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Sample records for chemical shifts torsion

  1. 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.

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

    International Nuclear Information System (INIS)

    Shen Yang; Bax, Ad

    2013-01-01

    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 χ 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

  3. Assignment of protein backbone resonances using connectivity, torsion angles and 13Cα chemical shifts

    International Nuclear Information System (INIS)

    Morris, Laura C.; Valafar, Homayoun; Prestegard, James H.

    2004-01-01

    A program is presented which will return the most probable sequence location for a short connected set of residues in a protein given just 13 C α chemical shifts (δ( 13 C α )) and data restricting the φ and ψ backbone angles. Data taken from both the BioMagResBank and the Protein Data Bank were used to create a probability density function (PDF) using a multivariate normal distribution in δ( 13 C α ), φ, and ψ space for each amino acid residue. Extracting and combining probabilities for particular amino acid residues in a short proposed sequence yields a score indicative of the correctness of the proposed assignment. The program is illustrated using several proteins for which structure and 13 C α chemical shift data are available

  4. Chemical shift imaging: a review

    International Nuclear Information System (INIS)

    Brateman, L.

    1986-01-01

    Chemical shift is the phenomenon that is seen when an isotope possessing a nuclear magnetic dipole moment resonates at a spectrum of resonance frequencies in a given magnetic field. These resonance frequencies, or chemical shifts, depend on the chemical environments of particular nuclei. Mapping the spatial distribution of nuclei associated with a particular chemical shift (e.g., hydrogen nuclei associated with water molecules or with lipid groups) is called chemical shift imaging. Several techniques of proton chemical shift imaging that have been applied in vivo are presented, and their clinical findings are reported and summarized. Acquiring high-resolution spectra for large numbers of volume elements in two or three dimensions may be prohibitive because of time constraints, but other methods of imaging lipid of water distributions (i.e., selective excitation, selective saturation, or variations in conventional magnetic resonance imaging pulse sequences) can provide chemical shift information. These techniques require less time, but they lack spectral information. Since fat deposition seen by chemical shift imaging may not be demonstrated by conventional magnetic resonance imaging, certain applications of chemical shift imaging, such as in the determination of fatty liver disease, have greater diagnostic utility than conventional magnetic resonance imaging. Furthermore, edge artifacts caused by chemical shift effects can be eliminated by certain selective methods of data acquisition employed in chemical shift imaging

  5. chemical shift tensors in helical peptides by dipolar-modulated chemical shift recoupling NMR

    International Nuclear Information System (INIS)

    Yao Xiaolan; Yamaguchi, Satoru; Hong Mei

    2002-01-01

    The Cα chemical shift tensors of proteins contain information on the backbone conformation. We have determined the magnitude and orientation of the Cα chemical shift tensors of two peptides with α-helical torsion angles: the Ala residue in G*AL (φ=-65.7 deg., ψ=-40 deg.), and the Val residue in GG*V (φ=-81.5 deg., ψ=-50.7 deg.). The magnitude of the tensors was determined from quasi-static powder patterns recoupled under magic-angle spinning, while the orientation of the tensors was extracted from Cα-Hα and Cα-N dipolar modulated powder patterns. The helical Ala Cα chemical shift tensor has a span of 36 ppm and an asymmetry parameter of 0.89. Its σ 11 axis is 116 deg. ± 5 deg. from the Cα-Hα bond while the σ 22 axis is 40 deg. ± 5 deg. from the Cα-N bond. The Val tensor has an anisotropic span of 25 ppm and an asymmetry parameter of 0.33, both much smaller than the values for β-sheet Val found recently (Yao and Hong, 2002). The Val σ 33 axis is tilted by 115 deg. ± 5 deg. from the Cα-Hα bond and 98 deg. ± 5 deg. from the Cα-N bond. These represent the first completely experimentally determined Cα chemical shift tensors of helical peptides. Using an icosahedral representation, we compared the experimental chemical shift tensors with quantum chemical calculations and found overall good agreement. These solid-state chemical shift tensors confirm the observation from cross-correlated relaxation experiments that the projection of the Cα chemical shift tensor onto the Cα-Hα bond is much smaller in α-helices than in β-sheets

  6. Unraveling the meaning of chemical shifts in protein NMR.

    Science.gov (United States)

    Berjanskii, Mark V; Wishart, David S

    2017-11-01

    Chemical shifts are among the most informative parameters in protein NMR. They provide wealth of information about protein secondary and tertiary structure, protein flexibility, and protein-ligand binding. In this report, we review the progress in interpreting and utilizing protein chemical shifts that has occurred over the past 25years, with a particular focus on the large body of work arising from our group and other Canadian NMR laboratories. More specifically, this review focuses on describing, assessing, and providing some historical context for various chemical shift-based methods to: (1) determine protein secondary and super-secondary structure; (2) derive protein torsion angles; (3) assess protein flexibility; (4) predict residue accessible surface area; (5) refine 3D protein structures; (6) determine 3D protein structures and (7) characterize intrinsically disordered proteins. This review also briefly covers some of the methods that we previously developed to predict chemical shifts from 3D protein structures and/or protein sequence data. It is hoped that this review will help to increase awareness of the considerable utility of NMR chemical shifts in structural biology and facilitate more widespread adoption of chemical-shift based methods by the NMR spectroscopists, structural biologists, protein biophysicists, and biochemists worldwide. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Contact-less magneto-elastic torsional sensor based on phase-shift measurements

    International Nuclear Information System (INIS)

    Buchenau, D; Schmidt, G; Eckert, S

    2014-01-01

    We report on the development of a contact-less measurement technique for torsional shear stress τ in ferromagnetic axles or hollow shafts, based on the magneto-elastic effect. In general, two different measuring principles for ferromagnetic materials can be realized, based on: the evaluation of the change of magnetic polarization influenced by shear stress ΔJ(τ) or the change of the magnetic susceptibility Δχ A (τ). The comprehension of the magnetic polarization or the magnetic susceptibility in a sensor concept requires an external magnetic field. Alternating magnetic fields were used as shear stress can disturb not only the amplitude but also the phase distribution of the applied magnetic field. As a result of a torsional moment acting on an axle or hollow shaft, an angle of twist η appears, which is constant over the length of the twisted object. This angle of twist can be understood as a shift of infinitesimal thin cross-sections in which the whole length of the axle is separated. Besides the macroscopic deformation effect, shear forces also affect the Weiss-domains in the micro-scale of the ferromagnetic material. The effects in the micro-scale are the base of the magneto-elastic effect. The combination of the deformation effect in the macro-scale and the deformation of the Weiss-domains in the micro-scale leads to a sophisticated measurement principle for torsional stress in axles or hollow shafts. Magneto-sensitive detectors along or around the measurement object open up the possibility for a contact-less detection of torsional stress in ferromagnetic materials. Besides a strong measuring signal, free from electromagnetic interference, the introduced contact-less measurement principle offers different advantages, like independence from compression strength, nominal tensile stress, impact load, ferromagnetic hysteresis effects and independence of the temperature-dependent electrical conductivity of the axle or hollow shaft. The characteristics of such

  8. Ocular torsion produced by unilateral chemical inactivation of the cerebellar flocculus in alert cats.

    Science.gov (United States)

    Chin, Shinki; Fukushima, Kikuro; Fukushima, Junko; Kase, Manabu; Ohno, Shigeaki

    2002-09-01

    Vertical eye movements are executed by the vertical recti and oblique muscle pairs. Since each of these pairs rotates the eye in both vertical and torsional directions, torsional components must be controlled to execute appropriate, purely vertical eye movements. To test whether the cerebellar flocculus is involved in the control of torsional eye position, we examined the effects of unilateral chemical inactivation of the flocculus on ocular torsion in alert cats. Pitch-responding floccular regions were first identified, then the GABA agonist muscimol was injected unilaterally into the identified regions. Ocular torsion was examined photographically. Unilateral muscimol infusion into pitch-responding areas in the rostral and middle parts of the flocculus resulted in significant intorsion of the eye ipsilateral to the infusion. Gaze-holding was also impaired following downward saccades induced by visual stimuli. Although the contralateral eye showed a tendency towards extorsion, the effects were not significant. Muscimol infusion into the caudal flocculus did not induce consistent effects on ocular torsion. The cerebellar flocculus plays a key role in the maintenance of torsional eye position.

  9. Empirical isotropic chemical shift surfaces

    International Nuclear Information System (INIS)

    Czinki, Eszter; Csaszar, Attila G.

    2007-01-01

    A list of proteins is given for which spatial structures, with a resolution better than 2.5 A, are known from entries in the Protein Data Bank (PDB) and isotropic chemical shift (ICS) values are known from the RefDB database related to the Biological Magnetic Resonance Bank (BMRB) database. The structures chosen provide, with unknown uncertainties, dihedral angles φ and ψ characterizing the backbone structure of the residues. The joint use of experimental ICSs of the same residues within the proteins, again with mostly unknown uncertainties, and ab initio ICS(φ,ψ) surfaces obtained for the model peptides For-(l-Ala) n -NH 2 , with n = 1, 3, and 5, resulted in so-called empirical ICS(φ,ψ) surfaces for all major nuclei of the 20 naturally occurring α-amino acids. Out of the many empirical surfaces determined, it is the 13C α ICS(φ,ψ) surface which seems to be most promising for identifying major secondary structure types, α-helix, β-strand, left-handed helix (α D ), and polyproline-II. Detailed tests suggest that Ala is a good model for many naturally occurring α-amino acids. Two-dimensional empirical 13C α - 1 H α ICS(φ,ψ) correlation plots, obtained so far only from computations on small peptide models, suggest the utility of the experimental information contained therein and thus they should provide useful constraints for structure determinations of proteins

  10. MR chemical shift imaging of human atheroma

    International Nuclear Information System (INIS)

    Mohiaddin, R.H.; Underwood, R.; Firmin, D.; Abdulla, A.K.; Rees, S.; Longmore, D.

    1988-01-01

    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

  11. Combined chemical shift changes and amino acid specific chemical shift mapping of protein-protein interactions

    Energy Technology Data Exchange (ETDEWEB)

    Schumann, Frank H.; Riepl, Hubert [University of Regensburg, Institute of Biophysics and Physical Biochemistry (Germany); Maurer, Till [Boehringer Ingelheim Pharma GmbH and Co. KG, Analytical Sciences Department (Germany); Gronwald, Wolfram [University of Regensburg, Institute of Biophysics and Physical Biochemistry (Germany); Neidig, Klaus-Peter [Bruker BioSpin GmbH, Software Department (Germany); Kalbitzer, Hans Robert [University of Regensburg, Institute of Biophysics and Physical Biochemistry (Germany)], E-mail: hans-robert.kalbitzer@biologie.uni-regensburg.de

    2007-12-15

    Protein-protein interactions are often studied by chemical shift mapping using solution NMR spectroscopy. When heteronuclear data are available the interaction interface is usually predicted by combining the chemical shift changes of different nuclei to a single quantity, the combined chemical shift perturbation {delta}{delta}{sub comb}. In this paper different procedures (published and non-published) to calculate {delta}{delta}{sub comb} are examined that include a variety of different functional forms and weighting factors for each nucleus. The predictive power of all shift mapping methods depends on the magnitude of the overlap of the chemical shift distributions of interacting and non-interacting residues and the cut-off criterion used. In general, the quality of the prediction on the basis of chemical shift changes alone is rather unsatisfactory but the combination of chemical shift changes on the basis of the Hamming or the Euclidian distance can improve the result. The corrected standard deviation to zero of the combined chemical shift changes can provide a reasonable cut-off criterion. As we show combined chemical shifts can also be applied for a more reliable quantitative evaluation of titration data.

  12. Protein Structure Determination Using Chemical Shifts

    DEFF Research Database (Denmark)

    Christensen, Anders Steen

    chemical shifts. The method is benchmarked on folding simulations of five small proteins. In four cases the resulting structures are in excellent agreement with experimental data, the fifth case fail likely due to inaccuracies in the energy function. For the Chymotrypsin Inhibitor protein, a structure......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...... is determined using only chemical shifts recorded and assigned through automated processes. The CARMSD to the experimental X-ray for this structure is 1.1. Å. Additionally, the method is combined with very sparse NOE-restraints and evolutionary distance restraints and tested on several protein structures >100...

  13. Sigmatropic proton shifts: a quantum chemical study.

    Science.gov (United States)

    Wang, Yi; Yu, Zhi-Xiang

    2017-09-13

    A quantum chemical study of [1,j] sigmatropic proton shifts in polyenyl anions and related conjugated systems has been performed. We found that the Woodward-Hoffmann rules can be applied to understand the stereochemical outcome of these sigmatropic rearrangements, showing that [1,j] sigmatropic proton shift occurs antarafacially when j = 4n + 2, while suprafacial proton shift is symmetry-allowed when j = 4n. The activation barriers for [1,j] proton shifts in polyenyl anions C j H j+3 - are 48.2 (j = 2), 32.8 (j = 4), 21.0 (j = 6), 40.5 (j = 8), and 49.1 (j = 10) kcal mol -1 , respectively. This trend can be explained by the trade-off between stereoelectronic requirement and ring strain in the proton shift transition structure. Among these reactions, only the [1,6] proton shift with the lowest activation barrier can occur intramolecularly under mild reaction conditions. The others are unlikely to take place in a direct manner. Consequently, proton shuttles are generally required to facilitate these sigmatropic proton shifts through a protonation/deprotonation mechanism.

  14. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Woonghee, E-mail: whlee@nmrfam.wisc.edu [University of Wisconsin-Madison, National Magnetic Resonance Facility at Madison, and Biochemistry Department (United States); Yu, Wookyung [Center for Proteome Biophysics, Pusan National University, Department of Physics (Korea, Republic of); Kim, Suhkmann [Pusan National University, Department of Chemistry and Chemistry Institute for Functional Materials (Korea, Republic of); Chang, Iksoo [Center for Proteome Biophysics, Pusan National University, Department of Physics (Korea, Republic of); Lee, Weontae, E-mail: wlee@spin.yonsei.ac.kr [Yonsei University, Structural Biochemistry and Molecular Biophysics Laboratory, Department of Biochemistry (Korea, Republic of); Markley, John L., E-mail: markley@nmrfam.wisc.edu [University of Wisconsin-Madison, National Magnetic Resonance Facility at Madison, and Biochemistry Department (United States)

    2012-10-15

    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.

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

    Science.gov (United States)

    Lee, Woonghee; Yu, Wookyung; Kim, Suhkmann; Chang, Iksoo; Lee, Weontae; Markley, John L

    2012-10-01

    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.edu.

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

    Science.gov (United States)

    Lee, Woonghee; Yu, Wookyung; Kim, Suhkmann; Chang, Iksoo

    2012-01-01

    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.edu. PMID:22903636

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

    International Nuclear Information System (INIS)

    Lee, Woonghee; Yu, Wookyung; Kim, Suhkmann; Chang, Iksoo; Lee, Weontae; Markley, John L.

    2012-01-01

    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.

  19. Sequential nearest-neighbor effects on computed {sup 13}C{sup {alpha}} chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Vila, Jorge A. [Cornell University, Baker Laboratory of Chemistry and Chemical Biology (United States); Serrano, Pedro; Wuethrich, Kurt [The Scripps Research Institute, Department of Molecular Biology (United States); Scheraga, Harold A., E-mail: has5@cornell.ed [Cornell University, Baker Laboratory of Chemistry and Chemical Biology (United States)

    2010-09-15

    To evaluate sequential nearest-neighbor effects on quantum-chemical calculations of {sup 13}C{sup {alpha}} chemical shifts, we selected the structure of the nucleic acid binding (NAB) protein from the SARS coronavirus determined by NMR in solution (PDB id 2K87). NAB is a 116-residue {alpha}/{beta} protein, which contains 9 prolines and has 50% of its residues located in loops and turns. Overall, the results presented here show that sizeable nearest-neighbor effects are seen only for residues preceding proline, where Pro introduces an overestimation, on average, of 1.73 ppm in the computed {sup 13}C{sup {alpha}} chemical shifts. A new ensemble of 20 conformers representing the NMR structure of the NAB, which was calculated with an input containing backbone torsion angle constraints derived from the theoretical {sup 13}C{sup {alpha}} chemical shifts as supplementary data to the NOE distance constraints, exhibits very similar topology and comparable agreement with the NOE constraints as the published NMR structure. However, the two structures differ in the patterns of differences between observed and computed {sup 13}C{sup {alpha}} chemical shifts, {Delta}{sub ca,i}, for the individual residues along the sequence. This indicates that the {Delta}{sub ca,i} -values for the NAB protein are primarily a consequence of the limited sampling by the bundles of 20 conformers used, as in common practice, to represent the two NMR structures, rather than of local flaws in the structures.

  20. Discrete torsion

    International Nuclear Information System (INIS)

    Sharpe, Eric

    2003-01-01

    In this article we explain discrete torsion. Put simply, discrete torsion is the choice of orbifold group action on the B field. We derive the classification H 2 (Γ,U(1)), the twisted sector phases appearing in string loop partition functions, Douglas's description of discrete torsion for D-branes in terms of a projective representation of the orbifold group, and outline how the results of Vafa and Witten fit into this framework. In addition, we observe that additional degrees of freedom (known as shift orbifolds) appear in describing orbifold group actions on B fields, in addition to those classified by H 2 (Γ,U(1)), and explain how these degrees of freedom appear in terms of twisted sector contributions to partition functions and in terms of orbifold actions on D-brane worldvolumes. This paper represents a technically simplified version of prior papers by the author on discrete torsion. We repeat here technically simplified versions of results from those papers, and have included some new material

  1. Using chemical shift perturbation to characterise ligand binding.

    Science.gov (United States)

    Williamson, Mike P

    2013-08-01

    Chemical shift perturbation (CSP, chemical shift mapping or complexation-induced changes in chemical shift, CIS) follows changes in the chemical shifts of a protein when a ligand is added, and uses these to determine the location of the binding site, the affinity of the ligand, and/or possibly the structure of the complex. A key factor in determining the appearance of spectra during a titration is the exchange rate between free and bound, or more specifically the off-rate koff. When koff is greater than the chemical shift difference between free and bound, which typically equates to an affinity Kd weaker than about 3μM, then exchange is fast on the chemical shift timescale. Under these circumstances, the observed shift is the population-weighted average of free and bound, which allows Kd to be determined from measurement of peak positions, provided the measurements are made appropriately. (1)H shifts are influenced to a large extent by through-space interactions, whereas (13)Cα and (13)Cβ shifts are influenced more by through-bond effects. (15)N and (13)C' shifts are influenced both by through-bond and by through-space (hydrogen bonding) interactions. For determining the location of a bound ligand on the basis of shift change, the most appropriate method is therefore usually to measure (15)N HSQC spectra, calculate the geometrical distance moved by the peak, weighting (15)N shifts by a factor of about 0.14 compared to (1)H shifts, and select those residues for which the weighted shift change is larger than the standard deviation of the shift for all residues. Other methods are discussed, in particular the measurement of (13)CH3 signals. Slow to intermediate exchange rates lead to line broadening, and make Kd values very difficult to obtain. There is no good way to distinguish changes in chemical shift due to direct binding of the ligand from changes in chemical shift due to allosteric change. Ligand binding at multiple sites can often be characterised, by

  2. Rapid and reliable protein structure determination via chemical shift threading.

    Science.gov (United States)

    Hafsa, Noor E; Berjanskii, Mark V; Arndt, David; Wishart, David S

    2018-01-01

    Protein structure determination using nuclear magnetic resonance (NMR) spectroscopy can be both time-consuming and labor intensive. Here we demonstrate how chemical shift threading can permit rapid, robust, and accurate protein structure determination using only chemical shift data. Threading is a relatively old bioinformatics technique that uses a combination of sequence information and predicted (or experimentally acquired) low-resolution structural data to generate high-resolution 3D protein structures. The key motivations behind using NMR chemical shifts for protein threading lie in the fact that they are easy to measure, they are available prior to 3D structure determination, and they contain vital structural information. The method we have developed uses not only sequence and chemical shift similarity but also chemical shift-derived secondary structure, shift-derived super-secondary structure, and shift-derived accessible surface area to generate a high quality protein structure regardless of the sequence similarity (or lack thereof) to a known structure already in the PDB. The method (called E-Thrifty) was found to be very fast (often chemical shift refinement, these results suggest that protein structure determination, using only NMR chemical shifts, is becoming increasingly practical and reliable. E-Thrifty is available as a web server at http://ethrifty.ca .

  3. Chemical shift of UL 3 edges in different uranium compounds ...

    Indian Academy of Sciences (India)

    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 ...

  4. A probabilistic approach for validating protein NMR chemical shift assignments

    International Nuclear Information System (INIS)

    Wang Bowei; Wang, Yunjun; Wishart, David S.

    2010-01-01

    It has been estimated that more than 20% of the proteins in the BMRB are improperly referenced and that about 1% of all chemical shift assignments are mis-assigned. These statistics also reflect the likelihood that any newly assigned protein will have shift assignment or shift referencing errors. The relatively high frequency of these errors continues to be a concern for the biomolecular NMR community. While several programs do exist to detect and/or correct chemical shift mis-referencing or chemical shift mis-assignments, most can only do one, or the other. The one program (SHIFTCOR) that is capable of handling both chemical shift mis-referencing and mis-assignments, requires the 3D structure coordinates of the target protein. Given that chemical shift mis-assignments and chemical shift re-referencing issues should ideally be addressed prior to 3D structure determination, there is a clear need to develop a structure-independent approach. Here, we present a new structure-independent protocol, which is based on using residue-specific and secondary structure-specific chemical shift distributions calculated over small (3-6 residue) fragments to identify mis-assigned resonances. The method is also able to identify and re-reference mis-referenced chemical shift assignments. Comparisons against existing re-referencing or mis-assignment detection programs show that the method is as good or superior to existing approaches. The protocol described here has been implemented into a freely available Java program called 'Probabilistic Approach for protein Nmr Assignment Validation (PANAV)' and as a web server (http://redpoll.pharmacy.ualberta.ca/PANAVhttp://redpoll.pharmacy.ualberta.ca/PANAV) which can be used to validate and/or correct as well as re-reference assigned protein chemical shifts.

  5. Validation of archived chemical shifts through atomic coordinates

    Science.gov (United States)

    Rieping, Wolfgang; Vranken, Wim F

    2010-01-01

    The public archives containing protein information in the form of NMR chemical shift data at the BioMagResBank (BMRB) and of 3D structure coordinates at the Protein Data Bank are continuously expanding. The quality of the data contained in these archives, however, varies. The main issue for chemical shift values is that they are determined relative to a reference frequency. When this reference frequency is set incorrectly, all related chemical shift values are systematically offset. Such wrongly referenced chemical shift values, as well as other problems such as chemical shift values that are assigned to the wrong atom, are not easily distinguished from correct values and effectively reduce the usefulness of the archive. We describe a new method to correct and validate protein chemical shift values in relation to their 3D structure coordinates. This method classifies atoms using two parameters: the per-atom solvent accessible surface area (as calculated from the coordinates) and the secondary structure of the parent amino acid. Through the use of Gaussian statistics based on a large database of 3220 BMRB entries, we obtain per-entry chemical shift corrections as well as Z scores for the individual chemical shift values. In addition, information on the error of the correction value itself is available, and the method can retain only dependable correction values. We provide an online resource with chemical shift, atom exposure, and secondary structure information for all relevant BMRB entries (http://www.ebi.ac.uk/pdbe/nmr/vasco) and hope this data will aid the development of new chemical shift-based methods in NMR. Proteins 2010. © 2010 Wiley-Liss, Inc. PMID:20602353

  6. Double torsion fracture mechanics testing of shales under chemically reactive conditions

    Science.gov (United States)

    Chen, X.; Callahan, O. A.; Holder, J. T.; Olson, J. E.; Eichhubl, P.

    2015-12-01

    Fracture properties of shales is vital for applications such as shale and tight gas development, and seal performance of carbon storage reservoirs. We analyze the fracture behavior from samples of Marcellus, Woodford, and Mancos shales using double-torsion (DT) load relaxation fracture tests. The DT test allows the determination of mode-I fracture toughness (KIC), subcritical crack growth index (SCI), and the stress-intensity factor vs crack velocity (K-V) curves. Samples are tested at ambient air and aqueous conditions with variable ionic concentrations of NaCl and CaCl2, and temperatures up to 70 to determine the effects of chemical/environmental conditions on fracture. Under ambient air condition, KIC determined from DT tests is 1.51±0.32, 0.85±0.25, 1.08±0.17 MPam1/2 for Marcellus, Woodford, and Mancos shales, respectively. Tests under water showed considerable change of KIC compared to ambient condition, with 10.6% increase for Marcellus, 36.5% decrease for Woodford, and 6.7% decrease for Mancos shales. SCI under ambient air condition is between 56 and 80 for the shales tested. The presence of water results in a significant reduction of the SCI from 70% to 85% compared to air condition. Tests under chemically reactive solutions are currently being performed with temperature control. K-V curves under ambient air conditions are linear with stable SCI throughout the load-relaxation period. However, tests conducted under water result in an initial cracking period with SCI values comparable to ambient air tests, which then gradually transition into stable but significantly lower SCI values of 10-20. The non-linear K-V curves reveal that crack propagation in shales is initially limited by the transport of chemical agents due to their low permeability. Only after the initial cracking do interactions at the crack tip lead to cracking controlled by faster stress corrosion reactions. The decrease of SCI in water indicates higher crack propagation velocity due to

  7. Chemical Shift Imaging (CSI) by precise object displacement

    OpenAIRE

    Leclerc, Sebastien; Trausch, Gregory; Cordier, Benoit; Grandclaude, Denis; Retournard, Alain; Fraissard, Jacques; Canet, Daniel

    2006-01-01

    International audience; A mechanical device (NMR lift) has been built for displacing vertically an object (typically a NMR sample tube) inside the NMR probe with an accuracy of 1 Μm. A series of single pulse experiments are performed for incremented vertical positions of the sample. With a sufficiently spatially selective rf field, one obtains chemical shift information along the displacement direction (one dimensional Chemical Shift Imaging – CSI). Knowing the vertical radio-frequency (rf) f...

  8. PROSHIFT: Protein chemical shift prediction using artificial neural networks

    International Nuclear Information System (INIS)

    Meiler, Jens

    2003-01-01

    The importance of protein chemical shift values for the determination of three-dimensional protein structure has increased in recent years because of the large databases of protein structures with assigned chemical shift data. These databases have allowed the investigation of the quantitative relationship between chemical shift values obtained by liquid state NMR spectroscopy and the three-dimensional structure of proteins. A neural network was trained to predict the 1 H, 13 C, and 15 N of proteins using their three-dimensional structure as well as experimental conditions as input parameters. It achieves root mean square deviations of 0.3 ppm for hydrogen, 1.3 ppm for carbon, and 2.6 ppm for nitrogen chemical shifts. The model reflects important influences of the covalent structure as well as of the conformation not only for backbone atoms (as, e.g., the chemical shift index) but also for side-chain nuclei. For protein models with a RMSD smaller than 5 A a correlation of the RMSD and the r.m.s. deviation between the predicted and the experimental chemical shift is obtained. Thus the method has the potential to not only support the assignment process of proteins but also help with the validation and the refinement of three-dimensional structural proposals. It is freely available for academic users at the PROSHIFT server: www.jens-meiler.de/proshift.html

  9. 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. Copyright © 2013 John Wiley & Sons, Ltd.

  10. 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.

  11. Bayesian inference of protein structure from chemical shift data.

    Science.gov (United States)

    Bratholm, Lars A; Christensen, Anders S; Hamelryck, Thomas; Jensen, Jan H

    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, 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.

  12. Evaluating amber force fields using computed NMR chemical shifts.

    Science.gov (United States)

    Koes, David R; Vries, John K

    2017-10-01

    NMR chemical shifts can be computed from molecular dynamics (MD) simulations using a template matching approach and a library of conformers containing chemical shifts generated from ab initio quantum calculations. This approach has potential utility for evaluating the force fields that underlie these simulations. Imperfections in force fields generate flawed atomic coordinates. Chemical shifts obtained from flawed coordinates have errors that can be traced back to these imperfections. We use this approach to evaluate a series of AMBER force fields that have been refined over the course of two decades (ff94, ff96, ff99SB, ff14SB, ff14ipq, and ff15ipq). For each force field a series of MD simulations are carried out for eight model proteins. The calculated chemical shifts for the 1 H, 15 N, and 13 C a atoms are compared with experimental values. Initial evaluations are based on root mean squared (RMS) errors at the protein level. These results are further refined based on secondary structure and the types of atoms involved in nonbonded interactions. The best chemical shift for identifying force field differences is the shift associated with peptide protons. Examination of the model proteins on a residue by residue basis reveals that force field performance is highly dependent on residue position. Examination of the time course of nonbonded interactions at these sites provides explanations for chemical shift differences at the atomic coordinate level. Results show that the newer ff14ipq and ff15ipq force fields developed with the implicitly polarized charge method perform better than the older force fields. © 2017 Wiley Periodicals, Inc.

  13. Frequency response of multipoint chemical shift-based spectral decomposition.

    Science.gov (United States)

    Brodsky, Ethan K; Chebrolu, Venkata V; Block, Walter F; Reeder, Scott B

    2010-10-01

    To provide a framework for characterizing the frequency response of multipoint chemical shift based species separation techniques. Multipoint chemical shift based species separation techniques acquire complex images at multiple echo times and perform maximum likelihood estimation to decompose signal from different species into separate images. In general, after a nonlinear process of estimating and demodulating the field map, these decomposition methods are linear transforms from the echo-time domain to the chemical-shift-frequency domain, analogous to the discrete Fourier transform (DFT). In this work we describe a technique for finding the magnitude and phase of chemical shift decomposition for input signals over a range of frequencies using numerical and experimental modeling and examine several important cases of species separation. Simple expressions can be derived to describe the response to a wide variety of input signals. Agreement between numerical modeling and experimental results is very good. Chemical shift-based species separation is linear, and therefore can be fully described by the magnitude and phase curves of the frequency response. The periodic nature of the frequency response has important implications for the robustness of various techniques for resolving ambiguities in field inhomogeneity.

  14. MR imaging of osteonecrosis using frequency selective chemical shift sequences

    International Nuclear Information System (INIS)

    Duda, S.H.; Laniado, M.; Schick, F.

    1993-01-01

    The MR appearance of osteonecrosis was assessed on selective fat- and water images to further evaluate the nature of double-line sign. Conventional T1- and T2-weighted SE and frequency selective chemical shift images of eight patients with avascular necrosis of the femoral head and three patients with bone infarcts were retrospectively reviewed. Eight of 11 patients showed a double-line sign on T2-weighted SE images. In these cases, correlation with selective water images revealed that a chemical shift artifact contributed to appearance and location of the hyperintense line. The authors conclude that chemical shift imaging improves our understanding of the nature of the double-line sign. (orig.) [de

  15. Bayesian inference of protein structure from chemical shift data

    DEFF Research Database (Denmark)

    Bratholm, Lars Andersen; Christensen, Anders Steen; Hamelryck, Thomas Wim

    2015-01-01

    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......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...

  16. Nucleic acid helix structure determination from NMR proton chemical shifts

    International Nuclear Information System (INIS)

    Werf, Ramon M. van der; Tessari, Marco; Wijmenga, Sybren S.

    2013-01-01

    We present a method for de novo derivation of the three-dimensional helix structure of nucleic acids using non-exchangeable proton chemical shifts as sole source of experimental restraints. The method is called chemical shift de novo structure derivation protocol employing singular value decomposition (CHEOPS) and uses iterative singular value decomposition to optimize the structure in helix parameter space. The correct performance of CHEOPS and its range of application are established via an extensive set of structure derivations using either simulated or experimental chemical shifts as input. The simulated input data are used to assess in a defined manner the effect of errors or limitations in the input data on the derived structures. We find that the RNA helix parameters can be determined with high accuracy. We finally demonstrate via three deposited RNA structures that experimental proton chemical shifts suffice to derive RNA helix structures with high precision and accuracy. CHEOPS provides, subject to further development, new directions for high-resolution NMR structure determination of nucleic acids.

  17. 15N NMR Chemical Shifts of Ring Substituted Benzonitriles

    Czech Academy of Sciences Publication Activity Database

    Žáček, Petr; Dransfeld, A.; Exner, Otto; Schraml, Jan

    2006-01-01

    Roč. 44, č. 12 (2006), s. 1073-1080 ISSN 0749-1581 R&D Projects: GA ČR(CZ) GA203/06/0738 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40550506 Keywords : Hammett correlation * chemical shifts * magnetic susceptibility Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.610, year: 2006

  18. A Core-Offset Mach Zehnder Interferometer Based on A Non-Zero Dispersion-Shifted Fiber and Its Torsion Sensing Application

    Directory of Open Access Journals (Sweden)

    Eduardo Huerta-Mascotte

    2016-06-01

    Full Text Available In this paper, an all-fiber Mach-Zehnder interferometer (MZI based on a non-zero dispersion-shifted fiber (NZ-DSF is presented. The MZI was implemented by core-offset fusion splicing one section of a NZ-DSF fiber between two pieces of single mode fibers (SMFs. Here, the NZ-DSF core and cladding were used as the arms of the MZI, while the core-offset sections acted as optical fiber couplers. Thus, a MZI interference spectrum with a fringe contrast (FC of about 20 dB was observed. Moreover, its response spectrum was experimentally characterized to the torsion parameter and a sensitivity of 0.070 nm/° was achieved. Finally, these MZIs can be implemented in a compact size and low cost.

  19. Appendicular Torsion

    Directory of Open Access Journals (Sweden)

    Siddharth Pramod Dubhashi

    2016-01-01

    Full Text Available Torsion of the vermiform appendix is a rare condition detectable only at operation. It can be primary or secondary. This is a case report of 52-year-old female with 180° anti-clockwise rotation of the appendix. Torsion can further leads to strangulation and infarction of the organ. Appendicular torsion could be included in the differential diagnosis of pain in right iliac fossa.

  20. Anisotropy of the fluorine chemical shift tensor in UF6

    International Nuclear Information System (INIS)

    Rigny, P.

    1965-04-01

    An 19 F magnetic resonance study of polycrystalline UF 6 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 UF 6 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 UF 6 molecule in the solid. (author) [fr

  1. Temperature dependence of 1H chemical shifts in proteins

    International Nuclear Information System (INIS)

    Baxter, Nicola J.; Williamson, Michael P.

    1997-01-01

    Temperature coefficients have been measured by 2D NMR methods for the amide and CαH proton chemical shifts in two globular proteins, bovine pancreatic trypsin inhibitor and hen egg-white lysozyme.The temperature-dependent changes in chemical shift are generally linear up to about 15 deg. below the global denaturation temperature, and the derived coefficients span a range of roughly -16 to +2 ppb/K for amide protons and -4 to +3 ppb/K for CαH. The temperature coefficients can be rationalized by the assumption that heating causes increases in thermal motion in the protein. Precise calculations of temperature coefficients derived from protein coordinates are not possible,since chemical shifts are sensitive to small changes in atomic coordinates.Amide temperature coefficients correlate well with the location of hydrogen bonds as determined by crystallography. It is concluded that a combined use of both temperature coefficients and exchange rates produces a far more reliable indicator of hydrogen bonding than either alone. If an amide proton exchanges slowly and has a temperature coefficient more positive than-4.5 ppb/K, it is hydrogen bonded, while if it exchanges rapidly and has a temperature coefficient more negative than -4.5 ppb/K, it is not hydrogen bonded. The previously observed unreliability of temperature coefficients as measures of hydrogen bonding in peptides may arise from losses of peptide secondary structure on heating

  2. TESTICULAR TORSION:

    African Journals Online (AJOL)

    TESTICULAR TORSION: EXPERIENCE IN THE MIDDLE BELT OF NIGERIA. S.A. KURANGA AND G.A. RAHMAN. Department of Surgery, University of l/orin Teaching Hospital, Ilorin, Nigeria. Objective To determine the fate of the testis affected by testicular torsion (TT) in relation to the duration of the symptoms and to.

  3. Solvent Effects on Oxygen-17 Chemical Shifts in Amides. Quantitative Linear Solvation Shift Relationships

    Science.gov (United States)

    Díez, Ernesto; Fabián, Jesús San; Gerothanassis, Ioannis P.; Esteban, Angel L.; Abboud, José-Luis M.; Contreras, Ruben H.; de Kowalewski, Dora G.

    1997-01-01

    A multiple-linear-regression analysis (MLRA) has been carried out using the Kamlet-Abboud-Taft (KAT) solvatochromic parameters in order to elucidate and quantify the solvent effects on the17O chemical shifts ofN-methylformamide (NMF),N,N-dimethylformamide (DMF),N-methylacetamide (NMA), andN,N-dimethylacetamide (DMA). The chemical shifts of the four molecules show the same dependence (in ppm) on the solvent polarity-polarizability, i.e., -22π*. The influence of the solvent hydrogen-bond-donor (HBD) acidities is slightly larger for the acetamides NMA and DMA, i.e., -48α, than for the formamides NMF and DMF, i.e., -42α. The influence of the solvent hydrogen-bond-acceptor (HBA) basicities is negligible for the nonprotic molecules DMF and DMA but significant for the protic molecules NMF and NMA, i.e., -9β. The effect of substituting the N-H hydrogen by a methyl group amounts to -5.9 ppm in NMF and 5.4 ppm in NMA. The effect of substituting the O=C-H hydrogen amounts to 5.5 ppm in NMF and 16.8 ppm in DMF. The model of specific hydration sites of amides by I. P. Gerothanassis and C. Vakka [J. Org. Chem.59,2341 (1994)] is settled in a more quantitative basis and the model by M. I. Burgar, T. E. St. Amour, and D. Fiat [J. Phys. Chem.85,502 (1981)] is critically evaluated.17O hydration shifts have been calculated for formamide (FOR) by the ab initio LORG method at the 6-31G* level. For a formamide surrounded by the four in-plane molecules of water in the first hydration shell, the calculated17O shift change due to the four hydrogen bonds, -83.2 ppm, is smaller than the empirical hydration shift, -100 ppm. The17O shift change from each out-of-plane water molecule hydrogen-bonded to the amide oxygen is -18.0 ppm. These LORG results support the conclusion that no more than four water molecules are hydrogen-bonded to the amide oxygen in formamide.

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

    International Nuclear Information System (INIS)

    Yoon, Young-Gui; Pfrommer, Bernd G.; Louie, Steven G.; Canning, Andrew

    2002-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Young-Gui; Pfrommer, Bernd G.; Louie, Steven G.; Canning, Andrew

    2002-03-03

    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.

  6. Random coil chemical shift for intrinsically disordered proteins: effects of temperature and pH

    International Nuclear Information System (INIS)

    Kjaergaard, Magnus; Brander, Søren; Poulsen, Flemming M.

    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 shifts and sequence correction factors determined for a GGXGG peptide series following the approach of Schwarzinger et al. (J Am Chem Soc 123(13):2970–2978, 2001). The chemical shifts are determined at neutral pH in order to match the conditions of most studies of intrinsically disordered proteins. 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, which allows the accurate random coil chemical shifts to be obtained at any pH. By correcting the random coil chemical shifts for the effects of temperature and pH, systematic biases of the secondary chemical shifts are minimized, which will improve the reliability of detection of transient secondary structure in disordered proteins.

  7. Chemical shift of U L3 edges in different uranium compounds ...

    Indian Academy of Sciences (India)

    Administrator

    the chemical environment of the metal ion. The change in absorption edge which could be attributed to different chemical environment of a metal ion inside a compound is generally known as the chemical shift. In the present study, the effect of chemical environ- ment on shifting of L3 X-ray absorption edge of uranium.

  8. Theoretical Modeling of 99 Tc NMR Chemical Shifts

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Gabriel B.; Andersen, Amity; Washton, Nancy M.; Chatterjee, Sayandev; Levitskaia, Tatiana G.

    2016-09-06

    Technetium (Tc) displays a rich chemistry due to the wide range of oxidation states (from -I to +VII) and ability to form coordination compounds. Determination of Tc speciation in complex mixtures is a major challenge, and 99Tc NMR spec-troscopy is widely used to probe chemical environments of Tc in odd oxidation states. However interpretation of the 99Tc NMR data is hindered by the lack of reference compounds. DFT computations can help fill this gap, but to date few com-putational studies have focused on 99Tc NMR of compounds and complexes. This work systematically evaluates the inclu-sion small percentages of Hartree-Fock exchange correlation and relativistic effects in DFT computations to support in-terpretation of the 99Tc NMR spectra. Hybrid functionals are found to perform better than their pure GGA counterparts, and non-relativistic calculations have been found to generally show a lower mean absolute deviation from experiment. Overall non-relativistic PBE0 and B3PW91 calculations are found to most accurately predict 99Tc NMR chemical shifts.

  9. Appendicular Torsion

    African Journals Online (AJOL)

    A‑2/103, Shivranjan Towers, Someshwarwadi, Pashan, Pune ‑ 411 008,. Maharashtra, India. E‑mail: spdubhashi@gmail.com. INTRODUCTION. Acute appendicitis presents with pain in right iliac fossa. Torsion of the vermiform appendix, though rare, also presents in a similar fashion, and it is detectable only at operation.[1].

  10. SimShiftDB; local conformational restraints derived from chemical shift similarity searches on a large synthetic database

    International Nuclear Information System (INIS)

    Ginzinger, Simon W.; Coles, Murray

    2009-01-01

    We present SimShiftDB, a new program to extract conformational data from protein chemical shifts using structural alignments. The alignments are obtained in searches of a large database containing 13,000 structures and corresponding back-calculated chemical shifts. SimShiftDB makes use of chemical shift data to provide accurate results even in the case of low sequence similarity, and with even coverage of the conformational search space. We compare SimShiftDB to HHSearch, a state-of-the-art sequence-based search tool, and to TALOS, the current standard tool for the task. We show that for a significant fraction of the predicted similarities, SimShiftDB outperforms the other two methods. Particularly, the high coverage afforded by the larger database often allows predictions to be made for residues not involved in canonical secondary structure, where TALOS predictions are both less frequent and more error prone. Thus SimShiftDB can be seen as a complement to currently available methods

  11. MR chemical shift imaging and spectroscopy of atherosclerotic plaque

    International Nuclear Information System (INIS)

    Vinitski, S.; Consigny, P.M.; Shapiro, M.J.; Janes, N.; Smullens, S.N.; Rifkin, M.D.

    1989-01-01

    The purpose of this study was to develop a technique for in vivo imaging and characterization of atherosclerotic plaque. The authors used a spin-echo technique with a short echo time (TE) of 11 msec. Lipid/water suppression was achieved by means of hybrid chemical shift imaging. Lesions were induced in three rabbits by a combination of balloon denudation of the abdominal aorta and a high-cholesterol diet. Following in vivo imaging of these rabbit aortas and human carotid arteries (1.5 T), the animals were killed or carotid endarterectomy was performed so that the plaques could be excised. The plaques were then analyzed in vitro both histologically and with high-resolution spectroscopy (8.5 T). Use of the short TE improved lesion visualization. The fat/water suppression showed only a small amount of mobile lipids in plaque. Both MR spectroscopic and histologic analysis corroborated these images. The composition of atherosclerotic plaques in both humans and rabbits was demonstrated to be heterogeneous, with predominantly nonmobile lipids. These results suggest that the combination of short TE MR imaging and fat/water suppression can identify plaque and delineate areas containing mobile lipids

  12. The PROSECCO server for chemical shift predictions in ordered and disordered proteins.

    Science.gov (United States)

    Sanz-Hernández, Máximo; De Simone, Alfonso

    2017-11-01

    The chemical shifts measured in solution-state and solid-state nuclear magnetic resonance (NMR) are powerful probes of the structure and dynamics of protein molecules. The exploitation of chemical shifts requires methods to correlate these data with the protein structures and sequences. We present here an approach to calculate accurate chemical shifts in both ordered and disordered proteins using exclusively the information contained in their sequences. Our sequence-based approach, protein sequences and chemical shift correlations (PROSECCO), achieves the accuracy of the most advanced structure-based methods in the characterization of chemical shifts of folded proteins and improves the state of the art in the study of disordered proteins. Our analyses revealed fundamental insights on the structural information carried by NMR chemical shifts of structured and unstructured protein states.

  13. Evaluation of fatty replacement in the normal thymus with chemical-shift MR imaging

    International Nuclear Information System (INIS)

    Inaoka, Tsutomu; Takahashi, Koji; Iwata, Kunihiro

    2004-01-01

    The purpose of this study was to evaluate a fatty replacement in the normal thymus with chemical-shift MR imaging and a correlation between chemical-shift ratio and age. Between December 2001 and January 2003, 30 normal subjects (15 males and 15 females 8-25 years, mean age 15.7 years) who underwent chemical-shift MR imaging for the thymus were assessed. Signal intensities of the thymus and the paraspinal muscle were measured and thymus/muscle ratios (T/M ratios) were calculated. We calculated signal intensity alterations between in-phase and opposed-phase images (chemical-shift ratios) and evaluated a correlation between age and them. A significant correlation between chemical-shift ratios and age was identified (r=0.725, p<.001). Chemical-shift MR imaging can depict fatty replacement in the normal thymus in the adolescence and young adults. (author)

  14. Identifying secondary structures in proteins using NMR chemical shift 3D correlation maps

    Science.gov (United States)

    Kumari, Amrita; Dorai, Kavita

    2013-06-01

    NMR chemical shifts are accurate indicators of molecular environment and have been extensively used as aids in protein structure determination. This work focuses on creating empirical 3D correlation maps of backbone chemical shift nuclei for use as identifiers of secondary structure elements in proteins. A correlated database of backbone nuclei chemical shifts was constructed from experimental structural data gathered from entries in the Protein Data Bank (PDB) as well as isotropic chemical shift values from the RefDB database. Rigorous statistical analysis of the maps led to the conclusion that specific correlations between triplets of backbone chemical shifts are best able to differentiate between different secondary structures such as α-helices, β-strands and turns. The method is compared with similar techniques that use NMR chemical shift information as aids in biomolecular structure determination and performs well in tests done on experimental data determined for different types of proteins, including large multi-domain proteins and membrane proteins.

  15. Testicular torsion

    DEFF Research Database (Denmark)

    Brasso, K; Andersen, L; Kay, L

    1993-01-01

    Thirty-five patients were examined 6-11 years after operation for torsion of the testis. Loss of testicular tissue was significantly associated with long preoperative duration of symptoms and with low postoperative sperm counts. The sex hormones were normal in the majority of patients but there w...... to the sperm count and concentration. Measurement of carnitine levels in seminal plasma, as a sign of vas deferens obstruction or dysfunction of epididymis, and of autoantibodies against spermatozoa revealed no significant findings....

  16. Temperature dependence of1H NMR chemical shifts and its influence on estimated metabolite concentrations.

    Science.gov (United States)

    Wermter, Felizitas C; Mitschke, Nico; Bock, Christian; Dreher, Wolfgang

    2017-12-01

    Temperature dependent chemical shifts of important brain metabolites measured by localised 1 H MRS were investigated to test how the use of incorrect prior knowledge on chemical shifts impairs the quantification of metabolite concentrations. Phantom measurements on solutions containing 11 metabolites were performed on a 7 T scanner between 1 and 43 °C. The temperature dependence of the chemical shift differences was fitted by a linear model. Spectra were simulated for different temperatures and analysed by the AQSES program (jMRUI 5.2) using model functions with chemical shift values for 37 °C. Large differences in the temperature dependence of the chemical shift differences were determined with a maximum slope of about ±7.5 × 10 -4  ppm/K. For 32-40 °C, only minor quantification errors resulted from using incorrect chemical shifts, with the exception of Cr and PCr. For 1-10 °C considerable quantification errors occurred if the temperature dependence of the chemical shifts was neglected. If 1 H MRS measurements are not performed at 37 °C, for which the published chemical shift values have been determined, the temperature dependence of chemical shifts should be considered to avoid systematic quantification errors, particularly for measurements on animal models at lower temperatures.

  17. Empirical correlation between protein backbone 15N and 13C secondary chemical shifts and its application to nitrogen chemical shift re-referencing

    International Nuclear Information System (INIS)

    Wang Liya; Markley, John L.

    2009-01-01

    The linear analysis of chemical shifts (LACS) has provided a robust method for identifying and correcting 13 C chemical shift referencing problems in data from protein NMR spectroscopy. Unlike other approaches, LACS does not require prior knowledge of the three-dimensional structure or inference of the secondary structure of the protein. It also does not require extensive assignment of the NMR data. We report here a way of extending the LACS approach to 15 N NMR data from proteins, so as to enable the detection and correction of inconsistencies in chemical shift referencing for this nucleus. The approach is based on our finding that the secondary 15 N chemical shift of the backbone nitrogen atom of residue i is strongly correlated with the secondary chemical shift difference (experimental minus random coil) between the alpha and beta carbons of residue i - 1. Thus once alpha and beta 13 C chemical shifts are available (their difference is referencing error-free), the 15 N referencing can be validated, and an appropriate offset correction can be derived. This approach can be implemented prior to a structure determination and can be used to analyze potential referencing problems in database data not associated with three-dimensional structure. Application of the LACS algorithm to the current BMRB protein chemical shift database, revealed that nearly 35% of the BMRB entries have δ 15 N values mis-referenced by over 0.7 ppm and over 25% of them have δ 1 H N values mis-referenced by over 0.12 ppm. One implication of the findings reported here is that a backbone 15 N chemical shift provides a better indicator of the conformation of the preceding residue than of the residue itself

  18. Deuterium isotope effects on 13C chemical shifts of 10-Hydroxybenzo[h]quinolines

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Kamounah, Fadhil S.; Gryko, Daniel T.

    2013-01-01

    Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be nega...

  19. Quantum chemical calculation and experimental measurement of the 13C chemical shift tensors of vanillin and 3,4-dimethoxybenzaldehyde

    Science.gov (United States)

    Zheng, Guang; Hu, Jianzhi; Zhang, Xiaodong; Shen, Lianfang; Ye, Chaohui; Webb, Graham A.

    1997-03-01

    The principal values of the 13C nuclear magnetic resonance chemical shift tensors in vanillin and 3,4-dimethoxybenzaldehyde are reported. Theoretical results of the 13C chemical shift tensors were obtained by employing the gauge included atomic orbital (GIAO) approach. The geometrical parameters were optimized by using the MNDO method. The observed chemical shifts of these two compounds were determined in powders by using the recently introduced magic angle turning (MAT) experiment. The results presented in this paper clearly demonstrate the importance of using tensor information in the study of molecular structures.

  20. Temperature-dependent chemical shift in the aqueous solution of xenon

    OpenAIRE

    Peuravaara, P. (Petri)

    2017-01-01

    Abstract At standard pressure, the chemical shift of Xe-129 in an aqueous solution of xenon exhibits a maximum as a function of temperature at 311 K, which is in contrast to the well-known density maximum of water at 277 K. In the present work, this phenomenon is studied by means of a molecular dynamics simulation, where the xenon chemical shift is computed quantum-chemically for snapshots of the simulation trajectory. Also...

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

    International Nuclear Information System (INIS)

    Karp, Jerome M.; Erylimaz, Ertan; Cowburn, David

    2015-01-01

    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

  2. Substructure elucidation and chemical shift estimation using the nuclear magnetic resonance spectral database

    International Nuclear Information System (INIS)

    Yamamoto, Osamu; Hayamizu, Kikuko; Yanagisawa, Masaru

    1989-01-01

    A computer system for substructure elucidation and chemical shift estimation by the use of nuclear magnetic resonance (NMR) spectra is described. In this system, substructures in a molecule can be elucidated by specifying chemical shift values or ranges, and conversely chemical shift values can be estimated by specifying substructures for both 1 H- and 13 C-NMR data. The retrieval of data can be performed interactively between 1 H- and 13 C-NMR data. It is possible to estimate all chemical shift values for a compound by giving its chemical structure. The search file for these purposes is created for signals (or signal groups) from a large number of 1 H- and 13 C-NMR spectra in our database. The information contained in the search file consists of substructures and the corresponding chemical shift values. A line notation system has been developed to plot chemical structures with spectral assignments of NMR signals and to extract substructures corresponding to particular chemical shift values. (author)

  3. Stereospecific assignment of the asparagine and glutamine sidechain amide protons in proteins from chemical shift analysis

    Energy Technology Data Exchange (ETDEWEB)

    Harsch, Tobias; Schneider, Philipp; Kieninger, Bärbel; Donaubauer, Harald; Kalbitzer, Hans Robert, E-mail: hans-robert.kalbitzer@biologie.uni-regensburg.de [University of Regensburg, Institute of Biophysics and Physical Biochemistry and Centre of Magnetic Resonance in Chemistry and Biomedicine (Germany)

    2017-02-15

    Side chain amide protons of asparagine and glutamine residues in random-coil peptides are characterized by large chemical shift differences and can be stereospecifically assigned on the basis of their chemical shift values only. The bimodal chemical shift distributions stored in the biological magnetic resonance data bank (BMRB) do not allow such an assignment. However, an analysis of the BMRB shows, that a substantial part of all stored stereospecific assignments is not correct. We show here that in most cases stereospecific assignment can also be done for folded proteins using an unbiased artificial chemical shift data base (UACSB). For a separation of the chemical shifts of the two amide resonance lines with differences ≥0.40 ppm for asparagine and differences ≥0.42 ppm for glutamine, the downfield shifted resonance lines can be assigned to H{sup δ21} and H{sup ε21}, respectively, at a confidence level >95%. A classifier derived from UASCB can also be used to correct the BMRB data. The program tool AssignmentChecker implemented in AUREMOL calculates the Bayesian probability for a given stereospecific assignment and automatically corrects the assignments for a given list of chemical shifts.

