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1

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

2

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

PubMed Central

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these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents.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

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

2013-01-01

3

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

4

High resolution magic angle spinning (HR-MAS) NMR spectroscopy of human osteoarthritic cartilage  

PubMed Central

Osteoarthritis (OA) is a degenerative disease of the joint and results in changes in the biochemical composition of cartilage. Studies have been undertaken in the past that have used high resolution NMR spectroscopy to study the biochemical composition of porcine, canine and bovine cartilage. In this study high resolution magical angle spinning (HRMAS) NMR spectroscopy at 11.7 T has been used to characterize metabolites and detect differences in the spectral signature of human knee articular cartilage from non-OA healthy cadaver knees and samples acquired from severe OA patients at the time of total knee replacement surgery. A statistically significant difference in the alanine (1.47 ppm), N-acetyl (2.04 ppm), choline (3.25 ppm) and glycine (3.55 ppm) metabolite levels is observed between healthy and OA specimens. The results of the study indicate that a decrease in the intensity of N-acetyl resonance occurs in later stages of OA. A positive correlation of the N-acetyl levels as measured by 1H HR-MAS NMR spectroscopy with the total proteoglycan content in the same cartilage specimens as measured by the GAG assay was observed. This indicates that N-acetyl can serve as an important bio-marker of OA disease progression. A decrease in the alanine concentration in OA may be attributed to the degradation of the collagen framework with disease progression and eventual loss of the degradation products that are transported from cartilage into the synovial cavity. PMID:21850648

Shet, Keerthi; Siddiqui, Sarmad M.; Yoshihara, Hikari; Kurhanewicz, John; Ries, Michael; Li, Xiaojuan

2011-01-01

5

Assessing the fate and transformation of plant residues in the terrestrial environment using HR-MAS NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Plant litter decomposition plays a fundamental role in carbon and nitrogen cycles, provides key nutrients to the soil environment and represents a potentially large positive feedback to atmospheric CO 2. However, the full details of decomposition pathways and products are unknown. Here we present the first application of HR-MAS NMR spectroscopy on 13C and 15N labeled plant materials, and apply this approach in a preliminary study to monitor the environmental degradation of the pine and wheatgrass residues over time. In HR-MAS, is it possible to acquire very high resolution NMR data of plant biomass, and apply the vast array of multidimensional experiments available in conventional solution-state NMR. High levels of isotopic enrichment combined with HR-MAS significantly enhance the detection limits, and provide a wealth of information that is unattainable by any other method. Diffusion edited HR-MAS NMR data reveal the rapid loss of carbohydrate structures, while two-dimensional (2-D) HR-MAS NMR spectra demonstrate the relatively fast loss of both hydrolysable and condensed tannin structures from all plant tissues studied. Aromatic (partially lignin) and aliphatic components (waxes, cuticles) tend to persist, along with a small fraction of carbohydrate, and become highly functionalized over time. While one-dimensional (1-D) 13C HR-MAS NMR spectra of fresh plant tissue reflect compositional differences between pine and grass, these differences become negligible after decomposition suggesting that recalcitrant carbon may be similar despite the plant source. Two-dimensional 1H- 15N HR-MAS NMR analysis of the pine residue suggests that nitrogen from specific peptides is either selectively preserved or used for the synthesis of what appears to be novel structures. The amount of relevant data generated from plant components in situ using HR-MAS NMR is highly encouraging, and demonstrates that complete assignment will yield unprecedented structural knowledge of plant cell components, and provide a powerful tool with which to assess carbon sequestration and transformation in the environment.

Kelleher, Brian P.; Simpson, Myrna J.; Simpson, Andre J.

2006-08-01

6

LC/ESI-MS n and 1H HR-MAS NMR analytical methods as useful taxonomical tools within the genus Cystoseira C. Agardh (Fucales; Phaeophyceae).  

PubMed

Species of the genus Cystoseira are particularly hard to discriminate, due to the complexity of their morphology, which can be influenced by their phenological state and ecological parameters. Our study emphasized on the relevance of two kinds of analytical tools, (1) LC/ESI-MS(n) and (2) (1)H HR-MAS NMR, also called in vivo NMR, to identify Cystoseira specimens at the specific level and discuss their taxonomy. For these analyses, samples were collected at several locations in Brittany (France), where Cystoseira baccata, C. foeniculacea, C. humilis, C. nodicaulis and C. tamariscifolia were previously reported. To validate our chemical procedure, the sequence of the ITS2 has been obtained for each species to investigate their phylogenetic relationships at a molecular level. Our study highlighted the consistency of the two physico-chemical methods, compared to "classical" molecular approach, in studying taxonomy within the genus Cystoseira. Especially, LC/ESI-MS(n) and phylogenetic analyses converged into the discrimination of two taxonomical groups among the 5 species. The occurrence of some specific signals in the (1)H HR-MAS NMR spectra and/or some characteristic chemical compounds during LC/ESI-MS(n) analysis could be regarded as discriminating factors. LC/ESI-MS(n) and (1)H HR-MAS NMR turned out to be two relevant and innovative techniques to discriminate taxonomically this complex genus. PMID:21111182

Jégou, Camille; Culioli, Gérald; Kervarec, Nelly; Simon, Gaëlle; Stiger-Pouvreau, Valérie

2010-12-15

7

Separation of small metabolites and lipids in spectra from biopsies by diffusion-weighted HR-MAS NMR: a feasibility study.  

PubMed

High Resolution Magic Angle Spinning (HR-MAS) NMR allows metabolic characterization of biopsies. HR-MAS spectra from tissues of most organs show strong lipid contributions that are overlapping metabolite regions, which hamper metabolite estimation. Metabolite quantification and analysis would benefit from a separation of lipids and small metabolites. Generally, a relaxation filter is used to reduce lipid contributions. However, the strong relaxation filter required to eliminate most of the lipids also reduces the signals for small metabolites. The aim of our study was therefore to investigate different diffusion editing techniques in order to employ diffusion differences for separating lipid and small metabolite contributions in the spectra from different organs for unbiased metabonomic analysis. Thus, 1D and 2D diffusion measurements were performed, and pure lipid spectra that were obtained at strong diffusion weighting (DW) were subtracted from those obtained at low DW, which include both small metabolites and lipids. This subtraction yielded almost lipid free small metabolite spectra from muscle tissue. Further improved separation was obtained by combining a 1D diffusion sequence with a T2-filter, with the subtraction method eliminating residual lipids from the spectra. Similar results obtained for biopsies of different organs suggest that this method is applicable in various tissue types. The elimination of lipids from HR-MAS spectra and the resulting less biased assessment of small metabolites have potential to remove ambiguities in the interpretation of metabonomic results. This is demonstrated in a reproducibility study on biopsies from human muscle. PMID:25368873

Diserens, G; Vermathen, M; Precht, C; Broskey, N T; Boesch, C; Amati, F; Dufour, J-F; Vermathen, P

2015-01-01

8

Identification of Streptococcus pneumoniae Serotype 11E, Serovariant 11Av and Mixed Populations by High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) Spectroscopy and Flow Cytometric Serotyping Assay (FCSA)  

PubMed Central

Background Recent studies have identified Streptococcus pneumoniae serotype 11E and serovariant 11Av among isolates previously typed as 11A by classical serotyping methods. Serotype 11E and serovariant 11Av differ from serotype 11A by having totally or partially inactive wcjE, a gene in cps locus coding for an O-acetyl transferase. Serotype 11E is rare among carriage isolates but common among invasive isolates suggesting that it survives better during invasion. Aim of this work was to investigate the epidemiology of serotype 11A in a pneumococcal collection using a new serotyping approach based on High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) spectroscopy to distinguish serotypes 11A and 11E. Methods A collection of 48 (34 invasive and 14 carriage) S. pneumoniae isolates from Italy, previously identified as serotype 11A by the Quellung reaction, were investigated by wcjE sequencing, HR-MAS NMR spectroscopy and the reference flow cytometric serotyping assay (FCSA) based on monoclonal antibodies. Results HR-MAS NMR spectra from serotypes 11A and 11E showed different NMR peaks indicating that HR-MAS NMR could be used to distinguish these serotypes, although HR-MAS NMR could not distinguish serotype 11Av from serotype 11E unambiguously. Thirty-eight isolates were confirmed to be serotype 11A, 8 isolates with a mutated wcjE were serotype 11E, 1 isolate belonged to serovariant 11Av, and 1 isolate was a mixed population 11A/11Av. All 11E isolates were identified among invasive isolates. Conclusions We proved that HR-MAS NMR can be of potential use for pneumococcal serotyping. The detection of serotype 11E among invasive isolates in our collection, supports previous epidemiological studies suggesting that mutations in wcjE can represent a mechanism promoting pneumococcal survival during invasion. The discovery of a spectrum of immunochemical diversity within established serotypes should stimulate efforts to develop new serotyping approaches. PMID:24967818

Camilli, Romina; Spencer, Brady L.; Moschioni, Monica; Pinto, Vittoria; Berti, Francesco; Nahm, Moon H.; Pantosti, Annalisa

2014-01-01

9

Photo-Cross-Linked Poly(dl-lactide)Based Networks. Structural Characterization by HR-MAS NMR Spectroscopy and Hydrolytic Degradation Behavior  

Microsoft Academic Search

To date, biodegradable networks and particularly their kinetic chain lengths have been characterized by analysis of their degradation products in solution. We characterize the network itself by NMR analysis in the solvent-swollen state under magic angle spinning conditions. The networks were prepared by photoinitiated cross-linking of poly(dl-lactide)?dimethacrylate macromers (5 kg\\/mol) in the presence of an unreactive diluent. Using diffusion filtering

Ferry P. W. Melchels; Aldrik H. Velders; Jan Feijen; Dirk W. Grijpma

2010-01-01

10

Towards quantitative CP-MAS NMR  

Microsoft Academic Search

Many of the combined cross polarization—magic angle spinning (CP-MAS) experiments that have been developed over the past ten years for structural studies of chemical and biological systems rely on the measurement of quantitative signal intensities. However, one of the drawbacks of the CP technique is that the efficiency of polarization transfer depends on the strength of the heteronuclear dipolar interaction

Günther Metz; Martine Ziliox; Steven O. Smith

1996-01-01

11

Dynamic Nuclear Polarization CARBON-13 NMR of Diamond Films and Rotating Gradient Mas-Nmr Imaging  

NASA Astrophysics Data System (ADS)

^{13}C NMR, with and without dynamic nuclear polarization and ESR measurements are presented on three chemical vapor deposited diamond films. By microwave irradiation with a frequency close to the Larmor frequency of the unpaired electrons present in the diamond films, the ^{13} C signal is enhanced resulting in ^ {13}C direct and cross polarization spectra that are almost impossible to measure without DNP. The resolution of NMR imaging of solids is hampered by the large NMR linewidths of static solid samples. MAS NMR imaging measurements are presented where MAS removes the linebroadening, while the gradient rotates synchronously with the spinner.

Lock, Herman

12

Broadband solid-state MAS NMR of paramagnetic systems.  

PubMed

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 LiFe0.5Mn0.5PO4 which is typical of the complexity of the paramagnetic systems that are currently under study. PMID:25669740

Pell, Andrew J; Pintacuda, Guido

2015-02-01

13

Coherence selection in double CP MAS NMR spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

2008-11-01

14

High temperature 17O MAS NMR study of calcia, magnesia, scandia and yttria stabilized zirconia  

Microsoft Academic Search

High-resolution 17O MAS NMR can provide unique constraints on local structure and oxide ion dynamics in conductive zirconia ceramics of interest for fuel cells and other technologies. We describe here NMR and bulk conductivity measurements for scandia, yttria, calcia, and magnesia stabilized zirconias, including MAS NMR spectra collected in situ at temperatures up to 700 °C. All of the cubic compounds

Namjun Kim; Cheng-Han Hsieh; Hong Huang; Fritz B. Prinz; Jonathan F. Stebbins

2007-01-01

15

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

16

HR-MAS MR Spectroscopy of Breast Cancer Tissue Obtained with Core Needle Biopsy: Correlation with Prognostic Factors  

PubMed Central

The purpose of this study was to examine the correlation between high-resolution magic angle spinning (HR-MAS) magnetic resonance (MR) spectroscopy using core needle biopsy (CNB) specimens and histologic prognostic factors currently used in breast cancer patients. After institutional review board approval and informed consent were obtained for this study, CNB specimens were collected from 36 malignant lesions in 34 patients. Concentrations and metabolic ratios of various choline metabolites were estimated by HR-MAS MR spectroscopy using CNB specimens. HR-MAS spectroscopic values were compared according to histopathologic variables [tumor size, lymph node metastasis, histologic grade, status of estrogens receptor (ER), progesterone receptor (PR), HER2 (a receptor for human epidermal growth factor), and Ki-67, and triple negativity]. Multivariate analysis was performed with Orthogonal Projections to Latent Structure-Discriminant Analysis (OPLS-DA). HR-MAS MR spectroscopy quantified and discriminated choline metabolites in all CNB specimens of the 36 breast cancers. Several metabolite markers [free choline (Cho), phosphocholine (PC), creatine (Cr), taurine, myo-inositol, scyllo-inositol, total choline (tCho), glycine, Cho/Cr, tCho/Cr, PC/Cr] on HR-MAS MR spectroscopy were found to correlate with histologic prognostic factors [ER, PR, HER2, histologic grade, triple negativity, Ki-67, poor prognosis]. OPLS-DA multivariate models were generally able to discriminate the status of histologic prognostic factors (ER, PR, HER2, Ki-67) and prognosis groups. Our study suggests that HR-MAS MR spectroscopy using CNB specimens can predict tumor aggressiveness prior to surgery in breast cancer patients. In addition, it may be helpful in the detection of reliable markers for breast cancer characterization. PMID:23272149

Choi, Ji Soo; Baek, Hyeon-Man; Kim, Suhkmann; Kim, Min Jung; Youk, Ji Hyun; Moon, Hee Jung; Kim, Eun-Kyung; Han, Kyung Hwa; Kim, Dong-hyun; Kim, Seung Il; Koo, Ja Seung

2012-01-01

17

Factor analysis of (27) Al MAS NMR spectra for identifying nanocrystalline phases in amorphous geopolymers.  

PubMed

Nanostructured materials offer enhanced physicochemical properties because of the large interfacial area. Typically, geopolymers with specifically synthesized nanosized zeolites are a promising material for the sorption of pollutants. The structural characterization of these aluminosilicates, however, continues to be a challenge. To circumvent complications resulting from the amorphous character of the aluminosilicate matrix and from the low concentrations of nanosized crystallites, we have proposed a procedure based on factor analysis of (27) Al MAS NMR spectra. The capability of the proposed method was tested on geopolymers that exhibited various tendencies to crystallize (i) completely amorphous systems, (ii) X-ray amorphous systems with nanocrystalline phases, and (iii) highly crystalline systems. Although the recorded (27) Al MAS NMR spectra did not show visible differences between the amorphous systems (i) and the geopolymers with the nanocrystalline phase (ii), the applied factor analysis unambiguously distinguished these materials. The samples were separated into the well-defined clusters, and the systems with the evolving crystalline phase were identified even before any crystalline fraction was detected by X-ray powder diffraction. Reliability of the proposed procedure was verified by comparing it with (29) Si MAS NMR spectra. Factor analysis of (27) Al MAS NMR spectra thus has the ability to reveal spectroscopic features corresponding to the nanocrystalline phases. Because the measurement time of (27) Al MAS NMR spectra is significantly shorter than that of (29) Si MAS NMR data, the proposed procedure is particularly suitable for the analysis of large sets of specifically synthesized geopolymers in which the formation of the limited fractions of nanocrystalline phases is desired. Copyright © 2013 John Wiley & Sons, Ltd. PMID:24027195

Urbanova, Martina; Kobera, Libor; Brus, Jiri

2013-09-11

18

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

PubMed

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

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

2004-04-01

19

Elucidating proline dynamics in spider dragline silk fibre using 2H-13C HETCOR MAS NMR.  

PubMed

(2)H-(13)C HETCOR MAS NMR is performed on (2)H/(13)C/(15)N-Pro enriched A. aurantia dragline silk. Proline dynamics are extracted from (2)H NMR line shapes and T1 in a site-specific manner to elucidate the backbone and side chain molecular dynamics for the MaSp2 GPGXX ?-turn regions for spider dragline silk in the dry and wet, supercontracted states. PMID:24686512

Shi, Xiangyan; Yarger, Jeffery L; Holland, Gregory P

2014-05-14

20

Structural aspects in ultrathin cellulose microfibrils followed by 13C CP-MAS NMR  

Microsoft Academic Search

13C CP-MAS NMR was used to study the ultrastructural aspects of ultrathin microfibrils extracted from sugar beet pulp. Depending on the stocking condition, the cellulose microfibrils contained different amounts of the polymorphs I? and I?. Structural changes were followed after a purification treatment. It was found that the crystallinity, as measured by solid-state NMR, increases as the purification proceeds. This

L. Heux; E. Dinand; M. R. Vignon

1999-01-01

21

CP/MAS (13)C NMR study of cellulose and cellulose derivatives. 1. Complete assignment of the CP/MAS (13)C NMR spectrum of the native cellulose.  

PubMed

The precise assignments of cross polarization/magic angle spinning (CP/MAS) (13)C NMR spectra of cellulose I(alpha) and I(beta) were performed by using (13)C labeled cellulose biosynthesized by Acetobacter xylinum (A. xylinum) ATCC10245 strain from culture medium containing D-[1,3-(13)C]glycerol or D-[2-(13)C]glucose as a carbon source. On the CP/MAS (13)C NMR spectrum of cellulose from D-[1,3-(13)C]glycerol, the introduced (13)C labeling were observed at C1, C3, C4, and C6 of the biosynthesized cellulose. In the case of cellulose biosynthesized from D-[2-(13)C]glucose, the transitions of (13)C labeling to C1, C3, and C5 from C2 were observed. With the quantitative analysis of the (13)C transition ratio and comparing the CP/MAS (13)C NMR spectrum of the Cladophora cellulose with those of the (13)C labeled celluloses, the assignments of the cluster of resonances which belong to C2, C3, and C5 of cellulose, which have not been assigned before, were performed. As a result, all carbons of cellulose I(alpha) and I(beta) except for C1 and C6 of cellulose I(alpha) and C2 of cellulose I(beta) were shown in equal intensity of doublet in the CP/MAS spectrum of the native cellulose, which suggests that two inequivalent glucopyranose residues were contained in the unit cells of both cellulose I(alpha) and I(beta) allomorphs. PMID:12071760

Kono, Hiroyuki; Yunoki, Shunji; Shikano, Tamio; Fujiwara, Masashi; Erata, Tomoki; Takai, Mitsuo

2002-06-26

22

Multivariate Data Analysis of In Situ Pulp Kinetics Using C CP\\/MAS NMR  

Microsoft Academic Search

C CP\\/MAS NMR spectra of birch pulp samples were measured at regular intervals during the kraft pulping process. General multivariate data analysis methods based on principal components were used to extract the spectral information content and to relate these components to chemical descriptors such as lignin content. It was shown that this approach has an improved predictive ability relative to

Lars Wallbäcks; Ulf Edlund; Bo Nordén

1989-01-01

23

Crystallinity of cellulose, as determined by CP\\/MAS NMR and XRD methods  

Microsoft Academic Search

The crystallinity of six cellulose samples with different origin and treatment was determined using x-ray diffraction (XDR) and nuclear magnetic resonance with cross polarization and magic angle sample spinning (CP\\/MAS NMR) methods. The numerical results for crystallinity obtained by using curve fitting methods in both cases correlated very well. It was concluded that the values for the crystallinity can be

R. Teeäär; R. Serimaa; T. Paakkarl

1987-01-01

24

{sup 17}O MAS NMR investigation of the structure of calcium silicate hydrate gel  

SciTech Connect

This paper presents the results of a systematic investigation of the structure of hydrothermally synthesized calcium silicate hydrate gel using {sup 17}O MAS NMR at 11.7 T and MAS frequencies up to 12 kHz. The results support the previously proposed defect-tobermorite structural model for C-S-H. At least six O-sites have been identified, two NBO, BO, Ca-OH, Si-OH, and H{sub 2}O. The compositional variation of the relative intensities of the signal for different sites measured by {sup 17}O NMR is consistent with that calculated from {sup 29}Si NMR results for the same samples. The chemical shifts of the NBO and BO sites become more deshielded (more positive) with increasing C/S ratio.

Cong, X.; Kirkpatrick, R.J. [Univ. of Illinois, Urbana, IL (United States)

1996-06-01

25

NMR local range investigations in amorphous starchy substrates I. Structural heterogeneity probed by 13C CP–MAS NMR  

Microsoft Academic Search

The 13C CP–MAS (Cross Polarization and Magic Angle Spinning) NMR signatures of a series of amorphous and semi-crystalline samples prepared from various starchy substrates (native potato starch, amylopectin, amylose) following different techniques of preparation (casting, freeze drying, solvent exchange) are compared. Decompositions of the C1 resonance spectra reveal the existence of four or five main types of ?(1–4) linkages, which

H Bizot; J Emery; J. Y Buzaré; A Buléon

2001-01-01

26

Decomposition of adsorbed VX on activated carbons studied by 31P MAS NMR.  

PubMed

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. 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)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. PMID:16830567

Columbus, Ishay; Waysbort, Daniel; Shmueli, Liora; Nir, Ido; Kaplan, Doron

2006-06-15

27

CP\\/MAS NMR Examination of Some Australian Woods and Their Chemical and Biochemical Degradation Residues  

Microsoft Academic Search

Solid-state C-CP\\/MAS NMR has been used to obtain structural information on three Australian sapwoods (two hardwoods and one softwood), their residues after chemical treatment, and the frasses obtained after digestion by wood-eating termites and beetles. Whole wood spectra indicate substantial differences in both the lignin and hemicellulose components between the hardwoods and the softwood.Spectra of residues clearly show that the

P. F. Barron; R. L. Frost; L. Doimo; M. J. Kennedy

1985-01-01

28

CP\\/MAS NMR investigations of silica gel surfaces modified with aminopropylsilane  

Microsoft Academic Search

Aminopropyl chemically bonded phases for high performance liquid chromatography (HPLC) have been prepared using mono- and trifunctional methoxyor ethoxysilanes. Three types of silica gel with different surface characteristics were used as support for the chemically bonded phases (CBPs). Surface characteristics of the packings before and after chemical modification were determined by porosity parameters, elemental analysis and CP\\/MAS NMR spectroscopy.29Si and13C

K. Albert; R. Brindle; J. Schmid; B. Buszewski; E. Bayer

1994-01-01

29

Multidimensional CP-MAS 13C NMR of uniformly enriched chlorophyll  

Microsoft Academic Search

The progress toward structure refinement of solid-type uniformly 13C enriched ([U-13C]) chlorophyll-containing biological preparations is summarised. Solid state carbon chemical shifts of aggregated [U-13C] bacteriochlorophyll (BChl) c in intact chlorosomes of Chlorobium tepidum and in [U-13C] BChl c aggregates were determined by the application of homonuclear (13C?13C) magic angle spinning (MAS) NMR dipolar correlation spectroscopy. It was found that the

B.-J. van Rossum; G. J. Boender; F. M. Mulder; J. Raap; T. S. Balaban; A. Holzwarth; K. Schaffner; S. Prytulla; H. Oschkinat; H. J. M. de Groot

1998-01-01

30

Demineralization of marine and freshwater sediments for CP\\/MAS 13C NMR analysis  

Microsoft Academic Search

A method was developed to demineralize sediment trap material and marine sediments containing labile organic matter (OM), in preparation for cross polarization and magic angle spinning (CP\\/MAS) solid-state 13C NMR analysis. Carbonate and silicate minerals were dissolved with HCl and a mixture of dilute HCl\\/HF, respectively. Demineralization kinetics were assessed for a range of freshwater and marine sediments, as well

Yves Gélinas; Jeff A. Baldock; John I. Hedges

2001-01-01

31

DETERMINATION OF BRANCHING RATIOS OF STARCH IN FLOURS BY 1H MAS NMR SPECTROSCOPY  

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% DMSO/ D2O freeze dried again, finally moistened with D2O, and placed in a spherical 4 m...

32

CP\\/MAS 13C NMR analysis of cellulase treated bleached softwood kraft pulp  

Microsoft Academic Search

Fully bleached softwood kraft pulps were hydrolyzed with cellulase (1,4-(1,3:1,4)-?-d-glucan 4-glucano-hydrolase, EC 3.2.1.4) from Trichoderma reesei. Supra-molecular structural features of cellulose during enzymatic hydrolysis were examined by using CP\\/MAS 13C NMR spectra in combination with line-fitting analysis. Different types of cellulose allomorphs (cellulose I?, cellulose I?, para-crystalline) and amorphous regions were hydrolyzed to a different extent by the enzyme used.

Yunqiao Pu; Cherie Ziemer; Arthur J. Ragauskas

2006-01-01

33

Reduction of spin diffusion artifacts from 2D zfr-INADEQUATE MAS NMR spectra  

NASA Astrophysics Data System (ADS)

The primary shortcoming of the z-filtered refocused INADEQUATE MAS NMR pulse sequence is the possibility of artifacts introduced during the z-filter due to spin diffusion where by extra peaks in the single-quantum dimension (from other sites in the molecule) appear correlated with a given double-quantum frequency. This is a problem when the spinning speeds are too slow (less than 15 kHz) to sufficiently average the proton-proton homonuclear dipolar couplings. This would be especially important when working with large volume rotors that are difficult to spin fast enough to completely average the homonuclear couplings. In our experiments we used the frequency-switched Lee-Goldberg (FSLG) method of homonuclear decoupling during the z-filter to remove the artifact peaks. This method has the advantage of being quite easy to setup and implement on most modern NMR spectrometers.

Baltisberger, Jay H.; Musapelo, Thabiso; Sutton, Brian; Reynolds, Anthony; Gurung, Laxman

2011-01-01

34

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

35

With the view of enhancing the resolution in solid state NMR, we investigated the use of single crystals in CP-MAS. Model  

E-print Network

a significantly wider impact on structure determination than previously thought. Increasing 13C CP-MAS NMR of Florida. Citation: S. Dugar, R. Fu., N.S. Dalal, Increasing 13C CP-MAS NMR Resolution Using SingleWith the view of enhancing the resolution in solid state NMR, we investigated the use of single

36

Re-evaluating boron speciation in biogenic calcite and aragonite using 11B MAS NMR  

NASA Astrophysics Data System (ADS)

Understanding the partitioning of aqueous boron species into marine carbonates is critical for constraining the boron isotope system for use as a marine pH proxy. Previous studies have assumed that boron was incorporated into carbonate through the preferential uptake of tetrahedral borate B(OH) 4-. In this study we revisit this assumption through a detailed solid state 11B magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic study of boron speciation in biogenic and hydrothermal carbonates. Our new results contrast with those of the only previous NMR study of carbonates insofar as we observe both trigonal and tetrahedral coordinated boron in almost equal abundances in our biogenic calcite and aragonite samples. In addition, we observe no strict dependency of boron coordination on carbonate crystal structure. These NMR observations coupled with our earlier re-evaluation of the magnitude of boron isotope fractionation between aqueous species suggest that controls on boron isotope composition in marine carbonates, and hence the pH proxy, are more complex that previously suggested.

Klochko, Kateryna; Cody, George D.; Tossell, John A.; Dera, Przemyslaw; Kaufman, Alan J.

2009-04-01

37

A 4-mm Probe for C-13 CP/MAS NMR of Solids at 21.15 T  

SciTech Connect

With the recent announcement of a persistent 21.15 Tesla (i.e., 900 MHz for 1H NMR) narrow-bore (54 mm bore) superconducting magnet by Oxford Instruments and the associated Unity INOVA-900 console by Varian Inc. we were challenged with the task of designing a double-resonance broadband solid-state magic-angle spinning (MAS) NMR probe in particular for evaluating the 13C-{1H} cross-polarization (CP) MAS NMR experiment on this magnet and spectrometer system. In this communication we report the successful construction of an efficient X-1H/19F double resonance multinuclear MAS probe for this purpose along with our preliminary results on its performance at the 900 MHz spectrometer.

Jakobsen, Hans J. (Aarhus, University of); Daugaard, P (Aarhus, University of); Hald, E (Aarhus, University of); Rice, D (Varian Inc.); Kupce, Eriks (Varian NMR Instruments); Ellis, Paul D. (BATTELLE (PACIFIC NW LAB))

2002-05-31

38

A 4-mm probe for C-13 CP/MAS NMR of solids at 21.15 T  

SciTech Connect

With a recent announcement of a persistent 21.15 Tesla (i.e., 900 MHz for 1H NMR) narrow-bore (54 mm bore) superconducting magnet by Oxford instruments and the associated Unity INOVA-900 console by Varian Inc. We were challenged with the task of designing a double resonance broadband solid-state magnetic magic-angle spinning (MAS) NMR probe. In particular for evaluating the 13C-(1H) cross-polarization (CP) MAS NMR experiment on this magnet and spectrometer system. In this communication we report the successful construction of an efficient X-1H/19F double resonance multinuclear MAS probe for this purpose along with our preliminary results on its performance at the 900 MHz spectrometer.

Jakobsen, Hans J. (Aarhus, University of); Daugaard, P (Aarhus, University of); Hald, E (Aarhus, University of); Rice, D (Varian Inc.); Kupce, Eriks (Varian NMR Instruments); Ellis, Paul D. (BATTELLE (PACIFIC NW LAB))

2001-12-01

39

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

PubMed

Glasses have been synthesized in the system P2O5SiO2K2OMgOCaO modified by addition of MoO3. Glasses were prepared by conventional fusion method from 40g batches. The influence of Mo-cations on the analysed glass structure was investigated by means of Raman and (31)P MAS-NMR techniques. It has been found that molybdate units can form Mo[MoO4/MoO6]OP and/or Mo[MoO4/MoO6]OSi 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. PMID:25216461

Szumera, Magdalena

2015-02-25

40

Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy  

PubMed Central

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

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

41

Sensitivity enhancement using paramagnetic relaxation in MAS solid-state NMR of perdeuterated proteins  

NASA Astrophysics Data System (ADS)

Previously, Ishii et al., could show that chelated paramagnetic ions can be employed to significantly decrease the recycle delay of a MAS solid-state NMR experiment [N.P. Wickramasinghe, M. Kotecha, A. Samoson, J. Past, Y. Ishii, Sensitivity enhancement in C-13 solid-state NMR of protein microcrystals by use of paramagnetic metal ions for optimizing H-1 T-1 relaxation, J. Magn. Reson. 184 (2007) 350-356]. Application of the method is limited to very robust samples, for which sample stability is not compromised by RF induced heating. In addition, probe integrity might be perturbed in standard MAS PRE experiments due to the use of very short duty cycles. We show that these deleterious effects can be avoided if perdeuterated proteins are employed that have been re-crystallized from D 2O:H 2O = 9:1 containing buffer solutions. The experiments are demonstrated using the SH3 domain of chicken ?-spectrin as a model system. The labeling scheme allows to record proton detected 1H, 15N correlation spectra with very high resolution in the absence of heteronuclear dipolar decoupling. Cu-edta as a doping reagent yields a reduction of the recycle delay by up to a factor of 15. In particular, we find that the 1H T1 for the bulk H N magnetization is reduced from 4.4 s to 0.3 s if the Cu-edta concentration is increased from 0 mM to 250 mM. Possible perturbations like chemical shift changes or line broadening due to the paramagnetic chelate complex are minimal. No degradation of our samples was observed in the course of the experiments.

Linser, Rasmus; Chevelkov, Veniamin; Diehl, Anne; Reif, Bernd

2007-12-01

42

Higher order amyloid fibril structure by MAS NMR and DNP spectroscopy.  

PubMed

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 residues buried within the interior of the fibrils. PMID:24304221

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

2013-12-26

43

Determination of the degree of acetylation of chitin materials by 13C CP\\/MAS NMR spectroscopy  

Microsoft Academic Search

13C CP\\/MAS NMR spectroscopy has been shown to be a powerful tool to quantify the degree of acetylation of chitin and chitosan. In order to optimise the parameters which afford quantitative 13C cross-polarisation magic-angle spinning NMR spectra, a detailed relaxation study has been carried out on selected chitin and deacetylated chitin samples. A relaxation delay of 5 s and a

M. L. Duarte; M. C. Ferreira; M. R. Marvão; João Rocha

2001-01-01

44

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

Microsoft Academic Search

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

Kristina Wickholm; Per Tomas Larsson; Tommy Iversen

1998-01-01

45

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

SciTech Connect

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.

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

2009-08-01

46

PFG-assisted selection and suppression of 1H NMR signals in the solid state under fast MAS  

NASA Astrophysics Data System (ADS)

Under fast MAS conditions, techniques for 1H signal selection and suppression, which have originally been developed for solution-state NMR, become applicable to solids. In this work, we describe how WATERGATE and DANTE pulse sequences can be used under MAS to selectively excite or suppress peaks in 1H solid-state spectra. As known from the liquid-state analogues, signal selection and/or suppression is supported by pulsed-field gradients which selectively dephase and rephase transverse magnetisation. Under MAS, the required field gradients are provided by a simple pair of coils which have been built into a standard fast-MAS probe. PFG-assisted techniques enable efficient selection or suppression of 1H peaks in a single transient of the pulse sequence without the need for phase cycles. Therefore, these tools can readily be incorporated into solid-state MAS NMR experiments, which is demonstrated here for 1H- 1H double-quantum NMR spectra of supramolecular systems. In the examples presented here, the 1H signals of interest are relatively weak and need to be observed despite the presence of the strong 1H signal of long alkyl sidechains. PFG-assisted suppression of this strong perturbing signal is shown to be particularly useful for obtaining unambiguous results.

Fischbach, Ingrid; Thieme, Karena; Hoffmann, Anke; Hehn, Manfred; Schnell, Ingo

2003-11-01

47

PFG-assisted selection and suppression of 1H NMR signals in the solid state under fast MAS.  

PubMed

Under fast MAS conditions, techniques for 1H signal selection and suppression, which have originally been developed for solution-state NMR, become applicable to solids. In this work, we describe how WATERGATE and DANTE pulse sequences can be used under MAS to selectively excite or suppress peaks in 1H solid-state spectra. As known from the liquid-state analogues, signal selection and/or suppression is supported by pulsed-field gradients which selectively dephase and rephase transverse magnetisation. Under MAS, the required field gradients are provided by a simple pair of coils which have been built into a standard fast-MAS probe. PFG-assisted techniques enable efficient selection or suppression of 1H peaks in a single transient of the pulse sequence without the need for phase cycles. Therefore, these tools can readily be incorporated into solid-state MAS NMR experiments, which is demonstrated here for 1H-1H double-quantum NMR spectra of supramolecular systems. In the examples presented here, the 1H signals of interest are relatively weak and need to be observed despite the presence of the strong 1H signal of long alkyl sidechains. PFG-assisted suppression of this strong perturbing signal is shown to be particularly useful for obtaining unambiguous results. PMID:14568521

Fischbach, Ingrid; Thieme, Karena; Hoffmann, Anke; Hehn, Manfred; Schnell, Ingo

2003-11-01

48

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

E-print Network

A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi t A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrom- eter of Physics, University of Warwick, CV4 7AL, United Kingdom b School of Physics and Astronomy, University

Watts, Anthony

49

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

50

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

PubMed

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

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

2012-06-20

51

(13)C CP MAS NMR and crystal structure of methyl glycopyranosides.  

PubMed

The X-ray diffraction analysis, (13)C CP MAS NMR spectra and powder X-ray diffraction patterns were obtained for selected methyl glycosides: alpha- and beta-d-lyxopyranosides (1, 2), alpha- and beta-l-arabinopyranosides (3, 4), alpha- and beta-d-xylopyranosides (5, 6) and beta-d-ribopyranoside (7) and the results were confirmed by GIAO DFT calculations of shielding constants. In X-ray diffraction analysis of 1 and 2, a characteristic shortening and lengthening of selected bonds was observed in molecules of 1 due to anomeric effect and, in crystal lattice of 1 and 2, hydrogen bonds of different patterns were present. Also, an additional intramolecular hydrogen bond with the participation of ring oxygen atom was observed in 1. The observed differences in chemical shifts between solid state and solution come from conformational effects and formation of various intermolecular hydrogen bonds. The changes in chemical shifts originating from intermolecular hydrogen bonds were smaller in magnitude than conformational effects. Furthermore, the powder X-ray diffraction (PXRD) performed for 4, 5 and 7 revealed that 7 existed as a mixture of two polymorphs, and one of them probably consisted of two non-equivalent molecules. PMID:18547551

Paradowska, Katarzyna; Gubica, Tomasz; Temeriusz, Andrzej; Cyra?ski, Micha? K; Wawer, Iwona

2008-09-01

52

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

NASA Astrophysics Data System (ADS)

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.

Szumera, Magdalena

2015-02-01

53

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

SciTech Connect

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.

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

2009-09-01

54

Experimental aspects in acquisition of wide bandwidth solid-state MAS NMR spectra of low-? nuclei with different opportunities on two commercial NMR spectrometers.  

