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1

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

PubMed

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

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

2013-12-01

2

Application of HR-MAS NMR spectroscopy for studying chemotype variations of Withania somnifera (L.) Dunal.  

PubMed

Withania somnifera (L.) Dunal (Solanaceae), commonly known as Ashwagandha, is one of the most valued Indian medicinal plants with a number of pharmaceutical and nutraceutical applications. Metabolic profiling has been performed by HR-MAS NMR spectroscopy on fresh leaf and root tissue specimens from four chemotypes of W. somnifera. The HR-MAS NMR spectroscopy of lyophilized defatted leaf tissue specimens clearly distinguishes resonances of medicinally important secondary metabolites (withaferin A and withanone) and its distinctive quantitative variability among the chemotypes. A total of 41 metabolites were identified from both the leaf and root tissues of the chemotypes. The presence of methanol in leaf and root tissues of W. somnifera was detected by HR-MAS NMR spectroscopy. Multivariate principal component analysis (PCA) on HR-MAS (1) H NMR spectra of leaves revealed clear variations in primary metabolites among the chemotypes. The results of the present study demonstrated an efficient method, which can be utilized for metabolite profiling of primary and secondary metabolites in medicinally important plants. PMID:21915899

Bharti, S K; Bhatia, Anil; Tewari, S K; Sidhu, O P; Roy, Raja

2011-10-01

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.  

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; ?ojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

2013-01-01

5

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

PubMed Central

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

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

2011-01-01

6

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

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

7

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

PubMed Central

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

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

2014-01-01

8

Quantitative assessment of preloaded 4-alkoxybenzyl alcohol resins for solid-phase peptide syntheses by 1D and 2D HR-MAS NMR.  

PubMed

The quality of preloaded Wang resins is very important for the success of solid-phase peptide syntheses (SPPS). A critical factor is the capping of remaining hydroxyl groups after loading with the first amino acid, since these free alcohols lead to truncated sequences during the following SPPS steps. Because the detection of hydroxyl groups by color tests is difficult and unreliable, the capping efficiency is often controlled by time-consuming peptide test syntheses. Here, we describe a two-dimensional, high resolution magic angle spinning NMR method for the quantitative determination of remaining 4-alkoxybenzyl alcohols in Fmoc-Xaa-Wang resins with a detection limit of 1 mol-%. The NMR method was validated with samples of known ratios between Fmoc-Ala-Wang and 4-alkoxybenzylalcohol resin. Application to a set of preloaded Fmoc-Ala- and Fmoc-Thr(tBu)-Wang test resins demonstrated that the full range of essential amino acids can be quantified without further spectrometer calibration. Compared to established test synthesis protocols, the NMR method represents not only advantages in terms of time and cost savings but also eliminates all inaccuracies due to further sample treatment like SPPS and cleavage from the resin. PMID:23035754

Rentsch, Daniel; Stähelin, Christian; Obkircher, Markus; Hany, Roland; Simeunovic, Marina; Samson, Daniel; Loidl, Günther; Dick, Fritz

2012-11-12

9

MAS NMR and FTIR spectra of framework aluminosilicates  

NASA Astrophysics Data System (ADS)

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb 2+, Cd 2+, Ni 2+ and Cr 3+) into the zeolite structure. After decomposition of the spectra into component peaks differences caused by ion exchange were observed. Additionally, NMR spectra of kalsilite (framework aluminosilicate, not belonging to zeolite group) and other zeolites (chabazite, heulandite and analcime) were measured. 27Al MAS NMR spectra of all the samples studied were compared with the FTIR spectra measured in the middle infrared region. Based on the results obtained it has been proved that the interpretation of spectra obtained using these two different techniques can give some information concerning changes occurring in various framework aluminosilicate structures.

Mozgawa, W.; Fojud, Z.; Handke, M.; Jurga, S.

2002-09-01

10

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

PubMed

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

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

2010-12-01

11

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

PubMed Central

High Resolution – Magic Angle Spinning (HR-MAS) spectroscopy provides rich biochemical profiles that require accurate quantification to permit biomarker identification and to understand the underlying pathological mechanisms. Meanwhile, quantification of HR-MAS data from prostate tissue samples is challenging due to significant overlap between the resonant peaks, the presence of short T2? metabolites such as citrate or polyamines (T2 from 25 to 100 msec) and macromolecules, and variations in chemical shifts and T2?s within a metabolite’s spin systems. Since existing methods do not address these challenges completely, a new quantification method was developed and optimized for HR-MAS data acquired with an ultra short TE and over 30,000 data points. The proposed method, named HR-QUEST (High Resolution – QUEST), iteratively employs the QUEST time-domain semi-parametric strategy with a new model function that incorporates prior knowledge from whole and subdivided metabolite signals. With these features, HR-QUEST is able to independently fit the chemical shifts and T2?s of a metabolite’s spin systems, a necessity for HR-MAS data. By using the iterative fitting approach, it is able to account for significant contributions from macromolecules and to handle shorter T2 metabolites, such as citrate and polyamines. After subdividing the necessary metabolite basis signals, the root mean square (RMS) of the residual was reduced by 52% for measured HR-MAS data from prostate tissue. Monte Carlo studies on simulated spectra with varied macromolecular contributions showed that the iterative fitting approach (6 iterations) coupled with inclusion of long T2 macromolecule components in the basis set improve the quality of the fit, as assessed by the reduction of the RMS of the residual and of the RMS error of the metabolite signal estimate, by 27% and 71% respectively. With this optimized configuration, HR-QUEST was applied to measured HR-MAS prostate data and reliably quantified 16 metabolites and reference signals with estimated Cramér Rao Bounds ?5%.

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

2011-01-01

12

MAS NMR and FTIR spectra of framework aluminosilicates  

Microsoft Academic Search

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb2+, Cd2+, Ni2+ and Cr3+) into the zeolite structure. After decomposition of the spectra

W. Mozgawa; Z Fojud; M Handke; S Jurga

2002-01-01

13

Heteronuclear Double-Quantum MAS NMR Spectroscopy in Dipolar Solids  

NASA Astrophysics Data System (ADS)

A new pulse sequence for high-resolution solid-state heteronuclear double-quantum MAS NMR spectroscopy of dipolar-coupled spin- {1}/{2} nuclei is introduced. It is based on the five-pulse sequence known from solution-state NMR, which is here applied synchronously to both spin species. The heteronuclear double-quantum (HeDQ) spinning-sideband patterns produced by this experiment are shown to be sensitive to the heteronuclear distance, as well as the relative orientations of the chemical-shift and dipolar tensors. In particular, it is shown that the HeDQ patterns exhibit an enhanced sensitivity to the chemical shielding tensors as compared with the single-quantum spinning-sideband patterns. The detection of HeDQ patterns via the I and S spins is discussed. The isolated 13C- 1H spin pair in deuterated ammonium formate with 13C in natural abundance was chosen as a model system, and the perturbing influence of dipolar couplings to surrounding protons on the 13C- 1H DQ coherence is discussed. The pulse sequence can also be used as a heteronuclear double-quantum filter, hence providing information about heteronuclear couplings, and thus allowing the differentiation of quaternary and CH n bonded carbons. The elucidation of 13C- 1H dipolar proximities is presented for a sample of bisphenol A polycarbonate with 13C in natural abundance, recorded with a broadband version of the synchronized five-pulse sequence.

Saalwächter, Kay; Graf, Robert; Demco, Dan E.; Spiess, Hans W.

1999-08-01

14

Quantification of metabolites in breast cancer patients with different clinical prognosis using HR MAS MR spectroscopy.  

PubMed

Absolute quantitative measures of breast cancer tissue metabolites can increase our understanding of biological processes. Electronic REference To access In vivo Concentrations (ERETIC) was applied to high resolution magic angle spinning MR spectroscopy (HR MAS MRS) to quantify metabolites in intact breast cancer samples. The ERETIC signal was calibrated using solutions of creatine and TSP. The largest relative errors of the ERETIC method were 8.4%, compared to 4.4% for the HR MAS MRS method using TSP as a standard. The same MR experimental procedure was applied to intact tissue samples from breast cancer patients with clinically defined good (n?=?13) and poor (n?=?16) prognosis. All samples were examined by histopathology for relative content of different tissue types and proliferation index (MIB-1) after MR analysis. The resulting spectra were analyzed by quantification of tissue metabolites (?-glucose, lactate, glycine, myo-inositol, taurine, glycerophosphocholine, phosphocholine, choline and creatine), by peak area ratios and by principal component analysis. We found a trend toward lower concentrations of glycine in patients with good prognosis (1.1?µmol/g) compared to patients with poor prognosis (1.9?µmol/g, p?=?0.067). Tissue metabolite concentrations (except for ?-glucose) were also found to correlate to the fraction of tumor, connective, fat or glandular tissue by Pearson correlation analysis. Tissue concentrations of ?-glucose correlated to proliferation index (MIB-1) with a negative correlation factor (-0.45, p?=?0.015), consistent with increased energy demand in proliferating tumor cells. By analyzing several metabolites simultaneously, either in ratios or by metabolic profiles analyzed by PCA, we found that tissue metabolites correlate to patients' prognoses and health status five years after surgery. This study shows that the diagnostic and prognostic potential in MR metabolite analysis of breast cancer tissue is greater when combining multiple metabolites (MR Metabolomics). PMID:20101607

Sitter, Beathe; Bathen, Tone F; Singstad, Trond E; Fjøsne, Hans E; Lundgren, Steinar; Halgunset, Jostein; Gribbestad, Ingrid S

2010-05-01

15

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

16

Dynamic nuclear polarisation enhanced (14)N overtone MAS NMR spectroscopy.  

PubMed

Dynamic nuclear polarisation (DNP) has been used to obtain magic angle spinning (14)N(OT) (nitrogen-14 overtone) solid-state NMR spectra from several model amino acids, with both direct and indirect observation of the (14)N(OT) signal. The crystalline solids were impregnated with biradical solutions of organic liquids that do not dissolve the crystalline phase. The bulk phase was then polarized via(1)H spin diffusion from the highly-polarized surface (1)H nuclei, resulting in (1)H DNP signal enhancements of around two orders of magnitude. Cross polarisation from (1)H nuclei directly to the (14)N overtone transition is demonstrated under magic angle spinning, using a standard pulse sequence with a relatively short contact time (on the order of 100 ?s). This method can be used to acquire (14)N overtone MAS powder patterns that match closely with simulated line shapes, allowing isotropic chemical shifts and quadrupolar parameters to be measured. DNP enhancement also allows the rapid acquisition of 2D (14)N(OT) heteronuclear correlation spectra from natural abundance powder samples. (1)H-(14)N(OT) HETCOR and (13)C-(14)N(OT) HMQC pulse sequences were used to observe all single-bond H-N and C-N correlations in histidine hydrochloride monohydrate, with the spectra obtained in a matter of hours. Due to the high natural abundance of the (14)N isotope (99.6%) and the advantages of observing the overtone transition, these methods provide an attractive route to the observation of C-N correlations from samples at natural isotopic abundance and enable the high resolution measurement of (14)N chemical shifts and quadrupolar interaction parameters. PMID:24847776

Rossini, Aaron J; Emsley, Lyndon; O'Dell, Luke A

2014-06-01

17

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

18

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

PubMed

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

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

2009-02-01

19

Temperature calibration for high-temperature MAS NMR to 913 K: 63Cu MAS NMR of CuBr and CuI, and 23Na MAS NMR of NaNbO3.  

PubMed

The solid-state phase transitions of CuBr, CuI and NaNbO(3) can be readily observed using (63)Cu and (23)Na high-temperature magic-angle spinning nuclear magnetic resonance spectroscopy. Temperature has large, linear effects on the peak maximum of (63)Cu in each solid phase of CuBr and CuI, and there is large jump in shift across each phase transition. The (23)Na MAS NMR peak intensities and the line widths in NaNbO(3) also clearly show its high-temperature transition to the cubic phase. These data can be used to calibrate high-temperature MAS NMR probes up to 913 K, which is two hundred degrees higher than the commonly-used temperature calibration based on the chemical shift of (207)Pb in Pb(NO(3))(2). PMID:21546224

Wu, Jingshi; Kim, Namjun; Stebbins, Jonathan F

2011-09-01

20

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

21

In situ high temperature MAS NMR study of the mechanisms of catalysis. Ethane aromatization on Zn-modified zeolite BEA  

Microsoft Academic Search

Ethane conversion into aromatic hydrocarbons over Zn-modified zeolite BEA has been analyzed by high-temperature MAS NMR spectroscopy. Information about intermediates (Zn-ethyl species) and reaction products (mainly toluene and methane), which were formed under the conditions of a batch reactor, was obtained by 13C MAS NMR. Kinetics of the reaction, which was monitored by 1H MAS NMR in situ at the

Sergei S. Arzumanov; Anton A. Gabrienko; Dieter Freude; Alexander G. Stepanov

2009-01-01

22

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

PubMed

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

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

2014-05-14

23

Characterization of Slow Chromophore Reorientation in Nonlinear Optical Polymers by Two-Dimensional MAS NMR.  

National Technical Information Service (NTIS)

Two-dimensional 15N MAS NMR spectrometry was used to characterize slow reorientation of the chromophore at temperatures well below T sub g in the prototypical nonlinear optical (NLO) polymer 10% 4-nitroaniline-15N2/poly(methyl methacrylate). Qualitative a...

S. Taylor-Myers J. G. Nuzzo J. F. Haw

1993-01-01

24

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

25

CP-MAS NMR analysis of carbohydrate fractions of soybean hulls and endosperm  

Microsoft Academic Search

CP-MAS NMR spectroscopy was used to identify soybean cellulose and pectin extracts and to investigate the kinetics of cross polarization. The in vitro incubation of cellulose and pectin, extracted from soya hull and endosperm, respectively, with sheep rumen fluid was followed with this technique. The difference in enzymatic degradability between ChSS and DASS, two pectins with identical monosaccharide composition, was

Carel T. M Fransen; Harmen van Laar; Johannis P Kamerling; Johannes F. G Vliegenthart

2000-01-01

26

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

27

Optimized multiple quantum MAS lineshape simulations in solid state NMR  

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

28

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

SciTech Connect

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

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

1996-06-01

29

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

PubMed

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

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

2000-07-01

30

Contribution of 43Ca MAS NMR for probing the structural configuration of calcium in glass  

NASA Astrophysics Data System (ADS)

The 43Ca MAS NMR spectra obtained for three calcium silicate glasses containing aluminum and/or sodium are analyzed. The 43Ca NMR parameters are shown to be highly sensitive to variations in its chemical environment. The transition from a charge-compensating role of [AlO 4] - groups to a network-modifying role near nonbridging oxygen atoms results in an increase of both the isotropic chemical shift and the quadrupolar coupling constant of 43Ca. This effect can be related to the first coordination shell of calcium (through the Ca-O bond distance) which is affected by the chemical environment beyond the first neighbors of calcium.

Angeli, Frédéric; Gaillard, Marina; Jollivet, Patrick; Charpentier, Thibault

2007-06-01

31

2D five quantum MAS NMR using rotationally induced coherence transfer  

NASA Astrophysics Data System (ADS)

Rotation-induced 5Q?1Q coherence transfer (RIACT) for 5Q MAS NMR experiments is shown unequivocally for 17O ( I=5/2) for compounds with quadrupolar interactions in the range ˜3-7.3 MHz. 5Q RIACT has distinct advantages over the methods used to excite 5Q MAS NMR hitherto through much reduced sensitivity to the electric field gradient. It is also less sensitive to spinning speed than 3Q RIACT on an I=5/2 nucleus whilst producing similar signal intensity. The 2D 5Q RIACT 17O spectrum of zeolite Na-A is better resolved than the previously published higher field 3Q spectrum with all three sites being clearly visible.

Mildner, T.; Smith, M. E.; Dupree, R.

1999-06-01

32

Long-term stability of rotor-controlled MAS frequencies to 0.1 Hz proved by 14N MAS NMR experiments and simulations.  

PubMed

Experimental and simulated 14N MAS NMR spectra of the NH4+ ions in the two polymorphs, mS60 and mP60, of (NH4)2MoO4 are used to illustrate that a long-term stability of rotor-controlled MAS frequencies to 0.1 Hz can be achieved using commercial instrumentation (MAS speed controller and 7.5 mm MAS probe with a single marked rotor) attached to a highly pressure-stabilized air supply. A new modification of the STARS simulation software employs a Gaussian distribution for the experimental spinning frequency around the frequency set for the MAS speed controller. A simulated spectrum is then obtained by summation of several calculated spectra for evenly spaced spinning frequencies around the set frequency with relative weight factors corresponding to the Gaussian distribution. PMID:17196856

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

2007-03-01

33

Evaluation of the ERETIC Method as an Improved Quantitative Reference for 1H HR-MAS Spectroscopy of Prostate Tissue  

PubMed Central

The Electronic REference To access In vivo Concentrations (ERETIC) method was applied to 1H HR-MAS spectroscopy. The accuracy, precision, and stability of ERETIC as a quantitative reference were evaluated in solution and human prostate tissue samples. For comparison, the reliability of 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid (TSP) as a quantitation reference was also evaluated. The ERETIC and TSP peak areas were found to be stable in solution over the short-term and long-term, with long-term relative standard deviations (RSDs) of 4.10% and 2.60%, respectively. Quantification of TSP in solution using the ERETIC peak as a reference and a calibrated, rotor-dependent conversion factor yielded results with a precision ?2.9% and an accuracy error ?4.2% when compared with the expected values. The ERETIC peak area reproducibility was superior to TSP’s reproducibility, corrected for mass, in both prostate surgical and biopsy samples (4.53% vs. 21.2% and 3.34% vs. 31.8%, respectively). Furthermore, the tissue TSP peaks exhibited only 27.5% of the expected area, which would cause an overestimation of metabolite concentrations if used as a reference. The improved quantification accuracy and precision provided by ERETIC may enable the detection of smaller metabolic differences that may exist between individual tissue samples and disease states.

Albers, Mark J.; Butler, Thomas N.; Rahwa, Iman; Bao, Nguyen; Keshari, Kayvan R.; Swanson, Mark G.; Kurhanewicz, John

2010-01-01

34

Evaluation of the ERETIC method as an improved quantitative reference for 1H HR-MAS spectroscopy of prostate tissue.  

PubMed

The Electronic REference To access In vivo Concentrations (ERETIC) method was applied to (1)H HR-MAS spectroscopy. The accuracy, precision, and stability of ERETIC as a quantitative reference were evaluated in solution and human prostate tissue samples. For comparison, the reliability of 3-(trimethylsilyl)propionic-2,2,3,3-d(4) acid (TSP) as a quantitation reference was also evaluated. The ERETIC and TSP peak areas were found to be stable in solution over the short-term and long-term, with long-term relative standard deviations (RSDs) of 4.10% and 2.60%, respectively. Quantification of TSP in solution using the ERETIC peak as a reference and a calibrated, rotor-dependent conversion factor yielded results with a precision < or =2.9% and an accuracy error < or =4.2% when compared with the expected values. The ERETIC peak area reproducibility was superior to TSP's reproducibility, corrected for mass, in both prostate surgical and biopsy samples (4.53% vs. 21.2% and 3.34% vs. 31.8%, respectively). Furthermore, the tissue TSP peaks exhibited only 27.5% of the expected area, which would cause an overestimation of metabolite concentrations if used as a reference. The improved quantification accuracy and precision provided by ERETIC may enable the detection of smaller metabolic differences that may exist between individual tissue samples and disease states. PMID:19235261

Albers, Mark J; Butler, Thomas N; Rahwa, Iman; Bao, Nguyen; Keshari, Kayvan R; Swanson, Mark G; Kurhanewicz, John

2009-03-01

35

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

36

13C CP MAS NMR and DFT study of vascular-selective drugs felodipine and amlodipine  

NASA Astrophysics Data System (ADS)

Amlodipine besylate (AM) and felodipine (FL) have been studied in solid by 13C CP MAS NMR and DFT. The spectra have been successfully reproduced from the theoretical calculations of the nuclear magnetic shielding tensors, using the GIAO method, after the SCF partial geometry optimisation. A very good correlation between the 13C chemical shifts and quadrupole coupling constants for chlorobenzene, AM and FL was obtained. 13C NMR as well as 35Cl NQR do not differentiate between S and R enantiomers of AM and FL due to the symmetry of the 4-aryl ring comprising one (AM) or two (FL) chlorine atoms oriented in a perpendicular fashion over the 1,4-DHP ring.

Latosi?ska, J. N.

2008-09-01

37

A 27Al MAS NMR study of a sol–gel produced alumina: Identification of the NMR parameters of the ?-Al 2O 3 transition alumina phase  

Microsoft Academic Search

27Al MAS NMR has been used to study a sol–gel prepared alumina annealed at various temperatures. Two-field simulation of the sample heated to 1200°C confirmed the presence of corundum, as suggested by XRD, and also the presence of nanocrystalline ?-Al2O3. 27Al MAS NMR chemical shifts, quadrupolar coupling constants and asymmetry parameters are reported for the tetrahedral and octahedral aluminium sites

L. A. O’Dell; S. L. P. Savin; A. V. Chadwick; M. E. Smith

2007-01-01

38

SLOW-MAS NMR METHODS TO STUDY METABOLIC PROCESSES IN VIVO AND IN VITRO  

SciTech Connect

In vitro and in vivo 1H NMR spectroscopy is widely used to measure metabolic profiles in cells, tissues, animals, and humans and to use them, e.g., for diagnosis and therapy response evaluations. However, the spectra often suffer from poor resolution due to variations in the isotropic bulk magnetic susceptibility present in biological objects, resulting in a broadening of the NMR lines. In principle this broadening can be averaged to zero by the technique of magic angle spinning (MAS), where the sample is rotated about an axis making an angle of 54o44’ relative to the external magnetic field. However, a problem is that in a standard MAS experiment spinning speeds of a kHz or more are required in order to avoid the occurrence of spinning sidebands (SSBs) in the spectra, which renders analysis of the spectra difficult again. At these spinning speeds the large centrifugal forces cause severe structural damage in larger biological objects, so that this method cannot be used to study metabolic processes in intact samples. In solid state NMR several methods have been developed where slow MAS is combined with special radio frequency pulse sequences to eliminate spinning side bands or separate them from the isotropic spectrum so that a SSB-free high-resolution isotropic spectrum is obtained. It has been shown recently that two methods, phase-adjusted spinning sidebands (PASS) and phase-corrected magic angle turning (PHORMAT), can successfully be modified for applications in biological materials (1, 2). With PASS MAS speeds as low as 40 Hz can be employed, allowing non or minimally invasive in vitro studies of excised tissues and organs. This method was used, amongst other things, to study post mortem changes in the proton metabolite spectra in excised rabbit muscle tissue (3). With PHORMAT the NMR sensitivity is reduced and longer measuring times are required, but with this methodology the MAS speed can be reduced to ~1 Hz. This makes PHORMAT amenable for in vivo applications, as was demonstrated in a living mouse (4). In this presentation the principles and limitations of PASS and PHORMAT will be briefly discussed and illustrated with spectra obtained on a variety of biological objects. Moreover, it will be shown that PASS can be employed to study metabolic processes in biofilms and other living microbial systems. Finally, on-going work to develop PASS and PHORMAT spectroscopic imaging and to improve the performance of both techniques will be discussed. It is anticipated that slow- and ultra-slow-MAS will significantly enhance the utility of proton MR spectroscopy for biomedical research in living cell systems and live animals, and in future perhaps even in the clinic, in the latter case by rotating the external magnetic field rather than the patient.

Wind, Robert A.; Bertram, Hanne Christine; Hu, Jian Zhi

2005-09-25

39

In Situ 13C MAS NMR Study of n-Hexane Conversion on Pt and Pd Supported on Basic Materials  

Microsoft Academic Search

n-Hexane conversion was studiedin situon Pt and Pd supported on aluminum-stabilized magnesium oxide and Pt on Zeoite KL catalysts (Pt\\/Mg(Al)O, Pd\\/Mg(Al)O and Pt\\/KL) by means of13C MAS NMR spectroscopy.n-Hexane 1-13C was used as a labelled reactant. Forty NMR lines corresponding to 14 different products were resolved and identified. The NMR line assignments were confirmed by adsorption of model compounds. The

Irina I. Ivanova; Anne Pasau-Claerbout; Michaèl Seirvert; Niels Blom; Eric G. Derouane

1996-01-01

40

HR-MAS NMR metabolomics of 'Swingle' citrumelo rootstock genetically modified to overproduce proline.  

PubMed

The accumulation of proline is a typical physiological response to abiotic stresses in higher plants. 'Swingle' citrumelo, an important rootstock for citrus production, has been modified with a mutated ?(1) -pyrroline-5-carboxylate synthetase gene (VaP5CSF129A) linked to the cauliflower mosaic virus 35S promoter to induce the overproduction of free proline. This paper presents a comparative metabolomic study of nontransgenic versus transgenic 'Swingle' citrumelo plants with high endogenous proline. (1) H high-resolution magic angle spinning nuclear magnetic resonance spectroscopy and multivariate analysis showed significant differences in some metabolites between the nontransgenic and transgenic leaves and roots. The overproduction of proline has reduced the sucrose content in transgenic leaves, revealing a metabolic cost for these plants. In roots, the high level of free proline acts for the adjustment of cation-anion balance, causing the reduction of acetic acid content. The same sucrose level in roots indicates that they can be considered as sucrose sink. Similar behavior may be waited for fruits produced on transgenic rootstock. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24842075

de Oliveira, Caroline S; Carlos, Eduardo F; Vieira, Luiz G E; Lião, Luciano M; Alcantara, Glaucia B

2014-08-01

41

An experimental study of decoupling sequences for multiple-quantum and high-resolution MAS experiments in solid-state NMR.  

PubMed

Recently, a sequence for heteronuclear dipolar decoupling in solid-state NMR, namely SWf-TPPM, was introduced by us. Under magic-angle spinning (MAS), the decoupling efficiency of the sequence was unaffected over a range of values for various experimental parameters such as the pulse length, pulse phase, and 1H resonance offset. We here demonstrate its use in multiple-quantum (MQ) and high-resolution (HR) MAS experiments. This sequence further improves the MQMAS spectra compared to the earlier reported decoupling sequences with improved immunity to any missets of the pulse length, pulse phase and decoupler offset. In contrast, for HRMAS, the simple CW scheme is as efficient as any of the decoupling schemes that were studied. PMID:18098152

Thakur, Rajendra Singh; Kurur, Narayanan D; Madhu, P K

2008-02-01

42

13C CP/MAS NMR and DFT studies of thiazides  

NASA Astrophysics Data System (ADS)

The 13C MAS solid state NMR spectra of four sulphonamide derivatives of 1,2,4-benzothiadiazine-1,1-dioxides, commonly known as thiazides, were recorded and the chemical shifts and chemical shift anisotropy (CSA) were measured. Analysis of the experimental 13C shielding parameters was supported by DFT theoretical calculations carried out within the gauge-including atomic orbital (GIAO), semiempirical Typed Neglect of Differential Overlap (TNDO/2) approach and by the spectra estimations performed by ChemNMR Pro 6.0, ACD-I/LAB, SpecInfo and gNMR. It was found that the chemical shifts obtained with ChemNMR Pro 6.0, ACD-I/LAB, SpecInfo and gNMR were insensitive to the substitution effects, whereas the semiempirical TNDO/2 and density functional theory (DFT) B3LYP/6-311+G(2d,p) methods allowed estimation of the influence of substituents on the chemical shielding and consequently, the chemical shift. The influence of the substituents at C3 position of the ring on the chemical shifts was analysed on the basis of the experimental data and results of the DFT calculations. The values of the chemical shifts and the low values of the anisotropy parameter for the C3 atom in HCTZ, TCTZ and ATZ, strongly indicated that three thiazides HCTZ, TCTZ and ATZ occurred in the form of HCTZ type with the C3 carbon atom participating in a single bond. The following ordering of the substituents according to the increasing electron accepting properties was found: -H<-CH 2SCH 2CH?CH 2<-CHCl 2. A detailed analysis of the inductive and coupling effects was made on the basis of 13C chemical shifts and chemical shielding tensor asymmetry parameters on the C3 and C6 carbon atoms.

Latosi?ska, J. N.

2003-02-01

43

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

2013-11-21

44

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

PubMed Central

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

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

2014-01-01

45

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.

