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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

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

3

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

PubMed

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

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

2013-01-01

4

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

PubMed Central

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

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

2011-01-01

5

Exploring high-resolution magic angle spinning (HR-MAS) NMR spectroscopy for metabonomic analysis of apples.  

PubMed

Classical liquid-state high-resolution (HR) NMR spectroscopy has proved a powerful tool in the metabonomic analysis of liquid food samples like fruit juices. In this paper the application of (1)H high-resolution magic angle spinning (HR-MAS) NMR spectroscopy to apple tissue is presented probing its potential for metabonomic studies. The (1)H HR-MAS NMR spectra are discussed in terms of the chemical composition of apple tissue and compared to liquid-state NMR spectra of apple juice. Differences indicate that specific metabolic changes are induced by juice preparation. The feasibility of HR-MAS NMR-based multivariate analysis is demonstrated by a study distinguishing three different apple cultivars by principal component analysis (PCA). Preliminary results are shown from subsequent studies comparing three different cultivation methods by means of PCA and partial least squares discriminant analysis (PLS-DA) of the HR-MAS NMR data. The compounds responsible for discriminating organically grown apples are discussed. Finally, an outlook of our ongoing work is given including a longitudinal study on apples. PMID:23146259

Vermathen, Martina; Marzorati, Mattia; Vermathen, Peter

2012-01-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

8

Real time HR-MAS NMR: application in reaction optimization, mechanism elucidation and kinetic analysis for heterogeneous reagent catalyzed small molecule chemistry.  

PubMed

A novel application of in situ (1)H high-resolution magic angle spinning (HR-MAS) NMR technique for real-time monitoring of H(2)SO(4)-silica promoted formation of 2, 2-disubstituted quinozolin-4(3H)-ones is reported. The detailed NMR spectroscopic data led to elucidation of the mechanism, reaction optimization, kinetics and quantitative analysis of the product accurately and efficiently. The translation of the optimized parameters obtained by (1)H HR-MAS NMR in the wet laboratory provided similar results. It is proposed that (1)H HR-MAS has a potential utility for optimization of various organic transformations in solid supported catalyzed reactions. PMID:18853391

Roy, Abhijeet Deb; Jayalakshmi, K; Dasgupta, Somnath; Roy, Raja; Mukhopadhyay, Balaram

2008-12-01

9

The Effect of Antitumor Glycosides on Glioma Cells and Tissues as Studied by Proton HR-MAS NMR Spectroscopy  

PubMed Central

The effect of the treatment with glycolipid derivatives on the metabolic profile of intact glioma cells and tumor tissues, investigated using proton high resolution magic angle spinning (1H HR-MAS) nuclear magnetic resonance (NMR) spectroscopy, is reported here. Two compounds were used, a glycoside and its thioglycoside analogue, both showing anti-proliferative activity on glioma C6 cell cultures; however, only the thioglycoside exhibited antitumor activity in vivo. At the drug concentrations showing anti-proliferative activity in cell culture (20 and 40 µM), significant increases in choline containing metabolites were observed in the 1H NMR spectra of the same intact cells. In vivo experiments in nude mice bearing tumors derived from implanted C6 glioma cells, showed that reduction of tumor volume was associated with significant changes in the metabolic profile of the same intact tumor tissues; and were similar to those observed in cell culture. Specifically, the activity of the compounds is mainly associated with an increase in choline and phosphocholine, in both the cell cultures and tumoral tissues. Taurine, a metabolite that has been considered a biomarker of apoptosis, correlated with the reduction of tumor volume. Thus, the results indicate that the mode of action of the glycoside involves, at least in part, alteration of phospholipid metabolism, resulting in cell death. PMID:24194925

Garcia-Alvarez, Isabel; Garrido, Leoncio; Romero-Ramirez, Lorenzo; Nieto-Sampedro, Manuel; Fernandez-Mayoralas, Alfonso; Campos-Olivas, Ramon

2013-01-01

10

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

PubMed Central

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

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

2014-01-01

11

Quantitative Aspects of 27Al MAS NMR of Calcium Aluminoferrites  

Microsoft Academic Search

27Al MAS NMR spectra of synthetic calcium aluminoferrites, Ca2AlxFe2?xO5 with x = 0.93, 1, 1.33, reveal only a few percent of the expected intensity for the 27Al central transition, indicating that the calcium aluminoferrite phase in Portland cements can barely be observed by 27Al MAS NMR. This result supports the use of 27Al MAS NMR for quantitative analysis of the

Jørgen Skibsted; Hans J. Jakobsen; Christopher Hall

1998-01-01

12

Interaction of phenol with NaX zeolite as studied by 1H MAS NMR, 29Si MAS NMR and 29Si CP MAS NMR spectroscopy  

Microsoft Academic Search

The interaction of phenol with zeolite NaX has been studied by 1H and 29Si MAS and 29Si-CP-MAS NMR spectroscopy. A large displacement of the chemical shift of hydroxyl protons from 1.2 ppm in the crystalline state to about 9 ppm occurs upon H-bonding of phenol to basic oxygen atoms of the zeolite. An enhancement of the 29Si-CP-MAS signal is observed

T Beutel; M.-J Peltre; B. L Su

2001-01-01

13

Chemical shift referencing in MAS solid state NMR  

Microsoft Academic Search

Solid state 13C magic angle spinning (MAS) NMR spectra are typically referenced externally using a probe which does not incorporate a field frequency lock. Solution NMR shifts on the other hand are more often determined with respect to an internal reference and using a deuterium based field frequency lock. Further differences arise in solution NMR of proteins and nucleic acids

Corey R Morcombe; Kurt W Zilm

2003-01-01

14

Characterization of intervertebral disc degeneration by high-resolution magic angle spinning (HR-MAS) spectroscopy.  

PubMed

The goal of this study was to determine the ability of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy to distinguish different stages of intervertebral disc degeneration (IVDD). 17 discs were removed from human cadavers and analyzed them using 1D and 2D (total correlation spectroscopy (TOCSY)) (1)H HR-MAS spectroscopy, and T(1) and T(2) relaxation time measurements to determine the chemical composition and changes in chemical environment of discs with increasing levels of degeneration (Thompson grade). Among the significant findings were that spectra were very similar for samples taken from annular and nuclear regions of discs, and that visually apparent changes were observed in the spectra of the annular and nuclear samples from discs with increasing Thompson grade. Area ratios of the N-acetyl to choline (Cho) regions, and Cho to carbohydrate (Carb) regions of the spectra allowed us to discriminate between discs of increasing Thompson grade with minimal overlap of individual ratios. Changes in T(1) and T(2) relaxation times of the chemical constituents of disc spectra were not significantly correlated to the degree of degeneration. The results of this study support the feasibility of using in vivo spectroscopy for detecting chemical changes associated with disc degeneration. PMID:15723415

Keshari, Kayvan R; Zektzer, Andrew S; Swanson, Mark G; Majumdar, Sharmila; Lotz, Jeffrey C; Kurhanewicz, John

2005-03-01

15

Protein MAS NMR methodology and structural analysis of protein assemblies  

E-print Network

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

Bayro, Marvin J

2010-01-01

16

Zur Bestimmung chemischer Verschiebungen der NMR-Frequenzen bei Quadrupolkernen aus den MAS-NMR-Spektren  

Microsoft Academic Search

Die allgemeinen Ausdrücke für den NMR-Zentralübergang für Quadrupolkerne mit halbzahligem Spin bei Probenrotation, die von BEHRENS [1, 2] unter Berücksichtigung von Quadrupolwechselwirkungseffekten 2. Ordnung für beliebige Neigungswinkel der Rotationsachse abgeleitet wurden, werden für den praktisch interessierenden Fall der Probenrotation um den magischen Winkel (magic angle spinning, MAS) in einer den Ausgangsformeln für das Ruhespektrum (ohne Probenrotation) analogen Form dargestellt. Am

D. Müller

1982-01-01

17

Structural study of a lead–barium–aluminum phosphate glass by MAS-NMR spectroscopy  

Microsoft Academic Search

The 31P- and 27Al-MAS-NMR spectra of a lead–barium–aluminum phosphate glass were measured and analyzed, and the short range structure of the glass are discussed. The 31P-MAS-NMR spectrum of the glass studied has a single isotropic peak at ?4.76 ppm, indicating that orthophosphate species are the dominant P-sites in the glass. The 27Al-MAS-NMR spectrum of the glass shows that the aluminum

Guo Gongyi

1998-01-01

18

2D multiquantum MAS-NMR spectroscopy of 27Al in aluminophosphate molecular sieves  

Microsoft Academic Search

Two-dimensional multiquantum MAS-NMR spectroscopy (2D-MQ) has been applied to the discrimination of the different 27Al sites in several aluminophosphate molecular sieves. It is shown that a new quintuple-quantum MAS-NMR method (2D-5Q) gives an extraordinary improved resolution compared to the DOR or DAS technique. The pure-absorption 2D spectra allow the direct determination of the number of different species, the correct determination

C. Fernandez; J. P. Amoureux

1995-01-01

19

Asymmetric doublets in MAS NMR: coherent and incoherent mechanisms.  

PubMed

It has been long noted that J-resolved doublets observed in solid-state MAS experiments are asymmetric. The asymmetry has been attributed to a coherent interference effect involving dipolar and CSA interactions. Recently, Bernd Reif and co-workers suggested that under fast MAS conditions the coherent portion of the effect is suppressed and it becomes possible to observe an incoherent mechanism reminiscent of TROSY. The researchers were able to observe the characteristic TROSY-type patterns in (15)N-(1)H(N) spectra of heavily deuterated protein samples (Chevlekov, Diehl, and Reif, previous article in this issue). In the present computer simulation study, we seek to obtain a unified picture of this phenomenon, including both coherent and incoherent aspects. The chosen model focuses on the (15)N-(1)H(N) pair from a polycrystalline sample subject to magic angle spinning. To mimic local dynamics, we assume that the corresponding peptide plane jumps between two orientations. The simulations demonstrate that this simple model reproduces both coherent and incoherent behavior, depending on the MAS speed and the time scale of local dynamics. Furthermore, semianalytical expressions can be derived for both coherent and incoherent (Redfield) limits. Of particular interest is the possibility to use solution-style Redfield results to probe internal protein motions, especially slower motions on the nanosecond time scale. Our simulations show that the differential relaxation measurement permits accurate determination of (15)N dipolar-CSA cross correlations already at moderately high MAS speed (ca 15 kHz). PMID:18157846

Skrynnikov, N R

2007-12-01

20

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

SciTech Connect

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

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

2005-02-01

21

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

22

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

E-print Network

Reduction of spin diffusion artifacts from 2D zfr-INADEQUATE MAS NMR spectra Jay H. Baltisberger 2010 Available online 29 October 2010 Keywords: Solid-state NMR Zero-quantum coherences z s t r a c t The primary shortcoming of the z-filtered refocused INADEQUATE MAS NMR pulse sequence

Baltisberger, Jay H.

23

Characterization of the Liquid-Ordered State by Proton MAS NMR  

PubMed Central

We investigated if magic angle spinning (MAS) 1H NMR can be used as a tool for detection of liquid-ordered domains (rafts) in membranes. In experiments with the lipids SOPC, DOPC, DPPC, and cholesterol we demonstrated that 1H MAS NMR spectra of liquid-ordered domains (lo) are distinctly different from liquid-disordered (ld) and solid-ordered (so) membrane regions. At a MAS frequency of 10 kHz the methylene proton resonance of hydrocarbon chains in the ld phase has a linewidth of ?50 Hz. The corresponding linewidth is ?1 kHz for the lo phase and several kHz for the so phase. According to results of 1H NMR dipolar echo spectroscopy, the broadening of MAS resonances in the lo phase results from an increase in effective strength of intramolecular proton dipolar interactions between adjacent methylene groups, most likely because of a lower probability of gauche/trans isomerization in lo. In spectra recorded as a function of temperature, the onset of lo domain (raft) formation is seen as a sudden onset of line broadening. Formation of small domains yielded homogenously broadened resonance lines, whereas large lo domains (diameter >0.3 ?m) in an ld environment resulted in superposition of the narrow resonances of the ld phase and the much broader resonances of lo. 1H MAS NMR may be applied to detection of rafts in cell membranes. PMID:16387785

Polozov, Ivan V.; Gawrisch, Klaus

2006-01-01

24

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

Microsoft Academic Search

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for

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

2004-01-01

25

Temperature Gradients and Sample Heating in Variable Temperature High Speed MAS NMR Spectroscopy  

Microsoft Academic Search

High speed magic angle spinning NMR spectroscopy offers the possibility of im- proving the process of coherent averaging of various parts of the nuclear spin Hamil- tonian in the solid state ( 1-6). This considerably reduces the intensities of rotational sidebands. This isa great advantage especially in cross-polarization MAS experiments at high magnetic fields, where rotational sidebands mostly stem from

Institutftir Physikalische; Johannes Hess Strasse

26

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

NASA Astrophysics Data System (ADS)

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

Paik, Younkee

27

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

PubMed

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

Mihaliuk, Eugene; Gullion, Terry

2011-10-01

28

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

SciTech Connect

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

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

2006-06-15

29

Lip1 Lip2 Lip3 Naa Cr Cho PCho GPCho Identifying constituent tumor tissues subclasses in HR-MAS spectra using advanced blind source separation techniques  

E-print Network

tissues subclasses in HR-MAS spectra using advanced blind source separation techniques A. Croitor Sava, D. This heterogeneity is reflected both in the grade of malignancy and in the tumor tissue type. Histopathological histopathological features. Still, till now, accurate grading of glial tumors has not been completely achieved by HR

30

Improved background suppression in 1H MAS NMR using composite pulses  

NASA Astrophysics Data System (ADS)

A well known feature of 1H MAS NMR spectroscopy, particularly of solids where the concentration of 1H nuclei is low, is the presence in the spectrum of a significant broad "background" signal arising from 1H nuclei that are outside the MAS rotor and radiofrequency coil, probably located on the surfaces of the static components of the probehead. A popular method of suppressing this unwanted signal is the "depth pulse" method, consisting of a 90° pulse followed by one or two 180° pulses that are phase cycled according to the "Exorcycle" scheme, which removes signal associated with imperfect 180° pulses. Consequently, only spins in the centre of the radiofrequency coil contribute to the 1H MAS spectrum, while those experiencing a low B1 field outside the coil are suppressed. Although very effective at removing background signal from the spectrum, one drawback with this approach is that significant loss of the desired signal from the sample also occurs. Here we investigate the 1H background suppression problem and, in particular, the use of novel antisymmetric passband composite pulses to replace the simple pulses in a depth pulse experiment. We show that it is possible to improve the intensity of the 1H signals of interest while still maintaining effective background suppression. We expect that these results will be relevant to 1H MAS NMR studies of, for example, nominally perdeuterated biological samples or nominally anhydrous inorganic materials.

Odedra, Smita; Wimperis, Stephen

2012-08-01

31

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. PMID:20161144

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

2009-01-01

32

Enhanced sensitivity by nonuniform sampling enables multidimensional MAS NMR spectroscopy of protein assemblies.  

PubMed

We report dramatic sensitivity enhancements in multidimensional MAS NMR spectra by the use of nonuniform sampling (NUS) and introduce maximum entropy interpolation (MINT) processing that assures the linearity between the time and frequency domains of the NUS acquired data sets. A systematic analysis of sensitivity and resolution in 2D and 3D NUS spectra reveals that with NUS, at least 1.5- to 2-fold sensitivity enhancement can be attained in each indirect dimension without compromising the spectral resolution. These enhancements are similar to or higher than those attained by the newest-generation commercial cryogenic probes. We explore the benefits of this NUS/MaxEnt approach in proteins and protein assemblies using 1-73-(U-(13)C,(15)N)/74-108-(U-(15)N) Escherichia coli thioredoxin reassembly. We demonstrate that in thioredoxin reassembly, NUS permits acquisition of high-quality 3D-NCACX spectra, which are inaccessible with conventional sampling due to prohibitively long experiment times. Of critical importance, issues that hinder NUS-based SNR enhancement in 3D-NMR of liquids are mitigated in the study of solid samples in which theoretical enhancements on the order of 3-4 fold are accessible by compounding the NUS-based SNR enhancement of each indirect dimension. NUS/MINT is anticipated to be widely applicable and advantageous for multidimensional heteronuclear MAS NMR spectroscopy of proteins, protein assemblies, and other biological systems. PMID:22667827

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

2012-06-28

33

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

NASA Astrophysics Data System (ADS)

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

Okazaki, M.; McDowell, C. A.

1983-11-01

34

Physical properties and MAS-NMR studies of titanium phosphate-based glasses  

Microsoft Academic Search

In this study, for a series phosphate-based glasses ((P2O5)0.45(CaO)0.3(Na2O)0.25?x(TiO2)x, 0?x?0.15), their degradation, ion release, surface and thermal properties have been determined. The results show that adding TiO2 was associated with a significant increase in density and glass transition temperature, but a decrease in degradation rate and ion release. 31P solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) showed that the local structure

Azadeh Kiani; Lindsay S. Cahill; Ensanya Ali Abou Neel; John V. Hanna; Mark E. Smith; Jonathan C. Knowles

2010-01-01

35

Cation disorder determined by MAS {sup 27}Al NMR in high dose neutron irradiated spinel  

SciTech Connect

Spinel (MgAl{sub 2}O{sub 4}) single crystals which had been neutron irradiated to high doses (53-250 dpa) were examined using {sup 27}Al magic angle spinning (MAS) nuclear magnetic resonance (NMR). The sensitivity of this procedure to a specific cation (Al) residing in different crystallographic environments allowed one to determine the distribution of the Al between the two cation sites in the spinel structure. The samples were irradiated at two different temperatures (400 and 750{degrees}C) and various doses. These results indicate that the Al was nearly fully disordered over the two lattice sites after irradiation.

Cooper, E.A.; Sickafus, K.E.; Hughes, C.D.; Earl, W.L. [Los Alamos National Lab., NM (United States); Hollenberg, G.W.; Garner, F.A. [Pacific Northwest Labs., Richland, WA (United States); Bradt, R.C. [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Metallurgical and Materials Engineering

1995-12-31

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

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

38

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. PMID:24842075

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

2014-08-01

39

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. PMID:24971307

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

2014-01-01

40

Surface Sensitive Studies of the Acidic Dissolution of Olivine with 1H-29Si CP MAS and 19F MAS NMR  

NASA Astrophysics Data System (ADS)

To understand the role of minerals and their surfaces in carbon dioxide sequestration, the rates and mechanisms of mineral dissolution and transformation must be studied under environmentally-relevant conditions. Olivine exists in mafic rocks, and the sequestration of carbon dioxide in such systems has been suggested as a disposal strategy. In this study, dissolution reactions of natural olivine ((Mg,Fe)2SiO4) and synthetic forsterite (Mg2SiO4) were followed with solid-state nuclear magnetic resonance (NMR) spectroscopy after exposure to acid in batch reactors. Olivine and forsterite were ground to a particle size of 20-50 ?m, and roughly one gram of sample was allowed to react for up to 336 hours in solutions with an initial pH ~ 3. Magnesium, iron, and silicon concentrations were measured at each stage of dissolution via ICP analysis and changes in solution pH were monitored. The mechanism of dissolution is dependant upon the chemistry at the solid-liquid interface, requiring surface selective analysis techniques, but this is difficult with non-ideal samples. Since simple Bloch decay NMR experiments only provide a bulk (average) measurement, more advanced NMR methods have been utilized to isolate information from the surface. Cross polarization magic angle spinning (CP MAS) NMR utilizes through-space magnetization transfer from nuclei present only at the interface (such as 1H) to nearby nuclei, and therefore 1H-29Si CP MAS experiments produce localized signals from silicon at or near to the surface. Results are presented detailing changes in silicate speciation as a function of dissolution time for synthetic forsterite. The presence of paramagnetic iron located in the olivine lattice causes a broadening of the 29Si NMR signal, and therefore in studies of the natural samples a surrogate has been utilized in the form of a probe molecule that binds selectively to surface hydroxyl sites. The probe molecule, (3,3,3- trifluoropropyl)dimethylchlorosilane (TFS), provides a strong 19F NMR signal so that 19F MAS NMR can be used for the quantification of reactive surface hydroxyl species. The NMR signal is normalized against a known standard to provide a quantitative measurement (surface hydroxyl sites/g of sample) at each time increment, and we find a linear dependence of surface hydroxyl sites on total dissolution time.

Davis, M. C.; Mueller, K. T.

2006-05-01

41

Interaction of local anesthetics with lipid bilayers investigated by ¹H MAS NMR spectroscopy.  

PubMed

The membrane location of the local anesthetics (LA) lidocaine, dibucaine, tetracaine, and procaine hydrochloride as well as their influence on phospholipid bilayers were studied by ³¹P and ¹H magic-angle spinning (MAS) NMR spectroscopy. The ³¹P NMR spectra of the LA/lipid preparations confirmed that the overall bilayer structure of the membrane remained preserved. The relation between the molecular structure of the LAs and their membrane localization and orientation was investigated quantitatively using induced chemical shifts, nuclear Overhauser enhancement spectroscopy, and paramagnetic relaxation rates. All three methods revealed an average location of the aromatic rings of all LAs in the lipid-water interface of the membrane, with small differences between the individual LAs depending on their molecular properties. While lidocaine is placed in the upper chain/glycerol region of the membrane, for dibucaine and procaine the maximum of the distribution are slightly shifted into the glycerol region. Finally for tetracaine the aromatic ring is placed closest to the aqueous phase in the glycerol/headgroup region of the membrane. The hydrophobic side chains of the LA molecules dibucaine and tetracaine were located deeper in the membrane and showed an orientation towards the hydrocarbon core. In contrast the side chains of lidocaine and procaine are oriented towards the aqueous phase. PMID:22842001

Weizenmann, Nicole; Huster, Daniel; Scheidt, Holger A

2012-12-01

42

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

43

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

Microsoft Academic Search

Recent 27Al 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 ?iso=5.0 ppm and the quadrupole product parameter PQ=1.2 MHz, has been characterized in detail by 27Al MAS

Morten Daugaard Andersen; Hans J. Jakobsen; Jørgen Skibsted

2006-01-01

44

27Al Multiple-Quantum MAS NMR of Mechanically Treated Bayerite (?-Al(OH) 3) and Silica Mixtures  

Microsoft Academic Search

Two-dimensional 27Al multiple-quantum magic angle spinning (MQMAS) NMR experiments are used to study mixtures of bayerite (?-Al(OH)3) with either silicic acid (SiO2.nH2O) or silica gel (SiO2) that have been ground together for varying lengths of time. This mechanical treatment produces changes in the 27Al MAS and MQMAS NMR spectra that correspond to the formation of new Al species. Mean values

Sharon E. Ashbrook; Kenneth J. D. MacKenzie; Stephen Wimperis

2001-01-01

45

Evolution of crystalline aluminates from hybrid gel-derived precursors studied by XRD and multinuclear solid state MAS NMR  

Microsoft Academic Search

X-ray amorphous calcium aluminate gels of dialuminate and hexaluminate composition were prepared, the former by two methods, and their thermal crystallisation was monitored by thermal analysis, X-ray powder diffraction and 27Al MAS NMR. Both gel compositions lose a large amount of solvent and organic by-products below 600°C, forming amorphous precursors with 27Al NMR spectra containing resonances corresponding to tetrahedral and

K. J. D MacKenzie; M Schmücker; M. E Smith; I. J. F Poplett; T Kemmitt

2000-01-01

46

Evolution of crystalline aluminates from hybrid gel-derived precursors studied by XRD and multinuclear solid state MAS NMR  

Microsoft Academic Search

A hybrid gel synthesis is described which produces crystalline lanthanum hexaluminate at 1200°C without the intermediate appearance of LaAlO3. XRD in conjunction with 27Al and 139La MAS NMR indicates that until the exothermic appearance of ?-alumina at about 900°C, the gel remains amorphous and contains Al in three types of site, one of which is characterised by an NMR resonance

K. J. D MacKenzie; M Schmucker; L Mayer

1999-01-01

47

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

48

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

49

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

50

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

E-print Network

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

Markhasin, Evgeny

2014-01-01

51

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

USGS Publications Warehouse

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

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

2005-01-01

52

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

Microsoft Academic Search

Zinc borophosphate glasses doped with TeO2 with different B2O3\\/P2O5 ratio were prepared, their basic properties were determined and their structure was studied by 11B MAS NMR and Raman spectroscopies. Structural studies were devoted to the investigation of changes in boron coordination in the dependence on changes in TeO2 content and in B2O3\\/P2O5 ratio in the borophosphate glasses. A special attention

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

53

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

PubMed

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

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

2013-01-01

54

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

PubMed

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

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

2014-09-01

55

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

Microsoft Academic Search

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

Jianwen Ni; Charles E. Frazier

1998-01-01

56

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

57

Evolution of crystalline aluminates from hybrid gel-derived precursors studied by XRD and multinuclear solid-state MAS NMR  

Microsoft Academic Search

Hybrid gels of celsian composition were prepared from Al alkoxide, tetrathylorthosilicate (TEOS) and Ba acetate and their structure evolution was studied up to 1300°C by thermal analysis and X-ray diffraction. Information on their pre-crystallization behaviour was also provided by 27Al, 29Si and 137Ba MAS NMR spectroscopy. Apart from some excess Ba acetate which decomposed to traces of BaCO3 and BaO

K. J. D MacKenzie; T Kemmitt

1999-01-01

58

Evolution of crystalline aluminates from hybrid gel-derived precursors studied by XRD and multinuclear solid-state MAS NMR  

Microsoft Academic Search

The thermal evolution of structure in a hybrid gel of YAG composition (Y3Al5O12) prepared from aluminum alkoxide and yttrium acetate was studied up to 1250°C. XRD indicates that the gels are amorphous <900°C, when they abruptly crystallize to YAG and hexagonal YAlO3. The latter exists only briefly, being fully converted to YAG by 1000°C. 27Al MAS NMR shows that after

K. J. D MacKenzie; T Kemmitt

1999-01-01

59

Surface Species Formed during Aniline Methylation on Zeolite H–Y Investigated by in Situ MAS NMR Spectroscopy  

Microsoft Academic Search

Aniline alkylation with methanol on zeolite H–Y has been studied using in situ13C MAS NMR spectroscopy under batch conditions. To clarify the main reaction pathways, the conversion of methanol as well as the interaction of aniline with surface methoxy groups were investigated under similar conditions. Methanol-13C and methyl iodide-13C were used as labeled reactants. Co -adsorption of aniline and methanol-13C

Irina I. Ivanova; Elena B. Pomakhina; Alexander I. Rebrov; Michael Hunger; Yuryi G. Kolyagin; Jens Weitkampz

2001-01-01

60

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

Microsoft Academic Search

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

Jacqueline A. Henuningson; Roger H. Newman DSIR

1985-01-01

61

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

Microsoft Academic Search

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

Eva-Lena Hult; Per Tomas Larsson; Tommy Iversen

2000-01-01

62

27Al multiple-quantum MAS NMR of mechanically treated bayerite (alpha-Al(OH)3) and silica mixtures.  

PubMed

Two-dimensional 27Al multiple-quantum magic angle spinning (MQMAS) NMR experiments are used to study mixtures of bayerite (alpha-Al(OH)3) with either silicic acid (SiO2.nH2O) or silica gel (SiO2) that have been ground together for varying lengths of time. This mechanical treatment produces changes in the 27Al MAS and MQMAS NMR spectra that correspond to the formation of new Al species. Mean values of the quadrupolar interaction (PQ) and isotropic chemical shift (deltacs) are extracted from the two-dimensional 27Al NMR spectra for each of these species. The presence of significant distributions of both 27Al quadrupolar and chemical shift parameters is demonstrated and the effect of grinding duration on the magnitudes of these distributions is discussed. PMID:11846239

Ashbrook, S E; MacKenzie, K J; Wimperis, S

2001-01-01

63

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

SciTech Connect

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

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

2008-02-15

64

71 Ga NMR of reference Ga IV, Ga V, and Ga VI compounds by MAS and QPASS, extension of gallium\\/aluminum NMR parameter correlation  

Microsoft Academic Search

We report new measurements of NMR parameters for 71Ga in gallium bearing oxide reference compounds, ranging from perfectly ordered systems to disordered crystalline structures and their aluminate counterparts. Static, MAS, and QPASS spectra are obtained at magnetic fields ranging from 7.0 to 18.8 T. With these results we enhance the previously established correlation between isotropic chemical shifts of 71Gaand27Al and

Dominique Massiot; Thomas Vosegaard; Nathalie Magneron; Dominique Trumeau; Valérie Montouillout; Patrick Berthet; Thierry Loiseau; Bruno Bujoli

1999-01-01

65

Characterization of Calcium Aluminate Hydrates and Related Hydrates of Cement Pastes by (27)Al MQ-MAS NMR.  

