sup o}C. Since crystalline Li{sub 3}PO{sub 4}, as observed by {sup 31}P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li{sub 3}PO{sub 4} does not act as a nucleating agent for lithium silicate phases. Moreover, {sup 31}P NMR indicates the formation of M-PO{sub 4} (M=B, Al or Ti) complexes. The presence of BO{sub 3} and BO{sub 4} structural units in all the glass/glass-ceramic samples is revealed through {sup 11}B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO{sub 3}) increases at the expense of tetrahedrally coordinated B (BO{sub 4}). The {sup 27}Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization. - Graphical abstract: {sup 11}B MAS-NMR spectra of LAS glass heat treated at different temperatures, showing the evolution of the residual glass matrix during the crystallization treatment. High-field (18.8 T) NMR enables us to record high resolution spectra, from which the glass network modifications could be related to the formation of intermediate lithium silicate crystalline phases.

  10. A MAS-NMR study of the location of (+)-totarol, a diterpenoid bioactive molecule, in phospholipid model membranes.

    PubMed

    Bernabeu, Angela; Shapiro, S; Villalaín, José

    2002-10-01

    (+)-Totarol, a diterpenoid isolated from Podocarpus spp., is a potent antioxidant and antibacterial agent. Although the mechanism of action of this hydrophobic molecule is poorly understood, recent work from our laboratories suggests that it could be due to membranotropic interactions. The location of (+)-totarol in membranes and its interaction with membrane components is therefore of considerable interest. High resolution magic angle spinning (MAS) natural abundance 13C nuclear magnetic resonance studies were undertaken to assess the location of (+)-totarol in model membranes composed of egg yolk phosphatidylcholine (EYL). 13C spin-lattice relaxation times (T(1)) of both the phospholipid and (+)-totarol molecules in the presence of Gd(3+) were measured to obtain information on molecular distances. Our results indicate that (+)-totarol is situated in the upper region of the membrane, with its hydroxyl group located in the vicinity of the C-3/4 carbon atoms of the phospholipid acyl chain, and nearly perpendicular with respect to the phospholipid acyl chain axis. Such a location of (+)-totarol in the membrane would be expected to compromise the functional integrity of the membrane and account, at least in part, for its antibacterial effects. PMID:12270671

  11. 31P MAS-NMR study of flux-grown rare-earth element orthophosphate (monazite/xenotime) solid solutions: Evidence of random cation distribution from paramagnetically shifted NMR resonances

    SciTech Connect

    Palke, A. C. [Stanford University] [Stanford University; Stebbins, J. F. [Stanford University] [Stanford University; Boatner, Lynn A [ORNL] [ORNL

    2013-01-01

    We present 31P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectra of flux-grown solid solutions of La1-xCexPO4 ( x between 0.027 and 0.32) having the monoclinic monazite structure, and of Y1-xMxPO4 (M = Vn+, Ce3+, Nd3+, x between 0.001 and 0.014) having the tetragonal zircon structure. Paramagnetically shifted NMR resonances are observed in all samples due to the presence of paramagnetic Vn+, Ce3+, and Nd3+ in the diamagnetic LaPO4 or YPO4. As a first-order observation, the number and relative intensity of these peaks is related to the symmetry and structure of the diamagnetic host phase. The presence of paramagnetic shifts allows for increased resolution between NMR resonances for distinct atomic species which leads to the observation of low intensity peaks related to PO4 species having more than one paramagnetic neighbor two or four atomic bonds away. Through careful analysis of peak areas and comparison with predictions for simple models, it was determined that solid solutions in the systems examined here are characterized by complete disorder (random distribution) of diamagnetic La3+ or Y3+ with the paramagnetic substitutional species Ce3+ and Nd3+. The increased resolution given by the paramagnetic interactions also leads to the observation of splitting of specific resonances in the 31P NMR spectra that may be caused by local, small-scale distortions from the substitution of ions having dissimilar ionic radii.

  12. (Na{sub 4}BH{sub 4}){sup 3+} guests inside aluminosilicate, gallosilicate and aluminogermanate sodalite host frameworks studied by {sup 1}H, {sup 11}B, and {sup 23}Na MAS NMR spectroscopy

    SciTech Connect

    Buhl, J.-Ch. [Institut fuer Mineralogie, Universitaet Hannover, Callinstrasse 3, 30167 Hannover (Germany); Murshed, M.M., E-mail: mmurshe@uni-goettingen.de [Department of Crystallography, Georg-August-University of Goettingen, Goldschmidtstrasse 1, 37077 Goettingen (Germany)

    2009-07-01

    We report tetrahydroborate aluminosilicate, gallosilicate and aluminogermanate sodalites studied by {sup 11}B, {sup 1}H and {sup 23}Na MAS NMR spectroscopy. The spectral parameters are consistent with the local environments of each investigated nucleus obtained from the crystal structures. The {sup 11}B MAS NMR spectra exhibit a sharp narrow line at about -49.0 ppm, which is assigned to BH{sub 4}{sup -} enclathrated into the sodalite framework matrix. The lineshape of the signal shows no quadrupolar interactions due to discreteness and high symmetry of the BH{sub 4}{sup -} unit as well as possible fast dynamic site exchange of hydrogen atoms. The {sup 23}Na MAS NMR signals also show a narrow Gaussian lineshape, which clearly indicates a single type of sodium coordination, and a centrosymmetrical charge distribution around the sodium atom. The {sup 1}H MAS NMR spectra can clearly distinguish between hydrogen in BH{sub 4}{sup -} anions (-0.6 ppm), H{sub 3}O{sub 2}{sup -} anions (1.2 ppm) and H{sub 2}O molecules (5.0 ppm). The structural properties of BH{sub 4}{sup -} intercalation into sodalite framework matrix help connect the microporous materials to hydride-containing A, X and Y type zeolites.

  13. 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

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after OM application, which was consistent with other studies (Wang et al., 2001). The content of the WSS increased after the OM application indicating that the increase of labile organic carbon. The C/H mole ratio of the HS could reflect the degree of condensation (Dou et al., 1995). Effects on HA chemical and optical properties. The chemical and optical properties of HA were listed. The C/H ratios decreased after OM application, from 0.830 (CKbr) to 0.754 (O2). While ?lgK increased, from 0.623 (CKbr) to 0.658 (O2). The HA structure tended to become simpler. The C/H ratio of the HA decreased after OM application. This indicates that OM application decreased the degree of condensation. The ?lgK values can be used as the index of HA molecule complexity in the soil. If ?lgK increased, the molecular structure becomes simpler. After OM application, ?lgK increased indicating that the molecular structure became simpler. Effects on HA thermal properties. It could be seen that HA had exothermic peaks in moderate and high temperature regions. After OM application, heat (H2) of exothermic peak increased in moderate temperature region, while heat (H3) of exothermic peak decreased in high temperature region. The the heat ratio of exothermic peaks in high temperature region to moderate (H3/H2) decreased. From CKbr to O2, H3/H2 decreased from 4.31 to0.86. The HA had moderate and high temperature exothermic peaks. The heat of exothermic peaks in the moderate temperature region might show that aliphatic compounds decomposed and peripheral functional groups decarboxylated. The heat of the exothermic peaks in the high temperature region might show that the HA was oxidized completely and inter-aromatic structures in the molecule decomposed. The heat ratio of the high to moderate temperature exothermic regions (H3/H2) decreased significantly after PM application, indicating that the proportion of aromatic structure decreased and the HA molecular structure simplified. Effects on CP-MAS-13C-NMR spectrum of HA. The CP-MAS- 13C-NMR spectra of the HA were quite similar to each other

  14. Quantitative MAS NMR characterization of the LiMn(1/2)Ni(1/2)O(2) electrode/electrolyte interphase.

    PubMed

    Cuisinier, M; Martin, J F; Moreau, P; Epicier, T; Kanno, R; Guyomard, D; Dupré, N

    2012-04-01

    The conditions in which degradation processes at the positive electrode/electrolyte interface occur are still incompletely understood and traditional surface analytical techniques struggle to characterize and depict accurately interfacial films. In the present work, information on the growth and evolution of the interphases upon storage and cycling as well as their electrochemical consequences are gathered in the case of LiNi(1/2)Mn(1/2)O(2) with commonly used LiPF(6) (1M in EC/DMC) electrolyte. The use of (7)Li, (19)F and (31)P MAS NMR, made quantitative through the implementation of empirical calibration, is combined with transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) to probe the elements involved in surface species and to unravel the inhomogenous architecture of the interphase. At room temperature, contact with the electrolyte leads to a covering of the oxide surface first by LiF and lithiated organic species are found on the outer part of the interphase. At 55°C, not only the interphase proceeds in further covering of the surface but also thickens resulting in an increase of 240% of lithiated species and the presence of -POF(2) fluorophosphates. The composition gradient within the interphase depth is also strongly affected by the temperature. In agreement with the electrochemical performance, quantitative NMR surface analyses show that the use of LiBOB-modified electrolyte results in a Li-enriched interphase, intrinsically less resistive than the standard LiPF(6)-based interphase, comprised of a mixture of resistive LiF with non lithiated species. PMID:21978533

  15. I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics

    SciTech Connect

    Ziegeweid, M.A.

    1995-11-29

    NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of {sup 14}N via the quadrupolar interaction. Because {sup 14}N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe {sup 14}N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional {sup 13}C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}({eta}{sup 1}-C{sub 5}H{sub 5}){sub 2}, Zr({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}({eta}{sup 1}-C{sub 5}H{sub 5}) and Sn({eta}{sup 1}-C{sub 5}H{sub 5}){sub 4}. This work was undertaken in the hope of gaining insight into the intramolecuhrr dynamics, specifically which fluxional processes exist in the solid state, by what mechanism rearrangements are occurring, and the activation energies by which these processes are governed.

  16. Identifying Inter-Residue Resonances in Crowded 2D 13C-13C Chemical Shift Correlation Spectra of Membrane Proteins by Solid-State MAS NMR Difference Spectroscopy

    PubMed Central

    Miao, Yimin; Cross, Timothy A.; Fu, Riqiang

    2013-01-01

    The feasibility of using difference spectroscopy, i.e. subtraction of two correlation spectra at different mixing times, for substantially enhanced resolution in crowded two-dimensional 13C-13C chemical shift correlation spectra is presented. With the analyses of 13C-13C spin diffusion in simple spin systems, difference spectroscopy is proposed to partially separate the spin diffusion resonances of relatively short intra-residue distances from the longer inter-residue distances, leading to a better identification of the inter-residue resonances. Here solid-state magic-angle-spinning (MAS) NMR spectra of the full length M2 protein embedded in synthetic lipid bilayers have been used to illustrate the resolution enhancement in the difference spectra. The integral membrane M2 protein of Influenza A virus assembles as a tetrameric bundle to form a protonconducting channel that is activated by low pH and is essential for the viral lifecycle. Based on known amino acid resonance assignments from amino acid specific labeled samples of truncated M2 sequences or from time-consuming 3D experiments of uniformly labeled samples, some inter-residue resonances of the full length M2 protein can be identified in the difference spectra of uniformly 13C labeled protein that are consistent with the high resolution structure of the M2 (22–62) protein (Sharma et al. 2010). PMID:23708936

  17. Effects of solvent concentration and composition on protein dynamics: (13)C MAS NMR studies of elastin in glycerol-water mixtures.

    PubMed

    Demuth, Dominik; Haase, Nils; Malzacher, Daniel; Vogel, Michael

    2015-08-01

    We use (13)C CP MAS NMR to investigate the dependence of elastin dynamics on the concentration and composition of the solvent at various temperatures. For elastin in pure glycerol, line-shape analysis shows that larger-scale fluctuations of the protein backbone require a minimum glycerol concentration of ~0.6g/g at ambient temperature, while smaller-scale fluctuations are activated at lower solvation levels of ~0.2g/g. Immersing elastin in various glycerol-water mixtures, we observe at room temperature that the protein mobility is higher for lower glycerol fractions in the solvent and, thus, lower solvent viscosity. When decreasing the temperature, the elastin spectra approach the line shape for the rigid protein at 245K for all studied samples, indicating that the protein ceases to be mobile on the experimental time scale of ~10(-5)s. Our findings yield evidence for a strong coupling between elastin fluctuations and solvent dynamics and, hence, such interaction is not restricted to the case of protein-water mixtures. Spectral resolution of different carbon species reveals that the protein-solvent couplings can, however, be different for side chain and backbone units. We discuss these results against the background of the slaving model for protein dynamics. PMID:25917596

  18. Piperazinium dihydrogen phosphate, C 4H 12N 2(H 2PO 4) 2: Synthesis, 31P CP/MAS NMR, structural and thermal investigations

    NASA Astrophysics Data System (ADS)

    Jensen, Torben R.; Jørgensen, Jens-Erik; Hazell, Rita G.; Jakobsen, Hans J.; Chevallier, Marie-Agnes; Jørgensen, Lene; Wiedermann, Aleksandra

    2007-01-01

    A new piperazinium dihydrogen orthophosphate, C 4H 12N 2(H 2PO 4) 2 was discovered and characterized by combining information from X-ray diffraction, 31P CP/MAS NMR and thermal analysis (TG/DTA). The compound C 4H 12N 2(HPO 4)·H 2O, was also studied in order to compare these two similar materials. The hydrothermal stability is investigated for the system: 1.0 C 4H 10N 2: n H 3PO 4: 55-60 H 2O, 0.5 < n < 3. The reaction mixtures with pH in the range 1.6-8.4 were placed at a fixed temperature in the range 20-180 °C for ca. 5 days. C 4H 12N 2(H 2PO 4) 2 was obtained when n > ca. 2. A crystal of piperazinium dihydrogen phosphate, C 4H 12N 2(H 2PO 4) 2 was structurally investigated using X-ray diffraction: triclinic, space group P1¯, a = 7.023(2), b = 7.750(3), c = 12.203(4) Å, ? = 84.668(7), ? = 81.532(7) and ? = 63.174(6)°, V = 586.0(4) Å 3 and Z = 2. The reactivity of C 4H 12N 2(H 2PO 4) 2 was investigated by systematic solvothermal syntheses.

  19. Structural investigations of silicate-phosphate glasses containing MoO3 by FTIR, Raman and 31P MAS NMR spectroscopies

    NASA Astrophysics Data System (ADS)

    Szumera, Magdalena

    2014-09-01

    Molybdenum is a transition metal (refers to the “d” block of the periodic table) whose atom has an incomplete d sub-shell. It is known that in silicate glasses molybdenum may exist under four oxidation states: Mo6+, Mo5+, Mo4+ and Mo3+, simultaneously molybdenum cations, depending on their content in the glass network, may either be a glass forming component, or act as a modifier. The contemporary literature data show studies conducted mostly on the structure of silicate, phosphate, borate and borosilicate glasses containing molybdenum ions, but not silicate-phosphate glasses. Therefore, the author has undertaken detailed studies using FTIR, Raman and 31P MAS NMR techniques in order to examine the effect of MoO3 addition into the structure of silicate-phosphate glasses from SiO2sbnd P2O5sbnd K2Osbnd CaOsbnd MgO system. On the basis of obtained results it was concluded that molybdenum ions in the analysed glasses act as a modifier, which follows from the gradual breakage of oxygen bridges, i.e. Psbnd Osbnd P, Sisbnd Osbnd Si, and Sisbnd Osbnd P, and the following formation of connections such as Mo[MoO4]sbnd Osbnd Si and/or Mo[MoO4]sbnd Osbnd P. In summary, it is concluded that the increase of MoO3 content (up to 4.4 mol.%) in the structure of glasses of SiO2sbnd P2O5sbnd K2Osbnd MgOsbnd CaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation.

  20. Transferred hyperfine interaction and structure in LiMn2O4 and Li2MnO3 coexisting phases:mA XRD and 7Li NMR-MAS study

    Microsoft Academic Search

    Piercarlo Mustarelli; Vincenzo Massarotti; Marcella Bini; Doretta Capsoni

    1997-01-01

    X-ray diffraction (XRD) and 7MAS measurements have been performed on LiMn2O4 (lithium cationic fraction, x=0.333), Li2MnO3 (x=0.667), and the intermediate composition with x=0.40. The use of magic angle spinning produces complex manifolds of the spinning sidebands. The predominant interaction affecting the NMR spectrum is the transferred hyperfine coupling (TFHI) between the Mn ions and the Li spins. TFHI parameters are

  1. Deactivation of HDT catalysts by formation of silica gels from silicone oil. Characterization of spent catalysts from HDT of coker naphtha using [sup 29]Si and [sup 13]C CP/MAS NMR

    SciTech Connect

    Kellberg, L.; Jakobsen, H.J. (Univ. of Aarhus (Germany)); Zeuthen, P. (Haldor Topsoe Research Labs., Lyngby (Germany))

    1993-09-01

    Catalysts used for hydrotreating of coker naphtha are found to deactivate very quickly because of deposition of Si-containing species on their surface. These species originate from the silicone oil (polydimethylsiloxane) added to the coker unit in order to suppress foaming during the coking process. Six samples of a spent catalyst from a HDT reactor have been analyzed by [sup 29]Si MAS, [sup 29]Si CP/MAS, and [sup 13]C CP/MAS NMR spectroscopy. From these studies it is concluded that the silicone oil in the naphtha feed is transformed (oxidized) to modified silica gels, i.e., silica with a partly methylated surface, under the operating conditions of the catalyst. Physi- or chemisorption of the silica gels on the catalyst explains the fast irreversible loss of activity during HDT of coker naphtha. 23 refs., 3 figs., 2 tabs.

  2. In Vivo Detection of the Cyclic Osmoregulated Periplasmic Glucan of Ralstonia solanacearum by High-Resolution Magic Angle Spinning NMR

    NASA Astrophysics Data System (ADS)

    Wieruszeski, J.-M.; Bohin, A.; Bohin, J.-P.; Lippens, G.

    2001-07-01

    We investigate the mobility of the osmoregulated periplasmic glucans of Ralstonia solanacearum in the bacterial periplasm through the use of high-resolution (HR) NMR spectroscopy under static and magic angle spinning (MAS) conditions. Because the nature of periplasm is far from an isotropic aqueous solution, the molecules could be freely diffusing or rather associated to a periplasmic protein, a membrane protein, a lipid, or the peptidoglycan. HR MAS NMR spectroscopy leads to more reproducible results and allows the in vivo detection and characterization of the complex molecule.

  3. High-Resolution 1H NMR Spectroscopy of Fish Muscle, Eggs and Small Whole Fish via Hadamard-Encoded Intermolecular Multiple-Quantum Coherence

    PubMed Central

    Cai, Honghao; Chen, Yushan; Cui, Xiaohong; Cai, Shuhui; Chen, Zhong

    2014-01-01

    Background and Purpose Nuclear magnetic resonance (NMR) spectroscopy has become an important technique for tissue studies. Since tissues are in semisolid-state, their high-resolution (HR) spectra cannot be obtained by conventional NMR spectroscopy. Because of this restriction, extraction and high-resolution magic angle spinning (HR MAS) are widely applied for HR NMR spectra of tissues. However, both of the methods are subject to limitations. In this study, the feasibility of HR 1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC) technique is explored using fish muscle, fish eggs, and a whole fish as examples. Materials and Methods Intact salmon muscle tissues, intact eggs from shishamo smelt and a whole fish (Siamese algae eater) are studied by using conventional 1D one-pulse sequence, Hadamard-encoded iMQC sequence, and HR MAS. Results When we use the conventional 1D one-pulse sequence, hardly any useful spectral information can be obtained due to the severe field inhomogeneity. By contrast, HR NMR spectra can be obtained in a short period of time by using the Hadamard-encoded iMQC method without shimming. Most signals from fatty acids and small metabolites can be observed. Compared to HR MAS, the iMQC method is non-invasive, but the resolution and the sensitivity of resulting spectra are not as high as those of HR MAS spectra. Conclusion Due to the immunity to field inhomogeneity, the iMQC technique can be a proper supplement to HR MAS, and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning. The acquisition time of the proposed method is greatly reduced by introduction of the Hadamard-encoded technique, in comparison with that of conventional iMQC method. PMID:24466083

  4. MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li{sub 2}O/Al{sub 2}O{sub 3} ratio

    SciTech Connect

    Ananthanarayanan, A. [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kothiyal, G.P., E-mail: gpkoth@barc.gov.i [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Montagne, L.; Revel, B. [UCCS - Unite de Catalyse et Chimie du Solide - UMR CNRS 8181, Ecole Nationale Superieure de Chimie de Lille, Universite des Sciences et Technologies de Lille, BP 108, 59562 Villeneuve d'Ascq Cedex (France)

    2010-01-15

    Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi{sub 2}O-71.7SiO{sub 2}-(17.7-x)Al{sub 2}O{sub 3}-4.9K{sub 2}O-3.2B{sub 2}O{sub 3}-2.5P{sub 2}O{sub 5} (5.1<=x<=12.6) upon heat treatment were studied. {sup 29}Si, {sup 27}Al, {sup 31}P and {sup 11}B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO{sub 3} and BO{sub 4} units. {sup 27}Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, {sup 11}B (high field 18.8 T) and {sup 29}Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi{sub 2}O{sub 6}, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), lithium metasilicate (Li{sub 2}SiO{sub 3}) and quartz (SiO{sub 2}) were identified in the {sup 29}Si NMR spectra of the glass-ceramics. {sup 31}P NMR spectra of the glass-ceramics revealed the presence of Li{sub 3}PO{sub 4} and a mixed phase (Li,K){sub 3}PO{sub 4} at low alkali concentrations. - Graphical Abstract: The {sup 11}B MAS-NMR spectra of lithium aluminum silicate (LAS) glass-ceramics indicating the formation of Li/KBSiO{sub 6} phase. This phase is isostructural with virgilite and cannot be distinguished in X-ray diffractograms.

  5. Unique Backbone-Water Interaction Detected in Sphingomyelin Bilayers with 1H/31P and 1H/13C HETCOR MAS NMR Spectroscopy

    PubMed Central

    Holland, Gregory P.; Alam, Todd M.

    2008-01-01

    Two-dimensional 1H/31P dipolar heteronuclear correlation (HETCOR) magic-angle spinning nuclear magnetic resonance (NMR) is used to investigate the correlation of the lipid headgroup with various intra- and intermolecular proton environments. Cross-polarization NMR techniques involving 31P have not been previously pursued to a great extent in lipid bilayers due to the long 1H-31P distances and high degree of headgroup mobility that averages the dipolar coupling in the liquid crystalline phase. The results presented herein show that this approach is very promising and yields information not readily available with other experimental methods. Of particular interest is the detection of a unique lipid backbone-water intermolecular interaction in egg sphingomyelin (SM) that is not observed in lipids with glycerol backbones like phosphatidylcholines. This backbone-water interaction in SM is probed when a mixing period allowing magnetization exchange between different 1H environments via the nuclear Overhauser effect (NOE) is included in the NMR pulse sequence. The molecular information provided by these 1H/31P dipolar HETCOR experiments with NOE mixing differ from those previously obtained by conventional NOE spectroscopy and heteronuclear NOE spectroscopy NMR experiments. In addition, two-dimensional 1H/13C INEPT HETCOR experiments with NOE mixing support the 1H/31P dipolar HETCOR results and confirm the presence of a H2O environment that has nonvanishing dipolar interactions with the SM backbone. PMID:18390621

  6. A Chemical, XRD, and 27Al MAS NMR Investigation of Miocene Gulf Coast Shales with Application to Understanding Illite\\/Smectite Crystal-Chemistry

    Microsoft Academic Search

    Paul A. Schroeder

    1993-01-01

    This study assesses the distribution of A1 and Fe in mixed-layer illite\\/smectites (I\\/S) in shales undergoing burial diagenetic changes, using evidence from 27A1 NMR, XRD, and chemical analyses. Samples studied include a sequence of mixed-layer I\\/S (ranging from 40% to 68% illite layers) in shales from a well located in the Caillou Island Oil Field, Terrebonne Parish, Louisiana, as well

  7. Structural characterisation of phosphate materials: new insights into the spatial proximities between phosphorus and quadrupolar nuclei using the D-HMQC MAS NMR technique.

    PubMed

    Tricot, G; Lafon, O; Trébosc, J; Delevoye, L; Méar, F; Montagne, L; Amoureux, J-P

    2011-10-01

    We show in this article how the spatial proximity between phosphorus and quadrupolar nuclei can be efficiently and easily investigated with the D-HMQC (Dipolar Hetero-nuclear Multiple-Quantum Coherences) NMR technique. Compared to the commonly used CP-HETCOR (Cross-Polarisation HETero-nuclear CORrelation) sequence, the D-HMQC pulse scheme exhibits a higher sensitivity and a better robustness with respect to spinning frequency, electronic shielding and quadrupole interaction, and thus does not require time-consuming and complicated optimisation procedures. The advantages of the D-HMQC are demonstrated in this article through the acquisition of (31)P/S through-space two-dimensional correlation NMR spectra providing unreported structural information on (i) a sodium alumino-silicate glass doped with only 3% of P(2)O(5), (ii) a potassium boro-phosphate glass containing BO(3) and BO(4) groups and (iii) a crystalline zirconium vanado-phosphate. All these systems, representative of the most important mixed phosphate network materials, cannot be correctly investigated with the conventional CP-HETCOR NMR technique. PMID:21853181

  8. Characterization of the wound-induced material in Citrus paradisi fruit peel by carbon-13 CP-MAS solid state NMR spectroscopy.

    PubMed

    Lai, Simona; Lai, Adolfo; Stange, Richard R; McCollum, T Greg; Schirra, Mario

    2003-05-01

    Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated under conditions favourable for the accumulation of defence related material. Histochemical examination revealed that tissues adjacent to inoculated injuries contained phloroglucinol-HCl (PG-HCl) reactive material. Solvent washed cell wall preparations of intact and injured-inoculated peel were further purified using a mixture of cell wall degrading enzymes. Samples from injured inoculated tissue contained PG-HCl reactive globular material in addition to the fragments of xylem and cuticle found in controls. The principal chemical moieties of the material that accumulates in grapefruit injuries during wound-healing were studied by solid state 13C cross-polarization magic angle spinning NMR. A complete assignment of the NMR signals was made. From the analysis evidence was found that cellulose and hemicellulose are the biopolymers present in the intact peel samples, in addition, relevant quantities of cutin were found in the residues of enzyme digest. The NMR difference spectrum intact- wounded peels showed resonances which were attributed to all major functional groups of the aromatic-aliphatic suberin polyester of new material produced by the wounds. Information on the latter polyester was obtained by analyzing the T(1)rho (1H) relaxation. PMID:12711139

  9. Spin-transfer pathways in paramagnetic lithium transition-metal phosphates from combined broadband isotropic solid-state MAS NMR spectroscopy and DFT calculations.

    PubMed

    Clément, Raphaële J; Pell, Andrew J; Middlemiss, Derek S; Strobridge, Fiona C; Miller, Joel K; Whittingham, M Stanley; Emsley, Lyndon; Grey, Clare P; Pintacuda, Guido

    2012-10-17

    Substituted lithium transition-metal (TM) phosphate LiFe(x)Mn(1-x)PO(4) materials with olivine-type structures are among the most promising next generation lithium ion battery cathodes. However, a complete atomic-level description of the structure of such phases is not yet available. Here, a combined experimental and theoretical approach to the detailed assignment of the (31)P NMR spectra of the LiFe(x)Mn(1-x)PO(4) (x = 0, 0.25, 0.5, 0.75, 1) pure and mixed TM phosphates is developed and applied. Key to the present work is the development of a new NMR experiment enabling the characterization of complex paramagnetic materials via the complete separation of the individual isotropic chemical shifts, along with solid-state hybrid DFT calculations providing the separate hyperfine contributions of all distinct Mn-O-P and Fe-O-P bond pathways. The NMR experiment, referred to as aMAT, makes use of short high-powered adiabatic pulses (SHAPs), which can achieve 100% inversion over a range of isotropic shifts on the order of 1 MHz and with anisotropies greater than 100 kHz. In addition to complete spectral assignments of the mixed phases, the present study provides a detailed insight into the differences in electronic structure driving the variations in hyperfine parameters across the range of materials. A simple model delimiting the effects of distortions due to Mn/Fe substitution is also proposed and applied. The combined approach has clear future applications to TM-bearing battery cathode phases in particular and for the understanding of complex paramagnetic phases in general. PMID:23004936

  10. Elemental and structural analysis of silicon forms in herbal drugs using silicon-29 MAS NMR and WD-XRF spectroscopic methods.

    PubMed

    Pajchel, L; Nykiel, P; Kolodziejski, W

    2011-12-01

    The objective of this work was to study concentration of silicon and its structural forms present in herbal drugs. Equisetum arvense and Urtica dioica L. from teapot bags, dietary supplements (tablets and capsules) containing those herbs, dry extract obtained from a teapot bag of E. arvense, and samples of the latter herb harvested in wild habitat over four months were studied using wavelength dispersive X-ray spectroscopy (WD-XRF) and high-resolution solid-state (29)Si NMR. The highest concentration of Si, ca. 27mg/g, was found in the herbal material from the teapot bags containing E. arvense. The Si content in natural E. arvense (whole plants) increased from May to August by ca. 7mg/g, reaching value 26mg/g. Three different silicon forms were detected in the studied herbal samples: Si(OSi)4 (Q(4)), Si(OH)(OSi)3 (Q(3)) and Si(OH)2(OSi)2 (Q(2)). Those sites were populated in E. arvense in the following order: Q(4)?Q(3)>Q(2). A dramatic, ca. 50-fold decrease of the Si concentration during the infusion process was observed. The infusion process and the subsequent drying procedure augmented population of the Q(4) sites at the cost of the Q(2) sites. The WD-XRF and (29)Si NMR methods occurred useful and complementary in the study of herbal materials. PMID:21813258

  11. Stoichiometric compounds of magnesium dichloride with ethanol for the supported Ziegler-Natta catalysis: first recognition and multidimensional MAS NMR study.

    PubMed

    Sozzani, Piero; Bracco, Silvia; Comotti, Angiolina; Simonutti, Roberto; Camurati, Isabella

    2003-10-22

    Ethanol associates easily with MgCl(2) to form adducts of complex architecture, but until now available characterization methods have failed to identify the pure stoichiometric compounds and their structures. To remedy this, we set about applying homonuclear and heteronuclear 2D correlated solid-state NMR spectroscopy to identify the pure compounds and the ethanol-to-magnesium coordination pattern. High spinning speed and Lee-Goldburg sequences were able to reduce the hydrogen spin-diffusion and homonuclear coupling in the crystalline solid, thus achieving high resolution also in the hydrogen domain. On this basis, the pure adducts, of interest as catalyst supports for Ziegler-Natta polymerization, were isolated for the first time. Magnesium coordination sites with given numbers of ligands and their multiplicity in the crystal cells were determined in the new-found stoichiometric complexes. Variable temperature and 2D carbon-carbon exchange NMR, as well as relaxation times in the fast motion regime, revealed the disordering phenomena generated by ethanol dynamics in the crystal. Decoding the intriguing polymorphism of the precursors permits to trace the genealogy of tailored MgCl(2) titanate granules, active as highly productive catalysts for the stereospecific polymerization of olefins. PMID:14558837

  12. Paramagnetic Prussian Blue Analogues CsM(II)[M(III)(CN)6]. The Quest for Spin on Cesium Ions by Use of (133)Cs MAS NMR Spectroscopy.

    PubMed

    Köhler, Frank H; Storcheva, Oksana

    2015-07-20

    The (133)Cs magic-angle spinning NMR spectra of the paramagnetic compounds CsM(II)[M(III)(CN)6], M(II) = Ni, Co, Fe, Mn; M(II) = Co, Fe, yield unusually large and temperature-dependent signal shifts (up to -950 ppm relative to CsCl at 298 K). Comparison with the spectra of the diamagnetic analogues CsM[Co(CN)6], M = Zn, Cd, shows that the shifts are largely due to the unpaired electrons. This is ascribed to through-bond transfer of spin to the Cs(+) ions, while the through-space effect of the magnetic moments on the signal shifts is shown to be virtually negligible. The mechanism inducing negative spin at Cs(+) is discussed. The magnitude of the spin density (average: |5.8 × 10(-3)| (a.u.) (-3)) suggests that Cs(+) is involved in magnetic exchange interactions of corresponding Prussian blue derivatives. PMID:26134712

  13. Following solid-acid-catalyzed reactions by MAS NMR spectroscopy in liquid phase--zeolite-catalyzed conversion of cyclohexanol in water.

