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1

Differentiation of mobile and immobile pesticides on anionic clays by 1H HR MAS NMR spectroscopy.  

PubMed

Adsorbed vs. intercalated MCPA (4-chloro-2-methylphenoxyacetic acid) in highly hydrated clays taken as a soil model were clearly distinguished by 1H HR MAS NMR; adsorbed herbicide gave sharp signals indicating high mobility while intercalated herbicide gave very wide unresolved spectra due to its strong interaction with the solid matrix. PMID:12240117

Combourieu, B; Inacio, J; Delort, A M; Forano, C

2001-11-01

2

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

PubMed

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these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents.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; Lojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

2013-10-09

3

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.

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

2013-01-01

4

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

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 CO2. 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

In vivo 31 P and 1 H HR-MAS NMR spectroscopy analysis of the unstarved Aporrectodea caliginosa (Lumbricidae)  

Microsoft Academic Search

This study demonstrates that 31P and 1H high resolution-magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR), a recently developed NMR technique, can be applied to the in vivo analysis of metabolites from an unstarved earthworm. The endogeic earthworm Aporrectodea caliginosa was cut into lengths and then the different body parts (anterior, middle, posterior) with the gut content were analyzed. With

Delphine Bon; Véronique Gilard; Stéphane Massou; Guénola Pérès; Myriam Malet-Martino; Robert Martino; Franck Desmoulin

2006-01-01

7

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

2010-10-08

8

1H HR-MAS NMR spectroscopy of tumor-induced local metabolic "field-effects" enables colorectal cancer staging and prognostication.  

PubMed

Colorectal cancer (CRC) is a major cause of morbidity and mortality in developed countries. Despite operative advances and the widespread adoption of combined-modality treatment, the 5-year survival rarely exceeds 60%. Improving our understanding of the biological processes involved in CRC development and progression will help generate new diagnostic and prognostic approaches. Previous studies have identified altered metabolism as a common feature in carcinogenesis, and quantitative measurement of this altered activity (metabonomics/metabolomics) has the potential to generate novel metabolite-based biomarkers for CRC diagnosis, staging and prognostication. In the present study we applied high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy to analyze metabolites in intact tumor samples (n = 83) and samples of adjacent mucosa (n = 87) obtained from 26 patients undergoing surgical resection for CRC. Orthogonal partial least-squares discriminant analysis (OPLS-DA) of metabolic profiles identified marked biochemical differences between cancer tissue and adjacent mucosa (R(2) = 0.72; Q(2) = 0.45; AUC = 0.91). Taurine, isoglutamine, choline, lactate, phenylalanine, tyrosine (increased concentrations in tumor tissue) together with lipids and triglycerides (decreased concentrations in tumor tissue) were the most discriminant metabolites between the two groups in the model. In addition, tumor tissue metabolic profiles were able to distinguish between tumors of different T- and N-stages according to TNM classification. Moreover, we found that tumor-adjacent mucosa (10 cm from the tumor margin) harbors unique metabolic field changes that distinguish tumors according to T- and N-stage with higher predictive capability than tumor tissue itself and are accurately predictive of 5-year survival (AUC = 0.88), offering a highly novel means of tumor classification and prognostication in CRC. PMID:23240862

Jiménez, Beatriz; Mirnezami, Reza; Kinross, James; Cloarec, Olivier; Keun, Hector C; Holmes, Elaine; Goldin, Robert D; Ziprin, Paul; Darzi, Ara; Nicholson, Jeremy K

2013-01-16

9

HR MAS MR spectroscopy in metabolic characterization of cancer.  

PubMed

One of the central hallmarks of cancer is the rapid and infinite cellular proliferation. In order to cope with increased requirement for building blocks and energy, cancer cells develop abnormal metabolic properties. Detailed assessment of cancer cell metabolism can provide biological information for use in both drug discovery and development of personalized cancer therapy. Analysis of intact tissue using high resolution magic angle spinning (HR MAS) magnetic resonance spectroscopy (MRS) gives qualitative and quantitative metabolite measures with minimal sample preparation. Multivariate statistical methods are important tools for analysis of complex MR data and have in recent years been used for analysis of HR MAS data from intact tissue. HR MAS analysis of intact tissue allows combination of metabolomic data with genomic or proteomic data, and can therefore be used both for exploring the molecular biology of cancer and for clinical improvements in cancer diagnostics, prognostics and treatment planning. In this review, the basic concepts of HR MAS are presented, and its use in characterisation of cancer metabolism is discussed with specific focus on selected pathways such as choline metabolism and glycolysis. The use of HR MAS in analysis of amino acids and lipid metabolism in cancer is also reviewed. Finally, the expected role of HR-MAS in metabolic characterisation in the near future is discussed. PMID:20809888

Moestue, Siver; Sitter, Beathe; Bathen, Tone Frost; Tessem, May-Britt; Gribbestad, Ingrid Susann

2011-01-01

10

High resolution MAS-NMR in combinatorial chemistry.  

PubMed

High-resolution magic angle spinning (hr-MAS) NMR is a powerful tool for characterizing organic reactions on solid support. Because magic angle spinning reduces the line-broadening due to dipolar coupling and variations in bulk magnetic susceptibility, line widths approaching those obtained in solution-phase NMR can be obtained. The magic angle spinning method is amenable for use in conjunction with a variety of NMR-pulse sequences, making it possible to perform full-structure determinations and conformational analysis on compounds attached to a polymer support. Diffusion-weighted MAS-NMR methods such as SPEEDY (Spin-Echo-Enhanced Diffusion-Filtered Spectroscopy) can be used to remove unwanted signals from the solvent, residual reactants, and the polymer support from the MAS-NMR spectrum, leaving only those signals arising from the resin-bound product. This review will present the applications of high-resolution magic angle spinning NMR for use in combinatorial chemistry research. PMID:11288068

Shapiro, M J; Gounarides, J S

11

MAS PFG NMR Studies of Mixtures in Porous Materials  

NASA Astrophysics Data System (ADS)

Pulsed field gradient (PFG) and magic angle spinning (MAS) NMR techniques have been successfully combined for the study of mixture diffusion in porous materials. Using a modular setup of commercially available components, gradient pulses of up to +/-2.6 T/m can be applied coinciding with fast sample rotation at the magic angle. Methods for the proper alignment of all components are presented along with protocols for MAS PFG NMR experiments. Finally, first diffusion measurements of n-hexane and benzene being adsorbed together in the metal-organic framework MOF-5 are presented.

Gratz, Marcel; Hertel, Stefan; Wehring, Markus; Schlayer, Stefan; Stallmach, Frank; Galvosas, Petrik

2011-03-01

12

On-cell MAS NMR: physiological clues from living cells.  

PubMed

While structural information on biomolecules is mainly obtained from purified in vitro samples, NMR can also be applied in the context of entire cells or organisms. The present study describes maturation processes in living Salmonella enterica serovar Typhimurium, a prevalent cause for human gastroenteritis. In our physiological study, we follow the composition of the O-antigen on the outer bacterial membrane with high-resolution MAS NMR spectroscopy. We detect and characterize an evolution of the O-antigen composition, in particular of the O-acetylation state of the O-antigen, a factor that can play an important role in vaccine development. PMID:23030432

Zandomeneghi, Giorgia; Ilg, Karin; Aebi, Markus; Meier, Beat H

2012-10-15

13

Proton HR-MAS spectroscopy and quantitative pathologic analysis of MRI/3D-MRSI-targeted postsurgical prostate tissues.  

PubMed

Proton high-resolution magic angle spinning ((1)H HR-MAS) NMR spectroscopy and quantitative histopathology were performed on the same 54 MRI/3D-MRSI-targeted postsurgical prostate tissue samples. Presurgical MRI/3D-MRSI targeted healthy and malignant prostate tissues with an accuracy of 81%. Even in the presence of substantial tissue heterogeneity, distinct (1)H HR-MAS spectral patterns were observed for different benign tissue types and prostate cancer. Specifically, healthy glandular tissue was discriminated from prostate cancer based on significantly higher levels of citrate (P = 0.04) and polyamines (P = 0.01), and lower (P = 0.02) levels of the choline-containing compounds choline, phosphocholine (PC), and glycerophosphocholine (GPC). Predominantly stromal tissue lacked both citrate and polyamines, but demonstrated significantly (P = 0.01) lower levels of choline compounds than cancer. In addition, taurine, myo-inositol, and scyllo-inositol were all higher in prostate cancer vs. healthy glandular and stromal tissues. Among cancer samples, larger increases in choline, and decreases in citrate and polyamines (P = 0.05) were observed with more aggressive cancers, and a MIB-1 labeling index correlated (r = 0.62, P = 0.01) with elevated choline. The elucidation of spectral patterns associated with mixtures of different prostate tissue types and cancer grades, and the inclusion of new metabolic markers for prostate cancer may significantly improve the clinical interpretation of in vivo prostate MRSI data. PMID:14587005

Swanson, Mark G; Vigneron, Daniel B; Tabatabai, Z Laura; Males, Ryan G; Schmitt, Lars; Carroll, Peter R; James, Joyce K; Hurd, Ralph E; Kurhanewicz, John

2003-11-01

14

A general protocol for temperature calibration of MAS NMR probes at arbitrary spinning speeds.  

PubMed

A protocol using (207)Pb NMR of solid lead nitrate was developed to determine the temperature of magic-angle spinning (MAS) NMR probes over a range of nominal set temperatures and spinning speeds. Using BioMAS and FastMAS probes with typical sample spinning rates of 8 and 35 kHz, respectively, empirical equations were devised to predict the respective sample temperatures. These procedures provide a straightforward recipe for temperature calibration of any MAS probe. PMID:21036557

Guan, Xudong; Stark, Ruth E

2010-10-20

15

A General Protocol for Temperature Calibration of MAS NMR Probes at Arbitrary Spinning Speeds  

PubMed Central

A protocol using 207Pb NMR of solid lead nitrate was developed to determine the temperature of magic-angle spinning (MAS) NMR probes over a range of nominal set temperatures and spinning speeds. Using BioMAS and fastMAS probes with typical sample spinning rates of 8 and 35 kHz, respectively, empirical equations were devised to predict the respective sample temperatures. These procedures provide a straightforward recipe for temperature calibration of any MAS probe.

Guan, Xudong; Stark, Ruth E.

2010-01-01

16

Characterization of brivanib therapy response in hepatocellular carcinoma xenografts using 1H HR-MAS spectroscopy and histopathology.  

PubMed

Angiogenesis inhibition is an attractive therapeutic strategy in the management of solid tumors. Vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) are key factors in growth and neovascularization of hepatocellular carcinoma (HCC). Brivanib is a novel, orally available dual tyrosine kinase inhibitor that selectively targets the key angiogenesis receptors VEGF?R2, FGF?R1 and FGF?R2. Recently, high?resolution magic angle spinning magnetic resonance spectroscopy (HR?MAS MRS) has provided the opportunity to investigate more detailed metabolic profiles from intact tissue specimens that are correlated with histopathology and is thus, a promising tool for monitoring changes induced by treatment. In the present study, 1H HR?MAS MRS and immunohistochemistry were used to investigate the antitumor efficacy of brivanib in HCC xenograft models. Tumor growth was significantly suppressed in brivanib?treated mice compared with the controls and treatment was associated with the inhibition of angiogenesis, increased apoptosis and inhibition of cell proliferation. Furthermore, HR?MAS techniques showed altered metabolic profiles between the two groups. HR?MAS spectra demonstrated a significant decrease in choline metabolite levels in the treated groups, concurrent with decreased cell proliferation and increased apoptosis. The results showed that 1H HR?MAS MRS provides quantitative metabolite information that may be used to analyze the efficacy of brivanib treatment in Hep3B tumor xenografts. Thus, the HR?MAS MRS technique may be a complementary method to support histopathological results and increase its potential for use in the clinic. PMID:24064967

Yang, Jehoon; Song, Kyoung Doo; Kim, Jae-Hun; Im, Geun-Ho; Yoon, Seulgi; Namgung, Misun; Hwang, Jung-Hyun; Lee, Jung Hee; Choi, Dongil

2013-09-18

17

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.

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

18

Structural studies of geopolymers by 29 Si and 27 Al MAS-NMR  

Microsoft Academic Search

A systematic study of geopolymers by 29Si and 27Al MAS NMR has been carried out in an attempt to understand polymer structural details. 27Al MAS NMR data shows that transient aluminium species are formed during the reaction of metakaolin with NaOH. Interaction of silicate anions with the aluminium sites of metakaolin was evident during the synthesis of geopolymers as observed

Puyam S. Singh; Tim Bastow; Mark Trigg

2005-01-01

19

Measuring proton shift tensors with ultrafast MAS NMR  

NASA Astrophysics Data System (ADS)

A new proton anisotropic–isotropic shift correlation experiment is described which operates with ultrafast MAS, resulting in good resolution of isotropic proton shifts in the detection dimension. The new experiment makes use of a recoupling sequence designed using symmetry principles which reintroduces the proton chemical shift anisotropy in the indirect dimension. The experiment has been used to measure the proton shift tensor parameters for the OH hydrogen-bonded protons in tyrosine·HCl and citric acid at Larmor frequencies of up to 850 MHz.

Miah, Habeeba K.; Bennett, David A.; Iuga, Dinu; Titman, Jeremy J.

2013-10-01

20

A quantitative comparison of metabolite signals as detected by in vivo MRS with ex vivo 1H HR-MAS for childhood brain tumours.  

PubMed

(1)H MRS provides a powerful method for investigating tumour metabolism by allowing the measurement of metabolites in vivo. Recently, the technique of (1)H high-resolution magic angle spinning (HR-MAS) has been shown to produce high-quality data, allowing the accurate measurement of many metabolites present in unprocessed biopsy tissue. The purpose of this study was to evaluate the agreement between the techniques of in vivo MRS and ex vivo HR-MAS for investigating childhood brain tumours. Short-TE (30 ms), single-voxel, in vivo MRS was performed on 16 paediatric patients with brain tumours at 1.5 T. A frozen biopsy sample was available for each patient. HR-MAS was performed on the biopsy samples, and metabolite quantities were determined from the MRS and HR-MAS data using the LCModel and TARQUIN algorithms, respectively. Linear regression was performed on the metabolite quantities to asses the agreement between MRS and HR-MAS. Eight of the 12 metabolite quantities were found to correlate significantly (P < 0.05). The four worst correlating metabolites were aspartate, scyllo-inositol, glycerophosphocholine and N-acetylaspartate, and, except for glycerophosphocholine, this error was reflected in their higher Cramer-Rao lower bounds (CRLBs), suggesting that low signal-to-noise was the greatest source of error for these metabolites. Glycerophosphocholine had a lower CRLB implying that interference with phosphocholine and choline was the most significant source of error. The generally good agreement observed between the two techniques suggests that both MRS and HR-MAS can be used to reliably estimate metabolite quantities in brain tumour tissue and that tumour heterogeneity and metabolite degradation do not have an important effect on the HR-MAS metabolite profile for the tumours investigated. HR-MAS can be used to improve the analysis and understanding of MRS data. PMID:19067434

Wilson, Martin; Davies, Nigel P; Grundy, Richard G; Peet, Andrew C

2009-02-01

21

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

22

Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials  

Microsoft Academic Search

Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and

Younkee Paik

2003-01-01

23

Geopolymer formation processes at room temperature studied by 29Si and 27Al MAS-NMR  

Microsoft Academic Search

A systematic study of 29Si and 27Al MAS-NMR has been carried out in an attempt to understand the reaction mechanism of the geopolymer formation at room temperature. For selected compositions, reactions were followed at selected times after the initial mixing of the reactants until the final products formed. The reactants were silicate anions, metakaolin and aqueous alkali. Silicate anions from

Puyam S. Singh; Mark Trigg; Iko Burgar; Timothy Bastow

2005-01-01

24

Probing crystal structures and transformation reactions of ammonium molybdates by 14N MAS NMR spectroscopy.  

PubMed

The unique high-resolution feature offered by 14N magic-angle spinning (MAS) NMR spectroscopy of ammonium ions has been used to characterize the crystal structures of various ammonium molybdates by their 14N quadrupole coupling parameters, i.e., CQ, the quadrupole coupling constant, and etaQ, the asymmetry parameter. Two polymorphs of diammonium monomolybdate, (NH4)2MoO4, recently structurally characterized by single-crystal X-ray diffraction (XRD) and named mS60 and mP60, show distinct but different 14N MAS NMR spectra from each of which two sets of characteristic 14N CQ and etaQ values have been obtained. Similarly, the well-characterized ammonium polymolybdates (NH4)2Mo2O7, (NH4)6Mo7O24.4H2O, and (NH4)6Mo8O27.4H2O also give rise to distinct and characteristic 14N MAS NMR spectra. In particular, it is noted that simulation of the experimental (NH4)6Mo7O24.4H2O spectrum requires an iterative fit with six independent NH4+ sites. For the slow spinning frequencies employed (nu(r) = 1500-3000 Hz), all 14N MAS NMR spectra of the ammonium molybdates in this study are fingerprints of their identity. These different 14N MAS NMR fingerprints are shown to be an efficient tool in qualitative and quantitative assessment of the decomposition of (NH4)2MoO4 in humid air. Finally, by a combination of the 14N and 95Mo MAS NMR experiments performed here, it has become clear that a recent report of the 95Mo MAS spectra and data for the mS60 and mP60 polymorphs of (NH4)2MoO4 are erroneous because the sample examined had decomposed to (NH4)2Mo2O7. PMID:17173446

Hove, Anders R; Bildsøe, Henrik; Skibsted, Jørgen; Brorson, Michael; Jakobsen, Hans J

2006-12-25

25

High-resolution 1H MAS RFDR NMR of biological membranes  

NASA Astrophysics Data System (ADS)

The combination of magic angle spinning (MAS) with the high-resolution 1H NOESY NMR experiment is an established method for measuring through-space 1H…1H dipolar couplings in biological membranes. The segmental motion of the lipid acyl chains along with the overall rotational diffusion of the lipids provides sufficient motion to average the 1H dipolar interaction to within the range where MAS can be effective. One drawback of the approach is the relatively long NOESY mixing times needed for relaxation processes to generate significant crosspeak intensity. In order to drive magnetization transfer more rapidly, we use solid-state radiofrequency driven dipolar recoupling (RFDR) pulses during the mixing time. We compare the 1H MAS NOESY experiment with a 1H MAS RFDR experiment on dimyristoylphosphocholine, a bilayer-forming lipid and show that the 1H MAS RFDR experiment provides considerably faster magnetization exchange than the standard 1H MAS NOESY experiment. We apply the method to model compounds containing basic and aromatic amino acids bound to membrane bilayers to illustrate the ability to locate the position of aromatic groups that have penetrated to below the level of the lipid headgroups.

Aucoin, Darryl; Camenares, Devin; Zhao, Xin; Jung, Jay; Sato, Takeshi; Smith, Steven O.

2009-03-01

26

Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials  

NASA Astrophysics Data System (ADS)

Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and deuterium-intercalated pyrolusite and ramsdellite were detected by NMR, for the first time, and their locations and motions in the structures were analyzed by applying variable temperature NMR techniques. Discharge mechanisms of EMD in alkaline (aqueous) electrolytes were studied, in conjunction with step potential electrochemical spectroscopic (SPECS) method, and five distinctive discharge processes were proposed. EMD is usually heat-treated at about 300--400°C to remove water to be used in lithium batteries. Details of the effects of heat-treatment, such as structural and compositional changes as a function of heat-treatment temperature, were studied by a combination of MAS NMR, XRD, and thermogravimetric analysis. Lithium local environments in heat-treated EMD (HEMD) that were discharged in lithium cells, were described in terms of related environments found in model compounds pyrolusite and ramsdellite where specific Li + sites were detected by MAS NMR and the hyperfine shift scale method of Grey et al. Acid-leaching of Li2MnO3 represents an approach for synthesizing new or modified manganese oxide electrode materials for lithium rechargeable batteries. Progressive removal of lithium from specific crystallographic sites, followed by a gradual change of the crystal structure, was monitored by a combination of NMR and XRD techniques.

Paik, Younkee

27

Using heat to control the sample spinning speed in MAS NMR.  

PubMed

A new approach using temperature to control the spinning speed of a sample rotor in magic-angle spinning NMR is presented. Instead of an electro-mechanical valve that regulates the flow of drive gas to control the spinning speed in traditional MAS NMR systems, we use a small heater wire located directly in the stator. The sample spinning speed is controlled very accurately with a surprisingly low heating power of 1 W. Results on a benchtop unit demonstrate the capability of the system. PMID:21820341

Mihaliuk, Eugene; Gullion, Terry

2011-07-23

28

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

29

Tetrahedral site ordering in synthetic gallium albite: A 29Si MAS NMR study  

NASA Astrophysics Data System (ADS)

The ordering of Si in the tetrahedral sites of gallium albite (NaGaSi3O8) has been studied by MAS NMR and Rietveld structure refinement of X-ray powder diffraction data. Low structural state (ordered) material was annealed at about 800°C under a load pressure of 1 kbar, and by Rietveld refinement has tetrahedral-site occupancies for Si of T1O = 0.24(3), T1m = 0.89(2), T2O = 0.98(2), and T2m = 0.89(2), respectively. Corresponding Si occupancies for high structural state (disordered) material are 0.71(2), 0.78(1), 0.76(2), and 0.74(2), respectively. The 29Si MAS NMR spectra of low gallium albite is equivalent to the three-peak spectrum of natural (Amelia) albite, with resonances at -89.6, -96.4, and -104.2 ppm but with relative peak areas of 0.79:1.0:0.77. The tetrahedral-site occupancies derived from the MAS NMR spectrum are in good agreement with those obtained by Rietveld refinement and, in particular, indicate that the -96.4 ppm peak must correspond to Si in T2O. This is the first independent assignment of the 29Si peak at -96 ppm in the spectrum of ordered albite to the T2O site. A peak at -96 ppm is also resolved in the spectrum of high gallium albite. The systematic differences in peak position between the 29Si MAS NMR spectra of low gallium albite and those of Amelia albite cannot be explained simply by the direct replacement of Al by Ga, without a change in angle at the bridging oxygen atoms.

Sherriff, Barbara L.; Fleet, Michael E.; Burns, Peter C.

1991-09-01

30

27Al and 29Si MAS–NMR studies of structural changes in hybrid aluminosilicate gels  

Microsoft Academic Search

Aluminosilicate gels with stoichiometric and nonstoichiometric compositions were synthesized by means of colloidal sol-gel method and their mullitization behavior was studied by X-ray diffraction (XRD), 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS–NMR) experiments. Particular attention was given to the structural changes of matrix accompanying the formation of mullite. The various coordinated Al occupancies were clarified by simulating

Hailei Zhao; Keisuke Hiragushi; Yasuo Mizota

2002-01-01

31

29Si MAS NMR study of the structure of calcium silicate hydrate  

Microsoft Academic Search

This paper presents the results of a comprehensive investigation of single-phase calcium silicate hydrate (C?S?H) with known compositions using the combined capabilities of 29Si magic angle spinning (MAS) NMR, powder X-ray diffraction (XRD), and chemical analysis of the solution and solid. C?S?H gels with C\\/S ratios ranging from 0.4 to 1.85 have been synthesized by hydration of highly reactive ?-C2S

Xiandong Cong; R. James Kirkpatrick

1996-01-01

32

Effects of Fluoride on in vitro Enamel Demineralization Analyzed by F MAS-NMR.  

PubMed

The mechanistic action of fluoride on inhibition of enamel demineralization was investigated using (19)F magic angle spinning nuclear magnetic resonance (MAS-NMR). The aim of this study was to monitor the fluoride-mineral phase formed on the enamel as a function of the concentration of fluoride ions [F(-)] in the demineralizing medium. The secondary aim was to investigate fluorapatite formation on enamel in the mechanism of fluoride anti-caries efficacy. Enamel blocks were immersed into demineralization solutions of 0.1 M acetic acid (pH 4) with increasing concentrations of fluoride up to 2,262 ppm. At and below 45 ppm [F(-)] in the solution, (19)F MAS-NMR showed fluoride-substituted apatite formation, and above 45 ppm, calcium fluoride (CaF2) formed in increasing proportions. Further increases in [F(-)] caused no further reduction in demineralization, but increased the proportion of CaF2 formed. Additionally, the combined effect of strontium and fluoride on enamel demineralization was also investigated using (19)F MAS-NMR. The presence of 43 ppm [Sr(2+)] in addition to 45 ppm [F(-)] increases the fraction of fluoride-substituted apatite, but delays formation of CaF2 when compared to the demineralization of enamel in fluoride-only solution. PMID:23712030

Mohammed, N R; Kent, N W; Lynch, R J M; Karpukhina, N; Hill, R; Anderson, P

2013-05-23

33

Discrimination of patients with microsatellite instability colon cancer using 1H HR MAS MR spectroscopy and chemometric analysis.  

PubMed

The primary aim of this study was to analyze human colon cancer and normal adjacent tissue using (1)H HR MAS MR spectroscopy and chemometric analyses, evaluating possible biomarkers for colon cancer. The secondary aim was to investigate metabolic profiles of tissue samples (n = 63, 31 patients) with microsatellite instability (MSI-H) compared to microsatellite stable (MSS) colon tissue. Our hypothesis was that this method may provide an alternative to MSI genotyping. Cancer samples were clearly separated from normal adjacent mucosa by 100% accuracy. Several metabolites such as lactate, taurine, glycine, myo-inositol, scyllo-inositol, phosphocholine (PC), glycerophosphocholine (GPC), creatine, and glucose were identified as potential biomarkers for cancer detection. Adenomas (n = 4) were also separated from cancer and normal samples mainly based on higher GPC and PC levels. Interestingly, metabolic differences in normal colon mucosa between MSI-H and MSS patients were observed. MSI status was validated with 80% accuracy with a sensitivity and specificity of 79% and 82%, respectively, including both cancer and normal samples The metabolic differences between MSI-H and MSS may be very interesting in the early detection of cancer development and of high clinical importance in the work of improving diagnosis and characterization of colon cancer. PMID:20507057

Tessem, May-Britt; Selnaes, Kirsten M; Sjursen, Wenche; Tranø, Gerd; Giskeødegård, Guro F; Bathen, Tone F; Gribbestad, Ingrid S; Hofsli, Eva

2010-07-01

34

TRAPDOR double-resonance and high-resolution MAS NMR for structural and template studies in zeolite ZSM-5  

Microsoft Academic Search

A combination of 27Al magic-angle spinning (MAS)\\/multiple-quantum (MQ) MAS, and 27Al–{14N} TRAnsfer of Population in DOuble-Resonance (TRAPDOR) nuclear magnetic resonance (NMR) was used to study aluminium environments in zeolite ZSM-5. 27Al–{14N} TRAPDOR experiments, in combination with 14N NMR were employed to show that the two tetrahedral peaks observed in the 27Al MAS\\/3Q-MAS spectra of as-synthesized ZSM-5 are due to aluminium

Anuji Abraham; Roel Prins; Jeroen A. van Bokhoven; Ernst R. H. van Eck; Arno P. M. Kentgens

2009-01-01

35

Metabolic, pathologic, and genetic analysis of prostate tissues: quantitative evaluation of histopathologic and mRNA integrity after HR-MAS spectroscopy.  

PubMed

The impact of high-resolution magic angle spinning (HR-MAS) spectroscopy on the histopathologic and mRNA integrity of human prostate tissues was evaluated. Forty prostate tissues were harvested at transrectal ultrasound (TRUS) guided biopsy (n?=?20) or radical prostatectomy surgery (n?=?20), snap-frozen on dry ice, and stored at -80°C until use. Twenty-one samples (n?=?11 biopsy, n?=?10 surgical) underwent HR-MAS spectroscopy prior to histopathologic and cDNA microarray analysis, while 19 control samples (n?=?9 biopsy, n?=?10 surgical) underwent only histopathologic and microarray analysis. Frozen tissues were sectioned at 14-µm intervals and placed on individual histopathology slides. Every 8th slide was stained with hematoxylin and eosin (H&E) and used to target areas of predominantly epithelial tissue on the remaining slides for mRNA integrity and cDNA microarray analysis. Histopathologic integrity was graded from 1 (best) to 5 (worst) by two 'blinded' pathologists. Histopathologic integrity scores were not significantly different for post-surgical tissues (HR-MAS vs controls); however, one pathologist's scores were significantly lower for biopsy tissues following HR-MAS while the other pathologist's scores were not. mRNA integrity assays were performed using an Agilent 2100 Bioanalyzer and the electrophoretic traces were scored with an RNA integrity number (RIN) from 1 (degraded) to 10 (intact). RIN scores were not significantly different for surgical tissues, but were significantly lower for biopsy tissues following HR-MAS spectroscopy. The isolated mRNA then underwent two rounds of amplification, conversion to cDNA, coupling to Cy3 and Cy5 dyes, microarray hybridization, imaging, and analysis. Significance analysis of microarrays (SAM) identified no significantly over- or under-expressed genes, including 14 housekeeping genes, between HR-MAS and control samples of surgical and biopsy tissues (5% false discovery rate). This study demonstrates that histopathologic and genetic microarray analysis can be successfully performed on prostate surgical and biopsy tissues following HR-MAS analysis; however, biopsy tissues are more fragile than surgical tissues. PMID:20033906

Santos, Carissa F; Kurhanewicz, John; Tabatabai, Z Laura; Simko, Jeffry P; Keshari, Kayvan R; Gbegnon, Akpene; Santos, Romelyn Delos; Federman, Scot; Shinohara, Katsuto; Carroll, Peter R; Haqq, Christopher M; Swanson, Mark G

2009-12-23

36

Metabolic, pathologic, and genetic analysis of prostate tissues: quantitative evaluation of histopathologic and mRNA integrity after HR-MAS spectroscopy  

PubMed Central

The impact of high-resolution magic angle spinning (HR-MAS) spectroscopy on the histopathologic and mRNA integrity of human prostate tissues was evaluated. Forty prostate tissues were harvested at transrectal ultrasound (TRUS) guided biopsy (n =20) or radical prostatectomy surgery (n =20), snap-frozen on dry ice, and stored at ?80°C until use. Twenty-one samples (n =11 biopsy, n =10 surgical) underwent HR-MAS spectroscopy prior to histopathologic and cDNA microarray analysis, while 19 control samples (n =9 biopsy, n =10 surgical) underwent only histopathologic and microarray analysis. Frozen tissues were sectioned at 14-?m intervals and placed on individual histopathology slides. Every 8th slide was stained with hematoxylin and eosin (H&E) and used to target areas of predominantly epithelial tissue on the remaining slides for mRNA integrity and cDNA microarray analysis. Histopathologic integrity was graded from 1 (best) to 5 (worst) by two ‘blinded’ pathologists. Histopathologic integrity scores were not significantly different for post-surgical tissues (HR-MAS vs controls); however, one pathologist’s scores were significantly lower for biopsy tissues following HR-MAS while the other pathologist’s scores were not. mRNA integrity assays were performed using an Agilent 2100 Bioanalyzer and the electrophoretic traces were scored with an RNA integrity number (RIN) from 1 (degraded) to 10 (intact). RIN scores were not significantly different for surgical tissues, but were significantly lower for biopsy tissues following HR-MAS spectroscopy. The isolated mRNA then underwent two rounds of amplification, conversion to cDNA, coupling to Cy3 and Cy5 dyes, microarray hybridization, imaging, and analysis. Significance analysis of microarrays (SAM) identified no significantly over- or under-expressed genes, including 14 housekeeping genes, between HR-MAS and control samples of surgical and biopsy tissues (5% false discovery rate). This study demonstrates that histopathologic and genetic microarray analysis can be successfully performed on prostate surgical and biopsy tissues following HR-MAS analysis; however, biopsy tissues are more fragile than surgical tissues.

Santos, Carissa F.; Kurhanewicz, John; Tabatabai, Z. Laura; Simko, Jeffry P.; Keshari, Kayvan R.; Gbegnon, Akpene; Santos, Romelyn DeLos; Federman, Scot; Shinohara, Katsuto; Carroll, Peter R.; Haqq, Christopher M.; Swanson, Mark G.

2010-01-01

37

The Local Structure of Bismuth-Borates Characterized by 11B MAS NMR  

NASA Astrophysics Data System (ADS)

Bismuth-borate glasses and vitroceramics belonging to xBi2O3 . (100 - x) B2O3 system, 0 <= x <= 93, doped with 0.5 mol% MnO are investigated by 11B Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). The 11B MAS NMR results indicate the presence of three- and tetra-coordinated boron in all investigated bismuth borates. While the fraction of the tetra-coordinated boron present a large maximum in the range 20 <= x <= 60 in the bismuth-borate glasses, this maximum is reduced to the range 20 <= x <= 37.5 in the samples obtained after heat treatment. Crystalline phases are developed in the samples with high bismuth content, x >= 60, by heat treatment at 550°C, in which two types of three-coordinated boron are identified. The mean values of the NMR parameters like chemical shift, asymmetry parameter and quadrupolar coupling constant are less influenced by the bismuth/boron ratio, showing that boron structural units are relatively stable on the entire investigated composition range.

Vasilescu, M.; Simon, S.

38

Ammonia Vapor Removal by Cu3(BTC)2 and Its Characterization by MAS NMR  

PubMed Central

Adsorption equilibria and NMR experiments were performed to study the adsorption and interactions of ammonia with metal-organic framework (MOF) HKUST-1, or Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate). Ammonia capacities determined from chemical breakthrough measurements show significantly higher uptake capacities than from adsorption alone, suggesting a stronger interaction involving a potential reaction with the Cu3(BTC)2 framework. Indeed, 1H MAS NMR reveals that a major disruption of the relatively simple spectrum of Cu3(BTC)2 occurs to generate a composite spectrum consistent with Cu(OH)2 and (NH4)3BTC species under humid conditions—the anticipated products of a copper(II) carboxylate reacted with limited ammonia. These species are not detected under dry conditions; however, reaction stoichiometry combined with XRD results suggests the partial formation of an indeterminate diammine copper (II) complex with some residual Cu3(BTC)2 structure retained. Cu(II)-induced paramagnetic shifts exhibited by various species in 1H and 13C MAS NMR spectra are consistent with model compounds and previous literature. Although results show extensive ammonia capacity of Cu3(BTC)2, much of the capacity is due to reaction with the structure itself, causing a permanent loss in porosity and structural integrity.

Peterson, Gregory W.; Wagner, George W.; Balboa, Alex; Mahle, John; Sewell, Tara; Karwacki, Christopher J.

2009-01-01

39

Enhanced Sensitivity by Nonuniform Sampling Enables Multidimensional MAS NMR Spectroscopy of Protein Assemblies  

PubMed Central

We report dramatic sensitivity enhancements in multidimensional MAS NMR spectra by the use of nonuniform sampling (NUS) and introduce Maximum Entropy Interpolation (MINT) processing that assures the linearity between the time- and frequency domains of the NUS acquired datasets. A systematic analysis of sensitivity and resolution in 2D and 3D NUS spectra reveals that with NUS at least one-and-a-half to two-fold sensitivity enhancement can be attained in each indirect dimension without compromising the spectral resolution. These enhancements are similar to or higher than those attained by the newest-generation commercial cryogenic probes. We explore the benefits of this NUS/MaxEnt approach in proteins and protein assemblies using 1-73-(U-13C,15N)/74-108-(U-15N) E. coli thioredoxin reassembly. We demonstrate that in thioredoxin reassembly, NUS permits acquisition of high-quality 3D-NCACX spectra, which are inaccessible with conventional sampling due to prohibitively long experiment times. Of critical importance, issues which hinder NUS-based SNR enhancement in 3D-NMR of liquids are mitigated in the study of solid samples where theoretical enhancements on the order of 3-4 fold are accessible by compounding the NUS-based SNR enhancement of each indirect dimension. NUS/MINT is anticipated to be widely applicable and advantageous for multidimensional heteronuclear MAS NMR spectroscopy of proteins, protein assemblies, and other biological systems.

Paramasivam, Sivakumar; Suiter, Christopher L.; Hou, Guangjin; Sun, Shangjin; Palmer, Melissa; Hoch, Jeffrey C.; Rovnyak, David; Polenova, Tatyana

2012-01-01

40

C CP-MAS NMR of Azacycle-Thiourea Inclusion Compounds  

Microsoft Academic Search

C CP-MAS NMR spectra of thiourea host-guest inclusion compounds containing amines, 1-azabicyclo[2.2.2]octane, 1,4-diazabicyclo[2.2.2]octane, 3-azabicyclo[3.2.2]nonane and 1, 3, 5, 7 tetrazadamantane at 25°C are reported. Chemical shifts of the confined guest molecule with respect to those diluted in CDCl3 and CCl4 reveal a weaker interaction of the amine with the medium. The magnitude of the average of the C–N residual dipolar

Paul Jara; Nicolás Yutronic; Guillermo González

1998-01-01

41

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

42

6 Li MAS NMR and in situ X-ray studies of lithium nickel manganese oxides  

Microsoft Academic Search

In situ XRD and 6Li MAS NMR spectroscopy have been carried out during the first charge process for the layered cathode material Li[Li1\\/9Ni3\\/9Mn5\\/9]O2. In situ XRD results showed that the c-parameters of the Li[Li1\\/9Ni3\\/9Mn5\\/9]O2 material increase only slightly at the end of charge. The Mn and Ni K-edge EXAFS results revealed that this compound contains localized clusters resembling the local

Won-Sub Yoon; Namjun Kim; Xiao-Qing Yang; James McBreen; Clare P Grey

2003-01-01

43

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

44

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.; Rossum, Barth-Jan van; Oschkinat, Hartmut

2012-03-01

45

Evaluation of lactate and alanine as metabolic biomarkers of prostate cancer using 1 H HR-MAS spectroscopy of biopsy tissues  

Microsoft Academic Search

The goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using 1H high-resolution magic angle spinning (HR-MAS) spectroscopy of snap-frozen transrectal ultrasound (TRUS)-guided prostate biopsy tissues. A long-echo-time rotor-synchronized Carr-Pur- cell-Meiboom-Gill (CPMG) sequence including an electronic reference to access in vivo concentrations (ERETIC) standard was used to determine the concentrations

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

2008-01-01

46

Probing the mobility of ibuprofen confined in MCM-41 materials using MAS-PFG NMR and hyperpolarised-(129)Xe NMR spectroscopy.  

PubMed

The continuous-flow hyperpolarised (HP)-(129)Xe NMR and magic angle spinning-pulsed field gradient (MAS-PFG) NMR techniques have been used for the first time to study the distribution and the dynamics of ibuprofen encapsulated in MCM-41 with two different pore diameters. PMID:24100415

Guenneau, Flavien; Panesar, Kuldeep; Nossov, Andrei; Springuel-Huet, Marie-Anne; Azaïs, Thierry; Babonneau, Florence; Tourné-Péteilh, Corine; Devoisselle, Jean-Marie; Gédéon, Antoine

2013-10-16

47

The acidity of niobic acid studied by 1H broad-line NMR at 4 K and H MAS NMR at room temperature: comparison with other solid acids  

Microsoft Academic Search

The acidity of niobium pentoxide calcined at 573 K has been studied by interacting water molecules and the solid acid using 1H broad-line NMR at 4 K and MAS NMR at room temperature. 1H Broad-line NMR in ‘rigid lattice’ conditions allows the determination of the numbers of the oxygen-protonated species (H3O+ and H2O ··· HO species, unreacted OH groups or

Patrice Batamack; Robert Vincent; Jacques Fraissard

1996-01-01

48

Metallic Li colloids studied by Li-7 MAS NMR in electron-irradiated LiF  

NASA Astrophysics Data System (ADS)

Li-7 MAS NMR spectra of 2.5 MeV electron-irradiated LiF crystals have been measured in a field of 9.4 T. Besides the resonance line of the ionic compound, a second well-separated spectrum is observed in the region of the Knight shift value for metallic lithium. At room temperature, the latter can be decomposed into two components with different Knight shift and linewidth values. When the temperature is increased, line narrowing takes place at first, indicating shortening of correlation times for self-diffusion, independently in both components. Above 370 K, both lines broaden and approach each other before collapsing into a single line. The high ppm component disappears after crossing the melting temperature of metallic lithium (454 K). The two lines are attributed to different types of metallic Li: one to bulk-like metal, the other to Li present initially under pressure and relaxing to the former under thermal treatment.

Zogal, O. J.; Beuneu, F.; Vajda, P.; Florian, P.; Massiot, D.

49

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 D2O:H2O = 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 HN 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

50

Increasing 13C CP-MAS NMR resolution using single crystals: application to model octaethyl porphyrins.  

PubMed

Octaethyl porphyrin (OEP) and its Ni and Zn derivatives are considered as model compounds in biochemical, photophysical, and fossil fuel chemistry. They have thus been investigated by high-resolution solid-state (13)C NMR using powders, but peak assignment has been difficult because of large line widths. Arguing that a significant cause of broadening might be the anisotropic bulk magnetic susceptibility, we utilized single crystals in our (13)C cross-polarization magic angle spinning (CP-MAS) measurements and observed a nearly 2-fold line narrowing. This enhanced resolution enabled us to assign chemical shifts to each carbon for all the three compounds. The new assignments are now in agreement with X-ray structural data and allowed us to probe the motional dynamics of the methyl and methylene carbons of the OEP side chains. It is apparent that the use of single crystals in (13)C CP-MAS measurements has a significantly wider impact than previously thought. PMID:22679901

Dugar, Sneha; Fu, Riqiang; Dalal, Naresh S

2012-07-24

51

Residue specific hydration of primary cell wall potato pectin identified by solid-state 13C single-pulse MAS and CP/MAS NMR spectroscopy.  