PubMed

27Al multi quantum (MQ) MAS NMR spectroscopy was used for the first time to characterize calcium aluminate hydrates, which are of importance in the chemistry of high alumina and Portland cements. Substitution sites of silicon by aluminum in the calcium silicate hydrates (C-S-H) which are the main component of Portland cement paste were studied too. Synthetic samples of Ca(3)Al(OH)(12), [CaAl(OH)(4)][OH(H(2)O)(1.5)], [Ca(2)Al(OH)(6)](OH).3H(2)O, [Ca(2)Al(OH)(6)](2)(CO(3)).5H(2)O, [Mg(2)Al(OH)(6)](CO(3))(0.5).3H(2)O, Al(OH)(3), and C-S-H substituted by aluminum were prepared. In most of the samples, the two dimension 3Q-MAS NMR spectra allow one, more easily than the MAS-only NMR spectra, to obtain the chemical shift, delta(iso), and the quadrupolar parameters nu(Q) and eta, which label each site and bring information on its symmetry and environment. The distributions of the aluminum environments were observed for each site. In [Ca(2)Al(OH)](6)(OH).3H(2)O, (27)Al MAS spectrum demonstrates the presence of two octahedral aluminum sites. In the C-S-H substituted with Al, tetrahedral aluminum is observed, in bridging and nonbridging sites of the silicate chains, mostly in the bridging sites for the sample investigated. PMID:11670472

Faucon, P.; Charpentier, T.; Bertrandie, D.; Nonat, A.; Virlet, J.; Petit, J. C.

1998-07-27

66

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

67

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

Microsoft Academic Search

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

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

1999-01-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

69

Directly and indirectly detected through-bond heteronuclear correlation solid-state NMR spectroscopy under fast MAS  

NASA Astrophysics Data System (ADS)

Two-dimensional through-bond 1H{ 13C} solid-state NMR experiments utilizing fast magic angle spinning (MAS) and homonuclear multipulse 1H decoupling are presented. Remarkable efficiency of polarization transfer can be achieved at MAS rates exceeding 40 kHz, which is instrumental in these measurements. Schemes utilizing direct and indirect detection of heteronuclei are compared in terms of resolution and sensitivity. A simple procedure for optimization of 1H homonuclear decoupling sequences under these conditions is proposed. The capabilities of these techniques were confirmed on two naturally abundant solids, tripeptide N- formyl- L-methionyl- L-leucyl- L-phenylalanine (f-MLF-OH) and brown coal.

Mao, Kanmi; Pruski, Marek

2009-12-01

70

Slow motions in microcrystalline proteins as observed by MAS-dependent 15N rotating-frame NMR relaxation  

NASA Astrophysics Data System (ADS)

15N NMR relaxation rate R1? measurements reveal that a substantial fraction of residues in the microcrystalline chicken alpha-spectrin SH3 domain protein undergoes dynamics in the ?s-ms timescale range. On the basis of a comparison of 2D site-resolved with 1D integrated 15N spectral intensities, we demonstrate that the significant fraction of broad signals in the 2D spectrum exhibits the most pronounced slow mobility. We show that 15N R1?'s in proton-diluted protein samples are practically free from the coherent spin-spin contribution even at low MAS rates, and thus can be analysed quantitatively. Moderate MAS rates (10-30 kHz) can be more advantageous in comparison with the rates >50-60 kHz when slow dynamics are to be identified and quantified by means of R1? experiments.

Krushelnitsky, Alexey; Zinkevich, Tatiana; Reif, Bernd; Saalwächter, Kay

2014-11-01

71

Domains in binary SOPC/POPE lipid mixtures studied by pulsed field gradient 1H MAS NMR.  

PubMed

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

Polozov, Ivan V; Gawrisch, Klaus

2004-09-01

72

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

PubMed Central

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

Polozov, Ivan V.; Gawrisch, Klaus

2004-01-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

74

71Ga NMR of reference GaIV, GaV, and GaVI compounds by MAS and QPASS, extension of gallium/aluminum NMR parameter correlation.  

PubMed

We report new measurements of NMR parameters for 71Ga in gallium bearing oxide reference compounds, ranging from perfectly ordered systems to disordered crystalline structures and their aluminate counterparts. Static, MAS, and QPASS spectra are obtained at magnetic fields ranging from 7.0 to 18.8 T. With these results we enhance the previously established correlation between isotropic chemical shifts of 71Ga and 27Al and propose a correlation between gallium and aluminum electric field gradients (EFG). This correlation shows that the EFG at 71Ga sites are generally three times greater than those at equivalent 27Al sites. PMID:10672940

Massiot, D; Vosegaard, T; Magneron, N; Trumeau, D; Montouillout, V; Berthet, P; Loiseau, T; Bujoli, B

1999-12-01

75

High-field 19.6 T 27Al solid-state MAS NMR of in vitro aluminated brain tissue  

NASA Astrophysics Data System (ADS)

The combination of 27Al high-field solid-state NMR (19.6 T) with rapid spinning speeds (17.8 kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10 mM Al 3+ (as AlCl 3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10 mM AlCl 3. The spectra of these model systems show multiple Al 3+ binding sites, good signal/noise ratios and apparent chemical shift dispersions. A single broad peak (-3 to 11 ppm) is seen for the aluminated ARPE-19 cells, consistent with reported solution-state NMR chemical shifts of Al-transferrin. The aluminated brain tissue has a considerably different 27Al MAS NMR spectrum. In addition to the transferrin-type resonance, additional peaks are seen. Tentative assignments include: -9 to -3 ppm, octahedral AlO 6 (phosphate and water); 9 ppm, condensed AlO 6 units (Al-O-Al bridges); 24 ppm, tetrahedral AlO 3N and/or octahedral Al-carbonate; and 35 ppm, more N-substituted aluminum and /or tetrahedral AlO 4. Thus, brain tissue is susceptible to a broad range of coordination by aluminum. Furthermore, the moderate 27Al C Q values (all less than 10 MHz) suggest future NMR studies may be performed at 9.4 T and a spin rate of 20 kHz.

Bryant, Pamela L.; Lukiw, Walter J.; Gan, Zhehong; Hall, Randall W.; Butler, Leslie G.

2004-10-01

76

Incorporation of phosphorus guest ions in the calcium silicate phases of Portland cement from 31P MAS NMR spectroscopy.  

PubMed

Portland cements may contain small quantities of phosphorus (typically below 0.5 wt % P(2)O(5)), originating from either the raw materials or alternative sources of fuel used to heat the cement kilns. This work reports the first (31)P MAS NMR study of anhydrous and hydrated Portland cements that focuses on the phase and site preferences of the (PO(4))(3-) guest ions in the main clinker phases and hydration products. The observed (31)P chemical shifts (10 to -2 ppm), the (31)P chemical shift anisotropy, and the resemblance of the lineshapes in the (31)P and (29)Si MAS NMR spectra strongly suggest that (PO(4))(3-) units are incorporated in the calcium silicate phases, alite (Ca(3)SiO(5)) and belite (Ca(2)SiO(4)), by substitution for (SiO(4))(4-) tetrahedra. This assignment is further supported by a determination of the spin-lattice relaxation times for (31)P in alite and belite, which exhibit the same ratio as observed for the corresponding (29)Si relaxation times. From simulations of the intensities, observed in inversion-recovery spectra for a white Portland cement, it is deduced that 1.3% and 2.1% of the Si sites in alite and belite, respectively, are replaced by phosphorus. Charge balance may potentially be achieved to some extent by a coupled substitution mechanism where Ca(2+) is replaced by Fe(3+) ions, which may account for the interaction of the (31)P spins with paramagnetic Fe(3+) ions as observed for the ordinary Portland cements. A minor fraction of phosphorus may also be present in the separate phase Ca(3)(PO(4))(2), as indicated by the observation of a narrow resonance at delta((31)P) = 3.0 ppm for two of the studied cements. (31)P{(1)H} CP/MAS NMR spectra following the hydration of a white Portland cement show that the resonances from the hydrous phosphate species fall in the same spectral range as observed for (PO(4))(3-) incorporated in alite. This similarity and the absence of a large (31)P chemical shift ansitropy indicate that the hydrous (PO(4))(3-) species are incorporated in the interlayers of the calcium-silicate-hydrate (C-S-H) phase, the principal phase formed upon hydration of alite and belite. PMID:20481523

Poulsen, Søren L; Jakobsen, Hans J; Skibsted, Jørgen

2010-06-21

77

SCAM-STMAS: satellite-transition MAS NMR of quadrupolar nuclei with self-compensation for magic-angle misset  

NASA Astrophysics Data System (ADS)

Several methods are available for the acquisition of high-resolution solid-state NMR spectra of quadrupolar nuclei with half-integer spin quantum number. Satellite-transition MAS (STMAS) offers an approach that employs only conventional MAS hardware and can yield substantial signal enhancements over the widely used multiple-quantum MAS (MQMAS) experiment. However, the presence of the first-order quadrupolar interaction in the satellite transitions imposes the requirement of a high degree of accuracy in the setting of the magic angle on the NMR probehead. The first-order quadrupolar interaction is only fully removed if the sample spinning angle, ?, equals cos-1(1/ 3) exactly and rotor synchronization is performed. The required level of accuracy is difficult to achieve experimentally, particularly when the quadrupolar interaction is large. If the magic angle is not set correctly, the first-order splitting is reintroduced and the spectral resolution is severely compromised. Recently, we have demonstrated a novel STMAS method (SCAM-STMAS) that is self-compensated for angle missets of up to ±1° via coherence transfer between the two different satellite transitions ST +( mI=+3/2?+1/2) and ST -( mI=-1/2?-3/2) midway through the t1 period. In this work we describe in more detail the implementation of SCAM-STMAS and demonstrate its wider utility through 23Na ( I=3/2), 87Rb ( I=3/2), 27Al ( I=5/2), and 59Co ( I=7/2) NMR. We discuss linewidths in SCAM-STMAS and the limits over which angle-misset compensation is achieved and we demonstrate that SCAM-STMAS is more tolerant of temporary spinning rate fluctuations than STMAS, resulting in less " t1 noise" in the two-dimensional spectrum. In addition, alternative correlation experiments, for example involving the use of double-quantum coherences, that similarly display self-compensation for angle misset are investigated. The use of SCAM-STMAS is also considered in systems where other high-order interactions, such as third-order quadrupolar effects or second-order quadrupole-CSA cross-terms, are present. Finally, we show that the sensitivity of the experiment can be improved through the use of amplitude-modulated pulses.

Ashbrook, Sharon E.; Wimperis, Stephen

2003-06-01

78

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

SciTech Connect

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

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

2006-02-15

79

Study of structural units in glassy and crystalline xNa{sub 2}S+(1-x)B{sub 2}S{sub 3} by MAS and 2D-MQ MAS {sup 11}B NMR  

SciTech Connect

Two-dimensional multiple-quantum (2D-MQ) NMR of {sup 11}B in conjunction with traditional high speed magic angle spinning (MAS) at different magnetic fields was applied to elucidate the structure of glasses and polycrystals in the series xNa{sub 2}S + (1-x)B{sub 2}S{sub 3}. The computer simulation of MAS spectra was used to augment the experimental data to provide the quadrupole and chemical shift parameters as well as quantitative information. A remarkable enhancement of resolution of the 2D-MQ MAS NMR proved instrumental in finding and identifying various structural units in xNa{sub 2}S + (1-x)B{sub 2}S{sub 3}. In the low-alkali region (0 {le} x {le} 0.33), rapid structural change takes place from thioboroxyl rings to BS{sub 4} units, whereas metathioborate and orthothioborate units are formed in the high-alkali region (0.5 {le} x {le} 0.8). In addition, the fingerprints of B{sub 2}OS{sub 2}, B{sub 2}O{sub 2}S, and B{sub 2}O{sub 3} structures were identified and quantified in the 2D-MQ MAS NMR spectra of glassy and crystalline samples.

Pruski, M. [Ames Lab., IA (United States)

1996-12-31

80

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

81

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

PubMed

The advantages offered by ultra-fast (>60 kHz) magic angle spinning (MAS) rotation for the study of biological samples, notably containing paramagnetic centers are explored. It is shown that optimal conditions for performing solid-state (13)C NMR under 60 kHz MAS are obtained with low-power CW (1)H decoupling, as well as after a low-power (1)H,(13)C cross-polarization step at a double-quantum matching condition. Acquisition with low-power decoupling highlights the existence of rotational decoupling sidebands. The sideband intensities and the existence of first and second rotary conditions are explained in the framework of the Floquet-van Vleck theory. As a result, optimal (13)C spectra of the oxidized, paramagnetic form of human copper zinc superoxide dismutase (SOD) can be obtained employing rf-fields which do not exceed 40 kHz during the whole experiment. This enables the removal of unwanted heating which can lead to deterioration of the sample. Furthermore, combined with the short (1)H T(1)s, this allows the repetition rate of the experiments to be shortened from 3 s to 500 ms, thus compensating for the sensitivity loss due to the smaller sample volume in a 1.3 mm rotor. The result is that 2D (13)C-(13)C correlation could be acquired in about 24 h on less than 1 mg of SOD sample. PMID:19028122

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

2009-02-01

82

[sup 31]P and [sup 27]Al MAS NMR investigations of some lead phosphate glasses. [Magic Angle Spin Nuclear Magnetic Resonance  

SciTech Connect

The [sup 31]P MAS NMR spectra were measured and analyzed for the two phosphate glasses that contain distinct metals (i.e., In or Ba), different amounts of PbO, and the same content of P[sub 2]O[sub 5] and Al[sub 2]O[sub 3]. The [sup 31]P MAS NMR spectra for the two glasses have a single isotropic peak at [minus]3.77 or [minus]4.76 ppm, indicating that orthophosphate species are the dominant P sites in the glasses studied. The [sup 27]Al MAS NMR spectrum measured for the lead-barium-aluminum phosphate glass shows that the aluminum ions present in the glass are in 4-, 5-, and 6-fold coordination with oxygen and that the Al(OP)[sub 4] is the dominant moiety for the glass, suggesting the formation of orthophosphate species in the glass.

Gongyi, G. (Shanghai Jiao Tong Univ. (China). Dept. of Materials Science and Engineering)

1999-03-01

83

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

PubMed

Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy have been used to investigate the acetylation of raw cotton samples with acetic anhydride without solvents in the presence of different amounts of 4-dimethylaminopyridine (DMAP) catalyst. This is a continuation of our previous investigation of acetylation of commercial cotton in an effort to develop hydrophobic, biodegradable, cellulosic sorbent materials for cleaning up oil spills. The FTIR data have again provided a clear evidence for successful acetylation. The NMR results further confirm the successful acetylation. The extent of acetylation was quantitatively determined using the weight percent gain (WPG) due to acetylation and by calculating the ratio R between the intensity of the acetyl C=O stretching band at 1740-1745 cm(-1) and the intensity of C-O stretching vibration of the cellulose backbone at about 1020-1040 cm(-1). The FTIR technique was found to be highly sensitive and reliable for the determination of the extent of acetylation. The level of acetylation of the raw cotton samples was found to be much higher than that of cotton fabrics and the previously studied commercial cotton. The variation of the R and WPG with reaction time, amount of DMAP catalyst and different samples of raw cotton is discussed. PMID:15249021

Adebajo, Moses O; Frost, Ray L

2004-08-01

84

29Si NMR in solid state with CPMG acquisition under MAS  

SciTech Connect

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

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

2008-05-20

85

Characteristics of zero-quantum correlation spectroscopy in MAS NMR experiments  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

87

Supramolecular assembly of dendritic polymers elucidated by 1H and 13C solid-state MAS NMR spectroscopy.  

PubMed

Advanced solid-state NMR methods under fast magic-angle spinning (MAS) are used to study the structure and dynamics of large supramolecular systems, which consist of a polymer backbone with dendritic side groups and self-assemble into a columnar structure. The NMR experiments are performed on as-synthesized samples, i.e., no isotopic enrichment is required. The analysis of (1)H NMR chemical-shift effects as well as dipolar (1)H-(1)H or (1)H-(13)C couplings provide site-specific insight into the local structure and the segmental dynamics, in particular, of phenyl rings and -CH(2)O- linking units within the dendrons. Relative changes of (1)H chemical shifts (of up to -3 ppm) serve as distance constraints and allow protons to be positioned relative to aromatic rings. Together with dipolar spinning sideband patterns, pi-pi packing phenomena and local order parameters (showing variations between 30% and 100%) are selectively and precisely determined, enabling the identification of the dendron cores as the structure-directing moieties within the supramolecular architecture. The study is carried out over a representative selection of systems which reflect characteristic differences, such as different polymer backbones, sizes of dendritic side groups, or length and flexibility of linking units. While the polymer backbone is found to have virtually no effect on the overall structure and properties, the systems are sensitively affected by changing the generation or the linkage of the dendrons. The results help to understand the self-assembly process of dendritic moieties and aid the chemical design of self-organizing molecular structures. PMID:14570506

Rapp, Almut; Schnell, Ingo; Sebastiani, Daniel; Brown, Steven P; Percec, Virgil; Spiess, Hans Wolfgang

2003-10-29

88

Satellite-Transition MAS NMR of Spin I=3\\/2, 5\\/2, 7\\/2, and 9\\/2 Nuclei: Sensitivity, Resolution, and Practical Implementation  

Microsoft Academic Search

The satellite-transition MAS (STMAS) experiment offers an alternative approach to established methods such as dynamic angle spinning (DAS), double rotation (DOR), and multiple-quantum MAS (MQMAS) for obtaining high-resolution NMR spectra of half-integer quadrupolar nuclei. Unlike the multiple-quantum experiment, STMAS involves two-dimensional correlation of purely single-quantum coherences; satellite transitions in t1 (or F1) and the central transition in t2 (or F2).

Sharon E. Ashbrook; Stephen Wimperis

2002-01-01

89

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

90

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. 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

2008-01-01

91

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

PubMed Central

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

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

2013-01-01

92

Determination of structural topology of a membrane protein in lipid bilayers using polarization optimized experiments (POE) for static and MAS solid state NMR spectroscopy.  

PubMed

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

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

2013-10-01

93

Spectral editing in 13C solid-state NMR at high magnetic field using fast MAS and spin-echo dephasing.  

PubMed

A simple method is proposed for separating NMR resonances from protonated and non-protonated aromatic carbons in solids under fast magic angle spinning (MAS). The approach uses a MAS-synchronized spin-echo to exploit the differences in rotational recoupling of the dipolar interactions while fully refocusing the isotropic chemical shifts. This strategy extends the relevant time scale of spin evolution to milliseconds and circumvents the limitation of the traditional dipolar dephasing method, which in fast rotating solids is disrupted by rotational refocusing. The proposed approach can be used for quantitative measurement of carbon aromaticities in complex solids with poorly resolved spectra, as demonstrated for model compounds. PMID:22951436

Mao, Kanmi; Kennedy, Gordon J; Althaus, Stacey M; Pruski, Marek

2012-01-01

94

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

95

In situ {sup 13}C MAS NMR study of n-hexane conversion on Pt and Pd supported on basic materials  

SciTech Connect

n-Hexane conversion was studied in situ on Pt and Pd supported on aluminum-stabilized magnesium oxide and Pt on Zeolite KL catalysts (Pt/Mg(Al)O, Pd/Mg(Al)O and Pt/KL) by means of {sup 13}C MAS NMR spectroscopy. n-Hexane 1-{sup 13}C 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 NMR results were further quantified and compared with continuous flow microreactor tests. Four parallel reaction pathways were identified under flow conditions: isomerization, cracking, dehydrocyclization, and dehydrogenation. Aromatization occurs via two reaction routes: (1) n-hexane dehydrogenation towards hexadienes and hexatrienes, followed by dehydrogenation of a cyclic intermediate. The former reaction pathway is prevented under NMR batch conditions. High pressures induced in the NMR cells at high reaction temperatures (573, 653 K) shift the reaction equilibrium towards hydrogenation. NMR experiments showed that on Pt catalysts aromatization occurs via a cyclohexane intermediate, whereas on Pd it takes place via methylcyclopentane ring enlargement. 54 refs., 15 figs., 3 tabs.

Ivanova, I.I.; Pasau-Claerbout, A.; Seivert, M.; Derouane, E.G. [Facultes Universitaires N.D. de la Paix, Namur (Belgium)] [and others] [Facultes Universitaires N.D. de la Paix, Namur (Belgium); and others

1996-02-01

96

Incorporation of aluminum in the calcium silicate hydrate (C-S-H) of hydrated portland cements: a high-field 27Al and 29Si MAS NMR investigation.  

PubMed

The calcium silicate hydrate (C-S-H) phase resulting from hydration of a white Portland cement (wPc) in water and in a 0.3 M NaAlO(2) solution has been investigated at 14 and 11 hydration times, respectively, ranging from 6 h to 1 year by (27)Al and (29)Si MAS NMR spectroscopy. (27)Al MAS NMR spectra recorded at 7.05, 9.39, 14.09, and 21.15 T have allowed a determination of the (27)Al isotropic chemical shift (delta(iso)) and quadrupolar product parameter (P(Q) = C(Q)) for tetrahedrally coordinated Al incorporated in the C-S-H phase and for a pentacoordinated Al site. The latter site may originate from Al(3+) substituting for Ca(2+) ions situated in the interlayers of the C-S-H structure. The spectral region for octahedrally coordinated Al displays resonances from ettringite, monosulfate, and a third aluminate hydrate phase (delta(iso) = 5.0 ppm and P(Q) = 1.20 MHz). The latter phase is tentatively ascribed to a less-crystalline aluminate gel or calcium aluminate hydrate. The tetrahedral Al incorporated in the C-S-H phase has been quantitatively determined from (27)Al MAS spectra at 14.09 T and indirectly observed quantitatively in (29)Si MAS NMR spectra by the Q(2)(1Al) resonance at -81.0 ppm. A linear correlation is observed between the (29)Si MAS NMR intensity for the Q(2)(1Al) resonance and the quantity of Al incorporated in the C-S-H phase from (27)Al MAS NMR for the different samples of hydrated wPc. This correlation supports the assignment of the resonance at delta(iso)((29)Si) = -81.0 ppm to a Q(2)(1Al) site in the C-S-H phase and the assignment of the (27)Al resonance at delta(iso)((27)Al) = 74.6 ppm, characterized by P(Q)((27)Al) = 4.5 MHz, to tetrahedrally coordinated Al in the C-S-H. Finally, it is shown that hydration of wPc in a NaAlO(2) solution results in a C-S-H phase with a longer mean chain length of SiO(4) tetrahedra and an increased quantity of Al incorporated in the chain structure as compared to the C-S-H phase resulting from hydration of wPc in water. PMID:12665361

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

2003-04-01

97

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

Microsoft Academic Search

Recent ²⁷Al 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 δ {sub iso} = 5.0 ppm and the quadrupole product parameter P {sub Q} = 1.2 MHz,

Morten Daugaard Andersen; Hans J. Jakobsen; Jorgen. Skibsted

2006-01-01

98

A 27Al MAS, MQMAS and off-resonance nutation NMR study of aluminium containing silica-based sol-gel materials  

Microsoft Academic Search

Aluminium containing hybrid materials were prepared via the sol-gel method using aluminium sec-butoxide complexed with ethylacetoacetate (Al(OBus)2EAA or Al(OBus)3EAA mixtures). As silanes, phenyltrimethoxysilane (PhTMS) or phenyltriethoxysilane (PhTES), 3-glycidoxypropyl trimethoxysilane (Glymo) and tetraethylorthosilicate (TEOS) were used. After room temperature drying of the samples the 27Al single pulse excitation (SPE) magic angle spinning (MAS) NMR shows that octahedral (5 ppm) and tetrahedral

M. P. J. Peeters; A. P. M. Kentgens

1997-01-01

99

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

PubMed

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

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

2014-07-21

100

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

101

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

102

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

SciTech Connect

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

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

1998-11-30

103

{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

104

A 27Al MAS, MQMAS and off-resonance nutation NMR study of aluminium containing silica-based sol-gel materials.  

PubMed

Aluminium containing hybrid materials were prepared via the sol-gel method using aluminium sec-butoxide complexed with ethylacetoacetate (Al(OBus)2EAA or Al(OBus)3/EAA mixtures). As silanes, phenyltrimethoxysilane (PhTMS) or phenyltriethoxysilane (PhTES), 3-glycidoxypropyl trimethoxysilane (Glymo) and tetraethylorthosilicate (TEOS) were used. After room temperature drying of the samples the 27Al single pulse excitation (SPE) magic angle spinning (MAS) NMR shows that octahedral (5 ppm) and tetrahedral (55 ppm) coordinated aluminium species are present in the materials. The relative amount of these two species depends on the preparation method. However, the Al(IV)/Al(VI) ratio is lower than 3 (typically 2.3) in all materials, indicating the presence of a small amount of an aluminate phase. Annealing of the samples at 100, 150 and 200 degrees C results in the formation of an extra signal at 30 ppm (peak maximum measured at 11.7 T). Based on the resonance frequency this signal is generally assigned to a pentahedrally coordinated aluminium species. Hydration/dehydration processes of annealed samples were studied with 27Al SPE MAS NMR, multiple-quantum MAS NMR (MQMAS) and off-resonance nutation NMR. Upon hydration of the annealed sample the signal intensity around 30 ppm decreases in intensity and at the same time the intensity of the signal around 55 ppm increases by the same amount (tetrahedrally coordinated aluminium). The MQMAS spectra reveal that the signal around 30 ppm is not caused by a fivefold-coordinated aluminium species but mainly by tetrahedrally coordinated aluminium species in a distorted environment, experiencing large quadrupole induced shifts and small chemical shifts due to conformational changes in the polymeric network. From the MQMAS NMR spectra it can be concluded that the linebroadening observed in the 27Al MAS NMR spectra is due to both a distribution in isotropic chemical shifts and a distribution in quadrupole coupling constants (Cqcc = e2qQ/h). Hydration of the sample results in a decrease of the average Cqcc for the tetrahedrally coordinated aluminium from 6 to 4 MHz, whereas the average Cqcc of the octahedrally coordinated aluminium is hardly influenced (4 MHz). These MQMAS results are confirmed by off-resonance nutation experiments. PMID:9477450

Peeters, M P; Kentgens, A P

1997-12-01

105

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

106

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

PubMed Central

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

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

2009-01-01

107

Strategies for extracting NMR parameters from 23Na MAS, DOR and MQMAS spectra. A case study for Na4P2O7.  

PubMed

The 23Na magic-angle spinning (MAS), double rotation (DOR) and multiple-quantum magic-angle spinning (MQMAS) NMR spectra of anhydrous sodium pyrophosphate, Na4P2O7, measured at five different Larmor frequencies (nuL) ranging from 105.8 MHz (corresponding to 400 MHz 1H frequency) to 211.6 MHz (800 MHz) are analysed and the complete set of NMR parameters (C(qcc), etaQ and delta(iso)) of the four crystallographically inequivalent sodium sites were determined with high accuracy. Different approaches of spectra evaluation are discussed and their results are compared. The most reliable results are obtained from a combined evaluation of five DOR and three MQMAS spectra but also from two DOR and one MAS spectra or even from a single MQMAS spectrum all data can be derived. It is shown that Na4P2O7 may serve as a useful reference material for experimental set-up and reliability tests of the various NMR experiments. PMID:10672941

Engelhardt, G; Kentgens, A P; Koller, H; Samoson, A

1999-12-01

108

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

109

17O and 27Al MAS and 3QMAS NMR Study of Synthetic and Natural Layer Silicates  

E-print Network

of ground- water and the adsorption and transport of nuclear waste and heavy metals.1-3 Many layer silicates the oxygen sites, as well as the most shielded chemical shift of about 37-44 ppm. Analysis of the 27 Al MAS and metal adsorbates. Such detailed structural information is difficult to obtain from con- ventional X

Puglisi, Joseph

110

High-field 19.6T 27Al solid-state MAS NMR of in vitro aluminated brain tissue  

Microsoft Academic Search

The combination of 27Al high-field solid-state NMR (19.6T) with rapid spinning speeds (17.8kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10mM Al3+ (as AlCl3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10mM AlCl3. The spectra of these model systems show multiple Al3+ binding sites, good signal\\/noise ratios

Pamela L. Bryant; Walter J. Lukiw; Zhehong Gan; Randall W. Hall; Leslie G. Butler

2004-01-01

111

High-field 19.6 T 27Al solid-state MAS NMR of in vitro aluminated brain tissue  

Microsoft Academic Search

The combination of 27Al high-field solid-state NMR (19.6T) with rapid spinning speeds (17.8kHz) is used to acquire 27Al NMR spectra of total RNA human brain temporal lobe tissues exposed to 0.10mM Al3+ (as AlCl3) and of human retinal pigment epithelial cells (ARPE-19), grown in 0.10mM AlCl3. The spectra of these model systems show multiple Al3+ binding sites, good signal\\/noise ratios

Pamela L. Bryant; Walter J. Lukiw; Zhehong Gan; Randall W. Hall; Leslie G. Butler

2004-01-01

112

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

PubMed

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

Honda, Hisashi

2013-01-01

113

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

114

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

SciTech Connect

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

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

2000-05-01

115

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

116

High-resolution double-quantum {sup 31}P MAS NMR study of the intermediate-range order in crystalline and glass lead phosphates  

SciTech Connect

The authors have investigated the structure of binary lead phosphate glasses using 1D {sup 31}P MAS and 2D {sup 31}P double-quantum NMR. The distribution of the Q{sub n} phosphate species, determined from the simulation of 1D MAS spectra, indicates a significant disproportionation reaction (2Q{sub n} {leftrightarrow} Q{sub n+1} + Q{sub n{minus}1}) near the pyrophosphate composition. As demonstrated on crystalline reference samples, 2D double-quantum experiments can be used to determine the connectivities between Q{sub n} groups. This allows the authors to probe the phosphorus connectivity scheme in the glass network and to show that the Q{sub n} chemical shift is influenced by the type of the bonded PO{sub 4} tetrahedron. By analyzing quantitative 1D MAS spectra and 2D double-quantum spectra, the phosphorus connectivity scheme in the glass structure and its evolution with composition have been determined.