PubMed

The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-? nuclei, using (14)N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1T and Bruker, 19.6T), have been compared/evaluated and optimized from an experimental NMR and an electronic engineering point of view, to account for the huge differences in these spectra. The large differences in their spectral appearances, employing the recommended/standard experimental set-up for the two different spectrometers, are shown to be associated with quite large differences in the electronic design of the two types of preamplifiers, which are connected to their respective probes through a 50? cable, and are here completely accounted for. This has led to different opportunities for optimum performances in the acquisition of nearly ideal wide bandwidth spectra for low-? nuclei on the two spectrometers by careful evaluation of the length for the 50? probe-to-preamp cable for the Varian system and appropriate changes to the bandwidth (Q) of the NMR probe used on the Bruker spectrometer. Earlier, we reported quite distorted spectra obtained with Varian Unity INOVA spectrometers (at 11.4 and 14.1T) in several exploratory wide bandwidth (14)N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed (14)N MAS spectra correspondingly acquired at 19.6T on a Bruker spectrometer. It is shown that our upgraded version of the STARS simulation/iterative-fitting software is capable of providing identical sets for the molecular spectral parameters and corresponding fits to the experimental spectra, which fully agree with the electronic measurements, despite the highly different appearances for the MAS NMR spectra acquired on the Varian and Bruker spectrometers. PMID:21704544

Jakobsen, Hans J; Bildsøe, Henrik; Gan, Zhehong; Brey, William W

2011-08-01

55

Proton-detected heteronuclear single quantum correlation NMR spectroscopy in rigid solids with ultra-fast MAS  

PubMed Central

In this article, we show the potential for utilizing proton-detected heteronuclear single quantum correlation (HSQC) NMR in rigid solids under ultra-fast magic angle spinning (MAS) conditions. The indirect detection of carbon-13 from coupled neighboring hydrogen nuclei provides a sensitivity enhancement of 3 - 4 fold in crystalline amino acids over direct-detected versions. Furthermore, the sensitivity enhancement is shown to be significantly larger for disordered solids that display inhomogeneously broadened carbon-13 spectra. Latrodectus hesperus (Black Widow) dragline silk is given as an example where the sample is mass-limited and the sensitivity enhancement for the proton-detected experiment is 8 - 13 fold. The ultra-fast MAS proton-detected HSQC solid-state NMR technique has the added advantage that no proton homonuclear decoupling is applied during the experiment. Further, well-resolved, indirectly observed carbon-13 spectra can be obtained in some cases without heteronuclear proton decoupling. PMID:19857977

Holland, Gregory P.; Cherry, Brian R.; Jenkins, Janelle E.; Yarger, Jeffery L.

2009-01-01

56

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

USGS Publications Warehouse

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.

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

2005-01-01

57

A CP\\/MAS C NMR Study of the Effect of Steam Explosion Processes on Wood Composition and Structure  

Microsoft Academic Search

Two wood species - the softwood Pinus radiata and the hardwood Eucalyptus regnans have been examined by CP\\/MAS C NMR spectroscopy before and after treatment by two steam explosion processes, namely, the Canadian Iotech Process and the Australian Siropulper process.While the main effects of treatment appeared to be, in general, similar for both processes and both species of wood, e.g.

Jacqueline A. Henuningson; Roger H. Newman DSIR

1985-01-01

58

CP\\/MAS Carbon13 NMR Study of Spin Relaxation Phenomena of Cellulose Containing Crystalline and Noncrystalline Components  

Microsoft Academic Search

Cross-polarization, C rotating frame spin-lattice relaxation and C laboratory frame spin-lattice relaxation processes have been studied for different cellulose samples by CP\\/MAS C NMR spectroscopy. It was found that the CP process can be described by a simple thermodynamic model and relative intensities of the respective resonance lines are consistent with the atomic ratios for the spectra obtained at a

F. Horii; A. Hirai; R. Kitamaru

1984-01-01

59

The heterogeneous nature of microbial products as shown by solid-state 13 C CP\\/MAS NMR spectroscopy  

Microsoft Academic Search

Homoionic Na-, Ca-, and Al-clays were prepared from the 13C-labelled (99.9% atom) glucose were incorporated into the artificial soils to study the effects of clay types, exchangeable cations and clay contents on the mineralization of glucose-carbon and glucose-derived organic materials. Chemical transformation of glucose-carbon upon incorporation into microbial products and metabolites, was followed using solid-state13C CP\\/MAS NMR spectroscopy.

A. Golchin; P. Clarke; J. M. Oades

1996-01-01

60

Crystallinity and structuring role of water in native and recrystallized starches by 13C CP-MAS NMR spectroscopy  

Microsoft Academic Search

Amorphous, native, and recrystallized starches were studied by 13C CP-MAS NMR spectroscopy with respect to their behavior with hydration. The study of space groups, associated to crystalline polymorphs (B2 and P61 for A and B forms, respectively), provided decomposition rules for the spectral part due to crystalline phases. Moreover, the subtraction of a standard amorphous spectrum apparently showed the existence

H Bizot; J Emery; J. Y Buzaré; A Buléon

1999-01-01

61

A comparative CP\\/MAS 13C-NMR study of cellulose structure in spruce wood and kraft pulp  

Microsoft Academic Search

CP\\/MAS 13C-NMR spectroscopy in combination with spectral fitting was used to study the supermolecular structure of the cellulose fibril in spruce wood and spruce kraft pulp. During pulping, structures contributing to inaccessible surfaces in the wood cellulose are converted to the cellulose Iß allomorph, that is, the degree of order is increased. This increase is also accompanied by a conversion

Eva-Lena Hult; Per Tomas Larsson; Tommy Iversen

2000-01-01

62

N CP\\/MAS NMR Study of the Isocyanate\\/Wood Adhesive Bondline. Effects of Structural Isomerism  

Microsoft Academic Search

Structurally isomeric N-labeled polymeric methylenebis(phenylisocyanate), pMDI, adhesives were synthesized. One resin had a high content of 4,4?-MDI, and another was prepared with a high content of 2,4?-MDI. Both resins were cured with wood (Liriodendron tulipifera) for various times and temperatures and then analyzed using N CP\\/MAS NMR. It was found that resin polymerization occurs via the reaction of isocyanate with

Jianwen Ni; Charles E. Frazier

1998-01-01

63

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 ...

64

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

NASA Astrophysics Data System (ADS)

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 13C-13C 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-13C labelled samples, spin diffusion leads to propagation of signal enhancement to all 13C 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.

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

2014-09-01

65

Characterization of solid polymer dispersions of active pharmaceutical ingredients by 19F MAS NMR and factor analysis.  

PubMed

In this contribution the ability of (19)F MAS NMR spectroscopy to probe structural variability of poorly water-soluble drugs formulated as solid dispersions in polymer matrices is discussed. The application potentiality of the proposed approach is demonstrated on a moderately sized active pharmaceutical ingredient (API, Atorvastatin) exhibiting extensive polymorphism. In this respect, a range of model systems with the API incorporated in the matrix of polvinylpyrrolidone (PVP) was prepared. The extent of mixing of both components was determined by T(1)((1)H) and T(1?)((1)H) relaxation experiments, and it was found that the API forms nanosized domains. Subsequently it was found out that the polymer matrix induces two kinds of changes in (19)F MAS NMR spectra. At first, this is a high-frequency shift reaching 2-3 ppm which is independent on molecular structure of the API and which results from the long-range polarization of the electron cloud around (19)F nucleus induced by electrostatic fields of the polymer matrix. At second, this is broadening of the signals and formation of shoulders reflecting changes in molecular arrangement of the API. To avoid misleading in the interpretation of the recorded (19)F MAS NMR spectra, because both the contributions act simultaneously, we applied chemometric approach based on multivariate analysis. It is demonstrated that factor analysis of the recorded spectra can separate both these spectral contributions, and the subtle structural differences in the molecular arrangement of the API in the nanosized domains can be traced. In this way (19)F MAS NMR spectra of both pure APIs and APIs in solid dispersions can be directly compared. The proposed strategy thus provides a powerful tool for the analysis of new formulations of fluorinated pharmaceutical substances in polymer matrices. PMID:22421443

Urbanova, Martina; Brus, Jiri; Sedenkova, Ivana; Policianova, Olivia; Kobera, Libor

2013-01-01

66

Characterization of solid polymer dispersions of active pharmaceutical ingredients by 19F MAS NMR and factor analysis  

NASA Astrophysics Data System (ADS)

In this contribution the ability of 19F MAS NMR spectroscopy to probe structural variability of poorly water-soluble drugs formulated as solid dispersions in polymer matrices is discussed. The application potentiality of the proposed approach is demonstrated on a moderately sized active pharmaceutical ingredient (API, Atorvastatin) exhibiting extensive polymorphism. In this respect, a range of model systems with the API incorporated in the matrix of polvinylpyrrolidone (PVP) was prepared. The extent of mixing of both components was determined by T1(1H) and T1?(1H) relaxation experiments, and it was found that the API forms nanosized domains. Subsequently it was found out that the polymer matrix induces two kinds of changes in 19F MAS NMR spectra. At first, this is a high-frequency shift reaching 2-3 ppm which is independent on molecular structure of the API and which results from the long-range polarization of the electron cloud around 19F nucleus induced by electrostatic fields of the polymer matrix. At second, this is broadening of the signals and formation of shoulders reflecting changes in molecular arrangement of the API. To avoid misleading in the interpretation of the recorded 19F MAS NMR spectra, because both the contributions act simultaneously, we applied chemometric approach based on multivariate analysis. It is demonstrated that factor analysis of the recorded spectra can separate both these spectral contributions, and the subtle structural differences in the molecular arrangement of the API in the nanosized domains can be traced. In this way 19F MAS NMR spectra of both pure APIs and APIs in solid dispersions can be directly compared. The proposed strategy thus provides a powerful tool for the analysis of new formulations of fluorinated pharmaceutical substances in polymer matrices.

Urbanova, Martina; Brus, Jiri; Sedenkova, Ivana; Policianova, Olivia; Kobera, Libor

67

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

PubMed

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

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

2014-09-01

68

Double cross-polarization MAS NMR in the assignment of abundant-spin resonances: 19F-{29Si}-19F FBCP/MAS NMR of fluoride ions incorporated in calcium silicate hydrate (C-S-H) phases  

NASA Astrophysics Data System (ADS)

A new version of the double cross-polarization MAS NMR experiment, which transfers polarization Forth and Back (FBCP) between high- and low-? spin nuclei, is presented. The pulse sequence is demonstrated by 19F-{29Si}-19F and 19F-{13C}-19F FBCP NMR spectra of a mixture of cuspidine (Ca4Si2O7F2) and Teflon (-CF2-)n. The experiment is useful for assignment of the high-? spin resonances, as demonstrated by 19F-{29Si}-19F FBCP NMR of a fluoride-containing calcium-silicate-hydrate (C-S-H) phase, where the 19F resonance from fluoride ions incorporated in the interlayer structure of the C-S-H phase is identified.

Tran, Thuan T.; Bildsøe, Henrik; Jakobsen, Hans J.; Skibsted, Jørgen

2012-08-01

69

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

NASA Astrophysics Data System (ADS)

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

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

70

High field DNP and cryogenic MAS NMR : novel instrumentation and applications  

E-print Network

Solid State Nuclear Magnetic Resonance (ssNMR) spectroscopy has blossomed over the last two decades. As ssNMR is progressively applied to more challenging systems, the sensitivity remains one of its major limiting factors. ...

Markhasin, Evgeny

2014-01-01

71

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

SciTech Connect

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.

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

72

Glasses in the system phosphorus-sulfur: A sup 31 P spin-echo and high-speed MAS-NMR study of atomic distribution and local order  

Microsoft Academic Search

The structural organization of glasses in the system P-S is investigated by modern solid-state NMR techniques. Throughout the entire region of glass formation, S=PSââ groups are found to be the principal short-range-order environment. These units are identified, in conjunction with parallel studies of crystalline model compounds, by a characteristic ³¹P MAS-NMR (MAS = magic angle spinning) sideband intensity pattern, indicating

Michael. Tullius; David. Lathrop; Hellmut. Eckert

1990-01-01

73

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

NASA Astrophysics Data System (ADS)

The plasticizing - antiplasticizing effect of water and glycerol contents on native corn starch samples is investigated by FT-Raman and 13C 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.

Cozar, O.; Filip, C.; Cioica, N.; Coţa, C.; Tripon, C.; Nagy, E. M.

2013-11-01

74

A 13C CP\\/MAS NMR spectroscopy and AFM study of the structure of Glucagel™, a gelling ?-glucan from barley  

Microsoft Academic Search

The structure of Glucagel™, a mixed-linked (1?3), (1?4)-?-d-glucan extracted from barley, was examined using 13C CP\\/MAS NMR spectroscopy and atomic force microscopy (AFM). Results from 13C CP\\/MAS NMR spectroscopy showed that Glucagel™ contained regions with two distinct conformations. In some of the regions the ?-glucan chains associated to form a unique conformation, the A-conformation, while in the other regions the

Keith R. Morgan; Clive J. Roberts; Saul J. B. Tendler; Martyn C. Davies; Phil M. Williams

1999-01-01

75

Bain AD, Dumont RS. Introduction to Floquet theory. The calculation of spinning sideband intensities in MAS NMR. Concepts Magn Reson 2001; 13: 159-  

E-print Network

Bain AD, Dumont RS. Introduction to Floquet theory. The calculation of spinning sideband intensities in MAS NMR. Concepts Magn Reson 2001; 13: 159- 170. ABSTRACT In magic-angle spinning (MAS the simulation of the lineshape considerably. A simple case is that of a spin-1/2 with an anisotropic chemical

Hitchcock, Adam P.

76

Study of potassium O,O'-Dibutyldithiophosphate combining DFT, 31P CP/MAS NMR and infrared spectroscopy.  

PubMed

Dithiophosphates are used in many different industrial applications. To explain their functions and properties in these applications, a fundamental understanding on a molecular level is needed. Potassium O, O'-Dibutyldithiophosphate and its anion have been investigated by means of a combination of DFT and (31)P CP/MAS NMR and infrared spectroscopy. Several low-energy conformations were studied by DFT. Three different conformations with significantly different torsion angles of the O-C bond relative to the O-P-O plane were selected for further studies of infrared frequencies and (31)P NMR chemical-shift tensors. A good agreement between theoretical and experimental results was obtained, especially when the IR spectra or (31)P chemical shift tensor parameters of all three conformations were added, indicating that, because of the low energy difference between the conformations, the molecules are rapidly fluctuating between them. PMID:18942802

Hellström, Pär; Larsson, Anna-Carin; Fredriksson, Andreas; Holmgren, Allan; Oberg, Sven

2008-11-20

77

Residual methyl protonation in perdeuterated proteins for multi-dimensional correlation experiments in MAS solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

NMR studies involving perdeuterated proteins focus in general on exchangeable amide protons. However, non-exchangeable sites contain as well a small amount of protons as the employed precursors for protein biosynthesis are not completely proton depleted. The degree of methyl group protonation is in the order of 9% for CD 2H using >97% deuterium enriched glucose. We show in this manuscript that this small amount of residual protonation is sufficient to perform 2D and 3D MAS solid-state NMR experiments. In particular, we suggest a HCCH-TOBSY type experiment which we successfully employ to assign the methyl resonances in aliphatic side chains in a perdeuterated sample of the SH3 domain of chicken ?-spectrin.

Agarwal, Vipin; Reif, Bernd

2008-09-01

78

13C CP MAS NMR and GIAO-CHF calculations of coumarins.  

PubMed

13C cross-polarization magic-angle spinning NMR spectra were recorded for a series of solid coumarins. Ab initio calculations of shielding constants were performed with the use of GIAO-CHF method. The combined CPMAS NMR and theoretical approach was successful in characterizing solid-state conformations of coumarins; a relationship sigma (ppm) = -1.032 xdelta + 205.28 (R(2) = 0.9845) can be used to obtain structural information for coumarins, for which solid-state NMR or crystal structure data are not available. PMID:12633833

Zolek, Teresa; Paradowska, Katarzyna; Wawer, Iwona

2003-01-01

79

Domains in Binary SOPC/POPE Lipid Mixtures Studied by Pulsed Field Gradient 1H MAS NMR  

PubMed Central

We studied domain formation in mixtures of the monounsaturated lipids SOPC and POPE as a function of temperature and composition by NMR. Magic angle spinning at kHz frequencies restored resolution of 1H NMR lipid resonances in the fluid phase, whereas the linewidth of gel-phase lipids remained rather broad and spinning frequency dependent. In regions of fluid- and gel-phase coexistence, spectra are a superposition of resonances from fluid and gel domains, as indicated by the existence of isosbestic points. Quantitative determination of the amount of lipid in the coexisting phases is straightforward and permitted construction of a binary phase diagram. Lateral rates of lipid diffusion were determined by 1H MAS NMR with pulsed field gradients. At the onset of the phase transition near 25°C apparent diffusion rates became diffusion time dependent, indicating that lipid movement is obstructed by the formation of gel-phase domains. A percolation threshold at which diffusion of fluid-phase lipid becomes confined to micrometer-size domains was observed when ?40% of total lipid had entered the gel phase. The results indicate that common phosphatidylethanolamines may trigger domain formation in membranes within a physiologically relevant temperature range. This novel NMR approach may aid the study of lipid rafts. PMID:15345553

Polozov, Ivan V.; Gawrisch, Klaus

2004-01-01

80

Characterisation of alkali ions in the Y-type zeolites by multi MAS NMR studies  

Microsoft Academic Search

The NaY zeolites exchanged with other alkali cations (Li+, K+, Rb+ and Cs+) are characterised by high resolution solid state 29Si-, 27A1-, 23Na- and 133Cs-NMR. The chemical shifts of the various Si(nAl) n=0, 1, 2, 3 and 4 configurations show particular changes as a function of the alkali counter-cations. The NMR line stemming from the Si(1Al) shows the greatest linewidth

I Hannus; I Kiricsi; P Lentz; J. B Nagy

1999-01-01

81

Double-Quantum-Filtered Rotational-Resonance MAS NMR in the Presence of Large Chemical Shielding Anisotropies  

NASA Astrophysics Data System (ADS)

Double-quantum filtration under rotational resonance MAS NMR conditions where the chemical shielding anisotropies involved exceed the differences in isotropic chemical shielding is considered by means of numerical simulations and 13C MAS NMR experiments. The responses of two different pulse sequences, suitable for double-quantum filtration specifically under rotational resonance conditions, to large chemical shielding anisotropies are compared. In the presence of large chemical shielding anisotropies a very recently introduced pulse sequence (T. Karlsson, M. Edén, H. Luthman, and M. H. Levitt, J. Magn. Reson.145, 95-107, 2000) suffers losses in double-quantum-filtration efficiencies. The double-quantum-filtration efficiency of another pulse sequence (N. C. Nielsen, F. Creuzet, R. G. Griffin, and M. H. Levitt, J. Chem. Phys.96, 5668-5677, 1992) is less afflicted by the presence of large chemical shielding anisotropies. Both sequences deliver double-quantum-filtered lineshapes that sensitively reflect chemical shielding tensor orientations. It is further shown that double-quantum-filtered rotational-resonance lineshapes of spin systems composed of more than two spins offer a suitable experimental approach for determining chemical shielding tensor orientations for cases where conventional rotational-resonance experiments are not applicable due to the presence of additional background resonances.

Bechmann, Matthias; Helluy, Xavier; Sebald, Angelika

2001-09-01

82

Quantification of Choline- and Ethanolamine-Containing Metabolites in Human Prostate Tissues Using 1H HR-MAS Total Correlation Spectroscopy  

PubMed Central

A fast and quantitative 2D high-resolution magic angle spinning (HR-MAS) total correlation spectroscopy (TOCSY) experiment was developed to resolve and quantify the choline- and ethanolamine-containing metabolites in human prostate tissues in ?1 hr prior to pathologic analysis. At a 40-ms mixing time, magnetization transfer efficiency constants were empirically determined in solution and used to calculate metabolite concentrations in tissue. Phosphocholine (PC) was observed in 11/15 (73%) cancer tissues but only 6/32 (19%) benign tissues. PC was significantly higher (0.39 ± 0.40 mmol/kg vs. 0.02 ± 0.07 mmol/kg, z = 3.5), while ethanolamine (Eth) was significantly lower in cancer versus benign prostate tissues (1.0 ± 0.8 mmol/kg vs. 2.3 ± 1.9 mmol/kg, z = 3.3). Glycerophosphocholine (GPC) (0.57± 0.87 mmol/kg vs. 0.29± 0.26 mmol/kg, z = 1.2), phosphoethanolamine (PE) (4.4± 2.2 mmol/kg vs. 3.4± 2.6 mmol/kg, z = 1.4), and glycerophosphoethanolamine (GPE) (0.54± 0.82 mmol/kg vs. 0.15± 0.15 mmol/kg, z = 1.8) were higher in cancer versus benign prostate tissues. The ratios of PC/GPC (3.5± 4.5 vs. 0.32± 1.4, z = 2.6), PC/PE (0.08± 0.08 vs. 0.01± 0.03, z = 3.5), PE/Eth (16± 22 vs. 2.2± 2.0, z = 2.4), and GPE/Eth (0.41± 0.51 vs. 0.06± 0.06, z = 2.6) were also significantly higher in cancer versus benign tissues. All samples were pathologically interpretable following HR-MAS analysis; however, degradation experiments showed that PC, GPC, PE, and GPE decreased 7.7± 2.2%, while Cho+mI and Eth increased 18% in 1 hr at 1°C and a 2250 Hz spin rate. PMID:18581409

Swanson, Mark G.; Keshari, Kayvan R.; Tabatabai, Z. Laura; Simko, Jeffry P.; Shinohara, Katsuto; Carroll, Peter R.; Zektzer, Andrew S.; Kurhanewicz, John

2008-01-01

83

Acceleration of natural-abundance solid-state MAS NMR measurements on bone by paramagnetic relaxation from gadolinium-DTPA  

NASA Astrophysics Data System (ADS)

Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans.

Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

2014-07-01

84

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

PubMed

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

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

2001-01-01

85

Deuterium MAS NMR studies of dynamics on multiple timescales: histidine and oxalic Acid.  

PubMed

Deuterium ((2) H) magic-angle spinning (MAS) nuclear magnetic resonance is applied to monitor the dynamics of the exchanging labile deuterons of polycrystalline L-histidine hydrochloride monohydrate-d7 and ?-oxalic acid dihydrate-d6 . Direct experimental evidence of fast dynamics is obtained from T1Z and T1Q measurements. Further motional information is extracted from two-dimensional single-quantum (SQ) and double-quantum (DQ) MAS spectra. Differences between the SQ and DQ linewidths clearly indicate the presence of motions on intermediate timescales for the carboxylic moiety and the D2 O in ?-oxalic acid dihydrate, and for the amine group and the D2 O in L-histidine hydrochloride monohydrate. Comparison of the relaxation rate constants of Zeeman and quadrupolar order with the relaxation rate constants of the DQ coherences suggests the co-existence of fast and slow motional processes. PMID:25358952

Chan-Huot, Monique; Wimperis, Stephen; Gervais, Christel; Bodenhausen, Geoffrey; Duma, Luminita

2015-01-12

86

CP-MAS NMR of highly mobile hydrated biopolymers: Polysaccharides of Allium cell walls  

Microsoft Academic Search

The most highly mobile polysaccharides of hydrated Allium cepa (onion) cell walls were not visible in cross-polarisation magic-angle spinning (CP-MAS) 13C spectra recorded using a conventional CP contact time of 0.5 ms. These polysaccharides showed very slow CP and thus did not appear in the 3C spectrum until the contact time was extended to 2 ms or more. A spectrum

Marie-Ann Ha; Boyd W. Evans; Michael C. Jarvis; David C. Apperley; Alan M. Kenwright

1996-01-01

87

CP/MAS ¹³C NMR study of pulp hornification using nanocrystalline cellulose as a model system.  

PubMed

The hornification process of paper pulp was investigated using solid-state (13)C NMR spectroscopy. Nanocrystalline cellulose was used to serve as a model system of the crystalline parts of the fibrils in pulp fibers. Characterization of the nanocrystalline cellulose dimensions was carried out using scanning electron microscopy. The samples were treated by drying and wetting cycles prior to NMR analysis where the hornification phenomenon was recorded by spectral changes of the cellulose C-4 carbon signals. An increase of the crystalline signal and a decrease of the signals corresponding to the accessible amorphous domains were found for both paper pulp and nanocrystalline cellulose. These spectral changes grew stronger with repeating drying and wetting cycles. The results show that cellulose co-crystallization contribute to hornification. Another conclusion is that the surfaces of higher hydrophobicity in cellulose fibrils have an increased preference for aggregation. PMID:23218380

Idström, Alexander; Brelid, Harald; Nydén, Magnus; Nordstierna, Lars

2013-01-30

88

A CP\\/MAS 13C NMR investigation of molecular ordering in celluloses  

Microsoft Academic Search

The individual states of order of cellulose found within Valonia, Cladophora, Halocynthia, cotton and wood cellulose were quantified by non-linear least-squares fitting of the 13C NMR spectra. The results from the spectral fittings indicated that a cellulose form giving signals at ? 104.5 (C-1 region) and ? 88.1–88.5 (C-4 region) was present in all the investigated samples. Partial signal suppression

Per Tomas Larsson; Kristina Wickholm; Tommy Iversen

1997-01-01

89

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

90

A cross-polarization based rotating-frame separated-local-field NMR experiment under ultrafast MAS conditions  

NASA Astrophysics Data System (ADS)

Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent advances in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional 1H-13C dipolar coupling/chemical shift correlation experiment using 13C detected cross-polarization with a variable contact time (CPVC) and systematically study the conditions for its optimal performance at 60 kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H - w1C = ±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly 13C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of 1H-13C dipolar couplings are insensitive to 1H/13C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated 1H detected avenues for ultrafast MAS.

Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas; Ramamoorthy, Ayyalusamy

2015-01-01

91

A cross-polarization based rotating-frame separated-local-field NMR experiment under ultrafast MAS conditions.  

PubMed

Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent advances in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional (1)H-(13)C dipolar coupling/chemical shift correlation experiment using (13)C detected cross-polarization with a variable contact time (CPVC) and systematically study the conditions for its optimal performance at 60kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H-w1C=±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly (13)C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of (1)H-(13)C dipolar couplings are insensitive to (1)H/(13)C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated (1)H detected avenues for ultrafast MAS. PMID:25486635

Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas; Ramamoorthy, Ayyalusamy

2015-01-01

92

Source indicators of humic substances: an elemental composition, solid state 13C CP\\/MAS NMR and Py-GC\\/MS Study  

Microsoft Academic Search

Humic substances (HS) isolated from swamp water, surface soil, peat and brown coal were characterized using elemental composition, solid state 13C CP\\/MAS NMR and Py-GC\\/MS analysis. A substantial amount of information with regard to the source, maturity, depositional environment and degree of degradation of humic substances was obtained. The elemental composition, atomic ratio, 13C NMR spectra and Py-GC\\/MS results indicated

X. Q Lu; J. V Hanna; W. D Johnson

2000-01-01

93

Determination of Structural Topology of a Membrane Protein in Lipid -Bilayers using Polarization Optimized Experiments (POE) for Static and MAS Solid State NMR Spectroscopy  

PubMed Central

The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments (POE), for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ? 0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional O-ssNMR and MAS-ssNMR. PMID:23963722

Mote, Kaustubh R.; Gopinath, T.; Veglia, Gianluigi

2013-01-01

94

Interactions of fullerenes and calixarenes in the solid state studied with [sup 13]C CP-MAS NMR  

SciTech Connect

We report our findings on the interactions of fullerenes with calixarenes, forming a solid-state complex between C[sub 60] and 4-tert-butylcalix[8]arene, and solid state NMR of this complex. Complexation of C[sub 60] with calix[8]arene can occur in CS[sub 2] and in benzene solution, leading to the formation of a solid-state complex. The experiments indicate a 1:1 stoichiometry for the complex. C[sub 70] does not form similar complexes with calix[8]arenes, leading to the possibility of transferring C[sub 60] to the solid phase, separating it from C[sub 70] remaining in solution. The solid-state complexation in benzene, leading to precipitation, provides strong evidence for establishment of an interaction between C[sub 60] and 1. A change of the conformation of the calixarene upon complexation is indicated by the OH shift in the IR and the solid-state CP-MAS NMR data. 17 refs., 2 figs.

Williams, R.M.; Zwier, J.M.; Verhoeven, J.W. (Univ. of Amsterdam (Netherlands)); Nachtegaal, G.H.; Kentgens, A.P.M. (Univ. of Nijmegen (Netherlands))

1994-07-27

95

Proton-detected scalar coupling based assignment strategies in MAS solid-state NMR spectroscopy applied to perdeuterated proteins  

NASA Astrophysics Data System (ADS)

Assignment of proteins in MAS (magic angle spinning) solid-state NMR relies so far on correlations among heteronuclei. This strategy is based on well dispersed resonances in the 15N dimension. In many complex cases like membrane proteins or amyloid fibrils, an additional frequency dimension is desirable in order to spread the amide resonances. We show here that proton detected HNCO, HNCA, and HNCACB type experiments can successfully be implemented in the solid-state. Coherences are sufficiently long lived to allow pulse schemes of a duration greater than 70 ms before incrementation of the first indirect dimension. The achieved resolution is comparable to the resolution obtained in solution-state NMR experiments. We demonstrate the experiments using a triply labeled sample of the SH3 domain of chicken ?-spectrin, which was re-crystallized in H 2O/D 2O using a ratio of 1/9. We employ paramagnetic relaxation enhancement (PRE) using EDTA chelated Cu II to enable rapid data acquisition.

Linser, Rasmus; Fink, Uwe; Reif, Bernd

2008-07-01

96

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

PubMed

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

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

2015-01-01

97

Comparative study of two fractions of riverine dissolved organic matter using various analytical pyrolytic methods and a 13C CP\\/MAS NMR approach  

Microsoft Academic Search

Two fractions of dissolved organic matter (DOM) from a French river, the Gartempe, were obtained using the XAD resin fractionation procedure and were termed hydrophobic acid (HPOA) and transphilic acid (TPIA) according to this method. The composition of these two fractions was investigated with solid state CP\\/MAS 13C NMR, Curie point pyrolysis at 650 °C, with and without tetramethylammonium hydroxide

Joëlle Templier; Sylvie Derenne; Jean-Philippe Croué; Claude Largeau

2005-01-01

98

Solid state 13 C CP MAS NMR characterization of the chemical structure of terrestrial organic matter from areas with differing vegetational backgrounds  

Microsoft Academic Search

Twelve samples of terrestrial organic matter from areas of different vegetational background were selected for study. The samples were examined with solid state 13C NMR using Cross Polarisation and Magic Angle Spinning (CP MAS). The examination was done on whole soil samples, because isolation and separation of humic substances may alter the chemical structure of the organic matter. The soil

Marit Krosshavn; Jon Björgum; Timothy E. Southon; Eiliv Steinnes

99

The study of a monocotyledon abscission zone using microscopic, chemical, enzymatic and solid state 13C CP\\/MAS NMR analyses  

Microsoft Academic Search

We have investigated distinguishing features in cells of the abscission zone of a monocotyledon fruit, the oil palm Elaeis guineensis. The cell walls of the abscission zone and the subtending mesocarp and pedicel have been analysed by light and transmission electron microscopy, by chemical methods and by solid state 13C CP\\/MAS NMR spectroscopy. Results show that these abscission zone cells

Janice Henderson; Heather A. Davies; Stephen J. Heyes; Daphne J. Osborne

2001-01-01

100

Following Solid-Acid-Catalyzed Reactions by MAS NMR Spectroscopy in Liquid Phase -Zeolite-Catalyzed Conversion of Cyclohexanol in Water  

SciTech Connect

The catalytic conversion of cyclohexanol on zeolite HBEA in hot liquid water leads to dehydration as well as alkylation products. A novel micro autoclave suitable for application in MAS NMR at high temperatures and pressures is developed and successfully applied to obtain new insight into the mechanistic pathway leading to an understanding of the reactions under selected experimental conditions.

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

2014-01-07

101

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...

102

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...

103

A 13C CP\\/MAS NMR evaluation of the structural changes in wheat straw subjected to different chemical and biological pulping conditions  

Microsoft Academic Search

Wheat straw pulps prepared by chemical (soda) and biological (enzymatic or fungal) treatments were analyzed by 13C CP\\/MAS NMR spectrometry under quantitative acquisition conditions. The most significant changes reflected in the spectra as a result of soda cooking correspond to: (i) decrease of methoxyl content of the residual lignin (56, 153, 147 and 135 ppm), and (ii) deacetylation of hemicellulose

M. E. Guadalix; G. Almendros; A. T. Martínez; F. J. González-Vila; U. Lankes

1997-01-01

104

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

105

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)

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.

Lim, Ae Ran

2014-06-01

106

A 29Si MAS-NMR study of Cd7[Ge6Si]O21 pyroxmangite  

NASA Astrophysics Data System (ADS)

Synthetic (SiGe)-pyroxenoids are often observed to have superperiods. Whether or not these superperiods grow in connection with Si-Ge ordering is a fundamental question. The size difference between Ge and Si tetrahedra leads to CdGeO3 having the pyroxmangite structure, whereas CdSiO3 has the wollastonite structure. Consequently, considerable strain is expected for a pyroxenoid with a disordered Ge-Si distribution. A 29Si MAS-NMR study of a Cd-pyroxmangite of nominal composition Cd7[Ge6Si]O7 points to considerable Si clustering, probably as GeSiSiSiGe triples corresponding to the wollastonite-like units of the siebener chain. It is proposed that such ordering relieves strain within the tetrahedral chain. Residual strain is also relieved by insertion of an extra pair of GeO4 tetrahedra into the pyroxene-like component of the siebener-chain units, leading to single neuner-chain units which terminate the superperiods. This growth pattern is cyclic. The presence of several types of superperiod may reflect similar energetics for different Ge-Si-ordering patterns within the siebener chains. Ordering of Si-rich unit cells and of unit cells having no Si is proposed as the reason for the occurrence of the superperiods in Cd-pyroxmangite.

Czank, M.; Welch, M. D.; Liu, S.

107

Hydration properties and phosphorous speciation in native, gelatinized and enzymatically modified potato starch analyzed by solid-state MAS NMR.  

PubMed

Hydration of granular, gelatinized and molecularly modified states of potato starch in terms of molecular mobility were analyzed by (13)C and (31)P solid-state MAS NMR. Gelatinization (GEL) tremendously reduced the immobile fraction compared to native (NA) starch granules. This effect was enhanced by enzyme-assisted catalytic branching with branching enzyme (BE) or combined BE and ?-amylase (BB) catalyzed exo-hydrolysis. Carbons of the glycosidic ?-1,6 linkages required high hydration rates before adopting uniform chemical shifts indicating solid-state disorder and poor water accessibility. Comparative analysis of wheat and waxy maize starches demonstrated that starches were similar upon gelatinization independent of botanical origin and that the torsion angles of the glycosidic linkages were averages of the crystalline A and B type structures. In starch suspension phosphorous in immobile regions was only observed in NA starch. Moreover phosphorous was observed in a minor pH-insensitive form and as major phosphate in hydrated GEL and BE starches. PMID:23911477

Larsen, Flemming H; Kasprzak, Miros?aw M; Lærke, Helle N; Knudsen, Knud Erik B; Pedersen, Sven; Jørgensen, Anne S; Blennow, Andreas

2013-09-12

108

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

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.

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

2009-07-01

109

{sup 13}C chemical shift anisotropies for carbonate ions in cement minerals and the use of {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR in studies of Portland cement including limestone additions  

SciTech Connect

{sup 13}C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed {sup 13}C MAS or {sup 13}C({sup 1}H) CP/MAS NMR spectra (9.4 T or 14.1 T) for {sup 13}C in natural abundance. The variation in the {sup 13}C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in {sup 13}C MAS NMR spectra. However, it is shown that by combining {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends {sup 29}Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in {sup 27}Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate. -- Highlights: •{sup 13}C chemical shift anisotropies for inorganic carbonates from {sup 13}C MAS NMR. •Narrow {sup 13}C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR. •Limestone accelerates the hydration for alite in Portland – limestone cements. •Limestone reduces the amount of aluminium incorporated in the C-S-H phase.

Sevelsted, Tine F. [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark)] [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); Herfort, Duncan [Aalborg Portland A/S,Cementir Holding S.p.A., DK-9100 Aalborg (Denmark)] [Aalborg Portland A/S,Cementir Holding S.p.A., DK-9100 Aalborg (Denmark); Skibsted, Jørgen, E-mail: jskib@chem.au.dk [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark)] [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark)

2013-10-15

110

Complexation of lead(II) with O, O ?-dialkyldithiophosphate ligands: 31P and 13C CP\\/MAS NMR and single-crystal X-ray diffraction studies  

Microsoft Academic Search

Polycrystalline lead(II) complexes with O,O?-dipropyl- and O,O?-di-cyclo-hexyldithiophosphate ions were prepared and studied by means of 31P, 31C CP\\/MAS NMR spectroscopy and single-crystal X-ray diffraction. Prepared complexes are characterised by polynuclear structures, in which pairs of dithiophosphate groups asymmetrically link neighbouring lead atoms, forming infinite linear zigzag chains. In spite of the same combined structural function, dithiophosphate ligands in both complexes

Anna-Carin Larsson; Alexander V Ivanov; Oleg N Antzutkin; Andrey V Gerasimenko; Willis Forsling

2004-01-01

111

Comparison between CP\\/MAS 13C-NMR and pyrolysis-GC\\/MS in the structural characterization of humins and humic acids of soil and sediments  

Microsoft Academic Search

The chemical structure of humins (HUs) and humic acids (HAs) of terrestrial and marine environments was investigated by cross-polarization\\u000a magic angle spinning 13C-nuclear magnetic resonance spectroscopy (CP\\/ MAS 13C-NMR) and pyrolysis-gas chromatography\\/mass spectrometry (Py-GC\\/MS). Samples of HUs and HAs were obtained from sediments\\u000a of the Adriatic Sea, the Lagoon of Ravenna (Adriatic Sea) and the Bubano Lake as well as

D. Fabbri; M. Mongardi; L. Montanari; G. C. Galletti; G. Chiavari; R. Scotti

1998-01-01

112

Solid-state NMR structure characterization of a 13CO-Labeled Ir(I) complex with a P,N-donor ligand including ultrafast MAS methods.  