PubMed

Hydration of rhamnogalacturonan-I (RG-I) derived from potato cell wall was analyzed by (13)C single-pulse (SP) magic-angle-spinning (MAS) and (13)C cross-polarization (CP) MAS nuclear magnetic resonance (NMR) and supported by (2)H SP/MAS NMR experiments. The study shows that the arabinan side chains hydrate more readily than the galactan side chains and suggests that the overall hydration properties can be controlled by modifying the ratio of these side chains. Enzymatic modification of native (NA) RG-I provided samples with reduced content of arabinan (sample DA), galactan (sample DG), or both side chains (sample DB). Results of these samples suggested that hydration properties were determined by the length and character of the side chains. NA and DA exhibited similar hydration characteristics, whereas DG and DB were difficult to hydrate because of the less hydrophilic properties of the rhamnose-galacturonic acid (Rha-GalA) backbone in RG-I. Potential food ingredient uses of RG-I by tailoring of its structure are discussed. PMID:21462966

Larsen, Flemming H; Byg, Inge; Damager, Iben; Diaz, Jerome; Engelsen, Søren B; Ulvskov, Peter

2011-04-14

52

Broadband inversion for MAS NMR with single-sideband-selective adiabatic pulses.  

PubMed

We explain how and under which conditions it is possible to obtain an efficient inversion of an entire sideband family of several hundred kHz using low-power, sideband-selective adiabatic pulses, and we illustrate with some experimental results how this framework opens new avenues in solid-state NMR for manipulating spin systems with wide spinning-sideband (SSB) manifolds. This is achieved through the definition of the criteria of phase and amplitude modulation for designing an adiabatic inversion pulse for rotating solids. In turn, this is based on a framework for representing the Hamiltonian of the spin system in an NMR experiment under magic angle spinning (MAS). Following earlier ideas from Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], the so-called "jolting frame" is used, which is the interaction frame of the anisotropic interaction giving rise to the SSB manifold. In the jolting frame, the shift modulation affecting the nuclear spin is removed, while the Hamiltonian corresponding to the RF field is frequency modulated and acquires a spinning-sideband pattern, specific for each crystallite orientation. PMID:21241090

Pell, Andrew J; Kervern, Gwendal; Emsley, Lyndon; Deschamps, Michaäl; Massiot, Dominique; Grandinetti, Philip J; Pintacuda, Guido

2011-01-14

53

Characterization of cation environments in polycrystalline forsterite by Mg-25 MAS, MQMAS, and QCPMG NMR  

SciTech Connect

Forsterite (Mg2SiO4) is a silicate mineral frequently studied in the Earth sciences as it has a simple crystal structure and fast dissolution kinetics (elemental release rates under typical conditions on the order of 10-7 mol/m2/s1). During the dissolution process, spectroscopic techniques are often utilized to augment solution chemical analysis and to provide data for determining reaction mechanisms. Nuclear magnetic resonance (NMR) is able to interrogate the local bonding arrangement and coordination of a particular nuclide to obtain in structural information. Although previous NMR studies have focused on the silicon and oxygen environments in forsterite, studies focusing on the two nonequivalent magnesium environments in forsterite are limited to a few single-crystal studies. In this study, we present the results of 25Mg MAS, MQMAS, and static QCMG experiments performed on a powdered sample of pure synthetic forsterite. We also present spectral fits obtained from simulation software packages, which directly provide quadrupolar parameters for 25Mg nuclei occupying each of the two nonequivalent magnesium sites in the forsterite structure. These results are compared to calculations of the electric field gradient tenor conducted in previous ab initio studies to make definitive assignments correlating each peak to their respective magnesium site in the forsterite structure. Although previous NMR investigations of forsterite have focused on single-crystal samples, we have focused on powdered forsterite as the increased surface area of powdered samples makes them more amenable to laboratory-scale dissolution studies and, ultimately, the products from chemical weathering may be monitored an quantified.

Davis, Michael C.; Brouwer, William J.; Lipton, Andrew S.; Gan, Zhehong; Mueller, Karl T.

2010-11-01

54

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

55

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

56

The distribution of sodium ions in aluminosilicate glasses: a high-field Na-23 MAS and 3Q MAS NMR study  

NASA Astrophysics Data System (ADS)

The local configurations around sodium ions in silicate glasses and melts and their distributions have strong implications for the dynamic and static properties of melts and thus may play important roles in magmatic processes. The quantification of distributions among charge-balancing cations, including Na + in aluminosilicate glasses and melts, however, remains a difficult problem that is relevant to high-temperature geochemistry as well as glass science. Here, we explore the local environment around Na + in charge-balanced aluminosilicate glasses (the NaAlO 2-SiO 2 join) and its distribution using 23Na magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy at varying magnetic fields of 9.4, 14.1, and 18.8 T, as well as triple-quantum (3Q)MAS NMR spectroscopy at 9.4 T, to achieve better understanding of the extent of disorder around this cation. We quantify the extent of this disorder in terms of changes in Na-O distance ( d[Na-O]) distributions with composition and present a structural model favoring a somewhat ordered Na distribution, called a "perturbed" Na distribution model. The peak position in 23Na MAS spectra of aluminosilicate glasses moves toward lower frequencies with increasing Si/Al ratios, implying that the average d(Na-O) increases with increasing R. The peak width is significantly reduced at higher fields (14.1 and 18.8 T) because of the reduced effect of second-order quadrupolar interaction, and 23Na MAS NMR spectra thus provide relatively directly the Na chemical shift distribution and changes in atomic environment with composition. Chemical shift distributions obtained from 23Na 3Q MAS spectra are consistent with MAS NMR data, in which deshielding decreases with R. The average distances between Na and the three types of bridging oxygens (BOs) (Na-{Al-O-Al}, Na-{Si-O-Al}, and Na-{Si-O-Si}) were obtained from the correlation between d(Na-O) and isotropic chemical shift. The calculated d(Na-{Al-O-Al}) of 2.52 Å is shorter than the d(Na-{Si-O-Si}) of 2.81 Å, and d(Na-{Al-O-Al}) shows a much narrower distribution than the other types of BOs. 23Na chemical shifts in binary (Al-free) sodium silicate glasses are more deshielded and have ranges distinct from those of aluminosilicate glasses, implying that d(Na-NBO) (nonbridging oxygen) is shorter than d(Na-BO) and that d(Na-{Si-O-Si}) in binary silicates can be shorter than that in aluminosilicate glasses. The results given here demonstrate that high-field 23Na NMR is an effective probe of the Na + environment, providing not only average structural information but also chemically and topologically distinct chemical shift ranges (distributions) and their variation with composition and their effects on static and dynamic properties.

Lee, Sung Keun; Stebbins, Jonathan F.

2003-05-01

57

Structure of Cl-containing silicate and aluminosilicate glasses: A 35Cl MAS-NMR study  

NASA Astrophysics Data System (ADS)

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for the nuclide in inorganic chlorides. Peak widths are primarily due to quadrupole interactions and to a lesser extent to chemical shift distributions. Peak positions are quite different for the Na- and Ca-containing glasses, suggesting that most Cl - coordination environments contain network modifier cations. Comparison of peak positions and shapes for silicate and aluminosilicate glasses containing either Na or Ca suggests that there is no obvious contribution from Cl - bonded to Al, and relative quantitation of peak areas indicates that there is no systematic undercounting of 35Cl spins in the aluminous vs. the Al-free samples. In Ca-Na silicate glasses with varying Ca/(Ca + Na), the mixed-cation glasses have intermediate chemical shifts between those of the end members, implying that there is not a strong preference of either Ca 2+ or of Na + around Cl -. Hydrous Na-aluminosilicate glasses with H 2O contents up to 5.9 wt% show a shift to higher frequency NMR signal with increasing H 2O content, while the quadrupole coupling constant ( CQ) remains constant at ˜3.3 MHz. However, the change in frequency is much smaller than that expected if H 2O systematically replaced Na + in the first-neighbor coordination shell around Cl -. A series of hydrous Ca-aluminosilicate glasses with H 2O contents up to 5.5 wt% show no shift in NMR signal with increasing H 2O content. The CQ remains constant at ˜4.4 MHz, again suggesting no direct interaction between Cl - and H 2O in these samples.

Sandland, Travis O.; Du, Lin-Shu; Stebbins, Jonathan F.; Webster, James D.

2004-12-01

58

Regional metabolic alteration of Alzheimer's disease in mouse brain expressing mutant human APP-PS1 by 1H HR-MAS.  

PubMed

This study aimed to find the most sensitive brain region of APP-PS1 mice in early-stage Alzheimer's disease (AD) and to compare the findings with wild-type mouse brain using (1)H high resolution magic angle spectroscopy (HR-MAS). At 18 and 35 weeks of age, the object recognition test was performed with both APP-PS1 and wild-type mice, and the metabolite concentrations were measured in six brain regions at 38-42 weeks using (1)H HR-MAS. Compared to that of wild-type mice, the memory index of the APP-PS1 mice at 18 weeks was not significantly different; however, the memory index of the APP-PS1 mice at 35 weeks was significantly lower. Similar to the results of the (1)H HR-MAS, the [N-acetyl aspartate (NAA)+acetate (Acet)] level in APP-PS1 mice was decreased in the hippocampus and temporal cortex, and the myo-inositol (mIns) level was increased in the entire brain. In addition, scyllo-inositol (sIns) was also elevated in the frontal, occipital, and parietal cortices, hippocampus and thalamus. These findings demonstrated that the behavioral abnormalities of the APP-PS1 mice started at about 30 weeks of age and that the hippocampus and temporal cortex were the most sensitive regions during early-stage AD. In addition, the results of this study confirmed that an increase of mIns and sIns precedes the reduction of the NAA level. These findings demonstrated that the metabolism of the APP-PS1 mouse was associated with early-stage AD. Furthermore, the regional neurochemical profile of APP-PS1 mouse can be used to investigate the pathophysiological mechanisms associated with AD. PMID:20307581

Woo, Dong-Cheol; Lee, Sung-Ho; Lee, Do-Wan; Kim, Sang-Young; Kim, Goo-Young; Rhim, Hyang-Shuk; Choi, Chi-Bong; Kim, Hwi-Yool; Lee, Chang-Uk; Choe, Bo-Young

2010-03-20

59

29Si MAS NMR, XRD and FESEM studies of rice husk silica for the synthesis of zeolites  

Microsoft Academic Search

We have used rice husk ash as a silica source for the synthesis of zeolites. Amorphous silica is a highly reactive silicon source, but not all silica which is amorphous to XRD is equally suitable. The local structure of amorphous silica was investigated by 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and field emission scanning electron microscopy (FESEM) in

Halimaton Hamdan; Mohd Nazlan Mohd Muhid; Salasiah Endud; Endang Listiorini; Zainab Ramli

1997-01-01

60

Acetylation of raw cotton for oil spill cleanup application: an FTIR and 13C MAS NMR spectroscopic investigation  

Microsoft Academic Search

Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy have been used to investigate the acetylation of raw cotton samples with acetic anhydride without solvents in the presence of different amounts of 4-dimethylaminopyridine (DMAP) catalyst. This is a continuation of our previous investigation of acetylation of commercial cotton in an effort to develop hydrophobic, biodegradable, cellulosic sorbent materials for cleaning

Moses O Adebajo; Ray L Frost

2004-01-01

61

11B and 89Y MAS NMR and magnetic characterization of Y B  

NASA Astrophysics Data System (ADS)

11B and 89Y MAS NMR spectra at room temperature and magnetization in the temperature range (2-300 K) were measured on a powder specimen of Y B4. The three different 11B Knight shifts (34.7, 12.6 and 5.4 ppm) for the crystallographic sites B1(4e), B2(4h) and B3(8j), respectively, were observed in a magnetic field of 17.6 T. The 89Y isotropic Knight shift (294.6 ppm) and K,K and K components of the Knight shift tensor have been determined. The spin-lattice relaxation times, T(11B)=4.5s and T(89Y)=5.5s, were measured at room temperature. Analysis of the magnetization data have indicated that Y B4 is a diamagnetic compound with the temperature independent component of its magnetic susceptibility equal to -5.9?10-9(m3/kg). Some of these data were referred to those of CaBC(x=0.21), LaB,NdB and YSiB.

?oga?, O. J.; Florian, P.; Massiot, D.; Paluch, S.; Shitsevalova, N.; Borshchevsky, D. F.

2009-05-01

62

Multinuclear MAS NMR study of the microporous aluminophosphate AlPO4-17 and the related silicoaluminophosphate SAPO-17.  

PubMed

AlPO4-17 and SAPO-17 in their as-synthesized, calcined, and calcined and subsequently rehydrated forms have been studied by 27Al and 31P MAS NMR. Pronounced structural changes caused by template removal and rehydration can unambiguously be attributed to a change in the coordination number (on calcination: 5-->4, on rehydration/dehydration: 4<-->6) of part of the framework aluminium atoms. The different resonance lines can be assigned to crystallographically inequivalent sites present in the modified ERI framework. 27Al quadrupolar coupling parameters of the two aluminium sites in the calcined AlPO4-17 (CQ = 4.4 MHz and 2.1 MHz) were determined by recording spectra at different field strengths. The isotropic chemical shifts were obtained from rotation sidebands of the (+/- 3/2, +/- 1/2) satellite transitions. 2D 27Al nutation MAS NMR was used to corroborate the line assignment for the as-synthesized and the rehydrated AlPO4-17. By using 13C MAS NMR it was shown that the occluded template (cyclohexylamine) is present as ions. For the first time, a splitting of the 29Si NMR line caused by crystallographically inequivalent sites in a SAPO-type material is reported. The line splitting of 4.3 ppm is comparable with that observed for isostructural aluminosilicate erionite. PMID:1365725

Zibrowius, B; Lohse, U

1992-07-01

63

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

64

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

PubMed

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- to 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- to 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

2009-10-04

65

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

NASA Astrophysics Data System (ADS)

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- to 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- to 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.

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

2010-01-01

66

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

67

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.

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

68

A CP\\/MAS 13C-NMR study of cellulose structure on the surface of refined kraft pulp fibers  

Microsoft Academic Search

The average lateral fibril and fibril aggregate dimensions and the crystallinity of the cellulose in a spruce kraft pulp were investigated by CP\\/MAS 13C-NMR spectroscopy in combination with spectral fitting. Cellulose isolated by chlorite-delignification and acid hydrolysis from fines fractions enriched in surface material and long fiber fractions enriched in bulk material exhibited no major differences in either lateral dimensions

Eva-Lena Hult; Tiina Liitiä; Sirkka Liisa Maunu; Bo Hortling; Tommy Iversen

2002-01-01

69

Silicate species exchange, viscosity, and crystallization in a low-silica melt: In situ high-temperature MAS NMR spectroscopy  

Microsoft Academic Search

High-resolution, magic-angle-spinning (MAS), 29Si NMR spectra have been obtained for a sodium silicate glass and liquid (60 mol% Si02) to temperatures over 600 °C. Crys- tallization was monitored in situ, and motional averaging of the peaks for distinct silicate anionic species (Q2 and Q3 species) in the liquid was observed. Modeling of the spectra yielded species exchange frequencies. The inverses

J. F. STEBBINS; S. SEN; I. FARNAN

1995-01-01

70

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 ...

71

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

72

Reactions of the nerve agent simulant diisopropyl fluorophosphate with self-decontaminating adsorbents. A 31 P MAS NMR study  

Microsoft Academic Search

The room temperature decompositions of the nerve agent simulant diisopropyl fluorophosphate (DFP) sorbed on ?-alumina, polydivinylbenzene (impregnated with NaOH, polyethylene glycol and polyethylenimine) (DVB\\/NaOH), and Ambergard® XE-555, were studied in situ using 31P MAS NMR. Hydrolysis of the P–F bond of DFP was observed on all three sorbents, which effectively detoxifies nerve agents. On XE-555, the competing process of micropore

George W. Wagner; Philip W. Bartram

1999-01-01

73

Reactions of the mustard simulant 2-chloroethyl phenyl sulfide with self-decontaminating sorbents. A 13C MAS NMR study  

Microsoft Academic Search

Decomposition reactions for the mustard simulant 2-chloroethyl phenyl sulfide (13C-labelled, CEPS?) sorbed on ?-alumina, polydivinylbenzene (impregnated with NaOH, polyethylene glycol and polyethylenimine) (DVBNaOH), and Ambergard® XE-555, were characterized in situ using 13C MAS NMR. CEPS? hydrolyzes on ?-alumina to form 2-hydroxyethyl phenyl sulfide. On DVBNaOH, CEPS? eliminates HCl to yield vinyl phenyl sulfide. No products were observed on XE-555, where

George W. Wagner; Philip W. Bartram

1996-01-01

74

31P MAS NMR study of the hydrolysis of O,S-diethyl phenylphosphonothioate on reactive sorbents  

Microsoft Academic Search

31P MAS NMR was used to monitor the hydrolysis of O,S-diethyl phenylphosphonothioate (DEPPT) sorbed on gammaalumina, XE-555 (a mixture of strong-acid\\/strong-base ion exchange resins and a carbonaceous adsorbent), and a polydivinylbenzene sorbent impregnated with NaOH. The products were identified to determine the amount of P?OP?S bond hydrolysis occurring on the sorbents. The relative order of reactivity observed for the sorbents

George W. Wagner; Philip W. Bartram

1995-01-01

75

NaLSX zeolite with chemisorbed methyl groups studied by powder neutron diffraction and 13C MAS NMR  

NASA Astrophysics Data System (ADS)

Powder samples of NaLSX faujasite (Si/Al =1) in dehydrated state and with adsorbed methyl iodide were investigated by neutron diffraction and 13C MAS NMR. The distribution of Na+ cations and chemisorbed methylium ions in the frame of NaLSX was estimated by Rietveld refinement. Surface methoxy group were located mostly at O1 and O4 lattice oxygen. The changes in populations of cationic sites after chemisorption were detected.

Vratislav, Stanislav; Dlouhá, Maja; Bosá?ek, Vladimír

2004-07-01

76

Characterization of Plasma Polymerized Hydrocarbons Using CP-MAS Carbon-13 NMR.  

National Technical Information Service (NTIS)

Plasma polymerized hydrocarbons made from ethane and methane were produced under different reactor conditions and probed by solid-state carbon-13 nuclear magnetic resonance (NMR) with cross-polarization and magic angle sample spinning. NMR experiments pro...

D. L. Cho F. D. Blum H. Yasuda R. J. Gambogi

1991-01-01

77

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

NASA Astrophysics Data System (ADS)

The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-? nuclei, using 14N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1 T and Bruker, 19.6 T), 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 14.1 T) in several exploratory wide bandwidth 14N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed 14N MAS spectra correspondingly acquired at 19.6 T 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.

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

2011-08-01

78

Electronic Shieldings and Electric Field Gradients in Rubidium Sulfate Studied by 87Rb MAS NMR  

Microsoft Academic Search

Determination of the magnitudes and relative orientation of quadrupolar and chemical-shift tensors can be carried out from a precise analysis of the powder MAS spectra even when the second-order quadrupolar interaction is dominant. This has been illustrated by the study of the 87Rb MAS spectra of rubidium sulfate at 196.3 MHz.

C. Fernandez; J. P. Amoureux; P. Bodart

1995-01-01

79

Conversion of propan-2-ol on zeolites LaNaY and HY investigated by gas chromatography and in situ MAS NMR spectroscopy under continuous-flow conditions  

SciTech Connect

The conversion of propan-2-ol on zeolites HY and LaNaY has been investigated by gas chromatography (GC) and in situ {sup 1}H and {sup 13}C MAS NMR spectroscopy under continuous-flow conditions using a new MAS NMR microreactor with cylindrical catalyst bed. At reaction temperatures of T = 373 K and T = 393 K a propan-2-ol conversion of 50 and 100%, respectively, and the formation of propene, diisopropyl. ether, and small amounts of acetone was determined by GC. Applying in situ {sup 1}H and {sup 13}C MAS NMR spectroscopy, the initial step of the reaction was found to be the physisorption of propan-2-ol on Bronsted acid sites. A formation of isopropoxy species could be excluded by {sup 13}C MAS NMR spectroscopy. {sup 1}H MAS NMR spectroscopy indicated that the Bronsted acid sites of the zeolites LaNaY and HY were hydrated by water molecules in the first part of the induction period. These water molecules were formed in result of the propan-2-ol dehydration. The strong low-field shift of the {sup 1}H MAS NMR signals of the hydrated Bronsted acid sites is due to a partial protonation of adsorbed water molecules. At T = 393 K, a significant {sup 13}C MAS NMR signal of strongly bonded acetone molecules appeared at 220 ppm in the spectra of zeolites LaNaY and HY. As demonstrated by propan-2-ol conversion on a partially dealuminated zeolite HY, this by-reaction is promoted by extra-framework aluminium species. The formation of coke precursors which caused {sup 13}C MAS NMR signals at 10-50 ppm is explained by an oligomerization of propene. In situ {sup 13}C MAS NMR experiments carried out under a continuous flow of propene showed that the above-mentioned coke precursors are also formed on partially rehydrated zeolite HY. 25 refs., 14 figs., 1 tab.

Hunger, M.; Horvath, T. [Univ of Stuttgart (Germany)

1997-04-01

80

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

81

Application of LC-NMR and HR-NMR to the characterization of biphenyl impurities in the synthetic route development for vestipitant, a novel NK1 antagonist  

Microsoft Academic Search

Vestipitant (1) is a novel NK1 antagonist currently under investigation for the treatment of CNS disorders and emesis. The first synthetic step comprised a Grignard synthesis. An impurity was identified and initially expected to be a symmetric biphenyl. This paper reports the work to synthesise the supposed structure and the spectroscopic analyses (LC-NMR and HR-NMR) to correctly identify the real

Stefano Provera; Luca Martini; Giuseppe Guercio; Lucilla Turco; Laura Costa; Carla Marchioro

2010-01-01

82

Application of LC-NMR and HR-NMR to the characterization of biphenyl impurities in the synthetic route development for vestipitant, a novel NK1 antagonist.  

PubMed

Vestipitant (1) is a novel NK1 antagonist currently under investigation for the treatment of CNS disorders and emesis. The first synthetic step comprised a Grignard synthesis. An impurity was identified and initially expected to be a symmetric biphenyl. This paper reports the work to synthesise the supposed structure and the spectroscopic analyses (LC-NMR and HR-NMR) to correctly identify the real structure and understand the chemical pathway of the impurity. PMID:20478677

Provera, Stefano; Martini, Luca; Guercio, Giuseppe; Turco, Lucilla; Costa, Laura; Marchioro, Carla

2010-04-29

83

Structural characteristics of marine sedimentary humic acids by CP\\/MAS 13C NMR spectroscopy  

Microsoft Academic Search

Humic acids from sediments of different depositional environments have been studied by solid-state 13C NMR and the results compared with the traditional wet chemical analysis. Results obtained are well in agreement with the previous literature reports that the carboxyl content measured by NMR correlated better with the total acidity, as well as with the carboxyl content obtained by wet chemical

Sugandha Sardessai; Solimabi Wahidullah

1998-01-01

84

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 CD2H 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

85

Niobium oxide acidity studied by proton broad-line NMR at 4 K and MAS NMR at room temperature  

Microsoft Academic Search

The quantitative study of the Brønsted acidity of niobic acid (Nb2O5·xH2O) using broad-line1H NMR at 4 K has been performed by interacting niobic acid, pretreated at 573 K under vacuum, with water molecules. The number of oxyprotonated species (H3O+ and H2O...HO species formed, unreacted acidic OH groups or excess H2O molecules) deduced from the simulations of the broad-line1H NMR spectra

Patrice Batamack; Robert Vincent; Jacques Fraissard

1996-01-01

86

MAS NMR of the Drug Resistant S31N M2 Proton Transporter from Influenza A  

PubMed Central

We report chemical shift assignments of the drug-resistant S31N mutant of M218-60 determined with magic angle spinning (MAS) 3D spectra acquired with a 15N-13C ZF-TEDOR transfer followed by 13C-13C mixing by RFDR. The MAS spectra reveal two sets of resonances, indicating that the tetramer assembles as a dimer of dimers, similar to the wild type channel. The two sets of chemical shifts are shown to be in close proximity at residue H37, and assignments reveal a difference in the helix torsion angles, as predicted by TALOS+, for the key resistance residue N31. In contrast to wild type M218-60, chemical shift changes are minimal with addition of the inhibitor rimantadine, suggesting that the drug does not bind to S31N.

Andreas, Loren B.; Eddy, Matthew T.; Chou, James J.; Griffin, Robert G.

2012-01-01

87

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

88

Structural studies of boron and tellurium coordination in zinc borophosphate glasses by 11B MAS NMR and Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Zinc borophosphate glasses doped with TeO2 with different B2O3/P2O5 ratio were prepared, their basic properties were determined and their structure was studied by 11B MAS NMR and Raman spectroscopies. Structural studies were devoted to the investigation of changes in boron coordination in the dependence on changes in TeO2 content and in B2O3/P2O5 ratio in the borophosphate glasses. A special attention was devoted to the formation of mixed structural units B(OP)4-n(OTe)n in the studied borophosphate glasses, where by the deconvolution of 11B MAS NMR spectra quantitative data on the number of BO3 and B(OP)4-n(OTe)n mixed structural units were obtained. Raman spectra showed shortening of phosphate chains both with increasing TeO2 and B2O3 content. Raman spectra also showed that with the replacement of P2O5 by B2O3 in the studied glasses TeO4 units are replaced by TeO3 units as the number of oxygen atoms in the glass decreases when the B2O3/P2O5 ratio increases.

Vosejpková, Kate?ina; Koudelka, Ladislav; ?ernošek, Zden?k; Mošner, Petr; Montagne, Lionel; Revel, Bertrand

2012-02-01

89

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

PubMed Central

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

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

2008-01-01

90

Spectral editing in solid-state MAS NMR of quadrupolar nuclei using selective satellite inversion  

Microsoft Academic Search

A sensitivity enhancement method based on selective adiabatic inversion of a satellite transition has been employed in a (?\\/2)CT–(?)ST1–(?\\/2)CT spectral editing sequence to both enhance and resolve multisite NMR spectra of quadrupolar nuclei. In addition to a total enhancement of 2.5 times for spin 3\\/2 nuclei, enhancements up to 2.0 times is reported for the edited sites in a mixture

Krishna K. Dey; S. Prasad; Jason T. Ash; Michael Deschamps; Philip J. Grandinetti

2007-01-01

91

Study of the conversion of methanol to dimethyl ether on zeolite HZSM-5 using in situ flow MAS NMR.  

PubMed

The conversion of methanol to gasoline (MTG) range hydrocarbons on zeolite catalyst HZSM-5 has been studied extensively using solid-state NMR. We have studied the reaction under batch and flow conditions using an isolated flow variable-temperature (VT) MAS NMR probe. This probe was developed to study heterogeneous catalysis reactions in situ at temperatures greater than 300 degrees C with reactant flow. In the batch studies, when 13C-labeled methanol was adsorbed on zeolite HZSM-5, sealed, and heated to 250 degrees C, dimethyl ether was formed. Two-dimensional exchange NMR shows that dimethyl ether was in equilibrium with methanol at 250 degrees C. When 13C-methanol was flowed over HZSM-5 at temperatures > or = 200 degrees C, only dimethyl ether was observed. Between 160 degrees C and 200 degrees C, both methanol and dimethyl ether were observed. The flow results are significant in that they suggest that there is no equilibrium between methanol and dimethyl ether in the catalyst at high temperatures, and that surface methoxy groups do not exist on the catalyst at high temperatures. PMID:10811434

Carlson, L K; Isbester, P K; Munson, E J

2000-05-01

92

Solid-state [sup 1]H MAS NMR characterization of [gamma]-alumina and modified [gamma]-aluminas  

SciTech Connect

[gamma]-alumina is used extensively as a catalyst support material. [sup 1]H single pulse MAS and CPMG T[sub 2]/CSA-filter NMR experiments have been performed in order to characterize the hydroxyl structure of [gamma]-alumina, as well as fluoride- and phosphate-modified [gamma]-alumina materials. The authors have shown that problems associated with the strong homonuclear dipole-dipole interactions between protons of neighboring OH groups can be overcome by isotopic dilution of the alumina surface protons by deuterium exchange. Partially deuterated [gamma]-alumina yields resonances at around -0.3, 0.3, 1.5, 2.4, 4.0, 5.0, 6.5, 7.1, and 7.8 ppm. CPMG T[sub 2]/CSA-filter NMR experiments performed on alumina calcined at 700[degrees]C show that five different types of hydroxyl groups are present. CPMG T[sub 2]/CSA-filter NMR of deuterated F/Al[sub 2]O[sub 3] produces a resonance at 11.5 ppm in addition to a range of resonances between -0.2 and 7 ppm. NMR data for calcined P/Al[sub 2]O[sub 3] and P-Mo(12)/Al[sub 2]O[sub 3] (wt% P = 0.0-10.0) show that polymeric orthophosphates produce a resonance at 3.4 ppm, while the monomeric orthophosphate species gives rise to a resonance at 1.2 ppm. 41 refs., 6 figs.

DeCanio, E.C.; Edwards, J.C. (Texaco Research and Development Department, Beacon, NY (United States)); Bruno, J.W. (Wesleyan Univ., Middletown, CT (United States))

1994-07-01

93

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

NASA Astrophysics Data System (ADS)

Asymmetries in the manifold of spinning sidebands (ssbs) from the satellite transitions have been observed in variable-temperature 27Al MAS NMR spectra of alum (KAl(SO4)2 · 12H2O), recorded in the temperature range from -76 to 92 °C. The asymmetries decrease with increasing temperature and reflect the fact that the ssbs exhibit systematically different linewidths for different spectral regions of the manifold. From spin-echo 27Al NMR experiments on a single-crystal of alum, it is demonstrated that these variations in linewidth originate from differences in transverse (T2) relaxation times for the two inner (m = 1/2 ? m = 3/2 and m = -1/2 ? m = -3/2) and correspondingly for the two outer (m = 3/2 ? m = 5/2 and m = -3/2 ? m = -5/2) satellite transitions. T2 relaxation times in the range 0.5 3.5 ms are observed for the individual satellite transitions at -50 °C and 7.05 T, whereas the corresponding T1 relaxation times, determined from similar saturation-recovery 27Al NMR experiments, are almost constant (T1 = 0.07 0.10 s) for the individual satellite transitions. The variation in T2 values for the individual 27Al satellite transitions for alum is justified by a simple theoretical approach which considers the cross-correlation of the local fluctuating fields from the quadrupolar coupling and the heteronuclear (27Al 1H) dipolar interaction on the T2 relaxation times for the individual transitions. This approach and the observed differences in T2 values indicate that a single random motional process modulates both the quadrupolar and heteronuclear dipolar interactions for 27Al in alum at low temperatures.

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

2005-04-01

94

Fast acquisition of multi-dimensional spectra in solid-state NMR enabled by ultra-fast MAS  

NASA Astrophysics Data System (ADS)

The advantages offered by ultra-fast (>60 kHz) magic angle spinning (MAS) rotation for the study of biological samples, notably containing paramagnetic centers are explored. It is shown that optimal conditions for performing solid-state 13C NMR under 60 kHz MAS are obtained with low-power CW 1H decoupling, as well as after a low-power 1H,13C cross-polarization step at a double-quantum matching condition. Acquisition with low-power decoupling highlights the existence of rotational decoupling sidebands. The sideband intensities and the existence of first and second rotary conditions are explained in the framework of the Floquet-van Vleck theory. As a result, optimal 13C spectra of the oxidized, paramagnetic form of human copper zinc superoxide dismutase (SOD) can be obtained employing rf-fields which do not exceed 40 kHz during the whole experiment. This enables the removal of unwanted heating which can lead to deterioration of the sample. Furthermore, combined with the short 1H T1s, this allows the repetition rate of the experiments to be shortened from 3 s to 500 ms, thus compensating for the sensitivity loss due to the smaller sample volume in a 1.3 mm rotor. The result is that 2D 13C-13C correlation could be acquired in about 24 h on less than 1 mg of SOD sample.

Laage, Ségolène; Sachleben, Joseph R.; Steuernagel, Stefan; Pierattelli, Roberta; Pintacuda, Guido; Emsley, Lyndon

2009-02-01

95

29Si MAS NMR relaxation study of shocked Coconino Sandstone from Meteor Crater, Arizona  

NASA Astrophysics Data System (ADS)

29Si nuclear magnetic resonance (NMR) spectroscopy was used to characterize the silica phases in a moderately-shocked Coconino sandstone from Meteor Crater, Arizona. The spectra were recorded using direct polarization, magic-angle spinning, and variable delay times in a saturation recovery pulse sequence. Resonances observed at -97.3, -107.1, -113.9 and -191.2 ppm were assigned to a densified hydrous form of amorphous silica (D phase), quartz, coesite and stishovite phases, respectively. The relative percentages were estimated as 1.7, 80.6, 16.4 and 1.3% for the D, quartz, coesite, and stishovite phases. The power-law recoveries of the magnetization for the quartz and coesite phases can be interpreted in terms of their phase geometries.

Myers, S. A.; Cygan, R. T.; Assink, R. A.; Boslough, M. B.

96

Quantitative {sup 29}Si MAS NMR spectroscopy of cement and silica fume containing paramagnetic impurities  

SciTech Connect

The low natural abundance and the long spin lattice relaxation time of {sup 29}Si lead to long measurement times and/or low signal-to-noise ratios using {sup 29}Si magic angle spinning NMR spectroscopy. By contrast, samples containing paramagnetic iron ions have much shorter relaxation times, making measurements up to seven times more efficient, but at the same time making quantitative analysis unreliable. To solve the problem, the spin-lattice relaxation times of ordinary Portland cement (opc) and silica fume with and without iron content has been determined with inversion recovery experiments. The effect of varying the spectrum repetition time on the quantitative analysis is demonstrated for mixtures of opc with silica fume. For opc and silica fume with iron impurities repetition times as short as 5 s has permitted accurate quantitative analysis of the silicates present in these materials.

Hilbig, H. [Center of Building Materials (CBM), Technische Universitaet Muenchen, Baumbachstr. 7, D-81245 Munich (Germany)]. E-mail: hilbig@cbm.bv.tum.de; Koehler, F.H. [Department Chemie, Technische Universitaet Muenchen, D-85747 Garching (Germany); Schiessl, P. [Center of Building Materials (CBM), Technische Universitaet Muenchen, Baumbachstr. 7, D-81245 Munich (Germany)

2006-02-15

97

Analysis of Hydroperoxides in Solid Polyethylene by MAS (13)C NMR and EPR  

SciTech Connect

{sup 13}C-enriched polyethylene was subjected to {gamma}-irradiation in the presence of air at 25 and 80 C for total doses ranging from 71 to 355 kGy. Significant quantities of hydroperoxides were detected in the 25 C irradiated sample by {sup 13}C magic angle spinning NMR spectroscopy. This method of detection was performed on the solid polymer and required no chemical derivatization or addition of solvent. The chemical stability and subsequent products of the hydroperoxide species were studied by annealing the irradiated samples in air at temperatures ranging from 22 to 110 C. A time-temperature superposition analysis provided an activation energy of 108 kJ/mol for the hydroperoxide decomposition process. The primary products of hydroperoxide decomposition were ketones and secondary alcohols with lesser amounts of acids and esters. EPR measurements suggest that the reactive hydroperoxide species reside in the amorphous phase of polyethylene, consistent with degradation occurring in the amorphous phase.

ASSINK,ROGER A.; CELINA,MATHIAS C.; DUNBAR,TIMOTHY D.; ALAM,TODD M.; CLOUGH,ROGER LEE; GILLEN,KENNETH T.

1999-11-19

98

Influence of glass chemical composition on the Na–O bond distance: a 23Na 3Q-MAS NMR and molecular dynamics study  

Microsoft Academic Search

The sodium environment in oxide glasses was investigated by 23Na multiple-quantum magic-angle spinning (MQ-MAS) NMR spectroscopy and compared with molecular dynamics simulations. In the experimental approach, a spectrum-inversion was employed taking into account the transfer efficiency involved in the MQ-MAS experiment. This allowed the reconstruction of the underlying two-dimensional distribution of the isotropic chemical shift correlated with the quadrupolar interaction.

F. Angeli; J.-M Delaye; T Charpentier; J.-C Petit; D Ghaleb; P Faucon

2000-01-01

99

Structural characterization of glass from the inversion of ²³Na and ²⁷Al 3Q-MAS NMR spectra  

Microsoft Academic Search

A spectrum-inversion approach to extract information from MQ-MAS NMR spectra in glasses is presented. This allows the reconstruction of the underlying two-dimensional distribution of the isotropic chemical shift correlated to the quadrupolar interaction. The dependence upon the quadrupolar interaction and the RF field strength of coherence transfers involved in the MQ-MAS experiment are taken into account in the present approach.

F. Angeli; T. Charpentier; P. Faucon; J.-C. Petit

1999-01-01

100

Acetylation of raw cotton for oil spill cleanup application: an FTIR and 13C MAS NMR spectroscopic investigation  

NASA Astrophysics Data System (ADS)

Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy have been used to investigate the acetylation of raw cotton samples with acetic anhydride without solvents in the presence of different amounts of 4-dimethylaminopyridine (DMAP) catalyst. This is a continuation of our previous investigation of acetylation of commercial cotton in an effort to develop hydrophobic, biodegradable, cellulosic sorbent materials for cleaning up oil spills. The FTIR data have again provided a clear evidence for successful acetylation. The NMR results further confirm the successful acetylation. The extent of acetylation was quantitatively determined using the weight percent gain (WPG) due to acetylation and by calculating the ratio R between the intensity of the acetyl C?O stretching band at 1740-1745 cm -1 and the intensity of C?O stretching vibration of the cellulose backbone at about 1020-1040 cm -1. The FTIR technique was found to be highly sensitive and reliable for the determination of the extent of acetylation. The level of acetylation of the raw cotton samples was found to be much higher than that of cotton fabrics and the previously studied commercial cotton. The variation of the R and WPG with reaction time, amount of DMAP catalyst and different samples of raw cotton is discussed.

Adebajo, Moses O.; Frost, Ray L.

2004-08-01

101

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 H2O/D2O using a ratio of 1/9. We employ paramagnetic relaxation enhancement (PRE) using EDTA chelated CuII to enable rapid data acquisition.

Linser, Rasmus; Fink, Uwe; Reif, Bernd

2008-07-01

102

Identification of fluorine sites at the surface of fluorinated gamma-alumina by two-dimensional MAS NMR.  

PubMed

By means of 27Al triple quantum Magic-Angle Spinning Nuclear Magnetic Resonance (3QMAS NMR) and 27Al[19F] WISE MAS NMR, we were able to detect three different Al-F sites on the surface of fluorinated gamma-alumina. Three 19F resonances at 9, 20, and 33 ppm (from C6F6) correlated to 27Al resonances in the octahedral range. While the positions of the maxima in the 27Al dimension were ill-defined due to the inherently low efficiency of the 27Al[19F] CPMAS process, the center of gravity of the lines shifted significantly upfield in that dimension with increasing wt.% F. Tentatively, these three resonances were assigned to (VI)Al(O(6-n)Fn) (n = 1, 2, 3) environments on the F/gamma-Al2O3 surface. At F contents above levels corresponding to the full fluorination of the gamma-Al2O3 surface, neoformation of an AlF3 x 3H2O phase was also evidenced with an 19F resonance at -8 ppm and with an 27Al resonance at -17 ppm. PMID:10811433

Fischer, L; Harlé, V; Kasztelan, S; d'Espinose de la Caillerie, J B

2000-05-01

103

MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P2O5 and TiO2 nucleants  

NASA Astrophysics Data System (ADS)

Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li2O-4.0Al2O3-68.6SiO2-3.0K2O-2.6B2O3-0.5P2O5-0.9TiO2 was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by 29Si, 31P, 11B and 27Al MAS-NMR. XRD and 29Si NMR showed that lithium metasilicate (Li2SiO3) is the first phase to c form followed by cristobalite (SiO2) and lithium disilicate (Li2Si2O5). 29Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 °C. Since crystalline Li3PO4, as observed by 31P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li3PO4 does not act as a nucleating agent for lithium silicate phases. Moreover, 31P NMR indicates the formation of M-PO4 (M=B, Al or Ti) complexes. The presence of BO3 and BO4 structural units in all the glass/glass-ceramic samples is revealed through 11B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO3) increases at the expense of tetrahedrally coordinated B (BO4). The 27Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization.

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

2010-06-01

104

Cl-35 and F-19 MAS NMR Studies on Silicate and Aluminosilicate Glasses Containing Multiple Volatile Species.  

