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Sample records for chemical shift anisotropy

  1. Anisotropy of the fluorine chemical shift tensor in UF6

    International Nuclear Information System (INIS)

    An 19F magnetic resonance study of polycrystalline UF6 is presented. The low temperature complex line can be analyzed as the superposition of two distinct lines, which is attributed to a distortion of the UF6 octahedron in the solid. The shape of the two components is studied. Their width is much larger than the theoretical dipolar width, and must be explained by large anisotropies of the fluorine chemical shift tensors. The resulting shape functions of the powder spectra are determined. The values of the parameters of the chemical shift tensors yield estimates of the characters of the U-F bonds, and this gives some information on the ground state electronic wave function of the UF6 molecule in the solid. (author)

  2. Determination of nuclear distances and chemical-shift anisotropy from 1H MAS NMR sideband patterns of surface OH groups

    Science.gov (United States)

    Fenzke, Dieter; Hunger, Michael; Pfeifer, Harry

    A procedure is described which allows a separate determination of the proton-aluminum distance and of the chemical-shift anisotropy for the bridging OH groups of crystalline molecular sieves from their 'H MAS NMR sideband patterns. For the bridging OH groups which point into the 6-rings of the framework (line "c"), the 1H- 27Al distance could be determined to be 0.237 ± 0.004 and 0.234 ± 0.004 nm for molecular sieves of type H-Y and SAPO-5, respectively. In contrast, for the bridging OH groups of the 12-rings (line "b"), the corresponding distances are equal and distinctly larger, 0.248 ± 0.004 nm. Within the limits of error, the values of the chemical-shift anisotropy are equal (about 19 ± 2 ppm) except for line b of SAPO-5, which exhibits a much smaller value of 14.5 ± 2 ppm.

  3. Anisotropy of the Chemical Shift Tensor for Fluorines in UF6 : Application to the Fluorine Atom Movement Model

    International Nuclear Information System (INIS)

    R. Blinc et al. have made an initial study of polycrystalline uranium hexafluoride using the magnetic resonance of fluorine at 40 Mc/s. The low-temperattire spectrum (t 6 octahedron has one long axis and two short axes, the fluorine atoms are divided among two different types of site. The change in the spectrum with temperature (coalescence of the two lines) suggests movement of the fluorine atoms between the two types of site. By repeating these experiments at 56.4 Mc/s and 94 Mc/s, we have been able to demonstrate the existence of considerable axial anisotropy of the chemical shift tensor (about 650 ppm). The absorption line obtained for a powder in these conditions is complex, and to study it we must envisage a line-shape function f(h), which is the probability that a grain of powder is so orientated that it resonates for the value h of the field. In the absence of movement (low-temperature spectrum) the line-shape function for each of the two lines (corresponding to the two types of site) is of the form obtained for equivalent atoms. It is known that the parameters of chemical shift tensors give information on chemical bond character. We are thus led, for example, to attribute a considerable ionic character (I ≃ 1/2) to the bonds between the uranium and the two most distant fluorine atoms. In the presence of movement the line-shape function is very different, and depends on the type of movement. For UF6, study of the shape of the single line (t > 20°C) in cases where we have anisotropy, shows that the fluorine atoms of the same molecule interchange with each other, each atom remaining in each of the positions for about 5 μsec at 30°C, with an activation energy of about 0.5 eV. (author)

  4. Determination of the Orientation and Dynamics of Ergosterol in Model Membranes Using Uniform 13C Labeling and Dynamically Averaged 13C Chemical Shift Anisotropies as Experimental Restraints

    Science.gov (United States)

    Soubias, O.; Jolibois, F.; Massou, S.; Milon, A.; Réat, V.

    2005-01-01

    A new strategy was established to determine the average orientation and dynamics of ergosterol in dimyristoylphosphatidylcholine model membranes. It is based on the analysis of chemical shift anisotropies (CSAs) averaged by the molecular dynamics. Static 13C CSA tensors were computed by quantum chemistry, using the gauge-including atomic-orbital approach within Hartree-Fock theory. Uniformly 13C-labeled ergosterol was purified from Pichia pastoris cells grown on labeled methanol. After reconstitution into dimyristoylphosphatidylcholine lipids, the complete 1H and 13C assignment of ergosterol's resonances was performed using a combination of magic-angle spinning two-dimensional experiments. Dynamically averaged CSAs were determined by standard side-band intensity analysis for isolated 13C resonances (C3 and ethylenic carbons) and by off-magic-angle spinning experiments for other carbons. A set of 18 constraints was thus obtained, from which the sterol's molecular order parameter and average orientation could be precisely defined. The validity of using computed CSAs in this strategy was verified on cholesterol model systems. This new method allowed us to quantify ergosterol's dynamics at three molar ratios: 16 mol % (Ld phase), 30 mol % (Lo phase), and 23 mol % (mixed phases). Contrary to cholesterol, ergosterol's molecular diffusion axis makes an important angle (14°) with the inertial axis of the rigid four-ring system. PMID:15923221

  5. Determination of NH proton chemical shift anisotropy with 14N-1H heteronuclear decoupling using ultrafast magic angle spinning solid-state NMR

    Science.gov (United States)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-12-01

    The extraction of chemical shift anisotropy (CSA) tensors of protons either directly bonded to 14N nuclei (I = 1) or lying in their vicinity using rotor-synchronous recoupling pulse sequence is always fraught with difficulty due to simultaneous recoupling of 14N-1H heteronuclear dipolar couplings and the lack of methods to efficiently decouple these interactions. This difficulty mainly arises from the presence of large 14N quadrupolar interactions in comparison to the rf field that can practically be achieved. In the present work it is demonstrated that the application of on-resonance 14N-1H decoupling with rf field strength ∼30 times weaker than the 14N quadrupolar coupling during 1H CSA recoupling under ultrafast MAS (90 kHz) results in CSA lineshapes that are free from any distortions from recoupled 14N-1H interactions. With the use of extensive numerical simulations we have shown the applicability of our proposed method on a naturally abundant L-Histidine HCl·H2O sample.

  6. Overall structure and sugar dynamics of a DNA dodecamer from homo- and heteronuclear dipolar couplings and 31P chemical shift anisotropy

    International Nuclear Information System (INIS)

    The solution structure of d(CGCGAATTCGCG)2 has been determined on the basis of an exceptionally large set of residual dipolar couplings. In addition to the heteronuclear 13C-1H and 15N-1H and qualitative homonuclear 1H-1H dipolar couplings, previously measured in bicelle medium, more than 300 quantitative 1H-1H and 22 31P-1H dipolar restraints were obtained in liquid crystalline Pf1 medium, and 22 31P chemical shift anisotropy restraints. High quality DNA structures can be obtained solely on the basis of these new restraints, and these structures are in close agreement with those calculated previously on the basis of 13C-1H and 15N-1H dipolar couplings. In the newly calculated structures, 31P-1H dipolar and 3JsubH3'Psub couplings and 31P CSA data restrain the phosphodiester backbone torsion angles. The final structure represents a quite regular B-form helix with a modest bending of ∼10 deg., which is essentially independent of whether or not electrostatic terms are used in the calculation. Combined, the number of homo- and heteronuclear dipolar couplings significantly exceeds the number of degrees of freedom in the system. Results indicate that the dipolar coupling data cannot be fit by a single structure, but are compatible with the presence of rapid equilibria between C2'-endo and C3'-endo deoxyribose puckers (sugar switching). The C2'-H2'/H2'' dipolar couplings in B-form DNA are particularly sensitive to sugar pucker and yield the largest discrepancies when fit to a single structure. To resolve these discrepancies, we suggest a simplified dipolar coupling analysis that yields N/S equilibria for the ribose sugar puckers, which are in good agreement with previous analyses of NMR JHH couplings, with a population of the minor C3'-endo form higher for pyrimidines than for purines

  7. Protein Chemical Shift Prediction

    CERN Document Server

    Larsen, Anders S

    2014-01-01

    The protein chemical shifts holds a large amount of information about the 3-dimensional structure of the protein. A number of chemical shift predictors based on the relationship between structures resolved with X-ray crystallography and the corresponding experimental chemical shifts have been developed. These empirical predictors are very accurate on X-ray structures but tends to be insensitive to small structural changes. To overcome this limitation it has been suggested to make chemical shift predictors based on quantum mechanical(QM) calculations. In this thesis the development of the QM derived chemical shift predictor Procs14 is presented. Procs14 is based on 2.35 million density functional theory(DFT) calculations on tripeptides and contains corrections for hydrogen bonding, ring current and the effect of the previous and following residue. Procs14 is capable at performing predictions for the 13CA, 13CB, 13CO, 15NH, 1HN and 1HA backbone atoms. In order to benchmark Procs14, a number of QM NMR calculatio...

  8. 13C chemical shift anisotropies for carbonate ions in cement minerals and the use of 13C, 27Al and 29Si MAS NMR in studies of Portland cement including limestone additions

    International Nuclear Information System (INIS)

    13C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed 13C MAS or 13C(1H) CP/MAS NMR spectra (9.4 T or 14.1 T) for 13C in natural abundance. The variation in the 13C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in 13C MAS NMR spectra. However, it is shown that by combining 13C MAS and 13C(1H) 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 29Si 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 27Al 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: •13C chemical shift anisotropies for inorganic carbonates from 13C MAS NMR. •Narrow 13C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by 13C MAS and 13C(1H) 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

  9. Orientational constraints as three-dimensional structural constraints from chemical shift anisotropy: the polypeptide backbone of gramicidin A in a lipid bilayer.

    OpenAIRE

    Mai, W.; Hu, W; Wang, C; Cross, T A

    1993-01-01

    Chemical shifts observed from samples that are uniformly aligned with respect to the magnetic field can be used as very high-resolution structural constraints. This constraint takes the form of an orientational constraint rather than the more familiar distance constraint. The accuracy of these constraints is dependent upon the quality of the tensor characterization. Both tensor element magnitudes and tensor orientations with respect to the molecular frame need to be considered. Here these con...

  10. A Short History of Three Chemical Shifts

    Science.gov (United States)

    Nagaoka, Shin-ichi

    2007-01-01

    A short history of chemical shifts in nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA) and Mossbauer spectroscopy, which are useful for chemical studies, is described. The term chemical shift is shown to have originated in the mistaken assumption that nuclei of a given element would all undergo resonance at the…

  11. 129Xe NMR of xenon adsorbed on the molecular sieves AlPO 4-11 and SAPO-11. Chemical shift anisotropy related to the asymmetry of the adsorption zones

    Science.gov (United States)

    Springuel-Huet, M. A.; Fraissard, J.

    1989-01-01

    The form of the 129Xe NMR signal of xenon adsorbed at low concentration on the molecular sieves SAPO-11 and AlPO 4-11 corresponds to a highly anisotropic chemical shift which expresses the asymmetry of the channels in which the xenon is located. To the asymmetry of the xenon-wall interaction is added that of the xenon-xenon interaction when the channels are largely filled.

  12. Geometric effects on carbon-13 chemical shifts

    International Nuclear Information System (INIS)

    In the course of our investigations on carbon-13 chemical shifts of tetracyclic dodecanes, we managed to show that a large number of chemical shift differences between members of the series and models provided by bicyclic analogs could be attributed to steric effects. There are examples, however, where this is clearly not the case. In order to investigate apparent anomalies we calculated structures of interest and looked into the relationships between molecular geometry and chemical shifts. As the assignment of some of the key structures in these analysis were made by comparison with model compounds and crucial experiments that could remove ambiguities were missing, we prepared and interpreted two spectra which are presented

  13. MR chemical shift imaging of human atheroma

    International Nuclear Information System (INIS)

    The lipid content of atheromatous plaques has been measured with chemical shift MR imaging by taking advantage of the different resonance frequencies of protons in lipid and water. Fifteen postmortem aortic specimens of the human descending aorta and the aortae of seven patients with documented peripheral vascular disease were studied at 0.5 T. Spin-echo images were used to localize the lesions before acquisition of the chemical shift images. The specimens were examined histologically, and the lipid distribution in the plaque showed good correlation with the chemical shift data. Validation in vivo and clinical applications remain to be established

  14. Chemical shift anisotropies of /sup 1/H in H/sub 2/O(s), H/sub 2/S(s), and C/sub 6/H/sub 6/(s)

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, L. M.

    1977-10-01

    The proton NMR in powdered samples of H/sub 2/O(s), H/sub 2/S(s), and C/sub 6/H/sub 6/(s) have been studied by multiple pulse line narrowing techniques. The resultant spectra provide nuclear magnetic shielding tensors that are (at least approximately) axially symmetric. The anisotropy is 34.2 +- 1.0 ppM for ice, 11.1 +- 1.0 ppM for the highest-temperature phase of solid hydrogen sulfide, and -5.3 +- 0.3 for benzene. Comparisons are made with previous experimental and theoretical work.

  15. Accessible surface area from NMR chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Hafsa, Noor E.; Arndt, David; Wishart, David S., E-mail: david.wishart@ualberta.ca [University of Alberta, Department of Computing Science (Canada)

    2015-07-15

    Accessible surface area (ASA) is the surface area of an atom, amino acid or biomolecule that is exposed to solvent. The calculation of a molecule’s ASA requires three-dimensional coordinate data and the use of a “rolling ball” algorithm to both define and calculate the ASA. For polymers such as proteins, the ASA for individual amino acids is closely related to the hydrophobicity of the amino acid as well as its local secondary and tertiary structure. For proteins, ASA is a structural descriptor that can often be as informative as secondary structure. Consequently there has been considerable effort over the past two decades to try to predict ASA from protein sequence data and to use ASA information (derived from chemical modification studies) as a structure constraint. Recently it has become evident that protein chemical shifts are also sensitive to ASA. Given the potential utility of ASA estimates as structural constraints for NMR we decided to explore this relationship further. Using machine learning techniques (specifically a boosted tree regression model) we developed an algorithm called “ShiftASA” that combines chemical-shift and sequence derived features to accurately estimate per-residue fractional ASA values of water-soluble proteins. This method showed a correlation coefficient between predicted and experimental values of 0.79 when evaluated on a set of 65 independent test proteins, which was an 8.2 % improvement over the next best performing (sequence-only) method. On a separate test set of 92 proteins, ShiftASA reported a mean correlation coefficient of 0.82, which was 12.3 % better than the next best performing method. ShiftASA is available as a web server ( http://shiftasa.wishartlab.com http://shiftasa.wishartlab.com ) for submitting input queries for fractional ASA calculation.

  16. Accessible surface area from NMR chemical shifts

    International Nuclear Information System (INIS)

    Accessible surface area (ASA) is the surface area of an atom, amino acid or biomolecule that is exposed to solvent. The calculation of a molecule’s ASA requires three-dimensional coordinate data and the use of a “rolling ball” algorithm to both define and calculate the ASA. For polymers such as proteins, the ASA for individual amino acids is closely related to the hydrophobicity of the amino acid as well as its local secondary and tertiary structure. For proteins, ASA is a structural descriptor that can often be as informative as secondary structure. Consequently there has been considerable effort over the past two decades to try to predict ASA from protein sequence data and to use ASA information (derived from chemical modification studies) as a structure constraint. Recently it has become evident that protein chemical shifts are also sensitive to ASA. Given the potential utility of ASA estimates as structural constraints for NMR we decided to explore this relationship further. Using machine learning techniques (specifically a boosted tree regression model) we developed an algorithm called “ShiftASA” that combines chemical-shift and sequence derived features to accurately estimate per-residue fractional ASA values of water-soluble proteins. This method showed a correlation coefficient between predicted and experimental values of 0.79 when evaluated on a set of 65 independent test proteins, which was an 8.2 % improvement over the next best performing (sequence-only) method. On a separate test set of 92 proteins, ShiftASA reported a mean correlation coefficient of 0.82, which was 12.3 % better than the next best performing method. ShiftASA is available as a web server ( http://shiftasa.wishartlab.com http://shiftasa.wishartlab.com ) for submitting input queries for fractional ASA calculation

  17. Random coil chemical shift for intrinsically disordered proteins

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Brander, Søren; Poulsen, Flemming Martin

    2011-01-01

    Secondary chemical shift analysis is the main NMR method for detection of transiently formed secondary structure in intrinsically disordered proteins. The quality of the secondary chemical shifts is dependent on an appropriate choice of random coil chemical shifts. We report random coil chemical....... Temperature has a non-negligible effect on the (13)C random coil chemical shifts, so temperature coefficients are reported for the random coil chemical shifts to allow extrapolation to other temperatures. The pH dependence of the histidine random coil chemical shifts is investigated in a titration series...

  18. Protein Structure Determination Using Chemical Shifts

    DEFF Research Database (Denmark)

    Christensen, Anders Steen

    In this thesis, a protein structure determination using chemical shifts is presented. The method is implemented in the open source PHAISTOS protein simulation framework. The method combines sampling from a generative model with a coarse-grained force field and an energy function that includes che...... residues. For Rhodopsin (225 residues) a structure is found at 2.5 Å CA-RMSD from the experimental X-ray structure, and a structure is determined for the Savinase protein (269 residues) with 2.9 Å CA-RMSD from the experimental X-ray structure....

  19. Chemical shift MR imaging of the skin

    International Nuclear Information System (INIS)

    MR imaging with conventional spin-echo pulse sequences has not found wide application in the evaluation of skin pathology. This paper reports that this study was designed to determine the value of chemical shift imaging (CSI) compared with conventional pulse sequences for the noninvasive evaluation of connective tissue and neoplastic disease of the skin and underlying fascia. The studies were acquired in patients and volunteers on a whole-body system at 1.5 T and small surface coils. Comparisons were made between T1- and T2-weighted gradient-echo, spin-echo, and hybrid lipid and water-suppressed CSI series (Chopper-Dixon combined with frequency-selective pulse). CSI improves detail in the hypodermis by eliminating unwanted (lipid) signal and chemical shift misregistration artifact. The detail of water-based signal is improved in the deeper layers of the skin by improved tissue contrast and elimination of the disturbing adjacent dominant fat-based signal. MR imaging has the potential to provide information that can complement skin biopsy. A more optimal choice of pulse sequences can improve the sensitivity of MR imaging to water-based pathology and allow noninvasive visualization of deep layers. The CSI sequences may be useful in the evaluation of infiltrative and neoplastic disease of the skin, particularly as they are adapted into microimaging methods with local gradient coils

  20. Prediction of proton chemical shifts in RNA - Their use in structure refinement and validation

    International Nuclear Information System (INIS)

    An analysis is presented of experimental versus calculated chemical shifts of the non-exchangeable protons for 28 RNA structures deposited in the Protein Data Bank, covering a wide range of structural building blocks. We have used existing models for ring-current and magnetic-anisotropy contributions to calculate the proton chemical shifts from the structures. Two different parameter sets were tried: (i) parameters derived by Ribas-Prado and Giessner-Prettre (GP set) [(1981) J. Mol. Struct.,76, 81-92.]; (ii) parameters derived by Case [(1995) J. Biomol. NMR, 6, 341-346]. Both sets lead to similar results. The detailed analysis was carried using the GP set. The root-mean-square-deviation between the predicted and observed chemical shifts of the complete database is 0.16 ppm with a Pearson correlation coefficient of 0.79. For protons in the usually well-defined A-helix environment these numbers are, 0.08 ppm and 0.96, respectively. As a result of this good correspondence, a reliable analysis could be made of the structural dependencies of the 1H chemical shifts revealing their physical origin. For example, a down-field shift of either H2' or H3' or both indicates a high-syn/syn χ-angle. In an A-helix it is essentially the 5'-neighbor that affects the chemical shifts of H5, H6 and H8 protons. The H5, H6 and H8 resonances can therefore be assigned in an A-helix on the basis of their observed chemical shifts. In general, the chemical shifts were found to be quite sensitive to structural changes. We therefore propose that a comparison between calculated and observed 1H chemical shifts is a good tool for validation and refinement of structures derived from NOEs and J-couplings

  1. Probabilistic Approach to Determining Unbiased Random-coil Carbon-13 Chemical Shift Values from the Protein Chemical Shift Database

    International Nuclear Information System (INIS)

    We describe a probabilistic model for deriving, from the database of assigned chemical shifts, a set of random coil chemical shift values that are 'unbiased' insofar as contributions from detectable secondary structure have been minimized (RCCSu). We have used this approach to derive a set of RCCSu values for 13Cα and 13Cβ for 17 of the 20 standard amino acid residue types by taking advantage of the known opposite conformational dependence of these parameters. We present a second probabilistic approach that utilizes the maximum entropy principle to analyze the database of 13Cα and 13Cβ chemical shifts considered separately; this approach yielded a second set of random coil chemical shifts (RCCSmax-ent). Both new approaches analyze the chemical shift database without reference to known structure. Prior approaches have used either the chemical shifts of small peptides assumed to model the random coil state (RCCSpeptide) or statistical analysis of chemical shifts associated with structure not in helical or strand conformation (RCCSstruct-stat). We show that the RCCSmax-ent values are strikingly similar to published RCCSpeptide and RCCSstruct-stat values. By contrast, the RCCSu values differ significantly from both published types of random coil chemical shift values. The differences (RCCSpeptide-RCCSu) for individual residue types show a correlation with known intrinsic conformational propensities. These results suggest that random coil chemical shift values from both prior approaches are biased by conformational preferences. RCCSu values appear to be consistent with the current concept of the 'random coil' as the state in which the geometry of the polypeptide ensemble samples the allowed region of (φ,ψ)-space in the absence of any dominant stabilizing interactions and thus represent an improved basis for the detection of secondary structure. Coupled with the growing database of chemical shifts, this probabilistic approach makes it possible to refine

  2. Probabilistic validation of protein NMR chemical shift assignments

    International Nuclear Information System (INIS)

    Data validation plays an important role in ensuring the reliability and reproducibility of studies. NMR investigations of the functional properties, dynamics, chemical kinetics, and structures of proteins depend critically on the correctness of chemical shift assignments. We present a novel probabilistic method named ARECA for validating chemical shift assignments that relies on the nuclear Overhauser effect data. ARECA has been evaluated through its application to 26 case studies and has been shown to be complementary to, and usually more reliable than, approaches based on chemical shift databases. ARECA is available online at http://areca.nmrfam.wisc.edu/ http://areca.nmrfam.wisc.edu/

  3. Probabilistic validation of protein NMR chemical shift assignments

    Energy Technology Data Exchange (ETDEWEB)

    Dashti, Hesam [University of Wisconsin-Madison, Graduate Program in Biophysics, Biochemistry Department (United States); Tonelli, Marco; Lee, Woonghee; Westler, William M.; Cornilescu, Gabriel [University of Wisconsin-Madison, Biochemistry Department, National Magnetic Resonance Facility at Madison (United States); Ulrich, Eldon L. [University of Wisconsin-Madison, BioMagResBank, Biochemistry Department (United States); Markley, John L., E-mail: markley@nmrfam.wisc.edu, E-mail: jmarkley@wisc.edu [University of Wisconsin-Madison, Biochemistry Department, National Magnetic Resonance Facility at Madison (United States)

    2016-01-15

    Data validation plays an important role in ensuring the reliability and reproducibility of studies. NMR investigations of the functional properties, dynamics, chemical kinetics, and structures of proteins depend critically on the correctness of chemical shift assignments. We present a novel probabilistic method named ARECA for validating chemical shift assignments that relies on the nuclear Overhauser effect data. ARECA has been evaluated through its application to 26 case studies and has been shown to be complementary to, and usually more reliable than, approaches based on chemical shift databases. ARECA is available online at http://areca.nmrfam.wisc.edu/ http://areca.nmrfam.wisc.edu/.

  4. Proton chemical shift tensors determined by 3D ultrafast MAS double-quantum NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy, E-mail: ramamoor@umich.edu [Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055 (United States)

    2015-10-14

    Proton NMR spectroscopy in the solid state has recently attracted much attention owing to the significant enhancement in spectral resolution afforded by the remarkable advances in ultrafast magic angle spinning (MAS) capabilities. In particular, proton chemical shift anisotropy (CSA) has become an important tool for obtaining specific insights into inter/intra-molecular hydrogen bonding. However, even at the highest currently feasible spinning frequencies (110–120 kHz), {sup 1}H MAS NMR spectra of rigid solids still suffer from poor resolution and severe peak overlap caused by the strong {sup 1}H–{sup 1}H homonuclear dipolar couplings and narrow {sup 1}H chemical shift (CS) ranges, which render it difficult to determine the CSA of specific proton sites in the standard CSA/single-quantum (SQ) chemical shift correlation experiment. Herein, we propose a three-dimensional (3D) {sup 1}H double-quantum (DQ) chemical shift/CSA/SQ chemical shift correlation experiment to extract the CS tensors of proton sites whose signals are not well resolved along the single-quantum chemical shift dimension. As extracted from the 3D spectrum, the F1/F3 (DQ/SQ) projection provides valuable information about {sup 1}H–{sup 1}H proximities, which might also reveal the hydrogen-bonding connectivities. In addition, the F2/F3 (CSA/SQ) correlation spectrum, which is similar to the regular 2D CSA/SQ correlation experiment, yields chemical shift anisotropic line shapes at different isotropic chemical shifts. More importantly, since the F2/F1 (CSA/DQ) spectrum correlates the CSA with the DQ signal induced by two neighboring proton sites, the CSA spectrum sliced at a specific DQ chemical shift position contains the CSA information of two neighboring spins indicated by the DQ chemical shift. If these two spins have different CS tensors, both tensors can be extracted by numerical fitting. We believe that this robust and elegant single-channel proton-based 3D experiment provides useful atomistic

  5. Conformational propensities of intrinsically disordered proteins from NMR chemical shifts

    International Nuclear Information System (INIS)

    The realization that a protein can be fully functional even in the absence of a stable three-dimensional structure has motivated a large number of studies describing the conformational behaviour of these proteins at atomic resolution. Here, we review recent advances in the determination of local structural propensities of intrinsically disordered proteins (IDPs) from experimental NMR chemical shifts. A mapping of the local structure in IDPs is of paramount importance in order to understand the molecular details of complex formation, in particular, for IDPs that fold upon binding or undergo structural transitions to pathological forms of the same protein. We discuss experimental strategies for the spectral assignment of IDPs, chemical shift prediction algorithms and the generation of representative structural ensembles of IDPs on the basis of chemical shifts. Additionally, we highlight the inherent degeneracies associated with the determination of IDP sub-state populations from NMR chemical shifts alone. (authors)

  6. An evaluation of chemical shift index-based secondary structure determination in proteins: Influence of random coil chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Mielke, S.P.; Krishnan, V.V. [Biophysics Graduate Group, University of California, Davis (United States)], E-mail: krish@llnl.gov

    2004-10-15

    Random coil chemical shifts are commonly used to detect protein secondary structural elements in chemical shift index (CSI) calculations. Though this technique is widely used and seems reliable for folded proteins, the choice of reference random coil chemical shift values can significantly alter the outcome of secondary structure estimation. In order to evaluate these effects, we present a comparison of secondary structure content calculated using CSI, based on five different reference random coil chemical shift value sets, to that derived from three-dimensional structures. Our results show that none of the reference random coil data sets chosen for evaluation fully reproduces the actual secondary structures. Among the reference values generally available to date, most tend to be good estimators only of helices. Based on our evaluation, we recommend the experimental values measured by Schwarzinger et al. (2000), and statistical values obtained by Lukin et al. (1997), as good estimators of both helical and sheet content.

  7. Bayesian inference of protein structure from chemical shift data

    DEFF Research Database (Denmark)

    Bratholm, Lars Andersen; Christensen, Anders Steen; Hamelryck, Thomas Wim; Jensen, Jan Halborg

    2015-01-01

    Protein chemical shifts are routinely used to augment molecular mechanics force fields in protein structure simulations, with weights of the chemical shift restraints determined empirically. These weights, however, might not be an optimal descriptor of a given protein structure and predictive model...... chain Monte Carlo simulations of three small proteins (ENHD, Protein G and the SMN Tudor Domain) using the PROFASI force field and the chemical shift predictor CamShift. Using a clustering-criterion for identifying the best structure, together with the addition of a solvent exposure scoring term, the......, result in overall better convergence to the native fold, suggesting that both types of distribution might be useful in different aspects of the protein structure prediction....

  8. Bayesian inference of protein structure from chemical shift data

    Directory of Open Access Journals (Sweden)

    Lars A. Bratholm

    2015-03-01

    Full Text Available Protein chemical shifts are routinely used to augment molecular mechanics force fields in protein structure simulations, with weights of the chemical shift restraints determined empirically. These weights, however, might not be an optimal descriptor of a given protein structure and predictive model, and a bias is introduced which might result in incorrect structures. In the inferential structure determination framework, both the unknown structure and the disagreement between experimental and back-calculated data are formulated as a joint probability distribution, thus utilizing the full information content of the data. Here, we present the formulation of such a probability distribution where the error in chemical shift prediction is described by either a Gaussian or Cauchy distribution. The methodology is demonstrated and compared to a set of empirically weighted potentials through Markov chain Monte Carlo simulations of three small proteins (ENHD, Protein G and the SMN Tudor Domain using the PROFASI force field and the chemical shift predictor CamShift. Using a clustering-criterion for identifying the best structure, together with the addition of a solvent exposure scoring term, the simulations suggests that sampling both the structure and the uncertainties in chemical shift prediction leads more accurate structures compared to conventional methods using empirical determined weights. The Cauchy distribution, using either sampled uncertainties or predetermined weights, did, however, result in overall better convergence to the native fold, suggesting that both types of distribution might be useful in different aspects of the protein structure prediction.

  9. Counterion influence on chemical shifts in strychnine salts

    Energy Technology Data Exchange (ETDEWEB)

    Metaxas, Athena E.; Cort, John R.

    2013-05-01

    The highly toxic plant alkaloid strychnine is often isolated in the form of the anion salt of its protonated tertiary amine. Here we characterize the relative influence of different counterions on 1H and 13C chemical shifts in several strychnine salts in D2O, methanol-d4 (CD3OD) and chloroform-d (CDCl3) solvents. In organic solvents, but not in water, substantial variation in chemical shifts of protons near the tertiary amine was observed among different salts. These secondary shifts reveal differences in the way each anion influences electronic structure within the protonated amine. The distributions of secondary shifts allow salts to be easily distinguished from each other as well as from the free base form. The observed effects are much greater in organic solvents than in water. Slight concentration-dependence in chemical shifts of some protons near the amine was observed for two salts in CDCl3, but this effect is small compared to the influence of the counterion. Distinct chemical shifts in different salt forms of the same compound may be useful as chemical forensic signatures for source attribution and sample matching of alkaloids such as strychnine and possibly other organic acid and base salts.

  10. Counterion influence on chemical shifts in strychnine salts.

    Science.gov (United States)

    Metaxas, Athena E; Cort, John R

    2013-05-01

    The highly toxic plant alkaloid strychnine is often isolated in the form of the anion salt of its protonated tertiary amine. Here, we characterize the relative influence of different counterions on (1)H and (13)C chemical shifts in several strychnine salts in D2O, methanol-d4 (CD3OD), and chloroform-d (CDCl3) solvents. In organic solvents but not in water, substantial variation in chemical shifts of protons near the tertiary amine was observed among different salts. These secondary shifts reveal differences in the way each anion influences electronic structure within the protonated amine. The distributions of secondary shifts allow salts to be easily distinguished from each other as well as from the free base form. Slight concentration dependence in chemical shifts of some protons near the amine was observed for two salts in CDCl3, but this effect is small compared with the influence of the counterion. Distinct chemical shifts in different salt forms of the same compound may be useful as chemical forensic signatures for source attribution and sample matching of alkaloids such as strychnine and possibly other organic acid and base salts. PMID:23495106

  11. Elucidating the Link between NMR Chemical Shifts and Electronic Structure in d(0) Olefin Metathesis Catalysts.

    Science.gov (United States)

    Halbert, Stéphanie; Copéret, Christophe; Raynaud, Christophe; Eisenstein, Odile

    2016-02-24

    The nucleophilic carbon of d(0) Schrock alkylidene metathesis catalysts, [M] = CHR, display surprisingly low downfield chemical shift (δiso) and large chemical shift anisotropy. State-of-the-art four-component relativistic calculations of the chemical shift tensors combined with a two-component analysis in terms of localized orbitals allow a molecular-level understanding of their orientations, the magnitude of their principal components (δ11 > δ22 > δ33) and associated δiso. This analysis reveals the dominating influence of the paramagnetic contribution yielding a highly deshielded alkylidene carbon. The largest paramagnetic contribution, which originates from the coupling of alkylidene σMC and π*MC orbitals under the action of the magnetic field, is analogous to that resulting from coupling σCC and π*CC in ethylene; thus, δ11 is in the MCH plane and is perpendicular to the MC internuclear direction. The higher value of carbon-13 δiso in alkylidene complexes relative to ethylene is thus due to the smaller energy gap between σMC and π*MC vs this between σCC and π*CC in ethylene. This effect also explains why the highest value of δiso is observed for Mo and the lowest for Ta, the values for W and Re being in between. In the presence of agostic interaction, the chemical shift tensor principal components orientation (δ22 or δ33 parallel or perpendicular to πMX) is influenced by the MCH angle because it determines the orientation of the alkylidene CHR fragment relative to the MC internuclear axis. The orbital analysis shows how the paramagnetic terms, understood with a localized bond model, determine the chemical shift tensor and thereby δiso. PMID:26787258

  12. Data requirements for reliable chemical shift assignments in deuterated proteins

    International Nuclear Information System (INIS)

    The information required for chemical shift assignments in large deuterated proteins was investigated using a Monte Carlo approach (Hitchens et al., 2002). In particular, the consequences of missing amide resonances on the reliability of assignments derived from Cα and CO or from Cα and Cβ chemical shifts was investigated. Missing amide resonances reduce both the number of correct assignments as well as the confidence in these assignments. More significantly, a number of undetectable errors can arise when as few as 9% of the amide resonances are missing from the spectra. However, the use of information from residue specific labeling as well as local and long-range distance constraints improves the reliability and extent of assignment. It is also shown that missing residues have only a minor effect on the assignment of protein-ligand complexes using Cα and CO chemical shifts and Cα inter-residue connectivity, provided that the known chemical shifts of the unliganded protein are utilized in the assignment process

  13. Constraints on the source of ultra-high energy cosmic rays using anisotropy vs chemical composition

    CERN Document Server

    Liu, Ruo-Yu; Lemoine, Martin; Wang, Xiang-Yu; Waxman, Eli

    2013-01-01

    The joint analysis of anisotropy signals and chemical composition of ultra-high energy cosmic rays offers strong potential for shedding light on the sources of these particles. Following up on an earlier idea, this paper studies the anisotropies produced by protons of energy >E/Z, assuming that anisotropies at energy >E have been produced by nuclei of charge Z, which share the same magnetic rigidity. We calculate the number of secondary protons produced through photodisintegration of the primary heavy nuclei. Making the extreme assumption that the source does not inject any proton, we find that the source(s) responsible for anisotropies such as reported by the Pierre Auger Observatory should lie closer than ~20-30, 80-100 and 180-200 Mpc if the anisotropy signal is mainly composed of oxygen, silicon and iron nuclei respectively. A violation of this constraint would otherwise result in the secondary protons forming a more significant anisotropy signal at lower energies. Even if the source were located closer t...

  14. Improving 3D structure prediction from chemical shift data

    International Nuclear Information System (INIS)

    We report advances in the calculation of protein structures from chemical shift nuclear magnetic resonance data alone. Our previously developed method, CS-Rosetta, assembles structures from a library of short protein fragments picked from a large library of protein structures using chemical shifts and sequence information. Here we demonstrate that combination of a new and improved fragment picker and the iterative sampling algorithm RASREC yield significant improvements in convergence and accuracy. Moreover, we introduce improved criteria for assessing the accuracy of the models produced by the method. The method was tested on 39 proteins in the 50–100 residue size range and yields reliable structures in 70 % of the cases. All structures that passed the reliability filter were accurate (<2 Å RMSD from the reference)

  15. Calculations of NMR chemical shifts with APW-based methods

    Science.gov (United States)

    Laskowski, Robert; Blaha, Peter

    2012-01-01

    We present a full potential, all electron augmented plane wave (APW) implementation of first-principles calculations of NMR chemical shifts. In order to obtain the induced current we follow a perturbation approach [Pickard and Mauri, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.63.245101 63, 245101 (2001)] and extended the common APW + local orbital (LO) basis by several LOs at higher energies. The calculated all-electron current is represented in traditional APW manner as Fourier series in the interstitial region and with a spherical harmonics representation inside the nonoverlapping atomic spheres. The current is integrated using a “pseudocharge” technique. The implementation is validated by comparison of the computed chemical shifts with some “exact” results for spherical atoms and for a set of solids and molecules with available published data.

  16. Improving 3D structure prediction from chemical shift data

    Energy Technology Data Exchange (ETDEWEB)

    Schot, Gijs van der [Utrecht University, Computational Structural Biology, Bijvoet Center for Biomolecular Research, Faculty of Science-Chemistry (Netherlands); Zhang, Zaiyong [Technische Universitaet Muenchen, Biomolecular NMR and Munich Center for Integrated Protein Science, Department Chemie (Germany); Vernon, Robert [University of Washington, Department of Biochemistry (United States); Shen, Yang [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States); Vranken, Wim F. [VIB, Department of Structural Biology (Belgium); Baker, David [University of Washington, Department of Biochemistry (United States); Bonvin, Alexandre M. J. J., E-mail: a.m.j.j.bonvin@uu.nl [Utrecht University, Computational Structural Biology, Bijvoet Center for Biomolecular Research, Faculty of Science-Chemistry (Netherlands); Lange, Oliver F., E-mail: oliver.lange@tum.de [Technische Universitaet Muenchen, Biomolecular NMR and Munich Center for Integrated Protein Science, Department Chemie (Germany)

    2013-09-15

    We report advances in the calculation of protein structures from chemical shift nuclear magnetic resonance data alone. Our previously developed method, CS-Rosetta, assembles structures from a library of short protein fragments picked from a large library of protein structures using chemical shifts and sequence information. Here we demonstrate that combination of a new and improved fragment picker and the iterative sampling algorithm RASREC yield significant improvements in convergence and accuracy. Moreover, we introduce improved criteria for assessing the accuracy of the models produced by the method. The method was tested on 39 proteins in the 50-100 residue size range and yields reliable structures in 70 % of the cases. All structures that passed the reliability filter were accurate (<2 A RMSD from the reference)

  17. Magnetic shift of the chemical freezeout and electric charge fluctuations

    CERN Document Server

    Fukushima, Kenji

    2016-01-01

    We discuss the effect of a strong magnetic field on the chemical freezeout points in the ultra-relativistic heavy-ion collision. As a result of the inverse magnetic catalysis or the magnetic inhibition, the crossover onset to hot and dense matter out of quarks and gluons should be shifted to a lower temperature. To quantify this shift we employ the hadron resonance gas model and an empirical condition for the chemical freezeout. We point out that the charged particle abundances are significantly affected by the magnetic field so that the electric charge fluctuation is largely enhanced especially at high baryon density. The charge conservation partially cancels the enhancement but our calculation shows that the electric charge fluctuation could serve as a magnetometer.

  18. Estimation of optical chemical shift in nuclear spin optical rotation

    International Nuclear Information System (INIS)

    Highlights: • Analytical theory of nuclear spin optical rotation (NSOR) is further developed. • Derive formula of NSOR ratio R between different nuclei in a same molecule. • Calculated results of R agree with the experiments. • Analyze influence factors on R and chemical distinction by NSOR. - Abstract: A recently proposed optical chemical shift in nuclear spin optical rotation (NSOR) is studied by theoretical comparison of NSOR magnitude between chemically non-equivalent or different element nuclei in the same molecule. Theoretical expressions of the ratio R between their NSOR magnitudes are derived by using a known semi-empirical formula of NSOR. Taking methanol, tri-ethyl-phosphite and 2-methyl-benzothiazole as examples, the ratios R are calculated and the results approximately agree with the experiments. Based on those, the important influence factors on R and chemical distinction by NSOR are discussed

  19. Chemical-shift MRI of exogenous lipoid pneumonia

    Energy Technology Data Exchange (ETDEWEB)

    Cox, J.E.; Choplin, R.H.; Chiles, C. [Wake Forest Univ., Winston-Salem, NC (United States)

    1996-05-01

    Exogenous lipoid pneumonia results from the aspiration or inhalation of fatty substances, such as mineral oil found in laxatives or nasal medications containing liquid paraffin. We present standard and lipid-sensitive (chemical-shift) MR findings in a patient with histologically confirmed lipoid pneumonia. The loss of signal intensity in an area of airspace disease on opposed-phase imaging was considered specific for the presence of lipid. 14 refs., 3 figs.

  20. Substituent effects on 61Ni NMR chemical shifts

    OpenAIRE

    Bühl, Michael; Peters, Dietmund; Herges, Rainer

    2009-01-01

    Ni-61 chemical shifts of Ni(all-trans-cdt) L (cdt = cyclododecatriene, L = none, CO, PMe3), Ni(CO)(4), Ni(C2H4)(2)(PMe3), Ni(cod)(2) (cod = cyclooctadiene) and Ni(PX3)(4) (X = Me, F, Cl) are computed at the GIAO (gauge-including atomic orbitals), BPW91, B3LYP and BHandHLYP levels, using BP86-optimised geometries and an indirect referencing scheme. For this set of compounds, substituent effects on delta(Ni-61) are better described with hybrid functionals than with the pure BPW91 functional. On...

  1. NMR chemical shifts in amino acids: Effects of environments, electric field, and amine group rotation

    International Nuclear Information System (INIS)

    The authors present calculations of NMR chemical shifts in crystalline phases of some representative amino acids such as glycine, alanine, and alanyl-alanine. To get an insight on how different environments affect the chemical shifts, they study the transition from the crystalline phase to completely isolated molecules of glycine. In the crystalline limit, the shifts are dominated by intermolecular hydrogen-bonds. In the molecular limit, however, dipole electric field effects dominate the behavior of the chemical shifts. They show that it is necessary to average the chemical shifts in glycine over geometries. Tensor components are analyzed to get the angle dependent proton chemical shifts, which is a more refined characterization method

  2. Computational Assignment of Chemical Shifts for Protein Residues

    CERN Document Server

    Bratholm, Lars A

    2013-01-01

    Fast and accurate protein structure prediction is one of the major challenges in structural biology, biotechnology and molecular biomedicine. These fields require 3D protein structures for rational design of proteins with improved or novel properties. X-ray crystallography is the most common approach even with its low success rate, but lately NMR based approaches have gained popularity. The general approach involves a set of distance restraints used to guide a structure prediction, but simple NMR triple-resonance experiments often provide enough structural information to predict the structure of small proteins. Previous protein folding simulations that have utilised experimental data have weighted the experimental data and physical force field terms more or less arbitrarily, and the method is thus not generally applicable to new proteins. Furthermore a complete and near error-free assignment of chemical shifts obtained by the NMR experiments is needed, due to the static, or deterministic, assignment. In this ...

  3. Accurate calculation of (31)P NMR chemical shifts in polyoxometalates.

    Science.gov (United States)

    Pascual-Borràs, Magda; López, Xavier; Poblet, Josep M

    2015-04-14

    We search for the best density functional theory strategy for the determination of (31)P nuclear magnetic resonance (NMR) chemical shifts, δ((31)P), in polyoxometalates. Among the variables governing the quality of the quantum modelling, we tackle herein the influence of the functional and the basis set. The spin-orbit and solvent effects were routinely included. To do so we analysed the family of structures α-[P2W18-xMxO62](n-) with M = Mo(VI), V(V) or Nb(V); [P2W17O62(M'R)](n-) with M' = Sn(IV), Ge(IV) and Ru(II) and [PW12-xMxO40](n-) with M = Pd(IV), Nb(V) and Ti(IV). The main results suggest that, to date, the best procedure for the accurate calculation of δ((31)P) in polyoxometalates is the combination of TZP/PBE//TZ2P/OPBE (for NMR//optimization step). The hybrid functionals (PBE0, B3LYP) tested herein were applied to the NMR step, besides being more CPU-consuming, do not outperform pure GGA functionals. Although previous studies on (183)W NMR suggested that the use of very large basis sets like QZ4P were needed for geometry optimization, the present results indicate that TZ2P suffices if the functional is optimal. Moreover, scaling corrections were applied to the results providing low mean absolute errors below 1 ppm for δ((31)P), which is a step forward in order to confirm or predict chemical shifts in polyoxometalates. Finally, via a simplified molecular model, we establish how the small variations in δ((31)P) arise from energy changes in the occupied and virtual orbitals of the PO4 group. PMID:25738630

  4. Random coil chemical shifts in acidic 8 M urea: Implementation of random coil shift data in NMRView

    International Nuclear Information System (INIS)

    Studies of proteins unfolded in acid or chemical denaturant can help in unraveling events during the earliest phases of protein folding. In order for meaningful comparisons to be made of residual structure in unfolded states, it is necessary to use random coil chemical shifts that are valid for the experimental system under study. We present a set of random coil chemical shifts obtained for model peptides under experimental conditions used in studies of denatured proteins. This new set, together with previously published data sets, has been incorporated into a software interface for NMRView, allowing selection of the random coil data set that fits the experimental conditions best

  5. Pitfalls of adrenal imaging with chemical shift MRI

    International Nuclear Information System (INIS)

    Chemical shift (CS) MRI of the adrenal glands exploits the different precessional frequencies of fat and water protons to differentiate the intracytoplasmic lipid-containing adrenal adenoma from other adrenal lesions. The purpose of this review is to illustrate both technical and interpretive pitfalls of adrenal imaging with CS MRI and emphasize the importance of adherence to strict technical specifications and errors that may occur when other imaging features and clinical factors are not incorporated into the diagnosis. When performed properly, the specificity of CS MRI for the diagnosis of adrenal adenoma is over 90%. Sampling the in-phase and opposed-phase echoes in the correct order and during the same breath-hold are essential requirements, and using the first echo pair is preferred, if possible. CS MRI characterizes more adrenal adenomas then unenhanced CT but may be non-diagnostic in a proportion of lipid-poor adenomas; CT washout studies may be able to diagnose these lipid-poor adenomas. Other primary and secondary adrenal tumours and supra-renal disease entities may contain lipid or gross fat and mimic adenoma or myelolipoma. Heterogeneity within an adrenal lesion that contains intracytoplasmic lipid could be due to myelolipoma, lipomatous metaplasia of adenoma, or collision tumour. Correlation with previous imaging, other imaging features, clinical history, and laboratory investigations can minimize interpretive errors

  6. Diagnostic value of chemical shift artifact in distinguishing benign lymphadenopathy

    International Nuclear Information System (INIS)

    Purpose: Today, distinguishing metastatic lymph nodes from secondary benign inflammatory ones via using non-invasive methods is increasingly favorable. In this study, the diagnostic value of chemical shift artifact (CSA) in magnetic resonance imaging (MRI) was evaluated to distinguish benign lymphadenopathy. Subjects and methods: A prospective intraindividual internal review board-approved study was carried out on 15 men and 15 women having lymphadenopathic lesions in different locations of the body who underwent contrast-enhanced dynamic MR imaging at 1.5 T. Then, the imaging findings were compared with pathology reports, using the statistics analyses. Results: Due to the findings of the CSA existence in MRI, a total of 56.7% of the studied lesions (17 of 30) were identified as benign lesions and the rest were malignant, whereas the pathology reports distinguished twelve malignant and eighteen benign cases. Furthermore, the CSA findings comparing the pathology reports indicated that CSA, with confidence of 79.5%, has a significant diagnostic value to differentiate benign lesions from malignant ones. Conclusion: Our study demonstrated that CSA in MR imaging has a suitable diagnostic potential nearing readiness for clinical trials. Furthermore, CSA seems to be a feasible tool to differentiate benign lymph nodes from malignant ones; however, further studies including larger numbers of patients are required to confirm our results.

  7. Applications of Chemical Shift Imaging to Marine Sciences

    Directory of Open Access Journals (Sweden)

    Haakil Lee

    2010-08-01

    Full Text Available The successful applications of magnetic resonance imaging (MRI in medicine are mostly due to the non-invasive and non-destructive nature of MRI techniques. Longitudinal studies of humans and animals are easily accomplished, taking advantage of the fact that MRI does not use harmful radiation that would be needed for plain film radiographic, computerized tomography (CT or positron emission (PET scans. Routine anatomic and functional studies using the strong signal from the most abundant magnetic nucleus, the proton, can also provide metabolic information when combined with in vivo magnetic resonance spectroscopy (MRS. MRS can be performed using either protons or hetero-nuclei (meaning any magnetic nuclei other than protons or 1H including carbon (13C or phosphorus (31P. In vivo MR spectra can be obtained from single region ofinterest (ROI or voxel or multiple ROIs simultaneously using the technique typically called chemical shift imaging (CSI. Here we report applications of CSI to marine samples and describe a technique to study in vivo glycine metabolism in oysters using 13C MRS 12 h after immersion in a sea water chamber dosed with [2-13C]-glycine. This is the first report of 13C CSI in a marine organism.

  8. 19-Fluorine nuclear magnetic resonance chemical shift variability in trifluoroacetyl species

    OpenAIRE

    Sloop, Joseph

    2013-01-01

    Joseph C SloopSchool of Science and Technology, Georgia Gwinnett College, Lawrenceville, GA, USAAbstract: This review examines the variability of chemical shifts observed in 19-fluorine (19F) nuclear magnetic resonance spectra for the trifluoroacetyl (TFA) functional group. The range of 19F chemical shifts reported spectra for the TFA group varies generally from −85 to −67 ppm relative to CFCl3. The literature revealed several factors that impact chemical shifts of the TFA...

  9. Practical use of chemical shift databases for protein solid-state NMR: 2D chemical shift maps and amino-acid assignment with secondary-structure information

    International Nuclear Information System (INIS)

    We introduce a Python-based program that utilizes the large database of 13C and 15N chemical shifts in the Biological Magnetic Resonance Bank to rapidly predict the amino acid type and secondary structure from correlated chemical shifts. The program, called PACSYlite Unified Query (PLUQ), is designed to help assign peaks obtained from 2D 13C–13C, 15N–13C, or 3D 15N–13C–13C magic-angle-spinning correlation spectra. We show secondary-structure specific 2D 13C–13C correlation maps of all twenty amino acids, constructed from a chemical shift database of 262,209 residues. The maps reveal interesting conformation-dependent chemical shift distributions and facilitate searching of correlation peaks during amino-acid type assignment. Based on these correlations, PLUQ outputs the most likely amino acid types and the associated secondary structures from inputs of experimental chemical shifts. We test the assignment accuracy using four high-quality protein structures. Based on only the Cα and Cβ chemical shifts, the highest-ranked PLUQ assignments were 40–60 % correct in both the amino-acid type and the secondary structure. For three input chemical shifts (CO–Cα–Cβ or N–Cα–Cβ), the first-ranked assignments were correct for 60 % of the residues, while within the top three predictions, the correct assignments were found for 80 % of the residues. PLUQ and the chemical shift maps are expected to be useful at the first stage of sequential assignment, for combination with automated sequential assignment programs, and for highly disordered proteins for which secondary structure analysis is the main goal of structure determination.

  10. A procedure to validate and correct the 13C chemical shift calibration of RNA datasets

    International Nuclear Information System (INIS)

    Chemical shifts reflect the structural environment of a certain nucleus and can be used to extract structural and dynamic information. Proper calibration is indispensable to extract such information from chemical shifts. Whereas a variety of procedures exist to verify the chemical shift calibration for proteins, no such procedure is available for RNAs to date. We present here a procedure to analyze and correct the calibration of 13C NMR data of RNAs. Our procedure uses five 13C chemical shifts as a reference, each of them found in a narrow shift range in most datasets deposited in the Biological Magnetic Resonance Bank. In 49 datasets we could evaluate the 13C calibration and detect errors or inconsistencies in RNA 13C chemical shifts based on these chemical shift reference values. More than half of the datasets (27 out of those 49) were found to be improperly referenced or contained inconsistencies. This large inconsistency rate possibly explains that no clear structure–13C chemical shift relationship has emerged for RNA so far. We were able to recalibrate or correct 17 datasets resulting in 39 usable 13C datasets. 6 new datasets from our lab were used to verify our method increasing the database to 45 usable datasets. We can now search for structure–chemical shift relationships with this improved list of 13C chemical shift data. This is demonstrated by a clear relationship between ribose 13C shifts and the sugar pucker, which can be used to predict a C2′- or C3′-endo conformation of the ribose with high accuracy. The improved quality of the chemical shift data allows statistical analysis with the potential to facilitate assignment procedures, and the extraction of restraints for structure calculations of RNA.

  11. Correlation of magnetocrystalline anisotropy of Fe0.5Pd0.5 alloy with chemical order

    International Nuclear Information System (INIS)

    We study the magnetocrystalline anisotropy of Fe0.5Pd0.5 alloy using the first-principles spin-polarized relativistic Korringa-Kohn-Rostoker coherent-potential approximation. We investigate the effect of long-ranged chemical order on the magnitude as well as the direction of easy magnetization. We find that in this alloy, the chemical order enhances the magnitude of the magnetocrystalline anisotropy energy as well as altering the easy axis. In particular, for the L10 ordered alloy the easy axis is perpendicular to the alternating layers of Fe and Pd with quite large magnetocrystalline anisotropy energy 124 μeV. These observations are in very good agreement with experiments. We also find that it is the electronic structure in the vicinity of the Fermi surface that is responsible for this effect. (author)

  12. Carbon-13 magnetic resonance chemical shift additivity relationships of clinically used furocoumarins and furchromones

    International Nuclear Information System (INIS)

    The natural abundance carbon-13 nuclear magnetic resonance spectra of various clinically used furocoumarins and furochromones have been studied. The assignments of carbon chemical shift values were based on the theory of chemical shift, additivity rules, SFORD spectra and model compounds. (author)

  13. Method of evaluating chemical shifts of X-ray emission lines in molecules and solids

    OpenAIRE

    Lomachuk, Yuriy V.; Titov, Anatoly V.

    2013-01-01

    Method of evaluating chemical shifts of X-ray emission lines for sufficiently heavy atoms (beginning from period 4 elements) in chemical compounds is developed. This method is based on the pseudopotential model and one-center restoration method (to reconstruct the proper electronic structure in heavy-atom cores). The approximations of instantaneous transition and frozen inner core spinors of the atom are used for derivation of an expression for chemical shift as a difference between mean valu...

  14. Inferential protein structure determination and refinement using fast, electronic structure based backbone amide chemical shift predictions

    CERN Document Server

    Christensen, Anders S

    2015-01-01

    This report covers the development of a new, fast method for calculating the backbone amide proton chemical shifts in proteins. Through quantum chemical calculations, structure-based forudsiglese the chemical shift for amidprotonen in protein has been parameterized. The parameters are then implemented in a computer program called Padawan. The program has since been implemented in protein folding program Phaistos, wherein the method andvendes to de novo folding of the protein structures and to refine the existing protein structures.

  15. Correlation of chemical shifts predicted by molecular dynamics simulations for partially disordered proteins

    International Nuclear Information System (INIS)

    There has been a longstanding interest in being able to accurately predict NMR chemical shifts from structural data. Recent studies have focused on using molecular dynamics (MD) simulation data as input for improved prediction. Here we examine the accuracy of chemical shift prediction for intein systems, which have regions of intrinsic disorder. We find that using MD simulation data as input for chemical shift prediction does not consistently improve prediction accuracy over use of a static X-ray crystal structure. This appears to result from the complex conformational ensemble of the disordered protein segments. We show that using accelerated molecular dynamics (aMD) simulations improves chemical shift prediction, suggesting that methods which better sample the conformational ensemble like aMD are more appropriate tools for use in chemical shift prediction for proteins with disordered regions. Moreover, our study suggests that data accurately reflecting protein dynamics must be used as input for chemical shift prediction in order to correctly predict chemical shifts in systems with disorder

  16. A robust algorithm for optimizing protein structures with NMR chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Berjanskii, Mark; Arndt, David; Liang, Yongjie; Wishart, David S., E-mail: david.wishart@ualberta.ca [University of Alberta, Department of Computing Science (Canada)

    2015-11-15

    Over the past decade, a number of methods have been developed to determine the approximate structure of proteins using minimal NMR experimental information such as chemical shifts alone, sparse NOEs alone or a combination of comparative modeling data and chemical shifts. However, there have been relatively few methods that allow these approximate models to be substantively refined or improved using the available NMR chemical shift data. Here, we present a novel method, called Chemical Shift driven Genetic Algorithm for biased Molecular Dynamics (CS-GAMDy), for the robust optimization of protein structures using experimental NMR chemical shifts. The method incorporates knowledge-based scoring functions and structural information derived from NMR chemical shifts via a unique combination of multi-objective MD biasing, a genetic algorithm, and the widely used XPLOR molecular modelling language. Using this approach, we demonstrate that CS-GAMDy is able to refine and/or fold models that are as much as 10 Å (RMSD) away from the correct structure using only NMR chemical shift data. CS-GAMDy is also able to refine of a wide range of approximate or mildly erroneous protein structures to more closely match the known/correct structure and the known/correct chemical shifts. We believe CS-GAMDy will allow protein models generated by sparse restraint or chemical-shift-only methods to achieve sufficiently high quality to be considered fully refined and “PDB worthy”. The CS-GAMDy algorithm is explained in detail and its performance is compared over a range of refinement scenarios with several commonly used protein structure refinement protocols. The program has been designed to be easily installed and easily used and is available at http://www.gamdy.ca http://www.gamdy.ca.

  17. A robust algorithm for optimizing protein structures with NMR chemical shifts

    International Nuclear Information System (INIS)

    Over the past decade, a number of methods have been developed to determine the approximate structure of proteins using minimal NMR experimental information such as chemical shifts alone, sparse NOEs alone or a combination of comparative modeling data and chemical shifts. However, there have been relatively few methods that allow these approximate models to be substantively refined or improved using the available NMR chemical shift data. Here, we present a novel method, called Chemical Shift driven Genetic Algorithm for biased Molecular Dynamics (CS-GAMDy), for the robust optimization of protein structures using experimental NMR chemical shifts. The method incorporates knowledge-based scoring functions and structural information derived from NMR chemical shifts via a unique combination of multi-objective MD biasing, a genetic algorithm, and the widely used XPLOR molecular modelling language. Using this approach, we demonstrate that CS-GAMDy is able to refine and/or fold models that are as much as 10 Å (RMSD) away from the correct structure using only NMR chemical shift data. CS-GAMDy is also able to refine of a wide range of approximate or mildly erroneous protein structures to more closely match the known/correct structure and the known/correct chemical shifts. We believe CS-GAMDy will allow protein models generated by sparse restraint or chemical-shift-only methods to achieve sufficiently high quality to be considered fully refined and “PDB worthy”. The CS-GAMDy algorithm is explained in detail and its performance is compared over a range of refinement scenarios with several commonly used protein structure refinement protocols. The program has been designed to be easily installed and easily used and is available at http://www.gamdy.ca http://www.gamdy.ca

  18. Mineral Moessbauer spectroscopy: correlations between chemical shift and quadrupole splitting parameters

    International Nuclear Information System (INIS)

    The variety of coordination numbers, symmetries, distortions and ligand environments in thermally-stable iron-bearing minerals provide wide ranges of chemical shift (δ) and quadrupole splitting (Δ) parameters, which serve to characterize the crystal chemistries and site occupancies of Fe2+ and Fe3+ ions in minerals of terrestrial and extraterrestrial origins. Correlations between ferrous and ferric chemical shifts enable thermally-induced electron delocalization behavior in mixed-valence Fe2+-Fe3+ minerals to be identified, while chemical shift versus quadrupole splitting correlations serve to identify nanophase ferric oxides and oxyhydroxides in oxidized minerals and in meteorites subjected to aqueous oxidation before and after they arrived on Earth. (orig.)

  19. Protein structure validation and refinement using amide proton chemical shifts derived from quantum mechanics

    DEFF Research Database (Denmark)

    Christensen, Anders Steen; Linnet, Troels Emtekær; Borg, Mikael;

    2013-01-01

    We present the ProCS method for the rapid and accurate prediction of protein backbone amide proton chemical shifts - sensitive probes of the geometry of key hydrogen bonds that determine protein structure. ProCS is parameterized against quantum mechanical (QM) calculations and reproduces high level...... QM results obtained for a small protein with an RMSD of 0.25 ppm (r = 0.94). ProCS is interfaced with the PHAISTOS protein simulation program and is used to infer statistical protein ensembles that reflect experimentally measured amide proton chemical shift values. Such chemical shift...

  20. Combined Effects of Noise and Shift Work on Workers’ Physiological Parameters in a Chemical Industry

    OpenAIRE

    M. Motamedzade; S. Ghazaiee

    2003-01-01

    This study was conducted to determine the combined effects of noise and shift work on physiological parameters including body temperature, heart rate and blood pressure. This study was performed in a chemical industry in Tehran in 1993. The workers’ physiological parameters was recorded at the beginning and at the end of all work shifts. Groups under study included : day workers (n=115) , day workers with continuous noise exposure (n=44) , two-shift workers without...

  1. PPM-One: a static protein structure based chemical shift predictor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dawei; Brüschweiler, Rafael, E-mail: bruschweiler.1@osu.edu [The Ohio State University, Campus Chemical Instrument Center (United States)

    2015-07-15

    We mined the most recent editions of the BioMagResDataBank and the protein data bank to parametrize a new empirical knowledge-based chemical shift predictor of protein backbone atoms using either a linear or an artificial neural network model. The resulting chemical shift predictor PPM-One accepts a single static 3D structure as input and emulates the effect of local protein dynamics via interatomic steric contacts. Furthermore, the chemical shift prediction was extended to most side-chain protons and it is found that the prediction accuracy is at a level allowing an independent assessment of stereospecific assignments. For a previously established set of test proteins some overall improvement was achieved over current top-performing chemical shift prediction programs.

  2. Chemical shifts and coupling constants of C8H10N4O2

    Science.gov (United States)

    Jain, M.

    This document is part of Subvolume D3 `Chemical Shifts and Coupling Constants for Carbon-13: Heterocycles' of Volume 35 `Nuclear Magnetic Resonance (NMR) Data' of Landolt-Börnstein Group III `Condensed Matter'

  3. Quantitative chemical-shift MR imaging cutoff value: Benign versus malignant vertebral compression – Initial experience

    Directory of Open Access Journals (Sweden)

    Dalia Z. Zidan

    2014-09-01

    Conclusion: Quantitative chemical shift MR imaging could be a valuable addition to standard MR imaging techniques and represent a rapid problem solving tool in differentiating benign from malignant vertebral compression, especially in patients with known primary malignancies.

  4. PPM-One: a static protein structure based chemical shift predictor

    International Nuclear Information System (INIS)

    We mined the most recent editions of the BioMagResDataBank and the protein data bank to parametrize a new empirical knowledge-based chemical shift predictor of protein backbone atoms using either a linear or an artificial neural network model. The resulting chemical shift predictor PPM-One accepts a single static 3D structure as input and emulates the effect of local protein dynamics via interatomic steric contacts. Furthermore, the chemical shift prediction was extended to most side-chain protons and it is found that the prediction accuracy is at a level allowing an independent assessment of stereospecific assignments. For a previously established set of test proteins some overall improvement was achieved over current top-performing chemical shift prediction programs

  5. Supramolecular chemical shift reagents inducing conformational transitions: NMR analysis of carbohydrate homooligomer mixtures

    DEFF Research Database (Denmark)

    Beeren, Sophie; Meier, Sebastian

    2015-01-01

    We introduce the concept of supramolecular chemical shift reagents as a tool to improve signal resolution for the NMR analysis of homooligomers. Non-covalent interactions with the shift reagent can constrain otherwise flexible analytes inducing a conformational transition that results in signal...

