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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

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

PubMed Central

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these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents.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

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

2013-01-01

4

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

5

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

PubMed Central

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

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

2013-01-01

6

HR-MAS NMR spectroscopy: an innovative tool for the characterization of iron oxide nanoparticles tracers for molecular imaging.  

PubMed

The development of molecular imaging by MRI requires the use of contrast agents able to recognize specifically a peculiar target at the molecular level. Iron oxide nanoparticles grafted with small organic molecules represent an interesting platform for molecular imaging. The characterization of the surface of these nanoparticles is an important step in the development of these molecular agents, and HR-MAS NMR spectroscopy appears to be a very interesting tool. The use of 1D and 2D NMR spectra is indeed very helpful to investigate the covalent grafting of organic molecules at the nanoparticle surface. DOSY spectra could also be very helpful, but we will show here that it is not possible to obtain accurate DOSY spectra on iron oxide nanoparticles. PMID:25544033

Henoumont, Céline; Laurent, Sophie; Muller, Robert N; Vander Elst, Luce

2015-02-01

7

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

García-Álvarez, Isabel; Garrido, Leoncio; Romero-Ramírez, Lorenzo; Nieto-Sampedro, Manuel; Fernández-Mayoralas, Alfonso; Campos-Olivas, Ramón

2013-01-01

8

Rapid 3D MAS NMR Spectroscopy at Critical Sensitivity  

E-print Network

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

Matsuki, Yoh

9

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

10

Broadband solid-state MAS NMR of paramagnetic systems.  

PubMed

The combination of new magnet and probe technology with increasingly sophisticated pulse sequences has resulted in an increase in the number of applications of solid-state nuclear magnetic resonance (NMR) spectroscopy to paramagnetic materials and biomolecules. The interaction between the paramagnetic metal ions and the NMR-active nuclei often yields crucial structural or electronic information about the system. In particular the application of magic-angle spinning (MAS) has been shown to be crucial to obtaining resolution that is sufficiently high for studying complex systems. However such systems are generally extremely difficult to study as the shifts and shift anisotropies resulting from the same paramagnetic interaction broaden the spectrum beyond excitation and detection, and the paramagnetic relaxation enhancement (PRE) shortens the lifetimes of the excited signals considerably. One specific area that has therefore been receiving significant attention in recent years, and for which great improvements have been seen, is the development of broadband NMR sequences. The development of new excitation and inversion sequences for paramagnetic systems under MAS has often made the difference between the spectrum being unobtainable, and a complete NMR study being possible. However the development of the new sequences must explicitly take account of the modulation of the anisotropic shift interactions due to the sample rotation, with the resulting spin dynamics often being complicated considerably. The NMR sequences can either be helped or hindered by MAS, with the efficiency of some pulse schemes being destroyed, and others being greatly enhanced. This review describes the pulse sequences that have recently been proposed for broadband excitation, inversion, and refocussing of the signal components of paramagnetic systems. In doing so we define exactly what is meant by "broadband" under spinning conditions, and what the perfect pulse scheme should deliver. We also give a unified description of the spin dynamics under MAS which highlights the strengths and weaknesses of the various schemes, and which can be used as guidance for future research in this area. All the reviewed pulse schemes are evaluated both with simulations and experimental data obtained on the battery material LiFe0.5Mn0.5PO4 which is typical of the complexity of the paramagnetic systems that are currently under study. PMID:25669740

Pell, Andrew J; Pintacuda, Guido

2015-02-01

11

Neutron diffraction and MAS NMR of Cesium Tungstate defect pyrochlores  

SciTech Connect

Defect-pyrochlores based on the formulation CsM {sub 0.5}W{sub 1.5}O{sub 6} (M=Ti, Ti/Zr, Zr and Hf) have been studied using neutron diffraction and magic-angle spinning nuclear magnetic resonance (MAS NMR). The results show that structural changes are linearly linked to the change in ionic-radius for the B-site, e.g. the unit cell changes from 10.2763 A for CsTi{sub 0.5}W{sub 1.5}O{sub 6} to 10.3820 A for CsZr{sub 0.4}W{sub 1.6}O{sub 6}. Changes in the NMR chemical shift correlate with the change in electronegativity on the B-site, and show the presence of only one Cs crystal site.

Whittle, K.R. [Department of Earth Sciences, Cambridge Centre for Ceramic Immobilisation (C3i), University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)]. E-mail: kwhi02@esc.cam.ac.uk; Lumpkin, G.R. [Department of Earth Sciences, Cambridge Centre for Ceramic Immobilisation (C3i), University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Ashbrook, S.E. [Department of Earth Sciences, Cambridge Centre for Ceramic Immobilisation (C3i), University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)

2006-02-15

12

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

PubMed Central

High Resolution – Magic Angle Spinning (HR-MAS) spectroscopy provides rich biochemical profiles that require accurate quantification to permit biomarker identification and to understand the underlying pathological mechanisms. Meanwhile, quantification of HR-MAS data from prostate tissue samples is challenging due to significant overlap between the resonant peaks, the presence of short T2? metabolites such as citrate or polyamines (T2 from 25 to 100 msec) and macromolecules, and variations in chemical shifts and T2?s within a metabolite’s spin systems. Since existing methods do not address these challenges completely, a new quantification method was developed and optimized for HR-MAS data acquired with an ultra short TE and over 30,000 data points. The proposed method, named HR-QUEST (High Resolution – QUEST), iteratively employs the QUEST time-domain semi-parametric strategy with a new model function that incorporates prior knowledge from whole and subdivided metabolite signals. With these features, HR-QUEST is able to independently fit the chemical shifts and T2?s of a metabolite’s spin systems, a necessity for HR-MAS data. By using the iterative fitting approach, it is able to account for significant contributions from macromolecules and to handle shorter T2 metabolites, such as citrate and polyamines. After subdividing the necessary metabolite basis signals, the root mean square (RMS) of the residual was reduced by 52% for measured HR-MAS data from prostate tissue. Monte Carlo studies on simulated spectra with varied macromolecular contributions showed that the iterative fitting approach (6 iterations) coupled with inclusion of long T2 macromolecule components in the basis set improve the quality of the fit, as assessed by the reduction of the RMS of the residual and of the RMS error of the metabolite signal estimate, by 27% and 71% respectively. With this optimized configuration, HR-QUEST was applied to measured HR-MAS prostate data and reliably quantified 16 metabolites and reference signals with estimated Cramér Rao Bounds ?5%. PMID:20842756

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

2011-01-01

13

A 31P and 1H MAS NMR study of phosphate sorption onto calcium carbonate  

Microsoft Academic Search

The sorption of inorganic phosphate by two calcium carbonates, characterized by specific surface areas equivalent to 0.37 and 22 m 2 g-~, is studied using ~H and 3~p MAS NMR spectroscopy. The 3~p MAS and CP-MAS NMR spectra of the low-phosphate-concentration (0.79 ~mol P sorbed g-1 CaCO3) sample show that the sorbed phosphate is most likely unprotonated, but the 3~p

Z. R. HINEDI; S. GOLDBERG; A. C. CHANG

1992-01-01

14

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

E-print Network

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 ...

Ravera, Enrico

15

Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy  

E-print Network

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

Debelouchina, Galia T.

16

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

NASA Astrophysics Data System (ADS)

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

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

2004-04-01

17

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

PubMed

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

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

2004-04-01

18

Broadband solid-state MAS NMR of paramagnetic systems  

E-print Network

paramagnetic benchmark material The chosen paramagnetic system to illustrate the various concepts and properties of the broadband NMR sequences is the olivine LiFe0.5Mn0.5PO4, which is a cathode ma- terial [40, 41], comprising TMO6 octahedra and PO4 tetrahedra... .5Mn0.5PO4. The olivine crystal structure is shown in (a) showing the TMO6 octahedra, PO4 tetrahedra, and one-dimensional channels occupied by Li. In (b) is shown the local structure of the P site, which is coordinating to five transition-metal ion...

Pell, Andrew J.; Pintacuda, Guido

2014-12-26

19

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

20

1H High Resolution Magic-Angle Coil Spinning (HR-MACS) - NMR Metabolic Profiling of whole Saccharomyces cervisiae cells: A Demonstrative Study  

NASA Astrophysics Data System (ADS)

The low sensitivity of Nuclear Magnetic Resonance (NMR) is its prime shortcoming compared to other analytical methods for metabolomic studies. It relies on large sample volume (30–50 µl for HR-MAS) for rich metabolic profiling, hindering high-throughput screening especially when the sample requires a labor-intensive preparation or is a sacred specimen. This is indeed the case for some living organisms. This study evaluates a 1H HR-MAS approach for metabolic profiling of small volume (250 nl) whole bacterial cells, Saccharomyces cervisiae, using an emerging micro-NMR technology: high-resolution magic-angle coil spinning (HR-MACS). As a demonstrative study for whole cells, we perform two independent metabolomics studies identifying the significant metabolites associated with osmotic stress and aging.

Wong, Alan; Boutin, Celine; Aguiar, Pedro

2014-06-01

21

New options for measuring molecular diffusion in zeolites by MAS PFG NMR  

NASA Astrophysics Data System (ADS)

Combination of pulsed field gradient (PFG) NMR with magic-angle spinning (MAS) NMR is demonstrated to have remarkable advantages in comparison with conventional PFG NMR, if applied to diffusion measurements in beds of nanoporous particles, notably zeolites. These advantages are based on the effect of line narrowing and concern: (i) a prolongation of the intervals during which the magnetic field gradients may be applied and a corresponding enhancement in the sensitivity towards small molecular displacements, and (ii) an enhanced resolution in the chemical shift scale. Both options are illustrated by measuring the diffusion coefficient of n-butane adsorbed in silicalite-1.

Pampel, André; Fernandez, Moisés; Freude, Dieter; Kärger, Jörg

2005-05-01

22

Water solubility mechanism in hydrous aluminosilicate glasses: information from 27Al MAS and MQMAS NMR  

NASA Astrophysics Data System (ADS)

New 27Al NMR data are presented in order to clarify the discrepancies in the interpretation of the previous 27Al Magic Angle Spinning (MAS) spectra from hydrous aluminosilicate glasses. The 27Al MAS data have been collected at much higher magnetic field (14.1 and 17.6 T) than hitherto, and in addition, multiple quantum (MQ) MAS NMR data are presented for dry and hydrous nepheline glasses and NaAlSi 7.7O 17.4 glass that, according to the model of Zeng et al. (Zeng Q., Nekvasil H., and Grey C. P. 2000. In support of a depolymerisation model for water in sodium aluminosilicate glasses: Information from NMR spectroscopy. Geochim. Cosmochim. Acta64, 883-896), should produce a high fraction (up to 30%) of Al in Al Q 3-OH on hydration. Although small differences in the MAS spectra of anhydrous and hydrous nepheline glasses are observed, there is no evidence for the existence of significant (>˜2%) amounts of Q 3 Al-OH in these glasses in either the MAS or MQMAS data.

Padro, D.; Schmidt, B. C.; Dupree, R.

2003-04-01

23

13C CP/MAS NMR study of a genistein/piperazine complex  

NASA Astrophysics Data System (ADS)

13C CP/MAS NMR indicates that piperazine forms a hydrogen bond with the C7?OH group of genistein. The hydroxyl proton is transferred to the piperazine nitrogen atom. It is shown that the I- I*- S model of the polarization transfer in isolated spin clusters is also valid for quaternary carbon atoms.

Kolodziejski, Waclaw; Mazurek, Aleksander P.; Kasprzycka-Guttman, Teresa

2000-09-01

24

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

Microsoft Academic Search

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

R. Teeäär; R. Serimaa; T. Paakkarl

1987-01-01

25

Optimized multiple quantum MAS lineshape simulations in solid state NMR  

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

26

Using heat to control the sample spinning speed in MAS NMR  

NASA Astrophysics Data System (ADS)

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.

Mihaliuk, Eugene; Gullion, Terry

2011-10-01

27

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

28

High-speed MAS-NMR investigations on radiation-modified fluoropolymers.  

PubMed

Fluoropolymers possess an interesting combination of physical and chemical properties. In order to utilize these properties in combination with other materials, the compatibility of the fluoropolymers with those materials has to be improved by a suitable modification process. As one modification process the irradiation with high-energy electrons has been applied. High-speed MAS solid-state NMR has been used to characterize the structural changes in fluoropolymers resulting from the irradiation. The high MAS rotation frequencies, applied here, average the anisotropy of the chemical shift and the homonuclear dipolar coupling. Despite the fact that the electron irradiation results in a low concentration of modifications, the dynamic range of the solid-state NMR experiment is sufficient to detect and characterize the modifications. PMID:9808291

Scheler, U

1998-08-01

29

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

Microsoft Academic Search

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

Xiandong Cong; R. James Kirkpatrick

1996-01-01

30

15N CP\\/MAS NMR as an instrument in structure investigations of organosilicon polymers  

Microsoft Academic Search

15N solid state NMR without enrichment is rarely used because of the low sensitivity and low natural abundance of this nucleus.\\u000a As demonstrated on different nitrogen-containing polysilanes and polysilazanes, it can be shown that with the CP\\/MAS technique\\u000a spectra can be obtained in good quality and within acceptable measuring time. Three main different nitrogen sites – NSi3, NSi2H and NSiH2–

E. Brendler; E. Ebrecht; B. Thomas; G. Boden; T. Breuning

1999-01-01

31

High-speed MAS-NMR investigations on radiation-modified fluoropolymers  

Microsoft Academic Search

Fluoropolymers possess an interesting combination of physical and chemical properties. In order to utilize these properties in combination with other materials, the compatibility of the fluoropolymers with those materials has to be improved by a suitable modification process. As one modification process the irradiation with high-energy electrons has been applied. High-speed MAS solid-state NMR has been used to characterize the

Ulrich Scheler

1998-01-01

32

Effects of fluoride on in vitro enamel demineralization analyzed by ¹?F MAS-NMR.  

PubMed

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

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

2013-01-01

33

Impact of in situ MAS NMR techniques to the understanding of the mechanisms of zeolite catalyzed reactions.  

PubMed

The in situ MAS NMR studies of the mechanisms of zeolite catalyzed reactions are reviewed. The first part of the critical review contains brief information on the different experimental approaches used for the in situ MAS NMR studies under batch and flow conditions. In the second part, a cross reference index between the reactions studied, the catalysts used, the mechanistic information obtained and the corresponding literature sources is established. Finally, in the last part the most widely studied areas are discussed in more detail. In particular, the impact of in situ MAS NMR to unravel the mechanisms of olefin, alcohol and alkanes transformations over zeolite catalysts is analyzed (232 references). PMID:21038049

Ivanova, Irina I; Kolyagin, Yuriy G

2010-12-01

34

A 29Si MAS-NMR study of transition metal site occupancy in forsterite  

NASA Astrophysics Data System (ADS)

In this study, we address the problem of transition metal site occupancy in Mg-rich olivine using solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Transition metal substitution in olivine can occur in either of the two crystallographically unique octahedral sites: the smaller, more symmetric M1 site or the larger, more distorted M2 site. Site occupancy of the transition metal is expected to correlate with ionic radius and d-orbital structure. In NMR spectroscopy the presence of paramagnetic ions, such as transition metal ions, can produce accessory peaks referred to as "contact shifts," due to the interaction between unpaired electrons on the paramagnetic ion locally associated with the resonating nucleus. The position and intensity of the contact shifts are dependent on the geometrical association such as bond distances and bond angles between the paramagnetic ion and the resonating nucleus. 29Si MAS-NMR spectra collected on synthetic forsterite (Mg2SiO4) doped with minor amounts (0.2-5%) of individual, divalent, paramagnetic, transition metal cations (Mn, Co, Ni, or Cu) substituting for Mg in the octahedral sites, reveals multiple contact shifts. An interpretation of the number of such contact shifts and their relative intensities correlated with structural information of possible 29Si-M1 and 29Si-M2 configurations, potentially allows for the assignment of specific transition metals to individual M1 or M2 sites. An analysis of the MAS-NMR data will potentially bring a new level of confidence to transition metal site occupancy in forsterite.

Mccarty, R. J.; Palke, A.; Stebbins, J. F.; Hartman, S.

2012-12-01

35

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

36

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

PubMed

The human voltage dependent anion channel 1 (VDAC) is a 32 kDa ?-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5-0.3 ppm for (13)C line widths and <0.5 ppm (15)N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane ?-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported assignment approach and the great potential for even more complete assignment studies and de novo structure determination via (1)H detected MAS NMR. PMID:25634301

Eddy, Matthew T; Su, Yongchao; Silvers, Robert; Andreas, Loren; Clark, Lindsay; Wagner, Gerhard; Pintacuda, Guido; Emsley, Lyndon; Griffin, Robert G

2015-04-01

37

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

38

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

39

Pulsed field gradient MAS-NMR studies of the mobility of carboplatin in cubic liquid-crystalline phases  

NASA Astrophysics Data System (ADS)

A drug delivery system with cubic liquid-crystalline phase structure (cubic phase) containing the anti-cancer drug Carboplatin is studied. It is demonstrated that the combination of pulsed field gradient (PFG) NMR and MAS-NMR is a useful tool to study the biophysical properties of a cubic phase. The linewidth in 1H-NMR spectra is narrowed by MAS, which can be exploited to perform PFG diffusion NMR experiments under high-resolution conditions. Measurement of self-diffusion coefficients of all components of the cubic phase becomes possible. The influence of polyethylene glycol chains on the drug mobility is discussed. It is shown that polyethylene glycol chains interact with Carboplatin.

Pampel, André; Michel, Dieter; Reszka, Regina

2002-05-01

40

Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy  

PubMed Central

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

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

2014-01-01

41

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

Microsoft Academic Search

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

Kristina Wickholm; Per Tomas Larsson; Tommy Iversen

1998-01-01

42

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

PubMed

Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20 with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400 degrees C in argon (DeltaT=200 degrees C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting SiCN(O):Li ceramics were basically amorphous up to temperatures of 1000 degrees C and formed LiSi(2)N(3), graphite and silicon carbide as crystalline phases at higher temperatures. (7)Li MAS NMR spectroscopy was carried out to investigate the structure of the Li-containing phases and to study the reaction path of metallic Li with polysilazane. Based on the NMR spectra, there is almost no difference found in the chemical shift of the SiCN(O):Li ceramics obtained at different temperatures. Accordingly, Li is assigned to be mainly coordinated to N and O present as contaminant element. Relaxation time measurements showed that the most mobile Li(+) species seems to be present in the product obtained in the pyrolysis temperature range between 600 and 1000 degrees C. PMID:17418540

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

2007-04-01

43

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

PubMed

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

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

2011-05-01

44

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

Microsoft Academic Search

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

Moses O Adebajo; Ray L Frost

2004-01-01

45

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

Microsoft Academic Search

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

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

1997-01-01

46

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

47

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

48

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

NASA Astrophysics Data System (ADS)

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

Lee, Sung Keun; Stebbins, Jonathan F.

2003-05-01

49

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

PubMed

Glasses have been synthesized in the system P2O5-SiO2-K2O-MgO-CaO modified by addition of MoO3. Glasses were prepared by conventional fusion method from 40 g batches. The influence of Mo-cations on the analysed glass structure was investigated by means of Raman and (31)P MAS-NMR techniques. It has been found that molybdate units can form Mo[MoO4/MoO6]-O-P and/or Mo[MoO4/MoO6]-O-Si bonds with non-bridging oxygens atoms of Q2 methaphosphate units, resulting in the transformation of chain methaphosphate structure into pyrophosphate and finally into orthophosphate structure. It has been also found that increasing amount of MoO3 in the structure of investigated glasses causes their gradual depolymerization and molybdenum ions in the analysed glass matrix act as modifying cations. PMID:25216461

Szumera, Magdalena

2015-02-25

50

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

NASA Astrophysics Data System (ADS)

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

Szumera, Magdalena

2015-02-01

51

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

PubMed

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

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

2008-09-01

52

Characterisation of strongly bonded V(V) species in VO x \\/TiO 2 catalyst by static and MAS solid-state 51 V NMR spectroscopy  

Microsoft Academic Search

51V static and MAS NMR spectroscopy of central transition is shown to be an effective method for the characterisation of strongly bonded V(V) species in VOx\\/TiO2 catalysts. Simultaneous determination of quadrupole and CSA tensors parameters (i.e., CQ, ?Q, ??, ??) from both static and MAS NMR spectra of central transition permits the extraction of all NMR parameters with a reasonable

A. A Shubin; O. B Lapina; V. M Bondareva

1999-01-01

53

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

54

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

SciTech Connect

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

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

1997-04-01

55

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

56

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

57

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

58

Molecular dynamics of spider dragline silk fiber investigated by (2)h MAS NMR.  

PubMed

The molecular dynamics of the proteins that comprise spider dragline silk were investigated with solid-state (2)H magic angle spinning (MAS) NMR line shape and spin-lattice relaxation time (T1) analysis. The experiments were performed on (2)H/(13)C/(15)N-enriched N. clavipes dragline silk fibers. The silk protein side-chain and backbone dynamics were probed for Ala-rich regions (?-sheet and 31-helical domains) in both native (dry) and supercontracted (wet) spider silk. In native (dry) silk fibers, the side chains in all Ala containing regions undergo similar fast methyl rotations (>10(9) s(-1)), while the backbone remains essentially static (<10(2) s(-1)). When the silk is wet and supercontracted, the presence of water initiates fast side-chain and backbone motions for a fraction of the ?-sheet region and 31-helicies. ?-Sheet subregion 1 ascribed to the poly(Ala) core exhibits slower dynamics, while ?-sheet subregion 2 present in the interfacial, primarily poly(Gly-Ala) region that links the ?-sheets to disordered 31-helical motifs, exhibits faster motions when the silk is supercontracted. Particularly notable is the observation of microsecond backbone motions for ?-sheet subregion 2 and 31-helicies. It is proposed that these microsecond backbone motions lead to hydrogen-bond disruption in ?-sheet subregion 2 and helps to explain the decrease in silk stiffness when the silk is wet and supercontracted. In addition, water mobilizes and softens 31-helical motifs, contributing to the increased extensibility observed when the silk is in a supercontracted state. The present study provides critical insight into the supercontraction mechanism and corresponding changes in mechanical properties observed for spider dragline silks. PMID:25619304

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

2015-03-01

59

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

60

Solid-state (13)C CP MAS NMR spectroscopy of mushrooms gives directly the ratio between proteins and polysaccharides.  