NASA Astrophysics Data System (ADS)

Cl-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra have been collected at 14.1 and 18.8 T fields to determine the atomic scale structural environments of Cl in Ca- and Na-silicate and aluminosilicate glasses. Data, in addition to that previously presented, suggest that in mixed modifier (Ca-Na) silicate glasses, a large portion of Cl is in a mixed coordination environment (coordinated by both Ca and Na). Relative peak positions, however, suggest a slight preference for Cl to coordinate Na over Ca. Calculated quadrupolar coupling constants (CQ) increase as Ca/(Ca+Na) increases, indicating that the Cl site is on average more asymmetric at higher Ca/(Ca+Na) ratios. In a series of sodium aluminosilicate glasses containing both water and Cl, data previously presented show a shift to higher frequency NMR signal with increasing water content while CQ remains constant. This change in observed frequency suggests Cl is not directly associated with H2O in the samples and rather that the shift reflects a slight change in the average Cl coordination environment. Current work on a similar series of calcium aluminosilicate glasses promises to further elucidate the interaction of Cl and water in these glasses. While the addition of water has a significant effect on the environment of Cl in the glasses studied, the effect of F on the coordination environment of Cl in these glasses is much less pronounced. Previous work on F-containing mixed modifier silicate glasses has shown that F demonstrates a preference to coordinate higher field strength modifier cations. Preliminary 35Cl MAS NMR data suggest that the addition of F appears to slightly order the Cl environment, as evidenced by a slight narrowing of the peak. Conversely, in 19F data collected at 9.4 T, there is little to no noticeable effect on the environment of F with the addition of Cl in the compositions studied. The current 19F data do show a larger preference for Ca over Na coordination than previously reported.

Sandland, T. O.; Kiczenski, T. J.; Du, L.; Stebbins, J. F.

2003-12-01

105

29Si NMR in solid state with CPMG acquisition under MAS  

SciTech Connect

A remarkable enhancement of sensitivity can be often achieved in {sup 29}Si solid-state NMR by applying the well-known Carr-Purcell-Meiboom-Gill (CPMG) train of rotor-synchronized {pi} pulses during the detection of silicon magnetization. Here, several one- and two-dimensional (1D and 2D) techniques are used to demonstrate the capabilities of this approach. Examples include 1D {sup 29}Si{l_brace}X{r_brace} CPMAS spectra and 2D {sup 29}Si{l_brace}X{r_brace} HETCOR spectra of mesoporous silicas, zeolites and minerals, where X = {sup 1}H or {sup 27}Al. Data processing methods, experimental strategies and sensitivity limits are discussed and illustrated by experiments. The mechanisms of transverse dephasing of {sup 29}Si nuclei in solids are analyzed. Fast magic angle spinning, at rates between 25 and 40 kHz, is instrumental in achieving the highest sensitivity gain in some of these experiments. In the case of {sup 29}Si-{sup 29}Si double-quantum techniques, CPMG detection can be exploited to measure homonuclear J-couplings.

Wiench, J.W.; Lin, V.S.-Y.; Pruski, M.

2008-05-20

106

Characteristics of zero-quantum correlation spectroscopy in MAS NMR experiments  

NASA Astrophysics Data System (ADS)

Zero-quantum coherence generation and reconversion in magic-angle spinning solid-state NMR is analyzed. Two methods are discussed based on implementations using symmetry-based pulse sequences that utilize either isotropic J couplings or dipolar couplings. In either case, the decoupling of abundant proton spins plays a crucial role for the efficiency of the zero-quantum generation. We present optimized sequences for measuring zero-quantum single-quantum correlation spectra in solids, achieving an efficiency of 50% in ubiquitin. The advantages and disadvantages of zero-quantum single-quantum over single-quantum single-quantum correlation spectroscopy are explored, and similarities and differences with double-quantum single-quantum correlation spectroscopy are discussed. Finally, possible application of zero-quantum single-quantum experiments to polypeptides, where it can lead to better spectral resolution is investigated using ubiquitin, where we find high efficiency and high selectivity, but also increased line widths in the MQ dimension.

Köneke, Stephanie G.; van Beek, Jacco D.; Ernst, Matthias; Meier, Beat H.

2010-12-01

107

Condensation degree of burnt peat and plant residues and the reliability of solid-state VACP MAS 13C NMR spectra obtained from pyrogenic humic material  

Microsoft Academic Search

Charred organic matter is assumed to contain heavily condensed polycyclic aromatic domains with a considerable proportion of core carbons. To examine their possible underestimation using variable amplitude (VA) cross polarization (CP) magic angle spinning (MAS) 13C nuclear magnetic resonance (NMR), the condensation degree of a peat subjected to thermal oxidation at 350°C for up to 180s was examined by means

Heike Knicker; Kai Uwe Totsche; Gonzalo Almendros; Francisco J. González-Vila

2005-01-01

108

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

109

Satellite transitions in natural abundance solid-state 33S MAS NMR of alums—Sign change with zero-crossing of CQ in a variable temperature study  

NASA Astrophysics Data System (ADS)

Experiences obtained from recent improvements in the performance of solid-state 14N MAS NMR spectroscopy have been used in a natural abundance 33S MAS NMR investigation of the satellite transitions for this interesting spin I = 3/2 isotope. This study reports the first observation of manifolds of spinning sidebands for these transitions in 33S MAS NMR as observed for the two alums XAl(SO4)2·12H2O with X = NH4 and K. For the NH4-alum a variable temperature 33S MAS NMR study, employing the satellite transitions, shows that the 33S quadrupole coupling constant (CQ) exhibits a linear temperature dependence (in the range -35 °C to 70 °C) with a temperature gradient of 3.1 kHz/°C and undergoes a sign change with zero-crossing for CQ at 4 °C (277 K). For the isostructural K-alum a quite similar increase in the magnitude of CQ with increasing temperature is observed, and with a temperature gradient of 2.3 kHz/°C. Finally, for optimization purposes, a study on the effect of the applied pulse widths at constant rf field strength on the intensity and variation in second-order quadrupolar lineshape for the central (1/2 ? -1/2) transition of the K-alum has been performed.

Jakobsen, Hans J.; Hove, Anders R.; Bildsøe, Henrik; Skibsted, Jørgen

2006-06-01

110

6Li MAS NMR spectroscopy and first-principles calculations as a combined tool for the investigation of Li2MnSiO4 polymorphs.  

PubMed

Polymorphism of Li(2)MnSiO(4) was inspected by (6)Li MAS NMR spectroscopy. The detected isotropic shifts and spinning-sideband patterns were successfully reproduced by first-principles calculations and offered an insight into structural differences among the polymorphs. The approach for predicting isotropic shifts was also tested on several other Li-containing paramagnetic structures. PMID:20372695

Mali, Gregor; Meden, Anton; Dominko, Robert

2010-04-06

111

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...

112

sup 89 Y MAS NMR study of rare-earth pyrochlores: Paramagnetic shifts in the solid state  

SciTech Connect

{sup 89}Y MAS NMR spectra have been obtained from yttrium pyrochlores Y{sub 2-y}Ln{sub y}M{sub 2}O{sub 7} (Ln = Ce, Pr, Nd, Sm, Eu, Yb; M = Sn, Ti). Incorporation of the paramagnetic ions into the diamagnetic compounds was found to cause large reductions in the {sup 89}Y nuclear relaxation times enabling spectra to be accumulated in relatively short times in comparison to similar diamagnetic systems. In addition to the resonances of the diamagnetic end-member compounds, Y{sub 2}Sn{sub 2}O{sub 7} and Y{sub 2}Ti{sub 2}O{sub 7}, extra {sup 89}Y resonances were observed, due to the substitution of paramagnetic ions into the local coordination sphere surrounding an {sup 89}Y nucleus. The paramagnetic shifts were found to be proportional to the number of lanthanide ions substituted for yttrium in the first coordination sphere; the intensities of the resonances could be used to determine the concentration of paramagnetic rare-earth ions in the diamagnetic phase.

Grey, C.P.; Cheetham, A.K.; Dobson, C.M. (Univ. of Oxford (England)); Smith, M.; Dupree, R. (Univ. of Warwick, Coventry (England))

1990-06-06

113

Solid-state {sup 13}C MAS NMR study of methanol-to-hydrocarbon chemistry over H-SAPO-34  

SciTech Connect

{sup 13}C solid-state MAS NMR was used to probe the chemistry of a number of species involved in the methanol-to-hydrocarbon process over H-SAPO-34 molecular sieve at both high (573 K) and low (473-563 K) temperature ranges and at very low conversion (<0.1%). Isobutane was the only hydrocarbon product observed at 473 and 573 K. Evidence for the operation of a stepwise methylation reaction via surface-bound species derives from, first, the treatment of several samples with different loadings of methanol at 523-563 K and, second, when either [{sup 13}C]methanol is coadsorbed with [{sup 12}C]ethene over the catalyst or [{sup 12}C]ethene is reacted with pre-[{sup 13}C]methylated SAPO-34. The hydrocarbon products in these experiments were mainly isobutane and isopentane as well as methane, ethene, and propane. Based on these experimental findings, a number of mechanistic approaches concerning the very first stages of the reaction are discussed. 56 refs., 13 figs., 3 tabs.

Salehirad, F.; Anderson, M.A. [UMIST, Manchester (United Kingdom)

1996-12-01

114

The structural environments of cations adsorbed onto clays: 133Cs variable-temperature MAS NMR spectroscopic study of hectorite  

NASA Astrophysics Data System (ADS)

133Cs Variable-Temperature Magic-Angle-Spinning Nuclear Magnetic Resonance (VT-MAS NMR) spectroscopy shows that Cs on the clay mineral hectorite occurs in several distinctly different chemical environments, and that motional averaging of Cs between some of these sites occurs above ~ -40°C if water is present in the interlayer. At temperatures above ~ -10°C, spectra for slurries of hectorite in CsCl solutions yield two peaks, one due to Cs in solution, and the other due to Cs motionally averaged on the clay. At temperatures below ~ -60°C, motional averaging of the adsorbed Cs slows sufficiently to allow resolution of two peaks representing different Cs-environments on the clay. We use the Stern-Gouy model to explain these peaks, and assign one to Cs in the Stern layer (relatively tightly bound to the basal oxygens) and the other to Cs in the Gouy diffuse layer. A sample hydrated at 100% relative humidity yields similar results, except that there is no peak for Cs in the solution. Cs-exchanged hectorite dehydrated at 500°C yields peaks for two different sites on the clay, which we interpret to be due to a highly coordinated site (probably 12) and a less coordinated site (possibly 9), both in the interlayer. A sample partially dehydrated at 100°C yields similar peaks, but there also appears to be motional averaging of Cs over these two different Cs-environments in the interlayer.

Weiss, Charles Arthur, Jr.; Kirkpatrick, R. James; Altaner, Stephen P.

1990-06-01

115

Probing the mechanism of fluoride-ion conduction in LaF{sub 3} and strontium-doped LaF{sub 3} with high resolution {sup 19}F MAS NMR  

SciTech Connect

The {sup 19}F MAS NMR spectra of LaF{sub 3} and strontium-doped LaF{sub 3} demonstrate the different mobilities and activation energies for the different fluoride-ion jump pathways. High resolution {sup 19}F MAS NMR provides an extremely effective and unique method for probing the mechanism of fluoride-ion conduction. 17 refs., 4 figs.

Wang, F.; Grey, C.P. [State Univ. of New York, Stony Brook, NY (United States)

1997-05-01

116

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

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, 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 oriented solid-state NMR and magic angle spinning solid-state NMR. PMID:23963722

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

2013-08-21

117

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

118

Laser-supported high-temperature MAS NMR for time-resolved in situ studies of reaction steps in heterogeneous catalysis.  

PubMed

The temperature of zeolite samples containing various adsorbed molecules was rapidly changed (within 15 s) from room temperature to 600 K by means of a laser beam. The location of the sealed glass ampoule in a boron nitride container decreases the temperature gradient in the sample and avoids laser-induced reactions. The technique facilitates time-dependent magic-angle-spinning (MAS) NMR spectroscopy of high-temperature reactions which take place within 60 s. The H-D exchange in the hydrogen form of zeolites loaded with fully deuterated molecules, the methanol-to-gasoline conversion and the catalytic ethylbenzene disproportionation in zeolites were monitored by 13C and 1H MAS NMR by means of a "stop and go" method. PMID:8784954

Ernst, H; Freude, D; Mildner, T; Wolf, I

1996-04-01

119

29Si and 19F MAS NMR spectra of isolated 29Si(19F)2 and 29Si(19F)3 spin systems: experiments and simulations.  

PubMed

We consider 29Si and 19F MAS NMR spectra of isolated 29Si(19F)2 and 29Si(19F)3 spin systems in two organosilicon compounds of the type RR'SiF2 and RSiF3(R,R' = organic ligands). Experimental spectra are analysed by means of numerical simulations. It is found that the SiF3 group in RSiF3 is reorienting rapidly around the molecular Si-C bond direction in the solid state. The two 19F shielding tensors in RR'SiF2 have strongly differing orientations relative to the two Si-F bond directions in the molecule. Possibilities and limitations of straightforward MAS NMR approaches for the full characterisation of 29Si(19F)2 and 29Si(19F)3 spin systems and other dipolar coupled two and three-spin systems are discussed. PMID:14642422

Helluy, Xavier; Pietschnig, Rudolf; Sebald, Angelika

2003-12-01

120

Characterization of Na-X, NaA, and coal fly ash zeolites and their amorphous precursors by IR, MAS NMR and XPS  

Microsoft Academic Search

By fusion with sodium hydroxide followed by a hydrothermal reaction, fly ash and Alenriched fly ash were converted into Na-X and Na-A zeolites, respectively. The authentic Na-X, Na-A and fly ash zeolites as well as their amorphous precursors have been characterized by IR, 29Si and 27Al MAS NMR, XPS\\/AES, TG, and comparative ion-exchange studies of Cs and K with Na

N. Shigemoto; S. Sugiyama; H. Hayashi; K. Miyaura

1995-01-01

121

n Butane conversion on sulfated zirconia: in situ 13 C MAS NMR monitoring of the kinetics of the 13 C-label scrambling and isomerization  

Microsoft Academic Search

The kinetics of the conversion of 13C-labeled n-butane adsorbed on sulfated zirconia (SZ) were monitored by in situ13C MAS NMR spectroscopy. Rate constants of n- to isobutane isomerization and of the 13C-isotope scrambling from the primary to the secondary carbon atoms in n-butane were determined. The monomolecular scrambling of the 13C-label in adsorbed n-butane has an activation energy of 17 ± 3 kcal

A. G. Stepanov; M. V. Luzgin; S. S. Arzumanov; W. Wang; M. Hunger; D. Freude

2005-01-01

122

29Si and 13C MAS-NMR characterization of surface modification of micelle-templated silicas during the grafting of organic moieties and end-capping  

Microsoft Academic Search

The surface of micelle-templated silicas (MTS) was functionalized by silylation with 3-chloropropyltriethoxysilane in anhydrous toluene. The modified sample (Cl–MTS) was then end-capped by vapor phase treatment with hexamethyldisilazane (HMDZ), which led to the AZA–Cl–MTS sample. The textural properties of the support were preserved during the different modifications. A comparison of 29Si MAS-NMR spectra of Cl–MTS with those of the parent

Pierre Sutra; François Fajula; Daniel Brunel; Patrick Lentz; Guy Daelen; János B Nagy

1999-01-01

123

Molecular ordering of cellulose after extraction of polysaccharides from primary cell walls of Arabidopsis thaliana: a solid-state CP\\/MAS 13C NMR study  

Microsoft Academic Search

Solid-state CP\\/MAS 13C NMR spectroscopy was used to determine the effects of three different sequential extraction procedures, used to remove non-cellulosic polysaccharides, on the molecular ordering of cellulose in a cell-wall preparation containing mostly primary cell walls obtained from the leaves of the model dicotyledon, Arabidopsis thaliana. The extractions were 50 mM trans-1,2-diaminocyclohexane N,N,N?,N?-tetraacetic acid (CDTA) and 50 mM sodium

Lynette M. Davies; Philip J. Harris; Roger H. Newman

2002-01-01

124

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

SciTech Connect

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

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

1997-06-01

125

(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

126

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

127

Structural characterization of glass from the inversion of {sup 23}Na and {sup 27}Al 3Q-MAS NMR spectra  

SciTech Connect

A spectrum-inversion approach to extract information from MQ-MAS NMR spectra in glasses is presented. This allows the reconstruction of the underlying two-dimensional distribution of the isotropic chemical shift correlated to the quadrupolar interaction. The dependence upon the quadrupolar interaction and the RF field strength of coherence transfers involved in the MQ-MAS experiment are taken into account in the present approach. The performance of the inversion procedure is examined. Thereafter, the authors attempt to correlate the distributions of each interaction to structural local information. Two complex glasses (a borosilicate and a basaltic-like glass) have been studied using {sup 17}Al and {sup 23}Na 3Q-MAS NMR. These two nuclei allowed the investigation of their local environment. The interpretation of the different site distributions is discussed in terms of topological disorder, i.e., the distribution of specific geometrical parameters such as bond distances and angles. Using the empirical relationships previously established with crystalline silicate compounds, the distributions of the Na-O distance and the Al-O-Si bond angle have been determined from the extracted distributions of the isotropic chemical shift. The limits of the interpretation of quadrupolar interaction distributions are also discussed.

Angeli, F.; Charpentier, T.; Faucon, P.; Petit, J.C.

1999-11-25

128

MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li2O/Al2O3 ratio  

NASA Astrophysics Data System (ADS)

Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi2O-71.7SiO2-(17.7-x)Al2O3-4.9K2O-3.2B2O3-2.5P2O5 (5.1?x?12.6) upon heat treatment were studied. 29Si, 27Al, 31P and 11B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO3 and BO4 units. 27Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, 11B (high field 18.8 T) and 29Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi2O6, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li2Si2O5), lithium metasilicate (Li2SiO3) and quartz (SiO2) were identified in the 29Si NMR spectra of the glass-ceramics. 31P NMR spectra of the glass-ceramics revealed the presence of Li3PO4 and a mixed phase (Li,K)3PO4 at low alkali concentrations.

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

2010-01-01

129

In situ MAS NMR–UV\\/Vis investigation of H-SAPO-34 catalysts partially coked in the methanol-to-olefin conversion under continuous-flow conditions and of their regeneration  

Microsoft Academic Search

In situ13C MAS NMR and UV\\/Vis spectroscopy was applied to study the nature of organic deposits formed under continuous-flow conditions of the methanol-to-olefin (MTO) conversion on the silicoaluminophosphate H-SAPO-34. Simultaneously, the volatile reaction products were analyzed by on-line gas chromatography. At reaction temperatures of 573 and 623K, the occurrence of 13C MAS NMR signals of polyalkylated aromatics (18, 125–135ppm) was

Yijiao Jiang; Jun Huang; V. R. Reddy Marthala; Yean S. Ooi; Jens Weitkamp; Michael Hunger

2007-01-01

130

n-Butane isomerization over Cs-salts of H 3PW 12O 40: a mechanistic study by 1C MAS NMR  

Microsoft Academic Search

Reaction mechanism of skeletal isomerization of n-butane over Cs2.5H0.5PW12O40 catalyst was studied using 13C MAS NMR. The reaction proceeds mainly via a monomolecular mechanism at 80°C. The contribution of the bimolecular mechanism becomes more significant as the reaction temperature is increased to 150°C. Hydrogen suppresses the bimolecular mechanism, in particular on Pt-promoted Cs2.5H0.5PW12O40 catalyst. The latter catalyst is highly selective

Zhuona Ma; Weiming Hua; Yu Ren; Heyong He; Zi Gao

2003-01-01

131

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

132

Detection of Brønsted acid sites in zeolite HY with high-field 17O-MAS-NMR techniques  

NASA Astrophysics Data System (ADS)

The acidity and unique porous structures of zeolites play an important role in controlling the activity and selectivity of many zeolite-based catalysts. Although 27Al, 29Si and 1H NMR spectroscopy represent standard analytical tools with which to study these materials, 17O-NMR investigations are much less routine, owing to the very low natural abundance of 17O (0.037%), its relatively low resonant frequency and its large quadrupole moment. 17O-NMR resonances from framework oxygen sites in a variety of zeolites have been detected, but the 17O-NMR resonance from oxygen directly bound to the Brønsted acid site (Si-O(H)-Al) has remained elusive. Here we report the direct observation of this resonance in dehydrated zeolite HY, by using high magnetic-field strengths. 17O-1H double-resonance NMR experiments are used to prove unambiguously that the 17O signal arises from O nearby H atoms. A large quadrupolar coupling constant, the measure of the local distortion of this site, of 6.6 MHz is determined, which is similar to that obtained in ab initio calculations of zeolite HY-like clusters; this value drops to 5 MHz on acetone binding. The results presented in this paper open up methods for characterizing zeolite acidity and investigating H+-sorbent interactions.

Peng, Luming; Liu, Yun; Kim, Namjun; Readman, Jennifer E.; Grey, Clare P.

2005-03-01

133

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

134

Solid state {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na MAS NMR dipolar dephasing investigations of connectivity in sodium aluminophosphate glasses  

SciTech Connect

Solid state {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na MAS NMR dipolar dephasing experiments have been used to investigate the spatial distribution of aluminum and sodium cations with respect to the phosphate backbone for a series of sodium aluminophosphate glasses, xAl{sub 2}O{sub 3}{center_dot}50Na{sub 2}O{center_dot}(50{minus}x)P{sub 2}O{sub 5} (0{le} x {le} 17.5). From the {sup 31}P/{sup 27}Al and {sup 31}P/{sup 23}Na connectivity data gathered, information about the medium range order in these glasses is obtained. The expanded connectivity data allows for better identification and interpretation of the new resonances observed in the {sup 31}P MAS NMR spectra with the addition of alumina. The results of the dipolar dephasing experiments show that the sodium-phosphate distribution remains relatively unchanged for the glass series, and that the addition of aluminum occurs primarily through the depolymerization of the phosphate tetrahedral backbone.

LANG,DAVID P.; ALAM,TODD M.; BENCOE,DENISE N.

2000-05-01

135

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

2009-06-05

136

Efficient resonance assignment of proteins in MAS NMR by simultaneous intra- and inter-residue 3D correlation spectroscopy.  

PubMed

Resonance assignment is the first step in NMR structure determination. For magic angle spinning NMR, this is typically achieved with a set of heteronuclear correlation experiments (NCaCX, NCOCX, CONCa) that utilize SPECIFIC-CP (15)N-(13)C transfers. However, the SPECIFIC-CP transfer efficiency is often compromised by molecular dynamics and probe performance. Here we show that one-bond ZF-TEDOR (15)N-(13)C transfers provide simultaneous NCO and NCa correlations with at least as much sensitivity as SPECIFIC-CP for some non-crystalline samples. Furthermore, a 3D ZF-TEDOR-CC experiment provides heteronuclear sidechain correlations and robustness with respect to proton decoupling and radiofrequency power instabilities. We demonstrate transfer efficiencies and connectivities by application of 3D ZF-TEDOR-DARR to a model microcrystalline protein, GB1, and a less ideal system, GvpA in intact gas vesicles. PMID:23334347

Daviso, Eugenio; Eddy, Matthew T; Andreas, Loren B; Griffin, Robert G; Herzfeld, Judith

2013-01-19

137

Combining multinuclear high-resolution solid-state MAS NMR and computational methods for resonance assignment of glutathione tripeptide.  

PubMed

We present a complete set of experimental approaches for the NMR assignment of powdered tripeptide glutathione at natural isotopic abundance, based on J-coupling and dipolar NMR techniques combined with (1)H CRAMPS decoupling. To fully assign the spectra, two-dimensional (2D) high-resolution methods, such as (1)H-(13)C INEPT-HSQC/PRESTO heteronuclear correlations (HETCOR), (1)H-(1)H double-quantum (DQ), and (1)H-(14)N D-HMQC correlation experiments, have been used. To support the interpretation of the experimental data, periodic density functional theory calculations together with the GIPAW approach have been used to calculate the (1)H and (13)C chemical shifts. It is found that the shifts calculated with two popular plane wave codes (CASTEP and Quantum ESPRESSO) are in excellent agreement with the experimental results. PMID:22612309

Sardo, Mariana; Siegel, Renée; Santos, Sérgio M; Rocha, João; Gomes, José R B; Mafra, Luis

2012-06-12

138

Secondary structure of peptides 16 th . Characterization of proteins by means of 13 C NMR CP\\/MAS spectroscopy  

Microsoft Academic Search

50.3 or 75.4 MHz13C NMR cross-polarization\\/magic angle spinning spectra of human hair, horse hair, horse hoof, parrot feather, sperm whale myoglobin, and horse heart cytochrome C were measured. The spectra of human hair and horse hair indicate nearly equal mole fractions of?-sheets anda-helices and a low percentage of amorphous regions, whereas horse hoof contains a higher fraction of amorphous proteins.

H. R. Kricheldorf; D. Miiller

1984-01-01

139

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

PubMed

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

Magusin, P C; Hemminga, M A

1994-04-01

140

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

PubMed Central

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

Magusin, P C; Hemminga, M A

1994-01-01

141

Magnetic field dependence of 13 C photo-CIDNP MAS NMR in plant photosystems I and II  

Microsoft Academic Search

Photochemically induced dynamic nuclear polarization is observed in the two photosynthetic reaction centers of plants, photosystem\\u000a I (PSI) and photosystem II (PSII) by13C magic-angle spinning nuclear magnetic resonance (NMR) at three different magnetic fields 17.6, 9.4, and 4.7 T. There is\\u000a a significant difference in field dependence detected in the light-induced signal pattern of the two photosystems. For PSII\\u000a the

E. Roy; A. Diller; Alia; P. Gast; H. J. van Gorkom; H. J. M. de Groot; G. Jeschke; J. Matysik

2007-01-01

142

Characterization and comparison of two ligno-cellulosic substrates by (13)C CP/MAS NMR, XPS, conventional pyrolysis and thermochemolysis.  

PubMed

Ligno-cellulosic substrates (LCSs) isolated from wheat straw and bran exhibit high complexing capacities and may have important applications for metal removal from industrial effluents. These two LCSs were examined in the present work by spectroscopic and pyrolytic methods (solid state cross polarization magic angle spinning (CP/MAS) (13)C NMR, XPS, conventional Curie pyrolysis (Cupy)/GC/MS, and TMAH thermochemolysis/GC/MS). This combined study highlighted the limitation of some of the above methods when applied to ligno-cellulosic materials and the resulting biases and the usefulness of TMAH thermochemolysis. A large difference in composition was observed between bran- and straw-LCS due to a much higher contribution of alkyl moieties in the former. These moieties correspond to fatty acids esterified to the ligno-cellulosic macromolecular structure and such carboxylic functions should play an important role for metal complexation. PMID:12194046

Gauthier, A; Derenne, S; Dupont, L; Guillon, E; Largeau, C; Dumonceau, J; Aplincourt, M

2002-06-25

143

11B MAS NMR spectroscopic study of structural relaxation, aging, and memory effect at the atomic scale in a borosilicate glass.  

PubMed

Relaxation kinetics of boron coordination environments in a borosilicate glass in response to temperature jumps has been monitored using (11)B magic-angle spinning (MAS) NMR spectroscopy. The relaxation time scale of the BO4/BO3 ratio is found to be closely comparable with those of the bulk properties, namely, refractive index and viscosity, showing a close connection with one another. Samples partially equilibrated at a low temperature, when subjected to a positive temperature jump, display an initial rapid decrease followed by an increase in the BO4/BO3 ratio. This reversal in the trend of the variation of the BO4/BO3 ratio has been interpreted to be the signature of a memory effect, and the implications are discussed within the framework of the potential energy landscape model of glassy dynamics. PMID:17661507

Uzun, Sezen Soyer; Sen, Sabyasachi

2007-07-28

144

29Si{1H} CP-MAS NMR comparison and ATR-FTIR spectroscopic analysis of the diatoms Chaetoceros muelleri and Thalassiosira pseudonana grown at different salinities.  

PubMed

Diatoms are key indicators of marine environmental health. To further understand how diatoms respond to varying degrees of salinity, either due to climate change or brine waste discharge into marine environments, two different diatom species were studied. Thalassiosira pseudonana and Chaetoceros muelleri were cultured at three different salinities namely, 26 practical salinity units (PSU or parts per thousand), 36 PSU (standard salinity for culturing of seawater species) and 46 PSU. Changes in silica and organic content within the cultured diatoms were analysed using solid-state (29)Si{(1)H} cross-polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies coupled with analysis of variance. (29)Si CP-MAS NMR showed that qualitatively the Q4:Q3 area ratios of C. muelleri, grown away from standard salinities, increased in response to the formation of more condensed (2 ?SiOH ? ?Si-O-Si? + H2O) and/or an increase in closely associated organic matter to the Q4 component of the diatoms. This was not observed for T. pseudonana. However, both species showed the appearance of a new peak centered at 1575-1580 cm(-1) in the ATR-FTIR spectra, designated as the C?N band of nitrogenous purine-type compounds. Further, the C. muelleri species was shown to produce more extracellular polymeric substances at non-standard salinities. On this basis, results suggest that there is a strong relationship between diatom composition and salinity and that C. muelleri is more sensitive to its environment than T. pseudonana. PMID:23371532

La Vars, Sian M; Johnston, Martin R; Hayles, John; Gascooke, Jason R; Brown, Melissa H; Leterme, Sophie C; Ellis, Amanda V

2013-01-31

145

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

146

Simultaneous processing of solid-state NMR relaxation and 1D-MAS exchange data: the backbone dynamics of free vs. binase-bound barstar.  

PubMed

Two types of dynamic solid-state NMR experiments-relaxation and 1D-MAS exchange-were combined for the investigation of the backbone dynamics of a 15% randomly 15N-enriched protein barstar in both free and binase-bound states. The main novelty of this work is a simultaneous quantitative processing of the results of these two types of experiments that we call Simultaneous Relaxation and Exchange Data Analysis (SREDA) approach. It extends the well-known model-free approach such that it permits to discriminate between various motional models (jumps between different sites, wobbling in a cone, etc.). This objective cannot be achieved by analyzing the relaxation or exchange data separately. The SREDA approach was applied to probe a modification of the average backbone dynamics of barstar upon forming a complex with another protein binase. T(1) and off-resonance T(1rho) relaxation times of 15N backbone nuclei were measured at three temperatures between 0 and 45 degrees C, 1D-MAS exchange (CODEX) data were obtained at room temperature within the mixing time range from 0.3 to 200 ms. It has been found that the barstar backbone participates in two molecular processes with correlation times in the 10(-9)-10(-7) and 10(-3)-10(-2) s ranges. Forming the complex with binase results in a significant decrease of the amplitudes of both motions, suggesting that the complex is a more rigid and stable structure than free barstar. PMID:12922175

Krushelnitsky, Alexey G; Hempel, Günter; Reichert, Detlef

2003-08-21

147

{sup 29}Si and {sup 31}P MAS-NMR spectra of Li{sub 2}S-SiS{sub 2}-Li{sub 3}PO{sub 4} rapidly quenched glasses  

SciTech Connect

{sup 29}Si and {sup 31}P MAS-NMR spectra were measured for the Li{sub 2}S-SiS{sub 2}-Li{sub 3}PO{sub 4} glasses. {sup 29}Si MAS-NMR spectra revealed that a large number of silicon atoms in the glasses were coordinated with both sulfur and oxygen atoms. {sup 31}P MAS-NMR spectra showed that some phosphorus atoms were also coordinated with both sulfur and oxygen atoms. Such structural units resulted in the improvement of the conductivity and the glass stability against crystallization by the doping of Li{sub 3}PO{sub 4} to the Li{sub 2}S--SiS{sub 2} glasses.

Hirai, Koichi; Tatsumisago, Masahiro; Minami, Tsutomu [Osaka Prefecture Univ., Sakai, Osaka (Japan). Dept. of Applied Materials Science; Takahashi, Masanari [Osaka Municipal Technical Research Inst., Joyo, Osaka (Japan)

1996-02-01

148

13C MAS NMR of organic templates in zeolites 1 Dedicated to Professor Lovat V.C. Rees in recognition and appreciation of his lifelong devotion to zeolite science and his outstanding achievements in this field. 1  

Microsoft Academic Search

Cross-polarization (CP) combined with magic-angle spinning (MAS) is the most popular technique used for the high-resolution solid 13C study of occluded templates in zeolitic materials. Depending on the mobility of the incorporated templates the high-power decoupling (DEC) technique is more suitable to detect and to quantify templates in zeolites. By this technique, high-resolution MAS NMR spectra, displaying quantitative reliable 13C

M Kovalakova; B. H Wouters; P. J Grobet

1998-01-01

149

Al speciation in tropical podzols of the upper Amazon Basin: A solid-state 27Al MAS and MQMAS NMR study  

NASA Astrophysics Data System (ADS)

In the upper Amazon Basin, aluminum previously accumulated in lateritic formations is massively remobilised in soils by podzolization and exported in waters. We have investigated the speciation of aluminum in the clay-size fractions of eight horizons of waterlogged podzols lying in a depression of a plateau. The horizons illustrate the main steps involved in the podzolization of laterites. They belong to eluviated topsoil A horizons and illuviated subsoil Bhs, Bh and 2BCs horizons of weakly and better-expressed podzols located at the margin and centre of the depression. For the first time, aluminum speciation is quantitatively assessed in soils by spectroscopic methods, namely FTIR, 27Al magic angle spinning (MAS) and multiple-quantum magic angle spinning (MQMAS), nuclear magnetic resonance (NMR). The results thus obtained are compared to chemical extraction data. Solid-state 27Al MAS NMR spectra enable to distinguish Al bound to organic compounds from that incorporated in secondary mineral phases detected by FTIR. MQMAS experiments additionally show that both chemical shifts and quadrupolar constants are distributed for Al nuclei linked with organic compounds. Similar amounts of chelated Al are obtained from NMR spectra and chemical extractions. The study enables to highlight three major steps in the fate of aluminum. (i) Aluminum is first released by mineral weathering, feeds complexing sites of organic matter and accumulates in subsurface Bhs horizons of weakly expressed podzols (acidocomplexolysis). (ii) Complexes of aluminum with organic matter (Al OM) then migrate downwards in sandy horizons of better-expressed podzols and accumulate at depth in less permeable 2BCs horizons. (iii) The minor amounts of aluminum present in the 2BCs horizon of the downslope podzol show that aluminum is eventually exported towards the river network, either complexed with organic matter or as Al3+ ions after desorption from organic compounds, due to decreasing pH or biodegradation of organic ligands. The direct spectroscopic determination of Al-speciation during the formation of podzolic soils opens new perspectives to trace metal loads in the rivers of the upper Amazon Basin.

Bardy, Marion; Bonhomme, Christian; Fritsch, Emmanuel; Maquet, Jocelyne; Hajjar, Redouane; Allard, Thierry; Derenne, Sylvie; Calas, Georges

2007-07-01

150

Spin diffusion driven by R-symmetry sequences: applications to homonuclear correlation spectroscopy in MAS NMR of biological and organic solids.  

PubMed

We present a family of homonuclear (13)C-(13)C magic angle spinning spin diffusion experiments, based on R2(n)(v) (n = 1 and 2, v = 1 and 2) symmetry sequences. These experiments are well suited for (13)C-(13)C correlation spectroscopy in biological and organic systems and are especially advantageous at very fast MAS conditions, where conventional PDSD and DARR experiments fail. At very fast MAS frequencies the R2(1)(1), R2(2)(1), and R2(2)(2) sequences result in excellent quality correlation spectra both in model compounds and in proteins. Under these conditions, individual R2(n)(v) display different polarization transfer efficiency dependencies on isotropic chemical shift differences: R2(2)(1) recouples efficiently both small and large chemical shift differences (in proteins these correspond to aliphatic-to-aliphatic and carbonyl-to-aliphatic correlations, respectively), while R2(1)(1) and R2(2)(2) exhibit the maximum recoupling efficiency for the aliphatic-to-aliphatic or carbonyl-to-aliphatic correlations, respectively. At moderate MAS frequencies (10-20 kHz), all R2(n)(v) sequences introduced in this work display similar transfer efficiencies, and their performance is very similar to that of PDSD and DARR. Polarization transfer dynamics and chemical shift dependencies of these R2-driven spin diffusion (RDSD) schemes are experimentally evaluated and investigated by numerical simulations for [U-(13)C,(15)N]-alanine and the [U-(13)C,(15)N] N-formyl-Met-Leu-Phe (MLF) tripeptide. Further applications of this approach are illustrated for several proteins: spherical assemblies of HIV-1 U-(13)C,(15)N CA protein, U-(13)C,(15)N-enriched dynein light chain DLC8, and sparsely (13)C/uniformly (15)N enriched CAP-Gly domain of dynactin. Due to the excellent performance and ease of implementation, the presented R2(n)(v) symmetry sequences are expected to be of wide applicability in studies of proteins and protein assemblies as well as other organic solids by MAS NMR spectroscopy. PMID:21361320

Hou, Guangjin; Yan, Si; Sun, Shangjin; Han, Yun; Byeon, In-Ja L; Ahn, Jinwoo; Concel, Jason; Samoson, Ago; Gronenborn, Angela M; Polenova, Tatyana

2011-03-01

151

Atomic structure and dehydration mechanism of amorphous silica: Insights from 29Si and 1H solid-state MAS NMR study of SiO2 nanoparticles  

NASA Astrophysics Data System (ADS)

Detailed knowledge of the atomic structure of hydrous species on surface of amorphous silica and the effect of temperature and particle size on their atomic configurations are essential to understand the nature of fluids-amorphous silicates interactions and the dehydration processes in the amorphous oxides. Here, we report the 29Si, 1H MAS, and 1H-29Si heteronuclear correlation (HetCor) NMR spectra of 7 nm and 14 nm amorphous silica nanoparticles—a model system for natural amorphous silica—where previously unknown details of changes in their atomic structures with varying dehydration temperature and particle size are revealed. Diverse hydroxyl groups with varying atomic configurations and molecular water apparently show distinct dehydration trends. The dehydration (i.e., removal of water) of amorphous silica nanoparticles mostly results in the increase of isolated silanol by removing water molecules from hydrogen-bonded silanols associated water molecules. With further increase in dehydration temperature, the intensity of isolated silanol peak decreases above ˜873 K, suggesting that the condensation of isolated silanol may occur mainly above ˜873 K. The entire dehydration (and dehydroxylation) process completes at ˜1473 K. Both the water (i.e., physisorbed water and hydrogen-bonded water) and hydrogen-bonded silanol species show a dramatic change in the slope of intensity variation at ˜873 K, indicating that most of silanols is hydrogen-bonded to water rather than to other silanols. The fraction of hydrogen-bonded proton species is also much smaller in 14 nm amorphous silica nanoparticles than in 7 nm amorphous silica nanoparticles mainly due to the presences of larger fractions of water and hydrogen-bonded silanol species. 29Si NMR results show that with increasing dehydration temperature, the fraction of Q4 species apparently increases at the expense of Q2 and Q3 species. The fractions of Q2 and Q3 structures in 7 nm amorphous silica nanoparticles are larger than those in 14 nm amorphous silica nanoparticles. Dehydration of 7 nm amorphous silica nanoparticles occurs at a lower temperature than that of 14 nm amorphous silica nanoparticles. 29Si MAS NMR results show that a possible simultaneous dehydroxylation can also occur with removal of the hydrogen bonded silanol in the 7 nm silica nanoparticles. The energy penalty of dehydroxylation estimated from 29Si MAS NMR spectra varies with Q species and is smaller in 7 nm than in 14 nm amorphous silica nanoparticles. These results demonstrate that the particle size of nanoparticles plays an important role in controlling the hydrogen contents, and thus overall hydrogen bond strength of hydroxyl groups and atomic structure of silanols can control dehydroxylation of amorphous silica nanoparticles. The structural information and mechanistic details obtained from the current study provide insights into the structure of hydrous species and dehydration mechanisms in crystalline and amorphous silicates in diverse geological settings, highlighting usually unknown effects of particle size on the dehydration processes.

Kim, Hyun Na; Lee, Sung Keun

2013-11-01

152

A multi-technique approach using LC-NMR, LC-MS, semi-preparative HPLC, HR-NMR and HR-MS for the isolation and characterization of low-level unknown impurities in GW876008, a novel corticotropin-release factor 1 antagonist.  