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

    International Nuclear Information System (INIS)

    Cromsigt, Jenny A.M.T.C.; Hilbers, Cees W.; Wijmenga, Sybren S.

    2001-01-01

    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 1 H 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 1 H chemical shifts is a good tool for validation and refinement of structures derived from NOEs and J-couplings

  5. 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...

  6. 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.

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

    International Nuclear Information System (INIS)

    Li, Dawei; Brüschweiler, Rafael

    2015-01-01

    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

  8. 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 s...

  9. 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

  10. 29Si NMR Chemical Shift Calculation for Silicate Species by Gaussian Software

    Science.gov (United States)

    Azizi, S. N.; Rostami, A. A.; Godarzian, A.

    2005-05-01

    Hartree-Fock self-consistent-field (HF-SCF) theory and the Gauge-including atomic orbital (GIAO) methods are used in the calculation of 29Si NMR chemical shifts for ABOUT 90 units of 19 compounds of various silicate species of precursors for zeolites. Calculations have been performed at geometries optimized at the AM1 semi-empirical method. The GIAO-HF-SCF calculations were carried out with using three different basis sets: 6-31G*, 6-31+G** and 6-311+G(2d,p). To demonstrate the quality of the calculations the calculated chemical shifts, δ, were compared with the corresponding experimental values for the compounds in study. The results, especially with 6-31+g** are in excellent agreement with experimental values. The calculated chemical shifts, in practical point of view, appear to be accurate enough to aid in experimental peak assignments. The difference between the experimental and calculated 29Si chemical shift values not only depends on the Qn units but also it seems that basis set effects and the level of theory is more important. For the series of molecules studied here, the standard deviations and mean absolute errors for 29Si chemical shifts relative to TMS determined using Hartree--Fock 6-31+G** basis is nearly in all cases smaller than the errors for shifts determined using HF/6-311+G(2d,p).

  11. Chemical shift prediction for protein structure calculation and quality assessment using an optimally parameterized force field

    Science.gov (United States)

    Nielsen, Jakob T.; Eghbalnia, Hamid R.; Nielsen, Niels Chr.

    2011-01-01

    The exquisite sensitivity of chemical shifts as reporters of structural information, and the ability to measure them routinely and accurately, gives great import to formulations that elucidate the structure-chemical-shift relationship. Here we present a new and highly accurate, precise, and robust formulation for the prediction of NMR chemical shifts from protein structures. Our approach, shAIC (shift prediction guided by Akaikes Information Criterion), capitalizes on mathematical ideas and an information-theoretic principle, to represent the functional form of the relationship between structure and chemical shift as a parsimonious sum of smooth analytical potentials which optimally takes into account short-, medium-, and long-range parameters in a nuclei-specific manner to capture potential chemical shift perturbations caused by distant nuclei. shAIC outperforms the state-of-the-art methods that use analytical formulations. Moreover, for structures derived by NMR or structures with novel folds, shAIC delivers better overall results; even when it is compared to sophisticated machine learning approaches. shAIC provides for a computationally lightweight implementation that is unimpeded by molecular size, making it an ideal for use as a force field. PMID:22293396

  12. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    increases, since the metal atom transforms to a positive ion while participating in the formation of a chemical bond and this energy shift ( E) increases with an increase in the oxi- dation state or positive charge on the metal ions. Thus, as the valency ... the bond, electronegativity of the anion etc or in other words, the chemical ...

  13. Magnetic couplings in the chemical shift of paramagnetic NMR.

    Science.gov (United States)

    Vaara, Juha; Rouf, Syed Awais; Mareš, Jiří

    2015-10-13

    We apply the Kurland-McGarvey (J. Magn. Reson. 1970, 2, 286) theory for the NMR shielding of paramagnetic molecules, particularly its special case limited to the ground-state multiplet characterized by zero-field splitting (ZFS) interaction of the form S·D·S. The correct formulation for this problem was recently presented by Soncini and Van den Heuvel (J. Chem. Phys. 2013, 138, 054113). With the effective electron spin quantum number S, the theory involves 2S+1 states, of which all but one are low-lying excited states, between which magnetic couplings take place by Zeeman and hyperfine interactions. We investigate these couplings as a function of temperature, focusing on both the high- and low-temperature behaviors. As has been seen in work by others, the full treatment of magnetic couplings is crucial for a realistic description of the temperature behavior of NMR shielding up to normal measurement temperatures. At high temperatures, depending on the magnitude of ZFS, the effect of magnetic couplings diminishes, and the Zeeman and hyperfine interactions become effectively averaged in the thermally occupied states of the multiplet. At still higher temperatures, the ZFS may be omitted altogether, and the shielding properties may be evaluated using a doublet-like formula, with all the 2S+1 states becoming effectively degenerate at the limit of vanishing magnetic field. We demonstrate these features using first-principles calculations of Ni(II), Co(II), Cr(II), and Cr(III) complexes, which have ZFS of different sizes and signs. A non-monotonic inverse temperature dependence of the hyperfine shift is predicted for axially symmetric integer-spin systems with a positive D parameter of ZFS. This is due to the magnetic coupling terms that are proportional to kT at low temperatures, canceling the Curie-type 1/kT prefactor of the hyperfine shielding in this case.

  14. Protein Structure Validation and Refinement Using Chemical Shifts Derived from Quantum Mechanics

    DEFF Research Database (Denmark)

    Bratholm, Lars Andersen

    to within 3 A. Furthermore, a fast quantum mechanics based chemical shift predictor was developed together with methodology for using chemical shifts in structure simulations. The developed predictor was used for renement of several protein structures and for reducing the computational cost of quantum...... mechanics / molecular mechanics (QM/MM) computations of chemical shieldings. Several improvements to the predictor is ongoing, where among other things, kernel based machine learning techniques have successfully been used to improve the quantum mechanical level of theory used in the predictions....

  15. A quantum chemical study of H2S2: Intramolecular torsional mode and intermolecular interactions with rare gases.

    Science.gov (United States)

    Maciel, Glauciete S; Barreto, Patricia R P; Palazzetti, Federico; Lombardi, Andrea; Aquilanti, Vincenzo

    2008-10-28

    The structural and energetic properties of the H(2)S(2) molecule have been studied using density functional theory, second-order Moller-Plesset method, and coupled cluster theory with several basis sets. In order to extend previous work on intra- and intermolecular dynamics of the chirality changing modes for H(2)O(2) and its derivatives, our focus has been on the torsion around the S-S bond, along with an extensive characterization of the intermolecular potentials of H(2)S(2) with the rare gases (He, Ne, Ar, and Kr). Use is made of previously defined coordinates and expansion formulas for the potentials which allow for a faithful representation of geometrical and symmetry properties of these systems that involve the interaction of an atom with a floppy molecule. The potential energy surfaces obtained in this work are useful for classical and quantum mechanical simulations of molecular collisions responsible for chirality changing processes of possible interest in the modeling of prebiotic phenomena.

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

    International Nuclear Information System (INIS)

    Labudde, D.; Leitner, D.; Krueger, M.; Oschkinat, H.

    2003-01-01

    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

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

    Science.gov (United States)

    Labudde, D; Leitner, D; Krüger, M; Oschkinat, H

    2003-01-01

    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.

  18. Prediction of Xaa-Pro peptide bond conformation from sequence and chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-03-15

    We present a program, named Promega, to predict the Xaa-Pro peptide bond conformation on the basis of backbone chemical shifts and the amino acid sequence. Using a chemical shift database of proteins of known structure together with the PDB-extracted amino acid preference of cis Xaa-Pro peptide bonds, a cis/trans probability score is calculated from the backbone and {sup 13}C{sup {beta}} chemical shifts of the proline and its neighboring residues. For an arbitrary number of input chemical shifts, which may include Pro-{sup 13}C{sup {gamma}}, Promega calculates the statistical probability that a Xaa-Pro peptide bond is cis. Besides its potential as a validation tool, Promega is particularly useful for studies of larger proteins where Pro-{sup 13}C{sup {gamma}} assignments can be challenging, and for on-going efforts to determine protein structures exclusively on the basis of backbone and {sup 13}C{sup {beta}} chemical shifts.

  19. Equilibrium simulations of proteins using molecular fragment replacement and NMR chemical shifts.

    Science.gov (United States)

    Boomsma, Wouter; Tian, Pengfei; Frellsen, Jes; Ferkinghoff-Borg, Jesper; Hamelryck, Thomas; Lindorff-Larsen, Kresten; Vendruscolo, Michele

    2014-09-23

    Methods of protein structure determination based on NMR chemical shifts are becoming increasingly common. The most widely used approaches adopt the molecular fragment replacement strategy, in which structural fragments are repeatedly reassembled into different complete conformations in molecular simulations. Although these approaches are effective in generating individual structures consistent with the chemical shift data, they do not enable the sampling of the conformational space of proteins with correct statistical weights. Here, we present a method of molecular fragment replacement that makes it possible to perform equilibrium simulations of proteins, and hence to determine their free energy landscapes. This strategy is based on the encoding of the chemical shift information in a probabilistic model in Markov chain Monte Carlo simulations. First, we demonstrate that with this approach it is possible to fold proteins to their native states starting from extended structures. Second, we show that the method satisfies the detailed balance condition and hence it can be used to carry out an equilibrium sampling from the Boltzmann distribution corresponding to the force field used in the simulations. Third, by comparing the results of simulations carried out with and without chemical shift restraints we describe quantitatively the effects that these restraints have on the free energy landscapes of proteins. Taken together, these results demonstrate that the molecular fragment replacement strategy can be used in combination with chemical shift information to characterize not only the native structures of proteins but also their conformational fluctuations.

  20. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    ... 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 ...

  1. Deuterium isotope effects on 13C chemical shifts of negatively charged NH.N systems

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Pietrzak, Mariusz; Grech, Eugeniusz

    2013-01-01

    ” and equilibrium cases. NMR assignments of the former have been revised. The NH proton is deuteriated. The isotope effects on 13C chemical shifts are rather unusual in these strongly hydrogen bonded systems between a NH and a negatively charged nitrogen atom. The formal four-bond effects are found to be negative......Deuterium isotope effects on 13C chemical shifts are investigated in anions of 1,8-bis(4-toluenesulphonamido)naphthalenes together with N,N-(naphthalene-1,8-diyl)bis(2,2,2-trifluoracetamide) all with bis(1,8-dimethylamino)napthaleneH+ as counter ion. These compounds represent both “static...... indicating transmission via the hydrogen bond. In addition, unusual long range effects are seen. Structures, 1H and 13C NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using density functional theory methods...

  2. Theoretical Study of the NMR Chemical Shift of Xe in Supercritical Condition

    DEFF Research Database (Denmark)

    Lacerda Junior, Evanildo Gomes; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin

    2018-01-01

    In this work we investigate the level of theory necessary for reproducing the non-linear variation of the 129Xe nuclear magnetic resonance (NMR) chemical shift with the density of Xe in supercritical conditions. In detail we study how the 129Xe chemical shift depends under these conditions...... on electron correlation, relativistic and many-body effects. The latter are included using a sequential-QM/MM methodology, in which a classical MD simulation is performed first and the chemical shift is then obtained as an average of quantum calculations of 250 MD snapshots conformations carried out for Xen...... clusters (n =2-8 depending on the density). The analysis of the relativistic effects is made at the level of 4-component Hartree-Fock calculations (4c-HF) and electron correlation effects are considered using second order Møller-Plesset perturbation theory (MP2). To simplify the calculations...

  3. 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

    ). The 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...... correlation between computed and observed 1H NMR chemical shifts, including agreement between computed and observed chemical shift changes caused by O-methylation. The observed regularities can aid structure elucidation of partly O-methylated polyphenols, including many natural products and drugs...

  4. 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......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...

  5. Determination of deuterium fraction in heavy water by proton chemical shifts

    International Nuclear Information System (INIS)

    Kellomaeki, A.; Jutila, M.

    1979-01-01

    One nuclear magnetic resonance method used to determine the deuterium fraction of heavy water samples is based on the chemical shifts of dissolved fluoride ions depending on the deuterium content of the sample. This method presented indicated that the proton chemical shifts of the hydrogen form sulfonated polystyrene ion exchangers suspended in H 2 O--D 2 O mixtures are dependent on the deuterium content of the solvent. The strong polystyrene sulfuric acid ion exchangers are more practical: the concentration of the interior electrolytic solution is automatically regulated by the fairly constant swelling of the resin and the peak of the exterior water provides an internal standard in every sample. 2 figures

  6. 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.

  7. 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

    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....... The contributions from the neighboring residues are typically removed by using neighbor correction factors determined based on each residue's effect on glycine chemical shifts. Due to its unusual conformational freedom, glycine may be particularly unrepresentative for the remaining residue types. In this study, we...... 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, and may thus improve...

  8. Investigation of DOTA-Metal Chelation Effects on the Chemical Shift of 129 Xe

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, K; Slack, CC; Vassiliou, CC; Dao, P; Gomes, MD; Kennedy, DJ; Truxal, AE; Sperling, LJ; Francis, MB; Wemmer, DE; Pines, A

    2015-09-17

    Recent work has shown that xenon chemical shifts in cryptophane-cage sensors are affected when tethered chelators bind to metals. Here in this paper, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) linked to cryptophane-A. The shifts induced by the binding of Ca2+, Cu2+, Ce3+, Zn2+, Cd2+, Ni2+, Co2+, Cr2+, Fe3+, and Hg2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding with a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. Lastly, these sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs.

  9. Identification of helix capping and β-turn motifs from NMR chemical shifts

    International Nuclear Information System (INIS)

    Shen Yang; Bax, Ad

    2012-01-01

    We present an empirical method for identification of distinct structural motifs in proteins on the basis of experimentally determined backbone and 13 C β chemical shifts. Elements identified include the N-terminal and C-terminal helix capping motifs and five types of β-turns: I, II, I′, II′ 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 β-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.

  10. Enhanced measurement of residual chemical shift anisotropy for small molecule structure elucidation.

    Science.gov (United States)

    Liu, Yizhou; Cohen, Ryan D; Gustafson, Kirk R; Martin, Gary E; Williamson, R Thomas

    2018-03-05

    A method is introduced to measure residual chemical shift anisotropies conveniently and accurately in the mesophase of poly-γ-(benzyl-l-glutamate). The alignment amplitude is substantially enhanced over common methods which greatly benefits measurements particularly on sp 3 carbons. The approach offers significant improvements in data accuracy and utility for small molecule structure determination.

  11. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    The above chemical effect has been quantitatively described by determining the effective charges on Mn and Cr cations in the above compounds. Keywords. Mn K edge; Cr K edge; EXAFS; synchrotron radiation; energy shift; oxidation state; effective charge. 1. Introduction. It is well known that the X-ray absorption edge of a ...

  12. 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...

  13. 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.

  14. 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” ...

  15. Computation of Chemical Shifts for Paramagnetic Molecules: A Laboratory Experiment for the Undergraduate Curriculum

    Science.gov (United States)

    Pritchard, Benjamin P.; Simpson, Scott; Zurek, Eva; Autschbach, Jochen

    2014-01-01

    A computational experiment investigating the [superscript 1]H and [superscript 13]C nuclear magnetic resonance (NMR) chemical shifts of molecules with unpaired electrons has been developed and implemented. This experiment is appropriate for an upper-level undergraduate laboratory course in computational, physical, or inorganic chemistry. The…

  16. 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...

  17. Rapid chemical shift encoding with single-acquisition single-slab 3D GRASE.

    Science.gov (United States)

    Kim, Hahnsung; Kim, Dong-Hyun; Sohn, Chul-Ho; Park, Jaeseok

    2017-11-01

    To investigate the feasibility of chemical shift encoded, single-slab 3D GRASE for rapid fat-water separation within a single acquisition. The proposed method incorporates signal-to-noise-ratio-optimal chemical shift encoding into single-slab 3D GRASE with variable flip angles. Chemical shift induced phase information was encoded in succession to different positions in k-space by inserting phase encoding blips between adjacent lobes of the oscillating readout gradients. To enhance imaging efficiency, signal prescription-based variable flip angles were used in the long refocusing pulse train. After echo-independent phase correction, missing signals in k-echo space were interpolated using convolution kernels that span over all echoes. Fat-water separation in a single acquisition was performed using both multi-echo fast spin echo and GRASE as compared to conventional multiacquisition fast spin echo with echo shifts. The proposed single-slab 3D GRASE shows superior performance in accurately delineating cartilage structures compared to its counterpart, multi-echo 3D fast spin echo. Compared with multiacquisition fast spin echo with three echo shifts (63 min), the proposed method substantially speeds up imaging time (7 min), and achieves 0.6 mm isotropic resolution in knee imaging with reduced artifacts and noise. We successfully demonstrated the feasibility of rapid chemical shift encoding and separation using the proposed, single-acquisition single-slab 3D GRASE for high resolution isotropic imaging within clinically acceptable time. Magn Reson Med 78:1852-1861, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  18. Modeling NMR chemical shift: A survey of density functional theory approaches for calculating tensor properties.

    Science.gov (United States)

    Sefzik, Travis H; Turco, Domenic; Iuliucci, Robbie J; Facelli, Julio C

    2005-02-17

    The NMR chemical shift, a six-parameter tensor property, is highly sensitive to the position of the atoms in a molecule. To extract structural parameters from chemical shifts, one must rely on theoretical models. Therefore, a high quality group of shift tensors that serve as benchmarks to test the validity of these models is warranted and necessary to highlight existing computational limitations. Here, a set of 102 13C chemical-shift tensors measured in single crystals, from a series of aromatic and saccharide molecules for which neutron diffraction data are available, is used to survey models based on the density functional (DFT) and Hartree-Fock (HF) theories. The quality of the models is assessed by their least-squares linear regression parameters. It is observed that in general DFT outperforms restricted HF theory. For instance, Becke's three-parameter exchange method and mpw1pw91 generally provide the best predicted shieldings for this group of tensors. However, this performance is not universal, as none of the DFT functionals can predict the saccharide tensors better than HF theory. Both the orientations of the principal axis system and the magnitude of the shielding were compared using the chemical-shift distance to evaluate the quality of the calculated individual tensor components in units of ppm. Systematic shortcomings in the prediction of the principal components were observed, but the theory predicts the corresponding isotropic value more accurately. This is because these systematic errors cancel, thereby indicating that the theoretical assessment of shielding predictions based on the isotropic shift should be avoided.

  19. Rapid calculation of protein chemical shifts using bond polarization theory and its application to protein structure refinement.

    Science.gov (United States)

    Jakovkin, Igor; Klipfel, Marco; Muhle-Goll, Claudia; Ulrich, Anne S; Luy, Burkhard; Sternberg, Ulrich

    2012-09-21

    Although difficult to analyze, NMR chemical shifts provide detailed information on protein structure. We have adapted the semi-empirical bond polarization theory (BPT) to protein chemical shift calculation and chemical shift driven protein structure refinement. A new parameterization for BPT amide nitrogen chemical shift calculation has been derived from MP2 ab initio calculations and successfully evaluated using crystalline tripeptides. We computed the chemical shifts of the small globular protein ubiquitin, demonstrating that BPT calculations can match the results obtained at the DFT level of theory at very low computational cost. In addition to the calculation of chemical shift tensors, BPT allows the calculation of chemical shift gradients and consequently chemical shift driven geometry optimizations. We applied chemical shift driven protein structure refinement to the conformational analysis of a set of Trypanosoma brucei (the causative agent of African sleeping sickness) tryparedoxin peroxidase Px III structures. We found that the interaction of Px III with its reaction partner Tpx seems to be governed by conformational selection rather than by induced fit.

  20. 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 (δ(iso)) 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 δ(iso). 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 σ(MC) and π*(MC) orbitals under the action of the magnetic field, is analogous to that resulting from coupling σ(CC) 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 δ(iso) in alkylidene complexes relative to ethylene is thus due to the smaller energy gap between σ(MC) and π*(MC) vs this between σ(CC) and π*(CC) in ethylene. This effect also explains why the highest value of δ(iso) 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 π(MX)) 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 δ(iso).

  1. Evaluation of the application of chemical shift for the detection of lipid in brain lesion

    International Nuclear Information System (INIS)

    Lim, C.J.; Ng, K.H.; Ramli, N.; Azman, R.R.

    2011-01-01

    Non-invasive detection of the presence of lipids is particularly important in staging of intracranial tumours. Presence of lipid peak in aggressive intracranial tumours has been reported widely using MR spectroscopy. However this method has limitation due to long imaging time and artefacts formed by adjacent bones. Chemical shift MR imaging (with has shorter imaging time) is an alternative method that had been used to detect presence of lipid in vivo by means of signal intensity loss. The purpose of this study was to evaluate gradient echo in- and opposed-phase chemical shift pulse sequences for detection of lipid elements in brain lesion. Ten cylindered phantoms measuring 3 x 3 cm were filled with various mixtures of lipid and water: 0-90% lipid, in 10% step by weight. The gradient echo in- and opposed-phase chemical shift sequences were performed using a 1.5 T MRI (Magnetom Vision, Siemens) with a head coil. In addition, we performed MRI and chemical shift studies on 32 patients with brain lesion. We then analysed the association between out of phase intensity value and classification of the lesions. For phantom containing 50% lipid, maximum signal loss on opposed-phase images was observed. There were significant differences between in- and opposed-phase lipid-water phantom images (P = 0.0054). Most of the benign lesions fall into the positive out of phase intensity value, and malignant lesions fall into negative out of phase intensity value. We conclude that chemical shift artefact can be applied in detecting and characterising lipid elements in brain lesion.

  2. Isotope effects on chemical shifts in tautomeric systems with double proton transfer. Citronin

    International Nuclear Information System (INIS)

    Hansen, P.E.; Langgard, M.; Bolvig, S.

    1998-01-01

    Primary and secondary deuterium isotope effects on 1 H and 13 C chemical shifts are measured in citrinin, a tautomeric compound with an unusual doubly intramolecularly hydrogen bonded structure. The isotope effects are to a large extent dominated by equilibrium contributions and deuteration leads to more of the deuterated enol forms rather than the deuterated acid form. 1 H 13 C and 17 O nuclear shieldings are calculated using density functional ab initio methods. A very good correlation between calculated nuclear shieldings and experimental 1 H and 13 C chemical shifts is obtained. The tautomeric equilibrium can be analyzed based on the isotope effects on B-6 and C-8 carbons and shows an increase in the o-quinone form on lowering the temperature. Furthermore, upon deuteration the largest equilibrium shift is found for deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration is increasing at lower temperature. (author)

  3. 13C NMR Chemical Shifts of the Triclinic and Monoclinic Crystal forms of Valinomycin

    International Nuclear Information System (INIS)

    Kameda, Tsunenori; McGeorge, Gary; Orendt, Anita M.; Grant, David M.

    2004-01-01

    Two different crystalline polymorphs of valinomycin, the triclinic and monoclinic forms, have been studied by high resolution, solid state 13 C CP-MAS NMR spectroscopy. Although the two polymorphs of the crystal are remarkably similar, there are distinct differences in the isotropic chemical shifts between the two spectra. For the triclinic form, the carbon chemical shift tensor components for the alpha carbons adjacent to oxygen in the lactic acid and hydroxyisovaleric acid residues and the ester carbonyls of the valine residue were obtained using the FIREMAT experiment. From the measured components, it was found that the behavior of the isotropic chemical shift, δ iso , for valine residue ester carbonyl carbons is predominately influenced by the intermediate component, δ 22 . Additionally it was found that the smallest shift component, δ 33 , for the L-lactic acid (L-Lac) and D-α-hydroxyisovaleric acid (D-Hyi) C α -O carbon was significantly displaced depending upon the nature of individual amino acid residues, and it is the δ 33 component that governs the behavior of δ iso in these alpha carbons

  4. 13C solid-state NMR chemical shift anisotropy analysis of the anomeric carbon in carbohydrates.

    Science.gov (United States)

    Chen, Ying-Ying; Luo, Shun-Yuan; Hung, Shang-Cheng; Chan, Sunney I; Tzou, Der-Lii M

    2005-03-21

    (13)C NMR solid-state structural analysis of the anomeric center in carbohydrates was performed on six monosaccharides: glucose (Glc), mannose (Man), galactose (Gal), galactosamine hydrochloride (GalN), glucosamine hydrochloride (GlcN), and N-acetyl-glucosamine (GlcNAc). In the 1D (13)C cross-polarization/magic-angle spinning (CP/MAS) spectrum, the anomeric center C-1 of these carbohydrates revealed two well resolved resonances shifted by 3-5ppm, which were readily assigned to the anomeric alpha and beta forms. From this experiment, we also extracted the (13)C chemical shift anisotropy (CSA) tensor elements of the two forms from their spinning sideband intensities, respectively. It was found out that the chemical shift tensor for the alpha anomer was more axially symmetrical than that of the beta form. A strong linear correlation was obtained when the ratio of the axial asymmetry of the (13)C chemical shift tensors of the two anomeric forms was plotted in a semilogarithmic plot against the relative population of the two anomers. Finally, we applied REDOR spectroscopy to discern whether or not there were any differences in the sugar ring conformation between the anomers. Identical two-bond distances of 2.57A (2.48A) were deduced for both the alpha and beta forms in GlcNAc (GlcN), suggesting that the two anomers have essentially identical sugar ring scaffolds in these sugars. In light of these REDOR distance measurements and the strong correlation observed between the ratio of the axial asymmetry parameters of the (13)C chemical shift tensors and the relative population between the two anomeric forms, we concluded that the anomeric effect arises principally from interaction of the electron charge clouds between the C-1-O-5 and the C-1-O-1 bonds in these monosaccharides.

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

    International Nuclear Information System (INIS)

    Markin, Craig J.; Spyracopoulos, Leo

    2012-01-01

    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 (K D ) 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 K D 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 1 H– 15 N 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 (k off ). For experimentally determined kinetics in the fast exchange regime on the NMR timescale, k off ∼ 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 k off 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 k off values over a wide range, from 100 to 15,000 s −1 . The validity of line shape analysis for k off values approaching intermediate exchange (∼100 s −1 ), may be facilitated by more accurate K D measurements from NMR

  6. Gallbladder torsion. Case report

    DEFF Research Database (Denmark)

    Brasso, K; Rasmussen, O V

    1991-01-01

    Gallbladder torsion is a rare surgical emergency occurring primarily in elderly women. The anatomical background is a variation in the attachment of the gallbladder to the inferior margin of the liver. Increasing life span will probably lead to an increasing number of cases, and gallbladder torsion...

  7. Maxwell field with torsion

    Energy Technology Data Exchange (ETDEWEB)

    Fresneda, R., E-mail: rodrigo.fresneda@ufabc.edu.br [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil); Baldiotti, M.C.; Pereira, T.S., E-mail: baldiotti@uel.br, E-mail: tspereira@uel.br [Universidade Estadual de Londrina (UEL), Londrina, PR (Brazil). Departamento de Fisica

    2015-06-15

    We propose a gauge-invariant model of propagating torsion which couples to the Maxwell field and to charged particles. As a result, we have an Abelian gauge-invariant action leading to a theory with nonzero torsion consistent with available experimental data, which can be used to establish a lower bound for our new coupling parameter. (author)

  8. Postcesarean Splenic Torsion

    Directory of Open Access Journals (Sweden)

    Yu-Hui Huang

    2006-09-01

    Conclusion: Splenic torsion is a rare cause of acute abdominal pain during pregnancy or postpartum, and the symptoms vary depending on the degree of torsion. Early involvement of many complementary specialty services enabled early recognition of this rare entity and timely definitive treatment.

  9. Uniform fat suppression in hands and feet through the use of two-point Dixon chemical shift MR imaging

    NARCIS (Netherlands)

    Maas, M.; Dijkstra, P. F.; Akkerman, E. M.

    1999-01-01

    To assess the potential of two-point Dixon chemical shift magnetic resonance imaging to achieve uniform fat suppression in the distal parts of the extremities. Two-point Dixon chemical shift imaging was performed in 31 consecutive patients clinically suspected to have bone marrow disease. In some

  10. Modelling the acid/base 1H NMR chemical shift limits of metabolites in human urine.

    Science.gov (United States)

    Tredwell, Gregory D; Bundy, Jacob G; De Iorio, Maria; Ebbels, Timothy M D

    2016-01-01

    Despite the use of buffering agents the 1 H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. To investigate the acid, base and metal ion dependent 1 H NMR chemical shift variations and limits of the main metabolites in a complex biological mixture. Urine samples from five different individuals were collected and pooled, and pre-treated with Chelex-100 ion exchange resin. Urine samples were either treated with either HCl or NaOH, or were supplemented with various concentrations of CaCl 2 , MgCl 2 , NaCl or KCl, and their 1 H NMR spectra were acquired. Nonlinear fitting was used to derive acid dissociation constants and acid and base chemical shift limits for peaks from 33 identified metabolites. Peak pH titration curves for a further 65 unidentified peaks were also obtained for future reference. Furthermore, the peak variations induced by the main metal ions present in urine, Na + , K + , Ca 2+ and Mg 2+ , were also measured. These data will be a valuable resource for 1 H NMR metabolite profiling experiments and for the development of automated metabolite alignment and identification algorithms for 1 H NMR spectra.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, In-Sook Han; Jeon, Hyun Ju; Yu, Ji Sook; Lee, Chang Kiu [Kangwon National University, Chuncheon (Korea, Republic of)

    2010-06-15

    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.

  12. Chemical shift selective magnetic resonance imaging of the optic nerve in patients with acute optic neuritis

    DEFF Research Database (Denmark)

    Larsson, H B; Thomsen, C; Frederiksen, J

    1988-01-01

    of the 16 patients, abnormalities were seen. In one patient with bilateral symptoms, signal hyperintensity and swelling of the right side of the chiasm were found. In another patient the optic nerve was found diffusely enlarged with only a marginally increased signal in the second echo. In the third patient......Optic neuritis is often the first manifestation of multiple sclerosis (MS). Sixteen patients with acute optic neuritis and one patient with benign intracranial hypertension (BIH) were investigated by magnetic resonance imaging, using a chemical shift selective double spin echo sequence. In 3...... an area of signal hyperintensity and swelling was seen in the left optic nerve. In the patient with BIH the subarachnoid space which surrounds the optic nerves was enlarged. Even using this refined pulse sequence, avoiding the major artefact in imaging the optic nerve, the chemical shift artefact, lesions...

  13. From Raw Data to Protein Backbone Chemical Shifts Using NMRFx Processing and NMRViewJ Analysis.

    Science.gov (United States)

    Johnson, Bruce A

    2018-01-01

    Assignment of the chemical shifts of the backbone atoms (HN, N, CA, CB, and C) of proteins is often a prerequisite to using NMR information in the study of proteins. These chemical shifts and their perturbations are the basis for the analysis of protein dynamics, ligand binding, and backbone conformation. They are generally assigned prior to full side-chain assignments and the determination of the complete three-dimensional molecular structure. This chapter describes the use of two software packages, NMRFx Processor and NMRViewJ, in going from raw NMR data to backbone assignments. The step-by-step procedure describes processing of the data and the use of manual and automated features of the RunAbout tool in NMRViewJ to perform the assignments.

  14. Crime Scene Investigation: Clinical Application of Chemical Shift Imaging as a Problem Solving Tool

    Science.gov (United States)

    2016-02-26

    MDW/SGVU SUBJECT: Professional Presentation Approva l 26 FEB 2016 1. Your paper, entitled Crime Scene Investigation: Clinical Aoolication of...or technical information as a publication/presentation, a new 59 MDW Form 3039 must be submitted for review and approval.] Crime Scene Investiga...tion: Clinical Application of Chemical Shift Imaging as a Problem Solving Tool 1. TITLE OF MATERIAL TO BE PUBLISHED OR PRESENTED Crime Scene

  15. Chemical shift assignments of polyketide cyclase_like protein CGL2373 from Corynebacterium glutamicum.

    Science.gov (United States)

    Liang, Chunjie; Hu, Rui; Ramelot, Theresa A; Kennedy, Michael A; Li, Xuegang; Yang, Yunhuang; Zhu, Jiang; Liu, Maili

    2017-10-01

    Protein CGL2373 from Corynebacterium glutamicum, which is 155 amino acids long and 17.7 kDa, is a member of the polyketide_cyc2 family. As a potential polyketide cyclase, it may play an important role in the biosynthesis of aromatic polyketides that are the source of many bioactive molecules. Here we report the complete 1 H, 13 C and 15 N chemical shift assignments of CGL2373, which lays a foundation for further structural and functional research.

  16. Analysis of seven-membered lactones by computational NMR methods: proton NMR chemical shift data are more discriminating than carbon.

    Science.gov (United States)

    Marell, Daniel J; Emond, Susanna J; Kulshrestha, Aman; Hoye, Thomas R

    2014-01-17

    We report an NMR chemical shift study of conformationally challenging seven-membered lactones (1-11); computed and experimental data sets are compared. The computations involved full conformational analysis of each lactone, Boltzmann-weighted averaging of the chemical shifts across all conformers, and linear correction of the computed chemical shifts. DFT geometry optimizations [M06-2X/6-31+G(d,p)] and GIAO NMR chemical shift calculations [B3LYP/6-311+G(2d,p)] provided the computed chemical shifts. The corrected mean absolute error (CMAE), the average of the differences between the computed and experimental chemical shifts for each of the 11 lactones, is encouragingly small (0.02-0.08 ppm for (1)H or 0.8-2.2 ppm for (13)C). Three pairs of cis versus trans diastereomeric lactones were used to assess the ability of the method to distinguish between stereoisomers. The experimental shifts were compared with the computed shifts for each of the two possible isomers. We introduce the use of a "match ratio"--the ratio of the larger CMAE (worse fit) to the smaller CMAE (better fit). A greater match ratio value indicates better distinguishing ability. The match ratios are larger for proton data [2.4-4.0 (av = 3.2)] than for carbon [1.1-2.3 (av = 1.6)], indicating that the former provide a better basis for discriminating these diastereomers.

  17. Characterization of the conformational equilibrium between the two major substates of RNase A using NMR chemical shifts.

    Science.gov (United States)

    Camilloni, Carlo; Robustelli, Paul; De Simone, Alfonso; Cavalli, Andrea; Vendruscolo, Michele

    2012-03-07

    Following the recognition that NMR chemical shifts can be used for protein structure determination, rapid advances have recently been made in methods for extending this strategy for proteins and protein complexes of increasing size and complexity. A remaining major challenge is to develop approaches to exploit the information contained in the chemical shifts about conformational fluctuations in native states of proteins. In this work we show that it is possible to determine an ensemble of conformations representing the free energy surface of RNase A using chemical shifts as replica-averaged restraints in molecular dynamics simulations. Analysis of this surface indicates that chemical shifts can be used to characterize the conformational equilibrium between the two major substates of this protein. © 2012 American Chemical Society

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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

  19. 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

  20. Elucidation of the substitution pattern of 9,10-anthraquinones through the chemical shifts of peri-hydroxyl protons

    DEFF Research Database (Denmark)

    Schripsema, Jan; Danigno, Denise

    1996-01-01

    In 9,10-anthraquinones the chemical shift of a peri-hydroxyl proton is affected by the substituents in the other benzenoid ring. These effects are additive. They are useful for the determination of substitution patterns and have been used to revise the structures of six previously reported...... anthraquinones containing methoxyl, hydroxyl, methylenedioxy and beta-methyl substituents. Because the chemical shifts of the other protons are hardly affected by substitutions in the other ring, the characteristic chemical shifts for a wide variety of substitution patterns could be derived....

  1. Low-carbon Scenarios Development for Modal Shift in the Chemical Industry

    Directory of Open Access Journals (Sweden)

    Ocicka Barbara

    2017-01-01

    Full Text Available Supply chain managers have to deal with the performance requirement to significantly reduce CO2 emissions in searching for excellence in green business processes management. The purpose of this article is to examine the perspectives on low-carbon scenarios development for modal shift in the chemical industry. The author outlines main research findings from the Interreg Central Europe ChemMultimodal project realised by 14 partners from 7 countries, among others by Department of Logistics at Warsaw School of Economics in Poland. The project idea is focused on analysing the potential and growth opportunities for multimodal transport usage in chemical supply chain management. Firstly, the objectives, current status and methodology of the project are explained. Then, the results of the research carried out among chemical and logistics companies operating in Poland are discussed. Furthermore, there is recognised that transport modal shift decisions determine changes in supply chain configurations that might be supported by planning and management tools. Consequently, the elements of the ChemMultimodal toolbox are outlined and its potential significance for low-carbon scenarios development is highlighted. As a result, both theoretical and practical implications of the research findings are indicated.

  2. Torsion pendulum revisited

    Energy Technology Data Exchange (ETDEWEB)

    Bassan, Massimo [Dipartimento di Fisica, Università di Roma Tor Vergata, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy); De Marchi, Fabrizio, E-mail: fabrizio.demarchi@roma2.infn.it [Dipartimento di Fisica, Università di Roma Tor Vergata, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy); Marconi, Lorenzo [Dipartimento di Fisica ed Astronomia, Università degli Studi di Firenze, and INFN, Sezione di Firenze (Italy); Pucacco, Giuseppe [Dipartimento di Fisica, Università di Roma Tor Vergata, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy); Stanga, Ruggero [Dipartimento di Fisica ed Astronomia, Università degli Studi di Firenze, and INFN, Sezione di Firenze (Italy); Visco, Massimo [IAPS-INAF, and INFN, Sezione di Roma Tor Vergata, I-00133 Roma (Italy)

    2013-10-01

    We present an analysis of the motion of a simple torsion pendulum and we describe how, with straightforward extensions to the usual basic dynamical model, we succeed in explaining some unexpected features we found in our data, like the modulation of the torsion mode at a higher frequency and the frequency splitting of the swinging motion. Comparison with observed values yields estimates for the misalignment angles and other parameters of the model.

  3. Induced quantum torsion

    International Nuclear Information System (INIS)

    Denardo, G.; Spallucci, E.

    1985-07-01

    We study pregeometry in the framework of a Poincare gauge field theory. The Riemann-Cartan space-time is shown to be an ''effective geometry'' for this model in the low energy limit. By using Heat Kernel techniques we find the induced action for curvature and torsion. We obtain in this way the usual Einstein-Hilbert action plus an axial Maxwell term describing the propagation of a massless, axial vector torsion field. (author)

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

    International Nuclear Information System (INIS)

    Shen Yang; Bax, Ad

    2010-01-01

    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 13 C β 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 13 C β atoms, with standard deviations of 2.45, 1.09, 0.94, 1.14, 0.25 and 0.49 ppm for δ 15 N, δ 13 C', δ 13 C α , δ 13 C β , δ 1 H α and δ 1 H 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.

  5. 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

  6. Thymic hyperplasia and thymus gland tumors: differentiation with chemical shift MR imaging.

    Science.gov (United States)

    Inaoka, Tsutomu; Takahashi, Koji; Mineta, Masayuki; Yamada, Tomonori; Shuke, Noriyuki; Okizaki, Atsutaka; Nagasawa, Kenichi; Sugimori, Hiroyuki; Aburano, Tamio

    2007-06-01

    To prospectively evaluate chemical shift magnetic resonance (MR) imaging for differentiating thymic hyperplasia from tumors of the thymus gland. The institutional review board approved this study; informed consent was obtained and patient confidentiality was protected. The authors assessed 41 patients (17 male, 24 female; age range, 16-78 years) in whom thymic lesions were seen at chest computed tomography. Patients were assigned to a hyperplasia group (n=23) (18 patients with hyperplastic thymus associated with Graves disease and five with rebound thymic hyperplasia) and a tumor group (n=18) (seven patients with thymomas, four with invasive thymomas, five with thymic cancers, and two with malignant lymphomas). T2-weighted fast spin-echo and T1-weighted in-phase and opposed-phase MR images were obtained in all patients and visually assessed. A chemical shift ratio (CSR), determined by comparing the signal intensity of the thymus gland with that of the paraspinal muscle, was calculated for quantitative analysis. Mean CSRs for the patient groups and subgroups were analyzed by using Welch t and Newman-Keuls tests. Pthymus gland had homogeneous signal intensity in all 23 patients in the hyperplasia group and in 12 of the 18 patients in the tumor group. The mean CSR (+/- standard deviation) was 0.614 +/- 0.130 in the hyperplasia group and 1.026 +/- 0.039 in the tumor group. Mean CSRs in the patients with a hyperplastic thymus and Graves disease, rebound thymic hyperplasia, thymoma, invasive thymoma, thymic cancer, and malignant lymphoma were 0.594 +/- 0.120, 0.688 +/- 0.154, 1.033 +/- 0.043, 1.036 +/- 0.040, 1.020 +/- 0.044, and 0.997 +/- 0.010, respectively. The difference in CSR between the hyperplasia and tumor groups was significant (Pthymus gland signal intensity at chemical shift MR imaging; no tumor group patients had a decrease in thymus gland signal intensity. Chemical shift MR imaging can be used to differentiate thymic hyperplasia from thymic tumors. (c) RSNA

  7. 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.

  8. 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 - others: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

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

    Directory of Open Access Journals (Sweden)

    Benjamin Görling

    2016-09-01

    Full Text Available 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.

  10. Equilibrium simulations of proteins using molecular fragment replacement and NMR chemical shifts

    DEFF Research Database (Denmark)

    Boomsma, Wouter; Tian, Pengfei; Frellsen, J.

    2014-01-01

    Significance Chemical shifts are the most fundamental parameters measured in nuclear magnetic resonance spectroscopy. Since these parameters are exquisitely sensitive to the local atomic environment, they can provide detailed information about the three-dimensional structures of proteins. It has...... recently been shown that using such information directly as input in molecular simulations based on the molecular fragment replacement strategy can help the process of protein structure determination. Here, we show how to implement this strategy to determine not only the structures of proteins but also...

  11. Physical basis of the effect of hemoglobin on the 31P NMR chemical shifts of various phosphoryl compounds

    International Nuclear Information System (INIS)

    Kirk, K.; Kuchel, P.W.

    1988-01-01

    The marked difference between the intra- and extracellular 31 P NMR chemical shifts of various phosphoryl compounds when added to a red cell suspension may be largely understood in terms of the effects of hemoglobin on the 31 P NMR chemical shifts. The presence of [oxy- or (carbonmonoxy)-] hemoglobin inside the red cell causes the bulk magnetic susceptibility of the cell cytoplasm to be significantly less than that of the external solution. This difference is sufficient to account for the difference in the intra- and extracellular chemical shifts of the two phosphate esters trimethyl phosphate and triethyl phosphate. However, in the case of the compounds dimethyl methylphosphonate, diethyl methylphosphonate, and trimethylphosphine oxide as well as the hypophosphite, phenylphosphinate, and diphenylphosphinate ions, hemoglobin exerts an additional, much larger, effect, causing the 31 P NMR resonances to shift to lower frequency in a manner that cannot be accounted for in terms of magnetic susceptibility. Lysozyme is a protein structurally unrelated to hemoglobin and was shown to cause similar shifts to lower frequency of the resonances of these six compounds; this suggests that the mechanism may involve a property of proteins in general and not a specific property of hemoglobin. The effect of different solvents on the chemical shifts of the eight phosphoryl compounds provided an insight into the possible physical basis of the effect. It is proposed that, in addition to magnetic susceptibility effects, hemoglobin exerts its influence on phosphoryl chemical shifts by disrupting the hydrogen bonding of the phosphoryl group to solvent water

  12. Relativistic heavy atom effect on13C NMR chemical shifts initiated by adjacent multiple chalcogens.

    Science.gov (United States)

    Rusakov, Yu Yu; Rusakova, I L

    2018-02-07

    In this paper, we have investigated the cumulative peculiarity of the "heavy atom on light atom" effect on the 13 C NMR chemical shifts, initiated by the adjacent chalcogens. For this purpose, the most accurate hybrid computational scheme for the calculation of chemical shifts of carbon nuclei, directly bonded with several heavy chalcogens, is introduced and attested on the representative series of molecules. The best hybrid scheme combines the nonrelativistic coupled cluster-based approach with the different types of corrections, including vibrational, solvent, and relativistic. The dependences of the total relativistic corrections to carbon shielding constants in 2 series of model compounds, namely, X═ 13 C═Y (X, Y = O, S, Se, Te) and C(XH) m (YH) n (ZH) p (QH) s H 1-m H 1-n H 1-p H 1-s (X, Y, Z, Q = S, Se, Te and m, n, p, s = 0, 1), on the total atomic number of the adjacent chalcogens have been obtained. Copyright © 2018 John Wiley & Sons, Ltd.

  13. Chemical shift assignments of CHU_1110: an AHSA1-like protein from Cytophaga hutchinsonii.

    Science.gov (United States)

    Liang, Chunjie; He, Ting; Li, Tao; Yang, Yunhuang; Zhu, Jiang; Liu, Maili

    2018-04-01

    AHSA1 protein family is one of the four largest families in the Bet v1-like protein superfamily. The functions and structures of proteins in AHSA1 family are still largely unknown. CHU_1110 with 167 amino acids and a molecular weight of 19.2 kDa is a member of the AHSA1 family from Cytophaga hutchinsonii, a soil bacterium known for its ability to digest crystalline cellulose. Here we report the complete 1 H, 13 C and 15 N chemical shift assignments of CHU_1110. The secondary structural elements of CGL2373 are consistent with the canonical AHSA1 structure. However the sequence identity of CHU_1110 with other members of AHSA1 family with functional and structural reports, such as RHE_CH02687 from Rhizobium etli, Aha1 from Homo sapiens and Yndb from Bacillus subtilis, are very low, which may suggest a different function of CHU_1110. Our chemical shift assignments of CHU_1110 are essential for the following structural and functional research of CHU_1110.

  14. Chemical constituents of Ottonia corcovadensis Miq. from Amazon forest: 1H and 13C chemical shift assignments

    International Nuclear Information System (INIS)

    Facundo, Valdir A.; Morais, Selene M.; Braz Filho, Raimundo

    2004-01-01

    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-penta methoxyflavone (1), 3',4',5,7-tetra methoxyflavone (2) and 5-hydroxy-3',4',5',7-tetra methoxyflavone (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 1 H and 13 C 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. (author)

  15. Torsional changes in surgery for A-V phenomena.

    Science.gov (United States)

    Sharma, P; Halder, M; Prakash, P

    1997-03-01

    The role of torsion in the aetiopathogenesis of A-V phenomena has not been sufficiently emphasized. The success of vertical displacement of horizontal recti in correction of A or V has not been attributed to torsional changes. To evaluate this aspect, 21 cases of A or V phenomena were subjected to monocular recession-resection procedure with vertical shifting. Preoperative and postoperative torsional changes were evaluated on synoptophore (subjective torsion), and confirmed by fundus photography (objective torsion). Intorsion with A phenomenon was seen preoperatively in 5 of 8 cases which increased after surgery and was seen postoperatively in the other 3 cases also. Extorsion was observed in 5 of 13 cases pre operatively in 'V' phenomenon, but the changes in extorsion after surgery were less dramatic than those in intorsion. The oblique overactions were reduced in cases where they were present. Correction of A-V phenomena by torsion induced by vertical shifting of horizontal recti muscles is proposed, highlighting the role of torsion in A-V phenomena.

  16. Torsional changes in surgery for A-V phenomena

    Directory of Open Access Journals (Sweden)

    Sharma Pradeep

    1997-01-01

    Full Text Available The role of torsion in the aetiopathogenesis of A-V phenomena has not been sufficiently emphasized. The success of vertical displacement of horizontal recti in correction of A or V has not been attributed to torsional changes. To evaluate this aspect, 21 cases of A or V phenomena were subjected to monocular recession-resection procedure with vertical shifting. Preoperative and postoperative torsional changes were evaluated on synoptophore (subjective torsion, and confirmed by fundus photography (objective torsion. Intorsion with A phenomenon was seen preoperatively in 5 of 8 cases which increased after surgery and was seen postoperatively in the other 3 cases also. Extorsion was observed in 5 of 13 cases pre operatively in ′V′ phenomenon, but the changes in extorsion after surgery were less dramatic than those in intorsion. The oblique overactions were reduced in cases where they were present. Correction of A-V phenomena by torsion induced by vertical shifting of horizontal recti muscles is proposed, highlighting the role of torsion in A-V phenomena.

  17. Windowless dipolar recoupling: the detection of weak dipolar couplings between spin 1/2 nuclei with large chemical shift anisotropies

    Science.gov (United States)

    Gregory, D. M.; Mitchell, D. J.; Stringer, J. A.; Kiihne, S.; Shiels, J. C.; Callahan, J.; Mehta, M. A.; Drobny, G. P.

    1995-12-01

    A new homonuclear dipolar recoupling technique is described which uses a sequence of phase-shifted, windowless irradiations applied synchronously with sample spinning. Experiments performed on a series of doubly labeled dicarboxylic acids, alanine-1,3- 13C 2, and 2'-deoxythymidine-4,6- 13C 2 demonstrate that this new windowless dipolar recoupling pulse sequence can accurately determine internuclear distances from polycrystalline solids in cases where the coupled spins have large chemical shift anisotropies and large differences in isotropic chemical shift.

  18. 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.

  19. 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.

  20. Volume elements and torsion

    Science.gov (United States)

    Mosna, Ricardo A.; Saa, Alberto

    2005-11-01

    We reexamine here the issue of consistency of minimal action formulation with the minimal coupling procedure (MCP) in spaces with torsion. In Riemann-Cartan spaces, it is known that a proper use of the MCP requires that the trace of the torsion tensor be a gradient, Tμ=∂μθ, and that the modified volume element τθ=eθ√g dx1∧⋯∧dxn be used in the action formulation of a physical model. We rederive this result here under considerably weaker assumptions, reinforcing some recent results about the inadequacy of propagating torsion theories of gravity to explain the available observational data. The results presented here also open the door to possible applications of the modified volume element in the geometric theory of crystalline defects.

  1. 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…

  2. Higher Franz-Reidemeister torsion

    CERN Document Server

    Igusa, Kiyoshi

    2002-01-01

    The book is devoted to the theory of topological higher Franz-Reidemeister torsion in K-theory. The author defines the higher Franz-Reidemeister torsion based on Volodin's K-theory and Borel's regulator map. He describes its properties and generalizations and studies the relation between the higher Franz-Reidemeister torsion and other torsions used in K-theory: Whitehead torsion and Ray-Singer torsion. He also presents methods of computing higher Franz-Reidemeister torsion, illustrates them with numerous examples, and describes various applications of higher Franz-Reidemeister torsion, particularly for the study of homology of mapping class groups. Packed with up-to-date information, the book provides a unique research and reference tool for specialists working in algebraic topology and K-theory.

  3. Isolated Fallopian Tube Torsion

    Directory of Open Access Journals (Sweden)

    S. Kardakis

    2013-01-01

    Full Text Available Isolated torsion of the Fallopian tube is a rare gynecological cause of acute lower abdominal pain, and diagnosis is difficult. There are no pathognomonic symptoms; clinical, imaging, or laboratory findings. A preoperative ultrasound showing tubular adnexal masses of heterogeneous echogenicity with cystic component is often present. Diagnosis can rarely be made before operation, and laparoscopy is necessary to establish the diagnosis. Unfortunately, surgery often is performed too late for tube conservation. Isolated Fallopian tube torsion should be suspected in case of acute pelvic pain, and prompt intervention is necessary.

  4. 129Xe chemical shift in human blood and pulmonary blood oxygenation measurement in humans using hyperpolarized 129Xe NMR

    Science.gov (United States)

    Norquay, Graham; Leung, General; Stewart, Neil J.; Wolber, Jan

    2016-01-01

    Purpose To evaluate the dependency of the 129Xe‐red blood cell (RBC) chemical shift on blood oxygenation, and to use this relation for noninvasive measurement of pulmonary blood oxygenation in vivo with hyperpolarized 129Xe NMR. Methods Hyperpolarized 129Xe was equilibrated with blood samples of varying oxygenation in vitro, and NMR was performed at 1.5 T and 3 T. Dynamic in vivo NMR during breath hold apnea was performed at 3 T on two healthy volunteers following inhalation of hyperpolarized 129Xe. Results The 129Xe chemical shift in RBCs was found to increase nonlinearly with blood oxygenation at 1.5 T and 3 T. During breath hold apnea, the 129Xe chemical shift in RBCs exhibited a periodic time modulation and showed a net decrease in chemical shift of ∼1 ppm over a 35 s breath hold, corresponding to a decrease of 7–10 % in RBC oxygenation. The 129Xe‐RBC signal amplitude showed a modulation with the same frequency as the 129Xe‐RBC chemical shift. Conclusion The feasibility of using the 129Xe‐RBC chemical shift to measure pulmonary blood oxygenation in vivo has been demonstrated. Correlation between 129Xe‐RBC signal and 129Xe‐RBC chemical shift modulations in the lung warrants further investigation, with the aim to better quantify temporal blood oxygenation changes in the cardiopulmonary vascular circuit. Magn Reson Med 77:1399–1408, 2017. © 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:27062652

  5. Chemical shift assignments of the partially deuterated Fyn SH2-SH3 domain.

    Science.gov (United States)

    Kieken, Fabien; Loth, Karine; van Nuland, Nico; Tompa, Peter; Lenaerts, Tom

    2018-04-01

    Src Homology 2 and 3 (SH2 and SH3) are two key protein interaction modules involved in regulating the activity of many proteins such as tyrosine kinases and phosphatases by respective recognition of phosphotyrosine and proline-rich regions. In the Src family kinases, the inactive state of the protein is the direct result of the interaction of the SH2 and the SH3 domain with intra-molecular regions, leading to a closed structure incompetent with substrate modification. Here, we report the 1 H, 15 N and 13 C backbone- and side-chain chemical shift assignments of the partially deuterated Fyn SH3-SH2 domain and structural differences between tandem and single domains. The BMRB accession number is 27165.