PubMed

The solid-state (13)C CP MAS NMR technique has the potential of monitoring the chemical composition in the solid state of an intact food sample. This property has been utilized to study mushrooms of different species (Pleurotus ostreatus, Pleurotus eryngii, Pleurotus pulmunarius, and Lentinula edodes), already characterized by chemical analyses for protein and dietary fiber components. Solid-state (13)C CP MAS NMR spectroscopy reveals a large difference in the ratio between the glucidic and the proteic resonances probably depending on the mushroom species. An accurate inspection by model compounds and suitable mixtures of proteins and saccharides gives a methodology to interpret these experimental data. A good correlation (R(2) = 0.93; R(2) = 0.81) has been obtained by comparing the NMR data with the results of the chemical analyses. The results suggest the possibility to perform a taxonomic study and/or a nutritional study on the basis of the ratio between protein and polysaccharide levels determined by NMR or chemical methodologies. PMID:11087506

Pizzoferrato, L; Manzi, P; Bertocchi, F; Fanelli, C; Rotilio, G; Paci, M

2000-11-01

61

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

62

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

63

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

SciTech Connect

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

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

2013-11-13

64

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

PubMed

(15)N 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 (15)N spectral intensities, we demonstrate that the significant fraction of broad signals in the 2D spectrum exhibits the most pronounced slow mobility. We show that (15)N 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. PMID:25282442

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

2014-11-01

65

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

E-print Network

. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample larger electronic magnetic moments to nuclei, which opens the possibility for NMR signals to be increased gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1 H DNP

Watts, Anthony

66

31P MAS NMR: a useful tool for the evaluation of VX natural weathering in various urban matrixes.  

PubMed

The fate of chemical warfare agent VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) in various urban matrixes was monitored utilizing 31P MAS NMR. Chosen matrixes represent buildings, roads, pavement, and earth found in urban environments. In view of the high toxicity of VX, solid state NMR afforded a fairly safe experimental mode, omitting any chance for evaporation. Moreover, due to the nondestructive nature of these experiments, measurements could be repeated over and over using the same samples. Degradation rates of VX were obtained and compared to provide a list of relative reactivity toward VX: concrete > desert sand > beach sand > asphalt approximately to bitumen sheet. Chemical interactions between VX, its degradation products, and the matrixes were often expressed by widening of the peaks to the extent that mass balance could not be achieved. It is noteworthy that these experiments were usually carried out on crushed or milled specimens, allowing high reactivity and rapid reactions. PMID:16323796

Mizrahi, Dana M; Columbus, Ishay

2005-11-15

67

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

68

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

PubMed

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

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

2014-07-01

69

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

70

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

71

Alginate monomer composition studied by solution- and solid-state NMR – A comparative chemometric study  

Microsoft Academic Search

The potential of using 1H high-resolution (HR) magic angle spinning (MAS) nuclear magnetic resonance (NMR) of alginates suspended in D2O or 13C cross-polarisation (CP) MAS NMR of alginate powders as an alternative method to the traditional 1H solution-state NMR method for the analysis of the alginate monomer composition (mannuronate (M)\\/guluronate (G) ratio) has been investigated. The MAS NMR experiments can

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

2009-01-01

72

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

PubMed

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

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

2015-01-12

73

High-resolution proton-detected NMR of proteins at very fast MAS.  

PubMed

When combined with high-frequency (currently ?60kHz) magic-angle spinning (MAS), proton detection boosts sensitivity and increases coherence lifetimes, resulting in narrow ((1))H lines. Herein, we review methods for efficient proton detected techniques and applications in highly deuterated proteins, with an emphasis on 100% selected ((1))H site concentration for the purpose of sensitivity. We discuss the factors affecting resolution and sensitivity that have resulted in higher and higher frequency MAS. Next we describe the various methods that have been used for backbone and side-chain assignment with proton detection, highlighting the efficient use of scalar-based ((13))C-((13))C transfers. Additionally, we show new spectra making use of these schemes for side-chain assignment of methyl ((13))C-((1))H resonances. The rapid acquisition of resolved 2D spectra with proton detection allows efficient measurement of relaxation parameters used as a measure of dynamic processes. Under rapid MAS, relaxation times can be measured in a site-specific manner in medium-sized proteins, enabling the investigation of molecular motions at high resolution. Additionally, we discuss methods for measurement of structural parameters, including measurement of internuclear ((1))H-((1))H contacts and the use of paramagnetic effects in the determination of global structure. PMID:25797003

Andreas, Loren B; Le Marchand, Tanguy; Jaudzems, Kristaps; Pintacuda, Guido

2015-04-01

74

Low-power XiX decoupling in MAS NMR experiments.  

PubMed

Low-power XiX proton decoupling under fast magic-angle spinning is introduced. The method is applicable if the MAS frequency exceeds the proton-proton interactions. For rigid organic solids this is the case for MAS frequencies above approximately 40 kHz. It is shown that the quality of the decoupling as well as the sensitivity to frequency offsets can be improved compared to low-power continuous-wave decoupling. The decoupling efficiency is somewhat reduced compared to optimized high-power decoupling: in a peptide sample investigated at an MAS frequency of 50 kHz a loss of about 10% in signal intensity for CH3 and CH groups, and of about 40% for CH2 groups was observed. Taking into consideration, that the rf amplitude in the low-power XiX was about 15 times lower than in high-power XiX decoupling, such a reduction in line intensity is sometimes tolerable. PMID:12914849

Ernst, Matthias; Samoson, Ago; Meier, Beat H

2003-08-01

75

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

SciTech Connect

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

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

1994-07-01

76

17O MAS NMR and first principles calculations of ZrO2 polymorphs  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

77

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

PubMed

We demonstrate that a very simple experiment, Cross-Polarization with Variable Contact-time (CP-VC), is very efficient at ultra-fast MAS (?R ? 60 kHz) to measure accurately the C-H and N-H distances, and to analyze the dynamics of bio-molecules. This experiment can be performed with samples that are either (13)C or (15)N labeled or without any labeling. The method is very robust experimentally with respect to imperfect Hartman-Hahn setting, and presents a large scaling factor allowing a better dipolar determination, especially for long C-H or N-H distances, or for CH3 or NH3 moieties with three-site hopping. At ultra-fast MAS, it can be used quantitatively in a 2D way, because its scaling factor is then little dependent on the offsets. This robustness with respect to offset is related to the ultra-fast spinning speed, and hence to the related small rotor diameter. Indeed, these two specifications lead to efficient n = ±1 zero-quantum Hartman-Hahn CP-transfers with large RF-fields on proton and carbon or nitrogen channels, and large dipolar scaling factor. PMID:23727588

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

2013-08-01

78

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

PubMed

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

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

2015-01-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

80

A CP-MAS NMR study of n-alkanes included in urea: conformational dependences of the substituent effects for n-substituted alkanes  

NASA Astrophysics Data System (ADS)

Solid state CP-MAS NMR spectra have been obtained for the urea inclusion complexes of the substituted alkanes; tridecane, myristyl alcohol, dioctylamine, myristic acid, and stearonitrile. Changes in the substituent effects on the chemical shift values, on inclusion complex formation, from those of solution NMR spectra are discussed on the assumption that long-chain molecules in urea inclusion complexes have the all- trans conformation.

Okazaki, Masaharu; McDowell, Charles A.

1984-08-01

81

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

82

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

83

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

NASA Astrophysics Data System (ADS)

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

Adebajo, Moses O.; Frost, Ray L.

2004-08-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

85

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

SciTech Connect

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

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

1999-11-19

86

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

PubMed

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

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

2015-01-01

87

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

88

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

SciTech Connect

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

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

2014-01-07

89

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

90

The structural environments of cations adsorbed onto clays: A sup 133 CsMAS NMR spectroscopic study  

SciTech Connect

Chapter One investigates the local structural environment of adsorbed cations on the mineral hectorite using {sup 133}Ca Variable-Temperature Magic-Angle-Spinning Nuclear Magnetic Resonance (VT-MAS NMR) spectroscopy. The results show that Cs on hectorite occurs in several distinctly different chemical environments, and that motional averaging of Ca between some of these sites occurs above {approximately}{minus}40{degree}C if water is present in the interlayer. Above {approximately}{minus}10{degree}C, spectra for slurries of hectorite in CsCl solutions yield two peaks, one due to Cs in solution, and the other due to Cs motionally-averaged on the clay. Below {approximately}{minus}60{degree}C, motional averaging of the adsorbed Cs slows sufficiently to allow resolution of two peaks representing different Cs-environments on the clay. The Stern-Gouy model is employed to explain these peaks and assign one to Cs in the Stern layer (relatively tightly bound to the basal oxygens), and the other to Cs in the Gouy diffuse layer. Between {approximately}{minus}60 and {approximately}{minus}10{degree}C peaks for these two sites and a motionally-averaged peak are present. Cs-exchanged hectorite dehydrated at 500{degree}C yields peaks for two different sites on the clay, interpreted to be highly coordinated site (probably 12), and a less coordinated site (possibly 9), both in the interlayer. Chapter II discusses {sup 133}Cs MAS NMR results for a number of other Cs-exchanged clays and the relationship of chemical and structural parameters to the {sup 133}Cs chemical shift. Increased rotational distortions of the basal oxygen sheet, total layer charge and tetrahedral Al{sup 3+} for Si{sup 4+} substitution correlate with increased deshielding of the {sup 133}Cs chemical shifts for both hydrated slurry and anhydrous samples. Correlations for the slurries are poorer because of the distances between the clay silicate and the CO in solution.

Weiss, C.A. Jr.

1989-01-01

91

Enhanced sensitivity in high-resolution 1H solid-state NMR spectroscopy with DUMBO dipolar decoupling under ultra-fast MAS  

NASA Astrophysics Data System (ADS)

The solid-state NMR 1H homonuclear decoupling sequences in the DUMBO family are shown to be effective at ultra-fast MAS rates of up to 65 kHz. The sequences are applied to model compounds glycine and [2- 13C]- L-alanine as well as the dipeptide ?- L-Asp- L-Ala in windowed and continuous phase-modulated versions. They are shown to achieve especially impressive resolution when implemented in a 2D constant-time experiment. At 65 kHz MAS, 1H resolution using homonuclear decoupling is similar to that obtained at lower MAS rates, but peak intensity, and therefore spectral sensitivity, is improved by a factor of 5 over homonuclear-decoupled spectra at 10 kHz MAS.

Salager, Elodie; Stein, Robin S.; Steuernagel, Stefan; Lesage, Anne; Elena, Bénédicte; Emsley, Lyndon

2009-02-01

92

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

PubMed

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

Tatsuno, Hiroto; Aimi, Keitaro; Ando, Shinji

2007-05-01

93

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

SciTech Connect

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

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

1996-12-01

94

SILICON-29 Mas-Nmr and Esr Study on the Effect of Heat Treatment on the Structure of SiC-Si3N4 Composite Ultrafine Particles  

NASA Astrophysics Data System (ADS)

The effect of heat treatment on the structure of SiC-Si3N4 composite ultrafine particles was studied by 29Si MAS-NMR and ESR. 29Si MAS-NMR and ESR results showed that the local structure changed a little below 1573 K, at which the XRD pattern did not change significantly, but slight increase in crystalline size were observed. When the SiC-Si3N4 powder was heat-treated at 1773 K, most nitrogen atoms dissolved into ?-SiC lattice were removed from the ?-SiC lattice, and the remaining nitrogens were considered to exist in the boundary layer between SiC crystals as SiC3N unit in the particle.

Suzuki, Masaaki; Li, Xingguo; Nakata, Yoshinori; Nagai, Hideaki; Okutani, Takeshi

95

{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

96

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

Microsoft Academic Search

Multivariate curve resolution (MCR) was applied to 13C cross-polarisation (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of non-depolymerised alginate powders obtained from brown seaweed plus a pure mannuronate sample isolated from Pseudomonas fluorescens for estimation of the mannuronic acid\\/guluronic acid ratio (M\\/G ratio). An excellent MCR model with a correlation coefficient of r2=0.99 was established between the

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

2009-01-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

98

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

99

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

E-print Network

Resonance assignment is the first step in NMR structure determination. For magic angle spinning NMR, this is typically achieved with a set of heteronuclear correlation experiments (NCaCX, NCOCX, CONCa) that utilize SPECIFIC-CP ...

Daviso, Eugenio

100

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

101

(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

102

Global fold of human cannabinoid type 2 receptor probed by solid-state 13C-, 15N-MAS NMR and molecular dynamics simulations.  

PubMed

The global fold of human cannabinoid type 2 (CB2 ) receptor in the agonist-bound active state in lipid bilayers was investigated by solid-state (13)C- and (15)N magic-angle spinning (MAS) NMR, in combination with chemical-shift prediction from a structural model of the receptor obtained by microsecond-long molecular dynamics (MD) simulations. Uniformly (13)C- and (15)N-labeled CB2 receptor was expressed in milligram quantities by bacterial fermentation, purified, and functionally reconstituted into liposomes. (13)C MAS NMR spectra were recorded without sensitivity enhancement for direct comparison of C?, C?, and C=O bands of superimposed resonances with predictions from protein structures generated by MD. The experimental NMR spectra matched the calculated spectra reasonably well indicating agreement of the global fold of the protein between experiment and simulations. In particular, the (13) C chemical shift distribution of C? resonances was shown to be very sensitive to both the primary amino acid sequence and the secondary structure of CB2. Thus the shape of the C? band can be used as an indicator of CB2 global fold. The prediction from MD simulations indicated that upon receptor activation a rather limited number of amino acid residues, mainly located in the extracellular Loop 2 and the second half of intracellular Loop 3, change their chemical shifts significantly (? 1.5 ppm for carbons and ? 5.0 ppm for nitrogens). Simulated two-dimensional (13) C?(i)-(13)C=O(i) and (13)C=O(i)-(15)NH(i + 1) dipolar-interaction correlation spectra provide guidance for selective amino acid labeling and signal assignment schemes to study the molecular mechanism of activation of CB2 by solid-state MAS NMR. PMID:23999926

Kimura, Tomohiro; Vukoti, Krishna; Lynch, Diane L; Hurst, Dow P; Grossfield, Alan; Pitman, Michael C; Reggio, Patricia H; Yeliseev, Alexei A; Gawrisch, Klaus

2014-03-01

103

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

PubMed

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

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

2009-10-12

104

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

105

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

106

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

107

Ultrafast MAS solid-state NMR permits extensive 13C and 1H detection in paramagnetic metalloproteins.  

PubMed

We show here that by combining tailored approaches based on ultrafast (60 kHz) MAS on the Co(II)-replaced catalytic domain of matrix metalloproteinase 12 (CoMMP-12) we can observe and assign, in a highly paramagnetic protein in the solid state, (13)C and even (1)H resonances from the residues coordinating the metal center. In addition, by exploiting the enhanced relaxation caused by the paramagnetic center, and the low power irradiation enabled by the fast MAS, this can be achieved in remarkably short times and at very high field (21.2 T), with only less than 1 mg of sample. Furthermore, using the known crystal structure of the compound, we are able to distinguish and measure pseudocontact (PCS) contributions to the shifts up to the coordinating ligands and to unveil structural information. PMID:20356036

Bertini, Ivano; Emsley, Lyndon; Lelli, Moreno; Luchinat, Claudio; Mao, Jiafei; Pintacuda, Guido

2010-04-28

108

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

PubMed

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

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

2015-02-01

109

Analysis of affinity supports by 13C CP/MAS NMR spectroscopy: application to carbonyldiimidazole- and novel tresyl chloride-synthesized agarose and silica gels.  

PubMed

A major problem in affinity technology is the analysis of the synthesized solid supports, since liquid phase methodology can generally not be applied. Recently we reported a novel reaction sequence for the 2,2,2-trifluoroethanesulfonyl chloride (tresyl chloride) coupling of nucleophiles [Demiroglou et al. (1994) Angew. Chem. Int. Ed. Engl. 33, 120-123] to agarose and concluded that previously proposed structures could not be correct. However it was not possible for us to conclusively define the new reaction products because the agarose derivatives could not be solubilized for customary liquid state 13C NMR analysis. Therefore in this paper solid state 13C CP/MAS NMR spectroscopy is applied for the first time to the polysacharide agarose. Using alkyl agarose derivatives prepared by the carbonyldiimidazol method as control we found that reliable spectra in agreement with the published reaction mechanism could be obtained. The method was then applied to the novel reaction products of the tresyl chloride reaction. From the solid state 13C NMR spectra and other quantitative data it is concluded that a beta-sulfonyl carboxylic acid is generated during alkaline hydrolysis of tresyl agarose and that alkyl amines are coupled by a beta-sulfonyl amide bond in an elimination-addition reaction in the absence of SO- and SC-scission of the tresyl group. In the case of alkane thiol coupling the absence of SC-scission cannot be demonstrated indicating either a different reaction mechanism or possibly a mixture of reaction products. PMID:9052977

Zumbrink, T; Demiroglou, A; Jennissen, H P

1995-01-01

110

Use of CP\\/MAS solid-state NMR for the characterization of solvate molecules within estradiol crystal forms  

Microsoft Academic Search

To investigate the solvate molecules within estradiol crystal forms, four crystal forms of estradiol (EM, ET, EP and EC) were obtained by recrystallization from various organic solvents such as methanol, ethanol, isopropanol and acetone, and their physicochemical properties were characterized using XRD, TGA, DSC and solid-state NMR. The XRD patterns showed that the estradiol crystal forms were composed of high

Jeong-Sook Park; Hye Won Kang; Sung Jean Park; Chong-Kook Kim

2005-01-01

111

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

PubMed

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

Malfait, Wim J; Xue, Xianyu

2010-01-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

114

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

115

Crystal structure of ionic and non-ionic surfactants based on polyoxyethylenated dodecanol: A 13 C-CP-MAS-NMR and x-ray investigation  

Microsoft Academic Search

Crystal structure of monodisperse non-ionic surfactants having the general formula C12H25O-(CH2-CH2-O)nH (C12En),n=7,9, 10, 15, 16 and ionic derivatives, C12H25-O-(CH2-CH2-O)n-CH2COONa (C12EnC),n=3,4,5,6,7,9, 12 has been investigated by13C-CP-MAS-NMR and x-ray diffraction. A structural model, in which aliphatic and polyether segments are segregated in bilayers stacking parallel to the elongation direction of the molecules, fits the experimental data for both series. The experimental values

C. Corno; S. Ghelli; G. Perego; E. Platone

1991-01-01

116

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

117

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

PubMed Central

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

Magusin, P C; Hemminga, M A

1994-01-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

119

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

NASA Astrophysics Data System (ADS)

Tecto-aluminosilicate and peraluminous glasses have been prepared by conventional and laser heating techniques, respectively, in the CaO-Al 2O 3-SiO 2 system. The structure of these glasses were studied using Raman spectroscopy, X-ray absorption at the Al K-edge and 27Al NMR spectroscopy with two different high fields (400 and 750 MHz). Raman spectroscopy and X-ray absorption are techniques sensitive to the network polymerization and, in particular, show different signal as a function of silica content. However, these two techniques are less sensitive than NMR to describe the local aluminium environment. For tectosilicate glasses, aluminium in five-fold coordination, [5]Al, was found and a careful quantification allows the determination of a significant amount of [5]Al (7% in the anorthite glass). The proportion of [5]Al increases for the peraluminous glasses with small amounts (<2%) of six-fold coordination, [6]Al. The presence of [5]Al agrees with previous observations of the existence of nonbridging oxygens (NBOs) in tectosilicate compositions. However, the proportion of [5]Al in the present study indicates that no major proportion of triclusters (oxygen coordinated to three (Si,Al)O 4 tetrahedra) is required to explain these NBOS.

Neuville, Daniel R.; Cormier, Laurent; Massiot, Dominique

2004-12-01

120

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

121

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

122

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

NASA Astrophysics Data System (ADS)

In the upper Amazon Basin, aluminum previously accumulated in lateritic formations is massively remobilised in soils by podzolization and exported in waters. We have investigated the speciation of aluminum in the clay-size fractions of eight horizons of waterlogged podzols lying in a depression of a plateau. The horizons illustrate the main steps involved in the podzolization of laterites. They belong to eluviated topsoil A horizons and illuviated subsoil Bhs, Bh and 2BCs horizons of weakly and better-expressed podzols located at the margin and centre of the depression. For the first time, aluminum speciation is quantitatively assessed in soils by spectroscopic methods, namely FTIR, 27Al magic angle spinning (MAS) and multiple-quantum magic angle spinning (MQMAS), nuclear magnetic resonance (NMR). The results thus obtained are compared to chemical extraction data. Solid-state 27Al MAS NMR spectra enable to distinguish Al bound to organic compounds from that incorporated in secondary mineral phases detected by FTIR. MQMAS experiments additionally show that both chemical shifts and quadrupolar constants are distributed for Al nuclei linked with organic compounds. Similar amounts of chelated Al are obtained from NMR spectra and chemical extractions. The study enables to highlight three major steps in the fate of aluminum. (i) Aluminum is first released by mineral weathering, feeds complexing sites of organic matter and accumulates in subsurface Bhs horizons of weakly expressed podzols (acidocomplexolysis). (ii) Complexes of aluminum with organic matter (Al-OM) then migrate downwards in sandy horizons of better-expressed podzols and accumulate at depth in less permeable 2BCs horizons. (iii) The minor amounts of aluminum present in the 2BCs horizon of the downslope podzol show that aluminum is eventually exported towards the river network, either complexed with organic matter or as Al 3+ ions after desorption from organic compounds, due to decreasing pH or biodegradation of organic ligands. The direct spectroscopic determination of Al-speciation during the formation of podzolic soils opens new perspectives to trace metal loads in the rivers of the upper Amazon Basin.

