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Sample records for 1h-31p heteronuclear correlation

  1. Multiple quantum correlated spectroscopy revamped by asymmetric z-gradient echo detection signal intensity as a function of the read pulse flip angle as verified by heteronuclear 1H/31P experiments.

    PubMed

    Jiang, Bin; Liu, Huili; Liu, Maili; Ye, Chaohui; Mao, Xi-an

    2007-02-07

    Heteronuclear multiple quantum (n=+/-0 and n=+/-2) correlated spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) experiments were performed on the spins 31P and 1H in a H3PO4 solution in order to determine the optimum flip angle for the read pulse. It has been shown that for the negative quantum signals, the maximum signals appear at beta=0, and for the positive quantum signals, the maximum signals appear at beta=pi. The CRAZED signals were compared to the single quantum signals in two-pulse two-gradient experiments. It is found that the CRAZED signals can also be distinguished into gradient echoes and spin echoes. The gradient-echo-type CRAZED signal requires beta=0 and the spin-echo-type CRAZED signal requires beta=pi for maximum echo intensities, in the same way as in single quantum experiments.

  2. Probing phosphorylation by non-mammalian isoprenoid biosynthetic enzymes using (1)H-(31)P-(31)P correlation NMR spectroscopy.

    PubMed

    Majumdar, Ananya; Shah, Meha H; Bitok, J Kipchirchir; Hassis-LeBeau, Maria E; Freel Meyers, Caren L

    2009-09-01

    The biogenesis of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) is accomplished by the methylerythritol phosphate (MEP) pathway in plants, bacteria and parasites, making it a potential target for the development of anti-infective agents and herbicides. The biosynthetic enzymes comprising this pathway catalyze intriguing chemical transformations on diphosphate scaffolds, offering an opportunity to generate novel analogs in this synthetically challenging compound class. Such a biosynthetic approach to generating new diphosphate analogs may involve transformation through discrete diphosphate species, presenting unique challenges in structure determination and characterization of unnatural enzyme-generated diphosphate products produced in tandem. We have developed (1)H-(31)P-(31)P correlation NMR spectroscopy techniques for the direct characterization of crude MEP pathway enzyme products at low concentrations (200 microM to 5 mM) on a room temperature (non-cryogenic) NMR probe. Coupling the 100% natural abundance of the (31)P nucleus with the high intrinsic sensitivity of proton NMR, (1)H-(31)P-(31)P correlation spectroscopy is particularly useful for characterization of unnatural diphosphate enzyme products in the MEP pathway. As proof of principle, we demonstrate the rapid characterization of natural enzyme products of the enzymes IspD, E and F in tandem enzyme incubations. In addition, we have characterized several unnatural enzyme products using this technique, including new products of cytidyltransferase IspD bearing erythritol, glycerol and ribose components. The results of this study indicate that IspD may be a useful biocatalyst and highlight (1)H-(31)P-(31)P correlation spectroscopy as a valuable tool for the characterization of other unnatural products in non-mammalian isoprenoid biosynthesis.

  3. On-flow pulsed field gradient heteronuclear correlation spectrometry in off-line LC-SPE-NMR analysis of chemicals related to the chemical weapons convention.

    PubMed

    Koskela, Harri; Ervasti, Mia; Björk, Heikki; Vanninen, Paula

    2009-02-01

    Hyphenation of liquid chromatography with nuclear magnetic resonance spectroscopy (LC-NMR) is a useful technique in the analysis of complex samples. However, application of on-flow 1H NMR spectrometry during the LC-NMR analysis usually suffers from high intensity of eluent resonances. The poor dynamic range can be improved either with use of deuterated eluents or with various signal suppression schemes. Deuterated eluents are expensive, and peak-selective signal suppression schemes are often unsatisfactory when detection of chemicals at low concentration is needed. If the analytes have a common heteronucleus, on-flow pulsed field gradient heteronuclear correlation spectrometry can offer several benefits. The analytes can be monitored selectively, while the intense nondeuterated eluent and impurity background can be effectively eliminated. In our study, on-flow one-dimensional (1D) 1H-31P heteronuclear single quantum coherence (HSQC) spectrometry was utilized in the analysis of characteristic organophosphorus degradation products of nerve agents sarin and soman during chromatographic separation. These chemicals were not detectable by UV, so their retention times were monitored using on-flow 1D 1H-31P HSQC. This enabled application of LC-NMR combined with solid-phase extraction (LC-SPE-NMR) in analysis of these organophosphorus chemicals in an alkaline decontamination solution. The analytes were extracted from the SPE cartridges with deuterated eluent, and the off-line NMR analysis was performed using a mass-sensitive microcoil probe head. The used on-flow 1D 1H-31P HSQC approach offered a high dynamic range and good detection limit (ca. 10 microg/55 nmol) with a high sampling frequency (1 point per 2 s) in the acquired pseudo-two-dimensional spectrum. No significant impurity background was present in the off-line NMR samples, and identification of the extracted analytes was straightforward.

  4. Dynamic structures of intact chicken erythrocyte chromatins as studied by 1H-31P cross-polarization NMR.

    PubMed Central

    Akutsu, H; Nishimoto, S; Kyogoku, Y

    1994-01-01

    The dynamic properties of DNA in intact chicken erythrocyte cells, nuclei, nondigested chromatins, digested soluble chromatins, H1, H5-depleted soluble chromatins and nucleosome cores were investigated by means of single-pulse and 1H-31P cross-polarization NMR. The temperature dependence of the phosphorus chemical shift anisotropy was identical for the former three in the presence of 3 mM MgCl2, suggesting that the local higher order structure is identical for these chromatins. The intrinsic phosphorus chemical shift anisotropy of the nucleosome cores was -159 ppm. The chemical shift anisotropy of DNA in the chromatins can be further averaged by the motion of the linker DNA. The spin-lattice relaxation time in the rotating frame of the proton spins (T1p) of the nondigested chromatins was measured at various locking fields. The result was analyzed on the assumption of the isotropic motion to get a rough value of the correlation time of the motion efficient for the relaxation, which was eventually ascribed to the segmental motion of the linker DNA with restricted amplitude. The 30 nm filament structure induced by NaCl was shown to be dynamically different from that induced by MgCl2. Side-by-side compaction of 30-nm filaments was suggested to be induced in the MgCl2 concentration range higher than 0.3 mM. Biological significance of the dynamic structure was discussed in connection with the results obtained. PMID:7948693

  5. Evaluation of a New 1H/31P Dual-Tuned Birdcage Coil for 31P Spectroscopy

    PubMed Central

    Potter, WM; Wang, L; McCully, KK; Zhao, Q

    2013-01-01

    We introduce a new dual-tuned Hydrogen/Phosphorus (1H/31P) birdcage coil, referred to as split birdcage coil, and evaluate its performance using both simulations and magnetic resonance (MR) experiments on a 3 T MR scanner. The proposed coil simplifies the practical matters of tuning and matching, which makes the coil easily reproducible. Simulations were run with the Finite Difference in Time Domain (FDTD) method to evaluate the sensitivity and homogeneity of the magnetic field generated by the proposed 1H coils. Following simulations, MR experiments were conducted using both a phantom and human thigh to compare the proposed design with a currently available commercial dual-tuned flexible surface coil, referred to as flex surface coil, for signal to noise ratio (SNR) as well as homogeneity for the 31P coil. At regions deep within the human thigh, the split birdcage coil was able to acquire spectroscopic signal with a higher average SNR than the flex surface coil. For all regions except those close to the flex surface coil, the split birdcage coil matched or exceeded the performance of the flex surface coil. PMID:24039555

  6. In vivo absolute quantification for mouse muscle metabolites using an inductively coupled synthetic signal injection method and newly developed 1H/31P dual tuned probe

    PubMed Central

    Lee, Donghoon; Marro, Kenneth; Mathis, Mark; Shankland, Eric; Hayes, Cecil

    2013-01-01

    Purpose To obtain robust estimates of 31P metabolite content in mouse skeletal muscles using our recently developed MR absolute quantification method and a custom-built 1H/31P dual tuned radiofrequency (RF) coil optimized for mouse leg. Materials and Methods We designed and fabricated a probe consisting of two dual tuned 1H/31P solenoid coils: one leg was inserted to each solenoid. The mouse leg volume coil was incorporated with injector coils for MR absolute quantification. The absolute quantification method uses a synthetic reference signal injection approach and solves several challenges in MR absolute quantification including changes of coil loading and receiver gains. Results The 1H/31P dual tuned probe was composed of two separate solenoid coils, one for each leg, to increase coil filling factors and signal-to-noise ratio. Each solenoid was equipped with a second coil to allow injection of reference signals. 31P metabolite concentrations determined for normal mice were well within the expected range reported in the literature. Conclusion We developed an RF probe and an absolute quantification approach adapted for mouse skeletal muscle. PMID:24464912

  7. The Heteronuclear Single-Quantum Correlation (HSQC) Experiment: Vectors versus Product Operators

    ERIC Educational Resources Information Center

    de la Vega-Herna´ndez, Karen; Antuch, Manuel

    2015-01-01

    A vectorial representation of the full sequence of events occurring during the 2D-NMR heteronuclear single-quantum correlation (HSQC) experiment is presented. The proposed vectorial representation conveys an understanding of the magnetization evolution during the HSQC pulse sequence for those who have little or no quantum mechanical background.…

  8. 1H Photo-CIDNP Enhancements in Heteronuclear Correlation NMR Spectroscopy

    PubMed Central

    Sekhar, Ashok; Cavagnero, Silvia

    2009-01-01

    Photochemically induced dynamic nuclear polarization (photo-CIDNP) is usually employed as a probe of solvent exposure, in biomolecular NMR. The potential of the photo-CIDNP effect for sensitivity enhancement, however, remains poorly explored. Here, we introduce 1H-photo-CIDNP in heteronuclear correlation spectroscopy at low laser irradiation power (1 W), and compare the sensitivity of various 1H-Photo-CIDNP-enhanced- (HPE) 1H◻15N heteronuclear correlation pulse sequences, including HSQC, HMQC, and SOFAST-HMQC, in terms of their ability to detect the Trp indole Hε1 resonance. Both Trp and the Trp-containing protein apoHmpH were analyzed using flavin mononucleotide as photosensitizer in aqueous solutions either containing or lacking urea. We find that 1H◻15N photo-CIDNP-SOFAST-HMQC, denoted here as HPE-SOFAST-HMQC, yields a two-fold higher signal-to-noise per unit time than the parent SOFAST-HMQC for the solvent-exposed Trp of urea-unfolded apoHmpH. Thus, HPE-SOFAST-HMQC is the most sensitive heteronuclear correlation pulse sequence for the detection of solvent-exposed Trp. PMID:19462951

  9. Sequential acquisition of multi-dimensional heteronuclear chemical shift correlation spectra with 1H detection

    NASA Astrophysics Data System (ADS)

    Bellstedt, Peter; Ihle, Yvonne; Wiedemann, Christoph; Kirschstein, Anika; Herbst, Christian; Görlach, Matthias; Ramachandran, Ramadurai

    2014-03-01

    RF pulse schemes for the simultaneous acquisition of heteronuclear multi-dimensional chemical shift correlation spectra, such as {HA(CA)NH & HA(CACO)NH}, {HA(CA)NH & H(N)CAHA} and {H(N)CAHA & H(CC)NH}, that are commonly employed in the study of moderately-sized protein molecules, have been implemented using dual sequential 1H acquisitions in the direct dimension. Such an approach is not only beneficial in terms of the reduction of experimental time as compared to data collection via two separate experiments but also facilitates the unambiguous sequential linking of the backbone amino acid residues. The potential of sequential 1H data acquisition procedure in the study of RNA is also demonstrated here.

  10. Sequential acquisition of multi-dimensional heteronuclear chemical shift correlation spectra with 1H detection

    PubMed Central

    Bellstedt, Peter; Ihle, Yvonne; Wiedemann, Christoph; Kirschstein, Anika; Herbst, Christian; Görlach, Matthias; Ramachandran, Ramadurai

    2014-01-01

    RF pulse schemes for the simultaneous acquisition of heteronuclear multi-dimensional chemical shift correlation spectra, such as {HA(CA)NH & HA(CACO)NH}, {HA(CA)NH & H(N)CAHA} and {H(N)CAHA & H(CC)NH}, that are commonly employed in the study of moderately-sized protein molecules, have been implemented using dual sequential 1H acquisitions in the direct dimension. Such an approach is not only beneficial in terms of the reduction of experimental time as compared to data collection via two separate experiments but also facilitates the unambiguous sequential linking of the backbone amino acid residues. The potential of sequential 1H data acquisition procedure in the study of RNA is also demonstrated here. PMID:24671105

  11. Proton-detected heteronuclear single quantum correlation NMR spectroscopy in rigid solids with ultra-fast MAS

    PubMed Central

    Holland, Gregory P.; Cherry, Brian R.; Jenkins, Janelle E.; Yarger, Jeffery L.

    2009-01-01

    In this article, we show the potential for utilizing proton-detected heteronuclear single quantum correlation (HSQC) NMR in rigid solids under ultra-fast magic angle spinning (MAS) conditions. The indirect detection of carbon-13 from coupled neighboring hydrogen nuclei provides a sensitivity enhancement of 3 - 4 fold in crystalline amino acids over direct-detected versions. Furthermore, the sensitivity enhancement is shown to be significantly larger for disordered solids that display inhomogeneously broadened carbon-13 spectra. Latrodectus hesperus (Black Widow) dragline silk is given as an example where the sample is mass-limited and the sensitivity enhancement for the proton-detected experiment is 8 - 13 fold. The ultra-fast MAS proton-detected HSQC solid-state NMR technique has the added advantage that no proton homonuclear decoupling is applied during the experiment. Further, well-resolved, indirectly observed carbon-13 spectra can be obtained in some cases without heteronuclear proton decoupling. PMID:19857977

  12. Proton-detected heteronuclear single quantum correlation NMR spectroscopy in rigid solids with ultra-fast MAS.

    PubMed

    Holland, Gregory P; Cherry, Brian R; Jenkins, Janelle E; Yarger, Jeffery L

    2010-01-01

    In this article, we show the potential for utilizing proton-detected heteronuclear single quantum correlation (HSQC) NMR in rigid solids under ultra-fast magic angle spinning (MAS) conditions. The indirect detection of carbon-13 from coupled neighboring hydrogen nuclei provides a sensitivity enhancement of 3- to 4-fold in crystalline amino acids over direct-detected versions. Furthermore, the sensitivity enhancement is shown to be significantly larger for disordered solids that display inhomogeneously broadened carbon-13 spectra. Latrodectus hesperus (Black Widow) dragline silk is given as an example where the sample is mass-limited and the sensitivity enhancement for the proton-detected experiment is 8- to 13-fold. The ultra-fast MAS proton-detected HSQC solid-state NMR technique has the added advantage that no proton homonuclear decoupling is applied during the experiment. Further, well-resolved, indirectly observed carbon-13 spectra can be obtained in some cases without heteronuclear proton decoupling.

  13. Determination of size and sign of hetero-nuclear coupling constants from 2D 19F-13C correlation spectra

    NASA Astrophysics Data System (ADS)

    Ampt, Kirsten A. M.; Aspers, Ruud L. E. G.; Dvortsak, Peter; van der Werf, Ramon M.; Wijmenga, Sybren S.; Jaeger, Martin

    2012-02-01

    Fluorinated organic compounds have become increasingly important within the polymer and the pharmaceutical industry as well as for clinical applications. For the structural elucidation of such compounds, NMR experiments with fluorine detection are of great value due to the favorable NMR properties of the fluorine nucleus. For the investigation of three fluorinated compounds, triple resonance 2D HSQC and HMBC experiments were adopted to fluorine detection with carbon and/or proton decoupling to yield F-C, F-C{H}, F-C{Cacq} and F-C{H,Cacq} variants. Analysis of E.COSY type cross-peak patterns in the F-C correlation spectra led, apart from the chemical shift assignments, to determination of size and signs of the JCH, JCF, and JHF coupling constants. In addition, the fully coupled F-C HMQC spectrum of steroid 1 was interpreted in terms of E.COSY type patterns. This example shows how coupling constants due to different nuclei can be determined together with their relative signs from a single spectrum. The analysis of cross-peak patterns, as presented here, not only provides relatively straightforward routes to the determination of size and sign of hetero-nuclear J-couplings in fluorinated compounds, it also provides new and easy ways for the determination of residual dipolar couplings and thus for structure elucidation. The examples and results presented in this study may contribute to a better interpretation and understanding of various F-C correlation experiments and thereby stimulate their utilization.

  14. Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100kHz MAS

    SciTech Connect

    Nishiyama, Y.; Kobayashi, T.; Malon, M.; Singappuli-Arachchige, D.; Slowing, I. I.; Pruski, M.

    2015-02-16

    Two-dimensional 1H{13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimension without resorting to 1H–1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. As a result, the HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.

  15. Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100kHz MAS

    DOE PAGES

    Nishiyama, Y.; Kobayashi, T.; Malon, M.; ...

    2015-02-16

    Two-dimensional 1H{13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimensionmore » without resorting to 1H–1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. As a result, the HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.« less

  16. The covariance of the differences between experimental and theoretical chemical shifts as an aid for assigning two-dimensional heteronuclear correlation solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Czernek, Jiří; Brus, Jiří

    2014-07-01

    A robust method for the assignment of two-dimensional heteronuclear correlations in the solid-state NMR spectra is described. It statistically evaluates the differences between measured and theoretical (obtained from first-principles calculations of the NMR chemical shielding property of periodic materials) chemical shifts. The values of the covariance of these differences, and of the standard deviations of the respective linear correlations, are elucidative for the spectral assignment process. The efficacy of the method is demonstrated for three crystalline systems: L-tyrosine hydrochloride, L-tyrosine ansolvate, and the polymorphic form I of o-acetylsalicylic acid.

  17. SPAM-MQ-HETCOR: an improved method for heteronuclear correlation spectroscopy between quadrupolar and spin-1/2 nuclei in solid-state NMR.

    PubMed

    Wiench, Jerzy W; Tricot, Gregory; Delevoye, Laurent; Trebosc, Julien; Frye, James; Montagne, Lionel; Amoureux, Jean-Paul; Pruski, Marek

    2006-01-07

    The recently introduced concept of soft pulse added mixing (SPAM) is used in two-dimensional heteronuclear correlation (HETCOR) NMR experiments between half-integer quadrupolar and spin-1/2 nuclei. The experiments employ multiple quantum magic angle spinning (MQMAS) to remove the second order quadrupolar broadening and cross polarization (CP) or refocused INEPT for magnetization transfer. By using previously unexploited coherence pathways, the efficiency of SPAM-MQ-HETCOR NMR is increased by a factor of almost two without additional optimization. The sensitivity gain is demonstrated on a test sample, AlPO(4)-14, using CP and INEPT to correlate (27)Al and (31)P nuclei. SPAM-3Q-HETCOR is then applied to generate (27)Al-(31)P spectra of the devitrified 41Na(2)O-20.5Al(2)O(3)-38.5P(2)O(5) glass and the silicoaluminophosphate ECR-40. Finally, the method allowed the acquisition of the first high resolution solid-state correlation spectra between (27)Al and (29)Si.

  18. Al coordination and water speciation in hydrous aluminosilicate glasses: direct evidence from high-resolution heteronuclear 1H-27Al correlation NMR.

    PubMed

    Xue, Xianyu; Kanzaki, Masami

    2007-02-01

    In order to shed light on the dissolution mechanisms of water in depolymerized aluminosilicate melts/glasses, a comprehensive one- (1D) and two-dimensional (2D) NMR study has been carried out on hydrous Ca- and Mg-aluminosilicate glasses of a haplobasaltic composition. The applied techniques include 1D 1H MAS NMR and 27Al-->1H cross-polarization (CP) MAS NMR, and 2D 1H NOESY and double-quantum (DQ) MAS NMR, 27Al triple-quantum (3Q) MAS NMR and 27Al-->1H heteronuclear correlation (HETCOR) and 3QMAS/HETCOR NMR. Ab initio calculations were also performed to place additional constraints on the 1H NMR characteristics of AlOH and Si(OH)Al groups. This study has revealed, for the first time, the presence of free OH (i.e. (Ca, Mg)OH), SiOH and AlOH species, in addition to molecular H2O, in hydrous glasses of a depolymerized aluminosilicate composition. The AlOH groups are mostly associated with four-coordinate Al, but some are associated with five- and six-coordinate Al.

  19. Photoassociative production of ultracold heteronuclear ytterbium molecules

    SciTech Connect

    Borkowski, Mateusz; Ciurylo, Roman; Yamazaki, Rekishu; Takahashi, Yoshiro; Hara, Hideaki; Taie, Shintaro; Sugawa, Seiji; Takasu, Yosuke; Enomoto, Katsunari

    2011-09-15

    We report observations of photoassociation (PA) spectra near the intercombination line in isotopic mixtures of ultracold ytterbium gases. Several heteronuclear bound states have been found for the excited {sup 170}Yb{sup 174}Yb and {sup 174}Yb{sup 176}Yb molecules. We develop a single-channel mass-scaled interaction model for the excited state molecule which well reproduces the measured bound state energies. This is an important step toward optical control of interactions in mixtures of ultracold ytterbium gases using heteronuclear optical Feshbach resonances. The model developed is applicable in collisions of other similar systems, such as cadmium and mercury.

  20. Heteronuclear Multidimensional Protein NMR in a Teaching Laboratory

    ERIC Educational Resources Information Center

    Wright, Nathan T.

    2016-01-01

    Heteronuclear multidimensional NMR techniques are commonly used to study protein structure, function, and dynamics, yet they are rarely taught at the undergraduate level. Here, we describe a senior undergraduate laboratory where students collect, process, and analyze heteronuclear multidimensional NMR experiments using an unstudied Ig domain (Ig2…

  1. Ultracold Collisions Involving Heteronuclear Alkali Metal Dimers

    SciTech Connect

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.; Honvault, Pascal; Launay, Jean-Michel

    2005-05-27

    We carry out the first quantum dynamics calculations on ultracold atom-diatom collisions in isotopic mixtures. The systems studied are spin-polarized {sup 7}Li+{sup 6}Li{sup 7}Li, {sup 7}Li+{sup 6}Li{sub 2}, {sup 6}Li+{sup 6}Li{sup 7}Li, and {sup 6}Li+{sup 7}Li{sub 2}. Reactive scattering can occur for the first two systems even when the molecules are in their ground rovibrational states, but is slower than vibrational relaxation in homonuclear systems. Implications for sympathetic cooling of heteronuclear molecules are discussed.

  2. Ultracold Heteronuclear Molecules in a 3D Optical Lattice

    SciTech Connect

    Ospelkaus, C.; Ospelkaus, S.; Humbert, L.; Ernst, P.; Sengstock, K.; Bongs, K.

    2006-09-22

    We report on the creation of ultracold heteronuclear molecules assembled from fermionic {sup 40}K and bosonic {sup 87}Rb atoms in a 3D optical lattice. Molecules are produced at a heteronuclear Feshbach resonance on both the attractive and the repulsive sides of the resonance. We precisely determine the binding energy of the heteronuclear molecules from rf spectroscopy across the Feshbach resonance. We characterize the lifetime of the molecular sample as a function of magnetic field and measure lifetimes between 20 and 120 ms. The efficiency of molecule creation via rf association is measured and is found to decrease as expected for more deeply bound molecules.

  3. Heteronuclear compounds of arsenic and antimony

    NASA Astrophysics Data System (ADS)

    Mauser, James E.

    1982-09-01

    Volatilization of secondary metals such as arsenic, antimony, and bismuth, during the smelting of copper ores, is important because of environmental and resource considerations. The Bureau of Mines, United States Department of the Interior, has been studying copper concentrate roasting in conjunction with the volatility of these minor constituents. Some unusual vaporization behavior initiated this supplemental paper which shows that when the mixed sulfides of arsenic and antimony are heated, the volatilization of arsenic is retarded and the volatilization of antimony increased. Mixed oxides of arsenic and antimony also exhibit exceptional volatilization behavior. These anomalous vaporization behaviors are attributed to the formation of heteronuclear compounds of arsenic and antimony, but the colligative properties of solutions may also be a factor.

  4. High-resolution heteronuclear multi-dimensional NMR spectroscopy in magnetic fields with unknown spatial variations.

    PubMed

    Zhang, Zhiyong; Huang, Yuqing; Smith, Pieter E S; Wang, Kaiyu; Cai, Shuhui; Chen, Zhong

    2014-05-01

    Heteronuclear NMR spectroscopy is an extremely powerful tool for determining the structures of organic molecules and is of particular significance in the structural analysis of proteins. In order to leverage the method's potential for structural investigations, obtaining high-resolution NMR spectra is essential and this is generally accomplished by using very homogeneous magnetic fields. However, there are several situations where magnetic field distortions and thus line broadening is unavoidable, for example, the samples under investigation may be inherently heterogeneous, and the magnet's homogeneity may be poor. This line broadening can hinder resonance assignment or even render it impossible. We put forth a new class of pulse sequences for obtaining high-resolution heteronuclear spectra in magnetic fields with unknown spatial variations based on distant dipolar field modulations. This strategy's capabilities are demonstrated with the acquisition of high-resolution 2D gHSQC and gHMBC spectra. These sequences' performances are evaluated on the basis of their sensitivities and acquisition efficiencies. Moreover, we show that by encoding and decoding NMR observables spatially, as is done in ultrafast NMR, an extra dimension containing J-coupling information can be obtained without increasing the time necessary to acquire a heteronuclear correlation spectrum. Since the new sequences relax magnetic field homogeneity constraints imposed upon high-resolution NMR, they may be applied in portable NMR sensors and studies of heterogeneous chemical and biological materials.

  5. Versatile 1H-31P-31P COSY 2D NMR Techniques for the Characterization of Polyphosphorylated Small Molecules

    PubMed Central

    Majumdar, Ananya; Sun, Yan; Shah, Meha; Freel Meyers, Caren L.

    2010-01-01

    Di- and triphosphorylated small molecules represent key intermediates in a wide range of biological and chemical processes. The importance of polyphosphorylated species in biology and medicine underscores the need to develop methods for the detection and characterization of this compound class. We have reported two-dimensional HPP-COSY spectroscopy techniques to identify diphosphate-containing metabolic intermediates at sub-millimolar concentrations in the methylerythritol phosphate (MEP) isoprenoid biosynthetic pathway.1 In this work, we explore the scope of HPP-COSY based techniques to characterize a diverse group of small organic molecules bearing di- and tri-phosphorylated moieties. These include molecules containing P–O–P and P–C–P connectivities, multivalent P(III)–O–P(V) phosphorus nuclei with widely separated chemical shifts, as well as virtually overlapping 31P resonances exhibiting strong coupling effects. We also demonstrate the utility of these experiments to rapidly distinguish between mono- and diphosphates. A detailed protocol for optimizing these experiments to achieve best performance is presented. PMID:20408590

  6. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers

    SciTech Connect

    Fedorov, Dmitry A.; Varganov, Sergey A.; Derevianko, Andrei

    2014-05-14

    We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X{sup 1}Σ{sup +} electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm{sup −1} for LiNa and by no more than 114 cm{sup −1} for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm{sup −1}, and the discrepancies for the anharmonic correction are less than 0.1 cm{sup −1}. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

  7. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers.

    PubMed

    Fedorov, Dmitry A; Derevianko, Andrei; Varganov, Sergey A

    2014-05-14

    We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X(1)Σ(+) electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm(-1) for LiNa and by no more than 114 cm(-1) for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm(-1), and the discrepancies for the anharmonic correction are less than 0.1 cm(-1). We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

  8. Trimer and Tetramer Bound States in Heteronuclear Systems

    NASA Astrophysics Data System (ADS)

    Schmickler, Christiane H.; Hammer, Hans-Werner; Hiyama, Emiko

    2017-01-01

    The Efimov effect in heteronuclear cold atomic systems is experimentally more easily accessible than the Efimov effect for identical atoms, because of the potentially smaller scaling factor. We focus on the case of two or three heavy identical bosons and another atom. The former case was recently observed in a mixture of ^{133}Cs and ^{6}Li atoms. We employ the Gaussian Expansion Method as developed by Hiyama, Kino et al. (Prog Part Nucl Phys 51:223-307, 2003). This is a variational method that uses Gaussians that are distributed geometrically over a chosen range. Supplemental calculations are performed using the Skorniakov-Ter- Martirosian equation. Blume et al. (Phys Rev Lett 113:213201, 2014) previously investigated the scaling properties of heteronuclear systems in the unitary limit and at the three-body breakup threshold. We have completed this picture by calculating the behaviour on the positive scattering length side of the Efimov plot, focussing on the dimer threshold.

  9. Reaction monitoring using hyperpolarized NMR with scaling of heteronuclear couplings by optimal tracking.

    PubMed

    Zhang, Guannan; Schilling, Franz; Glaser, Steffen J; Hilty, Christian

    2016-11-01

    Off-resonance decoupling using the method of Scaling of Heteronuclear Couplings by Optimal Tracking (SHOT) enables determination of heteronuclear correlations of chemical shifts in single scan NMR spectra. Through modulation of J-coupling evolution by shaped radio frequency pulses, off resonance decoupling using SHOT pulses causes a user-defined dependence of the observed J-splitting, such as the splitting of (13)C peaks, on the chemical shift offset of coupled nuclei, such as (1)H. Because a decoupling experiment requires only a single scan, this method is suitable for characterizing on-going chemical reactions using hyperpolarization by dissolution dynamic nuclear polarization (D-DNP). We demonstrate the calculation of [(13)C, (1)H] chemical shift correlations of the carbanionic active sites from hyperpolarized styrene polymerized using sodium naphthalene as an initiator. While off resonance decoupling by SHOT pulses does not enhance the resolution in the same way as a 2D NMR spectrum would, the ability to obtain the correlations in single scans makes this method ideal for determination of chemical shifts in on-going reactions on the second time scale. In addition, we present a novel SHOT pulse that allows to scale J-splittings 50% larger than the respective J-coupling constant. This feature can be used to enhance the resolution of the indirectly detected chemical shift and reduce peak overlap, as demonstrated in a model reaction between p-anisaldehyde and isobutylamine. For both pulses, the accuracy is evaluated under changing signal-to-noise ratios (SNR) of the peaks from reactants and reaction products, with an overall standard deviation of chemical shift differences compared to reference spectra of 0.02ppm when measured on a 400MHz NMR spectrometer. Notably, the appearance of decoupling side-bands, which scale with peak intensity, appears to be of secondary importance.

  10. Reaction monitoring using hyperpolarized NMR with scaling of heteronuclear couplings by optimal tracking

    NASA Astrophysics Data System (ADS)

    Zhang, Guannan; Schilling, Franz; Glaser, Steffen J.; Hilty, Christian

    2016-11-01

    Off-resonance decoupling using the method of Scaling of Heteronuclear Couplings by Optimal Tracking (SHOT) enables determination of heteronuclear correlations of chemical shifts in single scan NMR spectra. Through modulation of J-coupling evolution by shaped radio frequency pulses, off resonance decoupling using SHOT pulses causes a user-defined dependence of the observed J-splitting, such as the splitting of 13C peaks, on the chemical shift offset of coupled nuclei, such as 1H. Because a decoupling experiment requires only a single scan, this method is suitable for characterizing on-going chemical reactions using hyperpolarization by dissolution dynamic nuclear polarization (D-DNP). We demonstrate the calculation of [13C, 1H] chemical shift correlations of the carbanionic active sites from hyperpolarized styrene polymerized using sodium naphthalene as an initiator. While off resonance decoupling by SHOT pulses does not enhance the resolution in the same way as a 2D NMR spectrum would, the ability to obtain the correlations in single scans makes this method ideal for determination of chemical shifts in on-going reactions on the second time scale. In addition, we present a novel SHOT pulse that allows to scale J-splittings 50% larger than the respective J-coupling constant. This feature can be used to enhance the resolution of the indirectly detected chemical shift and reduce peak overlap, as demonstrated in a model reaction between p-anisaldehyde and isobutylamine. For both pulses, the accuracy is evaluated under changing signal-to-noise ratios (SNR) of the peaks from reactants and reaction products, with an overall standard deviation of chemical shift differences compared to reference spectra of 0.02 ppm when measured on a 400 MHz NMR spectrometer. Notably, the appearance of decoupling side-bands, which scale with peak intensity, appears to be of secondary importance.

  11. Rapid screening for structural integrity of expressed proteins by heteronuclear NMR spectroscopy.

    PubMed Central

    Gronenborn, A. M.; Clore, G. M.

    1996-01-01

    A simple and rapid method based on 15N labeling and 1H-15N heteronuclear single quantum coherence spectroscopy is presented to directly assess the structural integrity of overexpressed proteins in crude Escherichia coli extracts without the need for any purification. The method is demonstrated using two different expression systems and two different proteins, the B1 immunoglobulin-binding domain of streptococcal protein G (56 residues) and human interleukin-1 beta (153 residues). It is shown that high quality 1H-15N correlation spectra, recorded in as little as 15 min and displaying only cross-peaks arising from the overexpressed protein of interest, can be obtained from crude E. coli extracts. PMID:8771212

  12. Two-photon photoassociation spectroscopy of an ultracold heteronuclear molecule

    NASA Astrophysics Data System (ADS)

    Dutta, Sourav; Pérez-Ríos, Jesús; Elliott, D. S.; Chen, Yong P.

    2017-01-01

    We report on two-photon photoassociation (PA) spectroscopy of ultracold heteronuclear LiRb molecules. This is used to determine the binding energies of the loosely bound levels of the electronic ground singlet and the lowest triplet states of LiRb. We observe strong two-photon PA lines with power broadened linewidths greater than 20 GHz at relatively low laser intensity of 30 W /c m2 . The implication of this observation on direct atom to molecule conversion using stimulated Raman adiabatic passage is discussed and the prospect for electronic ground-state molecule production is theoretically analyzed.

  13. Secondary structure and zinc ligation of human recombinant short-form stromelysin by multidimensional heteronuclear NMR.

    PubMed

    Gooley, P R; Johnson, B A; Marcy, A I; Cuca, G C; Salowe, S P; Hagmann, W K; Esser, C K; Springer, J P

    1993-12-07

    Stromelysin-1, a member of the matrix metalloendoprotease family, is a zinc protease involved in the degradation of connective tissue in the extracellular matrix. As a step toward determining the structure of this protein, multidimensional heteronuclear NMR experiments have been applied to an inhibited truncated form of human stromelysin-1. Extensive 1H, 13C, and 15N sequential assignments have been obtained with a combination of three- and four-dimensional experiments. On the basis of sequential and short-range NOEs and 13C alpha chemical shifts, two helices have been delineated, spanning residues Asp-111 to Val-127 and Leu-195 to Ser-206. A third helix spanning residues Asp-238 to Gly-247 is characterized by sequential NOEs and 13C alpha chemical shifts, but not short-range NOEs. The lack of the latter NOEs suggests that this helix is either distorted or mobile. Similarly, sequential and interstrand NOEs and 13C alpha chemical shifts characterize a four-stranded beta-sheet with three parallel strands (Arg-100 to Ile-101, Ile-142 to Ala-147, Asp-177 to Asp-181) and one antiparallel strand (Ala-165 to Tyr-168). Two zinc sites have been identified in stromelysin [Salowe et al. (1992) Biochemistry 31, 4535-4540]. The NMR spectral properties, including chemical shift, pH dependence, and proton coupling of the imidazole nitrogens of six histidine residues (151, 166, 179, 201, 205, and 211), invariant in the matrix metalloendoprotease family, suggest that these residues are zinc ligands. NOE data indicate that these histidines form two clusters: one ligates the catalytic zinc (His-201, -205, and -211), and the other ligates a structural zinc (His-151, -166, and -179). Heteronuclear multiple quantum correlated spectra and specific labeling experiments indicate His-151, -179, -201, -205, and -211 are in the N delta 1H tautomer and His-166 is in the N epsilon 2H tautomer.

  14. Tailored real-time scaling of heteronuclear couplings.

    PubMed

    Schilling, Franz; Glaser, Steffen J

    2012-10-01

    Heteronuclear couplings are a valuable source of molecular information, which is measured from the multiplet splittings of an NMR spectrum. Radiofrequency irradiation on one coupled nuclear spin allows to modify the effective coupling constant, scaling down the multiplet splittings in the spectrum observed at the resonance frequency of the other nuclear spin. Such decoupling sequences are often used to collapse a multiplet into a singlet and can therefore simplify NMR spectra significantly. Continuous-wave (cw) decoupling has an intrinsic non-linear offset dependence of the scaling of the effective J-coupling constant. Using optimal control pulse optimization, we show that virtually arbitrary off-resonance scaling of the J-coupling constant can be achieved. The new class of tailored decoupling pulses is named SHOT (Scaling of Heteronuclear couplings by Optimal Tracking). Complementing cw irradiation, SHOT pulses offer an alternative approach of encoding chemical shift information indirectly through off-resonance decoupling, which however makes it possible for the first time to achieve linear J scaling as a function of offset frequency. For a simple mixture of eight aromatic compounds, it is demonstrated experimentally that a 1D-SHOT {(1)H}-(13)C experiment yields comparable information to a 2D-HSQC and can give full assignment of all coupled spins.

  15. Application of heteronuclear couplings to conformational analysis of oligonucleotides

    SciTech Connect

    Zhu, G.; Live, D.; Bax, A.

    1994-12-01

    The value of vicinal coupling constants extracted from NMR spectra in deducing torsion angles for conformational analysis is well recognized. Due to the abundance of protons, their couplings have been mostly widely used. In many instances, couplings between protons and other nuclei may be a valuable complement to proton-proton couplings or, in some instances, may be the only coupling available to characterize the torsion angle about a bond. Recently, heteronuclear couplings have been used to great benefit in studies of isotopically enriched proteins, and this general approach has been extended to peptides at natural abundance. The possibility of using this approach to study oligonucleotides is also attractive but has not as yet been widely exploited. With the development of strategies for labeling such molecules, particularly RNAs, this may become an important component in conformational analysis. For DNA, labeling is less accessible, but sufficient quantities of unlabeled material are readily available for measuring these couplings at natural abundance. We chose several DNA systems to explore the usefulness of heteronuclear couplings in addressing the sugar conformation and the glycosidic torsion angle. Intensities of cross peaks in long-range HMQC experiments can be related to the couplings. Crosspeaks involving H1{prime} and C1{prime} atoms have been emphasized because of the superior shift dispersion at these positions between sugar protons and carbon atoms. Results will be shown for the self-complementary Dickerson duplex dodecamer sequence d(CGCGAATTCGCG) and for d(GGTCGG), which dimerizes to form a G-tetrad structure incorporating both syn and anti base orientations. The couplings provide a clear discrimination between presence of C3{prime}-endo and C2{prime}-endo conformations of the sugars and syn and anti bases arrangements.

  16. Phase identification and quantification in a devitrified glass using homo- and heteronuclear solid-state NMR.

    PubMed

    Tricot, Grégory; Delevoye, Laurent; Palavit, Gérard; Montagne, Lionel

    2005-11-14

    A complex mixture resulting from the devitrification of an aluminophosphate glass has been studied for the first time using a combination of homo- and heteronuclear solid-state NMR sequences that offers the advantage of subsequent quantification.

  17. Measurement of Magnitude and Sign of Heteronuclear Coupling Constants in Transition Metal Complexes.

    PubMed

    Otting; Soler; Messerle

    1999-04-01

    Sets of specifically tailored E.COSY-type correlation experiments and double-quantum/zero-quantum (DQ/ZQ) experiments are presented which enable the determination of sign and size of small heteronuclear coupling constants across the metal center of transition metal complexes. For the octahedrally coordinated complexes, [Ru(TPM)(H)(CO)(PPh3)]+[BF4]- (1) and [Ir(TPM)(H)(CO)(CO2CH3)]+[BF4]- (2), 14 of 15 and 15 of 15 possible two-bond scalar coupling constants across the metal center were measured, respectively, using 15N and 15N/13C enriched samples (TPM = tris(1-pyrazolyl)methane)). The reduced coupling constants 2KX-M-Y = 4pi2 2J/(hgammaXgammaY) were found to be positive when the coupled nuclei X and Y were trans with respect to the metal center, and negative when the coupled nuclei were in cis position. The validity of this sign rule was verified for JCC, JNN, JPN, JPC, JCN, JHP, JHC, and JHN couplings. Idiosyncracies associated with 2D NMR spectra for the sign determination of coupling constants with 15N which lead to corrections for the signs of JHN, JPN, and JCN couplings reported previously are discussed. Copyright 1999 Academic Press.

  18. Further perspective on the theory of heteronuclear decoupling

    NASA Astrophysics Data System (ADS)

    Skinner, Thomas E.

    2014-11-01

    An exact general theory of heteronuclear decoupling is presented for spin-1/2 IS systems. RF irradiation applied to the I spins both modifies and generates additional couplings between states of the system. The recently derived equivalence between the dynamics of any N-level quantum system and a system of classical coupled harmonic oscillators makes explicit the exact physical couplings between states. Decoupling is thus more properly viewed as a complex intercoupling. The sign of antiphase magnetization plays a fundamental role in decoupling. A one-to-one correspondence is demonstrated between ± 2SyIz and the sense of the S-spin coupling evolution. Magnetization Sx is refocused to obtain the desired decoupled state when ∫ 2SyIz dt = 0 . The exact instantaneous coupling at any time during the decoupling sequence is readily obtained in terms of the system states, showing that the creation of two-spin coherence is crucial for reducing the effective scalar coupling, as required for refocusing to occur. Representative examples from new aperiodic sequences as well as standard cyclic, periodic composite-pulse and adiabatic decoupling sequences illustrate the decoupling mechanism. The more general aperiodic sequences, obtained using optimal control, realize the potential inherent in the theory for significantly improved decoupling.

  19. Further perspective on the theory of heteronuclear decoupling.

    PubMed

    Skinner, Thomas E

    2014-11-01

    An exact general theory of heteronuclear decoupling is presented for spin-1/2 IS systems. RF irradiation applied to the I spins both modifies and generates additional couplings between states of the system. The recently derived equivalence between the dynamics of any N-level quantum system and a system of classical coupled harmonic oscillators makes explicit the exact physical couplings between states. Decoupling is thus more properly viewed as a complex intercoupling. The sign of antiphase magnetization plays a fundamental role in decoupling. A one-to-one correspondence is demonstrated between ±2SyIz and the sense of the S-spin coupling evolution. Magnetization Sx is refocused to obtain the desired decoupled state when ∫2SyIzdt=0. The exact instantaneous coupling at any time during the decoupling sequence is readily obtained in terms of the system states, showing that the creation of two-spin coherence is crucial for reducing the effective scalar coupling, as required for refocusing to occur. Representative examples from new aperiodic sequences as well as standard cyclic, periodic composite-pulse and adiabatic decoupling sequences illustrate the decoupling mechanism. The more general aperiodic sequences, obtained using optimal control, realize the potential inherent in the theory for significantly improved decoupling.

  20. Bruker AMX Y Channel Heteronuclear Decoupling Using a Linear Amplifier

    SciTech Connect

    Alam, Todd M.; Lang, David P.

    1999-08-02

    Under both static and common MAS conditions (< 15 kHz) the question of residual X-Y heteronuclear decoupling can become a complicating factor in the analysis of various NMR results. In our lab the impact of {sup 31}P-{sup 23}Na dipolar coupling on the observed {sup 23}Na M{sub 2} relaxation for a series of sodium phosphate glasses was recently investigated by employing continuous wave {sup 31}P decoupling during the entire pulse sequence. Initially these efforts were complicate by the inability to provide a gating pulse during the data acquisition using the standard Bruker nomenclature, go=2, for the acquisition loop. A pulse sequence to overcome these restrictions is given below. Our AMX400 instrument is configured with a 3 channel MCI, but utilizes a linear AMT amplifier on the 3rd channel (requiring gating pulse via the C4 program call during the entire time it is on). The standard acquisition loop has been replaced by direct adc and aq commands for data acquisition. Unlike the go=2 statement which does not allow a C4 gating command to be included, these individual acquisition commands can all include distinct C4 gating.

  1. Percolation of heteronuclear dimers irreversibly deposited on square lattices

    NASA Astrophysics Data System (ADS)

    Gimenez, M. C.; Ramirez-Pastor, A. J.

    2016-09-01

    The percolation problem of irreversibly deposited heteronuclear dimers on square lattices is studied. A dimer is composed of two segments, and it occupies two adjacent adsorption sites. Each segment can be either a conductive segment (segment type A ) or a nonconductive segment (segment type B ). Three types of dimers are considered: A A , B B , and A B . The connectivity analysis is carried out by accounting only for the conductive segments (segments type A ). The model offers a simplified representation of the problem of percolation of defective (nonideal) particles, where the presence of defects in the system is simulated by introducing a mixture of conductive and nonconductive segments. Different cases were investigated, according to the sequence of deposition of the particles, the types of dimers involved in the process, and the degree of alignment of the deposited objects. By means of numerical simulations and finite-size scaling analysis, the complete phase diagram separating a percolating from a nonpercolating region was determined for each case. Finally, the consistency of our results was examined by comparing with previous data in the literature for linear k -mers (particles occupying k adjacent sites) with defects.

  2. Percolation of heteronuclear dimers irreversibly deposited on square lattices.

    PubMed

    Gimenez, M C; Ramirez-Pastor, A J

    2016-09-01

    The percolation problem of irreversibly deposited heteronuclear dimers on square lattices is studied. A dimer is composed of two segments, and it occupies two adjacent adsorption sites. Each segment can be either a conductive segment (segment type A) or a nonconductive segment (segment type B). Three types of dimers are considered: AA, BB, and AB. The connectivity analysis is carried out by accounting only for the conductive segments (segments type A). The model offers a simplified representation of the problem of percolation of defective (nonideal) particles, where the presence of defects in the system is simulated by introducing a mixture of conductive and nonconductive segments. Different cases were investigated, according to the sequence of deposition of the particles, the types of dimers involved in the process, and the degree of alignment of the deposited objects. By means of numerical simulations and finite-size scaling analysis, the complete phase diagram separating a percolating from a nonpercolating region was determined for each case. Finally, the consistency of our results was examined by comparing with previous data in the literature for linear k-mers (particles occupying k adjacent sites) with defects.

  3. Studies in protein dynamics using heteronuclear nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Vugmeyster, Liliya

    Dynamic processes in proteins are important for their biological function. Several issues in protein dynamics are addressed by applying existing NMR methodologies to investigate dynamics of several small proteins. Amide H/D exchange rates have been measured for the N-terminal domain of the ribosomal protein L9, residues 1--56. The results suggest that the structure of the domain is preserved in isolation and that the stability of the isolated domain is comparable to the stability of this domain in intact L9. Single domain proteins can fold in vitro at rates in excess of 1 x 104 s-1. Measurement of folding rates of this magnitude poses a considerable technical challenge. Off-resonance 15N R1rho measurements are shown to be capable of measuring such fast protein folding rates. The measurements were performed on a sample of the peripheral subunit-binding domain from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus 15N labeled at Ala 11. Fast intramolecular motions (on ps-ns time scale) can be studied by heteronuclear laboratory frame NMR relaxation. The temperature dependence of the backbone dynamics of the 36-resiude subdomain of the F-actin bundling protein villin has been investigated by studying the temperature dependence of order parameters obtained from 15N relaxation measurements. The results support the hypothesis that one of the possible mechanisms of thermostability is to lower the heat capacity difference between the folded and unfolded states by lowering the contribution from the backbone dynamics. A commonly used model-free approach for the interpretation of the relaxation data for macromolecules in solution is modified to correct for the decoupling approximation between the overall and internal motions.

  4. Backbone assignments and secondary structure of the Escherichia coli enzyme-II mannitol A domain determined by heteronuclear three-dimensional NMR spectroscopy.

    PubMed Central

    Kroon, G. J.; Grötzinger, J.; Dijkstra, K.; Scheek, R. M.; Robillard, G. T.

    1993-01-01

    This report presents the backbone assignments and the secondary structure determination of the A domain of the Escherichia coli mannitol transport protein, enzyme-IImtl. The backbone resonances were partially assigned using three-dimensional heteronuclear 1H NOE 1H-15N single-quantum coherence (15N NOESY-HSQC) spectroscopy and three-dimensional heteronuclear 1H total correlation 1H-15N single-quantum coherence (15N TOCSY-HSQC) spectroscopy on uniformly 15N enriched protein. Triple-resonance experiments on uniformly 15N/13C enriched protein were necessary to complete the backbone assignments, due to overlapping 1H and 15N frequencies. Data obtained from three-dimensional 1H-15N-13C alpha correlation experiments (HNCA and HN(CO)CA), a three-dimensional 1H-15N-13CO correlation experiment (HNCO), and a three-dimensional 1H alpha-13C alpha-13CO correlation experiment (COCAH) were combined using SNARF software, and yielded the assignments of virtually all observed backbone resonances. Determination of the secondary structure of IIAmtl is based upon NOE information from the 15N NOESY-HSQC and the 1H alpha and 13C alpha secondary chemical shifts. The resulting secondary structure is considerably different from that reported for IIAglc of E. coli and Bacillus subtilis determined by NMR and X-ray. PMID:8401218

  5. Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel.

    PubMed

    Moore, Jay; Colón, Raul D; Tadanki, Sasidhar; Waddell, Kevin W

    2014-08-01

    The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins ((13)C and (1)H) at 12mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128kHz ((13)C) and 510kHz ((1)H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as

  6. Three-body recombination in heteronuclear systems at finite temperature with a large positive scattering length

    NASA Astrophysics Data System (ADS)

    Emmons, Samuel; Acharya, Bijaya; Platter, Lucas

    2017-01-01

    For an ultracold heteronuclear mixture with a large positive interspecies scattering length and negligible intraspecies scattering length, we determine the three-body recombination rate as a function of collision energy using universal functions of a single scaling variable. We use the zero-range approximation and the Skorniakov -Ter-Martirosian equation to calculate these scaling functions for a range of collision energies. Further, we explore the effects that a nonzero temperature has on three-body recombination, as well as the effects of the formation of deep dimers, for experimentally relevant heteronuclear gases such as the 6Li-133Cs mixture. NSF Grant Nos. PHY-1516077 and PHY-1555030.

  7. Engineering of an all-heteronuclear 5-qubit NMR quantum computer.

    PubMed

    Marx, Raimund; Pomplun, Nikolas; Bermel, Wolfgang; Zeiger, Heinz; Engelke, Frank; Fahmy, Amr F; Glaser, Steffen J

    2015-06-01

    The realization of an all-heteronuclear 5-qubit nuclear magnetic resonance quantum computer is reported, from the design and synthesis of a suitable molecule through the engineering of a prototype 6-channel probe head. Full control over the quantum computer is shown by a benchmark experiment.

  8. PAIN with and without PAR: variants for third-spin assisted heteronuclear polarization transfer.

    PubMed

    Agarwal, Vipin; Sardo, Mariana; Scholz, Ingo; Böckmann, Anja; Ernst, Matthias; Meier, Beat H

    2013-08-01

    In this article, we describe third-spin assisted heteronuclear recoupling experiments, which play an increasingly important role in measuring long-range heteronuclear couplings, in particular (15)N-(13)C, in proteins. In the proton-assisted insensitive nuclei cross polarization (PAIN-CP) experiment (de Paëpe et al. in J Chem Phys 134:095101, 2011), heteronuclear polarization transfer is always accompanied by homonuclear transfer of the proton-assisted recoupling (PAR) type. We present a phase-alternating experiment that promotes heteronuclear (e.g. (15)N → (13)C) polarization transfer while simultaneously minimizing homonuclear (e.g.(13)C → (13)C) transfer (PAIN without PAR). This minimization of homonuclear polarization transfer is based on the principle of the resonant second-order transfer (RESORT) recoupling scheme where the passive proton spins are irradiated by a phase-alternating sequence and the modulation frequency is matched to an integer multiple of the spinning frequency. The similarities and differences between the PAIN-CP and this het-RESORT experiment are discussed here.

  9. Measurement and applications of long-range heteronuclear scalar couplings: recent experimental and theoretical developments.

    PubMed

    Nath, Nilamoni; Lokesh; Suryaprakash, Nagarajarao

    2012-02-01

    The use of long-range heteronuclear couplings, in association with (1)H-(1)H scalar couplings and NOE restraints, has acquired growing importance for the determination of the relative stereochemistry, and structural and conformational information of organic and biological molecules. However, the routine use of such couplings is hindered by the inherent difficulties in their measurement. Prior to the advancement in experimental techniques, both long-range homo- and heteronuclear scalar couplings were not easily accessible, especially for very large molecules. The development of a large number of multidimensional NMR experimental methodologies has alleviated the complications associated with the measurement of couplings of smaller strengths. Subsequent application of these methods and the utilization of determined J-couplings for structure calculations have revolutionized this area of research. Problems in organic, inorganic and biophysical chemistry have also been solved by utilizing the short- and long-range heteronuclear couplings. In this minireview, we discuss the advantages and limitations of a number of experimental techniques reported in recent times for the measurement of long-range heteronuclear couplings and a few selected applications of such couplings. This includes the study of medium- to larger-sized molecules in a variety of applications, especially in the study of hydrogen bonding in biological systems. The utilization of these couplings in conjunction with theoretical calculations to arrive at conclusions on the hyperconjugation, configurational analysis and the effect of the electronegativity of the substituents is also discussed.

  10. Phosphopeptide binding to the N-terminal SH2 domain of the p85 alpha subunit of PI 3'-kinase: a heteronuclear NMR study.

    PubMed Central

    Hensmann, M.; Booker, G. W.; Panayotou, G.; Boyd, J.; Linacre, J.; Waterfield, M.; Campbell, I. D.

    1994-01-01

    The N-terminal src-homology 2 domain of the p85 alpha subunit of phosphatidylinositol 3' kinase (SH2-N) binds specifically to phosphotyrosine-containing sequences. Notably, it recognizes phosphorylated Tyr 751 within the kinase insert of the cytoplasmic domain of the activated beta PDGF receptor. A titration of a synthetic 12-residue phosphopeptide (ESVDY*VPMLDMK) into a solution of the SH2-N domain was monitored using heteronuclear 2D and 3D NMR spectroscopy. 2D-(15N-1H) heteronuclear single-quantum correlation (HSQC) experiments were performed at each point of the titration to follow changes in both 15N and 1H chemical shifts in NH groups. When mapped onto the solution structure of the SH2-N domain, these changes indicate a peptide-binding surface on the protein. Line shape analysis of 1D profiles of individual (15N-1H)-HSQC peaks at each point of the titration suggests a kinetic exchange model involving at least 2 steps. To characterize changes in the internal dynamics of the domain, the magnitude of the (15N-1H) heteronuclear NOE for the backbone amide of each residue was determined for the SH2-N domain with and without bound peptide. These data indicate that, on a nanosecond timescale, there is no significant change in the mobility of either loops or regions of secondary structure. A mode of peptide binding that involves little conformational change except in the residues directly involved in the 2 binding pockets of the p85 alpha SH2-N domain is suggested by this study. PMID:7522724

  11. Recent progress in heteronuclear long-range NMR of complex carbohydrates: 3D H2BC and clean HMBC.

    PubMed

    Meier, Sebastian; Petersen, Bent O; Duus, Jens Ø; Sørensen, Ole W

    2009-11-02

    The new NMR experiments 3D H2BC and clean HMBC are explored for challenging applications to a complex carbohydrate at natural abundance of (13)C. The 3D H2BC experiment is crucial for sequential assignment as it yields heteronuclear one- and two-bond together with COSY correlations for the (1)H spins, all in a single spectrum with good resolution and non-informative diagonal-type peaks suppressed. Clean HMBC is a remedy for the ubiquitous problem of strong coupling induced one-bond correlation artifacts in HMBC spectra of carbohydrates. Both experiments work well for one of the largest carbohydrates whose structure has been determined by NMR, not least due to the enhanced resolution offered by the third dimension in 3D H2BC and the improved spectral quality due to artifact suppression in clean HMBC. Hence these new experiments set the scene to take advantage of the sensitivity boost achieved by the latest generation of cold probes for NMR structure determination of even larger and more complex carbohydrates in solution.

  12. A pulse sequence for singlet to heteronuclear magnetization transfer: S2hM

    NASA Astrophysics Data System (ADS)

    Stevanato, Gabriele; Eills, James; Bengs, Christian; Pileio, Giuseppe

    2017-04-01

    We have recently demonstrated, in the context of para-hydrogen induced polarization (PHIP), the conversion of hyperpolarized proton singlet order into heteronuclear magnetisation can be efficiently achieved via a new sequence named S2hM (Singlet to heteronuclear Magnetisation). In this paper we give a detailed theoretical description, supported by an experimental illustration, of S2hM. Theory and experiments on thermally polarized samples demonstrate the proposed method is robust to frequency offset mismatches and radiofrequency field inhomogeneities. The simple implementation, optimisation and the high conversion efficiency, under various regimes of magnetic equivalence, makes S2hM an excellent candidate for a widespread use, particularly within the PHIP arena.

  13. Next-generation heteronuclear decoupling for high-field biomolecular NMR spectroscopy.

    PubMed

    Schilling, Franz; Warner, Lisa R; Gershenzon, Naum I; Skinner, Thomas E; Sattler, Michael; Glaser, Steffen J

    2014-04-22

    Ultra-high-field NMR spectroscopy requires an increased bandwidth for heteronuclear decoupling, especially in biomolecular NMR applications. Composite pulse decoupling cannot provide sufficient bandwidth at practical power levels, and adiabatic pulse decoupling with sufficient bandwidth is compromised by sideband artifacts. A novel low-power, broadband heteronuclear decoupling pulse is presented that generates minimal, ultra-low sidebands. The pulse was derived using optimal control theory and represents a new generation of decoupling pulses free from the constraints of periodic and cyclic sequences. In comparison to currently available state-of-the-art methods this novel pulse provides greatly improved decoupling performance that satisfies the demands of high-field biomolecular NMR spectroscopy.

  14. Enhanced association and dissociation of heteronuclear Feshbach molecules in a microgravity environment

    NASA Astrophysics Data System (ADS)

    D'Incao, J. P.; Krutzik, M.; Elliott, E.; Williams, J. R.

    2017-01-01

    We study the association and dissociation dynamics of weakly bound heteronuclear Feshbach molecules using transverse radio-frequency fields for expected parameters accessible through the microgravity environment of NASA's Cold Atom Laboratory (CAL) aboard the International Space Station, including subnanokelvin temperatures and atomic densities as low as 108/cm3 . We show that under such conditions, thermal and loss effects can be greatly suppressed, resulting in a high efficiency of both association and dissociation of Feshbach molecules with a mean size exceeding 104a0 and allowing for the coherence in atom-molecule transitions to be clearly observable. Our theoretical model for heteronuclear mixtures includes thermal, loss, and density effects in a simple and conceptually clear manner. We derive the temperature, density, and scattering length regimes of 41K-87Rb that allow optimal association or dissociation efficiency with minimal heating and loss to guide upcoming experiments with ultracold atomic gases in space.