Fayon, F.; Bessada, C.; Coutures, J.P.; Massiot, D.

1999-11-15

117

(119)Sn MAS NMR and first-principles calculations for the investigation of disorder in stannate pyrochlores.  

PubMed

The local structure and cation disorder in Y(2)Ti(2-x)Sn(x)O(7) pyrochlores, materials proposed for the encapsulation of lanthanide- and actinide-bearing radioactive waste, is studied using (119)Sn (I = 1/2) NMR spectroscopy. NMR provides an excellent probe of disorder, as it is sensitive to the atomic scale environment without the need for any long-range periodicity. However, the complex and overlapping spectral resonances that often result can be difficult to interpret. Here, we demonstrate how (119)Sn DFT calculations can be used to aid the spectral interpretation and assignment, confirming that Sn occupies only the six-coordinate pyrochlore B site, and that the Sn chemical shift is sensitive to the number of Sn/Ti on the neighbouring B sites. Although distinct resonances are resolved experimentally when the Ti content is low, there is significant spectral overlap for Ti-rich compositions. We establish that this is a result of two competing contributions to the Sn chemical shift; an upfield shift resulting from the incorporation of the more polarizing Ti(4+) cation onto the neighbouring B sites, and a concomitant downfield shift arising from the decrease in unit cell size. Despite the considerably easier spectral acquisition, the lower resolution in the (119)Sn spectra hinders the extraction of the detailed structural information previously obtained using (89)Y NMR. However, the spectra we obtain are consistent with a random distribution of Sn/Ti on the pyrochlore B sites. Finally, we consider whether an equilibrium structure has been achieved by investigating materials that have been annealed for different durations. PMID:21031216

Mitchell, Martin R; Reader, Simon W; Johnston, Karen E; Pickard, Chris J; Whittle, Karl R; Ashbrook, Sharon E

2011-01-14

118

Drastic sensitivity enhancement in 29Si MAS NMR of zeolites and mesoporous silica materials by paramagnetic doping of Cu2+.  

PubMed

The paramagnetic doping of Cu(2+) in both mesoporous silica materials and microporous silicate crystals (zeolites) can be used effectively to enhance the signal intensity of (29)Si solid state magic angle spinning NMR, as a result of shortening of the spin-lattice relaxation time, T1, by the paramagnetic effect, because of the Cu(2+) electronic relaxation time in the range of 10(-8) s. This leads to drastically reduced data-collection times, typically 80-fold shorter than that in mesoporous silica. We found that the estimated range of the paramagnetic effect of Cu(2+) doping in porous silicates was at least 1 nm. PMID:23824320

Inagaki, Satoshi; Kawamura, Izuru; Sasaki, Yukichi; Yoshida, Kaname; Kubota, Yoshihiro; Naito, Akira

2013-08-28

119

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

120

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

121

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

122

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

PubMed

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

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

2013-04-01

123

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

124

Structure and dynamics of zirconocene complexes in the solid state studied by sup 13 C CP/MAS NMR spectroscopy  

SciTech Connect

High-resolution one- and two-dimensional solid-state CP/MAS spectra of microcrystalline bent metallocene complexes of the type ({eta}{sup 5}-{sup R}Cp){sub 2}ZrL{sub 2} have been obtained at various temperatures (L = Cl, R = H (1), Me (2), Et (3), {sup t}Bu (4); L{sub 2} = s-cis-{eta}{sup 4}-C{sub 4}H{sub 6}, R = {sup t}Bu (8); L{sub 2} = s-cis-{eta}{sup 4}-C{sub 4}H{sub 6}, R = 1,1-dimethylpentyl (9); L{sub 2} = s-cis-{eta}{sup 4}-C{sub 4}H{sub 5}Me, R = {sup t}Bu (10)). Complexes 1-4 possess C{sub 2} molecular symmetry, while the overall symmetry of complexes 5 and 6 is close to C{sub s}. In 7-9 there is no element of symmetry, and 10 yields diastereoisomers (95:5).

Benn, R.; Grondey, H. (Max-Planck-Inst. fuer Kohlenforschung, Muelheim an der Ruhr (West Germany)); Erker, G.; Aul, R.; Nolte, R. (Univ. Wuerzburg (West Germany))

1990-09-01

125

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

126

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

127

Observation of four-coordinate aluminum oxynitride (AlO{sub 4-x}Nâ) environments in AlON solids by MAS ²⁷Al NMR at 14 T  

Microsoft Academic Search

The synthesis and magic angle spinning (MAS) [sup 27]Al NMR characterization of a series of aluminum oxynitride powders prepared at various AlN\\/Al[sub 2]O[sub 3] reaction ratios from 16.7 to 88.0 mole percent AlN are reported. The MAS NMR at 14 T reveal the presence of both six-(AlO[sub 6]) and four-coordinate (AlO[sub 4]) sites in lamda-AlON. Also observed were resonances dur

J. J. Fitzgerald; S. D. Kohl; G. Piedra

1994-01-01

128

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

SciTech Connect

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

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

2010-06-15

129

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

130

Precise side-chain conformation analysis of L-phenylalanine in ?-helical polypeptide by quantum-chemical calculation and 13C CP-MAS NMR measurement  

NASA Astrophysics Data System (ADS)

To clarify the positive role of side-chain conformation in the stability of protein secondary structure (main-chain conformation), we successfully calculated the optimization structure of a well-defined ?-helical octadecapeptide composed of L-alanine (Ala) and L-phenylalanine (Phe) residues, H-(Ala) 8-Phe-(Ala) 9-OH, based on the molecular orbital calculation with density functional theory (DFT/B3LYP/6-31G(d)). From the total energy and the precise secondary structural parameters such as main-chain dihedral angles and hydrogen-bond parameters of the optimized structure, we confirmed that the conformational stability of an ?-helix is affected dominantly by the side-chain conformation ( ?1) of the Phe residue in this system: model A ( T form: around 180° of ?1) is most stable in ?-helix and model B ( G + form: around -60° of ?1) is next stable, but model C ( G - form: around 60° of ?1) is less stable. In addition, we demonstrate that the stable conformation of poly( L-phenylalanine) is an ?-helix with the side-chain T form, by comparison of the carbonyl 13C chemical shift measured by 13C CP-MAS NMR and the calculated one.

Niimura, Subaru; Suzuki, Junya; Kurosu, Hiromichi; Yamanobe, Takeshi; Shoji, Akira

2010-04-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

132

Structural characterization of high-pressure C-Na2Si2O5 by single-crystal diffraction and 29Si MAS NMR  

NASA Astrophysics Data System (ADS)

Single crystals of C-Na2Si2O5 have been synthesized from the hydrothermal recrystallization of a glass. The title compound is monoclinic, space group P21/c with Z= 8 and unit-cell parameters a= 4.8521 (4)Å, b=23.9793(16)Å, c=8.1410(6)Å, ?=90.15(1)° and V=947.2(2)Å3. The structure has been determined by direct methods and belongs to the group of phyllosilicates. It is based on layers of tetrahedra with elliptically six-membered rings in chair conformation. The sequence of directedness within a single ring is UDUDUD. The sheets are parallel to (010) with linking sodium cations in five- and sixfold coordination. Concerning the shape and the conformation of the rings, C-Na2Si2O5 is closely related to ?-Na2Si2O5. However, both structures differ in the stacking sequences of the layers. A possible explanation for the frequently observed polysynthetic twinning of phase C is presented. In the 29Si MAS-NMR spectrum of C-Na2Si2O5 four well-resolved lines of equal intensity are observed at -86.0, -86.3, -87.4, and -88.2ppm. The narrow range of isotropic chemical shifts reflects the great similarity of the environments of the different Si sites. This lack of pronounced differences in geometry renders a reliable assignment of the resonance lines to the individual sites on the basis of known empiric correlations and geometrical features impossible.

Raki?, S.; Kahlenberg, V.; Weidenthaler, C.; Zibrowius, B.

133

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

PubMed

Molybdenum is a transition metal (refers to the "d" block of the periodic table) whose atom has an incomplete d sub-shell. It is known that in silicate glasses molybdenum may exist under four oxidation states: Mo6+, Mo5+, Mo4+ and Mo3+, simultaneously molybdenum cations, depending on their content in the glass network, may either be a glass forming component, or act as a modifier. The contemporary literature data show studies conducted mostly on the structure of silicate, phosphate, borate and borosilicate glasses containing molybdenum ions, but not silicate-phosphate glasses. Therefore, the author has undertaken detailed studies using FTIR, Raman and 31P MAS NMR techniques in order to examine the effect of MoO3 addition into the structure of silicate-phosphate glasses from SiO2P2O5K2OCaOMgO system. On the basis of obtained results it was concluded that molybdenum ions in the analysed glasses act as a modifier, which follows from the gradual breakage of oxygen bridges, i.e. POP, SiOSi, and SiOP, and the following formation of connections such as Mo[MoO4]OSi and/or Mo[MoO4]OP. In summary, it is concluded that the increase of MoO3 content (up to 4.4 mol.%) in the structure of glasses of SiO2P2O5K2OMgOCaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation. PMID:24759778

Szumera, M

2014-09-15

134

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

135

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

PubMed

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

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

2014-11-01

136

Observation of four-coordinate aluminum oxynitride (AlO{sub 4-x}N{sub x}) environments in AlON solids by MAS {sup 27}Al NMR at 14 T  

SciTech Connect

The synthesis and magic angle spinning (MAS) [sup 27]Al NMR characterization of a series of aluminum oxynitride powders prepared at various AlN/Al[sub 2]O[sub 3] reaction ratios from 16.7 to 88.0 mole percent AlN are reported. The MAS NMR at 14 T reveal the presence of both six-(AlO[sub 6]) and four-coordinate (AlO[sub 4]) sites in lamda-AlON. Also observed were resonances dur to four-coordinate AlNO[sub 3], AlN[sub 2]O[sub 2], and AlN[sub 3]O sites in the various AlON reaction products, as well as NMR peaks due to the unreacted AlN and Al[sub 2]O[sub 3]. The results of these investigations indicate that sufficient spectral resolution can be obtained via MAS at this field to distinguish and assign four-coordinate aluminum oxynitride moieties in these unique AlON ceramic materials.

Fitzgerald, J.J.; Kohl, S.D.; Piedra, G. [South Dakota State Univ., Brookings, SD (United States)

1994-11-01

137

Solid-State NMR Detection, Characterization, and Quantification of the Multiple Aluminum Environments in US-Y Catalysts by Al-27 MAS and MQMAS Experiments at Very High Field  

SciTech Connect

The detection of all of the aluminum present in steamed zeolite H-Y catalysts by (27)Al MAS NMR at 14.4 T (600 MHz for (1)H) and 18.8T (800 MHz for (1)H) is reported. Further, it is shown that it is possible by (27)Al MAS and MQMAS NMR measurements to clearly identify four separate aluminum environments which are characteristic of these materials and to unambiguously assign their coordinations. Average chemical shift and quadrupolar coupling parameters are used to accurately simulate the (27)Al MAS NMR spectra at 9.4 T (400 MHz for (1)H), 14.4 T (600 MHz for (1)H) and 18.8 T (800 MHz for (1)H) in terms of these four aluminum environments. In addition, these average chemical shift and quadrupolar coupling parameters are used to calculate peak positions in the (27)Al MQMAS isotropic dimension that are in good agreement with the experimental data acquired at 9.4 and 18.8 T.

Fyfe, Colin A.(8998) [8998; Bretherton, Jeremy L.(8998) [8998; Lam, Lau Y.(University of British Columbia) [University of British Columbia

2001-06-06

138

Na multiple-quantum MAS NMR of the perovskites NaNbO3 and Sharon E. Ashbrook,w*a  

E-print Network

, with a higher average bond distance) exhibit a lower chemical shift. The significant progress in the development. However, the development of techniques such as multiple-quantum (MQ) MAS1 and satel- lite-transition (ST accurately and easily. Despite the fairly small chemical shift range of 23 Na, some general trends

Paris-Sud XI, Université de

139

High Resolution 1H Detected 1H,13C Correlation Spectra in MAS Solid-State NMR using Deuterated Proteins with Selective 1  

E-print Network

-state nuclear magnetic resonance (ssNMR) has developed rapidly over the past few years. This development led pattern indicating the isotopic distribution. We show in this communication that, out of all expected decoupling yields a major improvement in the spectral quality (Figure 1B). Typical 13C line widths

Skrynnikov, Nikolai

140

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

SciTech Connect

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

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

2010-01-15

141

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

142

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

143

De?Novo 3D Structure Determination from Sub-milligram Protein Samples by Solid-State 100?kHz MAS NMR Spectroscopy.  

PubMed

Solid-state NMR spectroscopy is an emerging tool for structural studies of crystalline, membrane-associated, sedimented, and fibrillar proteins. A major limitation for many studies is still the large amount of sample needed for the experiments, typically several isotopically labeled samples of 10-20?mg each. Here we show that a new NMR probe, pushing magic-angle sample rotation to frequencies around 100?kHz, makes it possible to narrow the proton resonance lines sufficiently to provide the necessary sensitivity and spectral resolution for efficient and sensitive proton detection. Using restraints from such spectra, a well-defined de novo structure of the model protein ubiquitin was obtained from two samples of roughly 500??g protein each. This proof of principle opens new avenues for structural studies of proteins available in microgram, or tens of nanomoles, quantities that are, for example, typically achieved for eukaryotic membrane proteins by in-cell or cell-free expression. PMID:25225004

Agarwal, Vipin; Penzel, Susanne; Szekely, Kathrin; Cadalbert, Riccardo; Testori, Emilie; Oss, Andres; Past, Jaan; Samoson, Ago; Ernst, Matthias; Böckmann, Anja; Meier, Beat H

2014-11-01

144

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

Microsoft Academic Search

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

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

2001-01-01

145

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

146

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

SciTech Connect

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

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

2008-10-12

147

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

PubMed

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

Pajchel, L; Nykiel, P; Kolodziejski, W

2011-12-01

148

A study of the effects of hazardous inorganic wastes on the solidification/stabilization of different types of cements using high-resolution MAS NMR spectroscopy  

SciTech Connect

The disposal of hazardous industrial wastes is a major concern of environmental scientists. Solidification/stabilization often uses cement and cement-like materials is the treatment of hazardous wastes which are in liquid or sludge forms to produce a solid for land disposal. Although various procedures are commonly practices, little is known about the mechanism(s) of the processes. Portland cement clinker is a polyphase inorganic binder, and the principal phases C{sub 3}S (tricalcium silicate), C{sub 2}S (dicalcium silicate), C{sub 3}A (tricalcium aluminate), and C{sub 4}AF (tetracalcium alumino ferrite) present in the clinker are not pure. Solid-state {sup 29}Si and {sup 27}Al NMR spectroscopy was performed to determine the nature of silicate and aluminate species present in the clinkers, prior to hydration and after fixed cure times. The same was done for different types of cement with and without added impurities.

Akhter, H.; Chalasani, D.; Butler, L.G.; Jackisch, M.; Cartledge, F.K. (Louisiana State Univ., Baton Rouge (USA))

1990-01-01

149

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. PMID:24466083

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

2014-01-01

150

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

151

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

PubMed

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

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

2014-09-01

152

Characterization of framework and extra-framework aluminum species in non-hydrated zeolites Y by 27Al spin-echo, high-speed MAS, and MQMAS NMR spectroscopy at B0 = 9.4 to 17.6 T.  

PubMed

27Al spin-echo, high-speed MAS (nu(rot) = 30 kHz), and MQMAS NMR spectroscopy in magnetic fields of B0 = 9.4, 14.1, and 17.6 T were applied for the study of aluminum species at framework and extra-framework positions in non-hydrated zeolites Y. Non-hydrated gamma-Al2O3 and non-hydrated aluminum-exchanged zeolite Y (Al,Na-Y) and zeolite H,Na-Y were utilized as reference materials. The solid-state 27Al NMR spectra of steamed zeolite deH,Na-Y/81.5 were found to consist of four signals. The broad low-field signal is caused by a superposition of the signals of framework aluminum atoms in the vicinity of bridging hydroxyl protons and framework aluminum atoms compensated in their negative charge by aluminum cations (delta(iso) = 70 +/- 10 ppm, C(QCC) = 15.0 +/- 1.0 MHz). The second signal is due to a superposition of the signals of framework aluminum atoms compensated by sodium cations and tetrahedrally coordinated aluminum atoms in neutral extra-framework aluminum oxide clusters (delta(iso) = 65 +/- 5 ppm, C(QCC) = 8.0 +/- 0.5 MHz). The residual two signals were attributed to aluminum cations (delta(iso) = 35 +/- 5 ppm, C(QCC) = 7.5 +/- 0.5 MHz) and octahedrally coordinated aluminum atoms in neutral extra-framework aluminum oxide clusters (delta(iso) = 10 +/- 5 ppm, C(QCC) = 5.0 +/- 0.5 MHz). By chemical analysis and evaluating the relative solid-state 27Al NMR intensities of the different signals of aluminum species occurring in zeolite deH,Na-Y/81.5 in the non-hydrated state, the aluminum distribution in this material was determined. PMID:16240035

Jiao, Jian; Kanellopoulos, Johanna; Wang, Wei; Ray, Siddharth S; Foerster, Hans; Freude, Dieter; Hunger, Michael

2005-09-01

153

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

SciTech Connect

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

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

2003-01-01

154

Investigation of different apple cultivars by high resolution magic angle spinning NMR. A feasibility study.  

PubMed

(1)H HR-MAS NMR spectroscopy was applied to apple tissue samples deriving from 3 different cultivars. The NMR data were statistically evaluated by analysis of variance (ANOVA), principal component analysis (PCA), and partial least-squares-discriminant analysis (PLS-DA). The intra-apple variability of the compounds was found to be significantly lower than the inter-apple variability within one cultivar. A clear separation of the three different apple cultivars could be obtained by multivariate analysis. Direct comparison of the NMR spectra obtained from apple tissue (with HR-MAS) and juice (with liquid-state HR NMR) showed distinct differences in some metabolites, which are probably due to changes induced by juice preparation. This preliminary study demonstrates the feasibility of (1)H HR-MAS NMR in combination with multivariate analysis as a tool for future chemometric studies applied to intact fruit tissues, e.g. for investigating compositional changes due to physiological disorders, specific growth or storage conditions. PMID:22084979

Vermathen, Martina; Marzorati, Mattia; Baumgartner, Daniel; Good, Claudia; Vermathen, Peter

2011-12-28

155

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

SciTech Connect

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

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

2008-01-01

156

Thermal decomposition of monocalcium aluminate decahydrate (CaAl2O4.10H2O) investigated by in-situ synchrotron X-ray powder diffraction, thermal analysis and 27Al, 2H MAS NMR spectroscopy.  

PubMed

The stability of monocalcium aluminate decahydrate, with the nominal composition CaAl(2)O(4).10H(2)O (CAH(10)), has a decisive role for the strength development and durability of cementitious materials based on high alumina cements. This has prompted an investigation of the thermal transformation of crystalline monocalcium aluminate decahydrate in air to an amorphous phase by in-situ synchrotron X-ray powder diffraction in the temperature range from 25 to 500 degrees C, by DTA/TGA, and (2)H, (27)Al MAS NMR spectroscopy. The decomposition includes the loss of hydrogen-bonded water molecules in the temperature range up to 175 degrees C, coupled with a reduction of the unit cell volume from 1928 A(3) at 25 degrees C, to 1674 A(3) at 185 degrees C. Furthermore, X-ray diffraction shows that CaAl(2)O(4).10H(2)O starts to transform to an amorphous phase at approximately 65 degrees C. This phase is fully developed at approximately 175 degrees C and it converts to crystalline CaAl(2)O(4) when heated to 1300 degrees C. The thermal decomposition in the temperature range from approximately 65 to approximately 175 degrees C involves both formation of an amorphous phase including AlO(4) tetrahedra and structural changes in the remaining crystalline phase. PMID:18185861

Christensen, Axel Nørlund; Jensen, Torben R; Lebech, Bente; Hanson, Jonathan C; Jakobsen, Hans J; Skibsted, Jørgen

2008-01-28

157

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

158

?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

159

{sup 27}Al and {sup 23}Na MAS NMR and powder x-ray diffraction studies of sodium aluminate speciation and the mechanistics of aluminum hydroxide precipitation upon acid hydrolysis  

SciTech Connect

{sup 27}Al and {sup 23}Na MAS NMR, powder X-ray diffraction, and infrared spectroscopic investigations of freeze-dried sodium aluminates and aluminum hydroxides formed through acid hydrolysis have been undertaken, with OH/Al hydrolysis ratios between 5.3 and 2.8 being analyzed. Numerous {sup 27}AlNMR resonances were observed, the intensities of which vary as a function of OH/Al ratio, and these have been assigned to four-, five-, and six-coordinate aluminum species constituting a variety of structural moieties. The dominant species at an OH/Al ratio above 4.4 appears to be a Q{sup o}Na[Al(OH);{sub 4}] salt, as indicated by a {sup 27}Al resonance at 86.6 ppm. In addition, a second, broader resonance at 71.3 ppm demonstrates the simultaneous existence of further four-coordinate aluminum species linked thorough oxo bonds to other four-coordinate aluminums (e.g., Q{sup 2} [Al(OH);{sub 2}(OAl){sub 2}];{sup x-}). At an OH/Al ratio between 4.4 and 4.1, a water-soluble phase forms that contains both four- and six-coordinate aluminum. At OH/Al ratios fo 4.0 and below, a water-soluble phase forms that contains both four-and six-coordinate aluminum. AT OH/Al ratios of 4.0 and below, a water-insoluble phase exists possessing four-, five-, and six-coordinate aluminum. At OH/Al{le}3.9 range exhibits {sup 27}Al chemical shifts similar to those reported for transitional aluminas such as {gamma}-, {eta}-, and 0-Al{sub 2}O{sub 3} and an infrared spectrum similar to pseudo-spinel gels, suggesting that a pseudo-spinel intermediate is the first phase involved in the crystallization of gibbsite. The resonance assigned to five-coordinate aluminum probably results from species involved in the transformation of the pseudo-spinal phase to pseudo-boehmite. The formation of gibbssite on the acid hydrolysis of alkaline sodium aluminate solutions thus appears to follow the pathway pseudo-spinel {r_arrow} pseudo-boehmite {r_arrow} bayerite {r_arrow} gibbsite. 82 refs., 7 figs., 3 tabs.

Bradley, S.M.; Hanna, J.V. [Univ. of New South Wales, Sydney (Australia)

1994-08-24

160

2 H Chemical-shift resolution and dipolar 2 H- 1 H, 2 H- 15 N correlations in solid-state MAS NMR spectroscopy for structure determination and distance measurements in hydrogen-bonded systems  

Microsoft Academic Search

In solid-state NMR, deuteron (2H) spectroscopy can be performed in full analogy to1H spectroscopy, including2H chemical-shift resolution and2H-X dipolar correlation schemes, when the NMR experiments are conducted in a “rotor-synchronized” fashion under fast magic-angle\\u000a spinning. Here, 2H-X NMR experiments of this type, including2H-15N and2H-1H chemical-shift correlations and distance measurements, are introduced and demonstrated on cytosine monohydrate, whose acidic\\u000a protons can

Martin Schulz-Dobrick; Ingo Schnell

2005-01-01

161

13C, 15N NMR and CP-MAS as well as FT-IR and PM5 studies of Schiff base of gossypol with L-phenylalanine methyl ester in solution and solid  

NASA Astrophysics Data System (ADS)

The Schiff bases of racemic gossypol with L-phenylalanine amino acid methyl ester (GSBA) was studied by FT-IR, 13C and 15N NMR spectroscopy as well as by the PM5 semiempirical method. The spectroscopic methods have provided clear evidence that GSBA exists in the solid state and in solution as enamine-enamine tautomer. The existence of diastereoisomers is very well evidenced in the 13C NMR spectra in the solution by the double character of all carbon atoms' signals of the naphthalene rings. The structure of GSBA and the hydrogen bonds within this structure are discussed.

Przybylski, Piotr; Schilf, Wojciech; Brzezinski, Bogumi?

2005-01-01

162

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

SciTech Connect

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

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

2013-10-31

163

February 2008 HR Guidance  

E-print Network

to informal warnings refuted by employees and not taken further. Children and Vulnerable Adults Where subjectsFebruary 2008 HR Guidance Giving References Giving References 1 Difficult References 2 Model Reference 4 #12;#12;February 2008 1 HR Guidance Giving References Giving References Scope This guidance

Chittka, Lars

164

HR SERVICES COMMUNICATION SESSION  

E-print Network

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

165

A refined model of the chlorosomal antennae of the green bacterium Chlorobium tepidum from proton chemical shift constraints obtained with high-field 2-D and 3-D MAS NMR dipolar correlation spectroscopy.  

PubMed

Heteronuclear 2-D and 3-D magic-angle spinning NMR dipolar correlation spectroscopy was applied to determine solid-state (1)H shifts for aggregated bacteriochlorophyll c (BChl c) in uniformly (13)C-enriched light harvesting chlorosomes of the green photosynthetic bacterium Chlorobium tepidum. A complete assignment of 29 different observable resonances of the 61 protons of the aggregated BChl c in the intact chlorosomes is obtained. Aggregation shifts relative to monomeric BChl c in solution are detected for protons attached to rings I, II, and III/V and to their side chains. The 2(1)-H(3), 3(2)-H(3), and 3(1)-H resonances are shifted upfield by -2.2, -1, and -3.3 ppm, respectively, relative to monomeric BChl c in solution. Although the resonances are inhomogeneously broadened and reveal considerable global structural heterogeneity, the 5-CH and the 7-Me responses are doubled, which provides evidence for the existence of at least two relatively well-defined structurally different arrangements. Ab initio quantum chemical modeling studies were performed to refine a model for the self-assembled BChl c with two different types of BChl stacks. The BChl in the stacks can adopt either anti- or syn-configuration of the coordinative bond, where anti and syn designate the relative orientation of the Mg-OH bond relative to the direction of the 17-17(1) bond. The analogy between aggregation shifts for BChl c in the chlorosome and for self-assembled chlorophyll a/H(2)O is explored, and a bilayer model for the tubular supra-structure of sheets of BChl c is proposed, from a homology modeling approach. PMID:11327817

van Rossum, B J; Steensgaard, D B; Mulder, F M; Boender, G J; Schaffner, K; Holzwarth, A R; deGroot, H J

2001-02-13

166

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

167

Director HR Andrew J Smith  

E-print Network

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

Liley, David

168

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

169

HR Department ADOPTION LEAVE  

E-print Network

HR Department ADOPTION LEAVE JANUARY 2004 Approved by the Executive Board 27-Jan-04 Updated to adoption leave. Please contact your Human Resources Officer for further advice and information. Employees who become adoptive parents after 6 April 2003 are entitled to adoption leave and to receive Statutory

Doran, Simon J.

170

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

171

McCune-Albright Syndrome (MAS)  

MedlinePLUS

... Syndrome (MAS): Condition Information Skip sharing on social media links Share this: Page Content What is MAS? MAS is a genetic disorder that affects the skin, bones, and the production of certain hormones. Because of its effects on hormones, MAS often causes early puberty in girls. ...

172

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

173

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

174

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

175

workplace bullying HR : , workplace bullying.  