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

2007-07-01

123

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

NASA Astrophysics Data System (ADS)

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

Kim, Hyun Na; Lee, Sung Keun

2013-11-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

125

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

NASA Astrophysics Data System (ADS)

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

Dou, S.

2009-04-01

126

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

127

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

PubMed Central

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

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

2013-01-01

128

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

SciTech Connect

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

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

2012-07-15

129

In situ variable-temperature MAS sup 13 C NMR study of the reactions of isobutylene in zeolites HY and HZSM-5  

SciTech Connect

The low-temperature chemistry of isobutylene in zeolites HY and HZSM-5 was probed by in situ variable-temperature {sup 13}C NMR spectroscopy with magic-angle spinning (MAS). Isobutylene interacts with Bronsted acid sites of the zeolites at a temperature of ca. 123 K to form a hydrogen-bonded species, as indicated by 2{sup 13}{Delta}{delta} value (relative to the 2-{sup 13}C resonance of isobutylene) of 12 ppm in HY and a {Delta}{delta} value of 16 ppm in HZSM-5. The greater {Delta}{delta} value observed for hydrogen-bonded isobutylene in HZSM-5 is consistent with the acid sites in HZSM-5 being more acidic than those in HY. The maximum number of hydrogen-bonded species detected did not exceed the number of Bronsted acid sites in the zeolites. As the temperature was raised from 123 K, hydrogen-bonded isobutylene was presumably converted to an unobserved symmetrical intermediate (a tert-butylcarbenium ion) that either underwent deprotonation to re-form isobutylene and the acid site or reacted with another isobutylene molecule to form a dimer. Evidence for this process included scrambling between the 1- and 3-{sup 13}C labels of isobutylene. In all of the spectra obtained by either cross polarization or single-pulse excitation, no peaks were observed that could be assigned to a surface-bound silyl ether species. However, in experiments performed on the 2-methyl-2-propanol-2-{sup 13}C/HZSM-5 system, the formation of a surface-bound tert-butyl silyl ether species was observed, as was reported earlier by another laboratory.

Lazo, N.D.; Richardson, B.R.; Schettler, P.D.; White, J.L.; Munson, E.J.; Haw, J.F. (Texas A and M Coll., College Station (United States))

1991-11-14

130

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

131

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

132

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

133

Direct observation of 17O-185/187Re 1J-coupling in perrhenates by solid-state 17O VT MAS NMR: Temperature and self-decoupling effects  

NASA Astrophysics Data System (ADS)

17O MAS NMR spectra recorded at 14.1 T and room temperature (RT) for 17O-enriched samples of the two perrhenates, KReO4 and NH4ReO4, exhibit very similar overall appearances of the manifold of spinning sidebands (ssbs) for the satellite transitions (STs) and the central transition (CT). These overall appearances of the spectra are easily simulated in terms of the usual quadrupole coupling and chemical shift interaction parameters. However, a detailed inspection of the line shapes for the individual ssbs of the STs and, in particular, for the CT in the spectrum of KReO4 reveals line-shape features, which to our knowledge have not before been observed experimentally in 1D MAS NMR spectra for any quadrupolar nucleus, nor emerged from simulations for any combination of second-order quadrupolar interaction and chemical shift anisotropy. In contrast, such line-shape features are not observed for the corresponding ssbs (STs and CT) in the 14.1 T RT 17O MAS NMR spectrum of NH4ReO4. Considering the additional interaction of a combination of residual heteronuclear 17O-185/187Re dipolar and scalar J coupling between this spin pair of two quadrupolar nuclei, spectral simulations for KReO4 show that these interactions are able to account for the observed line shapes, although the expected 1J(17O-185/187Re) six-line spin-spin splittings are not resolved. Low-temperature, high-field (21.1 T) 17O VT MAS NMR spectra of both KReO4 and NH4ReO4 show that full resolution into six-line multiplets for the centerbands are achieved at -90 °C and -138 °C, respectively. This allows determination of 1J(17O-187Re) = -268 Hz and -278 Hz for KReO4 and NH4ReO4, respectively, i.e., an isotropic 1J coupling and its sign between two quadrupolar nuclei, observed for the first time directly from solid-state one-pulse 1D MAS NMR spectra, without resort to additional 1D or 2D experiments. Determination of T1(187Re) spin-lattice relaxation times, observed indirectly through a 2D 17O EXSY experiment for NH4ReO4 at several low temperatures, show that the dynamics observed for the ReO4- anion in the 17O VT MAS NMR spectra at low temperatures are caused by self-decoupling of 1J(17O-187Re). The 1J(17O-187Re) values determined here for ReO4- from solid-state 17O MAS NMR, along with literature 1J(17O-M) values for oxoanions (M being a quadrupolar nucleus) obtained from liquid-state NMR, have allowed correlations to be established between the reduced coupling constant 1K(17O-M) = 2?1J(17O-M)/(?17O?M?) and the atomic number of M.

Jakobsen, Hans J.; Bildsøe, Henrik; Brorson, Michael; Gan, Zhehong; Hung, Ivan

2013-05-01

134

Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics.  

PubMed

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

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

2015-01-01

135

Preparation and structural organisation of heteroleptic tetraphenylantimony(V) complexes comprising unidentately and bidentately coordinated O, O?-dialkyldithiophosphate groups: Multinuclear ( 13C, 31P) CP\\/MAS NMR and single-crystal X-ray diffraction studies  

Microsoft Academic Search

O,O?-dipropyldithiophosphate and O,O?-di-iso-butyldithiophosphate (Dtph) tetraphenylantimony(V) complexes of the general formula [Sb(C6H5)4{S2P(OR)2}] (R=C3H7, i-C4H9) were prepared and studied by means of 13C, 31P CP\\/MAS NMR spectroscopy and single-crystal X-ray diffraction. Distorted octahedral and trigonal bipyramidal molecular structures have been established for prepared complexes. These unexpected structural distinctions between chemically related compounds are defined by the principally different coordination modes of O,O?-dipropyldithiophosphate

Maxim A. Ivanov; Oleg N. Antzutkin; Vladimir V. Sharutin; Alexander V. Ivanov; Antonya P. Pakusina; Mikhail A. Pushilin; Willis Forsling

2007-01-01

136

Bacteriopheophytin a in the active branch of the reaction center of rhodobacter sphaeroides is not disturbed by the protein matrix as shown by 13C photo-CIDNP MAS NMR.  

PubMed

The electronic structure of bacteriopheophytin a (BPhe a), the primary electron acceptor (?A) in photosynthetic reaction centers (RCs) of the purple bacterium Rhodobacter sphaeroides, is investigated by photochemically induced dynamic nuclear polarization (photo-CIDNP) magic-angle spinning (MAS) NMR spectroscopy at atomic resolution. By using various isotope labeling systems, introduced by adding different (13)C selectively labeled ?-aminolevulinic acid precursors in the growing medium of R. sphaeroides wild type (WT), we were able to extract light-induced (13)C NMR signals originating from the primary electron acceptor. The assignments are backed by theoretical calculations. By comparison of these chemical shifts to those obtained from monomeric BPhe a in solution, it is demonstrated that ?A in the active branch appears to be electronically close to free bacteriopheophytin. Hence, there is little effect of the protein surrounding on the cofactor functionally which contributes with its standard redox potential to the electron transfer process that is asymmetric. PMID:23452037

Sai Sankar Gupta, Karthick Babu; Alia, A; Buda, Francesco; de Groot, Huub J M; Matysik, Jörg

2013-03-28

137

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

138

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

NASA Astrophysics Data System (ADS)

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

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

2001-07-01

139

High-resolution ¹H magic angle spinning NMR spectroscopy of intact Arctic char (Salvelinus Alpinus) muscle. Quantitative analysis of n-3 fatty acids, EPA and DHA.  

PubMed

The lipid and small metabolite profiles from intact muscles of Arctic char were investigated using (1)H high-resolution magic angle spinning ((1)H HR-MAS) NMR spectroscopy. Not only the total n-3 fatty acid content but also the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents of the muscle were obtained from the (1)H HR-MAS NMR spectra without pretreatment of the tissue or lipophilic extraction. A number of small metabolites could also be observed, where creatine/phosphocreatine, anserine and taurine were the most abundant. Thus, the use of (1)H HR-MAS NMR led to simplified analysis techniques that can give direct information on the nutritional value of the fish. PMID:20873863

Nestor, Gustav; Bankefors, Johan; Schlechtriem, Christian; Brännäs, Eva; Pickova, Jana; Sandström, Corine

2010-10-27

140

2D exchange NMR spectra under slow MAS: A simplified scheme to obtain pure-phase spectra without unwanted cross peaks  

PubMed

A simplified method for acquiring pure-phase two-dimensional exchange spectra under slow magic-angle spinning (MAS) is introduced. It combines rotor-synchronized 2D exchange spectroscopy with whole-echo acquisition leading to a simplification in data acquisition and data processing compared to the States-type data sampling using "time reversal" (A. Hagemeyer et al., Adv. Magn. Reson. 13, 85 (1989)). As an added benefit, it allows for well-defined mixing times of an arbitrary integer multiple of the MAS rotor period. The proposed method is, however, only applicable to samples where an echo of the free-induction decay can be obtained, i.e., where the inhomogenous linewidth is larger than the homogeneous linewidth. This is, for example, the case in rare-spin spectroscopy of samples with natural isotopic abundance. The usefulness of the new method is demonstrated, using 13C spectroscopy, on two model compounds. Copyright 1999 Academic Press. PMID:10329227

Ernst; Kentgens; Meier

1999-05-01

141

Towards homonuclear J solid-state NMR correlation experiments for half-integer quadrupolar nuclei: experimental and simulated 11B MAS spin-echo dephasing and calculated 2J(BB) coupling constants for lithium diborate.  

PubMed

Magic-angle spinning (MAS) NMR spin-echo dephasing is systematically investigated for the spin I = 3/2 (11)B nucleus in lithium diborate, Li(2)O·2B(2)O(3). A clear dependence on the quadrupolar frequency (?(Q)(PAS)/2? = 3C(Q)/[4I(2I- 1)]) is observed: the B3 (larger C(Q)) site dephases more slowly than the B4 site at all investigated MAS frequencies (5 to 20 kHz) at 14.1 T. Increasing the MAS frequency leads to markedly slower dephasing for the B3 site, while there is a much less evident effect for the B4 site. Considering samples at 5, 25, 80 (natural abundance) and 100% (11)B isotopic abundance, dephasing becomes faster for both sites as the (11)B isotopic abundance increases. The experimental behaviour is rationalised using density matrix simulations for two and three dipolar-coupled (11)B nuclei. The experimentally observed slower dephasing for the larger C(Q) (B3) site is reproduced in all simulations and is explained by the reintroduction of the dipolar coupling by the so-called "spontaneous quadrupolar-driven recoupling mechanism" having a different dependence on the MAS frequency for different quadrupolar frequencies. Specifically, isolated spin-pair simulations show that the spontaneous quadrupolar-driven recoupling mechanism is most efficient when the quadrupolar frequency is equal to twice the MAS frequency. While for isolated spin-pair simulations, increasing the MAS frequency leads to faster dephasing, agreement with experiment is observed for three-spin simulations which additionally include the homogeneous nature of the homonuclear dipolar coupling network. First-principles calculations, using the GIPAW approach, of the (2)J(11B-11B) couplings in lithium diborate, metaborate and triborate are presented: a clear trend is revealed whereby the (2)J(11B-11B) couplings increase with increasing B-O-B bond angle and B-B distance. However, the calculated (2)J(11B-11B) couplings are small (0.95, 1.20 and 2.65 Hz in lithium diborate), thus explaining why no zero crossing due to J modulation is observed experimentally, even for the sample at 25% (11)B where significant spin-echo intensity remains out to durations of ?200 ms. PMID:21321719

Barrow, Nathan S; Yates, Jonathan R; Feller, Steven A; Holland, Diane; Ashbrook, Sharon E; Hodgkinson, Paul; Brown, Steven P

2011-04-01

142

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

NASA Astrophysics Data System (ADS)

The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the13C and15N sites and the ?-lactam ring conformation.

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

1998-11-01

143

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

144

Structural, (197)Au Mössbauer and solid state (31)P CP/MAS NMR studies on bis (cis-bis(diphenylphosphino)ethylene) gold(I) complexes [Au(dppey)(2)]X for X = PF(6), I.  

PubMed

(197)Au Mössbauer spectra for the d(10) gold(i) phosphine complexes, [Au(dppey)(2)]X (X = PF(6), I; dppey = (cis-bis(diphenylphosphino)ethylene), and the single crystal X-ray structure and solid state (31)P CPMAS NMR spectrum of [Au(dppey)(2)]I are reported here. In [Au(dppey)(2)]I the AuP(4) coordination geometry is distorted from the approximately D(2) symmetry observed for the PF(6)(-) complex with Au-P bond lengths 2.380(2)-2.426(2) A and inter-ligand P-Au-P angles 110.63(5)-137.71(8) degrees . Quadrupole splitting parameters derived from the Mössbauer spectra are consistent with the increased distortion of the AuP(4) coordination sphere with values of 1.22 and 1.46 mm s(-1) for the PF(6)(-) and I(-) complexes respectively. In the solid state (31)P CP MAS NMR spectrum of [Au(dppey)(2)]I, signals for each of the four crystallographically independent phosphorus nuclei are observed, with the magnitude of the (197)Au quadrupole coupling being sufficiently large to produce a collapse of (1)J(Au-P) splitting from quartets to doublets. The results highlight the important role played by the counter anion in the determination of the structural and spectroscopic properties of these sterically crowded d(10) complexes. PMID:18615219

Healy, Peter C; Loughrey, Bradley T; Bowmaker, Graham A; Hanna, John V

2008-07-28

145

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

PubMed

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

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

2014-02-14

146

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

147

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

148

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

149

In situ solid state 11B MAS-NMR studies of the thermal decomposition of ammonia borane: mechanistic studies of the hydrogen release pathways from a solid state hydrogen storage material.  

PubMed

The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state (11)B and (11)B{(1)H} MAS-NMR techniques in external fields of 7.1 T and 18.8 T at a decomposition temperature of 88 degrees C, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the (11)B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH(3))(2)BH(2)](+)[BH(4)](-), and two BH(2)N(2) species believed to be the linear (NH(3)BH(2)NH(2)BH(3)) and cyclic dimer (NH(2)BH(2))(2) of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH(2)N(2) and BHN(3) species. The following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen is proposed: (i) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds; (ii) nucleation that yields reactive DADB from the mobile AB; and (iii) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen. PMID:17415495

Stowe, Ashley C; Shaw, Wendy J; Linehan, John C; Schmid, Benjamin; Autrey, Tom

2007-04-21

150

In situ solid state B-11 MAS-NMR studies of the thermal decomposition of ammonia borane: mechanistic studies of the hydrogen release pathways from a solid state hydrogen storage material  

SciTech Connect

The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state 11B{1H} MAS-NMR techniques in external fields of 7.06 T and 18.8 T at a decomposition temperature of 88 oC, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the 11B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH3)2BH2]+[BH4]-, and two BH2N2 species believed to be the linear (NH3BH2NH2BH3) and cyclic dimer (NH2BH2)2 of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH2N2 and BHN3 species. We propose the following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen: (1) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds, (2) nucleation that yields reactive DADB from the mobile AB and (3) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen. Support for this work by the U.S. Department of Energy, Office of Science, Basic Energy Sciences is gratefully acknowledged. A portion of the research described in this paper was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

Stowe, Ashley C.; Shaw, Wendy J.; Linehan, John C.; Schmid, Benjamin; Autrey, Thomas

2007-02-20

151

Quantifying hydrogen-bonding strength: the measurement of 2hJNN couplings in self-assembled guanosines by solid-state 15N spin-echo MAS NMR.  

PubMed

(2h)J(NN) hydrogen-bond mediated J couplings are measured in the solid state for two synthetic deoxyguanosine derivatives by (15)N MAS NMR spin-echo experiments. The use of rotor-synchronised Hahn-echo pulse train (RS-HEPT) (1)H decoupling, with a duty cycle of 6%, allows spin-echo durations out to 200 ms, hence enabling the accurate determination of J couplings as small as 3.8 Hz. A single-crystal X-ray diffraction structure exists for the shorter alkyl chain derivative dG(C(3))(2): the observation of significantly different (2h)J(NN) couplings, 6.2 +/- 0.4 and 7.4 +/- 0.4 Hz, for the two resolved N7 resonances is to be expected given the NH...N hydrogen-bonding distances of 2.91 and 2.83 A for the two distinct molecules in the asymmetric unit cell. For the longer alkyl chain derivative, dG(C(10))(2), for which there is no single-crystal diffraction structure, a (15)N refocused INADEQUATE spectrum (Pham et al., J. Am. Chem. Soc., 2005, 127, 16018-16019) has demonstrated the presence of N2-H...N7 intermolecular hydrogen-bonds indicative of a quartet-like structure. The (2h)J(NN) hydrogen-bond mediated J coupling of 5.9 +/- 0.2 Hz is at the lower end of the range (5.9-8.2 Hz) of (2h)J(NN) couplings determined from solution-state NMR of guanosine quartets in quadruplex DNA. A full discussion of the determination of error bars on the fitted parameters is given; specifically, error bars determined by a non-linear fitting (using the covariance matrix) or in a Monte-Carlo fashion are found to give effectively identical results. PMID:17664965

Pham, Tran N; Griffin, John M; Masiero, Stefano; Lena, Stefano; Gottarelli, Giovanni; Hodgkinson, Paul; Filip, Claudiu; Brown, Steven P

2007-07-14

152

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

153

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

PubMed

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

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

2011-11-01

154

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

155

A study of the conformational stability of poly(?-benzyl l-aspartate), poly(?-benzyl l-glutamate) and poly(?-benzyl l-aspartate)\\/poly(?-benzyl l-glutamate) blend in the solid state by variable-temperature 13C CP\\/MAS NMR  

Microsoft Academic Search

13C CP\\/MAS NMR experiments on polypeptides, poly(?-benzyl l-aspartate) (PBLA), poly(?-benzyl l-glutamate) (PBLG) and PBLA\\/PBLG blend have been carried out, in order to elucidate the conformational stability of the polypeptides in the solid state over a wide range of temperatures and its blending effect. The PBLA\\/PBLG blend with a mixture ratio of 1\\/1 is prepared by adding trifluoroacetic acid (TFA) solution

Katsuyoshi Murata; Etsuko Katoh; Shigeki Kuroki; Isao Ando

2004-01-01

156

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

Microsoft Academic Search

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

ANTHONY BIELECKI; DOUGLAS P. BURUM

1995-01-01

157

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

158

Structure in solid state of 3,3?-diindolylmethane derivatives, potent cytotoxic agents against human tumor cells, followed X-ray diffraction and 13C CP/MAS NMR analyses  

NASA Astrophysics Data System (ADS)

The 5,5'-disubstituted-3,3'-diindolylmethanes 1, 2 have been prepared and their structure was analyzed by X-ray and NMR techniques. The X-ray diffraction studies revealed interesting C-H⋯ ? intermolecular interactions which may play role in characterization of their biological features. In 1H and 13C NMR spectra in solution and in 13C CPMAS NMR spectra in solid state only a single pattern of signals was observed. Both compounds reduce the growth of MCF7 (breast), NCI-H460 (lung), and SF-268 (NCS) cells dramatically.

Maciejewska, Dorota; Wolska, Irena; Niemyjska, Maria; ?ero, Pawe?

2005-10-01

159

The RETSINA MAS Infrastructure  

Microsoft Academic Search

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

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

2003-01-01

160

MAS113 Semester 1 MAS113 Tutorial Workbook MAS113 Tutorial Workbook  

E-print Network

MAS113 Semester 1 MAS113 Tutorial Workbook MAS113 Tutorial Workbook Please bring this workbook (and your lecture notes) to all your tutorial classes. Where to go and what to do Your timetable will have two different rooms listed for your Wednesday tutorial class. · Weeks 1 and 2. Go to the computer room

Oakley, Jeremy

161

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

E-print Network

High-Frequency Dynamic Nuclear Polarization in MAS Spectra of Membrane and Soluble Proteins Melanie The success of these experiments is due largely to the ability to record multidimensional MAS NMR spectra this sensitivity problem, we have recently developed high-field dynamic nuclear polarization (DNP) experiments

Griffin, Robert G.