PubMed

The structural characterization of a (13)CO-labeled Ir(I) complex bearing an P,N-donor ligand (1-[2-(diphenylphosphino)ethyl]pyrazole), [Ir(PyP)((13)CO)Cl] is demonstrated using a series of tailored solid-state NMR techniques based on ultrafast (60 kHz) Magic Angle Spinning (MAS), which facilitates correlations with narrow proton line-widths. Our 1D (1)H MAS and 2D (13)C and (31)P CP-MAS NMR spectra provided structural information similar to that obtained using NMR spectroscopy in solution. We employed high-resolution 2D solid-state correlation spectroscopy ((1)H-(13)C HETCOR, (1)H-(31)P correlation) to characterize the networks of dipolar couplings between protons and carbon/phosphorus. (1)H-(1)H SQ-SQ correlation spectra showed the dipolar contacts between all protons in a similar fashion to its solution counterpart, NOESY. The use of the (1)H single quantum/double quantum experiments made it possible to observe the dipolar-coupling contacts between immediately adjacent protons. Additionally, internuclear (13)CO-(31)P distance measurements were performed using REDOR. The combination of all of these techniques made it possible to obtain comprehensive structural information on the molecule [Ir(PyP)((13)CO)Cl] in the solid state, which is in excellent agreement with the single crystal X-ray structure of the complex, and demonstrates the enormous value of ultrafast MAS NMR techniques for a broad range of future applications. PMID:24992359

Tregubov, Andrey A; Linser, Rasmus; Vuong, Khuong Q; Rawal, Aditiya; Gehman, John D; Messerle, Barbara A

2014-07-21

113

Solid state CP\\/MAS 13C NMR of the insoluble organic matter of the Orgueil and Murchison meteorites: quantitative study  

Microsoft Academic Search

Solid state CP\\/MAS 13C nuclear magnetic resonance (NMR) study of the insoluble organic fraction isolated by HF\\/HCl treatment under an inert atmosphere from the Orgueil and Murchison carbonaceous meteorites is reported. Based on these spectra, eight different types of carbons (aro- and ali-linked CH3, CH2, aliphatic C-linked to heteroelements, protonated and non-protonated aromatic C, carboxyls and carbonyls) were identified, their

Alain Gardinier; Sylvie Derenne; François Robert; Françoise Behar; Claude Largeau; Jocelyne Maquet

2000-01-01

114

Characterization of soil organic matter in different particle-size fractions in humid subalpine soils by CP\\/MAS 13C NMR  

Microsoft Academic Search

The particle-size separation of subalpine soils was used for delineating the different functional C pools of soil organic matter (SOM) by solid-state cross-polarization\\/magic-angle-spinning (CP\\/MAS) 13C NMR spectroscopy. The soils collected from hemlock forest and dwarfed bamboo grassland along the slope positions at elevations from 2550 to 3200 m in central Taiwan, received high precipitation (>3000 mm). The obtained data show

Jenn-Shing Chen; Chih-Yu Chiu

2003-01-01

115

1H, 13C MAS NMR and DFT GIAO study of quercetin and its complex with Al(III) in solid state.  

PubMed

Quercetin (Q) as a pentahydroxy flavonoid, has three possible chelating sites competing in complexation processes. (1)H and (13)C MAS NMR spectra were recorded for solid quercetin and its Al(III) complex (AlQ). (1)H MAS spectrum of quercetin shows a broad resonance at ca. 12 ppm that confirms the existence of intramolecular C5-OH … O=C4 hydrogen bond. Such a signal is absent in the spectrum of AlQ, which is in accordance with other spectroscopic data and the suggested model for the solid-state structure of the complex. DFT GIAO calculations were used to verify the experimental (13)C CPMAS NMR data and to suggest the best model structure for the complex AlQ. The calculated shielding constants for different conformers of isolated quercetin molecules, quercetin trimer as taken from the X-ray data, and different model structures for possible Al(III) complexes were compared with the (13)C CPMAS NMR experimental values. The results demonstrate the importance of intermolecular interactions when dealing with structures in solid state and the successful application of the combined DFT GIAO and (13)C CPMAS NMR approach. All data confirm that the chelating site of Q in the solid complex AlQ involves the deprotonated C5-OH and the C4=O groups at ring C, in contrast to the available studies performed in solution. PMID:22459171

Ahmedova, Anife; Paradowska, Katarzyna; Wawer, Iwona

2012-05-01

116

Identification of lithium-sulfur battery discharge products through 6Li and 33S solid-state MAS and 7Li solution NMR spectroscopy  

NASA Astrophysics Data System (ADS)

6Li and 33S solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy was used to identify the discharge products in lithium-sulfur (Li-S) battery cathodes. Cathodes were stopped at different potentials throughout battery discharge and measured ex-situ to obtain chemical shifts and T2 relaxation rates of the products formed. The chemical shifts in the spectra of both 6Li and 33S NMR demonstrate that long-chain, soluble lithium polysulfide species formed at the beginning of discharge are indistinguishable from each other (similar chemical shifts), while short-chain, insoluble polysulfide species that form at the end of discharge (presumably Li2S2 and Li2S) have a different chemical shift, thus distinguishing them from the soluble long-chain products. T2 relaxation measurements of discharged cathodes were also performed which resulted in two groupings of T2 rates that follow a trend and support the previous conclusions that long-chain polysulfide species are converted to shorter chain species during discharge. Through the complementary techniques of 1-D 6Li and 33S solid-state MAS NMR spectroscopy, solution 7Li and 1H NMR spectroscopy, and T2 relaxation rate measurements, structural information about the discharge products of Li-S batteries is obtained.

Huff, Laura A.; Rapp, Jennifer L.; Baughman, Jessi A.; Rinaldi, Peter L.; Gewirth, Andrew A.

2015-01-01

117

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

SciTech Connect

{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.

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

1998-11-30

118

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

NASA Astrophysics Data System (ADS)

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 TE13 fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE16 second-harmonic mode of the gyrotron) for DNP at 14.1 T (600 MHz 1H 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 1H and double channel HX mode for 284 MHz 1H, with MAS sample temperatures ?85 K. Initial data at 6.7 T and ˜1 W pulsed microwave power are presented with 13C enhancements of 60 for a frozen urea solution (1H-13C CP), 16 for bacteriorhodopsin in purple membrane (1H-13C CP) and 22 for 15N in a frozen glycine solution (1H-15N 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.

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

119

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

NASA Astrophysics Data System (ADS)

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.

Yang, Xiaorong; Müller, Klaus

2011-12-01

120

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

PubMed Central

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

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

2009-01-01

121

Applicability of solid-state 13C CP\\/MAS NMR analysis in Spodosols: chemical removal of magnetic materials  

Microsoft Academic Search

The presence of magnetic species, Fe in particular, decreases the effectiveness of nuclear magnetic resonance (NMR) analysis of soil organic matter (SOM), especially in Spodosols. This study was conducted to evaluate the utility of dithionite, stannous chloride, and hydrofluoric acid (HF) extraction for Fe removal and solid-state 13C NMR spectral enhancement in forested Spodosols. Extraction with 2% HF resulted in

K'o H Dai; Chris E Johnson

1999-01-01

122

Determining hydrogen-bond interactions in spider silk with 1H-13C HETCOR fast MAS solid-state NMR and DFT proton chemical shift calculations.  

PubMed

Two-dimensional (2D) (1)H-(13)C heteronuclear correlation (HETCOR) solid-state NMR spectra collected with fast magic angle spinning (MAS) are used in conjunction with density functional theory (DFT) proton chemical shift calculations to determine the hydrogen-bonding strength for ordered ?-sheet and disordered 310-helical structures in spider dragline silk. The hydrogen-bond strength is determined to be identical for both structures in spider silk with a 1.83-1.84 Å NH···OC hydrogen-bond distance. PMID:23774714

Holland, Gregory P; Mou, Qiushi; Yarger, Jeffery L

2013-07-28

123

Study on potassium iso-propylxanthate and its decomposition products: experimental 13C CP/MAS NMR combined with DFT calculations.  

PubMed

Solid-state (13)C NMR is believed to be a valuable tool for studying adsorption and speciation of xanthates on sulfide mineral surfaces, but to do that, model compounds of possible xanthate species need to be investigated. (13)C NMR chemical shift tensors for molecular fragments of potassium iso-propylxanthate and six of its decomposition products have been determined by combining DFT calculations and (13)C CP/MAS NMR experiments. DFT calculations were performed in NWChem using GIAO method for the NMR shielding tensor calculations. The results of the calculations are in good agreement with experimental data. In the -XCYZ moiety (X, Y, Z = O, S), the more sulfur atoms, the more deshielded the chemical shift becomes and the larger the span of the chemical shift tensor. The ?11 principal value has the largest influence on the span, decreasing when the number of sulfur atoms decreases and the number of oxygen atoms increases. The significant differences in chemical shifts make it possible to distinguish between different species and, hence, in future studies, interpret surface speciation. The tensor parameters can also aid in the interpretation. PMID:21309541

Larsson, Anna-Carin; Öberg, Sven

2011-03-01

124

Effects of added paramagnetic ions on the 13 C CP\\/MAS NMR spectrum of a de-ashed soil  

Microsoft Academic Search

A de-ashed soil was reacted with a series of paramagnetic (Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Pr3+, Eu3+) and non-paramagnetic (Na+, Ca2+, Zn2+) ions. Amendment with non-paramagnetic ions did not effect the NMR properties of the soil organic matter (SOM), whereas a number of NMR properties including signal intensity, broadness and relaxation rate constants (T1?H, T1H, T1C) were effected by the

Ronald J Smernik; J. Malcolm Oades

1999-01-01

125

CP/MAS (13)C NMR study of cellulose and cellulose derivatives. 2. Complete assignment of the (13)C resonance for the ring carbons of cellulose triacetate polymorphs.  

PubMed

Complex ring (13)C resonance lines of the cross-polarization/magic angle spinning (CP/MAS) (13)C NMR spectra of cellulose triacetate (CTA) I and CTA II were completely assigned, for the first time, by (13)C-enriched CTA allomorphs. The (13)C-enriched CTA I was prepared by heterogeneous acetylation of bacterial cellulose which was biosynthesized by Acetobacter xylinum (A. xylinum) ATCC10245 from culture medium containing D-(2-(13)C)-, D-(3-(13)C)-, or D-(5-(13)C)glucose as a carbon source, while CTA II samples were obtained by solution acetylation of the (13)C-enriched bacterial celluloses. From comparison of the spectra of normal CTA prepared from ramie with those of the enriched CTA samples, it was revealed that all carbons composed of CTA I appeared as a singlet, while those of CTA II except for C1 were shown as equal-intensity doublets in the CP/MAS (13)C NMR spectrum. This finding suggests that CTA I is made up of one kind of glucopyranose residue while there are two magnetically inequivalent sites in the unit cell of CTA II in the same population. PMID:12071761

Kono, Hiroyuki; Erata, Tomoki; Takai, Mitsuo

2002-06-26

126

Synthesis, Infra-red, CP/MAS-NMR characterization, structural study and electrical properties of the bis(4-amino-2-chloropyridinium) tetrachlorozincate (II) monohydrate  

NASA Astrophysics Data System (ADS)

Single crystals of the new ionic salt bis(4-amino-2-chloropyridinium) tetrachlorozincate (II) monohydrate, (C5H6N2Cl)2 ZnCl4?H2O, were grown by slow evaporation from aqueous solution at room temperature. The compound was characterized by IR, thermal analysis (TGA-DSC), single crystal X-ray diffraction, CP/MAS-NMR and impedance spectroscopy. The structure (4-amino-2-chloropyridinium)2 ZnCl4·H2O, [(CAP)2ZnCl4·H2O], consists of isolated H2O, isolated [ZnCl4]2- tetrahedral anions and 4-amino-2-chloropyridinium [C5H6N2Cl] + cations, CAP, which are connected together via N-H⋯Cl, N-H⋯O ((N: pyridinium) and (N: amine)), O-H⋯Cl and C-H⋯Cl hydrogen bonds. Cation-cation, offset-face-to-face interactions (?-? stacking) between identical antiparallel CAP (aromatic-aromatic), in which they may be effective in the stabilization of the crystal structure. Solid state CP/MAS-NMR spectra showed five isotropic resonances, 13C, confirming the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for a single crystal, revealed that the conduction in the material was due to a hopping process. This work aims to reveal the thermal properties of a new zinc (II) based organic-inorganic hybrid and the conductivity properties that these compounds exhibit.

Karâa, Najla; Hamdi, Besma; Ben Salah, Abdelhamid; Zouari, Ridha

2013-10-01

127

New opportunities in acquisition and analysis of natural abundance complex solid-state 33S MAS NMR spectra: (CH3NH3)2WS4.  

PubMed

Population transfer from the satellite transitions to the central transition in solid-state (33)S MAS NMR, employing WURST inversion pulses, has led to detection of the most complex (33)S MAS NMR spectrum observed so far. The spectrum is that of (CH(3)NH(3))(2)WS(4) and consists of three sets of overlapping resonances for the three non-equivalent S atoms, in accord with its crystal structure. It has been fully analyzed in terms of three sets of (33)S quadrupole coupling and anisotropic/isotropic chemical shift parameters along with their corresponding set of three Euler angles describing the relative orientation of the tensors for these two interactions. The three sets of spectral parameters have been assigned to the three different sulfur sites in (CH(3)NH(3))(2)WS(4) by relating the changes observed for the spectral parameters to the changes in crystal structures in a comparison with the corresponding data for the isostructural (NH(4))(2)WS(4) analog. PMID:19652832

Jakobsen, Hans J; Bildsøe, Henrik; Skibsted, Jørgen; Brorson, Michael; Srinivasan, Bikshandarkoil R; Näther, Christian; Bensch, Wolfgang

2009-08-28

128

A new aluminium-hydrate species in hydrated Portland cements characterized by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy  

SciTech Connect

Recent {sup 27}Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift {delta} {sub iso} = 5.0 ppm and the quadrupole product parameter P {sub Q} = 1.2 MHz, has been characterized in detail by {sup 27}Al MAS and {sup 27}Al{l_brace}{sup 1}H{r_brace} CP/MAS NMR for different hydrated white Portland cements and C-S-H phases. These experiments demonstrate that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH){sub 6} {sup 3-} or O {sub x}Al(OH){sub 6-x} {sup (3+x)-} units. The formation of the new aluminate hydrate is related to the formation of C-S-H at ambient temperatures, however, it decomposes by thermal treatment at temperatures of 70-90 {sup o}C. From the experiments in this work it is proposed that the new aluminate hydrate is either an amorphous/disordered aluminate hydroxide or a calcium aluminate hydrate, produced as a separate phase or as a nanostructured surface precipitate on the C-S-H phase. Finally, the possibilities of Al{sup 3+} for Ca{sup 2+} substitution in the principal layers and interlayers of the C-S-H structure are discussed.

Andersen, Morten Daugaard [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark); Jakobsen, Hans J. [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark); Skibsted, Jorgen [Instrument Centre for Solid-State NMR Spectroscopy, Department of Chemistry, University of Aarhus, DK-8000 Aarhus C (Denmark)]. E-mail: jskib@chem.au.dk

2006-01-15

129

Investigation of the Use of Solid State Cp/mas NMR for Characterization of Thermoplastic Polyamides and Unique Thermally Curable Polyamides Containing the Cyclobutene Moiety.  

NASA Astrophysics Data System (ADS)

A series of model diamides was synthesized from mono- and disubstituted amines with the diacid chloride of cyclobutene-1,2-dicarboxylic acid. Relative rates of thermolysis (by DSC) were dependent on the number and type of substituents. Thermolysis products were Diels-Alder dimers and spontaneously formed polymers. Thermal imidization of cycloadducts was possible in some cases with concomitant oxidation to N, N^'-disubstituted aromatic bisimides. Polyamides were prepared from cyclobutene-1,2 -dicarboxylic acid using low temperature condensation reaction conditions. The unusual solubility characteristics of the diacid as well as the instability of the diacid chloride severely limited formation of high molecular weight polymers. Secondary monomers were synthesized in order to take advantage of the more predictable reactivity of the aromatic carboxyl group. Secondary monomers were polymerized with diamine comonomers using low temperature condensation methods. Solid state ^{13}C CP/MAS NMR confirmed the polymer structure. The thermalized product was found to be insoluble, although swellable, in polar aprotic solvents. Solid state ^{13 }C NMR spectra of the thermal products confirmed crosslinking by intermolecular Diels-Alder cycloaddition. Several important aliphatic polyamides were characterized using high resolution techniques with an emphasis on the ^{15}N nucleus. Chemical shifts from ^{15}N CP/MAS were found to correlate with the alpha and gamma crystal forms found in aliphatic polyamides. This chemical shift difference is rationalized as a conformationally dependent interaction of the amide nitrogen with its substituents. Evidence is presented from molecular orbital calculations which support this theory. Nylon 6 and nylon 11 were synthesized with 20% and 99% ^{15}N enrichment, respectively. ^{15}N CP/MAS of the enriched nylon 6 showed the amorphous region of the polymer for the first time. ^{15 }N relaxation times (T_1, T_1_rho) confirmed the assignment of the crystalline and amorphous regions. The two component decay of the amorphous peak is thought to result from a liquid-like amorphous region and a glassy, noncrystalline "interphase" region. ^{15 }N CP/MAS of nylon 11 was used to observe the delta and delta^ ' crystal forms found in that polymer. Chemical shift anisotropy (CSA) spectra were obtained on the ^{15}N-enriched polyamides. At temperatures above T_{ rm g}, but below the polymer melting point, a narrow peak was observed in the CSA spectra of both polymers corresponding to the mobile amorphous component. Addition of plasticizer (caprolactam) to nylon 6 contributed to this mobility resulting in further narrowing of the amorphous peak.

Powell, Douglas Graham

1990-08-01

130

Rotor-encoded heteronuclear MQ MAS NMR spectroscopy of half-integer quadrupolar and spin I=1/2 nuclei.  

PubMed

A new two-dimensional heteronuclear multiple-quantum magic-angle spinning (MQ MAS) experiment is presented which combines high resolution for the half-integer quadrupolar nucleus with information about the dipolar coupling between the quadrupolar nucleus and a spin I=1/2 nucleus. Homonuclear MQ coherence is initially created for the half-integer quadrupolar nucleus by a single pulse as in a standard MQ MAS experiment. REDOR recoupling of the heteronuclear dipolar coupling then allows the creation of a heteronuclear multiple-quantum coherence comprising multiple- and single-quantum coherence of the quadrupolar and spin I=1/2 nucleus, respectively, which evolves during t1. Provided that the t1 increment is not rotor synchronized, rotor-encoded spinning-sideband patterns are observed in the indirect dimension. Simulated spectra for an isolated IS spin pair show that these patterns depend on the recoupling time, the magnitude of the dipolar coupling, the quadrupolar parameters, as well as the relative orientation of the quadrupolar and dipolar principal axes systems. Spectra are presented for Na2HPO4, with the heteronuclear 23Na-1HMQ MAS experiments beginning with the excitation of 23Na (spin I=3/2) three-quantum coherence. Coherence counting experiments demonstrate that four- and two-quantum coherences evolve during t1. The heteronuclear spinning-sideband patterns observed for the three-spin H-Na-H system associated with the Na(2) site are analyzed. For an IS2 system, simulated spectra show that, considering the free parameters, the spinning-sideband patterns are particularly sensitive to only, first, the angle between the two IS internuclear vectors and, second, the two heteronuclear dipolar couplings. It is demonstrated that the proton localization around the Na(2) site according to the literature crystal structure of Na2HPO4 is erroneous. Instead, the experimental data is consistent with two alternative different structural arrangements, whereby either there is a deviation of 10 degrees from linearity for the case of two identical Na-H distances, or there is a linear arrangement, but the two Na-H distances are different. Furthermore, the question of the origin of spinning-sidebands in the (homonuclear) MQ MAS experiment is revisited. It is shown that the asymmetric experimental MQ sideband pattern observed for the low-C(Q) Na(2) site in Na(2)HPO4 can only be explained by considering the 23Na chemical shift anisotropy. PMID:11820831

Lupulescu, Adonis; Brown, Steven P; Spiess, Hans Wolfgang

2002-01-01

131

13C CP\\/MAS NMR study of the interaction of bile acids with barley ?- d-glucan  

Microsoft Academic Search

Dietary ?-d-glucan is associated with low blood cholesterol levels due to increased excretion of bile acids, but there is little evidence for the mechanism involved in enhanced bile acid clearance. Solid-state 13C NMR spectroscopy has now been used to investigate the possibility of specific binding between a representative bile acid salt, glycocholic acid, and barley ?-glucan. From the similarity in

Richard K. Bowles; Keith R. Morgan; Richard H. Furneaux; Graeme D. Coles

1996-01-01

132

Efficient polarization transfer between spin-1/2 and ¹?N nuclei in solid-state MAS NMR spectroscopy.  

PubMed

Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as (14)N in solid-state NMR is severely challenged by the typical presence of large quadrupole coupling interactions. This has effectively prevented the use of the abundant (14)N spin as a probe to structural information and its use as an element in multi-dimensional solid-state NMR correlation experiments for assignment and structural characterization. In turn, this has been a contributing factor to the extensive use of isotope labeling in biological solid-state NMR, where (14)N is replaced with (15)N. The alternative strategy of using the abundant (14)N spins calls for methods enabling efficient polarization transfer between (14)N and its binding partners. This work demonstrates that the recently introduced (RESPIRATION)CP transfer method can be optimized to achieve efficient (1)H ?(14)N polarization transfer under magic angle spinning conditions. The method is demonstrated numerically and experimentally on powder samples of NH4NO3 and L-alanine. PMID:24880881

Basse, Kristoffer; Jain, Sheetal Kumar; Bakharev, Oleg; Nielsen, Niels Chr

2014-07-01

133

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

PubMed Central

A model membrane system composed of egg sphingomyelin (SM), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol was studied with static and magic angle spinning 31P NMR spectroscopy. This model membrane system is of significant biological relevance since it is known to form lipid rafts. 31P NMR under magic angle spinning conditions resolves the SM and DOPC headgroup resonances allowing for extraction of the 31P NMR parameters for the individual lipid components. The isotropic chemical shift, chemical shift anisotropy, and asymmetry parameter can be extracted from the spinning side band manifold of the individual components that form liquid-ordered and liquid-disordered domains. The magnitude of the 31P chemical shift anisotropy and the line width is used to determine headgroup mobility and monitor the gel-to-gel and gel-to-liquid crystalline phase transitions of SM as a function of temperature in these mixtures. Spin-spin relaxation measurements are in agreement with the line width results, reflecting mobility differences and some heterogeneities. It will be shown that the presence of DOPC and/or cholesterol greatly impacts the headgroup mobility of SM both above and below the liquid crystalline phase transition temperature, whereas DOPC displays only minor variations in these lipid mixtures. PMID:16533851

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

2006-01-01

134

Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy  

PubMed Central

Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H-15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600 MHz under 50 kHz magic angle spinning using ~ 0.5 mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H-15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra. PMID:24225529

Park, Sang Ho; Yang, Chen; Opella, Stanley J.; Mueller, Leonard J.

2013-01-01

135

Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H-15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600 MHz under 50 kHz magic angle spinning using ?0.5 mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H-15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra.

Park, Sang Ho; Yang, Chen; Opella, Stanley J.; Mueller, Leonard J.

2013-12-01

136

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

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.

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

137

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)

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.

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

2015-01-01

138

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

PubMed

There is considerable interest in the measurement of proton ((1)H) 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 (1)H/(1)H dipolar interaction makes it difficult to determine small size (1)H CSAs from the homogeneously broadened NMR spectra. Previously reported pulse sequences for (1)H 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 (1)H CSA in the indirect dimension of a 2D (1)H/(1)H 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 (1)H/(1)H correlation spectrum without decoupling (1)H/(1)H dipolar couplings but by using ultrafast MAS rates up to 70kHz. We successfully demonstrate that with a reasonable RF field requirement (<200kHz) 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 (1)H 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. PMID:25497846

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

2015-01-01

139

Solid state 31P MAS NMR spectroscopy and conductivity measurements on NbOPO4 and H3PO4 composite materials  

NASA Astrophysics Data System (ADS)

A systematic study of composite powders of niobium oxide phosphate (NbOPO4) and phosphoric acid (H3PO4) has been performed in order to characterize the material's ability to perform as an electrolyte material in medium temperature fuel cells and electrolyzers. Powders of H3PO4 contents between 13.1 and 74.2 M% were produced and characterized with powder X-ray diffraction, 31P MAS NMR and impedance spectroscopy. NMR revealed that a significant degree of dehydration and vaporization of H3PO4 takes place above 200 °C, and increases with temperature. At 500 °C the NbOPO4 and H3PO4 has reacted to form niobium pyrophosphate (Nb2P4O15). Impedance spectroscopy showed an increase in conductivity with increasing acid concentration, whereas the conductivity decreased slightly with increasing temperature. The highest conductivity measured was 2.5·10-3 S/cm for a sample containing 74.2 M% of H3PO4. Lastly, it was shown that NbOPO4 has no significant conductivity of its own.

Risskov Sørensen, Daniel; Nielsen, Ulla Gro; Skou, Eivind M.

2014-11-01

140

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

NASA Astrophysics Data System (ADS)

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.

Lim, Ae Ran; Lee, Kwang-Sei

2013-07-01

141

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

142

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

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.

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

2013-01-01

143

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

NASA Astrophysics Data System (ADS)

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

Dou, S.

2009-04-01

144

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

SciTech Connect

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.

Ziegeweid, M.A.

1995-11-29

145

Dynamic properties of P4O6S and P4O7:31P spin-echo and 31P MAS-NMR investigations.  

PubMed

The rotational dynamics of P4O6S and P4O7 in the solid state were studied by means of 31P NMR spectra of spinning and static powder samples in the temperature range of 153-295 K and 295-388 K, respectively. All spectra were simulated to confirm the type of the motion and to extract the time scales as a function of the temperature. Good agreement between experimental and theoretical data was obtained on the basis of a three-site jump model. For P4O6S, the activation energy and the pre-exponential factor derived from the lineshape simulations amount to 51(2) kJ/mol and 6(3) x 10(15) s(-1). For P4O7, the spectral analysis yields an activation energy of 67(1) kJ/mol and a pre-exponential factor of 6(2) x 10(14) s(-1). The dynamic behavior was checked independently by lineshape analyses under both MAS and static conditions. Activation energies are consistent within the errors for the lineshape analyses. Additionally, we have analyzed spin-lattice relaxation measurements, which show the correct trends for the activation energies. PMID:10499667

Hoffbauer, W; Wefing, S; Klösters, G; Frick, F; Jansen, M

1999-09-01

146

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

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

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

2013-01-01

147

Aggregation of [Au(CN)4]- anions: examination by crystallography and 15N CP-MAS NMR and the structural factors influencing intermolecular Au···N interactions.  

PubMed

To investigate the factors influencing the formation of intermolecular Au···NC interactions between [Au(CN)(4)](-) units, a series of [cation](n+)[Au(CN)(4)](n) double salts was synthesized, structurally characterized and probed by IR and (15)N{(1)H} CP-MAS NMR spectroscopy. Thus, [(n)Bu(4)N][Au(CN)(4)], [AsPh(4)][Au(CN)(4)], [N(PPh(3))(2)][Au(CN)(4)], [Co(1,10-phenanthroline)(3)][Au(CN)(4)](2), and [Mn(2,2';6',2''-terpyridine)(2)][Au(CN)(4)](2) show [Au(CN)(4)](-) anions that are well-separated from one another; no Au-Au or Au···NC interactions are present. trans-[Co(1,2-diaminoethane)(2)Cl(2)][Au(CN)(4)] forms a supramolecular structure, where trans-[Co(en)(2)Cl(2)](+) and [Au(CN)(4)](-) ions are found in separate layers connected by Au-CN···H-N hydrogen-bonding; weak Au···NC coordinate bonds complete octahedral Au(III) centers, and support a 2-D (4,4) network motif of [Au(CN)(4)](-)-units. A similar structure-type is formed by [Co(NH(3))(6)][Au(CN)(4)](3)·(H(2)O)(4). In [Ni(1,2-diaminoethane)(3)][Au(CN)(4)](2), intermolecular Au···NC interactions facilitate formation of 1-D chains of [Au(CN)(4)](-) anions in the supramolecular structure, which are separated from one another by [Ni(en)(3)](2+) cations. In [1,4-diazabicyclo[2.2.2]octane-H][Au(CN)(4)], the monoprotonated amine cation forms a hydrogen-bond to the [Au(CN)(4)](-) unit on one side, while coordinating to the axial sites of the gold(III) center through the unprotonated amine on the other, thereby generating a 2-D (4,4) net of cations and anions; an additional, uncoordinated [Au(CN)(4)](-)-unit lies in the central space of each grid. This body of structural data indicates that cations with hydrogen-bonding groups can induce intermolecular Au···NC interactions, while the cationic charge, shape, size, and aromaticity have little effect. While the ?(CN) values are poor indicators of the presence or absence of N-cyano bridging between [Au(CN)(4)](-)-units (partly because of the very low intensity of the observed bands), (15)N{(1)H} CP-MAS NMR reveals well-defined, ordered cyanide groups in the six diamagnetic compounds with chemical shifts between 250 and 275 ppm; the resonances between 260 and 275 ppm can be assigned to C-bound terminal ligands, while those subject to CN···H-N bonding resonate lower, around 250-257 ppm. The (15)N chemical shift also correlates with the intermolecular Au···N distances: the shortest Au-N distances also shift the (15)N peak to lower frequency. This provides a real, spectroscopically measurable electronic effect associated with the crystallographic observation of intermolecular Au···NC interactions, thereby lending support for their viability. PMID:21268652

Geisheimer, Andrew R; Wren, John E C; Michaelis, Vladimir K; Kobayashi, Masayuki; Sakai, Ken; Kroeker, Scott; Leznoff, Daniel B

2011-02-21

148

{sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange  

SciTech Connect

The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

Arevalo-Hidalgo, Ana G. [Department of Chemical Engineering, University of Puerto Rico-Mayagueez Campus, Mayagueez, PR 00681-9000 (Puerto Rico); Dugar, Sneha; Fu, Riqiang [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Hernandez-Maldonado, Arturo J., E-mail: arturoj.hernandez@upr.edu [Department of Chemical Engineering, University of Puerto Rico-Mayagueez Campus, Mayagueez, PR 00681-9000 (Puerto Rico)

2012-07-15

149

Rotation isomers of bis(diethyldithiocarbamato)zinc(II) adduct with pyridine, Zn(EDtc) 2·Py: ESR, 13C and 15N CP\\/MAS NMR and single-crystal X-ray diffraction studies  

Microsoft Academic Search

The adduct of bis(diethyldithiocarbamato)zinc(II) with pyridine, Zn(EDtc)2·Py, was prepared and studied by means of ESR (63Cu2+ and 65Cu2+ were used as spin labels), solid-state natural abundance 13C and 15N CP\\/MAS NMR spectroscopy and single-crystal X-ray diffraction data analysis. Two rotation isomers of the adduct were unambiguously determined by these three independent methods. It was found that these two isomers have

Alexander V. Ivanov; Valentina I. Mitrofanova; Mikael Kritikos; Oleg N. Antzutkin

1999-01-01

150

Structural characterization of phosphorus-based networks and clusters: 31P MAS NMR spectroscopy and magnetic shielding calculations on Hittorf's phosphorus.  

PubMed

The (31)P MAS NMR spectrum of Hittorf's phosphorus has been measured and assigned to the 21 crystallographically distinct phosphorus atoms based on two-dimensional dipolar correlation spectroscopies. Application of such 2D techniques to phosphorus-based networks is particularly challenging owing to the wide chemical shift dispersions, rapid irreversible decay of transverse magnetization, and extremely slow spin-lattice relaxation in these systems. Nevertheless, a complete assignment was possible by using the combination of correlated spectroscopy (COSY) and radiofrequency-driven dipolar recoupling (RFDR). The assignment is supported further by DFT-based ab initio chemical shift calculations using a cluster-model approach, which gives good agreement between experimental and calculated chemical shift values. The (31)P chemical shifts appear to be strongly correlated with the average P-P bond lengths within the P(P(1/3))(3) coordination environments, whereas no clear dependence on average P-P-P bond angles can be detected. Calculations of localized Kohn-Sham orbitals reveal that this bond-length dependence is reflected in energy variations in the corresponding localized p-p-? orbitals influencing the paramagnetic deshielding contribution in Ramsey's equation. In contrast, the contributions of the lone pairs to shielding differences are small and/or do not vary in a systematic manner for the different crystallographically distinct phosphorus sites. The combined spectroscopic and quantum chemical approach applied here and the increased theoretical understanding of (31)P chemical shifts will facilitate the structural elucidation of other phosphorus-based clusters and networks. PMID:21671290

Wiegand, Thomas; Eckert, Hellmut; Grimme, Stefan; Hoppe, Diana; Ruck, Michael

2011-07-25

151

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

PubMed

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 SiO2P2O5K2OCaOMgO 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. POP, SiOSi, and SiOP, and the following formation of connections such as Mo[MoO4]OSi and/or Mo[MoO4]OP. In summary, it is concluded that the increase of MoO3 content (up to 4.4 mol.%) in the structure of glasses of SiO2P2O5K2OMgOCaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation. PMID:24759778

Szumera, M

2014-09-15

152

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

NASA Astrophysics Data System (ADS)

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.

Szumera, Magdalena

2014-09-01

153

Pseudo-symmetry, rotation- and inversion-twinning of a structure with dinuclear and trinuclear Cd complexes. CP-MAS-NMR and IR spectroscopies characterisation  

NASA Astrophysics Data System (ADS)

The structure of the complex [C18H30Cd3Cl6N18S12·2(C18H30Cd2Cl3N18S12)·CdCl4], or [L6Cd3Cl6·2(L6Cd2Cl3)·CdCl4], with L being 2-amino-5-(methylthio)-1,3,4-thiadiazole, C3H5N3S2, crystallizes in the trigonal polar space group R3. The crystal packing features three chemically distinct cadmium complex species with eight crystallographically independent Cd(II) ions distributed over two types of L ligand complexes with two and three Cd(II) centers, respectively, and a tetrachlorocadmate(II) ion. The coordination environment of the cadmium ions in the dinuclear and trinuclear complexes is a distorted octahedron. The tetrachlorocadmate(II) is disordered around a crystallographic threefold rotation axis, which is, in turn, inducing disorder onto the two methyl-thio groups in closest proximity to a CdCl4 anion. The crystal under investigation was found to be twinned by rotational and inversion merohedry. In the higher symmetry setting, the trinuclear complex would feature exact inversion symmetry, and the two binuclear cationic complexes would be inversion counterparts of each other. The R3bar symmetry is broken by a mismatch of less than 1 Å between one pair of ligands L between the dinuclear cations, which feature slightly different rotational angles around the Cd ion in the otherwise symmetry equivalent complexes. This compound is also investigated by FT-IR and solid-state 13CCP-MAS NMR spectroscopies.

Soudani, Sarra; Zeller, Matthias; Wenger, Emmanuel; Jelsch, Christian; Lefebvre, Frédéric; Nasr, Cherif Ben

2014-10-01

154

Structure of Framework Aluminum Lewis Sites and Perturbed Aluminum Atoms in Zeolites as Determined by (27) Al{(1) H} REDOR (3Q) MAS NMR Spectroscopy and DFT/Molecular Mechanics.  

PubMed

Zeolites are highly important heterogeneous catalysts. Besides Brønsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors-"perturbed" AlFR atoms in hydrated zeolites-were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3 AlOH groups and are characterized by a broad (27) Al NMR resonance (?i =59-62 ppm, CQ =5 MHz, and ?=0.3-0.4) with a shoulder at 40 ppm in the (27) Al MAS NMR spectrum. Dehydroxylation of (SiO)3 AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3 Al Lewis sites exhibit an extremely broad (27) Al NMR resonance (?i ?67 ppm, CQ ?20 MHz, and ??0.1). PMID:25393612

Brus, Ji?í; Kobera, Libor; Schoefberger, Wolfgang; Urbanová, Martina; Klein, Petr; Sazama, Petr; Tabor, Edyta; Sklenak, Stepan; Fishchuk, Anna V; D?de?ek, Ji?í

2014-11-13

155

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

NASA Astrophysics Data System (ADS)

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.

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

2001-07-01

156

2H-13C HETCOR MAS NMR for indirect detection of 2H quadrupole patterns and spin-lattice relaxation rates  

NASA Astrophysics Data System (ADS)

Two-dimensional (2D) cross-polarization magic angle spinning (CP-MAS) 2H-13C heteronuclear correlation (HETCOR) experiments were utilized to indirectly detect site-specific deuterium MAS powder patterns. The 2H-13C cross-polarization efficiency is orientation-dependent and non-uniform for all crystallites. This leads to difficulty in extracting the correct 2H MAS quadrupole powder patterns. In order to obtain accurate deuterium line shapes, 13C spin lock rf field, spin lock rf ramp and CP contact time were carefully calibrated with the assistance of theoretical simulations. The extracted quadrupole patterns for U-[2H/13C/15N]-alanine indicate that the methyl deuterium undergoes classic, three-site jumping in the fast motion regime (10-8-10-12 s) and the methine deuterium has a rigid deuterium powder pattern. For U-[2H/13C/15N]-phenylalanine, indirectly detected deuterium line shapes illustrate that the aromatic ring undergoes 180° flips in the fast motion regime while 2H? and 2H? are completely rigid. The experimental deuterium line shapes for U-[2H/13C/15N]-proline reflect that 2H?, 2H? and 2H? are subjected to fast, two-site reorientations at an angle of (15 ± 5)°, (30 ± 5)° and (25 ± 10)° respectively. In addition, an approach that combines a composite inversion pulse with 2H-13C CP-MAS is applied to measure 2H spin-lattice relaxation times in a site-specific, 13C-detected fashion.

Shi, Xiangyan; Yarger, Jeffery L.; Holland, Gregory P.

2013-01-01

157

13C and 15N—Chemical Shift Anisotropy of Ampicillin and Penicillin-V Studied by 2D-PASS and CP\\/MAS NMR  

Microsoft Academic Search

The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP\\/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We

Oleg N. Antzutkin; Young K. Lee; Malcolm H. Levitt

1998-01-01

158

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

Microsoft Academic Search

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 ¹N via the quadrupolar interaction.