E-print Network

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

Chatziantoniou, Damianos

176

MAS Journal Instructions to Authors  

E-print Network

Prior to submission of a manuscript to the MAS Journal, authors should read and be familiar with the Journal’s policies. Journal Section: Authors should select the Journal Section to which they are submitting their manuscript for publication. Journal sections include: State Of The Art Reviews, Cross-Disciplinary Reviews, Teaching/Mentoring Science, and Original Research. Format: The manuscript should be prepared on standard page format (8.5 x 11.0 inches), double spaced, in a 12 point Times Roman typeface, with 1 inch margins. The manuscript should be prepared in Microsoft Word (MS Word 1997-2003 or higher. The manuscript should be divided into the following parts, in the following order: ? Title Page ? Funding sources and conflicts of interest ? Keywords and running title

unknown authors

177

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

178

Observation of NMR noise from solid samples  

PubMed Central

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

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

2010-01-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

180

Moving NMR  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

181

MAS 03 Marine Bloom Trajectory Prediction for AUV Mission Planning MAS 03.1 Overview  

E-print Network

kilometers) and small vertical extent (in 1-10 meters). Harmful Algal Blooms (the focus of this paper such predictions can be used to plan survey missions for AUVs. MAS 03.2 Approach The dynamics of an algal bloom canMAS 03 Marine Bloom Trajectory Prediction for AUV Mission Planning MAS 03.1 Overview Observing

California at Los Angeles, University of

182

HR Positions on the Internet.  

ERIC Educational Resources Information Center

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

Coghill, Carey Cox; Kirk, James J.

183

Career Tracks Presentation to HR  

E-print Network

Career Tracks Presentation to HR Contacts Compensation UC San Diego Campus Human Resources that is being implemented at all UC locations The Career Tracks framework aligns jobs with similar positions internally and in the external marketplace Career Tracks includes non-represented staff positions. Senior

Jun, Suckjoon

184

Reliable MAS performance prediction using queueing models  

Microsoft Academic Search

In this paper, we model a multi-agent system (MAS) in military logistics based on the systemic specifications of the capabilities and attributes of individual agents (TechSpecs). Assuring the survivability of the MAS that implements distributed planning and execution is a significant design-time and run-time challenge. Dynamic battlefield stresses in military logistics range from heavy computational loads (information warfare) to being

Nathan Gnanasambandam; Seokcheon Lee; Natarajan Gautam; Soundar R. T. Kumara; Wilbur Peng; Vikram Manikonda; Marshall Brinn; Mark Greaves

2004-01-01

185

Solid-state NMR characterization of the acid sites in cubic mesoporous Al-MCM-48 materials using trimethylphosphine oxide as a 31P NMR probe  

Microsoft Academic Search

The acidic properties of Al-MCM-48 with Si\\/Al ratios ranging from 10 to 67, synthesized with Gemini surfactant as the template, have been characterized by a combination of multinuclear solid-state 1H, 23Na, 27Al, 29Si and 31P MAS (magic angle spinning) NMR and some double-resonance NMR methods using trimethylphosphine oxide (TMPO) as a probe molecule. XRD and 27Al MAS NMR results indicated

Hsien-Ming Kao; Pai-Ching Chang; Yun-Wen Liao; Lung-Ping Lee; Chu-Hua Chien

2008-01-01

186

The evaluation of different MAS techniques at low spinning rates in aqueous samples and in the presence of magnetic susceptibility gradients  

SciTech Connect

It was recently demonstrated that the nuclear magnetic resonance (NMR) linewidths for stationary biological samples are dictated mainly by magnetic susceptibility gradients, and that phase-altered spinning sideband (PASS) and phase-corrected magic angle turning (PHORMAT) solid-state NMR techniques employing slow and ultra-slow magic angle spinning (MAS) frequencies can be used to overcome the static susceptibility broadening to yield high-resolution, spinning sideband (SSB)-free 1H NMR spectra.

Hu, Jian Zhi; Wind, Robert A.

2002-11-01

187

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

188

Learning Avatar Behaviours Project for MAS 732  

E-print Network

Learning Avatar Behaviours Project for MAS 732 Peter Gorniak MIT Media Lab 20 Ames Street Cambridge- based system and allows reasoning about beliefs as well as graceful degradation. The implementation is by now a well-studied field as summarized in (Boutilier et al., 1999). This way of thinking also has

Gorniak, Peter

189

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

PubMed

The prognosis for patients with pancreatic cancer is extremely poor, as evidenced by the disease's five-year survival rate of ~5%. New approaches are therefore urgently needed to improve detection, treatment, and monitoring of pancreatic cancer. MRS-detectable metabolic changes provide useful biomarkers for tumor detection and response-monitoring in other cancers. The goal of this study was to identify MRS-detectable biomarkers of pancreatic cancer that could enhance currently available imaging approaches. We used (1) H high-resolution magic angle spinning MRS to probe metabolite levels in pancreatic tissue samples from mouse models and patients. In mice, the levels of lipids dropped significantly in pancreata with lipopolysaccharide-induced inflammation, in pancreata with pre-cancerous metaplasia (4?week old p48-Cre;LSL-Kras(G12D) mice), and in pancreata with pancreatic intraepithelial neoplasia, which precedes invasive pancreatic cancer (8?week old p48-Cre LSL-Kras(G12D) mice), to 26?±?19% (p?=?0.03), 19?±?16% (p?=?0.04), and 26?±?10% (p?=?0.05) of controls, respectively. Lactate and taurine remained unchanged in inflammation and in pre-cancerous metaplasia but increased significantly in pancreatic intraepithelial neoplasia to 266?±?61% (p?=?0.0001) and 999?±?174% (p?

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

2014-11-01

190

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

PubMed

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

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

2007-02-01

191

Rock Art Interpretation within Indiana MAS Viviana Mascardi1  

E-print Network

Rock Art Interpretation within Indiana MAS Viviana Mascardi1 , Vincenzo Deufemia2 , Damiano to the Indiana MAS has been extended to cope with images, besides hand drawn sketches, and has been tested in the domain of Mount Bego's pre- historic rock art (southern French Alps). The way Indiana MAS holons

Mascardi, Viviana

192

High Resolution 3D Exchange NMR Spectroscopy and the Mapping of Connectivities between Half-integer Quadrupolar Nuclei  

E-print Network

in the present study but are resolved by MQMAS.8b,c Conventional 2D exchange MAS NMR experiments exhibit exHigh Resolution 3D Exchange NMR Spectroscopy and the Mapping of Connectivities between Half June 8, 2002 The nuclear magnetic resonance (NMR) of spin S > 1/2 nuclei is usually dominated

Frydman, Lucio

193

/sup 31/P-NMR study of borophosphate glasses  

SciTech Connect

It is shown that /sup 31/P nuclear magnetic resonance (NMR) spectroscopy with magic angle spinning (MAS) discriminates among different types of PO/sub 4/ units occurring in borophosphate glasses. The isotope /sup 31/P chemical shift of the PO/sub 4/ increases by nearly 70 ppm in going from the branching unit, neutral and covalently bonded, to the monomeric unit, which carries a -3 nominal charge. By using both stationary and MAS /sup 31/P spectra, the authors also obtain the average values, and distribution widths, for chemical shift anisotropy and the asymmetry factor of PO/sub 4/ units occurring in vitreous borophosphates. Analysis of these NMR spectra provides detailed information about the short-range order in these glasses. It is also shown that the /sup 31/P-NMR-MAS technique may contribute significantly to phase separation and crystallization studies of phosphorus-containing glasses.

Villa, M.; Carduner, K.R.; Chiodelli, G.

1987-07-01

194

A 31P-NMR study of borophosphate glasses  

NASA Astrophysics Data System (ADS)

It is shown that 31P nuclear magnetic resonance (NMR) spectroscopy with magic angle spinning (MAS) discriminates among different types of PO 4 units occurring in borophosphate glasses. The isotropic 31P chemical shift of the PO 4 increases by nearly 70 ppm in going from the "branching unit," neutral and covalently bonded, to the "monomeric unit," which carries a -3 nominal charge. By using both stationary and MAS 31P spectra, we also obtain the average values, and distribution widths, for chemical shift anisotropy and the asymmetry factor of PO 4 units occurring in vitreous borophosphates. Analysis of these NMR spectra provides detailed information about the short-range order in these glasses. It is also shown that the 31P-NMR-MAS technique may contribute significantly to phase separation and crystallization studies of phosphorus-containing glasses.

Villa, Marco; Carduner, Keith R.; Chiodelli, Gaetano

1987-07-01

195

POSTING 14-51 HR Coordinator  

E-print Network

applies to women as well as to men. Bishop's University is seeking a qualified and dedicated individual, and updating all HR databases and lists linked with the process in a timely and accurate fashion; Maintains

196

Time(24-hr) AerialAssist  

E-print Network

OnEffort? Day Month Year Time(24-hr) Lat-Deg Lat-N/S Long-Deg Long-E/W Beaufort Weather Obs N W N W N W . Daily Activity Log - Purse Seine - Large Pelagics Date/Time Position Lat-Min Long Time(24-hr) Lat-Deg Lat-N/S Long-Deg Long-E/W Beaufort Weather Obs.Cond. WaterTemp Speed(kn) NoX20

197

From precursors to non-oxide ceramics: Pyrolytic mechanisms studied by NMR  

SciTech Connect

The pyrolysis of a poly ethylsilazane was studied using a CO{sub 2}-laser beam heated solid state MAS-NMR probe head. Chemical structures of the intermediate stages could be identified. The analogy of the pyrolysis evolution for the following two different methods could be shown: (A) in an inert gas furnace conventionally prepared and (B) laser irradiated in the NMR probe head under magic-angle spinning (MAS) conditions. Samples prepared by method A were studied by {sup 29}Si MAS-NMR and samples prepared by method B were studied with an appropriate cross polarization time by {sup 29}Si CP-MAS-NMR. Both experiments showed the same mechanisms for the pyrolysis as the polymer is transformed into a Si{sub 3}N{sub 4}/C ceramic.

Sigmund, W.M.; Aldinger, F. [Univ. of Stuttgart (Germany). Inst. for Nonmetallic Inorganic Materials; Feike, M.; Spiess, H.W. [Max-Planck-Inst. for Polymer Research, Mainz (Germany)

1996-12-31

198

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

199

The Basics of NMR  

NSDL National Science Digital Library

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

Hornak, Joseph

2003-10-10

200

Water Adsorption on Pyrogenic Silica Followed by 1H MAS NMR  

PubMed

On the surface of two commercial pyrogenic silicas (Degussa and Cabot), five resonances were identified on the basis of the chemical shift, homonuclear coupling (T2), and spin-lattice relaxation behavior (T1). In accordance with previous studies we observed three different types of silanol groups: (i) weakly coupled (long T2), water inaccessible, isolated "internal" silanols at 1.8 ppm; (ii) weakly coupled, external "free" silanols revealed upon dehydration at 2.5 ppm; and (iii) strongly coupled external hydrogen bound silanols with an unresolved broad resonance between 3 and 7 ppm. The resonance of water, whose position between 2.6 and 4.6 ppm depended on water content, corresponded to two unresolved species of slightly different T1. By equating this resonance to the weighted average of two distinct populations of water, we were able to distinguish the first layer of strongly hydrogen bound water at 2.7 ppm from liquid-like water at 5 ppm. The first layer is complete for water relative humidity as low as 3.6% and corresponds to a surface coverage of 4.75 H2O/nm2. If we assumed a cristobalite-based surface structure, this meant a 1:1 ratio between surface hydroxyls and the first layer of physisorbed water. This ratio was the same for the two silicas regardless of surface area. Copyright 1997 Academic Press. Copyright 1997Academic Press PMID:9398426

d'espinose de la Caillerie JB; Aimeur; Kortobi; Legrand

1997-10-15

201

Coupling Amplification in 2D MAS NMR and Its Application to Torsion Angle Determination in Peptides  

Microsoft Academic Search

A technique for amplifying the apparent magnitudes of13C–1H and15N–1H dipolar interactions in magic-angle spinning experiments is described. By inserting rotor-synchronized 180° pulses in the evolution period of a 2D dipolar-chemical shift experiment, heteronuclear dipolar couplings are doubled or quadrupled relative to the spinning speed. The increased number of dipolar sidebands is desirable for retaining structural information in the indirectly detected

Mei Hong; John D. Gross; Chad M. Rienstra; Robert G. Griffin; Kristin K. Kumashiro; Klaus Schmidt-Rohr

1997-01-01

202

Multinuclear solid-state high-resolution and C-13 -{Al27} double-resonance magic-angle spinning NMR studies on aluminum alkoxides  

Microsoft Academic Search

A combination of Al-27 magic-angle spinning (MAS)\\/multiple quantum (MQ)-MAS, C-13-H-1 CPMAS, and C-13-{Al-27} transfer of population in double-resonance (TRAPDOR) nuclear magnetic resonance (NMR) were used for the structural elucidation of the aluminum alkoxides aluminum ethoxide, aluminum isopropoxide, and aluminum tertiarybutoxide. Aluminum alkoxides exist as oligomers with aluminum in different coordinations. High-resolution 27Al MAS NMR experiments with high-spinning speed distinguished the

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

2006-01-01

203

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

204

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

205

Proton Dynamics in Letovicite, (NH 4) 3H(SO 4) 2: A 1H and 14N NMR Spectroscopic Study  

Microsoft Academic Search

The improper ferroelastic phase letovicite (NH4)3H(SO4)2 has been studied by 1H MAS NMR as well as by static 14N NMR experiments in the temperature range of 296–425 K. The 1H MAS NMR resonance from ammonium protons can be well distinguished from that of acidic protons. A third resonance appears just below the phase transition temperature which is due to the

Michael Fechtelkord; Astrid Engelhardt; Josef-Christian Buhl; Lutz Schwalowsky; Ulrich Bismayer

2000-01-01

206

PERFORMANCE-LED HR Talent Management  

E-print Network

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

Meju, Max

207

HR: 07/01/08 CONFIDENTIALITY STATEMENT  

E-print Network

HR: 07/01/08 CONFIDENTIALITY STATEMENT RECRUITMENT / INTERVIEW / SELECTION PROCESS HUMAN RESOURCES of the Recruitment/Hiring Committee to read this admonition to the entire committee at the beginning of the process or begins any work. Failure to read this statement may result in cancellation of the recruitment. STATEMENT

Su, Xiao

208

About HR Compensation Employee Retirement and  

E-print Network

PPP-05 Pay Procedures PPP-06 Resignation and/or Termination PPP-07 Outside Employment & ExtraHOME About HR Compensation Employment Employee Retirement and Benefits Employee Relations Employee Development Job Descriptions Training Prospective Employees Employment Opportunities eJobs for Applicants e

Karsai, Istvan

209

MAS: learning support software platform for people with disabilities  

Microsoft Academic Search

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

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

2009-01-01

210

Aluminum binding to phosphatidylcholine lipid bilayer membranes: 27Al and 31P NMR spectroscopic studies  

Microsoft Academic Search

27Al and 31P nuclear magnetic resonance (NMR) spectroscopies were used to investigate aluminum interactions at pH 3.4 with model membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). A solution state 27Al NMR difference assay was developed to quantify aluminum binding to POPC multilamellar vesicles (MLVs). Corresponding one-dimensional (1D) fast magic angle spinning (MAS) 31P NMR spectra showed that aluminum induced the appearance of

Neil MacKinnon; Kevin J. Crowell; Andrew K. Udit; Peter M. Macdonald

2004-01-01

211

3QMAS of three aluminum polycations: space group consistency between NMR and XRD  

Microsoft Academic Search

Three aluminum polycations, Al13?-Keggin Johansson-type, Al13 Mögel-type and Al30 ?-Taulelle-type have been measured by 27Al solid state NMR, using MAS and 3QMAS spectroscopies. The number of inequivalent aluminum obtained by these high resolution NMR experiments leads to a comparison with their respective XRD results obtained on single crystal. In all three cases, the inequivalent sites measured by NMR and deduced

L. Allouche; C. Huguenard; F. Taulelle

2001-01-01

212

SedNMR: on the edge between solution and solid-state NMR.  

PubMed

Solid-state NMR (SS-NMR) of proteins requires that those molecules be immobilized, usually by crystallization, freezing, or lyophilization. However, self-crowding can also slow molecular rotation sufficiently to prevent the nuclear interactions from averaging. To achieve self-crowding, researchers can use a centrifugal field to create a concentration gradient or use regular ultracentrifugation to produce highly concentrated, gel-like solutions. Thus sedimented solute NMR (SedNMR) provides a simple method to prepare biological samples for SS-NMR experiments with minimal perturbation. This method may also give researchers a way to investigate species that are not otherwise accessible by NMR. We induce the sedimentation in one of two ways: (1) by the extreme centrifugal force exerted during magic angle spinning (MAS-induced sedimentation or in situ) or (2) by an ultracentrifuge (UC-induced sedimentation or ex situ). Sedimentation is particularly useful in situations where it is difficult to obtain protein crystals. Furthermore, because the proteins remain in a largely hydrated state, the sedimented samples may provide SS-NMR spectra that have better resolution than the spectra from frozen solutions or lyophilized powders. If sedimentation is induced in situ, the same protein sample can be used for both solution and SS-NMR studies. Finally, we show that in situ SedNMR can be used to detect the NMR signals of large molecular adducts that have binding constants that are too weak to allow for the selective isolation and crystallization of the complexed species. We can selectively induce sedimentation for the heaviest molecular species. Because the complexed molecules are subtracted from the bulk solution, the reaction proceeds further toward the formation of complexes. PMID:23470055

Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico

2013-09-17

213

P solid-state NMR studies of the dependence of inter-bilayer water dynamics on lipid headgroup structure and membrane peptides  

E-print Network

2D 1 H­31 P solid-state NMR studies of the dependence of inter-bilayer water dynamics on lipid moderate magic-angle spinning, making 1 H 1D and 2D MAS NMR the method of choice for investigating membrane group is not sufficiently strong to be detectable by NMR. Instead, water-31 P correlation peaks in 2D

Hong, Mei

214

A 31P-NMR study of borophosphate glasses  

Microsoft Academic Search

It is shown that 31P nuclear magnetic resonance (NMR) spectroscopy with magic angle spinning (MAS) discriminates among different types of PO4 units occurring in borophosphate glasses. The isotropic 31P chemical shift of the PO4 increases by nearly 70 ppm in going from the ``branching unit,'' neutral and covalently bonded, to the ``monomeric unit,'' which carries a -3 nominal charge. By

Marco Villa; Keith R. Carduner; Gaetano Chiodelli

1987-01-01

215

NMR studies of bond arrangements in alkali phosphate glasses  

SciTech Connect

Solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has become a powerful tool for the investigation of local structure and medium range order in glasses. Previous {sup 31}P MAS NMR studies have detailed the local structure for a series of phosphate glasses. Phosphate tetrahedra within the glass network are commonly described using the Q{sup n} notation, where n = 0, 1, 2, 3 and represents the number of bridging oxygens attached to the phosphate. Using {sup 31}P MAS NMR different phosphate environments are readily identified and quantified. In this paper, the authors present a brief description of recent one dimensional (1D) {sup 6}Li, {sup 7}Li and {sup 31}P MAS experiments along with two-dimensional (2D) {sup 31}P exchange NMR experiments for a series of lithium ultraphosphate glasses. From the 2D exchange experiments the connectivities between different Q{sup n} phosphate tetrahedra were directly measured, while the 1D experiments provided a measure of the P-O-P bond angle distribution and lithium coordination number as a function of Li{sub 2}O concentration.

Alam, T.M.; Brow, R.K.

1998-01-01

216

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

217

Name Rate Restrictions Alcatel DRIE $45/hr 2 Hour Min  

E-print Network

Name Rate Restrictions Alcatel DRIE $45/hr 2 Hour Min Brewer/Vac-HotPlate $10/use Use=2 hour CHA E-Beam Evaporator $30/hr 2 Hour min. Dicing Saw $30/hr 1 Hour min. Suss MA4-1 $25/hr 1 Hour min. Suss MA4-2 $25/hr 1 Hour min. PG $250/$350 per mask Solitec 1 Hotplate $10/use Use = 2 hour Solitec 2 Hotplate $10/use Use

Yoo, S. J. Ben

218

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

219

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

220

TCM 1231 (3 hr) Grade: HIST 2110 (3 hr) Grade: MATH 1112 -Trig Grade: POLS 1101 (3 hr) Grade: ENGL 1101 (3 hr) Grade: FYE 1220 (2 hr) Grade: Intro. to Constr. Mgnt. Sem.: The US: A Compr. Survey Sem.: Math Course (3 hr) Sem.: American Government Sem.: Com  

E-print Network

: ENGL 1101 (3 hr) Grade: FYE 1220 (2 hr) Grade: Intro. to Constr. Mgnt. Sem.: The US: A Compr. Survey Sem.: Math Course (3 hr) Sem.: American Government Sem.: Composition I Sem.: First Year Seminar Sem Graphics Sem.: Physics Course (3 hr) Sem.: Physics Lab I Sem.: Public Speaking Sem.: Composition II Sem

Hutcheon, James M.

221

48 CFR 538.271 - MAS contract awards.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

222

Resolution and Polarization Distribution in Cryogenic DNP/MAS Experiments  

E-print Network

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 ...

Barnes, Alexander

223

Scheduling on the MasPar SIMD parallel computer  

E-print Network

THE SCHEDULING ALGORITHMS A. Terminology B. Highest Level First Algorithm . C. Coffman/Graham Algorithm D. Clustering Algorithms III THE IVIASPAR. PARALLEL COMPUTER. A. MasPar Hardware B. MPL Programming Language C. Limitations IV PROGRAM DETAILS . A... THE SCHEDULING ALGORITHMS A. Terminology B. Highest Level First Algorithm . C. Coffman/Graham Algorithm D. Clustering Algorithms III THE IVIASPAR. PARALLEL COMPUTER. A. MasPar Hardware B. MPL Programming Language C. Limitations IV PROGRAM DETAILS . A...

Perkins, Keith Douglas

2012-06-07

224

Rapid proton-detected NMR assignment for proteins with fast magic angle spinning.  

PubMed

Using a set of six (1)H-detected triple-resonance NMR experiments, we establish a method for sequence-specific backbone resonance assignment of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of 5-30 kDa proteins. The approach relies on perdeuteration, amide (2)H/(1)H exchange, high magnetic fields, and high-spinning frequencies (?r/2? ? 60 kHz) and yields high-quality NMR data, enabling the use of automated analysis. The method is validated with five examples of proteins in different condensed states, including two microcrystalline proteins, a sedimented virus capsid, and two membrane-embedded systems. In comparison to contemporary (13)C/(15)N-based methods, this approach facilitates and accelerates the MAS NMR assignment process, shortening the spectral acquisition times and enabling the use of unsupervised state-of-the-art computational data analysis protocols originally developed for solution NMR. PMID:25102442

Barbet-Massin, Emeline; Pell, Andrew J; Retel, Joren S; Andreas, Loren B; Jaudzems, Kristaps; Franks, W Trent; Nieuwkoop, Andrew J; Hiller, Matthias; Higman, Victoria; Guerry, Paul; Bertarello, Andrea; Knight, Michael J; Felletti, Michele; Le Marchand, Tanguy; Kotelovica, Svetlana; Akopjana, Inara; Tars, Kaspars; Stoppini, Monica; Bellotti, Vittorio; Bolognesi, Martino; Ricagno, Stefano; Chou, James J; Griffin, Robert G; Oschkinat, Hartmut; Lesage, Anne; Emsley, Lyndon; Herrmann, Torsten; Pintacuda, Guido

2014-09-01

225

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

226

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

227

SuperWASP-N Extrasolar Planet Candidates Between 18hr < RA < 21hr  

Microsoft Academic Search

The SuperWASP-I instrument observed 6.7 million stars between 8-15 mag from\\u000aLa Palma during the 2004 May-September season. Our transit-hunting algorithm\\u000aselected 11,626 objects from the 184,442 stars within the range RA 18hr-21hr.\\u000aWe describe our thorough selection procedure whereby catalogue information is\\u000aexploited along with careful study of the SuperWASP data to filter out, as far\\u000aas possible, transit

D. J. Christian; W. I. Clarkson; A. Collier Cameron; B. Enoch; S. R. Kane; T. A. Lister; R. G. West; D. M. Wilson; A. Evans; A. Fitzsimmons; C. A. Haswell; C. Hellier; S. T. Hodgkin; K. Horne; J. Irwin; F. P. Keenan; A. J. Norton; J. Osborne; D. L. Pollacco; R. Ryans; I. Skillen; P. J. Wheatley; J. Barnes

2007-01-01

228

HR Excellence Action Plan Last updated:22nd May 2014  

E-print Network

through HR self-service Director of HR/Head of Organisational Development Researchers have an online space groups being created. 6.9 The current Harassment & Bullying Policy is being reviewed to be inclusive

Brierley, Andrew

229

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

230

Solid-state NMR spectroscopy of Pb-rich apatite.  

PubMed

Pb-containing hydroxylapatite phases synthesized under aqueous conditions were investigated by X-ray diffraction and solid-state nuclear magnetic resonance (NMR) techniques to determine the Pb, Ca distribution. 31P and 1H magic-angle spinning (MAS) NMR results indicate slight shifts of the isotropic chemical shift with increased Ca content and complex lineshapes at compositions with near equal amounts of Ca and Pb. 31P{207Pb} and 1H{207Pb} rotational-echo double resonance (REDOR) results for intermediate compositions show that resolved spectral features cannot be assigned simply in terms of local Ca, Pb configurations or coexisting phases. 207Pb MAS NMR spectra are easily obtained for these materials and contain well-resolved resonances for crystallographically unique A1 and A2 Pb sites. Splitting of the A1 and A2 207Pb resonances for pure hydroxyl-pyromorphite (Pb10(PO4)6(OH)2) compared to natural pyromorphite (Pb5(PO4)3Cl) suggests symmetry reduced from hexagonal. We find that 207Pb{1H} CP/MAS NMR is impractical in Pb-rich hydroxylapatites due to fast 207Pb relaxation. PMID:19821466

Mason, Harris E; Hirner, Joshua J; Xu, Wenqian; Parise, John B; Phillips, Brian L

2009-12-01

231

The value of HR in times of change  

Microsoft Academic Search

Purpose – This paper sets out to explore the value of HR in times of change, providing an overview of current organizational change issues and against this backdrop exploring perceptions and requirements of the HR function. It also seeks to look at the important role that HR can play in taking the lead in talent management activities that can help

Jo Hennessy; Claire McCartney

2008-01-01

232

Practical Considerations and Alternative Research Methods for Evaluating HR Programs  

Microsoft Academic Search

Program evaluation methods capitalizing on quasi-experimental designs are introduced as useful alternatives for evaluating human resources (HR) programs such as selection systems, training courses, performance measurement systems, and 360 degree feedback. A case study is presented to illustrate the benefits of program evaluation methods for evaluating HR programs. In addition, several post-hoc considerations that often moderate results from HR evaluations

Dale S. Rose; Karen E. Fiore

1999-01-01

233

HR managers and environmental sustainability: strategic leaders or passive observers?  

Microsoft Academic Search

In this paper, we explore the challenges posed to, and reactions of, human resource (HR) managers by the concept of environmental sustainability. From interviews with 14 New Zealand HR managers, we explore three related aspects of morality identified by Fineman: private, conventional, and enacted. Findings indicate that while the HR managers note a private position of environmental concern, they take

Candice Harris; Helen Tregidga

2011-01-01

234

HR managers and environmental sustainability: strategic leaders or passive observers?  

Microsoft Academic Search

In this paper, we explore the challenges posed to, and reactions of, human resource (HR) managers by the concept of environmental sustainability. From interviews with 14 New Zealand HR managers, we explore three related aspects of morality identified by Fineman: private, conventional, and enacted. Findings indicate that while the HR managers note a private position of environmental concern, they take

Candice Harris; Helen Tregidga

2012-01-01

235

28 October 2013 Page 1 of 5 HR191 HR191 JJOOBB DDEESSCCRRIIPPTTIIOONN  

E-print Network

POSTGRADUATE CONVENORS (HONOURS, MASTERS AND PHD PROGRAMMES) RESEARCH UNITS UNDERGRAD OFFICER (PC8) ADMINISTRATIVE ASSISTANT (To the Director) (PC 7) POSTGRAD OFFICER (PC 8 PG Administrator (PC7)UG Administrator (PC7) UG Administrator (PC7) Receptionist (PC5) #12;28 October 2013 Page 2 of 5 HR191 The main purpose

Jarrett, Thomas H.

236

Generalized biaxial shearing of MQMAS NMR spectra  

NASA Astrophysics Data System (ADS)

Two dimensional multiple quantum (MQ) MAS NMR experiments have become popular due to the wide applicability of this technique to structural questions in materials science, the abundance of half-integer spin nuclei in the periodic table, and the ease of implementation on typical solid state NMR instruments. In spite of the high-resolution theoretically possible from such experiments, the homogeneous and inhomogeneous broadening factors inherent in many samples of interest can make spectral analysis challenging. We present several possible spectral shearing schemes that may be useful for spectral analysis, and in particular we introduce shearing in the directly detected dimension. We suggest that for amorphous or disordered samples that give broad spectral features, shearing may be used as a general tool for optimal positioning of these features relative to one another and for the characterization of isotropic chemical and quadrupolar shifts.