    PubMed

    Vjunov, Aleksei; Hu, Mary Y; Feng, Ju; Camaioni, Donald M; Mei, Donghai; Hu, Jian Z; Zhao, Chen; Lercher, Johannes A

    2014-01-01

    A microautoclave magic angle spinning NMR rotor is developed enabling in?situ monitoring of solid-liquid-gas reactions at high temperatures and pressures. It is used in a kinetic and mechanistic study of the reactions of cyclohexanol on zeolite HBEA in 130?°C water. The (13) C?spectra show that dehydration of 1-(13) C-cyclohexanol occurs with significant migration of the hydroxy group in cyclohexanol and the double bond in cyclohexene with respect to the (13) C label. A simplified kinetic model shows the E1-type elimination fully accounts for the initial rates of 1-(13) C-cyclohexanol disappearance and the appearance of the differently labeled products, thus suggesting that the cyclohexyl cation undergoes a 1,2-hydride shift competitive with rehydration and deprotonation. Concurrent with the dehydration, trace amounts of dicyclohexyl ether are observed, and in approaching equilibrium, a secondary product, cyclohexyl-1-cyclohexene is formed. Compared to phosphoric acid, HBEA is shown to be a more active catalyst exhibiting a dehydration rate that is 100-fold faster per proton. PMID:24282024

  14. New insights on the structure of algaenan from Botryoccocus braunii race A and its hexane insoluble botryals based on multidimensional NMR spectroscopy and electrospray–mass spectrometry techniques

    Microsoft Academic Search

    Andre J Simpson; Xu Zang; Robert Kramer; Patrick G Hatcher

    2003-01-01

    Through solution state NMR spectroscopy and quadrupole-time-of-flight mass spectrometry (Q-TOF MS) studies of the hexane insoluble botryal extract of the algae Botryococcus braunii race A, coupled with high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy of the algaenan from this alga, it has been possible to advance the structural understanding of this geochemically important biopolymer. It was found that the hexane insoluble botryals

  15. Characterization of polysulfone and polysulfone/vanillin microcapsules by 1H NMR spectroscopy, solid-state 13C CP/MAS-NMR spectroscopy, and N2 adsorption-desorption analyses.

    PubMed

    Peña, Brisa; de Ménorval, Louis-Charles; Garcia-Valls, Ricard; Gumí, Tània

    2011-11-01

    Textile detergent and softener industries have incorporated perfume microencapsulation technology to improve their products. Perfume encapsulation allows perfume protection until use and provides a long-lasting fragrance release. But, certain industrial microcapsules show low encapsulation capacity and low material stability. Polysulfone capsules have been already proposed to solve these drawbacks. Among them, PSf/Vanillin capsules were considered as a desirable system. They present both good material stability and high encapsulation capacity. However, several factors such as the final location of the perfume in the polymeric matrix, the aggregation state that it has in the capsule and its interaction with the capsule components have not been studied yet. These factors can provide vast information about the capsule performance and its improvement. With the aim to characterize these parameters, the physical and chemical properties of PSf/Vanillin capsules have been investigated by nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and N(2) adsorption-desorption measurements. AFM micrograph and N(2) isotherms confirm that the presence of vanillin modify the physical structure of PSf/Vanillin microcapsules as it is trapped in the capsule porosity. NMR results show that vanillin is present in solid state in PSf/Vanillin microcapsules. PMID:22008282

  16. Examination of the structure in solid state of amino analogs of 4,4?-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, 13C CP/MAS NMR, and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota; Wolska, Irena; ?abi?ski, Jerzy

    2008-05-01

    A single crystal of X-ray diffraction structures is presented for 4,4'-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4'-[1,5-( N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/ gauche conformation, whereas in 3 - a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of N sbnd H···N in 2 and of C sbnd H···N in 3. Various conformations of both molecules were reflected in 13C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.

  17. The role of irregular unit, GAAS, on the secondary structure of Bombyx mori silk fibroin studied with 13C CP/MAS NMR and wide-angle X-ray scattering

    PubMed Central

    Asakura, Tetsuo; Sugino, Rena; Okumura, Tatsushi; Nakazawa, Yasumoto

    2002-01-01

    Bombyx mori silk fibroin is a fibrous protein whose fiber is extremely strong and tough, although it is produced by the silkworm at room temperature and from an aqueous solution. The primary structure is mainly Ala-Gly alternative copolypeptide, but Gly-Ala-Ala-Ser units appear frequently and periodically. Thus, this study aims at elucidating the role of such Gly-Ala-Ala-Ser units on the secondary structure. The sequential model peptides containing Gly-Ala-Ala-Ser units selected from the primary structure of B. mori silk fibroin were synthesized, and their secondary structure was studied with 13C CP/MAS NMR and wide-angle X-ray scattering. The 13C isotope labeling of the peptides and the 13C conformation-dependent chemical shifts were used for the purpose. The Ala-Ala units take antiparallel ?-sheet structure locally, and the introduction of one Ala-Ala unit in (Ala-Gly)15 chain promotes dramatical structural changes from silk I (repeated ?-turn type II structure) to silk II (antiparallel ?-sheet structure). Thus, the presence of Ala-Ala units in B. mori silk fibroin chain will be one of the inducing factors of the structural transition for silk fiber formation. The role of Tyr residue in the peptide chain was also studied and clarified to induce "locally nonordered structure." PMID:12142441

  18. Characterization of white Portland cement hydration and the C-S-H structure in the presence of sodium aluminate by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy

    SciTech Connect

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Joergen

    2004-05-01

    The effects of hydrating a white Portland cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.

  19. High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins

    E-print Network

    Griffin, Robert G.

    High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins Melanie of the principal promises of magic angle spinning (MAS) solid-state NMR (SSNMR) experiments is the possibility The success of these experiments is due largely to the ability to record multidimensional MAS NMR spectra

  20. Metabolite localization in living drosophila using High Resolution Magic Angle Spinning NMR.

    PubMed

    Sarou-Kanian, Vincent; Joudiou, Nicolas; Louat, Fanny; Yon, Maxime; Szeremeta, Frédéric; Même, Sandra; Massiot, Dominique; Decoville, Martine; Fayon, Franck; Beloeil, Jean-Claude

    2015-01-01

    We have developed new methods enabling in vivo localization and identification of metabolites through their (1)H NMR signatures, in a drosophila. Metabolic profiles in localized regions were obtained using HR-MAS Slice Localized Spectroscopy and Chemical Shift Imaging at high magnetic fields. These methods enabled measurement of metabolite contents in anatomic regions of the fly, demonstrated by a decrease in ?-alanine signals in the thorax of flies showing muscle degeneration. PMID:25892587

  1. {sup 29}Si, {sup 17}O liquid NMR and {sup 29}Si CP-MAS NMR characterization of siloxane-oxide materials, [(CH{sub 3}){sub 2}SiO/TiO{sub 2}, (CH{sub 3}){sub 2}SiO/ZrO{sub 2}

    SciTech Connect

    Babonneau, F. [Univ. Pierre et Marie Curie, Paris (France). Chimie de la Matiere Condensee

    1994-12-31

    Sol-gel derived siloxane oxide materials are an entirely new family of hybrid systems at the frontier between silicones and glasses or ceramics, with a large variety of potential applications. Better control of the chemistry involved in their preparation should lead to an improvement in their properties, and this requires an investigation of the whole process, from the solution to the final materials. Nuclear Magnetic Resonance is a very suitable technique for this purpose, and this paper will give some illustrations on model systems (CH{sub 3}){sub 2}SiO/TiO{sub 2}, (CH{sub 3}){sub 2}SiO/ZrO{sub 2}, prepared from dimethyldiethoxysilane and titanium or zirconium alkoxides. It is a focused mainly on the use of {sup 17}O solution NMR which clearly shows the formation of Si-O-Ti or Si-O-Zr bonds, but also their disappearance during the aging process. {sup 29}Si MAS-NMR spectra of dried gels confirm that the difunctional units are mainly in polydimethylsiloxane chains, and that the system is phase separated. However, the use of cross-polarization techniques involving {sup 1}H and {sup 29}Si nuclei allows the detection of a small number of units in a more constrained environment, certainly close to oxide-based particles.

  2. Experimental (X-ray, (13)C CP/MAS NMR, IR, RS, INS, THz) and Solid-State DFT Study on (1:1) Co-Crystal of Bromanilic Acid and 2,6-Dimethylpyrazine.

    PubMed

    ?uczy?ska, Katarzyna; Dru?bicki, Kacper; Lyczko, Krzysztof; Dobrowolski, Jan Cz

    2015-06-01

    A combined structural, vibrational spectroscopy, and solid-state DFT study of the hydrogen-bonded complex of bromanilic acid with 2,6-dimethylpyrazine is reported. The crystallographic structure was determined by means of low-temperature single-crystal X-ray diffraction, which reveals the molecular units in their native protonation states, forming one-dimensional infinite nets of moderate-strength O···H-N hydrogen bonds. The nature of the crystallographic forces, stabilizing the studied structure, has been drawn by employing the noncovalent interactions analysis. It was found that, in addition to the hydrogen bonding, the intermolecular forces are dominated by stacking interactions and C-H···O contacts. The thermal and calorimetric analysis was employed to probe stability of the crystal phase. The structural analysis was further supported by a computationally assisted (13)C CP/MAS NMR study, providing a complete assignment of the recorded resonances. The vibrational dynamics was explored by combining the optical (IR, Raman, TDs-THz) and inelastic neutron scattering (INS) spectroscopy techniques with the state-of-the-art solid-state density functional theory (DFT) computations. Despite the quasi-harmonic approximation assumed throughout the study, an excellent agreement between the theoretical and experimental data was achieved over the entire spectral range, allowing for a deep and possibly thorough understanding of the vibrational characteristics of the system. Particularly, the significant influence of the long-range dipole coupling on the IR spectrum has been revealed. On the basis of a wealth of information gathered, the recent implementation of a dispersion-corrected linear-response scheme has been extensively examined. PMID:25961154

  3. 1H and 13C MAS NMR analysis for the role of chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in [N(CH3)4]2CuCl4

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-01-01

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

  4. Solid-state 93Nb MAS NMR studies of single crystal Pb(Mg1\\/3Nb2\\/3)O3, (PMN) and Pb(Zn1\\/3Nb2\\/3)O3, (PZN) and related lead titanate solid-solution relaxor ferroelectrics

    Microsoft Academic Search

    John J. Fitzgerald; Jiong Huang; Jay S. Shore

    1999-01-01

    Solid-state 93Nb MAS NMR spectra measured at 14.1 Tesla of single crystal Pb(Mg1\\/3Nb2\\/3 (PMN), Pb(Zn1\\/3Nb2\\/3)O3 (PZN), 0.93 PMN\\/0.07 PT, and 0.92 PZN\\/0.08 PT, and polycrystalline PMN and 0.90 PMN\\/0.10 PT materials have two major resonances due to the central transition (+l\\/2?-l\\/2), a sharp peak at ?-900 ppm, and a broad resonance centered near -980 ppm. The sharp 93Nb signal has

  5. Data provided: Formula sheet MAS153/MAS159

    E-print Network

    Data provided: Formula sheet MAS153/MAS159 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester at the point (2,-3). (8 marks) MAS153/MAS159 1 Turn Over #12;MAS153/MAS159 # Solve log2(x + 1) + log2(x) = 1 (3 = ey . Show that z2 - 2xz - 1 = 0, and hence show that sinh-1 x = ln ( x + x2 + 1 ) . (5 marks) MAS153

  6. Patterns of Delegate MAS

    Microsoft Academic Search

    Tom Holvoet; Danny Weyns; Paul Valckenaers

    2009-01-01

    Delegate MAS has been proposed and investigated as an integrated coordination technique for so-called self-organising coordination-and-control applications. Delegate MAS consist of three types of light weight, ant-like agents that assist domain agents in their coordination tasks - the types are exploration, intention and feasibility ants. The technique is especially suitable for distributed applications in large-scale, dynamic systems. Literature shows that,

  7. Analysis of organic matter at the soil-water interface by NMR spectroscopy: Implications for contaminant sorption processes

    NASA Astrophysics Data System (ADS)

    Simpson, M. J.; Simpson, A. J.

    2009-04-01

    Contaminant sorption to soil organic matter (OM) is the main fate of nonionic, hydrophobic organic contaminants in terrestrial environments and a number of studies have suggested that both soil OM structure and physical conformation (as regulated by the clay mineral phase) govern contaminant sorption processes. A great deal of this evidence has come from macroscopic observations with contaminants and soil fractions as well as a recent mass balance approach where the sum of the parts exceeded the whole suggesting that the physical arrangement of OM in organo-mineral complexes may be more important than OM structure in sorption processes (1). In addition, recent studies with constructed organo-mineral complexes have suggested that aliphatic OM is preferred over aromatic moieties and suggests that clay minerals play an indirect role by governing the sorption of organic contaminants by controlling the surface accessibility of OM at the soil-water interface (2,3). To investigate this further, a number of soil samples were characterized by both solid-state 13C Cross Polarization Magic Angle Spinning (CPMAS) NMR and 1H High Resolution Magic Angle Spinning (HR-MAS) NMR. HR-MAS NMR is an innovative NMR method that allows one to examine samples that are semi-solid using liquid state NMR methods (ie: observe 1H which is more sensitive than 13C). With HR-MAS NMR, only those structures that are in contact with the solvent are NMR visible thus one can probe different components within a mixture using different solvents. The 1H HR-MAS NMR spectrum of a grassland soil swollen in water (D2O) is dominated by signals from alkyl and O-alkyl structures but signals from aromatic protons are negligible (the peak at ~8.2ppm is attributed to formic acid). When the soil is swollen in DMSO-d6, a solvent which is more penetrating and capable of breaking hydrogen bonds, aromatic signals are visible suggesting that the aromatic structures are buried within the soil matrix and do not exist at the soil-water interface. The 13C solid-state NMR data confirms that aromatic carbon is present in substantial amounts (estimated at ~40% of the total 13C signal) therefore, the lack of 1H aromatic signals in the HR-MAS NMR spectrum indicates that aromatic structures are buried and that the soil-water interface is dominated by aliphatic chains, carbohydrates, and peptides. The NMR data indicates that the mineral component of soils governs the physical conformation of OM at the soil-water interface. Consequently, one must consider that one-dimensional NMR methods provide an excellent overview of all the structures that are present but they do not provide direct information regarding which structures are available or accessible at the soil-water interface for contaminant interactions. References: (1) Bonin J.L. and Simpson M.J. 2007 Environmental Science & Technology 41:153-159. (2) Feng X., Simpson A.J., and Simpson M.J. 2006. Environmental Science & Technology 40:3260- 3266. (3) Simpson A.J. et al. 2006. Langmuir 22:4498-4503.

  8. NMR Investigations of Nanostructured Ceramics

    Microsoft Academic Search

    M. Edgar; M. Schubert; H. H. Limbach

    Nanostructured mesoporous silicates displaying hexagonally arranged channels, templated using a liquid crystal mesophase, were investigated using H-2 and N-15 NMR spectroscopy. It is shown that N-I5 MAS NMR spec- troscopy allows to estimate the surface acidity of mesoporous materials by measuring the N-H bond length via the N-15 chemical shift. Further, H-2 and N-15 NMR spectroscopy identify significant differences between

  9. RESTRICTED OPEN BOOK EXAMINATION (Not to be removed from the examination hall) Data provided: "Statistics Tables" by H.R. Neave

    E-print Network

    : "Statistics Tables" by H.R. Neave MAS 473 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2011 Registration number from U-Card (9 digits) to be completed by student MAS 473 1 Turn Over #12;MAS 473 Blank MAS 473 2 Continued #12;MAS 473 Figure 1 shows mean productivity scores for each of three randomly chosen

  10. RESTRICTED OPEN BOOK EXAMINATION (Not to be removed from the examination hall) Data provided: Statistics Tables by H.R. Neave

    E-print Network

    : Statistics Tables by H.R. Neave MAS5052 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010­2011 Basic it from the hall Registration number from U-Card (9 digits) to be completed by student MAS5052 1 Turn Over #12;MAS5052 Blank MAS5052 2 Continued #12;MAS5052 1 Data arising from a study into fuel consumption

  11. RESTRICTED OPEN BOOK EXAMINATION (Not to be removed from the examination hall) Data provided: "Statistics Tables" by H.R. Neave

    E-print Network

    : "Statistics Tables" by H.R. Neave MAS5052 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012­2013 Basic it from the hall Registration number from U-Card (9 digits) to be completed by student MAS5052 1 Turn Over #12;MAS5052 Blank MAS5052 2 Continued #12;MAS5052 1 The eruptions of the "Old Faithful" geyser

  12. Theoretical study of CP-VC: A simple, robust and accurate MAS NMR method for analysis of dipolar C-H interactions under rotation speeds faster than ca. 60 kHz

    NASA Astrophysics Data System (ADS)

    Paluch, P.; Trébosc, J.; Nishiyama, Y.; Potrzebowski, M. J.; Malon, M.; Amoureux, J. P.

    2015-03-01

    We show that Cross-Polarization with Variable Contact-time (CP-VC) allows an accurate determination of C-H dipolar interactions, which permits an easy detailed analysis of bond lengths and local dynamics, e.g. in biomolecules. The method presents a large dipolar scaling factor of 1/?2, leading to a better determination of dipolar interactions, especially for long C-H distances, and it allows the observation of very small local details such as those related either to CH2 three spin systems, or even to hydrogen bonds. CP-VC is very simple to set up and very robust with respect to most experimental parameters, such as: rf-offsets, chemical-shift anisotropies, imperfect Hartmann-Hahn setting, and rf-inhomogeneity. The only required condition is the use of a sufficiently fast MAS spinning speed of at least ca. 60 kHz.

  13. HR COMMUNICATIONS Program Coordinator

    E-print Network

    Ronquist, Fredrik

    HR COMMUNICATIONS Program Coordinator 51518 9254 04 VACANT University Business Administrator II TECHNOLOGY/ HR DATA MANAGEMENT/ COMMUNICATIONS RECORDS BENEFITS TIME & LABOR EMPLOYEE DATA MANAGEMENT EMPLOYMENT FACILITIES SATELLITE OFFICE EMPLOYEE & LABOR RELATIONS Director, Admin Svcs 55607 9250A 07 VACANT

  14. Application of REDOR subtraction for filtered MAS observation of labeled backbone carbons of membrane-bound fusion peptides

    E-print Network

    Weliky, David

    Application of REDOR subtraction for filtered MAS observation of labeled backbone carbons December 2001; revised 5 August 2002 Abstract Clean MAS observation of 13 C-labeled carbons in membrane-echo double-resonance spectroscopy (REDOR) is one of the most widely used magic angle spinning (MAS) NMR

  15. Complexes obtained by electrophilic attack on a dinitrogen-derived terminal molybdenum nitride: Electronic structure analysis by CP MAS solid state 15

    E-print Network

    Loening, Niko

    : Electronic structure analysis by CP MAS solid state 15 N NMR in combination with DFT calculations Emma L=NMo(N[CH3]Ph)3 (3m-C3) 3. 15 N Solid State CP MAS NMR Spectroscopy: Experimental Information and calculated 15 N CP MAS spectra for 1-BF3 3.3 Experimental, simulated and calculated 15 N CP MAS spectra for 1

  16. Binarity of the LBV HR Car

    E-print Network

    Rivinius, Th; de Wit, W J; Mehner, A; Martayan, Ch; Guieu, S; Bouquin, J -B Le

    2014-01-01

    VLTI/AMBER and VLTI/PIONIER observations of the LBV HR Car show an interferometric signature that could not possibly be explained by an extended wind, more or less symmetrically distributed around a single object. Instead, observations both in the Br$\\gamma$ line and the H-band continuum are best explained by two point sources (or alternatively one point source and one slightly extended source) at about 2 mas separation and a contrast ratio of about 1:5. These observations establish that HR Car is a binary, but further interpretation will only be possible with future observations to constrain the orbit. Under the assumption that the current separation is close to the maximum one, the orbital period can be estimated to be of the order of 5 years, similar as in the $\\eta$ Car system. This would make HR Car the second such LBV binary.

  17. Single-crystal and powder X-ray diffraction, 13C CP/MAS NMR, and DFT-GIAO calculations of methyl 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside and methyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside

    NASA Astrophysics Data System (ADS)

    Gubica, Tomasz; St?pie?, Dorota K.; Pisklak, Dariusz M.; Ostrowski, Andrzej; Cyra?ski, Micha? K.

    2013-03-01

    Single-crystal and powder X-ray diffraction, 13C CP/MAS NMR, and DFT-GIAO calculations of shielding constants were performed for methyl 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside (1) and methyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-?-D-galactopyranosyl)-?-D-glucopyranoside (2). 1 crystallizes with three molecules whereas 2 with two molecules in an independent part of the unit cell. The macroscopic sample of 1 consists of one polymorph, while for 2 two or three polymorphs were detected. The existence of different numbers of the molecules in the asymmetric units as well as different numbers of polymorphs of 1 and 2 was verified by solid-state NMR spectroscopy.

  18. HR SERVICES COMMUNICATION SESSION

    E-print Network

    ;Completed Projects 2013 · Data Cleansing ­ ­ New Processes Implementation ­ Audit Reports · Core Upgrade Level Agreement · Recruitment KPIs · HRIS KPIs #12;HR Services Projects ­ 2013 DMS Core Data Cleansing

  19. HR & Equity Annual Report

    E-print Network

    Sun, Yu

    PCB Waste Management ---------------------------------------- 34 Radioactive Waste Management for HR Staff-------------------------- 11 Health, Wellness & Family Quality of Work-Life Initiatives ---------------------------------- 12 Family Supports ---------------------------------------------------- 13 Health and Well

  20. C NMR Investigations of Fullerene Black

    Microsoft Academic Search

    M. Kanowski; G. Buntkowsky; H. Werner; M. Wohlers; R. Schlögl; H.-M. Vieth; K. Lüders

    1994-01-01

    Solid-state C NMR measurements on differently treated fullerene black samples are reported. The results show that no significant amounts of C60 molecules are entrapped in fullerene black in a way that they are not accessible for conventionally used toluene extraction. The broad distribution of chemical shifts in the C MAS NMR spectra confirms the large abundance of bent carbon structures

  1. Director HR Andrew J Smith

    E-print Network

    Liley, David

    Director HR Andrew J Smith Associate Director HR Shared Services Miya Chiba Associate Director Payroll Officer John Smith Systems & Project Analyst Blair Jordan HR Reporting Analyst Yana Zhang Manager

  2. Comprehensive multiphase NMR spectroscopy: Basic experimental approaches to differentiate phases in heterogeneous samples

    NASA Astrophysics Data System (ADS)

    Courtier-Murias, Denis; Farooq, Hashim; Masoom, Hussain; Botana, Adolfo; Soong, Ronald; Longstaffe, James G.; Simpson, Myrna J.; Maas, Werner E.; Fey, Michael; Andrew, Brian; Struppe, Jochem; Hutchins, Howard; Krishnamurthy, Sridevi; Kumar, Rajeev; Monette, Martine; Stronks, Henry J.; Hume, Alan; Simpson, André J.

    2012-04-01

    Heterogeneous samples, such as soils, sediments, plants, tissues, foods and organisms, often contain liquid-, gel- and solid-like phases and it is the synergism between these phases that determine their environmental and biological properties. Studying each phase separately can perturb the sample, removing important structural information such as chemical interactions at the gel-solid interface, kinetics across boundaries and conformation in the natural state. In order to overcome these limitations a Comprehensive Multiphase-Nuclear Magnetic Resonance (CMP-NMR) probe has been developed, and is introduced here, that permits all bonds in all phases to be studied and differentiated in whole unaltered natural samples. The CMP-NMR probe is built with high power circuitry, Magic Angle Spinning (MAS), is fitted with a lock channel, pulse field gradients, and is fully susceptibility matched. Consequently, this novel NMR probe has to cover all HR-MAS aspects without compromising power handling to permit the full range of solution-, gel- and solid-state experiments available today. Using this technology, both structures and interactions can be studied independently in each phase as well as transfer/interactions between phases within a heterogeneous sample. This paper outlines some basic experimental approaches using a model heterogeneous multiphase sample containing liquid-, gel- and solid-like components in water, yielding separate 1H and 13C spectra for the different phases. In addition, 19F performance is also addressed. To illustrate the capability of 19F NMR soil samples, containing two different contaminants, are used, demonstrating a preliminary, but real-world application of this technology. This novel NMR approach possesses a great potential for the in situ study of natural samples in their native state.

  3. Broadband solid-state MAS NMR of paramagnetic systems

    E-print Network

    Pell, Andrew J.; Pintacuda, Guido

    2014-12-26

    of the bare nucleus is described by the coupling of Iˆ with B0 through the identity matrix 1. This is modified by inclusion of the orbital contribution of the open shell to the chemical shielding ?orb, which is a generalisation of the chemical shielding... - lished by Pennanen and Vaara [50] as an extension of an earlier effort by Moon and Patchkovskii [51]. Pennanen and Vaara proposed the following form for ?p: ?p = ? µB ~?IkT g · ? SˆSˆ ? 0 ·A, (3) where k is the Boltzmann constant. The ZFS tensor is hidden...

  4. doi:10.1016/S0016-7037(02)00026-7 The distribution of sodium ions in aluminosilicate glasses: A high-field Na-23 MAS and 3Q

    E-print Network

    Puglisi, Joseph

    : A high-field Na-23 MAS and 3Q MAS NMR study SUNG KEUN LEE* and JONATHAN F. STEBBINS Department of the configurational properties of corresponding melts (Lee and Stebbins, 1999, 2000a, 2000b; Lee et al., 2001

  5. Hazendonk P, Bain AD, Grondey H, Harrison PHM, Dumont RS. Simulations of chemical exchange lineshapes in CP/MAS spectra using Floquet theory and

    E-print Network

    Hitchcock, Adam P.

    lineshapes in CP/MAS spectra using Floquet theory and sparse matrix methods. J Magn Reson 2000; 146: 33-42. ABSTRACT This paper presents a general method for simulating the effect of chemical exchange on MAS NMR spectra of solid samples. The complication in MAS spectra is that the Hamiltonian itself is time

  6. Moving NMR

    Microsoft Academic Search

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

    2008-01-01

    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

  7. HR Internet Guide

    NSDL National Science Digital Library

    The Human Resource (HR) Guide is a valuable resource to anyone in a human resource field of study or profession. The site contains a huge directory of anything and everything related to human resources. The top level sections are Selection/Staffing, Compensation, Law/Legal, Employee Behavior Problems, Job Analysis, Benefits, and On-Line Documents -- just to name a few. Plunging deeper in to any sub-topics leads to countless other branches and ultimately hundreds of pages. From basic definitions of HR terms such as Compensation, Merit Pay, and Work Sample Tests to forms, resources and links to information and materials on Workplace Violence, Employee Handbooks, and Workers Comp, this page is a good starting place for anyone seeking information about HR on the Internet.

  8. Limits of detection of polydimethylsiloxane in (29)Si NMR spectroscopy.

    PubMed

    Semchyschyn, D J; Macdonald, P M

    2000-04-01

    Limits of detection for neat poly(dimethylsiloxane) (PDMS), as detected via (29)Si NMR spectroscopy, were determined by the IUPAC, graphical, and propagation of errors methods from calibration curves obtained using a 7.05 Tesla superconducting magnet equipped with a magic angle spinning (MAS) NMR probe. Under conditions permitting full relaxation of the nuclear spins (recycle time >150 sec), the limit of detection with 128 transients was 1.7, 2.2, and 3.7 mg PDMS (23, 30, and 50 micromoles elemental Si) for the IUPAC, graphical, and propagation of errors methods, respectively. A higher limit of detection results when additional sources of uncertainty are considered. From the strict dependence of the limit of detection on the inverse of the square root of the number of transients signal-averaged, it is possible to extrapolate to a limit of detection of 183 microg PDMS (2.47 micromoles elemental Si) for a 24-hr signal averaging period. This limit of detection is 3 orders of magnitude higher than silicon levels found in human blood. PMID:10748438

  9. Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR–NMR correlation

    Microsoft Academic Search

    Qing-Xia Ruan; Ping Zhou

    2008-01-01

    In the present work, we investigated Na+ ion effect on the silk fibroin (SF) conformation. Samples are Na+-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na+] increases, partial silk fibroin conformation transit from helix-form to ?-form at certain Na+ ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR–NMR

  10. SCAR-B ER2 MAS

    Atmospheric Science Data Center

    2014-04-23

    SCAR-B ER2 MAS Project Title:  SCAR-B Discipline:  ... Platform:  NASA ER-2 Instrument:  MAS Spatial Coverage:  (-19.20, 34.96)(-116.36, -45.94) ... Readme Files:  Readme SCAR-B ER2 MAS Summaries Read Software Files :  C Code ...

  11. NMR Spectroscopy Protein-NMR

    E-print Network

    Schüler, Axel

    is investigated. 5. Methodological development of selective NMR pulse sequences for the application in bioorganic. Bioorganic & Medicinal Chemistry Volume 19, Issue 11 (2011), 3497­3501. PROTEINENGINEERINGANDBIOANALYTICS

  12. workplace bullying HR : , workplace bullying.

    E-print Network

    Chatziantoniou, Damianos

    . 2012 workplace bullying HR : , . 2012 workplace bullying on employee performance . #12;2012 & . 2012 : . 2012 Workplace bullying work " , / " . 2009 "Work-Life balance: - " . 2009 " Bullying " . 2009 " " . 2009

  13. HR Shared Services and the Realignment of HR.

    ERIC Educational Resources Information Center

    Reilly, P.

    This report examines how adopting the shared services model of human resources (HR) services delivery can help businesses achieve better alignment between their HR service and specific business needs. Chapter 1 provides background information on the research project underlying this report, which included the following data collection activities:…

  14. 1D to 3D NMR study of microporous alumino-phosphate Cludia Moraisa,b

    E-print Network

    Paris-Sud XI, Université de

    ) From one- to two- and three-dimensional MAS NMR solid state experiments involving 31 P and 27 Al we-HMQC opens new possibilities in describing details of three dimensional bounded networks. Keywords: NMR, 31P they involve abundant and sensitive nuclei (27 Al, 31 P) high resolution solid state NMR is a tool of choice

  15. Magic angle spinning NMR spectroscopy: a versatile technique for structural and dynamic analysis of solid-phase systems.

    PubMed

    Polenova, Tatyana; Gupta, Rupal; Goldbourt, Amir

    2015-06-01

    Magic Angle Spinning (MAS) NMR spectroscopy is a powerful method for analysis of a broad range of systems, including inorganic materials, pharmaceuticals, and biomacromolecules. The recent developments in MAS NMR instrumentation and methodologies opened new vistas to atomic-level characterization of a plethora of chemical environments previously inaccessible to analysis, with unprecedented sensitivity and resolution. PMID:25794311

  16. NMR Animations

    NSDL National Science Digital Library

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

  17. NMR tutorial

    NSDL National Science Digital Library

    Bogdal, Dariusz

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

  18. Solid-state NMR studies of the adsorption of acetylene on platinum/alumina catalysts

    E-print Network

    Lambregts, Marsha Jo Lupher

    1991-01-01

    is invisible in "C MAS spectra, presumably due to susceptibility broadening. This observation reconciles the conflicting conclusions of two previous NMR investigations of the system. This thesis underscores the need to apply complementary NMR techniques... REFERENCES 15 19 34 VITA 37 LIST OF FIGURES FIGURE PAGE A Langmuir isotherm obtained for a representative 10%Pt/rt-alumina catalyst sample. 16 uC CP/MAS NMR spectra obtained at a resonance frequency of 50 MHz. 20 uC Interrupted Decoupling MAS...

  19. RFID enhanced MAS for warehouse management

    Microsoft Academic Search

    A. García; Y. Chang; A. Abarca; C. Oh

    2007-01-01

    In this work, the design of a multi agent system (MAS) for inventory control at the main Spanish e-commerce retailer ‘Group Lo Monaco’ is presented, which will contribute to improve the picking process at the warehouse. The proposed system uses Radio-Frequency Identification (RFID) technology for product identification. A MAS is used to place orders to suppliers and the agent methodology

  20. VLBI imaging and astrometry of the Gravity Probe B guide star HR 8703

    NASA Astrophysics Data System (ADS)

    Ransom, Ryan R.

    Gravity Probe B (GP-B) is the spaceborne relativity experiment developed by NASA and Stanford University to test two predictions of general relativity (GR). The experiment will use four super-conducting gyroscopes, contained in a low-earth, polar orbiting spacecraft, to precisely measure the geodetic effect and the much smaller frame-dragging effect. According to GR, each of the effects will induce precessions in the gyroscopes. For the frame-dragging effect, the predicted precession is ˜42 mas/yr (mas ? milliarcsecond). The precessions will be measured with respect to a "guide star," namely the RS CVn binary star HR 8703 (IM Pegasi). The goal of the GP-B experiment is to measure the precessions with a standard error of about 0.5 mas/yr or better. To achieve this level of precision, the proper motion of the guide star must be determined in an inertial reference frame with a standard error ?0.15 mas/yr. Nineteen sets of very-long-baseline interferometry (VLBI) observations at 8.4 GHz between January 1997 and June 2001 were made of HR 8703 and two extragalactic reference sources, 3C454.3 and B2250+194, in support of GP-B. We produced VLBI images of 3C454.3 and B2250+194 for each observing session, and VLBI images of HR 8703 for all but one of the observing sessions. The images of HR 8703 show a variety of radio source structures which range from compact single-emission-region structures <1 mas in angular diameter to complex double-lobe structures with lobe separations of ˜1.5 mas. Moreover, images from temporal subsets of several observing sessions show on hour time scales both structural evolution in the emission source and motions of the radio centroid of up to ˜1 mas. This is the first time that hourly activity on or close to a star has been observed directly, apart from the activity on the Sun. Based upon an astrometric analysis of the phase-referenced positions obtained at each epoch, we have (1) made precise determinations of HR 8703's parallax and proper motion, and (2) apparently detected the major axis of the orbit of the primary giant star in the HR 8703 binary system. The proper motion determination demonstrates that the GP-B astrometric goal will be met with continued observations. The identification of the primary as the spatial origin of the radio emission in the binary system makes HR 8703 only the second close binary for which such an identification has unambiguously been made.