46

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

PubMed

Fully bleached softwood kraft pulps were hydrolyzed with cellulase (1,4-(1,3:1,4)-beta-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(alpha), cellulose I(beta), para-crystalline) and amorphous regions were hydrolyzed to a different extent by the enzyme used. Also observed was a rapid initial phase for hydrolysis of regions followed by a slow hydrolysis phase. Cellulose I(alpha), para-crystalline, and non-crystalline regions of cellulose are more susceptible to enzymatic hydrolysis than cellulose I(beta) during the initial phase. After the initial phase, all the regions are then similarly susceptible to enzymatic hydrolysis. PMID:16442511

Pu, Yunqiao; Ziemer, Cherie; Ragauskas, Arthur J

2006-04-10

47

In situ high temperature MAS NMR study of the mechanisms of catalysis. Ethane aromatization on Zn-modified zeolite BEA.  

PubMed

Ethane conversion into aromatic hydrocarbons over Zn-modified zeolite BEA has been analyzed by high-temperature MAS NMR spectroscopy. Information about intermediates (Zn-ethyl species) and reaction products (mainly toluene and methane), which were formed under the conditions of a batch reactor, was obtained by (13)C MAS NMR. Kinetics of the reaction, which was monitored by (1)H MAS NMR in situ at the temperature of 573K, provided information about the reaction mechanism. Simulation of the experimental kinetics within the frames of the possible kinetic schemes of the reaction demonstrates that a large amount of methane evolved under ethane aromatization arises from the stage of direct ethane hydrogenolysis. PMID:19186034

Arzumanov, Sergei S; Gabrienko, Anton A; Freude, Dieter; Stepanov, Alexander G

2009-04-01

48

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

PubMed

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

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

2013-12-26

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 D 2O:H 2O = 9:1 containing buffer solutions. The experiments are demonstrated using the SH3 domain of chicken ?-spectrin as a model system. The labeling scheme allows to record proton detected 1H, 15N correlation spectra with very high resolution in the absence of heteronuclear dipolar decoupling. Cu-edta as a doping reagent yields a reduction of the recycle delay by up to a factor of 15. In particular, we find that the 1H T1 for the bulk H N magnetization is reduced from 4.4 s to 0.3 s if the Cu-edta concentration is increased from 0 mM to 250 mM. Possible perturbations like chemical shift changes or line broadening due to the paramagnetic chelate complex are minimal. No degradation of our samples was observed in the course of the experiments.

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

2007-12-01

50

CP\\/MAS [sup 89]Y NMR spectroscopy: A facile method for characterizing yttrium-containing solids  

Microsoft Academic Search

Solid state CP\\/MAS [sup 89]Y NMR spectroscopy, which had previously been limited to air stable materials containing solvated water, has been extended to a series of air sensitive yttrium complexes with a chemical shift range of over 1,000 ppm. The results of this study demonstrate that [sup 89]Y CP\\/MAS spectra can be easily obtained on a broad range of complexes

Jiejun Wu; T. J. Boyle; J. L. Shreeve; J. W. Ziller; W. J. Evans

1993-01-01

51

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

Microsoft Academic Search

Under fast MAS conditions, techniques for 1H signal selection and suppression, which have originally been developed for solution-state NMR, become applicable to solids. In this work, we describe how WATERGATE and DANTE pulse sequences can be used under MAS to selectively excite or suppress peaks in 1H solid-state spectra. As known from the liquid-state analogues, signal selection and\\/or suppression is

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

2003-01-01

52

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

Microsoft Academic Search

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 1H 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

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

2010-01-01

53

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

PubMed

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

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

2005-01-01

54

In situ CF MAS NMR study of the pairwise incorporation of parahydrogen into olefins on rhodium-containing zeolites Y  

NASA Astrophysics Data System (ADS)

Formation of parahydrogen-induced polarization was investigated via hydrogenation of propene with parahydrogen on rhodium-modified zeolite Y (0.4[Rh]Na-Y) in the gas phase. The PASADENA (Parahydrogen and Synthesis Allow Dramatically Enhanced Nuclear Alignment) protocol was combined with in situ 1H MAS NMR under flow conditions for observing adsorbed reactants. Antiphase signals of hyperpolarized propane due to the pairwise incorporation of parahydrogen in propene were observed under MAS as well as static conditions. In the case of MAS rotors completely filled with pure zeolite, rapid relaxation of hyperpolarized propane inside the zeolite cages occurs, which was decreased in rotors with empty gas volume.

Henning, Harald; Dyballa, Michael; Scheibe, Matthias; Klemm, Elias; Hunger, Michael

2013-01-01

55

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

56

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

57

Study of the alkaline environment in mixed alkali compositions by multiple-quantum magic angle nuclear magnetic resonance (MQ–MAS NMR)  

Microsoft Academic Search

45S5 Bioglasses of the composition 46.1 SiO2–2.6 P2O5–26.9 CaO–(24.4?x) Na2O–xMe2O (Me=Li or K) have been investigated using MAS NMR and MQ–MAS NMR methods. The analysis of the 29Si MAS NMR spectrum revealed two lineshapes whose chemical shift is consistent with two silica Qn=2,3 species. The 31P MAS NMR spectrum reveals the effect of both Na and Ca ions. The chemical

A. Angelopoulou; V. Montouillout; D. Massiot; G. Kordas

2008-01-01

58

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

PubMed

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

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

2003-11-01

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

Solid-state MAS NMR studies on the hydrothermal stability of the zeolite catalysts for residual oil selective catalytic cracking  

Microsoft Academic Search

By using the solid-state MAS NMR technique, the hydrothermal stabilities (under 100% steam at 1073 K) of HZSM-5 zeolites modified by lanthanum and phosphorus have been studied. They are excellent zeolite catalysts for residual oil selective catalytic cracking (RSCC) processes. It was indicated that the introduction of phosphorus to the zeolite via impregnation with orthophosphoric acid led to dealumination as

Jianqin Zhuang; Ding Ma; Gang Yang; Zhimin Yan; Xiumei Liu; Xianchun Liu; Xiuwen Han; Xinhe Bao; Peng Xie; Zhongmin Liu

2004-01-01

61

Solid-state MAS NMR detection of the oxidation center in TS1 zeolite by in situ probe reaction  

Microsoft Academic Search

In this paper, the oxidation of trimethylphosphine as an in situ probe reaction was performed to monitor the oxidation ability of different Ti species in TS-1 zeolite by 31P MAS NMR spectra, which found for the first time direct evidence about the oxidation center of TS-1 zeolite.

Jinqing Zhuang; Ding Ma; Zhimin Yan; Feng Deng; Xiumei Liu; Xiuwen Han; Xinhe Bao; X. Wu Liu; Xinwen Guo; Xiangsheng Wang

2004-01-01

62

DNP-enhanced MAS NMR of bovine serum albumin sediments and solutions.  

PubMed

Protein sedimentation sans cryoprotection is a new approach to magic angle spinning (MAS) and dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy of proteins. It increases the sensitivity of the experiments by a factor of ?4.5 in comparison to the conventional DNP sample preparation and circumvents intense background signals from the cryoprotectant. In this paper, we investigate sedimented samples and concentrated frozen solutions of natural abundance bovine serum albumin (BSA) in the absence of a glycerol-based cryoprotectant. We observe DNP signal enhancements of ? ? 66 at 140 GHz in a BSA pellet sedimented from an aqueous solution containing the biradical polarizing agent TOTAPOL and compare this with samples prepared using the conventional protocol (i.e., dissolution of BSA in a glycerol/water cryoprotecting mixture). The dependence of DNP parameters on the radical concentration points to the presence of an interaction between TOTAPOL and BSA, so much so that a frozen solution sans cryoprotectant still gives ? ? 50. We have studied the interaction of BSA with another biradical, SPIROPOL, that is more rigid than TOTAPOL and has been reported to give higher enhancements. SPIROPOL was also found to interact with BSA, and to give ? ? 26 close to its maximum achievable concentration. Under the same conditions, TOTAPOL gives ? ? 31, suggesting a lesser affinity of BSA for SPIROPOL with respect to TOTAPOL. Altogether, these results demonstrate that DNP is feasible in self-cryoprotecting samples. PMID:24460530

Ravera, Enrico; Corzilius, Björn; Michaelis, Vladimir K; Luchinat, Claudio; Griffin, Robert G; Bertini, Ivano

2014-03-20

63

Photo-CIDNP MAS NMR beyond the T1 limit by fast cycles of polarization extinction and polarization generation  

NASA Astrophysics Data System (ADS)

In nanosecond-laser flash photo-CIDNP MAS NMR, polarization generation (PG) proceeds much faster than longitudinal spin relaxation. With a nanosecond-laser setup linked to the NMR console the repetition time of the experiment is then limited by the minimum recycle delay of the NMR spectrometer and the maximum repetition rate of laser flashes. These limits can only be reached if polarization left after the NMR experiment is completely canceled before the next laser flash. We introduce a presaturation pulse sequence, based on three (?/2) 13C pulses and optimized timing and phase cycling that allows for such efficient polarization extinction (PE). The technique is demonstrated on selectively isotope labeled bacterial reaction centers (RCs) of Rhodobacter ( Rb.) sphaeroides wildtype (WT). High-quality 13C photo-CIDNP MAS NMR spectra are obtained using cycle rates up to 4 Hz. The PE-PG strategy proposed here provides a general experimental scheme for reduction of measurement time in magnetic resonance experiments based on fast PG.

Daviso, Eugenio; Diller, Anna; Alia, A.; Matysik, Jörg; Jeschke, Gunnar

2008-01-01

64

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

65

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

2010-01-01

66

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

67

Application of temperature-programmed oxidation, multinuclear MAS NMR and DRIFT spectroscopy to the surface characterization of modified silica nanoparticles  

NASA Astrophysics Data System (ADS)

Grafting of organosilane-functionalized substances onto the surface of nano-sized silica particles was studied by temperature-programmed oxidation (TPO), solid-state 13C and 29Si MAS NMR and DRIFT spectroscopy. By using 29Si MAS NMR quantitative data on the proportions of the various grafted structures, grafting yields and the reactivity of the geminal and free silanols towards the coupling agent were obtained. For 3-(trimethoxysilyl)propylmethacrylate as coupling agent and maleic acid as catalyst, the TPO weight loss of about 24 wt.% revealed a hypothetical coverage of about 5.5 graft/nm 2. Compared to the surface concentration of 2-3-OH groups per nm 2, this value can be only explained by grafting precondensed silane molecules onto nano-sized silica, assuming a core shell principle.

Bauer, F.; Freyer, A.; Ernst, H.; Gläsel, H.-J.; Mehnert, R.

2001-07-01

68

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

69

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 O 1 and O 4 lattice oxygen. The changes in populations of cationic sites after chemisorption were detected.

Vratislav, Stanislav; Dlouhá, Maja; Bosá?ek, Vladim?´r.

70

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

71

Characterization of Acacia mangium polyflavonoid tannins by MALDI-TOF mass spectrometry and CP-MAS 13C NMR  

Microsoft Academic Search

The MALDI-TOF mass spectrometry (MS) and solid state CP-MAS 13C Nuclear Magnetic Resonance (NMR) spectroscopic technique were introduced to characterize Acacia mangium tannin (condensed tannins). The MALDI-TOF MS illustrated a series of peaks corresponding to oligomers of condensed tannins of up to 11 flavonoid units (3200Da). A. mangium condensed tannins were found to consist predominantly of prorobinetinidin combined with profisetinidin

Yeoh Beng Hoong; Antonio Pizzi; Harald Pasch

2010-01-01

72

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

Microsoft Academic Search

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

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

2005-01-01

73

The structure of acid treated sepiolites: small-angle X-ray scattering and multi MAS-NMR investigations  

Microsoft Academic Search

Structural changes in the chain silicate sepiolite brought about by acid treatment were studied by X-ray diffraction, gas adsorption and MAS-NMR methods. It was established that as the amount of iron and aluminum extracted from the mineral is increased, the specific surface area of the sample is also increased (from 195.2 to 306.6 m2\\/g) and the originally microporous structure is

Imre Dékány; László Turi; Antonio Fonseca; János B. Nagy

1999-01-01

74

Basicity of potassium-salt modified hydrotalcite studied by 1H MAS NMR using pyrrole as a probe molecule  

Microsoft Academic Search

Potassium nitrate is supported on calcined hydrotalcite by a wet mixing method to produce strong basic sites. X-ray powder diffraction patterns reveal that dropping of potassium salt on calcined hydrotalcite promotes the recovery of the layer structure on rehydration. Potassium species are dispersed on the surface homogeneously up to a loading amount of about 10wt.% KNO3. 1H MAS NMR results

Y. Wang; X. Wei Han; A. Ji; L. Y. Shi; S. Hayashi

2005-01-01

75

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

76

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

NASA Astrophysics Data System (ADS)

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

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

77

Synthesis, Characterization, and 1H and 71Ga MAS NMR Spectroscopy of a Novel Mg/Ga Double Layered Hydroxide  

NASA Astrophysics Data System (ADS)

A new brucite-like layered Mg/Ga double hydroxide (LDH) of composition [Mg 0.174Ga 0.256(OH) 2](CO 3) 0.134· mH 2O was synthesized by coprecipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073 K 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 523K and to decompose into a mixture of periclase MgO and amorphous Ga 2O 3at 823 K. Its changes with temperature were monitored by using 1H and 71Ga MAS NMR; 1H MAS NMR spectra revealed the loss of interlayer OH groups supporting the brucite-like structure on calcination at 823K.

Aramendía, María. Angeles; Borau, Victor; Jiménez, César; Marinas, José Maria; Romero, Francisco José; Ruiz, José Rafael

1997-06-01

78

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

79

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

PubMed

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

Aimi, Keitaro; Ando, Shinji

2004-07-01

80

New inserts and low temperature--two strategies to overcome the bottleneck in MAS NMR on wet gels.  

PubMed

MAS NMR experiments on wet and dry aluminium alkoxide fluoride gels are presented here for the first time. For the MAS studies on wet jelly like gels special inserts were developed which fit perfectly a 4mm rotor and allow rotation frequencies up to 12 kHz. Six different insert materials were tested concerning their suitability including different organic polymers ((poly(methyl methacrylate) (PMMA), poly(ether ether ketone) (PEEK), poly(vinylchloride) (PVC) and poly(tetrafluorethylene) (PTFE)), glass as well as pure quartz (SiO(2)). Alternatively, low-temperature MAS NMR experiments taken at 150K with the wet gel frozen directly in the rotor led to comparable results. (27)Al, (19)F, (13)C, (1)H were used as nuclear spin probes to identify local structures in the wet as well as in the dry xerogels. Both wet and dry gels consist of a network structure of AlF(6-x)OiPr(x) species (x: 0-3). The main structural units of the dried gel are already preformed in the jelly like gel and change only little at aging and drying processes. PMID:17949950

König, R; Scholz, G; Kemnitz, E

2007-11-01

81

Quantitation of crystalline material within a liquid vehicle using 1H/19F CP/MAS NMR.  

PubMed

A method to detect and quantify a small amount crystalline material within a liquid solution of solubilized material is described. 19F CP-MAS ssNMR was investigated as a technique to detect low levels (0.2 mg/g) of crystalline sodium (2R)-7-{3-[2-chloro-4-(2,2,2-trifluoroethoxy)phenoxy]propoxy}-2-methyl-3,4-dihydro-2H-chromane-2-carboxylate (I) within a solid mixture (with microcrystalline cellulose) and a slurry with a liquid vehicle (capric and caprylic acid triglycerides). The results demonstrate that the area of the 19F CP/MAS signal obtained in 25 min at 25 degrees C is linearly dependent (R2=0.997) on the mass of I within the ssNMR rotor. Slopes of CP-MAS peak area versus mass of I in the rotor were nearly identical for the solid mixture and slurry suspension. Signal-to-noise ratio for the low potency slurry suggest detection and quantitation of 0.1 mg of crystalline I in the rotor, corresponding to 2 mg/g of crystalline material within the slurry suspension. PMID:17051585

Farrer, Brian T; Peresypkin, Andrey; Wenslow, Robert M

2007-02-01

82

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

NASA Astrophysics Data System (ADS)

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

Lim, Ae Ran; Lim, Kye-Young

2014-05-01

83

Structural studies of bacterial cellulose through the solid-phase nitration and acetylation by CP\\/MAS 13 C NMR spectroscopy  

Microsoft Academic Search

The solid-phase nitration and acetylation processes of bacterial cellulose have been investigated mainly by CP\\/MAS 13C NMR spectroscopy to clarify the features of these reactions in relation to the characterization of the disordered component included in the microfibrils. CP\\/MAS 13C NMR spectra of bacterial and Valonia cellulose samples are markedly changed as the nitration progresses, in a similar way to

Hiroyuki Yamamoto; Fumitaka Horii; Asako Hirai

2006-01-01

84

MAS NMR, ESR and TPD studies of Mo\\/HZSM?5 catalysts: evidence for the migration of molybdenum species into the zeolitic channels  

Microsoft Academic Search

NH3?TPD, MAS NMR and ESR spectroscopies were employed to investigate Mo?modified HZSM?5 catalysts prepared by impregnation. It\\u000a was found that the modification of Mo ions results in a pronounced decrease in the intensity of 1H MAS NMR resonance originating from Brønsted acid sites in the zeolites and a distinct splitting of Mo5+ ESR signals, which is attributed to the interaction

Ding Ma; Weiping Zhang; Yuying Shu; Xiumei Liu; Yide Xu; Xinhe Bao

2000-01-01

85

13 C CP (cross-polarization) MAS (magic angle spinning) NMR and GIAO-CHF calculations of buspirone analogues  

Microsoft Academic Search

13C CP (cross-polarization) MAS (magic angle spinning) solid state NMR spectra of buspirone analogue 3a,4,7,7a-tetrahydro-2-{4-[4-(2-quinolinyl)-1-piperazinyl]butyl}-4,7-ethane-1H-isoindole-1,3(2H)-dione were recorded. In the spectra of hydrochloride and hydrobromide, two sets of signals appeared, in agreement with single crystal X-ray diffraction data indicating that in each of the salts two independent cations were present in the crystal unit. The largest shielding differences of 3.2–4.6 ppm

A. Szelejewska-Wo?niakowska; Z. Chilmonczyk; A. Le?; I. Wawer

1998-01-01

86

Carbothermal formation of ??-sialon from kaolinite and halloysite studied by 29Si and 27Al solid state MAS NMR  

Microsoft Academic Search

27Al and 29Si magic-angle spinning(MAS) nuclear magnetic resonance(NMR)and complementary X-ray diffraction (XRD) studies of carbothermal formation of sialons from kaolinite and halloysite confirm that the reaction involves the initial formation of mullite (3Al2O3·2SiO2) and amorphous silica. In the presence of carbon, Si-N bonds are formed at ˜1200 °C, giving a continuum of silicon oxynitride compositions which become progressively more N-rich.

K. J. D. Mackenzie; R. H. Meinhold; G. V. White; C. M. Sheppard; B. L. Sherriff

1994-01-01

87

CP-MAS 207 Pb with 19 F decoupling NMR spectroscopy: medium range investigation in fluoride materials  

Microsoft Academic Search

The isotropic chemical shift of 207Pb is used to perform structural investigations of crystalline fluoride compounds (PbF2, Pb2ZnF6, PbGaF5, Pb3Ga2F12 and Pb9Ga2F24) and transition metal fluoride glasses (TMFG) of the PZG family (PbF2–ZnF2–GaF3). Using 207Pb Cross Polarisation Magic Angle Spinning (CP-MAS) NMR with 19F decoupling, it is shown that the isotropic chemical shift of 207Pb varies on a large scale

B Bureau; G Silly; J. Y Buzaré

1999-01-01

88

Applications of the Bloch–Siegert Shift in Solid-State Proton-Dipolar-Decoupled 19F MAS NMR  

Microsoft Academic Search

In solid-state proton-dipolar-decoupled19F MAS NMR spectroscopy,19F chemical-shift data need to be corrected for the Bloch–Siegert shift. Assigning the single sharp19F resonance of 2-fluoroadamantane to its proton-coupled19F shift of ?174.4 ppm results in chemical-shift referencing that is independent of the amplitude of the proton-decoupling field. The Bloch–Siegert shift is also a useful tool to characterize the amplitude and homogeneity of the

Stephanie A. Vierkötter

1996-01-01

89

Temperature and hydration dependence of proton MAS NMR spectra in MCM-41: model based on motion induced chemical shift averaging.  

PubMed

The proton MAS NMR spectra in MCM-41 at low hydration levels (less than hydration amounting to one water molecule per surface hydroxyl group) show complex proton resonance peak structures, with hydroxyl proton resonances seen in dry MCM-41 disappearing as water is introduced into the pores and new peaks appearing, representing water and hydrated silanol groups. Surface hydroxyl group-water molecule chemical exchange and chemical shift averaging brought about by a water molecule visiting different surface hydrogen bonding sites have been proposed as possible causes for the observed spectral changes. In this report a simple model based on chemical shift averaging, due to the making and breaking of hydrogen bonds as water molecules move on the MCM-41 surface, is shown to fully reproduce the NMR spectra, both as a function of hydration and temperature. Surface proton-water proton chemical exchange is not required in this model at low hydration levels. PMID:23266020

Walia, Jaspreet; Crone, Joshua; Liang, Jianzhen; Niknam, Mohamad; Lemaire, Claude; Terry Thompson, R; Peemoeller, Hartwig

2013-02-01

90

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

NASA Astrophysics Data System (ADS)

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

Agarwal, Vipin; Reif, Bernd

2008-09-01

91

13 C CP\\/MAS NMR study of a wood\\/phenol–formaldehyde resin bondline  

Microsoft Academic Search

The dynamics and interactions of a wood powder\\/phenol–formaldehyde (PF) resin composite are evaluated by solid-state 13C NMR. A 13C labeled and perdeuterated PF resin, with low molecular weight distribution, is synthesized and cured in the neat state and also in combination with yellow-poplar wood powder. The 13C NMR spectral features and cross-polarization dynamics of the PF hydroxymethyl and methylene nuclei

Marie-Pierre G. Laborie; Charles E. Frazier

2006-01-01

92

13C and 1H MAS NMR studies of graphite oxide and its chemically modified derivatives  

Microsoft Academic Search

Graphite oxide (GO) and several of its derivatives have been studied using 13C and 1H NMR. The 13C NMR lines at 60, 70 and 130 ppm have been re-assigned. The > C?C < double bonds are relatively stable in comparison with the C?O?C and C?O?H groups. There are at least two magnetically inequivalent C?O?H sites, and the structure does not

Anton Lerf; Heyong He; Thomas Riedl; Michael Forster; Jacek Klinowski

1997-01-01

93

Quantification of ammonia binding sites in Davison (Type 3A) zeolite desiccant : a solid-state Nitrogen-15 MAS NMR spectroscopy investigation.  

SciTech Connect

The quantitative analysis of ammonia binding sites in the Davison (Type 3A) zeolite desiccant using solid-state {sup 15}N MAS NMR spectroscopy is reported. By utilizing 15N enriched ammonia ({sup 15}NH{sub 3}) gas, the different adsorption/binding sites within the zeolite were investigated as a function of NH{sub 3} loading. Using {sup 15}N MAS NMR multiple sites were resolved that have distinct cross-polarization dynamics and chemical shift behavior. These differences in the {sup 15}N NMR were used to characterize the adsorption environments in both the pure 3A zeolite and the silicone-molded forms of the desiccant.

Alam, Todd Michael; Holland, Gregory P.; Cherry, Brian Ray

2004-01-01

94

Sodium ion mobility in Na(x)CoO2 (0.6 < x < 0.75) cobaltites studied by 23Na MAS NMR.  

PubMed

Various P2 and P'3-Na(x)CoO(2) phases, with x ranging approximately from 0.6 to 0.75, have been studied by variable-temperature (23)Na magic angle spinning (MAS) NMR. Signal modification versus temperature plots clearly show that Na(+) ions are not totally mobile at room temperature on the NMR time scale. As the temperature increases, the line shape change of the (23)Na MAS NMR signal differs for the P2 and P'3 stackings and is interpreted by the differences of Na(+) ion sites and of sodium diffusion pathways in the two structures. PMID:19419150

Carlier, Dany; Blangero, Maxime; Ménétrier, Michel; Pollet, Michaël; Doumerc, Jean-Pierre; Delmas, Claude

2009-08-01

95

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

96

A combined 17 O RAPT and MQ-MAS NMR study of l-leucine  

Microsoft Academic Search

We report the application of rotor-assisted population transfer (RAPT) to measure the quadrupolar coupling constant (Cq) for spin 52 nuclei. Results from numerical simulations are presented on the magnitude of enhancement factor as a function of frequency offsets, i.e. the RAPT profile. Experimental O17 RAPT profile is traced for the amino acid l-leucine. In addition, results from MQ-MAS experiments are

Subramanian Prasad; Ted M. Clark; Ramesh Sharma; Hyung-Tae Kwak; Philip J. Grandinetti; Herbert Zimmermann

2006-01-01

97

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

PubMed

Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA=Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the (1)H T1 values were calculated from data collected by (1)H spin-inversion recovery method detected in natural-abundance (13)C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the (1)H T1 values can be successfully reduced by a factor of 3.5 using as low as 10mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the (13)C CPMAS spectra. These results obtained from (13)C-detected CPMAS experiments were further confirmed using (1)H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans. PMID:24881032

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

2014-07-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

100

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

NASA Astrophysics Data System (ADS)

High resolution proton spectra are obtained in MAS solid-state NMR in case samples are prepared using perdeuterated protein and D2O in the recrystallization buffer. Deuteration reduces drastically 1H, 1H dipolar interactions and allows to obtain amide proton line widths on the order of 20 Hz. Similarly, high-resolution proton spectra of aliphatic groups can be obtained if specifically labeled precursors for biosynthesis of methyl containing side chains are used, or if limited amounts of H2O in the bacterial growth medium is employed. This review summarizes recent spectroscopic developments to access structure and dynamics of biomacromolecules in the solid-state, and shows a number of applications to amyloid fibrils and membrane proteins.

Reif, Bernd

2012-03-01

101

Non-bridging oxygens in borate glasses: characterization by 11B and 17O MAS and 3QMAS NMR.  

PubMed

The concentrations of non-bridging oxygens (NBO) in oxide glasses has major effects on their properties and on those of their precursor glass melts. In borate and borosilicate glasses, the presence of NBO bonded to boron has generally been inferred from 11B NMR spectra and mass balance considerations. Here we report the direct observation of such NBO using 17O MAS and 3QMAS techniques, and compare estimates of their populations with those derived from high-resolution 11B MAS spectra. For the latter, two independent methods are used, based on the ratios of trigonal to tetrahedral boron and on the concentrations of trigonal boron sites with large quadrupolar asymmetry parameters. We include data on crystalline sodium pyroborate (Na4B2O5) and sodium metaborate (NaBO2), and several sodium and barium borate glasses. 17O chemical shifts and quadrupolar coupling constants for NBO bonded to boron vary considerably depending on their coordination environment. In borosilicates, peaks for this species may be hidden by overlap with B-O-Si or Si-O-Si resonances. PMID:10811425

Stebbins, J F; Zhao, P; Kroeker, S

2000-05-01

102

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

PubMed

Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear (13)C-(13)C correlation spectra. We demonstrate on model compounds and on 1-73-(U-(13)C,(15)N)/74-108-(U-(15)N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7-2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear (13)C-(13)C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

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

2014-06-01

103

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(SO 4) 2 · 12H 2O  

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(SO 4) 2 · 12H 2O), 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

104

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

105

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

PubMed

The goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using (1)H 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 (13)C spectroscopic imaging (SI) studies of prostate cancer patients. PMID:18727052

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

2008-09-01

106

A multinuclear 1H, 13C and 11B solid-state MAS NMR study of 16- and 18-electron organometallic ruthenium and osmium carborane complexes.  