Gehman, John D.; Provis, John L.

2009-09-01

237

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

238

MAS2-8 radar and digital control unit  

NASA Technical Reports Server (NTRS)

The design of the MAS 2-8 (2 to 8 GHz microwave-active spectrometer), a ground-based sensor system, is presented. A major modification in 1974 to the MAS 2-8, that of a control subsystem to automate the data-taking operation, is the prime focus. The digital control unit automatically changes all system parameters except FM rate and records the return signal on paper tape. The overall system operation and a detailed discussion of the design and operation of the digital control unit are presented.

Oberg, J. M.; Ulaby, F. T.

1974-01-01

239

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

E-print Network

1 Human Resources Consultancy (HR) in France: On the tendency of Web service innovating to e.David@loria.fr Abstract : The European market of management consultancy (MC) and human resources (HR) goes remarkably well and of promoting Management Consultancy profession in Europe. In the spheres of the professionals in HR

Paris-Sud XI, Université de

240

School of Mathematics and Statistics Module MAS302  

E-print Network

Outcomes 8 4. The Training Day 9 4.1 Overview 9 4.1.1 Education Today 9 4.1.2 Your Role in the School 9 4 for Trade and Industry, which enables young scientists and engineers to work in schools in a varietySchool of Mathematics and Statistics Module MAS302 Undergraduate Ambassadors Scheme 2013

Mitchener, Paul

241

QUEEN MARY, UNIVERSITY OF LONDON MAS 314 Design of Experiments  

E-print Network

. [19] A. PENFOLD STREET & D. J. STREET: Combinatorics of Experimental Design, Oxford University PressQUEEN MARY, UNIVERSITY OF LONDON MAS 314 Design of Experiments Reading List Spring 2007 [1] G. E. P. CLARKE & R. E. KEMPSON: Introduction to the Design and Analysis of Experiments, Arnold, London, 1997. [3

Bailey, R. A.

242

A Market-based MAS Framework for Microgrids  

Microsoft Academic Search

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

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

243

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. PMID:24903880

Rashid, Naeem; Ayyampalayam, Saravanaraj

2014-01-01

244

PReMAS: Simulator for resource management David P. Bunde  

E-print Network

leaves questions unanswered or creates work for the author, who may well have moved on to another project an entirely new simula- tor. While some differences between simulators arise from the different questions of simulation design. PReMAS has been developed to answer a series of research questions in High-Performance

Bunde, David

245

MAS and its related G protein-coupled receptors, Mrgprs.  

PubMed

The Mas-related G protein-coupled receptors (Mrgprs or Mas-related genes) comprise a subfamily of receptors named after the first discovered member, Mas. For most Mrgprs, pruriception seems to be the major function based on the following observations: 1) they are relatively promiscuous in their ligand specificity with best affinities for itch-inducing substances; 2) they are expressed in sensory neurons and mast cells in the skin, the main cellular components of pruriception; and 3) they appear in evolution first in tetrapods, which have arms and legs necessary for scratching to remove parasites or other noxious substances from the skin before they create harm. Because parasites coevolved with hosts, each species faced different parasitic challenges, which may explain another striking observation, the multiple independent duplication and expansion events of Mrgpr genes in different species as a consequence of parallel adaptive evolution. Their predominant expression in dorsal root ganglia anticipates additional functions of Mrgprs in nociception. Some Mrgprs have endogenous ligands, such as ?-alanine, alamandine, adenine, RF-amide peptides, or salusin-?. However, because the functions of these agonists are still elusive, the physiologic role of the respective Mrgprs needs to be clarified. The best studied Mrgpr is Mas itself. It was shown to be a receptor for angiotensin-1-7 and to exert mainly protective actions in cardiovascular and metabolic diseases. This review summarizes the current knowledge about Mrgprs, their evolution, their ligands, their possible physiologic functions, and their therapeutic potential. PMID:25244929

Bader, Michael; Alenina, Natalia; Andrade-Navarro, Miguel A; Santos, Robson A

2014-10-01

246

Does Transparency Lead to Pay Compression? Alexandre Mas*  

E-print Network

on employee compensation by race and sex, a proposed rule that would require companies to compare CEO payDoes Transparency Lead to Pay Compression? Alexandre Mas* Princeton University September 2014 in the public domain. This decline was largely accomplished through nominal pay cuts. The wage cuts were

Bou-Zeid, Elie

247

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

E-print Network

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

Aluas, Mihaela

248

The corona of HD 223460 (HR 9024)  

NASA Astrophysics Data System (ADS)

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

Gondoin, P.

2003-10-01

249

Solid state NMR — a powerful tool for the investigation of surface hydroxyl groups in zeolites and their interactions with adsorbed probe molecules  

NASA Astrophysics Data System (ADS)

Recent developments in the NMR spectroscopic investigation of surface hydroxyl groups in zeolites are reviewed in the present paper. The composition and porous structure of zeolites are briefly described. The structure and basic properties of surface hydroxyl groups (especially of bridging hydroxyl groups) in zeolites are explained. The influence of the magic angle spinning (MAS) technique on the 1H NMR spectrum of activated zeolites is described in detail. Different NMR spectroscopic methods which allow the measurement of the H?Al distance rH?Al between the protons and the 27Al nuclei in bridging hydroxyl groups are compared. The limitations of spectral resolution of the 1H MAS NMR spectra are discussed quantitatively on the basis of extended quantum chemical calculations. It is shown that the 1H NMR chemical shift ?H allows the measurement of the deprotonation energy of free surface hydroxyl groups in zeolites. The influence of electrostatic interactions upon ?H is discussed and a correlation between the 1H NMR chemical shift and the wavenumber of the stretching vibration of surface hydroxyl groups is stated. Further, 1H MAS NMR and IR spectroscopy are compared especially with respect to concentration measurements. Applications of low-temperature 1H MAS NMR spectroscopy to the investigation of the interaction between surface hydroxyl groups and adsorbed probe molecules are demonstrated. Finally, the present paper reviews recent NMR spectroscopic studies of probe molecules under the influence of bridging hydroxyl groups.

Brunner, Eike

1995-08-01

250

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

SciTech Connect

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

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

2013-06-01

251

Aluminium27 solid state NMR spectroscopic studies of chloride binding in Portland cement and blends  

Microsoft Academic Search

Alumina-rich pozzolanic and latent hydraulic binders such as pulverised fuel ash, metakaolin, and ground granulated blast furnace slag, together with silica fume, are frequently added to Portland cement concrete to improve performance and to retard chloride ingress and thereby inhibit chloride-induced corrosion of the carbon steel reinforcement. 27Al{1H} MAS and CP\\/MAS NMR spectroscopies have been used to follow both the

J. A. Chudek; G. Hunter; M. R. Jones; S. N. Scrimgeour; P. C. Hewlett; A. B. Kudryavtsev

2000-01-01

252

Quantitative determination of cephalexin in cephradine by NMR spectroscopy.  

PubMed

An NMR method to determine quantitatively the presence of cephalexin in cephradine was developed. The method is applicable to the chemical itself as well as to capsules and oral suspension formulations. The determination is based on the NMR signal arising from the five aromatic protons of the cephalexin molecule. Integration of this signal relative to a signal from cephradine provides the data necessary to determine the percentage of cephalexin present. The precision at the 2% cephalexin levels is +/- 0.18%. The time required to carry out a single analysis is about 10 min, and five analyses can be done in about 0.5 hr. PMID:702311

Warren, R J; Zarembo, J E; Staiger, D B; Post, A

1978-10-01

253

Nmr in drug discovery  

Microsoft Academic Search

NMR spectroscopy has evolved into an important technique in support of structure-based drug design. Here, we survey the principles that enable NMR to provide information on the nature of molecular interactions and, on this basis, we discuss current NMR-based strategies that can identify weak-binding compounds and aid their development into potent, drug-like inhibitors for use as lead compounds in drug

Maurizio Pellecchia; Daniel S. Sem; Kurt Wüthrich

2002-01-01

254

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

255

Exploring electrolyte organization in supercapacitor electrodes with solid-state NMR.  

PubMed

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 (13)C and (11)B 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 (13)C MAS-NMR spectroscopies), and the more disordered carbon shows a better capacitance and a better tolerance to high voltages. PMID:23416727

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

2013-04-01

256

Small NMR biomolecular sensors  

NASA Astrophysics Data System (ADS)

By combining the physics of nuclear magnetic resonance (NMR) and silicon radio-frequency (RF) integrated circuits, we recently created progressively smaller NMR systems, which we originally reported in Refs. [1-4]. Our strategy for NMR system miniaturization proved effective, culminating in the smallest prototype [3,4] that weighs 0.1 kg and can be held at the palm of the hand. These small, low-cost NMR systems can be useful as biomolecular sensors in the personalized medicine setting, and we demonstrated their ability to detect proteins, compounds, and human cancer cells. The present paper, which is not a new technical contribution, reviews these developments.

Sun, Nan; Liu, Yong; Qin, Ling; Lee, Hakho; Weissleder, Ralph; Ham, Donhee

2013-06-01

257

Aluminum binding to phosphatidylcholine lipid bilayer membranes: aluminum exchange lifetimes from 31P NMR spectroscopy  

Microsoft Academic Search

Two-dimensional (2D) 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) exchange spectroscopy (EXSY) demonstrated that aluminum binds to the phosphate group of phosphatidylcholine (PC) in multilamellar vesicles at pH 3.2, forming preferentially 2\\/1, in addition to 1\\/1 (PC\\/Al) complexes in slow exchange with one another, and with free PC, on the NMR timescale. Exchange rate constants between these three

Neil MacKinnon; Jay Ridgway; Kevin J. Crowell; Peter M. Macdonald

2006-01-01

258

An advanced NMR protocol for the structural characterization of aluminophosphate glasses  

Microsoft Academic Search

In this work a combination of complementary advanced solid-state nuclear magnetic resonance (NMR) strategies is employed to analyse the network organization in aluminophosphate glasses to an unprecedented level of detailed insight. The combined results from MAS, MQMAS and 31P-{27Al}-CP-heteronuclear correlation spectroscopy (HETCOR) NMR experiments allow for a detailed speciation of the different phosphate and aluminate species present in the glass.

Leo van Wüllen; Grégory Tricot; Sebastian Wegner

2007-01-01

259

User Guide for Faculty UBC Human Resources -HR Management Systems  

E-print Network

eRecruit User Guide for Faculty UBC Human Resources - HR Management Systems 2/1/2013 Please refer .........................................................................................................................................................................1 1 Accessing the Position Management/Recruitment Portal

Pulfrey, David L.

260

The structure of phosphate and borosilicate glasses and their structural evolution at high temperatures as studied with solid state NMR spectroscopy: Phase separation, crystallisation and dynamic species exchange  

NASA Astrophysics Data System (ADS)

In this contribution we present an in-depth study of the network structure of different phosphate based and borosilicate glasses and its evolution at high temperatures. Employing a range of advanced solid state NMR methodologies, complemented by the results of XPS, the structural motifs on short and intermediate length scales are identified. For the phosphate based glasses, at temperatures above the glass transition temperature Tg, structural relaxation processes and the devitrification of the glasses were monitored in situ employing MAS NMR spectroscopy and X-ray diffraction. Dynamic species exchange involving rapid P-O-P and P-O-Al bond breaking and reforming was observed employing in situ27Al and 31P MAS NMR spectroscopy and could be linked to viscous flow. For the borosilicate glasses, an atomic scale investigation of the phase separation processes was possible in a combined effort of ex situ NMR studies on glass samples with different thermal histories and in situ NMR studies using high temperature MAS NMR spectroscopy including 11B MAS, 29Si MAS and in situ29Si{ 11B} REAPDOR NMR spectroscopy.

Wegner, Sebastian; van Wüllen, Leo; Tricot, Gregory

2010-04-01

261

Solid State NMR Studies of the Aluminum Hydride Phases  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

262

NMR Spectroscopy - Theory  

NSDL National Science Digital Library

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

Lord, J. R.

2011-06-30

263

Lectures on pulsed NMR  

SciTech Connect

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

Pines, A.

1988-08-01

264

Lectures on pulsed NMR  

SciTech Connect

These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs.

Pines, A.

1986-09-01

265

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

NASA Astrophysics Data System (ADS)

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

Ruan, Qing-Xia; Zhou, Ping

2008-07-01

266

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.

2005-10-31

267

Silver and gold NMR.  

PubMed

Silver and gold, together with copper, form the transition metal group IB elements in the periodic table and possess very different nuclear magnetic resonance (NMR) spectroscopic properties. While there is only one gold isotope ((197)Au), which has a spin of 3/2 and therefore a quadrupole moment, silver occurs in two isotopic forms ((109)Ag and (109)Au), both of which have a spin 1/2 and similar NMR spectroscopic properties. The unfavorable properties of gold have prevented its NMR spectroscopic investigation thus far. On the other hand, there are several reports of silver NMR. However, the low sensitivity of silver, combined with its long relaxation times have rendered the direct detection of silver possible only with concentrations greater than a few tenth molar. Reviewed here are the general limitations of silver NMR and some techniques to partially overcome these limitations, as well as a summary of currently available chemical shift and scalar coupling data on (109)Ag. PMID:18475898

Zangger, K; Armitage, L M

1999-01-01

268

Customer value & construction of financial industries HR Management Model  

Microsoft Academic Search

Market competition among financial enterprises is becoming fierce day by day. The crux of the matte is to create more customer value. The traditional model of HR's value chain ignores the costumer value. There are the enormous defects. Customer value is the core link of service and management, the Keys for the sustainable development of financial industries. The HR Management

Meidong Qi; Yating Li

2010-01-01

269

STAFF LIST-HUMAN RESOURCES HR D36, Richmond Fax  

E-print Network

Human Resources STAFF LIST- HUMAN RESOURCES HR D36, Richmond Fax 5220 NAME TITLE Room EMAIL EXT Mrs Wilcock HR Administrator D36 a.wilcock1@bradford.ac.uk 3095 Miss Alexa Copley Recruitment Co-ordinator D36 a.copley@bradford.ac.uk 6016 Ms Nikki Hard Recruitment Administrator D36 n.hard@bradford.ac.uk 3071

Zharkova, Valentina V.

270

Phosphorus NMR of isolated perfused morris hepatomas  

SciTech Connect

The authors are developing techniques for the study of perfused solid tumors by NMR. Tissue-isolated solid hepatomas were grown to 1-2 cm diameter as described previously. The arterial supply was isolated and the tumors perfused (0.5 - 1.0 ml/min) in vitro at 25 C with a 15% suspension of red blood cells in Krebs-Henseliet solution. /sup 31/P-NMR spectra were acquired at 162 MHz in a specially-designed NMR probe using a solenoidal coil. Intracellular pH (monitored from the chemical shift of inorganic phosphate) and ATP levels were stable for up to 6 hrs during perfusion. During 30 min of global ischemia, ATP decreased by 75% and pH fell from 7.0 to 6.7. These changes were reversed by 1 hr reperfusion. In addition to ATP and phosphate, the spectra included a large resonance due to phosphomonoesters, as well as peaks consistent with glycerylphosphocholine, glyceryl-phosphoethanolamine, phosphocreatine, NAD, and UDPG. However, the most novel feature of the spectra was the presence of an unidentified peak in the phosphonate region (+ 16.9 ppm). The peak was not present in spectra of muscle, liver, brain, kidney, or fat tissues excised from the same animals. They are presently attempting to identify the compound that gives rise to this peak and to establish its metabolic origin.

Graham, R.A.; Meyer, R.A.; Brown, T.R.; Sauer, L.A.

1986-03-05

271

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

PubMed

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

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

2014-11-01

272

NMR at the Picomole Level of a DNA Adduct  

PubMed Central

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

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

2014-01-01

273

133Cs NMR study of cesium on the surfaces of kaolinite and illite  

Microsoft Academic Search

133Cs MAS NMR of Cs-exchanged illite, kaolinite, boehmite, and silica gel is shown to be a powerful tool to investigate the adsorption sites and atomic dynamics of Cs on mineral surfaces. Cesium is adsorbed on these mineral surfaces in primarily two ways: at sites relatively tightly bonded to the surface (Stern layer, Cs1) and at more loosely bonded sites in

Yeongkyoo Kim; R. James Kirkpatrick; Randall T. Cygan

1996-01-01

274

133 Cs NMR study of cesium on the surfaces of kaolinite and illite  

Microsoft Academic Search

133 Cs MAS NMR of Cs-exchanged illite, kaolinite, boehmite, and silica gel is shown to be a powerful tool to investigate the adsorption sites and atomic dynamics of Cs on mineral surfaces. Cesium is adsorbed on these mineral surfaces in primarily two ways: at sites relatively tightly bonded to the surface (Stern layer, Cs1) and at more loosely bonded sites

Yeongkyoo Kim; R. James Kirkpatrick; Randall T. Cygan

1996-01-01

275

THE JOURNAL OF CHEMICAL PHYSICS 138, 174203 (2013) Sideband separation experiments in NMR with phase incremented  

E-print Network

the conditions in which the latter can be minimized or removed entirely. © 2013 AIP Publishing LLC. [http-state Magic-Angle Spinning (MAS) NMR spectra of spin 1/2 nuclei the rotor-modulated fre- quency contribution of the sample within the rotor.3­5 Since the seminal work of Dixon,6 various methods for separating

Baltisberger, Jay H.

276

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

277

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

278

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

279

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

280

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. PMID:18026570

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

2008-01-01

281

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

E-print Network

MEMORANDUM TO: HR and Business Contacts FROM: Division of Human Resources DATE: August 23, 2013 Department of Treasury. There is no fee or cost for assistance from SC HELP. Please visit the SC HELP website

Almor, Amit

282

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

E-print Network

The human resources (HR) function has evolved significantly over the past several decades. It has grown in maturity and influence while simultaneously enduring great criticism from employees and managers. Meanwhile, ...

Eckman, Jeffrey M

2006-01-01

283

APO HR Specialists Assignments APO Duties Primary Backup  

E-print Network

APO HR Specialists Assignments APO Duties Primary Backup 2/9ths Policy (Faculty working in summer Reimbursement Anna Golackson Angie Rosas Website Questions/Problems Margy May APO Contacts Emuye Asfaw easfaw

Van Veen, Barry D.

284

Communications J,Org. Chem., Vol.40, No. 14, 1975 2141 for 7 hr led quantitatively to a mixture of the pseudo-acid  

E-print Network

Communications J,Org. Chem., Vol.40, No. 14, 1975 2141 for 7 hr led quantitatively to a mixture pure camptothe- cin 20-methoxycarbonyl derivative (12a) was obtained: uv (20% MeOH in CHCl3) 258 nm (eOH in CHC13),1 mp 276-278' The NMR, ir, uv, TLC, MS, and mixture melting point all confirmed the identity

Keinan, Ehud

285

Theorizing the links between e-HR and strategic HRM: a model, case illustration and reflections  

Microsoft Academic Search

In this paper we develop a model of e-human resources (e-HR) focusing on the relationship between HR strategy, e-HR goals and architectures, and positive and negative e-HR outcomes. This relationship is moderated by a number of key factors, including the organization and resources of the HR function, the absorptive capacity of HR, the skills and preferred styles of HR professionals,

Graeme Martin; Martin Reddington

2010-01-01

286

Probing Structure and Dynamics of Protein Assemblies by Magic Angle Spinning NMR Spectroscopy  

PubMed Central

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

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

2013-01-01

287

Study on Lignin–Glyoxal Reaction by MALDI-TOF and CP-MAS C-NMR  

Microsoft Academic Search

Matrix-Assisted Laser Desorption\\/Ionization Time-of-Flight (MALDI-TOF) mass spectrometry was used to elucidate lignin–glyoxal reactions. The reaction of glyoxal with a low molecular weight lignin involves a number of different reactions; in particular lignin depolymerization and recombination through condensation reactions with glyoxal to form glyoxalene bridges linking both lignin units and mainly fractions of lignin units derived from degradation during depolymerization. The

P. Navarrete; A. Pizzi; H. Pasch; L. Delmotte

2012-01-01

288

Thermal evolution of the Cl(-)-LiAl(2) layered double hydroxide: a multinuclear MAS NMR and XRD perspective.  

PubMed

Layered double hydroxides (LDHs) with a cation composition of LiAl(2) have a wide range of potential applications as catalysts, catalyst supports, and precursors for refractory oxide materials, including several industrially important lithium aluminate phases. The understanding of the calcination behavior of this group of LDH phases is essential to advancing these applications, and the research described here focuses on the thermal decomposition and structural evolution of LiAl(2)(OH)(6)Cl.nH(2)O in the temperature range of 20-1100 degrees C. (27)Al, (35)Cl, and (6,7)Li magic angle spinning nuclear magnetic resonance spectroscopy, powder X-ray diffraction, thermal analysis (including thermogravimetric and differential scanning calorimetry), and compositional analysis provide a highly consistent picture of the thermally induced phase formation and transformations of this LDH. The loss of the surface and interlayer water can begin as low as room temperature, depending on the relative humidity. Beginning at about 300 degrees C, the simultaneous volatilization of H(2)O and HCl and the exsolution of crystalline LiCl result in the formation of amorphous Li-Al-O-OH. By at least 500 degrees C, volumes with the structures of alpha-LiAlO(2) and LiAl(5)O(8) appear, and these phases become progressively more ordered with increasing temperature. LiCl begins to volatilize by 850 degrees C and is present only in trace amounts above ca. 1000 degrees C. alpha-LiAlO(2) converts to gamma-LiAlO(2) between 970 and 1100 degrees C. Because of the delithiation due to LiCl volatilization, the final products are dominated by LiAl(5)O(8), in contrast to the calcination products of previously studied LiAl(2) LDHs which are dominated by LiAlO(2). PMID:11720493

Hou, X; Kirkpatrick, R J

2001-12-01

289

Dynamic Effects in MAS and MQMAS NMR Spectra of Half-Integer Quadrupolar Nuclei: Calculations and an  

E-print Network

and an Application to the Double Perovskite Cryolite Mrignayani Kotecha, Santanu Chaudhuri, Clare P. Grey, and Lucio in the double perovskite cryolite, Na3AlF6. Dynamic line shape simulations invoking a second-order broadening with predictions stemming from molecular dynamic simulations on this double perovskite. 1. Introduction Solid state

Frydman, Lucio

290

FTIR and 27 Al MAS NMR analysis of the effect of framework Al-and Si-defects  

E-print Network

a,1 a J. Heyrovsky´ Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ hydrocarbon mixtures rich in the gasoline fraction (MTG) or low chain olefins (MTO) [3,4]. As feedstock

Sklenak, Stepan

291

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

NASA Astrophysics Data System (ADS)

We present new non-rotor-synchronized variants of the recently introduced refocused continuous wave (rCW) heteronuclear decoupling method significantly improving the performance relative to the original rotor-synchronized variants. Under non-rotor-synchronized conditions the rCW decoupling sequences provide more efficient decoupling, are easier to setup, and prove more robust towards experimental parameters such as radio frequency (rf) field amplitude and spinning frequency. This is demonstrated through numerical simulations substantiated with experimental results under different sample spinning and rf field amplitude conditions for powder samples of U-13C-glycine and U-13C-L-histidine·HCl·H2O.

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

2014-09-01

292

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

293

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

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

Miknis, F.P.

1992-04-01

294

Solid-state NMR characterization of Mowry Formation shales  

SciTech Connect

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

Miknis, F.P.

1992-04-01

295

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

PubMed

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

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

2006-01-01

296

Distributed Cooperation Solution Method of Complex System Based on MAS  

NASA Astrophysics Data System (ADS)

To adapt the model in reconfiguring fault diagnosing to dynamic environment and the needs of solving the tasks of complex system fully, the paper introduced multi-Agent and related technology to the complicated fault diagnosis, an integrated intelligent control system is studied in this paper. Based on the thought of the structure of diagnostic decision and hierarchy in modeling, based on multi-layer decomposition strategy of diagnosis task, a multi-agent synchronous diagnosis federation integrated different knowledge expression modes and inference mechanisms are presented, the functions of management agent, diagnosis agent and decision agent are analyzed, the organization and evolution of agents in the system are proposed, and the corresponding conflict resolution algorithm in given, Layered structure of abstract agent with public attributes is build. System architecture is realized based on MAS distributed layered blackboard. The real world application shows that the proposed control structure successfully solves the fault diagnose problem of the complex plant, and the special advantage in the distributed domain.

Weijin, Jiang; Yuhui, Xu

297

Advanced NMR Studies of Fluoropolymers.  

E-print Network

??The advanced NMR studies of fluoropolymers are focused on the Krytox® poly-(hexafluoropropylene oxide) (PHFPO) and poly(1-chloro-1-fluoroethylene) (PCFE). 2D NMR techniques were used to study the… (more)

Li, Xiaohong

2011-01-01

298

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

299

NMR planar microcoil for microanalysis  

Microsoft Academic Search

This article deals with the analysis of small sample volume by using a planar microcoil and a micromachined cavity. This microcoil is used as a nuclear magnetic resonance (NMR) radio frequency detection coil in order to perform in vitro NMR analysis of the sample introduced into the microcavity. It is a real challenging task to develop microsystem for NMR spectrum

B. Sorli; J. F. Chateaux; L. Quiquerez; L. Bouchet-Fakri; A. Briguet; P. Morin

2006-01-01

300

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

301

Phosphorous NMR in biology  

SciTech Connect

This book reviews the technique of phosphorous NMR and its relationship to every existing level of biology and biochemistry. The bulk of the book is broken into three sections: simple biomolecules; macromolecules/macromolecular assemblages; and complex systems necessary to maintain life. Topics include: relaxation time of inorganic phosphate, behavior of ATP with biological molecules and characterization of t-RNA.

Burt, C.T.

1987-01-01

302

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

303

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

304

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

NASA Astrophysics Data System (ADS)

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

Johnson, Robert L.; Schmidt-Rohr, Klaus

2014-02-01

305

Multiple wavelength microwave observations of the RS Canum Venaticorum stars UX Arietis, HR 1099, HR 5110, and II Pegasi  

NASA Technical Reports Server (NTRS)

The variabilities, core size and magnetic field of the RS CVn star UX Arietis was measured with the VLA at pairs of frequencies near 1415 MHz and 4835 MHz on June 10, 1985. Data were also gathered on HR 1099, HR 5110 and II Peg. UX Arietis exhibited variability on time scales ranging from 30 sec to 1 hr at 4835 MHz, but no detectable variations at 1415 MHz. An upper limit of 900 billion cm was placed on the size of the core emitting region, which is estimated to have a magnetic field strength of 15 G. The 30 sec variations are attributed to absorption by thermal plasma between the G5 and K1 companions of the UX Arietis system.

Willson, Robert F.; Lang, Kenneth R.

1987-01-01

306

The Description Logic ALCN HR+ Extended with Concrete Domains  

E-print Network

The Description Logic ALCN HR+ Extended with Concrete Domains: A Practically Motivated Approach, role hierarchies, transitively closed roles, generalized concept inclusions, and concrete domains. As in other languages based on concrete domains (e.g. ALC(D)) a so-called ex- istential predicate restriction

Moeller, Ralf

307

HR Staffing and Recruitment 6054 S Drexel Ave  

E-print Network

above): PreRecruitment Y N The department/unit prepared or updated the job description soHR Staffing and Recruitment 6054 S Drexel Ave Chicago, Illinois 60637 RECRUITMENT AND SELECTION that the requisition accurately reflects the position's current job duties, qualifications, working conditions

He, Chuan

308

Clinical Imaging of Bone Microarchitecture with HR-pQCT  

PubMed Central

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

Nishiyama, Kyle K.; Shane, Elizabeth

2014-01-01

309

Intragastrically administered tryptophan blocks gluconeogenesis in 48-hr starved rats  

Microsoft Academic Search

Tryptophan (TRP) has been reported to block the conversion of pyruvate (PYR) to phosphoenolpyruvate (PEP). The purpose of the present experiment was to determine the time course of the changes in phosphoenolpyruvate carboxykinase (PEPCK) activity and PEP production in response to intragastric intubation of 750 mg\\/kg BW TRP in 48-hr starved rats. Controls were intubated with a comparable volume of

Ali Moshirfar; Kalatu Kamara; Thomas W. Castonguay

1996-01-01

310

HR EMPLOYMENT LAW UPDATES WHAT ARE FIT NOTES?  