PubMed

A multi-technique approach was applied in order to fully characterize four low-level unknown impurities of GW876008, a novel CRF(1) receptor antagonist. Liquid chromatography (LC)-NMR spectroscopy was used in combination with LC-MS to obtain detailed information regarding the structure of the two major impurities present in batches of GW876008 and observed in the first synthetic scale-up for preclinical use. Two additional impurities were unexpectedly found at greater levels in a large scale synthesis for clinical use and their structure was elucidated by means of high resolution (HR)-MS and HR-NMR, after a small scale preparative HPLC purification step. This structural information was useful in terms of shedding light on the typical impurity profile of this new chemical entity with the aim to support the early development package for Phase I clinical studies. PMID:20619567

Provera, Stefano; Rovatti, Luca; Turco, Lucilla; Mozzo, Sebastiano; Spezzaferri, Alberto; Bacchi, Sergio; Ribecai, Arianna; Guelfi, Simone; Mingardi, Anna; Marchioro, Carla; Papini, Damiano

2010-06-22

153

Studies of rare-earth stannates by sup 119 Sn MAS NMR. The use of paramagnetic shift probes in the solid state  

SciTech Connect

{sup 119}Sn MAS NMR spectra have been obtained from members of a series of rare-earth stannates Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = La, Pr, Nd, Sm, Eu, Tm, Yb, Lu, and Y), all of which adopt the pyrochlore structure. Apart from La{sub 2}Sn{sub 2}O{sub 7}, Lu{sub 2}Sn{sub 2}O{sub 7}, and Y{sub 2}Sn{sub 2}O{sub 7}, these compounds are paramagnetic and exhibit a very large variation in {sup 119}Sn chemical shifts (from approximately +5,400 to {minus}4,200 ppm), which can be attributed principally to a Fermi contact shift mechanism. The spectra from the paramagnetic samples have large overall line widths associated with the substantial anisotropy of the shift, but the individual peaks within the spinning sideband manifolds remain sharp. Several tin pyrochlore solid solutions have also been studied (namely Y{sub 2-y}Ln{sub y}Sn{sub 2}O{sub 7} where Ln = Sm, Nd, Pr, and Eu and La{sub 2-y}Nd{sub y}Sn{sub 2}O{sub u}) by {sup 119}Sn MAS NMR. When the short relaxation times of nuclei close to paramagnetic centers were exploited, a series of peaks were observed, associated with the substitution of paramagnetic for diamagnetic lanthanide ions in the local coordination around a tin atom. For Y{sub 2-y}Sm{sub y}Sn{sub 2}O{sub 7} the composition of the solid solution could be determined from the intensities of these peaks. In the solid solutions the {sup 119}Sn nuclei were found to be sensitive not only to neighboring paramagnetic ions but also to paramagnetic ions in the second and third coordination spheres. The shifts induced in these cases arise primarily from a through-space dipolar pseudocontact mechanism and can be interpreted with a model for the site symmetry based on the crystal structure. 30 refs., 8 figs., 3 tabs.

Grey, C.P.; Dobson, C.M.; Cheetham, A.K.; Jakeman, R.J.B. (Univ. of Oxford (England))

1989-01-18

154

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

SciTech Connect

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

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

2009-07-01

155

Amino-acid selective experiments on uniformly 13C and 15N labeled proteins by MAS NMR: Filtering of lysines and arginines  

NASA Astrophysics Data System (ADS)

Amino-acid selective magic-angle spinning (MAS) NMR experiments can aid the assignment of ambiguous cross-peaks in crowded spectra of solid proteins. In particular for larger proteins, data analysis can be hindered by severe resonance overlap. In such cases, filtering techniques may provide a good alternative to site-specific spin-labeling to obtain unambiguous assignments that can serve as starting points in the assignment procedure. In this paper we present a simple pulse sequence that allows selective excitation of arginine and lysine residues. To achieve this, we make use of a combination of specific cross-polarization for selective excitation [M. Baldus, A.T. Petkova, J. Herzfeld, R.G. Griffin, Cross polarization in the tilted frame: assignment and spectral simplification in heteronuclear spin systems, Mol. Phys. 95 (1998) 1197 1207.] and spin diffusion for transfer along the amino-acid side-chain. The selectivity of the filter is demonstrated with the excitation of lysine and arginine side-chain resonances in a uniformly 13C and 15N labeled protein preparation of the ?-spectrin SH3 domain. It is shown that the filter can be applied as a building block in a 13C 13C lysine-only correlation experiment.

Jehle, Stefan; Rehbein, Kristina; Diehl, Anne; van Rossum, Barth-Jan

2006-12-01

156

Three-dimensional deuterium-carbon correlation experiments for high-resolution solid-state MAS NMR spectroscopy of large proteins.  

PubMed

Well-resolved (2)H-(13)C correlation spectra, reminiscent of (1)H-(13)C correlations, are obtained for perdeuterated ubiquitin and for perdeuterated outer-membrane protein G (OmpG) from E. coli by exploiting the favorable lifetime of (2)H double-quantum (DQ) states. Sufficient signal-to-noise was achieved due to the short deuterium T (1), allowing for high repetition rates and enabling 3D experiments with a (2)H-(13)C transfer step in a reasonable time. Well-resolved 3D (2)H(DQ)-(13)C-(13)C correlations of ubiquitin and OmpG were recorded within 3.5 days each. An essentially complete assignment of (2)H(DQ?) shifts and of a substantial fraction of (2)H(DQ?) shifts were obtained for ubiquitin. In the case of OmpG, (2)H(DQ?) and (2)H(DQ?) chemical shifts of a considerable number of threonine, serine and leucine residues were assigned. This approach provides the basis for a general heteronuclear 3D MAS NMR assignment concept utilizing pulse sequences with (2)H(DQ)-(13)C transfer steps and evolution of deuterium double-quantum chemical shifts. PMID:22038621

Lalli, Daniela; Schanda, Paul; Chowdhury, Anup; Retel, Joren; Hiller, Matthias; Higman, Victoria A; Handel, Lieselotte; Agarwal, Vipin; Reif, Bernd; van Rossum, Barth; Akbey, Umit; Oschkinat, Hartmut

2011-10-25

157

Amino-acid selective experiments on uniformly 13C and 15N labeled proteins by MAS NMR: Filtering of lysines and arginines.  

PubMed

Amino-acid selective magic-angle spinning (MAS) NMR experiments can aid the assignment of ambiguous cross-peaks in crowded spectra of solid proteins. In particular for larger proteins, data analysis can be hindered by severe resonance overlap. In such cases, filtering techniques may provide a good alternative to site-specific spin-labeling to obtain unambiguous assignments that can serve as starting points in the assignment procedure. In this paper we present a simple pulse sequence that allows selective excitation of arginine and lysine residues. To achieve this, we make use of a combination of specific cross-polarization for selective excitation [M. Baldus, A.T. Petkova, J. Herzfeld, R.G. Griffin, Cross polarization in the tilted frame: assignment and spectral simplification in heteronuclear spin systems, Mol. Phys. 95 (1998) 1197-1207.] and spin diffusion for transfer along the amino-acid side-chain. The selectivity of the filter is demonstrated with the excitation of lysine and arginine side-chain resonances in a uniformly 13C and 15N labeled protein preparation of the alpha-spectrin SH3 domain. It is shown that the filter can be applied as a building block in a 13C-13C lysine-only correlation experiment. PMID:16990042

Jehle, Stefan; Rehbein, Kristina; Diehl, Anne; van Rossum, Barth-Jan

2006-09-20

158

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

159

Combination of DQ and ZQ coherences for sensitive through-bond NMR correlation experiments in biosolids under ultra-fast MAS.  

PubMed

A double-zero quantum (DZQ)-refocused INADEQUATE experiment is introduced for J-based NMR correlations under ultra-fast (60 kHz) magic angle spinning (MAS). The experiment records two spectra in the same dataset, a double quantum-single quantum (DQ-SQ) and zero quantum-single quantum (ZQ-SQ) spectrum, whereby the corresponding signals appear at different chemical shifts in ?(1). Furthermore, the spin-state selective excitation (S(3)E) J-decoupling block is incorporated in place of the second refocusing echo of the INADEQUATE scheme, providing an additional gain in sensitivity and resolution. The two sub-spectra acquired in this way can be treated separately by a shearing transformation, producing two diagonal-free single quantum (SQ-SQ)-type spectra, which are subsequently recombined to give an additional sensitivity enhancement, thus offering an improvement greater than a factor of two as compared to the original refocused INADEQUATE experiment. The combined DZQ scheme retains transverse magnetization on the initially polarized (I) spin, which typically exhibits a longer transverse dephasing time (T(2)') than its through-bond neighbour (S). By doing so, less magnetization is lost during the refocusing periods in the sequence to give even further gains in sensitivity for the J correlations. The experiment is demonstrated for the correlation between the carbonyl (CO) and alpha (CA) carbons in a microcrystalline sample of fully protonated, [(15)N,(13)C]-labelled Cu(II),Zn(II) superoxide dismutase, and its efficiency is discussed with respect to other J-based schemes. PMID:22528552

Webber, Amy L; Pell, Andrew J; Barbet-Massin, Emeline; Knight, Michael J; Bertini, Ivano; Felli, Isabella C; Pierattelli, Roberta; Emsley, Lyndon; Lesage, Anne; Pintacuda, Guido

2012-04-23

160

Singlet-triplet separations measured by [sup 31]P[l brace][sup 1]H[r brace] NMR: Applications to quadruply bonded dimolybdenum and ditungsten complexes  

SciTech Connect

A series of quadruply bonded dimolybdenum and ditungsten compounds M[sub 2]X[sub 4](PP)[sub 2] (M = Mo, W; PP = bidentate phosphine ligands; X = Cl, Br, I) with internal rotational angles [chi] varying from 0.0 to 69.4[degrees] have been studied. Their [sup 31]P[l brace][sup 1]H[r brace] NMR spectra are characterized by their temperature-dependent shifts and line widths that broaden with increasing temperature. A nonlinear, least-squares fit of this temperature dependence of the paramagnetic shifts for their NMR signals allows the evaluation of the singlet-triplet energy separation ([minus]2J), the diamagnetic shift (H[sub dia]), and the electron-nucleus hyperfine coupling constant (A). The singlet-triplet energy separations for all the compounds investigated are found to be in the range 1200-3000 cm[sup [minus]1]. It is now clearly established that the ground state remains [sup 1]A[sub 1g] ([delta][sup 2]) even at [chi] = 45[degrees], where [sup 3]A[sub 2u] ([delta][delta]*) lies 1230 cm[sup [minus]1] above it. The [delta]-bond energy and electronic [delta]-barrier can also be experimentally estimated as 13.8[+-]0.5 kcal mol[sup [minus]1] and 10.3[+-]0.5 kcal mol[sup [minus]1], respectively. 32 refs., 3 figs., 1 tab.

Cotton, F.A.; Eglin, J.L.; Bo Hong; James, C.A. (Texas A M Univ., College Station (United States))

1993-05-12

161

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

SciTech Connect

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

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

1993-09-01

162

{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

163

HR, Streamlined  

ERIC Educational Resources Information Center

|Human Resources (HR) administrators are finding that as software modules are installed to automate various processes, they have more time to focus on strategic objectives. And as compliance with affirmative action and other employment regulations comes under increasing scrutiny, HR staffers are finding that software can deliver and track data…

Ramaswami, Rama

2008-01-01

164

Silicate-phosphate interactions in silicate glasses and melts: I. A multinuclear ( 27Al, 29Si, 31P) MAS NMR and ab initio chemical shielding ( 31P) study of phosphorous speciation in silicate glasses  

NASA Astrophysics Data System (ADS)

An investigation of the structure of sodium aluminum silicate glasses [composition (x)Na 2O, (1-x)Al 2O 3, 0.9SiO 2 perturbed through the addition of 2 mol.% P 2O 5] was performed using a combination of 27Al, 29Si, and 31P solid state NMR spectroscopy and ab initio chemical shielding calculations (GIAO method). Speciation within these glasses was estimated using a physically consistent method for the deconvolution of inhomogeneously broadened 31P MAS-NMR spectra by employing a combination of spinning sideband analysis with the results of ab initio shielding calculations. A minimum of 13 different phosphorus-bearing species were estimated to contribute to the spectral complexity in these glasses over the compositional range investigated. The majority of these species are oxygen-bridged to the silicate lattice. These are described as (Al,Si)Q pn species, where n corresponds to the number of bridging oxygens ( n = 1-4) and where there is variation in the Al/Si ratio of the tetrahedral nearest neighbors. In addition to the species bridging to the silicate lattice, nonlattice bridged Na-P type species, including ortho-, pyro-, and tripolyphosphates, are observed or deduced based on spectral behavior. A sharp crossover in the predominance of Na-P species relative to (Al,Si) Q pn dominant species occurs at low Al 2O 3 content. Within the group of nonbridging (Na-P) species, increased bulk aluminum content shifts the predominance from orthophosphate toward tripolyphosphate. Within the group of bridging [(Al,Si) Q pn] species, increasing bulk aluminum content shifts the predominance toward a greater number of oxygen bridges to the silicate lattice. To highlight the perturbative effect of 2 mol.% P 2O 5 addition on glass structure, 29Si MAS-NMR of P-bearing and P-absent glasses were compared. The speciation estimated from the combined 31P MAS-NMR and ab initio shielding calculations is consistent with 29Si MAS-NMR spectroscopic data. Analysis of 27Al MAS-NMR spectra for P-bearing and P-absent glasses reveals extensive Al-O-P interactions evident by systematic shifts in peak maxima to lower frequencies (greater shielding). Increases in the central transition peak half widths in the P-bearing samples reflect enhanced second-order quadrupolar interactions, also consistent with an abundance of (Al,Si) Q pn species. Analysis of the 27Al inner satellite transition sidebands reveals only a minor amount of VIAl. It is concluded that the addition of even a small amount of P 2O 5 (2 mol.%) results in a large perturbation of the structure of silicate glasses and should manifest significant effects on the physical properties of melts derived from them.

Cody, George D.; Mysen, Bjorn; Sághi-Szabó, Gotthard; Tossell, John A.

2001-07-01

165

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. To investigate this further, a number of soil samples were characterized by both solid-state 13 C 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.

Simpson, M.; Simpson, A.

2009-05-01

166

Enhanced conversion of triple to single-quantum coherence in the triple-quantum MAS NMR spectrosocopy of spin-5\\/2 nuclei  

Microsoft Academic Search

A new type of fast amplitude modulated pulse scheme is presented here that yields a significant sensitivity enhancement in the triple-quantum magic angle spinning NMR spectrum of a spin-5\\/2 nucleus. Enhancement is achieved by fast phase alternation of the triple to single-quantum conversion pulse, which transfers triple to single-quantum coherence in a direct, non-adiabatic manner. The success of this pulse

Amir Goldbourt; P. K. Madhu; Shimon Vega

2000-01-01

167

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

168

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

Microsoft Academic Search

Non-bridging oxygens (NBO's) play a significant role in the thermodynamic and transport properties in glasses and silicate melts. Previous oxygen-17 (O-17) triple quantum magic angle spinning (3QMAS NMR) data have shown the presence of NBO's in several calcium aluminosilicate (CAS) glasses on the CaAl2O4-SiO2 join (Stebbins and Xu 1997). The observed chemical shifts of these glasses are similar to those

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

2001-01-01

169

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

Microsoft Academic Search

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

Paul A. Schroeder

1993-01-01

170

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

PubMed

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

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

2011-08-18

171

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

172

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).

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

2013-01-01

173

Molecular vibrational analysis and MAS-NMR spectroscopy study of epilepsy drugs encapsulated in TiO2-sol-gel reservoirs.  

PubMed

A nanostructured matrix, consisting of titania, was designed in such a way that an antiepileptic drug could be encapsulated and released according to a well-defined time release schedule. The titania was synthesized by a sol-gel method in which titanium n-butoxide was used as the precursor for the formation of the sol. The synthesis was optimized to yield a homogeneous particle size with a high porosity and an anatase crystal structure. The antiepilectic drugs, phenytoine or valproic acid, were added during the gelation stage in order to obtain a homogeneous gel phase. The resulting nanostructured matrix including the drug showed only weak attractive forces, such as London forces, dipole-dipole coupling, and in some cases hydrogen bonds. The resulting assembly, referred to as a reservoir, was characterized using conventional FTIR and NMR spectroscopic techniques. Theoretical simulation studies were performed so as to obtain an understanding of the equilibrium electrostatic potential distribution and the relative charges on the titania and the anticonvulsants. PMID:16721794

Lopez, T; Navarrete, J; Conde, R; Ascencio, J A; Manjarrez, J; Gonzalez, R D

2006-09-01

174

Identifying inter-residue resonances in crowded 2D (13)C- (13)C chemical shift correlation spectra of membrane proteins by solid-state MAS NMR difference spectroscopy.  

PubMed

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 (13)C-(13)C chemical shift correlation spectra is presented. With the analyses of (13)C-(13)C 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 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 proton-conducting 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 (13)C labeled protein that are consistent with the high resolution structure of the M2 (22-62) protein (Sharma et al., Science 330(6003):509-512, 2010). PMID:23708936

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

2013-05-25

175

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

176

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

PubMed

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

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

2011-10-28

177

13C CP/MAS NMR Studies of Hemoprotein Models with and without an Axial Hindered Base: (13)C Shielding Tensors and Comparison with Hemoproteins and X-ray Structural Data.  

PubMed

13C cross-polarization magic-angle-spinning (CP/MAS) NMR spectra of several carbonmonoxide (93-99% (13)C enriched) hemoprotein models with 1,2-dimethylimidazole (1,2-diMeIm) and 1-methylimidazole (1-MeIm) as axial ligands are reported. This enables the (13)CO spinning sideband manifold to be measured and hence the principal components of the (13)CO chemical shift tensor to be obtained. Negative polar interactions in the binding pocket of the cap porphyrin model and inhibition of Fe-->CO back-donation result in a reduction in shielding anisotropy; on the contrary, positive distal polar interactions result in an increase in the shielding anisotropy and asymmetry parameter in some models. It appears that the axial hindered base 1,2-dimethylimidazole has little direct effect on the local geometry at the CO site, despite higher rates of CO desorption being observed for such complexes. This suggests that the mechanism by which steric interactions are released for the 1,2-diMeIm complexes compared to 1-MeIm complexes does not involve a significant increase in bending of the Fe-C-O unit. The asymmetry of the shielding tensor of all the heme model compounds studied is smaller than that found for horse myoglobin and rabbit hemoglobin. PMID:11666486

Gerothanassis, I. P.; Momenteau, M.; Barrie, P. J.; Kalodimos, C. G.; Hawkes, G. E.

1996-04-24

178

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

1997-02-26

179

Correlations between 31P chemical shift anisotropy and molecular structure in polycrystalline O,O'-dialkyldithiophosphate zinc(II) and nickel(II) complexes: 31P CP/MAS NMR and ab initio quantum mechanical calculation studies.  

PubMed

Different potassium salts and zinc(II) and nickel(II) O,O'-dialkyldithiophosphate complexes were studied by solid-state 31P CP/MAS and static NMR and ab initio quantum mechanical calculations. Spectra were obtained at different spinning frequencies, and the intensities of the spinning sidebands were used to estimate the chemical shift anisotropy parameters. Useful correlations between the shapes of the 31P chemical shift tensor and the type of ligand were found: terminal ligands have negative values of the skew kappa, while bridging and ionic ligands have positive values for this parameter. The experimental results were compared with known X-ray diffraction structures for some of these complexes as well as with ab initio quantum mechanical calculations, and a useful correlation between the delta22 component of the 31P chemical shift tensor and the S-P-S bond angle in the O,O'-dialkyldithiophoshate zinc(II) and nickel(II) complexes was found: delta22 increases more than 50 ppm with the increase of S-P-S bond angle from ca. 100 degrees to 120 degrees , while the other two principal values of the tensor, delta11 and delta33, are almost conserved. This eventually leads to the change in sign for kappa in the bridging type of ligand, which generally has a larger S-P-S bond angle than the terminally bound O,O'-dialkyldithiophosphate group forming chelating four-membered P(ss)Me heterocycles. PMID:15713100

Larsson, Anna-Carin; Ivanov, Alexander V; Forsling, Willis; Antzutkin, Oleg N; Abraham, Anu E; de Dios, Angel C

2005-02-23

180

Thermal Decomposition of Monocalcium Aluminate Decahydrate (CaAl2O4.10H2O) Investigated by in-situ Synchrotron X-ray Powder Diffraction, Thermal Analysis and 27Al, 2H MAS NMR Spectroscopy  

SciTech Connect

The stability of monocalcium aluminate decahydrate, with the nominal composition CaAl(2)O(4).10H(2)O (CAH(10)), has a decisive role for the strength development and durability of cementitious materials based on high alumina cements. This has prompted an investigation of the thermal transformation of crystalline monocalcium aluminate decahydrate in air to an amorphous phase by in-situ synchrotron X-ray powder diffraction in the temperature range from 25 to 500 degrees C, by DTA/TGA, and (2)H, (27)Al MAS NMR spectroscopy. The decomposition includes the loss of hydrogen-bonded water molecules in the temperature range up to 175 degrees C, coupled with a reduction of the unit cell volume from 1928 A(3) at 25 degrees C, to 1674 A(3) at 185 degrees C. Furthermore, X-ray diffraction shows that CaAl(2)O(4).10H(2)O starts to transform to an amorphous phase at approximately 65 degrees C. This phase is fully developed at approximately 175 degrees C and it converts to crystalline CaAl(2)O(4) when heated to 1300 degrees C. The thermal decomposition in the temperature range from approximately 65 to approximately 175 degrees C involves both formation of an amorphous phase including AlO(4) tetrahedra and structural changes in the remaining crystalline phase.

Christensen,A.; Jensen, T.; Lebech, B.; Hanson, J.; Jakobsen, J.; Skilbsted, J.

2008-01-01

181

Kinetics and mechanism of the beta- to alpha-CuAlCl(4) phase transition: a time-resolved (63)Cu MAS NMR and powder X-ray diffraction study.  

PubMed

The beta and alpha phases of CuAlCl(4) have been characterized by solid-state (27)Al and (63)Cu magic angle spinning nuclear magnetic resonance. The very short spin--lattice relaxation times of the copper spins, and the sensitivity of the I = 3/2 (63)Cu nucleus to the small differences in the local structure of Cu in the two phases, allowed (63)Cu spectra to be acquired in very short time periods (1 min), in which the beta and alpha phases were clearly resolved. This time resolution was exploited to follow the phase transition from the pseudohexagonal close-packed beta-CuAlCl(4) into the pseudocubic close-packed alpha-CuAlCl(4), which occurs above 100 degrees C. In situ time-resolved (63)Cu MAS NMR and synchrotron X-ray diffraction experiments were used to measure the kinetics of this phase transition as a function of temperature. The transformation was shown to be a first-order phase transition involving no intermediate phases with an activation energy of 138 kJ/mol. The kinetic data obey a first-order Avrami--Erofe'ev rate law. A one-dimensional growth mechanism is proposed that involves a combination of Cu(+) ion self-diffusion and a translational reorganization of the close-packed anion layers imposed by the periodic rotations of [AlCl(4)](-) tetrahedra. This beta to alpha phase transformation can be induced at ambient temperatures by low partial pressures of ethylene. PMID:11480977

Liu, H; Sullivan, R M; Hanson, J C; Grey, C P; Martin, J D

2001-08-01

182

Feasibility of 1H-high resolution-magic angle spinning NMR spectroscopy in the analysis of viscous cosmetic and pharmaceutical formulations.  

PubMed

The feasibility of (1)H-High Resolution-Magic Angle Spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy for the direct analysis of viscous cosmetic and pharmaceutical formulations such as creams, gels, and pastes is presented. Three examples are described: (i) the detection of chitosan in toothpaste, (ii) the analysis of dexamethasone acetate (DMA) in a cream, and (iii) the analysis of the local anesthetics, lidocaine and prilocaine, in a gel and a cream. All active components could be directly detected in their original commercial formulations without the need for laborious sample preparation steps. In addition, the possibility for HR-MAS-based quantifications and the analysis of dynamic properties of active components in different formulations applying HR-MAS diffusion-ordered NMR spectroscopy are shown. PMID:23537072

Marzorati, Mattia; Bigler, Peter; Plattner, Michel; Vermathen, Martina

2013-04-05

183

The RETSINA MAS Infrastructure  

Microsoft Academic Search

RETSINA is an implemented Multi-Agent System infrastructure that has been developed for several years and applied in many domains ranging from financial portfolio management to logistic planning. In this paper, we distill from our experience in developing MASs to clearly define a generic MAS infrastructure as the domain independent and reusable substratum that supports the agents' social interactions. In addition,

Katia P. Sycara; Massimo Paolucci; Martin Van Velsen; Joseph A. Giampapa

2003-01-01

184

The 3'-keto-diol equilibrium of trospectomycin sulfate bulk drug and freeze-dried formulation: solid-state carbon-13 cross-polarization magic angle spinning (CP/MAS) and high-resolution carbon-13 nuclear magnetic resonance (NMR) spectroscopy studies.  

PubMed

Understanding how moisture interacts with a drug or formulation is a critical component of product development. This study demonstrates how water affects the 3'-gem-diol<==>3'-keto equilibrium in trospectomycin sulfate bulk drug and freeze-dried formulation, as probed by solid-state carbon-13 cross-polarization magic angle spinning (CP/MAS) and high-resolution nuclear magnetic resonance (NMR) spectroscopy. Drying the bulk drug or formulation to low water levels dehydrates trospectomycin sulfate from the diol to the keto form. Carbon-13 CP/MAS NMR spectroscopy measures the keto drug concentration in solid samples directly. The bulk drug, which contains approximately 16% water, is more than 90% in the 3'-diol form. Oven drying to < 3% water converts approximately 75% of the drug to the 3'-keto form. The drug is formulated as a freeze-dried, sterile powder that can contain up to 12% water depending on the freeze-drying conditions. These studies show that the 3'-keto concentration rises uniformly (up to 75%) with decreasing residual water in the freeze-dried cake. The keto-diol equilibrium was also studied in solution by high-resolution carbon-13 NMR experiments, and it was found that raising the temperature or using dimethyl sulfoxide (DMSO) as a solvent also dehydrates the drug. For example, in aqueous solution at 25 degrees C, nearly all (> 95%) of the drug is in the 3'-diol form. After equilibration at 60 degrees C, however, the 3'-keto content increases to 7%, and in d6-DMSO solvent at 25 degrees C the drug is mostly (60%) in the 3'-keto form. PMID:8430063

Likar, M D; Taylor, R J; Fagerness, P E; Hiyama, Y; Robins, R H

1993-01-01

185

Refined magic-angle coil spinning resonator for nanoliter NMR spectroscopy: enhanced spectral resolution.  

PubMed

The magic-angle coil spinning (MACS) resonator allows a simple approach for nanoliter nuclear magnetic resonance (NMR) detections with enhanced sensitivity and high-resolution under sample magic-angle spinning (MAS). Currently, the spectral resolution acquired with MACS is not efficient for detailed characterization of semisolids like biopsies, where subhertz resolution is necessary. Here, we describe the two sources of line broadening from MACS, sample temperature gradient and anisotropic magnetic susceptibility, and present a refined high-resolution magic-angle coil spinning (HR-MACS) resonator that improves the spectral resolution. We demonstrate with the high quality HR-MACS NMR spectra of micronematodes and tissue biopsy, and illustrate its potential for NMR-based metabolomics of nanoliter tissue samples. PMID:23343461

Wong, Alan; Li, Xiaonan; Sakellariou, Dimitris

2013-02-06

186

Probing spin density and local structure in the Prussian blue analogues CsCd[Fe/Co(CN)6]·0.5H2O and Cd3[Fe/Co(CN)6]2·15H2O with solid-state MAS NMR spectroscopy.  

PubMed

Magic-angle spinning (MAS) NMR spectroscopy is used to study the local structure and spin delocalisation in Prussian blue analogues (PBAs). We selected two common archetypes of PBAs (A(I)M(II)[M(III)(CN)(6)]·xH(2)O and M(II)(3)[M(III)(CN)(6)](2)·xH(2)O, in which A(I) is an alkali ion, and M(II) and M(III) are transition-metal ions) that exhibit similar cubic frameworks but different microscopic structures. Whereas the first type of PBA contains interstitial alkali ions and does not exhibit any [M(III)(CN)(6)](3-) vacancies, the second type of PBA exhibits [M(III)(CN)(6)](3-) vacancies, but does not contain inserted alkali ions. In this study, we selected Cd(II) as a divalent metal in order to use the (113)Cd nuclei (I=1/2) as a probe of the local structure. Here, we present a complete MAS NMR study on two series of PBAs of the formulas Cd(II)(3)[Fe(III)(x)Co(III)(1-x)(CN)(6)](2)·15H(2)O with x=0 (1), 0.25 (2), 0.5 (3), 0.75 (4) and 1 (5), and CsCd(II)[Fe(III)(x)Co(III)(1-x)(CN)(6)]·0.5H(2)O with x=0 (6), 0.25 (7), 0.5 (8), 0.75 (9) and 1 (10). Interestingly, the presence of Fe(III) magnetic centres in the vicinity of the cadmium sites has a magnifying-glass effect on the NMR spectrum: it induces a striking signal spread such that the resolution is notably improved compared to that achieved for the diamagnetic PBAs. By doping the sample with varying amounts of diamagnetic Co(III) and comparing the NMR spectra of both types of PBAs, we have been able to give a view of the structure which is complementary to that usually obtained from X-ray diffraction studies. In particular, this study has shown that the vacancies are not randomly distributed in the mesoporous PBAs. Moreover the cadmium chemical shift, which is a measure of the hyperfine coupling, allows the estimation of the spin density on the cadmium nucleus, and consequently, the elucidation of the spin delocalisation mechanism in these compounds along with its dependency on structural parameters. PMID:21882267

Flambard, Alexandrine; Köhler, Frank H; Lescouëzec, Rodrigue; Revel, Bertrand

2011-08-31

187

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

188

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

189

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

190

A high?resolution solid?state NMR study on nano?structured HZSM?5 zeolite  

Microsoft Academic Search

Variations in the structure and acidity properties of HZSM?5 zeolites with reduction in crystal sizes down to nanoscale (less\\u000a than 100 nm) have been investigated by XRD, TEM and solid?state NMR with a system capable of in situ sample pretreatment.\\u000a As evidenced by a combination of 27Al MAS NMR, 29Si MAS, CP\\/MAS NMR and 1H MAS NMR techniques, the downsize

Weiping Zhang; Xinhe Bao; Xinwen Guo; Xiangsheng Wang

1999-01-01

191

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)] (AuAu) (1) and crystalline bis(O,O?-di-cyclo-hexylthiophosphoryl)disulphide, (cyclo-C6H11O)2P(S)SS(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)S(1)a, and a planar zigzag array [SPSSPS] 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

192

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

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

2013-07-04

194

Solid state NMR method for the determination of 3D zeolite framework/sorbate structures: 1H/29Si CP MAS NMR study of the high-loaded form of p-xylene in ZSM-5 and determination of the unknown structure of the low-loaded form.  

PubMed

A general protocol is described for structure determinations of organic sorbate-zeolite complexes based on the selective, through-space, distance-dependent transfer of magnetization from protons in selectively deuterated organics to framework silicon nuclei. The method was developed using the known structure of the high-loaded ZSM-5/p-xylene complex containing p-xylene-d(6) or p-xylene-d(4). It was then applied to determine the unknown structure of the low-loaded ZSM-5/p-xylene complex using NMR alone. For the high-loaded complex improved data were obtained below 273 K, where slow motions and exchange processes of the p-xylene are eliminated. The general approach was validated by the exact agreement of the experimental (1)H-(29)Si CPMAS spectra obtained at a specific contact time and the complete 24-line spectra simulated using 1/T(CP) vs M(2) correlations from only the six clearly resolved resonances. For the low-loaded complex the (29)Si resonances were assigned at 267 K, and variable contact time CP experiments were carried out between 243 and 173 K using the same specifically deuterated p-xylenes. All possible locations and orientations of the p-xylene guests were sampled, and those solutions that gave acceptable linear 1/T(CP) vs M(2) correlations were selected. The optimum p-xylene location in this temperature range was determined to be in the channel intersection with the long molecular axis parallel to [0,1,0] (ring center fractional coordinates {-0.009, 0.250, 0.541}) with the ring plane oriented at an angle of 30 +/- 3 degrees about the crystallographic b axis. A subsequent single-crystal X-ray study confirmed this predicted structure. PMID:15898806

Fyfe, Colin A; Diaz, Anix C; Grondey, Hiltrud; Lewis, Andrew R; Förster, Hans

2005-05-25

195

HR Positions on the Internet.  

ERIC Educational Resources Information Center

The question of whether the online job market reflects the trends predicted for the job market was examined in a study of a random sample of 690 Internet job postings over a 6-month period. Each listing was categorized by type of position, desired qualifications, salary, and job specifications. Of the human resources (HR) jobs posted, 7.2% were…

Coghill, Carey Cox; Kirk, James J.

196

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.

Sampol, Denys; Ostrofet, Eugene; Jobin, Marie-Lise; Raffard, Gerard; Sanchez, Stephane; Bouchaud, Veronique; Franconi, Jean-Michel; Bonvento, Gilles; Bouzier-Sore, Anne-Karine

2013-01-01

197

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

198

Observation of NMR noise from solid samples  

PubMed Central

We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes’ NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in 1H-MAS experiments.

Schlagnitweit, Judith; Dumez, Jean-Nicolas; Nausner, Martin; Jerschow, Alexej; Elena-Herrmann, Benedicte; Muller, Norbert

2010-01-01

199

Observation of NMR noise from solid samples.  

PubMed

We demonstrate that proton NMR noise signals, i.e. NMR spectra without excitation by radio frequency, can be obtained from solid samples. Experimental results are shown for static and magic-angle spinning conditions. In addition, a tuning procedure based on the probes' NMR noise characteristics and similar to the one described previously for liquids probes can also be used to optimize signal-to-noise ratios in ¹H-MAS experiments. PMID:20850362

Schlagnitweit, Judith; Dumez, Jean-Nicolas; Nausner, Martin; Jerschow, Alexej; Elena-Herrmann, Bénédicte; Müller, Norbert

2010-08-25

200

An insight in the surroundings of HR 4796  

NASA Astrophysics Data System (ADS)

Context. HR 4796 is a young, early A-type star harboring a well structured debris disk, shaped as a ring with sharp inner edges. The inner edge might be shaped by a yet unseen planet inside the ring; the outer one is not well understood. The star forms together with the M-type star HR 4796B, a binary system, with a projected separation of ? 560 AU. Aims: Our aim is to explore the surroundings of HR 4796A and B, both in terms of extended or point-like structures. Methods: Adaptive optics images at L'-band were obtained with NaCo in Angular Differential Mode and with Sparse Aperture Masking (SAM). We analyse the data as well as the artefacts that can be produced by ADI reduction on an extended structure with a shape similar to that of HR 4796A dust ring. We determine constraints on the presence of companions using SAM and ADI on HR 4796A, and ADI on HR 4796B. We also performed dynamical simulations of a disk of planetesimals and dust produced by collisions, perturbed by a planet located close to the disk outer edge. Results: The disk ring around HR 4796A is well resolved. We highlight the potential effects of ADI reduction of the observed disk shape and surface brightness distribution, and side-to-side asymmetries. We produce 2D maps of planet detection limits. No planet is detected around the star, with masses as low as 3.5 MJup at 0.5'' (58 AU) and less than 3 MJup in the 0.8-1'' range along the semi-major axis. We exclude massive brown dwarfs at separations as close as 60 mas (4.5 AU) from the star thanks to SAM data. The detection limits obtained allow us to exclude a possible close companion to HR 4796A as the origin of the offset of the ring center with respect to the star; they also allow to put interesting constraints on the (mass, separation) of any planet possibly responsible for the inner disk steep edge. Using detailed dynamical simulations, we show that a giant planet orbiting outside the ring could sharpen the disk outer edge and reproduce the STIS images published by Schneider et al. (2009). Finally, no planets are detected around HR 4796B with limits well below 1 MJup at 0.5'' (35 AU). Based on observations collected at the European Southern Observatory, Chile, ESO; run 085.C-0277A.

Lagrange, A.-M.; Milli, J.; Boccaletti, A.; Lacour, S.; Thebault, P.; Chauvin, G.; Mouillet, D.; Augereau, J. C.; Bonnefoy, M.; Ehrenreich, D.; Kral, Q.

2012-10-01

201

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

2008-03-25

202

Evaluation of high resolution magic-angle coil spinning NMR spectroscopy for metabolic profiling of nanoliter tissue biopsies.  

PubMed

High-resolution magic-angle sample spinning (HR-MAS) (1)H NMR spectroscopy of tissue biopsies combined with chemometric techniques has emerged as a valuable methodology for disease diagnosis and environmental assessments. However, the tissue mass required for such experiments is of the order of 10 mg, and this can compromise the metabolic evaluation because of tissue heterogeneity. Tissue availability is often a limitation for clinical studies due to histopathological requirements, which are currently the gold standard for diagnosis, for example, in the case of tumors. Here, we introduce the use of a rotating micro-NMR detector that optimizes the coil filling factor such that mass-limited samples can be measured. We show the results for measuring nanoliter volume tissue biopsies using a commercial HR-MAS probe for the first time. The method has been tested with bovine muscle and human gastric mucosal tumor tissue samples. The gain in mass sensitivity is approximate up to 17-fold, and the adequate spectral resolution (3 Hz) allows the measurement of the metabolite profiles in nanoliter volume samples, thereby limiting the ambiguity resulting from heterogeneous tissues; thus, the approach presents diagnostic potential for studies by metabonomics of mass-limited biopsies. PMID:22449140

Wong, Alan; Jiménez, Beatriz; Li, Xiaonan; Holmes, Elaine; Nicholson, Jeremy K; Lindon, John C; Sakellariou, Dimitris

2012-04-05

203

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

204

STRATEGIC E-HR: MATCHING E-BUSINESS VALUE DRIVERS AND HR MANAGEMENT TASKS  

Microsoft Academic Search

The scant e-HR literature has thus far focused on the shift from traditional HR Management to the adoption of e-HR. However, very little attention has been granted into understanding the strategic match between actual HR tasks and e-HR value creation. This paper embeds e-business logic into HR operations management. This is done by conceptualizing a framework for analyzing and evaluating

Bjørn-Tore Flåten; Rotem Shneor

2008-01-01

205

Motivations for HR outsourcing in Australia  

Microsoft Academic Search

The aims of this research are twofold; first, to determine which human resource (HR) functions are most commonly outsourced in Australian organisations and second, to explore the motivation to outsource these HR functions. Results from a nationwide survey identified recruitment and selection, training, occupational health and safety, payroll and employee benefits as the top five outsourced HR functions. The three

Pattanee Susomrith; Alan Brown

2012-01-01

206

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

2008-06-27

207

Management accounting system (MAS) change: field evidence  

Microsoft Academic Search

This paper critically discusses one of the prescriptions of traditional control literature according to which the management accounting system (MAS) should be adaptive to changes in the organizational and strategic context. Drawing from contingency and institutional theories, the paper drafts a framework to pragmatically identify key phases and features of the management accounting change process to highlight its organizational nature.

Laura Zoni; Andrea Dossi; Marco Morelli

2012-01-01

208

NMR studies of structure and ferroelectricity for Rochelle salt nanoparticles embedded in mesoporous sieves  

Microsoft Academic Search

NMR studies were carried out for Rochelle salt embedded in molecular sieves. 23Na magic angle spinning (MAS) and multiple quantum (MQ) MAS NMR spectra revealed a complex structure of the confined crystalline material. The major part of particles within nanopores had a structure similar to that of bulk Rochelle salt. The 23Na spin–lattice relaxation times at various temperatures associated with

Cheng Tien; E. V. Charnaya; M. K. Lee; S. V. Baryshnikov; D. Michel; W. Böhlmann

2008-01-01

209

The MasPar MP1 architecture  

Microsoft Academic Search

The MasPar MP-1 architecture is described. It is a massively parallel SIMD machine with the following key characteristics: scalable architecture in terms of the number of processing elements, system memory, and system communication bandwidth; reduced-instruction-set-computer-like instruction set design which leverages optimizing compiler technology; adherence to industry-standard floating point formats, specifically VAX and IEEE floating point; and an architectural design amenable

Tom Blank

1990-01-01

210

Variant Extensions to Prove MAS Behaviours  

Microsoft Academic Search

\\u000a In this article, it is shown how the behaviour of a multi-agent system can be validated thanks to proof. At first, the method\\u000a used is briefly presented [10]. Then, the variant notion is presented and an extension of this notion to prove MAS is introduced. In the third part, the proof technique is\\u000a illustrated for the prey-predator problem: the behaviour

Bruno Mermet; Dominique Fournier

2004-01-01

211

Angiotensin (1-7) induces MAS receptor internalization.  