  15. HR-HSBC: Measuring heteronuclear one-bond couplings with enhanced resolution.

    PubMed

    Görling, Benjamin; Bräse, Stefan; Luy, Burkhard

    2012-12-01

    Heteronuclear one-bond couplings have a variety of applications, and their accurate determination is the basis for obtaining specific structural information of mostly small organic compounds. In this context, it is of utmost importance to reduce signal overlap to a minimum, and a number of techniques has been introduced during the last decades. Here, we introduce a modified version of the HR-HMBC (Magn. Reson. Chem. 2010, 48, 179-183) for heteronuclear one-bond coupling measurements with improved resolution because of the J-resolved-like tilt of corresponding multiplet patterns. The pulse sequence is introduced, and its performance is compared with a standard ω(2)-coupled HSQC experiment. Example spectra on glucose and maltose demonstrate that signals can be resolved that overlap otherwise. The approach is discussed in detail.

  16. Characterization of heteronuclear decoupling through proton spin dynamics in solid-state nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    De Paëpe, Gaël; Eléna, Bénédicte; Emsley, Lyndon

    2004-08-01

    The work presented here aims at understanding the performance of phase modulated heteronuclear decoupling sequences such as Cosine Modulation or Two Pulse Phase Modulation. To that end we provide an analytical description of the intrinsic behavior of Cosine Modulation decoupling with respect to radio-frequency-inhomogeneity and the proton-proton dipolar coupling network. We discover through a Modulation Frame average Hamiltonian analysis that best decoupling is obtained under conditions where the heteronuclear interactions are removed but notably where homonuclear couplings are recoupled at a homonuclear Rotary Resonance (HORROR) condition in the Modulation Frame. These conclusions are supported by extensive experimental investigations, and notably through the introduction of proton nutation experiments to characterize spin dynamics in solids under decoupling conditions. The theoretical framework presented in this paper allows the prediction of the optimum parameters for a given set of experimental conditions.

  17. Homo- and Heteronuclear Multiple-Quantum Filters for Measurement of NMR Isotope Shifts

    NASA Astrophysics Data System (ADS)

    Wooten, E. W.; Dua, R. K.; Dotson, G. D.; Woodard, R. W.

    The measurement of NMR isotope shifts as mechanistic probes can be complicated by mixtures of isotopomers. Homo- and heteronuclear NMR techniques based on multiple-quantum filtration are presented and shown to be a useful aid in measuring such shifts. The effects of 1H/ 2H substitution and 16O/ 18O substitution on the nuclear shielding of 1H, 13C, and 31P in a multiply labeled phosphoenolpyruvate are measured and interpreted qualitatively in terms of their rovibrational origins.

  18. Long-range dispersion interactions. I. Formalism for two heteronuclear atoms

    SciTech Connect

    Zhang, J.-Y.; Mitroy, J.

    2007-08-15

    A general procedure for systematically evaluating the long-range dispersion interaction between two heteronuclear atoms in arbitrary states is outlined. The C{sub 6} dispersion parameter can always be written in terms of sum rules involving oscillator strengths only and formulas for a number of symmetry cases are given. The dispersion coefficients for excited alkali-metal atoms interacting with the ground-state H and He are tabulated.

  19. Methodology for solid state NMR off-resonance study of molecular dynamics in heteronuclear systems.

    PubMed

    Jurga, Kazimierz; Woźniak-Braszak, Aneta; Baranowski, Mikołaj

    2015-10-01

    Methodology for the study of dynamics in heteronuclear systems in the laboratory frame was described in the previous paper [1]. Now the methodology for the study of molecular dynamics in the solid state heteronuclear systems in the rotating frame is presented. The solid state NMR off-resonance experiments were carried out on a homemade pulse spectrometer operating at the frequency of 30.2 MHz for protons. This spectrometer includes a specially designed probe which contains two independently tuned and electrically isolated coils installed in the coaxial position on the dewar. A unique probe design allows working at three slightly differing frequencies off and on resonance for protons and at the frequency of 28.411 MHz for fluorine nuclei with complete absence of their electrical interference. The probe allows simultaneously creating rf magnetic fields at off-resonance frequencies within the range of 30.2-30.6 MHz and at the frequency of 28.411 MHz. Presented heteronuclear cross-relaxation off-resonance experiments in the rotating frame provide information about molecular dynamics.

  20. A unified heteronuclear decoupling strategy for magic-angle-spinning solid-state NMR spectroscopy

    SciTech Connect

    Equbal, Asif; Bjerring, Morten; Nielsen, Niels Chr. E-mail: ncn@inano.au.dk; Madhu, P. K. E-mail: ncn@inano.au.dk

    2015-05-14

    A unified strategy of two-pulse based heteronuclear decoupling for solid-state magic-angle spinning nuclear magnetic resonance is presented. The analysis presented here shows that different decoupling sequences like two-pulse phase-modulation (TPPM), X-inverse-X (XiX), and finite pulse refocused continuous wave (rCW{sup A}) are basically specific solutions of a more generalized decoupling scheme which incorporates the concept of time-modulation along with phase-modulation. A plethora of other good decoupling conditions apart from the standard, TPPM, XiX, and rCW{sup A} decoupling conditions are available from the unified decoupling approach. The importance of combined time- and phase-modulation in order to achieve the best decoupling conditions is delineated. The consequences of different indirect dipolar interactions arising from cross terms comprising of heteronuclear and homonuclear dipolar coupling terms and also those between heteronuclear dipolar coupling and chemical-shift anisotropy terms are presented in order to unfold the effects of anisotropic interactions under different decoupling conditions. Extensive numerical simulation results are corroborated with experiments on standard amino acids.

  1. Heteronuclear dipolar couplings, total spin coherence, and bilinear rotations in NMR spectroscopy

    SciTech Connect

    Garbow, J.R.

    1983-07-01

    In Chapter 1 a variety of different introductory topics are presented. The potential complexity of the nuclear magnetic resonsnace (NMR) spectra of molecules dissolved in liquid crystal solvents serves to motivate the development of multiple quantum (MQ) spectroscopy. The basics of MQ NMR are reviewed in Chapter 2. An experimental search procedure for the optimization of MQ pulse sequences is introduced. Chapter 3 discusses the application of MQ NMR techniques to the measurement of dipolar couplings in heteronuclear spin systems. The advantages of MQ methods in such systems are developed and experimental results for partially oriented (1-/sup 13/C) benzene are presented. Several pulse sequences are introduced which employ a two-step excitation of heteronuclear MQ coherence. A new multiple pulse method, involving the simultaneous irradiation of both rare and abundant spin species, is described. The problem of the broadening of MQ transitions due to magnetic field inhomogeneity is considered in Chapter 4. The method of total spin coherence transfer echo spectroscopy (TSCTES) is presented, with experimets on partially oriented acetaldehyde serving to demonstrate this new technique. TSCTES results in MQ spectra which are sensitive to all chemical shifts and spin-spin couplings and which are free of inhomogeneous broadening. In Chapter 5 the spectroscopy of spin systems of several protons and a /sup 13/C nucleus in the isotropic phase is discussed. The usefulness of the heteronuclear bilinear rotation as a calculational tool is illustrated. Compensated bilinear ..pi.. rotations, which are relatively insensitive to timing parameter missets, are presented. A new technique for homonuclear proton decoupling, Bilinear Rotation Decoupling, is described and its success in weakly coupled systems is demonstrated.

  2. Optical Autler-Townes spectroscopy in a heteronuclear mixture of laser-cooled atoms

    NASA Astrophysics Data System (ADS)

    Bruni, C.; Münchow, F.; Görlitz, A.

    2017-01-01

    We report on optical Autler-Townes spectroscopy in a heteronuclear mixture of {}^{87}Rb and {}^{176}Yb in a continuously loaded double-species magneto-optical trap. An excited vibrational level of Rb*Yb which is energetically close to the 5^2P_{1/2} state of Rb is coupled by a strong laser field to a vibrational level in the ground state of RbYb and probed by a weak probe laser field. The induced Autler-Townes splittings in the photoassociation spectra allow us to determine relative Franck-Condon factors of molecular transitions in RbYb.

  3. Selective charge asymmetric distribution in heteronuclear diatomic molecules in strong laser fields

    NASA Astrophysics Data System (ADS)

    Lai, Wei; Guo, Chunlei

    2015-07-01

    In this paper we study double-ionization-induced charge asymmetric dissociation (CAD) in heteronuclear diatomic molecules. In CO we find a selective charge distribution in two CAD channels, i.e., C2 ++O is abundantly produced but C +O2 + is nearly nonexistent. This cannot be explained by the ionization energy difference between the two channels alone. Our study shows that the C2 ++O channel is sequentially formed through an intermediate state C++O and the selective charge distribution is the result of electron distribution in CO when exposed to intense laser fields.

  4. Hydrothermal liquefaction oil and hydrotreated product from pine feedstock characterized by heteronuclear two-dimensional NMR spectroscopy and FT-ICR mass spectrometry

    SciTech Connect

    Sudasinghe, Nilusha; Cort, John R.; Hallen, Richard; Olarte, Mariefel; Schmidt, Andrew; Schaub, Tanner

    2014-12-01

    Hydrothermal liquefaction (HTL) crude oil and hydrotreated product from pine tree farm waste (forest product residual, FPR) have been analyzed by direct infusion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) in both positive- and negative-ionization modes and high-resolution twodimensional heteronuclear 1H-13C NMR spectroscopy. FT-ICR MS resolves thousands of compounds in complex oils and provides unparalleled compositional details for individual molecules for identification of compound class (heteroatom content), type (number of rings plus double bonds to carbon or double bond equivalents (DBE) and carbon number (degree of alkylation). Heteronuclear 1H-13C NMR spectroscopy provides one-bond and multiple-bond correlations between pairs of 1H and 13C chemical shifts that are characteristic of different organic functional groups. Taken together this information provides a picture of the chemical composition of these oils. Pyrolysis crude oil product from pine wood was characterized for comparison. Generally, pyrolysis oil is comprised of a more diverse distribution of heteroatom classes with higher oxygen number relative to HTL oil as shown by both positive- and negative-ion ESI FT-ICR MS. A total of 300 N1, 594 O1 and 267 O2 compounds were observed as products of hydrotreatment. The relative abundance of N1O1, N1O2, N1O3, N2, N2O1, N2O2 and O3 compounds are reduced to different degrees after hydrotreatment and other higher heteroatom containing species (O4-O10, N1O4, N1O5 and N2O3) are completely removed by hydrotreatment.

  5. The role of molecular electron distribution in strong-field ionization and dissociation of heteronuclear molecules

    NASA Astrophysics Data System (ADS)

    Lai, Wei; Guo, Chunlei

    2016-11-01

    A comparison study of double-ionization induced dissociation in strong laser fields between a homonuclear diatomic molecule, O2, and a heteronuclear diatomic molecule, NO, shows that two electrons can easily be removed from one O atom of O2 to form a O2++O, however, two electrons can hardly be removed from the O atom of NO to form a N+O2+. Instead, for NO, two electrons are preferentially removed from the N atom to form a N2++O, even though the N atom requires higher ionization energy than the O atom. This indicates that atomic ionization energy does not play a significant role here. Our further study on the formation dynamics of the N2++O channel shows that the initial electron distribution of the NO molecule plays an important role in influencing the strong-field ionization and dissociation of NO and this effect seems to commonly exist in heteronuclear molecules when interacting with strong laser fields.

  6. A critical evaluation of heteronuclear TOCSY (HEHAHA) experiments for 1H,6Li spin pairs.

    PubMed

    Bergander, Klaus; Hüls, Dietmar; Glaser, Steffen J; Günther, Harald; Luy, Burkhard

    2014-12-01

    Heteronuclear TOCSY (HEHAHA) experiments for (1) H,(6) Li spin pairs in organolithium compounds with adjacent strongly coupled (1) H,(1) H spin systems showed unexpected cross peak behaviour: for n-butyllithium (1) H,(6) Li cross peaks were completely missing, whereas for the dimer of (Z)-2-lithio-1-(o-lithiophenyl)ethane, a cross peak for remote protons was observed even at very short mixing times. It was assumed that strong magnetization transfer within the proton spin systems was responsible for these results, which prevented unambiguous chemical shift assignments. Selective experiments with the (6) Li,(1) H-HET-PLUSH-TACSY sequence then showed the expected (6) Li,(1) H cross peaks for the transfer via the directly coupled (1) H and (6) Li nuclei. For n-butyllithium transfer to H(Cα) via an unresolved heteronuclear coupling constant below 0.1 Hz is unambiguously observed. Cross peaks in the 2D (6) Li,(1) H-HET-PLUSH-TACSY spectra for the dimer of (Z)-2-lithio-1-(o-lithiophenyl)ethane are readily explained by the measured coupling network and the corresponding active mixing conditions.

  7. Band-selective heteronuclear dipolar recoupling with dual back-to-back pulses in rotating solids

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengfeng; Chen, Yanke; Yang, Jun

    2016-11-01

    We propose a robust band-selective heteronuclear 15N-13C recoupling method using dual back-to-back (BABA) pulses (DBP). It contains four 90° pulses in each rotor period and corresponding phase cycling on each channel (13C and 15N). DBP aims at rapid band-selective heteronuclear magnetization transfer between 15N and 13Cα/13C‧, whose efficiency is close to that of the well-known SPECIFIC CP in membrane proteins with relatively short relaxation time in rotating frame (T1ρ). Compared to SPECIFIC CP, DBP is very simple to set up and highly robust to RF variations. Thus, it can reduce the efforts in experimental optimization, especially for low-sensitive samples, and is very suitable for long-time or quantitative experiments. The efficacy of DBP is demonstrated by the E. coli diacylglycerol kinase (DAGK) proteoliposome. We anticipate that DBP would be useful for (segments of) membrane proteins that undergo the μs-ms timescale motions in magic-angle spinning (MAS) solid-state NMR.

  8. A new approach to the synthesis of heteronuclear propeller-like single molecule magnets.

    PubMed

    Totaro, Pasquale; Westrup, Kátia Cristina M; Boulon, Marie-Emmanuelle; Nunes, Giovana G; Back, Davi F; Barison, Andersson; Ciattini, Samuele; Mannini, Matteo; Sorace, Lorenzo; Soares, Jaísa F; Cornia, Andrea; Sessoli, Roberta

    2013-04-07

    Propeller-like [Fe(4)(L)(2)(dk)(6)] complexes, in which Hdk is a β-diketone and H(3)L is a tripodal alcohol, R-C(CH(2)OH)(3), exhibit tunable magnetic anisotropy barriers and retain their magnetic memory effect when chemically anchored on metal surfaces. Heteronuclear analogues of these M(4) complexes have been sought to afford a library of compounds with different total spin (S) values, but synthetic efforts described so far gave solid solutions containing M(4) in addition to the desired M(3)M' species. We now present a novel synthetic route to M(3)M' complexes featuring a central chromium(III) ion. The three-step preparation goes through coordination of Cr(III) by two equivalents of tripodal alkoxide (R = Et and Ph), followed by reaction of this complex "core" with the peripheral +III metal ions. Products have been characterised by chemical analyses together with (1)H-NMR, FTIR, W-band EPR, DC/AC magnetic susceptibility measurements and single crystal X-ray diffractometry. Due to the chemical inertness of Cr(III), this route yields 100% pure Fe(3)Cr complexes without metal scrambling; what is more, it is suitable for designing novel heteronuclear single molecule magnets (SMMs) with a variety of d- and f-metals and R groups.

  9. Heteronuclear gold(I)-silver(I) sulfanylcarboxylates: Synthesis, structure and cytotoxic activity against cancer cell lines.

    PubMed

    Barreiro, Elena; Casas, José S; Couce, María D; Sánchez, Agustín; Sordo, José; Vázquez-López, Ezequiel M

    2014-02-01

    Heteronuclear complexes of the type [AgAu(PPh3)2(xspa)] [H2xspa=3-(aryl)-2-sulfanylpropenoic acids; (x=3-phenyl-; 3-(2-chlorophenyl)-; 3-(o-methoxyphenyl)-; 3-(p-methoxyphenyl)-; 3-(p-hydroxyphenyl)-; 3-(2-furyl)-; 3-(2-thienyl)-; spa=2-sulfanylpropenoate)] were prepared by reacting the appropriate [Au(PPh3)(Hxspa)] precursor with Ag(PPh3)NO3. The compounds were characterized by spectroscopic methods, (IR; (1)H, (13)C and (31)P NMR) and mass spectrometry and the structures of the phenyl and p-methoxyphenyl derivatives were determined by X-ray diffraction. The in vitro antitumor activity against the HeLa-229, A2780 and A2780cis cell lines was determined and compared with that of cisplatin and the equivalent homonuclear gold(I) complexes.

  10. Tuning of Heteronuclear Interactions in a Degenerate Fermi-Bose Mixture

    SciTech Connect

    Ospelkaus, S.; Ospelkaus, C.; Humbert, L.; Sengstock, K.; Bongs, K.

    2006-09-22

    We demonstrate tuning of interactions between fermionic {sup 40}K and bosonic {sup 87}Rb atoms by Feshbach resonances and access the complete phase diagram of the harmonically trapped mixture from phase separation to collapse. On the attractive side of the resonance, we observe a strongly enhanced mean-field energy of the condensate due to the mutual mean-field confinement, predicted by a Thomas-Fermi model. As we increase heteronuclear interactions beyond a threshold, we observe an induced collapse of the mixture. On the repulsive side of the resonance, we observe vertical phase separation of the mixture in the presence of the gravitational force, thus entering a completely unexplored part of the phase diagram of the mixture. In addition, we identify the 515 G resonance as p wave by its characteristic doublet structure.

  11. Advanced In Vivo Heteronuclear MRS Approaches for Studying Brain Bioenergetics Driven by Mitochondria

    PubMed Central

    Zhu, Xiao-Hong; Du, Fei; Zhang, Nanyin; Zhang, Yi; Lei, Hao; Zhang, Xiaoliang; Qiao, Hongyan; Ugurbil, Kamil; Chen, Wei

    2017-01-01

    The greatest merit of in vivo magnetic resonance spectroscopy (MRS) methodology used in biomedical research is its ability for noninvasively measuring a variety of metabolites inside a living organ. It, therefore, provides an invaluable tool for determining metabolites, chemical reaction rates and bioenergetics, as well as their dynamic changes in the human and animal. The capability of in vivo MRS is further enhanced at higher magnetic fields because of significant gain in detection sensitivity and improvement in the spectral resolution. Recent progress of in vivo MRS technology has further demonstrated its great potential in many biomedical research areas, particularly in brain research. Here, we provide a review of new developments for in vivo heteronuclear 31P and 17O MRS approaches and their applications in determining the cerebral metabolic rates of oxygen and ATP inside the mitochondria, in both animal and human brains. PMID:18839099

  12. Two-center interference in high-order harmonic generation from heteronuclear diatomic molecules.

    PubMed

    Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lan, Pengfei; Lu, Peixiang

    2011-01-17

    Two-center interference for heteronuclear diatomic molecules (HeDM) is investigated. The minimum in the high-order harmonic spectrum, as a consequence of the destructive interference, is shifted to lower harmonic orders compared with that in a homonuclear case. This phenomenon is explained by performing phase analysis. It is found that, for an HeDM, the high harmonic spectrum contains information not only on the internuclear separation but also on the properties of the two separate centers, which implies the potential application of estimating the asymmetry of molecules and judging the linear combination of atomic orbitals (LCAO) for the highest occupied molecular orbital (HOMO). Moreover, the possibility to monitor the evolution of HOMO itself in molecular dynamics is also promised.

  13. Heteronuclear decoupling in MAS NMR in the intermediate to fast sample spinning regime

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Bjerring, Morten; Sharma, Kshama; Madhu, P. K.; Nielsen, Niels Chr.

    2016-01-01

    Heteronuclear spin decoupling in solid-state magic-angle spinning NMR is investigated to present methods overcoming interferences between rf irradiation and sample spinning in the intermediate to fast spinning regime. We demonstrate that a recent phase-alternated variant of refocused CW irradiation (rCWApA) provides efficient and robust decoupling in this regime. An extensive experimental and numerical comparison is presented for rCWApA and PISSARRO (phase-inverted supercycled sequence for attenuation of rotary resonance), previously introduced to quench rotary-resonance recoupling effects, under conditions with spinning frequencies between 30 and 60 kHz. Simulations are used to identify the effect of decoupling for various nuclear spin interactions.

  14. Epitope Mapping of Antigenic MUC1 Peptides to Breast Cancer Antibody Fragment B27.29: A Heteronuclear NMR Study

    SciTech Connect

    Grinstead, Jeffrey S.; Schuman, Jason T.; Campbell, Ann P.

    2003-11-13

    MUC1 mucin is a breast cancer-associated transmembrane glycoprotein, of which the extracellular domain is formed by the repeating 20-amino acid sequence GVTSAPDTRPAPGSTAPPAH. In neoplastic breast tissue, the highly immunogenic sequence PDTRPAP (in bold above) is exposed. Antibodies raised directly against MUC1-expressing tumors offer unique access to this neoplastic state, as they represent immunologically relevant ''reverse templates'' of the tumor-associated mucin. In a previous study [Grinstead, J. S., et al. (2002) Biochemistry 41, 9946-9961], 1H NMR methods were used to correlate the effects of cryptic glycosylation outside of the PDTRPAP core epitope sequence on the recognition and binding of Mab B27.29, a monoclonal antibody raised against breast tumor cells. In the study presented here, isotope-edited NMR methods, including 15N and 13C relaxation measurements, were used to probe the recognition and binding of the PDTRPAP epitope sequence to Fab B27.29. Two peptides were studied: a one-repeat MUC1 16mer peptide of the sequence GVTSAPDTRPAPGSTA and a two-repeat MUC1 40mer peptide of the sequence (VTSAPDTRPAPGSTAPPAHG)2. 15N and 13C NMR relaxation parameters were measured for both peptides free in solution and bound to Fab B27.29. The 13CR T1 values best represent changes in the local correlation time of the peptide epitope upon binding antibody, and demonstrate that the PDTRPAP sequence is immobilized in the antibody-combining site. This result is also reflected in the appearance of the 15N- and 13C-edited HSQC spectra, where line broadening of the same peptide epitope resonances is observed. The PDTRPAP peptide epitope expands upon the peptide epitope identified previously in our group as PDTRP by homonuclear NMR experiments [Grinstead, J. S., et al. (2002) Biochemistry 41, 9946-9961], and illustrates the usefulness of the heteronuclear NMR experiments. The implications of these results are discussed within the context of MUC1 breast cancer vaccine design.

  15. Heteronuclear three-dimensional NMR spectroscopy. Natural abundance sup 13 C chemical shift editing of sup 1 H- sup 1 H COSY spectra

    SciTech Connect

    Fesik, S.W.; Gampe, R.T. Jr.; Zuiderweg, E.R.P. )

    1989-01-18

    It has been demonstrated that heteronuclear 3D NMR spectroscopy can be effectively applied to small molecules with {sup 13}C at natural abundance. A 78mM solution of the aminoglycoside, kanamycin A was used for this experiment. The heteronuclear 3D NMR spectroscopy is shown to be a useful method for resolving spectral overlap in all frequency domains. 10 refs., 2 figs.

  16. S3 HMBC hetero: Spin-State-Selective HMBC for accurate measurement of long-range heteronuclear coupling constants

    NASA Astrophysics Data System (ADS)

    Hoeck, Casper; Gotfredsen, Charlotte H.; Sørensen, Ole W.

    2017-02-01

    A novel method, Spin-State-Selective (S3) HMBC hetero, for accurate measurement of heteronuclear coupling constants is introduced. The method extends the S3 HMBC technique for measurement of homonuclear coupling constants by appending a pulse sequence element that interchanges the polarization in 13C-1H methine pairs. This amounts to converting the spin-state selectivity from 1H spin states to 13C spin states in the spectra of long-range coupled 1H spins, allowing convenient measurement of heteronuclear coupling constants similar to other S3 or E.COSY-type methods. As usual in this type of techniques, the accuracy of coupling constant measurement is independent of the size of the coupling constant of interest. The merits of the new method are demonstrated by application to vinyl acetate, the alkaloid strychnine, and the carbohydrate methyl β-maltoside.

  17. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning.

    PubMed

    Shmyreva, Anna A; Safdari, Majid; Furó, István; Dvinskikh, Sergey V

    2016-06-14

    Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  18. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Shmyreva, Anna A.; Safdari, Majid; Furó, István; Dvinskikh, Sergey V.

    2016-06-01

    Orders of magnitude decrease of 207Pb and 199Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  19. NMR Scalar Couplings across Intermolecular Hydrogen Bonds between Zinc-Finger Histidine Side Chains and DNA Phosphate Groups.

    PubMed

    Chattopadhyay, Abhijnan; Esadze, Alexandre; Roy, Sourav; Iwahara, Junji

    2016-10-10

    NMR scalar couplings across hydrogen bonds represent direct evidence for the partial covalent nature of hydrogen bonds and provide structural and dynamic information on hydrogen bonding. In this article, we report heteronuclear (15)N-(31)P and (1)H-(31)P scalar couplings across the intermolecular hydrogen bonds between protein histidine (His) imidazole and DNA phosphate groups. These hydrogen-bond scalar couplings were observed for the Egr-1 zinc-finger-DNA complex. Although His side-chain NH protons are typically undetectable in heteronuclear (1)H-(15)N correlation spectra due to rapid hydrogen exchange, this complex exhibited two His side-chain NH signals around (1)H 14.3 ppm and (15)N 178 ppm at 35 °C. Through various heteronuclear multidimensional NMR experiments, these signals were assigned to two zinc-coordinating His side chains in contact with DNA phosphate groups. The data show that the Nδ1 atoms of these His side chains are protonated and exhibit the (1)H-(15)N cross-peaks. Using heteronuclear (1)H, (15)N, and (31)P NMR experiments, we observed the hydrogen-bond scalar couplings between the His (15)Nδ1/(1)Hδ1 and DNA phosphate (31)P nuclei. These results demonstrate the direct involvement of the zinc-coordinating His side chains in the recognition of DNA by the Cys2His2-class zinc fingers in solution.

  20. Solution secondary structure of calcium-saturated troponin C monomer determined by multidimensional heteronuclear NMR spectroscopy.

    PubMed Central

    Slupsky, C. M.; Reinach, F. C.; Smillie, L. B.; Sykes, B. D.

    1995-01-01

    The solution secondary structure of calcium-saturated skeletal troponin C (TnC) in the presence of 15% (v/v) trifluoroethanol (TFE), which has been shown to exist predominantly as a monomer (Slupsky CM, Kay CM, Reinach FC, Smillie LB, Sykes BD, 1995, Biochemistry 34, forthcoming), has been investigated using multidimensional heteronuclear nuclear magnetic resonance spectroscopy. The 1H, 15N, and 13C NMR chemical shift values for TnC in the presence of TFE are very similar to values obtained for calcium-saturated NTnC (residues 1-90 of skeletal TnC), calmodulin, and synthetic peptide homodimers. Moreover, the secondary structure elements of TnC are virtually identical to those obtained for calcium-saturated NTnC, calmodulin, and the synthetic peptide homodimers, suggesting that 15% (v/v) TFE minimally perturbs the secondary and tertiary structure of this stably folded protein. Comparison of the solution structure of calcium-saturated TnC with the X-ray crystal structure of half-saturated TnC reveals differences in the phi/psi angles of residue Glu 41 and in the linker between the two domains. Glu 41 has irregular phi/psi angles in the crystal structure, producing a kink in the B helix, whereas in calcium-saturated TnC, Glu 41 has helical phi/psi angles, resulting in a straight B helix. The linker between the N and C domains of calcium-saturated TnC is flexible in the solution structure. PMID:7670371

  1. Structural studies of the activation of the two component receiver domain NTRC by multidimensional heteronuclear NMR

    SciTech Connect

    Nohaile, Michael James

    1996-05-01

    Multidimensional heteronuclear NMR spectroscopy was used to investigate the N-terminal domain of the transcriptional enhancer NTRC (NiTrogen Regulatory protein C). This domain belongs to the family of receiver domains of two-component regulatory systems involved in signal transduction. Phosphorylation of NTRC at D54 leads to an activated form of the molecule which stimulates transcription of genes involved in nitrogen regulation. Three and four dimensional NMR techniques were used to determine an intermediate resolution structure of the unphosphorylated, inactive form of the N-terminal domain of NTRC. The structure is comprised of five α-helices and a five-stranded β-sheet in a (β/α)5 topology. Analysis of the backbone dynamics of NTRC indicate that helix 4 and strand 5 are significantly more flexible than the rest of the secondary structure of the protein and that the loops making up the active site are flexible. The short lifetime of phospho-NTRC hampers the study of this form. However, conditions for determining the resonance assignments and, possibly, the three dimensional structure of phosphorylated NTRC have been obtained. Tentative assignments of the phosphorylated form indicate that the majority of the changes that NTRC experiences upon phosphorylation occur in helix 3, strand 4, helix 4, strand 5, and the loop between strand 5 and helix 5 (the 3445 face of NTRC) as well as near the site of phosphorylation. In order to examine a stable, activated form of the protein, constitutively active mutants of NTRC were investigated.

  2. Heteronuclear cross-polarization in multinuclear multidimensional NMR: Prospects for triple-resonance CP

    SciTech Connect

    Majumdar, A.; Zuiderweg, E.R.P.

    1994-12-01

    Heteronuclear multiple-pulse-based Cross Polarization (HECP) between scalar coupled spins is gaining an important role in high-resolution multidimensional NMR of isotopically labeled biomolecules, especially in experiments involving net magnetization transfer. It has generally been observed that in these situations, the performance of HECP is superior to that of INEPT-based sequences. In particular, HECP-based three-dimensional HCCH spectroscopy is more efficient than the INEPT version of the same experiment. Differences in sensitivity have been intuitively attributed to relaxation effects and technical factors such as radiofrequency (rf) inhomogeneity We present theoretical analyses and computer simulations to probe the effects of these factors. Relaxation effects were treated phenomenologically; we found that relaxation differences are relatively small (up to 25%) between pulsed-free-precession (INEPT) and HECP-although always in favor of HECP. We explored the rf effects by employing a Gaussian distribution of rf amplitude over sample volume. We found that inhomogeneity effects significantly favor HECP over INEPT, especially under conditions of {open_quotes}matched {close_quotes} inhomogeneity in the two rf coils. The differences in favor of HECP indicate that an extension of HECP to triple resonance experiments (TRCP) in I -> S -> Q net transfers might yield better results relative to analogous INEPT-based net transfers. We theoretically analyze the possibilities of TRCP and find that transfer functions are critically dependent on the ratio J{sub IS}/J{sub SQ}. When J{sub IS} equals J{sub SQ}, we find that 100% transfer is possible for truly simultaneous TRCP and this transfer is obtained in a time 1.41 /J. The TRCP time requirement compares favorably with optimally concatenated INEPT-transfers, where net transfer I -> S -> Q is complete at 1.5 /J.

  3. Heteronuclear Adiabatic Relaxation Dispersion (HARD) for quantitative analysis of conformational dynamics in proteins.

    PubMed

    Traaseth, Nathaniel J; Chao, Fa-An; Masterson, Larry R; Mangia, Silvia; Garwood, Michael; Michaeli, Shalom; Seelig, Burckhard; Veglia, Gianluigi

    2012-06-01

    NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R(1ρ) and Carr-Purcell-Meiboom-Gill (CPMG) R(2) experiments are commonly used to characterize μs to ms dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the Heteronuclear Adiabatic Relaxation Dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R(1ρ) and transverse R(2ρ)) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (k(ex)∼10(4)-10(5) s(-1)). In this article, we show the sensitivity of the HARD method to slower exchange processes by measuring R(1ρ) and R(2ρ) relaxation rates for two soluble proteins (ubiquitin and 10C RNA ligase). One advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R(1ρ) and R(2ρ) that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is complementary to CPMG-based and rotating frame spin-lock R(1ρ) experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent.

  4. ELECTRONIC AND CHEMICAL PROPERTIES OF PD IN BIMETALLIC SYSTEMS: HOW MUCH DO WE KNOW ABOUT HETERONUCLEAR METAL-METAL BONDING?

    SciTech Connect

    RODRIGUEZ,J.A.

    2001-09-27

    The experimental and theoretical studies described above illustrate the complex nature of the heteronuclear metal-metal bond. In many cases, bimetallic bonding induces a significant redistribution of charge around the bonded metals. This redistribution of charge is usually linked to the strength of the bimetallic bond, affects the position of the core and valence levels of the metals, and can determine the chemical reactivity of the system under study. New concepts are emerging [22,23,34,36] and eventually the coupling of experiment and theory can be useful for designing more efficient bimetallic catalysts [98,106,107].

  5. Tautomeric states of the active-site histidines of phosphorylated and unphosphorylated IIIGlc, a signal-transducing protein from Escherichia coli, using two-dimensional heteronuclear NMR techniques.

    PubMed Central

    Pelton, J. G.; Torchia, D. A.; Meadow, N. D.; Roseman, S.

    1993-01-01

    IIIGlc is an 18.1-kDa signal-transducing phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system from Escherichia coli. The 1H, 15N, and 13C histidine ring NMR signals of both the phosphorylated and unphosphorylated forms of IIIGlc have been assigned using two-dimensional 1H-15N and 1H-13C heteronuclear multiple-quantum coherence (HMQC) experiments and a two-dimensional 13C-13C-1H correlation spectroscopy via JCC coupling experiment. The data were acquired on uniformly 15N-labeled and uniformly 15N/13C-labeled protein samples. The experiments rely on one-bond and two-bond J couplings that allowed for assignment of the signals without the need for the analysis of through-space (nuclear Overhauser effect spectroscopy) correlations. The 15N and 13C chemical shifts were used to determine that His-75 exists predominantly in the N epsilon 2-H tautomeric state in both the phosphorylated and unphosphorylated forms of IIIGlc, and that His-90 exists primarily in the N delta 1-H state in the unphosphorylated protein. Upon phosphorylation of the N epsilon 2 nitrogen of His-90, the N delta 1 nitrogen remains protonated, resulting in the formation of a charged phospho-His-90 moiety. The 1H, 15N, and 13C signals of the phosphorylated and unphosphorylated proteins showed only minor shifts in the pH range from 6.0 to 9.0. These data indicate that the pK alpha values for both His-75 and His-90 in IIIGlc and His-75 in phospho-IIIGlc are less than 5.0, and that the pK alpha value for phospho-His-90 is greater than 10. The results are presented in relation to previously obtained structural data on IIIGlc, and implications for proposed mechanisms of phosphoryl transfer are discussed. PMID:8518729

  6. Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR

    NASA Astrophysics Data System (ADS)

    Basse, Kristoffer; Shankar, Ravi; Bjerring, Morten; Vosegaard, Thomas; Nielsen, Niels Chr.; Nielsen, Anders B.

    2016-09-01

    We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization (RESPIRATIONCP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the RESPIRATIONCP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous 15N → 13CO and 15N → 13Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability.

  7. Refocused continuous-wave decoupling: A new approach to heteronuclear dipolar decoupling in solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Vinther, Joachim M.; Nielsen, Anders B.; Bjerring, Morten; van Eck, Ernst R. H.; Kentgens, Arno P. M.; Khaneja, Navin; Nielsen, Niels Chr.

    2012-12-01

    A novel strategy for heteronuclear dipolar decoupling in magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy is presented, which eliminates residual static high-order terms in the effective Hamiltonian originating from interactions between oscillating dipolar and anisotropic shielding tensors. The method, called refocused continuous-wave (rCW) decoupling, is systematically established by interleaving continuous wave decoupling with appropriately inserted rotor-synchronized high-power π refocusing pulses of alternating phases. The effect of the refocusing pulses in eliminating residual effects from dipolar coupling in heteronuclear spin systems is rationalized by effective Hamiltonian calculations to third order. In some variants the π pulse refocusing is supplemented by insertion of rotor-synchronized π/2 purging pulses to further reduce the residual dipolar coupling effects. Five different rCW decoupling sequences are presented and their performance is compared to state-of-the-art decoupling methods. The rCW decoupling sequences benefit from extreme broadbandedness, tolerance towards rf inhomogeneity, and improved potential for decoupling at relatively low average rf field strengths. In numerical simulations, the rCW schemes clearly reveal superior characteristics relative to the best decoupling schemes presented so far, which we to some extent also are capable of demonstrating experimentally. A major advantage of the rCW decoupling methods is that they are easy to set up and optimize experimentally.

  8. Synthesis, crystal structures, and properties of oxovanadium(IV)-lanthanide(III) heteronuclear complexes.

    PubMed

    Shi, Wei; Chen, Xiao-Yan; Zhao, Yan-Nan; Zhao, Bin; Cheng, Peng; Yu, Ao; Song, Hai-Bin; Wang, Hong-Gen; Liao, Dai-Zheng; Yan, Shi-Ping; Jiang, Zong-Hui

    2005-08-19

    A new series of oxovanadium(IV)-lanthanide(III) heteronuclear complexes [Yb(H2O)8]2[(VO)2(TTHA)](3)21 H2O (1), {[Ho(H2O)7(VO)2(TTHA)][(VO)2(TTHA)](0.5)} 8.5 H2O (2), {[Gd(H2O)7(VO)2(TTHA)][(VO)2(TTHA)](0.5)}8.5 H2O (3), {[Eu(H2O)7][(VO)2(TTHA)](1.5)} 10.5 H2O (4), and [Pr2(H2O)6(SO4)2][(VO)2(TTHA)] (5) (H6TTHA=triethylenetetraaminehexaacetic acid) were prepared by using the bulky flexible organic acid H(6)TTHA as structure-directing agent. X-ray crystallographic studies reveal that they contain the same [(VO)2(TTHA)]2- unit as building block, but the Ln3+ ion lies in different coordination environments. Although the lanthanide ions always exhibit similar chemical behavior, the structures of the complexes are not homologous. Compound 1 is composed of a [Yb(H2O)8]3+ ion and a [(VO)2(TTHA)]2- ion. Compounds 2 and 3 are isomorphous; both contain a trinuclear [Ln(H2O)7(VO)2(TTHA)]+ (Ln=Ho for 2 and Gd for 3) ion and a [(VO)2(TTHA)]2- ion. Compound 4 is an extended one-dimensional chain, in which each Eu3+ ion links two [(VO)2(TTHA)]2- ions. For 5, the structure is further assembled into a three-dimensional network with an interesting framework topology comprising V2Pr2 and V4Pr2 heterometallic lattices. Moreover, 4 and 5 are the first oxovanadium(IV)-lanthanide(III) coordination polymers and thus enlarge the realm of 3d-4f complexes. The IR, UV/Vis, and EPR spectra and the magnetic properties of the heterometallic complexes were studied. Notably, 2 shows unusual ferromagnetic interactions between the VO2+ and Ho3+ ions.

  9. Chemical interaction mechanism of 10-MDP with zirconia.

    PubMed

    Nagaoka, Noriyuki; Yoshihara, Kumiko; Feitosa, Victor Pinheiro; Tamada, Yoshiyuki; Irie, Masao; Yoshida, Yasuhiro; Van Meerbeek, Bart; Hayakawa, Satoshi

    2017-03-30

    Currently, the functional monomer 10-methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) was documented to chemically bond to zirconia ceramics. However, little research has been conducted to unravel the underlying mechanisms. This study aimed to assess the chemical interaction and to demonstrate the mechanisms of coordination between 10-MDP and zirconium oxide using (1)H and (31)P magic angle spinning (MAS) nuclear magnetic resonance (NMR) and two dimensional (2D) (1)H → (31)P heteronuclear correlation (HETCOR) NMR. In addition, shear bond-strength (SBS) tests were conducted to determine the effect of 10-MDP concentration on the bonding effectiveness to zirconia. These SBS tests revealed a 10-MDP concentration-dependent SBS with a minimum of 1-ppb 10-MDP needed. (31)P-NMR revealed that one P-OH non-deprotonated of the PO3H2 group from 10-MDP chemically bonded strongly to zirconia. (1)H-(31)P HETCOR NMR indicated that the 10-MDP monomer can be adsorbed onto the zirconia particles by hydrogen bonding between the P=O and Zr-OH groups or via ionic interactions between partially positive Zr and deprotonated 10-MDP (P-O(-)). The combination of (1)H NMR and 2D (1)H-(31)P HETCOR NMR enabled to describe the different chemical states of the 10-MDP bonds with zirconia; they not only revealed ionic but also hydrogen bonding between 10-MDP and zirconia.

  10. Chemical interaction mechanism of 10-MDP with zirconia

    PubMed Central

    Nagaoka, Noriyuki; Yoshihara, Kumiko; Feitosa, Victor Pinheiro; Tamada, Yoshiyuki; Irie, Masao; Yoshida, Yasuhiro; Van Meerbeek, Bart; Hayakawa, Satoshi

    2017-01-01

    Currently, the functional monomer 10-methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) was documented to chemically bond to zirconia ceramics. However, little research has been conducted to unravel the underlying mechanisms. This study aimed to assess the chemical interaction and to demonstrate the mechanisms of coordination between 10-MDP and zirconium oxide using 1H and 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) and two dimensional (2D) 1H → 31P heteronuclear correlation (HETCOR) NMR. In addition, shear bond-strength (SBS) tests were conducted to determine the effect of 10-MDP concentration on the bonding effectiveness to zirconia. These SBS tests revealed a 10-MDP concentration-dependent SBS with a minimum of 1-ppb 10-MDP needed. 31P-NMR revealed that one P-OH non-deprotonated of the PO3H2 group from 10-MDP chemically bonded strongly to zirconia. 1H-31P HETCOR NMR indicated that the 10-MDP monomer can be adsorbed onto the zirconia particles by hydrogen bonding between the P=O and Zr-OH groups or via ionic interactions between partially positive Zr and deprotonated 10-MDP (P-O−). The combination of 1H NMR and 2D 1H-31P HETCOR NMR enabled to describe the different chemical states of the 10-MDP bonds with zirconia; they not only revealed ionic but also hydrogen bonding between 10-MDP and zirconia. PMID:28358121

  11. A solid-state NMR study of the formation of molecular sieve SAPO-34.

    PubMed

    Yan, Zhimin; Chen, Banghao; Huang, Yining

    2009-04-01

    This work examined the formation of a catalytically important microporous material, SAPO-34, in the presence of HF under hydrothermal synthesis conditions. The local environments of P, Al, F and Si atoms in several solid phases obtained at different stages of crystallization were characterized by several solid-state NMR techniques including (31)P, (27)Al, (19)F and (29)Si MAS, (27)Al triple-quantum MAS, (31)P{(27)Al} transfer of populations in double-resonance, (27)Al{(31)P} rotational-echo double-resonance (REDOR), (27)Al-->(31)P heteronuclear correlation spectroscopy, (31)P{(19)F} and (27)Al{(19)F} REDOR as well as (1)H-->(31)P cross polarization. The NMR results provide the new insights into the formation of SAPO-34.

  12. Fluorine detected 2D NMR experiments for the practical determination of size and sign of homonuclear F-F and heteronuclear C-F multiple bond J-coupling constants in multiple fluorinated compounds.

    PubMed

    Aspers, Ruud L E G; Ampt, Kirsten A M; Dvortsak, Peter; Jaeger, Martin; Wijmenga, Sybren S

    2013-06-01

    The use of fluorine in molecules obtained from chemical synthesis has become increasingly important within the pharmaceutical and agricultural industry. NMR characterization of these compounds is of great value with respect to their structure elucidation, their screening in metabolomics investigations and binding studies. The favorable NMR properties of the fluorine nucleus make NMR with fluorine detection of great value in this respect. A suite of NMR 2D F-F- and F-C-correlation experiments with fluorine detection was applied to the assignment of resonances, (n)J(CF)- and (n)J(FF)-couplings as well as the determination of their size and sign. The utilization of this experiment suite was exemplarily demonstrated for a highly fluorinated vinyl alkyl ether. Especially F-C HSQC and J-scaled F-C HMBC experiments allowed determining the size of the J-couplings of this compound. The relative sign of its homo- and heteronuclear couplings was achieved by different combinations of 2D NMR experiments, including non-selective and F2-selective F-C XLOC, F2-selective F-C HMQC, and F-F COSY. The F2-one/two-site selective F-C XLOC versions were found highly useful, as they led to simplifications of the common E.COSY patterns and resulted in a higher confidence level of the assignment by using selective excitation. The combination of F2-one/two-site selective F-C XLOC experiments with a F2-one-site selective F-C HMQC experiment provided the signs of all (n)J(CF)- and (n)J(FF)-couplings in the vinyl moiety of the test compound. Other combinations of experiments were found useful as well for special purposes when focusing for example on homonuclear couplings a combination of F-F COSY-10 with a F2-one-site selective F-C HMQC could be used. The E.COSY patterns in the spectra demonstrated were analyzed by use of the spin-selective displacement vectors, and in case of the XLOC also by use of the DQ- and ZQ-displacement vectors. The variety of experiments presented shall contribute to

  13. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples.

  14. Dual-band selective double cross polarization for heteronuclear polarization transfer between dilute spins in solid-state MAS NMR

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengfeng; Miao, Yimin; Liu, Xiaoli; Yang, Jun; Li, Conggang; Deng, Feng; Fu, Riqiang

    2012-04-01

    A sinusoidal modulation scheme is described for selective heteronuclear polarization transfer between two dilute spins in double cross polarization magic-angle-spinning nuclear magnetic resonance spectroscopy. During the second N → C cross polarization, the 13C RF amplitude is modulated sinusoidally while the 15N RF amplitude is tangent. This modulation induces an effective spin-lock field in two selective frequency bands in either side of the 13C RF carrier frequency, allowing for simultaneous polarization transfers from 15N to 13C in those two selective frequency bands. It is shown by experiments and simulations that this sinusoidal modulation allows one to selectively polarize from 15N to its covalently bonded 13Cα and 13C' carbons in neighboring peptide planes simultaneously, which is useful for establishing the backbone connectivity between two sequential residues in protein structural elucidation. The selectivity and efficiency were experimentally demonstrated on a uniformly 13C,15N-labeled β1 immunoglobulin binding domain of protein G (GB1).

  15. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems

    NASA Astrophysics Data System (ADS)

    Baranowski, M.; Woźniak-Braszak, A.; Jurga, K.

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2 MHz and 28.411 MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins 1H are polarized in the magnetic field B0 while fluorine spins 19F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

  16. Parameter independent low-power heteronuclear decoupling for fast magic-angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Madhu, P. K.; Meier, Beat H.; Nielsen, Niels Chr.; Ernst, Matthias; Agarwal, Vipin

    2017-02-01

    Major advances have recently been made in the field of heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance (NMR). These developments have improved the resolution and sensitivity of the NMR spectrum of spins coupled to protons. One such new scheme, denoted as rCWApA, has proven to be robust with practically no need for parameter optimization [A. Equbal et al. Chem. Phys. Lett., 635, 339 (2015)]. Most of the experiments with rCWApA have been carried out in the regimes of slow to moderate magic-angle spinning while simultaneously applying high decoupling radio-frequency amplitudes. Here, we explore the performance of the rCWApA sequence and its predecessor rCWA in the regime of low-power radio-frequency irradiation and fast magic-angle spinning. The robustness of the refocused continuous-wave (rCW) schemes to experimental parameters such as pulse lengths and offset irradiation is demonstrated. Numerical simulations and analytical theory have been used to understand the effects of various nuclear spin interactions on the decoupling performance of the low-power rCW decoupling scheme relative to other decoupling methods. This has lead to the design of an "optimum low-power decoupling sequence" that can be used without parameter optimization. This result is particularly important in the context of samples with low signal to noise.

  17. Broadband cross-polarization-based heteronuclear dipolar recoupling for structural and dynamic NMR studies of rigid and soft solids

    SciTech Connect

    Kharkov, B. B.; Chizhik, V. I.; Dvinskikh, S. V.

    2016-01-21

    Dipolar recoupling is an essential part of current solid-state NMR methodology for probing atomic-resolution structure and dynamics in solids and soft matter. Recently described magic-echo amplitude- and phase-modulated cross-polarization heteronuclear recoupling strategy aims at efficient and robust recoupling in the entire range of coupling constants both in rigid and highly dynamic molecules. In the present study, the properties of this recoupling technique are investigated by theoretical analysis, spin-dynamics simulation, and experimentally. The resonance conditions and the efficiency of suppressing the rf field errors are examined and compared to those for other recoupling sequences based on similar principles. The experimental data obtained in a variety of rigid and soft solids illustrate the scope of the method and corroborate the results of analytical and numerical calculations. The technique benefits from the dipolar resolution over a wider range of coupling constants compared to that in other state-of-the-art methods and thus is advantageous in studies of complex solids with a broad range of dynamic processes and molecular mobility degrees.

  18. Direct writing of CoFe alloy nanostructures by focused electron beam induced deposition from a heteronuclear precursor.

    PubMed

    Porrati, F; Pohlit, M; Müller, J; Barth, S; Biegger, F; Gspan, C; Plank, H; Huth, M

    2015-11-27

    Recently, focused electron beam-induced deposition has been employed to prepare functional magnetic nanostructures with potential in nanomagnetic logic and sensing applications by using homonuclear precursor gases like Fe(CO)5 or Co2(CO)8. Here we show that an extension towards the fabrication of bi-metallic compounds is possible by using a single-source heteronuclear precursor gas. We have grown CoFe alloy magnetic nanostructures from the HFeCo3(CO)12 metal carbonyl precursor. The compositional analysis indicates that the samples contain about 80 at% of metal and 10 at% of carbon and oxygen. Four-probe magnetotransport measurements are carried out on nanowires of various sizes down to a width of 50 nm, for which a room temperature resistivity of 43 μΩcm is found. Micro-Hall magnetometry reveals that 50 nm × 250 nm nanobars of the material are ferromagnetic up to the highest measured temperature of 250 K. Finally, the transmission electron microscopy (TEM) microstructural investigation shows that the deposits consist of a bcc Co-Fe phase mixed with a FeCo2 O4 spinel oxide phase with nanograins of about 5 nm diameter.

  19. Broadband cross-polarization-based heteronuclear dipolar recoupling for structural and dynamic NMR studies of rigid and soft solids

    NASA Astrophysics Data System (ADS)

    Kharkov, B. B.; Chizhik, V. I.; Dvinskikh, S. V.

    2016-01-01

    Dipolar recoupling is an essential part of current solid-state NMR methodology for probing atomic-resolution structure and dynamics in solids and soft matter. Recently described magic-echo amplitude- and phase-modulated cross-polarization heteronuclear recoupling strategy aims at efficient and robust recoupling in the entire range of coupling constants both in rigid and highly dynamic molecules. In the present study, the properties of this recoupling technique are investigated by theoretical analysis, spin-dynamics simulation, and experimentally. The resonance conditions and the efficiency of suppressing the rf field errors are examined and compared to those for other recoupling sequences based on similar principles. The experimental data obtained in a variety of rigid and soft solids illustrate the scope of the method and corroborate the results of analytical and numerical calculations. The technique benefits from the dipolar resolution over a wider range of coupling constants compared to that in other state-of-the-art methods and thus is advantageous in studies of complex solids with a broad range of dynamic processes and molecular mobility degrees.

  20. Highly efficient (19)F heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation.

    PubMed

    Equbal, Asif; Basse, Kristoffer; Nielsen, Niels Chr

    2016-12-07

    We present heteronuclear (19)F refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle-spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent (13)C-(19)F dipolar coupling interactions while simultaneously suppressing strong anisotropic chemical shift as well as homonuclear (19)F-(19)F dipolar coupling effects as typically present in perfluorated compounds. In an extensive numerical and experimental analysis using a rigid, organic solid as a model compound, it becomes evident that the supercycled rCW schemes markedly improve the decoupling efficiency, leading to substantial enhancements in resolution and sensitivity when compared to previous state-of-the-art methods. Furthermore, considerable gains in robustness toward rf mismatch as well as offset in the radio-frequency carrier frequency are observed, all of which clearly render the new rCW schemes the methods of choice for (19)F decoupling in rigid, fluorinated compounds - which is further supported by a Floquet-based theoretical analysis.

  1. Series d-f Heteronuclear Metal-Organic Frameworks: Color Tunability and Luminescent Probe with Switchable Properties.

    PubMed

    Feng, Xun; Feng, Yuquan; Guo, Nan; Sun, Yiling; Zhang, Tian; Ma, Lufang; Wang, Liya

    2017-02-06

    A series of five unique d-f heteronuclear luminescent metal-organic frameworks (MOFs) in an entangled polyrotaxane array and the light-harvesting block homonuclear zinc compound have been isolated successfully and characterized. The series of isostructural polymers feature 3,4-connected (4.8(2))(4.8(3).9(2))(6.8.9)2(6.9(2))(8(3)) topology and high stability, exhibiting diverse void spaces. By taking advantage of the isostructural MOFs 2 and 3, the intensities of red and green emissions can be modulated by adjusting the ratios of Eu(III) and Tb(III) ions correspondingly, and white-light emission can be generated by a combination of different doped Tb(III) and Eu(III) concentrations. The Tb-Zn-based framework {[Tb3Zn6(bipy2)2(Hmimda)7 (H2O)3]·5H2O}n (3; H3mimda = 2-methyl-1-H-imidazole-4,5-dicarboxylic acid and bipy = 4,4'-bipyridine) can detect trace Mg(II) ion with relatively high sensitivity and selectivity. Dehydrated MOF 3a shows a remarkable emission quenching effect through the introduction of I2 solids. Further investigation indicates that it exhibits turn on/off switchable properties for small solvent molecules or heavy-metal ions. Steady/transient-state near-IR luminescence properties for MOFs 1, 4, and 5 were investigated under visible-light excitation.

  2. Broadband cross-polarization-based heteronuclear dipolar recoupling for structural and dynamic NMR studies of rigid and soft solids.

    PubMed

    Kharkov, B B; Chizhik, V I; Dvinskikh, S V

    2016-01-21

    Dipolar recoupling is an essential part of current solid-state NMR methodology for probing atomic-resolution structure and dynamics in solids and soft matter. Recently described magic-echo amplitude- and phase-modulated cross-polarization heteronuclear recoupling strategy aims at efficient and robust recoupling in the entire range of coupling constants both in rigid and highly dynamic molecules. In the present study, the properties of this recoupling technique are investigated by theoretical analysis, spin-dynamics simulation, and experimentally. The resonance conditions and the efficiency of suppressing the rf field errors are examined and compared to those for other recoupling sequences based on similar principles. The experimental data obtained in a variety of rigid and soft solids illustrate the scope of the method and corroborate the results of analytical and numerical calculations. The technique benefits from the dipolar resolution over a wider range of coupling constants compared to that in other state-of-the-art methods and thus is advantageous in studies of complex solids with a broad range of dynamic processes and molecular mobility degrees.

  3. Direct writing of CoFe alloy nanostructures by focused electron beam induced deposition from a heteronuclear precursor

    NASA Astrophysics Data System (ADS)

    Porrati, F.; Pohlit, M.; Müller, J.; Barth, S.; Biegger, F.; Gspan, C.; Plank, H.; Huth, M.

    2015-11-01

    Recently, focused electron beam-induced deposition has been employed to prepare functional magnetic nanostructures with potential in nanomagnetic logic and sensing applications by using homonuclear precursor gases like Fe(CO)5 or Co2(CO)8. Here we show that an extension towards the fabrication of bi-metallic compounds is possible by using a single-source heteronuclear precursor gas. We have grown CoFe alloy magnetic nanostructures from the HFeCo3(CO)12 metal carbonyl precursor. The compositional analysis indicates that the samples contain about 80 at% of metal and 10 at% of carbon and oxygen. Four-probe magnetotransport measurements are carried out on nanowires of various sizes down to a width of 50 nm, for which a room temperature resistivity of 43 μΩcm is found. Micro-Hall magnetometry reveals that 50 nm × 250 nm nanobars of the material are ferromagnetic up to the highest measured temperature of 250 K. Finally, the transmission electron microscopy (TEM) microstructural investigation shows that the deposits consist of a bcc Co-Fe phase mixed with a FeCo2 O4 spinel oxide phase with nanograins of about 5 nm diameter.

  4. Parameter independent low-power heteronuclear decoupling for fast magic-angle spinning solid-state NMR.

    PubMed

    Equbal, Asif; Madhu, P K; Meier, Beat H; Nielsen, Niels Chr; Ernst, Matthias; Agarwal, Vipin

    2017-02-28

    Major advances have recently been made in the field of heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance (NMR). These developments have improved the resolution and sensitivity of the NMR spectrum of spins coupled to protons. One such new scheme, denoted as rCW(ApA), has proven to be robust with practically no need for parameter optimization [A. Equbal et al. Chem. Phys. Lett., 635, 339 (2015)]. Most of the experiments with rCW(ApA) have been carried out in the regimes of slow to moderate magic-angle spinning while simultaneously applying high decoupling radio-frequency amplitudes. Here, we explore the performance of the rCW(ApA) sequence and its predecessor rCW(A) in the regime of low-power radio-frequency irradiation and fast magic-angle spinning. The robustness of the refocused continuous-wave (rCW) schemes to experimental parameters such as pulse lengths and offset irradiation is demonstrated. Numerical simulations and analytical theory have been used to understand the effects of various nuclear spin interactions on the decoupling performance of the low-power rCW decoupling scheme relative to other decoupling methods. This has lead to the design of an "optimum low-power decoupling sequence" that can be used without parameter optimization. This result is particularly important in the context of samples with low signal to noise.

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

    PubMed Central

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

    2013-01-01

    Resonance assignment is the first step in NMR structure determination. For magic angle spinning NMR, this is typically achieved with a set of heteronuclear correlation experiments (NCaCX, NCOCX, CONCa) that utilize SPECIFIC-CP 15N-13C transfers. However, the SPECIFIC-CP transfer efficiency is often compromised by molecular dynamics and probe performance. Here we show that one-bond ZF-TEDOR 15N-13C transfers provide simultaneous NCO and NCa transfers with at least as much sensitivity as SPECIFIC-CP for some non-crystalline samples. Furthermore, a 3D TEDOR-CC experiment provides heteronuclear sidechains correlations and robustness with respect to proton decoupling and radiofrequency power instabilities. We demonstrate transfer efficiencies and connectivities by application of 3D ZF-TEDOR-DARR to a model microcrystalline protein, GB1, and a less ideal system, GvpA in intact gas vesicles. PMID:23334347

  6. Backbone and side–chain heteronuclear resonance assignments and hyperfine NMR shifts in horse cytochrome c

    PubMed Central

    Liu, Weixia; Rumbley, Jon; Englander, S. Walter; Wand, A. Joshua

    2003-01-01

    The [H26N, H33N] mutant of horse heart cytochrome c was expressed in E. coli during growth on isotopically enriched minimal media. Complete resonance assignments of both the diamagnetic reduced (spin zero) and paramagnetic oxidized (spin ½) states of the protein were obtained using standard triple resonance and total correlation spectroscopy using the previously determined 1H chemical shifts of the wild-type protein as a guide. The correspondence of chemical shifts between the wild type and the mutant protein is excellent, indicating that they have nearly identical structures. The expanded library of chemical shifts for both redox states in both proteins allowed the refinement of the electron spin g-tensor of the oxidized states. The g-tensors of the oxidized states of the wild-type and [H26N, H33N] mutant proteins are closely similar, indicating that the subtle details of the ligand fields are nearly identical. The refined g-tensors were then used to probe for redox-dependent structure change in the two proteins. PMID:12931009

  7. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Sharma, Kshama; Madhu, P. K.; Agarwal, Vipin

    2016-09-01

    The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1 = n · νr). Recently, two schemes, namely, PISSARRO and rCWApA, have been shown to be less affected by the problem of MAS and RF interference, specifically at the n = 2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n = 1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40 kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power 1H irradiation of ca.195 kHz.