PubMed

The first (1)H, (13)C, (31)P and (11)B solid state MAS NMR studies of electron-deficient carborane-containing ruthenium and osmium complexes [Ru/Os(p-cym)(1,2-dicarba-closo-dodecaborane-1,2-dithiolate)] are reported. The MAS NMR data from these 16-electron complexes are compared to those of free carborane-ligand and an 18-electron triphenylphosphine ruthenium adduct, and reveal clear spectral differences between 16- and 18-electron organometallic carborane systems in the solid state. PMID:24554004

Barry, Nicolas P E; Kemp, Thomas F; Sadler, Peter J; Hanna, John V

2014-04-01

107

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

NASA Astrophysics Data System (ADS)

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

Linser, Rasmus; Fink, Uwe; Reif, Bernd

2008-07-01

108

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

Microsoft Academic Search

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

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

2005-01-01

109

Anisotropic indirect nuclear spin-spin coupling in InP: 31P CP NMR study under slow MAS condition  

NASA Astrophysics Data System (ADS)

The indirect nuclear spin-spin interaction tensor between neighboring 113,115In- 31P spins in Fe-doped InP semiconductor has been studied by 31P NMR spectra measured using CP of 113In ? 31P and 115In ? 31P under slow MAS condition. The isotropic ( Jiso) and anisotropic ( Janiso = 2/3[ J? - J?]) parts of the indirect interaction tensor are obtained from the spectral simulation. The acceptable combinations of these values are found to be as follows: ( Jiso, Janiso) = (224 ± 5, 500 ± 100 Hz) or (-224 ± 5, 2100 ± 100 Hz). Although, the coupling constants estimated in this study are slightly different from previously reported values of ? Jiso? = 350 Hz, Janiso = 1298 Hz [M. Engelsberg, R.E. Norberg, Phys. Rev. B 5 (1972) 3395] and of ? Jiso? = 225 ± 10, Janiso = (813 ± 50) or (1733 ± 50) Hz [M. Tomaselli et al., Phys. Rev. B 58 (1998) 8627], all of these has the trend that Janiso is rather larger than Jiso.

Iijima, Takahiro; Hashi, Kenjiro; Goto, Atsushi; Shimizu, Tadashi; Ohki, Shinobu

2006-02-01

110

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

PubMed

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

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

2013-09-12

111

3D NMR spectroscopy for resonance assignment and structure elucidation of proteins under MAS: novel pulse schemes and sensitivity considerations.  

PubMed

Two types of 3D MAS NMR experiments are introduced, which combine standard (NC,CC) transfer schemes with (1H,1H) mixing to simultaneously detect connectivities and structural constraints of uniformly 15N,13C-labeled proteins with high spectral resolution. The homonuclear CCHHC and CCC experiments are recorded with one double-quantum evolution dimension in order to avoid a cubic diagonal in the spectrum. Depending on the second transfer step, spin systems or proton-proton contacts can be determined with reduced spectral overlap. The heteronuclear NHHCC experiment encodes NH-HC proton-proton interactions, which are indicative for the backbone conformation of the protein. The third dimension facilitates the identification of the amino acid spin system. Experimental results on U-[15N,13C]valine and U-[15N,13C]ubiquitin demonstrate their usefulness for resonance assignments and for the determination of structural constraints. Furthermore, we give a detailed analysis of alternative multidimensional sampling schemes and their effect on sensitivity and resolution. PMID:15705514

Heise, Henrike; Seidel, Karsten; Etzkorn, Manuel; Becker, Stefan; Baldus, Marc

2005-03-01

112

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

PubMed

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

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

2005-11-30

113

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

NASA Astrophysics Data System (ADS)

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

Lim, Ae Ran

2014-06-01

114

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

115

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

PubMed

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

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

2009-08-28

116

A CRAMPS and 13C CP/MAS NMR examination of solid-solid transitions in n-Hexatriacontane (C36H74)  

NASA Astrophysics Data System (ADS)

The normal paraffins can undergo several transitions before melting and may thus serve as interesting model compounds for polyethylene, which also undergoes solid-solid transitions, the strongest and best-known being the so-called alpha transition. Our examination of n-Hexatriacontane (C36) has been greatly furthered by the use of the solid-state H-1 NMR technique known as CRAMPS (combined rotation and multiple pulse spectroscopy). This technique, combined with DSC and C-13 CP/MAS NMR, has allowed us to make tentative assignments for the molecular motions occurring at different temperatures below the melting point.

Stewart, Michael J.; Mathias, Lon J.

1994-07-01

117

Temperature-switched MAS NMR. A new method for time-resolved in situ studies of reaction steps in heterogeneous catalysis  

NASA Astrophysics Data System (ADS)

The temperature of zeolite samples containing adsorbed methanol molecules was switched from room temperature to 500-600 K within 30-40 s by means of a laser beam. The catalytic reaction was monitored by C-13 magic angle spinning nuclear magnetic resonance (MAS NMR) and H-1 MAS NMR, the latter in steps of one second. A two-dimensional Fourier-transformation of the difference between the time-dependent and the equilibrium state of the system gives a good representation of reaction steps. For the methanol conversion it was found that the primarily formed C3C4 alkanes are still involved in further reactions, whereas methane is an inert product under these conditions.

Ernst, H.; Freude, D.; Mildner, T.

1994-10-01

118

1H and 23Na MAS NMR spectroscopy of cationic species in CO2 selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange  

NASA Astrophysics Data System (ADS)

The location of extraframework cations in Sr2+ and Ba2+ ion-exchanged SAPO-34 was estimated by means of 1H and 23Na 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 CO2 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.

Arévalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernández-Maldonado, Arturo J.

2012-07-01

119

1H/ 2H-Dimethyl Sulfone as a Convenient Standard for Setting the Hartmann-Hahn Match in 1H- 2H CP/MAS NMR  

NASA Astrophysics Data System (ADS)

A physical mixture of powders and a molten mixture of 1H- and 2H-dimethyl sulfones were used to set the Hartmann-Hahn match in 1H- 2H CP/MAS NMR. There is no increase of spectral intensity for a mixture of powdered 1H- and 2H-sulfones compared with the MAS spectrum of pure 2H sulfone, but a considerable increase is found for the mixed melt and for bis[ tert-butyl(phenyl- d5) thiophosphoryl] disulfide. 1H- 2H CP/MAS offers increased signal intensity, shortens the accumulation time, and, in addition, provides a direct measure of the homogeneity of solids on a molecular level.

Potrzebowski, M. J.; Wasiak, J.; Ciesielski, W.; Klinowski, J.

120

Solid-State NMR Structure Characterization of a (13)CO-Labeled Ir(I) Complex with a P,N-Donor Ligand Including Ultrafast MAS Methods.  

PubMed

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

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

2014-07-21

121

Correlation of catalytic activity with infra-red, 29Si MAS NMR and acidity data for HCl-treated fine fractions of montmorillonites  

Microsoft Academic Search

The <2 ?m fractions of SAz-1 (Cheto, Arizona, USA) and JP (Jelšový Potok, Slovakia) montmorillonites were treated with 6 M HCl for 30, 300 and 900 minutes at 95°C. The materials obtained were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetry (TG), infrared (IR) spectroscopy, and 29Si MAS NMR spectroscopy. The number of acid sites was determined from the

Christopher Breen; Jana Madejová; Peter Komadel

1995-01-01

122

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

123

Isotropic susceptibility shift under MAS: the origin of the split water resonances in 1H MAS NMR spectra of cell suspensions.  

PubMed

Bulk susceptibility variations in a multiphase system such as cultured cells and tissue have two manifestations: a dipolar field component outside the regular heterogenous region which introduces linebroadening, and an isotropic field part which results in a frequency shift. Previous NMR studies have emphasized the utility of magic angle spinning for averaging the dipolar component, particularly if the spins of interest are limited to one phase of a multiphase system such as a sample of liquid with air pockets or glass beads. However, in analyzing spectra from complex multiphase systems, such as cell suspensions and tissues, etc., the isotropic part is often neglected, leading to questionable interpretation of experimental results. The present study demonstrates that under magic angle spinning, the water resonance in NMR experiments of cell suspensions is split into two resolved peaks due to the isotropic susceptibility shift. These two peaks are assigned to a central core of cell free water and an outer cylindrical ring of tightly packed cells in close association with water. A comprehensive theory for this splitting is provided based on a coaxis cylinder model with different susceptibilities. The frequency difference is shown to be dependent on the susceptibility difference and also on the angle of the rotor in the magnetic field. The splitting distance of the two water peaks can be used to measure the susceptibility difference of water in these two phases. The susceptibility difference was measured for three different cell types: 3T3 F442A preadipocyte cells, mouse embryonic stem cells, and human red blood cells. PMID:12939759

Chen, Jin-Hong; Enloe, Brian M; Xiao, Yong; Cory, D G; Singer, Samuel

2003-09-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

125

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

PubMed

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

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

2008-02-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

127

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

SciTech Connect

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

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

2013-10-15

128

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

PubMed

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

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

2012-02-01

129

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

NASA Astrophysics Data System (ADS)

A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE13 fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE16 second-harmonic mode of the gyrotron) for DNP at 14.1 T (600 MHz 1H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ˜1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz 1H and double channel HX mode for 284 MHz 1H, with MAS sample temperatures ?85 K. Initial data at 6.7 T and ˜1 W pulsed microwave power are presented with 13C enhancements of 60 for a frozen urea solution (1H-13C CP), 16 for bacteriorhodopsin in purple membrane (1H-13C CP) and 22 for 15N in a frozen glycine solution (1H-15N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design.

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

2012-02-01

130

Pr 2Sn 2O 7 and Sm 2Sn 2O 7 as High-Temperature Shift Thermometers in Variable-Temperature 119Sn MAS NMR  

NASA Astrophysics Data System (ADS)

Two shift thermometers have been developed in order to determine the exact sample temperature at elevated temperatures in MAS NMR. The probe was calibrated for different temperatures and bearing pressures using the structural phase transition NMR spectra of carbon tetrabromide (319.86 K), DABCO (351.08 K), rubidium nitrate (437 K), and lithium sodium sulfate (791 K). Temperature-dependent 119Sn MAS NMR spectra of Pr 2Sn 2O 7 and Sm 2Sn 2O 7 were then recorded. The temperature dependence is caused by the hyperfine interaction between the paramagnetic electron spin and the 119Sn nucleus. Pr 2Sn 2O 7 proved to be an extremely sensitive linear high-temperature shift thermometer: its sensitivity is 14.1 ppm/K at room temperature and 2.7 ppm/K at 790 K. Sm 2Sn 2O 7 also proved to be very sensitive to temperature, although its dependence was not linear. At room temperature its sensitivity is 1.1 ppm/K. The temperature dependence of the shift can be fitted to an equation derived from the Van Vleck equation, taking into account the ground and the first excited states of Sm 3+.

Vanmoorsel, G. J. M. P.; Vaneck, E. R. H.; Grey, C. P.

131

Compounds of L(+)-ascorbic acid with dimethylthallium(III), dimethyltin(IV), and dibutyltin(IV): Synthesis, solid-state spectroscopy (CP\\/MAS 13C NMR and IR), and multi-NMR behavior in aqueous solution  

Microsoft Academic Search

Reaction of L(+)-ascorbic acid (H2Asc) with TlMe2OOCCH3, SnMe2O, and SnBu2Cl2 (in this last case, in the presence of Et3N) afforded [TlMe2(HAsc)]·12C3H8O, [SnMe2(Asc)], and [SnBu2(Asc)], respectively. The new compounds were studied in the solid state by CP\\/MAS 13C NMR and IR spectroscopy, and in aqueous solution by 1H, 13C, 205Tl, and 119Sn NMR spectroscopy. The thallium compound behaves as a salt.

José S. Casas; María V. Castaño; María S. García-Tasende; Teresa Pérez-Alvarez; Agustín Sánchez; José Sordo

1996-01-01

132

13C chemical shift map of the active cofactors in photosynthetic reaction centers of Rhodobacter sphaeroides revealed by photo-CIDNP MAS NMR.  

PubMed

13C photo-CIDNP MAS NMR studies have been performed on reaction centers (RCs) of Rhodobacter sphaeroides wild type (WT) that have been selectively labeled with an isotope using [5-13C]-delta-aminolevulinic acid.HCl in all the BChl and BPhe cofactors at positions C-4, C-5, C-9, C-10, C-14, C-15, C-16, and C-20. 13C CP/MAS NMR and 13C-13C dipolar correlation photo-CIDNP MAS NMR provide a chemical shift map of the cofactors involved in the electron transfer process in the RC at the atomic scale. The 13C-13C dipolar correlation photo-CIDNP spectra reveal three strong components, originating from two BChl cofactors, called P1 and P2 and assigned to the special pair, as well as one BPhe, PhiA. In addition, there is a weak component observed that arises from a third BChl cofactor, denoted P3, which appears to originate from the accessory BChl BA. An almost complete set of assignments of all the aromatic carbon atoms in the macrocycles of BChl and BPhe is achieved in combination with previous photo-CIDNP studies on site-directed BChl/BPhe-labeled RCs [Schulten, E. A. M., Matysik, J., Alia, Kiihne, S., Raap, J., Lugtenburg, J., Gast, P., Hoff, A. J., and de Groot, H. J. M. (2002) Biochemistry 41, 8708-8717], allowing a comprehensive map of the ground-state electronic structure of the photochemically active cofactors to be constructed for the first time. The reasons for the anomaly of P2 and the origin of the polarization on P3 are discussed. PMID:17630781

Prakash, Shipra; Alia, A; Gast, Peter; de Groot, Huub J M; Jeschke, Gunnar; Matysik, Jörg

2007-08-01

133

High-resolution MAS NMR analysis of PI3-SH3 amyloid fibrils: Backbone conformation and implications for protofilament assembly and structure  

PubMed Central

The SH3 domain of the PI3 kinase (PI3-SH3 or PI3K-SH3) readily aggregates into fibrils in vitro and has served as an important model system to investigate the molecular properties and mechanism of formation of amyloid fibrils. We describe the molecular conformation of PI3-SH3 in amyloid fibril form as revealed by magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy. The MAS NMR spectra of these fibrils display excellent resolution, with narrow 13C and 15N line widths, representing a high degree of structural order and the absence of extensive molecular motion for the majority of the polypeptide chain. We have identified the spin-systems of 82 of the 86 residues in the protein, and obtained sequential resonance assignments for 75 of them. Chemical shift analysis indicates that the protein subunits making up the fibril adopt a compact conformation consisting of four well-defined ?-sheet regions and four random-coil elements with varying degrees of local dynamics or disorder. The backbone conformation of PI3-SH3 in fibril form differs significantly from that of the native state of the protein, both in secondary structure and in the location of dynamic or disordered segments. The site-specific MAS NMR analysis of PI3-SH3 fibrils we report here is compared with previously published mechanistic and structural data, resulting in a detailed interpretation of the factors that mediate fibril formation by PI3-SH3 and allowing us to propose a possible model of the core structure of the fibrils. Our results confirm the structural similarities between PI3-SH3 fibrils and amyloids directly related to degenerative or infectious diseases.

Bayro, Marvin J.; Maly, Thorsten; Birkett, Neil R.; MacPhee, Cait E.; Dobson, Christopher M.; Griffin, Robert G.

2010-01-01

134

High-resolution MAS NMR analysis of PI3-SH3 amyloid fibrils: backbone conformation and implications for protofilament assembly and structure .  

PubMed

The SH3 domain of the PI3 kinase (PI3-SH3 or PI3K-SH3) readily aggregates into fibrils in vitro and has served as an important model system in the investigation of the molecular properties and mechanism of formation of amyloid fibrils. We describe the molecular conformation of PI3-SH3 in amyloid fibril form as revealed by magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy. The MAS NMR spectra of these fibrils display excellent resolution, with narrow (13)C and (15)N line widths, representing a high degree of structural order and the absence of extensive molecular motion for the majority of the polypeptide chain. We have identified the spin systems of 82 of the 86 residues in the protein and obtained sequential resonance assignments for 75 of them. Chemical shift analysis indicates that the protein subunits making up the fibril adopt a compact conformation consisting of four well-defined beta-sheet regions and four random-coil elements with varying degrees of local dynamics or disorder. The backbone conformation of PI3-SH3 in fibril form differs significantly from that of the native state of the protein, both in secondary structure and in the location of dynamic or disordered segments. The site-specific MAS NMR analysis of PI3-SH3 fibrils we report here is compared with previously published mechanistic and structural data, resulting in a detailed interpretation of the factors that mediate fibril formation by PI3-SH3 and allowing us to propose a possible model of the core structure of the fibrils. Our results confirm the structural similarities between PI3-SH3 fibrils and amyloid assemblies directly related to degenerative and infectious diseases. PMID:20707313

Bayro, Marvin J; Maly, Thorsten; Birkett, Neil R; Macphee, Cait E; Dobson, Christopher M; Griffin, Robert G

2010-09-01

135

Chemisorption study of hydrogen and methane by 1 H MAS NMR and conversion of methane in the presence of ethylene on Ag-Y zeolite  

Microsoft Academic Search

1H MAS NMR showed that hydrogen dissociatively adsorbs on Ag-Y and generates acidic protons and silver-hydride species (Agn-H). The peak due to Agn-H was observed at ?0.1ppm together with peaks due to acidic protons in the supercages (3.9ppm) and in the sodalite cages (4.7ppm). The hydrogen chemisorption on Ag-Y is reversible. Thus, the peaks at 3.9 and ?0.1ppm disappeared by

Toshihide Baba; Hidenori Sawada; Toshiaki Takahashi; Muneyoshi Abe

2002-01-01

136

Characterization of white Portland cement hydration and the CSH structure in the presence of sodium aluminate by 27Al and 29Si MAS NMR spectroscopy  

Microsoft Academic Search

The effects of hydrating a white Portland cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO2) at 5 and 20 °C are investigated by 27Al and 29Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO2 accelerates the hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO4\\/AlO4

Morten Daugaard Andersen; Hans J. Jakobsen; Joergen Skibsted

2004-01-01

137

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

Microsoft Academic Search

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

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

2005-01-01

138

(23)Na multiple-quantum MAS NMR of the perovskites NaNbO(3) and NaTaO(3).  

PubMed

The distorted perovskites NaTaO(3) and NaNbO(3) have been studied using (23)Na multiple-quantum (MQ) MAS NMR. NaTaO(3) was prepared by high temperature solid state synthesis and the NMR spectra are consistent with the expected room temperature structure of the material (space group Pbnm), with a single crystallographic sodium site. Two samples of NaNbO(3) were studied. The first, a commercially available sample which was annealed at 900 degrees C, showed two crystallographic sodium sites, as expected for the room temperature structure of the material (space group Pbcm). The second sample, prepared by a low temperature hydrothermal method, showed the presence of four sodium sites, two of which match the expected room temperature structure and the second pair, another polymorph of the material (space group P21ma). This is consistent with powder X-ray diffraction data which showed weak extra peaks which can be accounted for by the presence of this second polymorph. Density functional theory (DFT) calculations support our conclusions, and aid assignment of the NMR spectra. Finally, we discuss the measured NMR parameters in relation to other studies of sodium in high coordination sites in the solid state. PMID:16855721

Ashbrook, Sharon E; Le Pollès, Laurent; Gautier, Régis; Pickard, Chris J; Walton, Richard I

2006-08-01

139

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

PubMed

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

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

2009-08-28

140

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

141

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

SciTech Connect

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

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

2006-01-15

142

Formation and decomposition of N,N,N-trimethylanilinium cations on zeolite H-Y investigated by in situ stopped-flow MAS NMR spectroscopy.  

PubMed

Methylation of aniline by methanol on zeolite H-Y has been investigated by in situ (13)C MAS NMR spectroscopy under flow conditions. The in situ (13)C continuous-flow (CF) MAS NMR experiments were performed at reaction temperatures between 473 and 523 K, molar methanol-to-aniline ratios of 1:1 to 4:1, and modified residence times of (13)CH(3)OH between 20 and 100 (g x h)/mol. The methylation reaction was shown to start at 473 K. N,N,N-Trimethylanilinium cations causing a (13)C NMR signal at 58 ppm constitute the major product on the catalyst surface. Small amounts of protonated N-methylaniline ([PhNH(2)CH(3)](+)) and N,N-dimethylaniline ([PhNH(CH(3))(2)](+)) were also observed at ca. 39 and 48 ppm, respectively. After increase of the temperature to 523 K, the contents of N,N-dimethylanilinium cations and ring-alkylated reaction products strongly increased, accompanied by a decrease of the amount of N,N,N-trimethylanilinium cations. With application of the in situ stopped-flow (SF) MAS NMR technique, the decomposition of N,N,N-trimethylanilinium cations on zeolite H-Y to N,N-dimethylanilinium and N-methylanilinium cations was investigated to gain a deeper insight into the reaction mechanism. The results obtained allow the proposal of a mechanism consisting of three steps: (i) the conversion of methanol to surface methoxy groups and dimethyl ether (DME); (ii) the alkylation of aniline with methanol, methoxy groups, or DME leading to an equilibrium mixture of N,N,N-trimethylanilinium, N,N-dimethylanilinium, and N-methylanilinium cations attached to the zeolite surface; (iii) the deprotonation of N,N-dimethylanilinium and N-methylanilinium cations causing the formation of N,N-dimethylaniline (NNDMA) and N-methylaniline (NMA) in the gas phase, respectively. The chemical equilibrium between the anilinium cations carrying different numbers of methyl groups is suggested to play a key role for the products distribution in the gas phase. PMID:12071765

Wang, Wei; Seiler, Michael; Ivanova, Irina I; Sternberg, Ulrich; Weitkamp, Jens; Hunger, Michael

2002-06-26

143

Structure and NMR assignment in AlPO 4-15: A combined study by diffraction, MAS NMR and first-principles calculations  

Microsoft Academic Search

A multi-technique investigation involving X-ray diffraction, solid-state NMR and first-principle calculations was carried out on the aluminophosphate material AlPO4-15. A synchrotron X-ray single-crystal diffraction study was carried out on the same sample as that used in solid-state NMR studies. The model from the single crystal study, together with a model from a literature high resolution study of the same material,

Peter J. Byrne; John E. Warren; Russell E. Morris; Sharon E. Ashbrook

2009-01-01

144

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

2013-03-01

145

Two-dimensional MAS NMR correlation protocols involving double-quantum filtering of quadrupolar spin-pairs  

NASA Astrophysics Data System (ADS)

Three two-dimensional (2D) NMR homonuclear correlation techniques invoking double-quantum (2Q) filtration of the central transitions of half-integer spins are evaluated numerically and experimentally. They correlate directly detected single-quantum (1Q) coherences in the t2 domain with either of 1Q, two-spin 2Q or single-spin multiple-quantum coherence-evolutions in the indirect (t1) dimension. We employ experimental 23Na and 27Al NMR on sodium sulfite and the natural mineral sillimanite (SiAl2O5), in conjunction with simulated 2D spectra from pairs of dipolar-recoupled spins-3/2 and 5/2 at different external magnetic fields, to compare the correlation strategies from the viewpoints of 2D spectral resolution, signal sensitivity, implementational aspects and their relative merits for establishing internuclear proximities and quadrupolar tensor orientations.

Edén, Mattias

2010-05-01

146

Efficient Resonance Assignment of Proteins in MAS NMR by Simultaneous Intra- and Inter-residue 3D Correlation Spectroscopy  

PubMed Central

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 15N-13C transfers. However, the SPECIFIC-CP transfer efficiency is often compromised by molecular dynamics and probe performance. Here we show that one-bond ZF-TEDOR 15N-13C transfers provide simultaneous NCO and NCa transfers with at least as much sensitivity as SPECIFIC-CP for some non-crystalline samples. Furthermore, a 3D TEDOR-CC experiment provides heteronuclear sidechains 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.

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

2013-01-01

147

Al environment in tectosilicate and peraluminous glasses: A 27Al MQ-MAS NMR, Raman, and XANES investigation  

Microsoft Academic Search

Tecto-aluminosilicate and peraluminous glasses have been prepared by conventional and laser heating techniques, respectively, in the CaO-Al2O3-SiO2 system. The structure of these glasses were studied using Raman spectroscopy, X-ray absorption at the Al K-edge and 27Al NMR spectroscopy with two different high fields (400 and 750 MHz). Raman spectroscopy and X-ray absorption are techniques sensitive to the network polymerization and,

Daniel R. Neuville; Laurent Cormier; Dominique Massiot

2004-01-01

148

27A1 MAS NMR AND ALUMINUM X-RAY ABSORPTION NEAR EDGE STRUCTURE STUDY OF IMOGOLITE AND ALLOPHANES  

Microsoft Academic Search

This paper compares the results of 27A1 nuclear magnetic resonance spectroscopy (NMR) and AI-K-edge X-ray Absorption Near Edge Structure (XANES) of natural imogolite and allophanes and some crystaUine reference minerals. All soil allophanes studied contain 4-coordinated A1 (AlIV). The highest relative proportion of A1TM, 21% of the total AI, was found in Si-rich allophane. This value is close to that

I R. J. KIRKPATRICK; B. MONTEZ; G. CALAS; A. M. FLANK; P. LAGARDE; UA CNRS

149

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

Microsoft Academic Search

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

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

1996-01-01

150

Efficient polarization transfer between spin-1/2 and 14N nuclei in solid-state MAS NMR spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

151

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

NASA Astrophysics Data System (ADS)

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

Powell, Douglas Graham

1990-08-01

152

Dipolar Assisted Assignment Protocol (DAAP) for MAS solid-state NMR of rotationally aligned membrane proteins in phospholipid bilayers  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

154

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

PubMed

Double cross polarization (DCP) has been widely used for heteronuclear polarization transfer between (13)C and (15)N in solid-state magic-angle spinning (MAS) NMR. However, DCP is such sensitive to experimental settings that small variations or deviations in RF fields would deteriorate its efficiency. Here, we report on asymmetric simultaneous phase-inversion cross polarization (referred as aSPICP) for selective polarization transfer between low-? (13)C and (15)N spins. We have demonstrated through simulations and experiments using biological solids that the asymmetric duration in the simultaneous phase-inversion cross polarization scheme leads to efficient polarization transfer between (13)C and (15)N even with large chemical shift anisotropies in the presence of B1 field variations or mismatch of the Hartmann-Hahn conditions. This could be very useful in the aspect of long-duration experiments for membrane protein studies at high fields. PMID:24691099

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

2014-05-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

156

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

SciTech Connect

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

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

2003-02-01

157

Surface alumina species on modified titanium dioxide: A solid-state (27)Al MAS and 3QMAS NMR investigation of catalyst supports.  

PubMed

(27)Al MAS and 3QMAS NMR have been used to study Al(2)O(3)/TiO(2) catalyst supports synthesized via excess-solution impregnation and surface sol-gel methods. Temperature and alumina loading level strongly affect chemical states of aluminum oxide species observed. Surface cations, Al(H2O)6(3+), a surface alumina monolayer, and disordered transitional aluminas (multilayers) and alpha-alumina, coexist on the TiO(2) surface. Chemical shift and quadrupole coupling constants are reported for the major species identified in 3QMAS experiments. Gold particle catalysts prepared from supports calcined at 500 degrees C have optimum catalytic activity in CO oxidation, and smallest gold particle size for supports, which show maximum monolayer type octahedral alumina on the titania surface. PMID:20542414

Hagaman, Edward W; Jiao, Jian; Chen, Banghao; Ma, Zhen; Yin, Hongfeng; Dai, Sheng

2010-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

159

The partial (1)H NMR spectra of Al-OH and molecular H(2)O in hydrous aluminosilicate glasses: Component-Resolved analysis of (27)Al-(1)H cross polarization and (1)H spin-echo MAS NMR spectra.  

PubMed

The Component-Resolved methodology was applied to (1)H spin-echo and (27)Al-(1)H cross polarization (CP) MAS NMR data of aluminosilicate glasses. The method was able to resolve two components with different T2 relaxation rates, hydroxyl groups (OH) and molecular water (H(2)O(mol)), from the spin-echo data and to determine partial spectra and the relative abundances of OH and H(2)O(mol). The algorithm resolved two to three components with different (27)Al-(1)H CP dynamics from the (27)Al-(1)H cross polarization data; the obtained partial NMR spectra for Al-OH are in excellent agreement with those obtained previously from the difference spectra between spectra with various contact times and confirm previous quantitative results and models for the Al-OH, Si-OH and H(2)O(mol) speciation (Malfait and Xue, 2010). PMID:20418075

Malfait, Wim J; Xue, Xianyu

2010-01-01

160

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

161

Solubilization and localization of weakly polar lipids in unsonicated egg phosphatidylcholine: A sup 13 C MAS NMR study  

SciTech Connect

The weakly polar lipids cholesteryl ester, triacylglycerol, and diacylglycerol incorporate to a limited extent into the lamellar structure of small unilamellar vesicles. The localization of the carbonyl group(s) at the aqueous interface was detected by ({sup 13}C)carbonyl chemical shift changes relative to the neat unhydrated lipid. This study uses {sup 13}C NMR to investigate the interactions of thes lipids with unsonicated (multilamellar) phosphatidylcholine, a model system for cellular membranes and surfaces of emulsion particles with low curvature. Magic angle spinning reduced the broad lines of the unsonicated dispersions to narrow lines comparable to those from sonicated dispersions. ({sup 13}C)Carbonyl chemical shifts revealed incorporation of the three lipids into the lamellar structure of the unsonicated phospholipids and a partial hydration of the carbonyl groups similar to that observed in small vesicles. Other properties of interfacial weakly polar lipids in multilayers were similar to those in small unilamellar bilayers. There is thus a general tendency of weakly polar lipids to incorparate at least to a small extent into the lamellar structure of phospholipids and take on interfacial properties that are distinct from their bulk-phase properties. This pool of surface-located lipid is likely to be directly involved in enzymatyic transformations and protein-mediated transport. The {sup 13}C magic angle spinning NMR method may be generally useful for determining the orientation of molecules in model membranes.