  1. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoaceticum metabolic profiles

    SciTech Connect

    Xue, Junfeng; Isern, Nancy G.; Ewing, R James; Liyu, Andrey V.; Sears, Jesse A.; Knapp, Harlan; Iversen, Jens; Sisk, Daniel R.; Ahring, Birgitte K.; Majors, Paul D.

    2014-06-20

    An in-situ nuclear magnetic resonance (NMR) bioreactor was developed and employed to monitor microbial metabolism under batch-growth conditions in real time. We selected Moorella thermoacetica ATCC 49707 as a test case. M. thermoacetica (formerly Clostridium thermoaceticum) is a strictly anaerobic, thermophilic, acetogenic, gram-positive bacterium with potential for industrial production of chemicals. The metabolic profiles of M. thermoacetica were characterized during growth in batch mode on xylose (a component of lignocellulosic biomass) using the new generation NMR bioreactor in combination with high-resolution, high sensitivity NMR (HR-NMR) spectroscopy. In-situ NMR measurements were performed using water-suppressed H-1 NMR spectroscopy at an NMR frequency of 500 MHz, and aliquots of the bioreactor contents were taken for 600 MHz HR-NMR spectroscopy at specific intervals to confirm metabolite identifications and expand metabolite coverage. M. thermoacetica demonstrated the metabolic potential to produce formate, ethanol and methanol from xylose, in addition to its known capability of producing acetic acid. Real-time monitoring of bioreactor conditions showed a temporary pH decrease, with a concomitant increase in formic acid during exponential growth. Fermentation experiments performed outside of the magnet showed that the strong magnetic field employed for NMR detection did not significantly affect cell metabolism. Use of the in-situ NMR bioreactor facilitated monitoring of the fermentation process in real time, enabling identification of intermediate and end-point metabolites and their correlation with pH and biomass produced during culture growth. Real-time monitoring of culture metabolism using the NMR bioreactor in combination with the HR-NMR spectroscopy will allow optimization of the metabolism of microorganisms producing valuable bioproducts.

  2. Fluid flow dynamics in MAS systems.

    PubMed

    Wilhelm, Dirk; Purea, Armin; Engelke, Frank

    2015-08-01

    The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor. PMID:26073599

  3. Analytica Chimica Acta 595 (2007) 38 Chemometric analysis applied in 1

    E-print Network

    Ferreira, Márcia M. C.

    2007-01-01

    Analytica Chimica Acta 595 (2007) 3­8 Chemometric analysis applied in 1 H HR-MAS NMR and FT-IR data This paper describes the potentiality of chemometric analysis applied in 1 H HR-MAS NMR and FT-IR data ­ nuclear magnetic resonance (HR-MAS NMR) and Fourier transform infrared (FT-IR) associated with chemometric

  4. A (1)H NMR metabolic profiling to the assessment of protein tyrosine phosphatase 1B role in liver regeneration after partial hepatectomy.

    PubMed

    Samino, Sara; Revuelta-Cervantes, Jesús; Vinaixa, Maria; Rodríguez, Miguel Ángel; Valverde, Angela M; Correig, Xavier

    2013-04-01

    Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of the tyrosine kinase growth factor signaling pathway, which is involved in major physiological mechanisms such as liver regeneration. We investigate early hepatic metabolic events produced by partial hepatectomy (PHx) for PTP1B deficient (PTP1B KO) and wild type (WT) mice using proton nuclear magnetic resonance spectroscopy. Metabolic response of the two genotypes produced 24 h upon PHx is compared using magic angle spinning high-resolution nuclear magnetic resonance ((1)H-HR-MAS-NMR) on intact liver tissues. In addition, genotype-associated metabolic profile changes were monitored during the first 48 h after PHx using high-resolution nuclear magnetic resonance ((1)H-HR-NMR) on liver extracts. A marked increase of lipid-related signals in regenerating livers was observed after 24 h PHx in either intact tissues or liver extracts studies. In spite of this common initial metabolic response, results obtained 48 h after PHx on liver extracts indicate a genotype-differential metabolic pattern. This metabolic pattern resulted in line with well known regenerative features such as more sustained cell proliferation, a better management of lipids as energy fuel and lessened liver injury for PTP1B KO mice as compared to WT. Taken together, these findings suggest the metabolic basis to the pivotal role of PTP1B in liver regeneration. PMID:23246914

  5. B. Sc. Examination 2005 MAS 335 Cryptography

    E-print Network

    Banaji,. Murad

    B. Sc. Examination 2005 MAS 335 Cryptography Duration: 2 hours Date and time: 6 May 2005, 10) Explain the difference between cryptography, steganography, and cryptanaly- sis. [3] (b) Explain the terms

  6. UBV photometry of HR 1176

    NASA Astrophysics Data System (ADS)

    Demircan, O.; Ozeren, F. F.; Derman, E.

    1989-12-01

    This paper presents photoelectric UBV observations of the suspected Ca II emission line star HR 1176. A period analysis of the observations by using the method of Shell-Metzner failed to yield any true period which is probably due to the large gaps in the observations, low-amplitude variation, and the nonconstancy of the period, or there may be no regular light variation. A visual inspection of the present observations shows no systematic or abrupt variability except some scatter. However, a long period eclipsing nature of HR 1176 cannot be ruled out.

  7. [superscript 15]N-[superscript 15]N Proton Assisted Recoupling in Magic Angle Spinning NMR

    E-print Network

    Lewandowski, Jozef R.

    We describe a new magic angle spinning (MAS) NMR experiment for obtaining [superscript 15]N?[superscript 15]N correlation spectra. The approach yields direct information about the secondary and tertiary structure of proteins, ...

  8. Data provided: Formula Sheet MAS140/151/152

    E-print Network

    Data provided: Formula Sheet MAS140/151/152 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2013­2014 MAS140 Mathematics (Chemical) MAS151 Civil Engineering Mathematics MAS152 Essential + 2x + 3)e-x using l'Hôpital's rule. A5 Find all the complex numbers z for which z3 = -1 + i. MAS140

  9. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoacetica metabolic profiles.

    PubMed

    Xue, Junfeng; Isern, Nancy G; Ewing, R James; Liyu, Andrei V; Sears, Jesse A; Knapp, Harlan; Iversen, Jens; Sisk, Daniel R; Ahring, Birgitte K; Majors, Paul D

    2014-10-01

    An in situ nuclear magnetic resonance (NMR) bioreactor was developed and employed to monitor microbial metabolism under batch growth conditions in real time. We selected Moorella thermoacetica ATCC 49707 as a test case. M. thermoacetica (formerly Clostridium thermoaceticum) is a strictly anaerobic, thermophilic, acetogenic, gram-positive bacterium with potential for industrial production of chemicals. The metabolic profiles of M. thermoacetica were characterized during growth in batch mode on xylose (a component of lignocellulosic biomass) using the new generation NMR bioreactor in combination with high-resolution NMR (HR-NMR) spectroscopy. In situ NMR measurements were performed using water-suppressed H-1 NMR spectroscopy at 500 MHz, and aliquots of the bioreactor contents were taken for 600-MHz HR-NMR spectroscopy at specific intervals to confirm metabolite identifications and expand metabolite coverage. M. thermoacetica demonstrated the metabolic potential to produce formate, ethanol, and methanol from xylose, in addition to its known capability of producing acetic acid. Real-time monitoring of bioreactor conditions showed a temporary pH decrease, with a concomitant increase in formic acid during exponential growth. Fermentation experiments performed outside of the magnet showed that the strong magnetic field employed for NMR detection did not significantly affect cell metabolism. Use of the in situ NMR bioreactor facilitated monitoring of the fermentation process, enabling identification of intermediate and endpoint metabolites and their correlation with pH and biomass produced during culture growth. Real-time monitoring of culture metabolism using the NMR bioreactor in combination with HR-NMR spectroscopy will allow optimization of the metabolism of microorganisms producing valuable bioproducts. PMID:24946863

  10. High-temperature in situ magic-angle spinning NMR studies of chemical reactions on catalysts

    E-print Network

    Oliver, F. Gregory

    1992-01-01

    on Catalysts. (August 1992) F. Gregory Oliver, B. S. , University of Texas at Tyler Chair of Advisory Committee: Dr. J. F. Haw A novel high-temperature magic-angle spinning (MAS) nuclear magnetic resonance (NMR) probe design for in situ catalysis... TABLE OF CONTENTS PAGE ABSTRACI' ACKNOWLEDGEMENT DEDICATION TABLE OF CONTENTS LIST OF FIGURES CHAPTER I INTRODUCTION II NMRTHEORY III EXPERIMENTAL High-Temperature MAS Module Heater and Probe Sample Preparation NMR Spectroscopy IV RESULTS...

  11. hr

    E-print Network

    our ?ght, the Heaven fcemeth to be joyned with the water, when we are at Sea, ..... towards the Smith of the Compa?'e : and this is when the Sun and the lhadows ..... The fame day and year fuppol'e that fome man found the Sun in 77 degrees ...

  12. Fundamental Science Tools for Geologic Carbon Sequestration and Mineral Carbonation Chemistry: In Situ Magic Angle Spinning (MAS) Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Hoyt, D. W.; Turcu, R. V.; Sears, J. A.; Rosso, K. M.; Burton, S. D.; Kwak, J.; Felmy, A. R.; Hu, J.

    2010-12-01

    GCS is one of the most promising ways of mitigating atmospheric greenhouse gases. Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly reactions occurring in low-water supercritical CO2(scCO2)-dominated environments where the chemistry has not been adequately explored. In situ probes that provide molecular-level information is desirable for investigating mechanisms and rates of GCS mineral carbonation reactions. MAS-NMR is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, or a supercritical state, or a mixture thereof. However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS rotor. In this work, we report development of a unique high pressure MAS NMR capability, and its application to mineral carbonation chemistry in scCO2 under geologically relevant temperatures and pressures. Our high pressure MAS rotor has successfully maintained scCO2 conditions with minimal leakage over a period of 72 hours. Mineral carbonation reactions of a model magnesium silicate (forsterite) reacted with 96 bars scCO2 containing varying amounts of H2O (both below and above saturation of the scCO2) were investigated at 50?C. Figure 1 shows typical in situ 13C MAS NMR spectra demonstrating that the peaks corresponding to the reactants, intermediates, and the magnesium carbonation products are all observed in a single spectrum. For example, the scCO2 peak is located at 126.1 ppm. Reaction intermediates include the aqueous species HCO3-(160 ppm), partially hydrated/hydroxylated magnesium carbonates(166-168 ppm), and can easily be distinguished from final product magnesite(170 ppm). The new capability and this model mineral carbonation process will be overviewed in light of fundamental geochemical science needs for GCS implementation. Figure 1. 13C MAS NMR spectra of forsterite exposed to scCO2 300% saturated with water at 96 bars and 50°C. MAS rate=2.1 kHz.

  13. Millimeter-Wave Atmospheric Sounder (MAS)

    NASA Technical Reports Server (NTRS)

    Hartmann, G. K.

    1988-01-01

    MAS is a remote sensing instrument for passive sounding (limb sounding) of the earth's atmosphere from the Space Shuttle. The main objective of the MAS is to study the composition and dynamic structure of the stratosphere, mesosphere, and lower thermosphere in the height range 20 to 100 km, the region known as the middle atmosphere. The MAS will be flown on the Atmospheric Laboratory for Applications and Science (ATLAS 1) NASA mission scheduled for late 1990. The Millimeter-Wave Atmospheric Sounder will provide, for the first time, information obtained simultaneously on the temperature and on ozone concentrations in the 20 to 90 km altitude region. The information will cover a large area of the globe, will have high accuracy and high vertical resolution, and will cover both day and night times. Additionally, data on the two important molecules, H2O and ClO, will also be provided.

  14. C NMR Spectra C NMR Spectra

    E-print Network

    Collum, David B.

    S16 1 H and 13 C NMR Spectra (see p S3) Me N-i-Pr #12;S17 1 H and 13 C NMR Spectra (see p S3) Me NBn #12;S18 1 H and 13 C NMR Spectra (see p S4) NBn #12;S19 1 H and 13 C NMR Spectra (see p S4) NBn Me Me Me #12;S20 1 H and 13 C NMR Spectra (see p S4) N-n-Bu Me Me Me #12;S21 1 H and 13 C NMR Spectra

  15. Investigation of fluorocarbon blowing agents in insulating polymer foams by 19F NMR imaging

    Microsoft Academic Search

    C. A. Fyfe; Z. Mei; H. Grondey

    1996-01-01

    Currently, there is no reliable and readily accessible technique with which the distribution and diffusion of blowing agents in rigid insulating foams can be detected and monitored. In this paper, we demonstrate that 19F NMR microscopic imaging together with 19F solid-state MAS NMR spectroscopy is ideally suited for such measurements and yield quantitatively reliable information that will be critical to

  16. Accelerating Nuclear Magnetic Resonance (NMR) Analysis of Soil Organic Matter with Dynamic Nuclear Polarization (DNP) Enhancement

    NASA Astrophysics Data System (ADS)

    Normand, A. E.; Smith, A. N.; Long, J. R.; Reddy, K. R.

    2014-12-01

    13C magic angle spinning (MAS) solid state Nuclear Magnetic Resonance (ssNMR) has become an essential tool for discerning the chemical composition of soil organic matter (SOM). However, the technique is limited due to the inherent insensitivity of NMR resulting in long acquisition times, especially for low carbon (C) soil. The pursuits of higher magnetic fields or concentrating C with hydrofluoric acid are limited solutions for signal improvement. Recent advances in dynamic nuclear polarization (DNP) have addressed the insensitivity of NMR. DNP utilizes the greater polarization of an unpaired electron in a given magnetic field and transfers that polarization to an NMR active nucleus of interest via microwave irradiation. Signal enhancements of up to a few orders of magnitude have been achieved for various DNP experiments. In this novel study, we conduct DNP 13C cross-polarization (CP) MAS ssNMR experiments of SOM varying in soil C content and chemical composition. DNP signal enhancements reduce the experiment run time allowing samples with low C to be analyzed in hours rather than days. We compare 13C CP MAS ssNMR of SOM with multiple magnetic field strengths, hydrofluoric acid treatment, and novel DNP approaches. We also explore DNP surface enhanced NMR Spectroscopy (SENP) to determine the surface chemistry of SOM. The presented results and future DNP MAS ssNMR advances will lead to further understanding of the nature and processes of SOM.

  17. Enhanced resolution and quantitation from `ultrahigh' eld NMR spectroscopy of glasses

    E-print Network

    Puglisi, Joseph

    for nuclear magnetic resonance (NMR) (e.g., 14.1 and 18.8 T) can enhance both resolution and sensitivity ®elds. Examples include site distinction of multiple boron groupings in 11 B MAS NMR spectra of borate in the devel- opment of structural and dynamical models of glass structure [1±3]. The chemical shift is a sen

  18. Magic-angle spinning solid-state multinuclear NMR on low-field instrumentation.

    PubMed

    Sørensen, Morten K; Bakharev, Oleg; Jensen, Ole; Jakobsen, Hans J; Skibsted, Jørgen; Nielsen, Niels Chr

    2014-01-01

    Mobile and cost-effective NMR spectroscopy exploiting low-field permanent magnets is a field of tremendous development with obvious applications for arrayed large scale analysis, field work, and industrial screening. So far such demonstrations have concentrated on relaxation measurements and lately high-resolution liquid-state NMR applications. With high-resolution solid-state NMR spectroscopy being increasingly important in a broad variety of applications, we here introduce low-field magic-angle spinning (MAS) solid-state multinuclear NMR based on a commercial ACT 0.45 T 62 mm bore Halbach magnet along with a homebuilt FPGA digital NMR console, amplifiers, and a modified standard 45 mm wide MAS probe for 7 mm rotors. To illustrate the performance of the instrument and address cases where the low magnetic field may offer complementarity to high-field NMR experiments, we demonstrate applications for (23)Na MAS NMR with enhanced second-order quadrupolar coupling effects and (31)P MAS NMR where reduced influence from chemical shift anisotropy at low field may facilitate determination of heteronuclear dipole-dipole couplings. PMID:24291330

  19. A Hybrid Intelligent Learning Algorithm in MAS

    Microsoft Academic Search

    SHUJUN ZHANG; QINGCHUN MENG; WEN ZHANG; CHANGHONG SONG

    Machine learning is a major branch of AI and a main research direction of multi-agent systems (MAS). With the emergence of various new complex systems, agent's individual ability and the system's intelligence level are urgently to be improved. Age nt learning methods and agent architecture are stud ied in this paper and a new hybrid intelligent learning al gorithm based

  20. MAS 335 Cryptography Notes 1 Spring 2008

    E-print Network

    Banaji,. Murad

    MAS 335 Cryptography Notes 1 Spring 2008 Introduction Cryptography refers to the art of protecting, the term cryptography is often used colloquially to include both cryptography and cryptanalysis. In these notes I will use the term cryptography exclusively. Cryptography is closely related to another part

  1. Soils, Pores, and NMR

    Microsoft Academic Search

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

    2010-01-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of

  2. MAS: Minorities in the Aquatic Sciences

    NSDL National Science Digital Library

    The Minorities in the Aquatic Sciences (MAS) program was initiated in 2001 to establish a database and electronic resources to link minority students interested in the aquatic sciences and to enhance their participation in aquatic science community activities and careers. The site includes a Minority Student Directory by which minority high school (junior and senior years), undergraduate and graduate students may introduce themselves and their work to the community-at-large. The MAS list also links minority students with the larger community by posting job, academic and other announcements of opportunity. The Profiles of Scientists section highlights individual achievements and perspectives with a goal of identifying minority mentors, role models, and established professionals. Also included are links to related publications and organizations.

  3. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS370 Sampling Theory and Design of

    E-print Network

    MAS370 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012­2013 MAS370 Sampling Theory) to be completed by student MAS370 1 Turn Over #12;MAS370 Blank MAS370 2 Continued #12;MAS370 1 A small experiment additional necessary parameter constraints. (3 marks) MAS370 3 Turn Over #12;MAS370 2 An experiment

  4. NMR Studies of Cartilage Dynamics, Diffusion, Degradation

    NASA Astrophysics Data System (ADS)

    Huster, Daniel; Schiller, Jürgen; Naji, Lama; et al.

    An increasing number of people is suffering from rheumatic diseases, and, therefore, methods of early diagnosis of joint degeneration are urgently required. For their establishment, however, an improved knowledge about the molecular organisation of cartilage would be helpful. Cartilage consists of three main components: Water, collagen and chondroitin sulfate (CS) that is (together with further polysaccharides and proteins) a major constituent of the proteoglycans of cartilage. 1H and 13C MAS (magic-angle spinning) NMR (nuclear magnetic resonance) opened new perspectives for the study of the macromolecular components in cartilage. We have primarily studied the mobilities of CS and collagen in bovine nasal and pig articular cartilage (that differ significantly in their collagen/polysaccharide content) by measuring 13C NMR relaxation times as well as the corresponding 13C CP (cross polarisation) MAS NMR spectra. These data clearly indicate that the mobility of cartilage macromolecules is broadly distributed from almost completely rigid (collagen) to highly mobile (polysaccharides), which lends cartilage its mechanical strength and shock-absorbing properties.

  5. Nanosatellites for earth environmental monitoring: The MicroMAS project

    Microsoft Academic Search

    W. Blackwell; G. Allen; C. Galbraith; T. Hancock; R. Leslie; I. Osaretin; L. Retherford; M. Scarito; C. Semisch; M. Shields; M. Silver; D. Toher; K. Wight; D. Miller; K. Cahoy; N. Erickson

    2012-01-01

    The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a 3D cubesat (30×10×10 cm, 4kg) hosting a passive microwave spectrometer operating near the 118.75-GHz oxygen absorption line. The focus of the first MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit at approximately 500-km altitude. A MicroMAS flight unit is currently being developed in

  6. Rock Art Interpretation within Indiana MAS Viviana Mascardi1

    E-print Network

    Mascardi, Viviana

    Rock Art Interpretation within Indiana MAS Viviana Mascardi1 , Vincenzo Deufemia2 , Damiano in the domain of Mount Bego's pre- historic rock art (southern French Alps). The way Indiana MAS holons the first results achieved within the project "Indiana MAS and the Digital Preservation of Rock Carvings

  7. 48 CFR 538.271 - MAS contract awards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...System 4 2014-10-01 2014-10-01 false MAS contract awards. 538.271 Section 538.271...Administering Federal Supply Schedules 538.271 MAS contract awards. (a) MAS awards will be for commercial items as defined...

  8. MAS275 Probability Modelling Example 24: Dr Jonathan Jordan

    E-print Network

    Jordan, Jonathan

    MAS275 Probability Modelling Example 24: Monopoly Dr Jonathan Jordan School of Mathematics and Statistics, University of Sheffield Spring Semester, 2014 Dr Jonathan Jordan MAS275 Probability Modelling #12 are labelled with a street or other location. Dr Jonathan Jordan MAS275 Probability Modelling #12;Monopoly

  9. MONITORED ACADEMIC STATUS (MAS) Causal Event(s)

    E-print Network

    Paulsson, Johan

    MONITORED ACADEMIC STATUS (MAS) Causal Event(s) or triggers Remedial Action and Requirements Resources and approved by PRB. Students on MAS may not serve on appointed committees at the School. At an appropriate time during the period of MAS the student must work with the Society to prepare a written account

  10. 2. MONITORED ACADEMIC STATUS (MAS) Causal Event(s)

    E-print Network

    Goodrich, Lisa V.

    2. MONITORED ACADEMIC STATUS (MAS) Causal Event(s) or triggers Remedial Action and Requirements and approved by PRB. Students on MAS may not serve on appointed committees at the School, are required to limit time during the period of MAS the student must work with the Society to prepare a written account

  11. 48 CFR 538.271 - MAS contract awards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...System 4 2013-10-01 2013-10-01 false MAS contract awards. 538.271 Section 538.271...Administering Federal Supply Schedules 538.271 MAS contract awards. (a) MAS awards will be for commercial items as defined...

  12. 48 CFR 538.271 - MAS contract awards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...System 4 2012-10-01 2012-10-01 false MAS contract awards. 538.271 Section 538.271...Administering Federal Supply Schedules 538.271 MAS contract awards. (a) MAS awards will be for commercial items as defined...

  13. 48 CFR 538.271 - MAS contract awards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...System 4 2011-10-01 2011-10-01 false MAS contract awards. 538.271 Section 538.271...Administering Federal Supply Schedules 538.271 MAS contract awards. (a) MAS awards will be for commercial items as defined...

  14. Matrise universitaire d'tudes avances (MAS) en physique

    E-print Network

    Loewith, Robbie

    Maîtrise universitaire d'études avancées (MAS) en physique CONDITIONS GENERALES Art. E 3 ­ Maîtrise universitaire d'études avancées (MAS) en physique 1. La Faculté décerne un master of advanced studies (MAS) en physique dont la traduction française à usage interne est « maîtrise universitaire d'études avancées en

  15. Fundamentals of NMR

    NSDL National Science Digital Library

    James, Thomas L.

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

  16. Microcoils and microsamples in solid-state NMR.

    PubMed

    Takeda, Kazuyuki

    2012-01-01

    Recent reports on microcoils are reviewed. The first part of the review includes a discussion of how the geometries of the sample and coil affect the NMR signal intensity. In addition to derivation of the well-known result that the signal intensity increases as the coil size decreases, the prediction that dilution of a small sample with magnetically inert matter leads to better sensitivity if a tiny coil is not available is given. The second part of the review focuses on the issues specific to solid-state NMR. They include realization of magic-angle spinning (MAS) using a microcoil and harnessing of such strong pulses that are feasible only with a microcoil. Two strategies for microcoil MAS, the piggyback method and magic-angle coil spinning (MACS), are reviewed. In addition, MAS of flat, disk-shaped samples is discussed in the context of solid-state NMR of small-volume samples. Strong RF irradiation, which has been exploited in wide-line spectral excitation, multiple-quantum MAS (MQMAS), and dipolar decoupling experiments, has been accompanied by new challenges regarding the Bloch-Siegert effect, the minimum time resolution of the spectrometer, and the time scale of pulse transient effects. For a possible solution to the latter problem, recent reports on active compensation of pulse transients are described. PMID:23083521

  17. New insights on the structure of algaenan from Botryoccocus braunii race A and its hexane insoluble botryals based on multidimensional NMR spectroscopy and electrospray-mass spectrometry techniques.

    PubMed

    Simpson, Andre J; Zang, Xu; Kramer, Robert; Hatcher, Patrick G

    2003-03-01

    Through solution state NMR spectroscopy and quadrupole-time-of-flight mass spectrometry (Q-TOF MS) studies of the hexane insoluble botryal extract of the algae Botryococcus braunii race A, coupled with high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy of the algaenan from this alga, it has been possible to advance the structural understanding of this geochemically important biopolymer. It was found that the hexane insoluble botryals in this study constitute a mixture of low molecular weight unsaturated aliphatic aldehydes and unsaturated hydrocarbons with an average chain length of about 40 carbons. Exact assignments were provided for many of the structural units present and describe the average constitution of the mixture as a whole. Reticulation of the low molecular weight chains via acetal and ester links explains the primary make up of algaenan. In this study, it is concluded that the algaenan results from the reticulation of low molecular weight hexane insoluble botryal species rather than the polyaldehyde as previously observed in studies of algae at alternate stages of their growth cycle. PMID:12620332

  18. HR 160 performance in coal gasification equipment

    SciTech Connect

    Whittaker, G.S. [Eastman Chemical Co., Kingsport, TN (United States)

    1995-12-31

    An alloy 825 water-cooled component failed by sulfidation enhanced thermal fatigue in a commercial coal gasification system. In an attempt to improve component life the material of construction was changed to Haynes HR-160. After several years of operating experience the HR-160 has not provided the desired improvement. Analysis shows the failure mechanism has remained the same.

  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. Abstract--Given High Resolution Magic Angle Spinning (HR-MAS) signals from several glioblastoma tumor subjects,

    E-print Network

    tumor subjects, the goal is to differentiate between tumor tissue types by separating the different for obtaining characteristic profiles for necrosis, high cellular tumor and border tumor tissue, and providing the contribution (abundance) of each tumor tissue to the profile of the spectra. The problem is formulated as a non

  1. Tridentate Phosphine Linkers for Immobilized Catalysts: Development and Characterization of Immobilized Rhodium Complexes and Solid-State NMR Studies of Polymers

    E-print Network

    Guenther, Johannes 1983-

    2012-08-16

    ) polymers. 13C CP/MAS (cross polarization with magic angle spinning) NMR and IR spectroscopy reveal that PEEK polymers show no detectable chemical change on the molecular level, while PPS polymers display signs of oxidation of the thioether group...

  2. CHHC and [superscript 1]H–[superscript 1]H magnetization exchange: Analysis by experimental solid-state NMR and 11-spin density-matrix simulations

    E-print Network

    Aluas, Mihaela

    A protocol is presented for correcting the effect of non-specific cross-polarization in CHHC solid-state MAS NMR experiments, thus allowing the recovery of the [superscript 1]H–[superscript 1]H magnetization exchange ...

  3. Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100 kHz MAS.

    PubMed

    Nishiyama, Y; Kobayashi, T; Malon, M; Singappuli-Arachchige, D; Slowing, I I; Pruski, M

    2015-01-01

    Two-dimensional (1)H{(13)C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in (1)H dimension without resorting to (1)H-(1)H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. The HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone. PMID:25773137

  4. Immobilization of Bisphosphinoamine Linkers on Silica: Identification of Previously Unrecognized Byproducts via

    E-print Network

    Bluemel, Janet

    Byproducts via 31P CP/MAS and Suspension HR-MAS Studies T. Posset, F. Rominger, and J. Blu¨mel* Organisch P CP/MAS and suspension HR-MAS NMR. Besides the desired immobilization, two main side reactions have (MAS) frequencies11 for our applications in order to improve the signal-to-noise ratio (S/ N

  5. Deuterated peptides and proteins: structure and dynamics studies by MAS solid-state NMR.

    PubMed

    Reif, Bernd

    2012-01-01

    Perdeuteration and back substitution of exchangeable protons in microcrystalline proteins, in combination with recrystallization from D(2)O-containing buffers, significantly reduce (1)H, (1)H dipolar interactions. This way, amide proton line widths on the order of 20 Hz are obtained. Aliphatic protons are accessible either via specifically protonated precursors or by using low amounts of H(2)O in the bacterial growth medium. The labeling scheme enables characterization of structure and dynamics in the solid-state without dipolar truncation artifacts. PMID:22167680

  6. Lipid bilayer-bound conformation of an integral membrane beta barrel protein by multidimensional MAS NMR

    E-print Network

    Eddy, Matthew T.

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa ?-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and ...

  7. The LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system

    NASA Astrophysics Data System (ADS)

    Maire, A.-L.; Skemer, A. J.; Hinz, P. M.; Desidera, S.; Esposito, S.; Gratton, R.; Marzari, F.; Skrutskie, M. F.; Biller, B. A.; Defrère, D.; Bailey, V. P.; Leisenring, J. M.; Apai, D.; Bonnefoy, M.; Brandner, W.; Buenzli, E.; Claudi, R. U.; Close, L. M.; Crepp, J. R.; De Rosa, R. J.; Eisner, J. A.; Fortney, J. J.; Henning, T.; Hofmann, K.-H.; Kopytova, T. G.; Males, J. R.; Mesa, D.; Morzinski, K. M.; Oza, A.; Patience, J.; Pinna, E.; Rajan, A.; Schertl, D.; Schlieder, J. E.; Su, K. Y. L.; Vaz, A.; Ward-Duong, K.; Weigelt, G.; Woodward, C. E.

    2015-04-01

    Context. Astrometric monitoring of directly imaged exoplanets allows the study of their orbital parameters and system architectures. Because most directly imaged planets have long orbital periods (>20 AU), accurate astrometry is challenging when based on data acquired on timescales of a few years and usually with different instruments. The LMIRCam camera on the Large Binocular Telescope is being used for the LBT Exozodi Exoplanet Common Hunt (LEECH) survey to search for and characterize young and adolescent exoplanets in L' band (3.8 ?m), including their system architectures. Aims: We first aim to provide a good astrometric calibration of LMIRCam. Then, we derive new astrometry, test the predictions of the orbital model of 8:4:2:1 mean motion resonance proposed for the system, and perform new orbital fitting of the HR 8799 bcde planets. We also present deep limits on a putative fifth planet inside the known planets. Methods: We use observations of HR 8799 and the ?1 Ori C field obtained during the same run in October 2013. Results: We first characterize the distortion of LMIRCam. We determine a platescale and a true north orientation for the images of 10.707 ± 0.012 mas/pix and -0.430 ± 0.076°, respectively. The errors on the platescale and true north orientation translate into astrometric accuracies at a separation of 1'' of 1.1 mas and 1.3 mas, respectively. The measurements for all planets agree within 3? with a predicted ephemeris. The orbital fitting based on the new astrometric measurements favors an architecture for the planetary system based on 8:4:2:1 mean motion resonance. The detection limits allow us to exclude a fifth planet slightly brighter or more massive than HR 8799 b at the location of the 2:1 resonance with HR 8799 e (~9.5 AU) and about twice as bright as HR 8799 cde at the location of the 3:1 resonance with HR 8799 e (~7.5 AU). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.