  8. Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments.

    PubMed

    Papaioannou, Vasileios; Lafitte, Thomas; Avendaño, Carlos; Adjiman, Claire S; Jackson, George; Müller, Erich A; Galindo, Amparo

    2014-02-07

    A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative properties of

  9. How to face the low intrinsic sensitivity of 2D heteronuclear NMR with fast repetition techniques: go faster to go higher !

    PubMed

    Farjon, Jonathan

    2017-04-13

    Nuclear Magnetic Resonance (NMR) is one of the most widely used analytical techniques in numerous domains where molecules are objects of investigation. However, major limitations of multidimensional NMR experiments come from their low sensitivity and from the long times needed for their acquisition. In order to overcome such limitations, fast repetition NMR techniques allowed for the reduction of 2D experimental time and for the conversion of the gained time into a higher number of scans leading to a better sensitivity. Thus, fast repetition 2D heteronuclear NMR techniques have allowed new advances in NMR, especially to access infomation on low abundant nuclei, to enhance the detection of low concentrated compounds and to probe weak interactions like hydrogen bonds at natural abundance.

  10. Significance of symmetry in the nuclear spin Hamiltonian for efficient heteronuclear dipolar decoupling in solid-state NMR: A Floquet description of supercycled rCW schemes

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Shankar, Ravi; Leskes, Michal; Vega, Shimon; Nielsen, Niels Chr.; Madhu, P. K.

    2017-03-01

    Symmetry plays an important role in the retention or annihilation of a desired interaction Hamiltonian in NMR experiments. Here, we explore the role of symmetry in the radio-frequency interaction frame Hamiltonian of the refocused-continuous-wave (rCW) pulse scheme that leads to efficient 1H heteronuclear decoupling in solid-state NMR. It is demonstrated that anti-periodic symmetry of single-spin operators (Ix, Iy, Iz) in the interaction frame can lead to complete annihilation of the 1H-1H homonuclear dipolar coupling effects that induce line broadening in solid-state NMR experiments. This symmetry also plays a critical role in cancelling or minimizing the effect of 1H chemical-shift anisotropy in the effective Hamiltonian. An analytical description based on Floquet theory is presented here along with experimental evidences to understand the decoupling efficiency of supercycled (concatenated) rCW scheme.

  11. Significance of symmetry in the nuclear spin Hamiltonian for efficient heteronuclear dipolar decoupling in solid-state NMR: A Floquet description of supercycled rCW schemes.

    PubMed

    Equbal, Asif; Shankar, Ravi; Leskes, Michal; Vega, Shimon; Nielsen, Niels Chr; Madhu, P K

    2017-03-14

    Symmetry plays an important role in the retention or annihilation of a desired interaction Hamiltonian in NMR experiments. Here, we explore the role of symmetry in the radio-frequency interaction frame Hamiltonian of the refocused-continuous-wave (rCW) pulse scheme that leads to efficient (1)H heteronuclear decoupling in solid-state NMR. It is demonstrated that anti-periodic symmetry of single-spin operators (Ix, Iy, Iz) in the interaction frame can lead to complete annihilation of the (1)H-(1)H homonuclear dipolar coupling effects that induce line broadening in solid-state NMR experiments. This symmetry also plays a critical role in cancelling or minimizing the effect of (1)H chemical-shift anisotropy in the effective Hamiltonian. An analytical description based on Floquet theory is presented here along with experimental evidences to understand the decoupling efficiency of supercycled (concatenated) rCW scheme.

  12. 19F single-quantum and 19F-33S heteronuclear multiple-quantum coherence NMR of SF6 in thermotropic nematogens and in the gas phase.

    PubMed

    Tervonen, Henri; Saunavaara, Jani; Ingman, L Petri; Jokisaari, Jukka

    2006-08-24

    (19)F single-quantum (SQC) and (19)F-(33)S heteronuclear multiple-quantum coherence (HMQC) NMR spectroscopy of sulfur hexafluoride (SF(6)) dissolved in thermotropic liquid crystals (TLCs) were used to investigate the properties of TLCs. On one hand, environmental effects on the NMR parameters of SF(6), (19)F nuclear shielding, (19)F-(33)S spin-spin coupling, secondary isotope effects of sulfur on (19)F shielding, and the self-diffusion coefficient in the direction of the external magnetic field were studied as well. The temperature dependence of the (19)F shielding of SF(6) in TLCs was modeled with a function that takes into account the properties of both TLC and SF(6). It appears that the TLC environment deforms the electronic system of SF(6) so that the (19)F shielding tensor becomes slightly anisotropic, with the anisotropy being from -0.5 to -1.4 ppm, depending upon the TLC solvent. On the contrary, no sign of residual dipolar coupling between (19)F and (33)S was found, meaning that the so-called deformational effects, which arise from the interaction between vibrational and reorientational motions of the molecule, on the geometry of the molecule are insignificant. Diffusion activation energies, E(a), were determined from the temperature dependence of the self-diffusion coefficients. In each TLC, E(a) increases when moving from an isotropic phase to a nematic phase. The spin-spin coupling constant, J((19)F,(33)S), increases by ca. 10 Hz when moving from the gas phase to TLC solutions. The secondary isotope shifts of (19)F shielding are practically independent of TLC solvent and temperature. For the first time, (19)F-(33)S heteronuclear multiple-quantum NMR spectra were recorded for SF(6) in the gas phase and in a liquid-crystalline solution.

  13. 4-Oxalocrotonate tautomerase, a 41-kDa homohexamer: backbone and side-chain resonance assignments, solution secondary structure, and location of active site residues by heteronuclear NMR spectroscopy.

    PubMed Central

    Stivers, J. T.; Abeygunawardana, C.; Whitman, C. P.; Mildvan, A. S.

    1996-01-01

    4-Oxalocrotonate tautomerase (4-OT), a homohexamer consisting of 62 residues per subunit, catalyzes the isomerization of unsaturated alpha-keto acids using Pro-1 as a general base (Stivers et al., 1996a, 1996b). We report the backbone and side-chain 1H, 15N, and 13C NMR assignments and the solution secondary structure for 4-OT using 2D and 3D homonuclear and heteronuclear NMR methods. The subunit secondary structure consists of an alpha-helix (residues 13-30), two beta-strands (beta 1, residues 2-8; beta 2, residues 39-45), a beta-hairpin (residues 50-57), two loops (I, residues 9-12; II, 34-38), and two turns (I, residues 30-33; II, 47-50). The remaining residues form coils. The beta 1 strand is parallel to the beta 2 strand of the same subunit on the basis of cross stand NH(i)-NH(j) NOEs in a 2D 15N-edited 1H-NOESY spectrum of hexameric 4-OT containing two 15N-labeled subunits/hexamer. The beta 1 strand is also antiparallel to another beta 1 strand from an adjacent subunit forming a subunit interface. Because only three such pairwise interactions are possible, the hexamer is a trimer of dimers. The diffusion constant, determined by dynamic light scattering, and the rotational correlation time (14.5 ns) estimated from 15N T1/T2 measurements, are consistent with the hexameric molecular weight of 41 kDa. Residue Phe-50 is in the active site on the basis of transferred NOEs to the bound partial substrate 2-oxo-1,6-hexanedioate. Modification of the general base, Pro-1, with the active site-directed irreversible inhibitor, 3-bromopyruvate, significantly alters the amide 15N and NH chemical shifts of residues in the beta-hairpin and in loop II, providing evidence that these regions change conformation when the active site is occupied. PMID:8845763

  14. Altered nitrogen metabolism associated with de-differentiated suspension cultures derived from root cultures of Datura stramonium studied by heteronuclear multiple bond coherence (HMBC) NMR spectroscopy.

    PubMed

    Fliniaux, Ophélie; Mesnard, François; Raynaud-Le Grandic, Sophie; Baltora-Rosset, Sylvie; Bienaimé, Christophe; Robins, Richard J; Fliniaux, Marc-André

    2004-05-01

    De-differentiation of transformed root cultures of Datura stramonium has previously been shown to cause a loss of tropane alkaloid synthetic capacity. This indicates a marked shift in physiological status, notably in the flux of primary metabolites into tropane alkaloids. Nitrogen metabolism in transformed root cultures of D. stramonium (an alkaloid-producing system) and de-differentiated suspension cultures derived therefrom (a non-producing system) has been compared using Nuclear Magnetic Resonance (NMR) spectroscopy. (15)N-Labelled precursors [((15)NH(4))(2)SO(4) and K(15)NO(3)] were fed and their incorporation into nitrogenous metabolites studied using Heteronuclear Multiple Bond Coherence (HMBC) NMR spectroscopy. In both cultures, the same amino acids were resolved in the HMBC spectra. However, marked differences were found in the intensity of labelling of a range of nitrogenous compounds. In differentiated root cultures, cross-peaks corresponding to secondary metabolites, such as tropine, were observed, whereas these were absent in the de-differentiated cultures. By contrast, N- acetylputrescine and gamma-aminobutyric acid (GABA) accumulated in the de-differentiated cultures to a much larger extent than in the root cultures. It can therefore be suggested that the loss of alkaloid biosynthesis was compensated by the diversion of putrescine metabolism away from the tropane pathway and toward the synthesis of GABA via N-acetylputrescine.

  15. Structures and standard molar enthalpies of formation of a series of Ln(III)-Cu(II) heteronuclear compounds with pyrazine-2,3-dicarboxylic acid

    NASA Astrophysics Data System (ADS)

    Yang, Qi; Xie, Gang; Wei, Qing; Chen, Sanping; Gao, Shengli

    2014-07-01

    Fifteen lanthanide-copper heteronuclear compounds, formulated as [CuLn2(pzdc)4(H2O)6]·xH2O (1-6(x=2), 8(x=3), 9-10(x=4); [CuLn2(pzdc)4(H2O)4]·xH2O (7, 12-13, 15(x=4), 14(x=5), 11(x=8) (Ln(III)=La(1); Ce(2); Pr(3); Nd(4); Sm(5); Eu(6); Gd(7); Tb(8); Dy(9); Ho(10); Er(11); Tm(12); Yb(13); Lu(14); Y(15); H2pzdc (C6H4N2O4)=pyrazine-2,3-dicarboxylic acid) have been hydrothermally synthesized. All compounds were characterized by element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analyses confirm that all compounds are isostructural and feature a 3D brick-like framework structure with {4.62}2{42.62.82}{63}2{65.8}2 topology. Using 1 mol cm-3 HCl(aq) as calorimetric solvent, with an isoperibol solution-reaction calorimeter, the standard molar enthalpies of formation of all compounds were determined by a designed thermochemical cycle. In addition, solid state luminescence properties of compounds 5, 6, 8 and 9 were studied in the solid state.

  16. Evidence for the binding of phosphate ion to the C-terminus region in Abeta1-40 using heteronuclear NMR analyses.

    PubMed

    Nagata-Uchiyama, Makiko; Abe, Yoshito; Monji, Akira; Kanba, Shigenobu; Ueda, Tadashi

    2010-02-01

    Amyloid fibril formation of amyloid beta peptide 1-40 (Abeta 1-40) was reported to be retarded in the presence of 150mM phosphate buffer at pH 7 [Monji, Ustumi, Ueda, Imoto, Yoshida, Hashioka, Tashiro and Tashiro, J. Neurochemistry, 77, 1425-1432 (2007)]. In order to elucidate the reason why phosphate ion retards the amyloid fibril formation, we examined the preferential binding sites of phosphate ion to Abeta 1-40 using chemical shift perturbation analysis of heteronuclear NMR. In titration analysis of (15)N-labeled Abeta1-40 in the presence of 150 mM phosphate ion or 150 mM chloride ion, we identified the residues affected by these ions in Abeta 1-40. As a result, we found the tendency that phosphate ion preferentially bound to some residues located on the C-terminus region where the region was reported to be the potential beta-strand region in Abeta1-40. Therefore, we suggested that phosphate ions interacted with the potential beta-strand region in Abeta1-40 to be hard to form beta-sheet in Abeta 1-40, resulting in retardation of the amyloid fibril formation.

  17. Opposite Dysregulation of Fragile-X Mental Retardation Protein and Heteronuclear Ribonucleoprotein C Protein Associates with Enhanced APP Translation in Alzheimer Disease.

    PubMed

    Borreca, Antonella; Gironi, Katia; Amadoro, Giusy; Ammassari-Teule, Martine

    2016-07-01

    Amyloid precursor protein (APP) is overexpressed in familiar and sporadic Alzheimer Disease (AD) patients suggesting that, in addition to abnormalities in APP cleavage, enhanced levels of APP full length might contribute to the pathology. Based on data showing that the two RNA binding proteins (RBPs), Fragile-X Mental Retardation Protein (FMRP) and heteronuclear Ribonucleoprotein C (hnRNP C), exert an opposite control on APP translation, we have analyzed whether expression and translation of these two RBPs vary in relation to changes in APP protein and mRNA levels in the AD brain at 1, 3, and 6 months of age. Here, we show that, as expected, human APP is overexpressed in hippocampal total extract from Tg2576 mice at all age points. APP overexpression, however, is not stable over time but reaches its maximal level in 1-month-old mutants in association with the stronger (i) reduction of FMRP and (ii) augmentation of hnRNP C. APP levels then decrease progressively as a function of age in close relationship with the gradual normalization of FMRP and hnRNP C levels. Consistent with the mouse data, expression of FMRP and hnRNP C are, respectively, decreased and increased in hippocampal synaptosomes from sporadic AD patients. Our findings identify two RBP targets that might be manipulated for reducing abnormally elevated levels of APP in the AD brain, with the hypothesis that acting upstream of amyloidogenic processing might contribute to attenuate the amyloid burden.

  18. Structure and chemistry of the heteronuclear oxo-cluster [VPO4]•+: a model system for the gas-phase oxidation of small hydrocarbons.

    PubMed

    Dietl, Nicolas; Wende, Torsten; Chen, Kai; Jiang, Ling; Schlangen, Maria; Zhang, Xinhao; Asmis, Knut R; Schwarz, Helmut

    2013-03-06

    The heteronuclear oxo-cluster [VPO4](•+) is generated via electrospray ionization and investigated with respect to both its electronic structure as well as its gas-phase reactivity toward small hydrocarbons, thus permitting a comparison to the well-known vanadium-oxide cation [V2O4](•+). As described in previous studies, the latter oxide exhibits no or just minor reactivity toward small hydrocarbons, such as CH4, C2H6, C3H8, n-C4H10, and C2H4, while substitution of one vanadium by a phosphorus atom yields the reactive [VPO4](•+) ion; the latter brings about oxidative dehydrogenation (ODH) of saturated hydrocarbons, e.g., propane and butane as well as oxygen-atom transfer (OAT) to unsaturated hydrocarbons, e.g. ethene, at thermal conditions. Further, the gas-phase structure of [VPO4](•+) is determined by IR photodissociation spectroscopy and compared to that of [V2O4](•+). DFT calculations help to elucidate the reaction mechanism. The results underline the crucial role of phosphorus in terms of C-H bond activation of hydrocarbons by mixed VPO clusters.

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

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-12-01

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

  20. Striking Doping Effects on Thermal Methane Activation Mediated by the Heteronuclear Metal Oxides [XAlO4 ](.+) (X=V, Nb, and Ta).

    PubMed

    Wu, Xiao-Nan; Li, Jilai; Schlangen, Maria; Zhou, Shaodong; González-Navarrete, Patricio; Schwarz, Helmut

    2017-01-18

    The thermal reactivity of the heteronuclear metal-oxide cluster cations [XAlO4 ](.+) (X=V, Nb, and Ta) towards methane has been studied by using mass spectrometry in conjunction with quantum mechanical calculations. Experimentally, a hydrogen-atom transfer (HAT) from methane is mediated by all the three oxide clusters at ambient conditions. However, [VAlO4 ](.+) is unique in that this cluster directly transforms methane into formaldehyde. The absence of this reaction for the Nb and Ta analogues demonstrates a striking doping effect on the chemoselectivity in the conversion of methane. Mechanistic aspects of the two reactions have been elucidated by quantum-chemical calculations. The HAT reactivity can be attributed to the significant spin density localized at the terminal oxygen atom (Ot(.-) ) of the cluster ions, while the ionic/covalent character of the Lewis acid-base unit [X-Ob ] plays a crucial role for the generation of formaldehyde. The mechanistic insight derived from this combined experimental/computational investigation may provide guidance for a more rational design of catalysts.

  1. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    SciTech Connect

    Hou, Guangjin E-mail: tpolenov@udel.edu; Lu, Xingyu E-mail: lexvega@comcast.net; Vega, Alexander J. E-mail: lexvega@comcast.net; Polenova, Tatyana E-mail: tpolenov@udel.edu

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear {sup 1}H-X (X = {sup 13}C, {sup 15}N, {sup 31}P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the {sup 1}H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the {sup 1}H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from {sup 1}H chemical shift anisotropy, while keeping the {sup 1}H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [{sup 15}N]-N-acetyl-valine and [U-{sup 13}C,{sup 15}N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate {sup 1}H-{sup 15}N dipolar couplings in the context of 3D experiments is presented on U-{sup 13}C,{sup 15}N-enriched dynein light chain protein LC8.

  2. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy.

    PubMed

    Hou, Guangjin; Lu, Xingyu; Vega, Alexander J; Polenova, Tatyana

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear (1)H-X (X = (13)C, (15)N, (31)P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the (1)H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the (1)H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from (1)H chemical shift anisotropy, while keeping the (1)H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [(15)N]-N-acetyl-valine and [U-(13)C,(15)N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate (1)H-(15)N dipolar couplings in the context of 3D experiments is presented on U-(13)C,(15)N-enriched dynein light chain protein LC8.

  3. 1H–13C hetero-nuclear dipole–dipole couplings of methyl groups in stationary and magic angle spinning solid-state NMR experiments of peptides and proteins

    PubMed Central

    Wu, Chin H.; Das, Bibhuti B.; Opella, Stanley J.

    2010-01-01

    13C NMR of isotopically labeled methyl groups has the potential to combine spectroscopic simplicity with ease of labeling for protein NMR studies. However, in most high resolution separated local field experiments, such as polarization inversion spin exchange at the magic angle (PISEMA), that are used to measure 1H–13C hetero-nuclear dipolar couplings, the four-spin system of the methyl group presents complications. In this study, the properties of the 1H–13C hetero-nuclear dipolar interactions of 13C-labeled methyl groups are revealed through solid-state NMR experiments on a range of samples, including single crystals, stationary powders, and magic angle spinning of powders, of 13C3 labeled alanine alone and incorporated into a protein. The spectral simplifications resulting from proton detected local field (PDLF) experiments are shown to enhance resolution and simplify the interpretation of results on single crystals, magnetically aligned samples, and powders. The complementarity of stationary sample and magic angle spinning (MAS) measurements of dipolar couplings is demonstrated by applying polarization inversion spin exchange at the magic angle and magic angle spinning (PISEMAMAS) to unoriented samples. PMID:19896874

  4. Heteronuclear Micro-Helmholtz Coil Facilitates µm-Range Spatial and Sub-Hz Spectral Resolution NMR of nL-Volume Samples on Customisable Microfluidic Chips.

    PubMed

    Spengler, Nils; Höfflin, Jens; Moazenzadeh, Ali; Mager, Dario; MacKinnon, Neil; Badilita, Vlad; Wallrabe, Ulrike; Korvink, Jan G

    2016-01-01

    We present a completely revised generation of a modular micro-NMR detector, featuring an active sample volume of ∼ 100 nL, and an improvement of 87% in probe efficiency. The detector is capable of rapidly screening different samples using exchangeable, application-specific, MEMS-fabricated, microfluidic sample containers. In contrast to our previous design, the sample holder chips can be simply sealed with adhesive tape, with excellent adhesion due to the smooth surfaces surrounding the fluidic ports, and so withstand pressures of ∼2.5 bar, while simultaneously enabling high spectral resolution up to 0.62 Hz for H2O, due to its optimised geometry. We have additionally reworked the coil design and fabrication processes, replacing liquid photoresists by dry film stock, whose final thickness does not depend on accurate volume dispensing or precise levelling during curing. We further introduced mechanical alignment structures to avoid time-intensive optical alignment of the chip stacks during assembly, while we exchanged the laser-cut, PMMA spacers by diced glass spacers, which are not susceptible to melting during cutting. Doing so led to an overall simplification of the entire fabrication chain, while simultaneously increasing the yield, due to an improved uniformity of thickness of the individual layers, and in addition, due to more accurate vertical positioning of the wirebonded coils, now delimited by a post base plateau. We demonstrate the capability of the design by acquiring a 1H spectrum of ∼ 11 nmol sucrose dissolved in D2O, where we achieved a linewidth of 1.25 Hz for the TSP reference peak. Chemical shift imaging experiments were further recorded from voxel volumes of only ∼ 1.5 nL, which corresponded to amounts of just 1.5 nmol per voxel for a 1 M concentration. To extend the micro-detector to other nuclei of interest, we have implemented a trap circuit, enabling heteronuclear spectroscopy, demonstrated by two 1H/13C 2D HSQC experiments.

  5. Heteronuclear Micro-Helmholtz Coil Facilitates µm-Range Spatial and Sub-Hz Spectral Resolution NMR of nL-Volume Samples on Customisable Microfluidic Chips

    PubMed Central

    Spengler, Nils; Höfflin, Jens; Moazenzadeh, Ali; Mager, Dario; MacKinnon, Neil; Badilita, Vlad; Wallrabe, Ulrike; Korvink, Jan G.

    2016-01-01

    We present a completely revised generation of a modular micro-NMR detector, featuring an active sample volume of ∼ 100 nL, and an improvement of 87% in probe efficiency. The detector is capable of rapidly screening different samples using exchangeable, application-specific, MEMS-fabricated, microfluidic sample containers. In contrast to our previous design, the sample holder chips can be simply sealed with adhesive tape, with excellent adhesion due to the smooth surfaces surrounding the fluidic ports, and so withstand pressures of ∼2.5 bar, while simultaneously enabling high spectral resolution up to 0.62 Hz for H2O, due to its optimised geometry. We have additionally reworked the coil design and fabrication processes, replacing liquid photoresists by dry film stock, whose final thickness does not depend on accurate volume dispensing or precise levelling during curing. We further introduced mechanical alignment structures to avoid time-intensive optical alignment of the chip stacks during assembly, while we exchanged the laser-cut, PMMA spacers by diced glass spacers, which are not susceptible to melting during cutting. Doing so led to an overall simplification of the entire fabrication chain, while simultaneously increasing the yield, due to an improved uniformity of thickness of the individual layers, and in addition, due to more accurate vertical positioning of the wirebonded coils, now delimited by a post base plateau. We demonstrate the capability of the design by acquiring a 1H spectrum of ∼ 11 nmol sucrose dissolved in D2O, where we achieved a linewidth of 1.25 Hz for the TSP reference peak. Chemical shift imaging experiments were further recorded from voxel volumes of only ∼ 1.5nL, which corresponded to amounts of just 1.5 nmol per voxel for a 1 M concentration. To extend the micro-detector to other nuclei of interest, we have implemented a trap circuit, enabling heteronuclear spectroscopy, demonstrated by two 1H/13C 2D HSQC experiments. PMID

  6. A study of dipolar interactions and dynamic processes of water molecules in tendon by 1H and 2H homonuclear and heteronuclear multiple-quantum-filtered NMR spectroscopy.

    PubMed

    Eliav, U; Navon, G

    1999-04-01

    The effect of proton exchange on the measurement of 1H-1H, 1H-2H, and 2H-2H residual dipolar interactions in water molecules in bovine Achilles tendons was investigated using double-quantum-filtered (DQF) NMR and new pulse sequences based on heteronuclear and homonuclear multiple-quantum filtering (MQF). Derivation of theoretical expressions for these techniques allowed evaluation of the 1H-1H and 1H-2H residual dipolar interactions and the proton exchange rate at a temperature of 24 degrees C and above, where no dipolar splitting is evident. The values obtained for these parameters at 24 degrees C were 300 and 50 Hz and 3000 s-1, respectively. The results for the residual dipolar interactions were verified by repeating the above measurements at a temperature of 1.5 degrees C, where the spectra of the H2O molecules were well resolved, so that the 1H-1H dipolar interaction could be determined directly from the observed splitting. Analysis of the MQF experiments at 1.5 degrees C, where the proton exchange was in the intermediate regime for the 1H-2H dipolar interaction, confirmed the result obtained at 24 degrees C for this interaction. A strong dependence of the intensities of the MQF signals on the proton exchange rate, in the intermediate and the fast exchange regimes, was observed and theoretically interpreted. This leads to the conclusion that the MQF techniques are mostly useful for tissues where the residual dipolar interaction is not significantly smaller than the proton exchange rate. Dependence of the relaxation times and signal intensities of the MQF experiments on the orientation of the tendon with respect to the magnetic field was observed and analyzed. One of the results of the theoretical analysis is that, in the fast exchange regime, the signal decay rates in the MQF experiments as well as in the spin echo or CPMG pulse sequences (T2) depend on the orientation as the square of the second-rank Legendre polynomial.

  7. Electronic Origins of the Variable Efficiency of Room-Temperature Methane Activation by Homo- and Heteronuclear Cluster Oxide Cations [XYO2](+) (X, Y = Al, Si, Mg): Competition between Proton-Coupled Electron Transfer and Hydrogen-Atom Transfer.

    PubMed

    Li, Jilai; Zhou, Shaodong; Zhang, Jun; Schlangen, Maria; Weiske, Thomas; Usharani, Dandamudi; Shaik, Sason; Schwarz, Helmut

    2016-06-29

    The reactivity of the homo- and heteronuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) toward methane was studied using Fourier transform ion cyclotron resonance mass spectrometry, in conjunction with high-level quantum mechanical calculations. The most reactive cluster by both experiment and theory is [Al2O2](•+). In its favorable pathway, this cluster abstracts a hydrogen atom by means of proton-coupled electron transfer (PCET) instead of following the conventional hydrogen-atom transfer (HAT) route. This mechanistic choice originates in the strong Lewis acidity of the aluminum site of [Al2O2](•+), which cleaves the C-H bond heterolytically to form an Al-CH3 entity, while the proton is transferred to the bridging oxygen atom of the cluster ion. In addition, a comparison of the reactivity of heteronuclear and homonuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) reveals a striking doping effect by aluminum. Thus, the vacant s-p hybrid orbital on Al acts as an acceptor of the electron pair from methyl anion (CH3(-)) and is therefore eminently important for bringing about thermal methane activation by PCET. For the Al-doped cluster ions, the spin density at an oxygen atom, which is crucial for the HAT mechanism, acts here as a spectator during the course of the PCET mediated C-H bond cleavage. A diagnostic plot of the deformation energy vis-à-vis the barrier shows the different HAT/PCET reactivity map for the entire series. This is a strong connection to the recently discussed mechanism of oxidative coupling of methane on magnesium oxide surfaces proceeding through Grignard-type intermediates.

  8. Optical Correlation

    NASA Technical Reports Server (NTRS)

    Cotariu, Steven S.

    1991-01-01

    Pattern recognition may supplement or replace certain navigational aids on spacecraft in docking or landing activities. The need to correctly identify terrain features remains critical in preparation of autonomous planetary landing. One technique that may solve this problem is optical correlation. Correlation has been successfully demonstrated under ideal conditions; however, noise significantly affects the ability of the correlator to accurately identify input signals. Optical correlation in the presence of noise must be successfully demonstrated before this technology can be incorporated into system design. An optical correlator is designed and constructed using a modified 2f configuration. Liquid crystal televisions (LCTV) are used as the spatial light modulators (SLM) for both the input and filter devices. The filter LCTV is characterized and an operating curve is developed. Determination of this operating curve is critical for reduction of input noise. Correlation of live input with a programmable filter is demonstrated.

  9. Estimation of conventional C-Hπ (arene), unconventional C-Hπ (chelate) and C-Hπ (thiocyanate) interactions in hetero-nuclear nickel(ii)-cadmium(ii) complexes with a compartmental Schiff base.

    PubMed

    Roy, Sourav; Drew, Michael G B; Bauzá, Antonio; Frontera, Antonio; Chattopadhyay, Shouvik

    2017-04-07

    Three new heteronuclear nickel(ii)/cadmium(ii) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)2] (1), [(SCN)(CH3CO2)Cd(L)Ni(CH3OH)2] (2) and [(SCN)(Cl)Cd(L)Ni(NH2CH2CH2CH2NH2)]n (3) {where H2L = N,N'-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N2O4 compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N2O2 environment and cadmium(ii) is placed in the outer O4 compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C-Hπ (chelate) interactions in the solid state of both complexes and C-Hπ (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2-6 ns.

  10. Interaction with DNA of a heteronuclear [Na2Cu4] coordination cluster obtained from the assembly of two hydroxo-bridged [Cu(II)2] units by a dimeric sodium nitrate template.

    PubMed

    Mandal, Debashree; Chauhan, Mala; Arjmand, Farukh; Aromí, Guillem; Ray, Debashis

    2009-11-14

    The heteronuclear [Na(2)Cu(4)(bemp)(2)(OH)(2)(NO(3))(2)(OH(2))(4)] x 5 H(2)O (1 x 5H(2)O; H(3)bemp: 2,6-bis-[(2-hydroxyethylimino)-methyl]-4-methyl-phenol) cluster has been synthesized in aqueous-methanol at room temperature and structurally characterized. The water soluble complex is obtained from the template assembly of two [Cu(2)(bemp)(OH)] neutral fragments through their weak oxophillic interactions with two interconnected NaNO(3) units as core. Four [Na(2)Cu(4)] units form a metal-organic cage arrangement in the crystal lattice that traps a (H(2)O)(7) cluster. Variable-temperature magnetic susceptibility measurements (2-300 K) reveals a strong antiferromagnetic coupling between the Cu(II) ions within the dimers with J = -124.1 cm(-1) (in the H = -2JS(1)S(2) convention). The interaction of complex 1 x 3H(2)O with calf thymus DNA (binding constant K(b), 4.6 x 10(4) M(-1)) in Tris buffer was studied by UV-visible and emission titration, and cyclic voltammetry. The hexanuclear Na(2)Cu(4) complex also binds double-stranded supercoiled plasmid pBR322 DNA and displays efficient hydrolytic cleavage. The hydrolytic mechanism is supported by evidence from DNA relegation employing T4 ligase assay and reactive oxygen species (ROS) quenching cleavage experiments.

  11. Correlative Tomography

    PubMed Central

    Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.

    2014-01-01

    Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640

  12. Proton-detected 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H-1H RFDR mixing on a natural abundant sample under ultrafast MAS

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-09-01

    In this contribution, we have demonstrated a proton detection-based approach on a natural abundant powdered L-Histidine HCl-H2O sample at ultrafast magic angle spinning (MAS) to accomplish 14N/14N correlation from a 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H finite-pulse radio frequency-driven recoupling (fp-RFDR). Herein the heteronuclear magnetization transfer between 14N and 1H has been achieved by HMQC experiment, whereas 14N/14N correlation is attained through enhanced 1H-1H spin diffusion process due to 1H-1H dipolar recoupling during the RFDR mixing. While the use of ultrafast MAS (90 kHz) provides sensitivity enhancement through increased 1H transverse relaxation time (T2), the use of micro-coil probe which can withstand strong 14N radio frequency (RF) fields further improves the sensitivity per unit sample volume.

  13. Correlative microscopy.

    PubMed

    Loussert Fonta, Céline; Humbel, Bruno M

    2015-09-01

    In recent years correlative microscopy, combining the power and advantages of different imaging system, e.g., light, electrons, X-ray, NMR, etc., has become an important tool for biomedical research. Among all the possible combinations of techniques, light and electron microscopy, have made an especially big step forward and are being implemented in more and more research labs. Electron microscopy profits from the high spatial resolution, the direct recognition of the cellular ultrastructure and identification of the organelles. It, however, has two severe limitations: the restricted field of view and the fact that no live imaging can be done. On the other hand light microscopy has the advantage of live imaging, following a fluorescently tagged molecule in real time and at lower magnifications the large field of view facilitates the identification and location of sparse individual cells in a large context, e.g., tissue. The combination of these two imaging techniques appears to be a valuable approach to dissect biological events at a submicrometer level. Light microscopy can be used to follow a labelled protein of interest, or a visible organelle such as mitochondria, in time, then the sample is fixed and the exactly same region is investigated by electron microscopy. The time resolution is dependent on the speed of penetration and fixation when chemical fixatives are used and on the reaction time of the operator for cryo-fixation. Light microscopy can also be used to identify cells of interest, e.g., a special cell type in tissue or cells that have been modified by either transfections or RNAi, in a large population of non-modified cells. A further application is to find fluorescence labels in cells on a large section to reduce searching time in the electron microscope. Multiple fluorescence labelling of a series of sections can be correlated with the ultrastructure of the individual sections to get 3D information of the distribution of the marked proteins: array

  14. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-21

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t{sub 1} and t{sub 3} periods, respectively. In addition to through-space and through-bond {sup 13}C/{sup 1}H and {sup 13}C/{sup 13}C chemical shift correlations, the 3D {sup 1}H/{sup 13}C/{sup 1}H experiment also provides a COSY-type {sup 1}H/{sup 1}H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ({sup 1}H/{sup 1}H chemical shift correlation spectrum) at different {sup 13}C chemical shift frequencies from the 3D {sup 1}H/{sup 13}C/{sup 1}H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the

  15. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

    PubMed Central

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-01

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D 1H/13C/1H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond 13C/1H and 13C/13C chemical shift correlations, the 3D 1H/13C/1H experiment also provides a COSY-type 1H/1H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices (1H/1H chemical shift correlation spectrum) at different 13C chemical shift frequencies from the 3D 1H/13C/1H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D 1H/13C/1H experiment would be useful to study the structure and dynamics of a variety of chemical and biological

  16. Multidimensional J-driven NMR correlations by single-scan offset-encoded recoupling

    NASA Astrophysics Data System (ADS)

    Lin, Yulan; Lupulescu, Adonis; Frydman, Lucio

    2016-04-01

    Two-dimensional (2D) correlations between bonded heteroatoms, lie at the cornerstone of many uses given to contemporary nuclear magnetic resonance (NMR). Improving the efficiency with which these correlations are established is an important topic in modern NMR, with potential applications in rapid chemical analysis and dynamic biophysical studies. Alternatives have been developed over the last decade to speed up these experiments, based among others on reducing the number of data points that need to be sampled, and/or shortening the inter-scan delays. Approaches have also been proposed to forfeit multi-scan schemes altogether, and complete full 2D correlations in a single shot. Here we explore and discuss a new alternative enabling the collection of such very fast - in principle, single-scan - acquisitions of 2D heteronuclear correlations among bonded species, which operates on the basis of a partial reintroduction of J couplings. Similar approaches had been proposed in the past based on collecting coupled spectra for arrays of off-resonance decoupling values; the proposal that is here introduced operates on the basis of suitably incorporating frequency-swept pulses, into spin-echo sequences. Thanks to the offset-dependent amplitude modulations of the in- and anti-phase components that such sequences impart, chemical shifts of coupled but otherwise unobserved nuclear species, can be extracted from the relative intensities and phases of J-coupled multiplets observed in one-dimensional acquisitions. A description of the steps needed to implement this rapid acquisition approach in a quantitative fashion, as well as applications of the ensuing sequences, are presented.

  17. Correlation of tryptophan fluorescence intensity decay parameters with sup 1 H NMR-determined rotamer conformations: (tryptophan sup 2 )oxytocin

    SciTech Connect

    Ross, J.B.A.; Schwartz, G.P.; Laws, W.R. ); Wyssbrod, H.R.; Porter, R.A. ); Michaels, C.A. )

    1992-02-18

    While the fluorescence decay kinetics of tyrosine model compounds can be explained in terms of heterogeneity derived from the three ground-state {chi}{sup 1} rotamers, a similar correlation has yet to be directly observed for a tryptophan residue. In addition, the asymmetric indole ring might also lead to heterogeneity from {chi}{sup 2} rotations. In this paper, the time-resolved and steady-state fluorescence properties of (tryptophan{sup 2})oxytocin at pH 3 are presented and compared with {sup 1}H NMR results. According to the unrestricted analyses of individual fluorescence decay curves taken as a function of emission wavelength-independent decay constants, only three exponential terms are required. In addition, the preexponential weighting factors (amplitudes) have the same relative relationship (weights) as the {sup 1}H NMR-determined {chi}{sup 1} rotamer populations of the indole side chain. {sup 15}N was used in heteronuclear coupling experiments to confirm the rotamer assignments. Inclusion of a linked function restricting the decay amplitudes to the {chi}{sup 1} rotamer populations in the individual decay curve analyses and in the global analysis confirms this correlation. According to qualitative nuclear Overhauser data, there are two {chi}{sup 2} populations.

  18. Pursuing structure in microcrystalline solids with independent molecules in the unit cell using 1H- 13C correlation data

    NASA Astrophysics Data System (ADS)

    Harper, James K.; Strohmeier, Mark; Grant, David M.

    2007-11-01

    The 1H- 13C solid-state NMR heteronuclear correlation (HETCOR) experiment is demonstrated to provide shift assignments in certain powders that have two or more structurally independent molecules in the unit cell (i.e. multiple molecules per asymmetric unit). Although this class of solids is often difficult to characterize using other methods, HETCOR provides both the conventional assignment of shifts to molecular positions and associates many resonances with specific molecules in the asymmetric unit. Such assignments facilitate conformational characterization of the individual molecules of the asymmetric unit and the first such characterization solely from solid-state NMR data is described. HETCOR offers advantages in sensitivity over prior methods that assign resonances in the asymmetric unit by 13C- 13C correlations and therefore allows shorter average analysis times in natural abundance materials. The 1H- 13C analysis is demonstrated first on materials with known shift assignments from INADEQUATE data (santonin and Ca(OAc) 2 phase I) to verify the technique and subsequently is extended to a pair of unknown solids: (+)-catechin and Ca(OAc) 2 phase II. Sufficient sensitivity and resolution is achieved in the spectra to provide assignments to one of the specific molecules of the asymmetric unit at over 54% of the sites.

  19. Determination of trace amounts of chemical warfare agent degradation products in decontamination solutions with NMR spectroscopy.

    PubMed

    Koskela, Harri; Rapinoja, Marja-Leena; Kuitunen, Marja-Leena; Vanninen, Paula

    2007-12-01

    Decontamination solutions are used for an efficient detoxification of chemical warfare agents (CWAs). As these solutions can be composed of strong alkaline chemicals with hydrolyzing and oxidizing properties, the analysis of CWA degradation products in trace levels from these solutions imposes a challenge for any analytical technique. Here, we present results of application of nuclear magnetic resonance spectroscopy for analysis of trace amounts of CWA degradation products in several untreated decontamination solutions. Degradation products of the nerve agents sarin, soman, and VX were selectively monitored with substantially reduced interference of background signals by 1D 1H-31P heteronuclear single quantum coherence (HSQC) spectrometry. The detection limit of the chemicals was at the low part-per-million level (2-10 microg/mL) in all studied solutions. In addition, the concentration of the degradation products was obtained with sufficient confidence with external standards.

  20. Structure of a glycerol teichoic acid-like O-specific polysaccharide of Proteus vulgaris O12.

    PubMed

    Perepelov, A V; Torzewska, A; Shashkov, A S; Senchenkova, S N; Rozalski, A; Knirel, Y A

    2000-02-01

    A phosphorylated O-specific polysaccharide (O-antigen) was obtained by mild acid degradation of Proteus vulgaris O12 lipopolysaccharide and studied by sugar and methylation analyses, 1H-, 13C- and 31P-NMR spectroscopy, including two-dimensional COSY, TOCSY, NOESY, H-detected 1H, 13C and 1H, 31P heteronuclear multiple-quantum coherence experiments. It was found that the polysaccharide consists of pentasaccharide repeating units connected via a glycerol phosphate group, and has the following structure: where FucNAc is 2-acetamido-2,6-dideoxygalactose and the degree of O-acetylation at position 4 of GalNAc is approximately 25%. Immunochemical studies with P. vulgaris O12 O-antiserum suggested that the lipopolysaccharide studied shares common epitopes with the lipopolysaccharide core of P. vulgaris O8 and with the O-antigens of P. penneri strains 8 and 63.

  1. Information-limiting correlations

    PubMed Central

    Moreno-Bote, Rubén; Beck, Jeffrey; Kanitscheider, Ingmar; Pitkow, Xaq; Latham, Peter; Pouget, Alexandre

    2015-01-01

    Computational strategies used by the brain strongly depend on the amount of information that can be stored in population activity, which in turn strongly depends on the pattern of noise correlations. In vivo, noise correlations tend to be positive and proportional to the similarity in tuning properties. Such correlations are thought to limit information, which has led to the suggestion that decorrelation increases information. In contrast, we found, analytically and numerically, that decorrelation does not imply an increase in information. Instead, the only information-limiting correlations are what we refer to as differential correlations: correlations proportional to the product of the derivatives of the tuning curves. Unfortunately, differential correlations are likely to be very small and buried under correlations that do not limit information, making them particularly difficult to detect. We found, however, that the effect of differential correlations on information can be detected with relatively simple decoders. PMID:25195105

  2. Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements

    PubMed Central

    Kurauskas, Vilius; Weber, Emmanuelle; Hessel, Audrey; Ayala, Isabel; Marion, Dominique; Schanda, Paul

    2016-01-01

    Transverse relaxation rate measurements in MAS solid-state NMR provide information about molecular motions occurring on nanoseconds-to-milliseconds (ns-ms) time scales. The measurement of heteronuclear (13C, 15N) relaxation rate constants in the presence of a spin-lock radio-frequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins has been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely (i) the role of CSA/dipolar cross-correlated relaxation (CCR), and (ii) the impact of fast proton spin flips (i.e. proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable, and that this cross-correlated relaxation rate constant depends on ns-ms motions, and can thus itself provide insight into dynamics. We find that proton spin-diffusion attenuates this cross-correlated relaxation, due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and the present manuscript reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation. PMID:27500976

  3. Optomechanical Quantum Correlation Thermometry

    NASA Astrophysics Data System (ADS)

    Purdy, T. P.; Grutter, K. E.; Davanco, M. I.; Srinivasan, K.; Taylor, J. M.

    We present an optomechanical approach for producing accurate thermometry over a wide temperature range using quantum Brownian motion. Optical measurements induce quantum correlations in an optomechanical system when quantum-limited intensity fluctuations of a probe laser drive mechanical motion. The size of the correlations in the weak probe limit are dictated by the scale of individual phonons. We have recently measured optomechanical quantum correlations in the cross correlation spectrum between the amplitude and phase fluctuations of a single probe laser interacting with a silicon nitride optomechanical crystal. These correlations are independent of thermally-induced Brownian motion. However, Brownian motion does simultaneously produce much larger correlation signals between other optical quadratures. A comparison of the size of thermally-induced correlations to quantum correlations allows us to absolutely calibrate Brownian motion thermometry to the mechanical energy quantization scale.

  4. Comparing dependent robust correlations.

    PubMed

    Wilcox, Rand R

    2016-11-01

    Let r1 and r2 be two dependent estimates of Pearson's correlation. There is a substantial literature on testing H0  : ρ1  = ρ2 , the hypothesis that the population correlation coefficients are equal. However, it is well known that Pearson's correlation is not robust. Even a single outlier can have a substantial impact on Pearson's correlation, resulting in a misleading understanding about the strength of the association among the bulk of the points. A way of mitigating this concern is to use a correlation coefficient that guards against outliers, many of which have been proposed. But apparently there are no results on how to compare dependent robust correlation coefficients when there is heteroscedasicity. Extant results suggest that a basic percentile bootstrap will perform reasonably well. This paper reports simulation results indicating the extent to which this is true when using Spearman's rho, a Winsorized correlation or a skipped correlation.

  5. IAA Correlator Center

    NASA Technical Reports Server (NTRS)

    Surkis, Igor; Ken, Voitsekh; Melnikov, Alexey; Mishin, Vladimir; Sokolova, Nadezda; Shantyr, Violet; Zimovsky, Vladimir

    2013-01-01

    The activities of the six-station IAA RAS correlator include regular processing of national geodetic VLBI programs Ru-E, Ru-U, and Ru-F. The Ru-U sessions have been transferred in e-VLBI mode and correlated in the IAA Correlator Center automatically since 2011. The DiFX software correlator is used at the IAA in some astrophysical experiments.

  6. Correlation after Asymmetrical Clipping,

    DTIC Science & Technology

    1987-02-01

    A general formula is derived for the correlation coefficient between clipped waveforms or among detection sequences, for the case where the clipping is asymmetric or the detection probability departs from 50%. The analytic arcsine law for symmetrical clipping is rehearsed and new analytic forms are found for asymmetrical clipping with high positive correlation, numerically low correlation and high negative correlation. Keywords: Sonar; Detection; Probability; Great Britain.

  7. VLBI Correlators in Kashima

    NASA Technical Reports Server (NTRS)

    Sekido, Mamoru; Takefuji, Kazuhiro

    2013-01-01

    Kashima Space Technology Center (KSTC) is making use of two kinds of software correlators, the multi-channel K5/VSSP software correlator and the fast wide-band correlator 'GICO3,' for geodetic and R&D VLBI experiments. Overview of the activity and future plans are described in this paper.

  8. Reverse Correlation in Neurophysiology

    ERIC Educational Resources Information Center

    Ringach, Dario; Shapley, Robert

    2004-01-01

    This article presents a review of reverse correlation in neurophysiology. We discuss the basis of reverse correlation in linear transducers and in spiking neurons. The application of reverse correlation to measure the receptive fields of visual neurons using white noise and m-sequences, and classical findings about spatial and color processing in…

  9. Modified Biserial Correlation Coefficients.

    ERIC Educational Resources Information Center

    Kraemer, Helena Chmura

    1981-01-01

    Asymptotic distribution theory of Brogden's form of biserial correlation coefficient is derived and large sample estimates of its standard error obtained. Its relative efficiency to the biserial correlation coefficient is examined. Recommendations for choice of estimator of biserial correlation are presented. (Author/JKS)

  10. Digital Correlation By Optical Convolution/Correlation

    NASA Astrophysics Data System (ADS)

    Trimble, Joel; Casasent, David; Psaltis, Demetri; Caimi, Frank; Carlotto, Mark; Neft, Deborah

    1980-12-01

    Attention is given to various methods by which the accuracy achieveable and the dynamic range requirements of an optical computer can be enhanced. A new time position coding acousto-optic technique for optical residue arithmetic processing is presented and experimental demonstration is included. Major attention is given to the implementation of a correlator operating on digital or decimal encoded signals. Using a convolution description of multiplication, we realize such a correlator by optical convolution in one dimension and optical correlation in the other dimension of a optical system. A coherent matched spatial filter system operating on digital encoded signals, a noncoherent processor operating on complex-valued digital-encoded data, and a real-time multi-channel acousto-optic system for such operations are described and experimental verifications are included.

  11. ALMA correlator computer systems

    NASA Astrophysics Data System (ADS)

    Pisano, Jim; Amestica, Rodrigo; Perez, Jesus

    2004-09-01

    We present a design for the computer systems which control, configure, and monitor the Atacama Large Millimeter Array (ALMA) correlator and process its output. Two distinct computer systems implement this functionality: a rack- mounted PC controls and monitors the correlator, and a cluster of 17 PCs process the correlator output into raw spectral results. The correlator computer systems interface to other ALMA computers via gigabit Ethernet networks utilizing CORBA and raw socket connections. ALMA Common Software provides the software infrastructure for this distributed computer environment. The control computer interfaces to the correlator via multiple CAN busses and the data processing computer cluster interfaces to the correlator via sixteen dedicated high speed data ports. An independent array-wide hardware timing bus connects to the computer systems and the correlator hardware ensuring synchronous behavior and imposing hard deadlines on the control and data processor computers. An aggregate correlator output of 1 gigabyte per second with 16 millisecond periods and computational data rates of approximately 1 billion floating point operations per second define other hard deadlines for the data processing computer cluster.

  12. Two new density correlations

    SciTech Connect

    Chien, M.C.H.; Monroy, M.R.

    1986-01-01

    The Liquid density predicted by the Peng-Robinson (P-R) equation of state is often off by 10% or more at temperature and pressure conditions encountered in most reservoirs. To improve the density predictions, two new density correlations have been developed. The first correlation is based on the chain-of-rotators (COR) equation of state and the second is based on the three-parameter Peng-Robinson (PR3) equation of state. The COR correlation is applicable to wider pressure and temperature ranges, but is computationally expensive. It is suited for interpreting fluid-analysis data, where no extensive phase-behavior calculations are needed. On the other hand, the PR3 correlation is more limited in its application range, but is computationally more efficient. It is particularly suited for compositional reservoir simulation where many density calculations are repeatedly carried out. In general, both correlations are comparable to the Standing-Katz correlation for liquid-density calculation and comparable to the P-R equation of state for vapor-density calculation. However, they are superior to the Standing-Katz correlation for liquid mixtures near critical points or liquid mixtures at high pressures. Overall, the COR equation of state gives an average prediction error of 1.9% for liquid densities and 2.7% for vapor densities, and the PR3 gives an average prediction error of less than 2% for both liquid and vapor densities.

  13. Correlation Plenoptic Imaging

    NASA Astrophysics Data System (ADS)

    D'Angelo, Milena; Pepe, Francesco V.; Garuccio, Augusto; Scarcelli, Giuliano

    2016-06-01

    Plenoptic imaging is a promising optical modality that simultaneously captures the location and the propagation direction of light in order to enable three-dimensional imaging in a single shot. However, in standard plenoptic imaging systems, the maximum spatial and angular resolutions are fundamentally linked; thereby, the maximum achievable depth of field is inversely proportional to the spatial resolution. We propose to take advantage of the second-order correlation properties of light to overcome this fundamental limitation. In this Letter, we demonstrate that the correlation in both momentum and position of chaotic light leads to the enhanced refocusing power of correlation plenoptic imaging with respect to standard plenoptic imaging.

  14. Hadronic Correlations and Fluctuations

    SciTech Connect

    Koch, Volker

    2008-10-09

    We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

  15. Haystack Observatory VLBI Correlator

    NASA Technical Reports Server (NTRS)

    Titus, Mike; Cappallo, Roger; Corey, Brian; Dudevoir, Kevin; Niell, Arthur; Whitney, Alan

    2013-01-01

    This report summarizes the activities of the Haystack Correlator during 2012. Highlights include finding a solution to the DiFX InfiniBand timeout problem and other DiFX software development, conducting a DBE comparison test following the First International VLBI Technology Workshop, conducting a Mark IV and DiFX correlator comparison, more broadband delay experiments, more u- VLBI Galactic Center observations, and conversion of RDV session processing to the Mark IV/HOPS path. Non-real-time e-VLBI transfers and engineering support of other correlators continued.

  16. A correlated electromechanical system

    NASA Astrophysics Data System (ADS)

    Mahboob, I.; Villiers, M.; Nishiguchi, K.; Hatanaka, D.; Fujiwara, A.; Yamaguchi, H.

    2017-03-01

    A correlation with phonons sustained by a pair of electromechanical resonators that differ both in size and frequency is demonstrated. In spite of the electromechanical resonators being spatially distinct, they can still be strongly dynamically coupled via a classical analogue of the beam splitter interaction with a cooperativity exceeding five, and parametric down-conversion which results in both resonators self-oscillating. This latter regime yields a classical variant of a two-mode squeezed state which is identified as perfectly correlated phase-locked vibrations between the two resonators. The creation of a correlation between two separate mechanical resonators suggests that extending this interaction to vacuum phonon states could enable a macroscopic two-mode squeezed state to be generated. Conversely, the ability to resolve the correlated state via the self-oscillations could be harnessed to build a new class of detector where an external stimulus neutralises the phase-locked vibrations.

  17. Ozone Correlative Measurements Workshop

    NASA Technical Reports Server (NTRS)

    Hilsenrath, E. (Editor)

    1985-01-01

    A study was conducted to determine the necessary parameters for the correlation of data on Earth ozone. Topics considered were: (1) measurement accuracy; (2) equipment considerations (SBUV); and (3) ground based measurements to support satellite data.

  18. Examining Correlates of Diversity.

    ERIC Educational Resources Information Center

    Raudenbush, Stephen W.; Bryk, Anthony S.

    1987-01-01

    Statistical methods are presented for studying "correlates of diversity," defined as characteristics of educational organizations that predict dispersion on the dependent variable. Strategies based on exact distribution theory and asymptotic normal approximation are considered. (TJH)

  19. Tsukuba VLBI Correlator

    NASA Technical Reports Server (NTRS)

    Kurihara, Shinobu; Nozawa, Kentaro

    2013-01-01

    The K5/VSSP software correlator (Figure 1), located in Tsukuba, Japan, is operated by the Geospatial Information Authority of Japan (GSI). It is fully dedicated to processing the geodetic VLBI sessions of the International VLBI Service for Geodesy and Astrometry. All of the weekend IVS Intensives (INT2) and the Japanese domestic VLBI observations organized by GSI were processed at the Tsukuba VLBI Correlator.

  20. Strongly correlated materials.

    PubMed

    Morosan, Emilia; Natelson, Douglas; Nevidomskyy, Andriy H; Si, Qimiao

    2012-09-18

    Strongly correlated materials are profoundly affected by the repulsive electron-electron interaction. This stands in contrast to many commonly used materials such as silicon and aluminum, whose properties are comparatively unaffected by the Coulomb repulsion. Correlated materials often have remarkable properties and transitions between distinct, competing phases with dramatically different electronic and magnetic orders. These rich phenomena are fascinating from the basic science perspective and offer possibilities for technological applications. This article looks at these materials through the lens of research performed at Rice University. Topics examined include: Quantum phase transitions and quantum criticality in "heavy fermion" materials and the iron pnictide high temperature superconductors; computational ab initio methods to examine strongly correlated materials and their interface with analytical theory techniques; layered dichalcogenides as example correlated materials with rich phases (charge density waves, superconductivity, hard ferromagnetism) that may be tuned by composition, pressure, and magnetic field; and nanostructure methods applied to the correlated oxides VO₂ and Fe₃O₄, where metal-insulator transitions can be manipulated by doping at the nanoscale or driving the system out of equilibrium. We conclude with a discussion of the exciting prospects for this class of materials.

  1. Cross-correlation beamforming

    NASA Astrophysics Data System (ADS)

    Ruigrok, Elmer; Gibbons, Steven; Wapenaar, Kees

    2016-10-01

    An areal distribution of sensors can be used for estimating the direction of incoming waves through beamforming. Beamforming may be implemented as a phase-shifting and stacking of data recorded on the different sensors (i.e., conventional beamforming). Alternatively, beamforming can be applied to cross-correlations between the waveforms on the different sensors. We derive a kernel for beamforming cross-correlated data and call it cross-correlation beamforming (CCBF). We point out that CCBF has slightly better resolution and aliasing characteristics than conventional beamforming. When auto-correlations are added to CCBF, the array response functions are the same as for conventional beamforming. We show numerically that CCBF is more resilient to non-coherent noise. Furthermore, we illustrate that with CCBF individual receiver-pairs can be removed to improve mapping to the slowness domain. An additional flexibility of CCBF is that cross-correlations can be time-windowed prior to beamforming, e.g., to remove the directionality of a scattered wavefield. The observations on synthetic data are confirmed with field data from the SPITS array (Svalbard). Both when beamforming an earthquake arrival and when beamforming ambient noise, CCBF focuses more of the energy to a central beam. Overall, the main advantage of CCBF is noise suppression and its flexibility to remove station pairs that deteriorate the signal-related beampower.

  2. Correlation-Peak Imaging

    NASA Astrophysics Data System (ADS)

    Ziegler, A.; Metzler, A.; Köckenberger, W.; Izquierdo, M.; Komor, E.; Haase, A.; Décorps, M.; von Kienlin, M.

    1996-08-01

    Identification and quantitation in conventional1H spectroscopic imagingin vivois often hampered by the small chemical-shift range. To improve the spectral resolution of spectroscopic imaging, homonuclear two-dimensional correlation spectroscopy has been combined with phase encoding of the spatial dimensions. From the theoretical description of the coherence-transfer signal in the Fourier-transform domain, a comprehensive acquisition and processing strategy is presented that includes optimization of the width and the position of the acquisition windows, matched filtering of the signal envelope, and graphical presentation of the cross peak of interest. The procedure has been applied to image the spatial distribution of the correlation peaks from specific spin systems in the hypocotyl of castor bean (Ricinus communis) seedlings. Despite the overlap of many resonances, correlation-peak imaging made it possible to observe a number of proton resonances, such as those of sucrose, β-glucose, glutamine/glutamate, lysine, and arginine.

  3. TOPS optical correlation program

    NASA Astrophysics Data System (ADS)

    Lindell, Scott D.

    1993-09-01

    Martin Marietta is conducting a TOPS optical correlation program in which several algorithms and four optical correlators involving two spatial light modulator technologies will be developed and tested. The program will culminate in 1994 with an automatic target recognition flight demonstration using a UH-1 helicopter flying a Fiber Optic Guide Missile (FOG-M) mission profile. The flight demonstration will be conducted by US Army Missile Command (MICOM) and Martin Marietta and will involve detecting, locating and tracking a M60A2 tank positioned among an array of five vehicle types. Current status of the TOPS program will be given.

  4. Correlation ion mobility spectroscopy

    DOEpatents

    Pfeifer, Kent B.; Rohde, Steven B.

    2008-08-26

    Correlation ion mobility spectrometry (CIMS) uses gating modulation and correlation signal processing to improve IMS instrument performance. Closely spaced ion peaks can be resolved by adding discriminating codes to the gate and matched filtering for the received ion current signal, thereby improving sensitivity and resolution of an ion mobility spectrometer. CIMS can be used to improve the signal-to-noise ratio even for transient chemical samples. CIMS is especially advantageous for small geometry IMS drift tubes that can otherwise have poor resolution due to their small size.