E-print Network

remains `not fit for work'. What this means to you, getting advice and support On receipt of a `fit noteHR EMPLOYMENT LAW UPDATES WHAT ARE FIT NOTES? Fit note is the informal name for the new Statement of Fitness for Work. The fit note replaced the sick note (medical statement or doctor's note) on 6 April 2010

Sussex, University of

311

TO: HR and Business Contacts FROM: Ro Kelly  

E-print Network

MEMORANDUM TO: HR and Business Contacts FROM: Ro Kelly Benefits Manager DATE: September 10, 2013 a health risk appraisal, lipid profile, chemistry profile, hemogram, blood pressure check, and height and weight check. Employees may register online for the Preventive Workplace Screening at www

Almor, Amit

312

Learning Culture, Line Manager and HR Professional Practice  

ERIC Educational Resources Information Center

Purpose: This paper aims to focus on the role of line management and learning culture in the development of professional practice for the human resource (HR) practitioner. Design/methodology/approach: Three-year longitudinal, matched-pair study involving five participants and their line managers. Findings: Two of the five participants experienced…

Harrison, Patricia

2011-01-01

313

HR ANNUAL REPORT April 1, 2012 March 31, 2013  

E-print Network

GHt place at tHe riGHt tiMe 20 DevelopinG our people 24 fosterinG a HealtHy workplace 28 enablinG Decision in effective HR management, allows us to contribute to the overall success of the university and make Memorial, fairness and communication. The leadership team of DHR was supportive of recommendations and initiated

Curnoe, S. H.

314

The California State University HR 200812 ATTACHMENT A  

E-print Network

employment decisions on valid job requirements. 1 See 41 CFR 60300 and 41 CFR 61300. 2 61 FR 1209The California State University HR 200812 ATTACHMENT A VETERAN SELF-IDENTIFICATION FORM (for use subject to the Vietnam Era Veterans Readjustment Assistance Act of 1974 (VEVRAA), as amended, which

Eirinaki, Magdalini

315

MARCH/APRIL 2011 www.tufts.edu/hr/index  

E-print Network

DEPARTMENT OF HUMAN RESOURCES MARCH/APRIL 2011 www.tufts.edu/hr/index periscopeperiscope Continued on next page Inside TUFTS NOw 2 ACTION PLANNING COMMITTEES UPDATE 3 INvESTMENT PLANNING wORkSHOPS 3 w the universi- ty's new official website for news and infor- mation, Tufts Now. The site merges Tufts' two major

Dennett, Daniel

316

OCTOBER 2011 www.tufts.edu/hr/index  

E-print Network

DEPARTMENT OF HUMAN RESOURCES SEPTEMBER/ OCTOBER 2011 www.tufts.edu/hr/index periscopeperiscope Continued on next page What about Tufts sparked your interest most as you considered the possibility of assuming the presidency? What got me really excited about becoming the President of Tufts was its strong

Dennett, Daniel

317

MAY/JUNE 2011 www.tufts.edu/hr/index  

E-print Network

DEPARTMENT OF HUMAN RESOURCES MAY/JUNE 2011 www.tufts.edu/hr/index periscopeperiscope Continued electronic technol- ogy (see the March-April Periscope for an article on the new Tufts web- site to bring the Tufts' com- munity closer together. In the recent Excellence at Work surveys conducted in each

Dennett, Daniel

318

NMR in rotating magnetic fields: Magic angle field spinning  

SciTech Connect

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

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

2004-09-10

319

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

PubMed

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

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

2010-09-28

320

Magic-Angle-Spinning NMR of the Drug Resistant S31N M2 Proton Transporter from Influenza A  

E-print Network

We report chemical shift assignments of the drug-resistant S31N mutant of M2[subscript 18–60] determined using 3D magic-angle-spinning (MAS) NMR spectra acquired with a [superscript 15]N–[superscript 13]C ZF-TEDOR transfer ...

Chou, James J.

321

Towards a better description of gallo-phosphate materials in solid state NMR: 1D and 2D correlation studies  

E-print Network

1 Towards a better description of gallo-phosphate materials in solid state NMR: 1D and 2D heteronuclear 31 P-71 Ga correlation using a MAS HMQC experiment in gallo-phosphate materials. The experiment experiment, gallo-phosphates. 1. Introduction Molecular sieves based on metal phosphates have been subject

Boyer, Edmond

322

Solid State Separated-Local-Field NMR Spectroscopy on Half-Integer Quadrupolar Nuclei: Principles and Applications  

E-print Network

and dynamics of a variety of boron-containing samples. These experimental SLF schemes were also extended to 3D NMR experiments that incorporate multiple-quantum MAS, thus enabling the resolution needed to studyHz) and use rotor-synchronized constant-time pulse sequences to achieve nearly arbitrary amplifications

Frydman, Lucio

323

EMSL Research and Capability Development Proposals High Temperature, Large Sample Volume, Constant Flow Magic Angle Spinning NMR Probe for a  

E-print Network

of reactants and removal of products does not interfere with the mechanics required for the discrete sample. Nitrogen carrier gas loaded with reactants was constantly injected into the bottom of a MAS NMR rotor through an axially placed hole in the rotor cap, which leads into sample volume. The sample is formed

324

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

325

II Seminario Informal (mas Formal) Sem^antica do PVS: Tipos Dependentes e Aplicac~oes  

E-print Network

II Semin´ario Informal (mas Formal) Sem^antica do PVS: Tipos Dependentes e Aplica¸c~oes Andr´e Luiz Outubro de 2004 Andr´e Luiz Galdino Universidade de Bras´ilia #12;II Semin´ario Informal (mas Formal) Sem´ilia #12;II Semin´ario Informal (mas Formal) Sem^antica do PVS: Tipos Dependentes e Aplica¸c~oes O que ´e

Ayala-Rincón, Mauricio

326

COMPOZER-based longitudinal cross-polarization via dipolar coupling under MAS  

NASA Astrophysics Data System (ADS)

We propose a cross polarization (CP) sequence effective under magic-angle spinning (MAS) which is tolerant to RF field inhomogeneity and Hartmann-Hahn mismatch. Its key feature is that spin locking is not used, as CP occurs among the longitudinal (Z) magnetizations modulated by the combination of two pulses with the opposite phases. We show that, by changing the phases of the pulse pairs synchronized with MAS, the flip-flop term of the dipolar interaction is restored under MAS.

Kamihara, Takayuki; Murakami, Miwa; Noda, Yasuto; Takeda, Kazuyuki; Takegoshi, K.

2014-08-01

327

?- NMR of Palladium foil  

NASA Astrophysics Data System (ADS)

Beta-detected NMR ( ?- NMR) of low-energy implanted 8Li + was studied in metallic palladium. The resonance was found to have a large negative shift with respect to the reference signal in the cubic insulator MgO. This shift exhibited significant temperature dependence on cooling below room temperature, approximately proportionate to the temperature-dependent spin susceptibility of pure Pd. Thus it is tentatively attributed to a Knight shift ( K) caused by a large negative hyperfine coupling; a phenomenon common in transition metal ions, but not in alkalis. However, the spin-lattice relaxation of 8Li is much slower than expected from the Korringa law for such a large K. We compare results from samples of very different thicknesses: 12.5 ?m foil and a 100 nm thin film.

Parolin, T. J.; Salman, Z.; Chakhalian, J.; Wang, D.; Keeler, T. A.; Hossain, Md.; Kiefl, R. F.; Chow, K. H.; Morris, G. D.; Miller, R. I.; MacFarlane, W. A.

2006-03-01

328

NMR Studies of Peroxidases.  

NASA Astrophysics Data System (ADS)

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

Veitch, Nigel Charles

329

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

PubMed

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

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

2005-01-01

330

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

PubMed Central

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

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

2013-01-01

331

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

Microsoft Academic Search

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

Andrea Ordanini; Giacomo Silvestri

2008-01-01

332

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

Microsoft Academic Search

BACKGROUND: The transcriptional cofactor, Hairless (HR), acts as one of the key regulators of hair follicle cycling; the loss of function mutations is the cause of the expression of the hairless phenotype in humans and mice. Recently, we reported a new Hr mutant mouse called 'Hairpoor' (HrHp). These mutants harbor a gain of the function mutation, T403A, in the Hr

Bong-Kyu Kim; In-Cheol Baek; Hwa-Young Lee; Jeong-Ki Kim; Hae-Hiang Song; Sungjoo K Yoon

2010-01-01

333

51V NMR Studies of Crystalline Monovalent and Divalent Metal Metavanadates  

Microsoft Academic Search

51V static and magic-angle spinning (MAS) NMR spectra of crystalline monovalent metal metavanadates LiVO3, alpha- and betaNaVO3, KVO3, CsVO3, beta-AgVO3, and NH4VO3 and divalent metal metavanadates M(VO3)2 (M = Mg, Ca, Sr, Ba, Zn, Pb) have been measured in order to establish the relationships between the various NMR parameters, such as isotropic chemical shift, deltaiso, chemical shift anisotropy, Deltadelta, the

Satoshi Hayakawa; Toshinobu Yoko; Sumio Sakka

1994-01-01

334

Adsorption-desorption induced structural changes of Cu-MOF evidenced by solid state NMR and EPR spectroscopy.  

PubMed

Adsorption-desorption induced structural changes of Cu(bpy)(H(2)O)(2)(BF(4)),(bpy) (bpy = 4,4'-bipyridine) [Cu-MOF] have been evidenced by combined NMR and EPR spectroscopy. Upon adsorption of probe molecules even at a few mbar, EPR spectra show that they are activated to form complexes at Cu(II) sites, which results in a change of the Cu-MOF's structure as indicated by a high-field shift of the (11)B MAS NMR. After desorption, both EPR and (11)B MAS NMR spectra evidenced that the structure of the Cu-MOF reversibly shifted to the original state. This observation indicates that MOFs can undergo structural changes during processes where adsorption-desorption steps are involved such as gas storage, separation, and catalysis. PMID:19159296

Jiang, Yijiao; Huang, Jun; Kasumaj, Besnik; Jeschke, Gunnar; Hunger, Michael; Mallat, Tamas; Baiker, Alfons

2009-02-18

335

class rooms H.R. Bright Building 1st  

E-print Network

309C Dr. Sarin 169164 311B 311A Dr. Song 129 Dr. D. Song 156 311C 118 311D 122 309D 118 309A Lounge Custodial Closets H.R. Bright Building ­ 3rd Floor 281 127 315D (Chen) 132 315A (Sarin) (Choe) (Ioerger) Dr. Shell (Kim) (Sarin)(DrSong) Dr. A. Jiang (Dr Chen) (Dr Chen) Kimberly Mallett Admin. Student

336

Forming the Dusty Ring in HR 4796A  

E-print Network

We describe planetesimal accretion calculations for the dusty ring observed in the nearby A0 star HR 4796A. Models with initial masses of 10-20 times the minimum mass solar nebula produce a ring of width 7-15 AU and height 0.3-0.6 AU at 70 AU in roughly 10 Myr. The ring has a radial optical depth of 1. These results agree with limits derived from infrared images and from the excess infrared luminosity.

Scott J. Kenyon; Kenneth Wood; Barbara A. Whitney; Michael J. Wolff

1999-08-11

337

Are Giant Planets Forming around HR 4796A?  

Microsoft Academic Search

We have obtained Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope STIS spectra of HR 4796A, a nearby 8 Myr old main-sequence star that possesses a dusty circumstellar disk whose inclination has been constrained from high-resolution near-infrared observations to be ~17° from edge-on. We searched for circumstellar absorption in the ground states of C II lambda1036.3, O I lambda1039.2, Zn

C. H. Chen; I. Kamp

2004-01-01

338

Is the HR8799 extrasolar system destined for planetary scattering?  

Microsoft Academic Search

The recent discovery of a three-planet extrasolar system of HR8799 by Marois et al. is a breakthrough in the field of the direct imaging. This great achievement raises questions on the formation and dynamical stability of the system, because Keplerian fits to astrometric data disrupt during ~0.2Myr. We search for stable, self-consistent N-body orbits with the so-called GAMP (genetic algorithm

Krzysztof Gozdziewski; Cezary Migaszewski

2009-01-01

339

The conscientious HR manager and the Rubik's Cube  

Microsoft Academic Search

Purpose – By examining the literature on the ethical dilemmas of H\\/RM practitioners, the paper aims to put an “H” in H\\/RM. Design\\/methodology\\/approach – Analysing the significant contribution which H\\/RM scholars have made in studying the ethical dilemmas of H\\/RM practitioners, the paper builds a view of an H\\/RM practitioner as a “conscientious HR manager” loosely connected to an ethical

Ian Steers

2009-01-01

340

class rooms H.R. Bright Building 1st  

E-print Network

Cao Cheng Cao Yixin Choi Jinho Chung Jiryang Creel James Crosby Ralph Duncan Brittany Fan Jia-hao Guo Elena Rodriguez #12;115 129 423D 423C 115 115 423B 423A (Welch) 115 115 419D 419C H.R. Bright Building Closets 127 416 415 Dr. Welch 127 Dr. Amato 141 143 414C 414B Dr. Hammond David Ramirez 117 120 414A 414D

341

The dynamical structure of the HR8799 inner debris disk  

NASA Astrophysics Data System (ADS)

The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar System where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanet dynamics and debris disc-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disc remains unknown, leaving a question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using University of New South Wales's Katana supercomputing facility to follow the dynamical evolution of a model inner disc comprising 250,000 particles for a period of 100 million years. These simulations will (1) characterise the extent and structure of the inner disk in detail and (2) provide the first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet(s) in the inner system.

Wittenmyer, Robert A.; Contro de Godoy, Bruna; Horner, Jonathan; Marshall, Jonathan P.

2014-11-01

342

New constraints on the dust surrounding HR 4796 A  

E-print Network

HR 4796 A is surrounded by a well-structured and very bright circumstellar disc shaped as an annulus with many interesting features: very sharp inner and outer edges, brightness asymmetries, center offset and suspected distortions in the ring. We aim to constrain the properties of the dust surrounding the star HR 4796A, in particular the grain size and composition. We also want to confirm and refine the morphological parameters derived from previous scattered light observations, and reveal the dust spatial extent in regions unexplored so far due to their proximity to the star. We have obtained new images in polarized light of the binary system HR\\ 4796A and B in the Ks and Lp band with the NaCo instrument at the Very Large Telescope (VLT). In addition, we revisit two archival data obtained in the Lp band with that same instrument and at 2.2 microns with the NICMOS instrument on the Hubble Space Telescope. We complement these observations with simulations using the radiative transfer code MCFOST to investigate...

Milli, Julien; Pinte, Christophe; Mouillet, Anne-marie Lagrangem David; Girard, Julien H; Augereau, Jean-Charles; de Boer, Jozua; Pueyo, Laurent; Choquet, Elodie

2014-01-01

343

A nitrogen NMR and X-ray investigation of some mesoionic 1,3-diazoles, 1,3-oxazoles and 1,3-thiazoles  

NASA Astrophysics Data System (ADS)

14N, 15N and 17O NMR and data are reported for some mesoionic 1,3-diazoles, 1,3-oxazoles and 1,3-thiadiazoles. Additionally, 15N CP/MAS NMR data are also given for five mesoionic 1,3-diazoles. The relation between compound structures and NMR parameters has been discussed. 15N chemical shift values for diazoles, taken from CP/MAS NMR measurements, are very similar to the values observed for compounds in the solution. These imply the structure similarity of compounds in both phases, and allow excluding the chain-ring equilibrium in the solution. The cyclic, 'mesoionic' structure of 1,3-diazole have been confirmed by X-ray diffraction study.

Ja?wi?ski, J.; Kamie?ski, B.; Staszewska-Krajewska, O.; Webb, G. A.

2003-02-01

344

Proton dynamics in letovicite, (NH4)3H(SO4)2: a 1H and 14N NMR spectroscopic study.  

PubMed

The improper ferroelastic phase letovicite (NH4)3H(SO4)2 has been studied by 1H MAS NMR as well as by static 14N NMR experiments in the temperature range of 296-425 K. The 1H MAS NMR resonance from ammonium protons can be well distinguished from that of acidic protons. A third resonance appears just below the phase transition temperature which is due to the acidic protons in the paraelastic phase. The lowering of the second moment M2 for the ammonium protons takes place in the same temperature range as the formation of domain boundaries, while the signals of the acidic protons suffer a line narrowing in the area of Tc. The static 14N NMR spectra confirm the temperature of the motional changes of the ammonium tetrahedra. Two-dimensional 1H NOESY spectra indicate a chemical exchange between ammonium protons and the acidic protons of the paraphase. PMID:11235029

Fechtelkord, M; Engelhardt, A; Buhl, J C; Schwalowsky, L; Bismayer, U

2000-01-01

345

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

346

48 CFR 538.270 - Evaluation of multiple award schedule (MAS) offers.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Evaluation of multiple award schedule (MAS) offers...Federal Supply Schedules 538.270 Evaluation of multiple award schedule (MAS) offers...though comparable discounts were not negotiated. (2) Award is otherwise in...

2012-10-01

347

48 CFR 538.270 - Evaluation of multiple award schedule (MAS) offers.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Evaluation of multiple award schedule (MAS) offers...Federal Supply Schedules 538.270 Evaluation of multiple award schedule (MAS) offers...though comparable discounts were not negotiated. (2) Award is otherwise in...

2010-10-01

348

48 CFR 538.270 - Evaluation of multiple award schedule (MAS) offers.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Evaluation of multiple award schedule (MAS) offers...Federal Supply Schedules 538.270 Evaluation of multiple award schedule (MAS) offers...though comparable discounts were not negotiated. (2) Award is otherwise in...

2013-10-01

349

48 CFR 538.270 - Evaluation of multiple award schedule (MAS) offers.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Evaluation of multiple award schedule (MAS) offers...Federal Supply Schedules 538.270 Evaluation of multiple award schedule (MAS) offers...though comparable discounts were not negotiated. (2) Award is otherwise in...

2011-10-01

350

NMR at low magnetic fields  

NASA Astrophysics Data System (ADS)

NMR provides outstanding information in chemistry and in medicine. But the equipment is expensive as high-field magnets are employed. Low-field NMR works with inexpensive permanent magnets. Until recently these did not provide fields sufficiently homogeneous for spectroscopy and were mostly used for relaxation measurements. Relaxation can also be measured outside the magnet, and small mobile NMR devices have been developed for non-destructive testing of large objects. Today small stray-field magnets and small magnets with homogeneous fields are available for relaxation analysis, imaging, and spectroscopy. Their availability is believed to be essential for shifting NMR analysis from a specialist's tool to a convenience tool.

Blümich, Bernhard; Casanova, Federico; Appelt, Stephan

2009-08-01

351

NMR properties of sedimented solutes.  

PubMed

This perspective paper is intended to give some insights into the recently proposed technique of NMR of solutes sedimented by ultracentrifugation in a rotor used for solid state NMR experiments. Sedimented "states" correspond to molecules with very little reorientational capability in extremely concentrated solutions. They provide solid state NMR spectra comparable in quality with those of the best microcrystalline samples. Here we report some experiments to look for chemicals which affect the properties of the sediment, and we show that it is possible to fill the rotor in a true ultracentrifuge and then record the spectra. The latter possibility opens new horizons for NMR of sedimented systems. PMID:22120590

Bertini, Ivano; Engelke, Frank; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico; Rosa, Camilla; Turano, Paola

2012-01-14

352

3D ¹?N/¹?N/¹H chemical shift correlation experiment utilizing an RFDR-based ¹H/¹H mixing period at 100 kHz MAS.  

PubMed

Homonuclear correlation NMR experiments are commonly used in the high-resolution structural studies of proteins. While (13)C/(13)C chemical shift correlation experiments utilizing dipolar recoupling techniques are fully utilized under MAS, correlation of the chemical shifts of (15)N nuclei in proteins has been a challenge. Previous studies have shown that the negligible (15)N-(15)N dipolar coupling in peptides or proteins necessitates the use of a very long mixing time (typically several seconds) for effective spin diffusion to occur and considerably slows down a (15)N/(15)N correlation experiment. In this study, we show that the use of mixing proton magnetization, instead of (15)N, via the recoupled (1)H-(1)H dipolar couplings enable faster (15)N/(15)N correlation. In addition, the use of proton-detection under ultrafast MAS overcomes the sensitivity loss due to multiple magnetization transfer (between (1)H and (15)N nuclei) steps. In fact, less than 300 nL (?1.1 micromole quantity) sample is sufficient to acquire the 3D spectrum within 5 h. Our results also demonstrate that a 3D (15)N/(15)N/(1)H experiment can render higher resolution spectra that will be useful in the structural studies of proteins at ultrafast MAS frequencies. 3D (15)N/(15)N/(1)H and 2D radio frequency-driven dipolar recoupling (RFDR)-based (1)H/(1)H experimental results obtained from a powder sample of N-acetyla-L-(15)N-valyl-L-(15)N-leucine at 70 and 100kHz MAS frequencies are presented. PMID:24801998

Nishiyama, Yusuke; Malon, Michal; Ishii, Yuji; Ramamoorthy, Ayyalusamy

2014-07-01

353

An advanced NMR protocol for the structural characterization of aluminophosphate glasses.  

PubMed

In this work a combination of complementary advanced solid-state nuclear magnetic resonance (NMR) strategies is employed to analyse the network organization in aluminophosphate glasses to an unprecedented level of detailed insight. The combined results from MAS, MQMAS and (31)P-{(27)Al}-CP-heteronuclear correlation spectroscopy (HETCOR) NMR experiments allow for a detailed speciation of the different phosphate and aluminate species present in the glass. The interconnection of these local building units to an extended three-dimensional network is explored employing heteronuclear dipolar and scalar NMR approaches to quantify P-O-Al connectivity by (31)P{(27)Al}-heteronuclear multiple quantum coherence (HMQC), -rotational echo adiabatic passage double resonance (REAPDOR) and -HETCOR NMR as well as (27)Al{(31)P}-rotational echo double resonance (REDOR) NMR experiments, complemented by (31)P-2D-J-RESolved MAS NMR experiments to probe P-O-P connectivity utilizing the through bond scalar J-coupling. The combination of the results from the various NMR approaches enables us to not only quantify the phosphate units present in the glass but also to identify their respective structural environments within the three-dimensional network on a medium length scale employing a modified Q notation, Q(n)(m),(AlO)(x), where n denotes the number of connected tetrahedral phosphate, m gives the number of aluminate species connected to a central phosphate unit and x specifies the nature of the bonded aluminate species (i.e. 4, 5 or 6 coordinate aluminium). PMID:17706927

van Wüllen, Leo; Tricot, Grégory; Wegner, Sebastian

2007-10-01

354

Ultraviolet spectroscopy of F and G supergiants with IUE. II - The hot companions of HR 2786 and HR 2859  

NASA Technical Reports Server (NTRS)

Hot companion stars in two binary systems are analyzed by means of IUE low-dispersion spectra. HR 2859B is found to be a B2 IV or V star, and analysis of ultraviolet to near-infrared photometry indicates the primary to be an early G star only one magnitude brighter in V with a magnitude of -4.0. A third star probably associated with this system was classified B9p Hg a probable visual absolute magnitude of about -1.6 is obtained for it. HR 2786 is now confirmed to have a hot secondary, for which a spectral class of B9-9.5 is obtained. With an assumed luminosity for this component, the G2 Ib primary then has a magnitude of -3.8.

Parsons, S. B.

1982-01-01

355

Physicochemical characterization of a Texas montmorillonite pillared with polyoxocations of aluminum. II. NMR and microcalorimetry results  

Microsoft Academic Search

Solid state magic angle spinning nuclear magnetic resonance (MAS NMR), together with microcalorimetry and XRD data, have been used to characterize a pillared interlayered clay (PILC) containing 1.3×10?4 mol Keggin ion\\/g PILC. The clay catalyst (Al13-PILC) was prepared by reacting a Texas Na-montmorillonite with Keggin ions, [Al13(O)4(OH)24(H2O)12 ]7+, from an aluminum chlorhydroxide (ACH) solution. Initially, Keggin ions H-bond with the

M. L Occelli; A Auroux; G. J Ray

2000-01-01

356

1H\\/ 27Al TRAPDOR NMR studies on aluminum species in dealuminated zeolites  

Microsoft Academic Search

Aluminum species in several dealuminated zeolites (ultrastable HY, HZSM-5 and mordenite) were investigated in detail by means of the newly introduced 1H\\/27Al TRAPDOR method in combination with 27Al MAS NMR, and the quadrupole coupling constants (QCCs) for aluminum atoms associated with these species were obtained. A signal at ca. 6.8 ppm, due to water molecules adsorbed on Lewis acid sites,

Feng Deng; Yong Yue; Chaohui Ye

1998-01-01

357

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

Microsoft Academic Search

This paper presents the results of the investigation of the hydration of alkali-activated slag (AAS) by nuclear magnetic resonance spectroscopy (NMR). The cross-polarization (CP) technique was used in combination with magic-angle spinning (MAS). This research was part of a systematic study of alkaline activation of slag by several different techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with

Shao-Dong Wang; Karen L Scrivener

2003-01-01

358

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

PubMed

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

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

1996-11-01

359

Double cross polarization ¹³C-NMR experiment in solid fossil fuel structure analysis  

Microsoft Academic Search

The Double Cross Polarization ¹³C-MAS\\/NMR experiment has been used to derive a new operational classification of solid fossil fuels based on chemical reactivity. The method requires labeling reactive sites in the organic matrix with a magnetically active isotope not present in the precursor material, and using the local, isolated dipole-dipole interaction between this nucleus and nearby ¹³C nuclei to detect

E. W. Hagaman; M. C. Woody

1988-01-01

360

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

Microsoft Academic Search

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

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

2000-01-01

361

Structural Characterization of MAO and Related Aluminum Complexes. 1. Solid-State 27 Al NMR with Comparison to EFG Tensors from ab Initio Molecular Orbital Calculations  

SciTech Connect

Aminato and propanolato aluminum clusters with 3-, 4-, and 6-coordinate aluminum sites are studied with three 27Al NMR techniques optimized for large 27Al Quadrupole coupling constants: field-swept, frequency-stepped, and high-field MAS NMR. The 27Al quadrupole coupling constants and asymmetry parameters of molecular species, both experimental and derived from ab initio molecular orbital calculations, are correlated with structure.

Bryant, Pamela L.; Harwell, Chris; Mrse, Anthony A.; Emery, Earl F.; Gan, Zhedong; Caldwell, Tod; Reyes, Arneil P.; Kuhns, Philip; Hoyt, David W.; Simeral, Larry S.; Hall, Randall W.; Butler, Leslie G.

2001-11-07

362

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

Microsoft Academic Search

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

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

2001-01-01

363

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

SciTech Connect

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

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

2008-07-04

364

LBT observations of the HR 8799 planetary system. First detection of HR 8799e in H band  

NASA Astrophysics Data System (ADS)

We have performed H and KS band observations of the planetary system around HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES Camera. The excellent instrument performance (Strehl ratios up to 80% in H band) enabled the detection of the innermost planet, HR 8799e, at H band for the first time. The H and KS magnitudes of HR 8799e are similar to those of planets c and d, with planet e being slightly brighter. Therefore, HR 8799e is likely slightly more massive than c and d. We also explored possible orbital configurations and their orbital stability. We confirm that the orbits of planets b, c and e are consistent with being circular and coplanar; planet d should have either an orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c. Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion resonances with c and d, while coplanar and circular orbits are allowed for a 5:2 resonance. The analysis of dynamical stability shows that the system is highly unstable or chaotic when planetary masses of about 5 MJ for b and 7 MJ for the other planets are adopted. Significant regions of dynamical stability for timescales of tens of Myr are found when adopting planetary masses of about 3.5, 5, 5, and 5 MJ for HR 8799b, c, d, and e respectively. These masses are below the current estimates based on the stellar age (30 Myr) and theoretical models of substellar objects. The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia.

Esposito, S.; Mesa, D.; Skemer, A.; Arcidiacono, C.; Claudi, R. U.; Desidera, S.; Gratton, R.; Mannucci, F.; Marzari, F.; Masciadri, E.; Close, L.; Hinz, P.; Kulesa, C.; McCarthy, D.; Males, J.; Agapito, G.; Argomedo, J.; Boutsia, K.; Briguglio, R.; Brusa, G.; Busoni, L.; Cresci, G.; Fini, L.; Fontana, A.; Guerra, J. C.; Hill, J. M.; Miller, D.; Paris, D.; Pinna, E.; Puglisi, A.; Quiros-Pacheco, F.; Riccardi, A.; Stefanini, P.; Testa, V.; Xompero, M.; Woodward, C.

2013-01-01

365

THz Dynamic Nuclear Polarization NMR  

PubMed Central

Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140–600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

Nanni, Emilio A.; Barnes, Alexander B.; Griffin, Robert G.; Temkin, Richard J.

2013-01-01

366

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

PubMed Central

We have isolated a cDNA clone encoding a precursor form of the diuretic hormone from the tobacco hornworm Manduca sexta (Mas-DH). Translation of the cDNA revealed a 138-amino acid precursor consisting of the Mas-DH amino acid sequence bounded by dibasic amino acid processing sites, a putative signal sequence, and additional peptide sequence on either side of the Mas-DH coding sequence. The region of the precursor upstream of the mature Mas-DH sequence shows limited (28%) homology to the cryptic region of the ovine corticotropin-releasing factor precursor. The Mas-DH RNA is 1.5-1.6 kilobases long; it is present in both the heads and bodies of adult and larval insects. In prewandering fifth stadium larvae, Mas-DH mRNA is expressed in brain, nerve cord, gut, and Malpighian tubules, but not in the fat body. There is a single genomic copy of the Mas-DH gene; the message is multiply spliced. Images PMID:1279702

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

1992-01-01

367

HR-2 mutations in human immunodeficiency virus type 1 gp41 restore fusion kinetics delayed by HR-1 mutations that cause clinical resistance to enfuvirtide.  