  6. Improvement of chemical shift selective saturation (CHESS) pulse for MR angiography

    International Nuclear Information System (INIS)

    Ishimori, Yoshiyuki; Sashie, Hiroyuki; Hiraga, Akira; Matsuda, Tsuyoshi

    2000-01-01

    We improved the fat suppression technique based on chemical shift selective saturation (CHESS). To do this, we shortened the duration of the CHESS pulse to achieve a short repetition time (TR) for MR angiography (MRA). A short-duration CHESS pulse causes broad frequency band saturation, creating extensive offset from the resonance frequency of water. In our phantom experiment, the best parameters of the short-duration CHESS pulse were 3.84 ms in duration, -650 Hz in offset frequency from water resonance, and had a 130-degree flip angle. With this technique, MRA will be able to be carried out without a significant increase in TR. Thus, better vessel contrast will be maintained in time-of-flight (TOF) MRA or contrast-enhanced MRA when using the maximum intensity projection (MIP) method. (author)

  7. Deuterium isotope effect on 13C chemical shifts of tetrabutylammonium salts of Schiff bases amino acids.

    Science.gov (United States)

    Rozwadowski, Z

    2006-09-01

    Deuterium isotope effects on 13C chemical shift of tetrabutylammonium salts of Schiff bases, derivatives of amino acids (glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and L-methionine) and various ortho-hydroxyaldehydes in CDCl3 have been measured. The results have shown that the tetrabutylammonium salts of the Schiff bases amino acids, being derivatives of 2-hydroxynaphthaldehyde and 3,5-dibromosalicylaldehyde, exist in the NH-form, while in the derivatives of salicylaldehyde and 5-bromosalicylaldehyde a proton transfer takes place. The interactions between COO- and NH groups stabilize the proton-transferred form through a bifurcated intramolecular hydrogen bond. Copyright (c) 2006 John Wiley & Sons, Ltd.

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

    International Nuclear Information System (INIS)

    Naruse, Shoji; Furuya, Seiichi; Ide, Mariko

    1992-01-01

    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.)

  9. Planar torsion spring

    Science.gov (United States)

    Ihrke, Chris A. (Inventor); Parsons, Adam H. (Inventor); Mehling, Joshua S. (Inventor); Griffith, Bryan Kristian (Inventor)

    2012-01-01

    A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.

  10. Electrostatically suspended torsion pendulum

    Science.gov (United States)

    Willemenot, E.; Touboul, P.

    2000-01-01

    A torsion pendulum without a torsion wire has been designed and realized, in order to measure very weak forces. The arm of this torsion pendulum (5.40 g, 1.32×10-6 kg m2 of inertia) is electrostatically suspended. Its 6 degrees of freedom are controlled thanks to electrostatic forces, and capacitive position sensing with a noise spectral density between 10-10 and 10-13 m/√Hz . The torque noise spectral density is 1.3×10-14 Nm/√Hz around 0.05 Hz with a 1/√f increase at lower frequency, corresponding to 10-8 rad/s2/√Hz , and 2×10-10 ms-2/√Hz with a lever arm of 2 cm. The residual seismic noise limit the performances above 0.1 Hz. The free oscillating mode has a torsion stiffness of 5.14×10-8 Nm/rad and a Q of 217. This new instrument allows on ground experiments on very weak parasitic forces inside space accelerometers developed in ONERA, with a good representativeness. For example, it is possible to measure electrostatic stiffnesses with high resolution thanks to the low torque noise spectral density; the electrostatic damping phenomenon is also well seen as illustrated by the rather low Q. The instrument design and operation are described, the main performances are given, and the possibilities offered are discussed.

  11. Testicular Torsion (For Parents)

    Science.gov (United States)

    ... securing the testicles to the scrotum. If your son had a torsion that resulted in the loss of a testicle, it's important to let him know that he can still lead a normal life, just like anyone else. The loss of one testicle won't prevent a man from having normal sexual relations and is unlikely ...

  12. Gallbladder torsion. Case report

    DEFF Research Database (Denmark)

    Brasso, K; Rasmussen, O V

    1991-01-01

    Gallbladder torsion is a rare surgical emergency occurring primarily in elderly women. The anatomical background is a variation in the attachment of the gallbladder to the inferior margin of the liver. Increasing life span will probably lead to an increasing number of cases, and gallbladder torsi...

  13. Tumour, Torsion or Trauma?

    African Journals Online (AJOL)

    he had described a typical case in an 18 year old who later developed torsion of the contra-lateral testis and suffered ... he visited our hospital where an ultrasound scan was ordered, which was reported as showing an enlarged .... Mills S.E., Carter D., Reuter V.E., et al. Sternberg's diagnostic surgical pathology. 2004;4th.

  14. Torsion induces gravity

    International Nuclear Information System (INIS)

    Aros, Rodrigo; Contreras, Mauricio

    2006-01-01

    In this work the Poincare-Chern-Simons and anti-de Sitter-Chern-Simons gravities are studied. For both, a solution that can be cast as a black hole with manifest torsion is found. Those solutions resemble Schwarzschild and Schwarzschild-AdS solutions, respectively

  15. Triorchidism with Torsion

    African Journals Online (AJOL)

    are retractile and more mobility is at increased risk for torsion. An increased prevalence of carcinoma has also been reported.[1]. Case Report. A 72-year-old man presented with vague pain in the lower abdomen and scrotum. There was no history of trauma and he stated that the pain was severe in nature and had been ...

  16. Spin-echo based diagonal peak suppression in solid-state MAS NMR homonuclear chemical shift correlation spectra

    Science.gov (United States)

    Wang, Kaiyu; Zhang, Zhiyong; Ding, Xiaoyan; Tian, Fang; Huang, Yuqing; Chen, Zhong; Fu, Riqiang

    2018-02-01

    The feasibility of using the spin-echo based diagonal peak suppression method in solid-state MAS NMR homonuclear chemical shift correlation experiments is demonstrated. A complete phase cycling is designed in such a way that in the indirect dimension only the spin diffused signals are evolved, while all signals not involved in polarization transfer are refocused for cancellation. A data processing procedure is further introduced to reconstruct this acquired spectrum into a conventional two-dimensional homonuclear chemical shift correlation spectrum. A uniformly 13C, 15N labeled Fmoc-valine sample and the transmembrane domain of a human protein, LR11 (sorLA), in native Escherichia coli membranes have been used to illustrate the capability of the proposed method in comparison with standard 13C-13C chemical shift correlation experiments.

  17. Quantum-Chemical Approach to NMR Chemical Shifts in Paramagnetic Solids Applied to LiFePO4and LiCoPO4.

    Science.gov (United States)

    Mondal, Arobendo; Kaupp, Martin

    2018-03-09

    A novel protocol to compute and analyze NMR chemical shifts for extended paramagnetic solids, accounting comprehensively for Fermi-contact (FC), pseudocontact (PC), and orbital shifts, is reported and applied to the important lithium ion battery cathode materials LiFePO 4 and LiCoPO 4 . Using an EPR-parameter-based ansatz, the approach combines periodic (hybrid) DFT computation of hyperfine and orbital-shielding tensors with an incremental cluster model for g- and zero-field-splitting (ZFS) D-tensors. The cluster model allows the use of advanced multireference wave function methods (such as CASSCF or NEVPT2). Application of this protocol shows that the 7 Li shifts in the high-voltage cathode material LiCoPO 4 are dominated by spin-orbit-induced PC contributions, in contrast with previous assumptions, fundamentally changing interpretations of the shifts in terms of covalency. PC contributions are smaller for the 7 Li shifts of the related LiFePO 4 , where FC and orbital shifts dominate. The 31 P shifts of both materials finally are almost pure FC shifts. Nevertheless, large ZFS contributions can give rise to non-Curie temperature dependences for both 7 Li and 31 P shifts.

  18. Shifts in Plant Chemical Defenses of Chile Pepper (Capsicum annuum L. Due to Domestication in Mesoamerica

    Directory of Open Access Journals (Sweden)

    Jose de Jesus Luna-Ruiz

    2018-04-01

    Full Text Available We propose that comparisons of wild and domesticated Capsicum species can serve as a model system for elucidating how crop domestication influences biotic and abiotic interactions mediated by plant chemical defenses. Perhaps no set of secondary metabolites (SMs used for plant defenses and human health have been better studied in the wild and in milpa agro-habitats than those found in Capsicum species. However, very few scientific studies on SM variation have been conducted in both the domesticated landraces of chile peppers and in their wild relatives in the Neotropics. In particular, capsaicinoids in Capsicum fruits and on their seeds differ in the specificity of their ecological effects from broad-spectrum toxins in other members of the Solanaceae. They do so in a manner that mediates specific ecological interactions with a variety of sympatric Neotropical vertebrates, invertebrates, nurse plants and microbes. Specifically, capsaicin is a secondary metabolite (SM in the placental tissues of the chile fruit that mediates interactions with seed dispersers such as birds, and with seed predators, ranging from fungi to insects and rodents. As with other Solanaceae, a wide range of SMs in Capsicum spp. function to ecologically mediate the effects of a variety of biotic and abiotic stresses on wild chile peppers in certain tropical and subtropical habitats. However, species in the genus Capsicum are the only ones found within any solanaceous genus that utilize capsaicinoids as their primary means of chemical defense. We demonstrate how exploring in tandem the evolutionary ecology and the ethnobotany of human-chile interactions can generate and test novel hypotheses with regard to how the domestication process shifts plant chemical defense strategies in a variety of tropical crops. To do so, we draw upon recent advances regarding the chemical ecology of a number of wild Capsicum species found in the Neotropics. We articulate three hypotheses regarding

  19. Contribution of magnetic susceptibility effects to transmembrane chemical shift differences in the 31P NMR spectra of oxygenated erythrocyte suspensions

    International Nuclear Information System (INIS)

    Kirk, K.; Kuchel, P.W.

    1988-01-01

    Triethyl phosphate, dimethyl methylphosphonate, and the hypophosphite ion all contain the phosphoryl functional group. When added to an oxygenated erythrocyte suspension, the former compound gives rise to a single 31 P NMR resonance, whereas the latter compounds give rise to separate intra- and extracellular 31 P NMR resonances. On the basis of experiments with intact oxygenated cell suspensions (in which the hematocrit was varied) and with oxygenated cell lysates (in which the lysate concentration was varied) it was concluded that the chemical shifts of the intra- and extracellular populations of triethyl phosphate differ as a consequence of the diamagnetic susceptibility of intracellular oxyhemoglobin but that this difference is averaged by the rapid exchange of the compound across the cell membrane. The difference is the magnetic susceptibility of the intra- and extracellular compartments contributes to the observed separation of the intra- and extracellular resonances of dimethyl methylphosphonate and hypophosphite. The magnitude of this contribution is, however, substantially less than that calculated using a simple two-compartment model and varies with the hematocrit of the suspension. Furthermore, it is insufficient to fully account for the transmembrane chemical shift differences observed for dimethyl methylphosphonate and hypophosphite. An additional effect is operating to move the intracellular resonances of these compounds to a lower chemical shift. The effect is mediated by an intracellular component, and the magnitude of the resultant chemical shift variations depends upon the chemical structure of the phosphoryl compound involved

  20. Torsional Ratcheting Actuating System

    Energy Technology Data Exchange (ETDEWEB)

    BARNES,STEPHEN MATTHEW; MILLER,SAMUEL L.; RODGERS,M. STEVEN; BITSIE,FERNANDO

    2000-01-24

    A new type of surface micromachined ratcheting actuation system has been developed at the Microelectronics Development Laboratory at Sandia National Laboratories. The actuator uses a torsional electrostatic comb drive that is coupled to an external ring gear through a ratcheting scheme. The actuator can be operated with a single square wave, has minimal rubbing surfaces, maximizes comb finger density, and can be used for open-loop position control. The prototypes function as intended with a minimum demonstrated operating voltage of 18V. The equations of motion are developed for the torsional electrostatic comb drive. The resonant frequency, voltage vs. displacement and force delivery characteristics are predicted and compared with the fabricated device's performance.

  1. Stability in quadratic torsion theories

    Energy Technology Data Exchange (ETDEWEB)

    Vasilev, Teodor Borislavov; Cembranos, Jose A.R.; Gigante Valcarcel, Jorge; Martin-Moruno, Prado [Universidad Complutense de Madrid, Departamento de Fisica Teorica I, Madrid (Spain)

    2017-11-15

    We revisit the definition and some of the characteristics of quadratic theories of gravity with torsion. We start from a Lagrangian density quadratic in the curvature and torsion tensors. By assuming that General Relativity should be recovered when the torsion vanishes and investigating the behaviour of the vector and pseudo-vector torsion fields in the weak-gravity regime, we present a set of necessary conditions for the stability of these theories. Moreover, we explicitly obtain the gravitational field equations using the Palatini variational principle with the metricity condition implemented via a Lagrange multiplier. (orig.)

  2. Stability in quadratic torsion theories

    Science.gov (United States)

    Vasilev, Teodor Borislavov; Cembranos, Jose A. R.; Valcarcel, Jorge Gigante; Martín-Moruno, Prado

    2017-11-01

    We revisit the definition and some of the characteristics of quadratic theories of gravity with torsion. We start from a Lagrangian density quadratic in the curvature and torsion tensors. By assuming that General Relativity should be recovered when the torsion vanishes and investigating the behaviour of the vector and pseudo-vector torsion fields in the weak-gravity regime, we present a set of necessary conditions for the stability of these theories. Moreover, we explicitly obtain the gravitational field equations using the Palatini variational principle with the metricity condition implemented via a Lagrange multiplier.

  3. Changes of brain metabolite concentrations during maturation in different brain regions measured by chemical shift imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bueltmann, Eva; Lanfermann, Heinrich [Hannover Medical School, Institute of Diagnostic and Interventional Neuroradiology, Hannover (Germany); Naegele, Thomas [University of Tuebingen, Department of Diagnostic and Interventional Neuroradiology, Radiological University Hospital, Tuebingen (Germany); Klose, Uwe [University of Tuebingen, Section of Experimental MR of the CNS, Department of Neuroradiology, Radiological University Hospital, Tuebingen (Germany)

    2017-01-15

    We examined the effect of maturation on the regional distribution of brain metabolite concentrations using multivoxel chemical shift imaging. From our pool of pediatric MRI examinations, we retrospectively selected patients showing a normal cerebral MRI scan or no pathologic signal abnormalities at the level of the two-dimensional 1H MRS-CSI sequence and an age-appropriate global neurological development, except for focal neurological deficits. Seventy-one patients (4.5 months-20 years) were identified. Using LC Model, spectra were evaluated from voxels in the white matter, caudate head, and corpus callosum. The concentration of total N-acetylaspartate increased in all regions during infancy and childhood except in the right caudate head where it remained constant. The concentration of total creatine decreased in the caudate nucleus and splenium and minimally in the frontal white matter and genu. It remained largely constant in the parietal white matter. The concentration of choline-containing compounds had the tendency to decrease in all regions except in the parietal white matter where it remained constant. The concentration of myoinositol decreased slightly in the splenium and right frontal white matter, remained constant on the left side and in the caudate nucleus, and rose slightly in the parietal white matter and genu. CSI determined metabolite concentrations in multiple cerebral regions during routine MRI. The obtained data will be helpful in future pediatric CSI measurements deciding whether the ratios of the main metabolites are within the range of normal values or have to be considered as probably pathologic. (orig.)

  4. Changes of brain metabolite concentrations during maturation in different brain regions measured by chemical shift imaging

    International Nuclear Information System (INIS)

    Bueltmann, Eva; Lanfermann, Heinrich; Naegele, Thomas; Klose, Uwe

    2017-01-01

    We examined the effect of maturation on the regional distribution of brain metabolite concentrations using multivoxel chemical shift imaging. From our pool of pediatric MRI examinations, we retrospectively selected patients showing a normal cerebral MRI scan or no pathologic signal abnormalities at the level of the two-dimensional 1H MRS-CSI sequence and an age-appropriate global neurological development, except for focal neurological deficits. Seventy-one patients (4.5 months-20 years) were identified. Using LC Model, spectra were evaluated from voxels in the white matter, caudate head, and corpus callosum. The concentration of total N-acetylaspartate increased in all regions during infancy and childhood except in the right caudate head where it remained constant. The concentration of total creatine decreased in the caudate nucleus and splenium and minimally in the frontal white matter and genu. It remained largely constant in the parietal white matter. The concentration of choline-containing compounds had the tendency to decrease in all regions except in the parietal white matter where it remained constant. The concentration of myoinositol decreased slightly in the splenium and right frontal white matter, remained constant on the left side and in the caudate nucleus, and rose slightly in the parietal white matter and genu. CSI determined metabolite concentrations in multiple cerebral regions during routine MRI. The obtained data will be helpful in future pediatric CSI measurements deciding whether the ratios of the main metabolites are within the range of normal values or have to be considered as probably pathologic. (orig.)

  5. 1H MR chemical shift imaging detection of phenylalanine in patients suffering from phenylketonuria (PKU)

    International Nuclear Information System (INIS)

    Sijens, Paul E.; Oudkerk, Matthijs; Reijngoud, Dirk-Jan; Spronsen, Francjan J. van; Leenders, Klaas L.; Valk, Harold W. de

    2004-01-01

    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 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. 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 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 2 of Phe in brain tissue was 215±120 ms (standard deviation). In the PKU patients the brain tissue Phe concentrations were 141±69 μM as opposed to 58±23 μM 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 2 of 215 ms still is good, while interfering signals from short-TE compounds are negligible. (orig.)

  6. {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.)

  7. Utilization of chemical shift MRI in the diagnosis of disorders affecting pediatric bone marrow

    International Nuclear Information System (INIS)

    Winfeld, Matthew; Ahlawat, Shivani; Safdar, Nabile

    2016-01-01

    MRI signal intensity of pediatric bone marrow can be difficult to interpret using conventional methods. Chemical shift imaging (CSI), which can quantitatively assess relative fat content, may improve the ability to accurately diagnose bone marrow abnormalities in children. Consecutive pelvis and extremity MRI at a children's hospital over three months were retrospectively reviewed for inclusion of CSI. Medical records were reviewed for final pathological and/or clinical diagnosis. Cases were classified as normal or abnormal, and if abnormal, subclassified as marrow-replacing or non-marrow-replacing entities. Regions of interest (ROI) were then drawn on corresponding in and out-of-phase sequences over the marrow abnormality or over a metaphysis and epiphysis in normal studies. Relative signal intensity ratio for each case was then calculated to determine the degree of fat content in the ROI. In all, 241 MRI were reviewed and 105 met inclusion criteria. Of these, 61 had normal marrow, 37 had non-marrow-replacing entities (osteomyelitis without abscess n = 17, trauma n = 9, bone infarction n = 8, inflammatory arthropathy n = 3), and 7 had marrow-replacing entities (malignant neoplasm n = 4, bone cyst n = 1, fibrous dysplasia n = 1, and Langerhans cell histiocytosis n = 1). RSIR averages were: normal metaphyseal marrow 0.442 (0.352-0.533), normal epiphyseal marrow 0.632 (0.566-698), non-marrow-replacing diagnoses 0.715 (0.630-0.799), and marrow-replacing diagnoses 1.06 (0.867-1.26). RSIR for marrow-replacing entities proved significantly different from all other groups (p < 0.05). ROC analysis demonstrated an AUC of 0.89 for RSIR in distinguishing marrow-replacing entities. CSI techniques can help to differentiate pathologic processes that replace marrow in children from those that do not. (orig.)

  8. Relativistic Spin-Orbit Heavy Atom on the Light Atom NMR Chemical Shifts: General Trends Across the Periodic Table Explained.

    Science.gov (United States)

    Vícha, Jan; Komorovsky, Stanislav; Repisky, Michal; Marek, Radek; Straka, Michal

    2018-04-20

    The importance of relativistic effects on the NMR parameters in heavy-atom (HA) compounds, particularly the SO-HALA (Spin-Orbit Heavy Atom on the Light Atom) effect on NMR chemical shifts, has been known for about 40 years. Yet, a general correlation between the electronic-structure and SO-HALA effect have been missing. By analyzing 1H NMR chemical shifts of the 6th-period hydrides (Cs-At) we discovered general electronic-structure principles and mechanisms that dictate the size and sign of the SO-HALA NMR chemical shifts. In brief, partially occupied HA valence shells induce relativistic shielding at the light atom (LA) nuclei, while empty HA valence shells induce relativistic deshielding. In particular, the LA nucleus is relativistically shielded in 5d2-5d8 and 6p4 HA hydrides and deshielded in 4f0, 5d0, 6s0, 6p0 HA hydrides. This general and intuitive concept explains periodic trends in the 1H NMR chemical shifts along the 6th-period hydrides (Cs-At) studied in this work. We present substantial evidence that the introduced principles have a general validity across the periodic table and can be extended to non-hydride LAs. The decades-old question why compounds with occupied frontier π molecular orbitals (MOs) cause SO-HALA shielding at the LA nuclei, while the frontier σ MOs cause deshielding is answered. We further derive connection between the SO-HALA NMR chemical shifts and Spin-Orbit-induced Electron Deformation Density (SO-EDD), a property, which can be obtained easily from differential electron densities and can be represented graphically. SO-EDD provides an intuitive understanding of the SO-HALA effect in terms of the depletion/concentration of the electron density at LA nuclei caused by spin-orbit coupling due to HA in the presence of magnetic field. Using an analogy between SO-EDD concept and arguments from classic NMR theory, the complex question of the SO-HALA NMR chemical shifts becomes easily understandable for a wide chemical audience.

  9. Pressure dependence of side chain 13C chemical shifts in model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    Science.gov (United States)

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

    2017-10-01

    For evaluating the pressure responses of folded as well as intrinsically unfolded proteins detectable by NMR spectroscopy the availability of data from well-defined model systems is indispensable. In this work we report the pressure dependence of 13 C chemical shifts of the side chain atoms in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH 2 (Xxx, one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of a number of nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The size of the polynomial pressure coefficients B 1 and B 2 is dependent on the type of atom and amino acid studied. For H N , N and C α the first order pressure coefficient B 1 is also correlated to the chemical shift at atmospheric pressure. The first and second order pressure coefficients of a given type of carbon atom 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 also are weakly correlated. The downfield shifts of the methyl resonances suggest that gauche conformers of the side chains are not preferred with pressure. The valine and leucine methyl groups in the model peptides were assigned using stereospecifically 13 C enriched amino acids with the pro-R carbons downfield shifted relative to the pro-S carbons.

  10. Hydrophobic clustering in nonnative states of a protein: Interpretation of chemical shifts in NMR spectra of denatured states of lysozyme

    International Nuclear Information System (INIS)

    Evans, P.A.; Topping, K.D.; Woolfson, D.N.; Dobson, C.M.

    1991-01-01

    Chemical shifts of resonances of specific protons in the 1H NMR spectrum of thermally denatured hen lysozyme have been determined by exchange correlation with assigned native state resonances in 2D NOESY spectra obtained under conditions where the two states are interconverting. There are subtle but widespread deviations of the measured shifts from the values which would be anticipated for a random coil; in the case of side chain protons these are virtually all net upfield shifts and it is shown that this may be the averaged effect of interactions with aromatic rings in a partially collapsed denatured state. In a very few cases, notably that of two sequential tryptophan residues, it is possible to interpret these effects in terms of specific, local interresidue interactions. Generally, however, there is no correlation with either native state shift perturbations or with sequence proximity to aromatic groups. Diminution of most of the residual shift perturbations on reduction of the disulfide cross-links confirms that they are not simply effects of residues adjacent in the sequence. Similar effects of chemical denaturants, with the disulfides intact, demonstrate that the shift perturbations reflect an enhanced tendency to side chain clustering in the thermally denatured state. The temperature dependences of the shift perturbations suggest that this clustering is noncooperative and is driven by small, favorable enthalpy changes. While the extent of conformational averaging is clearly much greater than that observed for a homologous protein, alpha-lactalbumin, in its partially folded molten globule state, the results clearly show that thermally denatured lysozyme differs substantially from a random coil, principally in that it is partially hydrophobically collapsed

  11. Conformational response of the phosphatidylcholine headgroup to bilayer surface charge: torsion angle constraints from dipolar and quadrupolar couplings in bicelles.

    Science.gov (United States)

    Semchyschyn, Darlene J; Macdonald, Peter M

    2004-02-01

    The effects of bilayer surface charge on the conformation of the phosphocholine group of phosphatidylcholine were investigated using a torsion angle analysis of quadrupolar and dipolar splittings in, respectively, (2)H and (13)C NMR spectra of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) labelled in the phosphocholine group with either deuterons (POPC-alpha-d(2), POPC-beta-d(2) and POPC-gamma-d(9)) or carbon-13 (POPC-alpha-(13)C and POPC-alphabeta-(13)C(2)) and incorporated into magnetically aligned bicelles containing various amounts of either the cationic amphiphile 1,2-dimyristoyl-3-trimethylammoniumpropane (DMTAP) or the anionic amphiphile 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG). Three sets of quadrupolar splittings, one from each of the three deuteron labelling positions, and three sets of dipolar splittings ((13)C(alpha)-(31)P, (13)C(alpha)-(13)C(beta), (13)C(beta)-(14)N), were measured at each surface charge, along with the (31)P residual chemical shift anisotropy. The torsion angle analysis assumed fast anisotropic rotation of POPC about its long molecular axis, thus projecting all NMR interactions onto that director axis of motion. Dipolar, quadrupolar and chemical shift anisotropies were calculated as a function of the phosphocholine internal torsion angles by first transforming into a common reference frame affixed to the phosphocholine group prior to motional averaging about the director axis. A comparison of experiment and calculation provided the two order parameters specifying the director orientation relative to the molecule, plus the torsion angles alpha(3), alpha(4) and alpha(5). Surface charge was found to have little effect on the torsion angle alpha(5) (rotations about C(alpha)-C(beta)), but to have large and inverse effects on torsion angles alpha(3) [rotations about P-O(11)] and alpha(4) [rotations about O(11)-C(alpha)], yielding a net upwards tilt of the P-N vector in the presence of cationic surface charge, and a

  12. Vanadium NMR Chemical Shifts of (Imido)vanadium(V) Dichloride Complexes with Imidazolin-2-iminato and Imidazolidin-2-iminato Ligands: Cooperation with Quantum-Chemical Calculations and Multiple Linear Regression Analyses.

    Science.gov (United States)

    Yi, Jun; Yang, Wenhong; Sun, Wen-Hua; Nomura, Kotohiro; Hada, Masahiko

    2017-11-30

    The NMR chemical shifts of vanadium ( 51 V) in (imido)vanadium(V) dichloride complexes with imidazolin-2-iminato and imidazolidin-2-iminato ligands were calculated by the density functional theory (DFT) method with GIAO. The calculated 51 V NMR chemical shifts were analyzed by the multiple linear regression (MLR) analysis (MLRA) method with a series of calculated molecular properties. Some of calculated NMR chemical shifts were incorrect using the optimized molecular geometries of the X-ray structures. After the global minimum geometries of all of the molecules were determined, the trend of the observed chemical shifts was well reproduced by the present DFT method. The MLRA method was performed to investigate the correlation between the 51 V NMR chemical shift and the natural charge, band energy gap, and Wiberg bond index of the V═N bond. The 51 V NMR chemical shifts obtained with the present MLR model were well reproduced with a correlation coefficient of 0.97.

  13. Torsional Rigidity of Minimal Submanifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, Vicente

    2006-01-01

    We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...

  14. Proton Chemical Shift Imaging of the Brain in Pediatric and Adult Developmental Stuttering.

    Science.gov (United States)

    O'Neill, Joseph; Dong, Zhengchao; Bansal, Ravi; Ivanov, Iliyan; Hao, Xuejun; Desai, Jay; Pozzi, Elena; Peterson, Bradley S

    2017-01-01

    Developmental stuttering is a neuropsychiatric condition of incompletely understood brain origin. Our recent functional magnetic resonance imaging study indicates a possible partial basis of stuttering in circuits enacting self-regulation of motor activity, attention, and emotion. To further characterize the neurophysiology of stuttering through in vivo assay of neurometabolites in suspect brain regions. Proton chemical shift imaging of the brain was performed in a case-control study of children and adults with and without stuttering. Recruitment, assessment, and magnetic resonance imaging were performed in an academic research setting. Ratios of N-acetyl-aspartate plus N-acetyl-aspartyl-glutamate (NAA) to creatine (Cr) and choline compounds (Cho) to Cr in widespread cerebral cortical, white matter, and subcortical regions were analyzed using region of interest and data-driven voxel-based approaches. Forty-seven children and adolescents aged 5 to 17 years (22 with stuttering and 25 without) and 47 adults aged 21 to 51 years (20 with stuttering and 27 without) were recruited between June 2008 and March 2013. The mean (SD) ages of those in the stuttering and control groups were 12.2 (4.2) years and 13.4 (3.2) years, respectively, for the pediatric cohort and 31.4 (7.5) years and 30.5 (9.9) years, respectively, for the adult cohort. Region of interest-based findings included lower group mean NAA:Cr ratio in stuttering than nonstuttering participants in the right inferior frontal cortex (-7.3%; P = .02), inferior frontal white matter (-11.4%; P stuttering sample included higher NAA:Cr and Cho:Cr ratios (regression coefficient, 197.4-275; P stuttering severity (r = 0.40-0.52; P = .001-.02). This spectroscopy study of stuttering demonstrates brainwide neurometabolite alterations, including several regions implicated by other neuroimaging modalities. Prior ascription of a role in stuttering to inferior frontal and superior temporal gyri, caudate, and other

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

    Energy Technology Data Exchange (ETDEWEB)

    Gokalp, Gokhan; Mutlu, Fatma Senturk; Yazici, Zeynep; Yildirim, Nalan [Uludag University Medical Faculty, Department of Radiology, Gorukle, Bursa (Turkey)

    2011-05-15

    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

  16. Calculation of the NMR chemical shift for a 4d1 system in a strong crystal field environment of trigonal symmetry with a threefold axis of quantization

    International Nuclear Information System (INIS)

    Ahn, Sang Woon; Oh, Se Woung; Ro, Seung Woo

    1986-01-01

    The NMR chemical shift arising from 4d electron angular momentum and 4d electron angular momentum and 4d electron spin dipolar-nuclear spin angular momentum interactions for a 4d 1 system in a strong crystal field environment of trigonal symmetry, where the threefold axis is chosen to be the axis of quantization axis, has been examined. A general expression using the nonmultipole expansion method (exact method) is derived for the NMR chemical shift. From this expression all the multipolar terms are determined. we observe that along the (100), (010), (110), and (111) axes the NMR chemical shifts are positive while along the (001) axis, it is negative. We observe that the dipolar term (1/R 3 ) is the dominant contribution to the NMR chemical shift except for along the (111) axis. A comparison of the multipolar terms with the exact values shows also that the multipolar results are exactly in agreement with the exact values around R≥0.2 nm. The temperature dependence analysis on the NMR chemical shifts may imply that along the (111) axis the contribution to the NMR chemical shift is dominantly pseudo contact interaction. Separation of the contributions of the Fermi and the pseudo contact interactions would correctly imply that the dipolar interaction is the dominant contribution to the NMR chemical shifts along the (100), (010), (001), and (110) axes, but along the (111) axis the Fermi contact interaction is incorrectly the dominant contribution to the NMR chemical shift. (Author)

  17. Backbone chemical shifts assignments, secondary structure, and ligand binding of a family GH-19 chitinase from moss, Bryum coronatum.

    Science.gov (United States)

    Shinya, Shoko; Nagata, Takuya; Ohnuma, Takayuki; Taira, Toki; Nishimura, Shigenori; Fukamizo, Tamo

    2012-10-01

    Family GH19 chitinases have been recognized as important in the plant defense against fungal pathogens. However, their substrate-recognition mechanism is still unknown. We report here the first resonance assignment of NMR spectrum of a GH19 chitinase from moss, Bryum coronatum (BcChi-A). The backbone signals were nearly completely assigned, and the secondary structure was estimated based on the chemical shift values. The addition of the chitin dimer to the enzyme solution perturbed the chemical shifts of HSQC resonances of the amino acid residues forming the putative substrate-binding cleft. Further NMR analysis of the ligand binding to BcChi-A will improve understanding of the substrate-recognition mechanism of GH-19 enzymes.

  18. Studies of 17 0 NMR chemical shift effects of the structural relationships of charge distributions on substituted ketones

    International Nuclear Information System (INIS)

    Leal, Katia Z.; Malvestiti, Ivani; Battiste, Merle A.

    1995-01-01

    Oxygen-17 NMR spectroscopy data, at natural abundance, in acetonitirle were obtained for a series of methyl alkyl ketones and alkyl-carboxylic acids in order to study substituent induced electronic effects on the carbonyl group. The trend in chemical shifts for the relatively unhindered ketones is a general increase shielding with increasing size of the alkyl group; however an steric chrownding becomes significant marked deshielding is observed and attributed to sterically induced depolarization of the C-O bond. Ionization potentials and net atomic charges for the methyl ketones and carboxylic acids are estimated using the MOPAC program and compared with those for substituted cyclohexanones, bicyclo-[2,2,2]-2-octanones. The 17 O - chemical shifts for some strined bridgehead methyl ketones are estimated from a correlation with 13 C - N.M.R. values for the carbonyl carbon. (author)

  19. New fat suppression method with no pre-saturation pulse. WCHASE (water chemical-shift selective excitation)

    International Nuclear Information System (INIS)

    Tokunaga, Yu; Miyazaki, Mitsue; Machida, Yoshio; Takai, Hiroshi; Kojima, Fumitoshi

    1998-01-01

    A new fat suppression method with no pre-saturation pulse, water chemical-shift selective excitation (WCHASE), was developed. The characteristic feature of WCHASE is as follows. First, narrowing the frequency bandwidth of the 90deg RF pulse to chemical shift between water and fat signals, about 230 Hz in 1.5 T. Next, the ratio of slice gradient amplitudes for 90deg and 180deg. RF pulses are optimized in order to eliminate fat components from all slices. Prior to the experiment, a brief phase map shimming was performed to adjust B 0 field inhomogeneity using first order gradients. The WCHASE technique was compared with CHESS and conventional spin echo without fat suppression on the brain of healthy volunteers. The experimental results showed better fat suppression effect with WCHASE compared to CHESS. (author)

  20. Development of 19F-NMR chemical shift detection of DNA B-Z equilibrium using 19F-NMR.

    Science.gov (United States)

    Nakamura, S; Yang, H; Hirata, C; Kersaudy, F; Fujimoto, K

    2017-06-28

    Various DNA conformational changes are in correlation with biological events. In particular, DNA B-Z equilibrium showed a high correlation with translation and transcription. In this study, we developed a DNA probe containing 5-trifluoromethylcytidine or 5-trifluoromethylthymidine to detect DNA B-Z equilibrium using 19 F-NMR. Its probe enabled the quantitative detection of B-, Z-, and ss-DNA based on 19 F-NMR chemical shift change.

  1. Towards the versatile DFT and MP2 computational schemes for 31P NMR chemical shifts taking into account relativistic corrections.

    Science.gov (United States)

    Fedorov, Sergey V; Rusakov, Yury Yu; Krivdin, Leonid B

    2014-11-01

    The main factors affecting the accuracy and computational cost of the calculation of (31)P NMR chemical shifts in the representative series of organophosphorous compounds are examined at the density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2) levels. At the DFT level, the best functionals for the calculation of (31)P NMR chemical shifts are those of Keal and Tozer, KT2 and KT3. Both at the DFT and MP2 levels, the most reliable basis sets are those of Jensen, pcS-2 or larger, and those of Pople, 6-311G(d,p) or larger. The reliable basis sets of Dunning's family are those of at least penta-zeta quality that precludes their practical consideration. An encouraging finding is that basically, the locally dense basis set approach resulting in a dramatic decrease in computational cost is justified in the calculation of (31)P NMR chemical shifts within the 1-2-ppm error. Relativistic corrections to (31)P NMR absolute shielding constants are of major importance reaching about 20-30 ppm (ca 7%) improving (not worsening!) the agreement of calculation with experiment. Further better agreement with the experiment by 1-2 ppm can be obtained by taking into account solvent effects within the integral equation formalism polarizable continuum model solvation scheme. We recommend the GIAO-DFT-KT2/pcS-3//pcS-2 scheme with relativistic corrections and solvent effects taken into account as the most versatile computational scheme for the calculation of (31)P NMR chemical shifts characterized by a mean absolute error of ca 9 ppm in the range of 550 ppm. Copyright © 2014 John Wiley & Sons, Ltd.

  2. The observed and calculated 1H and 13C chemical shifts of tertiary amines and their N-oxides

    Czech Academy of Sciences Publication Activity Database

    Pohl, Radek; Dračínský, Martin; Slavětínská, Lenka; Buděšínský, Miloš

    2011-01-01

    Roč. 49, č. 6 (2011), s. 320-327 ISSN 0749-1581 R&D Projects: GA ČR GA203/09/1919 Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR * 1H * 13C * in situ oxidation of tertiary amines * calculated chemical shifts * HF * MP2 * DFT Subject RIV: CC - Organic Chemistry Impact factor: 1.437, year: 2011

  3. Assessment of whole spine vertebral bone marrow fat using chemical shift-encoding based water-fat MRI.

    Science.gov (United States)

    Baum, Thomas; Yap, Samuel P; Dieckmeyer, Michael; Ruschke, Stefan; Eggers, Holger; Kooijman, Hendrik; Rummeny, Ernst J; Bauer, Jan S; Karampinos, Dimitrios C

    2015-10-01

    The assessment of bone marrow composition has recently gained significant attention due to its association with bone loss pathophysiology and cancer therapy-induced bone marrow damage. The purpose of our study was to investigate the anatomical variation of the vertebral bone marrow fat using chemical shift-encoding based water-fat MRI and to assess the repeatability of these measurements. Chemical shift-encoding based water-fat MRI of the whole spine was performed in 28 young, healthy subjects (17 males, 11 females, 26 ± 4 years). Six subjects were scanned three times with repositioning to assess the repeatability of these measurements. Proton density fat fraction (PDFF) maps were computed and manually segmented to obtain PDFF of C3-L5. Mean PDFF of all subjects significantly increased from C3 to L5 (P vertebral bone marrow fat could be reproducibly assessed by using chemical shift-encoding based water-fat MRI and showed anatomical variations. © 2015 Wiley Periodicals, Inc.

  4. 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.

  5. Derivation of 13C chemical shift surfaces for the anomeric carbons of oligosaccharides and glycopeptides using ab initio methodology

    Energy Technology Data Exchange (ETDEWEB)

    Swalina, Chet W.; Zauhar, Randy J.; DeGrazia, Michael J.; Moyna, Guillermo [University of the Sciences in Philadelphia, Department of Chemistry and Biochemistry (United States)

    2001-09-15

    The dependence between the anomeric carbon chemical shift and the glycosidic bond < {phi}, {psi}> dihedral angles in oligosaccharide and glycopeptide model compounds was studied by Gauge-Including Atomic Orbital (GIAO) ab initio calculations. Complete chemical shift surfaces versus {phi} and {psi} for d-Glcp-d-Glcp disaccharides with (1{sup {yields}}1), (1{sup {yields}}2), (1{sup {yields}}3), and (1{sup {yields}}4) linkages in both {alpha}- and {beta}-configurations were computed using a 3-21G basis set, and scaled to reference results from calculations at the 6-311G** level of theory. Similar surfaces were obtained for GlcNAcThr and GlcNAcSer model glycopeptides in {alpha}- and {beta}-configurations, using in this case different conformations for the peptide moiety. The results obtained for both families of model compounds are discussed. We also present the determination of empirical formulas of the form {sup 13}C{delta}=f({phi},{psi}) obtained by fitting the raw ab initio data to trigonometric series expansions suitable for use in molecular mechanics and dynamics simulations. Our investigations are consistent with experimental observations and earlier calculations performed on smaller glycosidic bond models, and show the applicability of chemical shift surfaces in the study of the conformational behavior of oligosaccharides and glycopeptides.

  6. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Tensile mechanical behavior of hollow and filled carbon nanotubes under tension or combined tension-torsion

    Science.gov (United States)

    Jeong, Byeong-Woo; Lim, Jang-Keun; Sinnott, Susan B.

    2007-01-01

    The tensile mechanical behavior of hollow and filled single-walled carbon nanotubes under tension or combined tension-torsion is examined using classical molecular dynamics simulations. These simulations indicate that the tensile strength under combined tension-torsion can be increased by filling the carbon nanotubes, and the amount of this increase depends on the kind of filling material. They also predict that the tensile strength under combined tension-torsion decreases linearly under applied torsion. The tensile strength can be modified by adjusting the system temperature and through chemical functionalization to the carbon nanotube walls.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wu Zhengrong; Delaglio, Frank [National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Chemical Physics (United States); Tjandra, Nico [National Heart, Lung and Blood Institute, National Cancer Institute, National Institutes of Health, Laboratory of Biophysical Chemistry (United States); Zhurkin, Victor B. [National Cancer Institute, National Institutes of Health, Laboratory of Experimental and Computational Biology (United States); Bax, Ad [National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Chemical Physics (United States)

    2003-08-15

    The solution structure of d(CGCGAATTCGCG){sub 2} has been determined on the basis of an exceptionally large set of residual dipolar couplings. In addition to the heteronuclear {sup 13}C-{sup 1}H and {sup 15}N-{sup 1}H and qualitative homonuclear {sup 1}H-{sup 1}H dipolar couplings, previously measured in bicelle medium, more than 300 quantitative {sup 1}H-{sup 1}H and 22 {sup 31}P-{sup 1}H dipolar restraints were obtained in liquid crystalline Pf1 medium, and 22 {sup 31}P 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 {sup 13}C-{sup 1}H and {sup 15}N-{sup 1}H dipolar couplings. In the newly calculated structures, {sup 31}P-{sup 1}H dipolar and {sup 3}JsubH3{sup '}Psub couplings and {sup 31}P CSA data restrain the phosphodiester backbone torsion angles. The final structure represents a quite regular B-form helix with a modest bending of {approx}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{sup '}-endo and C3{sup '}-endo deoxyribose puckers (sugar switching). The C2{sup '}-H2{sup '}/H2{sup ''} 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 J{sub HH} couplings, with a population of the minor C3{sup '}-endo form higher for

  9. Ovarian torsion: Echographic discoveries

    International Nuclear Information System (INIS)

    Triana R, Gustavo; Navas O, Claudia

    1994-01-01

    Patient of 31 years who consulted to the even service of urgencies to present of two hours of evolution intense pain in flank and region lumbar left, associated to vomit, present square similar 5 previous days to the entrance in the right side. Go Po, plans with DIU FUR, 8 previous days to the square. It is practiced Tran abdominal pelvic echography that shows left ovary of 6 x 5 x 3 cms, with multiple follicular images, of thick walls, with I liquidate free abdominal, highly suggestive of ovarian torsion although the patient didn't present square of sharp abdomen. It decides to suspend analgesic and to value it, presented sharp abdominal pain, reason why laparotomy was practiced, finding mass of 6 x 6 cms. of necrotic aspect, corresponding to the left ovary, which presented three turns on their axis. It is taken finish left salpingooferectomy

  10. Re-torsion of the ovaries

    DEFF Research Database (Denmark)

    Hyttel, Trine E W; Bak, Geske S; Larsen, Solveig B

    2015-01-01

    The increasing use of de-torsion of the ovaries may result in re-torsion. This review addresses risk of re-torsion and describes preventive strategies to avoid re-torsion in pre-menarcheal girls, and fertile and pregnant women. We clinically reviewed PubMed, Embase, Trip and Cochrane databases...

  11. Spin and torsion in gravitation

    CERN Document Server

    De Sabbata, Venzo

    1994-01-01

    This book gives an exposition of both the old and new results of spin and torsion effects on gravitational interactions with implications for particle physics, cosmology etc. Physical aspects are stressed and measurable effects in relation to other areas of physics are discussed.Among the topics discussed are: alternative ways of unifying gravity with electroweak and strong interactions by an energy dependent spin torsion coupling constant; the idea that all interactions can be understood as originating from spin curvature coupling; the possibility of cosmological models with torsion providing

  12. Torsion testing of bed joints

    DEFF Research Database (Denmark)

    Hansen, Klavs Feilberg; Pedersen, Carsten Mørk

    2008-01-01

    be carried out directly in a normal testing machine. The torsion strength is believed to be the most important parameter in out-of-plane resistance of masonry walls subjected to bending about an axis perpendicular to the bed joints. The paper also contains a few test results from bending of small walls about...... an axis perpendicular to the bed joints, which indicate the close connection between these results and results from torsion tests. These characteristics make the torsion strength well suited to act as substitute parameter for the bending strength of masonry about an axis perpendicular to the bed joints....

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

    NARCIS (Netherlands)

    L.N. van Wassenhove (Luk); B. Lebreton (Baptiste); P. 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

  14. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    ... 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.

  15. Thalassiosira spp. community composition shifts in response to chemical and physical forcing in the northeast Pacific Ocean.

    Directory of Open Access Journals (Sweden)

    Phoebe Dreux Chappell

    2013-09-01

    Full Text Available Diatoms are genetically diverse unicellular photosynthetic eukaryotes that are key primary producers in the ocean. Many of the over 100 extant diatom species in the cosmopolitan genus Thalassiosira are difficult to distinguish in mixed populations using light microscopy. Here we examine shifts in Thalassiosira spp. composition along a coastal to open ocean transect that encountered a three-month-old Haida eddy in the northeast Pacific Ocean. To quantify shifts in Thalassiosira species composition, we developed a targeted automated ribosomal intergenic spacer analysis (ARISA method to identify Thalassiosira spp. in environmental samples. As many specific fragment lengths are indicative of individual Thalassiosira spp., the ARISA method is a useful screening tool to identify changes in the relative abundance and distribution of specific species. The method also enabled us to assess changes in Thalassiosira community composition in response to chemical and physical forcing. Thalassiosira spp. community composition in the core of a three-month-old Haida eddy remained largely (>80% similar over a two-week period, despite moving 24 km southwestward. Shifts in Thalassiosira species correlated with changes in dissolved iron (Fe and temperature throughout the sampling period. Simultaneously tracking community composition and relative abundance of Thalassiosira species within the physical and chemical context they occurred allowed us to identify quantitative linkages between environmental conditions and community response.

  16. Constraining spacetime torsion with LAGEOS

    Science.gov (United States)

    March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone

    2011-11-01

    We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We analyze the motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. In the cases of autoparallel and extremal trajectories, we derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of Celestial Mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters.

  17. Variations of retinal nerve fiber layer thickness and ganglion cell-inner plexiform layer thickness according to the torsion direction of optic disc.

    Science.gov (United States)

    Lee, Kang Hoon; Kim, Chan Yun; Kim, Na Rae

    2014-02-20

    To examine the relationship between the optic disc torsion and peripapillary retinal nerve fiber layer (RNFL) thickness through a comparison with the macular ganglion cell inner plexiform layer complex (GCIPL) thickness measured by Cirrus optical coherence tomography (OCT). Ninety-four eyes of 94 subjects with optic disc torsion and 114 eyes of 114 subjects without optic disc torsion were enrolled prospectively. The participants underwent fundus photography and OCT imaging in peripapillary RNFL mode and macular GCIPL mode. The participants were divided into groups according to the presence or absence of optic disc torsion. The eyes with optic disc torsion were further divided into supranasal torsion and inferotemporal torsion groups according to the direction of optic disc torsion. The mean RNFL and GCIPL thicknesses for the quadrants and subsectors were compared. The superior and inferior peak locations of the RNFL were also measured according to the torsion direction. The temporal RNFL thickness was significantly thicker in inferotemporal torsion, whereas the GCIPL thickness at all segments was unaffected. The inferotemporal optic torsion had more temporally positioned superior peak locations of the RNFL than the nontorsion and supranasal-torted optic disc. Thickening of the temporal RNFL with a temporal shift in the superior peak within the eyes with inferotemporal optic disc torsion can lead to interpretation errors. The ganglion cell analysis algorithm can assist in differentiating eyes with optic disc torsion.

  18. 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.

  19. Bidirectional shifts of TRPM8 channel gating by temperature and chemical agents modulate the cold sensitivity of mammalian thermoreceptors.

    Science.gov (United States)

    Mälkiä, Annika; Madrid, Rodolfo; Meseguer, Victor; de la Peña, Elvira; Valero, María; Belmonte, Carlos; Viana, Félix

    2007-05-15

    TRPM8, a member of the melastatin subfamily of transient receptor potential (TRP) cation channels, is activated by voltage, low temperatures and cooling compounds. These properties and its restricted expression to small sensory neurons have made it the ion channel with the most advocated role in cold transduction. Recent work suggests that activation of TRPM8 by cold and menthol takes place through shifts in its voltage-activation curve, which cause the channel to open at physiological membrane potentials. By contrast, little is known about the actions of inhibitors on the function of TRPM8. We investigated the chemical and thermal modulation of TRPM8 in transfected HEK293 cells and in cold-sensitive primary sensory neurons. We show that cold-evoked TRPM8 responses are effectively suppressed by inhibitor compounds SKF96365, 4-(3-chloro-pyridin-2-yl)-piperazine-1-carboxylic acid (4-tert-butyl-phenyl)-amide (BCTC) and 1,10-phenanthroline. These antagonists exert their effect by shifting the voltage dependence of TRPM8 activation towards more positive potentials. An opposite shift towards more negative potentials is achieved by the agonist menthol. Functionally, the bidirectional shift in channel gating translates into a change in the apparent temperature threshold of TRPM8-expressing cells. Accordingly, in the presence of the antagonist compounds, the apparent response-threshold temperature of TRPM8 is displaced towards colder temperatures, whereas menthol sensitizes the response, shifting the threshold in the opposite direction. Co-application of agonists and antagonists produces predictable cancellation of these effects, suggesting the convergence on a common molecular process. The potential for half maximal activation of TRPM8 activation by cold was approximately 140 mV more negative in native channels compared to recombinant channels, with a much higher open probability at negative membrane potentials in the former. In functional terms, this difference translates

  20. Chemical Shift Artifact on Steady-State MRI Sequences for Detection of Vesical Wall Invasion in Placenta Percreta.

    Science.gov (United States)

    Kumar, Ishan; Verma, Ashish; Jain, Shivi; Jain, Madhu; Shukla, R C; Srivastava, Arvind

    2016-04-01

    Antenatal diagnosis of the invasiveness of a placenta percreta helps in planning the surgical approach, reducing blood loss and morbidity. Doppler sonography is the mainstay diagnostic modality with a sensitivity of 80-95 %. With the advent of high magnetic field MRI techniques, there has been recent interest in evaluation of placenta by MRI. On an extensive PUBMED search, we could not find any citations describing imaging, ultrasound, or MRI features to evaluate vesical wall invasion by placenta percreta. We attempt to evaluate transmyometrial vesical wall invasion by placenta percreta using chemical shift artifact as a marker of intact bladder-myometrial interface on steady-state MRI sequences. This is a prospective observational study, conducted at a university hospital. We have compiled clinico-radiological criteria for diagnosis of invasive placentae based on the existing body of evidences, in four patients. We further go on to analyze a specific proposed sign on a newly introduced MR imaging sequence i.e., loss of chemical shift artifact (India ink line) on steady-state GRE sequence (TrueFISP), to diagnose transmyometrial vesical invasion in placenta percreta. Though the sample size is small, the sensitivity, specificity, positive, and negative predictive value of the proposed sign for the purpose was 100 %. Loss of chemical shift artifact (India ink line) on steady-state GRE sequences at the vesico-myometrial junction in case of invasive placentae confirms vesical wall invasion, a prospective diagnoses of which can help in planning the surgical protocol and preventing potentially fatal blood loss.

  1. 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

    compared to single voxel methods. In the present study, the optimal voxel size is calculated from segmented human brain data and accompanying field maps. The optimal voxel size is found to be approximately 8 cc, but a wide range of values, 4-64 cc, can be chosen with little increase in estimated......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...

  2. Folding of small proteins by Monte Carlo simulations with chemical shift restraints without the use of molecular fragment replacement or structural homology.

    Science.gov (United States)

    Robustelli, Paul; Cavalli, Andrea; Dobson, Christopher M; Vendruscolo, Michele; Salvatella, Xavier

    2009-06-04

    It has recently been shown that protein structures can be determined from nuclear magnetic resonance (NMR) chemical shifts using a molecular fragment replacement strategy. In these approaches, structural motifs are selected from existing protein structures on the basis of chemical shift and sequence homology and assembled to generate new structures. Here, we demonstrate that it is also possible to determine structures of proteins by directly incorporating experimental NMR chemical shifts as structural restraints in conformational searches, without the use of structural homology and molecular fragment replacement. In this approach, a protein is folded from an extended conformation to its native state using a simulated annealing procedure that minimizes an energy function that combines a standard force field with a term that penalizes the differences between experimental and calculated chemical shifts. We provide an initial demonstration of this procedure by determining the structure of two small proteins, with alpha and beta folds, respectively.