  5. Rocket Auroral Correlator Experiment

    NASA Technical Reports Server (NTRS)

    LaBelle, James

    2003-01-01

    Dartmouth College provided a multi-channel high- and low- frequency wave receivers, including active sensors on deployable booms, to the Rocket Auroral Correlator Experiment launched from Poker Flat, Alaska, in January 2002. College also performed preliminary analysis of the data. Details are outlined in chronological order.

  6. Electromagnetic nonuniformly correlated beams.

    PubMed

    Tong, Zhisong; Korotkova, Olga

    2012-10-01

    A class of electromagnetic sources with nonuniformly distributed field correlations is introduced. The conditions on source parameters guaranteeing that the source generates a physical beam are derived. It is shown that the new sources are capable of producing beams with polarization properties that evolve on propagation in a manner much more complex compared to the well-known electromagnetic Gaussian Schell-model beams.

  7. Neuroanatomical Correlates of Intelligence

    ERIC Educational Resources Information Center

    Luders, Eileen; Narr, Katherine L.; Thompson, Paul M.; Toga, Arthur W.

    2009-01-01

    With the advancement of image acquisition and analysis methods in recent decades, unique opportunities have emerged to study the neuroanatomical correlates of intelligence. Traditional approaches examining global measures have been complemented by insights from more regional analyses based on pre-defined areas. Newer state-of-the-art approaches…

  8. Nonverbal Correlates of Anxiety.

    ERIC Educational Resources Information Center

    Eckman, Bruce K.

    Twenty college age males' hand shrugs, face-play manipulations, and frequency and duration of mutual eye contact were recorded in response to a female counterpart who varied her assertiveness and attractiveness in a two by two factorial design. Mutual eye contact, which increased under attractive conditions, was a useful negative correlate of…

  9. Correlation at sea

    NASA Astrophysics Data System (ADS)

    Hartman, Richard L.; Farr, Keith B.; McColgan, Michele W.; Smith, Ralph G.

    1997-03-01

    This paper discusses an optical correlator interfaces to a FLIR and laser rangefinder to aid aircraft landing aboard an aircraft carrier. The purpose was to recognize aircraft and provide precision track in spite of the engine plume which is visible in IR images. Toward the end of the program, an opportunity arose to piggyback on tests of a Navy FLIR system, on board the USS Enterprise. The Navy's developmental FLIR and laser rangefinder were mounted on the carrier and provided excellent imagery with concurrent range data. The correlator performed a limited set of experiments at sea, tracking an aircraft from 8000 feet until almost touchdown. The challenges to the correlator we operation in a harsh environment and real time interfacing with other hardware. Real time range information controlled a series of filters in the correlator. The system fit into a standard panel rack and utilized remote alignment. The system operated during the chock of aircraft launch and landing, with no need to open up the optical box.

  10. Correlated Attack Modeling (CAM)

    DTIC Science & Technology

    2003-10-01

    eywell’s Scyllarus correlation framework [18], and a simulated-annealing-based approach for detecting stealthy portscans [35]. For detecting multistep...California, May 12–15, 2002. [35] S. Staniford, J. A. Hoagland, and J. M. McAlerney. Practical automated detection of stealthy portscans . Journal of

  11. Correlates of School Stress.

    ERIC Educational Resources Information Center

    Matthews, Doris B.

    As part of a continuing series of research studies on stress in schools, this study examined the construct validity of peripheral temperature at the fingertips as a measure of school stress. Measurements were made in classes selected at random from 11 volunteer schools in South Carolina. Three types of correlational studies were undertaken: (1)…

  12. Computational correlates of consciousness.

    PubMed

    Cleeremans, Axel

    2005-01-01

    Over the past few years numerous proposals have appeared that attempt to characterize consciousness in terms of what could be called its computational correlates: Principles of information processing with which to characterize the differences between conscious and unconscious processing. Proposed computational correlates include architectural specialization (such as the involvement of specific regions of the brain in conscious processing), properties of representations (such as their stability in time or their strength), and properties of specific processes (such as resonance, synchrony, interactivity, or information integration). In exactly the same way as one can engage in a search for the neural correlates of consciousness, one can thus search for the computational correlates of consciousness. The most direct way of doing is to contrast models of conscious versus unconscious information processing. In this paper, I review these developments and illustrate how computational modeling of specific cognitive processes can be useful in exploring and in formulating putative computational principles through which to capture the differences between conscious and unconscious cognition. What can be gained from such approaches to the problem of consciousness is an understanding of the function it plays in information processing and of the mechanisms that subtend it. Here, I suggest that the central function of consciousness is to make it possible for cognitive agents to exert flexible, adaptive control over behavior. From this perspective, consciousness is best characterized as involving (1) a graded continuum defined over quality of representation, such that availability to consciousness and to cognitive control correlates with properties of representation, and (2) the implication of systems of meta-representations.

  13. From micro-correlations to macro-correlations

    NASA Astrophysics Data System (ADS)

    Eliazar, Iddo

    2016-11-01

    Random vectors with a symmetric correlation structure share a common value of pair-wise correlation between their different components. The symmetric correlation structure appears in a multitude of settings, e.g. mixture models. In a mixture model the components of the random vector are drawn independently from a general probability distribution that is determined by an underlying parameter, and the parameter itself is randomized. In this paper we study the overall correlation of high-dimensional random vectors with a symmetric correlation structure. Considering such a random vector, and terming its pair-wise correlation "micro-correlation", we use an asymptotic analysis to derive the random vector's "macro-correlation" : a score that takes values in the unit interval, and that quantifies the random vector's overall correlation. The method of obtaining macro-correlations from micro-correlations is then applied to a diverse collection of frameworks that demonstrate the method's wide applicability.

  14. Structure of the glycerol phosphate-containing O-polysaccharides and serological studies of the lipopolysaccharides of Proteus mirabilis CCUG 10704 (OE) and Proteus vulgaris TG 103 classified into a new Proteus serogroup, O54.

    PubMed

    Kołodziejska, Katarzyna; Perepelov, Andrei V; Zabłotni, Agnieszka; Drzewiecka, Dominika; Senchenkova, Sof'ya N; Zych, Krystyna; Shashkov, Alexander S; Knirel, Yuriy A; Sidorczyk, Zygmunt

    2006-07-01

    O-Polysaccharides were obtained from the lipopolysaccharides of Proteus mirabilis CCUG 10704 (OE) and Proteus vulgaris TG 103 and studied by chemical analyses and one- and two-dimensional (1)H and (13)C nuclear magnetic resonance spectroscopy, including rotating-frame nuclear Overhauser effect spectroscopy, H-detected (1)H,(13)C heteronuclear single-quantum spectroscopy and (1)H,(31)P heteronuclear multiple-quantum spectroscopy experiments. The Proteus mirabilis OE polysaccharide was found to have a trisaccharide repeating unit with a lateral glycerol phosphate group. The Proteus vulgaris TG 103 produces a similar O-polysaccharide, which differs in incomplete substitution with glycerol phosphate (c. 50% of the stoichiometric amount) and the presence of an O-acetyl group at position 6 of the 2-acetamido-2-deoxygalactose (GalNAc) residue. These structures are unique among the known bacterial polysaccharide structures. Based on the structural and serological data of the lipopolysaccharides, it is proposed to classify both strains studied into a new Proteus serogroup, O54, as two subgroups, O54a,54b and O54a,54c. The serological relatedness of the Proteus O54 and some other Proteus lipopolysaccharides is discussed.

  15. Correlators in nontrivial backgrounds

    SciTech Connect

    Mello Koch, Robert de; Ives, Norman; Stephanou, Michael

    2009-01-15

    Operators in N=4 super Yang-Mills theory with an R-charge of O(N{sup 2}) are dual to backgrounds which are asymtotically AdS{sub 5}xS{sup 5}. In this article we develop efficient techniques that allow the computation of correlation functions in these backgrounds. We find that (i) contractions between fields in the string words and fields in the operator creating the background are the field theory accounting of the new geometry, (ii) correlation functions of probes in these backgrounds are given by the free field theory contractions but with rescaled propagators and (iii) in these backgrounds there are no open string excitations with their special end point interactions; we have only closed string excitations.

  16. Correlations and Ostwald ripening

    NASA Technical Reports Server (NTRS)

    Marder, M.

    1987-01-01

    A previously developed model (Weins and Cahn, 1973) describing the growth of spheres of a second phase in metal alloys (Ostwald coarsening) is slightly modified to make it possible to study the complete time evolution of the system rather than simply the late-stage scaling behavior. Closed equations are obtained which describe the time evolution of two-particle correlations in the system. The development of the correlations is analyzed, and simpler expressions are found and solved numerically. The results are compared with experimental data for different systems (e.g., Ni-Al, Ni-Cr-Al, Co-Ni-Cr-Ti, Cu-Co, and MgO-Fe), alternate methods, and existing theories.

  17. Selective correlations; not voodoo.

    PubMed

    Rosenblatt, J D; Benjamini, Y

    2014-12-01

    The problem of "voodoo" correlations-exceptionally high observed correlations in selected regions of the brain-is well recognized in neuroimaging. It arises when quantities of interest are estimated from the same data that was used to select them as interesting. In statistical terminology, the problem of inference following selection from the same data is that of selective inference. Motivated by the unwelcome side-effects of splitting the data- the recommended remedy-we adapt the recent developments in selective inference in order to construct confidence intervals (CIs) with good reproducibility prospects, even if selection and estimation are done with the same data. These intervals control the expected proportion of non-covered correlations in the selected voxels-the False Coverage Rate (FCR). They extend further toward zero than standard intervals, thus attenuating the impression made by highly biased observed correlations. They do so adaptively, in that they coincide with the standard CIs when far away from the selection point. We complement existing analytic proofs with a simulation, showing that the proposed intervals control the FCR in realistic social neuroscience problems. We also suggest a "confidence calibration plot", to allow the intervals to be reported in a clear and interpretable way. Applying the proposed methodology on a loss-aversion study, we demonstrate that with the sample size and selection type employed, selection bias is considerable. Finally, selective intervals are compared to the currently recommended data-splitting approach. We discover that our approach has more power and typically more informative, as no data is discarded. Computation of the intervals is implemented in an accompanying software package.

  18. Proton-detected 3D (1)H/(13)C/(1)H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz.

    PubMed

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-28

    A proton-detected 3D (1)H/(13)C/(1)H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of (13)C-(1)H connectivities, and proximities of (13)C-(1)H and (1)H-(1)H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including (1)H-(1)H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) (1)H/(1)H and 2D (13)C/(1)H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of (1)H-(1)H proximity and (13)C-(1)H connectivity. In addition, the 2D (F1/F2) (1)H/(13)C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of (1)H-(1)H dipolar couplings, enables the measurement of proximities between (13)C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of (1)H-(1)H-(13)C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H2O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  19. Proton-detected 3D 1H/13C/1H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

    A proton-detected 3D 1H/13C/1H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of 13C-1H connectivities, and proximities of 13C-1H and 1H-1H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including 1H-1H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) 1H/1H and 2D 13C/1H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of 1H-1H proximity and 13C-1H connectivity. In addition, the 2D (F1/F2) 1H/13C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of 1H-1H dipolar couplings, enables the measurement of proximities between 13C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of 1H-1H-13C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ṡ H2O ṡ HCl demonstrate the efficiency of the 3D experiment.

  20. Neural correlates of gratitude.

    PubMed

    Fox, Glenn R; Kaplan, Jonas; Damasio, Hanna; Damasio, Antonio

    2015-01-01

    Gratitude is an important aspect of human sociality, and is valued by religions and moral philosophies. It has been established that gratitude leads to benefits for both mental health and interpersonal relationships. It is thus important to elucidate the neurobiological correlates of gratitude, which are only now beginning to be investigated. To this end, we conducted an experiment during which we induced gratitude in participants while they underwent functional magnetic resonance imaging. We hypothesized that gratitude ratings would correlate with activity in brain regions associated with moral cognition, value judgment and theory of mind. The stimuli used to elicit gratitude were drawn from stories of survivors of the Holocaust, as many survivors report being sheltered by strangers or receiving lifesaving food and clothing, and having strong feelings of gratitude for such gifts. The participants were asked to place themselves in the context of the Holocaust and imagine what their own experience would feel like if they received such gifts. For each gift, they rated how grateful they felt. The results revealed that ratings of gratitude correlated with brain activity in the anterior cingulate cortex and medial prefrontal cortex, in support of our hypotheses. The results provide a window into the brain circuitry for moral cognition and positive emotion that accompanies the experience of benefitting from the goodwill of others.

  1. Correlation Algorithm Library

    SciTech Connect

    2013-08-02

    CorAL is a software Library designed to aid in the analysis of femtoscipic data. Femtoscopic data are a class of measured quantities used in heavy-ion collisions to characterize particle emitting source sizes. The most common type of this data is two-particle correleations induced by the Hanbury-Brown/Twiss (HBT) Effect, but can also include correlations induced by final-state interactions between pairs of emitted particles in a heavy-ion collision. Because heavy-ion collisions are complex many particle systems, modeling hydrodynamical models or hybrid techniques. Using the CRAB module, CorAL can turn the output from these models into something that can be directley compared to experimental data. CorAL can also take the raw experimentally measured correlation functions and image them by inverting the Koonin-Pratt equation to extract the space-time emission profile of the particle emitting source. This source function can be further analyzed or directly compared to theoretical calculations.

  2. Cots Correlator Platform

    NASA Astrophysics Data System (ADS)

    Schaaf, Kjeld; Overeem, Ruud

    2004-06-01

    Moore’s law is best exploited by using consumer market hardware. In particular, the gaming industry pushes the limit of processor performance thus reducing the cost per raw flop even faster than Moore’s law predicts. Next to the cost benefits of Common-Of-The-Shelf (COTS) processing resources, there is a rapidly growing experience pool in cluster based processing. The typical Beowulf cluster of PC’s supercomputers are well known. Multiple examples exists of specialised cluster computers based on more advanced server nodes or even gaming stations. All these cluster machines build upon the same knowledge about cluster software management, scheduling, middleware libraries and mathematical libraries. In this study, we have integrated COTS processing resources and cluster nodes into a very high performance processing platform suitable for streaming data applications, in particular to implement a correlator. The required processing power for the correlator in modern radio telescopes is in the range of the larger supercomputers, which motivates the usage of supercomputer technology. Raw processing power is provided by graphical processors and is combined with an Infiniband host bus adapter with integrated data stream handling logic. With this processing platform a scalable correlator can be built with continuously growing processing power at consumer market prices.

  3. Neural correlates of gratitude

    PubMed Central

    Fox, Glenn R.; Kaplan, Jonas; Damasio, Hanna; Damasio, Antonio

    2015-01-01

    Gratitude is an important aspect of human sociality, and is valued by religions and moral philosophies. It has been established that gratitude leads to benefits for both mental health and interpersonal relationships. It is thus important to elucidate the neurobiological correlates of gratitude, which are only now beginning to be investigated. To this end, we conducted an experiment during which we induced gratitude in participants while they underwent functional magnetic resonance imaging. We hypothesized that gratitude ratings would correlate with activity in brain regions associated with moral cognition, value judgment and theory of mind. The stimuli used to elicit gratitude were drawn from stories of survivors of the Holocaust, as many survivors report being sheltered by strangers or receiving lifesaving food and clothing, and having strong feelings of gratitude for such gifts. The participants were asked to place themselves in the context of the Holocaust and imagine what their own experience would feel like if they received such gifts. For each gift, they rated how grateful they felt. The results revealed that ratings of gratitude correlated with brain activity in the anterior cingulate cortex and medial prefrontal cortex, in support of our hypotheses. The results provide a window into the brain circuitry for moral cognition and positive emotion that accompanies the experience of benefitting from the goodwill of others. PMID:26483740

  4. Interpreting correlations in biosequences

    NASA Astrophysics Data System (ADS)

    Herzel, H.; Trifonov, E. N.; Weiss, O.; Große, I.

    Understanding the complex organization of genomes as well as predicting the location of genes and the possible structure of the gene products are some of the most important problems in current molecular biology. Many statistical techniques are used to address these issues. A central role among them play correlation functions. This paper is based on an analysis of the decay of the entire 4×4 dimensional covariance matrix of DNA sequences. We apply this covariance analysis to human chromosomal regions, yeast DNA, and bacterial genomes and interpret the three most pronounced statistical features - long-range correlations, a period 3, and a period 10-11 - using known biological facts about the structure of genomes. For example, we relate the slowly decaying long-range G+C correlations to dispersed repeats and CpG islands. We show quantitatively that the 3-basepair-periodicity is due to the nonuniformity of the codon usage in protein coding segments. We finally show that periodicities of 10-11 basepairs in yeast DNA originate from an alternation of hydrophobic and hydrophilic amino acids in protein sequences.

  5. Variable angle correlation spectroscopy

    SciTech Connect

    Lee, Young Kyo

    1994-05-01

    In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with 13C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.

  6. Backbone dynamics of the antifungal Psd1 pea defensin and its correlation with membrane interaction by NMR spectroscopy.

    PubMed

    de Medeiros, Luciano Neves; Angeli, Renata; Sarzedas, Carolina G; Barreto-Bergter, Eliana; Valente, Ana Paula; Kurtenbach, Eleonora; Almeida, Fabio C L

    2010-02-01

    Plant defensins are cysteine-rich cationic peptides, components of the innate immune system. The antifungal sensitivity of certain exemplars was correlated to the level of complex glycosphingolipids in the membrane of fungi strains. Psd1 is a 46 amino acid residue defensin isolated from pea seeds which exhibit antifungal activity. Its structure is characterized by the so-called cysteine-stabilized alpha/beta motif linked by three loops as determined by two-dimensional NMR. In the present work we explored the measurement of heteronuclear Nuclear Overhauser Effects, R1 and R2 (15)N relaxation ratios, and chemical shift to probe the backbone dynamics of Psd1 and its interaction with membrane mimetic systems with phosphatidylcholine (PC) or dodecylphosphocholine (DPC) with glucosylceramide (CMH) isolated from Fusarium solani. The calculated R2 values predicted a slow motion around the highly conserved among Gly12 residue and also in the region of the Turn3 His36-Trp38. The results showed that Psd1 interacts with vesicles of PC or PC:CMH in slightly different forms. The interaction was monitored by chemical shift perturbation and relaxation properties. Using this approach we could map the loops as the binding site of Psd1 with the membrane. The major binding epitope showed conformation exchange properties in the mus-ms timescale supporting the conformation selection as the binding mechanism. Moreover, the peptide corresponding to part of Loop1 (pepLoop1: Gly12 to Ser19) is also able to interact with DPC micelles acquiring a stable structure and in the presence of DPC:CMH the peptide changes to an extended conformation, exhibiting NOE mainly with the carbohydrate and ceramide parts of CMH.

  7. Bootstrapped Deattenuated Correlation: Nonnormal Distributions

    ERIC Educational Resources Information Center

    Padilla, Miguel A.; Veprinsky, Anna

    2014-01-01

    Correlation attenuation due to measurement error and a corresponding correction, the deattenuated correlation, have been known for over a century. Nevertheless, the deattenuated correlation remains underutilized. A few studies in recent years have investigated factors affecting the deattenuated correlation, and a couple of them provide alternative…

  8. Strongly correlated Bose gases

    NASA Astrophysics Data System (ADS)

    Chevy, F.; Salomon, C.

    2016-10-01

    The strongly interacting Bose gas is one of the most fundamental paradigms of quantum many-body physics and the subject of many experimental and theoretical investigations. We review recent progress on strongly correlated Bose gases, starting with a description of beyond mean-field corrections. We show that the Efimov effect leads to non universal phenomena and to a metastability of the low temperature Bose gas through three-body recombination to deeply bound molecular states. We outline differences and similarities with ultracold Fermi gases, discuss recent experiments on the unitary Bose gas, and finally present a few perspectives for future research.

  9. Universal optimal quantum correlator

    NASA Astrophysics Data System (ADS)

    Buscemi, Francesco; Dall'Arno, Michele; Ozawa, Masanao; Vedral, Vlatko

    2014-10-01

    Recently, a novel operational strategy to access quantum correlation functions of the form Tr[AρB] was provided in [F. Buscemi, M. Dall'Arno, M. Ozawa and V. Vedral, arXiv:1312.4240]. Here we propose a realization scheme, that we call partial expectation values, implementing such strategy in terms of a unitary interaction with an ancillary system followed by the measurement of an observable on the ancilla. Our scheme is universal, being independent of ρ, A, and B, and it is optimal in a statistical sense. Our scheme is suitable for implementation with present quantum optical technology, and provides a new way to test uncertainty relations.

  10. Correlated multipartite quantum states

    NASA Astrophysics Data System (ADS)

    Batle, J.; Casas, M.; Plastino, A.

    2013-03-01

    We investigate quantum states that possess both maximum entanglement and maximum discord between the pertinent parties. Since entanglement (discord) is defined only for bipartite (two-qubit) systems, we use an appropriate sum over all bipartitions as the associated measure. The ensuing definition—not new for entanglement—is thus extended here to quantum discord. Also, additional dimensions within the parties are considered (qudits). We also discuss quantum correlations that induce Mermin's Bell-inequality violation for all multiqubit systems. One finds some differences when quantum mechanics is defined over the field of real or of complex numbers.

  11. Digital Image Correlation Engine

    SciTech Connect

    Turner, Dan; Crozier, Paul; Reu, Phil

    2015-10-06

    DICe is an open source digital image correlation (DIC) tool intended for use as a module in an external application or as a standalone analysis code. It's primary capability is computing full –field displacements and strains from sequences of digital These images are typically of a material sample undergoing a materials characterization experiment, but DICe is also useful for other applications (for example, trajectory tracking). DICe is machine portable (Windows, Linux and Mac) and can be effectively deployed on a high performance computing platform. Capabilities from DICe can be invoked through a library interface, via source code integration of DICe classes or through a graphical user interface.

  12. CONDITIONAL DISTANCE CORRELATION

    PubMed Central

    Wang, Xueqin; Pan, Wenliang; Hu, Wenhao; Tian, Yuan; Zhang, Heping

    2015-01-01

    Statistical inference on conditional dependence is essential in many fields including genetic association studies and graphical models. The classic measures focus on linear conditional correlations, and are incapable of characterizing non-linear conditional relationship including non-monotonic relationship. To overcome this limitation, we introduces a nonparametric measure of conditional dependence for multivariate random variables with arbitrary dimensions. Our measure possesses the necessary and intuitive properties as a correlation index. Briefly, it is zero almost surely if and only if two multivariate random variables are conditionally independent given a third random variable. More importantly, the sample version of this measure can be expressed elegantly as the root of a V or U-process with random kernels and has desirable theoretical properties. Based on the sample version, we propose a test for conditional independence, which is proven to be more powerful than some recently developed tests through our numerical simulations. The advantage of our test is even greater when the relationship between the multivariate random variables given the third random variable cannot be expressed in a linear or monotonic function of one random variable versus the other. We also show that the sample measure is consistent and weakly convergent, and the test statistic is asymptotically normal. By applying our test in a real data analysis, we are able to identify two conditionally associated gene expressions, which otherwise cannot be revealed. Thus, our measure of conditional dependence is not only an ideal concept, but also has important practical utility. PMID:26877569

  13. Attosecond correlation dynamics

    NASA Astrophysics Data System (ADS)

    Ossiander, M.; Siegrist, F.; Shirvanyan, V.; Pazourek, R.; Sommer, A.; Latka, T.; Guggenmos, A.; Nagele, S.; Feist, J.; Burgdörfer, J.; Kienberger, R.; Schultze, M.

    2016-11-01

    Photoemission of an electron is commonly treated as a one-particle phenomenon. With attosecond streaking spectroscopy we observe the breakdown of this single active-electron approximation by recording up to six attoseconds retardation of the dislodged photoelectron due to electronic correlations. We recorded the photon-energy-dependent emission timing of electrons, released from the helium ground state by an extreme-ultraviolet photon, either leaving the ion in its ground state or exciting it into a shake-up state. We identify an optical field-driven d.c. Stark shift of charge-asymmetric ionic states formed after the entangled photoemission as a key contribution to the observed correlation time shift. These findings enable a complete wavepacket reconstruction and are universal for all polarized initial and final states. Sub-attosecond agreement with quantum mechanical ab initio modelling allows us to determine the absolute zero of time in the photoelectric effect to a precision better than 1/25th of the atomic unit of time.

  14. Correlative Measurements Program

    NASA Technical Reports Server (NTRS)

    Parsons, C. L.

    1988-01-01

    The GSFC Correlative Measurements Program at the Wallops Flight Facility was represented on the Satellite/Satellite Intercomparisons Working Group. The Correlative Measurements Program uses the Rocket Ozonesonde (ROCOZ-A) and the Electrochemical Concentration Cell (ECC) balloon borne ozonesonde to measure the vertical profile of ozone amount in the atmosphere. The balloon work is described in a separate report. The ROCOZ-A instrument was used for many years to provide in situ truth data for various satellite ozone measuring systems, such as SBUV on Nimbus-7, SAGE-II, SBUV-II on the NOAA series of polar orbiting satellites, SME, LIMS, etc. The particular data sets of interest to the Ozone Trends Panel Working Group were collected at Natal, Brazil. The major results produced for and used by the Ozone Trends Panel are shown. The ROCOZ-A average ozone density profile is plotted versus altitude on the left. ECC ozonesondes were used for the portion of the profile below 20 km, the lower limit for ROCOZ-A. The difference between SAGE-II and ROCOZ-A average density profiles is shown.

  15. Hexagonalization of correlation functions

    NASA Astrophysics Data System (ADS)

    Fleury, Thiago; Komatsu, Shota

    2017-01-01

    We propose a nonperturbative framework to study general correlation functions of single-trace operators in N = 4 supersymmetric Yang-Mills theory at large N . The basic strategy is to decompose them into fundamental building blocks called the hexagon form factors, which were introduced earlier to study structure constants using integrability. The decomposition is akin to a triangulation of a Riemann surface, and we thus call it hexagonalization. We propose a set of rules to glue the hexagons together based on symmetry, which naturally incorporate the dependence on the conformal and the R-symmetry cross ratios. Our method is conceptually different from the conventional operator product expansion and automatically takes into account multi-trace operators exchanged in OPE channels. To illustrate the idea in simple set-ups, we compute four-point functions of BPS operators of arbitrary lengths and correlation functions of one Konishi operator and three short BPS operators, all at one loop. In all cases, the results are in perfect agreement with the perturbative data. We also suggest that our method can be a useful tool to study conformal integrals, and show it explicitly for the case of ladder integrals.

  16. PREFACE: Correlated Electrons (Japan)

    NASA Astrophysics Data System (ADS)

    Miyake, Kazumasa

    2007-03-01

    This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of strongly correlated electron systems under multiple-environment. The physics of strongly correlated electron systems (SCES) has attracted much attention since the discovery of superconductivity in CeCu_2 Si_2 by Steglich and his co-workers a quater-century ago. Its interest has been intensified by the discovery of high-Tc superconductivity in a series of cuprates with layered perovskite structure which are still under active debate. The present issue of Journal of Physics: Condensed Matter present some aspects of SCES physics on the basis of activities of a late project "Centre-Of-Excellence" supported by MEXT (Ministry of Education, Sports, Science, Culture and Technology of the Japanese Government). This project has been performed by a condensed matter physics group in the faculties of science and engineering science of Osaka University. Although this project also covers correlated phenomena in optics and nano-scale systems, we focus here on the issues of SCES related to superconductivity, mainly unconventional. The present issue covers the discussions on a new mechanism of superconductivity with electronic origin (critical valence fluctuation mechanism), interplay and unification of magnetism and superconductivity in SCES based on a systematic study of NQR under pressure, varieties of Fermi surface of Ce- and U-based SCES probed by the de Haas-van Alphen effect, electronic states probed by a bulk sensitive photoemission spectroscopy with soft X-ray, pressure induced superconductivity of heavy electron materials, pressure dependence of superconducting transition temperature based on a first-principle calculation, and new superconductors under very high-pressure. Some papers offer readers' reviews of the relevant fields and/or include new developments of this intriguing research field of SCES. Altogether, the papers within this issue outline some aspects of electronic states

  17. Lagged correlation networks

    NASA Astrophysics Data System (ADS)

    Curme, Chester

    Technological advances have provided scientists with large high-dimensional datasets that describe the behaviors of complex systems: from the statistics of energy levels in complex quantum systems, to the time-dependent transcription of genes, to price fluctuations among assets in a financial market. In this environment, where it may be difficult to infer the joint distribution of the data, network science has flourished as a way to gain insight into the structure and organization of such systems by focusing on pairwise interactions. This work focuses on a particular setting, in which a system is described by multivariate time series data. We consider time-lagged correlations among elements in this system, in such a way that the measured interactions among elements are asymmetric. Finally, we allow these interactions to be characteristically weak, so that statistical uncertainties may be important to consider when inferring the structure of the system. We introduce a methodology for constructing statistically validated networks to describe such a system, extend the methodology to accommodate interactions with a periodic component, and show how consideration of bipartite community structures in these networks can aid in the construction of robust statistical models. An example of such a system is a financial market, in which high frequency returns data may be used to describe contagion, or the spreading of shocks in price among assets. These data provide the experimental testing ground for our methodology. We study NYSE data from both the present day and one decade ago, examine the time scales over which the validated lagged correlation networks exist, and relate differences in the topological properties of the networks to an increasing economic efficiency. We uncover daily periodicities in the validated interactions, and relate our findings to explanations of the Epps Effect, an empirical phenomenon of financial time series. We also study bipartite community

  18. Liquid-Crystal Optical Correlator

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang

    1989-01-01

    Optical correlator uses commercially-available liquid-crystal television (LCTV) screen as spatial light modulator. Correlations with this device done at video frame rates, making such operations as bar-code recognition possible at reasonable cost. With further development, such correlator useful in automation, robotic vision, and optical image processing.

  19. Quantum phase transitions in bosonic heteronuclear pairing Hamiltonians

    SciTech Connect

    Hohenadler, M.; Silver, A. O.; Bhaseen, M. J.; Simons, B. D.

    2010-07-15

    We explore the phase diagram of two-component bosons with Feshbach resonant pairing interactions in an optical lattice. It has been shown in previous work to exhibit a rich variety of phases and phase transitions, including a paradigmatic Ising quantum phase transition within the second Mott lobe. We discuss the evolution of the phase diagram with system parameters and relate this to the predictions of Landau theory. We extend our exact diagonalization studies of the one-dimensional bosonic Hamiltonian and confirm additional Ising critical exponents for the longitudinal and transverse magnetic susceptibilities within the second Mott lobe. The numerical results for the ground-state energy and transverse magnetization are in good agreement with exact solutions of the Ising model in the thermodynamic limit. We also provide details of the low-energy spectrum, as well as density fluctuations and superfluid fractions in the grand canonical ensemble.

  20. Rotational Energy Transfer in Metastable States of Heteronuclear Molecules

    DTIC Science & Technology

    1989-01-01

    developed by Polanyi and Woodall1 1 in their studies of HF(v) relaxation and has been applied to a number of other species. Pritchard and co-workers 12 ,13...Chemiluminescence from the3 F + 12F Reaction," J. Chem. Phys. 74, 6508 (1981). 8. Clyne, Michael A.A. and McDermid, I. Stuart, "B3 H(0+ ) States of IF, ICI, and...State of ICI," 1984. 11. Polanyi , J.E. and Woodall, K.B., "Mechanisms of Rotational Relaxation," J. Chem. Phys. 56, 1563 (1972). 12. Pritchard, D.E

  1. Anatomical correlates of blepharospasm

    PubMed Central

    2012-01-01

    Background Focal dystonia is a neurological disorder characterized by unwanted muscle spasms. Blepharospasm is a focal dystonia producing an involuntary closure of the eyelid. Its etiology is unknown. Objective To investigate if there are structural changes in the white and grey matter of blepharospasm patients, and if the changes are related to disease features. Methods T1 and diffusion-weighted magnetic resonance imaging scans were collected from 14 female blepharospasm patients and 14 healthy matched controls. Grey matter volumes, fractional anisotropy (FA), and mean diffusivity maps were compared between the groups. Based on grey matter differences within the facial portion of the primary motor cortex, the corticobulbar tract was traced and compared between groups. Results Changes in grey matter in patients included the facial portion of the sensorimotor area and anterior cingulate gyrus. These changes did not correlate with disease duration. Corticobulbar tract volume and peak tract connectivity were decreased in patients compared with controls. There were no significant differences in FA or mean diffusivity between groups. Conclusions Grey matter changes within the primary sensorimotor and the anterior cingulate cortices in blepharospasm patients may help explain involuntary eyelid closure and the abnormal sensations often reported in this condition. PMID:23210426

  2. Correlates of Sensitive Technologies

    SciTech Connect

    Nelson, Paul

    2016-04-22

    By “Quantitative Empirical Analysis” (QEA) is intended the use of statistical methods to infer, from data that often tend to be of a historical nature, the characteristics of states that correlate with some designated dependent variable (e.g. proliferation of nuclear weapons). QEA is a well-established approach in the social sciences, but is not notably well-known among physical scientists, who tend to think of the social sciences as inherently qualitative. This article attempts to provide a snapshot of research, most of which has evolved over the past decade, involving the application of QEA to issues in which the dependent variable of interest is intended as some measure of nuclear proliferation. Standard practices in QEA are described, especially as they relate to data collection. The QEA approach is compared and contrasted to other quantitative approaches to studying proliferation-related issues, including a “figure of merit” approach that has largely been developed within the DOE complex, and two distinct methodologies termed in a recent US National Academy of Sciences study as “case by case” and “predefined framework.” Sample results from QEA applied to proliferation are indicated, as are doubts about such quantitative approaches. A simplistic decision-theoretic model of the optimal time for the international community to intervene in a possible proliferation scenario is used to illustrate the possibility of synergies between different approaches

  3. Allowing for Correlations between Correlations in Random-Effects Meta-Analysis of Correlation Matrices

    ERIC Educational Resources Information Center

    Prevost, A. Toby; Mason, Dan; Griffin, Simon; Kinmonth, Ann-Louise; Sutton, Stephen; Spiegelhalter, David

    2007-01-01

    Practical meta-analysis of correlation matrices generally ignores covariances (and hence correlations) between correlation estimates. The authors consider various methods for allowing for covariances, including generalized least squares, maximum marginal likelihood, and Bayesian approaches, illustrated using a 6-dimensional response in a series of…

  4. More Voodoo correlations: when average-based measures inflate correlations.

    PubMed

    Brand, Andrew; Bradley, Michael T

    2012-01-01

    A Monte-Carlo simulation was conducted to assess the extent that a correlation estimate can be inflated when an average-based measure is used in a commonly employed correlational design. The results from the simulation reveal that the inflation of the correlation estimate can be substantial, up to 76%. Additionally, data was re-analyzed from two previously published studies to determine the extent that the correlation estimate was inflated due to the use of an averaged based measure. The re-analyses reveal that correlation estimates had been inflated by just over 50% in both studies. Although these findings are disconcerting, we are somewhat comforted by the fact that there is a simple and easy analysis that can be employed to prevent the inflation of the correlation estimate that we have simulated and observed.

  5. Correlations of correlations: Secondary autocorrelations in finite harmonic systems.

    PubMed

    Plyukhin, Dan; Plyukhin, Alex V

    2015-10-01

    The momentum or velocity autocorrelation function C(t) for a tagged oscillator in a finite harmonic system decays like that of an infinite system for short times, but exhibits erratic behavior at longer time scales. We introduce the autocorrelation function of the long-time noisy tail of C(t) ("a correlation of the correlation"), which characterizes the distribution of recurrence times. Remarkably, for harmonic systems with same-mass particles this secondary correlation may coincide with the primary correlation C(t) (when both functions are normalized) either exactly, or over a significant initial time interval. When the tagged particle is heavier than the rest, the equality does not hold, correlations show nonrandom long-time scale pattern, and higher-order correlations converge to the lowest normal mode.

  6. SAW correlator spread spectrum receiver

    DOEpatents

    Brocato, Robert W

    2014-04-01

    A surface acoustic wave (SAW) correlator spread-spectrum (SS) receiver is disclosed which utilizes a first demodulation stage with a chip length n and a second demodulation stage with a chip length m to decode a transmitted SS signal having a code length l=n.times.m which can be very long (e.g. up to 2000 chips or more). The first demodulation stage utilizes a pair of SAW correlators which demodulate the SS signal to generate an appropriate code sequence at an intermediate frequency which can then be fed into the second demodulation stage which can be formed from another SAW correlator, or by a digital correlator. A compound SAW correlator comprising two input transducers and a single output transducer is also disclosed which can be used to form the SAW correlator SS receiver, or for use in processing long code length signals.

  7. Correlation Based Geomagnetic Field Modeling

    NASA Astrophysics Data System (ADS)

    Holschneider, M.; Mauerberger, S.; Lesur, V.; Baerenzung, J.

    2015-12-01

    We present a new method for determining geomagnetic field models. It is based on the construction of an a priori correlation structure derived from our knowledge about characteristic length scales and sources of the geomagnetic field. The magnetic field measurements are then seen as correlated random variables too and the inversion process amounts to compute the a posteriori correlation structure using Bayes theorem. We show how this technique allows the statistical separation of the various field contributions and the assessment of their uncertainties.

  8. Image correlation and sampling study

    NASA Technical Reports Server (NTRS)

    Popp, D. J.; Mccormack, D. S.; Sedwick, J. L.

    1972-01-01

    The development of analytical approaches for solving image correlation and image sampling of multispectral data is discussed. Relevant multispectral image statistics which are applicable to image correlation and sampling are identified. The general image statistics include intensity mean, variance, amplitude histogram, power spectral density function, and autocorrelation function. The translation problem associated with digital image registration and the analytical means for comparing commonly used correlation techniques are considered. General expressions for determining the reconstruction error for specific image sampling strategies are developed.

  9. Area correlation in transform domain

    NASA Astrophysics Data System (ADS)

    Merchant, S. N.; Rao, B. V.

    1983-10-01

    It has been shown that the optimal test statistic in the Neyman-Pearson sense for area correlation is the modified correlation coefficient. In order to reduce the heavy computational burden of such an optimal scheme, a sub-optimal scheme based on the utilization of linear transformations has been investigated. Feature selection based on the entropy concept, and through K-L expansion has also been investigated in area correlation applications through a simulation study.

  10. Why Are Experts Correlated? Decomposing Correlations between Judges

    ERIC Educational Resources Information Center

    Broomell, Stephen B.; Budescu, David V.

    2009-01-01

    We derive an analytic model of the inter-judge correlation as a function of five underlying parameters. Inter-cue correlation and the number of cues capture our assumptions about the environment, while differentiations between cues, the weights attached to the cues, and (un)reliability describe assumptions about the judges. We study the relative…

  11. Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-10-28

    A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  12. Personality Correlates of Polydrug Abuse.

    ERIC Educational Resources Information Center

    Kilpatrick, Dean G.; And Others

    Although the personality correlates of heroin addiction, LSD use, and marijuana smoking have been frequently investigated, relatively few data are available to describe the personality or lifestyle variables correlated with the pattern of polydrug abuse. In an attempt to gather such information, 17 polydrug users, selected from a group of 224…

  13. Improved Digital Image Correlation method

    NASA Astrophysics Data System (ADS)

    Mudassar, Asloob Ahmad; Butt, Saira

    2016-12-01

    Digital Image Correlation (DIC) is a powerful technique which is used to correlate two image segments to determine the similarity between them. A correlation image is formed which gives a peak known as correlation peak. If the two image segments are identical the peak is known as auto-correlation peak otherwise it is known as cross correlation peak. The location of the peak in a correlation image gives the relative displacement between the two image segments. Use of DIC for in-plane displacement and deformation measurements in Electronic Speckle Photography (ESP) is well known. In ESP two speckle images are correlated using DIC and relative displacement is measured. We are presenting background review of ESP and disclosing a technique based on DIC for improved relative measurements which we regard as the improved DIC method. Simulation and experimental results reveal that the proposed improved-DIC method is superior to the conventional DIC method in two aspects, in resolution and in the availability of reference position in displacement measurements.

  14. Psychophysical correlations, synchronicity and meaning.

    PubMed

    Atmanspacher, Harald

    2014-04-01

    The dual-aspect framework which Jung developed with Wolfgang Pauli implies that psychophysical phenomena are neither reducible to physical processes nor to conscious mental activity. Rather, they constitute a radically novel kind of phenomena, deriving from correlations between the physical and the mental. In synchronistic events, a particular subclass of psychophysical phenomena, these correlations are explicated as experienced meaning.

  15. Correlates of Cognitive Student Outcomes.

    ERIC Educational Resources Information Center

    Kohr, Richard L.

    A study of the correlates of cognitive achievement in Pennsylvania's Educational Quality Assessment Program was conducted by examining both individual (student level) and ecological (building level) correlations. Analyses were completed for grade levels 5, 8 and 11 for the 1985 state assessment. Twenty-four student derived condition variables or…

  16. Optical Correlator Performs Novelty Filtering

    NASA Technical Reports Server (NTRS)

    Liu, Duncan Tsuen-Hsi; Chao, Tien-Hsin; Cheng, Li-Jen

    1994-01-01

    Experimental real-time optical correlator performs correlation and novelty filtering in photorefractive crystal. Crystal oriented enabling cross-polarization diffraction: together with polarizing beam splitter, increases signal-to-noise ratio. Laser and optical components expand, collimate, and divide laser beam.

  17. Neural correlates of consciousness reconsidered.

    PubMed

    Neisser, Joseph

    2012-06-01

    It is widely accepted among philosophers that neuroscientists are conducting a search for the neural correlates of consciousness, or NCC. Chalmers (2000) conceptualized this research program as the attempt to correlate the contents of conscious experience with the contents of representations in specific neural populations. A notable claim on behalf of this interpretation is that the neutral language of "correlates" frees us from philosophical disputes over the mind/body relation, allowing the science to move independently. But the experimental paradigms and explanatory canons of neuroscience are not neutral about the mechanical relation between consciousness and the brain. I argue that NCC research is best characterized as an attempt to locate a causally relevant neural mechanism and not as an effort to identify a discrete neural representation, the content of which correlates with some actual experience. It might be said that the first C in "NCC" should stand for "causes" rather than "correlates."

  18. Cross-correlation of long-range correlated series

    NASA Astrophysics Data System (ADS)

    Arianos, Sergio; Carbone, Anna

    2009-03-01

    A method for estimating the cross-correlation Cxy(τ) of long-range correlated series x(t) and y(t), at varying lags τ and scales n, is proposed. For fractional Brownian motions with Hurst exponents H1 and H2, the asymptotic expression for Cxy(τ) depends only on the lag τ (wide-sense stationarity) and scales as a power of n with exponent H1+H2 for \\tau \\rightarrow 0 . The method is illustrated on: (i) financial series, to show the leverage effect; (ii) genomic sequences, to estimate the correlations between structural parameters along the chromosomes.

  19. Correlation dynamics of Green functions

    NASA Astrophysics Data System (ADS)

    Shun-Jin, Wang; Wei, Zuo; Wolfgang, Cassing

    1994-06-01

    We generalize the methods used in the theory of correlation dynamics and establish a set of equations of motion for many-body correlation Green functions in the nonrelativistic case. These nonlinear and coupled equations of motion describe the dynamical evolution of correlation Green functions of different order and transparently show how many-body correlations are generated by the different interaction terms in a genuine nonperturbative framework. The nonperturbative results of the conventional Green function theory are included in the present formalism as two limiting cases (the so-called ladder-diagram summation and ring-diagram summation) as well as the familiar correlation dynamics of density matrices in the equal-time limit. We present explicit expressions for three- and four-body correlation functions that can be used to dynamically restore the trace relations for spin-symmetric Fermi systems and study numerically the relative importance of two-, three- and four-body correlations for nuclear configurations close to the ground state.

  20. Correlation, Cost Risk, and Geometry

    NASA Technical Reports Server (NTRS)

    Dean, Edwin B.

    1992-01-01

    The geometric viewpoint identifies the choice of a correlation matrix for the simulation of cost risk with the pairwise choice of data vectors corresponding to the parameters used to obtain cost risk. The correlation coefficient is the cosine of the angle between the data vectors after translation to an origin at the mean and normalization for magnitude. Thus correlation is equivalent to expressing the data in terms of a non orthogonal basis. To understand the many resulting phenomena requires the use of the tensor concept of raising the index to transform the measured and observed covariant components into contravariant components before vector addition can be applied. The geometric viewpoint also demonstrates that correlation and covariance are geometric properties, as opposed to purely statistical properties, of the variates. Thus, variates from different distributions may be correlated, as desired, after selection from independent distributions. By determining the principal components of the correlation matrix, variates with the desired mean, magnitude, and correlation can be generated through linear transforms which include the eigenvalues and the eigenvectors of the correlation matrix. The conversion of the data to a non orthogonal basis uses a compound linear transformation which distorts or stretches the data space. Hence, the correlated data does not have the same properties as the uncorrelated data used to generate it. This phenomena is responsible for seemingly strange observations such as the fact that the marginal distributions of the correlated data can be quite different from the distributions used to generate the data. The joint effect of statistical distributions and correlation remains a fertile area for further research. In terms of application to cost estimating, the geometric approach demonstrates that the estimator must have data and must understand that data in order to properly choose the correlation matrix appropriate for a given estimate

  1. Ring correlations in random networks

    NASA Astrophysics Data System (ADS)

    Sadjadi, Mahdi; Thorpe, M. F.

    2016-12-01

    We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

  2. Nonclassicality of local bipartite correlations

    NASA Astrophysics Data System (ADS)

    Jebaratnam, C.; Aravinda, S.; Srikanth, R.

    2017-03-01

    Simulating quantum nonlocality and steering requires augmenting preshared randomness with nonvanishing communication cost. This prompts the question of how one may provide such an operational characterization for the quantumness of correlations due to even unentangled states. Here we show that for a certain class of states, such quantumness can be pointed out by superlocality, the requirement for a larger dimension of the preshared randomness to simulate the correlations than that of the quantum state that generates them. This provides an approach to define the nonclassicality of local multipartite correlations in convex operational theories.

  3. Digital correlator with fewer IC's

    NASA Technical Reports Server (NTRS)

    Apple, G. G.; Rubin, L.

    1979-01-01

    Digital correlator requires only few integrated circuits to determine synchronization of two 24-bit digital words. Circuit is easily reduced or expanded to accommodate shorter or longer words and can be utilized in industrial and commercial data processing and telecommunications.

  4. Electronic correlations in the ironpnictides

    SciTech Connect

    Qazilbash, M. M.; Hamlin, J. J.; Baumbach, R. E.; Zhang, Lijun; Singh, David J; Maple, M. B.; Basov, D. N.

    2009-01-01

    In correlated metals derived from Mott insulators, the motion of an electron is impeded by Coulomb repulsion due to other electrons. This phenomenon causes a substantial reduction in the electron's kinetic energy, leading to remarkable experimental manifestations in optical spectroscopy. The high-transition-temperature (Tc) superconducting cuprates are perhaps the most studied examples of such correlated metals. The occurrence of high-Tc superconductivity in the iron pnictides puts a spotlight on the relevance of correlation effects in these materials. Here, we present an infrared and optical study on single crystals of the iron pnictide superconductor LaFePO. We find clear evidence of electronic correlations in metallic LaFePO with the kinetic energy of the electrons reduced to half of that predicted by band theory of nearly free electrons. We deduce that electronic many-body effects are important in the iron pnictides despite the absence of a Mott transition.

  5. Transverse correlations in multiphoton entanglement

    SciTech Connect

    Wen Jianming; Rubin, Morton H.; Shih Yanhua

    2007-10-15

    We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N-photon state. The Klyshko's two-photon advanced-wave picture is generalized to the N-photon case.

  6. Glassy correlations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Goldbart, Paul; Mao, Xiaoming

    2009-03-01

    We address the physical properties of an isotropic melt or solution of nematogenic polymers that is then cross-linked beyond the vulcanization point. To do this, we construct a replica Landau theory involving a coupled pair of order- parameter fields: one describing vulcanization, the other describing local nematic order. Thermal nematic fluctuations, present at the time of cross-linking, are trapped by cross- linking into the vulcanized network. The resulting glassy nematic fluctuations are analyzed in the Gaussian approximation in two regimes. When the localization length is shorter than the thermal nematic correlation length, the nematic correlations are well captured as glassy correlations. In the opposite regime, fluctuations in the positions of the localized polymers partially wash out the glassy nematic correlations.

  7. Modernizing the JPL VLBI Correlator

    NASA Astrophysics Data System (ADS)

    Rogstad, S.; Goodhart, C. E.; Clark, J. E.; Finley, S.; Lanyi, G. E.; White, L. A.; Jacobs, Christopher S.>

    This poster will present the current capabilities of the JPL VLBI Correlator (JVC) and the general architecture of the equipment. In addition, the scientific and navigation uses of the JVC will be enumerated for background purposes. The JVC is a software correlator based on a Beowulf cluster of computers. It replaces a thirty year old correlator based on custom designed digital hardware. General comparisons between the old and new equipment will be made. The JVC makes use of a separate program, SoftC, to do the actual correlations. The JVC manages the sending of data to multiple machines in a Beowulf cluster each running SoftC in parallel on small chunks of the data. The basic architecture of SoftC will also be described.

  8. Why Waveform Correlation Sometimes Fails

    NASA Astrophysics Data System (ADS)

    Carmichael, J.

    2015-12-01

    Waveform correlation detectors used in explosion monitoring scan noisy geophysical data to test two competing hypotheses: either (1) an amplitude-scaled version of a template waveform is present, or, (2) no signal is present at all. In reality, geophysical wavefields that are monitored for explosion signatures include waveforms produced by non-target sources that are partially correlated with the waveform template. Such signals can falsely trigger correlation detectors, particularly at low thresholds required to monitor for smaller target explosions. This challenge is particularly formidable when monitoring known test sites for seismic disturbances, since uncatalogued natural seismicity is (generally) more prevalent at lower magnitudes, and could be mistaken for small explosions. To address these challenges, we identify real examples in which correlation detectors targeting explosions falsely trigger on both site-proximal earthquakes (Figure 1, below) and microseismic "noise". Motivated by these examples, we quantify performance loss when applying these detectors, and re-evaluate the correlation-detector's hypothesis test. We thereby derive new detectors from more general hypotheses that admit unknown background seismicity, and apply these to real data. From our treatment, we derive "rules of thumb'' for proper template and threshold selection in heavily cluttered signal environments. Last, we answer the question "what is the probability of falsely detecting an earthquake collocated at a test site?", using correlation detectors that include explosion-triggered templates. Figure Top: An eight-channel data stream (black) recorded from an earthquake near a mine. Red markers indicate a detection. Middle: The correlation statistic computed by scanning the template against the data stream at top. The red line indicates the threshold for event declaration, determined by a false-alarm on noise probability constraint, as computed from the signal-absent distribution using

  9. Local realism of macroscopic correlations.

    PubMed

    Ramanathan, R; Paterek, T; Kay, A; Kurzyński, P; Kaszlikowski, D

    2011-08-05

    We identify conditions under which correlations resulting from quantum measurements performed on macroscopic systems (systems composed of a number of particles of the order of the Avogadro number) can be described by local realism. We argue that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that macroscopic measurements do not reveal properties of individual particles.

  10. Local Realism of Macroscopic Correlations

    NASA Astrophysics Data System (ADS)

    Ramanathan, R.; Paterek, T.; Kay, A.; Kurzyński, P.; Kaszlikowski, D.

    2011-08-01

    We identify conditions under which correlations resulting from quantum measurements performed on macroscopic systems (systems composed of a number of particles of the order of the Avogadro number) can be described by local realism. We argue that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that macroscopic measurements do not reveal properties of individual particles.

  11. Nonglobal correlations in collider physics

    DOE PAGES

    Moult, Ian; Larkoski, Andrew J.

    2016-01-13

    Despite their importance for precision QCD calculations, correlations between in- and out-of-jet regions of phase space have never directly been observed. These so-called non-global effects are present generically whenever a collider physics measurement is not explicitly dependent on radiation throughout the entire phase space. In this paper, we introduce a novel procedure based on mutual information, which allows us to isolate these non-global correlations between measurements made in different regions of phase space. We study this procedure both analytically and in Monte Carlo simulations in the context of observables measured on hadronic final states produced in e+e- collisions, though itmore » is more widely applicable.The procedure exploits the sensitivity of soft radiation at large angles to non-global correlations, and we calculate these correlations through next-to-leading logarithmic accuracy. The bulk of these non-global correlations are found to be described in Monte Carlo simulation. They increase by the inclusion of non-perturbative effects, which we show can be incorporated in our calculation through the use of a model shape function. As a result, this procedure illuminates the source of non-global correlations and has connections more broadly to fundamental quantities in quantum field theory.« less

  12. The Murchison Widefield Array Correlator

    NASA Astrophysics Data System (ADS)

    Ord, S. M.; Crosse, B.; Emrich, D.; Pallot, D.; Wayth, R. B.; Clark, M. A.; Tremblay, S. E.; Arcus, W.; Barnes, D.; Bell, M.; Bernardi, G.; Bhat, N. D. R.; Bowman, J. D.; Briggs, F.; Bunton, J. D.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; deSouza, L.; Ewell-Wice, A.; Feng, L.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Herne, D.; Hewitt, J. N.; Hindson, L.; Hurley-Walker, N.; Jacobs, D.; Johnston-Hollitt, M.; Kaplan, D. L.; Kasper, J. C.; Kincaid, B. B.; Koenig, R.; Kratzenberg, E.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A.; Pathikulangara, J.; Pindor, B.; Prabu, T.; Procopio, P.; Remillard, R. A.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Salah, J. E.; Sault, R. J.; Udaya Shankar, N.; Srivani, K. S.; Stevens, J.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wyithe, J. S. B.

    2015-03-01

    The Murchison Widefield Array is a Square Kilometre Array Precursor. The telescope is located at the Murchison Radio-astronomy Observatory in Western Australia. The MWA consists of 4 096 dipoles arranged into 128 dual polarisation aperture arrays forming a connected element interferometer that cross-correlates signals from all 256 inputs. A hybrid approach to the correlation task is employed, with some processing stages being performed by bespoke hardware, based on Field Programmable Gate Arrays, and others by Graphics Processing Units housed in general purpose rack mounted servers. The correlation capability required is approximately 8 tera floating point operations per second. The MWA has commenced operations and the correlator is generating 8.3 TB day-1 of correlation products, that are subsequently transferred 700 km from the MRO to Perth (WA) in real-time for storage and offline processing. In this paper, we outline the correlator design, signal path, and processing elements and present the data format for the internal and external interfaces.

  13. Nonglobal correlations in collider physics

    SciTech Connect

    Moult, Ian; Larkoski, Andrew J.

    2016-01-13

    Despite their importance for precision QCD calculations, correlations between in- and out-of-jet regions of phase space have never directly been observed. These so-called non-global effects are present generically whenever a collider physics measurement is not explicitly dependent on radiation throughout the entire phase space. In this paper, we introduce a novel procedure based on mutual information, which allows us to isolate these non-global correlations between measurements made in different regions of phase space. We study this procedure both analytically and in Monte Carlo simulations in the context of observables measured on hadronic final states produced in e+e- collisions, though it is more widely applicable.The procedure exploits the sensitivity of soft radiation at large angles to non-global correlations, and we calculate these correlations through next-to-leading logarithmic accuracy. The bulk of these non-global correlations are found to be described in Monte Carlo simulation. They increase by the inclusion of non-perturbative effects, which we show can be incorporated in our calculation through the use of a model shape function. As a result, this procedure illuminates the source of non-global correlations and has connections more broadly to fundamental quantities in quantum field theory.

  14. Broadband finite-pulse radio-frequency-driven recoupling (fp-RFDR) with (XY8)4(1) super-cycling for homo-nuclear correlations in very high magnetic fields at fast and ultra-fast MAS frequencies.

    PubMed

    Shen, Ming; Hu, Bingwen; Lafon, Oliver; Trébosc, Julien; Chen, Qun; Amoureux, Jean-Paul

    2012-10-01

    We demonstrate that inter-residue (13)C-(13)C proximities (of about 380 pm) in uniformly (13)C-labeled proteins can be probed by applying robust first-order recoupling during several milliseconds in single-quantum single-quantum dipolar homo-nuclear correlation (SQ-SQ D-HOMCOR) 2D experiments. We show that the intensity of medium-range homo-nuclear correlations in these experiments is enhanced using broadband first-order finite-pulse radio-frequency-driven recoupling (fp-RFDR) NMR sequence with a nested (XY8)4(1) super-cycling. The robustness and the efficiency of the fp-RFDR-(XY8)4(1) method is demonstrated at high magnetic field (21.1T) and high Magic-Angle Spinning (MAS) speeds (up to 60 kHz). The introduced super-cycling, formed by combining phase inversion and a global four-quantum phase cycle, improves the robustness of fp-RFDR to (i) chemical shift anisotropy (CSA), (ii) spread in isotropic chemical shifts, (iii) rf-inhomogeneity and (iv) hetero-nuclear dipolar couplings for long recoupling times. We show that fp-RFDR-(XY8)4(1) is efficient sans (1)H decoupling, which is beneficial for temperature-sensitive biomolecules. The efficiency and the robustness of fp-RFDR-(XY8)4(1) is investigated by spin dynamics numerical simulations as well as solid-state NMR experiments on [U-(13)C]-L-histidine·HCl, a tetra-peptide (Fmoc-[U-(13)C,(15)N]-Val-[U-(13)C,(15)N]-Ala-[U-(13)C,(15)N]-Phe-Gly-t-Boc) and Al(PO(3))(3).

  15. A scalable correlator for multichannel diffuse correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Stapels, Christopher J.; Kolodziejski, Noah J.; McAdams, Daniel; Podolsky, Matthew J.; Fernandez, Daniel E.; Farkas, Dana; Christian, James F.

    2016-03-01

    Diffuse correlation spectroscopy (DCS) is a technique which enables powerful and robust non-invasive optical studies of tissue micro-circulation and vascular blood flow. The technique amounts to autocorrelation analysis of coherent photons after their migration through moving scatterers and subsequent collection by single-mode optical fibers. A primary cost driver of DCS instruments are the commercial hardware-based correlators, limiting the proliferation of multi-channel instruments for validation of perfusion analysis as a clinical diagnostic metric. We present the development of a low-cost scalable correlator enabled by microchip-based time-tagging, and a software-based multi-tau data analysis method. We will discuss the capabilities of the instrument as well as the implementation and validation of 2- and 8-channel systems built for live animal and pre-clinical settings.

  16. Recirculating cross-correlation detector

    DOEpatents

    Andrews, W.H. Jr.; Roberts, M.J.