PubMed

Angiotensin (Ang) (1-7) is the endogenous ligand for the G protein-coupled receptor Mas, a receptor associated with cardiac, renal, and cerebral protective responses. Physiological evidence suggests that Mas receptor (MasR) undergoes agonist-dependent desensitization, but the underlying molecular mechanism regulating receptor activity is unknown. We investigated the hypothesis that MasR desensitizes and internalizes on stimulation with Ang-(1-7). For this purpose, we generated a chimera between the MasR and the yellow fluorescent protein (YFP; MasR-YFP). MasR-YFP-transfected HEK 293T cells were incubated with Ang-(1-7), and the relative cellular distribution of MasR-YFP was observed by confocal microscopy. In resting cells, MasR-YFP was mostly localized to the cell membrane. Ang-(1-7) induced a redistribution of MasR-YFP to intracellular vesicles of various sizes after 5 minutes. Following the time course of [(125)I]Ang-(1-7) endocytosis, we observed that half of MasR-YFP underwent endocytosis after 10 minutes, and this was blocked by a MasR antagonist. MasR-YFP colocalized with Rab5, the early endosome antigen 1, and the adaptor protein complex 2, indicating that the R is internalized through a clathrin-mediated pathway and targeted to early endosomes after Ang-(1-7) stimulation. A fraction of MasR-YFP also colocalized with caveolin 1, suggesting that at some point MasR-YFP traverses caveolin 1-positive compartments. In conclusion, MasR undergoes endocytosis on stimulation with Ang-(1-7), and this event may explain the desensitization of MasR responsiveness. In this way, MasR activity and density may be tightly controlled by the cell. PMID:21670420

Gironacci, Mariela M; Adamo, Hugo P; Corradi, Gerardo; Santos, Robson A; Ortiz, Pablo; Carretero, Oscar A

2011-06-13

212

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

213

29Si and 17O NMR investigation of the structure of some crystalline calcium silicate hydrates  

Microsoft Academic Search

This paper presents the results of a systematic investigation of the structure of 17O-enriched, hydrothermally synthesized 1.1-nm tobermorite, 1.4-nm tobermorite, jennite, calciochondrodite, xonotlite, and hillebrandite, using 29Si magic angle spinning (MAS) NMR, 1H-29Si cross-polarization magic angle spinning (CPMAS) NMR, and 17O MAS NMR. The 17O and most of the 1H-29Si CPMAS results are the first reported for these phases. Six

Xiandong Cong; R. James Kirkpatrick

1996-01-01

214

Magic Angle Spinning NMR Based Metabolic Profiling of Head and Neck Squamous Cell Carcinoma Tissues  

PubMed Central

High-resolution magic-angle spinning (HR-MAS) proton NMR spectroscopy is used to explore the metabolic signatures of head and neck squamous cell carcinoma (HNSCC) which included matched normal adjacent tissue (NAT) and tumor originating from tongue, lip, larynx and oral cavity, and associated lymph-node metastatic (LN-Met) tissues. A total of 43 tissues (18 NAT, 18 Tumor and 7 LN-Met) from twenty-two HNSCC patients were analyzed. Principal Component Analysis of NMR data showed a clear classification between NAT and tumor tissues, however, LN-Met tissues were classified among tumor. A partial least squares discriminant analysis model generated from NMR metabolic profiles was used to differentiate normal from tumor samples (Q2 > 0.80, Receiver Operator Characteristic area under the curve > 0. 86, using 7-fold cross validation). HNSCC and LN-Met tissues showed elevated levels of lactate, amino acids including leucine, isoleucine, valine, alanine, glutamine, glutamate, aspartate, glycine, phenylalanine and tyrosine, choline containing compounds, creatine, taurine, glutathione and decreased levels of triglycerides. These elevated metabolites were associated with highly active glycolysis, increased amino acids influx (anaplerosis) into the TCA cycle, altered energy metabolism, membrane choline phospholipid metabolism, and oxidative and osmotic defense mechanisms. Moreover, decreased levels of triglycerides may indicate lipolysis followed by ?-oxidation of fatty acids that may exist to deliver bioenergy for rapid tumor cell proliferation and growth.

Somashekar, Bagganahalli S.; Kamarajan, Pachiyappan; Danciu, Theodora; Kapila, Yvonne L.; Chinnaiyan, Arul M.; Rajendiran, Thekkelnaycke M.; Ramamoorthy, Ayyalusamy

2011-01-01

215

Magic angle spinning NMR-based metabolic profiling of head and neck squamous cell carcinoma tissues.  

PubMed

High-resolution magic-angle spinning (HR-MAS) proton NMR spectroscopy is used to explore the metabolic signatures of head and neck squamous cell carcinoma (HNSCC) which included matched normal adjacent tissue (NAT) and tumor originating from tongue, lip, larynx and oral cavity, and associated lymph-node metastatic (LN-Met) tissues. A total of 43 tissues (18 NAT, 18 Tumor and 7 LN-Met) from 22 HNSCC patients were analyzed. Principal Component Analysis of NMR data showed a clear classification between NAT and tumor tissues, however, LN-Met tissues were classified among tumor. A partial least-squares discriminant analysis model generated from NMR metabolic profiles was used to differentiate normal from tumor samples (Q(2) > 0.80, Receiver Operator Characteristic area under the curve >0.86, using 7-fold cross validation). HNSCC and LN-Met tissues showed elevated levels of lactate, amino acids including leucine, isoleucine, valine, alanine, glutamine, glutamate, aspartate, glycine, phenylalanine and tyrosine, choline containing compounds, creatine, taurine, glutathione, and decreased levels of triglycerides. These elevated metabolites were associated with highly active glycolysis, increased amino acids influx (anaplerosis) into the TCA cycle, altered energy metabolism, membrane choline phospholipid metabolism, and oxidative and osmotic defense mechanisms. Moreover, decreased levels of triglycerides may indicate lipolysis followed by ?-oxidation of fatty acids that may exist to deliver bioenergy for rapid tumor cell proliferation and growth. PMID:21961579

Somashekar, Bagganahalli S; Kamarajan, Pachiyappan; Danciu, Theodora; Kapila, Yvonne L; Chinnaiyan, Arul M; Rajendiran, Thekkelnaycke M; Ramamoorthy, Ayyalusamy

2011-10-18

216

Angiotensin-(1-7) Induces Mas Receptor Internalization  

PubMed Central

Angiotensin (Ang) (1-7) is the endogenous ligand for the G protein-coupled receptor Mas, a receptor (R) associated with cardiac, renal and cerebral protective responses. Physiological evidence suggests that Mas R undergoes agonist-dependent desensitization, but the underlying molecular mechanism regulating R activity is unknown. We investigated the hypothesis that Mas R desensitizes and internalizes upon stimulation with Ang-(1-7). For this purpose, we generated a chimera between the Mas R and the fluorescent protein YFP (MasR-YFP). MasR-YFP transfected HEK 293T cells were incubated with Ang-(1-7) and the relative cellular distribution of MasR-YFP was observed by confocal microscopy. In resting cells, MasR-YFP was mostly localized to the cell membrane. Ang-(1-7) induced a redistribution of MasR-YFP to intracellular vesicles of various sizes after 5 min. Following the time course of [125I]Ang-(1-7) endocytosis we observed that half of MasR-YFP underwent endocytosis after 10 min and this was blocked by a Mas R antagonist. MasR-YFP colocalized with Rab5, the early endosome antigen 1 and the adaptor protein complex 2, indicating that the R is internalized through a clathrin-mediated pathway and targeted to early endosomes after Ang-(1-7) stimulation. A fraction of MasR-YFP also colocalized with caveolin-1 suggesting that at some point MasR-YFP traverses caveolin-1 positive compartments. In conclusion, Mas R undergoes endocytosis upon stimulation with Ang-(1-7) and this event may explain the desensitization of Mas R responsiveness. In this way, Mas R activity and density may be tightly controlled by the cell.

Gironacci, Mariela M.; Adamo, Hugo P.; Corradi, Gerardo; Santos, Robson A.; Ortiz, Pablo; Carretero, Oscar A.

2011-01-01

217

Validation Techniques for the MAS Corona Model  

NASA Astrophysics Data System (ADS)

In the interest of making competent predictions about the structure of the solar corona, we have developed the tools necessary to quantitatively compare the Magnetohydrodynamics Around a Sphere (MAS) numerical model to the observed corona. The SAIC coronal modeling group has written an algorithm that creates a two dimensional polarization brightness image of the corona from the model density output by computing the line of sight integral for scattered white light. Using the tools we developed for the CISM Data Explorer, the white light intensity is extracted from the image around the full disk of the Sun at a given radial height. A series of these images, spanning a Carrington rotation, are processed through this method into a Carrington Map, which we use for direct comparison against LASCO C2 polarization brightness data. Our validation will begin with a chi-squared comparison of model to observations of the latitude of the streamer belt brightness maximum during the Whole Sun Month.

Schmit, D.; Gibson, S.; Detoma, G.; Wiltberger, M.

2006-05-01

218

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

219

Infrared and 13C MAS nuclear magnetic resonance spectroscopic study of acetylation of cotton.  

PubMed

The acetylation of commercial cotton samples with acetic anhydride without solvents in the presence of about 5% 4-dimethylaminopyridine (DMAP) catalyst was followed using Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy. This preliminary investigation was conducted in an effort to develop hydrophobic, biodegradable, cellulosic materials for subsequent application in oil spill cleanup. The FTIR results provide clear evidence for successful acetylation though the NMR results indicate that the level of acetylation is low. Nevertheless, the overall results indicate that cotton fibres are potential candidates suitable for further development via acetylation into hydrophobic sorbent materials for subsequent oil spill cleanup application. The results also indicate that de-acetylation, the reverse of the equilibrium acetylation reaction, occurred when the acetylation reaction was prolonged beyond 3 h. PMID:14670512

Adebajo, Moses O; Frost, Ray L

2004-01-01

220

Infrared and 13C MAS nuclear magnetic resonance spectroscopic study of acetylation of cotton  

NASA Astrophysics Data System (ADS)

The acetylation of commercial cotton samples with acetic anhydride without solvents in the presence of about 5% 4-dimethylaminopyridine (DMAP) catalyst was followed using Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy. This preliminary investigation was conducted in an effort to develop hydrophobic, biodegradable, cellulosic materials for subsequent application in oil spill cleanup. The FTIR results provide clear evidence for successful acetylation though the NMR results indicate that the level of acetylation is low. Nevertheless, the overall results indicate that cotton fibres are potential candidates suitable for further development via acetylation into hydrophobic sorbent materials for subsequent oil spill cleanup application. The results also indicate that de-acetylation, the reverse of the equilibrium acetylation reaction, occurred when the acetylation reaction was prolonged beyond 3 h.

Adebajo, Moses O.; Frost, Ray L.

2004-01-01

221

Application of high-resolution magic-angle spinning NMR spectroscopy to define the cell uptake of MRI contrast agents.  

PubMed

A new method, based on proton high-resolution magic-angle spinning ((1)H 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. PMID:12165257

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

2002-06-01

222

NMR imaging  

SciTech Connect

Since hydrogen is the most abundant element in all living organisms, proton NMR lends itself well as a method of investigation in biology and medicine. NMR imaging has some special advantages as a diagnostic tool: no ionizing radiation is used, it is noninvasive; it provides a safer means of imaging than the use of x-rays, gamma rays, positrons, or heavy ions. In contrast with ultrasound, the radiation penetrates the bony structures without attenuation. In additional to morphological information, NMR imaging provides additional diagnostic insights through relaxation parameters, which are not available from other imaging methods. In the decade since the first primitive NMR images were obtained, the quality of images now obtained approaches those from CT x-ray scanners. Prototype instruments are being constructed for clinical evaluation and the first whole-body scanners are beginning to appear on the market at costs comparable to CT scanners. Primary differences in equipment for conventional NMR and NMR imaging are the much larger aperture magnets that are required for the examination of human subjects and the addition of coils to generate field gradients and facilities for manipulating the gradients. Early results from clinical trials in many parts of the world are encouraging, and in a few years, the usefuleness of this modality of medical imaging to the medical profession in diagnosis and treatment of disease will be defined. 10 figures.

Andrew, E.R.

1983-04-01

223

Eight outrageous statements about HR science  

Microsoft Academic Search

The thesis of this article is that HRM research falls short on all three of the criteria that define a successful science: rigor, relevance, cumulative progress. To bring HR research to the level of a successful science, programmatic, theory based research is needed in which there is a pursuit of important research questions and the use of diverse research methods.

Robert L. Dipboye

2007-01-01

224

Characterization of boron-doped diamonds using 11B high-resolution NMR at high magnetic fields  

Microsoft Academic Search

11B static\\/magic-angle spinning (MAS) NMR experiments are applied to four different B-doped diamond samples prepared by either high-pressure and high-temperature (HPHT) or CVD methods with various starting materials. Application of MAS enhances the spectral resolution appreciably and differences of the four B-doped diamond samples are well reflected in the corresponding MAS spectra. From the comparison among the MAS spectra, and

M. Murakami; T. Shimizu; M. Tansho; Y. Takano; S. Ishii; E. A. Ekimov; V. A. Sidorov; H. Sumiya; H. Kawarada; K. Takegoshi

2008-01-01

225

M&As: The Good, the Bad, and the Ugly  

Microsoft Academic Search

ABSTRACT M&As: The Good, the Bad, and the Ugly M&As should be defined to include mergers, acquisitions,takeovers, tender offers, alliances, joint ventures, minority equity investments, licensing, divestitures, spin-offs, split- ups, carve-outs, leveraged buyouts, leveraged recapitalizations,dual-cl ass recapitalizations, reorganizations,restructuring, and recontractingassociated withfinancial distress and other adjustments. M&As represent a neoclassical theory of how firms seek to enhance their capabilities and resources

Kenneth R. Ahern; J. Fred Weston

2006-01-01

226

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

227

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

2013-03-07

228

HR3626 - Double-Line Spectroscopic Binary  

NASA Astrophysics Data System (ADS)

Orbital elements are determined for the double-lined spectroscopic binary HR 3626, which had previously been recognized as being only a single-lined system. A mass ratio of 1.26 + 0.02 is determined, and a magnitude difference ?mB = 1.0 ± 0.2 is inferred from the photoelectric radial velocity dips. This leads to the conclusion that the system consists of a pair of G dwarf or subgiant stars.

Beavers, W. I.; Salzer, J. J.

1982-04-01

229

GRID-MAS integration and the principle of immanence  

Microsoft Academic Search

This position paper proposes to bring together the integra- tion of Grid and MAS with the notion of immanence. On one hand, Grid is known to be an extraordinary infrastructure for coordinating distributed computing resources and Virtual Organisations (VOs). On one other hand MAS interest focusses on complex behaviour of systems of agents. Immanence is a principle that emerges from

Pascal Dugenie

2008-01-01

230

Sex specific behavioural alterations in Mas-deficient mice  

Microsoft Academic Search

Male mice lacking the Mas protooncogene have been shown to exhibit an increased anxiety in the Elevated Plus Maze Task and sustained long-term potentiation in the hippocampus without effect on spatial learning in the Morris Water Maze Task. Here, we report behavioural studies in female mice lacking the Mas protooncogene. As for the males, we analysed the learning and anxiety

Thomas Walther; Jörg-Peter Voigt; Heidrun Fink; Michael Bader

2000-01-01

231

MAS: learning support software platform for people with disabilities  

Microsoft Academic Search

Initiatives which focus on the adaptation of technology to people with disabilities are steadily increasing. Assistive technology provides a promising means to help people with disabilities. This paper summarizes MAS, a flexible and scalable software platform designed to help people with disabilities. MAS integrates technologies in order to enable users to use adaptive games, designed to explore, measure, and develop

Fernando Paniagua Martín; Ricardo Colomo Palacios; Ángel García-Crespo

2009-01-01

232

Effects of felodipine combined with puerarin on ACE2-Ang (1-7)-Mas axis in renovascular hypertensive rat.  

PubMed

This study aimed to investigate the effect of combination of felodipine+puerarin on ACE2-Ang (1-7)-Mas axis, and to explore the protective effect of the combination against kidney in renovascular hypertensive rats. Goldblatt rats were randomly divided into 5 groups as follows: 4 groups which were treated with felodipine (Felo), puerarin (Pue), Felo+Pue, and Felo+captopril (Cap), respectively, and a control group of animals that were administrated with distilled water. Contents of Ang II and Ang (1-7) in renal tissues were determined by ELISA kit. The mRNA expression of ACE2/Mas and ACE/AT1 in kidneys was analyzed by RT-PCR. After 8weeks of treatment, compared with Goldblatt group, Felo+Pue reduced SBP, DBP and HR (p<0.01 or p<0.05), ameliorated renal interstitial fibrosis, decreased the level of Ang II and increased that of Ang (1-7), upregulated mRNA expression of ACE2 and Mas, decreased that of ACE and AT1, and downregulated protein expression of TGF-?1 in kidneys (p<0.01). Compared with Felo group, Felo+Pue decreased DBP and HR more markedly, attenuated fibrosis, decreased Ang II levels and increased those of Ang (1-7), upregulated mRNA expression of ACE2 in bilateral kidneys and that of Mas in ischemic kidney, downregulated that of ACE in bilateral kidneys and that of AT1 in ischemic kidney, and decreased expression of TGF-?1 protein significantly. In a word, a combination of Felo+Pue has a more efficient therapeutic effect on DBP and HR, and contributes to a better protection against renal interstitial fibrosis. PMID:23523569

Bai, Song; Huang, Zheng-Gui; Chen, Li; Wang, Jiang-Tao; Ding, Bo-Ping

2013-03-20

233

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

PubMed

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

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

2012-12-12

234

In situ NMR analysis of fluids contained in sedimentary rock  

PubMed

Limitations of resolution and absorption in standard chemical spectroscopic techniques have made it difficult to study fluids in sedimentary rocks. In this paper, we show that a chemical characterization of pore fluids may be obtained in situ by magic angle spinning (MAS) nuclear magnetic resonance (NMR), which is normally used for solid samples. 1H MAS-NMR spectra of water and crude oil in Berea sandstone show sufficient chemical shift resolution for a straightforward determination of the oil/water ratio. Copyright 1998 Academic Press. PMID:9716484

de Swiet TM; Tomaselli; Hurlimann; Pines

1998-08-01

235

NMR, XRD and IR study on microcrystalline opals  

Microsoft Academic Search

Microcrystalline opal-CT and opal-C were investigated by 29Si MAS NMR and 29Si {1H} cross polarisation MAS NMR spectroscopy, X-ray small angle scattering, X-ray powder diffraction and infrared absorption\\u000a spectroscopy. The results are compared with those for non-crystalline precious opal (opal-AG), non-crystalline hyalite (opal-AN),\\u000a moderately disordered cristobalite and with well ordered low-cristobalite and low-tridymite. Opal-C is confirmed to be strongly\\u000a stacking

H. Graetsch; H. Gies; I. Topalovi?

1994-01-01

236

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

237

A 29Si MAS NMR study of modified C–S–H nanostructures  

Microsoft Academic Search

The sustainability of cement-based materials is a core technical issue of national importance. The serviceability of the concrete infrastructure, especially bridges, has recently received considerable media attention. Concurrently, the nanoscience of cements has emerged as a new discipline with the potential to positively manipulate the nanostructure of calcium silicate hydrate (C–S–H) in order to achieve sustainability objectives. Organic\\/inorganic C–S–H nanocomposites

James J. Beaudoin; Laila Raki; Rouhollah Alizadeh

2009-01-01

238

Analysis of ?-irradiated synthetic bone grafts by 29Si MAS-NMR spectroscopy, calorimetry and XRD  

Microsoft Academic Search

Ca–Sr–Zn–Si glasses have demonstrated excellent biocompatibility both in vitro using the MTT assay with L929 mouse fibroblast cells, and in vivo using healthy and ovariectomized female Wistar rats. However, the biological evaluation of the materials was performed on glass granules that were autoclaved, rather than ?-irradiated; the sterilisation procedure required prior to implantation of these materials in the human body.

D. Boyd; S. Murphy; M. R. Towler; A. W. Wren; S. Hayakawa

2009-01-01

239

Characterization of mullite in silicoaluminous fly ash by XRD, TEM, and 29Si MAS NMR  

Microsoft Academic Search

Mullite contained in a silicoaluminous fly ash (originating from power plant of La Maxe, near Metz in the east of France) issue from bituminous coal combustion has been studied by X-ray diffraction, nuclear magnetic resonance of 29Si spinning at magic angle, and transmission electron microscopy linked with energy-dispersive spectroscopy. By using results from X-ray diffraction [1] and nuclear magnetic resonance

S. Gomes; M. François

2000-01-01

240

Analysis of Hydroperoxides in Solid Polyethylene by MAS (13)C NMR and EPR;Macromolecules.  

National Technical Information Service (NTIS)

13C-enriched polyethylene was subjected to y-irradiation in the presence of air at 25 and 80degC for total doses ranging from 71 to 355 kGy. Significant quantities of hydroperoxides were detected in the 25degC irradiated sample by 13C magic angle spinning...

Assink Celina Dunbar Alam Clough

1999-01-01

241

In vitro activity of cefodizime (HR-221).  

PubMed Central

The in vitro activity of cefodizime (HR-221), a new cephalosporin antibiotic, was compared with the activities of selected antimicrobial agents against a broad spectrum of aerobic bacteria. Cefodizime concentrations of 2 micrograms/ml inhibited about 90% of Enterobacteriaceae studied. Serratia marcescens required 8 micrograms/ml to inhibit 90% of strains. Among gram-positive cocci, 50% of strains were inhibited by 2 micrograms/ml of cefodizime (including methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, and penicillin-resistant Streptococcus pneumoniae). Pseudomonas aeruginosa was less susceptible to cefodizime. Cefotaxime, an antibiotic closely related to cefodizime structurally, was about fourfold more active.

Ahonkhai, V I; Cherubin, C E; Shulman, M A

1982-01-01

242

Further deep imaging of HR 7329 A (? Tel A) and its brown dwarf companion B  

NASA Astrophysics Data System (ADS)

About 4 arcsec south of the young A0-type star HR 7329, a faint companion candidate was found by Lowrance et al. Its spectral type of M7-8 is consistent with a young brown dwarf companion. Here we report 10 new astrometric imaging observations of the pair HR 7329 A and B, obtained with the Hubble Space Telescope and the Very Large Telescope, aimed at showing a common proper motion with high significance and possible orbital motion of B around A. With 11 yr of epoch difference between the first and our last image, we can reject the possibility by more than 21? that B would be a non-moving background object unrelated to A. We detect no change in position angle and small or no change in separation (2.91 ± 2.41 mas yr-1), so that the orbit of HR 7329 B around A is inclined and/or eccentric and/or the orbital motion is currently only in the radial direction. If HR 7329 B is responsible for the outer radius of the debris disc around HR 7329 A being 24 au, and if HR 7329 B currently is at its apastron at 200 au (4.2 arcsec at 47.7 pc), we determine its pericentre distance to be 71 au, its semimajor axis to be 136 au, and its eccentricity to be e = 0.47. From the magnitude differences between HR 7329 A and B and the 2MASS magnitudes for the HR 7329 A+B system, we can estimate the magnitudes of HR 7329 B (J = 12.06 ± 0.19, H = 11.75 ± 0.10, Ks = 11.6 ± 0.1, L = 11.1 ± 0.2 mag) and then, with a few otherwise known parameters, its luminosity and mass (20-50 Jupiter masses). In the deepest images available, we did not detect any additional companion candidates up to ?9 arcsec, but we determined the upper limits in the planetary mass regime. Based on observations made with ESO Telescopes at the La Silla and Paranal Observatories under programme IDs 65.L-0144, 083.C-0283 and 083.C-0276 (by us), and 073.C-0075, 077.C-0438, 081.C-0687, 081.C-0519 (from archive) and on observations made with the NASA/ESA Hubble Space Telescope (programme IDs 7226 and 10487).

Neuhäuser, R.; Ginski, C.; Schmidt, T. O. B.; Mugrauer, M.

2011-09-01

243

A MAS Application Research in City Traffic System  

Microsoft Academic Search

In this paper, we first analyze the problems regarding some of the current traffic control systems. Based on MAS and ITS system, we present an intelligent traffic system control approach which can be efficient to tackle the traffic congestion problems.

Chunmei Chi; Feng Gao

2010-01-01

244

A comparative spectroscopic investigation of three pseudopolymorphs of testosterone using solid-state i.r. and high-resolution solid-state NMR  

NASA Astrophysics Data System (ADS)

Three pseudopolymorphic forms of testosterone have been examined by i.r. and CP/MAS NMR spectroscopies. The transmittance i.r. data clearly distinguish the forms. The NMR work also provides clear distinctions and shows crystallographic splittings for the ? form only, in accordance with the X-ray data. The NMR spectra are fully assigned. The effect of crystallisation procedure on the NMR spectra was explored. NMR can be used to quantitatively assess mixtures of the ? and ? forms.

Fletton, Richard A.; Harris, Robin K.; Kenwright, Alan M.; Lancaster, Robert W.; Packer, Kenneth J.; Sheppard, Norman

245

Endothelin-1 downregulates Mas receptor expression in human cardiomyocytes.  

PubMed

Endothelin?1 (ET?1) and the renin?angiotensin system (RAS) are involved in the pathogenesis of cardiac dysfunction. The Mas receptor is a functional binding site for angiotensin (Ang)?(1?7), which is now considered a critical component of the RAS and exerts cardioprotective effects. To the best of our knowledge, the present study aimed to examine, for the first time, the effects of ET?1 on Mas expression in cultured human cardiomyocytes. Human cardiomyocytes were treated with ET?1 at different concentrations (1, 5, 10, 20 and 30 nM) for varied time periods (0.5, 1.5, 3, 4.5 or 6 h) with or without the transcription inhibitor actinomycin D, endothelin A (ETA) receptor blocker BQ123 and ETB receptor blocker BQ788, or different kinase inhibitors. ET?1 decreased the Mas mRNA level in a statistically significant dose- and time?dependent manner within 4.5 h, which was reflected in the dose?dependent downregulation of Mas promoter activity, Mas protein levels and Ang?(1?7) binding on the cell membrane. Actinomycin D (1 mg/ml), BQ123 (1 µM), p38 mitogen?activated protein kinase (MAPK) siRNA and inhibitor PD169316 (25 µM), completely eliminated the inhibitory effects of ET?1 on Mas expression in human cardiomyocytes. In conclusion, the present study demonstrated that ET?1 downregulates Mas expression at the transcription level in human cardiomyocytes via the ETA receptor by a p38 MAPK?dependent mechanism. This study provides novel insights into the function of ET?1 and the Ang?(1?7)/Mas axis in cardiac pathophysiology. PMID:23836146

Chen, Zhiheng; Tang, Yamei; Yang, Zuocheng; Liu, Shaojun; Liu, Yong; Li, Yan; He, Wei

2013-07-08

246

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

Microsoft Academic Search

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

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

1996-01-01

247

Hypocorticism and interrenal hyperplasia are not directly related to masculinization in XX mas ?1\\/ mas ?1 carp, Cyprinus carpio  

Microsoft Academic Search

This study reports on a homozygous XX male strain of common carp (E5), which fail to mount a normal cortisol stress response. Earlier classical genetic analysis had indicated that masculinization of E5 fish was caused by a putative recessive mutation (mas?1\\/mas?1). Hypocorticism in E5 fish was studied to investigate if it was related to masculinization. Head-kidney tissues isolated from E5

N. M. Ruane; J. G. D. Lambert; H. J. Th. Goos; J. Komen

2005-01-01

248

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

249

11B magnetic resonance imaging and MAS spectroscopy of trimethylborate-treated radiata pine wood.  

PubMed

Boron-11 nuclear magnetic resonance imaging and spectroscopy have been used to characterise the nature and distribution of boron compounds after preservative treatment of radiata pine wood with trimethylborate (TMB). One day after treatment, 11B magnetic resonance imaging microscopy showed significant differences in the morphological distribution of boron species, with there apparently being no treatment penetration of the latewood. 11B MAS NMR spectroscopy of freshly preservative-treated radiata pine wood, which had been separated into latewood and earlywood, showed the only boron species present in the latewood to be boric acid while in the earlywood both TMB and boric acid were initially present. Due to quadrupolar broadening and a short T2 value, the boric acid signal relaxed too quickly to be observable and this caused the apparent lack of 11B in the image when only boric acid was present. TMB undergoes hydrolysis to form boric acid and in radiata pine latewood, this hydrolysis reaction is rapid. PMID:10903086

Meder, R; Franich, R A; Callaghan, P T

1999-10-01

250

A supplementary coil for 2H decoupling with commercial HCN MAS probes  

NASA Astrophysics Data System (ADS)

Partial deuteration is a powerful tool to increase coherence life times and spectral resolution in proton solid-state NMR. The J coupling to deuterium needs, however, to be decoupled to maintain the good resolution in the (usually indirect) 13C dimension(s). We present a simple and reversible way to expand a commercial 1.3 mm HCN MAS probe with a 2H channel with sufficient field strength for J-decoupling of deuterium, namely 2-3 kHz. The coil is placed at the outside of the stator and requires no significant modifications to the probe. The performance and the realizable gains in sensitivity and resolution are demonstrated using perdeuterated ubiquitin, with selectively CHD2-labeled methyl groups.

Huber, Matthias; With, Oliver; Schanda, Paul; Verel, René; Ernst, Matthias; Meier, Beat H.

2012-01-01

251

Dynamic nuclear polarization NMR spectroscopy allows high-throughput characterization of microporous organic polymers.  

PubMed

Dynamic nuclear polarization (DNP) solid-state NMR was used to obtain natural abundance (13)C and (15)N CP MAS NMR spectra of microporous organic polymers with excellent signal-to-noise ratio, allowing for unprecedented details in the molecular structure to be determined for these complex polymer networks. Sensitivity enhancements larger than 10 were obtained with bis-nitroxide radical at 14.1 T and low temperature (?105 K). This DNP MAS NMR approach allows efficient, high-throughput characterization of libraries of porous polymers prepared by combinatorial chemistry methods. PMID:24028380

Blanc, Frédéric; Chong, Samantha Y; McDonald, Tom O; Adams, Dave J; Pawsey, Shane; Caporini, Marc A; Cooper, Andrew I

2013-10-02

252

gratterpalm uses HR as a strategic tool for growth  

Microsoft Academic Search

Purpose – The aim of this case study is to show how HR can help an organization meet its business goals. Investing strategically in HR can result in cost savings, enhanced productivity and improved customer service. Design\\/methodology\\/approach – The case study feature follows the development of HR at a retail marketing agency in the UK and its five-year journey from

Helen Saunders

2009-01-01

253

The Selection of City HR Environment Evaluation Indexes  

Microsoft Academic Search

HR environment was defined as the system, state and correlation of all the factors in a certain region, which can directly or indirectly satisfy basic human needs. It advanced that HR environment contains several fields, such as physical environment, social environment, political environment, economic environment, cultural environment, living environment and so on. The relation between human needs and HR environment

Hu Bei; Weng Qingxiong

2007-01-01

254

Separated local field NMR experiments on oriented samples rotating at the magic angle  

Microsoft Academic Search

Biophysical studies on membrane proteins by solid state NMR (SSNMR) can be carried out directly in a membrane environment.\\u000a Samples are usually prepared in form of multi-lamellar dispersions for magic angle sample spinning or as aligned multi-layers\\u000a for orientation dependent NMR experiments without sample rotation. A new development is the application of MAS NMR to aligned\\u000a samples (MAOSS; Magic Angle

Jakob J. Lopez; A. J. Mason; Christoph Kaiser; Clemens Glaubitz

2007-01-01

255

Estimation of V? O 2max from the ratio between HR max and HR rest – the Heart Rate Ratio Method  

Microsoft Academic Search

The effects of t??raining and\\/or ageing upon maximal oxygen uptake ( V?O 2max) and heart rate values at rest (HR rest) and maximal exercise (HR max), respectively, suggest a relationship between V?O 2max and the HR max-to-HR rest ratio which may be of use for indirect testing of V?O 2max. Fick principle calculations supplemented by literature data on maximum-to-rest ratios

Niels Uth; Henrik Sørensen; Kristian Overgaard; Preben K. Pedersen

2004-01-01

256

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

257

Solid-State NMR Studies of Ionic Surfactants Adsorbed on Cyanopropyl Bonded Phases: Implications for Micellar Liquid Chromatography  

Microsoft Academic Search

Solid-state13C NMR spectroscopy techniques, including cross polarization (CP), magic angle spinning (MAS), and high-power proton decoupling, have been used to study the interactions of two ionic surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), with the cyanopropyl bonded phase. Variable contact time CP\\/MAS13C NMR data suggest that the unusual behavior of cyanopropyl bonded phase columns in SDS and CTAB

Barry K. Lavine; Sumar Hendayana; Yifang He; William T. Cooper

1996-01-01

258

Multichannel astrometric photometer and photographic astrometric studies in the regions of Lalande 21185, BD 56 deg 2966, and HR 4784  

NASA Astrophysics Data System (ADS)

The parallaxes of stars determined from the multichannel astrometric photometer (MAP) in the regions of Lalande 21185, BD 56 deg 2966, and from photographic plates in the region of BD 56 deg 2966 and the region of HR 4783 and HR 4784 are reported. The parallax determined for Lalande 21185, 395.1 +/-1.0 mas yields what is believed to be the most precise distance modulus (-2.984 +/-0.0055) known for a star other than the sun. The absolute magnitude of Lalande 21185 is found to be 10.474 +/-0.008. No significant evidence of unseen companions is detected. The photographic study of BD 56 deg 2966 indicates that the long-term (65 yr) motion of the star is linear to better than +/-16 mas, while the MAP study indicates that the motion is linear to better than +/-2.5 mas over a period of some 5 yr. The photographically determined parallaxes are compared with those observed with the MAP. The photographically calculated standard errors are found to be in agreement with the standard error of the differences.

Gatewood, George; Stein, John; de Jonge, Joost K.; Persinger, Timothy; Reiland, Thomas; Stephenson, Bruce

1992-09-01

259

Welding Metallurgy of Alloy HR-160  

SciTech Connect

The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in alloy HR-160 was investigated by Varestraint testing, differential thermal analysis, and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 {deg}C and initiated solidification by a primary L - {gamma} reaction in which Ni, Si, and Ti segregated to the interdendritic liquid and Co segregated to the {gamma} dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at {approx} 1162 {deg}C by a eutectic-type L - [{gamma}+ (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7}] reaction. The (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7} phase is found to be analogous to the G phase which forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found to exist between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [{gamma} +(Ni,Co){sub l6}(Ti,Cr){sub 6}Si{sub 7}] eutectic-typr constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 {deg}C and the presence of 2 to 5 vol% solute rich interdendritic liquid which preferentially wets the grain boundaries and interdendritic regions.

DuPont, J.N.; Michael, J.R.; Newbury, B.D.

1999-05-28

260

A Market-based MAS Framework for Microgrids  

Microsoft Academic Search

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

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

261

MAS behavior modeling of virtual drone entity based on CLIPS  

Microsoft Academic Search

MAS is currently a popular method of behavior modeling .it is based on such mathematical model as finite state machine, expert system and soft computing which includes fuzzy logic, neural network, genetic algorithms etc. CLIPS has characteristic of function and nimble implement. If using it as mathematical model of agent, it will be convenient in plan and implement. In this

Hongge Yao

2011-01-01

262

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

Microsoft Academic Search

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

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

2009-01-01

263

The distribution of sodium ions in aluminosilicate glasses: a high-field Na23 MAS and 3Q MAS NMR study  

Microsoft Academic Search

The local configurations around sodium ions in silicate glasses and melts and their distributions have strong implications for the dynamic and static properties of melts and thus may play important roles in magmatic processes. The quantification of distributions among charge-balancing cations, including Na+ in aluminosilicate glasses and melts, however, remains a difficult problem that is relevant to high-temperature geochemistry as

Sung Keun Lee; Jonathan F. Stebbins

2003-01-01

264

Private Health Insurance Provisions of H.R. 3962  

Microsoft Academic Search

[Excerpt] This report summarizes key provisions affecting private health insurance, including provisions to raise revenues, in Division A of H.R. 3962, the Affordable Health Care for America Act, as introduced in the House of Representatives on October 29, 2009. H.R. 3962 is based on H.R. 3200, America’s Affordable Health Choices Act of 2009, which was originally introduced on July 14,

Hinda Chaikind; Bernadette Fernandez; Chris L Peterson; Paulette C Morgan; Mark Newsom; Janemarie Mulvey

2009-01-01

265

Very Thin Shim Coils for an NMR Probe.  

National Technical Information Service (NTIS)

In a previous report (AERE-R 7849 (1974)) which described the manufacture of a transverse quadrupole shim coil for the Varian HR 220 n.m.r. spectrometer, consideration was given to the design of coils which could be used on earlier models of the instrumen...

C. A. Baker

1975-01-01

266

Determination of NMR interaction parameters from double rotation NMR.  

PubMed

It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The (17)O nuclei in isotopically enriched l-alanine and OPPh(3) are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 +/- 20 ppm and 350 +/- 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of +/- 5-10 degrees . For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V(33) and delta(33)) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh(3) the principal axis of the (17)O EFG is found to be close to the O-P bond, and the (17)O-(31)P one-bond J coupling ((1)J(OP)=161 +/- 2 Hz) is determined to a much higher accuracy than previously. PMID:17707665

Hung, I; Wong, A; Howes, A P; Anupõld, T; Past, J; Samoson, A; Mo, X; Wu, G; Smith, M E; Brown, S P; Dupree, R

2007-08-03

267

An intelligent assistant design system based on CBR and MAS  

Microsoft Academic Search

This paper establishes a framework of Multi-Agent System (MAS)-based collaborative assistant design system which is applied to the Machining Center (MC), provides an expanded Object-Oriented Knowledge Representation (OOKR) for the cases storage, presents an effective reasoning algorithm for the chosen of appreciate production type according to the customization, and illustrates a prototype case study to show the practicability of this

Fang Li; Nan Chen

2009-01-01

268

Commercial facility site selection simulating based on MAS  

NASA Astrophysics Data System (ADS)

The location of commercial facility decides the benefit of the operator to a large degree. Existing location methods can express the static relationships between site selection result and location factors, but there still are some limites when express the dynamic and uncertain relationship between them. Hence, a dynamic, stochastic and forecastable location model should be built which can introduce the customer's behavior into the model and combine the macro pattern and micro spatial interaction. So the authors proposes Geosim-LM based on MAS. Geosim-LM has 3 kinds of agents, CustAgent, SiteAgent and GovAgent. They represent the customers, commercial fercilities and government. The land type, land price and traffic are the model environment. Then Geosim-LM is applied in the bank branches site evaluation and selection in Liwan district, Guangzhou. In existing bank branches site evaluation, there are 70% consistent in score grade between result of Geosim-LM after 200 round runing and actual rebust location. It proves the model is reliable and feasible. The conclusions can be get from the paper. MAS have advantages in location choice than existed methods. The result of Geosim-LM running can powerfully proves that building location model based on MAS is feasible.

Chao, Yi; Li, Qingquan; Zheng, Guizhou

2008-11-01

269

Classification of Ap-Stars HR 830 and 21 CVn  

Microsoft Academic Search

Two ambiguously classified Ap stars, HR 830 and 21 CVn, are studied. The observational data are compared with the data for normal stars alpha Del and alpha Lyr. The star HR 830 is classified as Ap of type Si based on the enhanced absorption in the Si lines and photometric variability in UBV. 21 CVn is classified as Ap Si

J. Zverko

1984-01-01

270

HR managers as ethical decision-makers: Mapping the terrain  

Microsoft Academic Search

Discourse surrounding the ethical responsibilities of human resource (HR) managers is in its infancy in Australia, despite an increasing concern with broad matters related to corporate governance and the ethical ‘behaviour’ of organisations. Recent industrial relations legislative changes in Australia arguably place greater responsibilities on HR managers, and raise issues related to the role they may take in promoting fairness

Diannah Lowry

2006-01-01

271

Human capital measures, strategy, and performance: HR managers' perceptions  

Microsoft Academic Search

Purpose – The purpose of this paper is to report the results of a survey and interviews with human resource (HR) professionals to identify and better understand their perceptions and expectations of human capital measures' (HCM) content, links to strategy, and impact on performance. Design\\/methodology\\/approach – This paper relies on a quantitative analysis of survey questionnaires collected from 104 HR

Stephen Gates; Pascal Langevin

2010-01-01

272

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

273

Planet Formation at Wide Separations: Constraints from HR 8799  

NASA Astrophysics Data System (ADS)

The three gas giants directly-imaged orbiting HR 8799 comprise the first planetary system detected at wide separations around a main sequence star. Core accretion scenarios, already strained at the outer limits of our solar system, have difficulty explaining planet formation at the larger distances of the HR 8799 planets, even around a central A star. Formation by gravitational instability (GI) is most plausible for massive planets at large separations. We demonstrate that for GI to form the planets around HR 8799, the protoplanetary disk must have passed through a fine-tuned region of parameter space at its transition from the Class I to the Class II phase. Orbital stability requirements imply that the HR 8799 planets occupy at least one and possibly two mean motion resonances, suggesting that they migrated toward one another and may have migrated substantially from their formation locations. We will discuss how the HR 8799 system constrains the formation and migration of distant planets.

Murray-Clay, Ruth; Kratter, K.; Youdin, A.

2009-09-01

274

Stationary interphases with extended alkyl chains: a comparative study on chain order by solid-state NMR spectroscopy.  

PubMed

Stationary interphases with long n-alkyl chains (n = 18, 22, 30, 34) have been examined by solid-state NMR spectroscopy. The determination of the silane functionality and the degree of cross-linking of silane ligands on the silica surface was performed by 29Si CP/MAS NMR spectroscopy. High-speed 1H MAS and 13C CP/MAS NMR spectroscopy were utilized to assess alkyl chain order and mobility of the different bonded phases. For this purpose, 1H NMR line widths and 13C chemical shifts have been evaluated. It is shown that stationary phase order and rigidity increase with alkyl chain length. In addition, the temperature-dependent trans/gauche conformational change occurs at higher temperatures for a polymeric C34 phase compared with a C30 sorbent. This behaviour is discussed in the context of previously reported chromatographic (HPLC) shape selectivity differences. PMID:9477449

Pursch, M; Brindle, R; Ellwanger, A; Sander, L C; Bell, C M; Händel, H; Albert, K

1997-12-01

275

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

276

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

277

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...