Hamilton, J.A. (Boston Univ. School of Medicine, MA (United States)); Fujito, D.T.; Hammer, C.F. (Georgetown Univ., Washington, DC (United States))

1991-03-19

162

Influence of sodium ion dynamics on the 23Na quadrupolar interaction in sodalite: a high-temperature 23Na MAS NMR study.  

PubMed

High-temperature 33Na MAS NMR experiments up to 873 K for a number of different sodalites (Na8[AlSiO4]6(NO3)2, Na8[AlSiO4]6(NO2)2, Na8[AlSiO4]6I2, Na7.9[AlSiO4]6(SCN)7.9 x 0.5H2O, Na8[AlGeO4]6(NO3)2, and Na7[AlSiO4]6(H3O2) x 4H2O) were carried out. The spectra of the first five sodalites consist of a quadrupolar MAS pattern with different quadrupolar coupling constants. The quadrupolar interaction for the thiocyanate sodalite, the nitrate aluminosilicate, and germanate sodalite decreases strongly passing a coalescence state on heating, while the quadrupolar interaction of the iodide and nitrite sample shows nearly no change. The basic hydrosodalite shows an asymmetric lineshape at room temperature and, between 350 and 370 K, a second line due to the evaporation of cage-water emerges. The linewidth increases with rising temperature. The temperature dependence of the quadrupolar interaction seems to be a function of the sodalite beta-cage expansion. Two conceivable jump mechanisms are proposed for a tetrahedral two-site jump between occupied and unoccupied tetrahedral sites. PMID:11270743

Fechtelkord, M

2000-01-01

163

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

165

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 Al 3+ 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

166

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

PubMed

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

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

2005-03-10

167

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

168

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

NASA Astrophysics Data System (ADS)

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

Dou, S.

2009-04-01

169

Structures and thermal and hydrothermal stabilities of sulfonated poly(organosiloxanes) by /sup 29/Si and /sup 13/C CP/MAS NMR  

SciTech Connect

High-resolution /sup 29/Si and /sup 13/C cross polarization/magic-angle spinning (CP/MAS) NMR spectroscopies have been applied to poly((sulfophenyl)siloxane) and poly((sulfopropyl)siloxane) in order to examine their thermal and hydrothermal stability. The effects of the treatments on the catalytic activity for the alcohol dehydration were also studied. Under nonsteaming conditions, both siloxanes have much higher thermal stability than Amberlyst-15. Thermal stability is in a decreasing order, poly((sulfophenyl)siloxane) (573 K) > poly((sulfopropyl)siloxane) (543 K) > Amberlyst-15 (468 K), while the thermal stability under steaming conditions is in the order of poly((sulfopropyl)siloxane) (543 K) > poly((sulfophenyl)siloxane) = Amberlyst-15 (468 K). The thermal degradation of the poly((sulfophenyl)siloxane) mainly occurs by the rupture of the C-Si bonds between the benzene ring and the siloxane chain. The steam greatly affects the thermal stability of poly((sulfophenyl)siloxane). Thus, under steaming conditions, thermal degradation occurred at much lower temperatures than under nonsteaming conditions. The thermal degradation of the poly((sulfopropyl)siloxane) mainly occurs at the C-C bond in the sulfopropyl groups. Steam does not affect the thermal stability of poly((sulfopropyl)siloxane).

Suzuki, S.; Ono, Y.; Nakata, S.; Asaoka, S.

1987-03-12

170

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

PubMed Central

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

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

2013-01-01

171

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

172

A sequential assignment procedure for proteins that have intermediate line widths in MAS NMR spectra: amyloid fibrils of human CA150.WW2.  

PubMed

The second WW domain (WW2) of CA150, a human transcriptional activator, forms amyloid fibrils in vitro under physiological conditions. Based on experimental constraints from MAS NMR spectroscopy experiments, alanine scanning and electron microscopy, a structural model of CA150.WW2 amyloid fibrils was calculated earlier. Here, the assignment strategy is presented and suggested as a general approach for proteins that show intermediate line width. The (13)C,(13)C correlation experiments were recorded on fully or partially (13)C-labelled fibrils. The earlier (13)C assignment (26 residues) was extended to 34 of the 40 residues by direct (13)C-excitation experiments by using a deuterated sample that showed strongly improved line width. A 3D HNC-TEDOR (transferred-echo double-resonance) experiment with deuterated CA150.WW2 fibrils yielded 14 amide nitrogen and proton resonance assignments. The obtained chemical shifts were compared with the chemical shifts determined with the natively folded WW domain. TALOS (Torsion angle likelihood obtained from shift and sequence similarity) predictions confirmed that, under physiological conditions, the fibrillar form of CA150.WW2 adopts a significantly different beta structure than the native WW-domain fold. PMID:18642254

Becker, Johanna; Ferguson, Neil; Flinders, Jeremy; van Rossum, Barth-Jan; Fersht, Alan R; Oschkinat, Hartmut

2008-08-11

173

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

174

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

PubMed

Molybdenum is a transition metal (refers to the "d" block of the periodic table) whose atom has an incomplete d sub-shell. It is known that in silicate glasses molybdenum may exist under four oxidation states: Mo(6+), Mo(5+), Mo(4+) and Mo(3+), simultaneously molybdenum cations, depending on their content in the glass network, may either be a glass forming component, or act as a modifier. The contemporary literature data show studies conducted mostly on the structure of silicate, phosphate, borate and borosilicate glasses containing molybdenum ions, but not silicate-phosphate glasses. Therefore, the author has undertaken detailed studies using FTIR, Raman and (31)P MAS NMR techniques in order to examine the effect of MoO3 addition into the structure of silicate-phosphate glasses from SiO2P2O5K2OCaOMgO system. On the basis of obtained results it was concluded that molybdenum ions in the analysed glasses act as a modifier, which follows from the gradual breakage of oxygen bridges, i.e. POP, SiOSi, and SiOP, and the following formation of connections such as Mo[MoO4]OSi and/or Mo[MoO4]OP. In summary, it is concluded that the increase of MoO3 content (up to 4.4mol.%) in the structure of glasses of SiO2P2O5K2OMgOCaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation. PMID:24759778

Szumera, Magdalena

2014-09-15

175

The crystal structure of BaPO3F revisited--a combined X-ray diffraction and solid-state 19F, 31P MAS NMR study.  

PubMed

Barium monofluorophosphate, BaPO3F, was prepared in a polycrystalline form by fast precipitation, whereas single crystals were obtained using a long-lasting gel growth method. The samples were characterized by powder- and single-crystal X-ray diffraction, which revealed orthorhombic symmetry for the polycrystalline material and monoclinic symmetry for the single crystals. Both phases belong to the same order-disorder (OD) family and can be derived from the baryte structure (BaSO4) by replacing the SO4(2-) anions with isoelectronic PO3F(2-) anions in two orientations. BaPO3F can crystallize in an infinite number of locally equivalent layer stacking sequences. The polycrystalline material represents the family structure and is characterized by a purely random stacking of layers. Its structure is isotypic with the baryte structure and contains disordered PO3F(2-) anions. The single crystals [P21/c, Z = 4, a = 11.3105(7) Å, b = 8.6934(5) Å, c = 9.2231(4) Å, ? = 127.819(3)°, R[F(2) > 2?(F(2))] = 0.036, 4146 structure factors, 110 parameters] crystallize as a polytype with a maximum degree of order (MDO), which can be regarded as a two-fold superstructure of the baryte-structure type. Fragments of the second MDO polytype are evidenced by systematic twinning by mirroring at (100). Solid-state (19)F and (31)P MAS NMR spectra of polycrystalline BaPO3F acquired at magnetic fields of 7.05 T and 14.09 T resolve resonances from two distinct (19)F sites and (31)P sites, in accordance with the local symmetry of the OD description. From these spectra, the (19)F chemical shift anisotropies and (1)J(P-F) couplings are determined for the two distinct (19)F sites and an average set of chemical shift anisotropy parameters for the two (31)P sites. PMID:23838743

Stöger, Berthold; Weil, Matthias; Skibsted, Jørgen

2013-08-28

176

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

PubMed

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 carbonate (giving Residue 1); 50 mM CDTA, 50 mM sodium carbonate and 1 M KOH (giving Residue 2); and 50 mM CDTA, 50 mM sodium carbonate and 4 M KOH (giving Residue 3). The molecular ordering of cellulose in Residue 1 was similar to that in unextracted walls: the cellulose was almost all crystalline, with 43% of molecules contained in crystallite interiors and similar proportions of the triclinic (I(alpha)) and monoclinic (I(beta)) crystal forms. Residue 2 was partly decrystallized and the remaining crystallites were mostly in the I(beta) form. Residue 3 was a mixture of cellulose II, cellulose I and amorphous cellulose. The presence of signals at 100.0 and 102.3 ppm in the spectra of Residues 1 and 2, but not of unextracted cell walls, suggested that the extractions giving these residues caused some of the non-cellulosic polysaccharides, possibly xyloglucans and galactoglucomannans, to become relatively well ordered, for example through interactions with cellulose crystallite surfaces. PMID:11909591

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

2002-04-01

177

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

NASA Astrophysics Data System (ADS)

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

Szumera, Magdalena

2014-09-01

178

13 C CP\\/MAS and 2 H NMR study of tert-butyl alcohol dehydration on H-ZSM-5 zeolite. Evidence for the formation of tert-butyl cation and tert-butyl silyl ether intermediates  

Microsoft Academic Search

The dehydration reaction of tert-butyl alcohol, selectively labelled with13C in CH3 or C-O groups (t-BuOH[2-13C2] andt-BuOH[1-13C]), as well as selectively deuterated in methyl groups (t-BuOH[2-2H9]), was studied on H-ZSM-5 zeolite simultaneously with13 C CP\\/MAS and2H solid state NMR. When adsorbed and dehydrated on zeolite at 296 K,t-BuOH[2-13C1] andt-BuOH[1-13C] give rise to identical13C CP\\/MAS NMR spectra of oligomeric aliphatic products. This

Alexander G. Stepanov; Kirill I. Zamaraev; John M. Thomas

1992-01-01

179

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

180

{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

181

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 with…

Ramaswami, Rama

2008-01-01

182

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

PubMed

Two-dimensional (2D) cross-polarization magic angle spinning (CP-MAS) (2)H-(13)C heteronuclear correlation (HETCOR) experiments were utilized to indirectly detect site-specific deuterium MAS powder patterns. The (2)H-(13)C cross-polarization efficiency is orientation-dependent and non-uniform for all crystallites. This leads to difficulty in extracting the correct (2)H MAS quadrupole powder patterns. In order to obtain accurate deuterium line shapes, (13)C spin lock rf field, spin lock rf ramp and CP contact time were carefully calibrated with the assistance of theoretical simulations. The extracted quadrupole patterns for U-[(2)H/(13)C/(15)N]-alanine indicate that the methyl deuterium undergoes classic, three-site jumping in the fast motion regime (10(-8)-10(-12)s) and the methine deuterium has a rigid deuterium powder pattern. For U-[(2)H/(13)C/(15)N]-phenylalanine, indirectly detected deuterium line shapes illustrate that the aromatic ring undergoes 180° flips in the fast motion regime while (2)H? and (2)H? are completely rigid. The experimental deuterium line shapes for U-[(2)H/(13)C/(15)N]-proline reflect that (2)H?, (2)H? and (2)H? are subjected to fast, two-site reorientations at an angle of (15±5)°, (30±5)° and (25±10)° respectively. In addition, an approach that combines a composite inversion pulse with (2)H-(13)C CP-MAS is applied to measure (2)H spin-lattice relaxation times in a site-specific, (13)C-detected fashion. PMID:23174312

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

2013-01-01

183

HR Explorer  

Microsoft Academic Search

At the European Laboratory for Particle Physics Research (CERN), Geneva Switzerland we are using OracleHR for managing our human resources since 1995. After the first year of production it became clear that there was a strong need for an easy-to-use Decision Support Tool exploring the data in OracleHR. This paper illustrates an approach which we have adopted to provide on-line

M Möller; J Purvis

1997-01-01

184

MAS NMR structure refinement of uniformly 13C enriched chlorophyll a/water aggregates with 2D dipolar correlation spectroscopy  

NASA Astrophysics Data System (ADS)

2D MAS dipolar correlation spectroscopy of uniformly 13C enriched chlorophyll a/water aggregates was performed using broadband RFDR to promote exchange of coherence through homonuclear dipolar couplings. It is shown experimentally that incorporation of TPPI and coherence pathway selection in the RFDR pulse scheme yields virtually pure 2D absorption lineshapes. From a series of 2D correlation spectra collected at two spinning speeds with different mixing times of ˜ 1 and ˜ 10 ms all 13C resonances of the chlorophyll a molecule were assigned. The spectra with the longer mixing times reveal through-space intermolecular polarization transfer. This demonstrates that structural information can be obtained from uniformly 13C enriched samples, which paves the way for a full structural characterization of amorphous solids.

Boender, G. J.; Raap, J.; Prytulla, S.; Oschkinat, H.; de Groot, H. J. M.

1995-05-01

185

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

PubMed

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

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

2012-10-17

186

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

187

2-THIOXO-1,3,2-DITHIAPHOSPHOLANES SOLIDSTATE MAS NMR AND CRYSTAL STRUCTURE INVESTIGATIONS AS WELL AS IGLO CALCULATIONS OF P SHIELDING TENSORS  

Microsoft Academic Search

2-Thioxo-1,3,2-dithiaphospholanes with P-substituents R = Me, Et, i-Pr, t-Bu, Ph, 3,5-Me2C6H3, and 4-MeOC6H4 were prepared and characterized by solution and high resolution solid-state P and C NMR spectroscopy. The influence of different alkyl and aryl substituents at the phosphorus atom on the anisotropy of P chemical shift and on the molecular structure is discussed. The orientation of the principal axes

Peggy Schwarz; Gisela Ohms; Kerstin Krüger; Gisbert Grossmann; Volker Kaiser

1998-01-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

189

Structural organization of silver(I) complexes with O,O?-dialkyl dithiophosphates: Solid-state 13 C and 31 P CP\\/MAS NMR and single-crystal X-ray diffraction studies  

Microsoft Academic Search

Silver(I) complexes with four symmetrically substituted O,O?-dialkyl derivatives of dithiophosphoric acid of the general formula\\u000a [Ag{S2P(OR)2}]\\u000a n\\u000a (R = C2H5, i-C3H7, C4H9, and s-C4H9) were obtained. Their structures and spectroscopic characteristics were studied by solid-state 13C and 31P CP\\/MAS NMR spectroscopy and X-ray diffraction analysis. The parameters of the anisotropy of the 31P chemical shift 31P-?\\u000a aniso\\u000a and ? (?

A. V. Ivanov; S. A. Zinkin; A. V. Gerasimenko; O. N. Antzutkin; W. Forsling

2007-01-01

190

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

PubMed Central

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

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

2014-01-01

191

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

PubMed

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

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

2014-02-14

192

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

PubMed

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

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

2014-01-01

193

Conformation and molecular packing of n-alkyl side chains protruding from ?-helical poly ( L-glutamates) as studied by 13C CP/MAS NMR spectroscopy  

NASA Astrophysics Data System (ADS)

13C NMR spectra of a series of poly( L-glutamates) with n-alkyl side chains of various lengths ( n = (number of carbon atoms in the alkyl group) = 8, 12, 14, 16 and 18) were recorded by the cross polarization/magic angle spinning method, in order to elucidate conformational features and molecular packing through the observation of 13 13C chemical shifts. From these experimental results, it was found that the main chain of the poly(?- n-alkyl L-glutamates) takes the ?-helical conformation irrespective of side chain length, and the n-alkyl side chains can participate in the crystallization if they are long enough. In these side chain crystallites, all- trans zigzag conformation of alkyl chain was clarified and the type of molecular packing was presumed based on the reference data of n-alkanes. Further, we discuss the conformation of n-alkyl side chains of poly( n-stearyl L-glutamate) in isotropic solution and liquid crystalline solution.

Tsukahara, Makoto; Yamanobe, Takeshi; Komoto, Tadashi; Watanabe, Junji; Ando, Isao; Uematsu, Ichitaro

1987-07-01

194

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

SciTech Connect

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

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

2004-05-01

195

?High Resolution-Magic-Angle Spinning NMR Spectroscopy for Metabolic Phenotyping of Caenorhabditis elegans.  

PubMed

Analysis of model organisms, such as the submillimeter-size Caenorhabditis elegans, plays a central role in understanding biological functions across species and in characterizing phenotypes associated with genetic mutations. In recent years, metabolic phenotyping studies of C. elegans based on (1)H high-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy have relied on the observation of large populations of nematodes, requiring labor-intensive sample preparation that considerably limits high-throughput characterization of C. elegans. In this work, we open new platforms for metabolic phenotyping of C. elegans mutants. We determine rich metabolic profiles (31 metabolites identified) from samples of 12 individuals using a (1)H NMR microprobe featuring high-resolution magic-angle coil spinning (HR-MACS), a simple conversion of a standard HR-MAS probe to ?HR-MAS. In addition, we characterize the metabolic variations between two different strains of C. elegans (wild-type vs slcf-1 mutant). We also acquire a NMR spectrum of a single C. elegans worm at 23.5 T. This study represents the first example of a metabolomic investigation carried out on a small number of submillimeter-size organisms, demonstrating the potential of NMR microtechnologies for metabolomics screening of small model organisms. PMID:24897622

Wong, Alan; Li, Xiaonan; Molin, Laurent; Solari, Florence; Elena-Herrmann, Bénédicte; Sakellariou, Dimitris

2014-06-17

196

Lead hydro sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: synthesis and structure determination by combining X-ray rietveld refinement, 1H MAS NMR FTIR and XANES spectroscopy.  

PubMed

Ion exchange of the sodium hydro sodalites [Na3(H2O)4]2-[Al3Si3O12]2 [Na4(H3O2)]2[Al3Si3O12]2 and [Na4(OH)]2[Al3Si3O12]2 with aqueous Pb(NO3)2 solutions yielded, whichever reactant sodalite phase was used, the same lead hydro sodalite, [Pb2(OH)-(H2O)3]2[Al3Si3O12]2. Thus, in the case of the non-basic reactant [Na3(H2O)4]2-[Al3Si3O12]2 an overexchange occurs with respect to the number of nonframework cationic charges. Rietveld structure refinement of the lead hydro sodalite based on powder X-ray diffraction data (cubic, a = 9.070 A, room temperature, space group P43n) revealed that the two lead cations within each polyhedral sodalite cage form an orientationally disordered dinuclear [Pb2(micro-OH)(micro-H2O)(H2O)2]3+ complex. Due to additional lead framework oxygen bonds the coordination environment of each metal cation (CN 3+3) is approximately spherical, and clearly the lead 6s electron lone pair is stereochemically inactive. This is also suggested by the absence of a small peak at 13.025 keV, attributed in other Pb2+-O compounds to an electronic 2p-6s transition, in the PbL3 edge XANES spectrum. 1H MAS NMR and FTIR spectra show that the hydrogen atoms of the aqua hydroxo complex (which could not be determined in the Rietveld analysis) are involved in hydrogen bonds of various strengths. PMID:11931109

Eiden-Assmann, S; Schneider, A M; Behrens, P; Wiebcke, M; Engelhardt, G; Felsche, J

2000-01-01

197

XRD and {sup 29}Si MAS-NMR spectroscopy across the {beta}-Lu{sub 2}Si{sub 2}O{sub 7}-{beta}-Y{sub 2}Si{sub 2}O{sub 7} solid solution  

SciTech Connect

Samples in the system Lu{sub 2-x}Y{sub x}Si{sub 2}O{sub 7} (0=MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the {sup 29}Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict {sup 29}Si chemical shifts in silicates is applied here to obtain the theoretical variation in {sup 29}Si chemical shift values in the system Lu{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} and the results compare favorably with the values obtained experimentally.

Becerro, Ana I. [Departamento de Quimica Inorganica-Instituto de Ciencia de Materiales de Sevilla, Universidad de Sevilla-CSIC. Avda. Americo Vespucio, s/n. 41092 Sevilla (Spain)]. E-mail: anieto@icmse.csic.es; Escudero, Alberto [Departamento de Quimica Inorganica-Instituto de Ciencia de Materiales de Sevilla, Universidad de Sevilla-CSIC. Avda. Americo Vespucio, s/n. 41092 Sevilla (Spain)

2005-01-15

198

SCAR-B MAS  

... properties. Study the impact of biomass burning and urban/industrial aerosol on the atmosphere and climate by measuring the properties of urban and industrial pollution dominated by sulfate particles. Project Title:  MAS ...

2013-01-10

199

Temperature Dependence of 207Pb MAS Spectra of Solid Lead Nitrate. An Accurate, Sensitive Thermometer for Variable-Temperature MAS  

Microsoft Academic Search

The remarkably sensitive temperature dependence of the207Pb chemical shift in magic-angle-spinning (MAS) spectra of lead nitrate provides an excellent method for thermometry in solid-state NMR. The temperature dependence is uniform over a range of at least ?130 to +150°C, and also the NMR sensitivity and linewidth are very favorable. It is demonstrated that lead nitrate can be used in MAS

ANTHONY BIELECKI; DOUGLAS P. BURUM

1995-01-01

200

Single-crystal growth and characterization of disilver(I) monofluorophosphate(V), Ag2PO3F: crystal structure, thermal behavior, vibrational spectroscopy, and solid-state 19F, 31P, and 109Ag MAS NMR spectroscopy.  

PubMed

Single crystals of disilver(I) monofluorophosphate(V), Ag2PO3F (1), were obtained by slow evaporation of a diluted aqueous Ag2PO3F solution. Compound 1 adopts a new structure type and crystallizes in the monoclinic space group C2/c with eight formula units and lattice parameters of a = 9.2456(8) A, b = 5.5854(5) A, c = 14.7840(13) A, and beta = 90.178(2) degrees. The crystal structure of 1 [R(F2 > 2sigma(F2) = 0.0268, wR(F2 all) = 0.0665] is composed of three crystallographically independent Ag+ cations and PO3F2- anions as single building units. The oxygen environment around each of the Ag+ cations is different, with one Ag+ in distorted octahedral (d(Ag-O) = 2.553 A), one in nearly rectangular (d(Ag-O) = 2.445 A), and one in distorted tetrahedral (d(Ag-O) = 2.399 A) coordination. Additional Ag-F contacts to more remote F atoms located at distances >2.80 A augment the coordination polyhedra for the two latter Ag+ cations. The monofluorophosphate anion deviates slightly from C3v symmetry and exhibits the characteristic differences in bond lengths, with a mean of 1.510 A for the P-O bonds and one considerably longer P-F bond of 1.575(2) A. Compound 1 was further characterized by vibrational spectroscopy (Raman and IR) and solid-state 19F, 31P, and 109Ag MAS NMR spectroscopy. The value for the isotropic one-bond P-F coupling constant in 1 is 1JPF = -1045 Hz. Thermal analysis (TG, DSC) revealed a reversible phase transition at 308 degrees C, which is very close to the decomposition range of 1. Under release of POF3, Ag4P2O7 and Ag3PO4 are the thermal decomposition products at temperatures above 450 degrees C. PMID:17257023

Weil, Matthias; Puchberger, Michael; Füglein, Ekkehard; Baran, Enrique J; Vannahme, Julia; Jakobsen, Hans J; Skibsted, Jørgen

2007-02-01

201

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  

Microsoft Academic Search

A multi-technique approach was applied in order to fully characterize four low-level unknown impurities of GW876008, a novel CRF1 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

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

2010-01-01

202

Mixed anion effect of silver ion conducting glasses in the systems AgIAg 2MoO 4Ag 3PO 4 and AgIAg 2MoO 4Ag 2PO 3.5 and structural study by 31P MAS-NMR  

Microsoft Academic Search

Glasses of various compositions were prepared in the systems AgI-Ag2MoO4-Ag3PO4 and AgI-Ag2MoO4-Ag2PO3.5; their silver ion conductivities were measured and the structures of constituent oxoanions were investigated by 31P MAS-NMR. In the AgI-Ag2MoO4-Ag3PO4 glasses with a constant AgI content, the conductivities linearly changed with the composition parameter y = [P]([P]+ [Mo]), which denotes the ratio of the number of phosphorus atoms

Nobuya Machida; Masashi Kawachi; Akira Ueda; Toshihiko Shigematsu; Norihiko Nakanishi; Masanari Takahashi; Tsutomu Minami

1995-01-01

203

Classification of commercial Catuaba samples by NMR, HPLC and chemometrics.  

PubMed

For over a century, Catuaba has been used in Brazilian folk medicine as an aphrodisiac even though the identity of the plant material employed is often uncertain. The species recommended by the Brazilian Pharmacopeia is Anemopaegma arvense (Bignoniaceae), but many other plants, regionally known as Catuaba, are commercialised. Frequently, the quality control of such a complex system is based on chemical markers that do not supply a general idea of the system. With the advent of the metabolomics approach, a global analysis of samples becomes possible. It appears that (1)H-NMR is the most useful method for such application, since it can be used as a wide-spectrum chemical analysis technique. Unfortunately, the generated spectra is complex so a possible approach is to look at the metabolite profile as a whole using multivariate methods, for example, by application of principal component analysis (PCA). In the present paper, we describe for the first time a proton high-resolution magic angle spinning nuclear magnetic resonance ((1)H-HR-MAS NMR) method coupled with PCA for the metabolomic analysis of some commercial Catuaba samples, which provided a reduction in the time required for such analysis. A comparative study of HPLC, HR-MAS and liquid-NMR techniques is also reported. PMID:17890569

Daolio, Cristina; Beltrame, Flávio L; Ferreira, Antonio G; Cass, Quezia B; Cortez, Diógenes Aparício Garcia; Ferreira, Márcia M C

2008-01-01

204

Penta-coordinated Al 3+ ions as preferential nucleation sites for BaO on ?-Al 2O 3: An ultra-high-magnetic field 27Al MAS NMR study  

Microsoft Academic Search

We report the first observation of preferential anchoring of an impregnated catalytic phase onto penta-coordinated Al3+ sites on the surface of ?-Al2O3. The interaction of barium oxide with a ?-alumina support was investigated by high resolution solid state 27Al magic angle spinning NMR at an ultra-high magnetic field of 21.1 T and at sample spinning rates of up to 23

Ja Hun Kwak; Jian Zhi Hu; Do Heui Kim; Janos Szanyi; Charles H. F. Peden

2007-01-01

205

Slow magic angle sample spinning: a non- or minimally invasive method for high-resolution 1H nuclear magnetic resonance (NMR) metabolic profiling.  

PubMed

High-resolution (1)H magic angle spinning nuclear magnetic resonance (NMR), using a sample spinning rate of several kilohertz 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 minimally 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 H(2)O, where an unusually large magnetic susceptibility field gradient is obtained. PMID:21207300

Hu, Jian Zhi

2011-01-01

206

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

207

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

2011-10-01

208

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

209

HR outsourcing: threat or opportunity?  

Microsoft Academic Search

Purpose – The debate on human resource (HR) outsourcing is polarised. HR outsourcing is seen as an opportunity for the HR function by some and as a threat by others. The first view suggests that HR outsourcing is an instrument creating time for HR to become a strategic partner. The second view considers HR outsourcing as a cost-cutting instrument gradually

Jeroen Delmotte; Luc Sels

2008-01-01

210

Quantification of amounts and (13)C content of metabolites in brain tissue using high- resolution magic angle spinning (13)C NMR spectroscopy.  