  8. V1 form to HR (payroll only)

    E-print Network

    diem, lodging, shipping, medical insurance, shuttle, etc. ** Administrative costs allowed (visa, Fed Ex,ins) THE VISITOR PROCESS Temp Liv per diem form to Travel Med ins info to HR CONTACTAPPROPRIATEOFFICESORBUSINESSES & Travel (payroll & other expenses) Visitor Process Matrix #12;

  9. Proton-Detected Solid-State NMR Spectroscopy of Bone with Ultrafast Magic Angle Spinning

    PubMed Central

    Mroue, Kamal H.; Nishiyama, Yusuke; Kumar Pandey, Manoj; Gong, Bo; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2015-01-01

    While obtaining high-resolution structural details from bone is highly important to better understand its mechanical strength and the effects of aging and disease on bone ultrastructure, it has been a major challenge to do so with existing biophysical techniques. Though solid-state NMR spectroscopy has the potential to reveal the structural details of bone, it suffers from poor spectral resolution and sensitivity. Nonetheless, recent developments in magic angle spinning (MAS) NMR technology have made it possible to spin solid samples up to 110?kHz frequency. With such remarkable capabilities, 1H-detected NMR experiments that have traditionally been challenging on rigid solids can now be implemented. Here, we report the first application of multidimensional 1H-detected NMR measurements on bone under ultrafast MAS conditions to provide atomistic-level elucidation of the complex heterogeneous structure of bone. Our investigations demonstrate that two-dimensional 1H/1H chemical shift correlation spectra for bone are obtainable using fp-RFDR (finite-pulse radio-frequency-driven dipolar recoupling) pulse sequence under ultrafast MAS. Our results infer that water exhibits distinct 1H?1H dipolar coupling networks with the backbone and side-chain regions in collagen. These results show the promising potential of proton-detected ultrafast MAS NMR for monitoring structural and dynamic changes caused by mechanical loading and disease in bone. PMID:26153138

  10. Understanding the NMR shifts in paramagnetic transition metal oxides using density functional theory calculations

    Microsoft Academic Search

    D. Carlier; M. Ménétrier; C. P. Grey; C. Delmas; G. Ceder

    2003-01-01

    The 6,7Li MAS NMR spectra of lithium ions in paramagnetic host materials are extremely sensitive to number and nature of the paramagnetic cations in the Li local environments and large shifts (Fermi contact shifts) are often observed. The work presented in this paper aims to provide a rational basis for the interpretation of the 6,7Li NMR shifts, as a function

  11. 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.

  12. Understanding NMR Spectroscopy

    NSDL National Science Digital Library

    Keeler, James

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

  13. Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR NMR correlation

    NASA Astrophysics Data System (ADS)

    Ruan, Qing-Xia; Zhou, Ping

    2008-07-01

    In the present work, we investigated Na + ion effect on the silk fibroin (SF) conformation. Samples are Na +-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na +] increases, partial silk fibroin conformation transit from helix-form to ?-form at certain Na + ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR-NMR correlation analysis reveals that silk fibroin undergoes several intermediate states during its conformation transition process as [Na +] increase. The appearance order of the intermediates is followed as: helix and/or random coil ? helix-like ? ?-sheet-like ? ?-sheet, which is the same as that produced by pH decrease from 6.8 to 4.8 in the resultant regenerated silk fibroin films. The binding sites of Na + to silk fibroin might involve the carbonyl oxygen atom of certain amino acids sequence which could promote the formation of ?-sheet conformation. Since the Na +sbnd O bond is weak, the ability of Na + inducing the secondary structure transition is weaker than those of Ca 2+, Cu 2+ and even K +. It is maybe a reason why the sodium content is much lower than potassium in the silkworm gland.

  14. MAS445 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012-2013

    E-print Network

    MAS445 MAS445 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012 questions, only your best four will be counted. #12;MAS445 MAS445 2 Continued 1. Let - -- - = 410 calculate the values of u at the grid points for 0625.0=t . (10 marks) #12;MAS445 MAS445 3 Turn Over 2. (i

  15. MAS340 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010-2011

    E-print Network

    MAS340 MAS340 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010, only your best four will be counted. #12;MAS340 MAS340 2 Continued 1. Let 540 252 025 A . (i) Find for 5.0t . (10 marks) #12;MAS340 MAS340 3 Turn Over 2. (i) Let , 10200 11010 01101 00210 A 970196202

  16. MAS244 Turn over SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2012 2013

    E-print Network

    MAS244 MAS244 Turn over SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2012 ­ 2013 Registration number from U-Card (9 digits) to be completed by student #12;MAS244 MAS244 2 Continued Blank Page #12;MAS244 MAS244 3 Turn over 1. (i) Show that the three planes 01363,142,1422 =++-=--=-- zyxzyxzyx

  17. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS113 Introduction to Probability and Statistics 2 hours

    E-print Network

    MAS113 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012­2013 MAS113 Introduction from U-Card (9 digits) to be completed by student MAS113 1 Turn Over #12;MAS113 Blank MAS113 2 Continued #12;MAS113 1 Let S be the set of outcomes that could result from rolling a six-sided die: S = {1

  18. MAS445 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010-2011

    E-print Network

    MAS445 MAS445 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010 questions, only your best four will be counted. #12;MAS445 MAS445 2 Continued 1. Let - -- - = 540;MAS445 MAS445 3 Turn Over 2. (i) Let , 10200 11010 01101 00210 - -- -- - =A

  19. MAS340 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012-2013

    E-print Network

    MAS340 MAS340 1 Turn Over SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012, only your best four will be counted. Graph paper is provided for question 5. #12;MAS340 MAS340 2) #12;MAS340 MAS340 3 Turn Over 2. (i) Let = - -- - = 862 393 137 , 320 131 013 BA

  20. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS473 Extended linear models 2 hours

    E-print Network

    MAS473 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012­2013 MAS473 Extended linear models the hall Registration number from U-Card (9 digits) to be completed by student MAS473 1 Turn Over #12;MAS473 Blank MAS473 2 Continued #12;MAS473 1 An experiment has been conducted to measure the fuel economy

  1. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS271 Methods for differential Equations 2 hours

    E-print Network

    MAS271 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2011­2012 MAS271 Methods on the stability of the point (0,0). (6 marks) MAS271 1 Question 2 continued on next page #12;MAS271 (continued marks) MAS271 2 Continued #12;MAS271 " (i) Show that the substitution z(x) = y(x) x renders Bessel

  2. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS273 Statistical Modelling 2 hours

    E-print Network

    MAS273 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2011­2012 MAS273 Statistical Modelling. MAS273 1 Turn Over #12;MAS273 1 In a survey conducted by the Wall Street Journal, adults who regularly would inspect to test this assumption. (3 marks) MAS273 2 Question 1 continued on next page #12;MAS273 1

  3. MAS244 1 Turn over SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2010-2011

    E-print Network

    MAS244 MAS244 1 Turn over SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2010 the planes intersect when a has this value? (8 marks) #12;MAS244 MAS244 2 Continued 2. Let 10015532 01054213 marks) (v) Find a non-zero vector in the kernel of T . (5 marks) #12;MAS244 MAS244 3 Turn over 3. Let

  4. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS271 Methods for differential Equations 2 hours

    E-print Network

    MAS271 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010­2011 MAS271 Methods. (6 marks) MAS271 1 Turn Over #12;MAS271 Find the equilibrium points for the following equation marks) MAS271 2 Question 4 continued on next page #12;MAS271 " (continued) (iii) By means

  5. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS370 Sampling Theory and Design of

    E-print Network

    MAS370 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2013­2014 MAS370 Sampling Theory not remove it from the hall Registration number from U-Card (9 digits) to be completed by student MAS370 1 Turn Over #12;MAS370 Blank MAS370 2 Continued #12;MAS370 1 A small experiment is being conducted

  6. Meconium aspiration syndrome (MAS) — Where do we go? Research perspectives

    Microsoft Academic Search

    Pekka O. Kääpä

    2009-01-01

    The pathogenetic cascade of meconium aspiration syndrome (MAS) in newborn infants is complex and still incompletely studied. The variable clinical presentation of MAS is basically connected with variation of the amount and consistency of aspirated meconium and also its distribution within the affected lungs. The contributing role of other factors, like intrauterine fetal compromises, lung maturity at the time of

  7. 48 CFR 538.272 - MAS price reductions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Regulations System 4 2011-10-01 2011-10-01 false MAS price reductions. 538.272 Section 538.272 Federal...Establishing and Administering Federal Supply Schedules 538.272 MAS price reductions. (a) Section 552.238-75,...

  8. 48 CFR 538.272 - MAS price reductions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Regulations System 4 2010-10-01 2010-10-01 false MAS price reductions. 538.272 Section 538.272 Federal...Establishing and Administering Federal Supply Schedules 538.272 MAS price reductions. (a) Section 552.238-75,...

  9. 48 CFR 538.272 - MAS price reductions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...Regulations System 4 2014-10-01 2014-10-01 false MAS price reductions. 538.272 Section 538.272 Federal...Establishing and Administering Federal Supply Schedules 538.272 MAS price reductions. (a) Section 552.238-75,...

  10. 48 CFR 538.272 - MAS price reductions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...Regulations System 4 2013-10-01 2013-10-01 false MAS price reductions. 538.272 Section 538.272 Federal...Establishing and Administering Federal Supply Schedules 538.272 MAS price reductions. (a) Section 552.238-75,...

  11. 48 CFR 538.272 - MAS price reductions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...Regulations System 4 2012-10-01 2012-10-01 false MAS price reductions. 538.272 Section 538.272 Federal...Establishing and Administering Federal Supply Schedules 538.272 MAS price reductions. (a) Section 552.238-75,...

  12. Flow measurements by NMR

    Microsoft Academic Search

    A. Caprihan; E. Fukushima

    1990-01-01

    We review the current status of liquid flow velocity studies by pulsed nuclear magnetic resonance (NMR). NMR is a non-invasive method that is most sensitive to protons, so that, combined with the recently developed imaging capabilities, it is now possible to obtain images of hydrodynamic parameters of interest for most common liquids. Such parameters can include, besides velocity, diffusion coefficient,

  13. NMR Spectroscopy - Theory

    NSDL National Science Digital Library

    Lord, J.R.

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

  14. 1 HR Strategy 2010 2012 / January 2011 Update University of Kent's HR Strategy 2010 2012

    E-print Network

    Banaji,. Murad

    made in: 6. Ensuring HR Systems and Processes are Efficient and Effective Strategy creation record of encouraging staff to achieve their ambitions. The University of Kent's HR Strategy was launched of the Strategy is on the themes of: 1. Developing Leadership Capabilities 2. Providing People Management

  15. Basics of NMR

    NSDL National Science Digital Library

    Hornak, Joseph P.

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

  16. RHODOPSIN-LIPID INTERACTIONS STUDIED BY NMR

    PubMed Central

    Soubias, Olivier; Gawrisch, Klaus

    2012-01-01

    The biophysical properties of the lipid matrix are known to influence function of integral membrane proteins. We report on a sample preparation method for reconstitution of membrane proteins which uses porous anodic aluminum oxide (AAO) filters with 200 nm-wide pores of high density. The substrate permits formation of tubular, single membranes that line the inner surface of pores. One square centimeter of filter with a thickness of 60 ?m yields on the order of 500 cm2 of solid-supported single bilayer surface, sufficient for NMR studies. The tubular bilayers are free of detergent, fully hydrated and accessible for ligands from one side of the membrane. The use of AAO filters greatly improves reproducibility of the reconstitution process such that the influence of protein on lipid order parameters can be studied with high resolution. As an example, results for the G protein-coupled receptor of class A, bovine rhodopsin, are shown. By 2H NMR order parameter measurements it is detected that rhodopsin insertion elastically deforms membranes near the protein. Furthermore, by 1H saturation-transfer NMR under conditions of magic-angle spinning (MAS), we demonstrate detection of preferences in interactions of rhodopsin with particular lipid species. It is assumed that function of integral membrane proteins depends on both protein-induced elastic deformations of the lipid matrix and preferences for interaction of the protein with particular lipid species in the first layer of lipids surrounding the protein. PMID:23374188

  17. C-13 NMR 68 Chem 355 Jasperse C-13 NMR

    E-print Network

    Jasperse, Craig P.

    isotopes for carbon, nitrogen, and oxygen are all NMR inactive! Fortunately at least carbon-13 is active carbon-13 NMR; later we will use hydrogen NMR. Both of these will be used later in the year, especially that have quantized spin states are referred to as "NMR active". Just as electrons have quantized spin

  18. NMR IN BIOMEDICINE NMR Biomed. in press

    E-print Network

    Loening, Niko

    . Copyright # 2005 John Wiley & Sons, Ltd. KEYWORDS: 31 P edited 1 H NMR; INEPT; choline compounds; human.interscience.wiley.com). DOI:10.1002/nbm.973 Quantification of phosphocholine and glycerophosphocholine with 31 P edited 1 H. Here, a new scheme that uses 31 P edited 1 H spectroscopy to quantify the concentrations of choline, PC

  19. 1H and 13C Solid-state NMR of Gossypium barbadense (Pima) Cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The interaction of water with cellulose and its influence on the nuclear spin dynamics in G. barbadense (Pima) cotton were investigated by 1H and 13C solid-state NMR techniques. 1H spin diffusion results from a Goldman-Shen experiment indicate that the water is multilayered. 1H MAS experiments pro...

  20. WHAT DOES P-31 NMR TELL US ABOUT PHOSPHORUS IN DAIRY MANURES?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solid-state P-31 MAS NMR analysis with high power decoupling and cross-polarization transfer techniques was used to investigate the organic and inorganic forms of phosphorous (P) in intact dairy manure samples collected from diary farms in the Northeastern United States. The total P concentration i...

  1. Solid State FT-IR and (31)P NMR Spectral Features of Phosphate Compounds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solid-state spectroscopic techniques, including Fourier transform infrared (FT-IR) and solid-state 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies, are powerful tools for evaluating metal speciation and transformation mechanisms of P compounds in the environment. Studie...

  2. Dynamic deuterium magic angle spinning NMR of a molecule grafted at the inner surface of a mesoporous material.

    PubMed

    Jayanthi, S; Frydman, V; Vega, S

    2012-08-30

    Deuterium magic angle spinning (MAS) NMR is used to study the dynamics of an organic molecule, N-[triethoxysilylpropyl]acetamide-d3, grafted at the inner surface of the mesoporous silica material, MCM-41. The grafted molecule has a deuterated methyl group at its free terminus to monitor its local mobility through changes in its dynamic (2)H-MAS NMR spectrum. Different spectra were recorded as a function of temperature from two different water containing samples. Observation shows that a major part of the grafted molecule remains static, irrespective of the temperature and hydration state of the sample, whereas the rest shows spectral changes indicative of a two-site jump motion of the methyl groups. Experimental observations were substantiated using molecular dynamic (MD) simulations of the grafted molecule. Subsequently, the MD results corroborate a model for the grafted molecules experiencing an exchange between two conformations consistent with the analysis of the (2)H-MAS NMR spectra. PMID:22853651

  3. HR Departments & Units Feb 24, 2014

    E-print Network

    Young, R. Michael

    ) Shannon James, Mgr, NC State Laura McGaha, Mgr, UNC-CH RECRUITMENT & STAFFING David Perryman, Asst Dir TRAINING & ORG DEVELOPMENT Kevin Rice, Director HR INFO SYSTEMS & TECHNOLOGY Todd Driver, Asst Dir PAYROLL MANAGEMENT Jen Mitchell, Asst Dir TAX MANAGEMENT Robin Nowlin, Asst Dir PAYROLL PROCESSING DEDUCTION

  4. HR use only: I. APPOINTEE DATA

    E-print Network

    : Travel Expenses: (appointee and family, if eligible) Estimated $ From: To: Air Fare $ Amended Travel Travel Approval: Signature: (Division, Lab or Program Director, as required) Date: Signature: Signature Resources PEID #: Org Unit: Travel Human Resources distributes data to: Coding: Today @ UCAR HR Initials

  5. PeopleSoft HR ECR Automation Process

    E-print Network

    Huang, Jianyu

    PeopleSoft HR ECR Automation Process Short Term Disability with Pay May 2011 #12;Processing a Short Term Disability with Pay ECR Search Page To process a Short Term Disability using the automated ECR. Possible approval areas are: Office of the Provost, Restricted Funds, Compensation, Position Management

  6. PeopleSoft HR ECR Automation Process

    E-print Network

    Huang, Jianyu

    PeopleSoft HR ECR Automation Process Long Term Disability May 2011 #12;Processing a Long Term Disability LTD ECR Search Page To process an LTD transaction using the automated ECR process, follow the menu: Approve or Deny. Possible approval areas are: Office of the Provost, Restricted Funds, Compensation

  7. HR System Access Request Form Security Administration, Human Resources (HR) For additional instructions and information, log onto http://hr.vanderbilt.edu/security/

    E-print Network

    Simaan, Nabil

    instructions and information, log onto http://hr.vanderbilt.edu/security/ Home Department VUnet IDHR EmployeeHR System Access Request Form Security Administration, Human Resources (HR) For additional ID Name Email AddressWork Phone Home Dept Name Effective Date of Access Operator Information I

  8. Resolution and Polarization Distribution in Cryogenic DNP/MAS Experiments

    E-print Network

    Barnes, Alexander

    This contribution addresses four potential misconceptions associated with high-resolution dynamic nuclear polarization/magic angle spinning (DNP/MAS) experiments. First, spectral resolution is not generally compromised at ...

  9. 48 CFR 538.271 - MAS contract awards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    (b) Before awarding any MAS contract, determine that the offered prices are fair and reasonable (see FAR subpart 15.4 and 538.270). Document the negotiation and your determination using FAR 15.406-3 as...

  10. Fast automated protein NMR data collection and assignment by ADAPT-NMR on Bruker spectrometers.

    PubMed

    Lee, Woonghee; Hu, Kaifeng; Tonelli, Marco; Bahrami, Arash; Neuhardt, Elizabeth; Glass, Karen C; Markley, John L

    2013-11-01

    ADAPT-NMR (Assignment-directed Data collection Algorithm utilizing a Probabilistic Toolkit in NMR) supports automated NMR data collection and backbone and side chain assignment for [U-(13)C, U-(15)N]-labeled proteins. Given the sequence of the protein and data for the orthogonal 2D (1)H-(15)N and (1)H-(13)C planes, the algorithm automatically directs the collection of tilted plane data from a variety of triple-resonance experiments so as to follow an efficient pathway toward the probabilistic assignment of (1)H, (13)C, and (15)N signals to specific atoms in the covalent structure of the protein. Data collection and assignment calculations continue until the addition of new data no longer improves the assignment score. ADAPT-NMR was first implemented on Varian (Agilent) spectrometers [A. Bahrami, M. Tonelli, S.C. Sahu, K.K. Singarapu, H.R. Eghbalnia, J.L. Markley, PLoS One 7 (2012) e33173]. Because of broader interest in the approach, we present here a version of ADAPT-NMR for Bruker spectrometers. We have developed two AU console programs (ADAPT_ORTHO_run and ADAPT_NMR_run) that run under TOPSPIN Versions 3.0 and higher. To illustrate the performance of the algorithm on a Bruker spectrometer, we tested one protein, chlorella ubiquitin (76 amino acid residues), that had been used with the Varian version: the Bruker and Varian versions achieved the same level of assignment completeness (98% in 20 h). As a more rigorous evaluation of the Bruker version, we tested a larger protein, BRPF1 bromodomain (114 amino acid residues), which yielded an automated assignment completeness of 86% in 55 h. Both experiments were carried out on a 500 MHz Bruker AVANCE III spectrometer equipped with a z-gradient 5 mm TCI probe. ADAPT-NMR is available at http://pine.nmrfam.wisc.edu/ADAPT-NMR in the form of pulse programs, the two AU programs, and instructions for installation and use. PMID:24091140

  11. The hot white-dwarf companions of HR 1608, HR 8210, and HD 15638

    Microsoft Academic Search

    Wayne Landsman; Theodore Simon; P. Bergeron

    1993-01-01

    We have obtained low-dispersion IUE spectra of the late-type stars HD 15638 (F3 V), HR 1608 (=63 Eridani, KO IV), and HR 8210 (A8m). Each of these stars had been detected as a strong EUV source with the Wide Field Camera aboard the ROSAT satellite. The short-wavelength IUE spectrum of each star reveals the presence of a hot white-dwarf companion.

  12. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS271 Methods for differential Equations 2 hours

    E-print Network

    MAS271 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2009­2010 MAS271 Methods marks) MAS271 1 Turn Over #12;MAS271 2 The equations governing the two competing species x and y are x) = e5x (1 - x) yn(x) = e5x cos (µnx) - sin(µnx) µn (n 1). (12 marks) MAS271 2 Question 3 continued

  13. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS273 Statistical Modelling 2 hours

    E-print Network

    MAS273 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2012­2013 MAS273 Statistical Modelling. MAS273 1 Turn Over #12;MAS273 1 Ethanol fuel was burned in a single-cylinder engine. For various for this model. If there is not sufficient information in the data, say so. Justify your answer. (3 marks) MAS273

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

    A suite of six hydrous (7 wt.% H 2O) sodium silicate glasses spanning sodium octasilicate to sodium disilicate in composition were analyzed using 29Si single pulse (SP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, 1H- 29Si cross polarization (CP) MAS NMR, and fast MAS 1H-NMR. From the 29Si SPMAS data it is observed that at low sodium compositions dissolved water significantly depolymerizes the silicate network. At higher sodium contents, however, dissolved H 2O does not affect a significant increase in depolymerization over that predicted based on the Na/Si ratio alone. The fast MAS 1H-NMR data reveal considerable complexity in proton environments in each of the glasses studied. The fast MAS 1H-NMR spectra of the highest sodium concentration glasses do not exhibit evidence of signficantly greater fractions of dissolved water as molecular H 2O than the lower sodium concentration glasses requiring that the decrease in polymerization at high sodium contents involves a change in sodium solution mechanism. Variable contact time 1H- 29Si cross polarization (CP) MAS NMR data reveal an increase in the rotating frame spin lattice relaxation rate constant ( T1?*) for various Q n species with increasing sodium content that correlates with a reduction in the average 1H- 29Si coupling strength. At the highest sodium concentration, however, T1?* drops significantly, consistent with a change in the Na 2O solution mechanism.

  15. HR 7275 - A new variable star

    NASA Technical Reports Server (NTRS)

    Fried, R. E.; Lovell, L. P.; Krisciunas, K.; Chamblis, C. R.; Detterline, P. K.; Landis, H. J.; Louth, H.; Eaton, J. A.; Hall, D. S.; Henry, G. W.

    1982-01-01

    Three years of photometry in V and B of the UBV system are presented to confirm the suspicion of Herbst (1973) that HR 7275 is a variable star. The photometry is used to derive the photometric period, which proves to be about 3% shorter than the spectroscopically determined optical period of 28.59 d. Total variation observed during the three years was 0.22 m in the V, and the light curve was always asymmetrical.

  16. Characterizing Surface Acidic Sites in Mesoporous-Silica-Supported Tungsten Oxide Catalysts Using Solid State NMR and Quantum Chemistry Calculations

    Microsoft Academic Search

    Jian Z. Hu; Ja Hun Kwak; Yong Wang; Mary Y. Hu; Romulus VF Turcu; Charles HF Peden

    2011-01-01

    The acidic sites in dispersed tungsten oxide supported on SBA-15 mesoporous silica were investigated using a combination of pyridine titration, both fast-, and slow-MAS ¹N NMR, static ²H NMR, and quantum chemistry calculations. It is found that the bridged acidic -OH groups in surface adsorbed tungsten dimers (i.e., W-OH-W) are the Broensted acid sites. The unusually strong acidity of these

  17. 47 CFR 101.1317 - Competitive bidding procedures for mutually exclusive MAS EA applications.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...bidding procedures for mutually exclusive MAS EA applications. 101.1317 Section...bidding procedures for mutually exclusive MAS EA applications. Mutually exclusive...applications for licenses in the portions of the MAS bands licensed on a geographic...

  18. 47 CFR 101.1317 - Competitive bidding procedures for mutually exclusive MAS EA applications.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...bidding procedures for mutually exclusive MAS EA applications. 101.1317 Section...bidding procedures for mutually exclusive MAS EA applications. Mutually exclusive...applications for licenses in the portions of the MAS bands licensed on a geographic...

  19. 47 CFR 101.1317 - Competitive bidding procedures for mutually exclusive MAS EA applications.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...bidding procedures for mutually exclusive MAS EA applications. 101.1317 Section...bidding procedures for mutually exclusive MAS EA applications. Mutually exclusive...applications for licenses in the portions of the MAS bands licensed on a geographic...

  20. 47 CFR 101.1317 - Competitive bidding procedures for mutually exclusive MAS EA applications.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...bidding procedures for mutually exclusive MAS EA applications. 101.1317 Section...bidding procedures for mutually exclusive MAS EA applications. Mutually exclusive...applications for licenses in the portions of the MAS bands licensed on a geographic...

  1. Solid-state NMR in the analysis of drugs and naturally occurring materials.

    PubMed

    Paradowska, Katarzyna; Wawer, Iwona

    2014-05-01

    This article presents some of the solid-state NMR (SSNMR) techniques used in the pharmaceutical and biomedical research. Solid-state magic angle spinning (MAS) NMR provides structural information on powder amorphous solids for which single-crystal diffraction structures cannot be obtained. NMR is non-destructive; the powder sample may be used for further studies. Quantitative results can be obtained, although solid-state NMR spectra are not normally quantitative. As compared with other techniques, MAS NMR is insensitive and requires a significant amount of the powder sample (2-100mg) to fill the 1.3-7 mm ZrO2 rotor. This is its main drawback, since natural compounds isolated from plants, microorganisms or cell cultures are difficult to obtain in quantities higher than a few milligrams. Multinuclear MAS NMR routinely uses (1)H and (13)C nuclei, less frequently (15)N, (19)F, (31)P, (77)Se, (29)Si, (43)Ca or (23)Na. The article focuses on the pharmaceutical applications of SSNMR, the studies were aimed to control over manufacturing processes (e.g. crystallization and milling) investigation of chemical and physical stability of solid forms both as pure drug and in a formulated product. SSNMR is used in combination with some other analytical methods (DSC, XRD, FT-IR) and theoretical calculations of NMR parameters. Biologically active compounds, such as amino acids and small peptides, steroids and flavonoids were studied by SSNMR methods (part 4) providing valuable structural information. The SSNMR experiments performed on biopolymers and large natural products like proteins, cellulose and lipid layers are commented upon briefly in part 5. PMID:24173236

  2. Image algebra preprocessor for the MasPar parallel computer

    NASA Astrophysics Data System (ADS)

    Meyer, Trevor E.; Davidson, Jennifer L.

    1991-07-01

    The development of a preprocessor for image algebra on the MasPar computer, a SIMD processor array, is discussed. One of the parallel languages used on the MasPar is MPL, a parallel version of the programming language C. This machine and language were chosen because of the close correspondence between MPL and image algebra and, as a result, MPL is easily extended to include image algebra. The preprocessor consists of three primary components: the lexical analyzer, the parser, and the code generator. The lexical analyzer converts the input stream into tokens the parser recognizes. The parser checks the program for syntax errors.The code generator produces MPL source code which is then compiled and run on the MasPar. The architecture of the MasPar computer is reviewed, and in particular the structures used for routing data through the array are examined. The parallel language MPL is also reviewed, with attention given to the methods in which the extensions to C in MPL interact with the MasPar architecture. The close correspondence between MPL and image algebra is specifically discussed. The authors present the structure and development of the image algebra preprocessor, including possible future extensions. Examples of image algebra preprocessor code and the corresponding MPL code produced by the preprocessor are given.

  3. 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.''

  4. SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 201314 Advanced Calculus -MAS202 2 hours

    E-print Network

    MAS202 SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2013­14 Advanced Calculus - MAS202 2 is exact and nd a potential function f for . (8 marks) MAS202 1 Turn Over #12;MAS202 ! In this question you and at the moment t = 1, i.e., u t |x=1,t=1. (3 marks) MAS202 2 Continued #12;MAS202 " (i) The random variables X

  5. MAS091 25.100 3:1:3 , 10:30-11:45

    E-print Network

    Kim, Yong Jung

    :: () [] MAS091 25.100 3:1:3 , 10:30-11:45 3435 [84] [] MAS101 I MAS101 25.101 I 3:1:3(6) , 10:30-11:45 301 [115] [] MAS102 A 25.102 II 3:1:3(6) , 10:30-11:45 412 [177] [Projector] MAS102 B 25.102 II 3:1:3(6) ,, 10:00-10:50 412 [177] [Projector] MAS102

  6. SCHOOL OF MATHEMATICS AND STATISTICS May 2011 MAS5050: Mathematical Methods for Statistics 2 hours

    E-print Network

    MAS5050 SCHOOL OF MATHEMATICS AND STATISTICS May 2011 MAS5050: Mathematical Methods for Statistics. (2 marks) MAS5050 1 Turn Over #12;MAS5050 2 (i) Find constants A and B such that 2 (n +1)(n +3) = A n loge x dx: (6 marks) (ii) e2 e x loge x dx: (6 marks) MAS5050 2 Continued #12;MAS5050 5 (i) Calculate

  7. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS6003 Linear models 3 hours

    E-print Network

    MAS6003 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2013­2014 MAS6003 Linear models 3 marks. Total marks 100. MAS6003 1 Turn Over #12;MAS6003 1 The level of light output of light bulbs by the plots. (3 marks) MAS6003 2 Question 1 continued on next page #12;MAS6003 2 4 6 8 10 12 14 -4-2024 Plot 1

  8. Investigation of molecular structure in solids by two-dimensional NMR exchange spectroscopy with magic angle spinning

    NASA Astrophysics Data System (ADS)

    Tycko, Robert; Weliky, David P.; Berger, Alan E.

    1996-11-01

    An approach to the investigation of molecular structures in disordered solids, using two-dimensional (2D) nuclear magnetic resonance (NMR) exchange spectroscopy with magic angle spinning (MAS), is described. This approach permits the determination of the relative orientation of two isotopically labeled chemical groups within a molecule in an unoriented sample, thus placing strong constraints on the molecular conformation. Structural information is contained in the amplitudes of crosspeaks in rotor-synchronized 2D MAS exchange spectra that connect spinning sideband lines of the two labeled sites. The theory for calculating the amplitudes of spinning sideband crosspeaks in 2D MAS exchange spectra, in the limit of complete magnetization exchange between the labeled sites, is presented in detail. A new technique that enhances the sensitivity of 2D MAS exchange spectra to molecular structure, called orientationally weighted 2D MAS exchange spectroscopy, is introduced. Symmetry principles that underlie the construction of pulse sequences for orientationally weighted 2D MAS exchange spectroscopy are explained. Experimental demonstrations of the utility of 2D MAS exchange spectroscopy in structural investigations of peptide and protein backbone conformations are carried out on a model 13C-labeled tripeptide, L-alanylglycylglycine. The dihedral angles ? and ? that characterize the peptide backbone conformation at Gly-2 are obtained accurately from the orientationally weighted and unweighted 2D 13C NMR exchange spectra.

  9. NMR in molecular crystals

    NASA Astrophysics Data System (ADS)

    Decressain, R.; Amoureux, J. P.; Carpentier, L.; Nagy, J. B.

    The 1H, 19F and 13C relaxation times of fluoroadamantane C10H15F are measured over a wide temperature range. These relaxation times are analysed with two dynamical descriptions: an isotropic rotational diffusion and a Frenkel jump model. In this jump model, the structural equilibrium positions are taken into account and therefore two molecular motions are able to explain adequately the experimental results obtained in the plastic phase: a three-fold uniaxial rotation around the dipolar C-F axis and a tumbling reorientation of this axis between <111> cubic axes. The refinements are first carried out using 1H and 19F NMR results in conjunction with the residence time deduced from the dielectric relaxation. Finally, by introducing the 13C NMR results obtained in the plastic phase a precise determination of the two residence time can be made from the NMR results alone.

  10. UVBY Photometry of the Magnetic Chemically Peculiar Stars HR 1297, 36 Aurigae, and HR 2722 and the Nonmagnetic Chemically Peculiar Stars HR 1576 and alpha CANCRI

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Brunhouse, Eric F.

    1998-11-01

    Differential Strömgren uvby photometric observations from the Four College Automated Photoelectric Telescope are presented for the magnetic CP stars HR 1297, 36 Aur, and HR 2722 and the nonmagnetic CP stars HR 1576 and alpha Cnc. Both the moderately rotating HR 1576, a mercury-manganese star, and alpha Cnc, a metallic-line star, are nonvariable. For HR 1297 we refined Winzer's period to 1.06457 days. Our period of 14.366 days for 36 Aur is an alias of Winzer's period and is in keeping with the sharp-lined nature of this star. We found a more accurate period of 2.31523 days for the low-amplitude variable HR 2722.

  11. Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization

    NASA Astrophysics Data System (ADS)

    Johnson, Robert L.; Schmidt-Rohr, Klaus

    2014-02-01

    A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) 13C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10 ms) cross polarization (CP) from 1H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradiation, by multiple 1-ms CP periods alternating with 1H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation (“ramp”) of the radio-frequency field strength, and it overcomes their main limitation, which is T1? relaxation of the spin-locked 1H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a “drop-in” replacement for previous CP methods and produces no additional data-processing burden. Compared to the only reliable quantitative 13C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quantitative NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, plant matter, a highly aromatic humic acid, and carbon materials made by low-temperature pyrolysis.

  12. Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization.