PubMed

Enfuvirtide (ENF) prevents the entry of human immunodeficiency virus type 1 (HIV-1) into cells by binding to the HR-1 region of the viral envelope (Env) protein gp41 subunit. Resistance to ENF arises via mutations in the drug binding site in HR-1. In addition, HR-2 mutations are commonly observed in ENF-resistant Env proteins, though their role remains unclear. We explored the mechanistic basis for clinical resistance to ENF and the role of HR-2 mutations. Using panels of ENF resistance-associated mutants for two patients, we found that mutations in HR-1 slowed the fusion kinetics and that mutations in HR-2 restored fusion rates. We assessed the differences in the rates of fusion of these mutants from a temperature-arrested state and observed similar trends, suggesting that the step of delay occurs after coreceptor engagement. Sensitivity to neutralizing antibodies was unchanged by the HR-1 and HR-2 mutants in each panel. Since this result was in contrast to those of a previous in vitro analysis where enhanced sensitivity to neutralization was demonstrated for heterologous Envs with ENF resistance-associated HR-1 changes, we examined the context dependence of HR-1 and HR-2 mutations by transferring the mutations seen in one patient into the Env context of another. These studies revealed that some, but not all, HR-1 mutations, when placed out of context (i.e., in a patient Env where they did not originally arise), enhance sensitivity to neutralizing antibodies. However, in most cases, HR-1 mutations in ENF-treated patients evolve in a manner that preserves pretreatment neutralization sensitivity so as to evade the pressures of the immune system. PMID:19153234

Ray, Neelanjana; Blackburn, Leslie A; Doms, Robert W

2009-04-01

368

10 MMBt/Hr AFBC Commercial Demonstration Cedar Lane Farms  

SciTech Connect

The objective of this project was to demonstrate and promote the commercialization of coal-fired atmospheric fluidized bed combustion (AFBC) systems, with limestone addition for SO2 emissions control and a baghouse for particulate emissions control. This AFBC system was targeted for small scale industrial-commercial-institutional space and process heat applications in the 4-40 MMBtu/hr size range. A cost effective and environmentally acceptable AFBC technology in this size range could displace a considerable amount of heating gas and oil with coal, while resulting in significant total cost savings to the owner/operators.

Harold M. Keener; Mary H. Wicks; Tom Machamer; Dave Hoecke; Don Bonk; Bob Brown

2005-10-31

369

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

370

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

371

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. PMID:21650191

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

2011-01-01

372

Solid-state NMR spectra of lipid-anchored proteins under magic angle spinning.  

PubMed

Solid-state NMR is a promising tool for elucidating membrane-related biological phenomena. We achieved the measurement of high-resolution solid-state NMR spectra for a lipid-anchored protein embedded in lipid bilayers under magic angle spinning (MAS). To date, solid-state NMR measurements of lipid-anchored proteins have not been accomplished due to the difficulty in supplying sufficient amount of stable isotope labeled samples in the overexpression of lipid-anchored proteins requiring complex posttranslational modification. We designed a pseudo lipid-anchored protein in which the protein component was expressed in E. coli and attached to a chemically synthesized lipid-anchor mimic. Using two types of membranes, liposomes and bicelles, we demonstrated different types of insertion procedures for lipid-anchored protein into membranes. In the liposome sample, we were able to observe the cross-polarization and the (13)C-(13)C chemical shift correlation spectra under MAS, indicating that the liposome sample can be used to analyze molecular interactions using dipolar-based NMR experiments. In contrast, the bicelle sample showed sufficient quality of spectra through scalar-based experiments. The relaxation times and protein-membrane interaction were capable of being analyzed in the bicelle sample. These results demonstrated the applicability of two types of sample system to elucidate the roles of lipid-anchors in regulating diverse biological phenomena. PMID:24517164

Nomura, Kaoru; Harada, Erisa; Sugase, Kenji; Shimamoto, Keiko

2014-03-01

373

Images of a fourth planet orbiting HR 8799.  

PubMed

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

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

2010-12-23

374

Restoration Technique for Pleiades-Hr Panchromatic Images  

NASA Astrophysics Data System (ADS)

17th of December 2011 from Kourou Space Centre, French Guyana. Like others high resolution optical satellites, it acquires both panchromatic images, with 70cm spatial resolution, and lower resolution multispectral images with 2.8m spatial resolution. Pleiades-HR is an optimized system, which means that the Modulation Transfer Function has a low value at Nyquist frequency, in order to reduce both the telescope diameter and aliasing effects. Shannon sampling condition is thus met at first order, which also makes classical ground processing, such as image matching or resampling, more justified for a mathematical point of view. Raw images are thus blurry which implies a deconvolution stage that restores sharpness but also increases the noise level in the high frequency domain. A denoising step, based upon wavelet packet coefficients thresholding/shrinkage technique, allows controlling the final noise level. Each of these methods includes numerous parameters that have to be assessed during the inflight commissioning period: deconvolution filter that depends on MTF assessment, instrumental noise model, noise level target for denoised images, wavelet packet decomposition level. This paper aims to precisely describe the deconvolution/denoising algorithms and how their main parameters have been set up during the inflight commissioning stage. Special attention will be given to structured noise induced by Pleiades-HR on board wavelet-based compression algorithm

Latry, C.; Fourest, S.; Thiebaut, C.

2012-07-01

375

Molecular dynamics of fullerene-nanowhiskers studied by solid state NMR  

NASA Astrophysics Data System (ADS)

The properties of molecular motion of as-grown C60 nanowhiskers and C70 nanowhiskers were investigated by 13C-CP/MAS NMR, wideline 13C-NMR and '1-NMR techniques. It was confirmed that m-xylene molecules are contained in both C60 and C70 nanowhisekers. It was found that C60 nanowhiskers exhibit an orientational order phase transition at 250 K. The activation energy of C60 molecules below 250 K was evaluated to be 14.7 kJ/mol, which is smaller than that of pristine C60 solid. For C70 nanowhiskers, no clear phase transition was found from 270 K to 170 K. The activation energy of C70 molecules was evaluated to be 13.7 kJ/mol between 270 K and 170 K, which is smaller than that of pristine C70 solid.

Ogata, H.; Motohashi, S.; Tsuchida, S.

2009-04-01

376

Understanding the leaching properties of heterogenized catalysts: a combined solid-state and PHIP NMR study.  

PubMed

Para-hydrogen induced polarization (PHIP) NMR in solution, combined with solid-state NMR, can be efficiently employed for the highly sensitive in-situ detection of the leaching properties of immobilized catalysts. The knowledge of this property is important for possible applications of PHIP experiments in medicine, biology or industry, where leached catalysts poison the solution of hyperpolarized products. As experimental example Wilkinson's catalyst RhCl(PPh(3))(3) (1) immobilized on mesoporous silica is chosen. As model reaction the hydrogenation of styrene in solvents with different polarities (methanol-d(4), acetone-d(6) and benzene-d(6)) is used. A (31)P solid-state MAS-NMR study reveals that there are two different species of catalysts on the silica, namely coordinatively bound catalysts and physisorbed catalyst. Only the second species exhibits substantial leaching, which is visible in a strong PHIP enhancement of the reaction product. PMID:21435842

Gutmann, Torsten; Ratajczyk, Tomasz; Xu, Yeping; Breitzke, Hergen; Grünberg, Anna; Dillenberger, Sonja; Bommerich, Ute; Trantzschel, Thomas; Bernarding, Johannes; Buntkowsky, Gerd

2010-11-01

377

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

378

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

379

Expression and cellular localization of the Mas receptor in the adult and developing mouse retina  

PubMed Central

Purpose Recent studies have provided evidence that a local renin-angiotensin system (RAS) exists in the retina and plays an important role in retinal neurovascular function. We have recently shown that increased expression of ACE2 and angiotensin (1-7) [Ang (1-7)], two components of the protective axis of the RAS, in the retina via adeno-associated virus (AAV)-mediated gene delivery, conferred protection against diabetes-induced retinopathy. We hypothesized that the protective molecular and cellular mechanisms of Ang (1-7) are mediated by its receptor, Mas, and the expression level and cellular localization dictate the response to Ang (1-7) and activation of subsequent protective signaling pathways. We tested this hypothesis by examining the expression and cellular localization of the Mas receptor in adult and developing mouse retinas. Methods The cellular localization of the Mas receptor protein was determined with immunofluorescence of the eyes of adult and postnatal day 1 (P1), P5, P7, P15, and P21 mice using the Mas receptor-specific antibody, and mRNA was detected with in situ hybridization of paraffin-embedded sections. Western blotting and real-time reverse-transcription (RT)–PCR analysis were performed to determine the relative levels of the Mas protein and mRNA in adult and developing retinas, as well as in cultured retinal Müller glial and RPE cells. Results In the adult eye, the Mas receptor protein was abundantly present in retinal ganglion cells (RGCs) and photoreceptor cells; a lower level of expression was observed in endothelial cells, Müller glial cells, and other neurons in the inner nuclear layer of the retina. In the developing retina, Mas receptor mRNA and protein expression was detected in the inner retina at P1, and the expression levels increased with age to reach the adult level and pattern by P15. In the adult mouse retina, Mas receptor mRNA was expressed at a much higher level when compared to angiotensin II (Ang II) type I (AT1R) and type II (AT2R) receptor mRNA. Conclusions The Mas receptor is expressed in developing and adult mouse retinas, and is more abundant in retinal neurons than in endothelial and Müller glial cells. These observations suggest that Mas receptor-mediated signaling may play important roles that extend beyond mediating the vascular effects of Ang (1-7) in developing and adult retinas. In addition, the relatively high expression of the Mas receptor when compared to AT1R suggests that they may play a more important role in maintaining normal retinal physiology than previously considered.

Prasad, Tuhina; Verma, Amrisha

2014-01-01

380

Toward Systemic MAS Development: Enforcing Decentralized Self-organization by Composition and Refinement of Archetype Dynamics  

Microsoft Academic Search

The utilization of self-organizing processes promises scala- bility, robustness and adaptivity in Multi-Agent Systems (MAS), solely based on decentralized coordination of individual actors. Bionic develop- ment approaches are being established, which reuse decentralized coor- dination mechanisms that are derived from natural self-organizing sys- tems. In this paper, we address analysis activities in incremental MAS development, concerning with the derivation of

Jan Sudeikat; Wolfgang Renz

2007-01-01

381

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

Microsoft Academic Search

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

Mathew Gregoski; Alexey Vertegel; Frank Treiber

2011-01-01

382

NMR measurement of pore structure  

SciTech Connect

An attempt was made to pursue [sup 129]Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, [sup 13]CO[sub 2], and [sup 15]N[sub 2]. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10[sup [minus]2] to 10[sup [minus]6]s.

Earl, W.L. (Los Alamos National Lab., NM (United States)); Kim, Yong-Wah (Los Alamos National Lab., NM (United States) New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics); Smith, D.M. (New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics)

1993-05-31

383

NMR measurement of pore structure  

SciTech Connect

An attempt was made to pursue {sup 129}Xe NMR as a pore measurement technique. Samples studied were synthetic imogolite (tubular aluminosilicate with gibbsite structure), sodium Y-zeolite, and an aerogel and a xerogel. Gases used were normal Xe, {sup 13}CO{sub 2}, and {sup 15}N{sub 2}. Although a completely general NMR technique for measuring pore size distributions may not be possible, information about molecular motion and interactions can be obtained, because NMR is sensitive to short range interactions (1 nm or less) and to molecular dynamics in the range 10{sup {minus}2} to 10{sup {minus}6}s.

Earl, W.L. [Los Alamos National Lab., NM (United States); Kim, Yong-Wah [Los Alamos National Lab., NM (United States)]|[New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics; Smith, D.M. [New Mexico Univ., Albuquerque, NM (United States). Center for Microengineered Ceramics

1993-05-31

384

Virtual HR: Strategic human resource management in the 21st century  

Microsoft Academic Search

This article explores the emergence of virtual HR in organizations as a response to the increased presence of external structural options to perform HR services as well as the growing sophistication of information technologies. We examine the motives that are encouraging HR managers to implement these virtual arrangement and, drawing from transaction cost economics and the resource-based view of the

Scott A. Snell

1998-01-01

385

hr.osu.edu/policy Page 1 of 1 Recruitment and Selection  

E-print Network

hr.osu.edu/policy Page 1 of 1 - Recruitment and Selection Policy 4.10 Office of Human Resources interpretation Human Resources Talent Acquisition 614-292-1050 hr.osu.edu/talent Compensation Human Resources Compensation 614-292-1050 hr.osu.edu/comp Medical Center employment Medical Center Human Resources, Employment

Howat, Ian M.

386

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

ERIC Educational Resources Information Center

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

Carter, Alison; Robinson, Dilys

387

Co-terminal: BS Civil Engineering + MAS Programs The BSCE+MAS co-terminal degree programs are designed for students to earn the Bachelor of Science in Civil Engineering  

E-print Network

Co-terminal: BS Civil Engineering + MAS Programs The BSCE+MAS co-terminal degree programs are designed for students to earn the Bachelor of Science in Civil Engineering (BSCE, normally 137 credit hours each of these programs identified below. Co-terminal: BS Civil Engineering +MAS Construction

Heller, Barbara

388

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

SciTech Connect

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

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

2013-01-07

389

Complete genome sequence of Desulfohalobium retbaense type strain (HR(100)).  

PubMed

Desulfohalobium retbaense (Ollivier et al. 1991) is the type species of the polyphyletic genus Desulfohalobium, which comprises, at the time of writing, two species and represents the family Desulfohalobiaceae within the Deltaproteobacteria. D. retbaense is a moderately halophilic sulfate-reducing bacterium, which can utilize H(2) and a limited range of organic substrates, which are incompletely oxidized to acetate and CO(2), for growth. The type strain HR(100) (T) was isolated from sediments of the hypersaline Retba Lake in Senegal. Here we describe the features of this organism, together with the complete genome sequence and annotation. This is the first completed genome sequence of a member of the family Desulfohalobiaceae. The 2,909,567 bp genome (one chromosome and a 45,263 bp plasmid) with its 2,552 protein-coding and 57 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project. PMID:21304676

Spring, Stefan; Nolan, Matt; Lapidus, Alla; Glavina Del Rio, Tijana; Copeland, Alex; Tice, Hope; Cheng, Jan-Fang; Lucas, Susan; Land, Miriam; Chen, Feng; Bruce, David; Goodwin, Lynne; Pitluck, Sam; Ivanova, Natalia; Mavromatis, Konstantinos; Mikhailova, Natalia; Pati, Amrita; Chen, Amy; Palaniappan, Krishna; Hauser, Loren; Chang, Yun-Juan; Jeffries, Cynthia D; Munk, Christine; Kiss, Hajnalka; Chain, Patrick; Han, Cliff; Brettin, Thomas; Detter, John C; Schüler, Esther; Göker, Markus; Rohde, Manfred; Bristow, Jim; Eisen, Jonathan A; Markowitz, Victor; Hugenholtz, Philip; Kyrpides, Nikos C; Klenk, Hans-Peter

2010-01-01

390

Direct imaging of multiple planets orbiting the star HR 8799  

SciTech Connect

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

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

2008-10-14

391

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

SciTech Connect

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

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

2012-08-01

392

1H and 2H NMR spectroscopic studies on the metabolism and biochemical effects of 2-bromoethanamine in the rat.  

PubMed

Male Fischer 344 rats were dosed with 2-bromoethanamine hydrobromide (BEA, N = 6) or [1,2,2,-2H4]-bromoethanamine hydrobromide (BEA-d4, N = 6) at 150 mg/kg i.p. and urine was collected -24 to 0 hr pre-dose and at 0-2 hr, 2-4 hr, 4-8 hr and 8-12 hr post-dose (p.d.). Urine samples were analysed directly using 500 and 600 MHz 1H NMR and 92.1 MHz 2H NMR spectroscopy. The major observed effect of BEA treatment was the induction of transient elevations in urinary glutaric acid (GTA) and adipic acid (ADA) excretion lasting up to 24 hr p.d. Most of the GTA was excreted in the 0-8 hr p.d. with maximal rates of 100-120 microM/hr for each rat occurring between 4 and 8 hr p.d. in animals treated with BEA or BEA-d4. GTA and ADA were shown to be of endogenous origin as there was no detectable incorporation of the 2H label into either compound following treatment of rats with BEA-d4. Following BEA-treatment there was an initial decrease in the levels of urinary citrate, succinate, 2-oxoglutarate and trimethylamine-N-oxide. A subsequent recovery of citrate and succinate was noted following the onset of medullary nephropathy. The abnormal urinary metabolite profiles were similar to that observed in the urine of humans with glutaric aciduria type II (an inborn error of metabolism) caused by a lack of mitochondrial fatty acyl coenzyme A dehydrogenases indicating that BEA or its metabolites have similar metabolic consequences. The BEA metabolite aziridine was detected by 1H and 2H NMR spectroscopy of the urine 8 hr p.d. together with BEA itself and two novel metabolites 2-oxazolidone (OX) and 5-hydroxy-2-oxazolidone (HOX). The formation of OX requires the reaction of BEA with endogenous bicarbonate followed by a cyclisation reaction eliminating HBr. Dosing rats with authentic OX resulted in the excretion of HOX but did not cause glutaric or adipic aciduria indicating that either aziridine or BEA itself was responsible for the presumed defect in mitochondrial metabolism. PMID:7763276

Holmes, E; Caddick, S; Lindon, J C; Wilson, I D; Kryvawych, S; Nicholson, J K

1995-05-17

393

Transformer-coupled NMR probe  

NASA Astrophysics Data System (ADS)

In this study, we propose an NMR probe circuit that uses a transformer with a ferromagnetic core for impedance matching. The ferromagnetic core provides a strong but confined coupling that result in efficient energy transfer between the sample coil and NMR spectrometer, while not disturbing the B1 field generated by the sample coil. We built a transformer-coupled NMR probe and found that it offers comparable performance (loss <1 dB) to a conventional capacitor-coupled circuit. Our probe operates over a wide frequency range (500 kHz-5 MHz in this example) without the need for matching adjustments. Such probes could be useful for low-field mobile NMR applications of multi-frequency operation, such as imaging, relaxation, and diffusion measurements, as well as NQR.

Utsuzawa, Shin; Mandal, Soumyajit; Song, Yi-Qiao

2012-03-01

394

THz Dynamic Nuclear Polarization NMR  

E-print Network

Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The ...

Nanni, Emilio Alessandro

395

Compact orthogonal NMR field sensor  

DOEpatents

A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

Gerald, II, Rex E. (Brookfield, IL); Rathke, Jerome W. (Homer Glen, IL)

2009-02-03

396

Solid state NMR studies of materials for energy technology  

NASA Astrophysics Data System (ADS)

Presented in this dissertation are NMR investigations of the dynamical and structural properties of materials for energy conversion and storage devices. 1H and 2H NMR was used to study water and methanol transportation in sulfonated poly(arylene ether ketone) based membranes for direct methanol fuel cells (DMFC). These results are presented in chapter 3. The amount of liquid in the membrane and ion exchange capacity (IEC) are two main factors that govern the dynamics in these membranes. Water and methanol diffusion coefficients also are comparable. Chapters 4 and 5 are concerned with 31P and 1H NMR in phosphoric acid doped PBI membranes (para-PBI and 2OH-PBI) as well as PBI membranes containing ionic liquids (H3PO4/PMIH2PO4/PBI). These membranes are designed for higher-temperature fuel cell operation. In general, stronger short and long range interactions were observed in the 2OH-PBI matrix, yielding reduced proton transport compared to that of para-PBI. In the case of H3PO4/PMIH2PO 4/PBI, both conductivity and diffusion are higher for the sample with molar ratio 2/4/1. Finally, chapter 6 is devoted to the 31P NMR MAS study of phosphorus-containing structural groups on the surfaces of micro/mesoporous activated carbons. Two spectral features were observed and the narrow feature identifies surface phosphates while the broad component identifies heterogeneous subsurface phosphorus environments including phosphate and more complex structure multiple P-C, P-N and P=N bonds.

Nambukara Kodiweera Arachchilage, Chandana K.

397

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

398

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

399

NMR insights into protein allostery  

PubMed Central

Allosterism is one of nature's principal methods for regulating protein function. Allosterism utilizes ligand binding at one site to regulate the function of the protein by modulating the structure and dynamics of a distant binding site. In this review, we first survey solution NMR techniques and how they may be applied to the study of allostery. Subsequently, we describe several examples of application of NMR to protein allostery and highlight the unique insight provided by this experimental technique. PMID:22198279

Manley, Gregory; Loria, J. Patrick

2014-01-01

400

NMR studies of some rifamycins  

NASA Astrophysics Data System (ADS)

The 13C and 1H NMR spectra of rifabutin 1 and five of its derivatives 2- 6, three of which are described for the first time, were assigned using 2D homo- and heteronuclear correlation NMR spectroscopy, proton exchange with deuterium, and selective proton decoupling methods to one bond and long distance. The study was also extended to the other well-known ansamycin antibiotics, rifamycin S 7 and rifampicin 8. Previous interpretations for the known compounds have been corrected.

Santos, L.; Medeiros, M. A.; Santos, S.; Costa, M. C.; Tavares, R.; Curto, M. J. M.

2001-05-01

401

NMR characterization of thin films  

DOEpatents

A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

Gerald, II, Rex E. (Brookfield, IL); Klingler, Robert J. (Glenview, IL); Rathke, Jerome W. (Homer Glen, IL); Diaz, Rocio (Chicago, IL); Vukovic, Lela (Westchester, IL)

2008-11-25

402

Polarization transfer NMR imaging  

DOEpatents

A nuclear magnetic resonance (NMR) image is obtained with spatial information modulated by chemical information. The modulation is obtained through polarization transfer from a first element representing the desired chemical, or functional, information, which is covalently bonded and spin-spin coupled with a second element effective to provide the imaging data. First and second rf pulses are provided at first and second frequencies for exciting the imaging and functional elements, with imaging gradients applied therebetween to spatially separate the nuclei response for imaging. The second rf pulse is applied at a time after the first pulse which is the inverse of the spin coupling constant to select the transfer element nuclei which are spin coupled to the functional element nuclei for imaging. In a particular application, compounds such as glucose, lactate, or lactose, can be labeled with .sup.13 C and metabolic processes involving the compounds can be imaged with the sensitivity of .sup.1 H and the selectivity of .sup.13 C.

Sillerud, Laurel O. (Los Alamos, NM); van Hulsteyn, David B. (Santa Fe, NM)

1990-01-01

403

Solid-State NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Due to the development of new techniques and further increase of magnetic field strength available for commercial applications, solid-state NMR spectroscopy became a routine method for the characterization of zeolites. As an important advantage, solid-state NMR spectroscopy allows the investigation of the local structure of nuclei in the solids under study. The specific behavior of zeolites often depends on local effects, such as framework defects, the substitution of framework atoms, guest compounds etc. Therefore, solid-state NMR spectroscopy is a widely applied analytical method for delivering structure data, which are complementary to those of diffraction methods suitable for investigating the long-range order. While early solid-state NMR spectroscopic studies often focused on the characterization of the zeolite framework in the as-synthesized and hydrated state, an increasing number of recent works is dealing with the investigation of the framework of dehydrated and calcined zeolites and of surface sites, i.e., on the determination of their concentration, strength, and accessibility. In all these applications, the advantage of solid-state NMR spectroscopy to be a quantitative method is utilized. The present chapter demonstrates the fundamentals, various techniques, and most important applications of solid-state NMR spectroscopy making this method to an important tool of research in zeolite science.

Hunger, Michael

404

NMR Relaxation and Petrophysical Properties  

NASA Astrophysics Data System (ADS)

NMR relaxation is routinely used in the field of geosciences to give basic petrophysical properties such as porosity, pore size distribution, saturation etc. In this tutorial, we focus on the pore size distribution deduced from NMR. We recall the basic principle used in the interpretation of the NMR signal and compare the results with other standard petrophysical techniques such as mercury pore size distribution, BET specific surface measurements, thin section visualizations. The NMR pore size distribution is a unique information available on water saturated porous media and can give similar results as MICP in certain situations. The scaling of NMR relaxation time distribution (s) into pore sizes (?m) requires the knowledge of the surface relaxivity (?m/s) and we recommend using specific surface measurements as an independent determination of solid surface areas. With usual surface relaxivities, the NMR technique can explore length-scales starting from nano-meters and ending around 100 ?m. Finally, we will introduce briefly recent techniques sensitive to the pore to pore diffusional exchange, providing new information on the connectivity of the pore network, but showing another possibility of discrepancy in the determination of pore size distribution with standard techniques.

Fleury, Marc

2011-03-01

405

Applications of high-resolution 1H solid-state NMR.  

PubMed

This article reviews the large increase in applications of high-resolution (1)H magic-angle spinning (MAS) solid-state NMR, in particular two-dimensional heteronuclear and homonuclear (double-quantum and spin-diffusion NOESY-like exchange) experiments, in the last five years. These applications benefit from faster MAS frequencies (up to 80 kHz), higher magnetic fields (up to 1 GHz) and pulse sequence developments (e.g., homonuclear decoupling sequences applicable under moderate and fast MAS). (1)H solid-state NMR techniques are shown to provide unique structural insight for a diverse range of systems including pharmaceuticals, self-assembled supramolecular structures and silica-based inorganic-organic materials, such as microporous and mesoporous materials and heterogeneous organometallic catalysts, for which single-crystal diffraction structures cannot be obtained. The power of NMR crystallography approaches that combine experiment with first-principles calculations of NMR parameters (notably using the GIPAW approach) are demonstrated, e.g., to yield quantitative insight into hydrogen-bonding and aromatic CH-? interactions, as well as to generate trial three-dimensional packing arrangements. It is shown how temperature-dependent changes in the (1)H chemical shift, linewidth and DQ-filtered signal intensity can be analysed to determine the thermodynamics and kinetics of molecular level processes, such as the making and breaking of hydrogen bonds, with particular application to proton-conducting materials. Other applications to polymers and biopolymers, inorganic compounds and bioinorganic systems, paramagnetic compounds and proteins are presented. The potential of new technological advances such as DNP methods and new microcoil designs is described. PMID:22177472

Brown, Steven P

2012-02-01

406

The effect of rotating substituent in 2,2,5,7,8-pentamethylchroman derivatives. X-ray, 13C CP MAS analysis and DFT analysis  

NASA Astrophysics Data System (ADS)

The aim of this study was to analyze the influence of rotating substituent at position 6 in 2,2,5,7,8-pentamethylchroman derivatives on geometry of the chroman ring. Three substituents have been chosen which differed in electro donor/acceptor properties (-NO2, -OH and -NH2). The substituents were rotated by 10° step from 0° to 180° whereas the geometries were fully optimized at B3LYP/6-311G** level of theory. The rotation barrier is related with a size of the substituent, being largest for the nitro group (5.9 kcal/mol) and smallest for the hydroxyl group (2.0 kcal/mol). The largest changes on geometry were observed in closest proximity of the substituents in the phenyl ring (due to steric effect) and C4A-C8A-O1-O2 angle in the chroman fragment, related to the antioxidant activity of a compound. The latter varied much stronger for electron-accepting substituent (the range -12.6° to -16.3°) than for electron donating ones (the variation range -17.1° to -18.9°), showing the rather high sensitivity in the first case. Apart from theoretical studies the crystal structure of newly synthesized 6-nitro-2,2,5,7,8-pentamethylchroman was determined by X-ray diffraction and studied by 13C NMR including solid-state 13C CP-MAS NMR.