PubMed

Metabolic pathway mapping using (13)C NMR spectroscopy has been used extensively to study interactions between neurons and glia in the brain. Established extraction procedures of brain tissue are time consuming and may result in degradation of labile substances. We examined the potential of mapping (13)C-enriched compounds in intact brain tissue using high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. Sprague-Dawley rats received an intraperitoneal injection of [1,6-(13)C]glucose, and 15 min later the animals were subjected to microwave fixation of the brain. Quantification of concentration and (13)C labelling of metabolites in intact rat thalamus were carried out based on exogenous ethylene glycol concentrations measured from (1)H NMR spectra using an ERETIC (Electronic REference To access In vivo Concentrations) signal. The results from intact tissue were compared with those from perchloric acid-extracted brain tissue. Amounts of (13)C labelling at different positions (C2, C3 and C4) in glutamate, glutamine, gamma-aminobutyric acid and aspartate measured in either intact tissue or perchloric acid extracts were not significantly different. Proton NMR spectra were used for quantification of six different amino acids plus lactate, inositol, N-acetylaspartate, creatine and phosphocreatine. Again, results were very similar when comparing the methods. To our knowledge, this is the first time quantitative (13)C NMR spectroscopy measurements have been carried out on intact brain tissue ex vivo using the HR-MAS technique. The results show that HR-MAS (13)C NMR spectroscopy in combination with (1)H NMR spectroscopy and the ERETIC method is useful for metabolic studies of intact brain tissue ex vivo. PMID:19012315

Risa, Oystein; Melø, Torun Margareta; Sonnewald, Ursula

2009-04-01

211

HR Internet Guide  

NSDL National Science Digital Library

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

2007-01-03

212

HR Structure and HR Knowledge Transfer between Subsidiaries in China  

ERIC Educational Resources Information Center

Purpose: This paper attempts to examine the issue concerning human resource (HR) structures and the transfer of HR knowledge to discover whether and how HR structure facilitates the transfer of HR knowledge between subsidiaries of an MNC in China. Design/methodology/approach: The investigation, being of an exploratory nature, follows the tradition…

Wang-Cowham, Cindy

2008-01-01

213

NMR Spectroscopy of Experimentally Shocked Silicate Minerals  

Microsoft Academic Search

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. ²⁹Si NMR spectra were determined for quartz and labradorite feldspar and ²⁷Al and ²³Na spectra for labradorite. Both minerals were shocked to 7.5, 16.4, and 22 GPA using the Sandia Momma Bear'' recovery fixtures. The MAS NMR results for quartz are in

R. T. Cygan; M. B. Boslough; R. J. Kirkpatrick

1991-01-01

214

NMR Study on the Acidity of TS1 Zeolite  

Microsoft Academic Search

The acidic properties of TS-1 and Silicalite-1 zeolites have been investigated by the solid-state MAS NMR technique capable of in situ sample pretreatment. As shown by a combination of the 31P MAS NMR and 1H MAS NMR techniques with trimethylphosphine, not only Brønsted acid sites but also Lewis acid sites exist in the TS-1 zeolites. Moreover, TS-1 zeolite is more

Jianqin Zhuang; Zhimin Yan; Xiumei Liu; Xianchun Liu; Xiuwen Han; Xinhe Bao; Ulrich Mueller

2002-01-01

215

HR 5341, HD 142070, HR 6967 & HR 8434 uvby phot. (Adelman, 2001)  

NASA Astrophysics Data System (ADS)

Differential Stroemgren uvby observations from the Four College Automated Photoelectric Telescope (FCAPT) are presented for the mCP stars HD 142070, HR 6967, and HR 8434 and the CP star HR 5341. The latter star is found to be constant. Improved periods were derived for HD 142070, 3.37189d, HR 6967, 3.91227d, and HR 8434, 1.43237d. Further observations of HD 142070 are needed to phase the magnetic data with the photometry, of HR 6967 to settle minor discrepancies between y and scaled Geneva V photometry, and of HR 8434 to resolve small discrepancies between two uvby photometric data sets. (5 data files).

Adelman, S. J.

2001-01-01

216

MIRLIN HR 4796 Page  

NSDL National Science Digital Library

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

1998-01-01

217

HR Shared Services and the Realignment of HR.  

National Technical Information Service (NTIS)

Contents: Introduction; Why Create an HR Shared Service; What are HR Shared Services and How Were They Introduced; Issues in How Shared Services are Delivered; The Benefits and Disbenefits of HR Shared Services; The Future of Shared Services; Issues in Cr...

P. Reilly

2000-01-01

218

HR Public meeting  

ScienceCinema

Cher(e)s collègues, En collaboration avec le Département HR, le Directeur général a le plaisir de vous convier à une réunion publique qui se tiendra le vendredi 25 juin 2010 à 9h30 dans l?Amphithéâtre principal (Bâtiment 500)*. Un café d?accueil y sera servi à partir de 9h. Cette réunion abordera les thèmes suivants : ? Valeurs de l?Organisation (Directeur général) ? Code de Conduite (Directeur général / Anne-Sylvie Catherin) ? Création du nouveau rôle d?Ombudsperson (Vincent Vuillemin) Ces présentations seront suivies d?une séance de questions-réponses. Nous espérons vous retrouver nombreux le 25 juin ! Meilleures salutations, Anne-Sylvie Catherin Chef du Département des Ressources humaines *Cette réunion sera retransmise simultanément dans l?Amphithéâtre BE de Prévessin (Bâtiment 864) et également disponible à l?adresse suivante : http://webcast.cern.ch -------------------------------------------------------- Dear colleagues, In collaboration with HR Department, the Director-General would like to invite you to an information meeting which will be held on Friday 25 June 2010 at 9:30 am in the Main Auditorium (Building 500)*. A welcome coffee will be available from 9:00 am. During this meeting, information will be given about: ? Organization?s values (Director-General) ? Code of Conduct (Director-General / Anne-Sylvie Catherin) ? New Ombudsperson role (Vincent Vuillemin) These presentations will be followed by a questions & answers session. We look forward to seeing you all on 25 June! Best regards, Anne-Sylvie Catherin Head, Human Resources Department *This meeting will be simultaneously retransmitted in BE Auditorium (Building 864) and available at the following address: http://webcast.cern.ch.

None

2011-10-06

219

HR Public meeting  

SciTech Connect

Cher(e)s collègues, En collaboration avec le Département HR, le Directeur général a le plaisir de vous convier à une réunion publique qui se tiendra le vendredi 25 juin 2010 à 9h30 dans l’Amphithéâtre principal (Bâtiment 500)*. Un café d’accueil y sera servi à partir de 9h. Cette réunion abordera les thèmes suivants : • Valeurs de l’Organisation (Directeur général) • Code de Conduite (Directeur général / Anne-Sylvie Catherin) • Création du nouveau rôle d’Ombudsperson (Vincent Vuillemin) Ces présentations seront suivies d’une séance de questions-réponses. Nous espérons vous retrouver nombreux le 25 juin ! Meilleures salutations, Anne-Sylvie Catherin Chef du Département des Ressources humaines *Cette réunion sera retransmise simultanément dans l’Amphithéâtre BE de Prévessin (Bâtiment 864) et également disponible à l’adresse suivante : http://webcast.cern.ch -------------------------------------------------------- Dear colleagues, In collaboration with HR Department, the Director-General would like to invite you to an information meeting which will be held on Friday 25 June 2010 at 9:30 am in the Main Auditorium (Building 500)*. A welcome coffee will be available from 9:00 am. During this meeting, information will be given about: • Organization’s values (Director-General) • Code of Conduct (Director-General / Anne-Sylvie Catherin) • New Ombudsperson role (Vincent Vuillemin) These presentations will be followed by a questions & answers session. We look forward to seeing you all on 25 June! Best regards, Anne-Sylvie Catherin Head, Human Resources Department *This meeting will be simultaneously retransmitted in BE Auditorium (Building 864) and available at the following address: http://webcast.cern.ch.

None

2010-06-25

220

Réunion publique HR  

SciTech Connect

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

None

2010-04-30

221

Réunion publique HR  

ScienceCinema

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

None

2011-10-06

222

Characterizations of F-superconductors and selected F-compounds, amorphous carbon and (VO) sub 2 P sub 2 O sub 7 by sup 19 F, sup 13 C, sup 1 H and sup 31 P NMR and a new probe for multiple pulse, MAS and DAS NMR  

SciTech Connect

NMR signals of {sup 19}F have been measured in the polycrystalline inorganic conductor Ag{sub 2}F and in the polycrystalline insulators AgF, YOF, EuOF, YF{sub 3}, CuF{sub 2}, BaF{sub 2} and KF to compare them to the signals found in the so-called 1-2-3-type'' compounds with claimed formulas RBa{sub 2}Cu{sub 3}O{sub 7-x}F{sub x} (R = Y and Eu). No evidence for a Knight-shifted, built-in fluorine-signal was found in the 1-2-3-type superconductors, whereas, Ag{sub 2}F shows a clearly downfield shifted {sup 19}F peak with reference to AgF. 32 refs., 10 figs.

Pan, Hongjun.

1991-04-03

223

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

PubMed Central

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

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

2013-01-01

224

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

PubMed

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

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

2013-01-01

225

HR Shared Services and the Realignment of HR.  

ERIC Educational Resources Information Center

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

Reilly, P.

226

Quantitative Aspects in CP/MAS Experiments on Whole Coals and Macerals.  

National Technical Information Service (NTIS)

Solid-state NMR spectra are now being obtained routinely for a wide variety of fossil-fuel materials, including coals, using cross-polarization (CP) techniques combined with high-power decoupling and magic-angle sample rotation (MAS). However, the quantit...

R. E. Botto R. Wilson R. Hayatsu R. L. McBeth R. G. Scott

1985-01-01

227

NMR spectroscopy of experimentally shocked silicate minerals.  

National Technical Information Service (NTIS)

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. (sup 29)Si NMR spectra were determined for quartz and labradorite feldspar and (sup 27)Al and (sup 23)Na spectra ...

R. T. Cygan M. B. Boslough R. J. Kirkpatrick

1991-01-01

228

RFID enhanced MAS for warehouse management  

Microsoft Academic Search

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

A. García; Y. Chang; A. Abarca; C. Oh

2007-01-01

229

Alloy NASA-HR-1  

NASA Technical Reports Server (NTRS)

NASA-HR-1 is a high-strength Fe-Ni-base superalloy that resists high-pressure hydrogen environment embrittlement (HEE), oxidation, and corrosion. Originally derived from JBK-75, NASA-HR-1 has exceptional HEE resistance that can be attributed to its gamma-matrix and eta-free (Ni3Ti) grain boundaries. The chemistry was formulated using a design approach capable of accounting for the simultaneous effects of several alloy additions. This approach included: (1) Systematically modifying gamma-matrix compositions based on JBK-75; (2) Increasing gamma (Ni3(Al,Ti)) volume fraction and adding gamma-matrix strengthening elements to obtain higher strength; and (3) Obtaining precipitate-free grain boundaries. The most outstanding attribute of NASA-HR-1 is its ability to resist HEE while showing much improved strength. NASA-HR-1 has approximately 25% higher yield strength than JXK-75 and exhibits tensile elongation of more than 20% with no ductility loss in a hydrogen environment at 5 ksi, an achievement unparalleled by any other commercially available alloy. Its Cr and Ni contents provide exceptional resistance to environments that promote oxidation and corrosion. Microstructural stability was maintained by improved solid solubility of the gamma-matrix, along with the addition of alloying elements to retard eta (Ni3Ti) precipitation. NASA-HR-1 represents a new system that greatly extends the compositional ranges of existing HEE-resistant Fe-Ni-base superalloys.

Chen, Po-Shou; Mitchell, Michael

2005-01-01

230

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

PubMed

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 (1)H and (13)C spectra for the different phases. In addition, (19)F performance is also addressed. To illustrate the capability of (19)F 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. PMID:22425441

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

231

Companions to peculiar red giants: HR 363 and HR 1105  

NASA Technical Reports Server (NTRS)

Recent IUE observations of two Tc-deficient S-type peculiar red giants that are also spectroscopic binaries, HR 363 and HR 1105 are reported. A 675 min SWP exposure of HR 363 shows emission lines of O I 1304 and Si II 1812 and a trace of continuum. Compared to the M giants, the far UV flux may be relatively larger, indicating a possible contribution from a white dwarf companion, but no high temperature emission lines are seen to indicate that this is an interacting system where mass-transfer recently occurred. However, HR 1105 appears to have a highly variable UV companion. In 1982, no UV flux was discerned for this system, but by 1986 C IV was strong, increasing by a factor of 3 in 1987 with prominent lines of Si III, C III, O III, Si IV, and N V. Using orbital parameters, these observations are consistent with high activity occuring when the side of the S-star primary illuminated by the companion faces the Earth, but since the IUE data were taken over 3 orbits, a secular change in the UV component cannot be excluded.

Ake, Thomas B., III; Johnson, Hollis R.; Perry, Benjamin F., Jr.

1988-01-01

232

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

233

High-resolution magic angle spinning NMR spectroscopy of human osteoarthritic cartilage.  

PubMed

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

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

2012-04-01

234

FIRE_CI2_ER2_MAS  

... Experiment (FIRE) Cirrus 2 NASA ER-2 Moderate Resolution Imaging Spectrometer (MODIS) Airborne Simulator (MAS) Data Project ... Order  ASDC Order Tool Parameters:  Infrared Radiance Visible Radiance Order Data:  ASDC Order ...

2014-04-28

235

A Model of Responsible M&As  

Microsoft Academic Search

Companies conduct mergers and acquisitions (M&As) to secure profits, continuous growth and added share value by gaining new resources, know-how, synergies, new markets and competitive advantage. They also try to increase the efficiency of operations during the merger or acquisition (M\\/A) process. M&As seldom reach the set goals. Companies concentrating on strategic and financial issues forget the multi-faceted character of

Tarja Ketola

2008-01-01

236

A new NMR technique to probe protein-ligand interaction.  

PubMed

Non covalent grafting of proteins on affinity phases is a very common approach for isolation, purification and re-concentration of tagged proteins. Many biophysical studies are conducted on these grafted proteins (surface plasmon resonance, quartz crystal microbalance, etc.) showing that the integrity and function of the protein is usually maintained. However, NMR studies of such samples were not undertaken so far, due to the broadening observed on this kind of heterogeneous samples. We present here the use of the HR-MAS technology to obtain 2D NMR spectra of the MAGI-1 PDZ2/6 protein domain, C13-labeled, tagged with a His-tag and grafted on a Nickel affinity resin. We optimized the C13 Methyl SOFAST HMQC experiment allowing important gains in terms of signal-to-noise. The gain comes from the gathering of proton magnetization from the resin material to the protein under study. Several methyl signals from the unstructured C-terminal tail, which is involved in the binding of the PDZ domain to C-terminal peptides of its partners, were observed and measured. The interaction of the bound PDZ domain with cognate peptides was monitored using <500?g of protein sample. A response proportional to the peptide Kd is obtained, indicating that the method can be used to rapidly and efficiently monitor protein-ligand interactions. PMID:24252720

Viéville, J M P; Charbonnier, S; Eberling, P; Starck, J-P; Delsuc, M-A

2014-02-01

237

Mas' Making and Pedagogy: Imagined Possibilities  

ERIC Educational Resources Information Center

In this article I draw on an ethnographic case study that examined mas' makers' perceptions of the learning/teaching practices at work in the production of costumes for Trinidad and Tobago's annual Carnival celebrations. During the 2005 Carnival season I spent four months in the field, my country of birth, and collected data through participant…

Fournillier, Janice B.

2009-01-01

238

Study of Thermal Mobility by Means of 1 H NMR Magic-Angle Spinning Sideband Analysis  

Microsoft Academic Search

.  \\u000a 1H nuclear magnetic resonance (NMR) magic-angle spinning (MAS) sideband patterns of molecules adsorbed in zeolites or related\\u000a materials both depend on the MAS frequency and the thermal mobility. By using a statistical NMR line shape theory a valuable\\u000a information on the thermal motion can be derived from the MAS sidebands. The conclusions are compared with the results of\\u000a longitudinal

Ö. F. Erdem; D. Michel

2008-01-01

239

Revisiting the optical interferometry observations of HR 4049  

NASA Astrophysics Data System (ADS)

Aims: We present high spatial resolution observations in the mid-infrared of the dusty core of the binary system HR 4049. Methods: We used the mid-infrared interferometer MIDI/VLTI with 40 m projected baselines. These observations provided two spectrally dispersed visibility curves at a spatial resolution of ~10 mas. Acquisition images and spectra are in addition obtained with a single telescope spatial resolution of ~250 mas. Results: The MIDI spectra show features due to emission lines (7.9, 8.6 and 11.3 micron) attributed to PAHs. The comparison between ISO and MIDI spectra and dispersed visibility curves allows us to investigate the budget of continuum and PAH emission from distant regions to the inner regions of the compact dusty structure. The flux balance between these different PAH features is different to the one seen in the large beam ISO spectrum, suggesting different contributions at varying locations from the central star for the different PAH species. These features are over-resolved (i.e. their correlated flux is close to zero), placing the bulk of their line forming region at least at 50-70 mas from the central star. The continuum extension is estimated to range between 23 and 27 mas using a Gaussian model, and is very close to the K-band sizes measured with VINCI/VLTI, implying that the emitting regions of the near and mid-IR are similar. The visibilities from the two different baselines do not allow us to constrain the shape of the continuum emitting region but noticeable differences between them suggest that the N band dusty environment is flattened in a direction that coincides with the one suggested by previous polarimetric observations. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory.

Menut, J.-L.; Chesneau, O.; Bakker, E.; Lopez, B.; Perrin, G.; Leinert, C.; Quirrenbach, A.

2009-03-01

240

HR outsourcing among Malaysian manufacturing companies  

Microsoft Academic Search

Purpose – The purpose of this paper is to investigate the trend of human resource (HR) outsourcing among manufacturing companies in Malaysia. Design\\/methodology\\/approach – The data for the study were obtained from survey responses from 232 manufacturing companies in Malaysia, of which were engaged in HR outsourcing. Descriptive analyses were performed to obtain the information on the practices of HR

Hasliza Abdul-Halim; Norbani Che-Ha

2010-01-01

241

MAS: Minorities in the Aquatic Sciences  

NSDL National Science Digital Library

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

242

Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta)  

Microsoft Academic Search

The chemical structure and interactions of the cell wall polysaccharides from the red edible seaweed Palmaria palmata were studied by liquid-like magic-angle-spinning (MAS) and cross-polarization MAS (CPMAS) solid-state 13C NMR spectroscopy. The liquid-like MAS and CPMAS 13C NMR spectra of the rehydrated algal powder revealed the presence of ?-(1?4)\\/?-(1?3)-linked d-xylan with chemical shifts close to those observed in the solution

Marc Lahaye; Corinne Rondeau-Mouro; Estelle Deniaud; Alain Buléon

2003-01-01

243

Nanosatellites for earth environmental monitoring: The MicroMAS project  

Microsoft Academic Search

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

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

2012-01-01

244

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

245

Performance of RINEPT is amplified by dipolar couplings under ultrafast MAS conditions.  

PubMed

The refocused insensitive nuclei enhanced by polarization transfer (RINEPT) technique is commonly used for heteronuclear polarization transfer in solution and solid-state NMR spectroscopy. Suppression of dipolar couplings, either by fast molecular motions in solution or by a combination of MAS and multiple pulse sequences in solids, enables the polarization transfer via scalar couplings. However, the presence of unsuppressed dipolar couplings could alter the functioning of RINEPT, particularly under fast/ultrafast MAS conditions. In this study, we demonstrate, through experiments on rigid solids complemented by numerical simulations, that the polarization transfer efficiency of RINEPT is dependent on the MAS frequency. In addition, we show that heteronuclear dipolar coupling is the dominant factor in the polarization transfer, which is strengthened by the presence of (1)H-(1)H dipolar couplings. In fact, the simultaneous presence of homonuclear and heteronuclear dipolar couplings is the premise for the polarization transfer by RINEPT, whereas the scalar coupling plays an insignificant role under ultrafast MAS conditions on rigid solids. Our results additionally reveal that the polarization transfer efficiency decreases with the increasing duration of RF pulses used in the RINEPT sequence. PMID:24792960

Zhang, Rongchun; Ramamoorthy, Ayyalusamy

2014-06-01

246

Performance of RINEPT is amplified by dipolar couplings under ultrafast MAS conditions  

NASA Astrophysics Data System (ADS)

The refocused insensitive nuclei enhanced by polarization transfer (RINEPT) technique is commonly used for heteronuclear polarization transfer in solution and solid-state NMR spectroscopy. Suppression of dipolar couplings, either by fast molecular motions in solution or by a combination of MAS and multiple pulse sequences in solids, enables the polarization transfer via scalar couplings. However, the presence of unsuppressed dipolar couplings could alter the functioning of RINEPT, particularly under fast/ultrafast MAS conditions. In this study, we demonstrate, through experiments on rigid solids complemented by numerical simulations, that the polarization transfer efficiency of RINEPT is dependent on the MAS frequency. In addition, we show that heteronuclear dipolar coupling is the dominant factor in the polarization transfer, which is strengthened by the presence of 1H-1H dipolar couplings. In fact, the simultaneous presence of homonuclear and heteronuclear dipolar couplings is the premise for the polarization transfer by RINEPT, whereas the scalar coupling plays an insignificant role under ultrafast MAS conditions on rigid solids. Our results additionally reveal that the polarization transfer efficiency decreases with the increasing duration of RF pulses used in the RINEPT sequence.

Zhang, Rongchun; Ramamoorthy, Ayyalusamy

2014-06-01

247

Quantitative NMR  

NSDL National Science Digital Library

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

Korir, Albert K.; Larive, Cynthia K.

2011-07-18

248

NMR Animations  

NSDL National Science Digital Library

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

2011-07-26

249

The MAS (mandibular advancement series) difference.  

PubMed

So now it may be seen what is meant by the term "The MAS Difference". The American orthodontic specialty has for the most part been slow, or even in isolated pockets, willfully resistant to expansion of orthodontic technique up out of the "Procrustean bed" of fixed appliance limitations to the panorama of attacking the teeth-bone-muscle triangle of malocclusion with separate techniques and appliance systems designed specifically for each. What makes this anathema to those of a broader view is that it is only with those expanded, combined fixed AND functional techniques, that one has any chance at all of rendering anything close to significantly successful treatment of major TMJ-pain-headache-dysfunction chronic pain problems. And that is serious stuff. So, if you want to do "ortho" you had better know "TMJ". And, if you want to do "TMJ", at least TMJ to any meaningful degree, you had better know "ortho", and that means the discipline of functional orthodontics (or "maxillofacial orthopedics" if you will). The "why" of it is easily understandable once one truly understands the orthopedic (condylar displacement), myofunctional (Class II neuromuscular sling), and neurological (chronic repetitive compression nerve damage) aspects of the common functionally induced TMJ problem. The "how" of it all is another matter. That is why knowledge of a broad variety of various specific orthodontic techniques is required for the clinician because there are a vast variety of malocclusive situations with their own unique demands. But in the broadest sense, since a major portion of the orthodontic patient population suffers from somewhat of a skeletal Class II relationship, or "Class II effect" with respect to the joint, somewhere in the proposed treatment plan for these patients the clinician will have to consider some form of mandibular advancement series, whatever that series may be. But it is that MAS difference that sets that clinician and his or her specific treatment plan apart from the older, more restricted ways. It is a difference we must pay attention to, for Nature surely will. PMID:11887674

Spahl, T J

2001-01-01

250

The HR76 fire control radar  

Microsoft Academic Search

The monopulse precision tracking radar HR-76 is an all solid-state system which weighs less than 3000 pounds. It can be mounted on small, high-speed patrol craft or be employed by larger vessels. The minimum requirements for the HR-76 fire control radar mission are considered, taking into account the acquisition and tracking of aircraft at 40 km, the search and detection

L. E. Kitchens

1980-01-01

251

NMR at low and ultralow temperatures.  

PubMed

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

Tycko, Robert

2013-09-17

252

The stability of nanosized HZSM-5 zeolite: a high-resolution solid-state NMR study  

Microsoft Academic Search

The thermal and hydrothermal stabilities of HZSM-5 zeolites with crystal sizes less than 100 nm have been studied by multinuclear solid-state NMR, combined with BET and XRD. As evidenced by 27Al and 29Si MAS as well as their corresponding cross-polarization\\/MAS NMR investigations, the thermal stability of nanosized HZSM-5 is not so good as that of microsized HZSM-5. This is due

Weiping Zhang; Xiuwen Han; Xiumei Liu; Xinhe Bao

2001-01-01

253

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

254

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

255

High resolution magic angle spinning NMR as a tool for unveiling the molecular enantiorecognition of omeprazole by amylose-based chiral phase.  

PubMed

Polysaccharide-based chiral stationary phases (CSP) demonstrate great versatility and higher chiral selectivity for a variety of chiral compounds in multimodal elution modes (normal, reverse and polar organic). The main role of CSP phenyl carbamate based derivatives as chiral selectors is the formation of diastereoisomeric complexes by means of ?-? interaction, dipole-dipole, hydrogen bonding and/or inclusion complex mechanisms. Nevertheless, the mechanism behind their enantioselectivity requires clarification. High resolution magic angle spinning nuclear magnetic resonance spectroscopy ((1)H HR/MAS NMR) has provided key information on the recognition process at the binding sites of the CSP surface. Herein we report the results obtained using omeprazole as a probe for these investigations. PMID:24503630

Barreiro, Juliana Cristina; de Campos Lourenço, Tiago; Silva, Lorena Mara A; Venâncio, Tiago; Cass, Quezia Bezerra

2014-03-21

256

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

257

ADP-MAS: A Math and Science Curriculum.  

ERIC Educational Resources Information Center

This curriculum, Academia del Pueblo-Math and Science (ADP-MAS), is an outgrowth of the National Council of La Raza's Project EXCEL, a supplemental educational enrichment model for at-risk Latino students to be operated by Latino community-based organizations or public institutions, including schools with substantial Latino populations. ADP-MAS…

National Council of La Raza, Washington, DC.

258

250 GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR  

Microsoft Academic Search

In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9 T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR

Vikram S. Bajaj; Melissa K. Hornstein; Kenneth E. Kreischer; Jagadishwar R. Sirigiri; Paul P. Woskov; Melody L. Mak-Jurkauskas; Judith Herzfeld; Richard J. Temkin; Robert G. Griffin

2007-01-01

259

250 GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR  

Microsoft Academic Search

In this paper, we describe a 250 {GHz} gyrotron oscillator, a critical component of an integrated system for magic angle spinning {(MAS)} dynamic nuclear polarization {(DNP)} experiments at 9 T, corresponding to 380 {MHz} {1H} frequency. The 250 {GHz} gyrotron is the first gyro-device designed with the goal of seamless integration with an {NMR} spectrometer for routine {DNP} enhanced {NMR}

Vikram S. Bajaj; Melissa K. Hornstein; Kenneth E. Kreischer; Jagadishwar R. Sirigiri; Paul P. Woskov; Melody L. Mak-Jurkauskas; Judith Herzfeld; Richard J. Temkin; Robert G. Griffin

2007-01-01

260

On the acid-dealumination of USY zeolite: a solid state NMR investigation  

Microsoft Academic Search

The dealumination of USY (ultrastable Y) zeolites by nitric acid and oxalic acid treatment was systematically investigated by multinuclear solid-state NMR and MQ MAS NMR experiments. The results show that both acids are very effective in removing non-framework Al as well as framework Al but that aluminum is extracted from the lattice at a higher rate by oxalic acid even

Zhimin Yan; Ding Ma; Jianqin Zhuang; Xianchun Liu; Xiumei Liu; Xiuwen Hana; Xinhe Bao; Fuxiang Chang; Lei Xu; Zhongmin Liu

2003-01-01

261

In vivo 13C NMR metabolite profiling: potential for understanding and assessing conifer seed quality  

Microsoft Academic Search

High-resolution 13C MAS NMR spectroscopy was used to profile a range of primary and secondary metabo- lites in vivo in intact whole seeds of eight different conifer species native to North America, including six of the Pinaceae family and two of the Cupressaceae family. In vivo 13C NMR provided information on the total seed oil content and fatty acid composition

Victor V. Terskikh; J. Allan Feurtado; Shane Borchardt; Michael Giblin; Suzanne R. Abrams; Allison R. Kermode

2009-01-01

262

Solid state NMR study of SEI formation in lithium ion batteries  

Microsoft Academic Search

Recently, rechargeable lithium ion batteries, which offer high energy density and long cycle life, are in great demand as power sources for our mobile electronic society. The formation of a solid electrolyte interphase (SEI) on the surface of electrodes in lithium ion batteries plays an essential role in their performance. This thesis presents solid state NMR and MAS NMR results

Dachun Zhao

2004-01-01

263

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

PubMed

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

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

2014-01-01

264

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

Microsoft Academic Search

Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20® with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400°C in argon (?T=200°C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting

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

2007-01-01

265

Rotationally induced triple quantum coherence excitation in MAS NMR spectroscopy of I=5/2 spins  

NASA Astrophysics Data System (ADS)

Rotationally induced excitation of triple quantum coherences is demonstrated unequivocally for I=5/2 nuclei from comparison of the variation of the observed and simulated lineshapes as a function of spin-lock time. A new pulse sequence is presented that produces purely absorptive lineshapes from such an experiment. An important observation is that the coherence transfer goes through a maximum at moderate rf fields.