    PubMed

    Johnson, Robert L; Schmidt-Rohr, Klaus

    2014-02-01

    A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) (13)C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10ms) cross polarization (CP) from (1)H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradiation, by multiple 1-ms CP periods alternating with (1)H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation ("ramp") of the radio-frequency field strength, and it overcomes their main limitation, which is T1? relaxation of the spin-locked (1)H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a "drop-in" replacement for previous CP methods and produces no additional data-processing burden. Compared to the only reliable quantitative (13)C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quantitative NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, plant matter, a highly aromatic humic acid, and carbon materials made by low-temperature pyrolysis. PMID:24374751

  13. Nuclear Overhauser effect (NOE) enhancement of 11B NMR spectra of borane adducts in the solid state.

    PubMed

    Ashbrook, Sharon E; Dowell, Nicholas G; Prokes, Ivan; Wimperis, Stephen

    2006-05-31

    A strong 11B {1H} nuclear Overhauser effect (NOE) enhancement can be observed in solid-state 11B NMR spectra of borane adducts, yielding fractional enhancements, fI{S} = (I - I0)/I0, of the magic angle spinning (MAS) NMR signal of up to 155%. This is an interesting and unusual observation as 11B (spin I = 3/2) is a quadrupolar nucleus and the corresponding NOE is completely absent in solution. More generally, it shows that the NOE may have a wider role to play in solid-state NMR studies of dynamics than has been envisaged hitherto. PMID:16719446

  14. NMR Relaxation and Petrophysical Properties

    Microsoft Academic Search

    Marc Fleury

    2011-01-01

    NMR relaxation is routinely used in the field of geosciences to give basic petrophysical properties such as porosity, pore size distribution, saturation etc. In this tutorial, we focus on the pore size distribution deduced from NMR. We recall the basic principle used in the interpretation of the NMR signal and compare the results with other standard petrophysical techniques such as

  15. Journes MAS 2010, Bordeaux Sries chronologiques valeurs entires

    E-print Network

    Boyer, Edmond

    Journées MAS 2010, Bordeaux Séries chronologiques à valeurs entières Session organisée par Lionel correctement par un modèle de séries chronologiques classique à valeurs réelles. Les premiers modèles). A simple integer-valued bilinear times series models. Advances in Applied Probability, 38 :120 [3] R

  16. Journes MAS 2010, Bordeaux Mthodes adaptatives pour les srieschronologiques

    E-print Network

    Boyer, Edmond

    : the thermodynamics of sta- tistical learning. IMS Lecture NotesMonograph Series, 56. Beachwood, OH, (2007). [5] Hart://wintenberger.fr> Session : Méthodes adaptatives pour les séries chronologiques inria-00495672,version1-28Jun2010 #12;Journées MAS 2010, Bordeaux Session : Méthodes adaptatives pour les séries chronologiques Choix de modèle

  17. MAS5051 Probability and Probability Distributions Contents of Blocks

    E-print Network

    Jordan, Jonathan

    MAS5051 Probability and Probability Distributions Contents of Blocks Block "Lectures" Topics A 1/2 1: Sample spaces and events 2: Defining probabilities B 3/4 3: Conditional probability 4 of linear combinations F 11/12 11: Bernoulli trials and the Binomial distribution 12: Binomial tables G 13

  18. Minimal access surgery (MAS)-related surgeon morbidity syndromes.

    PubMed

    Reyes, D A G; Tang, B; Cuschieri, A

    2006-01-01

    The benefits of minimal access surgery (MAS) in terms of accelerated recovery, reduced period of short-term disability, and patient outcome account for the widespread use of the laparoscopic approach by the majority of general surgeons. In adopting this approach with its current limitations and poor ergonomics, surgeons have been known to sustain surgery-related injuries encompassed by a spectrum best described as MAS-related surgeon morbidity syndromes, some of which are currently overlooked and poorly researched. Equivalent morbidities including the overuse syndrome (from overuse of certain muscle groups during long operations) have been documented in open surgery but are nowadays rare occurrences. As more advanced MAS operations are performed with long execution times, new patterns of neuromusculoskeletal injuries are being recognized. The surgical fatigue syndrome has also been described, though its complex nature is not fully understood. Virtually little is known on other long-term adverse effects on the surgeon following many years of operating from images displayed on a television monitor or LCD screen, and these include deterioration of visual acuity and function of the ocular muscles responsible for fixation-refixation of the eyeballs. The limited reported literature on the MAS-related surgeon morbidity syndromes identifies certain risk factors for these injuries pertaining to central and peripheral domains. Only improved knowledge of the etiology and underlying ergonomic factors based on investigative studies followed by improved instrumentation and operating room (OR) ergonomics will provide near- and long-term solutions. PMID:16333542

  19. Scheduling on the MasPar SIMD parallel computer

    E-print Network

    Perkins, Keith Douglas

    1995-01-01

    whose scheduling times are within 90% of optimal schedules 95% of the time. The highest level first algorithm was then modifies to handle the processor architecture on the Texas A&M University's MasPar parallel computer. These modifications included...

  20. Argumentation over Ontology Correspondences in MAS Loredana Laera

    E-print Network

    Paris-Sud XI, Université de

    Argumentation over Ontology Correspondences in MAS Loredana Laera University of Liverpool, UK lori agents can dynamically join or leave and no prior assumption can be made on the ontologies to align in the domain ontologies they commit to; and their perception of the world, and hence the choice of vocabulary

  1. Scheduling on the MasPar SIMD parallel computer 

    E-print Network

    Perkins, Keith Douglas

    1995-01-01

    whose scheduling times are within 90% of optimal schedules 95% of the time. The highest level first algorithm was then modifies to handle the processor architecture on the Texas A&M University's MasPar parallel computer. These modifications included...

  2. QUEEN MARY, UNIVERSITY OF LONDON MAS 314 Design of Experiments

    E-print Network

    Bailey, R. A.

    QUEEN MARY, UNIVERSITY OF LONDON MAS 314 Design of Experiments Reading List Spring 2007 [1] G. E. P. CLARKE & R. E. KEMPSON: Introduction to the Design and Analysis of Experiments, Arnold, London, 1997. [3] G. W. COBB: Design and Analysis of Experiments, Springer-Verlag, New York, 1998. [4] W. G. COCHRAN

  3. CURRRENT STATUS OF MAS FOR DISEASE RESISTANCE IN COMMON BEAN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diseases limit common bean production and quality worldwide. Genetic resistance provides effective and economical control of most diseases. Breeding for improved disease resistance has advanced through use of marker-assisted selection (MAS). Markers linked with major genes and QTL conditioning resis...

  4. A Market-based MAS Framework for Microgrids

    Microsoft Academic Search

    Z. F. Qiu; G. Deconinck; N. Gui; R. Duan; R. Belmans

    This paper proposes a distributed multi-agent system (MAS) framework for market-based control in Microgrids. The proposed system consists of two main entities, Energy Selling Agents (ESAs) and Energy Buying Agents (EBAs). In order to alleviate the internal complexity of the agent, three kinds of delegate mobile agents are designed. They are issued by the corresponding agents according to their different

  5. NMR Studies of Heat-Induced Transitions in Structure and Cation Binding Environments of a Strontium-Saturated Swelling Mica

    SciTech Connect

    Bowers, Geoffrey M.; Davis, Michael C.; Ravella, Ramesh; Komarneni, S.; Mueller, Karl T.

    2007-12-03

    In this work we combined Al, Si, F, and Na magic-angle spinning (MAS) nuclear magnetic resonance (NMR) to characterize the structure and interlayer cation environments in a strontium-saturated member of the swelling mica family before and after a heat induced collapse of the interlayer space.

  6. Multinuclear Solid-State NMR Studies of Polymers and Immobilized Sonogashira Catalysts for Cross-Coupling Reactions

    E-print Network

    Pope, Jacqueline Christine

    2014-08-28

    °C (ca. 600 °F). Interactions and reactions of H2O with the functional groups of the polymers are studied using D2O in combination with IR, 2H MAS, and 1H wideline solid-state NMR. Three different processes taking place during high-temperature steam...

  7. Morphology changes during radiation-thermal degradation of polyethylene and an EPDM copolymer by 13C NMR spectroscopy

    Microsoft Academic Search

    Roger A. Assink; Mathew Celina; Kenneth T. Gillen; Roger L. Clough; Todd M. Alam

    2001-01-01

    The ? radiation induced degradation of an EPDM copolymer was compared to that of a 13C enriched polyethylene at exposure temperatures of 22 and 80°C. Morphological changes were measured by MAS 13C NMR spectroscopy and DSC. By first examining the high quality and less complex spectra of 13C enriched polyethylene, a protocol for the interpretation and deconvolution of the more

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

    SciTech Connect

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

    2004-09-10

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

  9. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS422 Magnetohydrodynamics 2 hours

    E-print Network

    MAS422 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2010­2011 MAS422 Magnetohydrodynamics 2) to satisfy B t = 2 B x2 , what is the condition on d dt ? (6 marks) MAS422 1 Question 2 continued on next page #12;MAS422 (continued) (iii) Consider the magnetic induction equation in the case where

  10. MAS244 1 Turn over SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2009-2010

    E-print Network

    MAS244 MAS244 1 Turn over SCHOOL OF MATHEMATICS AND STATISTICS Autumn Semester 2009 for 3 and 2 so that the linear transformation T of part (ii) above is in Smith form. (9 marks) #12;MAS244 MAS244 2 Continued 3. A real 88× matrix A has minimum polynomial 20122 234 +-+- xxxx . The trace

  11. Lithium dynamics in LiMn2O4 probed directly by two-dimensional (7)Li NMR.

    PubMed

    Verhoeven, V W; de Schepper, I M; Nachtegaal, G; Kentgens, A P; Kelder, E M; Schoonman, J; Mulder, F M

    2001-05-01

    LiMn2O4 has been studied using magic-angle-spinning nuclear magnetic resonance (MAS NMR). 1D MAS NMR shows three Li resonances assigned to different crystallographic sites. At low temperatures an extra peak appears, indicating charge ordering of Mn3+ and Mn4+. Direct observation of the lithium dynamics was possible using rotor-synchronized 2D exchange NMR. A millisecond time scale exchange of lithium starts around 285 K between the 8a and the 16c site. At 380 K lithium even starts to hop between more than two sites. The activation energies and Li jump rates are derived and are in agreement with those determined macroscopically. PMID:11328163

  12. Multinuclear and magic-angle spinning NMR investigations of molecular organization in phospholipid-triglyceride aqueous dispersions.

    PubMed

    Li, K L; Tihal, C A; Guo, M; Stark, R E

    1993-09-28

    The supramolecular organization of multi-bilayers formed by aqueous egg phosphatidylcholine-triolein (PC-TO) mixtures has been investigated using 31P, 13C, and 1H nuclear magnetic resonance (NMR). For these emulsions, which mimic substrates in the early hydrolytic stages of fat digestion, the NMR spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that of sonicated vesicles and integrated peak intensities consistent with their chemical composition. Both 31P line shapes and MAS sideband patterns from the phosphocholine group indicate that mixing with triolein produces a PC bilayer which remains predominantly liquid crystalline in its organization; nevertheless, anomalous spectral features in MAS spectra may be attributed to additional phases in which the headgroups adopt a different orientation with respect to the bilayer normal, and tight packing enhances phosphorus-phosphorus interactions. 13C and 1H line widths monitored as a function of PC mole fraction, spinning speed, and decoupling strength show that the choline headgroups and glycerol backbones are anchored preferentially in the phospholipid-triglyceride assemblies, whereas all acyl chains become very fluid. The average degree of chain order also decreases for the mixed dispersions, as judged from spinning-sideband intensities in 1H MAS NMR spectra. The absence of proton spin-diffusion effects in the PC-TO multilayers is demonstrated by examination of their spinning sidebands and relaxation times, making it possible to use MAS-assisted two-dimensional NMR to assign overlapped 1H resonances and to identify proximal interactions between the two constituents. The usefulness of these NMR strategies in mechanistic studies of gastric fat digestion is also discussed. PMID:8399162

  13. 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.

  14. 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 peroxidase was essential in confirming the identity of residues participating in the aromatic donor molecule binding site of peroxidases.

  15. MAS 305 Algebraic Structures II Notes 11 Autumn 2006

    E-print Network

    Bailey, R. A.

    MAS 305 Algebraic Structures II Notes 11 Autumn 2006 Ring homomorphisms Definition Let R and S be rings, and let :R S be a function. Then is a ring homomorphism if (r1 +r2) = r1+r2 and (r1r2) = (r1)(r2) for all r1, r2 in R. A ring homomorphism which is a bijection is called an isomorphism

  16. Photosynthese und Photomorphogenese bei Farnvorkeimen von Dryopteris filix-mas

    Microsoft Academic Search

    H. Mohr; K. Ohlenroth

    1962-01-01

    Summary Under conditions of identical rate of photosynthesis (measured by dry weight increase under steady state conditions) growth and differentiation of the gametophytes of ferns (e.g.Dryopteris filix-mas) are completely different in red and blue light. In the blue light “normal” growth and morphogenesis take place and “normal” two or three-dimensional prothallia are formed (Fig. 3). In the red, however, the

  17. NMR study of the adsorption-desorption kinetics of dissolved tetraalanine in MCM-41 mesoporous material.

    PubMed

    Pizzanelli, Silvia; Kababya, Shifi; Frydman, Veronica; Landau, Miron; Vega, Shimon

    2005-04-28

    In this study we show how deuterium magic-angle spinning NMR spectroscopy can be used to investigate the adsorption-desorption kinetics of molecules in solution at surface-liquid interfaces. An aqueous solution of deuterium-labeled tetraalanine is inserted in the pores of MCM-41 mesoporous material, and its 2H MAS NMR spectrum is measured as a function of temperature and fraction of filling of the pores. Prior to this study, the different types of water in MCM-41 are characterized as a function of water loading of the pores. Analysis of 2H MAS sideband line shapes enabled the determination of the adsorption and desorption rates and the activation energies of desorption. PMID:16851938

  18. NMR characterization and sorption behavior of agricultural and forest soil humic substances

    NASA Astrophysics Data System (ADS)

    Li, Chengliang; Berns, Anne E.; Séquaris, Jean-Marie; Klumpp, Erwin

    2010-05-01

    Humic substances are the predominant components of the organic matter in the terrestrial system, which are not only important for the physicochemical properties of soil but are also dominant factors for controlling the environmental behaviors and fates of some organic contaminants, such as hydrophobic compounds. Nonylphenol [4-(1-ethyl-1, 3 dimethylpentyl) phenol] (NP), a ubiquitous hydrophobic pollutant, has recently focused the attention owing to its endocrine disruptors property. Sorption behavior of NP on humic substances, which were isolated from agricultural and forest soils, was investigated by using the dialysis technique at room temperature. 14C-labeled NP was used to quantify the partitioning behavior. Humic substances were characterized by 13C Cross-Polarization/Magic-Angle-Spinning Nuclear Magnetic Resonance (CP/MAS NMR). The results showed that the partition parameters of NP on various humic acids were slightly different. Relationships between partition coefficients and the functional groups of humic substances identified by CP/MAS NMR were analyzed.

  19. Investigations of adsorption sites on oxide surfaces using solid-state NMR and TPD-IGC

    NASA Astrophysics Data System (ADS)

    Golombeck, Rebecca A.

    The number and chemical identity of reactive sites on surfaces of glass affects the processing, reliability, and lifetime of a number of important commercial products. Surface site densities, distributions, and structural identities are closely tied to the formation and processing of the glass surface, and exert a direct influence on strength and coating performance. The surface of a glass sample may vary markedly from the composition and chemistry of the bulk glass. We are taking a physicochemical approach to understanding adsorption sites on pristine multicomponent glass fibers surfaces, directly addressing the effect of processing on surface reactivity. This project aimed to understand the energy distributions of surface adsorption sites, the chemical/structural identity of those sites, and the relationship of these glasses to glass composition, thermal history, and in future work, surface coatings. We have studied the bulk and surface structure as well as the surface reactivity of the glass fibers with solid-state nuclear magnetic resonance (NMR) spectroscopy, inverse gas chromatography (IGC), and computational chemistry methods. These methods, solid-state NMR and IGC, typically require high surface area materials; however, by using probe molecules for NMR experiments or packing a column at high density for IGC measurements, lower surface area materials, such as glass fibers, can be investigated. The glasses used within this study were chosen as representative specimens of fibers with potentially different reactive sites on their surfaces. The two glass compositions were centered around a nominal E-glass, which contains very little alkali cations and mainly alkaline earth cations, and wool glass, which contains an abundance of alkali cations. The concentration of boron was varied from 0 to 8 mole % in both fiber compositions. Fibers were drawn from each composition at a variety of temperatures and draw speeds to provide a range of glass samples with varying diameters and thermal histories. The bulk structural features in both compositions of glass fibers were identified using high-resolution 29Si, 27Al, and 11B magic-angle spinning (MAS) NMR spectroscopic measurements. In multi-component glasses, the determination of silicon, aluminum, and boron distributions becomes difficult due to the competitive nature of the network-modifying oxides among the network-forming oxides. In pure silicates, 29Si MAS NMR can often resolve resonances arising from silicate tetrahedron having varying numbers of bridging oxygens. In aluminoborosilicate glasses, aluminum is present in four-, five-, and six- coordination with oxygen as neighbors. The speciation of the aluminum can be determined using 27Al MAS NMR. The fraction of tetrahedral boron species in the glass fibers were measured using 11B MAS NMR, which is typically used to study the short-range structure of borate containing glasses such as alkali borate, borosilicate, and aluminoborosilicate glasses. While solid-state NMR is a powerful tool for elucidating bonding environments and coordination changes in the glass structure, it cannot quantitatively probe low to moderate surface area samples due to insufficient spins. Chemical probes either physisorbed or chemisorbed to the fiber's surface can increase the surface selectivity of NMR for analysis of samples with low surface areas and provide information about the local molecular structure of the reactive surface site. Common chemical probe molecules contain NMR active nuclei such as 19F or may be enriched with 13C. A silyating agent, (3,3,3-trifluoropropyl)dimethylchlorosilane (TFS), reacts with reactive surface hydroxyls, which can be quantified by utilizing the NMR active nucleus (19F) contained in the probe molecule. The observed 19F MAS NMR peak area is integrated and compared against a standard of known fluorine spins (concentration), allowing the number of reactive hydroxyl sites to be quantified. IGC is a method used to study the surface properties of a material by examining the retention behavior of a probe molecule. The I

  20. CHARACTERIZATION OF THE RED GIANT HR 2582 USING THE CHARA ARRAY

    SciTech Connect

    Baines, Ellyn K. [Remote Sensing Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); McAlister, Harold A.; Ten Brummelaar, Theo A.; Turner, Nils H.; Sturmann, Judit; Sturmann, Laszlo; Farrington, Christopher D.; Vargas, Norm [Center for High Angular Resolution Astronomy, Georgia State University, P.O. Box 3969, Atlanta, GA 30302-3969 (United States); Van Belle, Gerard T. [Lowell Observatory, Flagstaff, AZ 86001 (United States); Ridgway, Stephen T., E-mail: ellyn.baines@nrl.navy.mil [National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726-6732 (United States)

    2013-07-20

    We present the fundamental parameters of HR 2582, a high-mass red giant star whose evolutionary state is a mystery. We used the CHARA Array interferometer to directly measure the star's limb-darkened angular diameter (1.006 {+-} 0.020 mas) and combined our measurement with parallax and photometry from the literature to calculate its physical radius (35.76 {+-} 5.31 R{sub Sun }), luminosity (517.8 {+-} 17.5 L{sub Sun }), bolometric flux (14.8 {+-} 0.5 Multiplication-Sign 10{sup -8} erg s{sup -1} cm{sup -2}), and effective temperature (4577 {+-} 60 K). We then determined the star's mass (5.6 {+-} 1.7 M{sub Sun }) using our new values with stellar oscillation results from Baudin et al. Finally, using the Yonsei-Yale evolutionary models, we estimated HR 2582's age to be 165{sup +20}{sub -15} Myr. While our measurements do not provide the precision required to definitively state where the star is in its evolution, it remains an excellent test case for evaluating stellar interior models.

  1. Preservation of proteinaceous material during the degradation of the green alga Botryococcus braunii: A solid-state 2D 15N 13C NMR spectroscopy study

    Microsoft Academic Search

    Xu Zang; Reno T. Nguyen; H. Rodger Harvey; Heike Knicker; Patrick G. Hatcher

    2001-01-01

    Using solid-state cross-polarization-magic-angle-spinning (CPMAS) 13C and 15N nuclear magnetic resonance (NMR) and 2-D double cross polarization (DCP) MAS 15N 13C NMR techniques, microbially degraded Botryococcus braunii was analyzed to study the chemical nature of organic nitrogen in the algal residue. The amide linkage, as found in protein, was observed as the major nitrogen component in 201-day-old degraded algae. No significant

  2. NMR in biology and medicine

    SciTech Connect

    Chien, S.; Chien, H.

    1986-01-01

    This volume explores the applications of NMR in basic biological research and in clinical diagnosis. The contributors highlight the capabilities of NMR as a tool for studying living organisms at the molecular and cellular levels and detecting abnormalities in various organ systems. Included are solid-state and high-resolution NMR studies of the molecular structure and dynamic interactions of lipids, proteins, and nucleic acids. The latest developments in NMR zeugmatographic imaging and in musculoskeletal and cardiovascular magnetic resonance imaging are detailed. Concluding chapters review the uses of in vivo NMR spectroscopy to study energy metabolism and cellular biochemistry. Emphasis is placed on in vivo NMR spectroscopy studies that elucidate normal metabolic functions and their pathological disturbances.

  3. NMR study of /sup 29/Si in offretite

    SciTech Connect

    Iwamiya, J.H.

    1985-06-01

    Representative offretite samples have been prepared to study their physical and chemical properties by High Resolution Solid-State Nuclear Magnetic Resonance. A study of the spin lattice relaxation of the /sup 29/Si nuclei in the framework of offretite has shown that the dominant relaxation mechanism is the coupling of the /sup 29/Si nuclei to the paramagnetic centers in the zeolite framework. Corrobative evidence is provided by ESR measurements which indicate that different types of paramagnetic centers are present and that only one type of center is responsible for the observed relaxation of the /sup 29/Si nuclei. Furthermore, in these samples, the silicon nuclei located in different second coordination spheres have the same spin lattice relaxation rate. The effect of different calcination procedures on tetramethylammonium(TMA)-offretite has been monitored by /sup 29/Si magic angle spinning(MAS)-NMR and /sup 27/Al MAS-NMR. The results indirectly show that Broensted acid sites are formed when the TMA cations are oxidatively decomposed. Some of the aluminum atoms that are associated with the acid sites are randomly removed from the lattice, with the result that the framework becomes richer in silicon. Also, the severity of the calcination procedure appears to play a role in determining how much aluminum is removed from the lattice. 80 refs., 15 figs., 7 tabs.

  4. Studies of Fossil and Modern Spore Wall Biomacromolecules using 13C Solid State NMR

    Microsoft Academic Search

    ALAN R. HEMSLEY; ANDREW C. SCOTT; PATRICK J. BARRIE; WILLIAM G. CHALONER

    1996-01-01

    A range of Carboniferous lycophyte megaspore exines have been investigated using13C magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Their composition differs considerably from sporopollenin obtained from an extant lycophyte. The differences observed result in part from varying degrees of diagenesis.Fossil fern spores, gymnosperm megaspore-membranes and pollen have also been examined. These show a similar composition to the fossil lycophyte

  5. Immobilization and chelation of metal complexes with bifunctional phosphine ligands: a solid-state NMR study

    E-print Network

    Bluemel, Janet

    to bonding via one, two, or three siloxane bridges and there is also the possibility of cross- linking.' Therefore, we used the monoethoxy phosphine PPh2(C6H4)SiMe20Et1 that forms just one siloxane bridge when or an addition reaction to surface siloxane groups takes place.'3 This can be seen in the 29Si CP MAS NMR

  6. Real time neutron diffraction and NMR of the Empress II glass-ceramic system

    Microsoft Academic Search

    M. D. O’Donnell; R. G. Hill; N. Karpukhina; R. V. Law

    2011-01-01

    Objective. This study reports real time neutron diffraction on the Empress II glass-ceramic system.Methods. The commercial glass-ceramics was characterized by real time neutron diffraction, 31P and 29Si solid-state MAS-NMR, DSC and XRD.Results. On heating, the as-received glass ceramic contained lithium disilicate (Li2Si2O5), which melted with increasing temperature. This was revealed by neutron diffraction which showed the Bragg peaks for this

  7. Natural abundance 15N CP/MAS of nylons and aramids: A sensitive technique for examining crystalline composition and conformation in solid polyamides

    NASA Astrophysics Data System (ADS)

    Powell, Douglas G.; Sikes, Allison M.; Mathias, Lon J.

    1988-09-01

    We have examined a variety of polyamides and aramids using natural abundance 15N CP/MAS NMR. These have included commercially available A-B and AA-BB nylons, Kevlar and poly(p-benzamide) as well as a number of block and graft copolymers synthesized in our laboratory. Excellent correlation was observed between the type of crystalline form adopted by polyamides (alpha and gamma modifications) and the chemical shift of the rigid amide nitrogens. Values for the two forms center around 84 ppm (relative to glycine at 0 ppm) and 88 ppm, respectively. For some samples, unexplained peaks between the two main crystalline peaks are tentatively assigned to rigid amide conformations that are not X-ray active but are seen by NMR. Aramids show similar complexity. Block and graft copolymers display characteristic peaks for composition (aryl vs alkyl nitrogen substituents) and for conformation and crystallinity.

  8. The MicroMAS CubeSat Mission

    NASA Astrophysics Data System (ADS)

    Cahoy, K.; Blackwell, W. J.; Allen, G.; Bury, M.; Efromson, R.; Galbraith, C.; Hancock, T.; Leslie, V.; Osaretin, I.; Retherford, L.; Scarito, M.; Shields, M.; Toher, D.; Wight, K.; Miller, D.; Marinan, A.; Paek, S.; Peters, E.; Schmidt, F. H.; Alvisio, B.; Wise, E.; Masterson, R.; Franzim Miranda, D.; Crail, C.; Kingsbury, R.; Souffrant, A.; Orrego, L.; Eslinger, G.; Nicholas, A.; Pong, C.

    2012-12-01

    The recently published Midterm Assessment of NASA's Implementation of the Decadal Survey finds that, "The nation's Earth observing system is beginning a rapid decline in capability as long-running missions end and key new missions are delayed, lost, or canceled. The projected loss of observing capability could have significant adverse consequences for science and society." In this presentation, we explore low-cost, mission-flexible, and rapidly deployable spaceborne sensors that can meet stringent performance requirements pervading the NASA Earth Science measurement programs, including especially the recommended NRC Decadal Survey missions. New technologies have enabled a novel approach toward this science observational goal, and in this paper we describe recent technology develop efforts to address the challenges above through the use of CubeSat radiometers. The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a 3U cubesat (30x10x10 cm, ~4kg) hosting a passive microwave spectrometer operating near the 118.75-GHz oxygen absorption line. The focus of the first MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit at approximately 500-km altitude. A MicroMAS flight unit is currently being developed in anticipation of a 2014 launch to be provided by NASA. A parabolic reflector is mechanically rotated as the spacecraft orbits the earth, thus directing a cross-track scanned beam with FWHM beamwidth of 2.4-degrees, yielding an approximately 25-km diameter footprint from a nominal altitude of 500 km. Radiometric calibration is carried out using observations of cold space, the earth's limb, and an internal noise diode that is weakly coupled through the RF front-end electronics. A key technology feature is the development of an ultra-compact intermediate frequency processor module for channelization, detection, and A-to-D conversion. The antenna system and RF front-end electronics are highly integrated and miniaturized. A MicroMAS-2 mission is currently being planned using a multi-band spectrometer operating near 118 and 183 GHz in a sun-synchronous orbit of approximately 800-km altitude. A HyMAS-1 (Hyperspectral Microwave Atmospheric Satellite) mission with approximately 50 channels near 118 and 183 GHz is also being planned. In this talk, the mission concept of operations will be discussed, the radiometer payload will be described, and the spacecraft subsystems (avionics, power, communications, attitude determination and control, and mechanical structures) will be summarized. Test data from the recently completed MicroMAS Engineering Development Model (EDM) will also be presented. This work was sponsored by the National Oceanic and Atmospheric Administration under Air Force contract FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and not necessarily endorsed by the United States Government.

  9. The corona of HD 223460 (HR 9024)

    NASA Astrophysics Data System (ADS)

    Gondoin, P.

    2003-10-01

    HD 223460 (HR 9024), a chromospherically active late-type giant with a high X-ray luminosity, was observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. Analysis results suggest a scenario where the corona of HD 223460 is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The surface area coverage of these active regions may approach up to 30%. A hypothesis is that the interaction of these structures themselves induces a flaring activity on a small scale not visible in the EPIC light curves that is responsible for heating HD 223460 plasma to coronal temperatures of T >=107 K. The intense X-ray activity of HD 223460 is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that its rotation will spin down in the future with the effect of decreasing its helicity-related, dynamo-driven activity and suppressing large-scale magnetic structures in its corona.

  10. Elemental abundances of the B and A stars Gamma Geminorum, 7 Sextantis, HR 4817, and HR 5780

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.; Philip, A. G. D.

    1992-01-01

    Fine analyses of the B and A stars, Gamma Geminorum, 7 Sextantis, HR 4817, and HR 5780 are performed. Although the data cover rather limited spectral regions, still useful results were obtained. The data were mostly obtained at the KPNO coude feed telescope with CCD TI No. 3, camera 5, and grating A. The He/H ratio of HR 4817 confirms the similarity of many abundance values with those of the peculiar Mn star 53 Tauri. For the most part Gamma Gem, 7 Sex, and HR 5780 have derived abundances similar to those of other normal sharp-lined stars of similar effective temperature.

  11. Tumbling motions of NH2(CH3)2 ions in [NH2(CH3)2]2ZnCl4 studied using 1H MAS NMR and 13C CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Kim, Nam Hee; Choi, Jae Hun; Lim, Ae Ran

    2014-12-01

    The structure and the phase transition temperatures of [NH2(CH3)2]2ZnCl4 were determined using X-ray diffraction and DSC, respectively. The temperature dependence of chemical shifts and the spin-lattice relaxation time T1? in the rotating frame were measured for the 1H and 13C nuclei in [NH2(CH3)2]2ZnCl4. From these results, it was observed that the structural change by chemical shifts does not occur with temperature. However, T1? for 1H and 13C in [NH2(CH3)2]2ZnCl4 showed a minimum, and it is apparent that both T1? values are governed by the same tumbling motions. The activation energies of tumbling motions for 1H and 13C are nearly the same owing to the connection between CH3 and NH2 ions in the [NH2(CH3)2]+ group.

  12. Magic angle spinning NMR of proteins: high-frequency dynamic nuclear polarization and (1)h detection.

    PubMed

    Su, Yongchao; Andreas, Loren; Griffin, Robert G

    2015-06-01

    Magic angle spinning (MAS) NMR studies of amyloid and membrane proteins and large macromolecular complexes are an important new approach to structural biology. However, the applicability of these experiments, which are based on (13)C- and (15)N-detected spectra, would be enhanced if the sensitivity were improved. Here we discuss two advances that address this problem: high-frequency dynamic nuclear polarization (DNP) and (1)H-detected MAS techniques. DNP is a sensitivity enhancement technique that transfers the high polarization of exogenous unpaired electrons to nuclear spins via microwave irradiation of electron-nuclear transitions. DNP boosts NMR signal intensities by factors of 10(2) to 10(3), thereby overcoming NMR's inherent low sensitivity. Alternatively, it permits structural investigations at the nanomolar scale. In addition, (1)H detection is feasible primarily because of the development of MAS rotors that spin at frequencies of 40 to 60 kHz or higher and the preparation of extensively (2)H-labeled proteins. PMID:25839340

  13. The crystallization of hectorite clays as monitored by small angle X-ray scattering and NMR

    SciTech Connect

    Carrado, K. A.; Xu, L.; Seifert, S.; Gregory, D.; Song, K.; Botto, R. E.

    1999-12-13

    The authors have probed the 48-hr crystallization of a magnesium silicate clay called hectorite. Small angle X-ray scattering (SAXS) at the Advanced Photon Source using aliquots ex situ has revealed that data is consistent with ex situ XRD, TGA, AFM, and IR data in that all these techniques see clay crystallite beginning to form in the first few hours of reaction. Tetraethylammonium (TEA) ions are used to aid crystallization and become incorporated as the exchange cations within the interlayers. {sup 13}C NMR shows that 80% of the final TEA loading is accomplished in the first 10 hrs. {sup 29}Si NMR displays a visible clay silicate peak after just 1 hr. In addition, the first in situ study of clay crystallization of any kind was performed by in situ SAXS. Results are consistent with the ex situ data as well as showing the sensitivity of SAXS to sol gel reactions occurring on the order of minutes.