    1985-01-18

    A digital cross-correlation detector is provided in which two time-varying signals are correlated by repetitively comparing data samples stored in digital form to detect correlation between the two signals. The signals are sampled at a selected rate converted to digital form, and stored in separate locations in separate memories. When the memories are filled, the data samples from each memory are first fed word-by-word through a multiplier and summing circuit and each result is compared to the last in a peak memory circuit and if larger than the last is retained in the peak memory. Then the address line to leading signal memory is offset by one byte to affect one sample period delay of a known amount in that memory and the data in the two memories are then multiplied word-by-word once again and summed. If a new result is larger than a former sum, it is saved in the peak memory together with the time delay. The recirculating process continues with the address of the one memory being offset one additional byte each cycle until the address is shifted through the length of the memory. The correlation between the two signals is indicated by the peak signal stored in the peak memory together with the delay time at which the peak occurred. The circuit is faster and considerably less expensive than comparable accuracy correlation detectors.

  17. Neural Correlates of Stimulus Reportability

    PubMed Central

    Hulme, Oliver J.; Friston, Karl F.; Zeki, Semir

    2012-01-01

    Most experiments on the “neural correlates of consciousness” employ stimulus reportability as an operational definition of what is consciously perceived. The interpretation of such experiments therefore depends critically on understanding the neural basis of stimulus reportability. Using a high volume of fMRI data, we investigated the neural correlates of stimulus reportability using a partial report object detection paradigm. Subjects were presented with a random array of circularly arranged disc-stimuli and were cued, after variable delays (following stimulus offset), to report the presence or absence of a disc at the cued location, using variable motor actions. By uncoupling stimulus processing, decision, and motor response, we were able to use signal detection theory to deconstruct the neural basis of stimulus reportability. We show that retinotopically specific responses in the early visual cortex correlate with stimulus processing but not decision or report; a network of parietal/temporal regions correlates with decisions but not stimulus presence, whereas classical motor regions correlate with report. These findings provide a basic framework for understanding the neural basis of stimulus reportability without the theoretical burden of presupposing a relationship between reportability and consciousness. PMID:18823251

  18. Community Detection for Correlation Matrices

    NASA Astrophysics Data System (ADS)

    MacMahon, Mel; Garlaschelli, Diego

    2015-04-01

    A challenging problem in the study of complex systems is that of resolving, without prior information, the emergent, mesoscopic organization determined by groups of units whose dynamical activity is more strongly correlated internally than with the rest of the system. The existing techniques to filter correlations are not explicitly oriented towards identifying such modules and can suffer from an unavoidable information loss. A promising alternative is that of employing community detection techniques developed in network theory. Unfortunately, this approach has focused predominantly on replacing network data with correlation matrices, a procedure that we show to be intrinsically biased because of its inconsistency with the null hypotheses underlying the existing algorithms. Here, we introduce, via a consistent redefinition of null models based on random matrix theory, the appropriate correlation-based counterparts of the most popular community detection techniques. Our methods can filter out both unit-specific noise and system-wide dependencies, and the resulting communities are internally correlated and mutually anticorrelated. We also implement multiresolution and multifrequency approaches revealing hierarchically nested subcommunities with "hard" cores and "soft" peripheries. We apply our techniques to several financial time series and identify mesoscopic groups of stocks which are irreducible to a standard, sectorial taxonomy; detect "soft stocks" that alternate between communities; and discuss implications for portfolio optimization and risk management.

  19. LCP correlations with improved resolution

    NASA Astrophysics Data System (ADS)

    Heilborn, Lauren; McIntosh, Alan; Jedele, Andrea; Youngs, Mike; Zarrella, Andrew; Yennello, Sherry

    2016-09-01

    Nuclear Equation of State (EoS) is important to a fundamental understanding of nuclear matter. The density dependence of the asymmetry energy, the least constrained term in the EoS, is critical to describing exotic systems such as neutron-rich heavy-ion collisions and neutron stars. Correlation functions of particles emitted in heavy ion reactions (such a p-p correlations) have been predicted to be sensitive to the asymmetry energy. In order to measure correlation functions with high resolution, the Forward Array Using Silicon Technology (FAUST) at the Cyclotron Institute at Texas A&M University has been recently re-commissioned with position-sensitive silicons as the delta-E detectors. A new method of position calibration for FAUST has been developed to take advantage of the 200um position resolution within each detector. Data has been collected from reactions of 40Ar +70Zn, 40Ar +58Fe and 40Ca +58Ni at 40 MeV/nucleon. The three systems allow correlation functions to be compared for systems with varying (N-Z)/A while holding constant either the total charge or the total mass. Light charged particles have been measured, and preliminary investigation of correlations from this campaign will be shown. Transport simulations will also be compared and presented.

  20. Softc: An Operational Software Correlator

    NASA Technical Reports Server (NTRS)

    Lowe, Stephen T.

    2004-01-01

    Softc has been used operationally for spacecraft navigation at JPL for over 2 years and will be JPL's Mark 5 correlator next year. Softc was written to be as close to an ideal correlator as possible, making approximations only below 10(exp -13) seconds. The program can correlate real USB, real LSB, or complex I/Q data sampled with 1, 2, 4. or 8-bit resolution, and was developed with strong debugging tools that made final debugging relatively quick. Softc's algorithms and program structure are fully documented. Timing tests on a recent Intel CPU show Softc processes 8 lags of 1-bit sampled data at 10 MSamples/sec, independent of sample rate.

  1. Correlated optical and isotopic nanoscopy

    PubMed Central

    Saka, Sinem K.; Vogts, Angela; Kröhnert, Katharina; Hillion, François; Rizzoli, Silvio O; Wessels, Johannes T.

    2014-01-01

    The isotopic composition of different materials can be imaged by secondary ion mass spectrometry. In biology, this method is mainly used to study cellular metabolism and turnover, by pulsing the cells with marker molecules such as amino acids labelled with stable isotopes (15N, 13C). The incorporation of the markers is then imaged with a lateral resolution that can surpass 100 nm. However, secondary ion mass spectrometry cannot identify specific subcellular structures like organelles, and needs to be correlated with a second technique, such as fluorescence imaging. Here, we present a method based on stimulated emission depletion microscopy that provides correlated optical and isotopic nanoscopy (COIN) images. We use this approach to study the protein turnover in different organelles from cultured hippocampal neurons. Correlated optical and isotopic nanoscopy can be applied to a variety of biological samples, and should therefore enable the investigation of the isotopic composition of many organelles and subcellular structures. PMID:24718107

  2. Storage capacity of correlated perceptrons

    NASA Astrophysics Data System (ADS)

    Malzahn, D.; Engel, A.; Kanter, I.

    1997-06-01

    We consider an ensemble of K single-layer perceptrons exposed to random inputs and investigate the conditions under which the couplings of these perceptrons can be chosen such that prescribed correlations between the outputs occur. A general formalism is introduced using a multiperceptron cost function that allows one to determine the maximal number of random inputs as a function of the desired values of the correlations. Replica-symmetric results for K=2 and K=3 are compared with properties of two-layer networks of tree-structure and fixed Boolean function between hidden units and output. The results show which correlations in the hidden layer of multilayer neural networks are crucial for the value of the storage capacity.

  3. Physiological correlates of golf performance.

    PubMed

    Wells, Greg D; Elmi, Maryam; Thomas, Scott

    2009-05-01

    Golf is now a sport where physical training is an integral component of elite players' practice and contributes to the ability to play at a high level consistently and without injury. Relationships between physical conditioning and golf performance have not been reported. Therefore, the objective of this research was to identify physiological correlates of golf performance in elite golfers under laboratory (ball speed and distance) and tournament conditions (average score, greens in regulation, short game measures, and putting accuracy).The correlation analysis revealed significant associations between mass, height, body mass index, sit height, arm length, and predicted Vo2max and golf measures. Significant correlations were noted between anterior abdominal muscle endurance and driver carry distance (r = 0.38; P = 0.04) and average putt distance after a chip shot (r = -0.44; P = 0.03), between dominant side abdominal muscle endurance and average putt distance after a chip shot (r = -0.43; P = 0.03), and between nondominant-side abdominal muscle endurance and average putt distance after a sand shot (r = -0.59; P = 0.001). Further correlations were found among sit and reach and driver carry distance (r = -0.36; P = 0.04), 5-iron ball speed (r = - 0.41; P = 0.02), 5-iron carry distance (r = -0.44; P = 0.01), and score (r = 0.43; P = 0.03). Correlation analysis revealed significant associations among peripheral muscle test results, golf driver results, 5-iron ball measures, score, and putting efficacy.These results may be important for developing training programs based on sound physiological rationale and for the development of talent identification programs. Results suggest that core strength and stability, flexibility, balance, and peripheral muscle strength are correlated with golf performance and should be included in golf training programs.

  4. Minimum Bayes risk image correlation

    NASA Technical Reports Server (NTRS)

    Minter, T. C., Jr.

    1980-01-01

    In this paper, the problem of designing a matched filter for image correlation will be treated as a statistical pattern recognition problem. It is shown that, by minimizing a suitable criterion, a matched filter can be estimated which approximates the optimum Bayes discriminant function in a least-squares sense. It is well known that the use of the Bayes discriminant function in target classification minimizes the Bayes risk, which in turn directly minimizes the probability of a false fix. A fast Fourier implementation of the minimum Bayes risk correlation procedure is described.

  5. Correlation properties of loose groups

    SciTech Connect

    Maia, M.A.G.; Da Costa, L.N. )

    1990-02-01

    The two-point spatial correlation function for loose groups of galaxies is computed, using the recently compiled catalog of groups in the southern hemisphere. It is found that the correlation function for groups has a similar slope to that of galaxies but with a smaller amplitude, confirming an earlier result obtained from a similar analysis of the CfA group catalog. This implies that groups of galaxies are more randomly distributed than galaxies, which may be consistent with the predictions of Kashlinsky (1987) for a gravitational clustering scenario for the formation of large-scale structures. 21 refs.

  6. Contradictory correlations between derived scales.

    PubMed

    Thompson, M J; Hand, D J; Everitt, B S

    1991-08-01

    In a clinical trial one scale of pain relief is scored backwards relative to another (high on one corresponding to low on the other), with a consequent large negative correlation. But two derived scales of total pain, obtained by multiplying average pain relief on each scale by duration of pain (common to both pain relief measurements) gave an almost zero correlation. This apparent contradiction is explained by the inverse relationship between the pain relief scales and the large differences in duration of pain experienced by the patients.

  7. Converting Coherence to Quantum Correlations.

    PubMed

    Ma, Jiajun; Yadin, Benjamin; Girolami, Davide; Vedral, Vlatko; Gu, Mile

    2016-04-22

    Recent results in quantum information theory characterize quantum coherence in the context of resource theories. Here, we study the relation between quantum coherence and quantum discord, a kind of quantum correlation which appears even in nonentangled states. We prove that the creation of quantum discord with multipartite incoherent operations is bounded by the amount of quantum coherence consumed in its subsystems during the process. We show how the interplay between quantum coherence consumption and creation of quantum discord works in the preparation of multipartite quantum correlated states and in the model of deterministic quantum computation with one qubit.

  8. PREFACE: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Saxena, Siddharth S.; Littlewood, P. B.

    2012-07-01

    This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which

  9. Multilevel Modeling with Correlated Effects

    ERIC Educational Resources Information Center

    Kim, Jee-Seon; Frees, Edward W.

    2007-01-01

    When there exist omitted effects, measurement error, and/or simultaneity in multilevel models, explanatory variables may be correlated with random components, and standard estimation methods do not provide consistent estimates of model parameters. This paper introduces estimators that are consistent under such conditions. By employing generalized…

  10. Character Recognition Using Correlation Techniques.

    DTIC Science & Technology

    1984-12-01

    public release; distribution unlimited PREFACE The following thesis is a presentation of the results obtained during research on the use of correlation...47 6.3 ENERGY MODIFICATION PROCESS........................49 ViI. RESULTS ......................................................... 51 7.1 SAME...limited the study only to typed letters of the English alphabet.. This excluded stylized print (Script, Gothic, etc.), numerics (1, 23, 58, etc.), and

  11. Tetrachoric Correlation: A Permutation Alternative

    ERIC Educational Resources Information Center

    Long, Michael A.; Berry, Kenneth J.; Mielke, Paul W., Jr.

    2009-01-01

    An exact permutation test is provided for the tetrachoric correlation coefficient. Comparisons with the conventional test employing Student's t distribution demonstrate the necessity of using the permutation approach for small sample sizes and/or disproportionate marginal frequency totals. (Contains 4 tables.)

  12. The Physiological Correlates of Learning.

    ERIC Educational Resources Information Center

    Davis, Mary

    The author reviews the literature and makes tentative conclusions concerning the physiological correlates of learning and memory. Particular attention is given to the issues of spinal cord learning, subcortical learning, cerebral cortex learning, localization of learning within the brain (specificity vs. non-specificity), and association areas…

  13. Sample Size for Correlation Estimates

    DTIC Science & Technology

    1989-09-01

    graphs, and computer programs are developed to find the sample number needed for a desired confidence interval size. Nonparametric measures of...correlation (Spearman’s ra and Kendall’s tau) are also examined for appropriate sample numbers when a specific confidence interval size desired.

  14. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-01-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  15. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-08-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  16. Resistant multiple sparse canonical correlation.

    PubMed

    Coleman, Jacob; Replogle, Joseph; Chandler, Gabriel; Hardin, Johanna

    2016-04-01

    Canonical correlation analysis (CCA) is a multivariate technique that takes two datasets and forms the most highly correlated possible pairs of linear combinations between them. Each subsequent pair of linear combinations is orthogonal to the preceding pair, meaning that new information is gleaned from each pair. By looking at the magnitude of coefficient values, we can find out which variables can be grouped together, thus better understanding multiple interactions that are otherwise difficult to compute or grasp intuitively. CCA appears to have quite powerful applications to high-throughput data, as we can use it to discover, for example, relationships between gene expression and gene copy number variation. One of the biggest problems of CCA is that the number of variables (often upwards of 10,000) makes biological interpretation of linear combinations nearly impossible. To limit variable output, we have employed a method known as sparse canonical correlation analysis (SCCA), while adding estimation which is resistant to extreme observations or other types of deviant data. In this paper, we have demonstrated the success of resistant estimation in variable selection using SCCA. Additionally, we have used SCCA to find multiple canonical pairs for extended knowledge about the datasets at hand. Again, using resistant estimators provided more accurate estimates than standard estimators in the multiple canonical correlation setting. R code is available and documented at https://github.com/hardin47/rmscca.

  17. Correlation for Sessile Drop Evaporation

    NASA Astrophysics Data System (ADS)

    Kelly-Zion, Peter; Pursell, Christopher; Wassom, Gregory; Mandelkorn, Brenton; Nkinthorn, Chris

    2016-11-01

    To better understand how the evaporation of sessile drops and small puddles is controlled by the vapor phase transport mechanisms of mass diffusion and buoyancy-induced convection, the evaporation rates of eight liquids evaporating under a broad range of ambient conditions were correlated with physical and geometrical properties. Examination of the correlation provides valuable insight into how the roles of diffusive and convective transport change with physical and geometrical parameters. The correlation predicts measured evaporation rates to within a root-mean-square error of 7.3%. The correlation is composed of two terms, a term which provides the rate of evaporation under diffusion-only conditions, and a term which provides the influence of convection. This second term suggests the manner in which the processes of diffusion and convection are coupled. Both processes are dependent on the distribution of the vapor, through the molar concentration gradient for diffusion and through the mass density gradient for convection. The term representing the influence of convection is approximately inversely proportional to the square root of diffusivity, indicating the tendency of diffusive transport to reduce convection by making the vapor distribution more uniform. Financial support was provided by the ACS Petroleum Research Fund.

  18. Separating Spike Count Correlation from Firing Rate Correlation

    PubMed Central

    Vinci, Giuseppe; Ventura, Valérie; Smith, Matthew A.; Kass, Robert E.

    2016-01-01

    Populations of cortical neurons exhibit shared fluctuations in spiking activity over time. When measured for a pair of neurons over multiple repetitions of an identical stimulus, this phenomenon emerges as correlated trial-to-trial response variability via spike count correlation (SCC). However, spike counts can be viewed as noisy versions of firing rates, which can vary from trial to trial. From this perspective, the SCC for a pair of neurons becomes a noisy version of the corresponding firing-rate correlation (FRC). Furthermore, the magnitude of the SCC is generally smaller than that of the FRC, and is likely to be less sensitive to experimental manipulation. We provide statistical methods for disambiguating time-averaged drive from within-trial noise, thereby separating FRC from SCC. We study these methods to document their reliability, and we apply them to neurons recorded in vivo from area V4, in an alert animal. We show how the various effects we describe are reflected in the data: within-trial effects are largely negligible, while attenuation due to trial-to-trial variation dominates, and frequently produces comparisons in SCC that, because of noise, do not accurately reflect those based on the underlying FRC. PMID:26942746

  19. UPPER WIND CORRELATIONS IN SOUTHWESTERN UNITED STATES

    DTIC Science & Technology

    simple technique for using the correlations as a forecast aid is presented, including the necessary constants. The total vector correlation coefficient is compared to the vector stretch correlation coefficient ; the former is favored.

  20. Modeling correlation with flight data

    NASA Technical Reports Server (NTRS)

    Ehlers, H. K. F.

    1983-01-01

    The molecular contamination flow model (space 2 program) predicts the induced environment of the space shuttle orbiter/payload on orbit as well as the induced gas flow between the orbiter and payload surfaces. This computer program relates the input parameters which characterize the time dependent status of the orbiter/payload to the required output parameters. An application of the model to data from space transportation system flights 1, 2, and 3 shows that the model correlates well for direct flow and for return flux (STS-2/H2O). Correlation for return flux from other molecular sources/species appears to be within expectations but more analysis is required. The space 2 model seems to be an adequate predictive tool.

  1. Thermoelectric properties of correlated materials

    NASA Astrophysics Data System (ADS)

    Tomczak, Jan; Haule, Kristjan; Miyake, Takashi; Georges, Antoine; Kotliar, Gabriel

    2011-03-01

    The discovery of large Seebeck coefficients in transition metal compounds such as FeSi, FeSb2, or the iron pnictides, has stirred renewed interest in the potential merits of electronic correlation effects for thermoelectric properties. The notorious sensitivity in this class of materials to small changes in composition (doping, chemical pressure) and external stimuli (temperature, pressure), makes a reliable and, possibly, predictive description cumbersome, while at the same time providing an arena of possibilities in the search for high performance thermoelectrics. Based on state-of-the-art electronic structure methods (density functional theory with the dynamical mean field theory) we here compute the thermoelectric response for several of the above mentioned exemplary materials from first principles. With the ultimate goal to understand the origin of a large thermoelectricity in these systems, we discuss various many-body renormalizations, and identify correlation controlled ingredients that are pivotal for thermopower enhancements.

  2. Time-of-arrival correlations

    NASA Astrophysics Data System (ADS)

    Anastopoulos, Charis; Savvidou, Ntina

    2017-03-01

    We propose that measurements of time-of-arrival correlations in multipartite systems can sharply distinguish between different approaches to the time-of-arrival problem. To show this, we construct a positive-operator-valued measure for two distinct time-of-arrival measurements in a bipartite system, and we prove that the resulting probabilities differ strongly from ones defined in terms of probability currents. We also prove that time-of-arrival correlations are entanglement witnesses, a result suggesting the use of temporal observables for quantum information processing tasks. Finally, we construct the probabilities for sequential time-of-arrival measurements on a single particle. We derive the state-reduction rule for time-of-arrival measurements; it differs significantly from the standard one, because time-of-arrival measurements are not defined at a single predetermined moment of time.

  3. [Correlation between EEG and neuroimaging].

    PubMed

    Tobimatsu, Shozo

    2012-01-01

    The present state of knowledge of physiological mechanisms underlying nonepileptiform EEG abnormalities is reviewed to clarify the correlation between EEG and neuroimaging. Focal and widespread slow waves, background abnormalities, and bursts of rhythmic slow activity are discussed. EEG phenomena were correlated with lesion size, location, type (white matter vs. gray matter, high density vs. low density), and mass effect. Clinical and experimental accumulated over the past five decades suggest that polymorphic slow activity is generated in cerebral cortex by layers of pyramidal cells and is probably due to partial deafferentation from subcortical areas. Unilateral background activity changes are probably thalamic dysfunction, and bilateral paroxysmal slow activity is due to abnormal thalamocortical circuits combined with cortical pathology. Paroxysmal discharges indicate the presence of epilepsy with possible brain lesion(s). The EEG is a functional test and provides us complementary information to neuroimaging studies.

  4. Biphoton states in correlated turbulence

    NASA Astrophysics Data System (ADS)

    Roux, Filippus S.

    2017-02-01

    The effect of turbulence on a pair of photons propagating together through the same medium is analyzed. The behavior is compared to the case where these photons propagate separately through different turbulent media. The analysis is done with a multiple phase screen approach, by deriving and solving an infinitesimal propagation equation. We apply these results to the case where the initial photons are entangled in their spatial degrees of freedom with the aid of spontaneous parametric down-conversion. It is found that for this input state, the decay of entanglement in correlated media under the weak scintillation approximation is quicker than in uncorrelated media. Beyond the weak scintillation approximation, the entanglement in correlated media decays slower when it is close to zero—approaching zero asymptotically as a function of scintillation strength. This is contrary to the case in uncorrelated media where entanglement becomes zero at a finite scintillation strength.

  5. Correlated Electrons in Reduced Dimensions

    SciTech Connect

    Bonesteel, Nicholas E

    2015-01-31

    This report summarizes the work accomplished under the support of US DOE grant # DE-FG02-97ER45639, "Correlated Electrons in Reduced Dimensions." The underlying hypothesis of the research supported by this grant has been that studying the unique behavior of correlated electrons in reduced dimensions can lead to new ways of understanding how matter can order and how it can potentially be used. The systems under study have included i) fractional quantum Hall matter, which is realized when electrons are confined to two-dimensions and placed in a strong magnetic field at low temperature, ii) one-dimensional chains of spins and exotic quasiparticle excitations of topologically ordered matter, and iii) electrons confined in effectively ``zero-dimensional" semiconductor quantum dots.

  6. CMS results on multijet correlations

    SciTech Connect

    Safronov, Grigory

    2015-04-10

    We present recent CMS measurements on multijet correlations using forward and low-p{sub T} jets, focusing on searches for BFKL and saturation phenomena. In pp collisions at √(s)=7 TeV, azimuthal correlations in dijets separated in rapidity by up to 9.4 units were measured. The results are compared to BFKL- and DGLAP-based predictions. In pp collisions at √(s)=8 TeV, cross sections for jets with p{sub T} > 21 GeV and |y| < 4.7, and for track-jets with p{sub T} > 1 GeV (minijets) are presented. The minijet results are sensitive to the bound imposed by the total inelastic cross section, and are compared to various models for taming the growth of the 2 → 2 cross section at low p{sub T}.

  7. Semantic Event Correlation Using Ontologies

    NASA Astrophysics Data System (ADS)

    Moser, Thomas; Roth, Heinz; Rozsnyai, Szabolcs; Mordinyi, Richard; Biffl, Stefan

    Complex event processing (CEP) is a software architecture paradigm that aims at low latency, high throughput, and quick adaptability of applications for supporting and improving event-driven business processes. Events sensed in real time are the basic information units on which CEP applications operate and react in self-contained decision cycles based on defined processing logic and rules. Event correlation is necessary to relate events gathered from various sources for detecting patterns and situations of interest in the business context. Unfortunately, event correlation has been limited to syntactically identical attribute values instead of addressing semantically equivalent attribute meanings. Semantic equivalence is particularly relevant if events come from organizations that use different terminologies for common concepts.

  8. Object Tracking Through Adaptive Correlation

    DTIC Science & Technology

    1992-12-17

    would like to thank my advisor, Maj. Steven K. Rogers, along with the rest of my thesis committee, Capt. Dennis W. Ruck and Dr . Mark Oxley, for...rigorously by students at the Air Force Institute of Technology (AFIT) under the direction of Dr . Steven Rogers. These studies have examined many...utilizing this information, an adaptive template algorithm was developed. The algorithm began by checking the location of the correlation peak to see if the

  9. Radial Correlations Between Two Quarks

    NASA Astrophysics Data System (ADS)

    Green, A. M.; Koponen, J.; Pennanen, P.; Michael, C.

    2002-04-01

    In nuclear many-body problems the short-range correlation between two nucleons is well described by the corresponding correlation in the two-body problem. Therefore, as a first step in any attempt at an analogous description of many-quark systems, it is necessary to know the two-quark correlation. With this in mind, we study the light quark distribution in a heavy-light meson with a static heavy quark. The charge and matter radial distributions of these heavy-light mesons are measured on a lattice with a light quark mass about that of the strange quark. Both distributions can be well fitted upto r ≈ 0.7 fm with the exponential form wi2 (r), where Wi(r) = A exp(-r/ri). For the charge(c) and matter(m) distributions rc ≈ 0.32(2)fm and rm ≈ 0.24(2)fm. We also discuss the normalisation of the total charge (defined to be unity in the continuum limit) and matter integrated over all space, finding 1.30(5) and 0.4(1) respectively for a lattice spacing ≈ 0.17 fm.

  10. Quantum correlations beyond Tsirelson's bound

    NASA Astrophysics Data System (ADS)

    Berry, Dominic; Ringbauer, Martin; Fedrizzi, Alessandro; White, Andrew

    2014-03-01

    Violations of Bell inequalities show that there are correlations that cannot explained by any classical theory. Further violation, beyond Tsirelson's bound, shows that there are correlations that are not explained by quantum mechanics. Such super-quantum correlations would enable violation of information causality, where communication of one bit provides more than one bit of information [Nature 461, 1101 (2009)]. An unavoidable feature of all realistic Bell inequality experiments is loss. If one postselects on successful measurements, unentangled states can violate Bell inequalities. On the other hand, loss can be used to enhance the violation of Bell inequalities for entangled states. This can improve the ability to distinguish between entangled and unentangled states, despite loss. Here we report an optical experiment providing maximal violation of the CHSH-Bell inequality with entangled states. Due to loss and postselection, Tsirelson's bound is also violated. This enables us to more easily distinguish between entangled and unentangled states. In addition, it provides violation of information causality for the postselected data.

  11. Correlated Temporal and Spectral Variability

    NASA Technical Reports Server (NTRS)

    Swank, Jean H.

    2007-01-01

    The variability of neutron star and black hole X-ray sources has several dimensions, because of the roles played by different important time-scales. The variations on time scales of hours, weeks, and months, ranging from 50% to orders of magnitude, arise out of changes in the flow in the disk. The most important driving forces for those changes are probably various possible instabilities in the disk, though there may be effects with other dominant causes. The changes in the rate of flow appear to be associated with changes in the flow's configuration, as the accreting material approaches the compact object, for there are generally correlated changes in both the Xray spectra and the character of the faster temporal variability. There has been a lot of progress in tracking these correlations, both for Z and Atoll neutron star low-mass X-ray binaries, and for black hole binaries. I will discuss these correlations and review briefly what they tell us about the physical states of the systems.

  12. NMR studies of DNA duplexes singly cross-linked by different synthetic linkers.

    PubMed Central

    Altmann, S; Labhardt, A M; Bur, D; Lehmann, C; Bannwarth, W; Billeter, M; Wüthrich, K; Leupin, W

    1995-01-01

    Molecular modelling studies resulted in the design of a variety of non-nucleotidic covalent linkers to bridge the 3'-end of the (+)-strand and the 5'-end of the (-)-strand in DNA duplexes. Three of these linkers were synthesized and used to prepare singly cross-linked duplexes d(GTGGAATTC)-linker-d(GAATTCCAC). Linker I is an assembly of a propylene-, a phosphate- and a second propylene-group and is thought to mimic the backbone of two nucleotides. Linkers II and III consist of five and six ethyleneglycol units, respectively. The melting temperatures of the cross-linked duplexes are 65 degrees C for I and 73 degrees C for II and III, as compared with 36 degrees C for the corresponding non-linked nonadeoxynucleotide duplex. The three cross-linked duplexes were structurally characterized by nuclear magnetic resonance spectroscopy. The 1H and 31P resonance assignments in the DNA stem were obtained using standard methods. For the resonance assignment of the linker protons, two-dimensional 1H-31P heteronuclear COSY and two-quantum-experiments were used. Distance geometry calculations with NOE-derived distance constraints were performed and the resulting structures were energy-minimized. In duplex I, the nucleotides flanking the propylene-phosphate-propylene-linker do not form a Watson-Crick base pair, whereas in duplexes II and III the entire DNA stem is in a B-type double helix conformation. Images PMID:8532525

  13. Measures and models for angular correlation and angular-linear correlation. [correlation of random variables

    NASA Technical Reports Server (NTRS)

    Johnson, R. A.; Wehrly, T.

    1976-01-01

    Population models for dependence between two angular measurements and for dependence between an angular and a linear observation are proposed. The method of canonical correlations first leads to new population and sample measures of dependence in this latter situation. An example relating wind direction to the level of a pollutant is given. Next, applied to pairs of angular measurements, the method yields previously proposed sample measures in some special cases and a new sample measure in general.

  14. Iterative method for generating correlated binary sequences

    NASA Astrophysics Data System (ADS)

    Usatenko, O. V.; Melnik, S. S.; Apostolov, S. S.; Makarov, N. M.; Krokhin, A. A.

    2014-11-01

    We propose an efficient iterative method for generating random correlated binary sequences with a prescribed correlation function. The method is based on consecutive linear modulations of an initially uncorrelated sequence into a correlated one. Each step of modulation increases the correlations until the desired level has been reached. The robustness and efficiency of the proposed algorithm are tested by generating sequences with inverse power-law correlations. The substantial increase in the strength of correlation in the iterative method with respect to single-step filtering generation is shown for all studied correlation functions. Our results can be used for design of disordered superlattices, waveguides, and surfaces with selective transport properties.

  15. Variable Selection through Correlation Sifting

    NASA Astrophysics Data System (ADS)

    Huang, Jim C.; Jojic, Nebojsa

    Many applications of computational biology require a variable selection procedure to sift through a large number of input variables and select some smaller number that influence a target variable of interest. For example, in virology, only some small number of viral protein fragments influence the nature of the immune response during viral infection. Due to the large number of variables to be considered, a brute-force search for the subset of variables is in general intractable. To approximate this, methods based on ℓ1-regularized linear regression have been proposed and have been found to be particularly successful. It is well understood however that such methods fail to choose the correct subset of variables if these are highly correlated with other "decoy" variables. We present a method for sifting through sets of highly correlated variables which leads to higher accuracy in selecting the correct variables. The main innovation is a filtering step that reduces correlations among variables to be selected, making the ℓ1-regularization effective for datasets on which many methods for variable selection fail. The filtering step changes both the values of the predictor variables and output values by projections onto components obtained through a computationally-inexpensive principal components analysis. In this paper we demonstrate the usefulness of our method on synthetic datasets and on novel applications in virology. These include HIV viral load analysis based on patients' HIV sequences and immune types, as well as the analysis of seasonal variation in influenza death rates based on the regions of the influenza genome that undergo diversifying selection in the previous season.

  16. Precision protection through indirect correlations

    SciTech Connect

    Jin, Yao

    2016-04-15

    The dynamics of the quantum Fisher information of the parameters of the initial atomic state is studied, in the framework of open quantum systems, for a pair of static two-level atoms coupled to a bath of fluctuating vacuum scalar fields. Our results show that the correlations between the two atoms as well as the precision limit in quantum metrology are determined by the separation between the two atoms. Remarkably, when the separation between the two atoms approaches zero, the quantum Fisher information, thus the precision limit of the estimation of the parameters of the initial atomic state will be survived from the vacuum fluctuations after long time evolution.

  17. Preselected Sub-Poissonian Correlations

    NASA Technical Reports Server (NTRS)

    Pavicic, Mladen

    1996-01-01

    The simplest possible photon-number-squeezed states containing only two photons and exhibiting sub-poissonian statistics with the Fano factor approaching 0.5 have been used for a proposal of a loophole-free Bell experiment requiring only 67 percent of detection efficiency. The states are obtained by the fourth order interference first of two downconverted photons at an asymmetrical beam splitter and thereupon of two photons from two independent singlets at an asymmetrical beam splitter. In the latter set-up, the other two photons which nowhere interacted and whose paths never crossed appear entangled in a singlet-like correlated state.

  18. Speeding up local correlation methods

    SciTech Connect

    Kats, Daniel

    2014-12-28

    We present two techniques that can substantially speed up the local correlation methods. The first one allows one to avoid the expensive transformation of the electron-repulsion integrals from atomic orbitals to virtual space. The second one introduces an algorithm for the residual equations in the local perturbative treatment that, in contrast to the standard scheme, does not require holding the amplitudes or residuals in memory. It is shown that even an interpreter-based implementation of the proposed algorithm in the context of local MP2 method is faster and requires less memory than the highly optimized variants of conventional algorithms.

  19. Correlation dimension of complex networks.

    PubMed

    Lacasa, Lucas; Gómez-Gardeñes, Jesús

    2013-04-19

    We propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks and real-world networks such as the world air-transportation network or urban networks, and provides a computationally fast way for estimating the dimensionality of networks which only relies on the local information provided by the walkers.

  20. Pairing Correlations at High Spins

    NASA Astrophysics Data System (ADS)

    Ma, Hai-Liang; Dong, Bao-Guo; Zhang, Yan; Fan, Ping; Yuan, Da-Qing; Zhu, Shen-Yun; Zhang, Huan-Qiao; Petrache, C. M.; Ragnarsson, I.; Carlsson, B. G.

    The pairing correcting energies at high spins in 161Lu and 138Nd are studied by comparing the results of the cranked-Nilsson-Strutinsky (CNS) and cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) models. It is concluded that the Coriolis effect rather than the rotational alignment effect plays a major role in the reduction of the pairing correlations in the high spin region. Then we proposed an average pairing correction method which not only better reproduces the experimental data comparing with the CNS model but also enables a clean-cut tracing of the configurations thus the full-spin-range discussion on the various rotating bands.

  1. Image Alignment and Correlation System.

    DTIC Science & Technology

    1980-07-01

    THRESHOLD VS. THRESHOLD SET THRESHOLD TO GIVE NPT POINTS SEARCH FOR PROMINENT SPATIAL FREOENCIES ANDCOMPUTE S1U, SlV , SIUV VARIABLES FORENTER N LEAST...SIU, SlV , S1UV VARIABUS FOR LEAST SQUARES Y Figurell Flow Diagram for Subroutine MEASRE -54- CCIPUrE SlUP *SIVP VARIABLES FR LEASTr SJARES Lm . -55...table to the position of maximum correlation. Subroutine SUMPAR computes UU, UV, VV, UP and VP from the partial products SIU, SlV , SlUV, SlUP and S1VP

  2. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Ronning, Filip; Batista, Cristian

    2011-03-01

    Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context. The 2010 International Conference on Strongly Correlated Electron Systems was held in Santa Fe, New Mexico, a reunion of sorts from the 1989 International Conference on the Physics of Highly Correlated Electron Systems that also convened in Santa Fe. SCES 2010—co-chaired by John Sarrao and Joe Thompson—followed the tradition of earlier conferences, in this century, hosted by Buzios (2008), Houston (2007), Vienna (2005), Karlsruhe (2004), Krakow (2002) and Ann Arbor (2001). Every three years since 1997, SCES has joined the International Conference on Magnetism (ICM), held in Recife (2000), Rome (2003), Kyoto (2006) and Karlsruhe (2009). Like its predecessors, SCES 2010 topics included strongly correlated f- and d-electron systems, heavy-fermion behaviors, quantum-phase transitions, non-Fermi liquid phenomena, unconventional superconductivity, and emergent states that arise from electronic correlations. Recent developments from studies of quantum magnetism and cold atoms complemented the traditional subjects and were included in SCES 2010. 2010 celebrated the 400th anniversary of Santa Fe as well as the birth of astronomy. So what's the connection to SCES? The Dutch invention of the first practical telescope and its use by Galileo in 1610 and subsequent years overturned dogma that the sun revolved about the earth. This revolutionary, and at the time heretical, conclusion required innovative combinations of new instrumentation, observation and mathematics. These same combinations are just as important 400 years later and are the foundation of scientific discoveries that were discussed

  3. Novelty filtered optical correlator using photorefractive crystal

    NASA Technical Reports Server (NTRS)

    Liu, Duncan T. H.; Chao, Tien-Hsin; Cheng, Li-Jen

    1992-01-01

    We demonstrate a new optical correlator in which the correlation peak intensity is increased when the matched input object is moving. The basic configuration of the correlator is the same as a VanderLugt optical correlator consisting of a photorefractive crystal. The principal of this new correlator is based on the dynamic grating erasure property of photorefractive materials. The detail of this principle is described.

  4. Dipolar correlations in liquid water

    SciTech Connect

    Zhang, Cui; Galli, Giulia

    2014-08-28

    We present an analysis of the dipolar correlations in water as a function of temperature and density and in the presence of simple ionic solutes, carried out using molecular dynamics simulations and empirical potentials. We show that the dipole-dipole correlation function of the liquid exhibits sizable oscillations over nanodomains of about 1.5 nm radius, with several isosbestic points as a function of temperature; the size of the nanodomains is nearly independent on temperature and density, between 240 and 400 K and 0.9 and 1.3 g/cm{sup 3}, but it is substantially affected by the presence of solvated ions. In the same range of thermodynamic conditions, the decay time (τ) of the system dipole moment varies by a factor of about 30 and 1.5, as a function of temperature and density, respectively. At 300 K, we observed a maximum in τ as a function of density, and a corresponding shallow maximum in the tetrahedral order parameter, in a range where the diffusion coefficient, the pressure and the dielectric constant increase monotonically.

  5. Fiducial marker for correlating images

    DOEpatents

    Miller, Lisa Marie; Smith, Randy J.; Warren, John B.; Elliott, Donald

    2011-06-21

    The invention relates to a fiducial marker having a marking grid that is used to correlate and view images produced by different imaging modalities or different imaging and viewing modalities. More specifically, the invention relates to the fiducial marking grid that has a grid pattern for producing either a viewing image and/or a first analytical image that can be overlaid with at least one other second analytical image in order to view a light path or to image different imaging modalities. Depending on the analysis, the grid pattern has a single layer of a certain thickness or at least two layers of certain thicknesses. In either case, the grid pattern is imageable by each imaging or viewing modality used in the analysis. Further, when viewing a light path, the light path of the analytical modality cannot be visualized by viewing modality (e.g., a light microscope objective). By correlating these images, the ability to analyze a thin sample that is, for example, biological in nature but yet contains trace metal ions is enhanced. Specifically, it is desired to analyze both the organic matter of the biological sample and the trace metal ions contained within the biological sample without adding or using extrinsic labels or stains.

  6. The Neurogenetic Correlates of Consciousness

    NASA Astrophysics Data System (ADS)

    Grandy, John K.

    2013-09-01

    The neurogenetic correlates of consciousness (NgCC) is a new field of consciousness studies that focuses on genes that have an effect on or are involved in the continuum of neuron-based consciousness. A framework of consciousness based on the neural correlates of consciousness (NCC) has already been established by Francis Crick and Christof Kock. In this work I propose that there are NgCC underlying the NCC which are both active during the conscious experience. So how are genes involved? There are two significant connections between DNA and neurons that are involved in the conscious experience. First, any brain system can be adversely affected by underlying genetic abnormalities which can be expressed in an individual at birth, in adulthood, or later in life. Second, the DNA molecule does not lay dormant while the neuron runs on autopilot. DNA is active in translating and transcribing RNA and protein products that are utilized during neuron functioning. Without these products being continuously produced by the DNA during a conscious experience the neurons would cease to function correctly and be rendered unable to provide a continuum of human consciousness. Consequently, in addition to NCC, NgCC must be factored in when appreciating a conscious event. In this work I will discuss and explain some NgCC citing several examples.

  7. Strongly correlated perovskite fuel cells

    NASA Astrophysics Data System (ADS)

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram

    2016-06-01

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

  8. Correlations in cosmic density fields

    NASA Astrophysics Data System (ADS)

    Bromley, B. C.

    1994-12-01

    A method is proposed to place constraints on the functional form of the high-order correlation functions zetan that arise in cosmic density fields at large scales. This technique is based on a mass-in-cell statistic and a difference of mass in partitions of a cell. The relationship between these measures is sensitive to the formal structure of the zetan as well as their amplitudes. This relationship is quantified in several theoretical models of structure, based on the hierarchical clustering paradigm. The results lead to a test for specific types of hierarchical clustering that is sensitive to correlations of all orders. The method is applied to examples of simulated large-scaled structure dominated by cold dark matter. In the preliminary study, the hierarchical paradigm appears to be a realistic approximation over a broad range of the scales. Furthermore, there is evidence that graphs of low-order vertices are dominant. On the basis of simulated data a phenomological model is specified that gives a good representation of clustering from linear scales to the strongly clustered regime (zeta2 approximately 500).

  9. EEG, temporal correlations, and avalanches.

    PubMed

    Benayoun, Marc; Kohrman, Michael; Cowan, Jack; van Drongelen, Wim

    2010-12-01

    Epileptiform activity in the EEG is frequently characterized by rhythmic, correlated patterns or synchronized bursts. Long-range temporal correlations (LRTC) are described by power law scaling of the autocorrelation function and have been observed in scalp and intracranial EEG recordings. Synchronous large-amplitude bursts (also called neuronal avalanches) have been observed in local field potentials both in vitro and in vivo. This article explores the presence of neuronal avalanches in scalp and intracranial EEG in the context of LRTC. Results indicate that both scalp and intracranial EEG show LRTC, with larger scaling exponents in scalp recordings than intracranial. A subset of analyzed recordings also show avalanche behavior, indicating that avalanches may be associated with LRTC. Artificial test signals reveal a linear relationship between the scaling exponent measured by detrended fluctuation analysis and the exponent of the avalanche size distribution. Analysis and evaluation of simulated data reveal that preprocessing of EEG (squaring the signal or applying a filter) affect the ability of detrended fluctuation analysis to reliably measure LRTC.

  10. Strongly correlated perovskite fuel cells

    SciTech Connect

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D.; Ramanathan, Shriram

    2016-05-16

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines1, 2, 3, 4. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number5. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes6. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

  11. Oral health correlates of captivity.

    PubMed

    Kapoor, Varsha; Antonelli, Tyler; Parkinson, Jennifer A; Hartstone-Rose, Adam

    2016-08-01

    The predominant diet fed to captive carnivores in North America consists of ground meat formulated to provide full nutritional requirements. However, this ground meat diet completely lacks the mechanical properties (i.e., toughness and hardness) of the foods these animals would consume in the wild. The goal of this study is to evaluate the effect of captivity on oral health by comparing the prevalence of periodontal disease and dental calculus accumulation in wild and captive lions and tigers (Panthera leo and Panthera tigris), and to also correlate oral health with cranial morphology in these specimens. To achieve this, 34 adult lion and 29 adult tiger skulls were scored for the presence and extent of dental calculus and periodontal disease. These oral health scores were also compared to cranial deformations examined in a previous study. We found that the occurrence and severity of calculus buildup and periodontal disease was significantly higher in captive felids compared to their wild counterparts. Further, higher calculus accumulation occurred on the posterior teeth when compared to the anterior teeth, while an opposite trend for periodontal disease was observed. We also found a significant correlation between oral health and cranial morphology of lions and tigers. The results suggest that food mechanical properties are significant factors contributing to oral health in felids.

  12. The dynamics of correlated novelties

    NASA Astrophysics Data System (ADS)

    Tria, F.; Loreto, V.; Servedio, V. D. P.; Strogatz, S. H.

    2014-07-01

    Novelties are a familiar part of daily life. They are also fundamental to the evolution of biological systems, human society, and technology. By opening new possibilities, one novelty can pave the way for others in a process that Kauffman has called ``expanding the adjacent possible''. The dynamics of correlated novelties, however, have yet to be quantified empirically or modeled mathematically. Here we propose a simple mathematical model that mimics the process of exploring a physical, biological, or conceptual space that enlarges whenever a novelty occurs. The model, a generalization of Polya's urn, predicts statistical laws for the rate at which novelties happen (Heaps' law) and for the probability distribution on the space explored (Zipf's law), as well as signatures of the process by which one novelty sets the stage for another. We test these predictions on four data sets of human activity: the edit events of Wikipedia pages, the emergence of tags in annotation systems, the sequence of words in texts, and listening to new songs in online music catalogues. By quantifying the dynamics of correlated novelties, our results provide a starting point for a deeper understanding of the adjacent possible and its role in biological, cultural, and technological evolution.

  13. Strongly correlated perovskite fuel cells.

    PubMed

    Zhou, You; Guan, Xiaofei; Zhou, Hua; Ramadoss, Koushik; Adam, Suhare; Liu, Huajun; Lee, Sungsik; Shi, Jian; Tsuchiya, Masaru; Fong, Dillon D; Ramanathan, Shriram

    2016-06-09

    Fuel cells convert chemical energy directly into electrical energy with high efficiencies and environmental benefits, as compared with traditional heat engines. Yttria-stabilized zirconia is perhaps the material with the most potential as an electrolyte in solid oxide fuel cells (SOFCs), owing to its stability and near-unity ionic transference number. Although there exist materials with superior ionic conductivity, they are often limited by their ability to suppress electronic leakage when exposed to the reducing environment at the fuel interface. Such electronic leakage reduces fuel cell power output and the associated chemo-mechanical stresses can also lead to catastrophic fracture of electrolyte membranes. Here we depart from traditional electrolyte design that relies on cation substitution to sustain ionic conduction. Instead, we use a perovskite nickelate as an electrolyte with high initial ionic and electronic conductivity. Since many such oxides are also correlated electron systems, we can suppress the electronic conduction through a filling-controlled Mott transition induced by spontaneous hydrogen incorporation. Using such a nickelate as the electrolyte in free-standing membrane geometry, we demonstrate a low-temperature micro-fabricated SOFC with high performance. The ionic conductivity of the nickelate perovskite is comparable to the best-performing solid electrolytes in the same temperature range, with a very low activation energy. The results present a design strategy for high-performance materials exhibiting emergent properties arising from strong electron correlations.

  14. The dynamics of correlated novelties

    PubMed Central

    Tria, F.; Loreto, V.; Servedio, V. D. P.; Strogatz, S. H.

    2014-01-01

    Novelties are a familiar part of daily life. They are also fundamental to the evolution of biological systems, human society, and technology. By opening new possibilities, one novelty can pave the way for others in a process that Kauffman has called “expanding the adjacent possible”. The dynamics of correlated novelties, however, have yet to be quantified empirically or modeled mathematically. Here we propose a simple mathematical model that mimics the process of exploring a physical, biological, or conceptual space that enlarges whenever a novelty occurs. The model, a generalization of Polya's urn, predicts statistical laws for the rate at which novelties happen (Heaps' law) and for the probability distribution on the space explored (Zipf's law), as well as signatures of the process by which one novelty sets the stage for another. We test these predictions on four data sets of human activity: the edit events of Wikipedia pages, the emergence of tags in annotation systems, the sequence of words in texts, and listening to new songs in online music catalogues. By quantifying the dynamics of correlated novelties, our results provide a starting point for a deeper understanding of the adjacent possible and its role in biological, cultural, and technological evolution. PMID:25080941

  15. The Impact of Anisotropic Error Correlation Modelling

    NASA Technical Reports Server (NTRS)

    Swinbank, R.; Riishojgaard, L. P.; Menard, R.

    1999-01-01

    Most data assimilation systems assume isotropic forecast error correlations, but results from two dimensional Kalman Filter experiments indicate that the correlations can be far from isotropic. In this paper we use a simple two-dimensional data assimilation system, which analyses trace chemical species such as ozone, to assess different approaches to modelling the error correlations. We compare assimilation results using isotropic correlations with results obtained using different approaches to modelling anisotropic correlations: first, using correlations based on the concentrations of the trace chemicals, and secondly using an advective correlation model. We show that these relatively cheap ways of modelling anisotropic correlations give objectively better results than using isotropic correlations. We discuss the possible extension of these approaches to a full 3-D meteorological data assimilation system.

  16. Solar wind correlations: Statistical and case studies

    NASA Astrophysics Data System (ADS)

    Paularena, K. I.; Richardson, J. D.; Zastenker, G. N.; Dalin, P. A.

    1999-06-01

    Recent work on solar wind plasma correlations using data from several widely-separated spacecraft (IMP 8, INTERBALL-1, WIND, and ISEE-3) has shown that, for 6-hour periods, the average plasma correlation is ~0.7. The focus of these studies has been directed toward a statistical understanding of gross solar wind correlation behavior. In all correlations examined, lower average correlations are caused by the presence of many points from the low correlation subpopulation; nevertheless, data points from the high correlation population are still present. No single organizational factor has yet been found which adequately separates low-correlation periods from high-correlation periods. Some of the spread in correlations is due to the spatial orientations and dimensions of solar wind structures, and thus to the locational alignments of the spacecraft being correlated, but this does not adequately explain all the good or poor correlations since sometimes three nearby spacecraft show poor correlations, while sometimes three widely-separated space-craft show good correlations. Thus, in order to understand the underlying physics, detailed investigation of individual cases has been undertaken. These results will be important in assigning quality measures to space weather predictions using satellite measurements taken at L1, for example.

  17. EARLINET Correlative Measurements For CALIPSO

    NASA Astrophysics Data System (ADS)

    Pappalardo, G.

    2006-12-01

    EARLINET, the European Aerosol Research Lidar Network, is the first aerosol lidar network, established in 2000, with the main goal to provide a comprehensive, quantitative, and statistically significant data base for the aerosol distribution on a continental scale. At present, 24 stations distributed over Europe are part of the network: 10 single backscatter lidar stations, 7 Raman lidar stations with the Raman channel in the UV for independent measurements of aerosol extinction and backscatter, and 7 multi-wavelength Raman lidar stations (elastic channel at 1064 nm, 532 nm, 355 nm, Raman channels at 532 nm and 355 nm, plus depolarization channel at 532 nm) for the retrieval of aerosol microphysical properties. The network activity is based on scheduled measurements, a rigorous quality assurance program addressing both instruments and evaluation algorithms, and a standardized data exchange format. In order to collect unbiased data, all the network stations perform measurements simultaneously at three fixed dates a week. Lidar observations are performed on a regular schedule of one daytime measurement on Monday around noon, when the boundary layer is usually well developed, and two night time measurements per week (Monday and Thursday), with low background light, in order to perform Raman extinction measurements. Additional network measurements are performed to address specifically important processes that are localized either in space or time, like Saharan dust outbreaks, forest fires, volcanic eruptions, photochemical smog. EARLINET represents an optimal tool to validate CALIPSO lidar data and to provide the necessary information to fully exploit the information from that mission. In particular, aerosol extinction measurements, provided by the network, will be important for the aerosol retrievals from the CALIPSO backscatter lidar. EARLINET started correlative measurements for CALIPSO since 14 June 2006. These EARLINET correlative measurements are performed at

  18. Investigation of correlation classification techniques

    NASA Technical Reports Server (NTRS)

    Haskell, R. E.

    1975-01-01

    A two-step classification algorithm for processing multispectral scanner data was developed and tested. The first step is a single pass clustering algorithm that assigns each pixel, based on its spectral signature, to a particular cluster. The output of that step is a cluster tape in which a single integer is associated with each pixel. The cluster tape is used as the input to the second step, where ground truth information is used to classify each cluster using an iterative method of potentials. Once the clusters have been assigned to classes the cluster tape is read pixel-by-pixel and an output tape is produced in which each pixel is assigned to its proper class. In addition to the digital classification programs, a method of using correlation clustering to process multispectral scanner data in real time by means of an interactive color video display is also described.

  19. Electrophysiological correlates of change detection.

    PubMed

    Eimer, Martin; Mazza, Veronica

    2005-05-01

    To identify electrophysiological correlates of change detection, event-related brain potentials (ERPs) were recorded while participants monitored displays containing four faces in order to detect a face identity change across successive displays. Successful change detection was mirrored by an N2pc component at posterior electrodes contralateral to the side of a change, suggesting close links between conscious change detection and attention. ERPs on undetected-change trials differed from detected-change and no-change trials. We suggest that short-latency ERP differences between these trial types reflect trial-by-trial fluctuations in advance task preparation, whereas differences in the P3 time range are due to variations in the duration of perceptual and decision-related processing. Overall, these findings demonstrate that ERPs are a useful tool for dissociating processes underlying change blindness and change detection.

  20. Physiological correlates of mental workload

    NASA Technical Reports Server (NTRS)

    Zacharias, G. L.

    1980-01-01

    A literature review was conducted to assess the basis of and techniques for physiological assessment of mental workload. The study findings reviewed had shortcomings involving one or more of the following basic problems: (1) physiologic arousal can be easily driven by nonworkload factors, confounding any proposed metric; (2) the profound absence of underlying physiologic models has promulgated a multiplicity of seemingly arbitrary signal processing techniques; (3) the unspecified multidimensional nature of physiological "state" has given rise to a broad spectrum of competing noncommensurate metrics; and (4) the lack of an adequate definition of workload compels physiologic correlations to suffer either from the vagueness of implicit workload measures or from the variance of explicit subjective assessments. Using specific studies as examples, two basic signal processing/data reduction techniques in current use, time and ensemble averaging are discussed.

  1. Correlation effects in metallic cohesion

    NASA Astrophysics Data System (ADS)

    Haydock, Roger

    2014-03-01

    The electronic contribution to the cohesive energy of a correlated metal is the sum of the transition energies for adding successive electrons at successive Fermi levels until the system reaches its final electron density. This can be computed as the integral of energy over the projected density of transitions for adding single electrons to localized orbitals. In the case of independent electrons, this reduces to the usual integral over the projected density of states. As an example, cohesive energies for some simple transition metal structures are calculated using the recursion method* with a Hubbard repulsion between electrons. * Phys. Rev. B 61, 7953-64 Work supported by the Richmond F. Snyder gift to the University of Oregon.

  2. Vibration analysis using digital correlation

    NASA Technical Reports Server (NTRS)

    Gilbert, John A.; Lehner, David L.; Dudderar, T. Dixon; Matthys, Donald R.

    1988-01-01

    This paper demonstrates the use of a computer-based optical method for locating the positions of nodes and antinodes in vibrating members. Structured light patterns are projected at an angle onto the vibrating surface using a 35 mm slide projector. The vibrating surface and the projected images are captured in a time averaged photograph which is subsequently digitized. The inherent fringe patterns are filtered to determine amplitudes of vibration, and computer programs are used to compare the time averaged images to images recorded prior to excitation to locate nodes and antinodes. Some of the influences of pattern regularity on digital correlation are demonstrated, and a speckle-based method for determining the mode shapes and the amplitudes of vibration with variable sensitivity is suggested.

  3. Correlative microscopy of detergent granules.

    PubMed

    van Dalen, G; Nootenboom, P; Heussen, P C M

    2011-03-01

    The microstructure of detergent products for textile cleaning determines to a large extent the physical properties of these products. Correlative microscopy was used to reveal the microstructure by reconciling images obtained by scanning electron microscopy with energy dispersive X-ray analysis, X-ray microtomography and Fourier transform infrared microscopy. These techniques were applied on the same location of a subsample of a spray-dried detergent base powder embedded in polyacrylate. In this way, the three-dimensional internal and external structure of detergent granules could be investigated from milli to nano scale with detailed spatial information about the components present. This will generate knowledge how to design optimal microstructures for laundry products to obtain product properties demanded by the market. This method is also very useful for other powder systems used in a large variety of industries (e.g. for pharmaceutical, food, ceramic and metal industries).

  4. CORRELATIONS IN CONFINED QUANTUM PLASMAS

    SciTech Connect

    DUFTY J W

    2012-01-11

    This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed

  5. Correlated randomness and switching phenomena

    NASA Astrophysics Data System (ADS)

    Stanley, H. E.; Buldyrev, S. V.; Franzese, G.; Havlin, S.; Mallamace, F.; Kumar, P.; Plerou, V.; Preis, T.

    2010-08-01

    One challenge of biology, medicine, and economics is that the systems treated by these serious scientific disciplines have no perfect metronome in time and no perfect spatial architecture-crystalline or otherwise. Nonetheless, as if by magic, out of nothing but randomness one finds remarkably fine-tuned processes in time and remarkably fine-tuned structures in space. Further, many of these processes and structures have the remarkable feature of “switching” from one behavior to another as if by magic. The past century has, philosophically, been concerned with placing aside the human tendency to see the universe as a fine-tuned machine. Here we will address the challenge of uncovering how, through randomness (albeit, as we shall see, strongly correlated randomness), one can arrive at some of the many spatial and temporal patterns in biology, medicine, and economics and even begin to characterize the switching phenomena that enables a system to pass from one state to another. Inspired by principles developed by A. Nihat Berker and scores of other statistical physicists in recent years, we discuss some applications of correlated randomness to understand switching phenomena in various fields. Specifically, we present evidence from experiments and from computer simulations supporting the hypothesis that water’s anomalies are related to a switching point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell), and that the bubbles in economic phenomena that occur on all scales are not “outliers” (another Gladwell immortalization). Though more speculative, we support the idea of disease as arising from some kind of yet-to-be-understood complex switching phenomenon, by discussing data on selected examples, including heart disease and Alzheimer disease.

  6. A Two Factor ANOVA-like Test for Correlated Correlations: CORANOVA

    ERIC Educational Resources Information Center

    Bilker, Warren B.; Brensinger, Colleen; Gur, Ruben C.

    2004-01-01

    Testing homogeneity of correlations with Fisher's Z is inappropriate when correlations are themselves correlated. Suppose measurements of brain activation and performance are taken before and during a verbal memory task. Of interest are changes in activity gradients in specific regions, R1, R2, R3, and performance, V. The "correlated correlations"…

  7. 2004 Photon Correlation and Scattering Conference

    NASA Technical Reports Server (NTRS)

    Meyer, William (Editor); Smart, Anthony (Editor); Wegdam, Gerard (Editor); Dogariu, Aristide (Editor); Carpenter, Bradley (Editor)

    2004-01-01

    The Photon Correlation and Scattering (PCS) meeting welcomes all who are interested in the art and science of photon correlation and its application to optical scattering. The meeting is intended to enhance interactions between theory, applications, instrument design, and participants.