St?pie?, Dorota K.; Cyra?ski, Micha? K.; Dobrzycki, ?ukasz; Wa?ejko, Piotr; Baj, Aneta; Witkowski, Stanis?aw; Paradowska, Katarzyna; Wawer, Iwona

2014-11-01

407

HR Assistant Vice President: Suite 250 Nisbet 517-355-0290 Fax: 432-4921 Sharon Butler, Assistant Vice President  

E-print Network

-1751 Debbie Lake Hafke, Assistant Director lake@hr.msu.edu 517-884-0168 Arica Ackerson, Sr. HR Professional Analyst terzian@msu.edu 517-353-3121 ext. 262 Tim Hermen, Sr. HR Professional/Supervisor hermenti

408

27Al and 1H Solid State NMR Studies Show Evidence of TiAl3 and TiH2 in Ti-doped NaAlH4  

SciTech Connect

Previous X-ray Diffraction (XRD) and Nuclear Magnetic Resonance (NMR) studies on Ti-doped NaAlH{sub 4} revealed the reaction products of two heavily doped (33.3 at.%) samples that were solvent-mixed and mechanically-milled. This investigation revealed that nano-crystalline or amorphous Al{sub 2}O{sub 3} forms from the possible coordination of aluminum with oxygen atom of the furan ring system from added tetrahydrofuran (THF) in the solvent-mixed sample, and that TiAl{sub 3} forms in mechanically-milled samples. The present paper provides a more sophisticated NMR investigation of the these materials. On heavily doped (33.3 at.%) solvent-mixed samples, {sup 27}Al Magic Angle Spinning (MAS) NMR {sup 27}Al multiple quantum MAS (MQMAS) indicates the presence of an oxide layer of Al{sub 2}O{sub 3} on the surfaces of potentially bulk nanocrystalline Ti, nanocrystalline TiAl{sub 3}, and/or metallic aluminum. The {sup 1}H MAS NMR data also indicate the possible coordination of aluminum with the oxygen atom in the THF. On heavily doped samples that were mechanically milled, {sup 27}Al MAS NMR and static NMR confirms the presence of TiAl{sub 3}. In addition, the {sup 1}H MAS NMR and {sup 1}H spin-lattice relaxation (T{sub 1}) measurements are consistent with the presence of TiH{sub 2}. These results are in agreement with recent XAFS measurements indicating both Al and H within the first few coordination shells of Ti in the doped alanate.

Herberg, J; Maxwell, R; Majzoub, E

2005-05-26

409

sup 27 Al NMR studies of the aluminate sodalites Sr sub 8 (Al sub 12 O sub 24 )(CrO sub 4 ) sub 2 and Ca sub 8 (Al sub 12 O sub 24 )(WO sub 4 ) sub 2  

Microsoft Academic Search

The authors have studied ²⁷Al NMR spectra of powders of strontium chromate aluminate sodalite (SACr) and calcium tungstate aluminate sodalite (CAW) by the magic angle spinning (MAS) technique and of single-crystal SACr by a static method. They show that the precision in the determination of the quadrupole coupling constant (qcc) from MAS spectra is limited by residual broadening. Both in

J. J. van der Klink; W. S. Veeman; H. Schmid

1991-01-01

410

High-resolution (1)H NMR and magic angle spinning NMR spectroscopic investigation of the biochemical effects of 2-bromoethanamine in intact renal and hepatic tissue.  

PubMed

The metabolic consequences of xenobiotic-induced toxicity were investigated using high-resolution magic angle spinning (MAS) NMR spectroscopy of intact tissue. Renal papillary necrosis (RPN) was induced in Sprague-Dawley rats (n = 12) via a single i.p. dose of 250 mg/kg 2-bromoethanamine (BEA) hydrobromide. At 2, 4, 6, and 24 h after treatment with BEA, three animals were killed and tissue samples were obtained from liver, renal cortex, and renal medulla. Tissue samples were also removed at 2 and 24 h from matched controls (n = 6). (1)H MAS NMR spectroscopic techniques were used to analyze samples of intact tissue ( approximately 10 mg). Decreased levels of nonperturbing renal osmolytes (glycerophosphocholine, betaine, and myo-inositol) were observed in the renal papilla of BEA-treated animals at 6 and 24 h postdose (p.d.), concomitant with a relative increase in the tissue concentration of creatine. Increased levels of glutaric acid were found in all tissues studied in BEA-treated animals at 4 and 6 h p.d., indicating the inhibition of mitochondrial fatty acyl CoA dehydrogenases and mitochondrial dysfunction. Increased levels of trimethylamine-N-oxide occurred in the renal cortex at 6 h p.d. Changes in the metabolite profile of liver included an increase in the relative concentrations of triglycerides, lysine, and leucine. The novel application of (1)H MAS NMR to the biochemical analysis of intact tissues following a toxic insult highlights the potential of this technique as a toxicological probe in providing a direct link between urinary biomarkers of toxicity and histopathological evaluation of toxicological lesions. PMID:11323804

Garrod, S; Humpher, E; Connor, S C; Connelly, J C; Spraul, M; Nicholson, J K; Holmes, E

2001-05-01

411

Technology Enhanced Learning for People with Intellectual Disabilities and Cerebral Paralysis: The MAS Platform  

NASA Astrophysics Data System (ADS)

Education for students with disabilities now takes place in a wide range of settings, thus, including a wider range of assistive tools. As a result of this, one of the most interesting application domains of technology enhanced learning is related to the adoption of learning technologies and designs for people with disabilities. Following this unstoppable trend, this paper presents MAS, a software platform aimed to help people with severe intellectual disabilities and cerebral paralysis in their learning processes. MAS, as a technology enhanced learning platform, provides several tools that supports learning and monitoring for people with special needs, including adaptative games, data processing and monitoring tools. Installed in a special needs education institution in Madrid, Spain, MAS provides special educators with a tool that improved students education processes.

Colomo-Palacios, Ricardo; Paniagua-Martín, Fernando; García-Crespo, Ángel; Ruiz-Mezcua, Belén

412

Solid-state high-resolution 13C-NMR study of crosslinks in heavily gamma-irradiated polyethylene  

NASA Astrophysics Data System (ADS)

Chemical species produced by heavy ?-irradiation to high-density polyethylene were identified by solid-state high-resolution 13C-NMR, that is, by the CP-MAS method. The majority of chemical species responsible for crosslinks are tertiary carbons, even after such a heavy dosage as 995 Mrad of ?-irradiation. The MAS method, without CP, was used to detect selectively the NMR signal from 13C in amorphous regions. By using a Torchia pulse sequence, spectra from either crystalline or amorphous regions are observed selectively. The results indicate that short branches are produced preferentially in amorphous regions. More crosslinks are produced (by nearly 3.6 times) in amorphous regions than in crystalline regions.

Sohma, J.; Qun, Chen; Yuanshen, Wang; Xue-Wen, Qu; Shiotani, M.

413

Efficient design of multituned transmission line NMR probes: the electrical engineering approach.  

PubMed

Transmission line-based multi-channel solid state NMR probes have many advantages regarding the cost of construction, number of RF-channels, and achievable RF-power levels. Nevertheless, these probes are only rarely employed in solid state-NMR-labs, mainly owing to the difficult experimental determination of the necessary RF-parameters. Here, the efficient design of multi-channel solid state MAS-NMR probes employing transmission line theory and modern techniques of electrical engineering is presented. As technical realization a five-channel ((1)H, (31)P, (13)C, (2)H and (15)N) probe for operation at 7 Tesla is described. This very cost efficient design goal is a multi port single coil transmission line probe based on the design developed by Schaefer and McKay. The electrical performance of the probe is determined by measuring of Scattering matrix parameters (S-parameters) in particular input/output ports. These parameters are compared to the calculated parameters of the design employing the S-matrix formalism. It is shown that the S-matrix formalism provides an excellent tool for examination of transmission line probes and thus the tool for a rational design of these probes. On the other hand, the resulting design provides excellent electrical performance. From a point of view of Nuclear Magnetic Resonance (NMR), calibration spectra of particular ports (channels) are of great importance. The estimation of the ?/2 pulses length for all five NMR channels is presented. PMID:21316931

Frydel, J A; Krzystyniak, M; Pienkowski, D; Pietrzak, M; de Sousa Amadeu, N; Ratajczyk, T; Idzik, K; Gutmann, T; Tietze, D; Voigt, S; Fenn, A; Limbach, H H; Buntkowsky, G

2011-01-01

414

Use of a Copper-Chelated-Lipid Speeds Up NMR Measurements From Membrane Proteins  

PubMed Central

Recent studies have demonstrated the abilities of solid-state NMR techniques to solve atomic-level resolution structures and dynamics of membrane-associated proteins and peptides. However, high-throughput applications of solid-state NMR spectroscopy are hampered by long acquisition times due to the low sensitivity of the technique. In this study, we demonstrate the use of a paramagnetic copper-chelated-lipid to enhance the spin-lattice relaxation and therefore to speed-up solid-state NMR measurements. Fluid lamellar phase bicelles composed of a lipid, detergent, copper-chelated-lipid, and containing a uniformly-15N-labeled antimicrobial peptide, subtilosin A, are used at the room temperature. The use of a chelating lipid reduces the concentration of free copper and limits RF-induced heating, a major problem for fluid samples. Our results demonstrate 6.2 times faster and 2.7 folds improvement of S/N for solid-state NMR experiments under MAS and static conditions respectively. Further, solid-state NMR measurements are shown to be feasible even on nanomole concentration of a membrane-associated peptide. PMID:20433169

Yamamoto, Kazutoshi; Xu, Jiadi; Kawulka, Karen E.; Vederas, John C.; Ramamoorthy, Ayyalusamy

2010-01-01

415

Solid-State NMR Characterization of Aluminum Oxide Nanofibers  

SciTech Connect

Aluminum oxide nanofibers have been generated by an electrospinning process, creating fibers with diameters on the nanometer scale and aspect ratios greater than a thousand. These nanofibers have the potential of providing enhanced catalytic properties, due to their large surface area and controllable compositions. Solid-state NMR is being used to investigate both the bulk and surface properties of these materials. 27Al NMR has shown that no chemistry occurs during the electrospinning process, even though potentials in excess of 20 kV are applied to the sample. Thermal treatment of the fibers to convert them to alumina results in the formation of different phases, with the phases identified by the relative populations of 4-, 5-, and 6-coordinate alumina sites. Heating to 525°C or 1200°C produces a species similar to the catalytically active gamma-phase or conversion of the nanofibers into the thermodynamically stable ?-alumina phase, respectively. 1H-27Al CP/MAS has shown that the ?-alumina phase has a low population of surface hydroxyls, whereas the “gamma-alumina” form has a much higher fraction of 5-coordinate sites, compared to materials synthesized by traditional techniques. Organophosphates are being used as molecular probes in the characterization of the nanofiber surfaces. 31P CP/MAS data has revealed the presence of mono-, bi- and tri-denate bound phosphate groups on the surface, with the onset of surface alumina dissolution with sample heating. The application of 1H-31P HETCOR shows that the three different types of bound organophosphates are intermixed, rather than there being separate domains for each type. 31P-27Al CP is also being used to distinguish the types of surface alumina sites bound to the phosphate species.

Cross, Jennifer L.; Tuttle, Ricky W.; Ramsier, Rex D.; Espe, Mathew

2006-07-24

416

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

SciTech Connect

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

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

1994-03-28

417

Microfabricated inserts for magic angle coil spinning (MACS) wireless NMR spectroscopy.  

PubMed

This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the "magic angle" of 54.74° with respect to the direction of the magnetic field (magic angle spinning - MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G; Wallrabe, Ulrike

2012-01-01

418

Microfabricated Inserts for Magic Angle Coil Spinning (MACS) Wireless NMR Spectroscopy  

PubMed Central

This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the “magic angle” of 54.74° with respect to the direction of the magnetic field (magic angle spinning – MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G.; Wallrabe, Ulrike

2012-01-01

419

NMR characterization of shocked quartz  

SciTech Connect

We have characterized experimentally and naturally-shocked quartz (both synthetic and natural samples) by solid state nuclear magnetic resonance (NMR) spectroscopy. Relaxation analysis of experimentally-shocked samples provides a means for quantitative characterization of the amorphous/disordered silica component NMR spectra demonstrate that magnetization in both the amorphous and crystalline components follows power-law behavior as a function of recycle time. This observation is consistent with the relaxation of nuclear spins by paramagnetic impurities. A fractal dimension can be extracted from the power-law exponent associated with each phase, and relative abundances can be extracted from integrated intensities of deconvolved peaks. NMR spectroscopy of naturally-shocked sandstone from Meteor Crater, Arizona (USA) led to the discovery of a new amorphous hydroxylated silica phase. Solid state NMR spectra of both experimentally and naturally shocked quartz were unexpectedly rich in microstructural information, especially when combined with relaxation analysis and cross-polarization studies. We suggest solid state NMR as a potentially useful tool for examining shock-induced microstructural changes in other inorganic compounds, with possible implications for shock processing of structural ceramics.

Boslough, M.B.; Cygan, R.T.; Assink, R.A. [Sandia National Labs., Albuquerque, NM (United States); Kirkpatrick, R.J. [Illinois Univ., Urbana, IL (United States)

1994-03-01

420

NMR planar microcoil for microanalysis  

NASA Astrophysics Data System (ADS)

This article deals with the analysis of small sample volume by using a planar microcoil and a micromachined cavity. This microcoil is used as a nuclear magnetic resonance (NMR) radio frequency detection coil in order to perform in vitro NMR analysis of the sample introduced into the microcavity. It is a real challenging task to develop microsystem for NMR spectrum extraction for smaller and smaller sample volume. Moreover, it is advantageous that these microsystems could be integrated in a Micro Total Analysing System (? -TAS) as an analysing tool. In this paper, NMR theory, description, fabrication process and electrical characterization of planar microcoils receiver are described. Results obtained on NMR microspectroscopy experiments have been performed on water and ethanol, using a 1 mm diameter planar coil. This microcoil is tuned and matched at 85.13 MHz which is the Larmor frequency of proton in a 2 T magnetic field. This paper has been presented at “3e colloque interdisciplinaire en instrumentation (C2I 2004)”, École Normale Supérieure de Cachan, 29 30 janvier 2004.

Sorli, B.; Chateaux, J. F.; Quiquerez, L.; Bouchet-Fakri, L.; Briguet, A.; Morin, P.

2006-11-01

421

Determination of the average degree of quaternization of N, N, N-trimethylchitosan by solid state 13C NMR  

Microsoft Academic Search

A novel method in which the quaternary salt of chitosan, N,N,N-trimethylchitosan (TMC) was synthesized using dimethylsulfate as the methylant agent is described. Although the synthesis of chitosan quaternary salts has been reported extensively, there remains some uncertainty in determining the resultant average degree of quaternization, DQ¯, in the final products. Here we used CP-MAS 13C NMR spectroscopy, that was able

Douglas de Britto; Lucimara Aparecida Forato; Odílio B. G. Assis

2008-01-01

422

The thermal reactions of muscovite studied by high-resolution solid-state 29Si and 27AI NMR  

Microsoft Academic Search

Studies of two muscovites of different iron contents, using solid-state NMR with magic-angle-spinning (MAS) combined with X-ray powder diffraction, thermal analysis and57Fe Mössbauer spectroscopy, suggest that dehydroxylation occurs by a homogeneous rather than an inhomogeneous mechanism, forming a dehydroxylate in which the aluminium is predominantly 5-coordinate. On further decomposition at about 1100° C, the tetrahedral layer and interlayer K+ form

K. J. D. Mackenzie; I. W. M. Brown; C. M. Cardile; R. H. Meinhold

1987-01-01

423

Principles of Trust for MAS: Cognitive Anatomy, Social Importance, and Quantification  

Microsoft Academic Search

After arguing about the crucial importance of trust for Agents and MAS, we provide a definition of trust both as a mental state and as a social attitude and relation. We present the mental ingredients of trust: its specific beliefs and goals, with special attention to evaluations and expectations. We show the relation between trust and the mental background of

Cristiano Castelfranchi; Rino Falcone

1998-01-01

424

Specifying in B the Influence/Reaction Model to Study Situated MAS  

E-print Network

of the framework, involving simulation and study of the properties of the system. Keywords: Situated MAS systems, France (2011)" #12;2 Studia Informatica Universalis. which interact in a physical environment with each other or with the environment define the local level. It gives rise to the collective behaviours

Boyer, Edmond

425

An Assistance Infrastructure to Inform Agents for Decision Support in Open MAS  

E-print Network

, Maite Lopez-Sanchez2 , and Inmaculada Rodriguez2 1 Artificial Intelligence Research Institute (IIIA the system is hybrid (i.e partic- ipants can be both human and software agents) and its specification becomes MAS, systems are populated by heterogeneous agents trying to achieve particular and/or collective

López-Sánchez, Maite

426

MAS Media Arts and Studies KEY: # = new course * = course changed = course dropped  

E-print Network

,commoncarrier,andrelatedelectronicmediatechnologies,includingtheInternet.Thiscoursefocuses on the social, political, and policy dimensions of the adoption and use of communication technologies. Special of communication via multimedia. Practical, hands-on experience with various media used in computer media, culture, and power. MAS 201 COMMUNICATION TECHNOLOGIES AND SOCIETY. (3

MacAdam, Keith

427

The RoboCup Soccer Server and CMUnited Clients: Implemented Infrastructure for MAS Research  

E-print Network

The RoboCup Soccer Server and CMUnited Clients: Implemented Infrastructure for MAS Research ItsukiCup Soccer Server (Noda et al., 1998; Noda and Frank, 1998) and associated client code. The Robot Soccer World Cup, or RoboCup, is an international research initiative that uses the game of soccer as a domain

Stone, Peter

428

The Millimeter Wave Atmospheric Sounder (MAS): a shuttle-based remote sensing experiment  

Microsoft Academic Search

The Millimeter Wave Atmospheric Sounder (MAS) will be launched in the spring of 1992 as part of the ATLAS 1 (Atmospheric Laboratory for Application and Science) mission. Using passive limb-scanning millimeter-wave radiometry, it will sense the thermal emission produced by ozone at 184 GHz, water vapor at 183 GHz, chlorine monoxide at 204 GHz, and oxygen (for retrieval of temperature

Charles L. Croskey; Niklaus Kaempfer; Richard M. Belivacqua; G. K. Hartmann; Klaus F. Kunzi; Philip R. Schwartz; John J. Olivero; Salvador Enrique Puliafito; Christopher Aellig; Gerhard Umlauft; William B. Waltman; Werner Degenhardt

1992-01-01

429

Mitochondrial Regulation of Phosphocreatine\\/Inorganic Phosphate Ratios in Exercising Human Muscle: A Gated 31P NMR Study  

Microsoft Academic Search

31P NMR is used to determine the relationship between work output in the exercising human forearm and the steady-state capability of oxidative phosphorylation as measured by the phosphocreatine\\/inorganic phosphate ratio (PCr\\/Pi). Exercise intensities (one contraction per 5 sec) permitting comfortable continuation of activity for >1 hr produced PCr\\/Pi of about 1 for a subject of moderate training. Linear relationships between

Britton Chance; Scott Eleff; J. S. Leigh; David Sokolow; Alexander Sapega

1981-01-01

430

"Solvent Effects" in 1H NMR Spectroscopy.  

ERIC Educational Resources Information Center

Describes a simple undergraduate experiment in chemistry dealing with the "solvent effects" in nuclear magnetic resonance (NMR) spectroscopy. Stresses the importance of having students learn NMR spectroscopy as a tool in analytical chemistry. (TW)

Cavaleiro, Jose A. S.

1987-01-01

431

?-NMR of a thin Pt film  

NASA Astrophysics Data System (ADS)

We report beta-detected NMR ( ?-NMR) measurements on a 50 nm thick platinum (Pt) film grown on a magnesium oxide (MgO) substrate. The frequency of the ?-NMR resonance in Pt was compared to the MgO reference frequency to estimate the Knight shift at various temperatures (100-300 K). The Knight shift was found to be negative and strongly temperature dependent. The implications are discussed and compared to other transition metals that have been studied via ?-NMR previously.

Fan, I.; Chow, K. H.; Parolin, T. J.; Egilmez, M.; Hossain, M. D.; Jung, J.; Keeler, T. A.; Kiefl, R. F.; Kreitzman, S. R.; Levy, C. D. P.; Ma, R.; Morris, G. D.; Pearson, M. R.; Saadaoui, H.; Salman, Z.; Smadella, M.; Song, Q.; Wang, D.; Xu, M.; MacFarlane, W. A.

2009-04-01

432

West Virginia UniversitySHRM ESSENTIALS OF HR MANAGEMENT December 2 & 3, 2010 9am -4pm  

E-print Network

Management course covers introductory HR topics in a condensed, easy- to-understand format. Whether you updated with the latest HR developments, the SHRM Essentials of HR Management course provides a complete, the SHRM Essentials of HR Management course provides a solid foundation in human resource management

Mohaghegh, Shahab

433

QUANTITATIVE 15N NMR SPECTROSCOPY  

EPA Science Inventory

Line intensities in 15N NMR spectra are strongly influenced by spin-lattice and spin-spin relaxation times, relaxation mechanisms and experimental conditions. Special care has to be taken in using 15N spectra for quantitative purposes. Quantitative aspects are discussed for the 1...

434

NMR properties of alginate microbeads  

Microsoft Academic Search

Alginates are a family of unbranched polysaccharides with properties that vary widely depending on their composition. In the presence of multivalent cations (frequently Ca2+), alginates form a gel. Consequently, alginates have been used to encapsulate a variety of biological materials, including cells. In this study, we present NMR relaxation and diffusion data from alginate microbeads with similar size and properties

Nicholas E. Simpson; Samuel C. Grant; Stephen J. Blackband; Ioannis Constantinidis

2003-01-01

435

Deuterium Exchange Kinetics by NMR.  

ERIC Educational Resources Information Center

Describes a physical chemistry experiment which allows such concepts as kinetics, catalysis, isotope shifts, coupling constants, and the use of nuclear magnetic resonance (NMR) for quantitative work to be covered in the same exercise. Background information, experimental procedures used, and typical results obtained are included. (JN)

Roper, G. C.

1985-01-01

436

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves  

NASA Astrophysics Data System (ADS)

We report solid state 13C and 1H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, 1H and cross-polarized 13C NMR signals from 15N,13C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

Thurber, Kent R.; Tycko, Robert

2014-05-01

437

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves.  

PubMed

We report solid state (13)C and (1)H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, (1)H and cross-polarized (13)C NMR signals from (15)N,(13)C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations. PMID:24832263

Thurber, Kent R; Tycko, Robert

2014-05-14

438

Solid-state NMR studies of interstitial phosphorus atoms in rhodium carbonyl clusters.  

PubMed

Pure samples and as-prepared mixtures of Rh9 and Rh10 carbonyl clusters with interstitial P atoms have been studied quantitatively by 31P MAS and 1H-31P CP/MAS NMR. Information on the 31P chemical shift tensor of the Rh9 and Rh10 clusters has been derived from spinning sideband simulations. The chemical shift anisotropy is slightly larger in the Rh10 clusters (340-400 ppm) than in the Rh9 clusters (230-300 ppm), while the asymmetry parameters are similar (eta = 0.1-0.4). The results contribute to the understanding of the relationship between the shielding anisotropy and the structure of the cluster cavity. PMID:9211624

Rocha, J; Orion, I; Nahring, J; Heaton, B T; Fernandez, C; Amoureux, J P

1997-05-01

439

Hyperspectral Microwave Atmospheric Sounder (HyMAS) architecture and design accommodations  

NASA Astrophysics Data System (ADS)

The Hyperspectral Microwave Atmospheric Sounder (HyMAS) is being developed at Lincoln Laboratories and accommodated by the Goddard Space Flight Center for a flight opportunity on a NASA research aircraft. The term “ hyperspectral microwave” is used to indicate an all-weather sounding that performs equivalent to hyperspectral infrared sounders in clear air with vertical resolution of approximately 1 km. Deploying the HyMAS equipped scanhead with the existing Conical Scanning Microwave Imaging Radiometer (CoSMIR) shortens the path to a flight demonstration. Hyperspectral microwave is achieved through the use of independent RF antennas that sample the volume of the Earth's atmosphere through various levels of frequencies, thereby producing a set of dense, spaced vertical weighting functions. The simulations proposed for HyMAS 118/183-GHz system should yield surface precipitation rate and water path retrievals for small hail, soft hail, or snow pellets, snow, rainwater, etc. with accuracies comparable to those of the Advanced Technology Microwave Sounder. Further improvements in retrieval methodology (for example, polarization exploitation) are expected. The CoSMIR instrument is a packaging concept re-used on HyMAS to ease the integration features of the scanhead. The HyMAS scanhead will include an ultra-compact Intermediate Frequency Processor (IFP) module that is mounted inside the door to improve thermal management. The IFP is fabricated with materials made of Low-Temperature Co-fired Ceramic (LTCC) technology integrated with detectors, amplifiers, A/D conversion and data aggregation. The IFP will put out 52 channels of 16 bit data comprised of 4 - 9 channel data streams for temperature profiles and 2-8 channel streams for water vapor. With the limited volume of the existing CoSMIR scanhead and new HyMAS front end components, the HyMAS team at Goddard began preliminary layout work inside the new drum. Importing and re-using models of the shell, the s- an head computer, and the slip rings developed for CoSMIR was the starting point. The next step was to modify the antenna faceplate to accommodate the dimensions of the three dual polarization Gaussian Optics Antenna (GOA) assemblies. Two mechanical concepts for the core technology, the hyperspectral IFP, were captured in a design tradeoff. Connector models considered minimum bend radii for the IFP analog connectors. Hyperspectral imaging is accomplished by strategically using a short wavelength intermediate frequency of 18-29 GHz, and thus reducing the size of components in the connection of the front end to the IFP. The SMK (2.92mm) Series connector will lay near the hinge line to minimize its' flexing. The digital output of the IFP will use a Serial Peripheral Interface (SPI) that must be accommodated by the scan head computer. To make that computer more reliable, maintainable, and forward compatible with the 52 HyMAS channels, a testbed of the scan head, calibration, and archive computers and the PIC24 microprocessor that resides on the IFP is in development. The computers will be programmed using a new framework application called Interoperable Remote Component (IRC). This software allows flexibility to program computers that communicate with each other and can adapt easily to the emerging HyMAS requirements for data format, algorithms, and graphical user interface (GUI). It is expected that the CoSMIR instrument will cut over to the IRC after it is adapted on an updated CoSMIR testbed.

Hilliard, L.; Racette, P.; Blackwell, W.; Galbraith, C.; Thompson, E.

440

Hyperspectral Microwave Atmospheric Sounder (HyMAS) Architecture and Design Accommodations  

NASA Technical Reports Server (NTRS)

The Hyperspectral Microwave Atmospheric Sounder (HyMAS) is being developed at Lincoln Laboratories and accommodated by the Goddard Space Flight Center for a flight opportunity on a NASA research aircraft. The term "hyperspectral microwave" is used to indicate an all-weather sounding that performs equivalent to hyperspectral infrared sounders in clear air with vertical resolution of approximately 1 km. Deploying the HyMAS equipped scanhead with the existing Conical Scanning Microwave Imaging Radiometer (CoSMIR) shortens the path to a flight demonstration. Hyperspectral microwave is achieved through the use of independent RF antennas that sample the volume of the Earth s atmosphere through various levels of frequencies, thereby producing a set of dense, spaced vertical weighting functions. The simulations proposed for HyMAS 118/183-GHz system should yield surface precipitation rate and water path retrievals for small hail, soft hail, or snow pellets, snow, rainwater, etc. with accuracies comparable to those of the Advanced Technology Microwave Sounder. Further improvements in retrieval methodology (for example, polarization exploitation) are expected. The CoSMIR instrument is a packaging concept re-used on HyMAS to ease the integration features of the scanhead. The HyMAS scanhead will include an ultra-compact Intermediate Frequency Processor (IFP) module that is mounted inside the door to improve thermal management. The IFP is fabricated with materials made of Low-Temperature Co-fired Ceramic (LTCC) technology integrated with detectors, amplifiers, A/D conversion and data aggregation. The IFP will put out 52 channels of 16 bit data comprised of 4-9 channel data streams for temperature profiles and 2-8 channel streams for water vapor. With the limited volume of the existing CoSMIR scanhead and new HyMAS front end components, the HyMAS team at Goddard began preliminary layout work inside the new drum. Importing and re-using models of the shell, the scan head computer, and the slip rings developed for CoSMIR was the starting point. The next step was to modify the antenna faceplate to accommodate the dimensions of the three dual polarization Gaussian Optics Antenna (GOA) assemblies. Two mechanical concepts for the core technology, the hyperspectral IFP, were captured in a design tradeoff. Connector models considered minimum bend radii for the IFP analog connectors. Hyperspectral imaging is accomplished by strategically using a short wavelength intermediate frequency of 18-29 GHz, and thus reducing the size of components in the connection of the front end to the IFP. The SMK (2.92mm) Series connector will lay near the hinge line to minimize its flexing. The digital output of the IFP will use a Serial Peripheral Interface (SPI) that must be accommodated by the scan head computer. To make that computer more reliable, maintainable, and forward compatible with the 52 HyMAS channels, a testbed of the scan head, calibration, and archive computers and the PIC24 microprocessor that resides on the IFP is in development. The computers will be programmed using a new framework application called Interoperable Remote Component (IRC). This software allows flexibility to program computers that communicate with each other and can adapt easily to the emerging HyMAS requirements for data format, algorithms, and graphical user interface (GUI). It is expected that the CoSMIR instrument will cut over to the IRC after it is adapted on an updated CoSMIR testbed.

Hilliard, Lawrence; Racette, Paul; Blackwell, William; Galbraith, Christopher; Thompson, Erik

2013-01-01