162

Solid state NMR studies of covalent graphite fluorides (CF) n and (C 2F) n  

Microsoft Academic Search

Various covalent graphite fluorides were studied using solid state nuclear magnetic resonance (NMR). 19F magic angle spinning (MAS) NMR, 13C MAS NMR and 13C MAS NMR with 19F to 13C Cross Polarization (CP) allow both the presence of CF and CF2 groups and the carbon atoms hybridization, sp2 or sp3, to be determined. 19F spin–lattice relaxation time T1 of the

Jérôme Giraudet; Marc Dubois; Katia Guérin; André Hamwi; Francis Masin

2006-01-01

163

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

164

Binarity of the LBV HR Car  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

165

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

166

Syntheses and Vibrational and (13)C MAS-NMR Spectra of Bis(carbonyl)mercury(II) Undecafluorodiantimonate(V) ([Hg(CO)(2)][Sb(2)F(11)](2)) and of Bis(carbonyl)dimercury(I) Undecafluorodiantimonate ([Hg(2)(CO)(2)][Sb(2)F(11)](2)) and the Molecular Structure of [Hg(CO)(2)][Sb(2)F(11)](2).  

PubMed

The synthesis of bis(carbonyl)mercury(II) undecafluorodiantimonate(V), [Hg(CO)(2)][Sb(2)F(11)](2), and that of the corresponding mercury(I) salt [Hg(2)(CO)(2)][Sb(2)F(11)](2) are accomplished by the solvolyses of Hg(SO(3)F)(2) or of Hg(2)F(2), treated with fluorosulfuric acid, HSO(3)F, in liquid antimony(V) fluoride at 80 or 60 degrees C, respectively, in an atmosphere of CO (500-800 mbar). The resulting white solids are the first examples of metal carbonyl derivatives formed by a post-transition element. Both salts are characterized by FT-IR, FT-Raman, and (13)C-MAS-NMR spectroscopy. For [Hg(CO)(2)][Sb(2)F(11)], unprecedentedly high CO stretching frequencies (nu(av) = 2279.5 cm(-)(1)) and stretching force constant (f(r) = 21.0 +/- 0.1) x 10(2) Nm(-)(1)) are obtained. Equally unprecedented is the (1)J((13)C-(199)Hg) value of 5219 +/- 5 Hz observed in the (13)C MAS-NMR spectrum of the (13)C labeled isotopomers at delta = 168.8 +/- 0.1 ppm. The corresponding values (nu(av) = 2247 cm(-)(1), f(r) = (20.4 +/- 0.1) x 10(2) Nm(-)(1), (1)J((13)C-(199)Hg) = 3350 +/- 50 Hz and (2)J((13)C-(199)Hg) 850 +/- 50 Hz) are found for [Hg(2)(CO)(2)][Sb(2)F(11)](2), which has lower thermal stability (decomposition point in a sealed tube is 140 degrees C vs 160 degrees C for the Hg(II) compound) and a decomposition pressure of 8 Torr at 20 degrees C. The mercury(I) salt is sensitive toward oxidation to [Hg(CO)(2)][Sb(2)F(11)](2) during synthesis. Both linear cations (point group D(infinity)(h)()) are excellent examples of nonclassical (sigma-only) metal-CO bonding. Crystal data for [Hg(CO)(2)][Sb(2)F(11)](2): monoclinic, space group P2(1)/n; Z = 2; a = 7.607(2) Å; b = 14.001(3) Å; c = 9.730(2) Å; beta = 111.05(2) degrees; V = 967.1 Å(3); T = 195 K; R(F) = 0.035 for 1983 data (I(o) >/= 2.5sigma(I(o))) and 143 variables. The Hg atom lies on a crystallographic inversion center. The Hg-C-O angle is 177.7(7) degrees. The length of the mercury-carbon bond is 2.083(10) Å and of the C-O bond 1.104(12) Å respectively. The structure is stabilized in the solid state by a number of significant secondary interionic Hg- - -F and C- - -F contacts. PMID:11666168

Bodenbinder, M.; Balzer-Jöllenbeck, G.; Willner, H.; Batchelor, R. J.; Einstein, F. W. B.; Wang, C.; Aubke, F.

1996-01-01

167

MAS 04 Calibration and Observability MAS 04.1 Overview  

E-print Network

) measurements from the sensor themselves to improve our estimates of related system parameters. Visual is to demonstrate that it is possible to accurately calibrate the relative pose of these sensors in the field related to environment mapping and sampling by mobile sensor nodes. MAS 04.2 Approach We recently extend

California at Los Angeles, University of

168

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

169

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

170

McCune-Albright Syndrome (MAS)  

MedlinePLUS

... Albright 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 ...

171

HR Internet Guide  

NSDL National Science Digital Library

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

172

Responsibilities HR Responsibilities Recruitment  

E-print Network

, and if noted additional locations Collect EEO data Recruitment Process Search Process Approve list of applicants to interview Department Responsibilities HR Responsibilities Search Process Cont. ·Interview Classified Recruitment Flow Chart Create or revise based on VA - Interview , Reference Questions and Skill

Lawrence, Rick L.

173

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

E-print Network

-ordination environments in silicate glasses using 25 Mg MAS NMR. Also presented are 17 O MAS NMR spectra of a zeolite in the devel- opment of structural and dynamical models of glass structure [1±3]. The chemical shift is a sen- sitive probe of the local environment of a given isotope, hence providing an inventory of the spe- cies

Puglisi, Joseph

174

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

175

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

Microsoft Academic Search

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

Xiandong Cong; R. James Kirkpatrick

1996-01-01

176

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

177

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

178

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

PubMed Central

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

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

2014-01-01

179

Réunion publique HR  

SciTech Connect

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

None

2010-04-30

180

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

181

HR Shared Services and the Realignment of HR.  

ERIC Educational Resources Information Center

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

Reilly, P.

182

PEMBENIHAN IKAN MAS YANG EFEKTIF DAN EFISIEN  

Microsoft Academic Search

ABSTRAK Pembenihan ikan mas yang berkembang di Sulawesi Utara belum mampu memberikan pendapatan yang memadai bagi petani ikan. Umumnya petani ikan masih mengabaikan penggunaan pakan larva yang bermutu pada tahap pemeliharaan larva, sehingga pertumbuhan larva kurang optimum dan penggunaan pakan tidak efisien. Untuk mendukung pengembangan pembenihan ikan mas skala rumah tangga maka teknologi pembenihan yang ada di tingkat petani perlu

Zulkifli Mantau; J. B. M. Rawung

2004-01-01

183

NMR Spectroscopy  

NSDL National Science Digital Library

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

Shattuck, Thomas W.

184

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

185

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

NASA Astrophysics Data System (ADS)

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

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

2002-06-01

186

B. Sc. Examination 2005 MAS 335 Cryptography  

E-print Network

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

Banaji,. Murad

187

Research on embedded MAS based manipulator control  

Microsoft Academic Search

Purpose – Presents an embedded MAS (Multi-Agent System) based control method for multi link series manipulators. Design\\/methodology\\/approach – The manipulator's completing operation work is based on several agents' cooperation. The entire embedded MAS of a manipulator is implemented in one ARM7 microprocessor. The multi agents and the communications between the agents are constructed depending on the real-time multitasking capability and

Kejun Ning

2006-01-01

188

Quantitative NMR  

NSDL National Science Digital Library

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

Korir, Albert K.

189

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

PubMed

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

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

2015-04-01

190

NMR Animations  

NSDL National Science Digital Library

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

191

NMR tutorial  

NSDL National Science Digital Library

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

Bogdal, Dariusz

192

NMR imaging  

SciTech Connect

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

Andrew, E.R.

1983-04-01

193

Liquid Domains in Vesicles Investigated by NMR and Fluorescence Microscopy  

Microsoft Academic Search

We use 2H-NMR, 1H-MAS NMR, and fluorescence microscopy to detect immiscibility in three particular phospholipid ratios mixed with 30% cholesterol: 2:1 DOPC\\/DPPC, 1:1 DOPC\\/DPPC, and 1:2 DOPC\\/DPPC. Large-scale (?160nm) phase separation into liquid-ordered (Lo) and liquid-crystalline (L?) phases is observed by both NMR and fluorescence microscopy. By fitting superimposed 2H-NMR spectra, we quantitatively determine that the Lo phase is strongly

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

2004-01-01

194

Alloy NASA-HR-1  

NASA Technical Reports Server (NTRS)

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

Chen, Po-Shou; Mitchell, Michael

2005-01-01

195

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

196

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

E-print Network

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

Lewandowski, Jozef R.

197

User Guide: Liquids NMR  

E-print Network

User Guide: Liquids NMR Varian NMR Spectrometer Systems With VNMR 6.1C Software Pub. No. 01-999161-00, Rev. B0801 #12;User Guide: Liquids NMR Varian NMR Spectrometer Systems With VNMR 6.1C Software Pub. No. 01-999161-00, Rev. B0801 #12;User Guide: Liquids NMR Varian NMR Spectrometer Systems With VNMR 6.1C

Zhou, Pei

198

NMR, XRD and IR study on microcrystalline opals  

Microsoft Academic Search

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

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

1994-01-01

199

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

SciTech Connect

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

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

2014-06-20

200

Asteroseismology across the HR diagram  

E-print Network

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

M. J. P. F. G. Monteiro

2007-02-12

201

Asteroseismology Across the HR Diagram  

Microsoft Academic Search

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

202

Putting HR outsourcing into practice.  

PubMed

Faced with the time-consuming responsibility of human resources (HR) management, a growing number of medical practices are outsourcing their HR to professional employer organizations (PEOs) so they can concentrate on their core business. A PEO functions as an HR department-minus the high overhead-managing daily administrative tasks such as payroll processing and related tax filings, employee benefits, and workers' compensation coverage and claims resolution. PEOs help physicians' offices keep up with the piles of paperwork that never seem to shrink, freeing doctors to focus on patient care and building their practice. Because of their volume buying power, PEOs are able to offer employees of small medical practices big-company benefits-everything from health, dental, and vision coverage to long-term disability insurance and tuition assistance. A fledgling industry only a decade ago, HR outsourcing has morphed into a blossoming industry. Enlisting the services of a PEO is now considered de rigueur in many small business circles. PMID:17828839

Berger, Michael

2007-01-01

203

Contact your HR Partner LEADINGATUTSPROGRAM  

E-print Network

Framework 3 HR @ UTS 5 NEO 6 Privacy 8 Workforce Planning 10 Managing and Leading Change 12 Appointments 14 Management 2013 version: March 2013 2 of 44 GUIDE TO PEOPLE MANAGEMENT Introduction The Guide to People Management provides an overview of the most common people management topics. It has been developed to assist

University of Technology, Sydney

204

Career Tracks Presentation to HR  

E-print Network

Function/ Specialty A more specific area within a family Job Category Operational & Technical ProfessionalCareer Tracks Presentation to HR Contacts Compensation UC San Diego Campus Human Resources Compensation Unit #12;New Job Description System/Job Builder Career Tracks Overview Career Tracks Job Structure

Jun, Suckjoon

205

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.

206

MAS 335 Cryptography Notes 1 Spring 2008  

E-print Network

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

Banaji,. Murad

207

MAS501 Analysis for Engineers Spring 2011  

E-print Network

MAS501 Analysis for Engineers Spring 2011 · Instructor Information ­ Name: Jaywan Chung ­ Office: Korean ­ Text: Robert B. Ash, Real Variables with Basic Metric Space Topology You may find the book in the author's homepage: http://www.math.uiuc.edu/~r-ash/RV. html ­ Grading policy: Homework 30%, Midterm exam

Kim, Yong Jung

208

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

209

hr  

E-print Network

mid-dayand then he hath been running his courfe from his tiling. 5f} till he come .... midi}, they will yield youother If? winds, and will amount to 32 winds in all. ..... much as 30 minutes,ond one-“third part ofa degree is 20 minutes, one fourth I 5 ...

210

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

NASA Astrophysics Data System (ADS)

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

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

211

Solid state NMR spectroscopy study of molecular motion in cyclomaltoheptaose ( ?-cyclodextrin) crosslinked with epichlorohydrin 1 Paper presented at the IXth European Carbohydrate Symposium, Utrecht, The Netherlands, 6–11 July 1997; abstr. E-27, p. 465. 1  

Microsoft Academic Search

Dry and hydrated insoluble cyclomaltoheptaose (?-cyclodextrin, ?-CD) polymers have been investigated by solid state 13C NMR spectroscopy techniques such as cross polarization\\/magic angle spinning with dipolar decoupling (CP\\/MAS), magic angle spinning both with (DD-MAS) and without (MAS) dipolar decoupling and CP\\/MAS dipolar dephasing (dd-CP\\/MAS) to allow the assignment of the main 13C signals. In the solid state, the presence of

Grégorio Crini; Cesare Cosentino; Sabrina Bertini; Annamaria Naggi; Giangiacomo Torri; Carmen Vecchi; Ludovic Janus; Michel Morcellet

1998-01-01

212

Liquid Domains in Vesicles Investigated by NMR and Fluorescence Microscopy  

PubMed Central

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

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

2004-01-01

213

Efficient -Sheet Identification in Proteins by Solid-State NMR Spectroscopy  

E-print Network

Efficient -Sheet Identification in Proteins by Solid-State NMR Spectroscopy Daniel Huster, Satoru: An efficient two-dimensional magic-angle-spinning (MAS) NMR technique to selectively detect -sheet residues-helical and -sheet conformations give rise to distinctly different dipolar modulations. After one-half of a rotation

Hong, Mei

214

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

215

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

NASA Astrophysics Data System (ADS)

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

Zhang, Rongchun; Ramamoorthy, Ayyalusamy

2014-06-01

216

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

Microsoft Academic Search

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

Bjørn-Tore Flåten; Rotem Shneor

2008-01-01

217

NMR and pattern recognition studies on liver extracts and intact livers from rats treated with ?-naphthylisothiocyanate  

Microsoft Academic Search

The metabolite profiles from livers of toxin-treated rats were investigated using high resolution 1H NMR spectroscopy of aqueous (acetonitrile\\/water), lipidic (chloroform\\/methanol) extracts and magic angle spinning (MAS)-NMR spectroscopy of intact tissue. Rats were treated with the model cholestatic hepatotoxin, ?-naphthylisothiocyanate (ANIT, 150mg\\/kg) and NMR spectra of liver were analysed using principal components analysis (PCA) to extract novel toxicity biomarker information.

Nigel J Waters; Elaine Holmes; Catherine J Waterfield; R. Duncan Farrant; Jeremy K Nicholson

2002-01-01

218

C NMR Spectra C NMR Spectra  

E-print Network

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

Collum, David B.

219

eHR: An Introduction. IES Report.  

ERIC Educational Resources Information Center

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

Kettley, P.; Reilly, P.

220

Islamic challenges to HR in modern organizations  

Microsoft Academic Search

Purpose – This research is designed to answer questions: do Islamic teachings offer relevant perspectives on human resource (HR) issues? Are the treatments of HR issues in Islam compatible with evolving organizational concepts? Do current HR practices in countries with Muslim majority (CMM) resemble Islamic prescriptions? It aims to address these and other questions in line with early Islamic instructions.

Abbas J. Ali

2010-01-01

221

Mapping a strategic approach to HR leadership  

Microsoft Academic Search

Purpose – This paper aims to discuss the contribution that strategic human resourcing (HR) makes to organizational success and the crucial conversations that HR must orchestrate to truly fulfill its strategic role. Design\\/methodology\\/approach – Strategic HR has the potential to modernize management practice, bringing it into line with the needs of the twenty-first century organization. The paper acknowledges that while

Andrea Adams

2012-01-01

222

Multiperiodicity of HR 6534 Rafael Garrido  

E-print Network

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

Demoulin, Pascal

223

HR managers : Guardians of employee wellbeing?  

Microsoft Academic Search

This paper assesses the role of human resource (HR) managers adopting a strategic role and devolution of HR work to the line in work organisations, and details interviews with 46 line managers drawn from an exploratory study in three work organisations in the UK over a two-year period. The study finds that HR managers can be seen to be both

Douglas Renwick

2003-01-01

224

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

PubMed

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

Adebajo, Moses O; Frost, Ray L

2004-01-01

225

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

NASA Astrophysics Data System (ADS)

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

Adebajo, Moses O.; Frost, Ray L.

2004-01-01

226

Very Long Baseline Interferometry Imaging of the RS Canum Venaticorum Binary Star System HR 5110  

NASA Astrophysics Data System (ADS)

We present VLBI images of the RS CVn binary star HR 5110 (=BH CVn; HD 118216), obtained from observations made at 8.4 GHz on 1994 May 29/30 in support of the NASA/Stanford Gravity Probe B project. Our images show an emission region with a core-halo morphology. The core was 0.39+/-0.09 mas (FWHM) in size, or 66%+/-20% of the 0.6+/-0.1 mas diameter of the chromospherically active K subgiant star in the binary system. The halo was 1.95+/-0.22 mas (FWHM) in size, or 1.8+/-0.2 times the 1.1+/-0.1 mas separation of the centers of the K and F stars. (The uncertainties given for the diameter of the K star and its separation from the F star each reflect the level of agreement of the two most recent published determinations.) The core increased significantly in brightness over the course of the observations and seems to have been the site of flare activity that generated an increase in the total flux density of ~200% in 12 hr. The fractional circular polarization simultaneously decreased from ~10% to 2.5%.

Ransom, R. R.; Bartel, N.; Bietenholz, M. F.; Ratner, M. I.; Lebach, D. E.; Shapiro, I. I.; Lestrade, J.-F.

2003-04-01

227

Rock Art Interpretation within Indiana MAS Viviana Mascardi1  

E-print Network

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

Mascardi, Viviana

228

NAAP HR Diagram Explorer 1/9 HR Diagram Student Guide  

E-print Network

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

Farritor, Shane

229

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

230

NMR Studies of Cartilage Dynamics, Diffusion, Degradation  

NASA Astrophysics Data System (ADS)

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

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

231

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

PubMed

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

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

2013-06-10

232

Spectral editing of two-dimensional magic-angle-spinning solid-state NMR spectra for protein resonance assignment  

E-print Network

ARTICLE Spectral editing of two-dimensional magic-angle-spinning solid-state NMR spectra % for the CH selection experiment, and are demon- strated on well-characterized model proteins GB1 Recent progress in magic-angle-spinning (MAS) solid-state NMR (SSNMR) spectroscopy has made it possible

Hong, Mei

233

Possible Corotation of the Milliarcsecond Radio Structure of the Close Binary HR 1099  

NASA Astrophysics Data System (ADS)

We present the first VLBI images of the RS CVn binary star HR 1099 (=V711 Tauri, HD 22468) obtained from observations at 8.4 GHz in 1996 May and September made in support of the NASA/Stanford Gravity Probe B project. The first set of observations was made during a decay stage of a flare event. The second set of observations was made during a quiescent period. The detected emission region for the active epoch had an estimated major-axis length (FWHM) of 2.7+/-0.2 mas. This region consisted of a halo and two superimposed compact condensations that were oriented approximately east-west. The centers of the compact condensations were separated by 1.7+/-0.1 mas. Compared to the ~1.3 mas separation on the sky at this epoch of the centers of the stellar components of the binary, the observed separation of the condensations differs by only 0.4 mas, which is less than the ~0.6 mas angular radius of the larger component. During the observations, the compact western condensation rotated north-northwestward by 24deg+/-4deg, or by 0.7+/-0.1 mas, relative to the eastern condensation. We speculate that (1) either both condensations originate from the corona of the larger stellar component or one condensation is close to the surface of each of the two stellar components of the binary and (2) the relative rotation of the two condensations is a consequence of the rotation of the binary system. We speculate further that the halo is a consequence of flare-energized electrons confined by the magnetosphere of the larger stellar component or by the combined magnetospheres of the two stellar components. Our quiescent epoch, in contrast, was characterized by a single emission region with a major axis estimated to be 1.7+/-0.1 mas (FWHM).

Ransom, R. R.; Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Ratner, M. I.; Shapiro, I. I.; Lestrade, J.-F.

2002-06-01

234

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

235

PeopleSoft HR ECR Automation Process  

E-print Network

of the data specific to the job being updated. This data displays current information as of the effective datePeopleSoft HR ECR Automation Process Revise Existing SWB May 2011 #12;Processing a Short Work Break that will be reflected in PeopleSoft HR. This transaction can only be entered for an employee who has a future SWB row

Huang, Jianyu

236

PeopleSoft HR ECR Automation Process  

E-print Network

of the screen. This information is reflective of the data specific to the job being updated. This data displaysPeopleSoft HR ECR Automation Process Long Term Disability May 2011 #12;Processing a Long Term the Effective Date of the LTD. This is the Effective Date that will be reflected in PeopleSoft HR. 3. Select

Huang, Jianyu

237

PeopleSoft HR ECR Automation Process  

E-print Network

. This information is reflective of the data specific to the job being updated. This data displays currentPeopleSoft HR ECR Automation Process Short Term Disability with Pay May 2011 #12;Processing a Short that will be reflected in PeopleSoft HR. 3. Select "Short Term Disability with Pay" from the ECR Action drop down field

Huang, Jianyu

238

PeopleSoft HR ECR Automation Process  

E-print Network

", the following screen will display: NOTE: HR information specific to the employee, including important. This employee data is specific to the job being updated. This data displays current informationPeopleSoft HR ECR Automation Process: Return from Leave & Return from Short-Term Disability

Huang, Jianyu

239

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

240

A Candidate Substellar Companion to HR 7329  

E-print Network

We present the discovery of a candidate substellar companion from a survey of nearby, young stars with the NICMOS coronagraph on the Hubble Space Telescope. The H ~ 12 mag object was discovered approximately 4" from the young A0V star HR 7329. Using follow-up spectroscopy from STIS, we derive a spectral type between M7V and M8V with an effective temperature of ~ 2600 K. We estimate that the probability of a chance alignment with a foreground dwarf star of this nature is ~ 10^(-8) and therefore suggest the object (HR 7329B) is physically associated with HR 7329 with a projected separation of 200 AU. Current brown dwarf cooling models indicate a mass of less than 50 Jupiter masses for HR 7329B based on age estimates of < 30 Myr for HR7329A.