  6. AFNMR: automated fragmentation quantum mechanical calculation of NMR chemical shifts for biomolecules

    International Nuclear Information System (INIS)

    We evaluate the performance of the automated fragmentation quantum mechanics/molecular mechanics approach (AF-QM/MM) on the calculation of protein and nucleic acid NMR chemical shifts. The AF-QM/MM approach models solvent effects implicitly through a set of surface charges computed using the Poisson–Boltzmann equation, and it can also be combined with an explicit solvent model through the placement of water molecules in the first solvation shell around the solute; the latter substantially improves the accuracy of chemical shift prediction of protons involved in hydrogen bonding with solvent. We also compare the performance of AF-QM/MM on proteins and nucleic acids with two leading empirical chemical shift prediction programs SHIFTS and SHIFTX2. Although the empirical programs outperform AF-QM/MM in predicting chemical shifts, the differences are in some cases small, and the latter can be applied to chemical shifts on biomolecules which are outside the training set employed by the empirical programs, such as structures containing ligands, metal centers, and non-standard residues. The AF-QM/MM described here is implemented in version 5 of the SHIFTS software, and is fully automated, so that only a structure in PDB format is required as input

  7. Prediction of hydrogen and carbon chemical shifts from RNA using database mining and support vector regression

    International Nuclear Information System (INIS)

    The Biological Magnetic Resonance Data Bank (BMRB) contains NMR chemical shift depositions for over 200 RNAs and RNA-containing complexes. We have analyzed the 1H NMR and 13C chemical shifts reported for non-exchangeable protons of 187 of these RNAs. Software was developed that downloads BMRB datasets and corresponding PDB structure files, and then generates residue-specific attributes based on the calculated secondary structure. Attributes represent properties present in each sequential stretch of five adjacent residues and include variables such as nucleotide type, base-pair presence and type, and tetraloop types. Attributes and 1H and 13C NMR chemical shifts of the central nucleotide are then used as input to train a predictive model using support vector regression. These models can then be used to predict shifts for new sequences. The new software tools, available as stand-alone scripts or integrated into the NMR visualization and analysis program NMRViewJ, should facilitate NMR assignment and/or validation of RNA 1H and 13C chemical shifts. In addition, our findings enabled the re-calibration a ring-current shift model using published NMR chemical shifts and high-resolution X-ray structural data as guides

  8. Prediction of hydrogen and carbon chemical shifts from RNA using database mining and support vector regression.

    Science.gov (United States)

    Brown, Joshua D; Summers, Michael F; Johnson, Bruce A

    2015-09-01

    The Biological Magnetic Resonance Data Bank (BMRB) contains NMR chemical shift depositions for over 200 RNAs and RNA-containing complexes. We have analyzed the (1)H NMR and (13)C chemical shifts reported for non-exchangeable protons of 187 of these RNAs. Software was developed that downloads BMRB datasets and corresponding PDB structure files, and then generates residue-specific attributes based on the calculated secondary structure. Attributes represent properties present in each sequential stretch of five adjacent residues and include variables such as nucleotide type, base-pair presence and type, and tetraloop types. Attributes and (1)H and (13)C NMR chemical shifts of the central nucleotide are then used as input to train a predictive model using support vector regression. These models can then be used to predict shifts for new sequences. The new software tools, available as stand-alone scripts or integrated into the NMR visualization and analysis program NMRViewJ, should facilitate NMR assignment and/or validation of RNA (1)H and (13)C chemical shifts. In addition, our findings enabled the re-calibration a ring-current shift model using published NMR chemical shifts and high-resolution X-ray structural data as guides. PMID:26141454

  9. Prediction of hydrogen and carbon chemical shifts from RNA using database mining and support vector regression

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Joshua D.; Summers, Michael F. [University of Maryland Baltimore County, Howard Hughes Medical Institute (United States); Johnson, Bruce A., E-mail: bruce.johnson@asrc.cuny.edu [University of Maryland Baltimore County, Department of Chemistry and Biochemistry (United States)

    2015-09-15

    The Biological Magnetic Resonance Data Bank (BMRB) contains NMR chemical shift depositions for over 200 RNAs and RNA-containing complexes. We have analyzed the {sup 1}H NMR and {sup 13}C chemical shifts reported for non-exchangeable protons of 187 of these RNAs. Software was developed that downloads BMRB datasets and corresponding PDB structure files, and then generates residue-specific attributes based on the calculated secondary structure. Attributes represent properties present in each sequential stretch of five adjacent residues and include variables such as nucleotide type, base-pair presence and type, and tetraloop types. Attributes and {sup 1}H and {sup 13}C NMR chemical shifts of the central nucleotide are then used as input to train a predictive model using support vector regression. These models can then be used to predict shifts for new sequences. The new software tools, available as stand-alone scripts or integrated into the NMR visualization and analysis program NMRViewJ, should facilitate NMR assignment and/or validation of RNA {sup 1}H and {sup 13}C chemical shifts. In addition, our findings enabled the re-calibration a ring-current shift model using published NMR chemical shifts and high-resolution X-ray structural data as guides.

  10. AFNMR: automated fragmentation quantum mechanical calculation of NMR chemical shifts for biomolecules

    Energy Technology Data Exchange (ETDEWEB)

    Swails, Jason [Rutgers University, Department of Chemistry and Chemical Biology and BioMaPS Institute (United States); Zhu, Tong; He, Xiao, E-mail: xiaohe@phy.ecnu.edu.cn [East China Normal University, State Key Laboratory of Precision Spectroscopy, Institute of Theoretical and Computational Science (China); Case, David A., E-mail: case@biomaps.rutgers.edu [Rutgers University, Department of Chemistry and Chemical Biology and BioMaPS Institute (United States)

    2015-10-15

    We evaluate the performance of the automated fragmentation quantum mechanics/molecular mechanics approach (AF-QM/MM) on the calculation of protein and nucleic acid NMR chemical shifts. The AF-QM/MM approach models solvent effects implicitly through a set of surface charges computed using the Poisson–Boltzmann equation, and it can also be combined with an explicit solvent model through the placement of water molecules in the first solvation shell around the solute; the latter substantially improves the accuracy of chemical shift prediction of protons involved in hydrogen bonding with solvent. We also compare the performance of AF-QM/MM on proteins and nucleic acids with two leading empirical chemical shift prediction programs SHIFTS and SHIFTX2. Although the empirical programs outperform AF-QM/MM in predicting chemical shifts, the differences are in some cases small, and the latter can be applied to chemical shifts on biomolecules which are outside the training set employed by the empirical programs, such as structures containing ligands, metal centers, and non-standard residues. The AF-QM/MM described here is implemented in version 5 of the SHIFTS software, and is fully automated, so that only a structure in PDB format is required as input.

  11. Chemical shift MRI can aid in the diagnosis of indeterminate skeletal lesions of the spine

    Energy Technology Data Exchange (ETDEWEB)

    Douis, H. [University Hospital Birmingham, Department of Radiology, Birmingham (United Kingdom); Royal Orthopaedic Hospital, Department of Radiology, Birmingham (United Kingdom); Davies, A.M. [Royal Orthopaedic Hospital, Department of Radiology, Birmingham (United Kingdom); Jeys, L. [Royal Orthopaedic Hospital, Department of Orthopaedic Oncology, Birmingham (United Kingdom); Sian, P. [Royal Orthopaedic Hospital, Department of Spinal Surgery and Spinal Oncology, Birmingham (United Kingdom)

    2016-04-15

    To evaluate the role of chemical shift MRI in the characterisation of indeterminate skeletal lesions of the spine as benign or malignant. Fifty-five patients (mean age 54.7 years) with 57 indeterminate skeletal lesions of the spine were included in this retrospective study. In addition to conventional MRI at 3 T which included at least sagittal T1WI and T2WI/STIR sequences, patients underwent chemical shift MRI. A cut-off value with a signal drop-out of 20 % was used to differentiate benign lesions from malignant lesions (signal drop-out <20 % being malignant). There were 45 benign lesions and 12 malignant lesions. Chemical shift imaging correctly diagnosed 33 of 45 lesions as benign and 11 of 12 lesions as malignant. In contrast, there were 12 false positive cases and 1 false negative case based on chemical shift MRI. This yielded a sensitivity of 91.7 %, a specificity of 73.3 %, a negative predictive value of 97.1 %, a positive predictive value of 47.8 % and a diagnostic accuracy of 82.5 %. Chemical shift MRI can aid in the characterisation of indeterminate skeletal lesions of the spine in view of its high sensitivity in diagnosing malignant lesions. Chemical shift MRI can potentially avoid biopsy in a considerable percentage of patients with benign skeletal lesions of the spine. (orig.)

  12. Chemical shift MRI can aid in the diagnosis of indeterminate skeletal lesions of the spine

    International Nuclear Information System (INIS)

    To evaluate the role of chemical shift MRI in the characterisation of indeterminate skeletal lesions of the spine as benign or malignant. Fifty-five patients (mean age 54.7 years) with 57 indeterminate skeletal lesions of the spine were included in this retrospective study. In addition to conventional MRI at 3 T which included at least sagittal T1WI and T2WI/STIR sequences, patients underwent chemical shift MRI. A cut-off value with a signal drop-out of 20 % was used to differentiate benign lesions from malignant lesions (signal drop-out <20 % being malignant). There were 45 benign lesions and 12 malignant lesions. Chemical shift imaging correctly diagnosed 33 of 45 lesions as benign and 11 of 12 lesions as malignant. In contrast, there were 12 false positive cases and 1 false negative case based on chemical shift MRI. This yielded a sensitivity of 91.7 %, a specificity of 73.3 %, a negative predictive value of 97.1 %, a positive predictive value of 47.8 % and a diagnostic accuracy of 82.5 %. Chemical shift MRI can aid in the characterisation of indeterminate skeletal lesions of the spine in view of its high sensitivity in diagnosing malignant lesions. Chemical shift MRI can potentially avoid biopsy in a considerable percentage of patients with benign skeletal lesions of the spine. (orig.)

  13. From NMR chemical shifts to amino acid types: Investigation of the predictive power carried by nuclei

    International Nuclear Information System (INIS)

    An approach to automatic prediction of the amino acid type from NMR chemical shift values of its nuclei is presented here, in the frame of a model to calculate the probability of an amino acid type given the set of chemical shifts. The method relies on systematic use of all chemical shift values contained in the BioMagResBank (BMRB). Two programs were designed, one (BMRB stats) for extracting statistical chemical shift parameters from the BMRB and another one (RESCUE2) for computing the probabilities of each amino acid type, given a set of chemical shifts. The Bayesian prediction scheme presented here is compared to other methods already proposed: PROTYP (Grzesiek and Bax, J. Biomol. NMR, 3, 185-204, 1993) RESCUE (Pons and Delsuc, J. Biomol. NMR, 15, 15-26, 1999) and PLATON (Labudde et al., J. Biomol. NMR, 25, 41-53, 2003) and is found to be more sensitive and more specific. Using this scheme, we tested various sets of nuclei. The two nuclei carrying the most information are Cβ and Hβ, in agreement with observations made in Grzesiek and Bax, 1993. Based on four nuclei: Hβ, Cβ, Cα and C', it is possible to increase correct predictions to a rate of more than 75%. Taking into account the correlations between the nuclei chemical shifts has only a slight impact on the percentage of correct predictions: indeed, the largest correlation coefficients display similar features on all amino acids

  14. Enhanced conformational space sampling improves the prediction of chemical shifts in proteins.

    Science.gov (United States)

    Markwick, Phineus R L; Cervantes, Carla F; Abel, Barrett L; Komives, Elizabeth A; Blackledge, Martin; McCammon, J Andrew

    2010-02-01

    A biased-potential molecular dynamics simulation method, accelerated molecular dynamics (AMD), was combined with the chemical shift prediction algorithm SHIFTX to calculate (1)H(N), (15)N, (13)Calpha, (13)Cbeta, and (13)C' chemical shifts of the ankyrin repeat protein IkappaBalpha (residues 67-206), the primary inhibitor of nuclear factor kappa-B (NF-kappaB). Free-energy-weighted molecular ensembles were generated over a range of acceleration levels, affording systematic enhancement of the conformational space sampling of the protein. We have found that the predicted chemical shifts, particularly for the (15)N, (13)Calpha, and (13)Cbeta nuclei, improve substantially with enhanced conformational space sampling up to an optimal acceleration level. Significant improvement in the predicted chemical shift data coincides with those regions of the protein that exhibit backbone dynamics on longer time scales. Interestingly, the optimal acceleration level for reproduction of the chemical shift data has previously been shown to best reproduce the experimental residual dipolar coupling (RDC) data for this system, as both chemical shift data and RDCs report on an ensemble and time average in the millisecond range. PMID:20063881

  15. Ontogenetic shift in response to prey-derived chemical cues in prairie rattlesnakes Crotalus viridis viridis

    Directory of Open Access Journals (Sweden)

    Anthony J. SAVIOLA, David CHISZAR, Stephen P. MACKESSY

    2012-08-01

    Full Text Available Snakes often have specialized diets that undergo a shift from one prey type to another depending on the life stage of the snake. Crotalus viridis viridis (prairie rattlesnake takes different prey at different life stages, and neonates typically prey on ectotherms, while adults feed almost entirely on small endotherms. We hypothesized that elevated rates of tongue flicking to chemical stimuli should correlate with particular prey consumed, and that this response shifts from one prey type to another as individuals age. To examine if an ontogenetic shift in response to chemical cues occurred, we recorded the rate of tongue flicking for 25 neonate, 20 subadult, and 20 adult (average SVL = 280.9, 552, 789.5 mm, respectively wild-caught C. v. viridis to chemical stimuli presented on a cotton-tipped applicator; water-soluble cues from two ectotherms (prairie lizard, Sceloporus undulatus, and house gecko, Hemidactylus frenatus, two endotherms (deer mouse, Peromyscus maniculatus and lab mouse, Mus musculus, and water controls were used. Neonates tongue flicked significantly more to chemical cues of their common prey, S. undulatus, than to all other chemical cues; however, the response to this lizard’s chemical cues decreased in adult rattlesnakes. Subadults tongue flicked with a higher rate of tongue flicking to both S. undulatus and P. maniculatus than to all other treatments, and adults tongue flicked significantly more to P. maniculatus than to all other chemical cues. In addition, all three sub-classes demonstrated a greater response for natural prey chemical cues over chemical stimuli of prey not encountered in the wild (M. musculus and H. frenatus. This shift in chemosensory response correlated with the previously described ontogenetic shifts in C. v. viridis diet. Because many vipers show a similar ontogenetic shift in diet and venom composition, we suggest that this shift in prey cue discrimination is likely a general phenomenon among viperid

  16. Further conventions for NMR shielding and chemical shifts (IUPAC Recommendations 2008)

    Energy Technology Data Exchange (ETDEWEB)

    Harris, R.K. [University of Durham, Durham (United Kingdom). Dept. of Chemistry; Becker, E.D. [National Institutes of Health, Bethesda, MD (United States); Menezes, S.M. Cabral de [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES); Granger, P. [University Louis Pasteur, Strasbourg (France). Inst. of Chemistry; Hoffman, R.E. [The Hebrew University of Jerusalem, Safra Campus, Jerusalem (Israel). Dept. of Organic Chemistry; Zilm, K.W., E-mail: r.k.harris@durham.ac.uk [Yale University, New Haven, CT (United States). Dept. of Chemistry

    2008-07-01

    IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the {sup 1}H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3- (trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating {sup 13}C NMR chemical shifts in solids to the scales used for high resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice. (author)

  17. Further conventions for NMR shielding and chemical shifts (IUPAC Recommendations 2008)

    International Nuclear Information System (INIS)

    IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the 1H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3- (trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating 13C NMR chemical shifts in solids to the scales used for high resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice. (author)

  18. Effect of shifting cultivation on soil physical and chemical properties in Bandarban hill district, Bangladesh

    Institute of Scientific and Technical Information of China (English)

    Khandakar Showkat Osman; M. Jashimuddin; S. M. Sirajul Haque; Sohag Miah

    2013-01-01

    This study reports the effects of shifting cultivation at slashing stage on soil physicochemical properties at Bandarban Sadar Upazila in Chittagong Hill Tracts of Bangladesh. At this initial stage of shifting cultivation no general trend was found for moisture content, maximum water holding capacity, field capacity, dry and moist bulk density, parti-cle density for some chemical properties between shifting cultivated land and forest having similar soil texture. Organic matter was significantly (p≤0.05) lower in 1-year and 3-year shifting cultivated lands and higher in 2-year shifting cultivation than in adjacent natural forest. Significant differences were also found for total N, exchangeable Ca, Mg and K and in CEC as well as for available P. Slashed area showed higher soil pH. Deterioration in land quality starts from burning of slashing materials and continues through subsequent stages of shifting cultivation.

  19. Method for evaluating chemical shifts of x-ray emission lines in molecules and solids

    Science.gov (United States)

    Lomachuk, Yuriy V.; Titov, Anatoly V.

    2013-12-01

    A method of evaluating chemical shifts of x-ray emission lines for period four and heavier elements is developed. This method is based on the relativistic pseudopotential model and one-center restoration approach [Int. J. Quantum Chem.IJQCB20020-760810.1002/qua.20418 104, 223 (2005)] to recover a proper electronic structure in heavy-atom cores after the pseudopotential simulation of chemical compounds. The approximations of instantaneous transition and frozen core are presently applied to derive an expression for chemical shift as a difference between mean values of certain effective operator. The method allows one to avoid evaluation of small quantities (chemical shifts ˜0.01-1 eV) as differences of very large values (transition energies ˜1-100 keV in various compounds). The results of our calculations of chemical shifts for the Kα1, Kα2, and L transitions of group-14 metal cations with respect to neutral atoms are presented. Calculations of Kα1-line chemical shifts for the Pb core transitions in PbO and PbF2 with respect to those in the Pb atom are also performed and discussed. The accuracy of approximations used is estimated and the quality of the calculations is analyzed.

  20. Method of evaluating chemical shifts of X-ray emission lines in molecules and solids

    CERN Document Server

    Lomachuk, Yuriy V

    2013-01-01

    Method of evaluating chemical shifts of X-ray emission lines for sufficiently heavy atoms (beginning from period 4 elements) in chemical compounds is developed. This method is based on the pseudopotential model and one-center restoration method (to reconstruct the proper electronic structure in heavy-atom cores). The approximations of instantaneous transition and frozen inner core spinors of the atom are used for derivation of an expression for chemical shift as a difference between mean values of some effective operator. The method allows one to avoid evaluating small values (chemical shifts ~ 0.01{\\div}1 eV) as differences of very large values (transition energies ~ 1{\\div}100 keV in various compounds). The results of our calculations of chemical shifts for the K_{\\alpha1,2} and L transitions of the group 14 metal cations with respect to neutral atoms are presented. The calculations of chemical shift of K_{\\alpha1}-line in the Pb-core transition within PbO and PbF_2 with respect to the neutral Pb are also p...

  1. Protein backbone chemical shifts predicted from searching a database for torsion angle and sequence homology

    International Nuclear Information System (INIS)

    Chemical shifts of nuclei in or attached to a protein backbone are exquisitely sensitive to their local environment. A computer program, SPARTA, is described that uses this correlation with local structure to predict protein backbone chemical shifts, given an input three-dimensional structure, by searching a newly generated database for triplets of adjacent residues that provide the best match in φ/ψ/χ1 torsion angles and sequence similarity to the query triplet of interest. The database contains 15N, 1HN, 1Hα, 13Cα, 13Cβ and 13C' chemical shifts for 200 proteins for which a high resolution X-ray (≤2.4 A) structure is available. The relative importance of the weighting factors for the φ/ψ/χ1 angles and sequence similarity was optimized empirically. The weighted, average secondary shifts of the central residues in the 20 best-matching triplets, after inclusion of nearest neighbor, ring current, and hydrogen bonding effects, are used to predict chemical shifts for the protein of known structure. Validation shows good agreement between the SPARTA-predicted and experimental shifts, with standard deviations of 2.52, 0.51, 0.27, 0.98, 1.07 and 1.08 ppm for 15N, 1HN, 1Hα, 13Cα, 13Cβ and 13C', respectively, including outliers

  2. RefDB: A database of uniformly referenced protein chemical shifts

    International Nuclear Information System (INIS)

    RefDB is a secondary database of reference-corrected protein chemical shifts derived from the BioMagResBank (BMRB). The database was assembled by using a recently developed program (SHIFTX) to predict protein 1H, 13C and 15N chemical shifts from X-ray or NMR coordinate data of previously assigned proteins. The predicted shifts were then compared with the corresponding observed shifts and a variety of statistical evaluations performed. In this way, potential mis-assignments, typographical errors and chemical referencing errors could be identified and, in many cases, corrected. This approach allows for an unbiased, instrument-independent solution to the problem of retrospectively re-referencing published protein chemical shifts. Results from this study indicate that nearly 25% of BMRB entries with 13C protein assignments and 27% of BMRB entries with 15N protein assignments required significant chemical shift reference readjustments. Additionally, nearly 40% of protein entries deposited in the BioMagResBank appear to have at least one assignment error. From this study it evident that protein NMR spectroscopists are increasingly adhering to recommended IUPAC 13C and 15N chemical shift referencing conventions, however, approximately 20% of newly deposited protein entries in the BMRB are still being incorrectly referenced. This is cause for some concern. However, the utilization of RefDB and its companion programs may help mitigate this ongoing problem. RefDB is updated weekly and the database, along with its associated software, is freely available at http://redpoll.pharmacy.ualberta.ca and the BMRB website

  3. Differential diagnosis of adrenal masses by chemical shift and dynamic gadolinium enhanced MR imaging

    International Nuclear Information System (INIS)

    Chemical shift MRI is widely used for identifying adenomas, but it is not a perfect method. We determined whether combined dynamic MRI methods can lead to improved diagnostic accuracy. Fifty-seven adrenal masses were examined by chemical shift and dynamic MR imaging using 2 MR systems. The masses included 38 adenomas and 19 non-adenomas. In chemical shift MRI studies, the signal intensity index (SI) was calculated, and the lesions classified into 5 types in the dynamic MRI studies. Of the 38 adenomas studied, 37 had an SI greater than 0. In the dynamic MRI, 34 of 38 adenomas showed a benign pattern (type 1). If the SI for the adenomas in the chemical shift MRI was considered to be greater than 0, the positive predictive value was 0.9, and the negative predictive value was 0.94 and κ=0.79. If type 1 was considered to indicate adenomas in the dynamic MRI, the corresponding values were 0.94, 0.81 and κ=0.77 respectively. The results obtained when the 2 methods were combined were 1, 0.95 and κ=0.96 respectively. The chemical shift MRI was found to be useful for identifying adenomas in most cases. If the adrenal mass had a low SI (0< SI<5), dynamic MRI was also found to be helpful for making a differential diagnosis. (author)

  4. Prediction algorithm for amino acid types with their secondary structure in proteins (PLATON) using chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Labudde, D.; Leitner, D.; Krueger, M.; Oschkinat, H. [Forschungsinstitut fuer Molekulare Pharmakologie (Germany)], E-mail: oschkinat@fmp-berlin.de

    2003-01-15

    The algorithm PLATON is able to assign sets of chemical shifts derived from a single residue to amino acid types with its secondary structure (amino acid species). A subsequent ranking procedure using optionally two different penalty functions yields predictions for possible amino acid species for the given set of chemical shifts. This was demonstrated in the case of the {alpha}-spectrin SH3 domain and applied to 9 further protein data sets taken from the BioMagRes database. A database consisting of reference chemical shift patterns (reference CSPs) was generated from assigned chemical shifts of proteins with known 3D-structure. This reference CSP database is used in our approach for extracting distributions of amino acid types with their most likely secondary structure elements (namely {alpha}-helix, {beta}-sheet, and coil) for single amino acids by comparison with query CSPs. Results obtained for the 10 investigated proteins indicates that the percentage of correct amino acid species in the first three positions in the ranking list, ranges from 71.4% to 93.2% for the more favorable penalty function. Where only the top result of the ranking list for these 10 proteins is considered, 36.5% to 83.1% of the amino acid species are correctly predicted. The main advantage of our approach, over other methods that rely on average chemical shift values is the ability to increase database content by incorporating newly derived CSPs, and therefore to improve PLATON's performance over time.

  5. Protein structure validation and refinement using amide proton chemical shifts derived from quantum mechanics.

    Directory of Open Access Journals (Sweden)

    Anders S Christensen

    Full Text Available We present the ProCS method for the rapid and accurate prediction of protein backbone amide proton chemical shifts--sensitive probes of the geometry of key hydrogen bonds that determine protein structure. ProCS is parameterized against quantum mechanical (QM calculations and reproduces high level QM results obtained for a small protein with an RMSD of 0.25 ppm (r = 0.94. ProCS is interfaced with the PHAISTOS protein simulation program and is used to infer statistical protein ensembles that reflect experimentally measured amide proton chemical shift values. Such chemical shift-based structural refinements, starting from high-resolution X-ray structures of Protein G, ubiquitin, and SMN Tudor Domain, result in average chemical shifts, hydrogen bond geometries, and trans-hydrogen bond ((h3J(NC' spin-spin coupling constants that are in excellent agreement with experiment. We show that the structural sensitivity of the QM-based amide proton chemical shift predictions is needed to obtain this agreement. The ProCS method thus offers a powerful new tool for refining the structures of hydrogen bonding networks to high accuracy with many potential applications such as protein flexibility in ligand binding.

  6. Protein structure validation and refinement using amide proton chemical shifts derived from quantum mechanics

    CERN Document Server

    Christensen, Anders S; Borg, Mikael; Boomsma, Wouter; Lindorff-Larsen, Kresten; Hamelryck, Thomas; Jensen, Jan H

    2013-01-01

    We present the ProCS method for the rapid and accurate prediction of protein backbone amide proton chemical shifts - sensitive probes of the geometry of key hydrogen bonds that determine protein structure. ProCS is parameterized against quantum mechanical (QM) calculations and reproduces high level QM results obtained for a small protein with an RMSD of 0.25 ppm (r = 0.94). ProCS is interfaced with the PHAISTOS protein simulation program and is used to infer statistical protein ensembles that reflect experimentally measured amide proton chemical shift values. Such chemical shift-based structural refinements, starting from high-resolution X-ray structures of Protein G, ubiquitin, and SMN Tudor Domain, result in average chemical shifts, hydrogen bond geometries, and trans-hydrogen bond (h3JNC') spin-spin coupling constants that are in excellent agreement with experiment. We show that the structural sensitivity of the QM-based amide proton chemical shift predictions is needed to refine protein structures to this...

  7. Prediction algorithm for amino acid types with their secondary structure in proteins (PLATON) using chemical shifts

    International Nuclear Information System (INIS)

    The algorithm PLATON is able to assign sets of chemical shifts derived from a single residue to amino acid types with its secondary structure (amino acid species). A subsequent ranking procedure using optionally two different penalty functions yields predictions for possible amino acid species for the given set of chemical shifts. This was demonstrated in the case of the α-spectrin SH3 domain and applied to 9 further protein data sets taken from the BioMagRes database. A database consisting of reference chemical shift patterns (reference CSPs) was generated from assigned chemical shifts of proteins with known 3D-structure. This reference CSP database is used in our approach for extracting distributions of amino acid types with their most likely secondary structure elements (namely α-helix, β-sheet, and coil) for single amino acids by comparison with query CSPs. Results obtained for the 10 investigated proteins indicates that the percentage of correct amino acid species in the first three positions in the ranking list, ranges from 71.4% to 93.2% for the more favorable penalty function. Where only the top result of the ranking list for these 10 proteins is considered, 36.5% to 83.1% of the amino acid species are correctly predicted. The main advantage of our approach, over other methods that rely on average chemical shift values is the ability to increase database content by incorporating newly derived CSPs, and therefore to improve PLATON's performance over time

  8. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Hansen, Poul Erik

    2015-01-01

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static......” and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. All kinds of intramolecular hydrogen bonded systems will be treated, typical hydrogen bond donors: OH, NH, SH and NH+, typical acceptors C=O, C=N, C=S C=N−. The paper will be deal with both secondary...... and primary isotope effects on chemical shifts. These two types of isotope effects monitor the same hydrogen bond, but from different angles...

  9. Detection of initiation sites in protein folding of the four helix bundle ACBP by chemical shift analysis

    DEFF Research Database (Denmark)

    Modig, K.; Jürgensen, Vibeke Würtz; Lindorff-Larsen, K.;

    2007-01-01

    A simple alternative method for obtaining "random coil" chemical shifts by intrinsic referencing using the protein's own peptide sequence is presented. These intrinsic random coil backbone shifts were then used to calculate secondary chemical shifts, that provide important information on the resi...

  10. Pulse NMR in solids: chemical shift, lead fluoride, and thorium hydride

    International Nuclear Information System (INIS)

    The fluorine chemical shift of a single crystal CaF2 was measured up to 4 kilobar at room temperature using multiple pulse NMR. The pressure dependence of the shift is found to be --1.7 +- 1 ppM/kbar, while an overlap model predicts a shift of --0.46 ppM/kbar.The chemical shift tensor is separated into ''geometrical'' and ''chemical'' contributions, and comparison of the proposed model calculations with recent data on hydroxyl proton chemical shift tensors shows that the geometrical portion accounts for the qualitative features of the measured tensors. A study of fluoride ion motion in β-PbF2 doped with NaF was conducted by measurement of the 19F transverse relaxation time (T2), spin lattice relaxation time (T1) and the spin lattice relaxation time in the rotating frame (T/sub 1r). Two samples of Th4H15, prepared under different conditions but both having the proper ratio of H/Th (to within 1 percent), were studied. The structure of the Th4H15 suggested by x-ray measurements is confirmed through a moment analysis of the rigid lattice line shape

  11. What can we learn by computing 13Cα chemical shifts for X-ray protein models?

    International Nuclear Information System (INIS)

    The room-temperature X-ray structures of two proteins, solved at 1.8 and 1.9 Å resolution, are used to investigate whether a set of conformations, rather than a single X-ray structure, provides better agreement with both the X-ray data and the observed 13Cα chemical shifts in solution. The room-temperature X-ray structures of ubiquitin and of the RNA-binding domain of nonstructural protein 1 of influenza A virus solved at 1.8 and 1.9 Å resolution, respectively, were used to investigate whether a set of conformations rather than a single X-ray structure provides better agreement with both the X-ray data and the observed 13Cα chemical shifts in solution. For this purpose, a set of new conformations for each of these proteins was generated by fitting them to the experimental X-ray data deposited in the PDB. For each of the generated structures, which show R and Rfree factors similar to those of the deposited X-ray structure, the 13Cα chemical shifts of all residues in the sequence were computed at the DFT level of theory. The sets of conformations were then evaluated by their ability to reproduce the observed 13Cα chemical shifts by using the conformational average root-mean-square-deviation (ca-r.m.s.d.). For ubiquitin, the computed set of conformations is a better representation of the observed 13Cα chemical shifts in terms of the ca-r.m.s.d. than a single X-ray-derived structure. However, for the RNA-binding domain of nonstructural protein 1 of influenza A virus, consideration of an ensemble of conformations does not improve the agreement with the observed 13Cα chemical shifts. Whether an ensemble of conformations rather than any single structure is a more accurate representation of a protein structure in the crystal as well as of the observed 13Cα chemical shifts is determined by the dispersion of coordinates, in terms of the all-atom r.m.s.d. among the generated models; these generated models satisfy the experimental X-ray data with accuracy as good as

  12. Proton Magnetic Resonance and Human Thyroid Neoplasia III. Ex VivoChemical-Shift Microimaging

    Science.gov (United States)

    Rutter, Allison; Künnecke, Basil; Dowd, Susan; Russell, Peter; Delbridge, Leigh; Mountford, Carolyn E.

    1996-03-01

    Magnetic-resonance chemical-shift microimaging, with a spatial resolution of 40 × 40 μm, is a modality which can detect alterations to cellular chemistry and hence markers of pathological processes in human tissueex vivo.This technique was used as a chemical microscope to assess follicular thyroid neoplasms, lesions which are unsatisfactorily investigated using standard histopathological techiques or water-based magnetic-resonance imaging. The chemical-shift images at the methyl frequency (0.9 ppm) identify chemical heterogeneity in follicular tumors which are histologically homogeneous. The observed changes to cellular chemistry, detectable in foci of approximately 100 cells or less, support the existence of a preinvasive state hitherto unidentified by current pathological techniques.

  13. Sequence correction of random coil chemical shifts: correlation between neighbor correction factors and changes in the Ramachandran distribution

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Poulsen, Flemming Martin

    2011-01-01

    this study, we use random coil peptides containing glutamine instead of glycine to determine the random coil chemical shifts and the neighbor correction factors. The resulting correction factors correlate to changes in the populations of the major wells in the Ramachandran plot, which demonstrates that...... changes in the conformational ensemble are an important source of neighbor effects in disordered proteins. Glutamine derived random coil chemical shifts and correction factors modestly improve our ability to predict (13)C chemical shifts of intrinsically disordered proteins compared to existing datasets......Random coil chemical shifts are necessary for secondary chemical shift analysis, which is the main NMR method for identification of secondary structure in proteins. One of the largest challenges in the determination of random coil chemical shifts is accounting for the effect of neighboring residues...

  14. Parameter-free calculation of K alpha chemical shifts for Al, Si, and Ge oxides

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2001-01-01

    The chemical shifts of the K alpha radiation line from Al, Si, and Ge ions between their elemental and oxide forms are calculated within the framework of density functional theory using ultrasoft pseudopotentials. It is demonstrated that this theoretical approach yields quantitatively accurate re...... implanted in silica are found to be in excellent agreement with experimental data, providing support for the proposed atomic geometry....

  15. Database proton NMR chemical shifts for RNA signal assignment and validation

    International Nuclear Information System (INIS)

    The Biological Magnetic Resonance Data Bank contains NMR chemical shift depositions for 132 RNAs and RNA-containing complexes. We have analyzed the 1H NMR chemical shifts reported for non-exchangeable protons of residues that reside within A-form helical regions of these RNAs. The analysis focused on the central base pair within a stretch of three adjacent base pairs (BP triplets), and included both Watson–Crick (WC; G:C, A:U) and G:U wobble pairs. Chemical shift values were included for all 43 possible WC-BP triplets, as well as 137 additional triplets that contain one or more G:U wobbles. Sequence-dependent chemical shift correlations were identified, including correlations involving terminating base pairs within the triplets and canonical and non-canonical structures adjacent to the BP triplets (i.e. bulges, loops, WC and non-WC BPs), despite the fact that the NMR data were obtained under different conditions of pH, buffer, ionic strength, and temperature. A computer program (RNAShifts) was developed that enables convenient comparison of RNA 1H NMR assignments with database predictions, which should facilitate future signal assignment/validation efforts and enable rapid identification of non-canonical RNA structures and RNA-ligand/protein interaction sites.

  16. Chemical shifts in transition metal dithiocarbamates from infrared and X-ray photoelectron spectroscopies

    Science.gov (United States)

    Payne, R.; Magee, R. J.; Liesegang, J.

    1982-11-01

    Measurements of the IR stretching frequencies of the NC and MS bonds in transition-metal (M) dithiocarbamates show significant correlation with measurement of core level XPS chemical shifts. This is believed to be the first demonstration of such a correlation for a series of solid-phase compounds.

  17. Automated assignment of NMR chemical shifts based on a known structure and 4D spectra.

    Science.gov (United States)

    Trautwein, Matthias; Fredriksson, Kai; Möller, Heiko M; Exner, Thomas E

    2016-08-01

    Apart from their central role during 3D structure determination of proteins the backbone chemical shift assignment is the basis for a number of applications, like chemical shift perturbation mapping and studies on the dynamics of proteins. This assignment is not a trivial task even if a 3D protein structure is known and needs almost as much effort as the assignment for structure prediction if performed manually. We present here a new algorithm based solely on 4D [(1)H,(15)N]-HSQC-NOESY-[(1)H,(15)N]-HSQC spectra which is able to assign a large percentage of chemical shifts (73-82 %) unambiguously, demonstrated with proteins up to a size of 250 residues. For the remaining residues, a small number of possible assignments is filtered out. This is done by comparing distances in the 3D structure to restraints obtained from the peak volumes in the 4D spectrum. Using dead-end elimination, assignments are removed in which at least one of the restraints is violated. Including additional information from chemical shift predictions, a complete unambiguous assignment was obtained for Ubiquitin and 95 % of the residues were correctly assigned in the 251 residue-long N-terminal domain of enzyme I. The program including source code is available at https://github.com/thomasexner/4Dassign . PMID:27484442

  18. Ab Initio Calculations of Deuterium Isotope Effects on Chemical Shifts of Salt-Bridged Lysines

    DEFF Research Database (Denmark)

    Ullah, Saif; Ishimoto, Takayoshi; Williamson, Mike P.;

    2011-01-01

    Deuterium isotope effects measure the change in chemical shift on substitution of a proton by deuterium. They have been calculated by direct treatment of the H/D nuclear quantum effect using a multicomponent ab initio molecular orbital method based on a non-Born−Oppenheimer approximation. This me...

  19. Using NMR chemical shifts to calculate the propensity for structural order and disorder in proteins

    NARCIS (Netherlands)

    Tamiola, Kamil; Mulder, Frans A. A.

    2012-01-01

    NMR spectroscopy offers the unique possibility to relate the structural propensities of disordered proteins and loop segments of folded peptides to biological function and aggregation behaviour. Backbone chemical shifts are ideally suited for this task, provided that appropriate reference data are a

  20. Identification of helix capping and {beta}-turn motifs from NMR chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Shen Yang; Bax, Ad, E-mail: bax@nih.gov [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States)

    2012-03-15

    We present an empirical method for identification of distinct structural motifs in proteins on the basis of experimentally determined backbone and {sup 13}C{sup {beta}} chemical shifts. Elements identified include the N-terminal and C-terminal helix capping motifs and five types of {beta}-turns: I, II, I Prime , II Prime and VIII. Using a database of proteins of known structure, the NMR chemical shifts, together with the PDB-extracted amino acid preference of the helix capping and {beta}-turn motifs are used as input data for training an artificial neural network algorithm, which outputs the statistical probability of finding each motif at any given position in the protein. The trained neural networks, contained in the MICS (motif identification from chemical shifts) program, also provide a confidence level for each of their predictions, and values ranging from ca 0.7-0.9 for the Matthews correlation coefficient of its predictions far exceed those attainable by sequence analysis. MICS is anticipated to be useful both in the conventional NMR structure determination process and for enhancing on-going efforts to determine protein structures solely on the basis of chemical shift information, where it can aid in identifying protein database fragments suitable for use in building such structures.

  1. Noninvasive Temperature Mapping With MRI Using Chemical Shift Water-Fat Separation

    OpenAIRE

    Soher, Brian J.; Wyatt, Cory; Reeder, Scott B.; MacFall, James R.

    2010-01-01

    Tissues containing both water and lipids, e.g., breast, confound standard MR proton reference frequency-shift methods for mapping temperatures due to the lack of temperature-induced frequency shift in lipid protons. Generalized Dixon chemical shift–based water-fat separation methods, such as GE’s iterative decomposition of water and fat with echo asymmetry and least-squares estimation method, can result in complex water and fat images. Once separated, the phase change over time of the water s...

  2. Accuracy and precision of protein–ligand interaction kinetics determined from chemical shift titrations

    International Nuclear Information System (INIS)

    NMR-monitored chemical shift titrations for the study of weak protein–ligand interactions represent a rich source of information regarding thermodynamic parameters such as dissociation constants (KD) in the micro- to millimolar range, populations for the free and ligand-bound states, and the kinetics of interconversion between states, which are typically within the fast exchange regime on the NMR timescale. We recently developed two chemical shift titration methods wherein co-variation of the total protein and ligand concentrations gives increased precision for the KD value of a 1:1 protein–ligand interaction (Markin and Spyracopoulos in J Biomol NMR 53: 125–138, 2012). In this study, we demonstrate that classical line shape analysis applied to a single set of 1H–15N 2D HSQC NMR spectra acquired using precise protein–ligand chemical shift titration methods we developed, produces accurate and precise kinetic parameters such as the off-rate (koff). For experimentally determined kinetics in the fast exchange regime on the NMR timescale, koff ∼ 3,000 s−1 in this work, the accuracy of classical line shape analysis was determined to be better than 5 % by conducting quantum mechanical NMR simulations of the chemical shift titration methods with the magnetic resonance toolkit GAMMA. Using Monte Carlo simulations, the experimental precision for koff from line shape analysis of NMR spectra was determined to be 13 %, in agreement with the theoretical precision of 12 % from line shape analysis of the GAMMA simulations in the presence of noise and protein concentration errors. In addition, GAMMA simulations were employed to demonstrate that line shape analysis has the potential to provide reasonably accurate and precise koff values over a wide range, from 100 to 15,000 s−1. The validity of line shape analysis for koff values approaching intermediate exchange (∼100 s−1), may be facilitated by more accurate KD measurements from NMR-monitored chemical shift

  3. PACSY, a relational database management system for protein structure and chemical shift analysis

    International Nuclear Information System (INIS)

    PACSY (Protein structure And Chemical Shift NMR spectroscopY) is a relational database management system that integrates information from the Protein Data Bank, the Biological Magnetic Resonance Data Bank, and the Structural Classification of Proteins database. PACSY provides three-dimensional coordinates and chemical shifts of atoms along with derived information such as torsion angles, solvent accessible surface areas, and hydrophobicity scales. PACSY consists of six relational table types linked to one another for coherence by key identification numbers. Database queries are enabled by advanced search functions supported by an RDBMS server such as MySQL or PostgreSQL. PACSY enables users to search for combinations of information from different database sources in support of their research. Two software packages, PACSY Maker for database creation and PACSY Analyzer for database analysis, are available from http://pacsy.nmrfam.wisc.eduhttp://pacsy.nmrfam.wisc.edu.

  4. Identifying Stereoisomers by ab-initio Calculation of Secondary Isotope Shifts on NMR Chemical Shieldings

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Böhm

    2014-04-01

    Full Text Available We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2Hethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

  5. Substituent Chemical Shifts of (E)-1-Aryl-3-thienylpropen-1-ones

    International Nuclear Information System (INIS)

    Substituent chemical shifts were examined for the 2- and 3-thiophene derivatives of chalcone and compared to the thiophene series of derivatives with the phenyl series. The chemical shift values for the α-carbons of the enones showed and inverse correlation with the Hammett σ values, but the correlation coefficients were moderate (r = 0.836 - 0.878). On the other hand, the β-carbons showed a normal correlation with excellent correlation coefficients (r = 0.994). The absolute magnitude of the ρ values for the α-carbon are about half of those of the β-carbon. The observation may be the result of a through-space transition of the electronic effect of the substituents in addition to the through bond transition

  6. 1H chemical shift imaging characterization of human brain tumor and edema

    International Nuclear Information System (INIS)

    Longitudinal (T1) and transverse (T2) relaxation times of metabolites in human brain tumor, peritumoral edema, and unaffected brain tissue were assessed from point resolved spectroscopy (PRESS) 1H chemical shift imaging results at different repetition times (TR=1500 and 5000 ms; T1: n=19) and echo times (TE=135 and 270 ms; T2: n=7). Metabolite T1 and T2 relaxation times in unaffected brain tissue corresponded with those published for healthy volunteers. T2 relaxation times were reduced in tumor (choline, N-acetyl aspartate) and edema (choline, creatine) compared with unaffected brain tissue (p1H chemical shift imaging is most suited in the use of choline elevation as tumor marker. (orig.)

  7. Four-Component Relativistic DFT Calculations of (13)C Chemical Shifts of Halogenated Natural Substances.

    Science.gov (United States)

    Casella, Girolamo; Bagno, Alessandro; Komorovsky, Stanislav; Repisky, Michal; Saielli, Giacomo

    2015-12-14

    We have calculated the (13)C NMR chemical shifts of a large ensemble of halogenated organic molecules (81 molecules for a total of 250 experimental (13)C NMR data at four different levels of theory), ranging from small rigid organic compounds, used to benchmark the performance of various levels of theory, to natural substances of marine origin with conformational degrees of freedom. Carbon atoms bonded to heavy halogen atoms, particularly bromine and iodine, are known to be rather challenging when it comes to the prediction of their chemical shifts by quantum methods, due to relativistic effects. In this paper, we have applied the state-of-the-art four-component relativistic density functional theory for the prediction of such NMR properties and compared the performance with two-component and nonrelativistic methods. Our results highlight the necessity to include relativistic corrections within a four-component description for the most accurate prediction of the NMR properties of halogenated organic substances. PMID:26541625

  8. Protein backbone and sidechain torsion angles predicted from NMR chemical shifts using artificial neural networks

    International Nuclear Information System (INIS)

    A new program, TALOS-N, is introduced for predicting protein backbone torsion angles from NMR chemical shifts. The program relies far more extensively on the use of trained artificial neural networks than its predecessor, TALOS+. Validation on an independent set of proteins indicates that backbone torsion angles can be predicted for a larger, ≥90 % fraction of the residues, with an error rate smaller than ca 3.5 %, using an acceptance criterion that is nearly two-fold tighter than that used previously, and a root mean square difference between predicted and crystallographically observed (φ, ψ) torsion angles of ca 12º. TALOS-N also reports sidechain χ1 rotameric states for about 50 % of the residues, and a consistency with reference structures of 89 %. The program includes a neural network trained to identify secondary structure from residue sequence and chemical shifts

  9. Protein backbone and sidechain torsion angles predicted from NMR chemical shifts using artificial neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Shen Yang; Bax, Ad, E-mail: bax@nih.gov [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States)

    2013-07-15

    A new program, TALOS-N, is introduced for predicting protein backbone torsion angles from NMR chemical shifts. The program relies far more extensively on the use of trained artificial neural networks than its predecessor, TALOS+. Validation on an independent set of proteins indicates that backbone torsion angles can be predicted for a larger, {>=}90 % fraction of the residues, with an error rate smaller than ca 3.5 %, using an acceptance criterion that is nearly two-fold tighter than that used previously, and a root mean square difference between predicted and crystallographically observed ({phi}, {psi}) torsion angles of ca 12 Masculine-Ordinal-Indicator . TALOS-N also reports sidechain {chi}{sup 1} rotameric states for about 50 % of the residues, and a consistency with reference structures of 89 %. The program includes a neural network trained to identify secondary structure from residue sequence and chemical shifts.

  10. Using Neural Networks for 13C NMR Chemical Shift Prediction-Comparison with Traditional Methods

    Science.gov (United States)

    Meiler, Jens; Maier, Walter; Will, Martin; Meusinger, Reinhard

    2002-08-01

    Interpretation of 13C chemical shifts is essential for structure elucidation of organic molecules by NMR. In this article, we present an improved neural network approach and compare its performance to that of commonly used approaches. Specifically, our recently proposed neural network ( J. Chem. Inf. Comput. Sci. 2000, 40, 1169-1176) is improved by introducing an extended hybrid numerical description of the carbon atom environment, resulting in a standard deviation (std. dev.) of 2.4 ppm for an independent test data set of ˜42,500 carbons. Thus, this neural network allows fast and accurate 13C NMR chemical shift prediction without the necessity of access to molecule or fragment databases. For an unbiased test dataset containing 100 organic structures the accuracy of the improved neural network was compared to that of a prediction method based on the HOSE code ( hierarchically ordered spherical description of environment) using S PECI NFO. The results show the neural network predictions to be of quality (std. dev.=2.7 ppm) comparable to that of the HOSE code prediction (std. dev.=2.6 ppm). Further we compare the neural network predictions to those of a wide variety of other 13C chemical shift prediction tools including incremental methods (C HEMD RAW, S PECT OOL), quantum chemical calculation (G AUSSIAN, C OSMOS), and HOSE code fragment-based prediction (S PECI NFO, ACD/CNMR, P REDICTI T NMR) for the 47 13C-NMR shifts of Taxol, a natural product including many structural features of organic substances. The smallest standard deviations were achieved here with the neural network (1.3 ppm) and S PECI NFO (1.0 ppm).

  11. Relationship between electrophilicity index, Hammett constant and nucleus-independent chemical shift

    Indian Academy of Sciences (India)

    M Elango; R Parthasarathi; G Karthik Narayanan; A Md Sabeelullah; U Sarkar; N S Venkatasubramaniyan; V Subramanian; P K Chattaraj

    2005-01-01

    Inter-relationships between the electrophilicity index (), Hammett constant (ó) and nucleusindependent chemical shift (NICS (1) - NICS value one å ngstrom above the ring centre) have been investigated for a series of meta- and para-substituted benzoic acids. Good linear relationships between Hammett constant vs electrophilicity and Hammett constant vs NICS (1) values have been observed. However, the variation of NICS (1) against shows only a low correlation coefficient.

  12. Chemical shifts and EXAFS in some rare-earth metals and compounds

    International Nuclear Information System (INIS)

    The positions of the Lsub(111) absorption edge and accompanying Kossel and EXAFS oscillations of terbium, dysprosium and holmium in metals and compounds (acetate, carbonate, chloride, fluoride, nitrate, oxalate, oxide, phosphate and sulphate) have been measured. The chemical shifts of the main edge range from about 1 eV to about 10 eV and the EXAFS are observed up to about 150 eV. (author)

  13. On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study

    Science.gov (United States)

    Durbeej, Bo; Eriksson, Leif A.

    2003-06-01

    The structural origin of the bathochromic shift assumed by the electronic absorption spectrum of protein-bound astaxanthin, the carotenoid that upon binding to crustacyanin is responsible for the blue colouration of lobster shell, is investigated by means of quantum chemical methods. The calculations suggest that the bathochromic shift is largely due to one of the astaxanthin C4 keto groups being hydrogen-bonded to a histidine residue of the surrounding protein, and that the effect of this histidine is directly dependent on its protonation state. Out of the different methodologies (CIS, TD-DFT, and ZINDO/S) employed to calculate wavelengths of maximum absorption, the best agreement with experimental data is obtained using the semiempirical ZINDO/S method.

  14. Conformationally selective multidimensional chemical shift ranges in proteins from a PACSY database purged using intrinsic quality criteria

    Energy Technology Data Exchange (ETDEWEB)

    Fritzsching, Keith J., E-mail: kfritzsc@brandeis.edu [Brandeis University, Department of Chemistry (United States); Hong, Mei [Massachusetts Institute of Technology, Department of Chemistry (United States); Schmidt-Rohr, Klaus, E-mail: srohr@brandeis.edu [Brandeis University, Department of Chemistry (United States)

    2016-02-15

    We have determined refined multidimensional chemical shift ranges for intra-residue correlations ({sup 13}C–{sup 13}C, {sup 15}N–{sup 13}C, etc.) in proteins, which can be used to gain type-assignment and/or secondary-structure information from experimental NMR spectra. The chemical-shift ranges are the result of a statistical analysis of the PACSY database of >3000 proteins with 3D structures (1,200,207 {sup 13}C chemical shifts and >3 million chemical shifts in total); these data were originally derived from the Biological Magnetic Resonance Data Bank. Using relatively simple non-parametric statistics to find peak maxima in the distributions of helix, sheet, coil and turn chemical shifts, and without the use of limited “hand-picked” data sets, we show that ∼94 % of the {sup 13}C NMR data and almost all {sup 15}N data are quite accurately referenced and assigned, with smaller standard deviations (0.2 and 0.8 ppm, respectively) than recognized previously. On the other hand, approximately 6 % of the {sup 13}C chemical shift data in the PACSY database are shown to be clearly misreferenced, mostly by ca. −2.4 ppm. The removal of the misreferenced data and other outliers by this purging by intrinsic quality criteria (PIQC) allows for reliable identification of secondary maxima in the two-dimensional chemical-shift distributions already pre-separated by secondary structure. We demonstrate that some of these correspond to specific regions in the Ramachandran plot, including left-handed helix dihedral angles, reflect unusual hydrogen bonding, or are due to the influence of a following proline residue. With appropriate smoothing, significantly more tightly defined chemical shift ranges are obtained for each amino acid type in the different secondary structures. These chemical shift ranges, which may be defined at any statistical threshold, can be used for amino-acid type assignment and secondary-structure analysis of chemical shifts from intra

  15. Conformationally selective multidimensional chemical shift ranges in proteins from a PACSY database purged using intrinsic quality criteria

    International Nuclear Information System (INIS)

    We have determined refined multidimensional chemical shift ranges for intra-residue correlations (13C–13C, 15N–13C, etc.) in proteins, which can be used to gain type-assignment and/or secondary-structure information from experimental NMR spectra. The chemical-shift ranges are the result of a statistical analysis of the PACSY database of >3000 proteins with 3D structures (1,200,207 13C chemical shifts and >3 million chemical shifts in total); these data were originally derived from the Biological Magnetic Resonance Data Bank. Using relatively simple non-parametric statistics to find peak maxima in the distributions of helix, sheet, coil and turn chemical shifts, and without the use of limited “hand-picked” data sets, we show that ∼94 % of the 13C NMR data and almost all 15N data are quite accurately referenced and assigned, with smaller standard deviations (0.2 and 0.8 ppm, respectively) than recognized previously. On the other hand, approximately 6 % of the 13C chemical shift data in the PACSY database are shown to be clearly misreferenced, mostly by ca. −2.4 ppm. The removal of the misreferenced data and other outliers by this purging by intrinsic quality criteria (PIQC) allows for reliable identification of secondary maxima in the two-dimensional chemical-shift distributions already pre-separated by secondary structure. We demonstrate that some of these correspond to specific regions in the Ramachandran plot, including left-handed helix dihedral angles, reflect unusual hydrogen bonding, or are due to the influence of a following proline residue. With appropriate smoothing, significantly more tightly defined chemical shift ranges are obtained for each amino acid type in the different secondary structures. These chemical shift ranges, which may be defined at any statistical threshold, can be used for amino-acid type assignment and secondary-structure analysis of chemical shifts from intra-residue cross peaks by inspection or by using a provided

  16. Conformationally selective multidimensional chemical shift ranges in proteins from a PACSY database purged using intrinsic quality criteria.

    Science.gov (United States)

    Fritzsching, Keith J; Hong, Mei; Schmidt-Rohr, Klaus

    2016-02-01

    We have determined refined multidimensional chemical shift ranges for intra-residue correlations ((13)C-(13)C, (15)N-(13)C, etc.) in proteins, which can be used to gain type-assignment and/or secondary-structure information from experimental NMR spectra. The chemical-shift ranges are the result of a statistical analysis of the PACSY database of >3000 proteins with 3D structures (1,200,207 (13)C chemical shifts and >3 million chemical shifts in total); these data were originally derived from the Biological Magnetic Resonance Data Bank. Using relatively simple non-parametric statistics to find peak maxima in the distributions of helix, sheet, coil and turn chemical shifts, and without the use of limited "hand-picked" data sets, we show that ~94% of the (13)C NMR data and almost all (15)N data are quite accurately referenced and assigned, with smaller standard deviations (0.2 and 0.8 ppm, respectively) than recognized previously. On the other hand, approximately 6% of the (13)C chemical shift data in the PACSY database are shown to be clearly misreferenced, mostly by ca. -2.4 ppm. The removal of the misreferenced data and other outliers by this purging by intrinsic quality criteria (PIQC) allows for reliable identification of secondary maxima in the two-dimensional chemical-shift distributions already pre-separated by secondary structure. We demonstrate that some of these correspond to specific regions in the Ramachandran plot, including left-handed helix dihedral angles, reflect unusual hydrogen bonding, or are due to the influence of a following proline residue. With appropriate smoothing, significantly more tightly defined chemical shift ranges are obtained for each amino acid type in the different secondary structures. These chemical shift ranges, which may be defined at any statistical threshold, can be used for amino-acid type assignment and secondary-structure analysis of chemical shifts from intra-residue cross peaks by inspection or by using a provided

  17. SPARTA+: a modest improvement in empirical NMR chemical shift prediction by means of an artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Shen Yang; Bax, Ad, E-mail: bax@nih.go [National Institutes of Health, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases (United States)

    2010-09-15

    NMR chemical shifts provide important local structural information for proteins and are key in recently described protein structure generation protocols. We describe a new chemical shift prediction program, SPARTA+, which is based on artificial neural networking. The neural network is trained on a large carefully pruned database, containing 580 proteins for which high-resolution X-ray structures and nearly complete backbone and {sup 13}C{sup {beta}} chemical shifts are available. The neural network is trained to establish quantitative relations between chemical shifts and protein structures, including backbone and side-chain conformation, H-bonding, electric fields and ring-current effects. The trained neural network yields rapid chemical shift prediction for backbone and {sup 13}C{sup {beta}} atoms, with standard deviations of 2.45, 1.09, 0.94, 1.14, 0.25 and 0.49 ppm for {delta}{sup 15}N, {delta}{sup 13}C', {delta}{sup 13}C{sup {alpha}}, {delta}{sup 13}C{sup {beta}}, {delta}{sup 1}H{sup {alpha}} and {delta}{sup 1}H{sup N}, respectively, between the SPARTA+ predicted and experimental shifts for a set of eleven validation proteins. These results represent a modest but consistent improvement (2-10%) over the best programs available to date, and appear to be approaching the limit at which empirical approaches can predict chemical shifts.

  18. SPARTA+: a modest improvement in empirical NMR chemical shift prediction by means of an artificial neural network

    International Nuclear Information System (INIS)

    NMR chemical shifts provide important local structural information for proteins and are key in recently described protein structure generation protocols. We describe a new chemical shift prediction program, SPARTA+, which is based on artificial neural networking. The neural network is trained on a large carefully pruned database, containing 580 proteins for which high-resolution X-ray structures and nearly complete backbone and 13Cβ chemical shifts are available. The neural network is trained to establish quantitative relations between chemical shifts and protein structures, including backbone and side-chain conformation, H-bonding, electric fields and ring-current effects. The trained neural network yields rapid chemical shift prediction for backbone and 13Cβ atoms, with standard deviations of 2.45, 1.09, 0.94, 1.14, 0.25 and 0.49 ppm for δ15N, δ13C', δ13Cα, δ13Cβ, δ1Hα and δ1HN, respectively, between the SPARTA+ predicted and experimental shifts for a set of eleven validation proteins. These results represent a modest but consistent improvement (2-10%) over the best programs available to date, and appear to be approaching the limit at which empirical approaches can predict chemical shifts.

  19. Simulations of Xe-129 NMR chemical shift of atomic xenon dissolved in liquid benzene

    Czech Academy of Sciences Publication Activity Database

    Standara, Stanislav; Kulhánek, P.; Marek, R.; Horníček, Jan; Bouř, Petr; Straka, Michal

    2011-01-01

    Roč. 129, 3/5 (2011), s. 677-684. ISSN 1432-881X R&D Projects: GA ČR GA203/09/2037; GA ČR GAP208/11/0105 Grant ostatní: AV ČR(CZ) M200550902; European Reintegration Grant(XE) 230955; European Community(XE) 205872 Institutional research plan: CEZ:AV0Z40550506 Keywords : Xe-129 NMR chemical shift * dynamical averaging * density functional theory * Breit-Pauli perturbation theory * relativistic effects Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.162, year: 2011

  20. Three model space experiments on chemical reactions. [Gibbs adsorption, equilibrium shift and electrodeposition

    Science.gov (United States)

    Grodzka, P.; Facemire, B.

    1977-01-01

    Three investigations conducted aboard Skylab IV and Apollo-Soyuz involved phenomena that are of interest to the biochemistry community. The formaldehyde clock reaction and the equilibrium shift reaction experiments conducted aboard Apollo Soyuz demonstrate the effect of low-g foams or air/liquid dispersions on reaction rate and chemical equilibrium. The electrodeposition reaction experiment conducted aboard Skylab IV demonstrate the effect of a low-g environment on an electrochemical displacement reaction. The implications of the three space experiments for various applications are considered.

  1. Calculation of NMR chemical shifts. 7. Gauge-invariant INDO method

    Science.gov (United States)

    Fukui, H.; Miura, K.; Hirai, A.

    A gauge-invariant INDO method based on the coupled Hartree-Fuck perturbation theory is presented and applied to the calculation of 1H and 13C chemical shifts of hydrocarbons including ring compounds. Invariance of the diamagnetic and paramagnetic shieldings with respect to displacement of the coordinate origin is discussed. Comparison between calculated and experimental results exhibits fairly good agreement, provided that the INDO parameters of Ellis et al. (J. Am. Chem. Soc.94, 4069 (1972)) are used with the inclusion of all multicenter one-electron integrals.

  2. Model analysis of influences of the high-temperature reactor on location shifting in chemical industry

    International Nuclear Information System (INIS)

    An analysis is presented of the influences of High-Temperature Reactor on probable location shifting of big chemical plants, in the future. This is done by a spatial location model, that includes an investigation on 116 industrial locations within the first six countries of Common Market. The results of a computerized program show differences in location qualities when furnished either with traditional or with nuclear energy systems. In addition to location factor energy some other important factors, as subventions, taxes, labour, and transport costs are analysed, and their influence on industrial location is quantified. (orig.)

  3. NMR Chemical Shift Ranges of Urine Metabolites in Various Organic Solvents.

    Science.gov (United States)

    Görling, Benjamin; Bräse, Stefan; Luy, Burkhard

    2016-01-01

    Signal stability is essential for reliable multivariate data analysis. Urine samples show strong variance in signal positions due to inter patient differences. Here we study the exchange of the solvent of a defined urine matrix and how it affects signal and integral stability of the urinary metabolites by NMR spectroscopy. The exchange solvents were methanol, acetonitrile, dimethyl sulfoxide, chloroform, acetone, dichloromethane, and dimethyl formamide. Some of these solvents showed promising results with a single batch of urine. To evaluate further differences between urine samples, various acid, base, and salt solutions were added in a defined way mimicking to some extent inter human differences. Corresponding chemical shift changes were monitored. PMID:27598217

  4. Optimal voxel size for measuring global gray and white matter proton metabolite concentrations using chemical shift imaging

    DEFF Research Database (Denmark)

    Hanson, Lars Peter Grüner; Adalsteinsson, E; Pfefferbaum, A;

    2000-01-01

    Quantification of gray and white matter levels of spectroscopically visible metabolites can provide important insights into brain development and pathological conditions. Chemical shift imaging offers a gain in efficiency for estimation of global gray and white matter metabolite concentrations co...

  5. Qualitative Study of Substituent Effects on NMR 15N and 17O Chemical Shifts

    Science.gov (United States)

    Contreras, Rubén H.; Llorente, Tomás; Pagola, Gabriel I.; Bustamante, Manuel G.; Pasqualini, Enrique E.; Melo, Juan I.; Tormena, Cláudio F.

    2009-08-01

    A qualitative approach to analyze the electronic origin of substituent effects on the paramagnetic part of chemical shifts is described and applied to few model systems, where its potentiality can be appreciated. The formulation of this approach is based on the following grounds. The influence of different inter- or intramolecular interactions on a second-order property can be qualitatively predicted if it can be known how they affect the main virtual excitations entering into that second-order property. A set of consistent approximations are introduced in order to analyze the behavior of occupied and virtual orbitals that define some experimental trends of magnetic shielding constants. This approach is applied first to study the electronic origin of methyl-β substituent effects on both 15N and 17O chemical shifts, and afterward it is applied to a couple of examples of long-range substituent effects originated in charge transfer interactions such as the conjugative effect in aromatic compounds and σ-hyperconjugative interactions in saturated multicyclic compounds.

  6. Qualitative study of substituent effects on NMR (15)N and (17)O chemical shifts.

    Science.gov (United States)

    Contreras, Rubén H; Llorente, Tomás; Pagola, Gabriel I; Bustamante, Manuel G; Pasqualini, Enrique E; Melo, Juan I; Tormena, Cláudio F

    2009-09-10

    A qualitative approach to analyze the electronic origin of substituent effects on the paramagnetic part of chemical shifts is described and applied to few model systems, where its potentiality can be appreciated. The formulation of this approach is based on the following grounds. The influence of different inter- or intramolecular interactions on a second-order property can be qualitatively predicted if it can be known how they affect the main virtual excitations entering into that second-order property. A set of consistent approximations are introduced in order to analyze the behavior of occupied and virtual orbitals that define some experimental trends of magnetic shielding constants. This approach is applied first to study the electronic origin of methyl-beta substituent effects on both (15)N and (17)O chemical shifts, and afterward it is applied to a couple of examples of long-range substituent effects originated in charge transfer interactions such as the conjugative effect in aromatic compounds and sigma-hyperconjugative interactions in saturated multicyclic compounds. PMID:19685922

  7. Stereoelectronic effects on 1H nuclear magnetic resonance chemical shifts in methoxybenzenes

    DEFF Research Database (Denmark)

    Lambert, Maja; Olsen, Lars; Jaroszewski, Jerzy W

    2006-01-01

    differences are due to different conformational behavior of the OH and OCH3 groups; while the ortho-disubstituted OH group remains planar in polyphenols due to hydrogen bonding and conjugative stabilization, the steric congestion in ortho-disubstituted anisoles outweighs the conjugative effects and forces the......Investigation of all O-methyl ethers of 1,2,3-benzenetriol and 4-methyl-1,2,3-benzenetriol (3-16) by 1H NMR spectroscopy and density-functional calculations disclosed practically useful conformational effects on 1H NMR chemical shifts in the aromatic ring. While the conversion of phenol (2) to...... Ar-OCH3 torsion out of the ring plane, resulting in large stereoelectronic effects on the chemical shift of Hpara. Conformational searches and geometry optimizations for 3-16 at the B3LYP/6-31G** level, followed by B3LYP/6-311++G(2d,2p) calculations for all low-energy conformers, gave excellent...