  3. Chemical shift of U L3 edges in different uranium compounds ...

    Indian Academy of Sciences (India)

    Administrator

    same oxidation state of the metal ion, its X-ray absorption edge may appear at different energies in different materi- als, depending on the nature of ligands attached to the metal ion, coordination number, covalent character of the bond, electronegativity of the anion or in other words the chemical environment of the metal ion.

  4. Chemical shift of neutron resonances and some ideas on neutron resonances and scattering theory

    International Nuclear Information System (INIS)

    Ignatovich, V.K.; )

    2002-01-01

    The dependence of positions of neutron resonances in nuclei in condensed matter on chemical environment is considered. A possibility of theoretical description of neutron resonances, different from R-matrix theory is investigated. Some contradictions of standard scattering theory are discussed and a new approach without these contradictions is formulated [ru

  5. NMR chemical shift and J coupling parameterization and quantum mechanical reference spectrum simulation for selected nerve agent degradation products in aqueous conditions.

    Science.gov (United States)

    Koskela, Harri; Anđelković, Boban

    2017-10-01

    The spectral parameters of selected nerve agent degradation products relevant to the Chemical Weapons Convention, namely, ethyl methylphosphonate, isopropyl methylphosphonate, pinacolyl methylphosphonate and methylphosphonic acid, were studied in wide range of pH conditions and selected temperatures. The pH and temperature dependence of chemical shifts and J couplings was parameterized using Henderson-Hasselbalch-based functions. The obtained parameters allowed calculation of precise chemical shifts and J coupling constants in arbitrary pH conditions and typical measurement temperatures, thus facilitating quantum mechanical simulation of reference spectra in the chosen magnetic field strength for chemical verification. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Velocity encoding with the slice select refocusing gradient for faster imaging and reduced chemical shift-induced phase errors.

    Science.gov (United States)

    Middione, Matthew J; Thompson, Richard B; Ennis, Daniel B

    2014-06-01

    To investigate a novel phase-contrast MRI velocity-encoding technique for faster imaging and reduced chemical shift-induced phase errors. Velocity encoding with the slice select refocusing gradient achieves the target gradient moment by time shifting the refocusing gradient, which enables the use of the minimum in-phase echo time (TE) for faster imaging and reduced chemical shift-induced phase errors. Net forward flow was compared in 10 healthy subjects (N = 10) within the ascending aorta (aAo), main pulmonary artery (PA), and right/left pulmonary arteries (RPA/LPA) using conventional flow compensated and flow encoded (401 Hz/px and TE = 3.08 ms) and slice select refocused gradient velocity encoding (814 Hz/px and TE = 2.46 ms) at 3 T. Improved net forward flow agreement was measured across all vessels for slice select refocused gradient compared to flow compensated and flow encoded: aAo vs. PA (1.7% ± 1.9% vs. 5.8% ± 2.8%, P = 0.002), aAo vs. RPA + LPA (2.1% ± 1.7% vs. 6.0% ± 4.3%, P = 0.03), and PA vs. RPA + LPA (2.9% ± 2.1% vs. 6.1% ± 6.3%, P = 0.04), while increasing temporal resolution (35%) and signal-to-noise ratio (33%). Slice select refocused gradient phase-contrast MRI with a high receiver bandwidth and minimum in-phase TE provides more accurate and less variable flow measurements through the reduction of chemical shift-induced phase errors and a reduced TE/repetition time, which can be used to increase the temporal/spatial resolution and/or reduce breath hold durations. Copyright © 2013 Wiley Periodicals, Inc.

  7. SHIFTING WEED COMPOSITIONS AND BIOMASS PRODUCTION IN SWEET CORN FIELD TREATED WITH ORGANIC COMPOSTS AND CHEMICAL WEED CONTROLS

    Directory of Open Access Journals (Sweden)

    Marulak Simarmata

    2015-10-01

    Full Text Available The objectives of the research were to study the shift of weed compositions in sweet corn field treated with organic compost and chemical weed controls and to compare the effect of treatment combinations on weed growth, weed biomass and sweet corn biomass. The research was conducted in Bengkulu, Indonesia, from April to July 2014. Results showed that the number of weed species decreased after the trials from 14 to 13. There was a shift in weed compositions because 5 species of weeds did not emerge after the trials, but 4 new species were found. Chemical weed control used a herbiside mixture of atrazine and mesotrione applied during postemergence was the most effective method to control weeds, which was observed on decreased weed emergence and weed biomass down to 22.33 and 25.00 percent of control, respectively. Subsequently, biomass production of sweet corn increased up to 195.64 percent at the same trials. Biomass of weeds and sweet corn were also affected by the organic composts. Weed biomass was inhibited by treatment of composted empty fruith bunches of oil palm, whereas significantly increased of sweet corn biomass were observed in the plots of organic manure.

  8. Heat Integration of the Water-Gas Shift Reaction System for Carbon Sequestration Ready IGCC Process with Chemical Looping

    Energy Technology Data Exchange (ETDEWEB)

    Juan M. Salazara; Stephen E. Zitney; Urmila M. Diwekara

    2010-01-01

    Integrated gasification combined cycle (IGCC) technology has been considered as an important alternative for efficient power systems that can reduce fuel consumption and CO2 emissions. One of the technological schemes combines water-gas shift reaction and chemical-looping combustion as post gasification techniques in order to produce sequestration-ready CO2 and potentially reduce the size of the gas turbine. However, these schemes have not been energetically integrated and process synthesis techniques can be applied to obtain an optimal flowsheet. This work studies the heat exchange network synthesis (HENS) for the water-gas shift reaction train employing a set of alternative designs provided by Aspen energy analyzer (AEA) and combined in a process superstructure that was simulated in Aspen Plus (AP). This approach allows a rigorous evaluation of the alternative designs and their combinations avoiding all the AEA simplifications (linearized models of heat exchangers). A CAPE-OPEN compliant capability which makes use of a MINLP algorithm for sequential modular simulators was employed to obtain a heat exchange network that provided a cost of energy that was 27% lower than the base case. Highly influential parameters for the pos gasification technologies (i.e. CO/steam ratio, gasifier temperature and pressure) were calculated to obtain the minimum cost of energy while chemical looping parameters (oxidation and reduction temperature) were ensured to be satisfied.

  9. NMR Chemical Shift of a Helium Atom as a Probe for Electronic Structure of FH, F-, (FHF)-, and FH2.

    Science.gov (United States)

    Tupikina, E Yu; Efimova, A A; Denisov, G S; Tolstoy, P M

    2017-12-21

    In this work, we present the first results of outer electronic shell visualization by using a 3 He atom as a probe particle. As model objects we have chosen F - , FH, and FH 2 + species, as well as the hydrogen-bonded complex FH···F - at various H···F - distances (3.0, 2.5, 2.0, and 1.5 Å and equilibrium at ca. 1.14 Å). The interaction energy of investigated objects with helium atom (CCSD/aug-cc-pVTZ) and helium atom chemical shift (B3LYP/pcS-2) surfaces were calculated, and their topological analysis was performed. For comparison, the results of standard quantum mechanical approaches to electronic shell visualization were presented (ESP, ELF, ED, ∇ 2 ED). We show that the Laplacian of helium chemical shift, ∇ 2 δ He , is sensitive to fluorine atom lone pair localization regions, and it can be used for the visualization of the outer electronic shell, which could be used to evaluate the proton accepting ability. The sensitivity of ∇ 2 δ He to lone pairs is preserved at distances as large as 2.0-2.5 Å from the fluorine nucleus (in comparison with the distance to ESP minima, located at 1.0-1.5 Å or maxima of ELF, which are as close as 0.6 Å to the fluorine nucleus).

  10. Localized in vivo 1H spectroscopy and chemical shift imaging of the bone marrow in leukemic patients

    International Nuclear Information System (INIS)

    Bongers, H.; Schick, F.; Skalej, M.; Jung, W.I.; Einsele, H.

    1992-01-01

    Six healthy volunteers, ten patients with acute leukemia, one patient with hypersplenia and two with bone marrow carcinosis were studied. Nine patients with leukemia were restudied during chemotherapy. A double spin echo localization method, implemented on a 1.5 T whole body unit was used for 1 H magnetic resonance spectroscopy (MRS). A cubic (13 mm) 3 voxel was chosen in a midlumbar vertebra. For chemical shift imaging (CSI) the SENEX sequence was used. We recorded fat and water images in a representative midsagittal plane. Patients with acute leukemia and hypercellular bone marrow showed a severe reduction or loss of the bone marrow fat signal and an increased water signal. Water T1 increased during therapy in three patients. The bone marrow fat reappeared in the spectra and chemical shift images within 2 or 3 weeks in responders and remained unchanged or reappeared later in non-responders. A normal fat signal could be detected in leukemic patients without hypercellular bone marrow. Specificity was missing for 1 H MRS and CSI; marrow carcinosis and benign stimulation (hypersplenia) could not be separated from leukemia. In clinical routine, CSI may have advantages over 1 H MRS, because a large anatomic field can be examined. Inhomogeneous fat signal distributions can be detected and were seen in several cases during therapy. 1 H MRS and CSI allow non-invasive therapy monitoring of leukemic patients and might be of prognostic value. (orig.)

  11. Calculation of fluorine chemical shift tensors for the interpretation of oriented (19)F-NMR spectra of gramicidin A in membranes.

    Science.gov (United States)

    Sternberg, Ulrich; Klipfel, Marco; Grage, Stephan L; Witter, Raiker; Ulrich, Anne S

    2009-08-28

    A semi-empirical method for the prediction of chemical shifts, based on bond polarization theory, has recently been introduced for (13)C. Here, we extended this approach to calculate the (19)F chemical shift tensors of fluorine bound to aromatic rings and in aliphatic CF(3) groups. For the necessary parametrization, ab initio chemical shift calculations were performed at the MP2 level for a set of fluorinated molecules including tryptophan. The bond polarization parameters obtained were used to calculate the (19)F chemical shift tensors for several crystalline molecules, and to reference the calculated values on a chemical shift scale relative to CFCl(3). As a first biophysical application, we examined the distribution of conformations of a (19)F-labeled tryptophan side chain in the membrane-bound ion channel peptide, gramicidin A. The fluorine chemical shift tensors were calculated from snapshots of a molecular dynamics simulation employing the (19)F-parametrized bond polarization theory. In this MD simulation, published (2)H quadrupolar and (15)N-(1)H dipolar couplings of the indole ring were used as orientational constraints to determine the conformational distribution of the 5F-Trp(13) side chain. These conformations were then used to interpret the spectra of (19)F-labeled gramicidin A in fluid and gel phase lipid bilayers.

  12. Demystifying fluorine chemical shifts: electronic structure calculations address origins of seemingly anomalous (19)F-NMR spectra of fluorohistidine isomers and analogues.

    Science.gov (United States)

    Kasireddy, Chandana; Bann, James G; Mitchell-Koch, Katie R

    2015-11-11

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of (19)F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in (19)F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F isomer results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of (19)F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra.

  13. Demystifying fluorine chemical shifts: Electronic structure calculations address origins of seemingly anomalous 19F-NMR spectra of fluorohistidine isomers and analogues

    Science.gov (United States)

    Kasireddy, Chandana; Bann, James G.

    2015-01-01

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of 19F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in 19F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of 19F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra. PMID:26524669

  14. Quantitative analysis of deuterium using the isotopic effect on quaternary {sup 13}C NMR chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Tamim A., E-mail: tamim.darwish@ansto.gov.au [National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Locked Bag 21, Kirrawee DC, NSW 2232 (Australia); Yepuri, Nageshwar Rao; Holden, Peter J. [National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Locked Bag 21, Kirrawee DC, NSW 2232 (Australia); James, Michael [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168 (Australia)

    2016-07-13

    Quantitative analysis of specifically deuterated compounds can be achieved by a number of conventional methods, such as mass spectroscopy, or by quantifying the residual {sup 1}H NMR signals compared to signals from internal standards. However, site specific quantification using these methods becomes challenging when dealing with non-specifically or randomly deuterated compounds that are produced by metal catalyzed hydrothermal reactions in D{sub 2}O, one of the most convenient deuteration methods. In this study, deuterium-induced NMR isotope shifts of quaternary {sup 13}C resonances neighboring deuterated sites have been utilized to quantify the degree of isotope labeling of molecular sites in non-specifically deuterated molecules. By probing {sup 13}C NMR signals while decoupling both proton and deuterium nuclei, it is possible to resolve {sup 13}C resonances of the different isotopologues based on the isotopic shifts and the degree of deuteration of the carbon atoms. We demonstrate that in different isotopologues, the same quaternary carbon, neighboring partially deuterated carbon atoms, are affected to an equal extent by relaxation. Decoupling both nuclei ({sup 1}H, {sup 2}H) resolves closely separated quaternary {sup 13}C signals of the different isotopologues, and allows their accurate integration and quantification under short relaxation delays (D1 = 1 s) and hence fast accumulative spectral acquisition. We have performed a number of approaches to quantify the deuterium content at different specific sites to demonstrate a convenient and generic analysis method for use in randomly deuterated molecules, or in cases of specifically deuterated molecules where back-exchange processes may take place during work up. - Graphical abstract: The relative intensities of quaternary {sup 13}C {"1H,"2H} resonances are equal despite the different relaxation delays, allowing the relative abundance of the different deuterated isotopologues to be calculated using NMR fast

  15. Torsional Phacoemulsification and Tip Selection

    Directory of Open Access Journals (Sweden)

    Fırat Helvacıoğlu

    2014-10-01

    Full Text Available One of the recent advances in cataract surgery is torsional phacoemulsification. It was developed to increase the efficacy of ultrasonic emulsification. In torsional phacoemulsification, the torsional movement of the tip is translated to side-to-side cutting action with the aid of bent phaco tips. Lens material is cut in both directions, rather than only during a forward stroke. The efficiency of this technique is further enhanced by an improvement in followability provided by the inherent non-repulsive nature of the side-to-side motion. Tip selection is very important for the efficiency of torsional phacoemulsification. Theoretically, there are 2 ways to enhance the cutting efficiency of the tip. First is the stroke length; the 22-degree bent 30-degree Kelman mini-flared tip cuts longer than the 12-degree bent 30-degree mini-flared Kelman tip. Second is the angulation or bevel; the higher the degree (45 degrees, the better cutting efficiency. Retrospective analyses of the previously published clinical studies clearly demonstrated that the efficacy of the torsional phacoemulsification has positive correlation with both the aperture angles and neck angles of the tips. (Turk J Ophthalmol 2014; 44: 392-5

  16. Chemical Shifts of the Carbohydrate Binding Domain of Galectin-3 from Magic Angle Spinning NMR and Hybrid Quantum Mechanics/Molecular Mechanics Calculations.

    Science.gov (United States)

    Kraus, Jodi; Gupta, Rupal; Yehl, Jenna; Lu, Manman; Case, David A; Gronenborn, Angela M; Akke, Mikael; Polenova, Tatyana

    2018-03-22

    Magic angle spinning NMR spectroscopy is uniquely suited to probe the structure and dynamics of insoluble proteins and protein assemblies at atomic resolution, with NMR chemical shifts containing rich information about biomolecular structure. Access to this information, however, is problematic, since accurate quantum mechanical calculation of chemical shifts in proteins remains challenging, particularly for 15 N H . Here we report on isotropic chemical shift predictions for the carbohydrate recognition domain of microcrystalline galectin-3, obtained from using hybrid quantum mechanics/molecular mechanics (QM/MM) calculations, implemented using an automated fragmentation approach, and using very high resolution (0.86 Å lactose-bound and 1.25 Å apo form) X-ray crystal structures. The resolution of the X-ray crystal structure used as an input into the AF-NMR program did not affect the accuracy of the chemical shift calculations to any significant extent. Excellent agreement between experimental and computed shifts is obtained for 13 C α , while larger scatter is observed for 15 N H chemical shifts, which are influenced to a greater extent by electrostatic interactions, hydrogen bonding, and solvation.

  17. Dirac operators and Killing spinors with torsion

    International Nuclear Information System (INIS)

    Becker-Bender, Julia

    2012-01-01

    On a Riemannian spin manifold with parallel skew torsion, we use the twistor operator to obtain an eigenvalue estimate for the Dirac operator with torsion. We consider the equality case in dimensions four and six. In odd dimensions we describe Sasaki manifolds on which equality in the estimate is realized by Killing spinors with torsion. In dimension five we characterize all Killing spinors with torsion and obtain certain naturally reductive spaces as exceptional cases.

  18. PROPOSAL OF THE DYNAMIC ANALYSIS TECHNIQUE CONSIDERING INTERACTION BETWEEN BENDING AND TORSION AND NONLINEAR TORSION

    Science.gov (United States)

    Otsuka, Hisanori; Hattori, Masahiro

    When the structures, for example arch bridges are subjected bending moments and torsional moments, the strength and rigidity of the members decline compared to those of pure bending or torsion load condition. However, any analysis soft don't consider interrelation between bending and torsion ,and effects of torsional moments have not been considered severely in seismic design. In this study, the authors proposed analysis technique considering interaction between bending and torsion to estimate torsional moments severely, and formulized the analysis tools for this technique. These are interaction curve, skeleton for combined load, hysteresis for torsion. Moreover, the authors analyzed a RC arch bridge using this method, and inspected the validity of comparing the results obtained equivalent linear analysis about torsion and nonlinear torsional analysis not considering the interaction between bending and torsion.

  19. Painless Ovarian Torsion Mimicking a Uterine Myoma

    Directory of Open Access Journals (Sweden)

    Cheng-Kuo Lin

    2006-12-01

    Conclusion: Ovarian torsion is a significant cause of acute lower abdominal pain in women and is a gynecologic surgical emergency. Nevertheless, surgical strategies are usually impeded because of ambiguous warning signs. Clinicians may be misled by certain conditions such as silent ovarian torsion. Although there may be no specific indication, the diagnosis of ovarian torsion should be considered on finding a pelvic mass.

  20. The odd side of torsion geometry

    DEFF Research Database (Denmark)

    Conti, Diego; Madsen, Thomas Bruun

    2012-01-01

    We introduce and study a notion of `Sasaki with torsion structure' (ST) as an odd-dimensional analogue of Kähler with torsion geometry (KT). These are normal almost contact metric manifolds that admit a unique compatible connection with 3-form torsion. Any odd-dimensional compact Lie group is sho...

  1. Structural analysis of flavonoids in solution through DFT 1H NMR chemical shift calculations: Epigallocatechin, Kaempferol and Quercetin

    Science.gov (United States)

    De Souza, Leonardo A.; Tavares, Wagner M. G.; Lopes, Ana Paula M.; Soeiro, Malucia M.; De Almeida, Wagner B.

    2017-05-01

    In this work, we showed that comparison between experimental and theoretical 1H NMR chemical shift patterns, calculated using Density Functional Theory (DFT), can be used for the prediction of molecular structure of flavonoids in solution, what is experimentally accessible for gas phase (electron diffraction methods) and solid samples (X-ray diffraction). The best match between B3LYP/6-31G(d,p)-PCM 1H NMR calculations for B ring rotated structures and experimental spectra can provide information on the conformation adopted by polyphenols in solution (usually DMSO-d6, acetone-d6 as solvents), which may differ from solid state and gas phase observed structures, and also DFT optimized geometry in the vacuum.

  2. Chemical shift assignments of RHE_RS02845, a NTF2-like domain-containing protein from Rhizobium etli.

    Science.gov (United States)

    Li, Tao; Li, Shuangli; Liang, Chunjie; Zhu, Jiang; Liu, Maili; Yang, Yunhuang

    2018-03-23

    The nuclear transport factor 2 (NTF2) like superfamily includes members of the NTF2 family, delta-5-3-ketosteroid isomerases, and the beta subunit of ring hydroxygenases. This family plays important roles in both eukaryotic and prokaryotic cells, and is taken as a classic example of divergent evolution because proteins in this family exhibit diverse biological functions, although share common structural features. We cloned the gene RHE_RS02845 encoding a predicted NTF2-like domain-containing protein in Rhizobium etli, and prepared U- 13 C/ 15 N-labeled protein samples for its three-dimensional NMR structural determination. Here, chemical shift assignments for both backbone and side-chain atoms are reported, which is prerequisite for further structural calculation and functional research using NMR spectroscopy.

  3. 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...... shifts of all substructures from the proposed models. A full reconstruction makes sure that all carbons are accounted for and enables on the negative side to discuss structural elements identified from recorded spectra of humic substances that cannot be observed in the simulated spectrum. On the positive...... side missing structural elements in the models can be suggested. A number of proposed structures for humic and fulvic acids are discussed based on the above analysis....

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

    International Nuclear Information System (INIS)

    Li, G.-W.; Xu, Z.; Chen, Q.-W.; Tian, Y.-N.; Wang, X.-Y.; Zhou, L.; Chang, S.-X.

    2014-01-01

    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

  5. Chemical shifts as a novel measure of interactions between two binding sites of symmetric dialkyldimethylammonium bromides to {alpha}-cyclodextrin

    Energy Technology Data Exchange (ETDEWEB)

    Funasaki, Noriaki [Department of Physical Chemistry, Faculty of Pharmaceutical Sciences, 21st Century COE Program, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414 (Japan)]. E-mail: funasaki@mb.kyoto-phu.ac.jp; Ishikawa, Seiji [Department of Physical Chemistry, Faculty of Pharmaceutical Sciences, 21st Century COE Program, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414 (Japan); Hirota, Shun [Department of Physical Chemistry, Faculty of Pharmaceutical Sciences, 21st Century COE Program, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414 (Japan); PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan)

    2006-01-12

    Complex formation of {alpha}-cyclodextrin ({alpha}-CD) with decyltrimethylammonium (DeTAB), N,N-dioctyldimethylammonium (DOAB), and N,N-didecyldimethylammonium bromides (DDeAB) was investigated by proton NMR spectroscopy. Analysis of chemical shifts yielded macroscopic 1:1 and 1:2 binding constants (K {sub 1} and K {sub 2}) and chemical shift differences ({delta}{delta} {sub SD} and {delta}{delta} {sub SD2}) for the 1:1 and 1:2 complexes of DeTAB, DOAB, and DDeAB with {alpha}-CD. The K {sub 1} and K {sub 2} values of DDeAB were quantitatively explained on the basis of the assumption that the microscopic 1:1 binding constant of DDeAB is identical to the observed K {sub 1} value of DeTAB. The K {sub 2} value of DDeAB was also explained in terms of its observed K {sub 1} value and the independent binding of two alkyl chains. Furthermore, the {delta}{delta} {sub SD} and {delta}{delta} {sub SD2} values for protons of DDeAB and {alpha}-CD were quantitatively explained on the basis of the assumption that the geometry of the decyl group of DDeAB in an {alpha}-CD cavity is identical to that of DeTAB. The {delta}{delta} {sub SD} value was also explicable on the basis of the same geometric assumption and the observed {delta}{delta} {sub SD2} value for this system. Similar results were obtained for the 1:1 and 1:2 DOAB-{alpha}-CD complexes.

  6. Utility of chemical shift and diffusion-weighted imaging in characterization of hyperattenuating adrenal lesions at 3.0T

    International Nuclear Information System (INIS)

    Song, Jiqing; Zhang, Chengqi; Liu, Qingwei; Yu, Taifei; Jiang, Xuemei; Xia, Qinghua; Zhang, Yinan; Sequeiros, Roberto Blanco

    2012-01-01

    Objective: The purpose of our study was to evaluate the value of chemical shift imaging (CSI) and diffusion weighted imaging (DWI) at 3.0 T MRI in adrenal hyperattenuating lesions. Methods: Fifty-one hyperattenuating adrenal lesions in 40 patients were evaluated. Signal intensity index (SII), adrenal to spleen ratio (ASR) and apparent diffusion coefficient (ADC) were used as quantitative analysis parameters. Results: The mean SII, ASR and ADC values were: benign pheochromocytomas (n = 22), 7.04%; 0.96, 1.15 × 10 −3 mm 2 /s; lipid-poor adenomas (n = 18), 33.77%, 0.71, 1.07 × 10 −3 mm 2 /s; malignant tumors (n = 7), 11.24%; 1.00; 0.92 × 10 −3 mm 2 /s. There were significant differences between the lipid-poor adenomas and nonadenomas for SII and ASR, and there were significant differences between the benign and the malignant tumor ADC values. The optimal diagnostic threshold point of SII and ASR for lipid-poor adenomas was 11.96%, 0.83, the sensitivity and specificity were 88.9%, 97.5% and 97%, 83.3%. The optimal diagnostic threshold point of ADC value for benign lesions and malignant tumors was 1.04 × 10 −3 mm 2 /s, the sensitivity and specificity were 61.4% and 85.7%. Conclusion: Quantitative analysis of chemical shift MRI and DWI can help to characterize the hyperattenuating adrenal lesions, especially in differentiatiation between the lipid-poor adenomas, the benign pheochromocytomas, and the malignant tumors

  7. 31P NMR Chemical Shifts of Phosphorus Probes as Reliable and Practical Acidity Scales for Solid and Liquid Catalysts.

    Science.gov (United States)

    Zheng, Anmin; Liu, Shang-Bin; Deng, Feng

    2017-10-11

    Acid-base catalytic reaction, either in heterogeneous or homogeneous systems, is one of the most important chemical reactions that has provoked a wide variety of industrial catalytic processes for production of chemicals and petrochemicals over the past few decades. In view of the fact that the catalytic performances (e.g., activity, selectivity, and reaction mechanism) of acid-catalyzed reactions over acidic catalysts are mostly dictated by detailed acidic features, viz. type (Brønsted vs Lewis acidity), amount (concentration), strength, and local environments (location) of acid sites, information on and manipulation of their structure-activity correlation are crucial for optimization of catalytic performances as well as innovative design of novel effective catalysts. This review aims to summarize recent developments on acidity characterization of solid and liquid catalysts by means of experimental 31 P nuclear magnetic resonance (NMR) spectroscopy using phosphorus probe molecules such as trialkylphosphine (TMP) and trialkylphosphine oxides (R 3 PO). In particular, correlations between the observed 31 P chemical shifts (δ 31 P) of phosphorus (P)-containing probes and acidic strengths have been established in conjuction with density functional theory (DFT) calculations, rendering practical and reliable acidity scales for Brønsted and Lewis acidities at the atomic level. As illustrated for a variety of different solid and liquid acid systems, such as microporous zeolites, mesoporous molecular sieves, and metal oxides, the 31 P NMR probe approaches were shown to provide important acid features of various catalysts, surpassing most conventional methods such as titration, pH measurement, Hammett acidity function, and some other commonly used physicochemical techniques, such as calorimetry, temperature-programmed desorption of ammonia (NH 3 -TPD), Fourier transformed infrared (FT-IR), and 1 H NMR spectroscopies.

  8. TORSION OF THE VERMIFORM APPENDIX: A CASE REPORT

    Directory of Open Access Journals (Sweden)

    Dr. Imtiaz Wani

    2009-07-01

    Full Text Available Torsion of the vermiform appendix is a rare condition with few cases reported in the literature. Various factors predispose to torsion. Various factors predispose to torsion. We report a case of primary torsion of the vermiform appendix. The clinical presentation was indistinguishable from acute appendicitis and the diagnosis was made at operation. Appendix was preileal in position and the direction of torsion was anticlockwise. There was intrinsic torsion with no obvious factor for torsion identified. Appendectomy was performed.

  9. Graphic representation of 13C-nuclear magnetic resonance chemical shifts of oxygen-containing organosulfur compounds and its application to the structural analysis

    International Nuclear Information System (INIS)

    Sato, Soei; Nagata, Chikakiyo; Tanaka, Shigeyuki.

    1985-01-01

    A new method for the structural analysis of oxygen-containing organosulfur compounds was examined by 13 C-NMR spectroscopy. The 13 C-NMR spectra were measured for organosulfur compounds of various types such as sulfoxides, sulfones, sulfinic acids, sulfonyl chlorides, sulfonic acids and their salts, sulfuric acid ester compounds and sultam derivatives containing alkyl, alkenyl, alkinyl and aromatic ring groups. The spectra collected from literatures were also used. The 13 C-chemical shifts of α-carbon adjacent to sulfur atom in organosulfur compounds were classified according to the structural types of the compounds and classes of carbon atoms of alkane(CH 3 , CH 2 , > CH-, etc.), alkene, aromatic ring types. The graphic representation for these data was carried out in view of the structural analysis of these compounds. The chemical shifts for α-carbon of oxygen-containing organosulfur compounds were observed at lower-field range than that of sulfide and disulfide compounds. The chemical shifts of α-carbon are gradually shifted to lower-field in order of methyl, methylene, methyne and quaternary carbons. The chemical shifts of α-carbons were also affected by the adjacent groups and their structural types. Detailed graphic representations including adjacent groups were made for a series of compounds which have many kinds of β-groups. This method was succesfully applied to the structural analysis of a textile and polymer additive. (J.P.N.)

  10. Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe

    Science.gov (United States)

    Maeda, M.; Yamamoto, K.; Mizokawa, T.; Saini, N. L.; Arita, M.; Namatame, H.; Taniguchi, M.; Tan, G.; Zhao, L. D.; Kanatzidis, M. G.

    2018-03-01

    We have studied the electronic structure of SnSe and Na-doped SnSe by means of angle-resolved photoemission spectroscopy. The valence-band top reaches the Fermi level by the Na doping, indicating that Na-doped SnSe can be viewed as a degenerate semiconductor. However, in the Na-doped system, the chemical potential shift with temperature is unexpectedly large and is apparently inconsistent with the degenerate semiconductor picture. The large chemical potential shift and anomalous spectral shape are key ingredients for an understanding of the novel metallic state with the large thermoelectric performance in Na-doped SnSe.

  11. 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

    and retinoid receptors (ACTR). We find that small differences in the methyl carbon chemical shifts due to the ¿-gauche effect may provide information about the side chain rotamer distributions. However, the effects of neighboring residues on the methyl group chemical shifts obscure the direct observation...... 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 directly...

  12. Torsion - Vibration Couplings in the CH{_3}OO{\\cdot} Radical

    Science.gov (United States)

    Huang, Meng; Miller, Terry A.; McCoy, Anne B.; Hsu, Kuo-Hsiang; Huang, Yu-Hsuan; Lee, Yuan-Pern

    2016-06-01

    A partially rotationally resolved infrared spectrum of CH{_3}OO{\\cdot} in the CH stretch region has been reported. The rotational contour of the {ν_2} CH stretch band in the experimental spectrum can be simulated with an asymmetric rotor model. The simulation shows good agreement with the experimental spectrum except that the broadening of the Q-branch in the experimental spectrum remains unexplained. This broadening is likely due to the sequence band transitions from the torsionally excited levels populated at room temperature to combination levels involving the CH stretch and the same number of torsional quanta. A four dimension model involving three CH stretches and the CH{_3} torsion is applied to the CH{_3}OO{\\cdot} radical to obtain the frequencies and intensities of the vibrational transitions in the CH stretch region. Based on these calculations, the torsional sequence bands are calculated to be slightly shifted from the origin band, because of the couplings between the CH stretches and CH{_3} torsion, thereby causing the apparent broadening observed for the {ν_2} fundamental. Due to the accidental degeneracy of two different CH stretch and CH{_3} torsion combination levels which differ by one quantum in the torsional excitation, the frequencies of the torsional sequence bands will be very sensitive to details of the potential, which makes the shifts difficult to precisely predict with electronic structure calculations. Complementary analyses are now underway for the other two CH stretch vibrational bands, {ν_1} and {ν_9}. K.-H. Hsu, Y.-H. Huang, Y.-P. Lee, M. Huang, T. A. Miller and A. B. McCoy J. Phys. Chem. A, in press, DOI: 10.1021/acs.jpca.5b12334

  13. Intermolecular Interactions in Crystalline Theobromine as Reflected in Electron Deformation Density and (13)C NMR Chemical Shift Tensors.

    Science.gov (United States)

    Bouzková, Kateřina; Babinský, Martin; Novosadová, Lucie; Marek, Radek

    2013-06-11

    An understanding of the role of intermolecular interactions in crystal formation is essential to control the generation of diverse crystalline forms which is an important concern for pharmaceutical industry. Very recently, we reported a new approach to interpret the relationships between intermolecular hydrogen bonding, redistribution of electron density in the system, and NMR chemical shifts (Babinský et al. J. Phys. Chem. A, 2013, 117, 497). Here, we employ this approach to characterize a full set of crystal interactions in a sample of anhydrous theobromine as reflected in (13)C NMR chemical shift tensors (CSTs). The important intermolecular contacts are identified by comparing the DFT-calculated NMR CSTs for an isolated theobromine molecule and for clusters composed of several molecules as selected from the available X-ray diffraction data. Furthermore, electron deformation density (EDD) and shielding deformation density (SDD) in the proximity of the nuclei involved in the proposed interactions are calculated and visualized. In addition to the recently reported observations for hydrogen bonding, we focus here particularly on the stacking interactions. Although the principal relations between the EDD and CST for hydrogen bonding (HB) and stacking interactions are similar, the real-space consequences are rather different. Whereas the C-H···X hydrogen bonding influences predominantly and significantly the in-plane principal component of the (13)C CST perpendicular to the HB path and the C═O···H hydrogen bonding modulates both in-plane components of the carbonyl (13)C CST, the stacking modulates the out-of-plane electron density resulting in weak deshielding (2-8 ppm) of both in-plane principal components of the CST and weak shielding (∼ 5 ppm) of the out-of-plane component. The hydrogen-bonding and stacking interactions may add to or subtract from one another to produce total values observed experimentally. On the example of theobromine, we demonstrate

  14. Quartz crystal microbalance based on torsional piezoelectric resonators

    International Nuclear Information System (INIS)

    Buecking, W.; Du, B.; Turshatov, A.; Koenig, A. M.; Reviakine, I.; Bode, B.; Johannsmann, D.

    2007-01-01

    A quartz crystal microbalance (QCM) is described, which is based on a torsional resonator, rather than a conventional thickness-shear resonator. Typical applications are measurements of film thickness in the coating industry and monitoring of biofouling. The torsional QCM is about a factor of 100 less sensitive than the conventional QCM. On the other hand, it can probe film thicknesses in the range of hundreds of microns, which is impossible with the conventional QCM due to viscoelastic artifacts. Data acquisition and data analysis proceed in analogy to the conventional QCM. An indicator of the material's softness can be extracted from the bandwidth of the resonance. Within the small-load approximation, the frequency shift is independent of whether the sample is applied to the face or to the side of the cylinder. Details of the geometry matter if the viscoelastic properties of the sample are of interest

  15. Torsions of 3-dimensional manifolds

    CERN Document Server

    Wurzbacher, T

    2002-01-01

    From the reviews: "This is an excellent exposition about abelian Reidemeister torsions for three-manifolds." ―Zentralblatt Math "This monograph contains a wealth of information many topologists will find very handy. …Many of the new points of view pioneered by Turaev are gradually becoming mainstream and are spreading beyond the pure topology world. This monograph is a timely and very useful addition to the scientific literature." ―Mathematical Reviews

  16. Moduli space of torsional manifolds

    International Nuclear Information System (INIS)

    Becker, Melanie; Tseng, L.-S.; Yau, S.-T.

    2007-01-01

    We characterize the geometric moduli of non-Kaehler manifolds with torsion. Heterotic supersymmetric flux compactifications require that the six-dimensional internal manifold be balanced, the gauge bundle be Hermitian Yang-Mills, and also the anomaly cancellation be satisfied. We perform the linearized variation of these constraints to derive the defining equations for the local moduli. We explicitly determine the metric deformations of the smooth flux solution corresponding to a torus bundle over K3

  17. Torsional resistance of retreatment instruments.

    Science.gov (United States)

    Lopes, Hélio P; Elias, Carlos N; Vedovello, Gislaine A F; Bueno, Carlos E S; Mangelli, Marcelo; Siqueira, José F

    2011-10-01

    This study compared the torsional resistance of two brands of rotary nickel-titanium (NiTi) instruments indicated for endodontic retreatment. Mtwo retreatment instruments #15 and #25 (VDW, Munich, Germany) and ProTaper Universal retreatment instruments D2 and D3 (Maillefer/Dentsply, Ballaigues, Switzerland) were subjected to a torsional assay in clockwise rotation. The two parameters evaluated were maximum torque and angular deflection at failure. Fractured instruments had their fractured surfaces and helical shafts examined by scanning electron microscopy. The results indicated that the angular deflection at fracture decreased in the following order: Mtwo retreatment file #15 > Mtwo retreatment file #25 > ProTaper Universal retreatment file D2 > ProTaper Universal retreatment file D3. As for the maximum torque values, the results revealed the following descending order: ProTaper Universal file D2 > Mtwo retreatment file #25 > ProTaper Universal file D3 > Mtwo retreatment file #15. Scanning electron microscopic analysis revealed that plastic deformation occurred along the helical shaft of the fractured instruments. Fractured surfaces were of the ductile type. The instruments tested showed different torsional behavior depending on the parameter evaluated. If one considers that high angular deflection values may serve as a safety factor, then the Mtwo retreatment instruments showed significantly better results. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  18. 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

  19. 1H and 13C NMR Data on Hydroxy/methoxy Flavonoids and the Effects of Substituents on Chemical Shifts

    International Nuclear Information System (INIS)

    Yoon, Hyuk; Eom, Sung Lock; Hyun, Ji Ye; Jo, Geun Hyeong; Hwang, Do Seok; Lee, Sun Hee; Yong, Yeon Joong; Lee, Young Han; Lim, Yoong Ho; Park, Jun Cheol

    2011-01-01

    Polyphenols have recently been examined for such applications, and they are classified based on their carbon skeletons: phenolic acids with C6-C1 skeleton, hydrocinammates with C6-C 3 skeleton, stilbenes with C6-C2-C6 skeleton, and flavonoids with C6-C 3 -C6 skeleton.2 Of these compounds, flavonoids are ubiquitously found in most plants. Since flavonoids belong to polyphenols, they have many hydroxy groups. From a bioavailability point of view, hydroxy groups prevent cell membrane transport, and hydroxyflavonoids can be metabolized by O-methyltransferases. However, methoxylated flavonoids may not have these problems. Hydroxylated or methoxylated flavonoids are found from natural sources. Nuclear magnetic resonance (NMR) spectroscopy is widely used to identify different compounds including hydroxylated or methoxylated flavonoids. Because the position and the number of substituted hydroxy or/and methoxy groups will change the 1 H and 13 C chemical shifts, it is important to understand these changes so that the structures of newly isolated hydroxy/methoxy-flavonoids can be easily identified

  20. Influence of the chemical shift artifact on measurements of compact bone thickness in equine distal limb MR images.

    Science.gov (United States)

    Dimock, Abigail N; Spriet, Mathieu

    2010-01-01

    The effect of the chemical shift artifact, resulting from misregistration or phase cancellation at the interface between compact and trabecular bone, on apparent bone thickness was quantified in six isolated equine limbs. Sagittal T1-weighted spin echo (SE) and in-phase three-dimensional spoiled gradient echo (SPGR) images were acquired twice with a 1.5 T magnetic resonance (MR) unit, switching the frequency encoding direction between acquisitions. Out-of-phase SPGR images were also obtained. MR images with different frequency encoding directions were compared with each other and to radiographs made from corresponding 3-mm-bone sections. Compact bone thickness was significantly different when comparing images acquired with different frequency encoding directions for both SE and SPGR sequences. Significant differences were identified in the frequency but not the phase encoding direction when measurements of compact bone in MR images were compared with measurements obtained from thin section radiographs for the majority of surfaces studied (P 0.05). Measurements of compact bone from out-of-phase SPGR sequences were significantly different than from in-phase sequences (P echo sequences.

  1. Synthesis, three-dimensional structure, conformation and correct chemical shift assignment determination of pharmaceutical molecules by NMR and molecular modeling

    International Nuclear Information System (INIS)

    Azeredo, Sirlene O.F. de; Sales, Edijane M.; Figueroa-Villar, José D.

    2017-01-01

    This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. (author)

  2. Noninvasive measurements of cardiac high-energy phosphate metabolites in dilated cardiomyopathy by using 31P spectroscopic chemical shift imaging

    International Nuclear Information System (INIS)

    Hansch, A.; Rzanny, R.; Heyne, J.-P.; Reichenbach, J.R.; Kaiser, W.A.; Leder, U.

    2005-01-01

    Dilated cardiomyopathy (DCM) is accompanied by an impaired cardiac energy metabolism. The aim of this study was to investigate metabolic ratios in patients with DCM compared to controls by using spectroscopic two-dimensional chemical shift imaging (2D-CSI). Twenty volunteers and 15 patients with severe symptoms (left ventricular ejection fraction, LVEF 30%) of DCM were investigated. Cardiac 31 P MR 2D-CSI measurements (voxel size: 40 x 40 x 100 mm 3 ) were performed with a 1.5 T whole-body scanner. Measurement time ranged from 15 min to 30 min. Peak areas and ratios of different metabolites were evaluated, including high-energy phosphates (PCr, ATP), 2,3-diphosphoglycerate (2,3-DPG) and phosphodiesters (PDE). In addition, we evaluated how PCr/ATP ratios correlate with LVEF as an established prognostic factor of heart failure. The PCr/γ-ATP ratio was significantly decreased in patients with moderate and severe DCM and showed a linear correlation with reduced LVEFs. PDE/ATP ratios were significantly increased only in patients with severe DCM as compared to volunteers. Applying 31 P MRS with commonly-available 2D-CSI sequences is a valuable technique to evaluate DCM by determining PCr/ATP ratios noninvasively. In addition to reduced PCr/ATP ratios observed in patients suffering from DCM, significantly-increased PDE/ATP ratios were found in patients with severe DCM. (orig.)

  3. Synthesis, three-dimensional structure, conformation and correct chemical shift assignment determination of pharmaceutical molecules by NMR and molecular modeling

    Energy Technology Data Exchange (ETDEWEB)

    Azeredo, Sirlene O.F. de; Sales, Edijane M.; Figueroa-Villar, José D., E-mail: jdfv2009@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Grupo de Ressonância Magnética Nuclear e Química Medicinal

    2017-07-01

    This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. (author)

  4. Newton-Cartan gravity and torsion

    Science.gov (United States)

    Bergshoeff, Eric; Chatzistavrakidis, Athanasios; Romano, Luca; Rosseel, Jan

    2017-10-01

    We compare the gauging of the Bargmann algebra, for the case of arbitrary torsion, with the result that one obtains from a null-reduction of General Relativity. Whereas the two procedures lead to the same result for Newton-Cartan geometry with arbitrary torsion, the null-reduction of the Einstein equations necessarily leads to Newton-Cartan gravity with zero torsion. We show, for three space-time dimensions, how Newton-Cartan gravity with arbitrary torsion can be obtained by starting from a Schrödinger field theory with dynamical exponent z = 2 for a complex compensating scalar and next coupling this field theory to a z = 2 Schrödinger geometry with arbitrary torsion. The latter theory can be obtained from either a gauging of the Schrödinger algebra, for arbitrary torsion, or from a null-reduction of conformal gravity.

  5. Using torsion to manipulate spin currents

    Science.gov (United States)

    Fumeron, Sébastien; Berche, Bertrand; Medina, Ernesto; Santos, Fernando A. N.; Moraes, Fernando

    2017-02-01

    We address the problem of quantum particles moving on a manifold characterised by the presence of torsion along a preferential axis. In fact, such a torsion may be taylored by the presence of a single screw dislocation, whose Burgers vector measures the torsion amplitude. The problem, first treated in the relativistic limit describing fermions that couple minimally to torsion, is then analysed in the Pauli limit. We show that torsion induces a geometric potential and also that it couples generically to the phase of the wave function, giving rise to the possibility of using torsion to manipulate spin currents in the case of spinor wave functions. These results emerge as an alternative strategy for using screw dislocations in the design of spintronic-based devices.

  6. Quantum General Relativity, Torsion and Uncertainty Relations

    Science.gov (United States)

    de Sabbata, V.; Sivaram, C.; Borzeszkowski, H.-H. V.; Treder, H.-J.

    It is shown that in gravitational theories with torsion one is led to commutation rules corresponding to Landau-Peierls type uncertainty relations.Translated AbstractQuantisierte allgemeine Relativitätstheorie, Torsion und UnschärferelationenEs wird gezeigt, daß man in Gravitationstheorien mit Torsion zu Vertauschungsregeln geführt wird, die Landau-Peierls-artigen Unschärferelationen entsprechen.

  7. Tibial Torsion Among Filipinos: A Cadaveric Study

    Directory of Open Access Journals (Sweden)

    Villamin CAC

    2012-07-01

    Full Text Available Tibial torsion, the twisting of the tibia about its long axis, can affect rotational positioning in total knee replacement. This angle varies depending on the ethnicity of the subject. There are no published studies to date to determine the tibial torsion among Filipinos. In this study, 28 cadaveric limbs were examined. Our results show that the average tibial torsion among adult Filipinos is 28.9°.

  8. A complete set of NMR chemical shifts and spin-spin coupling constants for L-Alanyl-L-Alanine zwitterion and analysis of its conformational behavior

    Czech Academy of Sciences Publication Activity Database

    Bouř, Petr; Buděšínský, Miloš; Špirko, Vladimír; Kapitán, Josef; Šebestík, Jaroslav; Sychrovský, Vladimír

    2005-01-01

    Roč. 127, - (2005), 17079-17089 ISSN 0002-7863 R&D Projects: GA AV ČR(CZ) IAA4055104; GA ČR(CZ) GA203/05/0388 Institutional research plan: CEZ:AV0Z40550506 Keywords : NMR * chemical shifts * coupling constants Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.419, year: 2005

  9. 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.

  10. Automated Fragmentation Polarizable Embedding Density Functional Theory (PE-DFT) Calculations of Nuclear Magnetic Resonance (NMR) Shielding Constants of Proteins with Application to Chemical Shift Predictions

    DEFF Research Database (Denmark)

    Steinmann, Casper; Bratholm, Lars Andersen; Olsen, Jógvan Magnus Haugaard

    2017-01-01

    that are comparable with experiment. The introduction of a probabilistic linear regression model allows us to substantially reduce the number of snapshots that are needed to make comparisons with experiment. This approach is further improved by augmenting snapshot selection with chemical shift predictions by which we...

  11. High-Frequency H-1 NMR Chemical Shifts of Sn-II and Pb-II Hydrides Induced by Relativistic Effects: Quest for Pb-II Hydrides

    Czech Academy of Sciences Publication Activity Database

    Vícha, J.; Marek, R.; Straka, Michal

    2016-01-01

    Roč. 55, č. 20 (2016), s. 10302-10309 ISSN 0020-1669 Institutional support: RVO:61388963 Keywords : hydrides of TlI and PbII * high-frequency 1H chemical shifts * relativistic effects Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.857, year: 2016

  12. High-Frequency C-13 and Si-29 NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of TII and Pb-II: Decisive Role of Relativistic Effects

    Czech Academy of Sciences Publication Activity Database

    Vícha, J.; Marek, R.; Straka, Michal

    2016-01-01

    Roč. 55, č. 4 (2016), s. 1770-1781 ISSN 0020-1669 R&D Projects: GA ČR(CZ) GA14-03564S Institutional support: RVO:61388963 Keywords : high-frequency NMR chemical shifts * HALA effect * relativistic DFT calculations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.857, year: 2016

  13. Dirac operators and Killing spinors with torsion; Dirac-Operatoren und Killing-Spinoren mit Torsion

    Energy Technology Data Exchange (ETDEWEB)

    Becker-Bender, Julia

    2012-12-17

    On a Riemannian spin manifold with parallel skew torsion, we use the twistor operator to obtain an eigenvalue estimate for the Dirac operator with torsion. We consider the equality case in dimensions four and six. In odd dimensions we describe Sasaki manifolds on which equality in the estimate is realized by Killing spinors with torsion. In dimension five we characterize all Killing spinors with torsion and obtain certain naturally reductive spaces as exceptional cases.

  14. Ultimate Strength of Ship Hulls under Torsion

    DEFF Research Database (Denmark)

    Paik, Jeom Kee; Thayamballi, Anil K.; Pedersen, Preben Terndrup

    2001-01-01

    subjected to torsion. A procedure for calculating these stresses is briefly described. As an illustrative example, the distribution and magnitude of warping and shear stresses for a typical container vessel hull cross section under unit torsion is calculated by the procedure. By theoretical and numerical...... analyses, it is shown that the influence of torsion induced warping stresses on the ultimate hull girder bending strength is small for ductile hull materials while torsion induced shear stresses will of course reduce the ship hull ultimate bending moment....

  15. Primary splenic torsion in a Boston terrier

    International Nuclear Information System (INIS)

    Ohta, H.; Takagi, S.; Murakami, M.; Sasaki, N.; Yoshikawa, M.; Nakamura, K.; Hwang, S.J.; Yamasaki, M.; Takiguchi, M.

    2009-01-01

    A 7-year-old female Boston terrier was referred to Hokkaido University Veterinary Teaching Hospital with a history of hemoglobinuria and anemia for several days. Abdominal radiographs showed splenomegaly, and ultrasonography revealed a hypoechoic splenic parenchyma with interspersed linear echoes consistent with the ultrasonographic appearance of splenic torsion. Ultrasonography and computed tomography (CT) indicated a C-shaped spleen. Exploratory laparotomy confirmed the diagnosis of splenic torsion. A splenectomy was performed, and the dog recovered well without complications. This is the first report of splenic torsion in Boston terriers, and the usefulness of ultrasonographic and CT findings of the splenic torsion was also confirmed

  16. Primary splenic torsion in a Boston terrier.

    Science.gov (United States)

    OHTA, Hiroshi; TAKAGI, Satoshi; MURAKAMI, Masahiro; SASAKI, Noboru; YOSHIKAWA, Muneyoshi; NAKAMURA, Kensuke; HWANG, Shiang-Jyi; YAMASAKI, Masahiro; TAKIGUCHI, Mitsuyoshi

    2009-11-01

    A 7-year-old female Boston terrier was referred to Hokkaido University Veterinary Teaching Hospital with a history of hemoglobinuria and anemia for several days. Abdominal radiographs showed splenomegaly, and ultrasonography revealed a hypoechoic splenic parenchyma with interspersed linear echoes consistent with the ultrasonographic appearance of splenic torsion. Ultrasonography and computed tomography (CT) indicated a C-shaped spleen. Exploratory laparotomy confirmed the diagnosis of splenic torsion. A splenectomy was performed, and the dog recovered well without complications. This is the first report of splenic torsion in Boston terriers, and the usefulness of ultrasonographic and CT findings of the splenic torsion was also confirmed.

  17. 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.

  18. High SNR Acquisitions Improve the Repeatability of Liver Fat Quantification Using Confounder-corrected Chemical Shift-encoded MR Imaging.

    Science.gov (United States)

    Motosugi, Utaroh; Hernando, Diego; Wiens, Curtis; Bannas, Peter; Reeder, Scott B

    2017-10-10

    To determine whether high signal-to-noise ratio (SNR) acquisitions improve the repeatability of liver proton density fat fraction (PDFF) measurements using confounder-corrected chemical shift-encoded magnetic resonance (MR) imaging (CSE-MRI). Eleven fat-water phantoms were scanned with 8 different protocols with varying SNR. After repositioning the phantoms, the same scans were repeated to evaluate the test-retest repeatability. Next, an in vivo study was performed with 20 volunteers and 28 patients scheduled for liver magnetic resonance imaging (MRI). Two CSE-MRI protocols with standard- and high-SNR were repeated to assess test-retest repeatability. MR spectroscopy (MRS)-based PDFF was acquired as a standard of reference. The standard deviation (SD) of the difference (Δ) of PDFF measured in the two repeated scans was defined to ascertain repeatability. The correlation between PDFF of CSE-MRI and MRS was calculated to assess accuracy. The SD of Δ and correlation coefficients of the two protocols (standard- and high-SNR) were compared using F-test and t-test, respectively. Two reconstruction algorithms (complex-based and magnitude-based) were used for both the phantom and in vivo experiments. The phantom study demonstrated that higher SNR improved the repeatability for both complex- and magnitude-based reconstruction. Similarly, the in vivo study demonstrated that the repeatability of the high-SNR protocol (SD of Δ = 0.53 for complex- and = 0.85 for magnitude-based fit) was significantly higher than using the standard-SNR protocol (0.77 for complex, P < 0.001; and 0.94 for magnitude-based fit, P = 0.003). No significant difference was observed in the accuracy between standard- and high-SNR protocols. Higher SNR improves the repeatability of fat quantification using confounder-corrected CSE-MRI.