Ziegeweid

1995-01-01

159

1H NMR Relaxation in Urea  

E-print Network

Duer. Solid state 13 C CP MAS NMR study of molecular motionsKey Words: NMR; 1 H NMR; 13 C CP/MAS; 15 N CP/MAS; spin-NMR techniques are used to study such systems, the standard cross- polarization/magic angle spinning (CP/

Taylor, Robert E; Bacher, Alfred D; Dybowski, C.

2007-01-01

160

?-NMR  

NASA Astrophysics Data System (ADS)

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

Morris, Gerald D.

2014-01-01

161

Demineralization of marine and freshwater sediments for CP/MAS 13  

E-print Network

Demineralization of marine and freshwater sediments for CP/MAS 13 C NMR analysis Yves Ge´ linas a: Demineralization; Sedimentary organic matter; Sediment; CP/MAS 13 C NMR 1. Introduction OM buried in continental@ocean.washington.edu (Y. Ge´ linas). #12;Solid-state CP/MAS 13 C NMR is capable of compre- hensively characterizing

Long, Bernard

162

13C and 15N—Chemical Shift Anisotropy of Ampicillin and Penicillin-V Studied by 2D-PASS and CP/MAS NMR  

NASA Astrophysics Data System (ADS)

The principal values of the chemical shift tensors of all 13C and 15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensional phase adjusted spinning sideband (2D-PASS) and conventional CP/MAS experiments. The 13C and 15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl 13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the 13C and 15N sites and the ?-lactam ring conformation.

Antzutkin, Oleg N.; Lee, Young K.; Levitt, Malcolm H.

1998-11-01

163

Polycrystalline and surface O, O?-dialkyldithiophosphate zinc(II) complexes: preparation, 31P CP\\/MAS NMR and single-crystal X-ray diffraction studies  

Microsoft Academic Search

Dithiophosphate zinc(II) complexes with eight different O,O?-dialkyldithiophosphate ligands have been prepared in solid\\/liquid states and as surface complexes on a synthetic sphalerite, and studied by means of 31P NMR spectroscopy. All 31P resonances, corresponding to dithiophosphate ligands with different structural functions (i.e. terminal chelating or bridging between two metal atoms in bi- and tetranuclear complexes), have been assigned on the

Alexander V. Ivanov; Oleg N. Antzutkin; Anna-Carin Larsson; Mikael Kritikos; Willis Forsling

2001-01-01

164

Very fast MAS and MQMAS NMR studies of the spectroscopically challenging minerals kyanite and andalusite on 400, 500, and 800 MHz spectrometers  

Microsoft Academic Search

The well-characterized minerals kyanite and andalusite have long presented great challenges in using solid state 27Al NMR to determine the isotropic chemical shift ?CS, quadrupole coupling constant e2qQ\\/h, and asymmetry parameter ? for each of the inequivalent aluminum sites in these minerals. Indeed, these minerals have frequently been used to test advances in instrumentation. Recent advances in magnet technology (up

Lawrence B Alemany; Stefan Steuernagel; Jean-Paul Amoureux; Rhonda L Callender; Andrew R Barron

1999-01-01

165

Solid state structural analysis of new pentamidine analogs designed as chemotherapeutics that target DNA by X-ray diffraction and 13C, 15N CP/MAS NMR methods  

NASA Astrophysics Data System (ADS)

The paper presents the solid-state analysis of the crystalline form of 1,5- bis[(4-cyanophenyl)- N-methylamino]pentane ( 1) and polycrystalline powder sample of 1,5- bis[(4-amidinophenyl)- N-methylamino]pentane dihydrochloride ( 2). The methods used are X-ray diffraction technique and 13C, 15N CP/MAS NMR spectroscopy in an attempt to detect the effects of possible polymorphism. Both methods indicate that only single conformers exist in the solid-state for 1 and 2. 1,5- Bis[(4-cyanophenyl)- N-methylamino]pentane 1, crystallizes in the orthorhombic space group P2 12 12. The asymmetric unit contains one half of the ordered molecule. Only weak intermolecular interactions were found in solid-state, in which methyl groups are engaged.

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

2010-12-01

166

Hyperfine fields at the Li site in LiFePO(4)-type olivine materials for lithium rechargeable batteries: a (7)Li MAS NMR and SQUID study.  

PubMed

The (7)Li NMR isotropic shift for olivine LiMPO(4) (M = Fe, Mn, Co, Ni) is assigned to hyperfine coupling between the (7)Li nucleus and the transition metal unpaired electrons on the basis of the Curie-Weiss temperature dependence of the shift. The hyperfine shift arises from a linear combination of Li-O-M through-bond interactions wherein the unpaired A' electrons contribute a negative shift and the unpaired A' ' electrons contribute a positive shift. The hyperfine coupling constant is determined for each composition. PMID:11942811

Tucker, Michael C; Doeff, Marca M; Richardson, Thomas J; Fiñones, Rita; Cairns, Elton J; Reimer, Jeffrey A

2002-04-17

167

Indirectly detected through-bond chemical shift correlation NMR spectroscopy in solids under fast MAS: Studies of organic-inorganic hybrid materials  

NASA Astrophysics Data System (ADS)

Indirectly detected, through-bond NMR correlation spectra between 13C and 1H nuclei are reported for the first time in solid state. The capabilities of the new method are demonstrated using naturally abundant organic-inorganic mesoporous hybrid materials. The time performance is significantly better, almost by a factor of 10, than in the corresponding 13C detected experiment. The proposed scheme represents a new analytical tool for studying other solid-state systems and the basis for the development of more advanced 2D and 3D correlation methods.

Mao, Kanmi; Wiench, Jerzy W.; Lin, Victor S.-Y.; Pruski, Marek

2009-01-01

168

Indirectly detected through-bond chemical shift correlation NMR spectroscopy in solids under fast MAS: Studies of organic-inorganic hybrid materials  

SciTech Connect

Indirectly detected, through-bond NMR correlation spectra between {sup 13}C and {sup 1}H nuclei are reported for the first time in solid state. The capabilities of the new method are demonstrated using naturally abundant organic-inorganic mesoporous hybrid materials. The time performance is significantly better, almost by a factor of 10, than in the corresponding {sup 13}C detected experiment. The proposed scheme represents a new analytical tool for studying other solid-state systems and the basis for the development of more advanced 2D and 3D correlation methods.

Mao, Kanmi; Wiench, Jerzy; Lin, Victor S.-Y.; Pruski, Marek

2008-10-12

169

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

PubMed

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

Pajchel, L; Nykiel, P; Kolodziejski, W

2011-12-01

170

Synthesis, CP-MAS NMR Characterization, and Antibacterial Activities of Glycine and Histidine Complexes of Cd(SeCN)2 and Hg(SeCN)2  

PubMed Central

The synthesis and characterization of cadmium and mercury complexes of selenocyanate of the type [(L)M(SeCN)2] are described, where L is L-Histidine (His) or L-Glycine (Gly) and M is Cd2+ or Hg2+. These complexes are obtained by the reaction of 1 equivalent of respective amino acids with metal diselenocyanate precursor in a mixture of solvents (methanol?:?water = 1?:?1). These synthesized compounds are characterized by analytical and various spectroscopic techniques such as elemental analysis (EA), IR, H,1 and C13 NMR in solution and in the solid state for C13 and N15. The in vitro antibacterial activities of these complexes have been investigated with standard type cultures of Escherichia coli (MTCC 443), Klebsiella pneumoniae (MTCC 109), Pseudomonas aeruginosa (MTCC 1688), Salmonella typhi (MTCC 733), and Staphylococcus aureus (MTCC 737). PMID:23533372

Al-Maythalony, Bassem A.; Monim-ul-Mehboob, M.; Wazeer, Mohammed I. M.; Isab, Anvarhusein A.; Shaikh, M. Nasiruzzaman; Altuwaijri, Saleh

2013-01-01

171

Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR.  

PubMed

The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped (13)C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly (13)C, (15)N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700MHz and 900MHz (1)H resonance frequencies, respectively. For the single (13)C? of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three (13)C? signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment. PMID:25051542

Wu, Chin H; De Angelis, Anna A; Opella, Stanley J

2014-09-01

172

Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR  

NASA Astrophysics Data System (ADS)

The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped 13C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly 13C, 15N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700 MHz and 900 MHz 1H resonance frequencies, respectively. For the single 13C? of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three 13C? signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment.

Wu, Chin H.; De Angelis, Anna A.; Opella, Stanley J.

2014-09-01

173

The Amblygonite (LiAlPO{sub 4}F)-Montebrasite (LiAlPO{sub 4}OH) Solid Solution: A Combined powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR study  

SciTech Connect

The amblygonite-montebrasite series of minerals, common constituents of granitic pegmatites and topaz-bearing granites, show complete solid solution with ideal composition LiAlPO{sub 4}(F, OH). These compounds are ideal for studying F {leftrightarrow} OH solid solution in minerals because natural members of the series generally show little deviation from the ideal composition. In this study, we used powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR techniques to study the effect of F {leftrightarrow} OH substitution on the series. Lattice parameters refined from single-crystal neutron diffraction data show increasing b and decreasing a, c, and V with increasing F/(F + OH). The volume is highest for the OH end-member because of the presence of an additional atom (H). The a and c parameters decrease with increasing F/(F + OH) because the O-H vector is close to the a-c plane and the Al-OH/F vectors are approximately parallel to c. Lattice parameters refined from neutron powder diffraction patterns collected at lower T show that thermal contraction increases with F/(F + OH), presumably because the F anion takes up less space than the OH molecule. The results show that the OH/F position is always fully occupied. The H displacement ellipsoid shows little change with occupancy, which obviously corresponds negatively with increasing F/(F + OH). However, the Li displacement ellipsoid becomes extremely large and anisotropic with increasing F fraction. Most of the distortion is associated with the U{sub 3} eigenvalue, which lies between the c and c* directions. U{sub eq} values corresponding to the Li atom show a greater reduction with decreasing temperature than the other atoms. The temperature dependence of Li is the same regardless of F content. Even when extrapolated to absolute zero the Li displacement ellipsoid is very large, which implies a large static disorder.

Groat, Lee A. (University of British Columbia); Chakoumakos, Bryan C. (Oak Ridge National Laboratory); Brouwer, Darren H. (DEPT OF CHEMISTRY); Hoffman, Christina M. (Argonne National Laboratory); Fyfe, Colin A. (8998); Morell, Heiko (University of British Columbia); Schultz, Arthur J. (Argonne National Laboratory)

2003-01-01

174

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

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

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

2002-01-01

175

Combined MAS NMR and X-ray powder diffraction structural characterization of hydrofluorocarbon-134 adsorbed on zeolite NaY: Observation of cation migration and strong sorbate-cation interactions  

SciTech Connect

{sup 23}Na MAS NMR and synchrotron X-ray powder diffraction methods have been used to study the binding of hydrofluorocarbon-134 (HFC-134, CF{sub 2}HCF{sub 2}H) in zeolite NaY. A contraction of the volume of the unit cell is observed on gas adsorption, and the interaction of HFC-134 with the extraframework sodium cations is so strong that extraframework sodium cations in the sodalite cages (site I`) migrate into the supercages. These sodium cations are found on positions close to the site III` positions of zeolite NaX. Both ends of the HFC molecules are bound sodium cations, the HFC molecule bridging the site II and III` cations in the supercages. The strong cation-HFC interaction results in a considerable displacement of the sodium site II cation along the [111] direction into the supercage and an increase in the T-O-T bond angle for the three oxygen atoms coordinated to this cation. A decrease in the {sup 23}Na quadrupole coupling constant on HFC adsorption from 4.4 to less than 2.8 MHz, for the sodium cations originally located in the sodalite cages (site I`), is consistent with the sodium cation migrations. 26 refs., 7 figs., 5 tabs.

Grey, C.P.; Poshni, F.I. [SUNY Stony Brook, NY (United States)] [SUNY Stony Brook, NY (United States); Gualtieri, A.F. [Universita di Modena (Italy)] [Universita di Modena (Italy); Norby, P. [SUNY Stony Brook, NY (United States)] [SUNY Stony Brook, NY (United States); [Brookhaven National Lab., Upton, NY (United States); Hanson, J.C. [Brookhaven National Lab., Upton, NY (United States)] [Brookhaven National Lab., Upton, NY (United States); Corbin, D.R. [DuPont Central Research and Development, Wilmington, DE (United States)] [DuPont Central Research and Development, Wilmington, DE (United States)

1997-02-26

176

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

PubMed

The development of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy for intact tissue analysis and the correlations between the measured tissue metabolites and disease pathologies have inspired investigations of slow-spinning methodologies to maximize the protection of tissue pathology structures from HR-MAS centrifuging damage. Spinning sidebands produced by slow-rate spinning must be suppressed to prevent their complicating the spectral region of metabolites. Twenty-two human prostatectomy samples were analyzed on a 14.1T spectrometer, with HR-MAS spinning rates of 600 Hz, 700 Hz, and 3.0 kHz, a repetition time of 5 sec, and employing various rotor-synchronized suppression methods, including DANTE, WATERGATE, TOSS, and PASS pulse sequences. Among them, DANTE, as the simplest scheme, has shown the most potential in suppression of tissue water signals and spinning sidebands, as well as in quantifying metabolic concentrations. PMID:12939772

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

2003-09-01

177

Conformational isomerism of the binuclear N, N-pentamethylenedithiocarbamate cadmium(II) complex, [Cd 2{S 2CN(CH 2) 5} 4] on multinuclear ( 15N, 113Cd) CP\\/MAS NMR and single-crystal X-ray diffraction data  

Microsoft Academic Search

Crystalline N,N-cyclo-pentamethylenedithiocarbamate (PmDtc) cadmium(II) complex was prepared and studied by means of 15N, 113Cd CP\\/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the cadmium(II) compound comprises two centrosymmetric isomeric binuclear molecules [Cd2{S2CN(CH2)5}4], which display structural inequivalence in both 15N and 113Cd NMR and XRD data. There are pairs of the dithiocarbamate ligands exhibiting different structural functions in

Alexander V. Ivanov; Andrey V. Gerasimenko; Alexey A. Konzelko; Maxim A. Ivanov; Oleg N. Antzutkin; Willis Forsling

2006-01-01

178

The unique alternation of conformationally different (‘chair’-‘saddle’) eight-membered metallocycles [Cd 2S 4P 2] in the chains of cadmium dialkyldithiophosphates: 13C, 31P, 113Cd CP\\/MAS NMR and single-crystal X-ray diffraction studies  

Microsoft Academic Search

O,O?-Dipropyldithiophosphate and O,O?-dibutyldithiophosphate (Dtph) cadmium(II) complexes were prepared and studied by means of heteronuclear 31P, 113Cd, 31C CP\\/MAS NMR spectroscopy and single-crystal X-ray diffraction. Linear-chain polynuclear structures have been established for both cadmium(II) complexes, in which each pair of equivalent dithiophosphate groups, playing the same bridging structural function, asymmetrically links the neighbouring cadmium atoms. One remarkable structural feature of the

Alexander V. Ivanov; Andrey V. Gerasimenko; Oleg N. Antzutkin; Willis Forsling

2005-01-01

179

The silicalite(MFI)/p-nitroaniline system. I. Location of the sorbed molecules at medium and high pore-fillings. A study by X-ray powder diffraction, 29Si mas NMR and energy minimization calculations  

NASA Astrophysics Data System (ADS)

Structural investigation of the silicalite(MFI)/np-nitroaniline system by X-ray powder diffraction, establishes the existence of two single phased host/guest complexes corresponding to n=4 and 8 at medium and high pore-fillings respectively. Predictive studies by molecular mechanics simulations indicate that the pNAN molecules are located at the channel-intersections (for n=4) or in the elliptic channel-sections of the MFI topology (for n=8). 29Si solid-state mas NMR measurements show that the actual MFI framework symmetry of the silicalite.4pNAN complex is acentric Pn21a. Interpretation of the XRD pattern corresponding to the saturated silicalite. 8pNAN complex by Rietveld type structure refinements shows that two independent pNAN molecules are located on sites II (zig-zag channel sections) and sites III (straight channel sections). The van der Waals type interactions between the sorbed molecules take place at the channel-intersections (sites I). These sites are not occupied by extra-framework species. This is in agreement with the commensurability criterion already observed in several MFI/sorbate systems. Une étude structurale du système silicalite(MFI)/np-nitroaniline (pNAN) par diffraction des rayons X sur poudres, dans le domaine des concentrations 4

Mentzen, B. F.; Lefèbvre, F.

1998-05-01

180

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)

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.

Lim, Ae Ran

2014-01-01

181

Slow Magic Angle Sample Spinning: A Non- or Minimally Invasive Method for High- Resolution 1H Nuclear Magnetic Resonance (NMR) Metabolic Profiling  

SciTech Connect

High resolution 1H magic angle spinning nuclear magnetic resonance (NMR), using a sample spinning rate of several kHz or more (i.e., high resolution-magic angle spinning (hr-MAS)), is a well established method for metabolic profiling in intact tissues without the need for sample extraction. The only shortcoming with hr-MAS is that it is invasive and is thus unusable for non-destructive detections. Recently, a method called slow-MAS, using the concept of two dimensional NMR spectroscopy, has emerged as an alternative method for non- or minimal invasive metabolomics in intact tissues, including live animals, due to the slow or ultra-slow-sample spinning used. Although slow-MAS is a powerful method, its applications are hindered by experimental challenges. Correctly designing the experiment and choosing the appropriate slow-MAS method both require a fundamental understanding of the operation principles, in particular the details of line narrowing due to the presence of molecular diffusion. However, these fundamental principles have not yet been fully disclosed in previous publications. The goal of this chapter is to provide an in depth evaluation of the principles associated with slow-MAS techniques by emphasizing the challenges associated with a phantom sample consisting of glass beads and H2O, where an unusually large magnetic susceptibility field gradient is obtained.

Hu, Jian Z.

2011-05-01

182

Exploring abiotic stress on asynchronous protein metabolism in single kernels of wheat studied by NMR spectroscopy and chemometrics.  

PubMed

Extreme climate events are being recognized as important factors in the effects on crop growth and yield. Increased climatic variability leads to more frequent extreme conditions which may result in crops being exposed to more than one extreme event within a growing season. The aim of this study was to examine the implications of different drought treatments on the protein fractions in grains of winter wheat using (1)H nuclear magnetic resonance spectroscopy followed by chemometric analysis. Triticum aestivum L. cv. Vinjett was studied in a semi-field experiment and subjected to drought episodes either at terminal spikelet, during grain-filling or at both stages. Principal component trajectories of the total protein content and the protein fractions of flour as well as the (1)H NMR spectra of single wheat kernels, wheat flour, and wheat methanol extracts were analysed to elucidate the metabolic development during grain-filling. The results from both the (1)H NMR spectra of methanol extracts and the (1)H HR-MAS NMR of single kernels showed that a single drought event during the generative stage had as strong an influence on protein metabolism as two consecutive events of drought. By contrast, a drought event at the vegetative growth stage had little effect on the parameters investigated. For the first time, (1)H HR-MAS NMR spectra of grains taken during grain-filling were analysed by an advanced multiway model. In addition to the results from the chemical protein analysis and the (1)H HR-MAS NMR spectra of single kernels indicating that protein metabolism is influenced by multiple drought events, the (1)H NMR spectra of the methanol extracts of flour from mature grains revealed that the amount of fumaric acid is particularly sensitive to water deficits. PMID:19213725

Winning, H; Viereck, N; Wollenweber, B; Larsen, F H; Jacobsen, S; Søndergaard, I; Engelsen, S B

2009-01-01

183

Studies of Secondary Melanoma on C57BL/6J Mouse Liver Using 1H NMR Metabolomics  

SciTech Connect

NMR metabolomics, consisting of solid state high resolution (hr) magic angle spinning (MAS) 1H NMR (1H hr-MAS), liquid state high resolution 1H-NMR, and principal components analysis (PCA) has been used to study secondary metastatic B16-F10 melanoma in C57BL/6J mouse liver . The melanoma group can be differentiated from its control group by PCA analysis of the absolute concentrations or by the absolute peak intensities of metabolites from either 1H hr-MAS NMR data on intact liver tissues or liquid state 1H-NMR spectra on liver tissue extracts. In particular, we found that the absolute concentrations of alanine, glutamate, creatine, creatinine, fumarate and cholesterol are elevated in the melanoma group as compared to controls, while the absolute concentrations of succinate, glycine, glucose, and the family of linear lipids including long chain fatty acids, total choline and acylglycerol are decreased. The ratio of glycerophosphocholine to phosphocholine is increased by about 1.5 fold in the melanoma group, while the absolute concentration of total choline is actually lower in melanoma mice. These results suggest the following picture in secondary melanoma metastasis: Linear lipid levels are decreased by beta oxidation in the melanoma group, which contributes to an increase in the synthesis of cholesterol, and also provides an energy source input for TCA cycle. These findings suggest a link between lipid oxidation, the TCA cycle and the hypoxia-inducible factors (HIF) signal pathway in tumor metastases. Thus this study indicates that the metabolic profile derived from NMR analysis can provide a valuable bio-signature of malignancy and cell hypoxia in metastatic melanoma.

Feng, Ju; Isern, Nancy G.; Burton, Sarah D.; Hu, Jian Z.

2013-10-31

184

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

185

Solid-state ²°⁷Pb CP-MAS NMR of lead(II) compounds for the structural study of molecular routes to lead-based perovskite-phase materials  

Microsoft Academic Search

In this paper, the authors discuss the results of a study of the solid-state ²°⁷Pb NMR data for crystalline Pb(OâCCRâOH)â compounds, crystalline perovskite-phase PbMOâ (M = Ti, Zr), and an amorphous PbTiOâ precursor and proton T⁠relaxation times to investigate the potential of this technique to follow solid-state structural changes.

Alan D. Irwin; Clive D. Chandler; M. J. Hampden-Smith; R. Assink

1994-01-01

186

Solid-state {sup 207}Pb CP-MAS NMR of lead(II) compounds for the structural study of molecular routes to lead-based perovskite-phase materials  

SciTech Connect

In this paper, the authors discuss the results of a study of the solid-state {sup 207}Pb NMR data for crystalline Pb(O{sub 2}CCR{sub 2}OH){sub 2} compounds, crystalline perovskite-phase PbMO{sub 3} (M = Ti, Zr), and an amorphous PbTiO{sub 3} precursor and proton T{sub 1} relaxation times to investigate the potential of this technique to follow solid-state structural changes.

Irwin, A.D. [Butler Univ., Indianapolis, IN (United States); Chandler, C.D.; Hampden-Smith, M.J. [Univ. of New Mexico, Albuquerque, NM (United States); Assink, R. [Sandia National Lab., Albuquerque, NM (United States)

1994-03-16

187

HR COMMUNICATIONS Program Coordinator  

E-print Network

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

Ronquist, Fredrik

188

The structural reorganisation of bis(diethyldithiocarbamato)morpholine–zinc(II) and –copper(II) in the course of solid-state solvation with morpholine and benzene molecules studied by ESR, solid-state 13C and 15N CP\\/MAS NMR spectroscopy and single-crystal X-ray diffraction  

Microsoft Academic Search

Six forms of both non-solvated and solvated adducts of bis(diethyldithiocarbamato)–zinc(II) and –copper(II) with morpholine, of general formulas [M{O(CH2)4NH}{S2CN(C2H5)2}2] and [M{O(CH2)4NH}{S2CN(C2H5)2}2]·L (M=Zn(II) (1): L=O(CH2)4NH (2), C6H6 (3); M=Cu(II) (4): L=O(CH2)4NH (5), C6H6 (6)), have been prepared and studied by means of ESR, solid-state natural abundance 13C and 15N CP\\/MAS NMR spectroscopy and single crystal X-ray diffraction data. The existence of two

Alexander V. Ivanov; Mikael Kritikos; Oleg N. Antzutkin; Willis Forsling

2001-01-01

189

A fixation mode of gold from solutions using heterogeneous reaction of cadmium dicyclohexyl dithiophosphate with H[AuCl4]. Structural and (13C, 31P) CP/MAS NMR studies and thermal behaviour of crystalline polymeric gold(I) dicyclohexyl dithiophosphate and bis(dicyclohexylthiophosphoryl) disulphide  

NASA Astrophysics Data System (ADS)

Two novel compounds: polynuclear catena-poly[bis(?3-O,O'-di-cyclo-hexyldithiophosphato-S,S,S')digold(I)] (Ausbnd Au) (1) and crystalline bis(O,O'-di-cyclo-hexylthiophosphoryl)disulphide, (cyclo-C6H11O)2P(S)Ssbnd S(S)P(O-cyclo-C6H11)2 (2) were prepared using heterogeneous reaction between freshly precipitated binuclear cadmium(II) dithiophosphate (Dtph), [Cd2{S2P(O-cyclo-C6H11}4] and H[AuCl4] in 2 M hydrochloric acid. The isolated compounds 1 and 2 (the fixation mode of gold from the solution and the oxidised form of Dtph groups, respectively) have been studied by means of single-crystal X-ray diffraction, 13C and 31P cross-polarisation/magic-angle-spinning (CP/MAS) NMR spectroscopy and simultaneous thermal analysis (STA). Centrosymmetric binuclear molecule of 1, [Au2{S2P(O-cyclo-C6H11)2}2] comprises a pair of ?-bridging di-cyclo-hexyl Dtph ligands, linking two neighbouring gold atoms, and displays additional intramolecular aurophilic bond Au⋯Au. At the supramolecular level of structural self-organisation of complex 1, infinite polymeric zigzag chains arise due to pairs of the secondary bonds Au···S between neighbouring binuclear molecules. Centrosymmetric molecule of 2 displays two O,O'-di-cyclo-hexythiophosphoryl fragments, which are connected by the chemical bond S(1)sbnd S(1)a, and a planar zigzag array [Sdbnd Psbnd Ssbnd Ssbnd Pdbnd S] passing through the central part of the molecule. To characterise additionally the Dtph groups in both compounds 1 and 2, chemical shift anisotropy (CSA) parameters (?aniso and ?) were calculated from spinning sideband manifolds in experimental 31P MAS NMR spectra. The thermal behaviour of complex 1 was studied using simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour displays stepwise mass loss, comprising thermal decompositions of the organic and inorganic parts of 1 with gold(I) dithio-meta-phosphate and reduced metallic gold as the intermediate and the final products, respectively.

Ivanov, Alexander V.; Korneeva, Eugenia V.; Lutsenko, Irina A.; Gerasimenko, Andrey V.; Antzutkin, Oleg N.; Larsson, Anna-Carin; Sergienko, Valentin I.

2013-02-01

190

NMR crystallography: The effect of deuteration on high resolution 13 state NMR spectra of a 7-TM protein  

E-print Network

-transmembrane; NMR, nuclear magnetic resonance; MAS, magic angle spinning; DGK, diaglycerol kinase; CP, crossNMR crystallography: The effect of deuteration on high resolution 13 C solid state NMR spectra, and indirect, 9­17 ppm, dimensions). The measured 13 C NMR line-widths observed for both protonated

Watts, Anthony

191

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)

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.

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

2013-03-01

192

Studies of Secondary Melanoma on C57BL/6J Mouse Liver Using 1H NMR Metabolomics  

PubMed Central

NMR metabolomics, consisting of solid state high resolution magic angle spinning (HR-MAS) 1H-NMR, liquid state high resolution 1H-NMR, and principal components analysis (PCA) has been used to study secondary metastatic B16-F10 melanoma in C57BL/6J mouse liver. The melanoma group can be differentiated from its control group by PCA analysis of the estimates of absolute concentrations from liquid state 1H-NMR spectra on liver tissue extracts or by the estimates of absolute peak intensities of metabolites from 1H HR-MAS-NMR data on intact liver tissues. In particular, we found that the estimates of absolute concentrations of glutamate, creatine, fumarate and cholesterol are elevated in the melanoma group as compared to controls, while the estimates of absolute concentrations of succinate, glycine, glucose, and the family of linear lipids including long chain fatty acids, total choline and acyl glycerol are decreased. The ratio of glycerophosphocholine (GPC) to phosphocholine (PCho) is increased by about 1.5 fold in the melanoma group, while the estimate of absolute concentration of total choline is actually lower in melanoma mice. These results suggest the following picture in secondary melanoma metastasis: Linear lipid levels are decreased by beta oxidation in the melanoma group, which contributes to an increase in the synthesis of cholesterol, and also provides an energy source input for TCA cycle. These findings suggest a link between lipid oxidation, the TCA cycle and the hypoxia-inducible factors (HIF) signal pathway in tumor metastases. Thus, this study indicates that the metabolic profile derived from NMR analysis can provide a valuable bio-signature of malignancy and cell hypoxia in metastatic melanoma. PMID:24958263

Feng, Ju; Isern, Nancy G.; Burton, Sarah D.; Hu, Jian Zhi

2013-01-01

193

Assessment of a 1H high-resolution magic angle spinning NMR spectroscopy procedure for free sugars quantification in intact plant tissue.  

PubMed

In most plants, sucrose is the primary product of photosynthesis, the transport form of assimilated carbon, and also one of the main factors determining sweetness in fresh fruits. Traditional methods for sugar quantification (mainly sucrose, glucose and fructose) require obtaining crude plant extracts, which sometimes involve substantial sample manipulation, making the process time-consuming and increasing the risk of sample degradation. Here, we describe and validate a fast method to determine sugar content in intact plant tissue by using high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). The HR-MAS NMR method was used for quantifying sucrose, glucose and fructose in mesocarp tissues from melon fruits (Cucumis melo var. reticulatus and Cucumis melo var. cantalupensis). The resulting sugar content varied among individual melons, ranging from 1.4 to 7.3 g of sucrose, 0.4-2.5 g of glucose; and 0.73-2.83 g of fructose (values per 100 g fw). These values were in agreement with those described in the literature for melon fruit tissue, and no significant differences were found when comparing them with those obtained using the traditional, enzymatic procedure, on melon tissue extracts. The HR-MAS NMR method offers a fast (usually <30 min) and sensitive method for sugar quantification in intact plant tissues, it requires a small amount of tissue (typically 50 mg fw) and avoids the interferences and risks associated with obtaining plant extracts. Furthermore, this method might also allow the quantification of additional metabolites detectable in the plant tissue NMR spectrum. PMID:23824526

Delgado-Goñi, Teresa; Campo, Sonia; Martín-Sitjar, Juana; Cabañas, Miquel E; San Segundo, Blanca; Arús, Carles

2013-08-01

194

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

195

E/Z MAS demonstration  

SciTech Connect

Los Alamos National Laboratory has developed E/Z MAS, a new generation nuclear material accountability application based on the latest technology and designed for facilities required to track nuclear materials with a simple-to-use interface. E/Z MAS is based on years of experience spent developing nuclear material accounting systems. E/Z MAS uses a modern relational database with a web server and enables users on a classified local area network to interact with the database with web browsers. The E/Z MAS Demonstration poster session demonstrates the E/Z MAS functions required by an operational nuclear facility to track material as it enters and leaves a facility and to account for the material as it moves through a process. The generation of internal facility reports and external reports for the Russian Federal system will be demonstrated. Bar-code readers will be used to demonstrate the ability of EZ MAS to automate certain functions, such as physical inventories at facilities.

Boor, M.G.; Hurford, J.M.; Landry, R.P.; Martinez, B.J.; Solem, A.M.; Whiteson, R.; Zardecki, A.

1998-12-31

196

Director HR Andrew J Smith  

E-print Network

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

Liley, David

197

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

E-print Network

.5747 Garching, Germany 29Si CP MAS NMR shows that a transition-metalcomplex with two bifunctional phosphine or an addition reaction to surface siloxane groups takes place.'3 This can be seen in the 29Si CP MAS NMR-state NMR study Klaus D. Behringer and Janet Blumel" Anorganisch-chemisches Institut der TU Miinchen, 8

Bluemel, Janet

198

Glucose and lactate metabolism in the awake and stimulated rat: a 13C-NMR study  

PubMed Central

Glucose is the major energetic substrate for the brain but evidence has accumulated during the last 20 years that lactate produced by astrocytes could be an additional substrate for neurons. However, little information exists about this lactate shuttle in vivo in activated and awake animals. We designed an experiment in which the cortical barrel field (S1BF) was unilaterally activated during infusion of both glucose and lactate (alternatively labeled with 13C) in rats. At the end of stimulation (1 h) both S1BF areas were removed and analyzed by HR-MAS NMR spectroscopy to compare glucose and lactate metabolism in the activated area vs. the non-activated one. In combination with microwave irradiation HR-MAS spectroscopy is a powerful technical approach to study brain lactate metabolism in vivo. Using in vivo 14C-2-deoxyglucose and autoradiography we confirmed that whisker stimulation was effective since we observed a 40% increase in glucose uptake in the activated S1BF area compared to the ipsilateral one. We first determined that lactate observed on spectra of biopsies did not arise from post-mortem metabolism. 1H-NMR data indicated that during brain activation there was an average 2.4-fold increase in lactate content in the activated area. When [1-13C]glucose + lactate were infused 13C-NMR data showed an increase in 13C-labeled lactate during brain activation as well as an increase in lactate C3-specific enrichment. This result demonstrates that the increase in lactate observed on 1H-NMR spectra originates from newly synthesized lactate from the labeled precursor ([1-13C]glucose). It also shows that this additional lactate does not arise from an increase in blood lactate uptake since it would otherwise be unlabeled. These results are in favor of intracerebral lactate production during brain activation in vivo which could be a supplementary fuel for neurons. PMID:23755012

Sampol, Denys; Ostrofet, Eugène; Jobin, Marie-Lise; Raffard, Gérard; Sanchez, Stéphane; Bouchaud, Véronique; Franconi, Jean-Michel; Bonvento, Gilles; Bouzier-Sore, Anne-Karine

2013-01-01

199

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.

200

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

E-print Network

: 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 geometry for H2CNMo(N[CH3]Ph)3, 3m-Cs 2.12 Optimized geometry for [CH3CH2NMo(NH2)3]+ , [2d-m] 2.13 NMR

Loening, Niko

201

N NMR Investigation of the Covalent Binding of Reduced TNT  

E-print Network

. A comparison of quantitative liquid phase with solid- state CP/MAS 15N NMR indicated that the CP experiment15 N NMR Investigation of the Covalent Binding of Reduced TNT Amines to Soil Humic Acid, Model)slabeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR

202

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

NASA Astrophysics Data System (ADS)

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.

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

203

NMR Spectroscopy  

NSDL National Science Digital Library

Quiz questions from the organic chemistry question bank provide students with an excellent opportunity to review key concepts. These questions pertain to Nuclear magnetic resonance (NMR) spectroscopy and include topics such as: Chemical Shift, Proton NMR, and Carbon NMR.

Reich, Ieva

204

New Mechanistic Insights Regarding Pd/Cu Catalysts for the Sonogashira Reaction: HRMAS NMR Studies of Silica-Immobilized Systems  

E-print Network

-state NMR of the dry supports (CP/MAS),5 and HRMAS NMR,6 where the material is suspended in solventsNew Mechanistic Insights Regarding Pd/Cu Catalysts for the Sonogashira Reaction: HRMAS NMR Studies) and drying (in vacuo), a broad and unstructured 31P CP/MAS signal results (Figure 1, top). However, recording

Bluemel, Janet

205

Separate-Local-Field NMR Spectroscopy on Half-Integer Quadrupolar Nuclei Julia Grinshtein, Christopher V. Grant, and Lucio Frydman*  

E-print Network

anisotropy affecting these species generally restricts their solid-state NMR study to central field of high- resolution spin-1/2 solid-state NMR. Then, separate-local-field (SLF) MAS techniques such SLF measurements to solid-state quadrupolar NMR. Two main differences arise upon invoking SLF MAS

Frydman, Lucio

206

MIRLIN HR 4796 Page  

NSDL National Science Digital Library

National Aeronautics and Space Administration astronomers, using the Keck II telescope in Hawaii, along with a team of scientists from the Harvard-Smithsonian Center for Astrophysics and the University of Florida, Gainesville, using the Cerro Tololo Observatory in Chile, "have discovered what appears to be the clearest evidence yet of a budding solar system around a nearby star." HR 4796, about 220 light years from Earth, "shows a swirling disk of dust around the star" that portends the building of a star system. The MIRLIN (Mid-InfraRed Large-well Imager) page contains photos, more explanations, and a link to theoretical images and explanation of how a star system forms.

1998-01-01

207

Resin-bound chiral derivatizing agents for assignment of configuration by NMR spectroscopy.  