  8. Water-fat imaging and general chemical shift imaging with spectrum modeling

    Science.gov (United States)

    An, Li

    Water-fat chemical shift imaging (CSI) has been an active research area in magnetic resonance imaging (MRI) since the early 1980's. There are two main reasons for water- fat imaging. First, water-fat imaging can serve as a fat- suppression method. Removing the usually bright fatty signals not only extends the useful dynamic range of an image, but also allows better visualization of lesions or injected contrast, and removes chemical shift artifacts, which may contribute to improved diagnosis. Second, quantification of water and fat provides useful chemical information for characterizing tissues such as bone marrow, liver, and adrenal masses. A milestone in water- fat imaging is the Dixon method that can produce separate water and fat images with only two data acquisitions. In practice, however, the Dixon method is not always successful due to field inhomogeneity problems. In recent years, many variations of the Dixon method have been proposed to overcome the field inhomogeneity problem. In general, these methods can at best separate water and fat without identifying the two because the water and fat magnetization vectors are sampled symmetrically, only parallel and anti-parallel. Furthermore, these methods usually depend on two-dimensional phase unwrapping which itself is sensitive to noise and artifacts, and becomes unreliable when the images have disconnected tissues in the field-of-view (FOV). We will first introduce the basic principles of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) in chapter 1, and briefly review the existing water-fat imaging techniques in chapter 2. In chapter 3, we will introduce a new method for water-fat imaging. With three image acquisitions, a general direct phase encoding (DPE) of the chemical shift information is achieved, which allows an unambiguous determination of water and fat on a pixel by pixel basis. Details of specific implementations and noise performance will be discussed. Representative results

  9. Chemical potential shift in organic field-effect transistors identified by soft X-ray operando nano-spectroscopy

    Science.gov (United States)

    Nagamura, Naoka; Kitada, Yuta; Tsurumi, Junto; Matsui, Hiroyuki; Horiba, Koji; Honma, Itaru; Takeya, Jun; Oshima, Masaharu

    2015-06-01

    A chemical potential shift in an organic field effect transistor (OFET) during operation has been revealed by soft X-ray operando nano-spectroscopy analysis performed using a three-dimensional nanoscale electron-spectroscopy chemical analysis system. OFETs were fabricated using ultrathin (3 ML or 12 nm) single-crystalline C10-DNBDT-NW films on SiO2 (200 nm)/Si substrates with a backgate electrode and top source/drain Au electrodes, and C 1s line profiles under biasing at the backgate and drain electrodes were measured. When applying -30 V to the backgate, there is C 1s core level shift of 0.1 eV; this shift can be attributed to a chemical potential shift corresponding to band bending by the field effect, resulting in p-type doping.

  10. Chemical potential shift in organic field-effect transistors identified by soft X-ray operando nano-spectroscopy

    International Nuclear Information System (INIS)

    A chemical potential shift in an organic field effect transistor (OFET) during operation has been revealed by soft X-ray operando nano-spectroscopy analysis performed using a three-dimensional nanoscale electron-spectroscopy chemical analysis system. OFETs were fabricated using ultrathin (3 ML or 12 nm) single-crystalline C10-DNBDT-NW films on SiO2 (200 nm)/Si substrates with a backgate electrode and top source/drain Au electrodes, and C 1s line profiles under biasing at the backgate and drain electrodes were measured. When applying −30 V to the backgate, there is C 1s core level shift of 0.1 eV; this shift can be attributed to a chemical potential shift corresponding to band bending by the field effect, resulting in p-type doping

  11. Chemical potential shift in organic field-effect transistors identified by soft X-ray operando nano-spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nagamura, Naoka, E-mail: NAGAMURA.Naoka@nims.go.jp; Kitada, Yuta; Honma, Itaru [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tsurumi, Junto; Matsui, Hiroyuki; Takeya, Jun [Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Horiba, Koji [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Oshima, Masaharu [Synchrotron Radiation Research Organization, The University of Tokyo, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2015-06-22

    A chemical potential shift in an organic field effect transistor (OFET) during operation has been revealed by soft X-ray operando nano-spectroscopy analysis performed using a three-dimensional nanoscale electron-spectroscopy chemical analysis system. OFETs were fabricated using ultrathin (3 ML or 12 nm) single-crystalline C10-DNBDT-NW films on SiO{sub 2} (200 nm)/Si substrates with a backgate electrode and top source/drain Au electrodes, and C 1s line profiles under biasing at the backgate and drain electrodes were measured. When applying −30 V to the backgate, there is C 1s core level shift of 0.1 eV; this shift can be attributed to a chemical potential shift corresponding to band bending by the field effect, resulting in p-type doping.

  12. Reassigning the Structures of Natural Products Using NMR Chemical Shifts Computed with Quantum Mechanics: A Laboratory Exercise

    Science.gov (United States)

    Palazzo, Teresa A.; Truong, Tiana T.; Wong, Shirley M. T.; Mack, Emma T.; Lodewyk, Michael W.; Harrison, Jason G.; Gamage, R. Alan; Siegel, Justin B.; Kurth, Mark J.; Tantillo, Dean J.

    2015-01-01

    An applied computational chemistry laboratory exercise is described in which students use modern quantum chemical calculations of chemical shifts to assign the structure of a recently isolated natural product. A pre/post assessment was used to measure student learning gains and verify that students demonstrated proficiency of key learning…

  13. Improving the chemical shift dispersion of multidimensional NMR spectra of intrinsically disordered proteins

    Energy Technology Data Exchange (ETDEWEB)

    Bermel, Wolfgang [Bruker BioSpin GmbH (Germany); Bruix, Marta [Consejo Superior de Investigaciones Cientificas, Instituto de Quimica Fisica ' ' Rocasolano' ' (Spain); Felli, Isabella C., E-mail: felli@cerm.unifi.it [University of Florence, Department of Chemistry ' Ugo Shiff' (Italy); Kumar, M.V. Vasantha [University of Florence, Magnetic Resonance Center (Italy); Pierattelli, Roberta, E-mail: pierattelli@cerm.unifi.it [University of Florence, Department of Chemistry ' Ugo Shiff' (Italy); Serrano, Soraya [Consejo Superior de Investigaciones Cientificas, Instituto de Quimica Fisica ' ' Rocasolano' ' (Spain)

    2013-03-15

    Intrinsically disordered proteins (IDPs) have recently attracted the attention of the scientific community challenging the well accepted structure-function paradigm. In the characterization of the dynamic features of proteins nuclear magnetic resonance spectroscopy (NMR) is a strategic tool of investigation. However the peculiar properties of IDPs, with the lack of a unique 3D structure and their high flexibility, have a strong impact on NMR observables (low chemical shift dispersion, efficient solvent exchange broadening) and thus on the quality of NMR spectra. Key aspects to be considered in the design of new NMR experiments optimized for the study of IDPs are discussed. A new experiment, based on direct detection of {sup 13}C{sup {alpha}}, is proposed.

  14. Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors

    Energy Technology Data Exchange (ETDEWEB)

    Sweany, M; Bernstein, A; Dazeley, S; Dunmore, J; Felde, J; Svoboda, R; Tripathi, S M

    2011-09-21

    Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 {+-} 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 {+-} 0.03 for Carbostyril-124, and 1.20 {+-} 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.

  15. Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors

    International Nuclear Information System (INIS)

    Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultraviolet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as 1.88±0.02 for 4-Methylumbelliferone, stable within 0.5% over 50 days, 1.37±0.03 for Carbostyril-124, and 1.20±0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.

  16. Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors

    CERN Document Server

    Sweany, M; Dazeley, S; Dunmore, J; Felde, J; Svoboda, R; Tripathi, M

    2011-01-01

    Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 $\\pm$ 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 $\\pm$ 0.03 for Carbostyril-124, and 1.20 $\\pm$ 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modele...

  17. Clinical application of 1H-chemical-shift imaging (CSI) to brain diseases

    International Nuclear Information System (INIS)

    An H-1 chemical shift imaging (CSI) was developed as part of the clinical MRI system, by which magnetic resonance spectra (MRS) can be obtained from multiple small voxels and metabolite distribution in the brain can be visualized. The present study was to determine the feasibility and clinical potential of using an H-1 CSI. The device used was a Magnetom H 15 apparatus. The study population was comprised of 25 healthy subjects, 20 patients with brain tumor, 4 with ischemic disease, and 6 with miscellaneous degenerative disease. The H-1 CSI was obtained by the 3-dimensional Fourier transformation. After suppressing the lipid signal by the inversion-recovery method and the water signal by the chemical-shift selective pulse with a following dephasing gradient, 2-directional 16 x 16 phase encodings were applied to the 16 x 16∼18 x 18 cm field of view, in which a 8 x 8 x 2∼10 x 10 x 2 cm area was selected by the stimulated echo or spin-echo method. The metabolite mapping and its contour mapping were created by using the curve-fitted area, with interpolation to the 256 x 256 matrix. In the healthy group, high resolution spectra for N-acetyl aspartate (NAA), creatine, choline (Cho), and glutamine/glutamate were obtained from each voxel; and metabolite mapping and contour mapping also clearly showed metabolite distribution in the brain. In the group of brain tumor, an increased Cho and lactate and loss of NAA were observed, along with heterogeneity within the tumor and changes in the surrounding tissue; and there was a good correlation between lactate peak and tumor malignancy. The group of ischemic and degenerative disease had a decreased NAA and increased lactate on both spectra and metabolite mapping, depending on disease stage. These findings indicated that H-1 CSI is helpful for detecting spectra over the whole brain, as well as for determining metabolite distribution. (N.K.)

  18. A simple graphical approach to predict local residue conformation using NMR chemical shifts and density functional theory.

    Science.gov (United States)

    Shaghaghi, Hoora; Ebrahimi, Hossein Pasha; Fathi, Fariba; Bahrami Panah, Niloufar; Jalali-Heravi, Mehdi; Tafazzoli, Mohsen

    2016-05-30

    The dependency of amino acid chemical shifts on φ and ψ torsion angle is, independently, studied using a five-residue fragment of ubiquitin and ONIOM(DFT:HF) approach. The variation of absolute deviation of (13) C(α) chemical shifts relative to φ dihedral angle is specifically dependent on secondary structure of protein not on amino acid type and fragment sequence. This dependency is observed neither on any of (13) C(β) , and (1) H(α) chemical shifts nor on the variation of absolute deviation of (13) C(α) chemical shifts relative to ψ dihedral angle. The (13) C(α) absolute deviation chemical shifts (ADCC) plots are found as a suitable and simple tool to predict secondary structure of protein with no requirement of highly accurate calculations, priori knowledge of protein structure and structural refinement. Comparison of Full-DFT and ONIOM(DFT:HF) approaches illustrates that the trend of (13) C(α) ADCC plots are independent of computational method but not of basis set valence shell type. © 2016 Wiley Periodicals, Inc. PMID:26940760

  19. Fragment-based (13)C nuclear magnetic resonance chemical shift predictions in molecular crystals: An alternative to planewave methods.

    Science.gov (United States)

    Hartman, Joshua D; Monaco, Stephen; Schatschneider, Bohdan; Beran, Gregory J O

    2015-09-14

    We assess the quality of fragment-based ab initio isotropic (13)C chemical shift predictions for a collection of 25 molecular crystals with eight different density functionals. We explore the relative performance of cluster, two-body fragment, combined cluster/fragment, and the planewave gauge-including projector augmented wave (GIPAW) models relative to experiment. When electrostatic embedding is employed to capture many-body polarization effects, the simple and computationally inexpensive two-body fragment model predicts both isotropic (13)C chemical shifts and the chemical shielding tensors as well as both cluster models and the GIPAW approach. Unlike the GIPAW approach, hybrid density functionals can be used readily in a fragment model, and all four hybrid functionals tested here (PBE0, B3LYP, B3PW91, and B97-2) predict chemical shifts in noticeably better agreement with experiment than the four generalized gradient approximation (GGA) functionals considered (PBE, OPBE, BLYP, and BP86). A set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided based on these benchmark calculations. Statistical cross-validation procedures are used to demonstrate the robustness of these fits. PMID:26374002

  20. Fragment-based 13C nuclear magnetic resonance chemical shift predictions in molecular crystals: An alternative to planewave methods

    International Nuclear Information System (INIS)

    We assess the quality of fragment-based ab initio isotropic 13C chemical shift predictions for a collection of 25 molecular crystals with eight different density functionals. We explore the relative performance of cluster, two-body fragment, combined cluster/fragment, and the planewave gauge-including projector augmented wave (GIPAW) models relative to experiment. When electrostatic embedding is employed to capture many-body polarization effects, the simple and computationally inexpensive two-body fragment model predicts both isotropic 13C chemical shifts and the chemical shielding tensors as well as both cluster models and the GIPAW approach. Unlike the GIPAW approach, hybrid density functionals can be used readily in a fragment model, and all four hybrid functionals tested here (PBE0, B3LYP, B3PW91, and B97-2) predict chemical shifts in noticeably better agreement with experiment than the four generalized gradient approximation (GGA) functionals considered (PBE, OPBE, BLYP, and BP86). A set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided based on these benchmark calculations. Statistical cross-validation procedures are used to demonstrate the robustness of these fits

  1. Chemical shifts of the X-ray L3 absorption edge of europium in its trivalent halides

    International Nuclear Information System (INIS)

    Position of the Eu-L3 absorption edge has been studied in pure metal and in its trivalent halides, EuF3, EuCl3, EuBr3, and EuI3, employing a simple X-ray spectrometer with an LiF single crystal as the analyser. A linear relationship was established between the chemical shift and the effective charge on the absorbing rare earth atom. The chemical shifts have also been correlated to Moessbauer isomer shifts. The results have been discussed in terms of nature of chemical bonding, effective atomic charge on the absorbing atom and some other parameters relevant to the immediate local environment of the absorbing atom. (author)

  2. Attainable entanglement of unitary transformed thermal states in liquid-state nuclear magnetic resonance with the chemical shift

    CERN Document Server

    Ota, Y; Ohba, I; Yoshida, N; Mikami, Shuji; Ohba, Ichiro; Ota, Yukihiro; Yoshida, Noriyuki

    2006-01-01

    Recently, Yu, Brown, and Chuang [Phys. Rev. A {\\bf 71}, 032341 (2005)] investigated the entanglement attainable from unitary transformed thermal states in liquid-state nuclear magnetic resonance (NMR). Their research gave an insight into the role of the entanglement in a liquid-state NMR quantum computer. Moreover, they attempted to reveal the role of mixed-state entanglement in quantum computing. However, they assumed that the Zeeman energy of each nuclear spin which corresponds to a qubit takes a common value for all; there is no chemical shift. In this paper, we research a model with the chemical shifts and analytically derive the physical parameter region where unitary transformed thermal states are entangled, by the positive partial transposition (PPT) criterion with respect to any bipartition. We examine the effect of the chemical shifts on the boundary between the separability and the nonseparability, and find it is negligible.

  3. Shifts in microbial and chemical patterns within the marine sponge Aplysina aerophoba during a disease outbreak.

    Science.gov (United States)

    Webster, Nicole S; Xavier, Joana R; Freckelton, Marnie; Motti, Cherie A; Cobb, Rose

    2008-12-01

    The microbial community composition in affected and unaffected portions of diseased sponges and healthy control sponges of Aplysina aerophoba was assessed to ascertain the role of microbes in the disease process. Sponge secondary metabolites were also examined to assess chemical shifts in response to infection. The microbial profile and aplysinimine levels in unaffected tissue near the lesions closely reflected those of healthy sponge tissue, indicating a highly localized disease process. DGGE detected multiple sequences that were exclusively present in diseased sponges. Most notably, a Deltaproteobacteria sequence with high homology to a coral black band disease strain was detected in all sponge lesions and was absent from all healthy and unaffected regions of diseased sponges. Other potential pathogens identified by DGGE include an environmental Cytophaga strain and a novel Epsilonproteobacteria strain with no known close relatives. The disease process also caused a major shift in prokaryote community structure at a very high taxonomic level. Using 16S rRNA gene sequence analysis, only the diseased sponges were found to contain sequences belonging to the Epsilonproteobacteria and Firmicutes, and there was a much greater number of Bacteroidetes sequences within the diseased sponges. In contrast, only the healthy sponges contained sequences corresponding to the cyanobacteria and 'OP1' candidate division, and the healthy sponges were dominated by Chloroflexi and Gammaproteobacteria sequences. Overall bacterial diversity was found to be considerably higher in diseased sponges than in healthy sponges. These results provide a platform for future cultivation-based experiments to isolate the putative pathogens from A. aerophoba and perform re-infection trials to define the disease aetiology. PMID:18783385

  4. Nuclear magnetic resonance shielding constants and chemical shifts in linear 199Hg compounds: a comparison of three relativistic computational methods.

    Science.gov (United States)

    Arcisauskaite, Vaida; Melo, Juan I; Hemmingsen, Lars; Sauer, Stephan P A

    2011-07-28

    We investigate the importance of relativistic effects on NMR shielding constants and chemical shifts of linear HgL(2) (L = Cl, Br, I, CH(3)) compounds using three different relativistic methods: the fully relativistic four-component approach and the two-component approximations, linear response elimination of small component (LR-ESC) and zeroth-order regular approximation (ZORA). LR-ESC reproduces successfully the four-component results for the C shielding constant in Hg(CH(3))(2) within 6 ppm, but fails to reproduce the Hg shielding constants and chemical shifts. The latter is mainly due to an underestimation of the change in spin-orbit contribution. Even though ZORA underestimates the absolute Hg NMR shielding constants by ∼2100 ppm, the differences between Hg chemical shift values obtained using ZORA and the four-component approach without spin-density contribution to the exchange-correlation (XC) kernel are less than 60 ppm for all compounds using three different functionals, BP86, B3LYP, and PBE0. However, larger deviations (up to 366 ppm) occur for Hg chemical shifts in HgBr(2) and HgI(2) when ZORA results are compared with four-component calculations with non-collinear spin-density contribution to the XC kernel. For the ZORA calculations it is necessary to use large basis sets (QZ4P) and the TZ2P basis set may give errors of ∼500 ppm for the Hg chemical shifts, despite deceivingly good agreement with experimental data. A Gaussian nucleus model for the Coulomb potential reduces the Hg shielding constants by ∼100-500 ppm and the Hg chemical shifts by 1-143 ppm compared to the point nucleus model depending on the atomic number Z of the coordinating atom and the level of theory. The effect on the shielding constants of the lighter nuclei (C, Cl, Br, I) is, however, negligible. PMID:21806118

  5. Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

    International Nuclear Information System (INIS)

    The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5 × 1019 eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrative values of Z = 6,13,26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies

  6. Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

    CERN Document Server

    Abreu, P; Ahn, E J; Albuquerque, I F M; Allard, D; Allekotte, I; Allen, J; Allison, P; Castillo, J Alvarez; Alvarez-Muñiz, J; Ambrosio, M; Aminaei, A; Anchordoqui, L; Andringa, S; Antičić, T; Anzalone, A; Aramo, C; Arganda, E; Arqueros, F; Asorey, H; Assis, P; Aublin, J; Ave, M; Avenier, M; Avila, G; Bäcker, T; Balzer, M; Barber, K B; Barbosa, A F; Bardenet, R; Barroso, S L C; Baughman, B; Bäuml, J; Beatty, J J; Becker, B R; Becker, K H; Bellétoile, A; Bellido, J A; BenZvi, S; Berat, C; Bertou, X; Biermann, P L; Billoir, P; Blanco, F; Blanco, M; Bleve, C; Blümer, H; Boháčová, M; Boncioli, D; Bonifazi, C; Bonino, R; Borodai, N; Brack, J; Brogueira, P; Brown, W C; Bruijn, R; Buchholz, P; Bueno, A; Burton, R E; Caballero-Mora, K S; Caramete, L; Caruso, R; Castellina, A; Catalano, O; Cataldi, G; Cazon, L; Cester, R; Chauvin, J; Cheng, S H; Chiavassa, A; Chinellato, J A; Chou, A; Chudoba, J; Clay, R W; Coluccia, M R; Conceição, R; Contreras, F; Cook, H; Cooper, M J; Coppens, J; Cordier, A; Cotti, U; Coutu, S; Covault, C E; Creusot, A; Criss, A; Cronin, J; Curutiu, A; Dagoret-Campagne, S; Dallier, R; Dasso, S; Daumiller, K; Dawson, B R; de Almeida, R M; De Domenico, M; De Donato, C; de Jong, S J; De La Vega, G; Junior, W J M de Mello; Neto, J R T de Mello; De Mitri, I; de Souza, V; de Vries, K D; Decerprit, G; del Peral, L; Deligny, O; Dembinski, H; Dhital, N; Di Giulio, C; Diaz, J C; Castro, M L Díaz; Diep, P N; Dobrigkeit, C; Docters, W; D'Olivo, J C; Dong, P N; Dorofeev, A; Anjos, J C dos; Dova, M T; D'Urso, D; Dutan, I; Ebr, J; Engel, R; Erdmann, M; Escobar, C O; Etchegoyen, A; Luis, P Facal San; Tapia, I Fajardo; Falcke, H; Farrar, G; Fauth, A C; Fazzini, N; Ferguson, A P; Ferrero, A; Fick, B; Filevich, A; Filipčič, A; Fliescher, S; Fracchiolla, C E; Fraenkel, E D; Fröhlich, U; Fuchs, B; Gaior, R; Gamarra, R F; Gambetta, S; García, B; Gámez, D García; Garcia-Pinto, D; Gascon, A; Gemmeke, H; Gesterling, K; Ghia, P L; Giaccari, U; Giller, M; Glass, H; Gold, M S; Golup, G; Albarracin, F Gomez; Berisso, M Gómez; Gonçalves, P; Gonzalez, D; Gonzalez, J G; Gookin, B; Góra, D; Gorgi, A; Gouffon, P; Gozzini, S R; Grashorn, E; Grebe, S; Griffith, N; Grigat, M; Grillo, A F; Guardincerri, Y; Guarino, F; Guedes, G P; Guzman, A; Hague, J D; Hansen, P; Harari, D; Harmsma, S; Harton, J L; Haungs, A; Hebbeker, T; Heck, D; Herve, A E; Hojvat, C; Hollon, N; Holmes, V C; Homola, P; Hörandel, J R; Horneffer, A; Hrabovský, M; Huege, T; Insolia, A; Ionita, F; Italiano, A; Jarne, C; Jiraskova, S; Kadija, K; Kampert, K H; Karhan, P; Kasper, P; Kégl, B; Keilhauer, B; Keivani, A; Kelley, J L; Kemp, E; Kieckhafer, R M; Klages, H O; Kleifges, M; Kleinfeller, J; Knapp, J; Koang, D -H; Kotera, K; Krohm, N; Krömer, O; Kruppke-Hansen, D; Kuehn, F; Kuempel, D; Kulbartz, J K; Kunka, N; La Rosa, G; Lachaud, C; Lautridou, P; Leão, M S A B; Lebrun, D; Lebrun, P; de Oliveira, M A Leigui; Lemiere, A; Letessier-Selvon, A; Lhenry-Yvon, I; López, K Link R; Agüera, A Lopez; Louedec, K; Bahilo, J Lozano; Lucero, A; Ludwig, M; Lyberis, H; Maccarone, M C; Macolino, C; Maldera, S; Mandat, D; Mantsch, P; Mariazzi, A G; Marin, J; Marin, V; Maris, I C; Falcon, H R Marquez; Marsella, G; Martello, D; Martin, L; Martinez, H; Bravo, O Martínez; Mathes, H J; Matthews, J; Matthews, J A J; Matthiae, G; Maurizio, D; Mazur, P O; Medina-Tanco, G; Melissas, M; Melo, D; Menichetti, E; Menshikov, A; Mertsch, P; Meurer, C; Mićanović, S; Micheletti, M I; Miller, W; Miramonti, L; Mollerach, S; Monasor, M; Ragaigne, D Monnier; Montanet, F; Morales, B; Morello, C; Moreno, E; Moreno, J C; Morris, C; Mostafá, M; Moura, C A; Mueller, S; Muller, M A; Müller, G; Münchmeyer, M; Mussa, R; Navarra, G; Navarro, J L; Navas, S; Necesal, P; Nellen, L; Nelles, A; Nhung, P T; Niemietz, L; Nierstenhoefer, N; Nitz, D; Nosek, D; Nožka, L; Nyklicek, M; Oehlschläger, J; Olinto, A; Oliva, P; Olmos-Gilbaja, V M; Ortiz, M; Pacheco, N; Selmi-Dei, D Pakk; Palatka, M; Pallotta, J; Palmieri, N; Parente, G; Parizot, E; Parra, A; Parsons, R D; Pastor, S; Paul, T; Pech, M; Pȩkala, J; Pelayo, R; Pepe, I M; Perrone, L; Pesce, R; Petermann, E; Petrera, S; Petrinca, P; Petrolini, A; Petrov, Y; Petrovic, J; Pfendner, C; Phan, N; Piegaia, R; Pierog, T; Pieroni, P; Pimenta, M; Pirronello, V; Platino, M; Ponce, V H; Pontz, M; Privitera, P; Prouza, M; Quel, E J; Querchfeld, S; Rautenberg, J; Ravel, O; Ravignani, D; Revenu, B; Ridky, J; Riggi, S; Risse, M; Ristori, P; Rivera, H; Rizi, V; Roberts, J; Robledo, C; de Carvalho, W Rodrigues; Rodriguez, G; Martino, J Rodriguez; Rojo, J Rodriguez; Rodriguez-Cabo, I; Rodríguez-Frías, M D; Ros, G; Rosado, J; Rossler, T; Roth, M; Rouillé-d'Orfeuil, B; Roulet, E; Rovero, A C; Rühle, C; Salamida, F; Salazar, H; Salina, G; Sánchez, F; Santander, M; Santo, C E; Santos, E; Santos, E M; Sarazin, F; Sarkar, B; Sarkar, S; Sato, R; Scharf, N; Scherini, V; Schieler, H; Schiffer, P; Schmidt, A; Schmidt, F; Schmidt, T; Scholten, O; Schoorlemmer, H; Schovancova, J; Schovánek, P; Schröder, F; Schulte, S; Schuster, D; Sciutto, S J; Scuderi, M; Segreto, A; Settimo, M; Shadkam, A; Shellard, R C; Sidelnik, I; Sigl, G; Lopez, H H Silva; Śmiałkowski, A; Šmída, R; Snow, G R; Sommers, P; Sorokin, J; Spinka, H; Squartini, R; Stapleton, J; Stasielak, J; Stephan, M; Strazzeri, E; Stutz, A; Suarez, F; Suomijärvi, T; Supanitsky, A D; Šuša, T; Sutherland, M S; Swain, J; Szadkowski, Z; Szuba, M; Tamashiro, A; Tapia, A; Tartare, M; Taşcău, O; Ruiz, C G Tavera; Tcaciuc, R; Tegolo, D; Thao, N T; Thomas, D; Tiffenberg, J; Timmermans, C; Tiwari, D K; Tkaczyk, W; Peixoto, C J Todero; Tomé, B; Tonachini, A; Travnicek, P; Tridapalli, D B; Tristram, G; Trovato, E; Tueros, M; Ulrich, R; Unger, M; Urban, M; Galicia, J F Valdés; Valiño, I; Valore, L; Berg, A M van den; Varela, E; Cárdenas, B Vargas; Vázquez, J R; Vázquez, R A; Veberič, D; Verzi, V; Vicha, J; Videla, M; Villaseñor, L; Wahlberg, H; Wahrlich, P; Wainberg, O; Warner, D; Watson, A A; Weber, M; Weidenhaupt, K; Weindl, A; Westerhoff, S; Whelan, B J; Wieczorek, G; Wiencke, L; Wilczyńska, B; Wilczyński, H; Will, M; Williams, C; Winchen, T; Winders, L; Winnick, M G; Wommer, M; Wundheiler, B; Yamamoto, T; Yapici, T; Younk, P; Yuan, G; Yushkov, A; Zamorano, B; Zas, E; Zavrtanik, D; Zavrtanik, M; Zaw, I; Zepeda, A; Ziolkowski, M

    2011-01-01

    The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies $E>E_{th}=5.5\\times 10^{19}$ eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at $E>E_{th}$ are heavy nuclei with charge $Z$, the proton component of the sources should lead to excesses in the same regions at energies $E/Z$. We here report the lack of anisotropies in these directions at energies above $E_{th}/Z$ (for illustrative values of $Z=6,\\ 13,\\ 26$). If the anisotropies above $E_{th}$ are due to nuclei with charge $Z$, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.

  7. Comparison of Computed Tomography Histogram Analysis and Chemical-Shift Magnetic Resonance Imaging for Adrenal Mass Characterization

    International Nuclear Information System (INIS)

    Background: Computed tomography (CT) histogram analysis and chemical-shift magnetic resonance imaging (MRI) are currently used modalities for adrenal mass characterization. However, it is not yet clear which modality can be regarded as most sensitive in terms of adrenal mass characterization. Purpose: To prospectively compare CT histogram analysis and chemical-shift MRI in the characterization of adrenal masses. Material and Methods: Between May 2007 and November 2008, 93 patients (45 males, 48 females; mean age 56.7 years, range 22-85 years) with 109 adrenal masses prospectively underwent both unenhanced CT and chemical-shift MRI examinations. These masses consisted of 67 adenomas and 42 metastases. Histogram analysis was applied with a circular region of interest (ROI) that recorded mean attenuation, total number of pixels, number of negative pixels, and the percentage of negative pixels on unenhanced CT images for each adrenal mass. In the CT histogram analysis, a 10% negative pixel threshold for unenhanced CT was calculated. In chemical-shift MRI, signal intensity drop between in-phase and opposed-phase images was quantitatively calculated so that adrenal-to-spleen chemical-shift ratios and adrenal signal intensity indexes were determined for each of the adrenal masses. A mass was regarded as an adenoma if it contained more than 10% negative pixels by CT histogram analysis, showed an adrenal-to-spleen chemical-shift ratio of less than 0.71, and had an adrenal signal intensity index of more than 16.5% by chemical-shift MRI. The results were compared to reveal which method was most sensitive in the diagnosis of adrenal masses and whether or not a correlation exists between these two modalities. Final diagnoses were based on imaging follow-up of minimum 6 months, biopsy, surgery, and adrenal washout study. Results: On unenhanced CT examinations, all of the 67 adenomas and 21 out of 42 metastases exhibited negative pixels. None of the metastases showed more than 10

  8. Comparison of Computed Tomography Histogram Analysis and Chemical-Shift Magnetic Resonance Imaging for Adrenal Mass Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Halefoglu, A.M.; Yasar, A.; Bas, N.; Ozel, A.; Erturk, S.M.; Basak, M. (Dept. of Radiology, Sisli Etfal Training and Research Hospital, Sisli, Istanbul (Turkey))

    2009-11-15

    Background: Computed tomography (CT) histogram analysis and chemical-shift magnetic resonance imaging (MRI) are currently used modalities for adrenal mass characterization. However, it is not yet clear which modality can be regarded as most sensitive in terms of adrenal mass characterization. Purpose: To prospectively compare CT histogram analysis and chemical-shift MRI in the characterization of adrenal masses. Material and Methods: Between May 2007 and November 2008, 93 patients (45 males, 48 females; mean age 56.7 years, range 22-85 years) with 109 adrenal masses prospectively underwent both unenhanced CT and chemical-shift MRI examinations. These masses consisted of 67 adenomas and 42 metastases. Histogram analysis was applied with a circular region of interest (ROI) that recorded mean attenuation, total number of pixels, number of negative pixels, and the percentage of negative pixels on unenhanced CT images for each adrenal mass. In the CT histogram analysis, a 10% negative pixel threshold for unenhanced CT was calculated. In chemical-shift MRI, signal intensity drop between in-phase and opposed-phase images was quantitatively calculated so that adrenal-to-spleen chemical-shift ratios and adrenal signal intensity indexes were determined for each of the adrenal masses. A mass was regarded as an adenoma if it contained more than 10% negative pixels by CT histogram analysis, showed an adrenal-to-spleen chemical-shift ratio of less than 0.71, and had an adrenal signal intensity index of more than 16.5% by chemical-shift MRI. The results were compared to reveal which method was most sensitive in the diagnosis of adrenal masses and whether or not a correlation exists between these two modalities. Final diagnoses were based on imaging follow-up of minimum 6 months, biopsy, surgery, and adrenal washout study. Results: On unenhanced CT examinations, all of the 67 adenomas and 21 out of 42 metastases exhibited negative pixels. None of the metastases showed more than 10

  9. Chemical shift imaging and localised magnetic resonance spectroscopy in full-term asphyxiated neonates

    International Nuclear Information System (INIS)

    Diagnosis of brain lesions after birth anoxia-ischemia is essential for appropriate management. Clinical evaluation is not sufficient. MRI has been proven to provide useful information. To compare abnormalities observed with MRI, including diffusion-weighted imaging (DWI), localised magnetic resonance spectroscopy (MRS) and chemical shift imaging (CSI) and correlate these findings with the clinical outcome. Fourteen full-term neonates with birth asphyxia were studied. MRI, MRS and CSI were performed within the first 4 days of life. Lesions observed with DWI were correlated with outcome, but the apparent diffusion coefficient (ADC) did improve diagnostic confidence. The mean value of Lac/Cr for the neonates with a favourable outcome was statically lower than for those who died (0.22 vs 1.04; P = 0.01). The same results were observed for the Lac/NAA ratio (0.21 vs 1.23; P = 0.01). Data obtained with localised MRS and CSI were correlated for the ratio N-acetyl-aspartate/choline, but not for the other metabolites. No correlation was found between the ADC values and the metabolite ratios. Combination of these techniques could be helpful in our understanding of the physiopathological events occurring in neonates with asphyxia. (orig.)

  10. Repeatability of long and short echo-time in vivo proton chemical-shift imaging

    International Nuclear Information System (INIS)

    We carried out long (145 ms) and short (25 ms) echo time spectroscopic imaging of the brain (chemical-shift imaging, CSI) on two occasions 1 week apart on 15 healthy individuals. We found coefficients of variation (CVs) generally in the range 10-25% for long and 15-30% for short echo-time measurements. The CVs of metabolite ratios were higher by about 5-10%. Limits of agreement (defined as mean±2 SD of the week 1-week 2 differences) were wider at the shorter echo time. The modest repeatability may be due in part to the difficulty of repositioning spectroscopic voxels at a scale of 1 mm. The generally higher CVs and wider limits of agreement at TE25 ms suggest that the increased spectral complexity more than offsets the theoretical advantage of increased signal at short echo-times. Analysis of variance general linear modelling of metabolites and metabolite ratios showed that, in general, the subject, region of the brain and hemisphere were more important than the occasion in explaining the variability of results. Unless information on short-T2 metabolites is specifically required, better results can probably be achieved with longer echo-times. The magnitude of the CVs needs to be taken into account in the calculation of sample size for cross-sectional or linear studies. (orig.)

  11. Clinical evaluation of the cerebral energy metabolism with 31P chemical shift imaging in neurosurgical disorders

    International Nuclear Information System (INIS)

    Cerebral energy metabolism was evaluated by means of 31P chemical shift imaging (CSI) using the 2.0 T whole-body MRIS system. 31P CSI was carried out by means of Spectroscopic Imaging by Dephasing Amplitude Changing method, four-dimensional CSI, and three-dimensional CSI. Twenty three patients with cerebral infarction and 21 patients with hypertensive intracerebral hemorrhage were examined. In cerebral infarction, an acute infarction was seen as a low-signal area in the PCr and ATP images and as a high-signal area in the Pi image. A subacute and chronic infarction was seen as a low-signal area in all the images -- 31P, PCr, ATP, Pi, PDE and PME. Intracellular acidosis was noticed within 2 days after onset. The intracellular pH became alkaline at the subacute and chronic stages of infarction. The chronological changes in the phosphorus metabolites were evaluated by means of these methods. In hypertensive intracerebral hemorrhage, hematoma and perifocal edema in the acute stage were seen as low-signal areas in the 31P, PCr, and ATP images, and as high-signal areas in the Pi image. In the chronic stage, a hematoma was seen as a low-signal area in all the images -- 31P, PCr, ATP and Pi. 31P CSI is thus a practical tool for studying phosphate metabolites clinically. Changes in the phosphorus metabolism relative to the anatomy of interest were detected by the use of these methods. (author)

  12. Correlation of 1H NMR Chemical Shift for Aqueous Solutions by Statistical Associating Fluid Theory Association Model

    Institute of Scientific and Technical Information of China (English)

    许波; 李浩然; 王从敏; 许映杰; 韩世钧

    2005-01-01

    1H NMR chemical shifts of binary aqueous mixtures of acylamide, alcohol, dimethyl sulphoxide (DMSO), and acetone are correlated by statistical associating fluid theory (SAFT) association model. The comparison between SAFT association model and Wilson equation shows that the former is better for dealing with aqueous solutions. Finally, the specialties of both models are discussed.

  13. Optimal voxel size for measuring global gray and white matter proton metabolite concentrations using chemical shift imaging

    DEFF Research Database (Denmark)

    Hanson, Lars Peter Grüner; Adalsteinsson, E; Pfefferbaum, A; Spielman, D.M.

    2000-01-01

    Quantification of gray and white matter levels of spectroscopically visible metabolites can provide important insights into brain development and pathological conditions. Chemical shift imaging offers a gain in efficiency for estimation of global gray and white matter metabolite concentrations co...... concentration error (<15%). Magn Reson Med 44:10-18, 2000....

  14. Novel Folding Large-Scale Optical Switch Matrix with Total Internal Reflection Mirrors on Silicon-on-Insulator by Anisotropy Chemical Etching

    Institute of Scientific and Technical Information of China (English)

    LIU Jing-Wei; YU Jin-Zhong; CHEN Shao-Wu

    2005-01-01

    A compact optical switch matrix was designed, in which light circuits were folded by total internal reflective (TIR) mirrors. Two key elements, 2 × 2 switch and TIR mirror, have been fabricated on silicon-on-insulator wafer by anisotropy chemical etching. The 2 × 2 switch showed very low power consumption of 140mW and avery high speed of 8 ± 1 μs. An improved design for the TIR mirror was developed, and the fabricated mirror with smooth and vertical reflective facet showed low excess loss of 0.7 ± 0.3 dB at 1.55μm.

  15. A comparison of chemical shift sensitivity of trifluoromethyl tags: optimizing resolution in {sup 19}F NMR studies of proteins

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Libin; Larda, Sacha Thierry; Frank Li, Yi Feng [University of Toronto, UTM, Department of Chemistry (Canada); Manglik, Aashish [Stanford University School of Medicine, Department of Molecular and Cellular Physiology (United States); Prosser, R. Scott, E-mail: scott.prosser@utoronto.ca [University of Toronto, UTM, Department of Chemistry (Canada)

    2015-05-15

    The elucidation of distinct protein conformers or states by fluorine ({sup 19}F) NMR requires fluorinated moieties whose chemical shifts are most sensitive to subtle changes in the local dielectric and magnetic shielding environment. In this study we evaluate the effective chemical shift dispersion of a number of thiol-reactive trifluoromethyl probes [i.e. 2-bromo-N-(4-(trifluoromethyl)phenyl)acetamide (BTFMA), N-(4-bromo-3-(trifluoromethyl)phenyl)acetamide (3-BTFMA), 3-bromo-1,1,1-trifluoropropan-2-ol (BTFP), 1-bromo-3,3,4,4,4-pentafluorobutan-2-one (BPFB), 3-bromo-1,1,1-trifluoropropan-2-one (BTFA), and 2,2,2-trifluoroethyl-1-thiol (TFET)] under conditions of varying polarity. In considering the sensitivity of the {sup 19}F NMR chemical shift to the local environment, a series of methanol/water mixtures were prepared, ranging from relatively non-polar (MeOH:H{sub 2}O = 4) to polar (MeOH:H{sub 2}O = 0.25). {sup 19}F NMR spectra of the tripeptide, glutathione ((2S)-2-amino-4-{[(1R)-1-[(carboxymethyl)carbamoyl] -2-sulfanylethyl]carbamoyl}butanoic acid), conjugated to each of the above trifluoromethyl probes, revealed that the BTFMA tag exhibited a significantly greater range of chemical shift as a function of solvent polarity than did either BTFA or TFET. DFT calculations using the B3LYP hybrid functional and the 6-31G(d,p) basis set, confirmed the observed trend in chemical shift dispersion with solvent polarity.

  16. {sup 1}H MR chemical shift imaging detection of phenylalanine in patients suffering from phenylketonuria (PKU)

    Energy Technology Data Exchange (ETDEWEB)

    Sijens, Paul E.; Oudkerk, Matthijs [University Hospital Groningen, Department of Radiology, Hanzeplein 1, P.O. Box 30001, Groningen (Netherlands); Reijngoud, Dirk-Jan; Spronsen, Francjan J. van [University Hospital Groningen, Department of Pediatrics, Groningen (Netherlands); Leenders, Klaas L. [University Hospital Groningen, Department of Neurology, Groningen (Netherlands); Valk, Harold W. de [University Medical Centre of Utrecht, Department of Internal Medicine, Utrecht (Netherlands)

    2004-10-01

    Short echo time single voxel methods were used in previous MR spectroscopy studies of phenylalanine (Phe) levels in phenylketonuria (PKU) patients. In this study, apparent T{sub 2} relaxation time of the 7.3-ppm Phe multiplet signal in the brain of PKU patients was assessed in order to establish which echo time would be optimal. {sup 1}H chemical shift imaging (CSI) examinations of a transverse plain above the ventricles of the brain were performed in 10 PKU patients and 11 persons not suffering from PKU at 1.5 T, using four echo times (TE 20, 40, 135 and 270 ms). Phe was detectable only when the signals from all CSI voxels were summarized. In patients suffering from PKU the T{sub 2} relaxation times of choline, creatine and N-acetyl aspartate (NAA) were similar to those previously reported for healthy volunteers (between 200 and 325 ms). The T{sub 2} of Phe in brain tissue was 215{+-}120 ms (standard deviation). In the PKU patients the brain tissue Phe concentrations were 141{+-}69 {mu}M as opposed to 58{+-}23 {mu}M in the persons not suffering from PKU. In the detection of Phe, MR spectroscopy performed at TE 135 or 270 ms is not inferior to that performed at TE 20 or 40 ms (all previous studies). Best results were obtained at TE=135 ms, relating to the fact that at that particular TE, the visibility of a compound with a T{sub 2} of 215 ms still is good, while interfering signals from short-TE compounds are negligible. (orig.)

  17. Quantification of fat using chemical shift imaging and 1H-MR spectroscopy in phantom model

    International Nuclear Information System (INIS)

    Objective: To evaluate the accuracy of chemical shift imaging (CSI) and MR spectroscopy (MRS) for fat quantification in phantom model. Methods: Eleven phantoms were made according to the volume percentage of fat ranging from 0 to 100% with an interval of 10%. The fat concentration in the phantoms were measured respectively by CSI and MRS and compared using one-sample t test. The correlation between the two methods was also analyzed. The concentration of saturated fatty acids (FS), unsaturated fatty acids (FU) and the poly, unsaturation degree (PUD) were calculated by using MRS. Results: The fat concentration was (48.0±1.0)%, (57.0±0.5)%, (67.3±0.6)%, (77.3± 0.6)%, (83.3±0.6)% and (91.0±1.0)% respectively with fat volume of 50% to 100% by CSI. The fat concentration was (8.3±0.6)%, (16.3±0.7)%, (27.7±0.6)%, (36.0±1.0)%, (43.5± 0.6)% and (56.5±1.0)% respectively with fat volume of 10% to 60% by MRS, the fat concentration were underestimated by CSI and MRS (P<0.05), and had high linear correlation with the real concentration in phantoms (CSI: r=0.998, MRS: r=0.996, P<0.01). There was also a linear correlation between two methods (r=0.992, P<0.01) but no statistically significant difference (paired- samples t test, t=-0.125, P=0.903). By using MRS, the relative ratio of FS and FU in fat were 0. 15 and 0.85, the PUD was 0.0325, respectively, and highly consistent with these in phantoms. Conclusion: Both CSI and MRS are efficient and accurate methods in fat quantification at 7.0 T MR. (authors)

  18. Female sea lamprey shift orientation toward a conspecific chemical cue to escape a sensory trap

    Science.gov (United States)

    Brant, Cory O.; Johnson, Nicholas; Li, Ke; Buchinger, Tyler J.; Li, Weiming

    2016-01-01

    The sensory trap model of signal evolution hypothesizes that signalers adapt to exploit a cue used by the receiver in another context. Although exploitation of receiver biases can result in conflict between the sexes, deceptive signaling systems that are mutually beneficial drive the evolution of stable communication systems. However, female responses in the nonsexual and sexual contexts may become uncoupled if costs are associated with exhibiting a similar response to a trait in both contexts. Male sea lamprey (Petromyzon marinus) signal with a mating pheromone, 3-keto petromyzonol sulfate (3kPZS), which may be a match to a juvenile cue used by females during migration. Upstream movement of migratory lampreys is partially guided by 3kPZS, but females only move toward 3kPZS with proximal accuracy during spawning. Here, we use in-stream behavioral assays paired with gonad histology to document the transition of female preference for juvenile- and male-released 3kPZS that coincides with the functional shift of 3kPZS as a migratory cue to a mating pheromone. Females became increasingly biased toward the source of synthesized 3kPZS as their maturation progressed into the reproductive phase, at which point, a preference for juvenile odor (also containing 3kPZS naturally) ceased to exist. Uncoupling of female responses during migration and spawning makes the 3kPZS communication system a reliable means of synchronizing mate search. The present study offers a rare example of a transition in female responses to a chemical cue between nonsexual and sexual contexts, provides insights into the origins of stable communication signaling systems.

  19. Anomalous chemical shifts in X-ray photoelectron spectra of sulfur-containing compounds of silver (I) and (II)

    International Nuclear Information System (INIS)

    Highlights: • Ag 3d5/2 binding energy for Ag(II)SO4 is as large as 370.1 eV. • This is the largest value ever measured for a silver (II) compound. • Large shift is connected with the extreme oxidizing nature of Ag(II) species. • Ag(I)2S2O7 exhibits both positive and negative shifts with respect to metallic Ag. • Two distinct Ag(I) sites are responsible for large BE difference of 3.6 eV. - Abstract: Anomalous chemical shifts, i.e. cases when binding energy decreases with the increase of the oxidation state, have been well-documented for selected compounds of silver, and well understood based on analysis of initial- and final-state effects in the XPS spectra. Here we report two examples of even more exotic behaviour of chemical shifts for two silver compounds. The first one is Ag2S2O7 which exhibits both positive and negative substantial shifts with respect to metallic Ag for two distinct Ag(I) sites in its crystal structure, which differ by as much as 3.6 eV. Another is AgSO4, a rare example of oxo silver (II) salt, which exhibits “normal” chemical shift but the Ag 3d5/2 binding energy takes the largest value measured for a silver (II) compound (370.1 eV). This property is connected predominantly with the extremely strongly oxidizing nature of Ag(II) species

  20. Anomalous chemical shifts in X-ray photoelectron spectra of sulfur-containing compounds of silver (I) and (II)

    Energy Technology Data Exchange (ETDEWEB)

    Grzelak, A. [Faculty of Chemistry, University of Warsaw, Pasteur 1, 02093 Warsaw (Poland); Jaroń, T. [Centre of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw (Poland); Mazej, Z. [Department of Inorganic Chemistry and Technology, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Michałowski, T. [Faculty of Chemistry, University of Warsaw, Pasteur 1, 02093 Warsaw (Poland); Centre of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw (Poland); Szarek, P. [Centre of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw (Poland); Grochala, W., E-mail: w.grochala@cent.uw.edu.pl [Faculty of Chemistry, University of Warsaw, Pasteur 1, 02093 Warsaw (Poland); Centre of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw (Poland)

    2015-07-15

    Highlights: • Ag 3d{sub 5/2} binding energy for Ag(II)SO{sub 4} is as large as 370.1 eV. • This is the largest value ever measured for a silver (II) compound. • Large shift is connected with the extreme oxidizing nature of Ag(II) species. • Ag(I){sub 2}S{sub 2}O{sub 7} exhibits both positive and negative shifts with respect to metallic Ag. • Two distinct Ag(I) sites are responsible for large BE difference of 3.6 eV. - Abstract: Anomalous chemical shifts, i.e. cases when binding energy decreases with the increase of the oxidation state, have been well-documented for selected compounds of silver, and well understood based on analysis of initial- and final-state effects in the XPS spectra. Here we report two examples of even more exotic behaviour of chemical shifts for two silver compounds. The first one is Ag{sub 2}S{sub 2}O{sub 7} which exhibits both positive and negative substantial shifts with respect to metallic Ag for two distinct Ag(I) sites in its crystal structure, which differ by as much as 3.6 eV. Another is AgSO{sub 4}, a rare example of oxo silver (II) salt, which exhibits “normal” chemical shift but the Ag 3d{sub 5/2} binding energy takes the largest value measured for a silver (II) compound (370.1 eV). This property is connected predominantly with the extremely strongly oxidizing nature of Ag(II) species.

  1. Evaluation of vertebral bone marrow fat content by chemical-shift MRI in osteoporosis

    International Nuclear Information System (INIS)

    To quantitatively evaluate vertebral bone marrow fat content and investigate its association with osteoporosis with chemical-shift magnetic resonance imaging (CS-MRI). Fifty-six female patients (age range 50-65 years) with varying bone mineral densities as documented with dual x-ray absorptiometry (DXA) were prospectively included in the study. According to the DXA results, the patients were grouped as normal bone density, osteopenic, or osteoporotic. In order to calculate fat content, the lumbar region was visualized in the sagittal plane by CS-MRI sequence. ''Region of interest'' (ROI)s were placed within L3 vertebral bodies and air (our reference point) at different time points by different radiologists. Fat content was calculated through ''signal intensity (SI) suppression rate'' and ''SI Index''. The quantitative values were compared statistically with those obtained from DXA examinations. Kruskal-Wallis, and Mann-Whitney U tests were used for comparisons between groups. The reliability of the measurements performed by two radiologists was evaluated with the ''intraclass correlation coefficient''. This study was approved by an institutional review board and all participants provided informed consent to participate in the study. Eighteen subjects with normal bone density (mean T score, 0.39 ± 1.3 [standard deviation]), 20 subjects with osteopenia (mean T score, -1.79 ± 0.38), and 18 subjects with osteoporosis (mean T score, -3 ± 0.5) were determined according to DXA results. The median age was 55.9 (age range 50-64 years) in the normal group, 55.5 (age range 50-64 years) in the osteopenic group, and 55.1 (age range 50-65 years) in the osteoporotic group (p = 0.872). In the CS-MRI examination, the values of ''SI suppression ratio'' and ''SI Index'' (median [min:max]) were calculated by the first and second reader, independently. There was no statistically significant difference between the groups with regard to vertebral bone marrow fat content (p > 0

  2. Predicting 15N chemical shifts in proteins using the preceding residue-specific individual shielding surfaces from φ, ψi-1, and χ1torsion angles

    International Nuclear Information System (INIS)

    Empirical shielding surfaces are most commonly used to predict chemical shifts in proteins from known backbone torsion angles, φ and ψ. However, the prediction of 15N chemical shifts using this technique is significantly poorer, compared to that for the other nuclei such as 1Hα, 13Cα, and 13Cβ. In this study, we investigated the effects from the preceding residue and the side-chain geometry, χ1, on 15N chemical shifts by statistical methods. For an amino acid sequence XY, the 15N chemical shift of Y is expressed as a function of the amino acid types of X and Y, as well as the backbone torsion angles, φ and ψi-1. Accordingly, 380 empirical 'Preceding Residue Specific Individual (PRSI)' 15N chemical shift shielding surfaces, representing all the combinations of X and Y (except for Y=Pro), were built and used to predict 15N chemical shift from φ and ψi-1. We further investigated the χ1 effects, which were found to account for differences in 15N chemical shifts by ∼5 ppm for amino acids Val, Ile, Thr, Phe, His, Tyr, and Trp. Taking the χ1 effects into account, the χ1-calibrated PRSI shielding surfaces (XPRSI) were built and used to predict 15N chemical shifts for these amino acids. We demonstrated that 15N chemical shift predictions are significantly improved by incorporating the preceding residue and χ1 effects. The present PRSI and XPRSI shielding surfaces were extensively compared with three recently published programs, SHIFTX (Neal et al., 2003), SHIFTS (Xu and Case, 2001 and 2002), and PROSHIFT (Meiler, 2003) on a set of ten randomly selected proteins. A set of Java programs using XPRSI shielding surfaces to predict 15N chemical shifts in proteins were developed and are freely available for academic users at http://www.pronmr.com or by sending email to one of the authors Yunjun Wang

  3. Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

    OpenAIRE

    Arganda, E.; Arqueros Martínez, Fernando; Blanco Ramos, Francisco; García Pinto, Diego; Ortiz Ramis, Montserrat; Rosado Vélez, Jaime; Vázquez Peñas, José Ramón

    2011-01-01

    The Pierre Auger Collaboration has reported. evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > E-th = 5.5 x 10(19) eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > E-th are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at ener...

  4. A Paradigm Shift: Supply Chain Collaboration and Competition in and between Europe’s Chemical Clusters

    OpenAIRE

    Wassenhove, Luk; Lebreton, Baptiste; Letizia, Paolo

    2007-01-01

    textabstractWith the attention of the chemical industry focused on exploiting the low cost feedstocks in the Middle East and the growth markets of Brazil, Russia, India, China and South East Asia, this report provides a timely reminder to policy makers, chemical companies and logistics service providers of the significant opportunities for improving business potential in Europe’s chemical clusters. Europe is still the largest, most sophisticated global market for chemical products, with a wel...

  5. Ecological niche shifts and environmental space anisotropy: a cautionary note Desplazamientos en el nicho y la anisotropía del espacio ambiental: una nota precautoria

    OpenAIRE

    Jorge Soberón; A. Townsend Peterson

    2011-01-01

    The anisotropic structure of climatic space may cause significant (and to a large extent unappreciated) non-evolutionary niche shifts. This can be seen mostly in the context of spatial transferability of ecological niche models. We explore this effect using a virtual species in the United States. We created a simple virtual species by postulating its fundamental niche as an ellipse in a two-dimensional realistic climatic space. The climatic combinations defined by the ellipse were projected i...

  6. Multiple pancreatic metastases from clear cell renal carcinoma: diagnosis with chemical shift magnetic resonance imaging before surgery

    International Nuclear Information System (INIS)

    We present a case in which multiple pancreatic tumours were diagnosed as metastatic clear cell renal carcinomas with chemical shift MRI (CSI) before surgery. Radiologists may be unable to recognize the loss of intensity on CSI macroscopically. We believe that it is useful to make subtraction images and calculate signal intensity on CSI, even if the lesions are multiple metastatic tumours Copyright (2005) Blackwell Publishing Asia Pty Ltd

  7. Magnetic anisotropy and chemical long-range order in epitaxial ferrimagnetic CrPt sub 3 films

    CERN Document Server

    Maret, M; Köhler, J; Poinsot, R; Ulhaq-Bouillet, C; Tonnerre, J M; Berar, J F; Bucher, E

    2000-01-01

    Thin films of CrPt sub 3 were prepared by molecular beam epitaxy on both Al sub 2 O sub 3 (0 0 0 1) and MgO(0 0 1) substrates, either directly by co-deposition of Cr and Pt at high temperatures or after in situ annealing of superlattices [Cr(2 A)/Pt(7 A)]. In situ RHEED observations and X-ray diffraction measurements have allowed us to check the single-crystal quality of CrPt sub 3 films and to determine the degree of L1 sub 2 -type long-range order (LRO). In films co-deposited between 850 deg. C and 950 deg. C a nearly perfect LRO has been observed. As in bulk alloys, such ordering yields a ferrimagnetic order, while the disordered films are non-magnetic. In contrast with the ferromagnetic L1 sub 2 -type ordered CoPt sub 3 (1 1 1) films, the ferrimagnetic CrPt sub 3 (1 1 1) films exhibit perpendicular magnetic anisotropy with quality factors, K sub u /K sub d , as large as 5 and large coercivities around 450 kA/m. Such anisotropy could be related to the arrangement of Cr atoms, which owing to their large mag...

  8. Application of data mining tools for classification of protein structural class from residue based averaged NMR chemical shifts.

    Science.gov (United States)

    Kumar, Arun V; Ali, Rehana F M; Cao, Yu; Krishnan, V V

    2015-10-01

    The number of protein sequences deriving from genome sequencing projects is outpacing our knowledge about the function of these proteins. With the gap between experimentally characterized and uncharacterized proteins continuing to widen, it is necessary to develop new computational methods and tools for protein structural information that is directly related to function. Nuclear magnetic resonance (NMR) provides powerful means to determine three-dimensional structures of proteins in the solution state. However, translation of the NMR spectral parameters to even low-resolution structural information such as protein class requires multiple time consuming steps. In this paper, we present an unorthodox method to predict the protein structural class directly by using the residue's averaged chemical shifts (ACS) based on machine learning algorithms. Experimental chemical shift information from 1491 proteins obtained from Biological Magnetic Resonance Bank (BMRB) and their respective protein structural classes derived from structural classification of proteins (SCOP) were used to construct a data set with 119 attributes and 5 different classes. Twenty four different classification schemes were evaluated using several performance measures. Overall the residue based ACS values can predict the protein structural classes with 80% accuracy measured by Matthew correlation coefficient. Specifically protein classes defined by mixed αβ or small proteins are classified with >90% correlation. Our results indicate that this NMR-based method can be utilized as a low-resolution tool for protein structural class identification without any prior chemical shift assignments. PMID:25758094

  9. Predicting Heats of Explosion of Nitroaromatic Compounds through NBO Charges and 15N NMR Chemical Shifts of Nitro Groups

    Directory of Open Access Journals (Sweden)

    Ricardo Infante-Castillo

    2012-01-01

    Full Text Available This work presents a new quantitative model to predict the heat of explosion of nitroaromatic compounds using the natural bond orbital (NBO charge and 15N NMR chemical shifts of the nitro groups (15NNitro as structural parameters. The values of the heat of explosion predicted for 21 nitroaromatic compounds using the model described here were compared with experimental data. The prediction ability of the model was assessed by the leave-one-out cross-validation method. The cross-validation results show that the model is significant and stable and that the predicted accuracy is within 0.146 MJ kg−1, with an overall root mean squared error of prediction (RMSEP below 0.183 MJ kg−1. Strong correlations were observed between the heat of explosion and the charges (R2 = 0.9533 and 15N NMR chemical shifts (R2 = 0.9531 of the studied compounds. In addition, the dependence of the heat of explosion on the presence of activating or deactivating groups of nitroaromatic explosives was analyzed. All calculations, including optimizations, NBO charges, and 15NNitro NMR chemical shifts analyses, were performed using density functional theory (DFT and a 6-311+G(2d,p basis set. Based on these results, this practical quantitative model can be used as a tool in the design and development of highly energetic materials (HEM based on nitroaromatic compounds.

  10. Distinguishing between cystic teratomas and endometriomas of the ovary using chemical shift gradient echo magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Ishijima Hideyuki; Ishizaka Hiroshi; Inoue Tomio [Gunma University Hospital, Gunma (Japan). Depts. of Diagnostic Radiaology and Nuclear Medicine

    1996-02-01

    The purpose of this study was to evaluate the efficacy of chemical shift gradient echo magnetic resonance imaging (MRI) in distinguishing between cystic teratomas and endometriomas of the ovary, using a 1.5 T magnet. The study included 22 patients with 31 ovarian lesions (15 cystic teratomas and 16 endometriomas), which showed high signal intensity on T1-weighted spin echo images. Chemical shift gradient echo images with three different echo times (TE = 2.5, 4.5 and 6.5 ms) were obtained in all cases. Indices were calculated on the basis of the signal intensities of lesions on the chemical shift gradient echo images. All endometriomas had signal intensity indices of less than 2.1, while all cystic teratomas had signal intensity indices of 18.1 or greater. It was concluded that the method used in this study presents the following advantages: the acquisition time is short; it needs no special software; and it does not depend on magnetic field homogeneity. 11 refs., 4 figs.

  11. Chemical shift of Mn and Cr K-edges in X-ray absorption spectroscopy with synchrotron radiation

    Indian Academy of Sciences (India)

    D Joseph; A K Yadav; S N Jha; D Bhattacharyya

    2013-11-01

    Mn and Cr K X-ray absorption edges were measured in various compounds containing Mn in Mn2+, Mn3+ and Mn4+ oxidation states and Cr in Cr3+ and Cr6+ oxidation states. Few compounds possess tetrahedral coordination in the 1st shell surrounding the cation while others possess octahedral coordination. Measurements have been carried out at the energy dispersive EXAFS beamline at INDUS-2 Synchrotron Radiation Source at Raja Ramanna Centre for Advanced Technology, Indore. Energy shifts of ∼8–16 eV were observed for Mn K edge in the Mn-compounds while a shift of 13–20 eV was observed for Cr K edge in Cr-compounds compared to values in elementalMn and Cr, respectively. The different chemical shifts observed for compounds having the same oxidation state of the cation but different anions or ligands show the effect of different chemical environments surrounding the cations in determining their X-ray absorption edges in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on Mn and Cr cations in the above compounds.

  12. Ecological niche shifts and environmental space anisotropy: a cautionary note Desplazamientos en el nicho y la anisotropía del espacio ambiental: una nota precautoria

    Directory of Open Access Journals (Sweden)

    Jorge Soberón

    2011-12-01

    Full Text Available The anisotropic structure of climatic space may cause significant (and to a large extent unappreciated non-evolutionary niche shifts. This can be seen mostly in the context of spatial transferability of ecological niche models. We explore this effect using a virtual species in the United States. We created a simple virtual species by postulating its fundamental niche as an ellipse in a two-dimensional realistic climatic space. The climatic combinations defined by the ellipse were projected in the geography of the United States and 2 regions of equal area were selected. The structure of niche in the 2 areas is compared. It is shown that the 2 regions have differently positioned subsets of the environmental space, which creates "shifts" in the realized niches despite the fact that no evolution and no biotic interactions are present. The most parsimonious hypothesis when ecological niche modeling reveals shifts in the realized niche is that environmental space is heterogeneous. Without considering differences in the structure of environmental space no speculation about niche evolution or the role of competitors should be attempted.La estructura anisotrópica del espacio climático puede causar desplazamientos significativos no evolutivos en los nichos de las especies. Este efecto poco apreciado en la literatura se manifiesta con gran claridad cuando se realizan transferencias espaciales de modelos de nicho ecológico. Se explora este efecto utilizando una especie virtual en los Estados Unidos. Se creó una especie virtual simplificada postulando su nicho fundamental en forma de una elipse en un espacio realista de 2 dimensiones. Las combinaciones climáticas definidas por la elipse se proyectaron en la geografía de los Estados Unidos y se seleccionaron 2 regiones de igual superficie espacial. Se compara la estructura del nicho en las 2 regiones, mostrando que estas 2 regiones espaciales presentan subconjuntos distintos del espacio de variables

  13. Pressure dependence of backbone chemical shifts in the model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    Science.gov (United States)

    Erlach, Markus Beck; Koehler, Joerg; Crusca, Edson; Kremer, Werner; Munte, Claudia E; Kalbitzer, Hans Robert

    2016-06-01

    For a better understanding of nuclear magnetic resonance (NMR) detected pressure responses of folded as well as unstructured proteins the availability of data from well-defined model systems are indispensable. In this work we report the pressure dependence of chemical shifts of the backbone atoms (1)H(α), (13)C(α) and (13)C' in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH2 (Xxx one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of these nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The polynomial pressure coefficients B 1 and B 2 are dependent on the type of amino acid studied. The coefficients of a given nucleus show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure are also weakly correlated. PMID:27335085

  14. Transport anisotropy of LaAlO3/SrTiO3 interfaces on chemically patterned SrTiO3

    International Nuclear Information System (INIS)

    A few years ago high mobility electronic transport was found at the interface between the wide bandgap insulators SrTiO3 and LaAlO3. This conductive layer is confined to a few unit cells around the interface and it appears when LaAlO3 layers with thickness above 3-4 unit cells are grown on SrTiO3. It is known that TiO2/LaO interfaces are conductive, while SrO/AlO2 interfaces are insulating. Here we exploited this way to control the interface properties to produce large scale functional nanostructures. TiO2/AlO-SrO/LaO2 modulated interfaces have been prepared using thermally treated SrTiO3 surfaces with self-organized patterned chemical termination. The interface transport properties are found to be controlled according to these interface patterns. While the influence of the interface topology, e.g. terrace steps, is negligible, a strong transport anisotropy is observed when large-scale well oriented chemical patterns are realized. Our results show that bottom-up engineering of the interface chemical composition is a suitable strategy to influence the transport properties on large scales.

  15. Transition Ion Strikes Back: Large Magnetic Susceptibility Anisotropy in Cobalt(II) Clathrochelates.

    Science.gov (United States)

    Novikov, Valentin V; Pavlov, Alexander A; Belov, Alexander S; Vologzhanina, Anna V; Savitsky, Anton; Voloshin, Yan Z

    2014-11-01

    Transition-metal complexes are rarely considered as paramagnetic tags for NMR spectroscopy due to them generally having relatively low magnetic anisotropy. Here we report cobalt(II) cage complexes with the largest (among the transition-metal complexes) axial anisotropy of magnetic susceptibility, reaching as high as 12.6 × 10(-32) m(3) at room temperature. This remarkable anisotropy, which results from an unusual trigonal prismatic geometry of the complexes and translates into large negative value of the zero-field splitting energy, is high enough to promote reliable paramagnetic pseudocontact shifts at the distance beyond 2 nm. Our finding paves the way toward the applications of cobalt(II) clathrochelates as future paramagnetic tags. Given the incredible stability and functionalization versatility of clathrochelates, the fine-tuning of the caging ligand may lead to new chemically stable mononuclear single-molecule magnets, for which magnetic anisotropy is of importance. PMID:26278750

  16. Linear correlation of the barriers to pyramidal inversion of phosphorus with the 31P chemical shifts of acylphosphines

    International Nuclear Information System (INIS)

    The dependence of the inversion barriers (ΔG) of phosphorus compounds directly on a parameter of the inversion center, i.e., the chemical shift of the nucleus (delta31 P) were studied. The possibility of such an approach was justified by the correlation both of ΔG, and of delta31 P for phosphorus compounds with one and the same characteristics (the bond angles and electronegativities of the substituent). The acylphosphines (I-IX) were investigated in the range of variation of ΔG, accessible to dynamic NMR and in a fairly wide range of delta31 P

  17. Gradient-echo in-phase and opposed-phase chemical shift imaging: Role in evaluating bone marrow

    International Nuclear Information System (INIS)

    Chemical shift imaging (CSI) provides valuable information for assessing the bone marrow, while adding little to total examination time. In this article, we review the uses of CSI for evaluating bone marrow abnormalities. CSI can be used for differentiating marrow-replacing lesions from a range of non-marrow-replacing processes, although the sequence is associated with technical limitations and pitfalls. Particularly at 3 T, susceptibility artefacts are prevalent, and optimal technical parameters must be implemented with appropriate choices for echo times

  18. The Effect of Molecular Conformation on the Accuracy of Theoretical (1)H and (13)C Chemical Shifts Calculated by Ab Initio Methods for Metabolic Mixture Analysis.