Mildner, T.; Smith, M. E.; Dupree, R.

1999-02-01

266

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

267

13C MAS NMR studies of crystalline cholesterol and lipid mixtures modeling atherosclerotic plaques.  

PubMed Central

Cholesterol and cholesteryl esters are the predominant lipids of atherosclerotic plaques. To provide fundamental data for the quantitative study of plaque lipids in situ, crystalline cholesterol (CHOL) and CHOL/cholesteryl ester (CE) mixtures with other lipids were studied by solid-state nuclear magnetic resonance with magic-angle-sample spinning. Highly distinctive spectra for three different crystalline structures of CHOL were obtained. When CHOL crystals were mixed with isotropic CE oil, solubilized CHOL (approximately 13 mol % CHOL) was detected by characteristic resonances such as C5, C6, and C3; the excess crystalline CHOL (either anhydrous or monohydrate) remained in its original crystalline structure, without being affected by the coexisting CE. By use of 13C-enriched CHOL, the solubility of CHOL in the CE liquid-crystalline phase (approximately 8 mol %) was measured. When phosphatidylcholine was hydrated in presence of CHOL and CE, magic-angle-sampling nuclear magnetic resonance revealed liquid-crystalline CHOL/phosphatidylcholine multilayers with approximately an equal molar ratio of CHOL/phosphatidylcholine. Excess CHOL existed in the monohydrate crystalline form, and CE in separate oil or crystalline phases, depending on the temperature. The magic-angle-sampling nuclear magnetic resonance protocol for identifying different lipid phases was applied to intact (ex vivo) atherosclerotic plaques of cholesterol-fed rabbits. Liquid, liquid-crystalline, and solid phases of CE were characterized. Images FIGURE 2

Guo, W; Hamilton, J A

1996-01-01

268

Nondestructive high-resolution solid-state NMR of rotating thin films at the magic-angle.  

PubMed

We present a new approach to nondestructive magic-angle spinning (MAS) nuclear magnetic resonance (NMR) for thin films. In this scheme, the sample put on the top of a rotor is spun using the conventional MAS system, and the NMR signals are detected with an additional coil. Stable spinning of disk-shaped samples with diameters of 7 mm and 12 mm at 14.2 and 7 kHz are feasible. We present 7Li MAS NMR experiments of a thin-film sample of LiCoO2 with a thickness of 200 nm. Taking advantage of the nondestructive feature of the experiment, we also demonstrate ex situ experiments, by tracing conformation change upon annealing for various durations. This approach opens the door for in situ MAS NMR of thin-film devices as well. PMID:21958755

Inukai, Munehiro; Noda, Yasuto; Takeda, Kazuyuki

2011-12-01

269

Nondestructive high-resolution solid-state NMR of rotating thin films at the magic-angle  

NASA Astrophysics Data System (ADS)

We present a new approach to nondestructive magic-angle spinning (MAS) nuclear magnetic resonance (NMR) for thin films. In this scheme, the sample put on the top of a rotor is spun using the conventional MAS system, and the NMR signals are detected with an additional coil. Stable spinning of disk-shaped samples with diameters of 7 mm and 12 mm at 14.2 and 7 kHz are feasible. We present 7Li MAS NMR experiments of a thin-film sample of LiCoO 2 with a thickness of 200 nm. Taking advantage of the nondestructive feature of the experiment, we also demonstrate ex situ experiments, by tracing conformation change upon annealing for various durations. This approach opens the door for in situ MAS NMR of thin-film devices as well.

Inukai, Munehiro; Noda, Yasuto; Takeda, Kazuyuki

2011-12-01

270

NMR spectroscopy of experimentally shocked silicate minerals  

SciTech Connect

Magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques were used to analyze experimentally shocked quartz and feldspar powders. {sup 29}Si NMR spectra were determined for quartz and labradorite feldspar and {sup 27}Al and {sup 23}Na spectra for labradorite. Both minerals were shocked to 7.5, 16.4, and 22 GPA using the Sandia Momma Bear'' recovery fixtures. The MAS NMR results for quartz are in full agreement with previous measurements, indicating a high degree of reproducibility. Numerical decomposition of quartz data are consistent with two distinct phases: a defective crystalline quartz and an amorphous-like silica phase. There is a strong correlation between the fraction of amorphous phase and the mean peak shock pressure. The labradorite data are much more complicated, consisting of multiple peaks with no obvious correlation with shock pressure. No amorphous phase was evident from the NMR spectra of the shocked labradorite, nor were high pressure phases detectable for either mineral. 6 refs., 3 figs., 1 tab.

Cygan, R.T.; Boslough, M.B. (Sandia National Labs., Albuquerque, NM (USA)); Kirkpatrick, R.J. (Illinois Univ., Urbana, IL (USA). Dept. of Geology)

1991-01-01

271

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

272

The Many Faces of HR 1099  

Microsoft Academic Search

We propose to monitor, in high-dispersion, the far-ultraviolet emission of the archetype short-period RS Canum Venaticorum binary system, HR 1099 = V711 Tauri (K0 IV + G5 V) through two complete orbital revolutions. The tidally-locked RS CVn binaries have among the brightest chromospheres (T = 6000 K) and coronae (T ~ 10^6 K) known, and are thought to suffer intense

Thomas R. Ayres

1982-01-01

273

Instability Regions in the Upper HR Diagram  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

274

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

Microsoft Academic Search

.  In this work, we combine 27Al, 29Si, 19F, and 23Na magic-angle spinning (MAS) nuclear magnetic resonance (NMR) to characterize the structure and interlayer cation environments\\u000a in a strontium-saturated member of the swelling mica family before and after a heat-induced collapse of the interlayer space.\\u000a The 27Al and 29Si MAS NMR demonstrate that the sample consists mainly of swelling mica, though

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

2007-01-01

275

DETERMINATION OF SENSITIVITY COEFFICIENTS FOR ROCKWELL HARDNESS SCALES HR15N, HR30N, AND HRA  

Microsoft Academic Search

This report describes the work carried out to provide sensitivity coefficients for the Rockwell HRA and Superficial Rockwell HR15N and HR30N scales. Sensitivity coefficients were determined for the preliminary test force, total test force, force duration times, loading times, and loading rates. 2. EQUIPMENT The NPL test work was performed in a 1.5 kN hardness standard machine (Fig. 1). Which

Laurence Brice; Samuel Low; Rodney Jiggetts

276

BVRI photometry of HR 1105 (Adelman 1998)  

NASA Astrophysics Data System (ADS)

BVRI photometry of the extrinsic S star HR 1105 shows a stable periodic light variability with a period of 24.76 days superimposed upon long term changes presumably related to the orbital period. The variations are in phase for all four magnitudes with the amplitude of this variability being about the same for B and V, but smaller for R and even smaller for I. As the primary is a M3 III star, these brightness changes are mostly likely due to the pulsation of the primary star. (1 data file).

Adelman, S. J.

1998-02-01

277

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

278

Pleiades-Hr Image Quality Commissioning  

NASA Astrophysics Data System (ADS)

PLEIADES is the highest resolution civilian earth observing system ever developed in Europe. This imagery program is conducted by the French National Space Agency, CNES. It operates since 2012 a first satellite PLEIADES-HR launched on 2011 December 17th, a second one should be launched by the end of the year. Each satellite is designed to provide optical 70 cm resolution coloured images to civilian and defence users. The Image Quality requirements were defined from users studies from the different spatial imaging applications, taking into account the trade-off between on-board technological complexity and ground processing capacity. The assessment of the image quality and the calibration operation have been performed by CNES Image Quality team during the 6 month commissioning phase that followed the satellite launch. These activities cover many topics gathered in two families : radiometric and geometric image quality. The new capabilities offered by PLEIADES-HR agility allowed to imagine new methods of image calibration and performance assessment. Starting from an overview of the satellite characteristics, this paper presents all the calibration operations that were conducted during the commissioning phase and also gives the main results for every image quality performance.

Lebègue, L.; Greslou, D.; de Lussy, F.; Fourest, S.; Blanchet, G.,; Latry, C.; Lachérade, L.; Delvit, J. M.; Kubik, P.; Déchoz, C.; Amberg, V.; Porez-Nadal, F.

2012-07-01

279

Lithium in the Super-Beryllium-rich HG-MN Stars HR 6158 and HR 8915  

NASA Astrophysics Data System (ADS)

The chemically peculiar stars that inhabit the upper main sequence exhibit very extreme enhancements and deficiencies of several elements. In all likelihood, the primary cause of these anomalies is radiatively driven diffusion, although other mechanisms may also be important-such as mass loss and various kinds of mixing. Only by examining as many elements as possible will a cohesive theory explaining these abundance oddities materialize. To this end, we present high-resolution (R~62,500), high signal-to-noise ratio (S/N pixel^-1~120) observations of the 6708 Å Li I resonance doublet in a pair of Hg-Mn stars. No record of a lithium detection has been found for this type of chemically peculiar star. The atmospheres of the two program stars (HR 6158=28 Her=HD 149212; HR 8915=69 Peg=HD 220933) contain an inordinate amount of beryllium (Be) in fact, the Be abundances in these stars are among the highest known. While the LTE concentration of Be is several thousand times larger than cosmic [A(Be)_i~1.27] in both stars, lithium (Li) is detected in neither HR 6158 nor HR 8915. The calculated 3 sigma (99% confidence level) upper limits place the maximum Li enhancements at 50 times and 80 times cosmic [A(Li)_i~3.23] for HR 6158 and HR 8915, respectively, or ~100 times smaller than the Be overabundances. These Li upper limits, which argue against a ``nucleosynthesis'' origin for the Be surfeit, provide yet another means of constraining the physical process (or processes) responsible for the Hg-Mn phenomenon in some A stars.

Stephens, Alex; Deliyannis, Constantine P.

1999-04-01

280

NMR Studies of Cartilage Dynamics, Diffusion, Degradation  

NASA Astrophysics Data System (ADS)

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

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

281

Treatment of Noncitizens in H.R. 3200.  

National Technical Information Service (NTIS)

This report outlines the treatment of noncitizens (aliens) under H.R. 3200, Americas Affordable Health Choices Act of 2009. In particular, the report analyzes specific provisions in H.R. 3200, and whether there are eligibility requirements for noncitizens...

A. Siskin E. K. Lunder

2009-01-01

282

Microcoils and microsamples in solid-state NMR.  

PubMed

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

Takeda, Kazuyuki

2012-01-01

283

Attitude Assessment Using Pleiades-Hr Capabilities  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

284

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

PubMed

The pathogenetic cascade of meconium aspiration syndrome (MAS) in newborn infants is complex and still incompletely studied. The variable clinical presentation of MAS is basically connected with variation of the amount and consistency of aspirated meconium and also its distribution within the affected lungs. The contributing role of other factors, like intrauterine fetal compromises, lung maturity at the time of insult as well as direct and indirect effects of meconium and its components on the lung alveolar and vascular integrity and development, remains to be studied in further detail. Better understanding of the lung injury processes in MAS, specifically inflammatory injury and non-inflammatory apoptosis and their interplay, may offer new possibilities to treat the severely affected infants, and needs therefore to be explored. Systemic dispersion of intrapulmonary meconium and its components may further induce inflammatory circulatory changes and injurious effects in distant organs, but the mechanisms and clinical significance of these systemic complications are still poorly known. It is thus evident that lung injury processes and potent long-term consequences in various extrapulmonary organs, specifically the brain, as well as development of new approaches to their treatment and prevention form great challenges for future research of MAS. PMID:19819652

Kääpä, Pekka O

2009-10-01

285

Draft Genome Sequence of Geobacillus thermopakistaniensis Strain MAS1.  

PubMed

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

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

2014-01-01

286

Resolution and polarization distribution in cryogenic DNP/MAS experiments.  

PubMed

This contribution addresses four potential misconceptions associated with high-resolution dynamic nuclear polarization/magic angle spinning (DNP/MAS) experiments. First, spectral resolution is not generally compromised at the cryogenic temperatures at which DNP experiments are performed. As we demonstrate at a modest field of 9 T (380 MHz (1)H), 1 ppm linewidths are observed in DNP/MAS spectra of a membrane protein in its native lipid bilayer, and <0.4 ppm linewidths are reported in a crystalline peptide at 85 K. Second, we address the concerns about paramagnetic broadening in DNP/MAS spectra of proteins by demonstrating that the exogenous radical polarizing agents utilized for DNP are distributed in the sample in such a manner as to avoid paramagnetic broadening and thus maintain full spectral resolution. Third, the enhanced polarization is not localized around the polarizing agent, but rather is effectively and uniformly dispersed throughout the sample, even in the case of membrane proteins. Fourth, the distribution of polarization from the electron spins mediated via spin diffusion between (1)H-(1)H strongly dipolar coupled spins is so rapid that shorter magnetization recovery periods between signal averaging transients can be utilized in DNP/MAS experiments than in typical experiments performed at ambient temperature. PMID:20454732

Barnes, Alexander B; Corzilius, Björn; Mak-Jurkauskas, Melody L; Andreas, Loren B; Bajaj, Vikram S; Matsuki, Yoh; Belenky, Marina L; Lugtenburg, Johan; Sirigiri, Jagadishwar R; Temkin, Richard J; Herzfeld, Judith; Griffin, Robert G

2010-06-14

287

Draft Genome Sequence of Geobacillus thermopakistaniensis Strain MAS1  

PubMed Central

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

Rashid, Naeem; Ayyampalayam, Saravanaraj

2014-01-01

288

Resolution and polarization distribution in cryogenic DNP/MAS experiments  

PubMed Central

This contribution addresses four potential misconceptions associated with high-resolution dynamic nuclear polarization/magic angle spinning (DNP/MAS) experiments. First, spectral resolution is not generally compromised at the cryogenic temperatures at which DNP experiments are performed. As we demonstrate at a modest field of 9 T (380 MHz 1H), 1 ppm linewidths are observed in DNP/MAS spectra of a membrane protein in its native lipid bilayer, and <0.4 ppm linewidths are reported in a crystalline peptide at 85 K. Second, we address the concerns about paramagnetic broadening in DNP/MAS spectra of proteins by demonstrating that the exogenous radical polarizing agents utilized for DNP are distributed in the sample in such a manner as to avoid paramagnetic broadening and thus maintain full spectral resolution. Third, the enhanced polarization is not localized around the polarizing agent, but rather is effectively and uniformly dispersed throughout the sample, even in the case of membrane proteins. Fourth, the distribution of polarization from the electron spins mediated via spin diffusion between 1H–1H strongly dipolar coupled spins is so rapid that shorter magnetization recovery periods between signal averaging transients can be utilized in DNP/MAS experiments than in typical experiments performed at ambient temperature.

Barnes, Alexander B.; Corzilius, Bjorn; Mak-Jurkauskas, Melody L.; Andreas, Loren B.; Bajaj, Vikram S.; Matsuki, Yoh; Belenky, Marina L.; Lugtenburg, Johan; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Herzfeld, Judith; Griffin, Robert G.

2014-01-01

289

Divergence in HR Functional Roles in Local Government  

Microsoft Academic Search

In spite of a growing body of research on the position and role of HRM and the HR function in organizations, local government HRM has not received the attention it deserves. This article contributes to research on the role of the HR function by deploying a discursive perspective on how HR managers construct their function's role in the context of

Sara Lindström; Sinikka Vanhala

2011-01-01

290

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

291

How HR Leaders Can Add Value to an Organization  

ERIC Educational Resources Information Center

Generally speaking, it is safe to say that human resource leaders whole-heartedly believe that the HR function should add value to an organization. However, many wonder where to start. In this article, the authors outline three ways in which the HR function, and the HR leader, can create sustained value for an organization and its stakeholders.

Smallwood, Norm; Ulrich, Dave

2006-01-01

292

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

NASA Astrophysics Data System (ADS)

Four different coil designs for use with MAS in triple-resonance multi-nuclear experiments at high fields are compared, using a combination of finite element analysis (FEA) software and NMR experiments, with respect to RF field strength per unit power and relative sample heating, as governed by mean E/ B1 within the sample region. A commercial FEA package, Microwave Studio 5.1 by Computer Simulation Technology (CST) is shown to obtain remarkably accurate agreement with the experiments in QL, L, B, E, and mode frequencies in all cases. A simplified treatment of RF heating in NMR MAS samples is derived and shown to agree with the NMR experimental results within about 10% for two representative stator designs. The coil types studied include: (1) a variable-pitch solenoid outside a ceramic coilform, (2) a conventional solenoid very closely spaced to the MAS rotor, (3) a scroll coil, and (4) a segmented saddle cross coil (XC) for 1H with an additional solenoid over it for the two lower-frequency channels. The XC/solenoid is shown to offer substantial advantages in reduced decoupler heating, improved S/N, and improved compatibility with multinuclear tuning and high-power decoupling. This seems largely because the division of labor between two orthogonal coils allows them each, and their associated circuitry, to be separately optimized for their respective regimes.

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

2006-10-01

293

Using the HR intranet : An exploratory analysis of its impact on managerial satisfaction with the HR function  

Microsoft Academic Search

Purpose – The purpose of this paper is to explore the impact of the use of the human resources (HR) intranet at managerial levels in terms of internal customer satisfaction with the HR function. Design\\/methodology\\/approach – Using role theory to underpin the research, this study examines both the changing role of managers as well as managers' expectations of the HR

Cheryl Alleyne; Andrew Kakabadse; Nada Kakabadse

2007-01-01

294

sup 13 C solid-state NMR study of ethylene oxidation over supported silver catalysts  

Microsoft Academic Search

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag\\/SiOâ catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP\\/MAS), CP\\/MAS with dipolar dephasing, and

Hosseini

1992-01-01

295

[sup 13]C solid-state NMR study of ethylene oxidation over supported silver catalysts  

Microsoft Academic Search

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag\\/SiO[sub 2] catalyst at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP\\/MAS), CP\\/MAS with dipolar dephasing,

Hosseini

1992-01-01

296

Solid-state NMR as an analytical tool: quantitative aspects.  

PubMed

Analytical methods based on solid-state NMR are becoming increasingly popular. However, these flourishing activities bring up the issue of how accurately NMR can assess an analyte proportion in a solid sample. The use of a chemical intensity reference for this purpose is a natural but often unsuitable choice, due to sample stability or preciousness. We propose here a protocol to perform quantitative measurements in solid-state NMR, by calibration of the circuit response through a low-power pulse injected during the acquisition (the so-called ERETIC method). Although this method has been in use for some time in liquid-phase and in vivo NMR, we point out here some peculiarities and useful applications typical of solids. Namely, the temperature dependence of the signal intensity imposes care in the application to MAS experiments. PMID:16229992

Ziarelli, Fabio; Caldarelli, Stefano

2006-02-01

297

Near-ir Spectra Of The Planets HR8799b And HR8799c  

Microsoft Academic Search

The directly-imaged HR8799 system represents a unique window into exoplanet formation and evolution with three massive coeval planets accesible to characterization using adaptive optics on modern telescopes. One such window is spectroscopic characterization. We have used the OSIRIS near-IR integral field spectrograph on the W.M. Keck telescope to study the two outermost planets. Taking advantage of the 3-dimensional OSIRIS data

Bruce Macintosh; T. Barman; Q. M. Konopacky; C. Marois

2011-01-01

298

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

NASA Technical Reports Server (NTRS)

We have obtained low-dispersion IUE spectra of the late-type stars HD 15638 (F3 V), HR 1608 (=63 Eridani, KO IV), and HR 8210 (A8m). Each of these stars had been detected as a strong EUV source with the Wide Field Camera aboard the ROSAT satellite. The short-wavelength IUE spectrum of each star reveals the presence of a hot white-dwarf companion. We have fit the Lyman-alpha profile and UV continuum of each white dwarf using pure hydrogen models. The excellent fit of the data to the models provides confirmation of the Finley and Koester absolute calibration of the SWP camera of IUE. The UV data alone are insufficient to constrain the model gravity, but an additional constraint is provided by the photometric distance to the late-type primary. The most interesting of the three white dwarfs is the companion to HR 8210 for which our results imply a mass of 1.15 +0.05/-0.15 solar mass. This result is in good agreement with the lower limit on the mass derived from the spectroscopic orbit (greater than 1.1 solar mass), provided that the inclination is close to 90 deg.

Landsman, Wayne; Simon, Theodore; Bergeron, P.

1993-01-01

299

Very fast magic angle spinning 1H- 14N 2D solid-state NMR: Sub-micro-liter sample data collection in a few minutes  

Microsoft Academic Search

Substantial resolution and sensitivity enhancements of solid-state 1H detected 14N HMQC NMR spectra at very fast MAS rates up to 80kHz, in a 1mm MAS rotor, are presented. Very fast MAS enhances the 1H transverse relaxation time and efficiently decouples the 1H-14N interactions, both effects leading to resolution enhancement. The micro-coil contributes to the sensitivity increase via strong 14N rf

Yusuke Nishiyama; Yuki Endo; Takahiro Nemoto; Hiroaki Utsumi; Kazuo Yamauchi; Katsuya Hioka; Tetsuo Asakura

2011-01-01

300

The RAPPID Project: Symbiosis between Industrial Requirements and MAS Research  

Microsoft Academic Search

The RAPPID project (Responsible Agents for Product-Process Integrated Design) is developing agent- based software tools and methods that use market place dynamics among members of a distributed design team to coordinate set-based design of discrete manufactured products. This report describes the interplay of industrial requirements and Multi-Agent System (MAS) research in the design, implementation, and testing of RAPPID. Like any

H. Van Dyke Parunak; John A. Sauter; Mitchell Fleischer; Allen C. Ward

1999-01-01

301

An MAS Infrastructure for Implementing SWSA Based Semantic Services  

Microsoft Academic Search

The Semantic Web Services Initiative Architecture (SWSA) describes the overall process of semantic service execution in three\\u000a phases: discovery, engagement and enactment. To accomplish the specified requirements of these phases, it defines a conceptual\\u000a model which is based on semantic service agents that provide and consume semantic web services and includes architectural\\u000a and protocol abstractions. In this paper, an MAS

Önder Gürcan; Geylani Kardas; Özgür Gümüs; Erdem Eser Ekinci; Oguz Dikenelli

2007-01-01

302

Liquid domains in vesicles investigated by NMR and fluorescence microscopy.  

PubMed

We use (2)H-NMR, (1)H-MAS NMR, and fluorescence microscopy to detect immiscibility in three particular phospholipid ratios mixed with 30% cholesterol: 2:1 DOPC/DPPC, 1:1 DOPC/DPPC, and 1:2 DOPC/DPPC. Large-scale (>160 nm) phase separation into liquid-ordered (L(o)) and liquid-crystalline (L(alpha)) phases is observed by both NMR and fluorescence microscopy. By fitting superimposed (2)H-NMR spectra, we quantitatively determine that the L(o) phase is strongly enriched in DPPC and moderately enriched in cholesterol. Tie-lines estimated at different temperatures and membrane compositions are based on both (2)H-NMR observations and a previously published ternary phase diagram. (2)H- and (1)H-MAS NMR techniques probe significantly smaller length scales than microscopy experiments (submicron versus micron-scalp), and complex behavior is observed near the miscibility transition. Fluorescence microscopy of giant unilamellar vesicles shows micrometer-scale domains below the miscibility transition. In contrast, NMR of multilamellar vesicles gives evidence for smaller ( approximately 80 nm) domains just below the miscibility transition, whereas large-scale demixing occurs at a lower temperature, T(low). A transition at T(low) is also evident in fluorescence microscopy measurements of the surface area fraction of ordered phase in giant unilamellar vesicles. Our results reemphasize the complex phase behavior of cholesterol-containing membranes and provide a framework for interpreting (2)H-NMR experiments in similar membranes. PMID:15111407

Veatch, S L; Polozov, I V; Gawrisch, K; Keller, S L

2004-05-01

303

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

SciTech Connect

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

Murphy, Kelly A.; Washton, Nancy M.; Ryan, Joseph V.; Pantano, Carlo G.; Mueller, Karl T.

2013-06-01

304

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

305

Import of proteins into yeast mitochondria: the nuclear MAS2 gene encodes a component of the processing protease that is homologous to the MAS1-encoded subunit.  

PubMed Central

The mas2 mutant of Saccharomyces cerevisiae is temperature sensitive for import of proteins into mitochondria. To identify the lesion in this mutant, we have cloned and sequenced the wild-type MAS2 gene and determined the intracellular location of its protein product. MAS2 encodes an essential 53-kd protein that is located in the mitochondrial matrix and is homologous to the MAS1 protein, a previously identified subunit of the protease that cleaves presequences from mitochondrial precursor proteins. The activity of this enzyme is temperature sensitive in mas2 cells. Together with the results of the accompanying study these results show that MAS2 and MAS1 encode the two subunits of the processing protease. Images

Jensen, R E; Yaffe, M P

1988-01-01

306

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

2013-09-17

307

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

308

The MicroMAS CubeSat Mission  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

309

Exploring electrolyte organization in supercapacitor electrodes with solid-state NMR  

NASA Astrophysics Data System (ADS)

Supercapacitors are electrochemical energy-storage devices that exploit the electrostatic interaction between high-surface-area nanoporous electrodes and electrolyte ions. Insight into the molecular mechanisms at work inside supercapacitor carbon electrodes is obtained with 13C and 11B ex situ magic-angle spinning nuclear magnetic resonance (MAS-NMR). In activated carbons soaked with an electrolyte solution, two distinct adsorption sites are detected by NMR, both undergoing chemical exchange with the free electrolyte molecules. On charging, anions are substituted by cations in the negative carbon electrode and cations by anions in the positive electrode, and their proportions in each electrode are quantified by NMR. Moreover, acetonitrile molecules are expelled from the adsorption sites at the negative electrode alone. Two nanoporous carbon materials were tested, with different nanotexture orders (using Raman and 13C MAS-NMR spectroscopies), and the more disordered carbon shows a better capacitance and a better tolerance to high voltages.

Deschamps, Michaël; Gilbert, Edouard; Azais, Philippe; Raymundo-Piñero, Encarnación; Ammar, Mohammed Ramzi; Simon, Patrick; Massiot, Dominique; Béguin, François

2013-04-01

310

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

311

NMR Quantum Information Processing  

Microsoft Academic Search

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

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

2004-01-01

312

Dipolar recoupling in MAS spectra of biological solids  

Microsoft Academic Search

In combination with magic angle spinning, dipolar recoupling yields solid state NMR spectral assignments and provides constraints on internuclear distances and torsion angles. The method offers a fresh approach to structural studies of a variety of systems that cannot be examined with conventional tools available to structural biology.

Robert Griffin

1998-01-01

313

An Empirical HR Diagram for WN Stars  

NASA Astrophysics Data System (ADS)

The one-dimensional WN classification defined by Smith (1968, MNRAS 138, 109), based primarily on the relative strengths of Nsiii -- Nsv lines, has been described as unsuccessful because it fails to define a unique luminosity and temperature for a given spectral type (e.g. Conti ea 1983, ApJ 268, 228). Part of the problem lies in the lumping of ``weak'' and ``strong'' lined stars (Hiltner & Schild 1966, ApJ 143,770 ``A'' and ``B'' types) into the same spectral bins. Recently Hamann, Koesterke, & Wessolowski (1993, AA 274, 397) (HKW) have determined the luminosities and temperatures for 60% of the 71 apparently single WN stars in the updated Sixth Galactic WR Catalog of van der Hucht ea (1988, AA 199, 217), from the equivalent widths (EW) of Hesiilam 5412 and Hesilam 5876. I use their data to plot the EW_{lambda 5412} as a function of the ratio EW_{lambda 5412} / EW_{lambda 5876}. This plot shows a clear separation between ``weak'' lined and ``strong'' lined WN stars with a dividing line at EW_{lambda 5412} = --35 Angstroms. Both the strong and weak line sequences follow the N ionization classification along their respective curves. There is also a hint of a further bifurcation in the weak line sequence. I argue that this is an empirical HR diagram for the WN stars because for each sequence (weak and strong); there is a linear correlation between temperature and the equivalent width ratio, and an inverse linear correlation between the absolute visual magnitude and the EW_{lambda 5412}. (This second correlation is just the ``Baldwin Effect'' for WR stars; noted by Morris ea 1993, ApJ 414, L25). I will discuss a similar classification system by Smith, Shara, & Moffat (1995, IAUSymp 163, 48) who have suggested using the FWHM of Hesiilam 4686 in place of EW_{lambda 5412} and an additional third dimension measuring the H/He abundance ratio. I will also discuss the use of alternate luminosity (EW_{lambda 4686}) and temperature (EW_{lambda 4686} / EW_{lambda 10830}) indicators. This work has been supported by NAG5-619.