278

Protein structure determination with paramagnetic solid-state NMR spectroscopy.  

PubMed

Many structures of the proteins and protein assemblies that play central roles in fundamental biological processes and disease pathogenesis are not readily accessible via the conventional techniques of single-crystal X-ray diffraction and solution-state nuclear magnetic resonance (NMR). On the other hand, many of these challenging biological systems are suitable targets for atomic-level structural and dynamic analysis by magic-angle spinning (MAS) solid-state NMR spectroscopy, a technique that has far less stringent limitations on the molecular size and crystalline state. Over the past decade, major advances in instrumentation and methodology have prompted rapid growth in the field of biological solid-state NMR. However, despite this progress, one challenge for the elucidation of three-dimensional (3D) protein structures via conventional MAS NMR methods is the relative lack of long-distance data. Specifically, extracting unambiguous interatomic distance restraints larger than ?5 Å from through-space magnetic dipole-dipole couplings among the protein (1)H, (13)C, and (15)N nuclei has proven to be a considerable challenge for researchers. It is possible to circumvent this problem by extending the structural studies to include several analogs of the protein of interest, intentionally modified to contain covalently attached paramagnetic tags at selected sites. In these paramagnetic proteins, the hyperfine couplings between the nuclei and unpaired electrons can manifest themselves in NMR spectra in the form of relaxation enhancements of the nuclear spins that depend on the electron-nucleus distance. These effects can be significant for nuclei located up to ?20 Å away from the paramagnetic center. In this Account, we discuss MAS NMR structural studies of nitroxide and EDTA-Cu(2+) labeled variants of a model 56 amino acid globular protein, B1 immunoglobulin-binding domain of protein G (GB1), in the microcrystalline solid phase. We used a set of six EDTA-Cu(2+)-tagged GB1 mutants to rapidly determine the global protein fold in a de novo fashion. Remarkably, these studies required quantitative measurements of only approximately four or five backbone amide (15)N longitudinal paramagnetic relaxation enhancements per residue, in the complete absence of the usual internuclear distance restraints. Importantly, this paramagnetic solid-state NMR methodology is general and can be directly applied to larger proteins and protein complexes for which a significant fraction of the signals can be assigned in standard 2D and 3D MAS NMR chemical shift correlation spectra. PMID:23464364

Sengupta, Ishita; Nadaud, Philippe S; Jaroniec, Christopher P

2013-03-06

279

17O NMR Studies of Zeolites  

NASA Astrophysics Data System (ADS)

Multiple-quantum magic-angle spinning (MQMAS) and double rotation (DOR) techniques were applied in the fields of 17.6 T and 11.7 T to the study the 17O NMR of oxygen-17 enriched zeolites A, LSX and sodalite. In addition, some 29Si and 1H MAS NMR experiments were performed. Zeolites with the ratio Si/Al = 1 were chosen, in order to have an alternating distribution of silicon and aluminum atoms. A linear correlation between the isotropic value of the chemical shift and the Si-O-Al bond angle (taken from X-ray data) could be found for the zeolites A and LSX, but not for sodalites. Hydration of the zeolites causes a downfield 17O NMR chemical shift of about 8 ppm with respect to the dehydrated zeolites. Ion exchange of the hydrated zeolites generates stronger chemical shift effects. The increase of the basicity of the oxygen framework of the zeolite LSX is reflected by a downfield shift of ca. 10 ppm going from the lithium to the cesium form, and the substitution of sodium by thallium in the zeolite A causes a shift of 34 ppm for the O3 site. 17O DOR NMR spectra are superior to 17O 3QMAS NMR spectra, featuring a resolution increase by a factor of two and are about equal with respect to the sensitivity. The residual linewidths of the signals in the 17O DOR and 17O 5QMAS NMR spectra can be explained by a distribution of the Si-O-Al angles in the zeolites.

Freude, Dieter; Loeser, Thomas

280

Employee Returns: Linking HR Performance Indicators to Business Strategy.  

National Technical Information Service (NTIS)

Contents: Introduction; Strategic Context of Measurement; A Question of Balance; People Measures; Measuring HR; Benchmarking; Conclusion: Measurement in Context; Appendix A: Defining Hard Indicators; Appendix B: Deriving Indicators of Satisfaction and Com...

A. Carter D. Robinson

2000-01-01

281

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

282

CLEA: H-R Diagrams of Star Clusters  

NSDL National Science Digital Library

This lab illustrates how HR diagrams of star clusters are used to determine the distances and ages of the clusters. Students use real photometric data, star positions, and data analysis software to fit HR diagrams to various models. If desired, students can also measure the magnitudes and colors of the cluster stars using a simulated telescope, thus learning how astronomers collect the data. This is part of a larger collection of simulations, Project CLEA.

Marschall, Laurence; Snyder, Glenn; Cooper, P. R.; Hayden, Michael; Good, Rhonda

2008-08-28

283

Photochemically Induced Dynamic Nuclear Polarization (Photo-CIDNP) Magic-Angle Spinning NMR  

Microsoft Academic Search

Photochemically induced dynamic nuclear polarization (photo-CIDNP) is non-Boltzmann nuclear magnetization which can be observed\\u000a by NMR spectroscopy as enhanced absorptive (positive) or emissive (negative) signals. In solids, photo-CIDNP has been observed\\u000a since its discovery in 1994 in various photosynthetic reaction centers (RCs) by magic angle spinning (MAS) solid-state NMR.\\u000a The photo-CIDNP effect in solids can be explained by a combination

Eugenio Daviso; Gunnar Jeschke; Jörg Matysik

284

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

285

Silver-109 NMR spectroscopy of inorganic solids.  

PubMed

In this study the (109)Ag NMR spectra of the following solid inorganic silver-containing compounds were investigated: AgNO(3), AgNO(2), Ag(2)SO(4), Ag(2)SO(3), AgCO(3), Ag(3)PO(4), AgCl, AgBr, AgI, AgSO(3)CH(3), silver p-toluenesulfonate, NaAg(CN)(2), KAg(CN)(2), K(3)Ag(CN)(4), Me(4)NAgCl(2), silver diethylthiocarbamate, silver lactate, silver acetate, silver citrate, and bis[(N,N(1)-di-tert-butylformamidinato)silver(I)]. The magic angle spinning (MAS) spectra of all compounds were obtained. In some cases, when protons were available, the (1)H to (109)Ag cross-polarization (CP) technique was used to enhance the signal and shorten the experimental relaxation delay. It was possible to obtain slow MAS (or CP/MAS) or nonspinning spectra for 10 samples, allowing the determination of the principal components of the (109)Ag chemical shift (CS) tensors. The isotropic chemical shifts and the CS tensors are discussed in light of the available crystal structures. The need for an accepted standard for referencing (109)Ag chemical shifts and the use of AgSO(3)CH(3) as a CP setup sample are also discussed. PMID:15332810

Penner, Glenn H; Li, Wenli

2004-09-01

286

Hypocorticism and interrenal hyperplasia are not directly related to masculinization in XX mas(-1)/mas(-1) carp, Cyprinus carpio.  

PubMed

This study reports on a homozygous XX male strain of common carp (E5), which fail to mount a normal cortisol stress response. Earlier classical genetic analysis had indicated that masculinization of E5 fish was caused by a putative recessive mutation (mas(-1)/mas(-1)). Hypocorticism in E5 fish was studied to investigate if it was related to masculinization. Head-kidney tissues isolated from E5 fish showed a low cortisol-producing capacity in vitro, and also demonstrated a reduced sensitivity to stimulation with ACTH, when compared with an isogenic XY male carp strain (STD). There was no strain difference in androgen production by head-kidney tissues in vitro. E5 fish exhibited significant hyperplasia of the interrenal tissue (adrenal homologue of teleost fish) located in the head-kidney. Conversion of pregnenolone was significantly lower in E5 head-kidney homogenates, compared to STD homogenates, however, no strain difference was found in the conversion of 17alpha-hydroxyprogesterone into cortisol. Gonad homogenates incubated with pregnenolone showed no strain difference in conversion to corticosteroids and androgens. Results indicate that the interrenal hyperplasia and hypocorticism in this strain of carp may be due to a dysfunction of the 17alpha-hydroxylase activity of the enzyme P450c17 in the interrenal, but that this defect may not be the primary factor resulting in masculinization of these XX genotypes. PMID:15993106

Ruane, N M; Lambert, J G D; Goos, H J Th; Komen, J

2005-04-01

287

Geography of Domestic Mergers and Acquisitions (M&As): Evidence from Matched Firm-level Data  

Microsoft Academic Search

Böckerman P. and Lehto E. (2006) Geography of domestic mergers and acquisitions (M&As): evidence from matched firm-level data, Regional Studies40, 847–860. This paper explores domestic mergers and acquisitions (M&As) from the regional perspective. The Finnish evidence reveals that geographical closeness is a characteristic of great importance for domestic M&As. Thus, a great number of M&As occur within narrowly defined regions.

Petri Böckerman; Eero Lehto

2006-01-01

288

Clinical Experience with the Cervista HPV HR Assay  

PubMed Central

Testing for high-risk (HR) human papillomavirus (HPV) is a key component of current recommendations for cervical cancer screening. Herein is described our clinical experience using Cervista HPV HR, a testing platform recently approved by the US Food and Drug Administration for clinical use. Using data from a high-volume commercial laboratory, a retrospective analysis of cytologic and Cervista HPV HR test results from 56,501 samples was performed, and an indirect comparison was made with previous experience with 53,008 samples tested using the Hybrid Capture 2 platform. Of samples analyzed using Cervista HPV HR, 1.5% were of insufficient volume for testing and 1.1% yielded an insufficient signal from the internal control to be reported. In samples with a cytological interpretation of atypical squamous cells of undetermined significance, 48.5% (95% confidence interval [CI], 47.5 to 49.5) tested positive using Cervista HPV HR, compared with 59.4% (95% CI, 58.3 to 60.5) of samples using Hybrid Capture 2. Of samples from women aged 30 years or older with a negative cytological interpretation, 5.8% (95% CI, 5.6 to 6.1) tested positive using Cervista HPV HR, compared with 5.5% (95% CI, 5.3 to 5.7) of samples using Hybrid Capture 2. When stratified by five-year age groups between 30 and 65 years, positivity rates for high-risk human papillomavirus were similar in the Cervista HPV HR and Hybrid Capture 2 populations, and were consistent with expectations established by the literature.

Youens, Kenneth E.; Hosler, Gregory A.; Washington, Paula J.; Jenevein, E. Patrick; Murphy, Kathleen M.

2011-01-01

289

The Photo-Dissociation Region Surrounding HR 5171AB  

NASA Astrophysics Data System (ADS)

HR 5171AB is an example of how an extremely massive star, a hypergiant, and its hot companion play the dominant role in their local environment. Their effects are demonstrated by first creating and then shaping what is likely a large Photo-Dissociation Region (PDR, Radius ˜8 pc) out of the molecular cloud in which they formed. We present extremely sensitive Spitzer Space Telescope IRAC images, as well as MSX and IRAS/IRIS data, that show this region in the mid-IR with previously unseen detail. The PDR surrounding HR 5171 lies at the outermost limits of the RCW 80 HII region, and is spatially well correlated with a molecular cloud at the same kinematic distance. The mid-IR colors of the dust and gas surrounding HR 5171 show a definite lack of shocked material. When combined with the expected colors for dust in a uniform UV radiation field, the data make a strong case for a quiescent PDR. The origins of the PDR likely date to when HR 5171A was a main sequence O-type star (˜50 Mo), and the current sustaining ionization source is its companion HR 5171B (B0 Ibp). This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA.

Schuster, Michael T.; Marengo, M.; Hora, J. L.; Gehrz, R. D.; Humphreys, R. M.; Fazio, G.

2006-12-01

290

HR 7355 - another rapidly braking He-strong CP star?  

NASA Astrophysics Data System (ADS)

Context. Strong meridional mixing induced by rapid rotation is one reason why all hot main-sequence stars are not chemically peculiar. However, the finding that the He-strong CP star HR 7355 is a rapid rotator complicates this concept. Aims: Our goal is to explain the observed behaviour of HR 7355 based on period analysis of all available photometry. Methods: Over two years, we acquired 114 new BV observations of HR 7355 at observatories in Arizona, U.S.A and Cape Town, South Africa. We performed period analyses of the new observations along with new analyses of 732 archival measurements from the Hipparcos and ASAS projects. Results: We find that the light curves of HR 7355gt; in various filters are quite similar, with amplitudes 0.035(4), 0.036(4), and 0.038(3) mag in B, Hp, and V, respectively. The light curves are double-peaked, with unevenly deep minima. We substantially refine the rotational period to be P = 0.5214410(4)d, indicating that HR 7355gt; is the most rapidly rotating CP star known. Our period analyses reveal a possible lengthening of the rotational period with dot{P}/P = 2.4(8)×10-6 yr-1. Conclusions: We conclude that the shape and amplitude of HR 7355gt; light curves are typical of magnetic He-strong CP stars, for which light variations are the result of photospheric spots on the surface of a rotating star. We hypothesise that the light variations are caused mainly by an uneven distribution of overabundant helium on the star's surface. We briefly describe and discuss the cause of the rapid rotational braking of the star. Photometric data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/L7

Mikulášek, Z.; Krti?ka, J.; Henry, G. W.; de Villiers, S. N.; Paunzen, E.; Zejda, M.

2010-02-01

291

High threshold HR (highly reflective) coatings at 1064 nm  

SciTech Connect

We have conducted as extensive series of laser damage measurements on highly reflective (HR) dielectric coatings which have yielded 1064-nm thresholds as high as 40 J/cm{sup 2} for 8- to 10-ns pulses at pulse-repetition frequencies (PRF) of 10 Hz. Moreover, by laser conditioning these coatings with subthreshold pulses, the thresholds of some coatings were raised to levels exceeding 70 J/cm{sup 2}. These are the highest threshold dielectric HR coatings that we have tested in this regime. The coatings were originally developed to produce HR-overcoated metal mirrors for free-electron-laser (FEL) applications at high PRF. Our tests included coatings deposited on both dielectric substrates and molybdenum (Mo) substrates. In each category we also examined coatings with a pre-coat of Mo between the substrate and the HR stack. The improved dielectric HR stacks effectively shielded the Mo from the laser irradiation so that the thresholds of virtually all Mo samples exceeded levels of the best dielectric-enhanced and dielectric-HR-coated metal mirrors we have tested to date. In addition to the low PRF measurements, we also conducted 1064-nm damage tests at 6-kHz PRF using 65-ns pulses from the Kilroy damage test facility. The coatings survived thermal loading of fluences ranging from 2 to 10 J/cm{sup 2} with respective small spot sizes on the order of 1.2 to 0.3 mm (1/e{sup 2} diameter). 6 refs., 3 figs.

Rainer, F.; DeMarco, F.P.; Hunt, J.T.; Morgan, A.J. (Lawrence Livermore National Lab., CA (USA)); Mott, L.P.; Marcelja, F.; Greenberg, M.R. (Spectra Physics-Optics Corp., Mountain View, CA (USA))

1990-12-17

292

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

293

Solid-state NMR characterization of Wilkinson's catalyst immobilized in mesoporous SBA-3 silica.  

PubMed

The Wilkinson's catalyst [RhCl(PPh(3))(3)] has been immobilized inside the pores of amine functionalized mesoporous silica material SBA-3 and The structure of the modified silica surface and the immobilized rhodium complex was determined by a combination of different solid-state NMR methods. The successful modification of the silica surface was confirmed by (29)Si CP-MAS NMR experiments. The presence of the T(n) peaks confirms the successful functionalization of the support and shows the way of binding the organic groups to the surface of the mesopores. (31)P-(31)P J-resolved 2D MAS NMR experiments were conducted in order to characterize the binding of the immobilized catalyst to the amine groups of the linkers attached to the silica surface. The pure catalyst exhibits a considerable (31)P-(31)P J-coupling, well resolvable in 2D MAS NMR experiments. This J-coupling was utilized to determine the binding mode of the catalyst to the linkers on the silica surface and the number of triphenylphosphine ligands that are replaced by coordination bonds to the amine groups. From the absence of any resolvable (31)P-(31)P J-coupling in off-magic-angle-spinning experiments, as well as slow-spinning MAS experiments, it is concluded, that two triphenylphosphine ligands are replaced and that the catalyst is bonded to the silica surface through two linker molecules. PMID:20446319

Grünberg, Anna; Yeping, Xu; Breitzke, Hergen; Buntkowsky, Gerd

2010-06-18

294

Dynamic Deuterium Magic Angle Spinning NMR of a Molecule Grafted at the Inner Surface of a Mesoporous Material.  

PubMed

Deuterium magic angle spinning (MAS) NMR is used to study the dynamics of an organic molecule, N-[triethoxysilylpropyl]acetamide-d(3), grafted at the inner surface of the mesoporous silica material, MCM-41. The grafted molecule has a deuterated methyl group at its free terminus to monitor its local mobility through changes in its dynamic (2)H-MAS NMR spectrum. Different spectra were recorded as a function of temperature from two different water containing samples. Observation shows that a major part of the grafted molecule remains static, irrespective of the temperature and hydration state of the sample, whereas the rest shows spectral changes indicative of a two-site jump motion of the methyl groups. Experimental observations were substantiated using molecular dynamic (MD) simulations of the grafted molecule. Subsequently, the MD results corroborate a model for the grafted molecules experiencing an exchange between two conformations consistent with the analysis of the (2)H-MAS NMR spectra. PMID:22853651

Jayanthi, S; Frydman, V; Vega, S

2012-08-16

295

A solid-state NMR study of condensation/retrograde reactions during coal liquefaction  

SciTech Connect

The objective of this work is to perform an NMR study of the aromaticity in coal, coal derived products and/or model compounds generated by pyrolysis and thermal solubilization of coal in the presence of a hydrogen donor solvent. Cross Polarization with Magic-Angle Spinning (CP/MAS) will be used to measure the carbon aromaticity, and Combined Rotation and Multiple Pulse Spectroscopy (CRAMPS) NMR techniques will be used to measure the hydrogen aromaticity. From these NMR measurements the aromatic hydrogen-to-carbon ratio will be obtained and used to study condensation/retrograde reactions during coal liquefaction. 2 refs., 1 fig.

Miknis, F.P.

1989-11-01

296

Natural abundance high-resolution solid state 2 H NMR spectroscopy  

NASA Astrophysics Data System (ADS)

We report for the first time an approach for natural abundance solid state 2 H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1 H decoupling (HPPD) and 1 H- 2 H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2 H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2 H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1 H to 2 H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

Aliev, Abil E.; Harris, Kenneth D. M.; Apperley, David C.

1994-08-01

297

Bumping HR: Giving Principals More Say over Staffing  

ERIC Educational Resources Information Center

|In what may come as a surprise to many, principals have remarkably little control over who teaches in their schools. For the most part, the human resources (HR) department in a district's central office, not individual school principals, makes the final call about when to hire teachers, whom to hire and in which schools they are placed.…

National Council on Teacher Quality, 2010

2010-01-01

298

Employee benefits communication: proposing a PR-HR cooperative approach  

Microsoft Academic Search

Management and administration of employee benefits rightfully fall under the purview of the organization's human resource department. So, too, has responsibility for benefits communication, though HR managers may lack the training, time and experience needed to administer a formal communication effort. The researchers use data from two surveys to show the criticality of benefits to recruiting, retention and motivation of

Alan R. Freitag; Gaelle Picherit-Duthler

2004-01-01

299

The light curve of the eclipsing binary HR 4560  

NASA Astrophysics Data System (ADS)

In this paper, 704 photoelectric observations in the Johnson B-band of the eclipsing binary recently discovered in the multiple system HR 4560, are presented. All measurements were made at the Observatory of Mojón del Trigo in Granada (Spain) during the years 1979, 1980, and 1981. The light curve derived from these observations is also given.

Gimenez, A.; Garcia, J. M.; Quesada, J. A.

1984-10-01

300

HR as Partner: Building Strategic Partnerships on Campus  

ERIC Educational Resources Information Center

Human resources is in an excellent position in many institutions to initiate collaboration and cooperation with other campus departments. In this article, the leaders of the departments of HR and academic resources at the University of Nevada, Las Vegas, share their insights on the importance of partnership-building on campus and describe how a…

Connally, Sam; Neuman, Dawn

2006-01-01

301

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

302

An Ounce of Prevention: The Benefits of an HR Audit  

ERIC Educational Resources Information Center

|During her 13 years leading a school district human resources office, the author came to recognize that managing human capital is much more than recruiting, hiring, managing personnel records, and handling performance issues. In addition to implementing initiatives to increase the efficiency with which HR officers and staff perform those tasks,…

Seals, Brenda

2011-01-01

303

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

304

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. 55 figs.

Pines, A.

1986-09-01

305

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

306

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

307

A low optical depth region in the inner disk of the Herbig Ae star HR 5999  

NASA Astrophysics Data System (ADS)

Context. Circumstellar disks surrounding young stars are known to be the birthplaces of planetary systems, and the innermost astronomical unit is of particular interest. Near-infrared interferometric studies have revealed a complex morphology for the close environment surrounding Herbig Ae stars. Aims: We present new long-baseline spectro-interferometric observations of the Herbig Ae star, HR 5999, obtained in the H and K bands with the AMBER instrument at the VLTI, and aim to produce near-infrared images at the sub-AU spatial scale. Methods: We spatially resolve the circumstellar material and reconstruct images in the H and K bands using the MiRA algorithm. In addition, we interpret the interferometric observations using models that assume that the near-infrared excess is dominated by the emission of a circumstellar disk. We compare the images reconstructed from the VLTI measurements to images obtained using simulated model data. Results: The K-band image reveals three main elements: a ring-like feature located at ~0.65 AU, a low surface brightness region inside 0.65 AU, and a central spot. At the maximum angular resolution of our observations (B/? ~ 1.3 mas), the ring is resolved while the central spot is only marginally resolved, preventing us from revealing the exact morphology of the circumstellar environment. We suggest that the ring traces silicate condensation, i.e., an opacity change, in a circumstellar disk around HR 5999. We build a model that includes a ring at the silicate sublimation radius and an inner disk of low surface brightness responsible for a large amount of the near-infrared continuum emission. The model successfully fits the SED, visibilities, and closure phases in the H and K bands, and provides evidence of a low surface brightness region inside the silicate sublimation radius. Conclusions: This study provides milli-arcsecond resolution images of the environment of HR 5999 and additional evidence that in Herbig Ae stars, there is material in a low surface brightness region, probably a low optical depth region, located inside the silicate sublimation radius and of unknown nature. The possibility that the formation of such a region in a thick disk is related to disk evolution should be investigated. Based on observations collected at the VLTI (ESO Paranal, Chile) with programs 080.C-0056, 083.C-0298, 083.C-0144, 083.C-0334, 083.C-0170, 083.C-0857, 083.C-0864, 083.C-0602, 084.C-0590, 085.C-0769, 085.C-0502.Appendix A is available in electronic form at http://www.aanda.org

Benisty, M.; Renard, S.; Natta, A.; Berger, J. P.; Massi, F.; Malbet, F.; Garcia, P. J. V.; Isella, A.; Mérand, A.; Monin, J. L.; Testi, L.; Thiébaut, E.; Vannier, M.; Weigelt, G.

2011-07-01

308

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

309

Magnesium silicate dissolution investigated by Si29 MAS, H-1Si29 CPMAS, Mg25 QCPMG NMR  

Microsoft Academic Search

Olivine-(Mg,Fe)âSiOâ-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

M C Davis; David J Wesolowski

2009-01-01

310

An investigation into the structure and reactivity of calcium-zinc-silicate ionomer glasses using MAS-NMR spectroscopy  

Microsoft Academic Search

The suitability of Glass Polyalkenoate Cements (GPCs) for orthopaedic applications is retarded by the presence in the glass\\u000a phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and\\u000a its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium-free GPCs may\\u000a be formulated based on

D. Boyd; M. R. Towler; R. V. Law; R. G. Hill

2006-01-01

311

Repetitive sideband-selective double frequency sweeps for sensitivity enhancement of MAS NMR of half-integer quadrupolar nuclei  

NASA Astrophysics Data System (ADS)

A sensitivity enhancement scheme aiming at selective adiabatic inversion of a single set of satellite transition sidebands under magic angle spinning has been employed on samples of albite containing a single moderately distorted 27Al site and zoisite containing two highly distorted octahedral 27Al sites. Overall enhancements of ˜2.5 for albite and ˜3 for the two AlO6 sites of zoisite are reported by applying this scheme at different spinning speeds reflecting the versatility of this enhancement scheme which achieves significant signal-to-noise enhancements for the systems with moderately high quadrupolar coupling and high quadrupolar coupling. Repeating the sensitivity enhancement scheme and signal readout several times without allowing for spin-lattice relaxation leads to sensitivity enhancements of factors of ˜4 for albite and ˜5 for zoisite which substantially increases the detectability of the quadrupolar sites. The effectiveness of this scheme at high magnetic field under very fast magic angle spinning has been demonstrated. Finally, the possibility of performing spectral editing by selective enhancement of one of the quadrupolar sites in zoisite whilst keeping the other site unaffected has been explored.

Goswami, M.; van Bentum, P. J. M.; Kentgens, A. P. M.

2012-06-01

312

Dual-band selective double cross polarization for heteronuclear polarization transfer between dilute spins in solid-state MAS NMR  

PubMed Central

A sinusoidal modulation scheme is described for selective heteronuclear polarization transfer between two dilute spins in double cross polarization magic-angle-spinning nuclear magnetic resonance spectroscopy. During the second N ? C cross polarization, the 13C RF amplitude is modulated sinusoidally while the 15N RF amplitude is tangent. This modulation induces an effective spin-lock field in two selective frequency bands in either side of the 13C RF carrier frequency, allowing for simultaneous polarization transfers from 15N to 13C in those two selective frequency bands. It is shown by experiments and simulations that this sinusoidal modulation allows one to selectively polarize from 15N to its covalently bonded 13C? and 13C? carbons in neighboring peptide planes simultaneously, which is useful for establishing the back-bone connectivity between two sequential residues in protein structural elucidation. The selectivity and efficiency were experimentally demonstrated on a uniformly 13C,15N-labeled ?1 immunoglobulin binding domain of protein G (GB1).

Zhang, Zhengfeng; Miao, Yimin; Liu, Xiaoli; Yang, Jun; Li, Conggang; Deng, Feng; Fu, Riqiang

2012-01-01

313

Accurate measurement of one-bond H-X heteronuclear dipolar couplings in MAS solid-state NMR.  

PubMed

The accurate experimental determination of dipolar-coupling constants for one-bond heteronuclear dipolar couplings in solids is a key for the quantification of the amplitudes of motional processes. Averaging of the dipolar coupling reports on motions on time scales up to the inverse of the coupling constant, in our case tens of microseconds. Combining dipolar-coupling derived order parameters that characterize the amplitudes of the motion with relaxation data leads to a more precise characterization of the dynamical parameters and helps to disentangle the amplitudes and the time scales of the motional processes, which impact relaxation rates in a highly correlated way. Here. we describe and characterize an improved experimental protocol--based on REDOR--to measure these couplings in perdeuterated proteins with a reduced sensitivity to experimental missettings. Because such effects are presently the dominant source of systematic errors in experimental dipolar-coupling measurements, these compensated experiments should help to significantly improve the precision of such data. A detailed comparison with other commonly used pulse sequences (T-MREV, phase-inverted CP, R18(2)(5), and R18(1)(7)) is provided. PMID:21482161

Schanda, Paul; Meier, Beat H; Ernst, Matthias

2011-03-21

314

Dual-band selective double cross polarization for heteronuclear polarization transfer between dilute spins in solid-state MAS NMR  

NASA Astrophysics Data System (ADS)

A sinusoidal modulation scheme is described for selective heteronuclear polarization transfer between two dilute spins in double cross polarization magic-angle-spinning nuclear magnetic resonance spectroscopy. During the second N ? C cross polarization, the 13C RF amplitude is modulated sinusoidally while the 15N RF amplitude is tangent. This modulation induces an effective spin-lock field in two selective frequency bands in either side of the 13C RF carrier frequency, allowing for simultaneous polarization transfers from 15N to 13C in those two selective frequency bands. It is shown by experiments and simulations that this sinusoidal modulation allows one to selectively polarize from 15N to its covalently bonded 13C? and 13C' carbons in neighboring peptide planes simultaneously, which is useful for establishing the backbone connectivity between two sequential residues in protein structural elucidation. The selectivity and efficiency were experimentally demonstrated on a uniformly 13C,15N-labeled ?1 immunoglobulin binding domain of protein G (GB1).

Zhang, Zhengfeng; Miao, Yimin; Liu, Xiaoli; Yang, Jun; Li, Conggang; Deng, Feng; Fu, Riqiang

2012-04-01

315

NMR of TMV. Nuclear magnetic resonance of tobacco mosaic virus  

Microsoft Academic Search

This Thesis describes the application of conventional 13<\\/sup> C and 1<\\/sup> H high resolution Fourier Transform Nuclear Magnetic resonance (HR FT NMR) to Tobacco Mosaic Virus (TMV) and its protein oligo- and polymers and some other largebiological systems. The rod-like (TMV) consists of 2200 identical protein subunits protecting one RNA chain (molecular weight 42 x 10 6<\\/sup> ). The most

Wit de J. L

1978-01-01

316

Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The determination of a representative set of protein structures is a chief aim in structural genomics. Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems or membrane proteins. Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR. Almost complete 13C and 15N resonance assignments for a micro-crystalline preparation of the ?-spectrin Src-homology 3 (SH3) domain formed the basis for the extraction of a set of distance restraints. These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-13C]glycerol or [2-13C]glycerol as carbon sources. This allowed the observation of long-range distance correlations up to ~7Å. The calculated global fold of the ?-spectrin SH3 domain is based on 286 inter-residue 13C-13C and six 15N-15N restraints, all self-consistently obtained by solid-state MAS NMR. This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria.

Castellani, Federica; van Rossum, Barth; Diehl, Annette; Schubert, Mario; Rehbein, Kristina; Oschkinat, Hartmut

2002-11-01

317

Probing structure and dynamics of protein assemblies by magic angle spinning NMR spectroscopy.  

PubMed

In living organisms, biological molecules often organize into multicomponent complexes. Such assemblies consist of various proteins and carry out essential functions, ranging from cell division, transport, and energy transduction to catalysis, signaling, and viral infectivity. To understand the biological functions of these assemblies, in both healthy and disease states, researchers need to study their three-dimensional architecture and molecular dynamics. To date, the large size, the lack of inherent long-range order, and insolubility have made atomic resolution studies of many protein assemblies challenging or impractical using traditional structural biology methods such as X-ray diffraction and solution NMR spectroscopy. In the past 10 years, we have focused our work on the development and application of magic angle spinning solid-state NMR (MAS NMR) methods to characterize large protein assemblies at atomic-level resolution. In this Account, we discuss the rapid progress in the field of MAS NMR spectroscopy, citing work from our laboratory and others on methodological developments that have facilitated the in-depth analysis of biologically important protein assemblies. We emphasize techniques that yield enhanced sensitivity and resolution, such as fast MAS (spinning frequencies of 40 kHz and above) and nonuniform sampling protocols for data acquisition and processing. We also discuss the experiments for gaining distance restraints and for recoupling anisotropic tensorial interactions under fast MAS conditions. We give an overview of sample preparation approaches when working with protein assemblies. Following the overview of contemporary MAS NMR methods, we present case studies into the structure and dynamics of two classes of biological systems under investigation in our laboratory. We will first turn our attention to cytoskeletal microtubule motor proteins including mammalian dynactin and dynein light chain 8. We will then discuss protein assemblies from the HIV-1 retrovirus. PMID:23402263

Yan, Si; Suiter, Christopher L; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

2013-02-13

318

Study and characterization of crystalline hydrate\\/polymorph forms of 5,11-dihydro-11-ethyl-5-methyl-8-(2-(1-oxido-4-quinolinyl)ethyl-6H-dipyrido(3,2B:2?,3?-E)(1,4)diazepin-6-one by solid-state NMR and solution NMR  

Microsoft Academic Search

A novel inhibitor of reverse transcriptase was studied by solid-state NMR. Three phases of the compound were examined which included the dihydrate and two anhydrous polymorphs (Form I and Form III). By correlating 1H and 13C solution NMR with the solid-state 13C NMR CP\\/MAS and CPPI spectral editing experiments, comparative 13C assignments were made for each phase. Polymorphs of Form

N. C. Gonnella; John A. Smoliga; Scot Campbell; Carl A. Busacca; Michael Cerreta; Richard Varsolona; Daniel L. Norwood

2010-01-01

319

Common bean breeding for resistance against biotic and abiotic stresses: From classical to MAS breeding  

Microsoft Academic Search

Summary  Breeding for resistance to biotic and abiotic stresses of global importance in common bean is reviewed with emphasis on development\\u000a and application of marker-assisted selection (MAS). The implementation and adoption of MAS in breeding for disease resistance\\u000a is advanced compared to the implementation of MAS for insect and abiotic stress resistance. Highlighted examples of breeding\\u000a in common bean using molecular

Phillip N. Miklas; James D. Kelly; Steve E. Beebe; Matthew W. Blair

2006-01-01

320

MasABK proteins interact with proteins of the type IV pilin system to affect social motility of Myxococcus xanthus.  

PubMed

Gliding motility is critical for normal development of spore-filled fruiting bodies in the soil bacterium Myxococcus xanthus. Mutations in mgl block motility and development but one mgl allele can be suppressed by a mutation in masK, the last gene in an operon adjacent to the mgl operon. Deletion of the entire 5.5 kb masABK operon crippled gliding and fruiting body development and decreased sporulation. Expression of pilAGHI, which encodes type IV pili (TFP) components essential for social (S) gliding, several cryptic pil genes, and a LuxR family protein were reduced significantly in the ?mas mutant while expression of the myxalamide operon was increased significantly. Localization and two-hybrid analysis suggest that the three Mas proteins form a membrane complex. MasA-PhoA fusions confirmed that MasA is an integral cytoplasmic membrane protein with a ?100 amino acid periplasmic domain. Results from yeast two-hybrid assays showed that MasA interacts with the lipoprotein MasB and MasK, a protein kinase and that MasB and MasK interact with one another. Additionally, yeast two-hybrid analysis revealed a physical interaction between two gene products of the mas operon, MasA and MasB, and PilA. Deletion of mas may be accompanied by compensatory mutations since complementation of the ?mas social gliding and developmental defects required addition of both pilA and masABK. PMID:23342171

Fremgen, Sarah; Williams, Amanda; Furusawa, Gou; Dziewanowska, Katarzyna; Settles, Matthew; Hartzell, Patricia

2013-01-16

321

MasABK Proteins Interact with Proteins of the Type IV Pilin System to Affect Social Motility of Myxococcus xanthus  

PubMed Central

Gliding motility is critical for normal development of spore-filled fruiting bodies in the soil bacterium Myxococcus xanthus. Mutations in mgl block motility and development but one mgl allele can be suppressed by a mutation in masK, the last gene in an operon adjacent to the mgl operon. Deletion of the entire 5.5 kb masABK operon crippled gliding and fruiting body development and decreased sporulation. Expression of pilAGHI, which encodes type IV pili (TFP) components essential for social (S) gliding, several cryptic pil genes, and a LuxR family protein were reduced significantly in the ?mas mutant while expression of the myxalamide operon was increased significantly. Localization and two-hybrid analysis suggest that the three Mas proteins form a membrane complex. MasA-PhoA fusions confirmed that MasA is an integral cytoplasmic membrane protein with a ?100 amino acid periplasmic domain. Results from yeast two-hybrid assays showed that MasA interacts with the lipoprotein MasB and MasK, a protein kinase and that MasB and MasK interact with one another. Additionally, yeast two-hybrid analysis revealed a physical interaction between two gene products of the mas operon, MasA and MasB, and PilA. Deletion of mas may be accompanied by compensatory mutations since complementation of the ?mas social gliding and developmental defects required addition of both pilA and masABK.

Fremgen, Sarah; Williams, Amanda; Furusawa, Gou; Dziewanowska, Katarzyna; Settles, Matthew; Hartzell, Patricia

2013-01-01

322

Multinuclear (27Al, 29Si, 47,49Ti) solid-state NMR of titanium substituted zeolite USY.  

PubMed

Multinuclear solid-state NMR spectroscopy, employing 29Si MAS,27Al MAS/3Q-MAS and (47,49)Ti wide-line experiments, has been used for the structural characterization of titanium substituted ultra-stable zeolite Y (Ti-USY). 27Al MAS experiments show the presence of aluminum in four (Al(IV)), five (Al(V)), and six (Al(VI)) coordination, whereas the multiplicity within Al(IV) and Al(VI) is revealed by 27Al 3Q-MAS experiments. Two different tetrahedral and octahedral Al environments are resolved and their isotropic chemical shifts (delta(CS)) and second-order quadrupole interaction parameters (P(Q)) have been determined by a graphical analysis of the 3Q-MAS spectra. The emergence of signal with higher intensity at -101 ppm in the 29Si MAS spectrum of Ti-USY samples indicates the possible occurrence of Q4(3Si,1Ti) type silicon environments due to titanium substitution in the faujasite framework. High-field (11.74T) operation, using a probehead specially designed to handle a large sample volume, has enabled the acquisition of 47,49Ti static spectra and identification of the titanium environment in the zeolite. The chemical shielding and electric field gradient tensors for the titanium environment in the zeolite have been determined by a computer simulation of the quadrupolar broadened static 47,49Ti NMR spectra. PMID:12943913

Ganapathy, S; Gore, K U; Kumar, Rajiv; Amoureux, Jean-Paul

323

Selective Isotope Determination of Uranium using HR-RIMS  

SciTech Connect

The detection of lowest abundances of the ultra trace isotope {sup 236}U in environmental samples requires an efficient detection method which allows a high elemental and isotopic selectivity to suppress neighbouring isotopes of the same element and other background. High Resolution Laser Resonance Ionization Mass Spectrometry (HR-RIMS) uses the individual electron structure of each isotope to provide an outstanding element and isotope selective ionization.

Raeder, S.; Fies, S.; Wendt, K. D. A. [Institut fuer Physik, Johannes Gutenberg Universitaet Mainz, 55128 Mainz (Germany); Tomita, H. [Nagoya University (Japan)

2009-03-17

324

Spot activity in the RS CVn binary HR 1099  

Microsoft Academic Search

UBV photometry of HR 1099 obtained during the 1979-80 and 1980-81 observing seasons is presented. An analysis of the available\\u000a data shows that the brightness at the light curve maximum increases as the wave amplitude increases, while the brightness\\u000a at the light minimum remains almost the same. In terms of the starspot model it implies that there is always a

M. V. Mekkaden; A. V. Raveendran; S. Mohin

1982-01-01

325

The White Dwarf Companions of 56 Per and HR 3643  

Microsoft Academic Search

We have obtained low-dispersion IUE spectra of the stars 56 Persei (F4 V) and\\u000aHR 3643 (F7 II), as part of a survey of late-type stars with a 1565 A flux\\u000aexcess in the TD-1 ultraviolet sky survey. The IUE spectrum of each star\\u000areveals the presence of a hot white dwarf companion. We fit the Ly alpha\\u000aprofile and

Wayne Landsman; Theodore Simon; Pierre Bergeron

1995-01-01

326

NMR study of cell wall structure changes  

SciTech Connect

Xylans in hardwoods and grasses are extensively acetylated. This study attempts to isolate and quantify the effect that these acetyl esters have in the resistance of plant cell wall polysaccharides to cellulolytic enzymes. First, the in vitro deacetylation using mild aqueous hydroxylamine followed by characterization and enzyme digestion gives direct evidence that these acetyl groups play an important role in cell wall's resistance. /sup 13/C CP/MAS NMR proves to be an invaluable tool in the solid state characterization of biomass samples. Xylans from oat spelts were re-acetylated to various degrees. These acetylated xylans were then used as substates in enzymatic digestions. The results concur with the in vitro work.

Dale, B.E. (Texas A and M Univ., College Station, TX (USA)); Schroeder, H.A.; Mitchell, D.J. (C.S.U., Ft. Collins, CO (US)); Grohmann, K. (SERI, Golden, CO (US))

1988-01-01

327

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

328

A 13C solid-state NMR investigation of the alkynyl carbon chemical shift tensors for 2-butyne-1,4-diol.  