PubMed

A general methodology for assigning the configuration of chiral mono- and polyfunctional compounds by NMR is presented. The approach is based on the use of polystyrene-bound chiral derivatizing agents (CDA-resins) specifically designed to achieve the high-yield formation of the covalent linkages (amide or ester bonds) between the substrate and the chiral auxiliary within the NMR tube, without the need for other manipulations, on a microscale level and in a short time. The deuterated NMR solvents (CDCl3, CD3CN, CS2/CD2Cl2) are also the reaction solvents and separations, purifications or workups of any kind are not necessary prior to recording the spectra. The CDA-resins prepared included MPA, 9-AMA, BPG, MTPA, and 2-NTBA as auxiliary agents incorporated either as single enantiomers or as mixed combinations of the (R)- and the (S)-enantiomers at unequal and known ratios. The high versatility of these systems was successfully demonstrated in a variety of ways based on double and single derivatization, low temperature experiments, or the formation of metal complexes. The approach allowed the absolute configurations of chiral primary amines, primary and secondary alcohols, cyanohydrins, thiols, diols, triols, and amino alcohols to be determined. Extensive high-resolution magic angle spinning (HR-MAS) NMR experiments allowed the characterization of the new CDA-resins and enabled the study of their stability and regioselectivity. PMID:18582122

Porto, Silvia; Seco, José Manuel; Espinosa, Juan Félix; Quiñoá, Emilio; Riguera, Ricardo

2008-08-01

208

The biochemical and elemental compositions of marine plankton: A NMR perspective  

E-print Network

resonance (CP/MAS 13 C NMR). Using a mixing model that relates NMR spectral data to biochemical compositionThe biochemical and elemental compositions of marine plankton: A NMR perspective J.I. Hedges a,*, J. Although preliminary, this 13 C NMR-based estimate indicates elemental compositions and respiratory oxygen

Long, Bernard

209

Moving NMR  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

210

Réunion publique HR  

ScienceCinema

Chers Collègues,Je me permets de vous rappeler qu'une réunion publique organisée par le Département HR se tiendra aujourd'hui:Vendredi 30 avril 2010 à 9h30 dans l'Amphithéâtre principal (café offert dès 9h00).Durant cette réunion, des informations générales seront données sur:le CERN Admin e-guide, qui est un nouveau guide des procédures administratives du CERN ayant pour but de faciliter la recherche d'informations pratiques et d'offrir un format de lecture convivial;le régime d'Assurance Maladie de l'Organisation (présentation effectuée par Philippe Charpentier, Président du CHIS Board) et;la Caisse de Pensions (présentation effectuée par Théodore Economou, Administrateur de la Caisse de Pensions du CERN).Une transmission simultanée de cette réunion sera assurée dans l'Amphithéâtre BE de Prévessin et également disponible à l'adresse suivante: http://webcast.cern.chJe me réjouis de votre participation!Meilleures salutations,Anne-Sylvie CatherinChef du Département des Ressources humaines__________________________________________________________________________________Dear Colleagues,I should like to remind you that a plublic meeting organised by HR Department will be held today:Friday 30 April 2010 at 9:30 am in the Main Auditorium (coffee from 9:00 am).During this meeting, general information will be given about:the CERN Admin e-guide which is a new guide to the Organization's administrative procedures, drawn up to facilitate the retrieval of practical information and to offer a user-friendly format;the CERN Health Insurance System (presentation by Philippe Charpentier, President of the CHIS Board) and;the Pension Fund (presentation by Theodore Economou, Administrator of the CERN Pension Fund).A simultaneous transmission of this meeting will be broadcast in the BE Auditorium at Prévessin and will also be available at the following address. http://webcast.cern.chI look forward to your participation!Best regards,Anne-Sylvie CatherinHead, Human Resources Department

None

2011-10-06

211

Two dimensional NMR and NMR relaxation studies of coal structure  

SciTech Connect

This report covers the progress made on the title project during the past reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have been reinvestigating the prospects of using zero field NMR types of techniques for two dimensional NMR structural analysis of complex organic solids such as coals. Currently MAS spin rates are not sufficiently high to permit zero field in high field NMR for protons in typical organic solids, however they are compatible with {sup 13}C-{sup 13}C dipolar couplings. In collaboration with Dr. Robert Tycko of AT T Bell Laboratories, inventor of the zero field in high field NMR method, the authors have performed the first zero field in high field {sup 13}C NMR experiments. These results are described. 9 refs., 2 figs.

Zilm, K.W.

1989-01-01

212

Characterisation of sodium cations in dehydrated zeolite NaX by 23Na NMR spectroscopy  

Microsoft Academic Search

23Na MAS, 2D nutation MAS, and DOR NMR spectroscopy has been applied to characterise the location of sodium cations in dehydrated zeolite NaX (Si\\/Al = 1.23). The 23Na MAS NMR spectra recorded at three different magnetic field strengths were decomposed by computer simulation into five lines, which were attributed to five crystallographically distinct cation sites known from X-ray diffraction studies.

M. Feuerstein; M. Hunger; G. Engelhardt; J. P. Amoureux

1996-01-01

213

Immobilization of Carbonylnickel Complexes: A Solid-State NMR Study K. D. Behringer and J. Blu1mel*  

E-print Network

oxidation or cross-linking, and therefore narrow NMR lines, and it allows 13C CP/MAS NMR spectroscopy. 1Immobilization of Carbonylnickel Complexes: A Solid-State NMR Study K. D. Behringer and J. Blu1mel- and tricarbonylnickel complexes of these ligands are synthesized, characterized by 61Ni, 31P, 13C, and 1H NMR and IR

Bluemel, Janet

214

NMR Spectroscopy of Human Eye Tissues: A New Insight into Ocular Biochemistry  

PubMed Central

Background. The human eye is a complex organ whose anatomy and functions has been described very well to date. Unfortunately, the knowledge of the biochemistry and metabolic properties of eye tissues varies. Our objective was to reveal the biochemical differences between main tissue components of human eyes. Methods. Corneas, irises, ciliary bodies, lenses, and retinas were obtained from cadaver globes 0-1/2 hours postmortem of 6 male donors (age: 44–61 years). The metabolic profile of tissues was investigated with HR MAS 1H NMR spectroscopy. Results. A total of 29 metabolites were assigned in the NMR spectra of the eye tissues. Significant differences between tissues were revealed in contents of the most distant eye-tissues, while irises and ciliary bodies showed minimal biochemical differences. ATP, acetate, choline, glutamate, lactate, myoinositol, and taurine were identified as the primary biochemical compounds responsible for differentiation of the eye tissues. Conclusions. In this study we showed for the first time the results of the analysis of the main human eye tissues with NMR spectroscopy. The biochemical contents of the selected tissues seemed to correspond to their primary anatomical and functional attributes, the way of the delivery of the nutrients, and the location of the tissues in the eye. PMID:25525621

Kryczka, Tomasz; Wyl?ga?a, Edward; Dobrowolski, Dariusz; Midelfart, Anna

2014-01-01

215

NMR study of pore surface and size in the mesoporous material FSM-16  

Microsoft Academic Search

The surface structure, pore size distribution and pore wall thickness of the mesoporous material FSM-16 have been studied by X-ray powder diffraction (XRD), 1H and 29Si MAS NMR and 1H liquid-state NMR, and by applying surface silylation as a probe. The concentrations of surface hydroxyl groups for FSM-16 are estimated from 29Si MAS NMR, and amount to 3×1021 g?1, corresponding

Xiulan Xie; Masatoshi Satozawa; Kimio Kunimori; Shigenobu Hayashi

2000-01-01

216

Journal of Biomolecular NMR, 26: 4968, 2003. KLUWER/ESCOM  

E-print Network

Journal of Biomolecular NMR, 26: 49­68, 2003. KLUWER/ESCOM © 2003 Kluwer Academic Publishers, fusion, MAS, melittin, membrane, NMR, peptide, solid-state, two- dimensional Abstract 2D slow ­ bicinchoninic acid; CP ­ cross-polarization; CSA ­ chemical shift anisotropy; DQ ­ double quantum; DRAWS

Weliky, David

217

Two dimensional NMR and NMR relaxation studies of coal structure  

SciTech Connect

This report coves the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. 5 figs.

Zilm, K.W.

1988-01-01

218

Two dimensional NMR and NMR relaxation studies of coal structure  

SciTech Connect

This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. 3 figs.

Zilm, K.W.

1988-01-01

219

Antecedent of HR Competencies and Job Performance: Required IT Competencies for HR Professional in Digital Era  

Microsoft Academic Search

This study assimilated IT and HR literatures to investigate the relationships between IT competencies, HR competencies, and job performance for HR professionals. Drawing on a sample of 122 HR professionals from 8 financial service companies in Taiwan, our results show that IT competencies and HR competencies are positively and significantly associated with job performance, and HR competencies partially mediate the

Hung-Yue Suen; Hsiang-En Hsiao; Jiann-Min Yang

2011-01-01

220

Alternative Species Taxonomic Name: Cornus mas  

E-print Network

and provide color in the landscape when it is typically lacking. #12;Fruit: Cornus mas, again like Berberis, has red oval fruit. Bark: The bark is exfoliating and produces mottled patches of tans and browns

Hayden, Nancy J.

221

B. Sc. Examination 2005 MAS 335 Cryptography  

E-print Network

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

Banaji,. Murad

222

NMR Spectroscopy  

NSDL National Science Digital Library

This site contains web-based programs that allow the user to predict chemical shifts, spin-spin coupling patterns and NMR line shapes affected by dynamic chemical exchange. This site will be most useful for students with a good background in the fundamentals of NMR theory.

Shattuck, Thomas W.

2011-07-01

223

Application of High-Resolution Magic-Angle Spinning NMR Spectroscopy to Define the Cell Uptake of MRI Contrast Agents  

NASA Astrophysics Data System (ADS)

A new method, based on proton high-resolution magic-angle spinning ( 1H HR-MAS) NMR spectroscopy, has been employed to study the cell uptake of magnetic resonance imaging contrast agents (MRI-CAs). The method was tested on human red blood cells (HRBC) and white blood cells (HWBC) by using three gadolinium complexes, widely used in diagnostics, Gd-BOPTA, Gd-DTPA, and Gd-DOTA, and the analogous complexes obtained by replacing Gd(III) with Dy(III), Nd(III), and Tb(III) (i.e., complexes isostructural to the ones of gadolinium but acting as shift agents). The method is based on the evaluation of the magnetic effects, line broadening, or induced lanthanide shift (LIS) caused by these complexes on NMR signals of intra- and extracellular water. Since magnetic effects are directly linked to permeability, this method is direct. In all the tests, these magnetic effects were detected for the extracellular water signal only, providing a direct proof that these complexes are not able to cross the cell membrane. Line broadening effects (i.e., the use of gadolinium complexes) only allow qualitative evaluations. On the contrary, LIS effects can be measured with high precision and they can be related to the concentration of the paramagnetic species in the cellular compartments. This is possible because the HR-MAS technique provides the complete elimination of bulk magnetic susceptibility (BMS) shift and the differentiation of extra- and intracellular water signals. Thus with this method, the rapid quantification of the MRI-CA amount inside and outside the cells is actually feasible.

Calabi, Luisella; Alfieri, Goffredo; Biondi, Luca; De Miranda, Mario; Paleari, Lino; Ghelli, Stefano

2002-06-01

224

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

E-print Network

decoupling (10-s pulse delay, 24 scans). 21 "C MAS NMR spectra showing the melting of caffeine between 508 and 520 K. All spectra were obtained using single-pulse excitation with 'H decoupling (12-s pulse delay, 48 scans). 22 "C MAS NMR spectra showing... spectra were obtained using single pulse excitation with 'H decoupling (10-s pulse delay, 24 scans). 21 "C MAS NMR spectra showing the melting of caffeine between 508 and 520 K. All spectra were obtained using single-pulse excitation with 'H decoupling...

Oliver, F. Gregory

1992-01-01

225

Asteroseismology across the HR diagram  

E-print Network

High precision spectroscopy provides essential information necessary to fully exploit the opportunity of probing the internal structure of stars using Asteroseismology. In this work we discuss how Asteroseismology combined with High Precision Spectroscopy can establish a detailed view on stellar structure and evolution of stars across the HR diagramme.

M. J. P. F. G. Monteiro

2007-02-12

226

Asteroseismology Across the HR Diagram  

Microsoft Academic Search

High precision spectroscopy provides essential information necessary to fully exploit the opportunity of probing the internal\\u000a structure of stars using Asteroseismology. In this work we discuss how Asteroseismology combined with High Precision Spectroscopy can establish a detailed view on stellar structure and evolution of stars across the HR diagramme.

227

HR/Organizational Company Description  

E-print Network

HR/Organizational Company Description: One of the world's leading companies in the field of health, but foster a culture and environment so the millennial generation can succeed. Key Deliverables 1. Analyze adapt our current culture to fit the needs of the new generation of the workforce, or a way to implement

Dahl, David B.

228

hr  

E-print Network

us,both by day and night, the Whole Horizon, Wit his 2, d1. vi?ons. . c H A P. .... Meridians pa?e by the f'oref'aid I?ands, it is called refped'tilre. Longitude. And this .... [time thing, and lightning that me towards Which the three! doth Fall, until it ..... Sun at noon in my Alirolabe, and found it to be 35 degrees and three quarters.

229

NMR use to quantify phlorotannins: The case of Cystoseira tamariscifolia, a phloroglucinol-producing brown macroalga in Brittany (France).  

PubMed

Among the most renowned natural products from brown algae, phlorotannins are phloroglucinol polymers that have been extensively studied, both for their biotechnological potential and their interest in chemical ecology. The accurate quantification of these compounds is a key point to understand their role as mediators of chemical defense. In recent years, the Folin-Ciocalteu assay has remained a classic protocol for phlorotannin quantification, even though it frequently leads to over-estimations. Furthermore, the quantification of the whole pool of phlorotannins may not be relevant in ecological surveys. In this study, we propose a rapid (1)H qNMR method for the quantification of phlorotannins. We identified phloroglucinol as the main phenolic compound produced by the brown macroalga Cystoseira tamariscifolia. This monomer was detected in vivo using (1)H HR-MAS spectroscopy. We quantified this molecule through (1)H qNMR experiments using TSP as internal standard. The results are discussed by comparison with a standard Folin-Ciocalteu assay performed on purified extracts. The accuracy and simplicity of qNMR makes this method a good candidate as a standard phlorotannin assay. PMID:25640118

Jégou, Camille; Kervarec, Nelly; Cérantola, Stéphane; Bihannic, Isabelle; Stiger-Pouvreau, Valérie

2015-04-01

230

Quantitative NMR  

NSDL National Science Digital Library

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

Korir, Albert K.; Larive, Cynthia K.

2011-07-18

231

NMR tutorial  

NSDL National Science Digital Library

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

Bogdal, Dariusz

2011-07-19

232

High-resolution NMR with resistive and hybrid magnets: deconvolution using a field-fluctuation signal.  

PubMed

A method for compensating effect of field fluctuation is examined to attain high-resolution NMR spectra with resistive and hybrid magnets. In this method, time dependence of electromotive force induced for a pickup coil attached near a sample is measured synchronously with acquisition of NMR. Observed voltage across the pickup coil is converted to field fluctuation data, which is used to deconvolute NMR signals. The feasibility of the method is studied by (79)Br MAS NMR of KBr under a 30T magnetic field of a hybrid magnet. Twenty single-scan NMR signals were accumulated after the manipulation, resulting in a high-resolution NMR spectrum. PMID:17123849

Iijima, Takahiro; Takegoshi, K; Hashi, Kenjiro; Fujito, Teruaki; Shimizu, Tadashi

2007-02-01

233

MAS 335 Cryptography Notes 1 Spring 2008  

E-print Network

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

Banaji,. Murad

234

NMR at low and ultralow temperatures.  

PubMed

Solid state nuclear magnetic resonance (NMR) measurements at low temperatures have been common in physical sciences for many years and are becoming increasingly important in studies of biomolecular systems. This Account reviews a diverse set of projects from my laboratory, dating back to the early 1990s, that illustrate the motivations for low-temperature solid state NMR, the types of information that are available from the measurements, and likely directions for future research. These projects include NMR studies of both physical and biological systems, performed at low (cooled with nitrogen, down to 77 K) and ultralow (cooled with helium, below 77 K) temperatures, and performed with and without magic-angle spinning (MAS). NMR studies of physical systems often focus on phenomena that occur only at low temperatures. Two examples from my laboratory are studies of molecular rotation and orientational ordering in solid C60 at low temperatures and studies of unusual electronic states, called skyrmions, in two-dimensionally confined electron systems within semiconductor quantum wells. To study quantum wells, we used optical pumping of nuclear spin polarizations to enhance their NMR signals. The optical pumping phenomenon exists only at ultralow temperatures. In studies of biomolecular systems, low-temperature NMR has several motivations. In some cases, low temperatures suppress molecular tumbling, thereby permitting solid state NMR measurements on soluble proteins. Studies of AIDS-related peptide/antibody complexes illustrate this effect. In other cases, low temperatures suppress conformational exchange, thereby permitting quantitation of conformational distributions. Studies of chemically denatured states of the model protein HP35 illustrate this effect. Low temperatures and rapid freeze-quenching can also be used to trap transient intermediate states in a non-equilibrium kinetic process, as shown in studies of a transient intermediate in the rapid folding pathway of HP35. NMR sensitivity generally increases with decreasing sample temperature. Therefore, it can be useful to carry out experiments at the lowest possible temperatures, particularly in studies of biomolecular systems in frozen solutions. However, solid state NMR studies of biomolecular systems generally require rapid MAS. A novel MAS NMR probe design that uses nitrogen gas for sample spinning and cold helium only for sample cooling allows a wide variety of solid state NMR measurements to be performed on biomolecular systems at 20-25 K, where signals are enhanced by factors of 12-15 relative to measurements at room temperature. MAS NMR at ultralow temperatures also facilitates dynamic nuclear polarization (DNP), allowing sizeable additional signal enhancements and large absolute NMR signal amplitudes with relatively low microwave powers. Current research in my laboratory seeks to develop and exploit DNP-enhanced MAS NMR at ultralow temperatures, for example, in studies of transient intermediates in protein folding and aggregation processes and studies of peptide/protein complexes that can be prepared only at low concentrations. PMID:23470028

Tycko, Robert

2013-09-17

235

eHR: An Introduction. IES Report.  

ERIC Educational Resources Information Center

This document introduces the concept of electronic human resources (eHR) and its application. Chapter 1 presents a brief overview of the guide's development, purpose, and structure. Chapter 2 defines the concept of eHR as "the application of conventional, Web, and voice technologies to improve HR administration, transactions, and process…

Kettley, P.; Reilly, P.

236

Multiperiodicity of HR 6534 Rafael Garrido  

E-print Network

in the HR diagram StrË?omgren photometric indices for this star are: (b \\Gamma y) 0 = 0:108; m 0 = 0:177; c 0 causes a shift in the location of the star in the HR diagram i. e., affects the determination of its massMultiperiodicity of HR 6534 Rafael Garrido Instituto de Astrofisica de Andalucia, Apdo 3004, 18080

Demoulin, Pascal

237

Advanced NMR approaches in the characterization of coal  

SciTech Connect

A considerable effort in this project during the past few months has been focussed on the development of [sup 1]H and [sup 13]C NMR imaging techniques to yield spatially-resolved chemical shift (structure) information on coal. In order to yield the chemical shift information, a solid-state NMR imaging technique must include magic-angle spinning, so rotating gradient capabilities are indicated. A [sup 13]C MAS imaging probe and a [sup 1]H MAS imaging probe and the circuitry necessary for rotating gradients have been designed and constructed. The [sup 1]H system has already produced promising preliminary results, which are briefly described in this report.

Maciel, G.E.

1992-01-01

238

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.

239

MAS Infrastructure: Definitions, Needs and Prospects  

Microsoft Academic Search

This paper attempts to articulate the general role of infrastructure for multi-agent systems (MAS), and why infrastructure is a particularly critical is- sue if we are to increase the visibility and impact of multi-agent systems as a universal technology and solution. Second, it presents my current thinking on the socio-technical content of the needed infrastructure in four different corners of

Les Gasser

2000-01-01

240

NAAP HR Diagram Explorer 1/9 HR Diagram Student Guide  

E-print Network

Name: NAAP ­ HR Diagram Explorer 1/9 HR Diagram ­ Student Guide Background Information Work through Orionis O9 Radius (R) Temperature (T) Luminosity (L) 1 1 1 2 1 9 1 1/2 #12;NAAP ­ HR Diagram Explorer 2 Diagram Explorer Open the HR Diagram Explorer. Begin by familiarizing yourself with the capabilities

Farritor, Shane

241

Electronic Supporting Information NMR Crystallography of L-Arginine: Disentangling Crystallographic  

E-print Network

Electronic Supporting Information NMR Crystallography of L-Arginine: Disentangling Crystallographic Inequivalence and Polymorphism by One- and Two-Dimensional Solid- State NMR Spectroscopy Jose-Enrique Herbert, France Figure S1. Expansions of the 13 C CP/MAS spectrum of L-arginine (sample 1). The resonance lines

242

SPINEVOLUTION: A powerful tool for the simulation of solid and liquid state NMR experiments  

E-print Network

SPINEVOLUTION: A powerful tool for the simulation of solid and liquid state NMR experiments Mikhail 2005; revised 22 July 2005 Abstract Exact numerical simulations of NMR experiments are often required. Simulations of solid-state magic angle spinning (MAS) experiments can be particularly demanding both

Griffin, Robert G.

243

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

NASA Astrophysics Data System (ADS)

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 23Na MAS NMR with enhanced second-order quadrupolar coupling effects and 31P MAS NMR where reduced influence from chemical shift anisotropy at low field may facilitate determination of heteronuclear dipole-dipole couplings.

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

2014-01-01

244

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

PubMed

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

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

2014-01-01

245

TSNo s02-hunger124547-O On the Use of 31-P NMR Spectroscopy to Determine Chemical Forms of Phosphorus in Soils.  

E-print Network

sorbed under different reaction conditions are examined using CP-MAS 31P-NMR as a molecular spectroscopicTSNo s02-hunger124547-O Title On the Use of 31-P NMR Spectroscopy to Determine Chemical Forms 31P-NMR SPECTROSCOPY ASA-CSSA-SSSA Annual Meetings - October 21 - 25, 2001 - Charlotte, NC #12;

Sparks, Donald L.

246

Two dimensional NMR and NMR relaxation studies of coal structure  

SciTech Connect

This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coal models. Along the same lines the author are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. During the last quarter the authors has concentrated on improvements in cross polarization (CP) sequences with a goal of making the CP process insensitive to experimental conditions such as the Hartmann-Hahn mismatch. It has been found that the usual theories of CP are incorrect, and that the CP process is very heterogeneous in nature. This has significant implications on methods typically used in quantifying {sup 13}C CPMAS spectra of coals. 19 refs., 11 figs.

Zilm, K.W.

1989-01-01

247

Rock Art Interpretation within Indiana MAS Viviana Mascardi1  

E-print Network

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

Mascardi, Viviana

248

Solid state NMR of a molecular self-assembly: multinuclear approach to the cyanuric acid-melamine system.  

PubMed

[see structure]. Trinuclear MAS NMR, involving naturally abundant (13C, 15N) and easily deuterated (2H) nuclei, is shown to offer newer opportunities to study molecular self-assembly in noncrystalline supramolecular systems. PMID:11405745

Damodaran, K; Sanjayan, G J; Rajamohanan, P R; Ganapathy, S; Ganesh, K N

2001-06-14

249

13 C CP\\/MAS nuclear magnetic resonance study of the peroxide bleaching of ultra high yield chemimechanical pulp produced from sound and spruce budworm killed balsam fir  

Microsoft Academic Search

Summary The chemimechanical pulping (CMP) of sound balsam fir and the subsequent peroxide bleaching of the CMP pulp were investigated using solid state 13C CP\\/MAS NMR. A parallel study was made of a CMP pulp produced from spruce budworm killed balsam fir. Changes in the lignin and hemicellulose components were readily evident. The residual lignin and carbohydrate macromolecules in dead

J. M. Willis; F. G. Herring

1987-01-01

250

NMR spectroscopy  

SciTech Connect

In a method of heteronuclear decoupling in high resolution pulsed NMR spectroscopy, during acquisition of signals emanating from a nuclear species to be observed (e.g. carbon-13), irradiation of an interfering nuclear species (e.g. protons) is effected by means of a train of composite pulses, each of which approximately inverts the longitudinal magnetization. The pulses are of two types respectively having opposite R.F. phases, and the train constitutes a repeated sequence which consists of 2 /SUP N/ /sup +1/ pulses of each type (where N is a positive integer) and which has a form chosen in accordance with specific rules to ensure effective decoupling.

Levitt, M.H.; Frenkiel, Th.A.

1984-09-04

251

The Basics of NMR  

NSDL National Science Digital Library

This resource is an online textbook containing information about Nuclear Magnetic Resonance (NMR). Information inlcudes mathhematics of NMR, spin physics, Spectroscopy, pulse sequences, and NMR hardware. The "Practical Considerations" chapter emphasizes spectroscopic techniques.

Hornak, Joseph

2003-10-10

252

Analysis of cement/waste mixtures with solid-state NMR spectroscopy  

SciTech Connect

We have used solid-state {sup 2}H and {sup 13}C NMR spectroscopy to study the interaction of phenol with portland cement as a function of cure, loading, and hydration. The {sup 2}H NMR of deuterated phenol is used to follow the microscopic dynamics of a phenoxide ion: typically half of the phenoxide ions are freely mobile and half undergo restricted motion, which indicates bonding to the cement matrix. The {sup 13}C NMR, both CP/MAS sideband analysis and static hole-burning NMR, is consistent with this analysis. A new low-temperature, 18 Tesla field-swept NMR has been used to obtain {sup 27}Al NMR resonances that are otherwise difficult to obtain with conventional NMR methods, unfortunately, the resonance is rather featureless at 4.2 K, thus indicating a critical need for VT field-swept NMR.

Cartledge, F.K.; Butler, L.G. [Louisiana State Univ., Baton Rouge, LA (United States)

1995-12-31

253

Resolving the Asteroid Belt of HR 8799  

Microsoft Academic Search

In 2008, three orbiting planets were discovered and confirmed around HR8799 marking it as the first imaged extra solar planetary system with multiple planets. There are many similarities between HR8799 and our Solar System. IRAS and ISO detected a Kuiper belt around this star based on far infrared dust excess and Spitzer IRS spectroscopy revealed a separate population of warmer

Inseok Song; Christian Marois; Jennier Patience; Ben Zuckerman; Bruce Macintosh; Travis Barman; David Lafrenier; Rene Doyon

2009-01-01

254

HR-MAS MRS of the pancreas reveals reduced lipid and elevated lactate and taurine associated with early pancreatic cancer.  

PubMed

The prognosis for patients with pancreatic cancer is extremely poor, as evidenced by the disease's five-year survival rate of ~5%. New approaches are therefore urgently needed to improve detection, treatment, and monitoring of pancreatic cancer. MRS-detectable metabolic changes provide useful biomarkers for tumor detection and response-monitoring in other cancers. The goal of this study was to identify MRS-detectable biomarkers of pancreatic cancer that could enhance currently available imaging approaches. We used (1) H high-resolution magic angle spinning MRS to probe metabolite levels in pancreatic tissue samples from mouse models and patients. In mice, the levels of lipids dropped significantly in pancreata with lipopolysaccharide-induced inflammation, in pancreata with pre-cancerous metaplasia (4 week old p48-Cre;LSL-Kras(G12D) mice), and in pancreata with pancreatic intraepithelial neoplasia, which precedes invasive pancreatic cancer (8 week old p48-Cre LSL-Kras(G12D) mice), to 26 ± 19% (p = 0.03), 19 ± 16% (p = 0.04), and 26 ± 10% (p = 0.05) of controls, respectively. Lactate and taurine remained unchanged in inflammation and in pre-cancerous metaplasia but increased significantly in pancreatic intraepithelial neoplasia to 266 ± 61% (p = 0.0001) and 999 ± 174% (p < 0.00001) of controls, respectively. Importantly, analysis of patient biopsies was consistent with the mouse findings. Lipids dropped in pancreatitis and in invasive cancer biopsies to 29 ± 15% (p = 0.01) and 26 ± 38% (p = 0.02) of normal tissue. In addition, lactate and taurine levels remained unchanged in inflammation but rose in tumor samples to 244 ± 155% (p = 0.02) and 188 ± 67% (p = 0.02), respectively, compared with normal tissue. Based on these findings, we propose that a drop in lipid levels could serve to inform on pancreatitis and cancer-associated inflammation, whereas elevated lactate and taurine could serve to identify the presence of pancreatic intraepithelial neoplasia and invasive tumor. Our findings may help enhance current imaging methods to improve early pancreatic cancer detection and monitoring. PMID:25199993

Wang, Alan S; Lodi, Alessia; Rivera, Lee B; Izquierdo-Garcia, Jose L; Firpo, Matthew A; Mulvihill, Sean J; Tempero, Margaret A; Bergers, Gabriele; Ronen, Sabrina M

2014-11-01

255

HertzsprungâRussell (H-R) Diagrams  

NSDL National Science Digital Library

The HertzsprungâRussell (H-R) Diagrams model simulates HertzsprungâRussell (HR or H-R) diagram for groups of stars. The diagram is a scatter plot of steller luminosity vs. stellar temperature. The luminosity of stars is proportional to the star's radius squared and its temperature to the fourth power, and for Main Sequence stars, their luminosity is also proportional to their mass to the 3.5 power. Since the range of stellar luminosities and stellar temperatures is so large, the plot uses a log-log scale. The diagram is a way to understand stellar evolution. The HR diagram shows nearby stars, bright stars, and a user-defined star. One can also show the blackbody radiation curve and the user-defined star. The radius of the user-defined star (in Rsun) and the temperature of the user-defined star in Kelvin (5780 K is Tsun) can be changed.

Belloni, Mario

2010-11-11

256

Structural characterization of water-bearing silicate and aluminosilicate glasses by high-resolution solid-state NMR  

E-print Network

-resolution solid-state NMR Eric Robert1, , a , Alan Whittington2, , a, , b , Franck Fayona , Michel Pichavantc-resolution solid-state NMR techniques have been applied to hydrous silicate and aluminosilicate glasses: simple acquisition, cross-polarization (CP-MAS), heteronuclear correlation (HETCOR), dipolar dephasing, spin counting

Boyer, Edmond

257

On the period of HR 1362  

SciTech Connect

Photoelectric UBV observations, made in 1981 and 1982, of the active star HR 1362, are presented. A period analysis reveals many (all greater than 100 days) probable periods because of the large gaps in the data. If the most probable period around 330 d is true and represents the rotation period, as it does in all other active stars, then HR 1362 would be an extreme case of slow rotation. 11 refs.

Derman, E.; Demircan, O.; Ozeren, F.F. (Ankara Univ. (Turkey))

1989-07-01

258

Variable stars across the observational HR diagram  

Microsoft Academic Search

An overview of pulsating variable stars across the observational Hertzprung-Russel (HR) diagram is presented, together with a summary of their global properties. The HR diagram is presented with a third colour-coded dimension, visualizing the fraction of variable, the amplitude of variability or the period of variability. The distribution of variable stars in the other observational diagrams, such as the Period-Amplitude

Laurent Eyer; Nami Mowlavi

2008-01-01

259

Quantitative analysis of backbone motion in proteins using MAS solid-state NMR spectroscopy  

Microsoft Academic Search

We present a comprehensive analysis of protein dynamics for a micro-crystallin protein in the solid-state. Experimental data\\u000a include 15N T\\u000a 1 relaxation times measured at two different magnetic fields as well as 1H–15N dipole, 15N CSA cross correlated relaxation rates which are sensitive to the spectral density function J(0) and are thus a measure of T\\u000a 2 in the solid-state.

Veniamin Chevelkov; Uwe Fink; Bernd Reif

2009-01-01

260

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

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 ...

Aluas, Mihaela

261

Combined zero-quantum and spin-diffusion mixing for efficient homonuclear correlation spectroscopy under fast MAS: broadband recoupling and detection of long-range correlations.  

PubMed

Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35-40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD-RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD-RFDR sequences experimentally on a U-(13)C,(15)N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD-RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD-RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD-RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD-RFDR experiment is beneficial in a broad range of conditions, including both high and moderate MAS frequencies and magnetic fields. PMID:25420598

Lu, Xingyu; Guo, Changmiao; Hou, Guangjin; Polenova, Tatyana

2015-01-01

262

The thymus of the hairless rhino-j (hr/hr-j) mice  

PubMed Central

The hairless (hr) gene is expressed in a large number of tissues, primarily the skin, and a mutation in the hr gene is responsible for the typical cutaneous phenotype of hairless mice. Mutant hr mouse strains show immune defects involving especially T cells and macrophages, as well as an age-related immunodeficiency and an accelerated atrophy of the thymus. These data suggest that the hr mutation causes a defect of this organ, although hr transcripts have not been detected in fetal or adult mice thymus. The present study analyses the thymus of young (3 mo) and adult (9 mo) homozygous hr-rh-j mice (a strain of hairless mice) by means of structural techniques and immunohistochemistry to selectively identify thymic epithelial cells, dendritic cells, and macrophages. There were structural alterations in the thymus of both young and adult rh-rh-j mice, which were more severe in older animals. These alterations consisted of relative cortical atrophy, enlargement of blood vessels, proliferation of perivascular connective tissue, and the appearance of cysts. hr-rh-j mice also showed a decrease in the number of epithelial and dendritic cells, and macrophages. Taken together, present results strongly suggest degeneration and accelerated age-dependent regression of the thymus in hr-rh-j mice, which could explain at least in part the immune defects reported in hairless mouse strains. PMID:11327202

SAN JOSE, I.; GARCÍA-SUÁREZ, O.; HANNESTAD, J.; CABO, R.; GAUNA, L.; REPRESA, J.; VEGA, J. A.

2001-01-01

263

Variable stars across the observational HR diagram  

E-print Network

An overview of pulsating variable stars across the observational Hertzprung-Russel (HR) diagram is presented, together with a summary of their global properties. The HR diagram is presented with a third colour-coded dimension, visualizing the fraction of variable, the amplitude of variability or the period of variability. The distribution of variable stars in the other observational diagrams, such as the Period-Amplitude diagram, is also presented. Some of the progresses performed in the field of variable stars during the last decade are briefly summarized, and future projects that will improve our knowledge of variable stars are mentioned.

Laurent Eyer; Nami Mowlavi

2007-12-21

264

Fundamentals of NMR  

NSDL National Science Digital Library

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

James, Thomas L.

2011-03-30

265

Solid-State NMR Examination of Alteration Layers on a Nuclear Waste Glasses  

SciTech Connect

Solid-state NMR is a powerful tool for probing the role and significance of alteration layers in determining the kinetics for the corrosion of nuclear waste glass. NMR methods are used to probe the chemical structure of the alteration layers to elucidate information about their chemical complexity, leading to increased insight into the mechanism of altered layer formation. Two glass compositions were examined in this study: a glass preliminarily designed for nuclear waste immobilization (called AFCI) and a simplified version of this AFCI glass (which we call SA1R). Powdered glasses with controlled and known particles sizes were corroded at 90 °C for periods of one and five months with a surface-area to solution-volume ratio of 100,000 m-1. 1H-29Si CP-CPMG MAS NMR, 1H-27Al CP-MAS NMR, 1H-11B CP-MAS NMR, and 1H-23Na CP-MAS NMR experiments provide isolated structural information about the alteration layers, which differ in structure from that of the pristine glass. Both glasses studied here develop alteration layers composed primarily of [IV]Si species. Aluminum is also retained in the alteration layers, perhaps facilitated by the observed increase in coordination from [IV]Al to [VI]Al, which correlates with a loss of charge balancing cations. 1H-11B CP-MAS NMR observations indicated a retention of boron in hydrated glass layers, which has not been characterized by previous work. For the AFCI glass, secondary phase formation begins during the corrosion times considered here, and these neophases are detected within the alteration layers. We identify precursor phases as crystalline sodium metasilicates. An important finding is that layer thickness depends on the length of the initial alteration stages and varies only with respect to silicon species during the residual rate regime.

Murphy, Kelly A. [Penn State Univ., State College, PA (United States). Dept. of Chemistry; Washton, Nancy M. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Science Lab.; Ryan, Joseph V. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Pantano, Carlo G. [Penn State Univ., State College, PA (United States). Dept. of Materials Science and Engineering; Mueller, Karl T. [Penn State Univ., State College, PA (United States). Dept. of Chemistry; Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Science Lab.

2013-06-01

266

Advanced NMR approaches in the characterization of coal. [Quarterly] report No. 9  

SciTech Connect

A considerable effort in this project during the past few months has been focussed on the development of {sup 1}H and {sup 13}C NMR imaging techniques to yield spatially-resolved chemical shift (structure) information on coal. In order to yield the chemical shift information, a solid-state NMR imaging technique must include magic-angle spinning, so rotating gradient capabilities are indicated. A {sup 13}C MAS imaging probe and a {sup 1}H MAS imaging probe and the circuitry necessary for rotating gradients have been designed and constructed. The {sup 1}H system has already produced promising preliminary results, which are briefly described in this report.

Maciel, G.E.

1992-12-31

267

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

E-print Network

/y-alumina and subsequently evacuated. 25 "C Bloch Decay/MAS NMR spectra of cyclohexane adsorbed onto 10%Pt/y-alumina. 27 FT mass spectra taken at a field strength of 3-Tesla. 28 CAVERN uC CP/MAS NMR spectra of an overpressure of acetylene on 10%Pt/y-alumina adsorbed... pumped two-section ion cell, an Extrel 2001 data system, and a 3-Tesla Oxford superconducting magnet. ~~ Samples were introduced into the cell by a variable leak valve (at sample pressure of 4 x 10' torr). Ionization was performed by electron impact...

Lambregts, Marsha Jo Lupher

2012-06-07

268

Local structure in perovskite relaxor ferroelectrics: high-resolution 93Nb 3QMAS NMR  

Microsoft Academic Search

Solid solutions of (1-x)Pb(Mg1\\/3Nb2\\/3)O3xPb(Sc1\\/2Nb1\\/2)O3 (PMN\\/PSN) have been investigated using high-resolution 93Nb 3-quantum magic-angle spinning nuclear magnetic resonance experiments (3QMAS NMR). In previous MAS NMR investigations, the local B-cation ordering in these relaxor ferroelectric solid solutions was quantitatively determined. However, in conventional one-dimensional MAS spectra the effects of chemical shifts and quadrupole interaction are convoluted; this, in addition to the insufficient

Donghua H. Zhou; Gina L. Hoatson; Robert L. Vold

2004-01-01

269

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...

270

Multiple-quantum cross-polarization and two-dimensional MQMAS NMR of quadrupolar nuclei.  