  14. hr.osu.edu/policy Page 1 of 1 Whistleblower

    E-print Network

    Howat, Ian M.

    hr.osu.edu/policy Page 1 of 1 - Whistleblower Policy 1.40 Office of Human Resources Applies to: Faculty, Staff, Student Employees, Students, and Volunteers Resources Ohio Whistleblower Protection Law.ethicspoint.com/domain/en/report_custom.asp?clientid=7689 University Health System Human Resources 614-293-4988 Whistleblower Report Form hr.osu.edu/forms/whistleblower

  15. Fair Labor Standards UW-Madison HR Design

    E-print Network

    Winokur, Michael

    HR Design Fair Labor Standards Act Review UW-Madison HR Design Better stewardship. Stronger Labor Standards Act (FLSA) categories: The "academic staff" employee category will include all FLSA compliance with the law. Defining a process for the FLSA review of all classified exempt positions on campus

  16. HR Time and Labor Group Security Access Request Form

    E-print Network

    Weston, Ken

    HR Time and Labor Group Security Access Request Form **You must have the FSU_SS_MANAGER role in order to utilize Time and Labor Security Groups. This role can be requested in OMNI HR > eORR ­ Online): ______________________________ Department Name: _________________________________________ Email

  17. Outsourcing HR Services: The Role of Human Resource Intermediaries

    ERIC Educational Resources Information Center

    Kock, Henrik; Wallo, Andreas; Nilsson, Barbro; Hoglund, Cecilia

    2012-01-01

    Purpose: In this article, the area of interest is an emerging type of organisation called human resource intermediaries (HRIs), which focus on delivering human resource (HR) services to public sector organisations and private companies. The purpose of this article is, thus, to explore HRIs as deliverers of HR services. More specifically, the…

  18. TO: HR and Business Contacts FROM: Division of Human Resources

    E-print Network

    Almor, Amit

    TO: HR and Business Contacts FROM: Division of Human Resources DATE: September 6, 2012 RE: Human Resources Fall 2012 Forum The Division of Human Resources will sponsor an HR Forum from 1-4 p in person or by webinar. Any questions about the forum may be e-mailed to the Division of Human Resources

  19. TO: HR and Business Contacts FROM: Division of Human Resources

    E-print Network

    Almor, Amit

    MEMORANDUM TO: HR and Business Contacts FROM: Division of Human Resources DATE: October 25, 2013 RE: Human Resources Fall 2013 Forum The Division of Human Resources will sponsor an HR Forum from 1 to the Division of Human Resources' Organizational and Professional Development Office at hrtrain

  20. TO: HR and Business Contacts FROM: Division of Human Resources

    E-print Network

    Almor, Amit

    MEMORANDUM TO: HR and Business Contacts FROM: Division of Human Resources DATE: April 1, 2013 RE: Human Resources Spring 2013 Forum The Division of Human Resources will sponsor an HR Forum from 1-4 p-mailed to the Division of Human Resources' Professional Development Office at hrtrain@mailbox.sc.edu. Also, if you find

  1. Welding Metallurgy of Alloy HR-160

    SciTech Connect

    DuPont, J.N.; Michael, J.R.; Newbury, B.D.

    1999-05-28

    The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in alloy HR-160 was investigated by Varestraint testing, differential thermal analysis, and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 {deg}C and initiated solidification by a primary L - {gamma} reaction in which Ni, Si, and Ti segregated to the interdendritic liquid and Co segregated to the {gamma} dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at {approx} 1162 {deg}C by a eutectic-type L - [{gamma}+ (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7}] reaction. The (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7} phase is found to be analogous to the G phase which forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found to exist between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [{gamma} +(Ni,Co){sub l6}(Ti,Cr){sub 6}Si{sub 7}] eutectic-typr constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 {deg}C and the presence of 2 to 5 vol% solute rich interdendritic liquid which preferentially wets the grain boundaries and interdendritic regions.

  2. Efficient heteronuclear decoupling in MAS solid-state NMR using non-rotor-synchronized rCW irradiation

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Paul, Subhradip; Mithu, Venus Singh; Madhu, P. K.; Nielsen, Niels Chr.

    2014-09-01

    We present new non-rotor-synchronized variants of the recently introduced refocused continuous wave (rCW) heteronuclear decoupling method significantly improving the performance relative to the original rotor-synchronized variants. Under non-rotor-synchronized conditions the rCW decoupling sequences provide more efficient decoupling, are easier to setup, and prove more robust towards experimental parameters such as radio frequency (rf) field amplitude and spinning frequency. This is demonstrated through numerical simulations substantiated with experimental results under different sample spinning and rf field amplitude conditions for powder samples of U-13C-glycine and U-13C-L-histidine·HCl·H2O.

  3. Efficient heteronuclear decoupling in MAS solid-state NMR using non-rotor-synchronized rCW irradiation.

    PubMed

    Equbal, Asif; Paul, Subhradip; Mithu, Venus Singh; Madhu, P K; Nielsen, Niels Chr

    2014-09-01

    We present new non-rotor-synchronized variants of the recently introduced refocused continuous wave (rCW) heteronuclear decoupling method significantly improving the performance relative to the original rotor-synchronized variants. Under non-rotor-synchronized conditions the rCW decoupling sequences provide more efficient decoupling, are easier to setup, and prove more robust towards experimental parameters such as radio frequency (rf) field amplitude and spinning frequency. This is demonstrated through numerical simulations substantiated with experimental results under different sample spinning and rf field amplitude conditions for powder samples of U-(13)C-glycine and U-(13)C-L-histidine·HCl·H2O. PMID:25123538

  4. Cp\\/mas 13 c nmr and Electron Diffraction Study of Bacterial Cellulose Structure Affected by Cell Wall Polysaccharides

    Microsoft Academic Search

    Chisuzu Tokoh; Keiji Takabe; Junji Sugiyama; Minoru Fujita

    2002-01-01

    Acetobacterxylinum was cultured in Schramm–Hestrin medium containing pectin (pectin medium), xylan (xylan medium), or glucomannan (mannan medium). X-ray diffractometry revealed that xylan and glucomannan affected the size of the cellulose crystals and their d-spacing values. Solid-state cross polarization magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy indicated that the ratio of cellulose Ia was reduced by the addition of polysaccharides.

  5. CHARACTERIZATION OF THE WOUND INDUCED MATERIAL IN CITRUS FRUIT PEEL BY CARBON-13 CP-MAS SOLID STATE NMR SPECTROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There are conflicting views regarding the chemical composition of the induced, phloroglucinol-HCl (PG-HCl) reacting, material accumulating in injured citrus peel tissues. Grapefruit, Citrus paradisi, were injured, inoculated with Peicillium digitatum and incubated under contitions favorable to the a...

  6. 17O and 27Al MAS and 3QMAS NMR Study of Synthetic and Natural Layer Silicates

    E-print Network

    Puglisi, Joseph

    , and Jonathan F. Stebbins Department of Geological and Environmental Sciences, Stanford University, Stanford Broad Branch Rd. Washington, DC 20015. E-mail: s.lee@gl.ciw.edu. Phone: 202-478-8968. Fax: 202

  7. THz Dynamic Nuclear Polarization NMR

    PubMed Central

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

    2013-01-01

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

  8. Achievement of 1020MHz NMR.

    PubMed

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

    2015-07-01

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

  9. Human Resources Consultancy (HR) in France: On the tendency of Web service innovating to e-HR

    E-print Network

    Paris-Sud XI, Université de

    1 Human Resources Consultancy (HR) in France: On the tendency of Web service innovating to e.David@loria.fr Abstract : The European market of management consultancy (MC) and human resources (HR) goes remarkably well in human resources consultancy. It is a question of observing new related activities to management

  10. Sensitivity and resolution enhancement of oriented solid-state NMR: application to membrane proteins.

    PubMed

    Gopinath, T; Mote, Kaustubh R; Veglia, Gianluigi

    2013-11-01

    Oriented solid-state NMR (O-ssNMR) spectroscopy is a major technique for the high-resolution analysis of the structure and topology of transmembrane proteins in native-like environments. Unlike magic angle spinning (MAS) techniques, O-ssNMR spectroscopy requires membrane protein preparations that are uniformly oriented (mechanically or magnetically) so that anisotropic NMR parameters, such as dipolar and chemical shift interactions, can be measured to determine structure and orientation of membrane proteins in lipid bilayers. Traditional sample preparations involving mechanically aligned lipids often result in short relaxation times which broaden the (15)N resonances and encumber the manipulation of nuclear spin coherences. The introduction of lipid bicelles as membrane mimicking systems has changed this scenario, and the more favorable relaxation properties of membrane protein (15)N and (13)C resonances make it possible to develop new, more elaborate pulse sequences for higher spectral resolution and sensitivity. Here, we describe our recent progress in the optimization of O-ssNMR pulse sequences. We explain the theory behind these experiments, demonstrate their application to small and medium size proteins, and describe the technical details for setting up these new experiments on the new generation of NMR spectrometers. PMID:24160761

  11. Multinuclear NMR approach to coal fly ash characterization

    SciTech Connect

    Netzel, D.A.

    1991-09-01

    This report describes the application of various nuclear magnetic resonance (NMR) techniques to study the hydration kinetics and mechanisms, the structural properties, and the adsorption characteristics of coal fly ash. Coal fly ash samples were obtained from the Dave Johnston and Laramie River electric power generating plants in Wyoming. Hydrogen NMR relaxation times were measured as a function of time to observe the kinetics of hydration for the two coal fly ashes at different temperatures and water-to-cement ration. The kinetic data for the hydrated coal fly ashes were compared to the hydration of portland cement. The mechanism used to describe the kinetic data for the hydration of portland cement was applied, with reservation, to describe the hydration of the coal fly ashes. The results showed that the coal fly ashes differ kinetically from that of portland cement and from each other. Consequently, both coal fly ashes were judged to be poorer cementitious materials than portland cement. Carbon-13 NMR CP/MAS spectra were obtained for the anhydrous coal fly ashes in an effort to determine the type of organic species that may be present, either adsorbed on the surface or entrained.

  12. Characterization of Porous Medium Properties Using 2D NMR

    NASA Astrophysics Data System (ADS)

    Sun, Boqin; Dunn, Keh-Jim

    2003-03-01

    We have successfully applied the concept of 2D NMR to the characterization of properties of fluid-saturated porous medium. Using a two-windowed modified CPMG pulse sequence, we were able to explore the magnetic internal filed gradient distribution within the pore space of a fluid-saturated porous medium due to magnetic susceptibility contrast between the solid matrix and pore fluid. Similar scheme is used to identify and quantify different types of pore fluids, such as oil, water, and gas, based on the contrast in their diffusion coefficients. The magic angle spinning technique (MAS) can also be applied in the 2D NMR framework for delineating the chemical shift spectra of the pore fluids in a porous medium at different T1 or T2 relaxation times. The results can be displayed in a two-dimensional plot, with one axis being the T1 or T2 relaxation times, the other axis being the internal field gradient, diffusion coefficient, or chemical shift, and the third axis being the proton population. Our preliminary laboratory work indicates that the 2D NMR approach can be a powerful tool for the characterization of properties of fluid-saturated porous medium, such as fluid typing, oil viscosity determination, surface wettability, etc.

  13. MAS205 Complex Variables 2005-2006 Some Notes on Prerequisites

    E-print Network

    Prellberg, Thomas

    MAS205 Complex Variables 2005-2006 Some Notes on Prerequisites The course description specifies will start from scratch, now would be a good time to have a look at some notes, e.g. http://www.maths.qmul.ac.uk/reza/MAS 2 in http://www.maths.qmul.ac.uk/bjc/MAS102/MAS102 notes.pdf The more you remember of Calculus I

  14. A simulator for organisation-centred MAS adaptation in P2P sharing networks

    E-print Network

    López-Sánchez, Maite

    in a peer-to-peer (P2P) scenario. In particular, we describe our approach to MAS adaptation (2-LAMA), the P2 Assisted MAS Architecture (2-LAMA) [2]. As a case study, we apply this approach to a P2P sharing network- text of a rational world assumption. Specifically, we propose a Two Level Assisted MAS Architecture (2

  15. Why does meconium cause meconium aspiration syndrome? Current concepts of MAS pathophysiology

    Microsoft Academic Search

    Y. van Ierland; A. J. de Beaufort

    2009-01-01

    One in every 7 pregnancies ends with meconium-stained amniotic fluid and approximately 5% of these infants develop the meconium aspiration syndrome (MAS). MAS is a severe disease of the (mainly) term neonate, characterized by respiratory distress, pulmonary inflammation, persistent pulmonary hypertension and chronic hypoxia.The pathophysiology of MAS is multifactorial and complex. In this article, we discuss the mechanical and chemical

  16. AGOL: An Aspect-Oriented Domain-Specific Language for MAS

    Microsoft Academic Search

    Mercedes Amor; Alessandro Garcia; Lidia Fuentes

    2007-01-01

    Specific features of Multi-Agent Systems (MAS), such as autonomy, learning, mobility, coordination, are driving development concerns, which make evident the need for new design abstractions. Up to now, agent-oriented modeling languages have delivered basic MAS design abstractions -- such as goals and actions -- that explicitly tackle some of these concerns. However, the modularization of a plethora of fundamental MAS

  17. An Assistance Infrastructure to Inform Agents for Decision Support in Open MAS

    E-print Network

    López-Sánchez, Maite

    An Assistance Infrastructure to Inform Agents for Decision Support in Open MAS Pablo Almajano1 in Open MAS. Execution infrastructures me- diate agents interactions while enforcing the rules imposed in order to enable and evaluate different Assistance Services to agents in MAS. We also formalise

  18. Broadband Homonuclear Correlation Spectroscopy at High Magnetic Fields and MAS Frequencies

    E-print Network

    Griffin, Robert G.

    Broadband Homonuclear Correlation Spectroscopy at High Magnetic Fields and MAS Frequencies Gae¨l De spinning (MAS) experiments,7-14 and a large number of broadband homonuclear recoupling techniques have been; thus, there is no 1H decoupling present during the mixing period. It is axiomatic that MAS experiments

  19. Memoria 2011 Biblioteca y Archivo Universidad Autnoma de Madrid Cartoteca "Rafael Mas"

    E-print Network

    Autonoma de Madrid, Universidad

    Memoria 2011 Biblioteca y Archivo Universidad Autónoma de Madrid Cartoteca "Rafael Mas" 1 Memoria 2011Cartoteca "Rafael Mas" #12;Memoria 2011 Biblioteca y Archivo Universidad Autónoma de Madrid Universidad Autónoma de Madrid Cartoteca "Rafael Mas" 3 1.- Introducción: resumen del año La Cartoteca

  20. Memoria 2010 Biblioteca y Archivo Universidad Autnoma de Madrid Cartoteca "Rafael Mas"

    E-print Network

    Autonoma de Madrid, Universidad

    Memoria 2010 Biblioteca y Archivo Universidad Autónoma de Madrid Cartoteca "Rafael Mas" 1 Memoria 2010 Cartoteca "Rafael Mas" #12;Memoria 2010 Biblioteca y Archivo Universidad Autónoma de Madrid Universidad Autónoma de Madrid Cartoteca "Rafael Mas" 3 1.- Introducción: resumen del año La Cartoteca

  1. Variable temperature NMR characterization of ?-glycine

    NASA Astrophysics Data System (ADS)

    Taylor, R. E.; Dybowski, C.

    2008-10-01

    Proton NMR spin-lattice relaxation times in the laboratory frame ( T1) and in the rotating frame ( T1?) were measured as a function of temperature for a static sample of ?-glycine. Both T1 and T1? data can be fit quantitatively by a single thermally-activated motion (the modulation of the dipolar coupling by random hopping about the threefold axis of the -NH 3 group), with no addition of other mechanisms at any temperature between 173 and 415 K. An activation energy of 21.7 ± 1 kJ/mol was extracted and is compared with previously reported values for both ?- and ?-glycine. Such comparisons allow the correction of glycine polymorphs misidentified in the literature. The minimum in T1 at 325 K corresponds to a correlation time of 0.53 ns. Chemical shifts as a function of temperature were measured by 1H CRAMPS and by 13C and 15N CP/MAS experiments. These results are discussed relative to a previous report of anomalous electrical behavior in ?-glycine within this temperature range.

  2. NMR molecular photography

    E-print Network

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

    2002-08-21

    A procedure is described for storing a 2D pattern consisting of 32x32 = 1024 bits in a spin state of a molecular system and then retrieving the stored information as a stack of NMR spectra. The system used is a nematic liquid crystal, the protons of which act as spin clusters with strong intramolecular interactions. The technique used is a programmable multi-frequency irradiation with low amplitude. When it is applied to the liquid crystal, a large number of coherent long-lived 1H response signals can be excited, resulting in a spectrum showing many sharp peaks with controllable frequencies and amplitudes. The spectral resolution is enhanced by using a second weak pulse with a 90 phase shift, so that the 1024 bits of information can be retrieved as a set of well-resolved pseudo-2D spectra reproducing the input pattern.

  3. Deuterium Site Occupancy and Motion in ZrNiDx by High-Resolution ^2H NMR Spectroscopy

    Microsoft Academic Search

    Natalie L. Adolphi; Lisa A. Browder; Sharwari Badola Bowman Jr.

    2001-01-01

    Wideline and high-resolution Magic-Angle Spinning (MAS) ^2H NMR spectra indicate that two types of sites are occupied in ZrNiD_3.0, in a 2:1 ratio, in agreement with previous work. The sites occupied in the tri-hydride phase have been previously identified as Zr_3Ni and Zr_3Ni_2. In ZrNiD_1.0, two well-resolved lines of equal intensity are observed in the MAS spectrum, indicating that two

  4. Deuterium Site Occupancy and Motion in ZrNiDx by High-Resolution ^2H NMR Spectroscopy

    Microsoft Academic Search

    Natalie L. Adolphi; Lisa A. Browder; Sharwari Badola Bowman Jr.

    2000-01-01

    Wideline and high-resolution Magic-Angle Spinning (MAS) ^2H NMR spectra indicate that two types of sites are occupied in ZrNiD_3.0, in a 2:1 ratio, in agreement with previous work. The sites occupied in the tri-hydride phase have been previously identified as Zr_3Ni and Zr_3Ni_2. In ZrNiD_1.0, two well-resolved lines of equal intensity are observed in the MAS spectrum, indicating that two

  5. Variable-temperature solid-state NMR studies of iron(II) and iron(III) complexes 

    E-print Network

    Shepard, Patricia Arlene

    1989-01-01

    Fe(2-pic)&C12 EtQH at room temperature. This approach provides an excellent control over sample spin-state composition and allows all NMR relaxation measurements to be made at room temperature, thereby eliminating temperature... sequence. CT is the cross-polarization contact time. MH and MC denote the magnetization of the H and C nuclei, respectively. 2. Variable-temperature C CP/MAS spectra for Fe(2-pic)3C12 EtOH 31 Variable-composition C CP/MAS spectra for FexZnl x(2-pic)3C...

  6. BusinessandManagement extension.uci.edu/hr

    E-print Network

    Rose, Michael R.

    BusinessandManagement extension.uci.edu/hr Human Resources Management Certificate Program #12 Management Certificate Program UC Irvine Extension's Human Resources Management Certificate Program is highly sector. Course work stresses practical information and techniques useful in identifying, attracting

  7. Does HR add value? : diverse perspectives on human capital management

    E-print Network

    Eckman, Jeffrey M

    2006-01-01

    The human resources (HR) function has evolved significantly over the past several decades. It has grown in maturity and influence while simultaneously enduring great criticism from employees and managers. Meanwhile, ...

  8. University Policy No.: HR6315 Classification: Human Resources

    E-print Network

    Victoria, University of

    University Policy No.: HR6315 Classification: Human Resources SPECIALIST/INSTRUCTIONAL Approving is available from Human Resources. #12;1.4.3 Forty-eight hours written notice should be provided in the event

  9. NUMBER: HR 1.39 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.39 SECTION: Human Resources SUBJECT: Disciplinary Action and Termination for Cause Authorized by: Jane M. Jameson Issued by: Division of Human Resources OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET THE UNIVERSITY'S HUMAN RESOURCES POLICIES

  10. NUMBER: HR 1.24 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.24 SECTION: Human Resources SUBJECT: Appointment, Reassignment, and Promotion of Human Resources OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET THE UNIVERSITY'S HUMAN RESOURCES POLICIES

  11. NUMBER: HR 1.54 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.54 SECTION: Human Resources SUBJECT: Floater Services DATE: August 1988 REVISED: Division of Human Resources OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET THE UNIVERSITY'S HUMAN RESOURCES POLICIES

  12. THz Dynamic Nuclear Polarization NMR

    E-print Network

    Nanni, Emilio Alessandro

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The ...

  13. Compact orthogonal NMR field sensor

    DOEpatents

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

    2009-02-03

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

  14. Elemental abundances of the B and A stars. 2: Gamma Geminorum, HD 60825, 7 Sextantis, HR 4817, and HR 5780

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.; Philip, A. G. Davis

    1994-01-01

    We extend fine analyses of the B and A stars, gamma Geminorum, 7 Sextantis, HR 4817, and HR 5780 using additional spectroscopic data from the Kitt Peak National Observatory (KPNO) coude feed telescope with a TI CCD, camera 5, and grating A, and ATLAS9 model atmospheres. In addition we study HD 60825, which had colors similar to the FHB A stars, but was found to be a Population I star. HD 60825, as is gamma Gem, is a sharp-lined early-A star with nearly solar derived abundances. HR 5780 and 7 Sex are also examples of stars which for the most part have solar abundances. The newly derived abundances for HR 4817 reveal important differences with respect to 53 Tau, a somewhat similar HgMn star.

  15. NMR characterization of thin films

    DOEpatents

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

    2008-11-25

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

  16. Optical pumping and xenon NMR

    SciTech Connect

    Raftery, M.D.

    1991-11-01

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

  17. Optical pumping and xenon NMR

    SciTech Connect

    Raftery, M.D.

    1991-11-01

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

  18. NMR insights into protein allostery

    PubMed Central

    Manley, Gregory; Loria, J. Patrick

    2014-01-01

    Allosterism is one of nature's principal methods for regulating protein function. Allosterism utilizes ligand binding at one site to regulate the function of the protein by modulating the structure and dynamics of a distant binding site. In this review, we first survey solution NMR techniques and how they may be applied to the study of allostery. Subsequently, we describe several examples of application of NMR to protein allostery and highlight the unique insight provided by this experimental technique. PMID:22198279

  19. Multispectral Analysis of NMR Imagery

    NASA Technical Reports Server (NTRS)

    Butterfield, R. L.; Vannier, M. W. And Associates; Jordan, D.

    1985-01-01

    Conference paper discusses initial efforts to adapt multispectral satellite-image analysis to nuclear magnetic resonance (NMR) scans of human body. Flexibility of these techniques makes it possible to present NMR data in variety of formats, including pseudocolor composite images of pathological internal features. Techniques do not have to be greatly modified from form in which used to produce satellite maps of such Earth features as water, rock, or foliage.

  20. NMR Relaxation and Petrophysical Properties

    NASA Astrophysics Data System (ADS)

    Fleury, Marc

    2011-03-01

    NMR relaxation is routinely used in the field of geosciences to give basic petrophysical properties such as porosity, pore size distribution, saturation etc. In this tutorial, we focus on the pore size distribution deduced from NMR. We recall the basic principle used in the interpretation of the NMR signal and compare the results with other standard petrophysical techniques such as mercury pore size distribution, BET specific surface measurements, thin section visualizations. The NMR pore size distribution is a unique information available on water saturated porous media and can give similar results as MICP in certain situations. The scaling of NMR relaxation time distribution (s) into pore sizes (?m) requires the knowledge of the surface relaxivity (?m/s) and we recommend using specific surface measurements as an independent determination of solid surface areas. With usual surface relaxivities, the NMR technique can explore length-scales starting from nano-meters and ending around 100 ?m. Finally, we will introduce briefly recent techniques sensitive to the pore to pore diffusional exchange, providing new information on the connectivity of the pore network, but showing another possibility of discrepancy in the determination of pore size distribution with standard techniques.

  1. Gerhard Wider: Technical aspects of NMR spectroscopy with biological macromolecules .... Technical aspects of NMR spectroscopy

    E-print Network

    Wider, Gerhard

    Gerhard Wider: Technical aspects of NMR spectroscopy with biological macromolecules .... -1- Technical aspects of NMR spectroscopy with biological macromolecules and studies of hydration in solution aspects of NMR spectroscopy with biological macromolecules .... -2- Contents 1. Introduction 5 2. Basic

  2. 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

  3. Multiple non-coding exons and alternative splicing in the mouse Mas protooncogene.

    PubMed

    Alenina, Natalia; Böhme, Ilka; Bader, Michael; Walther, Thomas

    2015-09-01

    The Mas protooncogene encodes a G protein-coupled receptor with the common seven transmembrane domains, expressed mainly in the testis and brain. We provided evidence that Mas is a functional angiotensin-(1-7) receptor and can interact with the angiotensin II type1 (AT1) receptor. The gene is transcriptionally regulated during development in the brain and testis, but its structure was unresolved. In this study we used 5'- and 3'-RACE, RT-PCR, and RNase-protection assays to elucidate the complete Mas gene structure and organization. We identified 12 exons in the mouse Mas gene with 11 in the 5' untranslated mRNA, which can be alternatively spliced. We also showed that Mas transcription can start from 4 tissue-specific promoters, whereby testis-specific Mas mRNA is transcribed from two upstream promoters, and the expression of Mas in the brain starts from two downstream promoters. Alternative splicing and multiple promoter usage result in at least 12 Mas transcripts in which different 5' untranslated regions are fused to a common coding sequence. Moreover, termination of Mas mRNA is regulated by two different polyadenylation signals. The gene spans approximately 27kb, and the longest detected mRNA contains 2451bp. Thus, our results characterize the Mas protooncogene as the gene with the most complex gene structure of all described members of the gene family coding for G protein-coupled receptors. PMID:26003294

  4. Structure and ionic interactions of organic-inorganic composite polymer electrolytes studied by solid-state NMR and Raman spectroscopy.

    PubMed

    Joo, Chan Gyu; Bronstein, Lyudmila M; Karlinsey, Robert L; Zwanziger, Josef W

    2002-01-01

    Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic-inorganic composite, and spin diffusion measurements are used to determine the nanostructure of the polymer/composite blending. Multiple quantum spin counting is used to measure the ion aggregation. The NMR results are supported by Raman spectra, calorimetry, and impedance spectroscopy. From these experiments it is concluded that the composite suppresses polymer crystallization without suppressing its local mobility, and also suppresses the tendency for the ions to aggregate. This polymer composite thus appears very promising for application in lithium ion batteries. PMID:12469813

  5. HR-1 Mice: A New Inflammatory Acne Mouse Model

    PubMed Central

    Jang, Yong Hyun; Lee, Kyou Chae; Lee, Seok-Jong; Kim, Do Won

    2015-01-01

    Background There is no appropriate in vivo animal model that reflects the inflammatory response of human acne. Objective This study investigated the effect of Propionibacterium acnes on the development of inflammatory acne-like lesions in four mouse strains with different degrees of immune response for the development of an optimal mouse model of inflammatory acne. Methods Human P. acnes suspensions (108 and 109 colony forming unit [CFU]/µl) were injected into the backs of HR-1, BALB/c, vitamin D receptor-knockout (VDR k/o), and severe combined immunodeficiency disease mice. Inflammation levels were evaluated two weeks after injection of P. acnes suspensions. In addition, histopathological examination and immunohistochemical staining of the expressions of inflammatory biomarkers (i.e., CD4+/CD8+ T lymphocytes, neutrophils, myeloperoxidase, interleukin-1?, matrix metalloprotease (MMP)-2, MMP-3, MMP-9, toll-like receptor (TLR)-2, LL-37, and integrin ?6) were performed on tissue specimens. Results The HR-1 mouse strain exhibited the most remarkable inflammatory reaction with epithelial proliferation and microcomedone-like cyst formation. HR-1 mice also demonstrated aberrant integrin expression in the epidermis around both inflamed lesions and newly formed microcomedones. These findings were more prominent in the group receiving 109 CFU/µl P. acnes than 108 CFU/µl. MMP-9 expression in HR-1 mice was also upregulated around the microcomedone-like cysts. Finally, expression levels of TLR-2 and LL-37 were higher in HR-1 and BALB/c mice than the VDR k/o and SCID mice strains. Conclusion P. acnes induces acneiform inflammation with small microcomedones in HR-1 mice. Therefore, the HR-1 mouse strain represents a good candidate for the development of a new inflammatory acne mouse model.

  6. Cellular solid-state NMR investigation of a membrane protein using dynamic nuclear polarization.

    PubMed

    Yamamoto, Kazutoshi; Caporini, Marc A; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2015-01-01

    While an increasing number of structural biology studies successfully demonstrate the power of high-resolution structures and dynamics of membrane proteins in fully understanding their function, there is considerable interest in developing NMR approaches to obtain such information in a cellular setting. As long as the proteins inside the living cell tumble rapidly in the NMR timescale, recently developed in-cell solution NMR approaches can provide 3D structural information. However, there are numerous challenges to study membrane proteins inside a cell. Research in our laboratory is focused on developing a combination of solid-state NMR and biological approaches to overcome these challenges in order to obtain high-resolution structural insights into electron transfer processes mediated by membrane-bound proteins like mammalian cytochrome-b5, cytochrome-P450 and cytochrome-P450-reductase. In this study, we demonstrate the feasibility of using dynamic nuclear polarization (DNP) magic angle spinning (MAS) NMR spectroscopy for in-cell studies on a membrane-anchored protein. Our experimental results obtained from ¹³C-labeled membrane-anchored cytochrome-b5 in native Escherichia coli cells show a ~16-fold DNP signal enhancement. Further, results obtained from a 2D ¹³C/¹³C chemical shift correlation MAS experiment demonstrate the feasibility of suppressing the background signals from other cellular contents for high-resolution structural studies on membrane proteins. We believe that this study would pave new avenues for high-resolution structural studies on a variety of membrane-associated proteins and their complexes in the cellular context to fully understand their functional roles in physiological processes. PMID:25017802

  7. Microfabricated Inserts for Magic Angle Coil Spinning (MACS) Wireless NMR Spectroscopy

    PubMed Central

    Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G.; Wallrabe, Ulrike

    2012-01-01

    This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the “magic angle” of 54.74° with respect to the direction of the magnetic field (magic angle spinning – MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

  8. The role of Al in C–S–H: NMR, XRD, and compositional results for precipitated samples

    Microsoft Academic Search

    G. K. Sun; J. Francis Young; R. James Kirkpatrick

    2006-01-01

    X-ray diffraction, compositional analysis, and 29Si and 27Al MAS NMR spectroscopy of Al-substituted tobermorite-type C–S–H made by precipitation from solution provide significant new insight into the structural mechanisms of Al-substitution in this important and complicated phase. Al occurs in 4-, 5-, and 6-coordination (Al[4], Al[5], and Al[6]) and plays multiple structural roles. Al[4] occurs on the bridging tetrahedra of the

  9. Aspects of the chemical structure of soil organic materials as revealed by solid-state13C NMR spectroscopy

    Microsoft Academic Search

    J. A. Baldock; J. M. Oades; A. G. Waters; X. Peng; A. M. Vassallo; M. A. Wilson

    1992-01-01

    Solid-state cross-polarisation\\/magic-angle-spinning3C nuclear magnetic resonance (CP\\/MAS13C NMR) spectroscopy was used to characterise semi-quantitatively the organic materials contained in particle size and density fractions isolated from five different mineral soils: two Mollisols, two Oxisols and an Andosol. The acquired spectra were analysed to determine the relative proportion of carboxyl, aromatic, O-alkyl and alkyl carbon contained in each fraction. Although similar types

  10. Distributed Cooperation Solution Method of Complex System Based on MAS

    NASA Astrophysics Data System (ADS)

    Weijin, Jiang; Yuhui, Xu

    To adapt the model in reconfiguring fault diagnosing to dynamic environment and the needs of solving the tasks of complex system fully, the paper introduced multi-Agent and related technology to the complicated fault diagnosis, an integrated intelligent control system is studied in this paper. Based on the thought of the structure of diagnostic decision and hierarchy in modeling, based on multi-layer decomposition strategy of diagnosis task, a multi-agent synchronous diagnosis federation integrated different knowledge expression modes and inference mechanisms are presented, the functions of management agent, diagnosis agent and decision agent are analyzed, the organization and evolution of agents in the system are proposed, and the corresponding conflict resolution algorithm in given, Layered structure of abstract agent with public attributes is build. System architecture is realized based on MAS distributed layered blackboard. The real world application shows that the proposed control structure successfully solves the fault diagnose problem of the complex plant, and the special advantage in the distributed domain.