  8. The spatial structure of correlated neuronal variability.

    PubMed

    Rosenbaum, Robert; Smith, Matthew A; Kohn, Adam; Rubin, Jonathan E; Doiron, Brent

    2017-01-01

    Shared neural variability is ubiquitous in cortical populations. While this variability is presumed to arise from overlapping synaptic input, its precise relationship to local circuit architecture remains unclear. We combine computational models and in vivo recordings to study the relationship between the spatial structure of connectivity and correlated variability in neural circuits. Extending the theory of networks with balanced excitation and inhibition, we find that spatially localized lateral projections promote weakly correlated spiking, but broader lateral projections produce a distinctive spatial correlation structure: nearby neuron pairs are positively correlated, pairs at intermediate distances are negatively correlated and distant pairs are weakly correlated. This non-monotonic dependence of correlation on distance is revealed in a new analysis of recordings from superficial layers of macaque primary visual cortex. Our findings show that incorporating distance-dependent connectivity improves the extent to which balanced network theory can explain correlated neural variability.

  9. Arousal and Anxiety Correlates of Gymnastic Performance

    ERIC Educational Resources Information Center

    Basler, Marilyn L.; And Others

    1976-01-01

    Tests on a women's gymnastic team to explore correlation between arousal, anxiety, and performance, revealed limited relationships between performance and arousal/anxiety measures and indicated that gymnastic ability is the best correlate of gymnastic performance. (JD)

  10. Velocity correlations in simulations and observations

    NASA Astrophysics Data System (ADS)

    Wang, Yuyu; Rooney, Christopher; Feldman, Hume; Watkins, Richard

    2017-01-01

    We present an analysis of the two-point cosmic velocity correlation function. We calculate the correlations of the Cosmicflows catalogues and estimate the errors using the Millennium N-body simulations. We estimate the correlation coherence length, and combine the velocity correlation function expectations from linear theory to constrain the cosmological parameters Γ and β. Using the maximum likelihood method, we find a value of Γ = 0 .195-0 . 045 + 0 . 08 (95% CL) that is consistent with the Planck results.

  11. Wind-Tunnel/Flight Correlation, 1981

    NASA Technical Reports Server (NTRS)

    Mckinney, L. W. (Editor); Baals, D. D. (Editor)

    1982-01-01

    Wind-tunnel/flight correlation activities are reviewed to assure maximum effectiveness of the early experimental programs of the National Transonic Facility (NTF). Topics included a status report of the NTF, the role of tunnel-to-tunnel correlation, a review of past flight correlation research and the resulting data base, the correlation potential of future flight vehicles, and an assessment of the role of computational fluid dynamics.

  12. Surface Wear Measurement Using Optical Correlation Technique

    NASA Astrophysics Data System (ADS)

    Acinger, Kresimir

    1983-12-01

    The coherent optical correlation technique was applied for measuring the surface wear of a tappet (part of car engine), worn by friction with the camshaft. It was found that maximum correlation intensity decays exponentially with the number of wear cycles (i.e. camshaft revolutions). Tappets of the same make have an identical rate of correlation decay. Tappets of different makes have different rates of correlation decay which are in agreement with observed long term wear.

  13. Three-point correlations of galaxy clusters

    NASA Technical Reports Server (NTRS)

    Toth, Gabor; Hollosi, Joseph; Szalay, Alexander S.

    1989-01-01

    A relation between two- and three-point correlation functions similar to that of galaxies is presently established by estimating the irreducible angular three-point correlation function of Abell clusters in distance classes 5 and 6, for Galactic latitudes below 40 deg. The shape of the three-point correlation function is fully consistent with the quadratic scaling law found by Groth and Peebles (1977) for galaxies. The three-point correlation function is inconsistent with the expectations from biasing.

  14. Correlators with sℓ2 Yangian symmetry

    NASA Astrophysics Data System (ADS)

    Fuksa, J.; Kirschner, R.

    2017-01-01

    Correlators based on sℓ2 Yangian symmetry and its quantum deformation are studied. Symmetric integral operators can be defined with such correlators as kernels. Yang-Baxter operators can be represented in this way. Particular Yangian symmetric correlators are related to the kernels of QCD parton evolution. The solution of the eigenvalue problem of Yangian symmetric operators is described.

  15. A Note on the Dynamic Correlation Coefficient.

    DTIC Science & Technology

    1977-11-04

    The use of the dynamic correlation coefficient as a test of spuriousness in longitudinal designs was examined. It was shown that given conditions of...spuriousness and perfect stationarity, the dynamic correlation coefficient was positively, rather than inversely, related to spuriousness. It was...recommended that the dynamic correlation coefficient not be used in the future as a test of spuriousness. (Author)

  16. Correlation Distance of Mean Daytime Electron Content

    DTIC Science & Technology

    1977-08-22

    correlation coefficient for the 10 to 16 hour local time period when the diurnal values of TEC are generally highest. Little consistent seasonal differences...were found in the correlation coefficient values. Thus simple linear relations between station separation and correlation coefficient were chosen for

  17. Functional Multiple-Set Canonical Correlation Analysis

    ERIC Educational Resources Information Center

    Hwang, Heungsun; Jung, Kwanghee; Takane, Yoshio; Woodward, Todd S.

    2012-01-01

    We propose functional multiple-set canonical correlation analysis for exploring associations among multiple sets of functions. The proposed method includes functional canonical correlation analysis as a special case when only two sets of functions are considered. As in classical multiple-set canonical correlation analysis, computationally, the…

  18. Economic and Educational Correlates of TIMSS Results

    ERIC Educational Resources Information Center

    Mikk, Jaan

    2005-01-01

    The good knowledge of the correlates of educational achievement highlights the ways to the efficient use of economic and human capital in raising the efficiency of education. The present paper investigates the correlates and compares the values of the correlates for the Republic of Lithuania with the average international values. The data for the…

  19. Statistical correlations of crime with arrests

    NASA Astrophysics Data System (ADS)

    Kuelling, Albert C.

    1997-01-01

    Regression analysis shows that the overall crime rate correlates with the overall arrest rate. Violent crime only weakly correlates with the violent arrest rate, but strongly correlates with the property arrest rate. Contrary to common impressions, increasing arrest rates do not significantly increase loading on incarceration facilities.

  20. Correlation among proprioception, muscle strength, and balance.

    PubMed

    Wang, Huihui; Ji, Zhongqiu; Jiang, Guiping; Liu, Weitong; Jiao, Xibian

    2016-12-01

    [Purpose] To study the correlation among proprioception, muscle strength, and balance. [Subjects and Methods] A balance testing system (Biodex Balance System, BBS) and an isokinetic testing system (Biodex System 4, BS4) were used to test related indexes in 24 healthy young females. [Results] With the knee joint at 15 degree flexion, proprioception was significantly correlated with Limits of Stability-Time values, and was highly significantly correlated with Limits of Stability-Overall and Athlete Single Leg Medial/Lateral values. The sense of force was significantly correlated with Limits of Stability-Overall and Athlete Single Leg-Overall values. Quadriceps strength was significantly associated with Limits of Stability-Overall, Athlete Single Leg Medial/Lateral, and Athlete Double Leg-Overall values. The ratio of Quadriceps to Hamstring strength was significantly correlated with Athlete Single Leg Medial/Lateral, and Athlete Single Leg-Overall values. With the knee joint at 45°, proprioception was highly significantly correlated with dynamic balance, and was significantly correlated with double foot support under static balance; force sense had a high correlation with Limits of Stability-Overall, but no correlation with other indexes. Quadriceps strength had a significant correlation with dynamic and static balance; the ratio of Quadriceps/Hamstring had a highly significant correlation with Limits of Stability-Overall, Athlete Single Leg-Anterior/Posterior and Athlete Single Leg-Overall. [Conclusion] At different knee angles, the correlation differs among proprioception, force sense, quadriceps strength, the Quadriceps/Hamstring ratio, and balance.

  1. Cerebral correlates of visual awareness.

    PubMed

    Milner, A D

    1995-09-01

    While it may be a long time before we can specify the mechanisms through which a brain process achieves awareness, it may be possible to determine as a first step whether awareness is limited to the products of certain kinds of processing. In the domain of vision, for example, perceptual awareness might only be attainable in association with object-centred coding, configural representations of space, and other such forms of abstracted (non-retinocentric) coding. It appears that these forms of visual coding are anatomically restricted to telencephalic structures, and indeed it has been argued that they may be peculiar to, or at least visually dependent upon, the 'ventral stream' of visual areas with the cortex. It is suggested here that such a brain process would still not be able to enter visual awareness unless it was selectively amplified through neuronal gating of the kind that has been shown to be correlated with selective spatial attention. The present paper explores the extent to which this putative dual requirement for visual consciousness might form a basis for understanding the various phenomena of "covert vision" seen in patients suffering from hemianopia, apperceptive agnosia, and unilateral spatial neglect.

  2. Quantum correlations which imply causation

    PubMed Central

    Fitzsimons, Joseph F.; Jones, Jonathan A.; Vedral, Vlatko

    2015-01-01

    In ordinary, non-relativistic, quantum physics, time enters only as a parameter and not as an observable: a state of a physical system is specified at a given time and then evolved according to the prescribed dynamics. While the state can, and usually does, extend across all space, it is only defined at one instant of time. Here we ask what would happen if we defined the notion of the quantum density matrix for multiple spatial and temporal measurements. We introduce the concept of a pseudo-density matrix (PDM) which treats space and time indiscriminately. This matrix in general fails to be positive for measurement events which do not occur simultaneously, motivating us to define a measure of causality that discriminates between spatial and temporal correlations. Important properties of this measure, such as monotonicity under local operations, are proved. Two qubit NMR experiments are presented that illustrate how a temporal pseudo-density matrix approaches a genuinely allowed density matrix as the amount of decoherence is increased between two consecutive measurements. PMID:26675807

  3. Loops in inflationary correlation functions

    NASA Astrophysics Data System (ADS)

    Tanaka, Takahiro; Urakawa, Yuko

    2013-12-01

    We review the recent progress regarding the loop corrections to the correlation functions in the inflationary universe. A naive perturbation theory predicts that the loop corrections generated during inflation suffer from various infrared (IR) pathologies. Introducing an IR cutoff by hand is neither satisfactory nor enough to fix the problem of a secular growth, which may ruin the predictive power of inflation models if the inflation lasts sufficiently long. We discuss the origin of the IR divergences and explore the regularity conditions of the loop corrections for the adiabatic perturbation, the iso-curvature perturbation, and the tensor perturbation, in turn. These three kinds of perturbations have qualitative differences, but in discussing the IR regularity there is a feature common to all cases, which is the importance of the proper identification of observable quantities. Genuinely, observable quantities should respect the gauge invariance from the view point of a local observer. Interestingly, we find that the requirement of the IR regularity restricts the allowed quantum states.

  4. Structural correlates of prospective memory.

    PubMed

    Gordon, Brian A; Shelton, Jill T; Bugg, Julie M; McDaniel, Mark A; Head, Denise

    2011-12-01

    Prospective memory (PM) includes the encoding and maintenance of an intention, and the retrieval and execution of this intention at the proper moment in the future. The present study expands upon previous behavioral, electrophysiological, and functional work by examining the association between grey matter volume and PM. Estimates of grey matter volume in theoretically relevant regions of interest (prefrontal, parietal, and medial temporal) were obtained in conjunction with performance on two PM tasks in a sample of 39 cognitively normal and very mildly demented older adults. The first PM task, termed focal in the literature, is supported by spontaneous retrieval of the PM intention whereas the second, termed non-focal, relies on strategic monitoring processes for successful intention retrieval. A positive relationship was observed between medial temporal volume and accuracy on the focal PM task. An examination of medial temporal lobe subregions revealed that this relationship was strongest for the hippocampus, which is considered to support spontaneous memory retrieval. There were no significant structure-behavior associations for the non-focal PM task. These novel results confirm a relationship between behavior and underlying brain structure proposed by the multiprocess theory of PM, and extend findings on cognitive correlates of medial temporal lobe integrity.

  5. de Finetti reductions for correlations

    NASA Astrophysics Data System (ADS)

    Arnon-Friedman, Rotem; Renner, Renato

    2015-05-01

    When analysing quantum information processing protocols, one has to deal with large entangled systems, each consisting of many subsystems. To make this analysis feasible, it is often necessary to identify some additional structures. de Finetti theorems provide such a structure for the case where certain symmetries hold. More precisely, they relate states that are invariant under permutations of subsystems to states in which the subsystems are independent of each other. This relation plays an important role in various areas, e.g., in quantum cryptography or state tomography, where permutation invariant systems are ubiquitous. The known de Finetti theorems usually refer to the internal quantum state of a system and depend on its dimension. Here, we prove a different de Finetti theorem where systems are modelled in terms of their statistics under measurements. This is necessary for a large class of applications widely considered today, such as device independent protocols, where the underlying systems and the dimensions are unknown and the entire analysis is based on the observed correlations.

  6. Spatial correlation coefficient images for ultrasonic detection.

    PubMed

    Cepel, Raina; Ho, K C; Rinker, Brett A; Palmer, Donald D; Lerch, Terrence P; Neal, Steven P

    2007-09-01

    In ultrasonics, image formation and detection are generally based on signal amplitude. In this paper, we introduce correlation coefficient images as a signal-amplitude independent approach for image formation. The correlation coefficients are calculated between A-scans digitized at adjacent measurement positions. In these images, defects are revealed as regions of high or low correlation relative to the background correlations associated with noise. Correlation coefficient and C-scan images are shown to demonstrate flat-bottom-hole detection in a stainless steel annular ring and crack detection in an aluminum aircraft structure.

  7. Energetics of correlations in interacting systems

    NASA Astrophysics Data System (ADS)

    Friis, Nicolai; Huber, Marcus; Perarnau-Llobet, Martí

    2016-04-01

    A fundamental connection between thermodynamics and information theory arises from the fact that correlations exhibit an inherent work value. For noninteracting systems this translates to a work cost for establishing correlations. Here we investigate the relationship between work and correlations in the presence of interactions that cannot be controlled or removed. For such naturally coupled systems, which are correlated even in thermal equilibrium, we determine general strategies that can reduce the work cost of correlations, and illustrate these for a selection of exemplary physical systems.

  8. Quantifying meta-correlations in financial markets

    NASA Astrophysics Data System (ADS)

    Kenett, Dror Y.; Preis, Tobias; Gur-Gershgoren, Gitit; Ben-Jacob, Eshel

    2012-08-01

    Financial markets are modular multi-level systems, in which the relationships between the individual components are not constant in time. Sudden changes in these relationships significantly affect the stability of the entire system, and vice versa. Our analysis is based on historical daily closing prices of the 30 components of the Dow Jones Industrial Average (DJIA) from March 15th, 1939 until December 31st, 2010. We quantify the correlation among these components by determining Pearson correlation coefficients, to investigate whether mean correlation of the entire portfolio can be used as a precursor for changes in the index return. To this end, we quantify the meta-correlation - the correlation of mean correlation and index return. We find that changes in index returns are significantly correlated with changes in mean correlation. Furthermore, we study the relationship between the index return and correlation volatility - the standard deviation of correlations for a given time interval. This parameter provides further evidence of the effect of the index on market correlations and their fluctuations. Our empirical findings provide new information and quantification of the index leverage effect, and have implications to risk management, portfolio optimization, and to the increased stability of financial markets.

  9. Optical correlators: systems and domains of applications

    NASA Astrophysics Data System (ADS)

    Dragulinescu, Andrei; Cojoc, Dan

    2005-08-01

    The paper presents the basic concepts of the optical correlators. In our knowledge, it is the first systematic presentation of the applications of optical correlators. The main three types of optical correlators: the optical correlator in incoherent light, the optical correlator in coherent light (VanderLugt) and the joint transform correlator are presented. The optical correlators are very powerll systems used for image recognition, that perform a correlation between a bidimensional function which represents a Scene that must be analyzed and another bidimensional function that contains information about the reference function. This correlation is optically realized by a Fourier transform between the two functions. The optical Correlators have found a lot of applications for image recognition and target detection in various fields, such as the military field, robotics, medical field, industry a.s.o. Among the various applications of the optical correlators we can mention: digital fingerprints identification, credit card security, antique scripts recognition, determination of the cosmic ships and satellites behavior, amelioration of cancer tests precision, quality control etc.

  10. The correlates of research success.

    PubMed Central

    Evered, D C; Anderson, J; Griggs, P; Wakeford, R

    1987-01-01

    A survey was carried out of the undergraduate backgrounds and research achievements of 885 (94.1%) of all 940 medically qualified professors and readers in medical faculties in the United Kingdom. A total of 217 (24.5%) of the graduates in these senior academic positions had graduated from Oxford or Cambridge and 137 (15.5%) had an intercalated BSc. The corresponding figures for a control group matched for sex and date of graduation were 118 (13.3%) for Oxford and Cambridge (academic to control odds ratio 2.11:1) and 34 (3.8%) for the BSc (odds ratio 4.58:1). Those with an intercalated BSc in the clinical specialties raised substantially more research grants from the Medical Research Council than their peers from Oxford and Cambridge or those without a BSc. The Oxford and Cambridge group raised more grants in the non-clinical specialties. Bibliometric analysis was carried out on the United Kingdom graduates within the broad specialty of medicine (n = 218) matched for date of graduation. Academics with a BSc had a better publication record over 10 years (median number of original publications 72) than the Oxford and Cambridge group (median 59) and a substantially better record than those from other schools without a BSc (median 46). Citation analysis was carried out on subsets of the above sample matched for date of graduation and frequency of publication. Those with an intercalated BSc were cited more often (8.04 citations/paper) than the Oxford and Cambridge graduates (7.63) and substantially more than their peers without a BSc (4.16). These data show very clearly that research training or experience, or both, as an undergraduate has a substantial influence on career development and correlates positively with subsequent research performance many years later. PMID:3115391

  11. Clinicopathological correlations in cor pulmonale.

    PubMed Central

    Calverley, P M; Howatson, R; Flenley, D C; Lamb, D

    1992-01-01

    BACKGROUND: The relation between pulmonary disease and physiological abnormality in patients with hypoxic cor pulmonale is controversial and the association between arterial hypoxaemia and right ventricular hypertrophy has been challenged. To address these problems matched patients treated with and without domiciliary oxygen were studied. METHODS: Necropsy data were obtained on 19 patients (14 male), 10 of whom had been treated with domiciliary oxygen. Pulmonary artery pressure and total pulmonary vascular resistance as well as blood gas tensions during the breathing of air and oxygen were available for the six months before death. Formalin fixed lung slices were assessed for panacinar and centriacinar emphysema. Right and left ventricular weights were measured and their ratio (LV&S/RV) was used as an index of right ventricular hypertrophy. Carotid body weights were available in 14 cases. RESULTS: Fourteen patients died of respiratory failure and antemortem thrombus was found in the pulmonary arteries of eight cases. Physiological measurements were unrelated to the degree of macroscopic emphysema, pulmonary hypertension, or daytime blood gas tensions. When allowance was made for the higher "ambient" arterial oxygen tension (PaO2) of those who had oxygen, PaO2 was correlated with LV&S/RV (r = 0.79), absolute right ventricular weight (r = -0.53), and carotid body weight (r = 0.68). CONCLUSIONS: These data show that in hypoxic cor pulmonale in vivo physiological disturbances are poor indicators of the underlying disease process. The relation of "ambient" PaO2 to right ventricular hypertrophy and carotid body weight suggests that domiciliary oxygen therapy might lead to regression of such established disease. PMID:1412090

  12. Correlates of depression in bipolar disorder

    PubMed Central

    Moore, Paul J.; Little, Max A.; McSharry, Patrick E.; Goodwin, Guy M.; Geddes, John R.

    2014-01-01

    We analyse time series from 100 patients with bipolar disorder for correlates of depression symptoms. As the sampling interval is non-uniform, we quantify the extent of missing and irregular data using new measures of compliance and continuity. We find that uniformity of response is negatively correlated with the standard deviation of sleep ratings (ρ = –0.26, p = 0.01). To investigate the correlation structure of the time series themselves, we apply the Edelson–Krolik method for correlation estimation. We examine the correlation between depression symptoms for a subset of patients and find that self-reported measures of sleep and appetite/weight show a lower average correlation than other symptoms. Using surrogate time series as a reference dataset, we find no evidence that depression is correlated between patients, though we note a possible loss of information from sparse sampling. PMID:24352942

  13. Correlates of depression in bipolar disorder.

    PubMed

    Moore, Paul J; Little, Max A; McSharry, Patrick E; Goodwin, Guy M; Geddes, John R

    2014-02-07

    We analyse time series from 100 patients with bipolar disorder for correlates of depression symptoms. As the sampling interval is non-uniform, we quantify the extent of missing and irregular data using new measures of compliance and continuity. We find that uniformity of response is negatively correlated with the standard deviation of sleep ratings (ρ = -0.26, p = 0.01). To investigate the correlation structure of the time series themselves, we apply the Edelson-Krolik method for correlation estimation. We examine the correlation between depression symptoms for a subset of patients and find that self-reported measures of sleep and appetite/weight show a lower average correlation than other symptoms. Using surrogate time series as a reference dataset, we find no evidence that depression is correlated between patients, though we note a possible loss of information from sparse sampling.

  14. Clustering stocks using partial correlation coefficients

    NASA Astrophysics Data System (ADS)

    Jung, Sean S.; Chang, Woojin

    2016-11-01

    A partial correlation analysis is performed on the Korean stock market (KOSPI). The difference between Pearson correlation and the partial correlation is analyzed and it is found that when conditioned on the market return, Pearson correlation coefficients are generally greater than those of the partial correlation, which implies that the market return tends to drive up the correlation between stock returns. A clustering analysis is then performed to study the market structure given by the partial correlation analysis and the members of the clusters are compared with the Global Industry Classification Standard (GICS). The initial hypothesis is that the firms in the same GICS sector are clustered together since they are in a similar business and environment. However, the result is inconsistent with the hypothesis and most clusters are a mix of multiple sectors suggesting that the traditional approach of using sectors to determine the proximity between stocks may not be sufficient enough to diversify a portfolio.

  15. Correlates of Pediatric CPAP Adherence

    PubMed Central

    Hawkins, Stephen M.M.; Jensen, Emily L.; Simon, Stacey L.; Friedman, Norman R.

    2016-01-01

    pathophysiology of and to develop adherence-promoting and alternative interventions for pediatric OSA. Citation: Hawkins SM, Jensen EL, Simon SL, Friedman NR. Correlates of pediatric CPAP adherence. J Clin Sleep Med 2016;12(6):879–884. PMID:27092702

  16. Sensitivity of adjustment to parameter correlations and to response-parameter correlations

    SciTech Connect

    Wagschal, J.J.

    2011-07-01

    The adjusted parameters and response, and their respective posterior uncertainties and correlations, are presented explicitly as functions of all relevant prior correlations for the two parameters, one response case. The dependence of these adjusted entities on the various prior correlations is analyzed and portrayed graphically for various valid correlation combinations on a simple criticality problem. (authors)

  17. Measuring and modeling correlations in multiplex networks

    NASA Astrophysics Data System (ADS)

    Nicosia, Vincenzo; Latora, Vito

    2015-09-01

    The interactions among the elementary components of many complex systems can be qualitatively different. Such systems are therefore naturally described in terms of multiplex or multilayer networks, i.e., networks where each layer stands for a different type of interaction between the same set of nodes. There is today a growing interest in understanding when and why a description in terms of a multiplex network is necessary and more informative than a single-layer projection. Here we contribute to this debate by presenting a comprehensive study of correlations in multiplex networks. Correlations in node properties, especially degree-degree correlations, have been thoroughly studied in single-layer networks. Here we extend this idea to investigate and characterize correlations between the different layers of a multiplex network. Such correlations are intrinsically multiplex, and we first study them empirically by constructing and analyzing several multiplex networks from the real world. In particular, we introduce various measures to characterize correlations in the activity of the nodes and in their degree at the different layers and between activities and degrees. We show that real-world networks exhibit indeed nontrivial multiplex correlations. For instance, we find cases where two layers of the same multiplex network are positively correlated in terms of node degrees, while other two layers are negatively correlated. We then focus on constructing synthetic multiplex networks, proposing a series of models to reproduce the correlations observed empirically and/or to assess their relevance.

  18. Image Correlation Method for DNA Sequence Alignment

    PubMed Central

    Curilem Saldías, Millaray; Villarroel Sassarini, Felipe; Muñoz Poblete, Carlos; Vargas Vásquez, Asticio; Maureira Butler, Iván

    2012-01-01

    The complexity of searches and the volume of genomic data make sequence alignment one of bioinformatics most active research areas. New alignment approaches have incorporated digital signal processing techniques. Among these, correlation methods are highly sensitive. This paper proposes a novel sequence alignment method based on 2-dimensional images, where each nucleic acid base is represented as a fixed gray intensity pixel. Query and known database sequences are coded to their pixel representation and sequence alignment is handled as object recognition in a scene problem. Query and database become object and scene, respectively. An image correlation process is carried out in order to search for the best match between them. Given that this procedure can be implemented in an optical correlator, the correlation could eventually be accomplished at light speed. This paper shows an initial research stage where results were “digitally” obtained by simulating an optical correlation of DNA sequences represented as images. A total of 303 queries (variable lengths from 50 to 4500 base pairs) and 100 scenes represented by 100 x 100 images each (in total, one million base pair database) were considered for the image correlation analysis. The results showed that correlations reached very high sensitivity (99.01%), specificity (98.99%) and outperformed BLAST when mutation numbers increased. However, digital correlation processes were hundred times slower than BLAST. We are currently starting an initiative to evaluate the correlation speed process of a real experimental optical correlator. By doing this, we expect to fully exploit optical correlation light properties. As the optical correlator works jointly with the computer, digital algorithms should also be optimized. The results presented in this paper are encouraging and support the study of image correlation methods on sequence alignment. PMID:22761742

  19. Image correlation method for DNA sequence alignment.

    PubMed

    Curilem Saldías, Millaray; Villarroel Sassarini, Felipe; Muñoz Poblete, Carlos; Vargas Vásquez, Asticio; Maureira Butler, Iván

    2012-01-01

    The complexity of searches and the volume of genomic data make sequence alignment one of bioinformatics most active research areas. New alignment approaches have incorporated digital signal processing techniques. Among these, correlation methods are highly sensitive. This paper proposes a novel sequence alignment method based on 2-dimensional images, where each nucleic acid base is represented as a fixed gray intensity pixel. Query and known database sequences are coded to their pixel representation and sequence alignment is handled as object recognition in a scene problem. Query and database become object and scene, respectively. An image correlation process is carried out in order to search for the best match between them. Given that this procedure can be implemented in an optical correlator, the correlation could eventually be accomplished at light speed. This paper shows an initial research stage where results were "digitally" obtained by simulating an optical correlation of DNA sequences represented as images. A total of 303 queries (variable lengths from 50 to 4500 base pairs) and 100 scenes represented by 100 x 100 images each (in total, one million base pair database) were considered for the image correlation analysis. The results showed that correlations reached very high sensitivity (99.01%), specificity (98.99%) and outperformed BLAST when mutation numbers increased. However, digital correlation processes were hundred times slower than BLAST. We are currently starting an initiative to evaluate the correlation speed process of a real experimental optical correlator. By doing this, we expect to fully exploit optical correlation light properties. As the optical correlator works jointly with the computer, digital algorithms should also be optimized. The results presented in this paper are encouraging and support the study of image correlation methods on sequence alignment.

  20. Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning

    SciTech Connect

    Mao, Kanmi

    2011-01-01

    The development of fast magic angle spinning (MAS) opened up an opportunity for the indirect detection of insensitive low-γ nuclei (e.g., 13C and 15N) via the sensitive high-{gamma} nuclei (e.g., 1H and 19F) in solid-state NMR, with advanced sensitivity and resolution. In this thesis, new methodology utilizing fast MAS is presented, including through-bond indirectly detected heteronuclear correlation (HETCOR) spectroscopy, which is assisted by multiple RF pulse sequences for 1H-1H homonuclear decoupling. Also presented is a simple new strategy for optimization of 1H-1H homonuclear decoupling. As applications, various classes of materials, such as catalytic nanoscale materials, biomolecules, and organic complexes, are studied by combining indirect detection and other one-dimensional (1D) and two-dimensional (2D) NMR techniques. Indirectly detected through-bond HETCOR spectroscopy utilizing refocused INEPT (INEPTR) mixing was developed under fast MAS (Chapter 2). The time performance of this approach in 1H detected 2D 1H{l_brace}13C{r_brace} spectra was significantly improved, by a factor of almost 10, compared to the traditional 13C detected experiments, as demonstrated by measuring naturally abundant organic-inorganic mesoporous hybrid materials. The through-bond scheme was demonstrated as a new analytical tool, which provides complementary structural information in solid-state systems in addition to through-space correlation. To further benefit the sensitivity of the INEPT transfer in rigid solids, the combined rotation and multiple-pulse spectroscopy (CRAMPS) was implemented for homonuclear 1H decoupling under fast MAS (Chapter 3). Several decoupling schemes (PMLG5m$\\bar{x}$, PMLG5mm$\\bar{x}$x and SAM3) were analyzed to maximize the performance of through-bond transfer based

  1. Disordered strongly correlated electronic systems

    NASA Astrophysics Data System (ADS)

    Javan Mard, Hossein

    Disorder can have a vast variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this dissertation we study the effects of quenched disorder on electronic systmens at zero temperature. First, we perform variational studies of the interaction-localization problem to describe the interaction-induced renormalizations of the effective (screened) random potential seen by quasiparticles. Here we present results of careful finite-size scaling studies for the conductance of disordered Hubbard chains at half-filling and zero temperature. While our results indicate that quasiparticle wave functions remain exponentially localized even in the presence of moderate to strong repulsive interactions, we show that interactions produce a strong decrease of the characteristic conductance scale g* signaling the crossover to strong localization. This effect, which cannot be captured by a simple renormalization of the disorder strength, instead reflects a peculiar non-Gaussian form of the spatial correlations of the screened disordered potential, a hitherto neglected mechanism to dramatically reduce the impact of Anderson localization (interference) effects. Second, we formulate a strong-disorder renormalization-group (SDRG) approach to study the beta function of the tight-binding model in one dimension with both diagonal and off-diagonal disorder for states at the band center. We show that the SDRG method, when used to compute transport properties, yields exact results since it is identical to the transfer matrix method. The beta function is shown to be universal when only off-diagonal disorder is present even though single-parameter scaling is known to be violated. A different single-parameter scaling theory is formulated for this particular (particle-hole symmetric) case. Upon breaking particle-hole symmetry (by adding diagonal disorder), the beta function is shown to

  2. Angular correlations and high energy evolution

    SciTech Connect

    Kovner, Alex; Lublinsky, Michael

    2011-11-01

    We address the question of to what extent JIMWLK evolution is capable of taking into account angular correlations in a high energy hadronic wave function. Our conclusion is that angular (and indeed other) correlations in the wave function cannot be reliably calculated without taking into account Pomeron loops in the evolution. As an example we study numerically the energy evolution of angular correlations between dipole scattering amplitudes in the framework of the large N{sub c} approximation to JIMWLK evolution (the 'projectile dipole model'). Target correlations are introduced via averaging over an (isotropic) ensemble of anisotropic initial conditions. We find that correlations disappear very quickly with rapidity even inside the saturation radius. This is in accordance with our physical picture of JIMWLK evolution. The actual correlations inside the saturation radius in the target QCD wave function, on the other hand, should remain sizable at any rapidity.

  3. Correlated edge overlaps in multiplex networks

    NASA Astrophysics Data System (ADS)

    Baxter, Gareth J.; Bianconi, Ginestra; da Costa, Rui A.; Dorogovtsev, Sergey N.; Mendes, José F. F.

    2016-07-01

    We develop the theory of sparse multiplex networks with partially overlapping links based on their local treelikeness. This theory enables us to find the giant mutually connected component in a two-layer multiplex network with arbitrary correlations between connections of different types. We find that correlations between the overlapping and nonoverlapping links markedly change the phase diagram of the system, leading to multiple hybrid phase transitions. For assortative correlations we observe recurrent hybrid phase transitions.

  4. Correlation of Helium Solubility in Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2012-01-01

    A correlation has been developed for the equilibrium mole fraction of soluble gaseous helium in liquid nitrogen as a function of temperature and pressure. Experimental solubility data was compiled and provided by National Institute of Standards and Technology (NIST). Data from six sources was used to develop a correlation within the range of 0.5 to 9.9 MPa and 72.0 to 119.6 K. The relative standard deviation of the correlation is 6.9 percent.

  5. Correlation and prediction of gaseous diffusion coefficients.

    NASA Technical Reports Server (NTRS)

    Marrero, T. R.; Mason, E. A.

    1973-01-01

    A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.

  6. Correlation among proprioception, muscle strength, and balance

    PubMed Central

    Wang, Huihui; Ji, Zhongqiu; Jiang, Guiping; Liu, Weitong; Jiao, Xibian

    2016-01-01

    [Purpose] To study the correlation among proprioception, muscle strength, and balance. [Subjects and Methods] A balance testing system (Biodex Balance System, BBS) and an isokinetic testing system (Biodex System 4, BS4) were used to test related indexes in 24 healthy young females. [Results] With the knee joint at 15 degree flexion, proprioception was significantly correlated with Limits of Stability-Time values, and was highly significantly correlated with Limits of Stability-Overall and Athlete Single Leg Medial/Lateral values. The sense of force was significantly correlated with Limits of Stability-Overall and Athlete Single Leg-Overall values. Quadriceps strength was significantly associated with Limits of Stability-Overall, Athlete Single Leg Medial/Lateral, and Athlete Double Leg-Overall values. The ratio of Quadriceps to Hamstring strength was significantly correlated with Athlete Single Leg Medial/Lateral, and Athlete Single Leg-Overall values. With the knee joint at 45°, proprioception was highly significantly correlated with dynamic balance, and was significantly correlated with double foot support under static balance; force sense had a high correlation with Limits of Stability-Overall, but no correlation with other indexes. Quadriceps strength had a significant correlation with dynamic and static balance; the ratio of Quadriceps/Hamstring had a highly significant correlation with Limits of Stability-Overall, Athlete Single Leg-Anterior/Posterior and Athlete Single Leg-Overall. [Conclusion] At different knee angles, the correlation differs among proprioception, force sense, quadriceps strength, the Quadriceps/Hamstring ratio, and balance. PMID:28174475

  7. SAGE II aerosol correlative observations - Profile measurements

    NASA Technical Reports Server (NTRS)

    Osborn, M. T.; Rosen, J. M.; Mccormick, M. P.; Wang, Pi-Huan; Livinfston, J. M.

    1989-01-01

    Profiles of the aerosol extinction measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II are compared with profiles from five correlative experiments between November 1984 and July 1986. The correlative profiles were derived from six-channel dustsonde measurements and two-wavelength lidar backscatter data. The correlation between the dustsonde- and lidar-derived measurements and the SAGE II data is good, validating the SAGE II lower stratospheric aerosol extinction measurements.

  8. Response time correlations for platinum resistance thermometers

    NASA Technical Reports Server (NTRS)

    Pandey, D. K.; Ash, R. L.; Dillon-Townes, L. A.

    1985-01-01

    The 'plunge method' recommended by ASTM has been used to determine the time constant of 100-ohm platinum resistance thermometers (PRT) considered for use in the National Transonic Facility. It is shown that the response time of ventilated PRT can be correlated with the reciprocal of the heat transfer coefficient in a given field. Universal correlations are established for the 100- and 1000-ohm PRT with uncertainties of 20 and 30 percent, respectively. The correlations are found to be consistent with the uncertainty involved in heat transfer correlations available in the literature and are recommended for use in flowing liquids and gases.

  9. Parallel auto-correlative statistics with VTK.

    SciTech Connect

    Pebay, Philippe Pierre; Bennett, Janine Camille

    2013-08-01

    This report summarizes existing statistical engines in VTK and presents both the serial and parallel auto-correlative statistics engines. It is a sequel to [PT08, BPRT09b, PT09, BPT09, PT10] which studied the parallel descriptive, correlative, multi-correlative, principal component analysis, contingency, k-means, and order statistics engines. The ease of use of the new parallel auto-correlative statistics engine is illustrated by the means of C++ code snippets and algorithm verification is provided. This report justifies the design of the statistics engines with parallel scalability in mind, and provides scalability and speed-up analysis results for the autocorrelative statistics engine.

  10. The genetic correlation between procrastination and impulsivity.

    PubMed

    Loehlin, John C; Martin, Nicholas G

    2014-12-01

    The reported genetic correlation of 1.0 between the traits of procrastination and impulsivity (Gustavson, D. E., Miyake, A., Hewitt, J. K., & Friedman, N. P. (2014). Psychological Science), which was held to support an evolutionary origin of the relationship between the two traits, was tested in data from two large samples of twins from Australia. A genetic correlation of 0.299 was obtained. It was concluded that, although the presence of a genetic correlation between the two traits was supported, the modest magnitude of the correlation was such as to be consistent with many possible hypotheses, evolutionary and otherwise, about causal relationships between the traits in question.

  11. Burst Firing Enhances Neural Output Correlation

    PubMed Central

    Chan, Ho Ka; Yang, Dong-Ping; Zhou, Changsong; Nowotny, Thomas

    2016-01-01

    Neurons communicate and transmit information predominantly through spikes. Given that experimentally observed neural spike trains in a variety of brain areas can be highly correlated, it is important to investigate how neurons process correlated inputs. Most previous work in this area studied the problem of correlation transfer analytically by making significant simplifications on neural dynamics. Temporal correlation between inputs that arises from synaptic filtering, for instance, is often ignored when assuming that an input spike can at most generate one output spike. Through numerical simulations of a pair of leaky integrate-and-fire (LIF) neurons receiving correlated inputs, we demonstrate that neurons in the presence of synaptic filtering by slow synapses exhibit strong output correlations. We then show that burst firing plays a central role in enhancing output correlations, which can explain the above-mentioned observation because synaptic filtering induces bursting. The observed changes of correlations are mostly on a long time scale. Our results suggest that other features affecting the prevalence of neural burst firing in biological neurons, e.g., adaptive spiking mechanisms, may play an important role in modulating the overall level of correlations in neural networks. PMID:27242499

  12. Degree of correlation inside a financial market

    NASA Astrophysics Data System (ADS)

    Mantegna, Rosario Nunzio

    1997-05-01

    I present an empirical study of the correlations observed between pairs of time series of stock prices in the New York Stock Exchange. I verify that various degrees of correlations or anti-correlations are present inside a financial market and I study the time evolution of these correlations. I briefly discuss how these empirical observations might be consistent with the well accepted hypothesis of absence of arbitrage in an efficient financial market (i.e. that there is no way of extracting money from the market in a continuous way without risk).

  13. Kohn-Sham potential for a strongly correlated finite system with fractional occupancy

    NASA Astrophysics Data System (ADS)

    Benítez, A.; Proetto, C. R.

    2016-11-01

    Using a simplified one-dimensional model of a diatomic molecule, the associated interacting density and corresponding Kohn-Sham (KS) potential have been obtained analytically for all fractional molecule occupancies N between 0 and 2. For the homonuclear case, and in the dissociation limit, the exact Kohn-Sham potential builds a barrier at the midpoint between the two atoms, whose strength increases linearly with N , with 1 heteronuclear case, the dissociating KS potential besides the barrier also exhibits a plateau around the atom with the higher ionization potential, whose size (but not its strength) depends on N . An anomalous zero-order scaling of the Kohn-Sham potential with regards to the strength of the electron-electron repulsion is clearly displayed by our model; without this property both the unusual barrier and the plateau features will be absent.

  14. ANALYZING CORRELATIONS BETWEEN STREAM AND WATERSHED ATTRIBUTES

    EPA Science Inventory

    Bivariate correlation analysis has been widely used to explore relationships between stream and watershed attributes that have all been measured on the same set of watersheds or sampling locations. Researchers routinely test H0: =0 for each correlation in a large table and then ...

  15. Scaled density functional theory correlation functionals.

    PubMed

    Ghouri, Mohammed M; Singh, Saurabh; Ramachandran, B

    2007-10-18

    We show that a simple one-parameter scaling of the dynamical correlation energy estimated by the density functional theory (DFT) correlation functionals helps increase the overall accuracy for several local and nonlocal functionals. The approach taken here has been described as the "scaled dynamical correlation" (SDC) method [Ramachandran, J. Phys. Chem. A 2006, 110, 396], and its justification is the same as that of the scaled external correlation (SEC) method of Brown and Truhlar. We examine five local and five nonlocal (hybrid) DFT functionals, the latter group including three functionals developed specifically for kinetics by the Truhlar group. The optimum scale factors are obtained by use of a set of 98 data values consisting of molecules, ions, and transition states. The optimum scale factors, found with a linear regression relationship, are found to differ from unity with a high degree of correlation in nearly every case, indicating that the deviation of calculated results from the experimental values are systematic and proportional to the dynamic correlation energy. As a consequence, the SDC scaling of dynamical correlation decreases the mean errors (signed and unsigned) by significant amounts in an overwhelming majority of cases. These results indicate that there are gains to be realized from further parametrization of several popular exchange-correlation functionals.

  16. Using Dispersed Modes During Model Correlation

    NASA Technical Reports Server (NTRS)

    Stewart, Eric C.; Hathcock, Megan L.

    2017-01-01

    The model correlation process for the modal characteristics of a launch vehicle is well established. After a test, parameters within the nominal model are adjusted to reflect structural dynamics revealed during testing. However, a full model correlation process for a complex structure can take months of man-hours and many computational resources. If the analyst only has weeks, or even days, of time in which to correlate the nominal model to the experimental results, then the traditional correlation process is not suitable. This paper describes using model dispersions to assist the model correlation process and decrease the overall cost of the process. The process creates thousands of model dispersions from the nominal model prior to the test and then compares each of them to the test data. Using mode shape and frequency error metrics, one dispersion is selected as the best match to the test data. This dispersion is further improved by using a commercial model correlation software. In the three examples shown in this paper, this dispersion based model correlation process performs well when compared to models correlated using traditional techniques and saves time in the post-test analysis.

  17. The Bonn Astro/Geo Correlator

    NASA Technical Reports Server (NTRS)

    Bernhart, Simone; Alef, Walter; Bertarini, Alessandra; La Porta, Laura; Muskens, Arno; Rottmann, Helge; Roy, Alan

    2013-01-01

    The Bonn Distributed FX (DiFX) correlator is a software correlator operated jointly by the Max- Planck-Institut fur Radioastronomie (MPIfR), the Institut fur Geodasie und Geoinformation der Universitat Bonn (IGG), and the Bundesamt fur Kartographie und Geodasie (BKG) in Frankfurt.

  18. Correlation as Probability of Common Descent.

    ERIC Educational Resources Information Center

    Falk, Ruma; Well, Arnold D.

    1996-01-01

    One interpretation of the Pearson product-moment correlation ("r"), correlation as the probability of originating from common descent, important to the genetic measurement of inbreeding, is examined. The conditions under which "r" can be interpreted as the probability of "identity by descent" are specified, and the…

  19. Ultrasonic Detection Using Correlation Images (Preprint)

    DTIC Science & Technology

    2006-08-01

    for imaging and detection based on the similarity of adjacent signals, quantified by the correlation coefficient calculated between A-scans... Correlation coefficient images are introduced and shown with C-scan images to demonstrate flat-bottom-hole and crack detection in experimental data and planar

  20. On a Correlation Inequality and Its Applications

    DTIC Science & Technology

    1988-03-29

    LnF(overlined). For F NBUE it is shown that the correlation coefficient between X approx. = F and H(X) is bounded below by delta/mu, the...coefficient of variation of F, while for F NWUE the correlation coefficient is bounded below by mu/delta. Several applications of this inequality and its

  1. Personality Correlates of Pain Perception and Tolerance.

    ERIC Educational Resources Information Center

    Lukin, Penny R.; Ray, A. Bartow

    1982-01-01

    Explored personality correlates of pain perception and tolerance in a nonmedical sample and setting. Results showed no significant correlations with personality measures and cold-pressor scores, but a significant relationship between pain tolerance and cognitive focus; those who focused on the experimental situation had much shorter tolerance…

  2. On the insignificance of Herschel's sunspot correlation

    USGS Publications Warehouse

    Love, Jeffrey J.

    2013-01-01

    We examine William Herschel's hypothesis that solar-cycle variation of the Sun's irradiance has a modulating effect on the Earth's climate and that this is, specifically, manifested as an anticorrelation between sunspot number and the market price of wheat. Since Herschel first proposed his hypothesis in 1801, it has been regarded with both interest and skepticism. Recently, reports have been published that either support Herschel's hypothesis or rely on its validity. As a test of Herschel's hypothesis, we seek to reject a null hypothesis of a statistically random correlation between historical sunspot numbers, wheat prices in London and the United States, and wheat farm yields in the United States. We employ binary-correlation, Pearson-correlation, and frequency-domain methods. We test our methods using a historical geomagnetic activity index, well known to be causally correlated with sunspot number. As expected, the measured correlation between sunspot number and geomagnetic activity would be an unlikely realization of random data; the correlation is “statistically significant.” On the other hand, measured correlations between sunspot number and wheat price and wheat yield data would be very likely realizations of random data; these correlations are “insignificant.” Therefore, Herschel's hypothesis must be regarded with skepticism. We compare and contrast our results with those of other researchers. We discuss procedures for evaluating hypotheses that are formulated from historical data.

  3. Organizational Correlates of Management Training Interests.

    ERIC Educational Resources Information Center

    Tills, Marvin

    A study was made of a sample of Wisconsin manufacturing firms and a subsample of firms in different size categories to determine organizational correlates of management training interests. Correlations were sought between characteristics of firms (ownership, relationship to parent company, size of employment, market orientation, growth trends,…

  4. Correlated neural variability in persistent state networks.

    PubMed

    Polk, Amber; Litwin-Kumar, Ashok; Doiron, Brent

    2012-04-17

    Neural activity that persists long after stimulus presentation is a biological correlate of short-term memory. Variability in spiking activity causes persistent states to drift over time, ultimately degrading memory. Models of short-term memory often assume that the input fluctuations to neural populations are independent across cells, a feature that attenuates population-level variability and stabilizes persistent activity. However, this assumption is at odds with experimental recordings from pairs of cortical neurons showing that both the input currents and output spike trains are correlated. It remains unclear how correlated variability affects the stability of persistent activity and the performance of cognitive tasks that it supports. We consider the stochastic long-timescale attractor dynamics of pairs of mutually inhibitory populations of spiking neurons. In these networks, persistent activity was less variable when correlated variability was globally distributed across both populations compared with the case when correlations were locally distributed only within each population. Using a reduced firing rate model with a continuum of persistent states, we show that, when input fluctuations are correlated across both populations, they drive firing rate fluctuations orthogonal to the persistent state attractor, thereby causing minimal stochastic drift. Using these insights, we establish that distributing correlated fluctuations globally as opposed to locally improves network's performance on a two-interval, delayed response discrimination task. Our work shows that the correlation structure of input fluctuations to a network is an important factor when determining long-timescale, persistent population spiking activity.

  5. Intelligence and Semen Quality Are Positively Correlated

    ERIC Educational Resources Information Center

    Arden, Rosalind; Gottfredson, Linda S.; Miller, Geoffrey; Pierce, Arand

    2009-01-01

    Human cognitive abilities inter-correlate to form a positive matrix, from which a large first factor, called "Spearman's g" or general intelligence, can be extracted. General intelligence itself is correlated with many important health outcomes including cardio-vascular function and longevity. However, the important evolutionary question of…

  6. Correlation inequality for surface-scattering operators

    SciTech Connect

    Leuthausser, U.

    1985-03-01

    The principle of detailed balance leads to a correlation inequality for surface-scattering operators. The equilibrium energy accomodation coefficient ..cap alpha.. is expressed in terms of the correlation coefficient of the scattering probability and has an upper bound considerably less than 2.

  7. Transformation of stimulus correlations by the retina

    NASA Astrophysics Data System (ADS)

    Prentice, Jason; Simmons, Kristina; Tkacik, Gasper; Homann, Jan; Yee, Heather; Palmer, Stephanie; Nelson, Phillip; Balasubramanian, Vijay

    2014-03-01

    Correlations in the responses of sensory neurons seem to waste neural resources, but can carry cues about structured stimuli and help the brain correct for response errors. To assess how the retina negotiates this tradeoff, we measured simultaneous responses from many retinal ganglion cells presented with natural and artificial stimuli that varied in correlation structure. Responding to spatio-temporally structured stimuli such as natural movies, pairs of ganglion cells were more correlated than in response to white noise checkerboards, but were much less correlated than predicted by a non-adapting functional model of retinal response. Meanwhile, responding to stimuli with purely spatial correlations, pairs of ganglion cells showed increased correlations consistent with a static, non-adapting receptive field and nonlinearity. We found that in response to spatio- temporally correlated stimuli, ganglion cells had faster temporal kernels and tended to have stronger surrounds. These properties of individual cells, along with gain changes that opposed changes in effective contrast at the ganglion cell input, largely explained the pattern of correlations across stimuli.

  8. Holographic thermalization with initial long range correlation

    DOE PAGES

    Lin, Shu

    2016-01-19

    Here, we studied the evolution of the Wightman correlator in a thermalizing state modeled by AdS3-Vaidya background. A prescription was given for calculating the Wightman correlator in coordinate space without using any approximation. For equal-time correlator , we obtained an enhancement factor v2 due to long range correlation present in the initial state. This was missed by previous studies based on geodesic approximation. Moreover, we found that the long range correlation in initial state does not lead to significant modification to thermalization time as compared to known results with generic initial state. We also studied the spatially integrated Wightman correlatormore » and showed evidence on the distinction between long distance and small momentum physics for an out-of-equilibrium state. We also calculated the radiation spectrum of particles weakly coupled to O and found that lower frequency mode approaches thermal spectrum faster than high frequency mode.« less

  9. Finite element modelling of SAW correlator

    NASA Astrophysics Data System (ADS)

    Tikka, Ajay C.; Al-Sarawi, Said F.; Abbott, Derek

    2007-12-01

    Numerical simulations of SAW correlators so far are limited to delta function and equivalent circuit models. These models are not accurate as they do not replicate the actual behaviour of the device. Manufacturing a correlator to specifically realise a different configuration is both expensive and time consuming. With the continuous improvement in computing capacity, switching to finite element modelling would be more appropriate. In this paper a novel way of modelling a SAW correlator using finite element analysis is presented. This modelling approach allows the consideration of different code implementation and device structures. This is demonstrated through simulation results for a 5×2-bit Barker sequence encoded SAW correlator. These results show the effect of both bulk and leaky modes on the device performance at various operating frequencies. Moreover, the ways in which the gain of the correlator can be optimised though variation of design parameters will also be outlined.

  10. Correlated activity supports efficient cortical processing

    PubMed Central

    Hung, Chou P.; Cui, Ding; Chen, Yueh-peng; Lin, Chia-pei; Levine, Matthew R.

    2015-01-01

    Visual recognition is a computational challenge that is thought to occur via efficient coding. An important concept is sparseness, a measure of coding efficiency. The prevailing view is that sparseness supports efficiency by minimizing redundancy and correlations in spiking populations. Yet, we recently reported that “choristers”, neurons that behave more similarly (have correlated stimulus preferences and spontaneous coincident spiking), carry more generalizable object information than uncorrelated neurons (“soloists”) in macaque inferior temporal (IT) cortex. The rarity of choristers (as low as 6% of IT neurons) indicates that they were likely missed in previous studies. Here, we report that correlation strength is distinct from sparseness (choristers are not simply broadly tuned neurons), that choristers are located in non-granular output layers, and that correlated activity predicts human visual search efficiency. These counterintuitive results suggest that a redundant correlational structure supports efficient processing and behavior. PMID:25610392

  11. Unzipping of DNA with correlated base sequence.

    PubMed

    Allahverdyan, A E; Gevorkian, Zh S; Hu, Chin-Kun; Wu, Ming-Chya

    2004-06-01

    We consider force-induced unzipping transition for a heterogeneous DNA model with a correlated base sequence. Both finite-range and long-range correlated situations are considered. It is shown that finite-range correlations increase stability of DNA with respect to the external unzipping force. Due to long-range correlations the number of unzipped base pairs displays two widely different scenarios depending on the details of the base sequence: either there is no unzipping phase transition at all, or the transition is realized via a sequence of jumps with magnitude comparable to the size of the system. Both scenarios are different from the behavior of the average number of unzipped base pairs (non-self-averaging). The results can be relevant for explaining the biological purpose of correlated structures in DNA.

  12. Cross-Correlating DES and SPT

    NASA Astrophysics Data System (ADS)

    Baxter, Eric

    2017-01-01

    The Dark Energy Survey (DES) and the South Pole Telescope (SPT) provide a uniquely powerful combination of overlapping optical imaging and cosmic microwave background (CMB) data. Cross-correlations between DES and SPT are expected to arise from several physical effects, including gravitational lensing, the Sunyaev-Zel'dovich (SZ) effect, and the Integrated Sachs-Wolfe effect. The resultant correlations contain information not accessible to either experiment on its own. Measurement of these correlations offers several exciting possibilities, such as improved cosmological parameter constraints, improved understanding of systematics affecting the two experiments, and calibration of the masses of galaxy clusters at high redshift. In this talk I will summarize recent results obtained by cross-correlating early DES data with data from the SPT-SZ survey and will discuss prospects for future cross-correlation measurements with these two surveys.

  13. Estimation of the simple correlation coefficient.

    PubMed

    Shieh, Gwowen

    2010-11-01

    This article investigates some unfamiliar properties of the Pearson product-moment correlation coefficient for the estimation of simple correlation coefficient. Although Pearson's r is biased, except for limited situations, and the minimum variance unbiased estimator has been proposed in the literature, researchers routinely employ the sample correlation coefficient in their practical applications, because of its simplicity and popularity. In order to support such practice, this study examines the mean squared errors of r and several prominent formulas. The results reveal specific situations in which the sample correlation coefficient performs better than the unbiased and nearly unbiased estimators, facilitating recommendation of r as an effect size index for the strength of linear association between two variables. In addition, related issues of estimating the squared simple correlation coefficient are also considered.

  14. Optimization of photon correlations by frequency filtering

    NASA Astrophysics Data System (ADS)

    González-Tudela, Alejandro; del Valle, Elena; Laussy, Fabrice P.

    2015-04-01

    Photon correlations are a cornerstone of quantum optics. Recent works [E. del Valle, New J. Phys. 15, 025019 (2013), 10.1088/1367-2630/15/2/025019; A. Gonzalez-Tudela et al., New J. Phys. 15, 033036 (2013), 10.1088/1367-2630/15/3/033036; C. Sanchez Muñoz et al., Phys. Rev. A 90, 052111 (2014), 10.1103/PhysRevA.90.052111] have shown that by keeping track of the frequency of the photons, rich landscapes of correlations are revealed. Stronger correlations are usually found where the system emission is weak. Here, we characterize both the strength and signal of such correlations, through the introduction of the "frequency-resolved Mandel parameter." We study a plethora of nonlinear quantum systems, showing how one can substantially optimize correlations by combining parameters such as pumping, filtering windows and time delay.

  15. Betweenness centrality correlation in social networks

    NASA Astrophysics Data System (ADS)

    Goh, K.-I.; Oh, E.; Kahng, B.; Kim, D.

    2003-01-01

    Scale-free (SF) networks exhibiting a power-law degree distribution can be grouped into the assortative, dissortative, and neutral networks according to the behavior of the degree-degree correlation coefficient. Here we investigate the betweenness centrality (BC) correlation for each type of SF networks. While the BC-BC correlation coefficients behave similarly to the degree-degree correlation coefficients for the dissortative and neutral networks, the BC correlation is nontrivial for the assortative ones found mainly in social networks. The mean BC of neighbors of a vertex with BC gi is almost independent of gi, implying that each person is surrounded by almost the same influential environments of people no matter how influential the person may be.

  16. Phase sorting wave-particle correlator

    NASA Astrophysics Data System (ADS)

    Kletzing, C. A.; LaBelle, J.; Bounds, S. R.; Dolan, J.; Kaeppler, S. R.; Dombrowski, M.

    2017-02-01

    Wave-particle correlations, particularly of Langmuir waves and electrons, have been the subject of significant interest extending back to the 1970s. Often, these correlations have been simply observing modulation of the electrons at the plasma frequency with no phase resolution. The first phase-resolving correlators were developed at UC Berkeley in the late 1980s and reported by Ergun in the early 1990s. A design is presented which further improves on phase resolution in correlations of Langmuir waves and electrons with phase resolution of 22.5°. In this technique, a phase-locked loop (PLL) is used to lock onto the wave and subdivide the phase. Electrons are sorted on-the-fly as they arrive into the phase bins. Discussed are details of accurate timing, testing, and calibration of this system as well as results from rocket flights in which statistically significant phase correlations have been observed.

  17. Quantum correlations in connected multipartite Bell experiments

    NASA Astrophysics Data System (ADS)

    Tavakoli, Armin

    2016-04-01

    Bell experiments measure correlations between outcomes of a number of observers measuring on a shared physical state emitted from a single source. Quantum correlations arising in such Bell experiments have been intensively studied over the last decades. Much less is known about the nature of quantum correlations arising in network structures beyond Bell experiments. Such networks can involve many independent sources emitting states to observers in accordance with the network configuration. Here, we will study classical and quantum correlations in a family of networks which can be regarded as compositions of several independent multipartite Bell experiments connected together through a central node. For such networks we present tight Bell-type inequalities which are satisfied by all classical correlations. We study properties of the violations of our inequalities by probability distributions arising in quantum theory.

  18. Multifunction nonlinear signal processor - Deconvolution and correlation

    NASA Astrophysics Data System (ADS)

    Javidi, Bahram; Horner, Joseph L.

    1989-08-01

    A multifuncional nonlinear optical signal processor is described that allows different types of operations, such as image deconvolution and nonlinear correlation. In this technique, the joint power spectrum of the input signal is thresholded with varying nonlinearity to produce different specific operations. In image deconvolution, the joint power spectrum is modified and hard-clip thresholded to remove the amplitude distortion effects and to restore the correct phase of the original image. In optical correlation, the Fourier transform interference intensity is thresholded to provide higher correlation peak intensity and a better-defined correlation spot. Various types of correlation signals can be produced simply by varying the severity of the nonlinearity, without the need for synthesis of specific matched filter. An analysis of the nonlinear processor for image deconvolution is presented.

  19. Dynamical correlations after a quantum quench.

    PubMed

    Essler, Fabian H L; Evangelisti, Stefano; Fagotti, Maurizio

    2012-12-14

    We consider dynamic (non-equal-time) correlation functions of local observables after a quantum quench. We show that, in the absence of long-range interactions in the final Hamiltonian, the dynamics is determined by the same ensemble that describes static (equal-time) correlations. For many integrable models, static correlation functions of local observables after a quantum quench relax to stationary values, which are described by a generalized Gibbs ensemble. The same generalized Gibbs ensemble then determines dynamic correlation functions, and the basic form of the fluctuation dissipation theorem holds, although the absorption and emission spectra are not simply related as in the thermal case. For quenches in the transverse field Ising chain, we derive explicit expressions for the time evolution of dynamic order parameter correlators after a quench.