  19. Modern MRI tools for the characterization of acute demyelinating lesions: value of chemical shift and diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kueker, W.; Mehnert, F.; Mader, I.; Naegele, T. [Department of Neuroradiology, University of Tuebingen Medical School, Hoppe-Seyler-Str. 3, 72076, Tuebingen (Germany); Ruff, J. [Siemens Medical Solutions, Erlangen (Germany); Gaertner, S. [Department of Neurology, University of Tuebingen Medical School, Tuebingen (Germany)

    2004-06-01

    Acute demyelinating lesions occur in various inflammatory disorders of the CNS. Apart from multiple sclerosis, most cases can be attributed to an overshooting immunological response to infectious agents called acute disseminated encephalomyelitis (ADEM). ADEM, which is mostly characterized by a monophasic course, has a multiphasic variant (MDEM). The early application of corticosteroids has been shown to be beneficial for the outcome; thus, an early diagnosis is highly desirable. Furthermore, the differential diagnosis ruling out neoplastic disorders may be difficult using conventional MRI alone. The potential diagnostic value of advanced MR techniques such as chemical shift imaging (CSI) and diffusion-weighted imaging (DWI) was investigated in a patient with MDEM, who had a new lesion in continuity with the initial disease manifestation. CSI was performed at 1.5 T with a long echo time of 135 ms for the evaluation of N-acetyl-aspartate (NAA) and choline (Cho) and with short TE of 30 ms for macromolecules (mm) and myo-Inositol (mI). DWI was performed using a single-shot isotropic EPI sequence. Whereas acute and chronic areas of demyelination were neither distinguishable on T2- nor on contrast-enhanced T1-weigted images, CSI and DWI revealed different metabolite concentrations and diffusion characteristics within the composite lesion, clearly separating acute from chronic areas of demyelination. In conclusion, the addition of CSI and DWI may add to the diagnostic power of MRI in the setting of demyelinating disorders by identifying areas of acute and chronic demyelination, even in the absence of contrast enhancement. (orig.)

  20. Using chemical-shift MR imaging to quantify fatty degeneration within supraspinatus muscle due to supraspinatus tendon injuries

    Energy Technology Data Exchange (ETDEWEB)

    Gokalp, Gokhan; Yildirim, Nalan; Yazici, Zeynep [Uludag University Medical Faculty, Department of Radiology, Gorukle, Bursa (Turkey); Ercan, Ilker [Uludag University Medical Faculty, Department of Biostatistics, Gorukle, Bursa (Turkey)

    2010-12-15

    The objective of this study was to prospectively quantify the fatty degeneration of supraspinatus (SSP) muscle due to SSP tendon injuries by using chemical-shift magnetic resonance imaging (CS-MRI). Forty-one patients with suspected rotator cuff tear or impingement examined with MR arthrography were included in the study. The following images were obtained after injection of diluted gadolinium chelate into glenohumeral joint: fat-saturated T1-weighted spin echo in the coronal, axial, and sagittal-oblique plane; fat-saturated T2-weighted and intermediate-weighted fast spin-echo in the coronal-oblique plane; and T1-weighted spin echo in the sagittal-oblique plane. CS-MRI was performed in the coronal plane using a double-echo fast low-angle shot (FLASH) sequence. SSP tendon changes were classified as normal, tendinosis, and partial and complete tear according to MR arthrography findings. Fatty degeneration was quantified after measurement of signal intensity values within the region of interest (ROI) placed over SSP muscle. Signal intensity (SI) suppression ratio and SI index were calculated with the values obtained. Degrees of fatty degeneration depicted in normal subjects and subjects with rotator cuff injuries were compared. Median (min:max) was used as descriptive values. SI suppression ratio was -3.5% (-15.5:3.03) in normal subjects, whereas it was -13.5% (-28.55:-6.60), -30.7% (-41.5:-20.35), and -43.75% (-62:-24.90) in tendinosis, partial and complete tears, respectively. SI index was 0.75% (-6:11.5) in normal subjects. It was 10% (4.50:27), 26.5% (19.15:35.5), and 41% (23.9:57) in tendinosis, partial and complete tears, respectively. The increase in degree of fatty degeneration parallels the seriousness of tendon pathology. CS-MRI is a useful method for grading fat accumulation within SSP muscle. (orig.)

  1. Modern MRI tools for the characterization of acute demyelinating lesions: value of chemical shift and diffusion-weighted imaging

    International Nuclear Information System (INIS)

    Kueker, W.; Mehnert, F.; Mader, I.; Naegele, T.; Ruff, J.; Gaertner, S.

    2004-01-01

    Acute demyelinating lesions occur in various inflammatory disorders of the CNS. Apart from multiple sclerosis, most cases can be attributed to an overshooting immunological response to infectious agents called acute disseminated encephalomyelitis (ADEM). ADEM, which is mostly characterized by a monophasic course, has a multiphasic variant (MDEM). The early application of corticosteroids has been shown to be beneficial for the outcome; thus, an early diagnosis is highly desirable. Furthermore, the differential diagnosis ruling out neoplastic disorders may be difficult using conventional MRI alone. The potential diagnostic value of advanced MR techniques such as chemical shift imaging (CSI) and diffusion-weighted imaging (DWI) was investigated in a patient with MDEM, who had a new lesion in continuity with the initial disease manifestation. CSI was performed at 1.5 T with a long echo time of 135 ms for the evaluation of N-acetyl-aspartate (NAA) and choline (Cho) and with short TE of 30 ms for macromolecules (mm) and myo-Inositol (mI). DWI was performed using a single-shot isotropic EPI sequence. Whereas acute and chronic areas of demyelination were neither distinguishable on T2- nor on contrast-enhanced T1-weigted images, CSI and DWI revealed different metabolite concentrations and diffusion characteristics within the composite lesion, clearly separating acute from chronic areas of demyelination. In conclusion, the addition of CSI and DWI may add to the diagnostic power of MRI in the setting of demyelinating disorders by identifying areas of acute and chronic demyelination, even in the absence of contrast enhancement. (orig.)

  2. [Changes of torsional eye movements after lesion of the rostral interstitial nucleus of the MLF (riMLF)--analysis on listing's plane].

    Science.gov (United States)

    Suzuki, Y

    1995-11-01

    The changes of torsional eye movements after the riMLF (rostral interstitial nucleus of the medial longitudinal fasciculus) lesions with kainic acid have been investigated in three rhesus monkeys. After unilateral lesion, torsional rapid eye movements were lost to ipsi-torsional (extorsion of the ipsilateral eye and intorsion of the contralateral eye) side only, while vertical movements were still possible. All monkeys showed counter-torsional (intorsion of the ipsilateral eye and extorsion of the contralateral eye) shifts and thickening of Listing's plane. These changes of Listing's plane were always less in the dark. After the second contralateral lesions, all torsional and vertical rapid eye movements were permanently lost. Listing's plane moved to the opposite torsional direction beyond zero. On-average, the residual torsional shift in the light was only 17.4% of the shift in the light after the first lesion. Furthermore, the thickness of Listing's plane decreased to the level of the pre-lesion state. These results suggest that burst neurons in the riMLF are essential to generate vertical and/or torsional rapid eye movements and symmetrical activity of them is necessary to keep Listing's plane around zero and to minimize its variability. Yet, after bilateral lesions, Listing's law is still preserved, suggesting its neural implementation in parallel to or downstream of the riMLF.

  3. Simultaneous acute appendicitis with right testicular torsion

    Directory of Open Access Journals (Sweden)

    Tanveer Akhtar

    2012-01-01

    Full Text Available We present a child with both acute appendicitis and torsion of the right testis presenting at the same time. Testicular torsion possibly occurring due to vomiting in acute appendicitis so far has not been reported in the literature.

  4. Teenage testicular torsion. | Onuigbo | International Journal of ...

    African Journals Online (AJOL)

    Aim: To study testicular torsion in teenagers in the Igbo community. Method: A retrospective study was carried out as regards requests for pathological examination of specimens received at a Regional Reference Laboratory based in Enugu. Results: Over a period of 30 years, 28 surgical specimens of testicular torsion in ...

  5. Misdiagnosed Adult Testicular Torsion: Case Report | Ndaguatha ...

    African Journals Online (AJOL)

    Adult testicular torsion is thought to be rare if not relatively unusual. The rarity could be an underestimation since there are many episodes of missed torsions and misdiagnosis with other conditions of acute scrotum despite the now widespread ultra sound availability that are being reported in the literature. Such a ...

  6. Appendicular Torsion | Dubhashi | Nigerian Journal of Surgery

    African Journals Online (AJOL)

    . It can be primary or secondary. This is a case report of 52-year-old female with 180° anti-clockwise rotation of the appendix. Torsion can further leads to strangulation and infarction of the organ. Appendicular torsion could be included in the ...

  7. A retrospective cohort study of shift work and risk of cancer-specific mortality in German male chemical workers.

    Science.gov (United States)

    Yong, Mei; Nasterlack, Michael; Messerer, Peter; Oberlinner, Christoph; Lang, Stefan

    2014-02-01

    Human evidence of carcinogenicity concerning shift work is inconsistent. In a previous study, we observed no elevated risk of total mortality in shift workers followed up until the end of 2006. The present study aimed to investigate cancer-specific mortality, relative to shift work. The cohort consisted of male production workers (14,038 shift work and 17,105 day work), employed at BASF Ludwigshafen for at least 1 year between 1995 and 2005. Vital status was followed from 2000 to 2009. Cause-specific mortality was obtained from death certificates. Exposure to shift work was measured both as a dichotomous and continuous variable. While lifetime job history was not available, job duration in the company was derived from personal data, which was then categorized at the quartiles. Cox proportional hazard model was used to adjust for potential confounders, in which job duration was treated as a time-dependent covariate. Between 2000 and 2009, there were 513 and 549 deaths among rotating shift and day work employees, respectively. Risks of total and cancer-specific mortalities were marginally lower among shift workers when taking age at entry and job level into consideration and were statistically significantly lower when cigarette smoking, alcohol intake, job duration, and chronic disease prevalence at entry to follow-up were included as explanatory factors. With respect to mortality risks in relation to exposure duration, no increased risks were found in any of the exposure groups after full adjustment and there was no apparent trend suggesting an exposure-response relation with duration of shift work. The present analysis extends and confirms our previous finding of no excess risk of mortality associated with work in the shift system employed at BASF Ludwigshafen. More specifically, there is also no indication of an increased risk of mortality due to cancer.

  8. Solvent-induced chemical shifts of methoxyl nuclear resonance signals in chalcones by benzene and trifluoroacetic acid

    Science.gov (United States)

    Khurana, Shashi K.; Krishnamoorthy, V.; Parmar, Virinder S.

    The 1H NMR spectra of eight different methoxylated chalcones have separately been recorded, (1) in deuterated chloroform; (2) in a mixture (1:1) of deuterated chloroform and benzene; and (3) in a mixture of deuterated chloroform, benzene and trifluoroacetic acid (2:2:1) and the benzene induced and TFA induced shift values have been assigned to different methoxyl groups. These shift values can serve as a guide in determining the structures of natural or new chalcones. The steric, electronic and conformational factors are discussed to explain the shift values.

  9. Chemical shifts of K-X-ray absorption edges on copper in different compounds by X-ray absorption spectroscopy (XAS) with Synchrotron radiation

    Science.gov (United States)

    Joseph, D.; Basu, S.; Jha, S. N.; Bhattacharyya, D.

    2012-03-01

    Cu K X-ray absorption edges were measured in compounds such as CuO, Cu(CH3CO2)2, Cu(CO3)2, and CuSO4 where Cu is present in oxidation state of 2+, using the energy dispersive EXAFS beamline at INDUS-2 Synchrotron radiation source at RRCAT, Indore. Energy shifts of ˜4-7 eV were observed for Cu K X-ray absorption edge in the above compounds compared to its value in elemental copper. The difference in the Cu K edge energy shifts in the different compounds having same oxidation state of Cu shows the effect of different chemical environments surrounding the cation in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on Cu cations in the above compounds.

  10. NMR spectroscopic studies of a TAT-derived model peptide in imidazolium-based ILs: influence on chemical shifts and the cis/trans equilibrium state.

    Science.gov (United States)

    Wiedemann, Christoph; Ohlenschläger, Oliver; Mrestani-Klaus, Carmen; Bordusa, Frank

    2017-09-13

    NMR spectroscopy was used to study systematically the impact of imidazolium-based ionic liquid (IL) solutions on a TAT-derived model peptide containing Xaa-Pro peptide bonds. The selected IL anions cover a wide range of the Hofmeister series of ions. Based on highly resolved one- and two-dimensional NMR spectra individual 1 H and 13 C peptide chemical shift differences were analysed and a classification of IL anions according to the Hofmeister series was derived. The observed chemical shift changes indicate significant interactions between the peptide and the ILs. In addition, we examined the impact of different ILs towards the cis/trans equilibrium state of the Xaa-Pro peptide bonds. In this context, the IL cations appear to be of exceptional importance for inducing an alteration of the native cis/trans equilibrium state of Xaa-Pro bonds in favour of the trans-isomers.

  11. 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: 4.449, year: 2015 http://pubs.rsc.org/en/content/articlepdf/2015/cp/c5cp04214c

  12. Nonsuppressing normal thymus on chemical-shift MR imaging and anterior mediastinal lymphoma: differentiation with diffusion-weighted MR imaging by using the apparent diffusion coefficient.

    Science.gov (United States)

    Priola, Adriano Massimiliano; Priola, Sandro Massimo; Gned, Dario; Giraudo, Maria Teresa; Veltri, Andrea

    2018-04-01

    To prospectively evaluate usefulness of the apparent diffusion coefficient (ADC) in differentiating anterior mediastinal lymphoma from nonsuppressing normal thymus on chemical-shift MR, and to look at the relationship between patient age and ADC. Seventy-three young subjects (25 men, 48 women; age range, 9-29 years), who underwent chemical-shift MR and diffusion-weighted MR were divided into a normal thymus group (group A, 40 subjects), and a lymphoma group (group B, 33 patients). For group A, all subjects had normal thymus with no suppression on opposed-phase chemical-shift MR. Two readers measured the signal intensity index (SII) and ADC. Differences in SII and ADC between groups were tested using t-test. ADC was correlated with age using Pearson correlation coefficient. Mean SII±standard deviation was 2.7±1.8% for group A and 2.2±2.4% for group B, with no significant difference between groups (P=.270). Mean ADC was 2.48±0.38x10 -3 mm 2 /s for group A and 1.24±0.23x10 -3 mm 2 /s for group B. A significant difference between groups was found (Pnormal thymus at visual assessment • ADC is useful for distinguishing nonsuppressing normal thymus from mediastinal lymphoma • ADC is more accurate than transverse-diameter and surface-area in this discrimination • ADC of normal thymus is age dependent and increases with increasing age.

  13. Molecular and Silica-Supported Molybdenum Alkyne Metathesis Catalysts: Influence of Electronics and Dynamics on Activity Revealed by Kinetics, Solid-State NMR, and Chemical Shift Analysis.

    Science.gov (United States)

    Estes, Deven P; Gordon, Christopher P; Fedorov, Alexey; Liao, Wei-Chih; Ehrhorn, Henrike; Bittner, Celine; Zier, Manuel Luca; Bockfeld, Dirk; Chan, Ka Wing; Eisenstein, Odile; Raynaud, Christophe; Tamm, Matthias; Copéret, Christophe

    2017-12-06

    Molybdenum-based molecular alkylidyne complexes of the type [MesC≡Mo{OC(CH 3 ) 3-x (CF 3 ) x } 3 ] (MoF 0 , x = 0; MoF 3 , x = 1; MoF 6 , x = 2; MoF 9 , x = 3; Mes = 2,4,6-trimethylphenyl) and their silica-supported analogues are prepared and characterized at the molecular level, in particular by solid-state NMR, and their alkyne metathesis catalytic activity is evaluated. The 13 C NMR chemical shift of the alkylidyne carbon increases with increasing number of fluorine atoms on the alkoxide ligands for both molecular and supported catalysts but with more shielded values for the supported complexes. The activity of these catalysts increases in the order MoF 0 catalysts coupled with DFT/ZORA calculations rationalize the NMR spectroscopic signatures and discernible activity trends at the frontier orbital level: (1) increasing the number of fluorine atoms lowers the energy of the π*(M≡C) orbital, explaining the more deshielded chemical shift values; it also leads to an increased electrophilicity and higher reactivity for catalysts up to MoF 6 , prior to a sharp decrease in reactivity for MoF 9 due to the formation of stable metallacyclobutadiene intermediates; (2) the silica-supported catalysts are less active than their molecular analogues because they are less electrophilic and dynamic, as revealed by their 13 C NMR chemical shift tensors.

  14. MR imaging of osteonecrosis using frequency selective chemical shift sequences; Neue Aspekte in der MR-Diagnostik der Osteonekrose: Selektive Fett/Wasser-Bildgebung

    Energy Technology Data Exchange (ETDEWEB)

    Duda, S.H. [Abt. fuer Radiologische Diagnostik, Tuebingen Univ. (Germany); Laniado, M. [Abt. fuer Radiologische Diagnostik, Tuebingen Univ. (Germany); Schick, F. [Inst. fuer Physik, Tuebingen Univ. (Germany)

    1993-12-31

    The MR appearance of osteonecrosis was assessed on selective fat- and water images to further evaluate the nature of double-line sign. Conventional T1- and T2-weighted SE and frequency selective chemical shift images of eight patients with avascular necrosis of the femoral head and three patients with bone infarcts were retrospectively reviewed. Eight of 11 patients showed a double-line sign on T2-weighted SE images. In these cases, correlation with selective water images revealed that a chemical shift artifact contributed to appearance and location of the hyperintense line. The authors conclude that chemical shift imaging improves our understanding of the nature of the double-line sign. (orig.) [Deutsch] Das MR-tomographische Erscheinungsbild der Osteonekrose auf selektiven Fett- und Wasserbildern wurde analysiert, um das in der Literatur beschriebene Doppellinienzeichen naeher zu untersuchen. Hierfuer wurden sowohl die herkoemmlichen T1- und T2-gewichteten Spin-Echo-Sequenzen herangezogen, als auch frequenzselektive Bilder, die aufgrund chemischer Verschiebung gewonnen wurden (1,5 T). Es wurden die Untersuchungen von acht Patienten mit avaskulaerer Hueftkopfnekrose und von drei Patienten mit Knocheninfarkten retrospektiv ausgewertet. Acht von 11 Patienten zeigten ein Doppellinienzeichen auf den T2-gewichteten Bildern. Die Korrelation mit den selektiven Wasserbildern ergab, dass durch chemische Verschiebung bedingte Artefakte das Erscheinungsbild und den Ort der hyperintensen Linie beeinflussten. Die Bildgebung mit Hilfe der chemischen Verschiebung verbessert unser Verstaendnis der MRT-Charakteristika der Osteonekrose. (orig.)

  15. Torsion of the vermiform appendix: A case report | Wani | Internet ...

    African Journals Online (AJOL)

    Torsion of the vermiform appendix is a rare condition with few cases reported in the literature. Various factors predispose to torsion. Various factors predispose to torsion. We report a case of primary torsion of the vermiform appendix. The clinical presentation was indistinguishable from acute appendicitis and the diagnosis ...

  16. Acute and intermittent testicular torsion: Analysis of presentation ...

    African Journals Online (AJOL)

    Background: Testicular torsion compromises the blood supply to the testes and may result in testicular loss or damage if not dealt with promptly. It can occur either as acute testicular torsion (ATT) or intermittent testicular torsion (ITT). This study examines the presentation, management, and outcome of adult testicular torsion.

  17. Measurement of tibial torsion by computer tomography

    International Nuclear Information System (INIS)

    Jend, H.-H.; Heller, M.; Dallek, M.; Schoettle, H.

    1981-01-01

    A CT procedure for objective measurements of tibial torsion independent of axial rotation in the nearby joints is described. Transverse sections in defined planes of the tibia permit easy calculation of normal and abnormal congenital or posttraumatic angles of torsion. In 69 limbs normal tibial torsion was 40 0 +-9 0 . In a series of 42 limbs with complicated healing of a fracture of both bones of the leg it is shown that tibial maltorsion is a deformity which in most cases leads to arthrosis of the ankle joint. (Auth.)

  18. Measurement of tibial torsion by computer tomography

    Energy Technology Data Exchange (ETDEWEB)

    Jend, H.H.; Heller, M.; Dallek, M.; Schoettle, H. (Hamburg Univ. (Germany, F.R.))

    1981-01-01

    A CT procedure for objective measurements of tibial torsion independent of axial rotation in the nearby joints is described. Transverse sections in defined planes of the tibia permit easy calculation of normal and abnormal congenital or posttraumatic angles of torsion. In 69 limbs normal tibial torsion was 40/sup 0/+-9/sup 0/. In a series of 42 limbs with complicated healing of a fracture of both bones of the leg it is shown that tibial maltorsion is a deformity which in most cases leads to arthrosis of the ankle joint.

  19. MSTor version 2013: A new version of the computer code for the multi-structural torsional anharmonicity, now with a coupled torsional potential

    Science.gov (United States)

    Zheng, Jingjing; Meana-Pañeda, Rubén; Truhlar, Donald G.

    2013-08-01

    partition functions using the torsional eigenvalue summation method. Additional comments: The program package includes a manual, installation script, and input and output files for a test suite. Running time: There are 26 test runs. The running time of the test runs on a single processor of the Itasca computer is less than 2 s. References: [1] MS-T(C) method: Quantum Thermochemistry: Multi-Structural Method with Torsional Anharmonicity Based on a Coupled Torsional Potential, J. Zheng and D.G. Truhlar, Journal of Chemical Theory and Computation 9 (2013) 1356-1367, DOI: http://dx.doi.org/10.1021/ct3010722. [2] MS-T(U) method: Practical Methods for Including Torsional Anharmonicity in Thermochemical Calculations of Complex Molecules: The Internal-Coordinate Multi-Structural Approximation, J. Zheng, T. Yu, E. Papajak, I, M. Alecu, S.L. Mielke, and D.G. Truhlar, Physical Chemistry Chemical Physics 13 (2011) 10885-10907.

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

    International Nuclear Information System (INIS)

    Yu Risheng; Sun Jianzhong; Ding Wenhong; Xu Xiufang; Wang Zhikang

    2009-01-01

    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 (NaH 2 PO 4 ) 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

  1. Influence of temperature changes on torsional rigidity and damping coefficient of rubber torsional vibration damper

    Directory of Open Access Journals (Sweden)

    Wojciech HOMIK

    2011-01-01

    Full Text Available The short explanation of usefulness of rubber torsional dampers in crankshaft in multi-cylinder engines is presented. The description of the construction and operation of rubber torsional damper is also included. In the rubber torsional damper, the damping is achieved as the effect of internal friction resulting from the deformation of the rubber material. This deformation appears while the internal rubber elasticity is overloaded. Both the physical and mechanical rubber properties depend on temperature change. In cooperation with rubber dampers manufacturer the experimental investigations are made in order to establish the influence of temperature change on torsional stiffness and damping.

  2. Isolated torsion of fallopian tube. Radiological findings

    International Nuclear Information System (INIS)

    Tomas Fanjul, L.; Aldea Martinez, J.; Fernandez Matia, G.; Rodrigo Verguizas, J.; Fernandez Alvarez, G.; Galindo Vicente, M.C.

    1993-01-01

    Isolated tubal torsion is a very uncommon disorder that is rarely diagnosed preoperatively. We present a case and review the literature, which only provides ultrasonographic findings in 5 cases reported to date. 11 refs

  3. Torsion sensing based on patterned piezoelectric beams

    Science.gov (United States)

    Cha, Youngsu; You, Hangil

    2018-03-01

    In this study, we investigated the sensing characteristics of piezoelectric beams under torsional loads. We used partially patterned piezoelectric beams to sense torsion. In particular, the piezoelectric patches are located symmetrically with respect to the line of the shear center of the beam. The patterned piezoelectric beam is modeled as a slender beam, and its electrical responses are obtained by piezoelectric electromechanical equations. To validate the modeling framework, experiments are performed using a setup that forces pure torsional deformation. Three different geometric configurations of the patterned piezoelectric layer are used for the experiments. The frequency and amplitude of the forced torsional load are systematically varied in order to study the behavior of the piezoelectric sensor. Experimental results demonstrate that two voltage outputs of the piezoelectric beam are approximately out of phase with identical amplitude. Moreover, the length of the piezoelectric layers has a significant influence on the sensing properties. Our theoretical predictions using the model support the experimental findings.

  4. Integrated ecological and chemical food web accumulation modeling explains PAH temporal trends during regime shifts in a shallow lake.

    Science.gov (United States)

    Kong, Xiangzhen; He, Wei; Qin, Ning; Liu, Wenxiu; Yang, Bin; Yang, Chen; Xu, Fuliu; Mooij, Wolf M; Koelmans, Albert A

    2017-08-01

    Shallow lakes can switch suddenly from a turbid situation with high concentrations of phytoplankton and other suspended solids to a vegetated state with clear water, and vice versa. These alternative stable states may have a substantial impact on the fate of hydrophobic organic compounds (HOCs). Models that are fit to simulate impacts from these complex interactions are scarce. We developed a contaminant fate model which is linked to an ecosystem model (PCLake) for shallow lakes. This integrated model was successful in simulating long-term dynamics (1953-2012) of representative polycyclic aromatic hydrocarbons (PAHs) in the main biotic and abiotic components in a large shallow lake (Chaohu in China), which has undergone regime shifts in this period. Historical records from sediment cores were used to evaluate the model. The model revealed that regime shifts in shallow lakes had a strong impact on the fate of less hydrophobic compounds due to the large storage capacity of macrophytes, which accumulated up to 55.6% of phenanthrene in the clear state. The abrupt disappearance of macrophytes after the regime shift resulted in a sudden change in phenanthrene distribution, as the sediment became the major sink. For more hydrophobic compounds such as benzo(a)pyrene, the modeled impact of the regime shift was negligible for the whole environment, yet large for biotic compartments. This study is the first to provide a full mechanistic analysis of the impact of regime shifts on the fate of PAHs in a real lake ecosystem. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Internal torsion resistance in deflected shafts

    Directory of Open Access Journals (Sweden)

    Mahmoud T. El-Sayed

    2017-06-01

    The objective of the present work was to estimate the effect of internal torsional resistance in shafts which is caused by deflection, for the reason that it has the upper hand on misalignment problem. With the aim of fulfilling this objective, an experimental rig has been constructed to verify the existence of the torsional resistance in deflected shafts and its variation with the rotation angle.

  6. Torsion and geometrostasis in covariant superstrings

    Energy Technology Data Exchange (ETDEWEB)

    Zachos, C.

    1985-01-01

    The covariant action for freely propagating heterotic superstrings consists of a metric and a torsion term with a special relative strength. It is shown that the strength for which torsion flattens the underlying 10-dimensional superspace geometry is precisely that which yields free oscillators on the light cone. This is in complete analogy with the geometrostasis of two-dimensional sigma-models with Wess-Zumino interactions. 13 refs.

  7. Torsion of Wandering Gallbladder following Colonoscopy

    Directory of Open Access Journals (Sweden)

    Sean R. Warfe

    2013-01-01

    Full Text Available Torsion of the gallbladder is an uncommon condition that may present as an acute abdomen. Its preoperative diagnosis can often be challenging due to its variable presentation, with specific sonographic signs seen infrequently. We describe, to our knowledge, the first case of torsion of a wandering gallbladder following a colonoscopy in a 69-year-old female who presented with acute abdominal pain after procedure. This was discovered intraoperatively, and after a subsequent cholecystectomy, she had an uncomplicated recovery.

  8. Attentional Modulation of Eye Torsion Responses

    Science.gov (United States)

    Stevenson, Scott B.; Mahadevan, Madhumitha S.; Mulligan, Jeffrey B.

    2016-01-01

    Eye movements generally have both reflexive and voluntary aspects, but torsional eye movements are usually thought of as a reflexive response to image rotation around the line of sight (torsional OKN) or to head roll (torsional VOR). In this study we asked whether torsional responses could be modulated by attention in a case where two stimuli rotated independently, and whether attention would influence the latency of responses. The display consisted of rear-projected radial "pinwheel" gratings, with an inner annulus segment extending from the center to 22 degrees eccentricity, and an outer annulus segment extending from 22 degrees out to 45 degrees eccentricity. The two segments rotated around the center in independent random walks, stepping randomly 4 degrees clockwise or counterclockwise at 60 Hz. Subjects were asked to attend to one or the other while keeping fixation steady at the center of the display. To encourage attention on one or the other segment of the display, subjects were asked to move a joystick in synchrony with the back and forth rotations of one part of the image while ignoring the other. Eye torsion was recorded with the scleral search coil technique, sampled at 500 Hz. All four subjects showed roughly 50% stronger torsion responses to the attended compared to unattended segments. Latency varied from 100 to 150 msec across subjects and was unchanged by attention. These findings suggest that attention can influence eye movement responses that are not typically under voluntary control.

  9. Twist buckling of veins under torsional loading.

    Science.gov (United States)

    Garcia, Justin R; Sanyal, Arnav; Fatemifar, Fatemeh; Mottahedi, Mohammad; Han, Hai-Chao

    2017-06-14

    Veins are often subjected to torsion and twisted veins can hinder and disrupt normal blood flow but their mechanical behavior under torsion is poorly understood. The objective of this study was to investigate the twist deformation and buckling behavior of veins under torsion. Twist buckling tests were performed on porcine internal jugular veins (IJVs) and human great saphenous veins (GSVs) at various axial stretch ratio and lumen pressure conditions to determine their critical buckling torques and critical buckling twist angles. The mechanical behavior under torsion was characterized using a two-fiber strain energy density function and the buckling behavior was then simulated using finite element analysis. Our results demonstrated that twist buckling occurred in all veins under excessive torque characterized by a sudden kink formation. The critical buckling torque increased significantly with increasing lumen pressure for both porcine IJV and human GSV. But lumen pressure and axial stretch had little effect on the critical twist angle. The human GSVs are stiffer than the porcine IJVs. Finite element simulations captured the buckling behavior for individual veins under simultaneous extension, inflation, and torsion with strong correlation between predicted critical buckling torques and experimental data (R 2 =0.96). We conclude that veins can buckle under torsion loading and the lumen pressure significantly affects the critical buckling torque. These results improve our understanding of vein twist behavior and help identify key factors associated in the formation of twisted veins. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. 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.

  11. Hydrogen Atomic Positions of O-H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with ¹H-NMR Chemical Shifts and X-ray Diffraction Methods.

    Science.gov (United States)

    Siskos, Michael G; Choudhary, M Iqbal; Gerothanassis, Ioannis P

    2017-03-07

    The exact knowledge of hydrogen atomic positions of O-H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i) density functional theory (DFT) calculations after a structure has been determined by X-ray from single crystals or from powders; (ii) ¹H-NMR chemical shifts as constraints in DFT calculations, and (iii) use of root-mean-square deviation between experimentally determined and DFT calculated ¹H-NMR chemical shifts considering the great sensitivity of ¹H-NMR shielding to hydrogen bonding properties.

  12. Torsional oscillations of strange stars

    Directory of Open Access Journals (Sweden)

    Mannarelli Massimo

    2014-01-01

    Full Text Available Strange stars are one of the hypothetical compact stellar objects that can be formed after a supernova explosion. The existence of these objects relies on the absolute stability of strange collapsed quark matter with respect to standard nuclear matter. We discuss simple models of strange stars with a bare quark matter surface, thus standard nuclear matter is completely absent. In these models an electric dipole layer a few hundreds Fermi thick should exist close to the star surface. Studying the torsional oscillations of the electrically charged layer we estimate the emitted power, finding that it is of the order of 1045 erg/s, meaning that these objects would be among the brightest compact sources in the heavens. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. Although part of the radiated power should be absorbed by the electrosphere surrounding the strange star, a sizable fraction of photons should escape and be detectable.

  13. 31P MAS refocused INADEQUATE spin-echo (REINE) NMR spectroscopy: revealing J coupling and chemical shift two-dimensional correlations in disordered solids.

    Science.gov (United States)

    Guerry, Paul; Smith, Mark E; Brown, Steven P

    2009-08-26

    Two-dimensional (2D) variations in (2)J(P(1),P(1)), (2)J(P(1),P(2)), and (2)J(P(2),P(2)) are obtained--using the REINE (REfocused INADEQUATE spin-Echo) pulse sequence presented by Cadars et al. (Phys. Chem. Chem. Phys. 2007, 9, 92-103)--from pixel-by-pixel fittings of the spin-echo modulation for the 2D correlation peaks due to linked phosphate tetrahedra (P(1)-P(1), P(1)-P(2), P(2)-P(1), and P(2)-P(2)) in a (31)P refocused INADEQUATE solid-state MAS NMR spectrum of a cadmium phosphate glass, 0.575CdO-0.425P(2)O(5). In particular, separate variations for each 2D (31)P REINE peak are obtained which reveal correlations between the J couplings and the (31)P chemical shifts of the coupled nuclei that are much clearer than those evident in previously presented 2D z-filtered (31)P spin-echo spectra. Notably, such correlations between the J couplings and the (31)P chemical shifts are observed even though the conditional probability distributions extracted using the protocol of Cadars et al. (J. Am. Chem. Soc. 2005, 127, 4466-4476) indicate that there is no marked correlation between the (31)P chemical shifts of neighboring phosphate tetrahedra. For 2D peaks at the P(2) (31)P chemical shift in the direct dimension, there can be contributions from chains of three units (P(1)-P(2)-P(1)), chains of four units (P(1)-P(2)-P(2)-P(1)), or longer chains or rings (-P(2)-P(2)-P(2)-): for the representative glass considered here, best fits are obtained assuming a glass comprised predominantly of chains of four units. The following variations are found: (2)J(P(1),P(1)) = 13.4 +/- 0.3 to 14.8 +/- 0.5 Hz, (2)J(P(1),P(2)) = 15.0 +/- 0.3 to 18.2 +/- 0.3 Hz, and (2)J(P(2),P(2)) = 5.9 +/- 0.6 to 9.1 +/- 0.9 Hz from the fits to the P(1)-P(1), P(1)-P(2), and P(2)-P(2) peaks, respectively. The correlation of a particular J coupling with the (31)P chemical shifts of the considered nucleus and the coupled nucleus is quantified by the coefficients C(F(2)) and C(F(1)) that correspond to the

  14. CSI 3.0: a web server for identifying secondary and super-secondary structure in proteins using NMR chemical shifts.

    Science.gov (United States)

    Hafsa, Noor E; Arndt, David; Wishart, David S

    2015-07-01

    The Chemical Shift Index or CSI 3.0 (http://csi3.wishartlab.com) is a web server designed to accurately identify the location of secondary and super-secondary structures in protein chains using only nuclear magnetic resonance (NMR) backbone chemical shifts and their corresponding protein sequence data. Unlike earlier versions of CSI, which only identified three types of secondary structure (helix, β-strand and coil), CSI 3.0 now identifies total of 11 types of secondary and super-secondary structures, including helices, β-strands, coil regions, five common β-turns (type I, II, I', II' and VIII), β hairpins as well as interior and edge β-strands. CSI 3.0 accepts experimental NMR chemical shift data in multiple formats (NMR Star 2.1, NMR Star 3.1 and SHIFTY) and generates colorful CSI plots (bar graphs) and secondary/super-secondary structure assignments. The output can be readily used as constraints for structure determination and refinement or the images may be used for presentations and publications. CSI 3.0 uses a pipeline of several well-tested, previously published programs to identify the secondary and super-secondary structures in protein chains. Comparisons with secondary and super-secondary structure assignments made via standard coordinate analysis programs such as DSSP, STRIDE and VADAR on high-resolution protein structures solved by X-ray and NMR show >90% agreement between those made with CSI 3.0. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  15. Liver steatosis (LS) evaluated through chemical-shift magnetic resonance imaging liver enzymes in morbid obesity; effect of weight loss obtained with intragastric balloon gastric banding.

    Science.gov (United States)

    Folini, Laura; Veronelli, Annamaria; Benetti, Alberto; Pozzato, Carlo; Cappelletti, Marco; Masci, Enzo; Micheletto, Giancarlo; Pontiroli, Antonio E

    2014-01-01

    The aim of this study was to evaluate in morbid obesity clinical and metabolic effects related to weight loss on liver steatosis (LS), measured through chemical-shift magnetic resonance imaging (MRI) and liver enzymes. Forty obese subjects (8 M/32 W; BMI 42.8 ± 7.12 kg/m(2), mean ± SD) were evaluated for LS through ultrasound (US-LS), chemical-shift MRI (MRI-LS), liver enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyltransferase (GGT), alkaline phosphatase (ALP)], anthropometric parameters [weight, BMI, waist circumference (WC)], lipids, insulin, insulin resistance (HOMA-IR), glycated hemoglobin (HbA1c), oral glucose tolerance test, and body composition [fat mass (FM) and fat-free mass (FFM) at bio-impedance analysis (BIA)]. Anthropometric measures, MRI-LS, BIA, and biochemical parameters were reevaluated 6 months later in 18 subjects undergoing restrictive bariatric approach, i.e., intragastric balloon (BIB, n = 13) or gastric banding (LAGB, n = 5), and in 13 subjects receiving hypocaloric diet. At baseline, US-LS correlates only with MRI-LS, and the latter correlates with ALT, AST, and GGT. After 6 months, subjects undergoing BIB or LAGB had significant changes of BMI, weight, WC, ALT, AST, GGT, ALP, HbA1c, insulin, HOMA-IR, FM, FFM, and MRI-LS. Diet-treated obese subjects had no significant change of any parameter under study; change of BMI, fat mass, and fat-free mass was significantly greater in LAGB/BIB subjects than in diet-treated subjects. Change of MRI-LS showed a significant correlation with changes in weight, BMI, WC, GGT, ALP, and basal MRI-LS. Significant weight loss after BIB or LAGB is associated with decrease in chemical-shift MRI-LS and with reduction in liver enzymes; chemical-shift MRI and liver enzymes allow monitoring of LS in follow-up studies.

  16. 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)

  17. Refinement of labile hydrogen positions based on DFT calculations of 1H NMR chemical shifts: comparison with X-ray and neutron diffraction methods.

    Science.gov (United States)

    Siskos, Michael G; Choudhary, M Iqbal; Gerothanassis, Ioannis P

    2017-05-31

    Numerous gas phase electron diffraction, ultra-fast electron diffraction, X-ray and neutron diffraction experiments on β-dicarbonyl compounds exhibiting enol-enol tautomeric equilibrium, with emphasis on acetylacetone and dibenzoylmethane, have so far been reported with conflicting results on the structural details of the O-HO intramolecular hydrogen bond and resulted in alternative hypotheses on the intramolecular hydrogen bond potential function either a double minimum potential corresponding to two tautomeric forms in equilibrium or a single symmetrical one. We demonstrate herein, firstly, that the DFT calculated OH 1 H NMR chemical shifts of acetylacetone and dibenzoylmethane exhibit a strong linear dependence on the computed OO hydrogen bond length of ∼-50 ppm Å -1 and as a function of the O-HO bond angle of ∼1 ppm per degree, upon the transfer of the hydrogen atom from the ground state toward the transition state. Secondly, the refinement of labile hydrogen atomic positions in intramolecular hydrogen bonds based on the root-mean-square deviation between experimentally determined and DFT calculated 1 H NMR chemical shifts in solution can provide high resolution structures of O-H and O(H)O bond lengths and O-HO bond angles with an accuracy of ∼10 -2 Å and ∼0.5°, respectively. Thirdly, the calculated 1 H NMR chemical shifts in solution of the two ground state tautomers in equilibrium of acetylacetone and dibenzoylmethane are in excellent agreement with the experimental value, even for moderate basis sets for energy minimization. In contrast, the single symmetrical structure in a strongly delocalized system is a transition state with calculated 1 H NMR chemical shifts which strongly deviate from the experimental value. Fourth, the DFT calculated ground state O-H bond lengths of acetylacetone and dibenzoylmethane are in quantitative agreement with the literature data which take into account the effect of quantum nuclear motion. The DFT structural

  18. Hydrogen exchange rate of tyrosine hydroxyl groups in proteins as studied by the deuterium isotope effect on C(zeta) chemical shifts.

    Science.gov (United States)

    Takeda, Mitsuhiro; Jee, Jungoo; Ono, Akira Mei; Terauchi, Tsutomu; Kainosho, Masatsune

    2009-12-30

    We describe a new NMR method for monitoring the individual hydrogen exchange rates of the hydroxyl groups of tyrosine (Tyr) residues in proteins. The method utilizes (2S,3R)-[beta(2),epsilon(1,2)-(2)H(3);0,alpha,beta,zeta-(13)C(4);(15)N]-Tyr, zeta-SAIL Tyr, to detect and assign the (13)C(zeta) signals of Tyr rings efficiently, either by indirect (1)H-detection through 7-8 Hz (1)H(delta)-(13)C(zeta) spin couplings or by direct (13)C(zeta) observation. A comparison of the (13)C(zeta) chemical shifts of three Tyr residues of an 18.2 kDa protein, EPPIb, dissolved in H(2)O and D(2)O, revealed that all three (13)C(zeta) signals in D(2)O appeared at approximately 0.13 ppm ( approximately 20 Hz at 150.9 MHz) higher than those in H(2)O. In a H(2)O/D(2)O (1:1) mixture, however, one of the three signals for (13)C(zeta) appeared as a single peak at the averaged chemical shifts, and the other two appeared as double peaks at exactly the same chemical shifts in H(2)O and D(2)O, in 50 mM phosphate buffer (pH 6.6) at 40 degrees C. These three peaks were assigned to Tyr-36, Tyr-120, and Tyr-30, from the lower to higher chemical shifts, respectively. The results indicate that the hydroxyl proton of Tyr-120 exchanges faster than a few milliseconds, whereas those of Tyr-30 and Tyr-36 exchange more slowly. The exchange rate of the Tyr-30 hydroxyl proton, k(ex), under these conditions was determined by (13)C NMR exchange spectroscopy (EXSY) to be 9.2 +/- 1.1 s(-1). The Tyr-36 hydroxyl proton, however, exchanges too slowly to be determined by EXSY. These profound differences among the hydroxyl proton exchange rates are closely related to their relative solvent accessibility and the hydrogen bonds associated with the Tyr hydroxyl groups in proteins.

  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

    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 decreasing electronegativity of the halogen substituent (F, Cl, Br and I) was reflected in both nonrelativistic and relativistic NMR results as decreased values of chemical shifts of carbon atoms attached to halogen (C3 and C6) leading to a strong sensitivity to halogen atom type at 3 and 6 positions...

  20. 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.

  1. Torsion profiling of proteins using magnetic particles.

    Science.gov (United States)

    van Reenen, A; Gutiérrez-Mejía, F; van IJzendoorn, L J; Prins, M W J

    2013-03-05

    We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 10(3) and 5 × 10(3) pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  2. Solid-state NMR chemical-shift perturbations indicate domain reorientation of the DnaG primase in the primosome of Helicobacter pylori

    Energy Technology Data Exchange (ETDEWEB)

    Gardiennet, Carole [Université de Lorraine, CNRS, CRM2, UMR 7036 (France); Wiegand, Thomas [ETH Zurich, Physical Chemistry (Switzerland); Bazin, Alexandre [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Cadalbert, Riccardo [ETH Zurich, Physical Chemistry (Switzerland); Kunert, Britta; Lacabanne, Denis [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Gutsche, Irina [Université Grenoble Alpes, Institut de Biologie Structurale (IBS), CNRS, IBS, CEA, IBS (France); Terradot, Laurent, E-mail: l.terradot@ibcp.fr [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France); Meier, Beat H., E-mail: beme@ethz.ch [ETH Zurich, Physical Chemistry (Switzerland); Böckmann, Anja, E-mail: a.bockmann@ibcp.fr [Université de Lyon 1, Molecular Microbiology and Structural Biochemistry, Labex Ecofect, UMR 5086 CNRS (France)

    2016-03-15

    We here investigate the interactions between the DnaB helicase and the C-terminal domain of the corresponding DnaG primase of Helicobacter pylori using solid-state NMR. The difficult crystallization of this 387 kDa complex, where the two proteins interact in a six to three ratio, is circumvented by simple co-sedimentation of the two proteins directly into the MAS-NMR rotor. While the amount of information that can be extracted from such a large protein is still limited, we can assign a number of amino-acid residues experiencing significant chemical-shift perturbations upon helicase-primase complex formation. The location of these residues is used as a guide to model the interaction interface between the two proteins in the complex. Chemical-shift perturbations also reveal changes at the interaction interfaces of the hexameric HpDnaB assembly on HpDnaG binding. A structural model of the complex that explains the experimental findings is obtained.

  3. 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...... side missing structural elements in the models can be suggested. A number of proposed structures for humic and fulvic acids are discussed based on the above analysis....

  4. Ocular torsional movements in normal humans.

    Science.gov (United States)

    Kushner, B J; Kraft, S

    1983-06-01

    We conducted three studies of compensatory ocular torsional movements in normal human subjects, using changes in the axis of astigmatism, afterimages, and direct observation with cinematography. Measurements of changes in the axis of astigmatism and the subjects' subjective perception of afterimages with a superimposed Maddox rod showed a partial compensatory intorsion on head tilt to the ipsilateral side and extorsion on head tilt to the contralateral side. Cinematography demonstrated that the eye lags behind the head in a slow rolling movement as the head is tilted. Periodic rotary movements in the direction of the head tilt partially correct the lag and result in a partial compensatory torsion. A fourth experiment excluded false torsion as an artifact in these studies.

  5. Torsional rigidity of submanifolds with controlled geometry

    DEFF Research Database (Denmark)

    Hurtado, Ana; Markvorsen, Steen; Palmer, Vicente

    2009-01-01

    We prove explicit upper and lower bounds for the torsional rigidity of extrinsic domains of submanifolds ^m$ with controlled radial mean curvature in ambient Riemannian manifolds ^n$ with a pole $ and with sectional curvatures bounded from above and from below, respectively. These bounds are given...... in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped product model spaces. Our main results are obtained using methods from previously established isoperimetric inequalities, as found in e.g. [MP4] and [MP5]. As in [MP4] we also characterize the geometry...... of those situations in which the bounds for the torsional rigidity are actually attained and study the behavior at infinity of the so-called geometric average of the mean exit time for Brownian motion....

  6. Torsion in patients with superior oblique palsies: dynamic torsion during saccades and changes in Listing's plane.

    Science.gov (United States)

    Steffen, Heimo; Straumann, Dominik S; Walker, Mark F; Miller, Neil R; Guyton, David L; Repka, Michael X; Zee, David S

    2008-05-01

    The purpose was to assess intra- and post-saccadic torsion in superior oblique palsy (SOP) patients and the effect of surgery on torsion. Eleven patients with a presumed congenital SOP and five with acquired SOP performed 10 degrees vertical saccades over a range of +/-20 degrees. Eye movements were recorded with dual search coils. Dynamic torsion was calculated by subtracting the expected change in torsion during the saccade (based upon static torsion before and after the saccade) from the maximum intrasaccadic torsion. Eight healthy subjects were controls. We also examined the effects of surgery on dynamic torsion and the orientation of Listing's plane in patients with congenital SOP who were operated on either by weakening of the inferior oblique muscle on the affected eye (n=5), by recession of the inferior rectus muscle on the normal eye (n=4) or by both procedures (n=2). Postoperative recordings were obtained at least 1 month after surgery. Patients with congenital and acquired SOP showed an increased dynamic extorsion, primarily during downward saccades. Following a recession of the inferior oblique muscle in congenital SOP patients, half showed significant decreases in extorsion (up to 1.0 degrees) during downward saccades by the affected eye. Following surgery all showed a temporal rotation of Listing's plane (up to 15 degrees for primary position). Patients with a SOP show a characteristic pattern of dynamic torsion during vertical saccades differing from normals. Recession of the inferior oblique muscle leads to rotation of Listing's plane in all congenital SOP patients and causes large changes in dynamic torsion in a subgroup of them, perhaps reflecting the heterogeneity of congenital SOP.

  7. The relationship between torsional rigidity and bending strength ...

    African Journals Online (AJOL)

    torsional buckling resistance of bending members and when members are subjected to torsional loads. This study was based on a series of laboratory experiments on actual sized timber with the focus and emphasis on mechanical properties and ...

  8. Torsional Behavior of Axonal Microtubule Bundles

    Science.gov (United States)

    Lazarus, Carole; Soheilypour, Mohammad; Mofrad, Mohammad R.K.

    2015-01-01

    Axonal microtubule (MT) bundles crosslinked by microtubule-associated protein (MAP) tau are responsible for vital biological functions such as maintaining mechanical integrity and shape of the axon as well as facilitating axonal transport. Breaking and twisting of MTs have been previously observed in damaged undulated axons. Such breaking and twisting of MTs is suggested to cause axonal swellings that lead to axonal degeneration, which is known as “diffuse axonal injury”. In particular, overstretching and torsion of axons can potentially damage the axonal cytoskeleton. Following our previous studies on mechanical response of axonal MT bundles under uniaxial tension and compression, this work seeks to characterize the mechanical behavior of MT bundles under pure torsion as well as a combination of torsional and tensile loads using a coarse-grained computational model. In the case of pure torsion, a competition between MAP tau tensile and MT bending energies is observed. After three turns, a transition occurs in the mechanical behavior of the bundle that is characterized by its diameter shrinkage. Furthermore, crosslink spacing is shown to considerably influence the mechanical response, with larger MAP tau spacing resulting in a higher rate of turns. Therefore, MAP tau crosslinking of MT filaments protects the bundle from excessive deformation. Simultaneous application of torsion and tension on MT bundles is shown to accelerate bundle failure, compared to pure tension experiments. MAP tau proteins fail in clusters of 10–100 elements located at the discontinuities or the ends of MT filaments. This failure occurs in a stepwise fashion, implying gradual accumulation of elastic tensile energy in crosslinks followed by rupture. Failure of large groups of interconnecting MAP tau proteins leads to detachment of MT filaments from the bundle near discontinuities. This study highlights the importance of torsional loading in axonal damage after traumatic brain injury

  9. On the geometrization of electromagnetism by torsion

    International Nuclear Information System (INIS)

    Fonseca Neto, J.B. da.

    1984-01-01

    The possibility of electromagnetism geometrization using an four dimension Cartan geometry is investigated. The Lagrangian density which presents dual invariance for dyons electrodynamics formulated in term of two potentials is constructed. This theory by association of two potentials with track and with torsion pseudo-track and of the field with torsion covariant divergent is described. The minimum coupling of particle gravitational field of scalar and spinorial fields with dyon geometry theory by the minimum coupling of these fields with Cartan geometry was obtained. (author)

  10. The torsion of the multicell sections

    Directory of Open Access Journals (Sweden)

    Marcel STERE

    2010-09-01

    Full Text Available The paper is focused on the stress analysis of thin-walled multicell sections subjected to pure torsion. The shear flow and stiffness characteristics of the cross section for torsion are given. Example: aircraft wing section. The theory for thin-walled closed sections used in this paper was developed by Bredt [3]. The shear flows obtained are used in the design of skins and interior webs, ribs and fasteners at skin splices, skin web junctions and the joints where the ribs meet the skin or webs.

  11. Disseminated peritoneal leiomyomatosis mimicking ovarian torsion

    Directory of Open Access Journals (Sweden)

    Chau-Yang Tyan

    2015-01-01

    Full Text Available The presentation of disseminated peritoneal leiomyomatosis (DPL can be misleading. Herein, we present the case of a 42-year-old nulliparous female who had previously undergone a total hysterectomy and presented with an acute abdomen. A presumptive diagnosis of ovarian torsion was made based on the clinical findings and an ultrasonographic examination. A diagnostic laparoscopy was performed immediately. DPL was subsequently diagnosed based on an intra-operative frozen section during surgical exploration and the final histopathologic examination. This case illustrates an atypical presentation of DPL mimicking ovarian torsion.

  12. Torsional Performance of Wind Turbine Blades

    DEFF Research Database (Denmark)

    Branner, Kim; Berring, Peter; Berggreen, Christian

    2007-01-01

    The present work investigates how well different finite element modeling techniques can predict bending and torsion behavior of a wind turbine blade. Two shell models are investigated. One model has element offsets and the other has the elements at the mid-thickness surfaces of the model. The last...... two models investigated use a combination of shell and solid elements. The results from the numerical investigations are compared with measurements from testing of a section of a full-scale wind turbine blade. It is found that only the combined shell/solid models give reliable results in torsion. Both...

  13. Torsion of the fallopian tube: progression of sonographic features.

    Science.gov (United States)

    Richard, H M; Parsons, R B; Broadman, K F; Shapiro, R S; Yeh, H C

    1998-09-01

    Isolated torsion of the fallopian tube is a rare gynecologic condition that is difficult to diagnose preoperatively. We present the sonographic and CT findings over a 48-hour period in a case of isolated torsion of the fallopian tube. The radiologic features of isolated torsion have been described previously; however, to our knowledge, the progressive findings have not been previously reported.

  14. Testicular torsion: case report | Kuremu | East African Medical Journal

    African Journals Online (AJOL)

    This is a report of bilateral testicular torsion. The objective of the report is to highlight the serious implications of misdiagnosis of testicular torsion. Other than loss of the testis due to necrosis in unilateral torsion, immunological damage of the opposite testis occurs. Early, accurate diagnosis, and institution of the appropriate ...

  15. In Situ Solid-State Reactions Monitored by X-ray Absorption Spectroscopy: Temperature-Induced Proton Transfer Leads to Chemical Shifts.