  11. Decentralized method for complex task allocation in massive MAS

    NASA Astrophysics Data System (ADS)

    Brahmi, Zaki; Gammoudi, M. M.

    2008-06-01

    Task allocation is still a fundamental problem in Multi-Agents System (MAS). It allows the formation a coalition of agents to cooperate together in order to carry out a complex task. Generally, the process of task allocation requires calculating the value of all the possible allocations, then determining which optimal. In the context of Massive Multi-Agent Systems (MMAS), one agent generates all the possible coalitions and then calculates the value of each, is inefficient. Moreover, the traditional approaches based on the negotiation between agents, are impractical because of the complexity of communications between agents. In this paper we propose a decentralized method, based on grouping agents using the Formal Concepts Analysis (FCA) approach for the task allocation in MMAS. In our model, agents are fully cooperative and each task is composed of several subtasks. The proposed solution is based on two steps: i) computing groups of agents having similar characteristics in the objective to distribute the task allocation process among agents and minimize the communication between agents. ii) Finding the optimal allocation by sharing the task allocation process among groups of agents.

  12. COMPOZER-based longitudinal cross-polarization via dipolar coupling under MAS

    NASA Astrophysics Data System (ADS)

    Kamihara, Takayuki; Murakami, Miwa; Noda, Yasuto; Takeda, Kazuyuki; Takegoshi, K.

    2014-08-01

    We propose a cross polarization (CP) sequence effective under magic-angle spinning (MAS) which is tolerant to RF field inhomogeneity and Hartmann-Hahn mismatch. Its key feature is that spin locking is not used, as CP occurs among the longitudinal (Z) magnetizations modulated by the combination of two pulses with the opposite phases. We show that, by changing the phases of the pulse pairs synchronized with MAS, the flip-flop term of the dipolar interaction is restored under MAS.

  13. MAS based embedded control system design method and a robot development paradigm

    Microsoft Academic Search

    Kejun Ning; Ruqing Yang

    2006-01-01

    This paper summarizes a MAS based embedded control system design method for complex mechatronic system. Regarding the local controller as an agent-task and based on MAS viewpoint, a practical system can be modeled in firmware\\/software level. By using the multitasking capability of RTOS to realize the agent-tasks and using the system service of RTOS to construct the MAS’s coordination mechanism,

  14. Multinuclear solid state NMR investigation of two polymorphic forms of ciprofloxacin-saccharinate.

    PubMed

    Garro Linck, Y; Chattah, A K; Graf, R; Romañuk, C B; Olivera, M E; Manzo, R H; Monti, G A; Spiess, H W

    2011-04-14

    Two polymorphic forms of a novel pharmaceutical compound, ciprofloxacin-saccharinate (CIP-SAC), are analyzed using one dimensional (1D) and two dimensional (2D) (1)H nuclear magnetic resonance (NMR) at fast magic angle spinning (MAS). Additionally (15)N spectroscopy and (1)H-(13)C correlation experiments were performed to complement our conclusions. The 1D (1)H NMR spectra of CIP and complexes reveal valuable information about the ionic bonding between ciprofloxacin and saccharine. Additionally, these spectra allow us to perform a clear characterization of each solid form, giving the number of molecules per unit cell in one of the polymorphs. From 2D (1)H-(1)H spectra obtained through double quantum correlations we can arrive at important conclusions about the hydrogen bonding, conformation, and intra and inter-molecular interactions present in these compounds. Comparing and contrasting the (1)H-(1)H correlation data obtained for both polymorphic forms and taking into account the single crystal structure data existing for the solid form CIP-SAC (II) was possible to extract some conclusions on the polymorph CIP-SAC (I) where no single crystal information is available. (1)H MAS NMR is shown to be an important tool in the field of polymorphism and for the characterization of multicomponent pharmaceutical compounds. PMID:21384011

  15. A LOW-E MAGIC ANGLE SPINNING PROBE FOR BIOLOGICAL SOLID STATE NMR AT 750 MHz

    PubMed Central

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

    2009-01-01

    Crossed-coil NMR probes are a useful tool for reducing sample heating for biological solid state NMR. In a crossed-coil probe, the higher frequency 1H field, which is the primary source of sample heating in conventional probes, is produced by a separate low-inductance resonator. Because a smaller driving voltage is required, the electric field across the sample and the resultant heating is reduced. In this work we describe the development of a magic angle spinning (MAS) solid state NMR probe utilizing a dual resonator. This dual resonator approach, referred to as “Low-E,” was originally developed to reduce heating in samples of mechanically aligned membranes. The study of inherently dilute systems, such as proteins in lipid bilayers, via MAS techniques requires large sample volumes at high field to obtain spectra with adequate signal-to-noise ratio under physiologically relevant conditions. With the Low-E approach, we are able to obtain homogeneous and sufficiently strong radiofrequency fields for both 1H and 13C frequencies in a 4 mm probe with a 1H frequency of 750 MHz. The performance of the probe using windowless dipolar recoupling sequences is demonstrated on model compounds as well as membrane embedded peptides. PMID:19138870

  16. "EASY: A simple tool for simultaneously removing background, deadtime and acoustic ringing in quantitative NMR spectroscopy. Part II: Improved ringing suppression, application to quadrupolar nuclei, cross polarisation and 2D NMR".

    PubMed

    Jaeger, Christian; Hemmann, Felix

    2014-01-01

    A simple experiment for Elimination of Artifacts in NMR SpectroscopY (EASY) was introduced in Part I, and it was shown that NMR probe background signals, spectral distortions due to deadtime effects, and acoustic ringing can be eliminated simultaneously from solid-state NMR spectra. In this Part II, it is shown that acoustic ringing suppression can be improved up to one order of magnitude compared to the original EASY pulse sequence by inserting a delay ? between the two data acquisition scans of the EASY pulse sequence. The achievable ringing suppression depends on the length of this delay and is limited by the spin-lattice relaxation time T1. Furthermore, EASY is considered in conjunction with NMR of quadrupolar nuclei. For strong second-order broadening, EASY can be used to acquire either pure central transition MAS patterns or pure satellite transition NMR spectra. Two further modifications to EASY are introduced. One concerns improved ringing artifact suppression in experiments in which the central transition NMR signal is amplified by Rotor Assisted Population Transfer (RAPT). The second EASY modification enables the acquisition of quantitative NMR spectra if signals with different quadrupole coupling constants are present. In addition, acoustic ringing and (11)B stator signals are removed. Finally, it is demonstrated that the basic idea of EASY for removing ringing artifacts can be realized for heteronuclear one-dimensional and hetero- and homo-nuclear multi-dimensional NMR experiments using extended phase cycling. (15)N{(1)H} CPMAS and (15)N 2D Exchange NMR spectroscopy are considered as examples. PMID:25200102

  17. OBSERVATIONS AND ORBITAL ANALYSIS OF THE GIANT WHITE DWARF BINARY SYSTEM HR 5692

    SciTech Connect

    Stefanik, Robert P.; Torres, Guillermo; Latham, David W. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Landsman, Wayne [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Craig, Nathaniel; Murrett, James, E-mail: rstefanik@cfa.harvard.edu [Harvard College, Cambridge, MA 02138 (United States)

    2011-05-15

    We report spectroscopic observations of the red giant star HR 5692, previously known to be a binary system both from other spectroscopic work and from deviations in the astrometric motion detected by the Hipparcos satellite. Earlier International Ultraviolet Explorer (IUE) observations had shown the presence of a hot white dwarf companion to the giant primary. We have combined our radial velocity observations with other existing measurements and with the Hipparcos intermediate astrometric data to determine a complete astrometric-spectroscopic orbital solution, providing the inclination angle for the first time. We also determine an improved parallax for the system of 10.12 {+-} 0.67 mas. We derive the physical properties of the primary, and with an estimate of its mass from stellar evolution models (1.84 {+-} 0.40 M{sub sun}), we infer the mass of the white dwarf companion to be M{sub WD} = 0.59 {+-} 0.12 M{sub sun}. An analysis of an IUE white dwarf spectrum, using our parallax, yields T{sub eff} = 30, 400 {+-} 780 K, log g = 8.25 {+-} 0.15, and a mass M{sub WD} = 0.79 {+-} 0.09 M{sub sun}, in marginal agreement with the dynamical mass.

  18. Coherent and stochastic averaging in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Nevzorov, Alexander A.

    2014-12-01

    A new approach for calculating solid-state NMR lineshapes of uniaxially rotating membrane proteins under the magic-angle spinning conditions is presented. The use of stochastic Liouville equation (SLE) allows one to account for both coherent sample rotation and stochastic motional averaging of the spherical dipolar powder patterns by uniaxial diffusion of the spin-bearing molecules. The method is illustrated via simulations of the dipolar powder patterns of rigid samples under the MAS conditions, as well as the recent method of rotational alignment in the presence of both MAS and rotational diffusion under the conditions of dipolar recoupling. It has been found that it is computationally more advantageous to employ direct integration over a spherical grid rather than to use a full angular basis set for the SLE solution. Accuracy estimates for the bond angles measured from the recoupled amide 1H-15N dipolar powder patterns have been obtained at various rotational diffusion coefficients. It has been shown that the rotational alignment method is applicable to membrane proteins approximated as cylinders with radii of approximately 20 Å, for which uniaxial rotational diffusion within the bilayer is sufficiently fast and exceeds the rate 2 × 105 s-1.

  19. MMAE Co-terminal Degrees Summary Co-terminal Degrees within MMAE (MAS = master of engineering, i.e. non-thesis

    E-print Network

    Heller, Barbara

    MMAE Co-terminal Degrees Summary Co-terminal Degrees within MMAE (MAS + MAS Mechanical and Aerospace Engineering · BS Aerospace Engineering + MAS Mechanical and Aerospace Engineering · BS Mechanical Engineering + MAS Materials Science

  20. The influence of line managers and HR department on employees' affective commitment

    Microsoft Academic Search

    Caroline Gilbert; Sophie De Winne; Luc Sels

    2011-01-01

    Based on social exchange theory, we investigate the impact of HRM investments made by two important HR actors, line managers and HR department, on employees' affective commitment. More specifically, we examine the independent and joint impact of line managers' enactment of HR practices, their relations-oriented leadership behaviour and the HR department's service quality. Accordingly, we consider the largely neglected HRM

  1. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves

    SciTech Connect

    Thurber, Kent R., E-mail: thurberk@niddk.nih.gov; Tycko, Robert [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)] [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

    2014-05-14

    We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

  2. FAST-NMR: Functional Annotation Screening Technology Using NMR Spectroscopy

    E-print Network

    Powers, Robert

    .; Fellenberg, M.; Heumann, K.; Mewes, H.-W. Nucleic Acids Res. 2003, 31, 207. (4) Kanehisa, M.; Goto, S.; Kawashima, S.; Okuno, Y.; Hattori, M. Nucleic Acids Res. 2004, 32, D277. Figure 1. Functional information-ligand interactions are determined through a tiered NMR screen using a library composed of compounds with known

  3. A SENSITIVE NMR THERMOMETER FOR MULTINUCLEI FT NMR

    EPA Science Inventory

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

  4. University Policy No: HR6310 Classification: Human Resources

    E-print Network

    Victoria, University of

    University Policy No: HR6310 Classification: Human Resources POST DOCTORAL Approving authority Change: Mandated review: August, 2017 Associated Procedures: Procedures for the Appointment of Post-Doctoral as the supervisor and employer of a Post Doctoral Fellow; establish the responsibilities of the Post Doctoral

  5. Lymphedema Treatment Act (H.R.1608; 114th Congress)

    Cancer.gov

    The bill would require Medicare to cover certain lymphedema compression treatment items as “durable medical equipment.” H.R. 1608 was introduced by Rep. David Reichert (R-GA) on 3/25/15 and was referred to the Committees on Energy and Commerce and Ways

  6. HR 8799: A Link between ? Doradus Variables and ? Bootis Stars

    Microsoft Academic Search

    Richard O. Gray; Anthony B. Kaye

    1999-01-01

    On the basis of a new classi—cation-resolution spectrum, we —nd that HR 8799, a known member of the newly discovered c Doradus variable star class, is a j Bootis star. Spectral synthesis, in conjunction with —uxes from visible spectrophotometry and the TD -1 satellite, yields

  7. Learning Culture, Line Manager and HR Professional Practice

    ERIC Educational Resources Information Center

    Harrison, Patricia

    2011-01-01

    Purpose: This paper aims to focus on the role of line management and learning culture in the development of professional practice for the human resource (HR) practitioner. Design/methodology/approach: Three-year longitudinal, matched-pair study involving five participants and their line managers. Findings: Two of the five participants experienced…

  8. HR/OPL JAN 14 ORDINARY PATERNITY/PARTNER

    E-print Network

    Barker, Jon

    dd/mm/yy 3 Date of return to work dd/mm/yy If the child is born early, rights of entitlement with the above) for the child's upbringing, and 3 I am making the application to take time off work to support/placement of child). 2. Please read the Paternity/Partner Leave Policy and Procedure, available via the HR Family

  9. IN-RANGE PROGRESSION SJSU HR: 2/20/13

    E-print Network

    Su, Xiao

    IN-RANGE PROGRESSION GUIDELINES SJSU HR: 2/20/13 SUBJECT: IN-RANGE PROGRESSION DATE: February 19 the compensation requirements for In-Range Progression as stated in Collective Bargaining Unit Agreements for APC, CESUEU, SETC and SUPA. APC An in-range progression is defined as an increase in an employee's pay rate

  10. HR Manager Leadership in Quality Improvement in a College Environment

    ERIC Educational Resources Information Center

    Sharabi, Moshe

    2010-01-01

    Purpose: The purpose of this paper is to present the influence of the human resource (HR) manager on the quality of service in an academic college, and the human resource management (HRM) outcomes of the process. Design/methodology/approach: The paper relates to a customer satisfaction survey. More than 120 questionnaires were completed by the…

  11. NUMBER: HR 1.33 SECTION: Human Resources

    E-print Network

    Almor, Amit

    to South Carolina State law regarding labor and employment. B. Employees of the University of SouthNUMBER: HR 1.33 SECTION: Human Resources SUBJECT: Labor DATE: August 1988 REVISED: August 10, 2010 policy on labor relations and the relationship between the University and its employees, pursuant

  12. University Policy No.: HR6325 Classification: Human Resources

    E-print Network

    Victoria, University of

    University Policy No.: HR6325 Classification: Human Resources Approving Authority: Vice President and the remitting of income tax installments. 3.3 The specific criteria or tests used to determine the existence be done. If the extent of the University's control is nclear, other tests may be applied (see Appendix 1

  13. An Ounce of Prevention: The Benefits of an HR Audit

    ERIC Educational Resources Information Center

    Seals, Brenda

    2011-01-01

    During her 13 years leading a school district human resources office, the author came to recognize that managing human capital is much more than recruiting, hiring, managing personnel records, and handling performance issues. In addition to implementing initiatives to increase the efficiency with which HR officers and staff perform those tasks,…

  14. A possible architecture of the planetary system HR 8799

    Microsoft Academic Search

    Martin Reidemeister; Alexander V. Krivov; T. O. B. Schmidt; Simone Fiedler; Sebastian Müller; Torsten Löhne; Ralph Neuhäuser

    2009-01-01

    HR 8799 is a nearby A-type star with a debris disk and three planetary candidates, which have been imaged directly. We undertake a coherent analysis of various observational data for all known components of the system, including the central star, imaged companions, and dust. Our goal is to elucidate the architecture and evolutionary status of the system. We try to

  15. HR as Partner: Building Strategic Partnerships on Campus

    ERIC Educational Resources Information Center

    Connally, Sam; Neuman, Dawn

    2006-01-01

    Human resources is in an excellent position in many institutions to initiate collaboration and cooperation with other campus departments. In this article, the leaders of the departments of HR and academic resources at the University of Nevada, Las Vegas, share their insights on the importance of partnership-building on campus and describe how a…

  16. University Policy No.: HR6320 Classification: Human Resources

    E-print Network

    Victoria, University of

    University Policy No.: HR6320 Classification: Human Resources GUIDELINES FOR THE APPOINTMENT the offer of employment to a foreign worker requires validation by Human Resources Development Canada (HRDC only under strictly prescribed conditions and according to procedures that are acceptable to Human

  17. NUMBER: HR 1.77 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.77 SECTION: Human Resources SUBJECT: Bonuses DATE CREATED: October 2001 LATEST Issued by: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT IS NOT INTENDED TO CREATE CREATE ANY CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY

  18. NUMBER: HR 1.01 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.01 SECTION: Human Resources SUBJECT: Drug-Free Workplace DATE: September 1990 (REV Issued by: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT IS NOT INTENDED TO CREATE CREATE ANY CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY

  19. TO: HR and Business Contacts FROM: Division of Human Resources

    E-print Network

    Almor, Amit

    TO: HR and Business Contacts FROM: Division of Human Resources DATE: September 24, 2012 RE: Reminder: Human Resources Fall 2012 Forum This is a reminder that you will need to register online by the Division of Human Resources, this forum will include information about benefits updates to annual

  20. HR Contacts by Function Harvard Medical School Human Resources

    E-print Network

    Chou, James

    HR Contacts by Function Harvard Medical School Human Resources Stanley, Julie Chief Human Resources, Employment, & Compensation Leary, Simone Managing Senior Human Resources Consultant (617) 432-1226 Margiloff, Susan Senior Human Resources Consultant (617-432-2040 Thibodeau, Ryan Senior Human Resources Consultant

  1. University Policy No.: HR6305 Classification: Human Resources

    E-print Network

    Victoria, University of

    University Policy No.: HR6305 Classification: Human Resources EMPLOYMENT UNDER EXTERNALLY Approving. PROCEDURES The Department of Human Resources shall process all employment and related documents' letter will be prepared for the grantee by the Department of Human Resources. The grantee will sign

  2. NUMBER: HR 1.06 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.06 SECTION: Human Resources SUBJECT: Sick Leave DATE: July 1, 1995 (Rev.) REVISED: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT DOES NOT CREATE AN EMPLOYMENT CONTRACT CONTRACT OF EMPLOYMENT. THE UNIVERSITY OF SOUTH CAROLINA DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY

  3. NUMBER: HR 1.81 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.81 SECTION: Human Resources SUBJECT: Summer Compensation for Faculty DATE: July 1: Chris Byrd ISSUED BY: Division of Human Resources OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET THE UNIVERSITY'S HUMAN RESOURCES POLICIES. I. Policy A

  4. NUMBER: HR 1.15 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.15 SECTION: Human Resources SUBJECT: Holiday Leave DATE: October 2008 REVISED: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT IS NOT INTENDED TO CREATE AN EMPLOYMENT CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET

  5. NUMBER: HR 1.66 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.66 SECTION: Human Resources SUBJECT: Workers' Compensation DATE: August 1988 REVISED: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT IS NOT INTENDED TO CREATE AN EMPLOYMENT CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET

  6. NUMBER: HR 1.51 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.51 SECTION: Human Resources SUBJECT: Professional Development for University Authorized by: Chris Byrd Issued by: Division of Human Resources The language used in this document does of this paragraph create any contract of employment. The University of South Carolina Division of Human Resources

  7. NUMBER: HR 1.69 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.69 SECTION: Human Resources SUBJECT: Official Personnel Files and Records Release Authorized by: Judy Owens Issued by: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT OF THIS PARAGRAPH CREATE ANY CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY

  8. NUMBER: HR 1.42 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.42 SECTION: Human Resources SUBJECT: Grievance DATE: August 1988 REVISED: February: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT IS NOT INTENDED TO CREATE AN EMPLOYMENT CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET

  9. NUMBER: HR 1.12 SECTION: Human Resources

    E-print Network

    Almor, Amit

    1 NUMBER: HR 1.12 SECTION: Human Resources SUBJECT: Leave Without Pay DATE: August 1988 REVISED: Division of Human Resources THE LANGUAGE USED IN THIS DOCUMENT IS NOT INTENDED TO CREATE AN EMPLOYMENT CONTRACT OF EMPLOYMENT. THE UNIVERSITY'S DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET

  10. Knowledge management in the HR sector of RD organizations

    Microsoft Academic Search

    VALENTINA JANEV

    2008-01-01

    This paper presents a solution for managing the specific HR assets in research organizations, i.e. the scientific track record of scientists and researchers. The solution has already been installed at the Mihajlo Pupin Institute (MPI) in Belgrade as a part of the knowledge management initiative started a few years ago. It is based on SAP Human Capital Management (HCM) solution

  11. FREQUENTLY ASKED QUESTIONS: HR Organizational Readiness Project (HRORP)

    E-print Network

    Finzi, Adrien

    of HR-related data for non-faculty, staff positions in format required by the SAP enterprise resource planning (ERP) system. The collection of this data will allow Boston University to realize the full potential of its investment in SAP. It will also provide the essential building blocks for a modern Human

  12. Multi-Agent System (MAS) for short-term generation scheduling of a microgrid

    Microsoft Academic Search

    T. Logenthiran; D. Srinivasan; A. M. Khambadkone; H. N. Aung

    2010-01-01

    Microgrids are low voltage distribution networks comprising various distributed generators, storage devices and controllable loads. Microgrid can be operated in interconnected mode or islanded mode. Optimal generation scheduling is one of the microgrid energy management system's function for optimizing the microgrid operation. This paper presents a Multi-Agent System (MAS) for generation scheduling of a microgrid. The proposed MAS architecture has

  13. SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester MAS273 Statistical Modelling 2 hours

    E-print Network

    . The vari- ables are Energy (E) - usable energy recovered from waste (kcal/kg), Plastic (PL) - % plastic. MAS273 1 Turn Over #12;MAS273 1 This question concerns data on the energy content of municipal waste by weight, Water (W) - % moisture by weight. n heaps of municipal waste were obtained and the regression

  14. Psychometric Comparison of the Motivation Assessment Scale (MAS) and the Questions about Behavioral Function (QABF)

    ERIC Educational Resources Information Center

    Koritsas, S.; Iacono, T.

    2013-01-01

    Background: The Motivation Assessment Scale (MAS) and the Questions About Behavioral Function (QABF) are frequently used to assess the learned function of challenging behaviour in people with intellectual disability (ID). The aim was to explore and compare the psychometric properties of the MAS and the QABF. Method: Seventy adults with ID and…

  15. A stable amorphous statin: solid-state NMR and dielectric studies on dynamic heterogeneity of simvastatin.

    PubMed

    Nunes, Teresa G; Viciosa, M Teresa; Correia, Natália T; Danède, F; Nunes, Rita G; Diogo, Hermínio P

    2014-03-01

    Statins have been widely used as cholesterol-lowering agents. However, low aqueous solubility of crystalline statins and, consequently, reduced biovailability require seeking for alternative forms and formulations to ensure an accurate therapeutic window. The objective of the present study was to evaluate the stability of amorphous simvastatin by probing molecular dynamics using two nondestructive techniques: solid-state NMR and dielectric relaxation spectroscopy. Glassy simvastatin was obtained by the melt quench technique. (13)C cross-polarization/magic-angle-spinning (CP/MAS) NMR spectra and (1)H MAS NMR spectra were obtained from 293 K up to 333 K (Tg ? 302 K). The (13)C spin-lattice relaxation times in the rotating frame, T1?, were measured as a function of temperature, and the correlation time and activation energy data obtained for local motions in different frequency scales revealed strong dynamic heterogeneity, which appears to be essential for the stability of the amorphous form of simvastatin. In addition, the (1)H MAS measurements presented evidence for mobility of the hydrogen atoms in hydroxyl groups which was assigned to noncooperative secondary relaxations. The complex dielectric permittivity of simvastatin was monitored in isochronal mode at five frequencies (from 0.1 to 1000 kHz), by carrying out a heating/cooling cycle allowing to obtain simvastatin in the supercooled and glassy states. The results showed that no dipolar moment was lost due to immobilization, thus confirming that no crystallization had taken place. Complementarily, the present study focused on the thermal stability of simvastatin using thermogravimetric analysis while the thermal events were followed up by differential scanning calorimetry and dielectric relaxation spectroscopy. Overall, the results confirm that the simvastatin in the glass form reveals a potential use in the solid phase formulation on the pharmaceutical industry. PMID:24499472

  16. Using NMR for ligand discovery and optimization

    Microsoft Academic Search

    Hugo O Villar; Jiangli Yan; Mark R Hansen

    2004-01-01

    Several recent technology-driven advances in the area of NMR have rekindled an interest in the application of the technology to problems in drug discovery and development. A unique aspect of NMR is that it has applicability in broadly different areas of the drug discovery and optimization processes. NMR techniques for screening aimed at the discovery of novel ligands or low

  17. Quality Assessment of Horticultural Products by NMR

    Microsoft Academic Search

    B. P HILLS; C. J CLARK

    2003-01-01

    The potential for developing NMR as an on-line sensor of the internal quality of fruits and vegetables is discussed. The literature on the NMR of horticultural products is first surveyed for potentially useful correlations between NMR characteristics and internal quality factors in commercially important harvested products. This is followed by discussions on the cellular origins of these correlations and of

  18. Applications of NMR to food science

    Microsoft Academic Search

    E Alberti; P. S Belton; A. M Gil

    2002-01-01

    This report reviews the literature on the applications of NMR to food science from 1995 until March 2001. In order to be able to keep the number of references to manageable proportions, the number of papers referred to has been limited to those applications where NMR plays a major role in the experimental programme. Applications where NMR is simply used

  19. NMR spectroscopic analysis of lotusine.

    PubMed

    Yang, Jian

    2005-02-01

    Lotusine, a soluble alkaloid, is one of the major constituents of the Chinese medicine Lotus Plumule, and has antihypertension and antibacterial activity. In order to confirm the structures reported in the literature by explicit 1H and 13C assignments, we applied a series of NMR experiments including 1H-1H COSY, HSQC and HMBC. PMID:15562520

  20. Petrophysical applications of NMR imaging

    SciTech Connect

    Rothwell, W.P.; Vinegar, H.J.

    1985-12-01

    A system for obtaining high-resolution NMR images of oil field cores is described. Separate proton density and T/sub 2/ relaxation images are obtained to distinguish spatial variations of fluid-filled porosity and the physical nature of the pores. Results are presented for typical sandstones.

  1. Synthesis, solid-state NMR, and magnetic characterization of h-GaN containing magnetic ions

    NASA Astrophysics Data System (ADS)

    Purdy, A. P.; Yesinowski, J. P.; Hanbicki, A. T.

    2005-05-01

    GaN crystals doped with Mn ions were synthesized by the alkali metal flux method. Mixtures of metals were premelted to form an alloy and the alloy was mixed with Na/K and heated to 800 °C under 1400 psi N2 in an alumina crucible. Up to 2 mol% Mn could be incorporated into the h-GaN lattice, and the products were characterized by solid state NMR, magnetometry, Raman spectroscopy, and powder X-ray diffraction. The solid state MAS NMR spectra (71Ga, 69Ga, 14N) of the most heavily doped material, which is a normal paramagnet, have broad peaks that are shifted appreciably to higher frequency from the hexagonal GaN chemical shift position, probably due to Knight shifts.

  2. Solid state 13C NMR characterisation study on fourth generation Ziegler-Natta catalysts.

    PubMed

    Heikkinen, Harri; Liitiä, Tiina; Virkkunen, Ville; Leinonen, Timo; Helaja, Tuulamari; Denifl, Peter

    2012-01-01

    In this study, solid state (13)C NMR spectroscopy was utilised to characterize and identify the metal-ester coordination in active fourth generation (phthalate) Ziegler-Natta catalysts. It is known that different donors affect the active species in ZN catalysts. However, there is still limited data available of detailed molecular information how the donors and the active species are interplaying. One of the main goals of this work was to get better insight into the interactions of donor and active species. Based on the anisotropy tensor values (?(11), ?(22), ?(33)) from low magic-angle spinning (MAS) (13)C NMR spectra in combination with chemical shift anisotropy (CSA) calculations (?(aniso) and ?), both the coordinative metal (Mg/Ti) and the symmetry of this interaction between metal and the internal donor in the active catalyst (MgCl(2)/TiCl(4)/electron donor) system could be identified. PMID:22425229

  3. Solid-state /sup 13/C NMR and X-ray diffraction of dermatan sulfate

    SciTech Connect

    Winter, W.T.; Taylor, M.G.; Stevens, E.S.; Morris, E.R.; Rees, D.A.

    1986-05-29

    Dermatan sulfate in the solid state has been studied by /sup 13/C CP/MAS nmr and X-ray diffraction in order to establish the ring conformation of the L-iduronate moiety. The solid state nmr spectrum is similar to the solution spectrum obtained previously, indicating that a ring conformation at least approximating to /sup 1/C/sub 4/ predominates in the solid state. X-ray powder diffraction data from the same sample indicate the presence of the 8-fold helix form previously observed by fiber diffraction, and interpreted in terms of a /sup 4/C/sub 1/ ring form. A likely explanation of the results is that a distorted /sup 1/C/sub 4/ L-iduronate ring conformation, not considered in the initial X-ray analysis, may emerge to provide a satisfactory interpretation of all available physical-chemical data.

  4. Informing the HR Hiring Decision of IT Personnel: The HR Professional's View of IT Certification, Education, & Experience

    Microsoft Academic Search

    John E. Anderson; Kevin S. Barrett; Paul H. Schwager

    This study examined the importance of IT Certification from the HR Professional's perspective, specifically the value of certification in relation to education and experience in a hiring decision. We found that an increase in formal education was subsidized by a decreasing emphasis on ex- perience until a balance was reached. The relative weight of certification, however, was generally stable. A

  5. Using NMR for ligand discovery and optimization.

    PubMed

    Villar, Hugo O; Yan, Jiangli; Hansen, Mark R

    2004-08-01

    Several recent technology-driven advances in the area of NMR have rekindled an interest in the application of the technology to problems in drug discovery and development. A unique aspect of NMR is that it has applicability in broadly different areas of the drug discovery and optimization processes. NMR techniques for screening aimed at the discovery of novel ligands or low molecular weight structures for fragment-based build up procedures are being applied commonly in the industry. Application of NMR in structure-guided drug design and metabonomics are also becoming routine. We present an overview of some of the most recent NMR developments in these areas. PMID:15288248

  6. Role for NMR in structural genomics.

    PubMed

    Kennedy, Michael A; Montelione, Gaetano T; Arrowsmith, Cheryl H; Markley, John L

    2002-01-01

    The 2nd EMSL Workshop on Structural Genomics was held on 28th and 29th July 2000 at the Environmental Molecular Sciences Laboratory at the Department of Energy's Pacific Northwest National Laboratory in Richland, WA. The workshop focused on four topics: 1. The role for NMR in structural and functional genomics; 2. The technical challenges NMR faces for structural and functional genomics; 3. The potential need for a national NMR center for structural and functional genomics in the United States; and 4. Organization of the NMR community. This report summarizes the workshop proceedings and conclusions reached regarding the role of NMR in the emerging fields of structural and functional genomics. PMID:12836706

  7. C NMR Spectra (see p S10)

    E-print Network

    Collum, David B.

    S31 1 H and 13 C NMR Spectra (see p S10) NHBn Me Ph 10 #12;S32 1 H and 13 C NMR Spectra (see p S10) NHBn Me Ph 11 #12;S33 1 H and 13 C NMR Spectra (see p S11) NH-i-Pr n-Bu NH-i-Pr n-Bu 12 Me Me 13 #12;S34 1 H and 13 C NMR Spectra (see p S11)NH-i-Pr Me Ph 14 #12;S35 1 H and 13 C NMR Spectra (see p S11

  8. Atypical Signaling and Functional Desensitization Response of MAS Receptor to Peptide Ligands

    PubMed Central

    Tirupula, Kalyan C.; Desnoyer, Russell; Speth, Robert C.; Karnik, Sadashiva S.