    Science.gov (United States)

    Chikayama, Eisuke; Shimbo, Yudai; Komatsu, Keiko; Kikuchi, Jun

    2016-04-14

    NMR spectroscopy is a powerful method for analyzing metabolic mixtures. The information obtained from an NMR spectrum is in the form of physical parameters, such as chemical shifts, and construction of databases for many metabolites will be useful for data interpretation. To increase the accuracy of theoretical chemical shifts for development of a database for a variety of metabolites, the effects of sets of conformations (structural ensembles) and the levels of theory on computations of theoretical chemical shifts were systematically investigated for a set of 29 small molecules in the present study. For each of the 29 compounds, 101 structures were generated by classical molecular dynamics at 298.15 K, and then theoretical chemical shifts for 164 (1)H and 123 (13)C atoms were calculated by ab initio quantum chemical methods. Six levels of theory were used by pairing Hartree-Fock, B3LYP (density functional theory), or second order Møller-Plesset perturbation with 6-31G or aug-cc-pVDZ basis set. The six average fluctuations in the (1)H chemical shift were ±0.63, ± 0.59, ± 0.70, ± 0.62, ± 0.75, and ±0.66 ppm for the structural ensembles, and the six average errors were ±0.34, ± 0.27, ± 0.32, ± 0.25, ± 0.32, and ±0.25 ppm. The results showed that chemical shift fluctuations with changes in the conformation because of molecular motion were larger than the differences between computed and experimental chemical shifts for all six levels of theory. In conclusion, selection of an appropriate structural ensemble should be performed before theoretical chemical shift calculations for development of an accurate database for a variety of metabolites. PMID:26963288

  19. CMB Anisotropies by Collapsing Textures

    OpenAIRE

    Sousa, Kepa; Urrestilla, Jon

    2013-01-01

    CMB photons passing through a collapsing texture knot receive an energy shift, creating characteristic cold and hot spots on the sky. We calculate the anisotropy pattern produced by collapsing texture knots of arbitrary shape. The texture dynamics are solved numerically on a Minkowski background.

  20. Liver fat quantification: Comparison of dual-echo and triple-echo chemical shift MRI to MR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Satkunasingham, Janakan; Besa, Cecilia [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Bane, Octavia [Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Shah, Ami [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Oliveira, André de; Gilson, Wesley D.; Kannengiesser, Stephan [Siemens AG, Healthcare Sector, Erlangen (Germany); Taouli, Bachir, E-mail: bachir.taouli@mountsinai.org [Department of Radiology, Body MRI, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States); Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY 10029 (United States)

    2015-08-15

    Highlights: • We present a large cohort of patients who underwent dual and triple echo chemical shift imaging against multi-echo T{sub 2} corrected MR spectroscopy (MRS) for liver fat quantification. • Our data suggests that a triple-echo sequence is highly accurate for detection of liver fat, even in the presence of T{sub 2}{sup *} shortening, with minor discrepancies when compared with the advanced fat quantification method. - Abstract: Purpose: To assess the diagnostic value of MRI using dual-echo (2PD) and triple-echo (3PD) chemical shift imaging for liver fat quantification against multi-echo T{sub 2} corrected MR spectroscopy (MRS) used as the reference standard, and examine the effect of T{sub 2}{sup *} imaging on accuracy of MRI for fat quantification. Materials and methods: Patients who underwent 1.5 T liver MRI that incorporated 2PD, 3PD, multi-echo T{sub 2}{sup *} and MRS were included in this IRB approved prospective study. Regions of interest were placed in the liver to measure fat fraction (FF) with 2PD and 3PD and compared with MRS-FF. A random subset of 25 patients with a wide range of MRS-FF was analyzed with an advanced FF calculation method, to prove concordance with the 3PD. The statistical analysis included correlation stratified according to T{sub 2}{sup *}, Bland-Altman analysis, and calculation of diagnostic accuracy for detection of MRS-FF > 6.25%. Results: 220 MRI studies were identified in 217 patients (mean BMI 28.0 ± 5.6). 57/217 (26.2%) patients demonstrated liver steatosis (MRS-FF > 6.25%). Bland-Altman analysis revealed strong agreement between 3PD and MRS (mean ± 1.96 SD: −0.5% ± 4.6%) and weaker agreement between 2PD and MRS (4.7% ± 16.0%). Sensitivity of 3PD for diagnosing FF> 6.25% was higher than that of 2PD. 3PD-FF showed minor discrepancies (coefficient of variation <10%) from FF measured with the advanced method. Conclusion: Our large series study validates the use of 3PD chemical shift sequence for detection of

  1. Liver fat quantification: Comparison of dual-echo and triple-echo chemical shift MRI to MR spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • We present a large cohort of patients who underwent dual and triple echo chemical shift imaging against multi-echo T2 corrected MR spectroscopy (MRS) for liver fat quantification. • Our data suggests that a triple-echo sequence is highly accurate for detection of liver fat, even in the presence of T2* shortening, with minor discrepancies when compared with the advanced fat quantification method. - Abstract: Purpose: To assess the diagnostic value of MRI using dual-echo (2PD) and triple-echo (3PD) chemical shift imaging for liver fat quantification against multi-echo T2 corrected MR spectroscopy (MRS) used as the reference standard, and examine the effect of T2* imaging on accuracy of MRI for fat quantification. Materials and methods: Patients who underwent 1.5 T liver MRI that incorporated 2PD, 3PD, multi-echo T2* and MRS were included in this IRB approved prospective study. Regions of interest were placed in the liver to measure fat fraction (FF) with 2PD and 3PD and compared with MRS-FF. A random subset of 25 patients with a wide range of MRS-FF was analyzed with an advanced FF calculation method, to prove concordance with the 3PD. The statistical analysis included correlation stratified according to T2*, Bland-Altman analysis, and calculation of diagnostic accuracy for detection of MRS-FF > 6.25%. Results: 220 MRI studies were identified in 217 patients (mean BMI 28.0 ± 5.6). 57/217 (26.2%) patients demonstrated liver steatosis (MRS-FF > 6.25%). Bland-Altman analysis revealed strong agreement between 3PD and MRS (mean ± 1.96 SD: −0.5% ± 4.6%) and weaker agreement between 2PD and MRS (4.7% ± 16.0%). Sensitivity of 3PD for diagnosing FF> 6.25% was higher than that of 2PD. 3PD-FF showed minor discrepancies (coefficient of variation <10%) from FF measured with the advanced method. Conclusion: Our large series study validates the use of 3PD chemical shift sequence for detection of liver fat in the clinical environment, even in the presence of

  2. Characterization of interface abruptness and material properties in catalytically grown III-V nanowires: exploiting plasmon chemical shift

    International Nuclear Information System (INIS)

    We have studied the assessment of chemical composition changes in III-V heterostructured semiconductor nanowires (NWs) with nanometric spatial resolution using transmission electron microscopy methods. These materials represent a challenge for conventional spectroscopy techniques due to their high sensitivity to electron beam irradiation. Radiation damage strongly limits the exposure time to a few (5-10) s, which reduces the sensitivity of the traditionally used x-ray spectroscopy. The rather low counting statistics results in significant errors bars for EDS chemical quantification (5-10%) and interface width determination (few nanometers). Plasmon chemical shift is ideal in this situation, as its measurement requires very short exposure times (∼100 ms) and the plasmon peak energy can be measured with high precision (∼20 meV in this work). This high sensitivity allows the detection of subtle changes (1-2%) in composition or even the detection of a small plasmon energy (33 ± 7) meV change along usually assumed pure and homogeneous InAs segments. We have applied this approach to measure interface widths in heterostructure InAs/InP NWs grown using metal catalysts and also to determine the timescale (∼10 s) in which beam irradiation induces material damage in these wires. In particular, we have detected small As concentrations (4.4 ± 0.5)% in the final InP segment close to the Au catalyst, which leads to the conclusion that As diffuses through the metal nanoparticle during growth.

  3. Molecular structure and vibrational bands and 13C chemical shift assignments of both enmein-type diterpenoids by DFT study

    Science.gov (United States)

    Wang, Tao; Wu, Yi fang; Wang, Xue liang

    2014-01-01

    We report here theoretical and experimental studies on the molecular structure and vibrational and NMR spectra of both natural enmein type diterpenoids molecule (6, 7-seco-ent-kaurenes enmein type), isolated from the leaves of Isodon japonica (Burm.f.) Hara var. galaucocalyx (maxin) Hara. The optimized geometry, total energy, NMR chemical shifts and vibrational wavenumbers of epinodosinol and epinodosin have been determined using B3LYP method with 6-311G (d,p) basis set. A complete vibrational assignment is provided for the observed IR spectra of studied compounds. The calculated wavenumbers and 13C c.s. are in an excellent agreement with the experimental values. Quantum chemical calculations at the B3LYP/6-311G (d,p) level of theory have been carried out on studied compounds to obtain a set of molecular electronic properties (MEP,HOMO, LUMO and gap energies ΔEg). Electrostatic potential surfaces have been mapped over the electron density isosurfaces to obtain information about the size, shape, charge density distribution and chemical reactivity of the molecules.

  4. Acetylcholinesterase(AChE)-catalyzed hydrolysis of long-chain thiocholine esters:shift to a new chemical mechanism

    International Nuclear Information System (INIS)

    The kinetic and chemical mechanisms of AChE-catalyzed hydrolysis of short-chain thiocholine esters are relatively well documented. Up to propanoylthiocholine (PrTCh) the chemical mechanism is general acid-base catalysis by the active site catalytic triad. The chemical mechanism for the enzyme-catalyzed butyrylthio-choline(BuTCh) hydrolysis shifts to a parallel mechanism in which general base catalysis by E199 of direct water attack to the carbonyl carbon of the substrate. (Selwood, T., et al. J. Am. Chem. Soc. 1993, 115, 10477-10482) The long chain thiocholine esters such as hexanoylthiocholine (HexTCh), heptanoylthiocholine (HepTCh), and octanoylthiocholine (OcTCh) are hydrolyzed by electric eel acetylcholinesterase (AChE). The kinetic parameters are determined to show that these compounds have a lower Michaelis constant than BuTCh and the pH-Rate profile showed that the mechanism is similar to that of BuTCh hydrolysis. The solvent isotope effect and proton inventory of AChE-catalyzed hydrolysis of HexTCh showed that one proton transfer is involved in the transition state of the acylation stage. The relationship between the dipole moment and the Michaelis constant of the long chain thiocholine esters showed that the dipole moment is the most important factor for the binding of a substrate to the enzyme active site

  5. Acetylcholinesterase(AChE)-catalyzed hydrolysis of long-chain thiocholine esters:shift to a new chemical mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Dai Il; Shin, Young Ju [Donga Univ., Busan (Korea, Republic of); Lee, Eun Seok; Lee, Bong Ho [Hanbat National Univ., Daejon (Korea, Republic of); Moon, Tae Sung; Yoon, Chang No [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2003-01-01

    The kinetic and chemical mechanisms of AChE-catalyzed hydrolysis of short-chain thiocholine esters are relatively well documented. Up to propanoylthiocholine (PrTCh) the chemical mechanism is general acid-base catalysis by the active site catalytic triad. The chemical mechanism for the enzyme-catalyzed butyrylthio-choline(BuTCh) hydrolysis shifts to a parallel mechanism in which general base catalysis by E199 of direct water attack to the carbonyl carbon of the substrate. (Selwood, T., et al. J. Am. Chem. Soc. 1993, 115, 10477-10482) The long chain thiocholine esters such as hexanoylthiocholine (HexTCh), heptanoylthiocholine (HepTCh), and octanoylthiocholine (OcTCh) are hydrolyzed by electric eel acetylcholinesterase (AChE). The kinetic parameters are determined to show that these compounds have a lower Michaelis constant than BuTCh and the pH-Rate profile showed that the mechanism is similar to that of BuTCh hydrolysis. The solvent isotope effect and proton inventory of AChE-catalyzed hydrolysis of HexTCh showed that one proton transfer is involved in the transition state of the acylation stage. The relationship between the dipole moment and the Michaelis constant of the long chain thiocholine esters showed that the dipole moment is the most important factor for the binding of a substrate to the enzyme active site.

  6. Anisotropy of chemical bonding in semifluorinated graphite C2F revealed with angle-resolved X-ray absorption spectroscopy.

    Science.gov (United States)

    Okotrub, Alexander V; Yudanov, Nikolay F; Asanov, Igor P; Vyalikh, Denis V; Bulusheva, Lyubov G

    2013-01-22

    Highly oriented pyrolytic graphite characterized by a low misorientation of crystallites is fluorinated using a gaseous mixture of BrF(3) with Br(2) at room temperature. The golden-colored product, easily delaminating into micrometer-size transparent flakes, is an intercalation compound where Br(2) molecules are hosted between fluorinated graphene layers of approximate C(2)F composition. To unravel the chemical bonding in semifluorinated graphite, we apply angle-resolved near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and quantum-chemical modeling. The strong angular dependence of the CK and FK edge NEXAFS spectra on the incident radiation indicates that room-temperature-produced graphite fluoride is a highly anisotropic material, where half of the carbon atoms are covalently bonded with fluorine, while the rest of the carbon atoms preserve π electrons. Comparison of the experimental CK edge spectrum with theoretical spectra plotted for C(2)F models reveals that fluorine atoms are more likely to form chains. This conclusion agrees with the atomic force microscopy observation of a chain-like pattern on the surface of graphite fluoride layers. PMID:23214423

  7. Chemical structure elucidation from ¹³C NMR chemical shifts: efficient data processing using bipartite matching and maximal clique algorithms.

    Science.gov (United States)

    Koichi, Shungo; Arisaka, Masaki; Koshino, Hiroyuki; Aoki, Atsushi; Iwata, Satoru; Uno, Takeaki; Satoh, Hiroko

    2014-04-28

    Computer-assisted chemical structure elucidation has been intensively studied since the first use of computers in chemistry in the 1960s. Most of the existing elucidators use a structure-spectrum database to obtain clues about the correct structure. Such a structure-spectrum database is expected to grow on a daily basis. Hence, the necessity to develop an efficient structure elucidation system that can adapt to the growth of a database has been also growing. Therefore, we have developed a new elucidator using practically efficient graph algorithms, including the convex bipartite matching, weighted bipartite matching, and Bron-Kerbosch maximal clique algorithms. The utilization of the two matching algorithms especially is a novel point of our elucidator. Because of these sophisticated algorithms, the elucidator exactly produces a correct structure if all of the fragments are included in the database. Even if not all of the fragments are in the database, the elucidator proposes relevant substructures that can help chemists to identify the actual chemical structures. The elucidator, called the CAST/CNMR Structure Elucidator, plays a complementary role to the CAST/CNMR Chemical Shift Predictor, and together these two functions can be used to analyze the structures of organic compounds. PMID:24655374

  8. NMR chemical shift analysis of the conformational transition between the monomer and tetramer of melittin in an aqueous solution.

    Science.gov (United States)

    Miura, Yoshinori

    2016-05-01

    It is known that melittin in an aqueous solution undergoes a conformational transition between the monomer and tetramer by variation in temperature. The transition correlates closely with isomers of the proline residue; monomeric melittin including a trans proline peptide bond (trans-monomer) is involved directly in the transition, whereas monomeric melittin having a cis proline peptide bond (cis-monomer) is virtually not. The transition has been explored by using nuclear magnetic resonance spectroscopy in order to clarify the stability of the tetrameric conformation and the cooperativity of the transition. In the light of temperature dependence of chemical shifts of resonances from the isomeric monomers, we qualitatively estimate the temperature-, salt-, and concentration-dependence of the relative equilibrium populations of the trans-monomer and tetramer, and show that the tetramer has a maximum conformational stability at 30-45 °C and that the transition cooperativity is very low. PMID:26658745

  9. Backbone and stereospecific (13)C methyl Ile (δ1), Leu and Val side-chain chemical shift assignments of Crc.

    Science.gov (United States)

    Sharma, Rakhi; Sahu, Bhubanananda; Ray, Malay K; Deshmukh, Mandar V

    2015-04-01

    Carbon catabolite repression (CCR) allows bacteria to selectively assimilate a preferred compound among a mixture of several potential carbon sources, thus boosting growth and economizing the cost of adaptability to variable nutrients in the environment. The RNA-binding catabolite repression control (Crc) protein acts as a global post-transcriptional regulator of CCR in Pseudomonas species. Crc triggers repression by inhibiting the expression of genes involved in transport and catabolism of non-preferred substrates, thus indirectly favoring assimilation of preferred one. We report here a nearly complete backbone and stereospecific (13)C methyl side-chain chemical shift assignments of Ile (δ1), Leu and Val of Crc (~ 31 kDa) from Pseudomonas syringae Lz4W. PMID:24496608

  10. Microscopic structures of ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate in water probed by the relative chemical shift

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The relative chemical shifts (△δ) △δwere put forward to investigate the microscopic structure of 1-ethyl-3-methyl-imidazolium tetrafluoroborate (EmimBF4) during the dilution process with water.The concentration-dependent △δ(C2)H-(C4)H,△δ(C2)H-(C5)H and △δ(C4)H-(C5)H were analyzed.The results reveal that the variations of the microscopic structures of three aromatic protons are inconsistent.The strength of the H-bond between water and three aromatic protons follows the order:(C2)H···O > (C4)H···O > (C5)H···O.The concentration-dependent △δ(C6)H-(C7)H and △δ(C6)H-(C8)H indicate the formation of the H-bonds of (Calkyl)H···O is impossible,and more water is located around (C6)H than around (C7)H or (C8)H.The concentration-dependent △δ(C2)H-(C4)H and △δ(C2)H-(C5)H both increase rapidly when xwater > 0.9 or so,suggesting the ionic pairs of EmimBF4 are dissociated rapidly.The turning points of concentration-dependent △δ(C2)H-(C4)H and △δ(C2)H-(C5)H indicate that some physical properties of the EmimBF4/water mixtures also change at the corresponding concentration point.The microscopic structures of EmimBF4 in water could be clearly detected by the relative chemical shifts.

  11. Quantitative evaluation of vertebral marrow adipose tissue in postmenopausal female using MRI chemical shift-based water–fat separation

    International Nuclear Information System (INIS)

    Aim: To investigate the feasibility of assessing vertebral marrow adipose tissue using a magnetic resonance imaging (MRI) chemical shift-based water–fat separation technique at 3 T. Material and methods: A modified Dixon technique was performed to obtain the vertebral marrow fat fraction (FF) in a study of 58 postmenopausal females (age range 49.2–77.4 years), including 24 normal bone density, 19 osteopaenia, and 15 osteoporosis as documented with dual-energy X-ray absorptiometry. The reliability of FF measurements performed by two radiologists independently was evaluated with the intraclass correlation coefficient (ICC). Ten participants were scanned twice to assess the reproducibility of FF measurements. FF values were compared between each vertebral level and between groups. Results: The mean coefficient of variation of FF measurements was 2.1%. According to the ICC, the measurements were reliable (ICC = 0.900 for normal bone density, ICC = 0.937 for osteopaenia and ICC = 0.909 for osteoporosis, p < 0.001 for all). There was an inverse association between mean FF at L1–L4 vertebrae and lumbar spine BMD (r = −0.459, p = 0.006), which remained significant even after controlling for confounders (age, height, and body weight). FF values at different vertebral levels were significantly correlated to each other (r = 0.703–0.921, p < 0.05 for all). There was a general trend toward increased marrow adiposity for more inferior vertebral bodies. Patients with osteopaenia and osteoporosis had a higher marrow fat content compared with normal bone mass after adjusting for confounders, although no significant differences in each vertebral level and average marrow fat content were found between the osteopaenia and osteoporosis groups. Conclusion: Chemical shift-based water–fat separation enables the quantitation of vertebral marrow adiposity with excellent reproducibility, which appears to be a useful method to provide complementary information to osteoporosis

  12. Thickness-Dependent Binding Energy Shift in Few-Layer MoS2 Grown by Chemical Vapor Deposition.

    Science.gov (United States)

    Lin, Yu-Kai; Chen, Ruei-San; Chou, Tsu-Chin; Lee, Yi-Hsin; Chen, Yang-Fang; Chen, Kuei-Hsien; Chen, Li-Chyong

    2016-08-31

    The thickness-dependent surface states of MoS2 thin films grown by the chemical vapor deposition process on the SiO2-Si substrates are investigated by X-ray photoelectron spectroscopy. Raman and high-resolution transmission electron microscopy suggest the thicknesses of MoS2 films to be ranging from 3 to 10 layers. Both the core levels and valence band edges of MoS2 shift downward ∼0.2 eV as the film thickness increases, which can be ascribed to the Fermi level variations resulting from the surface states and bulk defects. Grainy features observed from the atomic force microscopy topographies, and sulfur-vacancy-induced defect states illustrated at the valence band spectra imply the generation of surface states that causes the downward band bending at the n-type MoS2 surface. Bulk defects in thick MoS2 may also influence the Fermi level oppositely compared to the surface states. When Au contacts with our MoS2 thin films, the Fermi level downshifts and the binding energy reduces due to the hole-doping characteristics of Au and easy charge transfer from the surface defect sites of MoS2. The shift of the onset potentials in hydrogen evolution reaction and the evolution of charge-transfer resistances extracted from the impedance measurement also indicate the Fermi level varies with MoS2 film thickness. The tunable Fermi level and the high chemical stability make our MoS2 a potential catalyst. The observed thickness-dependent properties can also be applied to other transition-metal dichalcogenides (TMDs), and facilitates the development in the low-dimensional electronic devices and catalysts. PMID:27488185

  13. Chemical shift measurements of chlorine K X-ray spectra using a high-resolution PIXE system

    International Nuclear Information System (INIS)

    A high-efficiency high-resolution wavelength-dispersive spectrograph with a von-Hamos configuration was developed for chemical state identification of elements in environmental samples using PIXE analysis. To evaluate the performance of this system, chlorine K X-ray spectra for NaCl, NH4Cl and polyvinylchloride (PVC) targets were measured and compared. Also, to study the applicability to environmental mixed samples, mixtures of NaCl and NH4Cl with different mixing ratios were measured. Through observation of Cl Kα1 X-ray from NaCl, the energy resolution of the system was determined to be 1.1 eV. For the NaCl sample, a Kβx line was observed at an energy, which is higher than that of the Kβ main peak by 2 eV, whereas no Kβx emission was observed for the NH4Cl sample. The chemical shift of the Kβ main peak for PVC relative to that for NaCl was about 1.2 eV. For NaCl-NH4Cl mixture targets, the relative intensity of Kβx satellite to the Kβ main line provided an indication of mixing ratio. Energies and relative intensity of Cl Kβ X-ray satellites for NaCl and NH4Cl samples calculated by a simple molecular-orbital method agreed only qualitatively with the experimental results

  14. Alterations in chemical shifts and exchange broadening upon peptide boronic acid inhibitor binding to α-lytic protease

    International Nuclear Information System (INIS)

    α-Lytic protease, a bacterial serine protease of 198 aminoacids (19800 Da), has been used as a model system for studies of catalytic mechanism, structure-function relationships, and more recently for studies of pro region-assisted protein folding. We have assigned the backbones of the enzyme alone, and of its complex with the tetrahedral transition state mimic N-tert-butyloxycarbonyl-Ala-Pro-boroVal, using double- and triple-resonance 3D NMR spectroscopy on uniformly15N- and 13C/15N-labeled protein.Changes in backbone chemical shifts between the uncomplexed and inhibited form of the protein are correlated with distance from the inhibitor, the displacement of backbone nitrogens, and change in hydrogen bond strength upon inhibitor binding (derived from previously solved crystal structures).A comparison of the solution secondary structure of the uninhibited enzyme with that of the X-ray structure reveals no significant differences.Significant line broadening, indicating intermediate chemical exchange, was observed in many of the active site amides (including three broadened to invisibility), and in a majority of cases the broadening was reversed upon addition of the inhibitor. Implications and possible mechanisms of this line broadening are discussed

  15. Development of multicomponent hybrid density functional theory with polarizable continuum model for the analysis of nuclear quantum effect and solvent effect on NMR chemical shift

    International Nuclear Information System (INIS)

    We have developed the multicomponent hybrid density functional theory [MC-(HF+DFT)] method with polarizable continuum model (PCM) for the analysis of molecular properties including both nuclear quantum effect and solvent effect. The chemical shifts and H/D isotope shifts of the picolinic acid N-oxide (PANO) molecule in chloroform and acetonitrile solvents are applied by B3LYP electron exchange-correlation functional for our MC-(HF+DFT) method with PCM (MC-B3LYP/PCM). Our MC-B3LYP/PCM results for PANO are in reasonable agreement with the corresponding experimental chemical shifts and isotope shifts. We further investigated the applicability of our method for acetylacetone in several solvents

  16. Theoretical study of the effective chemical shielding anisotropy (CSA) in peptide backbone, rating the impact of CSAs on the cross-correlated relaxations in L-alanyl-L-alanine

    Czech Academy of Sciences Publication Activity Database

    Benda, Ladislav; Bouř, Petr; Müller, N.; Sychrovský, Vladimír

    2009-01-01

    Roč. 113, č. 15 (2009), s. 5273-5281. ISSN 1520-6106 R&D Projects: GA AV ČR IAA400550701; GA AV ČR IAA400550702; GA MŠk MEB060705 Institutional research plan: CEZ:AV0Z40550506 Keywords : chemical shielding anisotropy * CSA * L-alanyl-L-alanine Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.471, year: 2009

  17. An optimized buffer system for NMR-based urinary metabonomics with effective pH control, chemical shift consistency and dilution minimization.

    Science.gov (United States)

    Xiao, Chaoni; Hao, Fuhua; Qin, Xiaorong; Wang, Yulan; Tang, Huiru

    2009-05-01

    NMR-based metabonomics has been widely employed to understand the stressor-induced perturbations to mammalian metabolism. However, inter-sample chemical shift variations for metabolites remain an outstanding problem for effective data mining. In this work, we systematically investigated the effects of pH and ionic strength on the chemical shifts for a mixture of 9 urinary metabolites. We found that the chemical shifts were decreased with the rise of pH but increased with the increase of ionic strength, which probably resulted from the pH- and ionic strength-induced alteration to the ionization equilibrium for the function groups. We also found that the chemical shift variations for most metabolites were reduced to less than 0.004 ppm when the pH was 7.1-7.7 and the salt concentration was less than 0.15 M. Based on subsequent optimization to minimize chemical shift variation, sample dilution and maximize the signal-to-noise ratio, we proposed a new buffer system consisting of K(2)HPO(4) and NaH(2)PO(4) (pH 7.4, 1.5 M) with buffer-urine volume ratio of 1 : 10 for human urinary metabonomic studies; we suggest that the chemical shifts for the proton signals of citrate and aromatic signals of histidine be corrected prior to multivariate data analysis especially when high resolution data were employed. Based on these, an optimized sample preparation method has been developed for NMR-based urinary metabonomic studies. PMID:19381385

  18. High accuracy NMR chemical shift corrected for bulk magnetization as a tool for structural elucidation of dilutable microemulsions. Part 1 - Proof of concept.

    Science.gov (United States)

    Hoffman, Roy E; Darmon, Eliezer; Aserin, Abraham; Garti, Nissim

    2016-02-01

    In microemulsions, changes in droplet size and shape and possible transformations occur under various conditions. They are difficult to characterize by most analytical tools because of their nano-sized structure and dynamic nature. Several methods are usually combined to obtain reliable information, guiding the scientist in understanding their physical behavior. We felt that there is a need for a technique that complements those in use today in order to provide more information on the microemulsion behavior, mainly as a function of dilution with water. The improvement of NMR chemical shift measurements independent of bulk magnetization effects makes it possible to study the very weak intermolecular chemical shift effects. In the present study, we used NMR high resolution magic angle spinning to measure the chemical shift very accurately, free of bulk magnetization effects. The chemical shift of microemulsion components is measured as a function of the water content in order to validate the method in an interesting and promising, U-type dilutable microemulsion, which had been previously studied by a variety of techniques. Phase transition points of the microemulsion (O/W, bicontinuous, W/O) and changes in droplet shape were successfully detected using high-accuracy chemical shift measurements. We analyzed the results and found them to be compatible with the previous studies, paving the way for high-accuracy chemical shifts to be used for the study of other microemulsion systems. We detected two transition points along the water dilution line of the concentrate (reverse micelles) corresponding to the transition from swollen W/O nano-droplets to bicontinuous to the O/W droplets along with the changes in the droplets' sizes and shapes. The method seems to be in excellent agreement with other previously studied techniques and shows the advantage of this easy and valid technique. PMID:25113928

  19. NMR spectroscopy of organic compounds of selenium and tellurium. Communication 9. Chemical shifts of 13C in isological series of unsaturated ethers, sulfides, selenides and tellurides

    International Nuclear Information System (INIS)

    The effects of heteroatoms Eh(Eh=O, S, Se, Te) on 13C chemical shifts in eleven isological series of R1-Eh-R2 unsaturated compounds are compared. A linear relation between 13C nuclei screening and tEh electronegativity is observed. An assumption is suggested that both likeness of the effects of 6A and 7A group elements on 13C chemical shifts of R1 and R2 substituents and their difference for elements of the 4A group are caused by unbonded interactions of the substituents with unshared electron pairs of heteroatoms

  20. Shifts in controls on the temporal coherence of throughfall chemical flux in Acadia National Park, Maine, USA

    Science.gov (United States)

    Nelson, Sarah J.; Webster, Katherine E.; Loftin, Cynthia S.; Weathers, Kathleen C.

    2013-01-01

    Major ion and mercury (Hg) inputs to terrestrial ecosystems include both wet and dry deposition (total deposition). Estimating total deposition to sensitive receptor sites is hampered by limited information regarding its spatial heterogeneity and seasonality. We used measurements of throughfall flux, which includes atmospheric inputs to forests and the net effects of canopy leaching or uptake, for ten major ions and Hg collected during 35 time periods in 1999–2005 at over 70 sites within Acadia National Park, Maine to (1) quantify coherence in temporal dynamics of seasonal throughfall deposition and (2) examine controls on these patterns at multiple scales. We quantified temporal coherence as the correlation between all possible site pairs for each solute on a seasonal basis. In the summer growing season and autumn, coherence among pairs of sites with similar vegetation was stronger than for site-pairs that differed in vegetation suggesting that interaction with the canopy and leaching of solutes differed in coniferous, deciduous, mixed, and shrub or open canopy sites. The spatial pattern in throughfall hydrologic inputs across Acadia National Park was more variable during the winter snow season, suggesting that snow re-distribution affects net hydrologic input, which consequently affects chemical flux. Sea-salt corrected calcium concentrations identified a shift in air mass sources from maritime in winter to the continental industrial corridor in summer. Our results suggest that the spatial pattern of throughfall hydrologic flux, dominant seasonal air mass source, and relationship with vegetation in winter differ from the spatial pattern of throughfall flux in these solutes in summer and autumn. The coherence approach applied here made clear the strong influence of spatial heterogeneity in throughfall hydrologic inputs and a maritime air mass source on winter patterns of throughfall flux. By contrast, vegetation type was the most important influence on

  1. Effect of spectra recording conditions on the example of chemical shifts calculation in CMR spectra of 1-pentylbenzoylformate

    OpenAIRE

    Mizyuk, Volodymyr; Shibanov, Volodymyr

    2011-01-01

    The concept of "compatible" and "incompatible" CMR spectra has been introduced. Application of compatibility increments (IC) allows to calculate the chemical shifts of C and C3 atoms of pentyloxyl fragment in 1-pentylbenzoylformate with a sufficiently good accuracy. Введено поняття "сумісних " і "несумісних " ЯМР спектрів. Застосування "інкрементів узгодження " дало можливість з достатньою точністю розрахувати хімічні зсуви атомів С2 і С пентилоксильного фрагменту в 1-пентилбензоїлформіаті....

  2. Cytoplasmic fat detection utilizing chemical shift gradient. Echo MR imaging in cases of clear cell renal cell carcinoma

    International Nuclear Information System (INIS)

    We investigated whether cytoplasmic fat in clear cell renal cell carcinoma (CCC) can be identified by chemical shift gradient-echo magnetic resonance imaging (CSI). CSI was performed for 22 cases of CCC and 30 cases of other renal tumors (including 16 cases of non-CCC), all of which were surgically proven. Signal reduction in out-of-phase images of these tumors was retrospectively evaluated and compared. The signal loss ratio (SLR) was defined and calculated. Fat staining of specimens from 16 tumors was performed and correlated with SLR. SLR was found to be significantly higher in CCC than in non-CCC (p<0.002). There was a significant correlation between the degree of fat staining positively of the specimens and SLR (p<0.01). When signal reduction in out-of-phase images suggested a diagnosis of CCC, a correct diagnosis of this entity was made in the resected renal tumors with a sensitivity, specificity, and accuracy of 82%, 93%, and 88%, respectively. CSI can demonstrate cytoplasmic fat in CCC, which helps to differentiate this entity from other renal tumors. (author)

  3. Quantitative evaluation of norcholesterol scintigraphy, CT attenuation value, and chemical-shift MR imaging for characterizing adrenal adenomas

    International Nuclear Information System (INIS)

    The objective of our study was to evaluate diagnostic ability and features of quantitative indices of three modalities: uptake rate on norcholesterol scintigraphy, computed tomography (CT) attenuation value, and fat suppression on chemical-shift magnetic resonance imaging (MRI) for characterizing adrenal adenomas. Image findings of norcholesterol scintigraphy, CT, and MRI were reviewed for 78 patients with functioning (n=48) or nonfunctioning (n=30) adrenal masses. The norcholesterol uptake rate, attenuation value on unenhanced CT, and suppression on in-phase to opposed-phase MRI were measured for adrenal masses. The norcholesterol uptake rate, CT attenuation value, and MR suppression index showed the sensitivity of 60%, 82%, and 100%, respectively, for functioning adenomas of <2.0 cm, and 96%, 79%, and 67%, respectively, for those of ≥2.0 cm. A statistically significant correlation was observed between size and norcholesterol uptake, and between CT attenuation value and MR suppression index. Regarding norcholesterol uptake, the adenoma-to-contralateral gland ratio was significantly higher in cortisol releasing than in aldosterone-releasing adenomas. The norcholesterol uptake rate was reliable for characterization of adenomas among adrenal masses of ≥2.0 cm. CT attenuation value and MR suppression index were well correlated with each other, and were useful regardless of mass size. (author)

  4. The study on temporal lobe epilepsy with single-voxel proton MR spectroscopy and chemical shift imaging

    International Nuclear Information System (INIS)

    Objective: To investigate the value of different proton MR spectroscopy techniques including single-voxel spectroscopy (SVS) and chemical shift imaging (CSI) in diagnosing patients with temporal lobe epilepsy. Methods: Sixty cases (40 normal, 20 temporal lobe epilepsy) experienced SVS and CSI. The volume of interest (VOI) of SVS was placed over the anterior hippocampus formation (HF) region, including part of the head and body of the HF. The VOI of CSI encompassed bilateral HF and the head, body and tail of HF. The VOI was divided into 5 voxels from anterior to posterior. The metabolite data of both SVS and CSI were obtained and the ratios of NAA/Cr and NAA/(Cho+Cr) were recorded or calculated. Results: The ipsilateral hippocampus to the seizure of TLE patients had lower ratios of NAA/(Cho+Cr) and NAA/Cr, and the differences compared with those of the normal group and contralateral subgroup were statistically significant (F=41.958, P1HMRS study improved the diagnostic yield of MR evaluation in TLE patients. There was a correlation between the ratio of NAA/(Cho+Cr) and the location of HF. Regional variation must be considered when interpreting proton spectra of the HF. (author)

  5. Solid state NMR chemical shift assignment and conformational analysis of a cellulose binding protein facilitated by optimized glycerol enrichment.

    Science.gov (United States)

    Ivanir, Hadar; Goldbourt, Amir

    2014-07-01

    Magic-angle spinning solid-state NMR has been applied to study CBM3b-Cbh9A (CBM3b), a cellulose binding module protein belonging to family 3b. It is a 146-residue protein having a unique nine-stranded β-sandwich fold, in which 35% of the structure is in a β-sheet conformation and the remainder of the protein is composed of loops and unstructured regions. Yet, the protein can be crystalized and it forms elongated needles. Close to complete chemical shift assignment of the protein was obtained by combining two- and three-dimensional experiments using a fully labeled sample and a glycerol-labeled sample. The use of an optimized protocol for glycerol-based sparse labeling reduces sample preparation costs and facilitates the assignment of the large number of aromatic signals in this protein. Conformational analysis shows good correlation between the NMR-predicted secondary structure and the reported X-ray crystal structure, in particular in the structured regions. Residues which show high B-factor values are situated mainly in unstructured regions, and are missing in our spectra indicating conformational flexibility rather than heterogeneity. Interestingly, long-range contacts, which could be clearly detected for tyrosine residues, could not be observed for aromatic phenylalanine residues pointing into the hydrophobic core, suggesting possible high ring mobility. These studies will allow us to further investigate the cellulose-bound form of CBM proteins. PMID:24824437

  6. Molecular structure and vibrational and chemical shift assignments of 3‧-chloro-4-dimethylamino azobenzene by DFT calculations

    Science.gov (United States)

    Toy, Mehmet; Tanak, Hasan

    2016-01-01

    In the present work, a combined experimental and theoretical study on ground state molecular structure, spectroscopic and nonlinear optical properties of azo compound 3‧-chloro-4-dimethlamino azobenzene are reported. The molecular geometry, vibrational wavenumbers and the first order hyperpolarizability of the title compound were calculated with the help of density functional theory computations. The optimized geometric parameters obtained by using DFT (B3LYP/6-311++G(d,p)) show good agreement with the experimental data. The vibrational transitions were identified based on the recorded FT-IR spectra in the range of 4000-400 cm-1 for solid state. The 1H isotropic chemical shifts with respect to TMS were also calculated using the gauge independent atomic orbital (GIAO) method and compared with the experimental data. Using the TD-DFT method, electronic absorption spectra of the title compound have been predicted, and good agreement is determined with the experimental ones. To investigate the NLO properties of the title compound, the polarizability and the first hyperpolarizability were calculated using the density functional B3LYP method with the 6-311++G(d,p) basis set. According to results, the title compound exhibits non-zero first hyperpolarizability value revealing second order NLO behavior. In addition, DFT calculations of the title compound, molecular electrostatic potential and frontier molecular orbitals were also performed at 6-311++G(d,p) level of theory.

  7. Differentiation of osteoporotic and neoplastic vertebral fractures by chemical shift {l_brace}in-phase and out-of phase{r_brace} MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Ragab, Yasser [Radiology Department, Faculty of Medicine, Cairo University (Egypt); Radiology Department, Dr Erfan and Bagedo General Hospital (Saudi Arabia)], E-mail: yragab61@hotmail.com; Emad, Yasser [Rheumatology and Rehabilitation Department, Faculty of Medicine, Cairo University (Egypt); Rheumatology and Rehabilitation Department, Dr Erfan and Bagedo General Hospital (Saudi Arabia)], E-mail: yasseremad68@yahoo.com; Gheita, Tamer [Rheumatology and Rehabilitation Department, Faculty of Medicine, Cairo University (Egypt)], E-mail: gheitamer@yahoo.com; Mansour, Maged [Oncology Department, Faculty of Medicine, Cairo University (Egypt); Oncology Department, Dr Erfan and Bagedo General Hospital (Saudi Arabia)], E-mail: magedmansour@yahoo.com; Abou-Zeid, A. [Public Health Department, Faculty of Medicine, Cairo University, Cairo (Egypt)], E-mail: alaabouzeid@yahoo.com; Ferrari, Serge [Division of Bone Diseases, Department of Rehabilitation and Geriatrics, and WHO, Collaborating Center for Osteoporosis Prevention, Geneva University Hospital (Switzerland)], E-mail: serge.ferrari@medecine.unige.ch; Rasker, Johannes J. [Rheumatologist University of Twente, Enschede (Netherlands)], E-mail: j.j.rasker@utwente.nl

    2009-10-15

    Objective: The objective of this study was to establish the cut-off value of the signal intensity drop on chemical shift magnetic resonance imaging (MRI) with appropriate sensitivity and specificity to differentiate osteoporotic from neoplastic wedging of the spine. Patients and methods: All patients with wedging of vertebral bodies were included consecutively between February 2006 and January 2007. A chemical shift MRI was performed and signal intensity after (in-phase and out-phase) images were obtained. A DXA was performed in all. Results: A total of 40 patients were included, 20 with osteoporotic wedging (group 1) and 20 neoplastic (group 2). They were 21 males and 19 females. Acute vertebral collapse was observed in 15 patients in group 1 and subacute collapse in another 5 patients, while in group 2, 11 patients showed acute collapse and 9 patients (45%) showed subacute vertebral collapse. On the chemical shift MRI a substantial reduction in signal intensity was found in all lesions in both groups. The proportional changes observed in signal intensity of bone marrow lesions on in-phase compared with out-of-phase images showed significant differences in both groups (P < 0.05). At a cut-off value of 35%, the observed sensitivity of out-of-phase images was 95%, specificity was 100%, positive predictive value was 100% and negative predictive value was 95.2%. Conclusion: A chemical shift MRI is useful in order to differentiate patients with vertebral collapse due to underlying osteoporosis or neoplastic process.

  8. Phosphorus Chemical Shifts in Drew-Dickerson Dodecamer and DNA Hairpin from MD-DFT Calculations: NMR Based Force Field Validation

    Czech Academy of Sciences Publication Activity Database

    Přecechtělová, J.; Munzarová, M. L.; Vaara, J.; Novák, P.; Dračínský, Martin; Sklenář, V.

    Ireland : University College Dublin, 2012. s. 72-72. [EUROMAR 2012. Magnetic Resonance Conference. 01.07.2012-05.07.2012, Dublin] Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR spectroscopy * phosphorus chemical shift * DFT calculations Subject RIV: CC - Organic Chemistry

  9. Probing the solvent shell with 195Pt chemical shifts: density functional theory molecular dynamics study of Pt(II) and Pt(IV) anionic complexes in aqueous solution.

    Science.gov (United States)

    Truflandier, Lionel A; Autschbach, Jochen

    2010-03-17

    Ab initio molecular dynamics (aiMD) simulations based on density functional theory (DFT) were performed on a set of five anionic platinum complexes in aqueous solution. (195)Pt nuclear magnetic shielding constants were computed with DFT as averages over the aiMD trajectories, using the two-component relativistic zeroth-order regular approximation (ZORA) in order to treat relativistic effects on the Pt shielding tensors. The chemical shifts obtained from the aiMD averages are in good agreement with experimental data. For Pt(II) and Pt(IV) halide complexes we found an intermediate solvent shell interacting with the complexes that causes pronounced solvent effects on the Pt chemical shifts. For these complexes, the magnitude of solvent effects on the Pt shielding constant can be correlated with the surface charge density. For square-planar Pt complexes the aiMD simulations also clearly demonstrate the influence of closely coordinated non-equatorial water molecules on the Pt chemical shift, relating the structure of the solution around the complex to the solvent effects on the metal NMR chemical shift. For the complex [Pt(CN)(4)](2-), the solvent effects on the Pt shielding constant are surprisingly small. PMID:20166712

  10. 13C NMR of methane in an AlPO4-11 molecular sieve: Exchange effects and shielding anisotropy

    Science.gov (United States)

    Koskela, Tuomas; Ylihautala, Mika; Jokisaari, Jukka; Vaara, Juha

    1998-12-01

    13C NMR spectra of 13CH4 in an AlPO4-11 molecular sieve reveal exchange effects between adsorbed and nonadsorbed methane gas. An application of pulsed field gradients is introduced to decrease nonadsorbed and exchanging gas signals in order to extract the chemical shift anisotropy line shape of the adsorbed gas. The resulting 13C shielding anisotropy of methane is compared to existing value for methane in related SAPO-11 material. Less anisotropic shielding is observed in AlPO4-11, most likely due to the lack of charge-compensating cations.

  11. Accuracy of chemical shift MR imaging in diagnosing indeterminate bone marrow lesions in the pelvis: review of a single institution's experience

    Energy Technology Data Exchange (ETDEWEB)

    Kohl, Chad A. [Mayo Clinic, Department of Radiology, Phoenix, AZ (United States); Radiology Ltd., Tucson, AZ (United States); Chivers, F.S.; Lorans, Roxanne; Roberts, Catherine C.; Kransdorf, Mark J. [Mayo Clinic, Department of Radiology, Phoenix, AZ (United States)

    2014-08-15

    To re-assess the accuracy of chemical shift imaging in diagnosing indeterminate bone marrow lesions as benign or malignant. We retrospectively reviewed our experience with MR imaging of the pelvis to assess the accuracy of chemical shift imaging in distinguishing benign from malignant bone lesions. Two musculoskeletal radiologists retrospectively reviewed all osseous lesions biopsied since 2006, when chemical shift imaging was added to our routine pelvic imaging protocol. Study inclusion criteria required (1) MR imaging of an indeterminate bone marrow lesion about the pelvis and (2) subsequent histologic confirmation. The study group included 50 patients (29 male, 21 female) with an average age of 67 years (range, 41-89 years). MR imaging results were evaluated using biopsy results as the ''gold standard.'' There were 27 malignant and 23 benign lesions. Chemical shift imaging using an opposed-phase signal loss criteria of less than 20 % to indicate a malignant lesion, correctly diagnosed 27/27 malignant lesions and 14/23 benign lesions, yielding a 100 % sensitivity, 61 % specificity, 75 % PPV, 100 % NPV, and 82 % accuracy. The area under the receiver operator characteristic (ROC) curve was 0.88. The inter-rater and intra-rater agreement K values were both 1.0. Chemical shift imaging is a useful adjunct MR technique to characterize focal and diffuse marrow abnormalities on routine non-contrast pelvic imaging. It is highly sensitive in identifying malignant disease. Despite its lower specificity, the need for biopsy could be eliminated in more than 60 % of patients with benign disease. (orig.)

  12. Diffusion-weighted imaging of the liver at 3 T using section-selection gradient reversal: emphasis on chemical shift artefacts and lesion conspicuity

    International Nuclear Information System (INIS)

    Aim: To assess the value of section-selection gradient reversal (SSGR) in liver diffusion-weighted imaging (DWI) by comparing it to conventional DWI with an emphasis on chemical shift artefacts and lesion conspicuity. Materials and methods: Forty-eight patients (29 men and 19 women; age range 33–80 years) with 48 liver lesions underwent two DWI examinations using spectral presaturation with inversion recovery fat suppression with and without SSGR at 3 T. Two reviewers evaluated each DWI (b = 100 and b = 800 image) with respect to chemical shift artefacts and liver lesion conspicuity using five-point scales and performed pairwise comparisons between the two DWIs. The signal-to-noise ratio (SNR) of the liver and the lesion and the lesion–liver contrast-to-noise ratio (CNR) were also calculated. Results: SSGR-DWI was significantly better than conventional DWI with respect to chemical shift artefacts and lesion conspicuity in both separate reviews and pairwise comparisons (p < 0.05). There were significant differences in the SNR of the liver (b = 100 and b = 800 images) and lesion (b = 800) between SSGR-DWI and conventional DWI (p < 0.05). Conclusion: Applying the SSGR method to DWI using SPIR fat suppression at 3 T could significantly reduce chemical shift artefacts without incurring additional acquisition time or SNR penalties, which leads to increased conspicuity of focal liver lesions. - Highlights: • Chemical shift artefact in liver DWI is markedly decreased by applying SSGR. • Liver lesion conspicuity is improved by applying SSGR to DWI. • In SNR of the liver, SSGR-DWI is better than conventional DWI

  13. Accuracy of chemical shift MR imaging in diagnosing indeterminate bone marrow lesions in the pelvis: review of a single institution's experience

    International Nuclear Information System (INIS)

    To re-assess the accuracy of chemical shift imaging in diagnosing indeterminate bone marrow lesions as benign or malignant. We retrospectively reviewed our experience with MR imaging of the pelvis to assess the accuracy of chemical shift imaging in distinguishing benign from malignant bone lesions. Two musculoskeletal radiologists retrospectively reviewed all osseous lesions biopsied since 2006, when chemical shift imaging was added to our routine pelvic imaging protocol. Study inclusion criteria required (1) MR imaging of an indeterminate bone marrow lesion about the pelvis and (2) subsequent histologic confirmation. The study group included 50 patients (29 male, 21 female) with an average age of 67 years (range, 41-89 years). MR imaging results were evaluated using biopsy results as the ''gold standard.'' There were 27 malignant and 23 benign lesions. Chemical shift imaging using an opposed-phase signal loss criteria of less than 20 % to indicate a malignant lesion, correctly diagnosed 27/27 malignant lesions and 14/23 benign lesions, yielding a 100 % sensitivity, 61 % specificity, 75 % PPV, 100 % NPV, and 82 % accuracy. The area under the receiver operator characteristic (ROC) curve was 0.88. The inter-rater and intra-rater agreement K values were both 1.0. Chemical shift imaging is a useful adjunct MR technique to characterize focal and diffuse marrow abnormalities on routine non-contrast pelvic imaging. It is highly sensitive in identifying malignant disease. Despite its lower specificity, the need for biopsy could be eliminated in more than 60 % of patients with benign disease. (orig.)

  14. Reproducibility of 31P MR spectroscopy detection in human liver with two-dimensional chemical shift imaging

    International Nuclear Information System (INIS)

    Objective: To study the reproducibility of relative quantification of phosphorus metabolites in human liver with two-dimensional chemical shift imaging(2D CSI). Methods: Using 2D CSI with FOV 200 mm and average times 40, 500 ml phosphate (NaH2PO4) solution phantom with 0.05 mol/L concentration was scanned 6 times, changing FOV to 280 mm, five healthy volunteers were scanned 6 times under respiration gating. The relative quantification of metabolites was derived from the integral values of peaks on the spectra, and then the errors of metabolite detection were obtained through data analysis. Results: (1) With FOV 200 mm and average times 40, phosphate solution phantom had a good reproducibility with the error less than 5.38%. Under respiration gating, the largest detection error of metabolites within five volunteers was phosphomonoesters (PME) 39.5%, inorganic phosphate (Pi) 40.4%, phosphodiesters (PDE) 23.2%, adenosine triphosphate; γ-ATP 24.3%, α-ATP 20.1%, β-ATP 24.9%, respectively. (2) The baseline of spectra was smoother and the error was less with respiration gating than that without respiration gating. (3) During the phantom test, with average times 40, change FOV to 280 mm and 400 mm, the detection errors were 4.96% and 4.47%. With FOV 200 mm and average times 20, 40, 80, the detection errors were 8.86%, 5.38% and 4.40%, corresponding acquisition time were 1.27 min, 2.53 min and 5.06 min. Conclusion: Detection of phosphorus metabolites in human liver with 2D CSI is a stable and useful technique. Scan parameters should be carefully selected, and other influencing factors of detection must be also noticed during examination. (authors)

  15. Combining ambiguous chemical shift mapping with structure-based backbone and NOE assignment from 15N-NOESY

    KAUST Repository

    Jang, Richard

    2011-01-01

    Chemical shift mapping is an important technique in NMRbased drug screening for identifying the atoms of a target protein that potentially bind to a drug molecule upon the molecule\\'s introduction in increasing concentrations. The goal is to obtain a mapping of peaks with known residue assignment from the reference spectrum of the unbound protein to peaks with unknown assignment in the target spectrum of the bound protein. Although a series of perturbed spectra help to trace a path from reference peaks to target peaks, a one-to-one mapping generally is not possible, especially for large proteins, due to errors, such as noise peaks, missing peaks, missing but then reappearing, overlapped, and new peaks not associated with any peaks in the reference. Due to these difficulties, the mapping is typically done manually or semi-automatically. However, automated methods are necessary for high-throughput drug screening. We present PeakWalker, a novel peak walking algorithm for fast-exchange systems that models the errors explicitly and performs many-to-one mapping. On the proteins: hBclXL, UbcH5B, and histone H1, it achieves an average accuracy of over 95% with less than 1.5 residues predicted per target peak. Given these mappings as input, we present PeakAssigner, a novel combined structure-based backbone resonance and NOE assignment algorithm that uses just 15N-NOESY, while avoiding TOCSY experiments and 13C- labeling, to resolve the ambiguities for a one-toone mapping. On the three proteins, it achieves an average accuracy of 94% or better. Copyright © 2011 ACM.

  16. Chemical shift of U L3 edges in different uranium compounds obtained by X-ray absorption spectroscopy with synchrotron radiation

    Indian Academy of Sciences (India)

    D Joseph; C Nayak; P Venu Babu; S N Jha; D Bhattacharyya

    2014-05-01

    Uranium L3 X-ray absorption edge was measured in various compounds containing uranium in U4+, U5+ and U6+ oxidation states. The measurements have been carried out at the Energy Dispersive EXAFS beamline (BL-08) at INDUS-2 synchrotron radiation source at RRCAT, Indore. Energy shifts of ∼ 2–3 eV were observed for U L3 edge in the U-compounds compared to their value in elemental U. The different chemical shifts observed for the compounds having the same oxidation state of the cation but different anions or ligands show the effect of different chemical environments surrounding the cations in determining their X-ray absorption edges in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on U cation in the above compounds.

  17. Phosphorus-31 nuclear magnetic resonance of double- and triple-helical nucleic acids. Phosphorus-31 chemical shifts as a probe of phosphorus-oxygen ester bond torsional angles

    International Nuclear Information System (INIS)

    The temperature dependence to the 31P NMR spectra of poly[d(GC)]-poly[d(GC)], d(GC)4, phenylalanine tRNA (yeast) and mixtures of poly(A) + oligo(U) is presented. The 31P NMR spectra of mixtures of complementary RNA and of the poly d(GC) self-complementary DNA provide torsional information on the phosphate ester conformation in the double, triple, and ''Z'' helix. The increasing downfield shift with temperature for the single-strand nucleic acids provides a measure of the change in the phosphate ester conformation in the single helix to coil conversion. A seperate upfield peak (20-26% of the total phosphates) is observed at lower temperatures in the oligo(U)-poly(A) mixtures which is assigned to the double helix/triple helix. Proton NMR and UV spectra confirm the presence of the multistrand forms. The 31P chemical shift for the double helix/triple helix is 0.2-0.5 ppm upfield from the chemical shift for the single helix which in turn is 1.0 ppm upfield from the chemical shift for the random coil conformation

  18. Automated prediction of 15N, 13Cα, 13Cβ and 13C' chemical shifts in proteins using a density functional database

    International Nuclear Information System (INIS)

    A database of peptide chemical shifts, computed at the density functional level, has been used to develop an algorithm for prediction of 15N and 13C shifts in proteins from their structure; the method is incorporated into a program called SHIFTS (version 4.0). The database was built from the calculated chemical shift patterns of 1335 peptides whose backbone torsion angles are limited to areas of the Ramachandran map around helical and sheet configurations. For each tripeptide in these regions of regular secondary structure (which constitute about 40% of residues in globular proteins) SHIFTS also consults the database for information about sidechain torsion angle effects for the residue of interest and for the preceding residue, and estimates hydrogen bonding effects through an empirical formula that is also based on density functional calculations on peptides. The program optionally searches for alternate side-chain torsion angles that could significantly improve agreement between calculated and observed shifts. The application of the program on 20 proteins shows good consistency with experimental data, with correlation coefficients of 0.92, 0.98, 0.99 and 0.90 and r.m.s. deviations of 1.94, 0.97, 1.05, and 1.08 ppm for 15N, 13Cα, 13Cβ and 13C', respectively. Reference shifts fit to protein data are in good agreement with 'random-coil' values derived from experimental measurements on peptides. This prediction algorithm should be helpful in NMR assignment, crystal and solution structure comparison, and structure refinement

  19. Multilayer MoS2 prepared by one-time and repeated chemical vapor depositions: anomalous Raman shifts and transistors with high ON/OFF ratio

    Science.gov (United States)

    Wu, Chong-Rong; Chang, Xiang-Rui; Chang, Shu-Wei; Chang, Chung-En; Wu, Chao-Hsin; Lin, Shih-Yen

    2015-11-01

    We show that multilayer molybdenum disulfide (MoS2) grown with the chemical vapor deposition (CVD) may exhibit quite distinct behaviors of Raman shifts from those of exfoliated ones. The anomalous Raman shifts depend on CVD growth modes and are attributed to the modified dielectric screening and interlayer coupling of MoS2 in various growth conditions. With repeated CVD growths, we demonstrated the precise control over the layer number of MoS2. A decently large drain current, high ON/OFF ratio of 105, and enhanced field-effect mobility can be achieved in transistors fabricated on the six-layer MoS2.

  20. First-principles calculation of spectral features, chemical shift and absolute threshold of ELNES and XANES using a plane wave pseudopotential method

    International Nuclear Information System (INIS)

    Spectral features, chemical shifts, and absolute thresholds of electron energy loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) for selected compounds, i.e. TiO2 (rutile), TiO2 (anatase), SrTiO3, Ti2O3, Al2O3, AlN and β-Ga2O3, were calculated by a plane wave pseudopotential method. Experimental ELNES/XANES of those compounds were well reproduced when an excited pseudopotential, which includes a core hole, was used. In addition to the spectral features, it was found that chemical shifts among different compounds were also reproduced by correcting the contribution of the excited pseudopotentials to the energy of the core orbital.

  1. Deciphering Noncovalent Interactions Accompanying 7,7,8,8-Tetracyanoquinodimethane Encapsulation within Biphene[n]arenes: Nucleus-Independent Chemical Shifts Approach.

    Science.gov (United States)

    Lande, Dipali N; Rao, Soniya S; Gejji, Shridhar P

    2016-07-18

    Binding of novel biphene[n]arene hosts to antiaromatic 7,7,8,8-tetracyanoquinodimethane (TCNQ) are investigated by DFT. Biphene[4]arene favors the inclusion complex through noncovalent interactions, such as hydrogen bonding, π-π stacking, C-H⋅⋅⋅π, and C-H⋅⋅⋅H-C dihydrogen bonding. Donor-acceptor complexation renders aromatic character to the guest through charge transfer. The formation of TCNQ anionic radicals through supramolecular π stacking significantly influences its chemical and photophysical behavior. Electron density reorganization consequent to encapsulation of TCNQ reflects in the shift of characteristic vibrations in the IR spectra. The accompanying aromaticities arising from the induced ring currents are analyzed by employing nucleus-independent chemical shifts based profiles. PMID:27028656

  2. Correlation between 1H NMR chemical shifts of hydroxyl protons in n-hexanol/cyclohexane and molecular association properties investigated using density functional theory

    Science.gov (United States)

    Flores, Mario E.; Shibue, Toshimichi; Sugimura, Natsuhiko; Nishide, Hiroyuki; Moreno-Villoslada, Ignacio

    2016-01-01

    Association of n-hexanol molecules in cyclohexane forming clusters is studied by DFT and 1H NMR. Geometry optimization, corrected binding energies, charge distributions, charge transfer energies, and 1H NMR chemical shifts have been obtained. The calculated chemical shifts of hydroxyl protons have been correlated to experimental data obtained in the range of n-hexanol molar fraction between 0.002 and 0.2, showing that n-hexanol molecules at a molar fraction around 0.1, where well-structured hydrogen bond networks are observed, tend to form linear pentamers and hexamers. The experimental data are consistent with the continuous linear association thermodynamic model, showing a dimensionless association constant of 284.

  3. Solid state NMR of proteins at high MAS frequencies: symmetry-based mixing and simultaneous acquisition of chemical shift correlation spectra

    Energy Technology Data Exchange (ETDEWEB)

    Bellstedt, Peter [Fritz Lipmann Institute, Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany); Herbst, Christian [Ubon Ratchathani University, Department of Physics, Faculty of Science (Thailand); Haefner, Sabine; Leppert, Joerg; Goerlach, Matthias; Ramachandran, Ramadurai, E-mail: raman@fli-leibniz.de [Fritz Lipmann Institute, Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany)

    2012-12-15

    We have carried out chemical shift correlation experiments with symmetry-based mixing sequences at high MAS frequencies and examined different strategies to simultaneously acquire 3D correlation spectra that are commonly required in the structural studies of proteins. The potential of numerically optimised symmetry-based mixing sequences and the simultaneous recording of chemical shift correlation spectra such as: 3D NCAC and 3D NHH with dual receivers, 3D NC Prime C and 3D C Prime NCA with sequential {sup 13}C acquisitions, 3D NHH and 3D NC Prime H with sequential {sup 1}H acquisitions and 3D CANH and 3D C'NH with broadband {sup 13}C-{sup 15}N mixing are demonstrated using microcrystalline samples of the {beta}1 immunoglobulin binding domain of protein G (GB1) and the chicken {alpha}-spectrin SH3 domain.

  4. Structure, solvent, and relativistic effects on the NMR chemical shifts in square-planar transition-metal complexes: assessment of DFT approaches

    Czech Academy of Sciences Publication Activity Database

    Vícha, J.; Novotný, J.; Straka, Michal; Repisky, M.; Ruud, K.; Komorovsky, S.; Marek, R.

    2015-01-01

    Roč. 17, č. 38 (2015), s. 24944-24955. ISSN 1463-9076 R&D Projects: GA ČR(CZ) GA14-03564S Institutional support: RVO:61388963 Keywords : NMR chemical shifts * transition metal complexes * relativistic effects * method calibration Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.493, year: 2014 http://pubs.rsc.org/en/content/articlepdf/2015/cp/c5cp04214c

  5. Anisotropy of rare-earth magnets

    Institute of Scientific and Technical Information of China (English)

    R.Skomski; D.J.Sellmyer

    2009-01-01

    Rare-earth intermetallics such as Nd2FeI4B and Sm-Co are widely used as high-performance permanent magnets,because they combine high magnetocrystalline anisotropy with reasonable magnetization and Curie temperature.The anisotropy is a combined effect of spin-orbit coupling and electrostatic crystal-field interactions.The main contribution comes from the rare-earth 4f electrons,which are well-screened from the crystalline environment but exhibit a strong spin-orbit coupling.In this limit,the magnetocrystalline anisotropy has a very transparent physical interpretation,the anisotropy energy essentially being equal to the energy of Hund's-rules 4f ion in the crystal field.The corresponding expression for the lowest-order uniaxial anisotropy constant K1 is used to discuss rare-earth substitutions,which have recently attracted renewed interest due to shifts in the rare-earth production and demand.Specific phenomena reviewed in this article are the enhancement of the anisotropy of Sm2Fe17 due to interstitial nitrogen,the use of Sm-Co magnets for high-temperature applications,and the comparison of rare-earth single-ion anisotropy with other single-ion and two-ion mechanisms.

  6. Reproducibility and influencing factors of 31P MR spectroscopy in rabbit liver with two-dimensional chemical shift imaging

    International Nuclear Information System (INIS)

    Objective: To investigate the reproducibility and influencing factors of relative quantification of phosphorus metabolites with two-dimensional chemical shift imaging (2D CSI) in rabbit liver. Methods: Using 2D CSI MRS, 500 ml phosphate (NaH2PO4) solution phantom with 0.05 mol/L concentration and one healthy rabbit were scanned 30 times respectively in one day and rescanned 30 times in the next day, and the stability of MR scanner and reproducibility of within-run and between-days in the same individual were analyzed. Each of thirty rabbits was scanned and rescanned one time respectively in different days, and the reproducibility of between-days in one group was analyzed. The data were statistically analyzed with t tests. Results: (1) Phosphate solution phantom had a good reproducibility of within-run with the coefficient variation (CV) of 4.92% and 5.12% respectively in different two days. No significant change of phosphorus metabolites was detected in between-days, which was 16.68±0.82 and 16.56± 0.85 respectively (t=0.665, P>0.05). (2) The CV of metabolites in one healthy rabbit ranged from 8.04% to 34.13%. Among the metabolites, β-ATP had the best reproducibility with the CV less than 10%. PME was 0.88±0.28 and 0.88±0.30, PDE was 4.35±0.66 and 4.35±0.66, Pi was 0.95±0.30 and 0.97±0.28, α-ATP was 5.58±0.60 and 5.61±0.61, β-ATP was 2.70±0.22 and 2.71± 0.22, γ-ATP was 2.20±0.63 and 2.18±0.44 respectively, no significant changes of metabolites were detected in between-days (P>0.05). (3) The CV of metabolites in 30 healthy rabbits ranged from 8.48% to 36.21%. Among the metabolites, β-ATP had the best reproducibility with CV less than 10%. PME was 0.84±0.30 and 0.79±0.28, PDE was 4.29±0.72 and 3.94±0.84, Pi was 0.91±0.28 and 0.92± 0.31, α-ATP was 5.65±0.66 and 5.36±0.60, β-ATP was 2.71±0.23 and 2.66±0.25, γ-ATP was 2.07±0.29 and 1.99±0.37 respectively, no significant changes of metabolites were detected in between-days (P>0

  7. Transport-induced shifts in condensate dew-point and composition in multicomponent systems with chemical reaction

    Science.gov (United States)

    Rosner, D. E.; Nagarajan, R.