PubMed

The alkynyl carbon chemical shift (CS) tensors for 2-butyne-1,4-diol are reported, based on analyses of the carbon-13 NMR spectra of stationary-powder and slow magic-angle spinning (MAS) samples for which the alkynyl carbon nuclei are enriched in 13C. NMR spectra of slow MAS samples exhibit spinning-frequency-dependent fine structure typical of crystallographically equivalent but magnetically distinct nuclei. Simulated spectra of slow MAS samples of this two-spin system are particularly sensitive to the relative orientations of the CS tensors. In addition, the value of 1J(13C, 13C), +175 +/- 10 Hz, is determined by examination of the total NMR lineshape of slow MAS samples. The CS tensors are almost axially symmetric, delta11 = 158.9 +/- 1.0 ppm and delta22 = 155.7 +/- 1.0 ppm; the direction of greatest shielding is approximately along the alkynyl C-C bond, delta33 = -57.8 +/- 2.0 ppm. Both the magnitudes of the principal components of the CS tensors and their orientations are in agreement with those predicted from first-principles calculations at the HF and MP2 levels of theory. This study demonstrates the importance of examining the NMR spectra of homonuclear two-spin systems with and without MAS under a variety of conditions (e.g., two or more applied magnetic fields and slow MAS). PMID:11949820

Bernard, Guy M; Wasylishen, Roderick E

329

Characterization of quenched high pressure phases in CaSiO3 system by XRD and 29Si NMR  

Microsoft Academic Search

We have studied quenched high pressure phases in the CaSiO3 system by x-ray diffraction (XRD) and 29Si MAS NMR, XRD study of the previously reported “?-CaSiO3 phase” synthesized at 12 GPa and 1500 °C reveals that it is actually a mixture of ?-Ca2SiO4 (larnite) and a previously unknown CaSi2O5 phase. This result is supported by the 29Si NMR spectra. Furthermore,

Masami Kanzaki; Jonathan F. Stebbins; Xianyu Xue

1991-01-01

330

Mobility of lipid in complexes of amylose–fatty acids by deuterium and 13C solid state NMR  

Microsoft Academic Search

Palmitic and lauric acid complexes with amylose were studied by solid state methods: 13C CP\\/MAS NMR, deuterium NMR, X-ray powder diffraction and differential scanning calorimetry (DSC). The crystalline amylose complexes were found to be in a V-type sixfold single chain helix. The melting points of the complexes were over 100°C, at least 40–50°C higher than the melting points of the

P Lebail; A Buleon; D Shiftan; R. H Marchessault

2000-01-01

331

Characterisation of TiO2 pigments by 27Al NMR  

NASA Astrophysics Data System (ADS)

Titanium oxide pigments, coated with SiO2-Al2O3 system, prepared following four different synthesis ways, have been characterised by 27Al high resolution solid-state NMR. The spectra of these “model" pigments depend upon the synthesis path and the annealing temperature. MQ-MAS experiments are used to separate the different contributions, which overlap in the usual single pulse experiment MAS spectrum. From CPMAS and REDOR experiments, it is possible to describe further the different Al6 species evidenced by MQ-MAS. Des pigments modèles d'oxydes de titane, recouverts avec des composés du système SiO2-Al2O3, provenant de quatre types de synthèse, ont été analysés par RMN 27Al haute résolution. Les spectres de ces pigments diffèrent selon le mode de synthèse et la température de recuit. Des expériences MQ-MAS sont mises en œuvre pour séparer les différentes contributions qui se recouvrent dans un spectre obtenu par simple impulsion MAS. A partir d'expériences CP-MAS et REDOR, il est possible de décrire de façon plus détaillée les différentes espèces Al6 mises en évidence par les expériences MQ-MAS.

Magnenet, C.; Massiot, D.; Klur, I.; Coutures, J.-P.

1998-02-01

332

Progressive saturation NMR relaxation  

NASA Astrophysics Data System (ADS)

The NMR spin-lattice relaxation rate, T-11, can be measured precisely by progressive saturation. This efficient technique is useful when T1 is long and the NMR signal is weak. We derive the quasiequilibrium spin response to excitation in the case of a Zeeman spectrum in the presence of quadrupolar interactions. Exact solutions for the recovery of magnetization under the influence of purely magnetic fluctuations for I=12, 32, and 52 are presented. This is the general solution to a problem that has been previously solved only for the I=12 case. An important example for the application of this technique is 17O NMR in cuprate superconductors (I=52). We show comparisons of the theory with the relaxation measured for high-temperature superconducting materials and the NMR-rates measured by this technique across the vortex-broadened spectrum at low temperature.

Mitrovi?, V. F.; Sigmund, E. E.; Halperin, W. P.

2001-07-01

333

NMR assignment of brazilein  

Microsoft Academic Search

The 1H and 13C NMR signals of brazilein from Caesalpinia sappan were assigned by HMBC correlations and the physicochemical data investigated. © 1997 Published by Elsevier Science Ltd. All rights reserved

Seon Kim Dong; Baek Nam-In; Ryang Oh Sei; Young Jung Keun; Seon Lee Im; Lee Hyeong-Kyu

1997-01-01

334

Recruitment and selection services: Efficiency and competitive reasons in the outsourcing of HR practices  

Microsoft Academic Search

While human resource (HR) activities have traditionally been performed internally, the outsourcing of HR practices is a rapidly increasing phenomenon. The accelerated rate of HR outsourcing also corresponds to a sweeping change in which non-transactional activities, such as recruitment, selection and training, are among the most outsourced HR practices. This article investigates the outsourcing decisions of recruiting and selection (R&S).

Andrea Ordanini; Giacomo Silvestri

2008-01-01

335

Commitment-based HR practices, different types of innovation activities and firm innovation performance  

Microsoft Academic Search

Research on human resource (HR) practices and innovation has increased in the strategic HR management literature over the last decades. Scholars suggest that commitment-based HR practices contribute to innovation performance of the firm. However, prior research puts little emphasis on the causal linkages among commitment-based HR practices, different types of innovation activities and firm innovation performance. This article opens the

Canan Ceylan

2012-01-01

336

NMR study of chemical exchange in mesoporous material MCM-41  

NASA Astrophysics Data System (ADS)

In this work we will explore behaviour of water molecules inside pores of mesoporous material MCM-41 and their interactions to the surface hydration sites, using proton NMR techniques. In NMR MAS experiments involving hydrated porous media, it is generally observed that the water and surface OH proton resonances tend to coalesce with increasing moisture content. It has been suggested that chemical exchange between surface OH groups and water may not be the only mechanism producing the coalescence in the mesoporous material MCM-41. [Chem. Eur. J. 10 (2004) 5689] Here the importance of such exchange was investigated in MCM-41, hydrated to one water molecule per OH group, using both NMR time domain and MAS techniques. The results suggest that the surface - water chemical exchange rate is too small to produce substantive proton spectral coalescence in the MCM-41 material at low hydration level. In the next step a hopping model for water molecules on surface of porous material has been introduced and resulting average resonance position for different proton species in mesoporous material MCM-41 based on this model, has been compared to experimental data.

Niknam, Mohamad; Liang, Jianzhen; Peemoeller, Hartwig

2012-02-01

337

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

338

Biomolecular solid state NMR with magic-angle spinning at 25 K  

PubMed Central

A magic-angle spinning (MAS) probe has been constructed which allows the sample to be cooled with helium, while the MAS bearing and drive gases are nitrogen. The sample can be cooled to 25 K using roughly 3 liters/hour of liquid helium, while the 4 mm diameter rotor spins at 6.7 kHz with good stability (±5 Hz) for many hours. Proton decoupling fields up to at least 130 kHz can be applied. This helium-cooled MAS probe enables a variety of one-dimensional and two-dimensional NMR experiments on biomolecular solids and other materials at low temperatures, with signal-to-noise proportional to 1/T. We show examples of low-temperature 13C NMR data for two biomolecular samples, namely the peptide A?14–23 in the form of amyloid fibrils and the protein HP35 in frozen glycerol/water solution. Issues related to temperature calibration, spin-lattice relaxation at low temperatures, paramagnetic doping of frozen solutions, and 13C MAS NMR linewidths are discussed.

Thurber, Kent R.; Tycko, Robert

2009-01-01

339

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

340

A solid-state NMR study of condensation/retrograde reactions during coal liquefaction  

SciTech Connect

The objective of this work is to perform an NMR study of the aromaticity in coals, coal derived products and/or compounds generated by pyrolysis and thermal solubilization of coal in the presence of a hydrogen donor solvent. Cross Polarization with Magic-Angle Spinning (CP/MAS) will be used to measure the carbon aromaticity, and Combined Rotation and Multiple Pulse Spectroscopy (CRAMPS) NMR techniques will be used to measure the hydrogen aromaticity. From these NMR measurements the aromatic hydrogen-to- carbon ratio will be obtained and used to study condensation/retrograde reactions during coal liquefaction. The study consists of four tasks: (1)develop NMR methods to determine aromatic carbon by CP/MAS and aromatic hydrogen by CRAMPS for low hydrogen containing organic solids such as coals, and coal residues; (2) characterize the feasibility of applying the NMR method for quantitative measures in coals; (3) analyze selected samples of coals and coal-derived products to demonstrate applicability of the NMR methods to study coal liquefaction, and (4) report the results to the Department of Energy. 4 refs., 5 figs., 2 tabs.

Miknis, F.P.

1990-01-01

341

A solid-state NMR study of condensation/retrograde reactions during coal liquefaction  

SciTech Connect

The objective of this work is to perform an NMR study of the aromaticity in coals, coal derived products and/or model compounds generated by pyrolysis and thermal solubilization of coal in the presence of a hydrogen donor solvent. Cross Polarization with Magic-Angle Spinning (CP/MAS) will be used to measure the carbon aromaticity, and Combined Rotation and Multiple Pulse Spectroscopy (CRAMPS) NMR techniques will be used to measure the hydrogen aromaticity. From these NMR measurements the aromatic hydrogen-to- carbon ratio will be obtained and used to study condensation/retrograde reactions during coal liquefaction. The study consists of the following tasks: develop NMR methods to determine aromatic carbon by CP/MAS and aromatic hydrogen by CRAMPS for low hydrogen containing organic solids such as coals, and coal residues; characterize the feasibility of applying the NMR methods for quantitative measurements in coals; and analyze selected samples of coals and coal-derived products to demonstrate applicability of the NMR methods to study-coal liquefaction. 5 refs., 7 figs., 1 tab.

Miknis, F.P.

1989-01-01

342

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

343

Gramaticalização da conjunção mas: reflexões a partir do modelo de Sweetser (1991)  

Microsoft Academic Search

The model proposed by Sweetser (1991) to analyze the conjunction 'but' appears to be very efficient in the reading of the conjunction 'mas' in entries of the Medieval Portuguese. The model also provides a better comprehension concerning conceptual motivations that would have led the item into grammaticalization. This text will show that entries of 'mas', in Medieval Portuguese, fit into

Ana Paula Rocha

344

Isotropic diffusion weighting in PGSE NMR by magic-angle spinning of the q-vector  

NASA Astrophysics Data System (ADS)

When PGSE NMR is applied to water in microheterogeneous materials such as liquid crystals, foodstuffs, porous rocks, and biological tissues, the signal attenuation is often multi-exponential, indicating the presence of pores having a range of sizes or anisotropic domains having a spread of orientations. Here we modify the standard PGSE experiment by introducing low-amplitude harmonically modulated gradients, which effectively make the q-vector perform magic-angle spinning (MAS) about an axis fixed in the laboratory frame. With this new technique, denoted q-MAS PGSE, the signal attenuation depends on the isotropic average of the local diffusion tensor. The capability of q-MAS PGSE to distinguish between pore size and domain orientation dispersion is demonstrated by experiments on a yeast cell suspension and a polydomain anisotropic liquid crystal. In the latter case, the broad distribution of apparent diffusivities observed with PGSE is narrowed to its isotropic average with q-MAS PGSE in a manner that is analogous to the narrowing of chemical shift anisotropy powder patterns using magic-angle sample spinning in solid-state NMR. The new q-MAS PGSE technique could be useful for resolving size/orientation ambiguities in the interpretation of PGSE data from, e.g., water confined within the axons of human brain tissue.

Eriksson, Stefanie; Lasic, Samo; Topgaard, Daniel

2013-01-01

345

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

346

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

Solid-state [sup 13]C and [sup 29]Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS [sup 13]C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of [sup 29]Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The [sup 29]Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

Miknis, F.P.

1992-04-01

347

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

Solid-state {sup 13}C and {sup 29}Si NMR measurements were carried out on a series of petroleum source rocks from the Mowry Formation of the Powder River Basin in Wyoming. The objectives of this study wereto use CP/MAS {sup 13}C NMR measurements to monitor changes in the carbon structure of the kerogen that result from depth of burial, and to examine the feasibility of {sup 29}Si NMR for studying the thermal alteration of clay minerals during diagenesis. Carbon and silicon NMR measurements were made on a suite of samples covering a present-day depth interval of 3,000 to 11,500 ft.In general, the NMR results endorsed other geochemical analyses that were performed on the source rocks as part of another study to examine pressure compartmentalization in the Mowry Formation. The carbon aromaticity of the kerogen increased with depth of burial, and at depths greater that approximately 10,000 ft the kerogen showed little capacity to generate additional oil because of the small fraction of residual aliphatic carbon. By combining NMR and Rock-Eval measurements, an estimate of the hydrogen budget was obtained. The calculations indicated that approximately 20% of the kerogen was converted to hydrocarbons, and that sufficient hydrogen was liberated from aromatization and condensation reactions to stabilize the generated products. The {sup 29}Si NMR spectra were characterized by a relatively sharp quartz resonance and a broad resonance from the clay minerals. With increasing depth of burial, the clay resonance became broader and shifted slightly downfield. These changes qualitatively support X-ray analysis that shows progressive alteration of illite to smectite with depth of burial.

Miknis, F.P.

1992-04-01

348

Simultaneous PET and NMR.  

PubMed

There is currently great interest in combining data from different imaging modalities, either by image registration methods that are performed after the data has been acquired or using new devices that can acquire data from two modalities simultaneously, or near simultaneously. In this paper a small prototype NMR-compatible PET scanner capable of acquiring PET images simultaneously with either NMR images or NMR spectra is described. In an associated paper [1], Pamela Garlick describes some investigations of cardiac metabolism that have been made using this system. One of the main challenges in constructing an NMR-compatible PET scanner is that photomultiplier tubes, which are an essential element of nearly all current PET systems, will not function in a high magnetic field. In collaboration with Simon Cherry and the Crump Institute of Biomedical Imaging at UCLA Medical School, a small (5.4 cm diameter) NMR-compatible PET scanner that will operate within the bore of an NMR magnet has been developed. Long optical fibres are used to transport light from the scintillation crystals that form the detector head to photomultiplier tubes situated in a low magnetic field region several metres from the magnet. This system has been used to perform simultaneous PET and NMR spectroscopy measurements with a 9.4T spectroscopy system, and has also been used to obtain simultaneous PET and MR images in several MRI scanners including a 4.7T small bore animal imaging system. Current efforts in the development of this technology are directed at experimental studies on small animals, both because this is less demanding technically and because it is in this area that applications are likely to appear first. However, there is no reason in principle why human PET-MR would not be feasible. Below, work with the prototype system and the next stage in its development are described, and some of the future possibilities and challenges are discussed. PMID:12519736

Marsden, Paul K; Strul, Daniel; Keevil, Stephen F; Williams, Steven C R; Cash, Diana

2002-11-01

349

Mechanistic insight into formation and changes of nanoparticles in MgF2 sols evidenced by liquid and solid state NMR.  

PubMed

The fluorolytic sol-gel reaction of magnesium methoxide with HF in methanol was studied by (19)F, (1)H and (13)C liquid and solid state NMR. In (19)F NMR five different species were identified, three of which belong to magnesium fluoride nanoparticles, i.e. NMR gave access to local structures of solid particles in suspensions. The long-term evolution of (19)F signals was followed and along with (19)F MAS NMR experiments of sols rotating at 13 kHz mechanistic insights into the ageing processes were obtained. PMID:22214975

Karg, M; Scholz, G; König, R; Kemnitz, E

2012-01-03

350

Classification of ischaemic episodes with ST/HR diagrams.  

PubMed

Coronary artery disease is the developed world's premier cause of mortality and the most probable cause of myocardial ischaemia. More advanced diagnostic tests aside, in electrocardiogram (ECG) analysis it manifests itself as a ST segment deviation, targeted by both exercise ECG and ambulatory ECG. In ambulatory ECG, besides ischaemic ST segment deviation episodes there are also non-ischaemic heart rate related episodes which aggravate real ischaemia detection. We present methods to transform the features developed for the heart rate adjustment of ST segment depression in exercise ECG for use in ambulatory ECG. We use annotations provided by the Long-Term ST Database to plot the ST/HR diagrams and then estimate the overall and maximal slopes of the diagrams in the exercise and recovery phase for each ST segment deviation episode. We also estimate the angle at the extrema of the ST/HR diagrams. Statistical analysis shows that ischaemic ST segment deviation episodes have significantly steeper overall and maximal slopes than heart rate related episodes, which indicates the explored features' utility for distinguishing between the two types of episodes. This makes the proposed features very useful in automated ECG analysis. PMID:22874369

Faganeli Pucer, Jana; Demšar, Janez; Kukar, Matjaž

2012-01-01

351

Enhanced Neon in the Coronae of HR 1099  

NASA Astrophysics Data System (ADS)

Chandra HETG spectra of the tidally interacting RS CVn-type binary HR 1099 (V711 Tau) have been analysed in order to investigate the abundances of elements in the coronae of the system. Analogous to the results of previous studies based on EUVE and ASCA observations, the high resolution X-ray spectrum is characterised by a general paucity of metals relative to the solar photosphere, but perhaps simply reflects the underlying stellar photospheric metallicity. The most striking feature of the spectrum, however, is the very strong Ly-? feature in H-like Ne. The only plausible explanation for the strength of the Ne lines is that the abundance of Ne in the coronae of HR 1099 is strongly enhanced relative to that of Fe, as compared to the solar (photospheric) mixture. We discuss the implications of this result in the context of stellar coronae and coronal abundances anomalies, draw attention to possible solar coronal analogies to the phenomena, and suggest possible reasons for the Ne enhancement. JJD, NSB, VK, BW and RS were supported by Chandra X-ray Center NASA contract NAS8-39073.

Drake, J. J.; Brickhouse, N. S.; Kashyap, V.; Smith, R.; Wargelin, B.; Laming, J. M.; Huenemoerder, D. P.

2000-10-01

352

Images of a fourth planet orbiting HR 8799.  

PubMed

High-contrast near-infrared imaging of the nearby star HR 8799 has shown three giant planets. Such images were possible because of the wide orbits (>25?astronomical units, where 1?au is the Earth-Sun distance) and youth (<100?Myr) of the imaged planets, which are still hot and bright as they radiate away gravitational energy acquired during their formation. An important area of contention in the exoplanet community is whether outer planets (>10?au) more massive than Jupiter form by way of one-step gravitational instabilities or, rather, through a two-step process involving accretion of a core followed by accumulation of a massive outer envelope composed primarily of hydrogen and helium. Here we report the presence of a fourth planet, interior to and of about the same mass as the other three. The system, with this additional planet, represents a challenge for current planet formation models as none of them can explain the in situ formation of all four planets. With its four young giant planets and known cold/warm debris belts, the HR 8799 planetary system is a unique laboratory in which to study the formation and evolution of giant planets at wide (>10?au) separations. PMID:21150902

Marois, Christian; Zuckerman, B; Konopacky, Quinn M; Macintosh, Bruce; Barman, Travis

2010-12-08

353

Dynamical simulations of the HR8799 planetary system  

NASA Astrophysics Data System (ADS)

HR8799 is a young (20-160 Myr) A-dwarf main sequence star with a debris disc detected by IRAS (InfraRed Astronomical Satellite). In 2008, it was one of two stars around which exoplanets were directly imaged for the first time. The presence of three Jupiter-mass planets around HR8799 provoked much interest in modelling the dynamical stability of the system. Initial simulations indicated that the observed planetary architecture was unstable on timescales much shorter than the lifetime of the star (~105 yr). Subsequent models suggested that the system could be stable if the planets were locked in a 1:2:4 mutual mean motion resonance (MMR). In this work, we have examined the influence of varying orbital eccentricity and the semi-major axis on the stability of the three-planet system, through dynamical simulations using the MERCURY n-body integrator. We find that, in agreement with previous work on this system, the 1:2:4 MMR is the most stable planetary configuration, and that the system stability is dominated by the interaction between the inner pair of planets. In contrast to previous results, we find that with small eccentricities, the three-planet system can be stable for timescales comparable to the system lifetime and, potentially, much longer.

Marshall, J.; Horner, J.; Carter, A.

2010-10-01

354

Solid-state NMR evidence for elastin-like beta-turn structure in spider dragline silk.  

PubMed

Two-dimensional homo- and heteronuclear solid-state MAS NMR experiments on (13)C/(15)N-proline labeled Argiope aurantia dragline silk provide evidence for an elastin-like beta-turn structure for the repetitive Gly-Pro-Gly-X-X motif prevalent in major ampullate spidroin 2 (MaSp2). PMID:20733981

Jenkins, Janelle E; Creager, Melinda S; Butler, Emily B; Lewis, Randolph V; Yarger, Jeffery L; Holland, Gregory P

2010-08-23

355

Solid state (sup 31)P NMR study of phosphonate binding sites in guanidine-functionalized, molecular imprinted silica xerogels.  

National Technical Information Service (NTIS)

Phosphonate binding sites in guanidine and ammonium surface-functionalized silica xerogels were prepared via the molecular imprinting technique and characterized using solid state (sup 31)P MAS NMR. One-point, two-point, and non-specific host-guest intera...

D. Y. Sasaki T. D. Alam

2000-01-01

356

The cation-chloride cotransporter, masBSC, is widely expressed in Manduca sexta tissues.  

PubMed

Cation-chloride cotransporters, including the Na-K-Cl cotransporter, play an important role in epithelial ion transport in insects. We have determined the tissue distribution of Manduca sexta bumetanide sensitive cotransporter (masBSC), a putative Na-K-Cl cotransporter that was originally cloned from M. sexta Malpighian tubules. We developed a polyclonal antibody (M6) against a C-terminal fragment of masBSC. masBSC protein was detected by M6 at an apparent molecular mass of approximately 220kDa in M. sexta foregut, midgut, hindgut, Malpighian tubule, salivary gland, fat body, trachea, and nerve cord. Higher expression was observed in the foregut than in other tissues. M6 stained the apical membrane of midgut epithelial cells in cross-sections of third instar larvae. The transcript of masBSC was detected by RT-PCR in midgut, Malpighian tubule, hindgut, trachea, nerve cord, and fat bodies. Taken together, these findings demonstrate that masBSC is widely expressed in M. sexta. While the specific function of masBSC remains unknown, the wide distribution indicates a role of masBSC in a broad range of tissues. PMID:16730744

Gillen, Christopher M; Blair, Cheyne R; Heilman, Neal R; Somple, Margaret; Stulberg, Michael; Thombre, Rhadha; Watson, Nicole; Gillen, Kathy M; Itagaki, Haruhiko

2006-03-02

357

Characterization of the precursor for Manduca sexta diuretic hormone Mas-DH.  

PubMed Central

We have isolated a cDNA clone encoding a precursor form of the diuretic hormone from the tobacco hornworm Manduca sexta (Mas-DH). Translation of the cDNA revealed a 138-amino acid precursor consisting of the Mas-DH amino acid sequence bounded by dibasic amino acid processing sites, a putative signal sequence, and additional peptide sequence on either side of the Mas-DH coding sequence. The region of the precursor upstream of the mature Mas-DH sequence shows limited (28%) homology to the cryptic region of the ovine corticotropin-releasing factor precursor. The Mas-DH RNA is 1.5-1.6 kilobases long; it is present in both the heads and bodies of adult and larval insects. In prewandering fifth stadium larvae, Mas-DH mRNA is expressed in brain, nerve cord, gut, and Malpighian tubules, but not in the fat body. There is a single genomic copy of the Mas-DH gene; the message is multiply spliced. Images

Digan, M E; Roberts, D N; Enderlin, F E; Woodworth, A R; Kramer, S J

1992-01-01

358

Angiotensin metabolites can stimulate receptors of the Mas-related genes family.  

PubMed

The Mas protooncogene encodes a G protein-coupled receptor, we identified, also by using the specific angiotensin-(1-7) antagonist A-779, to be associated with intracellular signaling of the angiotensin (Ang) II metabolite Ang-(1-7). Recently, Mas-related genes (Mrg) have been identified coding for the Mrg-receptor family. All family members share high sequence homology to Mas. Most of them are orphan receptors. To proof whether structure similarities of the Mrg receptors with Mas turn them into potential receptors for Ang-(1-7) or other Ang metabolites, we transfected COS or HEK293 cells with an assortment of Mrg receptors and investigated arachidonic acid (AA) release and transcriptional activation by recording serum response factor (SRF) activation after stimulation with Ang II, Ang III, Ang IV, and Ang-(1-7). None of the investigated receptors activated transcription via SRF. Ang-(1-7) stimulated AA release already in control vector-transfected COS cells, indicating the existence of an endogenous receptor (A-779 sensitive). Though less pronounced than for Mas, two of the six studied receptors (MrgD, MRG) initiated significant AA release after stimulation with Ang-(1-7). Interestingly, Mas, MrgD, and MRG mediated Ang IV-stimulated AA release that was highest for Mas. While Ang III activated Mas and MrgX2, Ang II stimulated AA release via Mas and MRG. Thus, we identified other receptors of the Mrg family to respond on Ang-(1-7) stimulation. Furthermore, we describe first an AT(1)-independent direct Ang IV signaling and show that Ang II and Ang III mediate signaling independent of their specific receptors AT(1) and AT(2), whereby the receptor specificity differs. PMID:18636314

Gembardt, Florian; Grajewski, Sonja; Vahl, Martin; Schultheiss, Heinz-Peter; Walther, Thomas

2008-07-18

359

Propofol up-regulates Mas receptor expression in dorsal root ganglion neurons.  

PubMed

Mas is a functional binding site for angiotensin (Ang)-(1-7), a critical component of the renin-angiotensin system that is involved in processing nociceptive information. A recent study reported the localization of Mas in rat dorsal root ganglia (DRG) and demonstrated that Ang-(1-7) produced a dose-dependent peripheral antinociceptive effect in rats through the Mas receptor by an opioid-independent mechanism. In the present study, we for the first time examined the effect of propofol on Mas expression in cultured DRG neurons. We treated rat DRG neurons with propofol at different concentrations (0.1, 0.5, 1, 5 or 10 microM) for different length of time (0.5, 1, 2, 4 or 6 h) with or without transcription inhibitor actinomycin D or different kinase inhibitors. Propofol increased the Mas receptormRNA level in a statistically significant dose- and time-dependent manner within 4 h, which led to dose-dependent up-regulation of the Mas receptor protein level as well as Ang-(1-7) binding on the cell membrane. Actinomycin D (1 mg/ml) and p38 mitogen-activated protein kinase inhibitor PD169316 (25 microM) completely abolished the effect of propofol on Mas receptor expression in DRG neurons. In conclusion, we demonstrate that propofol markedly up-regulates Mas receptor expression at the transcription level in DRG neurons by a p38 MAPK-dependent mechanism. This study provides new insights into the mechanisms of action of propofol in peripheral antinociception, and suggests a new regulatory mechanism on the Ang-(1-7)/Mas axis in the peripheral nervous system. PMID:24020123

Cao, Lijun; Xun, Junmei; Jiang, Xinghua; Tan, Rong

2013-08-01

360

Multidimensional 1H 13C HETCOR and FSLG-HETCOR NMR study of sphingomyelin bilayers containing cholesterol in the gel and liquid crystalline states  

Microsoft Academic Search

13C cross polarization magic angle spinning (CP-MAS) and 1H MAS NMR spectra were collected on egg sphingomyelin (SM) bilayers containing cholesterol above and below the liquid crystalline phase transition temperature (Tm). Two-dimensional (2D) dipolar heteronuclear correlation (HETCOR) spectra were obtained on SM bilayers in the liquid crystalline (Lalpha) state for the first time and display improved resolution and chemical shift

Gregory P. Holland; Todd M. Alam

2006-01-01

361

Multidimensional 1H– 13C HETCOR and FSLG-HETCOR NMR study of sphingomyelin bilayers containing cholesterol in the gel and liquid crystalline states  

Microsoft Academic Search

13C cross polarization magic angle spinning (CP-MAS) and 1H MAS NMR spectra were collected on egg sphingomyelin (SM) bilayers containing cholesterol above and below the liquid crystalline phase transition temperature (Tm). Two-dimensional (2D) dipolar heteronuclear correlation (HETCOR) spectra were obtained on SM bilayers in the liquid crystalline (L?) state for the first time and display improved resolution and chemical shift

Gregory P. Holland; Todd M. Alam

2006-01-01

362

Angiotensin metabolites can stimulate receptors of the Mas-related genes family  

Microsoft Academic Search

The Mas protooncogene encodes a G protein-coupled receptor, we identified, also by using the specific angiotensin-(1-7) antagonist\\u000a A-779, to be associated with intracellular signaling of the angiotensin (Ang) II metabolite Ang-(1-7). Recently, Mas-related\\u000a genes (Mrg) have been identified coding for the Mrg-receptor family. All family members share high sequence homology to Mas.\\u000a Most of them are orphan receptors. To proof

Florian Gembardt; Sonja Grajewski; Martin Vahl; Heinz-Peter Schultheiss; Thomas Walther

2008-01-01

363

The Reality of Old Moving Groups after Hipparcos -- HR1614  

NASA Astrophysics Data System (ADS)

It was Olin Eggen who first introduced the concept of moving groups, most famous is maybe the Hyades. The basic idea is that stars form in clusters and thus with similar space motion, on top of which the random motions of single stars are added, resulting in a modest velocity dispersion. Through the orbital motion in the galactic potential the group will stretch out into a tube-like structure and finally dissolve. The stars will appear, if the Sun happens to be inside the tube, all over the sky but may be identified as a group through their common space velocities. Thus the moving groups may provide the essential, and so far largely un-utilized, link between cluster and field stars. A large stumbling block for the study of the reality of moving groups has been the lack of reliable parallaxes. This has now been largely overcome by the observations by the Hipparcos satellite (ESA, 1997). Using the new parallaxes and recent radial velocities we perform, for the first time, an unbiased search in the UV-plane for the moving group HR1614. Combining the velocity data with high-quality photometric metallicities we find a concentration of stars with super-solar metallicities centered roughly on the UV-velocities of the star HR1614. Supported by dynamical simulations of the evolution of this moving group in the UV-plane of the member stars we confirm its existence and derive a new age from our new, well-defined, sample of member stars. The stars will provide the basis for future investigations of the abundance profile of the moving group. If field stars originate in clusters then the abundance ratios for stars in moving group should be identical to those of field stars in the solar neighbourghood. If the moving groups are not the source of the field stars then it is most likely that their star formation rate was different and the abundance ratios will be different. This is testable, in particular for metal-rich moving groups, such as HR1614.

Feltzing, S.

364

New Precision Orbits of Bright Double-lined Spectroscopic Binaries. VIII. HR 1528, HR 6993, 2 Sagittae, and 18 Vulpeculae  

NASA Astrophysics Data System (ADS)

Improved orbital elements for four A-star double-lined spectroscopic binaries have been determined with numerous new radial velocities. Three of the four systems, HR 1528, 2 Sge, and 18 Vul, have moderately short orbital periods of 7.05, 7.39, and 9.31 days, respectively, and also have circular or nearly circular orbits. Only HR 6993 with a period of 14.68 days has a significantly eccentric orbit. The close visual companion of 2 Sge has been detected spectroscopically, and its velocity measured. The orbital dimensions (a 1 sin i and a 2 sin i) and minimum masses (m 1 sin3 i and m 2 sin3 i) of the short-period binary components all have accuracies of 0.5% or better. We determine basic properties of the individual stars and compare them with solar-abundance evolutionary tracks to estimate their masses. Half of the eight components may be synchronously or pseudosynchronously rotating.

Fekel, Francis C.; Tomkin, Jocelyn; Williamson, Michael H.

2013-11-01

365

(29)Si NMR in LC-NMR analysis of silicones.  

PubMed

It is demonstrated using a practical example that indirect detection of (29)Si NMR signals is sufficiently sensitive in LC-NMR stop-flow arrangement to analyze mixtures of siloxane polymers. New cryogenic probes with better signal-to-noise ratio will turn this version of LC-NMR into a routine method for analysis of siloxane polymers. PMID:16261506

Blechta, Vratislav; Sýkora, Jan; Hetflejs, Jirí; Sabata, Stanislav; Schraml, Jan

2006-01-01

366

Ultraviolet and radio flares from UX Arietis and HR 1099  

SciTech Connect

Simultaneous observations of the RS CVn systems UX Ari and HR 1099 with the IUE satellite and the VLA are presented. Flaring activity is observed at ultraviolet wavelengths with the IUE when none is detected at radio wavelengths with the VLA. Radio flares with no detectable ultraviolet activity have also been observed. Thus, flares in the two spectral regions are either uncorrelated or weakly correlated. The flaring emission probably originates in different regions at the two wavelengths. Radio flares from RS CVn stars may originate in sources that are larger than, or comparable to, a star in size. This is in sharp contrast to compact, coherent radio flares from dwarf M stars. The ultraviolet flares from RS CVn stars probably originate in sources that are smaller than a component star. 18 references.

Lang, K.R.; Willson, R.F.

1988-05-01

367

Direct imaging of multiple planets orbiting the star HR 8799  

SciTech Connect

Direct imaging of exoplanetary systems is a powerful technique that can reveal Jupiter-like planets in wide orbits, can enable detailed characterization of planetary atmospheres, and is a key step towards imaging Earth-like planets. Imaging detections are challenging due to the combined effect of small angular separation and large luminosity contrast between a planet and its host star. High-contrast observations with the Keck and Gemini telescopes have revealed three planets orbiting the star HR 8799, with projected separations of 24, 38, and 68 astronomical units. Multi-epoch data show counter-clockwise orbital motion for all three imaged planets. The low luminosity of the companions and the estimated age of the system imply planetary masses between 5 and 13 times that of Jupiter. This system resembles a scaled-up version of the outer portion of our Solar System.

Marois, C; Macintosh, B; Barman, T; Zuckerman, B; Song, I; Patience, J; Lafreniere, D; Doyon, R

2008-10-14

368

MASSES, RADII, AND CLOUD PROPERTIES OF THE HR 8799 PLANETS  

SciTech Connect

The near-infrared colors of the planets directly imaged around the A star HR 8799 are much redder than most field brown dwarfs of the same effective temperature. Previous theoretical studies of these objects have concluded that the atmospheres of planets b, c, and d are unusually cloudy or have unusual cloud properties. Some studies have also found that the inferred radii of some or all of the planets disagree with expectations of standard giant planet evolution models. Here, we compare the available data to the predictions of our own set of atmospheric and evolution models that have been extensively tested against observations of field L and T dwarfs, including the reddest L dwarfs. Unlike some previous studies, we require mutually consistent choices for effective temperature, gravity, cloud properties, and planetary radius. This procedure thus yields plausible values for the masses, effective temperatures, and cloud properties of all three planets. We find that the cloud properties of the HR 8799 planets are not unusual but rather follow previously recognized trends, including a gravity dependence on the temperature of the L to T spectral transition-some reasons for which we discuss. We find that the inferred mass of planet b is highly sensitive to whether or not we include the H- and the K-band spectrum in our analysis. Solutions for planets c and d are consistent with the generally accepted constraints on the age of the primary star and orbital dynamics. We also confirm that, like in L and T dwarfs and solar system giant planets, non-equilibrium chemistry driven by atmospheric mixing is also important for these objects. Given the preponderance of data suggesting that the L to T spectral type transition is gravity dependent, we present an exploratory evolution calculation that accounts for this effect. Finally we recompute the bolometric luminosity of all three planets.

Marley, Mark S. [NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States); Saumon, Didier [Los Alamos National Laboratory, Mail Stop F663, Los Alamos, NM 87545 (United States); Cushing, Michael [Department of Physics and Astronomy, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Ackerman, Andrew S. [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Freedman, Richard, E-mail: Mark.S.Marley@NASA.gov, E-mail: dsaumon@lanl.gov, E-mail: michael.cushing@utoledo.edu, E-mail: andrew.ackerman@nasa.gov, E-mail: jfortney@ucolick.org, E-mail: freedman@darkstar.arc.nasa.gov [SETI Institute and NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States)

2012-08-01

369

Nuclear Magnetic Resonance (NMR) Guidelines.  

National Technical Information Service (NTIS)

Nuclear Magnetic Resonance (NMR) is a medical diagnostic imaging technique that applies the atomic principles of magnetic spin to visualize and analyze disease states in bodily tissues. NMR differs from the radiological devices in that (a) it does not uti...

R. Halpern

1983-01-01

370

Combined 17O NMR and 11B-31P double resonance NMR studies of sodium borophosphate glasses.  

PubMed

17O enriched sodium borophosphate glasses were prepared from isotopically enriched NaPO3 and H3BO3. These glasses have been studied by 17O, 11B and 31P NMR including 17O and 11B multiple quantum magic angle sample spinning (MQMAS), 11B-31P heteronuclear correlation (HETCOR) NMR and 11B{31P} rotational echo double resonance (REDOR). For comparison, the crystalline borophosphates BPO4 and Na5B2P3O13 were included in the investigations. The latter compound shows three sharp 31P resonances at -0.2, -2 and -8 ppm and two BO4 sites that can only be resolved by MQMAS. The 17O NMR spectra were recorded using both the static echo method at medium magnetic field (9.4 T) as well as MAS and MQMAS methods at high field (17.6 T). In total, five oxygen sites were identified in these borophosphate glasses: P-O-P, Na...O-P, P-O-B, B-O-B, Na...O-B. However, these five sites are not present simultaneously in any of the glasses. The 17O MQMAS spectra prove that P-O-B links play a major role in borophosphate glasses. These results are confirmed by the complementary 11B MAS spectra that show the presence of asymmetric and symmetric trigonal groups BO3a and BO3s and two tetrahedral BO4 units. 11B{31P} REDOR NMR is used to give independent information to assign the 11B lines to structural units present in the glasses. These REDOR measurements reveal that B-O-P bonds are present for each borate unit, including the BO3 groups. Particularly, a structural proposal for the two different BO4 resonances is given in terms of a different number of bonded phosphate tetrahedra. The 31P MAS spectra are usually broad and not well resolved. It is shown by 11B-31P HETCOR NMR that a possible structural assignment of a 31P signal at about -20 ppm to Q2 units as in binary sodium phosphate glasses is wrong and that the phosphate tetrahedron belonging to this resonance must be connected to borate groups. PMID:15589727

Zeyer-Düsterer, Michaela; Montagne, Lionel; Palavit, Gérard; Jäger, Christian

2005-01-01

371

Modern NMR Spectroscopy.  

ERIC Educational Resources Information Center

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

Jelinski, Lynn W.

1984-01-01

372

NMR in rotating magnetic fields: Magic angle field spinning  

SciTech Connect

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

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

2004-09-10

373

A high-resolution 19F NMR spectroscopic study of barium fluorozirconate glasses and related crystals  

Microsoft Academic Search

Fluorozirconate glasses have attracted considerable attention not only for their transparency in the infrared, but also due to their high fluorine ion conductivities and extreme fragility in the viscosity–temperature relationship. We report on structural studies of binary BaF2–ZrF4 glasses with 58–78mol% ZrF4 using high-resolution magic-angle-spinning 19F NMR. High-speed 19F MAS NMR allows us to resolve at least three unique fluorine

Randall E. Youngman; Sabyasachi Sen

2005-01-01

374

Motion analysis of structures (MAS) for flexible multibody systems: planar motion of solids  

Microsoft Academic Search

In this paper, an approach named Motion Analysis of Structures (MAS) is introduced to analyze planar motion of solids. The\\u000a theoretical basis of MAS is constructed on vector mechanics instead of analytical mechanics. Four procedures are involved\\u000a to embody this approach. Namely, (a) discretization of structure, (b) discretization of particle path, (c) evaluation of deformations\\u000a and internal forces, and (d) time integration. The first

Tung-Yueh Wu; Jyh-Jone Lee; Edward C. Ting

2008-01-01

375

ACE2–angiotensin-(1–7)–Mas axis and oxidative stress in cardiovascular disease  

Microsoft Academic Search

The renin–angiotensin–aldosterone system (RAAS) is a pivotal regulator of physiological homeostasis and diseases of the cardiovascular system. Recently, new factors have been discovered, such as angiotensin-converting enzyme 2 (ACE2), angiotensin-(1–7) and Mas. This newly defined ACE2–angiotensin-(1–7)–Mas axis was shown to have a critical role in the vasculature and in the heart, exerting mainly protective effects. One important mechanism of the

Luiza A Rabelo; Natalia Alenina; Michael Bader

2011-01-01

376

Photoplethysmograph (PPG) derived heart rate (HR) acquisition using an Android smart phone  

Microsoft Academic Search

Smart phone OEM camera technology enables PPG measurement of HR. HR readings acquired by a Motorola Droid#8482; using a self-developed Android HR application were compared to HR readings acquired by an electrocardiograph (ECG) and Nonin 9560BT pulse oximeter during three 5 min. periods (rest, reading aloud, video game). Subjects were 14, 20--58 year olds. Across all conditions, and device pairings

Mathew Gregoski; Alexey Vertegel; Frank Treiber

2011-01-01

377

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

378

Comparing the Effects of Lovastatin and Cornus Mas Fruit on Fibrinogen Level in Hypercholesterolemic Rabbits  

PubMed Central

BACKGROUND Atherosclerosis, which is a result of gradual deposition of lipids in the lower part of blood vessel endothelium, is the leading cause of mortality and morbidity around the world. It has been proved that some inflammatory blood markers such as fibrinogen can predict the risk for cardiovascular disease conditions, not only in cardiovascular patients, but also in those who do not have any manifestations of the atherosclerotic development. In this study, the effect of cornus mas l. was evaluated on fibrinogen of hypercholesterolemic rabbits and it was also compared with lovastatin drug. METHODS In this study, 25 New Zealand adult male rabbits were randomly divided into five groups of five. They were treated for 60 days by 5 different diets, namely basic, high cholesterol, regular plus 1 g/kgBW cornus mas L. powder, high cholesterol plus 1 g/kgBW cornus mas L. powder, and high cholesterol plus 10 mg/kgBW lovastatin. At the beginning and at the end of this period, blood samples were collected from the rabbits and their serum fibrinogen levels were measured. RESULTS Cornus mas L. powder and lovastatin significantly decreased fibrinogen levels in comparison with high cholesterol group (P < 0.05). Furthermore cornus mas L. powder could reduce the fibrinogen level more than lovastatin (P < 0.05). CONCLUSION The results indicated that consumption of cornus mas L. might be beneficial in atherosclerotic patients due to its reducing effects on fibrinogen.