    2014-01-01

    MAS is a G protein-coupled receptor (GPCR) implicated in multiple physiological processes. Several physiological peptide ligands such as angiotensin-(1–7), angiotensin fragments and neuropeptide FF (NPFF) are reported to act on MAS. Studies of conventional G protein signaling and receptor desensitization upon stimulation of MAS with the peptide ligands are limited so far. Therefore, we systematically analyzed G protein signals activated by the peptide ligands. MAS-selective non-peptide ligands that were previously shown to activate G proteins were used as controls for comparison on a common cell based assay platform. Activation of MAS by the non-peptide agonist (1) increased intracellular calcium and D-myo-inositol-1-phosphate (IP1) levels which are indicative of the activation of classical G?q-phospholipase C signaling pathways, (2) decreased G?i mediated cAMP levels and (3) stimulated G?12-dependent expression of luciferase reporter. In all these assays, MAS exhibited strong constitutive activity that was inhibited by the non-peptide inverse agonist. Further, in the calcium response assay, MAS was resistant to stimulation by a second dose of the non-peptide agonist after the first activation has waned suggesting functional desensitization. In contrast, activation of MAS by the peptide ligand NPFF initiated a rapid rise in intracellular calcium with very weak IP1 accumulation which is unlike classical G?q-phospholipase C signaling pathway. NPFF only weakly stimulated MAS-mediated activation of G?12 and G?i signaling pathways. Furthermore, unlike non-peptide agonist-activated MAS, NPFF-activated MAS could be readily re-stimulated the second time by the agonists. Functional assays with key ligand binding MAS mutants suggest that NPFF and non-peptide ligands bind to overlapping regions. Angiotensin-(1–7) and other angiotensin fragments weakly potentiated an NPFF-like calcium response at non-physiological concentrations (?100 µM). Overall, our data suggest that peptide ligands induce atypical signaling and functional desensitization of MAS. PMID:25068582

  9. Stacking structure of confined 1-butanol in SBA-15 investigated by solid-state NMR spectroscopy.

    PubMed

    Lin, Yun-Chih; Chou, Hung-Lung; Sarma, Loka Subramanyam; Hwang, Bing-Joe

    2009-10-12

    Understanding the complex thermodynamic behavior of confined amphiphilic molecules in biological or mesoporous hosts requires detailed knowledge of the stacking structures. Here, we present detailed solid-state NMR spectroscopic investigations on 1-butanol molecules confined in the hydrophilic mesoporous SBA-15 host. A range of NMR spectroscopic measurements comprising of (1)H spin-lattice (T(1)), spin-spin (T(2)) relaxation, (13)C cross-polarization (CP), and (1)H,(1)H two-dimensional nuclear Overhauser enhancement spectroscopy ((1)H,(1)H 2D NOESY) with the magic angle spinning (MAS) technique as well as static wide-line (2)H NMR spectra have been used to investigate the dynamics and to observe the stacking structure of confined 1-butanol in SBA-15. The results suggest that not only the molecular reorientation but also the exchange motions of confined molecules of 1-butanol are extremely restricted in the confined space of the SBA-15 pores. The dynamics of the confined molecules of 1-butanol imply that the (1)H,(1)H 2D NOESY should be an appropriate technique to observe the stacking structure of confined amphiphilc molecules. This study is the first to observe that a significant part of confined 1-butanol molecules are orientated as tilted bilayered structures on the surface of the host SBA-15 pores in a time-average state by solid-state NMR spectroscopy with the (1)H,(1)H 2D NOESY technique. PMID:19746482

  10. A tunable homonuclear dipolar decoupling scheme for high-resolution proton NMR of solids from slow to fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Gan, Zhehong; Madhu, P. K.; Amoureux, Jean-Paul; Trébosc, Julien; Lafon, Olivier

    2011-02-01

    A homonuclear dipolar decoupling scheme is introduced for obtaining proton high-resolution NMR spectra of solids under slow to fast magic-angle spinning (MAS). The basic unit is an extension of magic-echo sequence with its effective field tilted in the rotating frame, bracketed by two sandwich pulses. The angle of the tilt can be tuned for obtaining optimal spectral resolution according to the spinning frequency. Improved resolution has been obtained using this tunable sequence on a sample of glycine at 10 and 60 kHz of MAS compared with windowed phase-modulated Lee-Goldburg and magic-echo sandwich schemes.

  11. Binding of HIV-1 Vpr protein to the human homolog of the yeast DNA repair protein RAD23 (hHR23A) requires its xeroderma pigmentosum complementation group C binding (XPCB) domain as well as the ubiquitin-associated 2 (UBA2) domain.

    PubMed

    Jung, Jinwon; Byeon, In-Ja L; DeLucia, Maria; Koharudin, Leonardus M I; Ahn, Jinwoo; Gronenborn, Angela M

    2014-01-31

    The human homolog of the yeast DNA repair protein RAD23, hHR23A, has been found previously to interact with the human immunodeficiency virus, type 1 accessory protein Vpr. hHR23A is a modular protein containing an N-terminal ubiquitin-like (UBL) domain and two ubiquitin-associated domains (UBA1 and UBA2) separated by a xeroderma pigmentosum complementation group C binding (XPCB) domain. All domains are connected by flexible linkers. hHR23A binds ubiquitinated proteins and acts as a shuttling factor to the proteasome. Here, we show that hHR23A utilizes both the UBA2 and XPCB domains to form a stable complex with Vpr, linking Vpr directly to cellular DNA repair pathways and their probable exploitation by the virus. Detailed structural mapping of the Vpr contacts on hHR23A, by NMR, revealed substantial contact surfaces on the UBA2 and XPCB domains. In addition, Vpr binding disrupts an intramolecular UBL-UBA2 interaction. We also show that Lys-48-linked di-ubiquitin, when binding to UBA1, does not release the bound Vpr from the hHR23A-Vpr complex. Instead, a ternary hHR23A·Vpr·di-Ub(K48) complex is formed, indicating that Vpr does not necessarily abolish hHR23A-mediated shuttling to the proteasome. PMID:24318982

  12. Structure resolution of Ba{sub 5}Al{sub 3}F{sub 19} and Iivestigation of fluorine ion dynamics by synchrotron powder diffraction, variable-temperature solid-state NMR, and quantum computations.

    SciTech Connect

    Martineau, C.; Fayon, F.; Suchomel, M. R.; Allix, M.; Massiot, D.; Taulelle, F. (X-Ray Science Division); (Univ. de Versailles Saint-Quentin en Yvelines); (CNRS); (Univ. d'Orleans)

    2011-02-23

    The room temperature structure of Ba{sub 5}Al{sub 3}F{sub 19} has been solved using electron microscopy and synchrotron powder diffraction data. One-dimensional (1D) {sup 27}Al and ultrafast magic-angle-spinning (MAS) {sup 19}F NMR spectra have been recorded and are in agreement with the proposed structural model for Ba{sub 5}Al{sub 3}F{sub 19}. The {sup 19}F isotropic chemical shift and {sup 27}Al quadrupolar parameters have been calculated using the CASTEP code from the experimental and density functional theory geometry-optimized structures. After optimization, the calculated NMR parameters of both the {sup 19}F and {sup 27}Al nuclei show improved consistency with the experimental values, demonstrating that the geometry optimization step is necessary to obtain more accurate and reliable structural data. This also enables a complete and unambiguous assignment of the {sup 19}F MAS NMR spectrum of Ba{sub 5}Al{sub 3}F{sub 19}. Variable-temperature 1D MAS {sup 19}F NMR experiments have been carried out, showing the occurrence of fluorine ion mobility. Complementary insights were obtained from both two-dimensional (2D) exchange and 2D double-quantum dipolar recoupling NMR experiments, and a detailed analysis of the anionic motion in Ba{sub 5}Al{sub 3}F{sub 19} is proposed, including the distinction between reorientational processes and chemical exchange involving bond breaking and re-formation.

  13. Ultraviolet, optical, infrared, and microwave observations of HR 5110

    NASA Technical Reports Server (NTRS)

    Little-Marenin, I. R.; Simon, T.; Ayres, T. R.; Cohen, N. L.; Feldman, P. A.

    1986-01-01

    Near-IR JHKLM photometric data and VLBI and IUE radio burst data collected on the short-period spectroscopic binary HR 5110 are analyzed to classify the object. The observed broadband colors were indicative of an F2 IV primary and a spotted K0 IV secondary. The system is being viewed pole-on, so is observable in the UV since the K companion has filled its Roche lobe. In comparisons of such features of Algol and RS VCn stars as the mass ratio, orbital inclination, presence or absence of evidence for mass streams, accretion disks, and active regions, spectral signatures, etc., sufficient similarities are found to classify HR 5110 as an Algol system.

  14. Preservation of proteinaceous material during the degradation of the green alga Botryococcus braunii: A solid-state 2D 15N 13C NMR spectroscopy study

    NASA Astrophysics Data System (ADS)

    Zang, Xu; Nguyen, Reno T.; Harvey, H. Rodger; Knicker, Heike; Hatcher, Patrick G.

    2001-10-01

    Using solid-state cross-polarization-magic-angle-spinning (CPMAS) 13C and 15N nuclear magnetic resonance (NMR) and 2-D double cross polarization (DCP) MAS 15N 13C NMR techniques, microbially degraded Botryococcus braunii was analyzed to study the chemical nature of organic nitrogen in the algal residue. The amide linkage, as found in protein, was observed as the major nitrogen component in 201-day-old degraded algae. No significant amount of heterocyclic nitrogen, or evidence for melanoidin products, was found. The results strongly suggest that proteinaceous material can survive early diagenesis and be preserved via its encapsulation by refractory, macromolecular, organic matter.

  15. Structure of hydrous aluminosilicate glasses along the diopside anorthite join: A comprehensive one- and two-dimensional 1H and 27Al NMR study

    NASA Astrophysics Data System (ADS)

    Xue, Xianyu; Kanzaki, Masami

    2008-05-01

    We have taken a systematic approach utilizing advanced solid-state NMR techniques to gain new insights into the controversial issue concerning the dissolution mechanisms of water in aluminosilicate melts (glasses). A series of quenched anhydrous and hydrous (˜2 wt% H 2O) glass samples along the diopside (Di, CaMgSi 2O 6)—anorthite (An, CaAl 2Si 2O 8) join with varying An components (0, 20, 38, 60, 80, and 100 mol %) have been studied. A variety of NMR techniques, including one-dimensional (1D) 1H and 27Al MAS NMR, and 27Al ? 1H cross-polarization (CP) MAS NMR, as well as two-dimensional (2D) 1H double-quantum (DQ) MAS NMR, 27Al triple-quantum (3Q) MAS NMR, and 27Al ? 1H heteronuclear correlation NMR (HETCOR) and 3QMAS/HETCOR NMR, have been applied. These data revealed the presence of SiOH, free OH ((Ca,Mg)OH) and AlOH species in the hydrous glasses, with the last mostly interconnected with Si and residing in the more polymerized parts of the structure. Thus, there are no fundamental differences in water dissolution mechanisms for Al-free and Al-bearing silicate melts (glasses), both involving two competing processes: the formation of SiOH/AlOH that is accompanied by the depolymerization of the network structure, and the formation of free OH that has an opposite effect. The latter is more important for depolymerized compositions corresponding to mafic and ultramafic magmas. Aluminum is dominantly present in four coordination (Al IV), but a small amount of five-coordinate Al (Al V) is also observed in all the anhydrous and hydrous glasses. Furthermore, six-coordinate Al (Al VI) is also present in most of the hydrous glasses. As Al of higher coordinations are favored by high pressure, Al VIOH and Al VOH may become major water species at higher pressures corresponding to those of the Earth's mantle.

  16. Synthesis and conformational study of silk model polypeptides [Ala-Gly] 12 by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Kishi, Satoshi; Santos, Andres; Ishii, Osamu; Ishikawa, Kazuo; Kunieda, Shingo; Kimura, Hideaki; Shoji, Akira

    2003-04-01

    A series of well-defined model polypeptides of Bombyx mori silk fibroin, [Ala-Gly] n ( n=12 and 5-9), [Ala d4Gly] 12 and [Gly d2Ala] 12, (where Ala, Gly, Ala d4 and Gly d2 denote L-alanine, glycine, 2,3,3,3-deuterated L-alanine and 2,2-deuterated glycine residues, respectively), were successfully synthesized by an automatic solid phase peptide synthesizer. Followed by treatment with 9 M lithium bromide (LiBr) solution to convert their conformation from the silk II to the silk I form. We determined the intrinsic 1H, 13C and 15N NMR chemical shifts of Ala and Gly residues, characteristic to the silk I and silk II forms in Bombyx mori, by high-resolution and solid-state 13C CP-MAS, 1H CRAMPS, 1H- 13C HETCOR and 15N CP-MAS NMR measurements. Next, we demonstrated that it is necessary at least 12 amino acid residues ( n=6) in the [Ala-Gly] n-I series for the formation of stable silk I form by 13C CP-MAS NMR. Finally, we found that the intrinsic 1H and 13C chemical shifts of the specific deuterium labeled polypeptides, [Ala d4-Gly] 12 and [Gly d2-Ala] 12, cause a meaningful chemical shift displacement, suggesting that the deuterium interacts with proton and/or carbon atoms in the solid state. Thus, the selective deuterium labeling has a potential to useful for the structural analysis by 1H NMR in the solid state.

  17. Magic-angle-spinning NMR on solid biological systems. Analysis Of the origin of the spectral linewidths

    NASA Astrophysics Data System (ADS)

    Hemminga, M. A.; de Jager, P. A.; Krüse, J.; Lamerichs, R. M. J. N.

    Magic-angle-spinning (MAS) high-power 1H-decoupled 13C and 31P NMR has been applied to solid biological materials to obtain information about the mechanisms that determine the spectral linewidths. The line broadening in MAS 31P NMR spectra of solid tobacco mosaic virus (TMV) has been investigated by selective saturation and T2 measurements. About 90 Hz stems from homogeneous effects, whereas the inhomogeneous contribution is approximately 100 Hz. The inhomogeneous line broadening is assigned to macroscopic inhomogeneities in the sample and not to variations in the nucleotide bases along the RNA strand in TMV. It is concluded that sample preparation is of vital importance for obtaining well-resolved spectra. Under optimal preparation techniques the isotropic values of the chemical shift of the different 31P sites have been determined to obtain information about the secondary structure of the viral RNA. The chemical shift anisotropy has been determined from the relative intensities of the spinning side bands in the spectra. The chemical shift information is used to make a tentative assignment of the resonance in terms of the three structurally distinguishable phosphate groups in TMV. The origin of the linewidths in MAS NMR has been examined further by 13C NMR of approximately 10% 13C-enriched coat protein of cowpea chlorotic mottle virus, using selective excitation and saturation techniques, as well as measurements of the relaxation times T1 ? and T2. The C?O resonance in the spectrum is composed of an inhomogeneous and homogeneous part with a total linewidth of 700 Hz. The homogeneous linewidth, contributing with 200 Hz, is found to arise from slow molecular motions in the solid on a millisecond timescale.

  18. Why does PMLG proton decoupling work at 65 kHz MAS?

    NASA Astrophysics Data System (ADS)

    Leskes, Michal; Madhu, P. K.; Vega, Shimon

    2009-08-01

    Schemes such as phase-modulated Lee-Goldburg (PMLG) for homonuclear dipolar decoupling have been shown to yield high-resolution 1H spectra at high magic-angle spinning (MAS) frequencies of 50-70 kHz. This is at variance to the commonly held notion that these methods require MAS frequencies not comparable to the cycle frequencies of the pulse schemes. Here, a theoretical argument, based on bimodal Floquet theory, is presented to explain this aspect together with conditions where PMLG type of schemes may be successful at high MAS frequencies.

  19. The White Dwarf Companions of 56 Per and HR 3643

    Microsoft Academic Search

    Wayne Landsman; Theodore Simon; Pierre Bergeron

    1995-01-01

    We have obtained low-dispersion IUE spectra of the stars 56 Persei (F4 V) and\\u000aHR 3643 (F7 II), as part of a survey of late-type stars with a 1565 A flux\\u000aexcess in the TD-1 ultraviolet sky survey. The IUE spectrum of each star\\u000areveals the presence of a hot white dwarf companion. We fit the Ly alpha\\u000aprofile and

  20. HR 465 returning to rare-earth-maximum phase

    Microsoft Academic Search

    C. R. Cowley; J. B. Rice

    1981-01-01

    The spectroscopic variability of the unusual Ap star HR465 has been discussed by Wolff and Preston (1970), who show that the sharp-lined spectrum at the rare-earth-minimum phase is similar to that of many other Ap stars of the magnetic sequence. Studies of the rare-earth-maximum phase in the early 1960s had shown it to have a high density of lanthanide rare-earth

  1. CO detection of the extremely red galaxy HR10

    Microsoft Academic Search

    Paola Andreani; Andrea Cimatti; Laurent Loinard; Huub Röttgering

    2000-01-01

    CO J = 5 - 4 and J = 2 - 1 emission lines were detected towards the extremely red galaxy (ERG) HR10 (J164502+4626.4) at z=1.44. The CO intensities imply a molecular gas mass M(H_2) of 1.6 x 1011 h-2_50 M_sun, and, combined with the intensity of the dust continuum, a gas-to-dust mass ratio around 200-400 (assuming galactic values for

  2. ISOCAM imaging of AG CAR and HR Car

    Microsoft Academic Search

    N. R. Trams; L. B. F. M. Waters; R. H. M. Voors

    1996-01-01

    We present infrared images obtained with the ISOCAM instrument on board the Infrared Space Observatory of two Luminous Blue Variables (AG Car and HR Car). The images were obtained at eight wavelengths between 8.5 and 16mum using the Circular Variable Filters (CVFs), with a pixel size of 6 by 6arcsec and a total field of view of 192 by 192arcsec.

  3. The Dynamical Structure of HR 8799's Inner Debris Disk

    NASA Astrophysics Data System (ADS)

    Contro, B.; Wittenmyer, Robert A.; Horner, J.; Marshall, Jonathan P.

    2015-06-01

    The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system.

  4. HST WFPCII Observations of the Inner HR CAR Nebula

    NASA Astrophysics Data System (ADS)

    Hulbert, S. J.; Nota, A.; Clampin, M.; Pasquali, A.; Schulte-Ladbeck, R.

    1998-12-01

    We present HST WFPCII images of the HR Car taken in the light of H? . HR Car has previously been found to have a bipolar morphology consisting of two main lobes extending about 18'' from the central star, which seem to originate from a bright inner nebula about 4'' in radius. The inner nebula, observed from the ground as a compact structure, is resolved into individual clumps asymmetrically concentrated in a region 2--5'' east of the the central star. A jet-like filament, extending approximately 6'', stretches away from the inner nebula to the south-east. We describe the utility of using an observing strategy with HST based on identical observations taken at multiple spacecraft roll angles in order to recover the structure of the inner HR Car nebula. In absence of a coronograph, this technique allows us to subtract the stellar point spread function and study for the first time the inner nebular regions, only partially accessible from the ground.

  5. The Dynamical Structure of HR 8799's Inner Debris Disk.

    PubMed

    Contro, B; Wittenmyer, Robert A; Horner, J; Marshall, Jonathan P

    2015-06-01

    The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system. PMID:25862330

  6. Measuring material susceptibility using NMR

    NASA Astrophysics Data System (ADS)

    SanGiorgio, Paul; Zens, Albert

    2015-06-01

    We report on a method of measuring the high-field susceptibilities of paramagnetic and diamagnetic materials using only a standard NMR system equipped with pulsed field gradients. We demonstrate the accuracy and sensitivity of the technique by measuring a series of 99.9% copper wires with diameters between 0.16 mm and 0.79 mm. We measured the volumetric susceptibility of the copper to be ? = - 9.5 ± 0.2 ·10-6 , which agrees with the literature value of pure copper, - 9.6 ·10-6 . In addition to making quantitative measurements, this technique can also be used to evaluate the effectiveness of compensation schemes used to produce "zero-susceptibility" materials needed for construction of high-resolution NMR probes.

  7. Scalable NMR spectroscopy with semiconductor chips

    PubMed Central

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

    2014-01-01

    State-of-the-art NMR spectrometers using superconducting magnets have enabled, with their ultrafine spectral resolution, the determination of the structure of large molecules such as proteins, which is one of the most profound applications of modern NMR spectroscopy. Many chemical and biotechnological applications, however, involve only small-to-medium size molecules, for which the ultrafine resolution of the bulky, expensive, and high-maintenance NMR spectrometers is not required. For these applications, there is a critical need for portable, affordable, and low-maintenance NMR spectrometers to enable in-field, on-demand, or online applications (e.g., quality control, chemical reaction monitoring) and co-use of NMR with other analytical methods (e.g., chromatography, electrophoresis). As a critical step toward NMR spectrometer miniaturization, small permanent magnets with high field homogeneity have been developed. In contrast, NMR spectrometer electronics capable of modern multidimensional spectroscopy have thus far remained bulky. Complementing the magnet miniaturization, here we integrate the NMR spectrometer electronics into 4-mm2 silicon chips. Furthermore, we perform various multidimensional NMR spectroscopies by operating these spectrometer electronics chips together with a compact permanent magnet. This combination of the spectrometer-electronics-on-a-chip with a permanent magnet represents a useful step toward miniaturization of the overall NMR spectrometer into a portable platform. PMID:25092330

  8. NMR Measures of Heterogeneity Length

    NASA Astrophysics Data System (ADS)

    Spiess, Hans W.

    2002-03-01

    Advanced solid state NMR spectroscopy provides a wealth of information about structure and dynamics of complex systems. On a local scale, multidimensional solid state NMR has elucidated the geometry and the time scale of segmental motions at the glass transition. The higher order correlation functions which are provided by this technique led to the notion of dynamic heterogeneities, which have been characterized in detail with respect to their rate memory and length scale. In polymeric and low molar mass glass formers of different fragility, length scales in the range 2 to 4 nm are observed. In polymeric systems, incompatibility of backbone and side groups as in polyalkylmethacrylates leads to heteogeneities on the nm scale, which manifest themselves in unusual chain dynamics at the glass transition involving extended chain conformations. References: K. Schmidt-Rohr and H.W. Spiess, Multidimensional Solid-State NMR and Polymers,Academic Press, London (1994). U. Tracht, M. Wilhelm, A. Heuer, H. Feng, K. Schmidt-Rohr, H.W. Spiess, Phys. Rev. Lett. 81, 2727 (1998). S.A. Reinsberg, X.H. Qiu, M. Wilhelm, M.D. Ediger, H.W. Spiess, J.Chem.Phys. 114, 7299 (2001). S.A. Reinsberg, A. Heuer, B. Doliwa, H. Zimmermann, H.W. Spiess, J. Non-Crystal. Solids, in press (2002)

  9. MAS 335 Cryptography Notes 10: Public-key cryptography Spring 2008

    E-print Network

    Banaji,. Murad

    MAS 335 Cryptography Notes 10: Public-key cryptography Spring 2008 In this section we look at two-key cryptography. Neither of these schemes is used commercially as far as I know. But we will see later a good

  10. BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Newcomer, Jeffrey (Editor); Lobitz, Brad; Spanner, Michael; Strub, Richard; Lobitz, Brad

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study (BOREAS) Staff Science Aircraft Data Acquisition Program focused on providing the research teams with the remotely sensed aircraft data products they needed to compare and spatially extend point results. The MODIS Airborne Simulator (MAS) images, along with other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes biophysical parameter maps such as surface reflectance and temperature. Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-2 MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994, and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C130 navigation data in a MAS scan model. The data are provided in binary image format files.

  11. BOREAS Level-1B MAS Imagery At-sensor Radiance, Relative X and Y Coordinates

    NASA Technical Reports Server (NTRS)

    Strub, Richard; Strub, Richard; Newcomer, Jeffrey A.; Ungar, Stephen

    2000-01-01

    For BOReal Ecosystem-Atmosphere Study (BOREAS), the MODIS Airborne Simulator (MAS) images, along with the other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes detailed land cover and biophysical parameter maps such as fraction of Photosynthetically Active Radiation (fPAR) and Leaf Area Index (LAI). Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-1b MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994, and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C-130 INS data in a MAS scan model. The data are provided in binary image format files.

  12. Expression and cellular localization of the Mas receptor in the adult and developing mouse retina

    PubMed Central

    Prasad, Tuhina; Verma, Amrisha

    2014-01-01

    Purpose Recent studies have provided evidence that a local renin-angiotensin system (RAS) exists in the retina and plays an important role in retinal neurovascular function. We have recently shown that increased expression of ACE2 and angiotensin (1-7) [Ang (1-7)], two components of the protective axis of the RAS, in the retina via adeno-associated virus (AAV)-mediated gene delivery, conferred protection against diabetes-induced retinopathy. We hypothesized that the protective molecular and cellular mechanisms of Ang (1-7) are mediated by its receptor, Mas, and the expression level and cellular localization dictate the response to Ang (1-7) and activation of subsequent protective signaling pathways. We tested this hypothesis by examining the expression and cellular localization of the Mas receptor in adult and developing mouse retinas. Methods The cellular localization of the Mas receptor protein was determined with immunofluorescence of the eyes of adult and postnatal day 1 (P1), P5, P7, P15, and P21 mice using the Mas receptor-specific antibody, and mRNA was detected with in situ hybridization of paraffin-embedded sections. Western blotting and real-time reverse-transcription (RT)–PCR analysis were performed to determine the relative levels of the Mas protein and mRNA in adult and developing retinas, as well as in cultured retinal Müller glial and RPE cells. Results In the adult eye, the Mas receptor protein was abundantly present in retinal ganglion cells (RGCs) and photoreceptor cells; a lower level of expression was observed in endothelial cells, Müller glial cells, and other neurons in the inner nuclear layer of the retina. In the developing retina, Mas receptor mRNA and protein expression was detected in the inner retina at P1, and the expression levels increased with age to reach the adult level and pattern by P15. In the adult mouse retina, Mas receptor mRNA was expressed at a much higher level when compared to angiotensin II (Ang II) type I (AT1R) and type II (AT2R) receptor mRNA. Conclusions The Mas receptor is expressed in developing and adult mouse retinas, and is more abundant in retinal neurons than in endothelial and Müller glial cells. These observations suggest that Mas receptor-mediated signaling may play important roles that extend beyond mediating the vascular effects of Ang (1-7) in developing and adult retinas. In addition, the relatively high expression of the Mas receptor when compared to AT1R suggests that they may play a more important role in maintaining normal retinal physiology than previously considered. PMID:25352750

  13. NEW PRECISION ORBITS OF BRIGHT DOUBLE-LINED SPECTROSCOPIC BINARIES. IV. 66 ANDROMEDAE, HR 6979, AND HR 9059

    SciTech Connect

    Fekel, Francis C.; Williamson, Michael H. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Boulevard, Box 9501, Nashville, TN 37209 (United States); Tomkin, Jocelyn [Astronomy Department and McDonald Observatory, University of Texas, Austin, TX 78712 (United States)], E-mail: fekel@evans.tsuniv.edu, E-mail: jt@alexis.as.utexas.edu

    2010-04-15

    We have determined improved spectroscopic orbits for three double-lined binaries, 66 And (F4 V), HR 6979 (Am), and HR 9059 (F5 IV) using radial velocities from the 2.1 m telescope at McDonald Observatory, the coude feed telescope at Kitt Peak National Observatory, and 2 m telescope at Fairborn Observatory. The orbital periods range from 11.0 to 14.3 days, and all three systems have eccentric orbits. The new orbital dimensions (a {sub 1} sin i and a {sub 2} sin i) and minimum masses (m {sub 1} sin{sup 3} i and m {sub 2} sin{sup 3} i) have accuracies of 0.2% or better. All six components of the three binary systems are rotating more slowly than their predicted pseudosynchronous rotational velocities. Hipparcos photometry of HR 9059 shows that this system has partial eclipses. Its components are nearly identical in mass and are at the very end of their main-sequence lifetimes or perhaps have just begun to traverse the Hertsprung gap.

  14. A comparative evaluation of agent location mechanisms in large scale MAS

    Microsoft Academic Search

    David Ben-Ami; Onn Shehory

    2005-01-01

    Agents in open multi-agent systems (MAS) need means for locating other agents with which they may collaborate. To address this need, several agent location mechanisms were suggested. Two major approaches dominate agent location mechanisms: a centralized approach using middle agents, and a distributed, peer-to-peer approach. Agent designers, when designing agents to be part of open MAS, should consider these approaches,

  15. In vitro cytotoxic and antioxidative activity of Cornus mas and Cotinus coggygria

    Microsoft Academic Search

    Katarina Šavikin; Gordana Zduni?; Teodora Jankovi?; Tatjana Stanojkovi?; Zorica Jurani?; Nebojša Menkovi?

    2009-01-01

    Cytotoxicity and antioxidant properties of the methanol extracts of leaves and flowers of Cornus mas and Cotinus coggygria were studied, together with their chemical composition. Extracts of C. coggygria flowers and leaves showed better antioxidant activity in reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as in inhibition of lipid peroxidation (LP) than C. mas extracts. Preliminary results showed that all

  16. Comparing the Effects of Lovastatin and Cornus Mas Fruit on Fibrinogen Level in Hypercholesterolemic Rabbits

    PubMed Central

    Asgary, Sedigheh; Rafieian-Kopaei, Mahmoud; Adelnia, Azadeh; Kazemi, Somayeh; Shamsi, Fatemeh

    2010-01-01

    BACKGROUND Atherosclerosis, which is a result of gradual deposition of lipids in the lower part of blood vessel endothelium, is the leading cause of mortality and morbidity around the world. It has been proved that some inflammatory blood markers such as fibrinogen can predict the risk for cardiovascular disease conditions, not only in cardiovascular patients, but also in those who do not have any manifestations of the atherosclerotic development. In this study, the effect of cornus mas l. was evaluated on fibrinogen of hypercholesterolemic rabbits and it was also compared with lovastatin drug. METHODS In this study, 25 New Zealand adult male rabbits were randomly divided into five groups of five. They were treated for 60 days by 5 different diets, namely basic, high cholesterol, regular plus 1 g/kgBW cornus mas L. powder, high cholesterol plus 1 g/kgBW cornus mas L. powder, and high cholesterol plus 10 mg/kgBW lovastatin. At the beginning and at the end of this period, blood samples were collected from the rabbits and their serum fibrinogen levels were measured. RESULTS Cornus mas L. powder and lovastatin significantly decreased fibrinogen levels in comparison with high cholesterol group (P < 0.05). Furthermore cornus mas L. powder could reduce the fibrinogen level more than lovastatin (P < 0.05). CONCLUSION The results indicated that consumption of cornus mas L. might be beneficial in atherosclerotic patients due to its reducing effects on fibrinogen. PMID:22577405

  17. Exploring the central characteristics of HR shared services: evidence from a critical case study in the Netherlands

    Microsoft Academic Search

    Jeroen Meijerink; Tanya Bondarouk

    2012-01-01

    Human resource shared service centers (HR SSCs) are foreseen as improving HR service delivery for their end-users: employees, line managers and decentralized HR professionals. Although the concept expects the benefits of HR SSCs to come from centralizing knowledge and decentralizing the control exercised over an HR SSC, research into these two fundamental shared service characteristics is scarce. The purpose of

  18. Development of LC-13C NMR

    NASA Technical Reports Server (NTRS)

    Dorn, H. C.; Wang, J. S.; Glass, T. E.

    1986-01-01

    This study involves the development of C-13 nuclear resonance as an on-line detector for liquid chromatography (LC-C-13 NMR) for the chemical characterization of aviation fuels. The initial focus of this study was the development of a high sensitivity flow C-13 NMR probe. Since C-13 NMR sensitivity is of paramount concern, considerable effort during the first year was directed at new NMR probe designs. In particular, various toroid coil designs were examined. In addition, corresponding shim coils for correcting the main magnetic field (B sub 0) homogeneity were examined. Based on these initial probe design studies, an LC-C-13 NMR probe was built and flow C-13 NMR data was obtained for a limited number of samples.

  19. Frequency-swept pulse sequences for 19F heteronuclear spin decoupling in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Vinod Chandran, C.; Madhu, P. K.; Wormald, Philip; Bräuniger, Thomas

    2010-10-01

    Heteronuclear spin decoupling pulse sequences in solid-state NMR have mostly been designed and applied for irradiating 1H as the abundant nucleus. Here, a systematic comparison of different methods for decoupling 19F in rigid organic solids is presented, with a special emphasis on the recently introduced frequency-swept sequences. An extensive series of NMR experiments at different MAS frequencies was conducted on fluorinated model compounds, in combination with large sets of numerical simulations. From both experiments and simulations it can be concluded that the frequency-swept sequences SW f-TPPM and SW f-SPINAL deliver better and more robust spin decoupling than the original sequences SPINAL and TPPM. Whereas the existence of a large chemical shift anisotropy and isotropic shift dispersion for 19F does compromise the decoupling efficiency, the relative performance hierarchy of the sequences remains unaffected. Therefore, in the context of rigid organic solids under moderate MAS frequencies, the performance trends observed for 19F decoupling are very similar to those observed for 1H decoupling.

  20. Correlating fast and slow chemical shift spinning sideband patterns in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Orr, Robin M.; Duer, Melinda J.; Ashbrook, Sharon E.

    2005-06-01

    An experiment is presented that enables the measurement of small chemical shift anisotropy tensors under fast magic-angle spinning (MAS). The two-dimensional spectra obtained give a fast MAS sideband pattern in the directly observed dimension with the spinning sideband intensities equivalent to the chemical shift anisotropy scaled by a factor of N, or equivalently the sample spinning frequency scaled by 1/ N, in the indirectly observed dimension. The scaling factor may be arbitrarily varied by changing the number and timings of the rotor synchronized ?-pulses used. Desirable features of the experiment include a fixed length pulse sequence and efficient sampling of the indirectly observed dimension. In addition, neither quadrature detection in the indirect dimension nor storage periods are required, consequently no signal intensity is discarded by the pulse sequence. The experiment is demonstrated using 31P NMR of sodium phosphate and 13C NMR of fumaric acid monoethyl ester for which a scaling factor of N = 10.2 was employed.