Lowrance, P J; Kirkpatrick, J D; Becklin, E E; Weinberger, A J; Zuckerman, B; Plait, P; Malmuth, E; Heap, S; Schultz, A; Smith, B A; Terrile, R J; Hines, D C

2000-01-01

241

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

Microsoft Academic Search

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

S. Gomes; M. François

2000-01-01

242

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.

243

NMR analysis of biodiesel  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biodiesel is usually analyzed by the various methods called for in standards such as ASTM D6751 and EN 14214. Nuclear magnetic resonance (NMR) is not one of these methods. However, NMR, with 1H-NMR commonly applied, can be useful in a variety of applications related to biodiesel. These include monit...

244

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

Microsoft Academic Search

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

Pekka O. Kääpä

2009-01-01

245

MEBRL: Memory Evolution Based Reinforcement Learning Algorithm of MAS  

Microsoft Academic Search

A memory-evolution-based MAS reinforcement learning algorithm (MEBRL) inspired by a psychology memory model is presented. 3 types of different memory stores are used in the design of the algorithm and Learning Automata is used in the processes of agent memory evolution. Through the memory evolution procedure, the agent in the MAS could make a proper decision and share its information

Le Chang; Jiaben Yang

2001-01-01

246

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

SciTech Connect

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

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

2013-06-01

247

Tom LaPenta Chief HR Officer  

E-print Network

Tom LaPenta Chief HR Officer Chris Ulrich Director, Compensation & Benefits Kathy Corbitt Assoc Director, Educ & Wellness Anna Bloch Director, Payroll/ Records/HRIS Vacant Labor Relations Cecily Sawyer

Firestone, Jeremy

248

HR Departments & Units Feb 24, 2014  

E-print Network

Chancellor HR INFORMATION MANAGEMENT Brian Simet, Director PAYROLL Vacant, Director BENEFITS Joe Williams MANAGEMENT Jen Mitchell, Asst Dir TAX MANAGEMENT Robin Nowlin, Asst Dir PAYROLL PROCESSING DEDUCTION CHILDCARE CTR CAMPUS TRAINING ADMINISTRATION EPA PERSONNEL Jessie Sova, Director CENTRAL PERSONNEL FILES

Young, R. Michael

249

Variable stars across the observational HR diagram  

Microsoft Academic Search

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

Laurent Eyer; Nami Mowlavi

2008-01-01

250

Nuclear magnetic resonance (NMR) studies of the local structure of phosphorus chalcogenide glasses: an overview  

Microsoft Academic Search

An overview is given on recent nuclear magnetic resonance (NMR) structural studies of phosphorus chalcogenide glasses and melts. The detailed structural speciation of these systems has been derived on the basis of 31P dipolar spin-echo decay spectroscopy, magic-angle spinning (MAS), and variable temperature liquid-state NMR above the glass transition temperature. A specific feature in the binary phosphorus\\/chalcogen systems is the

Paul F. Mutolo; Michael Witschas; Guido Regelsky; Joern Schmedt auf der Guenne; H. Eckert

1999-01-01

251

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

NASA Astrophysics Data System (ADS)

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

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

2003-03-01

252

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

PubMed

Partial deuteration is a powerful tool to increase coherence life times and spectral resolution in proton solid-state NMR. The J coupling to deuterium needs, however, to be decoupled to maintain the good resolution in the (usually indirect) (13)C dimension(s). We present a simple and reversible way to expand a commercial 1.3mm HCN MAS probe with a (2)H channel with sufficient field strength for J-decoupling of deuterium, namely 2-3kHz. The coil is placed at the outside of the stator and requires no significant modifications to the probe. The performance and the realizable gains in sensitivity and resolution are demonstrated using perdeuterated ubiquitin, with selectively CHD(2)-labeled methyl groups. PMID:22088662

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

2012-01-01

253

Dual Processing of Two-Dimensional Exchange Data in Magic Angle Spinning NMR of Solids  

NASA Astrophysics Data System (ADS)

We discuss procedures for processing data in rotor-synchronized two-dimensional magic angle spinning (2D MAS) NMR exchange measurements for both structural and dynamical studies. We show, both mathematically and experimentally, that there are two distinct data processing procedures that lead to 2D MAS exchange spectra with purely absorptive crosspeaks. One procedure is that described previously by Hagemeyer, Schmidt-Rohr, and Spiess (HSS). The other procedure is related, but different, and leads to crosspeak intensities given by the formulae of Herzfeld, Roberts, and Griffin (HRG). In 2D MAS exchange experiments on doubly 13C-labeled l-alanylglycylglycine, we demonstrate that the HSS and HRG crosspeak intensities can be extracted separately from the same data set and contain independent information. Processing and analysis of 2D MAS exchange data with both the HSS and the HRG procedures may enhance utilization of the information content of 2D MAS exchange measurements.

Tycko, Robert; Berger, Alan E.

1999-11-01

254

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

255

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

E-print Network

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

Griffin, Robert G.

256

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

257

From AO Methodologies to MAS Infrastructures: The SODA Case Study  

Microsoft Academic Search

In the last years, research on agent-oriented (AO) methodologies and multi-agent system (MAS) infrastructures has developed\\u000a along two opposite paths: while AO methodologies have essentially undergone a top-down evolution pushed by contributions from\\u000a heterogeneous fields like human sciences, MAS infrastructures have mostly followed a bottom-up path growing from existing\\u000a and widespread (typically object-oriented) technologies. This dichotomy has produced a conceptual

Ambra Molesini; Enrico Denti; Andrea Omicini

258

Understanding NMR Spectroscopy  

NSDL National Science Digital Library

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

Keeler, James

259

POSTER PRESENTATION Open Access Design of HR1 and HR2 synthetic peptide  

E-print Network

POSTER PRESENTATION Open Access Design of HR1 and HR2 synthetic peptide analogs: Characterization chemically as monomeric or trimeric peptides. Punctial D-amino acid substitutions (C34M2 and C34 M4) were introduced at the more susceptible enzymatic cleavage sites. These peptides were then tested

Paris-Sud XI, Université de

260

Variable stars across the observational HR diagram  

E-print Network

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

Laurent Eyer; Nami Mowlavi

2007-12-21

261

Mobility of organic pollutants in soil components. What role can magic angle spinning NMR play?  

E-print Network

influence the movement of pesticides and hence their bioavailability and biotransformation processes. Direct pesticide unambiguously. In the present communication, a short review of MAS NMR techniques that allow covalent and non-covalent bond analysis is provided. The results obtained in our group on the adsorption

Boyer, Edmond

262

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

263

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.

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. 32 refs., 56 figs.

Pines, A.

1988-08-01

265

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

266

HR EMPLOYMENT LAW UPDATES TIME TO TRAIN  

E-print Network

an eligible employee's formal request for time away from their core duties to undertake training. Employees employers do not have to pay for the training or pay the employee for the time spent training. WhatHR EMPLOYMENT LAW UPDATES TIME TO TRAIN Since 6 April 2010 employers have had to seriously consider

Sussex, University of

267

The granulation boundary in the HR diagram  

Microsoft Academic Search

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

David F. Gray; Thomas Nagel

1989-01-01

268

Synthetic HR-diagrams for massive stars  

Microsoft Academic Search

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

E. Nasi; C. Forieri

1990-01-01

269

About HR Compensation Employee Retirement and  

E-print Network

Development Job Descriptions Training Prospective Employees Employment Opportunities eJobs for Applicants e Center Web Page ETSU Retirees Association Web Page Employee Development Center Online Training SupportHOME About HR Compensation Employment Employee Retirement and Benefits Employee Relations Employee

Karsai, Istvan

270

Eight outrageous statements about HR science  

Microsoft Academic Search

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

Robert L. Dipboye

2007-01-01

271

EMPLOYMENT EQUITY University Policy No: HR6100  

E-print Network

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

Victoria, University of

272

HR use only: I. APPOINTEE DATA  

E-print Network

work while at UCAR? Y N 10th 6. Do you have one or more family members living in your other 11th Location: Building: Room: Extension: Visit Coordinator: Extension: Export Compliance: Citizenship: Purpose Resources PEID #: Org Unit: Travel Human Resources distributes data to: Coding: Today @ UCAR HR Initials

273

NMR logging apparatus  

DOEpatents

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

Walsh, David O; Turner, Peter

2014-05-27

274

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.

275

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

276

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

E-print Network

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

Simaan, Nabil

277

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

278

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

SciTech Connect

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

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

2013-03-05

279

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

Microsoft Academic Search

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

Masami Kanzaki; Jonathan F. Stebbins; Xianyu Xue

1991-01-01

280

HR4049: signature of nova nucleosynthesis?  

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

281

HR 7275 - A new variable star  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

282

Steps toward a radio HR diagram  

Microsoft Academic Search

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

Frazer Owen

283

Instability regions in the upper HR diagram  

Microsoft Academic Search

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

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

2001-01-01

284

Nonthermal Radio Emission and the HR Diagram  

NASA Technical Reports Server (NTRS)

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

Gibson, D. M.

1985-01-01

285

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

286

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

SciTech Connect

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

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

2006-01-19

287

Solid-state NMR identification and quantification of newly formed aluminosilicate phases in weathered kaolinite systems.  

PubMed

The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3-, 1 mol kg-1 of OH-, and pH approximately 13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10(-3), 10(-4), and 10(-5) molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10(-5) m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10(-3) m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and the quantitative nature of the 27Al NMR data shows that cancrinite growth increases while sodalite reaches a steady state with respect to total aluminum in the solid phases. The data also relate the coupling of Cs sorption to the ripening of feldspathoid phases in this heterogeneous system as a function of time, and illustrate the important influence of co-contaminants on the environmental reaction kinetics studied here. PMID:16471594

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

2006-01-19

288

A generic negotiation model for MAS using XML  

Microsoft Academic Search

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

Philippe Mathieu; Marie-h El Ene Verrons

2003-01-01

289

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

PubMed

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

Kääpä, Pekka O

2009-10-01

290

ASTM001/MAS423 Solar System Solar Nebula & Planet Formation  

E-print Network

: Inner system Terrestrial Planets Mercury 0.39 AU Venus 0.72 AU Earth 1.00 AU Mars 1.52 AU Asteroid beltASTM001/MAS423 Solar System Solar Nebula & Planet Formation Craig B. Agnor Queen Mary, University of a solid planet. `Orderly' accretion. 'Runaway' accretion Discuss implications #12;Solar system structure

Agnor, Craig B.

291

Emergent Properties for Data Distribution in a Cognitive MAS  

E-print Network

Emergent Properties for Data Distribution in a Cognitive MAS Andrei Olaru, Cristian Gratie, cognitive agents become a promising solution for the solution of more complex problems. This paper presents without the need for these features to be controlled from the exterior. 1 Introduction Emergence is a key

Paris-Sud XI, Université de

292

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

293

Adiabatic TOCSY MAS in Liquids# E. Kupce,a,*  

E-print Network

1 Adiabatic TOCSY MAS in Liquids# E. Kupce,a,* P. A. Keifer b and M. Delepierre c a Varian Inc., 28, Manor Road, Walton-on Thames, Oxford, UK b Varian Inc., 3120 Hansen Way, Palo Alto, CA, USA c Lab. RMN,version1-25Jul2007 #12;3 INTRODUCTION The small active volumes and the high sensitivities of Varian

Boyer, Edmond

294

Marker assisted selection (MAS) for breeding high oleic Tifguard  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tifguard, a peanut cultivar released in 2007, has near immunity to root-knot nematode and high resistance to TSWV. However, its oil composition is within the normal O/L range. Pyramiding the disease resistant traits of ‘Tifguard’ and the high O/L trait using MAS is our current goal for breeding. ...

295

Racial Bias in the 2008 Presidential Election Alexandre Mas  

E-print Network

1 Racial Bias in the 2008 Presidential Election Alexandre Mas UC Berkeley, NBER Enrico Moretti UC for excellent research assistance. #12;1 1. Introduction We investigate whether racial attitudes had a negative pieces of indirect evidence point to the possibility that racial attitude did play a role. First

Bou-Zeid, Elie

296

MAS behavior modeling of virtual drone entity based on CLIPS  

Microsoft Academic Search

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

Hongge Yao

2011-01-01

297

Resolution and polarization distribution in cryogenic DNP/MAS experiments  

PubMed Central

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

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

2014-01-01

298

MAS420 Turn over Data provided: Formula Sheet  

E-print Network

, only your best four will be counted. #12;2 MAS420 Turn over 1 a) You are given that a periodic signal for the real periodic signal shown below in terms of the triangle function . State the period signal in the time domain? (5 marks) d) Consider the signal . Calculate and sketch the signal spectrum

299

CURRRENT STATUS OF MAS FOR DISEASE RESISTANCE IN COMMON BEAN  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

300

Artificial Urban Planning: Application of MAS in Urban Planning Education  

Microsoft Academic Search

Urban problems caused by fast urbanization become more and more complex, bringing new challenges to urban planning and its education. Therefor, proposition of artificial cities is put forward in this paper, based on which artificial urban planning research can be carried out. By adopting multi-agent system (MAS) method and according to features of Swarm simulation, the spatial evolution system model

Kou Xiaodong; Yang Lin; Cai Lin

2008-01-01

301

MAS6 encodes an essential inner membrane component of the yeast mitochondrial protein import pathway  

Microsoft Academic Search

To identify new components that mediate mitochondrial protein import, we analyzed mas6, an import mutant in the yeast Saccharomyces cerevisiae. mas6 mutants are temperature sensitive for viability, and accumulate mitochondrial precursor proteins at the restrictive temperature. We show that mas6 does not correspond to any of the presently identified im- port mutants, and we find that mitochondria isolated from mas6

Jermifer L. T. Emtage; Robert E. Jensen

1993-01-01

302

EPR and solid-state NMR studies of poly(dicarbon monofluoride) (C2F)n.  

PubMed

Poly(dicarbon monofluoride) (C2F)n was studied by electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (NMR). The effects of physisorbed oxygen on the EPR and NMR relaxation were underlined and extrapolated to poly(carbon monofluoride) (CF)n and semi-covalent graphite fluoride prepared at room temperature. Physisorbed oxygen molecules are shown to be an important mechanism of both electronic and nuclear relaxations, resulting in apparent spin-lattice relaxation time and line width during NMR and EPR measurements, respectively. The effect of paramagnetic centers on the 19F spin-lattice relaxation was underlined in accordance with the high electron spin density determined by EPR. 19F magic angle spinning (MAS) NMR, 13C MAS NMR, and 13C MAS NMR with 19F to 13C cross polarization (CP) underline the presence of two types of carbon atoms, both sp3 hybridized: some covalently bonded to fluorine and the others linked exclusively to carbon atoms. Finally, a C-F bond length of 0.138 +/- 0.002 nm has been determined thanks to the re-introduction of dipolar coupling using cross polarization. PMID:16800480

Dubois, Marc; Giraudet, Jérôme; Guérin, Katia; Hamwi, André; Fawal, Ziad; Pirotte, Pascal; Masin, Francis

2006-06-22

303

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

304

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

PubMed

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

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

2013-11-01

305

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

PubMed

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

Paradowska, Katarzyna; Wawer, Iwona

2014-05-01

306

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

SciTech Connect

Geological carbon sequestration (GCS) is one of the most promising ways of mitigating atmospheric greenhouse gases (1-3). Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly in low-water supercritical CO2 (scCO2)-dominated environments where the chemistry has not been adequately explored. In situ probes that provide molecular-level information is desirable for investigating mechanisms and rates of GCS mineral carbonation reactions. MAS-NMR is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, or a supercritical state, or a mixture thereof (4,5). However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS rotor (6,7), where non-metal materials must be used. In this work, we report development of a unique high pressure MAS NMR capability, and its application to mineral carbonation chemistry in scCO2 under geologically relevant temperatures and pressures.

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

2011-03-27

307

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

PubMed Central

A magic-angle spinning (MAS) probe has been constructed which allows the sample to be cooled with helium, while the MAS bearing and drive gases are nitrogen. The sample can be cooled to 25 K using roughly 3 liters/hour of liquid helium, while the 4 mm diameter rotor spins at 6.7 kHz with good stability (±5 Hz) for many hours. Proton decoupling fields up to at least 130 kHz can be applied. This helium-cooled MAS probe enables a variety of one-dimensional and two-dimensional NMR experiments on biomolecular solids and other materials at low temperatures, with signal-to-noise proportional to 1/T. We show examples of low-temperature 13C NMR data for two biomolecular samples, namely the peptide A?14–23 in the form of amyloid fibrils and the protein HP35 in frozen glycerol/water solution. Issues related to temperature calibration, spin-lattice relaxation at low temperatures, paramagnetic doping of frozen solutions, and 13C MAS NMR linewidths are discussed. PMID:18922715

Thurber, Kent R.; Tycko, Robert

2009-01-01

308

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

309

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

310

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

PubMed

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

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

2012-02-28

311

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

312

DEPARTMENT/CANDIDATE o DRAFT DUE IFAS HR JULY 13  

E-print Network

DEPARTMENT/CANDIDATE o DRAFT DUE IFAS HR JULY 13 IFAS HR o REVIEW PACKETS o COMMENTS BACK TO CANDIDATE JULY 30 CANDIDATE o REVISE PACKET AS NEEDED o UPLOAD FINAL PACKET AUGUST 6 DEPARTMENT HR o ADD REVIEW AND ASSESS o ASSESSMENTS TO CANDIDATE AUGUST 27. The candidate has five calendar days thereafter

Watson, Craig A.

313

DEPARTMENT/CANDIDATE o DRAFT DUE IFAS HR JULY 11  

E-print Network

DEPARTMENT/CANDIDATE o DRAFT DUE IFAS HR JULY 11 IFAS HR o REVIEW PACKETS o COMMENTS BACK TO CANDIDATE JULY 25 CANDIDATE o REVISE PACKET AS NEEDED o UPLOAD FINAL PACKET AUGUST 4 DEPARTMENT HR o ADD REVIEW AND ASSESS o ASSESSMENTS TO CANDIDATE AUGUST 25. The candidate has five calendar days thereafter

Jawitz, James W.

314

MAGNETIC FIELDS IN THE HR DIAGRAM Jeffrey L. Linsky  

E-print Network

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

Linsky, Jeffrey L.

315

Evolution of HR Diagrams So as a cluster ages, the  

E-print Network

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

Barnes, Joshua Edward

316

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

E-print Network

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

D'Antona, Francesca

317

HR DEPARTMENT POLICY ON THE EMPLOYMENT OF EX-OFFENDERS  

E-print Network

is made available on the HR website for all potential applicants to see when applying for a job. 2. CodeHR DEPARTMENT 1 POLICY ON THE EMPLOYMENT OF EX-OFFENDERS June 2009 #12;HR DEPARTMENT 2 1. Policy background. This policy confirms the University's specific commitment to ensuring that ex

Doran, Simon J.

318

gratterpalm uses HR as a strategic tool for growth  

Microsoft Academic Search

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

Helen Saunders

2009-01-01

319

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

320

NMR crystallography: the use of chemical shifts  

NASA Astrophysics Data System (ADS)

Measurements of chemical shifts obtained from magic-angle spinning NMR spectra (together with quantum mechanical computations of shielding) can provide valuable information on crystallography. Examples are given of the determination of crystallographic asymmetric units, of molecular symmetry in the solid-state environment, and of crystallographic space group assignment. Measurements of full tensor components for 199Hg have given additional coordination information. The nature of intermolecular hydrogen bonding in cortisone acetate polymorphs and solvates is obtained from chemical shift information, also involving measurement of the full tensor parameters. The resulting data have been used as restraints, built into the computation algorithm, in the analysis of powder diffraction patterns to give full crystal structures. A combination of quantum mechanical computation of shielding and measurement of proton chemical shifts (obtained by high-speed MAS) leads to the determination of the position of a proton in an intermolecular hydrogen bond. A recently-developed computer program specifically based on crystallographic repetition has been shown to give acceptable results. Moreover, NMR chemical shifts can distinguish between static and dynamic disorder in crystalline materials and can be used to determine modes and rates of molecular exchange motion.

Harris, Robin K.

2004-10-01

321

31P Solid-state NMR based monitoring of permeation of cell penetrating peptides into skin  

PubMed Central

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

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

2013-01-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

323

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

PubMed Central

The mas2 mutant of Saccharomyces cerevisiae is temperature sensitive for import of proteins into mitochondria. To identify the lesion in this mutant, we have cloned and sequenced the wild-type MAS2 gene and determined the intracellular location of its protein product. MAS2 encodes an essential 53-kd protein that is located in the mitochondrial matrix and is homologous to the MAS1 protein, a previously identified subunit of the protease that cleaves presequences from mitochondrial precursor proteins. The activity of this enzyme is temperature sensitive in mas2 cells. Together with the results of the accompanying study these results show that MAS2 and MAS1 encode the two subunits of the processing protease. Images PMID:3061808

Jensen, R E; Yaffe, M P

1988-01-01

324

B.Sc. EXAMINATION BY COURSE UNIT MAS 329 Topology  

E-print Network

B.Sc. EXAMINATION BY COURSE UNIT MAS 329 Topology 10.00am, Tuesday 25th May 2004 Duration: 2 hours. (b) Give three metrics on Rn which define the same topology on Rn . (c) Let (X, d) be a metric space compact. 2. (a) Explain what is meant by a topology on a set X. (b) Suppose R has the usual topology and X

Jackson, Bill

325

Photosynthese und Photomorphogenese bei Farnvorkeimen von Dryopteris filix-mas  

Microsoft Academic Search

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

H. Mohr; K. Ohlenroth

1962-01-01

326

Quantitation of aliphatic suberin in Quercus suber L. cork by FTIR spectroscopy and solid-state (13)C-NMR spectroscopy.  