    1985-01-01

    Partial heterogeneous condensation phenomena in multicomponent reacting systems are analyzed taking into consideration the chemical element transport phenomena. It is demonstrated that the dew-point surface temperature in chemically reactive systems is not a purely thermodynamic quantity, but is influenced by the multicomponent diffusion and Soret-mass diffusion phenomena. Several distinct dew-points are shown to exist in such systems and, as a result of transport constraints, the 'sharp' locus between two chemically distinct condensates is systematically moved to a difference mainstream composition.

  8. Prediction of microvascular invasion of hepatocellular carcinomas with gadoxetic acid-enhanced MR imaging: Impact of intra-tumoral fat detected on chemical-shift images

    Energy Technology Data Exchange (ETDEWEB)

    Min, Ji Hye [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Kim, Young Kon, E-mail: jmyr@dreamwiz.com [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Lim, Sanghyeok [Department of Radiology, Guri Hospital, Hanyang University College of Medicine, Guri (Korea, Republic of); Jeong, Woo Kyoung; Choi, Dongil; Lee, Won Jae [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2015-06-15

    Highlights: • Intra-tumoral fat detected with MR imaging may suggest lower risk for MVI of HCC. • Alfa-fetoprotein, tumor size, and fat component were associated with MVI of HCC. • Chemical shift MRI should be considered for the evaluation of HCC. - Abstract: Purpose: To investigate the impact of intra-tumoral fat detected by chemical-shift MR imaging in predicting the MVI of HCC. Materials and methods: Gadoxetic acid-enhanced MR imaging of 365 surgically proven HCCs from 365 patients (306 men, 59 women; mean age, 55.6 years) were evaluated. HCCs were classified into two groups, fat-containing and non-fat-containing, based on the presence of fat on chemical-shift images. Fat-containing HCCs were subdivided into diffuse or focal fatty change groups. Logistic regression analyses were used to identify clinical and MR findings associated with MVI. Results: Based on MR imaging, 66 tumors were classified as fat-containing HCCs and 299 as non-fat-containing HCCs. Among the 66 fat-containing HCCs, 38 (57.6%) showed diffuse fatty changes and 28 (42.4%) showed focal fatty changes. MVI was present in 18 (27.3%) fat-containing HCCs and in 117 (39.1%) non-fat-containing HCCs (P = 0.07). Univariate analysis revealed that serum alpha-fetoprotein (AFP) and tumor size were significantly associated with MVI (P < 0.001). A multiple logistic regression analysis showed that log AFP (odds ratio 1.178, P = 0.0016), tumor size (odds ratio 1.809, P < 0.001), and intra-tumoral fat (odds ratio 0.515, P = 0.0387) were independent variables associated with MVI. Conclusion: Intra-tumoral fat detected with MR imaging may suggest lower risk for MVI of HCC and, therefore, a possibly more favorable prognosis, but the clinical value of this finding is uncertain.

  9. Secondary structural analysis of proteins based on 13C chemical shift assignments in unresolved solid-state NMR spectra enhanced by fragmented structure database

    International Nuclear Information System (INIS)

    Magic-angle-spinning solid-state 13C NMR spectroscopy is useful for structural analysis of non-crystalline proteins. However, the signal assignments and structural analysis are often hampered by the signal overlaps primarily due to minor structural heterogeneities, especially for uniformly-13C,15N labeled samples. To overcome this problem, we present a method for assigning 13C chemical shifts and secondary structures from unresolved two-dimensional 13C–13C MAS NMR spectra by spectral fitting, named reconstruction of spectra using protein local structures (RESPLS). The spectral fitting was conducted using databases of protein fragmented structures related to 13Cα, 13Cβ, and 13C′ chemical shifts and cross-peak intensities. The experimental 13C–13C inter- and intra-residue correlation spectra of uniformly isotope-labeled ubiquitin in the lyophilized state had a few broad peaks. The fitting analysis for these spectra provided sequence-specific Cα, Cβ, and C′ chemical shifts with an accuracy of about 1.5 ppm, which enabled the assignment of the secondary structures with an accuracy of 79 %. The structural heterogeneity of the lyophilized ubiquitin is revealed from the results. Test of RESPLS analysis for simulated spectra of five different types of proteins indicated that the method allowed the secondary structure determination with accuracy of about 80 % for the 50–200 residue proteins. These results demonstrate that the RESPLS approach expands the applicability of the NMR to non-crystalline proteins exhibiting unresolved 13C NMR spectra, such as lyophilized proteins, amyloids, membrane proteins and proteins in living cells.

  10. Prediction of microvascular invasion of hepatocellular carcinomas with gadoxetic acid-enhanced MR imaging: Impact of intra-tumoral fat detected on chemical-shift images

    International Nuclear Information System (INIS)

    Highlights: • Intra-tumoral fat detected with MR imaging may suggest lower risk for MVI of HCC. • Alfa-fetoprotein, tumor size, and fat component were associated with MVI of HCC. • Chemical shift MRI should be considered for the evaluation of HCC. - Abstract: Purpose: To investigate the impact of intra-tumoral fat detected by chemical-shift MR imaging in predicting the MVI of HCC. Materials and methods: Gadoxetic acid-enhanced MR imaging of 365 surgically proven HCCs from 365 patients (306 men, 59 women; mean age, 55.6 years) were evaluated. HCCs were classified into two groups, fat-containing and non-fat-containing, based on the presence of fat on chemical-shift images. Fat-containing HCCs were subdivided into diffuse or focal fatty change groups. Logistic regression analyses were used to identify clinical and MR findings associated with MVI. Results: Based on MR imaging, 66 tumors were classified as fat-containing HCCs and 299 as non-fat-containing HCCs. Among the 66 fat-containing HCCs, 38 (57.6%) showed diffuse fatty changes and 28 (42.4%) showed focal fatty changes. MVI was present in 18 (27.3%) fat-containing HCCs and in 117 (39.1%) non-fat-containing HCCs (P = 0.07). Univariate analysis revealed that serum alpha-fetoprotein (AFP) and tumor size were significantly associated with MVI (P < 0.001). A multiple logistic regression analysis showed that log AFP (odds ratio 1.178, P = 0.0016), tumor size (odds ratio 1.809, P < 0.001), and intra-tumoral fat (odds ratio 0.515, P = 0.0387) were independent variables associated with MVI. Conclusion: Intra-tumoral fat detected with MR imaging may suggest lower risk for MVI of HCC and, therefore, a possibly more favorable prognosis, but the clinical value of this finding is uncertain

  11. Other compounds isolated from Simira glaziovii and the {sup 1}H and {sup 13}C NMR chemical shift assignments of new 1-epi-castanopsol

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Marcelo F. de; Vieira, Ivo J. Curcino [Universidade Federal Rural do Rio de Janeiro, Seropedica, RJ (Brazil). Dept. de Quimica; Braz-Filho, Raimundo [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacases, RJ (Brazil). Centro de Ciencias Tecnologicas. Lab. de Ciencias Quimicas; Carvalho, Mario G. de, E-mail: mgeraldo@ufrrj.br [Universidade Federal do Rio de Janeiro (NPPN/UFRJ), RJ (Brazil). Centro de Ciencias da Saude. Nucleo de Pesquisa em Produtos Naturais

    2012-07-01

    A new triterpene, 1-epi-castanopsol, besides eleven known compounds: sitosterol, stigmasterol, campesterol, lupeol, lupenone, simirane B, syringaresinol, scopoletin, isofraxidin, 6,7,8-trimethoxycoumarin and harman, were isolated from the wood of Simira glaziovii. The structures of the known compounds were defined by 1D, 2D {sup 1}H, {sup 13}C NMR spectra data analyses and comparison with literature data. The detailed spectral data analyses allowed the definition of the structure of the new 1-epi isomer of castanopsol and performance of {sup 1}H and {sup 13}C NMR chemical shift assignments. (author)

  12. (1)H, (13)C, and (15)N chemical shift assignments of cyanobacteriochrome NpR6012g4 in the green-absorbing photoproduct state.

    Science.gov (United States)

    Lim, Sunghyuk; Yu, Qinhong; Rockwell, Nathan C; Martin, Shelley S; Lagarias, J Clark; Ames, James B

    2016-04-01

    Cyanobacteriochromes (CBCRs) are cyanobacterial photosensory proteins with a tetrapyrrole (bilin) chromophore that belong to the phytochrome superfamily. Like phytochromes, CBCRs photoconvert between two photostates with distinct spectral properties. NpR6012g4 from Nostoc punctiforme is a model system for widespread CBCRs with conserved red/green photocycles. Atomic-level structural information for the photoproduct state in this subfamily is not known. Here, we report NMR backbone chemical shift assignments of the light-activated state of NpR6012g4 (BMRB no. 26577) as a first step toward determining its atomic resolution structure. PMID:26537963

  13. Other compounds isolated from Simira glaziovii and the 1H and 13C NMR chemical shift assignments of new 1-epi-castanopsol

    International Nuclear Information System (INIS)

    A new triterpene, 1-epi-castanopsol, besides eleven known compounds: sitosterol, stigmasterol, campesterol, lupeol, lupenone, simirane B, syringaresinol, scopoletin, isofraxidin, 6,7,8-trimethoxycoumarin and harman, were isolated from the wood of Simira glaziovii. The structures of the known compounds were defined by 1D, 2D 1H, 13C NMR spectra data analyses and comparison with literature data. The detailed spectral data analyses allowed the definition of the structure of the new 1-epi isomer of castanopsol and performance of 1H and 13C NMR chemical shift assignments. (author)

  14. 1H and 13C NMR Chemical Shift Assignments and Conformational Analysis for the Two Diastereomers of the Vitamin K Epoxide Reductase Inhibitor Brodifacoum

    International Nuclear Information System (INIS)

    Proton and 13C NMR chemical shift assignments and 1H-1H scalar couplings for the two diastereomers of the vitamin K epoxide reductase (VKOR) inhibitor brodifacoum have been determined from acetone solutions containing both diastereomers. Data were obtained from homo- and heteronuclear correlation spectra acquired at 1H frequencies of 750 and 900 MHz over a 268-303 K temperature range. Conformations inferred from scalar coupling and 1-D NOE measurements exhibit large differences between the diastereomers. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  15. 129Xe-NMR of xenon adsorbed on zeolites: determination of the dimensions of the void space from the chemical shift δ(129Xe)

    International Nuclear Information System (INIS)

    The chemical shift δS of xenon adsorbed on zeolite and extrapolated to zero concentration depends only on the internal void space of the solid. The smaller the channels or cavities, or the more restricted the diffusion, the greater δS becomes. We have calculated the theoretical values of the mean free path l-bar of xenon adsorbed in various zeolites. We deduce from them the dependence of the δS on l-bar. It is now possible to determine the dimensions of any void space in which xenon can be adsorbed. 4 refs.; 2 figs.; 3 tabs

  16. 13C-NMR chemical shift databases as a quick tool to evaluate structural models of humic substances

    DEFF Research Database (Denmark)

    Nyrop Albers, Christian; Hansen, Poul Erik

    2010-01-01

    Models for humic and fulvic acids are discussed based on 13C liquid state NMR spectra combined with results from elemental analysis and titration studies. The analysis of NMR spectra is based on a full reconstruction of the NMR spectrum done with help of 13C-NMR data bases by adding up chemical s...

  17. DFT Studies on Thermal Stabilities,Electronic Structures, and 13C Chemical Shifts of C24O2 Based on Fullerene C24(D6)

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen; ZHANG Jing

    2011-01-01

    Quantum chemical calculations on some possible equilibrium geometries of C2402 isomers derived from C24 (D6) and C240 have been performed using density functional theory (DFT) method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C2402 isomers at the ground state have been calculated at the B3LYP/6-31G(d) level of theory. And the 1,4,2,5-C2402 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies,IR spectrum, and 13C chemical shifts of various C2402 isomers have been calculated and analyzed.

  18. Quantitative and qualitative shifts in defensive metabolites define chemical defense investment during leaf development in Inga, a genus of tropical trees.

    Science.gov (United States)

    Wiggins, Natasha L; Forrister, Dale L; Endara, María-José; Coley, Phyllis D; Kursar, Thomas A

    2016-01-01

    Selective pressures imposed by herbivores are often positively correlated with investments that plants make in defense. Research based on the framework of an evolutionary arms race has improved our understanding of why the amount and types of defenses differ between plant species. However, plant species are exposed to different selective pressures during the life of a leaf, such that expanding leaves suffer more damage from herbivores and pathogens than mature leaves. We hypothesize that this differential selective pressure may result in contrasting quantitative and qualitative defense investment in plants exposed to natural selective pressures in the field. To characterize shifts in chemical defenses, we chose six species of Inga, a speciose Neotropical tree genus. Focal species represent diverse chemical, morphological, and developmental defense traits and were collected from a single site in the Amazonian rainforest. Chemical defenses were measured gravimetrically and by characterizing the metabolome of expanding and mature leaves. Quantitative investment in phenolics plus saponins, the major classes of chemical defenses identified in Inga, was greater for expanding than mature leaves (46% and 24% of dry weight, respectively). This supports the theory that, because expanding leaves are under greater selective pressure from herbivores, they rely more upon chemical defense as an antiherbivore strategy than do mature leaves. Qualitatively, mature and expanding leaves were distinct and mature leaves contained more total and unique metabolites. Intraspecific variation was greater for mature leaves than expanding leaves, suggesting that leaf development is canalized. This study provides a snapshot of chemical defense investment in a speciose genus of tropical trees during the short, few-week period of leaf development. Exploring the metabolome through quantitative and qualitative profiling enables a more comprehensive examination of foliar chemical defense investment

  19. Final Technical Report: A Paradigm Shift in Chemical Processing: New Sustainable Chemistries for Low-VOC Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Kenneth F.

    2006-07-26

    The project employed new processes to make emulsion polymers from reduced levels of petroleum-derived chemical feedstocks. Most waterborne paints contain spherical, emulsion polymer particles that serve as the film-forming binder phase. Our goal was to make emulsion polymer particles containing 30 percent feedstock that would function as effectively as commercial emulsions made from higher level feedstock. The processes developed yielded particles maintained their film formation capability and binding capacity while preserving the structural integrity of the particles after film formation. Rohm and Haas Company (ROH) and Archer Daniels Midland Company (ADM) worked together to employ novel polymer binders (ROH) and new, non-volatile, biomass-derived coalescing agents (ADM). The University of Minnesota Department of Chemical Engineering and Material Science utilized its unique microscopy capabilities to characterize films made from the New Emulsion Polymers (NEP).

  20. Comparative molecular field analysis and comparative molecular similarity index analysis studies on 1H NMR chemical shift of NH group of diaryl triazene derivatives.

    Science.gov (United States)

    Rofouie, M K; Salahinejad, M; Ghasemi, J B; Aghaei, A

    2013-05-01

    Comparative molecular field analysis (CoMFA), comparative molecular field analysis region focusing (CoMFA-RF) for optimizing the region for the final partial least square analysis, and comparative molecular similarity indices analysis (CoMSIA) methods were employed to develop three-dimensional quantitative structure-activity relationship (3D-QSAR) models of (1)H NMR chemical shift of NH proton of diaryl triazene derivatives. The best orientation was searched by all-orientation search (AOS) strategy to minimize the effect of the initial orientation of the structures. The predictive abilities of CoMFA-RF and CoMSIA models were determined using a test set of ten compounds affording predictive correlation coefficients of 0.721 and 0.754, respectively, indicating good predictive power. For further model validation, cross validation (leave one out), progressive scrambling, and bootstrapping were also applied. The accuracy and speed of obtained 3D-QSAR models for the prediction of (1)H NMR chemical shifts of NH group of diaryl triazene derivatives were greater compared to some computational well-known procedures. PMID:23456682

  1. Fractional enrichment of proteins using [2-{sup 13}C]-glycerol as the carbon source facilitates measurement of excited state {sup 13}Cα chemical shifts with improved sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Ahlner, Alexandra; Andresen, Cecilia; Khan, Shahid N. [Linköping University, Division of Chemistry, Department of Physics, Chemistry and Biology (Sweden); Kay, Lewis E. [The University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry, One King’s College Circle (Canada); Lundström, Patrik, E-mail: patlu@ifm.liu.se [Linköping University, Division of Chemistry, Department of Physics, Chemistry and Biology (Sweden)

    2015-07-15

    A selective isotope labeling scheme based on the utilization of [2-{sup 13}C]-glycerol as the carbon source during protein overexpression has been evaluated for the measurement of excited state {sup 13}Cα chemical shifts using Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion (RD) experiments. As expected, the fractional incorporation of label at the Cα positions is increased two-fold relative to labeling schemes based on [2-{sup 13}C]-glucose, effectively doubling the sensitivity of NMR experiments. Applications to a binding reaction involving an SH3 domain from the protein Abp1p and a peptide from the protein Ark1p establish that accurate excited state {sup 13}Cα chemical shifts can be obtained from RD experiments, with errors on the order of 0.06 ppm for exchange rates ranging from 100 to 1000 s{sup −1}, despite the small fraction of {sup 13}Cα–{sup 13}Cβ spin-pairs that are present for many residue types. The labeling approach described here should thus be attractive for studies of exchanging systems using {sup 13}Cα spin probes.

  2. Brain temperature and pH measured by 1H chemical shift imaging of a thulium agent

    OpenAIRE

    Coman, Daniel; Trubel, Hubert K.; Rycyna, Robert E.; Hyder, Fahmeed

    2009-01-01

    Temperature and pH are two of the most important physiological parameters and are believed to be tightly regulated because they are intricately related to energy metabolism in living organisms. Temperature and/or pH data in mammalian brain are scarce, however, mainly due to lack of precise and non-invasive methods. At 11.7T, we demonstrate that a thulium-based macrocyclic complex infused through the blood stream can be used to obtain temperature and pH maps of rat brain in vivo by 1H chemical...

  3. Correlations of the chemical shift on fasly rotating biological solids by means of NMR spectroscopy; Korrelationen der chemischen Verschiebung an schnell rotierenden biologischen Festkoerpern mittels NMR-Spektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Herbst, Christian

    2010-04-27

    The basic aim of the thesis was the development and improvement of homo- and heteronuclear feedback sequences for the generation of correlation spectra of the chemical shift. In a first step the possibility of the acquisition of {sup 13}C-{sup 13} correlation spectra of the chemical shift by means of inversion pulses with low RF power factor was studied. Furthermore it was shown that broad-band phase-modulated inversion and universal rotational pulses can be constructed by means of global optimization procedures like the genetic algorithms under regardment of the available RF field strength. By inversion, universal rotational, and 360 pulses as starting values of the optimization efficient homonuclear CN{sub n}{sup {nu}} and RN{sub n}{sup {nu}} mixing sequences as well as heteronuclear RN{sub n}{sup {nu}{sub s},{nu}{sub k}} feedback sequences were generated. The satisfactory power of the numerically optimized sequences was shown by means of the simulation as well by means of correlation experiments of the chemical shift of L-histidine, L-arginine, and the (CUG){sub 97}-RNA. This thesis deals furthermore with the possibility to acquire simultaneously different signals with several receivers. By means of numerically optimized RN{sub n}{sup {nu}{sub s},{nu}{sub k}} pulse sequences both {sup 15}N-{sup 13}C and {sup 13}C-{sup 15}N correlation spectra were simultaneously generated. Furthermore it could be shown that the simultaneous acquisition of 3D-{sup 15}N-{sup 13}C-{sup 13}C and {sup 13}C-{sup 15}N-({sup 1}H)-{sup 1}H correlation spectra is possible. By this in only one measurement process resonance assignments can be met and studies of the global folding performed. A further application of several receivers is the simultaneous acquisition of CHHC, NHHN, NHHC, as well as CHHN spectra. By such experiments it is possible to characterize the hydrogen-bonding pattern and the glycosidic torsion angle {sup {chi}} in RNA. This was demonstrated by means of the (CUG){sub 97

  4. Spin-orbit ZORA and four-component Dirac-Coulomb estimation of relativistic corrections to isotropic nuclear shieldings and chemical shifts of noble gas dimers

    DEFF Research Database (Denmark)

    Jankowska, Marzena; Kupka, Teobald; Stobiński, Leszek;

    2016-01-01

    Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for non-relativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton and xenon dimers and free atoms. Relativistic...... corrections were calculated with the scalar and spin-orbit zeroth-order regular approximation Hamiltonian in combination with the large Slater-type basis set QZ4P as well as with the 4-component Dirac-Coulomb Hamiltonian using Dyall’s acv4z basis sets. The relativistic corrections to the nuclear magnetic...... shieldings and chemical shifts are combined with non-relativistic CCSD(T) calculations using the very large polarization-consistent basis sets aug-pcSseg-4 for He, Ne and Ar, aug-pcSseg-3 for Kr and the AQZP basis set for Xe. For the dimers also zero-point vibrational corrections obtained at the CCSD...

  5. The interplay between transient a-helix formation and side chain rotamer distributions in disordered proteins probed by methyl chemical shifts

    DEFF Research Database (Denmark)

    Kjærgaard, Magnus; Iesmantavicius, Vytautas; Poulsen, Flemming M

    2011-01-01

    shifts can in principle report the conformations of aliphatic side chains in disordered proteins and in order to examine this two model systems were chosen: the acid denatured state of acyl-CoA binding protein (ACBP) and the intrinsically disordered activation domain of the activator for thyroid hormone...... allow a quantitative analysis of the ensemble of ¿(2)-angles of especially leucine residues in disordered proteins. The changes in the rotamer distributions upon denaturation correlate to the changes upon helix induction by the co-solvent trifluoroethanol, suggesting that the side chain conformers are......The peptide backbones of disordered proteins are routinely characterized by NMR with respect to transient structure and dynamics. Little experimental information is, however, available about the side chain conformations and how structure in the backbone affects the side chains. Methyl chemical...

  6. 1H chemical shift imaging of the brain in guanidino methyltransferase deficiency, a creatine deficiency syndrome; guanidinoacetate accumulation in the gray matter

    International Nuclear Information System (INIS)

    MR spectroscopy results in a mild case of guanidinoacetate methyltransferase (GAMT) deficiency are presented. The approach differs from previous MRS studies in the acquisition of a chemical shift imaging spectral map showing gray and white matter with the corresponding spectra in one overview. MR spectroscopy revealed guanidinoacetate (GAA) in the absence of creatine. New is that GAA signals are more prominent in gray matter than in white. In the prevailing view, that enzyme deficiency is localized in liver and pancreas and that all GAA is transported into the brain from the blood and the cerebrospinal fluid, this would be compatible with a more limited uptake and/or better clearance of GAA from the white matter compared to the grey matter. (orig.)

  7. Chemical shifts of 17O, 183W NMR and state of [ZW10O36]n-heteropolyanions in aqueous solutions

    International Nuclear Information System (INIS)

    By 17O, 183W NMR aqueous solutions of Na- and K-salts of heteropolyanions (HPA) [ZW10O36]n-, where Z = La3+-Er3+, Ce3+, Th4+, U4+, have been studied. HPA in aqueous solution exist as inert in the NMR time scale (1-100 ms) complexes, moreover, coordination sphere of Z is filled with O atoms of oxotungstate ligands, as in crystal state. The character of paramagnetic shifts (LIS) of all HPA atoms has been defined - in O and W atoms nearest to Z in LIS contact contribution prevails, for W-O-W bridge atoms and internal O atom dipole contribution prevails, for the rest atoms the dipole and contact contributions are comparable. The change in chemical shifts in lanthanide series depends not only on magnetic properties of element, but also on structural change in HPA. The width of 17O NMR lines for HPA studied (except HPA containing gadolinium) is determined by quadrupole mechanism of nuclear magnetic relaxation. 24 refs., 2 figs., 3 tabs

  8. Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative (1)H and (13)C NMR chemical shifts.

    Science.gov (United States)

    Marekha, Bogdan A; Kalugin, Oleg N; Bria, Marc; Idrissi, Abdenacer

    2015-09-21

    Mixtures of ionic liquids (ILs) with polar aprotic solvents in different combinations and under different conditions (concentration, temperature etc.) are used widely in electrochemistry. However, little is known about the key intermolecular interactions in such mixtures depending on the nature of the constituents and mixture composition. In order to systematically address the intermolecular interactions, the chemical shift variation of (1)H and (13)C nuclei has been followed in mixtures of imidazolium ILs 1-n-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate (BmimTfO) and 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) with molecular solvent acetonitrile (AN) over the entire composition range at 300 K. The concept of relative chemical shift variation is proposed to assess the observed effects on a unified and unbiased scale. We have found that hydrogen bonds between the imidazolium ring hydrogen atoms and electronegative atoms of anions are stronger in BmimBF4 and BmimTfO ILs than those in BmimTFSI and BmimPF6. Hydrogen atom at position 2 of the imidazolium ring is substantially more sensitive to interionic hydrogen bonding than those at positions 4-5 in the case of BmimTfO and BmimTFSI ILs. These hydrogen bonds are disrupted upon dilution in AN due to ion dissociation which is more pronounced at high dilutions. Specific solvation interactions between AN molecules and IL cations are poorly manifested. PMID:26278514

  9. 31P-MR spectroscopy of all regions of the human heart at 1.5 T with acquisition-weighted chemical shift imaging

    International Nuclear Information System (INIS)

    Aim: Aim of this study was to show whether or not acquisition-weighted chemical shift imaging (AW-CSI) allows the determination of PCr and ATP in the lateral and posterior wall of the human heart at 1.5 T. Methods: 12 healthy volunteers were examined using a conventional chemical shift imaging (CSI) and an AW-CSI. The sequences differed only in the number of repetitions for each point in k space. A hanning function was used as filter function leading to 7 repetitions in the center of the k space and 0 in the corners. Thus, AW-CSI had the same resolution as the CSI sequence. The results for both sequences were analyzed using identically positioned voxels in the septal, anterior, lateral and posterior wall. Results: The determined averaged AW-CSI signal to noise ratios were higher for PCr by a factor of 1.3 and for ATP by 1.4 than those of CSI. The PCr/ATP ratios were higher by a factor of 1.2 - 1.3 and showed a smaller standard deviation in all locations for AW-CSI. The mean PCr/ATP ratios determined by AW-CSI of septal, lateral and posterior wall were almost identical (1.72 - 1.76), while it was higher in the anterior wall (1.9). Conclusions: The reduced contamination in AW-CSI improves the signal to noise ratio and the determination of the PCr/ATP ratio in cardiac 31P spectroscopy compared to CSI with the same resolution. The results in volunteers indicate that AW-CSI renders 31P spectroscopy of the lateral and posterior wall of the human heart feasible for patient studies at 1.5 T. (orig.)

  10. The anisotropy of granular materials

    OpenAIRE

    Alonso-Marroquin, F.; Luding, S.; Herrmann, H. J.

    2004-01-01

    The effect of the anisotropy on the elastoplastic response of two dimensional packed samples of polygons is investigated here, using molecular dynamics simulation. We show a correlation between fabric coefficients, characterizing the anisotropy of the granular skeleton, and the anisotropy of the elastic response. We also study the anisotropy induced by shearing on the subnetwork of the sliding contacts. This anisotropy provides an explanation to some features of the plastic deformation of gra...

  11. Impact of chemical and structural anisotropy on the electrophoretic mobility of spherical soft multilayer particles: the case of bacteriophage MS2.

    Science.gov (United States)

    Langlet, Jérémie; Gaboriaud, Fabien; Gantzer, Christophe; Duval, Jérôme F L

    2008-04-15

    We report a theoretical investigation of the electrohydrodynamic properties of spherical soft particles composed of permeable concentric layers that differ in thickness, soft material density, chemical composition, and flow penetration degree. Starting from a recent numerical scheme developed for the computation of the direct-current electrophoretic mobility (mu) of diffuse soft bioparticles, the dependence of mu on the electrolyte concentration and solution pH is evaluated taking the known three-layered structure of bacteriophage MS2 as a supporting model system (bulk RNA, RNA-protein bound layer, and coat protein). The electrokinetic results are discussed for various layer thicknesses, hydrodynamic flow penetration degrees, and chemical compositions, and are discussed on the basis of the equilibrium electrostatic potential and hydrodynamic flow field profiles that develop within and around the structured particle. This study allows for identifying the cases where the electrophoretic mobility is a function of the inner structural and chemical specificity of the particle and not only of its outer surface properties. Along these lines, we demonstrate the general inapplicability of the notions of zeta potential (zeta) and surface charge for quantitatively interpreting electrokinetic data collected for such systems. We further shed some light on the physical meaning of the isoelectric point. In particular, numerical and analytical simulations performed on structured soft layers in indifferent electrolytic solution demonstrate that the isoelectric point is a complex ionic strength-dependent signature of the flow permeation properties and of the chemical and structural details of the particle. Finally, the electrophoretic mobilities of the MS2 virus measured at various ionic strength levels and pH values are interpreted on the basis of the theoretical formalism aforementioned. It is shown that the electrokinetic features of MS2 are to a large extent determined not only

  12. An automated system designed for large scale NMR data deposition and annotation: application to over 600 assigned chemical shift data entries to the BioMagResBank from the Riken Structural Genomics/Proteomics Initiative internal database

    International Nuclear Information System (INIS)

    Biomolecular NMR chemical shift data are key information for the functional analysis of biomolecules and the development of new techniques for NMR studies utilizing chemical shift statistical information. Structural genomics projects are major contributors to the accumulation of protein chemical shift information. The management of the large quantities of NMR data generated by each project in a local database and the transfer of the data to the public databases are still formidable tasks because of the complicated nature of NMR data. Here we report an automated and efficient system developed for the deposition and annotation of a large number of data sets including 1H, 13C and 15N resonance assignments used for the structure determination of proteins. We have demonstrated the feasibility of our system by applying it to over 600 entries from the internal database generated by the RIKEN Structural Genomics/Proteomics Initiative (RSGI) to the public database, BioMagResBank (BMRB). We have assessed the quality of the deposited chemical shifts by comparing them with those predicted from the PDB coordinate entry for the corresponding protein. The same comparison for other matched BMRB/PDB entries deposited from 2001–2011 has been carried out and the results suggest that the RSGI entries greatly improved the quality of the BMRB database. Since the entries include chemical shifts acquired under strikingly similar experimental conditions, these NMR data can be expected to be a promising resource to improve current technologies as well as to develop new NMR methods for protein studies.

  13. Dynamics-based selective 2D {sup 1}H/{sup 1}H chemical shift correlation spectroscopy under ultrafast MAS conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy, E-mail: ramamoor@umich.edu [Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055 (United States)

    2015-05-28

    Dynamics plays important roles in determining the physical, chemical, and functional properties of a variety of chemical and biological materials. However, a material (such as a polymer) generally has mobile and rigid regions in order to have high strength and toughness at the same time. Therefore, it is difficult to measure the role of mobile phase without being affected by the rigid components. Herein, we propose a highly sensitive solid-state NMR approach that utilizes a dipolar-coupling based filter (composed of 12 equally spaced 90° RF pulses) to selectively measure the correlation of {sup 1}H chemical shifts from the mobile regions of a material. It is interesting to find that the rotor-synchronized dipolar filter strength decreases with increasing inter-pulse delay between the 90° pulses, whereas the dipolar filter strength increases with increasing inter-pulse delay under static conditions. In this study, we also demonstrate the unique advantages of proton-detection under ultrafast magic-angle-spinning conditions to enhance the spectral resolution and sensitivity for studies on small molecules as well as multi-phase polymers. Our results further demonstrate the use of finite-pulse radio-frequency driven recoupling pulse sequence to efficiently recouple weak proton-proton dipolar couplings in the dynamic regions of a molecule and to facilitate the fast acquisition of {sup 1}H/{sup 1}H correlation spectrum compared to the traditional 2D NOESY (Nuclear Overhauser effect spectroscopy) experiment. We believe that the proposed approach is beneficial to study mobile components in multi-phase systems, such as block copolymers, polymer blends, nanocomposites, heterogeneous amyloid mixture of oligomers and fibers, and other materials.

  14. High resolution spectroscopy and chemical shift imaging of hyperpolarized 129Xe dissolved in the human brain in vivo at 1.5 tesla

    Science.gov (United States)

    Rao, Madhwesha; Stewart, Neil J.; Norquay, Graham; Griffiths, Paul D.

    2016-01-01

    Purpose Upon inhalation, xenon diffuses into the bloodstream and is transported to the brain, where it dissolves in various compartments of the brain. Although up to five chemically distinct peaks have been previously observed in 129Xe rat head spectra, to date only three peaks have been reported in the human head. This study demonstrates high resolution spectroscopy and chemical shift imaging (CSI) of 129Xe dissolved in the human head at 1.5 Tesla. Methods A 129Xe radiofrequency coil was built in‐house and 129Xe gas was polarized using spin‐exchange optical pumping. Following the inhalation of 129Xe gas, NMR spectroscopy was performed with spectral resolution of 0.033 ppm. Two‐dimensional CSI in all three anatomical planes was performed with spectral resolution of 2.1 ppm and voxel size 20 mm × 20 mm. Results Spectra of hyperpolarized 129Xe dissolved in the human head showed five distinct peaks at 188 ppm, 192 ppm, 196 ppm, 200 ppm, and 217 ppm. Assignment of these peaks was consistent with earlier studies. Conclusion High resolution spectroscopy and CSI of hyperpolarized 129Xe dissolved in the human head has been demonstrated. For the first time, five distinct NMR peaks have been observed in 129Xe spectra from the human head in vivo. Magn Reson Med 75:2227–2234, 2016. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:27080441

  15. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations, Part I: Chemical shifts assignment.

    Science.gov (United States)

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika Agnieszka; Szeleszczuk, Łukasz; Wawer, Iwona

    2016-04-15

    Solid-state NMR is an excellent and useful method for analyzing solid-state forms of drugs. In the (13)C CP/MAS NMR spectra of the solid dosage forms many of the signals originate from the excipients and should be distinguished from those of active pharmaceutical ingredient (API). In this work the most common pharmaceutical excipients used in the solid drug formulations: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. Their (13)C CP/MAS NMR spectra were recorded and the signals were assigned, employing the results (R(2): 0.948-0.998) of GIPAW calculations and theoretical chemical shifts. The (13)C ssNMR spectra for some of the studied excipients have not been published before while for the other signals in the spectra they were not properly assigned or the assignments were not correct. The results summarize and complement the data on the (13)C ssNMR analysis of the most common pharmaceutical excipients and are essential for further NMR studies of API-excipient interactions in the pharmaceutical formulations. PMID:26845204

  16. Comprehensive signal assignment of 13C-labeled lignocellulose using multidimensional solution NMR and 13C chemical shift comparison with solid-state NMR.

    Science.gov (United States)

    Komatsu, Takanori; Kikuchi, Jun

    2013-09-17

    A multidimensional solution NMR method has been developed using various pulse programs including HCCH-COSY and (13)C-HSQC-NOESY for the structural characterization of commercially available (13)C labeled lignocellulose from potatoes (Solanum tuberosum L.), chicory (Cichorium intybus), and corn (Zea mays). This new method allowed for 119 of the signals in the (13)C-HSQC spectrum of lignocelluloses to be assigned and was successfully used to characterize the structures of lignocellulose samples from three plants in terms of their xylan and xyloglucan structures, which are the major hemicelluloses in angiosperm. Furthermore, this new method provided greater insight into fine structures of lignin by providing a high resolution to the aromatic signals of the β-aryl ether and resinol moieties, as well as the diastereomeric signals of the β-aryl ether. Finally, the (13)C chemical shifts assigned in this study were compared with those from solid-state NMR and indicated the presence of heterogeneous dynamics in the polysaccharides where rigid cellulose and mobile hemicelluloses moieties existed together. PMID:24010724

  17. Hepatic steatosis assessment with {sup 1}H-spectroscopy and chemical shift imaging at 3.0 T before hepatic surgery: Reliable enough for making clinical decisions?

    Energy Technology Data Exchange (ETDEWEB)

    Koelblinger, Claus, E-mail: claus.koelblinger@meduniwien.ac.at [Department of Radiology, Medical University of Vienna (Austria); Krssak, Martin, E-mail: martin.krssak@meduniwien.ac.at [Department of Radiology, Medical University of Vienna (Austria); Maresch, Judith, E-mail: judith.maresch@meduniwien.ac.at [Department of Pathology, Medical University of Vienna (Austria); Wrba, Fritz, E-mail: fritz.wrba@meduniwien.ac.at [Department of Pathology, Medical University of Vienna (Austria); Kaczirek, Klaus, E-mail: klaus.kaczirek@meduniwien.ac.at [Department of Surgery, Medical University of Vienna (Austria); Gruenberger, Thomas, E-mail: thomas.gruenberger@meduniwien.ac.at [Department of Surgery, Medical University of Vienna (Austria); Tamandl, Dietmar, E-mail: dietmar.tamandl@meduniwien.ac.at [Department of Surgery, Medical University of Vienna (Austria); Ba-Ssalamah, Ahmed, E-mail: ahmed.ba-ssalamah@meduniwien.ac.at [Department of Radiology, Medical University of Vienna (Austria); Berger-Kulemann, Vanessa, E-mail: vanessa.berger-kulemann@meduniwien.ac.at [Department of Radiology, Medical University of Vienna (Austria); Weber, Michael, E-mail: michael.weber@meduniwien.ac.at [Department of Radiology, Medical University of Vienna (Austria); Schima, Wolfgang, E-mail: wolfgang.schima@khgh.at [Department of Radiology, KH Goettlicher Heiland and Herz-Jesu Krankenhaus, Dornbacher Strasse 20-28, 1170 Vienna (Austria)

    2012-11-15

    Purpose: To compare the accuracy of liver fat quantification using chemical shift imaging (CSI) and H1 MR-spectroscopy (MRS) at 3.0 T in patients undergoing liver resection. Methods: Totally 35 patients were included in this prospective IRB approved study. The histopathologically assessed liver fat was compared to the hepatic fat fractions calculated with CSI (with and without spleen correction) and MRS. Spearman's rank correlation and Fisher z-test were used for correlation analysis. Sensitivity and specificity regarding the detection of marked steatosis were calculated for the different modalities and compared using the McNemar test. Results: MRS (r = .85) and CSI with spleen correction (r = .85) showed a significantly better correlation (p = .03) with histology compared to CSI without spleen correction (r = .67). Sensitivity and specificity for the detection of marked steatosis was 100% (12/12) and 87% (20/23) for MRS and 92% (11/12) and 83% (19/23) for CSI with spleen correction (p > .12). Conclusion: For the assessment of hepatic steatosis both CSI with spleen correction and MRS at 3.0 T, show a good correlation with histology. CSI without spleen correction should not be used. Sensitivity and specificity for the detection of marked steatosis are high with both modalities. However, results that are scattered around the cut-off values are not reliable enough for clinical decisions.

  18. The value of 15-minute delayed contrast-enhanced CT to differentiate hyperattenuating adrenal masses compared with chemical shift MR imaging

    International Nuclear Information System (INIS)

    To investigate the diagnostic performance of 15-min delayed contrast-enhanced computed tomography (15-DECT) compared with that of chemical shift magnetic resonance (CSMR) imaging in differentiating hyperattenuating adrenal masses and to perform subgroup analysis in underlying malignancy and non-malignancy. This study included 478 adrenal masses in 453 patients examined with 15-DECT and 235 masses in 217 patients examined with CSMR. Relative percentage washout (RPW) and absolute percentage washout (APW) on 15-DECT, and signal intensity index (SII) and adrenal-to-spleen ratio (ASR) on CSMR were measured. Sensitivity, specificity and accuracy of 15-DECT and CSMR were analysed for characterisation of adrenal adenoma. Subgroup analyses were performed in patients with and without underlying malignancy. Attenuation and size of the masses on unenhanced CT correlated with the risk of non-adenoma. RPW calculated from 15-DECT showed the highest diagnostic performance for characterising hyperattenuating adrenal masses regardless of underlying malignancy, and the sensitivity, specificity and accuracy were 91.7 %, 74.8 % and 88.1 %, respectively in all patients. The risk of non-adenoma increased approximately threefold as mass size increased 1 cm or as its attenuation value increased by 10 Hounsfield units. 15-DECT was more accurate than CSMR in characterising hyperattenuating adrenal masses regardless of underlying malignancy. (orig.)

  19. Scan time reduction in {sup 23}Na-Magnetic Resonance Imaging using the chemical shift imaging sequence. Evaluation of an iterative reconstruction method

    Energy Technology Data Exchange (ETDEWEB)

    Weingaertner, Sebastian; Konstandin, Simon; Schad, Lothar R. [Heidelberg Univ., Mannheim (Germany). Computer Assisted Clinical Medicine; Wetterling, Friedrich [Heidelberg Univ., Mannheim (Germany). Computer Assisted Clinical Medicine; Dublin Univ. (Ireland) Trinity Inst. of Neuroscience; Fatar, Marc [Heidelberg Univ., Mannheim (Germany). Dept. of Neurology; Neumaier-Probst, Eva [Heidelberg Univ., Mannheim (Germany). Dept. of Neuroradiology

    2015-07-01

    To evaluate potential scan time reduction in {sup 23}Na-Magnetic Resonance Imaging with the chemical shift imaging sequence (CSI) using undersampled data of high-quality datasets, reconstructed with an iterative constrained reconstruction, compared to reduced resolution or reduced signal-to-noise ratio. CSI {sup 23}Na-images were retrospectively undersampled and reconstructed with a constrained reconstruction scheme. The results were compared to conventional methods of scan time reduction. The constrained reconstruction scheme used a phase constraint and a finite object support, which was extracted from a spatially registered {sup 1}H-image acquired with a double-tuned coil. The methods were evaluated using numerical simulations, phantom images and in-vivo images of a healthy volunteer and a patient who suffered from cerebral ischemic stroke. The constrained reconstruction scheme showed improved image quality compared to a decreased number of averages, images with decreased resolution or circular undersampling with weighted averaging for any undersampling factor. Brain images of a stroke patient, which were reconstructed from three-fold undersampled k-space data, resulted in only minor differences from the original image (normalized root means square error < 12%) and an almost identical delineation of the stroke region (mismatch < 6%). The acquisition of undersampled {sup 23}Na-CSI images enables up to three-fold scan time reduction with improved image quality compared to conventional methods of scan time saving.

  20. The value of 15-minute delayed contrast-enhanced CT to differentiate hyperattenuating adrenal masses compared with chemical shift MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Hyun Jung; Choi, Hyuck Jae; Cho, Kyoung-Sik [Asan Medical Center, University of Ulsan College of Medicine, Department of Radiology and Research Institute of Radiology, Seoul (Korea, Republic of); Kim, Hwa Jung; Kim, Sun-Ok [Asan Medical Center, University of Ulsan College of Medicine, Cancer Center, Department of Clinical Epidemiology and Biostatistics, Seoul (Korea, Republic of)

    2014-06-15

    To investigate the diagnostic performance of 15-min delayed contrast-enhanced computed tomography (15-DECT) compared with that of chemical shift magnetic resonance (CSMR) imaging in differentiating hyperattenuating adrenal masses and to perform subgroup analysis in underlying malignancy and non-malignancy. This study included 478 adrenal masses in 453 patients examined with 15-DECT and 235 masses in 217 patients examined with CSMR. Relative percentage washout (RPW) and absolute percentage washout (APW) on 15-DECT, and signal intensity index (SII) and adrenal-to-spleen ratio (ASR) on CSMR were measured. Sensitivity, specificity and accuracy of 15-DECT and CSMR were analysed for characterisation of adrenal adenoma. Subgroup analyses were performed in patients with and without underlying malignancy. Attenuation and size of the masses on unenhanced CT correlated with the risk of non-adenoma. RPW calculated from 15-DECT showed the highest diagnostic performance for characterising hyperattenuating adrenal masses regardless of underlying malignancy, and the sensitivity, specificity and accuracy were 91.7 %, 74.8 % and 88.1 %, respectively in all patients. The risk of non-adenoma increased approximately threefold as mass size increased 1 cm or as its attenuation value increased by 10 Hounsfield units. 15-DECT was more accurate than CSMR in characterising hyperattenuating adrenal masses regardless of underlying malignancy. (orig.)

  1. Shifting Attention

    Science.gov (United States)

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  2. Tuning Exchange Anisotropy of Exchange-Biased System

    Institute of Scientific and Technical Information of China (English)

    XU Yan; HU Jing-Guo; R.L.Stamps

    2008-01-01

    Exchange anisotropy in FM/AFM bilayers has given a lot of static magnetization properties such as enhanced coercivity and magnetization loop shifts.These phenomena are primarily from the effective anisotropies intro-duced into a ferromagnet by exchange coupling with a strongly anisotropic antiferromagnet.These effective anisotropies can also be used to explain the dynamic consequences of exchange-biased bilayers.In this article,the dynamic con-sequences such as exchange-induced susceptibility,exchange-induced permeability,and the corresponding domain wall characteristics in the exchange-biased structures of ferromagnet/antiferromagnetl/antiferromagnet2 are studied.The results show that the second antiferromagnetic layer can largely affect the dynamic consequences of exchange-biased bilayers.Especially in the ease of critical temperature,the effects become more obvious.Practically,the exchange anisotropy of biased bilayer system can be tuned by exchange coupling with the second antiferromagnetic layer.

  3. SAFT缔合模型关联含水体系的1H NMR%Correlation of 1H NMR Chemical Shift for Aqueous Solutions by Statistical Associating Fluid Theory Association Model

    Institute of Scientific and Technical Information of China (English)

    许波; 李浩然; 王从敏; 许映杰; 韩世钧

    2005-01-01

    1H NMR chemical shifts of binary aqueous mixtures of acylamide, alcohol, dimethyl sulphoxide (DMSO), and acetone are correlated by statistical associating fluid theory (SAFT) association model. The comparison between SAFT association model and Wilson equation shows that the former is better for dealing with aqueous solutions. Finally, the specialties of both models are discussed.

  4. Determination of the Tautomeric Equilibria of Pyridoyl Benzoyl -Diketones in the Liquid and Solid State through the use of Deuterium Isotope Effects on 1H and 13C NMR Chemical Shifts and Spin Coupling Constants

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Borisov, Eugeny V.; Lindon, John C.

    2015-01-01

    The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on 1H and 13C chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in th...

  5. Detection of fat in lipomatous tumors of the myometrium by means of computed tomography and chemical shift magnetic resonance imaging; Deteccion de grasa en tumores lipomatosos del miometrio mediante TC y RM con tecnica de Desplazamiento Quimico

    Energy Technology Data Exchange (ETDEWEB)

    Costa, S.; Marti-Bonmati, L.; Delgado, F.; Ripolles, T. [Hospital Universitario Doctor Peset. Valencia (Spain)

    2000-07-01

    Lipomatous tumors of the myometrium are rare lesions composed of varying amounts of mature fatty tissue. Our objective was to assess the computed tomography (CT) and magnetic resonance MR findings associated with these tumors and determine the utility of the chemical shift imaging technique in the detection of fact within these focal uterine masses. Lipomatous focal uterine lesions were detected in three women by means of ultrasound. The patients underwent CT and MR using the chemical shift imaging technique and in-phase and opposed phase T1-weighted gradient-echo images. Qualitative and quantitative analyses of the results were carried out, based on the attenuations and relations of signal intensity. The tumors were hypoattenuated in CT seans and hyperintense in T1-weighted images, showing a decreased signal in opposed phase T1-weighted images when compared with in-phase images. The percentage change (between 2% and 3%) is probably proportional to the differing proportions of fact and muscle elements present in these lipoleiomyomas. Lipomatous tumors of the myometrium are uterine lesions with a varying proportion of fact. Their fat composition can be detected by CT and MR. The chemical shift imaging technique reveals the variations in the proportions of fat in these tumors. Since the presence of fat within uterine lesions is virtually diagnostic of the myometrial lipomatous tumor, the chemical shift imaging technique contributes to the characterization of these lesions. (Author) 11 refs.

  6. Topographical Anisotropy and Wetting of Ground Stainless Steel Surfaces

    OpenAIRE

    Cornelia Bellmann; Alfredo Calvimontes; Marc Mauermann

    2012-01-01

    Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different mechanically modified stainless steel surfaces. The surfaces were analyzed using high-resolution confocal microscopy, resulting in detailed information about the topographic properties. In addition, static water contact angle measurements were carried out to characterize the surface heterogeneity of the samples. The effect of morphological anisotropy on water contact angle anisotropy w...

  7. Anisotropy in OLEDs

    Science.gov (United States)

    Callens, M. K.; Yokoyama, D.; Neyts, K.

    2015-09-01

    Small-molecule OLEDs, deposited by thermal evaporation, allow for precise control over layer thicknesses. This enables optimisation of the optical behaviour of the stack which ultimately determines the outcoupling efficiency. In terms of optical outcoupling there are limits to the efficiency by which the generated electromagnetic radiation can be extracted from the stack. These limitations are linked to the refractive indices of the individual layers. Values for maximum outcoupling efficiency are sometimes calculated under the implicit assumptions that the OLED stack is planar, that all layers are isotropic with a certain refractive index and that the emitters are not preferentially oriented. In reality it is known that these assumptions are not always valid, be it intentional or unintentional. In our work we transcend these limiting assumptions and look at different forms of anisotropy in OLEDs. Anisotropy in OLEDs comes in three distinct flavours; 1. Geometrical anisotropy, as for example in gratings, lenses or other internal or external scattering centres, 2. Anisotropic emitters, where the orientation significantly influences the direction in which radiation is emitted and 3. Anisotropic optical materials, where their anisotropic nature breaks the customary assumption of isotropic OLED materials. We investigate the effect of these anisotropic features on the outcoupling efficiency and ultimately, on the external quantum efficiency (EQE).

  8. {sup 31}P-MR spectroscopy of all regions of the human heart at 1.5 T with acquisition-weighted chemical shift imaging; P-MR-Spektroskopie aller Wandabschnitte des menschlichen Herzens bei 1,5 T mit akquisitionsgewichteter Chemical-shift-Bildgebung

    Energy Technology Data Exchange (ETDEWEB)

    Koestler, H.; Beer, M.; Buchner, S.; Sandstede, J.; Pabst, T.; Kenn, W.; Hahn, D. [Wuerzburg Univ. (Germany). Abt. fuer Roentgendiagnostik; Landschuetz, W.; Kienlin, M. von [Wuerzburg Univ. (Germany). Physikalisches Inst.; Neubauer, S. [Dept. of Cardiovascular Medicine, John Radcliffe Hospital, Oxford (United Kingdom)

    2001-12-01

    Aim: Aim of this study was to show whether or not acquisition-weighted chemical shift imaging (AW-CSI) allows the determination of PCr and ATP in the lateral and posterior wall of the human heart at 1.5 T. Methods: 12 healthy volunteers were examined using a conventional chemical shift imaging (CSI) and an AW-CSI. The sequences differed only in the number of repetitions for each point in k space. A hanning function was used as filter function leading to 7 repetitions in the center of the k space and 0 in the corners. Thus, AW-CSI had the same resolution as the CSI sequence. The results for both sequences were analyzed using identically positioned voxels in the septal, anterior, lateral and posterior wall. Results: The determined averaged AW-CSI signal to noise ratios were higher for PCr by a factor of 1.3 and for ATP by 1.4 than those of CSI. The PCr/ATP ratios were higher by a factor of 1.2 - 1.3 and showed a smaller standard deviation in all locations for AW-CSI. The mean PCr/ATP ratios determined by AW-CSI of septal, lateral and posterior wall were almost identical (1.72 - 1.76), while it was higher in the anterior wall (1.9). Conclusions: The reduced contamination in AW-CSI improves the signal to noise ratio and the determination of the PCr/ATP ratio in cardiac {sup 31}P spectroscopy compared to CSI with the same resolution. The results in volunteers indicate that AW-CSI renders {sup 31}P spectroscopy of the lateral and posterior wall of the human heart feasible for patient studies at 1.5 T. (orig.) [German] Ziel: Ziel der Arbeit war es zu untersuchen, ob die akquisitionsgewichtete Chemical-shift-Bildgebung (AW-CSI) die Bestimmung von PCr und ATP in der Seiten- und Hinterwand des menschlichen Herzens an einem klinischen 1,5 T MR-Tomographen erlaubt. Methoden: 12 gesunde Probanden wurden jeweils mit einer chemical shift imaging (CSI) und einer AW-CSI-Sequenz untersucht. Die Sequenzen unterschieden sich lediglich in der Anzahl der Wiederholungen der einzelnen

  9. Utility of chemical-shift MR imaging in detecting small amounts of fat in extrahepatic abdominal tumors; Utilidad de la tecnica de desplazamiento quimico den RM para la deteccion de pequenas cantidades de grasa en tumores abdominales extrahepaticos

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J.; Falco, J.; Puig, J.; Donoso, L. [Unidad de Diagnostico por Imagen de Alta Tecnologia (UDIAT). Sabadell (Spain)

    1999-07-01

    To determine the utility of the chemical shift technique in magnetic resonance imaging (MRI) to confirm small amounts of fat in extrahepatic intraabdominal tumours. 7 extrahepatic abdominal tumours that are suspected to have fat as seen in the axial computed tomography (TC) are analysed retrospectively. In order to confirm the fat content, the chemical displacement technique with gradient echo sequences (GE) in phase (P) and in opposite phase (OP) was used with MRI 1 T equipment. The tumours corresponded to renal angiomyolipoma (AML) (n=4), intraperitoneal liposarcoma (n=1), retroperitoneal liposarcoma (n=1) and intraabdominal extramedular hematopoiesis (n=1). To confirm the existence of fat in the tumours, we used a quantitative percentage variation parameter of the intensity of the signals (VIS) between the images in P and OP, according to the formula: IS{sub (}p)-IS({sub o}p)x100/IS{sub (}op), where IS is the intensity of the signal. The chemical shift technique showed fat in the seven tumours. Upon visual inspection, all the tumoral areas that were suspected to have fat showed a notable difference in the signal intensity, being hypointense in OP and hyperintense in P. In these areas the average VIS percentage was 170% while in the rest of the tumour the average VIS percentage was 3%. The chemical shift technique with RG sequences can be easily used in MRI equipment and allows us to confirm if a specific abdominal tumour has fat, even if there is only a small quantity. (Author) 13 refs.

  10. Laser-induced nuclear orientation and gamma anisotropy in sodium

    International Nuclear Information System (INIS)

    The use of laser optical pumping to induce nuclear orientation in several isotopes and one isomer of atomic sodium vapor is described. Essentially complete nuclear polarization, P > 90%, has been achieved in stable 23Na when pumping with modest laser intensities (I approx. = 10 mW/cm2). The volume of the sample cell was approximately 10 cc, and was filled with a sodium density of about 10'' atoms/cc. Complete coverage of the Doppler distribution was accomplished with the use of trace amounts (less than or equal to 1 torr) of argon buffer gas to induce velocity changing collisions. A theoretical model which accurately predicts the amount of polarization is developed. The orientation of nuclei which are unstable to gamma decay can manifest itself in anisotropic gamma ray emission. This anisotropy can be used to measure isotope and isomer shifts, from which nuclear properties can be derived. Gamma anisotropy was observed in two systems, 22Na and /sup 24m/Na. From the observed anisotropy in /sup 24m/Na, a negative sign for the g factor is determined. Values are derived for the magnetic moment, μ = 2.56 +- 0.64 nm, and the isomer shift, deltaν/sub 24m/ = 288 +- 191 MHz (D1 line). A model is described which relates various laser and fubber gas parameters to the observed gamma anisotropy lineshape. This model facilitates the extraction of physical parameters from knowledge of the laser frequency at which the anisotropy is a maximum

  11. Flow stress anisotropy

    DEFF Research Database (Denmark)

    Winther, G.

    1996-01-01

    stress Variation in the rolling plane, which may be as high as 20%, are presented. The traditional Taylor model is applied to the data to account for the effect of texture. However, texture effects alone are not enough to explain all of the observed anisotropy. New models which take the combined effects...... of texture and deformation microstructure into account are presented. The models are based on the Taylor and Sachs models but modified with an anisotropic critical shear stress to account for the effect of the microstructure. The agreement between experimental data and model predictions is definitely better...

  12. Flow stress anisotropy

    DEFF Research Database (Denmark)

    Winther, G.

    1996-01-01

    stress Variation in the rolling plane, which may be as high as 20%, are presented. The traditional Taylor model is applied to the data to account for the effect of texture. However, texture effects alone are not enough to explain all of the observed anisotropy. New models which take the combined effects...... of texture and deformation microstructure into account are presented. The models are based on the Taylor and Sachs models but modified with an anisotropic critical shear stress to account for the effect of the microstructure. The agreement between experimental data and model predictions is definitely...

  13. Double-echo gradient chemical shift MR imaging fails to differentiate minimal fat renal angiomyolipomas from other homogeneous solid renal tumors

    International Nuclear Information System (INIS)

    Highlights: •Diagnosis of AMLs with minimal fat (mfAMLs) is still challenging with MRI. •Drop of signal on opposed-phase MR imaging is not specific of mfAMLs. •Double-echo gradient-echo sequences cannot accurately differentiate renal mfAMLs from other renal tumors. -- Abstract: Objectives: The purpose of this retrospective study was to evaluate the diagnostic performance of double-echo gradient chemical shift (GRE) magnetic resonance (MR) imaging for the differentiation of angiomyolipomas with minimal fat (mfAML) from other homogeneous solid renal tumors. Methods: Between 2005 and 2010 in two institutions, all histologically proven homogenous solid renal tumors imaged with computed tomography and MR imaging, including GRE sequences, have been retrospectively selected. A total of 118 patients (mean age: 61 years; range: 20–87) with 119 tumors were included. Two readers measured independently the signal intensity (SI) on GRE images and calculated SI index (SII) and tumor-to-spleen ratio (TSR) on in-phase and opposed-phase images. Intra- and interreader agreement was obtained. Cut-off values were derived from the receiver operating characteristic (ROC) curve analysis. Results: Twelve mfAMLs in 11 patients were identified (mean size: 2.8 cm; range: 1.2–3.5), and 107 non-AML tumors (3.2 cm; 1–7.8) in 107 patients. The intraobserver reproducibility of SII and TSR was excellent with an intraclass correlation coefficient equal to 0.99 [0.98–0.99]. The coefficient of correlation between the readers was 0.99. The mean values of TSR for mfAMLs and non-mfAMLs were −7.0 ± 22.8 versus −8.2 ± 21.2 for reader 1 and −6.7 ± 22.8 versus −8.4 ± 20.9 for reader 2 respectively. No significant difference was noticed between the two groups for SII (p = 0.98) and TSR (p = 0.86). Only 1 out of 12 mfAMLs and 11 of 107 non-AML tumors presented with a TSR inferior to −30% (p = 0.83). Conclusion: In a routine practice, GRE sequences cannot be a confident tool to

  14. Double-echo gradient chemical shift MR imaging fails to differentiate minimal fat renal angiomyolipomas from other homogeneous solid renal tumors

    Energy Technology Data Exchange (ETDEWEB)

    Ferré, R., E-mail: kn638@yahoo.fr [Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France); Cornelis, F. [Department of Radiology, Pellegrin Hospital, Place Amélie Raba Léon, 33076 Bordeaux (France); Verkarre, V. [Department of Pathology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France); Eiss, D.; Correas, J.M. [Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France); Grenier, N. [Department of Radiology, Pellegrin Hospital, Place Amélie Raba Léon, 33076 Bordeaux (France); Hélénon, O. [Department of Radiology, Necker Hospital, 149 rue de Sèvres, 75730 Paris (France)

    2015-03-15

    Highlights: •Diagnosis of AMLs with minimal fat (mfAMLs) is still challenging with MRI. •Drop of signal on opposed-phase MR imaging is not specific of mfAMLs. •Double-echo gradient-echo sequences cannot accurately differentiate renal mfAMLs from other renal tumors. -- Abstract: Objectives: The purpose of this retrospective study was to evaluate the diagnostic performance of double-echo gradient chemical shift (GRE) magnetic resonance (MR) imaging for the differentiation of angiomyolipomas with minimal fat (mfAML) from other homogeneous solid renal tumors. Methods: Between 2005 and 2010 in two institutions, all histologically proven homogenous solid renal tumors imaged with computed tomography and MR imaging, including GRE sequences, have been retrospectively selected. A total of 118 patients (mean age: 61 years; range: 20–87) with 119 tumors were included. Two readers measured independently the signal intensity (SI) on GRE images and calculated SI index (SII) and tumor-to-spleen ratio (TSR) on in-phase and opposed-phase images. Intra- and interreader agreement was obtained. Cut-off values were derived from the receiver operating characteristic (ROC) curve analysis. Results: Twelve mfAMLs in 11 patients were identified (mean size: 2.8 cm; range: 1.2–3.5), and 107 non-AML tumors (3.2 cm; 1–7.8) in 107 patients. The intraobserver reproducibility of SII and TSR was excellent with an intraclass correlation coefficient equal to 0.99 [0.98–0.99]. The coefficient of correlation between the readers was 0.99. The mean values of TSR for mfAMLs and non-mfAMLs were −7.0 ± 22.8 versus −8.2 ± 21.2 for reader 1 and −6.7 ± 22.8 versus −8.4 ± 20.9 for reader 2 respectively. No significant difference was noticed between the two groups for SII (p = 0.98) and TSR (p = 0.86). Only 1 out of 12 mfAMLs and 11 of 107 non-AML tumors presented with a TSR inferior to −30% (p = 0.83). Conclusion: In a routine practice, GRE sequences cannot be a confident tool to

  15. Tough Shift

    DEFF Research Database (Denmark)

    Brewer, Robert S.; Verdezoto, Nervo; Holst, Thomas;

    2015-01-01

    people to change their behavior at home. Leveraging prior research on encouraging reductions in residential energy use through game play, we introduce ShareBuddy: a casual mobile game intended to encourage players not only to reduce, but also to shift their electricity use. We conducted two field studies...... integrating real-world resource use into a game....

  16. Fluid Shifts

    Science.gov (United States)

    Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Johnston, S.; Ploutz-Snyder, R.; Smith, S.

    2016-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low-Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 50% of ISS astronauts experienced more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's preflight conditions and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. METHODS: We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by

  17. Morphology effects on exchange anisotropy in Co–CoO nanocomposite films

    International Nuclear Information System (INIS)

    Co–CoO composite films were prepared by solution chemical technique using amine-modified nitrates and acetates in methanol. We study how particle size and porosity can be tuned through the synthesis parameters and how this influences the magnetic properties. Phase content and microstructure were characterised with grazing incidence X-ray diffraction and electron microscopy, and the magnetic properties were studied by magnetometry and magnetic force microscopy. Composite films were obtained by heating spin-coated films in Ar followed by oxidation in air at room temperature, and the porosity and particle size of the films were controlled by gas flow and heating rate. The synthesis yielded dense films with a random distribution of metal and oxide nanoparticles, and layered films with porosity and sintered primary particles. Exchange anisotropy, revealed as a shift towards negative fields of the magnetic hysteresis curve, was found in all films. The films with a random distribution of metal and oxide nanoparticles displayed a significantly larger coercivity and exchange anisotropy field compared to the films with a layered structure, whereas the layered films displayed a larger nominal saturation magnetisation. The magnitude of the coercivity decreased with increasing Co grain size, whereas increased porosity caused an increased tilt of the magnetic hysteresis curve. - Highlights: • Co–CoO nanocomposite thin films were synthesised using solution chemical methods. • Porosity and metal particle size were tuned through gas-flow during synthesis. • Magnetic characterisation shows that increased Co–CoO interface increases coercivity. • Random structures show much larger exchange anisotropy compared to layered films. • Stray fields due to porosity cause decreasing squareness in magnetic hysteresis

  18. Angular dependence of hysteresis shift in oblique deposited ferromagnetic/antiferromagnetic coupled bilayers

    Science.gov (United States)

    Oliveira, A. B.; Rodriguez-Suarez, R. L.; Michea, S.; Vega, H.; Azevedo, A.; Rezende, S. M.; Aliaga, C.; Denardin, J.

    2014-07-01

    The angular dependence of the hysteresis shift has been investigated in ferromagnetic/antiferromagnetic (NiFe/IrMn) bilayers grown by oblique deposition under the influence of a static magnetic field applied perpendicular to the uniaxial anisotropy direction induced during the growth process. It was found that at low oblique deposition angles, the unidirectional anisotropy field is much greater than the uniaxial anisotropy field and the corresponding anisotropies directions are noncollinear. In these conditions, the angular dependence of the hysteresis loop shift exhibits the well know cosine like shape but demanding a phase shift. Contrary to this, at high oblique deposition angle (70°), the uniaxial anisotropy plays the fundamental role and the anisotropies directions are collinear. In this case, the exchange bias displays a jump phenomenon. The numerical calculations are consistent with the experimental data obtained from magneto-optical Kerr effect and ferromagnetic resonance.