PubMed

Cross-polarization from (1)H to the multiple-quantum coherences of a quadrupolar nucleus is used in combination with the two-dimensional multiple-quantum magic angle spinning (MQMAS) NMR experiment in order to extract high-resolution CPMAS NMR spectra. The technique is demonstrated on (23)Na (S = 3/2), (17)O, (27)Al (both S = 5/2), and (45)Sc (S = 7/2) nuclei, showing the applicability of multiple-quantum cross-polarization to systems with differing spin quantum number, gyromagnetic ratio, and relative nuclide abundance. The utility of this two-dimensional MAS NMR experiment for spectral editing and site-specific measurement of cross-polarization intensities is demonstrated. The possibility of direct cross-polarization to higher order multiple-quantum coherences is also considered and three-, five-, and seven-quantum cross-polarized (45)Sc MAS NMR spectra are presented. PMID:11097815

Ashbrook, S E; Wimperis, S

2000-12-01

271

PERFORMANCE-LED HR Talent Management  

E-print Network

CPHR CENTRE FOR PERFORMANCE-LED HR Talent Management: Time To Question The Tablets of Stone? White 2. What Is Talent Management? Four Philosophies 3 The Key People Approach: Talent Management As A Categorisation Of People 4 The Key Practices Approach: Talent Management As The Presence Of Key HRM Practices 7

Meju, Max

272

EMPLOYMENT EQUITY University Policy No: HR6100  

E-print Network

Page 1 EMPLOYMENT EQUITY University Policy No: HR6100 Classification: Human Resources Approving of diverse backgrounds and needs, and which provides equitable access to employment opportunities of a job. 4.00 Designated Groups as defined in the Employment Equity Act and Federal Contractors Program

Victoria, University of

273

The granulation boundary in the HR diagram  

Microsoft Academic Search

A granulation boundary in the H-R diagram is found. The boundary runs smoothly from spectral type G1 Ib to near F0 on the main sequence. On the cool side of the boundary, the spectral line bisectors are of the classical type associated with granulation. On the hot side the bisectors show a reversed slope and curvature indicative of some other

David F. Gray; Thomas Nagel

1989-01-01

274

Synthetic HR-diagrams for massive stars  

Microsoft Academic Search

Observations of luminous stars are compared to synthetic HR diagrams generated from three sets of evolutionary models with different treatment of mass loss, convective overshoot, and considering or not variations in the opacity due to heavy elements. We take into account also different values for the slope of the initial mass function, and the possibility that a fraction of the

E. Nasi; C. Forieri

1990-01-01

275

PeopleSoft HR ECR Automation Process  

E-print Network

Term Disability with Pay ECR Search Page To process a Short Term Disability using the automated ECR. 2. Enter the Effective Date of the Short Term Disability. This is the Effective DatePeopleSoft HR ECR Automation Process Short Term Disability with Pay May 2011 #12;Processing a Short

Huang, Jianyu

276

NMR characterization of synthetic and modified aluminum orthophosphates  

Microsoft Academic Search

³¹P, ²⁷Al, and ¹H MAS-NMR spectra of aluminum phosphates (Al\\/P = 1), obtained from different salts (nitrate, chloride, and sulfate) have been analyzed. Thermal treatment of samples results in the transformation of amorphous into crystalline AlPOâ samples (tridymite or α-cristobalite polymorphs). Structural changes induced by thermal treatments or incorporation of foreign ions (Li{sup +}, F⁻, or SOâ²⁻) are also analyzed

J. Sanz; J. M. Campelo; J. M. Marinas

1991-01-01

277

New insights into the bonding arrangements of L- and D-glutamates from solid state 17O NMR  

NASA Astrophysics Data System (ADS)

Magic angle spinning (MAS) from L- and D-glutamic acid-HCl at 14.1 T produces highly structured and very similar NMR spectra. Lines from all 4 oxygen sites are readily distinguished and assigned. These 17O NMR spectra are very different from the previously reported 17O spectrum of the D, L-form presumably because that was a racemic crystal. 17O NMR from L-monosodium glutamate-HCl is very different again requiring the application of double angle rotation and 3 quantum MAS NMR to provide resolution of 5 different sites. Hence high resolution 17O solid state NMR techniques offer possible new insight into biochemical bonding processes.

Lemaitre, V.; Pike, K. J.; Watts, A.; Anupold, T.; Samoson, A.; Smith, M. E.; Dupree, R.

2003-03-01

278

Influence of heteronuclear dipolar interactions on magic angle spinning NMR spectra of solids containing isolated three-spin systems  

NASA Astrophysics Data System (ADS)

Average Hamiltonian theory (AHT) is used to predict magic angle spinning (MAS) NMR spectra arising from isolated three-spin (I = 1/2) systems consisting of two crystallographically equivalent spins (A and A') and a third heteronuclear spin (X). Under conditions of rapid sample spinning, the theory predicts the AA' region of the MAS NMR spectra to consist of two equally intense peaks separated by the heteronuclear indirect spin-spin coupling constant JAX = JA'X, analogous to the situation in solution NMR studies. However, under slow spinning conditions the theory indicates a general eight-peak MAS spectrum for the AA' region. Furthermore, it is shown that the two A-spin sub-spectra which arise from the two allowed spin states of X (mX = ±1/2) are different in that one is 'squeezed' while the other is 'stretched'. Qualitatively, the heteronuclear dipolar interactions between the X spin and the crystallographically equivalent spins are responsible for the different A-spin sub-spectra associated with mX = +1/2 and mX = -1/2. In accord with theory, the 199Hg satellite peaks observed in 31P MAS NMR spectra of Hg(PPh3)2(NO3)2 (A, A' = 31P; X = 199Hg) depend on the spin state of the 199Hg nucleus. In contrast, the heteronuclear dipolar interaction does not contribute to the linewidths observed in MAS NMR spectra of heteronuclear two-spin systems.

Wu, Gang; Wasylishen, Roderick E.

279

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

HR System Access Request Form Security Administration, Human Resources (HR) For additional instructions and information, log onto http://hr.vanderbilt.edu/security/ Home Department VUnet IDHR Employee the user have an e-password? (e-password is required for system access) Yes No Access Information Action

Simaan, Nabil

280

THE CHARA ARRAY ANGULAR DIAMETER OF HR 8799 FAVORS PLANETARY MASSES FOR ITS IMAGED COMPANIONS  

SciTech Connect

HR 8799 is an hF0 mA5 {gamma} Doradus-, {lambda} Bootis-, Vega-type star best known for hosting four directly imaged candidate planetary companions. Using the CHARA Array interferometer, we measure HR 8799's limb-darkened angular diameter to be 0.342 {+-} 0.008 mas (an error of only 2%). By combining our measurement with the star's parallax and photometry from the literature, we greatly improve upon previous estimates of its fundamental parameters, including stellar radius (1.44 {+-} 0.06 R{sub Sun }), effective temperature (7193 {+-} 87 K, consistent with F0), luminosity (5.05 {+-} 0.29 L{sub Sun }), and the extent of the habitable zone (HZ; 1.62-3.32 AU). These improved stellar properties permit much more precise comparisons with stellar evolutionary models, from which a mass and age can be determined, once the metallicity of the star is known. Considering the observational properties of other {lambda} Bootis stars and the indirect evidence for youth of HR 8799, we argue that the internal abundance, and what we refer to as the effective abundance, is most likely near solar. Finally, using the Yonsei-Yale evolutionary models with uniformly scaled solar-like abundances, we estimate HR 8799's mass and age considering two possibilities: 1.516{sup +0.038}{sub -0.024} M{sub Sun} and 33{sup +7}{sub -13.2} Myr if the star is contracting toward the zero-age main sequence or 1.513{sup +0.023}{sub -0.024} M{sub Sun} and 90{sup +381}{sub -50} Myr if it is expanding from it. This improved estimate of HR 8799's age with realistic uncertainties provides the best constraints to date on the masses of its orbiting companions, and strongly suggests they are indeed planets. They nevertheless all appear to orbit well outside the HZ of this young star.

Baines, Ellyn K. [Remote Sensing Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); White, Russel J.; Jones, Jeremy; Boyajian, Tabetha; McAlister, Harold A.; Ten Brummelaar, Theo A.; Turner, Nils H.; Sturmann, Judit; Sturmann, Laszlo; Goldfinger, P. J.; Farrington, Christopher D.; Riedel, Adric R. [Center for High Angular Resolution Astronomy, Georgia State University, P.O. Box 3969, Atlanta, GA 30302-3969 (United States); Huber, Daniel [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Ireland, Michael [Department of Physics and Astronomy, Macquarie University, New South Wales, NSW 2109 (Australia); Von Braun, Kaspar [NASA Exoplanet Science Institute, California Institute of Technology, 770 S. Wilson Ave., MS 100-22, Pasadena, CA 91125-2200 (United States); Ridgway, Stephen T., E-mail: ellyn.baines@nrl.navy.mil [Kitt Peak National Observatory, National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726-6732 (United States)

2012-12-10

281

Solid State NMR Studies of the Aluminum Hydride Phases  

NASA Technical Reports Server (NTRS)

Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.

Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.

2006-01-01

282

High-Temperature Steam-Treatment of PBI, PEKK, and a PEKK-PBI Blend: A Solid-State NMR and IR Spectroscopic Study  

E-print Network

High-Temperature Steam-Treatment of PBI, PEKK, and a PEKK-PBI Blend: A Solid-State NMR and IR-treated at 149 C (300 F) and 316 C (600 F). IR and solid- state NMR spectroscopy are used to study chemical angle spinning (CP/MAS) upon steam-treatment are reversible, and not of a chemical nature, indicating

Bluemel, Janet

283

Using a cross-coil to reduce RF heating by an order of magnitude in triple-resonance multinuclear MAS at high fields.  

PubMed

Four different coil designs for use with MAS in triple-resonance multi-nuclear experiments at high fields are compared, using a combination of finite element analysis (FEA) software and NMR experiments, with respect to RF field strength per unit power and relative sample heating, as governed by mean E/B(1) within the sample region. A commercial FEA package, Microwave Studio 5.1 by Computer Simulation Technology (CST) is shown to obtain remarkably accurate agreement with the experiments in Q(L), L, B, E, and mode frequencies in all cases. A simplified treatment of RF heating in NMR MAS samples is derived and shown to agree with the NMR experimental results within about 10% for two representative stator designs. The coil types studied include: (1) a variable-pitch solenoid outside a ceramic coilform, (2) a conventional solenoid very closely spaced to the MAS rotor, (3) a scroll coil, and (4) a segmented saddle cross coil (XC) for (1)H with an additional solenoid over it for the two lower-frequency channels. The XC/solenoid is shown to offer substantial advantages in reduced decoupler heating, improved S/N, and improved compatibility with multinuclear tuning and high-power decoupling. This seems largely because the division of labor between two orthogonal coils allows them each, and their associated circuitry, to be separately optimized for their respective regimes. PMID:16860580

Doty, F David; Kulkarni, Jatin; Turner, Christopher; Entzminger, George; Bielecki, Anthony

2006-10-01

284

HR4049: signature of nova nucleosynthesis?  

NASA Astrophysics Data System (ADS)

The post-Asymptotic Giant Branch (AGB) star HR4049 is in an eccentric binary system with a relatively short period probably surrounded by a dusty circumbinary disk. Extremely anomalous oxygen isotopic ratios, 16O/17O ?16O/18O ? 7, have been measured from CO2 molecules likely residing in the disk. Such a composition cannot be explained in the framework of AGB and post-AGB evolution while it can be qualitatively associated with the nucleosynthesis occurring during nova outbursts. We discuss nova models, the presence of a white dwarf companion to HR4049 and possible scenarios for the dynamical evolution of this binary system. Circumbinary disks in which mixing occurs between redgiant and nova material may also be invoked as the site of formation of some rare types of meteoritic presolar grains.

Lugaro, M.; Pols, O.; Karakas, A. I.; Tout, C. A.

2005-07-01

285

THE DEBRIS DISK AROUND HR 8799  

SciTech Connect

We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T approx 150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T approx 45 K) with a sharp inner edge orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.

Su, K. Y. L.; Rieke, G. H.; Smith, P. S.; Misselt, K. A. [Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States); Stapelfeldt, K. R.; Bryden, G. [JPL/Caltech, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Malhotra, R. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Moro-Martin, A. [Department of Astrophysical Science, Princeton University, Princeton, NJ 08544 (United States); Williams, J. P., E-mail: ksu@as.arizona.ed [Institute for Astronomy, University of Hawaii (United States)

2009-11-01

286

Instability regions in the upper HR diagram  

Microsoft Academic Search

The following instability regions for blueward evolving-supergiants are outlined and compared. (1) Areas in the Hertzsprung-Russell (HR) diagram where stars are dynamically unstable. (2) Areas where the effective acceleration in the upper part of the photospheres is negative, hence directed outward. (3) Areas where the sonic points of the stellar winds (where vwind=vsound) are situated inside the photospheres, at a

Cornelis de Jager; Alex Lobel; Hans Nieuwenhuijzen; Richard Stothers

2001-01-01

287

Steps toward a radio HR diagram  

Microsoft Academic Search

We discuss the possibility of establishing a set of observational parameters for radio galaxies which could be used to study radio source evolution in the same way that the Hertzsprung-Russell diagram is used to understand stellar evolution. As a first step towards a radio H-R diagram, we show that the FRI\\/II break is a function of both radio and optical

Frazer Owen

288

AXEL HALL, LEKTOR VISKIPTADEILD | FYRIRLESTRAMARAON HR  

E-print Network

;www.hr.is 65 70 75 80 85 90 95 -4 0 4 8 12 Belief in women's right to work and hours worked Beliefin women's right to a job (%) Difference between actual and predicted hours Denmark Finland Iceland Norway mann OECD gögn 1.300 1.400 1.500 1.600 1.700 1.800 1.900 2.000 2.100 2.200 1970 1972 1974 1976 1978

Karlsson, Brynjar

289

Nonthermal Radio Emission and the HR Diagram  

NASA Technical Reports Server (NTRS)

Perhaps the most reliable indicator of non-radiative heating/momentum in a stellar atmosphere is the presence of nonthermal radio emission. To date, 77 normal stellar objects have been detected and identified as nonthermal sources. These stellar objects are tabulated herein. It is apparent that non-thermal radio emission is not ubiquitous across the HR diagram. This is clearly the case for the single stars; it is not as clear for the binaries unless the radio emission is associated with their late-type components. Choosing to make this association, the single stars and the late-type components are plotted together. The following picture emerges: (1) there are four locations on the HR diagram where non-thermal radio stars are found; (2) the peak incoherent 5 GHz luminosities show a suprisingly small range for stars within each class; (3) the fraction of stellar energy that escapes as radio emission can be estimated by comparing the integrated maximum radio luminosity to the bolometric luminosity; (4) there are no apparent differences in L sub R between binaries with two cool components, binaries with one hot and one cool component, and single stars for classes C and D; and (5) The late-type stars (classes B, C, and D) are located in parts of the HR diagram where there is reason to suspect that the surfaces of the stars are being braked with respect to their interiors.

Gibson, D. M.

1985-01-01

290

Instability Regions in the Upper HR Diagram  

NASA Technical Reports Server (NTRS)

The following instability regions for blueward evolving supergiants are outlined and compared: (1) Areas in the Hertzsprung-Russell(HR) diagram where stars are dynamically unstable. (2) Areas where the effective acceleration in the upper part of the photospheres is negative, hence directed outward. (3) Areas where the sonic points of the stellar wind (Where wind velocity = sound velocity) are situated inside the photospheres, at a level deeper than tau(sub Ross) = 0.01. We compare the results with the positions of actual stars in the HR diagram and we find evidence that the recent strong contraction of the yellow hypergiant HR8752 was initiated in a period during which (g(sub eff)) is less than 0, whereupon the star became dynamically unstable. The instability and extreme shells around IRC+10420 are suggested to be related to three factors: (g(sub eff)) is less than 0; the sonic point is situated inside the photosphere; and the star is dynamically unstable.

deJager, Cornelis; Lobel, Alex; Nieuwenhuijzen, Hans; Stothers, Richard; Hansen, James E. (Technical Monitor)

2001-01-01

291

Bispectrum speckle interferometry of the Orion Trapezium stars: detection of a close (33 mas) companion of ?1 Ori C  

NASA Astrophysics Data System (ADS)

We present bispectrum speckle interferometry observations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-limited images with an unprecedented resolution ?/D of 57 mas and 76 mas were obtained in the H- and K-band, respectively. The H and K images of ?1 Ori C (the star responsible for the proplyds) show for the first time that ?1 Ori C is a close binary with a separation of only ~ 33 mas (H-band observation). The sub-arcsecond companions of ?1 Ori A and ?1 Ori B reported by Petr et al. (1998) are confirmed. We use the magnitudes and colors of the companions to derive information about their stellar properties from the H-R diagram. In addition we briefly discuss the multiplicity of the Trapezium stars. Considering both, the visual and spectroscopic companions of the 4 Trapezium stars, it has been found that there are at least 7 companions, i.e. at least 1.75 companions per primary on average. This number is clearly higher than that found for the low-mass stars in the Orion Nebula cluster as well as in the field population. This suggests that the mechanisms operative in the formation of high-mass multiple systems in the dense Trapezium cluster and of low-mass stars are different.

Balega, Yu. Yu.; Weigelt, G.; Preibish, T.; Zinnecker, H.

292

Bispectrum speckle interferometry of the Orion Trapezium stars: detection of a close (33 mas) companion of Theta^1Ori C  

NASA Astrophysics Data System (ADS)

We present bispectrum speckle interferometry observations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-limited images with an unprecedented resolution lambda/D of 57 mas and 76 mas were obtained in the H- and K-band, respectively. The H and K images of Theta^1Ori C (the star responsible for the proplyds) show for the first time that Theta^1Ori C is a close binary with a separation of only ~33 mas (H-band observation). The sub-arcsecond companions of Theta^1Ori A and Theta^1Ori B reported by Petr et al. (1998) are confirmed. We use the magnitudes and colors of the companions to derive information about their stellar properties from the HR-diagram and find them to be intermediate- or low-mass pre-main sequence stars. In addition we briefly discuss the multiplicity of the Trapezium stars. Considering both, the visual and the spectroscopic companions of the 4 Trapezium stars, there are at least 7 companions, i.e. at least 1.75 companions per primary on average. This number is clearly higher than that found for the low-mass stars in the Orion Nebula cluster as well as in the field population. This suggests that a different mechanism is at work in the formation of high-mass multiple systems in the dense Trapezium cluster than for low-mass stars.

Weigelt, Gerd; Preibisch, Thomas; Schertl, Dieter; Balega, Yuri; Zinnecker, Hans

293

Bispectrum speckle interferometry of the Orion Trapezium stars: detection of a close (33 mas) companion of Theta (1) ORI C  

NASA Astrophysics Data System (ADS)

We present bispectrum speckle interferometry observations with the SAO 6 m telescope of the four brightest stars in the Orion Trapezium. Diffraction-limited images with an unprecedented resolution lambda /D of 57 mas and 76 mas were obtained in the H- and K-band, respectively. The H and K images of Theta (1) Ori C (the star responsible for the proplyds) show for the first time that Theta (1) Ori C is a close binary with a separation of only ~ 33 mas (H-band observation). The sub-arcsecond companions of Theta (1) Ori A and Theta (1) Ori B reported by Petr et al. (1998) are confirmed. We use the magnitudes and colors of the companions to derive information about their stellar properties from the HR-diagram. In addition we briefly discuss the multiplicity of the Trapezium stars. Considering both, the visual and the spectroscopic companions of the 4 Trapezium stars, there are at least 7 companions, i.e. at least 1.75 companions per primary on average. This number is clearly higher than that found for the low-mass stars in the Orion Nebula cluster as well as in the field population. This suggests that a different mechanism is at work in the formation of high-mass multiple systems in the dense Trapezium cluster than for low-mass stars. Based on data collected at the SAO 6~m telescope in Russia.

Weigelt, Gerd; Balega, Yuri; Preibisch, Thomas; Schertl, Dieter; Schöller, Markus; Zinnecker, Hans

1999-07-01

294

High-Temperature Steam-Treatment of PBI, PEEK, and PEKK Polymers with H2O and D2O: A Solid-State NMR Study  

E-print Network

-treatment with D2O at 315 °C (top). Figure S7. 13 C CP/MAS NMR spectra of melt-molded PEKK as received (a), after-State NMR Study Jacqueline C. Pope,a Hung-Jue Sue,b Tim Bremner,b,c * Janet Blümela, * a Department-treatment with D2O at 150 °C and 315 °C. Figure S4. 2 H MAS NMR spectrum of melt-molded PBI after steam- treatment

Bluemel, Janet

295

Solid-state NMR studies of theophylline co-crystals with dicarboxylic acids.  

PubMed

In this work, three polycrystalline materials containing co-crystals of theophylline with malonic, maleic, and glutaric acids were studied using (13)C, (15)N and (1)H solid-state NMR and FT-IR spectroscopy. The NMR assignments were supported by gauge including projector augmented waves (GIPAW) calculations of chemical shielding, performed using X-ray determined geometry. The experimental (13)C cross polarization/magic angle spinning (CP/MAS) NMR results and the calculated isotropic chemical shifts were in excellent agreement. A rapid and convenient method for theophylline co-crystals crystal structure analysis has been proposed for co-crystals, which are potentially new APIs. PMID:25194346

Pindelska, Edyta; Sokal, Agnieszka; Szeleszczuk, Lukasz; Pisklak, Dariusz Maciej; Kolodziejski, Waclaw

2014-11-01

296

Measurement of long-range interatomic distances by solid-state tritium-NMR spectroscopy.  

PubMed

For the structural determination of a ligand bound to an amorphous macromolecular system, solid-state NMR can be used to provide interatomic distances. It is shown here that selective labeling in discrete locations with tritium enables accurate measurement of long-range distances owing to the high gyromagnetic ratio of this nucleus, without structural modification of the molecule. This approach gives access to the largest NMR distance ever measured between two nuclei (14.4 A). (3)H MAS NMR appears to be a promising tool for structural applications in the biological and material sciences. PMID:20092274

Yuen, Alexander K L; Lafon, Olivier; Charpentier, Thibault; Roy, Myriam; Brunet, Francine; Berthault, Patrick; Sakellariou, Dimitrios; Robert, Bruno; Rimsky, Sylvie; Pillon, Florence; Cintrat, Jean-Christophe; Rousseau, Bernard

2010-02-17

297

Understanding NMR Spectroscopy  

NSDL National Science Digital Library

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

Keeler, James

2011-04-15

298

Elemental analysis by NMR.  

PubMed

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

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

2012-11-01

299

Heteronuclear Recoupling in Solid-State Magic-Angle-Spinning NMR via Overtone Irradiation  

E-print Network

Heteronuclear Recoupling in Solid-State Magic-Angle-Spinning NMR via Overtone Irradiation Sungsool undergoing magic-angle- spinning (MAS) is introduced, based on the overtone irradiation of one of the coupled nuclei. It is shown that when I is a quadrupole, for instance 14N, irradiating this spin at a multiple

Frydman, Lucio

300

Multidimensional solid-state NMR studies of the structure and dynamics of pectic  

E-print Network

-angle-spinning (MAS) solid-state NMR (SSNMR) to investigate the structural role of pectins in the plant CW. Intact of pectin signals, confirming partial pectin removal by chelating agents and sodium carbonate. Importantly of the primary CW with mobility and flexibility, which may be important for pectin functions. This study

Hong, Mei

301

Homonuclear NMR Correlations between Half-Integer Quadrupolar Nuclei Undergoing Magic-Angle Spinning  

E-print Network

-Angle Spinning Mattias Ede´n and Lucio Frydman* Chemical Physics Department, Weizmann Institute of Science, Reho-integer quadrupolar nuclei undergoing magic-angle-spinning (MAS). Various spin interactions that do not commute in the application of solid-state nuclear magnetic resonance (NMR) techniques on nuclei possessing a spin S > 1

Frydman, Lucio

302

RHODOPSIN-LIPID INTERACTIONS STUDIED BY NMR  

PubMed Central

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

Soubias, Olivier; Gawrisch, Klaus

2012-01-01

303

Evolution of HR Diagrams So as a cluster ages, the  

E-print Network

Evolution of HR Diagrams So as a cluster ages, the main sequence `burns down' in order. lifetime Diagram to Determine the Age of a Star Cluster #12;Evolution of HR Diagrams So as a cluster ages, the main of plotting stars, we represent them with a line of constant age. Using the H-R Diagram to Determine the Age

Barnes, Joshua Edward

304

The HR Diagram of Globular Clusters: Theorist' view(s)  

E-print Network

The HR Diagram of Globular Clusters: Theorist' view(s) F. D'Antona Osservatorio Astronomico di Roma, Italy Abstract: I list the characteristic features of Globular Cluster (GC) HR diagrams which provide by looking at the composite HR diagram of the GC NGC 6397 shown in figure 1, and illustrated in figure 2

D'Antona, Francesca

305

MAGNETIC FIELDS IN THE HR DIAGRAM Jeffrey L. Linsky  

E-print Network

MAGNETIC FIELDS IN THE HR DIAGRAM Jeffrey L. Linsky JILA/University of Colorado and NIST Solar. What are the consequences of this behavior in a dynamic atmosphere? 1 A Tour Through the HR Diagram of the HR Diagram. Questions to ask during our tour: ffl What direct or indirect techniques can measure

Linsky, Jeffrey L.

306

Changes in surface structure of sodium aluminoborosilicate glasses during aqueous corrosion analyzed by using NMR  

NASA Astrophysics Data System (ADS)

Aqueous corrosion tests were performed for aluminoborosilicate glasses with different Na contents at 90 °C for 20 days. Multi-nuclear solid-state nuclear magnetic resonance (NMR) techniques were employed to characterize the structures of the pristine and altered glasses. 11B magic-angle spinning (MAS) NMR spectra showed the same line shape for the pristine and altered glasses, indicating that B species such as BO3 and BO4 were released into the solution congruently with the same fraction during the static dissolution experiments. The reconstruction of Si on the glass surface as hydrated phases was confirmed by the 29Si MAS and 1H ?29Si cross-polarization magic-angle spinning NMR spectra of the altered glasses. 23Na MAS and triple-quantum magic-angle spinning NMR spectra showed that part of the Na released from pristine glasses was incorporated in the hydrated phases, which can be identified by a 23Na chemical shift at ?iso = - 3.3 ppm. The availability of these structural data by employing solid-state NMR techniques can provide a better understanding of the formation of the hydrated phases and the effect of dissolution behavior on the glass composition.

Ohkubo, Takahiro; Iwadate, Yasuhiko; Deguchi, Kenzo; Ohki, Shinobu; Shimizu, Tadashi

2015-02-01

307

Flow measurements by NMR  

Microsoft Academic Search

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,

A. Caprihan; E. Fukushima

1990-01-01

308

NMR Spectroscopy - Theory  

NSDL National Science Digital Library

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

Lord, J. R.

2011-06-30

309

Lectures on pulsed NMR  

SciTech Connect

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

Pines, A.

1988-08-01

310

NMR logging apparatus  

DOEpatents

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

Walsh, David O; Turner, Peter

2014-05-27

311

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

PubMed

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

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

2011-09-01

312

QUEEN MARY, UNIVERSITY OF LONDON MAS 314 Design of Experiments  

E-print Network

QUEEN MARY, UNIVERSITY OF LONDON MAS 314 Design of Experiments Assignment 10 For discussion on 20 available for the experiment. They are arranged in a 5 Ã? 5 rectangle. Construct a suitable design. 3 A road safety organization wishes to compare four makes of car-tyre. The organi- zation has four test cars

Bailey, R. A.

313

A generic negotiation model for MAS using XML  

Microsoft Academic Search

In this paper, we present a generic negotiation model for multi-agent systems (MAS), built in three levels: a communication level, a negotiation level and a strategic level, which is the only level specific to the application. XML files are used to configure the system, freeing the end-user with recompilations each time he wants to change a parameter. The aim of

Philippe Mathieu; Marie-h El Ene Verrons

2003-01-01

314

ASTM001/MAS423 Solar System Craig B. Agnor  

E-print Network

ASTM001/MAS423 Solar System Tides Craig B. Agnor Queen Mary, University of London April 17, 2008 constructively/destructively depending on orientation and phase of the Sun and Moon. And they have important and this results in energy loss and a phase shift in the tidal response of the planet. The specific or tidal

Agnor, Craig B.

315

THE MAS WHEAT PROJECT: IMPACT OF GENOMICS ON WHEAT BREEDING  

Technology Transfer Automated Retrieval System (TEKTRAN)

In 2001 twelve wheat breeding center and research laboratories formed a consortium designed to increase the use of marker assisted selection (MAS) in public wheat breeding programs. The strategy of the project is to introgress by backcrossing more than 23 disease resistance genes and 21 quality-rela...

316

Draft Genome Sequence of Geobacillus thermopakistaniensis Strain MAS1.  

PubMed

Geobacillus thermopakistaniensis strain MAS1 was isolated from a hot spring located in the Northern Areas of Pakistan. The draft genome sequence was 3.5 Mb and identified a number of genes of potential industrial importance, including genes encoding glycoside hydrolases, pullulanase, amylopullulanase, glycosidase, and alcohol dehydrogenases. PMID:24903880

Siddiqui, Masood Ahmed; Rashid, Naeem; Ayyampalayam, Saravanaraj; Whitman, William B

2014-01-01

317

Graduate trainee -Corporate HR The Corporate HR unit at Group level in Statkraft is responsible for Organisational development initiatives,  

E-print Network

and processes in Statkraft and the HR network. The Corporate HR unit consists of a team of five experienced HR of people, leadership, and competence in light of business strategy Strong analytical skills and learning at a strategic and practical level Fluent in English both written and orally ­ fluency in German, Spanish

Løw, Erik

318

NMR at the Picomole Level of a DNA Adduct  

PubMed Central

We investigate the limit of detection for obtaining NMR data of a DNA adduct using modern microscale NMR instrumentation, once the adduct has been isolated at the pmol level. Eighty nanograms (130 pmol) of a DNA adduct standard, N-(2?-deoxyguanosin-8-yl)-2-acetylaminofluorene 5?-monophosphate (AAF-dGMP), in 1.5 ?L of D2O with 10% methanol-d4, in a vial, was completely picked up as a droplet suspended in a fluorocarbon liquid, and loaded efficiently into a microcoil probe. This work demonstrates a practical manual method of droplet microfluidic sample loading, previously demonstrated using automated equipment, which provides a several-fold advantage over conventional flow injection. Eliminating dilution during injection and confining the sample into the observed volume realizes the full theoretical mass sensitivity of a microcoil, comparable to a micro-cryo probe. With 80 ng, an NMR spectrum acquired over 40 hr showed all of the resonances seen in a standard spectrum of AAF-dGMP, with a S/N of at least 10, despite broadening due to previously-noted effects of conformational exchange. Also a 2D TOCSY spectrum (total correlation spectroscopy) was acquired on 1.6 ?g in 18 hr. This work helps to define the utility of NMR in combination with other analytical methods for the structural characterization of a small amount of a DNA adduct. PMID:24028148

Kautz, Roger; Wang, Poguang; Giese, Roger W.

2014-01-01

319

High Resolution Magic Angle Spinning 1H-NMR Metabolic Profiling of Nanoliter Biological Tissues at High Magnetic Field  

SciTech Connect

It is demonstrated that a high resolution magic angle spinning 1H-NMR spectrum of biological tissue samples with volumes as small as 150 nanoliters, or 0.15 mg in weight, can be acquired in a few minutes at 21.1 T magnetic field using a commercial 1.6 mm fast-MAS probe with minor modification of the MAS rotor. The strategies of sealing the samples inside the MAS rotor to avoid fluid leakage as well as the ways of optimizing the signal to noise are discussed.

Feng, Ju; Hu, Jian Z.; Burton, Sarah D.; Hoyt, David W.

2013-03-05

320

Attitude Assessment Using Pleiades-Hr Capabilities  

NASA Astrophysics Data System (ADS)

Since SPOT1, the French national space centre (CNES) has worked on improving the geometry of Earth observation spacecrafts. The accuracy of sensor calibration is one of the main key points for any Earth observation application such as orthorectification, DEM generation or surface change detection. For the last twenty years CNES has developed two families of methods: absolute methods and relative methods. These methods are used to characterize a pushbroom acquisition along the detector line and the time line. By this way, the viewing directions are measured and the residual of the spacecraft's attitude angles (not restituted by the Attitude and Orbit Control System) is estimated. This information can complete the geometric model of all the scenes acquired by the instrument and is used in all geometric applications. This paper presents new attitude assessment methods taking advantage of the capabilities of Pléiades-HR in terms of agility and focal plane arrangement - panchromatic band and multispectral (MS) bands.

Delevit, J. M.; Greslou, D.; Amberg, V.; Dechoz, C.; de Lussy, F.; Lebegue, L.; Latry, C.; Artigues, S.; Bernard, L.

2012-07-01

321

NMR quantum information processing  

E-print Network

Quantum computing exploits fundamentally new models of computation based on quantum mechanical properties instead of classical physics, and it is believed that quantum computers are able to dramatically improve computational power for particular tasks. At present, nuclear magnetic resonance (NMR) has been one of the most successful platforms amongst all current implementations. It has demonstrated universal controls on the largest number of qubits, and many advanced techniques developed in NMR have been adopted to other quantum systems successfully. In this review, we show how NMR quantum processors can satisfy the general requirements of a quantum computer, and describe advanced techniques developed towards this target. Additionally, we review some recent NMR quantum processor experiments. These experiments include benchmarking protocols, quantum error correction, demonstrations of algorithms exploiting quantum properties, exploring the foundations of quantum mechanics, and quantum simulations. Finally we summarize the concepts and comment on future prospects.

Dawei Lu; Aharon Brodutch; Jihyun Park; Hemant Katiyar; Tomas Jochym-O'Connor; Raymond Laflamme

2015-01-07

322

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

PubMed

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

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

2013-11-01

323

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

NASA Astrophysics Data System (ADS)

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-13C, U-15N]-labeled proteins. Given the sequence of the protein and data for the orthogonal 2D 1H-15N and 1H-13C 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 1H, 13C, and 15N 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.

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

2013-11-01

324

Solid-state 17O NMR of pharmaceutical compounds: salicylic acid and aspirin.  

PubMed

We report solid-state NMR characterization of the (17)O quadrupole coupling (QC) and chemical shift (CS) tensors in five site-specifically (17)O-labeled samples of salicylic acid and o-acetylsalicylic acid (Aspirin). High-quality (17)O NMR spectra were obtained for these important pharmaceutical compounds under both static and magic angle spinning (MAS) conditions at two magnetic fields, 14.0 and 21.1 T. A total of 14 (17)O QC and CS tensors were experimentally determined for the seven oxygen sites in salicylic acid and Aspirin. Although both salicylic acid and Aspirin form hydrogen bonded cyclic dimers in the solid state, we found that the potential curves for the concerted double proton transfer in these two compounds are significantly different. In particular, while the double-well potential curve in Aspirin is nearly symmetrical, it is highly asymmetrical in salicylic acid. This difference results in quite different temperature dependencies in (17)O MAS spectra of the two compounds. A careful analysis of variable-temperature (17)O MAS NMR spectra of Aspirin allowed us to obtain the energy asymmetry (?E) of the double-well potential, ?E = 3.0 ± 0.5 kJ/mol. We were also able to determine a lower limit of ?E for salicylic acid, ?E > 10 kJ/mol. These asymmetrical features in potential energy curves were confirmed by plane-wave DFT computations, which yielded ?E = 3.7 and 17.8 kJ/mol for Aspirin and salicylic acid, respectively. To complement the solid-state (17)O NMR data, we also obtained solid-state (1)H and (13)C NMR spectra for salicylic acid and Aspirin. Using experimental NMR parameters obtained for all magnetic nuclei present in salicylic acid and Aspirin, we found that plane-wave DFT computations can produce highly accurate NMR parameters in well-defined crystalline organic compounds. PMID:23879687

Kong, Xianqi; Shan, Melissa; Terskikh, Victor; Hung, Ivan; Gan, Zhehong; Wu, Gang

2013-08-22

325

IN SITU MAGIC ANGLE SPINNING NMR FOR STUDYING GEOLOGICAL CO(2) SEQUESTRATION  

SciTech Connect

Geological carbon sequestration (GCS) is one of the most promising ways of mitigating atmospheric greenhouse gases (1-3). Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly 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 (4,5). 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 (6,7), where non-metal materials must be used. 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.

Hoyt, David W.; Turcu, Romulus VF; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Kwak, Ja Hun; Felmy, Andrew R.; Hu, Jian Z.

2011-03-27

326

The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for Its Imaged Companions  

E-print Network

HR 8799 is an hF0 mA5 gamma Doradus, lambda Bootis, Vega-type star best known for hosting four directly imaged candidate planetary companions. Using the CHARA Array interferometer, we measure HR 8799's limb-darkened angular diameter to be 0.342 +/- 0.008 mas; this is the smallest interferometrically measured stellar diameter to date, with an error of only 2%. By combining our measurement with the star's parallax and photometry from the literature, we greatly improve upon previous estimates of its fundamental parameters, including stellar radius (1.44 +/- 0.06 R_Sun), effective temperature (7193 +/- 87 K, consistent with F0), luminosity (5.05 +/- 0.29 L_Sun), and the extent of the habitable zone (1.62 AU to 3.32 AU). These improved stellar properties permit much more precise comparisons with stellar evolutionary models, from which a mass and age can be determined, once the metallicity of the star is known. Considering the observational properties of other lambda Bootis stars and the indirect evidence for youth...

Baines, Ellyn K; Huber, Daniel; Jones, Jeremy; Boyajian, Tabetha; McAlister, Harold A; Brummelaar, Theo A ten; Sturmann, Judit; Sturmann, Laszlo; Turner, Nils H; Goldfinger, P J; Farrington, Christopher D; Riedel, Adric R; Ireland, Michael; von Braun, Kaspar; Ridgway, Stephen T

2012-01-01

327

CHARACTERIZATION OF THE RED GIANT HR 2582 USING THE CHARA ARRAY  

SciTech Connect

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.

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

328

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

NASA Astrophysics Data System (ADS)

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.

Johnson, Robert L.; Schmidt-Rohr, Klaus

2014-02-01

329

Quantitative identification of metastable magnesium carbonate minerals by solid-state (13)c NMR spectroscopy.  