    Science.gov (United States)

    Stevens, Joanna S; Walczak, Monika; Jaye, Cherno; Fischer, Daniel A

    2016-10-24

    The dramatic colour and phase alteration with the solid-state, temperature-dependent reaction between squaric acid and 4,4'-bipyridine has been probed in situ with X-ray absorption spectroscopy. The electronic and chemical sensitivity to the local atomic environment through chemical shifts in the near-edge X-ray absorption fine structure (NEXAFS) revealed proton transfer from the acid to the bipyridine base through the change in nitrogen protonation state in the high-temperature form. Direct detection of proton transfer coupled with structural analysis elucidates the nature of the solid-state process, with intermolecular proton transfer occurring along an acid-base chain followed by a domino effect to the subsequent acid-base chains, leading to the rapid migration along the length of the crystal. NEXAFS thereby conveys the ability to monitor the nature of solid-state chemical reactions in situ, without the need for a priori information or long-range order. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Comparison of CT and chemical-shift MRI for differentiating thymoma from non-thymomatous conditions in myasthenia gravis: value of qualitative and quantitative assessment

    International Nuclear Information System (INIS)

    Priola, A.M.; Priola, S.M.; Gned, D.; Giraudo, M.T.; Fornari, A.; Veltri, A.

    2016-01-01

    Aim: To evaluate the usefulness of computed tomography (CT) and chemical-shift magnetic resonance imaging (MRI) in patients with myasthenia gravis (MG) for differentiating thymoma (THY) from thymic lymphoid hyperplasia (TLH) and normal thymus (NT), and to determine which technique is more accurate. Materials and methods: Eighty-three patients with generalised MG who underwent surgery were divided into the TLH/NT group (A; 65 patients) and THY group (B; 24 patients). Differences in qualitative characteristics and quantitative data (CT: radiodensity in Hounsfield units; MRI: signal intensity index [SII]) between groups were tested using Fisher's exact test and Student's t-test. Logistic regression models were estimated for both qualitative and quantitative analyses. At quantitative analysis, discrimination abilities were determined according to the area under the receiver operating characteristic (ROC) curve (AUROC) with computation of optimal cut-off points. The diagnostic accuracies of CT and MRI were compared using McNemar's test. Results: At qualitative assessment, MRI had higher accuracy than CT (96.4%, 80/83 and 86.7%, 72/83, respectively). At quantitative analysis, both the radiodensity and SII were significantly different between groups (p<0.0001). For CT, at quantitative assessment, the AUROC of the radiodensity in discriminating between groups was 0.904 (optimal cut-off point, 20 HU) with an accuracy of 77.1% (64/83). For MRI, the AUROC of the SII was 0.989 (optimal cut-off point, 7.766%) with an accuracy of 96.4% (80/83), which was significantly higher than CT (p<0.0001). By using optimal cut-off points for cases with an erroneous diagnosis at qualitative assessment, accuracy improved both for CT (89.2%, 74/83) and MRI (97.6%, 81/83). Conclusion: Quantitative analysis is useful in evaluating patients with MG and improves the diagnostic accuracy of CT and MRI based on qualitative assessment. Chemical-shift MRI is more reliable than CT in

  17. Calibration of the torsional and lateral spring constants of cantilever sensors.

    Science.gov (United States)

    Parkin, John D; Hähner, Georg

    2014-06-06

    A method suitable for the calibration of the spring constants of all torsional and lateral eigenmodes of micro- and nanocantilever sensors is described. Such sensors enable nanomechanical measurements and the characterization of nanomaterials, for example with atomic force microscopy. The method presented involves the interaction of a flow of fluid from a microchannel with the cantilever beam. Forces imparted by the flow cause the cantilever to bend and induce a measurable change of the torsional and lateral resonance frequencies. From the frequency shifts the cantilever spring constants can be determined. The method does not involve physical contact between the cantilever or its tip and a hard surface. As such it is non-invasive and does not risk damage to the cantilever. Experimental data is presented for two rectangular microcantilevers with fundamental flexural spring constants of 0.046 and 0.154 N m(-1). The experimentally determined torsional stiffness values are compared with those obtained by the Sader method. We demonstrate that the torsional spring constants can be readily calibrated using the method with an accuracy of around 15%.

  18. Plant-based torsional actuator with memory

    Science.gov (United States)

    Nayomi Plaza; Samuel L. Zelinka; Don S. Stone; Joseph E. Jakes

    2013-01-01

    A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg􀀀1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-...

  19. FLEXURAL, TORSIONAL AND DISTORTIONAL BUCKLING OF ...

    African Journals Online (AJOL)

    neutral equilibrium of axially compressed single-cell box column with deformable cross-sections. The study ... FLEXURAL, TORSIONAL AND DISTORTIONAL BUCKLING OF SINGLE-CELL THIN-WALLED BOX COLUMNS cr. P : Critical buckling load. S: ... and v of a thin-walled closed structure in series form as follows: (1).

  20. Torsional Performance of Wind Turbine Blades

    DEFF Research Database (Denmark)

    Branner, Kim; Berring, Peter; Berggreen, Christian

    2007-01-01

    The present work investigates how well different finite element modeling techniques can predict bending and torsion behavior of a wind turbine blade. Two shell models are investigated. One model has element offsets and the other has the elements at the mid-thickness surfaces of the model. The las...

  1. Torsion of the gallbladder: a case report

    Directory of Open Access Journals (Sweden)

    Ijaz Samia

    2008-07-01

    Full Text Available Abstract Introduction Torsion of the gallbladder is a rare condition that most commonly affects the elderly. Pre-operative diagnosis is the exception rather than the rule. Any delay in treatment can be fatal as the gallbladder may rupture, leading to biliary peritonitis. Case presentation We present the case of an 80-year-old woman who was admitted with right upper quadrant pain initially thought to be secondary to acute cholecystitis. Subsequent ultrasound and computed tomography scans of the abdomen revealed signs suggestive of acute cholecystitis but neither modality detected any gallstones. As the patient's symptoms failed to resolve on conservative management, she was taken to theatre for an open cholecystectomy. Intra-operatively, the gallbladder had undergone complete torsion and appeared gangrenous. A routine cholecystectomy followed and she recovered from the operation without incident. Conclusion It is rare to diagnose torsion of the gallbladder pre-operatively despite advances in diagnostic imaging. However, this differential diagnosis should be borne in mind particularly in the elderly patient, without proven gallstones, who fails to improve on conservative management. An emergency cholecystectomy is indicated in the event of diagnosing torsion of the gallbladder to avert the potentially lethal sequelae of biliary peritonitis.

  2. Management and Outcome of Testicular Torsion

    African Journals Online (AJOL)

    multiruka1

    MSH, AFS, CGH: Research International East. Africa Limited. Coast Province General Hospital report 2015. 8. Lee SM, Huh JS, BaekM, et al. A Nationwide. Epidemiological Study of Testicular Torsion in. Korea. J Korean Med Sci. 2014; 29(12): 1684–1687. 9. Cattolica EV, Karol JB, Rankin KN, et al. High. Testicular Salvage ...

  3. Right paratesticular abscess mimicking neonatal testicular torsion ...

    African Journals Online (AJOL)

    U.O. Ezomike

    Right paratesticular abscess mimicking neonatal testicular torsion and caused by Proteus mirabilis. U.O. Ezomikea,∗. , M.A. Ituena, S.C. Ekpemoa, S.O. Ekenzeb a Department of Surgery, Federal Medical Centre Umuahia, Abia State, Nigeria b Sub-Department of Pediatric Surgery, University of Nigeria Teaching Hospital, ...

  4. Conformal deformation of Riemann space and torsion

    International Nuclear Information System (INIS)

    Pyzh, V.M.

    1981-01-01

    Method for investigating conformal deformations of Riemann spaces using torsion tensor, which permits to reduce the second ' order equations for Killing vectors to the system of the first order equations, is presented. The method is illustrated using conformal deformations of dimer sphere as an example. A possibility of its use when studying more complex deformations is discussed [ru

  5. Torsion of the gallbladder: a case report.

    Science.gov (United States)

    Ijaz, Samia; Sritharan, Kaji; Russell, Neil; Dar, Manzoor; Bhatti, Tahir; Ormiston, Michael

    2008-07-24

    Torsion of the gallbladder is a rare condition that most commonly affects the elderly. Pre-operative diagnosis is the exception rather than the rule. Any delay in treatment can be fatal as the gallbladder may rupture, leading to biliary peritonitis. We present the case of an 80-year-old woman who was admitted with right upper quadrant pain initially thought to be secondary to acute cholecystitis. Subsequent ultrasound and computed tomography scans of the abdomen revealed signs suggestive of acute cholecystitis but neither modality detected any gallstones. As the patient's symptoms failed to resolve on conservative management, she was taken to theatre for an open cholecystectomy. Intra-operatively, the gallbladder had undergone complete torsion and appeared gangrenous. A routine cholecystectomy followed and she recovered from the operation without incident. It is rare to diagnose torsion of the gallbladder pre-operatively despite advances in diagnostic imaging. However, this differential diagnosis should be borne in mind particularly in the elderly patient, without proven gallstones, who fails to improve on conservative management. An emergency cholecystectomy is indicated in the event of diagnosing torsion of the gallbladder to avert the potentially lethal sequelae of biliary peritonitis.

  6. Pseudotopological quasilocal energy of torsion gravity

    Science.gov (United States)

    Ko, Sheng-Lan; Lin, Feng-Li; Ning, Bo

    2017-08-01

    Torsion gravity is a natural extension to Einstein gravity in the presence of fermion matter sources. In this paper we adopt Wald's covariant method of calculating the Noether charge to construct the quasilocal energy of the Einstein-Cartan-fermion system, and find that its explicit expression is formally independent of the coupling constant between the torsion and axial current. This seemingly topological nature is unexpected and is reminiscent of the quantum Hall effect and topological insulators. However, a coupling dependence does arise when evaluating it on shell, and thus the situation is pseudotopological. Based on the expression for the quasilocal energy, we evaluate it for a particular solution on the entanglement wedge and find agreement with the holographic relative entropy obtained before. This shows the equivalence of these two quantities in the Einstein-Cartan-fermion system. Moreover, the quasilocal energy in this case is not always positive definite, and thus it provides an example of a swampland in torsion gravity. Based on the covariant Noether charge, we also derive the nonzero fermion effect on the Komar angular momentum. The implications of our results for future tests of torsion gravity in gravitational-wave astronomy are also discussed.

  7. The spectrum of axisymmetric torsional Alfven waves

    International Nuclear Information System (INIS)

    Sy, W.N.

    1977-03-01

    The spectrum of axisymmetric torsional Alfven waves propagating in a cylindrical, non-uniform, resistive plasma waveguide has been analysed by a method of singular perturbations. A simple condition has been derived which predicts whether the spectrum is continuous or discrete under given physical conditions. Application of this result to resolve an apparent discrepancy in experimental observations is briefly discussed. (Author)

  8. Bonding and XPS chemical shifts in ZrSiO4 versus SiO2 and ZrO2: Charge transfer and electrostatic effects

    International Nuclear Information System (INIS)

    Guittet, M.J.; Gautier-Soyer, M.; Crocombette, J.P.

    2001-01-01

    The degree of ionic/covalent character in oxides has a great influence on the electronic structure and the material's properties. A simple phenomenological rule is currently used to predict the evolution of covalence/ionicity in mixed oxides compared to the parent ones, and is also widely used to interpret the x-ray photoelectron spectroscopy (XPS) binding-energy shifts of the cations in terms of charge transfer. We test the validity of this simple rule and its application to XPS of mixed oxides with a prototypical system: zircon ZrSiO 4 and parent oxides ZrO 2 and SiO 2 . The ionic charges on Si, Zr, and O were extracted from the density functional theory in the local density approximation calculations in the plane-wave formalism. In agreement with the predictions of the phenomenological rule, the most ionic cation (Zr) becomes more ionic in ZrSiO 4 than in ZrO 2 , while the more covalent one (Si) experiences a corresponding increase in covalence with respect to SiO 2 . The XPS chemical shifts of the O 1s, Si 2p, and Zr 3d 5/2 photoelectron lines in the three oxides were measured and the respective contributions of charge transfer and electrostatic effects (initial state), as well as extra-atomic relaxation effects (final state) evaluated. The validity of the phenomenological rule of mixed oxides used in x-ray electron spectroscopy as well as the opportunity to use the O1s binding-energy shifts to derive a scale of covalence in silicates is discussed

  9. Evaluation of the Aromaticity of a Non-Planar Carbon Nano-Structure by Nucleus-Independent Chemical Shift Criterion: Aromaticity of the Nitrogen- Doped Corannulene

    Directory of Open Access Journals (Sweden)

    A. Reisi-Vanani

    2014-04-01

    Full Text Available Substitution of two or four carbon atoms by nitrogen in the corannulene molecule as a carbon nanostructure was done and the obtained structures were optimized at MP2/6-31G(d level of theory. Calculations of the nucleus-independent chemical shift (NICS were performed to analyze the aromaticity of the corannulene rings and its derivatives upon doping with N at B3LYP/6-31G(d level of theory. Results showed NICS values in six-membered and five-membered rings of two and four N atoms doped corannulene are different and very dependent to number and position of the N atoms. The values of the mean NICS of all N-doped structures are more positive than intact corannulene that show insertion of N atom to the structures causes to decreasing aromaticity of them.

  10. 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)

    Koestler, H.; Beer, M.; Buchner, S.; Sandstede, J.; Pabst, T.; Kenn, W.; Hahn, D.

    2001-01-01

    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 31 P spectroscopy compared to CSI with the same resolution. The results in volunteers indicate that AW-CSI renders 31 P spectroscopy of the lateral and posterior wall of the human heart feasible for patient studies at 1.5 T. (orig.) [de

  11. Comparison of CT and chemical-shift MRI for differentiating thymoma from non-thymomatous conditions in myasthenia gravis: value of qualitative and quantitative assessment.

    Science.gov (United States)

    Priola, A M; Priola, S M; Gned, D; Giraudo, M T; Fornari, A; Veltri, A

    2016-03-01

    To evaluate the usefulness of computed tomography (CT) and chemical-shift magnetic resonance imaging (MRI) in patients with myasthenia gravis (MG) for differentiating thymoma (THY) from thymic lymphoid hyperplasia (TLH) and normal thymus (NT), and to determine which technique is more accurate. Eighty-three patients with generalised MG who underwent surgery were divided into the TLH/NT group (A; 65 patients) and THY group (B; 24 patients). Differences in qualitative characteristics and quantitative data (CT: radiodensity in Hounsfield units; MRI: signal intensity index [SII]) between groups were tested using Fisher's exact test and Student's t-test. Logistic regression models were estimated for both qualitative and quantitative analyses. At quantitative analysis, discrimination abilities were determined according to the area under the receiver operating characteristic (ROC) curve (AUROC) with computation of optimal cut-off points. The diagnostic accuracies of CT and MRI were compared using McNemar's test. At qualitative assessment, MRI had higher accuracy than CT (96.4%, 80/83 and 86.7%, 72/83, respectively). At quantitative analysis, both the radiodensity and SII were significantly different between groups (pquantitative assessment, the AUROC of the radiodensity in discriminating between groups was 0.904 (optimal cut-off point, 20 HU) with an accuracy of 77.1% (64/83). For MRI, the AUROC of the SII was 0.989 (optimal cut-off point, 7.766%) with an accuracy of 96.4% (80/83), which was significantly higher than CT (pqualitative assessment, accuracy improved both for CT (89.2%, 74/83) and MRI (97.6%, 81/83). Quantitative analysis is useful in evaluating patients with MG and improves the diagnostic accuracy of CT and MRI based on qualitative assessment. Chemical-shift MRI is more reliable than CT in differentiating THYs from non-thymomatous conditions. Copyright © 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  12. Electronic structure and (1)H NMR chemical shifts in host-guest complexes of cucurbit[6]uril and sym-tetramethyl cucurbit[6]uril with imidazole derivatives.

    Science.gov (United States)

    Dixit, Priyanka H; Pinjari, Rahul V; Gejji, Shridhar P

    2010-10-14

    Binding patterns and (1)H NMR chemical shifts in the complexes of protonated N-(4-hydroxylphenyl)imidazole (g1), N-(4-aminophenyl)imidazole (g2), 2-phenylimidazole (g3) guests with cucurbit[6]uril (CB[6]), and sym-substituted tetramethyl cucurbit[6]uril (TMeCB[6]) in the gas phase as well as in water have been investigated using the density functional theory. It has been shown that the inclusion complexes of g1 and g2 with CB[6] or TMeCB[6] exhibit selective encapsulation of the phenyl moiety with its substituents binding to portal oxygens on the lower rim of the host and imidazole protons facilitate C-H···O interactions externally with upper rim ureido oxygens. On the other hand, the lowest-energy g3 complex encapsulates the imidazole ring within the host, engendering N-H···O interactions with portal oxygens on the upper rim of the host with the phenyl ring residing outside the cavity owing to an absence of para-substituent and show qualitatively different host-guest binding patterns. Calculated (1)H NMR spectra of the complexes in water reveal shielding of phenyl ring protons within the host cavity which exhibit signals at 0.2-0.5 ppm, whereas the protons of the imidazole ring participating in hydrogen bonded interactions exhibit deshielding, and the corresponding (1)H NMR signals are downshifted by 1.1-1.5 ppm in the spectra compared to those in the unbound guest. (1)H NMR chemical shifts of inclusion complexes thus obtained are in consonant with δ(H) patterns observed in experiments reported in the literature.

  13. Including Torsional Anharmonicity in Canonical and Microcanonical Reaction Path Calculations.

    Science.gov (United States)

    Zheng, Jingjing; Truhlar, Donald G

    2013-07-09

    We reformulate multistructural variational transition state theory by removing the approximation of calculating torsional anharmonicity only at stationary points. The multistructural method with torsional anharmonicity is applied to calculate the reaction-path free energy of the hydrogen abstraction from the carbon-1 position in isobutanol by OH radical. The torsional potential anharmonicity along the reaction path is taken into account by a coupled torsional potential. The calculations show that it can be critical to include torsional anharmonicity in searching for canonical and microcanonical variational transition states. The harmonic-oscillator approximation fails to yield reasonable free energy curves along the reaction path.

  14. [Conservative surgery of ovarian torsion in pediatrics].

    Science.gov (United States)

    Abad, P; Rigol, S; Ezzedine, H; Durán, C; Ortega, D; Martí, M; Pinyot, J

    2003-10-01

    The authors describe the case of two girls diagnosed of ovarian torsion secondary to a cyst. They were operated on by conservative ovarian therapy regardless the time of evolution and ovary macroscopical aspect. These 2 patients were 9 and 13 years old, with abdominal colic pain of 48 and 36 hours of evolution. The diagnosis by doppler sonography was ovarian torsion, with a 4 cms cyst in the right ovary in the first case and a 5 cms cyst in the left ovary in the second patient. Both patients were operated on. After untwisting the ovary, we instille warm saline solution to this ovary and, after waiting for 10 minutes, we resect the ovarian cyst and it recuperates partial and heterogeneous its pink colour. We advise to the family about the possibility of surgical reintervention if the ovary is not viable. After 10 and 12 days of surgical intervention, the Doppler sonography has confirmed the existence of ovary flow and the symmetry of affected ovary in comparation to the opposite on. At the present, both patients are asymptomatic, with exhaustive ultrasound controls. Ovarian torsion is the most frequent complication of ovarian tumours of pediatrics (3-16%) and this is a real emergency in gynecology. Traditionally, it has been recommended the exeresis of ovarian torsion. Regardless the blue aspect of isquemic ovary affected by torsion and the time of evolution, in our experience when there is a minimal possibility of ovarian viability, it is possible to follow a conservative therapy because the macroscopical aspect of the ovary is not necessarily related with the following evolution of the case.

  15. 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.

    Science.gov (United States)

    Kobayashi, Naohiro; Harano, Yoko; Tochio, Naoya; Nakatani, Eiichi; Kigawa, Takanori; Yokoyama, Shigeyuki; Mading, Steve; Ulrich, Eldon L; Markley, John L; Akutsu, Hideo; Fujiwara, Toshimichi

    2012-08-01

    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 (1)H, (13)C and (15)N 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.

  16. A data-oriented self-calibration and robust chemical-shift encoding by using clusterization (OSCAR): Theory, optimization and clinical validation in neuromuscular disorders.

    Science.gov (United States)

    Siracusano, G; La Corte, A; Gaeta, M; Finocchio, G

    2018-01-01

    Multi-echo Chemical Shift-Encoded (CSE) methods for Fat-Water quantification are growing in clinical use due to their ability to estimate and correct some confounding effects. State of the art CSE water/fat separation approaches rely on a multi-peak fat spectrum with peak frequencies and relative amplitudes kept constant over the entire MRI dataset. However, the latter approximation introduces a systematic error in fat percentage quantification in patients where the differences in lipid chemical composition are significant (such as for neuromuscular disorders) because of the spatial dependence of the peak amplitudes. The present work aims to overcome this limitation by taking advantage of an unsupervised clusterization-based approach offering a reliable criterion to carry out a data-driven segmentation of the input MRI dataset into multiple regions. Results established that the presented algorithm is able to identify at least 4 different partitions from MRI dataset under which to perform independent self-calibration routines and was found robust in NMD imaging studies (as evaluated on a cohort of 24 subjects) against latest CSE techniques with either calibrated or non-calibrated approaches. Particularly, the PDFF of the thigh was more reproducible for the quantitative estimation of pathological muscular fat infiltrations, which may be promising to evaluate disease progression in clinical practice. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. NUMERICAL INVESTIGATION OF CURVATURE AND TORSION EFFECTS ON WATER FLOW FIELD IN HELICAL RECTANGULAR CHANNELS

    Directory of Open Access Journals (Sweden)

    A. H. ELBATRAN

    2015-07-01

    Full Text Available Helical channels have a wide range of applications in petroleum engineering, nuclear, heat exchanger, chemical, mineral and polymer industries. They are used in the separation processes for fluids of different densities. The centrifugal force, free surface and geometrical effects of the helical channel make the flow pattern more complicated; hence it is very difficult to perform physical experiment to predict channel performance. Computational Fluid Dynamics (CFD can be suitable alternative for studying the flow pattern characteristics in helical channels. The different ranges of dimensional parameters, such as curvature and torsion, often cause various flow regimes in the helical channels. In this study, the effects of physical parameters such as curvature, torsion, Reynolds number, Froude number and Dean Number on the characteristics of the turbulent flow in helical rectangular channels have been investigated numerically, using a finite volume RANSE code Fluent of Ansys workbench 10.1 UTM licensed. The physical parameters were reported for range of curvature (δ of 0.16 to 0.51 and torsion (λ of 0.032 to 0.1 .The numerical results of this study showed that the decrease in the channel curvature and the increase in the channel torsion numbers led to the increase of the flow velocity inside the channel and the change in the shape of water free surface at given Dean, Reynolds and Froude numbers.

  18. A lanthanide complex with dual biosensing properties: CEST (chemical exchange saturation transfer) and BIRDS (biosensor imaging of redundant deviation in shifts) with europium DOTA-tetraglycinate.

    Science.gov (United States)

    Coman, Daniel; Kiefer, Garry E; Rothman, Douglas L; Sherry, A Dean; Hyder, Fahmeed

    2011-12-01

    Responsive contrast agents (RCAs) composed of lanthanide(III) ion (Ln3R) complexes with a variety of1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA4S) derivatives have shown great potential as molecular imaging agents for MR. A variety of LnDOTA–tetraamide complexes have been demonstrated as RCAs for molecular imaging using chemical exchange saturation transfer (CEST). The CEST method detects proton exchange between bulk water and any exchangeable sites on the ligand itself or an inner sphere of bound water that is shifted by a paramagnetic Ln3R ion bound in the core of the macrocycle. It has also been shown that molecular imaging is possible when the RCA itself is observed (i.e. not its effect on bulk water) using a method called biosensor imaging of redundant deviation in shifts (BIRDS). The BIRDS method utilizes redundant information stored in the nonexchangeable proton resonances emanating from the paramagnetic RCA for ambient factors such as temperature and/or pH.Thus, CEST and BIRDS rely on exchangeable and nonexchangeable protons, respectively, for biosensing. We posited that it would be feasible to combine these two biosensing features into the same RCA (i.e. dual CEST and BIRDS properties). A complex between europium(III) ion (Eu3R) and DOTA–tetraglycinate [DOTA–(gly)S4] was used to demonstrate that its CEST characteristics are preserved, while its BIRDS properties are also detectable. The in vitro temperature sensitivity of EuDOTA–(gly)S4 was used to show that qualitative MR contrast with CEST can be calibrated using quantitative MR mapping with BIRDS, thereby enabling quantitative molecular imaging at high spatial resolution.

  19. Torsional oscillator studies of rotating 3He-A in a slab

    International Nuclear Information System (INIS)

    Walmsley, P.M.Paul M.; Cousins, D.J.Derek J.; Hall, H.E.Henry E.; Golov, A.I.Andrei I.

    2003-01-01

    Using a rotating cryostat we have manipulated l-textures of 3 He-A in a 0.26 mm-thick slab contained in a torsional oscillator. Application of a magnetic field or a counterflow due to rotation lead to a sudden distortion of a uniform texture. The uniformity of the initial texture can be characterized by the resulting shift in frequency and bandwidth of the torsional resonance. With a certain density of vortices induced by rotation a uniform texture can be stabilized even in presence of magnetic. The optimal speed of rotation to prepare a uniform texture while cooling through T c was found. The critical velocities for the flow-induced textural transition and vortex nucleation are determined

  20. Torsion ratchet associated with mechanical hysteresis

    International Nuclear Information System (INIS)

    Han, S.; Wack, B.

    1987-01-01

    The experimental determination of behavior of material like metals, is often obtained with a tube shape sample. For the traction-compression and internal pressure test the direction of the solicitation principal axes is maintened constant. On the contrary the torsion test is a rotational solicitation and thus is accompagnied by secondary effects. For these reasons we conduct some cyclic torsion tests, with or without axial force, and attempt to measure as precisely as possible the axial deformation. The tests are run at a low strain rate and at room temperature so as to reduce as much as possible the influence of the viscosity phenomena and consequently to obtain results whose interpretation may be less complex. (orig./GL)

  1. Torsion and transverse bending of cantilever plates

    Science.gov (United States)

    Reissner, Eric; Stein, Manuel

    1951-01-01

    The problem of combined bending and torsion of cantilever plates of variable thickness, such as might be considered for solid thin high-speed airplane or missile wings, is considered in this paper. The deflections of the plate are assumed to vary linearly across the chord; minimization of the potential energy by means of the calculus of variations then leads to two ordinary linear differential equations for the bending deflections and the twist of the plate. Because the cantilever is analyzed as a plate rather than as a beam, the effect of constraint against axial warping in torsion is inherently included. The application of this method to specific problems involving static deflection, vibration, and buckling of cantilever plates is presented. In the static-deflection problems, taper and sweep are considered.

  2. Comparison of qualitative and quantitative evaluation of diffusion-weighted MRI and chemical-shift imaging in the differentiation of benign and malignant vertebral body fractures.

    Science.gov (United States)

    Geith, Tobias; Schmidt, Gerwin; Biffar, Andreas; Dietrich, Olaf; Dürr, Hans Roland; Reiser, Maximilian; Baur-Melnyk, Andrea

    2012-11-01

    The objective of our study was to compare the diagnostic value of qualitative diffusion-weighted imaging (DWI), quantitative DWI, and chemical-shift imaging in a single prospective cohort of patients with acute osteoporotic and malignant vertebral fractures. The study group was composed of patients with 26 osteoporotic vertebral fractures (18 women, eight men; mean age, 69 years; age range, 31 years 6 months to 86 years 2 months) and 20 malignant vertebral fractures (nine women, 11 men; mean age, 63.4 years; age range, 24 years 8 months to 86 years 4 months). T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. A DW reverse fast imaging with steady-state free precession (PSIF) sequence at different delta values was evaluated qualitatively. A DW echo-planar imaging (EPI) sequence and a DW single-shot turbo spin-echo (TSE) sequence at different b values were evaluated qualitatively and quantitatively using the apparent diffusion coefficient. Opposed-phase sequences were used to assess signal intensity qualitatively. The signal loss between in- and opposed-phase images was determined quantitatively. Two-tailed Fisher exact test, Mann-Whitney test, and receiver operating characteristic analysis were performed. Sensitivities, specificities, and accuracies were determined. Qualitative DW-PSIF imaging (delta = 3 ms) showed the best performance for distinguishing between benign and malignant fractures (sensitivity, 100%; specificity, 88.5%; accuracy, 93.5%). Qualitative DW-EPI (b = 50 s/mm(2) [p = 1.00]; b = 250 s/mm(2) [p = 0.50]) and DW single-shot TSE imaging (b = 100 s/mm(2) [p = 1.00]; b = 250 s/mm(2) [p = 0.18]; b = 400 s/mm(2) [p = 0.18]; b = 600 s/mm(2) [p = 0.39]) did not indicate significant differences between benign and malignant fractures. DW-EPI using a b value of 500 s/mm(2) (p = 0.01) indicated significant differences between benign and malignant vertebral fractures. Quantitative DW-EPI (p = 0.09) and qualitative opposed-phase imaging (p = 0

  3. Torsional Tribological Behavior and Torsional Friction Model of Polytetrafluoroethylene against 1045 Steel.

    Science.gov (United States)

    Wang, Shibo; Niu, Chengchao

    2016-01-01

    In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T-θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model.

  4. Torsional Tribological Behavior and Torsional Friction Model of Polytetrafluoroethylene against 1045 Steel

    Science.gov (United States)

    Wang, Shibo; Niu, Chengchao

    2016-01-01

    In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T–θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324

  5. Torsional asymmetry in suspension bridge systems

    Czech Academy of Sciences Publication Activity Database

    Malík, Josef

    2015-01-01

    Roč. 60, č. 6 (2015), s. 677-701 ISSN 0862-7940 R&D Projects: GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : suspension bridge * Hamilton principle * vertical and torsional oscillation * uniqueness * existence Subject RIV: BA - General Mathematics Impact factor: 0.507, year: 2015 http://link.springer.com/article/10.1007%2Fs10492-015-0117-3

  6. Torsion of a giant mesenteric lipoma

    Energy Technology Data Exchange (ETDEWEB)

    Wolko, Jonathan D.; Rosenfeld, David L.; Lazar, Michael J.; Underberg-Davis, Sharon J. [Department of Radiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, P.O. Box 19, New Brunswick, NJ 08903-0019 (United States)

    2003-01-01

    Mesenteric lipoma is a rare benign neoplastic condition that can grow to be very large and mimic other midgut fatty tumors. These benign tumors can cause various gastrointestinal symptoms such as obstruction and abdominal pain. We report the case of a 9-year-old boy who presented with a small bowel obstruction caused by torsion of a large mesenteric lipoma. This is an important but unusual tumor and should be considered in the differential of fatty lesions within the mesentery. (orig.)

  7. Electrostatically actuated torsional resonant sensors and switches

    KAUST Repository

    Younis, Mohammad I.

    2016-12-29

    Embodiments in accordance of a torsional resonant sensor disclosure is configured to actuate a beam structure using electrostatic actuation with an AC harmonic load (e.g., AC and DC voltage sources) that is activated upon detecting a particular agent having a mass above a predefined level. In various embodiments, the beam structure may be different types of resonant structures that is at least partially coated or layered with a selective material.

  8. Spacetime thermodynamics in the presence of torsion

    Science.gov (United States)

    Dey, Ramit; Liberati, Stefano; Pranzetti, Daniele

    2017-12-01

    It was shown by Jacobson in 1995 that the Einstein equation can be derived as a local constitutive equation for an equilibrium spacetime thermodynamics. With the aim to understand if such thermodynamical description is an intrinsic property of gravitation, many attempts have been made so far to generalize this treatment to a broader class of gravitational theories. Here we consider the case of the Einstein-Cartan theory as a prototype of theories with nonpropagating torsion. In doing so, we study the properties of Killing horizons in the presence of torsion, establish the notion of local causal horizon in Riemann-Cartan spacetimes, and derive the generalized Raychaudhuri equation for these kinds of geometries. Then, starting with the entropy that can be associated to these local causal horizons, we derive the Einstein-Cartan equation by implementing the Clausius equation. We outline two ways of proceeding with the derivation depending on whether we take torsion as a geometric field or as a matter field. In both cases we need to add internal entropy production terms to the Clausius equation as the shear and twist cannot be taken to be 0 a priori for our setup. This fact implies the necessity of a nonequilibrium thermodynamics treatment for the local causal horizon. Furthermore, it implies that a nonzero twist at the horizon in general contributes to the Hartle-Hawking tidal heating for black holes with possible implications for future observations.

  9. Inhibition of thermolysin by phosphonamidate transition-state analogues: measurement of 31P-15N bond lengths and chemical shifts in two enzyme-inhibitor complexes by solid-state nuclear magnetic resonance.

    Science.gov (United States)

    Copié, V; Kolbert, A C; Drewry, D H; Bartlett, P A; Oas, T G; Griffin, R G

    1990-10-02

    31P and 15N chemical shifts and 31P-15N bond lengths have been measured with solid-state NMR techniques in two inhibitors of thermolysin, carbobenzoxy-Glyp-L-Leu-L-Ala (ZGpLA) and carbobenzoxy-L-Phep-L-Leu-L-Ala (ZFpLA), both as free lithium salts and when bound to the enzyme. Binding of both inhibitors to thermolysin results in large changes in the 31P chemical shifts. These changes are more dramatic for the tighter binding inhibitor ZFpLA, where a approximately 20 ppm downfield movement of the 31P isotropic chemical shift (sigma iso) is observed. This shift is due to changes in the shift tensor elements sigma 11 and sigma 22, while sigma 33 remains essentially constant. We observed a similar pattern for ZGpLA, but only a approximately 5 ppm change occurs in sigma iso. The changes in the 15N chemical shifts for both inhibitors are small upon binding, amounting to downfield shifts of 2 and 4 ppm for ZGpLA and ZFpLA, respectively. This indicates that there are no changes in the protonation state of the 15N in either the ZFpLA- or the ZGpLA-thermolysin complex. NMR distance measurements yield a P-N bond length rP-N = 1.68 +/- 0.03 A for the tight binding inhibitor ZFpLA both in its free lithium salt form and in its thermolysin-ZFpLA complex, a distance that is much shorter than the 1.90-A distance reported by X-ray crystallography studies [Holden et al. (1987) Biochemistry 26, 8542-8553].(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Isolated Penile Torsion in Brothers: A Case Report

    Directory of Open Access Journals (Sweden)

    Metin Gunduz

    2012-04-01

    Full Text Available Penile torsion can be congenital and associated with hypospadias and chordee, or can be acquired after circumcision. The incidence of isolated neonatal penile torsion was 1.7 to 27% in the literature. The majority were between 10 and deg; and 20 and deg;. Generally, torsion was to the left in cases. The techniques for correction of penile torsion described in the literature are penile de-gloving and reattaching of skin, resection of Buck's fascia incising the base of the penis and removing angular ellipses of corporeal tissue with subsequent plication of tunica, and dorsal dartos flap rotation in severe cases. In conclusion, penile torsion may be familial. Therefore, brothers should be examined carefully. The degloving and realignment technique is successful in isolated penile torsion. [Arch Clin Exp Surg 2012; 1(2.000: 122-124

  11. Fast Torsional Artificial Muscles from NiTi Twisted Yarns.

    Science.gov (United States)

    Mirvakili, Seyed M; Hunter, Ian W

    2017-05-17

    Torsional artificial muscles made of multiwalled carbon nanotube/niobium nanowire yarns have shown remarkable torsional speed and gravimetric torque. The muscle structure consists of a twisted yarn with half of its length infiltrated with a stimuli-responsive guest material such as paraffin wax. The volumetric expansion of the guest material creates the torsional actuation in the yarn. In the present work, we show that this type of actuation is not unique to wax-infiltrated carbon multiwalled nanotube (MWCNT) or niobium nanowire yarns and that twisted yarn of NiTi alloy fibers also produces fast torsional actuation. By gold-plating half the length of a NiTi twisted yarn and Joule heating it, we achieved a fully reversible torsional actuation of up to 16°/mm with peak torsional speed of 10 500 rpm and gravimetric torque of 8 N·m/kg. These results favorably compare to those of MWCNTs and niobium nanowire yarns.

  12. Chemical shift effect predicting lymph node status in rectal cancer using high-resolution MR imaging with node-for-node matched histopathological validation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongmei; Zhang, Chongda; Ye, Feng; Liu, Yuan; Zhou, Chunwu [Chinese Academy of Medical Sciences and Peking Union Medical College, Department of Diagnostic Radiology, National Cancer Center/Cancer Hospital, ChaoYang District, Beijing (China); Zheng, Zhaoxu [Chinese Academy of Medical Sciences and Peking Union Medical College, Department of Colorectal Oncology, National Cancer Center/Cancer Hospital, ChaoYang District, Beijing (China); Zou, Shuangmei [Chinese Academy of Medical Sciences and Peking Union Medical College, Department of Pathology, National Cancer Center/Cancer Hospital, ChaoYang District, Beijing (China)

    2017-09-15

    To evaluate the value of the chemical shift effect (CSE) as well as other criteria for the prediction of lymph node status. Twenty-nine patients who underwent radical surgery of rectal cancers were studied with pre- and postoperative specimen MRI. Lymph nodes were harvested from transverse whole-mount specimens and compared with in vivo and ex vivo images to obtain a precise slice-for-section match. Preoperative MR characteristics including CSE, as well as other predictors, were evaluated by two readers independently between benign and metastatic nodes. A total of 255 benign and 35 metastatic nodes were obtained; 71.4% and 69.4% of benign nodes were detected with regular CSE for two readers, whereas 80.0% and 74.3% of metastatic nodes with absence of CSE. The CSE rendered areas under the ROC curve (AUC) of 0.879 and 0.845 for predicting nodal status for two readers. The criteria of nodal location, border, signal intensity and minimum distance to the rectal wall were also useful but with AUCs (0.629-0.743) lower than those of CSE. CSE is a reliable predictor for differentiating benign from metastatic nodes. Additional criteria should be taken into account when it is difficult to determine the nodal status by using only a single predictor. (orig.)

  13. Scan time reduction in ²³Na-Magnetic Resonance Imaging using the chemical shift imaging sequence: Evaluation of an iterative reconstruction method.

    Science.gov (United States)

    Weingärtner, Sebastian; Wetterling, Friedrich; Konstandin, Simon; Fatar, Marc; Neumaier-Probst, Eva; Schad, Lothar R

    2015-09-01

    To evaluate potential scan time reduction in (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 (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 (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 scan time reduction with improved image quality compared to conventional methods of scan time saving. Copyright © 2014. Published by Elsevier GmbH.

  14. 2D relayed anisotropy correlation NMR: Characterization of the 13C' chemical shift tensor orientation in the peptide plane of the dipeptide AibAib

    International Nuclear Information System (INIS)

    Heise, Bert; Leppert, Joerg; Wenschuh, Holger; Ohlenschlaeger, Oliver; Goerlach, Matthias; Ramachandran, Ramadurai

    2001-01-01

    An approach to the determination of the orientation of the carbonyl chemical shift (CS) tensor in a 13 C'- 15 N- 1 H dipolar coupled spin network is proposed. The method involves the measurement of the Euler angles of the 13 C'- 15 N and 15 N- 1 H dipolar vectors in the 13 C' CS tensor principal axes system, respectively, via a 13 C- 15 N REDOR experiment and by a 2D relayed anisotropy correlation of the 13 C' CSA (ω 2 ) and 15 N- 1 H dipolar interaction (ω 1 ). Via numerical simulations the sensitivity of the ω 1 cross sections of the 2D spectrum to the Euler angles of the 15 N- 1 H bond vector in the 13 C' CSA frame is shown. Employing the procedure outlined in this work, we have determined the orientation of the 13 C' CS tensor in the peptide plane of the dipeptide AibAib-NH 2 (Aib = α-aminoisobutyric acid). The Euler angles are found to be (χ CN , ψ CN ) = (34 deg. ± 2 deg., 88 deg. ± 2 deg.) and (χ NH , ψ NH ) = (90 deg. ± 10 deg., 80 deg. ± 10 deg.). From the measured Euler angles it is seen that the σ 33 and σ 22 components of the 13 C' CS tensor approximately lie in the peptide plane

  15. 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

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

    International Nuclear Information System (INIS)

    Koelblinger, Claus; Krššák, Martin; Maresch, Judith; Wrba, Fritz; Kaczirek, Klaus; Gruenberger, Thomas; Tamandl, Dietmar; Ba-Ssalamah, Ahmed; Berger-Kulemann, Vanessa; Weber, Michael; Schima, Wolfgang

    2012-01-01

    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.

  17. Comparison of diffusion-weighted images using short inversion time inversion recovery or chemical shift selective pulse as fat suppression in patients with breast cancer

    International Nuclear Information System (INIS)

    Kazama, Toshiki; Nasu, Katsuhiro; Kuroki, Yoshifumi; Nawano, Shigeru; Ito, Hisao

    2009-01-01

    Fat suppression is essential for diffusion-weighted imaging (DWI) in the body. However, the chemical shift selective (CHESS) pulse often fails to suppress fat signals in the breast. The purpose of this study was to compare DWI using CHESS and DWI using short inversion time inversion recovery (STIR) in terms of fat suppression and the apparent diffusion coefficient (ADC) value. DWI using STIR, DWI using CHESS, and contrast-enhanced T1-weighted images were obtained in 32 patients with breast carcinoma. Uniformity of fat suppression, ADC, signal intensity, and visualization of the breast tumors were evaluated. In 44% (14/32) of patients there was insufficient fat suppression in the breasts on DWI using CHESS, whereas 0% was observed on DWI using STIR (P<0.0001). The ADCs obtained for DWI using STIR were 4.3% lower than those obtained for DWI using CHESS (P<0.02); there was a strong correlation of the ADC measurement (r=0.93, P<0.001). DWI using STIR may be excellent for fat suppression; and the ADC obtained in this sequence was well correlated with that obtained with DWI using CHESS. DWI using STIR may be useful when the fat suppression technique in DWI using CHESS does not work well. (author)

  18. Painless inter epididymal testicular torsion of the spermatic cord

    Directory of Open Access Journals (Sweden)

    Salomon V. Romano

    2007-02-01

    Full Text Available Inter epididymal testicular torsion of the spermatic cord is extremely rare and usually diagnosed at surgery. We present an unusual case of spermatic cord torsion in a 14-year-old male patient. It is important to highlight that the torsion occurred only on the distal half of the epididymis leaving the head untwisted and edematous. In addition, the fact that this condition was painless made this case extremely rare and motivated our presentation.

  19. Painless inter epididymal testicular torsion of the spermatic cord

    OpenAIRE

    Salomon V. Romano; Haime S. Hernan; Norberto Fredotovich

    2007-01-01

    Inter epididymal testicular torsion of the spermatic cord is extremely rare and usually diagnosed at surgery. We present an unusual case of spermatic cord torsion in a 14-year-old male patient. It is important to highlight that the torsion occurred only on the distal half of the epididymis leaving the head untwisted and edematous. In addition, the fact that this condition was painless made this case extremely rare and motivated our presentation.

  20. Secondary Torsion of Vermiform Appendix with Mucinous Cystadenoma

    OpenAIRE

    Maki Kitagawa; Tatsuya Kotani; Takeshi Yamano; Hideaki Tsurudome; Tomoya Hatakeyama; Yoshiaki Kuriu; Hiroshi Nishi; Masaharu Yabe

    2007-01-01

    Torsion of the vermiform appendix is a rare disorder, which causes abdominal symptoms indistinguishable from acute appendicitis. We report a case (a 34-year-old male) of secondary torsion of the vermiform appendix with mucinous cystadenoma. This case was characterized by mild inflammatory responses, pentazocine-resistant abdominal pain, and appendiceal tumor, which was not enhanced by the contrast medium on computed tomography presumably because of reduced blood flow by the torsion. These fin...

  1. Isolated fallopian tube torsion during pregnancy: a case report.

    Science.gov (United States)

    Lee, D H; Park, Y K

    2015-01-01

    Isolated fallopian tube torsion is a rare pregnancy-related complication. It is frequently misdiagnosed as acute appendicitis or ovarian torsion owing to the lack of specific symptoms or signs. Here, the authors report a case of a 35-year-old primigravida at 30 weeks and six days of gestation who had presented with right isolated fallopian tube torsion and a history of right oophorectomy. The authors propose that isolated fallopian tube torsion should be included in the list of differential diagnosis when encountered with patients complaining of lower abdominal pain.

  2. Ultrasonographic features of prenatal testicular torsion: Case report

    Directory of Open Access Journals (Sweden)

    Elif Ağaçayak

    2013-01-01

    Full Text Available Although prenatal testicular torsion (PNTT is rarely observed,it is an important condition that can cause bilateralvanishing testis. Generally, PNTT cases observed asextravaginal torsion and treatment is emergency surgicalop-eration. In this article, 39 week presented a case diagnosedin the prenatal testicular torsion. PNTT diagnosiswas confirmed by Doppler ultrasonography and emergencysurgery was performed. Extravaginal left testiculartorsion gangrene and necrosis of the testis was observedin the operation. Left orchiectomy was performed andintrauter-ine ultrasonographic diagnosis was found to becorrect.Key words: Testicular torsion, prenatal diagnosis, features,ultrasonography

  3. Secondary Torsion of Vermiform Appendix with Mucinous Cystadenoma

    Directory of Open Access Journals (Sweden)

    Maki Kitagawa

    2007-06-01

    Full Text Available Torsion of the vermiform appendix is a rare disorder, which causes abdominal symptoms indistinguishable from acute appendicitis. We report a case (a 34-year-old male of secondary torsion of the vermiform appendix with mucinous cystadenoma. This case was characterized by mild inflammatory responses, pentazocine-resistant abdominal pain, and appendiceal tumor, which was not enhanced by the contrast medium on computed tomography presumably because of reduced blood flow by the torsion. These findings may be helpful for the preoperative diagnosis of secondary appendiceal torsion.

  4. Torsion of vermiform appendix with fecalith: a case report

    Science.gov (United States)

    Wani, Imtiaz; Kitagawa, Maki; Rather, Mudasir; Singh, Jang; Bhat, Gulam; Nazir, Mir

    2008-01-01

    Introduction Torsion of the vermiform appendix is a rare disorder, which causes abdominal symptoms indistinguishable from acute appendicitis and is found by chance during the laparotomy. Case presentation We report a case (a 76-year-old male) suffering of torsion of the vermiform appendix with fecalith. It was twisted 540 degrees in an anti-clockwise direction. Appendectomy was done. Conclusion Appendiceal torsion may be assocated with the presence of fecalith. This case is the oldest one among the patients with appendiceal torsion reported to literature. PMID:18577201

  5. Secondary Torsion of Vermiform Appendix with Mucinous Cystadenoma

    Science.gov (United States)

    Kitagawa, Maki; Kotani, Tatsuya; Yamano, Takeshi; Tsurudome, Hideaki; Hatakeyama, Tomoya; Kuriu, Yoshiaki; Nishi, Hiroshi; Yabe, Masaharu

    2007-01-01

    Torsion of the vermiform appendix is a rare disorder, which causes abdominal symptoms indistinguishable from acute appendicitis. We report a case (a 34-year-old male) of secondary torsion of the vermiform appendix with mucinous cystadenoma. This case was characterized by mild inflammatory responses, pentazocine-resistant abdominal pain, and appendiceal tumor, which was not enhanced by the contrast medium on computed tomography presumably because of reduced blood flow by the torsion. These findings may be helpful for the preoperative diagnosis of secondary appendiceal torsion. PMID:21487469

  6. Proton resonance frequency chemical shift thermometry: experimental design and validation toward high-resolution noninvasive temperature monitoring and in vivo experience in a nonhuman primate model of acute ischemic stroke.

    Science.gov (United States)

    Dehkharghani, S; Mao, H; Howell, L; Zhang, X; Pate, K S; Magrath, P R; Tong, F; Wei, L; Qiu, D; Fleischer, C; Oshinski, J N

    2015-06-01

    Applications for noninvasive biologic temperature monitoring are widespread in biomedicine and of particular interest in the context of brain temperature regulation, where traditionally costly and invasive monitoring schemes limit their applicability in many settings. Brain thermal regulation, therefore, remains controversial, motivating the development of noninvasive approaches such as temperature-sensitive nuclear MR phenomena. The purpose of this work was to compare the utility of competing approaches to MR thermometry by using proton resonance frequency chemical shift. We tested 3 methodologies, hypothesizing the feasibility of a fast and accurate approach to chemical shift thermometry, in a phantom study at 3T. A conventional, paired approach (difference [DIFF]-1), an accelerated single-scan approach (DIFF-2), and a new, further accelerated strategy (DIFF-3) were tested. Phantom temperatures were modulated during real-time fiber optic temperature monitoring, with MR thermometry derived simultaneously from temperature-sensitive changes in the water proton chemical shift (∼0.01 ppm/°C). MR thermometry was subsequently performed in a series of in vivo nonhuman primate experiments under physiologic and ischemic conditions, testing its reproducibility and overall performance. Chemical shift thermometry demonstrated excellent agreement with phantom temperatures for all 3 approaches (DIFF-1: linear regression R(2) = 0.994; P thermometry and present in vivo applications under physiologic and ischemic conditions in a primate stroke model. © 2015 by American Journal of Neuroradiology.

  7. Determination of accurate 1H positions of an alanine tripeptide with anti-parallel and parallel β-sheet structures by high resolution 1H solid state NMR and GIPAW chemical shift calculation.

    Science.gov (United States)

    Yazawa, Koji; Suzuki, Furitsu; Nishiyama, Yusuke; Ohata, Takuya; Aoki, Akihiro; Nishimura, Katsuyuki; Kaji, Hironori; Shimizu, Tadashi; Asakura, Tetsuo

    2012-11-25

    The accurate (1)H positions of alanine tripeptide, A(3), with anti-parallel and parallel β-sheet structures could be determined by highly resolved (1)H DQMAS solid-state NMR spectra and (1)H chemical shift calculation with gauge-including projector augmented wave calculations.

  8. The torsional barriers of two equivalent methyl internal rotations in 2,5-dimethylfuran investigated by microwave spectroscopy

    Science.gov (United States)

    Van, Vinh; Bruckhuisen, Jonas; Stahl, Wolfgang; Ilyushin, Vadim; Nguyen, Ha Vinh Lam

    2018-01-01

    The microwave spectrum of 2,5-dimethylfuran was recorded using two pulsed molecular jet Fourier transform microwave spectrometers which cover the frequency range from 2 to 40 GHz. The internal rotations of two equivalent methyl tops with a barrier height of approximately 439.15 cm-1 introduce torsional splittings of all rotational transitions in the spectrum. For the spectral analysis, two different computer programs were applied and compared, the PAM-C2v-2tops code based on the principal axis method which treats several torsional states simultaneously, and the XIAM code based on the combined axis method, yielding accurate molecular parameters. The experimental work was supplemented by quantum chemical calculations. Two-dimensional potential energy surfaces depending on the torsional angles of both methyl groups were calculated and parametrized.

  9. 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…

  10. Torsional superelasticity of NiTi archwires.

    Science.gov (United States)

    Bolender, Yves; Vernière, Anne; Rapin, Christophe; Filleul, Marie-Pierryle

    2010-11-01

    To reproduce and compare the intraoral torsional behavior of 10 commonly used preformed upper NiTi 0.017 x 0.025 archwires in 0.018-slot brackets at 20 degrees C, 35 degrees C, and 55 degrees C. Ten upper preformed NiTi archwires were compared to a multibraided stainless steel wire. An original testing bench was used to reproduce palatal root torque applied onto an upper central incisor with a maximum value of 1540 g x mm. Ten samples of each wire type were tested at 20 degrees C, 35 degrees C, and 55 degrees C each. Loading and unloading at 20 degrees C revealed three categories of wires: a group of four NiTi wires of relative stiffness bereft of any superelasticity, a group of six NiTi wires displaying some horizontal plateau, and finally the stainless steel wire of lesser stiffness. Testing at the average oral temperature of 35 degrees C produced the same three categories of wires, with only 2 of 10 NiTi wires displaying a superelastic effect (Copper NiTi 35 degrees C and 40 degrees C). None of the NiTi wires was superelastic at 55 degrees C. Moments increased with temperature as the martensite was replaced by the more rigid austenite. This study showed that most NiTi wires did not exhibit in torsion the superelastic effect traditionally described in bending. The combination of straight-wire prescriptions and rectangular superelastic NiTi archwires did not provide optimal constant moments necessary to gain third-order control of tooth movement early in treatment. A braided stainless steel rectangular archwire displayed better torsional behavior at 35 degrees C than most NiTi archwires of the same dimensions.

  11. Toward laboratory torsional spine magnetic reconnection

    Science.gov (United States)

    Chesny, David L.; Orange, N. Brice; Oluseyi, Hakeem M.; Valletta, David R.