McCandliss, Stephan R.

1995-05-01

314

14N NMR in AlN and BN.  

PubMed

A characterisation by 14N NMR of the binary nitrides AlN and BN is presented. Both the static and magic angle spinning (MAS) lineshapes have been investigated in order to determine, or set upper limits on, the nuclear quadrupole coupling (Cq) at the nitrogen site. Additional data are given for the Cq values at the Al and B sites. A comparison is made with other similar (mainly wurtzite) binary compounds for which Cq is known at each atomic site. PMID:9603625

Bastow, T J; Massiot, D; Coutures, J P

1998-02-01

315

Characterization of acid sites on ?-alumina and chlorinated ?-alumina by 31 P NMR of adsorbed trimethylphosphine  

Microsoft Academic Search

31P MAS NMR of adsorbed trimethylphosphine (TMP) has been used to characterize the surface acid properties of ?-alumina and\\u000a chlorinated ?-alumina. Combined with thermodesorption of TMP, NMR has allowed the determination of the strength distribution\\u000a of Brønsted and Lewis acid sites on these samples. ?-alumina chlorination with 1,2-dichloropropane at 500°C first increases\\u000a the numbers of ``strong'' Lewis and ``strong'' Brønsted

D. Guillaume; S. Gautier; I. Despujol; F. Alario; P. Beccat

1997-01-01

316

Analysis of Radiation Induced Degradation in FPC461 Fluoropolymers by Variable Temperature Multinuclear NMR  

Microsoft Academic Search

Solid state nuclear magnetic resonance techniques have been used to investigate aging mechanisms in a vinyl chloride:chlorotrifluoroethylene copolymer, FPC-461, due to exposure to γ-radiation. Solid state ¹H MAS NMR spectra revealed structural changes of the polymer upon irradiation under both air and nitrogen atmospheres. Considerable degradation is seen with ¹H NMR in the vinyl chloride region of the polymer, particularly

S C Chinn; T S Wilson; R S Maxwell

2004-01-01

317

Analysis of radiation induced degradation in FPC461 fluoropolymers by variable temperature multinuclear NMR  

Microsoft Academic Search

Solid state nuclear magnetic resonance techniques have been used to investigate aging mechanisms in a vinyl chloride:chlorotrifluoroethylene copolymer, FPC-461, due to exposure to ?-radiation. Solid state 1H MAS NMR spectra revealed structural changes in the polymer upon irradiation under both air and nitrogen atmospheres. Considerable degradation is seen with 1H NMR in the vinyl chloride region of the polymer, particularly

Sarah C. Chinn; Thomas S. Wilson; Robert S. Maxwell

2006-01-01

318

Comparison of the 1Hr and 8Hr National Ambient Air Quality Standards for Ozone Using Models3  

Microsoft Academic Search

In 1997, the U.S. Environmental Protection Agency revised the National Ambient Air Quality Standard governing ozone (O3), adding an 8-hr standard of 0.08 ppm and phasing out the 1-hr requirement of 0.12 ppm. The 8-hr standard is intended to provide greater protection for human health. This research examines spatial and temporal patterns of exceedances of the standards using monitoring data

Michelle Bell; Hugh Ellis

2003-01-01

319

CHARACTERIZATION OF THE RED GIANT HR 2582 USING THE CHARA ARRAY  

SciTech Connect

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

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

2013-07-20

320

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

321

The Antithrombotic Effect of Angiotensin-(1-7) Involves Mas-Mediated NO Release from Platelets  

PubMed Central

The antithrombotic effect of angiotensin(Ang)-(1–7) has been reported, but the mechanism of this effect is not known. We investigated the participation of platelets and receptor Mas-related mechanisms in this action. We used Western blotting to test for the presence of Mas protein in rat platelets and used fluorescent-labeled FAM-Ang-(1–7) to determine the specific binding for Ang-(1–7) and its displacement by the receptor Mas antagonist A-779 in rat platelets and in Mas?/ ? and Mas+/+ mice platelets. To test whether Ang-(1–7) induces NO release from platelets, we used the NO indicator DAF-FM. In addition we examined the role of Mas in the Ang-(1–7) antithrombotic effect on induced thrombi in the vena cava of male Mas?/ ? and Mas+/+ mice. The functional relevance of Mas in hemostasis was evaluated by determining bleeding time in Mas+/+ and Mas?/ ? mice. We observed the presence of Mas protein in platelets, as indicated by Western Blot, and displacement of the binding of fluorescent Ang-(1–7) to rat platelets by A-779. Furthermore, in Mas+/+ mouse platelets we found specific binding for Ang-(1–7), which was absent in Mas?/ ? mouse platelets. Ang-(1–7) released NO from rat and Mas+/+ mouse platelets, and A-779 blocked this effect. The NO release stimulated by Ang-(1–7) was abolished in Mas?/ ? mouse platelets. Ang-(1–7) inhibited thrombus formation in Mas+/+ mice. Strikingly, this effect was abolished in Mas?/ ?mice. Moreover, Mas deficiency resulted in a significant decrease in bleeding time (8.50 ± 1.47 vs. 4.28 ± 0.66 min). This study is the first to show the presence of Mas protein and specific binding for Ang-(1–7) in rat and mouse platelets. Our data also suggest that the Ang-(1–7) antithrombotic effect involves Mas-mediated NO release from platelets. More importantly, we showed that the antithrombotic effect of Ang-(1–7) in vivo is Mas dependent and that Mas is functionally important in hemostasis.

Fraga-Silva, Rodrigo Araujo; Pinheiro, Sergio Veloso Brant; Goncalves, Andrey Christian Costa; Alenina, Nathalia; Bader, Michael; Santos, Robson Augusto Souza

2008-01-01

322

African American Accounting Majors and the 150-hr Requirement  

ERIC Educational Resources Information Center

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

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

2010-01-01

323

HR BPO service models for small and medium enterprises  

Microsoft Academic Search

Purpose – The goal of this research is first to investigate the outsourcing needs of small and medium enterprises (SMEs) in each of the following HR sub-processes: recruiting, training, HR administration, payroll, and benefit processes. Then, the outsourcing needs are analyzed against the characteristics of the companies such as company size, operating environment, culture and information technology maturity. Lastly, integrated

Gyeung-Min Kim; Hyun Jung Won

2007-01-01

324

A generic, computerized nuclear materials accountability system (NucMAS) and its layered products  

Microsoft Academic Search

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

J. M. Jr

1989-01-01

325

Application of Six Sigma methodology DMAIC in HR project management —A case study of Motorola SC HR DSS project  

Microsoft Academic Search

HR project management has been an important and exciting topic in both academic research and practical conduct. The Human Resource Management areas identified by the Six Sigma approach are frequently appearing as topics in the management literature. This paper presents a typical example in which Six Sigma methodology DMAIC is applied in a Motorola Supply Chain HR project on 3

Yun-na Liu; Kang Li

2011-01-01

326

NMR study of heterogeneity in pyridine-N-oxide...HCl crystal  

NASA Astrophysics Data System (ADS)

An origin of narrow 1H NMR signals in pyridine-N-oxide (PyO)...HCl crystal has been investigated by means of MAS, SPEDAS, NOESY and COSY techniques. Spectra of crystalline samples are compared with those of solid phase obtained from liquid PyO...HCl solutions (in acetonitile/H2O) after the heterogeneous phase separation. It has been concluded that partially resolved peaks in 1H NMR spectra of solids are related with heterogeneity of spin system and presence of different H-bond clusters of water molecules. NOESY spectra show no cross-peaks even at very long mixing time (500 ms). This indicates there is no exchange process between spins causing different peaks, and thus the corresponding molecular aggregates are captured in “islands of mobility8 without any channels sufficient for exchange. Appearance of MAS side bands as “pseudo8 cross-peaks in 2D NMR spectra using MAS/COSY technique is reported. In the case of accidental coincidence of spinning frequency (? MAS ) with spectral distances between some diagonal signals, intensive non-diagonal peaks are observed at the corresponding cross-positions. A misleading conclusion concerning spin coupling is easy to avoid using various ? MAS .

Balevicius, Vytautas; Gacesa, Alexandar; Plavec, Janez

2004-03-01

327

Solid State NMR Methods for Coal Science. Progress Report, September 15, 1983-December 31, 1983.  

National Technical Information Service (NTIS)

Several novel NMR spectroscopic techniques are being developed for application to coal science. Multiple pulse decoupling techniques are being developed to allow high resolution scalar coupled exp 13 C CP-MAS spectra of coals to be obtained. This method w...

K. W. Zilm

1984-01-01

328

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

National Technical Information Service (NTIS)

The 13(sub C) 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 o...

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

1991-01-01

329

1H, 13C NMR studies and GIAO\\/DFT calculations of substituted N-(4-aryl-1-piperazinylbutyl) derivatives, new analogues of buspirone  

Microsoft Academic Search

13C cross-polarisation (CP) magic angle spinning (MAS) NMR data are reported for seven piperazinylbutyl derivatives of 1,4-dichloro-dibenzo[e,h]bicyclo[2,2,3]octane-2,3-dicarboimide, new analogues of buspirone (anxiolytic drug). The assignment of solid state 13C NMR spectra were made with an aid of variable contact time experiments, as well as by comparison with solution data and calculated shielding constants. 13C CPMAS NMR spectra showed a disorder

Maciej Pisklak; Jerzy Kossakowski; Miros?aw Perli?ski; Iwona Wawer

2004-01-01

330

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 2H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1H decoupling (HPPD) and 1H- 2H 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 2H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1H to 2H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

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

1994-08-01

331

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

332

Antimicrobial activity of HR810 against 419 strict anaerobic bacteria.  

PubMed Central

HR810 and four other new beta-lactams were tested against 419 recent clinical anaerobic bacterial isolates. HR810 was found to have an antimicrobial spectrum most similar to that of cefotaxime, inhibiting 52.6% of Bacteroides fragilis group strains and 97.2% of all other anaerobic strains at an MIC of less than or equal to 16 micrograms/ml. Cefoxitin was found to have a narrower antimicrobial spectrum against the gram-positive anaerobic bacteria (8.4 to 10.1% less) than HR810 and cefotaxime, respectively.

Jones, R N; Gerlach, E H

1985-01-01

333

Structure and Ionic Interactions of Organic–Inorganic Composite Polymer Electrolytes Studied by Solid-State NMR and Raman Spectroscopy  

Microsoft Academic Search

Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic–inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic–inorganic composite, and spin diffusion measurements are used to

Chan Gyu Joo; Lyudmila M Bronstein; Robert L Karlinsey; Josef W Zwanziger

2002-01-01

334

RHODOPSIN-LIPID INTERACTIONS STUDIED BY NMR  

PubMed Central

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

Soubias, Olivier; Gawrisch, Klaus

2012-01-01

335

Methane Dehydro-aromatization over Mo\\/HZSM-5 in the Absence of Oxygen: A Multinuclear Solid-State NMR Study of the Interaction between Supported Mo Species and HZSM-5 Zeolite with Different Crystal Sizes  

Microsoft Academic Search

The interaction between Mo species and a conventionally microsized and particularly nanosized HZSM-5 support was studied by high-resolution multinuclear solid-state NMR techniques. As proved by 27Al and 29Si MAS as well as CP\\/MAS NMR investigations, this interaction was so strong that the framework aluminum of both microsized and nanosized HZSM-5 zeolites could be extracted. With increasing Mo loading, more nonframework

Weiping Zhang; Ding Ma; Xiuwen Han; Xiumei Liu; Xinhe Bao; Xinwen Guo; Xiangsheng Wang

1999-01-01

336

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

337

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

SciTech Connect

Bulk magnetization and {sup 1}H static and magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of two magnetically heterogeneous model systems based on laponite (LAP) layered silicate or polystyrene (PS) with low and high proton concentration, respectively, and ferrimagnetic Fe{sub 2}O{sub 3} nano- or micro-particles have been studied. In LAP+Fe{sub 2}O{sub 3}, a major contribution to the NMR signal broadening is due to the dipolar coupling between the magnetic moments of protons and magnetic particles. In PS+Fe{sub 2}O{sub 3}, due to the higher proton concentration in polystyrene and stronger proton–proton dipolar coupling, an additional broadening is observed, i.e. {sup 1}H MAS NMR spectra of magnetically heterogeneous systems are sensitive to both proton–magnetic particles and proton–proton dipolar couplings. An increase of the volume magnetization by ?1 emu/cm{sup 3} affects the {sup 1}H NMR signal width in a way that is similar to an increase of the proton concentration by ?2×10{sup 22}/cm{sup 3}. {sup 1}H MAS NMR spectra, along with bulk magnetization measurements, allow the accurate determination of the hydrogen concentration in magnetically heterogeneous systems.

Levin, E. M.; Bud& #x27; ko, S. L.

2011-04-28

338

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

339

Multinuclear NMR studies of mixed Ca1-xSrxF2 crystals  

NASA Astrophysics Data System (ADS)

The local environments of fluorine and calcium ions in Ca1-xSrxF2 single crystals have been studied using F19 and C43a magic-angle spinning (MAS) NMR spectroscopies. The fluorine speciation is found to depend on both the distribution of cations (Ca and Sr) around each fluorine site in the fluorite lattice, as well as fluctuations in the ionic character of bonding between fluorine and these cations. The natural abundance C43a MAS NMR results show a clear relation between C43a chemical shielding and bond distances in halides, with increasing shielding as the fluorite lattice expands and Ca-F distances lengthen. When taken together, the results from F19 and C43a NMR are consistent with a random substitution of Sr for Ca in the mixed fluoride system.

Youngman, R. E.; Smith, C. M.

2008-07-01

340

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

SciTech Connect

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

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

2013-03-05

341

Basics of NMR  

NSDL National Science Digital Library

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

Hornak, Joseph P.

342

Sodium cation locations in zeolite omega studied by 23Na VASS NMR  

NASA Astrophysics Data System (ADS)

Overlapping 23Na NMR signals of zeolite Na-omega are observed by a 2D MAS quadrupolar nutation NMR spectrum and VASS NMR spectra. The low-field Lorentzian shape component centered at - 3 ppm is assigned to the signal of mobile Na + cations located in twelve-membered ring channels. The high-field component, varying considerably with the spinning angles of VASS NMR spectra, is assigned to the signal of less mobile Na + cations located in gmelinite cages. The partition between two categories of Na + cations is determined by the simulation of VASS NMR spectra with the theoretical consideration extended to more general case that both the quadrupolar and chemical shift anisotropic interactions coexist.

Chen, T. H.; Wang, J. Z.; Li, H. X.; Wang, K. X.; Deng, F.; Du, Y. R.; Ding, D. T.

1995-05-01

343

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

NASA Astrophysics Data System (ADS)

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

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

1988-09-01

344

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

NASA Technical Reports Server (NTRS)

We extend fine analyses of the B and A stars, gamma Geminorum, 7 Sextantis, HR 4817, and HR 5780 using additional spectroscopic data from the Kitt Peak National Observatory (KPNO) coude feed telescope with a TI CCD, camera 5, and grating A, and ATLAS9 model atmospheres. In addition we study HD 60825, which had colors similar to the FHB A stars, but was found to be a Population I star. HD 60825, as is gamma Gem, is a sharp-lined early-A star with nearly solar derived abundances. HR 5780 and 7 Sex are also examples of stars which for the most part have solar abundances. The newly derived abundances for HR 4817 reveal important differences with respect to 53 Tau, a somewhat similar HgMn star.

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

1994-01-01

345

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

346

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

347

Network connectivity in aluminoborosilicate glasses: A high-resolution 11B, 27Al and 17O NMR study  

Microsoft Academic Search

O-17 enriched calcium and potassium aluminoborosilicate glasses with compositions similar (or analogous) to commercial E-glass were made and studied by 11B, 27Al and 17O NMR in order to explore the network speciation and mixing. Fractions of non-bridging oxygens associated with silicon and boron can be obtained simply from 17O magic angle spinning (MAS) NMR, while bridging oxygen populations result from

Lin-Shu Du; Jonathan F. Stebbins

2005-01-01

348

On the Nature of Reaction-Controlled Phase Transfer Catalysts for Epoxidation of Olefin: A 31 P NMR Investigation  

Microsoft Academic Search

[p-C5H5NC16H33]3[PW4O16] was reported to be an excellent epoxidation catalyst which exhibited a unique reaction-controlled phase transfer behavior. In the paper, the composition and structural changes of the reaction-controlled phase transfer catalyst during and after reaction have been investigated by 31P NMR spectroscopy. The 31P MAS NMR confirmed that the original catalyst was a mixture of heteropoly tungstophosphates. When the catalyst

Yangying Chen; Jianqin Zhuang; Xiumei Liu; Jinbo Gao; Xiuwen Han; Xinhe Bao; Ning Zhou; Shuang Gao; Zuwei Xi

2004-01-01

349

Solid-state NMR characterization of a controlled-pore glass and of the effects of electron irradiation  

Microsoft Academic Search

Controlled-pore glasses (CPGs) are silica-based materials which provide an adequate model system for a better understanding of the radiation chemistry of glasses, especially under nanoscopic confinement. This paper presents a characterization of a nanoporous CPG before and after electron irradiation using multinuclear solid-state magnetic resonance (NMR). 1H MAS NMR has been used for studying the surface proton sites and it

F. Brunet; T. Charpentier; S. Le Caër; J.-P. Renault

2008-01-01

350

Investigation of rhodium complexes in micro- and mesoporous materials by computer modeling, FTIR, and 31 P MAS NMR  

Microsoft Academic Search

Tetracarbonyldichlororhodium(I) [Rh(CO)2(? -Cl)]2 entrapped in faujasite type zeolites reacted with phosphines PMe3- xPhx at 393-463 K to a different extent. Although according to computational studies phosphines with x<2 should be small enough\\u000a to enter the micropore system, the reaction was in no case complete and led to a mixture of products as observed by IR spectroscopy.\\u000a Furthermore surface-bonded rhodium carbonyl complexes

A. Janssen; J. P. M. Niederer; W. F. Hoëlderich

1997-01-01

351

Application of 11B MAS-NMR to the characterization of boron in coal fly ash generated from Nantun coal  

Microsoft Academic Search

Boron and its compounds are environmentally hazardous substance and are well-known condensed products that appear in coal fly ash during combustion of coal in coal-fired electric power stations. In a previous study, we suggested that boron in coal fly ash obtained from Nantun coal in China, identified as Ash–N, may exist on the surface of relatively large coal fly ash

Shunsuke Kashiwakura; Takafumi Takahashi; Hideki Maekawa; Tetsuya Nagasaka

2010-01-01

352

Solid-State NMR Identification and Quantification of Newly Formed Aluminosilicate Phases in Weathered Kaolinite Systems  

SciTech Connect

The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3 -, 1 mol kg-1 of OH-, and pH ~13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10-3, 10-4, and 10-5 molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10-5 m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10-3 m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and the quantitative nature of the 27Al NMR data shows that cancrinite growth increases while sodalite reaches a steady state with respect to total aluminum in the solid phases. The data also relate the coupling of Cs sorption to the ripening of feldspathoid phases in this heterogeneous system as a function of time, and illustrate the important influence of co-contaminants on the environmental reaction kinetics studied here.

Crosson, Garry S.; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary K.; O'Day, Peggy A.; Mueller, Karl T.

2006-01-19

353

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

354

Multinuclear NMR studies of relaxor ferroelectrics  

NASA Astrophysics Data System (ADS)

Multinuclear NMR of 93Nb, 45Sc, and 207Pb has been carried out to study the structure, disorder, and dynamics of a series of important solid solutions: perovskite relaxor ferroelectric materials (1-x) Pb(Mg1/3Nb 2/3)O3-x Pb(Sc1/2Nb1/2)O 3 (PMN-PSN). 93Nb NMR investigations of the local structure and cation order/disorder are presented as a function of PSN concentration, x. The superb fidelity and accuracy of 3QMAS allows us to make clear and consistent assignments of spectral intensities to the 28 possible nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb), where each number ranges from 0 to 6 and their sum is 6. For most of the 28 possible nBn configurations, isotropic chemical shifts and quadrupole product constants have been extracted from the data. The seven configurations with only larger cations, Mg 2+ and Sc3+ (and no Nb5+) are assigned to the seven observed narrow peaks, whose deconvoluted intensities facilitate quantitative evaluation of, and differentiation between, different models of B-site (chemical) disorder. The "completely random" model is ruled out and the "random site" model is shown to be in qualitative agreement with the NMR experiments. To obtain quantitative agreement with observed NMR intensities, the random site model is slightly modified by including unlike-pair interaction energies. To date, 45Sc studies have not been as fruitful as 93Nb NMR because the resolution is lower in the 45Sc spectra. The lower resolution of 45Sc spectra is due to a smaller span of isotropic chemical shift (40 ppm for 45Sc vs. 82 ppm for 93Nb) and to the lack of a fortuitous mechanism that simplifies the 93Nb spectra; for 93Nb the overlap of the isotropic chemical shifts of 6-Sc and 6-Nb configurations results in the alignment of all the 28 configurations along only seven quadrupole distribution axes. Finally we present variable temperature 207Pb static, MAS, and 2D-PASS NMR studies. Strong linear correlations between isotropic and anisotropic chemical shifts show that Pb-O bonds vary from more ionic to more covalent environments. Distributions of Pb-O bond lengthes are also quantitatively described. Such distributions are used to examine two competing models of Pb displacements; the shell model and the unique direction model. Only the latter model is able to reproduce the observed Pb-O distance distribution.

Zhou, Donghua

355

On the Human Resource Integration Measures in the Overseas M&As of Chinese Manufacture Enterprises  

Microsoft Academic Search

Global enterprise Mergers and Acquisitions (M&As) are sweeping the world. In China, the M&As have been in large scale. Not only there are transnational corporations entering China, but also Chinese manufacture enterprises expand to overseas to have M&As, during which human resource management is an very important element. The human resources of the merged enterprise themselves is the strategic target

Hu Feng; Hang Zhou; P. R. China

2010-01-01

356

Behind M&As in China and the United States: Networks, learning, and institutions  

Microsoft Academic Search

Few scholars would dispute the argument that mergers and acquisitions (M&As) are different in China and the United States,\\u000a but we know little about how they differ. This article reports one of the first studies that systematically compares and contrasts\\u000a how M&As differ in these two countries. While prior research on M&As tends to emphasize economic and financial explanations\\u000a while

Haibin Yang; Sunny Li Sun; Mike W. Peng

2011-01-01

357

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

358

Rh18 and hrS blood groups and antibodies.  

PubMed

Anti-hrS, also known as the Shabalala antibody, is unlikely to be found in unabsorbed human serum. The term 'anti-hrS, was devised by Shapiro in 1960 to describe the antibodies remaining in the absorbed serum after anti-Rh18 had been absorbed with R2R2 red cells. R2R2-absorbed anti-Rh18 (anti-hrS), although an interesting research tool, is therefore clinically irrelevant. Unabsorbed anti-Rh18, on the other hand, is a clinically significant antibody. It is compatible not only with Rh-'deleted' and Rhnull red cells, as described by Shapiro, but is also compatible with the red cells of numbers of Southern African Blacks and Coloureds (mixed race) who have Ro, Rou or R2r phenotypes. Anti-Rh18 causes haemolytic disease of the newborn and, when uncontaminated with other antibodies, is a further reagent for resolving Rh grouping problems. PMID:8036793

Moores, P

1994-01-01

359

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

360

Mas-Mediated Antioxidant Effects Restore the Functionality of Angiotensin Converting Enzyme 2-Angiotensin-(1-7)-Mas Axis in Diabetic Rat Carotid  

PubMed Central

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

Gomes, Mayara Santos; Restini, Carolina Baraldi Araujo

2014-01-01

361

13C and 15N CP/MAS, 1H-15N SCT CP/MAS and FTIR spectroscopy as tools for qualitative detection of the presence of zwitterionic and non-ionic forms of ansa-macrolide 3-formylrifamycin SV and its derivatives in solid state.  

PubMed

(13)C, (15)N CP/MAS, including (1)H-(13)C and (1)H-(15)N short contact time CP/MAS experiments, and FTIR methods were applied for detailed structural characterization of ansa-macrolides as 3-formylrifamycin SV (1) and its derivatives (2-6) in crystal and in powder forms. Although HPLC chromatograms for 2/CH3 OH and 2/CH3 CCl3 were the same for rifampicin crystals dissolved in respective solvents, the UV-vis data recorded for them were different in 300-375?nm region. Detailed solid state (13)C and (15)N CP/MAS NMR and FTIR studies revealed that rifampicin (2), in contrast to 3-formylrifamycin SV (1) and its amino derivatives (3-6), can occur in pure non-ionic or zwitterionic forms in crystal and in pure these forms or a mixture of them in a powder. Multinuclear CP/MAS and FTIR studies demonstrated also that 3-6 derivatives were present exclusively in pure zwitterionic forms, both in powder and in crystal. On the basis of the solid state NMR and FTIR studies, two conformers of 3-formylrifamycin SV were detected in powder form due to the different orientations of carbonyl group of amide moiety. The PM6 molecular modeling at the semi-empirical level of theory, allowed visualization the most energetically favorable non-ionic and zwitterionic forms of 1-6 antibiotics, strongly stabilized via intramolecular H-bonds. FTIR studies indicated that the originally adopted forms of these type antibiotics in crystal or in powder are stable in standard laboratory conditions in time. The results presented point to the fact that because of a possible presence of two forms of rifampicin (compound 2), quantification of the content of this antibiotic in relevant pharmaceuticals needs caution. PMID:24347399

Przybylski, Piotr; Pyta, Krystian; Klich, Katarzyna; Schilf, Wojciech; Kamie?ski, Bohdan

2014-01-01

362

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

363

The fate of the solid matter orbiting HR 4796A  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

364

The spectroscopic-speckle triple system HR 5472  

NASA Astrophysics Data System (ADS)

DAO coude radial velocities obtained between 1975 and 1990 have been used to revise Harper and Blanchet's (1937) spectroscopic orbital elements of the single-line triple system HR 5472. A visual orbit for the long-period pair, derived from the data presented by McAlister and Hartkopf (1988) and by McAlister et al. (1990), is in good agreement with the spectroscopic one, and a solution has been obtained which fits the speckle and spectroscopic data simultaneously. Even though only the primary star's spectrum has been observed, that solution makes it possible to put some limits on the masses of the components of HR 5472.

Barlow, D. J.; Scarfe, C. D.

1991-12-01

365

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

PubMed

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

Paradowska, Katarzyna; Wawer, Iwona

2014-05-01

366

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

PubMed

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

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

2013-08-22

367

Solid state NMR study of nanodiamond surface chemistry.  

PubMed

Solid state NMR measurements using 13C, 1H and 19F nuclei (MAS, CP-MAS) underline the surface chemistry of nanodiamonds from different synthesis (detonation, high pressure high temperature and shock compression). The comparison of the spin-lattice relaxation times T1 and physicochemical characterization (spin densities of dangling bonds, specific surface area and Raman and infrared spectroscopies) for the various samples, as synthesized, chemically purified and fluorinated allows the nature and the location of the various groups, mainly C-OH, C-H and C-F to be investigated. C-OH groups are located only on the surface whereas C-H and dangling bonds seem to be distributed in the whole volume. Fluorination was studied as a chemical treatment for purification and change of the hydrophobicity through the conversion of the C-OH groups into covalent C-F bonds. PMID:22119523

Dubois, Marc; Guérin, Katia; Batisse, Nicolas; Petit, Elodie; Hamwi, André; Komatsu, Naoki; Kharbache, Hayat; Pirotte, Pascal; Masin, Francis

2011-11-01

368

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

369

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

PubMed

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

Johnson, Robert L; Schmidt-Rohr, Klaus

2014-02-01

370

Indirectly detected heteronuclear correlation solid-state NMR spectroscopy of naturally abundant 15N nuclei.  