PubMed

This work determined that the percentage of suberin in cork may be found by solid-state (13)C cross polarization/magic angle spinning (CP/MAS) NMR spectroscopy and by FTIR with photoacoustic detection (FTIR-PAS) spectroscopy. A linear relationship is found between the suberin content measured through CP/MAS spectral areas and that measured gravimetrically. Furthermore, application of a partial least squares (PLS1) regression model to the NMR and gravimetric data sets clearly correlates the two sets, enabling suberin quantification with 90% precision. Suberin quantitation by FTIR-PAS spectroscopy is also achieved by a PLS1 regression model, giving 90% accurate estimates of the percentage of suberin in cork. Therefore, (13)C-CP/MAS NMR and FTIR-PAS proved to be useful and accurate noninvasive techniques to quantify suberin in cork, thus avoiding the traditional time consuming and destructive chemical methods. PMID:11054654

Lopes, M H; Neto, C P; Barros, A S; Rutledge, D; Delgadillo, I; Gil, A M

2000-01-01

327

Training and 24-hr urinary catecholamine excretion.  

PubMed

We examined the effects of 28 weeks of training on 24-hr urinary catecholamine excretion and mood (evaluated using the Recovery-Stress Questionnaire for Athletes RESTQ-Sport) among seven national young female tennis players. Data were collected after a 1-month rest (September, T (1)), 3 months after T1(T2) and 7 months after T1(T3). Standardized Stress and Standardized Recovery scores and RESTQ-Index were computed. The training load increased by 161 % between T1 and T2 and by 55 % between T2 and T3. The performance (wins/total number of matches) decreased throughout the study. Urinary catecholamine excretion presented an U-shaped curve with a significant increase in 24-hr urinary catecholamine excretions, and epinephrine/norepinephrine ratio from T1 to T2 (T1 vs. T2: epinephrine: + 100 %, p < 0.05; norepinephrine: + 30 %, p < 0.05. Then, at T3, urinary catecholamine excretions and the epinephrine/norepinephrine ratio decreased significantly to values lower than the values observed at T1. A decrease in RESTQ-Index throughout the study was mainly based on a large increase in the Standardized Stress score. Changes in specific stress and recovery scales of the RESTQ-Sport for athletes and changes in catecholamine values indicated a state of heavy training stress and incomplete recovery at the end of the study. PMID:18651370

Filaire, E; Rouveix, M; Duclos, M

2009-01-01

328

Rheological and NMR studies of polyethylene/calcium carbonate composites.  

PubMed

Rheometry, 13C CP/MAS NMR spectra and 1H spin-lattice relaxation times T1 and T1rho have been employed to study the structure and molecular dynamics in composites of polyethylene (LDPE) with calcium carbonate filler. It has been found that the addition of the filler into the polymer leads to an increase in composite rigidity and a decrease in mobility in its crystalline regions. The presence of the filler affects the crystallization process making the crystal structure less perfect and reduces the size of the crystallites. PMID:14698410

Nowaczyk, G; G?owinkowski, S; Jurga, S

2004-01-01

329

The MicroMAS CubeSat Mission  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

330

Phosphate Ions in Bone: Identification of a Calcium–Organic Phosphate Complex by 31 P Solid-State NMR Spectroscopy at Early Stages of Mineralization  

Microsoft Academic Search

Previous 31P cross-polarization and differential cross-polarization magic angle spinning (CP\\/MAS and DCP\\/MAS) solid-state NMR spectroscopy studies of native bone and of the isolated crystals of the calcified matrix synthesized by osteoblasts in cell culture identified and characterized the major PO 4 -3 phosphate components of the mineral phase. The isotropic and anisotropic chemical shift parameters of the minor HPO 4

Y. Wu; J. L. Ackerman; E. S. Strawich; C. Rey; H.-M. Kim; M. J. Glimcher

2003-01-01

331

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

332

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

333

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

334

CHARACTERIZATION OF THE RED GIANT HR 2582 USING THE CHARA ARRAY  

SciTech Connect

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

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

2013-07-20

335

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

336

Investigation of Li in Clay Interlayers at Different Temperatures by NMR  

NASA Astrophysics Data System (ADS)

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

Kim, Y.; Lee, J.

2007-12-01

337

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

E-print Network

A simulator for organisation-centred MAS adaptation in P2P sharing networks Jordi Campos and Maite in a peer-to-peer (P2P) scenario. In particular, we describe our approach to MAS adaptation (2-LAMA), the P2, Coordination, Organisation, P2P, MAS 1. INTRODUCTION Organisational centred multi-agent systems (OCMAS) have

López-Sánchez, Maite

338

ACCELERATED LIGHT-INDUCED AGING OF ?-, ?-, AND ?-C-ENRICHED CELL WALL-DEHYDROGENATION POLYMERS STUDIED WITH SOLID STATE C NMR SPECTROSCOPY  

Microsoft Academic Search

Light-induced aging of lignocellulosic materials has been studied with a new technique involving selectively ?-, ?-, and ?-C-enriched cell wall-dehydrogenation polymers (CW-DHPs) and solid state C NMR spectroscopy. The results from cross-polarization magic angle spinning (CP\\/MAS) C NMR experiments of unirradiated and irradiated CW-DHP have revealed mainly a decrease in the amount of end-groups of both coniferaldehyde and coniferyl alcohol type. The

Jim Parkås; Magnus Paulsson; D. L. VanderHart; Ulla Westermark

2002-01-01

339

A TQM Approach to HR Performance Evaluation Criteria  

Microsoft Academic Search

In contrast to previous research on HR performance evaluation in quality organisational environments, which is mainly confined to the literature and theory-based studies, this paper provides a partial answer to the question: ‘what is a typical quality-oriented HR performance evaluation system’? In this study, an attempt is made to highlight the key generic criteria of a quality-driven HR performance evaluation

Ebrahim Soltani; Robert van der Meer; John Gennard; Terry Williams

2003-01-01

340

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

341

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

342

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

343

Structure and orientation of dynorphin bound to lipid bilayers by 13C solid-state NMR  

NASA Astrophysics Data System (ADS)

Secondary structure and orientation of dynorphin bound to dimyristoylphosphatidylcholine (DMPC) bilayer were investigated by solid-state 13C NMR spectroscopy. For this purpose, 13C NMR spectra of the site-specifically 13C-labeled dynorphin were measured in the membrane-bound state under static, magic angle spinning (MAS), and slow MAS conditions. In the static experiment, magnetically oriented vesicle system (MOVS) induced by dynorphin was successfully used to investigate the orientation of dynorphin bound to the lipid bilayers. It was found that dynorphin adopts an ?-helical structure in the N-terminus from Gly 2 to Leu 5 by analyses of the isotropic chemical shifts obtained from the MAS experiments. In contrast, it adopts disordered conformations from the center to the C-terminus and is located on the membrane surface. The static 13C NMR spectra indicated that MOVS-bound dynorphin was oriented to the magnetic field and rotated rapidly about the bilayer normal. Subsequently, we analyzed the 13C chemical shift tensors of carbonyl carbons in the peptide backbone by considering the rotational motion of the N-terminal ?-helix. It was revealed that the N-terminal ?-helix is inserted into the membrane with the tilt angle of 21° to the bilayer normal. This structure suggests a possibility that dynorphin interacts with the extracellular loop II of the ?-receptor through a helix-helix interaction.

Uezono, Takiko; Toraya, Shuichi; Obata, Maki; Nishimura, Katsuyuki; Tuzi, Satoru; Saitô, Hazime; Naito, Akira

2005-07-01

344

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

345

Antecedents of front-line managers' perceptions of HR role stressors  

Microsoft Academic Search

Purpose – Based on role theory, this paper seeks to investigate the impact of HR devolution characteristics (number of devolved HR tasks), characteristics of the HR devolution context (level of support from the HR department, and presence of institutionalised incentives to perform the allotted HR tasks well), and personal characteristics of the front-line managers (HR competency) on front-line managers' perceptions

Caroline Gilbert; Sophie De Winne; Luc Sels

2011-01-01

346

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

347

31 P and 51 V MAS-NMR Characterisation of Mixed Vanadium and Titanium Phosphates Prepared from Molecular Precursors  

Microsoft Academic Search

Coprecipitation of mixed vanadium and titanium phosphates has been performed by reacting a mixed solution of vanadium alkoxide (VO(OPrn)3) and titanium alkoxide (Ti(OPrn)4) with anhydrous phosphoric acid (H3PO4). The goal is to obtain a mixture at a molecular level of phosphates with both acidic and redox properties. In protic solvents, such as propanol, the vanadium phosphate precipitation is slow, so,

S. A. Ennaciri; C. R’kha; P. Barboux; J. Livage; J. Maquet

2005-01-01

348

Enzymatic hydrolysis of ionic liquid-pretreated celluloses: contribution of CP-MAS 13C NMR and SEM.  

PubMed

The supramolecular structure of four model celluloses was altered prior to their enzymatic saccharification using two ionic liquid pretreatments: one with the commonly used 1-ethyl-3-methylimidazolium acetate ([Emim](+)[CH(3)COO](-)) and the other with the newly developed 1-ethyl-3-methylimidazolium methylphosphonate ([Emim](+)[MeO(H)PO(2)](-)). The estimation of crystallinity index (CrI) by solid state (13)C nuclear magnetic resonance for each untreated/pretreated celluloses was compared with the performances of their enzymatic hydrolysis. For ?-cellulose, both pretreatments led to a significant decrease in CrI from 25% to 5% but had no effect on glucose yields. In contrast, The [Emim](+)[MeO(H)PO(2)](-) pretreatment on the long fibers of cellulose had no significant effect on the CrI although a conversion yield in glucose of 88% is obtained versus 32% without pretreatment. However, scanning electron microscopy analysis suggested a loss of fiber organization induced by both ionic liquid pretreatments leading to a larger accessibility by cellulases to the cellulose surface. PMID:21612918

Husson, Eric; Buchoux, Sébastien; Avondo, Carine; Cailleu, Dominique; Djellab, Karim; Gosselin, Isabelle; Wattraint, Olivier; Sarazin, Catherine

2011-08-01

349

CHARACTERIZATION OF THE WOUND INDUCED MATERIAL IN CITRUS FRUIT PEEL BY CARBON-13 CP-MAS SOLID STATE NMR SPECTROSCOPY  

Technology Transfer Automated Retrieval System (TEKTRAN)

There are conflicting views regarding the chemical composition of the induced, phloroglucinol-HCl (PG-HCl) reacting, material accumulating in injured citrus peel tissues. Grapefruit, Citrus paradisi, were injured, inoculated with Peicillium digitatum and incubated under contitions favorable to the a...

350

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

351

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

E-print Network

Torino, Via P. Giuria 7, 10125 Torino, Italy a r t i c l e i n f o Article history: Received 3 January for analysis of the population of framework Al- and Si-related defective sites. Beside framework Al atoms in regular Td coordination, perturbed Td coordinated Al atoms and partly extra-framework Al species

Sklenak, Stepan

352

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

E-print Network

of Geology, University of Illinois at Urbana-Champaign, 245 Natural History Building, 1301 West Green Street of ground- water and the adsorption and transport of nuclear waste and heavy metals.1-3 Many layer silicates

Puglisi, Joseph

353

Two phase morphology limits lithium diffusion in TiO(2)(anatase): a (7)Li MAS NMR study.  

PubMed

7Li magic angle spinning solid-state nuclear magnetic resonance is applied to investigate the lithium local environment and lithium ion mobility in tetragonal anatase TiO(2) and orthorhombic lithium titanate Li(0.6)TiO(2). Upon lithium insertion, an increasing fraction of the material changes its crystallographic structure from anatase TiO(2) to lithium titanate Li(0.6)TiO(2). Phase separation occurs, and as a result, the Li-rich lithium titanate phase is coexisting with the Li-poor TiO(2) phase containing only small Li amounts approximately equal to 0.01. In both the anatase and the lithium titanate lattice, Li is found to be hopping over the available sites with activation energies of 0.2 and 0.09 eV, respectively. This leads to rapid microscopic diffusion rates at room temperature (D(micr) = 4.7 x 10(-12) cm(2)s(-1) in anatase and D(micr) = 1.3 x 10(-11) cm(2)s(-1) in lithium titanate). However, macroscopic intercalation data show activation energies of approximately 0.5 eV and smaller diffusion coefficients. We suggest that the diffusion through the phase boundary is determining the activation energy of the overall diffusion and the overall diffusion rate itself. The chemical shift of lithium in anatase is independent of temperature up to approximately 250 K but decreases at higher temperatures, reflecting a change in the 3d conduction electron densities. The Li mobility becomes prominent from this same temperature showing that such electronic effects possibly facilitate the mobility. PMID:11707123

Wagemaker, M; van de Krol, R; Kentgens, A P; van Well, A A; Mulder, F M

2001-11-21

354

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

E-print Network

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

Shubitidze, Fridon

355

Soils, Pores, and NMR  

NASA Astrophysics Data System (ADS)

Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 < 5 ms. Moreover, the dependence of the relaxation rate on magnetic field strength allows the identification of 2D diffusion at the interfaces as the mechanism which governs the relaxation process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about the connectivity of the pore system. Examples are given for T1-T2 correlation of some soil samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a Natural soil: Comparison of Relaxometric Imaging, T1 - T2 Correlation and Fast-Field Cycling NMR." The Open Magnetic Resonance Journal: in print. Pohlmeier, A., S. Haber-Pohlmeier, et al. (2009). "A Fast Field Cycling NMR Relaxometry Study of Natural Soils." Vadose Zone J. 8: 735-742. Stingaciu, L. R., A. Pohlmeier, et al. (2009). "Characterization of unsaturated porous media by high-field and low-field NMR relaxometry." Water Resources Research 45: W08412

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

2010-05-01

356

Welding Metallurgy of Alloy HR-160  

SciTech Connect

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

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

1999-05-28

357

Outsourcing HR Services: The Role of Human Resource Intermediaries  

ERIC Educational Resources Information Center

Purpose: In this article, the area of interest is an emerging type of organisation called human resource intermediaries (HRIs), which focus on delivering human resource (HR) services to public sector organisations and private companies. The purpose of this article is, thus, to explore HRIs as deliverers of HR services. More specifically, the…

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

2012-01-01

358

African American Accounting Majors and the 150-hr Requirement  

ERIC Educational Resources Information Center

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

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

2010-01-01

359

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

360

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

E-print Network

Human capital measures, strategy, and performance: HR managers' perceptions Stephen Gates AUDENCIA.1108/09513571011010628 #12;1 Human capital measures, strategy, and performance: HR managers' perceptions Abstract: Purpose to identify and better understand their perceptions and expectations of Human capital (HC) measures' content

Boyer, Edmond

361

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

E-print Network

MEMORANDUM TO: HR and Business Contacts FROM: Division of Human Resources DATE: October 25, 2013 RE: Human Resources Fall 2013 Forum The Division of Human Resources will sponsor an HR Forum from 1 to the Division of Human Resources' Organizational and Professional Development Office at hrtrain

Almor, Amit

362

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

E-print Network

TO: HR and Business Contacts FROM: Division of Human Resources DATE: September 6, 2012 RE: Human Resources Fall 2012 Forum The Division of Human Resources will sponsor an HR Forum from 1-4 p in person or by webinar. Any questions about the forum may be e-mailed to the Division of Human Resources

Almor, Amit

363

HR diagrams derived from the Michigan Spectral Catalogue  

Microsoft Academic Search

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

N. Houk; R. Fesen

1978-01-01

364

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

Microsoft Academic Search

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

Cornelis Jager

1990-01-01

365

In vitro activity of HR 810, a new cephalosporin.  

PubMed Central

The in vitro susceptibility of 409 clinical isolates to HR 810, a new cephalosporin, was evaluated and compared with their susceptibility to aztreonam, cefazolin, ceftazidime, imipenem, moxalactam, piperacillin, and gentamicin. On a weight basis, the activity of HR 810 against gram-negative bacilli was equivalent or superior to that of the other beta-lactam agents except imipenem. PMID:6593000

Bertram, M A; Bruckner, D A; Young, L S

1984-01-01

366

GERALD SCHWARTZ SCHOOL OF BUSINESS Accounting, Finance, Management/HR  

E-print Network

GERALD SCHWARTZ SCHOOL OF BUSINESS Accounting, Finance, Management/HR DEPARTMENT OF BUSINESS ADMINISTRATION The Department of Business Administration of the Gerald Schwartz School of Business is seeking interest from possible candidates for faculty positions in finance, management/HR, and accounting

367

Anode consumption on a subsea X-mas tree  

SciTech Connect

Anode consumption and coating breakdown on a X-mas tree installed at the Troll Field in the Norwegian North Sea was investigated after 5 years. A comparison with a spare tree and one tree being exposed for only 3--4 months was done. The epoxy coating has several blisters, in particular on stainless steel surfaces. Water inside the blisters has a pH of 13-14 indicating that the cathodic reaction occurs inside them. The anode dimensions indicate an overall anode consumption of approximately 20%, while the design allows 27% after 5 years. This indicates that the original design is quite conservative. If the design had been done according to present day design rules, the conservatism would be reduced; an overall anode consumption of 23% is then likely (still less than allowed 27%).

Lye, R.E. [Norsk Hydro Research Centre, Porsgrunn (Norway)

1998-12-31

368

NMR spectroscopic studies of "titanocene"  

E-print Network

NMR SPECTROSCOPIC STUDIES OF "TITANOCENE" A Thea is by DONALD FLOYD BIRKELBACH Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1971 Ma)or Sub...)cot: Chemistry NMR SPECTROSCOPIC STUDIES OF "TITANOCENE" A Thesis by DONALD FLOYD BIRKELBACH Approved as to style and content by: (C ai"iman of Committee) (Head of Department) (Member) (Member) (Member) (Memb er) (Member) May 1971 ABSTRACT NMR...

Birkelbach, Donald Floyd

1971-01-01

369

Study the Effects of Mechanical Activation on Li-N-H Systems With 1H and 6Li Solid-State NMR  

SciTech Connect

To gain insight into the effects of mechanical activation (MA) on the hydrogen desorption of the lithium amide (LiNH2) and lithium hydride (LiH) mixture, LiNH2 and LiH+LiNH2 were mechanically activated by high-energy ball milling. The formed products were studied with in situ 1H and 6Li nuclear magic angle spinning (MAS) magnetic resonance (NMR) spectroscopy from ambient temperature to 180 degrees C. Up-field chemical shift was observed in 6Li MAS NMR spectra with increased milling time, indicating that average local electronic structure around Li nuclei was modified during MA. 1H MAS NMR was used to dynamically probe ammonia release from the activated LiNH2 at temperature as low as 50 degrees C. In the case of activated LiH+LiNH2 mixtures, the 1H MAS NMR results implied that MA enhanced the dehydrogenation reaction of LiNH2+LiH=Li2NH+H2 and suppressed ammonia generation as well.

Lu, Chun; Hu, Jian Zhi; Kwak, Ja Hun; Yang, Z Gary; Ren, Ruiming; Markmaitree, Tippawan; Shaw, Leonard D.

2007-07-10

370

NMR, PDF and RMC study of the positive electrode material Li(Ni0.5Mn0.5)O2 synthesized by ion-exchange methods{{  

E-print Network

with the Reverse Monte Carlo (RMC) technique and 6 Li Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR group R3¯m) and consists of a layered structure. In the material prepared by using a mixed nickel structural work on this system,8 we applied Pair Distribution Function (PDF) analysis, in combination

Ceder, Gerbrand

371

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

SciTech Connect

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

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

1999-12-13

372

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

373

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

374

NMR Spectroscopy of Azo Dyes  

Microsoft Academic Search

The known NMR spectroscopy data on different types of synthetic azo and polyazo dyes, including metal complexes, are correlated. The fundamentally new opportunities in the NMR spectroscopy of 1H, 13C, and 15N nuclei in solving problems of structural chemistry in this field of industrial chemistry are demonstrated. The bibliography includes 124 references.

L A Fedorov

1988-01-01

375

NMR Spectroscopy of Azo Dyes  

NASA Astrophysics Data System (ADS)

The known NMR spectroscopy data on different types of synthetic azo and polyazo dyes, including metal complexes, are correlated. The fundamentally new opportunities in the NMR spectroscopy of 1H, 13C, and 15N nuclei in solving problems of structural chemistry in this field of industrial chemistry are demonstrated. The bibliography includes 124 references.

Fedorov, L. A.

1988-10-01

376

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

377

Two-dimensional NMR spectroscopy  

SciTech Connect

Written for chemists and biochemists who are not NMR spectroscopists, but who wish to use the new techniques of two-dimensional NMR spectroscopy, this book brings together for the first time much of the practical and experimental data needed. It also serves as information source for industrial, academic, and graduate student researchers who already use NMR spectroscopy, but not yet in two dimensions. The authors describe the use of 2-D NMR in a wide variety of chemical and biochemical fields, among them peptides, steroids, oligo- and poly-saccharides, nucleic acids, natural products (including terpenoids, alkaloids, and coal-derived heterocyclics), and organic synthetic intermediates. They consider throughout the book both the advantages and limitations of using 2-D NMR.

Croasmun, W.R.; Carlson, R.M.K.

1987-01-01

378

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

Microsoft Academic Search

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

Hu Feng; Hang Zhou; P. R. China

2010-01-01

379

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

Microsoft Academic Search

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

Haibin Yang; Sunny Li Sun; Mike W. Peng

2011-01-01

380

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

381

Searching for microporous, strongly basic catalysts: experimental and calculated 29Si NMR spectra of heavily nitrogen-doped Y zeolites.  