Asgary, Sedigheh; Rafieian-Kopaei, Mahmoud; Adelnia, Azadeh; Kazemi, Somayeh; Shamsi, Fatemeh

2010-01-01

379

Magic-angle-spinning NMR studies of acid sites in zeolite H-ZSM-5  

SciTech Connect

{sup 1}H, {sup 13}C, {sup 27}Al, and {sup 29}Si magic-angle-spinning (MAS) NMR was used to elucidate the nature of the catalytic activity of zeolite H-ZSM-5. {sup 1}H MAS NMR of sealed samples after mild hydrothermal dealumination shows that the enhanced activity for n-hexane cracking is not due to an enhanced Bronstead acidity. The concentrations of the various OH groups and aluminous species suggest that the reason for the enhanced catalytic activity is the interaction of the n-hexane molecule with a bridging hydroxyl group and with extra-framework aluminium species, which give rise to the enhanced activity, cannot be easily removed from their positions, and are therefore immobilized by the zeolitic framework.

Brunner, E.; Ernst, H.; Freude, D.; Froehlich, T.; Hunger, M.; Pfeifer, H. (Sektion Physik der Universitaet Leipzig (Germany))

1991-01-01

380

The rehydration of metakaolinite to kaolinite: Evidence from solid-state NMR and cognate techniques  

SciTech Connect

The authors have studied the process of rehydroxylation of metakaolinite to kaolinite by {sup 27}Al and {sup 29}Si MAS NMR in tandem with Fourier transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric analysis, specific surface area measurement, atomic absorption spectrophotometry, and electron microscopy. The efficiency of the process strongly depends on temperature. The reaction is initiated at the edges of metakaolinite particles and is followed by diffusion of the water into their bulk. Regions of the metakaolinite structure, which locally retain the symmetry of kaolinite, act as nuclei for the reconstitution of kaolinite particles. The latter grown perpendicular to the c{sup *} axis and their edges are parallel to those of metakaolinite, showing that rehydroxylation is a topotactic solid-state process. {sup 27}Al and {sup 29}Si MAS NMR reveal that metakaolinite is an ill-defined mixture of amorphous silica nd alumina, and can be transformed into kaolinite by a correct choice of experimental conditions.

Rocha, J.; Klinowski, J. (Univ. of Cambridge (England)); Adams, J.M. (ECC International Limited, Cornwall (England))

1990-12-01

381

Employee Returns: Linking HR Performance Indicators to Business Strategy. IES Report 365.  

ERIC Educational Resources Information Center

This document is a practical guide that demonstrates how human resource (HR) professionals can use performance measurement to link HR to organizational strategy and business objectives, and thereby raise the profile of HR within their organization. The following are among the topics examined: (1) the strategic context of measurement (the role…

Carter, Alison; Robinson, Dilys

382

HR fables: schizophrenia, selling your soul in dystopia, fuck the employees, and sleepless nights  

Microsoft Academic Search

Aesop's fables are used to gather HR fables and these fables are told mainly in the words of the protagonists of these moral stories, HR practitioners. Leaving the moral meaning of the fables for the reader to interpret so the reader can ethically connect with the morality of HR work, the personal narratives of practitioners and their humanity, the fables

Ian Steers

2008-01-01

383

The role of the HR department in organisational change in a British university  

Microsoft Academic Search

Purpose – The purpose of this paper is to analyse the role of human resources (HR) in organisational change at higher education institutions (HEIs) and the perceptions of those within the organisation towards the HR department and their capability in leading a change initiative. Design\\/methodology\\/approach – The objectives were achieved through a case study in which an HR department at

Charlotte Edgley-Pyshorn; Jeroen Huisman

2011-01-01

384

The role of cardiorespiratory fitness and weight status on 24-hr ambulatory blood pressure among adolescents  

Microsoft Academic Search

BACKGROUND: This observational research study investigated the association of cardiorespiratory fitness and weight status with repeated measures of 24-hr ambulatory blood pressure (24-hr ABP). Little is known about these associations and few data exist examining the interaction between cardiorespiratory fitness and weight status and the contributions of each on 24-hr ABP in youth. ^ METHODS: This research study used secondary

Devin C Volding

2012-01-01

385

Activation of angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis attenuates the cardiac reactivity to acute emotional stress.  

PubMed

Recent data indicate the brain angiotensin-converting enzyme/ANG II/AT1 receptor axis enhances emotional stress responses. In this study, we investigated whether its counterregulatory axis, the angiotensin-converting enzyme 2 (ACE2)/ANG-(1-7)/Mas axis, attenuate the cardiovascular responses to acute emotional stress. In conscious male Wistar rats, the tachycardia induced by acute stress (air jet 10 l/min) was attenuated by intravenous injection of ANG-(1-7) [? heart rate (HR): saline 136 ± 22 vs. ANG-(1-7) 61 ± 25 beats/min; P < 0.05]. Peripheral injection of the ACE2 activator compound, XNT, abolished the tachycardia induced by acute stress. We found a similar effect after intracerebroventricular injections of either ANG-(1-7) or XNT. Under urethane anesthesia, the tachycardia evoked by the beta-adrenergic agonist was markedly reduced by ANG-(1-7) [?HR: saline 100 ± 16 vs. ANG-(1-7) 18 ± 15 beats/min; P < 0.05]. The increase in renal sympathetic nerve activity (RSNA) evoked by isoproterenol was also abolished after the treatment with ANG-(1-7) [?RSNA: saline 39% vs. ANG-(1-7) -23%; P < 0.05]. The tachycardia evoked by disinhibition of dorsomedial hypothalamus neurons, a key nucleus for the cardiovascular response to emotional stress, was reduced by ?45% after intravenous injection of ANG-(1-7). In cardiomyocyte, the incubation with ANG-(1-7) (1 ?M) markedly attenuated the increases in beating rate induced by isoproterenol. Our data show that activation of the ACE2/ANG-(1-7)/Mas axis attenuates stress-induced tachycardia. This effect might be either via the central nervous system reducing anxiety level and/or interfering with the positive chronotropy mediated by activation of cardiac ? adrenergic receptors. Therefore, ANG-(1-7) might contribute to reduce the sympathetic load to the heart during situations of emotional stress, reducing the cardiovascular risk. PMID:23873801

Lima, Augusto Martins; Xavier, Carlos Henrique; Ferreira, Anderson José; Raizada, Mohan K; Wallukat, Gerd; Velloso, Elizabeth Portugal Pimenta; Santos, Robson Augusto Sousa Dos; Fontes, Marco Antônio Peliky

2013-07-19

386

Application of Solid-State Nuclear Magnetic Resonance (NMR) to the Study of Skin Hydration  

Microsoft Academic Search

The solid-state nuclear magnetic resonance (NMR) technique of carbon-13 cross-polarization\\/magic angle spinning (CP\\/MAS) has been successfully used to obtain high-resolution spectra of whole-thickness, hairy rat skin and to characterize the influence of hydration on the efficiency of cross-polarization and the proton spin-lattice relaxation time in the rotating frame (T1?H). Spectra obtained with hydrated samples, which were obtained with 50% more

Timothy Wiedmann

1988-01-01

387

An NMR study of the occupation of C(sub 60) interstitial sites by oxygen molecules  

Microsoft Academic Search

The C-13 NMR of FCC C(sub 60) under magic angle spinning (MAS) conditions yields linewidths on the order of 1 Hz at fields of 4.7 T. The spectrum consists of a primary resonance at 143.7 ppm and a minor peak shifted 0.7 ppm downfield. The intensity of the minor resonance relative to the primary resonance was found to vary from

R. A. Assink; D. A. Loy; J. E. Schirber; B. Morosin

1991-01-01

388

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

Microsoft Academic Search

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

Shao-Dong Wang; Karen L Scrivener

2003-01-01

389

Investigation of Polymorphism in Aspartame and Neotame Using Solid-State NMR Spectroscopy  

Microsoft Academic Search

We have been studying the artificial sweeteners aspartame (l-aspartyl-l-phenylalanine methyl ester) and neotame (N-(3,3-dimethylbutyl)-l-aspartyl-l-phenylalanine methyl ester) as compounds which exhibit polymorphism. 13C CP\\/MAS NMR shows that aspartame exists in three distinct forms at room temperature, depending on preparation conditions. For two of the forms, there exists three resonances for each carbon, indicating three crystallographically inequivalent sites and therefore three distinct

Mark T Zell; Brian E Padden; David J. W Grant; Stephen A Schroeder; Kurt L Wachholder; Indra Prakash; Eric J Munson

2000-01-01

390

Gender difference in the proportionality factor between the mass specific VO2max and the ratio between HR(max) and HR(rest).  

PubMed

The maximal rate of oxygen uptake uptake (VO2max) is an important determinant of cardiorespiratory fitness and aerobic performance. Estimation of VO2max from body mass (BM), maximal heart rate (HR (max)) and resting heart rate (HR(rest)) has recently been conducted in a group of well-trained men using the equation: dot VO2max = BM.PF.(HR(max)/HR(rest)), where PF denotes the proportionality factor between HR(max)/HR(rest) and the mass specific VO2max. Fick principle calculations show that PF is given as the product of the mass specific resting oxygen uptake (VO2rest) and the maximum-to-resting ratios for stroke volume and the arterio-venous O2 difference. Due to women's lower mass specific VO2rest, a gender PF difference was hypothesised. In the present study PF was examined in a sample of 27 trained female subjects, and compared with a similar study conducted in men. Significant gender difference was observed in PF, but there was no gender difference when lean BM replaced BM in the PF calculation. Accordingly, VO2max could be estimated indirectly by the following equation: dot VO2max = BM.PF.(HR(max)/HR(rest)), where PF is 14.5 ml.min(-1).kg(-1) for women and 15.3 ml.min(-1).kg(-1) for men. Cross validation showed that the SEE was 0.22 l/min (approximately 6.8 %). PMID:16237622

Uth, N

2005-11-01

391

Gene expression profile of the skin in the 'hairpoor' (HrHp) mice by microarray analysis  

PubMed Central

Background The transcriptional cofactor, Hairless (HR), acts as one of the key regulators of hair follicle cycling; the loss of function mutations is the cause of the expression of the hairless phenotype in humans and mice. Recently, we reported a new Hr mutant mouse called 'Hairpoor' (HrHp). These mutants harbor a gain of the function mutation, T403A, in the Hr gene. This confers the overexpression of HR and HrHp is an animal model of Marie Unna hereditary hypotrichosis in humans. In the present study, the expression profile of HrHp/HrHp skin was investigated using microarray analysis to identify genes whose expression was affected by the overexpression of HR. Results From 45,282 mouse probes, differential expressions in 43 (>2-fold), 306 (>1.5-fold), and 1861 genes (>1.2-fold) in skin from HrHp/HrHp mice were discovered and compared with skin from wild-type mice. Among the 1861 genes with a > 1.2-fold increase in expression, further analysis showed that the expression of eight genes known to have a close relationship with hair follicle development, ascertained by conducting real-time PCR on skin RNA produced during hair follicle morphogenesis (P0-P14), indicated that four genes, Wif1, Casp14, Krt71, and Sfrp1, showed a consistent expression pattern with respect to HR overexpression in vivo. Conclusion Wif1 and Casp14 were found to be upregulated, whereas Krt71 and Sfrp1 were downregulated in cells overexpressing HR in transient transfection experiments on keratinocytes, suggesting that HR may transcriptionally regulate these genes. Further studies are required to understand the mechanism of this regulation by the HR cofactor.

2010-01-01

392

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

NASA Astrophysics Data System (ADS)

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

Golombeck, Rebecca A.

393

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

Microsoft Academic Search

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

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

2001-01-01

394

Solid-state C NMR Study of Scleroglucan Polysaccharide. Effect of the Drying Process and Hydration on Scleroglucan Structure and Dynamics  

Microsoft Academic Search

High-resolution solid-state C CP\\/MAS NMR was used to study the evolution of a polysaccharide (scleroglucan) conformation from the anhydrous to the hydrated form. The influence of a thermo-mechanical treatment applied during the drying process of scleroglucan is analyzed both on the dried and rehydrated product. C NMR spectra, C relaxation times (T1C) and H relaxation times in the rotating frame

M. Jeannin; S. A. Rezzoug; Z. Maache-rezzoug; S. Cohendoz; K. Allaf

2001-01-01

395

Aquifer test plan for the 100-HR-3 Operable Unit  

SciTech Connect

This test plan directs hydrologic testing activities planned at three existing Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) wells in the 100-HR-3 Operable Unit of the Hanford Site. Three additional wells will be installed near these existing wells and used as additional testing arid observation points during the field activities. Figure 1 shows the locations of the three test sites. A primary objective of the testing program is to provide more detailed hydraulic characterization information for the unconfined aquifer and targeted test sites than provided by the initial reconnaissance-level slug testing of Vukelich. A second objective is to evaluate the applicability of slug interference and dipole flow tests for detailed hydraulic characterization in an unconfined aquifer. This aquifer testing program will also be useful for substantiating hydraulic conductivities reported from previous slug tests and evaluating the effects of filter pack volume/configuration on slug test data. Vukelich recommended additional testing to address the latter two issues.

Swanson, L.C.; Hartman, M.J.

1994-03-28

396

HR 1362 - A test case for stellar dynamo theories  

NASA Astrophysics Data System (ADS)

An analysis of 11 yr of photometry of HR 1362 = EK Eri has shown a well-established photometric period of 335 days. This confirms an earlier period determination of about 310 days from 3 yr of APT data and is consistent with a new v sin i determination of 2 + or - 2 km/s. Recent Ca II H and K observations show moderately strong H and K emission lines at a flux level of log F prime (K) of about 6.5 ergs sq m/s. If the photometric period is interpreted as the rotation period, this surface flux is more than one order of magnitude larger than what can be expected from empirical activity versus rotation relationships. The spectrum and the U-B and B-V colors are consistent with a single G8 III-IV spectral classification, while the V-R and V-I values indicate a small color excess, typical of chromospherically active stars.

Strassmeier, Klaus G.; Hall, Douglas S.; Barksdale, William S.; Jusick, Anthony T.; Henry, Gregory W.

1990-02-01

397

Carbon and Oxygen in the Spectrum of HR 8799c  

NASA Astrophysics Data System (ADS)

The field of exoplanet spectroscopy has grown tremendously in the last decade. With the discovery of gas giant planets at wide separations from their host stars via direct imaging, it is now possible to obtain exoplanet spectra with unprecedented spectral resolution. We present a medium resolution spectrum of the directly imaged exoplanet HR 8799c. This K band spectrum was obtained using the integral field spectrograph OSIRIS on the Keck II telescope. Our spectrum shows numerous, well-resolved molecular lines from water and carbon monoxide (CO). There is no clear evidence for methane absorption, in spite of a best fit temperature of ~1100 K. We find a best fit surface gravity log(g) ~ 4.0, consistent with the inferred young age for the system 30 Myr), and a continuum morphology consistent with previously-inferred dust clouds. Using the water and CO lines, we are able to estimate the C/O ratio for this planet. We find a ratio slightly higher than stellar 0.65), favoring a core-accretion process for its formation rather than gravitational instability.

Konopacky, Quinn M.; Barman, T. S.; Macintosh, B.; Marois, C.

2013-01-01

398

HR8752 evolving through the void (Nieuwenhuijzen+ 2012)  

NASA Astrophysics Data System (ADS)

The main paper on the hypergiant HR8752 evolving through the void combines observational data from various sources: new spectral data, new and already published (B-V), V data. it also describes a new three-dimensional chebychev interpolating code, and gives information on the temperature calibration for hypergiants, and adds some extra Tables on colour excess and historical context (cf. below). The electronic appendix contains a number of tables, too large for publishing in the paper. In the text and in the appendix, they are referred to as Table Axx, resp. Cxx. We note, however, that tables A1.1 to A1.6 in Section 2 of the main paper are here referred to as tables appena11 to appena16. The observational tables appena11 to appena16, appena2, appena3, appena4 all refer to Section 2 in the main paper, while tables appena5, appena6, appena7, appena8 are used in Section 3 of the main paper. The technical table appenc1 describes the three-dimensional chebychev interpolation method used in Section 2 of the main paper. The second technical table appenc2 describes the (hypergiant) temperature calibration and transformation codes between Mk, Teff, and (B-V) data, used in Section 3 of the main paper. Table appena9 discusses some measured colour excesses (Section 3.3 of the main paper). Table appena10 discusses the possibility of historical context (Section 5.11 of the main paper). (20 data files).

Nieuwenhuijzen, H.; de Jager, C.; Kolka, I.; Israelian, G.; Lobel, A.; Zsoldos, E.; Maeder, A.; Meynet, G.

2012-06-01

399

Human Pharmacology of Cefotaxime (HR 756), a New Cephalosporin  

PubMed Central

Cefotaxime (HR 756) is a new semisynthetic parenteral cephalosporin with exceptional activity against gram-negative organisms and considerable stability against their ?-lactamases. To study its pharmacokinetic properties, 0.5-, 1-, and 2-g doses were administered to each of six volunteers intravenously over 15 min, followed by a sustaining infusions of 0.5, 1, and 2 g/h, respectively, for 3 consecutive hours. The loading doses produced mean peak levels of 41, 93, and 160 ?g/ml, and mean steady-state serum concentrations were 27, 64, and 138 ?g/ml, respectively. The mean terminal half-life was 75 ± 7 min. The total volume of distribution averaged 0.22 ± 0.03 liters/kg of body weight. Total body and renal clearances were 232 ± 30 and 145 ± 24 ml/min per 1.73 m2, respectively; 63 ± 9% of the administered dose was excreted through the kidneys in 24 h. To determine the effect of cefotaxime on the renal tubules, urinary alanine aminopeptidase excretion was measured before, during, and after the infusions. It remained within the normal range in all instances; however, 48 ± 14% of the total daily alanine aminopeptidase output was recovered during the infusion period. Side effects were dose related and included fatigue, loose stools, and night sweats. No significant changes in hematology, serum chemistry, or urinalysis were recorded.

Luthy, Ruedi; Munch, Reiner; Blaser, Jurg; Bhend, Hansjorg; Siegenthaler, Walter

1979-01-01

400

Investigation of Li in Clay Interlayers at Different Temperatures by NMR  

NASA Astrophysics Data System (ADS)

We used 6Li and 7Li MAS NMR to investigate the environmental changes of Li in the interlayer of clay minerals at room and high (250°C) temperatures. We also checked the usefulness 6Li NMR in studying Li in interlayer. Hectorite, Wyoming-montmorillonite, beidellite, and lepidollite were used for our study. 6Li NMR spectra show narrower peaks than those of 7Li NMR, but S/N ratio is low and there are no noticeable chemical shift changes, which makes it difficult to apply 6Li NMR to get information on Li environment in clay interlayers. 7Li NMR spectra, however, show changes in the peak width and quadrupole pattern, providing information on the Li environment in the interlayer, even though the change in chemical shift is not observed. In montmorillonite, two different environments of Li are observed, one having narrow peak with typical quadrupole pattern, and another having broad peak without that pattern. At high temperature, the broad peak becomes relatively, narrow which was also obserbed in the 7Li NMR spectra obtained from beidellite, but not hectorite. This changes are attributed to the coordination changes in the water molecules around Li which is tightly bonded on the basal oxygen of Si tetrahedra as inner-sphere complexes. The narrow peak in montmorillnoite can be assigned to the Li bonded as outer-sphere complexes.

Kim, Y.; Lee, J.

2007-12-01

401

Mg/Al Ordering in Layered Double Hydroxides Revealed by Multinuclear NMR Spectroscopy  

SciTech Connect

The anion-exchange ability of layered double hydroxides (LDHs) has been exploited to create materials for use in catalysis, drug delivery, and environmental remediation. The specific cation arrangements in the hydroxide layers of hydrotalcite-like LDHs, of general formula Mg2+1–xAl3+xOH2(Anionn– x/n)·yH2O, have, however, remained elusive, and their elucidation could enhance the functional optimization of these materials. We applied rapid (60 kilohertz) magic angle spinning (MAS) to obtain high-resolution hydrogen-1 nuclear magnetic resonance (1H NMR) spectra and characterize the magnesium and aluminum distribution. These data, in combination with 1H-27Al double-resonance and 25Mg triple-quantum MAS NMR data, show that the cations are fully ordered for magnesium:aluminum ratios of 2:1 and that at lower aluminum content, a nonrandom distribution of cations persists, with no Al3+-Al3+ close contacts. The application of rapid MAS NMR methods to investigate proton distributions in a wide range of materials is readily envisaged.

Sideris, Paul J.; Nielsen, Ulla G.; Gan, Zhehong; Grey, Clare P.

2008-07-04

402

Human resource managers' role consistency and HR performance indicators: the moderating effect of interpersonal trust in Taiwan  

Microsoft Academic Search

This study explores the consistency between human resource (HR) managers' roles and HR performance indicators. In particular it considers the moderating effects of interpersonal trust on the relationship between HR managers' roles and HR performance indicators. We selected 116 HR managers from the top 500 manufacturing companies in Taiwan as our sample, and hierarchical regression analysis was conducted to test

Huo-Tsan Chang; Nai-Wen Chi

2007-01-01

403

Exploring the central characteristics of HR shared services: evidence from a critical case study in the Netherlands  

Microsoft Academic Search

Human resource shared service centers (HR SSCs) are foreseen as improving HR service delivery for their end-users: employees, line managers and decentralized HR professionals. Although the concept expects the benefits of HR SSCs to come from centralizing knowledge and decentralizing the control exercised over an HR SSC, research into these two fundamental shared service characteristics is scarce. The purpose of

Jeroen Meijerink; Tanya Bondarouk

2012-01-01

404

Deuterium Magic Angle Spinning NMR Used to Study the Dynamics of Peptides Adsorbed onto Polystyrene and Functionalized Polystyrene Surfaces  

PubMed Central

LK?14 is a 14 amino acid peptide with a periodic sequence of leucine and lysine residues consistent with an amphipathic ?-helix. This “hydrophobic periodicity” has been found to result in an ?-helical secondary structure at air-water interfaces and on both polar and non-polar solid polymer surfaces. In this paper the dynamics of LK?14 peptides, selectively deuterated at a single leucine and adsorbed onto polystyrene and carboxylated polystyrene beads, are studied using 2H Magic Angle Spinning (MAS) solid state NMR over a 100 degree temperature range. We first demonstrate the sensitivity enhancement possible with 2H MAS techniques, which in turn enables us to obtain high quality 2H NMR spectra for selectively deuterated peptides adsorbed onto solid polymer surfaces. An extensive literature shows that the dynamics of leucine side chains are sensitive to the local structural environment of the protein. Therefore the degree to which the dynamics of leucine side chains and the backbone of the peptide LK?14 are influenced by surface proximity and surface chemistry is studied as a function of temperature with 2H MAS NMR. It is found that the dynamics of the leucine side chains in LK?14 depend strongly upon the orientation of the polymer on the surface, which in turn depends on whether the LK?14 peptide adsorbs onto a polar or non-polar surface. 2H MAS line shapes therefore permit probes of surface orientation over a wide temperature range.

Breen, Nicholas F.; Li, Kun; Olsen, Gregory L.; Drobny, Gary P.

2011-01-01

405

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

406

2D NMR Metabonomic Analysis  

PubMed Central

Motivation Comparative metabolic profiling by nuclear magnetic resonance (NMR) is showing increasing promise for identifying inter-individual differences to drug response. Two dimensional (2D) 1H-13C NMR can reduce spectral overlap, a common problem of 1D 1H NMR. However, the peak alignment tools for 1D NMR spectra are not well suited for 2D NMR. An automated and statistically robust method for aligning 2D NMR peaks is required to enable comparative metabonomic analysis using 2D NMR. Results A novel statistical method was developed to align NMR peaks that represent the same chemical groups across multiple 2D NMR spectra. The degree of local pattern match among peaks in different spectra is assessed using a similarity measure, and a heuristic algorithm maximizes the similarity measure for peaks across the whole spectrum. This peak alignment method was used to align peaks in 2D NMR spectra of endogenous metabolites in liver extracts obtained from four inbred mouse strains in the study of acetaminophen-induced liver toxicity. This automated alignment method was validated by manual examination of the top fifty peaks as ranked by signal intensity. Manual inspection of 1872 peaks in 39 different spectra demonstrated that the automated algorithm correctly aligned 1810 (96.7%) peaks. Availability Algorithm is available upon request. Contact guochun.liao@roche.com

Zheng, Ming; Lu, Peng; Liu, Yanzhou; Pease, Joseph; Usuka, Jonathan; Liao, Guochun; Peltz, Gary

2007-01-01

407

Welding metallurgy of Alloy HR-160{reg{underscore}sign}  

SciTech Connect

The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in Alloy HR-160{reg{underscore}sign} was investigated by Varestraint testing, differential thermal analysis and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1,387 C and initiated solidification by a primary L {r{underscore}arrow}{gamma} reaction in which Ni, Si and Ti segregated to the interdendritic liquid and cosegregated to the {gamma} dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at {approximately} 1,162 C by a eutectic-type L{r{underscore}arrow}[{gamma}+(Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7}] reaction. The (Ni,Co){sub 16}(Ti,CR){sub 6}Si{sub 7} phase is found to be analogous to the G phase that forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [{gamma}+(Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7}] eutectic-type constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 C and the presence of 2--5 vol-% solute-rich interdendritic liquid that preferentially wets the grain boundaries and interdendritic regions.

DuPont, J.N.; Michael, J.R.; Newbury, B.D.

1999-12-01

408

Bidimensional spectroscopy of HR Del shell with GMOS-IFU  

NASA Astrophysics Data System (ADS)

The slow and bright classical nova HR Del 1967 was observed in the optical using GEMINI-NORTH GMOS-IFU in 2002 with a spectral range from 0.4 ?m to 1 ?m, a resolution of ˜ 300 km/s, and spatial resolution of ˜ 0''.5. Line intensity maps were obtained for H? +[NII], [OIII] 5007, H? and helium lines. The shell showed a bipolar and clumped structure resembling the shell observed in 1998 (Harman and O'Brien 2003). The [OIII] 5007 map showed seven bright knots. Models of the central source, shell and knots spectra were performed using CLOUDY 94 (Ferland et al. 1998) and RA3D (Diaz 2001). Central source spectra were best fitted with a T_{eff} = 60000 K, log(g) = 6 and log(L_*) = 36.6 Rauch atmosphere model. Shell H-density law was modeled using a power law with ? parameter -1.2 and mass = 4.1 × 10^{-4} M_?. The knots spectra were fitted as gaussian condensations with ˜ 50000cm^{-3} peak H-density and ˜ 20000cm^{-3} average H-density. HeII 4686 emission was found in the knots. The HeII origin is atributted to projected emission from diffuse matter in front of the knots, hypothesis corroborated by about the same HeII intensity observed outside the knots. Physical parameters of the condensations were obtained from our analysis and helium abundances were recalculated. A peak density contrast N/N_S = 270 was found when compared to the medium outside the knots. Electron temperatures ˜ 9500 K, electron densities ˜ 20000cm^{-3} and helium number abundance ˜ 0.2 were derived. Our results showed a constant helium abundance within a narrow radius range which is consistent with impulsive ejection (Kato and Hachisu 1994).

Augusto, A.; Diaz, M.

2006-06-01

409

NIR Imaging of the HR4796A Circumstellar Disk  

NASA Astrophysics Data System (ADS)

We report the first near infrared imaging of a circumstellar annular disk around the young (~ 10Myr) star HR4796A. Observations obtained on 15 March and 16 August, 1998, using the HST/NICMOS coronagraph, reveal a ring-like symmetrical structure seen at 1.1 and 1.6 microns peaking in reflected intensity ~70AU (1.1") from the central A0V star. The annulus, with a characteristic width of ~15AU (0.2"), is abruptly truncated at both the inner and outer edges. The interior region of the disk-plane appears to be optically thin, and may be relatively free of scattering material. These observations, which place the major axis of the ring at a PA of ~28 degrees, inclined ~75 degrees, are in good agreement with the nearly contemporaneous (16 March) thermal infrared detection of an inner truncated disk seen in emission as reported by Koerner, et. al (1998, ApJ, 503, L83) and Jayawardhana, et. al. (1998, ApJ, 503, L79). The confinement of material to this relatively narrow zone implies dynamical constraints on the disk particles by one or more yet unseen orbiting bodies. We report these results as part of the NICMOS IDT Environments of Nearby Stars program. This work is supported by NASA grant NAG 5-3042. This paper is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555.

Smith, B. A.; Schneider, G.; Becklin, E. E.; Koerner, D. W.; Meier, R.; Terrile, R. J.; Hines, D. C.; Lowrance, P. J.; Thompson, R. I.

1998-12-01

410

Soils, Pores, and NMR  

NASA Astrophysics Data System (ADS)

Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 < 5 ms. Moreover, the dependence of the relaxation rate on magnetic field strength allows the identification of 2D diffusion at the interfaces as the mechanism which governs the relaxation process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about the connectivity of the pore system. Examples are given for T1-T2 correlation of some soil samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a Natural soil: Comparison of Relaxometric Imaging, T1 - T2 Correlation and Fast-Field Cycling NMR." The Open Magnetic Resonance Journal: in print. Pohlmeier, A., S. Haber-Pohlmeier, et al. (2009). "A Fast Field Cycling NMR Relaxometry Study of Natural Soils." Vadose Zone J. 8: 735-742. Stingaciu, L. R., A. Pohlmeier, et al. (2009). "Characterization of unsaturated porous media by high-field and low-field NMR relaxometry." Water Resources Research 45: W08412

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

2010-05-01

411

Technology Enhanced Learning for People with Intellectual Disabilities and Cerebral Paralysis: The MAS Platform  

NASA Astrophysics Data System (ADS)

Education for students with disabilities now takes place in a wide range of settings, thus, including a wider range of assistive tools. As a result of this, one of the most interesting application domains of technology enhanced learning is related to the adoption of learning technologies and designs for people with disabilities. Following this unstoppable trend, this paper presents MAS, a software platform aimed to help people with severe intellectual disabilities and cerebral paralysis in their learning processes. MAS, as a technology enhanced learning platform, provides several tools that supports learning and monitoring for people with special needs, including adaptative games, data processing and monitoring tools. Installed in a special needs education institution in Madrid, Spain, MAS provides special educators with a tool that improved students education processes.

Colomo-Palacios, Ricardo; Paniagua-Martín, Fernando; García-Crespo, Ángel; Ruiz-Mezcua, Belén

412

ACE2, angiotensin-(1–7), and Mas: the other side of the coin.  

PubMed

The renin–angiotensin system (RAS) has recently been extended by the addition of a novel axis consisting of the angiotensin-converting enzyme 2 (ACE2), the heptapeptide angiotensin (1–7) (Ang-(1–7)), and the G protein-coupled receptor Mas. ACE2 converts the vasoconstrictive and pro-oxidative peptide angiotensin II (Ang II) into Ang-(1–7) which exerts vasodilatory and antioxidative effects via its receptor Mas. Thereby, ACE2 regulates the local actions of the RAS in cardiovascular tissues and the ACE2/Ang-(1–7)/Mas axis exerts protective actions in hypertension, diabetes, and other cardiovascular disorders. Consequently, this novel RAS axis represents a promising therapeutic target for cardiovascular and metabolic diseases. PMID:23463883

Bader, Michael

2013-01-01

413

NMR in biology and medicine  

SciTech Connect

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

Chien, S.; Chien, H.

1986-01-01

414

Daphnia HR96 is a Promiscuous Xenobiotic and Endobiotic Nuclear Receptor  

PubMed Central

Daphnia pulex is the first crustacean to have its genome sequenced. The genome project provides new insight and data into how an aquatic crustacean may respond to environmental stressors, including toxicants. We cloned Daphnia pulex HR96 (DappuHR96), a nuclear receptor orthologous to the CAR/PXR/VDR group of nuclear receptors. In Drosophila melanogaster, (hormone receptor 96) HR96 responds to phenobarbital exposure and has been hypothesized as a toxicant receptor. Therefore, we set up a transactivation assay to test whether DappuHR96 is a promiscuous receptor activated by xenobiotics and endobiotics similar to the constitutive androstane receptor (CAR) and the pregnane X-receptor (PXR). Transactivation assays performed with a GAL4-HR96 chimera demonstrate that HR96 is a promiscuous toxicant receptor activated by a diverse set of chemicals such as pesticides, hormones, and fatty acids. Several environmental toxicants activate HR96 including estradiol, pyriproxyfen, chlorpyrifos, atrazine, and methane arsonate. We also observed repression of HR96 activity by chemicals such as triclosan, androstanol, and fluoxetine. Nearly 50% of the chemicals tested activated or inhibited HR96. Interestingly, unsaturated fatty acids were common activators or inhibitors of HR96 activity, indicating a link between diet and toxicant response. The omega-6 and omega-9 unsaturated fatty acids linoleic and oleic acid activated HR96, but the omega-3 unsaturated fatty acids alpha-linolenic acid and docosahexaenoic acid inhibited HR96, suggesting that these two distinct sets of lipids perform opposing roles in Daphnia physiology. This also provides a putative mechanism by which the ratio of dietary unsaturated fats may affect the ability of an organism to respond to a toxic insult. In summary, HR96 is a promiscuous nuclear receptor activated by numerous endo- and xenobiotics.

Karimullina, Elina; Li, Yangchun; Ginjupalli, Gautam; Baldwin, William S.

2012-01-01

415

Rheo NMR and shear banding  

Microsoft Academic Search

The phenomenon of shear banding in complex fluids has been investigated using NMR velocimetry and NMR spectroscopy, mostly\\u000a in wormlike micelle systems, but more recently in colloidal systems and multilayer vesicles. A particular advantage of NMR\\u000a is the ability to simultaneously investigate structural ordering and to compare such ordering with local strain rates. In\\u000a this paper, we describe the basics

Paul T. Callaghan

2008-01-01

416

14N overtone NMR spectra under magic angle spinning: experiments and numerically exact simulations.  

PubMed

It was recently shown that high resolution (14)N overtone NMR spectra can be obtained directly under magic angle spinning (MAS) conditions [L. A. O'Dell and C. I. Ratcliffe, Chem. Phys. Lett. 514, 168 (2011)]. Preliminary experimental results showed narrowed powder pattern widths, a frequency shift that is dependent on the MAS rate, and an apparent absence of spinning sidebands, observations which appeared to be inconsistent with previous theoretical treatments. Herein, we reproduce these effects using numerically exact simulations that take into account the full nuclear spin Hamiltonian. Under sample spinning, the (14)N overtone signal is split into five (0, ±1, ±2) overtone sidebands separated by the spinning frequency. For a powder sample spinning at the magic angle, the +2?(r) sideband is dominant while the others show significantly lower signal intensities. The resultant MAS powder patterns show characteristic quadrupolar lineshapes from which the (14)N quadrupolar parameters and isotropic chemical shift can be determined. Spinning the sample at other angles is shown to alter both the shapes and relative intensities of the five overtone sidebands, with MAS providing the benefit of averaging dipolar couplings and shielding anisotropy. To demonstrate the advantages of this experimental approach, we present the (14)N overtone MAS spectrum obtained from L-histidine, in which powder patterns from all three nitrogen sites are clearly resolved. PMID:23425463

O'Dell, Luke A; Brinkmann, Andreas

2013-02-14

417

14N overtone NMR spectra under magic angle spinning: Experiments and numerically exact simulations  

NASA Astrophysics Data System (ADS)

It was recently shown that high resolution 14N overtone NMR spectra can be obtained directly under magic angle spinning (MAS) conditions [L. A. O'Dell and C. I. Ratcliffe, Chem. Phys. Lett. 514, 168 (2011)]. Preliminary experimental results showed narrowed powder pattern widths, a frequency shift that is dependent on the MAS rate, and an apparent absence of spinning sidebands, observations which appeared to be inconsistent with previous theoretical treatments. Herein, we reproduce these effects using numerically exact simulations that take into account the full nuclear spin Hamiltonian. Under sample spinning, the 14N overtone signal is split into five (0, +/-1, +/-2) overtone sidebands separated by the spinning frequency. For a powder sample spinning at the magic angle, the +2?r sideband is dominant while the others show significantly lower signal intensities. The resultant MAS powder patterns show characteristic quadrupolar lineshapes from which the 14N quadrupolar parameters and isotropic chemical shift can be determined. Spinning the sample at other angles is shown to alter both the shapes and relative intensities of the five overtone sidebands, with MAS providing the benefit of averaging dipolar couplings and shielding anisotropy. To demonstrate the advantages of this experimental approach, we present the 14N overtone MAS spectrum obtained from L-histidine, in which powder patterns from all three nitrogen sites are clearly resolved.

O'Dell, Luke A.; Brinkmann, Andreas

2013-02-01

418

Quantitative solid state NMR analysis of residues from acid hydrolysis of loblolly pine wood.  

PubMed

The composition of solid residues from hydrolysis reactions of loblolly pine wood with dilute mineral acids is analyzed by (13)C Cross Polarization Magic Angle Spinning (CP MAS) NMR spectroscopy. Using this method, the carbohydrate and lignin fractions are quantified in less than 3h as compared to over a day using wet chemical methods. In addition to the quantitative information, (13)C CP MAS NMR spectroscopy provides information on the formation of additional extractives and pseudo lignin from the carbohydrates. Being a non-destructive technique, NMR spectroscopy provides unambiguous evidence of the presence of side reactions and products, which is a clear advantage over the wet chemical analytical methods. Quantitative results from NMR spectroscopy and proximate analysis are compared for the residues from hydrolysis of loblolly pine wood under 13 different conditions; samples were treated either at 150 degrees C or 200 degrees C in the presence of various acids (HCl, H(2)SO(4), H(3)PO(4), HNO(3) and TFA) or water. The lignin content determined by both methods differed on averaged by 2.9 wt% resulting in a standard deviation of 3.5 wt%. It is shown that solid degradation products are formed from saccharide precursors under harsh reaction conditions. These degradation reactions limit the total possible yield of monosaccharides from any subsequent reaction. PMID:19477123

Sievers, Carsten; Marzialetti, Teresita; Hoskins, Travis J C; Valenzuela Olarte, Mariefel B; Agrawal, Pradeep K; Jones, Christopher W

2009-05-23

419

Quantifying the fraction of glycine and alanine in beta-sheet and helical conformations in spider dragline silk using solid-state NMR.  

PubMed

Solid-state two-dimensional refocused INADEQUATE MAS NMR experiments resolve distinct helical and beta-sheet conformational environments for both alanine and glycine in Nephila clavipes dragline silk fibers; the fraction of alanine and glycine in beta-sheet structures is determined to be 82% +/- 4% and 28% +/- 5%, respectively. PMID:18997954

Holland, Gregory P; Jenkins, Janelle E; Creager, Melinda S; Lewis, Randolph V; Yarger, Jeffery L

2008-09-29

420

Flagellin from Pseudomonas syringae pv. tabaci induced hrp -independent HR in tomato  

Microsoft Academic Search

We have previously shown that flagellin of Pseudomonas syringae pv. tabaci is an elicitor that induces a hypersensitive reaction (HR) in nonhost tomato cells. Flagellin is the major HR elicitor produced by this pathogen, as shown by the inability of a flagellin-defective mutant, ?fliC, to induce HR. Also, a ?fliD mutant that secretes large amounts of monomer flagellins induces a

Mizuri Marutani; Fumiko Taguchi; Rena Shimizu; Yoshishige Inagaki; Kazuhiro Toyoda; Tomonori Shiraishi; Yuki Ichinose

2005-01-01