  20. Theory of correlations in stochastic neural networks

    NASA Astrophysics Data System (ADS)

    Ginzburg, Iris; Sompolinsky, Haim

    1994-10-01

    One of the main experimental tools in probing the interactions between neurons has been the measurement of the correlations in their activity. In general, however, the interpretation of the observed correlations is difficult since the correlation between a pair of neurons is influenced not only by the direct interaction between them but also by the dynamic state of the entire network to which they belong. Thus a comparison between the observed correlations and the predictions from specific model networks is needed. In this paper we develop a theory of neuronal correlation functions in large networks comprising several highly connected subpopulations and obeying stochastic dynamic rules. When the networks are in asynchronous states, the cross correlations are relatively weak, i.e., their amplitude relative to that of the autocorrelations is of order of 1/N, N being the size of the interacting populations. Using the weakness of the cross correlations, general equations that express the matrix of cross correlations in terms of the mean neuronal activities and the effective interaction matrix are presented. The effective interactions are the synaptic efficacies multiplied by the gain of the postsynaptic neurons. The time-delayed cross-correlation matrix can be expressed as a sum of exponentially decaying modes that correspond to the (nonorthogonal) eigenvectors of the effective interaction matrix. The theory is extended to networks with random connectivity, such as randomly dilute networks. This allows for a comparison between the contribution from the internal common input and that from the direct interactions to the correlations of monosynaptically coupled pairs. A closely related quantity is the linear response of the neurons to external time-dependent perturbations. We derive the form of the dynamic linear response function of neurons in the above architecture in terms of the eigenmodes of the effective interaction matrix. The behavior of the correlations and the

  1. Interpreting Canonical Correlation Analysis through Biplots of Structure Correlations and Weights.

    ERIC Educational Resources Information Center

    ter Braak, Cajo J. F.

    1990-01-01

    Canonical weights and structure correlations are used to construct low dimensional views of the relationships between two sets of variables. These views, in the form of biplots, display familiar statistics: correlations between pairs of variables, and regression coefficients. (SLD)

  2. From correlation functions to event shapes

    NASA Astrophysics Data System (ADS)

    Belitsky, A. V.; Hohenegger, S.; Korchemsky, G. P.; Sokatchev, E.; Zhiboedov, A.

    2014-07-01

    We present a new approach to computing event shape distributions or, more precisely, charge flow correlations in a generic conformal field theory (CFT). These infrared finite observables are familiar from collider physics studies and describe the angular distribution of global charges in outgoing radiation created from the vacuum by some source. The charge flow correlations can be expressed in terms of Wightman correlation functions in a certain limit. We explain how to compute these quantities starting from their Euclidean analogues by means of a nontrivial analytic continuation which, in the framework of CFT, can be performed elegantly in Mellin space. The relation between the charge flow correlations and Euclidean correlation functions can be reformulated directly in configuration space, bypassing the Mellin representation, as a certain Lorentzian double discontinuity of the correlation function integrated along the cuts. We illustrate the general formalism in N=4 SYM, making use of the well-known results on the four-point correlation function of half-BPS scalar operators. We compute the double scalar flow correlation in N=4 SYM, at weak and strong coupling and show that it agrees with known results obtained by different techniques. One of the remarkable features of the N=4 theory is that the scalar and energy flow correlations are proportional to each other. Imposing natural physical conditions on the energy flow correlations (finiteness, positivity and regularity), we formulate additional constraints on the four-point correlation functions in N=4 SYM that should be valid at any coupling and away from the planar limit. presence of intrinsic infrared (IR) divergences; integration over the phase space of the final state and subsequent intricate IR cancellations; necessity for summation over all final states. Let us comment on each of these points. They are very well understood in the context of perturbation theory no IR divergences are present in the correlation

  3. Estimation of rank correlation for clustered data.

    PubMed

    Rosner, Bernard; Glynn, Robert J

    2017-04-11

    It is well known that the sample correlation coefficient (Rxy ) is the maximum likelihood estimator of the Pearson correlation (ρxy ) for independent and identically distributed (i.i.d.) bivariate normal data. However, this is not true for ophthalmologic data where X (e.g., visual acuity) and Y (e.g., visual field) are available for each eye and there is positive intraclass correlation for both X and Y in fellow eyes. In this paper, we provide a regression-based approach for obtaining the maximum likelihood estimator of ρxy for clustered data, which can be implemented using standard mixed effects model software. This method is also extended to allow for estimation of partial correlation by controlling both X and Y for a vector U_ of other covariates. In addition, these methods can be extended to allow for estimation of rank correlation for clustered data by (i) converting ranks of both X and Y to the probit scale, (ii) estimating the Pearson correlation between probit scores for X and Y, and (iii) using the relationship between Pearson and rank correlation for bivariate normally distributed data. The validity of the methods in finite-sized samples is supported by simulation studies. Finally, two examples from ophthalmology and analgesic abuse are used to illustrate the methods. Copyright © 2017 John Wiley & Sons, Ltd.

  4. An ultrasonic pseudorandom signal-correlation system

    NASA Astrophysics Data System (ADS)

    Elias, C. M.

    1980-01-01

    A working ultrasonic pseudorandom signal-correlation system is described which, unlike ultrasonic random signal-correlation systems, does not require an acoustic delay line. Elimination of the delay line allows faster data acquisition and better range resolution. The system uses two identical shift-register type generators to produce pseudonoise bursts which are subsequences of a 65 535-bit complementary m-sequence. One generator produces the transmitted bursts while the other generates identical reference bursts which start at a variable correlation delay time after the transmitted bursts. The reference bursts are cross-correlated with the received echoes to obtain the approximate impulse response of the transducer/specimen system under test. Range sidelobes are reduced by transmitting and correlating many bursts at a given correlation delay before incrementing the delay. Signal-to-sidelobe ratios of greater than 47 dB have been obtained using this method. Limitations of the system due to sampling constraints and the pseudonoise power spectrum are discussed, and the system design and implementation are outlined. Results of experimental characterization of the system show that the pseudorandom signal-correlation system has approximately the same range resolution as a conventional pulse-echo system but can yield a significant increase in signal-to-noise ratio (SNR).

  5. Inverse Ising inference with correlated samples

    NASA Astrophysics Data System (ADS)

    Obermayer, Benedikt; Levine, Erel

    2014-12-01

    Correlations between two variables of a high-dimensional system can be indicative of an underlying interaction, but can also result from indirect effects. Inverse Ising inference is a method to distinguish one from the other. Essentially, the parameters of the least constrained statistical model are learned from the observed correlations such that direct interactions can be separated from indirect correlations. Among many other applications, this approach has been helpful for protein structure prediction, because residues which interact in the 3D structure often show correlated substitutions in a multiple sequence alignment. In this context, samples used for inference are not independent but share an evolutionary history on a phylogenetic tree. Here, we discuss the effects of correlations between samples on global inference. Such correlations could arise due to phylogeny but also via other slow dynamical processes. We present a simple analytical model to address the resulting inference biases, and develop an exact method accounting for background correlations in alignment data by combining phylogenetic modeling with an adaptive cluster expansion algorithm. We find that popular reweighting schemes are only marginally effective at removing phylogenetic bias, suggest a rescaling strategy that yields better results, and provide evidence that our conclusions carry over to the frequently used mean-field approach to the inverse Ising problem.

  6. Using Neural Networks to Describe Tracer Correlations

    NASA Technical Reports Server (NTRS)

    Lary, D. J.; Mueller, M. D.; Mussa, H. Y.

    2003-01-01

    Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH4-N2O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and CH4 volume mixing ratio (v.m.r.). In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH4-N2O correlation with a correlation co- efficient of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE) which has continuously observed CH4, (but not N2O) from 1991 till the present. The neural network Fortran code used is available for download.

  7. Ion Correlations at Electrified Soft Matter Interfaces

    NASA Astrophysics Data System (ADS)

    Laanait, Nouamane

    2011-07-01

    Ion correlations have been suggested as the underlying mechanism of a number of counterintuitive phenomena in soft condensed-matter, such as like-charge attraction. Recently, several theoretical models have emerged, attempting to address these electrostatic correlations, beyond the mean field description of the Poisson-Boltzmann theory. The central prediction of these theories, the ion density profile, has remained untested by measurements with microscopic resolution. In this work, we present the first molecular-level tests of an ion correlations model. Analysis of synchrotron x-ray reflectivity using a phenomenological model reveals ion condensation at the liquid/liquid interface, when polarized with an electric field. Tuning the density of this ionic layer allows for a detailed study of ion correlations as a function of the Coulomb coupling strength in the system. We propose a density functional theory that aims to describe electrostatic ion correlations and explicitly includes solvent effects through an ion-solvent interaction potential, mapped out using Molecular Dynamics simulations. The proposed model predicts global electrostatic properties of the system that are in excellent agreement with thermodynamic measurements of the interfacial excess charge, with no adjustable parameters. Comparison of the density profiles to the x-ray data indicates that a nonlocal free functional based on the Debye-Hückel-Hole theory of a one-component plasma, adequately describes ion-ion interactions up to a correlation strength of 4 kBT. We anticipate this result to be of relevance in other strongly correlated soft matter systems.

  8. On correlations in IMRT planning aims.

    PubMed

    Roy, Arkajyoti; Das, Indra J; Nohadani, Omid

    2016-11-01

    The purpose was to study correlations amongst IMRT DVH evaluation points and how their relaxation impacts the overall plan. 100 head-and-neck cancer cases, using the Eclipse treatment planning system with the same protocol, are statistically analyzed for PTV, brainstem, and spinal cord. To measure variations amongst the plans, we use (i) interquartile range (IQR) of volume as a function of dose, (ii) interquartile range of dose as a function of volume, and (iii) dose falloff. To determine correlations for institutional and ICRU goals, conditional probabilities and medians are computed. We observe that most plans exceed the median PTV dose (average D50 = 104% prescribed dose). Furthermore, satisfying D50 reduced the probability of also satisfying D98, constituting a negative correlation of these goals. On the other hand, satisfying D50 increased the probability of satisfying D2, suggesting a positive correlation. A positive correlation is also observed between the PTV V105 and V110. Similarly, a positive correlation between the brainstem V45 and V50 is measured by an increase in the conditional median of V45, when V50 is violated. Despite the imposed institutional and international recommendations, significant variations amongst DVH points can occur. Even though DVH aims are evaluated independently, sizable correlations amongst them are possible, indicating that some goals cannot be satisfied concurrently, calling for unbiased plan criteria. PACS number(s): 87.55.dk, 87.53.Bn, 87.55.Qr, 87.55.de.

  9. On correlations in IMRT planning aims.

    PubMed

    Roy, Arkajyoti; Das, Indra J; Nohadani, Omid

    2016-11-08

    The purpose was to study correlations amongst IMRT DVH evaluation points and how their relaxation impacts the overall plan. 100 head-and-neck cancer cases, using the Eclipse treatment planning system with the same protocol, are statisti-cally analyzed for PTV, brainstem, and spinal cord. To measure variations amongst the plans, we use (i) interquartile range (IQR) of volume as a function of dose, (ii) interquartile range of dose as a function of volume, and (iii) dose falloff. To determine correlations for institutional and ICRU goals, conditional probabilities and medians are computed. We observe that most plans exceed the median PTV dose (average D50 = 104% prescribed dose). Furthermore, satisfying D50 reduced the probability of also satisfying D98, constituting a negative correlation of these goals. On the other hand, satisfying D50 increased the probability of satisfying D2, suggesting a positive correlation. A positive correlation is also observed between the PTV V105 and V110. Similarly, a positive correlation between the brainstem V45 and V50 is measured by an increase in the conditional median of V45, when V50 is violated. Despite the imposed institutional and international recommenda-tions, significant variations amongst DVH points can occur. Even though DVH aims are evaluated independently, sizable correlations amongst them are possible, indicating that some goals cannot be satisfied concurrently, calling for unbiased plan criteria.

  10. Neural population densities shape network correlations

    NASA Astrophysics Data System (ADS)

    Lefebvre, Jérémie; Perkins, Theodore J.

    2012-02-01

    The way sensory microcircuits manage cellular response correlations is a crucial question in understanding how such systems integrate external stimuli and encode information. Most sensory systems exhibit heterogeneities in terms of population sizes and features, which all impact their dynamics. This work addresses how correlations between the dynamics of neural ensembles depend on the relative size or density of excitatory and inhibitory populations. To do so, we study an apparently symmetric system of coupled stochastic differential equations that model the evolution of the populations’ activities. Excitatory and inhibitory populations are connected by reciprocal recurrent connections, and both receive different stimuli exhibiting a certain level of correlation with each other. A stability analysis is performed, which reveals an intrinsic asymmetry in the distribution of the fixed points with respect to the threshold of the nonlinearities. Based on this, we show how the cross correlation between the population responses depends on the density of the inhibitory population, and that a specific ratio between both population sizes leads to a state of zero correlation. We show that this so-called asynchronous state subsists, despite the presence of stimulus correlation, and most importantly, that it occurs only in asymmetrical systems where one population outnumbers the other. Using linear approximations, we derive analytical expressions for the root of the cross-correlation function and study how the asynchronous state is impacted by the model's parameters. This work suggests a possible explanation for why inhibitory cells outnumber excitatory cells in the visual system.

  11. Bayesian Correlation Analysis for Sequence Count Data

    PubMed Central

    Lau, Nelson; Perkins, Theodore J.

    2016-01-01

    Evaluating the similarity of different measured variables is a fundamental task of statistics, and a key part of many bioinformatics algorithms. Here we propose a Bayesian scheme for estimating the correlation between different entities’ measurements based on high-throughput sequencing data. These entities could be different genes or miRNAs whose expression is measured by RNA-seq, different transcription factors or histone marks whose expression is measured by ChIP-seq, or even combinations of different types of entities. Our Bayesian formulation accounts for both measured signal levels and uncertainty in those levels, due to varying sequencing depth in different experiments and to varying absolute levels of individual entities, both of which affect the precision of the measurements. In comparison with a traditional Pearson correlation analysis, we show that our Bayesian correlation analysis retains high correlations when measurement confidence is high, but suppresses correlations when measurement confidence is low—especially for entities with low signal levels. In addition, we consider the influence of priors on the Bayesian correlation estimate. Perhaps surprisingly, we show that naive, uniform priors on entities’ signal levels can lead to highly biased correlation estimates, particularly when different experiments have widely varying sequencing depths. However, we propose two alternative priors that provably mitigate this problem. We also prove that, like traditional Pearson correlation, our Bayesian correlation calculation constitutes a kernel in the machine learning sense, and thus can be used as a similarity measure in any kernel-based machine learning algorithm. We demonstrate our approach on two RNA-seq datasets and one miRNA-seq dataset. PMID:27701449

  12. Bayesian Correlation Analysis for Sequence Count Data.

    PubMed

    Sánchez-Taltavull, Daniel; Ramachandran, Parameswaran; Lau, Nelson; Perkins, Theodore J

    2016-01-01

    Evaluating the similarity of different measured variables is a fundamental task of statistics, and a key part of many bioinformatics algorithms. Here we propose a Bayesian scheme for estimating the correlation between different entities' measurements based on high-throughput sequencing data. These entities could be different genes or miRNAs whose expression is measured by RNA-seq, different transcription factors or histone marks whose expression is measured by ChIP-seq, or even combinations of different types of entities. Our Bayesian formulation accounts for both measured signal levels and uncertainty in those levels, due to varying sequencing depth in different experiments and to varying absolute levels of individual entities, both of which affect the precision of the measurements. In comparison with a traditional Pearson correlation analysis, we show that our Bayesian correlation analysis retains high correlations when measurement confidence is high, but suppresses correlations when measurement confidence is low-especially for entities with low signal levels. In addition, we consider the influence of priors on the Bayesian correlation estimate. Perhaps surprisingly, we show that naive, uniform priors on entities' signal levels can lead to highly biased correlation estimates, particularly when different experiments have widely varying sequencing depths. However, we propose two alternative priors that provably mitigate this problem. We also prove that, like traditional Pearson correlation, our Bayesian correlation calculation constitutes a kernel in the machine learning sense, and thus can be used as a similarity measure in any kernel-based machine learning algorithm. We demonstrate our approach on two RNA-seq datasets and one miRNA-seq dataset.

  13. Redundant correlation effect on personalized recommendation

    NASA Astrophysics Data System (ADS)

    Qiu, Tian; Han, Teng-Yue; Zhong, Li-Xin; Zhang, Zi-Ke; Chen, Guang

    2014-02-01

    The high-order redundant correlation effect is investigated for a hybrid algorithm of heat conduction and mass diffusion (HHM), through both heat conduction biased (HCB) and mass diffusion biased (MDB) correlation redundancy elimination processes. The HCB and MDB algorithms do not introduce any additional tunable parameters, but keep the simple character of the original HHM. Based on two empirical datasets, the Netflix and MovieLens, the HCB and MDB are found to show better recommendation accuracy for both the overall objects and the cold objects than the HHM algorithm. Our work suggests that properly eliminating the high-order redundant correlations can provide a simple and effective approach to accurate recommendation.

  14. Top Quark Spin Correlations at the Tevatron

    SciTech Connect

    Head, Tim; /Manchester U.

    2010-07-01

    Recent measurements of the correlation between the spin of the top and the spin of the anti-top quark produced in proton anti-proton scattering at a center of mass energy of {radical}s = 1.96 Tev by the CDF and D0 collaborations are discussed. using up to 4.3 fb{sup -1} of data taken with the CDF and D0 detectors the spin correlation parameter C, the degree to which the spins are correlated, is measured in dileptonic and semileptonic final states. The measurements are found to be in agreement with Standard Model predictions.

  15. Teleportation-induced correlated quantum channels.

    PubMed

    Caruso, F; Giovannetti, V; Palma, G M

    2010-01-15

    Quantum teleportation of an n-qubit state performed using as an entangled resource a general bipartite state of 2n qubits instead of n Bell states is equivalent to a correlated Pauli channel. This yields a new characterization of such channels in terms of many-body correlation functions of the teleporting media. It provides a relatively simple method for determining whether a correlated quantum channel is able to reliably convey quantum messages by studying the entanglement properties of the teleportation mediating system. Our model is then generalized to the continuous-variable case.

  16. Quantum correlations among optical and vibrational quanta

    NASA Astrophysics Data System (ADS)

    Carlig, Sergiu; Macovei, Mihai A.

    2014-05-01

    We investigate the feasibility of correlating an optical cavity field and a vibrational phonon mode. A laser pumped quantum dot fixed on a nanomechanical resonator beam interacts as a whole with the optical resonator mode. When the quantum dot variables are faster than the optical and phonon ones, we obtain a final master equation describing the involved modes only. Increasing the temperature, which directly affects the vibrational degrees of freedom, one can as well influence the cavity photon intensity, i.e., the optical and phonon modes are correlated. Furthermore, the corresponding Cauchy-Schwarz inequality is violated demonstrating the quantum nature of those correlations.

  17. Magnitude and sign correlations in heartbeat fluctuations

    NASA Technical Reports Server (NTRS)

    Ashkenazy, Y.; Ivanov, P. C.; Havlin, S.; Peng, C. K.; Goldberger, A. L.; Stanley, H. E.

    2001-01-01

    We propose an approach for analyzing signals with long-range correlations by decomposing the signal increment series into magnitude and sign series and analyzing their scaling properties. We show that signals with identical long-range correlations can exhibit different time organization for the magnitude and sign. We find that the magnitude series relates to the nonlinear properties of the original time series, while the sign series relates to the linear properties. We apply our approach to the heartbeat interval series and find that the magnitude series is long-range correlated, while the sign series is anticorrelated and that both magnitude and sign series may have clinical applications.

  18. Multichannel correlation recognition method of optical images

    NASA Astrophysics Data System (ADS)

    Wang, Hongxia; He, Junfa; Sun, Honghui

    2000-10-01

    In this paper a multi-channel real-time hybrid joint transform correlator is proposed. In this correlator, the computer control is used to divide the screen into several equal size windows, reference images of the windows are all the same one and object images are adopted from different frames of image sequences by CCD, twice Fourier transforms of every channel images are realized by using hololens array. Areas of LCLV and the output light energy can be used effectively. The correlation performance can be improved.

  19. Discovering correlated fermions using quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Wagner, Lucas K.; Ceperley, David M.

    2016-09-01

    It has become increasingly feasible to use quantum Monte Carlo (QMC) methods to study correlated fermion systems for realistic Hamiltonians. We give a summary of these techniques targeted at researchers in the field of correlated electrons, focusing on the fundamentals, capabilities, and current status of this technique. The QMC methods often offer the highest accuracy solutions available for systems in the continuum, and, since they address the many-body problem directly, the simulations can be analyzed to obtain insight into the nature of correlated quantum behavior.

  20. The IAA RAS Correlator First Results

    NASA Technical Reports Server (NTRS)

    Surkis, Igor; Melnikov, Alexey; Shantyr, Violet; Zimovsky, Vladimir

    2010-01-01

    In 2009 the national Russian VLBI observations were processed by the new correlator ARC (Astrometric Radiointerferometric Correlator). The ARC is a VSI-H correlator and equipped with Mark 5B playback terminals. During 2009 ARC was used to process a series of VLBI sessions, observed on stations Svetloe, Zelenchukskaya, and Badary. NGS files were formed, and EOP parameters were obtained by IAA RAS Analysis Center. The accuracies of the pole coordinates and UT1-UTC were 1-2 mas and 0.07-0.1 ms, respectively.

  1. Measurement of exciton correlations using electrostatic lattices

    NASA Astrophysics Data System (ADS)

    Remeika, M.; Leonard, J. R.; Dorow, C. J.; Fogler, M. M.; Butov, L. V.; Hanson, M.; Gossard, A. C.

    2015-09-01

    We present a method for determining correlations in a gas of indirect excitons in a semiconductor quantum well structure. The method involves subjecting the excitons to a periodic electrostatic potential that causes modulations of the exciton density and photoluminescence (PL). Experimentally measured amplitudes of energy and intensity modulations of exciton PL serve as an input to a theoretical estimate of the exciton correlation parameter and temperature. We also present a proof-of-principle demonstration of the method for determining the correlation parameter and discuss how its accuracy can be improved.

  2. Long-range correlations in nucleotide sequences

    NASA Technical Reports Server (NTRS)

    Peng, C. K.; Buldyrev, S. V.; Goldberger, A. L.; Havlin, S.; Sciortino, F.; Simons, M.; Stanley, H. E.

    1992-01-01

    DNA sequences have been analysed using models, such as an n-step Markov chain, that incorporate the possibility of short-range nucleotide correlations. We propose here a method for studying the stochastic properties of nucleotide sequences by constructing a 1:1 map of the nucleotide sequence onto a walk, which we term a 'DNA walk'. We then use the mapping to provide a quantitative measure of the correlation between nucleotides over long distances along the DNA chain. Thus we uncover in the nucleotide sequence a remarkably long-range power law correlation that implies a new scale-invariant property of DNA. We find such long-range correlations in intron-containing genes and in nontranscribed regulatory DNA sequences, but not in complementary DNA sequences or intron-less genes.

  3. Correlation dynamics after short-pulse photoassociation

    SciTech Connect

    Koch, Christiane P.; Kosloff, Ronnie

    2010-06-15

    Two atoms in an ultracold gas are correlated at short interatomic distances due to threshold effects in which the potential energy of their interaction dominates the kinetic energy. The correlations manifest themselves in a distinct nodal structure of the density matrix at short interatomic distances. Pump-probe spectroscopy has recently been suggested [Phys. Rev. Lett. 103, 260401 (2009)] to probe these pair correlations: A suitably chosen, short photoassociation laser pulse depletes the ground-state pair density within the photoassociation window, creating a nonstationary wave packet in the electronic ground state. The dynamics of this nonstationary wave packet is monitored by time-delayed probe and ionization pulses. Here we discuss how the choice of the pulse parameters affects the experimental feasibility of this pump-probe spectroscopy of two-body correlations.

  4. Hardness/intensity correlations among BATSE bursts

    NASA Technical Reports Server (NTRS)

    Paciesas, William S.; Pendleton, Geoffrey N.; Kouveliotou, Chryssa; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.

    1992-01-01

    Conclusions about the nature of gamma-ray bursts derived from the size-frequency distribution may be altered if a significant correlation exists between burst intensity and spectral shape. Moreover, if gamma-ray bursts have a cosmological origin, such a correlation may be expected to result from the expansion of the universe. We have performed a rudimentary search of the BATSE bursts for hardness/intensity correlations. The range of spectral shapes was determined for each burst by computing the ratio of the intensity in the range 100-300 keV to that in 55-300 keV. We find weak evidence for the existence of a correlation, the strongest effect being present when comparing the maximum hardness ratio for each burst with its maximum rate.

  5. A Short Existence Proof for Correlation Dimension

    NASA Astrophysics Data System (ADS)

    Manning, Anthony; Simon, Károly

    1998-02-01

    The Grassberger-Hentschel-Procaccia correlation dimension has been put on a rigorous basis by Pesin and Tempelman. We simplify their proof that this dimension is given in terms of the measure of neighborhoods of the diagonal.

  6. Geometric aspects of uncertainty and correlation

    NASA Technical Reports Server (NTRS)

    Abe, Sumiyoshi

    1993-01-01

    The fact that the metric induced on the quantum evolution submanifold of the protective Hilbert space describes the uncertainties and correlations of the operators generating the quantum-state evolution and exhibits the inherently-quantized geometry is discussed.

  7. Higher order correlations of IRAS galaxies

    NASA Technical Reports Server (NTRS)

    Meiksin, Avery; Szapudi, Istvan; Szalay, Alexander

    1992-01-01

    The higher order irreducible angular correlation functions are derived up to the eight-point function, for a sample of 4654 IRAS galaxies, flux-limited at 1.2 Jy in the 60 microns band. The correlations are generally found to be somewhat weaker than those for the optically selected galaxies, consistent with the visual impression of looser clusters in the IRAS sample. It is found that the N-point correlation functions can be expressed as the symmetric sum of products of N - 1 two-point functions, although the correlations above the four-point function are consistent with zero. The coefficients are consistent with the hierarchical clustering scenario as modeled by Hamilton and by Schaeffer.

  8. Hidden geometric correlations in real multiplex networks

    NASA Astrophysics Data System (ADS)

    Kleineberg, Kaj-Kolja; Boguñá, Marián; Ángeles Serrano, M.; Papadopoulos, Fragkiskos

    2016-11-01

    Real networks often form interacting parts of larger and more complex systems. Examples can be found in different domains, ranging from the Internet to structural and functional brain networks. Here, we show that these multiplex systems are not random combinations of single network layers. Instead, they are organized in specific ways dictated by hidden geometric correlations between the layers. We find that these correlations are significant in different real multiplexes, and form a key framework for answering many important questions. Specifically, we show that these geometric correlations facilitate the definition and detection of multidimensional communities, which are sets of nodes that are simultaneously similar in multiple layers. They also enable accurate trans-layer link prediction, meaning that connections in one layer can be predicted by observing the hidden geometric space of another layer. And they allow efficient targeted navigation in the multilayer system using only local knowledge, outperforming navigation in the single layers only if the geometric correlations are sufficiently strong.

  9. Temporal evolution of financial-market correlations.

    PubMed

    Fenn, Daniel J; Porter, Mason A; Williams, Stacy; McDonald, Mark; Johnson, Neil F; Jones, Nick S

    2011-08-01

    We investigate financial market correlations using random matrix theory and principal component analysis. We use random matrix theory to demonstrate that correlation matrices of asset price changes contain structure that is incompatible with uncorrelated random price changes. We then identify the principal components of these correlation matrices and demonstrate that a small number of components accounts for a large proportion of the variability of the markets that we consider. We characterize the time-evolving relationships between the different assets by investigating the correlations between the asset price time series and principal components. Using this approach, we uncover notable changes that occurred in financial markets and identify the assets that were significantly affected by these changes. We show in particular that there was an increase in the strength of the relationships between several different markets following the 2007-2008 credit and liquidity crisis.

  10. Velocity correlations in laboratory insect swarms

    NASA Astrophysics Data System (ADS)

    Ni, R.; Ouellette, N. T.

    2015-12-01

    In contrast to animal groups such as bird flocks or migratory herds that display net, directed motion, insect swarms do not possess global order. Without such order, it is difficult to define and characterize the transition to collective behavior in swarms; nevertheless, visual observation of swarms strongly suggests that swarming insects do behave collectively. It has recently been suggested that correlation rather than order is the hallmark of emergent collective behavior. Here, we report measurements of spatial velocity correlation functions in laboratory mating swarms of the non-biting midge Chironomus riparius. Although we find some correlation at short distances, our swarms are in general only weakly correlated, in contrast to what has been observed in field studies. Our results hint at the potentially important role of environmental conditions on collective behavior, and suggest that general indicators of the collective nature of swarming are still needed.

  11. Learning Bayesian Networks from Correlated Data

    NASA Astrophysics Data System (ADS)

    Bae, Harold; Monti, Stefano; Montano, Monty; Steinberg, Martin H.; Perls, Thomas T.; Sebastiani, Paola

    2016-05-01

    Bayesian networks are probabilistic models that represent complex distributions in a modular way and have become very popular in many fields. There are many methods to build Bayesian networks from a random sample of independent and identically distributed observations. However, many observational studies are designed using some form of clustered sampling that introduces correlations between observations within the same cluster and ignoring this correlation typically inflates the rate of false positive associations. We describe a novel parameterization of Bayesian networks that uses random effects to model the correlation within sample units and can be used for structure and parameter learning from correlated data without inflating the Type I error rate. We compare different learning metrics using simulations and illustrate the method in two real examples: an analysis of genetic and non-genetic factors associated with human longevity from a family-based study, and an example of risk factors for complications of sickle cell anemia from a longitudinal study with repeated measures.

  12. Correlates of frailty among homeless adults.

    PubMed

    Salem, Benissa E; Nyamathi, Adeline M; Brecht, Mary-Lynn; Phillips, Linda R; Mentes, Janet C; Sarkisian, Catherine; Leake, Barbara

    2013-10-01

    Frailty, a relatively unexplored concept among vulnerable populations, may be a significant issue for homeless adults. This cross-sectional study assessed correlates of frailty among middle age and older homeless adults (N = 150, 40-73). A Pearson (r) bivariate correlation revealed a weak relationship between frailty and being female (r = .230, p < .01). Significant moderate negative correlations were found between frailty and resilience (r = -.395, p < .01), social support (r = -.377, p < .01), and nutrition (r = -.652, p < .01). Furthermore, Spearman's rho (r s) bivariate correlations revealed a moderate positive relationship between frailty and health care utilization (r(s) = .444, p < .01). A stepwise backward linear regression analysis was conducted and in the final model, age, gender, health care utilization, nutrition, and resilience were significantly related to frailty. Over the next two decades, there is an anticipated increase in the number of homeless adults which will necessitate a greater understanding of the needs of this hard-to-reach population.

  13. Synchronous correlation matrices and Connes’ embedding conjecture

    SciTech Connect

    Dykema, Kenneth J.; Paulsen, Vern

    2016-01-15

    In the work of Paulsen et al. [J. Funct. Anal. (in press); preprint arXiv:1407.6918], the concept of synchronous quantum correlation matrices was introduced and these were shown to correspond to traces on certain C*-algebras. In particular, synchronous correlation matrices arose in their study of various versions of quantum chromatic numbers of graphs and other quantum versions of graph theoretic parameters. In this paper, we develop these ideas further, focusing on the relations between synchronous correlation matrices and microstates. We prove that Connes’ embedding conjecture is equivalent to the equality of two families of synchronous quantum correlation matrices. We prove that if Connes’ embedding conjecture has a positive answer, then the tracial rank and projective rank are equal for every graph. We then apply these results to more general non-local games.

  14. Temporal evolution of financial-market correlations

    NASA Astrophysics Data System (ADS)

    Fenn, Daniel J.; Porter, Mason A.; Williams, Stacy; McDonald, Mark; Johnson, Neil F.; Jones, Nick S.

    2011-08-01

    We investigate financial market correlations using random matrix theory and principal component analysis. We use random matrix theory to demonstrate that correlation matrices of asset price changes contain structure that is incompatible with uncorrelated random price changes. We then identify the principal components of these correlation matrices and demonstrate that a small number of components accounts for a large proportion of the variability of the markets that we consider. We characterize the time-evolving relationships between the different assets by investigating the correlations between the asset price time series and principal components. Using this approach, we uncover notable changes that occurred in financial markets and identify the assets that were significantly affected by these changes. We show in particular that there was an increase in the strength of the relationships between several different markets following the 2007-2008 credit and liquidity crisis.

  15. Quantum correlations require multipartite information principles.

    PubMed

    Gallego, Rodrigo; Würflinger, Lars Erik; Acín, Antonio; Navascués, Miguel

    2011-11-18

    Identifying which correlations among distant observers are possible within our current description of nature, based on quantum mechanics, is a fundamental problem in physics. Recently, information concepts have been proposed as the key ingredient to characterize the set of quantum correlations. Novel information principles, such as information causality or nontrivial communication complexity, have been introduced in this context and successfully applied to some concrete scenarios. We show in this work a fundamental limitation of this approach: no principle based on bipartite information concepts is able to singleout the set of quantum correlations for an arbitrary number of parties. Our results reflect the intricate structure of quantum correlations and imply that new and intrinsically multipartite information concepts are needed for their full understanding.

  16. Propagating wave correlations in complex systems

    NASA Astrophysics Data System (ADS)

    Creagh, Stephen C.; Gradoni, Gabriele; Hartmann, Timo; Tanner, Gregor

    2017-01-01

    We describe a novel approach for computing wave correlation functions inside finite spatial domains driven by complex and statistical sources. By exploiting semiclassical approximations, we provide explicit algorithms to calculate the local mean of these correlation functions in terms of the underlying classical dynamics. By defining appropriate ensemble averages, we show that fluctuations about the mean can be characterised in terms of classical correlations. We give in particular an explicit expression relating fluctuations of diagonal contributions to those of the full wave correlation function. The methods have a wide range of applications both in quantum mechanics and for classical wave problems such as in vibro-acoustics and electromagnetism. We apply the methods here to simple quantum systems, so-called quantum maps, which model the behaviour of generic problems on Poincaré sections. Although low-dimensional, these models exhibit a chaotic classical limit and share common characteristics with wave propagation in complex structures.

  17. Electron correlation dynamics in atoms and molecules.

    PubMed

    Nest, M; Ludwig, M; Ulusoy, I; Klamroth, T; Saalfrank, P

    2013-04-28

    In this paper, we present quantum dynamical calculations on electron correlation dynamics in atoms and molecules using explicitly time-dependent ab initio configuration interaction theory. The goals are (i) to show that in which cases it is possible to switch off the electronic correlation by ultrashort laser pulses, and (ii) to understand the temporal evolution and the time scale on which it reappears. We characterize the appearance of correlation through electron-electron scattering when starting from an uncorrelated state, and we identify pathways for the preparation of a Hartree-Fock state from the correlated, true ground state. Exemplary results for noble gases, alkaline earth elements, and selected molecules are provided. For Mg we show that the uncorrelated state can be prepared using a shaped ultrashort laser pulse.

  18. Long-range correlations in nucleotide sequences

    NASA Astrophysics Data System (ADS)

    Peng, C.-K.; Buldyrev, S. V.; Goldberger, A. L.; Havlin, S.; Sciortino, F.; Simons, M.; Stanley, H. E.

    1992-03-01

    DNA SEQUENCES have been analysed using models, such as an it-step Markov chain, that incorporate the possibility of short-range nucleotide correlations1. We propose here a method for studying the stochastic properties of nucleotide sequences by constructing a 1:1 map of the nucleotide sequence onto a walk, which we term a 'DNA walk'. We then use the mapping to provide a quantitative measure of the correlation between nucleotides over long distances along the DNA chain. Thus we uncover in the nucleotide sequence a remarkably long-range power law correlation that implies a new scale-invariant property of DNA. We find such long-range correlations in intron-containing genes and in nontranscribed regulatory DNA sequences, but not in complementary DNA sequences or intron-less genes.

  19. On the measurability of quantum correlation functions

    NASA Astrophysics Data System (ADS)

    de Lima Bernardo, Bertúlio; Azevedo, Sérgio; Rosas, Alexandre

    2015-05-01

    The concept of correlation function is widely used in classical statistical mechanics to characterize how two or more variables depend on each other. In quantum mechanics, on the other hand, there are observables that cannot be measured at the same time; the so-called incompatible observables. This prospect imposes a limitation on the definition of a quantum analog for the correlation function in terms of a sequence of measurements. Here, based on the notion of sequential weak measurements, we circumvent this limitation by introducing a framework to measure general quantum correlation functions, in principle, independently of the state of the system and the operators involved. To illustrate, we propose an experimental configuration to obtain explicitly the quantum correlation function between two Pauli operators, in which the input state is an arbitrary mixed qubit state encoded on the polarization of photons.

  20. On the measurability of quantum correlation functions

    SciTech Connect

    Lima Bernardo, Bertúlio de Azevedo, Sérgio; Rosas, Alexandre

    2015-05-15

    The concept of correlation function is widely used in classical statistical mechanics to characterize how two or more variables depend on each other. In quantum mechanics, on the other hand, there are observables that cannot be measured at the same time; the so-called incompatible observables. This prospect imposes a limitation on the definition of a quantum analog for the correlation function in terms of a sequence of measurements. Here, based on the notion of sequential weak measurements, we circumvent this limitation by introducing a framework to measure general quantum correlation functions, in principle, independently of the state of the system and the operators involved. To illustrate, we propose an experimental configuration to obtain explicitly the quantum correlation function between two Pauli operators, in which the input state is an arbitrary mixed qubit state encoded on the polarization of photons.

  1. Current correlations in a Majorana beam splitter

    NASA Astrophysics Data System (ADS)

    Haim, Arbel; Berg, Erez; von Oppen, Felix; Oreg, Yuval

    2015-12-01

    We study current correlations in a T junction composed of a grounded topological superconductor and of two normal-metal leads which are biased at a voltage V . We show that the existence of an isolated Majorana zero mode in the junction dictates a universal behavior for the cross correlation of the currents through the two normal-metal leads of the junction. The cross correlation is negative and approaches zero at high bias voltages as -1 /V . This behavior is robust in the presence of disorder and multiple transverse channels, and persists at finite temperatures. In contrast, an accidental low-energy Andreev bound state gives rise to nonuniversal behavior of the cross correlation. We employ numerical transport simulations to corroborate our conclusions.

  2. This Issue: Correlates of a Defective School.

    ERIC Educational Resources Information Center

    Gilman, David Alan

    1992-01-01

    Describes correlates of defective schools: perks for very few; faulty communication; adult-centered programs; special interest group indulgence; poor professional relationships; personnel warehousing; incompetent consultants; literal interpretation of technicalities; imperial leadership; intimate relationships among personnel; incoherent…

  3. Generalized interferometry - I: theory for interstation correlations

    NASA Astrophysics Data System (ADS)

    Fichtner, Andreas; Stehly, Laurent; Ermert, Laura; Boehm, Christian

    2017-02-01

    We develop a general theory for interferometry by correlation that (i) properly accounts for heterogeneously distributed sources of continuous or transient nature, (ii) fully incorporates any type of linear and nonlinear processing, such as one-bit normalization, spectral whitening and phase-weighted stacking, (iii) operates for any type of medium, including 3-D elastic, heterogeneous and attenuating media, (iv) enables the exploitation of complete correlation waveforms, including seemingly unphysical arrivals, and (v) unifies the earthquake-based two-station method and ambient noise correlations. Our central theme is not to equate interferometry with Green function retrieval, and to extract information directly from processed interstation correlations, regardless of their relation to the Green function. We demonstrate that processing transforms the actual wavefield sources and actual wave propagation physics into effective sources and effective wave propagation. This transformation is uniquely determined by the processing applied to the observed data, and can be easily computed. The effective forward model, that links effective sources and propagation to synthetic interstation correlations, may not be perfect. A forward modelling error, induced by processing, describes the extent to which processed correlations can actually be interpreted as proper correlations, that is, as resulting from some effective source and some effective wave propagation. The magnitude of the forward modelling error is controlled by the processing scheme and the temporal variability of the sources. Applying adjoint techniques to the effective forward model, we derive finite-frequency Fréchet kernels for the sources of the wavefield and Earth structure, that should be inverted jointly. The structure kernels depend on the sources of the wavefield and the processing scheme applied to the raw data. Therefore, both must be taken into account correctly in order to make accurate inferences on

  4. Design of exchange-correlation functionals through the correlation factor approach

    SciTech Connect

    Pavlíková Přecechtělová, Jana E-mail: Matthias.Ernzerhof@UMontreal.ca

    2015-10-14

    The correlation factor model is developed in which the spherically averaged exchange-correlation hole of Kohn-Sham theory is factorized into an exchange hole model and a correlation factor. The exchange hole model reproduces the exact exchange energy per particle. The correlation factor is constructed in such a manner that the exchange-correlation energy correctly reduces to exact exchange in the high density and rapidly varying limits. Four different correlation factor models are presented which satisfy varying sets of physical constraints. Three models are free from empirical adjustments to experimental data, while one correlation factor model draws on one empirical parameter. The correlation factor models are derived in detail and the resulting exchange-correlation holes are analyzed. Furthermore, the exchange-correlation energies obtained from the correlation factor models are employed to calculate total energies, atomization energies, and barrier heights. It is shown that accurate, non-empirical functionals can be constructed building on exact exchange. Avenues for further improvements are outlined as well.

  5. Optimizing correlation techniques for improved earthquake location

    USGS Publications Warehouse

    Schaff, D.P.; Bokelmann, G.H.R.; Ellsworth, W.L.; Zanzerkia, E.; Waldhauser, F.; Beroza, G.C.

    2004-01-01

    Earthquake location using relative arrival time measurements can lead to dramatically reduced location errors and a view of fault-zone processes with unprecedented detail. There are two principal reasons why this approach reduces location errors. The first is that the use of differenced arrival times to solve for the vector separation of earthquakes removes from the earthquake location problem much of the error due to unmodeled velocity structure. The second reason, on which we focus in this article, is that waveform cross correlation can substantially reduce measurement error. While cross correlation has long been used to determine relative arrival times with subsample precision, we extend correlation measurements to less similar waveforms, and we introduce a general quantitative means to assess when correlation data provide an improvement over catalog phase picks. We apply the technique to local earthquake data from the Calaveras Fault in northern California. Tests for an example streak of 243 earthquakes demonstrate that relative arrival times with normalized cross correlation coefficients as low as ???70%, interevent separation distances as large as to 2 km, and magnitudes up to 3.5 as recorded on the Northern California Seismic Network are more precise than relative arrival times determined from catalog phase data. Also discussed are improvements made to the correlation technique itself. We find that for large time offsets, our implementation of time-domain cross correlation is often more robust and that it recovers more observations than the cross spectral approach. Longer time windows give better results than shorter ones. Finally, we explain how thresholds and empirical weighting functions may be derived to optimize the location procedure for any given region of interest, taking advantage of the respective strengths of diverse correlation and catalog phase data on different length scales.

  6. Pfaffian Correlation Functions of Planar Dimer Covers

    NASA Astrophysics Data System (ADS)

    Aizenman, Michael; Valcázar, Manuel Laínz; Warzel, Simone

    2017-01-01

    The Pfaffian structure of the boundary monomer correlation functions in the dimer-covering planar graph models is rederived through a combinatorial/topological argument. These functions are then extended into a larger family of order-disorder correlation functions which are shown to exhibit Pfaffian structure throughout the bulk. Key tools involve combinatorial switching symmetries which are identified through the loop-gas representation of the double dimer model, and topological implications of planarity.

  7. Monogamy of quantum entanglement and other correlations

    SciTech Connect

    Koashi, Masato; Winter, Andreas

    2004-02-01

    It has been observed by numerous authors that a quantum system being entangled with another one limits its possible entanglement with a third system: this has been dubbed the 'monogamous nature of entanglement'. In this paper we present a simple identity which captures the trade off between entanglement and classical correlation, which can be used to derive rigorous monogamy relations. We also prove various other trade offs of a monogamy nature for other entanglement measures and secret and total correlation measures.

  8. Biochemical correlates of neurosensory changes in weightlessness

    NASA Technical Reports Server (NTRS)

    Leach, Carolyn S.; Reschke, Millard F.

    1989-01-01

    The possible existence of a relationship between space motion sickness and chemical and biochemical variables measured in body fluids is studied. Clinical chemistry and endocrine measurements from blood and urine samples taken before and after Space Shuttle flights were analyzed along with the occurrence of SMS during flight and provocative testing before flight. Significant positive correlations were observed with serum chloride and significant negative correlations with serum phosphate, serum uric acid, and plasma thyroid stimulating hormone.

  9. Decay of correlation for random intermittent maps

    NASA Astrophysics Data System (ADS)

    Bahsoun, Wael; Bose, Christopher; Duan, Yuejiao

    2014-07-01

    We study a class of random transformations built over finitely many intermittent maps sharing a common indifferent fixed point. Using a Young-tower technique, we show that the map with the fastest relaxation rate dominates the asymptotics. In particular, we prove that the rate of correlation decay for the annealed dynamics of the random map is the same as the sharp rate of correlation decay for the map with the fastest relaxation rate.

  10. Correlation of Spacecraft Mission and Project Costs

    NASA Technical Reports Server (NTRS)

    Swan, Christopher; Jarrett, Shawn

    2007-01-01

    A key component of any cost risk analysis is the level of correlation between individual elements of cost. This analysis supplements the available historical records with the cost estimates from the JPL Advanced Design Team. The costs from actual JPL flight projects are then used to validate the results, clearly indicating that, on average, the correlation between elements of cost is between 0.4 and 0.7.

  11. Percolation of secret correlations in a network

    SciTech Connect

    Leverrier, Anthony; Garcia-Patron, Raul

    2011-09-15

    In this work, we explore the analogy between entanglement and secret classical correlations in the context of large networks--more precisely, the question of percolation of secret correlations in a network. It is known that entanglement percolation in quantum networks can display a highly nontrivial behavior depending on the topology of the network and on the presence of entanglement between the nodes. Here we show that this behavior, thought to be of a genuine quantum nature, also occurs in a classical context.

  12. Prediction Theory of Periodically Correlated Stochastic Processes

    DTIC Science & Technology

    2015-05-12

    SECURITY CLASSIFICATION OF: The research dealt with the prediction problem for periodically correlated sequences, that is the stochastic sequences...was to develop an alternative technique for analysis such sequences . In the first published paper we 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND...Aug-2014 Approved for Public Release; Distribution Unlimited Final Report: Prediction Theory of Periodically Correlated Stochastic Processes. The

  13. Temperature-polarization correlations from tensor fluctuations

    SciTech Connect

    Crittenden, R.G.; Coulson, D.; Turok, N.G. |

    1995-11-15

    We study the polarization-temperature correlations on the cosmic microwave sky resulting from an initial scale-invariant spectrum of tensor (gravity wave) fluctuations, such as those which might arise during inflation. The correlation function has the opposite sign to that for scalar fluctuations on large scales, raising the possibility of a direct determination of whether the microwave anisotropies have a significant tensor component. We briefly discuss the important problem of estimating the expected foreground contamination.

  14. Pair correlation and twin primes revisited

    PubMed Central

    Conrey, Brian

    2016-01-01

    We establish a connection between the conjectural two-over-two ratios formula for the Riemann zeta-function and a conjecture concerning correlations of a certain arithmetic function. Specifically, we prove that the ratios conjecture and the arithmetic correlations conjecture imply the same result. This casts a new light on the underpinnings of the ratios conjecture, which previously had been motivated by analogy with formulae in random matrix theory and by a heuristic recipe. PMID:27843409

  15. Digital Correlation Microwave Polarimetry: Analysis and Demonstration

    NASA Technical Reports Server (NTRS)

    Piepmeier, J. R.; Gasiewski, A. J.; Krebs, Carolyn A. (Technical Monitor)

    2000-01-01

    The design, analysis, and demonstration of a digital-correlation microwave polarimeter for use in earth remote sensing is presented. We begin with an analysis of three-level digital correlation and develop the correlator transfer function and radiometric sensitivity. A fifth-order polynomial regression is derived for inverting the digital correlation coefficient into the analog statistic. In addition, the effects of quantizer threshold asymmetry and hysteresis are discussed. A two-look unpolarized calibration scheme is developed for identifying correlation offsets. The developed theory and calibration method are verified using a 10.7 GHz and a 37.0 GHz polarimeter. The polarimeters are based upon 1-GS/s three-level digital correlators and measure the first three Stokes parameters. Through experiment, the radiometric sensitivity is shown to approach the theoretical as derived earlier in the paper and the two-look unpolarized calibration method is successfully compared with results using a polarimetric scheme. Finally, sample data from an aircraft experiment demonstrates that the polarimeter is highly-useful for ocean wind-vector measurement.

  16. Concordance correlation coefficient applied to discrete data.

    PubMed

    Carrasco, Josep L; Jover, Lluis

    2005-12-30

    In any field in which decisions are subject to measurements, interchangeability between the methods used to obtain these measurements is essential. To consider methods as interchangeable, a certain degree of agreement is needed between the measurements they provide. The concordance correlation coefficient is an index that assesses the strength of agreement and it has been widely applied in situations in which measurements are made on a continuous scale. Recently the concordance correlation coefficient has been defined as a specific intraclass correlation coefficient estimated by the variance components of a Normal-Normal mixed linear model. Although this coefficient was defined for the continuous scale case, it may also be used with a discrete scale. In this case the data are often transformed and normalized, and the concordance correlation is applied. This study discusses the expression of the concordance correlation coefficient for discrete Poisson data by means of the Poisson-Normal generalized linear mixed model. The behaviour of the concordance correlation coefficient estimate is assessed by means of a simulation study, in which the estimates were compared using four models: three Normal-Normal mixed models with raw data, log-transformed data and square-root transformed data, and the Poisson-Normal generalized linear mixed model. An example is provided in which two different methods are used to measure CD34+ cells.

  17. Effect of noise correlations on randomized benchmarking

    NASA Astrophysics Data System (ADS)

    Ball, Harrison; Stace, Thomas M.; Flammia, Steven T.; Biercuk, Michael J.

    2016-02-01

    Among the most popular and well-studied quantum characterization, verification, and validation techniques is randomized benchmarking (RB), an important statistical tool used to characterize the performance of physical logic operations useful in quantum information processing. In this work we provide a detailed mathematical treatment of the effect of temporal noise correlations on the outcomes of RB protocols. We provide a fully analytic framework capturing the accumulation of error in RB expressed in terms of a three-dimensional random walk in "Pauli space." Using this framework we derive the probability density function describing RB outcomes (averaged over noise) for both Markovian and correlated errors, which we show is generally described by a Γ distribution with shape and scale parameters depending on the correlation structure. Long temporal correlations impart large nonvanishing variance and skew in the distribution towards high-fidelity outcomes—consistent with existing experimental data—highlighting potential finite-sampling pitfalls and the divergence of the mean RB outcome from worst-case errors in the presence of noise correlations. We use the filter-transfer function formalism to reveal the underlying reason for these differences in terms of effective coherent averaging of correlated errors in certain random sequences. We conclude by commenting on the impact of these calculations on the utility of single-metric approaches to quantum characterization, verification, and validation.

  18. Phase correlation of foreign exchange time series

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chya

    2007-03-01

    Correlation of foreign exchange rates in currency markets is investigated based on the empirical data of USD/DEM and USD/JPY exchange rates for a period from February 1 1986 to December 31 1996. The return of exchange time series is first decomposed into a number of intrinsic mode functions (IMFs) by the empirical mode decomposition method. The instantaneous phases of the resultant IMFs calculated by the Hilbert transform are then used to characterize the behaviors of pricing transmissions, and the correlation is probed by measuring the phase differences between two IMFs in the same order. From the distribution of phase differences, our results show explicitly that the correlations are stronger in daily time scale than in longer time scales. The demonstration for the correlations in periods of 1986-1989 and 1990-1993 indicates two exchange rates in the former period were more correlated than in the latter period. The result is consistent with the observations from the cross-correlation calculation.

  19. Holographic thermalization with initial long range correlation

    SciTech Connect

    Lin, Shu

    2016-01-19

    Here, we studied the evolution of the Wightman correlator in a thermalizing state modeled by AdS3-Vaidya background. A prescription was given for calculating the Wightman correlator in coordinate space without using any approximation. For equal-time correlator , we obtained an enhancement factor v2 due to long range correlation present in the initial state. This was missed by previous studies based on geodesic approximation. Moreover, we found that the long range correlation in initial state does not lead to significant modification to thermalization time as compared to known results with generic initial state. We also studied the spatially integrated Wightman correlator and showed evidence on the distinction between long distance and small momentum physics for an out-of-equilibrium state. We also calculated the radiation spectrum of particles weakly coupled to O and found that lower frequency mode approaches thermal spectrum faster than high frequency mode.

  20. Node Survival in Networks under Correlated Attacks

    PubMed Central

    Hao, Yan; Armbruster, Dieter; Hütt, Marc-Thorsten

    2015-01-01

    We study the interplay between correlations, dynamics, and networks for repeated attacks on a socio-economic network. As a model system we consider an insurance scheme against disasters that randomly hit nodes, where a node in need receives support from its network neighbors. The model is motivated by gift giving among the Maasai called Osotua. Survival of nodes under different disaster scenarios (uncorrelated, spatially, temporally and spatio-temporally correlated) and for different network architectures are studied with agent-based numerical simulations. We find that the survival rate of a node depends dramatically on the type of correlation of the disasters: Spatially and spatio-temporally correlated disasters increase the survival rate; purely temporally correlated disasters decrease it. The type of correlation also leads to strong inequality among the surviving nodes. We introduce the concept of disaster masking to explain some of the results of our simulations. We also analyze the subsets of the networks that were activated to provide support after fifty years of random disasters. They show qualitative differences for the different disaster scenarios measured by path length, degree, clustering coefficient, and number of cycles. PMID:25932635

  1. High-Fidelity Coding with Correlated Neurons

    PubMed Central

    da Silveira, Rava Azeredo; Berry, Michael J.

    2014-01-01

    Positive correlations in the activity of neurons are widely observed in the brain. Previous studies have shown these correlations to be detrimental to the fidelity of population codes, or at best marginally favorable compared to independent codes. Here, we show that positive correlations can enhance coding performance by astronomical factors. Specifically, the probability of discrimination error can be suppressed by many orders of magnitude. Likewise, the number of stimuli encoded—the capacity—can be enhanced more than tenfold. These effects do not necessitate unrealistic correlation values, and can occur for populations with a few tens of neurons. We further show that both effects benefit from heterogeneity commonly seen in population activity. Error suppression and capacity enhancement rest upon a pattern of correlation. Tuning of one or several effective parameters can yield a limit of perfect coding: the corresponding pattern of positive correlation leads to a ‘lock-in’ of response probabilities that eliminates variability in the subspace relevant for stimulus discrimination. We discuss the nature of this pattern and we suggest experimental tests to identify it. PMID:25412463

  2. Broadcasting of quantum correlations: Possibilities and impossibilities

    NASA Astrophysics Data System (ADS)

    Chatterjee, Sourav; Sazim, Sk; Chakrabarty, Indranil

    2016-04-01

    In this work, we extensively study the problem of broadcasting of quantum correlations (QCs). This includes broadcasting of quantum entanglement as well as correlations that go beyond the notion of entanglement (QCsbE). It is quite well known from the "no-broadcasting theorem" that perfect broadcasting of QCs is not possible. However, it does not rule out the possibility of partial broadcasting of QCs where we can get lesser correlated states from a given correlated state. In order to have a holistic view of broadcasting, we investigate this problem by starting with a most general representation of two qubit mixed states in terms of the Bloch vectors. As a cloning transformation we have used universal symmetric optimal Buzek-Hillery (BH) cloner both locally and nonlocally. Unlike entanglement, we find that it is impossible to broadcast QCsbE optimally. Lastly, we generalize these results for any symmetric or asymmetric cloning machines as well. This result brings out a fundamental difference between the correlations defined from the perspective of entanglement and the correlations measure which claims to go beyond entanglement.

  3. Node Survival in Networks under Correlated Attacks.

    PubMed

    Hao, Yan; Armbruster, Dieter; Hütt, Marc-Thorsten

    2015-01-01

    We study the interplay between correlations, dynamics, and networks for repeated attacks on a socio-economic network. As a model system we consider an insurance scheme against disasters that randomly hit nodes, where a node in need receives support from its network neighbors. The model is motivated by gift giving among the Maasai called Osotua. Survival of nodes under different disaster scenarios (uncorrelated, spatially, temporally and spatio-temporally correlated) and for different network architectures are studied with agent-based numerical simulations. We find that the survival rate of a node depends dramatically on the type of correlation of the disasters: Spatially and spatio-temporally correlated disasters increase the survival rate; purely temporally correlated disasters decrease it. The type of correlation also leads to strong inequality among the surviving nodes. We introduce the concept of disaster masking to explain some of the results of our simulations. We also analyze the subsets of the networks that were activated to provide support after fifty years of random disasters. They show qualitative differences for the different disaster scenarios measured by path length, degree, clustering coefficient, and number of cycles.

  4. Nonlinear backbone torsional pair correlations in proteins

    NASA Astrophysics Data System (ADS)

    Long, Shiyang; Tian, Pu

    2016-10-01

    Protein allostery requires dynamical structural correlations. Physical origin of which, however, remain elusive despite intensive studies during last two and half decades. Based on analysis of molecular dynamics (MD) simulation trajectories for ten proteins with different sizes and folds, we found that nonlinear backbone torsional pair (BTP) correlations, which are mainly spatially long-ranged and are dominantly executed by loop residues, exist extensively in most analyzed proteins. Examination of torsional motion for correlated BTPs suggested that such nonlinear correlations are mainly associated aharmonic torsional state transitions and in some cases strongly anisotropic local torsional motion of participating torsions, and occur on widely different and relatively longer time scales. In contrast, correlations between backbone torsions in stable α helices and β strands are mainly linear and spatially short-ranged, and are more likely to associate with harmonic local torsional motion. Further analysis revealed that the direct cause of nonlinear contributions are heterogeneous linear correlations. These findings implicate a general search strategy for novel allosteric modulation sites of protein activities.