  19. Oxygen 17 NMR in the evaluation of oxygen bounding with central ion using hydrolysis products of niobium, tantalum, arsenic, antimony pentafluorides as an example. Symbasis in the change of 17O and 19F chemical shifts

    International Nuclear Information System (INIS)

    Hydrolysis products of niobium, tantalum, antimony and arsenic pentafluorides in acetonitrile solution were studied by the methods of 17O and 19F NMR. In 17O NMR spectra of niobium and tantalum pentafluorides hydrolysis products resonance signals of oxo-, hydroxo- and aquafluorocomplexes were defined. Considerable shift of 17O NMR resonance signals towards weak field making up about 300 m.p., may indicate a higher covalency (Π-character) of Nb-O bond compared to Ta-O one. Symbasis in the change of chemical shifts in 17O NMR and 19F NMR of the relevant hexafluorides and hydrolysis products was detected implying similarity of chemical bond nature in oxygen and fluorine

  20. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  1. A Series of Diamagnetic Pyridine Monoimine Rhenium Complexes with Different Degrees of Metal-to-Ligand Charge Transfer: Correlating (13) C NMR Chemical Shifts with Bond Lengths in Redox-Active Ligands.

    Science.gov (United States)

    Sieh, Daniel; Kubiak, Clifford P

    2016-07-18

    A set of pyridine monoimine (PMI) rhenium(I) tricarbonyl chlorido complexes with substituents of different steric and electronic properties was synthesized and fully characterized. Spectroscopic (NMR and IR) and single-crystal X-ray diffraction analyses of these complexes showed that the redox-active PMI ligands are neutral and that the overall electronic structure is little affected by the choices of the substituent at the ligand backbone. One- and two-electron reduction products were prepared from selected starting compounds and could also be characterized by multiple spectroscopic methods and X-ray diffraction. The final product of a one-electron reduction in THF is a diamagnetic metal-metal-bonded dimer after loss of the chlorido ligand. Bond lengths in and NMR chemical shifts of the PMI ligand backbone indicate partial electron transfer to the ligand. Two-electron reduction in THF also leads to the loss of the chlorido ligand and a pentacoordinate complex is obtained. The comparison with reported bond lengths and (13) C NMR chemical shifts of doubly reduced free pyridine monoaldimine ligands indicates that both redox equivalents in the doubly reduced rhenium complex investigated here are located in the PMI ligand. With diamagnetic complexes varying over three formal reduction stages at the PMI ligand we were, for the first time, able to establish correlations of the (13) C NMR chemical shifts with the relevant bond lengths in redox-active ligands over a full redox series. PMID:27319753

  2. Easy and unambiguous sequential assignments of intrinsically disordered proteins by correlating the backbone {sup 15}N or {sup 13}C′ chemical shifts of multiple contiguous residues in highly resolved 3D spectra

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, Yuichi; Kulminskaya, Natalia V.; Mulder, Frans A. A., E-mail: fmulder@chem.au.dk [Aarhus University, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO) (Denmark)

    2015-02-15

    Sequential resonance assignment strategies are typically based on matching one or two chemical shifts of adjacent residues. However, resonance overlap often leads to ambiguity in resonance assignments in particular for intrinsically disordered proteins. We investigated the potential of establishing connectivity through the three-bond couplings between sequentially adjoining backbone carbonyl carbon nuclei, combined with semi-constant time chemical shift evolution, for resonance assignments of small folded and larger unfolded proteins. Extended sequential connectivity strongly lifts chemical shift degeneracy of the backbone nuclei in disordered proteins. We show here that 3D (H)N(COCO)NH and (HN)CO(CO)NH experiments with relaxation-optimized multiple pulse mixing correlate up to seven adjacent backbone amide nitrogen or carbonyl carbon nuclei, respectively, and connections across proline residues are also obtained straightforwardly. Multiple, recurrent long-range correlations with ultra-high resolution allow backbone {sup 1}H{sup N}, {sup 15}N{sup H}, and {sup 13}C′ resonance assignments to be completed from a single pair of 3D experiments.

  3. Anisotropy of weakly vibrated granular flows.

    Science.gov (United States)

    Wortel, Geert H; van Hecke, Martin

    2015-10-01

    We experimentally probe the anisotropy of weakly vibrated flowing granular media. Depending on the driving parameters-flow rate and vibration strength-this anisotropy varies significantly. We show how the anisotropy collapses when plotted as a function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggest that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a crucial role in determining the rheology of granular flows. PMID:26565148

  4. Anisotropy of Weakly Vibrated Granular Flows

    OpenAIRE

    Wortel, Geert; Van Hecke, Martin

    2014-01-01

    We experimentally probe the anisotropy of the fabric of weakly vibrated, flowing granular media. Depending on the driving parameters --- flow rate and vibration strength --- this anisotropy varies significantly. We show how the anisotropy collapses when plotted as function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggests that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a ...

  5. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N., E-mail: niranjan@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Radhika, R. [Crystal Growth Centre, Anna University, Chennai (India); Kozakov, A.T. [Research Institute of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); Pandian, R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Chakravarty, S. [UGC-DAE CSR, Kalpakkam (India); Ravindran, T.R.; Dash, S.; Tyagi, A.K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

  6. Friction anisotropy in boronated graphite

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient

  7. Shifting densities

    OpenAIRE

    Mille, Matthieu

    2000-01-01

    In this paper, the author adopt a time-geography approach to examine the temporal variation of urban density by analysing spatial load changes at different times of the day at the communal and community level. The evolution of means of transport coupled with the abandon of the notion of direct proximity to the urban dwelling place provide the basis for this new approach to the study of urban densities. The shift towards spatial specialisation within cities has lead to radical changes in the f...

  8. Anisotropy of magnetic susceptibility in alkali feldspar and plagioclase

    Science.gov (United States)

    Biedermann, Andrea R.; Pettke, Thomas; Angel, Ross J.; Hirt, Ann M.

    2016-04-01

    Feldspars are the most abundant rock-forming minerals in the Earth's crust, but their magnetic properties have not been rigorously studied. This work focuses on the intrinsic magnetic anisotropy of 31 feldspar samples with various chemical compositions. Because feldspar is often twinned or shows exsolution textures, measurements were performed on twinned and exsolved samples as well as single crystals. The anisotropy is controlled by the diamagnetic susceptibility and displays a consistent orientation of principal susceptibility axes; the most negative or minimum susceptibility is parallel to [010], and the maximum (least negative) is close to the crystallographic [001] axis. However, the magnetic anisotropy is weak when compared to other rock-forming minerals, 1.53 × 10-9 m3 kg-1 at maximum. Therefore, lower abundance minerals, such as augite, hornblende or biotite, often dominate the bulk paramagnetic anisotropy of a rock. Ferromagnetic anisotropy is not significant in most samples. In the few samples that do show ferromagnetic anisotropy, the principal susceptibility directions of the ferromagnetic subfabric do not display a systematic orientation with respect to the feldspar lattice. These results suggest that palaeointensity estimates of the geomagnetic field made on single crystals of feldspar will not be affected by a systematic orientation of the ferromagnetic inclusions within the feldspar lattice.

  9. Anisotropy in solid inflation

    International Nuclear Information System (INIS)

    In the model of solid / elastic inflation, inflation is driven by a source that has the field theoretical description of a solid. To allow for prolonged slow roll inflation, the solid needs to be extremely insensitive to the spatial expansion. We point out that, because of this property, the solid is also rather inefficient in erasing anisotropic deformations of the geometry. This allows for a prolonged inflationary anisotropic solution, providing the first example with standard gravity and scalar fields only which evades the conditions of the so called cosmic no-hair conjecture. We compute the curvature perturbations on the anisotropic solution, and the corresponding phenomenological bound on the anisotropy. Finally, we discuss the analogy between this model and the f(φ)F2 model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton φ and a vector field. We remark that the bispectrum of the curvature perturbations in solid inflation is enhanced in the squeezed limit and presents a nontrivial angular dependence, as had previously been found for the f(φ)F2 model

  10. Anisotropy in rotating drums

    Science.gov (United States)

    Povall, Timothy; McBride, Andrew; Govender, Indresan

    2015-11-01

    An anisotropic relationship between the stress and the strain rate has been observed in two-dimensional simulations of rotating drums. The objective of this work is to investigate the structure of the constitutive relation using three-dimensional discrete-element-method simulations of a rotating drum containing identical rigid spheres for a range of rotational speeds. Anisotropy is quantified from the alignment of the stress and strain rate tensors, with the strain rate computed using a least-squares fit. It is shown that in certain regions there is a strong anisotropic relationship, regardless of the speed of rotation. The effective friction coefficient is examined in order to determine the phase space in which the μ (I) rheology is valid. Lastly, a depth-averaged approach through the flowing layer is employed to determine the relationship between the velocity tangential to the equilibrium surface and the height of the flowing layer. A power-law relationship that approaches linear at high speeds is observed. Supported by NRF/DST Scarce Skills (South Africa).

  11. Neutrino Anisotropies after Planck

    CERN Document Server

    Gerbino, Martina; Said, Najla

    2013-01-01

    We present new constraints on the rest-frame sound speed, c_eff^2, and the viscosity parameter, c_vis^2, of the Cosmic Neutrino Background from the recent measurements of the Cosmic Microwave Background anisotropies provided by the Planck satellite. While broadly consistent with the ex- pectations of c_eff^2 = c_vis^2 = 1/3 in the standard scenario, the Planck dataset hints for a higher value of the viscosity parameter, with c_vis^2 = 0.60 +/- 0.18 at 68% c.l., and a lower value of the sound speed, with c_eff^2 = 0.304 +/- 0.013 at 68% c.l.. We find a correlation between the neutrino parameters and the lensing amplitude of the temperature power spectrum A_L. When the latter parameter is allowed to vary, we find a better consistency with the standard model with c_vis^2 = 0.51 +/- 0.22, c_eff^2 = 0.311 +/- 0.019 and A_L = 1.08 +/- 0.18 at 68% c.l.. This result indicates that the anomalous large value of A_L measured by Planck could be connected to non-standard neutrino properties. Including additional datasets ...

  12. Flow stress anisotropy in aluminium

    DEFF Research Database (Denmark)

    Juul Jensen, D.; Hansen, N.

    1990-01-01

    The plastic anisotropy of cold-rolled high purity aluminum (99.996%) and commercially pure aluminum (99.6%) has been investigated. Sample parameters were the initial grain size and the degree of plastic strain (ϵ < 3.00). Flow stresses (0.2% offset) were measured at room temperature by uniaxial...... tension as a function of the angle between the tensile axis and the rolling direction. Textures were determined by neutron diffraction, and Taylor M-factors were calculated. The microstructures were studied by TEM. It was found that the flow stress varies significantly with orientation both at low and...... high strains. It is shown that for most experimental conditions, texture effects alone cannot explain the observed anisotropy, and microstructural anisotropy effects have to be taken into account. In those cases, a correlation between the microstructural anisotropy and the development of microbands is...

  13. Secondary anisotropies of the CMB

    International Nuclear Information System (INIS)

    The Cosmic Microwave Background fluctuations provide a powerful probe of the dark ages of the universe through the imprint of the secondary anisotropies associated with the reionization of the universe and the growth of structure. We review the relation between the secondary anisotropies and the primary anisotropies that are directly generated by quantum fluctuations in the very early universe. The physics of secondary fluctuations is described, with emphasis on the ionization history and the evolution of structure. We discuss the different signatures arising from the secondary effects in terms of their induced temperature fluctuations, polarization and statistics. The secondary anisotropies are being actively pursued at present, and we review the future and current observational status

  14. Braneworld cosmological models with anisotropy

    International Nuclear Information System (INIS)

    For a cosmological Randall-Sundrum braneworld with anisotropy, i.e., of Bianchi type, the modified Einstein equations on the brane include components of the five-dimensional Weyl tensor for which there are no evolution equations on the brane. If the bulk field equations are not solved, this Weyl term remains unknown, and many previous studies have simply prescribed it as ad hoc. We construct a family of Bianchi braneworlds with anisotropy by solving the five-dimensional field equations in the bulk. We analyze the cosmological dynamics on the brane, including the Weyl term, and shed light on the relation between anisotropy on the brane and the Weyl curvature in the bulk. In these models, it is not possible to achieve geometric anisotropy for a perfect fluid or scalar field - the junction conditions require anisotropic stress on the brane. But the solutions can isotropize and approach a Friedmann brane in an anti-de Sitter bulk

  15. Braneworld cosmological models with anisotropy

    Science.gov (United States)

    Campos, Antonio; Maartens, Roy; Matravers, David; Sopuerta, Carlos F.

    2003-11-01

    For a cosmological Randall-Sundrum braneworld with anisotropy, i.e., of Bianchi type, the modified Einstein equations on the brane include components of the five-dimensional Weyl tensor for which there are no evolution equations on the brane. If the bulk field equations are not solved, this Weyl term remains unknown, and many previous studies have simply prescribed it as ad hoc. We construct a family of Bianchi braneworlds with anisotropy by solving the five-dimensional field equations in the bulk. We analyze the cosmological dynamics on the brane, including the Weyl term, and shed light on the relation between anisotropy on the brane and the Weyl curvature in the bulk. In these models, it is not possible to achieve geometric anisotropy for a perfect fluid or scalar field—the junction conditions require anisotropic stress on the brane. But the solutions can isotropize and approach a Friedmann brane in an anti de Sitter bulk.

  16. Braneworld cosmological models with anisotropy

    CERN Document Server

    Campos, A; Matravers, D; Sopuerta, C F; Campos, Antonio; Maartens, Roy; Matravers, David; Sopuerta, Carlos F.

    2003-01-01

    For a cosmological Randall-Sundrum braneworld with anisotropy, i.e., of Bianchi type, the modified Einstein equations on the brane include components of the five-dimensional Weyl tensor for which there are no evolution equations on the brane. If the bulk field equations are not solved, this Weyl term remains unknown, and many previous studies have simply prescribed it ad hoc. We construct a family of Bianchi braneworlds with anisotropy by solving the five-dimensional field equations in the bulk. We analyze the cosmological dynamics on the brane, including the Weyl term, and shed light on the relation between anisotropy on the brane and Weyl curvature in the bulk. In these models, it is not possible to achieve geometric anisotropy for a perfect fluid or scalar field -- the junction conditions require anisotropic stress on the brane. But the solutions can isotropize and approach a Friedmann brane in an anti-de Sitter bulk.

  17. Dynamic and rotatable exchange anisotropy in Fe/KNiF3/FeF2 trilayers

    Science.gov (United States)

    Widuch, S.; Stamps, R. L.; Skrzypek, D.; Celinski, Z.

    2011-10-01

    Results from ferromagnetic resonance experiments carried out on epitaxially grown Fe/KNiF3/FeF2 trilayers are presented. Exchange coupling between the KNiF3, a weak anisotropy antiferromagnet, and the Fe leads to shifts in the resonance field of the ferromagnet. The field shifts can be described by a temperature-dependent exchange anisotropy H_{dyn}^{AFM} . H_{dyn}^{AFM} depends on the orientation direction of the applied field relative to the magnetic anisotropy axis, and a non-monotonic dependence on KNiF3 thickness. Three thickness regimes appear that correspond to different values of exchange bias in each region. A qualitative understanding of the basis for these three thickness regimes due to spin canting at the interfaces is presented. Our results illustrate a method to tune the value of exchange anisotropy using a combination of different antiferromagnets.

  18. Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Li Hongyan [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Klem, Michael T.; Sebby, Karl B.; Singel, David J. [Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Young, Mark [Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Douglas, Trevor [Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Idzerda, Yves U. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States)], E-mail: Idzerda@montana.edu

    2009-02-15

    Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles' easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size.

  19. Halogen effect on structure and 13C NMR chemical shift of 3,6-disubstituted-N-alkyl carbazoles

    DEFF Research Database (Denmark)

    Radula-Janik, Klaudia; Kupka, Teobald; Ejsmont, Krzysztof; Daszkiewicz, Zdzislaw; Sauer, Stephan P. A.

    2013-01-01

    Structures of selected 3,6-dihalogeno-N-alkyl carbazole derivatives were calculated at the B3LYP/6-311++G(3df,2pd) level of theory and their 13C NMR isotropic nuclear shieldings were predicted using density functional theory (DFT). The model compounds contained 9H-, N-methyl and N-ethyl derivatives....... The relativistic effect of Br and I atoms on nuclear shieldings was modeled using the spin-orbit ZORA method. Significant heavy atom shielding effects for the carbon atom directly bonded with bromine and iodine were observed (~ -10 and ~ -30 ppm while the other carbon shifts were practically...

  20. Magnetic and structural anisotropies of Co2FeAl Heusler alloy epitaxial thin films

    Science.gov (United States)

    Gabor, M. S.; Petrisor, T., Jr.; Tiusan, C.; Hehn, M.; Petrisor, T.

    2011-10-01

    This paper shows the correlation between chemical order, lattice strains, and magnetic properties of Heusler Co2FeAl films epitaxially grown on MgO(001). A detailed magnetic characterization is performed using vector-field magnetometery combined with a numerical Stoner-Wohlfarth analysis. We demonstrate the presence of three types of in-plane anisotropies: one biaxial, as expected for the cubic symmetry, and two uniaxial. The three anisotropies show different behavior with the annealing temperature. The biaxial anisotropy shows a monotonic increase. The uniaxial anisotropy that is parallel to the hard biaxial axes (related to chemical homogeneity) decreases, while the anisotropy that is supposed to have a magnetostatic origin remains constant.

  1. Fabrication of epitaxial Fe nanodot arrays and anisotropy engineering

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, H. M.; Kim, S. H.; Lee, H. S.; Lee, J. [Yonsei University, Seoul (Korea, Republic of)

    2010-04-15

    Arrays of Fe nanodots were fabricated from an epitaxial Fe (20 nm) film on Cu (001)/Si(001) by using laser interference lithography and chemical wet etching. The nanodots were aligned parallel to the two magnetic hard directions of the film and were arranged on rectangular lattices of different periods in order to engineer the magnetic anisotropy of the system by using the shape of array. As the separation between dots along one direction decrease from 550 nm to 150 nm, the dipole interaction effect became strong, and finally a uniaxial magnetic anisotropy were realized.

  2. Topographical Anisotropy and Wetting of Ground Stainless Steel Surfaces

    Directory of Open Access Journals (Sweden)

    Cornelia Bellmann

    2012-12-01

    Full Text Available Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different mechanically modified stainless steel surfaces. The surfaces were analyzed using high-resolution confocal microscopy, resulting in detailed information about the topographic properties. In addition, static water contact angle measurements were carried out to characterize the surface heterogeneity of the samples. The effect of morphological anisotropy on water contact angle anisotropy was investigated. The correlation between topography and wetting was studied by means of a model of wetting proposed in the present work, that allows quantifying the air volume of the interface water drop-stainless steel surface.

  3. Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of 13C chemical shifts

    Directory of Open Access Journals (Sweden)

    Simone Di Micco

    2013-12-01

    Full Text Available In this paper the stereostructural investigation of two new oxygenated polyketides, plakilactones G and H, isolated from the marine sponge Plakinastrella mamillaris collected at Fiji Islands, is reported. The stereostructural studies began on plakilactone H by applying an integrated approach of the NOE-based protocol and quantum mechanical calculations of 13C chemical shifts. In particular, plakilactone H was used as a template to extend the application of NMR-derived interproton distances to a highly flexible molecular system with simultaneous assignment of four non-contiguous stereocenters. Chemical derivatization and quantum mechanical calculations of 13C on plakilactone G along with a plausible biogenetic interconversion between plakilactone G and plakilactone H allowed us to determine the absolute configuration in this two new oxygenated polyketides.

  4. Two-dimensional NMR measurement and point dipole model prediction of paramagnetic shift tensors in solids

    Energy Technology Data Exchange (ETDEWEB)

    Walder, Brennan J.; Davis, Michael C.; Grandinetti, Philip J. [Department of Chemistry, Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210 (United States); Dey, Krishna K. [Department of Physics, Dr. H. S. Gour University, Sagar, Madhya Pradesh 470003 (India); Baltisberger, Jay H. [Division of Natural Science, Mathematics, and Nursing, Berea College, Berea, Kentucky 40403 (United States)

    2015-01-07

    A new two-dimensional Nuclear Magnetic Resonance (NMR) experiment to separate and correlate the first-order quadrupolar and chemical/paramagnetic shift interactions is described. This experiment, which we call the shifting-d echo experiment, allows a more precise determination of tensor principal components values and their relative orientation. It is designed using the recently introduced symmetry pathway concept. A comparison of the shifting-d experiment with earlier proposed methods is presented and experimentally illustrated in the case of {sup 2}H (I = 1) paramagnetic shift and quadrupolar tensors of CuCl{sub 2}⋅2D{sub 2}O. The benefits of the shifting-d echo experiment over other methods are a factor of two improvement in sensitivity and the suppression of major artifacts. From the 2D lineshape analysis of the shifting-d spectrum, the {sup 2}H quadrupolar coupling parameters are 〈C{sub q}〉 = 118.1 kHz and 〈η{sub q}〉 = 0.88, and the {sup 2}H paramagnetic shift tensor anisotropy parameters are 〈ζ{sub P}〉 = − 152.5 ppm and 〈η{sub P}〉 = 0.91. The orientation of the quadrupolar coupling principal axis system (PAS) relative to the paramagnetic shift anisotropy principal axis system is given by (α,β,γ)=((π)/2 ,(π)/2 ,0). Using a simple ligand hopping model, the tensor parameters in the absence of exchange are estimated. On the basis of this analysis, the instantaneous principal components and orientation of the quadrupolar coupling are found to be in excellent agreement with previous measurements. A new point dipole model for predicting the paramagnetic shift tensor is proposed yielding significantly better agreement than previously used models. In the new model, the dipoles are displaced from nuclei at positions associated with high electron density in the singly occupied molecular orbital predicted from ligand field theory.

  5. Influence of Chemical Effect on the Kβ/Kα Intensity Ratios and Kβ Energy Shift of Co, Ni, Cu, and Zn Complexes

    Institute of Scientific and Technical Information of China (English)

    G. Apaydma, V. Ayhkg; Z. Biyiklioglu; E. Tirasoglu; H. Kantekin

    2008-01-01

    Chemical effects on the Kβ/Kα intensity ratios and ΔE energy differences for Co, Ni, Cu, and Zn complexes were investigated. The samples were excited by 59.5 keV γ-rays from a 241 Am annular radioactive source. K X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. We observed the effects of different ligands on the Kβ/Kα intensity ratios and ΔE energy differences for Co, Ni, Cu, and Zn complexes. We tried to investigate chemical effects on central atoms using the behaviors of different ligands in these complexes. The experimental values of Kβ/Kα were compared with the theoretical and other experimental values of pure Co, Ni, Cu, and Zn.

  6. Determination of the configuration in six-membered saturated heterocycles (N, P, S, Se) and their oxidation products using experimental and calculated NMR chemical shifts

    Czech Academy of Sciences Publication Activity Database

    Buděšínský, Miloš; Vaněk, Václav; Dračínský, Martin; Pohl, Radek; Poštová Slavětínská, Lenka; Sychrovský, Vladimír; Pícha, Jan; Císařová, I.

    2014-01-01

    Roč. 70, č. 25 (2014), s. 3871-3886. ISSN 0040-4020 R&D Projects: GA ČR GA203/09/1919; GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : six-membered saturated heterocycles (N, P, S, Se) * oxidation products * configuration * NMR * quantum chemical calculations * X-ray structures Subject RIV: CC - Organic Chemistry Impact factor: 2.641, year: 2014

  7. Hash: a program to accurately predict protein H{sup {alpha}} shifts from neighboring backbone shifts

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Jianyang, E-mail: zengjy@gmail.com [Tsinghua University, Institute for Interdisciplinary Information Sciences (China); Zhou Pei [Duke University Medical Center, Department of Biochemistry (United States); Donald, Bruce Randall [Duke University, Department of Computer Science (United States)

    2013-01-15

    Chemical shifts provide not only peak identities for analyzing nuclear magnetic resonance (NMR) data, but also an important source of conformational information for studying protein structures. Current structural studies requiring H{sup {alpha}} chemical shifts suffer from the following limitations. (1) For large proteins, the H{sup {alpha}} chemical shifts can be difficult to assign using conventional NMR triple-resonance experiments, mainly due to the fast transverse relaxation rate of C{sup {alpha}} that restricts the signal sensitivity. (2) Previous chemical shift prediction approaches either require homologous models with high sequence similarity or rely heavily on accurate backbone and side-chain structural coordinates. When neither sequence homologues nor structural coordinates are available, we must resort to other information to predict H{sup {alpha}} chemical shifts. Predicting accurate H{sup {alpha}} chemical shifts using other obtainable information, such as the chemical shifts of nearby backbone atoms (i.e., adjacent atoms in the sequence), can remedy the above dilemmas, and hence advance NMR-based structural studies of proteins. By specifically exploiting the dependencies on chemical shifts of nearby backbone atoms, we propose a novel machine learning algorithm, called Hash, to predict H{sup {alpha}} chemical shifts. Hash combines a new fragment-based chemical shift search approach with a non-parametric regression model, called the generalized additive model, to effectively solve the prediction problem. We demonstrate that the chemical shifts of nearby backbone atoms provide a reliable source of information for predicting accurate H{sup {alpha}} chemical shifts. Our testing results on different possible combinations of input data indicate that Hash has a wide rage of potential NMR applications in structural and biological studies of proteins.

  8. Enhanced spectral resolution in RNA HCP spectra for measurement of 3JC2'P and 3JC4'P couplings and 31P chemical shift changes upon weak alignment

    International Nuclear Information System (INIS)

    The 'out-and-back' 3D HCP experiment, using gradient- and sensitivity-enhanced detection, provides a convenient method for assignment of the 31P NMR spectra and accurate measurement of the 31P chemical shifts of ribonucleic acids. The 13C resolution in such spectra can be doubled, at the cost of a 50% reduction in sensitivity, by combining 13C evolution during the 13C-31P de- and rephasing periods. The multiple connectivities observable for a given 31P, including correlations to the intranucleotide C5'H2 and C4'H groups, and the C2'H, C3'H and C4'H groups of the preceding nucleotide, permit independent measurements of the 31P shift. The 13C spectrum of these groups is typically crowded for an RNA molecule in isotropic solution and overlap becomes more problematic in media used to achieve partial alignment. However, many of these correlations are resolvable in the combined-evolution HCP spectrum. The difference in 31P chemical shift between isotropic solution and a medium containing liquid crystalline Pf1 provides information on the orientation of phosphate groups. The intensities measured in the 3D HCP spectrum, obtained for an isotropic sample, yield values for the 3JC2'P and 3JC4'P couplings, thereby providing important restraints for the backbone torsion angles ε and β. The experiments are illustrated for a uniformly 13C-enriched, 24-residue stem-loop RNA sequence, and results for the helical stem region show close agreement between observed Δδ(31P) values and those predicted for a model A-form RNA helix when using a uniform 31P CSA tensor. This confirms that Δδ(31P) values can be used directly as restraints in refining nucleic acid structures

  9. Spin confinement by anisotropy modulation

    Energy Technology Data Exchange (ETDEWEB)

    Bland, J.A.C. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom)]. E-mail: jacb1@phy.cam.ac.uk; Lew, W.S.; Li, S.P.; Lopez-Diaz, L.; Vaz, C.A.F. [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Natali, M.; Chen, Y. [Laboratoire de Photonique et de Nanostructures, CNRS-LPN, Marcoussis (France)

    2002-10-07

    The spin configuration in a magnet is in general a 'natural' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic domain wall-the 'anisotropy constrained' magnetic wall. Micromagnetic simulations indicate that the wall is asymmetric, has a small out-of-plane component and has no mobility under external perturbation. (author)

  10. Spin confinement by anisotropy modulation

    Science.gov (United States)

    Bland, J. A. C.; Lew, W. S.; Li, S. P.; Lopez-Diaz, L.; Vaz, C. A. F.; Natali, M.; Chen, Y.

    2002-10-01

    The spin configuration in a magnet is in general a `natural' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic domain wall-the `anisotropy constrained' magnetic wall. Micromagnetic simulations indicate that the wall is asymmetric, has a small out-of-plane component and has no mobility under external perturbation.

  11. Spacetime anisotropy affects cosmological entanglement

    CERN Document Server

    Pierini, Roberto; Mancini, Stefano

    2016-01-01

    Most existing cosmological entanglement studies are focused on the isotropic Robertson-Walker (RW) spacetime. Here we go beyond this limitation and study the influence of anisotropy on entanglement generated by dynamical spacetime. Since the isotropic spacetime is viewed as a background medium and the anisotropy is incorporated as perturbation, we decompose entanglement entropy into isotropic and anisotropic contributions. The latter is shown to be non-negligible by analyzing two cosmological models with weak and conformal coupling. We also show the possibility of using entanglement to infer about universe features.

  12. Amiba Observation of CMB Anisotropies

    Science.gov (United States)

    Ng, Kin-Wang

    2003-03-01

    The Array for Microwave Background Anisotropies (AMiBA), a 13-element dual-channel 85-105 GHz interferometer array with full polarization capabilities, is being built to search for high redshift clusters of galaxies via the Sunyaev-Zel'dovich effect as well as to probe the polarization properties of the cosmic microwave background (CMB). We discuss several important issues in the observation of the CMB anisotropies such as observing strategy, l space resolution and mosaicing, optimal estimation of the power spectra, and ground pickup removal.

  13. Synthesis, antimicrobial evaluation and theoretical prediction of NMR chemical shifts of thiazole and selenazole derivatives with high antifungal activity against Candida spp.

    Science.gov (United States)

    Łączkowski, Krzysztof Z.; Motylewska, Katarzyna; Baranowska-Łączkowska, Angelika; Biernasiuk, Anna; Misiura, Konrad; Malm, Anna; Fernández, Berta

    2016-03-01

    Synthesis and investigation of antimicrobial activities of novel thiazoles and selenazoles is presented. Their structures were determined using NMR, FAB(+)-MS, HRMS and elemental analyses. To support the experiment, theoretical calculations of the 1H NMR shifts were carried out for representative systems within the DFT B3LYP/6-311++G** approximation which additionally confirmed the structure of investigated compounds. Among the derivatives, compounds 4b, 4h, 4j and 4l had very strong activity against reference strains of Candida albicans ATCC and Candida parapsilosis ATCC 22019 with MIC = 0.49-7.81 μg/ml. In the case of compounds 4b, 4c, 4h - 4j and 4l, the activity was very strong against of Candida spp. isolated from clinical materials, i.e. C. albicans, Candida krusei, Candida inconspicua, Candida famata, Candida lusitaniae, Candida sake, C. parapsilosis and Candida dubliniensis with MIC = 0.24-15.62 μg/ml. The activity of several of these was similar to the activity of commonly used antifungal agent fluconazole. Additionally, compounds 4m - 4s were found to be active against Gram-positive bacteria, both pathogenic staphylococci Staphylococcus aureus ATCC with MIC = 31.25-125 μg/ml and opportunistic bacteria, such as Staphylococcus epidermidis ATCC 12228 and Micrococcus luteus ATCC 10240 with MIC = 7.81-31.25 μg/ml.

  14. K Variations and Anisotropy: Microstructure Effect and Numerical Predictions

    Institute of Scientific and Technical Information of China (English)

    李旭东; 李华清

    2003-01-01

    Computer experiments were performed on simulated polycrystalline material samples that possess locally anisotropic microstructures to investigate stress intensity factor ( K ) variations and anisotropy along fronts of microcracks of different sizes. The anisotropic K , arising from inhomogeneous stresses in broken grains, was determined for planar microcracks by using a weight function-based numerical technique. It has been found that the grain-orientation-geometry-induced local anisotropy produces large variations in K along front of microcracks, when the crack size is of the order of few grain diameters. Synergetic effect of grain orientation and geometry of broken grains control K variations and evolution along the microcrack front. The K variations may diminish at large crack sizes, signifying a shift of K calculation to bulk stress dependence from local stress dependence. Local grain geometry and texture may lead to K anisotropy, producing unusually higher/lower K at a segment of the crack front. Either K variation or anisotropy cannot be ignored when assessing a microcrack.

  15. Ultrasonic characterization of CFRP anisotropy

    Czech Academy of Sciences Publication Activity Database

    Kling, M.; Tokar, Daniel; Převorovský, Zdeněk

    Praha: ČVUT v Praze, 2015 - (Hobza, T.), s. 71-80 ISBN 978-80-01-05841-1. [Stochastic and Physical Monitoring Systems 2015. Praha (CZ), 22.06.2015-27.06.2015] Institutional support: RVO:61388998 Keywords : anisotropy * carbon fiber -reinforced plastic * ultrasonic testing * signal processing Subject RIV: BI - Acoustics

  16. Cosmic ray anisotropy and its time variations

    International Nuclear Information System (INIS)

    Cosmic ray anisotropy is analysed on the base of the data of the worldwide network of neutron monitors for the period of 1958-1972. 11-year variation of anisotropy phase and amplitude is investigated. Three-dimensional cosmic ray anisotropy in interplanetary space is calculated. (orig./WBU)

  17. 1H, 13C and 13N chemical shifts and 1H-15N and 13C-15N heteronuclear spin-spin coupling constants n the NMR spectra of 5-substituted furfural oximes

    International Nuclear Information System (INIS)

    The 1H, 13C, and 15N NMR spectra of 15N-enriched 5-substituted furfural oximes were investigated. It was shown that the chemical shifts of the ring atoms and the oxime group correlate satisfactorily with the F and R substituent constants, whereas their sensitivity to the effect of the substituents is lower than in monosubstituted furan derivatives. The constants of spin-spin coupling between the ring protons and the oxime group were determined. An analysis of the 1H-1H spin-spin coupling constants (SSCC) on the basis of their stereospecificity indicates that the E isomers have primarily an s-trans conformation in polar dimethyl sulfoxide, whereas the Z isomers, on the other hand, have an s-cis conformation. The signs of the direct and geminal 13C-15N SSCC were determined for 5-trimethylsilylfurfural oxime

  18. Iboga alkaloids from Peschiera affinis (Apocynaceae) - unequivocal {sup 1}H and {sup 13}C chemical shift assignments: antioxidant activity; Alcaloides iboga de Peschiera affinis (Apocynaceae) - atribuicao inequivoca dos deslocamentos quimicos dos atomos de hidrogenio e carbono: atividade antioxidante

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Allana Kellen L.; Magalhaes, Ticiane S.; Monte, Francisco Jose Q.; Mattos, Marcos Carlos de; Oliveira, Maria Conceicao F. de; Almeida, Maria Mozarina B.; Lemos, Telma L.G.; Braz-Filho, Raimundo [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Quimica Organica e Inorganica], e-mail: tlemos@dqoi.ufc.br

    2009-07-01

    Six known alkaloids iboga type and the triterpene {alpha}- and {beta}-amyrin acetate were isolated from the roots and stems of Peschiera affinis. Their structures were characterized on the basis of spectral data mainly NMR and mass spectra. 1D and 2D NMR spectra were also used to unequivocal {sup 1}H and {sup 13}C chemical shift assignments of alkaloids. The ethanolic extract of roots, alkaloidic and no-alkaloidic fractions and iso-voacristine hydroxyindolenine and voacangine were evaluated for their antioxidative properties using an autographic assay based on {beta}-carotene bleaching on TLC plates, and also spectrophotometric detection by reduction of the stable DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical. (author)

  19. Hard X-ray photoelectron spectra (HXPES) of bulk non-conductor vitreous SiO2: Minimum linewidths and surface chemical shifts

    International Nuclear Information System (INIS)

    Highlights: • Electronic structure of non-conducting glass studied by hard X-ray photoelectron spectroscopy. • A thin film of Cr was deposited on the vitreous SiO2 glass to overcome the sample charging. • Excellent O 1s and Si 1s linewidths were obtained, matching those reported using the laboratory based Kratos Axis Ultra spectrometer equipped with a magnetic compensation system. • The bulk and interface states of non-conducting samples are studied as a function of photon energy. - Abstract: Hard X-ray photoelectron spectra (2200 eV to 5000 eV photon energies) have been obtained for the first time on a bulk non-conductor, vitreous SiO2, on a high resolution (E/ΔE of 10,000) synchrotron beamline at the Canadian Light Source (CLS). To minimize charging and differential charging, the SiO2 was coated with very thin layers (0.5 to 1.5 nm) of Cr metal. The O 1s linewidth obtained at 2500 eV photon energy was 1.26 eV—the minimum linewidth for SiO2—and in good agreement with that obtained at 1486 eV on a Kratos Axis Ultra spectrometer equipped with a magnetic charge compensation system. The Si 1s linewidth of 1.5 eV, somewhat broader than that previously obtained at 1486 eV on the Si 2p3/2 line of 1.16 eV, is mainly due to the much larger inherent Si 1s linewidth (0.5 eV) compared to the inherent Si 2p linewidth (<0.1 eV). Both linewidths are dominated by the large final state vibrational broadening previously described. The Cr coating produces surface monolayers of interfacial Cr “suboxide” (Cr-subox), Cr metal, and a surface Cr oxide (Cr-surfox). Cr-subox (Si−O−Cr) gives rise to the weak near-surface Si 1s peak, while both oxides give rise to both the weak surface O 1s peak and the Cr 2p oxide peak. Both the O 1s and Si 1s surface peaks are shifted by ∼2 eV relative to the large bulk Si 1s and O 1s peaks. The weak Si 1s and O 1s surface peaks along with the Cr 2p oxide peak decrease in intensity greatly as the photon energy increases, due to an

  20. Using NMR chemical shift imaging to monitor swelling and molecular transport in drug-loaded tablets of hydrophobically modified poly(acrylic acid): methodology and effects of polymer (in)solubility.

    Science.gov (United States)

    Knöös, Patrik; Topgaard, Daniel; Wahlgren, Marie; Ulvenlund, Stefan; Piculell, Lennart

    2013-11-12

    A new technique has been developed using NMR chemical shift imaging (CSI) to monitor water penetration and molecular transport in initially dry polymer tablets that also contain small low-molecular weight compounds to be released from the tablets. Concentration profiles of components contained in the swelling tablets could be extracted via the intensities and chemical shift changes of peaks corresponding to protons of the components. The studied tablets contained hydrophobically modified poly(acrylic acid) (HMPAA) as the polymer component and griseofulvin and ethanol as hydrophobic and hydrophilic, respectively, low-molecular weight model compounds. The water solubility of HMPAA could be altered by titration with NaOH. In the pure acid form, HMPAA tablets only underwent a finite swelling until the maximum water content of the polymer-rich phase, as confirmed by independent phase studies, had been reached. By contrast, after partial neutralization with NaOH, the polyacid became fully miscible with water. The solubility of the polymer affected the water penetration, the polymer release, and the releases of both ethanol and griseofulvin. The detailed NMR CSI concentration profiles obtained highlighted the clear differences in the disintegration/dissolution/release behavior for the two types of tablet and provided insights into their molecular origin. The study illustrates the potential of the NMR CSI technique to give information of importance for the development of pharmaceutical tablets and, more broadly, for the general understanding of any operation that involves the immersion and ultimate disintegration of a dry polymer matrix in a solvent. PMID:24106807

  1. Anisotropies in the gravitational wave background as a probe of the cosmic string network

    CERN Document Server

    Kuroyanagi, Sachiko; Yonemaru, Naoyuki; Kumamoto, Hiroki

    2016-01-01

    Pulsar timing arrays are one of the powerful tools to test the existence of cosmic strings through searching for the gravitational wave background. The amplitude of the background connects to information on cosmic strings such as the tension and string network properties. In addition, one may be able to extract more information on properties of cosmic strings by measuring anisotropies in the gravitational wave (GW) background. In this paper, we provide estimates of the level of anisotropy expected in the GW background generated by cusps on cosmic strings. We find that the anisotropy level strongly depends on the initial loop size $\\alpha$, and thus we may be able to put constraint on $\\alpha$ by measuring the anisotropy of the GW background. We also find that certain regions of the parameter space can be probed by shifting the observation frequency of GWs.

  2. Magnetoresistance Anisotropy in WTe2

    Science.gov (United States)

    Thoutam, Laxman Raju; Wang, Yonglei; Xiao, Zhili; Das, Saptarshi; Luican Mayer, Adina; Divan, Ralu; Crabtree, George W.; Kwok, Wai Kwong

    We report the angle dependence of the magnetoresistance in WTe2. Being a layered material, WTe2 is considered to be electronically two-dimensional (2D). Our results demonstrate that it is in fact 3D with an anisotropy of effective mass as small as 2. We measured the magnetic field dependence of the sample resistance R(H) at various angles between the applied magnetic field with respect to the c-axis of the crystal and found that they can be scaled based on the mass anisotropy, which changes from ~2 to ~5 with decreasing temperature in the Fermi liquid state. We will also discuss the origin of the turn-on temperature behavior in this material.

  3. Microwave Anisotropies from Random Sources

    CERN Document Server

    Ferreira, P G

    1996-01-01

    I report on recent developments in the theory of cosmic background radiation perturbations. I describe ways of modeling alternatives to the canonical Gaussian theories within the standard framework of cosmological perturbation theory. Some comments are made on using these techniques to resolve the uncertainties in theories of structure formation with topological defects. (To appear in the proceedings of the XXXIth Moriond meeting, ``Microwave Background Anisotropies'')

  4. Structure-based predictions of 13C-NMR chemical shifts for a series of 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indoles derivatives using GA-based MLR method

    Science.gov (United States)

    Ghavami, Raouf; Sadeghi, Faridoon; Rasouli, Zolikha; Djannati, Farhad

    2012-12-01

    Experimental values for the 13C NMR chemical shifts (ppm, TMS = 0) at 300 K ranging from 96.28 ppm (C4' of indole derivative 17) to 159.93 ppm (C4' of indole derivative 23) relative to deuteride chloroform (CDCl3, 77.0 ppm) or dimethylsulfoxide (DMSO, 39.50 ppm) as internal reference in CDCl3 or DMSO-d6 solutions have been collected from literature for thirty 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indole derivatives containing different substituted groups. An effective quantitative structure-property relationship (QSPR) models were built using hybrid method combining genetic algorithm (GA) based on stepwise selection multiple linear regression (SWS-MLR) as feature-selection tools and correlation models between each carbon atom of indole derivative and calculated descriptors. Each compound was depicted by molecular structural descriptors that encode constitutional, topological, geometrical, electrostatic, and quantum chemical features. The accuracy of all developed models were confirmed using different types of internal and external procedures and various statistical tests. Furthermore, the domain of applicability for each model which indicates the area of reliable predictions was defined.

  5. The role of pressure anisotropy on the maximum mass of cold compact stars

    Indian Academy of Sciences (India)

    S Karmakar; S Mukherjee; S Sharma; S D Maharaj

    2007-06-01

    We study the physical features of a class of exact solutions for cold compact anisotropic stars. The effect of pressure anisotropy on the maximum mass and surface red-shift is analysed in the Vaidya–Tikekar model. It is shown that maximum compactness, red-shift and mass increase in the presence of anisotropic pressures; numerical values are generated which are in agreement with observation.

  6. [Cosmic Microwave Background (CMB) Anisotropies

    Science.gov (United States)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10-7, where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  7. [Cosmic Microwave Background (CMB) Anisotropies

    Science.gov (United States)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10(exp -7), where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  8. On the magnetocrystalline anisotropy of greigite (Fe3S4)

    Science.gov (United States)

    Winklhofer, Michael; Chang, Liao; Eder, Stephan H. K.

    2014-04-01

    ferrimagnetic mineral greigite (cubic Fe3S4) is well known as an intracellular biomineralization product in magnetic bacteria and as a widely occurring authigenic mineral in anoxic sediments. Due to the lack of suitable single-crystal specimens, the magnetic anisotropy parameters of greigite have remained poorly constrained, to the point where not even the easy axis of magnetization is known. Here we report on an effort to determine the anisotropy parameters on the basis of ferromagnetic resonance (FMR) powder spectroscopy on hydrothermally synthesized, chemically pure greigite microcrystals dispersed in a nonmagnetic matrix. In terms of easy axis orientations, the FMR data are consistent with or , or less likely, a more general type. With a g factor of 2.09, the anisotropy field is about 90 mT and in some samples may reach 125 mT, compared to 30 mT for cubic magnetite. This confirms the dominating role of cubic anisotropy on the magnetic properties of greigite, which we show to be responsible for large SIRM/k values. K1 is in the range -15 … -23 J/m3 () or +10 … +15 kJ/m3 (), yielding upper limits of 44 or 34 nm for the superparamagnetic grain size, respectively.

  9. Magnetic anisotropy of crystalline Fe films grown on (001) GaAs substrates using Ge buffer layers

    Science.gov (United States)

    Bac, Seul-Ki; Lee, Hakjoon; Lee, Sangyeop; Choi, Seonghoon; Yoo, Taehee; Lee, Sanghoon; Liu, X.; Furdyna, J. K.

    2016-05-01

    Magnetic anisotropy of Fe films grown on (001) GaAs substrates using Ge buffer layers were investigated by planar Hall effect measurements. In addition to phenomena arising from dominant cubic symmetry of the Fe specimen, the study of angular dependence of magnetization reversal revealed breaking of this symmetry in the form of systematic asymmetric shifts of magnetic hysteresis loops around the crystallographic directions. We ascribe such symmetry breaking to an admixture of uniaxial anisotropy associated with the [100] direction in the Fe film. To determine the parameters associated with this uniaxial anisotropy, we quantitatively analyze the asymmetric shifts of the hysteresis loop centers from the directions. Even though the value of these parameters turns out to be relatively small compared to that of the cubic anisotropy (by about two orders of magnitude), they survive up to room temperature.

  10. Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles.

    Science.gov (United States)

    Pérez, N; Guardia, P; Roca, A G; Morales, M P; Serna, C J; Iglesias, O; Bartolomé, F; García, L M; Batlle, X; Labarta, A

    2008-11-26

    The effect of surface anisotropy on the distribution of energy barriers in magnetic fine particles of nanometer size is discussed within the framework of the Tln(t/τ(0)) scaling approach. The comparison between the distributions of the anisotropy energy of the particle cores, calculated by multiplying the volume distribution by the core anisotropy, and of the total anisotropy energy, deduced by deriving the master curve of the magnetic relaxation with respect to the scaling variable Tln(t/τ(0)), enables the determination of the surface anisotropy as a function of the particle size. We show that the contribution of the particle surface to the total anisotropy energy can be well described by a size-independent value of the surface energy per unit area which permits the superimposition of the distributions corresponding to the particle core and effective anisotropy energies. The method is applied to a ferrofluid composed of non-interacting Fe(3-x)O(4) particles of 4.9 nm average size and x about 0.07. Even though the size distribution is quite narrow in this system, a relatively small value of the effective surface anisotropy constant K(s) = 2.9 × 10(-2) erg cm(-2) gives rise to a dramatic broadening of the total energy distribution. The reliability of the average value of the effective anisotropy constant, deduced from magnetic relaxation data, is verified by comparing it to that obtained from the analysis of the shift of the ac susceptibility peaks as a function of the frequency. PMID:21836285

  11. On the calculation of Mossbauer isomer shift

    NARCIS (Netherlands)

    Filatov, Michael

    2007-01-01

    A quantum chemical computational scheme for the calculation of isomer shift in Mossbauer spectroscopy is suggested. Within the described scheme, the isomer shift is treated as a derivative of the total electronic energy with respect to the radius of a finite nucleus. The explicit use of a finite nuc

  12. Continuously tunable all-in-fiber devices based on thermal and electrical control of negative dielectric anisotropy liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Wei, Lei; Eskildsen, Lars; Weirich, Johannes;

    2009-01-01

    We infiltrate photonic crystal fibers with a negative dielectric anisotropy liquid crystal. 396nm bandgap shift is obtained in the temperature range 22°C-80°C, and 67 nm shift of long-wavelength bandgap edge is achieved by applying a voltage of 200Vrms. The polarization sensitivity and correspond......We infiltrate photonic crystal fibers with a negative dielectric anisotropy liquid crystal. 396nm bandgap shift is obtained in the temperature range 22°C-80°C, and 67 nm shift of long-wavelength bandgap edge is achieved by applying a voltage of 200Vrms. The polarization sensitivity and...

  13. Pseudocontact shifts from mobile spin labels

    CERN Document Server

    Suturina, E

    2016-01-01

    This paper presents a detailed analysis of the pseudocontact shift (PCS) field induced by a mobile spin label that is viewed as a probability density distribution with an associated magnetic susceptibility. It is demonstrated that anisotropy in this density can lead to significant deviations from the commonly used point dipole approximation for PCS. Analytical and numerical solutions are presented for the general partial differential equation that describes the non-point case. It is also demonstrated that it is possible to reconstruct paramagnetic centre probability distributions from experimental PCS data.

  14. Lichtinduzierte Generierung und Charakterisierung optischer Anisotropie

    OpenAIRE

    Jung, Carl Christoph

    2005-01-01

    Eine Nutzung der optischen Anisotropie dünner Schichten ist vor allem für die Displaytechnologie, die optische Datenspeicherung und für optische Sicherheitselemente von hoher Bedeutung. Diese Doktorarbeit befasst sich mit theoretischen und experimentellen Untersuchung von dreidimensionaler Anisotropie und dabei insbesondere mit der Untersuchung von lichtinduzierter dreidimensionaler Anisotropie in organischen dünnen Polymer-Schichten. Die gewonnenen Erkentnisse und entwickelten Methoden könne...

  15. Anomalous Nernst Effect with Magnetocrystalline Anisotropy (110)

    Science.gov (United States)

    Chesman, Carlos; Costa Neto, Jose; Department of Physics-UFRN Team

    2014-03-01

    When a ferromagnetic material is submitted to a temperature gradient and the magnetic field generates voltage on the edges of the samples, this is called the Anomalous Nernst Effect (ANE). The Heusler alloys that currently exhibit this effect are the most promising for spintronics and spin caloritronics. In this study we perform a theoretical investigation of voltage curves associated to the ANE, when the material displays magnetocrystalline anisotropy for experimental results in two configurations, ANE versus applied magnetic field and planar angle variations of ANE. We analyzed three types of magnetocrystalline anisotropy: cubic anisotropy (100) with C4 symmetry, uniaxial anisotropy with C2 symmetry and cubic anisotropy (110). The aim was to prove that cubic anisotropy (110) is equivalent to anisotropy (100) combined with uniaxial anisotropy. Theoretical fitting of experimental ANE data demonstrates this total equivalence and that a new interpretation with the use of cubic anisotropy (110) may be due to the atomic arrangement of the so-called full-Heusler. Comparative analyses of Co2FeAl and Co2MnGe alloys will be presented. CNPq, CAPES, FAPERN.

  16. Seismic Anisotropy Along the Eurasian-Arabian Plate Boundary

    Science.gov (United States)

    Sandvol, E. A.; Skobeltsyn, G.; Turkelli, N.; Polat, G.; Yetirmishli, G.; Godoladze, T.; Mellors, R. J.; Gok, R.

    2014-12-01

    The Anatolian plateau and Caucasus are part of the orogenic belt that formed as the result of the closure of the Neo Tethys Ocean and the ensuing continental collision of Arabian and Eurasian plates. Multiple tomographic studies of both P and S wave velocities all show a broad low velocity zone beneath East Anatolian and North Iranian plateaus. The low velocity zone appears to range from the Moho to a depth 150 km, which suggests asthenospheric material underlying a very thin lithosphere of eastern Anatolia. This low velocity zone coincides with widespread Late Miocene - Quaternary calc-alkaline volcanic products of mantle origin. This very shallow asthenosphere strongly implies that any present day anisotropy is likely to reflect very recent mantle deformation. In order to image seismic anisotropy and improve understanding of the nature of mantle deformation in young continental collision zone we analyzed data from the IRIS station KIV and the regional seismic networks of Turkey, Azerbaijan and Georgia to determine shear wave splitting fast polarization directions and delay times in the region. Our results show that the fast polarization directions are quite uniformly parallel to NE-SW across the East Anatolian Plateau and the westernmost part of the Greater Caucasus. The observed delay times decrease northward with the shortest located in the western Greater Caucasus. However, to the east, the fast polarization direction rotates clockwise until it becomes parallel to the EW topographic? trend in the Lesser Caucasus where the delay times are the largest in the region. The situation becomes more complex north of the Lesser Caucasus, in the central and eastern parts of the Greater Caucasus, where the fast polarization directions shift abruptly to the NNE-SSW. Furthemore, we find relatively strong evidence of layered anisotropy using a new method we have developed to image multi-layered polarization anisotropy from teleseismic core phases such as SKS.

  17. EFFECT OF SANDSTONE ANISOTROPY ON ITS HEAT AND MOISTURE TRANSPORT PROPERTIES

    Directory of Open Access Journals (Sweden)

    Jan Fořt

    2015-09-01

    Full Text Available Each type of natural stone has its own geological history, formation conditions, different chemical and mineralogical composition, which influence its possible anisotropy. Knowledge in the natural stones anisotropy represents crucial information for the process of stone quarrying, its correct usage and arrangement in building applications. Because of anisotropy, many natural stones exhibit different heat and moisture transport properties in various directions. The main goal of this study is to analyse several anisotropy indices and their effect on heat transport and capillary absorption. For the experimental determination of the anisotropy effect, five types of sandstone coming from different operating quarries in the Czech Republic are chosen. These materials are often used for restoration of culture heritage monuments as well as for other building applications where they are used as facing slabs, facade panels, decoration stones, paving, etc. For basic characterization of studied materials, determination of their bulk density, matrix density and total open porosity is done. Chemical composition of particular sandstones is analysed by X-Ray Fluorescence. Anisotropy is examined by the non-destructive measurement of velocity of ultrasonic wave propagation. On the basis of ultrasound testing data, the relative anisotropy, total anisotropy and anisotropy coefficient are calculated. Then, the measurement of thermal conductivity and thermal diffusivity in various directions of samples orientation is carried out. The obtained results reveal significant differences between the parameters characterizing the heat transport in various directions, whereas these values are in accordance with the indices of anisotropy. Capillary water transport is described by water absorption coefficient measured using a sorption experiment, which is performed for distilled water and 1M NaCl water solution.  The measured data confirm the effect of anisotropy which is

  18. A comparative quantitative analysis of the IDEAL (iterative decomposition of water and fat with echo asymmetry and least-squares estimation) and the CHESS (chemical shift selection suppression) techniques in 3.0 T L-spine MRI

    Science.gov (United States)

    Kim, Eng-Chan; Cho, Jae-Hwan; Kim, Min-Hye; Kim, Ki-Hong; Choi, Cheon-Woong; Seok, Jong-min; Na, Kil-Ju; Han, Man-Seok

    2013-03-01

    This study was conducted on 20 patients who had undergone pedicle screw fixation between March and December 2010 to quantitatively compare a conventional fat suppression technique, CHESS (chemical shift selection suppression), and a new technique, IDEAL (iterative decomposition of water and fat with echo asymmetry and least squares estimation). The general efficacy and usefulness of the IDEAL technique was also evaluated. Fat-suppressed transverse-relaxation-weighed images and longitudinal-relaxation-weighted images were obtained before and after contrast injection by using these two techniques with a 1.5T MR (magnetic resonance) scanner. The obtained images were analyzed for image distortion, susceptibility artifacts and homogenous fat removal in the target region. The results showed that the image distortion due to the susceptibility artifacts caused by implanted metal was lower in the images obtained using the IDEAL technique compared to those obtained using the CHESS technique. The results of a qualitative analysis also showed that compared to the CHESS technique, fewer susceptibility artifacts and more homogenous fat removal were found in the images obtained using the IDEAL technique in a comparative image evaluation of the axial plane images before and after contrast injection. In summary, compared to the CHESS technique, the IDEAL technique showed a lower occurrence of susceptibility artifacts caused by metal and lower image distortion. In addition, more homogenous fat removal was shown in the IDEAL technique.

  19. Comparison of clinical semi-quantitative assessment of muscle fat infiltration with quantitative assessment using chemical shift-based water/fat separation in MR studies of the calf of post-menopausal women

    Energy Technology Data Exchange (ETDEWEB)

    Alizai, Hamza; Nardo, Lorenzo; Karampinos, Dimitrios C.; Joseph, Gabby B.; Yap, Samuel P.; Baum, Thomas; Krug, Roland; Majumdar, Sharmila; Link, Thomas M. [University of California, San Francisco, Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States)

    2012-07-15

    The goal of this study was to compare the semi-quantitative Goutallier classification for fat infiltration with quantitative fat-fraction derived from a magnetic resonance imaging (MRI) chemical shift-based water/fat separation technique. Sixty-two women (age 61 {+-} 6 years), 27 of whom had diabetes, underwent MRI of the calf using a T1-weighted fast spin-echo sequence and a six-echo spoiled gradient-echo sequence at 3 T. Water/fat images and fat fraction maps were reconstructed using the IDEAL algorithm with T2* correction and a multi-peak model for the fat spectrum. Two radiologists scored fat infiltration on the T1-weighted images using the Goutallier classification in six muscle compartments. Spearman correlations between the Goutallier grades and the fat fraction were calculated; in addition, intra-observer and inter-observer agreement were calculated. A significant correlation between the clinical grading and the fat fraction values was found for all muscle compartments (P < 0.0001, R values ranging from 0.79 to 0.88). Goutallier grades 0-4 had a fat fraction ranging from 3.5 to 19%. Intra-observer and inter-observer agreement values of 0.83 and 0.81 were calculated for the semi-quantitative grading. Semi-quantitative grading of intramuscular fat and quantitative fat fraction were significantly correlated and both techniques had excellent reproducibility. However, the clinical grading was found to overestimate muscle fat. (orig.)

  20. Sofic Tree-Shifts

    OpenAIRE

    Aubrun, Nathalie; Béal, Marie-Pierre

    2013-01-01

    We introduce the notion of sofic tree-shifts which corresponds to symbolic dynamical systems of infinite ranked trees accepted by finite tree automata. We show that, contrary to shifts of infinite sequences, there is no unique reduced deterministic irreducible tree automaton accepting an irreducible sofic tree-shift, but that there is a unique synchronized one, called the Fischer automaton of the tree-shift. We define the notion of almost of finite type tree-shift which are sofic tree-shifts accepted...

  1. Anisotropy resolved multidimensional emission spectroscopy (ARMES): A new tool for protein analysis.

    Science.gov (United States)

    Groza, Radu Constantin; Li, Boyan; Ryder, Alan G

    2015-07-30

    Structural analysis of proteins using the emission of intrinsic fluorophores is complicated by spectral overlap. Anisotropy resolved multidimensional emission spectroscopy (ARMES) overcame the overlap problem by the use of anisotropy, with chemometric analysis, to better resolve emission from different fluorophores. Total synchronous fluorescence scan (TSFS) provided information about all the fluorophores that contributed to emission while anisotropy provided information about the environment of each fluorophore. Here the utility of ARMES was demonstrated via study of the chemical and thermal denaturation of human serum albumin (HSA). Multivariate curve resolution (MCR) analysis of the constituent polarized emission ARMES data resolved contributions from four emitters: fluorescence from tryptophan (Trp), solvent exposed tyrosine (Tyr), Tyr in a hydrophobic environment, and room temperature phosphorescence (RTP) from Trp. The MCR scores, anisotropy, and literature validated these assignments and showed all the expected transitions during HSA unfolding. This new methodology for comprehensive intrinsic fluorescence analysis of proteins is applicable to any protein containing multiple fluorophores. PMID:26320645

  2. Nonlinear ferromagnetic resonance shift in nanostructures

    Science.gov (United States)

    Guo, Feng; Belova, Lyuba; McMichael, Robert

    2014-03-01

    In dynamic magnetic systems, various experiments have shown that the ferromagnetic resonance frequency can shift up or down with increasing driving power in the nonlinear regime. The resonance shift is important in understanding nonlinear physics in nanomagnets and for applications of spin-torque oscillators. Here, we present a systematic study on the sign of the nonlinear coefficient, i.e. the direction of the resonance field/frequency shift. We use ferromagnetic resonance force microscopy (FMRFM) to measure the ferromagnetic resonance of a series of submicron NiFe ellipses with varying aspect ratios. We find the sign of the resonance shift is determined by both the applied field and the anisotropy field. Our measurement and micromagnetic modeling results are in qualitative agreement with a macro-spin analysis developed by Slavin and Tiberkevich. However, both measurement and modeling results exhibit values of the nonlinear coefficient that are more positive (meaning that the resonance tends to shift toward low field direction) than are predicted by the macrospin model. We attribute the difference to the non-uniformity of the precession modes in the ellipses. By analogy with standing spin waves, we show that nonuniform precession tends to increase the nonlinear frequency coefficient through a magnetostatic mechanism.

  3. Influence of substituents on chemical shift of {delta}({sup 13}C) in the series of 5-methyl-5H-indole [2,3-b]quinoline derivatives; Wplyw podstawnikow na przesuniecie chemiczne {sigma}({sup 13}C) w serii pochodnych 5-metylo-5H-indolo-[2,3-b]chinoliny

    Energy Technology Data Exchange (ETDEWEB)

    Kamienska-Trela, K.; Kania, L.; Kaczmarek, L. [Inst. Chemii Organicznej, Polska Akademia Nauk, Warsaw (Poland)

    1994-12-31

    {sup 13}C NMR spectra of series of 5-methyl-5H-indole quinoline substituted with different groups and their number have been measured. The influence of steric and electronic properties of substituents on observed chemical shifts of {sup 13}C nuclei have been discussed. 1 fig., 1 tab.

  4. Spectroscopic (FT-IR, FT-Raman and UV-Visible) investigations, NMR chemical shielding anisotropy (CSA) parameters of 2,6-Diamino-4-chloropyrimidine for dye sensitized solar cells using density functional theory.

    Science.gov (United States)

    Gladis Anitha, E; Joseph Vedhagiri, S; Parimala, K

    2014-10-24

    The molecular structure, geometry optimization, vibrational frequencies of organic dye sensitizer 2,6-Diamino-4-chloropyrimidine (DACP) were studied based on Hartree-Fock (HF) and density functional theory (DFT) using B3LYP methods with 6-311++G(d,p) basis set. Ultraviolet-Visible (UV-Vis) spectrum was investigated by time dependent DFT (TD-DFT). Features of the electronic absorption spectrum in the UV-Visible regions were assigned based on TD-DFT calculation. The absorption bands are assigned to transitions. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer DACP is due to an electron injection process from excited dye to the semiconductor's conduction band. The observed and the calculated frequencies are found to be in good agreement. The energies of the frontier molecular orbitals (FMOS) have also been determined. The chemical shielding anisotropic (CSA) parameters are calculated from the NMR analysis, Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. PMID:25459717

  5. Anisotropy of successive air showers

    Science.gov (United States)

    Ochi, N.; Wada, T.; Yamashita, Y.; Ohashi, A.; Yamamoto, I.; Nakatsuka, T.; Large Area Air Shower (LAAS) Group

    2001-04-01

    We have investigated the anisotropy of successive air shower (SAS) events, which we define as the detection of many air showers within a short time window, using data from six stations of the Large Area Air Shower (LAAS) group. On the criterion of 22 air showers within 20 minutes, five SAS events are found against 1.4 expected from the Poisson distribution in Okayama University station's data. From six stations' data, we find 24 SAS events in total. By plotting them in equatorial coordinates, it is revealed that SAS events are observed more frequently when the Galactic plane is around the zenith. This can be attributed to a hypothetical small flux of ultra-high-energy γ-rays from the direction of the Galactic plane superposed on conventional cosmic rays. If this hypothesis is true, the analytical procedure used here has potential to measure ultra-high-energy γ-ray sources by even small air shower arrays like ours.

  6. Anisotropy of successive air showers

    International Nuclear Information System (INIS)

    We have investigated the anisotropy of successive air shower (SAS) events, which we define as the detection of many air showers within a short time window, using data from six stations of the Large Area Air Shower (LAAS) group. On the criterion of 22 air showers within 20 minutes, five SAS events are found against 1.4 expected from the Poisson distribution in Okayama University station's data. From six stations' data, we find 24 SAS events in total. By plotting them in equatorial coordinates, it is revealed that SAS events are observed more frequently when the Galactic plane is around the zenith. This can be attributed to a hypothetical small flux of ultra-high-energy γ-rays from the direction of the Galactic plane superposed on conventional cosmic rays. If this hypothesis is true, the analytical procedure used here has potential to measure ultra-high-energy γ-ray sources by even small air shower arrays like ours

  7. CMB anisotropy science: a review

    CERN Document Server

    Challinor, Anthony

    2012-01-01

    The cosmic microwave background (CMB) provides us with our most direct observational window to the early universe. Observations of the temperature and polarization anisotropies in the CMB have played a critical role in defining the now-standard cosmological model. In this contribution we review some of the basics of CMB science, highlighting the role of observations made with ground-based and balloon-borne Antarctic telescopes. Most of the ingredients of the standard cosmological model are poorly understood in terms of fundamental physics. We discuss how current and future CMB observations can address some of these issues, focusing on two directly relevant for Antarctic programmes: searching for gravitational waves from inflation via B-mode polarization, and mapping dark matter through CMB lensing.