PubMed

Two-dimensional indirectly detected through-space and through-bond (1)H{(15)N} solid-state NMR experiments utilizing fast magic angle spinning (MAS) and homonuclear multipulse (1)H decoupling are evaluated. Remarkable efficiency of polarization transfer can be achieved at a MAS rate of 40 kHz by both cross-polarization and INEPT, which makes these methods applicable for routine characterizations of natural abundance solids. The first measurement of 2D (1)H{(15)N} HETCOR spectrum of natural abundance surface species is also reported. PMID:24287060

Althaus, Stacey M; Mao, Kanmi; Stringer, John A; Kobayashi, Takeshi; Pruski, Marek

2014-01-01

371

A combined deuterium NMR and quantum chemical investigation of inequivalent hydrogen bonds in organic solids.  

PubMed

Deuterium magic angle spinning (MAS) NMR spectroscopy and quantum chemical calculations are used to investigate organic solids in which inequivalent hydrogen bonds are present. The use of (2)H MAS allows one to measure the chemical shift, ?, quadrupolar coupling constant, C(Q), and asymmetry in the quadrupolar interaction, ?(Q), for each type of hydrogen bond present in the system. Quantum chemical calculations of the magnetic shielding (?, which can be related to ?) and the electric field gradient (EFG, which can be related to C(Q)) are compared to the experimental results and are discussed with respect to the relative strengths of the hydrogen bonds within each system. PMID:22883448

Webber, Renee; Penner, Glenn H

2012-01-01

372

HR 8799: A Link between ? Doradus Variables and ? Bootis Stars  

Microsoft Academic Search

On the basis of a new classi—cation-resolution spectrum, we —nd that HR 8799, a known member of the newly discovered c Doradus variable star class, is a j Bootis star. Spectral synthesis, in conjunction with —uxes from visible spectrophotometry and the TD -1 satellite, yields

Richard O. Gray; Anthony B. Kaye

1999-01-01

373

Managing the HR dimension of international project operations  

Microsoft Academic Search

While much is known about the role of HRM in achieving positive outcomes in foreign subsidiary and international joint venture contexts, there has been a paucity of research into HRM issues in international project operations. In this paper, we develop an analytical framework to demonstrate the HR activities of each stage of the international project lifecycle, drawing upon supporting data

Catherine L. Welch; Denice E. Welch; Marja Tahvanainen

2008-01-01

374

What role for HR during mergers and acquisitions?  

Microsoft Academic Search

Purpose – Examines why most of what appear at first to be good merger or acquisition deals fail. Design\\/methodology\\/approach – Describes five steps through which HR can help to make a merger or acquisition a success. Findings – Highlights the importance of: making the vision tangible; getting the right integration team; good communication; ensuring that performance reviews are correctly focused

Paul J. Siegenthaler

2011-01-01

375

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

376

Clinical Imaging of Bone Microarchitecture with HR-pQCT  

PubMed Central

Osteoporosis, a disease characterized by loss of bone mass and structural deterioration, is currently diagnosed by dual-energy x-ray absorptiometry (DXA). However, DXA does not provide information about bone microstructure, which is a key determinant of bone strength. Recent advances in imaging permit the assessment of bone microstructure in vivo using high-resolution peripheral quantitative computed tomography (HR-pQCT). From these data, novel image processing techniques can be applied to characterize bone quality and strength. To date, most HR-pQCT studies are cross-sectional comparing subjects with and without fracture. These studies have shown that HR-pQCT is capable of discriminating fracture status independent of DXA. Recent longitudinal studies present new challenges in terms of analyzing the same region of interest and multisite calibrations. Careful application of analysis techniques and educated clinical interpretation of HR-pQCT results have improved our understanding of various bone-related diseases and will no doubt continue to do so in the future.

Nishiyama, Kyle K.; Shane, Elizabeth

2014-01-01

377

Clinical imaging of bone microarchitecture with HR-pQCT.  

PubMed

Osteoporosis, a disease characterized by loss of bone mass and structural deterioration, is currently diagnosed by dual-energy x-ray absorptiometry (DXA). However, DXA does not provide information about bone microstructure, which is a key determinant of bone strength. Recent advances in imaging permit the assessment of bone microstructure in vivo using high-resolution peripheral quantitative computed tomography (HR-pQCT). From these data, novel image processing techniques can be applied to characterize bone quality and strength. To date, most HR-pQCT studies are cross-sectional comparing subjects with and without fracture. These studies have shown that HR-pQCT is capable of discriminating fracture status independent of DXA. Recent longitudinal studies present new challenges in terms of analyzing the same region of interest and multisite calibrations. Careful application of analysis techniques and educated clinical interpretation of HR-pQCT results have improved our understanding of various bone-related diseases and will no doubt continue to do so in the future. PMID:23504496

Nishiyama, Kyle K; Shane, Elizabeth

2013-06-01

378

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

379

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

2012-02-28

380

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

SciTech Connect

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

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

2007-12-03

381

Variable temperature system using vortex tube cooling and fiber optic temperature measurement for low temperature magic angle spinning NMR  

Microsoft Academic Search

We describe the construction and operation of a variable temperature (VT) system for a high field fast magic angle spinning (MAS) probe. The probe is used in NMR investigations of biological macromolecules, where stable setting and continuous measurement of the temperature over periods of several days are required in order to prevent sample overheating and degradation. The VT system described

Rachel W. Martin; Kurt W. Zilm

2004-01-01

382

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

383

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

384

Development of a generic, computerized nuclear material accountability system: NucMAS  

Microsoft Academic Search

The application NucMAS provides basic computerized accountability functions for the Savannah River Plant (SRP) Separations Department Material Balance Areas (MBA's). These functions include data entry, data management, calculations, and report generation. NucMAS can be used both for routine reporting to the SRP central Material Control and Accounting (MC and A) system and for rapid ad hoc queries in emergency situations.

M. D. Cornell; J. M. OLeary

1987-01-01

385

Psychometric Comparison of the Motivation Assessment Scale (MAS) and the Questions about Behavioral Function (QABF)  

ERIC Educational Resources Information Center

Background: The Motivation Assessment Scale (MAS) and the Questions About Behavioral Function (QABF) are frequently used to assess the learned function of challenging behaviour in people with intellectual disability (ID). The aim was to explore and compare the psychometric properties of the MAS and the QABF. Method: Seventy adults with ID and…

Koritsas, S.; Iacono, T.

2013-01-01

386

Multiple mean motion resonances in the HR 8799 planetary system  

NASA Astrophysics Data System (ADS)

HR 8799 is a nearby star hosting at least four ˜10 mJup planets in wide orbits up to ˜70 au, detected through the direct, high-contrast infrared imaging. Large companions and debris discs reported interior to ˜10 au, and exterior to ˜100 au indicate massive protoplanetary disc in the past. The dynamical state of the HR 8799 system is not yet fully resolved, due to limited astrometric data covering tiny orbital arcs. We construct a new orbital model of the HR 8799 system, assuming rapid migration of the planets after their formation in wider orbits. We found that the HR 8799 planets are likely involved in double Laplace resonance, 1e:2d:4c:8b MMR. Quasi-circular planetary orbits are coplanar with the stellar equator and inclined by ˜25° to the sky plane. This best-fitting orbital configuration matches astrometry, debris disc models, and mass estimates from cooling models. The multiple mean motion resonance (MMR) is stable for the age of the star ˜160 Myr, for at least 1 Gyr unless significant perturbations to the N-body dynamics are present. We predict four configurations with the fifth hypothetical innermost planet HR 8799f in ˜9.7 au, or ˜7.5 au orbit, extending the MMR chain to triple Laplace resonance 1f:2e:4d:8c:16b MMR or to the 1f:3e:6d:12c:24b MMR, respectively. Our findings may establish strong boundary conditions for the system formation and its early history.

Go?dziewski, Krzysztof; Migaszewski, Cezary

2014-06-01

387

Practical aspects of Lee–Goldburg based CRAMPS techniques for high-resolution 1H NMR spectroscopy in solids: Implementation and applications  

Microsoft Academic Search

Elucidating the local environment of the hydrogen atoms is an important problem in materials science. Because 1H spectra in solid-state nuclear magnetic resonance (NMR) suffer from low resolution due to homogeneous broadening, even under magic-angle spinning (MAS), information of chemical interest may only be obtained using certain high-resolution 1H MAS techniques. 1H Lee–Goldburg (LG) CRAMPS (Combined Rotation And Multiple-Pulse Spectroscopy)

Cristina Coelho; João Rocha; P. K. Madhu; Luís Mafra

2008-01-01

388

(31)P solid-state NMR based monitoring of permeation of cell penetrating peptides into skin.  

PubMed

The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R8, R11, and YKA) through skin intercellular lipids using (31)P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, and sections (0-60, 61-120, and 121-180?m) were collected and analyzed for (31)P NMR signal. The concentration-dependent shift of 0, 25, 50, 100, and 200mg/ml of TAT on skin layers, diffusion of TAT, R8, R11, and YKA in the skin and time dependent permeation of R11 was measured on various skin sections using (31)P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in (31)P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100mg/ml CPP concentration. R11 and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R11 penetration up to 180?m within 30min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, (31)P solid-state NMR can be used to track CPP penetration into different skin layers. PMID:23702274

Desai, Pinaki R; Cormier, Ashley R; Shah, Punit P; Patlolla, Ram R; Paravastu, Anant K; Singh, Mandip

2014-02-01

389

NMR imaging microscopy  

SciTech Connect

In the past several years, proton nuclear magnetic resonance (NMR) imaging has become an established technique in diagnostic medicine and biomedical research. Although much of the work in this field has been directed toward development of whole-body imagers, James Aguayo, Stephen Blackband, and Joseph Schoeninger of the Johns Hopkins University School of Medicine working with Markus Hintermann and Mark Mattingly of Bruker Medical Instruments, recently developed a small-bore NMR microscope with sufficient resolution to image a single African clawed toad cell (Nature 1986, 322, 190-91). This improved resolution should lead to increased use of NMR imaging for chemical, as well as biological or physiological, applications. The future of NMR microscopy, like that of many other newly emerging techniques, is ripe with possibilities. Because of its high cost, however, it is likely to remain primarily a research tool for some time. ''It's like having a camera,'' says Smith. ''You've got a way to look at things at very fine levels, and people are going to find lots of uses for it. But it is a very expensive technique - it costs $100,000 to add imaging capability once you have a high-resolution NMR, which itself is at least a $300,000 instrument. If it can answer even a few questions that can't be answered any other way, though, it may be well worth the cost.''

Not Available

1986-10-01

390

Heteronuclear X-Y double-resonance solid-state NMR: Techniques for structural characterization of inorganic materials  

NASA Astrophysics Data System (ADS)

Since the introduction of the Magic Angle Spinning (MAS) technique, solid state NMR has become an increasingly important tool in the characterization of inorganic materials. Solid state NMR experiments, however, can be very time consuming due to the low sensitivities and/or low natural abundances for many of the NMR active nuclei. Furthermore, under MAS conditions, interactions arising from the dipolar coupling are averaged to zero and any dipolar information lost. The goal of this research is to develop and apply double resonance NMR techniques which (1) may increase the sensitivity of many NMR active nuclei and (2) may preserve the resolution achieved by MAS while re-introducing the dipolar coupling information. Because of the dependence on the internuclear distance, r, the heteronuclear dipole coupling can be exploited to obtain information on local environments, internuclear distances, and to aid in spectral editing and phase identification. This study focuses on the double resonance techniques: Cross Polarization with Magic Angle Spinning (CPMAS), Heteronuclear Double Quantum Filtering (HDQF), Spin Echo Double Resonance (SEDOR), and Rotational Echo DOuble Resonance (REDOR). These techniques may be used to examine a wide variety of systems. The application of these techniques to the following systems will be demonstrated: (1) Semiconductor alloys in the CdSiAssb{2-x}Psb{x} system; (2) Crystalline and amorphous ternary Al-P-Se system; (3) Crystalline and amorphous borosilicates; (4) Zirconium phosphate substituted with vanadium.

Hudalla, Christopher John

391

Probing the local structural environment of calcium by natural-abundance solid-state 43 Ca NMR  

NASA Astrophysics Data System (ADS)

New natural-abundance 43 Ca magic angle spinning (MAS) NMR data measured at high magnetic field ( 14.1 T ) is presented for a range of crystalline calcium-containing binary and ternary inorganic compounds. The combination of high field, moderate MAS (up to 4.5 kHz ), and large sample volume (a 9.5 mm diameter MAS rotor) means that a good signal-to-noise ratio can generally be obtained in a time ( ˜12 h ) that makes 43 Ca NMR a feasible approach for determining information about calcium siting in a wide range of materials of physical interest. This study greatly increases the number of 43 Ca NMR parameters determined for solid materials in the literature, extending reports to local nearest-neighbor coordinations to other than oxygen. These data show that the isotropic chemical shift range is >250 ppm and typically that the quadrupole interaction is <4 MHz . In ternary compounds where Ca is coordinated in the nearest-neighbor shell by only oxygen, the isotropic 43 Ca chemical shift correlates well to the mean Ca-O distance, consistent with the only previous study. In binary compounds the isotropic 43 Ca chemical shift does not appear to be correlated with the mean Ca-X bond length. The extension of natural-abundance 43 Ca MAS NMR studies to amorphous materials are reported by examining sol-gel prepared calcium silicate materials. The data show that in the initial amorphous mixture at lower temperatures (120 350°C) the calcium environment is more like that in the parent calcium nitrate than a silicate, and that further heat treatment causes very significant broadening of the calcium resonance. The implications of this observation for the use of natural-abundance 43 Ca MAS NMR structural studies of amorphous materials are examined.

Lin, Zhongjie; Smith, M. E.; Sowrey, F. E.; Newport, R. J.

2004-06-01

392

ups Her, phi Her & HR 7018 abundances (Adelman+, 2001)  

NASA Astrophysics Data System (ADS)

Elemental abundances analyses are performed for the Mercury-Manganese stars ? Her, ? Her, and HR 7018 consistent with previous studies of this series using spectrograms obtained with Reticon and CCD detectors. Comparisons of the first two analyses with those performed using coadded photographic plates show the general consistency of the derived elemental abundances. For ? Her and for ? Her, abundances were newly found for O, and for Al, V, Zn, and Ce, respectively. HR 7018 is discovered to be a single-lined spectroscopic binary. Its Sc abundance is the smallest of any class member with derived abundances and its Sr abundance the largest of any known HgMn star. A correlation analysis of the most complete abundance sets for 20 HgMn stars shows that the abundances of some elements are correlated with one another and some are functions of the stellar effective temperature. (2 data files).

Adelman, S. J.; Gulliver, A. F.; Rayle, K. E.

2001-01-01

393

The influence of line managers and HR department on employees' affective commitment  

Microsoft Academic Search

Based on social exchange theory, we investigate the impact of HRM investments made by two important HR actors, line managers and HR department, on employees' affective commitment. More specifically, we examine the independent and joint impact of line managers' enactment of HR practices, their relations-oriented leadership behaviour and the HR department's service quality. Accordingly, we consider the largely neglected HRM

Caroline Gilbert; Sophie De Winne; Luc Sels

2011-01-01

394

HR practices during post-merger conflict and merger performance  

Microsoft Academic Search

An extensive body of literature has investigated financial and strategic variables as predictors of mergers and acquisitions (M&A) performance without finding clear relationships. The literature does not investigate remedies for conflicts in M&A. This paper aims to develop a knowledge-based theory of M&A integration, drawing upon research on HR practices in M&A, the resource-based view of the firm, and international

Yaakov Weber; Dalia Rachman-Moore; Shlomo Yedidia Tarba

2012-01-01

395

Detached eclipsing binaries with very unequal members - HR 7464  

NASA Astrophysics Data System (ADS)

Waelkens and Rufener's (1983) photoelectric lightcurve (as yet unexplored) of the newly discovered eclipsing binary HR 7464 has been analyzed. The photometric solution presented here reveals that this binary is an A5m + G main sequence detached system, which is particularly remarkable for the great dissimilarity between its members. The frequency of detached eclipsing pairs with very unequal members (i.e., with low mass ratio) is then discussed; some bimodality in the innate mass ratio distribution of close binaries is inferred.

Giuricin, G.; Mardirossian, F.; Mezzetti, M.

1984-06-01

396

Relationships between HR and VO2 in the obese  

Microsoft Academic Search

BYRNE, N. M., and A. P. HILLS. Relationships between HR and VO2 in the obese. Med. Sci. Sports Exerc., Vol. 34, No. 9, pp. 1419 -1427, 2002.Purpose: To enable more targeted exercise prescription for the obese, the purpose of this study was to consider relationships between relative indices of VO2peak ,VO2R, HRpeak, and HRR in a sample of obese adults.

NUALA M. BYRNE; ANDREW P. HILLS

397

Practical NMR imaging  

SciTech Connect

This book contains the following chapters: General principles; Siting and installation of x-ray equipment; Practical testing; The image slice; NMR in clinical practice; Development of tissue contrast in magnetic resonance imaging; The clinical use of contrast agents in magnetic resonance imaging; Advanced imaging techniques; In vivo spectroscopy; and Safety considerations.

Foster, M.A.; Hutchison, J.M.S.

1987-01-01

398

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

399

Educational NMR Software  

NASA Astrophysics Data System (ADS)

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

Lundberg, Peter

1997-12-01

400

NMR magnet technology at MIT  

SciTech Connect

The design and construction of high field superconducting NMR magnets has much in common with other types of adiabatic superconducting magnets. However, two issues have a particular relevance to NMR magnets. They are field drift and homogeneity. In this paper the control of these factors in the particular context of high field NMR spectrometer magnets is examined.

Williams, J.E.C.; Bobrov, E.S.; Iwasa, Y.; Punchard, W.F.B.; Wrenn, J.; Zhukovsky, A. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Francis Bitter National Magnet Lab.)

1992-01-01

401

NMR Characterization of Mechanical Waves  

Microsoft Academic Search

NMR characterization of biological tissues or materials (MR elastography) is a challenging and promising area of research. A review of ongoing progress in acoustic wave detection and characterization using NMR is given. After recalling some basic physical principles of acoustics (strain–stress relationship, viscoelasticity), NMR methods for shear or longitudinal wave detection are described, emphasizing pioneer works. Both spectroscopic and imaging

GUILLAUME MADELIN; NATHALIE BARIL; JACQUES DONALD DE CERTAINES; JEAN-MICHEL FRANCONI; ERIC THIAUDIÈRE

2004-01-01

402

Molecular dynamics of ethylene glycol adsorbed in NaX: NMR and broadband dielectric spectroscopy studies  

Microsoft Academic Search

Proton spin relaxation and broadband dielectric spectroscopy are applied to study the dynamics of ethylene glycol adsorbed in NaX, EG\\/NaX. The molecular mobility strongly depends on the pore filling factor which may be controlled by high-resolution 1H MAS NMR measurements. Although EG in bulk shows a Vogel–Fulcher–Tammann type of activation, temperature dependent relaxation rate measurements for the EG\\/NaX systems always

Özlen F. Erdem; Dieter Michel

2006-01-01

403

The role of Al in CSH: NMR, XRD, and compositional results for precipitated samples  

Microsoft Academic Search

X-ray diffraction, compositional analysis, and ²⁹Si and ²⁷Al MAS NMR spectroscopy of Al-substituted tobermorite-type C-S-H made by precipitation from solution provide significant new insight into the structural mechanisms of Al-substitution in this important and complicated phase. Al occurs in 4-, 5-, and 6-coordination (Al[4], Al[5], and Al[6]) and plays multiple structural roles. Al[4] occurs on the bridging tetrahedra of the

G. K. Sun; J. Francis Young; R. James. Kirkpatrick

2006-01-01

404

Solid-state NMR evaluation of the silane structure on nanoporous silica fillers  

Microsoft Academic Search

Coupling agents play a critical role in the function of organic\\/inorganic composite materials. However, the structure of these compounds as they reside on the filler surface is not well understood. Solid-state CP-MAS 13C and Si FT-NMR were used to study the coupling of ?-methacryloxypropyltrimethoxysilane (MPS) on experimental nanoporous silica fillers following exposure to different coupling environments. The progressive consumption of

Jiazhong Luo; John Lannutti; Robert Seghi

2001-01-01

405

A high-resolution sup 13 C solid-state NMR study of meso-tetraphenylporphyrin and its zinc(II) complex  

SciTech Connect

High-resolution {sup 13}C solid-state NMR spectra of meso-tetraphenylporphyrin (TPP) and its zinc(II) complex (ZnTPP) are assigned by reference to low-temperature solution NMR results and using {sup 1}H- {sup 13}C cross-polarization magic-angle-spinning (CP/MAS). The splittings of the signals from pyrrole carbons in TPP are attributed to kinetic solid-state states involved in the migration of the central hydrogen atom.

Rocha, J.; Kolodziejski, W.; Klinowski, J. (Univ. of Cambridge (United Kingdom)); Cavaleiro, J.A.S. (Univ. of Aveiro (Portugal))

1992-01-01

406

BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format  

NASA Technical Reports Server (NTRS)

The BOReal Ecosystem-Atmosphere Study (BOREAS) Staff Science Aircraft Data Acquisition Program focused on providing the research teams with the remotely sensed aircraft data products they needed to compare and spatially extend point results. The MODIS Airborne Simulator (MAS) images, along with other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes biophysical parameter maps such as surface reflectance and temperature. Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-2 MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994, and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C130 navigation data in a MAS scan model. The data are provided in binary image format files.

Hall, Forrest G. (Editor); Newcomer, Jeffrey (Editor); Lobitz, Brad; Spanner, Michael; Strub, Richard; Lobitz, Brad

2000-01-01

407

BOREAS Level-1B MAS Imagery At-sensor Radiance, Relative X and Y Coordinates  

NASA Technical Reports Server (NTRS)

For BOReal Ecosystem-Atmosphere Study (BOREAS), the MODIS Airborne Simulator (MAS) images, along with the other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes detailed land cover and biophysical parameter maps such as fraction of Photosynthetically Active Radiation (fPAR) and Leaf Area Index (LAI). Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-1b MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994, and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C-130 INS data in a MAS scan model. The data are provided in binary image format files.

Strub, Richard; Strub, Richard; Newcomer, Jeffrey A.; Ungar, Stephen

2000-01-01

408

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.

409

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

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

2013-10-01

410

In vitro cytotoxic and antioxidative activity of Cornus mas and Cotinus coggygria  

Microsoft Academic Search

Cytotoxicity and antioxidant properties of the methanol extracts of leaves and flowers of Cornus mas and Cotinus coggygria were studied, together with their chemical composition. Extracts of C. coggygria flowers and leaves showed better antioxidant activity in reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as in inhibition of lipid peroxidation (LP) than C. mas extracts. Preliminary results showed that all

Katarina Šavikin; Gordana Zduni?; Teodora Jankovi?; Tatjana Stanojkovi?; Zorica Jurani?; Nebojša Menkovi?

2009-01-01

411

The Research about Chinese Corporations' Performance Transition from Overseas Technology-Acquiring M&As  

Microsoft Academic Search

This article comparatively analyzes performance transition in two years that attributes to overseas technology-acquiring M&As carried out by listed companies in Shanghai and Shenzhen Stock Exchanges during 2000 to 2005. The result indicates, in the two years before and after M&As, those companies achieve a obvious rise in their net capital yield, main operating income growth rate and capital liability

Wang Qian; Wang Ying-chun; Feng Qi

2008-01-01

412

Conceptual Modelling within the MAS-CommonKADS Plus OPEN Method Engineering Approach  

Microsoft Academic Search

Evaluation of the MAS-CommonKADS approach for the development of agent-oriented software leads us to propose a number of conceptual modelling elements for inclusion in the metamodelling-based OPEN method engineering approach. In order to support the concepts in MAS-CommonKADS using this existing process framework (namely OPEN), we identify three new tasks, together with two new subtasks and ten additional work products

Quynh-nhu Numi Tran; Brian Henderson-sellers; John K. Debenham; Cesar Gonzalez-perez

2005-01-01

413

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

414

The planetary system host HR8799: on its ? Bootis nature  

NASA Astrophysics Data System (ADS)

HR8799 is a ? Bootis, ? Doradus star hosting a planetary system and a debris disc with two rings. This makes this system a very interesting target for asteroseismic studies. This work is devoted to the determination of the internal metallicity of this star, linked with its ? Bootis nature (i.e. solar surface abundances of light elements and subsolar surface abundances of heavy elements), taking advantage of its ? Doradus pulsations. This is the most accurate way of obtaining this information, and this is the first time that such a study is performed for a planetary-system-host star. We have used the equilibrium code CESAM and the non-adiabatic pulsational code GRACO. We have applied the frequency ratio method (FRM) and the time-dependent convection theory to estimate the mode identification, the Brunt-Vaïsälä frequency integral and the mode instability, making the selection of the models possible. When the non-seismological constraints (i.e. HR8799's position in the Hertzsprung-Russell diagram) are used, the solar abundance models are discarded. This result contradicts one of the main hypotheses for explaining the ? Bootis nature, namely the accretion/diffusion of gas by a star with solar abundance. Therefore, according to this result, a revision of this hypothesis is needed. The inclusion of accurate internal chemical mixing processes seems to be necessary to explain the peculiar abundances observed in the surface of stars with internal subsolar metallicities. The use of the asteroseismological constraints, like those provided by the FRM or the instability analysis, provides a very accurate determination of the physical characteristics of HR8799. However, the dependence of the results on the inclination angle i still remains. The determination of this angle, more accurate multicolour photometric observations and high-resolution spectroscopy can definitively fix the mass and metallicity of this star.

Moya, A.; Amado, P. J.; Barrado, D.; Hernández, A. García; Aberasturi, M.; Montesinos, B.; Aceituno, F.

2010-07-01

415

COULD THE PLANETS AROUND HR 8799 BE BROWN DWARFS?  

SciTech Connect

We consider the limiting case for orbital stability of the companions to HR 8799. This case is only consistent with ages for the system of {approx}100 Myr, not with the 1 Gyr age proposed from asteroseismology. The discrepancy probably arises because the inclination of the star is smaller than assumed in analyzing the asteroseismology data. Given this young age, the best estimates of the companion masses place them by a small margin on the planet side of the division between planets and brown dwarfs.

Moro-Martin, Amaya [Departamento de Astrofisica, CAB (CSIC-INTA), Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz, 28850 Madrid (Spain); Rieke, George H.; Su, Kate Y. L. [Steward Observatory, University of Arizona, 933 North Cherry Ave., Tucson, AZ 85721 (United States)

2010-10-01

416

Sloan Digital Sky Survey - H-R Diagram  

NSDL National Science Digital Library

This website, containing information from the Sloan Digital Sky Survey, provides students with the opportunity to make a H-R Diagram for different star systems. It goes through the relation between the color of a star and its surface temperature, in order to obtain a preliminary diagram. Then, using data from the Hipparcos probe, and the Pleiades system, the student is able to calculate the distance to several stars, which leads to the final version of the Diagram. The same concept is applied to Globular Clusters, and the student is able to tell the age of it by looking at its color.

2009-09-16

417

Hyperfine Structure and Nuclear Moments of 17Hr Bromine76  

Microsoft Academic Search

The nuclear spin, the nuclear magnetic-dipole interaction constant a, and the nuclear electric-quadrupole interaction constant b, have been determined for 17-hr bromine-76 by an atomic-beam experiment. The results are: I=1, |a|=345.422+\\/-0.014 Mc\\/sec, |b|=314.329+\\/-0.022 Mc\\/sec, ba=0.9100+\\/-0.0001. The nuclear magnetic-dipole and electric-quadrupole moments are calculated to be, respectively, mu=+\\/-0.5479+\\/-0.0001 nuclear magneton, and Q=-\\/+0.27+\\/-0.01 barn. The sign of mu, though not determined, is

Edgar Lipworth; Thomas M. Green; Hugh L. Garvin; William A. Nierenberg

1960-01-01

418

hr-law: Human Rights Law Mailing List  

NSDL National Science Digital Library

hr-law is a mailing list for law students studying international human rights or humanitarian law, or who are just interested in the subject. The purpose of the list is to provide a forum where people can share information, experiences and ideas. Some of the appropriate topics for this list include: information on how to do research in the human rights area, and sharing of hints; exchanging help on papers or research projects; discussion of topics related to human rights law; and sharing information on employment, internship and volunteer opportunities.

419

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

420

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