  5. Nonlinear backbone torsional pair correlations in proteins

    PubMed Central

    Long, Shiyang; Tian, Pu

    2016-01-01

    Protein allostery requires dynamical structural correlations. Physical origin of which, however, remain elusive despite intensive studies during last two and half decades. Based on analysis of molecular dynamics (MD) simulation trajectories for ten proteins with different sizes and folds, we found that nonlinear backbone torsional pair (BTP) correlations, which are mainly spatially long-ranged and are dominantly executed by loop residues, exist extensively in most analyzed proteins. Examination of torsional motion for correlated BTPs suggested that such nonlinear correlations are mainly associated aharmonic torsional state transitions and in some cases strongly anisotropic local torsional motion of participating torsions, and occur on widely different and relatively longer time scales. In contrast, correlations between backbone torsions in stable α helices and β strands are mainly linear and spatially short-ranged, and are more likely to associate with harmonic local torsional motion. Further analysis revealed that the direct cause of nonlinear contributions are heterogeneous linear correlations. These findings implicate a general search strategy for novel allosteric modulation sites of protein activities. PMID:27708342

  6. Angular correlations near the Fermi energy

    SciTech Connect

    Fox, D.; Cebra, D.A.; Karn, J.; Parks, C.; Pradhan, A.; Vander Molen, A.; van der Plicht, J.; Westfall, G.D.; Wilson, W.K.; Tickle, R.S.; and others

    1988-07-01

    Angular correlations between light particles have been studied to probe the extent to which a thermally equilibrated system is formed in heavy ion collisions near the Fermi energy. Single-light-particle inclusive energy spectra and two-particle large-angle correlations were measured for 40 and 50 MeV/nucleon C+C, Ag, and Au. The single-particle inclusive energy spectra are well fit by a three moving source parametrization. Two-particle large-angle correlations are shown to be consistent with emission from a thermally equilibrated source when the effects of momentum conservation are considered. Single-particle inclusive spectra and light-particle correlations at small relative momentum were measured for 35 MeV/nucleon N+Ag. Source radii were extracted from the two-particle correlation functions and were found to be consistent with previous measurements using two-particle correlations and the coalescence model. The temperature of the emitting source was extracted from the relative populations of states using the quantum statistical model and was found to be 4.8/sub -2.4//sup +2.8/ MeV, compared to the 14 MeV temperature extracted from the slopes of the kinetic energy spectra.

  7. Strong correlations in gravity and biophysics

    NASA Astrophysics Data System (ADS)

    Krotov, Dmitry

    The unifying theme of this dissertation is the use of correlations. In the first part (chapter 2), we investigate correlations in quantum field theories in de Sitter space. In the second part (chapters 3,4,5), we use correlations to investigate a theoretical proposal that real (observed in nature) transcriptional networks of biological organisms are operating at a critical point in their phase diagram. In chapter 2 we study the infrared dependence of correlators in various external backgrounds. Using the Schwinger-Keldysh formalism we calculate loop corrections to the correlators in the case of the Poincare patch and the complete de Sitter space. In the case of the Poincare patch, the loop correction modifies the behavior of the correlator at large distances. In the case of the complete de Sitter space, the loop correction has a strong dependence on the infrared cutoff in the past. It grows linearly with time, suggesting that at some point the correlations become strong and break the symmetry of the classical background. In chapter 3 we derive the signatures of critical behavior in a model organism, the embryo of Drosophila melanogaster. They are: strong correlations in the fluctuations of different genes, a slowing of dynamics, long range correlations in space, and departures from a Gaussian distribution of these fluctuations. We argue that these signatures are observed experimentally. In chapter 4 we construct an effective theory for the zero mode in this system. This theory is different from the standard Landau-Ginsburg description. It contains gauge fields (the result of the broken translational symmetry inside the cell), which produce observable contributions to the two-point function of the order parameter. We show that the behavior of the two-point function for the network of N genes is described by the action of a relativistic particle moving on the surface of the N - 1 dimensional sphere. We derive a theoretical bound on the decay of the correlations and

  8. Quantum correlations of lights in macroscopic environments

    NASA Astrophysics Data System (ADS)

    Sua, Yong Meng

    This dissertation presents a detailed study in exploring quantum correlations of lights in macroscopic environments. We have explored quantum correlations of single photons, weak coherent states, and polarization-correlated/polarization-entangled photons in macroscopic environments. These included macroscopic mirrors, macroscopic photon number, spatially separated observers, noisy photons source and propagation medium with loss or disturbances. We proposed a measurement scheme for observing quantum correlations and entanglement in the spatial properties of two macroscopic mirrors using single photons spatial compass state. We explored the phase space distribution features of spatial compass states, such as chessboard pattern by using the Wigner function. The displacement and tilt correlations of the two mirrors were manifested through the propensities of the compass states. This technique can be used to extract Einstein-Podolsky-Rosen correlations (EPR) of the two mirrors. We then formulated the discrete-like property of the propensity P b(m,n), which can be used to explore environmental perturbed quantum jumps of the EPR correlations in phase space. With single photons spatial compass state, the variances in position and momentum are much smaller than standard quantum limit when using a Gaussian TEM 00 beam. We observed intrinsic quantum correlations of weak coherent states between two parties through balanced homodyne detection. Our scheme can be used as a supplement to decoy-state BB84 protocol and differential phase-shift QKD protocol. We prepared four types of bipartite correlations +/- cos2(theta1 +/- theta 2) that shared between two parties. We also demonstrated bits correlations between two parties separated by 10 km optical fiber. The bits information will be protected by the large quantum phase fluctuation of weak coherent states, adding another physical layer of security to these protocols for quantum key distribution. Using 10 m of highly nonlinear

  9. Ferreting out correlations from trajectory data

    NASA Astrophysics Data System (ADS)

    Cukier, Robert I.

    2011-12-01

    Thermally driven materials characterized by complex energy landscapes, such as proteins, exhibit motions on a broad range of space and time scales. Principal component analysis (PCA) is often used to extract modes of motion from protein trajectory data that correspond to coherent, functional motions. In this work, two other methods, maximum covariance analysis (MCA) and canonical correlation analysis (CCA) are formulated in a way appropriate to analyze protein trajectory data. Both methods partition the coordinates used to describe the system into two sets (two measurement domains) and inquire as to the correlations that may exist between them. MCA and CCA provide rotations of the original coordinate system that successively maximize the covariance (MCA) or correlation (CCA) between modes of each measurement domain under suitable constraint conditions. We provide a common framework based on the singular value decomposition of appropriate matrices to derive MCA and CCA. The differences between and strengths and weaknesses of MCA and CCA are discussed and illustrated. The application presented here examines the correlation between the backbone and side chain of the peptide met-enkephalin as it fluctuates between open conformations, found in solution, to closed conformations appropriate to when it is bound to its receptor. Difficulties with PCA carried out in Cartesian coordinates are found and motivate a formulation in terms of dihedral angles for the backbone atoms and selected atom distances for the side chains. These internal coordinates are a more reliable basis for all the methods explored here. MCA uncovers a correlation between combinations of several backbone dihedral angles and selected side chain atom distances of met-enkephalin. It could be used to suggest residues and dihedral angles to focus on to favor specific side chain conformers. These methods could be applied to proteins with domains that, when they rearrange upon ligand binding, may have

  10. Triplet correlation functions in liquid water

    NASA Astrophysics Data System (ADS)

    Dhabal, Debdas; Singh, Murari; Wikfeldt, Kjartan Thor; Chakravarty, Charusita

    2014-11-01

    Triplet correlations have been shown to play a crucial role in the transformation of simple liquids to anomalous tetrahedral fluids [M. Singh, D. Dhabal, A. H. Nguyen, V. Molinero, and C. Chakravarty, Phys. Rev. Lett. 112, 147801 (2014)]. Here we examine triplet correlation functions for water, arguably the most important tetrahedral liquid, under ambient conditions, using configurational ensembles derived from molecular dynamics (MD) simulations and reverse Monte Carlo (RMC) datasets fitted to experimental scattering data. Four different RMC data sets with widely varying hydrogen-bond topologies fitted to neutron and x-ray scattering data are considered [K. T. Wikfeldt, M. Leetmaa, M. P. Ljungberg, A. Nilsson, and L. G. M. Pettersson, J. Phys. Chem. B 113, 6246 (2009)]. Molecular dynamics simulations are performed for two rigid-body effective pair potentials (SPC/E and TIP4P/2005) and the monatomic water (mW) model. Triplet correlation functions are compared with other structural measures for tetrahedrality, such as the O-O-O angular distribution function and the local tetrahedral order distributions. In contrast to the pair correlation functions, which are identical for all the RMC ensembles, the O-O-O triplet correlation function can discriminate between ensembles with different degrees of tetrahedral network formation with the maximally symmetric, tetrahedral SYM dataset displaying distinct signatures of tetrahedrality similar to those obtained from atomistic simulations of the SPC/E model. Triplet correlations from the RMC datasets conform closely to the Kirkwood superposition approximation, while those from MD simulations show deviations within the first two neighbour shells. The possibilities for experimental estimation of triplet correlations of water and other tetrahedral liquids are discussed.

  11. Triplet correlation functions in liquid water

    SciTech Connect

    Dhabal, Debdas; Chakravarty, Charusita; Singh, Murari; Wikfeldt, Kjartan Thor

    2014-11-07

    Triplet correlations have been shown to play a crucial role in the transformation of simple liquids to anomalous tetrahedral fluids [M. Singh, D. Dhabal, A. H. Nguyen, V. Molinero, and C. Chakravarty, Phys. Rev. Lett. 112, 147801 (2014)]. Here we examine triplet correlation functions for water, arguably the most important tetrahedral liquid, under ambient conditions, using configurational ensembles derived from molecular dynamics (MD) simulations and reverse Monte Carlo (RMC) datasets fitted to experimental scattering data. Four different RMC data sets with widely varying hydrogen-bond topologies fitted to neutron and x-ray scattering data are considered [K. T. Wikfeldt, M. Leetmaa, M. P. Ljungberg, A. Nilsson, and L. G. M. Pettersson, J. Phys. Chem. B 113, 6246 (2009)]. Molecular dynamics simulations are performed for two rigid-body effective pair potentials (SPC/E and TIP4P/2005) and the monatomic water (mW) model. Triplet correlation functions are compared with other structural measures for tetrahedrality, such as the O–O–O angular distribution function and the local tetrahedral order distributions. In contrast to the pair correlation functions, which are identical for all the RMC ensembles, the O–O–O triplet correlation function can discriminate between ensembles with different degrees of tetrahedral network formation with the maximally symmetric, tetrahedral SYM dataset displaying distinct signatures of tetrahedrality similar to those obtained from atomistic simulations of the SPC/E model. Triplet correlations from the RMC datasets conform closely to the Kirkwood superposition approximation, while those from MD simulations show deviations within the first two neighbour shells. The possibilities for experimental estimation of triplet correlations of water and other tetrahedral liquids are discussed.

  12. Understanding the amplitudes of noise correlation measurements

    USGS Publications Warehouse

    Tsai, Victor C.

    2011-01-01

    Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.

  13. [NMR study of complex formation of aromatic ligands with heptadeoxynucleotide 5'-d(GCGAAGC) forming stable hairpin structure in aqueous solution].

    PubMed

    Veselkov, A N; Eaton, R J; Semanin, A V; Pakhomov, V I; Dymant, L N; Karavaev, L; Davies, D V

    2002-01-01

    Complex formation of hairpin-producing heptadeoxynucleotide 5'-d(GCGAAGC) with aromatic molecules: acridine dye proflavine and anthracycline antibiotic daunomycin was studied by one-dimensional 1H NMR and two-dimensional correlation 1H-1H (2M-TOCSY, 2M-NOESY), 1H-31P (2M-HMBC) NMR spectroscopy (500 and 600 MHz) in aqueous solution. Concentration and temperature dependences for the chemical shifts of ligand protons were measured, molecular models of equilibrium in solution were developed, and equilibrium thermodynamic parameters for the formation of intercalation complexes were calculated. Spatial structures of dye and antibiotic complexes with the heptamer hairpin were constructed on the basis of 2M-NOE data and the calculated values of limiting chemical shifts of ligand protons.

  14. DSN Beowulf Cluster-Based VLBI Correlator

    NASA Technical Reports Server (NTRS)

    Rogstad, Stephen P.; Jongeling, Andre P.; Finley, Susan G.; White, Leslie A.; Lanyi, Gabor E.; Clark, John E.; Goodhart, Charles E.

    2009-01-01

    The NASA Deep Space Network (DSN) requires a broadband VLBI (very long baseline interferometry) correlator to process data routinely taken as part of the VLBI source Catalogue Maintenance and Enhancement task (CAT M&E) and the Time and Earth Motion Precision Observations task (TEMPO). The data provided by these measurements are a crucial ingredient in the formation of precision deep-space navigation models. In addition, a VLBI correlator is needed to provide support for other VLBI related activities for both internal and external customers. The JPL VLBI Correlator (JVC) was designed, developed, and delivered to the DSN as a successor to the legacy Block II Correlator. The JVC is a full-capability VLBI correlator that uses software processes running on multiple computers to cross-correlate two-antenna broadband noise data. Components of this new system (see Figure 1) consist of Linux PCs integrated into a Beowulf Cluster, an existing Mark5 data storage system, a RAID array, an existing software correlator package (SoftC) originally developed for Delta DOR Navigation processing, and various custom- developed software processes and scripts. Parallel processing on the JVC is achieved by assigning slave nodes of the Beowulf cluster to process separate scans in parallel until all scans have been processed. Due to the single stream sequential playback of the Mark5 data, some ramp-up time is required before all nodes can have access to required scan data. Core functions of each processing step are accomplished using optimized C programs. The coordination and execution of these programs across the cluster is accomplished using Pearl scripts, PostgreSQL commands, and a handful of miscellaneous system utilities. Mark5 data modules are loaded on Mark5 Data systems playback units, one per station. Data processing is started when the operator scans the Mark5 systems and runs a script that reads various configuration files and then creates an experiment-dependent status database

  15. Quantum Correlations and the Measurement Problem

    NASA Astrophysics Data System (ADS)

    Bub, Jeffrey

    2014-10-01

    The transition from classical to quantum mechanics rests on the recognition that the structure of information is not what we thought it was: there are operational, i.e., phenomenal, probabilistic correlations that lie outside the polytope of local correlations. Such correlations cannot be simulated with classical resources, which generate classical correlations represented by the points in a simplex, where the vertices of the simplex represent joint deterministic states that are the common causes of the correlations. The `no go' hidden variable theorems tell us that we can't shoe-horn phenomenal correlations outside the local polytope into a classical simplex by supposing that something has been left out of the story. The replacement of the classical simplex by the quantum convex set as the structure representing probabilistic correlations is the analogue for quantum mechanics of the replacement of Newton's Euclidean space and time by Minkowski spacetime in special relativity. The nonclassical features of quantum mechanics, including the irreducible information loss on measurement, are generic features of correlations that lie outside the classical simplex. This paper is an elaboration of these ideas, which have their source in work by Pitowsky (J. Math. Phys. 27:1556, 1986; Math. Program. 50:395, 1991; Phys. Rev. A 77:062109, 2008), Garg and Mermin (Found. Phys. 14:1-39, 1984), Barrett (Phys. Rev. A 75:032304, 2007; Phys. Rev. A 7:022101, 2005) and others, e.g., Brunner et al. (arXiv:1303.2849, 2013), but the literature goes back to Boole (An Investigation of the Laws of Thought, Dover, New York, 1951). The final section looks at the measurement problem of quantum mechanics in this context. A large part of the problem is removed by seeing that the inconsistency in reconciling the entangled state at the end of a quantum measurement process with the definiteness of the macroscopic pointer reading and the definiteness of the correlated value of the measured micro

  16. Correlations Between Neutral and Ionized Solar Wind

    NASA Astrophysics Data System (ADS)

    Collier, M.; Pilkerton, B.; Moore, T.

    The Low Energy Neutral Atom (LENA) Imager on the IMAGE spacecraft has observed the neutral component of the solar wind (JGR, 106, 24,893, 2001) independently adumbrated by Akasofu and Dessler about forty years ago. Neutral solar wind is formed by solar wind charge exchange with interstellar neutrals, dust and the Earth's exosphere, in addition to any intrinsically neutral component. Here we report the results of a statistical study correlating the solar wind fluxes observed by ACE during late 2000 and throughout 2001 with neutral solar wind fluxes observed by LENA. The average correlation coefficient between the neutral and ionized solar wind is 0.66 with "good" correlations (peak correlation coefficient above 0.80) occurring about 28% of the time. The results are similar to those obtained by in-situ multi-spacecraft correlation studies. In this study, however, IMAGE is almost never in the solar wind or magnetosheath. The slope of the relationship between the neutral solar wind flux and the solar wind flux shows a peak in the upstream direction, but shifted toward higher ecliptic longitudes than the interstellar neutral (ISN) flow direction by about 20 degrees. The estimated peak interstellar neutral upstream density is about 10-2 cm-3.

  17. Correlations between neutral and ionized solar wind

    NASA Astrophysics Data System (ADS)

    Pilkerton, B. M.; Collier, M. R.; Moore, T. E.

    We report results of a statistical study correlating ionized solar wind (ISW) fluxes observed by ACE during late 2000 and throughout 2001 with neutral solar wind (NSW) fluxes observed by IMAGE/LENA over the same period. The average correlation coefficient between the neutral and ionized solar wind is 0.66 with correlations greater than 0.80 occurring about 29% of the time. Correlations appear to be driven by high solar wind flux variability, similar to results obtained by in situ multi-spacecraft correlation studies. In this study, however, IMAGE remains inside the magnetosphere on over 95% of its orbits. As a function of day of year, or equivalently ecliptic longitude, the slope of the relationship between the neutral solar wind flux and the ionized solar wind flux shows an enhancement near the upstream direction, but the symmetry point appears shifted toward higher ecliptic longitudes than the interstellar neutral (ISN) flow direction by about 20°. The estimated peak interstellar neutral upstream density inside of 1 AU is about 7 × 10 -3 cm -3.

  18. Temporal correlation coefficient for directed networks.

    PubMed

    Büttner, Kathrin; Salau, Jennifer; Krieter, Joachim

    2016-01-01

    Previous studies dealing with network theory focused mainly on the static aggregation of edges over specific time window lengths. Thus, most of the dynamic information gets lost. To assess the quality of such a static aggregation the temporal correlation coefficient can be calculated. It measures the overall possibility for an edge to persist between two consecutive snapshots. Up to now, this measure is only defined for undirected networks. Therefore, we introduce the adaption of the temporal correlation coefficient to directed networks. This new methodology enables the distinction between ingoing and outgoing edges. Besides a small example network presenting the single calculation steps, we also calculated the proposed measurements for a real pig trade network to emphasize the importance of considering the edge direction. The farm types at the beginning of the pork supply chain showed clearly higher values for the outgoing temporal correlation coefficient compared to the farm types at the end of the pork supply chain. These farm types showed higher values for the ingoing temporal correlation coefficient. The temporal correlation coefficient is a valuable tool to understand the structural dynamics of these systems, as it assesses the consistency of the edge configuration. The adaption of this measure for directed networks may help to preserve meaningful additional information about the investigated network that might get lost if the edge directions are ignored.

  19. Fluorescence correlation spectroscopy in semiadhesive wall proximity.

    PubMed

    Sanguigno, Luigi; De Santo, Ilaria; Causa, Filippo; Netti, Paolo A

    2011-11-01

    With examination of diffusion in heterogeneous media through fluorescence correlation spectroscopy, the temporal correlation of the intensity signal shows a long correlation tail and the characteristic diffusion time results are no longer easy to determine. Excluded volume and sticking effects have been proposed to justify such deviations from the standard behavior since all contribute and lead to anomalous diffusion mechanisms . Usually, the anomalous coefficient embodies all the effects of environmental heterogeneity providing too general explanations for the exotic diffusion recorded. Here, we investigated whether the reason of anomalies could be related to a lack of an adequate interpretative model for heterogeneous systems and how the presence of obstacles on the detection volume length scale could affect fluorescence correlation spectroscopy experiments. We report an original modeling of the autocorrelation function where fluorophores experience reflection or adsorption at a wall placed at distances comparable with the detection volume size. We successfully discriminate between steric and adhesion effects through the analysis of long time correlations and evaluate the adhesion strength through the evaluation of probability of being adsorbed and persistence time at the wall on reference data. The proposed model can be readily adopted to gain a better understanding of intracellular and nanoconfined diffusion opening the way for a more rational analysis of the diffusion mechanism in heterogeneous systems and further developing biological and biomedical applications.

  20. Correlation functions of Coulomb branch operators

    NASA Astrophysics Data System (ADS)

    Gerchkovitz, Efrat; Gomis, Jaume; Ishtiaque, Nafiz; Karasik, Avner; Komargodski, Zohar; Pufu, Silviu S.

    2017-01-01

    We consider the correlation functions of Coulomb branch operators in four-dimensional N = 2 Superconformal Field Theories (SCFTs) involving exactly one antichiral operator. These extremal correlators are the "minimal" non-holomorphic local observables in the theory. We show that they can be expressed in terms of certain determinants of derivatives of the four-sphere partition function of an appropriate deformation of the SCFT. This relation between the extremal correlators and the deformed four-sphere partition function is non-trivial due to the presence of conformal anomalies, which lead to operator mixing on the sphere. Evaluating the deformed four-sphere partition function using supersymmetric localization, we compute the extremal correlators explicitly in many interesting examples. Additionally, the representation of the extremal correlators mentioned above leads to a system of integrable differential equations. We compare our exact results with previous perturbative computations and with the four-dimensional tt ∗ equations. We also use our results to study some of the asymptotic properties of the perturbative series expansions we obtain in N = 2 SQCD.

  1. Modelling collinear and spatially correlated data.

    PubMed

    Liverani, Silvia; Lavigne, Aurore; Blangiardo, Marta

    2016-08-01

    In this work we present a statistical approach to distinguish and interpret the complex relationship between several predictors and a response variable at the small area level, in the presence of (i) high correlation between the predictors and (ii) spatial correlation for the response. Covariates which are highly correlated create collinearity problems when used in a standard multiple regression model. Many methods have been proposed in the literature to address this issue. A very common approach is to create an index which aggregates all the highly correlated variables of interest. For example, it is well known that there is a relationship between social deprivation measured through the Multiple Deprivation Index (IMD) and air pollution; this index is then used as a confounder in assessing the effect of air pollution on health outcomes (e.g. respiratory hospital admissions or mortality). However it would be more informative to look specifically at each domain of the IMD and at its relationship with air pollution to better understand its role as a confounder in the epidemiological analyses. In this paper we illustrate how the complex relationships between the domains of IMD and air pollution can be deconstructed and analysed using profile regression, a Bayesian non-parametric model for clustering responses and covariates simultaneously. Moreover, we include an intrinsic spatial conditional autoregressive (ICAR) term to account for the spatial correlation of the response variable.

  2. Autonomous planetary landing guidance by optical correlation

    NASA Astrophysics Data System (ADS)

    Knopp, Jerome; Juday, Richard D.; Monroe, Stanley E., Jr.

    1992-07-01

    We describe our planned use of optical correlation in landmark navigation associated with planetary landing. Standard correlation provides 'pointing-to' information, giving the vector to the landmark from the spacecraft in the spacecraft frame. The synthetic estimation filter (SEF) provides 'pointing-from' information, estimating the vector from the landmark to the spacecraft. Digital and optical SEFs were constructed and compared using a Martian-like 3D modelboard to provide test images. The digital SEF worked reasonably well, but the optical SEF did not perform as expected. The optical SEF was implemented with a liquid crystal television (LCTV) correlator that had been used successfully in previous SEF experiments using a spacecraft model. The results suggest the SLM model for the LCTV needs further refinements. Both the digital and optical filter provided good pointing-to results. We did not plot the correlation surface for the digital SEF response, and though it is less sharp than the POF, it had only a one-pixel variation in the peak location. Surface plots for the conventional optical phase-only filter produced a correlation peak that was sharp enough to be located within two pixels.

  3. Autonomous planetary landing guidance by optical correlation

    NASA Technical Reports Server (NTRS)

    Knopp, Jerome; Juday, Richard D.; Monroe, Stanley E., Jr.

    1992-01-01

    We describe our planned use of optical correlation in landmark navigation associated with planetary landing. Standard correlation provides 'pointing-to' information, giving the vector to the landmark from the spacecraft in the spacecraft frame. The synthetic estimation filter (SEF) provides 'pointing-from' information, estimating the vector from the landmark to the spacecraft. Digital and optical SEFs were constructed and compared using a Martian-like 3D modelboard to provide test images. The digital SEF worked reasonably well, but the optical SEF did not perform as expected. The optical SEF was implemented with a liquid crystal television (LCTV) correlator that had been used successfully in previous SEF experiments using a spacecraft model. The results suggest the SLM model for the LCTV needs further refinements. Both the digital and optical filter provided good pointing-to results. We did not plot the correlation surface for the digital SEF response, and though it is less sharp than the POF, it had only a one-pixel variation in the peak location. Surface plots for the conventional optical phase-only filter produced a correlation peak that was sharp enough to be located within two pixels.

  4. Understanding volatility correlation behavior with a magnitude cross-correlation function

    NASA Astrophysics Data System (ADS)

    Jun, Woo Cheol; Oh, Gabjin; Kim, Seunghwan

    2006-06-01

    We propose an approach for analyzing the basic relation between correlation properties of the original signal and its magnitude fluctuations by decomposing the original signal into its positive and negative fluctuation components. We use this relation to understand the following phenomenon found in many naturally occurring time series: the magnitude of the signal exhibits long-range correlation, whereas the original signal is short-range correlated. The applications of our approach to heart rate variability signals and high-frequency foreign exchange rates reveal that the difference between the correlation properties of the original signal and its magnitude fluctuations is induced by the time organization structure of the correlation function between the magnitude fluctuations of positive and negative components. We show that this correlation function can be described well by a stretched-exponential function and is related to the nonlinearity and the multifractal structure of the signals.

  5. Correlation estimation with singly truncated bivariate data.

    PubMed

    Im, Jongho; Ahn, Eunyong; Beck, Namseon; Kim, Jae Kwang; Park, Taesung

    2017-02-27

    Correlation coefficient estimates are often attenuated for truncated samples in the sense that the estimates are biased towards zero. Motivated by real data collected in South Sudan, we consider correlation coefficient estimation with singly truncated bivariate data. By considering a linear regression model in which a truncated variable is used as an explanatory variable, a consistent estimator for the regression slope can be obtained from the ordinary least squares method. A consistent estimator of the correlation coefficient is then obtained by multiplying the regression slope estimator by the variance ratio of the two variables. Results from two limited simulation studies confirm the validity and robustness of the proposed method. The proposed method is applied to the South Sudanese children's anthropometric and nutritional data collected by World Vision. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Coherent photoacoustic-ultrasound correlation and imaging.

    PubMed

    Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    2014-09-01

    Both photoacoustics and ultrasound have been researched extensively but separately. In this letter, we report an initial study on the coherent correlation between pulsed photoacoustic wave and pulse-echo ultrasound wave. By illuminating an object with a pulsed laser and external ultrasound sequentially, both the endogenous photoacoustic wave and pulse-echo ultrasound wave are received and coherently correlated, demonstrating enhanced signal-to-noise ratio. Image contrast of the proposed coherent photoacoustic-ultrasound imaging is also demonstrated to be improved significantly on vessel-mimicking phantom, due to fusion of the optical absorption and ultrasound reflection contrasts by coherent correlation of either conventional laser-induced photoacoustic imaging or pulse-echo ultrasound imaging separately.

  7. Exotic Superconductivity in Correlated Electron Systems

    SciTech Connect

    Mu, Gang; Sandu, Viorel; Li, Wei; Shen, Bing

    2015-05-25

    Over the past decades, the search for high-Tc superconductivity (SC) and its novel superconducting mechanisms is one of the most challenging tasks of condensed matter physicists and material scientists, wherein the most striking achievement is the discovery of high-c and unconventional superconductivity in strongly correlated 3d-electron systems, such as cuprates and iron pnictides/chalcogenides. Those exotic superconductors display the behaviors beyond the scope of the BCS theory (in the SC states) and the Landau-Fermi liquid theory (in the normal states). In general, such exotic superconductivity can be seen as correlated electron systems, where there are strong interplays among charge, spin, orbital, and lattice degrees of freedom. Thus, we focus on the exotic superconductivity in materials with correlated electrons in the present special issue.

  8. Hardness correlation for uranium and its alloys

    SciTech Connect

    Humphreys, D L; Romig, Jr, A D

    1983-03-01

    The hardness of 16 different uranium-titanium (U-Ti) alloys was measured on six (6) different hardness scales (R/sub A/, R/sub B/, R/sub C/, R/sub D/, Knoop, and Vickers). The alloys contained between 0.75 and 2.0 wt % Ti. All of the alloys were solutionized (850/sup 0/C, 1 h) and ice-water quenched to produce a supersaturated martensitic phase. A range of hardnesses was obtained by aging the samples for various times and temperatures. The correlation of various hardness scales was shown to be virtually identical to the hardness-scale correlation for steels. For more-accurate conversion from one hardness scale to another, least-squares-curve fits were determined for the various hardness-scale correlations. 34 figures, 5 tables.

  9. Evolution of particle velocity correlations in sedimentation

    NASA Astrophysics Data System (ADS)

    Guazzelli, Elisabeth

    2000-11-01

    The problem of velocity fluctuations in sedimentation is still unresolved. The velocity fluctuations are observed experimentally to form into characteristic correlated regions [see Segre et al. (1997) and Bernard-Michel (2000)]. The origin of these correlations is still an open question. How correlation between particle velocities develops in a well mixed suspension? What is the ultimate structure of the sedimenting suspension? To tackle these questions, particle velocity fields are measured using particle image velocimetry. The sedimentation process is observed to be dominated by velocity fluctuation structures of the size of the container in the initial moments after the mixing, which diminish with time down to a size of the order of 20 interparticle spacings.

  10. Particle Correlations with the PHENIX Experiment

    SciTech Connect

    Johnson, S C

    2002-01-20

    Results of identical pion correlations from the first year of data collection with the PHENIX detector at RHIC ({radical}S{sub NN} = 130 GeV) are presented. PHENIX has good particle identification using an electromagnetic calorimeter for timing, leading to identified pions from .2 to 1 GeV/c. This extends the range of previously measured correlation radii at this energy to (k{sub T}) = 633MeV/c. The beam energy dependence of the HBT radii are studied in depth and no significant dependence of the transverse radii is present. The longitudinal correlation length has a moderate energy dependence. Furthermore, theoretical predictions of R{sub out}/R{sub side} severely underpredict the measured ratio, which is consistent with unity for all k{sub T}. The implications of these results are considered.

  11. RELAP5/MOD2 models and correlations

    SciTech Connect

    Dimenna, R.A.; Larson, J.R.; Johnson, R.W.; Larson, T.K.; Miller, C.S.; Streit, J.E.; Hanson, R.G.; Kiser, D.M.

    1988-08-01

    A review of the RELAP5/MOD2 computer code has been performed to assess the basis for the models and correlations comprising the code. The review has included verification of the original data base, including thermodynamic, thermal-hydraulic, and geothermal conditions; simplifying assumptions in implementation or application; and accuracy of implementation compared to documented descriptions of each of the models. An effort has been made to provide the reader with an understanding of what is in the code and why it is there and to provide enough information that an analyst can assess the impact of the correlation or model on the ability of the code to represent the physics of a reactor transient. Where assessment of the implemented versions of the models or correlations has been accomplished and published, the assessment results have been included.

  12. Car Accident Reconstruction and Head Injury Correlation

    NASA Astrophysics Data System (ADS)

    Chawla, A.; Grover, V.; Mukherjee, S.; Hassan, A. M.

    2013-04-01

    Estimation of brain damage remains an elusive issue and controlled tests leading to brain damage cannot be carried out on volunteers. This study reconstructs real-world car accidents to estimate the kinematics of the head impact. This data is to be used to estimate the head injury measures through computer simulations and then correlate reported skull as well as brain damage to impact measures; whence validating the head FE model (Willinger, IJCrash 8:605-617, 2003). In this study, two crash cases were reconstructed. Injury correlation was successful in one of these cases in that the injuries to the brain of one of the car drivers could be correlated in terms of type, location and severity when compared with the tolerance limits of relevant injury parameters (Willinger, IJCrash 8:605-617, 2003).

  13. Band models and correlations for infrared radiation

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.

    1975-01-01

    Absorption of infrared radiation by various line and band models are briefly reviewed. Narrow band model relations for absorptance are used to develop 'exact' formulations for total absorption by four wide band models. Application of a wide band model to a particular gas largely depends upon the spectroscopic characteristic of the absorbing-emitting molecule. Seven continuous correlations for the absorption of a wide band model are presented and each one of these is compared with the exact (numerical) solutions of the wide band models. Comparison of these results indicate the validity of a correlation for a particular radiative transfer application. In radiative transfer analyses, use of continuous correlations for total band absorptance provides flexibilities in various mathematical operations.

  14. Vorticity, defects and correlations in active turbulence

    PubMed Central

    Thampi, Sumesh P.; Golestanian, Ramin; Yeomans, Julia M.

    2014-01-01

    We describe a numerical investigation of a continuum model of an active nematic, concentrating on the regime of active turbulence. Results are presented for the effect of three parameters, activity, elastic constant and rotational diffusion constant, on the order parameter and flow fields. Defects and distortions in the director field act as sources of vorticity, and thus vorticity is strongly correlated to the director field. In particular, the characteristic length of decay of vorticity and order parameter correlations is controlled by the defect density. By contrast, the decay of velocity correlations is determined by a balance between activity and dissipation. We highlight the role of microscopic flow generation mechanisms in determining the flow patterns and characteristic scales of active turbulence and contrast the behaviour of extensile and contractile active nematics. PMID:25332382

  15. Generalized hydrodynamic correlations and fractional memory functions

    NASA Astrophysics Data System (ADS)

    Rodríguez, Rosalio F.; Fujioka, Jorge

    2015-12-01

    A fractional generalized hydrodynamic (GH) model of the longitudinal velocity fluctuations correlation, and its associated memory function, for a complex fluid is analyzed. The adiabatic elimination of fast variables introduces memory effects in the transport equations, and the dynamic of the fluctuations is described by a generalized Langevin equation with long-range noise correlations. These features motivate the introduction of Caputo time fractional derivatives and allows us to calculate analytic expressions for the fractional longitudinal velocity correlation function and its associated memory function. Our analysis eliminates a spurious constant term in the non-fractional memory function found in the non-fractional description. It also produces a significantly slower power-law decay of the memory function in the GH regime that reduces to the well-known exponential decay in the non-fractional Navier-Stokes limit.

  16. Photon correlation system for fluorescence lifetime measurements

    NASA Astrophysics Data System (ADS)

    Morgan, C. G.; Murray, J. G.; Mitchell, A. C.

    1995-07-01

    The construction and testing of a dual-channel photon correlator is reported for the frequency domain imaging of fluorescence lifetimes using photon-counting detection. A light source modulated at radio frequency excites fluorescence, which is detected using an imaging single-photon detector. After discrimination, single-photon events are processed in parallel by the correlation circuit, the purpose of which is to allow both the mean phase delay and the demodulation of fluorescence to be calculated relative to a reference signal derived from the modulated excitation source. Outputs from the correlator are integrated in a computer, resulting in accumulation of images which have been statistically filtered by sine and cosine transforms, and which can be manipulated within the computer to generate a resultant image where contrast depends on fluorescence lifetime rather than fluorescence intensity.

  17. Vorticity, defects and correlations in active turbulence.

    PubMed

    Thampi, Sumesh P; Golestanian, Ramin; Yeomans, Julia M

    2014-11-28

    We describe a numerical investigation of a continuum model of an active nematic, concentrating on the regime of active turbulence. Results are presented for the effect of three parameters, activity, elastic constant and rotational diffusion constant, on the order parameter and flow fields. Defects and distortions in the director field act as sources of vorticity, and thus vorticity is strongly correlated to the director field. In particular, the characteristic length of decay of vorticity and order parameter correlations is controlled by the defect density. By contrast, the decay of velocity correlations is determined by a balance between activity and dissipation. We highlight the role of microscopic flow generation mechanisms in determining the flow patterns and characteristic scales of active turbulence and contrast the behaviour of extensile and contractile active nematics.

  18. Electron correlation by polarization of interacting densities

    NASA Astrophysics Data System (ADS)

    Whitten, Jerry L.

    2017-02-01

    Coulomb interactions that occur in electronic structure calculations are correlated by allowing basis function components of the interacting densities to polarize dynamically, thereby reducing the magnitude of the interaction. Exchange integrals of molecular orbitals are not correlated. The modified Coulomb interactions are used in single-determinant or configuration interaction calculations. The objective is to account for dynamical correlation effects without explicitly introducing higher spherical harmonic functions into the molecular orbital basis. Molecular orbital densities are decomposed into a distribution of spherical components that conserve the charge and each of the interacting components is considered as a two-electron wavefunction embedded in the system acted on by an average field Hamiltonian plus r12-1. A method of avoiding redundancy is described. Applications to atoms, negative ions, and molecules representing different types of bonding and spin states are discussed.

  19. Signatures of correlation in transition metal oxides

    NASA Astrophysics Data System (ADS)

    Gatti, Matteo; Guzzo, Matteo; Reining, Lucia

    Photoemission satellites are a genuine fingerprint of electronic correlation that cannot be interpreted within the quasiparticle band-structure picture. Here we show that they can be understood in terms of the coupling between different elementary excitations, as in the case of plasmon sidebands. Using examples from different correlated materials, we discuss how this coupling can be explained by advanced calculations based on first-principles many-body perturbation theory that combine GW-like approximations for the self-energy with the cumulant expansion of the Green's function. This approach is not limited to low-energy satellites, but allows for a consistent explanation of signatures of correlation over a wide range of binding energies.

  20. Saturation scale fluctuations and multiparticle rapidity correlations

    NASA Astrophysics Data System (ADS)

    Bzdak, Adam; Dusling, Kevin

    2016-10-01

    We study the effect of intrinsic fluctuations of the proton saturation momentum scale on event-by-event rapidity distributions. Saturation scale fluctuations generate an asymmetry in the single-particle rapidity distribution in each event resulting in genuine n -particle correlations having a component linear in the rapidities of the produced particles, y1⋯yn . We introduce a color domain model that naturally explains the centrality dependence of the two-particle rapidity correlations recently measured by ATLAS [M. Aaboud et al. (ATLAS Collaboration), arXiv:1606.08170] while constraining the probability distribution of saturation scale fluctuations in the proton. Predictions for n =4 , 6, and 8 particle correlations find that the four- and eight-particle cumulants change sign at an intermediate multiplicity, a signature which could be tested experimentally.

  1. Macroscopically local correlations can violate information causality.

    PubMed

    Cavalcanti, Daniel; Salles, Alejo; Scarani, Valerio

    2010-01-01

    Although quantum mechanics is a very successful theory, its foundations are still a subject of intense debate. One of the main problems is that quantum mechanics is based on abstract mathematical axioms, rather than on physical principles. Quantum information theory has recently provided new ideas from which one could obtain physical axioms constraining the resulting statistics one can obtain in experiments. Information causality (IC) and macroscopic locality (ML) are two principles recently proposed to solve this problem. However, none of them were proven to define the set of correlations one can observe. In this study, we show an extension of IC and study its consequences. It is shown that the two above-mentioned principles are inequivalent: if the correlations allowed by nature were the ones satisfying ML, IC would be violated. This gives more confidence in IC as a physical principle, defining the possible correlation allowed by nature.

  2. Magnetic correlations in a classic Mott system

    SciTech Connect

    Bao, W.; Broholm, C.; Aeppli, G.; Carter, S.A.; Dai, D.; Frost, C.D.; Honig, J.M.; Metcalf, P.

    1997-07-01

    The metal-insulator transition in V{sub 2}O{sub 3} causes a fundamental change in its magnetism. While the antiferromagnetic insulator (AFI) is a Heisenberg localized spin system, the antiferromagnetism in the strongly correlated metal is determined by a Fermi surface instability. Paramagnetic fluctuations in the metal and insulator represent similar spatial spin correlations, but are unrelated to the long range order in the AFI. The phase transition to the AFI induces an abrupt switching of magnetic correlations to a different magnetic wave vector. The AFI transition, therefore, is not a conventional spin order-disorder transition. Instead it is accounted for by an ordering in the occupation of the two degenerate d-orbitals at the Fermi level.

  3. Correlation between hepcidin level and renal anemia.

    PubMed

    Yang, L-N; Zhang, P; Tang, F; Wang, G; Li, F-E

    2014-09-12

    Anemia in patients with chronic renal insufficiency (CRI) is related to the chronic inflammatory state, low iron absorption rate, and low utilization rate. As a key protein for iron metabolism, hepcidin plays an important role in CRI anemia. The study aimed to determine the correlation between hepcidin level and renal anemia. Ninety CRI anemia patients treated in our hospital from February 2012 to December 2012 were enrolled in the study to compare with a healthy control group of 40 cases by measuring the hepcidin level and analyzing the correlation between hepcidin level and CRI anemia. The hepcidin level was significantly higher in the CRI anemia group than the control group; there was a positive correlation between hepcidin level and serum ferritin as well as IL-6 level. Hepcidin level was significantly related to degree of anemia, indicating that an increase in hepcidin level will result in anemia.

  4. Exotic Superconductivity in Correlated Electron Systems

    DOE PAGES

    Mu, Gang; Sandu, Viorel; Li, Wei; ...

    2015-05-25

    Over the past decades, the search for high-Tc superconductivity (SC) and its novel superconducting mechanisms is one of the most challenging tasks of condensed matter physicists and material scientists, wherein the most striking achievement is the discovery of high-c and unconventional superconductivity in strongly correlated 3d-electron systems, such as cuprates and iron pnictides/chalcogenides. Those exotic superconductors display the behaviors beyond the scope of the BCS theory (in the SC states) and the Landau-Fermi liquid theory (in the normal states). In general, such exotic superconductivity can be seen as correlated electron systems, where there are strong interplays among charge, spin, orbital,more » and lattice degrees of freedom. Thus, we focus on the exotic superconductivity in materials with correlated electrons in the present special issue.« less

  5. Fuzzy correlations of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Hartmann, Dieter H.; Linder, Eric V.; Blumenthal, George R.

    1991-01-01

    The origin of gamma-ray bursts is not known, both in the sense of the nature of the source emitting the radiation and literally, the position of the burst on the sky. Lacking unambiguously identified counterparts in any wavelength band studied to date, statistical approaches are required to determine the burster distance scale. Angular correlation analysis is one of the most powerful tools in this regard. However, poor detector resolution gives large localization errors, effectively beam smearing the positions. The resulting fuzzy angular correlation function is investigated and the generic isotropization that smearing induces on any intrinsic clustering is discussed. In particular, the extent to which gamma-ray burst observations by the BATSE detector aboard the Gamma-Ray Observatory might recover an intrinsic source correlation is investigated.

  6. Electrostatic correlations near charged planar surfaces

    PubMed Central

    Deng, Mingge; Em Karniadakis, George

    2014-01-01

    Electrostatic correlation effects near charged planar surfaces immersed in a symmetric electrolytes solution are systematically studied by numerically solving the nonlinear six-dimensional electrostatic self-consistent equations. We compare our numerical results with widely accepted mean-field (MF) theory results, and find that the MF theory remains quantitatively accurate only in weakly charged regimes, whereas in strongly charged regimes, the MF predictions deviate drastically due to the electrostatic correlation effects. We also observe a first-order like phase-transition corresponding to the counterion condensation phenomenon in strongly charged regimes, and compute the phase diagram numerically within a wide parameter range. Finally, we investigate the interactions between two likely-charged planar surfaces, which repulse each other as MF theory predicts in weakly charged regimes. However, our results show that they attract each other above a certain distance in strongly charged regimes due to significant electrostatic correlations. PMID:25194382

  7. Einstein-Podolsky Correlation for Light Polarization

    NASA Astrophysics Data System (ADS)

    Mizrahi, Salomon S.; Moussa, Miled H. Y.

    Considering a classical source of light (macroscopic), we propose an experiment, based on the principles of the Einstein-Podolsky-Rosen-Bohm correlation, for which one expects to obtain the same polarization correlation coefficient as the one predicted by the quantum theory, when photons are counted in coincidence. The results of a numerical simulation give good ground to believe that the conjectured experiment is reasonable. So, one may argue that the property of light called polarization, that is manifest at any level — microscopic and macroscopic — and which has a precise description in both, the quantum and the classical theories, leads to coincident results under correspondingly similar experimental procedures. Therefore the EPRB correlation is a consequence of that property of light, independently whether it is viewed as constituted by photons or by electromagnetic waves.

  8. Multitime correlation functions in nonclassical stochastic processes

    NASA Astrophysics Data System (ADS)

    Krumm, F.; Sperling, J.; Vogel, W.

    2016-06-01

    A general method is introduced for verifying multitime quantum correlations through the characteristic function of the time-dependent P functional that generalizes the Glauber-Sudarshan P function. Quantum correlation criteria are derived which identify quantum effects for an arbitrary number of points in time. The Magnus expansion is used to visualize the impact of the required time ordering, which becomes crucial in situations when the interaction problem is explicitly time dependent. We show that the latter affects the multi-time-characteristic function and, therefore, the temporal evolution of the nonclassicality. As an example, we apply our technique to an optical parametric process with a frequency mismatch. The resulting two-time-characteristic function yields full insight into the two-time quantum correlation properties of such a system.

  9. Pairing phenomena in strongly correlated Fermi liquids

    NASA Astrophysics Data System (ADS)

    Krotscheck, E.; Smith, R. A.; Jackson, A. D.

    1981-12-01

    The correlated-basis-function method is extended to deal with pairing phenomena in strongly correlated Fermi liquids. With a variational ansatz for the model wave function we derive the "correlated" analog of the conventional Bardeen-Cooper-Schrieffer (or Balian-Werthamer), Anderson-Brinkman-Morel theory of pairing. A suitable (and well-controlled) set of approximations brings the theory into a form identical to the conventional theories, but with the bare interaction replaced by a weak effective interaction and the bare single-particle energies replaced by an effective single-particle spectrum. As usual, liquid 3He provides a very stringent test of the theory, as both the interaction and the experimental facts are pretty clear. The variational estimates for the pairing interaction are improved by nonorthogonal perturbation theory. We find the expected enhancement of the attraction in P waves, although the restriction to effective two-body interactions appears to be insufficient to generate P-wave pairing.

  10. Information hiding technique using optical correlators

    NASA Astrophysics Data System (ADS)

    Kim, Kyu-Tae; Kim, Jung-Jin; Kim, Eun-Soo

    2001-08-01

    During the past few years a variety of techniques have emerged to hide specific information within multimedia data for copyright protection, tamper-proofing and secret communication. The schemes for information hiding that have been proposed so far used either digital signal processing software or hardware. So they inevitably have a problem in some applications like automatic copyright control system, which need fast data-extracting scheme. In this paper, we show that the newly proposed optical correlator-based information hiding system has an advantage in that sense. In this scheme it is possible to simultaneously extract all the data hidden in one stego image and furthermore it is also possible to simultaneously extract all the data hidden in several stego images using optical correlators such as matched spatial filter and joint transform correlator.

  11. Multitarget tracking using sensors with known correlations

    NASA Astrophysics Data System (ADS)

    Mahler, Ronald

    2016-05-01

    This paper is the fourth in a series aimed at weakening the independence assumptions that are typically presumed in multitarget tracking. Specifically, we assume that, in a multisensory scenario, the sensors are not necessarily independent but, rather, have known correlations (i.e., their joint single-target joint likelihood function is known). From this, we construct a multitarget measurement model for sensors with known correlations. From this model we derive, as an illustrative example, the filtering equations for a probability hypothesis density (PHD) filter for sensors with known correlations. We emphasize the two-sensor case of this filter, for which the measurement-update equations involve a summation over all measurement-to-measurement associations between the two sensors.

  12. Correlation of tertiary formations of Alaska

    USGS Publications Warehouse

    MacNeil, F.S.; Wolfe, J.A.; Miller, D.J.; Hopkins, D.M.

    1961-01-01

    Recent stratigraphic and paleontologic studies have resulted in substantial revision of the age assignments and inter-basin correlations of the Tertiary formations of Alaska as given in both an earlier compilation by P. S. Smith (1939) and a tentative chart prepared for distribution at the First International Symposium on Arctic Geology at Calgary, Alberta (Miller, MacNeil, and Wahrhaftig, 1960). Current work in Alaska by the U. S. Geological Survey and several oil companies is furnishing new information at a rapid rate and further revisions may be expected. The correlation chart (Fig. 1), the first published chart to deal exclusively with the Tertiary of Alaska, had the benefit of a considerable amount of stratigraphic data and fossil collections from some oil companies, but recent surface mapping and drilling by other oil companies in several Tertiary basins undoubtedly must have produced much more information. Nevertheless, the extent of available data justifies the publication of a revised correlation chart at this time.

  13. Spatial mapping of correlation profile in Brillouin optical correlation domain analysis

    NASA Astrophysics Data System (ADS)

    Somepalli, Bhargav; Venkitesh, Deepa; Srinivasan, Balaji

    2017-04-01

    We report an approach to spatially map the correlation profile along the sensing fiber in Brillouin optical correlation domain analysis by pulsing the pump radiation. Simulations are carried out to demonstrate the influence of frequency modulation parameters of a narrow linewidth source on the width of the correlation profile and its peak position. The simulation results are validated through controlled experiments. The correlation profile is mapped over 1 km long fiber with spatial resolution of 1 m, limited only by the finite lifetime of acoustic phonons in the silica fiber.

  14. Elimination of a genetic correlation between the sexes via artificial correlational selection.

    PubMed

    Delph, Lynda F; Steven, Janet C; Anderson, Ingrid A; Herlihy, Christopher R; Brodie, Edmund D

    2011-10-01

    Genetic correlations between the sexes can constrain the evolution of sexual dimorphism and be difficult to alter, because traits common to both sexes share the same genetic underpinnings. We tested whether artificial correlational selection favoring specific combinations of male and female traits within families could change the strength of a very high between-sex genetic correlation for flower size in the dioecious plant Silene latifolia. This novel selection dramatically reduced the correlation in two of three selection lines in fewer than five generations. Subsequent selection only on females in a line characterized by a lower between-sex genetic correlation led to a significantly lower correlated response in males, confirming the potential evolutionary impact of the reduced correlation. Although between-sex genetic correlations can potentially constrain the evolution of sexual dimorphism, our findings reveal that these constraints come not from a simple conflict between an inflexible genetic architecture and a pattern of selection working in opposition to it, but rather a complex relationship between a changeable correlation and a form of selection that promotes it. In other words, the form of selection on males and females that leads to sexual dimorphism may also promote the genetic phenomenon that limits sexual dimorphism.

  15. WCEDS: A waveform correlation event detection system

    SciTech Connect

    Young, C.J.; Beiriger, J.I.; Trujillo, J.R.; Withers, M.M.; Aster, R.C.; Astiz, L.; Shearer, P.M.

    1995-08-01

    We have developed a working prototype of a grid-based global event detection system based on waveform correlation. The algorithm comes from a long-period detector but we have recast it in a full matrix formulation which can reduce the number of multiplications needed by better than two orders of magnitude for realistic monitoring scenarios. The reduction is made possible by eliminating redundant multiplications in the original formulation. All unique correlations for a given origin time are stored in a correlation matrix (C) which is formed by a full matrix product of a Master Image matrix (M) and a data matrix (D). The detector value at each grid point is calculated by following a different summation path through the correlation matrix. Master Images can be derived either empirically or synthetically. Our testing has used synthetic Master Images because their influence on the detector is easier to understand. We tested the system using the matrix formulation with continuous data from the IRIS (Incorporate Research Institutes for Seismology) broadband global network to monitor a 2 degree evenly spaced surface grid with a time discretization of 1 sps; we successfully detected the largest event in a two hour segment from October 1993. The output at the correct gridpoint was at least 33% larger than at adjacent grid points, and the output at the correct gridpoint at the correct origin time was more than 500% larger than the output at the same gridpoint immediately before or after. Analysis of the C matrix for the origin time of the event demonstrates that there are many significant ``false`` correlations of observed phases with incorrect predicted phases. These false correlations dull the sensitivity of the detector and so must be dealt with if our system is to attain detection thresholds consistent with a Comprehensive Test Ban Treaty (CTBT).

  16. How Structure Determines Correlations in Neuronal Networks

    PubMed Central

    Pernice, Volker; Staude, Benjamin; Cardanobile, Stefano; Rotter, Stefan

    2011-01-01

    Networks are becoming a ubiquitous metaphor for the understanding of complex biological systems, spanning the range between molecular signalling pathways, neural networks in the brain, and interacting species in a food web. In many models, we face an intricate interplay between the topology of the network and the dynamics of the system, which is generally very hard to disentangle. A dynamical feature that has been subject of intense research in various fields are correlations between the noisy activity of nodes in a network. We consider a class of systems, where discrete signals are sent along the links of the network. Such systems are of particular relevance in neuroscience, because they provide models for networks of neurons that use action potentials for communication. We study correlations in dynamic networks with arbitrary topology, assuming linear pulse coupling. With our novel approach, we are able to understand in detail how specific structural motifs affect pairwise correlations. Based on a power series decomposition of the covariance matrix, we describe the conditions under which very indirect interactions will have a pronounced effect on correlations and population dynamics. In random networks, we find that indirect interactions may lead to a broad distribution of activation levels with low average but highly variable correlations. This phenomenon is even more pronounced in networks with distance dependent connectivity. In contrast, networks with highly connected hubs or patchy connections often exhibit strong average correlations. Our results are particularly relevant in view of new experimental techniques that enable the parallel recording of spiking activity from a large number of neurons, an appropriate interpretation of which is hampered by the currently limited understanding of structure-dynamics relations in complex networks. PMID:21625580

  17. Correlations in quantum plasmas. II. Algebraic tails

    NASA Astrophysics Data System (ADS)

    Cornu, F.

    1996-05-01

    For a system of point charges that interact through the three-dimensional electrostatic Coulomb potential (without any regularization) and obey the laws of nonrelativistic quantum mechanics with Bose or Fermi statistics, the static correlations between particles are shown to have a 1/r6 tail, at least at distances that are large with respect to the length of exponential screening. After a review of previous work, a term-by-term diagrammatic proof is given by using the formalism of paper I, where the quantum particle-particle correlations are expressed in terms of classical-loop distribution functions. The integrable graphs of the resummed Mayer-like diagrammatics for the loop distributions contain bonds between loops that decay either exponentially or algebraically, with a 1/r3 leading term analogous to a dipole-dipole interaction. This reflects the fact that the charge-charge or multipole-charge interactions between clusters of particles surrounded by their polarization clouds are exponentially screened, as at a classical level, whereas the multipole-multipole interactions are only partially screened. The correlation between loops decays as 1/r3, but the spherical symmetry of the quantum fluctuations makes this power law fall to 1/r5, and the harmonicity of the Coulomb potential eventually enforces the correlations between quantum particles to decay only as 1/r6. The coefficient of the 1/r6 tail at low density is planned to be given in a subsequent paper. Moreover, because of Coulomb screening, the induced charge density, which describes the response to an external infinitesimal charge, is shown to fall off as 1/r8, while the charge-charge correlation in the medium decreases as 1/r10. However, in spite of the departure of the quantum microscopic correlations from the classical exponential clustering, the total induced charge is still essentially determined by the exponentially screened charge-charge interactions, as in classical macroscopic electrostatics.

  18. Reference Correlation for the Viscosity of Ethane

    NASA Astrophysics Data System (ADS)

    Vogel, Eckhard; Span, Roland; Herrmann, Sebastian

    2015-12-01

    A new representation of the viscosity for the fluid phase of ethane includes a zero-density correlation and a contribution for the critical enhancement, initially both developed separately, but based on experimental data. The higher-density contributions are correlated as a function of the reduced density δ = ρ/ρc and of the reciprocal reduced temperature τ = Tc/T (ρc—critical density and Tc—critical temperature). The final formulation contains 14 coefficients obtained using a state-of-the-art linear optimization algorithm. The evaluation and choice of the selected primary data sets is reviewed, in particular with respect to the assessment used in earlier viscosity correlations. The new viscosity surface correlation makes use of the reference equation of state for the thermodynamic properties of ethane by Bücker and Wagner [J. Phys. Chem. Ref. Data 35, 205 (2006)] and is valid in the fluid region from the melting line to temperatures of 675 K and pressures of 100 MPa. The viscosity in the limit of zero density is described with an expanded uncertainty of 0.5% (coverage factor k = 2) for temperatures 290 < T/K < 625, increasing to 1.0% at temperatures down to 212 K. The uncertainty of the correlated values is 1.5% in the range 290 < T/K < 430 at pressures up to 30 MPa on the basis of recent measurements judged to be very reliable as well as 4.0% and 6.0% in further regions. The uncertainty in the near-critical region (1.001 < 1/τ < 1.010 and 0.8 < δ < 1.2) increases with decreasing temperature up to 3.0% considering the available reliable data. Tables of the viscosity calculated from the correlation are listed in an appendix for the single-phase region, for the vapor-liquid phase boundary, and for the near-critical region.

  19. Image Correlation Microscopy for Uniform Illumination

    PubMed Central

    Gaborski, Thomas R.; Sealander, Michael N.; Ehrenberg, Morton; Waugh, Richard E.; McGrath, James L.

    2011-01-01

    Image cross-correlation microscopy (ICM) is a technique that quantifies the motion of fluorescent features in an image by measuring the temporal autocorrelation function decay in a time-lapse image sequence. ICM has traditionally employed laser-scanning microscopes because the technique emerged as an extension of laser-based fluorescence correlation spectroscopy (FCS). In this work, we show that image correlation can also be used to measure fluorescence dynamics in uniform illumination or wide-field imaging systems and we call our new approach uniform illumination image correlation microscopy (UI-ICM). Wide-field microscopy is not only a simpler, less expensive imaging modality, but it offers the capability of greater temporal resolution over laser-scanning systems. In traditional laser-scanning ICM, lateral mobility is calculated from the temporal de-correlation of an image, where the characteristic length is the illuminating laser beam width. In wide-field microscopy, the diffusion length is defined by the feature size using the spatial autocorrelation function (SACF). Correlation function decay in time occurs as an object diffuses from its original position. We show that theoretical and simulated comparisons between Gaussian and uniform features indicate the temporal autocorrelation function (TACF) depends strongly on particle size and not particle shape. In this report, we establish the relationships between the SACF feature size, TACF characteristic time and the diffusion coefficient for UI-ICM using analytical, Monte-Carlo and experimental validation with particle tracking algorithms. Additionally, we demonstrate UI-ICM analysis of adhesion molecule domain aggregation and diffusion on the surface of human neutrophils. PMID:20055917

  20. Modular networks of word correlations on Twitter

    PubMed Central

    Mathiesen, Joachim; Yde, Pernille; Jensen, Mogens H.

    2012-01-01

    Complex networks are important tools for analyzing the information flow in many aspects of nature and human society. Using data from the microblogging service Twitter, we study networks of correlations in the occurrence of words from three different categories, international brands, nouns and US major cities. We create networks where the strength of links is determined by a similarity measure based on the rate of co-occurrences of words. In comparison with the null model, where words are assumed to be uncorrelated, the heavy-tailed distribution of pair correlations is shown to be a consequence of groups of words representing similar entities. PMID:23139863