    2017-12-01

    Magnetic reconnection is a fundamental energy conversion mechanism in nature. Major attempts to study this process in controlled settings on Earth have largely been limited to reproducing approximately two-dimensional (2-D) reconnection dynamics. Other experiments describing reconnection near three-dimensional null points are non-driven, and do not induce any of the 3-D modes of spine fan, torsional fan or torsional spine reconnection. In order to study these important 3-D modes observed in astrophysical plasmas (e.g. the solar atmosphere), laboratory set-ups must be designed to induce driven reconnection about an isolated magnetic null point. As such, we consider the limited range of fundamental resistive magnetohydrodynamic (MHD) and kinetic parameters of dynamic laboratory plasmas that are necessary to induce the torsional spine reconnection (TSR) mode characterized by a driven rotational slippage of field lines - a feature that has yet to be achieved in operational laboratory magnetic reconnection experiments. Leveraging existing reconnection models, we show that within a 3$ apparatus, TSR can be achieved in dense plasma regimes ( 24~\\text{m}-3$ ) in magnetic fields of -1~\\text{T}$ . We find that MHD and kinetic parameters predict reconnection in thin current sheets on time scales of . While these plasma regimes may not explicitly replicate the plasma parameters of observed astrophysical phenomena, studying the dynamics of the TSR mode within achievable set-ups signifies an important step in understanding the fundamentals of driven 3-D magnetic reconnection and the self-organization of current sheets. Explicit control of this reconnection mode may have implications for understanding particle acceleration in astrophysical environments, and may even have practical applications to fields such as spacecraft propulsion.

  12. Transverse posterior element fractures associated with torsion

    International Nuclear Information System (INIS)

    Abel, M.S.

    1989-01-01

    Six examples of a previously undescribed class of transverse vertebral element fractures are presented. These fractures differ from Chance and Smith fractures and their variants in the following respects: (1) the etiology is torsion and not flexion; (2) there is neither distraction of posterior ring fragments nor posterior ligament tears; (3) in contrast to Chance and Smith fractures, extension of the fracture into the vertebral body is absent or minimal; (4) the transverse process of the lumbar vertebra is avulsed at its base with a vertical fracture, not split horizontally. These fractures occur in cervical, lumbar, and sacral vertebrae in normal or compromised areas of the spine. (orig.)

  13. Possible role of torsion in gravitational theories

    International Nuclear Information System (INIS)

    Nieh, H.T.

    1983-01-01

    Torsion is of interest in an indirect way, in that it has the potential of being an important ingredient in a future successful quantum theory of gravitation. Einstein's theory of gravitation, despite its simplicity and elegance, and its successes in large-scale gravitational phenomena, can only be regarded as a macroscopic classical theory. It is a non-renormalizable quantum field theory, and, therefore, lacks the status of a good microscopic theory. It is the search for a successful quantum field theory of gravitation that poses as one of the great challenges to theoretical physics today. (Auth.)

  14. HEAT TREATMENTS INFLUENCE ON THE BREAKING TORSION OF WOOL TYPE FIBERS

    Directory of Open Access Journals (Sweden)

    BORDEIANU Demetra Lăcrămioara

    2014-05-01

    Full Text Available In order to convert the textile fibers in yarns, these must be subjected to twisting operation which confers them a certain tensile strength. Twisting also results in certain effects, such as crepe effect. The importance of knowing the twisting behavior consists in the possibility to avoid fiber degradation as the result of an excessive twisting. The present work took for study three types of chemical fibers (wool-type rayon, wool-type polyester, wool-type polyacrylonitrile and two types of wool fibers S11 and S12. The main characteristics of wool type chemical fibers (fiber count, nominal length, breaking length, relative elongation, brightness and of wool fibers (diameter, almeter length, uster irregularit have been measured. Then the fibers were subjected to thermal treatments in certain conditions. From the researches performed for the both wool blends, S11 and S21, one can notice that the torsional rigidity/stiffness increases after the thermal treatment and the wool fibers changes their handle accordingly. The rayon fibers present the biggest torsional rigidity, as compared to the other types of analyzed fibers, both untreated and heat treated. After heat treatment, the rayon fibers considerable improves their handle. The variation coefficient of breaking torsion increases in the case of heat treated polyester and poly-acrylonitrile fibers while for rayon and wool fibers this coefficient decreases.

  15. Anatomical Variation of Age-Related Changes in Vertebral Bone Marrow Composition Using Chemical Shift Encoding-Based Water–Fat Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Thomas Baum

    2018-04-01

    Full Text Available Assessment of vertebral bone marrow composition has been proposed as imaging biomarker for osteoporosis, hematopoietic, and metabolic disorders. We investigated the anatomical variation of age-related changes of vertebral proton density fat fraction (PDFF using chemical shift encoding-based water–fat magnetic resonance imaging (MRI. 156 healthy subjects were recruited (age range 20–29 years: 12/30 males/females; 30–39: 15/9; 40–49: 4/14; 50–59: 9/27; 60–69: 5/19; 70–79: 4/8. An eight-echo 3D spoiled gradient-echo sequence at 3T MRI was used for chemical shift-encoding based water–fat separation at the lumbar spine. Vertebral bodies of L1–L4 were manually segmented to extract PDFF values at each vertebral level. PDFF averaged over L1–L4 was significantly (p < 0.05 higher in males than females in the twenties (32.0 ± 8.0 vs. 27.2 ± 6.0% and thirties (35.3 ± 6.7 vs. 27.3 ± 6.2%. With increasing age, females showed an accelerated fatty conversion of the bone marrow compared to men with no significant (p > 0.05 mean PDFF differences in the forties (32.4 ± 8.4 vs. 34.5 ± 6.8% and fifties (42.0 ± 6.1 vs. 40.5 ± 9.7%. The accelerated conversion process continued resulting in greater mean PDFF values in females than males in the sixties (40.2 ± 6.9 vs. 48.8 ± 7.7%; p = 0.033 and seventies (43.9 ± 7.6 vs. 50.5 ± 8.2%; p = 0.208, though the latter did not reach statistical significance. Relative age-related PDFF change from the twenties to the seventies increased from 16.7% (L1 to 51.4% (L4 in males and 76.8% (L1 to 85.7% (L4 in females. An accelerated fatty conversion of bone marrow was observed in females with increasing age particularly evident after menopause. Relative age-related PDFF changes showed an anatomical variation with most pronounced changes at lower lumbar vertebral levels in both sexes.

  16. The use of chemical shift temperature gradients to establish the paramagnetic susceptibility tensor orientation: Implication for structure determination/refinement in paramagnetic metalloproteins

    International Nuclear Information System (INIS)

    Xia Zhicheng; Nguyen, Bao D.; La Mar, Gerd N.

    2000-01-01

    The use of dipolar shifts as important constraints in refining molecular structure of paramagnetic metalloproteins by solution NMR is now well established. A crucial initial step in this procedure is the determination of the orientation of the anisotropic paramagnetic susceptibility tensor in the molecular frame which is generated interactively with the structure refinement. The use of dipolar shifts as constraints demands knowledge of the diamagnetic shift, which, however, is very often not directly and easily accessible. We demonstrate that temperature gradients of dipolar shifts can serve as alternative constraints for determining the orientation of the magnetic axes, thereby eliminating the need to estimate the diamagnetic shifts. This approach is tested on low-spin, ferric sperm whale cyanometmyoglobin by determining the orientation, anisotropies and anisotropy temperature gradients by the alternate routes of using dipolar shifts and dipolar shift gradients as constraints. The alternate routes ultimately lead to very similar orientation of the magnetic axes, magnetic anisotropies and magnetic anisotropy temperature gradients which, by inference, would lead to an equally valid description of the molecular structure. It is expected that the use of the dipolar shift temperature gradients, rather than the dipolar shifts directly, as constraints will provide an accurate shortcut in a solution structure determination of a paramagnetic metalloprotein

  17. Comparison of modified two-point dixon and chemical shift encoded MRI water-fat separation methods for fetal fat quantification.

    Science.gov (United States)

    Giza, Stephanie A; Miller, Michael R; Parthasarathy, Prasiddha; de Vrijer, Barbra; McKenzie, Charles A

    2018-01-10

    Fetal fat is indicative of the energy balance within the fetus, which may be disrupted in pregnancy complications such as fetal growth restriction, macrosomia, and gestational diabetes. Water-fat separated MRI is a technique sensitive to tissue lipid content, measured as fat fraction (FF), and can be used to accurately measure fat volumes. Modified two-point Dixon and chemical shift encoded MRI (CSE-MRI) are water-fat separated MRI techniques that could be applied to imaging of fetal fat. Modified two-point Dixon has biases present that are corrected in CSE-MRI which may contribute to differences in the fat measurements. To compare the measurement of fetal fat volume and FF by modified two-point Dixon and CSE-MRI. Cross-sectional study for comparison of two MRI pulse sequences. Twenty-one pregnant women with singleton pregnancies. 1.5T, modified two-point Dixon and CSE-MRI. Manual segmentation of total fetal fat volume and mean FF from modified 2-point Dixon and CSE-MRI FF images. Reliability was assessed by calculating the intraclass correlation coefficient (ICC). Agreement was assessed using a one-sample t-test on the fat measurements difference values (modified two-point Dixon - CSE-MRI). The difference scores were tested against a value of 0, which would indicate that the measurements were identical. The fat volume and FF measured by modified two-point Dixon and CSE-MRI had excellent reliability, demonstrated by ICCs of 0.93 (P Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018. © 2018 International Society for Magnetic Resonance in Medicine.

  18. Grey and white matter differences in brain energy metabolism in first episode schizophrenia: 31P-MRS chemical shift imaging at 4 Tesla.

    Science.gov (United States)

    Jensen, J Eric; Miller, Jodi; Williamson, Peter C; Neufeld, Richard W J; Menon, Ravi S; Malla, Ashok; Manchanda, Rahul; Schaefer, Betsy; Densmore, Maria; Drost, Dick J

    2006-03-31

    Altered high energy and membrane metabolism, measured with phosphorus magnetic resonance spectroscopy (31P-MRS), has been inconsistently reported in schizophrenic patients in several anatomical brain regions implicated in the pathophysiology of this illness, with little attention to the effects of brain tissue type on the results. Tissue regression analysis correlates brain tissue type to measured metabolite levels, allowing for the extraction of "pure" estimated grey and white matter compartment metabolite levels. We use this tissue analysis technique on a clinical dataset of first episode schizophrenic patients and matched controls to investigate the effect of brain tissue specificity on altered energy and membrane metabolism. In vivo brain spectra from two regions, (a) the fronto-temporal-striatal region and (b) the frontal-lobes, were analyzed from 12 first episode schizophrenic patients and 11 matched controls from a (31)P chemical shift imaging (CSI) study at 4 Tesla (T) field strength. Tissue regression analyses using voxels from each region were performed relating metabolite levels to tissue content, examining phosphorus metabolite levels in grey and white matter compartments. Compared with controls, the first episode schizophrenic patient group showed significantly increased adenosine triphosphate levels (B-ATP) in white matter and decreased B-ATP levels in grey matter in the fronto-temporal-striatal region. No significant metabolite level differences were found in grey or white matter compartments in the frontal cortex. Tissue regression analysis reveals grey and white matter specific aberrations in high-energy phosphates in first episode schizophrenia. Although past studies report inconsistent regional differences in high-energy phosphate levels in schizophrenia, the present analysis suggests more widespread differences that seem to be strongly related to tissue type. Our data suggest that differences in grey and white matter tissue content between past

  19. Investigation method of torsional properties and damages of glass/epoxy composite pipes

    Directory of Open Access Journals (Sweden)

    Putić Slaviša S.

    2006-01-01

    Full Text Available Pipes made of composites glass fiber/epoxy resin are predominantly used in the chemical industry, construction, infrastructure and war technique. The pipes made for this purpose are in their use exposed to static and dynamic loading. Depending on the purpose, the pipes, especially those in complex structures, can be loaded by torsion. In that case, exceeding allowed tensions can cause damages such as cracking the fibers and matrix delamination. These damages can lead to the appearance of cracks on the pipes and in many cases to complete breakage of the pipe. Because of this, it is very important to evaluate composite pipes exposed to torsion and find out in which way the construction is weakened, what actually is the main goal of this paper.

  20. Kernel density estimation applied to bond length, bond angle, and torsion angle distributions.

    Science.gov (United States)

    McCabe, Patrick; Korb, Oliver; Cole, Jason

    2014-05-27

    We describe the method of kernel density estimation (KDE) and apply it to molecular structure data. KDE is a quite general nonparametric statistical method suitable even for multimodal data. The method generates smooth probability density function (PDF) representations and finds application in diverse fields such as signal processing and econometrics. KDE appears to have been under-utilized as a method in molecular geometry analysis, chemo-informatics, and molecular structure optimization. The resulting probability densities have advantages over histograms and, importantly, are also suitable for gradient-based optimization. To illustrate KDE, we describe its application to chemical bond length, bond valence angle, and torsion angle distributions and show the ability of the method to model arbitrary torsion angle distributions.

  1. Correlation of severity of penile torsion with type of hypospadias ...

    African Journals Online (AJOL)

    Objective: This study was carried out to evaluate the correlation between the severity of penile torsion on the one hand and the degree of ventral penile curvature and the type of hypospadias on the other. We also assessed the effectiveness of correction of chordee and torsion by penile degloving and mobilization of the ...

  2. Perinatal testicular torsion: literature review and local experience ...

    African Journals Online (AJOL)

    The prognosis in TUDT is guarded and contralateral fixation was not practiced, except in a 5-week-old infant. Early orchiopexy at 3–6 months is recommended. Cooperation between surgeons, neonatologists, and parents is mandatory to avoid time delay. Keywords: intrauterine testicular torsion, postnatal testicular torsion, ...

  3. Torsion of the Spermatic Cord: Is Bilateral Orchidopexy Really ...

    African Journals Online (AJOL)

    Aim: To evaluate the rationale for bilateral orchidopexy as treatment for unilateral torsion of the testis, by determining how frequently the contralateral testis shows an abnormal pathology in unilateral testicular torsion. Patients and Methods:This is a retrospective study using adult urology patients treated for both acute and ...

  4. experimental and analytical comparison of torsion, bending moment

    African Journals Online (AJOL)

    HOD

    by shear design. Less attention was paid in the past by reinforced concrete designers to these effects of torsion in reinforced concrete members. When torsion is encountered in reinforced ... and composite nature of the material and presence of cracks [2]. .... principles and some limited design equations for a generalized ...

  5. Penile Torsion: an Overlooked Anomaly with Distal Hypospadias

    African Journals Online (AJOL)

    HussamHassan

    with posterior hypospadias had associating penile torsion. Follow-up showed satisfactory correction of penile torsion in 3 out of 9 patients in group A; and in 8 out of ... using MillenMed DICOM viewer program for image analysis, based on the orientation of the urethral groove (meatus) relative to the vertical position (fig. B). P ...

  6. A Patient Presenting with Concurrent Testis Torsion and Epididymal Leiomyoma

    Directory of Open Access Journals (Sweden)

    E. Arpali

    2013-01-01

    Full Text Available Leiomyomas are the second most common tumors of epididymis. Patients with leiomyomas are sometimes misdiagnosed with testicular tumors. A Case of a patient with a scrotal mass presenting with testicular torsion is reported. Concurrent occurrence of testicular torsion and epididymal leiomyoma is an extremely rare condition.

  7. Torsion of right middle lobe after a right upper lobectomy

    Directory of Open Access Journals (Sweden)

    Chen Tung-Ying

    2009-04-01

    Full Text Available Abstract Lobar torsion after lung resection is a quite rare complication. A 50-year-old woman presented typical features on chest radiographs and CT(computed tomography scan of lobar torsion after a right upper lobectomy. After emergency lobectomy of right middle lobe, the patient recovered well and discharged 10 days after the second operation.

  8. Torsional Strengthening of RC Beams Using GFRP Composites

    Science.gov (United States)

    Patel, Paresh V.; Jariwala, Vishnu H.; Purohit, Sharadkumar P.

    2016-09-01

    Fiber reinforced polymer as an external reinforcement is used extensively for axial, flexural and shear strengthening in structural systems. The strengthening of members subjected to torsion is recently being explored. The loading mechanism of beams located at the perimeter of buildings which carry loads from slabs, joists and beams from one side of the member generates torsion that are transferred from the beams to the columns. In this work an experimental investigation on the improvement of the torsional resistance of reinforced concrete beams using Glass Fiber Reinforced Polymer (GFRP) is presented. Total 24 RC beams have been cast in this work. Ten beams of dimension 150 mm × 150 mm × 1300 mm are subjected to pure torsion while fourteen beams of 150 mm × 150 mm × 1700 mm are subjected to combined torsion and bending. Two beams in each category are designated as control specimen and remaining beams are strengthened by GFRP wrapping of different configurations. Pure torsion on specimens is applied using specially fabricated support mechanism and universal testing machine. For applying combined torsion and bending a loading frame and test set up are fabricated. Measurements of angle of twist at regular interval of torque, torsion at first crack, and ultimate torque, are obtained for all specimens. Results of different wrapping configurations are compared for control and strengthened beams to suggest effective GFRP wrapping configuration.

  9. Prediction of Torsional Strength for Very High Early Strength Geopolymer

    Directory of Open Access Journals (Sweden)

    Woraphot PRACHASAREE

    2017-11-01

    Full Text Available Very early high strength geopolymers are gaining acceptance as alternative repair materials for highways and other infrastructure. In this study, a very rapid geopolymer binder based on Metakaolin (MK and Parawood ash (PWA, developed by the authors, was experimentally tested and a prediction model for its torsional strength is proposed. The geopolymer samples were subjected to uniaxial compression, flexural beam, and torsion tests. The modulus of rupture and torsional strength in terms of compression strength were found to be well approximated by 0.7(f’c1/2 and 1/7(x2y (f’c1/2, respectively. Also an interaction relation to describe combined bending and torsion was developed in this study. In addition, the effects of aspect ratio (y/x were studied on both torsional strength and combined bending and torsion. It was found that an aspect ratio of y/x = 3 significantly reduced the torsional resistance, to about 50 % of the torsional strength of a square section.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.17280

  10. Mechanical origins of rightward torsion in early chick brain development

    Science.gov (United States)

    Chen, Zi; Guo, Qiaohang; Dai, Eric; Taber, Larry

    2015-03-01

    During early development, the neural tube of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This torsional deformation is one of the major organ-level left-right asymmetry events in development. Previous studies suggested that bending is mainly due to differential growth, however, the mechanism for torsion remains poorly understood. Since the heart almost always loops rightwards that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is lacking, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. Moreover, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model and a 3D printed physical model are employed to help interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, and further reveals that the asymmetric development in one organ can induce the asymmetry of another developing organ through mechanics, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''. Z.C. is supported by the Society in Science - Branco Weiss fellowship, administered by ETH Zurich. L.A.T acknowledges the support from NIH Grants R01 GM075200 and R01 NS070918.

  11. Torsion of the Spermatic Cord: An Exemplary Early Presentation ...

    African Journals Online (AJOL)

    ... still the norm. In the index patient, the presentation time was very short. In our environment, patients with torsion of the spermatic cord can present early and be operated promptly if we can provide public health education, mobile phones, commercial taxis, and good road networks. Keywords: Spermatic cord, testis, torsion ...

  12. Manual Detorsion of Testicular Torsion - A Primary Care Intervention ...

    African Journals Online (AJOL)

    Testicular torsion is one of the known acute urological emergencies that require prompt intervention. Salvage of the testis is only possible if derotation is performed within 6 hours of onset of symptoms. The objective of this paper is to report successful manual detorsion of the testes of patients with testicular torsion.

  13. Effect of irregularity on torsional surface waves in an initially ...

    Indian Academy of Sciences (India)

    Effect of irregularity on torsional surface waves in an initially stressed anisotropic porous layer sandwiched between homogeneous and non-homogeneous half- ... Torsional wave; anisotropy; initial stress; irregularity; non-homogeneity ... Department of Applied Mathematics, Indian School of Mines, Dhanbad 826 004, India.

  14. Case series on testicular torsion: an educational emergency for sub ...

    African Journals Online (AJOL)

    305 records ... Testicular torsion remains a common surgical emergency of adolescent males presenting with sudden onset of intense scrotal pain in Africa. While the magnitude of testicular torsion is not known it has been identified as a cause of male infertility. Testicular loss in Africa is directly related to delay in surgery and ...

  15. CONSTRAINING SPACETIME TORSION WITH THE MOON, MERCURY AND LAGEOS

    Directory of Open Access Journals (Sweden)

    Riccardo March

    2013-12-01

    Full Text Available We consider an extension of Einstein General Relativity where, beside the Riemann curvature tensor, we suppose the presence of a torsion tensor. Using a parametrized theory based on symmetry arguments, we report on some results concerning the constraints that can be put on torsion parameters by studying the orbits of a test body in the solar system.

  16. Severe congenital penile torsion with anterior urethral diverticulum ...

    African Journals Online (AJOL)

    On examination, he was found to be a case of severe congenital penile torsion with diversion and rotation of median raphae in a counterclockwise fashion upto the midline dorsally confirming 180◦ torsion. During voiding, there was appearance of a swelling in distal penile region with passage of urinary drops while ...

  17. Intermittent Testicular Torsion | Obi | Nigerian Journal of Clinical ...

    African Journals Online (AJOL)

    Methods: Clinical and demographic data of all patients treated for intermittent testicular torsion from January 2007 to June 2015 were prospectively collected in a pro forma and analyzed. A diagnosis of intermittent torsion was made on the basis of recurrent scrotal pain, presence of abnormal testicular lie in otherwise normal ...

  18. Primary omental torsion in children: case report | Khalid | Pan ...

    African Journals Online (AJOL)

    Primary omental torsion in children: case report. Khattala Khalid, Tenorkorang Snr Somuah, Elmadi Aziz, Rami Mohamed, Bouabdallah Youssef. Abstract. Primary omental torsion is a rare cause of acute abdominal pain, we report a case of 10-year-old boy admitted with crampy abdominal pain, routine laboratory tests and ...

  19. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L.; Broer, R.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the

  20. Turbulence Modeling of Torsional Couette Flows

    Directory of Open Access Journals (Sweden)

    Sofia Haddadi

    2008-01-01

    Full Text Available The present study considers the numerical modeling of the turbulent flow inside a rotor-stator cavity subjected or not to a superimposed throughflow. Extensive numerical predictions based on one-point statistical modeling using a low Reynolds number second-order full stress transport closure (RSM model are performed mainly in the case of turbulent flows with merged boundary layers known as turbulent torsional Couette flows and belonging to regime III of Daily and Nece (1960. The RSM model has already shown its capability of predicting accurately the mean and turbulent fields in various rotating disk configurations (Poncet, 2005; Poncet et al., 2005, 2007, 2008. For the first time, a detailed mapping of the hydrodynamic flow over a wide range of rotational Reynolds numbers (180 000≤Re≤10 000 000, aspect ratios of the cavity (0.02≤G≤0.05, and flow rate coefficients (−10000≤Cw≤10000 is here provided in the turbulent torsional Couette flow regime.

  1. Lung lobe torsion in seven juvenile dogs.

    Science.gov (United States)

    Latimer, Christian R; Lux, Cassie N; Sutton, Jessie S; Culp, William T N

    2017-12-15

    CASE DESCRIPTION 7 juvenile (< 12 months old) dogs with lung lobe torsion were evaluated. CLINICAL FINDINGS All patients were male; breeds included Pug (n = 5), Chinese Shar-Pei (1), and Bullmastiff (1). Dyspnea and lethargy were the most common initial complaints, with a duration of clinical signs ranging from 1 to 10 days. A CBC showed leukocytosis and neutrophilia in all dogs. Anemia was present in 6 dogs, 2 of which received packed RBC transfusions. The diagnosis was made on the basis of results of thoracic radiography, CT, ultrasonography, or a combination of modalities. The left cranial lung lobe was most commonly affected (n = 4), followed by the right middle lung lobe (2) and the right cranial lung lobe (1). TREATMENT AND OUTCOME A lateral intercostal thoracotomy with lobectomy of the affected lobe was performed in all patients. All dogs survived to be discharged between 1 and 2 days postoperatively. Six of 7 owners contacted for follow-up information 7 to 170 months after discharge reported satisfaction with the treatment and no apparent signs of recurrence of disease. CLINICAL RELEVANCE The juvenile patients of this report were successfully treated surgically with no apparent complications. Clinicians should be aware of the possibility of lung lobe torsion when evaluating young dogs with clinical signs related to the respiratory system, including those with vague signs, to avoid undue delays in treatment.

  2. The Reidemeister torsion of 3-manifolds

    CERN Document Server

    Nicolaescu, Liviu I

    2003-01-01

    This is a state-of-the-art introduction to the work of Franz Reidemeister, Meng Taubes, Turaev, and the author on the concept of torsion and its generalizations. Torsion is the oldest topological (but not with respect to homotopy) invariant that in its almost eight decades of existence has been at the center of many important and surprising discoveries. During the past decade, in the work of Vladimir Turaev, new points of view have emerged, which turned out to be the "right ones" as far as gauge theory is concerned. The book features mostly the new aspects of this venerable concept. The theoretical foundations of this subject are presented in a style accessible to those, who wish to learn and understand the main ideas of the theory. Particular emphasis is upon the many and rather diverse concrete examples and techniques which capture the subleties of the theory better than any abstract general result. Many of these examples and techniques never appeared in print before, and their choice is often justified by ...

  3. Krukenberg Tumor: A Rare Cause of Ovarian Torsion

    Directory of Open Access Journals (Sweden)

    Sameer Sandhu

    2012-01-01

    Full Text Available Ovarian torsion is the fifth most common gynecological surgical emergency. Ovarian torsion is usually associated with a cyst or a tumor, which is typically benign. The most common is mature cystic teratoma. We report the case of a 43-year-old woman who came to the Emergency Department with rare acute presentation of bilateral Krukenberg tumors, due to unilateral ovarian torsion. In this case report, we highlight the specific computed tomography (CT features of ovarian torsion and demonstrate the unique radiological findings on CT imaging. Metastasis to the ovary is not rare and 5 to 10% of all ovarian malignancies are metastatic. The stomach is the common primary site in most Krukenberg tumors (70%; an acute presentation of metastatic Krukenberg tumors with ovarian torsion is rare and not previously reported in radiology literature.

  4. Physics of detecting torsion and placing limits on its effects

    International Nuclear Information System (INIS)

    Stoeger, W.R.

    1985-01-01

    The essential principles of torsion-detection physics are presented, and an evaluation is conducted of several conceivable types of experiments and observations for actually detecting torsion fields, reemphasizing also the evident impossibility of successfully searching for its manifestations among cosmological relics. In particular, a polarized body, with net intrinsic (fundamental-particle) spin, is essential for detecting a torsion field. One which possesses only orbital angular momentum - rotation - or an unpolarized intrinsic spin density will not feel torsion. The fundamental problem in searching for such fields is the extremely small basic unit of the coupling or interaction energy between the torsion field and spin. The best way of maximizing the total interaction energy is to increase the spin density of the source sigma-s and at the same time the spin number SD of the detector. 15 references

  5. Peculiar torsion dynamical response of spider dragline silk

    Science.gov (United States)

    Liu, Dabiao; Yu, Longteng; He, Yuming; Peng, Kai; Liu, Jie; Guan, Juan; Dunstan, D. J.

    2017-07-01

    The torsional properties of spider dragline silks from Nephila edulis and Nephila pilipes spiders are investigated by using a torsion pendulum technique. A permanent torsional deformation is observed after even small torsional strain. This behaviour is quite different from that of the other materials tested here, i.e., carbon fiber, thin metallic wires, Kevlar fiber, and human hair. The spider dragline thus displays a strong energy dissipation upon the initial excitation (around 75% for small strains and more for a larger strain), which correspondingly reduces the amplitude of subsequent oscillations around the new equilibrium position. The variation of torsional stiffness in relaxation dynamics of spider draglines for different excitations is also determined. The experimental result is interpreted in the light of the hierarchical structure of dragline silk.

  6. 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

  7. Lanthanide shift reagents, binding, shift mechanisms and exchange

    International Nuclear Information System (INIS)

    Boer, J.W.M. de

    1977-01-01

    Paramagnetic lanthanide shift reagents, when added to a solution of a substrate, induce shifts in the nuclear magnetic resonance (NMR) spectrum of the substrate molecules. The induced shifts contain information about the structure of the shift reagent substrate complex. The structural information, however, may be difficult to extract because of the following effects: (1) different complexes between shift reagent and substrate may be present in solution, e.g. 1:1 and 1:2 complexes, and the shift observed is a weighed average of the shifts of the substrate nuclei in the different complexes; (2) the Fermi contact interaction, arising from the spin density at the nucleus, contributes to the induced shift; (3) chemical exchange effects may complicate the NMR spectrum. In this thesis, the results of an investigation into the influence of these effects on the NMR spectra of solutions containing a substrate and LSR are presented. The equations describing the pseudo contact and the Fermi contact shift are derived. In addition, it is shown how the modified Bloch equations describing the effect of the chemical exchange processes occurring in the systems studied can be reduced to the familiar equations for a two-site exchange case. The binding of mono- and bifunctional ethers to the shift reagent are reported. An analysis of the induced shifts is given. Finally, the results of the experiments performed to study the exchange behavior of dimethoxyethane and heptafluorodimethyloctanedionato ligands are presented

  8. Determination of pKa values of tenoxicam from 1H NMR chemical shifts and of oxicams from electrophoretic mobilities (CZE) with the aid of programs SQUAD and HYPNMR.

    Science.gov (United States)

    Rodríguez-Barrientos, Damaris; Rojas-Hernández, Alberto; Gutiérrez, Atilano; Moya-Hernández, Rosario; Gómez-Balderas, Rodolfo; Ramírez-Silva, María Teresa

    2009-12-15

    In this work it is explained, by the first time, the application of programs SQUAD and HYPNMR to refine equilibrium constant values through the fit of electrophoretic mobilities determined by capillary zone electrophoresis experiments, due to the mathematical isomorphism of UV-vis absorptivity coefficients, NMR chemical shifts and electrophoretic mobilities as a function of pH. Then, the pK(a) values of tenoxicam in H(2)O/DMSO 1:4 (v/v) have been obtained from (1)H NMR chemical shifts, as well as of oxicams in aqueous solution from electrophoretic mobilities determined by CZE, at 25 degrees C. These values are in very good agreement with those reported by spectrophotometric and potentiometric measurements.

  9. 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

    , in the solution state the 2-bond and 3-bond J(1H–13C) coupling constants have been used to confirm the equilibrium positions. The isotope effects due to deuteriation at the OH position are shown to be superior to chemical shift in determination of equilibrium positions of these almost symmetrical -pyridoyl......-benzoyl methanes. The assignments of the NMR spectra are supported by calculations of the chemical shifts at the DFT level. The equilibrium positions are shown to be different in the liquid and the solid state. In the liquid state the 4-pyridoyl derivative is at the B-form (C-1 is OH), whereas the 2-and 3-pyridoyl...... derivatives are in the A-form. In the solid state all three compounds are on the B-form. The 4-pyridoyl derivative shows unusual deuterium isotope effects in the solid, which are ascribed to a change of the crystal structure of the deuteriated compound...

  10. Dynamic Bending and Torsion Stiffness Derivation from Modal Curvatures and Torsion Rates

    Science.gov (United States)

    MAECK, J.; DE ROECK, G.

    1999-08-01

    In order to maintain the reliability of civil engineering structures, considerable effort is currently spent on developing a non-destructive vibration testing method for monitoring the structural integrity of constructions. The technique must be able to observe damage, secondly to localize the damage; and finally to give an idea of the severity of the damage. Within the framework of relating changes of measured modal parameters to changes in the integrity of the structure, it is important to be able to determine the dynamic stiffness in each section of the structure from measured modal characteristics.A damaged structure results in a dynamic stiffness reduction of the cracked sections. The dynamic stiffnesses provide directly an indication of the extension of the cracked zones in the structure. The dynamic stiffness reduction can also be associated with a degree of cracking in a particular zone.In an experimental programme, a concrete beam of 6 m length is subjected to an increasing static load to produce cracks. After each static perload, the beam is tested dynamically in a free-free set-up. The change in modal parameters is then related to damage in the beam.The technique that will be presented in the paper to predict the damage location and intensity is a direct stiffness derivation from measured modal displacement derivatives. Using the bending modes, the dynamic bending stiffness can be derived from modal curvatures. Using the torsional modes, the dynamic torsion stiffness can be derived from modal torsion rates.

  11. Lanthanide ion (III) complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate for dual biosensing of pH with chemical exchange saturation transfer (CEST) and biosensor imaging of redundant deviation in shifts (BIRDS).

    Science.gov (United States)

    Huang, Yuegao; Coman, Daniel; Ali, Meser M; Hyder, Fahmeed

    2015-01-01

    Relaxivity-based magnetic resonance of phosphonated ligands chelated with gadolinium (Gd(3+)) shows promise for pH imaging. However instead of monitoring the paramagnetic effect of lanthanide complexes on the relaxivity of water protons, biosensor (or molecular) imaging with magnetic resonance is also possible by detecting either the nonexchangeable or the exchangeable protons on the lanthanide complexes themselves. The nonexchangeable protons (e.g. -CHx, where 3 ≥ x ≥ 1) are detected using a three-dimensional chemical shift imaging method called biosensor imaging of redundant deviation in shifts (BIRDS), whereas the exchangeable protons (e.g. -OH or -NHy , where 2 ≥ y ≥ 1) are measured with chemical exchange saturation transfer (CEST) contrast. Here we tested the feasibility of BIRDS and CEST for pH imaging of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP(8-)) chelated with thulium (Tm(3+) ) and ytterbium (Yb(3+)). BIRDS and CEST experiments show that both complexes are responsive to pH and temperature changes. Higher pH and temperature sensitivities are obtained with BIRDS for either complex when using the chemical shift difference between two proton resonances vs using the chemical shift of a single proton resonance, thereby eliminating the need to use water resonance as reference. While CEST contrast for both agents is linearly dependent on pH within a relatively large range (i.e. 6.3-7.9), much stronger CEST contrast is obtained with YbDOTA-4AmP(5-) than with TmDOTA-4AmP(5-). In addition, we demonstrate the prospect of using BIRDS to calibrate CEST as new platform for quantitative pH imaging. Copyright © 2014 John Wiley & Sons, Ltd.

  12. Proton Resonance Frequency Chemical Shift Thermometry: Experimental Design and Validation Towards High-Resolution Non-Invasive Temperature Monitoring, and in vivo Experience in a Non-human Primate Model of Acute Ischemic Stroke

    Science.gov (United States)

    Dehkharghani, Seena; Mao, Hui; Howell, Leonard; Zhang, Xiaodong; Pate, K S; Magrath, P R; Tong, Frank; Wei, L; Qiu, D; Fleischer, C; Oshinski, J N

    2016-01-01

    BACKGROUND AND PURPOSE Applications for non-invasive biological temperature monitoring are widespread in biomedicine, and of particular interest in the context of brain temperature regulation, where traditionally costly and invasive monitoring schemes limit their applicability in many settings. Brain thermal regulation therefore remains controversial, motivating the development of non-invasive approaches such as temperature-sensitive NMR phenomena. The purpose of this work was to compare the utility of competing approaches to MR thermometry (MRT) employing proton resonance frequency chemical shift. Three methodologies were tested, hypothesizing the feasibility of a fast and accurate approach to chemical shift thermometry, in a phantom study at 3.0 Tesla. MATERIALS AND METHODS A conventional, paired approach (DIFF-1), an accelerated single-scan approach (DIFF-2), and a new, further accelerated strategy (DIFF-3) were tested. Phantom temperatures were modulated during real-time fiber optic temperature monitoring, with MRT derived simultaneously from temperature-sensitive changes in the water proton chemical shift (~0.01 ppm/°C). MRT was subsequently performed in a series of in vivo non-human primate experiments under physiologic and ischemic conditions testing its reproducibility and overall performance. RESULTS Chemical shift thermometry demonstrated excellent agreement with phantom temperatures for all three approaches (DIFF-1 linear regression R2=0.994, p<0.001, acquisition time 4 min 40 s; DIFF-2 R2=0.996, p<0.001, acquisition time 4 min; DIFF-3 R2=0.998, p<0.001, acquisition time 40 s). CONCLUSION These findings confirm the comparability in performance of three competing approaches MRT, and present in vivo applications under physiologic and ischemic conditions in a primate stroke model. PMID:25655874

  13. Torsion based universal MEMS logic device

    KAUST Repository

    Ilyas, Saad

    2015-10-28

    In this work we demonstrate torsion based complementary MEMS logic device, which is capable, of performing INVERTER, AND, NAND, NOR, and OR gates using one physical structure within an operating range of 0-10 volts. It can also perform XOR and XNOR with one access inverter using the same structure with different electrical interconnects. The paper presents modeling, fabrication and experimental calculations of various performance features of the device including lifetime, power consumption and resonance frequency. The fabricated device is 535 μm by 150 μm with a gap of 1.92 μm and a resonant frequency of 6.51 kHz. The device is capable of performing the switching operation with a frequency of 1 kHz.

  14. Combined bending-torsion fatigue reliability. III

    Science.gov (United States)

    Kececioglu, D.; Chester, L. B.; Nolf, C. F., Jr.

    1975-01-01

    Results generated by three, unique fatigue reliability research machines which can apply reversed bending loads combined with steady torque are presented. AISI 4340 steel, grooved specimens with a stress concentration factor of 1.42 and 2.34, and Rockwell C hardness of 35/40 were subjected to various combinations of these loads and cycled to failure. The generated cycles-to-failure and stress-to-failure data are statistically analyzed to develop distributional S-N and Goodman diagrams. Various failure theories are investigated to determine which one represents the data best. The effects of the groove, and of the various combined bending-torsion loads, on the S-N and Goodman diagrams are determined. Two design applications are presented which illustrate the direct useability and value of the distributional failure governing strength and cycles-to-failure data in designing for specified levels of reliability and in predicting the reliability of given designs.

  15. Plant-based torsional actuator with memory

    Science.gov (United States)

    Plaza, Nayomi; Zelinka, Samuel L.; Stone, Don S.; Jakes, Joseph E.

    2013-07-01

    A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg-1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-activated, shape memory twist effect. Over 70% of the twist in a wetted bundle can be locked-in by drying under constraint and then released by rewetting the bundle. Our results indicate that hemicelluloses dominate the shape fixity mechanism and lignin is primarily responsible for remembering the bundle’s original form. The bundles demonstrate proof of a high specific torque actuator with large angles of rotation and shape memory twist capabilities that can be used in microactuators, sensors, and energy harvesters.

  16. Torsional malalignment, how much significant in the trochanteric fractures?

    Science.gov (United States)

    Kim, Tae Young; Lee, Yong Beom; Chang, Jun Dong; Lee, Sang Soo; Yoo, Jae Hyun; Chung, Kook Jin; Hwang, Ji Hyo

    2015-11-01

    The rotational alignment is definitely important in the long bones such as tibias and femurs. We also predict the importance of rotational alignment in the trochanteric fractures. So we measured torsional malalignment in trochanteric fracture and anlaysed their risk factors and their clinical significance. A total of 109 inpatients who had undergone internal fixation following trochanteric fracture and a postoperative pelvic CT scan between 2008 and 2013, with at least one year follow-up, were selected. Factors that affect torsional malalignment, such as age, gender, fracture stability, injured area, operative time, time of surgery after admission, and ASA status, were investigated. Factors that affect the patients' clinical results in malrotation, including ambulation time after surgery, postoperative complication rates, pain assessment of VAS one year postoperatively and Koval score, were also investigated. Of the 109 subjects, torsional malalignment was observed in 28 (25.7%) subjects with a mean torsional malalignment angle of 20.7° (range: -31.2° to 27.1°). Torsional malalignment risk factors were fracture stability (p=0.021) and operative time (p=0.043). In terms of the time to ambulation after surgery, the postoperative complication rates, and the VAS and Koval scores at one year postoperatively, no statistically significant difference was observed between the torsional malalignment patients and the non-deformity patients. In this study, 25.7% of the patients who had undergone internal fixation following trochanteric fracture experienced torsional malalignment. Major factors of the torsional malalignment were an unstable fracture and the consequent delay in the operative time. But the torsional malalignment was deemed to have no effect on clinical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Ultrafine grained Cu processed by compression with oscillatory torsion

    OpenAIRE

    K. Rodak

    2007-01-01

    Purpose: The aim of this work is a study of Cu microstructure after severe plastic deformation process by usingcompression with oscillatory torsion test.Design/methodology/approach: Cu samples were deformed at torsion frequency (f) changed from 0 Hz(compression) to 1.8 Hz under a constant torsion angle (α) ≈8° and compression speed (v)=0.1mm/s. Structuralinvestigations were conducted by using light microscopy (LM) and transmission electron microscopy (TEM).Findings: The structural analysis ma...

  18. 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...... real-world resource use into a game....

  19. The effect of hydrogen bonding on torsional dynamics: A combined far-infrared jet and matrix isolation study of methanol dimer

    DEFF Research Database (Denmark)

    Kollipost, F.; Andersen, Jonas; Wallin Mahler Andersen, Denise

    2014-01-01

    The effect of strong intermolecular hydrogen bonding on torsional degrees of freedom is investigated by far-infrared absorption spectroscopy for different methanol dimer isotopologues isolated in supersonic jet expansions or embedded in inert neon matrices at low temperatures. For the vacuum......-isolated and Ne-embedded methanol dimer, the hydrogen bond OH librational mode of the donor subunit is finally observed at ∼560 cm(-1), blue-shifted by more than 300 cm(-1) relative to the OH torsional fundamental of the free methanol monomer. The OH torsional mode of the acceptor embedded in neon is observed...... in order to quantify the contribution of vibrational anharmonicity for this important class of intermolecular hydrogen bond vibrational motion....

  20. Stability of self-accelerating Universe in modified gravity with dynamical torsion: The case of small background torsion

    Science.gov (United States)

    Nikiforova, Vasilisa

    2018-03-01

    We consider the model of modified gravity with dynamical torsion. This model was found to have promising stability properties about various backgrounds. The model admits a self-accelerating solution. We have shown previously that if the parameters are adjusted in such a way that the torsion is much greater than the effective cosmological constant, the self-accelerating solution is unstable: there are exponentially growing modes. Here, we study the scalar perturbations in the case when the torsion is of the order of the effective cosmological constant. We find that there are no exponential instabilities.

  1. Evaluation of left ventricular torsion in children with hypertrophic cardiomyopathy.

    Science.gov (United States)

    Prinz, Christian; Faber, Lothar; Horstkotte, Dieter; Körperich, Hermann; Moysich, Axel; Haas, Nikolaus; Kececioglu, Deniz; Thorsten Laser, Kai

    2014-04-01

    To evaluate the role of torsion in hypertrophic cardiomyopathy in children. A total of 88 children with idiopathic hypertrophic cardiomyopathy (n = 24) and concentric hypertrophy (n = 20) were investigated with speckle-tracking echocardiography and compared with age- and gender-matched healthy controls (n = 44). In hypertrophic cardiomyopathy, we found increased torsion (2.8 ± 1.6 versus 1.9 ± 1.0°/cm [controls], p Hypertrophic cardiomyopathy patients demonstrated a negative correlation between left ventricular muscle mass and torsion (r = -0.7, p hypertrophic cardiomyopathy is characterised by predominantly enhanced systolic basal clockwise rotation. Diastolic untwisting is delayed in both groups. Torsion may be an interesting marker to guide patients with hypertrophic cardiomyopathy.

  2. Isolated adnexal torsion in a 20-week spontaneous twin pregnancy

    Directory of Open Access Journals (Sweden)

    Ilker Kahramanoglu

    2016-01-01

    Discussion: Adnexal torsion as a cause of acute abdomen may be kept in mind in pregnants, even if there is no predisposing factor. Laparoscopy may be performed safely in 2nd trimester for acute abdomen.

  3. Outcomes of Surgery for Posterior Polar Cataract Using Torsional Ultrasound

    Directory of Open Access Journals (Sweden)

    Selçuk Sızmaz

    2013-10-01

    Full Text Available Purpose: The aim of this study is to report outcomes of surgery for posterior polar cataract using torsional ultrasound. Material and Method: Medical records of 26 eyes of 21 consecutive patients with posterior polar cataract who had cataract surgery using the torsional phacoemulsification were evaluated retrospectively. The surgical procedure used, phacoemulsification parameters, intraoperative complications, and postoperative visual outcome were recorded. Results: Of the 26 eyes, 24 (92.3% had small to medium posterior polar opacity. Two eyes had large opacity. All surgeries were performed using the torsional handpiece. Posterior capsule rupture occurred in 4 (15.3% eyes. The mean visual acuity improved significantly after surgery (p<0.001. The postoperative visual acuity was worse than 20/20 in 5 eyes. The cause of the low acuity was amblyopia. Discussion: Successful surgical results and good visual outcome can be achieved with phacoemulsification using the torsional handpiece. (Turk J Ophthalmol 2013; 43: 345-7

  4. Ovarian sparing surgery in cases of giant torsioned ovarian masses

    Directory of Open Access Journals (Sweden)

    Yesim Bayoglu Tekin

    2015-12-01

    Full Text Available Ovarian torsion is a rare gynecological emergency. ovarian torsion is often seen in reproductive ages and salphingooopherectomy is performed for the treatment. However, surgically excision of one of the ovaries early in life causes severe damage to the future fertility. Many case series that were published recently, has been shown low complication rate of ovarian sparing surgery at ovarian torsion and have been preserved from the organ loss. In this study we presented 3 cases at young ages with giant torsioned adnexal masses managed by ovarian sparing surgery at laparotomy and revised the literature in the light of these cases. [J Contemp Med 2015; 5(4.000: 253-256

  5. Damping of Torsional Beam Vibrations by Control of Warping Displacement

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker; Hoffmeyer, David; Ejlersen, Christian

    2016-01-01

    Supplemental damping of torsional beam vibrations is considered by viscous bimoments acting on the axial warping displacement at the beam supports. The concept is illustrated by solving the governing eigenvalue problem for various support configurations with the applied bimoments represented...

  6. Torsion of a wandering spleen | Carapinha | South African Journal of ...

    African Journals Online (AJOL)

    Abstract. Torsion of a wandering spleen is a rare and difficult diagnosis in the paediatric population, with death a possible outcome. In this paper we present our experience of a single case and discuss the embryology and management thereof.

  7. Amplitude-temperature analysis of hard rubber by torsional vibration

    Czech Academy of Sciences Publication Activity Database

    Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Cibulka, Jan; Košina, Jan

    2016-01-01

    Roč. 821, č. 2016 (2016), s. 295-302 ISSN 1660-9336 Institutional support: RVO:61388998 Keywords : hard rubber * torsion vibration * finite deformation * parameter identification Subject RIV: BI - Acoustics

  8. Primary torsion of vermiform appendix mimicking acute appendicitis.

    Science.gov (United States)

    Marsdin, Emma L; Griffiths, Carl

    2011-10-28

    Acute appendicitis is a common condition, 8% of the developed world have an appendicectomy in their lifetime. However, torsion of the appendix is a rare disorder first described in 1918 presenting in a manner undistinguishable from acute appendicitis. The authors describe a case of a 48-year-old man who presented with a short history consistent with acute appendicitis. At open appendicectomy, was found to have an acute clockwise torsion of the vermiform appendix at a point 0.5 cm from its base. Histological examination of the specimen was consistent with torsion of the appendix but no underlying cause for the torsion was identified. The postoperative recovery was uneventful; the patient received intravenous antibiotics for a further 48 h and was discharged home without any complications.

  9. Standardized education and parental awareness are lacking for testicular torsion.

    Science.gov (United States)

    Friedman, Ariella A; Ahmed, Haris; Gitlin, Jordan S; Palmer, Lane S

    2016-06-01

    Testicular torsion leads to orchiectomy in 30-50% of cases, which may cause psychological upset and parental guilt over a potentially avertable outcome. Presentation delay is an important modifiable cause of orchiectomy; yet, families are not routinely educated about torsion or its urgency. The present study assessed parental knowledge regarding acute scrotal pain. An anonymous survey was distributed to parents in Urology and ENT offices, asking about their children's gender and scrotal pain history, urgency of response to a child's acute scrotal pain, and familiarity with testicular torsion. Surveys of 479 urology and 59 ENT parents were analyzed. The results between the two were not statistically different. Among the urology parents, 34% had heard of testicular twisting/torsion, most commonly through friends, relatives or knowing someone with torsion (35%); only 17% were informed by pediatricians (Summary Figure). Parents presenting for a child's scrotal pain were significantly more likely to have heard of torsion (69%) than those presenting for other reasons (30%, OR 5.24, P parents of boys had spoken with their children about torsion. Roughly three quarters of them would seek emergent medical attention - by day (75%) or night (82%) - for acute scrotal pain. However, urgency was no more likely among those who knew about torsion. This was the first study to assess parental knowledge of the emergent nature of acute scrotal pain in a non-urgent setting, and most closely approximating their level of knowledge at the time of pain onset. It also assessed parents' hypothetical responses to the scenario, which was markedly different than documented presentation times, highlighting a potential area for improvement in presentation times. Potential limitations included lack of respondent demographic data, potential sampling bias of a population with greater healthcare knowledge or involvement, and assessment of parents only. Parental knowledge of testicular torsion was

  10. Anthropometric study of angle of femoral torsion in Maharashtrian population

    Directory of Open Access Journals (Sweden)

    Anil Kumar Dwivedi

    2016-01-01

    Full Text Available Introduction: Angle of femoral torsion is a normal torsion or twist present in femur that plays an important role in stability and function of the hip joint. The angle of femoral torsion can be defined as the angle formed by femoral condyle′s plane (bicondylar plane and a plane passing through center of neck and femoral head. Abnormal angle of femoral torsion has been implicated in the etiology of hip osteoarthrosis and developmental dysplasia of hip joint. Materials and Methods: This study was carried out on unpaired 280, adult human femora devoid of any gross pathology, 139 male (65 right and 74 left, and 141 female (71 right and 70 left from bone banks of three medical colleges of Maharashtra. The gender of each specimen was determined by the established practice. Femora were evaluated by Kingsley Olmsted method, and data were tabulated and statistically analyzed. Results: The average angle of femoral torsion 13.39° and 11.23° on the right and left side respectively in male, 16.21° and 13.23° on the right and left side, respectively, in female. Statistical analysis using Student′s "t"-test revealed significant difference (P < 0.05, greater angle of femoral torsion in female and on the right side. Conclusion: Knowledge of angle of femoral torsion is becoming significant nowadays with an increase in demand for total hip replacement, as the angle of femoral torsion is crucial to attain a normal activity of the replaced joint.

  11. Torsion of the greater omentum: A rare preoperative diagnosis

    International Nuclear Information System (INIS)

    Tandon, Ankit Anil; Lim, Kian Soon

    2010-01-01

    Torsion of the greater omentum is a rare acute abdominal condition that is seldom diagnosed preoperatively. We report the characteristic computed tomography (CT) scan findings and the clinical implications of this unusual diagnosis in a 41-year-old man, who also had longstanding right inguinal hernia. Awareness of omental torsion as a differential diagnosis in the acute abdomen setting is necessary for correct patient management

  12. High rank elliptic curves with torsion ℤ/4ℤ.

    Science.gov (United States)

    Khoshnam, Foad; Moody, Dustin

    2016-01-01

    Working over the field ℚ( t ), Kihara constructed an elliptic curve with torsion group ℤ/4ℤ and five independent rational points, showing the rank is at least five. Following his approach, we give a new infinite family of elliptic curves with torsion group ℤ/4ℤ and rank at least five. This matches the current record for such curves. In addition, we give specific examples of these curves with high ranks 10 and 11.

  13. Model of Structural Fragmentation Induced by High Pressure Torsion

    Czech Academy of Sciences Publication Activity Database

    Kratochvíl, J.; Kružík, Martin; Sedláček, R.

    2010-01-01

    Roč. 25, č. 1 (2010), s. 88-98 ISSN 1606-5131 Institutional research plan: CEZ:AV0Z10750506 Keywords : High-pressure torsion * intergranular glide * homogeneous deformation mode Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.649, year: 2010 http://library.utia.cas.cz/separaty/2010/MTR/kruzik-model of structural fragmentation induced by high pressure torsion.pdf

  14. Torsional Moment Measurement on Bucket Wheel Shaft of Giant Machine

    Directory of Open Access Journals (Sweden)

    Jiří FRIES

    2011-06-01

    Full Text Available Bucket wheel loading at the present time (torsional moment on wheel shaft, peripheral cutting force is determined from electromotor incoming power or reaction force measured on gearbox hinge. Both methods together are weighted by steel construction absorption of driving units and by inertial forces of motor rotating parts. In the article is described direct method of the torsional moment measurement, which eliminates mentioned unfavourable impacts except absorption of steel construction of bucket wheel itself.

  15. The variation of torsion with vergence and elevation.

    Science.gov (United States)

    Porrill, J; Ivins, J P; Frisby, J P

    1999-11-01

    Two recently developed kinematic models of human eye movements predict systematic departures from Listing's law which are associated with changes in vergence. This vergence-dependent torsion t is proportional to elevation e and vergence v, that is t = kev/2. The proposed value for k is either 1 (Van Rijn, L. J., & Van den Berg, A. V. (1993). Vision Research, 33, 691-708) or 1/2 (Minken, A. W. H., Gielen, C. C. A. M., & Van Gisbergen, J. A. M. (1995). Vision Research, 35, 93-102). One implication of both models is that an eye with a constant fixation direction should exhibit systematic torsional variation during movements of the other eye. This paper therefore examines the torsion produced by moving a fixation target inwards and outwards along the line-of-sight of the right eye at five different viewing elevations (0, +/- 15 and +/- 30 degrees). In a monocular analysis, each eye generally showed intorsion during convergence at positive elevation angles, whereas extorsion occurred at negative elevations; the opposite was true during divergence. However, the torsion response was visibly different between the five subjects, and depended on the direction of target motion. In a binocular analysis, cycloversion (mean of left and right eye torsion) varied dramatically both between subjects and between convergence and divergence; however, cyclovergence (torsional difference) was much less variable. Least-squares methods were used to estimate the constant k from monocular torsion, yielding values between 0.2 and 1.0; however, corresponding estimates based on cyclovergence were all close to 1/2. These findings support suggestions that a binocular control system couples the three-dimensional movements of the eyes, and that an existing model of monocular torsion should be generalised to the binocular case.