PubMed

Nitrogen substituted zeolites with high crystallinity and microporosity are obtained by nitrogen substitution for oxygen in zeolite Y. The substitution reaction is performed under ammonia flow by varying the temperature and reaction time. We examine the effect of aluminum content and charge-compensating cation (H(+)/Na(+)/NH(4)(+)) on the degree of nitrogen substitution and on the preference for substitution of Si-O-Al vs Si-O-Si linkages in the FAU zeolite structure. Silicon-29 magic angle spinning (MAS) nuclear magnetic resonance (NMR) and (1)H/(29)Si cross-polarization MAS NMR spectroscopy have been used to probe the different local environments of the nitrogen-substituted zeolites. Experimental data are compared to simulated NMR spectra obtained by constructing a compendium (>100) of zeolite clusters with and without nitrogen, and by performing quantum calculations of chemical shifts for the NMR-active nuclei in each cluster. The simulated NMR spectra, which assume peak intensities predicted by statistical analysis, agree remarkably well with the experimental data. The results show that high levels of nitrogen substitution can be achieved while maintaining porosity, particularly for NaY and low-aluminum HY materials, without significant loss in crystallinity. Experiments performed at lower temperatures (750-800 degrees C) show a preference for substitution at Si-OH-Al sites. No preference is seen for reactions performed at higher temperatures and longer reaction times (e.g., 850 degrees C and 48 h). PMID:19722674

Dogan, Fulya; Hammond, Karl D; Tompsett, Geoffrey A; Huo, Hua; Conner, W Curtis; Auerbach, Scott M; Grey, Clare P

2009-08-12

382

MMAE Co-terminal Degrees Summary Co-terminal Degrees within MMAE (MAS = master of engineering, i.e. non-thesis  

E-print Network

+ MAS Mechanical and Aerospace Engineering · BS Aerospace Engineering + MAS Mechanical and Aerospace Engineering · BS Mechanical Engineering + MAS Materials Science and Engineering · BS Aerospace Engineering + MAS Materials Science and Engineering

Heller, Barbara

383

Association of dissolved aluminum with silica: Connecting molecular structure to surface reactivity using NMR  

NASA Astrophysics Data System (ADS)

We studied uptake mechanisms for dissolved Al on amorphous silica by combining bulk-solution chemistry experiments with solid-state Nuclear Magnetic Resonance techniques ( 27Al magic-angle spinning (MAS) NMR, 27Al{ 1H} cross-polarization (CP) MAS NMR and 29Si{ 1H} CP-MAS NMR). We find that reaction of Al (1 mM) with amorphous silica consists of at least three reaction pathways; (1) adsorption of Al to surface silanol sites, (2) surface-enhanced precipitation of an aluminum hydroxide, and (3) bulk precipitation of an aluminosilicate phase. From the NMR speciation and water chemistry data, we calculate that 0.20 (±0.04) tetrahedral Al atoms nm -2 sorb to the silica surface. Once the surface has sorbed roughly half of the total dissolved Al (˜8% site coverage), aluminum hydroxides and aluminosilicates precipitate from solution. These precipitation reactions are dependent upon solution pH and total dissolved silica concentration. We find that the Si:Al stoichiometry of the aluminosilicate precipitate is roughly 1:1 and suggest a chemical formula of NaAlSiO 4 in which Na + acts as the charge compensating cation. For the adsorption of Al, we propose a surface-controlled reaction mechanism where Al sorbs as an inner-sphere coordination complex at the silica surface. Analogous to the hydrolysis of Al(OH)63+, we suggest that rapid deprotonation by surface hydroxyls followed by dehydration of ligated waters results in four-coordinate (>SiOH) 2Al(OH) 2 sites at the surface of amorphous silica.

Houston, J. R.; Herberg, J. L.; Maxwell, R. S.; Carroll, S. A.

2008-07-01

384

HR User Group Meeting Agenda South Meeting Room, Newcomb Hall  

E-print Network

Staffing Changes: Michelle Small joined HR Consulting Services (HRCS) as an HRCS Consultant on August 18 Center Benefit and Wellness Fair, Main Hospital, Dining Conference Room, 7 am to 3 pm #12;2 Questions

Acton, Scott

385

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

386

NUMBER: HR 1.21 SECTION: Human Resources  

E-print Network

NUMBER: HR 1.21 SECTION: Human Resources SUBJECT: Educational Leave DATE: August 1988 REVISED: Division of Human Resources CAROLINA DIVISION OF HUMAN RESOURCES HAS THE AUTHORITY TO INTERPRET THE UNIVERSITY'S HUMAN RESOURCES

Almor, Amit

387

SVM spatio-temporal vegetation classification using HR satellite images  

Microsoft Academic Search

This paper proposes a new HR spatio-temporal vegetation classification approach based on SVM. A multi-band SVM approach is first applied on satellite images time series then a graph based SVM algorithm is used for temporal analysis.

S. Réjichi; F. Chaâbane

2011-01-01

388

SVM spatio-temporal vegetation classification using HR satellite images  

NASA Astrophysics Data System (ADS)

This paper proposes a new HR spatio-temporal vegetation classification approach based on SVM. A multi-band SVM approach is first applied on satellite images time series then a graph based SVM algorithm is used for temporal analysis.

Réjichi, S.; Chaâbane, F.

2011-11-01

389

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

PubMed

The chemical structure and interactions of the cell wall polysaccharides from the red edible seaweed Palmaria palmata were studied by liquid-like magic-angle-spinning (MAS) and cross-polarization MAS (CPMAS) solid-state 13C NMR spectroscopy. The liquid-like MAS and CPMAS 13C NMR spectra of the rehydrated algal powder revealed the presence of beta-(1-->4)/beta-(1-->3)-linked D-xylan with chemical shifts close to those observed in the solution 13C NMR spectrum of the polysaccharide. Observation of mix-linked xylan in the liquid-like MAS 13C NMR spectrum indicated that part of this cell wall polysaccharide is loosely held in the alga. The CPMAS NMR spectrum of the dry algal powder alcohol insoluble residue (AIR) showed broad peaks most of which corresponded to the mix-linked xylan. Hydration of AIR induced a marked increase in the signal resolution also in the CPMAS NMR spectra together with a shift of the C-3 and C-4 signals of the (1-->3)- and (1-->4)-linked xylose, respectively. Such modifications were present in the spectrum of hydrated (1-->3)-linked xylan from the green seaweed Caulerpa taxifolia and absent in that of (1-->4)-linked xylan from P. palmata. This result emphasizes the important role of (1-->3) linkages on the mix-linked xylan hydration-induced conformational rearrangement. The mix-linked xylan signals were observed in the CPMAS NMR spectrum of hydrated residues obtained after extensive extractions by NaOH or strong chaotropic solutions indicating strong hydrogen bonds or covalent linkages. T(1 rho) relaxations were measured close or above 10 ms for the mix-linked xylan in the dry and hydrated state in AIR and indicated that the overall xylan chains likely remain rigid. Rehydration of the mix-linked xylan lead to a decrease in the motion of protons bounded to the C-1 and C-4 carbons of the (1-->4)-linked xylose supporting the re-organization of the xylan chains under hydration involving junction-zones held by hydrogen bonds between adjacent (1-->4)-linked xylose blocks. The CPMAS NMR spectrum of both dry and rehydrated residues obtained after NaOH and HCl extractions demonstrated the presence of cellulose and (1-->4)-linked xylans. The structures of the different polysaccharides are discussed in relation to their interactions and putative functions on the cell wall mechanical properties in P. palmata. PMID:12860427

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

2003-07-22

390

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

PubMed Central

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

Gomes, Mayara Santos; Restini, Carolina Baraldi Araujo

2014-01-01

391

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.

392

The genetic deletion of Mas abolishes salt induced hypertension in mice.  

PubMed

The G protein-coupled receptor Mas is a physiological antagonist of the angiotensin II type 1 receptor and is associated with angiotensin-(1-7) signaling. We investigated the effect of Mas-deficiency on blood pressure regulation under physiological conditions and salt load using radiotelemetry. Mas-knockout mice and their wild-type controls received a telemetry implant in the carotid artery. One week after surgery, animals were monitored for 3 days receiving normal diet (0.6% NaCl) followed by one-week high-salt diet (8% NaCl). Under same high-salt diet, another set of mice was placed in individual metabolic cages for 4 days. Basal mean arterial pressure, heart rate and locomotor activity displayed normal day-night rhythm in Mas-deficient mice. Mas-knockout mice were normotensive. High dietary NaCl ingestion did not alter heart rate or locomotor activity in both groups, but significantly increased night time mean arterial pressure in control mice whereas this increase was blunted in Mas-deficient mice. Baseline food and water intake and urine osmolality were not different between both genotypes. Under high-salt diet, water consumption and food intake were equally increased in wild-type controls and Mas-knockout, but urinary electrolytes and osmolality were significantly higher in Mas-knockout. Taken together, basal hemodynamic parameters are unchanged in Mas-knockout mice. In contrast to wild-type controls, telemetric mean arterial pressure measurement revealed salt resistance in Mas-deficient animals, probably due to their higher urinary NaCl excretion. This is the first direct proof that Mas blockade might be a new option in the treatment of salt-sensitive hypertension. PMID:22652430

Heringer-Walther, Silvia; Gembardt, Florian; Perschel, Frank Holger; Katz, Norbert; Schultheiss, Heinz-Peter; Walther, Thomas

2012-08-15

393

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

394

NMR Sample Policy Version: 20 Jul 2006  

E-print Network

NMR Sample Policy Version: 20 Jul 2006 Task: NMR Sample Preparation Equipment Used: Centrifuge, p Assessment NMR002 `Protein NMR Sample Preparation' on the Cancer Studies COSHH database covers a number bacteria. 3. Low: Use of any biological hazard is discouraged and must follow all COSHH regulations. Some

Birmingham, University of

395

Diversification versus specialization: an event study of M&As in the European banking industry  

Microsoft Academic Search

This study examines the stock market valuation in terms of expected gains of mergers and acquisitions (M&As) amongst banks that were announced from 1991 to 2001 in 13 European markets. M&As are classified according to activity, geographic specialization or diversification. A bivariate GARCH model is used to estimate abnormal returns taking beta conditional variability into account. The results document that

Laetitia Lepetit; Stéphanie Patry; Philippe Rous

2004-01-01

396

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

E-print Network

MAS473 SCHOOL OF MATHEMATICS AND STATISTICS Spring Semester 2013­2014 MAS473 Extended linear models to investigate the time taken for a clot to form in a sample of blood, when treated with a drug. Three drugs are compared. There are ten volunteers in the study. Each volunteer donates six blood samples, and each drug

397

Multi-Agent System (MAS) for short-term generation scheduling of a microgrid  

Microsoft Academic Search

Microgrids are low voltage distribution networks comprising various distributed generators, storage devices and controllable loads. Microgrid can be operated in interconnected mode or islanded mode. Optimal generation scheduling is one of the microgrid energy management system's function for optimizing the microgrid operation. This paper presents a Multi-Agent System (MAS) for generation scheduling of a microgrid. The proposed MAS architecture has

T. Logenthiran; D. Srinivasan; A. M. Khambadkone; H. N. Aung

2010-01-01

398

Evidence of depolymerisation of amorphous silica at medium- and short-range order: XANES, NMR and CP-SEM contributions  

Microsoft Academic Search

This work reports medium- and short-range order of changes of amorphous silica submitted to chemical degradation. Structural changes were studied, using X-ray absorption near edge structure (XANES), nuclear magnetic resonance 29Si NMR-MAS and controlled pressure scanning electron microscope (CP-SEM). The depolymerisation of amorphous SiO2 compounds mainly induces the formation of Q3 species and alkali-rich domains. The XANES Si K-edge spectra

L. Khouchaf; A. Hamoudi; P. Cordier

2009-01-01

399

The role of Al in C–S–H: NMR, XRD, and compositional results for precipitated samples  

Microsoft Academic Search

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

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

2006-01-01

400

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

401

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

402

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

403

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

SciTech Connect

We report spectroscopic observations of the red giant star HR 5692, previously known to be a binary system both from other spectroscopic work and from deviations in the astrometric motion detected by the Hipparcos satellite. Earlier International Ultraviolet Explorer (IUE) observations had shown the presence of a hot white dwarf companion to the giant primary. We have combined our radial velocity observations with other existing measurements and with the Hipparcos intermediate astrometric data to determine a complete astrometric-spectroscopic orbital solution, providing the inclination angle for the first time. We also determine an improved parallax for the system of 10.12 {+-} 0.67 mas. We derive the physical properties of the primary, and with an estimate of its mass from stellar evolution models (1.84 {+-} 0.40 M{sub sun}), we infer the mass of the white dwarf companion to be M{sub WD} = 0.59 {+-} 0.12 M{sub sun}. An analysis of an IUE white dwarf spectrum, using our parallax, yields T{sub eff} = 30, 400 {+-} 780 K, log g = 8.25 {+-} 0.15, and a mass M{sub WD} = 0.79 {+-} 0.09 M{sub sun}, in marginal agreement with the dynamical mass.

Stefanik, Robert P.; Torres, Guillermo; Latham, David W. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Landsman, Wayne [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Craig, Nathaniel; Murrett, James, E-mail: rstefanik@cfa.harvard.edu [Harvard College, Cambridge, MA 02138 (United States)

2011-05-15

404

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

405

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

406

Multispectral Analysis of NMR Imagery  

NASA Technical Reports Server (NTRS)

Conference paper discusses initial efforts to adapt multispectral satellite-image analysis to nuclear magnetic resonance (NMR) scans of human body. Flexibility of these techniques makes it possible to present NMR data in variety of formats, including pseudocolor composite images of pathological internal features. Techniques do not have to be greatly modified from form in which used to produce satellite maps of such Earth features as water, rock, or foliage.

Butterfield, R. L.; Vannier, M. W. And Associates; Jordan, D.

1985-01-01

407

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.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

2010-06-15

408

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

409

(13)C, (15)N CPMAS NMR and GIAO DFT calculations of stereoisomeric oxindole alkaloids from Cat's Claw (Uncaria tomentosa).  

PubMed

Oxindole alkaloids, isolated from the bark of Uncaria tomentosa [Willd. ex Schult.] Rubiaceae, are considered to be responsible for the biological activity of this herb. Five pentacyclic and two tetracyclic alkaloids were studied by solid-state NMR and theoretical GIAO DFT methods. The (13)C and (15)N CPMAS NMR spectra were recorded for mitraphylline, isomitraphylline, pteropodine (uncarine C), isopteropodine (uncarine E), speciophylline (uncarine D), rhynchophylline and isorhynchophylline. Theoretical GIAO DFT calculations of shielding constants provide arguments for identification of asymmetric centers and proper assignment of NMR spectra. These alkaloids are 7R/7S and 20R/20S stereoisomeric pairs. Based on the (13)C CP MAS chemical shifts the 7S alkaloids (delta C3 70-71ppm) can be easily and conveniently distinguished from 7R (deltaC3 74.5-74.9ppm), also 20R (deltaC20 41.3-41.7ppm) from the 20S (deltaC20 36.3-38.3ppm). The epiallo-type isomer (3R, 20S) of speciophylline is characterized by a larger (15)N MAS chemical shift of N4 (64.6ppm) than the allo-type (3S, 20S) of isopteropodine (deltaN4 53.3ppm). (15)N MAS chemical shifts of N1-H in pentacyclic alkaloids are within 131.9-140.4ppm. PMID:19019638

Paradowska, Katarzyna; Wolniak, Micha?; Pisklak, Maciej; Gli?ski, Jan A; Davey, Matthew H; Wawer, Iwona

2008-11-01

410

High-resolution EEG (HR-EEG) and magnetoencephalography (MEG).  

PubMed

High-resolution EEG (HR-EEG) and magnetoencephalography (MEG) allow the recording of spontaneous or evoked electromagnetic brain activity with excellent temporal resolution. Data must be recorded with high temporal resolution (sampling rate) and high spatial resolution (number of channels). Data analyses are based on several steps with selection of electromagnetic signals, elaboration of a head model and use of algorithms in order to solve the inverse problem. Due to considerable technical advances in spatial resolution, these tools now represent real methods of ElectroMagnetic Source Imaging. HR-EEG and MEG constitute non-invasive and complementary examinations, characterized by distinct sensitivities according to the location and orientation of intracerebral generators. In the presurgical assessment of drug-resistant partial epilepsies, HR-EEG and MEG can characterize and localize interictal activities and thus the irritative zone. HR-EEG and MEG often yield significant additional data that are complementary to other presurgical investigations and particularly relevant in MRI-negative cases. Currently, the determination of the epileptogenic zone and functional brain mapping remain rather less well-validated indications. In France, in 2014, HR-EEG is now part of standard clinical investigation of epilepsy, while MEG remains a research technique. PMID:25648821

Gavaret, M; Maillard, L; Jung, J

2015-03-01

411

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

412

Medical applications of NMR imaging and NMR spectroscopy with stable isotopes. Summary  

SciTech Connect

The current status of NMR imaging and NMR spectroscopy are summarized. For the most part examples from the March 1983 Puerto Rico symposium are used to illustrate the utility of NMR in medicine. 18 refs., 5 figs.

Matwiyoff, N.A.

1983-01-01

413

Atypical Signaling and Functional Desensitization Response of MAS Receptor to Peptide Ligands  

PubMed Central

MAS is a G protein-coupled receptor (GPCR) implicated in multiple physiological processes. Several physiological peptide ligands such as angiotensin-(1–7), angiotensin fragments and neuropeptide FF (NPFF) are reported to act on MAS. Studies of conventional G protein signaling and receptor desensitization upon stimulation of MAS with the peptide ligands are limited so far. Therefore, we systematically analyzed G protein signals activated by the peptide ligands. MAS-selective non-peptide ligands that were previously shown to activate G proteins were used as controls for comparison on a common cell based assay platform. Activation of MAS by the non-peptide agonist (1) increased intracellular calcium and D-myo-inositol-1-phosphate (IP1) levels which are indicative of the activation of classical G?q-phospholipase C signaling pathways, (2) decreased G?i mediated cAMP levels and (3) stimulated G?12-dependent expression of luciferase reporter. In all these assays, MAS exhibited strong constitutive activity that was inhibited by the non-peptide inverse agonist. Further, in the calcium response assay, MAS was resistant to stimulation by a second dose of the non-peptide agonist after the first activation has waned suggesting functional desensitization. In contrast, activation of MAS by the peptide ligand NPFF initiated a rapid rise in intracellular calcium with very weak IP1 accumulation which is unlike classical G?q-phospholipase C signaling pathway. NPFF only weakly stimulated MAS-mediated activation of G?12 and G?i signaling pathways. Furthermore, unlike non-peptide agonist-activated MAS, NPFF-activated MAS could be readily re-stimulated the second time by the agonists. Functional assays with key ligand binding MAS mutants suggest that NPFF and non-peptide ligands bind to overlapping regions. Angiotensin-(1–7) and other angiotensin fragments weakly potentiated an NPFF-like calcium response at non-physiological concentrations (?100 µM). Overall, our data suggest that peptide ligands induce atypical signaling and functional desensitization of MAS. PMID:25068582

Tirupula, Kalyan C.; Desnoyer, Russell; Speth, Robert C.; Karnik, Sadashiva S.

2014-01-01

414

Coherent and stochastic averaging in solid-state NMR  

NASA Astrophysics Data System (ADS)

A new approach for calculating solid-state NMR lineshapes of uniaxially rotating membrane proteins under the magic-angle spinning conditions is presented. The use of stochastic Liouville equation (SLE) allows one to account for both coherent sample rotation and stochastic motional averaging of the spherical dipolar powder patterns by uniaxial diffusion of the spin-bearing molecules. The method is illustrated via simulations of the dipolar powder patterns of rigid samples under the MAS conditions, as well as the recent method of rotational alignment in the presence of both MAS and rotational diffusion under the conditions of dipolar recoupling. It has been found that it is computationally more advantageous to employ direct integration over a spherical grid rather than to use a full angular basis set for the SLE solution. Accuracy estimates for the bond angles measured from the recoupled amide 1H-15N dipolar powder patterns have been obtained at various rotational diffusion coefficients. It has been shown that the rotational alignment method is applicable to membrane proteins approximated as cylinders with radii of approximately 20 Å, for which uniaxial rotational diffusion within the bilayer is sufficiently fast and exceeds the rate 2 × 105 s-1.

Nevzorov, Alexander A.

2014-12-01

415

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves  

SciTech Connect

We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

Thurber, Kent R., E-mail: thurberk@niddk.nih.gov; Tycko, Robert [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)] [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

2014-05-14

416

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

417

Solvation and crystal effects in bilirubin studied by NMR spectroscopy and density functional theory.  

PubMed

The open-chain tetrapyrrole compound bilirubin was investigated in chloroform and dimethyl sulfoxide solutions by liquid-state NMR and as solid by (1)H, (13)C, and (15)N magic-angle spinning (MAS) solid-state NMR spectroscopy. Density functional theory (DFT) calculations were performed to interpret the data, using the B3LYP exchange-correlation functional to optimize geometries and to compute NMR chemical shieldings by the gauge-including atomic orbital method. The dependence of geometries and chemical shieldings on the size of the basis sets was investigated for the reference molecules tetramethylsilane, NH(3), and H(2)O, and for bilirubin as a monomer and in clusters consisting of up to six molecules. In order to assess the intrinsic errors of the B3LYP approximation in calculating NMR shieldings, complete basis set estimates were obtained for the nuclear shielding values of the reference molecules. The experimental liquid-state NMR data of bilirubin are well reproduced by a monomeric bilirubin molecule using the 6-311+G(2d,p) basis set for geometry optimization and for calculating chemical shieldings. To simulate the bilirubin crystal, a hexameric model was required. It was constructed from geometry-optimized monomers using information from the X-ray structure of bilirubin to fix the monomeric entities in space and refined by partial optimization. Combining experimental (1)H-(13)C and (1)H-(15)N NMR correlation spectroscopy and density functional theory, almost complete sets of (1)H, (13)C, and (15)N chemical shift assignments were obtained for both liquid and solid states. It is shown that monomeric bilirubin in chloroform solution is formed by 3-vinyl anti conformers, while bilirubin crystals are formed by 3-vinyl syn conformers. This conformational change leads to characteristic differences between the liquid- and solid-state NMR resonances. PMID:21846145

Rohmer, Thierry; Matysik, Jörg; Mark, Franz

2011-10-27

418

The fate of the solid matter orbiting HR 4796A  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

419

High-resolution solid-state oxygen-17 NMR of actinide-bearing compounds: an insight into the 5f chemistry.  