  8. Statistical anisotropy from inflationary magnetogenesis

    CERN Document Server

    Giovannini, Massimo

    2016-01-01

    Provided the quantum fluctuations are amplified in the presence of a classical gauge field configuration the resulting curvature perturbations exhibit a mild statistical anisotropy which should be sufficiently weak not to conflict with current observational data. The curvature power spectra induced by weakly anisotropic initial states are computed here for the first time when the electric and the magnetic gauge couplings evolve at different rates as it happens, for instance, in the relativistic theory of van der Waals interactions. After recovering the results valid for coincident gauge couplings, the constraints imposed by the isotropy and the homogeneity of the initial states are discussed. The obtained bounds turn out to be more stringent than naively expected and cannot be ignored when discussing the underlying magnetogenesis scenarios.

  9. Pseudospin anisotropy of trilayer semiconductor quantum Hall ferromagnets

    Science.gov (United States)

    Miravet, D.; Proetto, C. R.

    2016-08-01

    When two Landau levels are brought to a close coincidence between them and with the chemical potential in the integer quantum Hall regime, the two Landau levels can just cross or collapse while the external or pseudospin field that induces the alignment changes. In this work, all possible crossings are analyzed theoretically for the particular case of semiconductor trilayer systems, using a variational Hartree-Fock approximation. The model includes tunneling between neighboring layers, bias, intralayer, and interlayer Coulomb interaction among the electrons. We have found that the general pseudospin anisotropy classification scheme used in bilayers applies also to the trilayer situation, with the simple crossing corresponding to an easy-axis ferromagnetic anisotropy analogy, and the collapse case corresponding to an easy-plane ferromagnetic analogy. An isotropic case is also possible, with the levels just crossing or collapsing depending on the filling factor and the quantum numbers of the two nearby levels. While our results are valid for any integer filling factor ν (=1 ,2 ,3 ,... ), we have analyzed in detail the crossings at ν =3 and 4, and we have given clear predictions that will help in their experimental search. In particular, the present calculations suggest that by increasing the bias, the trilayer system at these two filling factors can be driven from an easy-plane anisotropy regime to an easy-axis regime, and then can be driven back to the easy-plane regime. This kind of reentrant behavior is a unique feature of the trilayers, compared with the bilayers.

  10. Complete assignment of 1H, 13C and 15N chemical shifts for bovine β-lactoglobulin: Secondary structure and topology of the native state is retained in a partially unfolded form

    International Nuclear Information System (INIS)

    Although β-lactoglobulin (β-LG) has been studied extensively for more than 50 years, its physical properties in solution are not yet understood fully in terms of its three-dimensional (3D) structure. For example, despite a recent high-resolution crystal structure, it is still not clear why the two common variants of bovine β-LG which differ by just two residues have different aggregation properties during milk processing. We have conducted solution-state NMR studies on a recombinant form of the A variant of β-LG at low pH conditions where the protein is partially unfolded and exists as a monomer rather than a dimer. Using a13 C,15N-labelled sample, expressed in Pichia pastoris, we have employed the standard combination of 3D heteronuclear NMR techniques to obtain near complete assignments of proton, carbon and nitrogen resonances. Using a novel pulse sequence we were able to obtain additional assignments, in particular those of methyl groups in residues preceding proline within the sequence. From chemical shifts and on the basis of inter-residue NOEs, we have inferred the secondary structure and topology of monomeric β-LG A. It includes eight antiparallel β-strands arranged in a barrel, flanked by an α-helix, which is typical of a member of the lipocalin family. A detailed comparison with the crystal structure of the dimeric form (for a mixture of A and B variants) at pH 6.5 reveals a close resemblance in both secondary structure and overall topology. Both forms have a ninth β-strand which, at the higher pH, forms part of the dimer interface. These studies represent the first full NMR assignment of β-LG and will form the basis for a complete characterisation of the solution structure and dynamics of this protein and its variants

  11. Constituintes químicos de Ottonia corcovadensis Miq. da floresta Amazônica: atribuição dos deslocamentos químicos dos átomos de hidrogênio e carbono Chemical constituents of Ottonia corcovadensis Miq. from Amazon forest: ¹h and 13c chemical shift assignments

    Directory of Open Access Journals (Sweden)

    Valdir A. Facundo

    2004-02-01

    Full Text Available In an ethanolic extract of leaves of Ottonia corcovadensis (Piperaceae were identified sixteen terpenoids of essential oil and the three flavonoids 3',4',5,5',7-pentamethoxyflavone (1, 3',4',5,7-tetramethoxyflavone (2 and 5-hydroxy-3',4',5',7-tetramethoxyflavone (3 and cafeic acid (4. Two amides (5 and 6 were isolated from an ethanolic extract of the roots. The structures were established by spectral analysis, meanly NMR (1D and 2D and mass spectra. Extensive NMR analysis was also used to complete ¹H and 13C chemical shift assignments of the flavonoids and amides. The components of the essential oil were identified by computer library search, retention indices and visual interpretation of mass spectra.

  12. 磁共振化学位移成像评估椎体骨髓脂肪含量的应用%Application of assessing fat content of vertebral bone marrow with chemical-shift MRI

    Institute of Scientific and Technical Information of China (English)

    雷立存; 任庆云; 母建奎; 祁宇轩; 何丽; 刘斋

    2015-01-01

    目的:探讨磁共振化学位移成像技术评估绝经后女性椎体骨髓脂肪含量的可行性。方法选取56例绝经后女性患者的腰椎1~4椎体(共计224个椎体),所有患者均行磁共振化学位移成像和双能X线吸收法骨密度测定,得出每个椎体信号下降指数和骨密度值,按照骨密度T分数分为骨量正常组,骨量减少组和骨质疏松组,分析三组椎体信号下降指数的差异,探讨不同骨密度组椎体信号下降指数的变化规律。结果56例患者224个椎体按照T分数进行分组,骨量正常组68个,骨量减少组72个,骨质疏松组84个,骨量正常组,骨量减少组和骨质疏松组椎体信号下降指数的中位数分别是60.57%(67.86%~45.34%),58.22%(69.29%~49.49%),56.80%(67.52%~36.00%),骨质疏松组同正常组、骨量减少组比较具有统计学差异(P<0.05),正常组、骨量减少组比较无统计学差异(P>0.05)。结论磁共振化学位移成像通过测定椎体下降指数可以反映椎体脂肪含量的变化,对骨质疏松做出诊断,具有较高的应用价值。%Objective To investigate the feasibility for assessing the fat content of vertebral bone marrow in postmenopausal women with chemical-shift MRI technique..Methods Lumbar vertebral body.(L1-L4)(224 vertebral body) of 56 cases of postmeno-pausal women were selected and all patients were performed with chemical-shift MRI and dual-energy X-ray absorptiometry (DXA).to obtain signal decline index and bone density..The patients were divided into normal group,.osteopenia group and osteoporosis group according to DXA results,.and the difference of signal decline index among three groups was analyzed so as to investigate the law of signal decline index of vertebrae of groups with different bone density. Results 68 subjects in normal group,.72 subjects with osteopenia and 84 subjects with

  13. Primordial anisotropies in gauged hybrid inflation

    International Nuclear Information System (INIS)

    We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations

  14. High resolution NMR theory and chemical applications

    CERN Document Server

    Becker, Edwin D

    1969-01-01

    High Resolution NMR: Theory and Chemical Applications focuses on the applications of nuclear magnetic resonance (NMR), as well as chemical shifts, lattices, and couplings. The book first offers information on the theory of NMR, including nuclear spin and magnetic moment, spin lattice relaxation, line widths, saturation, quantum mechanical description of NMR, and ringing. The text then ponders on instrumentation and techniques and chemical shifts. Discussions focus on the origin of chemical shifts, reference compounds, empirical correlations of chemical shifts, modulation and phase detection,

  15. CMB Anisotropies: Their Discovery and Utilization

    CERN Document Server

    Smoot, George F

    2008-01-01

    This article is a written and modified version of a talk presented at the conference `A Century of Cosmology' held at San Servolo, Venice, Italy, in August 2007. The talk focuses on some of the cosmology history leading to the discovery and exploitation of Cosmic Microwave Background (CMB) Radiation anisotropies. We have made tremendous advances first in the development of the techniques to observe these anisotropies and in observing and interpreting them to extract their contained cosmological information. CMB anisotropies are now a cornerstone in our understanding of the cosmos and our future progress in the field. This is an outcome that Dennis Sciama hoped for and encouraged.

  16. Magnetic Domain Confinement by Anisotropy Modulation

    Science.gov (United States)

    Li, S. P.; Lew, W. S.; Bland, J. A.; Lopez-Diaz, L.; Vaz, C. A.; Natali, M.; Chen, Y.

    2002-02-01

    The spin configuration in a magnet is in general a ``natural'' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic wall-the ``anisotropy constrained'' magnetic wall.

  17. Apparent resistivity of azimuthal anisotropy layered media

    Institute of Scientific and Technical Information of China (English)

    阮爱国; 毛桐恩; 李清河; 葛双成

    2002-01-01

    The electric field, equations of boundary conditions and calculation formula of apparent resistivity are derived for azimuthal anisotropy layered media with DC method based on anisotropic Ohm(s law. Taking Schlumberger symmetric system as an example and using recurrence formula of nuclear function, the paper theoretically simulates a model of four layers with the same anisotropy coefficient for each layer. The deep sounding curves of resistivity and the pattern of contours are obtained for the model. The results shows the theoretical formula of this paper is correct, the deep sounding curves not only exhibit the difference of resistivity among layers but also indicate the anisotropy characteristics of layers.

  18. Implementing OpenShift

    CERN Document Server

    Miller, Adam

    2013-01-01

    A standard tutorial-based approach to using OpenShift and deploying custom or pre-built web applications to the OpenShift Online cloud.This book is for software developers and DevOps alike who are interested in learning how to use the OpenShift Platform-as-a-Service for developing and deploying applications, how the environment works on the back end, and how to deploy their very own open source Platform-as-a-Service based on the upstream OpenShift Origin project.

  19. Quantized beam shifts

    CERN Document Server

    Kort-Kamp, W J M; Dalvit, D A R

    2015-01-01

    We predict quantized Imbert-Fedorov, Goos-H\\"anchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant $\\alpha$, while the Goos- H\\"anchen ones in multiples of $\\alpha^2$. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  20. Fracture toughness anisotropy in shale

    Science.gov (United States)

    Chandler, Michael R.; Meredith, Philip G.; Brantut, Nicolas; Crawford, Brian R.

    2016-03-01

    The use of hydraulic fracturing to recover shale gas has focused attention on the fundamental fracture properties of gas-bearing shales, but there remains a paucity of available experimental data on their mechanical and physical properties. Such shales are strongly anisotropic, so that their fracture propagation trajectories depend on the interaction between their anisotropic mechanical properties and the anisotropic in situ stress field in the shallow crust. Here we report fracture toughness measurements on Mancos shale determined in all three principal fracture orientations: Divider, Short Transverse, and Arrester, using a modified short-rod methodology. Experimental results for a range of other sedimentary and carbonate rocks are also reported for comparison purposes. Significant anisotropy is observed in shale fracture toughness measurements at ambient conditions, with values, as high as 0.72 MPa m1/2 where the crack plane is normal to the bedding, and values as low as 0.21 MPa m1/2 where the crack plane is parallel to the bedding. For cracks propagating nonparallel to bedding, we observe a tendency for deviation toward the bedding-parallel orientation. Applying a maximum energy release rate criterion, we determined the conditions under which such deviations are more or less likely to occur under more generalized mixed-mode loading conditions. We find for Mancos shale that the fracture should deviate toward the plane with lowest toughness regardless of the loading conditions.

  1. Higher order anisotropies in the Buda-Lund model -- disentangling flow and density field anisotropies

    CERN Document Server

    Lökös, Sándor; Csörgő, Tamás; Tomášik, Boris

    2016-01-01

    The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and fits the observed elliptic flow and oscillating HBT radii successfully. Due to fluctuations in energy depositions, the fireball shape however fluctuates on an event-by-event basis. The transverse plane asymmetry can be translated into a series of multipole anisotropy coefficients. These anisotropies then result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we detail an extension of the Buda-Lund model to multipole anisotropies and investigate the resulting flow coefficients and oscillations of HBT radii.

  2. Shell effects and fission fragments angular anisotropy

    International Nuclear Information System (INIS)

    The impact of the shell corrections attenuation effect with growth of the fissionable nuclei temperature on the angular anisotropy of the fission fragments is considered. The experimental data on the anisotropy of the fission fragments angular distributions of the compound nucleus, formed in the 4He + 238U reactions, are analyzed within the frames of the transition states model in the fission barriers saddle point and statistic theory of nuclear reactions. The obvious kind of the shell corrections attenuation function is obtained

  3. Conductivity-type anisotropy in molecular solids

    OpenAIRE

    Ostrick, J. R.; Dodabalapur, A.; Torsi, L.; Lovinger, A, J.; Kwock, E. W.; Miller, T. M.; Galvin, M; Berggren, Magnus; Katz, H. E.

    1997-01-01

    Thin polycrystalline films of perylenetetracarboxylic dianyhydride (PTCDA), an organic molecular solid, exhibits substantial anisotropies in its electronic transport properties. Only electrons transport in the directions along molecular planes, while mainly holes transport in the direction normal to molecular planes. A series of measurements on both field effect transistors with PTCDA active layers and light emitting diodes with PTCDA transport layers documents the anisotropy seen in the elec...

  4. The Cosmic Microwave Background Anisotropy Experiments

    OpenAIRE

    Smoot, George F.

    1997-01-01

    This paper reports a summary of the contents contents of six hours of lectures on the CMB anisotropy experiments given at the Strasbourg NATO school on the CMB and cosmology. (Its companion paper, astro-ph/9705101 reports the lectures on the CMB spectrum.) A context is set as a bridge from the theoretical CMB anisotropy lectures and the experimental situation. The COBE DMR results are reveiwed in detail and as pioneer for future space missions. Current and planned experiments are discussed in...

  5. CMB Anisotropies: Their Discovery and Utilization

    OpenAIRE

    Smoot, George F.

    2008-01-01

    This article is a written and modified version of a talk presented at the conference `A Century of Cosmology' held at San Servolo, Venice, Italy, in August 2007. The talk focuses on some of the cosmology history leading to the discovery and exploitation of Cosmic Microwave Background (CMB) Radiation anisotropies. We have made tremendous advances first in the development of the techniques to observe these anisotropies and in observing and interpreting them to extract their contained cosmologic...

  6. Magnetic anisotropy in rare-earth metals

    DEFF Research Database (Denmark)

    Nielsen, Mourits; Bjerrum Møller, Hans; Lindgård, Per-Anker; Mackintosh, A.R.

    1970-01-01

    The magnetic field dependence of the energy of long- wavelength magnons in Tb-10%Ho has been studied by inelastic neutron scattering. The results agree with the `frozen-lattice' model, provided that the second-order magnetoelastic effect is taken into account. The planar anisotropy is almost...... entirely the result of magnetoelastic effects. The temperature dependences of the anisotropy parameters have been deduced from the results...

  7. Seismic anisotropy in the Sumatra subduction zone

    OpenAIRE

    R. Collings; Rietbrock, A.; Lange, Dietrich; F. Tilmann; S. Nippress; D. Natawidjaja

    2013-01-01

    An important tool for understanding deformation occurring within a subduction zone is the measurement of seismic anisotropy through observations of shear wave splitting (SWS). In Sumatra, two temporary seismic networks were deployed between December 2007 and February 2009, covering the fore arc between the fore-arc islands to the back arc. We use SKS and local SWS measurements to determine the type, amount, and location of anisotropy. Local SWS measurements from the fore-arc islands exhibit t...

  8. Shifted Independent Component Analysis

    DEFF Research Database (Denmark)

    Mørup, Morten; Madsen, Kristoffer Hougaard; Hansen, Lars Kai

    2007-01-01

    Delayed mixing is a problem of theoretical interest and practical importance, e.g., in speech processing, bio-medical signal analysis and financial data modelling. Most previous analyses have been based on models with integer shifts, i.e., shifts by a number of samples, and have often been carried...

  9. OpenShift cookbook

    CERN Document Server

    Gulati, Shekhar

    2014-01-01

    If you are a web application developer who wants to use the OpenShift platform to host your next big idea but are looking for guidance on how to achieve this, then this book is the first step you need to take. This is a very accessible cookbook where no previous knowledge of OpenShift is needed.

  10. Pulse EPR-enabled interpretation of scarce pseudocontact shifts induced by lanthanide binding tags

    Energy Technology Data Exchange (ETDEWEB)

    Abdelkader, Elwy H.; Yao, Xuejun [Australian National University, Research School of Chemistry (Australia); Feintuch, Akiva [Weizmann Institute of Science, Department of Chemical Physics (Israel); Adams, Luke A.; Aurelio, Luigi; Graham, Bim [Monash University, Monash Institute of Pharmaceutical Sciences (Australia); Goldfarb, Daniella [Weizmann Institute of Science, Department of Chemical Physics (Israel); Otting, Gottfried, E-mail: gottfried.otting@anu.edu.au [Australian National University, Research School of Chemistry (Australia)

    2016-01-15

    Pseudocontact shifts (PCS) induced by tags loaded with paramagnetic lanthanide ions provide powerful long-range structure information, provided the location of the metal ion relative to the target protein is known. Usually, the metal position is determined by fitting the magnetic susceptibility anisotropy (Δχ) tensor to the 3D structure of the protein in an 8-parameter fit, which requires a large set of PCSs to be reliable. In an alternative approach, we used multiple Gd{sup 3+}-Gd{sup 3+} distances measured by double electron–electron resonance (DEER) experiments to define the metal position, allowing Δχ-tensor determinations from more robust 5-parameter fits that can be performed with a relatively sparse set of PCSs. Using this approach with the 32 kDa E. coli aspartate/glutamate binding protein (DEBP), we demonstrate a structural transition between substrate-bound and substrate-free DEBP, supported by PCSs generated by C3-Tm{sup 3+} and C3-Tb{sup 3+} tags attached to a genetically encoded p-azidophenylalanine residue. The significance of small PCSs was magnified by considering the difference between the chemical shifts measured with Tb{sup 3+} and Tm{sup 3+} rather than involving a diamagnetic reference. The integrative sparse data approach developed in this work makes poorly soluble proteins of limited stability amenable to structural studies in solution, without having to rely on cysteine mutations for tag attachment.

  11. Does deformation saturate seismic anisotropy?

    Science.gov (United States)

    Tatham, D. J.; Lloyd, G. E.; Butler, R. W.; Casey, M.

    2006-12-01

    The progressive simple shear deformation that characterizes ductile fault zones in the crust involves both rotation and intensification of the strain ellipsoid. These mathematic predictions have been confirmed repeatedly by finite strain determinations in outcrop studies of natural shear zones and used to test geodynamic models of mountain belts. Seismic anisotropy (SA) methods offer the opportunity to pursue these approaches in situ. First however, we must calibrate the magnitude and orientation of the SA ellipsoid against naturally deformed tectonites of known strain state and microstructure. Here we present data from a field analogue of mafic ductile crust in an amphibolite-facies shear zone developed in a deformed mafic dyke embedded within the Lewisian Gneiss (Badcall, NW Scotland). Deflection of pre-existing linear and planar elements and attenuation of the dyke into the shear zone are used to determine the strain gradient. Specimens collected along this gradient were used to establish the geometric fabric intensity defined by different minerals (hornblende grain alignment and ellipticity of plagioclase clots). Finally, petrophysical properties were calculated for the specimens using the SEM-EBSD measured populations of lattice preferred orientations (LPO) for all mineral phases. It is the hornblende-plagioclase LPO, combined in their modal proportions and modulated by the individual mineral single crystal elastic properties, which define the SA profile across the shear zone. Hornblende develops a strong preferred dimensional orientation and hence LPO at shear strains of about 2, whereas the plagioclase LPO remains close to random regardless of bulk strain. The modelled SA of the samples is dominated therefore by the amphibole LPO. Although the values of bulk shear strain vary across the shear zone (0 at the margins to greater than 12 in the centre), the calculated intensity of SA saturates at a shear strain of about 2. These results, if typical of large

  12. Performance of the Microwave Anisotropy Probe AST-201 Star Trackers

    Science.gov (United States)

    Ward, David K.; vanBezooijen, Roelof; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe (MAP) was launched to create a full-sky map of the cosmic microwave background. MAP incorporates two modified Lockheed Martin AST-201 (Autonomous Star Tracker) star trackers. The AST-201 employs an eight element radiation hardened lens assembly which is used to focus an image on a charge coupled device (CCD). The CCD image is then processed by a star identification algorithm which outputs a three-axis attitude. A CCD-shift algorithm called Time Delayed Integration (TDI) was also included in each star tracker. In order to provide some radiation effect filtering during MAP's three to five phasing loop passes through the Van Allen radiation belts, a simple pixel filtering scheme was implemented, rather than using a more complex, but more robust windowing algorithm. The trackers also include a fiber optic data interface. This paper details the ground testing that was accomplished on the MAP trackers.

  13. On the problem of electron-induced anisotropy effect in As2S3-based glasses

    International Nuclear Information System (INIS)

    Effect of electron-induced anisotropy was observed in glassy As2S3-based samples irradiated by accelerated electrons (E=2.8 MeV) in the perpendicular plane to the probe light. Spectral and compositional dependences of this effect and its time stability at room temperature were discussed. It was supposed that the microstructural mechanism of the anisotropy effect was connected with electron-induced formation of new oriented (relatively to the electron flow) defects in the form of broken chemical bonds

  14. Quantum engineering of spin and anisotropy in magnetic molecular junctions

    Science.gov (United States)

    Jacobson, Peter; Herden, Tobias; Muenks, Matthias; Laskin, Gennadii; Brovko, Oleg; Stepanyuk, Valeri; Ternes, Markus; Kern, Klaus

    2015-10-01

    Single molecule magnets and single spin centres can be individually addressed when coupled to contacts forming an electrical junction. To control and engineer the magnetism of quantum devices, it is necessary to quantify how the structural and chemical environment of the junction affects the spin centre. Metrics such as coordination number or symmetry provide a simple method to quantify the local environment, but neglect the many-body interactions of an impurity spin coupled to contacts. Here, we utilize a highly corrugated hexagonal boron nitride monolayer to mediate the coupling between a cobalt spin in CoHx (x=1,2) complexes and the metal contact. While hydrogen controls the total effective spin, the corrugation smoothly tunes the Kondo exchange interaction between the spin and the underlying metal. Using scanning tunnelling microscopy and spectroscopy together with numerical simulations, we quantitatively demonstrate how the Kondo exchange interaction mimics chemical tailoring and changes the magnetic anisotropy.

  15. Anisotropies in the cosmic neutrino background after Wilkinson Microwave Anisotropy Probe five-year data

    International Nuclear Information System (INIS)

    We search for the presence of cosmological neutrino background (CNB) anisotropies in recent Wilkinson Microwave Anisotropy Probe (WMAP) five-year data using their signature imprinted on modifications to the cosmic microwave background (CMB) anisotropy power spectrum. By parameterizing the neutrino background anisotropies with the speed viscosity parameter cvis, we find that the WMAP five-year data alone provide only a weak indication for CNB anisotropies with cvis2>0.06 at the 95% confidence level. When we combine CMB anisotropy data with measurements of galaxy clustering, the SN-Ia Hubble diagram, and other cosmological information, the detection increases to cvis2>0.16 at the same 95% confidence level. Future data from Planck, combined with a weak lensing survey such as the one expected with DUNE from space, will be able to measure the CNB anisotropy parameter at about 10% accuracy. We discuss the degeneracy between neutrino background anisotropies and other cosmological parameters such as the number of effective neutrinos species and the dark energy equation of state

  16. Velocity anisotropy in tidally limited star clusters

    CERN Document Server

    Tiongco, Maria; Varri, Anna Lisa

    2015-01-01

    We explore the long-term evolution of the anisotropy in the velocity space of star clusters starting with different structural and kinematical properties. We show that the evolution of the radial anisotropy strength and its radial variation within a cluster contain distinct imprints of the cluster initial structural properties, dynamical history, and of the external tidal field of its host galaxy. Initially isotropic and compact clusters with small initial values of the ratio of the half-mass to Jacobi radius, $r_h/r_J$, develop a strong radial anisotropy during their long-term dynamical evolution. Many clusters, if formed with small values of $r_h/r_J$, should now be characterized by a significant radial anisotropy increasing with the distance from the cluster centre, reaching its maximum at a distance between 0.2 $r_J$ and 0.4 $r_J$, and then becoming more isotropic or mildly tangentially anisotropic in the outermost regions. A similar radial variation of the anisotropy can also result from an early violent...

  17. The expected anisotropy in solid inflation

    International Nuclear Information System (INIS)

    Solid inflation is an effective field theory of inflation in which isotropy and homogeneity are accomplished via a specific combination of anisotropic sources (three scalar fields that individually break isotropy). This results in specific observational signatures that are not found in standard models of inflation: a non-trivial angular dependence for the squeezed bispectrum, and a possibly long period of anisotropic inflation (to drive inflation, the ''solid'' must be very insensitive to any deformation, and thus background anisotropies are very slowly erased). In this paper we compute the expected level of statistical anisotropy in the power spectrum of the curvature perturbations of this model. To do so, we account for the classical background values of the three scalar fields that are generated on large (superhorizon) scales during inflation via a random walk sum, as the perturbation modes leave the horizon. Such an anisotropy is unavoidably generated, even starting from perfectly isotropic classical initial conditions. The expected level of anisotropy is related to the duration of inflation and to the amplitude of the squeezed bispectrum. If this amplitude is close to its current observational limit (so that one of the most interesting predictions of the model can be observed in the near future), we find that a level of statistical anisotropy F2 gives frozen and scale invariant vector perturbations on superhorizon scales

  18. Surface anisotropy characterisation with meteosat observations

    Science.gov (United States)

    Lattanzio, A.; Govaerts, Y. M.; Pinty, B.

    Surface albedo, or more precisely Directional Hemispherical Reflectance (DHR), is the integral the Bi-directional Reflectance Factor (BRF) of the surface over all angles of the upward hemisphere. The retrieval of the DHR trough space observations requires accounting for the scattering and absorption processes in the atmosphere as well as for the angular anisotropy of the surface, the two systems being radiatively coupled. The accuracy achieved in the albedo estimation depends thus on the density of the angular sampling and the reliability of the atmospheric correction. Pinty et al. demonstrated the possibility to derive reliable surface albedo from observations acquired by Meteosat, the European meteorological geostationary satellite. The purpose of this presentation is to analyse the accuracy of this new Meteosat Surface Albedo (MSA) product, including the effects due to instrument changes and associated calibration uncertainties. In particular, the consistency of the surface anisotropy characterisation is examined in detail. To this end, observations acquired by two adjacent geostationary spacecrafts, i.e., Meteosat-7 and Meteosat-5 have been processed with the MSA algorithm. These satellites are located respectively at 0 and 63 degrees East. Data acquired by these two instruments overlap over a large area encompassing most of Africa and the Arabian Peninsula. The consistency of the surface anisotropy retrieval is evaluated through a reconstruction of the Meteosat-5 (-7) observations with the Meteosat-7 (-5) surface anisotropy characterisation. No differences larger than the calibration uncertainties have been found, which indicates that the MSA algorithm accounts correctly for the surface anisotropy and instrument differences.

  19. Large Friction Anisotropy of a Polydiacetylene Monolayer

    International Nuclear Information System (INIS)

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties

  20. Measurements of magnetic anisotropy in sickle cells

    International Nuclear Information System (INIS)

    Room temperature magnetic measurements in deoxigenated sickle cells showed the existence of magnetic anisotropy, Δchi=1,29 x 10-3. This effect was supposed paramagnetic and considered to be due to the iron atoms of the hemoglobin molecules which are one over the other, forming ordered chains inside the erythrocytes. Low temperature (liquid He - 4,2K) measurements of the magnetic anisotropy of sickle cells and normal red blood cells diluted in a cryoprotector was made to confirm the paramagnetic origin of the fenomena. For that purpose it was used a superconductor magnetometer coupled to a SQUID, developed in the 'Laboratorio do Estado Solido do Departamento de Fisica da PUC-RJ'. The results obtained seem to confirm the expected paramagnetic anisotropy and, furthermore, suggest the presence of magnetic interactions among the iron atoms in the sickle cells samples. (Author)

  1. Hydraulic Conductivity Anisotropy of Heterogeneous Unsaturated Soils

    Science.gov (United States)

    Sun, Dongmin; Zhu, Jianting

    2010-05-01

    The effects of saturation degree (or capillary pressure) on hydraulic conductivity anisotropy in unsaturated soils have not been fully understood. This study developed an approach based on a conceptualization of combining the neural network based pedo-transfer function (PTF) results with the thin layer concept to explore the capillary pressure-dependent anisotropy in relation to soil texture and soil bulk density. The main objective is to examine how anisotropy characteristics are related to the relationships between hydraulic parameters and the basic soil attributes such as texture and bulk density. The hydraulic parameters are correlated with the texture and bulk density based on the pedo-transfer function (PTF) results. It is demonstrated that non-monotonic behavior of the unsaturated soil anisotropy in relation to the capillary pressure is only observed when the saturated hydraulic conductivity and the shape parameter are both related to the mean particle diameter. When only one hydraulic parameter is related to the grain diameter or when both are not related to the same attribute simultaneously, the unsaturated soil anisotropy increases monotonically with the increasing capillary pressure head. Therefore, it is suggested that this behavior is mainly due to the coupled dependence of the layer saturated hydraulic conductivities and the shape factors on the texture and bulk density. The correlation between the soil grain diameter and bulk density decreases the anisotropy effects of the unsaturated layered soils. The study illustrates that the inter-relationships of soil texture, bulk density, and hydraulic properties may cause vastly different characteristics of anisotropic unsaturated soils.

  2. Absorption driven focus shift

    Science.gov (United States)

    Harrop, N.; Wolf, S.; Maerten, O.; Dudek, K.; Ballach, S.; Kramer, R.

    2016-03-01

    Modern high brilliance near infrared lasers have seen a tremendous growth in applications throughout the world. Increased productivity has been achieved by higher laser power and increased brilliance of lasers. Positive impacts on the performance and costs of parts are opposed to threats on process stability and quality, namely shift of focus position over time. A high initial process quality will be reduced by contamination of optics, eventually leading to a focus shift or even destruction of the optics. Focus analysis at full power of multi-kilowatt high brilliance lasers is a very demanding task because of high power densities in the spot and the high power load on optical elements. With the newly developed high power projection optics, the High-Power Micro-Spot Monitor High Brilliance (HP-MSM-HB) is able to measure focus diameter as low as 20 μm at power levels up to 10 kW at very low internal focus shift. A main driving factor behind thermally induced focus shift is the absorption level of the optical element. A newly developed measuring system is designed to determine the relative absorption level in reference to a gold standard. Test results presented show a direct correlation between absorption levels and focus shift. The ability to determine the absorption level of optical elements as well as their performance at full processing power before they are put to use, enables a high level of quality assurance for optics manufacturers and processing head manufacturers alike.

  3. Electromagnetic surface wave induced magnetic anisotropy

    International Nuclear Information System (INIS)

    Femtosecond laser induced electromagnetic surface waves, supported by a gold overlayer on top of a magnetic iron garnet (IG) single-crystalline film, are demonstrated to induce a change in the magnetic anisotropy of the IG. This effect is found to be similar to the previously reported photo-induced magnetic anisotropy in this material. However, its dependence on the polarization of the light and orientation of the magnetization is found to be different. This electromagnetic surface wave control of the spins opens new interesting possibilities for all-optical ultrafast control of the magnetization at a nanometre length scale.

  4. Electromagnetic surface wave induced magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Le Guyader, L [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Kirilyuk, A; Rasing, Th [IMM, Radboud University Nijmegen, Toernooiveld 1, 6525ED Nijmegen (Netherlands); Smolyaninov, I I [Department of Electrical and Computer Engineering, University of Maryland, College Park, MD (United States)], E-mail: loic.leguyader@psi.ch

    2009-05-21

    Femtosecond laser induced electromagnetic surface waves, supported by a gold overlayer on top of a magnetic iron garnet (IG) single-crystalline film, are demonstrated to induce a change in the magnetic anisotropy of the IG. This effect is found to be similar to the previously reported photo-induced magnetic anisotropy in this material. However, its dependence on the polarization of the light and orientation of the magnetization is found to be different. This electromagnetic surface wave control of the spins opens new interesting possibilities for all-optical ultrafast control of the magnetization at a nanometre length scale.

  5. Anisotropy of the Topopah Spring Member Tuff

    International Nuclear Information System (INIS)

    Mechanical properties of the tuffaceous rocks within Yucca Mountain are needed for near and far-field modeling of the potential nuclear waste repository. If the mechanical properties are significantly anisotropic (i.e., direction-dependent), a more complex model is required. Relevant data from tuffs tested in earlier studies indicate that elastic and strength properties are anisotropic. This scoping study confirms the elastic anisotropy and concludes some tuffs are transversely isotropic. An approach for sampling and testing the rock to determine the magnitude of the anisotropy is proposed

  6. Temperature Anisotropies in a Universe with Global Defects

    OpenAIRE

    Coulson, David

    1994-01-01

    We present a technique of calculating microwave anisotropies from global defects in a reionised universe. We concentrate on angular scales down to one degree where we expect the nongaussianity of the temperature anisotropy in these models to become apparent.

  7. Magnetic anisotropy in rare-earth metals

    DEFF Research Database (Denmark)

    Nielsen, Mourits; Bjerrum Møller, Hans; Lindgård, Per-Anker;

    1970-01-01

    The magnetic field dependence of the energy of long- wavelength magnons in Tb-10%Ho has been studied by inelastic neutron scattering. The results agree with the `frozen-lattice' model, provided that the second-order magnetoelastic effect is taken into account. The planar anisotropy is almost enti...

  8. Effective anisotropy through traveltime and amplitude matching

    KAUST Repository

    Wang, Hui

    2014-08-05

    Introducing anisotropy to seismic wave propagation reveals more realistic physics of our Earth\\'s subsurface as compared to the isotropic assumption. However wavefield modeling, the engine of seismic inverse problems, in anisotropic media still suffers from computational burdens, in particular with complex anisotropy such as transversely isotropic (TI) and Orthorhombic anisotropy. We develop effective isotropic velocity and density models to package the effects of anisotropy such that the wave propagation behavior using these effective models approximate those of the original anisotropic model. We build these effective models through the high frequency asymptotic approximation based on the eikonal and transport equations. We match the geometrical behavior of the wave-fields, given by traveltimes, from the anisotropic and isotropic eikonal equations. This matching yields the effective isotropic velocity that approximates the kinematics of the anisotropic wavefield. Equivalently, we calculate the effective densities by equating the anisotropic and isotropic transport equations. The effective velocities and densities are then fed into the isotropic acoustic variable density wave equation to obtain cheaper anisotropic wavefields. We justify our approach by testing it on an elliptical anisotropic model. The numerical results demonstrate a good matching of both traveltime and amplitude between anisotropic and effective isotropic wavefields.

  9. What we learn from CMB Anisotropies

    CERN Document Server

    CERN. Geneva

    2007-01-01

    George Smoot shared the 2006 Nobel Prize with John Mathere for the discovery of the fluctuations of the cosmic microwave background. In this talk (which will not be the same as the Nobel lecture), he will discuss what we have learned about the universe in the recent past from these anisotropies.

  10. Angular anisotropy representation by probability tables

    International Nuclear Information System (INIS)

    In this paper, we improve point-wise or group-wise angular anisotropy representation by using probability tables. The starting point of this study was to give more flexibility (sensitivity analysis) and more accuracy (ray effect) to group-wise anisotropy representation by Dirac functions, independently introduced at CEA (Mao, 1998) and at IRSN (Le Cocq, 1998) ten years ago. Basing ourselves on our experience of cross-section description, acquired in CALENDF (Sublet et al., 2006), we introduce two kinds of moment based probability tables, Dirac (DPT) and Step-wise (SPT) Probability Tables where the angular probability distribution is respectively represented by Dirac functions or by a step-wise function. First, we show how we can improve equi-probable cosine representation of point-wise anisotropy by using step-wise probability tables. Then we show, by Monte Carlo techniques, how we can obtain a more accurate description of group-wise anisotropy than the one usually given by a finite expansion on a Legendre polynomial basis (that can induce negative values) and finally, we describe it by Dirac probability tables. This study is carried out in the framework of GALILEE project R and D activities (Coste-Delclaux, 2008). (authors)

  11. Anisotropy of Magnetic Properties in Textured Materials

    OpenAIRE

    J. A. Szpunar

    1989-01-01

    A short survey is presented of techniques and methods used to correlate the texture with the magnetic anisotropy of various properties of soft and hard magnetic materials. Also, examples of magnetic materials are discussed with emphasis on techniques of processing which optimize the texture.

  12. Azimuthal anisotropy of jet quenching at LHC

    Indian Academy of Sciences (India)

    I P Lokhtin; S V Petrushanko; L I Sarycheva; A M Snigirev

    2003-05-01

    We analyze the azimuthal anisotropy of jet spectra due to energy loss of hard partons in quark–gluon plasma, created initially in nuclear overlap zone in collisions with non-zero impact parameter. The calculations are performed for semi-central Pb–Pb collisions at LHC energy.

  13. Impact of rock anisotropy on fracture development

    Institute of Scientific and Technical Information of China (English)

    Lianbo Zeng; Jiyong Zhao; Shengju Zhu; Weiliang Xiong; Yonghong He; Jianwen Chen

    2008-01-01

    Experiments on uniaxial and triaxial rock mechanics and rock acoustic emissions have been conducted for research on the impact of rock anisotropy on the development of the fractures of different directions by taking as an example the ultra-low-permeability sandstone reservoir in the Upper Triassic Yanchang Formation within the Ordos Basin. The experimental results prove the existence of anisotropy of the rock mechanical property in the different directions on the plane, which is the chief reason for the production of impacts on the development of different assemblages of fractures in the geological periods. The rock anisotropy usually restricts the development of one assemblage of conjugate shear fractures. The fractures in the Yanchang Formation within the Ordos Basin are mainly shear fractures that formed under two tectonic actions. Theoretically, here, four assemblages of shear fractures should have developed, but due to the effect of a strong rock anisotropy, in each period one assemblage of fractures chiefly developed. Thus, two assemblages of fractures are usually developed in every part at present.

  14. Anisotropy of Wood in the Microwave Region

    Science.gov (United States)

    Ziherl, Sasa; Bajc, Jurij; Urankar, Bernarda; Cepic, Mojca

    2010-01-01

    Wood is transparent for microwaves and due to its anisotropic structure has anisotropic dielectric properties. A laboratory experiment that allows for the qualitative demonstration and quantitative measurements of linear dichroism and birefringence in the microwave region is presented. As the proposed experiments are based on the anisotropy (of…

  15. Tuning the Magnetic Anisotropy of Single Molecules.

    Science.gov (United States)

    Heinrich, Benjamin W; Braun, Lukas; Pascual, Jose I; Franke, Katharina J

    2015-06-10

    The magnetism of single atoms and molecules is governed by the atomic scale environment. In general, the reduced symmetry of the surrounding splits the d states and aligns the magnetic moment along certain favorable directions. Here, we show that we can reversibly modify the magnetocrystalline anisotropy by manipulating the environment of single iron(II) porphyrin molecules adsorbed on Pb(111) with the tip of a scanning tunneling microscope. When we decrease the tip-molecule distance, we first observe a small increase followed by an exponential decrease of the axial anisotropy on the molecules. This is in contrast to the monotonous increase observed earlier for the same molecule with an additional axial Cl ligand ( Nat. Phys. 2013 , 9 , 765 ). We ascribe the changes in the anisotropy of both species to a deformation of the molecules in the presence of the attractive force of the tip, which leads to a change in the d level alignment. These experiments demonstrate the feasibility of a precise tuning of the magnetic anisotropy of an individual molecule by mechanical control. PMID:25942560

  16. Ultrasonic evaluation of local biological tissue anisotropy

    Czech Academy of Sciences Publication Activity Database

    Tokar, Daniel; Převorovský, Zdeněk; Hradilová, Jana

    Brno: University of Technology, 2014. s. 26-27. ISBN 978-80-214-5019-6. [European Conference on Non-Destructive Testing (ECNDT 2014) /11./. 06.10.2014-10.10.2014, Praha] Institutional support: RVO:61388998 Keywords : ultrasonic testing (UT) * signal processing * medical application * anisotropy Subject RIV: BI - Acoustics

  17. Surface stress anisotropy of Ge(001)

    NARCIS (Netherlands)

    Middel, M.T.; Zandvliet, H.J.W.; Poelsema, Bene

    2002-01-01

    By analyzing the equilibrium shape of vacancy islands on the Ge(001) surface we have determined the surface stress anisotropy, i.e., the difference between the compressive stress component along the substrate dimer rows and the tensile stress component perpendicular to the substrate dimer rows. In o

  18. Gaussian Anisotropy In Strange Quark Stars

    CERN Document Server

    Panahi, H; Eghdami, I

    2015-01-01

    In this paper for studying the anisotropic strange quark stars, we assume that the radial pressure inside the anisotropic star is a superposition of pressure in an isotropic case plus a Gaussian perturbation term. Considering a proportionality between electric charge density and the density of matter, we solve the TOV equation for different cases numerically. Our results indicate that anisotropy increases the maximum mass $M_{max}$ and also its corresponding radius $R$ for a typical strange quark star. According to our calculations, an anisotropy amplitude of $A=3\\times10^{33}Nm^{-2}$ with a standard deviation of $\\sigma=3\\times10^{3}m$ leads to a neutron star of 1.97$M_{\\odot}$. Furthermore, electric charge not only increases the maximum mass and its corresponding radius, but also raises up the anisotropy factor. We can see that the tangential pressure $p_{t}$ and anisotropy factor $\\Delta$ unlike the radial pressure $p_{r}$ have a maximum on the surface and this maximum increases by adding electric charge e...

  19. Gold Spiky Nanodumbbells: Anisotropy in Gold Nanostars

    OpenAIRE

    Novikov, Sergey M.; Sánchez-Iglesias, Ana; Schmidt, Mikołaj K.; Chuvilin, Andrey; Aizpurua, Javier; Grzelczak, Marek; Liz-Marzán, Luis M.

    2013-01-01

    A new type of gold nanoparticle—called “spiky nanodumbbells”—is introduced. These particles combine the anisotropy of nanorods with sharp nanoscale features of nanostars, which are important for SERS applications. Both the morphology and the optical response of the particles are characterized in detail, and the experimental results are compared with FDTD simulations, showing good agreement.

  20. Competing anisotropies in holmium-erbium superlattices

    DEFF Research Database (Denmark)

    Simpson, J.A.; McMorrow, D.F.; Cowley, R.A.; Jehan, D.A.; Ward, R.C.C.; Wells, M.R.; Clausen, K.N.

    1994-01-01

    The effect of competing crystal-field anisotropies on magnetic order has been investigated in a series of Ho/Er superlattices. For temperatures in the interval T(N)(Er) less-than-or-equal-to T less-than-or-equal-to T(N)(Ho) the Ho basal-plane order propagates coherently through the paramagnetic E...

  1. A Shift of Power

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Administrative reforms are shifting prefecture government powers to the county level in an effort to boost local economies on July 8, the government of China’s southernmost Hainan Province announced that it was to hand over 177 of its administrative powers to county-level governments. The move practically dismantled the powers of the

  2. Anisotropy and texture. Studies in magnetic media

    International Nuclear Information System (INIS)

    The rapid development of magnetic materials for recording media applications increased the demands for new and more precise experimental investigation techniques. In respect with these demands, this project is focused on experimental analyses of advanced particulate media and magnetic thin film samples. A new extended rotational remanence technique for anisotropy field measurements was developed. The technique is suitable for samples that contain aligned or partially aligned particles and provides both: in-plane anisotropy field distributions and the in-plane anisotropy field. This technique was also extended to out-of-plane anisotropy field measurements. Rotational hysteresis was introduced as an alternative method for anisotropy field measurements. This applies well in the case of samples without texture or samples having very small magnetic moment (i.e. thin films). The two techniques for anisotropy field measurement compare well and the experimental results were interpreted in terms of inter-particles interactions. Two measurement methods for determination of the demagnetizing field acting perpendicular to a sample plane were also developed. The first method is based on the in-plane and out-of-plane anisotropy field determination using an extended rotational remanence technique. The second method can provide the demagnetizing field starting from in-plane and out-of-plane transverse hysteresis loops. Comparison between the results from the two methods showed good agreement. Furthermore, the demagnetizing field values were used to calculate the magnetic coating thickness, so the two methods provide a non-destructive method for magnetic thickness measurements in film samples. The in-plane easy axis distribution (EAD) was experimentally determined using vector VSM techniques. Correlations between in-plane tape texture and magnetic thickness were obtained for a series of advanced MP tapes. A theoretical approach was used in order to relate the orientation ratio to

  3. Multi-scale characterization of topographic anisotropy

    Science.gov (United States)

    Roy, S. G.; Koons, P. O.; Osti, B.; Upton, P.; Tucker, G. E.

    2016-05-01

    We present the every-direction variogram analysis (EVA) method for quantifying orientation and scale dependence of topographic anisotropy to aid in differentiation of the fluvial and tectonic contributions to surface evolution. Using multi-directional variogram statistics to track the spatial persistence of elevation values across a landscape, we calculate anisotropy as a multiscale, direction-sensitive variance in elevation between two points on a surface. Tectonically derived topographic anisotropy is associated with the three-dimensional kinematic field, which contributes (1) differential surface displacement and (2) crustal weakening along fault structures, both of which amplify processes of surface erosion. Based on our analysis, tectonic displacements dominate the topographic field at the orogenic scale, while a combination of the local displacement and strength fields are well represented at the ridge and valley scale. Drainage network patterns tend to reflect the geometry of underlying active or inactive tectonic structures due to the rapid erosion of faults and differential uplift associated with fault motion. Regions that have uniform environmental conditions and have been largely devoid of tectonic strain, such as passive coastal margins, have predominantly isotropic topography with typically dendritic drainage network patterns. Isolated features, such as stratovolcanoes, are nearly isotropic at their peaks but exhibit a concentric pattern of anisotropy along their flanks. The methods we provide can be used to successfully infer the settings of past or present tectonic regimes, and can be particularly useful in predicting the location and orientation of structural features that would otherwise be impossible to elude interpretation in the field. Though we limit the scope of this paper to elevation, EVA can be used to quantify the anisotropy of any spatially variable property.

  4. Tunable exchange bias-like effect in patterned hard-soft two-dimensional lateral composites with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hierro-Rodriguez, A., E-mail: ahierro@fc.up.pt; Alvarez-Prado, L. M.; Martín, J. I.; Alameda, J. M. [Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo S/N, 33007 Oviedo (Spain); Centro de Investigación en Nanomateriales y Nanotecnología—CINN (CSIC—Universidad de Oviedo—Principado de Asturias), Parque Tecnológico de Asturias, 33428 Llanera (Spain); Teixeira, J. M. [IN-IFIMUP, Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua Campo Alegre 687, 4169-007 Porto (Portugal); Vélez, M. [Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo S/N, 33007 Oviedo (Spain)

    2014-09-08

    Patterned hard-soft 2D magnetic lateral composites have been fabricated by e-beam lithography plus dry etching techniques on sputter-deposited NdCo{sub 5} thin films with perpendicular magnetic anisotropy. Their magnetic behavior is strongly thickness dependent due to the interplay between out-of-plane anisotropy and magnetostatic energy. Thus, the spatial modulation of thicknesses leads to an exchange coupled system with hard/soft magnetic regions in which rotatable anisotropy of the thicker elements provides an extra tool to design the global magnetic behavior of the patterned lateral composite. Kerr microscopy studies (domain imaging and magneto-optical Kerr effect magnetometry) reveal that the resulting hysteresis loops exhibit a tunable exchange bias-like shift that can be switched on/off by the applied magnetic field.

  5. Tunable exchange bias-like effect in patterned hard-soft two-dimensional lateral composites with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Patterned hard-soft 2D magnetic lateral composites have been fabricated by e-beam lithography plus dry etching techniques on sputter-deposited NdCo5 thin films with perpendicular magnetic anisotropy. Their magnetic behavior is strongly thickness dependent due to the interplay between out-of-plane anisotropy and magnetostatic energy. Thus, the spatial modulation of thicknesses leads to an exchange coupled system with hard/soft magnetic regions in which rotatable anisotropy of the thicker elements provides an extra tool to design the global magnetic behavior of the patterned lateral composite. Kerr microscopy studies (domain imaging and magneto-optical Kerr effect magnetometry) reveal that the resulting hysteresis loops exhibit a tunable exchange bias-like shift that can be switched on/off by the applied magnetic field.

  6. Lunar Laser-Ranging Detection of Light-Speed Anisotropy and Gravitational Waves

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2010-04-01

    Full Text Available The Apache Point Lunar Laser-ranging Operation (APOLLO, in NM, can detect pho- ton bounces from retroreflectors on the moon surface to 0.1ns timing resolution. This facility enables not only the detection of light speed anisotropy, which defines a local preferred frame of reference — only in that frame is the speed of light isotropic, but also fluctuations / turbulence (gravitational waves in the flow of the dynamical 3-space rela- tive to local systems / observers. So the APOLLO facility can act as an e ective “gravi- tational wave” detector. A recently published small data set from November 5, 2007, is analysed to characterise both the average anisotropy velocity and the wave / turbulence effects. The results are consistent with some 13 previous detections, with the last and most accurate being from the spacecraft earth-flyby Doppler-shift NASA data.

  7. Lunar Laser-Ranging Detection of Light-Speed Anisotropy and Gravitational Waves

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2010-04-01

    Full Text Available The Apache Point Lunar Laser-ranging Operation (APOLLO, in NM, can detect photon bounces from retroreflectors on the moon surface to 0.1ns timing resolution. This facility enables not only the detection of light speed anisotropy, which defines a local preferred frame of reference - only in that frame is the speed of light isotropic, but also fluctuations/turbulence (gravitational waves in the flow of the dynamical 3-space relative to local systems/observers. So the APOLLO facility can act as an effective "gravitational wave" detector. A recently published small data set from November 5, 2007, is analysed to characterise both the average anisotropy velocity and the wave/turbulence effects. The results are consistent with some 13 previous detections, with the last and most accurate being from the spacecraft earth-flyby Doppler-shift NASA data.

  8. Beyond the small-angle approximation for MBR anisotropy from seeds

    International Nuclear Information System (INIS)

    In this paper we give a general expression for the energy shift of massless particles traveling through the gravitational field of an arbitrary matter distribution as calculated in the weak field limit in an asymptotically flat space-time. It is not assumed that matter is nonrelativistic. We demonstrate the surprising result that if the matter is illuminated by a uniform brightness background that the brightness pattern observed at a given point in space-time (modulo a term dependent on the observer's velocity) depends only on the matter distribution on the observer's past light cone. These results apply directly to the cosmological MBR anisotropy pattern generated in the immediate vicinity of an object such as a cosmic string or global texture. We apply these results to cosmic strings, finding a correction to previously published results in the small-angle approximation. We also derive the full-sky anisotropy pattern of a collapsing texture knot

  9. Shifts that divide population

    Science.gov (United States)

    Muneepeerakul, Rachata; Qubbaj, Murad; Aggarwal, Rimjhim; Anderies, John M.; Janssen, Marco

    2014-05-01

    How does a population of organisms in an ecosystem or of people in a society respond to rapid shifts in the environment? Answers to this question are critical to our ability to anticipate and cope with a changing ecohydrological system. We have developed a generic model of adaptation mechanisms, based on replicator dynamics, in which we derive a simple and insightful threshold condition that separates two important types of responses: 'cohesive transition' in which the whole population changes gradually together, and 'population-dividing transition' in which the population splits into two groups with one eventually dominating the other. The threshold depends on the magnitude of the shift and the shape of the fitness landscape. Division in populations can fundamentally alter the functioning of and induce subsequent feedbacks within the system; knowing the condition that gives rise to such division is thus fundamentally important.

  10. New shifted hybrid inflation

    International Nuclear Information System (INIS)

    A new shifted hybrid inflationary scenario is introduced which, in contrast to the older one, relies only on renormalizable superpotential terms. This scenario is automatically realized in a concrete extension of the 'minimal' supersymmetric Pati-Salam model which naturally leads to a moderate violation of Yukawa unification so that, for μ>0, the predicted b-quark mass is acceptable even with universal boundary conditions. It is shown that this extended model possesses a classically flat 'shifted' trajectory which acquires a slope via one-loop radiative corrections and can be used as inflationary path. The constraints from the cosmic background explorer can be met with natural values of the relevant parameters. Also, there is no disastrous production of magnetic monopoles after inflation since the Pati-Salam gauge group is already broken on the 'shifted' path. The relevant part of inflation takes place at values of the inflaton field which are not much smaller than the 'reduced' Planck scale and, thus, supergravity corrections could easily invalidate inflation. It is, however, shown that inflation can be kept intact provided that an extra gauge singlet with a superheavy vacuum expectation value, which originates from D-terms, is introduced and a specific form of the Kaehler potential is used. Moreover, it is found that, although the supergravity corrections are sizable, the constraints from the cosmic background explorer can again be met by readjusting the values of the parameters which were obtained with global supersymmetry. (author)

  11. Measuring remanence anisotropy of hematite in red beds: anisotropy of high-field isothermal remanence magnetization (hf-AIR)

    Science.gov (United States)

    Bilardello, Dario; Kodama, Kenneth P.

    2009-09-01

    The potential of using high-field anisotropy of isothermal remanence magnetization (hf-AIR) measurements for determining the origin of natural remanent magnetization in red beds and for identifying and correcting possible red-bed inclination shallowing was investigated for specimens of the Carboniferous Shepody Formation of New Brunswick and Nova Scotia, Canada. The technique makes it possible for a typical paleomagnetic laboratory to measure the remanence anisotropy of high-coercivity hematite. High-field (hf) AIR was used in conjunction with 100 mT alternating field (af) and 120°C thermal demagnetization to separate the contribution of hematite to the remanence anisotropy from that of magnetite/maghemite and goethite, respectively. A 5-T impulse DC magnetic field was used for the hf-AIR to reset the magnetic moment of high-coercivity hematite so that demagnetization between AIR orientations was not necessary. The ability of a 5-T field to reset the magnetization was tested by generating an isothermal remanent magnetization acquisition curve for hematite by using impulse DC magnetic fields up to 5 T in one orientation and followed by applying a field in the opposite direction at each step. Each field application was treated by 120°C heating and 100 mT af demagnetization before measurement. At 5 T, the difference between the magnetizations applied in opposite directions disappeared indicating that no magnetic memory persisted at this field strength. We performed a validity and reproducibility test of our hf-AIR measurement technique by measuring three specimens multiple times along two orthogonal coordinate systems. The method yielded highly reproducible results and, on rotating the specimen's coordinates, the fabric rotated by 90° as expected, showing that it is not an artifact of the technique. We also measured hf-AIR on samples that had previously been chemically demagnetized in 3N HCl to remove the secondary, chemically grown pigmentary hematite. The hf

  12. Preparation and Fluorescence Anisotropy Study of a Ribonuclease-Lucifer Yellow Conjugate

    Science.gov (United States)

    Malone, C. C.; Sumida, J.; Pusey, M. L.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have prepared a chemical derivative of ribonuclease A (RNase) with lucifer yellow (LY). The rotational dynamics of the LY-RNase conjugate were characterized by steady state and time resolved fluorescence techniques. Steady state anisotropy measurements were performed at varying viscosities at 10C and 20C, and the rotational correlation time of both RNase and the covalently linked LY probe were determined by time resolved frequency domain measurements. Our data suggest that the fluorophore is rigidly bound at 10C.

  13. Fourfold magnetic anisotropy, coercivity and magnetization reversal of Co/V bilayers grown on MgO(0 0 1)

    International Nuclear Information System (INIS)

    Magnetic anisotropy and magnetization reversal of Al/Co/V/MgO(0 0 1) thin films have been investigated. The films were fabricated by magnetron sputtering. The roles of both Co and V layers thicknesses have been studied. Magnetic characterization has been carried out by transverse susceptibility (TS) measurements and hysteresis loops. Cobalt is grown in the hcp structure on V with the c axis parallel to the film plane. Two types of hcp Co crystal are grown with the c axes perpendicular to each other. This structure gives rise to a fourfold magnetic anisotropy. When the V layer thickness is below 40 A a superimposed uniaxial anisotropy develops, the effect of which is a depression in the TS, in agreement with theoretical calculations. This uniaxial anisotropy is induced by the substrate and due to a discontinuous growth of the V layer. For hcp Co grown on V, the magnetic anisotropy rapidly increases with Co layer thickness. In this case, unexpected shifted hysteresis loops along the hard axes were observed when the films were not saturated. This has been explained by taking into account the magnetization reversal along the hard axis: it proceeds via magnetization rotation of some portions of the film at high fields, and by domain wall motion of the rest of the film at lower field values

  14. Evolution of Tidally Truncated Globular Clusters with Anisotropy

    CERN Document Server

    Takahashi, K; Inagaki, S

    1997-01-01

    The evolution of tidally truncated globular clusters is investigated by integrating two-dimensional Fokker-Planck equation that allows the development of velocity anisotropy. We start from the isotropic Plummer model with tidal cut off and followed the evolution through the corecollapse. The heating by three-binary is included to obtain the evolution past the corecollapse. The anisotropy in velocity dispersion develops during the precollapse evolution. However, the anisotropy becomes highly depressed during the post-collapse evolution because of rapid loss of radial orbits. Maximum radial anisotropy appears just after the beginning of the expansion, and degree of anisotropy decreases slowly as the total mass of the cluster decreases. Thus it may be possible to determine the evolutionary status of a cluster if the velocity anisotropy can be measured in the sense that the postcollapse clusters always have very little degree of anisotropy. The structure of the post-collapse cluster can be well fitted to King mod...

  15. The Cosmic Microwave Background Anisotropy Experiments

    CERN Document Server

    Smoot, G F

    1997-01-01

    This paper reports a summary of the contents contents of six hours of lectures on the CMB anisotropy experiments given at the Strasbourg NATO school on the CMB and cosmology. (Its companion paper, astro-ph/9705101 reports the lectures on the CMB spectrum.) A context is set as a bridge from the theoretical CMB anisotropy lectures and the experimental situation. The COBE DMR results are reveiwed in detail and as pioneer for future space missions. Current and planned experiments are discussed in preference to reviewing already completed observations. The NASA MidEX mission MAP is discussed in some detail including figures. The ESA M3 mission Max Planck Surveyor is also reviewed in some detail though its final configuration is not yet fully settled. The recent history and current versions are presented. Tables and references for experiments are included.

  16. Anisotropies in the cosmic microwave background: Theory

    Energy Technology Data Exchange (ETDEWEB)

    Dodelson, S.

    1998-02-01

    Anisotropies in the Cosmic Microwave Background (CMB) contain a wealth of information about the past history of the universe and the present values of cosmological parameters. I online some of the theoretical advances of the last few years. In particular, I emphasize that for a wide class of cosmological models, theorists can accurately calculate the spectrum to better than a percent. The spectrum of anisotropies today is directly related to the pattern of inhomogeneities present at the time of recombination. This recognition leads to a powerful argument that will enable us to distinguish inflationary models from other models of structure formation. If the inflationary models turn out to be correct, the free parameters in these models will be determined to unprecedented accuracy by the upcoming satellite missions.

  17. Physics of the cosmic microwave background anisotropy

    CERN Document Server

    Bucher, Martin

    2015-01-01

    Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The current status of CMB experiments and experimental techniques with an emphasis toward future observations, particularly in polarization, is reviewed. The physics of foreground emissions, especially of polarized dust, is discussed in detail, since this area is likely to become crucial for measurements of the B modes of the CMB polarization at ever greater sensitivity.

  18. Reionization Revisited: Secondary CMB Anisotropies and Polarization

    OpenAIRE

    Hu, Wayne

    1999-01-01

    Secondary CMB anisotropies and polarization provide a laboratory to study structure formation in the reionized epoch. We consider the kinetic Sunyaev-Zel'dovich effect from mildly nonlinear large-scale structure and show that it is a natural extension of the perturbative Vishniac effect. If the gas traces the dark matter to overdensities of order 10, as expected from simulations, this effect is at least comparable to the Vishniac effect at arcminute scales. On smaller scales, it may be used t...

  19. Interferometric Observation of Cosmic Microwave Background Anisotropies

    CERN Document Server

    White, M; Dragovan, M; White, Martin; Carlstrom, John E.; Dragovan, Mark

    1999-01-01

    We present a formalism for analyzing interferometric observations of Cosmic Microwave Background (CMB) anisotropy and polarization data. The formalism is based upon the ell-space expansion of the angular power spectrum favoured in recent years. Explicit discussions of maximum likelihood analysis, power spectrum reconstruction, parameter estimation, imaging and polarization are given. As an example, several calculations for the Degree Angular Scale Interferometer (DASI) and Cosmic Background Interferometer (CBI) experiments are presented.

  20. Anisotropy of SANS in metallic glasses

    International Nuclear Information System (INIS)

    SANS in metallic glasses is anisotropic and depends on the ribbon's orientation. Pd-based melt spun and Ni-based electrochemically deposited glasses exhibit different anisotropies. Both glasses contain scattering centers of the order of 40nm wide in the ribbon plane. In the melt-spun alloy, the scatterers are very thin along the thickness perpendicular to the substrate. In the deposited alloy however, the defects are long along the thickness perpendicular to the electrode

  1. Seismic Anisotropy Beneath the Sumatra Subduction Zone

    OpenAIRE

    R. Collings; Rietbrock, A.; S. Mippress; Lange, D.; D. Natawidjaja; B. Suwargadi; Frederik Tilmann

    2011-01-01

    The Sumatra subduction zone is located on the eastern side of the Sunda Arc between the Sunda Strait and the Andaman Islands, where the Indo-Australian plate is subducting beneath the Eurasian plate. An important tool in understanding the style and geometry of deformation within a subduction zone is the measurement of seismic anisotropy, through observations of shear wave splitting, which provides information about the mantle flow. In Sumatra two temporary seismic networks were deployed withi...

  2. Assessment of velocity anisotropy in rocks

    Czech Academy of Sciences Publication Activity Database

    Lokajíček, Tomáš; Goel, R. K.; Rudajev, Vladimír; Dwivedi, R.D.

    2013-01-01

    Roč. 57, January (2013), s. 142-152. ISSN 1365-1609 R&D Projects: GA ČR(CZ) GA205/08/0676; GA AV ČR IAA300130906; GA ČR(CZ) GAP104/12/0915 Institutional research plan: CEZ:AV0Z30130516 Keywords : elastic anisotropy * acoustic emission * uniaxial loading * hydrostatic loading Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.424, year: 2013

  3. Ultrasonic evaluation of local human skin anisotropy

    Czech Academy of Sciences Publication Activity Database

    Tokar, Daniel; Převorovský, Zdeněk; Hradilová, Jana

    2014-01-01

    Roč. 19, č. 12 (2014). ISSN 1435-4934. [European Conference on Non-Destructive Testing (ECNDT 2014) /11./. Praha, 06.10.2014-10.10.2014] Institutional support: RVO:61388998 Keywords : anisotropy * ultrasonic testing * human skin in-vivo * fabric-fiber composite * signal processing Subject RIV: BI - Acoustics http://www.ndt.net/events/ECNDT2014/app/content/Paper/324_Tokar.pdf

  4. Gaussian Anisotropy In Strange Quark Stars

    OpenAIRE

    Panahi, H.; Monadi, R.; Eghdami, I.

    2015-01-01

    In this paper for studying the anisotropic strange quark stars, we assume that the radial pressure inside the anisotropic star is a superposition of pressure in an isotropic case plus a Gaussian perturbation term. Considering a proportionality between electric charge density and the density of matter, we solve the TOV equation for different cases numerically. Our results indicate that anisotropy increases the maximum mass $M_{max}$ and also its corresponding radius $R$ for a typical strange q...

  5. Relativistic Density Functional Treatment of Magnetic Anisotropy

    OpenAIRE

    Zhang, Hongbin

    2009-01-01

    Spin-orbit coupling (SOC) reduces the spatial symmetry of ferromagnetic solids. That is, the physical properties of ferromagnetic materials are anisotropic, depending on the magnetization direction. In this thesis, by means of numerical calculations with full-relativistic density functional theory, we studied two kinds of physical properties: surface magnetic anisotropy energy (MAE) and anisotropic thermoelectric power due to Lifshitz transitions. After a short introduction to ...

  6. Anisotropy estimation properties for microstructural models

    Czech Academy of Sciences Publication Activity Database

    Beneš, Viktor; Hlawiczková, M.; Gokhale, A. M.; Vander Voort, G. F.