PubMed

In the conversion of CO2 to mineral carbonates for the permanent geosequestration of CO2, there are multiple magnesium carbonate phases that are potential reaction products. Solid-state (13)C NMR is demonstrated as an effective tool for distinguishing magnesium carbonate phases and quantitatively characterizing magnesium carbonate mixtures. Several of these mineral phases include magnesite, hydromagnesite, dypingite, and nesquehonite, which differ in composition by the number of waters of hydration or the number of crystallographic hydroxyl groups. These carbonates often form in mixtures with nearly overlapping (13)C NMR resonances which makes their identification and analysis difficult. In this study, these phases have been investigated with solid-state (13)C NMR spectroscopy, including both static and magic-angle spinning (MAS) experiments. Static spectra yield chemical shift anisotropy (CSA) lineshapes that are indicative of the site-symmetry variations of the carbon environments. MAS spectra yield isotropic chemical shifts for each crystallographically inequivalent carbon and spin-lattice relaxation times, T1, yield characteristic information that assist in species discrimination. These detailed parameters, and the combination of static and MAS analyses, can aid investigations of mixed carbonates by (13)C NMR. PMID:25437754

Moore, Jeremy K; Surface, J Andrew; Brenner, Allison; Skemer, Philip; Conradi, Mark S; Hayes, Sophia E

2015-01-01

330

The MicroMAS CubeSat Mission  

NASA Astrophysics Data System (ADS)

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.

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

331

Water speciation in sodium silicate glasses (quenched melts): A comprehensive NMR study  

NASA Astrophysics Data System (ADS)

Dissolution mechanism of water is an important factor governing how the dissolved water affects the physical and thermodynamic properties of silicate melts and glasses. Our previous studies have demonstrated that 1H MAS NMR in combination with 29Si-1H and 27Al-1H double-resonance NMR experiments is an effective approach for unambiguously differentiating and quantifying different water species in quenched silicate melts (glasses). Several contrasting dissolution mechanisms have been revealed depending on the melt composition: for relatively polymerized melts, the formation of SiOH/AlOH species (plus molecular H2O) and depolymerization of the network structure dominate; whereas for depolymerized Ca-Mg silicate melts, free OH (e.g. MgOH) become increasingly important (cf. [1]). The proportion of free OH species has been shown to decrease with both increasing melt polymerization (silica content) and decreasing field strength of the network modifying cations (from Mg to Ca). Our previous 1H and 29Si MAS NMR results for hydrous Na silicate glasses of limited compositions (Na2Si4O9 and Na2Si2O5) were consistent with negligible free OH (NaOH) species and depolymerizing effect of water dissolution [2]. On the other hand, there were also other studies that proposed the presence of significant NaOH species in hydrous glasses near the Na2Si2O5 composition. The purpose of this study is apply the approach of combined 1H MAS NMR and double-resonance (29Si-1H and 23Na-1H) NMR to gain unambiguous evidence for the OH speciation in Na silicate glasses (melts) as a function of composition. Hydrous Na silicate glasses containing mostly ? 1 wt% H2O for a range of Na/Si ratios from 0.33 to 1.33 have been synthesized by rapidly quenching melts either at 0.2 GPa using an internally heated gas pressure vessel or at 1 GPa using a piston cylinder high-pressure apparatus. NMR spectra have been acquired using a 9.4 T Varian Unity-Inova spectrometer. The 29Si and 1H chemical shifts are reported relative to TMS. The 1H MAS NMR spectra show broad peaks covering a chemical shift range of 1 to 17 ppm, with peak maxima near 4 and 15 ppm for more Si-rich compositions and near 12 ppm for less Si-rich compositions. The 1H-29Si-1H and 23Na-1H cross-polarization (CP) MAS NMR spectra for all the hydrous Na silicate glasses suggest negligible NaOH species, which, if present, should show enhanced relative intensity with 23Na-1H CP and the opposite with 1H-29Si-1H CP. All the observed 1H NMR intensities can be attributed to SiOH species of a range of hydrogen-bonding distances, plus a small amount of molecular H2O for higher water-content samples that contribute to intensities around 6 ppm. In conclusion, our combined 1H MAS NMR and double-resonance (1H-29Si-1H and 23Na-1H CP) MAS NMR study on Na silicate glasses of a range of Na/Si ratios has confirmed that water dissolves predominantly as SiOH and molecular H2O species in Na silicate melts (glasses), consistent with the trend predicted from studies on the Ca-Mg silicate system [1,2]. References:[1] Xue, X. Y.; Kanzaki, M. J. Am. Ceram. Soc. 2009, 92, 2803-2830. [2] Xue, X. Y.; Kanzaki, M. Geochim. Cosmochim. Acta 2004, 68, 5027-5057.

Xue, X.; Kanzaki, M.; Eguchi, J.

2012-12-01

332

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

Microsoft Academic Search

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

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

2001-01-01

333

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

SciTech Connect

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.

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

2007-12-03

334

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

335

NMR imaging microscopy  

SciTech Connect

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.''

Not Available

1986-10-01

336

Dynamics of SARS-coronavirus HR2 domain in the prefusion and transition states  

NASA Astrophysics Data System (ADS)

The envelope glycoproteins S1 and S2 of severe acute respiratory syndrome coronavirus (SARS-CoV) mediate viral entry by conformational change from a prefusion state to a postfusion state that enables fusion of the viral and target membranes. In this work we present the characterization of the dynamic properties of the SARS-CoV S2-HR2 domain (residues 1141-1193 of S) in the prefusion and newly discovered transition states by NMR 15N relaxation studies. The dynamic properties of the different states, which are stabilized under different experimental conditions, extend the current model of viral membrane fusion and give insight into the design of structure-based antagonists of SARS-CoV in particular, as well as other enveloped viruses such as HIV.

McReynolds, Susanna; Jiang, Shaokai; Rong, Lijun; Caffrey, Michael

2009-12-01

337

Outsourcing HR Services: The Role of Human Resource Intermediaries  

ERIC Educational Resources Information Center

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…

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

2012-01-01

338

TO: HR and Business Contacts FROM: Division of Human Resources  

E-print Network

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

Almor, Amit

339

TO: HR and Business Contacts FROM: Division of Human Resources  

E-print Network

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

Almor, Amit

340

TO: HR and Business Contacts FROM: Division of Human Resources  

E-print Network

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

Almor, Amit

341

BusinessandManagement extension.uci.edu/hr  

E-print Network

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 the Human Resources Management program, courses being offered in upcoming quarters, and HR industry tips

Rose, Michael R.

342

HR Time and Labor Group Security Access Request Form  

E-print Network

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: __________________________________________________________________________________________ EMPLOYEE ACKNOWLEDGEMENT: I acknowledge that I occupy a position of special trust with duties

Weston, Ken

343

HR diagrams derived from the Michigan Spectral Catalogue  

Microsoft Academic Search

The data used for the HR diagrams are taken from a volume prepared by Houk and Cowley (1975) and a second volume prepared by Houk (1978). The absolute magnitudes were taken mainly from the Landolt-Boernstein tables. The graphs provided include HR diagrams for normal stars of quality 1 and 2, and errors in HD magnitudes as a function of p.e.

N. Houk; R. Fesen

1978-01-01

344

An explanation of the ‘granulation boundary’ in the HR diagram  

Microsoft Academic Search

The granulation boundary is a line running in the HR diagram from about F0V stars to G1Ib. It divides the HR diagram in two regions in which the ‘spectral line bisector’ behaves differently. To the right (cooler stars) the Fraunhofer lines in stellar spectra show the characteristics typical for convective motions. For hot stars it indicates the presence of large

Cornelis Jager

1990-01-01

345

African American Accounting Majors and the 150-hr Requirement  

ERIC Educational Resources Information Center

The study provides information on African American accounting majors' views regarding 150-hr issues. The authors collected data from 152 students at two schools. Students at one school supported the requirement while those at the other school did not. However, students believed that the 150-hr requirement enhances the quality of certified public…

Booker, Quinton; Hill, Cecil L.; Wright, Carl

2010-01-01

346

HR May 1, 2007 Type of Evaluation: new revised appeal  

E-print Network

HR May 1, 2007 Type of Evaluation: new revised appeal Position Title for PDQ EVALUATION #12;Appeal: The following individual(s) wishes to submit an appeal of the JJEC's recent rating: Incumbent Dean/Director HR Director Ratings of the following factors are being appealed: 1

Northern British Columbia, University of

347

100 ton/hr fume incinerator recovers 52 million Btu/hr  

SciTech Connect

The fume incinerator at the Neville Island plant of USS Chemicals in Pittsburgh, PA required substantial maintenance and yearly overhaul to keep it operating. Because the plant operates 7 days/week, 24 hours/day, downtime represented a serious problem, and the incinerator used to burn the waste gas from the phthalic anhydride reactor was causing problems. To solve this problem, the plant installed an 80 ft long thermal oxidation system capable of incinerating 100 tons of waste gas maintaining clean exhaust from its 100 ft stack. A heat recovery system added to this incinerator saved approximately 1.5 million Btu/hr by preheating the combustion air. (JMT)

Not Available

1982-05-01

348

Solid-state NMR study of various mono- and divalent cation forms of the natural zeolite natrolite.  

PubMed

Here we present the one-dimensional (29)Si and (27)Al MAS NMR and two-dimensional (27)Al MQMAS and DQF-STMAS NMR spectra of the monovalent (Na(+), K(+), Rb(+), Cs(+) and NH4(+)) and divalent (Ca(2+), Sr(2+) and Ba(2+)) cation forms of the natural zeolite natrolite (framework type NAT) with complete Si-Al ordering over the crystallographically distinct tetrahedral sites and with the same hydration state (hydrated, partially dehydrated or fully dehydrated). In the case of monovalent cation-exchanged natrolites, the differences in their crystal symmetry evidenced by (29)Si MAS NMR were found to be in good agreement with those determined by crystallographic analyses. However, (27)Al DQF-STMAS NMR spectroscopy shows the presence of two distinct Al sites in dehydrated K-NAT, Rb-NAT and NH4-NAT, suggesting that their actual crystal symmetry is lower than the reported one (i.e., orthorhombic Fdd2). The MAS NMR results also show that the space group of hydrated Ca-NAT is lower than that (monoclinic F1d1) of hydrated scolecite, the natural calcium counterpart of natrolite, which is also the case with hydrated Sr-NAT and Ba-NAT. We believe that the unexpected diversity in the crystal symmetry of natrolite caused by exchange of various mono- and divalent ions, as well as by dehydration, may be inherently due to the high framework flexibility of this natural zeolite. PMID:23588621

Park, Min Bum; Vicente, Aurélie; Fernandez, Christian; Hong, Suk Bong

2013-05-28

349

A simulator for organisation-centred MAS adaptation in P2P sharing networks  

E-print Network

A simulator for organisation-centred MAS adaptation in P2P sharing networks Jordi Campos and Maite}@iiia.csic.es ABSTRACT We present a simulator to compare different approaches to organisation-centred MAS adaptation, Coordination, Organisation, P2P, MAS 1. INTRODUCTION Organisational centred multi-agent systems (OCMAS) have

López-Sánchez, Maite

350

Human Resources Consultancy (HR) in France: On the tendency of Web service innovating to e-HR  

E-print Network

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

Paris-Sud XI, Université de

351

UVBY photometry of the chemically peculiar stars Alpha Andromedae, HD 184905, HR 8216, and HR 8434  

NASA Astrophysics Data System (ADS)

Differential Stroemgren uvby photometric observations from the Four College Automated Photoelectric Telescope of four chemical peculiar stars is presented and analyzed. The peculiar Hg-Mn star ? And is found not to be a photometric variable within the errors of measurement contrary to some published studies. Observations of the magnetic CP star HD 184905 were used to refine the zero epoch and the period which was found to be 1.85435 days. Our photometry and that of Morrison & Wolff are generally quite similar. We find evidence for two sub-minima within the broad minimum in both u and y. The cool magnetic CP star HR 8216 is non-variable in agreement with previous studies that suggested it was constant or a very long period variable. The CP star HR 8434 has a period of 1.43242 days and shows a generally in phase variation of u, v, b, and y. The light curves have two nearly equally maximum and a sharp minimum. The largest amplitude is for u, 0.085 mag.

Adelman, S. J.; Brown, B. H.; Caliskan, H.; Reese, D. F.; Adelman, C. J.

1994-08-01

352

{sup 29}Si and {sup 27}Al NMR study of alkali-activated slag  

SciTech Connect

This paper presents the results of the investigation of the hydration of alkali-activated slag (AAS) by nuclear magnetic resonance spectroscopy (NMR). The cross-polarization (CP) technique was used in combination with magic-angle spinning (MAS). This research was part of a systematic study of alkaline activation of slag by several different techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with X-ray microanalysis of energy dispersive spectra (EDS), differential thermal analysis (DTA) and calorimetry. This NMR study provides information on the polymerization of silicates, the role of aluminates in cement hydration and the nanostructure of C-S-H gel.

Wang, S.-D.; Scrivener, Karen L

2003-05-01

353

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

PubMed

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

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

2008-12-11

354

NMR METHODS IN FOOD CHEMISTRY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Nuclear Magnetic Resonance (NMR) spectroscopy has enormously facilitated investigations into structural aspects of simple molecules and complex polymers. NMR has developed far beyond the simple running of a proton or carbon spectrum. Today there are literally thousands of “NMR experiments” and varia...

355

Educational NMR Software  

NASA Astrophysics Data System (ADS)

A description of a compilation of computer programs (EduNMRSoft) suitable for teaching NMR at an introductory to advanced level is presented. Each program is categorised and described by function, hardware requirements, availability, author, and references in the list. The compilation is available in electronic form at http://www.chem.umu.se/divisions/fk/EduNMRSoft.html.

Lundberg, Peter

1997-12-01

356

Benford distributions in NMR  

E-print Network

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

Gaurav Bhole; Abhishek Shukla; T. S. Mahesh

2014-06-27

357

Applied computational electromagnetic society Journal, pages: 112-126, March, 2004 A hybrid full MAS and Combined MAS/TSA Algorithm for  

E-print Network

full MAS and Combined MAS/TSA Algorithm for Electromagnetic Induction Sensing F. Shubitidze (1) , K. O and Engineering Laboratory, 72, Lyme Road, Hanover NH, 03755, USA Abstract ­Electromagnetic induction (EMI of ultra-wideband (1 Hz- 300 kHz) electromagnetic induction problems [1] - [6]. For a highly conducting

Shubitidze, Fridon

358

High-temperature steam-treatment of PBI, PEEK, and PEKK polymers with H2O and D2O: A solid-state NMR study  

E-print Network

-state NMR study Jacqueline C. Pope a , Hung-Jue Sue b , Tim Bremner b, c, ** , Janet Blümel a 2014 Keywords: Steam-treatment of PBI, PEEK, PEKK Solid-state NMR Water and D2O uptake polymers a b with D2O steam at temperatures of 150 and 315 C. All samples are studied by TGA, IR, 13 C CP/MAS, 1 H

Bluemel, Janet

359

A Solid-State NMR Study of Tungsten Methyl Group Dynamics in [W(5-C5Me5)Me4][PF6  

E-print Network

A Solid-State NMR Study of Tungsten Methyl Group Dynamics in [W(5-C5Me5)Me4][PF6] Douglas C. Maus Spinning (MAS) 13C and static 2H NMR studies of the dynamics of the methyl groups coordinated to tungsten in [WCp*Me4][PF6] (Cp* ) 5-C5Me5). The temperature-dependent broadening of the axial methyl 13C line can

Griffin, Robert G.

360

An NMR study of acid sites on chlorided alumina catalysts using trimethylphosphine as a probe  

Microsoft Academic Search

The MAS-NMR spectra of adsorbed trimethylphosphine (TMP) were used to determine the concentration of Brønsted and Lewis acid sites on pure and chlorinated?-Al2O3 samples. Chlorination with CHCl3,CCl4 or AlCl3 promoted the formation of Brønsted acid centers, which are characterized by the protonated adduct of TMP. This adduct has a31P chemical shift of ca. -3.8 ppm and a JP-H scalar coupling

Hong Sang; Hon Yue Chu; Jack H. Lunsford

1994-01-01

361

Characterisation of sodium cations in dehydrated zeolite NaX by 23Na NMR spectroscopy.  

PubMed

23Na MAS, 2D nutation MAS, and DOR NMR spectroscopy has been applied to characterise the location of sodium cations in dehydrated zeolite NaX (Si/Al = 1.23). The 23Na MAS NMR spectra recorded at three different magnetic field strengths were decomposed by computer simulation into five lines, which were attributed to five crystallographically distinct cation sites known from X-ray diffraction studies. The assignments of the lines follow from electric field gradient calculations at the 23Na nuclei applying a simple point charge model based on crystal structure data. A weak Gaussian line at low field (delta iso = -6 ppm) is assigned to sodium cations at site I, two broad quadrupole patterns at the high-field side of the spectra are attributed to site I' (delta iso = -19 ppm, QCC = 5.2 MHz, eta = 0) and site II cations (delta iso = -15 ppm, QCC = 4.6 MHz, eta = 0), and two quadrupolar lines dominating the central region of the spectra originate from Na+ at two different III' sites (delta iso = -13 and -29 ppm, QCC = 2.6 and 1.6 MHz, eta = 0.7 and 0.9, respectively). Na+ ions located on a second I' site could be identified from the DOR NMR spectra. The line assignment is further corroborated by the reasonable agreement of the site occupancies estimated from the line intensities with those determined by X-ray diffraction. In addition, sodium site populations of five dehydrated zeolites NaX and NaY with Si/Al ratios between 1.09 and 4.0 were derived from the 23Na MAS NMR spectra. PMID:8986022

Feuerstein, M; Hunger, M; Engelhardt, G; Amoureux, J P

1996-11-01

362

Elemental Abundance Analyses with DAO Spectrograms - Part Twelve - the Mercury / Manganese Stars HR:4072A and HR:7775 and the Metallic Lined Star HR:4072B  

NASA Astrophysics Data System (ADS)

This paper presents fine analyses of three sharp-lined stars, the mercury-manganese stars HR 4072A and 7775 and the metallic-lined star HR 4072B, consistent with previous studies of this series. MR 4072A and 7775 exhibit Pt II, Au II and Hg II lines in their spectra, while HR 7775 also shows lines of several singly ionized rare earth species. MR 4072B is very deficient in both Ca and Sc, the signature of the Am stars. For the HgMn stars, [C/Si] marginally anticorrelates with log Si/H as in normal A and ? Boo stars. The large He depletions and other departures from the solar pattern, however, argue strongly against a simple Venn-Lambert hypothesis for these stars.

Adelman, S. J.

1994-01-01

363

Chemical shift tensor determination using magnetically oriented microcrystal array (MOMA): 13C solid-state CP NMR without MAS.  

PubMed

Chemical shift tensors for the carboxyl and methyl carbons of L-alanine crystals were determined using a magnetically oriented microcrystal array (MOMA) prepared from a microcrystalline powder sample of L-alanine. A MOMA is a single-crystal-like composite in which microcrystals are aligned three-dimensionally in a matrix resin. The single-crystal rotation method was applied to the MOMA to determine the principal values and axes of the chemical shift tensors. The result showed good agreement with the literature data for the single crystal of L-alanine. This demonstrates that the present technique is a powerful tool for determining the chemical shift tensor of a crystal from a microcrystal powder sample. PMID:22975237

Kusumi, R; Kimura, F; Song, G; Kimura, T

2012-10-01

364

Efficient heteronuclear decoupling in MAS solid-state NMR using non-rotor-synchronized rCW irradiation  

NASA Astrophysics Data System (ADS)

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.

Equbal, Asif; Paul, Subhradip; Mithu, Venus Singh; Madhu, P. K.; Nielsen, Niels Chr.

2014-09-01

365

Cp\\/mas 13 c nmr and Electron Diffraction Study of Bacterial Cellulose Structure Affected by Cell Wall Polysaccharides  

Microsoft Academic Search

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.

Chisuzu Tokoh; Keiji Takabe; Junji Sugiyama; Minoru Fujita

2002-01-01

366

Efficient heteronuclear decoupling in MAS solid-state NMR using non-rotor-synchronized rCW irradiation.  

PubMed

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

Equbal, Asif; Paul, Subhradip; Mithu, Venus Singh; Madhu, P K; Nielsen, Niels Chr

2014-09-01

367

NUMBER: HR 1.54 SECTION: Human Resources  

E-print Network

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

Almor, Amit

368

University Policy No.: HR6315 Classification: Human Resources  

E-print Network

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

Victoria, University of

369

NUMBER: HR 1.39 SECTION: Human Resources  

E-print Network

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

Almor, Amit

370

NUMBER: HR 1.24 SECTION: Human Resources  

E-print Network

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

Almor, Amit

371

Does HR add value? : diverse perspectives on human capital management  

E-print Network

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, ...

Eckman, Jeffrey M

2006-01-01

372

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

NASA Astrophysics Data System (ADS)

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

Angeli, Frédéric; Villain, Olivier; Schuller, Sophie; Ispas, Simona; Charpentier, Thibault

2011-05-01

373

Structural Characterization of Humic Materials Using ^13C NMR Techniques: A Comparison of Solution- and Solid-State Methods  

NASA Astrophysics Data System (ADS)

The analysis of the carbon type distribution and chemical structure of natural organic matter (NOM) by ^13C NMR spectroscopy is an important technique for understanding its origins and reactivity. While prior work has used solution-state NMR techniques, solid-state NMR has the potential to provide this information using less instrument time and sample manipulation, while providing an array of advanced filtering techniques. Analyses of four isolated humic materials with ^13C solid-state magic angle spinning (MAS) NMR techniques are described, including three commercially available samples and one fulvic acid sample isolated from the Rio Grande in New Mexico. This study demonstrates the utility of solid-state ^13C NMR for aquatic NOM structural characterization, comparing these results to the existing solution-state determinations. The solid-state ^13C MAS NMR results are used to determine % carbon distribution, estimates of elemental composition (%C, %H, %(O+N)), aromatic fraction (fa), nonprotonated aromatic fraction (faN), an estimate of aromatic cluster size, and ratio of sp^2 to sp^3 carbons. A Gaussian deconvolution method is introduced that allows for a detailed analysis of carbon type.

Clewett, Catherine; Alam, Todd; Osantowski, Eric; Pullin, Michael

2011-10-01

374

224} studied by NMR  

SciTech Connect

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.

Furukawa, Y; Fang, X; Kögerler, P

2014-05-14

375

NMR Quantum Computing  

Microsoft Academic Search

Quantum computing is at the forefront of scientific and technological research and development of the 21st century. NMR quantum\\u000a computing is one the most mature technologies for implementing quantum computation. It utilizes the motion of spins of nuclei\\u000a in custom-designed molecules manipulated by RF pulses. The motion is on a nano- or microscopic scale governed by the Schr¨odinger\\u000a equation in

Zhigang Zhang; Goong Chen; Zijian Diao; Philip R. Hemmer

376

NMR Studies of Peroxidases.  

NASA Astrophysics Data System (ADS)

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

Veitch, Nigel Charles

377

Probing the nanostructure, interfacial interaction, and dynamics of chitosan-based nanoparticles by multiscale solid-state NMR.  

PubMed

Chitosan-based nanoparticles (NPs) are widely used in drug and gene delivery, therapy, and medical imaging, but a molecular-level understanding of the internal morphology and nanostructure size, interface, and dynamics, which is critical for building fundamental knowledge for the precise design and efficient biological application of the NPs, remains a great challenge. Therefore, the availability of a multiscale (0.1-100 nm) and nondestructive analytical technique for examining such NPs is of great importance for nanotechnology. Herein, we present a new multiscale solid-state NMR approach to achieve this goal for the investigation of chitosan-poly(N-3-acrylamidophenylboronic acid) NPs. First, a recently developed (13)C multiple cross-polarization magic-angle spinning (MAS) method enabled fast quantitative determination of the NPs' composition and detection of conformational changes in chitosan. Then, using an improved (1)H spin-diffusion method with (13)C detection and theoretical simulations, the internal morphology and nanostructure size were quantitatively determined. The interfacial coordinated interaction between chitosan and phenylboronic acid was revealed by one-dimensional MAS and two-dimensional (2D) triple-quantum MAS (11)B NMR. Finally, dynamic-editing (13)C MAS and 2D (13)C-(1)H wide-line separation experiments provided details regarding the componential dynamics of the NPs in the solid and swollen states. On the basis of these NMR results, a model of the unique nanostructure, interfacial interaction, and componential dynamics of the NPs was proposed. PMID:25372426

Wang, Fenfen; Zhang, Rongchun; Wu, Qiang; Chen, Tiehong; Sun, Pingchuan; Shi, An-Chang

2014-12-10

378

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

PubMed

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

Yoon, Ji Won

2014-11-01

379

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)

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.

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

1994-01-01

380

Elemental abundances of the B and A stars. 2: Gamma Geminorum, HD 60825, 7 Sextantis, HR 4817, and HR 5780  

NASA Astrophysics Data System (ADS)

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.

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

1994-12-01

381

Solid State NMR Studies of Energy Conversion and Storage Materials  

NASA Astrophysics Data System (ADS)

NMR (Nuclear magnetic resonance) spectroscopy is utilized to study energy conversion and storage materials. Different types of NMR techniques including Magic Angle Spinning, Cross-polarization and relaxation measurement experiments were employed. Four different projects are discussed in this dissertation. First, three types of CFx battery materials were investigated. Electrochemical studies have demonstrated different electrochemical performances by one type, delivering superior performance over the other two. 13C and 19F MAS NMR techniques are employed to identify the atomic/molecular structural factors that might account for differences in electrochemical performance among different types. Next as the second project, layered polymer dielectrics were investigated by NMR. Previous studies have shown that thin film capacitors are improved by using alternate layers of two polymers with complementary properties: one with a high breakdown strength and one with high dielectric constant as opposed to monolithic layers. 13C to 1H cross-polarization techniques were used to investigate any inter-layer properties that may cause the increase in the dielectric strength. The third project was to study two types of thermoelectric materials. These samples were made of heavily doped phosphorous and boron in silicon by two different methods: ball-milled and annealed. These samples were investigated by NMR to determine the degree of disorder and obtain insight into the doping efficiency. The last ongoing project is on a lithium-ion battery system. The nature of passivating layers or the solid electrolyte interphase (SEI) formed on the electrodes surface is important because of the direct correlation between the SEI and the battery life time/durability. Multinuclear (7Li, 19F, 31P) techniques are employed to identify the composition of the SEI formation of both positive and negative electrodes.

Jankuru Hennadige, Sohan Roshel De Silva

382

Slow motion of confined molecules: NMR and broadband dielectric spectroscopy investigations.  

PubMed

Nuclear magnetic resonance (NMR) and broadband dielectric spectroscopy are used to investigate the dynamics of small glass-forming molecules confined to restricted geometries. Ethylene glycol molecules are embedded in the supercages of NaX zeolites. The combined application of NMR and broadband dielectric spectroscopy advances the understanding of the slowing down of the motion near the glass transition temperature of these confined molecules. In combination with nuclear spin relaxation and nuclear magnetic resonance spectroscopy, dielectric relaxation studies on glass forming molecules allow conclusions on the character of the motion. High resolution 1H magic angle spinning (MAS) NMR measurements not only enable a characterisation of the state of the adsorbed molecules via a chemical shift analysis. By means of an analysis of MAS spinning sidebands we may also estimate a correlation time the meaning of which will be discussed in comparison to the results of longitudinal proton spin relaxation measurements. In addition to broadband dielectric spectroscopy slow molecular motions of partially deuterated ethylene glycol adsorbed in NaX are studied by means of 2H NMR line-shape analysis. PMID:18464423

Erdem, Ozlen F; Pampel, André; Michel, Dieter

2008-02-01

383

Molecular structure of crude beeswax studied by solid-state 13C NMR  

PubMed Central

13C Solid-state NMR experiments were performed to investigate the structure of beeswax in the native state (crude beeswax) for the first time. From quantitative direct polarization 13C MAS NMR spectrum, it was found that the fraction of internal-chain methylene (int-(CH2)) component compared to other components of crude beeswax was over 95%. The line shape of the int-(CH2) carbon resonance region was comprehensively analyzed in terms of NMR chemical shift. The 13C broad peak component covering from 31 to 35ppm corresponds to int-(CH2) carbons with trans conformation in crystalline domains, whereas the sharp signal at 30.3 ppm corresponds to gauche conformation in the non-crystalline domain. From peak deconvolution of the aliphatic region, it was found that over 85% of the int-(CH2) has a crystal structure and several kinds of molecular packing for int-(CH2), at least three, exist in the crystalline domain. Abbreviation: NMR nuclear magnetic resonance int-(CH2) internal-chain methylene CP cross-polarization MAS magic angle spinning PMID:15861244

Kameda, Tsunenori

2004-01-01

384

High-Resolution Magic Angle Spinning 1H NMR Spectroscopy of Intact Liver and Kidney: Optimization of Sample Preparation Procedures and Biochemical Stability of Tissue during Spectral Acquisition  

Microsoft Academic Search

High-resolution magic angle spinning (MAS) 1H NMR spectroscopy has been used to investigate the biochemical composition of whole rat renal cortex and liver tissue samples. The effects of a number of sample preparation procedures and experimental variables have been investigated systematically in order to optimize spectral quality and maximize information recovery. These variables include the effects of changing the sample

N. J. Waters; S. Garrod; R. D. Farrant; J. N. Haselden; S. C. Connor; J. Connelly; J. C. Lindon; E. Holmes; J. K. Nicholson

2000-01-01

385

The stoichiometry of synthetic alunite as a function of hydrothermal aging investigated by solid-state NMR spectroscopy, powder X-ray diffraction and infrared spectroscopy  

NASA Astrophysics Data System (ADS)

The stoichiometry of a series of synthetic alunite [nominally KAl3(SO4)2(OH)6] samples prepared by hydrothermal methods as a function of reaction time (1-31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 1H MAS NMR spectra recorded at high magnetic field (21.1 T, 900 MHz) allowed for a clear separation of the different proton environments and for quantitative determination of the aluminum vacancy concentration as a function of time. The concentration of structural defects determined from, i.e., aluminum vacancies was reduced from 4 to 1 %, as the reaction time was extended from one to 31 days based on 1H MAS NMR. This was further supported by an increase of the unit cell parameter c, which is indicative of the relative concentration of potassium defects present, from 17.261(1) to 17.324(5) Å. Solid-state 27Al MAS NMR revealed a decrease in the defect concentration as a function of time and showed the presence of 7-10 % impurities in the samples.

Grube, Elisabeth; Nielsen, Ulla Gro

2014-11-01

386

Determination of the Average Aromatic Cluster Size of Fossil Fuels by Solid-State NMR at High Magnetic Field  

SciTech Connect

We show that the average aromatic cluster size in complex carbonaceous materials can be accurately determined using fast magic-angle spinning (MAS) NMR at a high magnetic field. To accurately quantify the nonprotonated aromatic carbon, we edited the 13C spectra using the recently reported MAS-synchronized spin–echo, which alleviated the problem of rotational recoupling of 1H-13C dipolar interactions associated with traditional dipolar dephasing experiments. The dependability of this approach was demonstrated on selected Argonne Premium coal standards, for which full sets of basic structural parameters were determined with high accuracy.

Mao, Kanmi [ExxonMobile Research and Engineering Co.; Kennedy, Gordon J. [ExxonMobile Research and Engineering Co.; Althaus, Stacey M. [Ames Laboratory; Pruski, Marek [Ames Laboratory

2013-01-07

387

Sensitivity and resolution enhancement of oriented solid-state NMR: application to membrane proteins.  

PubMed

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

Gopinath, T; Mote, Kaustubh R; Veglia, Gianluigi

2013-11-01

388

Solid-state {sup 29}Si NMR analysis of amorphous silicon nitride powder  

SciTech Connect

Solid-state {sup 29}Si NMR techniques were used to characterize laser-synthesized silicon nitride powder prepared from the reaction of silane with ammonia. When the powder is exposed to water vapor, a hydrated layer rapidly forms at the surface. A comparison of {sup 29}Si cross polarization (CP) and Bloch decay (BD)-MAS-NMR spectra revealed differences between surface and bulk compositions. CP-NMR identified Si-NH{sub x} (x = 1, 2) species with a chemical shift of {minus}45 ppm in the as-synthesized (unexposed) powder. In BD-NMR spectra, the nitride resonance is observed at {minus}48 ppm. For the hydrated powder, CP-NMR identified additional {triple_bond}Si-OH (Q{sup 3}), {double_bond}Si-(OH){sub 2} (Q{sup 2}), and SiO{sub 2} (Q{sup 4}) species present at the surface. The CP-NMR spectra were corrected for T{sub 1pH} relaxation effects and deconvoluted into individual components in order to extract quantitative measurements of the various species present.

Leone, E.A.; Curran, S.; Kotun, M.E. [AlliedSignal Inc., Morristown, NJ (United States); Carrasquillo, G.; Weeren, R. van; Danforth, S.C. [Rutgers-the State Univ., Piscataway, NJ (United States). Center for Ceramic Research

1996-02-01

389

Multinuclear NMR approach to coal fly ash characterization  

SciTech Connect

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.

Netzel, D.A.

1991-09-01

390

OBSERVATIONS AND ORBITAL ANALYSIS OF THE GIANT WHITE DWARF BINARY SYSTEM HR 5692  

SciTech Connect

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.

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

391

MAS-mediated antioxidant effects restore the functionality of angiotensin converting enzyme 2-angiotensin-(1-7)-MAS axis in diabetic rat carotid.  

PubMed

We hypothesized that endothelial AT1-activated NAD(P)H oxidase-driven generation of reactive oxygen species during type I-diabetes impairs carotid ACE2-angiotensin-(1-7)-Mas axis functionality, which accounts for the impaired carotid flow in diabetic rats. We also hypothesized that angiotensin-(1-7) chronic treatment of diabetic rats restores carotid ACE2-angiotensin-(1-7)-Mas axis functionality and carotid flow. Relaxant curves for angiotensin II or angiotensin-(1-7) were obtained in carotid from streptozotocin-induced diabetic rats. Superoxide or hydrogen peroxide levels were measured by flow cytometry in carotid endothelial cells. Carotid flow was also determined. We found that endothelial AT1-activated NAD(P)H oxidase-driven generation of superoxide and hydrogen peroxide in diabetic rat carotid impairs ACE2-angiotensin-(1-7)-Mas axis functionality, which reduces carotid flow. In this mechanism, hydrogen peroxide derived from superoxide dismutation inhibits ACE2 activity in generating angiotensin-(1-7) seemingly by activating I(Cl,SWELL0, while superoxide inhibits the nitrergic Mas-mediated vasorelaxation evoked by angiotensin-(1-7). Angiotensin-(1-7) treatment of diabetic rats restored carotid ACE2-angiotensin-(1-7)-Mas axis functionality by triggering a positive feedback played by endothelial Mas receptors, that blunts endothelial AT1-activated NAD(P)H oxidase-driven generation of reactive oxygen species. Mas-mediated antioxidant effects also restored diabetic rat carotid flow, pointing to the contribution of ACE2-angiotensin-(1-7)-Mas axis in maintaining carotid flow. PMID:24877125

Pernomian, Larissa; Gomes, Mayara Santos; Restini, Carolina Baraldi Araujo; de Oliveira, Ana Maria

2014-01-01

392

The fate of the solid matter orbiting HR 4796A  

NASA Technical Reports Server (NTRS)

We have obtained optical spectra, 2 micrometers speckle images, and an upper limit to the 800 micrometers flux for HR 4796A, and optical spectra for its physical companion separated by 7.7 arcsecs, HR 4796B. We detect H-beta, H-gamma, and the calcium H and K lines in emission from HR 4796B; these data are consistent with the hypothesis that it is later than spectral type M2 and lies substantially above the main-sequence. From the location of HR 4796B on the H-R diagram, the estimated age of this star is 3 x 10(exp 6) yr, and assuming this age for the entire system, we find from our 2 micrometers speckle data that there is no close stellar companion to HR 4796A (M greater than 0.125 solar mass) between 11 and 120 AU from the star. From the IRAS and ground-based photometry, it seems that there is a hole in the dust distribution around HR 4796A with an inner radius of between approximately 40 and approximately 200 AU. The observed circumstellar dust grains, which lie at D greater than 40 AU from the star, are likely to be at least 3 micrometers in radius in order to be gravitationally bound to HR 4796A, if the circumstellar dust cloud is optically thin. Since they are larger than almost all interstellar grains, the circumstellar dust grains probably grew by coalescence. Because the existing grains at D greater than 40 AU have undergone measurable coalescence, it is possible that particles that presumably once existed at D less than 40 AU, where the collision times were shorter than at D greater than 40 AU, grew into macroscopic objects. A likely explanation for the dust hole is that there is a companion located at about half the inner radius of the dust hole, or between 20 and 100 AU from the star. If such a companion exists, it must have a mass less than 0.125 solar mass. Since grain coalescence has occurred, this putative companion possibly could be a planet.

Jura, M.; Ghez, A. M.; White, Russell J.; Mccarthy, D. W.; Smith, R. C.; Martin, P. G.

1995-01-01

393

NMR Spectroscopy in Ionic Liquds  

NASA Astrophysics Data System (ADS)

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

Giernoth, Ralf

394

MAS6061 1 Turn Over PLEASE LEAVE THIS EXAM PAPER ON YOUR DESK.  