PubMed

A massive interest has been generated lately by the improvement of solid-state magic-angle spinning (MAS) NMR methods for the study of a broad range of paramagnetic organic and inorganic materials. The open-shell cations at the origin of this paramagnetism can be metals, transition metals, or rare-earth elements. Actinide-bearing compounds and their 5f unpaired electrons remain elusive in this intensive research area due to their well-known high radiotoxicity. A dedicated effort enabling the handling of these highly radioactive materials now allows their analysis using high-resolution MAS NMR (>55 kHz). Here, the study of the local structure of a series of actinide dioxides, namely, ThO2, UO2, NpO2, PuO2, and AmO2, using solid-state (17)O MAS NMR is reported. An important increase of the spectral resolution is found due to the removal of the dipolar broadening proving the efficiency of this technique for structural analysis. The NMR parameters in these systems with numerous and unpaired 5f electrons were interpreted using an empirical approach. Single-ion model calculations were performed for the first time to determine the z component of electron spin on each of the actinide atoms, which is proportional to the shifts. A similar variation thereof was observed only for the heavier actinides of this study. PMID:24926812

Martel, Laura; Magnani, Nicola; Vigier, Jean-Francois; Boshoven, Jacobus; Selfslag, Chris; Farnan, Ian; Griveau, Jean-Christophe; Somers, Joseph; Fanghänel, Thomas

2014-07-01

420

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

Microsoft Academic Search

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

Caroline Gilbert; Sophie De Winne; Luc Sels

2011-01-01

421

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

422

Component/OEM XC-HR50 High Frame Rate Monochrome Camera  

E-print Network

with a compact, robust body, these cameras are ideal for demanding inspection applications such as semiconductor® Component/OEM XC-HR50 High Frame Rate Monochrome Camera XC-HR70 High Frame Rate Monochrome Camera XC-56 Monochrome Video Camera XC-HR57 High Frame Rate Monochrome Camera XC-HR58 High Frame Rate

Demoulin, Pascal

423

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

424

Spinning-rate encoded chemical shift correlations from rotational resonance solid-state NMR experiments  

PubMed Central

Structural measurements in magic-angle-spinning (MAS) solid-state NMR rely heavily on 13C-13C distance measurements. Broadbanded recoupling methods are used to generate many cross-peaks, but have complex polarization transfer mechanisms that limit the precision of distance constraints and can suffer from weak intensities for distant peaks due to relaxation, the broad distribution of polarization, as well as dipolar truncation. Frequency-selective methods that feature narrow-banded recoupling can reduce these effects. Indeed, rotational resonance (R2) experiments have found application in many different biological systems, where they have afforded improved precision and accuracy. Unfortunately, a highly selective transfer mechanism also leads to few cross-peaks in the resulting spectra, which complicates the extraction of multiple constraints. R2-width (R2W) measurements that scan a range of MAS rates to probe the R2 matching conditions of one or more sites can improve precision, and also permit multiple simultaneous distance measurements. Unfortunately, multidimensional R2W can be very time-consuming. Here, we present an approach that facilitates the acquisition of 2D-like spectra based on a series of 1D R2W experiments, by taking advantage of the chemical shift information encoded in the MAS rates where matching occurs. This yields a more time-efficient experiment with many of the benefits of more conventional multidimensional R2W measurements. The obtained spectra reveal long-distance 13C-13C cross-peaks resulting from R2-mediated polarization transfer. This experiment also enables the efficient setup and targeted implementation of traditional R2 or R2W experiments. Analogous applications may extend to other variable-MAS and frequency-selective solid-state NMR experiments. PMID:23475055

Li, Jun; van der Wel, Patrick C. A.

2013-01-01

425

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

426

An Ounce of Prevention: The Benefits of an HR Audit  

ERIC Educational Resources Information Center

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

Seals, Brenda

2011-01-01

427

Draft Genome Sequence of Bordetella trematum Strain HR18  

PubMed Central

The genus Bordetella is reportedly a human or animal pathogen and environmental microbe. We report the draft genome sequence of Bordetella trematum strain HR18, which was isolated from the rumen of Korean native cattle (Hanwoo; Bos taurus coreanae). It is the first genome sequence of a Bordetella sp. isolated from the rumen of cattle. PMID:25573930

Chang, Dong-Ho; Jin, Tae-Eun; Rhee, Moon-Soo; Jeong, Haeyoung; Kim, Seil

2015-01-01

428

HR Manager Leadership in Quality Improvement in a College Environment  

ERIC Educational Resources Information Center

Purpose: The purpose of this paper is to present the influence of the human resource (HR) manager on the quality of service in an academic college, and the human resource management (HRM) outcomes of the process. Design/methodology/approach: The paper relates to a customer satisfaction survey. More than 120 questionnaires were completed by the…

Sharabi, Moshe

2010-01-01

429

HR Department WRITING REFERENCES FOR STAFF & STUDENTS NOTES OF  

E-print Network

HR Department WRITING REFERENCES FOR STAFF & STUDENTS ­ NOTES OF GUIDANCE 1. Introduction 1 to check the truth of statements of fact which are made in writing or verbally. At their best not send anything else unless you believe that it is absolutely essential e.g. in order to clarify a reply

Doran, Simon J.

430

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

E-print Network

TO: HR and Business Contacts FROM: Division of Human Resources DATE: September 24, 2012 RE: Reminder: Human Resources Fall 2012 Forum This is a reminder that you will need to register online by the Division of Human Resources, this forum will include information about benefits updates to annual

Almor, Amit

431

HR diagram and asteroseismic analysis of models for ??Hydri  

Microsoft Academic Search

A detailed review of the models for the star ? Hydri is done by adjusting the evolutionary sequences to the most recent bolometric, spectroscopic and astrometric data. The dependence of the solution on some of the relevant modelling parameters is analysed and the degeneracy of the solution using the HR diagram analysis discussed. Recent ground-based observations, and the forthcoming asteroseismic

J. Fernandes

2003-01-01

432

Stellar magnetic fields across the HR diagram: observational evidence  

Microsoft Academic Search

This review presents most recent measurements of magnetic fields in various types of stars and substellar objects across the H-R diagram with the emphasis on measurement methods, observational and modeling biases, and the role of magnetic fields in stellar evolution.

Svetlana V. Berdyugina

2009-01-01

433

Ring Nebulae around Massive Stars throughout the HR Diagram  

Microsoft Academic Search

Massive stars evolve across the HR diagram, losing mass along the way and forming a variety of ring nebulae. During the main sequence stage, the fast stellar wind sweeps up the ambient interstellar medium to form an interstellar bubble. After a massive star evolves into a red giant or a luminous blue variable, it loses mass copiously to form a

You-Hua Chu

2002-01-01

434

IN-RANGE PROGRESSION SJSU HR: 2/20/13  

E-print Network

IN-RANGE PROGRESSION GUIDELINES SJSU HR: 2/20/13 SUBJECT: IN-RANGE PROGRESSION DATE: February 19 the compensation requirements for In-Range Progression as stated in Collective Bargaining Unit Agreements for APC, CESUEU, SETC and SUPA. APC An in-range progression is defined as an increase in an employee's pay rate

Su, Xiao

435

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

E-print Network

and all matters not listed below Employee and Labor Relations, Office of Human Resources 614-292-2800 ohrc matters Employee and Labor Relations, Office of Human Resources 614-292-2800 ohrc@hr.osu.edu hrhr.osu.edu/policy Page 1 of 1 - Whistleblower Policy 1.40 Office of Human Resources Applies to

Howat, Ian M.

436

HR & Payroll March 2009 Posting Date Guidelines for  

E-print Network

HR & Payroll March 2009 Posting Date Guidelines for Recruitment Instructional, Research. · If the ad states that review of applications will begin on a specific date, the closing date cannot in the job announcement stating when review of applications will begin (that date must comply with close date

437

HR update March 5, 2012 Information follows regarding  

E-print Network

HR update March 5, 2012 Information follows regarding: Appointment End Dates for Graduate, setting salary funding levels, running reports and queries, viewing the job data record before entering funding data, adding appointment level funding, searching for employee funding levels, and specific case

Balser, Teri C.

438

Atypical Employment Relationships and Commitment: Wishful Thinking or HR Challenge?  

Microsoft Academic Search

Nowadays, simultaneously maintaining flexible working practices and commitment is an important topic for HR managers since they both can contribute to organisational success. However, many HRM researchers and practitioners are unsure whether these can go together as job security is often seen as a necessary condition for commitment. Since relatively little research has yet been completed, this article contributes to

Nicole Torka

2004-01-01

439

NUMBER: HR 1.90 SECTION: Human Resources  

E-print Network

1 NUMBER: HR 1.90 SECTION: Human Resources SUBJECT: Background and Employment Verification Checks and undergraduate) as applicable based on specific responsibilities, who are being considered for employment of Information Act. II. Procedures A. Individuals Covered By the Policy 1. Successful Job Applicants

Almor, Amit

440

NUMBER: HR 1.84 SECTION: Human Resources  

E-print Network

1 NUMBER: HR 1.84 SECTION: Human Resources SUBJECT: Minimum Wage, Official Workweek, and Overtime generally must meet certain tests regarding their job duties. The Wage and Hour Division of the U.S. Department of Labor has outlined specific requirements that must be met in order to qualify for exemption

Almor, Amit

441

University Policy No.: HR6320 Classification: Human Resources  

E-print Network

University Policy No.: HR6320 Classification: Human Resources GUIDELINES FOR THE APPOINTMENT worker is exempt through an international agreement or falls within #12;one of the specific exemption to work in Canada. Usually, it is valid only for a specified job and length of time. With one exception

Victoria, University of

442

Are gaint planets forming around HR 4796A?  

NASA Technical Reports Server (NTRS)

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 degrees from edge-on.

Chen, C. H.; Kamp, I.

2004-01-01

443

To be completed by HR Representative [ ] I-9 documentation _______________________________________  

E-print Network

Veteran (date of separation) ____________________ Race/Ethnicity: Are you Hispanic or Latino? [ ] Yes the definitions of the Race/Ethnicity categories, please see your HR representative Citizenship (check one _______________________________________ ________________________________________________________ Official Start Date: / / Sam Fox School Student Employment Authorization A. Employment Information Name

Subramanian, Venkat

444

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

445

HR-Compensation Compensation Actions Checklist ePAF # Position #  

E-print Network

HR-Compensation Compensation Actions Checklist ePAF # Position # Below are the required documents by Compensation Action EstablishingaPosition FTEChange Liability/Home DepartmentChange OutofCycleMerit Increase occupied) Employment Application* (if occupied) Position Change ePAF (if vacant) Position

Wu, Shin-Tson

446

13C-NMR study of 4-azasteroids in solution and solid state.  

PubMed

A group of biologically active 4-azasteroids was studied by 13C-NMR spectroscopy in solution and in the solid phase. A full assignment of signals in the spectra of samples in chloroform was performed for thirteen 4-azasteroids using two-dimensional techniques. Substituent and steric effects of a nitrogen atom, and their influence on chemical shifts of the neighboring carbon atoms are discussed. CP MAS spectra were obtained for five 4-azasteroids including finasteride. The spectra confirmed polymorphism of the latter compound. In addition to the polymorphic forms that are already known, a new molecular complex of finasteride with dioxane is reported. PMID:11996935

Morzycki, Jacek W; Wawer, Iwona; Gryszkiewicz, Agnieszka; Maj, Jadwiga; Siergiejczyk, Leszek; Zaworska, Alicja

2002-06-01

447

Matrix-Free DNP-Enhanced NMR Spectroscopy of Liposomes Using a Lipid-Anchored Biradical.  

PubMed

Magic-angle spinning dynamic nuclear polarization (MAS-DNP) has been proven to be a powerful technique to enhance the sensitivity of solid-state NMR (SSNMR) in a wide range of systems. Here, we show that DNP can be used to polarize lipids using a lipid-anchored polarizing agent. More specifically, we introduce a C16-functionalized biradical, which allows localization of the polarizing agents in the lipid bilayer and DNP experiments to be performed in the absence of excess cryo-protectant molecules (glycerol, dimethyl sulfoxide, etc.). This constitutes another original example of the matrix-free DNP approach that we recently introduced. PMID:25663569

Fernández-de-Alba, Carlos; Takahashi, Hiroki; Richard, Alexandre; Chenavier, Yves; Dubois, Lionel; Maurel, Vincent; Lee, Daniel; Hediger, Sabine; De Paëpe, Gaël

2015-03-16

448

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

449

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

450

77 FR 43084 - Multiple Award Schedule (MAS) Program Continuous Open Season-Operational Change  

Federal Register 2010, 2011, 2012, 2013, 2014

...Multiple Award Schedule (MAS) Program Continuous Open Season- Operational Change AGENCY...contractors and generally, has operated under continuous open solicitations or ``seasons...to modify its current practice of a continuous open season for all Schedules to a...

2012-07-23

451

77 FR 58996 - Multiple Award Schedule (MAS) Program Continuous Open Season-Operational Change; Extension of...  

Federal Register 2010, 2011, 2012, 2013, 2014

...ADMINISTRATION [Notice-QDA-2012-01; Docket No. 2012-0002; Sequence 17] Multiple Award Schedule (MAS) Program Continuous Open Season-- Operational Change; Extension of Comment Period AGENCY: Federal Acquisition Service (FAS), General...

2012-09-25

452

MAS 335 Cryptography Notes 10: Public-key cryptography Spring 2008  

E-print Network

MAS 335 Cryptography Notes 10: Public-key cryptography Spring 2008 In this section we look at two-key cryptography. Neither of these schemes is used commercially as far as I know. But we will see later a good

Banaji,. Murad

453

Why doesn't this HR department get any respect?  

PubMed

Since becoming managing partner of human resources at Loft Securities more than a year ago, Luke Robinson has tried everything he can think of to change his department's reputation as an administrative backwater. But he's swimming against the tide. Ever since the retirement of a charismatic CEO in 1995, the firm has suffered a slow bleed of good people. The new CEO doesn't have a flair for attracting and retaining talented people, and the HR department hasn't been able to pick up the slack. Robinson has done his best to turn things around. He's met with just about everyone, from senior executives to administrative assistants to external contacts. And, when he found out that recruiting wasn't Loft's only problem, he took a variety of concrete steps. Among other things, he established internal service standards and performance guarantees for his department. He created "listening posts" and implemented and "HR ambassador" program. And he drafted plans for a program to help educate all the company's employees about the role of HR--specifically, how it can contribute to creating and upholding the firm's strategy for success. But Robinson has run over some major speed bumps. Just before he joined the company, HR sullied its reputation by mishandling the investigation of a discrimination charge. And while on Robinson's watch, HR botched the issuance of year-end bonus checks for the managing directors and vice presidents. The frustrations are piling up, leading Robinson to entertain thoughts of bailing out. Five commentators on this fictional case study explain why he should avoid quitting and how he can help his department earn new respect. PMID:10177864

Galford, R

1998-01-01

454

Are mergers and acquisitions contagious? - Conceptualising parallel M&As among customers and suppliers  

Microsoft Academic Search

Mapping the number of completed mergers and acquisitions (M&As) over the past few decades would produce a line roughly following the fluctuations of the business cycle. The most recent peak was marked by the numerous M&As occurring in the late 1990s and in early 2000 (Bengtsson and Skärvad 2001; Weston and Weaver 2001), followed by the recession starting in late

Christina Öberg; Johan Holtström

455

U.S. Geological Survey mineral databases; MRDS and MAS/MILS  

USGS Publications Warehouse

These two CD-ROM's contain the latest version of the Mineral Resources Data System (MRDS) database and the Minerals Availability System/Minerals Industry Location System (MAS/MILS) database for coverage of North America and the world outside North America. The records in the MRDS database each contain almost 200 data fields describing metallic and nonmetallic mineral resources, deposits, and commodities. The records in the MAS/MILS database each contain almost 100 data fields describing mines and mineral processing plans.

McFaul, E.J.; Mason, G.T.; Ferguson, W.B.; Lipin, B.R.

2000-01-01

456

Host-guest interactions in fluorinated polymer electrolytes: A 7Li-13C NMR study  

NASA Astrophysics Data System (ADS)

Gel-type electrolytes based on fluorinated polymers are of interest for electrochemical devices. We present a 7Li-13C solid-state NMR and modulated differential scanning calorimetry (MDSC) study of gel electrolytes based on a copolymer poly(vinylidene fluoride) (PVdF)-hexafluoropropylene (HFP) activated with a nonaqueous solution ethylene carbonate (EC)-propylene carbonate (PC)-LiN(CF3SO2)2. We show that the narrowing of the Li lineshape is decoupled from the glass transition. The behavior of the longitudinal relaxation times, T1, confirms that the host polymer matrix simply behaves like a quasiinert cage for the solution. These results are confirmed by 13C NMR at the magic angle (MAS) data, which show that the presence of the polymer does not significantly affect the chemical shift changes induced in the EC/PC carbons by the imide salt.

Mustarelli, P.; Quartarone, E.; Capiglia, C.; Tomasi, C.; Ferloni, P.; Magistris, A.

1999-08-01

457

Intergrowth and interfacial structure of biomimetic fluorapatite-gelatin nanocomposite: a solid-state NMR study.  

PubMed

The model system fluorapatite-gelatin allows mimicking the formation conditions on a lower level of complexity compared to natural dental and bone tissues. Here, we report on solid-state NMR investigations to examine the structure of fluorapatite-gelatin nanocomposites on a molecular level with particular focus on organic-inorganic interactions. Using (31)P, (19)F, and (1)H MAS NMR and heteronuclear correlations, we found the nanocomposite to consist of crystalline apatite-like regions (fluorapatite and hydroxyfluorapatite) in close contact with a more dissolved (amorphous) layer containing first motifs of the apatite crystal structure as well as the organic component. A scheme of the intergrowth region in the fluorapatite-gelatin nanocomposite, where mineral domains interact with organic matrix, is presented. PMID:24354406

Vyalikh, Anastasia; Simon, Paul; Rosseeva, Elena; Buder, Jana; Kniep, Rüdiger; Scheler, Ulrich

2014-01-23

458

Solid-state (17) o NMR spectroscopy of paramagnetic coordination compounds.  

PubMed

High-quality solid-state (17) O (I=5/2) NMR spectra can be successfully obtained for paramagnetic coordination compounds in which oxygen atoms are directly bonded to the paramagnetic metal centers. For complexes containing V(III) (S=1), Cu(II) (S=1/2), and Mn(III) (S=2) metal centers, the (17) O isotropic paramagnetic shifts were found to span a range of more than 10?000?ppm. In several cases, high-resolution (17) O NMR spectra were recorded under very fast magic-angle spinning (MAS) conditions at 21.1?T. Quantum-chemical computations using density functional theory (DFT) qualitatively reproduced the experimental (17) O hyperfine shift tensors. PMID:25694203

Kong, Xianqi; Terskikh, Victor V; Khade, Rahul L; Yang, Liu; Rorick, Amber; Zhang, Yong; He, Peng; Huang, Yining; Wu, Gang

2015-04-13

459

A Novel ?/?-Hydrolase Gene IbMas Enhances Salt Tolerance in Transgenic Sweetpotato  

PubMed Central

Salt stress is one of the major environmental stresses in agriculture worldwide and affects crop productivity and quality. The development of crops with elevated levels of salt tolerance is therefore highly desirable. In the present study, a novel maspardin gene, named IbMas, was isolated from salt-tolerant sweetpotato (Ipomoea batatas (L.) Lam.) line ND98. IbMas contains maspardin domain and belongs to ?/?-hydrolase superfamily. Expression of IbMas was up-regulated in sweetpotato under salt stress and ABA treatment. The IbMas-overexpressing sweetpotato (cv. Shangshu 19) plants exhibited significantly higher salt tolerance compared with the wild-type. Proline content was significantly increased, whereas malonaldehyde content was significantly decreased in the transgenic plants. The activities of superoxide dismutase (SOD) and photosynthesis were significantly enhanced in the transgenic plants. H2O2 was also found to be significantly less accumulated in the transgenic plants than in the wild-type. Overexpression of IbMas up-regulated the salt stress responsive genes, including pyrroline-5-carboxylate synthase, pyrroline-5-carboxylate reductase, SOD, psbA and phosphoribulokinase genes, under salt stress. These findings suggest that overexpression of IbMas enhances salt tolerance of the transgenic sweetpotato plants by regulating osmotic balance, protecting membrane integrity and photosynthesis and increasing reactive oxygen species scavenging capacity. PMID:25501819

Song, Xuejin; He, Shaozhen; Liu, Qingchang

2014-01-01

460

Push-through Direction Injectin NMR Automation  

EPA Science Inventory

Nuclear magnetic resonance (NMR) and mass spectrometry (MS) are the two major spectroscopic techniques successfully used in metabolomics studies. The non-invasive, quantitative and reproducible characteristics make NMR spectroscopy an excellent technique for detection of endogeno...