    2001-01-01

    Roč. 46, 2/3 (2001), s. 93-98. ISSN 1044-5803 R&D Projects: GA ČR GA201/99/0269 Grant ostatní: NSF(US) DMR-9816618 Institutional research plan: AV0Z1075907 Keywords : anisotropy * fibre system * Prokhorov distance Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.447, year: 2001

  7. Microwave anisotropies from the Galactic halo

    CERN Document Server

    Walker, M; Mori, M; Walker, Mark; Ohishi, Michiko; Mori, Masaki

    2002-01-01

    Models in which a large fraction of the Galactic dark matter takes the form of cold gas clouds imply that there is thermal microwave emission from the Galactic dark halo. Such models can therefore be directly constrained by existing data on the microwave sky, and in particular the very sensitive observations of microwave anisotropies. To this end we have computed the anisotropy power-spectrum expected for a Galactic dark halo made of cold, dense gas clouds, including the effects of clustering with a CDM-like mass spectrum of mini-halo substructure. The power-spectrum displays two peaks: one, at l~50, is the Poisson noise for the mini-halos, and the second, much larger and at much higher l, is the Poisson noise of the individual clouds. The predicted fluctuation amplitude on degree-scales is a small (~1%) fraction of the observed (~70 micro-K) anisotropies if one considers small areas of sky at high Galactic latitude, increasing by a factor of a few for large areas of sky around 30 degrees latitude. Consequent...

  8. Measuring Anisotropies in the Cosmic Neutrino Background

    CERN Document Server

    Lisanti, Mariangela; Tully, Christopher G

    2014-01-01

    Neutrino capture on tritium has emerged as a promising method for detecting the cosmic neutrino background (CvB). We show that relic neutrinos are captured most readily when their spin vectors are anti-aligned with the polarization axis of the tritium nuclei and when they approach along the direction of polarization. As a result, CvB observatories may measure anisotropies in the cosmic neutrino velocity and spin distributions by polarizing the tritium targets. A small dipole anisotropy in the CvB is expected due to the peculiar velocity of the lab frame with respect to the cosmic frame and due to late-time gravitational effects. The PTOLEMY experiment, a tritium observatory currently under construction, should observe a nearly isotropic background. This would serve as a strong test of the cosmological origin of a potential signal. The polarized-target measurements may also constrain non-standard neutrino interactions that would induce larger anisotropies and help discriminate between Majorana versus Dirac neu...

  9. Effective surface anisotropy in polycrystalline ferromagnetic nanowires

    International Nuclear Information System (INIS)

    Highlights: • Here we make a mixing of two models. A macroscopic and a microscopic model. • The principal idea in this paper is to write the free magnetic energy for a soft magnetic cylindrical nanowire and make the comparison with our previous models. • The model is tested to determine the effective constant in Ni nanowires. - Abstract: Here we express the effective surface anisotropy for soft ferromagnetic nanowires as the function of the micro-structural behaviors. Many papers about these systems determine the reversal modes for the magnetization to explain magnetic properties of the nanowires. Our previous works related morphological structure with magnetic properties. The principal idea in this paper is to write the free magnetic energy for a soft magnetic cylindrical nanowire and make the comparison with our previous models. In this way we include the macroscopic effective anisotropy due to the disordered atoms and ignoring other microstructure terms related in our previous works. From this idea and our last model to these systems, we made an association that permit to express the effective anisotropy in function of the principal morphological characteristics of nanowires. The model is tested to determine the numerical value of the mentioned constant in Ni nanowires obtained by electrodeposition in porous anodic aluminum oxide membranes using the Transmission Electron Microscopy

  10. Dynamical anisotropy of the optical propagation paths

    Science.gov (United States)

    Arsenyan, Tatiana I.; Pisklin, Maksim V.; Suhareva, Natalia A.; Zotov, Aleksey M.

    2015-11-01

    Dynamics of laser beam intensity profile spatial modulations over a model tropospheric path with the controlled meteorological parameters was studied. Influence of the underlying surface temperature as well as the side wind load were considered. The increase of dynamic anisotropic disturbances saturation with the path length was observed. Spatio-temporal correlation characteristics of the directivity pattern in the signal beam registration plane were obtained. Proposed method of the experimental samples analysis on the base of chronogram with the following definition of the dynamic structure tensors array allows to estimate local and averaged projections of the flow velocities over the chosen spatio-temporal region and to restore their geometry in the zone of intersection with the signal beam. Additional characteristics suggested for the diagonalized local structure tensors such as local energy capacity and local structuredness are informative for the estimation of the inhomogeneities spatial dimensions, time of access through the section considered, the dynamics of energetic jets. The concepts of rotational and translational dynamic anisotropy are introduced to discriminate the types of the changes of the local ellipsoids axes orientation as well as their values. Rotational anisotropy shows itself in the changes of the local ellipsoids orientation, thus characterizing the illumination variation over the beam cross-section. Translational anisotropy describes the difference between the axes values for local ellipsoids.

  11. Getting Anisotropy in the Seismic Data Processing

    Directory of Open Access Journals (Sweden)

    Edenia de la Caridad Camejo Cordero

    2013-06-01

    Full Text Available In a conventional processing of seismic data (processing of only one type of wave, P or S, to getimages for hydrocarbons exploration, an isotropic model of the earth is assumed. Studies havedemonstrated that in areas with evidences of anisotropy, the conventional process of time migrationproduces images with poor resolution or erroneous lateral localization of structural events with highinclinations, due to variations in the elastic properties according to the direction of propagation of theseismic waves. At present this topic is of great importance in seismic acquisitions because of thevast employ of the far offset (large distances source–receptor. To, compensate this negative effectsis a priority objective to improve the seismic information. To obtain the anisotropy first started from asequence of high density processing that takes into consideration the characteristics of the earth;and data can be analyzed in all volume. As a final result; getting the comparison between the timemigration stack, with the application of standard normal Moveout correction (NMO and the others,that takes into consideration the obtained anisotropy values, allowing an improvement in the continuityof the reflectors in the seismic images, and at the same time a more reliable interpretation, with theconsequent decrease of the uncertainty and the risks in the oil exploration.

  12. Shifted genus expanded W ∞ algebra and shifted Hurwitz numbers

    Science.gov (United States)

    Zheng, Quan

    2016-05-01

    We construct the shifted genus expanded W ∞ algebra, which is isomorphic to the central subalgebra A ∞ of infinite symmetric group algebra and to the shifted Schur symmetrical function algebra Λ* defined by Okounkov and Olshanskii. As an application, we get some differential equations for the generating functions of the shifted Hurwitz numbers; thus, we can express the generating functions in terms of the shifted genus expanded cut-and-join operators.

  13. Repetition and Translation Shifts

    Directory of Open Access Journals (Sweden)

    Simon Zupan

    2006-06-01

    Full Text Available Repetition manifests itself in different ways and at different levels of the text. The first basic type of repetition involves complete recurrences; in which a particular textual feature repeats in its entirety. The second type involves partial recurrences; in which the second repetition of the same textual feature includes certain modifications to the first occurrence. In the article; repetitive patterns in Edgar Allan Poe’s short story “The Fall of the House of Usher” and its Slovene translation; “Konec Usherjeve hiše”; are compared. The author examines different kinds of repetitive patterns. Repetitions are compared at both the micro- and macrostructural levels. As detailed analyses have shown; considerable microstructural translation shifts occur in certain types of repetitive patterns. Since these are not only occasional; sporadic phenomena; but are of a relatively high frequency; they reduce the translated text’s potential for achieving some of the gothic effects. The macrostructural textual property particularly affected by these shifts is the narrator’s experience as described by the narrative; which suffers a reduction in intensity.

  14. Fabrication of electrodeposited Co nanowire arrays with perpendicular anisotropy

    Science.gov (United States)

    Ge, Shihui; Ma, Xiao; Li, Chao; Li, Wei

    2001-05-01

    Co nanowire arrays have been electrodeposited into polycarbonate membranes with nanosized pores at different voltages. By means of X-ray diffraction, electron diffraction, vibrating sample magnetometer, their microstructures and magnetic properties were investigated at full length. The sample prepared at -1.2 V, 250 mA/cm 2 shows perpendicular anisotropy, but the one deposited at -1.0V, 125 mA/cm 2 has no perpendicular anisotropy. This different magnetic behavior can be explained from their different microstructures. X-ray diffraction and electron diffraction evidence that the former sample is amorphous, and the latter is polycrystalline. In the polycrystalline sample, due to the competition of shape anisotropy and magnetocrystal anisotropy, the sample does not display perpendicular anisotropy. But magnetocrystal anisotropy is very small in amorphous sample, therefore, shape anisotropy plays a dominant role which leads to strong perpendicular anisotropy because of shape anisotropy. Furthermore, applying a magnetic field during deposition, Co grains will preferentially grow with c-axis along the wire axis, which also leads to strong perpendicular anisotropy.

  15. Fabrication of electrodeposited Co nanowire arrays with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Co nanowire arrays have been electrodeposited into polycarbonate membranes with nanosized pores at different voltages. By means of X-ray diffraction, electron diffraction, vibrating sample magnetometer, their microstructures and magnetic properties were investigated at full length. The sample prepared at -1.2 V, 250 mA/cm2 shows perpendicular anisotropy, but the one deposited at -1.0V, 125 mA/cm2 has no perpendicular anisotropy. This different magnetic behavior can be explained from their different microstructures. X-ray diffraction and electron diffraction evidence that the former sample is amorphous, and the latter is polycrystalline. In the polycrystalline sample, due to the competition of shape anisotropy and magnetocrystal anisotropy, the sample does not display perpendicular anisotropy. But magnetocrystal anisotropy is very small in amorphous sample, therefore, shape anisotropy plays a dominant role which leads to strong perpendicular anisotropy because of shape anisotropy. Furthermore, applying a magnetic field during deposition, Co grains will preferentially grow with c-axis along the wire axis, which also leads to strong perpendicular anisotropy

  16. Chemical recycling of carbon dioxide emissions from a cement plant into dimethyl ether, a case study of an integrated process in France using a Reverse Water Gas Shift (RWGS) step

    International Nuclear Information System (INIS)

    Recycling of carbon dioxide (CO2) and hydrogen (H2) into liquid fuel technology has recently gained wide public interest since it is a potential pathway to increase the liquid fuel supply and to mitigate CO2 emissions simultaneously. In France, the majority of the electricity production is derived from nuclear and renewable energy which have a low CO2 footprint. This electricity power enables a potential for massive hydrogen production with low carbon emissions. We studied the possibility to develop this technology at an industrial scale in the French context on a typical industrial example of a cement manufacture in the south of France. An integrated process is proposed, which enables the use of the heat released by the CO2 to fuel process to help to capture the CO2 released by the cement manufacture. Some technological issues are discussed, and a potential solution is proposed for the catalyst used in the critical step of the Reverse Water Gas-Shift reaction (RWGS) of the process. (authors)

  17. On the problem of electron-induced anisotropy effect in As{sub 2}S{sub 3}-based glasses

    Energy Technology Data Exchange (ETDEWEB)

    Balitska, V.O.; Shpotyuk, O.I. E-mail: karat@ipm.lviv.ua

    2000-05-02

    Effect of electron-induced anisotropy was observed in glassy As{sub 2}S{sub 3}-based samples irradiated by accelerated electrons (E=2.8 MeV) in the perpendicular plane to the probe light. Spectral and compositional dependences of this effect and its time stability at room temperature were discussed. It was supposed that the microstructural mechanism of the anisotropy effect was connected with electron-induced formation of new oriented (relatively to the electron flow) defects in the form of broken chemical bonds.

  18. Phase shifting interferometer

    Science.gov (United States)

    Sommargren, Gary E.

    1999-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  19. The investigation of chemical interaction and energy level alignment at Bepp2/Fe65Co35 interface

    Science.gov (United States)

    Wang, Zhen; Pan, Weiwei; Wang, Jinguo; Xu, Chunlong; Hou, Zhaoyang; Zuo, Yalu; Xi, Li

    2016-05-01

    In a bilayer system of Bepp2-FeCo, the element content variation and chemical states of the Bepp2-FeCo interface were investigated using X-ray and ultraviolet photoelectron spectroscopy with Ar ion etching. Chemical reaction was observed for Co and Fe with Bepp2 at the interface. Ultraviolet photoelectron spectroscopy results showed a downward energy shift of -1.0 eV at the interface. This behavior was attributed to the formation of an interface dipole layer. The hole injection barrier ΦpB was 2.0 eV, and the electronic injection barrier ΦnB was 0.6 eV. Moreover, only as the FeCo thickness is less than 3 nm, an uniaxial anisotropy can be induced on the organic layer with the investigation of magnetic optical Kerr effect, this can be used as a multi-function devices.

  20. An Atomic Linear Stark Shift Violating P But Not T Arising From the Electroweak Nuclear Anapole Moment

    OpenAIRE

    Bouchiat, Marie-Anne; Bouchiat, Claude

    2001-01-01

    We propose a direct method of detection of the nuclear anapole moment. It is based on the existence of a linear Stark shift for alkali atoms in their ground state perturbed by a quadrupolar interaction potential and a magnetic field. This shift is proportional to the T-even pseudoscalar built from the quadrupolar potential symmetry axis, the directions of the applied electric and magnetic fields.It involves on the one hand the anisotropy of the hyperfine interaction induced by the quadrupolar...

  1. Determination of anisotropy to enhance the durability of natural stone

    International Nuclear Information System (INIS)

    Anisotropy is a petrophysical property of natural stone and other construction materials that determines their quality and resistance to decay due to a variety of agents, such as water. A study was conducted on nine types of stone widely used in Spain's built heritage, using six previously defined anisotropy indices. These indices can be used to determine the degree of anisotropy, which helps explain the differential decay observed in stone materials quarried in the same bed and used to build the same structure. The conclusion reached is that anisotropy should be determined in the natural stone used both to restore the architectural heritage and in new construction, since the appropriate choice of material quality ensures greater resistance to decay and, therefore, increased durability. Materials with the lowest possible anisotropy should be selected, as this property governs their hydraulic behaviour: the lower the anisotropy in a material, the better its behaviour in relation to water and the longer its durability

  2. Extending Velocity Channel Analysis for Studying Turbulence Anisotropies

    CERN Document Server

    Kandel, Dinesh; Pogosyan, Dmitri

    2016-01-01

    We extend the analysis of the fluctuations in the velocity slices of Position-Position- Velocity (PPV) spectroscopic data from Doppler broadened lines, i.e. Velocity Channel Analysis (VCA) introduced by Lazarian & Pogosyan (2000), to study anisotropy of the underlying velocity and density turbulence statistics that arises from the presence of magnetic field. In particular, we study analytically how the measurable anisotropy of the statistics of the channel map fluctuations changes with the thickness of velocity channels. In agreement with the earlier VCA studies we find that the anisotropy of the thick channels reflects the anisotropy of the density field, while the relative contribution of density and velocity fluctuations to the thin velocity channels depends on the density spectral slope. We show that the anisotropies arising from Alfven, slow and fast modes are different, in particular, the anisotropy in PPV created by fast modes is opposite to that created by Alfven and slow modes and this can be use...

  3. Low-temperature magnetic anisotropy in micas and chlorite

    DEFF Research Database (Denmark)

    Biedermann, Andrea R.; Bender Koch, Christian; Lorenz, Wolfram E A;

    2014-01-01

    use the magnetic anisotropy to understand a rock fabric, it is necessary to identify the minerals responsible for the magnetic anisotropy. Techniques have been developed to separate contributions of the ferrimagnetic, antiferromagnetic, paramagnetic, and diamagnetic susceptibilities to the anisotropy......Phyllosilicates, such as micas and chlorite, are common rock-forming minerals and often show preferred orientation in deformed rocks. In combination with single-crystal anisotropy, this leads to anisotropy of physical properties in the rock, such as magnetic susceptibility. In order to effectively...... of magnetic susceptibility. Because diamagnetic and paramagnetic susceptibility are both linearly dependent on field, separation of the anisotropic contributions requires understanding how the degree of anisotropy of the paramagnetic susceptibility changes as a function of temperature. Note that...

  4. Effect of Stress and Saturation on Shear Wave Anisotropy: Laboratory Observations Using Laser Doppler Interferometry

    Science.gov (United States)

    Lebedev, M.; Collet, O.; Bona, A.; Gurevich, B.

    2015-12-01

    Estimations of hydrocarbon and water resources as well as reservoir management during production are the main challenges facing the resource recovery industry nowadays. The recently discovered reservoirs are not only deep but they are also located in complicated geological formations. Hence, the effect of anisotropy on reservoir imaging becomes significant. Shear wave (S-wave) splitting has been observed in the field and laboratory experiments for decades. Despite the fact that S-wave splitting is widely used for evaluation of subsurface anisotropy, the effects of stresses as well fluid saturation on anisotropy have not been understood in detail. In this paper we present the laboratory study of the effect of stress and saturation on S-wave splitting for a Bentheim sandstone sample. The cubic sample (50mm3), porosity 22%, density 1890kg/m3) was placed into a true-triaxial cell. The sample was subjected to several combinations of stresses varying from 0 to 10MPa and applied to the sample in two directions (X and Y), while no stress was applied to the sample in the Z-direction. The sample's bedding was nearly oriented parallel to Y-Z plane. The ultrasonic S-waves were exited at a frequency of 0.5MHz by a piezoelectric transducer and were propagating in the Z-direction. Upon wave arrival onto the free surface the displacement of the surface was monitored by a Laser Doppler interferometer. Hodograms of the central point of the dry sample (Fig. 1) demonstrate how S-wave polarizations for both "fast" and "slow" S-waves change when increasing the stress in the X direction, while the stress in direction Y is kept constant at 3 MPa. Polarization of the fast S wave is shifted towards the X-axis (axis of the maximum stress). While both S-wave velocities increase with stress, the anisotropy level remains the same. No shift of polarization of fast wave was observed when the stress along the Y-axis was kept at 3 MPa, while the stress along the X-axis was increasing. However, in

  5. Lichtinduzierte Generierung und Charakterisierung optischer Anisotropie. - [überarb. Diss.

    OpenAIRE

    Jung, Carl Christoph

    2005-01-01

    Eine Nutzung der optischen Anisotropie dünner Schichten ist vor allem für die Displaytechnologie, die optische Datenspeicherung und für optische Sicherheitselemente von hoher Bedeutung. Diese Doktorarbeit befasst sich mit theoretischen und experimentellen Untersuchung von dreidimensionaler Anisotropie und dabei insbesondere mit der Untersuchung von lichtinduzierter dreidimensionaler Anisotropie in organischen dünnen Polymer-Schichten. Die gewonnenen Erkentnisse und entwickelten Methoden könne...

  6. Anisotropies in the Gravitational-Wave Stochastic Background

    CERN Document Server

    Olmez, S; Siemens, X

    2011-01-01

    We consider anisotropies in the stochastic background of gravitational-waves (SBGW) arising from random fluctuations in the number of gravitational-wave sources. We first develop the general formalism which can be applied to different cosmological or astrophysical scenarios. We then apply this formalism to calculate the anisotropies of SBGW associated with the fluctuations in the number of cosmic string loops, considering both cosmic string cusps and kinks. We calculate the anisotropies as a function of angle and frequency.

  7. Anisotropies in the Gravitational-Wave Stochastic Background

    OpenAIRE

    Olmez, S.; Mandic, V.; Siemens, X.

    2011-01-01

    We consider anisotropies in the stochastic background of gravitational-waves (SBGW) arising from random fluctuations in the number of gravitational-wave sources. We first develop the general formalism which can be applied to different cosmological or astrophysical scenarios. We then apply this formalism to calculate the anisotropies of SBGW associated with the fluctuations in the number of cosmic string loops, considering both cosmic string cusps and kinks. We calculate the anisotropies as a ...

  8. Anisotropies in the gravitational-wave stochastic background

    International Nuclear Information System (INIS)

    We consider anisotropies in the stochastic background of gravitational-waves (SBGW) arising from random fluctuations in the number of gravitational-wave sources. We first develop the general formalism which can be applied to different cosmological or astrophysical scenarios. We then apply this formalism to calculate the anisotropies of SBGW associated with the fluctuations in the number of cosmic string loops, considering both cosmic string cusps and kinks. We calculate the anisotropies as a function of angle and frequency

  9. Influence of spin on fission fragments anisotropy

    Directory of Open Access Journals (Sweden)

    Ghodsi Omid N.

    2005-01-01

    Full Text Available An analysis of selected fission fragment angular distribution when at least one of the spins of the projectile or target is appreciable in induced fission was made by using the statistical scission model. The results of this model predicate that the spins of the projectile or target are affected on the nuclear level density of the compound nucleus. The experimental data was analyzed by means of the couple channel spin effect formalism. This formalism suggests that the projectile spin is more effective on angular anisotropies within the limits of energy near the fusion barrier.

  10. Shape anisotropy of polymers in disordered environment.

    Science.gov (United States)

    Blavatska, Viktoria; Janke, Wolfhard

    2010-11-14

    We study the influence of structural obstacles in a disordered environment on the size and shape characteristics of long flexible polymer macromolecules. We use the model of self-avoiding random walks on diluted regular lattices at the percolation threshold in space dimensions d=2 and d=3. Applying the pruned-enriched Rosenbluth method, we numerically estimate rotationally invariant universal quantities such as the averaged asphericity and prolateness of polymer chain configurations. Our results quantitatively reveal the extent of anisotropy of macromolecules due to the presence of structural defects. PMID:21073228

  11. Skyrmion Dynamics in Perpendicular Magnetic Anisotropy Nanostructures

    International Nuclear Information System (INIS)

    Full text: Topological solitons in perpendicular magnetic anisotropy (PMA) nanostructures have a rich excitation spectrum that is directly linked to their topological properties, as described by their Skyrmion number. They have been predicted to exhibit intriguing dynamics well as ultra-fast switching. We provide here direct imaging of dynamics of PMA topological solitons in CoB/Pt nanostructures with picosecond time resolution, using Scanning Transmission soft X-ray Microscopy. Specifically, we observe breathing-like and translational dynamical behaviour. We thereby establish a link between the dynamics of PMA solitons and their underlying topology, while also providing a much wider scope for dynamical experiments in magnetic elements. (author)

  12. Three-layer model for exchange anisotropy

    Science.gov (United States)

    Rezende, S. M.; Azevedo, A.; de Aguiar, F. M.; Fermin, J. R.; Egelhoff, W. F.; Parkin, S. S.

    2002-08-01

    Recent x-ray absorption measurements have indicated that the interface between the antiferromagnetic (AF) and the ferromagnetic (FM) layers in AF/FM bilayers instead of being abrupt, consists of a thin layer with uncompensated spins. Here the effect of an interfacial layer between the AF and FM layers on the ferromagnetic resonance response is investigated using a three-layer model for the exchange anisotropy. The calculated dependence of the resonance field with the azimuthal angle of the in-plane external field agrees quite well with experimental data in several samples, lending support to the existence of the uncompensated interfacial layer.

  13. Cosmology with cosmic microwave background anisotropy

    Indian Academy of Sciences (India)

    Tarun Sourdeep

    2006-10-01

    Measurements of CMB anisotropy and, more recently, polarization have played a very important role in allowing precise determination of various parameters of the `standard' cosmological model. The expectation of the paradigm of inflation and the generic prediction of the simplest realization of inflationary scenario in the early Universe have also been established - `acausally' correlated initial perturbations in a flat, statistically isotropic Universe, adiabatic nature of primordial density perturbations. Direct evidence for gravitational instability mechanism for structure formation from primordial perturbations has been established. In the next decade, future experiments promise to strengthen these deductions and uncover the remaining crucial signature of inflation - the primordial gravitational wave background.

  14. Anisotropy in cohesive, frictional granular media

    International Nuclear Information System (INIS)

    The modelling of cohesive, frictional granular materials with a discrete particle molecular dynamics is reviewed. From the structure of the quasi-static granular solid, the fabric, stress, and stiffness tensors are determined, including both normal and tangential forces. The influence of the material properties on the flow behaviour is also reported, including relations between the microscopic attractive force and the macroscopic cohesion as well as the dependence of the macroscopic friction on the microscopic contact friction coefficient. Related to the dynamics, the anisotropy of both structure and stress are exponentially approaching the maximum

  15. Isotope Shifts and Isomer Shifts in Muonic Atoms

    International Nuclear Information System (INIS)

    Recent results on isotope shifts (142-146,148,150 Nd, 92,95-97 Mo, 50,52-54Cr) and isomer shifts (182,184,186W) are summarized in this paper. First, the merits and disadvantages of the three different isotope shift methods (optical h.f.s. spectra, electronic X-rays and muonic X-rays) are briefly outlined. The sensitivities of model dependence of the observed isotope shifts by these three methods are also introduced and discussed. The main emphasis of the paper is to show and to explain how the muonic isotope shift results may be used to normalize the optical isotope shift results and obtain the specific mass corrections occurring in optical results. The energy shifts of nuclear gamma rays as the result of the dynamic E2 interactions in several deformed nuclei have been precisely measured. The calculated shifts of the centre of gravity of the unresolved magnetic doublet are first applied to the observed shifts. The remaining shifts may be interpreted as the isomer effects, i.e. the effect of charge distribution on the transition energy, A comparison of the isomer effects by the muonic atom method and by the Mössbauer technique is included. (author)

  16. Shift work in a security environment

    International Nuclear Information System (INIS)

    Human beings are diurnal species, normally active by day and asleep by night. Yet over thirty million Americans struggle with work schedules that include an off-normal work effort. The railroads, law enforcement, health services, Department of Defense, factory workers, chemical plants and public services, communications and utility workers must provide some form of around-the-clock effort. Shift work has been around since the advent of recorded history. There has always been a need for some type of off-normal service and assistance. The impact of shift work is replete with tales and factual evidence of an increased personnel error rate; disorders, both personal and family, and of course, increased accident events. In recent memory, the Three Mile Island Nuclear Plant incident, Union Carbide's explosion in Bhopal, and the Chernobyl Nuclear Plant catastrophe all occurred during off-normal working hours. Yet management overall has done little to correct the production-driven twelve hour, seven day week shift mentality of the nineteenth century. Most schedules in use today are nothing more than cosmetic variations of the old production schedules. This could be driven by a management consideration of the worker's response to change coupled with a reluctant buy-in of responsibility for the effects of change. Florida Power Corporation has developed for its nuclear security force, a unique work schedule which attempts to employ the sound principles of circadian rhythms coupled with a comprehensive training program to counter the problems associated with shift work. The results over the last four years have seen a marked reduction in the generic problems of personnel errors, absenteeism, unscheduled overtime and turnover rates. Utilization and understanding of this scheduling process for rotational shift work needs to be assessed to determine if the benefits are site specific or provide an expected response to the problems of shift work

  17. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  18. Analytic spectra of CMB anisotropies and polarization generated by scalar perturbations in synchronous gauge

    International Nuclear Information System (INIS)

    The temperature anisotropies and polarization of the cosmic microwave background (CMB) radiation not only serve as indispensable cosmological probes, but also provide a unique channel to detect relic gravitational waves (RGW) at very long wavelengths. Analytical studies of the anisotropies and polarization improve our understanding of various cosmic processes and help to separate the contribution of RGW from that of density perturbations. We present a detailed analytical calculation of CMB temperature anisotropies αk and polarization βk generated by scalar metric perturbations in synchronous gauge, parallel to our previous work with RGW as a generating source. This is realized primarily by an analytic time integration of Boltzmann's equation, yielding the closed forms of αk and βk. Approximations, such as the tight-coupling approximation for photons a priori to the recombination and the long-wavelength limit for scalar perturbations, are used. The residual gauge modes in scalar perturbations are analyzed and a proper joining condition of scalar perturbations at the radiation-matter equality is chosen, ensuring the continuity of energy perturbation. The resulting analytic expressions of the multipole moments of polarization aEl and of temperature anisotropies aTl are explicit functions of the scalar perturbations, recombination time, recombination width, photon-free streaming damping factor, baryon fraction, initial amplitude, primordial scalar spectral index and the running index. These results show that a longer recombination width yields higher amplitudes of polarization on large scales and more damping on small scales, and that a late recombination time shifts the peaks of CXX'l to larger angular scales. Calculations show that aEl is generated in the presence of the quadrupole α2 of temperature anisotropies via scattering, both having similar structures and being smaller than the total aTl, which consists of the contributions from the monopole, dipole

  19. The study of the shape anisotropy in patterned permalloy films

    Institute of Scientific and Technical Information of China (English)

    Zhang Dong; Zhai Ya; Zhai Hong-Ru

    2007-01-01

    In this paper a systematic ferromagnetic resonance study shows that an in-plane magnetic anisotropy in the patterned micron octagon permalloy (Ni80Fe20) elements is mainly determined by the element geometry. The easy-axis is along the edge of the elements, and the hard-axis is along the diagonal. The shape anisotropy of the octagon elements is determined by square and equilateral octagon, and the theoretical calculation was studied on the shape anisotropy. The shape anisotropy of rectangular was calculated by using the same theory.

  20. Random and uniform anisotropy in soft magnetic nanocrystalline alloys (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Flohrer, Sybille, E-mail: Sybille.Flohrer@vacuumschmelze.co [VACUUMSCHMELZE GmbH and Co. KG, Gruener Weg 37, D-63450 Hanau (Germany); Herzer, Giselher [VACUUMSCHMELZE GmbH and Co. KG, Gruener Weg 37, D-63450 Hanau (Germany)

    2010-05-15

    In amorphous and nanocrystalline transition metal based alloys with low magnetostriction, the soft magnetic properties are mainly determined by magneto-elastic and annealing-induced anisotropies which are uniform on a scale much larger than the exchange correlation length. Though, in the nanocrystalline case, there are situations where the random magneto-crystalline anisotropy of the grains becomes relevant. The present paper surveys the interplay between the random magneto-crystalline and the uniform field-induced anisotropy in nanocrystalline FeCuNbSiB soft magnets. Typical examples where the contribution of the random anisotropy becomes particularly visible in the magnetic domain structure will be reviewed.

  1. Computing magnetic anisotropy constants of single molecule magnets

    Indian Academy of Sciences (India)

    S Ramasesha; Shaon Sahoo; Rajamani Raghunathan; Diptiman Sen

    2009-09-01

    We present here a theoretical approach to compute the molecular magnetic anisotropy parameters, and for single molecule magnets in any given spin eigenstate of exchange spin Hamiltonian. We first describe a hybrid constant -valence bond (VB) technique of solving spin Hamiltonians employing full spatial and spin symmetry adaptation and we illustrate this technique by solving the exchange Hamiltonian of the Cu6Fe8 system. Treating the anisotropy Hamiltonian as perturbation, we compute the and values for various eigenstates of the exchange Hamiltonian. Since, the dipolar contribution to the magnetic anisotropy is negligibly small, we calculate the molecular anisotropy from the single-ion anisotropies of the metal centers. We have studied the variation of and by rotating the single-ion anisotropies in the case of Mn12Ac and Fe8 SMMs in ground and few low-lying excited states of the exchange Hamiltonian. In both the systems, we find that the molecular anisotropy changes drastically when the single-ion anisotropies are rotated. While in Mn12Ac SMM values depend strongly on the spin of the eigenstate, it is almost independent of the spin of the eigenstate in Fe8 SMM. We also find that the value is almost insensitive to the orientation of the anisotropy of the core Mn(IV) ions. The dependence of on the energy gap between the ground and the excited states in both the systems has also been studied by using different sets of exchange constants.

  2. Theoretical and experimental investigation of optical absorption anisotropy in β-Ga2O3.

    Science.gov (United States)

    Ricci, F; Boschi, F; Baraldi, A; Filippetti, A; Higashiwaki, M; Kuramata, A; Fiorentini, V; Fornari, R

    2016-06-01

    The question of optical bandgap anisotropy in the monoclinic semiconductor β-Ga2O3 was revisited by combining accurate optical absorption measurements with theoretical analysis, performed using different advanced computation methods. As expected, the bandgap edge of bulk β-Ga2O3 was found to be a function of light polarization and crystal orientation, with the lowest onset occurring at polarization in the ac crystal plane around 4.5-4.6 eV; polarization along b unambiguously shifts the onset up by 0.2 eV. The theoretical analysis clearly indicates that the shift in the b onset is due to a suppression of the transition matrix elements of the three top valence bands at Γ point. PMID:26952789

  3. Theoretical and experimental investigation of optical absorption anisotropy in β-Ga2O3

    Science.gov (United States)

    Ricci, F.; Boschi, F.; Baraldi, A.; Filippetti, A.; Higashiwaki, M.; Kuramata, A.; Fiorentini, V.; Fornari, R.

    2016-06-01

    The question of optical bandgap anisotropy in the monoclinic semiconductor β-Ga2O3 was revisited by combining accurate optical absorption measurements with theoretical analysis, performed using different advanced computation methods. As expected, the bandgap edge of bulk β-Ga2O3 was found to be a function of light polarization and crystal orientation, with the lowest onset occurring at polarization in the ac crystal plane around 4.5-4.6 eV polarization along b unambiguously shifts the onset up by 0.2 eV. The theoretical analysis clearly indicates that the shift in the b onset is due to a suppression of the transition matrix elements of the three top valence bands at Γ point.

  4. An experimental test of the viscous anisotropy hypothesis for partially molten rocks

    CERN Document Server

    Qi, Chao; Katz, Richard F; Takei, Yasuko

    2014-01-01

    Chemical differentiation of rocky planets occurs by melt segregation away from the region of melting. The mechanics of this process, however, are complex and incompletely understood. In partially molten rocks undergoing shear deformation, melt pockets between grains align coherently in the stress field; it has been hypothesized that this anisotropy in microstructure creates an anisotropy in the viscosity of the aggregate. With the inclusion of anisotropic viscosity, continuum, two-phase-flow models reproduce the emergence and angle of melt-enriched bands that form in laboratory experiments. In the same theoretical context, these models also predict sample-scale melt migration due to a gradient in shear stress. Under torsional deformation, melt is expected to segregate radially inward. Here we present new torsional deformation experiments on partially molten rocks that test this prediction. Microstructural analyses of the distribution of melt and solid reveal a radial gradient in melt fraction, with more melt ...

  5. Contribution of individual interfaces in the MgO/Co/Pd trilayer to perpendicular magnetic anisotropy upon annealing

    International Nuclear Information System (INIS)

    The contribution of each interface of the MgO/Co/Pd trilayer to the perpendicular magnetic anisotropy (PMA) was studied by changing chemical and crystalline structures through annealing. We found that volumetric anisotropy in the MgO/Co/Pd trilayer was significantly increased due to enhanced magnetoelastic anisotropy caused by stress built up most likely at the MgO/Co interface during annealing. When the trilayer was annealed at 400 °C, the alloy formation at the Co/Pd interface additionally increased the volumetric anisotropy. Our x-ray magnetic circular dichroism study supported that those structural modifications led to an increase in the orbital moment through spin-orbit coupling (SOC) along the film normal two times larger than that of the as-deposited trilayer, thereby enhancing PMA greatly. Our experimental results prove that the Co/Pd interface, rather than the MgO/Co interface, plays an essential role in inducing strong PMA in the trilayer. The precise investigation of annealing effect on both volumetric and interfacial anisotropies can provide a methodological solution to improve the SOC of the trilayer that can serve as the core unit of spintronic devices

  6. Contribution of individual interfaces in the MgO/Co/Pd trilayer to perpendicular magnetic anisotropy upon annealing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Minseok; Kim, Sanghoon; Ko, Jungho; Hong, Jongill, E-mail: hong.jongill@yonsei.ac.kr [Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2015-03-09

    The contribution of each interface of the MgO/Co/Pd trilayer to the perpendicular magnetic anisotropy (PMA) was studied by changing chemical and crystalline structures through annealing. We found that volumetric anisotropy in the MgO/Co/Pd trilayer was significantly increased due to enhanced magnetoelastic anisotropy caused by stress built up most likely at the MgO/Co interface during annealing. When the trilayer was annealed at 400 °C, the alloy formation at the Co/Pd interface additionally increased the volumetric anisotropy. Our x-ray magnetic circular dichroism study supported that those structural modifications led to an increase in the orbital moment through spin-orbit coupling (SOC) along the film normal two times larger than that of the as-deposited trilayer, thereby enhancing PMA greatly. Our experimental results prove that the Co/Pd interface, rather than the MgO/Co interface, plays an essential role in inducing strong PMA in the trilayer. The precise investigation of annealing effect on both volumetric and interfacial anisotropies can provide a methodological solution to improve the SOC of the trilayer that can serve as the core unit of spintronic devices.

  7. Antiretroviral therapy: Shifting sands.

    Science.gov (United States)

    Sashindran, V K; Chauhan, Rajeev

    2016-01-01

    HIV/AIDS has been an extremely difficult pandemic to control. However, with the advent of antiretroviral therapy (ART), HIV has now been transformed into a chronic illness in patients who have continued treatment access and excellent long-term adherence. Existing indications for ART initiation in asymptomatic patients were based on CD4 levels; however, recent evidence has broken the shackles of CD4 levels. Early initiation of ART in HIV patients irrespective of CD4 counts can have profound positive impact on morbidity and mortality. Early initiation of ART has been found not only beneficial for patients but also to community as it reduces the risk of transmission. There have been few financial concerns about providing ART to all HIV-positive people but various studies have proven that early initiation of ART not only proves to be cost-effective but also contributes to economic and social growth of community. A novel multidisciplinary approach with early initiation and availability of ART at its heart can turn the tide in our favor in future. Effective preexposure prophylaxis and postexposure prophylaxis can also lower transmission risk of HIV in community. New understanding of HIV pathogenesis is opening new vistas to cure and prevention. Various promising candidate vaccines and drugs are undergoing aggressive clinical trials, raising optimism for an ever-elusive cure for HIV. This review describes various facets of tectonic shift in management of HIV. PMID:26900224

  8. The Anisotropy of Replicated Aluminum Foams

    Directory of Open Access Journals (Sweden)

    Eugeny L. Furman

    2014-01-01

    Full Text Available The replication casting process gives the open-cell aluminum foams that can be used in many industrial applications as well as in filtering technology. The essential requirement for filters is the uniformity of filtering degree which is defined by the minimal pore size. However the structure of replication castings is often inhomogeneous and the minimal pore radius is decreasing in the direction of melt infiltration. The objective of this investigation is to study the dynamics of melt impregnation of the porous medium by vacuum suction to identify the possibility of reducing the anisotropy. Theoretical data illustrate the processes at the boundary between melt and gas medium. The experiments were carried out using the replication aluminum samples produced according to commercial technology. It was found that the permeability coefficient varies throughout the height of castings. A method for estimation of pressure on the line of melt movement was proposed. The resistance of NaCl layer and circular vents of the mold causes the inhomogeneity of castings. Finally the ways of minimizing the anisotropy were offered.

  9. Texture and anisotropy analysis of Qusaiba shales

    KAUST Repository

    Kanitpanyacharoen, Waruntorn

    2011-02-17

    Scanning and transmission electron microscopy, synchrotron X-ray diffraction, microtomography and ultrasonic velocity measurements were used to characterize microstructures and anisotropy of three deeply buried Qusaiba shales from the Rub\\'al-Khali basin, Saudi Arabia. Kaolinite, illite-smectite, illite-mica and chlorite show strong preferred orientation with (001) pole figure maxima perpendicular to the bedding plane ranging from 2.4-6.8 multiples of a random distribution (m.r.d.). Quartz, feldspars and pyrite crystals have a random orientation distribution. Elastic properties of the polyphase aggregate are calculated by averaging the single crystal elastic properties over the orientation distribution, assuming a nonporous material. The average calculated bulk P-wave velocities are 6.2 km/s (maximum) and 5.5 km/s (minimum), resulting in a P-wave anisotropy of 12%. The calculated velocities are compared with those determined from ultrasonic velocity measurements on a similar sample. In the ultrasonic experiment, which measures the effects of the shale matrix as well as the effects of porosity, velocities are smaller (P-wave maximum 5.3 km/s and minimum 4.1 km/s). The difference between calculated and measured velocities is attributed to the effects of anisotropic pore structure and to microfractures present in the sample, which have not been taken into account in the matrix averaging. © 2011 European Association of Geoscientists & Engineers.

  10. Cosmic microwave anisotropies from BPS semilocal strings

    CERN Document Server

    Urrestilla, Jon; Hindmarsh, Mark; Kunz, Martin; Liddle, Andrew R

    2007-01-01

    We present the first ever calculation of cosmic microwave background CMB anisotropy power spectra from semilocal cosmic strings, obtained via simulations of a classical field theory. Semilocal strings are a type of non-topological defect arising in some models of inflation motivated by fundamental physics, and are thought to relax the constraints on the symmetry breaking scale as compared to models with (topological) cosmic strings. We derive constraints on the model parameters, including the string tension parameter mu, from fits to cosmological data, and find that in this regard BPS semilocal strings resemble textures more than topological strings. The observed microwave anisotropy at l=10 is reproduced if Gmu = 4.9x10^{-6} (G is Newton's constant). However as with other defects the spectral shape does not match observations, and in models with inflationary perturbations plus semilocal strings the 95% confidence level upper bound is Gmu<1.9x10^{-6} when CMB data, Hubble Key Project and Big Bang Nucleosyn...

  11. α-Zr self-diffusion anisotropy

    International Nuclear Information System (INIS)

    Self-diffusion coefficients (D) have been measured in nominally pure (NP) α-Zr single crystals (∼ 50 ppma Fe) in the range 867-1107 K, in directions either parallel (Dpa) or perpendicular (Dpe) to the c-axis. Measurements were also made on high-purity (HP) α-Zr single crystals (95Zr) counting. Sectioning was done with a sputtering device, or a microtome (some NP experiments at 1107 K). D values for NP Zr are about an order of magnitude higher than the corresponding values for HP Zr. Diffusion anisotropy is complicated. The sputter-sectioned NP Zr specimens show increasing anisotropy ratios (AR = Dpa/Dpe), from 1.0 to 3.2, with decreasing temperatures, whereas AR = 0.53 for both the microtome-sectioned NP and sputter-sectioned HP Zr: the low AR value is consistent with expectations based on intrinsic self-diffusion in hcp metals with c/a < 1.633. (author). 12 refs., 1 tab., 3 figs

  12. Electromagnetic Instabilities Excited by Electron Temperature Anisotropy

    Institute of Scientific and Technical Information of China (English)

    陆全明; 王连启; 周艳; 王水

    2004-01-01

    One-dimensional particle-in-cell simulations are performed to investigate the nonlinear evolution of electromagnetic instabilities excited by the electron temperature anisotropy in homogeneous plasmas with different parameters. The results show that the electron temperature anisotropy can excite the two right-hand electromagnetic instabilities, one has the frequency higher than Ωe, the other is the whistler instability with larger amplitude,and its frequency is below Ωe. Their dispersion relations are consistent with the prediction from the cold plasma theory. In the initial growth stage (prediction from linear theory), the frequency of the dominant mode (the mode whose amplitude is large enough) of the whistler wave almost does not change, but in the saturation stage the situation is different. In the case that the ratio of electron plasma frequency to cyclotron frequency is larger than 1, the frequency of the dominant mode of the whistler wave drifts from high to low continuously. However, for the case of the ratio smaller than 1, besides the original dominant mode of the whistler wave whose frequency is about 2.6ωe, another dominant mode whose frequency is about 1.55ωe also begins to be excited at definite time,and its amplitude increases with time until it exceeds the original dominant mode.

  13. Results from the Wilkinson Microwave Anisotropy Probe

    Science.gov (United States)

    Komatsu, E.; Bennett, Charles L.; Komatsu, Eiichiro

    2015-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of temperature and polarization over the entire sky in five microwave frequency bands. These full-sky maps were used to obtain measurements of temperature and polarization anisotropy of the cosmic microwave background with the unprecedented accuracy and precision. The analysis of two-point correlation functions of temperature and polarization data gives determinations of the fundamental cosmological parameters such as the age and composition of the universe, as well as the key parameters describing the physics of inflation, which is further constrained by three-point correlation functions. WMAP observations alone reduced the flat ? cold dark matter (Lambda Cold Dark Matter) cosmological model (six) parameter volume by a factor of > 68, 000 compared with pre-WMAP measurements. The WMAP observations (sometimes in combination with other astrophysical probes) convincingly show the existence of non-baryonic dark matter, the cosmic neutrino background, flatness of spatial geometry of the universe, a deviation from a scale-invariant spectrum of initial scalar fluctuations, and that the current universe is undergoing an accelerated expansion. The WMAP observations provide the strongest ever support for inflation; namely, the structures we see in the universe originate from quantum fluctuations generated during inflation.

  14. Scanning anisotropy parameters in complex media

    KAUST Repository

    Alkhalifah, Tariq Ali

    2011-03-21

    Parameter estimation in an inhomogeneous anisotropic medium offers many challenges; chief among them is the trade-off between inhomogeneity and anisotropy. It is especially hard to estimate the anisotropy anellipticity parameter η in complex media. Using perturbation theory and Taylor’s series, I have expanded the solutions of the anisotropic eikonal equation for transversely isotropic (TI) media with a vertical symmetry axis (VTI) in terms of the independent parameter η from a generally inhomogeneous elliptically anisotropic medium background. This new VTI traveltime solution is based on a set of precomputed perturbations extracted from solving linear partial differential equations. The traveltimes obtained from these equations serve as the coefficients of a Taylor-type expansion of the total traveltime in terms of η. Shanks transform is used to predict the transient behavior of the expansion and improve its accuracy using fewer terms. A homogeneous medium simplification of the expansion provides classical nonhyperbolic moveout descriptions of the traveltime that are more accurate than other recently derived approximations. In addition, this formulation provides a tool to scan for anisotropic parameters in a generally inhomogeneous medium background. A Marmousi test demonstrates the accuracy of this approximation. For a tilted axis of symmetry, the equations are still applicable with a slightly more complicated framework because the vertical velocity and δ are not readily available from the data.

  15. 1H-MAS-NMR Chemical Shifts in Hydrogen-Bonded Complexes of Chlorophenols (Pentachlorophenol, 2,4,6-Trichlorophenol, 2,6-Dichlorophenol, 3,5-Dichlorophenol, and p-Chlorophenol) and Amine, and H/D Isotope Effects on 1H-MAS-NMR Spectra

    OpenAIRE

    Hisashi Honda

    2013-01-01

    Chemical shifts (CS) of the 1H nucleus in N···H···O type hydrogen bonds (H-bond) were observed in some complexes between chlorophenols [pentachlorophenol (PCP), 2,4,6-tricholorophenol (TCP), 2,6-dichlorophenol (26DCP), 3,5-dichlorophenol (35DCP), and p-chlorophenol (pCP)] and nitrogen-base (N-Base) by solid-state high-resolution 1H-NMR with the magic-angle-spinning (MAS) method. Employing N-Bases with a wide range of pKa values (0.65–10.75), 1H-MAS-NMR CS values of bridging H atoms in H-bonds...

  16. Study of cosmic ray anisotropy along with interplanetary and solar wind plasma parameters

    International Nuclear Information System (INIS)

    Cosmic ray intensity data recorded with ground-based neutron monitor at Deep River were investigated taking into account the associated interplanetary magnetic field and solar wind plasma data during 1981-94. A large number of days having abnormally high/low amplitudes for successive number of five or more days as compared to annual average amplitude of diurnal anisotropy have been taken as high/low amplitude anisotropic wave train events (HAE/LAE). The results clearly indicate that the time of maximum of diurnal variation significantly remains in the 18-Hr direction for majority of the HAE/LAE cases. The phase of enhanced diurnal anisotropy shows a remarkable systematic shift towards later hours as compared to the co-rotational direction for some of the HAE cases, whereas it shows a remarkable systematic shift towards earlier hours for some of the LAE cases as compared to the co-rotational direction. The occurrence of these high/low amplitude events is found to be independent of the nature of the IMF polarity. The high-speed solar wind streams (HSSWSs) do not play any significant role in causing these types of events. The source responsible for these unusual anisotropic wave trains in CR has been proposed. (authors)

  17. Influence of anisotropy and position-dependent effective mass on electro-optic effect of impurity doped quantum dots in presence of Gaussian white noise

    Science.gov (United States)

    Saha, Surajit; Ganguly, Jayanta; Pal, Suvajit; Ghosh, Manas

    2016-08-01

    We study the modulation of electro-optic effect (EOE) of impurity doped QD under the influence of geometrical anisotropy and position-dependent effective mass (PDEM) in presence of Gaussian white noise. Always a comparison has been made between fixed effective mass (FEM) and PDEM to understand the role of the latter. In addition, the role of mode of application of noise (additive/multiplicative) has also been analyzed. The EOE profiles are found to be enriched with shift of peak position and maximization of peak intensity. The observations reveal sensitive interplay between noise and anisotropy/PDEM to fine-tune the features of EOE profiles.

  18. Portable shift register

    International Nuclear Information System (INIS)

    An electronics package for a small, battery-operated, self-contained, neutron coincidence counter based on a portable shift-register (PSR) has been developed. The counter was developed for applications not adequately addressed by commercial packages, including in-plant measurements to demonstrate compliance with regulations (domestic and international), in-plant process control, and in-field measurements (environmental monitoring or safeguards). Our package's features, which address these applications, include the following: Small size for portability and ease of installation;battery or mains operation; a built-in battery to power the unit and a typical detector such as a small sample counter, for over 6 h if power lines are bad or noisy, if there is a temporary absence of power, or if portability is desired; complete support, including bias, for standard neutron detectors; a powerful communications package to easily facilitate robust external control over a serial port; and a C-library to simplify creating external control programs in computers or other controllers. Whereas the PSR specifically addresses the applications mentioned above, it also performs all the measurements made by previous electronics packages for neutron coincidence counters developed at Los Alamos and commercialized. The PSR electronics package, exclusive of carrying handle, is 8 by 10 by 20 cm; it contains the circuit boards, battery, and bias supply and weighs less than 2 kg. This instrument package is the second in an emerging family of portable measurement instruments being developed; the first was the Miniature and Modular Multichannel Analyzer (M3CA). The PSR makes extensive use of hardware and software developed for the M3CA; like the M3CA, it is intended primarily for use with an external controller interfaced over a serial channel

  19. Energy phase shift as mechanism for catalysis

    KAUST Repository

    Beke-Somfai, Tamás

    2012-05-01

    Catalysts are agents that by binding reactant molecules lower the energy barriers to chemical reaction. After reaction the catalyst is regenerated, its unbinding energy recruited from the environment, which is associated with an inevitable loss of energy. We show that combining several catalytic sites to become energetically and temporally phase-shifted relative to each other provides a possibility to sustain the overall reaction by internal \\'energy recycling\\', bypassing the need for thermal activation, and in principle allowing the system to work adiabatically. Using an analytical model for superimposed, phase-shifted potentials of F 1-ATP synthase provides a description integrating main characteristics of this rotary enzyme complex. © 2012 Elsevier B.V. All rights reserved.

  20. Shape-shifting colloids via stimulated dewetting.

    Science.gov (United States)

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-01-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly. PMID:27426418

  1. Instrument Measures Shift In Focus

    Science.gov (United States)

    Steimle, Lawrence J.

    1992-01-01

    Optical components tested at wavelengths from ultraviolet to infrared. Focus-shift-measuring instrument easy to use. Operated in lighted room, without having to make delicate adjustments while peering through microscope. Measures distance along which focal point of converging beam of light shifted by introduction of nominally plane parallel optical component into beam. Intended primarily for measuring focus shifts produced by windows and filters at wavelengths from 120 to 1,100 nanometers. Portable, compact, and relatively inexpensive for degree of precision.

  2. Zero-shifted accelerometer outputs

    Science.gov (United States)

    Galef, Arnold

    1986-08-01

    It is claimed that the commonly appearing zero-shift in pyroshock data is usually a symptom of a malfunctioning measurement system, so that the data can not be repaired (by high-pass filtering or equivalent) unless tests can be devised that permit the demonstration that the system is operating in a linear mode in all respects other than the shift. The likely cause of the zero-shift and its prevention are discussed.

  3. Relationships between brain water content and diffusion tensor imaging parameters (apparent diffusion coefficient and fractional anisotropy) in multiple sclerosis

    International Nuclear Information System (INIS)

    Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8 x 8 x 2 cm3 containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm3 were compared. The water content was increased in patients compared with controls (GM: 244±21 vs. 194±10 a.u.; WM: 245±32 vs. 190±11 a.u.), FA decreased (GM: 0.226±0.038 vs. 0.270±0.020; WM: 0.337±0.044 vs. 0.402±0.011) and ADC increased [GM: 1134±203 vs. 899±28 (x 10-6 mm2/s); WM: 901±138 vs. 751±17 (x 10-6 mm2/s)]. Correlations of water content with FA and ADC in WM were strong (r=-0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=-0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=-0.88; P<0.00001) than in GM (r=-0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue. (orig.)

  4. Quantized beam shifts in graphene

    Energy Technology Data Exchange (ETDEWEB)

    de Melo Kort-Kamp, Wilton Junior [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sinitsyn, Nikolai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalvit, Diego Alejandro Roberto [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-08

    We predict the existence of quantized Imbert-Fedorov, Goos-Hanchen, and photonic spin Hall shifts for light beams impinging on a graphene-on-substrate system in an external magnetic field. In the quantum Hall regime the Imbert-Fedorov and photonic spin Hall shifts are quantized in integer multiples of the fine structure constant α, while the Goos-Hanchen ones in multiples of α2. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field.

  5. Measurements of cosmic ray anisotropies from Pioneers 10 and 11

    International Nuclear Information System (INIS)

    Cosmic ray anisotropy measurements are performed by the University of California, San Diego experiments on Pioneers 10 and 11. A directional Cerenkov counter sensitive to protons and α particles with kinetic energies >= 480 MeV/nucleon is used to determine east-west and north-south anisotropies. (orig./WBU)

  6. Magnetisation reversal in anisotropy graded Co/Pd multilayers

    International Nuclear Information System (INIS)

    We demonstrate high precision controllability of the magnetization reversal nucleation process in [Co/Pd]8 multilayer films consisting of two sets of bilayers with high and low perpendicular anisotropy, respectively. The anisotropy of the entire film is set by the degree of Co/Pd interfacial mixing during deposition which provides fine control of the anisotropy of an individual bilayer in the multilayer stack. The relative number of each type of bilayer is used to select the magnetisation reversal behavior such that changing one bilayer changes the properties of the entire multilayer through anisotropy averaging. A simple extension to the sputtering protocol would provide multilayer films with fully graded anisotropy, while maintaining a constant saturation magnetization opening new possibilities for the creation of highly engineered multilayer structures for spin torque devices and future magnetic recording media

  7. Structural anisotropy in amorphous Fe-Tb thin films

    International Nuclear Information System (INIS)

    We have used conventional and anomalous dispersion x-ray scattering to study the near-neighbor atomic environments in sputter-deposited amorphous Fe-Tb thin films with a large perpendicular magnetic anisotropy. The as-deposited films show a clear structural anisotropy, with more Fe-Tb near neighbor pairs in the out-of-plane direction. Upon annealing, the magnetic anisotropy drops significantly, and we see a corresponding reduction in the structural anisotropy. The number of Fe-Tb near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Fe-Tb near neighbors becomes more uniform upon annealing. We conclude that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure. copyright 1996 The American Physical Society

  8. Discriminating neurogenic from myopathic disease via measurement of muscle anisotropy.

    Science.gov (United States)

    Garmirian, Lindsay P; Chin, Anne B; Rutkove, Seward B

    2009-01-01

    Skeletal muscle is electrically anisotropic, with a tendency for applied electrical current to flow more readily along muscle fibers than across them. In this study, we assessed a method for non-invasive measurement of anisotropy to determine its potential to serve as a new technique for distinguishing neurogenic from myopathic disease. Measurements were made on the biceps brachii and tibialis anterior muscles in 15 normal subjects and 12 patients with neuromuscular disease (6 with amyotrophic lateral sclerosis and 6 with various myopathies) using 50 kHZ applied current. Consistent multi-angle anisotropic patterns were found for reactance and phase in both muscles in normal subjects. Normalized anisotropy differences for each subject were defined, and group average values identified. The amyotrophic lateral sclerosis (ALS) patients demonstrated increased and distorted anisotropy patterns, whereas myopathic patients demonstrated normal or reduced anisotropy. These results suggest that non-invasive measurement of muscle anisotropy has potential for diagnosis of neuromuscular diseases. PMID:19058193

  9. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

    DEFF Research Database (Denmark)

    Bairagi, K.; Bellec, A.; Repain, V.; Chacon, C.; Girard, Y.; Garreau, Y.; Lagoute, J.; Rousset, S.; Breitwieser, R.; Hu, Yu-Cheng; Chao, Yen Cheng; Pai, Woei Wu; Li, D.; Smogunov, A.; Barreteau, Cyrille

    2015-01-01

    We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a...... function of the C60 coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between C60 pz and Co dz2 orbitals. By generalizing these arguments, we also demonstrate that the hybridization of C60 with a Fe(110......) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems....

  10. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    Directory of Open Access Journals (Sweden)

    Yuan Lu

    2016-05-01

    Full Text Available Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ∼16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  11. Intrinsic anisotropy-defined magnetization reversal in submicron ring magnets

    Science.gov (United States)

    Li, S. P.; Lew, W. S.; Bland, J. A. C.; Natali, M.; Lebib, A.; Chen, Y.

    2002-12-01

    We report a study of the effect of magnetocrystalline anisotropy in the magnetization reversal of submicron Co rings fabricated by nanoimprint lithography. For weak magnetocrystalline anisotropy, the complete reversal takes place via a transition from saturation at large negative fields, into a vortex configuration at small fields, and back to reverse saturation at large positive fields. When the anisotropy strength is increased to a critical value, the intermediate vortex configuration no longer exists in the magnetization reversal along the easy axis; instead, the reversal occurs through a rapid jump. However, when the applied field direction is far from the easy axis, the presence of the magnetocrystalline anisotropy favors local vortex nucleation, and this leads to a similar switching process as found for low anisotropy. Micromagnetic simulations indicate that the magnetization reversal process of the rings, starts from a buckling-like reverse domain nucleation, followed by local vortex formation and an avalanche process of local vortex nucleation.

  12. Polarization and dilepton anisotropy in pion-nucleon collisions

    CERN Document Server

    Speranza, Enrico; Friman, Bengt

    2016-01-01

    Hadronic polarization and the related anisotropy of the dilepton angular distribution are studied for the reaction $\\pi N \\rightarrow Ne^+ e^-$. We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the $N(1520)$ and $N(1440)$ resonances, which are essential at the collision energy of the recent data obtained by the HADES collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unravelling the resonance contributions to this process.

  13. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    Science.gov (United States)

    Lu, Yuan; Zhou, Tie-ge; Shao, Bin; Zuo, Xu; Feng, Min

    2016-05-01

    Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ˜16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  14. Adhesion and size dependent friction anisotropy in boron nitride nanotubes

    International Nuclear Information System (INIS)

    The frictional properties of individual multiwalled boron nitride nanotubes (BN-NTs) synthesized by chemical vapour deposition (CVD) and deposited on a silicon substrate are investigated using an atomic force microscope tip sliding along (longitudinal sliding) and across (transverse sliding) the tube’s principal axis. Because of the tube’s transverse deformations during the tip sliding, a larger friction coefficient is found for the transverse sliding as compared to the longitudinal sliding. Here, we show that the friction anisotropy in BN-NTs, defined as the ratio between transverse and longitudinal friction forces per unit area, increases with the nanotube–substrate contact area, estimated to be proportional to (LNTRNT)1/2, where LNT and RNT are the length and the radius of the nanotube, respectively. Larger contact area denotes stronger surface adhesion, resulting in a longitudinal friction coefficient closer to the value expected in the absence of transverse deformations. Compared to carbon nanotubes (C-NTs), BN-NTs display a friction coefficient in each sliding direction with intermediate values between CVD and arc discharge C-NTs. CVD BN-NTs with improved tribological properties and higher oxidation temperature might be a better candidate than CVD C-NTs for applications in extreme environments. (paper)

  15. Fine structure constant variation or spacetime anisotropy?

    International Nuclear Information System (INIS)

    Recent observations on the quasar absorption spectra supply evidence for the variation of the fine structure constant α. In this paper, we propose another interpretation of the observational data on the quasar absorption spectra: a scenario with spacetime inhomogeneity and anisotropy. Maybe the spacetime is characterized by the Finsler geometry instead of the Riemann one. The Finsler geometry admits fewer symmetries than the Riemann geometry does. We investigate the Finslerian geodesic equations in the Randers spacetime (a special Finsler spacetime). It is found that the cosmological redshift in this spacetime deviates from the one in general relativity. The modification term to the redshift could be generally revealed as a monopole plus dipole function of spacetime locations and directions. We suggest that this modification corresponds to the spatial monopole and dipole of α variation in the quasar absorption spectra. (orig.)

  16. CMB Anisotropies from a Gradient Mode

    CERN Document Server

    Mirbabayi, Mehrdad

    2014-01-01

    A pure gradient mode must have no observable dynamical effect at linear level. We confirm this by showing that its contribution to the dipolar power asymmetry of CMB anisotropies vanishes, if Maldacena's consistency condition is satisfied. To this end, the existing second order Sachs-Wolfe formula in the squeezed limit is extended to include a gradient in the long mode and to account for the change in the location of the last scattering surface induced by this mode. At second order, a gradient mode generated in Single-field inflation is shown to induce a quadrupole moment. For instance in a matter-dominated model it is equal to 5/18 times the square of the linear gradient part. This quadrupole can be cancelled by superposing a quadratic perturbation. The result is shown to be a non-linear extension of Weinberg's adiabatic modes: a long-wavelength physical mode which looks locally like a coordinate transformation.

  17. Creep anisotropy of Zircaloy cladding tubes

    International Nuclear Information System (INIS)

    First of all, a survey is given on the texture of Zircaloy cladding tubes obtained depending on the manufacturing conditions, and the state of knowledge on the anisotropy of the mechanical properties of the zirconium alloys connected with the texture is outlined. Theoretical formulations are set up for the phenomenological representation of the anisotropic creep. The results of tension and compression tests and the thus obtained creep site curves exhibit distinct differences with tubes having different textures. Furthermore, on asymmetry regarding compressive tensile stress is found in such a manner that the material under compression stress is more resistant to creep. Finally, discussions follow on the deformation mechanisms and a comparison with flow processes as well as indications on the significance of these creep results within the framework of fuel rod design are given. (IHoe/LH)

  18. Orientational anisotropy and interfacial transport in polycrystals

    Science.gov (United States)

    Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

    2016-04-01

    Interfacial diffusion is governed to a large degree by geometric parameters that are determined by crystallographic orientation. In this study, we assess the impact of orientational anisotropy on mass transport at internal interfaces, focusing on the role of preferred crystallographic orientation (i.e., texture) on mass diffusion in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion for polycrystals having various grain-orientation distributions. By relating grain misorientation to grain-boundary energies and, via the Borisov relation, to the diffusivity, we link microstructure variability to kinetics. Our aim is to correlate shape features of the orientation distribution, such as the location and shapes of peaks, with the calculated effective diffusivity. Finally, we discuss the role of crystallographic constraints, such as those associated with grain junctions, in determining the effective diffusivity of a polycrystal.

  19. Perpendicular anisotropy in Fe/Ag multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Fetzer, C.; Szucs, I.S.; Dezsi, I. [KFKI Research Institute for Particle and Nuclear Physics, Budapest (Hungary); Kaptas, D.; Kiss, L.F.; Vincze, I. [Research Institute for Solid State Physics and Optics, Budapest (Hungary); Balogh, J.

    2008-08-15

    The direction of the spontaneous magnetization changes from out of plane to in plane at around x=0.6 in[Ag(2.6 nm)/Fe(x nm)]{sub 10} multilayers (0.2{<=}x{<=}1) prepared on Si(111) substrate by vacuum evaporation. Transmission Moessbauer spectroscopy measurements of removed samples with a thick capping layer are compared to conversion electron Moessbauer spectroscopy measurements of samples on the Si substrate with a thin capping layer. The stress arising because of the application of a thick capping layer and the removal of the samples from the substrate is shown to have negligible effect on the spontaneous magnetization. The results support that the appearance of the perpendicular anisotropy below x=0.6 is an intrinsic property of Fe/Ag multilayers. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Resolving Spacecraft Earth-Flyby Anomalies with Measured Light Speed Anisotropy

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2008-07-01

    Full Text Available Doppler shift observations of spacecraft, such as Galileo, NEAR, Cassini, Rosetta and MESSENGER in earth flybys, have all revealed unexplained speed “anomalies” — that the Doppler-shift determined speeds are inconsistent with expected speeds. Here it is shown that these speed anomalies are not real and are actually the result of using an incorrect relationship between the observed Doppler shift and the speed of the space- craft — a relationship based on the assumption that the speed of light is isotropic in all frames, viz invariant. Taking account of the repeatedly measured light-speed anisotropy the anomalies are resolved ab initio . The Pioneer 10 / 11 anomalies are discussed, but not resolved. The spacecraft observations demonstrate again that the speed of light is not invariant, and is isotropic only with respect to a dynamical 3-space. The existing Doppler shift data also offers a resource to characterise a new form of gravitational waves, the dynamical 3-space turbulence, that has also been detected by other tech- niques. The Einstein spacetime formalism uses a special definition of space and time coordinates that mandates light speed invariance for all observers, but which is easily misunderstood and misapplied.