E-print Network

of a significant difference in the gender adjusted odds of asthma for 2009 compared to 1999? (1 mark) #12;MAS6061 Provided: Neaves Tables Graph Paper SCHOOL OF MATHEMATICS AND STATISTICS MAS6061 Session 2012-2013 3 Hours etiology. Explain the difference between these two measures. (4 marks) (ii) In a recent study of asthma

395

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

E-print Network

. MAS273 1 Turn Over #12;MAS273 1 In a survey conducted by the Wall Street Journal, adults who regularly used various products were asked to name a TV commercial they had seen for a specified product category in the past week. Each naming of a commercial is termed a "retained impression". For each product the TV

396

E/Z MAS: An easy-to-use computerized materials control and accountability system  

SciTech Connect

Nuclear facilities that handle and process nuclear materials are required to track their nuclear holdings and to keep adequate records that manage and control the inventory of those holdings. The complexity of a system that does this job is directly proportional to the complexity of the facility`s operations. This paper describes an approach to computerized materials protection, control, and accountability (MPC and A) that was introduced by Los Alamos National Laboratory (LANL) in the fall of 1997. This new system, E/Z MAS, is the latest addition to the LANL suite of computerized MPC and A tools, which also includes the CoreMAS system. E/Z MAS was initially designed to address the needs of those facilities that have small to modest MPC and A needs but has been expanded to provide full functionality for any facility. The system name, E/Z MAS, reflects the system`s easy-to-use characteristics, which include ease of installation and ease of software maintenance. Both CoreMAS and E/Z MAS have been provided to facilities in the Former Soviet Union to assist them in implementing a computerized MPC and A system that meets their needs. In this paper the authors will address the functionality of CoreMAS and E/Z MAS, and an argument in favor of intranet-based material control and accountability will be advanced.

Anderson, L.K.; Boor, M.G.; Hurford, J.M.; Landry, R.P.; Martinez, B.J.; Solem, A.M.; Whiteson, R.; Zardecki, A.

1998-12-31

397

Psychometric Comparison of the Motivation Assessment Scale (MAS) and the Questions about Behavioral Function (QABF)  

ERIC Educational Resources Information Center

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…

Koritsas, S.; Iacono, T.

2013-01-01

398

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 of the engine. E : Equivalence ratio is a measure of the richness of the air and ethanol fuel mixture A and B having unknown weights and respectively, are measured on a spring balance separately. A third

399

Two-dimensional NMR spectroscopy  

SciTech Connect

Written for chemists and biochemists who are not NMR spectroscopists, but who wish to use the new techniques of two-dimensional NMR spectroscopy, this book brings together for the first time much of the practical and experimental data needed. It also serves as information source for industrial, academic, and graduate student researchers who already use NMR spectroscopy, but not yet in two dimensions. The authors describe the use of 2-D NMR in a wide variety of chemical and biochemical fields, among them peptides, steroids, oligo- and poly-saccharides, nucleic acids, natural products (including terpenoids, alkaloids, and coal-derived heterocyclics), and organic synthetic intermediates. They consider throughout the book both the advantages and limitations of using 2-D NMR.

Croasmun, W.R.; Carlson, R.M.K.

1987-01-01

400

Association of dissolved aluminum with silica: Connecting molecular structure to surface reactivity using NMR  

NASA Astrophysics Data System (ADS)

We studied uptake mechanisms for dissolved Al on amorphous silica by combining bulk-solution chemistry experiments with solid-state Nuclear Magnetic Resonance techniques ( 27Al magic-angle spinning (MAS) NMR, 27Al{ 1H} cross-polarization (CP) MAS NMR and 29Si{ 1H} CP-MAS NMR). We find that reaction of Al (1 mM) with amorphous silica consists of at least three reaction pathways; (1) adsorption of Al to surface silanol sites, (2) surface-enhanced precipitation of an aluminum hydroxide, and (3) bulk precipitation of an aluminosilicate phase. From the NMR speciation and water chemistry data, we calculate that 0.20 (±0.04) tetrahedral Al atoms nm -2 sorb to the silica surface. Once the surface has sorbed roughly half of the total dissolved Al (˜8% site coverage), aluminum hydroxides and aluminosilicates precipitate from solution. These precipitation reactions are dependent upon solution pH and total dissolved silica concentration. We find that the Si:Al stoichiometry of the aluminosilicate precipitate is roughly 1:1 and suggest a chemical formula of NaAlSiO 4 in which Na + acts as the charge compensating cation. For the adsorption of Al, we propose a surface-controlled reaction mechanism where Al sorbs as an inner-sphere coordination complex at the silica surface. Analogous to the hydrolysis of Al(OH)63+, we suggest that rapid deprotonation by surface hydroxyls followed by dehydration of ligated waters results in four-coordinate (>SiOH) 2Al(OH) 2 sites at the surface of amorphous silica.

Houston, J. R.; Herberg, J. L.; Maxwell, R. S.; Carroll, S. A.

2008-07-01

401

A generic, computerized nuclear materials accountability system (NucMAS) and its layered products  

SciTech Connect

NucMAS provides a material balance area with a computerized data management system for nuclear materials accountability. NucMAS is a generic application. It handles the data management and reporting functions for different processing facilities by storing all process-specific information as data rather than procedure. A NucMAS application is configured for each facility it supports. NucMAS and its layered products are compatible with three types of data clients. Core NucMAS has a screen-oriented user interface to support the accountability clerk as a client. Accountability clerks enter data from operating logs and laboratory analyses one to three days after actual processing. Layered products support process operators and automated systems as near-real-time and real-time data clients. The core and layered products use a data-driven approach which results in software that is configurable and maintainable. 3 refs., 5 figs.

Davis, Jr, J M

1989-01-01

402

NUMBER: HR 1.01 SECTION: Human Resources  

E-print Network

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

Almor, Amit

403

NUMBER: HR 1.51 SECTION: Human Resources  

E-print Network

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

Almor, Amit

404

HR Contacts by Function Harvard Medical School Human Resources  

E-print Network

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

Chou, James

405

University Policy No.: HR6320 Classification: Human Resources  

E-print Network

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

Victoria, University of

406

NUMBER: HR 1.12 SECTION: Human Resources  

E-print Network

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

Almor, Amit

407

University Policy No.: HR6305 Classification: Human Resources  

E-print Network

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

Victoria, University of

408

NUMBER: HR 1.06 SECTION: Human Resources  

E-print Network

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

Almor, Amit

409

NUMBER: HR 1.77 SECTION: Human Resources  

E-print Network

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

Almor, Amit

410

NUMBER: HR 1.69 SECTION: Human Resources  

E-print Network

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

Almor, Amit

411

NUMBER: HR 1.15 SECTION: Human Resources  

E-print Network

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

Almor, Amit

412

NUMBER: HR 1.81 SECTION: Human Resources  

E-print Network

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

Almor, Amit

413

TO: HR and Business Contacts FROM: Division of Human Resources  

E-print Network

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

Almor, Amit

414

NUMBER: HR 1.66 SECTION: Human Resources  

E-print Network

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

Almor, Amit

415

NUMBER: HR 1.42 SECTION: Human Resources  

E-print Network

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

Almor, Amit

416

HR Manager Leadership in Quality Improvement in a College Environment  

ERIC Educational Resources Information Center

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…

Sharabi, Moshe

2010-01-01

417

NUMBER: HR 1.27 SECTION: Human Resources  

E-print Network

1 NUMBER: HR 1.27 SECTION: Human Resources SUBJECT: Nepotism DATE: December 1990 (Rev.) 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

Almor, Amit

418

Clinical Imaging of Bone Microarchitecture with HR-pQCT  

PubMed Central

Osteoporosis, a disease characterized by loss of bone mass and structural deterioration, is currently diagnosed by dual-energy x-ray absorptiometry (DXA). However, DXA does not provide information about bone microstructure, which is a key determinant of bone strength. Recent advances in imaging permit the assessment of bone microstructure in vivo using high-resolution peripheral quantitative computed tomography (HR-pQCT). From these data, novel image processing techniques can be applied to characterize bone quality and strength. To date, most HR-pQCT studies are cross-sectional comparing subjects with and without fracture. These studies have shown that HR-pQCT is capable of discriminating fracture status independent of DXA. Recent longitudinal studies present new challenges in terms of analyzing the same region of interest and multisite calibrations. Careful application of analysis techniques and educated clinical interpretation of HR-pQCT results have improved our understanding of various bone-related diseases and will no doubt continue to do so in the future. PMID:23504496

Nishiyama, Kyle K.; Shane, Elizabeth

2014-01-01

419

Draft Genome Sequence of Bordetella trematum Strain HR18.  

PubMed

The genus Bordetella is reportedly a human or animal pathogen and environmental microbe. We report the draft genome sequence of Bordetella trematum strain HR18, which was isolated from the rumen of Korean native cattle (Hanwoo; Bos taurus coreanae). It is the first genome sequence of a Bordetella sp. isolated from the rumen of cattle. PMID:25573930

Chang, Dong-Ho; Jin, Tae-Eun; Rhee, Moon-Soo; Jeong, Haeyoung; Kim, Seil; Kim, Byoung-Chan

2015-01-01

420

Ring Nebulae around Massive Stars throughout the HR Diagram  

Microsoft Academic Search

Massive stars evolve across the HR diagram, losing mass along the way and forming a variety of ring nebulae. During the main sequence stage, the fast stellar wind sweeps up the ambient interstellar medium to form an interstellar bubble. After a massive star evolves into a red giant or a luminous blue variable, it loses mass copiously to form a

You-Hua Chu

2002-01-01

421

HR diagram and asteroseismic analysis of models for ??Hydri  

Microsoft Academic Search

A detailed review of the models for the star ? Hydri is done by adjusting the evolutionary sequences to the most recent bolometric, spectroscopic and astrometric data. The dependence of the solution on some of the relevant modelling parameters is analysed and the degeneracy of the solution using the HR diagram analysis discussed. Recent ground-based observations, and the forthcoming asteroseismic

J. Fernandes

2003-01-01

422

Stellar magnetic fields across the HR diagram: observational evidence  

Microsoft Academic Search

This review presents most recent measurements of magnetic fields in various types of stars and substellar objects across the H-R diagram with the emphasis on measurement methods, observational and modeling biases, and the role of magnetic fields in stellar evolution.

Svetlana V. Berdyugina

2009-01-01

423

Magnetism of the He-weak star HR 2949†  

NASA Astrophysics Data System (ADS)

A magnetic field and rotational line profile variability (lpv) is found in the He-weak star HR 2949. The field measured from metallic lines varies in a clearly non-sinusoidal way, and shows a phase lag relative to the morphologically similar He i equivalent width variations. The surface abundance patterns are strong and complex, and visible even in the hydrogen lines.

Rivinius, Thomas; Wade, Gregg A.; Townsend, Richard H. D.; Shultz, Matthew; Grunhut, Jason H.; Stahl, Otmar; Stahl

2011-07-01

424

Draft Genome Sequence of Bordetella trematum Strain HR18  

PubMed Central

The genus Bordetella is reportedly a human or animal pathogen and environmental microbe. We report the draft genome sequence of Bordetella trematum strain HR18, which was isolated from the rumen of Korean native cattle (Hanwoo; Bos taurus coreanae). It is the first genome sequence of a Bordetella sp. isolated from the rumen of cattle. PMID:25573930

Chang, Dong-Ho; Jin, Tae-Eun; Rhee, Moon-Soo; Jeong, Haeyoung; Kim, Seil

2015-01-01

425

Solid state NMR studies of materials for energy technology  

NASA Astrophysics Data System (ADS)

Presented in this dissertation are NMR investigations of the dynamical and structural properties of materials for energy conversion and storage devices. 1H and 2H NMR was used to study water and methanol transportation in sulfonated poly(arylene ether ketone) based membranes for direct methanol fuel cells (DMFC). These results are presented in chapter 3. The amount of liquid in the membrane and ion exchange capacity (IEC) are two main factors that govern the dynamics in these membranes. Water and methanol diffusion coefficients also are comparable. Chapters 4 and 5 are concerned with 31P and 1H NMR in phosphoric acid doped PBI membranes (para-PBI and 2OH-PBI) as well as PBI membranes containing ionic liquids (H3PO4/PMIH2PO4/PBI). These membranes are designed for higher-temperature fuel cell operation. In general, stronger short and long range interactions were observed in the 2OH-PBI matrix, yielding reduced proton transport compared to that of para-PBI. In the case of H3PO4/PMIH2PO 4/PBI, both conductivity and diffusion are higher for the sample with molar ratio 2/4/1. Finally, chapter 6 is devoted to the 31P NMR MAS study of phosphorus-containing structural groups on the surfaces of micro/mesoporous activated carbons. Two spectral features were observed and the narrow feature identifies surface phosphates while the broad component identifies heterogeneous subsurface phosphorus environments including phosphate and more complex structure multiple P-C, P-N and P=N bonds.

Nambukara Kodiweera Arachchilage, Chandana K.

426

Solid-state 13C NMR and molecular modeling studies of acetyl aleuritolic acid obtained from Croton cajucara Benth  

NASA Astrophysics Data System (ADS)

Solid-state 13C nuclear magnetic resonance ( 13C NMR) with magic-angle spinning (MAS) and with cross-polarization and magic-angle spinning (CP/MAS) spectra, and differential scanning calorimetry (DSC) techniques were used to obtain structural data from a sample of acetyl aleuritolic acid (AAA) extracted from the stem bark of Croton cajucara Benth. (Euphorbiaceae) and recrystallized from acetone. Since solid-state 13C NMR results suggested the presence of more than one molecule in the unitary cell for the AAA, DSC analysis and molecular modeling calculations were used to access this possibility. The absence of phase transition peaks in the DSC spectra and the dimeric models of AAA simulated using the semi-empirical PM3 method are in agreement with that proposal.

da Silva San Gil, Rosane Aguiar; Albuquerque, Magaly Girão; de Alencastro, Ricardo Bicca; da Cunha Pinto, Angelo; do Espírito Santo Gomes, Fabiano; de Castro Dantas, Tereza Neuma; Maciel, Maria Aparecida Medeiros

2008-08-01

427

Atypical Signaling and Functional Desensitization Response of MAS Receptor to Peptide Ligands  

PubMed Central

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

Tirupula, Kalyan C.; Desnoyer, Russell; Speth, Robert C.; Karnik, Sadashiva S.

2014-01-01

428

Ex situ NMR and neutron diffraction study of structure and lithium motion in Li 7MnN 4  

Microsoft Academic Search

Li7MnN4 was prepared and characterised by both long and short range probes of structure. The results of the Rietveld refinement of its crystal structure from Powder Neutron Diffraction data are in agreement with previous determination from single crystal X-ray diffraction data. The 6Li MAS-NMR spectrum of this compound contained five main resonances, which could be assigned to the five different

Jordi Cabana; Nicolas Dupré; Gwenaëlle Rousse; Clare P. Grey; M. Rosa Palacín

2005-01-01

429

Solid state NMR methods for coal science. Progress report, July 1, 1983-September 31, 1984  

SciTech Connect

This report covers the progress made on the title project during the last quarter. While a good deal of our time has been spent setting up our new NMR laboratory, we have made several significant advances in solid state NMR technique development that will have important applications in structure determination of coal, coal products and other fossil fuels. We have developed a CP/MAS probe that is routinely capable of producing decoupling fields in excess of 100 KHz without excessive power consumption and that has a very homogeneous radio frequency field. This piece of equipment has proven crucial to the success of a number of new techniques we are developing. In addition to increasing our sensitivity, the intensity, and homogeneity of the R.F. field, this probe now makes a number of multiple pulse techniques feasible. One avenue that has been pursued this quarter is understanding how to better decouple and thus increase the resolution of /sup 13/C CP/MAS spectra. It has been found that improved decoupling does lead to an increase in resolution in coal C-13 CP-MAS spectra. Preliminary results indicate it is now possible to resolve four bands in the aliphatic region and to substantially narrow CH/sub 2/ resonances in whole coals. 4 figures.

Zilm, K.W.

1984-12-01

430

NMR flow tube for online NMR reaction monitoring.  

PubMed

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

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

2014-12-16

431

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

PubMed

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

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

2011-01-01

432

(13)C, (15)N CPMAS NMR and GIAO DFT calculations of stereoisomeric oxindole alkaloids from Cat's Claw (Uncaria tomentosa).  

PubMed

Oxindole alkaloids, isolated from the bark of Uncaria tomentosa [Willd. ex Schult.] Rubiaceae, are considered to be responsible for the biological activity of this herb. Five pentacyclic and two tetracyclic alkaloids were studied by solid-state NMR and theoretical GIAO DFT methods. The (13)C and (15)N CPMAS NMR spectra were recorded for mitraphylline, isomitraphylline, pteropodine (uncarine C), isopteropodine (uncarine E), speciophylline (uncarine D), rhynchophylline and isorhynchophylline. Theoretical GIAO DFT calculations of shielding constants provide arguments for identification of asymmetric centers and proper assignment of NMR spectra. These alkaloids are 7R/7S and 20R/20S stereoisomeric pairs. Based on the (13)C CP MAS chemical shifts the 7S alkaloids (delta C3 70-71ppm) can be easily and conveniently distinguished from 7R (deltaC3 74.5-74.9ppm), also 20R (deltaC20 41.3-41.7ppm) from the 20S (deltaC20 36.3-38.3ppm). The epiallo-type isomer (3R, 20S) of speciophylline is characterized by a larger (15)N MAS chemical shift of N4 (64.6ppm) than the allo-type (3S, 20S) of isopteropodine (deltaN4 53.3ppm). (15)N MAS chemical shifts of N1-H in pentacyclic alkaloids are within 131.9-140.4ppm. PMID:19019638

Paradowska, Katarzyna; Wolniak, Micha?; Pisklak, Maciej; Gli?ski, Jan A; Davey, Matthew H; Wawer, Iwona

2008-11-01

433

Solid-State NMR Characterization of Aluminum Oxide Nanofibers  

SciTech Connect

Aluminum oxide nanofibers have been generated by an electrospinning process, creating fibers with diameters on the nanometer scale and aspect ratios greater than a thousand. These nanofibers have the potential of providing enhanced catalytic properties, due to their large surface area and controllable compositions. Solid-state NMR is being used to investigate both the bulk and surface properties of these materials. 27Al NMR has shown that no chemistry occurs during the electrospinning process, even though potentials in excess of 20 kV are applied to the sample. Thermal treatment of the fibers to convert them to alumina results in the formation of different phases, with the phases identified by the relative populations of 4-, 5-, and 6-coordinate alumina sites. Heating to 525°C or 1200°C produces a species similar to the catalytically active gamma-phase or conversion of the nanofibers into the thermodynamically stable ?-alumina phase, respectively. 1H-27Al CP/MAS has shown that the ?-alumina phase has a low population of surface hydroxyls, whereas the “gamma-alumina” form has a much higher fraction of 5-coordinate sites, compared to materials synthesized by traditional techniques. Organophosphates are being used as molecular probes in the characterization of the nanofiber surfaces. 31P CP/MAS data has revealed the presence of mono-, bi- and tri-denate bound phosphate groups on the surface, with the onset of surface alumina dissolution with sample heating. The application of 1H-31P HETCOR shows that the three different types of bound organophosphates are intermixed, rather than there being separate domains for each type. 31P-27Al CP is also being used to distinguish the types of surface alumina sites bound to the phosphate species.

Cross, Jennifer L.; Tuttle, Ricky W.; Ramsier, Rex D.; Espe, Mathew

2006-07-24

434

A LOW-E MAGIC ANGLE SPINNING PROBE FOR BIOLOGICAL SOLID STATE NMR AT 750 MHz  

PubMed Central

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

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

2009-01-01

435

THz Dynamic Nuclear Polarization NMR  

E-print Network

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 ...

Nanni, Emilio Alessandro

436

Ring Nebulae around Massive Stars throughout the HR Diagram  

E-print Network

Massive stars evolve across the HR diagram, losing mass along the way and forming a variety of ring nebulae. During the main sequence stage, the fast stellar wind sweeps up the ambient interstellar medium to form an interstellar bubble. After a massive star evolves into a red giant or a luminous blue variable, it loses mass copiously to form a circumstellar nebula. As it evolves further into a WR star, the fast WR wind sweeps up the previous mass loss and forms a circumstellar bubble. Observations of ring nebulae around massive stars not only are fascinating, but also are useful in providing templates to diagnose the progenitors of supernovae from their circumstellar nebulae. In this review, I will summarize the characteristics of ring nebulae around massive stars throughout the HR diagram, show recent advances in X-ray observations of bubble interiors, and compare supernovae's circumstellar nebulae with known types of ring nebulae around massive stars.

You-Hua Chu

2002-08-07

437

LBT observations of the HR8799 planetary system  

NASA Astrophysics Data System (ADS)

We present here observations of the HR8799 planetary system performed in H and Ks band exploiting the AO system at the Large Binocular Telescope and the PISCES camera. Thanks to the excellent performence of the instrument we were able to detect for the first time the inner known planet of the system (HR8799) in the H band. Precise photometric and astrometric measures have been taken for all the four planets. Further, exploiting ours and previous astrometric results, we were able to put some limits on the planetary orbits of the four planets. The analysis of the dinamical stability of the system seems to show lower planetary masses than the ones adopted until now.

Mesa, D.; Arcidiacono, C.; Claudi, R. U.; Desidera, S.; Esposito, S.; Gratton, R.; Masciadri, E.

2013-09-01

438

NMR insights into protein allostery  

PubMed Central

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

Manley, Gregory; Loria, J. Patrick

2014-01-01

439

Multispectral Analysis of NMR Imagery  

NASA Technical Reports Server (NTRS)

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.

Butterfield, R. L.; Vannier, M. W. And Associates; Jordan, D.

1985-01-01

440

NMR characterization of thin films  

DOEpatents

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

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

2008-11-25

441

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves  

SciTech Connect

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.

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

442

Spatially resolved submillimeter imaging of the HR 8799 debris disk  

NASA Astrophysics Data System (ADS)

Dynamical interactions between planets and debris disks may sculpt the disk structure and impact planetary orbits, but only a few systems with both imaged planets and spatially resolved debris disks are known. With the Caltech Submm Observatory (CSO), we have observed the HR 8799 debris disk at 350 ?m. The 350 ?m map is the first spatially resolved measurement of the debris disk encircling the HR 8799 planetary system at this wavelength. Both the flux and size of the emission are consistent with a Kuiper belt of dust extending from ~100-300 AU. Although the resolution of the current map is limited, the map shows an indication of offset asymmetric emission, and several scenarios for this possibility are explored with radiative transfer calculations of a star-disk system and N-body numerical simulations of planet-disk interactions with parameters representative of the HR 8799 system. Based on observations obtained at the Caltech Submillimeter Observatory.Figures 3 and 4 are available in electronic form at http://www.aanda.org

Patience, J.; Bulger, J.; King, R. R.; Ayliffe, B.; Bate, M. R.; Song, I.; Pinte, C.; Koda, J.; Dowell, C. D.; Kovács, A.

2011-07-01

443

"Decoupled" Proton NMR Spectra  

NASA Astrophysics Data System (ADS)

High-resolution proton NMR spectra are recorded in a new form where all resonances are singlets at the chemical-shift frequencies, with no spin-spin splittings. These "decoupled" proton spectra are derived from two-dimensional J spectra after real Fourier transformation (without frequency discrimination in F1) so that each spin multiplet lies along both the 45° and the 135° diagonal, forming a pattern similar to St. Andrew's cross, with C 4 symmetry. The chemical shifts are located by searching for these centers of symmetry with a postacquisition data-processing algorithm. This is designed to facilitate the separation of overlapping and interpenetrating spin multiplets. The method is illustrated with applications to the 400 MHz high-resolution proton spectra of dehydrotestosterone and 4-androsten-3,17-dione. It is also possible to separate the spectra of components in a mixture and this is illustrated by breaking down the spectrum of an aqueous solution of D-glucose into subspectra from the ? and ? anomers, in order to follow the time evolution of the mutarotation.

Woodley, M.; Freeman, R.

444

Polarization transfer NMR imaging  

DOEpatents

A nuclear magnetic resonance (NMR) image is obtained with spatial information modulated by chemical information. The modulation is obtained through polarization transfer from a first element representing the desired chemical, or functional, information, which is covalently bonded and spin-spin coupled with a second element effective to provide the imaging data. First and second rf pulses are provided at first and second frequencies for exciting the imaging and functional elements, with imaging gradients applied therebetween to spatially separate the nuclei response for imaging. The second rf pulse is applied at a time after the first pulse which is the inverse of the spin coupling constant to select the transfer element nuclei which are spin coupled to the functional element nuclei for imaging. In a particular application, compounds such as glucose, lactate, or lactose, can be labeled with .sup.13 C and metabolic processes involving the compounds can be imaged with the sensitivity of .sup.1 H and the selectivity of .sup.13 C.

Sillerud, Laurel O. (Los Alamos, NM); van Hulsteyn, David B. (Santa Fe, NM)

1990-01-01

445

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

SciTech Connect

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

Matwiyoff, N.A.

1983-01-01

446

School of Marine and Atmospheric Sciences (SoMAS) Strategic Plan --2008  

E-print Network

1 School of Marine and Atmospheric Sciences (SoMAS) Strategic Plan -- 2008 Overview Few in marine biogeochemistry, fisheries and sustainability, coastal oceanography, marine ecology to forge strong interdisciplinary programs with the engineering, medical, natural and social science

Zhang, Minghua

447

BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format  

NASA Technical Reports Server (NTRS)

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.

Hall, Forrest G. (Editor); Newcomer, Jeffrey (Editor); Lobitz, Brad; Spanner, Michael; Strub, Richard; Lobitz, Brad

2000-01-01

448

MAS 335 Cryptography Notes 10: Public-key cryptography Spring 2008  

E-print Network

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

Banaji,. Murad

449

Intercomparison of MAS, AVIRIS, and HIS data from FIRE cirrus 2  

NASA Technical Reports Server (NTRS)

The NASA ER-2 flight on 5 Dec. 1991 is unique among the FIRE Cirrus 2 missions in that data were acquired simultaneously by the MODIS Airborne Simulator (MAS), the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), and the High Resolution Interferometer Sounder (HIS). These data represent a unique source of information about the spatial and spectral properties of cirrus clouds. The MAS is a new instrument which will aid in defining algorithms and building an understanding of the ability of the Moderate Resolution Imaging Spectroradiometer (MODIS) to remotely sense atmospheric conditions for assessing global change. In order to establish confidence in the absolute calibration accuracy of the MAS radiances, an inter-comparison of MAS radiances with AVIRIS and HIS has been undertaken.

Gumley, Liam E.; King, Michael D.; Tsay, Si-Chee; Gao, Bo-Cai; Arnold, G. Thomas

1993-01-01

450

Solvation and crystal effects in bilirubin studied by NMR spectroscopy and density functional theory.  

PubMed

The open-chain tetrapyrrole compound bilirubin was investigated in chloroform and dimethyl sulfoxide solutions by liquid-state NMR and as solid by (1)H, (13)C, and (15)N magic-angle spinning (MAS) solid-state NMR spectroscopy. Density functional theory (DFT) calculations were performed to interpret the data, using the B3LYP exchange-correlation functional to optimize geometries and to compute NMR chemical shieldings by the gauge-including atomic orbital method. The dependence of geometries and chemical shieldings on the size of the basis sets was investigated for the reference molecules tetramethylsilane, NH(3), and H(2)O, and for bilirubin as a monomer and in clusters consisting of up to six molecules. In order to assess the intrinsic errors of the B3LYP approximation in calculating NMR shieldings, complete basis set estimates were obtained for the nuclear shielding values of the reference molecules. The experimental liquid-state NMR data of bilirubin are well reproduced by a monomeric bilirubin molecule using the 6-311+G(2d,p) basis set for geometry optimization and for calculating chemical shieldings. To simulate the bilirubin crystal, a hexameric model was required. It was constructed from geometry-optimized monomers using information from the X-ray structure of bilirubin to fix the monomeric entities in space and refined by partial optimization. Combining experimental (1)H-(13)C and (1)H-(15)N NMR correlation spectroscopy and density functional theory, almost complete sets of (1)H, (13)C, and (15)N chemical shift assignments were obtained for both liquid and solid states. It is shown that monomeric bilirubin in chloroform solution is formed by 3-vinyl anti conformers, while bilirubin crystals are formed by 3-vinyl syn conformers. This conformational change leads to characteristic differences between the liquid- and solid-state NMR resonances. PMID:21846145

Rohmer, Thierry; Matysik, Jörg; Mark, Franz

2011-10-27

451

Expression and cellular localization of the Mas receptor in the adult and developing mouse retina  

PubMed Central

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

Prasad, Tuhina; Verma, Amrisha

2014-01-01

452

U.S. Geological Survey mineral databases; MRDS and MAS/MILS  

USGS Publications Warehouse

These two CD-ROM's contain the latest version of the Mineral Resources Data System (MRDS) database and the Minerals Availability System/Minerals Industry Location System (MAS/MILS) database for coverage of North America and the world outside North America. The records in the MRDS database each contain almost 200 data fields describing metallic and nonmetallic mineral resources, deposits, and commodities. The records in the MAS/MILS database each contain almost 100 data fields describing mines and mineral processing plans.

McFaul, E.J.; Mason, G.T.; Ferguson, W.B.; Lipin, B.R.

2000-01-01

453

documentados, mas existe. Basta recor-dar a notcia do 'sumio' do voo MH 370  

E-print Network

documentados, mas existe. Basta recor- dar a notícia do 'sumiço' do voo MH 370 da Malaysian destroços. Mas nada 'desaparece' na História da aviação. Mesmo que, ao contrário do voo MH 370, até hoje não encontrados a flutuar pertenciam, de facto, ao voo MH 370, Braga Campos apon- tava para a tese da queda em

Instituto de Sistemas e Robotica

454

High-resolution solid-state oxygen-17 NMR of actinide-bearing compounds: an insight into the 5f chemistry.  

PubMed

A massive interest has been generated lately by the improvement of solid-state magic-angle spinning (MAS) NMR methods for the study of a broad range of paramagnetic organic and inorganic materials. The open-shell cations at the origin of this paramagnetism can be metals, transition metals, or rare-earth elements. Actinide-bearing compounds and their 5f unpaired electrons remain elusive in this intensive research area due to their well-known high radiotoxicity. A dedicated effort enabling the handling of these highly radioactive materials now allows their analysis using high-resolution MAS NMR (>55 kHz). Here, the study of the local structure of a series of actinide dioxides, namely, ThO2, UO2, NpO2, PuO2, and AmO2, using solid-state (17)O MAS NMR is reported. An important increase of the spectral resolution is found due to the removal of the dipolar broadening proving the efficiency of this technique for structural analysis. The NMR parameters in these systems with numerous and unpaired 5f electrons were interpreted using an empirical approach. Single-ion model calculations were performed for the first time to determine the z component of electron spin on each of the actinide atoms, which is proportional to the shifts. A similar variation thereof was observed only for the heavier actinides of this study. PMID:24926812

Martel, Laura; Magnani, Nicola; Vigier, Jean-Francois; Boshoven, Jacobus; Selfslag, Chris; Farnan, Ian; Griveau, Jean-Christophe; Somers, Joseph; Fanghänel, Thomas

2014-07-01

455

A Novel ?/?-Hydrolase Gene IbMas Enhances Salt Tolerance in Transgenic Sweetpotato  

PubMed Central

Salt stress is one of the major environmental stresses in agriculture worldwide and affects crop productivity and quality. The development of crops with elevated levels of salt tolerance is therefore highly desirable. In the present study, a novel maspardin gene, named IbMas, was isolated from salt-tolerant sweetpotato (Ipomoea batatas (L.) Lam.) line ND98. IbMas contains maspardin domain and belongs to ?/?-hydrolase superfamily. Expression of IbMas was up-regulated in sweetpotato under salt stress and ABA treatment. The IbMas-overexpressing sweetpotato (cv. Shangshu 19) plants exhibited significantly higher salt tolerance compared with the wild-type. Proline content was significantly increased, whereas malonaldehyde content was significantly decreased in the transgenic plants. The activities of superoxide dismutase (SOD) and photosynthesis were significantly enhanced in the transgenic plants. H2O2 was also found to be significantly less accumulated in the transgenic plants than in the wild-type. Overexpression of IbMas up-regulated the salt stress responsive genes, including pyrroline-5-carboxylate synthase, pyrroline-5-carboxylate reductase, SOD, psbA and phosphoribulokinase genes, under salt stress. These findings suggest that overexpression of IbMas enhances salt tolerance of the transgenic sweetpotato plants by regulating osmotic balance, protecting membrane integrity and photosynthesis and increasing reactive oxygen species scavenging capacity. PMID:25501819

Song, Xuejin; He, Shaozhen; Liu, Qingchang

2014-01-01

456

MAS5, a yeast homolog of DnaJ involved in mitochondrial protein import.  

PubMed Central

The nuclear mas5 mutation causes temperature-sensitive growth and defects in mitochondrial protein import at the nonpermissive temperature in the yeast Saccharomyces cerevisiae. The MAS5 gene was isolated by complementation of the mutant phenotypes, and integrative transformation demonstrated that the complementing fragment encoded the authentic MAS5 gene. The deduced protein sequence of the cloned gene revealed a polypeptide of 410 amino acids which is homologous to Escherichia coli DnaJ and the yeast DnaJ log SCJ1. Northern (RNA blot) analysis revealed that MAS5 is a heat shock gene whose expression increases moderately at elevated temperatures. Cells with a deletion mutation in MAS5 grew slowly at 23 degrees C and were inviable at 37 degrees C, demonstrating that MAS5 is essential for growth at increased temperatures. The deletion mutant also displayed a modest import defect at 23 degrees C and a substantial import defect at 37 degrees C. These results indicate a role for a DnaJ cognate protein in mitochondrial protein import. Images PMID:1729605

Atencio, D P; Yaffe, M P

1992-01-01

457

The Consistency of the Pandemic Simulations between the SEIR Model and the MAS Model  

NASA Astrophysics Data System (ADS)

There are two main methods for pandemic simulations: the SEIR model and the MAS model. The SEIR model can deal with simulations quickly for many homogeneous populations with simple ordinary differential equations; however, the model cannot accommodate many detailed conditions. The MAS model, the multi-agent simulation, can deal with detailed simulations under the many kinds of initial and boundary conditions with simple social network models. However, the computing cost will grow exponentially as the population size becomes larger. Thus, simulations in the large-scale model would hardly be realized unless supercomputers are available. By combining these two methods, we may perform the pandemic simulations in the large-scale model with lower costs. That is, the MAS model is used in the early stage of a pandemic simulation to determine the appropriate parameters to be used in the SEIR model. With these obtained parameters, the SEIR model may then be used. To investigate the validity of this combined method, we first compare the simulation results between the SEIR model and the MAS model. Simulation results of the MAS model and the SEIR model that uses the parameters obtained by the MAS model simulation are found to be close to each other.

Toyosaka, Yuki; Hirose, Hideo

458

A Novel ?/?-Hydrolase Gene IbMas Enhances Salt Tolerance in Transgenic Sweetpotato.  

PubMed

Salt stress is one of the major environmental stresses in agriculture worldwide and affects crop productivity and quality. The development of crops with elevated levels of salt tolerance is therefore highly desirable. In the present study, a novel maspardin gene, named IbMas, was isolated from salt-tolerant sweetpotato (Ipomoea batatas (L.) Lam.) line ND98. IbMas contains maspardin domain and belongs to ?/?-hydrolase superfamily. Expression of IbMas was up-regulated in sweetpotato under salt stress and ABA treatment. The IbMas-overexpressing sweetpotato (cv. Shangshu 19) plants exhibited significantly higher salt tolerance compared with the wild-type. Proline content was significantly increased, whereas malonaldehyde content was significantly decreased in the transgenic plants. The activities of superoxide dismutase (SOD) and photosynthesis were significantly enhanced in the transgenic plants. H2O2 was also found to be significantly less accumulated in the transgenic plants than in the wild-type. Overexpression of IbMas up-regulated the salt stress responsive genes, including pyrroline-5-carboxylate synthase, pyrroline-5-carboxylate reductase, SOD, psbA and phosphoribulokinase genes, under salt stress. These findings suggest that overexpression of IbMas enhances salt tolerance of the transgenic sweetpotato plants by regulating osmotic balance, protecting membrane integrity and photosynthesis and increasing reactive oxygen species scavenging capacity. PMID:25501819

Liu, Degao; Wang, Lianjun; Zhai, Hong; Song, Xuejin; He, Shaozhen; Liu, Qingchang

2014-01-01

459

NEW PRECISION ORBITS OF BRIGHT DOUBLE-LINED SPECTROSCOPIC BINARIES. IV. 66 ANDROMEDAE, HR 6979, AND HR 9059  

SciTech Connect

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.

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

460

Development of DNP-Enhanced High-Resolution Solid-State NMR System for the Characterization of the Surface Structure of Polymer Materials  

NASA Astrophysics Data System (ADS)

A dynamic nuclear polarization (DNP)-enhanced cross-polarization/magic-angle spinning (DNP/CP/MAS) NMR system has been developed by combining a 200 MHz Chemagnetics CMX-200 spectrometer operating at 4.7 T with a high-power 131.5 GHz Gyrotron FU CW IV. The 30 W sub-THz wave generated in a long pulse TE _{{41}}^{{(1)}} mode with a frequency of 5 Hz was successfully transmitted to the modified Doty Scientific low-temperature CP/MAS probe through copper smooth-wall circular waveguides. Since serious RF noises on NMR signals by arcing in the electric circuit of the probe and undesired sample heating were induced by the continuous sub-THz wave pulse irradiation with higher powers, the on-off sub-THz wave pulse irradiation synchronized with the NMR detection was developed and the appropriate setting of the irradiation time and the cooling time corresponding to the non-irradiation time was found to be very effective for the suppression of the arcing and the sample heating. The attainable maximum DNP enhancement was more than 30 folds for C1 13 C-enriched D-glucose dissolved in the frozen medium containing mono-radical 4-amino-TEMPO. The first DNP/CP/MAS 13 C NMR spectra of poly(methyl methacrylate) (PMMA) sub-micron particles were obtained at the dispersed state in the same frozen medium, indicating that DNP-enhanced 1H spins effectively diffuse from the medium to the PMMA particles through their surface and are detected as high-resolution 13 C spectra in the surficial region to which the 1H spins reach. On the basis of these results, the possibility of the DNP/CP/MAS NMR characterization of the surface structure of nanomaterials including polymer materials was discussed.

Horii, Fumitaka; Idehara, Toshitaka; Fujii, Yutaka; Ogawa, Isamu; Horii, Akifumi; Entzminger, George; Doty, F. David

2012-07-01