  16. Displacement of rectus muscle pulleys by torsional muscle surgery for treatment of full macular translocation-induced incyclotropia.

    Science.gov (United States)

    Kono, Reika; Ohtsuki, Hiroshi; Okanobu, Hirotaka; Kinugasa, Kazushi

    2005-07-01

    To elucidate the coronal plane locations of extraocular muscle (EOM) pulleys following torsional muscle surgery. Case report. A 76-year-old man underwent advancement of the anterior part of the inferior oblique muscle to treat full macular translocation-induced incyclotropia. Postoperatively, magnetic resonance imaging was used to obtain contiguous, 2-mm-thick coronal orbital images. On each MRI image, the cross-sectional area and center of the EOM was computed, and all rectus EOM positions were translated to the coordinate origin at the area centroid of the globe at the level of pulleys. The superior rectus pulley was displaced temporally, and the lateral rectus pulley was displaced inferiorly more than 2 SD from normal subjects. Coronal plane locations of EOM pulleys of the ipsilateral eye showed extorsion compared with that of the contralesional eye. Torsional muscle surgery causes an extorsional shift of the superior and lateral rectus pulleys.

  17. ESTIMATING TORSION OF DIGITAL CURVES USING 3D IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Christoph Blankenburg

    2016-04-01

    Full Text Available Curvature and torsion of three-dimensional curves are important quantities in fields like material science or biomedical engineering. Torsion has an exact definition in the continuous domain. However, in the discrete case most of the existing torsion evaluation methods lead to inaccurate values, especially for low resolution data. In this contribution we use the discrete points of space curves to determine the Fourier series coefficients which allow for representing the underlying continuous curve with Cesàro’s mean. This representation of the curve suits for the estimation of curvature and torsion values with their classical continuous definition. In comparison with the literature, one major advantage of this approach is that no a priori knowledge about the shape of the cyclic curve parts approximating the discrete curves is required. Synthetic data, i.e. curves with known curvature and torsion, are used to quantify the inherent algorithm accuracy for torsion and curvature estimation. The algorithm is also tested on tomographic data of fiber structures and open foams, where discrete curves are extracted from the pore spaces.

  18. Bicavitary effusion secondary to liver lobe torsion in a dog

    Directory of Open Access Journals (Sweden)

    Khan Z

    2016-04-01

    Full Text Available Zaheda Khan,1 Kathryn Gates,2 Stephen A Simpson,31Emergency and Critical Care, Animal Specialty and Emergency Center, Los Angeles, CA, 2Emergency and Critical Care, Advanced Critical Care, Emergency and Specialty Services, Culver City, CA 3Emergency and Critical Care, Southern California Veterinary Specialty Hospital, Irvine, CA, USA Abstract: We described the diagnosis and successful treatment of pleural and peritoneal effusion secondary to liver lobe torsion in a dog. A 12-year-old female spayed Borzoi dog was referred for heart failure. Emergency room thoracic and abdominal ultrasound showed a large volume of pleural effusion with mild peritoneal effusion and an abdominal mass. Pleural fluid analysis classified the effusion as exudative. A complete ultrasound revealed mild peritoneal effusion and decreased blood flow to the right liver lobe. Other causes of bicavitary effusion were ruled out based on blood work, ultrasound, echocardiogram, and computed tomography. The patient was taken to surgery and diagnosed with caudate liver lobe torsion and had a liver lobectomy. At the 2-week postoperative recheck, the patient was doing well and there was complete resolution of the pleural effusion. Liver lobe torsion is a rare occurrence in dogs and can be difficult to diagnose. Clinical signs are nonspecific for liver lobe torsion and patients may present in respiratory distress with significant pleural fluid accumulation. When assessing patients with pleural and peritoneal effusion, liver lobe torsion should be considered as a differential diagnosis.Keywords: pleural effusion, peritoneal effusion, hepatic torsion

  19. Numerical Analysis of Stress and Strain in Specimens with Rectangular Cross-Section Subjected to Torsion and Bending with Torsion

    Directory of Open Access Journals (Sweden)

    Faszynka Sebastian

    2016-03-01

    Full Text Available The paper presents an analysis of the state of stress and crack tip opening displacement (strain in specimens with rectangular cross-section subjected to torsion and combined bending with torsion. The specimens were made of the EN AW-2017A aluminium alloy. The specimens had an external unilateral notch, which was 2 mm deep and its radius was 22.5 mm. The tests were performed at constant moment amplitude MT = MBT = 15.84 N·m and under stress ratio R = −1. The exemplary results of numerical computations being obtained by using the FRANC3D software were shown in the form of stress and crack tip opening displacement (CTOD maps. The paper presents the differences of fatigue cracks growth under torsion and bending with torsion being derived by using the FRANC3D software.

  20. Anharmonicity of Coupled Torsions: The Extended Two-Dimensional Torsion Method and Its Use To Assess More Approximate Methods.

    Science.gov (United States)

    Simón-Carballido, Luis; Bao, Junwei Lucas; Alves, Tiago Vinicius; Meana-Pañeda, Rubén; Truhlar, Donald G; Fernández-Ramos, Antonio

    2017-08-08

    In this work we present the extended two-dimensional torsion (E2DT) method and use it to analyze the performance of several methods that incorporate torsional anharmonicity more approximately for calculating rotational-vibrational partition functions. Twenty molecules having two hindered rotors were studied for temperatures between 100 and 2500 K. These molecules present several kinds of situations; they include molecules with nearly separable rotors, molecules in which the reduced moments of inertia change substantially with the internal rotation, and molecules presenting compound rotation. Partition functions obtained by the rigid-rotor harmonic oscillator approximation, a method involving global separability of torsions and the multistructural methods without explicit potential coupling [MS-T(U)] and with explicit potential coupling [MS-T(C)] of torsions, are compared to those obtained with a quantized version - called the extended two-dimensional torsion (E2DT) method - of the extended hindered rotor approximation of Vansteenkiste et al. ( Vansteenkiste et al. J. Chem. Phys. 2006 , 124 , 044314 ). In the E2DT method, quantum effects due to the torsional modes were incorporated by the two-dimensional nonseparable method, which is a method that is based on the solution of the torsional Schrödinger equation and that includes full coupling in both the kinetic and potential energy. By comparing other methods to the E2DT method and to experimental thermochemical data, this study concludes that the harmonic approximation yields very poor results at high temperatures; the global separation of torsions from the rest of the degrees of freedom is not justified even when an accurate method to treat the torsions is employed; it is confirmed that methods based on less complete potential energy coupling of torsions, such as MS-T(U), are not accurate when dealing with rotors with different barrier heights, and more complete inclusion of torsional coupling to the method in MS

  1. Magnetic resonance imaging findings in adnexial torsion

    Energy Technology Data Exchange (ETDEWEB)

    Trindade, Ronald Meira Castro; Quadros, Marianne Siquara de [Hospital Albert Einstein, Sao Paulo, SP (Brazil). Instituto de Ensino e Pesquisa], e-mail: rtrindade@einstein.br; Baroni, Ronaldo Hueb; Rosemberg, Michelle; Racy, Marcelo de Castro Jorge; Tachibana, Adriano [Hospital Albert Einstein, Sao Paulo, SP (Brazil); Funari, Marcelo Buarque de Gusmao [Hospital Albert Einstein, Sao Paulo, SP (Brazil). Imaging Service

    2010-01-15

    Adnexial torsion is an unusual event, but a major cause of abdominal pain in women. It is often associated with ovarian tumor or cyst, but can occur in normal ovaries, especially in children. The twisting of adnexial structures may involve the ovary or tube, but frequently affects both. In most cases, it is unilateral, with slight predilection for the right size. In imaging findings, increased ovarian volume and adnexial masses are observed, with reduced or absent vascularisation. In cases of undiagnosed or untreated complete twist, hemorrhagic necrosis may occur leading to complications; in that, peritonitis is the most frequent. Early diagnosis helps preventing irreversible damage with conservative treatment, thereby saving the ovary. Limitations in performing physical examination, possible inconclusive results in ultrasound and exposure to radiation in computed tomography makes magnetic resonance imaging a valuable tool in emergency assessment of gynecological diseases. The objective of this study was to report two confirmed cases of adnexial twist, emphasizing the contribution of magnetic resonance imaging in the diagnosis of this condition. (author)

  2. Fluid Shifts

    Science.gov (United States)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; hide

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with 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 now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to 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 determine if a relation exists 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 any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. 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, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  3. Shifting Blame?

    DEFF Research Database (Denmark)

    Garofalo, Orsola; Rott, Christina

    2017-01-01

    either the decision maker or a spokesperson communicates the decided allocation to recipients, who then determine whether to punish either of them. We find that receivers punish both the decision maker and the spokesperson more often, and more heavily, for unfair allocations communicated...... by the spokesperson if there is room for shifting blame. The increased punishment results from the messenger’s style of delivery: spokespersons are more likely than decision makers to express emotional regret instead of rational need. Receivers seem to punish the former style of communication because they view...

  4. The effect of torsional muscle dysfunction and surgery on eye position under general anesthesia.

    Science.gov (United States)

    McCall, L C; Isenberg, S J; Apt, L

    1993-01-01

    Under general anesthesia, normal eyes exhibit 2.0 degrees to 2.5 degrees of extorsion. To investigate the effect of torsional muscle dysfunction and surgery on eye position under general anesthesia, we measured the torsional change before and after torsional muscle surgery in 26 eyes of 18 patients with clinical torsional muscle dysfunction. Under general anesthesia, compared with normals, eyes with preoperative intorter overaction or extorter underaction demonstrated a significant intorsional change (P extorsion while intorter strengthening procedures and extorter weakening procedures produced measurable intorsion. Superior oblique tenotomy produced a greater net torsional change than inferior oblique weakening surgery (P < .01). Under general anesthesia, eyes with preoperative torsional muscle dysfunction exhibit torsion in the direction consistent with the dysfunction. After surgery on the torsional muscles, a measurable torsional effect can be demonstrated while the patient is still under general anesthesia.

  5. Backbone and side-chain 1H, 13C, and 15N chemical shift assignments for the apo-form of the lytic polysaccharide monooxygenase NcLPMO9C

    OpenAIRE

    Courtade, Gaston; Wimmer, Reinhard; Dimarogona, Maria; Sandgren, Mats; Eijsink, Vincent; Aachmann, Finn Lillelund

    2016-01-01

    The apo-form of the 23.3 kDa catalytic domain of the AA9 family lytic polysaccharide monooxygenase NcLPMO9C from Neurospora crassa has been isotopically labeled and recombinantly expressed in Pichia pastoris. In this paper, we report the 1H, 13C, and 15N chemical shift assignments of this LPMO. © Springer Verlag. The final publication is available at https://link.springer.com/article/10.1007%2Fs12104-016-9683-x. This is the authors' accepted and refereed manuscript to the article.

  6. Chemical shift assignments for the apo-form of the catalytic domain, the linker region, and the carbohydrate-binding domain of the cellulose-active lytic polysaccharide monooxygenase ScLPMO10C.

    Science.gov (United States)

    Courtade, Gaston; Forsberg, Zarah; Vaaje-Kolstad, Gustav; Eijsink, Vincent G H; Aachmann, Finn L

    2017-10-01

    The apo-form of the 21.4 kDa catalytic domain and the 10.7 kDa carbohydrate binding domain of the AA10 family lytic polysaccharide monooxygenase ScLPMO10C from Streptomyces coelicolor have been isotopically labeled and recombinantly expressed in Escherichia coli. In this paper, we report the 1 H, 13 C, and 15 N chemical shift assignments of each individual domain as well as an ensemble of the assignment for the full-length protein, including its approximately 30-amino acid long linker.

  7. Conformational Landscape and Torsion-Rotation-Vibration Effects in the Two Conformers of Methyl Vinyl Ketone, a Major Oxidation Product of Isoprene.

    Science.gov (United States)

    Zakharenko, Olena; Motiyenko, Roman A; Aviles Moreno, Juan Ramon; Huet, Thérèse R

    2017-08-31

    Methyl vinyl ketone is the second major oxidation product of isoprene, and as such an important volatile organic compound present in the troposphere. In the present study, quantum chemical calculations coupled to high-resolution millimeter-wave spectroscopy have been performed to characterize the ground and first excited vibrational states of the two stable conformers. Equilibrium structures, internal rotation barriers, and relative energies have been calculated at the MP2 and M062X levels of theory. Experimental molecular parameters have been obtained that model the rotational and torsional structures, including splitting patterns due to the internal rotation of the methyl group. For the most stable antiperiplanar (s-trans) conformer, the set of parameters obtained for the ground state should be useful to further model IR spectra up to room temperature. By combining theoretical and experimental data, we obtained a relative energy value of 164 ± 30 cm -1 in the gas phase between the more stable antiperiplanar and the less stable synperiplanar conformers. Moreover, we compared our system with related molecules for the variation in the barriers of methyl rotors in different molecular environments. In addition, the inverse sequence of A and E tunneling substates for the rotational lines of the first excited skeletal torsional state and Coriolis-type coupling with methyl torsion have been observed. For the less stable synperiplanar (cis) conformer, molecular parameters for the ground and first excited torsional states as well as of the first excited skeletal torsional state are presented.

  8. 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.

  9. [Torsion of wandering spleen in a teenager: about a case].

    Science.gov (United States)

    Dème, Hamidou; Akpo, Léra Géraud; Fall, Seynabou; Badji, Nfally; Ka, Ibrahima; Guèye, Mohamadou Lamine; Touré, Mouhamed Hamine; Niang, El Hadj

    2016-01-01

    Wandering or migrating spleen is a rare anomaly which is usually described in children. Complications, which include pedicle torsion, are common and can be life-threatening. We report the case of a 17 year-old patient with a long past medical history of epigastric pain suffering from wandering spleen with chronic torsion of the pedicle. The clinical picture was marked by spontaneously painful epigastric mass, evolved over the past 48 hours. Abdominal ultrasound objectified heterogeneous hypertrophied ectopic spleen in epigastric position and a subcapsular hematoma. Doppler showed a torsion of splenic pedicle which was untwisted 2 turns and a small blood stream on the splenic artery. Abdominal CT scan with contrast injection showed a lack of parenchymal enhancement of large epigastric ectopic spleen and a subcapsular hematoma. The diagnosis of wandering spleen with chronic torsion of the pedicle complicated by necrosis and subcapsular hematoma was confirmed. The patient underwent splenectomy. The postoperative course was uneventful. We here discuss the contribution of ultrasound and CT scan in the diagnosis of wandering spleen with chronic torsion of the pedicle.

  10. Whirling sign : an imaging finding indicating ovarian torsion

    International Nuclear Information System (INIS)

    Cha, Jang Gyu; Kim, Young Hwa; Kim, Hyun Jung; Chang, Yu Jin; Kim, Young Tong; Cho, Won Soo; Bae, Won Kyung; Kim, Il Young

    1997-01-01

    To present a diagnostic sign on MRI and US in patients with ovarian torsion. We present characteristic imaging findings in eight patients with surgically-proven ovarian torsion. MRI was performed in four patients, CT in six and US in all patients;the procedures including eight transabdominal US (TAS) and three transvaginal US (TVS). In each study, imaging findings were analyzed for the appearance of twisted pedicle and the presence of a 'whirling sign'. The pedicle which indicates ovarian torsion was detected on MRI in all 4 patients, on TAS in 4/7, on TVS in 3/3, and on CT in 4/6. A specific 'whirling sign' was detected on MRI in 2/4 patients, on TAS in 2/4, and on TVS in all three. On CT a 'whirling sign' was not detected. The 'whirling sign' on both MRI and US is a characteristic finding of ovarian torsion;in a patient with adnexal mass and complaining of lower abdominal pain, the presence of this sign is very useful for the diagnosis of ovarian torsion

  11. Prune belly syndrome, splenic torsion, and malrotation: a case report.

    Science.gov (United States)

    Tran, Sifrance; Grossman, Eric; Barsness, Katherine A

    2013-02-01

    An 18 year old male with a history of prune belly syndrome (PBS) presented with acute abdominal pain and palpable left upper quadrant mass. Computed tomography (CT) of the abdomen revealed a medialized spleen with a "whirl sign" in the splenic vessels, consistent with splenic torsion. Coincidentally, the small bowel was also noted to be on the right side of the abdomen, while the colon was located on the left, indicative of malrotation. Emergent diagnostic laparoscopy confirmed splenic torsion and intestinal malrotation. Successful laparoscopic reduction of the splenic torsion was achieved, however, conversion to an open procedure by a vertical midline incision was necessary owing to the patient's unique anatomy. Open splenopexy with a mesh sling and Ladd's procedure were subsequently performed. Malrotation and wandering spleen are known, rare associated anomalies in PBS; however, both have not been reported concurrently in a patient with PBS in the literature. In patients with PBS, acute abdominal pain, and an abdominal mass, high clinical suspicion for gastrointestinal malformations and prompt attention can result in spleen preservation and appropriate malrotation management. We present a case of a teenager who presented with a history of PBS, acute abdominal pain, and a palpable abdominal mass. The patient was found to have splenic torsion and intestinal malrotation. The clinical findings, diagnostic imaging, and surgical treatment options of splenic torsion are reviewed. Copyright © 2013 Elsevier Inc. All rights reserved.

  12. Torsion of abdominal appendages presenting with acute abdominal pain

    International Nuclear Information System (INIS)

    Al-Jaberi, Tareq M.; Gharabeih, Kamal I.; Yaghan, Rami J.

    2000-01-01

    Diseases of abnormal appendages are rare causes of abdominal pain in all age groups. Nine patients with torsion and infraction of abdominal appendages were retrospectively reviewed. Four patients had torsion and infarction of the appendices epiploicae, four patients had torsion and infarction of the falciform ligament. The patient with falciform ligament disease represents the first reported case of primary torsion and infarction of the falciform ligament, and the patient with the transverse colon epiplocia represents the first reported case of vibration-induced appendix epiplocia torsion and infarction. The patient with the falciform ligament disease presented with a tender upper abdominal mass and the remaining patients were operated upon with the preoperative diagnosis of acute appendicitis. The presence of normal appendix with free serosanguinous fluid in the peritoneal cavity should raise the possibility of a disease and calls for further evaluation of the intra-abdominal organs. If the diagnosis is suspected preoperatively, CT scan and ultrasound may lead to a correct diagnosis and possibly conservative management. Laparoscopy is playing an increasing diagnostic and therapeutic role in such situations. (author)

  13. On unified field theories, dynamical torsion and geometrical models: II

    International Nuclear Information System (INIS)

    Cirilo-Lombardo, D.J.

    2011-01-01

    We analyze in this letter the same space-time structure as that presented in our previous reference (Part. Nucl, Lett. 2010. V.7, No.5. P.299-307), but relaxing now the condition a priori of the existence of a potential for the torsion. We show through exact cosmological solutions from this model, where the geometry is Euclidean RxO 3 ∼ RxSU(2), the relation between the space-time geometry and the structure of the gauge group. Precisely this relation is directly connected with the relation of the spin and torsion fields. The solution of this model is explicitly compared with our previous ones and we find that: i) the torsion is not identified directly with the Yang-Mills type strength field, ii) there exists a compatibility condition connected with the identification of the gauge group with the geometric structure of the space-time: this fact leads to the identification between derivatives of the scale factor a with the components of the torsion in order to allow the Hosoya-Ogura ansatz (namely, the alignment of the isospin with the frame geometry of the space-time), and iii) of two possible structures of the torsion the 'tratorial' form (the only one studied here) forbid wormhole configurations, leading only to cosmological instanton space-time in eternal expansion

  14. Optical fiber accelerometer based on MEMS torsional micromirror

    Science.gov (United States)

    Zeng, Fanlin; Zhong, Shaolong; Xu, Jing; Wu, Yaming

    2008-03-01

    A novel structure of optical fiber accelerometer based on MEMS torsional micro-mirror is introduced, including MEMS torsional micro-mirror and optical signal detection. The micro-mirror is a non-symmetric one, which means that the torsional bar supporting the micro-mirror is not located in the axis where the center of the micro-mirror locates. The optical signal detection is composed of PIN diode and dual fiber collimator, which is very sensitive to the coupling angle between the input fiber and output fiber. The detection principle is that acceleration is first transformed into torsional angle of the micro-mirror, then, optical insertion loss of the dual fiber collimator caused by the angle can be received by PIN. So under the flow of acceleration to torsional angle to optical signal attenuation to optical power detection, the acceleration is detected. The theory about sensing and optical signal detect of the device are discussed in this paper. The sensitive structure parameters and performance parameters are calculated by MATLAB. To simulate the static and modal analysis, the finite element analysis, ANSYS, is employed. Based on the above calculation, several optimization methods and the final structure parameters are given. The micro-mirror is completed by using silicon-glass bonding and deep reactive ion etching (DRIE). In the experiment, the acceleration is simulated by electrostatic force and the test results show that the static acceleration detection agrees with the theory analysis very well.

  15. Crack path in aeronautical titanium alloy under ultrasonic torsion loading

    Directory of Open Access Journals (Sweden)

    A. Nikitin

    2016-01-01

    Full Text Available This paper discusses features of fatigue crack initiation and growth in aeronautical VT3-1 titanium alloy under pure torsion loading in gigacycle regime. Two materials: extruded and forged VT3-1 titanium alloys were studied. Torsion fatigue tests were performed up to fatigue life of 109 cycles. The results of the torsion tests were compared with previously obtained results under fully reversed axial loading on the same alloys. It has been shown that independently on production process as surface as well subsurface crack initiation may appear under ultrasonic torsion loading despite the maximum stress amplitude located at the specimen surface. In the case of surface crack initiation, a scenario of crack initiation and growth is similar to HCF regime except an additional possibility for internal crack branching. In the case of subsurface crack, the initiation site is located below the specimen surface (about 200 μm and is not clearly related to any material flaw. Internal crack initiation is produced by shear stress in maximum shear plane and early crack growth is in Mode II. Crack branching is limited in the case of internal crack initiation compared to surface one. A typical ‘fish-eye’ crack can be observed at the torsion fracture surface, but mechanism of crack initiation seems not to be the same than under axial fatigue loading.

  16. Autoparallel vs. Geodesic Trajectories in a Model of Torsion Gravity

    Directory of Open Access Journals (Sweden)

    Luis Acedo

    2015-11-01

    Full Text Available We consider a parametrized torsion gravity model for Riemann–Cartan geometry around a rotating axisymmetric massive body. In this model, the source of torsion is given by a circulating vector potential following the celestial parallels around the rotating object. Ours is a variant of the Mao, Tegmark, Guth and Cabi (MTGC model in which the total angular momentum is proposed as a source of torsion. We study the motion of bodies around the rotating object in terms of autoparallel trajectories and determine the leading perturbations of the orbital elements by using standard celestial mechanics techniques. We find that this torsion model implies new gravitational physical consequences in the Solar system and, in particular, secular variations of the semi-major axis of the planetary orbits. Perturbations on the longitude of the ascending node and the perihelion of the planets are already under discussion in the astronomical community, and if confirmed as truly non-zero effects at a statistically significant level, we might be at the dawn of an era of torsion phenomenology in the Solar system.

  17. Autoparallel vs. Geodesic Trajectories in a Model of Torsion Gravity

    Science.gov (United States)

    Acedo, Luis

    2015-11-01

    We consider a parametrized torsion gravity model for Riemann-Cartan geometry around a rotating axisymmetric massive body. In this model, the source of torsion is given by a circulating vector potential following the celestial parallels around the rotating object. Ours is a variant of the Mao, Tegmark, Guth and Cabi (MTGC model) in which the total angular momentum is proposed as a source of torsion. We study the motion of bodies around the rotating object in terms of autoparallel trajectories and determine the leading perturbations of the orbital elements by using standard celestial mechanics techniques. We find that this torsion model implies new gravitational physical consequences in the Solar system and, in particular, secular variations of the semi-major axis of the planetary orbits. Perturbations on the longitude of the ascending node and the perihelion of the planets are already under discussion in the astronomical community, and if confirmed as truly non-zero effects at a statistically significant level, we might be at the dawn of an era of torsion phenomenology in the Solar system.

  18. Elevated temperature axial and torsional fatigue behavior of Haynes 188

    Science.gov (United States)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1995-01-01

    The results are reported for high-temperature axial and torsional low-cycle fatigue experiments performed at 760 C in air on thin-walled tubular specimens of Haynes 188, a wrought cobalt-based superalloy. Data are also presented for mean coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. This data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME Boiler and Pressure Code), Manson-Halford, modified multiaxiality factor (proposed in this paper), modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The modified multiaxiality factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

  19. Residual torsional properties of composite shafts subjected to impact loadings

    International Nuclear Information System (INIS)

    Sevkat, Ercan; Tumer, Hikmet

    2013-01-01

    Highlights: • Impact loading reduces the torsional strength of composite shaft. • Impact energy level determines the severity of torsional strength reduction. • Hybrid composite shafts can be manufactured by mixing two types of filament. • Maximum torque capacity of shafts can be estimated using finite element method. - Abstract: This paper presents an experimental and numerical study to investigate residual torsional properties of composite shafts subjected to impact loadings. E-glass/epoxy, carbon/epoxy and E-glass–carbon/epoxy hybrid composite shafts were manufactured by filament winding method. Composite shafts were impacted at 5, 10, 20 and 40 J energy levels. Force–time and energy–time histories of impact tests were recorded. One composite shaft with no impact, and four composite shafts with impact damage, five in total, were tested under torsion. Torque-twisting angle relations for each test were obtained. Reduction at maximum torque and maximum twisting angle induced by impact loadings were calculated. While 5 J impact did not cause significant reduction at maximum torque and maximum twisting angle, remaining impact loadings caused 34–67% reduction at maximum torque, and 30–61% reduction at maximum twisting angle. Reductions increased with increasing energy levels and varied depending on the material of composite shafts. The 3-D finite element (FE) software, Abaqus, incorporated with an elastic orthotropic model, was then used to simulate the torsion tests. Good agreement between experimental and numerical results was achieved

  20. Shifting Sugars and Shifting Paradigms

    Science.gov (United States)

    Siegal, Mark L.

    2015-01-01

    No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face. PMID:25688600

  1. Shifting sugars and shifting paradigms.

    Directory of Open Access Journals (Sweden)

    Mark L Siegal

    2015-02-01

    Full Text Available No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face.

  2. Is there substituent cross-interaction effect in all the conjugated systems containing Cdbnd N polar bond? The substituent effects on the NMR chemical shifts of 2,5-disubstituted pyrimidines

    Science.gov (United States)

    Yuan, Hua; Zhang, Yan; Chen, Chun-Ni; Li, Meng-Yang

    2018-03-01

    The substituent cross-interaction effect in the substituted benzylidene anilines (p-Xsbnd C6H4sbnd CHdbnd Nsbnd C6H4sbnd Y-p) has been observed and widely investigated. In order to investigate whether the substituent cross-interaction effect exist in all the conjugated systems containing Cdbnd N polar bond, this paper employed 2-X-5-Y pyrimidines as the model compounds for study. The influences of substituents X and Y on the 1H NMR and 13C NMR chemical shifts of 2, 5-disubsitituted pyrimidines have been systematically investigated. Quantitative structure-chemical shifts relationship models have been built for δ(H4,6), δ(C2), δ(C4,6) and δ(C5) with four to six molecular descriptors. These models were confirmed of good stability and predictive performances by leave-one-out cross validation. This study indicates that the substituent effects of 2,5-disubstituted pyrimidines are much more complex than that of the substituted benzylidene anilines. More structural factors besides of Hammett parameter should be taken into consideration. Different from the substituted benzylidene anilines, the cross-interaction effect (Δσ2) of substituents X and Y has little contribution to δ(H4,6), δ(C2), δ(C5) and δ(C4,6) of 2,5-disubstituted pyrimidines.

  3. Novel application of chemical shift gradient echo in- and opposed-phase sequences in 3 T MRI for the detection of H-MRS visible lipids and grading of glioma.

    Science.gov (United States)

    Ramli, Norlisah; Khairy, Azua Mohd; Seow, Pohchoo; Tan, Li Kuo; Wong, Jeannie Hsiu Ding; Ganesan, Dharmendra; Rahmat, Kartini

    2016-07-01

    We evaluated the feasibility of using chemical shift gradient-echo (GE) in- and opposed-phase (IOP) imaging to grade glioma. A phantom study was performed to investigate the correlation of (1)H MRS-visible lipids with the signal loss ratio (SLR) obtained using IOP imaging. A cross-sectional study approved by the institutional review board was carried out in 22 patients with different glioma grades. The patients underwent scanning using IOP imaging and single-voxel spectroscopy (SVS) using 3T MRI. The brain spectra acquisitions from solid and cystic components were obtained and correlated with the SLR for different grades. The phantom study showed a positive linear correlation between lipid quantification at 0.9 parts per million (ppm) and 1.3 ppm with SLR (r = 0.79-0.99, p classification probabilities for grade II (SII = 1), grade III (SIII = 0.50) and grade IV (SIV = 0.89). The results underscore the lipid quantification differences in grades of glioma and provide a more comprehensive characterization by using SLR in chemical shift GE IOP imaging. SLR in IOP sequence demonstrates good performance in glioma grading. • Strong correlation was seen between lipid concentration and SLR obtained using IOP • IOP sequence demonstrates significant differences in signal loss within the glioma grades • SLR at solid tumour portions was the best measure for differentiation • This sequence is applicable in a research capacity for glioma staging armamentarium.

  4. Abnormalities of Penile Curvature: Chordee and Penile Torsion

    Directory of Open Access Journals (Sweden)

    Sylvia Montag

    2011-01-01

    Full Text Available Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4–10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical techniques include penile degloving and dorsal plication. This paper will review the current theories for the etiology of penile curvature, discuss the spectrum of severity of congenital chordee and penile torsion, and present varying surgical techniques for the correction of penile curvature in the absence of hypospadias.

  5. Increased external tibial torsion in Osgood-Schlatter disease.

    Science.gov (United States)

    Gigante, Antonio; Bevilacqua, Claudia; Bonetti, Massimo G; Greco, Francesco

    2003-08-01

    We studied the relationship between Osgood-Schlatter disease and torsional abnormalities of the lower limb in 21 boys with this condition and 20 age- and sex-matched controls. 3 groups of knees (20 control knees, 21 symptomatic and 21 asymptomatic or less symptomatic knees) were subjected to clinical, radiographic and CT evaluation. We found no statistically significant differences between patients and controls, as regards femoral anteversion, patellar congruence angle, patellar tilt angle and anterior tibial tuberosity-trochlear groove distance, but the condylomalleolar angle and tibial torsion angle were greater in patients. We found no differences between symptomatic and asymptomatic or less symptomatic knees in any of the parameters. All the symptomatic knees were on the side preferentially involved in jumping and sprinting. This increase in external tibial torsion may play a role as a predisposing mechanical factor in the onset of Osgood-Schlatter disease in male athletes.

  6. Mechanical Design of AM Fabricated Prismatic Rods under Torsion

    Directory of Open Access Journals (Sweden)

    Manzhirov Alexander V.

    2017-01-01

    Full Text Available We study the stress-strain state of viscoelastic prismatic rods fabricated or repaired by additive manufacturing technologies under torsion. An adequate description of the processes involved is given by methods of a new scientific field, mechanics of growing solids. Three main stages of the deformation process (before the beginning of growth, in the course of growth, and after the termination of growth are studied. Two versions of statement of two problems are given: (i given the torque, find the stresses, displacements, and torsion; (ii given the torsion, find the stresses, displacements, and torque. Solution methods using techniques of complex analysis are presented. The results can be used in mechanical and instrument engineering.

  7. In vitro transcription of a torsionally constrained template

    DEFF Research Database (Denmark)

    Bentin, Thomas; Nielsen, Peter E

    2002-01-01

    RNA polymerase (RNAP) and the DNA template must rotate relative to each other during transcription elongation. In the cell, however, the components of the transcription apparatus may be subject to rotary constraints. For instance, the DNA is divided into topological domains that are delineated...... of torsionally constrained DNA by free RNAP. We asked whether or not a newly synthesized RNA chain would limit transcription elongation. For this purpose we developed a method to immobilize covalently closed circular DNA to streptavidin-coated beads via a peptide nucleic acid (PNA)-biotin conjugate in principle...... mimicking a SAR/MAR attachment. We used this construct as a torsionally constrained template for transcription of the beta-lactamase gene by Escherichia coli RNAP and found that RNA synthesis displays similar characteristics in terms of rate of elongation whether or not the template is torsionally...

  8. Simple currents versus orbifolds with discrete torsion - a complete classification

    International Nuclear Information System (INIS)

    Kreuzer, M.; Schellekens, A.N.

    1993-01-01

    We give a complete classification of all simple current modular invariants, extending previous results for (Z p ) k to arbitrary centers. We obtain a simple explicit formula for the most general case. Using orbifold techniques to this end, we find a one-to-one correspondence between simple current invariants and subgroups of the center with discrete torsions. As a by-product, we prove the conjectured monodromy independence of the total number of such invariants. The orbifold approach works in a straightforward way for symmetries of odd order, but some modifications are required to deal with symmetries of even order. With these modifications the orbifold construction with discrete torsion is complete within the class of simple current invariants. Surprisingly, there are cases where discrete torsion is a necessity rather than a possibility. (orig.)

  9. Standing torsional waves in a fully saturated, porous, circular cylinder

    CERN Document Server

    Solorza, S; 10.1111/j.1365-246X.2004.02198.x

    2004-01-01

    For dynamic measurement of the elastic moduli of a porous material saturated with viscous fluid using the resonance-bar technique, one also observes attenuation. In this article we have carried out the solution of the boundary-value problem associated with standing torsional oscillations of a finite, poroelastic, circular cylinder cast in the framework of volume-averaged theory of poroelasticity. Analysing this solution by eigenvalue perturbation approach we are able to develop expressions for torsional resonance and temporal attenuation frequencies in which the dependence upon the material properties are transparent. It shows how the attenuation is controlled by the permeability and the fluid properties, and how the resonance frequency drops over its value for the dry solid-frame due to the drag effect of fluid mass. Based upon this work we have a firm basis to determine solid-frame shear modulus, permeability, and tortuosity factor from torsional oscillation experiments.

  10. Fault diagnosis of planetary gearboxes via torsional vibration signal analysis

    Science.gov (United States)

    Feng, Zhipeng; Zuo, Ming J.

    2013-04-01

    Torsional vibration signals are theoretically free from the amplitude modulation effect caused by time variant vibration transfer paths due to the rotation of planet carrier and sun gear, and therefore their spectral structure are simpler than transverse vibration signals. Thus, it is potentially easy and effective to diagnose planetary gearbox faults via torsional vibration signal analysis. We give explicit equations to model torsional vibration signals, considering both distributed gear faults (like manufacturing or assembly errors) and local gear faults (like pitting, crack or breakage of one tooth), and derive the characteristics of both the traditional Fourier spectrum and the proposed demodulated spectra of amplitude envelope and instantaneous frequency. These derivations are not only effective to diagnose single gear fault of planetary gearboxes, but can also be generalized to detect and locate multiple gear faults. We validate experimentally the signal models, as well as the Fourier spectral analysis and demodulation analysis methods.

  11. 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

  12. Seismic performance of square RC bridge columns under combined loading including torsion with low shear.

    Science.gov (United States)

    2009-12-01

    During earthquake excitations, reinforced concrete bridge columns can be subjected to a combination of axial load, shear force, : flexural moments, and torsional moments. The torsional moment can be much more significant in columns of bridges that ar...

  13. Deep learning methods for protein torsion angle prediction.

    Science.gov (United States)

    Li, Haiou; Hou, Jie; Adhikari, Badri; Lyu, Qiang; Cheng, Jianlin

    2017-09-18

    Deep learning is one of the most powerful machine learning methods that has achieved the state-of-the-art performance in many domains. Since deep learning was introduced to the field of bioinformatics in 2012, it has achieved success in a number of areas such as protein residue-residue contact prediction, secondary structure prediction, and fold recognition. In this work, we developed deep learning methods to improve the prediction of torsion (dihedral) angles of proteins. We design four different deep learning architectures to predict protein torsion angles. The architectures including deep neural network (DNN) and deep restricted Boltzmann machine (DRBN), deep recurrent neural network (DRNN) and deep recurrent restricted Boltzmann machine (DReRBM) since the protein torsion angle prediction is a sequence related problem. In addition to existing protein features, two new features (predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments) are used as input to each of the four deep learning architectures to predict phi and psi angles of protein backbone. The mean absolute error (MAE) of phi and psi angles predicted by DRNN, DReRBM, DRBM and DNN is about 20-21° and 29-30° on an independent dataset. The MAE of phi angle is comparable to the existing methods, but the MAE of psi angle is 29°, 2° lower than the existing methods. On the latest CASP12 targets, our methods also achieved the performance better than or comparable to a state-of-the art method. Our experiment demonstrates that deep learning is a valuable method for predicting protein torsion angles. The deep recurrent network architecture performs slightly better than deep feed-forward architecture, and the predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments are useful features for improving prediction accuracy.

  14. Primary decomposition of torsion R[X]-modules

    Directory of Open Access Journals (Sweden)

    William A. Adkins

    1994-01-01

    Full Text Available This paper is concerned with studying hereditary properties of primary decompositions of torsion R[X]-modules M which are torsion free as R-modules. Specifically, if an R[X]-submodule of M is pure as an R-submodule, then the primary decomposition of M determines a primary decomposition of the submodule. This is a generalization of the classical fact from linear algebra that a diagonalizable linear transformation on a vector space restricts to a diagonalizable linear transformation of any invariant subspace. Additionally, primary decompositions are considered under direct sums and tensor product.

  15. A black hole with torsion in 5D Lovelock gravity

    Science.gov (United States)

    Cvetković, B.; Simić, D.

    2018-03-01

    We analyze static spherically symmetric solutions of five dimensional (5D) Lovelock gravity in the first order formulation. In the Riemannian sector, when torsion vanishes, the Boulware–Deser black hole represents a unique static spherically symmetric black hole solution for the generic choice of the Lagrangian parameters. We show that a special choice of the Lagrangian parameters, different from the Lovelock Chern–Simons gravity, leads to the existence of a static black hole solution with torsion, the metric of which is asymptotically anti-de Sitter (AdS). We calculate the conserved charges and thermodynamical quantities of this black hole solution.

  16. Massless fermions and Kaluza--Klein theory with torsion

    International Nuclear Information System (INIS)

    Wu, Y.; Zee, A.

    1984-01-01

    A pure Kaluza--Klein theory contains no massless fermion in four-dimensional theory. We investigate the effect of introducing torsion on the internal manifold and find that there are massless fermions. The hope is that given an isometry group the representation to which these fermions belong is fixed, in contrast to the situation in Yang--Mills theory. We show that this is indeed the case, but the representations do not appear to be the ones favored by current theoretical prejudice. The cases with parallelizable torsions on a group manifold as the internal manifold are analyzed in detail

  17. Spontaneous compactification and Ricci-flat manifolds with torsion

    International Nuclear Information System (INIS)

    McInnes, B.

    1985-06-01

    The Freund-Rubin mechanism is based on the equation Rsub(ik)=lambdagsub(ik) (where lambda>0), which, via Myers' Theorem, implies ''spontaneous'' compactification. The difficulties connected with the cosmological constant in this approach can be resolved if torsion is introduced and lambda set equal to zero, but then compactification ''by hand'' is necessary, since the equation Rsub(ik)=0 can be satisfied both on compact and on non-compact manifolds. In this paper we discuss the global geometry of Ricci-flat manifolds with torsion, and suggest ways of restoring the ''spontaneity'' of the compactification. (author)

  18. [Torsion of the vermiform appendix associated with intussusception].

    Science.gov (United States)

    Baeza-Herrera, Carlos; García-Cabello, Luis Manuel; León-Cruz, Alberto; Martínez-Rivera, María de Lourdes

    2006-01-01

    Vermiform appendix torsion is a rare condition, with only 25 cases recorded in the international literature. Our patient is the first case associated with intussusception. A 2-month-old female infant suddenly developed severe abdominal pain due to ileoceal intussusception. During surgical exploration, a tight intussusception was reduced. Three days later, a new laparotomy was required and we found torsion and perforation of the vermiform appendix. The patient underwent appendectomy, but there was dehiscence of the appendiceal stump and cecal perforation requiring a new surgical exploration. The patient had an uneventful recovery.

  19. Temporal discrimination threshold: VBM evidence for an endophenotype in adult onset primary torsion dystonia.

    OpenAIRE

    REILLY, RICHARD; WHELAN, ROBERT

    2009-01-01

    PUBLISHED Familial adult-onset primary torsion dystonia is an autosomal dominant disorder with markedly reduced penetrance. Most adult-onset primary torsion dystonia patients are sporadic cases. Disordered sensory processing is found in adult-onset primary torsion dystonia patients; if also present in their unaffected relatives this abnormality may indicate non-manifesting gene carriage. Temporal discrimination thresholds (TDTs) are abnormal in adult-onset primary torsion dystonia, but the...

  20. Ultrasonographic diagnosis of torsion of testicular appendages; Diagnostico por ecografia de la torsion de los apendices testiculares

    Energy Technology Data Exchange (ETDEWEB)

    Esparza, J.; Gonzalez, A.; Cordero, J. L. [Hospital Virgen del Camino. Pamplona (Spain)

    2000-07-01

    To determine the efficacy of ultrasound in boys presenting torsion of a testicular appendage. A series of 30 boys with acute scrotal pain due to torsion of a testicular appendage was studied. Nine patients underwent surgery. The clinical findings and course in the remaining 21 suggested the presence of this abnormality. All of them underwent conventional and color Doppler ultrasound using a 7.5 MHz transducer. In 15 boys, ultrasound images depicted the affected appendage as a mass between the epididymal head and the testicle. In 13 cases, only signs of a inflammatory reaction, with enlargement of the epididymal head and tunicas presenting hyperflow and hydrocele, mimicking acute epididymities. In two cases, the images were normal. There is no definitive, distinguishing ultrasound image corresponding to testicular appendage torsion. Therefore, this diagnostic technique should be accompanied by clinical assessment. (Author) 14 refs.

  1. APPLICATION OF THE METHOD OF DIMENSIONALITY REDUCTION TO CONTACTS UNDER NORMAL AND TORSIONAL LOADING

    Directory of Open Access Journals (Sweden)

    Emanuel Willert

    2015-08-01

    In view of all this, the torsional contact problems have been disregarded until now, although it is known that torsion is a major reason of wear and possible failure of system components. Therefore, in the present paper, we extend the MDR to contacts of axisymmetric profiles under superimposed normal and torsional loading.

  2. Synthesis, structural characterization and study of blue shift in optical properties of zinc oxide nano particles prepared by chemical route method

    Science.gov (United States)

    Taunk, P. B.; Das, R.; Bisen, D. P.; Tamrakar, Raunak Kumar

    2015-12-01

    We report the synthesis and optical properties of ZnO nano particle using TEA (Tri Ethanol Amine) and without TEA by chemical route method. By decreasing the concentration of TEA, reaction rate is decreases and inter planner spacing d is increases, band gap is increased from 4.1 to 4.8 eV. In case of without TEA band gap is obtained 3.4 eV. Morphology, growth and the nature of crystalline of the powder samples were performed by X- ray Diffraction (XRD); UV spectrophotometer, scanning electron microscope (SEM) and Photoluminescence (PL). Luminescence properties are discussed by probing the photoluminescence properties of ZnO nano particles with TEA at different molar concentrations.

  3. Determination of the Glass-Transition Temperature of GRPS and CFRPS Using a Torsion Pendulum in Regimes of Freely Damped Vibrations and Quasi-Stastic Torsion of Specimens

    Science.gov (United States)

    Startsev, V. O.; Lebedev, M. P.; Molokov, M. V.

    2018-03-01

    A method to measure the glass-transition temperature of polymers and polymeric matrices of composite materials with the help of an inverse torsion pendulum over a wide range of temperatures is considered combining the method of free torsional vibrations and a quasi-static torsion of specimens. The glass-transition temperature Tg of a KMKS-1-80. T10 fiberglass, on increasing the frequency of freely damped torsional vibrations from 0.7 to 9.6 Hz, was found to increase from 132 to 140°C. The value of Tg of these specimens, determined by measuring the work of their torsion through a small fixed angle was 128.6°C ± 0.8°C. It is shown that the use of a torsion pendulum allows one to determine the glass-transition temperature of polymeric or polymer matrices of PCMs in dynamic and quasi-static deformation regimes of specimens.

  4. From Porous to Dense Nanostructured β-Ti alloys through High-Pressure Torsion.

    Science.gov (United States)

    Afonso, Conrado R M; Amigó, Angelica; Stolyarov, Vladimir; Gunderov, Dmitri; Amigó, Vicente

    2017-10-19

    β-Ti alloys have low elastic modulus, good specific strength and high corrosion resistance for biomaterial applications. Noble elements, such as Nb, Ta and Mo, are used to obtain β-Ti due to their chemical biocompatibility. However, due to their refractory nature, β-Ti requires specific processing routes. Powder metallurgy (P/M) allows for the development of new β-Ti alloys with decreasing costs, but dealing with high-elemental-content alloys can lead to a lack of diffusion and grain growth. One method to refine the structure and improve mechanical properties is a severe plastic deformation technique through high-pressure torsion (HPT). The aim of this work was to evaluate the conversion of P/M porous β-Ti-35Nb-10Ta-xFe alloys to dense nanostructures through high-pressure torsion in one deformation step and the influence of the structure variation on the properties and microstructure. TEM analysis and ASTAR crystallographic mapping was utilized to characterize the nanostructures, and the properties of P/M β Ti-35Nb-10Ta-xFe alloys processed by HPT were compared. The initial microstructure consisted mainly by the β-Ti phase with some α-Ti phase at the grain boundaries. The HPT process refined the microstructure from 50 µm (P/M) down to nanostructured grains of approximately 50 nm.

  5. Torsion Pendulum Experiment at the International Physics Olympiad

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 6. Torsion Pendulum Experiment at the International Physics Olympiad. Sandeep Bala. Classroom Volume 5 Issue 6 June 2000 pp 76-85. Fulltext. Click here to view fulltext PDF. Permanent link:

  6. Axial Torsion of Gangrenous Meckel's Diverticulum Causing Small ...

    African Journals Online (AJOL)

    dividing the band. Resection and anastomosis of the small bowel including the MD was performed. We hereby report a rare and unusual complication of a MD. Although treatment outcome is generally good, pre-operative diagnosis is often difficult. Key words: Axial torsion, Meckel's diverticulum, small bowel obstruction.

  7. Effect of irregularity on torsional surface waves in an initially ...

    Indian Academy of Sciences (India)

    The Earth is considered as an initially stressed body with a layered ... Keywords. Torsional wave; anisotropy; initial stress; irregularity; non-homogeneity. J. Earth Syst. Sci., DOI 10.1007/s12040-016-0689-7, 125, No. 4, June 2016, pp. 885–895 ...... wave dispersion in a finitely prestrained hollow sandwich circular cylinder; J.

  8. Torsional vibrations of infinite composite poroelastic cylinders | Shah ...

    African Journals Online (AJOL)

    The displacements of second and third torsional modes are determined and presented graphically for the ratio of radius of composite poroelastic solid cylinder to the radius of the inner solid cylinder. Results of previous works are shown as special case of the present analysis. By ignoring liquid effects, the results of purely ...

  9. Torsional vibration of thin-walled elastic beams with doubly ...

    African Journals Online (AJOL)

    In this paper, the problem of analyzing the torsional vibration of thin-walled elastic beams, with open cross-sections that are doubly symmetric and traversed by moving concentrated masses at constant speeds is addressed. The mathematical model adopted accounts for both the gravitational and inertial effects of the ...

  10. The ground state torsion rotation spectrum of CH2DOH

    Science.gov (United States)

    Pearson, John C.; Yu, Shanshan; Drouin, Brian J.

    2012-10-01

    The ground state torsion rotation spectrum of CH2DOH has been completely characterized through J = 30 and Ka = 10, 9, 9 in the three torsional sub-states of the ground state; e0, e1, and o1, respectively. Additional a-type assignments are presented to Ka = 11 in each of the torsional sub-states. The data has been analyzed with an empirical power series model as well as an empirical internal axis model. Over 8000 transitions have been assigned and fit with near experimental accuracy over the range of 4-1628 GHz. The characterization of the spectrum allows for a complete set of ground state term values enabling a better understanding of the infrared spectrum. Comparison of the torsional contributions of the Hamiltonian with normal methanol provides great insight into the nature of the asymmetric-top asymmetric-frame internal rotation problem. The comparison with normal methanol also provides a relatively straightforward transformation from the well understood C3V internal rotation problem to the completely asymmetric internal rotation problem. The data and analysis provide some practical wisdom on the impacts of breaking the symmetry and the choice of models for addressing the nearly three fold completely asymmetric internal rotation problem.

  11. Influence of rigid boundary on the propagation of torsional surface ...

    Indian Academy of Sciences (India)

    Influence of rigid boundary on the propagation of torsional surface wave in an inhomogeneous layer. Shishir Gupta. ∗. , Rehena Sultana and Santimoy Kundu. Department of Applied Mathematics, Indian School of Mines, Dhanbad 826 004, India. ∗. Corresponding author. e-mail: shishir ism@yahoo.com. The present work ...

  12. Influence of rigid boundary on the propagation of torsional surface ...

    Indian Academy of Sciences (India)

    ered media are very important to seismologists in understanding the cause and ... layered media. Bhattacharya (1975) investigated the torsional wave propagation in a two layered circular cylinder with imperfect bond. Vardoulakis. (1984) has shown that ...... Naturalist Society in Zurich 66 181–195. Ozturk A and Akbarov S D ...

  13. Penile Torsion: an Overlooked Anomaly with Distal Hypospadias ...

    African Journals Online (AJOL)

    The angle of penile rotation was measured on an end-on digital photograph of the penis, using MillenMed DICOM viewer program for image analysis. Two techniques were used to correct penile torsion. In group A (9 patients), we used the technique of degloving and repositioning the penile skin. In group B (10 patients), we ...

  14. Portal venous thrombosis developing after torsion of a wandering ...

    African Journals Online (AJOL)

    The etiological factors are the congenital absence of the ligaments that hold the spleen in its normal anatomic position, or the relaxation of these ligaments resulting from conditions like trauma and abdominal surgery. We aimed to present a rare case with torsion of wandering spleen that consequently developed thrombosis ...

  15. Penile torsion correction by diagonal corporal plication sutures

    Directory of Open Access Journals (Sweden)

    Brent W. Snow

    2009-02-01

    Full Text Available Penile torsion is commonly encountered. It can be caused by skin and dartos adherence or Buck’s fascia attachments. The authors suggest a new surgical approach to solve both problems. If Buck’s fascia involvement is demonstrated by artificial erection then a new diagonal corporal plication suture is described to effectively solve this problem.

  16. In vitro transcription of a torsionally constrained template

    DEFF Research Database (Denmark)

    Bentin, Thomas; Nielsen, Peter E

    2002-01-01

    of torsionally constrained DNA by free RNAP. We asked whether or not a newly synthesized RNA chain would limit transcription elongation. For this purpose we developed a method to immobilize covalently closed circular DNA to streptavidin-coated beads via a peptide nucleic acid (PNA)-biotin conjugate in principle...

  17. Ocular torsion before and after 1 hour centrifugation

    NARCIS (Netherlands)

    Groen, E.; Graaf, B. de; Bles, W.; Bos, J.E.

    1996-01-01

    To assess a possible otolith contribution to effects observed following prolonged expo-sure to hyper gravity, we used video-oculography to measure ocular torsion during static and dynamic conditions of lateral body tilt (roll) before and after one hour of centrifugation with a Gx-load of 3G. Static

  18. Ocular torsion before and after 1 hour centrifugation

    NARCIS (Netherlands)

    Groen, Eric; De Graaf, Bernd; Bles, Willem; Bos, Jelte E.

    1996-01-01

    To assess a possible otolith contribution to effects observed following prolonged exposure to hypergravity, we used video oculography to measure ocular torsion during static and dynamic conditions of lateral body tilt (roll) before and after t h of centrifugation with a G(x)-load of 3 G. Static tilt

  19. Investigation of torsional vibrations in thick walled hollow poroelastic ...

    Indian Academy of Sciences (India)

    Abstract. This paper deals with the study of torsional vibrations of thick walled hollow poroelastic cylinder using Biot's extension theory. Considering the boundaries to be stress free, the frequency equation is obtained in the presence of dissipation which is transcendental and complex valued in nature. In the special case of ...

  20. Timoshenko-Wagner-Kappus Torsion Bending Theory and Wind ...

    Indian Academy of Sciences (India)

    Timoshenko-Wagner-Kappus Torsion Bending. Theory and Wind Tunnel Balance Design. S P Govinda Raju and K R Y Simha. S P Govinda Raju is a. Professor at the. Aero- space Engineering. Department, Indian. Institute of Science,. Bangalore. His interests are fluid mechanics, aircraft design, testing and analysis.